CN1035790C - Compensator for liquid crystal oisplay - Google Patents

Abstract

The present invention relates to a liquid crystal display which comprises a polarizing layer, an analyzer, liquid crystal layers between the polarizing layer and the analyzer, a first electrode of the first main surface approaching to the liquid crystal layers and a second electrode of the second main surface approaching to the liquid crystal layers. After the first electrode and the second electrode are connected with a voltage source, voltage penetrating through the liquid crystal layers can be applied. A multilayer film compensator is arranged between a polarizer and the analyzer and comprises a first group of film layers with first refractivity and first thickness, and the first group of film layers are mutually interleaved with a second group of film layers with second refractivity and second thickness. The first refractivity, the second refractivity and a thickness value make phase delay generated by multilayer films in a certain visual angle opposite to symbols which have equal sizes and are generated by the liquid crystal layers arrayed in the same direction.

Description

Compensator for liquid crystal oisplay

The present invention relates to a kind of design of liquid crystal indicator, particularly a kind of making shows that the visual field is maximum technology.

Be subjected to the birefringent influence of liquid crystal layer owing to pass the light of liquid crystal thin layer, and this can be by the Control of Voltage of passing this layer, so liquid crystal is usually used in the electronic display unit.It is because control is much smaller from the required power of the light of outer light source (comprising natural light) reflection or the transmission power more required than luminescent material other display device that liquid crystal indicator relatively is suitable for.At present, be widely used in liquid crystal indicator in digital watch, counter, pocket computer and other various electronic and have long, advantage such as operating voltage is low and power is little of life-span.

The information of many liquid crystal displays is expressed as delegation's numeral or character, and they are produced by some segmented electrodes that are arranged in a pattern.Each section is connected on the driving circuit by independent joint, and it is added to voltage on the appropriate combination of electrode section, and the light that sees through electrode section by control shows required information.Picture information or TV face face can obtain by cell array, and pixel is interconnected by the X-Y sequential addressing mode between two orthogonal conductors.More advanced addressing scheme adopts thin film transistor (TFT) array to control the driving voltage at each pixel place.This scheme is mainly used in the twisted nematic liquid crystal display device, but also is applied to high performance supertwist type liquid crystal indicator.

Contrast is one of most important factor of determining the liquid crystal indicator quality.The principal element of restriction liquid crystal indicator contrast is the light amount of leaking by display under dark attitude.In bright environment, for example in the sun, a large amount of reflections and scattering background light time are arranged, this problem is more outstanding.In addition, it is relevant with the visual angle that liquid-crystal apparatus produces visual sharpness, especially true in having the array address formula device of a large amount of scan electrodes.The image contrast of typical liquid crystal indicator be a maximal value in respect to the very little visual angle of vertical incidence line, and contrast decline when increasing at the visual angle.This loss of contrast is owing to cause at the light that sees through dark attitude pixel leakage with great visual angle down.In colour liquid crystal display device, the serious colour cast that leakage of light also can cause saturated color and greyscale color from.To use for avionics be vital in these restrictions, because the copilot is very important to the observation of driver's display.Like this, providing a kind of LCD that can produce high-quality high-contrast image in wide visual field just will be important improvement to prior art.

Multilayer film by the particular design of in LCD, packing into; And compensating phase delay intrinsic in this display, the present invention can make surprising improvement to observation contrast and the color effect of this display device on the inclination visual angle.

Comprise according to LCD of the present invention: a polarizing layer, an analyzer layer, one places the liquid crystal layer between this polarizing layer and the analyzer layer, first electrode of contiguous liquid crystal layer first first type surface, and second electrode that is adjacent to liquid crystal layer second first type surface.When electrode was linked voltage source, they can apply a voltage that passes liquid crystal layer.A multilayer film compensator is set between polarizing layer and analyzer layer, this compensator comprises first group of rete, every layer has first refractive index and first thickness, and they and second group of rete are in interleaved relation with each other, and every layer of second group of rete has second refractive index and second thickness.The numerical value of first and second refractive indexes and thickness makes the phase delay equal and opposite in direction of the phase delay of in certain angular field of view multilayer film and the liquid crystal layer under the homeotropic state and opposite in sign.

