US20040202798A1 - Compensation films for lcd - Google Patents
Compensation films for lcd Download PDFInfo
- Publication number
- US20040202798A1 US20040202798A1 US10/413,331 US41333103A US2004202798A1 US 20040202798 A1 US20040202798 A1 US 20040202798A1 US 41333103 A US41333103 A US 41333103A US 2004202798 A1 US2004202798 A1 US 2004202798A1
- Authority
- US
- United States
- Prior art keywords
- optically anisotropic
- compensation film
- anisotropic layer
- optical compensation
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/13363—Birefringent elements, e.g. for optical compensation
- G02F1/133632—Birefringent elements, e.g. for optical compensation with refractive index ellipsoid inclined relative to the LC-layer surface
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K2323/00—Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
- G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
- G02F1/1396—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2413/00—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates
- G02F2413/10—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates with refractive index ellipsoid inclined, or tilted, relative to the LC-layer surface O plate
- G02F2413/105—Indexing scheme related to G02F1/13363, i.e. to birefringent elements, e.g. for optical compensation, characterised by the number, position, orientation or value of the compensation plates with refractive index ellipsoid inclined, or tilted, relative to the LC-layer surface O plate with varying inclination in thickness direction, e.g. hybrid oriented discotic LC
Definitions
- the present invention relates to an optical compensation film useful for application to a liquid crystal display, particularly to an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display. It comprises two layers having retardation values and different tilt angles both within prescribed limitations.
- Optic axis herein refers to the direction in which propagating light does not see birefringence.
- a plate, C-plate and O-plate herein are the plates in which the optic axis is in the plane of the plate, perpendicular to the plate and tilted with respect to the plane of the plate, respectively.
- Polarizer and Analyzer refer to elements that polarize electromagnetic wave. However, one closer to the source of the light will be called polarizer while the one closer to the viewer will be called analyzer. Polarizing elements herein refers to both of polarizer and analyzer.
- Viewing direction herein is defined as a set of polar viewing angle ax and azimuthal viewing angle ⁇ as shown in FIG. 1 with respect to a liquid crystal display 101 .
- the polar viewing angle ax is measured from display normal direction 103 and the azimuthal viewing angle ⁇ spans between an appropriate reference direction 105 in the plane of the display surface 107 and the projection 108 of the arrow 109 onto the display surface 107 .
- Various display image properties, such as contrast ratio, color and brightness are functions of angles ⁇ and ⁇ .
- Azimuthal angle ⁇ and tilt angle ⁇ are herein used to specify the direction of an optic axis.
- the azimuthal angle ⁇ is used, as their tilt angle ⁇ is zero.
- FIG. 2 shows the definition of the azimuthal angle ⁇ and tilt angle ⁇ to specify the direction of the optic axis 201 with respect to the x-y-z coordinate system 203 .
- the x-y plane is parallel to the display surface 107
- the z-axis is parallel to the display normal direction 103 .
- the azimuthal angle ⁇ is the angle between the x-axis and the projection of the optic axis 201 onto the x-y plane.
- the tilt angle ⁇ is the angle between the optic axis 201 and the x-y plane.
- ON (OFF) state herein refers to the state with (without) an applied electric field to the liquid crystal display 101 .
- Isocontrast plot herein shows a change in a contrast ratio from different viewing directions.
- Isocontrast line on which the contrast ratio is constant (such as 10, 50 and 100), is plotted in polar format.
- the area enclosed within the isocontrast line with contrast ratio, for example, 10 is the viewing angle range with contrast ratio 10 or higher.
- Lamination herein means a process of making a single sheet of film by uniting two or more films.
- Ordinary-Mode Twisted Nematic Liquid Crestal Display herein means a Twisted Nematic Liquid Crystal Display having the direction of the liquid crystal optic axis at cell surface 311 (or 312 ) substantially perpendicular to the transmission axis direction of the adjacent polarizing element 307 (or 309 ).
- Liquid crystals are widely used for electronic displays.
- a liquid crystal cell is typically situated between a pair of polarizer and analyzers.
- An incident light polarized by the polarizer passes through a liquid crystal cell and is affected by the molecular orientation of the liquid crystal, which can be altered by the application of a voltage across the cell. The altered light goes into the analyzer.
- the transmission of light from an external source including ambient light, can be controlled.
- the energy required to achieve this control is generally much less than required for the luminescent materials used in other display types such as cathode ray tubes (CRT).
- liquid crystal technology is used for a number of electronic imaging devices, including but not limited to digital watches, calculators, portable computers, electronic games for which light-weight, low-power consumption and long-operating life are important features.
- Contrast, color reproduction, and stable gray scale intensities are important quality attributes for electronic displays, which employ liquid crystal technology.
- the primary factor limiting the contrast of a liquid crystal display (LCD) is the propensity for light to “leak” through liquid crystal elements or cells, which are in the dark or “black” pixel state.
- the leakage and hence contrast of a liquid crystal display are also dependent on the direction from which the display screen is viewed.
- the leakage problem not only degrades the contrast but also causes color or hue shifts with an associated degradation of color reproduction.
- LCDs are quickly replacing CRTs as monitors for desktop computers and other office or house hold appliances. It is also expected that the number of LCD television monitors with a larger screen size will sharply increase in the near future. However, unless problems of viewing angle dependence such as coloration, degradation in contrast, and an inversion of brightness are solved, LCD's application as a replacement of the traditional CRT will be limited.
- FIG. 3A is a schematic of a TN-LCD 313 .
- a liquid crystal cell 301 is positioned between a polarizer 303 and an analyzer 305 .
- Their transmission axes 307 , 309 are crossed, meaning that the transmission (or equivalently, absorption) axes of a polarizer and an analyzer form angle 90 ⁇ 10°.
- the optic axis of liquid crystal shows azimuthal rotation of 90° in the OFF state across the cell thickness direction.
- the direction of the liquid crystal optic axes 311 , 312 at the cell surfaces is indicated by a single head arrow.
- the liquid crystal optic axes 311 , 312 have a small tilt angle ⁇ s with respect to the cell surfaces in order to prevent the reverse twist. Namely, the tilt is consistent with the sense (clock or counter-clock wise) of the azimuthal rotation in the liquid crystal optic axis in the cell thickness direction.
- the azimuthal angle between the of transmission axes 307 of the polarizer 303 and the optic axis 311 of the liquid crystal on the nearest cell surface is 90°.
- Un-polarized incoming light is linearly polarized by the polarizer 303 and its plane of polarization rotates 90° while traveling through the liquid crystal cell 301 .
- the plane of polarization of out-coming light from the cell 301 is parallel to the transmission axis 309 of analyzer 305 and will transmit through the analyzer 305 .
- the liquid crystal With sufficiently high-applied voltage, the liquid crystal becomes perpendicular to the cell plane except in the close vicinity of the bounding plates. In this ON state, the incoming polarized light essentially does not see birefringence and thus it is blocked by the analyzer.
- This mode of bright OFF state and dark ON state combined with the angular relation between liquid crystal optic axes at the cell surfaces and transmission axes of the polarizing elements is called Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display (O-mode NW-TN-LCD).
- O-mode NW-TN-LCD Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display
- E-mode NW-TN-LCD Extraordinary-mode Normally White Twisted Nematic Liquid Crystal Display
- Most of the current applications of Normally White Liquid Crystal Display are that of O-mode.
- the isocontrast plot of the display 313 is shown in FIG. 3B.
- the lines 315 , 317 , 319 are isocontrast lines for contrast ratios, 10 , 50 , 100 , respectively.
- the azimuthal angle ⁇ is measured from a reference direction 105 (shown in FIG.
- the display fails to maintain contrast ratio 10 or higher in the range required for many applications. Viewing angle range with contrast 10 or higher is limited as the area enclosed within the isocontrast line 10 , 315 , is small.
- the compensation films consist of optically anisotropic layer deposited on the substrate.
- the substrate can be flexible film such as triacetyl-cellulose or rigid such as glass.
- the optically anisotropic layer is generally made of liquid crystal polymers. As it is necessary to align the optic axis of the liquid crystal polymer in the desired direction (making the anisotropic layer as A, C or O-plate), an alignment layer is often deposited between the optically anisotropic layer and substrate or between the two optically anisotropic layers. The thickness of the anisotropic layer depends on the property of its constituent material and LCD to which it is applied.
- the compensation films are typically inserted anywhere between the liquid crystal cell and the polarizers.
- the function of compensation film in general, is to undo the retardation experienced by the propagating light while traveling through the liquid crystal cell.
- birefringence experienced by the obliquely propagating light is cancelled by the film. This gives us uniform dark state resulting in improved viewing angle characteristic.
- U.S. Pat. No. 5,619,352 discloses the usage of combinations of O-plates.
- the basic idea is to compensate the ON state of TN-LCD by a stack of O-plates that have similar or complementary optical symmetries of the ON state liquid crystal cell. This was done by approximating the ON state of TN-LCD by three representative parts: two regions closed to the cell bounding plates and cell middle section. In the middle of the cell, the liquid crystal optic axis is almost perpendicular to the cell plane with large change in the azimuthal angle of liquid crystal optic axis. In the vicinity of the bounding plates, tilt in liquid crystal optic axis is small with almost fixed azimuthal angle. In comparison to the previous compensation technology, the stability of gray scale as well as viewing angle characteristic has been improved.
- European Patent Application 1143271A2 discloses compensation film comprising two layers of O-plates.
- the tilt angle of optic axis increases continuously or stepwise in the film thickness direction in the first O-plate whereas it decreases continuously or stepwise in the second O-plate.
- These two O-plates are disposed on the substrate with negative C-plate property or biaxial plate having optical property close to that of negative C-plate.
- negative C-plates the ordinary refraction index is larger than the extraordinary one, and the optic axis is perpendicular to the plates.
- the film is used one side of the liquid crystal cell.
