JP2005189272A - Particle for display device and image display medium using same, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for a display device which has low specific gravity and small force acting on the gravity, and an image display medium which is good in image display maintenance characteristic against external impact even in case of perpendicular installation, and is less changed in image density in spite of repetitive rewriting and an image forming apparatus using the image display medium. <P>SOLUTION: The image display medium comprises particles for a display device having the nature that the medium can be electrostatically charged in positive or negative and having colors, a pair of substrates which are arranged to face each other, and particle groups consisting of at least two or more particles sealed into a gap between the pair of the substrates. The particle groups have the nature that one thereof can be electrostatically charged in positive and the other one in negative by an external stimulus. In the image display medium the particles which can be electrostatically charged in positive or negative have the colors different from each other and at least one particles among the particles that can be electrostatically charged in positive or negative are the particles for the display device. An electric field generating means for generating the electric fields meeting the images is disposed between the pair of the substrates of the image display medium. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image display medium using particles and capable of repeated rewriting, and an image forming apparatus.

  Conventionally, display technologies such as Twisting Ball Display (two-color coating particle rotation display), electrophoresis, magnetophoresis, thermal rewritable medium, and liquid crystal having memory properties have been proposed as image display media that can be rewritten repeatedly. . Although the display technique is excellent in image memory performance, there is a problem in that the display surface cannot be displayed in white like paper and the contrast is low.

  As a display technology using toner that solves the above problems, conductive colored toner and white particles are sealed between opposing electrode substrates, and conductive through a charge transport layer provided on the inner surface of the electrode of the non-display substrate. Charge is injected into the conductive colored toner, and the injected conductive colored toner is moved to the display substrate side facing the non-display substrate by an electric field between the electrode substrates, and the conductive colored toner is transferred to the display side substrate. A display technique has been proposed in which an image is displayed based on the contrast between conductive colored toner and white particles attached to the inside (Japan Hardcopy '99 paper, p249-252). This display technique is excellent in that the image display medium is entirely composed of solid, and white and black (color) display can be switched 100% in principle. However, in the above technique, there are conductive colored toners that do not contact the charge transport layer provided on the inner surface of the electrode of the non-display substrate, and conductive colored toners that are isolated from other conductive colored toners. Since the conductive colored toner does not move due to an electric field and is present in the substrate at random without being injected, there is a problem that the density contrast is lowered.

For the purpose of improving such a problem, a plurality of types of particle groups having different colors and charging characteristics and encapsulated between the substrates so as to be movable between the substrates by an applied electric field, Has been proposed (see, for example, Patent Document 1). According to this proposal, it is described that high whiteness and density contrast can be obtained.
However, in this image display medium, when using titanium oxide, which is an inorganic pigment, as a colorant for display particles, it is necessary to increase the amount of pigment added in order to improve the whiteness and the concealability of the base. is there. Since such display particles have a high specific gravity, it has been difficult to use them for vertical image display media. In addition, pigments with a large oil absorption amount are difficult to disperse in monomers, etc., which are constituents of display particles, especially in a particle manufacturing technique prepared by a wet manufacturing method, and cannot be added in an increased amount. It was difficult to improve power and concealment.
JP 2001-31225 A

  In more detail, the colorant inherent in the display particles used in the above-described conventional image display medium is used in a state of being dispersed inside the particles, and the dispersion level is not controlled. It was present in the display particles at random. For this reason, in order to increase the coloring power or hiding property of the display particles, it is necessary to increase the addition amount of the colorant. In particular, the hiding colorant has many inorganic pigments, and the inorganic pigment has a large primary particle size. Therefore, in order to improve coloring power and hiding property, a larger amount of addition than that of the organic pigment system is required. there were. As a result, the specific gravity of the display particles increases, and the force acting on the gravity increases. Therefore, when used in an image display medium, the adhesion due to the charge generated by frictional charging between these display particles and the substrate is reduced. In other words, the acting force against gravity is antagonized, the adhesion force is weakened against external stimuli (vibration), the display particles are detached from the display substrate, and display defects are caused. In addition, display particles having a large specific gravity are aggregated between display particles, and this causes a lower adhesion than the display particles and the substrate, making it difficult to maintain a stable display image. When the process is repeated, there is a problem that the image density decreases.

An object of the present invention is to solve the above problems and achieve the following objects.
That is, an object of the present invention is to provide particles for a display device having a low specific gravity and a small acting force on gravity.
Further, the present invention provides an image display medium that has good image display maintainability against external impacts even when installed vertically, and has a small change in image density even when rewritten over a long period of time. Another object is to provide an image forming apparatus using a display medium.

In order to solve the above problems, the present inventors have intensively studied as follows.
First, when producing an image display medium, particles composed of at least first particles (particles charged with one polarity) and second particles (particles charged with the other polarity) enclosed between a pair of substrates. Are mixed and stirred in a stirring vessel at a predetermined rate.
It is considered that each particle is charged by frictional charging between particles and between the particles and the inner wall of the container during the mechanical stirring and mixing process. Thereafter, the mixed particles are sealed between the pair of substrates so as to have a predetermined volume filling rate. The particles encapsulated between the substrates reciprocate between the substrates according to the electric field by switching the polarity of the DC voltage applied between the substrates or by applying the AC voltage (initialization process).

  Also in this process, each particle means between the particles and the particle and the substrate surface (the surface facing the other substrate. In the following, unless otherwise specified, the substrate surface means the surface facing the other substrate. It is thought that the battery will collide and be triboelectrically charged. At this time, the first particles and the second particles are charged to different polarities and try to adhere and aggregate between the particles due to the Coulomb attractive force between the first particles and the second particles. The two types of particles are separated according to the direction of the last applied electric field, and each adheres to a predetermined substrate. Next, by applying an electric field according to the image signal, the first particles and the second particles are separated and moved according to the electric field and are attached to different substrates.

In other words, if the electrostatic force acting on each charged particle by an externally applied electric field is greater than the Coulomb force between particles, the image force between the particle and the substrate surface, or the force due to the contact potential difference, two types of particles Are considered to separate and move to the opposite substrates and adhere to each other.
The charged particles adhering to the substrate are considered to be adhered and fixed to the substrate by image force generated between the substrate surface and van der Waals force between the particles and the substrate.

In addition, when the image display medium (image forming apparatus) is installed vertically, a moment with respect to the mass of the particles acts in the direction of gravity between the charged particles attached on the substrate and the substrate. If the adhesion force of the particles to the substrate and the attractive force of the particles in the direction of gravity (peeling force for the substrate) antagonize, it contributes to the display if the electric adhesion force is large, and the image if the peeling force is strong. It becomes a display defect.
From the above, in order not to cause image display defects, it is important to reduce the specific gravity of the particles so that the particle peeling force to the substrate is larger than the particle adhesion force to the substrate. is there.
Therefore, the present inventors have found the following present invention in order to achieve the above-mentioned problems based on the knowledge as described above.

That is, the present invention
<1> A particle for a display device having a property and color that can be positively or negatively charged and having colored fine particles having a colorant supported on the surface of the fine polymer particles.

