JP2001034202A - Image display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve density contrast and a visual field angle of a display pixel by encapsulating plural kinds of particles having masking property in a space between a display substrate and a counter substrate and using two kinds of particles having different color and volume resistivity. SOLUTION: The display substrate 100a and the counter substrate 100b are arranged to face each other in parallel through spacer particles. Besides spacer particles, nearly equivalent amount of two kinds of particles having different color and volume resistivity, black conductive particles 105 and white insulated particles 106, for example, are encapsulated therein so that volume filling rate in a void is about 50%. The black conductive particles 105 are, for example, carbon particles having 7.0 μm average grain size and 1370 kg/m3 volume density and the white insulated particles 106 are, for example, crosslinked polyacrylic acid ester having 15 μm average grain size and 1090 kg/m3 volume density. Image of high contrast is formed in a state where the black conductive particles 105 are densely stuck to a part corresponding to the image of the display substrate 100a side and the white insulated particles 106 are densely stuck to a nonimage part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art Conventionally, as a so-called electronic paper technique,
Many display technologies such as rotation of colored particles, electrophoresis, thermal rewritable, liquid crystal, and electrochromy are known. Among them, as a display technology using toner, a conductive colored toner and white particles are sealed between opposing substrates, and charges are injected into the conductive colored toner via a charge transport layer provided on the inner surface of a non-display substrate. Then, the charged electrically conductive toner moves toward the display substrate, which is located opposite to the non-display substrate, by an electric field between the substrates, and the electrically conductive colored toner adheres to the display substrate, and the electrically conductive colored toner and the white color become white. It is known that an image is displayed by contrast with particles. In the above prior art, there is room for improvement in low contrast, narrow viewing angle, and the like.

[0002]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image display which can be used repeatedly and which can be output to paper using a copying machine or a printer. It is an object to improve the density contrast and the viewing angle of a display image in a medium.

[0003]

The above object of the present invention is attained by providing the following image display medium. (1) A display substrate, and a counter substrate disposed at a predetermined interval facing the display substrate, and a plurality of types of different colors having concealing properties in a gap between the display substrate and the counter substrate. An image display medium enclosing particles, wherein the particles are at least two types of particles having different colors and different volume resistivity. (2) Among at least two kinds of particles having different colors and volume resistivity, at least one kind of particles has a volume resistivity of 10 ⁷ Ω · cm or less, and at least one kind of particles has a volume resistivity of not more than 10 Ω · cm. The image display medium according to the above (1), wherein the volume is greater than the volume resistivity of the particles by 10 ² Ω · cm or more. (3) Among at least two types of particles having different colors and volume resistivity, at least one type of particles has an average particle size of 1/1000 or more and 9/10 or less of the interval, and at least one type of particles. The average particle size of 5/10 or more of the interval is 9/10
The image display medium according to the above (1) or (2), wherein: (4) The image display medium according to any one of (1) to (3), wherein the average particle diameter of at least two types of particles having different colors and volume resistivity is substantially the same. In this image display medium, the average particle size of at least two types of particles is 1/10 of the distance between opposed substrates.
It is preferably at least 00 and at most 9/10.

(5) In at least two kinds of particles having different colors and volume resistivity, the particle diameter is ±± the average particle diameter.
30% or more by weight of particles within 50%, preferably
The image display medium according to any one of the above (1) to (4), wherein the content is 50% or more. (6) The image display medium according to any one of (1) to (5), wherein the sphericity of at least two kinds of particles having different colors and volume resistivity is 0.1 or more and 1 or less. . (7) The image display medium according to any one of (1) to (6), wherein the specific surface area shape factor of at least two types of particles having different colors and volume resistivity is 15 or less. (8) The image display medium according to any one of (1) to (7), wherein the surface energy of at least two kinds of particles having different colors and volume resistivity is 2 J / m ² or less. .

(9) The image according to any one of (1) to (8), wherein the angle of repose of at least two kinds of particles having different colors and volume resistivity is 80 ° or less. Display medium. (10) At least 2 different in color and volume resistivity
The image display medium according to any one of (1) to (9), wherein the longitudinal elastic modulus of each type of particles is 1 MPa or more and 300 GPa or less. (11) At least two different colors and different volume resistivity
Type of volume density of the particles, the image display medium according to any one of (1) to which is characterized in that at 21500kg / m ³ or less at 10 kg / m ³ or more (11).

(12) The image display as described in any one of (1) to (10) above, wherein the melting point of at least two kinds of particles having different colors and volume resistivity is 70 ° C. or more. Medium. (13) At least two different color and volume resistivity
The image display medium according to any one of (1) to (12), wherein the types of particles have different spectral reflection characteristics. (14) At least 2 different in color and volume resistivity
Any one of the above (1) to (13), wherein at least one kind of the particles is colorless and transparent or white, and at least one kind of the particles is black.
2. The image display medium according to 1. (15) The image display medium according to (14), wherein the colorless transparent particles have a refractive index of 1.2 or more and 1.85 or less. (16) The image display medium according to (14), wherein the white particles have a reflection density of 0.2 or less. (17) The image display medium according to (14), wherein the reflection density of the black particles is 0.3 or more. .

(18) A display substrate, a counter substrate facing the display substrate at a predetermined interval, and means for partitioning a gap between the display substrate and the counter substrate into minute cells,
An image display medium in which a plurality of types of particles having different concealing properties and different colors are encapsulated in each micro cell, wherein the particles are at least two types of particles having different colors and different volume resistivity. Display medium. (19) At least 2 different in color and volume resistivity
(18) The image display medium according to (18), wherein at least one of the kinds of particles contains a yellow pigment, a magenta pigment, or a cyan pigment. (20) At least 2 different in color and volume resistivity
The image display medium according to (18) or (19), wherein at least one of the types of particles contains a red pigment, a green pigment, or a blue pigment. (21) At least 2 different in color and volume resistivity
(1) to (20), wherein at least one kind of the particles has a metallic color.
The image display medium according to any one of the above.

