JP2010156774A - Display medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium where degradations in light resistance and reflection characteristic are suppressed, and also to provide a display device. <P>SOLUTION: The display medium is provided with: a pair of electrodes; a photoconductive layer which is provided between the pair of electrodes and shows electric characteristic distribution corresponding to intensity distribution of irradiated exposing light; a display layer which is provided between the pair of electrodes and to which divided voltage distributed according to the electric characteristic distribution of the photoconductive layer by voltage applied to the pair of electrodes is applied, to display an image by the optical characteristic distribution in accordance with the divided voltage; and an isolation layer which is arranged in contact with at least the photoconductive layer between the photoconductive layer and the display layer, and the ion density of which is 5×10<SP>-5</SP>C/cm<SP>3</SP>or more and 10×10<SP>-5</SP>C/cm<SP>3</SP>or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display medium and a display device.

As a display medium replacing paper, a display medium using a cholesteric liquid crystal and a photoconductive layer in which free electrons move due to an internal photoelectric effect when irradiated with light under an electric field has been proposed.
In display media that are currently under development, for example, in a display medium in which a display layer that is a cholesteric liquid crystal layer and a photoconductive layer that is a photoconductor layer are stacked between a pair of electrodes, a voltage is applied to the pair of electrodes. A desired recorded image is written by exposing the photoconductive layer in a state where is applied. Specifically, when exposure is performed with a voltage applied to a pair of electrodes, a photocurrent flows through the photoconductive layer, and the partial pressure related to the exposed area of the liquid crystal layer increases, so that the exposed area changes homeotropically. When the voltage is released, it changes to the planar state. Thereby, an image is written.

  Here, when a voltage is applied between the electrodes, holes generated in the charge generation layer of the photoconductive layer move in the charge transport layer due to the influence of the electric field, and in an ideal state, the holes disappear by releasing the voltage application. However, there is a case where a residual potential is generated due to a hole remaining without being eliminated by holes trapped in the trap level.

  Various attempts have been made to reduce this residual potential. For example, in Patent Document 1, immediately after the application of a voltage pulse for writing an image on a display medium, the residual charge remaining on the display medium is canceled. As described above, a technique for applying an auxiliary pulse continuous to the voltage pulse has been proposed.

  In addition, as a technique for suppressing sensitivity deterioration of a display medium, for example, Patent Document 2 discloses that a charge generation layer includes a charge generation layer including a charge generation material, a binder, and a proton-based solvent that does not damage the charge transport layer. A technique for making a liquid dispersion for use has been proposed.

Patent Document 3 proposes a technique for improving the symmetry during AC driving by providing a DC component removal film between the photoconductive layer and the display layer.
Japanese Patent Laid-Open No. 2005-196062 JP 2002-196291 A JP 2000-180888 A

  An object of the present invention is to provide a display medium and a display device in which deterioration of light resistance and reflection characteristics is suppressed as compared with a case where the configuration of the present invention is not provided.

The above problem is solved by the following means. That is,
The invention according to claim 1 is provided between a pair of electrodes, a photoconductive layer provided between the pair of electrodes and exhibiting an electrical property distribution according to an intensity distribution of irradiated exposure light, and the pair of electrodes. A display is provided in which a partial pressure distributed according to the electrical characteristic distribution of the photoconductive layer by the voltage applied to the pair of electrodes is applied and an image is displayed by the optical characteristic distribution according to the partial pressure And an ion concentration of 5 × 10 ⁻⁵ C / cm ³ or more and 10 × 10 ⁻⁵ C / cm ³ between the photoconductive layer and the display layer. Hereinafter, a display medium including an isolation layer.

  The invention according to claim 2 is the display medium according to claim 1, wherein the isolation layer is made of a water-soluble resin.

  The invention according to claim 3 is the display medium according to claim 1 or 2, wherein the moisture content of the isolation layer is 2% or less.

According to a fourth aspect of the present invention, there is provided a pair of electrodes, a photoconductive layer provided between the pair of electrodes and exhibiting an electrical characteristic distribution according to the intensity distribution of the exposed exposure light, and the pair of electrodes. A display is provided in which a partial pressure distributed according to the electrical characteristic distribution of the photoconductive layer by the voltage applied to the pair of electrodes is applied and an image is displayed by the optical characteristic distribution according to the partial pressure And an ion concentration of 5 × 10 ⁻⁵ C / cm ³ or more and 10 × 10 ⁻⁵ C / cm ³ between the photoconductive layer and the display layer. A display device comprising: a display medium including the following isolation layer; a voltage applying device that applies a voltage to the pair of electrodes; and an irradiation device that irradiates the display medium with the exposure light.

  According to the first aspect of the present invention, there is an effect that a display medium in which deterioration of light resistance and reflection characteristics is suppressed is provided as compared with the case where the configuration of the present invention is not provided.

  According to the invention which concerns on Claim 2, compared with the case where it does not have the structure of this invention, there exists an effect that the erosion to a photoconductive layer is suppressed.

  According to the invention concerning Claim 3, compared with the case where it does not have the structure of this invention, there exists an effect that deterioration of light resistance is further suppressed.

  According to the invention which concerns on Claim 4, compared with the case where it does not have the structure of this invention, there exists an effect that the display apparatus by which deterioration of light resistance and reflection characteristics was suppressed is provided.

  An embodiment of a display device and an optical writing method of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the display device 10 according to the present embodiment includes a display medium 12 and a writing device 14.

  In the present embodiment, the display medium 12 includes, in order from the display surface side (X side in FIG. 1), the substrate 13, the electrode 15, the liquid crystal layer 17, the light absorption layer 19, the laminate layer 18, the isolation layer 21, and the photoconductive material. The layer 20, the electrode 22, and the substrate 24 are laminated.

  The substrate 13 and the substrate 24 are members for the purpose of holding each functional layer between the substrates and maintaining the structure of the display medium 12. The substrate 13 and the substrate 24 are sheet-shaped objects having a strength that can withstand external force. The substrate 13 provided on the display surface side is at least incident light, and the substrate 24 provided on the side opposite to the display surface is described later. At least the exposure light is transmitted. Moreover, it is preferable that these board | substrates 13 and the board | substrate 24 have flexibility.

Specific materials constituting the substrate 13 and the substrate 24 include inorganic sheets (for example, glass / silicon), polymer films (for example, PET (polyethylene terephthalate), polysulfone, PES (polyethersulfone), PC (polycarbonate), and polyethylene. Naphthalate, polyethylene, polystyrene, polyimide) and the like.
In this embodiment, since an organic material is used for the photoconductive layer (charge generation layer, charge transport layer), there is no heat treatment step at a high temperature, so that a flexible substrate can be obtained, molding is easy, and cost is reduced. In view of the above, it is advantageous to use a light-transmitting polymer film substrate.
The thickness of the substrate 13 and the substrate 24 is preferably in the range of 50 μm to 500 μm.

  The electrodes 15 and 22 are members for applying a voltage applied from a writing device 14, which will be described in detail later, to each functional layer in the display medium 12. For this reason, the electrode 15 and the electrode 22 are conductive, the electrode 15 provided on the display surface side is at least incident light, and the electrode 22 provided on the side opposite to the display surface is at least exposure light described later. To Penetrate. In the present embodiment, “conductive” and “conductive” indicate those having a sheet resistance of 500 Ω / □ or less.