<2> The display device particle according to <1>, wherein the colorant is an inorganic pigment.

<3> The display device particle according to <1> or <2>, wherein the polymer fine particle is crosslinked.

<4> A pair of substrates arranged opposite to each other, and a particle group composed of at least two kinds of particles enclosed in a gap between the pair of substrates. By external stimulation, the two or more kinds of particles are An image display medium in which at least one of them has the property of being positively charged and at least one of the other can be negatively charged, and the positively and negatively charged particles have different colors.
The image display medium according to any one of <1> to <3>, wherein at least one kind of the positively and negatively chargeable particles is a particle for a display device.

<5> The image display medium according to <4>, wherein at least one of the positively and negatively charged particles is white.

<6> The image display medium according to <5>, wherein the white particles contain a color material, and the color material is titanium oxide.

<7> An image forming apparatus for forming an image on the image display medium according to any one of <4> to <6>,
An image forming apparatus comprising an electric field generating means for generating an electric field corresponding to an image between the pair of substrates.

Dispersion of coloring components (colored fine particles) can be controlled three-dimensionally by using colored fine particles having a colorant supported on the surface of the polymer fine particles as the colorant as in the display device particles of the present invention. Thus, it is possible to satisfy the concealing property and the coloring power with a small addition amount. As a result, the specific gravity of the display device particles that are display particles can be kept low. By using the display device particles in an image display medium (image forming apparatus) installed vertically, image display defects caused by external stimuli (vibration) can be suppressed, and rewriting can be repeated over a long period of time. Also, the change in image density can be reduced.
In addition, for example, in a particle manufacturing technique prepared by a wet manufacturing method, for example, a suspension particle method, even when a highly oil-absorbing pigment is dispersed in a monomer, the pigment is supported on the surface of the polymer fine particles. By using fine particles, the amount of oil absorption relative to the amount added can be suppressed, and the coloring power and concealability can be easily improved.

ADVANTAGE OF THE INVENTION According to this invention, the particle | grains for display devices with a low specific gravity and a small action force with respect to gravity can be provided.
In addition, according to the present invention, an image display medium that has good image display maintainability against external impact even when installed vertically and has a small change in image density even when rewritten over a long period of time. An image forming apparatus using the image display medium can be provided.

The present invention is described in detail below.
<Display device particles>
The particles for a display device of the present invention are characterized in that they have a property and color that can be positively or negatively charged, and have colored fine particles having a colorant supported on the surface of the fine polymer particles. More specifically, the display device particles of the present invention include at least colored fine particles (coloring material), a charge control agent, and a resin.
Below, each component which comprises the particle | grains for display devices of this invention is demonstrated.

[Colored fine particles having a colorant supported on the surface of the polymer fine particles]
The colored fine particles in the present invention are formed by supporting a colorant as a child particle on the surface of polymer fine particles as a mother particle.
Here, as the colorant used, carbon black, titanium black, magnetic powder, other organic, inorganic black pigment, rutile titanium oxide, anatase titanium oxide, zinc white, lead white, zinc sulfide, oxidation Use white pigments such as aluminum, silicon oxide, zirconium oxide, and chromatic colorants such as phthalocyanine, quinacridone, azo, condensation, insoluble lake pigments, and inorganic oxide dyes and pigments. Can do.

  Specific examples of inorganic pigments that are suitable as chromatic colorants include cobalt violet, manganese violet, cobalt blue, ultramarine, cerulean blue, Prussian blue, manganese blue, viridan, chrome oxide green, and cobalt. Green, Tail Belt, Earth Green, Cadmium Yellow, Yellow Ocher, Nickel Titanium Yellow, Bismuth Vanadium Yellow, Chrome Yellow, Cadmium Orange, Lead Tan, Chrome Vermillion, Vermillion, Iron Oxide Red, Siena Soil, Amber Soil, Bandai Brown Ivory black, peach black, lamp black, mars black, composite oxide black, titanium white, silver white, zinc white, ceramic white, etc. That.

  Other pigments suitable as a chromatic colorant include aniline blue, calcoyl blue, deyupon oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3 can be exemplified as a representative one.

Among these colorants, it is preferable to use a pigment.
Such a colorant is preferably in the form of particles in order to be supported on the surface of the polymer fine particles.
As a particle diameter, 0.01 micrometer-5 micrometers can be used by an average primary particle diameter, Preferably 0.05 micrometer-3 micrometers can be used conveniently.

Examples of the polymer fine particles include cross-linked PMMA particles and cross-linked styrene-acrylic particles. Cross-linked particles are preferable as exemplified here. The polymer fine particles can be produced by an emulsion polymerization method, a suspension polymerization method or the like.
As a particle diameter, it is an average primary particle diameter, 0.1 micrometer-100 micrometers can be used, Preferably 1 micrometer-30 micrometers can be used favorably.
The ratio of the particle diameter of the colorant to the particle diameter of the polymer fine particles is preferably in the range of colorant / polymer fine particles = 1/1000 to 1/10, more preferably in the range of 1/100 to 1/20.

Colored fine particles are produced by supporting the colorant on the surface of such polymer fine particles.
From the viewpoint of fixing the colorant by embedding the colorant in the surface of the polymer fine particle, the ratio of the polymer fine particle to the colorant is preferably 10 to 130%, more preferably 20 to 100% in terms of surface coverage. 80% is more preferable.
The surface coverage is calculated by calculating the area equivalent to a circle from the average primary particle diameter of the colorant, dividing by the surface area of the polymer fine particles, and multiplying by 100, and is expressed in%.

The method for producing the colored fine particles is to mix polymer fine particles as mother particles and colorant as child particles so as to have an appropriate blend, made by Nara Machinery Co., Ltd .: Hybridizer, manufactured by Tokuju Kogakusho: Theta Composer, Manufactured by Hosokawa Micron: It can be produced by a mechano-fusion method such as Ong Mill.
The colored fine particles may be produced by processing in combination with a functional material acting on charge control and a resistance adjusting agent, if necessary, in addition to the above-described colorant.

(Charge control agent)
A charge control agent is added to the display device particles of the present invention in order to control chargeability.
As the charge control agent, known ones used for toner materials for electrophotography can be used, for example, quaternary ammonium salts such as cetylpyridyl chloride, P-51, P-53 (manufactured by Orient Chemical Industries), Examples thereof include salicylic acid-based metal complexes, phenol-based condensates, tetraphenyl-based compounds, calixarene compounds, metal oxide fine particles, and metal oxide fine particles surface-treated with various coupling agents. Moreover, as a charge control agent, a colorless thing or a thing with low coloring power is preferable. The addition amount is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 0.5 to 5% by mass.

[Resistance adjuster]
Furthermore, a resistance adjuster may be added to the display device particles of the present invention, if necessary.
As the resistance adjuster, an inorganic fine powder having a resistance value of 1 × 10 ⁶ Ωcm or less can be used. For example, fine particles coated with tin oxide, titanium oxide, zinc oxide, iron oxide, various conductive oxides ( For example, tin oxide-coated titanium oxide and the like. Further, the resistance adjusting agent is preferably colorless or has a low coloring power. The addition amount is preferably in a range that does not hinder the color of the particles for display device colored with the above-mentioned colored fine particles, and specifically in the range of 0.1% by mass to 10% by mass.

