WO2004107031A1

WO2004107031A1 - Display drive method and image display unit

Info

Publication number: WO2004107031A1
Application number: PCT/JP2004/007265
Authority: WO
Inventors: Shuhei Tsuchie; Norio Nihei
Original assignee: Bridgestone Corporation
Priority date: 2003-05-27
Filing date: 2004-05-27
Publication date: 2004-12-09
Also published as: JPWO2004107031A1

Abstract

A display drive method in an image display unit, comprising the steps of sealing particle groups or powder and particles to between opposing substrates, at least one of which being transparent, giving an electric field to particle groups or powder and particles from two kinds of electrodes at different potentials, and moving and send particle groups or powder and particles flying to display an image, wherein a voltage is applied to between electrodes using a method under which one electrode is kept at the ground potential, and an ac voltage or a single-polarity voltage, of which value gradually changes over time and at least during an increasing process, is applied to the other electrode to thereby display an image.

Description

Specification

Display driving method and image display device

Technical field

The present invention relates to an image display driving method and an image display used in a reversible image display device capable of repeatedly performing an image display by utilizing the flying movement of a particle group or the movement of a powdery fluid due to Coulomb force or the like. It concerns the device.

Background art

[0002] Conventionally, as an image display device replacing a liquid crystal (LCD), an image display device (display) using a technology such as an electrophoresis method, an electoric chromium method, a thermal method, and a two-color particle rotation method has been proposed. Being done.

[0003] These image display devices provide next-generation inexpensive display devices because of their advantages such as obtaining a wide viewing angle close to ordinary printed matter, low power consumption, and having a memory function, as compared with LCDs. It is considered as a device and is expected to be applied to displays for mobile terminals and electronic paper.

[0004] Recently, an electrophoresis method has been proposed in which a dispersion liquid composed of dispersed particles and a coloring solution is microencapsulated, and the dispersion liquid is disposed between opposing substrates. However, in the electrophoresis method, since particles of high specific gravity such as titanium oxide are dispersed in a solution of low specific gravity, it is difficult to sediment and maintain the stability of the dispersed state immediately. Since a dye or the like is added to the solution for applying the toner, there is a problem in that it has a problem in long-term storage stability and lacks image repetition stability. Even with microencapsulation, the cell size has been reduced to the microcapsule level, and apparently such defects are unlikely to appear, but the essential problems have not been solved at all.

[0005] On the other hand, a method that does not use a solution at all has been proposed in contrast to an electrophoresis method using particle behavior in a solution (for example, Zhao Guorai and three others, "New Toner Display Device (1 ), July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total), "Japan Hardcopy '99", pp.249-252). This method utilizes the behavior of particles in a gas consisting of particles and a substrate. In this method, no solution is used, so the electrophoresis method The problem of sedimentation and aggregation of particles is solved.

However, in a dry image display panel as described above, the drive voltage applied between the electrodes in order to apply an electric field to a particle group or the like for image display has a voltage value at a certain point in time. We used a pulse-like rectangular wave that rises and falls. In recent years, it has been found that, when an image is displayed by driving with this rectangular wave, the panel display characteristics are deteriorated, and the life of the number of inversions and the contrast are adversely affected.

Disclosure of the invention

An object of the present invention is to provide a display driving method and an image display device which solve the above-mentioned problems, do not deteriorate panel display characteristics, and do not adversely affect the number of reversals and the life of contrast. is there.

[0008] In the first invention of the display driving method of the present invention, particles are encapsulated between opposing substrates, at least one of which is transparent, and an electric field is applied to two types of electrode forces having different potentials to fly the particles. A display driving method in an image display device for displaying an image by moving the electrode, wherein one electrode potential is set to a ground potential, and the other electrode is supplied with an alternating voltage or a voltage whose voltage value gradually changes at least in an increasing process with time. An image is displayed by applying a voltage by a method of applying a unipolar voltage.

[0009] In a second aspect of the display driving method of the present invention, a powder fluid is sealed between opposing substrates, at least one of which is transparent, and an electric field is applied to the powder fluid from two types of electrodes having different potentials. A display driving method for an image display device that displays an image by moving a fluid, wherein one electrode potential is set to a ground potential, and the other electrode is provided with an alternating voltage whose voltage value gradually changes at least in an increasing process with time. An image is displayed by applying a voltage by a method of applying a voltage or a unipolar voltage.