(22) Any of (1) to (21), wherein at least one of the at least two types of particles having different colors and volume resistivity has a conductive coating layer. 2. The image display medium according to item 1. (23) The image display medium according to the above (22), wherein the conductive coating layer has a volume resistivity of 10 ⁷ Ω · cm or less. (24) At least 2 different in color and volume resistivity
The image display medium according to any one of (1) to (21), wherein at least one kind of the particles has a charge transporting coating layer. (25) The image display medium according to (24), wherein the charge transporting coating layer has an electron transporting property. (26) The image display medium according to (24), wherein the charge transporting coating layer has a hole transporting property. (27) At least 2 different in color and volume resistivity
The image display medium according to any one of (1) to (26), wherein at least one type of the particles covers at least 40% of the image display area. (28) At least 2 different in color and volume resistivity
The image display medium according to any one of (1) to (27), wherein the mixing ratio of the types of particles is in the range of 1/9 to 9/1.

(29) The display substrate and the counter substrate are a laminate in which a light-transmitting support, a light-transmitting electrode layer, and a light-transmitting charge transport layer are sequentially laminated, and the electrode layer of the display substrate is a pixel electrode. The image display medium according to any one of (1) to (28), wherein the electrode layers of the display substrate and the counter substrate are matrix electrodes. (30) The image display medium according to any one of (1) to (28), wherein the display substrate and the opposing substrate are formed of a resin layer having a charge transporting property. (31) The display substrate is a laminate in which a light-transmissive support, a light-transmissive electrode layer, a light-transmissive charge generation layer, and a light-transmissive charge-transport layer are sequentially laminated, and the opposing substrate is a light-transmissive support,
(1) or (2) wherein the light-transmissive electrode layer and the light-transmissive charge transport layer are sequentially laminated.
The image display medium according to any one of 8).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention includes a display substrate and a counter substrate facing the display substrate (hereinafter, the display substrate and the counter substrate may be referred to as “a pair of substrates”), and is concealed between the display substrate and the counter substrate. An image display medium enclosing a plurality of types of particles having different properties and different colors, wherein the particles include at least two types of particles having different colors and different volume resistivity. (1) The image display medium of the present invention uses a plurality of types of particles having different concealing properties and different colors and at least two types of particles having different colors and volume resistivity as the particles, so that an image can be formed. Particles of different types can be selectively arranged in an area and a non-image area by an electric field or the like, and the density contrast and the viewing angle of the obtained image can be improved. Furthermore, the characteristics of the image display medium can be improved by selecting the characteristics of at least two types of particles having the concealing properties and different in color and volume resistivity as shown in the following (2) to (17). For example, density contrast, density uniformity, sharpness, viewing angle,
Display responsiveness, repetitive display, image retention, and life can be improved. These are listed below.

(2) The volume resistivity of at least one kind of particles is set to 10 ⁷ Ω · cm or less, and the volume resistivity of at least one kind of particles is made 10 ² Ω · cm or more larger than the volume resistivity of the particles. Is preferred. By setting the volume resistivity of the two types of particles in this way, sufficient charge is injected from the substrate into the low volume resistivity particles, and the particles become highly charged particles and can easily move along the electric field. On the other hand, particles with high volume resistivity do not have electric charge injected, so that movement due to an electric field is small. As a result, if an electric field is formed in the image area, highly conductive particles can be selectively moved to the image area. It is possible to display an image with high contrast and a wide viewing angle.

(3) The average particle diameter of at least one kind of particles is set to 1/1000 or more with respect to the distance between a pair of opposing substrates.
9/10 or less, the average particle size of at least one type of particles is 5/1
By setting the value to be not less than 00 and not more than 9/10, selective movement of the particles is facilitated, and a high-definition image can be displayed. (4) By making the average particle diameters of at least two types of particles substantially the same, it is possible to prevent a phenomenon that different types of particles adhere to each other, and to increase the stability of particle movement. Therefore, high-speed display of an image with a high contrast and a wide viewing angle can be performed for a long time. Also in this case at least 2
By setting the average particle size of the types of particles to 1/1000 or more and 9/10 or less with respect to the distance between the opposing substrates, it is possible to prevent particles of different types from adhering to each other and to prevent the movement of the particles. Can be increased, and a high-definition image can be displayed. Here, “substantially the same” means that the average particle size of any one of the two types of particles is in the range of ± 10% of the average particle size of the other particle.

(5) For at least two types of particles,
The weight ratio of particles whose particle size is within ± 50% of the average particle size is
When the content is 30% or more, the mobility of particles is improved, and image display can be performed stably and at high speed, and the uniformity and definition of image density are improved. Furthermore, the weight ratio of particles having a particle size within ± 50% of the average particle size is set to 50% or more, and by uniformly dispersing the particles over the entire surface of the substrate, the distance between the substrates can be maintained with high precision. It becomes possible. As a result, the ease of movement of the particles is improved, image display can be performed stably and at high speed, and aggregation and the like of the particles can be prevented for a long period of time, so that the reliability and life of the medium are improved. (6) By setting the sphericity of at least two types of particles to be 0.1 or more and 1 or less, the mobility of the particles is improved, image display can be performed stably and at high speed, and aggregation of particles can be prevented for a long period of time. The reliability and service life are improved. (7) The specific surface area shape factor of at least two types of particles is 15
By doing so, the ease of movement of the particles is improved, image display can be performed stably and at high speed, and the aggregation and the like of the particles can be prevented for a long time, so that the reliability and life of the medium are improved. (8) Reduce the surface energy of at least two types of particles to ² J / m ²
By doing so, the ease of movement of the particles is improved, image display can be performed stably and at high speed, and the aggregation and the like of the particles can be prevented for a long time, so that the reliability and life of the medium are improved.