In certain embodiments more, liquid crystal layer has thickness d _LAnd birefringence △ n _L, and multi-layered compensation device thickness and birefringence are d _CAnd △ n _C, and | △ n _L| d _L=| △ n _C| d _CAmong the embodiment that designs in order to provide The optimal compensation in wide angular field of view, the o optical index of liquid crystal layer and e optical index are n _OLAnd n _EL, and the o anaclasis of multilayer film and e optical index are respectively n _OCAnd n _EC, n _EC=n _EL, n _OC=n _ELAnd d _CoIn addition, the equivalent refractive index of multilayer film satisfies following formula: wherein nO is the equivalent O optical index of multilayer film, and ne is the equivalent e optical index of multilayer film, n ₁Be first refractive index, n ₂Be second refractive index, d ₁Be first thickness, d ₂Be second thickness, and ∧=d ₁+ d ₂Be the cycle of multilayer film.

Fig. 1 is the curve map of liquid crystal molecules tilt angle on each position of liquid crystal device under the various states;

Fig. 2 is illustrated in the synoptic diagram that liquid crystal aligning unit is orientated in the liquid crystal device gap when applying highfield;

Fig. 3 be the expression typical white twisted nematic device under wide-angle with alive transmission curves figure;

Fig. 4 is the side cross-sectional views of twisted nematic transmission liquid crystal display device;

Fig. 5 is the enlarged drawing of multilayer film part among Fig. 4.

In flat-panel monitor, extensively adopt several typical liquid crystal devices.The active matrix addressing makes this display device can produce high-resolution full-colour image under considerable replacing speed.When facing LCD and watch, can see high quality image, but image variation and contrast descend with great visual angle the time.This is that liquid crystal media contains a large amount of anisotropic liquid crystal molecules because liquid crystal device is the birefringence effect work by liquid crystal media.This material is positive single axial birefringence (n _e＞n _o, i.e. e optical index n _eGreater than O optical index n _o), and the e optical index is relevant with the arrangement of long molecular axis.Material changes along with the inclination angle of light the phase delay effect of printing opacity, making that image quality is relatively poor with great visual angle the time (shows ＂ Viewing Characteristics of the Twisted Nematic Display ＂ referring to Penz, Proceeding of the S.I.D, 19 volumes, the 43rd page (1978); People such as Grinberg show ＂ Transmission Characteristics of a Twisted Nematic Liquid-Crystal Layer ＂, Journal of the Optical Society of America, 66 volumes, the 1003rd page (1976)).But, adopt a kind of optical compensatory element just can proofread and correct unwanted angle effect to liquid crystal device, thereby on great visual angle, keep high-contrast as far as possible.

Required optical compensation type is to determine according to used type of display (Chang Hei or Chang Bai).In normal black scope, the twisted-nematic device places between two polarizers that optical axis is parallel to each other, and the polarizer optical axis (be the outlying observation person a side) is orientated identical with liquid crystal aligning unit at the device back side.Under making alive state not, by the first polarizer polarizing, and the polarization direction is rotated by the distortion angle of device by device the time from the light of backlight vertical incidence.This follows (being also referred to as waveguiding effect) by thermal insulation and causes.Distortion angle is decided to be 90 ° so that light is output polarizer stops.When to the device making alive, liquid crystal molecule is forced to be tending towards arranging by electric field, has eliminated the twisted nematic symmetry.Under this orientation, the vertical sub-device wall of the optical axis of device (C axle).Liquid crystal layer shows isotropy to vertical incidence light, has eliminated waveguiding effect, thereby polarization state is constant when light passes liquid crystal layer, and light can pass the output polarization device like this.Can be by treating that illuminated area optionally applies voltage and just can paint with pattern on display.

But when wide-angle is observed, light will appear in the dark space (not powering up nip) of normal black scope, this is owing to the angular dependence (-dance) late effect that light produced of passing liquid crystal layer under this angle causes, and the angular dependence (-dance) that promptly non-normal incidence light produces polarization state changes.Can adopt the optics symmetry similar to twist cell but compensating element, its effect of can reversing recovers contrast.A kind of method is in the liquid crystal layer back of work a distortion device that spiral is opposite to be set.Other method is to adopt one or more A-plate compensators.It is that its e light optical axis is perpendicular to the normal incidence optical propagation direction because compensating element, is consistent with the optics symmetry of twisted nematic device, and the both is the single axial birefringence material that these compensation methodes are worked.Owing to be easy to obtain having the symmetric material of required optics, these compensation methodes are widely used.Adopt the anti-phase distortion device of liquid crystal and A-plate delayer to make by strained polymer (for example polyvinyl alcohol (PVA) (PVA)).

