JPWO2004107031A1 - Display driving method and image display apparatus - Google Patents

Abstract

A particle group or powdered fluid is sealed between opposing substrates at least one of which is transparent, an electric field is applied to the particle group or powdered fluid from two types of electrodes having different potentials, and the particles or powdered fluid fly and move to display an image. A display driving method for an image display device, in which one electrode is set to a ground potential between electrodes, and an alternating voltage or unipolar voltage whose voltage value gradually changes over time is applied to the other electrode at least over time. A voltage is applied by the method to display an image.

Description

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

  2. Description of the Related Art Conventionally, image display devices (displays) using techniques such as electrophoresis, electrochromic, thermal, and two-color particle rotation have been proposed as image display devices that replace liquid crystal (LCD).

  These image display devices are considered as next-generation inexpensive display devices because of their advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and memory function compared to LCDs. Therefore, it is expected to expand to displays for portable terminals, electronic paper, and the like.

  Recently, an electrophoretic method has been proposed in which a dispersion composed of dispersed particles and a colored solution is microencapsulated and disposed between opposing substrates. However, in the electrophoresis method, particles of high specific gravity such as titanium oxide are dispersed in a solution of low specific gravity, so that it is easy to settle, it is difficult to maintain the stability of the dispersed state, and the solution is used for coloring. Since dyes and the like are added to the toner, there is a problem in long-term storage stability and lack of image repetition stability. Even with microencapsulation, the cell size is reduced to the microcapsule level, and such defects are hardly made to appear, and the essential problems are not solved.

  On the other hand, a method that does not use a solution at all has been proposed in contrast to an electrophoresis method that utilizes particle behavior in a solution (for example, Kuniori Tsuji, three others, “New Toner Display Device (I)”, 1999). July 21, 2009, Annual Meeting of the Imaging Society of Japan (83 times in total), “Japan Hardcopy '99” Proceedings, p. 249-252). This method uses particle behavior in a gas composed of particles and a substrate. In this method, since no solution is used, the problem of sedimentation and aggregation of particles, which has been a problem in the electrophoresis method, is solved.

  However, in the dry image display panel as described above, as a drive voltage applied between the electrodes for applying an electric field to the particle group for image display, the voltage value rises / falls instantaneously at a certain point in time. A pulsed rectangular wave was used. 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 inversion and the contrast are adversely affected.

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

  According to a first aspect of the display driving method of the present invention, a particle group is enclosed between opposing substrates at least one of which is transparent, an electric field is applied to the particle group from two types of electrodes having different potentials, and the particles fly and move. A display driving method in an image display device that displays one of the electrodes, wherein one electrode potential is a ground potential, and an alternating voltage or a unipolar voltage whose voltage value gradually changes over time is applied to the other electrode. An image is displayed by applying a voltage by the method described above.

  Further, the second invention of the display driving method of the present invention moves the powder fluid by enclosing the powder fluid between the opposing substrates at least one of which is transparent, and applying an electric field to the powder fluid from two types of electrodes having different potentials. A display driving method in an image display device for displaying an image, wherein one electrode potential is a ground potential, and the other electrode is an alternating voltage or a unipolar voltage whose voltage value gradually changes over time with at least an increasing process. An image is displayed by applying a voltage by a method of applying.

  In the first and second inventions of the display driving method of the present invention, one electrode potential is set to the ground potential, and the other electrode has an alternating voltage or unipolarity whose voltage value gradually changes at least in the increasing process with time. A display driving method and an image display device that do not deteriorate the panel display characteristics and do not adversely affect the life of the number of inversions and the contrast by displaying an image by applying a voltage by applying a voltage can be obtained. it can.

  As a preferred example of the first and second inventions of the display driving method of the present invention, the alternating voltage or the unipolar voltage gradually changes in voltage value at least in the increasing process with time in the form of a sine wave, and The alternating voltage or unipolar voltage is a trapezoidal wave or staircase wave, and the voltage value gradually changes over time, and the alternating voltage or unipolar voltage is a triangular wave or ramp wave. Depending on the shape, the voltage value may gradually change over time, at least in the course of increasing. In either case, the present invention can be more suitably implemented.

  The image display device of the present invention displays an image according to the display driving method described above.