(9) The angle of repose of at least two types of particles
By setting the angle to 80 ° or less, the ease of movement of the particles is improved, image display can be performed stably and at high speed, and the aggregation and the like of the particles can be prevented for a long period of time, so that the reliability and life of the medium are improved. (10) By making the longitudinal elastic modulus of at least two kinds of particles 1 MPa or more and 300 GPa or less, the ease of movement of the particles is improved, image display can be performed stably and at high speed, and the aggregation of particles can be prevented for a long time, Further, since the particles are less deteriorated due to repeated display, the reliability and life of the medium are improved. (11) by at least two kinds of 21500kg / m ³ volume density of particles in the 10 kg / m ³ or more or less, the image display improved mobility of the particles can be performed stably at high speed.

(12) The melting point of at least two kinds of particles is 70
C. or higher can prevent aggregation of particles for a long period of time even in a high-temperature environment, and improve the reliability and life of the medium because the particles are less deteriorated by repeated display. (13) By making the spectral reflection characteristics of a plurality of types of particles different from each other, a high-contrast image can be displayed. (14) By making at least one kind of particles colorless and transparent or white, and making at least one kind of particles black,
A natural and high-contrast image can be displayed like a normal black-and-white print image. (15) By setting the refractive index of the colorless transparent particles to 1.2 or more and 1.85 or less, the whiteness in the non-image area can be improved, and a natural and high-contrast image like a normal black and white print image Display becomes possible.

(16) By setting the reflection density of the white particles to 0.2 or less, the whiteness in the non-image area can be improved, and a natural and high-contrast image display like a normal black and white print image can be achieved. Becomes possible. (17) By setting the reflection density of the black particles to 0.3 or more, the density of the image area can be improved, and a natural and high-contrast image can be displayed as in a normal black and white print image.

Further, by using the following particles, the following characteristics can be obtained in addition to the above characteristics. (18) at least one kind of particles contains a yellow pigment,
At least one type of particle contains magenta pigment and at least one type of particle contains cyan pigment, enabling natural and high-contrast color image display like a normal color print image Becomes (19) Because at least one kind of particles contains a red pigment, at least one kind of particles contains a green pigment, and at least one kind of particles contains a blue pigment, color reproduction of a color display image The area can be enlarged, and a high-quality image can be displayed. (20) By making at least one type of particles exhibit a metallic color, an impressive image display in which an image region has a metallic color or a non-image region has a metallic color can be achieved.

(21) By providing a conductive coating layer on the surface of at least one kind of particles, the selection range of the particle material is expanded, and the medium can be manufactured at low cost.

(22) The volume resistivity of the conductive coating layer is 10 ⁷
By setting the resistance to Ω · cm or less, a sufficient charge can be injected from the substrate, and the movement of particles by an electric field or the like becomes easy. In addition, stable movement can be ensured for a long time, and the reliability and life of the medium are improved. (23) By providing a charge transporting coating layer on the surface of at least one kind of particles, sufficient charge injection from the substrate becomes possible, and the movement of the particles by an electric field or the like becomes easy.
In addition, stable movement can be ensured for a long time, and the reliability and life of the medium are improved. (24) Since the charge-transporting coating layer has an electron-transporting property, a sufficient charge can be injected from the substrate, and particles can be easily moved by an electric field or the like. In addition, stable movement can be ensured for a long time, and the reliability and life of the medium are improved. Furthermore, since the polarity of the injected charge can be selected, the charge state after charge injection is stable,
The performance of holding onto the substrate is improved, and stable image display can be performed for a long time. (25) Since the charge transporting coating layer of (24) has a hole transporting property, it is possible to inject sufficient charges from the substrate and to facilitate the movement of particles by an electric field or the like. In addition, stable movement can be ensured for a long time, and the reliability and life of the medium are improved. Furthermore, since the polarity of the injected charge can be selected, the charge state after the injection of the charge is stabilized, and the performance of holding and adhering to the substrate is improved, so that a stable image display can be performed for a long time. By combining the configuration of (24) and the configuration of (25), particles having different charged electrode properties can be obtained. As a result, selective movement of particles becomes easier,
The image display can be speeded up and the contrast can be improved, and the aggregation and the like of particles can be prevented for a long period of time, so that the reliability and life of the medium can be improved.

(26) By making the coverage of the particles with respect to the display area of at least one kind of particles 40% or more, the ease of movement of the particles is improved, and the image display can be performed stably and at high speed. Aggregation and the like can be prevented, thereby improving the reliability and life of the medium. (27) By setting the mixing ratio of at least two types of particles having different colors and volume resistivity in the range of 1/9 to 9/1, mixing of foreign particles in both the image area and the non-image area is reduced. Can improve the contrast.

Next, the particles having different color and volume resistivity will be described more specifically. As particles having different volume resistivity, for example, a combination of conductive particles and insulating particles can be used. Here, the conductivity refers to a material having a volume efficiency of 10 ⁷ Ω · cm or less, and the insulation refers to a material having a volume efficiency of 10 ⁹ Ω · cm or more. The conductive particles include carbon black, nickel, silver,
Metal particles such as gold, tin, and the like, or particles in which these are coated or contained on the particle surface are preferable. For example, spherical conductive particles obtained by electroless nickel plating on the surface of fine particles composed of a crosslinked copolymer containing divinylbenzene as a main component (e.g., Micropearl NI manufactured by Sekisui Chemical Co., Ltd.) ), And then spherical conductive particles (Micropearl AU manufactured by Sekisui Chemical Co., Ltd.) plated with gold. In addition, spherical conductive particles of amorphous carbon obtained by carbonizing and sintering a thermosetting phenolic resin (Univex GC manufactured by Unitika Ltd.)
P, H-Type: Volume resistivity ≤10 ^-2 Ωcm, and spherical conductive particles coated with a metal such as gold or silver (UniVex GCP conductive particles manufactured by Unitika Ltd .: Volume resistivity ≤ 1
^0-4 Ω · cm), and spherical conductive particles (Admafine, manufactured by Admatechs Co., Ltd.) in which the surfaces of spherical oxide fine particles of silica and alumina are coated with Ag and tin oxide.