[0010] In the first invention and the second invention of the display driving method of the present invention, one electrode potential is set to a ground potential, and the other electrode is supplied with an alternating voltage whose voltage value gradually changes at least in an increasing process with time. Alternatively, by applying a voltage by a method of applying a unipolar voltage and displaying an image, a display driving method and an image display device that do not deteriorate the panel display characteristics and do not adversely affect the number of reversals and the contrast are provided. Obtainable.

[0011] Preferred examples of the first invention and the second invention of the display driving method of the present invention include an alternating voltage and Means that the unipolar voltage gradually changes over time in the form of a sine wave, at least in the process of increasing, and that the alternating voltage or unipolar voltage increases at least over time in the form of a trapezoidal or staircase wave The voltage value may gradually change during the process, and the voltage value may gradually change at least in the process of increasing the AC voltage or the unipolar voltage with time in the form of a triangular wave or a ramp wave at least over time. In any case, the present invention can be more preferably implemented.

[0012] Further, an image display device of the present invention is characterized in that an image is displayed according to the above-described display driving method.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing an example of a display method in an image display device of the present invention.

FIG. 2 is a diagram showing another example of a display method in the image display device of the present invention.

FIGS. 3 (a) and 3 (f) are diagrams for explaining examples of a display driving method according to a conventional example and an example of the present invention, respectively.

FIG. 4 is a graph showing an example of a result obtained by repeating white display and black display at the same frequency and obtaining the relationship between the density and the number of inversions in the conventional example and the present invention example.

FIG. 5 is a graph showing an example of a result obtained by repeatedly performing white display and black display at the same frequency and obtaining the relationship between the density difference and the number of inversions in black and white display for the conventional example and the present invention example. is there.

[FIG. 6] FIG. 6 shows another example of a result obtained by repeating white display and black display at the same frequency and obtaining the relationship between the density difference and the number of inversions in the black and white display for the conventional example and the present invention example. It is a graph.

[FIG. 7] FIG. 7 shows still another example of the result obtained by repeating white display and black display at the same frequency and obtaining the relationship between the density difference and the number of inversions in the black and white display for the conventional example and the present invention example. FIG.

8 (a) -1 (f) are diagrams for explaining other examples of the display driving method of the conventional example and the example of the present invention, respectively.

FIGS. 9 (a) and 9 (f) are diagrams for explaining still another example of the display driving method according to the example of the present invention. FIG. 10 is a diagram showing an example of a shape of a partition wall in the image display device of the present invention.

[0014] In the image display panel according to the first and second inventions of the present invention, electrodes are passed through the display panel in which at least two or more types of particle groups or powder fluids are sealed between opposing substrates. An electric charge is provided in the substrate. Particles or powder fluid charged at low potential are attracted toward the high potential electrode by Coulomb force, and particles or powder fluid charged at high potential are attracted toward the low potential electrode by Coulomb force. The particles are attracted and the particles or powder fluid reciprocate between the electrodes to display an image. Therefore, it is necessary to design a display panel so that the particles or the powder fluid can move uniformly and maintain stability during repetition or storage.

FIG. 1 and FIG. 2 are diagrams each showing a configuration of an example of an image display panel to which the present invention is applied. In the image display panel to which the present invention is applied as shown in FIG. 1, two types of particles (here, white particles 3W and black particles 3B) having different charging characteristics and optical reflectivity are placed between the substrates 1 and 2. An image is displayed by applying an electric field to the encapsulated particle group 3 from the electrodes 5 and 6 provided on the substrate and moving the particles in a direction perpendicular to the substrates 1 and 2. In this method, as shown in Fig. 2, the space between the substrates 1 and 2 is divided by a partition wall 4 to have a structure with a plurality of cells, and the particle group 3 is enclosed in the structure to form an image display panel. It can also be configured. The electrodes provided on the substrate may be on either side of the substrate or may be embedded inside the substrate. Further, the above configuration is the same even when a powder fluid is used instead of the particle group.

