JP2006313196A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display element which has full-color image reproducing properties and in particular, has improved color reproduction and contrast in the display element having memory properties. <P>SOLUTION: In the display element having a liquid crystal dispersion layer, in which a chiral nematic liquid crystal capable of selectively reflecting the desired wavelength region of visible light is dispersed in binder, a black color image formation layer of forming an image exhibiting substantially black color is disposed, separated from the liquid crystal dispersion layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display element comprising a binder and a chiral nematic liquid crystal composition dispersed in the binder.

  In recent years, with the increase in computer operating speed, the spread of network infrastructure, the increase in capacity and price of data storage, information such as documents and images provided on printed paper has been processed as digital information. It has come to be distributed as simple electronic information. In addition to electronic books that are viewed personally, there is a movement to directly output electronic information of printed materials such as advertisements to electronic posters and the like. Currently, liquid crystal displays, LED displays, and the like are used, but it has also been proposed to use display elements called electronic paper.

  As electronic paper technology used for such display, electrophoresis, powder transfer, chiral nematic liquid crystal, electrochromic, etc. have been proposed, but chiral nematic liquid crystal is particularly suitable for color display. It is.

  The chiral nematic liquid crystal is a method in which a chiral agent is added to the nematic liquid crystal and the liquid crystal molecules have a twisted structure to selectively reflect light (Bragg reflection) to express different colors. The desired color can be reflected by selecting the type and amount of the chiral agent.

  It has been disclosed that full-color display using chiral nematic liquid crystals can be obtained by laminating chiral nematic liquid crystal layers having different reflection colors (see, for example, Patent Documents 1 and 2).

  However, full-color display using chiral nematic liquid crystals has a basic drawback. A chiral nematic liquid crystal is basically a substance that repeats a selective reflection state (planar state) and a transparent state (focal conic state) by applying an electric field, and therefore cannot express black. For this reason, a black layer is usually provided in the lowest layer, and this layer is shown in a transparent state in all layers.

  For this reason, the black density becomes relatively low, the overall contrast is lowered, and there is no reproduction of “black tightening” that is well evaluated for printed matter. In addition, there is a drawback that fine reproduction such as characters is difficult to obtain.

Further, since black is always present in the lowermost layer, there is a disadvantage that the color reproduction range becomes narrow as when black paper is painted.
Japanese Patent No. 3209254 JP 2003-22843 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a display element with improved full color image reproducibility, particularly color reproduction and contrast, in a display element having a memory property.

  The above problem could be solved by the following configuration.

(Claim 1)
In a display device having a liquid crystal dispersion layer in which chiral nematic liquid crystal that selectively reflects a desired wavelength range of visible light in a binder is dispersed, an image showing substantially black is formed separately from the liquid crystal dispersion layer A display element comprising a black image forming layer.

(Claim 2)
A plurality of liquid crystal dispersion layers in which chiral nematic liquid crystals that selectively reflect the desired wavelength range of visible light are dispersed in a binder are laminated, and the wavelength peaks reflected by each liquid crystal dispersion layer are different. The display element according to claim 1.

(Claim 3)
The display element according to claim 1, wherein the black image forming layer is provided closer to the image viewing side than the total liquid crystal dispersion layer.

(Claim 4)
The display element according to claim 1, wherein the black image forming layer is a liquid crystal dispersion layer in which a chiral nematic liquid crystal in which a black dichroic dye is dispersed or dissolved is dispersed in a binder.

(Claim 5)
The display element according to claim 1, wherein the black image forming layer is a layer that forms an image using an electrochromic method.

(Claim 6)
The display element according to claim 1, wherein the black image forming layer is a layer that forms an image using an electrolytic deposition method.

  ADVANTAGE OF THE INVENTION According to this invention, the display element which improved the color reproduction and contrast in the display element with a memory property can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The present inventor applied black image forming layer in the constituent layer to improve black tightening in response to the problem that black reproducibility is poor and the overall contrast is lowered in full color display using chiral nematic liquid crystal. Thus, a chiral nematic liquid crystal display device having excellent gradation can be obtained.

