JP2005234516A - Panel for image display, and image display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive panel for image display whose image contrast is not reduced even if the panel is repetitively used and which has excellent durability by avoiding complicated influence on particles (or powdery fluid) in frictional charge characteristics and to provide an image display apparatus using the same. <P>SOLUTION: In the panel for image display wherein a plurality of cells 11 divided by partitions 4 are formed between two substrates 1 and 2 which are opposed to each other and at least one of which is transparent, at least two particle groups 3 or at least two powdery fluid groups 3 are encapsulated in the cells and the particle groups or the powdery fluid groups are moved to display an image by imparting an electric field to the particle groups or the powdery fluid groups, the inner surface of the cells in which at least the two particle groups or at least the two powdery fluid groups are to be encapsulated is coated with one material to form a coating layer 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display panel and an image display apparatus using the same, and in particular, a reversible image capable of repeatedly performing image display by utilizing particle flight movement or powder fluid movement by Coulomb force or the like. The present invention relates to an image display panel used in a display device and an image display device equipped with the image display panel.

  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 mobile 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.
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

  However, in these image display devices, there is a problem in that the image contrast is impaired due to the phenomenon that the encapsulated particles do not move while adhering gradually or the particles do not move while adhering to the partition wall when repeatedly used. Therefore, it was insufficient in terms of durability for repeated use.

  One of the causes is that there are multiple materials that make up the surrounding environment that comes in contact with the particles (or powder fluid) when they are moving, resulting in a complex influence on the frictional charging characteristics that the particles (or powder fluid) are subjected to. Conceivable.

  The object of the present invention is to solve the above-mentioned problems, avoid the complicated influence on the frictional charging characteristics that the particles (or powder fluid) receive, and the image contrast does not decrease even when used repeatedly, and has excellent durability. An object is to provide an inexpensive image display panel and an image display device using the panel.

  In the image display panel of the present invention, a plurality of cells partitioned by a partition wall are formed between two opposing substrates, at least one of which is transparent, and at least two kinds of particle groups or at least 2 are formed in the cells. An image display panel that encloses at least two types of powder fluid and applies an electric field to the particle group or powder fluid to move the particle group or powder fluid to display an image, and includes at least two types of particle groups Alternatively, the cell inner surface enclosing at least two kinds of powder fluids is formed by coating one kind of material.

  As a suitable example of the image display panel of the present invention, two kinds of particles (particle 1 and particle 2) or 2 having different optical reflectances contained in at least two kinds of particle groups or at least two kinds of powder fluids. The charged train of the types of powder fluid (powder fluid 1 and powder fluid 2) and the coating material forming the cell inner surface is in the order of particle 1 (or powder fluid 1) -coating material-particle 2 (or powder fluid 2). And two types of particles or two types of powder fluids having different optical reflectances contained in at least two or more types of particle groups or at least two or more types of powder fluids, and the cell inner surface is formed. In some cases, the charging characteristics (in order of the charge train) of the coating material to be measured are measured by the blow-off method using the same carrier particles.

  The image display apparatus of the present invention is characterized by mounting the image display panel having the above-described configuration.

  According to the image display panel of the present invention, the contact environment of particles (or powder fluid) formed of a plurality of materials such as a substrate material and a partition wall material is constituted by one kind of material, whereby particles (or powder fluid) ) To avoid the complicated influence on the triboelectric charging characteristics, and it is possible to obtain an inexpensive image display panel having excellent durability and an image display device using the same, in which the image contrast does not decrease even when used repeatedly. .

  First, the basic configuration of the image display panel of the present invention will be described. In the image display panel of the present invention, an electric field is applied to the particle group or the powder fluid by some means on the image display panel in which the particle group or the powder fluid is sealed between two opposing substrates. To the substrate part (or electrode part) charged at a high potential, particles or powder fluid charged at a low potential are attracted by Coulomb force or the like, and toward the substrate part (or electrode part) charged at a low potential. Thus, particles or powder fluid charged at a high potential are attracted by Coulomb force or the like, and the particles or powder fluid reciprocates between the substrates (or between the electrodes), thereby displaying an image.