Examples of the insulating particles include commercially available glass beads, white fused alumina particles, and spherical particles made of a crosslinked copolymer containing divinylbenzene as a main component (Micropearl SP, Micropearl SP, manufactured by Sekisui Chemical Co., Ltd.). BB),
Fine particles of cross-linked polymethyl methacrylate (MBX-20 black and white manufactured by Sekisui Chemical Co., Ltd.), fine particles of polytetrafluoroethylene (Rublon L manufactured by Daikin Industries, SST-2 manufactured by Shamrock Technologies Inc.), silicone Resin fine particles (Tospearl manufactured by Toshiba Silicone Co., Ltd.), MB-C, MBE, EMA, SBX, BMX, manufactured by Sekisui Plastics
ARX-15, UB, and Toray Treceram. Usable are ordinary electrophotographic toners and transparent toners in which pigments are not dispersed.

As the two kinds of particles having different colors and different volume resistivity in the present invention, the conductive particles and the insulating particles as described above include various colors (including chromatic, achromatic, and transparent). Are given. For example, in addition to black conductive particles (carbon black in the above conductive particles, metal color, etc.) and white insulating particles (white fused alumina particles in the above insulating particles, glass beads, transparent toner, etc. (Including transparent ones) as well as yellow, magenta,
Colored insulating particles to which pigments such as cyan pigments and red, green, and blue pigments are added, and a hexagonal layered compound composed of ITO, indium / zinc oxide, and indium oxide (In ₂ O ₃ ( ZnO) _n , n is an integer of 3 or more; IDIXO manufactured by Idemitsu Kosan Co., Ltd .; tinted oxide doped with a transparent conductive material such as antimony oxide; It is also possible to combine the insulating particles with the white conductive or insulating particles as described above. Further, full-color image display is possible by using colored particles and enclosing them in an image display medium as described below.

Next, an image display medium using the particles will be described with reference to the drawings. FIG. 1 shows an example of the image display medium of the present invention. As shown in FIG.
And a counter substrate (non-display substrate) 100b are disposed to face each other in parallel via spacer particles (not shown). The distance between the two substrates is suitably 6 to 15000 μm, preferably 20 to 750 μm, for example, about 100 μm. The display substrate 100a and the counter substrate 100b are each a support 101a,
The pixel electrode layer 102 and the uniform electrode layer 104 are provided on 101b, and the charge transport layers 103a and 103b are further provided thereon. In FIG. 1, reference numeral 108 denotes an electrode driving device. The supports 101a and 101b are preferably plastic films excellent in strength, flexibility and light transmittance, and the film thickness is suitably about 10 to 1000 μm.
For example, a polyethylene terephthalate film having a thickness of about 100 μm is used. The pixel electrode layer 102 and the uniform electrode layer 104 are preferably light-transmitting conductive films, and have a thickness of 0.0
About 5 to 1 μm is appropriate. For example, an ITO film having a thickness of about 0.1 μm manufactured by vapor deposition is used.

As the components constituting the charge transport layer, the components used for the charge transport layer constituting the electrostatic latent image carrier of the electrophotographic apparatus can be applied without any particular limitation. Alternatively, a self-supporting resin or the like having charge transport ability is used. The thickness is suitably about 1 to 50 μm. Among the charge transport substances added to the binder resin, hydrazone compounds, stilbene compounds, pyrazoline compounds, and arylamine compounds are used as hole transport substances, and fluorenone compounds, diphenoquinone derivatives, pyran compounds, and zinc oxide are used as electron transport substances. Is mentioned. The layer containing the hole transporting substance enables transport of holes, and the layer containing the electron transporting substance enables transport of negative charges. As the binder resin, a polycarbonate resin or the like is preferably used. As the charge transport layer, for example, a charge transport layer having a thickness of about 5 μm, in which Ae (triphenylamine) is dispersed as a charge transport material in a binder containing a polycarbonate resin as a main component, is used.

The self-supporting resin having charge transporting ability will be described later. In the charge transport layers 103a and 103b in which triphenylamine (hole transport substance) is dispersed, only holes are transported. Pixel electrode layer 102, uniform electrode layer 104
The electrode drive device that supplies the voltage at a predetermined timing
108 is connected. In the pixel electrode layer 102, a voltage is selectively supplied to each minute electrode corresponding to a pixel in accordance with an image signal. Between the display substrate and the counter substrate, in addition to the spacer particles, two types of particles having different colors and volume resistivity, for example, black conductive particles (average particle diameter of 7.0 μm and volume density of 1370)
Kg / m ³ carbon particles) 105 and white insulating particles (cross-linked polyacrylic acid ester having an average particle size of 15 μm and a volume density of 1090 kg / m ³ ) 106 are almost equivalent, and the volume filling ratio in the voids is 50%. It is enclosed so that it becomes a degree.

FIG. 2 shows the principle of displaying an image on the display substrate using the image display medium shown in FIG. FIG. 2 (A) shows an initial state of the image display medium, and shows black conductive particles.
105 and the white insulating particles 106 are sealed in a mixed state. Switching between each pixel electrode 102 and uniform electrode 104
Connected via 110. In the initial state, the switching is off. In the display stage, as shown in FIG. 2B, a low voltage is applied to the image area pixel electrode 102b, a high voltage is applied to the non-image area pixel electrode 102a, and the uniform electrode 104 on the counter substrate side.
When an intermediate voltage is supplied to the pixel, a positive charge is induced in a portion of the uniform electrode 104 facing the pixel electrode 102b. The induced positive charges are injected into the black conductive particles 105 via the charge transport layer 103b, and the conductive particles 105 are in a positively charged state and move toward the opposite low potential pixel electrode 102b. The moved black conductive particles 105 reach the pixel electrode 102b and are charged by the adhesion force such as a mirror image force or a Van der Waals force.
It is held in a state attached to 103a. In this way,
Image display is performed by attaching black conductive particles 105 only to the image portion and keeping the white insulating particles 106 dense in the non-image portion. When erasing an image, if the pixel electrodes 102a and 102b are set to a high potential and the uniform electrode 104 is set to a low potential, the black conductive particles 105 move downward over the entire surface, and the image is erased. As described above, black conductive particles are densely attached to the portion corresponding to the image on the display substrate side, while white insulating particles are densely attached to the non-image portion, and a high-contrast image is obtained. Been formed. It was much better than conventional display media.