A feature of the present invention resides in an image display driving method in the image display panel having the above-described configuration. That is, in the image display panel having the above-described configuration, in both the example using the particle group and the example using the powder fluid, one of the electrodes 5 and 6 is set to the ground potential, and the other is increased at least in the process of increasing with time. It is characterized in that an image is displayed by applying a voltage between the electrodes 5 and 6 by applying an alternating voltage or a unipolar voltage whose voltage value gradually changes. In the present invention, the applied voltage is defined as "alternating voltage or unipolar voltage whose voltage value gradually changes at least in the process of increasing with time", as in a conventional pulse-shaped rectangular wave. The voltage value rises / falls instantaneously, especially in a moment This is to exclude a voltage having a shape that rises (increases) in time. The alternating voltage means a voltage crossing GND, and the unipolar voltage means a voltage not crossing GND.

FIGS. 3A and 3F are diagrams for explaining examples of the display driving method of the conventional example and the example of the present invention, respectively. 3A to 3F, the potential of the electrode 6 is set to the ground potential in each of the examples. Here, in the conventional example shown in FIG. 3A, an alternating voltage composed of a pulsed rectangular wave is applied to the electrode 5. On the other hand, in the example of the present invention shown in FIG. 3B, an alternating voltage composed of a sine wave is applied to the electrode 5. In the example of the present invention shown in FIG. 3C, an alternating voltage composed of a trapezoidal wave is applied to the electrode 5. Further, in the example of the present invention shown in FIG. 3D, an alternating voltage composed of a staircase wave is applied to the electrode 5. Furthermore, in the example of the present invention shown in FIG. 3 (e), an alternating voltage composed of a ramp wave is applied to the electrode 5. In the example of the present invention shown in FIG. 3 (f), an alternating voltage consisting of a triangular wave is applied to the electrode 5.

[0018] Among the display driving methods of the conventional example and the present invention example shown in FIGS. 3 (a) and 1 (f), in the case of an alternating voltage composed of a pulse-shaped rectangular wave of the conventional example shown in FIG. 3 (a). The white display and the black display were repeated at the same frequency for the alternating voltage consisting of the sine wave of the present invention shown in Fig. 3 (b), and the relationship between the density and the number of inversions was obtained. Fig. 4 shows the results. From the results shown in FIG. 4, it can be seen that when driving with the sine wave of the example of the present invention, the density reduction due to repeated inversion in both black display and white display is small, whereas in the conventional rectangular wave, as the inversion is repeated, It can be seen that the decrease in density is large, and the decrease in black density is particularly remarkable. FIG. 5 shows the relationship between the number of inversions and the density difference in monochrome display in the same example as FIG. From this, it can be seen that the density difference in black-and-white display is small even when reversal is repeated in the sine wave according to the present invention, whereas the density difference in black-and-white display is significantly reduced in the conventional rectangular wave according to repetition of reversal. You can see that

Next, according to the display driving methods of the conventional example and the present invention example shown in FIGS. 3A and 3F, the results of measuring the density difference when white display and black display are repeated at the same frequency are shown. And Figure 6 and Figure 7. As can be seen from the results of FIGS. 6 and 7, in the example of the present invention, not only the sine wave but also the trapezoidal wave, the staircase wave, the ramp wave, and the triangular wave show a small decrease in the density difference at the time of monochrome display due to repeated inversion. On the other hand, the conventional rectangular wave displays black and white according to the repetition of inversion. It can be seen that the density difference at the time is greatly reduced. Further, it can be seen that there is no particularly significant difference between the sine wave and the trapezoidal wave, the staircase wave, the ramp wave, and the triangular wave in the examples of the present invention.

FIGS. 8 (a) -1 (f) and 9 (a) -1 (f) are diagrams for explaining other examples of the display driving method of the conventional example and the present invention example, respectively. Here, in the conventional example shown in FIG. 8 (a), an example in which a unipolar voltage composed of a pulsed rectangular wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 8 (b). In the conventional example shown in ()), the example shown in FIG. 8 (a) and the example in which the voltage applied to the electrode is inverted are shown. In the example of the present invention shown in FIG. 8 (c), FIG. 8 (d) shows an example in which a unipolar voltage composed of a sine wave is applied to one electrode 5 and the other electrode 6 is connected to GND. In the example of the present invention, an example shown in FIG. 8C and an example in which the voltage applied to the electrode is inverted are shown. Further, in the example of the present invention shown in FIG. 8 (e), FIG. 8 (f) shows an example in which a unipolar voltage consisting of a trapezoidal wave is applied to one electrode 5 and the other electrode 6 is connected to GND. In the example of the present invention, an example shown in FIG. 8 (e) and an example in which the voltage applied to the electrode is inverted are shown.