FIG. 1 is a diagram showing an example of a display method in an image display apparatus of the present invention.
FIG. 2 is a diagram showing another example of the display method in the image display apparatus of the present invention.
[FIG. 3] FIGS. 3A to 3F are diagrams for explaining an example of a display driving method of a conventional example and an example of the present invention, respectively.
[FIG. 4] FIG. 4 is a graph showing an example of a result obtained by repeating white display and black display at the same frequency for a conventional example and an example of the present invention and obtaining a relationship between the density and the number of inversions.
[FIG. 5] FIG. 5 is a graph showing an example of a result obtained by repeating white display and black display at the same frequency for the conventional example and the example of the present invention, and obtaining the relationship between the density difference and the number of inversions during the monochrome display. is there.
[FIG. 6] FIG. 6 shows another example of the result obtained by repeating the white display and the black display at the same frequency for the conventional example and the example of the present invention, and obtaining the relationship between the density difference and the number of inversions during the monochrome display. It is a graph.
[FIG. 7] FIG. 7 shows still another example of the result obtained by repeating the white display and the black display at the same frequency for the conventional example and the example of the present invention, and obtaining the relationship between the density difference and the number of inversions during the monochrome display. It is a graph to show.
[FIG. 8] FIGS. 8A to 8F are diagrams for explaining another example of the display driving method of the conventional example and the example of the present invention, respectively.
[FIG. 9] FIGS. 9A to 9F are diagrams for explaining still another example of the display driving method of the present invention.
FIG. 10 is a diagram showing an example of the shape of the partition wall in the image display device of the present invention.

  In the image display panel that is the subject of the first and second inventions of the present invention, electric charges are introduced into the substrate through the electrodes in the display panel in which at least two kinds of particle groups or powder fluid are sealed between the opposing substrates. Is granted. Towards the high potential electrode side, particles or powder fluid charged at a low potential are attracted by Coulomb force, and toward the low potential electrode side, particles or powder fluid charged at a high potential are attracted by Coulomb force. The particles are attracted and the group of particles or powder fluid reciprocates between the electrodes, thereby displaying an image. Therefore, it is necessary to design the display panel so that the particle group or the powder fluid can move uniformly and maintain the stability during repetition or storage.

  FIG. 1 and FIG. 2 are diagrams each showing a configuration of an example of an image display panel that is an object of the present invention. In the image display panel shown in FIG. 1, the two types of particle groups (in this case, the white particle group 3W and the black particle group 3B) having different charging characteristics and optical reflectance are arranged between the substrates 1 and 2. An image is displayed by applying an electric field to the enclosed 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, a structure having a plurality of cells is formed by dividing a gap between the substrates 1 and 2 by a partition wall 4, and a particle group 3 is enclosed in the structure to constitute an image display panel. You can also The electrode provided on the substrate may be on either the inside or outside of the substrate, or may be embedded in the substrate. The above configuration is the same even when a powder fluid is used instead of the particle group.

  A feature of the present invention is 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 either the example using the particle group or the example using the powder fluid, one of the electrodes 5 and 6 is set to the ground potential, and the voltage value is increased at least in an increasing process with time. An image is displayed by applying a voltage between the electrodes 5 and 6 by applying a gradually changing alternating voltage or unipolar voltage. In the present invention, the voltage to be applied is defined as “alternating voltage or unipolar voltage whose voltage value gradually changes at least over time”. This is to exclude a voltage having a shape in which the voltage value increases / decreases in an instant, particularly a shape in which the voltage value increases / increases in an instant. An alternating voltage refers to a voltage that crosses GND, and a unipolar voltage refers to a voltage that does not cross GND.

  FIGS. 3A to 3F are diagrams for explaining an example 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 the ground potential in any 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. In contrast, 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. 3 (d), an alternating voltage consisting of a staircase wave is applied to the electrode 5. Furthermore, in the example of the present invention shown in FIG. 3E, an alternating voltage composed of a ramp wave is applied to the electrode 5. In the example of the present invention shown in FIG. 3F, an alternating voltage composed of a triangular wave is applied to the electrode 5.