  Therefore, it is necessary to design the image display panel so that the particle group or the powder fluid can move uniformly and maintain the stability during repetition or storage. Here, as the force applied to the particles or the powder fluid, in addition to the force attracted by the Coulomb force between the particles or the powder fluid, an electric image force with the electrode, an intermolecular force, a liquid cross-linking force, gravity and the like can be considered.

An example of the image display panel of the present invention will be described with reference to FIGS.
In the example shown in FIG. 1, two or more different types of particles 3 (here, white particles 3W and black particles 3B are shown) are connected to the substrates 1 and 2 according to the electric field applied from the outside of the substrates 1 and 2. The black particles 3B are moved vertically and the observer visually recognizes the black particles 3B, or the white particles 3W are visually recognized by the observer. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
In the example shown in FIG. 2, two or more kinds of particles 3 having different colors (here, white particles 3W and black particles 3B are shown) are placed between the electrode 5 provided on the substrate 1 and the electrode 6 provided on the substrate 2. Depending on the electric field generated by applying a voltage, the substrate is moved perpendicularly to the substrates 1 and 2 so that the black particles 3B are visually recognized by the observer, or black is displayed, or the white particles 3W are visually recognized by the observer. To display a white color. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
In the example shown in FIG. 3, according to the electric field which generate | occur | produces by applying the voltage between the electrode 5 and the electrode 6 which provided the particle | grains 3 (here white particle | grain 3W) of one type of color 3 on the board | substrate 1 in FIG. The white particles 3W are moved in the direction parallel to the substrates 1 and 2 and the white particles 3W are visually recognized by the observer, or the color of the electrode 6 or the substrate 1 is visually recognized by the observer. The color is displayed. A partition cell 4 is provided between the substrates 1 and 2 in a lattice shape, for example, to define a display cell.
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.

  FIG. 4 and FIG. 5 are diagrams for explaining characteristic portions of the image display panel of the present invention. 4 shows an example using white particles 3W and black particles 3B as at least two kinds of particles 3, and FIG. 5 shows an example using white powder fluid 3W and black powder fluid 3B as at least two kinds of powder fluid 3. Indicates. In the example shown in FIG. 4 and FIG. 5, the image display panel of the present invention has at least two or more characteristic portions (here, two types of white particles 3W or white powder fluid 3W and black particles 3B or black powder fluid 3B). ), In other words, the coating layer 12 is provided on the inner surface of the cell 11 by coating the inner surface of the partition wall 4 and the inner surfaces of the substrates 1 and 2 with one kind of material. .

  By providing the coating layer 12 made of one kind of material on the inner surface of the cell 11 in this way, the particles 3 (or powders) usually formed by a plurality of materials such as the materials of the substrates 1 and 2 and the material of the partition walls 4 are used. The contact environment of the fluid 3) can be a single material. As a result, it is possible to avoid an intricate influence on the frictional charging characteristics that the particles 3 (or the powder fluid 3) receive, and to obtain an inexpensive image display panel with excellent durability that does not decrease the image contrast even when used repeatedly. Can do.

  In the example shown in FIGS. 4 and 5, two types of particles having different optical reflectance: particle 1 (for example, white particle 3W) and particle 2 (for example, black particle 3B) or two types of powdered fluid: powdered fluid 1 (for example, The charged train of the white powder fluid 3W), the powder fluid 2 (for example, the black powder fluid 3B), and the coating material forming the cell inner surface is particle 1 (or powder fluid 1) -coating material-particle 2 (or powder fluid 2). It is preferable to configure so that the order of By comprising in this way, the influence of the coating layer provided in the inner surface of the cell 11 can be decreased more.

  Moreover, it is preferable to perform all the measurement of the charging characteristics of the two types of particles 3 (or powder fluid 3) and the charging characteristics of the coating material by the blow-off method using the same carrier particles. Only when the same carrier particle is used as a reference, the charged train is defined, and the defined charged train is configured in the order of particle 1 (or powder fluid 1) -coating material-particle 2 (or powder fluid 2). As a result, display characteristics of image display and durability in repeated use are improved.