- the average tilt angle of two O-plates may assume different values. Examples 8 and 16, for example use combinations of average tilt angles 42° and 31°, and 20° and 89°, respectively.
- Van de Witte et al. also disclosed in WO 97/44409 that the combination of two O-plates are used to compensate the Twisted Nematic Displays.
- the compensation films are applied for both sides of the liquid crystal cell.
- the two O-plates can take different tilt angles, for example, 40° and 50°.
- the tilt angles are preferably larger than 100 but no more than 70°.
- FIG. 4A shows the O-mode NW-TN-LCD 421 with two hybrid-aligned compensation films 407 , 415 placed adjacent to the liquid crystal cell 409 .
- the optic axes 423 , 424 change their tilt angles gradually in the film thickness direction while keeping their azimuthal angles constant. The tilt angle changes from a few degree to 80°, thus the average tilt angle is approximately 40°.
- the pair of hybrid-aligned film 407 , 415 is placed such that azimuthal angle between the optic axes of compensation films and the liquid crystals optic axes 411 , 413 of nearest cell surface is 90°.
- the azimuthal angle of transmission axes 403 , 419 of the analyzer 401 and the polarizer 417 are equal to that of the optic axes 423 , 424 of compensation films 407 , 415 , respectively.
- the thickness of the compensation films 407 , 415 is 0.42 ⁇ m and the phase retardation values is 100 nm.
- the negative C-plates 405 represent the optical properties of tri-acetyl cellulose substrate.
- FIG. 4B shows the isocontrast plot of the display 421 .
- the compensation film disclosed in the co-pending U.S. patent application Ser. No. 10/318,773 uses two layers having different retardation values and different tilt angles both within prescribed limitations. It significantly improved the viewing angle of NW-TN-LCD.
- the application of the compensation film disclosed in the application is limited to E-mode NW-TN-LCD. The film gives unsatisfactory viewing angle characteristics when it is applied to O-mode NW-TN-LCD.
- the prior art compensators using O-plate improved the viewing angle characteristic by reducing the light leakage in the ON state of O-mode NW-TN-LCD.
- viewing angle characteristic still remain unsatisfactory.
- large viewing angle range with contrast ratio 10 or less namely, the area outside of the isocontrast line 10 , 427 in the isocontrast plot shown in FIG. 4B of prior art display 421 shown in FIG. 4A
- the display with this viewing angle characteristic is certainly not applicable for LCD-TV or application that needs large viewing angle range, such as avionics displays.
- the invention provides an optical compensation film for Ordinary mode Normally White Twisted Nematic Liquid Crystal Displays comprising, a first and a second optically anisotropic layers containing positively birefringent material disposed on a substrate, wherein the optic axis of said first optically anisotropic layer tilts in a first plane with an average tilt angle between 10° and 60°, and the optic axis of said second optically anisotropic layer tilts in a second plane with an average tilt angle between 0° and 30°, and said average tilt angle of said first optically anisotropic layer and said average tilt angle of said second optically anisotropic layer are different, and said first and said second planes are perpendicular to the plane of said optical compensation film with the angle between said first and said second planes being 90 ⁇ 100, and the retardation defined by (ne 1 ⁇ no 1 )d 1 of said first optically anisotropic layer is between 60 nm and 220 nm and the retardation defined by (ne 2
- the compensation film can be used in conjunction with an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display for an improved viewing angle characteristic.
- the invention also includes a display incorporating the film of the invention.
- FIG. 1 shows the definition of a viewing angle direction.
- FIG. 2 shows the definition of the tilt and azimuthal angles to specify a direction of an optic axis.
- FIG. 3A is a prior art O-mode NW-TN-LCD without a compensation film.
- FIG. 3B is an isocontrast plot of the prior art O-mode NW-TN-LCD shown in FIG. 3A.
- FIG. 4A is a prior art O-mode NW-TN-LCD with hybrid-aligned compensation films having 40′ average tilt and thickness 0.42 ⁇ m and phase retardation of 100 nm.
- FIG. 4B is an isocontrast plot of the prior art O-mode NW-TN-LCD shown in FIG. 4A.
- FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are elevation schematics of the compensation film.
- FIG. 6A, FIG. 6B and FIG. 6C are diagrams showing the structure of the compensation film.
- the tilt angle of optic axis is constant, while in FIG. 6B, it varies in the film thickness direction.
- FIG. 6A and FIG. 6B show left-handed films, whereas FIG. 6C corresponds to a right-handed film.
- FIGS. 7A through 7F are graphs showing the range of retardations R 1 and R 2 for different combination of the tilt angles ⁇ C1 and ⁇ C2 (or equivalently ⁇ av1 and ⁇ av2 ) and R sub .
- FIG. 8B is an isocontrast plot of the O-mode NW-TN-LCD shown in FIG. 8A.
- FIG. 8D is an isocontrast plot of the O-mode NW-TN-LCD shown in FIG. 8C.
- An optical compensation film for an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display of the present invention comprises a first and a second optically anisotropic layers containing positively birefringent material disposed on a substrate, wherein the optic axis of said first optically anisotropic layer tilts in a first plane with an average tilt angle between 10° and 60°, and the optic axis of said second optically anisotropic layer tilts in a second plane with an average tilt angle between 0° and 30°, and said average tilt angle of said first optically anisotropic layer and said average tilt angle of said second optically anisotropic layer are different, and said first and said second planes are perpendicular to a plane of said optical compensation film, and an angle between said first and said second plane is 90 ⁇ 100, and the retardation defined by (ne 1 -no 1 )d 1 of said first optically anisotropic layer is between 60 nm and 220 nm and the retardation defined by (ne 2
- FIG. 5A shows the elevation view of the optical compensation film 500 , which contains a positively birefringent material oriented with its optic axis tilted in a plane perpendicular to the film plane.
- Two birefringent material layers or optically anisotropic layers 501 , 503 are deposited on the substrate 509 , which is parallel to the film plane.
- the first layer 501 and second layer 503 have different average tilt angle in the optic axis.
- the average tilt angle ⁇ av is the average of tilt angle over the thickness of the optically anisotropic layer, i.e., ⁇ 0 d ⁇ ⁇ ⁇ ( z ) ⁇ ⁇ z d ,
- the retardation of optically anisotropic layer is defined by (ne ⁇ no)d at the wavelength of 550 mm, where ne and no are the extraordinary and ordinary refractive indices of the positively birefringent material, respectively, and d, the thickness of the birefringent material layer or optically anisotropic layer
- thickness of the two anisotropic layers with the same retardation must be equal provided their birefringence (ne-no) are the same.
- the two optically anisotropic layers contain different positively anisotropic materials. Namely, the first optically anisotropic layer contains positively birefringent material with ne, and no 1 while the second optically anisotropic layer contains positively birefringent material with ne 2 and no 2 .
- optical materials may have up to three different principal indices of refraction and can be classified as either isotropic or anisotropic based on the relationship of these indices. When all three of its principal indices are equal, a material is said to be isotropic. When anisotropic, a material can be either uniaxial, or biaxial. If two principal indices are equal, a material is called uniaxial. A uniaxial material is uniquely characterized, as having an ordinary index, referred as no, an extraordinary index ne and two angles describing the orientation of its optical axis, the axis of ne. When ne is greater than no, a uniaxial material is positively birefringent.
- ne When ne is smaller than no, a uniaxial material is negatively birefringent. Controlling birefringent behavior is particularly useful in the fabrication and application of optical films.
- a material When all three refractive indices are different, a material is said to be biaxial, uniquely specified by its principal indices nx 0 , ny 0 , nz 0 , and three orientation angles.
- Some of biaxial materials show weak biaxiality meaning that two of their three principal indices are very close, which is often considered equally as the ordinary refractive index for a uniaxial material.
- “optically anisotropic layer” is used to refer the birefringent material layer.
- the substrate 509 functions as a mechanical support and has certain optical property.
- the material for substrate can be polymer or other optically transparent material.
- the substrate can take flexible or rigid form as long as it has enough strength for manufacturing process and actual application. Optically, it has a characteristic of negative C-plate, namely, C-plate with a relation ne s ⁇ no s , where ne s and no s are extraordinary and ordinary refraction indices of substrate.
- the out-of-plane retardation R sub (ne s ⁇ no s )d s of the substrate defined at the wavelength of 550 mm with thickness d, is preferably in the range of ⁇ 200 nm to ⁇ 60 nm.
- a substrate with biaxial optical property can also be used.
- the optically property of the substrate is specified by three independent indices of refraction, nx s , ny s , and nz s , where nx s is the maximum index of refraction and ny s is the minimum index refraction both in the plane of the substrate and nz s is the index of refraction in the thickness direction of the substrate.
- the difference between nx s and ny s is small, that is (nx s ⁇ ny s )/(nx s +ny s ) ⁇ 0.05, and the relation nx s >ny s >nz s is satisfied.
- the substrate can comprise of multiple of layers or coatings to attain the sufficient negative value of R sub .
- R sub ⁇ 60 nm
- R sub ⁇ 120 nm
- films with insufficient negative value of R sub can be coated with a layer of organic or inorganic compound.
- a layer of particular polymer such as polyimide or discotic liquid crystal compounds gives high negative value of R sub .
- Optically isotropic materials, such as glass or some polymer films, can be a substrate when coated or laminated with layers or a layer having sufficient negative value of R sub .
- Alignment layers 505 , 507 enforce the predetermined azimuthal ⁇ and tilt ⁇ angles of optic axis in the first and the second optically anisotropic layers 501 , 503 .
- the alignment direction is generated by mechanically rubbing the surface of the alignment layer.
- the alignment layer contains a polymeric material such as polyvinyl alcohol or polyimide.
- electromagnetic radiation of the alignment layer or photo-alignment method is known to generate the specific orientation of the optic axis.
- the direction of optic axis in the optically anisotropic layer is controlled by the material contained in the alignment layer, amount of an exposure, wavelength of the radiation, the thickness of alignment layer and other possible parameters.