  Among the display driving methods of the conventional example and the example of the present invention shown in FIGS. 3A to 3F, the case of the alternating voltage composed of pulsed rectangular waves of the conventional example shown in FIG. In the case of the alternating voltage consisting of the Sin wave of the example of the present invention shown in FIG. 3B, white display and black display were repeated at the same frequency, and the relationship between the density and the number of inversions was obtained. The results are shown in FIG. From the result of FIG. 4, when driven by the sine wave of the present invention example, the density drop due to repeated inversion in both black display and white display is small, whereas in the rectangular wave of the conventional example, the density drop decreases as the inversion is repeated. It can be seen that the decrease in black density is particularly significant. FIG. 5 shows the relationship between the number of inversions and the density difference during monochrome display in the same example as in FIG. From this, in the Sin wave of the present invention, the decrease in density difference during black and white display is small even when the inversion is repeated, whereas in the rectangular wave of the conventional example, the density difference during black and white display greatly decreases as the reversal is repeated. I understand.

  Next, according to the display driving method of the conventional example and the example of the present invention shown in FIGS. 3A to 3F, the results of measuring the density difference when white display and black display are repeated at the same frequency are shown in FIG. As shown in FIG. As can be seen from the results of FIGS. 6 and 7, the present invention has a small decrease in density difference during black and white display due to repeated inversion not only in the Sin wave but also in the trapezoidal wave, staircase wave, ramp wave, and triangular wave example. On the other hand, in the rectangular wave of the conventional example, it can be seen that the density difference at the time of black and white display greatly decreases as the inversion is repeated. Further, it can be seen that there is no significant difference between the Sin wave, the trapezoidal wave, the staircase wave, the ramp wave, and the triangular wave among the examples of the present invention.

  FIGS. 8A to 8F and FIGS. 9A to 9F are diagrams for explaining other examples of the display driving method of the conventional example and the example of the present invention, respectively. Here, in the conventional example shown in FIG. 8A, 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. The conventional example shown in FIG. 8 shows an example in which the voltage applied to the electrode is reversed from the example shown in FIG. Further, in the example of the present invention shown in FIG. 8C, an example in which a unipolar voltage composed of a Sin wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. In the invention example, the example shown in FIG. 8C and the example in which the voltage applied to the electrode is reversed are shown. Further, in the example of the present invention shown in FIG. 8 (e), an example in which a unipolar voltage composed of a trapezoidal wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 8 (f). The invention example shows an example in which the voltage applied to the electrode is reversed from the example shown in FIG.

  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. 9B. In the example of the present invention, the example shown in FIG. 9A and the example in which the voltage applied to the electrode is reversed are shown. Further, in the present invention example shown in FIG. 9C, an example in which a unipolar voltage composed of a ramp wave is applied to one electrode 5 and the other electrode 6 is connected to GND is shown in FIG. 9D. In the example of the invention, an example in which the voltage applied to the electrode is reversed from the example shown in FIG. 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). FIG. 9E shows an example in which the voltage applied to the electrode is reversed.

  Again, as in the example described above, white display and black at the same frequency are performed according to the display driving method of the conventional example and the example of the present invention shown in FIGS. 8 (a) to 8 (f) and FIGS. 9 (a) to 9 (f). As a result of repeating the display, in the examples of the present invention shown in FIGS. 8C and 8D and FIGS. 9A to 9F, the decrease in density difference during monochrome display due to repetitive inversion is small, whereas the conventional example. Then, it was found that the density difference at the time of black and white display greatly decreases as the inversion is repeated. Further, the degree of decrease in density difference during black and white display due to repeated reversal was almost the same for both alternating voltage and unipolar voltage.

  From the above results, it was found that according to the display driving method of the present invention, the panel display characteristics are not deteriorated, and the life of the number of inversions and the contrast are not adversely affected. Therefore, an image display device having preferable characteristics can be obtained by using the display driving method of the present invention.

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

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

  Particles can be produced by kneading and pulverizing the necessary resins, charge control agents, colorants, and other additives, or by polymerizing from monomers, or using existing particles as resins, charge control agents, colorants, etc. You may coat with an additive.

  Examples of resins, charge control agents, colorants, and other additives will be given below.