Similarly, in the example of the present invention shown in FIG. 9A, an example in which a unipolar voltage composed of a staircase wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 9) shows an example of the present invention shown in FIG. 9 (a) and an example in which the voltage applied to the electrode is inverted. Further, in the example of the present invention shown in FIG. 9 (c), an example in which a unipolar voltage consisting of a ramp wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 9 (d). In the invention example, the example shown in FIG. 9C and the example in which the voltage applied to the electrode is inverted are shown. Further, in the example of the present invention shown in FIG. 9 (e), an example in which a unipolar voltage consisting of a triangular wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 9 (f). In the example, the example shown in FIG. 9 (e) and the example in which the voltage applied to the electrode is inverted are shown.

[0022] Here, similarly to the above-described example, according to the display driving method of the conventional example and the example of the present invention shown in Figs. 8 (a) and 1 (f) and Figs. As a result of repeating display and black display, in the example of the present invention shown in FIGS. 8 (c), (d) and FIGS. 9 (a)-(f), the decrease in density difference during black-and-white display due to repeated inversion is small. On the other hand, in the conventional example, it was found that the density difference at the time of black-and-white display was greatly reduced as the reversal was repeated. Further, the degree of reduction in the density difference during the black and white display due to the repetition of the inversion was almost the same for both the alternating voltage and the unipolar voltage.

From the above results, according to the display driving method of the present invention, the panel display characteristics do not deteriorate, It was found that the number of reversals and the contrast were not adversely affected. Therefore, by using the display driving method of the present invention, an image display device having preferable characteristics can be obtained.

Hereinafter, each component of the image display device of the present invention will be described in detail in the order of particles, liquid powder, and common components.

First, the particles used in the first invention of the present invention will be described.

[0026] Particles can be prepared by kneading and pulverizing a necessary resin, charge control agent, colorant, and other additives, or by polymerizing from a monomer, or by converting existing particles into a resin, a charge control agent, and coloring. , Even if coated with other additives.

Hereinafter, examples of the resin, the charge control agent, the colorant, and other additives will be described.

Examples of the resin include urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, Fluororesins and the like can be used, and two or more kinds can be mixed.In particular, polyester resins, acrylic urethane resins, acrylic urethane silicone resins, acrylic urethane fluororesins, urethane resins, and the like are used for controlling the adhesion to the substrate. Fluororesins are preferred.

[0029] Examples of the charge control agent include a quaternary ammonium salt compound, a Nigguchi syn dye, a triphenylmethane compound, and an imidazole derivative in the case of imparting a positive charge. Examples thereof include metal-containing azo dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

Examples of the coloring agent include dyes such as basic and acidic dyes, and examples include Nigguchi Shin, Methylene Blue, Quinoline Yellow, Rose Bengal and the like.

[0031] Examples of inorganic additives include titanium oxide, zinc white, zinc sulfide, antimony oxide, calcium carbonate, lead white, tanolek, silica, calcium silicate, alumina white, cadmium yellow, cadmium red, and cadmium. Orange, titanium yellow, navy blue, ultramarine, cobalt vinyl, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, aluminum powder and the like.

[0032] Here, in order to further improve the repetition durability, the resin constituting the particles may be used. It is effective to control the stability, especially the water absorption and the solvent insolubility.

[0033] The water absorption of the resin constituting the particles sealed between the substrates is preferably 3% by weight or less, particularly preferably 2% by weight or less. The water absorption is measured according to ASTM D570, and the measurement conditions are 23 ° C for 24 hours.

[0034] With respect to the solvent insolubility of the resin constituting the particles, the solvent insolubility of the particles represented by the following relational expression is preferably 50% or more, particularly preferably 70% or more.

Solvent insolubility (%) = (B / A) x 100

(However, A indicates the weight before immersing the resin in the solvent, and B indicates the weight after immersing the resin in a good solvent at 25 ° C for 24 hours.)

[0035] When the solvent insolubility is less than 50%, bleeding occurs on the particle surface during long-term storage, which affects the adhesion to the particles, hinders the movement of the particles, and hinders the image display durability. May be.

[0036] The solvent (good solvent) for measuring the solvent insolubility may be methylethyl ketone or the like for a fluororesin, methanol or the like for a polyamide resin, methyl ethyl ketone or toluene for an acrylurethane resin, or acetone for a melamine resin. For silicone resins such as isopropanol and the like, toluene is preferred.