Although these compensation techniques produce effect, make also defectiveness of this method of state for normal black-labour.The image and the device gap of normal black scope are relative.Like this, in order to keep black uniformly image just should make liquid crystal device very thick, this has caused the liquid crystal reflection time oversize, or under Gooch-Tarry minimal value state, work (referring to ＂ The Optical Propertiesof Twisted Nematic Liquid Crystal Structures with TwistAngles≤90 ° of ＂ that show such as Gooch, Journal of Physics D, 8 volumes, the 1575th page (1975)) however this method makes that the manufacturing tolerance in liquid crystal device gap is inaccessible.In addition, anti-phase skew compensation Technology Need inserts second liquid crystal device in light path, increased cost, weight and volume greatly.Owing to these reasons, be sought after the normal white display of compensation to avoid these shortcomings.

In normal white display device structure, 90 ° of twisted nematic devices are placed between the polarizer of quadrature, make the axis of homology of each polarizer parallel with the directed unit orientation of liquid crystal molecule in its zone of vicinity.This compares with normal black scope, and it is bright and dark regional opposite.Not alive zone presents bright attitude in normal white display, and the making alive zone presents dark attitude.Though when wide-angle is observed, still exist in the problem of apparent dark space printing opacity, cause the reason difference of this problem, and its correction needs another kind of optical compensatory element.Liquid crystal molecule is arranged with applied field in the making alive zone.If this arrangement is desirable, then in the device major axis of all liquid crystal molecules all perpendicular to glass substrate.This arrangement that is called in the same way structure has the optics symmetry of positive birefringence C-plate.Normal white display shows isotropy to vertical incidence light under the making alive state, and then light is blocked by the polarizer of quadrature.

When observing at a certain angle, produce the loss of contrast and be since in the same way liquid crystal layer non-normal incident light is not manifested isotropy.Because the birefringence of this layer, the light of incident at a certain angle be with two kinds of mode transfer, and the phase shift between two kinds of patterns increases with the incident angle of light.The position correlativity of incident angle has relatively produced elliptical polarization, and it can not be eliminated fully by second polarizer, has then produced leakage of light.Because C-plate symmetry, this birefringence does not have horizontal correlativity.What obviously optical compensatory element was required also is C-plate symmetry, but has negative birefringence (n _e＜n _o).The phase shift that this compensator produces is opposite with the phase shifted symbols that liquid crystal layer produces, thereby recovers original polarization state, makes light be output the polarizer blocking-up.Past does not adopt this technology to be owing to be difficult to maybe can not constitute to have the symmetric C-plate of required optics compensator.Past does not find to stretch or comperession polymer has the method for the symmetric large area uniform film of negative C-plate optics with formation, also can not make compensator with negative birefringence crystal such as sapphires.For making this compensator effective, the phase delay numerical value of this plate must be identical with the phase delay that liquid crystal produces, and phase delay also must be same with liquid crystal phase with the pace of change at visual angle.These restrictions mean that the thickness of negative compensating plate should be 10 micron number magnitudes, and this makes this method be difficult to realize because need one of polishing as thin as a wafer have correct (bearing) birefringent plate, require the surperficial keeping parallelism of plate simultaneously.Because this display sizes is bigger, obtaining of the negative birefringence crystal of this size also is one of main difficulty.Existing compensation technique adopts the A-plate compensator of quadrature.Yet this structure can not produce (C-plate) the symmetric compensator that has level.Because these difficulties, tendency adopts normal black scope in this area, although normal white display is if there is the adequate compensation device just can produce high quality image.The present invention has proposed the solution of this compensator for the first time.

In fact, can not make the desirable arrangement in the same way of liquid crystal molecule acquisition in the display device even apply high voltage.This is because liquid crystal molecule has avoided near the molecule tilt the glass to arrange with electric field attached to the mode on the glass substrate.But arrange with electric field basically from the molecule that substrate is far away, so the overall optics symmetry of liquid crystal layer can be considered to positive birefringence C-plate.Fig. 1 is the curve map of each position tilt angle in the twisted nematic liquid crystals device, is illustrated in no extra electric field (thick dashed line), highfield (solid line), and the ideal exemplary distribution at molecule tilt angle in the whole liquid crystal layer under (short dash line) state in the same way.This pitch angle is the angle of molecular long axis (directed unit) and glass baseplate surface.It should be noted that most of molecule is approximately arrangement in the same way under strong electric field condition.