  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, fluorine resin, etc. Two or more types can be mixed, and polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, urethane resin, fluororesin are particularly suitable for controlling the adhesion with the substrate. .

  Examples of charge control agents include quaternary ammonium salt compounds, nigrosine dyes, triphenylmethane compounds, imidazole derivatives and the like in the case of imparting positive charges, and metal-containing azo compounds in the case of imparting negative charges. Examples thereof include dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

  Examples of the colorant include basic and acidic dyes such as nigrosine, methylene blue, quinoline yellow, and rose bengal.

  Examples of 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, cadmium orange, titanium yellow, Examples include bitumen, ultramarine blue, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, manganese ferrite black, cobalt ferrite black, copper powder, and aluminum powder.

  Further, in order to further improve the repeated durability here, it is effective to manage the stability of the resin constituting the particles, particularly the water absorption rate and the solvent insolubility rate.

  The water absorption of the resin constituting the particles to be 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. and 24 hours.

Regarding the solvent insolubility of the resin constituting the particles, the solvent insolubility of the particles represented by the following relational formula is preferably 50% or more, particularly 70% or more.
Solvent insolubility (%) = (B / A) × 100
(However, A represents the weight of the resin before dipping in the solvent, and B represents the weight after dipping the resin in a good solvent at 25 ° C. for 24 hours.)

  If the solvent insolubility is less than 50%, bleeding may occur on the particle surface during long-term storage, affecting the adhesion with the particle and hindering the movement of the particle, which may impair the image display durability.

  The solvent (good solvent) for measuring the solvent insolubility is methyl ethyl ketone, etc. for fluororesins, methanol, etc. for polyamide resins, methyl ethyl ketone, toluene, etc. for acrylic urethane resins, acetone, isopropanol, etc. for melamine resins, silicone As the resin, toluene or the like is preferable.

  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 in μm that the particle diameter is 50% larger than this and 50% smaller than this, and d (0.1) is the ratio of particles smaller than 10%. % Is a numerical value expressing the particle diameter in μm, and d (0.9) is a numerical value expressing the particle diameter in which 90% or less of the particles are less than this in μm.)

  By keeping Span within a range of 5 or less, the size of each particle is uniform, and uniform particle movement becomes possible.

  Furthermore, the average particle diameter d (0.5) of each particle is preferably 0.1 to 50 μm. If it is larger than this range, the sharpness on the display is lacking, and if it is smaller than this range, the cohesive force between the particles is too large, which hinders the movement of the particles.

  Furthermore, regarding the correlation of each particle, the ratio of the d (0.5) of the particle having the minimum diameter to the d (0.5) of the particle having the maximum diameter among the used particles is 50 or less, preferably 10 or less. Is important.

  Even if the particle size distribution Span is reduced, particles having different charging properties move in opposite directions, so that the particle sizes of the particles are close to each other, and each particle can be easily moved in the opposite direction by an equivalent amount. This is within this range.

  The particle size distribution and the particle size can be obtained from a laser diffraction / scattering method or the like. When laser light is irradiated onto particles to be measured, a light intensity distribution pattern of diffracted / scattered light is spatially generated, and this light intensity pattern has a corresponding relationship with the particle diameter, so that the particle diameter and particle diameter distribution can be measured. .

  The particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a measuring machine of Mastersizer 2000 (Malvern Instruments Ltd.), particles were introduced into a nitrogen stream, and attached analysis software (software based on volume reference distribution using Mie theory) The particle size and particle size distribution can be measured.

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

  The “powder fluid” in the present invention is a substance in an intermediate state of both fluid and particle characteristics that exhibits fluidity by itself without borrowing the force of gas or liquid. For example, liquid crystal is defined as an intermediate phase between a liquid and a solid, and has fluidity that is a characteristic of liquid and anisotropy (optical properties) that is a characteristic of solid (Heibonsha: Encyclopedia) . On the other hand, the definition of particle is an object with a finite mass even if it is negligible, and is said to be affected by gravity (Maruzen: Physics Encyclopedia). Here, even in the case of particles, there are special states of gas-solid fluidized bed and liquid-solid fluids. When gas is flowed from the bottom plate to the particles, upward force is applied to the particles according to the velocity of the gas. Is a gas-solid fluidized bed that is in a state where it can easily flow when it balances with gravity, and it is also called a liquid-solid fluidized state that is fluidized by a fluid (ordinary) Company: Encyclopedia). As described above, the gas-solid fluidized bed body and the liquid-solid fluid are in a state of using a gas or liquid flow. In the present invention, it has been found that a substance in a state of fluidity can be produced specifically without borrowing the force of such gas and liquid, and this is defined as powder fluid.

