JP2005331903A - Driving method of image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method of an image display device for eliminating lowering and irregularities in the contrast caused by crosstalks. <P>SOLUTION: The driving method of the image display device seals at least two kinds of image display media of a first color and a second color between two facing substrates, at least one of which is transparent, and displays images by giving an electric field to the image display media from an electrode and moving the image display media. A pulse-like voltage, consisting of a plurality of voltages with a drive voltage being in a switching-on state and a voltage of a threshold or lower, in which the image display media being in a switching-off state start moving is applied as the drive voltage applied on the electrode for generating the electric field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, at least two kinds of image display media of a first color and a second color are sealed between two opposing substrates at least one of which is transparent, and an electric field is applied from the electrodes to the image display media. The present invention relates to a method for driving an image display device that displays an image by moving an image display medium.

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

  Compared to LCDs, these conventional technologies have advantages such as a wide viewing angle close to that of ordinary printed materials, low power consumption, and a memory function. It is considered as a technology that can be used for mobile phones, and is expected to expand to image display for portable terminals, electronic paper, and the like. Particularly recently, an electrophoretic method in which a dispersion liquid composed of dispersed particles and a colored solution is encapsulated and disposed between opposing substrates has been proposed and is expected.

  However, the electrophoresis method has a problem that the response speed becomes slow due to the viscous resistance of the liquid because the particles migrate in the liquid. Furthermore, since particles with high specific gravity such as titanium oxide are dispersed in a solution with low specific gravity, it is easy to settle, and it is difficult to maintain the stability of the dispersed state, and there is a problem of lack of image repetition stability. . Even when microencapsulation is performed, the cell size is set to the microcapsule level, and the above-described drawbacks are hardly made to appear, and the essential problems are not solved at all.

  On the other hand, a method in which conductive particles and a charge transport layer are incorporated into a part of a substrate without using a solution is proposed instead of an electrophoresis method using behavior in a solution (see, for example, Non-Patent Document 1). ). However, the structure is complicated because the charge transport layer and further the charge generation layer are arranged, and it is difficult to inject the charges into the conductive particles.

As one method for solving the above-mentioned various problems, an image display medium made of a particle group or a powder fluid is sealed between opposing substrates at least one of which is transparent, and an electric field is applied to the image display medium, whereby the image display medium There is known an image display device that displays an image by moving the.
趙 Kuniori and three others, “New Toner Display Device (I)”, July 21, 1999, Annual Meeting of the Imaging Society of Japan (83 times in total) “Japan Hardcopy'99” Proceedings, p.249-252

  In the image display device using the image display medium described above, a row electrode composed of a plurality of electrodes extending in the row direction on one substrate side, and a column electrode composed of a plurality of electrodes extending in the column direction on the other substrate side. On the other hand, when displaying an image of one screen by scanning from one end of the row electrode to the other end and applying a voltage, crosstalk occurs when driving to display a matrix or when driving a segment dynamically. There was a problem that occurred.

  Crosstalk is a phenomenon in which signals from other lines are originally mixed in the telephone, but in this case, crosstalk is actually affected by other rows even though the column electrode is not selected. This is a phenomenon in which a different image is displayed. In the display by the passive matrix driving of the image display device using the image display medium described above, a voltage for holding the display is applied to the non-selected row of the column electrode. Due to the influence of the holding voltage applied by the number of rows of the column electrodes, the contrast is lowered, and depending on the display pattern, light and shade are generated in the image display, resulting in unevenness.

  An object of the present invention is to provide a method for driving an image display apparatus that can eliminate the above-described problems and eliminate the reduction in contrast and the unevenness of shading caused by crosstalk.

According to the driving method of the image display device of the present invention, at least two kinds of image display media of the first color and the second color are sealed between two opposing substrates, at least one of which is transparent, and an image is formed from the electrode. In a driving method of an image display device in which an electric field is applied to a display medium and an image is displayed by moving the image display medium, a driving voltage applied to an electrode to generate an electric field is an on-state driving voltage and an off-state. A pulse-like voltage composed of a plurality of voltages with a voltage equal to or lower than a threshold value at which a certain image display medium starts moving is applied. Here, the drive voltage V is larger than the threshold voltage V ₁ (V> V ₁ > V ₀ : V ₀ is a voltage equal to or lower than the threshold).