- the alignment layer needs to be sensitive to the wavelength of radiation.
- a radiation in ultraviolet region is used for polymeric alignment layer containing UV sensitive functional group such as cinnamate group.
- FIG. 5B shows the alternate configuration of the compensation film 515 .
- the optically anisotropic layers, 501 , 503 are sandwiched between the two substrates 509 , 511 that may or may not be identical to each other. Alignment layers are 505 and 507 . This case potentially arises when the compensation films are manufactured by laminating two separate optically anisotropic layers disposed on two separate substrates.
- the laminating interface is located between the two anisotropic layers, 501 and 503 .
- FIG. 5C shows Other possible lamination case for a compensation film 517 . Where the laminating interface is now located between the optically anisotropic layer 501 and the substrate 511 .
- the compensation film 519 without alignment layers 505 , 507 is also possible.
- the optic axis direction in optically anisotropic layers 501 , 503 is controlled by an external force such as electric, magnetic field or shear flow forces. Then the optic axis direction is frozen by, for example, polymerization or quenching of the optically anisotropic layers while the external field is being applied.
- layers of inorganic compounds deposited by certain methods and with conditions give desired direction of optic axes as well as the retardation.
- An optically anisotropic layer is characterized by the indices of refraction, retardation (or equivalently thickness) and the direction of optic axis.
- the direction of optic axis is specified by its tilt ⁇ and azimuthal angles ⁇ .
- FIG. 6 A, FIG. 6B and FIG. 6C show the structure of the film 500 schematically.
- the optic axis of the first optically anisotropic layer 601 is tilted in a first plane 608
- the optic axis of the second optically anisotropic layer 603 is tilted in a second plane 607 . Both first plane 608 and second plane 607 are perpendicular to the film plane or substrate 609 .
- the angle formed between the first plane 608 and the second plane 607 is 90 ⁇ 10°.
- the first plane preferably contains the optic axis of liquid crystal on the nearest cell surface to the compensation flms.
- Two optically anisotropic layers 601 , 603 are deposited on the alignment layers 605 .
- the substrate 609 supports the whole structure as well as giving necessary optical property for the compensation films. Arrows indicate the direction of optic axis in the optically anisotropic layers.
- the optic axis in the optically anisotropic layer tilts in the plane perpendicular to the liquid crystal cell plane and the plane of the substrate 609 .
- the tilt angle ⁇ may stay constant as ⁇ C1 and ⁇ C2 (FIG. 6A and FIG. 6C) or vary in the thickness direction of the optically anisotropic layer from ⁇ v1 to ⁇ v2 or ⁇ v3 to ⁇ v4 (FIG. 6B).
- the average tilt angle ⁇ av ⁇ 0 d ⁇ ⁇ ⁇ ( z ) ⁇ ⁇ z d
- the compensation film 500 of the present invention possesses combination of retardation values and different tilt angle of optic axis between the two optically anisotropic layers that are given in a particular range given below.
- the combination in the given range of tilt and the retardation provide much improved viewing angle performance of O-mode NW-TN-LCD.
- the tilt angle ⁇ C1 of the first optically anisotropic layer 601 is preferably in the range 10° ⁇ C1 ⁇ 60° or more preferably 15° ⁇ C1 ⁇ 50°.
- the tilt angle ⁇ C2 for the second anisotropic layer 603 is preferably 0° ⁇ C2 ⁇ 30° or more preferably 0° ⁇ C2 ⁇ 20°.
- the average of the tilt angle ⁇ av1 for the first layer 601 are preferably in the range 10° ⁇ av1 ⁇ 60°, or more preferably 15° ⁇ av1 ⁇ 50°.
- the average tilt angle ⁇ av2 is given 0° ⁇ av2 ⁇ 30°or more preferably 0° ⁇ av2 ⁇ 20°.
- the tilt angles ⁇ C1 and ⁇ C2 (or equivalently ⁇ av1 , and ⁇ av2 ) assume different values.
- the difference between the two angles, ⁇ C1 - ⁇ C2 (or equivalently, ⁇ av1 - ⁇ av2 ) is larger than 10° but not more than 60°.
- Various combinations, such as varying tilt in the first optically anisotropic layer 601 and constant tilt in the second one 603 can equally function as a compensation film.
- the films shown in the FIGS. 6A and 6B are left-handed, meaning that the optic axis 601 rotates counter-clockwise to optic axis 603 as one follows the direction of increasing thickness indicated by an arrow 613 .
- the optic axis 601 rotates counter clockwise to 603 in the direction of increasing thickness indicated by an arrow 613 .
- the handed ness of the compensation film and that of liquid crystal cell is preferably the same.
- the retardation of the first optically anisotropic layer R 1 is defined as (ne 1 ⁇ no 1 )d 1 , where d 1 is the thickness of the first optically anisotropic layer.
- the retardation of the second optically anisotropic layer R 2 is equally defined as (ne 2 ⁇ no 2 )d 2 .
- the value of R 1 is in the range 60 nm ⁇ R 1 ⁇ 220 nm and R 2 is in the range 85 nm ⁇ R 2 ⁇ 210 nm.
- the preferable values for the retardation, R 1 and R 2 for the first 601 and the second 603 optically anisotropie layers depend on each other and also on the combination of angles ⁇ C1 and ⁇ C2 (or equivalently, ⁇ av1 and ⁇ av2 ) between the two layers, 601 and 603 .
- FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E and FIG. 7F show the range of the preferable values for R 1 and R 2 for a given combination of tilt angles and R sub as tabulated in the Table 1. TABLE 1 The values of tilt angles and R sub corresponding to FIGS. 7A through 7E.
- FIG. 8A is the schematic of the O-mode NW-TN-LCD 851 with the compensation film 500 according to the invention.
- the optically anisotropic layers 801 and 803 (corresponding to layers 601 , 603 , respectively, in FIGS. 6A and 6B) are shown separately disposed on the substrate 829 .
- the alignment layers are not shown in FIG. 8A.
- the TN liquid crystal cell 809 is placed between two pairs of optically anisotropic layers 803 .
- Arrows 819 indicate the direction of liquid crystal optic axis at the cell surfaces.
- the direction of optic axis in optically anisotropic layers 801 and 803 is shown by the arrows 811 and 813 , respectively.
- the double-headed arrows 823 , 825 show the transmission axes of polarizer 831 and analyzer 833 , which have azimuthal angle ⁇ of 45° (or 225°) and 135° (or 315°), respectively.
- the azimuthal angle between the transmission axis of polarizing elements and optic axis of liquid crystal on the nearest cell surface to the polarizing elements is 90°.
- the display 851 is O-mode NW-TN-LCD. Azimuthal angles of optic axes and the transmission axes are given in the parenthesis.
- the optic axis 811 of the first anisotropic layer 801 tilts in the plane that contains the optic axis of liquid crystal on the nearest cell surface.
- the compensation film 515 with the structure such as in FIG. 5B.
- the corresponding display 855 is shown in FIG. 8C.
- FIG. 8B and FIG. 8D are isocontrast plots for the display 851 and 855 shown in FIG. 8A and FIG. 8C, respectively.
- the lines 835 , 837 and 839 are isocontrast lines with contrast ratio 10 , 50 and 100 , respectively.
- the lines 427 , 429 , 431 are isocontrast lines for contrast ratio 10 , 50 and 100 , respectively.
- FIG. 8D It can be seen both in FIG. 8D and FIG. 8D that the area enclosed by the isocontrast line 10 , 835 , is much larger than their counter part by the line 427 in the isocontrast plot shown in FIG. 4B.
- the display 851 has a contrast ratio higher than 50 in wide viewing angle range.
- the display 855 has achieved much wider viewing angle range with contrast ratio 10 or higher in comparison to the prior art display 421 .
- the prior art display 421 has significant viewing angle portion with contrast less than 10 that is located outside of the isocontrast line 10 in the isocontrast plot shown in FIG. 4B.
- a display with a better viewing angle characteristic has a larger average viewing angle of ⁇ at the same contrast ratio.
- display 851 of the invention has significantly wider viewing angle range for the same contrast ratio in comparison to the Prior Art Display 421 .
- average viewing angle range with contrast 100 or higher is expanded to 41° from 23°.
- FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E and FIG. 7F clearly show that the retardations, R 1 and R 2 , and tilt angles of the first and the second optically anisotropic layers as well as the substrate retardation R sub need to be optimized simultaneously.
- R sub the retardations R 1 and R 2 depend on each other, and their range differs for a different tilt angle combination.
- FIGS. 9A through 9D are isocontrast plots of O-mode NW-TN-LCD such as shown in FIG. 4A or FIG.
- FIGS. 9A through 9D the lines 901 , 903 and 905 correspond to isocontrast line with contrast ratio 10 , 50 and 100 , respectively. TABLE 3 Values of tilt angles and retardation of the optically anisotropic layers corresponding to the isocontrast plots FIGS. 9A through 9D.
- FIG. 9D is the isocontrast plot of the O-modc NW-TN-LCD display with compensation film having ⁇ C1 and ⁇ C1 (or equivalently ⁇ av1 and ⁇ av2 ) and R 1 , R 2 and R sub that are in the range suitable for E-mode NW-TN-LCD disclosed in co-pending U.S. patent application Ser. No. 10/318,773. It is clear that the simple application of a film with parameters tuned for E-mode does not give satisfactory viewing angle characteristic when it is applied to O-mode display. The isocontrast plot in FIG.
- EP Application 1143271A2 and WO 97/44409 discusses the combination of different tilt angles between the two O-plates. However, it is a surprising result that particular combinations of two tit angles ⁇ C1 , ⁇ C2 (or equivalently ⁇ av1 and ⁇ av2 ), the retardations R 1 , R 2 , and the retardation of the substrate R sub result in unforeseeable and significant improvements in the viewing angle range.