  The electrode 15 and the electrode 22 are made of metal (for example, gold, aluminum), metal oxide (for example, indium oxide, tin oxide, indium tin oxide (ITO)), conductive organic polymer (for example, polythiophene-based or polyaniline-based), and the like. The formed conductive thin film is mentioned. A known functional film such as an adhesion improving film, an antireflection film, or a gas barrier film may be formed on the front surface and / or the back surface of each of the electrodes 15 and 22.

The electrodes 15 and 22 are formed by sputtering on each of the substrate 13 and the substrate 24. However, the electrodes 15 and 22 are not necessarily formed by sputtering, and may be formed by printing, CVD, vapor deposition, or the like.

  The photoconductive layer 20 is provided between the electrode 15 and the electrode 22 and has an internal photoelectric effect. The impedance characteristic changes according to the irradiation intensity of the exposure light, so that the photoconductive layer 20 corresponds to the intensity distribution of the exposure light. It is a layer showing a distribution of electrical characteristics.

  In the present embodiment, the photoconductive layer 20 has a dual CGL structure in which a charge generation layer (CGL) 20A, a charge transport layer (CTL) 20B, and a charge generation layer (CGL) 20C are sequentially stacked from the display surface side. However, the present invention is not limited to this configuration as long as at least the charge generation layer 20A and the charge transport layer 20B are stacked in order from the display surface side.

  The charge generation layer 20A is a layer having a function of generating charge by absorbing exposure light. That is, the exposure light indicates light in the absorption wavelength region absorbed by the charge generation layer 20A of the photoconductive layer 20. The charge generation layer 20A absorbs exposure light to generate excitons (a pair of electrons and holes), and becomes free carriers in the charge generation layer 20A or at the interface between the charge generation layer 20A and the charge transport layer 20B. Those that can be separated efficiently are preferred.

  Examples of the charge generation layer 20A include a material in which a charge generation material is dispersed in a binder resin. Examples of the charge generating material include metal or metal-free phthalocyanine pigments, squalium pigments, azulenium pigments, perylene pigments, indigo pigments, bisazo pigments, trisazo pigments, quinacridone pigments, pyrrolopyrrole pigments, dibromoanthanthrone pigments, and the like, However, a charge generation material mainly composed of one or a mixture of chlorogallium phthalocyanine, hydroxygallium phthalocyanine, or titanyl phthalocyanine, which is a phthalocyanine pigment, is preferable.

  As hydroxygallium phthalocyanine, the black angle (2θ ± 0.2 °) of the X-ray diffraction spectrum is i) 7.5 °, 9.9 °, 12.5 °, 16.3 °, 18.6 °, 25 1 ° and 28.3 °, ii) 7.7 °, 16.5 °, 25.1 ° and 26.6 °, iii) 7.9 °, 16.5 °, 24.4 ° and 27. 6 °, iv) 7.0 °, 7.5 °, 10.5 °, 11.7 °, 12.7 °, 17.3 °, 18.1 °, 24.5 °, 26.2 ° and 27.1 °, v) 6.8 °, 12.8 °, 15.8 ° and 26.0 ° or vi) 7.4 °, 9.9 °, 25.0 °, 26.2 ° and 28 A crystal structure having a strong diffraction peak at 2 ° is particularly preferable because of high charge generation efficiency.

As chlorogallium phthalocyanine, in the X-ray diffraction spectrum, the Bragg angle (2θ ± 0.2 °) is at least 7.4 °, 16.6 °, 25.5 ° and 28.3 °, or 6.8 °, Strong diffraction peaks at 17.3 °, 23.6 ° and 26.9 °, or 8.7 ° to 9.2 °, 17.6 °, 24.0 °, 27.4 ° and 28.8 ° A crystal structure having a high charge generation efficiency is particularly preferable.
Further, as titanyl phthalocyanine, the black angle (2θ ± 0.2 °) of the X-ray diffraction spectrum is 9.5 °, 9.7 °, 11.7 °, 15.0 °, 23.5 °, 24 A crystal structure having diffraction peaks at 1 ° and 27.3 ° is particularly preferable because of high charge generation efficiency.

  Binder resins that can be used for the charge generation layer 20A include polyvinyl butyral resin, polyarylate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer resin, carboxyl-modified vinyl chloride-vinyl acetate copolymer resin, polyamide resin (nylon). Resin), acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, and the like are applicable. In particular, polyvinyl butyral resin and carboxyl-modified vinyl chloride-vinyl acetate copolymer resin are preferable binder resins because the charge generating material is well dispersed.

  The mixing ratio (low molecular compound / binder resin) of the low molecular compound and the binder resin in the charge generation layer 20A (including the charge transport material when it is added) is 1/10 to 20/1. It is preferable to set it as the range, and it is more preferable to set it as the range of 1/1 thru | or 10/1.

  As a method for producing the charge generation layer 20A, in addition to a dry film forming method such as a vacuum deposition method or a sputtering method, a spin coating method using a solvent, a dip method, a blade coating method, a roll coating method, a spray coating method, or the like can be applied. It is. Neither method requires substrate heating or strict process control in a-Si or photodiode fabrication. However, when the charge transporting material is used as a mixture, it is preferably produced by coating using a solvent from the standpoint of ease of production. The solvent is preferably a solvent that does not damage at least the charge transport layer 20B (such as swelling of the charge transport layer or generation of cracks). For this reason, as a solvent used as the solvent for forming the charge generation layer 20A, although it depends on the material constituting the charge transport layer 20B, generally, solvents such as alcohols, ketones, ethers and esters are effective. . Among them, a solvent having a hydroxyl group in a molecule such as alcohol is most suitable as a solvent for the coating solution for forming the charge generation layer 20A formed on the charge transport layer using a polycarbonate resin as a binder.

Regarding the preparation of the coating solution for forming the charge generation layer 20A, the charge generation material and the charge transport material to be added as necessary are added to the solvent (or a solution in which the binder resin is dissolved) at the preferable mixing ratio. Mix and disperse. As a mixing / dispersing method, a conventional method using a ball mill, a roll mill, a sand mill, an attritor, an ultrasonic wave, or the like is applied. When dispersing, it is effective to set the particle size of the charge generation material to 0.5 μm or less, desirably 0.3 μm or less, and more desirably 0.15 μm or less.
The concentration of the solid content of the charge generation layer 20A forming coating solution is preferably in the range of 1% by mass to 30% by mass. If it is less than 1% by mass, the film thickness may be too thin to obtain electrical characteristics, and if it exceeds 30% by mass, the viscosity may be too high and film formation may be difficult. On the other hand, if it is less than 1% by mass or exceeds 30% by mass, there may be a problem that the dispersion stability of the charge generating material particles is poor and the storage stability and film formability are deteriorated.

  The film thickness of the charge generation layer 20A is preferably in the range of 10 nm to 1 μm, and more preferably in the range of 20 nm to 500 nm. When the thickness is less than 10 nm, the photosensitivity is insufficient and it may be difficult to produce a uniform or near-uniform film. When the thickness is greater than 1 μm, the photosensitivity is saturated and peeling is likely to occur due to in-film stress. There is.

