JP2010185946A - Displaying medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displaying medium which easily adjusts a difference in threshold value between a variation in a focal conic state and that in a planar state between a plurality of liquid crystal layers provided between a pair of electrodes: and to provide a display device. <P>SOLUTION: The impedance of a dispersing medium 41 is different between a plurality of liquid crystal layers (a liquid crystal layer 20B and a liquid crystal layer 20G) which are provided between a pair of electrodes 16A and 16B, the dispersing medium 41 dispersing cholesteric liquid crystal 42 contained in each of the liquid crystal layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In recent years, with the spread of personal computers and the development of the information society such as the Internet, the consumption of paper as so-called short-lived documents for the purpose of temporary browsing of electronic information has been increasing. Realization of a rewritable display medium instead of paper is desired for reasons such as conservation of the global environment such as resource protection and improvement of the office environment.

  In view of this, a display medium using cholesteric liquid crystal has been proposed as a display medium that replaces paper having memory characteristics with no power supply and capable of rewriting images in a short time by an external device (for example, Patent Document 1). reference).

  In Patent Document 1, a plurality of liquid crystal layers are provided between a pair of electrodes, and liquid crystal materials having different impedances are used as liquid crystal materials included in each liquid crystal layer. As a result, the plurality of liquid crystal layers provided between the pair of electrodes are selectively changed in state (change in state between the planar and the focal conic).

Japanese Patent Laid-Open No. 10-177191

  In the present invention, the difference in threshold of state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes can be easily adjusted as compared with the case without the configuration of the present invention. It is an object to provide a display medium and a display device.

  The above-mentioned subject is achieved by the following present invention. That is,

  The invention according to claim 1 includes a pair of electrodes and a plurality of liquid crystal layers provided between the pair of electrodes and having different impedances, and the plurality of liquid crystal layers includes the cholesteric liquid crystal and the cholesteric liquid crystal. A display medium having different impedances of the dispersion medium between the plurality of liquid crystal layers.

  The invention according to claim 2 is the display medium according to claim 1, wherein the dispersion medium contained in at least one of the plurality of liquid crystal layers includes a dielectric material.

  The invention according to claim 3 is the display medium according to claim 1 or 2, wherein impedances of the cholesteric liquid crystals between the plurality of liquid crystal layers are different from each other.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the volume resistivity of each of the plurality of liquid crystal layers is 1 × 10 ⁶ Ωm or more and 10 ¹⁶ Ωm or less. It is a display medium of description.

  The invention according to claim 5 further includes a photoconductive layer provided between the pair of electrodes and exhibiting an electrical characteristic distribution according to the intensity distribution of the light by absorbing light in a predetermined wavelength region. The display medium according to claim 1, wherein the display medium is a display medium.

  The invention according to claim 6 includes a pair of electrodes and a plurality of liquid crystal layers provided between the pair of electrodes and having different impedances, and the plurality of liquid crystal layers includes the cholesteric liquid crystal and the cholesteric liquid crystal. A display medium including an encapsulated microcapsule and a dispersion medium in which the microcapsule is dispersed, wherein the impedance of the dispersion medium between the plurality of liquid crystal layers is different from each other, and a voltage applying unit that applies a voltage to the pair of electrodes. And a display device.

  The invention according to claim 7 is a light which is provided between a pair of electrodes and between the pair of electrodes and exhibits an electrical characteristic distribution according to the intensity distribution of the light by absorbing light in a predetermined wavelength region. A conductive layer; and a plurality of liquid crystal layers provided between the pair of electrodes and having different impedances, the plurality of liquid crystal layers including a cholesteric liquid crystal, a microcapsule enclosing the cholesteric liquid crystal, and the microcapsule A dispersion medium in which the impedance of the dispersion medium between the plurality of liquid crystal layers is different from each other, voltage application means for applying a voltage to the pair of electrodes, and the display medium according to image data And an irradiation means for irradiating the light.

  According to the first aspect of the present invention, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes as compared with the case without the configuration of the present invention. There is an effect that a display medium in which the difference is easily adjusted is provided.

  According to the second aspect of the present invention, as compared with the case where the configuration of the present invention is not provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes. There is an effect that a display medium in which the difference is easily adjusted is provided.

  According to the third aspect of the present invention, as compared with the case where the configuration of the present invention is not provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes. There is an effect that the difference between the two increases easily.

  According to the fourth aspect of the present invention, as compared with the case where the configuration of the present invention is not provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes. It is possible to provide a display medium in which the difference between the two is easily adjusted and the state change occurs effectively and selectively.

  According to the fifth aspect of the present invention, in the configuration in which the photoconductive layer is further provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes is also provided. There is an effect that a display medium in which the difference is easily adjusted is provided.

  According to the sixth aspect of the present invention, as compared with the case where the configuration of the present invention is not provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes. There is an effect that a display device for writing an image on a display medium in which the difference between the two is easily adjusted is provided.

  According to the seventh aspect of the present invention, as compared with the case where the configuration of the present invention is not provided, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes. There is an effect that a display device for writing an image on a display medium in which the difference between the two is easily adjusted is provided.

It is a block diagram which shows an example of the display medium and display apparatus in embodiment of this invention. It is a schematic diagram which shows an example of a liquid-crystal layer. It is a schematic explanatory drawing which shows the relationship between the molecular orientation of a cholesteric liquid crystal, and an optical characteristic, (A) is a planar state, (B) is a focal conic state, (C) is a schematic diagram which shows a homeotropic state. It is a diagram which shows the electro-optic response of a cholesteric liquid crystal layer. It is a diagram which shows the relationship between the voltage applied to this pair of electrodes, and the normalized reflectance of each liquid crystal layer about the two liquid crystal layers laminated | stacked between a pair of electrodes. It is a block diagram which shows an example of the form different from FIG. 1 of the display medium and display apparatus in embodiment of this invention. It is a diagram which shows the relationship between the frequency of the sample adjusted in the Example and the comparative example, and an electrostatic capacitance. It is a diagram which shows the electro-optical response of the liquid crystal layer in an Example. It is a diagram which shows the electro-optical response of the liquid crystal layer in a comparative example.

  The display medium according to the present embodiment includes a pair of electrodes and a plurality of liquid crystal layers provided between the pair of electrodes and having different impedances, and the plurality of liquid crystal layers includes the cholesteric liquid crystal and the cholesteric liquid crystal. And a dispersion medium in which the impedance of the dispersion medium between the plurality of liquid crystal layers is different from each other.

  As described above, in the display medium of this embodiment, the impedance of the dispersion medium included in each liquid crystal layer is different between the plurality of liquid crystal layers provided between the pair of electrodes. For this reason, impedances between the plurality of liquid crystal layers provided between the pair of electrodes have different values. Therefore, when a voltage is applied between the pair of electrodes, the partial pressures applied to each of the plurality of liquid crystal layers provided between the pair of electrodes have different values. For this reason, by adjusting the impedance of the dispersion medium in each liquid crystal layer, as a result, the threshold value of the state change between the focal conic and the planar between the plurality of liquid crystal layers provided between the pair of electrodes (details will be described later). ) Are easily adjusted, and each of the plurality of liquid crystal layers provided between the pair of electrodes is easily and selectively driven (state change between the focal conic and the planar).

  Here, in each liquid crystal layer, the impedance of the liquid crystal layer is adjusted by using materials having different impedances as the liquid crystal material of the cholesteric liquid crystal without adjusting the impedance of the dispersion medium as in the present embodiment. Although the method can be considered, the types of liquid crystal materials selected as liquid crystal materials having different impedances are limited, and there is a problem of compatibility between the liquid crystal materials when adjusting the impedance by mixing a plurality of liquid crystal materials. It was difficult to easily adjust the impedance of each liquid crystal layer.