- tilt angles ⁇ C1 and ⁇ C2 (or equivalently ⁇ av1 and ⁇ av2 ) for a given pair of R 1 , R 2 and R sub .
- the invention offers excellent manufacturing flexibility.
- nx s the maximum index of refraction in the plane of the substrate with the biaxial optical property
- ny s the minimum index of refraction in the plane of the substrate with the biaxial optical property
- nz s the index of refraction in the thickness direction of the substrate with the biaxial optical property
Abstract
Description
- Reference is made to commonly-assigned co-pending U.S. patent application Ser. No. 10/318,773, entitled COMPENSATION FILMS FOR LCDS, the disclosure of which is incorporated herein.
- The present invention relates to an optical compensation film useful for application to a liquid crystal display, particularly to an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display. It comprises two layers having retardation values and different tilt angles both within prescribed limitations.
- The following terms have the definitions as stated below.
- Optic axis herein refers to the direction in which propagating light does not see birefringence.
- A plate, C-plate and O-plate herein are the plates in which the optic axis is in the plane of the plate, perpendicular to the plate and tilted with respect to the plane of the plate, respectively.
- Polarizer and Analyzer herein refer to elements that polarize electromagnetic wave. However, one closer to the source of the light will be called polarizer while the one closer to the viewer will be called analyzer. Polarizing elements herein refers to both of polarizer and analyzer. Viewing direction herein is defined as a set of polar viewing angle ax and azimuthal viewing angle β as shown in FIG. 1 with respect to a
liquid crystal display 101. The polar viewing angle ax is measured from displaynormal direction 103 and the azimuthal viewing angle β spans between anappropriate reference direction 105 in the plane of thedisplay surface 107 and theprojection 108 of the arrow 109 onto thedisplay surface 107. Various display image properties, such as contrast ratio, color and brightness are functions of angles α and β. - Azimuthal angle φ and tilt angle θ are herein used to specify the direction of an optic axis. For the transmission axes of the polarizer and the analyzer, only the azimuthal angle φ is used, as their tilt angle θ is zero. FIG. 2 shows the definition of the azimuthal angle φ and tilt angle θ to specify the direction of the
optic axis 201 with respect to thex-y-z coordinate system 203. The x-y plane is parallel to thedisplay surface 107, and the z-axis is parallel to the displaynormal direction 103. The azimuthal angle φ is the angle between the x-axis and the projection of theoptic axis 201 onto the x-y plane. The tilt angle θ is the angle between theoptic axis 201 and the x-y plane. - ON (OFF) state herein refers to the state with (without) an applied electric field to the
liquid crystal display 101. - Isocontrast plot herein shows a change in a contrast ratio from different viewing directions. Isocontrast line, on which the contrast ratio is constant (such as 10, 50 and 100), is plotted in polar format. The concentric circle corresponds to polar viewing angle α=20°, 40°, 60° and 80° (outer most circle) and the radial lines indicates azimuthal viewing angle β=0°, 45°, 90°, 135°, 180°, 225°, 270° and 315°. The area enclosed within the isocontrast line with contrast ratio, for example,10 is the viewing angle range with
contrast ratio 10 or higher. - Lamination herein means a process of making a single sheet of film by uniting two or more films.
- Ordinary-Mode Twisted Nematic Liquid Crestal Display herein means a Twisted Nematic Liquid Crystal Display having the direction of the liquid crystal optic axis at cell surface311 (or 312) substantially perpendicular to the transmission axis direction of the adjacent polarizing element 307 (or 309).
- Liquid crystals are widely used for electronic displays. In these display systems, a liquid crystal cell is typically situated between a pair of polarizer and analyzers. An incident light polarized by the polarizer passes through a liquid crystal cell and is affected by the molecular orientation of the liquid crystal, which can be altered by the application of a voltage across the cell. The altered light goes into the analyzer. By employing this principle, the transmission of light from an external source, including ambient light, can be controlled. The energy required to achieve this control is generally much less than required for the luminescent materials used in other display types such as cathode ray tubes (CRT). Accordingly, liquid crystal technology is used for a number of electronic imaging devices, including but not limited to digital watches, calculators, portable computers, electronic games for which light-weight, low-power consumption and long-operating life are important features.
- Contrast, color reproduction, and stable gray scale intensities are important quality attributes for electronic displays, which employ liquid crystal technology. The primary factor limiting the contrast of a liquid crystal display (LCD) is the propensity for light to “leak” through liquid crystal elements or cells, which are in the dark or “black” pixel state. Furthermore, the leakage and hence contrast of a liquid crystal display are also dependent on the direction from which the display screen is viewed. Typically the optimum contrast is observed only within a narrow viewing angle range centered about the normal incidence (α=0′) to the display and falls offrapidly as the polar viewing angle α is increased. In color displays, the leakage problem not only degrades the contrast but also causes color or hue shifts with an associated degradation of color reproduction.
- LCDs are quickly replacing CRTs as monitors for desktop computers and other office or house hold appliances. It is also expected that the number of LCD television monitors with a larger screen size will sharply increase in the near future. However, unless problems of viewing angle dependence such as coloration, degradation in contrast, and an inversion of brightness are solved, LCD's application as a replacement of the traditional CRT will be limited.
- Among various LCD modes, Twisted Nematic (TN) LCD is one of the most prevalent ones. FIG. 3A is a schematic of a TN-
LCD 313. Aliquid crystal cell 301 is positioned between apolarizer 303 and ananalyzer 305. Theirtransmission axes analyzer form angle 90±10°. Inside the liquid crystal cell, the optic axis of liquid crystal shows azimuthal rotation of 90° in the OFF state across the cell thickness direction. In FIG. 3A, the direction of the liquid crystaloptic axes optic axes transmission axes 307 of thepolarizer 303 and theoptic axis 311 of the liquid crystal on the nearest cell surface is 90°. The same relation holds for thetransmission axis 309 of theanalyzer 305 and the liquid crystaloptic axis 312 at the cell surface. Un-polarized incoming light is linearly polarized by thepolarizer 303 and its plane of polarization rotates 90° while traveling through theliquid crystal cell 301. The plane of polarization of out-coming light from thecell 301 is parallel to thetransmission axis 309 ofanalyzer 305 and will transmit through theanalyzer 305. With sufficiently high-applied voltage, the liquid crystal becomes perpendicular to the cell plane except in the close vicinity of the bounding plates. In this ON state, the incoming polarized light essentially does not see birefringence and thus it is blocked by the analyzer. This mode of bright OFF state and dark ON state combined with the angular relation between liquid crystal optic axes at the cell surfaces and transmission axes of the polarizing elements is called Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display (O-mode NW-TN-LCD). On the other hand, if the transmission axes of polarizing elements are parallel to the liquid crystal optic axis of the nearest cell surface, the corresponding display is called Extraordinary-mode Normally White Twisted Nematic Liquid Crystal Display (E-mode NW-TN-LCD). Most of the current applications of Normally White Liquid Crystal Display are that of O-mode. - In the display normal viewing direction (α=0), one can obtain high contrast between the ON and OFF states. However, when the display is viewed from an oblique direction, the propagating light sees birefringence in ON state, thus it is not completely blocked by the analyzer. The isocontrast plot of the
display 313 is shown in FIG. 3B. Thelines transmission axis 307 of the polarizer 303 (namely, β=45°, 225° line corresponds to 307). The display fails to maintaincontrast ratio 10 or higher in the range required for many applications. Viewing angle range withcontrast 10 or higher is limited as the area enclosed within theisocontrast line isocontrast line 10 runs through α=43° for the horizontal viewing direction (β=0°, 180′). In the vertical direction, α=30°, 80° for β=90°, 270°, respectively. Within the viewing angle range outside of theline 315, the contrast ratio between the On and the Off state becomes less than 10. - One of the common methods to improve the viewing angle characteristic of TN-LCD is to use the compensation films. In some cases, the compensation films consist of optically anisotropic layer deposited on the substrate. The substrate can be flexible film such as triacetyl-cellulose or rigid such as glass. The optically anisotropic layer is generally made of liquid crystal polymers. As it is necessary to align the optic axis of the liquid crystal polymer in the desired direction (making the anisotropic layer as A, C or O-plate), an alignment layer is often deposited between the optically anisotropic layer and substrate or between the two optically anisotropic layers. The thickness of the anisotropic layer depends on the property of its constituent material and LCD to which it is applied. The compensation films are typically inserted anywhere between the liquid crystal cell and the polarizers. The function of compensation film, in general, is to undo the retardation experienced by the propagating light while traveling through the liquid crystal cell. By using the compensation film in the ON state of O-mode NW-TN-LCD, birefringence experienced by the obliquely propagating light is cancelled by the film. This gives us uniform dark state resulting in improved viewing angle characteristic.
- Various compensation methods have been suggested. U.S. Pat. No. 5,619,352 discloses the usage of combinations of O-plates. The basic idea is to compensate the ON state of TN-LCD by a stack of O-plates that have similar or complementary optical symmetries of the ON state liquid crystal cell. This was done by approximating the ON state of TN-LCD by three representative parts: two regions closed to the cell bounding plates and cell middle section. In the middle of the cell, the liquid crystal optic axis is almost perpendicular to the cell plane with large change in the azimuthal angle of liquid crystal optic axis. In the vicinity of the bounding plates, tilt in liquid crystal optic axis is small with almost fixed azimuthal angle. In comparison to the previous compensation technology, the stability of gray scale as well as viewing angle characteristic has been improved.
- European Patent Application 1143271A2 discloses compensation film comprising two layers of O-plates. The tilt angle of optic axis increases continuously or stepwise in the film thickness direction in the first O-plate whereas it decreases continuously or stepwise in the second O-plate. These two O-plates are disposed on the substrate with negative C-plate property or biaxial plate having optical property close to that of negative C-plate. In negative C-plates, the ordinary refraction index is larger than the extraordinary one, and the optic axis is perpendicular to the plates. The film is used one side of the liquid crystal cell. The average tilt angle of two O-plates may assume different values. Examples 8 and 16, for example use combinations of average tilt angles 42° and 31°, and 20° and 89°, respectively.