  Although it is not clear why the display characteristics of image display and the durability in repeated use are improved by designing the image display panel as described above, two kinds of particles (or powder fluid) particles (or powders) Fluid)), the adsorption force acting between the coating material and particles (or powder fluid) is optimized, and as a result, the balance of the charging characteristics of the particles (or powder fluid) after encapsulation between the substrates is balanced. It is considered suitable.

  Carrier particles used for measurement of charging characteristics by the blow-off method are limited to the same one. By using the same carrier particles, the positioning of the two types of particles (or powder fluid) and the charge train of the coating material is determined. The order of the charged particles of the particles (or powder fluid) and the coating material cannot be determined.

  Hereinafter, each constituent part of the image display device equipped with the image display panel of the present invention will be described in detail in the order of particles, powdered fluid, and common constituent parts.

First, the particles used in the image display device of the present invention will be described.
Particles can be produced by kneading and pulverizing the necessary resin, charge control agent, colorant, and other additives, or polymerizing from monomers, or existing particles as resin, charge control agent, colorant It may be coated with other additives.
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, 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 used in 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, particles are introduced into a nitrogen stream, and 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 device 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, especially It was found that the saturation value of the charging behavior of the two types of particles is the dominant factor. In addition, in the charge train, it is important to know the difference in charge characteristics between the two types of particles and the contact environment and the difference in the charge train, that is, the work function, but this is difficult by simple measurement.

  As a result of intensive studies, the present inventors have determined the appropriateness of the two types of particles by measuring the charge amount of each material and the material constituting the cell inner surface with which the particles are in contact, using the same carrier particles in the blow-off method. It was found that the range of the charging characteristic value and the relative relationship with the inner surface of the cell in contact with the two kinds of particles can be evaluated, and by defining this by the surface charge density, It was found that the charged train can be predicted.

  The measurement method will be described in detail later. The particles and the carrier particles, and the cell inner surface forming material and the carrier particles are sufficiently brought into contact with each other by a blow-off method, and the saturation charge amount is measured, respectively. The amount of charge per unit weight of the cell inner surface forming material can be measured. Then, by separately obtaining the average particle diameter and specific gravity of the particles and the cell inner surface forming material, the surface charge density of the particles and the cell inner surface forming material can be calculated.

In the image display device, the particle diameter of the particles used is small and the influence of gravity is so small that it can be ignored. Therefore, the specific gravity of the particles does not affect the movement of the particles. However, regarding the charge amount of the particles, even if the average charge amount per unit weight is the same for the particles having the same particle diameter, the charge amount to be held when the specific gravity of the particles is two times different will be two times different. Therefore, it was found that the charging characteristics of the particles used in the image display device are preferably evaluated by the surface charge density (unit: μC / m ² ) that is independent of the specific gravity of the particles.

  When the difference in surface charge density between the particles is within an appropriate range, the two types of particles retain a sufficient amount of charge by contact with each other and retain the function of moving by an electric field.

  Here, in order to make the chargeability of the two kinds of particles existing close to each other in the display panel sufficient, the surface charge density of the two kinds of particles needs to have some difference, It's not good. In image display devices based on particle movement, when the particle size of the particle is large, the electric image force tends to be a factor that mainly determines the flying electric field (voltage) of the particle, so this particle is moved with a low electric field (voltage). For this purpose, a lower charge amount is better. In addition, when the particle size of the particle is small, non-electric forces such as intermolecular force and liquid crosslinking force are often determinants of the flying electric field (voltage), so this particle is moved with a low electric field (voltage). Therefore, a higher charge amount is better. However, since this greatly depends on the surface properties (material / shape) of the particles, it cannot be generally defined by the particle diameter and the charge amount.