  On the other hand, in the display medium of this embodiment, the impedance of each liquid crystal layer is easily adjusted by adjusting the impedance of each liquid crystal layer by adjusting the impedance of the dispersion medium itself in the liquid crystal layer.

The method for adjusting the impedance of the dispersion medium will be described in detail later, but a method of containing a dielectric material (hereinafter referred to as a dielectric) or a dispersion medium having a different capacitance for each liquid crystal layer is used. The method of doing is mentioned. By adjusting the type and content of the dielectric contained in the dispersion medium, the electrostatic capacity of the dispersion medium is easily adjusted, and as a result, the impedance is easily adjusted.
Moreover, as a method for adjusting the impedance of the dispersion medium, a method of adding a conductive compound can be mentioned. Examples of the conductive compound include inorganic compounds.

  Further, by adjusting the impedance of the dispersion medium of each liquid crystal layer and further adjusting the impedance of the liquid crystal material of each liquid crystal layer, the threshold of state change between the planar layers and the focal conic between each liquid crystal layer is further expanded.

As described above, the capacitance (impedance) of each liquid crystal layer is adjusted, but each liquid crystal layer after adjustment is insulative (volume resistivity is 1 × 10 ⁶ Ωm or more and 10 ¹⁶ Ωm or less. Range, the same shall apply hereinafter). When each liquid crystal layer is conductive (volume resistivity is 1 × 10 ⁻⁴ Ωm or less, hereinafter the same), when a voltage is applied between the pair of electrodes, the liquid crystal layer is provided between the pair of electrodes. In some cases, the above-described state change in each of the plurality of liquid crystal layers does not occur.

  Hereinafter, one embodiment of the display medium and the display device in this embodiment will be described in detail.

  As shown in FIG. 1, the display device 17 according to the present embodiment includes a display medium 10 and a writing device 11 that writes an image on the display medium 10.

  The display medium 10 has a configuration in which a display element 24 and a display element 26 are laminated via a substrate 15 between a substrate 12 and a substrate 14. In the present embodiment, the case where the display medium 10 is configured by stacking two layers of display elements (the display element 24 and the display element 26) will be described. The display element 24 (detailed later) may be provided with at least one display element 24 having a structure in which a plurality of liquid crystal layers are stacked on each other, or may be provided with two or more display elements 24. A configuration in which a plurality of display elements 26 having a configuration in which one liquid crystal layer is stacked between electrodes is further provided may be employed.

  The display element 24 is configured by laminating a light shielding layer 22R, a liquid crystal layer 20G, and a liquid crystal layer 20B between the electrode 16A and the electrode 16B. The display element 26 is configured by laminating a light shielding layer 22C and a liquid crystal layer 20R between a pair of electrodes 18A and 18B.

  Each of the liquid crystal layer 20G, the liquid crystal layer 20B, and the liquid crystal layer 20R has a function of modulating a selective reflection state and a transmission state of light of a specific color by an electric field, and the selected state is maintained without an electric field. When the liquid crystal layer 20G, the liquid crystal layer 20B, and the liquid crystal layer 20R are in a selective reflection state of light of a specific color by an electric field, they selectively reflect different colors of incident light. Hereinafter, the liquid crystal layer 20 </ b> A, the liquid crystal layer 20 </ b> B, and the liquid crystal layer 20 </ b> C will be collectively referred to as the liquid crystal layer 20.

  In the present embodiment, as shown in FIG. 1, the display element 24 will be described in the case where two liquid crystal layers are provided between a pair of electrodes (between the electrodes 16A and 16B). The liquid crystal layer 20G and the liquid crystal layer 20B) in the display element 24, as will be described in detail later, the impedance between the liquid crystal layers is different by adjusting the impedance of the dispersion medium included in each liquid crystal layer to be different. The liquid crystal layer may have a configuration in which three or more liquid crystal layers are provided between a pair of electrodes.

  The display medium 10 corresponds to the display medium of the present invention, and the liquid crystal layer 20G and the liquid crystal layer 20B correspond to the liquid crystal layer of the display medium of the present invention. The display device 17 corresponds to the display device of the present invention.

  As shown in FIG. 2, the liquid crystal layer 20 has a configuration in which a cholesteric liquid crystal 42 is dispersed in a dispersion medium 41. The cholesteric liquid crystal may be included in the microcapsule 44.

  The selective reflection wavelength regions (display color wavelength regions) in the liquid crystal layer 20B, the liquid crystal layer 20G, and the liquid crystal layer 20R when the light of the cholesteric liquid crystal 42 is in the selective reflection state are different from each other. For example, the liquid crystal layer 20B is configured by a cholesteric liquid crystal 42 that selectively reflects B (blue) light, and the liquid crystal layer 20G is configured by a cholesteric liquid crystal 42 that selectively reflects G (green) light. 20R is composed of a cholesteric liquid crystal 42 that selectively reflects the color of R (red).

The reflection wavelength region (display color wavelength region) of each of the liquid crystal layer 20B, the liquid crystal layer 20G, and the liquid crystal layer 20R is adjusted by the helical pitch of the cholesteric liquid crystal 42 included in each liquid crystal layer 20. The helical pitch of the cholesteric liquid crystal 42 is adjusted by the amount of chiral agent added to the nematic liquid crystal. Further, in order to compensate for the temperature dependence of the helical pitch of the cholesteric liquid crystal 42, a known method of adding a plurality of chiral agents having different twisting directions or opposite temperature dependences may be used.
In addition, as an auxiliary member that assists in changing the optical characteristics of the liquid crystal, it may be used in combination with passive optical components such as a polarizing plate, a retardation plate, and a reflection plate, or a dichroic dye may be added to the liquid crystal.

  As shown in FIG. 3A, the cholesteric liquid crystal 42 has a planar structure in which the spiral axis is perpendicular to the cell surface and causes the above-described selective reflection phenomenon with respect to incident light. As shown in FIG. Focal conic, whose axis is almost parallel to the cell surface and transmits the incident light while being slightly scattered forward, and as shown in FIG. 5C, the spiral structure is unwound and the liquid crystal director is directed in the direction of the electric field. Three states are shown, which are almost completely transmitting homeotropic.

  Of the above three states, the planar and focal conic exist bistable with no voltage. Therefore, the orientation state of the cholesteric liquid crystal is not uniquely determined with respect to the voltage applied between the electrodes sandwiching the liquid crystal layer 20, and when the planar is in the initial state, with the increase of the applied voltage, In the order of planar, focal conic, and homeotropic, when the focal conic is in the initial state, it changes in the order of focal conic and homeotropic as the applied voltage increases (see FIG. 4).

  On the other hand, when the partial pressure applied to the liquid crystal layer 20 suddenly becomes zero, the planar and focal conic remain as they are, and the homeotropic has a characteristic of changing to a planar (see FIG. 4). . For this reason, the liquid crystal layer 20 is selected to be planar (selective reflection state) or focal conic (transmission state) as the final phase state.

  Specifically, by applying a voltage between the electrodes and then releasing the voltage application, the liquid crystal layer 20 when the partial pressure applied to the liquid crystal layer 20 is suddenly reduced to zero is switched as shown in FIG. Shows behavior. When the voltage applied between the electrodes (for example, between the electrodes 16A and 16B) before the voltage application is released is equal to or higher than Vfh (upper threshold voltage), the cholesteric liquid crystal is changed from homeotropic to planar after the voltage application is released. In a reflection state, when it is between Vpf (lower threshold voltage) and Vfh, it becomes a transmission state due to focal conic. It becomes a transmission state.

In FIG. 4, the vertical axis represents the normalized light reflectance, and the light reflectance is normalized with the maximum light reflectance being 100 and the minimum light reflectance being 0. In addition, there is a transition region between the planar, focal conic, and homeotropic states, so that the normalized light reflectance is 50 or more when the selective light reflection state is less than 50 and the normalized light reflectance is less than 50. The state is defined as a state, a threshold voltage for planar and focal conic state change is defined as an upper threshold voltage Vpf, and a threshold voltage for focal conic and homeotropic state change is defined as a lower threshold voltage Vfh.
In the present embodiment, the “threshold for changing state between focal conic and homeotropic” indicates the upper threshold voltage Vpf and the lower threshold voltage Vfh.