〔resin〕
Examples of the resin constituting the display device particles of the present invention include polyolefin resins, polystyrene, acrylic resins, methacrylic resins, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, vinyl chloride, polyvinyl butyral, and the like; polyvinyl chloride-vinyl acetate Polymer; Styrene-acrylic acid copolymer; Copolymer resin such as styrene-methacrylic acid copolymer, straight silicon resin composed of organosiloxane bond, and modified resin thereof: polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride Fluorine resin such as: polyester, polyurethane, polycarbonate; amino resin; epoxy resin.
Further, as the resin constituting the display device particles of the present invention, a known binder resin known as a main component of a conventional electrophotographic toner can be used without any problem.

  These may be used alone or in combination with a plurality of resins. Moreover, you may use what bridge | crosslinked these resin. Among these, it is particularly preferable to use a resin containing a crosslinking component.

[Other additives]
Furthermore, other additives other than the above-described components can be used within a range not affecting the hue. Examples of such additives include fine polymer particles smaller than the diameter of the display device particles, for example, for reducing the specific gravity of the display device particles. As this polymer fine particle, a conventionally known polymer can be used, but it is preferable to use a polymer having a specific gravity lower than that of the colored fine particle used together, and when the polymer fine particle itself has a color, a display device In consideration of the color of the colored fine particles contained in the particles for use, it is preferable to select and use them appropriately.

  Specifically, as the material constituting the polymer fine particles, for example, polystyrene resin, polymethyl methacrylate resin, urea polymarin resin, styrene / acrylic resin, polyethylene resin, polyvinylidene fluoride resin, etc. are used alone or in combination. However, the present invention is not limited to these. These resins preferably have a crosslinked structure, and more preferably have a higher refractive index than the resin contained in the display device particles.

As the polymer fine particles, those having a shape such as a spherical shape, an irregular shape, and a flat shape can be used, but a spherical shape is more preferable.
The volume average particle diameter of the polymer fine particles is not particularly limited as long as it is smaller than the particles for display devices, but is preferably 10 μm or less, and more preferably 5 μm or less. The particle size distribution should be sharp, and more preferably monodisperse.

Furthermore, from the viewpoint of producing particles for a display device having a smaller specific gravity, it is preferable that part or all of the polymer fine particles are made of hollow particles. The volume average particle diameter of the hollow particles is not particularly limited as long as it is smaller than the particles for display devices, but is preferably 10 μm or less, and more preferably 5 μm or less. In particular, in the case of hollow particles, from the viewpoint of light scattering, the volume average particle diameter is more preferably in the range of 0.1 to 1 μm, and particularly preferably in the range of 0.2 to 0.5 μm. preferable.
Here, “hollow particles” refer to those having voids inside the particles. The porosity is preferably 10 to 90%. Further, the “hollow particles” may be in the form of a hollow capsule, or the outer wall of the particles may be in a porous state.

  Also, hollow particles in the form of hollow capsules have a difference in refractive index at the interface between the resin layer in the outer shell and the air layer inside the particles, and those in which the outer wall is porous have refraction between the outer wall and the cavity. Since the whiteness can be increased and the concealability can be improved by utilizing light scattering caused by the difference in rate, it is particularly preferable that the white display device particles are included.

  In the display device particles of the present invention, the amount of polymer fine particles (hollow particles) added is preferably in the range of 1 to 40% by mass, and in the range of 1 to 20% by mass with respect to the entire display device particles. More preferably, it is within.

[Method for producing particles for display device]
The particles for display device of the present invention may be produced by a wet production method such as suspension polymerization, emulsion polymerization, or dispersion polymerization, or may be produced by a conventional pulverization classification method. The particles obtained by the wet manufacturing method become spherical particles, and the particles obtained by the pulverization classification method become amorphous particles.
Further, heat treatment may be performed in order to make the spherical particles and irregular particles obtained by these production methods uniform in shape.
Examples of the method for aligning the particle size distribution include a method of adjusting the granulation conditions in the above-described wet manufacturing method and classifying the particles once obtained.
When adjusting the granulation conditions in the wet manufacturing method, adjust the stirring speed when dispersing the oil phase in which the materials constituting the particles for display devices are dispersed in the aqueous phase, or use a surfactant. In this case, the particle size distribution of the particles can be controlled by adjusting the concentration.

  In addition, as a method of classifying the particles, for example, various vibrating sieves, ultrasonic sieves, pneumatic sieves, and wet sieves, a method using a rotor rotary classifier using the principle of centrifugal force, a wind classifier, etc. However, it is not limited to these. These can be adjusted to a desired particle size distribution either alone or in combination. In particular, when adjusting precisely, it is preferable to use a wet sieve. When a classifier is used, for example, in a rotary classifier, components on the fine powder side / coarse powder side can be selectively removed from the particles before classification by controlling the number of rotations. Moreover, as a sieve, it is preferable to use a nylon sieve at the point that the distribution of opening is narrow and a high yield can be obtained.

  The volume average particle diameter of the display device particles cannot be generally specified, but in order to obtain a good image, the volume average particle diameter is preferably in the range of about 0.1 to 30 μm, and preferably 2 to 20 μm. Within the range is more preferable, and within the range of 2 to 15 μm is further preferable.

  The shape of the particles for display device is desirably close to a true sphere. In the case of particles close to a true sphere, the contact between the particles is almost a point contact, and the contact between the particle and the substrate surface is also almost a point contact, and van der Waals force between the particles and between the particle and the substrate surface. Adhesive force based on is reduced. Therefore, even if the substrate surface is a derivative, it is considered that the charged particles can move smoothly in the substrate by the electric field.

  The display device particles of the present invention have a smaller amount of colorant added than the case where the colorant is added to the display device particle as it is by using the above-described colored fine particles as the colorant. Even in the state, it is possible to satisfy the concealability and coloring power. As a result, the specific gravity of the display device particles themselves can be kept low.

<Image display medium>
The image display medium of the present invention comprises a pair of substrates arranged opposite to each other, and a particle group composed of at least two types of particles enclosed in a gap between the pair of substrates. An image display medium in which at least one of the above particles has a property of being positively charged and at least one of the other particles can be negatively charged, and the positively and negatively charged particles have different colors. There,
At least one of the positively and negatively charged particles is the above-described display device particle of the present invention.

In the image display medium of the present invention, positively charged particles (hereinafter sometimes referred to as “first particles”) and negatively charged particles (hereinafter “second particles”). ) Are different in color from each other, so that a density contrast is obtained between the image portion made of the first particles and the image portion made of the second particles.
In the image display medium of the present invention, the image display medium of the present invention uses the particles for display device of the present invention with reduced specific gravity as at least one of the first particles and the second particles. Thus, even when the image display medium is installed vertically, image display defects caused by external stimuli (vibration) can be suppressed, and even if rewritten over a long period of time, the change in image density is reduced. can do.
In the above description, the expression is based on the premise that there is one kind of positively charged first particle and one of negatively charged second particle. In the case of two or more types, if one of them is composed of the particles for a display device of the present invention, the same mechanism of action as described above is used. The effect is demonstrated.