  As a preferred example of the driving method of the image display device of the present invention, the duty ratio of the pulse voltage (= pulse width / (pulse width + off state time)) is 0.9 or less, and the off state time. May be 0.1 msec or more.

  According to the driving method of the image display device of the present invention, the driving voltage applied to the electrode to generate the electric field is equal to or lower than the threshold value at which the driving voltage in the on state and the image display medium in the off state start moving. By applying a pulse-like voltage composed of a plurality of voltages with the voltage, it is possible to eliminate a decrease in contrast and unevenness in density due to crosstalk.

  First, a basic configuration of an image display panel included in an image display device that is an object of the present invention will be described. In the image display panel used in the present invention, an electric field is applied to an image display medium (particle group or powder fluid) sealed between two opposing substrates. Along with the applied electric field direction, the image display medium charged at a low potential toward the high potential side is attracted by Coulomb force, and the image display medium charged at a high potential toward the low potential side. Images are displayed by being attracted by a Coulomb force or the like and reciprocatingly moving due to a change in the electric field direction due to the potential switching. Therefore, it is necessary to design the image display panel so that the image display medium moves uniformly and can maintain stability during repetition or storage. Here, when a particle group is used as the image display medium, the force applied to the particles is not only the force attracted by the Coulomb force between the particles, but also the electric image force between the electrode and the substrate, the intermolecular force, the liquid crosslinking force, Gravity is considered.

An example of an image display panel used in the image display device of the present invention will be described with reference to FIGS. 1 (a) and (b) to FIGS. 2 (a) and 2 (b).
In the example shown in FIGS. 1A and 1B, two or more different types of particles 3 (here, white particles 3W and black particles 3B) are added from electrodes provided outside the substrates 1 and 2. Depending on the applied electric field, the substrate is moved perpendicularly to the substrates 1 and 2 so that the black particles 3B are visually recognized by the observer and black display is performed, or the white particles 3W are visually recognized by the observer and white display is performed. ing. In the example shown in FIG. 1B, in addition to the example shown in FIG. 1A, partition walls 4 are provided, for example, in a lattice shape between the substrates 1 and 2 to define display cells.
In the example shown in FIGS. 2A and 2B, two or more kinds of particles 3 having different colors (here, white particles 3W and black particles 3B are shown) are provided on the substrate 1 and the electrode 5 provided on the substrate 1, respectively. Depending on the electric field generated by applying a voltage between the electrode 6 and the electrode 6, the substrate is moved perpendicularly to the substrates 1 and 2 so that the black particles 3B are visually recognized by the observer, or a white display is performed. The particle 3W is visually recognized by an observer and white display is performed. In the example shown in FIG. 2B, in addition to the example shown in FIG. 2A, partition walls 4 are provided, for example, in a lattice form between the substrates 1 and 2 to define display cells.
The above description can be similarly applied to the case where the white particles 3W are replaced with the white powder fluid and the black particles 3B are replaced with the black powder fluid.

The feature of the driving method of the image display device according to the present invention is that, in the image display device having the above-described configuration, the drive voltage V that is in the on state has been continuously applied for image display in the past, but is in the on state. The point is to apply a pulsed voltage that reciprocates between the driving voltage V and a voltage V _{0 that} is equal to or lower than a threshold value at which the image display medium in the off state starts to move. In other words, the crosstalk is reduced by controlling the off time using a new concept of the off state time (= off time) in which the voltage V ₀ below the threshold is applied. At this time, V ₀ and V can take a plurality of values, and may be gradually changed.

FIG. 3 is a diagram showing an example of a pulse voltage using the driving method of the image display apparatus of the present invention. In the example shown in FIG. 3, the pulse voltage used in the present invention is a pulse using a drive voltage that is in an on state and a voltage that is equal to or less than a threshold value (V ₁ ) at which the image display medium that is in an off state starts to move. Indicated. As a preferred example of the present invention, the duty ratio of the pulse voltage (= pulse width / (pulse width + off state time)) is 0.9 or less, and the off state time is 0.1 msec or more. There is. Both examples will be described in detail in examples described later.

  Hereinafter, each member which comprises the image display apparatus used as the object of this invention is demonstrated.