  The cholesteric liquid crystal 42 is a liquid crystal material containing an optically active compound. 1) A method of adding an optically active compound or the like called a chiral agent to nematic liquid crystal, or 2) An optically active liquid crystal material such as a cholesterol derivative is used. It is obtained by the method. In the former case, the nematic liquid crystal material is known as cyanobiphenyl, phenylcyclohexane, phenylbenzoate, cyclohexylbenzoate, azomethine, azobenzene, pyrimidine, dioxane, cyclohexylcyclohexane, stilbene, tolan, etc. A nematic liquid crystal-containing composition is utilized. As the chiral agent, a cholesterol derivative or a compound having an optically active group such as a 2-methylbutyl group is used.

  Additives such as pigments and particles may be added to the cholesteric liquid crystal 42. Further, it may be gelled using a crosslinkable polymer or a hydrogen bonding gelling agent, or may be any of a polymer liquid crystal, a medium molecular liquid crystal, a low molecular liquid crystal, or a mixture thereof. The helical pitch of the cholesteric liquid crystal can be changed depending on the type and amount of the chiral agent and the material of the liquid crystal. The wavelength of selective reflection may be the ultraviolet wavelength region or the infrared wavelength region in addition to the visible wavelength region.

The cholesteric liquid crystal 42 is dispersed in the dispersion medium 41 after being granulated.
Examples of the particle formation method include a method of emulsifying and dispersing at least a dispersed phase composed of cholesteric liquid crystal in a continuous phase that is incompatible with the dispersed phase, for example, an aqueous phase.
As the emulsification means, after mixing the dispersed phase and the continuous phase, a method of dispersing the dispersed phase as fine droplets by mechanical shearing force such as a homogenizer, or passing the dispersed phase through the porous film in the continuous phase A membrane emulsification method, a microchannel method, or the like that is extruded and dispersed as fine droplets can be employed. In particular, the latter film emulsification method and the microchannel method are preferable because the dispersion of the particle size of the emulsified droplets is reduced and a liquid crystal drop having a uniform particle size can be formed. A small amount of a surfactant or protective colloid for stabilizing the emulsification may be mixed in the continuous phase during emulsification.
The cholesteric liquid crystal 42 may be encapsulated in a microcapsule 44, and a polymer material is used as the material.

Examples of the polymer material constituting the microcapsule 44 include polyvinyl butyral resin, polyvinyl formal resin, polyvinyl acetal resin such as partially acetalized polyvinyl butyral resin in which part of butyral is modified with formal, acetoacetal, or the like, styrene , Polystyrene resins obtained by polymerizing methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, poly 2-ethylhexyl methacrylate, polylauryl methacrylate, etc. Methacrylic acid ester polymer, polyarylate resin (polycondensate of bisphenol A and phthalic acid, etc.), polycarbonate resin, polyester resin, modified ether type polyester resin, phenoxy Fat, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, urea-formaldehyde resin, melamine-formaldehyde resin, acrylic resin, methacrylic resin, polyacrylamide resin, polyamide resin, polyvinyl pyridine resin, cellulose resin, polyurethane resin , Coumarin resin, Tempel resin, Phenol resin, Melamine resin, Epoxy resin, Silicone resin, Polyvinyl alcohol resin, Polyvinylpyrrolidone resin, Vinyl chloride-vinyl acetate copolymer, Hydroxyl-modified vinyl chloride-vinyl acetate copolymer, Carboxyl-modified chloride Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer and other vinyl chloride-vinyl acetate copolymers, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile Lil copolymer, styrene - alkyd resin, a silicone - alkyd resin, phenol - formaldehyde, such as a polypeptide of the gelatin. These polymers may be used alone or in combination of two or more.
Among these, a polyurethane resin and a melamine resin are preferably used because of excellent mechanical strength such as pressure and bending and excellent display characteristics.

  As a method of encapsulating the cholesteric liquid crystal 42 in the microcapsule 44 composed of the polymer, a microcapsule method can be mentioned.

  As the microcapsule method, 1) a phase separation method in which an aqueous polymer solution in which cholesteric liquid crystal 42 is dispersed is phase-separated to form a film as microcapsule 44 on the liquid crystal droplet surface of cholesteric liquid crystal 42; 2) polymer and cholesteric Liquid-liquid drying method in which the liquid crystal 42 is dissolved in a common solvent and dispersed in the aqueous phase to evaporate the solvent. 3) A mixed solution (oil-phase liquid) of the cholesteric liquid crystal 42 and the oil-soluble monomer A is water. An interfacial polymerization method in which a film is formed by adding a water-soluble monomer B and dispersing the monomer A and the monomer B in an interfacial polymerization reaction. 4) a monomer in the cholesteric liquid crystal 42 or in the aqueous phase. For example, an in situ polymerization method in which a film as a microcapsule 44 is formed using a polymer that is dissolved by heating and polymerized by heating or the like is used.

-Phase separation method-
In the phase separation method, as the polymer constituting the microcapsule 44 mentioned above, two kinds of water-soluble polymers; for example, gelatin and gum arabic, protein and polysaccharide, protein and protein, protein and nucleic acid, polysaccharide and It is compatible with water in a complex coacervation method in which an aqueous solution of nucleic acid or the like is phase-separated into a concentrated phase and a diluted phase by controlling pH and temperature, or in a water-soluble polymer solution such as polyvinyl alcohol, gelatin, or alkyl cellulose. For example, a simple coacervation method in which an alcohol or acetone is added to cause phase separation is used.

-In-liquid drying method-
In the in-liquid drying method, the above-described polymer constituting the microcapsule 44 is dissolved in a low-boiling solvent together with liquid crystal, dispersed in an aqueous phase, and the solvent is volatilized by reducing pressure or heating. Is done.

-Interfacial polymerization method-
In the interfacial polymerization method, the oil-soluble monomer A includes a polyvalent compound having a plurality of functional groups such as basic acid halide, haloformate, isocyanate, isothiocyanate, ketene, carbodiimide, epoxy, glycidyl ether, oxazoline, ethyleneimine, and lactone. As the water-soluble monomer B, a polyvalent compound having a plurality of functional groups such as amine, alcohol, carboxylic acid, mercaptan and phenol is used.

-In situ polymerization method-
The in situ polymerization method is performed by 1) a method of polymerizing an oil-soluble monomer A and a monomer C, or 2) a method of using a monomer D that can be polymerized alone such as a radical polymerizable monomer. In the case of 1), the monomer A described in the section of the interfacial polymerization method can be similarly used as the monomer A, and basic acid halide, haloformate, isocyanate, isothiocyanate, ketene, carbodiimide, epoxy, glycidyl ether, oxazoline, ethyleneimine A polyvalent compound having a plurality of functional groups such as lactone in one molecule can be used. As the monomer C, a polyvalent compound having a plurality of functional groups such as amine, alcohol, carboxylic acid, mercaptan and phenol in one molecule is used. In the case of 2), the monomer D includes a polyvalent epoxy compound, a polyvalent isocyanate compound, an unsaturated hydrocarbon compound; for example, styrene, isoprene, butadiene, vinyl chloride, vinylidene chloride, acrylonitrile, acrylic acid derivatives, methacrylic acid derivatives, etc. Is used. A wall material can also be formed from the aqueous phase, in which case a water-soluble monomer such as melamine / formaldehyde is used.

The average particle size of the formed cholesteric liquid crystal particles is preferably 4 μm or more and 20 μm or less, and more preferably 5 μm or more and 9 μm or less.
If the average particle size is less than 4 μm, good display contrast may not be obtained. If it exceeds 20 μm, the unevenness of the surface of the liquid crystal layer becomes considerably large, and there is a problem that the flat surface cannot be obtained or the driving voltage becomes high.
The average particle size of the microcapsules 44 is measured as a volume average particle size using a Coulter counter.