In the case of particles having an average particle diameter of 0.1 to 50 μm, the present inventors are one of two types of particles (particle 1 and particle 2) measured by the blow-off method using the same carrier particles and a cell inner surface forming material. In the order of particle 1-cell inner surface forming material-particle 2, the absolute value of the surface charge density of the two types of particles is in the range of 10 to 150 μC / m ² , and It has been found that when the absolute value of the difference in surface charge density is in the range of ²⁰ to 100 μC / m ² , it can be suitably used as an image display panel.

Next, the powder fluid used in the image display device 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 pulverized fluid used 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. 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.

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 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, 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 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 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, fluorine resin, etc. 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 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 a substance 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.

Furthermore, in the present invention, it is important to manage the gas in the voids surrounding the particle group or the powder fluid between the substrates, which contributes to the improvement of display stability. Specifically, it is important that the relative humidity at 25 ° C. is 60% RH or less, preferably 50% RH or less, more preferably 35% RH or less with respect to the humidity of the gas in the gap.
In FIG. 1, the void portion refers to the portion occupied by the electrodes 5 and 6, the particle group (or powder fluid) 3, the portion occupied by the partition wall 4, and the device seal portion from the portion sandwiched between the opposing substrate 1 and substrate 2. The gas part which the so-called particle group (or powdered fluid) except it contacts shall be pointed out.
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, filling of particles or powder fluid, assembly of the substrate, etc. are performed in a predetermined humidity environment, It is important to apply a sealing material and a sealing method to prevent moisture intrusion.

The distance between the substrate in the image display panel of the present invention is not limited as long as the particle group or powder fluid can move and maintain the contrast, but is usually adjusted to 10 to 500 μm, preferably 10 to 200 μm.
The volume occupancy of the particle group or powder fluid in the space between the opposing substrates is preferably 5 to 70%, more preferably 5 to 60%. If it exceeds 70%, the movement of particles or powder fluid is hindered, and if it is less than 5%, the contrast tends to be unclear.

Next, the substrate used in the image display device of the present invention will be described.
At least one of the substrate 1 and the substrate 2 is a transparent substrate capable of confirming the color of the particle group or the 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 preferred. Examples of the substrate material include polymer sheets such as polyethylene terephthalate, polyethersulfone, polyethylene, and polycarbonate, and inorganic sheets such as glass and quartz. What is the substrate thickness? 2 to 5000 μm, preferably 5 to 1000 μm is suitable. If the thickness is too thin, it becomes difficult to maintain the strength and the uniformity of the distance between the substrates. If the thickness is too thick, the sharpness as a display function and a decrease in contrast occur. In particular, in the case of electronic paper use, it lacks flexibility.

  A display method in the case where no electrode is provided on the substrate is a group of colored particles that give an electrostatic latent image to the external surface of the substrate and are charged with a predetermined characteristic by an electric field generated according to the electrostatic latent image. Alternatively, the particle fluid or the powder fluid arranged corresponding to the electrostatic latent image is visually recognized from the outside of the display panel through the transparent substrate by attracting or repelling the powder fluid to the substrate. This electrostatic latent image is formed by transferring an electrostatic latent image formed by an ordinary electrophotographic system using an electrophotographic photosensitive member onto the display panel substrate of the present invention, or by ion flow. A latent image can be directly formed.

  When the electrodes are provided on the substrate, the colored particles or powdered fluid charged to the specified characteristics are attracted by the electric field generated at each electrode position on the substrate by the external voltage input to the electrode part. This is a method of visually recognizing a group of particles or powder fluid arranged corresponding to the electrode potential from the outside of the display panel by being repelled or repelled.

  The electrode provided on the transparent substrate side is formed of a conductive material that is transparent and can be patterned, and examples include metals such as indium oxide and aluminum, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. Examples of the forming method include vacuum deposition and coating. 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 electrode provided on the back substrate side is formed of a conductive material that does not need to be transparent and can be patterned. For example, metals such as indium oxide, aluminum, gold, silver, copper, polyaniline, polypyrrole, polythiophene, etc. Examples of the forming method such as vacuum deposition and coating can be given. 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.
In this case, the external voltage input may be superimposed with direct current or alternating current.