  That is, the pulverulent fluid in the present invention is in an intermediate state having both the characteristics of particles and liquid, as in the definition of liquid crystal (liquid and solid intermediate phase), and is the characteristic of the above-mentioned particles. It is a substance that is extremely unaffected and exhibits a unique state with high fluidity. 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 used as a dispersoid in the image display device of the present invention. Is.

  An image display device that is an object of the present invention encloses 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 opposing substrates, at least one of which is transparent Such a powder fluid can be easily and stably moved by a Coulomb force or the like by applying a low voltage.

  As described above, the powdered fluid is a substance in an intermediate state between the fluid and the particle, which exhibits fluidity by itself without borrowing the force of gas or liquid. This powder fluid can be in an aerosol state in particular, and in the image display device of the present invention, a solid substance is used in a state of relatively stably floating as a dispersoid in the gas.

  The range of the aerosol state is preferably such that the apparent volume of the pulverized fluid when it is floated is twice or more that when it is not suspended, more preferably 2.5 times or more, and particularly preferably 3 times or more. Although an upper limit is not specifically limited, It is preferable that it is 12 times or less.

  If the apparent volume of the pulverized fluid is less than twice that of the unfloating state, it is difficult to control the display, and if it is more than 12 times, the powder fluid will be overloaded when sealed in the device. Inconvenience in handling occurs. The apparent volume at the maximum floating time is measured as follows. That is, the powdered fluid is put into a closed container that allows the powdered fluid to permeate, and the container itself is vibrated or dropped to create a maximum floating state, and the apparent volume at that time is measured from the outside of the container. Specifically, in a container with a lid (trade name: iBoy: manufactured by ASONE Co., Ltd.) having a diameter (inner diameter) of 6 cm and a height of 10 cm, a powder fluid equivalent to 1/5 of the volume as a powder fluid when not floating. And 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 maximum floating time.

In addition, the image display device of the present invention preferably has a temporal change in the apparent volume of the powder fluid that satisfies the following formula.
V ₁₀ / V ₅ > 0.8
Here, V ₅ represents an apparent volume (cm ³ ) 5 minutes after the maximum floating time, and V ₁₀ represents an apparent volume (cm ³ ) 10 minutes after the maximum floating time. In the image display device of the present invention, the apparent volumetric change V ₁₀ / V ₅ of the powder fluid is preferably larger than 0.85, and more preferably larger than 0.9. When V ₁₀ / V ₅ is 0.8 or less, it becomes the same as when ordinary so-called particles are used, and it becomes impossible to ensure the effect of high-speed response and durability as in the present invention.

  Moreover, the average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and particularly preferably 0.9 to 8 μm. . If it is smaller than 0.1 μm, it is difficult to control the display, and if it is larger than 20 μm, it is possible to display but the concealment rate is lowered and it is difficult to make the device thin. The average particle diameter (d (0.5)) of the particulate material constituting the powder fluid is the same as d (0.5) in the next particle diameter distribution Span.

The particle substance constituting the powder fluid preferably has a particle size distribution span shown by the following formula of less than 5, more preferably less than 3.
Particle size distribution Span = (d (0.9) -d (0.1)) / d (0.5)
Here, d (0.5) is a numerical value expressed in μm of the particle diameter that 50% of the particulate material constituting the powder fluid is larger than this and 50% is smaller than this, and d (0.1) is less than this. A numerical value in which the ratio of the particle substance constituting the powder fluid is 10%, expressed in μm, and d (0.9) is the particle diameter in which the particulate substance constituting the powder fluid is 90% μm It is a numerical value expressed by By setting the particle size distribution Span of the particulate material constituting the powder fluid to 5 or less, the sizes are uniform and uniform powder fluid movement is possible.