  The dispersion medium 41 has a function of holding the cholesteric liquid crystal 42 and suppressing the flow of the cholesteric liquid crystal 42 (change in image) due to deformation of the display medium 10, and does not dissolve in the constituent material of the cholesteric liquid crystal 42. A polymer material using a liquid that is incompatible with the constituent material as a solvent is preferably used. The dispersion medium 41 is desired to be a transparent material having a strength that can withstand external forces.

  Examples of the dispersion medium 41 having the above characteristics include water-soluble polymer materials such as gelatin, polyvinyl alcohol, cellulose derivatives, polyacrylic acid polymers, ethyleneimine, polyethylene oxide, polyacrylamide, polystyrene sulfonate, polyamidine, isoprene sulfone. Acid polymers or materials that can be emulsified in water, such as fluororesins, silicone resins, acrylic resins, urethane resins, epoxy resins, polyester resins, polyamide resins, olefin resins, vinyl resins, phenol resins, urea resins, Glass, ceramic, etc. are used. The dispersion medium 41 is not necessarily colorless, and may be colored in a desired color in consideration of the display effect.

  The dispersion medium 41 may be used in the form of a precursor instead of the final composition. For example, the resin may be used in the form of a monomer or oligomer, and the glass or ceramic may be used in the form of a sol-gel material such as a metal alkoxide. In this case, in the process of forming the display medium 10, after the constituent material of the liquid crystal layer 20 is applied on the substrate, the precursor of the dispersion medium 41 is converted into the final composition by a curing process such as heating, ultraviolet irradiation, and electron beam irradiation. A conversion process is required.

  Here, as described above, in the display medium 10 of the present embodiment, the dispersion medium 41 included in each of the liquid crystal layer 20B and the liquid crystal layer 20G, which are a plurality of liquid crystal layers, provided between the pair of electrodes. Impedances are different from each other.

  As a method for adjusting the impedance of the dispersion medium 41 in the plurality of liquid crystal layers provided between the pair of electrodes to different values, there is a method of adding a dielectric to the dispersion medium 41 as described above. It is done. That is, by adjusting the kind of dielectric material contained in the dispersion medium 41 in the plurality of liquid crystal layers 20 (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes, the content of the dielectric material, and the like. The impedance between the liquid crystal layers 20 is adjusted to have different values.

  Note that a high dielectric is added to the dispersion medium 41 in all of the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes, and the addition amount and the type of the high dielectric are adjusted. As a result, the impedance of the dispersion medium 41 between the plurality of liquid crystal layers may be adjusted to have different values, or only one of the dispersion medium 41 of the liquid crystal layer 20B and the liquid crystal layer 20G is high. You may adjust so that the electrostatic capacitance (as a result impedance) between liquid crystal layers may become a different value by adding a dielectric material.

  As the dielectric added to the dispersion medium 41, it is desirable to use a high dielectric from the viewpoint of adjusting the impedance by effectively adjusting the capacitance of the dispersion medium 41.

Specific examples of the high dielectric material include BaTiO ₃ , SrTiO ₃ , CaSnO ₃ , BaSnO ₃ , BaZrO ₃ , and other barium titanate ferroelectrics, lead zirconate titanate, TiO ₂ , MgTiO _{3, and the} like. Is mentioned. Among these, since the dielectric constant is very large, it is desirable to use a barium titanate ferroelectric.

  The particle size of the high dielectric contained in the dispersion medium 41 is important. If the particle size of the high dielectric is large, it becomes difficult to stably disperse it in the dispersion medium 41, and transparency of the obtained liquid crystal layer 20 is lost. For this reason, the average particle size of the high dielectric contained in the dispersion medium 41 is 200 nm (0.1 μm) or less, preferably 100 nm or less, and particularly preferably 50 nm or less.

  The average particle size of the high dielectric material is measured by a dynamic light scattering method using a nanotrack particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). The diameter was measured. Measurement conditions were measured at 25 ° C. for a sample prepared by diluting 10 μl of a high dielectric dispersion with 10 ml of water.

The electrostatic capacity (F) of the dispersion medium 41 and the dispersion medium 41 to which a high dielectric material is added is measured by the following method.
Specifically, the change in capacitance with respect to frequency is measured with an impedance analyzer (Toyo Technica Co., Ltd., 126096W).

  As a method for dispersing the high dielectric material (the additive having a high electrostatic capacity dispersed in the dispersion medium 41) in the dispersion medium 41, a normal dispersion method is used without limitation.

  In order to obtain the liquid crystal layer 20 having a high capacitance, it is preferable to contain as much high dielectric material as the dispersion medium 41. However, the liquid crystal layer 20 itself may be added in a range that does not lose transparency. It is desirable to adjust.

  Specifically, the content of the high dielectric material contained in the dispersion medium 41 is preferably 20% or less (volume ratio), and more preferably 10% or less.

The liquid crystal layer 20 can be formed by printing methods such as screen printing, letterpress printing, intaglio printing, flat plate printing, flexographic printing, spin coating, bar coating, dip coating, roll coating, knife coating, and die coating. Using a coating method such as a printing method, a printing device or a coating device suitable for each method may be used.
The layer thickness of the liquid crystal layer 20 is desirably 5 μm or more and 30 μm or less.

  Each of the substrate 12, the substrate 14, and the substrate 15 has an insulating property. Each of the substrate 12, the substrate 14, and the substrate 15 is transparent (transmits 80% or more of light having a wavelength of 380 nm to 780 nm).

  For the substrate 12, the substrate 15, and the substrate 14, an inorganic sheet such as glass and silicon, or a polymer film such as polyethylene terephthalate, polysulfone, polyethersulfone, polycarbonate, and polyethylene naphthalate is preferably used.

  The electrode 16A, the electrode 16B, the electrode 18A, and the electrode 18B have conductivity (volume resistance of 2000 Ωcm or less, the same applies hereinafter) and are transparent.

The electrode 16A, the electrode 16B, the electrode 18A, and the electrode 18B are electrically conductive such as a metal film such as ITO (Indium Tin Oxide) and Au, an oxide such as SnO ₂ and ZnO, and a film of a conductive polymer such as polypyrrole. The body is used. These electrode 16A, electrode 16B, electrode 18A, and electrode 18B are provided by sputtering, printing, CVD, vapor deposition, or the like.

  When the image is displayed on the liquid crystal layer 20 sandwiched between the same electrodes as each layer, the light shielding layer 22R and the light shielding layer 22C are on the non-display surface side of the display medium 10 (in FIG. External light incident from the side opposite to the arrow X and the display image are optically separated to suppress deterioration in image quality.

  For the light shielding layer 22R and the light shielding layer 22C, a material that absorbs light from an external light source, incident light, light having a wavelength of external light, or the like is used. For example, a resin in which a pigment is dispersed, a resin in which a dye is dissolved, or a dye is used. Resin color materials such as dyed resin are used.

  Specifically, the light shielding layer 22C has a color in the selective reflection state of the liquid crystal layer 20R stacked between the same electrodes (electrodes 18A and 18B) as the light shielding layer 22C (in this embodiment, red). ). Further, the light shielding layer 22R is a color in the selective reflection state of the liquid crystal layer 20B and the liquid crystal layer 20G that are stacked between the same electrodes (electrode 16A and electrode 16B) as the light shielding layer 22R (blue and green in the present embodiment). ).

  In the display element 26 of the display medium 10 configured as described above, when the voltage applying unit 28B is controlled by the control of the control unit 39 and a voltage is applied between the electrode 18A and the electrode 18B from the voltage applying unit 28B. A partial pressure is applied to each layer including the liquid crystal layer 20R, which is laminated between the electrode 18A and the electrode 18B. Then, the change in the voltage distribution applied to the liquid crystal layer 20R changes the orientation of the liquid crystal in the liquid crystal layer 20R, and an image is displayed / recorded on the liquid crystal layer 20R.