  The shape of the partition wall 4 is optimally set according to the type of particle group or powder fluid involved in the display, and is not limited in general. However, the partition wall width is 2 to 100 μm, preferably 3 to 50 μm. Is adjusted to 10 to 1000 μm, preferably 10 to 500 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. 6, the display cells formed by the ribs 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 substrate plane direction, and the arrangement is a lattice. And honeycomb shapes 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 blasting method, a photolithography method, and an additive method.

Next, the inner surface forming material of the cell 11 used in the image display panel of the present invention will be described.
In the present invention, as shown in FIGS. 4 and 5, in order to make the inner surface of the cell 11 in contact with the particles (or powder fluid) 3 uniform, the cell formed of the partition wall 4 and the substrates 1 and 2 is used. The inner surface of 11 is coated with one type of material to form a coating layer 12. The cell inner surface forming material (coating material) includes particles 1 (or powder fluid 1) -coating material-particles 2 in a charge train with two types of particles (or powder fluid) having different charging characteristics filled in the cell 11. It is important to select the one in the order of (or powder fluid 2).

  The coating material is not particularly limited as long as the material satisfies the above requirements in the charge train, but urethane resin, acrylic resin, polyester resin, urethane-modified acrylic resin, silicone resin, nylon resin, epoxy resin, styrene resin, butyral resin, Examples of the resin include vinylidene chloride resin, melamine resin, phenol resin, and fluororesin, and two or more kinds can be mixed. In particular, polyester resin, acrylic urethane resin, acrylic urethane silicone resin, acrylic urethane fluororesin, urethane resin, and fluororesin are suitable from the viewpoint of controlling the adhesion force between the particles (or powder fluid) and the substrate. A charge control agent may be added to these resins to adjust the charge train with the two kinds of particles (or powder fluid). As a coating method, any method such as a dipping method, a spray method, a roll coater method, and a brush coating method may be used.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples. The image display panels obtained in the examples and comparative examples were evaluated according to the following criteria.

“Production of image display panels”
First, a substrate with electrodes (7 cm × 7 cm □) was prepared, ribs with a height of 200 μm were formed on the substrate, and striped partition walls were formed.
Ribs were formed as follows. First, the paste is a glass powder obtained by melting, cooling and grinding a mixture of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , Bi ₂ O ₃ and ZnO as an inorganic powder, and a thermosetting epoxy resin as a resin. Was prepared, and a paste prepared to have a viscosity of 12000 cps with a solvent was prepared. Next, the paste was applied onto a prepared substrate, heated and cured at 150 ° C., and this application to curing was repeated to adjust the thickness (corresponding to the height of the partition wall) to 50 μm. Next, a dry photoresist was applied, and a mask was formed so that a partition wall pattern having a line of 50 μm, a space of 400 μm, and a pitch of 450 μm was formed by exposure to etching. Next, excess portions were removed by sandblasting so as to obtain a predetermined partition wall shape, thereby forming a desired striped partition wall.

  Particles (or powder fluid) are coated with one kind of material on the surface with the partition wall and the surface of the other substrate that are made in this manner and the inner surface of the cell in contact with the particles (or powder fluid). Was enclosed in a cell to produce an image display panel.

"Measurement of electrification characteristics of particles (or powder fluid) and coating materials"
<Blow-off measurement principle and method>
In the blow-off method, a mixture of powder and carrier particles is placed in a cylindrical container with nets on both ends, and high-pressure gas is blown from one end to separate the powder and carrier particles, and the powder is opened from the mesh openings. Blow off only. At this time, the charge amount equal to the charge amount taken away from the container by the powder remains in the carrier particles. All of the electric flux due to this charge is collected by the Faraday cage, and the capacitor is charged by this amount. Therefore, by measuring the potential across the capacitor, the charge quantity Q of the powder is
Q = CV (C: Capacitor capacity, V: Voltage across capacitor)
As required.
TB-200 manufactured by Toshiba Chemical Co. was used as a blow-off powder charge measuring device.
In the present invention, the same carrier particle (carrier particle F963-2535 manufactured by Powder Tech Co., Ltd.) is used, and the charge density per unit weight of the object to be measured (particle or powder fluid and coating material made into particles) ( μC / g) was measured, and the surface charge density (μC / mm ² ) of the particles (or powder fluid) and the coating material was calculated from the average particle diameter and specific gravity obtained separately.