  As for the substrate, at least one of the substrates is a transparent substrate 2 on which the color of the image display medium can be confirmed from the outside of the apparatus, and a material having high visible light transmittance and good heat resistance is preferable. The substrate 1 may be transparent or opaque. Examples of substrate materials include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, polycarbonate, polyimide, and acrylic, flexible materials such as metal sheets, and flexible materials such as glass and quartz. There are no inorganic sheets. The thickness of the substrate is preferably from 2 to 5000 μm, more preferably from 5 to 2000 μm. If it is too thin, it will be difficult to maintain the strength and the uniform spacing between the substrates, and if it is thicker than 5000 μm, a thin image display device will be obtained. There is an inconvenience.

  Regarding the electrode provided on each substrate side, the electrode 6 provided on the side of the substrate 2 that needs to be transparent on the viewing side is formed of a conductive material that is transparent and can be patterned. For example, aluminum, silver, nickel Examples include metals such as copper and gold, transparent conductive metal oxides such as ITO, indium oxide, conductive tin oxide, and conductive zinc oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. A method of forming a thin film by a method, a CVD (chemical vapor deposition) method, a coating method, or the like, or a method of applying a conductive agent mixed with a solvent or a synthetic resin binder is used. Note that the electrode thickness is not particularly limited as long as the conductivity can be secured and the light transmittance is not hindered, and is preferably 3 to 1000 nm, preferably 5 to 400 nm. The material and thickness of the electrode 5 provided on the substrate 1 side are the same as those of the electrode 6 described above, but need not be transparent. In this case, the external voltage input may be superimposed with direct current or alternating current.

  The shape of the partition 4 provided as necessary is optimally set depending on the type of the image display medium involved in the display, and is not limited in general, but the width of the partition is 2 to 100 μm, preferably 3 to 50 μm. Is adjusted to 10 to 500 μm, preferably 10 to 200 μm. In forming the partition walls, a both-rib method in which ribs are formed on each of the opposing substrates and then bonded, and a one-rib method in which ribs are formed only on one substrate are conceivable. In the present invention, any method is preferably used.

  As shown in FIG. 4, the display cells formed by the partition walls made up of these 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. The shape and the mesh shape are exemplified. 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.

  Next, the particles used as the image display medium in the image display device of the present invention will be described. The particles can contain a charge control agent, a colorant, an inorganic additive, and the like, if necessary, in the resin as the main component, as in the conventional case. Examples of resins, charge control agents, colorants, and other additives will be given below.

  Examples of the resin include urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, acrylic fluororesin, silicone resin, acrylic silicone resin, epoxy resin, polystyrene resin, styrene Acrylic resin, polyolefin resin, butyral resin, vinylidene chloride resin, melamine resin, phenol resin, fluororesin, polycarbonate resin, polysulfone resin, polyether resin, polyamide resin and the like can be mentioned, and two or more kinds can be mixed. In particular, acrylic urethane resin, acrylic silicone resin, acrylic fluororesin, acrylic urethane silicone resin, acrylic urethane fluororesin, fluororesin, and silicone resin are suitable from the viewpoint of controlling the adhesive force with the substrate.

  The charge control agent is not particularly limited. Examples of the negative charge control agent include salicylic acid metal complexes, metal-containing azo dyes, metal-containing oil-soluble dyes (including metal ions and metal atoms), and quaternary ammonium salt systems. Examples thereof include compounds, calixarene compounds, boron-containing compounds (benzyl acid boron complexes), and nitroimidazole derivatives. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane compounds, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and the like. In addition, metal oxides such as ultrafine silica, ultrafine titanium oxide and ultrafine alumina, nitrogen-containing cyclic compounds such as pyridine and derivatives and salts thereof, various organic pigments, resins containing fluorine, chlorine, nitrogen, etc. are also charged. It can also be used as a control agent.

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

Yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of the orange colorant include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

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.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment.

  The particles of the present invention preferably have an average particle diameter d (0.5) in the range of 0.1 to 50 μm and are uniform and uniform. If the average particle diameter d (0.5) is larger than this range, the display is not clear. If the average particle diameter d (0.5) is smaller than this range, the cohesive force between the particles becomes too large, which hinders the movement of the particles.

Furthermore, in the present invention, regarding the particle size distribution of each particle, the particle size distribution Span represented by the following formula is 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 size is 50% larger than this and 50% smaller than this, and d (0.1) is a particle whose ratio is 10% or less. (Numerical value expressed in μm, and d (0.9) is a numerical value expressed in μm for a particle diameter of 90% or less.)
By keeping Span within a range of 5 or less, the size of each particle is uniform, and uniform particle movement becomes possible.