  On the other hand, in the display element 24 in which a plurality of liquid crystal layers are stacked between a pair of electrodes, the voltage application unit 28A is controlled by the control of the control unit 39, and the voltage is applied between the voltage application unit 28A and the electrodes 16A and 16B. When applied, each partial pressure is applied to each layer stacked between the electrode 16A and the electrode 16B. At this time, as described above in the present embodiment, the liquid crystal layer 20B and the liquid crystal layer 20G as a plurality of liquid crystal layers provided between the pair of electrodes have different electrostatic capacities of the dispersion media 41 included therein. Therefore, the impedances of the liquid crystal layer 20B and the liquid crystal layer 20G are different from each other. For this reason, the partial pressure relating to the liquid crystal layer 20B and the partial pressure relating to the liquid crystal layer 20G have different values.

  For example, it is assumed that the high dielectric described above is contained only in the dispersion medium 41 in the liquid crystal layer 20G in the liquid crystal layer 20B and the liquid crystal layer 20G. In this case, the relationship between the voltage applied to the electrodes 16A and 16B of the display medium 10 and the normalized reflectance in the liquid crystal layer 20B of the display medium 10 is the relationship of the diagram 60B shown in FIG. The relationship between the voltage applied to the electrodes 16A and 16B and the normalized reflectance in the liquid crystal layer 20G of the display medium 10 is the relationship of the diagram 60G shown in FIG.

That is, when the impedance of the dispersion medium 41 is not adjusted, an upper threshold value that is a threshold value of a state change between the focal conic and the homeotropic in the liquid crystal layer 20G and the liquid crystal layer 20B, and the planar and focal conic It is considered that the lower threshold value, which is the threshold value for the state change in between, has the same value.
On the other hand, in the display medium 10 of the present embodiment, the impedance of the dispersion medium 41 included in each of the liquid crystal layer 20G and the liquid crystal layer 20B is adjusted to have different values. For this reason, as shown in FIG. 5, the focal conic and the homeotropic in the liquid crystal layer 20G having the dispersion medium 41 having a high capacity (adjusted to increase the electrostatic capacity) by adding a high dielectric substance. Is a threshold value of the state change between the focal value and the homeotropic in the liquid crystal layer 20B in which the high dielectric material is not added to the dispersion medium 41. The voltage value B2 as the upper threshold value is different (in FIG. 5, the relationship of B2 <G2), and the difference between these threshold values easily increases.

  Similarly, as shown in FIG. 5, in the liquid crystal layer 20G having the dispersion medium 41 having a high capacity (adjusted so as to increase the electrostatic capacity) by adding a high dielectric, planar and focal conic The voltage value G1 as the lower threshold value that is the threshold value for the state change during the period is different from the voltage value B2 as the lower threshold value that is the threshold value for the state change in the liquid crystal layer 20B (B1 <G1 in FIG. 5). ), And the difference between these thresholds easily increases.

  In the above embodiment, the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) stacked between the pair of electrodes are adjusted so that the electrostatic capacities of the dispersion media 41 included in the liquid crystal layer are different from each other. In the above description, the impedance is adjusted to a different value, and thus the capacitance (and impedance) is adjusted to be different between the liquid crystal layers. However, the cholesteric liquid crystal 42 included in each liquid crystal layer is further adjusted. By appropriately selecting a constituent material (liquid crystal material), the impedance of the cholesteric liquid crystal 42 itself may be further adjusted.

In this manner, in addition to the adjustment of the capacitance of the dispersion medium 41, the capacitance of the cholesteric liquid crystal 42 contained in the microcapsule 44 (as a result, the impedance) is further adjusted, so that each liquid crystal layer 20 It is possible to further increase the difference between the state change threshold values (upper threshold value, lower threshold value).

The capacitance (F) of the liquid crystal layer 20 is measured by the following method.
Specifically, the change in capacitance with respect to frequency is measured with an impedance analyzer (Toyo Technica Co., Ltd., 126096W).

  Note that in this embodiment, the case where the plurality of liquid crystal layers provided between the pair of electrodes is two layers has been described. Specifically, the case where one photoconductive layer 24R, two liquid crystal layers 20B, and 20G are provided between the electrode 16A and the electrode 16B has been described. However, the plurality of liquid crystal layers provided between the pair of electrodes may be adjusted so that the electric resistance values between the liquid crystal layers are different because the impedances of the dispersion media 41 included in the liquid crystal layers are different from each other. Needless to say, three or more layers may be used.

  Next, the writing device 11 that writes an image on the display medium 10 and the display device 17 that includes the display medium 10 and the writing device 11 will be described.

  As shown in FIG. 1, the display device 17 includes a writing device 11 and the display medium 10. The writing device 11 includes a control unit 39 and a voltage application unit 28. The voltage application unit 28 is connected to the control unit 39 so as to be able to exchange signals.

  In the present embodiment, the voltage application unit 28 corresponds to a voltage application unit.

  The control unit 39 is configured as a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and controls each unit in the writing device 11.

  The voltage application unit 28 includes a voltage application unit 28A and a voltage application unit 28B. The voltage application unit 28A is connected to the electrodes 16A and 16B of the display medium 10 so as to be able to send and receive signals, and applies a voltage to the electrodes 16A and 16B. The voltage application unit 28B is connected to the electrodes 18A and 18B of the display medium 10 so as to be able to exchange signals, and applies a voltage to the electrodes 18A and 18B.

  The writing device 11 is provided with a slot (not shown) for mounting the display medium 10, and is provided in the slot (not shown) by mounting the display medium 10 in this slot (not shown). The electrode 16A and the electrode 16B of the display medium 10 are electrically connected to the voltage application unit 28A through a connector (not shown) or the like, and the electrode 18A and the electrode 18B of the display medium 10 are electrically connected to the voltage application unit 28B. Configured to be connected.

  The voltage application unit 28 may be configured to be able to apply a voltage based on the signal input from the control unit 39 to the electrode 16A and the electrode 16B, and the electrode 18A and the electrode 18B of the display medium 10, but is faster. From the viewpoint of speed display, it is preferable that AC output is possible and that the slew rate is high. As the voltage application unit 28, for example, a bipolar high voltage amplifier is used.

  In the display device 17 configured as described above, the voltage is applied to either the electrode 16A and the electrode 16B of each display element 24 and the display element 26 or the electrode 18A and the electrode 18B by the voltage application unit 28 under the control of the control unit 39. As a result, an image is formed on the display medium 10.

  Here, as described above, the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes 16A and 16B of the display medium 10 are dispersed in the liquid crystal layer 20B and the liquid crystal layer 20G. By adjusting the impedances 41 to be different from each other, they are adjusted to have different electrical resistance values. For this reason, the difference in the threshold of state change between the focal conic and the planar between the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes is in a widened state. Therefore, in the display device 17, between the electrode 16A and the electrode 16B, between the focal conic and the planar according to the relationship between the applied voltage of each liquid crystal layer 20B and the liquid crystal layer 20G and the normalized reflectance (see FIG. 5). By applying a voltage having a voltage value that causes the state change selectively, only one of the liquid crystal layer 20B and the liquid crystal layer 20G changes to a focal conic state or changes to a planar state, or both of them change to a focal conic state. Alternatively, it is possible to change the state to the planar.

  Note that the display medium 10 described in the above embodiment may further include a display medium having a photoconductive layer.

  In this case, for example, as shown in FIG. 6, each of the display element 24 and the display element 26 in the display medium 10 described in FIG. 1 further includes a photoconductive layer 10A (see FIG. 6). )And it is sufficient. In addition, the display device 13 may include the display medium 10A and the writing device 11A that writes an image on the display medium 10A.