Fig. 2 is the synoptic diagram of liquid crystal aligning unit orientation when adding highfield at home and abroad in the device gap.Continuous variation can be broken down into three liquid crystal areas, and each district all has optics symmetry separately.Near each glass substrate place is that symmetry is the zone of A-plate, and its e light optical axis is pressed substrate friction direction and arranged.Be one betwixt and have the symmetric big zone of positive C-plate.Negative C-plate compensator is to be used for proofreading and correct the relevant phase shift of angle that produces by this regional light.Effectively degree depends on whether this regional optics symmetry occupies an leading position in a certain particular state of liquid crystal device, i.e. the molecule degree of arranging with electric field.This means and in selected state, adopt highfield can make compensation effectively, because it makes molecule more approach to arrange in the same way.

The panchromatic LCD of not compensated generally has bigger change color in field range.Correspondingly, perhaps the zone that has a kind of color when vertical angle is observed can show desaturated color when wide-angle is observed, or even shows its complementary color.Its origin cause of formation is in descending the identical physical mechanism of promptly apparent dark space light leak with causing the wide-angle contrast.

Panchromatic demonstration realizes by at the display element place red, green, blue transmitting filter being set.In the normally white color monitor,, make red pixel be in non-selected state simultaneously and demonstrate red area by selecting (power up and be pressed on) blueness and green pixel so that they are light tight.This scheme can operate as normal when right-angle view, but blueness and green pixel begin printing opacity when wide-angle, thereby makes red being washed out.In normal white display, can reduce this effect by C-plate compensator.Can eliminate the color unsaturation by reducing dark attitude light leak.

Fig. 3 is the curve map that transmittance changes with impressed voltage when the normally-white twisted-nematic type device of wide-angle typical case in observation.This example draws in 40 ° of surface level off-normal and the data that obtained under the visual angle of 8 ° of vertical plane off-normal.Drawn among the figure and do not compensated the transmission curve of (solid line) and C-plate compensation (dotted line) two kinds of displays.Variation tendency has counter-rotating in the compensation display, so the numerical value the when transmissivity under high voltage can surpass medium voltate.When display is worked in the gray scale mode, promptly adopt medium voltate to drive the clear zone so that when showing than low-light (level), this especially can make troubles.Selecting voltage so that clear zone when having very low illumination, nominally be that the transmittance of dark pixel perhaps can be above the transmittance in this clear zone.Under uncompensated situation, greyscale color can manifest complementary color, rather than washes out primary colors simply.For example, be that bolarious zone can manifest cyan when certain angle is observed during normal incidence.By eliminate the counter-rotating of this variation tendency at transmission curve, C-plate compensator can reduce the counter-rotating of color in normal white display.

A notable feature of the present invention is that the stacked dielectric that adopts the alternate thin films by the material of different refractivity to constitute obtains required compensation.This stepped construction can be used as a kind of synthetic birefringence thin plate and uses.The multilayer film compensator of Gou Chenging can show negative birefringence in this way, in addition, by selecting suitable thicknesses of layers and material, can accurately design the required birefringenct property of multi-layer film structure.This membrane structure provides a kind of powerful measure that is used for compensating effectively the unfavourable phase delay that produces under the LCD homeotropic state.

Introduce optical theory of the present invention basis now, consider 60 ° of visual angles of an off-normal, the phase delay Γ that the positive birefringence of liquid crystal material produces is about: $\mathrm{\Γ}=\frac{1}{2}\frac{2\mathrm{\π}}{\mathrm{\λ}}(n_{\mathrm{eL}}-n_{\mathrm{oL}})d_L---\left(1\right)$ N wherein _ELAnd n _OLBe the liquid-crystal refractive-index of arranging in the same way, d _LBe the thickness of liquid crystal device, go into for wavelength of light and (should note n _ELVary by angle of view).For example, suppose the d of liquid crystal _L=6 microns, and n _EL-n _OL=0.1, then phase delay is ∏ for wavelength is 0.6 micron light.This phase delay numerical value makes liquid crystal produce serious light leak on the inclination visual angle.

