JP2000347483A - Image forming method and image display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording method by which an image having excellent image quality is formed on plain paper and in which the power consumption is made low while keeping the device compact and inexpensive by selectively applying voltage to a particle layer and selectively sticking conductive particles to a medium to form an image. SOLUTION: The conductive particles 4 are enclosed between a medium 1 provided with a charge transporting layer 3 and a medium 2 to which the voltage can be applied. The layer 3 where positive hole transporting material is mixed in insulating resin transports only positive hole and does not transport electron. Since the particles 4 in which the charge is injected from a substrate electrode to which positive voltage is applied have the charge, they move to an upper transparent electrode. Furthermore, the particles 4 move to the electrode on an opposite side by making the voltage of the electrode reverse. At this time, white particulates 5 are mixed as the insulating particles, black color obtained till then disappears and white appears because the particles 5 are observed from the transparent electrode. Thus, white and black images are rewritten.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming method using conductive particles and an image display medium in an electrostatic recording field and an image display medium using an electrostatic recording method.

[0002]

2. Description of the Related Art Conventionally, there have been proposed a number of methods for forming an image by electrostatically charging particles by charging the particles using conductive particles. For example, an image forming method using conductive magnetic particles and a recording electrode is described in A.I. R. Kotz: J.
Appl. Photo. Eng. 7, (2), p44, 1
981 or K.I. Okuna et. al. And Pro
c. Japan Hardcopy 91, p117,
1991 and the like. Also, USP
No. 4,155,093 discloses a method of forming an electrostatic latent image on a dielectric and developing with conductive particles, and US Pat. No. 4,396,927 discloses a method of developing conductive particles by exposing from the back of a transparent roller or belt member having a photosensitive layer on the surface. It is shown.

[0003] These recording systems are characterized in that the driving voltage is low. Also, harmful substances such as ozone are generated in a charger or the like, but there is no such concern because no charger is used. Also, as a matter of course, there is an advantage that the recording apparatus can be simplified and downsized because the number of recording steps is small.

On the other hand, as an image display method using conductive particles, Proc. Japan Hardcopy 89,
pp. 151, 1989 and Proc. Japan Hard
copy 91, p133, 1991, which can display a large screen and hold the display.
There is a problem that it is difficult to reduce the size and it takes time to rewrite the display image.

[0005] The method of directly forming a particle image using conductive particles has many advantages in comparison with conventional electrophotographic recording devices and electrostatic recording devices. However, there are very few examples which have been put to practical use as a recording apparatus as compared with an electrophotographic recording apparatus or an electrostatic recording apparatus.

One of the biggest reasons is that when conductive particles are used, the particle image formed on the image bearing member is
It is very difficult to transfer to plain paper. When transferring a particle image from an image bearing member to plain paper, an ordinary electrophotographic recording device or the like employs an electrostatic transfer method. This conveys the plain paper recording paper and makes the image bearing member and the recording paper come into close contact with each other at the transfer section. Next, an electric field such that the charged particles are electrostatically attracted to the recording paper is formed between the recording paper and the image bearing member. The electrostatic transfer includes corona transfer, roller transfer, and the like, depending on the means for forming an electrostatic field.

[0007] The corona transfer method is a method in which a charge having a polarity opposite to that of the charged particles is applied to the back surface of the recording paper by a corona charger. The charged particles are transferred onto the recording paper by the electrostatic force acting between the charged particles and the charge of the opposite polarity.

In the roller transfer method, an electric field is formed by pressing a conductive rubber roller to which a voltage is applied from the back surface of a recording paper or a dielectric roller having a dielectric film provided on the surface of the conductive rubber roller. is there. In any case, the basic principle of electrostatic transfer is exactly the same, in which charged particles are attracted from an image bearing member to recording paper by electrostatic force and transferred.

However, when conductive particles are used,
When such electrostatic transfer is performed, remarkable deterioration of image quality occurs. This is because, because the particles are conductive, the charge of the particles leaks to the recording paper, and the particles cannot be firmly held on the recording paper by electrostatic force. Therefore, it is difficult to transfer the particle image to plain paper, and even if the transfer is performed, the image is disturbed.