Next, another example of the image display medium of the present invention will be described with reference to FIGS. The image display medium of this example has a basic configuration similar to that of FIG. 1, but as shown in FIG. 3, a display substrate 100a and a counter substrate (non-display substrate) 100b are formed of a charge transport layer having a hole transport property. It differs from that of FIG. 1 in that it is composed of only 103a and 103b. The thickness of the charge transport layer is 10 to 1000 μm, preferably 50 to 500 μm.
Is appropriate. Since the pair of substrates is composed of only the charge transport layer, a resin having the same self-supporting property as that of the above-mentioned support is used for this layer, and a structure which is strong against an external force applied to the image display medium such as bending and elongation. Is preferred. The self-supporting resin having the charge transporting ability will be described later. By using such a resin layer, a visible light transmitting layer having a charge transporting ability can be obtained. In addition to the spacer particles (not shown) between the substrates, two similar to those used in the image display medium of FIG.
Kinds of particles, black conductive particles 105 and white insulating particles 1
06 is sealed at the same filling rate. The image display medium in this example performs image display using an apparatus having a configuration as shown in FIG. That is, the image display medium 401 is passed between the electrostatic latent image carrier 402 and the conductive roller 403, and a display operation is performed at this time. The electrostatic latent image carrier 402 holds an electrostatic latent image produced by performing negative charging and image portion exposure in exactly the same manner as in a normal electrophotographic image forming process.

Before the display operation, the image display medium is initialized. That is, a DC voltage is supplied to the conductive roller 402 so that the opposing substrate is at a low potential and the display substrate is at a high potential, and the black conductive particles 105 are uniformly dispersed in the same manner as described in FIGS. To the lower side. After the initialization, the electrostatic latent image on the surface of the electrostatic latent image carrier 402 is brought into contact with the image display medium, and at the same time, the conductive roller is pressed from below the counter substrate. The electrostatic latent image has a low potential (negative polarity and a large absolute value) in the image portion and a high potential in the non-image portion. If the potential of the conductive roller is set in the middle, the image in FIG. An image in which the black conductive particles 105 adhere to the image area and the white insulating particles 106 adhere to the non-image area can be formed on the same principle as the display medium. A high quality display image can be obtained. The image display medium of this example has a simple structure of a pair of substrates and can be manufactured at low cost, and can display images with a high contrast and a wide viewing angle as in the case of FIG. In addition, stable image display can be achieved without repeated aggregation when particles are used. Image display operation can be performed using a normal electrophotographic device,
There is also an advantage that no special device is required.

Examples of the self-supporting resin having the charge transporting ability include a charge transporting polymer. For example, polyvinyl carbazole, US Pat. No. 4,806,443
Polycarbonate by polymerization of a specific dihydroxyarylamine and bischloroformate described in the specification
U.S. Pat. No. 4,806,444 describes a polycarbonate obtained by polymerization of a specific dihydroxyarylamine and phosgene; U.S. Pat. No. 4,801,517 describes a bishydroxyalkylarylamine and bischloroformate; Polycarbonate by polymerization with phosgene, described in U.S. Pat. Nos. 4,937,165 and 4,959,288, with certain dihydroxyarylamines or bishydroxyalkylarylamines and bischloroformates. Polycarbonate by polymerization or polyester by polymerization with bisacyl halide, US Pat. No. 5,034,296
Or polyester of an arylamine having a specific fluorene skeleton described in the specification of JP-A No. 4983,482, a polyurethane described in U.S. Pat. No. 4,983,482, and a specific bisstyrylbisarylamine described in JP-B-59-28903. Polyester with the main chain as
JP-A-61-20953, JP-A-1-13445
6, JP-A-1-134457, JP-A-1-134457
134462, JP-A-4-1330065,
Polymers having a pendant charge-transporting substituent such as hydrazone or triarylamine described in JP-A-4-133066 and the like, “The Sixth International Co.
ngress on Advances in Non-impactPrinting Technolog
ies, 306, (1990). "and a polymer having a tetraarylbenzidine skeleton.

Further, for example, a charge transporting polymer represented by the following formula (I-1) or (I-2) described in JP-A-8-253568 can be used. In the general formula (I-1) or (I-2), Y represents a divalent hydrocarbon group, Z represents a divalent hydrocarbon group, and A is represented by the following formula (I-3). . In the formula (I-3), R ₁ and R ₂ each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a substituted amino group,
Or a halogen atom, and X represents a substituted or unsubstituted 2
And n represents an integer of 1 to 5, and k represents 0.
Or represents 1. Formula (I-1) or (I-2)
Wherein B and B 'each independently represent a group -O- (Y-
O) mH or a group -O- (YO) m-CO-ZC
O-OR '(where R' represents a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, Y represents a divalent hydrocarbon group, Z
Represents a divalent hydrocarbon group, and m represents an integer of 1 to 5. ), M represents an integer of 1 to 5, and p represents an integer of 5 to 5000. Further, the compound represented by the general formula (I-1) or (I-
X in 2) may be a charge transporting polymer represented by the following structural formula (II) or (III). By using a self-supporting resin having a charge transporting ability, a structure that is strong against external force applied to the image display medium such as bending and elongation can be obtained.