Examples of the charge generation layer 20C include a material in which a charge generation material is dispersed in a binder resin as in the case of the charge generation layer 20A. The charge generation material exemplified in the charge generation layer 20A described above is used.
The charge generation layer 20C is preferably the same charge generation material as the charge generation layer 20A described above from the standpoint of ease of manufacture. However, in the display medium 12 of the present embodiment, the charge generation layer 20C, together with the electrode 22, It only has to function as a blocking layer (details will be described later) that suppresses reinjection of the charge flowing from the charge transport layer 20B into the charge transport layer 20B, and there is no problem even if the materials are different.

  Further, a binder resin that can be used for the charge generation layer 20A is used for the charge generation layer 20C. Since the mixing ratio of the charge generation material and the binder resin, the preparation of the coating liquid, the formation method, the film thickness, and the like in the charge generation layer 20C are the same as those described in the charge generation layer 20A, detailed description thereof is omitted.

  The charge transport layer 20B is a layer having a function of drifting in the direction of an applied electric field when charges generated in the charge generation layer 20A are injected. Generally, the charge transport layer 20B has a thickness several tens of times that of the charge generation layer 20A. For this reason, the capacitance of the charge transport layer 20B, the dark current of the charge transport layer 20B, and the current flowing in the charge transport layer 20B determine the light-dark impedance of the entire photoconductive layer 20.

  The charge transport layer 20B is configured to include a charge transport material, and the injection of holes from the charge generation layer 20A is efficiently generated (the ionization potential is preferably close to the charge generation layer 20A). It is preferable that the positive holes hop and move at high speed. In order to increase the impedance when the exposure light is not exposed, it is preferable that the dark current due to the heat carrier is low.

As the charge transport material contained in the charge transport layer 20B, benzidine, carbazole, oxadiazole, hydrazone, stilbene, triphenylamine, triphenylmethane, or the like is applied. Note that the charge transporting material is almost hole transporting, and in this embodiment, the charge transporting layer 20B is described as being a hole transporting layer, but is not limited to this form and functions as an electron transporting layer. Layers may be used.
In addition, charge transporting polymers having the molecular structure of these charge transporting materials in the main chain or side chain can also be used. In particular, those having a charge transporting molecular structure in the main chain exemplified in JP-A-2007-279371 are preferred. When a charge transporting polymer is used as the charge transporting material, a binder resin described later is not necessarily used.

Examples of the binder resin contained in the charge transport layer 20B include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, and vinylidene chloride. -Applicable to acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, etc. is there.
In particular, a polycarbonate resin is preferable when it is used as a binder for a charge transport layer, since it has excellent charge transport characteristics and an excellent balance of strength, flexibility, and transparency.

  The mixing ratio of the charge transport material and the binder resin (charge transport material / binder resin) in the charge transport layer 20B is preferably in the range of 1/10 to 10/1, more preferably in the range of 3/7 to 7/3. .

  As a method for producing the charge transport layer 20B, a dry film forming method such as a vacuum deposition method or a sputtering method, a spin coating method using a solvent, a dip method, a blade coating method, a roll coating method, or the like can be applied. In the case of solvent coating, aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, ketones such as acetone and 2-butanone, and halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride. Ordinary organic solvents such as cyclic or linear ethers such as tetrahydrofuran and ethyl ether are used alone or in admixture of two or more.

  The thickness of the charge transport layer 20B is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 3 μm to 20 μm. When the thickness of the charge transport layer 20B is 0.1 μm or more and 100 μm or less, the withstand voltage is high and the reliability is ensured, and impedance matching with the functional element is facilitated and the design is facilitated.

  The liquid crystal layer 17 is provided on the display surface side from the photoconductive layer 20 via a laminate layer 18 and a light absorption layer 19 described later.

  The liquid crystal layer 17 has a function of modulating a reflection / transmission state of incident light by an electric field by utilizing a change in an optical interference state of a cholesteric (chiral nematic) liquid crystal, and the selected state is maintained in an electric field. Those of nature are used. The liquid crystal layer preferably has a structure that is not deformed by an external force such as bending or pressure.

  As the liquid crystal layer 17 of the present embodiment, a liquid crystal layer in which a liquid crystal layer of a self-holding type liquid crystal composite composed of a cholesteric liquid crystal and a transparent resin is formed is used. That is, the liquid crystal layer 17 of the present embodiment is a liquid crystal layer that does not require a spacer or the like because it has a self-holding property as a composite. In the present embodiment, the liquid crystal layer 17 is configured by dispersing a cholesteric liquid crystal 17B in a polymer matrix (transparent resin) 11. In the present embodiment, the liquid crystal layer 17 is described as a liquid crystal layer of a self-holding liquid crystal composite, but it is not essential that the liquid crystal layer 17 is a self-holding liquid crystal composite. Of course, it may be configured.

  The cholesteric liquid crystal 17B has a function of modulating the reflection / transmission state of a specific color light in incident light, and liquid crystal molecules are twisted and aligned in a spiral shape. Interference reflection of specific light depending on The alignment of the liquid crystal molecules is changed by the electric field, and the reflection state is changed. The cholesteric liquid crystal 17B has a high reflectivity with respect to an applied voltage, has excellent display performance, and has a memory property, so that it is particularly effectively used for the display medium 12 of the present embodiment. When the liquid crystal layer 17 is a self-holding type liquid crystal composite, it is preferable that the drop size is uniform and the single layer is densely arranged.

  Specific liquid crystals that can be used as the cholesteric liquid crystal 17B include steroid cholesterol derivatives, nematic liquid crystals and smectic liquid crystals (for example, Schiff base, azo, azoxy, benzoate, biphenyl, terphenyl, cyclohexyl). Carboxylic acid ester, phenylcyclohexane, biphenylcyclohexane, pyrimidine, dioxane, cyclohexylcyclohexane ester, cyclohexylethane, cyclohexane, tolan, alkenyl, stilbene, condensed polycyclic), or a mixture thereof In addition, those added with a chiral agent (for example, steroidal cholesterol derivatives, Schiff bases, azos, esters, biphenyls) can be mentioned.

  As a form in which the liquid crystal layer 17 forms a self-holding type liquid crystal composite composed of a cholesteric liquid crystal 17B and a polymer matrix 17A, a PNLC (Polymer Network Liquid Crystal) structure including a network-like resin in a continuous phase of cholesteric liquid crystal, A PDLC (Polymer Dispersed Liquid Crystal) structure (including microencapsulated ones) in which cholesteric liquid crystal is dispersed in a droplet form in a polymer skeleton is used to form a PNLC structure or PDLC structure. An anchoring effect is produced at the interface between the polymer and the polymer, and the planar or focal conic holding state without electric field becomes more stable.