In order to solve the above-mentioned problem, when conductive particles are used, a transfer method other than the electrostatic transfer is used. Usually, a pressure transfer system is used. In the pressure transfer method, a high pressure is applied to the particle image and the recording paper to make them adhere to each other, so that the particles are softened and transferred to the recording paper. Although high transfer efficiency is obtained, a very large pressure needs to be applied, and mechanical strength is required and driving torque is increased. Therefore, it is difficult to use the pressure transfer method in a small-sized and low power consumption recording apparatus. There is also a disadvantage that only an image bearing member having a strength capable of withstanding a large pressure can be used. A method other than pressure transfer is a method in which particles are transferred to an adhesive intermediate medium using the adhesive force of the intermediate medium. Then, the image is transferred and fixed from the intermediate medium to recording paper by heat or the like. It is characterized by high transfer efficiency and little degradation of image quality.
Since there is a step of retransfer to recording paper, there is a disadvantage that the apparatus becomes large and complicated. Further, for example, see JP-A-6-9555
A method has been proposed in which particles are thermally melted and transfer is performed using the adhesive force as in No. 18, but there is a problem that image deterioration such as thickening occurs. There is also a method in which transfer to plain paper is not performed and a special insulating recording paper is used in order to prevent the charge of the charged particles from leaking.

On the other hand, for an image display medium, characters and images are conventionally created as digital data by a computer, an electronic camera, or the like, and the confirmation is performed by displaying on a CRT or a liquid crystal display. Further, when the data is distributed or stored as a document, it is recorded on a paper medium by a printer. It is widely used as so-called hard copy. As characters and displays, liquid crystal display panels and plasma display panels are used for image display on televisions and computers. Among them, researches on liquid crystal enlargement, thinning, and reflection type have been promoted, and liquid crystal is becoming a central existence as an image display medium.

These display digital data instantaneously,
The next screen can be displayed instantly. However, it is difficult to carry around the apparatus at all times, and there are many drawbacks such as eyestrain when working for a long time, and the inability to display when the power is turned off. In addition, the hard copy is easier to read the text than the display and less fatigued, and can be read in a free posture.
Furthermore, it has the feature that it is lightweight and can be carried freely. However, hard copies are discarded after they are used,
Although it is recycled, it requires much labor and cost, so that there is a problem in resource saving.

A rewritable paper-like display medium having both the advantages of a display and a hard copy as described above can be used repeatedly over and over after recording an image. is there. Conventionally, there are the following technologies having such features.

As a rewritable image display medium, a transparent opaque rewritable marking medium, which is a thin film in which a low molecular compound is dispersed in a polymer film and which can stably repeat a transparent opaque phase change by heating, A coloring / erasing type rewritable marking which can repeat coloring / decoloring of a leuco dye depending on a difference in a heating temperature or a cooling rate after heating has been studied and is used as a rewritable card.
Also, an electrophoretic display that microscopically encapsulates white fine particles and an insulating liquid to display an image by electrophoresis, or a twist ball that displays images by rotating two color-coded fine spherical particles embedded in a resin thin film A type display medium is being studied. However, there are many problems such as poor image contrast and deterioration due to repetition.

Similar to the present invention, a form in which conductive particles are sealed between transparent electrodes, and a form in which conductive particles are sealed between transparent electrodes having a dielectric material on the surface can be conceived. When a particle layer containing conductive particles is sealed with a transparent electrode and a voltage is applied,
Electric charges are injected from the electrodes into the conductive particles that are in contact with the electrodes and are charged. Now, the particles in contact with the positive electrode are positively charged, and when the Coulomb attraction between the particles and the negative electrode becomes larger than the gravity of the particles, the particles move toward the negative electrode. When the particles reach the negative electrode, electrons are injected from the electrode, and the particles are negatively charged. After that, it moves toward the positive electrode due to the Coulomb force with the positive electrode. As a result, the particles reciprocate between the two electrodes. In this,
The image cannot be formed by fixing the particles on the electrode. Next, when the electrode coated with the insulating resin thin film is used as one of the electrodes, the particles injected with electric charge by the other electrode move toward this electrode and are fixed to the surface of the insulating resin thin film. Since the particles are fixed by the Coulomb attraction between the charges on the electrodes and the particle charges, the fixed particles can be seen from above by using a transparent electrode for the electrodes. However, there is a problem in that a high voltage is required to switch the polarity of the electrode applied in reverse to separate the particles, and the particles cannot be easily separated.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a recording apparatus using conductive particles, which can form an image having excellent image quality on plain paper, and which is small in size, low in cost and low in power consumption. An object of the present invention is to provide a method and an image display medium capable of rewriting an image with good image contrast and no deterioration due to repetition.