  Furthermore, regarding the correlation between the particles, the ratio of d (0.5) of the particles having the minimum diameter to d (0.5) of the particles having the maximum diameter among the used particles is set to 50 or less, preferably 10 or less. It is essential. Even if the particle size distribution Span is reduced, particles with different charging characteristics move in opposite directions, so that the particle size is close to each other and each particle can be easily moved in the opposite direction by the 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. .
Here, the particle size and particle size distribution in the present invention are obtained from a volume-based distribution. Specifically, using a Mastersizer2000 (Malvern Instruments Ltd.) measuring instrument, put particles into a nitrogen stream and use the attached analysis software (software based on volume-based distribution using Mie theory). The diameter and particle size distribution can be measured.

  The charge amount of the particles naturally depends on the measurement conditions, but the charge amount of the particles in the image display panel almost depends on the initial charge amount, the contact with the partition wall, the contact with the substrate, the charge decay with the elapsed time, In particular, it was found that the saturation value of the charging behavior of the particles is the dominant factor.

  As a result of intensive studies, the present inventors have found that by using the same carrier particles in the blow-off method and measuring the charge amount of the particles, it is possible to evaluate the range of the appropriate charging characteristic value of the particles used for the image display medium. It was.

  Next, the powder fluid used as the image display medium in the image display device of the present invention will be described. In addition, about the name of the powder fluid used with the image display apparatus of this invention, the present applicant has acquired the right of "electronic powder fluid (trademark)".

  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.

The image display panel which is an object of the present invention encloses a powder fluid exhibiting high fluidity in an aerosol state in which solid particles are stably suspended as a dispersoid in a gas between opposite 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 pulverized fluid used in the present invention is a substance in the intermediate state of both fluid and particle characteristics that 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 floating is at least twice, more preferably 2.5 times or more, and particularly preferably three times or more that when it is not floating. 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 an airtight container that allows the powdered fluid to permeate, 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.

Moreover, in this invention, what the time change of the apparent volume of a powder fluid satisfy | fills following Formula is preferable.
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 time change V ₁₀ / V ₅ of the apparent volume of the powder fluid is preferably larger than 0.85, particularly 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, the display is not clear. 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 represented 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 a particle diameter in which 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 becomes possible.

  The above particle size distribution and particle size 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 Mastersizer2000 (Malvern Instruments Ltd.) measuring machine, the powdered fluid was introduced into the nitrogen stream, and the 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.

  As the colorant, various organic or inorganic pigments and dyes as exemplified below can be used.

Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon and the like.
Examples of blue colorants include C.I. I. Pigment blue 15: 3, C.I. I. Pigment Blue 15, Bituminous Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Indanthrene Blue BC and the like.
Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment Red 2 etc.

Yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral first yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment Yellow 12 etc.
Examples of green colorants include chrome green, chromium oxide, pigment green B, C.I. I. Pigment Green 7, Malachite Green Lake, Final Yellow Green G, etc.
Examples of the orange colorant include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment Orange 31 etc.
Examples of purple colorants include manganese purple, first violet B, and methyl violet lake.
Examples of white colorants include zinc white, titanium oxide, antimony white, and zinc sulfide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white. Examples of various dyes such as basic, acidic, disperse, and direct dyes include nigrosine, methylene blue, rose bengal, quinoline yellow, and ultramarine blue.

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.
These pigments and inorganic additives can be used alone or in combination. Of these, carbon black is particularly preferable as the black pigment, and titanium oxide is preferable as the white pigment.

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 powdered 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 for fixing the inorganic fine particles is important. For example, using a hybridizer (manufactured by Nara Machinery Co., Ltd.), 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.

Furthermore, in the present invention, it is important to manage the gas in the gap surrounding the image display medium between the substrates, which contributes to improved display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, and more preferably 35% RH or less with respect to the humidity of the gas in the gap.
This void portion refers to the electrodes 5 and 6 and the image display medium (particles) from the portion sandwiched between the opposing substrate 1 and substrate 2 in FIGS. 1 (a), 1 (b) to 2 (a), (b). It refers to the gas portion in contact with the so-called image display medium, excluding the group or powdered fluid 3) occupied portion, the partition 4 occupied portion (if present), and the device seal portion.
The gas in the gap is not limited as long as it is in the humidity region described above, but dry air, dry nitrogen, dry argon, dry helium, dry carbon dioxide, dry methane, and the like are preferable. This gas needs to be sealed in the apparatus so that the humidity is maintained. For example, the image display medium is filled and the substrate is assembled in a predetermined humidity environment. It is important to apply a sealing material and a sealing method to prevent the above.