  The PNLC structure or PDLC structure is a known method for phase-separating a polymer and a liquid crystal, for example, an acrylic, thiol, or epoxy polymer precursor that is polymerized by heat, light, electron beam, or the like. A polymer with low solubility of liquid crystal such as PIPS (Polymerization Induced Phase Separation) method, which is polymerized from a uniform phase state and phase-separated, polyvinyl alcohol, and the like, mixed and stirred, suspended, and liquid crystal The emulsion method in which droplets are dispersed in a polymer, the TIPS (Thermally Induced Phase Separation) method in which a thermoplastic polymer and liquid crystal are mixed, cooled to a homogeneous phase and then cooled and phase separated, and the polymer and liquid crystal Is dissolved in a solvent such as chloroform. Evaporation but is formed by a polymer and SIPS for phase separation and a liquid crystal (Solvent Induced Phase Separation) method, but is not particularly limited.

  The polymer matrix 17A holds the cholesteric liquid crystal 17B and has a function of suppressing liquid crystal flow (image change) due to deformation of the display medium 12, and does not dissolve in the liquid crystal material and is not compatible with the liquid crystal. A polymer material using a liquid as a solvent is preferably used. In addition, the polymer matrix 17A is desirably a material that has strength to withstand external force and exhibits high transparency to at least incident light and exposure light.

  Materials that can be used as the polymer matrix 17A include water-soluble polymer materials (for example, gelatin, polyvinyl alcohol, cellulose derivatives, polyacrylic acid polymers, ethyleneimine, polyethylene oxide, polyacrylamide, polystyrene sulfonate, polyamidine, isoprene). Sulfonic acid polymers), or materials that can be emulsified in water (for example, fluororesin, silicone resin, acrylic resin, urethane resin, epoxy resin).

  Between the liquid crystal layer 17 and the photoconductive layer 20, a separating layer 21, a laminate layer 18, and a light absorption layer 19 are stacked in this order from the side of the photoconductive layer 20 in contact with the charge generation layer 20 </ b> A.

The laminate layer 18 is a layer provided for the purpose of absorbing unevenness and bonding when the functional layers formed on the inner surfaces of the upper and lower substrates are bonded together. The laminate layer 18 is made of a polymer material having a low glass transition point, and a material that adheres and adheres to a layer to be bonded by heat or pressure (in this embodiment, the isolation layer 21 and the liquid crystal layer 17) is selected. . In the present embodiment, it is desirable that the laminate layer 18 is configured as an insulating layer. In the present embodiment, “insulation” and “insulation” are those having a sheet resistance of 10 ¹⁰ Ω / □ or more as a guide.

  Suitable materials for the laminate layer 18 include adhesive polymer materials (for example, urethane resin, epoxy resin, acrylic resin, silicone resin).

The light absorption layer (light-shielding layer) 19 optically separates exposure light and incident light to prevent malfunction due to mutual interference, and optically displays external light and display image incident from the non-display surface side of the display medium 12 during display. It is a layer provided for the purpose of separating and preventing deterioration of image quality. However, for this purpose, the light absorption layer 19 is required to have a function of absorbing at least light in the absorption wavelength region of the charge generation layer 20A and light in the reflection wavelength region of the liquid crystal layer 17.
In addition, since the display medium 12 of this Embodiment demonstrates as the structure provided with the light absorption layer 19, the color of this light absorption layer 19 is visually recognized as the color of the image displayed, but light The structure in which the absorption layer 19 is not provided may be sufficient. In this case, the color of the photoconductive layer 20 is visually recognized as the color of the displayed image.

  Specifically, the light absorbing layer 19 is an inorganic pigment (for example, cadmium-based, chromium-based, cobalt-based, manganese-based, or carbon-based), or an organic dye or an organic pigment (azo-based, anthraquinone-based, indigo-based, tri-based). Phenylmethane, nitro, phthalocyanine, perylene, pyrrolopyrrole, quinacridone, polycyclic quinone, squalium, azurenium, cyanine, pyrylium, anthrone) Alternatively, these are formed by a wet coating method or the like in which a coating solution is prepared by dispersing or dissolving these in a suitable solvent together with a polymer binder (for example, polyvinyl alcohol resin, polyacrylic resin, etc.), and applying and drying the coating solution. The The film thickness of the light absorption layer 19 is desirably 1 μm or more and 10 μm or less.

  The isolation layer 21 is a layer having a function of isolating the photoconductive layer 20 from each layer such as the laminate layer 18 that may damage the photoconductive layer 20 depending on the material when laminated in direct contact. The isolation layer 21 is provided between the display layer 17, the photoconductive layer 20, and the interlayer, and is provided by being laminated in direct contact with the photoconductive layer 20.

In the present embodiment, the isolation layer 21 has an ion concentration of 5 × 10 ⁻⁵ C / cm ³ or more and 10 × 10 ⁻⁵ C / cm ³ or less, and more preferably 6 × 10 ⁻⁵ C / cm ^3. The above is 7 × 10 ⁻⁵ C / cm ³ or less.

It is considered that when the ion concentration of the isolation layer 21 is within the above range, deterioration of light resistance in the display medium 12 is suppressed, and deterioration of reflection characteristics is suppressed by suppressing residual potential.
That is, when the ion concentration of the isolation layer 21 is less than 5 × 10 ⁻⁵ C / cm ³ , the reflectance decreases when left under irradiation with a fluorescent lamp or the like. The cause of the deterioration in light resistance is considered as follows. Even if there is no electric field, the photodegraded photoconductive layer is gradually discharged from the charge generation layer by the internal electric field, and charges are accumulated in the photoconductive layer. As the charge accumulation progresses, the excess charge is not lost during the next driving, and the normal charge movement is prevented, so that the photo output is lowered and the reflectance characteristics are deteriorated. Although it has not necessarily been clarified about the action of ions in the isolation layer, it is presumed that the presence of ions moderately disperses charges and prevents excessive charge accumulation.
Further, when the ion concentration of the isolation layer 21 exceeds 10 × 10 ⁻⁵ C / cm ³ , the reflectance is also lowered. The reason why the amount of ions in the isolation layer influences the residual potential is not necessarily speculated, but the effect of moisture and interaction can be seen. .

As described above, in the display medium 12, by applying a voltage between the electrode 15 and the electrode 22 and irradiating the photoconductive layer 20 with exposure light, the electrical property distribution of the photoconductive layer 20 is changed, By applying a partial pressure distributed according to the change in the electrical characteristic distribution to the display layer 17, the orientation of the cholesteric liquid crystal in the display layer 17 is changed according to the partial pressure to form an image on the display layer 17. Is done.
As described above, an image is formed on the display medium 12 by the change in the reflectance of the liquid crystal layer 17 due to the exposure light irradiation and voltage application to the display medium 12.
In the present embodiment, the “reflection characteristic” indicates the response of the change in reflectance due to voltage application to the liquid crystal layer 17. That is, “good reflection characteristics” means a state in which the reflectance of the liquid crystal layer 17 changes to the extent that it is visually recognized as a difference in hue by applying a voltage exceeding a specific voltage value. “The reflection characteristic is bad” indicates a state in which the reflectance of the liquid crystal layer 17 is not changed to the extent that it is recognized as a change in hue even when a voltage having the same voltage value is applied.