[0017]

Means for Solving the Problems As described above, the object of the present invention is to provide (1) particles containing at least conductive particles between a medium 1 having a charge transport layer on its surface and a medium 2 to which a voltage can be applied. Forming an image by selectively applying a voltage to the particle layer to selectively adhere conductive particles on the medium 1 ", and (2) (2) the medium (2) comprising a substrate, an electrode, and a charge transport layer, and selectively applying a voltage to selectively move the conductive particles on the medium 1 onto the medium 2; Image forming method according to item 1) ”, (3)
(4) The image forming method according to (2), wherein the conductive particles repeatedly move between the medium 1 and the medium 2 by selectively applying a voltage.
"The image forming method according to the above (2) and (3), wherein the medium 1 comprises a transparent substrate, a transparent electrode and a charge transport layer", (5) "the medium 1 and the medium 2 The image forming method according to any one of the above (1) to (4), wherein conductive particles and insulating particles having a different color from the conductive particles are mixed therebetween.

Further, the above object is achieved by providing (6) the conductive particles and the conductive particles between the medium 1 having the charge transport layer on the surface layer and the medium 2 comprising the substrate, the electrode and the charge transport layer according to the present invention (6). (7) An image display medium characterized by enclosing colored insulating particles, (7) The medium (1), wherein the medium 1 comprises a transparent substrate, a transparent electrode, and a charge transport layer. Image display medium ".

Further, the object is as described in (8) of the present invention, wherein the medium 2 is a roller or a belt member on which individually controllable electrodes are formed. Image forming method ", (9)" Medium 2 is
(1) The image forming method according to the above (1), wherein at least a roller or a belt member having a dielectric material on a surface layer and forming an electrostatic latent image in advance is used.
0) The image forming method according to the above (1) and (8) to (9), wherein the conductive particle image formed on the medium 1 is electrostatically transferred. Achieved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

Here, the image forming method of the present invention will be outlined. The conductive particles are sealed between a medium 1 provided with a charge transport layer, which is widely used in an organic photoreceptor for electrophotography, and a medium 2 to which a voltage can be applied. The charge transport layer in which a hole transport material is mixed in an insulating resin transports only holes and does not transport electrons. Now, consider the case where a positive charge is applied on a medium to which a voltage can be applied. A positive charge is injected into the conductive particles, causing the particles to become positively charged. When the threshold value is exceeded, the particles adhere to the charge transport layer of the counter electrode and are fixed by Coulomb force due to the particle charges. At this time, electrons are not injected into the charge transport layer. Further, the positive charges of the particles cannot be injected because the injection into the charge transport layer is blocked. As a result, the charge transport layer exhibits an insulating property, and the particles adhere to the charge transport layer for a long time, and retain the charge. Further, when the particles are brought into contact with a transfer medium such as plain paper and applied with a negative voltage, the transfer efficiency is high and the transfer is possible without disturbance of the image. Here, when an insulating layer is provided instead of the charge transport layer, although there is no leakage and the particles retain the charge, they cannot be transferred unless an extremely high charge is applied, or an electrostatic latent image is formed on the insulating layer. This causes problems such as afterimage particles.

In addition, an image rewritable display device having a good image contrast and no deterioration due to repetition is provided with a charge transport layer widely used in an organic photoreceptor for electrophotography. This can be achieved by realizing an image display medium enclosing insulating fine particles.

The charge transport layer in which a hole transport material is dissolved in an insulating resin transports only holes and does not transport electrons. Now, consider a case where conductive particles are attached to a positive electrode provided with a charge transport layer. The holes injected from the transparent electrode into the charge transport layer are transported through the charge transport layer and then injected into the conductive particles to charge the particles positively. Above a certain threshold, the particles move towards the negative electrode. Particles adhere to the charge transport layer on the negative electrode and are fixed by Coulomb force due to the negative electrode and the particle charge. At this time, electrons are not injected from the transparent electrode into the charge transport layer. Further, the positive charges of the particles cannot be injected because the injection into the charge transport layer is blocked. As a result, the charge transport layer exhibits insulating properties, and the particles adhere to the charge transport layer for a long time. When a voltage is applied in reverse, holes are injected from the transparent electrode to which the particles have adhered, are transported through the charge transport layer, and are then injected into the particles to positively charge the particles. Thereafter, the particles move to the opposite negative electrode. By observing the movement of the particles from above the transparent electrode, adhesion and removal of the particles can be observed.