- Van de Witte et al. also disclosed in WO 97/44409 that the combination of two O-plates are used to compensate the Twisted Nematic Displays. The compensation films are applied for both sides of the liquid crystal cell. This case, too, the two O-plates can take different tilt angles, for example, 40° and 50°. The tilt angles are preferably larger than 100 but no more than 70°.
- In EP 0854376 discloses the use of hybrid-aligned film to compensate O-mode NW-TN-LCDs. FIG. 4A shows the O-mode NW-TN-
LCD 421 with two hybrid-alignedcompensation films liquid crystal cell 409. In the hybrid-alignedfilms optic axes film optic axes transmission axes analyzer 401 and thepolarizer 417 are equal to that of theoptic axes compensation films compensation films plates 405 represent the optical properties of tri-acetyl cellulose substrate. The retardation of the substrates 405 Rsub with negative C-plate property defined by Rsub=(nes−nos)ds is −60 nm, where ne, and no, are extraordinary and ordinary indices of refraction, respectively and d, is the thickness of the substrate. FIG. 4B shows the isocontrast plot of thedisplay 421. Thelines contrast ratios uncompensated display 313. - The compensation film disclosed in the co-pending U.S. patent application Ser. No. 10/318,773, uses two layers having different retardation values and different tilt angles both within prescribed limitations. It significantly improved the viewing angle of NW-TN-LCD. However, the application of the compensation film disclosed in the application is limited to E-mode NW-TN-LCD. The film gives unsatisfactory viewing angle characteristics when it is applied to O-mode NW-TN-LCD.
- The prior art compensators using O-plate improved the viewing angle characteristic by reducing the light leakage in the ON state of O-mode NW-TN-LCD. However, viewing angle characteristic still remain unsatisfactory. For example, in the
prior art display 421 shown in FIG. 4A, large viewing angle range withcontrast ratio 10 or less (namely, the area outside of theisocontrast line prior art display 421 shown in FIG. 4A) remains. The display with this viewing angle characteristic is certainly not applicable for LCD-TV or application that needs large viewing angle range, such as avionics displays. Also, prior arts do not focus on the systematic optimizations of parameters, e.g., the retardation and tilt angle combination along with the optical properties of the substrate. Thus, the range of parameters that offers functional compensation films for O-mode NW-TN-LCD is limited. Therefore there is a strong need for new compensation films that offer significantly higher contrast for wider viewing angle range than the displays with prior art compensation films for O-mode NW-TN-LCD. Also, the need is there to have a wider range of parameters for compensation films that lead to flexible manufacturing conditions. - The invention provides an optical compensation film for Ordinary mode Normally White Twisted Nematic Liquid Crystal Displays comprising, a first and a second optically anisotropic layers containing positively birefringent material disposed on a substrate, wherein the optic axis of said first optically anisotropic layer tilts in a first plane with an average tilt angle between 10° and 60°, and the optic axis of said second optically anisotropic layer tilts in a second plane with an average tilt angle between 0° and 30°, and said average tilt angle of said first optically anisotropic layer and said average tilt angle of said second optically anisotropic layer are different, and said first and said second planes are perpendicular to the plane of said optical compensation film with the angle between said first and said second planes being 90±100, and the retardation defined by (ne1−no1)d1 of said first optically anisotropic layer is between 60 nm and 220 nm and the retardation defined by (ne2−no2)d2 of the said second optically anisotropic layers is between 85 nm and 210 nm, where ne1 and no1 are extraordinary and ordinary indices of refraction of said positively birefringent material of said first optically anisotropic layer, respectively, and ne2 and no2 are extraordinary and ordinary indices of refraction of said positively birefringent material of said second optically anisotropic layer, respectively, and d, and d2 are thickness of said first and said second optically anisotropic layer, respectively.
- The compensation film can be used in conjunction with an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display for an improved viewing angle characteristic. The invention also includes a display incorporating the film of the invention.
- While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed that the invention will be better understood from the following description when taken in conjunction with the accompanying drawings, wherein:
- FIG. 1 shows the definition of a viewing angle direction.
- FIG. 2 shows the definition of the tilt and azimuthal angles to specify a direction of an optic axis.
- FIG. 3A is a prior art O-mode NW-TN-LCD without a compensation film.
- FIG. 3B is an isocontrast plot of the prior art O-mode NW-TN-LCD shown in FIG. 3A.
- FIG. 4A is a prior art O-mode NW-TN-LCD with hybrid-aligned compensation films having 40′ average tilt and thickness 0.42 μm and phase retardation of 100 nm. The substrate has a retardation of Rsub=−60 nm.
- FIG. 4B is an isocontrast plot of the prior art O-mode NW-TN-LCD shown in FIG. 4A.
- FIG. 5A, FIG. 5B, FIG. 5C and FIG. 5D are elevation schematics of the compensation film.
- FIG. 6A, FIG. 6B and FIG. 6C are diagrams showing the structure of the compensation film. In FIG. 6A and FIG. 6C, the tilt angle of optic axis is constant, while in FIG. 6B, it varies in the film thickness direction. FIG. 6A and FIG. 6B show left-handed films, whereas FIG. 6C corresponds to a right-handed film.
- FIGS. 7A through 7F are graphs showing the range of retardations R1 and R2 for different combination of the tilt angles θC1 and θC2 (or equivalently θav1 and θav2) and Rsub. The compensation films having R1 and R2 within the shaded area allow a
contrast ratio 10 line extending to polar viewing angle α=60° or higher at azimuthal viewing angles β=0, 90°, 180° and 270°. - FIG. 8A is an O-mode NW-TN-LCD with compensation film having parameters θC1=40°, θC2=10° (or equivalently θav1=40°, θav1=10°), R1=140 nm, R2=−120 nm and Rsub=−120 nm according to the invention.
- FIG. 8B is an isocontrast plot of the O-mode NW-TN-LCD shown in FIG. 8A.
- FIG. 8C is an O-mode NW-TN-LCD with compensation film having parameters θC1=40°, θC2=0° (or equivalently θav1=40°, θav1=0°), R1=140 nm, R2=120 nm. Two substrates have different retardation Rsub1−60 nm and Rsub2−60 nm.
- FIG. 8D is an isocontrast plot of the O-mode NW-TN-LCD shown in FIG. 8C.
- FIG. 9A is an isocontrast plot of the O-mode NW-TN-LCD with compensation film with θC1=40°, θC2=40° (or equivalently θav1=40°, θav2=40°), R1=140 nm, Rsub=140 nm and Rsub=−120 nm.
- FIG. 9B is an isocontrast plot of the O-mode NW-TN-LCD with compensation film with θC1=0°, θC2=0° (or equivalently θav1=0°, θav2=0°), R1=120 nm, R2=120 nm and Rsub=−120 nm.
- FIG. 9C is an isocontrast plot of the O-mode NW-TN-LCD with compensation film with θC1=40°, θC2=10° (or equivalently θav1=40°, θav2=10°), R1=140 nm, R2=120 nm and Rsub=−160 nm.
- FIG. 9D is an isocontrast plot of the O-mode NW-TN-LCD with compensation film with θC1=50°, θC2=5° (or equivalently θav1=50°, θav2=5°), R1=100 nm, R2=40 nm and Rsub=−160 nm.
- Reference will now be made to the drawings in which the various elements of the present invention will be given numerical designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.
- An optical compensation film for an Ordinary-mode Normally White Twisted Nematic Liquid Crystal Display of the present invention comprises a first and a second optically anisotropic layers containing positively birefringent material disposed on a substrate, wherein the optic axis of said first optically anisotropic layer tilts in a first plane with an average tilt angle between 10° and 60°, and the optic axis of said second optically anisotropic layer tilts in a second plane with an average tilt angle between 0° and 30°, and said average tilt angle of said first optically anisotropic layer and said average tilt angle of said second optically anisotropic layer are different, and said first and said second planes are perpendicular to a plane of said optical compensation film, and an angle between said first and said second plane is 90±100, and the retardation defined by (ne1-no1)d1 of said first optically anisotropic layer is between 60 nm and 220 nm and the retardation defined by (ne2−no2)d2 of the said second optically anisotropic layers is between 85 nm and 210 nm, where ne, and no, are extraordinary and ordinary indices of refraction of said positively birefringent material of said first optically anisotropic layer, respectively, and ne2 and no2 are extraordinary and ordinary indices of refraction of said positively birefringent material of said second optically anisotropic layer, respectively, and d1 and d2 are thickness of the said first and said second optically anisotropic layer, respectively. In the following, the present invention will be explained in detail.
- FIG. 5A shows the elevation view of the
optical compensation film 500, which contains a positively birefringent material oriented with its optic axis tilted in a plane perpendicular to the film plane. Two birefringent material layers or opticallyanisotropic layers substrate 509, which is parallel to the film plane. Thefirst layer 501 andsecond layer 503 have different average tilt angle in the optic axis. The average tilt angle θav is the average of tilt angle over the thickness of the optically anisotropic layer, i.e., - where θ(z) is the tilt angle at the height of z measured in the thickness direction of the optically anisotropic layers,501, 503, with the thickness d. If the tilt angle is constant throughout the thickness direction of the anisotropic layer, namely θ(z)=θC, then we have θav=θC. If the tilt angle varies linearly throughout in the thickness direction of the optically anisotropic layer, θav is equal to the average of the tilt angle at z=0 and z=d, thus θav={θ(z=0)+θ(z=d)}/2. The retardation of optically anisotropic layer is defined by (ne−no)d at the wavelength of 550 mm, where ne and no are the extraordinary and ordinary refractive indices of the positively birefringent material, respectively, and d, the thickness of the birefringent material layer or optically anisotropic layer Thus thickness of the two anisotropic layers with the same retardation must be equal provided their birefringence (ne-no) are the same. There are cases in which the two optically anisotropic layers contain different positively anisotropic materials. Namely, the first optically anisotropic layer contains positively birefringent material with ne, and no1 while the second optically anisotropic layer contains positively birefringent material with ne2 and no2.