The distance between the substrates in the image display panel provided in the image display device of the present invention is not limited as long as the image display medium can be moved and the contrast can be maintained, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm. .
The volume occupancy of the image display medium in the space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of the image display medium is hindered. If it is less than 5%, the contrast tends to be unclear.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Contrast and drive voltage margin>
The margin between contrast and driving voltage, which is an index for evaluating the driving method of the image display device of the present invention, was defined by conducting the following experiment.

1. Experimental method In order to measure the influence of crosstalk, the simplest test pattern was displayed by various driving methods, and the reflectance was measured by changing the voltage.
1.1. Test Pattern FIG. 5 shows a test pattern displayed by passive matrix driving. In FIG. 5, (a) is a black solid region, (b) is a white solid region, and (c) to (f) are regions affected by crosstalk. Details are given in the next section.

1.2. Explanation of Typical Reflectance-Applied Voltage Characteristics FIG. 6 shows a display screen when a test pattern is displayed, and FIG. 7 shows typical reflectance-applied voltage characteristics measured. As shown in FIG. 6, 5 × 5 measurement points were assigned, and the reflectance at each point when the test pattern was displayed by gradually applying the write voltage from 0 V was measured. Of these, the value obtained by averaging the portions enclosed by the squares is taken as the reflectance of each region, and in FIG. 7, a characteristic curve of applied voltage on the horizontal axis and reflectance on the vertical axis is drawn. Hereinafter, each line shown in FIG. 7 will be described. The matrix drive in this experiment was performed as shown in Table 1 below. In the following description, the potential applied to the column-side electrode is represented as +, and the potential difference is represented. For example, if a voltage of 0V is applied to the column and a voltage of 50V is applied to the row, the potential difference between the electrodes is -50V.

(1) Region 1-1
A voltage of 0 (V) is applied when the line is selected, and a crosstalk voltage of -V / 2 is applied in the first half of the scan and V / 2 in the second half when the line is not selected. This area is selected in the first half of the scan, but when the applied voltage increases, it is greatly affected by the crosstalk in the second half of the scan and shifts to black despite white display.

(2) Region 1-5
When a line is selected, a V voltage is applied. When a line is not selected, a crosstalk voltage of −V / 2 is applied in the first half of the scan and V / 2 is applied in the second half. This region selected in the second half of the scan is hardly affected by crosstalk, and therefore shows the same tendency as the region 5.

(3) Region 2-1
When a line is selected, a V voltage is applied. When a line is not selected, a crosstalk voltage of V / 2 is applied in the first half of the scan and -V / 2 is applied in the second half. This area selected in the first half of the scan is greatly affected by crosstalk in the second half of the scan when the applied voltage increases, and shifts to white regardless of black display.

(4) Region 2-5
When the line is selected, a voltage of 0 (V) is applied. When the line is not selected, a crosstalk voltage of V / 2 is applied in the first half of the scan and -V / 2 is applied in the second half. This area is selected in the second half of the scan, but unlike the area 1-5, it is selected at 0 (V), so that the influence of crosstalk received in the first half remains. For this reason, when the applied voltage increases, the color shifts to black slightly despite white display.

(5) Region 4
A voltage of 0 (V) is applied when the line is selected, and a voltage of −V / 2 is always applied when the line is not selected. This region remains in white display, which serves as a white reference for each display method.

(6) Region 5
This region where a voltage of V is applied when the line is selected and a voltage of V / 2 is always applied when the line is not selected remains black, and this is the black reference for each display method.

2. Evaluation method Contrast is an important evaluation item for halftone display. The most important area among the areas is the area 2-1. No matter how low the minimum black reflectance is, the area 2-1 is shifted to the white side due to the influence of crosstalk, so the contrast is limited to the reflectance of this area. Although the area 1-1 is also greatly affected by the crosstalk, the change due to the crosstalk occurs on the higher voltage side than the area 2-1. Since the purpose is to obtain a good display at a lower voltage in order to reduce power consumption, the crosstalk in the area 1-1 can be ignored.
Here, the evaluation method in this experiment is defined as follows.