  Hereinafter, in the image display medium of the present invention, the first particles and the second particles, that is, the particles that can be positively and negatively charged are collectively referred to as “display particles”. Both of the display particles are preferably composed of the display device particles of the present invention, but conventionally known display device particles that do not contain colored fine particles may be used in combination.

In the image display medium of the present invention, one of the display particles is preferably white, in other words, it is preferable that one of the display particles includes a white color material. By making one particle white, the coloring power and density contrast of the other particle can be improved. At this time, titanium oxide is preferable as a white color material for making one particle white. By using titanium oxide as the color material, the hiding power can be increased in the range of the wavelength of visible light, and the density contrast can be further improved. As the white color material, rutile type titanium oxide is particularly preferable.
Here, as described above, the white color material is preferably colored fine particles having a white colorant (preferably titanium oxide) supported on the surface of the polymer fine particles. That is, it is a preferred embodiment that the white display particles in the image display medium of the present invention are the display device particles of the present invention.

Below, the board | substrate which comprises the image display medium of this invention is demonstrated.
In the image display medium of the present invention, a pair of substrates disposed opposite to each other is used as the substrate, and particles for display device are enclosed in a gap between the pair of substrates.
In addition, when controlling the charged state of particles that can be positively or negatively charged using an electric field as an external stimulus, a conductive plate-like body (conductive substrate) is used as the substrate. In this case, in order to have a function as an image display medium, at least one of the pair of substrates needs to be a transparent conductive substrate. At this time, the side of the image display medium on which the transparent conductive substrate is provided becomes the image display surface.

  The conductive substrate may be conductive, or may be a conductive surface of an insulating support, and may be crystalline or amorphous. Examples of the conductive substrate in which the substrate itself is conductive include metals such as aluminum, stainless steel, nickel, and chromium and alloy crystals thereof, and semiconductors such as Si, GaAs, GaP, GaN, SiC, and ZnO.

  Examples of the insulating support include a polymer film, glass, quartz, and ceramic. Conductive treatment of the insulating support is performed by vapor deposition, sputtering, ion plating, or the like using the metal or gold, silver, copper, etc. mentioned in the specific example of the conductive substrate in which the substrate itself is conductive. A film can be formed.

  As the transparent conductive substrate, a conductive substrate in which a transparent electrode is formed on one surface of an insulating transparent support, or a transparent support having conductivity itself is used. Examples of the transparent support having conductivity per se include transparent conductive materials such as ITO (Indium-Tin Oxide), zinc oxide, tin oxide, lead oxide, indium oxide, and copper iodide.

Insulating transparent supports include transparent inorganic materials such as glass, quartz, sapphire, MgO, LiF, and CaF ₂ , and transparent organic resins such as fluorine resin, polyester, polycarbonate, polyethylene, polyethylene terephthalate, and epoxy. A film or plate-like body, optical fiber, selfoc optical plate, or the like can be used.

  As a transparent electrode provided on one side of the transparent support, a transparent conductive material such as ITO, zinc oxide, tin oxide, lead oxide, indium oxide, copper iodide is used, and by a method such as vapor deposition, ion plating, sputtering, etc. A formed one or a thin one made of metal such as Al, Ni, Au or the like so as to be translucent by vapor deposition or sputtering is used.

In addition, the surface on the side where the substrates face each other (hereinafter may be abbreviated as “opposing surface”) may affect the charging polarity of the display device particles. For this reason, it is also preferable to provide a protective layer having an appropriate surface state on the facing surface.
This protective layer can be selected mainly from the viewpoint of adhesion of the display device particles to the substrate facing surface and the charged column, transparency of the substrate, and prevention of contamination of the surface of the facing surface. Specific examples of the material for the protective layer include polycarbonate resin, vinyl silicone resin, and fluorine group-containing resin. For the selection of the resin, a material constituting the surface of the display device particle to be used or a material having a small frictional charge difference from the display device particle is selected.

<Image forming apparatus>
The image forming apparatus of the present invention is an image forming apparatus for forming an image on the above-described image display medium of the present invention, and generates an electric field according to image information between a pair of substrates constituting the image display medium of the present invention. An electric field generating means is provided.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an image forming apparatus of the present invention using an image display medium of the present invention will be described in detail with reference to the drawings. In addition, what has the same function attaches | subjects the same code | symbol through all the drawings, and the description may be abbreviate | omitted.

-First embodiment-
FIG. 1 is a schematic configuration diagram illustrating an example (first embodiment) of an image forming apparatus according to the present invention.
The image forming apparatus 12 according to the first embodiment includes a voltage applying unit 201 as shown in FIG. The image display medium 10 is provided with a spacer 204 between the display substrate 14 on the image display side and the non-display substrate 16 facing the display substrate 14 so as to seal the outer periphery of these two substrates. Black particles 18 and white particles 20 are enclosed as display device particles in a gap partitioned by the substrate 14, the non-display substrate 16 and the spacer 204. A transparent electrode 205 is attached to the opposing surfaces of the display substrate 14 and the non-display substrate 16 as will be described later, but the transparent electrode 205 provided on the opposing surface of the non-display substrate 16 is grounded, and the display substrate The transparent electrodes 205 provided on the 14 opposing surfaces are connected to the voltage applying means 201.

Next, details of the image display medium 10 will be described with reference to specific examples of individual configurations.
For the display substrate 14 and the non-display substrate 16 constituting the image display medium 10, for example, a 7059 glass substrate having a size of 50 × 50 × 1.1 mm and an ITO transparent electrode provided as the transparent electrode 205 on the opposite surface is used. can do. A polycarbonate resin layer 206 (a layer made of polycarbonate resin (PC-Z) having a thickness of 5 μm) is provided on the surface of the transparent electrode 205 provided on the opposing surface of the display substrate 14 and the non-display substrate 16.
As the spacer 204, a space formed by cutting out a central portion of a 40 × 40 × 0.3 mm silicon rubber plate into a 15 × 15 mm square can be used.

When the image display medium 10 is manufactured, this silicon rubber plate is placed on the opposite surface side of the non-display substrate 16. Next, as display device particles, for example, titanium oxide-containing spherical white particles 20 with a volume average particle diameter of 20 μm and carbon-containing spherical black particles 18 with a volume average particle diameter of 20 μm are used in a mass ratio of 3 to 2. After mixing, about 15 mg of the mixed particles are shaken off through a screen into a square-cut portion of a silicon rubber plate placed on the opposite surface side of the non-display substrate 16. Thereafter, the opposite surface side of the display substrate 14 is brought into close contact with the silicon rubber plate, the two substrates are pressed and held with a double clip, and the silicon rubber plate and the two substrates are brought into close contact to form the image display medium 10.
In the description of FIG. 1 and the drawings shown below, the display device particles 18 and 20 are for the display device of the present invention, in which the colored fine particles having the colorant supported on the surface of the polymer fine particles are contained as described above. Particles.