[0032]

Embedded image

Next, still another example of the image display medium of the present invention will be described. FIG. 5 shows the configuration of the image display medium.
In FIG. 5, the present image display medium includes a display substrate 500a and a counter substrate 50a.
Reference numeral 0b is arranged in parallel with and opposed to the image display medium of FIG. 1 via spacer particles (not shown). Display board
500a has a support 501a, an electrode layer 502a, a charge generation layer 50
3, and a laminate in which the charge transport layer 504a is provided in order. The opposite substrate 500b is provided on the same support 501b as the electrode layer 50.
2b and a charge transport layer 504b are sequentially provided. Support 50
As 1a and 501b, those similar to the support of the image display medium in FIG. 1 can be used. For example, a polyethylene terephthalate film having a thickness of about 100 μm is used. Electrode layers 502a and 502b
The same as that in the image display medium of FIG. 1 is used. For example, an ITO film having a thickness of 0.1 μm produced by vapor deposition is used. As the charge transport layer, the same charge transport layer as that of the image display medium in FIG. 1 can be used. For example, the thickness is obtained by dispersing Ae (triphenylamine) as a charge transport material in a binder containing a polycarbonate resin as a main component. A charge transport layer of about 5 μm is used. In this charge transport layer, only holes are transported. As the components constituting the charge generation layer, the components used for the charge generation layer constituting the electrostatic latent image carrier of the electrophotographic apparatus can be applied without any particular limitation. Suitably the thickness is in the range of 0.05 to 30 μm, preferably 1 to 10 μm. For example, a layer containing a phthalocyanine compound is used. Between both substrates, spacer particles (not shown) and two kinds of particles similar to those used in the image display medium of FIG. 1, black conductive particles 105 and white insulating particles 106 are sealed at the same filling rate. .

The image display medium shown in FIG. 5 displays an image based on the principle shown in FIG. By default,
The black conductive particles and the white insulating particles are sealed in a mixed state (see FIG. 5). First, as shown in FIG. 6A, in the process of initialization, the electrode 502a on the display substrate side is set to a low potential and the electrode 502b on the counter substrate side is set to a high potential. By injecting positive charges only from the opposite substrate side electrode 502b and positively charging the black conductive particles 105, the black conductive particles 105 are uniformly moved in the direction of the display substrate side electrode 502a. After the initialization, the display substrate side electrode 502a is set to a high potential and the counter substrate side electrode 502b is set to a low potential.
When light irradiation is performed on the non-image area as shown in FIG. 2, a hole-electron pair is generated in the charge generation layer of the irradiated area, and the hole moves downward according to the electric field and the positive charge is transferred to the black conductive particles 105. inject. The positively charged black conductive particles 105 move toward the opposing substrate side electrode 502b according to the electric field. On the other hand, in the non-light-irradiated portion, the charge is not injected into the black conductive particles 105 due to the presence of the charge generation layer, so that no movement is performed. In this manner, the black conductive particles 105 are adhered only to the image portion, and the white insulating particles 106 are densely formed in the non-image portion, whereby an image is displayed.

Since the image display medium of this example displays an image by light irradiation, a high-definition image can be displayed, and an image with a high contrast and a wide viewing angle can be displayed. Further, even when repeatedly used, stable image display is possible without aggregation of particles.

Next, FIG. 7 shows an example of an image display medium capable of performing full-color display using the two kinds of particles having different volume resistivity. The image display medium of this example is similar in basic configuration and operation to the image display medium shown in FIG. That is, the display substrate 100a is obtained by stacking the pixel electrode layer 102 and the charge transport layer 103a on the support 101a, and the counter substrate is obtained by stacking the uniform electrode layer 104 and the charge transport layer 103b on the support 101b. It is. By providing and partitioning a plurality of partitions 905 corresponding to pixels between the display substrate 100a and the opposing substrate 100b, the gap between the display substrate 100a and the opposing substrate 100b is formed at a constant interval, that is, minute cells corresponding to the pixels are formed. ing. Each microcell has white insulating particles 106 and yellow particles 90
2. Magenta particles 903 and cyan particles 904 are sealed in separate cells. The same white insulating particles as those used in the image display medium of FIG. 1 are used. The colored particles are obtained by dispersing a predetermined amount of each pigment and a transparent conductive material in a resin. In each of the micro cells, the white insulating particles and the colored conductive particles are almost equal in volume, and the volume filling in the voids is performed. It is sealed so that the rate is about 50%. In each minute cell, the conductive colored particles are charged and moved by the same operation as in the case of the image display medium of FIG. 1 and adhered to the display substrate. By performing the attaching operation in accordance with the image signal corresponding to each cell, a color image can be displayed. Regarding the color of the colored particles, besides yellow, magenta and cyan,
The color gamut can be adjusted by adding red, green, blue, black, and the like as appropriate. The image display medium of this example can display a full-color image using three conductive colored particles, and can display an image with a high contrast and a wide viewing angle as in the case of FIG. Further, even when repeatedly used, stable image display is possible without aggregation of particles.