The ion concentration is a value measured as follows.
The ion concentration was determined from the capacity at 0.1 Hz in impedance measurement. That is, in the frequency-dependent behavior of the capacitance, the influence of ions in the film is noticeable in a frequency region lower than 10 Hz, because the responsiveness of ions is low in a high-frequency electric field of 10 Hz or higher. Therefore, the difference (ΔC) between 10 Hz and 0.1 Hz is defined as the action of the charge due to ions. That is, here, the ion concentration is treated as the charge concentration. Since the phenomenon of the present invention is affected not by the kind of ions but by the amount of charge, such a measuring method was used.

Regarding the ion concentration of the isolation layer 21, when a single isolation layer 21 is obtained, the isolation layer 21 is laminated on the ITO substrate, and an electrode is formed thereon. Is calculated. Further, when the isolation layer 21 is formed on the photoconductive layer 20, after measuring the impedance, the isolation layer 21 is peeled off, and after measuring the impedance of the photoconductive layer 20, the ion concentration of the other layers is calculated. Then, the ion concentration of the isolation layer 21 is calculated, or the impedance of the single layer of the photoconductive layer 20 is measured in advance, and then the ion density of the isolation layer 21 is measured.
Of course, the conductivity of the aqueous solution may be measured to correspond to the ion concentration. Since the ink concentration adjusted to the same viscosity and the ion concentration measured from the impedance correspond to the conductivity, they may be derived from the conductivity.

  Moreover, it is preferable that the moisture content of the isolation layer 21 is 2% or less. Reduction in reflectance is suppressed. When there is a lot of moisture, the action of impurity ions contained in the isolation layer becomes active, and the residual potential is generated immediately after the drive voltage pulse is applied due to the influence of ion conduction, which reduces the reflectivity of the display layer. To do. When the moisture content of the isolation layer 21 is 2% or less, the action of ions can be suppressed. The moisture content is preferably close to 0%, but if it is 2% or less, there is no sufficient moisture.

The moisture content of the isolation layer 21 means a value defined by the following formula (1).
Formula (1) MC = 100 × (Wd−Wa) / Ws
Here, in the formula (1), MC is the moisture content (%) of the isolation layer 21, Wd is the mass (mg) of the material constituting the isolation layer 21 in the display medium 12, and Wa is in the display medium 12 having the mass Wd. The dry dry mass (mg) when the material constituting the isolation layer 21 is completely dried, Ws indicates the material constituting the isolation layer 21 in the display medium 12 having a mass Wd at room temperature and normal humidity (23 ° C., 47 RH). % Or more and 50RH% or less) means the mass (mg) when the moisture absorption is saturated.

  Note that Wd, Wa, and Ws specifically mean values measured by the following procedure. First, immediately after the display medium 12 is disassembled so that the isolation layer 21 is exposed, or when the display medium 12 is assembled, the member including the photoconductive layer 20 and the isolation layer 21 and the side including the liquid crystal layer 17 are included. Immediately before the member and the laminate layer 18 are bonded together, the mass of a sample obtained by collecting only a certain amount of the isolation layer 21 is measured. And let the mass at this time be Wd.

Subsequently, the sample for which the mass Wd has been measured is heat-treated at a temperature that does not cause thermal denaturation. This heat treatment continues until the mass of the sample stops decreasing and does not change with respect to the heating time. The mass at this time is defined as Wa.
The heating temperature and the heating time are selected according to the material constituting the sample. As a general guide, the heating temperature is 60 ° C. or more and 120 ° C. or less, and the heating time is about 5 minutes or more. For example, when the isolation layer 21 is made of polyvinyl alcohol, the sample may be heat-treated at 90 ° C. for 10 minutes or more.

Subsequently, the sample for which the mass Wa has been measured is left in a room temperature and normal humidity environment (23 ° C., 47 RH% to 50 RH%) until moisture absorption is saturated. This moisture absorption process continues until the increase in the mass of the sample stops and does not change with respect to the standing time. The mass at this time is defined as Wa.
The standing time is selected according to the material constituting the sample, but as a general guideline, it is about 5 minutes or more. For example, when the water-soluble resin constituting the isolation layer 21 is polyvinyl alcohol, the sample may be left in a room temperature and humidity environment for 10 minutes or more.

  The isolation layer 21 is made of a water-soluble resin because a solvent that dissolves the underlying photoconductive layer cannot be used. The water-soluble resin is selected from known water-soluble resins. Specifically, a resin having a solubility in water at a temperature of 20 ° C. of 80 g / 100 g or more is used.

Polyvinyl alcohol is preferable as the water-soluble resin, and other examples include gelatin, agar, casein, sodium polyacrylate, polyethylene oxide, and the like. Two or more water-soluble resins may be used in combination. The content of the water-soluble resin contained in the isolation layer 21 is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 8% by mass or less.
If the content of the water-soluble resin is 1% by mass or more and 10% by mass or less, it is considered that an effect that a coating liquid having an optimum concentration for application can be obtained.

  As a specific method for adjusting the isolation layer 21 to have the above ion concentration, for example, a method using an ion exchange resin or a method using a reverse osmosis membrane for the material constituting the isolation layer 21. By using a known method such as a method using electrodeposition or a method using ultrafiltration, it is preferable to remove the impurity ions contained in the material that constitutes the isolation layer 21, and The ion concentration is adjusted to the range. The polyvinyl alcohol (PVA) used as the isolation layer 21 contains many impurity ions such as sodium ions and acetate ions derived from the production method. For example, an ion exchange resin is used. In the conventional deionization method, since the degree of purification is increased by repeating the number of ion exchanges, the ion concentration can be controlled by the number of ion exchanges.

  In the display medium 12 having the above configuration, when a voltage is applied between the electrode 15 and the electrode 22, a partial pressure is applied to each layer stacked between the electrode 15 and the electrode 22. In this state, when the photoconductive layer 20 is irradiated with exposure light, the resistance distribution of the photoconductive layer 20 changes according to the irradiated exposure light, and therefore, the amount applied to the liquid crystal layer 17 according to the exposure light. The pressure increases. When the voltage distribution applied to the liquid crystal layer 17 changes, the orientation of the liquid crystal changes, so that information corresponding to the exposure light is displayed and recorded on the liquid crystal layer 17.

  The display medium 12 according to the present embodiment includes a laminate in which a substrate 13, an electrode 15, a liquid crystal layer 17, a light absorption layer 19, and a laminate layer 18 on the display surface side are laminated, and a substrate 24 on the back side. The electrode 22, the photoconductive layer 20, and the stacked body in which the isolation layer 21 is stacked are bonded to each other.

  And before bonding these two types of laminated bodies, about the isolation | separation layer 21, apply | coat the material by which the ion concentration was adjusted using the specific method for adjusting so that it may become the ion concentration mentioned above. Thus, the isolation layer 21 adjusted to an ion concentration in the above range is formed.

  In addition, before laminating these laminates, a drying treatment process is performed in which at least one kind of drying treatment selected from heat drying treatment, reduced pressure drying treatment, and dehumidification drying treatment in a low temperature and low humidity environment is performed. Thus, the moisture content of the isolation layer 21 is adjusted to be 2% or less.

  As the drying treatment conditions, the material composition (particularly the type and content of the water-soluble resin) constituting the separation layer 21 and the drying treatment method so that the moisture content of the separation layer 21 is controlled to 2% or less. Is selected accordingly. However, as the drying treatment method, the moisture content of the isolation layer 21 is controlled easily and in a short time among the heat drying treatment, the reduced pressure drying treatment, and the dehumidification drying treatment in a low temperature and low humidity environment. It is most desirable to employ a drying process.