-Second Embodiment-
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a schematic configuration diagram showing another example (second embodiment) of the image forming apparatus of the present invention, and the image forming apparatus 12 for forming an image on the image display medium 10 using a simple matrix. It is shown.
In the plane direction of the image display medium 10 in which a plurality of display device particle groups (not shown) having different charging properties are enclosed, electrodes 403An and 404Bn (n is a positive number) for controlling voltages in the vertical and horizontal directions. They are arranged to have a simple matrix structure. The electrode 403An is connected to the power source 405A of the electric field generator 405 configured by the waveform generator 405B and the power source 405A, and the electrode 404Bn is the power source 402A of the electric field generator 402 configured by the waveform generator 402B and the power source 402A. It is connected to the. The electrode 404Bn, the power source 405A, and the electrode 403An are connected to the sequencer 406.

  When displaying an image, the electric field generator 402 or the electric field generator 405 generates a potential at each electrode 403An, 404Bn, and the sequencer 406 controls the potential driving timing of the electrode to drive the voltage of each electrode. An electric field that can drive display device particles is applied to the electrodes 403A1 to An on one surface in units of one row, and an electric field corresponding to image information is simultaneously applied to the electrodes 404B1 to Bn on the other surface. Can be made.

3 to 5 illustrate examples of schematic cross-sectional views of the image forming unit (image display medium 10) on an arbitrary surface of the image forming apparatus 12 illustrated in FIG.
The display device particles 18 and 20 are in contact with the electrode surface or the substrate surface, and at least one surface of the substrate 14 or the substrate 16 is transparent so that the color of the display device particles 18 and 20 can be seen from the outside. It is something that can be done. As shown in FIG. 3, the electrodes 403A and 404B may be integrated by being embedded on the side facing the substrates 14 and 16, or embedded in the substrates 14 and 16 as shown in FIG. The display substrate 14 and the non-display substrate 16 may be separated from each other at a position slightly away from the surface opposite to the surface facing the display substrate 14 and the non-display substrate 16 as shown in FIG. Good.

  By appropriately setting the electric field in the image forming apparatus 12, display by simple matrix driving becomes possible. The display device particles 18 and 20 can be driven as long as they have a threshold value for movement with respect to the electric field, and the display device particles 18 and 20 are limited in color, charge polarity, charge amount, and the like. Not receive.

-Third embodiment-
Hereinafter, a third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 6 is a schematic configuration diagram showing another example (third embodiment) of the image forming apparatus of the present invention, and specifically shows an image forming apparatus using print electrodes.
The image forming apparatus 12 shown in FIG. 6 includes a print electrode 11 and a counter electrode 26 that is disposed opposite to the print electrode 11 and connected to the ground.
The image display medium 10 can be conveyed in the direction of arrow B between the print electrode 11 and the counter electrode 26. The image display medium 10 is composed of a pair of substrates (a display substrate 14 and a non-display substrate 16) and display device particles 18 and 20 enclosed between the substrates. The side is brought close to or in contact with the counter electrode 26, and the display substrate side is carried close to the print electrode 11.
The print electrode 11 includes a substrate 13 and an electrode 15 provided on the display substrate 14 side of the substrate 13, and the print electrode 11 is connected to a power source (not shown).

Next, the arrangement and shape of the electrode 15 provided on the display substrate 14 side of the print electrode 11 will be described. FIG. 7 is a schematic diagram showing an example of an electrode pattern provided on the print electrode. In FIG. 6, the surface of the print electrode 11 on which the electrode 15 is provided is moved from the non-display substrate 16 side toward the display substrate 14. It shows the case where it sees.
As shown in FIG. 7A, the electrode 15 is in a direction (that is, main scanning direction) substantially orthogonal to the conveyance direction of the image display medium 10 (the direction of arrow B in the figure) on one surface of the display substrate 14. Are arranged in a row at predetermined intervals according to the resolution of the image. The electrodes 15 may have a square shape as shown in FIG. 7B, or may be arranged in a matrix as shown in FIG. 7C.

Next, details of the printing electrode will be described. FIG. 8 shows a schematic configuration diagram of the print electrode.
As shown in FIG. 8, an AC power source 17 </ b> A and a DC power source 17 </ b> B are connected to each electrode 15 via a connection control unit 19. The connection control unit 19 has one end connected to the electrode 15 and the other end connected to the AC power source 17A, and once connected to the electrode 15 and the other end connected to the DC power source 17B. It is composed of a plurality of switches including the switch 21B.

  The switches 21A and 21B are ON / OFF controlled by the control unit 60, and electrically connect the AC power source 17A and the DC power source 17B to the electrode 15. Thereby, it is possible to apply an AC voltage, a DC voltage, or a voltage obtained by superimposing the AC voltage and the DC voltage.

Next, the operation in the third embodiment will be described.
First, when the image display medium 10 is transported in the direction of arrow B in the drawing by a transport means (not shown) and transported between the print electrode 11 and the counter electrode 26, the control unit 60 instructs the connection control unit 19. All the switches 21A are turned on. Thereby, an AC voltage is applied to all the electrodes 15 from the AC power source 17A.
Here, the image display medium 10 is a medium in which two or more kinds of display device particle groups are sealed in a space in a pair of substrates having no electrodes.

  When an AC voltage is applied to the electrode 15, the black particles 18 and the white particles 20 in the image display medium 10 reciprocate between the display substrate 14 and the non-display substrate 16. As a result, the black particles 18 and the white particles 20 are frictionally charged due to the friction between the display device particles and the friction between the display device particles and the substrate. For example, the black particles 18 are positively charged and the white particles 20 are not charged. Or negatively charged. In the following description, it is assumed that the white particles 20 are negatively charged.

  Then, the control unit 60 instructs the connection control unit 19 to turn on only the switch 17B corresponding to the electrode 15 at the position corresponding to the image data, and applies a DC voltage to the electrode 15 at the position corresponding to the image data. For example, a DC voltage is applied to the non-image area, and no DC voltage is applied to the image area.

  As a result, when a DC voltage is applied to the electrode 15, the positively charged black particles 18 in the portion where the print electrode 11 is opposed to the display substrate 14 as shown in FIG. Move to the display substrate 16 side. Further, the negatively charged white particles 20 on the non-display substrate 16 side move to the display substrate 14 side by the action of an electric field. Therefore, since only the white particles 20 appear on the display substrate 14 side, no image is displayed in a portion corresponding to the non-image portion.

On the other hand, when a DC voltage is not applied to the electrode 15, the positively charged black particles 18 in the portion where the print electrode 11 faces the display substrate 14 are maintained as they are on the display substrate 14 side due to the action of the electric field. The Further, the positively charged black particles 18 on the non-display substrate 16 side move to the display substrate 14 side by the action of an electric field. Accordingly, since only the black particles 18 appear on the display substrate 14 side, an image is displayed in a portion corresponding to the image portion.
Thereby, since only the black particles 18 appear on the display substrate 14 side, an image is displayed in a portion corresponding to the image portion.