  The writing device 11 </ b> A includes a light irradiation unit 34, a control unit 38, and a voltage application unit 40. The light irradiation unit 34 and the voltage application unit 40 are connected to the control unit 38 so as to be able to exchange signals.

  The display medium 10 </ b> A is configured by laminating a display element 30 and a display element 32 through a substrate 15 between a substrate 12 and a substrate 14.

  The display element 30 is configured by laminating a photoconductive layer 24R, a light shielding layer 22R, a liquid crystal layer 20G, and a liquid crystal layer 20B between the electrode 16A and the electrode 16B. The display element 32 is configured by laminating a photoconductive layer 26C, a light shielding layer 22C, and a liquid crystal layer 20R between a pair of electrodes 18A and 18B.

  The display medium 10A has the same function as the display medium 10 except that the display medium 10 described with reference to FIG. 1 is provided with the photoconductive layer 24R and the photoconductive layer 26C. The same reference numerals are given to the portions, and detailed description is omitted.

  The photoconductive layer 24R and the photoconductive layer 26C have absorption wavelength regions that are different from each other with respect to the irradiated light. When irradiated with light in the wavelength region of the absorption wavelength region under an electric field, the photoconductive layer 24R and the photoconductive layer 26C have internal photoelectric effects. The movement of free electrons occurs, and the electric resistance value decreases according to the intensity of light.

  For example, the color when the liquid crystal layer 20R stacked in the state sandwiched between the same electrodes as the photoconductive layer 26C (between the electrodes 18A and 18B in FIG. 1) is in a selective reflection state is red. Then, as the photoconductive layer 26C, a cyan color photoconductive layer whose electric resistance value is changed by absorbing red light is used as the photoconductive layer 26C.

  Similarly, the color when the liquid crystal layer 20B and the liquid crystal layer 20G sandwiched between the same electrodes as the photoconductive layer 24R (between the electrodes 16A and 16B in FIG. 1) are in the selective reflection state is blue. Assuming that it is green, as the photoconductive layer 24R, a red photoconductive layer whose electric resistance value changes by absorbing blue light is used as the photoconductive layer 24R.

  Thereby, for example, a voltage is applied to the electrode 16A and the electrode 16B from a voltage application unit 40A (details will be described later), and blue light is irradiated from the light irradiation unit 34 to the photoconductive layer 24R, thereby the electrode 16A. And the partial pressure distributed according to the electrical characteristic distribution by the light irradiation to the photoconductive layer 24R by the voltage applied between the electrodes 16B is applied to the liquid crystal layer 20B and the liquid crystal layer 20G.

  Here, for the liquid crystal layer 20B and the liquid crystal layer 20G, if the constituent materials other than the color component adjusting material (for example, the addition amount of the chiral agent) are the same, the partial pressure applied to the liquid crystal layer 20B and the liquid crystal layer 20G is substantially the same. Value. However, in the display medium 10A of the present embodiment, as described above, the impedance of the dispersion medium 41 included in the liquid crystal layer 20B and the liquid crystal layer 20G is adjusted so that the impedances are different from each other. There is a difference in the threshold of state change between the focal conic and the planar between the liquid crystal layers of the liquid crystal layer 20B and the liquid crystal layer 20G provided between the electrode 16A and the electrode 16B, and is provided between the pair of electrodes. Each of the plurality of liquid crystal layers is easily and selectively driven (state change between the focal conic and the planar).

  The photoconductive layer 24R and the photoconductive layer 26C include (a) a layer composed of an amorphous silicon, a compound semiconductor such as ZnSe, CdS, etc. as an inorganic semiconductor material, and (b) an anthracene as an organic semiconductor material. Examples thereof include a layer composed of polyvinyl carbazole, (c) a layer composed of a mixture or laminate of a charge generation material that generates a charge by light irradiation and a charge transport material that generates a charge transfer by an electric field.

  Note that the photoconductive layer 24R and the photoconductive layer 26C have the internal photoelectric effect as described above, and the electrical resistance value changes according to the intensity of the irradiated light, so that AC driving is possible. In addition, it is desirable to drive symmetrically with the irradiated light. From this point of view, as shown in FIG. 6, the photoconductive layer 24R has a pair of charge generation layers sandwiching the charge transport layer (CTL) 24B from above and below. It is desirable that the (CGL) 24A and the charge generation layer 24C have a three-layer structure in which they are stacked. The photoconductive layer 26C also preferably has a three-layer structure in which a pair of charge generation layer 26A and charge generation layer 26D are stacked so as to sandwich the charge transport layer 26B from above and below.

  The charge generation layer 24A, the charge generation layer 24C, the charge generation layer 26A, and the charge generation layer 26D have a function of generating free electrons by absorbing exposure light (details will be described later) irradiated for writing from the writing device 11A. It is a layer which has. Examples of the charge generation material constituting each of the charge generation layer 24A, the charge generation layer 24C, the charge generation layer 26A, and the charge generation layer 26D include, for example, perylene-based, phthalocyanine-based, bisazo-based, dithiopytochelopyrrole-based, squarylium-based Examples include azulenium-based and thiapyrylium / polycarbonate-based compounds.

Examples of the charge transport material constituting the charge transport layer 24B and the charge transport layer 26B include trinitrofluorene-based, polyvinylcarbazole-based, oxadiazole-based, pyralizone-based, hydrazone-based, stilbene-based, triphenylamine-based, Phenylmethane-based compounds, diamine-based compounds, polyvinyl alcohol to which LiClO ₄ is added, polyethylene oxide, and the like, and composites of charge generating materials and charge transporting materials include laminates, mixtures, and microcapsules.

  Next, the writing device 11A that writes an image on the display medium 10A and the display device 13 that includes the display medium 10A and the writing device 11A will be described.

  As shown in FIG. 6, the display device 13 includes a writing device 11A and the display medium 10A. The writing device 11 </ b> A includes a light irradiation unit 34, a control unit 38, and a voltage application unit 40. The light irradiation unit 34 and the voltage application unit 40 are connected to the control unit 38 so as to be able to exchange signals. The light irradiation unit 34 corresponds to the irradiation unit of the display device of the present invention, and the voltage application unit 40 corresponds to the voltage application unit.

  The control unit 38 is configured as a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and controls each unit in the writing device 11A.

  The voltage application unit 40 includes a voltage application unit 40A and a voltage application unit 40B. The voltage application unit 40A is connected to the electrodes 16A and 16B of the display medium 10A so as to transmit and receive signals, and applies a voltage to the electrodes 16A and 16B. The voltage application unit 40B is connected to the electrodes 18A and 18B of the display medium 10A so as to transmit and receive signals, and applies a voltage to the electrodes 18A and 18B.

The writing device 11A is provided with a slot (not shown) for mounting the display medium 10A, and is provided in the slot (not shown) by mounting the display medium 10A in this slot (not shown). The electrode 16A and the electrode 16B of the display medium 10A are electrically connected to the voltage application unit 40A via a connector (not shown) or the like, and the electrode 18A and the electrode 18B of the display medium 10A are electrically connected to the voltage application unit 40B. Configured to be connected.
In addition, when the display medium 10A is installed in a slot (not shown) of the writing device 11A, the light irradiation unit 34 can irradiate exposure light from the substrate 14 side to the substrate 12 side of the display medium 10A. Become.

  The voltage application unit 40 may be configured to be able to apply a voltage based on the signal input from the control unit 38 to the electrode 16A and the electrode 16B, and the electrode 18A and the electrode 18B of the display medium 10A. From the viewpoint of speed display, it is preferable that AC output is possible and that the slew rate is high. For example, a bipolar high voltage amplifier is used as the voltage application unit 40.

  The light irradiation unit 34 irradiates a plurality of photoconductive layers (the photoconductive layer 24R and the photoconductive layer 26C) of the display medium 10A with light, and the same number of photoconductive layers as the number of the photoconductive layers included in the display medium 10A. The light source includes a plurality of light sources that emit light in different wavelength regions.