  The particle size distribution and particle size of the particulate material constituting the above powder fluid can be obtained from a laser 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 this light intensity pattern has a corresponding relationship with the particle diameter, so the particle diameter and particle diameter distribution are measured. it can. This particle size and particle size distribution are obtained from a volume-based distribution. Specifically, using a Mastersizer 2000 (Malvern Instruments Ltd.) measuring machine, a powdered fluid was introduced into a nitrogen stream, and attached analysis software (software based on volume reference distribution using Mie theory) Measurements can be made.

  Preparation of powder fluid can be done by kneading and pulverizing the necessary resin, charge control agent, colorant, and other additives, or by polymerization from monomers, and adding existing particles to resin, charge control agent, colorant, and other It may be coated with an agent. Hereinafter, the resin, charge control agent, 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, and fluorine resin. Two or more types can also be mixed. In particular, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, urethane resin, and fluororesin are preferable from the viewpoint of controlling the adhesive force with the substrate.

  Examples of charge control agents include quaternary ammonium salt compounds, nigrosine dyes, triphenylmethane compounds, imidazole derivatives and the like in the case of imparting positive charges, and metal-containing azo compounds in the case of imparting negative charges. Examples thereof include dyes, salicylic acid metal complexes, and nitroimidazole derivatives.

  Examples of the colorant include basic and acidic dyes such as nigrosine, methylene blue, quinoline yellow, and rose bengal.

  Examples of 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, cadmium orange, titanium yellow, Examples include bitumen, ultramarine, cobalt blue, cobalt green, cobalt violet, iron oxide, carbon black, copper powder, and aluminum powder.

  However, even if such a material is kneaded and coated without any ingenuity, a powder fluid that shows an aerosol state cannot be produced. The production method of the powder fluid showing the aerosol state is not clear, but is exemplified as follows.

  First, it is appropriate to fix inorganic fine particles having an average particle diameter of 20 to 100 nm, preferably 20 to 80 nm, to the surface of the particulate material constituting the powder fluid. Furthermore, it is appropriate that the inorganic fine particles are treated with silicone oil. Here, examples of the inorganic fine particles include silicon dioxide (silica), zinc oxide, aluminum oxide, magnesium oxide, cerium oxide, iron oxide, and copper oxide. The method of fixing the inorganic fine particles is important. For example, using a hybridizer (manufactured by Nara Machinery Co., Ltd.) or mechanofusion (manufactured by Hosokawa Micron 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 manage the stability of the resin constituting the powder fluid, particularly the water absorption rate and the solvent insolubility rate. The water absorption rate of the resin constituting the powder fluid to be 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 condition is 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 70% or more.
Solvent insolubility (%) = (B / A) × 100
(However, A represents the weight of the resin before dipping in the solvent, and B represents the weight after dipping the resin in a good solvent at 25 ° C. for 24 hours.)

  If this solvent insolubility is less than 50%, bleeding occurs on the surface of the particulate material that constitutes the powder fluid during long-term storage, which affects the adhesion with the powder fluid and hinders the movement of the powder fluid, resulting in improved image display durability. May cause problems. The solvent (good solvent) for measuring the solvent insolubility is methyl ethyl ketone, etc. for fluororesins, methanol, etc. for polyamide resins, methyl ethyl ketone, toluene, etc. for acrylic urethane resins, acetone, isopropanol, etc. for melamine resins, silicone resins, etc. In this case, toluene or the like is preferable.

  Moreover, about the filling amount of a particle group or powder fluid, the volume occupation rate of a particle group or powder fluid is 5-70 vol% of the space | gap part between opposing board | substrates, Preferably it is 5-60 vol%, More preferably, it is 5 It is preferable to adjust so that it may become 55 vol%. When the volume occupancy of the particle group or the powder fluid is less than 5 vol%, a clear image display cannot be performed, and when it is greater than 70 vol%, the particle group or the powder fluid is difficult to move. Here, the spatial volume refers to a volume capable of being filled with a so-called particle group or powder fluid excluding the occupied portion of the partition wall 4 and the device seal portion from the portion sandwiched between the opposing substrate 1 and substrate 2. .

  Next, the substrate will be described.