(1) Contrast (line 11 in FIG. 7)
The normal contrast is represented by the ratio between the maximum reflectance of white and the minimum reflectance of black. In this experiment, it was defined as follows in consideration of the matters described above. That is, the contrast was defined as the ratio of the reflectance of the lowest (highest: black erased white writing) level of the line 2-1 to the reflectance of the white (black: black erased white writing) display at that time. A higher contrast is better.

(2) Drive voltage margin (line 12 in FIG. 7)
The drive voltage margin is 10% higher than the difference between the reflectance of the lowest (highest: black erased white) level on line 2-1 and the reflectivity of the white (black: black erased white) display at that time. It was defined as the width of the line 2-1. A wider drive voltage margin is better.

<Pulse drive voltage>
The pulsed drive voltage was examined using the contrast and the drive voltage margin defined as described above as indices. In this experiment, the voltage V ₀ = 0 (V) which is equal to or lower than the threshold value was set.

(1) Duty ratio First, as the driving voltage, three kinds of pulse-like voltages of 4 pulses with a pulse width of 0.2 msec, 8 pulses with a pulse width of 0.08 msec, and 8 pulses with a pulse width of 0.2 msec are used. Contrast was measured when the duty ratio of the pulse voltage was varied. The results are shown in FIG. In FIG. 8, the duty ratio on the horizontal axis is shown as a logarithm. From the results of FIG. 8, it can be seen that when the duty ratio exceeds 0.9, the contrast is lowered, and it is preferable that the duty ratio is 0.9 or less.

  Next, as the driving voltage, three kinds of pulse voltages of 4 pulses with a pulse width of 0.2 msec, 8 pulses with a pulse width of 0.08 msec, and 8 pulses with a pulse width of 0.2 msec are used, and the duty of each pulse voltage is used. Margins were measured when the ratio was varied. The results are shown in FIG. From the results of FIG. 9, it can be seen that the smaller the duty ratio, the larger the margin, and the smaller the duty ratio, the better.

(2) About off time Based on the data obtained about the relationship between the duty ratio and the contrast or the margin, the relationship between the off time and the margin was examined. The results are shown in FIG. From the results of FIG. 10, it can be seen that the off-time is less than 0.1 msec, the margin becomes small, and the off-time is preferably 0.1 msec or more.

  An image display device of the present invention includes a display unit of a mobile device such as a notebook computer, PDA, mobile phone, and handy terminal, electronic paper such as an electronic book and an electronic newspaper, a bulletin board such as a signboard, a poster, and a blackboard, a calculator, a household appliance, It is suitably used for display parts for automobile supplies, 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.

(A), (b) is a figure which shows an example of the image display apparatus using the particle | grains of this invention, respectively. (A), (b) is a figure which shows the other example of the image display apparatus using the particle | grains of this invention, respectively. It is a figure which shows an example of the pulse voltage using the drive method of the image display apparatus of this invention. It is a figure which shows an example of the shape of the partition in the image display panel used for the image display apparatus of this invention. It is a figure which shows an example of the test pattern displayed by passive matrix drive. It is a figure which shows a display screen and a measurement area | region when a test pattern is actually displayed. It is a graph which shows the relationship between the applied voltage measured in each area | region shown in FIG. 6, and a reflectance. It is a graph which shows the relationship between the duty ratio and contrast in a pulse-shaped drive voltage. It is a graph which shows the relationship between the duty ratio in a pulse-shaped drive voltage, and a margin. It is a graph which shows the relationship between the OFF time and a margin in a pulse-like drive voltage.

Explanation of symbols

1, 2 Substrate 3 Particles (powder fluid)
3W white particles (white powder fluid)
3B Black particles (black powder fluid)
4 Bulkhead 5, 6 Electrode

Claims (3)

  At least two kinds of image display media of the first color and the second color are sealed between two opposing substrates, at least one of which is transparent, and an electric field is applied from the electrodes to the image display medium. In the driving method of the image display apparatus for displaying an image by moving the threshold, the driving voltage applied to the electrode for generating an electric field is a threshold at which the driving voltage in the on state and the image display medium in the off state start to move. A driving method of an image display device, wherein a pulsed voltage composed of a plurality of voltages with a voltage equal to or lower than a value is applied.   2. The method of driving an image display device according to claim 1, wherein the duty ratio of the pulse voltage (= pulse width / (pulse width + time in off state)) is 0.9 or less.   2. The method for driving an image display device according to claim 1, wherein the off-state time is 0.1 msec or more.

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