A kind of periodicity stratified medium shows the symmetric birefringent characteristic of C-plate.For light transmission, the character of this medium is similar to even single axial birefringence material.During much larger than thicknesses of layers, for two material multilayer film, its equivalent refractive index no and ne are determined by following formula at wavelength: ${{\mathrm{<figure-callout\; id="2"\; label="n\; o"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_o}^2=\frac{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">d</figure-callout>}}_1}{\mathrm{\&Lambda;}}{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_1}^2+\frac{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}{\mathrm{\&Lambda;}}{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}^2---\left(2\right)$ $\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_e}^2}=\frac{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">d</figure-callout>}}_1}{\mathrm{\&Lambda;}}\frac{1}{{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_1}^2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">d</figure-callout>}}_2}{\mathrm{\&Lambda;}}\frac{1}{{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C9310253800181.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}^2}---\left(3\right)$ N wherein ₁And n ₂Be the refractive index of first and second film material, d ^- ₁Be the thickness that constitutes rete by first material, d ₂Be the thickness that constitutes rete by second material, ∧=d ₁+ d ₂Be cycle of multilayer film (see Yeh shown " Optical Waves in Layered Media ＂, the 135th page (Wiley 1988)).Should note being away from principal reflection band, because these expression formulas are not considered the chromatic dispersion of quarter-wave band into/4 structures by the approximate optical wavelength that is only applicable to that (2), (3) formula provide.Can see that this periodic structure is at its cycle always negative (n of its birefringence during much smaller than wavelength _o＞n _e).By selecting to have the film material of suitable refractive index and thickness, the n of compound multilayer film _oAnd n _eAll can accurately be set.

After this stratified medium was added liquid crystal display device, the phase delay that liquid crystal produced of Pai Lieing can be compensated in the same way.If n _OLAnd n _ELFor the O optical index and the e optical index of the liquid crystal arranged in the same way, be to obtain The optimal compensation, film material should select make liquid crystal layer the amassing of birefringence and its thickness of birefringence and the long-pending and multilayer film of its thickness equate and opposite.In order to obtain the The optimal compensation to phase delay on all angles, the refractive index of C-compensator should be set at:

n _eC＝n _oL

And

n _oC＝n _eL

(4) n wherein _EcAnd n _OcE light and O optical index for compensator.In addition, for the most effective compensation on all angles, the thickness of C-compensator should equal the thickness of liquid crystal layer.But those skilled in the art knows that the equivalent length of the aligning part in the same way of liquid crystal (being the part that is designated as " C-symmetry " among Fig. 2) should be determined by rule of thumb.Like this, for given liquid crystal device, the optimum thickness of multilayer film C-compensator is preferably determined by experiment.

Fig. 4 is the schematic cross-section of the normal white liquid crystal display of twisted nematic transmission-type according to the present invention (LCD).This display comprises polarizer layer 402 and analyzer layer 404, is provided with the liquid crystal layer 406 that is made of the nematic liquid crystal material between them.For normal white display, be in 90 ° by label 408 (the expression polarization direction the is in the drawing surface) polarizer that marks and the polarization direction of analyzer.First transparency electrode 412 and second transparency electrode 414 are set being adjacent to liquid crystal layer two opposite surfaces place, thereby can apply the voltage that passes liquid crystal layer by voltage source 416.Liquid crystal layer is sandwiched between a pair of glass plate 418,420 in addition.As described below, the inside surface of glass plate 418,420 contiguous liquid crystal layers 406 carries out physical treatment by wiping.The above-mentioned rete of 422,424 pairs of displays of substrate provides support.

All know in the LCD field and (for example show " The MolecularPhysics of Liquid-Crystal Devices " referring to Kahn, Physics Today, Deng 68 pages of (Mays, nineteen eighty-two)), when the material of liquid crystal layer 406 be in nematic phase and the inside surface (near the surface of liquid crystal layer 406) of plate 418 and 420 by wiping, and under the orthogonal situation of wiping direction, when not adding any voltage, directed first n of liquid crystal material can arrange with the wiping direction in the zone near plate 418 and 420.In addition, directed unit smoothly reverses 90 ° angles from first first type surface near plate 418 to second first type surface near plate 420 along the path in the layer 406.Like this, when not adding external electric field, the polarized light of input its polarization direction when passing liquid crystal layer is rotated 90 °.When glass plate and liquid crystal layer place between the polarizer (for example polarizer 408 and analyzer 410) of quadrature, to arrange along the polarization direction of analyzer 410 by the polarizer 408 polarizings and by the light (as light 426 representatives) of display, and pass through analyzer.But behind voltage in addition enough big on electrode 418 and 420, extra electric field makes the directed unit of liquid crystal material then is parallel to electric field and arranges.When liquid crystal material was in this state, the light by the polarizer 408 (by light 428 expressions) can be stopped to fall by analyzer 410.Like this, alive electrode pair can produce the dark areas of demonstration, and light can produce illuminated area by the zone of added electric field not.Know all that in the LCD field adopting just can character display or picture information with the suitable electrode pattern of selected combination driving.