  The average particle diameter is determined by the method described above, specifically, using a Mastersizer 2000 (Malvern Instruments Ltd.) measuring machine, and each of the particles (or powder fluid) and the coating material in the form of particles are put into a nitrogen stream. , Measured with the attached analysis software (software based on volume-based distribution using Mie theory), and the specific gravity was also measured using a hydrometer (trade name: Multi-Volume Densimeter H1305) manufactured by Shimadzu Corporation Measured respectively.

"Evaluation of display function"
Black-white display was repeated by applying a voltage of 250 V to the image display device incorporating the manufactured image display panel to invert the potential. The evaluation of the display function was performed on the contrast ratio, and the initial measurement was repeated after 10,000 times and after 100,000 times using a reflection image densitometer. Here, the contrast ratio is: contrast ratio = reflection density during black display / reflection density during white display.

<Example 1>
Particle 1 was produced by the following method. First, acrylic urethane resin EAU53B (manufactured by Asia Industry Co., Ltd.) / IPDI crosslinking agent Excel Hardener HX (manufactured by Asia Industry Co., Ltd.), carbon black (MA100: produced by Mitsubishi Chemical Corporation), 4 parts by weight, charge control 2 parts by weight of the agent Bontron N07 (made by Orient Chemical Co., Ltd.) was added and kneaded. Next, the particle diameter was adjusted by pulverization and classification with a jet mill.
Particle 2 was prepared by the following method. First, acrylic urethane resin EAU53B (manufactured by Asia Industry Co., Ltd.) / IPDI crosslinking agent Excel Hardener HX (manufactured by Asia Industry Co., Ltd.), 10 parts by weight of titanium oxide, charge control agent Bontron E89 (manufactured by Orient Chemical Co., Ltd.) 2 parts by weight were added and kneaded. Next, the particle diameter was adjusted by pulverization and classification with a jet mill.
The inner surface of the cell was coated with an acrylic urethane resin EAU53B (manufactured by Asia Kogyo Co., Ltd.) / IPDI-based crosslinking agent Excel Hardener HX (manufactured by Asia Kogyo Co., Ltd.).
The display function was evaluated using an image display device incorporating an image display panel produced with these particle groups. The results are shown in Table 1.

<Example 2>
The powder fluid 1 was produced as follows. First, after suspension polymerization using a styrene monomer, an azo compound (5 parts by weight), a charge control agent Bontron N07 (5 parts by weight manufactured by Orient Chemical Co., Ltd.), and an initiator AIBN (0.5 parts by weight). Then, the particle diameters were aligned using a classifier. Next, using a hybridizer apparatus (manufactured by Nara Machinery Co., Ltd.), silica H2050 (manufactured by Wacker Co., Ltd.) and silica SS20 (manufactured by Nippon Silica Co., Ltd.) are introduced into these particles, and 5 minutes at 4800 rpm. It was processed and fixed on the surface of the polymerized particles, and adjusted to become a powder fluid.
The powder fluid 2 was produced as follows. First, after suspension polymerization using methyl methacrylate monomer, TiO ₂ (20 parts by weight), charge control agent Bontron E89 (5 parts by weight, manufactured by Orient Chemical Co., Ltd.) initiator AIBN (0.5 parts by weight), The particle size was aligned using a classifier. Next, using a hybridizer device (manufactured by Nara Machinery Co., Ltd.), silica H2000 / 4 (manufactured by Wacker Co., Ltd.) and silica SS20 (manufactured by Nippon Silica Co., Ltd.) are introduced into these particles, and rotation is performed at 4800 rpm. It was treated for 5 minutes, fixed on the surface of the polymerized particles, and adjusted to become a powder fluid.
The inner surface of the cell was coated with methyl methacrylate.
The display function was evaluated using an image display device incorporating an image display panel produced with these powder fluids. The results are shown in Table 1.