The conductive particles placed between the upper transparent electrode provided with the charge transport layer and the substrate electrode are charged from the substrate electrode to which a positive voltage is applied, and the particles have a charge. It moves to the upper transparent electrode by the Coulomb force between a certain negative charge. The particles adhered to the charge transport layer on the upper electrode are kept as they are. Then, when viewed from the upper transparent electrode, the conductive particles appear to be constricted over the entire surface of the electrode. Therefore, when black particles are used as the conductive particles, black is observed. Further, reversing the voltage on the electrodes causes the particles to move to the opposite electrode. At this time, if white fine particles are mixed as insulating particles, the black color thus far disappears, and the white fine particles are observed from the transparent electrode, resulting in white particles. This makes it possible to rewrite white and black images.

FIGS. 1 and 2 show the principle of the image display medium of the present invention.
This will be described. (A) shows the position of particles when a negative voltage is applied to the upper electrode of the rewritable particle display medium of the present invention. (B) shows the position of the particles after applying a negative voltage to the upper electrode of the rewritable particle display medium of the present invention. Black display is obtained from the upper electrode. (C) shows the position of the particles when a positive voltage is applied to the upper electrode of the rewritable particle display medium of the present invention. (D) shows the position of the particles after applying a positive voltage to the upper electrode of the rewritable particle display medium of the present invention. White display is obtained from the upper electrode. (E) is an enlarged schematic top view of the rewritable particle display medium of the present invention, showing the state of black display after applying a negative voltage to the upper electrode and the state of white display after application of the positive voltage.

FIG. 2 is a schematic side enlarged view of the rewritable particle display thin film medium of the present invention. A thin film of the charge transport layer 3 is provided on the upper part. In an image display medium coated with a conductive toner and white particles uniformly on an electrode provided with a charge transport layer and covered with a charge transport layer, the image was formed on the surface of the electrophotographic photoreceptor on the charge transport layer surface. An image can be obtained by directly contacting the electrostatic latent image. Further, an image can be formed by forming an electrostatic pattern directly on the medium by ion flow. FIG. 2A shows the state of the particles after the positive charges have been applied to the entire surface, and the particles appear white when viewed from above. (B) shows the state of the particles after a negative charge has been applied to a part of the surface, and only the voltage applied part appears to be colored.

FIG. 3 shows an image forming method using individually controllable electrodes, which is an embodiment of the image forming method of the present invention. The conductive colored particles 4 are supplied from the hopper 10 onto a sleeve 12 having a rotatable magnetic roller 11 inside and microelectrodes embedded therein. A voltage is applied to the electrode on the sleeve, and the conductive colored particles 4 are adhered and developed on the developing roller 13 having the charge transport layer 3 on the surface. The conductive colored particle image formed on the developing roller 13 is transferred to a transfer medium 15 such as plain paper by the transfer roller 14.
Here, the applied voltage is preferably from 24 to 48V.

FIG. 4 shows another embodiment of an image forming method using a roller having a dielectric material on the surface layer and forming an electrostatic latent image in advance. Plamag roller 16 having a dielectric layer on its surface
An electrostatic latent image is formed thereon using the stylus electrode 17. The conductive colored particles 4 are supplied from the hopper 10, and the conductive colored particles 4 are adhered and developed on the developing roller 13 having the charge transport layer 3 as a surface layer. The conductive colored particle image formed on the developing roller 13 is transferred to a transfer medium 15 such as plain paper by the transfer roller 14. After the development is completed, the plastic roller 16 is cleaned by the cleaning device 18.

The charge transporting layer used in the present invention is the same as that used for the organic photoreceptor for electrophotography, and is a thin film in which a charge transporting material is dissolved in a binder resin and solidified. Known materials are used as the charge transport material, and oxadiazole, hydrazone, and arylamine derivatives described in “Basics and Application of Electrophotography” (edited by the Electrophotographic Society, 1988, Corona) are used. As the binder resin, a polycarbonate resin, a polyester resin, an acrylic resin, or the like having good compatibility with the charge transport material is used.