Notable feature of the present invention has provided the multilayer film compensator 430 that places between polarizing layer and the analyzer layer in display, to improve the observation characteristic of LCD in wide angular field of view.This compensator comprises first group of rete with first refractive index, and it is in interleaved relation with each other with second group of rete with second refractive index.The thickness of first and second refractive index value and first group and second group rete should be chosen as and make the phase delay equal and opposite in direction of the phase delay of multilayer film and liquid crystal layer but opposite in sign.The amplification side cross-sectional view of in Fig. 5, having drawn multilayer film 430.The first group of rete 432,434,436 that has first thickness d 1 shown in the figure ...And second group of rete 438,440,442 with second thickness d 2 ...The technician of field of optical films is clear, in order to express notion of the present invention effectively, the thickness of rete has been exaggerated with respect to the physical size of multilayer film, and the rete number that draws is lower than in the multilayer film of reality the general number that adopts, shown in the dotted line at multilayer film middle part.

Replace the multilayer film compensator that rete forms although comprise a kind of two groups of constituting by two kinds of optical materials in the most preferred embodiment given here, but those skilled in the art will know that, the notion of multilayer film compensator also can be applicable to more complicated multi-layer film structure, it can comprise the cycle film layer structure that is made of three kinds or more kinds of material, perhaps the different thicknesses of layers differences of certain material wherein.In addition, notion of the present invention can be applicable to reflection-type and transmission type lcd device.

It is the super-twist nematic device that another kind can adopt LCD of the present invention, and it makes it to come addressing by simple multiplication to the response characteristic of voltage, thus the difficulty of having avoided the cost that the active array addressing brings and having made.The supertwist structure obtains by mix chiral additives in nematic liquid crystalline material, and it makes device that total distortion of 270 ° be arranged.The super-twist nematic device generally is used for often black structure, and it often adopts the above-mentioned compensation technique that is used for normal black scope.Yet this device also can be worked under normal white mode, and this normal white supertwist display can strengthen the visual field by additional multilayer film compensator of the present invention.And then it is in the LCD of its part duty with homeotropic state that compensation mechanism of the present invention can be applicable to any.The LCD of other type, for example the ferroelectric liquid crystals display then can obtain wide visual field by the present invention and improved under the ordered state with C-axial symmetry.

Introduced most preferred embodiment of the present invention above.But to one skilled in the art, improvement and other embodiment are conspicuous.For example, another kind of embodiment can adopt the substrate of stratified medium as display.The present invention also can be used for color monitor, and wherein color filter places the electrod-array of display.In addition, the available equivalents element substitutes element given here, and its part or mutual relationship can be put upside down or exchange, and some feature of the present invention can be used separately.In addition, the detailed structure of LCD, for example the active array addressing circuit this be not introduced be since these details be that field of liquid crystal display is known.Correspondingly, embodiment only is schematic but not exclusive, and claim is further pointed out four corner of the present invention.

Above not dike and list of references of the present invention:

Kaneko，Lipuid-Crystal?Matrix?Displays，in?Advances?inImage?Pickup?and?Display，Volume?4，Pages?2-86(B.Kazan?ed.1981)

Claims (2)

1. LCD is characterized in that comprising:

A polarizing layer;

An analyzer layer;

One places the liquid crystal layer between polarizing layer and the analyzer layer;

First electrode near liquid crystal layer first first type surface;

Second electrode near liquid crystal layer second first type surface; They can apply a voltage that passes liquid crystal layer when receiving first and second electrodes on the voltage source;

One places the multilayer film compensator between polarizing layer and the analyzer layer, comprise first group of rete with first refractive index and first thickness, it replaces mutually with second group of rete with second refractive index and second thickness, the numerical value of first and second refractive indexes and thickness make the phase delay that in certain angular field of view, produces by multilayer film with the phase delay equal and opposite in direction of the liquid crystal layer generation of homeotropic state opposite in sign.

2. display as claimed in claim 1 is characterized in that: the e optical index of described multilayer film equals the O optical index of described liquid crystal layer; And the O optical index of described multilayer film equals the optical index of described liquid crystal layer e; And the thickness of this liquid crystal layer equals the thickness of these multilayer film.

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