  At least one of the substrate 1 and the substrate 2 is a transparent substrate capable of confirming the color of particles or powder fluid from the outside of the apparatus, and a material having high visible light transmittance and good heat resistance is preferable. The presence or absence of flexibility is appropriately selected depending on the application. For example, it is not flexible for applications such as materials that are flexible for applications such as electronic paper, mobile phones, PDAs, and portable devices such as notebook computers. Material is used.

  Examples of the substrate material include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, and polycarbonate, and inorganic sheets such as glass and quartz.

  The substrate thickness is suitably 2 to 5000 μm, preferably 5 to 1000 μm. If it is too thin, it will be difficult to maintain strength and spacing uniformity between the substrates, and if it is too thick, the display function will be sharp and the contrast will decrease. Especially in the case of electronic paper applications.

  Electrode forming materials for electrodes provided on the substrate include metals such as aluminum, silver, nickel, copper, and gold, conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide, polyaniline, and polypyrrole. Examples thereof include conductive polymers such as polythiophene, which are appropriately selected and used. As a method for forming an electrode, a method of forming the above-described materials into a thin film by sputtering, vacuum deposition, CVD (chemical vapor deposition), coating, or the like, or mixing a conductive agent with a solvent or a synthetic resin binder. The method of apply | coating is used. The electrode provided on the viewing side substrate needs to be transparent, but the electrode provided on the back side substrate does not need to be transparent. In any case, the above-mentioned material that is conductive and capable of pattern formation can be suitably used.

  Next, the partition will be described.

  The shape of the partition wall of the present invention is appropriately set appropriately depending on the size of the particles involved in the display or the size of the powder fluid, and is not generally limited, but the partition wall width is 10 to 1000 μm, preferably 10 to 500 μm. The thickness is adjusted to 10 to 500 μm, preferably 10 to 200 μm.

  Further, in forming the partition wall, a both-rib method in which ribs are formed after forming ribs on both opposing substrates and a one-rib method in which ribs are formed only on one substrate can be considered. Is also applicable.

  As shown in FIG. 10, the display cells formed by the ribs are exemplified by a square shape, a triangular shape, a line shape, a circular shape, and a hexagonal shape as viewed from the plane of the substrate. And a mesh shape. It is better to make the portion corresponding to the cross section of the partition wall visible from the display side (the area of the frame portion of the display cell) as small as possible, and the sharpness of the image display increases. 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, the photolithography method using a resist film is preferably used.

  The image display device of the present invention includes a display unit of a mobile device such as a notebook computer, a PDA, a mobile phone, and a handy terminal, an electronic paper such as an electronic book and an electronic newspaper, a signboard, a poster, a bulletin board such as a blackboard, a calculator, a household appliance, It is suitably used for display parts for automobile goods, card display parts such as point cards and IC cards, electronic advertisements, electronic POPs, electronic price tags, electronic musical scores, and display parts for RF-ID devices.

Claims (9)

This is a display driving method in an image display device in which a particle group is enclosed between opposing substrates at least one of which is transparent, an electric field is applied to the particle group from two types of electrodes having different potentials, and the particles are moved by flying. One electrode potential is set to the ground potential, and an image is displayed by applying a voltage to the other electrode by applying an alternating voltage or a unipolar voltage whose voltage value gradually changes over time. And a display driving method. The display driving method according to claim 1, wherein the alternating voltage or the unipolar voltage has a sine wave shape and the voltage value gradually changes at least in the course of increasing with time. 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 in at least an increasing process with time. 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 the voltage value gradually changes at least in an increasing process with time. This is a display driving method in an image display device in which a powder fluid is sealed between opposing substrates, at least one of which is transparent, an electric field is applied to the powder fluid from two types of electrodes having different potentials, and the powder fluid is moved to display an image. One electrode potential is set to the ground potential, and an image is displayed by applying a voltage to the other electrode by applying an alternating voltage or a unipolar voltage whose voltage value gradually changes over time. And a display driving method. 6. The display driving method according to claim 5, wherein the voltage value of the alternating voltage or unipolar voltage gradually changes in the form of a sine wave and increases at least with time. 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 in at least an increasing process with time. 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 an increasing process with time. An image display device that displays an image according to the display driving method according to claim 1.

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