  The heating and drying treatment conditions are not particularly limited as long as the material constituting the isolation layer 21 is in a range that does not deteriorate due to heat denaturation. Is desirable, and it is more desirable to select in the range of 90 ° C to 100 ° C. When the heating temperature is less than 60 ° C., moisture taken into the isolation layer 21 is not volatilized, and it becomes difficult to control the moisture content of the isolation layer 21 to 2% or less, or a long time is required for the heat drying process. There is a case. On the other hand, when the heating temperature exceeds 120 ° C., thermal denaturation of the material constituting the isolation layer 21 may be easily caused.

  The heating time depends on the heating temperature and the like, but is preferably 5 minutes or more, and more preferably 10 minutes or more. If the heating time is less than 5 minutes, it may be difficult to control the moisture content of the isolation layer 21 to 2% or less. The upper limit of the heating time is not particularly limited, but it is preferably 10 minutes or less for practical use because the productivity of the display medium is lowered.

  The heating and drying conditions particularly suitable when using polyvinyl alcohol as the water-soluble resin are preferably in the range of 60 ° C. to 120 ° C., more preferably in the range of 90 ° C. to 100 ° C. The time is preferably in the range of 5 minutes to 90 minutes, and more preferably in the range of 10 minutes to 30 minutes.

  Moreover, as pressure reduction processing conditions, it is desirable that a pressure is -0.1 MPa or less.

  On the other hand, the dehumidifying and drying treatment conditions in a low-temperature and low-humidity environment are preferably carried out in the range of a temperature of 40 ° C. to 60 ° C. and a humidity of about 1 RH% to 10 RH%. In addition, when it is difficult to control the moisture content of the isolation layer 21 to 0.5% or less by this treatment alone, it may be used in combination with other treatment methods.

  After finishing the drying treatment step, a step of bonding these two kinds of laminates is performed. Here, the time (waiting time) from the end of the drying process to the execution of the bonding process is preferably within 5 minutes, and more preferably within 2 minutes. If the waiting time exceeds 5 minutes, the moisture in the atmosphere is likely to be taken into the isolation layer 21 again before the bonding step is performed, so the moisture content of the isolation layer 21 constituting the display medium is 2%. May be exceeded.

Note that the electrodes constituting the display medium are formed on a substrate by using a known film formation method such as a sputtering method or a vacuum evaporation method. For the liquid crystal layer 17, the photoconductive layer 20, and other layers, a known liquid phase film formation such as a spin coating method or a dip coating method is performed using a solution in which materials constituting these layers are dissolved in a solvent. Although a method is used, a vacuum deposition method or a sputtering method is also employed depending on the material constituting the layer.
As a solvent that can be used in the liquid phase film forming method, a solvent that dissolves the material constituting the layer is selected. For example, aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, acetone, -Ordinary organic solvents such as ketones such as butanone and cyclopentanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether Or it mixes and uses 2 or more types.

  And using the film-forming method demonstrated above, after preparing the said 2 types of laminated body and performing the said drying process, these 2 types of laminated bodies are bonded together. Thereafter, the display medium 12 of the present embodiment is manufactured through a process such as sealing the end face of the cell where these two types of laminates are bonded together with a sealing material such as an epoxy resin.

  The display device 10 of the present embodiment is a device that writes an image on the optical writing type display medium 12.

  Hereinafter, the display device 10 of the present embodiment will be described in detail. In the display device 10 according to the present embodiment, the case where the display medium 12 having the configuration shown in FIG. 1 is used as the display medium 12 will be described.

  The writing device 14 is a device for writing an image on the display medium 12. An exposure device 30 that scans and exposes the exposure light to the display medium 12, and a voltage is applied between the electrodes 15 and 22 of the display medium 12. And a control unit 28 which is electrically connected to the exposure apparatus 30 and the voltage application unit 26 and controls them.

The exposure apparatus 30 irradiates the display medium 12 with exposure light as light in an absorption wavelength region absorbed by the photoconductive layer 20 of the display medium 12 on the display medium 12, and the light source 30 </ b> A covers the entire area of the display medium 12. , And a drive unit 30B that scans and drives.
The irradiation area of the exposure light emitted from the light source 30A on the liquid crystal layer 17 may be smaller than the area corresponding to each pixel of the image displayed on the liquid crystal layer 17 when the light source 30A is not scanned. Preferably, exposure and non-exposure of the light source 30A are adjusted, and the light source 30A is scanned and driven by the driving unit 30B, so that exposure and non-exposure of exposure light are performed according to each pixel of the image displayed on the liquid crystal layer 17. Adjusted.

  The light source 30A is not particularly limited as long as it irradiates desired exposure light (spectrum / intensity / spatial frequency) to the photoconductive layer 20 of the display medium 12 based on an input signal from the control unit 28. is not. Note that the exposure light irradiated by the light source 30 </ b> A is preferably light having a large energy in the absorption wavelength region of the photoconductive layer 20.

Specifically, as the light source 30A, a cold cathode tube, a xenon lamp, a halogen lamp, a light emitting diode (LED), an EL, a laser, or the like arranged in a one-dimensional array is used. Examples of the driving unit 30B include a polygon mirror and a driving device that scans the light source 30A one-dimensionally or two-dimensionally.
Furthermore, various optical elements (for example, a microlens array, a cell hook lens array, a prism array, and a viewing angle adjustment sheet) may be used in combination.

  Based on the input signal from the control unit 28, the voltage application unit 26 applies a voltage having a polarity and a voltage value corresponding to the input signal between the electrodes 15 and 22 of the display medium 12 to the input signal. What is necessary is just to apply for the corresponding time. As the voltage application unit 26, for example, a bipolar high voltage amplifier or the like is used.

  Specifically, the voltage application to the display medium 12 by the voltage application unit 26 is performed between the electrode 15 and the electrode 22 via the contact terminal 25. Here, the contact terminal 25 is a member that makes contact with the voltage application unit 26 and the electrode 15 and the electrode 22 of the display medium 12, and has high conductivity. In addition, one having a small contact resistance with the voltage application unit 26 is selected. The contact terminal 25 preferably has a structure that can be separated from either the electrode 15 and the electrode 22 or the voltage applying unit 26 so that the display medium 12 and the writing device 14 can be separated. .

  The contact terminal 25 was made of metal (for example, gold / silver / copper / aluminum / iron), carbon, a composite in which these were dispersed in a polymer, or a conductive polymer (for example, polythiophene-based / polyaniline-based). Examples of the terminal include a clip / connector shape that sandwiches an electrode.

  The control unit 28 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The control unit 28 is a device of the writing device 14 according to a program stored in the ROM. Each unit is controlled, and the voltage application unit 26 and the exposure device 30 are controlled so that an image corresponding to image data acquired from an external device or the like via a wireless line or a wired line is displayed on the display medium 12.