  In the display device 13 having the above-described configuration, a voltage is applied to either the electrode 16A and the electrode 16B of each display element 30 and the display element 32 or the electrode 18A and the electrode 18B by the voltage application unit 40 under the control of the control unit 38. However, light corresponding to a blue or red image is emitted from the light irradiation unit 34 to the photoconductive layer 24R and the photoconductive layer 26C of the display medium 10A from the substrate 14 side to the substrate 12 side of the display medium 10A. As a result, an image is formed on the display medium 10A.

  Here, as described above, the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes 16A and 16B of the display medium 10A are dispersed in the liquid crystal layer 20B and the liquid crystal layer 20G. By adjusting the impedances 41 to be different from each other, the impedances are adjusted to be different from each other. For this reason, there is a difference in the state change threshold between the focal conic and the planar between the plurality of liquid crystal layers (the liquid crystal layer 20B and the liquid crystal layer 20G) provided between the pair of electrodes. Therefore, in the display device 13, between the electrode 16A and the electrode 16B, the focal conic and the planar are changed according to the relationship between the applied voltage of each liquid crystal layer 20B and the liquid crystal layer 20G and the normalized reflectance (see FIG. 5). By applying a voltage having a voltage value that selectively causes a state change between them, only one of the liquid crystal layer 20B and the liquid crystal layer 20G is changed to a focal conic state or a planar state, or both are changed to a focal point. It is possible to change state to conic or planar.

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

―Preparation of liquid crystal coating solution―
The following paints were prepared as cholesteric liquid crystal microcapsule paints.

--Cholesteric liquid crystal microcapsule paint G1 (paint for green liquid crystal layer 20G)-
An appropriate amount of chiral agent R1011 (manufactured by Merck) and chiral agent R811 (manufactured by Merck) was added to nematic liquid crystal E44 (manufactured by Merck) to prepare a cholesteric liquid crystal so that the peak wavelength of selective reflection was 530 nm. Polyisocyanate compound Takenate D-110N (manufactured by Takeda Pharmaceutical Co., Ltd.) and ethyl acetate were added to each to prepare an oil phase composition, which was put into a 1% polyvinyl alcohol aqueous solution, stirred and emulsified to be 10 μm. A diameter o / w emulsion was prepared. This was heated at 60 ° C. for 3 hours to obtain a microcapsule composed of polyurethane in which cholesteric liquid crystal was encapsulated. After the microcapsules are collected by centrifugation, a polyvinyl alcohol aqueous solution as a dispersion medium for dispersing the microcapsules (BaTiO ₃ (volume average particle size 150 nm) as a high dielectric is 7.7 masses with respect to 100 mass% of polyvinyl alcohol). % To obtain a cholesteric liquid crystal microcapsule paint G.

--Cholesteric liquid crystal microcapsule paint G2 (paint for green liquid crystal layer 20G)-
In the preparation of the cholesteric liquid crystal microcapsule coating G1, in the coating G1, BaTiO ₃ as a high dielectric was added to a polyvinyl alcohol aqueous solution as a dispersion medium for dispersing the microcapsules. A cholesteric liquid crystal microcapsule coating G2 was prepared by the same method as the coating B1 except that no dielectric was added.

--Cholesteric liquid crystal microcapsule paint B (paint for blue liquid crystal layer 20B)-
The cholesteric liquid crystal is adjusted so that the peak wavelength of selective reflection becomes 470 nm by adjusting the addition amount of the chiral agent R1011 (manufactured by Merck) and the chiral agent R811 (manufactured by Merck) used in the adjustment of the cholesteric liquid crystal microcapsule coating G2. Microcapsule paint B was prepared.

―Measurement of capacitance of liquid crystal coating solution―
Each of the cholesteric liquid crystal microcapsule paint G1, the cholesteric liquid crystal microcapsule paint G2, and the cholesteric liquid crystal microcapsule paint B is applied to a PET resin film on which an ITO electrode having a 10 mm × 10 mm pattern is applied and dried, and then dried to 12 μm. After forming a thick liquid crystal layer, a PET resin film on which an ITO electrode having a 10 mm × 10 mm pattern was further formed as a counter substrate. As a result, the liquid crystal layer composed of the cholesteric liquid crystal microcapsule coating G1 is sandwiched between the pair of electrodes, and the liquid crystal layer composed of the cholesteric liquid crystal microcapsule coating G2 is sandwiched between the pair of electrodes. Sample 2 was formed in a state where a liquid crystal layer composed of Sample 2 and cholesteric liquid crystal microcapsule paint B was sandwiched between a pair of electrodes.
For each of Samples 1 to 3, an AC bias voltage (amplitude 1 V) is applied to each electrode, and the frequency of the voltage is changed from 1.0 × 10 ² Hz to 1.0 × 10 ³ Hz. The capacitance (F) of each liquid crystal layer when it was changed was measured using an impedance analyzer (Toyo Technica Corp., 126096W).

As shown in FIG. 7, the measurement result shown by the diagram 70 was obtained for the sample 1, and the measurement result shown by the diagram 72 was obtained for the sample 2 and the sample 3.
Moreover, when the value of the electrostatic capacitance at 100 Hz was compared, it was 5.74 × 10 ⁻¹⁰ F for sample 1 and 3.46 × 10 ⁻¹⁰ F for sample 2 and sample 3. For this reason, it turns out that the electrostatic capacity was easily adjusted to about 1.7 times by addition of the high dielectric material to the dispersion medium. For this reason, it can be said that the impedance was easily adjusted to have different values.

  Therefore, the electrostatic capacity (resulting in the liquid crystal layer (sample 1) in which the high dielectric material is added to the dispersion medium) and the liquid crystal layer (sample 2 and sample 3) in which the high dielectric material is not added to the dispersion medium are obtained. The result was that the impedance was easily made different by the addition of the high dielectric.

Example 1
―Preparation of display media―
In Example 1, a display medium having only the display element 24 out of the display element 24 and the display element 26 in the display medium shown in FIG. 1 was manufactured. In particular,
A commercially available ITO-deposited PET resin film having a 10 mm × 10 mm pattern is used as the substrate 14 and the electrode 16B, and an aqueous solution of partially saponified polyvinyl alcohol (PVA) in which a pyrrolopyrrole pigment is dispersed is used as the light shielding layer 22R. Spin coated.

  On the other hand, a PET resin film (corresponding to the substrate 12) on which an ITO electrode was formed as the electrode 16A was prepared.

  Further, the above-prepared cholesteric liquid crystal microcapsule coating B (coating for the blue liquid crystal layer 20B, no addition of a high dielectric material to the dispersion medium) is applied and dried on the electrode 16A of the film and dried to 12 μm. After the thick liquid crystal layer 20B is formed, the cholesteric liquid crystal microcapsule coating G1 adjusted as described above (paint for the green liquid crystal layer 20G, with a high dielectric material added to the dispersion medium) is applied and dried. Thus, a liquid crystal layer 20G having a thickness of 12 μm was formed.

  Then, the obtained two substrates are bonded using an acrylic resin adhesive sheet so that the formed liquid crystal layer 20G and the formed light shielding layer 22R face each other. Was made.

―Evaluation―
--Measurement of electro-optic response characteristics of display medium 1--
A voltage was applied to the display medium 1 manufactured in Example 1 in the same manner as described above using the writing device 11 shown in FIG.