The particles used in the present invention are preferably magnetic particles containing magnetic powder from the viewpoint of transportation of the particles. Particles suitable for the present invention, polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-butadiene copolymer, styrene-maleate copolymer, polyethylene copolymer, Ferrite and iron oxide are contained in binder resins such as polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, aliphatic or alicyclic hydrocarbon resin.
It is preferable to mix a powder of about 70 parts by weight, pulverize and classify the powder to 3 to 20 μm, and fix a conductive fine powder such as carbon black or conductive titanium oxide around the powder. In addition, it is possible to create color particles by selecting a color pigment contained therein, as a color pigment, a polyazo pigment benzimidazolone-based pigment for yellow, a phthalocyanine pigment for blue, a brilliant carmine for red, Quinacridone pigments and the like can be used. In order to form chromatic particles, it is preferable that the magnetic material be covered with titanium or the like to cover the color of the magnetic material.

The particles are required to be electrically conductive because charges are injected from the electrode, and generally, 10 ＾ 6 ＾ 10 ＾ 9Ω.
Particles having a resistance value of cm are used.

By forming an image using the method shown in FIGS. 3 and 4, it was possible to obtain an image with good dot quality and excellent image quality on plain paper with a low applied voltage of, for example, 24 to 48 V. .

Other additives include, for example, colloidal silica, hydrophobic silica, fatty acid metal salts (such as zinc stearate and aluminum stearate), metal oxides (such as titanium oxide, aluminum oxide, tin oxide and antimony oxide), It may contain a fluoropolymer or the like.

Next, a method for displaying an image on a rewritable medium according to the present invention will be described. Create a matrix of transparent electrodes on a glass substrate or film,
The medium of the present invention is formed in each cell. An image can be displayed by controlling each cell to be colored and white by switching the polarity of the applied voltage. Further, when this cell is divided into red, blue, and yellow for display, full-color display becomes possible.

Further, in an image display medium in which conductive particles and white particles are uniformly coated on an electrode provided with a charge transporting layer and coated thereon with a charge transporting layer, the surface of the charge transporting layer is covered with an electrophotographic photosensitive member. An image can be obtained by directly contacting the electrostatic latent image formed on the surface. Further, an image can be formed by forming an electrostatic pattern directly on the medium by ion flow.

In the present invention, a transparent electrode is formed by forming an oxide thin film mainly composed of indium and tin on a glass surface or a transparent film, or a so-called conductive polymer such as polyacetylene, polypyrrole or polythiophene on a glass or a transparent film. Can be used.

The particles having a color different from that of the conductive particles may be anything as long as they have a different color tone from the particles. For example, fine particles of light color or white are preferably used. These particles do not need to react particularly when a voltage is applied between the electrodes, and therefore need to be insulative. Since the conductive particles move from one electrode to the other electrode by passing through many fine particles, it is desired that the particles have a small cohesive force and a high fluidity. As examples thereof, white fine particles such as titanium oxide particles, zinc oxide particles, white pigment-containing polymer particles, silica particles, and fluorocarbon particles can be preferably used.

As the conductive particles, all the above-mentioned particles can be used, and in the image display medium, inorganic particles such as spherical iron powder can be further used.

[0039]

EXAMPLES The present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

(Example 1) (Preparation of charge transport layer) Charge transport agent (hydrazone derivative; Hydrazone, manufactured by Annan) 1 part Resin (polymethyl methacrylate resin; PMMA, manufactured by Mitsubishi Rayon Co., Ltd.) 1 part in tetrahydrofuran Mix and mix with a spin coater.
It was applied on a TO glass substrate. Drying was performed for 2 hours with a vacuum dryer to form a charge transport layer having a thickness of 3 μm.

(Preparation of Particle Display Cell) A space is formed by sandwiching a 100 μm transparent film between two transparent electrode ITO substrates coated with a charge transport layer. One part of conductive particles (BLSP, manufactured by Titanium Industry Co., Ltd.) and one part of white insulating fine powder (manufactured by Nippon Carbon, fluorocarbon) were mixed and sealed in the space.