  In this way, the black particles 18 and the white particles 20 move according to the image, and the image is displayed on the display substrate 14 side. Note that when the white particles 20 are not charged, only the black particles 18 move under the influence of the electric field. Since the black particles 18 at the portion where the image is not displayed move to the non-display substrate 16 and are hidden by the white particles 20 from the display substrate 14 side, the image can be displayed. Further, even after the electric field generated between the substrates of the image display medium 10 disappears, the displayed image is maintained by the adhesion force inherent to the display device particles. In addition, since these display device particles can move again when an electric field is generated between the substrates, the image forming apparatus 12 can repeatedly display images.

  In this way, since the particles for display device charged with air as a medium are moved by the electric field, safety is high. In addition, since air has a low viscous resistance, high-speed response can be satisfied.

-Fourth embodiment-
Hereinafter, a fourth embodiment of the present invention will be described in detail with reference to the drawings. FIG. 9 is a schematic configuration diagram showing another example (fourth embodiment) of the image forming apparatus of the present invention, and shows an image forming apparatus using an electrostatic latent image carrier.
The image forming apparatus 12 shown in FIG. 9 includes a drum-shaped electrostatic latent image carrier 24 that can rotate in the direction of an arrow A, and a drum-shaped counter electrode 26 that can be rotated in the direction of an arrow C and is disposed opposite thereto. The image display medium 10 in which display device particles are sealed between a pair of substrates in the arrow B direction between the electrostatic latent image carrier 24 and the counter electrode 26 can be inserted.

  A charging device 80 is disposed around the electrostatic latent image carrier 24 so as to be close to the electrostatic latent image carrier 24 on the substantially opposite side to the side where the counter electrode 26 is provided. A light beam scanning device 82 is arranged so that an electrostatic latent image can be formed on the surface of the electrostatic latent image carrier 24 on the arrow A direction side, and the electrostatic latent image forming unit 22 is configured by these three members. Has been.

As the electrostatic latent image carrier 24, a photosensitive drum 24 can be used. The photoconductive drum 24 is formed by forming a photoconductive layer 24B on the outer peripheral side of a drum-shaped conductive base 24A such as aluminum or SUS, and various known materials can be used as the photoconductive layer 24B. . For example, inorganic photoconductive materials such as α-Si, α-Se, As ₂ Se ₃ and organic photoconductive materials such as PVK / TNF can be used, and these can be obtained by plasma CVD, vapor deposition or dipping. Can be formed. Moreover, you may form a charge transport layer, an overcoat layer, etc. as needed. The conductive substrate 24A is grounded.

  The charging device 80 uniformly charges the surface of the electrostatic latent image carrier 24 to a desired potential. The charging device 80 may be any device as long as the surface of the photosensitive drum 24 can be charged to an arbitrary potential. In this embodiment, a high voltage is applied to the electrode wire and the electrostatic latent image carrier 24 is connected to the charging device 80. It is assumed that a corotron that generates corona discharge and uniformly charges the surface of the photosensitive drum 24 is used. In addition to this, various known chargers such as a conductive roll member, a brush, a film member, etc. are brought into contact with the photosensitive drum 24 and a voltage is applied to the photosensitive drum 24 to charge the surface of the photosensitive drum. can do.

  The light beam scanning device 82 irradiates a surface of a charged electrostatic latent image carrier 24 with a minute spot light based on an image signal, and forms an electrostatic latent image on the electrostatic latent image carrier 24. is there. The light beam scanning device 82 may be any device that irradiates the surface of the photosensitive drum 24 with a light beam in accordance with image information and forms an electrostatic latent image on the uniformly charged photosensitive drum 24. In this embodiment, a laser beam adjusted to a predetermined spot diameter by an imaging optical system including a polygon mirror 84, a folding mirror 86, a light source and a lens (not shown) provided in the light beam scanning device 82 is used as an image signal. This is a ROS (Raster Output Scanner) device that optically scans the surface of the photosensitive drum 24 by the polygon mirror 84 while being turned on and off accordingly. In addition, an LED head or the like in which LEDs are arranged according to a desired resolution may be used.

The counter electrode 26 is made of a conductive roll member having elasticity, for example. As a result, the image display medium 10 can be more closely attached. Further, the counter electrode 26 is disposed at a position facing the electrostatic latent image carrier 24 with the image display medium 10 conveyed by a conveying means (not shown) in the direction of arrow B in the figure. The counter electrode 26 is connected to a DC voltage power supply 28. The counter electrode 26 is applied with a bias voltage V _B by the DC voltage power supply 28. For example, as shown in FIG. 10, the bias voltage V _{B to be} applied is V _{H for} the potential of the positively charged portion on the electrostatic latent image carrier 24 and V _{L for the} portion that is not charged. In this case, the voltage is set to an intermediate potential between the two.

Next, the operation in the fourth embodiment will be described.
When the electrostatic latent image carrier 24 starts to rotate in the direction of arrow A in FIG. 9, an electrostatic latent image is formed on the electrostatic latent image carrier 24 by the electrostatic latent image forming unit 22. On the other hand, the image display medium 10 is conveyed in the direction of arrow B in the figure by a conveying means (not shown), and is conveyed between the electrostatic latent image carrier 24 and the counter electrode 26.

Here, a bias voltage V _B as shown in FIG. 10 is applied to the counter electrode 26, and the potential of the electrostatic latent image carrier 24 at a position facing the counter electrode 26 is V _H. Therefore, when the portion of the electrostatic latent image carrier 24 facing the display substrate 14 is charged with a positive charge (non-image portion), it faces the electrostatic latent image carrier 24 of the display substrate 14. When the black particles 18 are attached to the portion, the positively charged black particles 18 move from the display substrate 14 side to the non-display substrate 16 side and adhere to the non-display substrate 16. Thereby, since only the white particles 20 appear on the display substrate 14 side, an image is not displayed in a portion corresponding to the non-image portion.

On the other hand, when the portion facing the display substrate 14 of the electrostatic latent image carrier 24 is not charged with a positive charge (image portion), the black particles 18 are formed on the portion facing the counter electrode 26 of the non-display substrate 16. Is attached, the potential of the electrostatic latent image carrier 24 at the position facing the counter electrode 26 is _VL , so that the charged black particles 18 are displayed from the non-display substrate 16 side. It moves to the substrate 14 side and adheres to the display substrate 14. Thereby, since only the black particles 18 appear on the display substrate 14 side, an image is displayed in a portion corresponding to the image portion.

  In this way, the black particles 18 move according to the image, and the image is displayed on the display substrate 14 side. Even after the electric field generated between the substrates of the image display medium 10 disappears, the displayed image is maintained by the inherent adhesion force of the particles and the mirror image force between the particles and the substrate. Further, since the black particles 18 and the white particles 20 can move again when an electric field is generated between the substrates, the image forming apparatus 12 can repeatedly display images.

  As described above, since the bias voltage is applied to the counter electrode 26, the black particles 18 are moved regardless of whether the black particles 18 are attached to the display substrate 14 or the non-display substrate 16. Can do. For this reason, it is not necessary to adhere the black particles 18 to one substrate side in advance. In addition, an image with high contrast and sharpness can be formed. Furthermore, since particles charged with air as a medium are moved by an electric field, safety is high. In addition, since air has a low viscous resistance, high-speed response can be satisfied.