Then, after applying a rectangular wave of 500 V AC bias voltage (amplitude 500 V, frequency 100 Hz) as a reset voltage to the electrodes 16 A and 16 B for 200 msec, the voltage of the rectangular wave applied between the electrodes 16 A and 16 B is 0 V. The reflectance when the voltage is suddenly raised to 0 V after applying voltage of each voltage value for 200 msec, gradually from 1 to 400 V, is measured with an integrating sphere spectrocolorimeter (CM2002, manufactured by Minolta). When measured, the relationship between the normalized reflectance and the applied voltage is as shown in FIG. The line 74 in FIG. 8 is a value obtained by normalizing the reflectance at 530 nm, and the line 72 is a value obtained by normalizing the reflectance at 470 nm.
For this reason, the lower threshold value of the liquid crystal layer 20G (the normalized reflectivity is 0.1, the state change threshold value between the planar and the focal conic) is 163 V, and the upper threshold value (normalized reflectivity is 0.9). Value, threshold of change of state between focal conic and homeotropic) was 259V.
The lower threshold value of the liquid crystal layer 20B (normalized reflectance is a value of 0.1, the threshold value of the state change between the planar and the focal conic) is 143 V, and the upper threshold value (normalized reflectance is a value of 0.9, the focal value). The state change threshold between conic and homeotropic) was 277V.

  As the voltage application unit 28, a high voltage amplifier manufactured by Matsusada Precision Co., Ltd. and a personal computer incorporating a waveform generation board manufactured by National Instruments Co., Ltd. were used as a device having a function corresponding to the control unit 39.

  Therefore, among the liquid crystal layer 20G and the liquid crystal layer 20B in the display medium 1 adjusted in the first embodiment, the liquid crystal layer 20G having a configuration in which a high dielectric is added to the dispersion medium is more than the liquid crystal layer 20B. In addition, both the lower threshold value and the lower threshold value are increased, and it can be said that the difference in threshold value between the liquid crystal layer 20G and the liquid crystal layer 20B is easily adjusted.

―Evaluation of writing to display media―
With respect to the display medium 1 manufactured in Example 1, a symmetric rectangular wave pulse voltage with a frequency of 100 Hz and 400 V was applied to the electrodes 16A and 16B for 200 ms using the writing device 11 shown in FIG. It became.

  Next, when the voltage value of the pulse voltage was 105 V, the display medium turned green. Further, after applying 400 V of a rectangular wave reset voltage at a frequency of 100 Hz for 200 ms and setting the voltage value of the pulse voltage to 255 V, the display medium turned blue. For this reason, it can be said that the liquid crystal layer 20B and the liquid crystal layer 20G which are a plurality of liquid crystal layers stacked between the pair of electrodes are easily and selectively driven.

(Comparative Example 1)
―Preparation of display media―
In Example 1, the adjusted cholesteric liquid crystal microcapsule coating G1 (with a high dielectric material added) was used as the liquid crystal layer 20G. In Comparative Example 1, the adjusted cholesteric liquid crystal microcapsule was used instead of the coating G1. A display medium 2 was prepared under the same conditions and the same manufacturing method as in Example 1 except that G2 (no addition of high dielectric material) was used.

―Evaluation ――― Measurement of electro-optic response characteristics of Display Medium 2 (without adding high dielectric material to dispersion medium) ―
A voltage was applied to the display medium 2 manufactured in Comparative Example 1 in the same manner as described above using the writing device 11 shown in FIG.

Then, after applying a rectangular wave with an AC bias of 500 V (amplitude 500 V, frequency 100 Hz) as a reset voltage to the electrodes 16A and 16B for 200 milliseconds, the voltage of the rectangular wave applied between the electrodes 16A and 16B is changed from 0V. Measure gradually with an integrating sphere spectrocolorimeter (CM2002, manufactured by Minolta Co., Ltd.) when the voltage is gradually increased to 400 V and each voltage value is applied for 200 seconds and then the voltage is suddenly reduced to 0 V. As a result, the relationship between the normalized reflectance and the applied voltage is as shown in FIG. The line 76 in FIG. 9 is a value obtained by normalizing the reflectance at 530 nm, and the line 74 is a value obtained by normalizing the reflectance at 470 nm.
The lower threshold value of the liquid crystal layer 20G (normalized reflectance is a value of 0.1, the threshold of state change between the planar and focal conic) is 151 V, and the upper threshold value (normalized reflectance is a value of 0.9, focal The state change threshold between conic and homeotropic) was 268V.
The relationship between the normalized reflectance (Y value) and the applied voltage is the value shown in the diagram 74 of FIG. 9 and overlaps the diagram 76. Therefore, the lower threshold value (value of normalized reflectance is 0.1, the threshold value of state change between the planar and the focal conic) is 153 V, and the upper threshold value (value of normalized reflectance is 0.9). , The threshold of change in state between focal conic and homeotropic) was 267 V, both of which were almost the same as those of the liquid crystal layer 20G.

  Therefore, in Comparative Example 1 in which the high dielectric material was not added to the dispersion medium for all of the plurality of liquid crystal layers provided between the pair of electrodes, the state change threshold value between these liquid crystal layers 20G and 20B There was no difference.

―Evaluation of writing to display media―
With respect to the display medium 2 manufactured in Comparative Example 1, when the writing device 11 shown in FIG. 1 is used to apply a symmetrical rectangular wave pulse voltage with a frequency of 100 Hz and 400 V to the electrodes 16A and 16B for 200 ms, the display medium is transparent. It became.

Next, although the voltage value of the pulse voltage was changed, no matter which voltage is applied, green that is a color peculiar to the liquid crystal layer 20G and blue that is a peculiar color to the liquid crystal layer 20B are displayed. There wasn't.
For this reason, the selective driving of the liquid crystal layer 20B and the liquid crystal layer 20G, which are a plurality of liquid crystal layers stacked between a pair of electrodes, has not been realized in Comparative Example 1.

10, 10A Display medium 13, 17 Display device 16A, 16B Electrode 20B, 20G Liquid crystal layer 24R, 26C Photoconductive layer 34 Light irradiation unit 40 Voltage application unit

Claims (7)

A pair of electrodes;
A plurality of liquid crystal layers provided between the pair of electrodes and having different impedances;
With
The plurality of liquid crystal layers include a cholesteric liquid crystal and a dispersion medium in which the cholesteric liquid crystal is dispersed, and the impedance of the dispersion medium between the plurality of liquid crystal layers is different from each other.   The display medium according to claim 1, wherein the dispersion medium included in at least one of the plurality of liquid crystal layers includes a dielectric material.   The display medium according to claim 1, wherein impedances of the cholesteric liquid crystal between the plurality of liquid crystal layers are different from each other. 4. The display medium according to claim 1, wherein a volume resistivity of each of the plurality of liquid crystal layers is 1 × 10 ⁶ Ωm or more and 10 ¹⁶ Ωm or less.   The photoconductive layer further comprising a photoconductive layer provided between the pair of electrodes and exhibiting an electrical characteristic distribution according to an intensity distribution of the light by absorbing light in a predetermined wavelength region. The display medium according to any one of claims 1 to 4. A pair of electrodes;
A plurality of liquid crystal layers provided between the pair of electrodes and having different impedances;
With
The plurality of liquid crystal layers include a cholesteric liquid crystal, a microcapsule enclosing the cholesteric liquid crystal, and a dispersion medium in which the microcapsule is dispersed, and display media having different impedances of the dispersion medium between the plurality of liquid crystal layers When,
Voltage applying means for applying a voltage to the pair of electrodes;
A display device comprising: A pair of electrodes;
A photoconductive layer provided between the pair of electrodes and exhibiting an electrical characteristic distribution according to an intensity distribution of the light by absorbing light in a predetermined wavelength region;
A plurality of liquid crystal layers provided between the pair of electrodes and having different impedances;
With
The plurality of liquid crystal layers include a cholesteric liquid crystal, a microcapsule enclosing the cholesteric liquid crystal, and a dispersion medium in which the microcapsule is dispersed, and display media having different impedances of the dispersion medium between the plurality of liquid crystal layers When,
Voltage applying means for applying a voltage to the pair of electrodes;
Irradiating means for irradiating the display medium with the light according to image data;
A display device comprising:

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