[0037] The particles are preferably spherical.

In the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is set to less than 5, preferably less than 3.

Span = (d (0.9) -d (0.1)) /d(0.5)

(However, d (0.5) is a numerical value expressed by / im that 50% of the particles are larger and 50% is smaller than this, and d (0.1) is the ratio of particles smaller than 10%. The particle diameter is expressed in μm, and d (0.9) is the particle diameter in which 90% of the particles are 90%.

[0039] By setting the Span within the range of 5 or less, the size of each particle can be uniform and uniform particle movement can be achieved.

[0040] Further, the average particle diameter d (0.5) of each particle is set to 0.150 xm. If the size is larger than this range, the sharpness of the display will be poor, and if the size is smaller than this range, the cohesion between the particles will be too large, which will hinder the movement of the particles. [0041] Furthermore, regarding the correlation of each particle, of the particles used, the ratio of d (0.5) of the particle having the minimum diameter to d (0.5) of the particle having the maximum diameter is 50 or less, preferably 10 or less. It is important to do so.

[0042] Even if the particle size distribution Span is reduced, particles having different charging characteristics move in opposite directions to each other, so that particles having similar particle sizes can easily move in the opposite direction with equivalent weight. Is preferable, and this falls within this range.

The particle size distribution and the particle size described above can be determined by a laser diffraction / scattering method or the like. When a laser beam is applied to the particles to be measured, a spatial light intensity distribution pattern of the diffracted Z scattered light is generated, and since this light intensity pattern has a correspondence with the particle size, the particle size and the particle size distribution can be measured. .

[0044] The particle size and the particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, the particles are introduced into a nitrogen gas stream, and the particles are analyzed using the attached analysis software (software based on volume-based distribution using Mie theory). Measurements of diameter and particle size distribution can be made.

Next, the powder fluid used in the second invention of the present invention will be described.

[0046] The "powder fluid" in the present invention is a substance in an intermediate state between a fluid and a particle exhibiting fluidity by itself without using the power of gas or liquid. For example, a liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity, a characteristic of liquid, and anisotropy (optical properties), a characteristic of solid (Heibonsha: Encyclopedia) ). On the other hand, the definition of a particle is an object having a finite mass, even if it is negligible, and is said to be affected by gravity (Maruzen: Encyclopedia of Physics). Here, particles also have a special state of gas-solid fluidized bed or liquid-solid fluid. When gas flows from the bottom plate to the particles, an upward force acts on the particles corresponding to the velocity of the gas. A fluid that can easily flow when it balances gravity is called a gas-solid fluidized bed, and a fluidized state by the same fluid is called a liquid-solid fluid. (Heibonsha: Encyclopedia). As described above, the gas-solid fluidized bed and the liquid-solid fluid are in a state utilizing the flow of gas or liquid. In the present invention, it has been found that a substance in a state of exhibiting fluidity can be specifically produced without using the power of such a gas or the power of a liquid, and this is defined as a powder fluid. [0047] That is, the powder fluid in the present invention is an intermediate state having both characteristics of particles and liquid, and has the characteristics of the particles described above, similarly to the definition of liquid crystal (intermediate phase between liquid and solid). A substance that exhibits a unique state of high fluidity that is extremely insensitive to gravity. Such a substance can be obtained in an aerosol state, that is, a dispersion system in which a solid or liquid substance is stably suspended as a dispersoid in a gas, and the solid substance is regarded as a dispersoid in the image display device of the present invention. Is what you do.

[0048] The image display device to which the present invention is applied is a powder fluid that exhibits high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid in a gas between opposed substrates, at least one of which is transparent. Such a powder fluid can be easily and stably moved by applying Coulomb force or the like when a low voltage is applied.

[0049] As described above, the powder fluid is a substance in an intermediate state between a fluid and a particle that exhibits fluidity by itself without using the power of gas or liquid. The powdered fluid can be in an aerosol state, and is used in the image display device of the present invention in a state where a solid substance is relatively stably suspended as a dispersoid in a gas.

[0050] The range of the aerosol state is preferably at least twice as large as the apparent volume at the time of the maximum suspension of the powder fluid, more preferably at least 2.5 times, particularly preferably at least three times the non-suspended volume. You. The upper limit is not particularly limited, but is preferably 12 times or less.