- As is well known in the art, optical materials may have up to three different principal indices of refraction and can be classified as either isotropic or anisotropic based on the relationship of these indices. When all three of its principal indices are equal, a material is said to be isotropic. When anisotropic, a material can be either uniaxial, or biaxial. If two principal indices are equal, a material is called uniaxial. A uniaxial material is uniquely characterized, as having an ordinary index, referred as no, an extraordinary index ne and two angles describing the orientation of its optical axis, the axis of ne. When ne is greater than no, a uniaxial material is positively birefringent. When ne is smaller than no, a uniaxial material is negatively birefringent. Controlling birefringent behavior is particularly useful in the fabrication and application of optical films. When all three refractive indices are different, a material is said to be biaxial, uniquely specified by its principal indices nx0, ny0, nz0, and three orientation angles. Some of biaxial materials show weak biaxiality meaning that two of their three principal indices are very close, which is often considered equally as the ordinary refractive index for a uniaxial material. In the following, “optically anisotropic layer” is used to refer the birefringent material layer.
- The
substrate 509 functions as a mechanical support and has certain optical property. The material for substrate can be polymer or other optically transparent material. The substrate can take flexible or rigid form as long as it has enough strength for manufacturing process and actual application. Optically, it has a characteristic of negative C-plate, namely, C-plate with a relation nes<nos, where nes and nos are extraordinary and ordinary refraction indices of substrate. The out-of-plane retardation Rsub=(nes−nos)ds of the substrate defined at the wavelength of 550 mm with thickness d, is preferably in the range of −200 nm to −60 nm. A substrate with biaxial optical property can also be used. In this case, the optically property of the substrate is specified by three independent indices of refraction, nxs, nys, and nzs, where nxs is the maximum index of refraction and nys is the minimum index refraction both in the plane of the substrate and nzs is the index of refraction in the thickness direction of the substrate. For the biaxial plate to be used as a substrate, the difference between nxs and nys is small, that is (nxs−nys)/(nxs+nys)≦0.05, and the relation nxs>nys>nzs is satisfied. In this case the out-of-plane retardation, Rsub is defined by Rsub={nzs−(nxs+nys)/2}at the wavelength of 550 nm. The substrate can comprise of multiple of layers or coatings to attain the sufficient negative value of Rsub. For example, if a sheet of polymer film gives Rsub=−60 nm, one obtains Rsub=−120 nm by laminating two sheets of the same film. Or if necessary, films with insufficient negative value of Rsub can be coated with a layer of organic or inorganic compound. As is well known to someone who is skilled in the art, a layer of particular polymer, such as polyimide or discotic liquid crystal compounds gives high negative value of Rsub. Optically isotropic materials, such as glass or some polymer films, can be a substrate when coated or laminated with layers or a layer having sufficient negative value of Rsub. - Alignment layers505, 507 enforce the predetermined azimuthal φ and tilt θ angles of optic axis in the first and the second optically
anisotropic layers anisotropic layers - FIG. 5B shows the alternate configuration of the
compensation film 515. The optically anisotropic layers, 501, 503 are sandwiched between the twosubstrates compensation film 517 is shown in FIG. 5C. Where the laminating interface is now located between the opticallyanisotropic layer 501 and thesubstrate 511. The sum of the retardations of the two substrates (Rsub1 for 509 and Rsub2 for 511) Rsub1+Rsub2=Rsub is, preferably, in the range between −200 nm to −60 nm. It is also possible to laminate two films on the substrate sides, that is, lamination interface is located between the two-substrate sides. - As shown in FIG. 5D, the
compensation film 519 without alignment layers 505, 507 is also possible. The optic axis direction in opticallyanisotropic layers - An optically anisotropic layer is characterized by the indices of refraction, retardation (or equivalently thickness) and the direction of optic axis. The direction of optic axis is specified by its tilt θ and azimuthal angles φ. FIG.6A, FIG. 6B and FIG. 6C show the structure of the
film 500 schematically. The optic axis of the first opticallyanisotropic layer 601 is tilted in afirst plane 608, and the optic axis of the second opticallyanisotropic layer 603 is tilted in asecond plane 607. Bothfirst plane 608 andsecond plane 607 are perpendicular to the film plane orsubstrate 609. The angle formed between thefirst plane 608 and thesecond plane 607 is 90±10°. When the compensation films are placed between the polarizing elements and the liquid crystal cell, the first plane preferably contains the optic axis of liquid crystal on the nearest cell surface to the compensation flms. Two opticallyanisotropic layers substrate 609 supports the whole structure as well as giving necessary optical property for the compensation films. Arrows indicate the direction of optic axis in the optically anisotropic layers. The optic axis in the optically anisotropic layer tilts in the plane perpendicular to the liquid crystal cell plane and the plane of thesubstrate 609. The tilt angle θ may stay constant as θC1 and θC2 (FIG. 6A and FIG. 6C) or vary in the thickness direction of the optically anisotropic layer from θv1 to θv2 or θv3 to θv4 (FIG. 6B). In the varying case, the average tilt angle - is used instead of entire tilt profile θ(z) to specify the tilt angle within the optically anisotropic layers. One obtains comparable optical properties from an optically anisotropic layer with a constant tilt θC and an optically anisotropic layer with varying tilt having θav=θC.
- Although a compensation film having similar structure as shown in FIGS. 5A through 6C are well known, the
compensation film 500 of the present invention possesses combination of retardation values and different tilt angle of optic axis between the two optically anisotropic layers that are given in a particular range given below. The combination in the given range of tilt and the retardation provide much improved viewing angle performance of O-mode NW-TN-LCD. In the constant tilt angle case as shown in FIG. 6A and FIG. 6C, the tilt angle θC1 of the first opticallyanisotropic layer 601 is preferably in therange 10°≦θC1≦60° or more preferably 15°≦θC1≦50°. On the other hand, the tilt angle θC2 for the secondanisotropic layer 603 is preferably 0°<θC2≦30° or more preferably 0°≦θC2≦20°. In case of varying tilt angle as shown in FIG. 6B, the average of the tilt angle θav1 for thefirst layer 601 are preferably in therange 10°≦θav1≦60°, or more preferably 15°≦θav1≦50°. For the second opticallyanisotropic layer 603, the average tilt angle θav2 is given 0°≦θav2≦30°or more preferably 0°≦θav2≦20°. The tilt angles θC1 and θC2 (or equivalently θav1, and θav2) assume different values. Preferably, the difference between the two angles, θC1-θC2 (or equivalently, θav1-θav2) is larger than 10° but not more than 60°. Various combinations, such as varying tilt in the first opticallyanisotropic layer 601 and constant tilt in the second one 603 can equally function as a compensation film. The films shown in the FIGS. 6A and 6B are left-handed, meaning that theoptic axis 601 rotates counter-clockwise tooptic axis 603 as one follows the direction of increasing thickness indicated by anarrow 613. If it rotates counter-clockwise in the thickness direction as shown in FIG. 6C, it is called right handed twist Theoptic axis 601 rotates counter clockwise to 603 in the direction of increasing thickness indicated by anarrow 613. The handed ness of the compensation film and that of liquid crystal cell is preferably the same. - The retardation of the first optically anisotropic layer R1 is defined as (ne1−no1)d1, where d1 is the thickness of the first optically anisotropic layer. The retardation of the second optically anisotropic layer R2 is equally defined as (ne2−no2)d2. The value of R1 is in the
range 60 nm≦R1≦220 nm and R2 is in the range 85 nm≦R2≦210 nm. For a given Rsub, the preferable values for the retardation, R1 and R2 for the first 601 and the second 603 optically anisotropie layers depend on each other and also on the combination of angles θC1 and θC2 (or equivalently, θav1 and θav2) between the two layers, 601 and 603. FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E and FIG. 7F show the range of the preferable values for R1 and R2 for a given combination of tilt angles and Rsub as tabulated in the Table 1.TABLE 1 The values of tilt angles and Rsub corresponding to FIGS. 7A through 7E. θC1 (or θav1) θC2 (or θav2) Rsub (nm) 15° 0° −120 25° 0° −120 40° 0° −120 40° 10° −120 45° 15° −140 40° 0° −160 - The compensation films having R1 and R2 within the shaded area allow a
contrast ratio 10 line extending to polar viewing angle α=60° or higher at azimuthal viewing angles β=0°, 90°, 180° and 270°, simultaneously. - FIG. 8A is the schematic of the O-mode NW-TN-