  The embodiments of the image forming apparatus of the present invention using the image display medium of the present invention have been described above with reference to the drawings. However, the image forming apparatus of the present invention is not limited to these embodiments. It can be set as desired. Moreover, although the color combination of the particle | grains for display devices was made into black and white, it is not necessarily limited to this combination, The particle | grains for display devices which have a desired color can be selected suitably as needed.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the following examples and comparative examples, the image display medium and the image forming apparatus (the image display medium and the image forming apparatus shown in FIG. 1) according to the first embodiment described above were used. At this time, the size and material of each member were the same as those already described.

(Colored fine particles 1)
80 parts by weight of crosslinked PMMA having an average primary particle diameter of 3 μm and 20 parts by weight of titanium oxide having an average primary particle diameter of 0.3 μm are premixed by a sample mill, and a surface immobilization device (hybridizer: manufactured by Nara Machinery Co., Ltd.). ) At room temperature at a rotational peripheral speed of 100 m / s and a processing time of 15 minutes, to produce colored fine particles 1.

(Colored fine particles 2)
90 parts by weight of crosslinked PMMA having an average primary particle diameter of 1 μm and 10 parts by weight of titanium oxide having an average primary particle diameter of 0.1 μm are premixed by a sample mill, and a surface immobilization device (hybridizer: manufactured by Nara Machinery Co., Ltd.). ) At room temperature at a rotational peripheral speed of 100 m / s and a processing time of 15 minutes to produce colored fine particles 2.

(Colored fine particles 3)
90 parts by weight of crosslinked PMMA having an average primary particle diameter of 3 μm and 10 parts by weight of cobalt blue having an average primary particle diameter of 0.5 μm are premixed by a sample mill, and a surface immobilization device (hybridizer: manufactured by Nara Machinery Co., Ltd.). ) At room temperature at a rotational peripheral speed of 100 m / s and a processing time of 15 minutes, to produce colored fine particles 3.

(Preparation of white particles-1)
-Preparation of dispersion A1-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A1.
<Composition>
・ Cyclohexyl methacrylate: 76 parts by mass ・ Colored fine particles 1 (white): 20 parts by mass ・ Hollow particles: 3 parts by mass (SX866 (A): JSR, primary particle size: 0.3 μm)
Charge control agent: 1 part by mass (SBT-5-0016: manufactured by Orient Kogyo Co., Ltd.)

-Preparation of charcoal dispersion B-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a charcoal dispersion B.
<Composition>
-Calcium carbonate: 40 parts by mass-Water: 60 parts by mass

-Preparation of mixture C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution C.
<Composition>
Charcoal cal dispersion B: 8.5g
・ 20% saline: 50 g

Next, dispersion A1: 35 g, ethylene glycol dimethacrylate 1 g, and polymerization initiator AIBN: 0.35 g were weighed, mixed sufficiently, and deaerated with an ultrasonic machine for 2 minutes. This was added to the mixed solution C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, sufficiently degassed under reduced pressure using an injection needle, and sealed with nitrogen gas. In this state, particles were produced by reacting at 65 ° C. for 15 hours. The obtained fine particle powder was dispersed in ion exchange water, calcium carbonate was decomposed with hydrochloric acid water, and filtration was performed. Thereafter, it was washed with sufficient distilled water to obtain unclassified white particles. Subsequently, the openings were passed through nylon sieves of 10 μm and 15 μm to make the particle sizes uniform. This was dried to obtain white particles-1 having a volume average particle diameter of 13.0 μm. The specific gravity of white particles-1 was 1.19 g / cm ³ .

(Preparation of white particle-2)
In the production of white particles-1, white particles-2 were obtained in the same manner as the production of white particles-1, except that the dispersion A1 was replaced with the dispersion A2 having the following composition. The volume average particle diameter of the white particles-2 was 12.8 μm, and the specific gravity was 1.20 g / cm ³ .
<Composition of Dispersion A2>
・ Cyclohexyl methacrylate: 81 parts by mass ・ Colored fine particles 2 (white): 15 parts by mass ・ Hollow particles: 3 parts by mass (SX866 (A): JSR, primary particle size: 0.3 μm)
Charge control agent: 1 part by mass (SBT-5-0016: manufactured by Orient Kogyo Co., Ltd.)

(Preparation of blue particle-1)
In the production of white particles-1, blue particles-1 were obtained in the same manner as in the production of white particles-1, except that the dispersion A1 was replaced with a dispersion A3 having the following composition. Blue particles-1 had a volume average particle diameter of 13.2 μm and a specific gravity of 1.18 g / cm ³ .
<Composition of dispersion A3>
・ Cyclohexyl methacrylate: 75 parts by mass ・ Colored fine particles 3 (blue): 24 parts by mass ・ Diethylaminoethyl methacrylate monomer: 1 part by mass

(Preparation of blue particle-2)
In the production of white particles-1, blue particles-2 were obtained in the same manner as the production of white particles-1, except that the dispersion A1 was replaced with the dispersion A4 having the following composition. Blue particles-2 had a volume average particle diameter of 13.1 μm and a specific gravity of 1.39 g / cm ³ .
<Composition of Dispersion A4>
・ Cyclohexyl methacrylate: 75 parts by mass • Cobalt blue: 24 parts by mass (average primary particle size: 0.5 μm)
・ Diethylaminoethyl methacrylate monomer: 1 part by mass

(Preparation of white particles-3)
In the production of white particles-1, white particles-3 were obtained in the same manner as in the production of white particles-1, except that the dispersion A1 was replaced with the dispersion A5 having the following composition. The volume average particle diameter of the white particles-3 was 13.0 μm, and the specific gravity was 1.58 g / cm ³ .
<Composition of Dispersion A5>
-Cyclohexyl methacrylate: 61 parts by mass-Titanium oxide (white): 35 parts by mass (Taipaque CR63: manufactured by Ishihara Sangyo Co., Ltd., primary particle size: 0.3 μm)
Hollow particles: 3 parts by mass (SX866 (A): JSR, primary particle size: 0.3 μm)
Charge control agent: 1 part by mass (SBT-5-0016: manufactured by Orient Kogyo Co., Ltd.)

(Preparation of black particles-1)
In the production of white particles-1, black particles-1 were obtained in the same manner as the production of white particles-1, except that the dispersion A1 was replaced with the dispersion A6 having the following composition. The volume average particle diameter of the black particles-1 was 12.9 μm, and the specific gravity was 1.21 g / cm ³ .
<Composition of Dispersion A6>
-Methyl methacrylate monomer: 89 parts by mass-Diethylaminoethyl methacrylate monomer: 1 part by mass-Microlith black: 10 parts by mass (manufactured by Ciba Specialty Chemicals)

(Example 1)
As particles 18 and 20 for display devices, a predetermined amount of particle mixture in which white particles-1 and black particles-1 are mixed so that the mixing ratio (mass ratio) of white particles: black particles is 6: 5, respectively. The image display medium and the image forming apparatus according to the first embodiment were manufactured using the above.