[0051] If the apparent volume at the time of maximum floating of the powder fluid is smaller than twice that of the non-floating state, it becomes difficult to control the display, and if it is larger than 12 times, the powder fluid will fly too much when sealed in the device. Inconvenience in handling such as The apparent volume at the time of maximum suspension is measured as follows. That is, the powdered fluid is put into a closed container through which the powdered fluid can be seen, and the container itself is vibrated or dropped to create a maximum floating state, and the apparent volume at that time is measured for the external force of the container. Specifically, a polypropylene container with a 6 cm diameter (inner diameter) and a 10 cm height (product name: Iboy: Az-One Co., Ltd.) has a volume equivalent to 1/5 of the volume of powder fluid when not suspended. Fill the powder fluid, set the container on a shaker, and shake at a distance of 6 cm at 3 reciprocations / sec for 3 hours. The apparent volume immediately after stopping shaking is the apparent volume at the time of maximum suspension.

[0052] Further, the image display device of the present invention is preferably one in which the temporal change of the apparent volume of the powder fluid satisfies the following expression. V / V> 0.8

10 5

Here, V is the apparent volume (cm ³ ) 5 minutes after the maximum suspension, and V is 10

5 10

Shows the apparent volume (cm ³ ) after minutes. In the image display device of the present invention, it is preferable that the temporal change V / V of the apparent volume of the powder fluid is larger than 0.85, and it is preferable that the volume change is larger than 0.9.

10 5

Is particularly preferred. If V / V is 0.8 or less, the field using ordinary so-called particles

10 5

In this case, the effects of high-speed response and durability as in the present invention cannot be secured.

[0053] Further, the average particle diameter (d (0.5)) of the particulate matter constituting the powder fluid is preferably 0.1 to 2 Ozm, more preferably 0.515 xm, and particularly preferably 0.5. 9 8 xm. If it is smaller than 0. l xm, it will be difficult to control the display. If it is larger than 20 zm, it will be possible to display, but the concealment ratio will decrease, making it difficult to make the device thinner. The average particle size (d (0.5)) of the particulate matter constituting the powder fluid is the same as d (0.5) in the following particle size distribution Span.

The particle material constituting the powder fluid preferably has a particle diameter distribution Span represented by the following formula of less than 5, more preferably less than 3.

Particle size distribution Span = (d (0.9) -d (0.l)) / d (0.5)

Here, d (0.5) is a numerical value expressing the particle diameter in m that 50% of the particulate matter constituting the powder fluid is larger than 50% and smaller than 50%, and d (0.1) is less than this. Numerical value expressed as / im, the particle diameter at which the ratio of the particulate matter constituting the powdered fluid is 10%, and d (0.9) is the particle diameter at which the particulate matter constituting the powdered fluid is 90% or less. In / m. By setting the particle size distribution Span of the particulate matter constituting the powder fluid to 5 or less, the size becomes uniform and the powder fluid can be moved uniformly.

[0055] The particle size distribution and the particle size of the particulate matter constituting the powder fluid can be determined by a laser single diffraction / scattering method or the like. When laser light is irradiated to the powder fluid to be measured, a light intensity distribution pattern of diffracted / scattered light is generated spatially, and since this light intensity pattern has a correspondence with the particle size, the particle size and the particle size distribution are reduced. Can be measured. The particle size and the particle size distribution are obtained from a volume-based distribution. In particular,

Using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, a powder fluid is injected into a nitrogen stream, and measurement can be performed using the attached analysis software (software based on volume-based distribution using Mie theory). it can. [0056] The powder fluid can be prepared by kneading and pulverizing a necessary resin, a charge control agent, a colorant, and other additives, or by polymerizing from a monomer, by converting existing particles into a resin, a charge control agent, and a colorant. And other additives. Hereinafter, the resin, the charge control agent, the colorant, and other additives constituting the powder fluid will be exemplified.

Examples of the resin include urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, Fluororesin and the like can be used, and two or more kinds can be mixed.In particular, from the viewpoint of controlling the adhesive force with the substrate, atalinole urethane resin, acryl urethane silicone resin, acryl urethane fluoro resin, urethane resin, and fluoro resin are preferable. It is.