LCD 851 with thecompensation film 500 according to the invention. The opticallyanisotropic layers 801 and 803 (corresponding tolayers substrate 829. The alignment layers are not shown in FIG. 8A. The TNliquid crystal cell 809 is placed between two pairs of opticallyanisotropic layers 803.Arrows 819 indicate the direction of liquid crystal optic axis at the cell surfaces. The direction of optic axis in opticallyanisotropic layers arrows layer 801 and R2=120 nm forlayer 803. Thesubstrate 829 is a negative C-plate with the retardation (nes−nos)ds=−120 nm. The double-headedarrows polarizer 831 andanalyzer 833, which have azimuthal angle φ of 45° (or 225°) and 135° (or 315°), respectively. The azimuthal angle between the transmission axis of polarizing elements and optic axis of liquid crystal on the nearest cell surface to the polarizing elements is 90°. Thus thedisplay 851 is O-mode NW-TN-LCD. Azimuthal angles of optic axes and the transmission axes are given in the parenthesis. Theoptic axis 811 of the firstanisotropic layer 801 tilts in the plane that contains the optic axis of liquid crystal on the nearest cell surface. Alternatively, one can use thecompensation film 515 with the structure such as in FIG. 5B. Thecorresponding display 855 is shown in FIG. 8C. In this display, tilt angles are such that θav1=θC1=40° and θav2=θC2=0° and the phase retardation value R1 forlayer 801 is 140 nm and that of 803 R2 is set at 120 nm. There areadditional substrate layers 853 between the secondanisotropic layer 803 and theliquid crystal cell 809. The retardation of thesubstrates - FIG. 8B and FIG. 8D are isocontrast plots for the
display lines contrast ratio - For a comparison, FIG. 43 shows the isocontrast plot of the display421 (shown in FIG. 4A) with a prior art compensation film in which the optically anisotropic layers with
hybrid alignment phase retardation value 100 nm with a substrate having Rsub32 −60 nm. Thelines contrast ratio - It can be seen both in FIG. 8D and FIG. 8D that the area enclosed by the
isocontrast line line 427 in the isocontrast plot shown in FIG. 4B. Thedisplay 851 has a contrast ratio higher than 50 in wide viewing angle range. Thedisplay 855 has achieved much wider viewing angle range withcontrast ratio 10 or higher in comparison to theprior art display 421. On the other hand, theprior art display 421 has significant viewing angle portion with contrast less than 10 that is located outside of theisocontrast line 10 in the isocontrast plot shown in FIG. 4B. - Table 2 shows average viewing angle (average value of polar viewing angle α at β=0°, 90°, 180°, 270°) that corresponds to the particular contrast ratios (50, 100 and 200) for the
prior art display 421 in FIG. 4A (Prior Art Display), and thedisplay 851 in FIG. 8A. A display with a better viewing angle characteristic has a larger average viewing angle of α at the same contrast ratio. It is demonstrated thatdisplay 851 of the invention has significantly wider viewing angle range for the same contrast ratio in comparison to thePrior Art Display 421. For example, average viewing angle range withcontrast 100 or higher is expanded to 41° from 23°.TABLE 2 Comparison of average viewing angle between the prior art compensation film and the one according to the current invention. Average Viewing Average Viewing Angle Iso- Angle Current Invention Contrast Prior Art film Film 50 29° 49° 100 23° 41° 200 20° 35° - FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, FIG. 7E and FIG. 7F clearly show that the retardations, R1 and R2, and tilt angles of the first and the second optically anisotropic layers as well as the substrate retardation Rsub need to be optimized simultaneously. For fixed value of Rsub, the retardations R1 and R2 depend on each other, and their range differs for a different tilt angle combination. According to FIG. 7C, for example, at Rsub=−120 nm, if the average tilt of the first layer is 40° and that of the second is 0° and R1 is 120 nm, then we have preferable value for R2 given by 90 nm≦R2≦160 nm. If the angles θC1 and θC2 (or equivalently, θav1 and θav2) are respectively 40°and 10°, and R1=120 nm, we have preferable range 115 nm≦R2≦145 nm as indicated by FIG. 7D. Comparison of FIGS. 7C and 7F gives the Rsub dependence of optimum values for R1 and R2 for the same tilt angles. The necessity of the simultaneous optimization is clearly demonstrated in the contrast plots FIGS. 9A through 9D. They are isocontrast plots of O-mode NW-TN-LCD such as shown in FIG. 4A or FIG. 8A but with different parameter for tilt angles θC1 and θC2 (or equivalently θav1 and θav2), and retardations R1 and R2, and Rsub as given in Table 3. In FIGS. 9A through 9D, the
lines contrast ratio TABLE 3 Values of tilt angles and retardation of the optically anisotropic layers corresponding to the isocontrast plots FIGS. 9A through 9D. θC1 or θav1 θC2 or θav2 R1 (nm) R2 (nm) Rsub (nm) 40° 40° 140 140 −120 0° 0° 120 120 −120 40° 10° 140 120 −200 50° 5° 100 40 −160 - FIG. 9A and FIG. 9B show that simultaneous change in the tilt angles θC1 and θC2 (or equivalently, θav1 and θav2) does not necessarily give a satisfactory performance in viewing angle characteristic. Neither one of them has an
isocontrast 10 line extending α=60° or higher simultaneously at β=0°, 90°, 180° and 270°. - Combination of two tilt angles and the values for R1 and R2 as used in the
display 851 in FIG. 8A with larger negative value of Rsub shows degradation in display performance in comparison to thedisplay - FIG. 9D is the isocontrast plot of the O-modc NW-TN-LCD display with compensation film having θC1 and θC1 (or equivalently θav1 and θav2) and R1, R2 and Rsub that are in the range suitable for E-mode NW-TN-LCD disclosed in co-pending U.S. patent application Ser. No. 10/318,773. It is clear that the simple application of a film with parameters tuned for E-mode does not give satisfactory viewing angle characteristic when it is applied to O-mode display. The isocontrast plot in FIG. 9D shows good viewing angle characteristic compared to the
Prior Art Display 421 in the diagonal direction (β=45°, 135°, 225°, 315°), however, no significant improvement is achieved in horizontal (β=0°, 180°) and the vertical (β=90°, 270°) directions. The performance is clearly inferior to that of thedisplays - EP Application 1143271A2 and WO 97/44409 discusses the combination of different tilt angles between the two O-plates. However, it is a surprising result that particular combinations of two tit angles θC1, θC2 (or equivalently θav1 and θav2), the retardations R1, R2, and the retardation of the substrate Rsub result in unforeseeable and significant improvements in the viewing angle range.
- Additional benefit of the current invention is that it offers wide range of parameters θC1, θC2 (or equivalently θav1 and θav2), R1, R2 and Rsub of the compensation film that has superior performance than the prior art displays, such as the one 421 shown in FIG. 4A. It offers wide tolerance in R1 and R2 for some combinations of tilt angles. As shown in the FIG. 7C, when θC1=40° and θC2=0° (or equivalently θav1=40° and θav1=0°) the possible range of the R1 and R2 are given by 70 nm≦R1≦190 nm and 90 nm≦R2≦170 nm. This holds also true for the tilt angles θC1 and θC2 (or equivalently θav1 and θav2) for a given pair of R1, R2 and Rsub. For example, if R1=120 nm and R2=100 nm with Rsub=−120 nm, the possible range for tilt angles are 25°≦θav1≦50° and 0°≦θav1≦10°. Thus the invention offers excellent manufacturing flexibility.
- The entire contents of the patents and other publications referred to in this specification are incorporated herein by reference.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
ratio 10 -
-
ratio 100 -
-
analyzer 401 -
-
-
-
-
-
-
-
polarizer 417 -
-
compensation film 407 -
compensation film 415 -
ratio 10 -
-
ratio 100 -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
anisotropic layer 801 -
anisotropic layer 803 -
-
-
-
-
-
-
ratio 10 -
-
ratio 100 -
-
-
-
ratio 10 -
-
ratio 100 - d thickness of the optically anisotropic layer
- d1 thickness of the first optically anisotropic layer
- d2 thickness of the second optically anisotropic layer
- ds thickness of the substrate
- ne extraordinary refractive index of the positively birefringent material
- no ordinary refractive index of the positively birefringent material
- ne1 extraordinary refractive index of the positively birefringent material of the first optically anisotropic layer
- no1 ordinary refractive index of the positively birefringent material of the first optically anisotropic layer
- ne2 extraordinary refractive index of the positively birefringent material of the second optically anisotropic layer
- no2 ordinary refractive index of the positively birefringent material of the second optically anisotropic layer
- nes extraordinary index of the substrate
- nos ordinary index of the substrate
- nxs the maximum index of refraction in the plane of the substrate with the biaxial optical property
- nys the minimum index of refraction in the plane of the substrate with the biaxial optical property
- nzs the index of refraction in the thickness direction of the substrate with the biaxial optical property
- R1 retardation of the first optically anisotropic layer
- R2 retardation of the second optically anisotropic layer
- Rsub retardation of the substrate
- Rsub1 retardation of the substrate
- Rsub1 retardation of the substrate
- α polar viewing angle
- β azimuthal viewing angle
- φ azimuthal angle of optic axis
- θ tilt angle of optic axis
- θC constant tilt angle of optic axis of optically anisotropic layers θav average tilt angle of optic axis of optically anisotropic layers
- θC1 constant tilt angle of optic axis of the first optically anisotropic layer θC2 constant tilt angle of optic axis of the second optically anisotropic layer
- θav1 average tilt angle of optic axis of the first optically anisotropic layer
- θav2 average tilt angle of optic axis of the second optically anisotropic layer
- θv1 tilt angle of optic axis
- θv2 tilt angle of optic axis
- θv3 tilt angle of optic axis
- θv4 tilt angle of optic axis
- θs liquid crystal tilt angle at the surfaces
Claims (30)
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/413,331 US6805924B1 (en) | 2003-04-14 | 2003-04-14 | Compensation films for LCD |
PCT/US2004/010750 WO2004092815A2 (en) | 2003-04-14 | 2004-04-07 | Compensating films having titled optic axes for lcd |
JP2006509792A JP4932475B2 (en) | 2003-04-14 | 2004-04-07 | Twisted nematic liquid crystal display with compensation film |
TW093110169A TWI379127B (en) | 2003-04-14 | 2004-04-13 | Compensation films for lcd |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/413,331 US6805924B1 (en) | 2003-04-14 | 2003-04-14 | Compensation films for LCD |