In the present invention, the characteristics of the particles are defined as follows. (1) Volume resistivity JIS C-231 using bulk material constituting particles
Measure according to 8. (2) Average particle size (d) It is defined by the formula of d = Σmdp / M. Here, d is the average particle diameter, m is the weight of the particle group in a predetermined particle diameter section, dp
Represents the central value of the particle size classification, and M represents the total weight. (3) Sphericity Sphericity is defined by (dpv / dps) ² . Here, dpv is the equivalent volume sphere equivalent diameter (diameter of a sphere having the same volume as the volume of the particle), and dps is the equivalent area sphere equivalent diameter (diameter of a circle having the same area as the projection area of the particle). Meaning respectively. (4) Specific surface area shape factor Defined by specific surface area shape factor = dp × s / v. Here, dp is a representative diameter (short axis diameter, long axis diameter, thickness, biaxial arithmetic average diameter, triaxial arithmetic average diameter, triaxial geometric average diameter, projected area circle equivalent diameter, equivalent surface area sphere equivalent diameter, equal volume sphere S indicates the actual surface area, and v indicates the volume. (5) is defined by the surface energy _{(σ) σ = σ 1 (} 1 + cosθ) 2/4. Here, σ is the surface energy, σ ₁ is the surface tension of the liquid, and θ is the contact angle of the liquid with the particles alone or the bulk material constituting the particles. (6) Angle of repose The angle of repose means an angle formed by a slope of a mountain formed by a group of particles and a deposition surface when particles are deposited in a mountain shape on a surface. (7) Young's modulus E defined by E = F × L / (A × ΔL)
Means The bulk material constituting the particles is formed into a rectangular parallelepiped test piece having a predetermined size (cross-sectional area A, length L), a predetermined load F is applied in the length direction, a deformation amount ΔL is measured, and inserted and calculated. Find the Young's modulus. (8) Refractive index Using a bulk material constituting particles, ASTM D54
Measure according to 2-70. (9) Reflection Density The bulk material constituting the particles is used to form a sheet, and then measured using a commercially available reflection densitometer (such as a Macbeth densitometer).

[0038]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited to these Examples. Examples 1 to 10 and Comparative Examples 1 and 2 Images were displayed using the image display medium having the structure shown in FIG. 1, and the density contrast, the viewing angle, and the like were evaluated. The particles used were as shown in Table 1 and were combined as shown in Table 2. A polyethylene terephthalate film of about 100 μm as a support, a pixel electrode made of an ITO film of about 0.1 μm in thickness, and triphenylamine as a charge transport material dispersed in a binder containing polycarbonate resin as a main component. A display substrate in which a charge transport layer having a thickness of about 5 μm was sequentially laminated was manufactured. A counter substrate was manufactured in the same manner except that a uniform electrode was used instead of the matrix electrode as the electrode layer. Both substrates were arranged at an interval of about 100 μm, and in the gap, a combination of particles shown in Tables 1 and 2 was used.
Two types of particles having different colors and volume resistivity were encapsulated. The image display medium manufactured in this manner is wired as shown in FIG. 2, a low voltage is applied to the image area pixel electrode 102b, a high voltage is applied to the non-image area pixel electrode 102a, and a uniform electrode on the counter substrate side. When an intermediate voltage is supplied to 104, an image is displayed in the image area based on the principle described above. Table 3 shows the results. The particles A in Table 1 are spherical conductive particles of amorphous carbon obtained by carbonizing and curing a thermosetting phenol resin (manufactured by Unitika, Univex GCP, H-typ).
e) are standard black conductive particles, and particle B is standard white insulating particles made of a crosslinked polyacrylate. The black insulating particles of the particles C are made of a resin having a crosslinked polymethyl methacrylate resin as a main component and carbon black dispersed therein, and the white conductive particles of the particles D are formed of particles of a crosslinked polyacrylic acid ester.
It is coated with ITO. The black conductive particles and the white insulating particles of the particles E to H and the particle N are particles having the same components as the particles A and the particles B, respectively, and are obtained by classification so as to have predetermined average particle diameters and particle diameter distributions. Things. Further, the black conductive particles of the particles I are particles having the same components as the particles A, and are formed by forming the particles into a layer after carbonization and firing, and deforming them under pressure. The black conductive particles of the particles J are produced by using particles having the same components as the particles A and coating the surface with a metal layer. The black conductive particles of the particles K are obtained by dispersing carbon black in a low-hardness silicone rubber material and adjusting the color and volume resistivity. The black conductive particles L are obtained by dispersing carbon black in a wax-based low-melting resin material and adjusting the color and volume resistivity. The black conductive particles of the particles M are foamed particles produced by the same process as commercially available foamed particles using a base material in which carbon black is dispersed in a resin material and the color and the volume resistivity are adjusted.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

As shown in Table 3, Examples 1 to 10 which are the image display media of the present invention are all excellent in density contrast and viewing angle, and can be sufficiently used as image display media. In contrast, Comparative Example 1
Comparative Example 2 is inferior in both the density contrast and the viewing angle, and cannot be used as an image display medium. Table 3 shows the average particle size of the particles, the weight ratio of particles having a particle size within ± 50% of the average particle size, sphericity, specific surface area shape factor, surface energy, angle of repose, refractive index, and reflection density. It has been shown that the above-described performance can be obtained by variously changing the elastic modulus, the melting point, and the volume density.

Embodiment 11 In this embodiment, an image was displayed using the image display medium shown in FIG. As a display substrate, the thickness is about 100
A 0.1 μm thick ITO film formed by evaporation on a μm polyethylene terephthalate film, a charge generation layer of about 0.1 μm composed of a phthalocyanine-based compound, and a charge transport material in a binder mainly composed of polycarbonate resin. Triphenylamine dispersed as
A substrate having a 5 μm charge transport layer laminated in this order was used. In the charge transport layer, only holes are transported. As the counter substrate, a laminated body including a support, an electrode layer, and a charge transport layer having a structure excluding the charge generation layer among the four layers of the display substrate was used.

In addition to the spacer particles, the standard black conductive particles 105 and the standard white insulating particles 106 used in Example 1 were substantially equal in amount between the two substrates with an interval of 100 μm. Was sealed so that the volume filling ratio was about 50% to obtain an image display medium. As described in the description of FIG. 5, when no voltage is applied, black conductive particles and white insulating particles are mixed. Next, the display substrate side electrode is set to a low potential, the counter substrate side electrode is set to a high potential, and the black conductive particles are uniformly moved in the direction of the display substrate side electrode to perform initialization.
After that, when the display substrate side electrode was set to the high potential and the counter substrate electrode side was set to the low potential, the non-image portion was irradiated with light, and the black conductive particles in the irradiated portion moved toward the counter substrate side electrode. Then, the non-image portion was formed in a state where the white insulating particles were dense in the irradiated portion, and the black conductive particles adhered only to the non-irradiated portion to form an image portion. The evaluation of the displayed image is shown in Table 4 below.