(Display Operation) A negative voltage of 3 is applied to the upper ITO electrode.
When 00V was applied, the upper electrode turned black. As a result of measuring the reflection density of the upper electrode at that time, it was as follows. Reflection density when negative electrode is applied D (-) = 0.9

Next, when the upper electrode was positively applied, the upper electrode turned white. As a result of measuring the reflection density of the upper electrode at that time, it was as follows. Reflection density when positive electrode is applied D (+) = 0.6

The density difference between black and white at this time is as follows. Difference in reflection density between black and white display C = D (-)-D (+) = 0.3

When the polarity of the voltage was further switched to the first negative, the upper electrode changed to black and showed the same reflection density as described above. When the polarity was made positive, the color became white, and the same reflection density was exhibited. The black and white display of the upper electrode by switching the polarity was performed about 100 times, but could be repeated stably.

(Example 2) After displaying black on the upper electrode in Example 1, the voltage was turned off and the apparatus was left for one week. Thereafter, the reflection density on the upper electrode was measured. As a result, it was the same as the reflection density 0.9 at the start of display. From this, it was confirmed that the display can be stably maintained for a long time even after the voltage is turned off.

Example 3 IT on a polyester film
An O deposition electrode was provided, and a thin film having the charge transport layer of Example 1 formed thereon was prepared. Then, the mixture of the conductive particles and the white particles of Example 1 was spread thinly on the gold electrode thin film on which one charge transport layer was formed. Thereafter, a charge transport layer thin film having a thickness of about 80 microns was overlaid to produce a particle display thin film.

When partial negative corona charging was performed on the particle display thin film, the film turned black and an image was formed. Further, when positive corona charging was performed on the entire surface, the image disappeared and became white. This could be repeated many times. This display thin film was lightweight and portable like a paper medium, and could be folded.

[0049]

As described above, according to the present invention, the image forming method according to the present invention is capable of forming an image with excellent image quality on plain paper, and is small in size, low in cost and low in power consumption. In addition, it is possible to provide an image display medium capable of rewriting an image having a high contrast and having no deterioration due to repetition, and an image display medium such as a paper medium which is lightweight, portable, and foldable.

[0050]

[Brief description of the drawings]

FIG. 1 is a principle diagram showing a configuration of a rewritable particle display medium of the present invention and a state of particle movement before and after voltage application.

FIG. 2 is an enlarged schematic side view of the rewritable particle display thin film medium of the present invention.

FIG. 3 shows a schematic diagram of an image forming method using a controllable electrode of the present invention.

FIG. 4 is a schematic view of an image forming method using a member having a dielectric material on a surface layer of the present invention.

[0051]

[Explanation of symbols]

 Reference Signs List 1 substrate 2 conductive layer 3 charge transport layer 4 conductive colored particles 5 white particles 6 glass substrate 7 power supply 10 hopper 11 magnetic roller 12 sleeve with electrodes 13 developing roller 14 transfer roller 15 transfer medium 16 Plamag roller 17 having a dielectric layer on its surface 17 Stylus electrode 18 Cleaning device

Claims (10)

[Claims] 1. A particle layer containing at least conductive particles is formed between a medium 1 having a charge transport layer on a surface layer and a medium 2 capable of applying a voltage, and a voltage is selectively applied to the particle layer. Forming an image by selectively adhering conductive particles on a medium 1. 2. The medium 2 comprises a substrate, an electrode, and a charge transport layer, and selectively applies a voltage to selectively move the conductive particles on the medium 1 onto the medium 2. The image forming method according to claim 1. 3. The image forming method according to claim 2, wherein the conductive particles repeatedly move between the medium 1 and the medium 2 by selectively applying a voltage. 4. The image forming method according to claim 2, wherein the medium 1 comprises a transparent substrate, a transparent electrode, and a charge transport layer. 5. The image forming method according to claim 1, wherein conductive particles and insulating particles having a different color from the conductive particles are mixed between the medium 1 and the medium 2. 6. The method according to claim 1, wherein conductive particles and insulating particles of a different color from the conductive particles are sealed between the medium having the charge transport layer and the medium having the charge transport layer and the substrate. Image display medium. 7. The image display medium according to claim 6, wherein the medium 1 comprises a transparent substrate, a transparent electrode, and a charge transport layer. 8. The image forming method according to claim 1, wherein the medium 2 is a roller or a belt member on which individually controllable electrodes are formed. 9. The image forming method according to claim 1, wherein the medium 2 is at least a roller or a belt member having a dielectric material on a surface layer and forming an electrostatic latent image in advance. 10. The image forming method according to claim 1, wherein the conductive particle image formed on the medium 1 is electrostatically transferred onto a transfer medium.