The display medium 12 may be integrated with the writing device 14 or may be configured to be separable from the writing device 14. When the display medium 12 is configured to be separable from the writing device 14, for example, the display medium 12 is mounted in a slot or the like (not shown) so that the electrodes 15 and 22 of the display medium 12 are voltageated. What is necessary is just to comprise so that it can be irradiated with exposure light from the exposure apparatus 30 of the liquid crystal layer 17 of the display medium 12, and the batch exposure apparatus 32 while being connected so that a voltage can be applied from the application part 26. FIG.
As described above, when the display medium 12 is configured to be separable from the writing device 14, it is easy to distribute only the display medium 12 alone, and it is easy to browse, circulate, distribute, and the like. Provided. In addition, by attaching the display medium 12 to the slot of the writing device 14 again, it is possible to write a new image and erase the written image.

  In the display device 10 configured as described above, an image is displayed on the display medium 12 by controlling the voltage application unit 26 and the exposure device 30 according to the image data of the image to be written under the control of the control unit 28. Is written. Specifically, under the control of the control unit 28, a voltage is applied between the electrode 15 and the electrode 22 from the voltage application unit 26, and the light source 30A is displayed on the display medium 12 in the drive unit 30B of the exposure apparatus 30. In addition, the exposure light is irradiated from the light source 30A according to the image at the destination. As a result, an image is written on the display medium 12.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention.

Example 1
(Preparation of display medium)
A charge generation layer was formed on the ITO film of a polyethylene terephthalate (PET) substrate (thickness: 125 μm) on which an ITO film (sheet resistance: 300Ω / □) was formed as an electrode. Specifically, first, hydroxygallium phthalocyanine (X-ray diffraction spectrum black angle (2θ ± 0.2 °) is 7.0 °, 7.5 °, 10.5 °, 11.7 °, 12. 7), 17.3 [deg.], 18.1 [deg.], 24.5 [deg.], 26.2 [deg.] And 27.1 [deg.] Having a strong diffraction peak as a charge generation material, and alcohol-soluble polyvinyl butyral (Sekisui) as a binder resin A 2% by weight dispersion (coating solution A) was prepared by using Esreck BH-3) manufactured by Kagakusha Co., Ltd., and having a mass ratio of 1: 1 and dispersing with butanol using a dyno mill. This was applied to a substrate by spin coating and then dried to form a charge generation layer having a light transmittance of 20% at a wavelength of 780 nm.

  Next, a charge transport layer was formed on the charge generation layer. Specifically, first, charge transport material N, N-bis (3,4-dimethylphenyl) bisphenyl-4-amine and polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Inc., Z300) {} as a binder resin, After mixing at a ratio of 1: 1, this was dissolved in monochlorobenzene to prepare a 10 mass% solution (coating solution B). This was applied with an applicator (Gap: 100 μm) and dried to form a 16 μm thick charge transport layer on the lower charge generation layer.

Further, using a coating solution having the same composition except that the solid content concentration is 4% by mass with respect to the coating solution A, the coating solution is applied onto the charge transport layer by a spin coating method, dried, and light having a wavelength of 780 nm is obtained. A charge generation layer having a transmittance of 80% was formed. A photoconductive layer was formed as described above.
Furthermore, on the formed photoconductive layer, an isolation layer for isolating a laminate layer and a photoconductive layer to be adjusted in a later step was formed by the following method.

Specifically, an isolation layer was formed on the photoconductive layer as follows.
First, a material was prepared by dispersing 50% by weight of a diketopyrrolopyrrole pigment (pigment: “trade name chromophthal” manufactured by Ciba Specialty Chemicals) in a resin solution in which a polyvinyl alcohol resin was dissolved in a water-soluble (solvent). This was subjected to ion concentration adjustment treatment using an ion exchange resin (“trade name Diaion” manufactured by Mitsubishi Chemical Corporation) (conditions: cation PK216H, anion WA30). This ion concentration adjusted material was applied with an applicator to a thickness of 1 μm, and was then heat-dried by being left in a 90 ° C. environment for 10 minutes to form an isolation layer with adjusted ion concentration and moisture content.

When the ion concentration of this isolation layer was measured, it was 6.5 × 10 ⁻⁵ C / cm ³ .
A specific method for measuring the ion concentration is as follows. An isolation layer having a film thickness of 1 μm was produced on the electrode substrate, and another electrode substrate was bonded via an adhesive layer having a thickness of 5 μm, and then impedance was measured. As the analysis software, an impedance analyzer Solartron 1260 was used.

Moreover, the moisture content of this isolation layer was measured.
The measuring method of moisture content is as follows. Sample (Ws was prepared by forming an isolation layer on a PET substrate and the initial weight was measured. While the sample was dried in an oven at 60 ° C. to 90 ° C., the reduction in weight due to drying temperature and time was measured. The minimum weight saturated was Wa, and the sample was allowed to stand overnight at 23 ° C. and 47% RH to 50% RH, and the weight was measured to obtain Ws. The water content is estimated to be 2% or less.

On the other hand, 84 parts by mass of nematic liquid crystal E7 (manufactured by Merck), 10.8 parts by mass of chiral agent R811 (manufactured by Merck), and 2.7 parts by mass of chiral agent R1011 (manufactured by Merck) are mixed and selected. 100 parts of cholesteric liquid crystal having a reflection wavelength of 650 nm was obtained. 1000 parts by mass of ethyl acetate with 10 parts by mass of this cholesteric liquid crystal, Takenate D-110N (manufactured by Takeda Pharmaceutical Co., Ltd.) as the polyvalent isocyanate, and 3 parts of octadecanol (manufactured by Aldrich) as the precursor of the vertical alignment component An oil phase composition was prepared by dissolving in. This was put into 10,000 parts by mass of a 1% by weight polyvinyl alcohol aqueous solution, and stirred and dispersed with a mixer to prepare an emulsion having a volume average particle diameter of 7 μm.
To this, 100 parts by mass of a 10% aqueous solution of polyallylamine (manufactured by Nittobo Co., Ltd.) was added and heated at 70 ° C. for 2 hours to obtain microcapsules having polyurea as a wall material. After collecting the obtained microcapsules by centrifugation, a coating solution C was prepared by adding a 10% by weight aqueous solution of polyvinyl alcohol containing polyvinyl alcohol in an amount of 1/3 based on the mass of the solid component.

  A liquid crystal layer (thickness: 50 μm) was formed on the ITO film surface of the PET film with the ITO film by applying the coating liquid C by a wire bar method. Next, carbon black is dispersed in an aqueous polyvinyl alcohol solution (solid content: 10% by mass), and this dispersion is applied onto the liquid crystal layer surface of the display element to form a black light absorption layer (thickness: 3 μm). did. Thereby, a PET film in which an ITO electrode, a liquid crystal layer, and a light absorption layer were laminated was prepared.

-Adjustment of display medium-
Furthermore, Dick Dry WS-321A / LD-55 (Dainippon Ink Chemical Co., Ltd.), which is a dry laminate adhesive, is formed on the prepared laminate of the ITO electrode, liquid crystal layer, and light absorption layer on the PET film. Kogyo Co., Ltd.) was applied and dried to form a 5 μm thick laminate layer. On this laminate layer, the laminate subjected to the above-mentioned drying treatment (the laminate in which the isolation layer is formed on the photoconductive layer) is laminated and adhered so that the substrates are on the outermost sides, and then bonded together. Was laminated at 90 ° C. to obtain a display medium.
Note that the time from the end of the drying process of the isolation layer to the end of the bonding of the two laminates is 2 minutes, and the atmosphere at that time is a temperature of 23 ° C. and a humidity of 50 RH%.