  Next, when a DC voltage of 100 V is applied to the transparent electrode 205, a part of the negatively charged white particles 20 on the non-display substrate 16 side starts to move to the display substrate 14 side by the action of the electric field, and the DC voltage When 200 V was applied, many white particles 20 moved to the display substrate 14 side and the display density was almost saturated (hereinafter, the voltage at which the display density is saturated is abbreviated as “driving voltage”). At this time, the black particles 18 charged to positive polarity moved to the non-display substrate 16 side, and a black and white image was displayed. Thereafter, even when the voltage was set to 0 V, the particles on the display substrate did not move, and the display density of the black and white image did not change.

[Evaluation of image density by repeated rewriting]
In order to evaluate the temporal stability of image quality (reflection density) before and after repeated display, repeated display was performed under the following driving condition A, and then repeated display was further performed under the driving condition B. The results are shown in Table 1. The reflection density was measured and evaluated as shown below.

(1) Driving condition A
-Polarity switching interval of voltage between display substrate 14 and non-display substrate 16: 1 second-Applied voltage: set to driving voltage-Polarity switching: 1600 cycles (2) Driving condition B
• Voltage polarity switching interval between display substrate 14 and non-display substrate 16: 0.1 second • Applied voltage: set to drive voltage • Polarity switching: 16000 cycles

-Reflection density-
The reflection density was measured with an X-Rite 939 densitometer (manufactured by X-Rite), and the difference between the black density (which may be a blue density in other examples and comparative examples) and the white density was determined. The evaluation criteria are as follows.
○: The difference between black density (or blue density) and white density is 0.6 or more Δ: The difference between black density (or blue density) and white density is 0.4 or more to less than 0.6 ×: Black density ( (Or blue density) and white density are less than 0.4

[Evaluation of image display maintainability against external impact]
The image forming apparatus was installed vertically, the image was displayed, the power was turned off, and the vibration was applied from the outside (lightly with a rubber hammer, impacted 5 times, and the impact resistance of the image was evaluated. It evaluated using the sensory evaluation index shown.
○: Particle dropout is small and no image defect is observed.
Δ: When viewed from a short distance, some image defects are observed, but when they are 2 m or more away from the image forming apparatus, the image defects are not recognized and can be used.
X: Image defects are conspicuous even at a distance of 2 m or more, and the level is unusable.

(Example 2)
As the particles 18 and 20 for display devices, a predetermined amount of a mixture of particles obtained by mixing white particles-2 and black particles-1 so that the mixing ratio (mass ratio) of white particles: black particles is 6: 5. The image display medium and the image forming apparatus according to the first embodiment were manufactured using the above. Next, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
As particles 18 and 20 for display devices, a predetermined amount of particle mixture in which blue particles-1 and white particles-1 are mixed so that the mixing ratio (mass ratio) of blue particles: white particles is 6: 5, respectively. The image display medium and the image forming apparatus according to the first embodiment were manufactured using the above. Next, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
As the particles 18 and 20 for display devices, a predetermined amount of particle mixture in which white particles-3 and black particles-1 are mixed such that the mixing ratio (mass ratio) of white particles: black particles is 6: 5. The image display medium and the image forming apparatus according to the first embodiment were manufactured using the above. Next, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
As the particles 18 and 20 for display devices, a predetermined amount of a particle mixture in which white particles-3 and blue particles-2 are mixed so that the mixing ratio (mass ratio) of white particles: blue particles is 5: 5, respectively. The image display medium and the image forming apparatus according to the first embodiment were manufactured using the above. Next, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

As apparent from Table 1, in Examples 1 to 3, the display image had little deterioration in reflection density over time, and a good display image could be obtained even after long-term repeated display. Further, the evaluation of impact resistance was satisfactory.
On the other hand, in Comparative Examples 1 and 2, the reflection density of the display image deteriorated with time, and a display image with good image quality could not be obtained after long-term repeated display. In the evaluation of impact resistance, it was at a level that could not be used.

1 is a schematic configuration diagram illustrating an example (first embodiment) of an image forming apparatus of the present invention. It is a schematic block diagram which shows the other example (2nd Embodiment) of the image forming apparatus of this invention. 3 shows an example of a schematic cross-sectional view of an image forming unit (image display medium 10) on an arbitrary surface of the image forming apparatus 12 shown in FIG. FIG. 9 shows another example of a schematic cross-sectional view of an image forming unit (image display medium 10) on an arbitrary surface of the image forming apparatus 12 shown in FIG. FIG. 9 shows another example of a schematic cross-sectional view of an image forming unit (image display medium 10) on an arbitrary surface of the image forming apparatus 12 shown in FIG. It is a schematic block diagram which shows the other example (3rd Embodiment) of the image forming apparatus of this invention. It is a schematic diagram which shows the pattern of the electrode of a printing electrode. It is a schematic block diagram of a printing electrode. It is a schematic block diagram which shows the other example (4th Embodiment) of the image forming apparatus of this invention. It is a figure which shows the electric potential in an electrostatic latent image carrier and a counter electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image display medium 11 Print electrode 12 Image forming apparatus 13 Display substrate 14 surface 14 of print electrode 11 Display substrate 15 Electrode 16 Non-display substrate 17A AC power supply 17B DC power supply 18 Display device particles (black particles)
19 Connection Control Unit 20 Display Device Particles (White Particles)
22 Electrostatic latent image forming unit 24 Electrostatic latent image carrier (photosensitive drum)
24A conductive substrate 24B photoconductive layer 26 counter electrode 28 DC voltage power supply 60 controller 80 charging device 82 light beam scanning device 84 polygon mirror 86 folding mirror 204 spacer 205 transparent electrode 206 polycarbonate layer 402 electric field generator 402A power source 402B waveform generator 403 Electrode An
404 Electrode Bn
405 Electric field generator 405A Power source 405B Waveform generator 406 Sequencer

Claims (7)

  A particle for a display device having a property and color that can be charged positively or negatively and having colored fine particles having a colorant supported on the surface of the fine polymer particles.   The display device particle according to claim 1, wherein the colorant is an inorganic pigment.   The display device particle according to claim 1, wherein the polymer fine particle is crosslinked. A pair of substrates arranged opposite to each other and a group of particles composed of at least two types of particles enclosed in a gap between the pair of substrates. By external stimulation, the two or more types of particles are at least An image display medium in which one type is positive and at least one other type can be negatively charged, and the positively and negatively charged particles have different colors.
The image display medium according to any one of claims 1 to 3, wherein at least one kind of particles that can be positively and negatively charged is the particle for a display device.   The image display medium according to claim 4, wherein at least one kind of the positively and negatively charged particles is white.   The image display medium according to claim 5, wherein the white particles contain a color material, and the color material is titanium oxide. An image forming apparatus for forming an image on an image display medium according to any one of claims 4 to 6,
An image forming apparatus comprising an electric field generating means for generating an electric field corresponding to an image between the pair of substrates.

Images