[0058] Examples of the charge control agent include a quaternary ammonium salt-based compound, a Nigguchi syn dye, a triphenylmethane-based compound, and an imidazole derivative in the case of imparting a positive charge. Examples thereof include metal-containing azo dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

Examples of the colorant include dyes such as basic and acidic dyes, and examples include Nigguchi Shin, Methylene Blue, Quinoline Yellow, Rose Bengal and the like.

Examples of the inorganic additives include titanium oxide, zinc white, zinc sulfide, antimony oxide, calcium carbonate, lead white, talc, silica, calcium silicate, alumina white, cadmium yellow, cadmium red, and cadmium. Orange, titanium yellow, navy blue, ultramarine, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, copper powder, aluminum powder and the like.

[0061] Even if such a material is kneaded and coated without any ingenuity while applying force, it is not possible to produce a powder fluid showing an aerosol state in the air. It is not clear how the powdered fluid that shows the aerosol state is determined, but the following is an example.

[0062] First, it is appropriate to fix inorganic fine particles having an average particle diameter of 20 100 nm, preferably 280 nm on the surface of the particle material constituting the powder fluid. Further, it is appropriate that the inorganic fine particles are treated with silicone oil. Here, as the inorganic fine particles, silicon dioxide (silica), zinc oxide, aluminum oxide, magnesium oxide, cerium oxide , Iron oxide, copper oxide and the like. The method of fixing the inorganic fine particles is important. For example, using a hybridizer (manufactured by Nara Machinery Co., Ltd.) ゃ mechanofusion (manufactured by Hosokawa Miclon Co., Ltd.) or the like, under certain limited conditions (for example, processing time) ), A powder fluid showing an aerosol state can be produced.

Here, in order to further improve the repeated durability, it is effective to control the stability of the resin constituting the powder fluid, in particular, the water absorption and the solvent insolubility. The water absorption of the resin that constitutes the powder fluid sealed between the substrates is preferably 3% by weight or less, particularly preferably 2% by weight or less. The water absorption was measured in accordance with ASTM-D570, and the measurement conditions were 23 ° C for 24 hours. Regarding the solvent insolubility of the resin constituting the powder fluid, the solvent insolubility of the powder fluid represented by the following relational expression is preferably 50% or more, particularly preferably 70% or more.

Solvent insolubility (%) = (B / A) x 100

[0064] If the solvent insolubility is less than 50%, bleeding occurs on the surface of the particulate matter composing the powdery fluid during long-term storage, which affects the adhesion to the powdery fluid and hinders the movement of the powdery fluid. The durability may be impaired. When measuring the solvent insolubility, the solvent (good solvent) is methyl ethyl ketone or the like for a fluororesin, methanol or the like for a polyamide resin, methyl ethyl ketone or toluene for an acrylic urethane resin, or melamine resin for a melamine resin. For silicone resins such as acetone and isopropanol, toluene is preferred.

[0065] As for the filling amount of the particle group or the powder fluid, the volume occupancy of the particle group or the powder fluid is 5 to 70 vol%, preferably 5 to 60 vol%, more preferably 5 to 70 vol% of the gap between the opposing substrates. It is preferable to adjust so as to be 55 vol%. If the volume occupancy of the particle group or powder fluid is less than 5 vol%, clear image display will not be possible, and if it is greater than 70 vol%, the particle group or powder fluid will move. Here, the space volume refers to a volume that can be filled with a so-called particle group or powder fluid, excluding a portion sandwiched between the opposing substrates 1 and 2 and excluding a portion occupied by the partition 4 and a device sealing portion. And

Next, the substrate will be described.

[0067] At least one of the substrate 1 and the substrate 2 can confirm the color of the particles or powder fluid from the outside of the apparatus. It is preferable to use a material which is a transparent substrate having high visible light transmittance and good heat resistance. The presence or absence of flexibility is appropriately selected depending on the application.For example, flexible materials are used for applications such as electronic paper, and flexible materials are used for applications such as mobile phones, PDAs, and portable devices such as notebook computers. Re, materials are used.

[0068] Examples of the substrate material include a polymer sheet such as polyethylene terephthalate, polyether sulfone, polyethylene, and polycarbonate, and an inorganic sheet such as glass and quartz.

The thickness of the substrate is preferably 25000 μπι, preferably 51000 μm. If the thickness is too small, it is difficult to maintain the strength and uniformity between the substrates. However, a decrease in contrast occurs, and particularly in the case of an electronic paper application, it lacks flexibility.