Publications (2)
Publication Number | Publication Date |
---|---|
US20040202798A1 true US20040202798A1 (en) | 2004-10-14 |
US6805924B1 US6805924B1 (en) | 2004-10-19 |
Family
ID=33131398
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/413,331 Expired - Lifetime US6805924B1 (en) | 2003-04-14 | 2003-04-14 | Compensation films for LCD |
Country Status (4)
Country | Link |
---|---|
US (1) | US6805924B1 (en) |
JP (1) | JP4932475B2 (en) |
TW (1) | TWI379127B (en) |
WO (1) | WO2004092815A2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007147921A1 (en) * | 2006-06-16 | 2007-12-27 | Universitat Jaume I | Method for compensating for optical aberrations by means of tn-lcd-type liquid crystal screens, and device for implementing same |
KR101247846B1 (en) * | 2005-04-12 | 2013-03-26 | 후지필름 가부시키가이샤 | Optical compensation film and liquid crystal display |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006145566A (en) * | 2004-11-16 | 2006-06-08 | Nec Lcd Technologies Ltd | Liquid crystal display |
US8237876B2 (en) * | 2005-05-25 | 2012-08-07 | Kim Leong Tan | Tilted C-plate retarder compensator and display systems incorporating the same |
US7714945B2 (en) * | 2005-09-09 | 2010-05-11 | Jds Uniphase Corporation | Optimally clocked trim retarders |
US7671946B2 (en) * | 2005-10-18 | 2010-03-02 | Jds Uniphase Corporation | Electronically compensated LCD assembly |
TW200842417A (en) * | 2006-12-28 | 2008-11-01 | Sony Corp | Optical compensation plate, liquid crystal display device, projection type liquid crystal display device, display device manufacturing method, and adjusting method |
DK1980902T3 (en) * | 2007-04-10 | 2015-07-27 | Jds Uniphase Corp | Twisted nematic XLCD CONTRAST COMPENSATION WITH rocked PLADEFORSINKERE |
JP2009042294A (en) * | 2007-08-06 | 2009-02-26 | Nitto Denko Corp | Liquid crystal panel and liquid crystal display device |
JP2014142618A (en) * | 2012-12-28 | 2014-08-07 | Fujifilm Corp | Optical film, polarizing plate, liquid crystal display device, and manufacturing method of optical film |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5557434A (en) * | 1994-09-30 | 1996-09-17 | Rockwell International | Optical compensator including an o-plate for super-twist nematic liquid crystal display |
US5589963A (en) * | 1994-09-30 | 1996-12-31 | Gunning, Iii; William J. | Pixelated compensators for twisted nematic liquid crystal displays |
US5594568A (en) * | 1993-12-15 | 1997-01-14 | Ois Optical Imaging Systems, Inc. | LCD with a pair of retardation films on one side of normally white liquid crystal layer |
US5619352A (en) * | 1994-04-04 | 1997-04-08 | Rockwell International Corporation | LCD splay/twist compensator having varying tilt and /or azimuthal angles for improved gray scale performance |
US5737048A (en) * | 1993-12-15 | 1998-04-07 | Ois Optical Imaging Systems, Inc. | Liquid crystal display having high contrast viewing zone centered in positive or negative vertical region with retarder's retardation equal to 100-250 nanometers |
US5777709A (en) * | 1995-02-03 | 1998-07-07 | Ois Optical Imaging Systems, Inc. | Liquid crystal display with two positive tilted retardation films and two negative retardant films |
US5907378A (en) * | 1993-12-15 | 1999-05-25 | Ois Optical Imaging Systems, Inc. | Normally white twisted nematic liquid crystal display including retardation films for improving viewing characteristics |
US6169590B1 (en) * | 1993-12-02 | 2001-01-02 | Ois Optical Imaging Systems, Inc. | Liquid crystal display with optical compensator |
US6359671B1 (en) * | 2000-02-23 | 2002-03-19 | Planar Systems, Inc. | High contrast liquid crystal device |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
TW494263B (en) | 1996-05-17 | 2002-07-11 | Koninkl Philips Electronics Nv | Liquid-crystal display device, compensator layer and method of manufacturing a retardation foil |
TW472081B (en) * | 1996-09-17 | 2002-01-11 | Merck Patent Gmbh | Optical retardation film |
US6266114B1 (en) * | 1999-07-14 | 2001-07-24 | Rockwell Collins, Inc. | Method and apparatus for compensating a liquid crystal display |
US6867834B1 (en) * | 1999-09-16 | 2005-03-15 | Merck Patent Gmbh | Optical compensator for LCD including stacked films of only one O-plate, one A-plate and two negative C-plate retarders |
JP2002207125A (en) * | 2000-04-03 | 2002-07-26 | Konica Corp | Optical compensation sheet and liquid crystal display device |
TW522260B (en) | 2000-04-03 | 2003-03-01 | Konishiroku Photo Ind | Optical compensation sheet and liquid crystal display |
-
2003
- 2003-04-14 US US10/413,331 patent/US6805924B1/en not_active Expired - Lifetime
-
2004
- 2004-04-07 WO PCT/US2004/010750 patent/WO2004092815A2/en active Application Filing
- 2004-04-07 JP JP2006509792A patent/JP4932475B2/en not_active Expired - Fee Related
- 2004-04-13 TW TW093110169A patent/TWI379127B/en not_active IP Right Cessation
Patent Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6169590B1 (en) * | 1993-12-02 | 2001-01-02 | Ois Optical Imaging Systems, Inc. | Liquid crystal display with optical compensator |
US5594568A (en) * | 1993-12-15 | 1997-01-14 | Ois Optical Imaging Systems, Inc. | LCD with a pair of retardation films on one side of normally white liquid crystal layer |
US5737048A (en) * | 1993-12-15 | 1998-04-07 | Ois Optical Imaging Systems, Inc. | Liquid crystal display having high contrast viewing zone centered in positive or negative vertical region with retarder's retardation equal to 100-250 nanometers |
US5907378A (en) * | 1993-12-15 | 1999-05-25 | Ois Optical Imaging Systems, Inc. | Normally white twisted nematic liquid crystal display including retardation films for improving viewing characteristics |
US6028651A (en) * | 1993-12-15 | 2000-02-22 | Ois Optical Imaging Systems, Inc. | Normally white twisted nematic liquid crystal display including retardation films for improving viewing characteristics |
US6229588B1 (en) * | 1993-12-15 | 2001-05-08 | Ois Optical Imaging Systems, Inc. | Normally white LCD including first and second biaxial retarders |
US5619352A (en) * | 1994-04-04 | 1997-04-08 | Rockwell International Corporation | LCD splay/twist compensator having varying tilt and /or azimuthal angles for improved gray scale performance |
US5557434A (en) * | 1994-09-30 | 1996-09-17 | Rockwell International | Optical compensator including an o-plate for super-twist nematic liquid crystal display |
US5589963A (en) * | 1994-09-30 | 1996-12-31 | Gunning, Iii; William J. | Pixelated compensators for twisted nematic liquid crystal displays |
US5589963C1 (en) * | 1994-09-30 | 2001-06-26 | Rockwell International Corp | Pixelated compensators for twisted nematic liquid crystal displays |
US5777709A (en) * | 1995-02-03 | 1998-07-07 | Ois Optical Imaging Systems, Inc. | Liquid crystal display with two positive tilted retardation films and two negative retardant films |
US6359671B1 (en) * | 2000-02-23 | 2002-03-19 | Planar Systems, Inc. | High contrast liquid crystal device |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR101247846B1 (en) * | 2005-04-12 | 2013-03-26 | 후지필름 가부시키가이샤 | Optical compensation film and liquid crystal display |
WO2007147921A1 (en) * | 2006-06-16 | 2007-12-27 | Universitat Jaume I | Method for compensating for optical aberrations by means of tn-lcd-type liquid crystal screens, and device for implementing same |
ES2298044A1 (en) * | 2006-06-16 | 2008-05-01 | Universitat Jaume I (70%) | Method for compensating for optical aberrations by means of tn-lcd-type liquid crystal screens, and device for implementing same |
Also Published As
Publication number | Publication date |
---|---|
WO2004092815A2 (en) | 2004-10-28 |
US6805924B1 (en) | 2004-10-19 |
TWI379127B (en) | 2012-12-11 |
JP4932475B2 (en) | 2012-05-16 |
WO2004092815A3 (en) | 2005-01-20 |
TW200500747A (en) | 2005-01-01 |
JP2006523864A (en) | 2006-10-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6831722B2 (en) | Compensation films for LCDs | |
US6819381B2 (en) | Compensation films for liquid crystal displays | |
EP2259131B1 (en) | Liquid crystal display | |
EP2383604B1 (en) | Liquid crystal display apparatus | |
EP2437106B1 (en) | Liquid crystal display device | |
EP2487536B1 (en) | Liquid-crystal display device | |
US6937308B2 (en) | In-plane switching liquid crystal display with compensation film | |
EP2693243B1 (en) | Integrated O Film for Improving viewing angle of TN-LCD, and Polarizer Plate and TN-LCD including the same | |
US7006184B2 (en) | Bend aligned namatic liquid crystal imaging display with compensation film | |
US8508696B2 (en) | Polarizing plate and display apparatus having the same | |
US9250473B2 (en) | Polarizing plate and display apparatus having the same | |
US20030103182A1 (en) | Vertically aligned liquid crystal imaging component with compensation layer | |
US6805924B1 (en) | Compensation films for LCD | |
EP1724632A1 (en) | A single-polarizer reflective bistable twisted nematic (BTN) liquid crystal display device | |
US7193670B2 (en) | Compensator for liquid crystal display with two compensation sheets |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: EASTMAN KODAK COMPANY, NEW YORK Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ISHIKAWA, TOMOHIRO;MI, XIANG-DONG;REEL/FRAME:013981/0012 Effective date: 20030414 |
|
FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
CC | Certificate of correction | ||
AS | Assignment |
Owner name: NITTO DENKO CORPORATION,JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EASTMAN KODAK COMPANY;REEL/FRAME:018816/0960 Effective date: 20061219 Owner name: NITTO DENKO CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EASTMAN KODAK COMPANY;REEL/FRAME:018816/0960 Effective date: 20061219 |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
FEPP | Fee payment procedure |
Free format text: PAYER NUMBER DE-ASSIGNED (ORIGINAL EVENT CODE: RMPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
FPAY | Fee payment |
Year of fee payment: 8 |
|
FPAY | Fee payment |
Year of fee payment: 12 |