<Comparative Example 1>
The display function was evaluated using an image display device incorporating an image display panel produced in the same manner as in Example 1 except that the inner surface of the cell was not coated. The results are shown in Table 1.

<Comparative example 2>
The display function was evaluated using an image display device incorporating an image display panel produced in the same manner as in Example 2 except that the inner surface of the cell was not coated. The results are shown in Table 1.

<Comparative Example 3>
Acrylic urethane resin EAU53B (manufactured by Asia Kogyo Co., Ltd.) / IPDI crosslinking agent Excel Hardener HX (manufactured by Asia Kogyo Co., Ltd.) with 10 parts by weight of charge control agent Bontron E89 (manufactured by Orient Chemical Co., Ltd.) The display function was evaluated using an image display device incorporating an image display panel produced in the same manner as in Example 1 except that the display function was performed in step 1). The results are shown in Table 1.

<Comparative example 4>
An image display device incorporating an image display panel produced in the same manner as in Example 2 except that the coating on the inner surface of the cell was performed with methyl methacrylate monomer to which 10 parts by weight of charge control agent Bontron E89 (manufactured by Orient Chemical Co., Ltd.) was added. Was used to evaluate the display function. The results are shown in Table 1.

  From the results in Table 1, it can be seen that Examples 1 and 2 according to the present invention can keep the contrast ratio after repetition high as compared with Comparative Examples 1 to 4.

  The image display panel of the present invention does not decrease the image contrast even when it is used repeatedly, and an image display device equipped with this image display panel is a display unit of a mobile device such as a notebook computer, PDA, mobile phone, handy terminal, etc. , Electronic paper such as electronic books, electronic newspapers, bulletin boards such as signboards, posters, blackboards, display units such as calculators, home appliances, automobile supplies, card display units such as point cards and IC cards, electronic advertisements, electronic POPs, electronic It is suitably used for a price tag, an electronic score, a display part of an RF-ID device, and the like.

It is a figure which shows an example of the drive method in the image display panel used with the image display apparatus of this invention. It is a figure which shows the other example of the drive method in the image display panel used with the image display apparatus of this invention. It is a figure which shows an example of the structure of the image display panel used with the image display apparatus of this invention. It is a figure for demonstrating an example of the characteristic part of the image display panel used with the image display apparatus of this invention. It is a figure for demonstrating the other example of the characteristic part of the image display panel used with 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 with the image display apparatus of this invention.

Explanation of symbols

1, 2 Substrate 3 Particles (powder fluid)
3W white particles (white powder fluid)
3B Black particles (black powder fluid)
4 Partition 5, 6 Electrode 11 Cell 12 Coating layer

Claims (4)

  Forming a plurality of cells partitioned by a partition wall between two opposing substrates, at least one of which is transparent, enclosing at least two types of particle groups or at least two types of powder fluid in the cells; An image display panel that displays an image by applying an electric field to a particle group or a powder fluid to move the particle group or the powder fluid, and includes at least two kinds of particle groups or at least two kinds of powder fluids An image display panel, wherein an inner surface of a cell to be sealed is formed by coating one kind of material.   Two types of particles (particles 1 and 2) or two types of powder fluids (powder fluid 1 and powder fluid 2) having different optical reflectivities contained in at least two or more types of particle groups or at least two or more types of powder fluids 2 and the coating material forming the cell inner surface is in the order of particle 1 (or powder fluid 1) -coating material-particle 2 (or powder fluid 2). The image display panel described in 1.   The charging characteristics of the coating material forming the cell inner surface are the same as the two kinds of particles or two kinds of powder fluids having different optical reflectivities contained in at least two kinds of particle groups or at least two kinds of powder fluids. The image display panel according to claim 3, wherein the image display panel is measured by a blow-off method using the carrier particles.   An image display device comprising the image display panel according to claim 1.

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