[0070] Examples of an electrode forming material for the electrodes provided on the substrate include metals such as aluminum, silver, nickel, copper, and gold; conductive metal oxides such as ιτο, indium oxide, conductive tin oxide, and conductive zinc oxide; Conductive polymers such as polyaniline, polypyrrole, and polythiophene are exemplified, and are appropriately selected and used. Examples of the method for forming an electrode include a method of forming the above-described materials into a thin film by a sputtering method, a vacuum evaporation method, a CVD (chemical vapor deposition) method, a coating method, or a method in which a conductive agent is mixed with a solvent or a synthetic resin binder. Or a method of applying by spraying. The electrodes provided on the viewing side substrate need to be transparent, but the electrodes provided on the back side substrate do not need to be transparent. In any case, the above-mentioned conductive material capable of forming a pattern can be suitably used.

Next, the partition will be described.

[0072] The shape of the partition wall of the present invention is optimally set as appropriate depending on the size of particles involved in the display or the size of the powdery fluid, and is not particularly limited, but the width of the partition wall is 10 to 1000 zm, preferably 10 500 zm. The height of the septum is adjusted to 10-500 μm, preferably 10-200 μm.

[0073] In forming the partition, a two-rib method in which ribs are formed on each of the opposing substrates and then bonding, and a one-rib method in which the ribs are formed only on one substrate are conceivable. Ming is applicable to both.

[0074] The display cell formed by the rib-made partition walls has a substrate plane as shown in FIG. Seen from the direction, a square, a triangle, a line, a circle, and a hexagon are exemplified, and the arrangement is exemplified by a lattice shape, a honeycomb shape, and a mesh shape. It is better to make the part (area of the frame part of the display cell) corresponding to the cross-section of the partition seen from the display side as small as possible. Here, examples of the method for forming the partition include a screen printing method, a sand blast method, a photolithography method, and an additive method. Of these, a photolithography method using a resist film is preferably used.

Industrial applicability

The image display device of the present invention includes a display section of a mopile device such as a notebook computer, a PDA, a mobile phone, a handy terminal, an electronic book such as an electronic book and an electronic newspaper, a signboard, a booster, a bulletin board such as a blackboard, a calculator, and a home appliance. It is suitably used for display parts for automobiles, etc., card display parts such as point cards and IC cards, electronic advertisements, electronic POP, electronic price tags, electronic music scores, and display parts for RF-ID devices.

Claims

The scope of the claims

[1] Display on an image display device that encloses a particle group between opposing substrates, at least one of which is transparent, applies an electric field to the particle group from two types of electrodes with different potentials, and moves the particles to move and display an image In the driving method, one electrode potential is set to the ground potential, and a voltage is applied to the other electrode by a method of applying an alternating voltage or a unipolar voltage whose voltage value gradually changes at least in an increasing process with time. And displaying an image.

2. The display drive method according to claim 1, wherein the alternating voltage or the unipolar voltage gradually changes with time in at least an increasing process in the form of a sine wave.

3. The display driving method according to claim 1, wherein the alternating voltage or the unipolar voltage has a trapezoidal wave shape or a staircase wave shape, and the voltage value gradually changes at least in a process of increasing with time.

4. The display driving method according to claim 1, wherein the alternating voltage or the unipolar voltage has a triangular wave shape or a ramp wave shape and a voltage value gradually changes at least in a process of increasing with time.

[5] A display drive in an image display device that encloses a powder fluid between opposed substrates at least one of which is transparent, applies an electric field to the powder fluid from two types of electrodes having different electric potentials, moves the powder fluid, and displays an image. Applying a voltage to the other electrode by applying an alternating voltage or a unipolar voltage whose voltage value gradually changes at least in the course of increase with time to the other electrode, A display driving method characterized by displaying an image.

6. The display driving method according to claim 5, wherein the alternating voltage or the unipolar voltage gradually changes with time in at least an increasing process in the form of a sine wave.

7. The display driving method according to claim 5, wherein the alternating voltage or the unipolar voltage has a trapezoidal wave shape or a staircase wave shape, and the voltage value gradually changes at least in a process of increasing with time.

[8] The display driving method according to claim 5, wherein the alternating voltage or the unipolar voltage has a triangular wave shape or a ramp wave shape, and the voltage value gradually changes at least in a process of increasing with time.

[9] An image is displayed according to the display driving method according to any one of claims 1 to 8. Characteristic image display device.