―Evaluation of reflection characteristics―
With respect to this display medium, writing was performed by applying a writing voltage in an environment of 25 ° C. and 50% RH and irradiating 150 μJ of light with an exposure amount of 150 μJ for 0.2 seconds. The reflectance at the time of display was measured using a Minolta CM-3600d, and the change in reflectance with respect to the initial heating (initial) over time (that is, the reflectance change rate) was obtained. The results shown are obtained. From this result, compared with the comparative example which will be described later, in the display medium adjusted in Example 1, when a voltage value of 650 V or more is applied, a change in reflectance of 40% or more is observed, and favorable reflection is achieved. The characteristics were obtained.

―Light resistance evaluation―
The display medium prepared in Example 1 was subjected to a light resistance test using a fluorescent lamp in an environment of 25 ° C. and 50% RH. The irradiation amount was adjusted so that the distance between the fluorescent lamp and the sample was adjusted, and the irradiation amount of 25,000 Lux exposed the photoconductive layer side. When the relationship between the exposure time and the relative reflectance was examined, the result shown in the diagram 60B of FIG. 4 was obtained.

  The relative reflectance means a display medium in which the photoconductive layer is not provided and the display layer prepared in Example 1 is sandwiched between the PET films provided with the ITO electrodes used in Example 1. When a voltage is applied to the display layer, the maximum reflectance obtained in the display layer is measured by changing the applied voltage, and the ratio to the maximum reflectance is shown.

For this reason, even after exposure for 250 hours, the change in relative reflectance was small compared to the evaluation results of comparative examples described later, and good light resistance was obtained.
Moreover, it can be said that favorable light resistance was obtained compared with Example 2 mentioned later which made the moisture content of the isolation layer 2% or more.

(Example 2)
In Example 2, the display medium adjusted in Example 1 was not subjected to the drying step when forming the isolation layer (that is, the drying process before bonding the two types of laminates), and the moisture content of the isolation layer was 5 A display medium was produced in the same manner as in Example 1 except that the content was adjusted to be%.
In detail, in Example 2, after applying the ion-concentration-adjusted material to the thickness of 1 μm with an applicator, which was performed at the time of forming the isolation layer in Example 1, heat drying by leaving for 10 minutes in a 90 ° C. environment. A display medium was manufactured using the same method as in Example 1 except that the “treatment” was not performed.

In addition, although the ion concentration of the isolation layer of the display medium prepared in Example 2 was 6.5 × 10 ⁻⁵ C / cm ³ which was the same as that in Example 1, the water content was 5%.

―Evaluation of reflection characteristics―
With respect to this display medium, when a writing voltage is applied in the same manner as in Example 1 and irradiation is performed with light having an exposure amount of 150 μJ for 0.2 seconds, then the writing is performed by releasing the voltage and white display is performed. 3 was measured using a CM-3600d manufactured by Minolta, and the change in reflectivity (that is, the reflectivity change rate) with respect to the initial heating (initial) over time was determined. The result shown in the diagram 62A of FIG. Obtained. From this result, compared with the comparative example described later, in the display medium adjusted in Example 2, a large change in reflectivity is observed when a voltage value of 650 V or more is applied, resulting in good reflection characteristics. It was.

―Light resistance evaluation―
The display medium prepared in Example 2 was subjected to the same light resistance test as in Example 1. As a result, even after 300 hours exposure, no reduction in reflectance was observed.
For this reason, even after exposure for 250 hours, the change in relative reflectance was small compared to the evaluation results of comparative examples described later, and good light resistance was obtained.

(Examples 3 to 6, Comparative Examples 1 to 2)
Hereinafter, a display medium was produced in the same manner as in Example 1 except that the ion concentration and moisture content were adjusted to the values shown in Table 1, and the reflection characteristics and light resistance were evaluated in the same manner as in Example 1. These are shown in Table 1.

  In Table 1, with respect to the evaluation result of the reflectance, when a reflectance change of 35% or more is observed by applying a voltage of 650 V or more, the evaluation “◯” indicating no problem is given. When the reflectance change is less than 25% and 25% or more, the evaluation is “△” indicating that it is within the allowable range, and when the reflectance change is less than 25%, the evaluation is “not acceptable”. Indicated.

In Table 1, the light resistance time in the light resistance evaluation indicates the exposure time when the relative reflectance is 80% or less in the light resistance evaluation.
Further, in the light resistance evaluation, when the exposure time is 200 minutes or more, “◯” indicating that there is no problem is set, and when the exposure time is over 100 minutes and less than 200 minutes, the allowable range “Δ” indicating that the exposure time is within the range, and “x” indicating that the exposure time is 100 minutes or less is not acceptable.

It is a schematic block diagram which shows one form of the display apparatus of this embodiment. It is a diagram which shows the evaluation result of the reflectance characteristic in an Example and a comparative example. It is a diagram which shows the evaluation result of the reflectance characteristic in an Example and a comparative example. It is a diagram which shows the evaluation result of light resistance in an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 15 Electrode 17 Liquid crystal layer 18 Laminate layer 19 Light absorption layer 20 Photoconductive layer 21 Isolation layer 22 Electrode 26 Voltage application part 28 Control part 30 Exposure apparatus 30A Light source

Claims (4)

A pair of electrodes;
A photoconductive layer provided between the pair of electrodes and exhibiting an electrical property distribution according to the intensity distribution of the irradiated exposure light;
A partial pressure is applied between the pair of electrodes and distributed according to the electrical characteristic distribution of the photoconductive layer by the voltage applied to the pair of electrodes, and according to the optical characteristic distribution according to the partial pressure. A display layer on which the image is displayed;
Isolation between the photoconductive layer and the display layer in contact with at least the photoconductive layer and having an ion concentration of 5 × 10 ⁻⁵ C / cm ³ or more and 10 × 10 ⁻⁵ C / cm ³ or less. Layers,
A display medium comprising:   The display medium according to claim 1, wherein the isolation layer is made of a water-soluble resin.   The display medium according to claim 1, wherein a moisture content of the isolation layer is 2% or less. A pair of electrodes;
A photoconductive layer provided between the pair of electrodes and exhibiting an electrical property distribution according to the intensity distribution of the irradiated exposure light;
A partial pressure is applied between the pair of electrodes and distributed according to the electrical characteristic distribution of the photoconductive layer by the voltage applied to the pair of electrodes, and according to the optical characteristic distribution according to the partial pressure. A display layer on which the image is displayed;
Isolation between the photoconductive layer and the display layer in contact with at least the photoconductive layer and having an ion concentration of 5 × 10 ⁻⁵ C / cm ³ or more and 10 × 10 ⁻⁵ C / cm ³ or less. Layers,
A display medium comprising:
A voltage applying device for applying a voltage to the pair of electrodes;
An irradiation device for irradiating the display medium with the exposure light;
A display device comprising:

Images