[0045]

[Table 4]

Further, an image display medium having the same structure as described above was prepared by changing the particles used and the combination thereof as shown in Table 5, and the characteristics of the displayed image were examined. In Table 5, the black conductive particles used were particles A, which are the standard black conductive particles of Table 1, and the white insulating particles used were the particles B, which were the standard white insulating particles. Further, as the black insulating particles, particles C (the volume resistivity is equivalent to the standard white insulating particles and the spectral characteristics are equivalent to the standard black conductive particles), which are the black insulating particles in Table 1, are used; As the white conductive particles, particles D (the volume resistivity is equivalent to the black conductive particles and the spectral characteristics are equivalent to the white insulating particles), which are the white conductive particles in Table 1 above, were used. Table 6 shows the evaluation of the display image characteristics.

[0047]

[Table 5]

[0048]

[Table 6]

[0049]

As described above, in the present invention, a plurality of types of particles having different concealing properties and different colors are used as particles to be sealed in the gap between the display substrate and the counter substrate, and have different colors and different volume resistivity. By using at least two types of particles,
A density contrast and a wide viewing angle, which cannot be obtained by the prior art, are obtained.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross-sectional view of an example of an image display medium of the present invention.

2A and 2B are conceptual diagrams illustrating the image display principle of the image display medium of FIG. 1, wherein FIG. 2A shows an initial state and FIG. 2B shows an image display state.

FIG. 3 is a diagram schematically showing a cross-sectional view of another example of the image display medium of the present invention.

4 is a conceptual diagram showing the principle of displaying an image on the image display medium of FIG. 3 using an electrostatic latent image carrier.

FIG. 5 is a diagram schematically showing a cross-sectional view of another example of the image display medium of the present invention.

6 is a conceptual diagram showing the principle of displaying an image by irradiating the image display medium of FIG. 5 with light, and FIG. 6A is a diagram illustrating an initialization process for arranging conductive particles on a display substrate side. 6 (B)
Indicates a process of irradiating light thereafter to display an image.

FIG. 7 is a diagram schematically illustrating a cross-sectional view of an example of an image display medium capable of performing color display.

[Explanation of symbols]

100a, 500a: display substrate, 100b, 500b: counter substrate (non-display substrate), 105; black conductive particles, 106: white insulating particles,
402: electrostatic latent image carrier, 905: partition

Continued on the front page (72) Inventor Yoshiro Yamaguchi 430 Green Tech Nakai, Nakai-cho, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Yoshinori Machida 430 Green Tech Nakai, Nakai-cho, Ashigara-Kami, Kanagawa Fuji Xerox Co., Ltd. (72) Inventor Shota Oba 430 Green Tech Nakai, Nakai-cho, Ashigara-Kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Motohiko Sakemaki 430 Green Tech Nakai, Nakai-cho, Nakai-cho, Ashigaruga-gun, Kanagawa Fuji Xerox Co., Ltd. (72) Invention Person Minoru Koshimizu 430 Green Tech Nakai, Nakai-cho, Ashigagami-gun, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Takeo Kakinuma 430 Green Tech Nakai, Nakai-cho, Nakai-machi, Ashigara-gun, Kanagawa Prefecture Fuji Xerox Co., Ltd. F-term (reference) 2H029 DB00 DB13 5C094 AA06 AA12 BA75 BA84 CA24 GA10 GB01 JA02 JA07 JA08 JA09

Claims (11)

[Claims] 1. A display device comprising: a display substrate; and a counter substrate disposed at a predetermined distance from and facing the display substrate. What is claimed is: 1. An image display medium encapsulating different kinds of particles, wherein the particles are at least two kinds of particles having different colors and different volume resistivity. 2. A method according to claim 1, wherein at least one of the at least two kinds of particles having different color and volume resistivity has a volume resistivity of 10 ⁷ Ω · cm or less and a volume resistivity of at least one kind of particles. Is 10 ² Ωcm from the volume resistivity of the particles.
2. The image display medium according to claim 1, wherein the image display medium is larger than the above. 3. An average particle diameter of at least one of the at least two kinds of particles having different color and volume resistivity is not less than 1/1000 and not more than 9/10 of the interval, and at least one kind of particles is different. 3. The image display medium according to claim 1, wherein the average particle diameter of the particles is 5/100 or more and 9/10 or less of the interval. 4. 4. The image display according to claim 1, wherein the at least two kinds of particles having different colors and volume resistivity have substantially the same average particle diameter. Medium. 5. A weight ratio of particles having a particle diameter within ± 50% of an average particle diameter of at least two kinds of particles having different colors and volume resistivity is 30% or more. The image display medium according to any one of claims 1 to 4. 6. The method according to claim 1, wherein the sphericity of at least two types of particles having different colors and volume resistivity is 0.1 or more and 1 or less. Image display medium. 7. The image according to claim 1, wherein the specific surface area shape factor of at least two kinds of particles having different colors and volume resistivity is 15 or less. Display medium. 8. The method according to claim 1, wherein the surface energy of at least two kinds of particles having different colors and volume resistivity is 2 J / m ² or less.
Item 15. The image display medium according to Item 1. 9. The image display according to claim 1, wherein the angle of repose of at least two types of particles having different colors and volume resistivity is 80 ° or less. Medium. 10. The method according to claim 1, wherein the longitudinal elastic modulus of at least two kinds of particles having different colors and volume resistivity is not less than 1 MPa and not more than 300 GPa. Image display medium. 11. The volume density of at least two kinds of particles having different colors and volume resistivity is 21500 kg at 10 kg / m ³ or more.
/ m ³ image display medium according to any one of claims 1 to 10, characterized in that less.