  Details of the display element of the present invention will be described below.

  The display element of the present invention has a liquid crystal dispersion layer in which chiral nematic liquid crystal that selectively reflects a desired wavelength range of visible light is dispersed in a binder, and is substantially black, which is different from the liquid crystal dispersion layer. As a constituent layer, a black image forming layer for forming an image showing In addition to the liquid crystal dispersion layer and the black image forming layer, the constituent layer may be composed of a plurality of layers such as an intermediate layer containing only a binder not containing a liquid crystal composition, a filter layer containing a dye, and the like, and a light shielding layer.

(binder)
As the binder of the display element of the present invention, a hydrophilic binder is preferably used. Examples thereof include binders described in Research Disclosure (hereinafter abbreviated as RD), Volume 176 Item / 17643 (December 1978), Volume 308 Item / 308119 (December 1989), and JP-A-64. Examples described in pages (71) to (75) of No. 13546.

  The binder suitable for the present invention is transparent or translucent, generally colorless, and may be a medium that forms a film, such as a natural polymer or a synthetic polymer. For example, gelatin, gum arabic, poly (vinyl alcohol), Hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene- Maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes) ), Phenoxy resin, poly (Vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, poly (amides), and the like.

  The binder may be hydrophilic or hydrophobic, but in the present invention, a hydrophobic transparent binder can be used as long as it is incompatible with the liquid crystal composition. Examples of the hydrophobic transparent binder include polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, polyester, polycarbonate, polyacrylic acid, and polyurethane. Among the hydrophobic binders, polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, and polyester are particularly preferably used.

Two or more of these binders may be used in combination, and the coating amount of the binder is preferably 100 g or less per m ² , and particularly preferably 20 g or less.

  The binder according to the present invention is important for securing the film strength of the liquid crystal dispersion layer, particularly when the counter electrode is used. In order to make the film thickness constant together with the binder, a resin pillar structure or spacer particles may be used. Although possible, it is preferable not to use them because of simplification of the process. Gelatin is a preferred binder that can provide a constituent layer having a uniform film thickness in each step of heat dissolution, coating, cooling set, and drying. Examples of other than gelatin include, for example, carrageenan in polyvinyl alcohols. It is possible to take steps similar to those of gelatin by using a thickening polysaccharide such as gel or gellan gum in combination, and in this case, a constituent layer having a uniform film thickness can be obtained.

  In addition, examples of the binder used in the present invention include aqueous solvent dispersions such as polyurethane resins, polyacrylic resins, and silicone resins, photo-curing resins, thermosetting resins, and thermoplastic resins.

  In the display element of the present invention, it is preferable that at least one of the binders is gelatin or a gelatin derivative.

  Examples of gelatin that can be used in the present invention include acid-treated gelatin and alkali-treated gelatin, as well as enzyme-treated gelatin and gelatin derivatives that undergo enzyme treatment in the gelatin production process, that is, amino groups and imino as functional groups in the molecule. It may be modified by treatment with a reagent having a group, a hydroxyl group, or a carboxyl group, and a group obtained by reaction with the group. The general method for producing gelatin is well known and is described, for example, in T.W. H. James: The Theory of Photographic Process 4th. ed. Reference can be made to descriptions such as 1977 (Maccillan), p. 55, Science Photo Handbook (above), p. 72-75 (Maruzen), Photographic Engineering Basics-Silver Salt Photo Hen, pages 119-124 (Corona).

  In the present invention, when gelatin is used as a binder, it can be hardened with a hardener. Examples of hardeners preferably used in the present invention include U.S. Pat. No. 4,678,739, column 41, 4,791,042, JP-A-59-116655, JP-A-62-245261, Examples thereof include hardeners described in 61-18842, 61-249054, 61-245153, and JP-A-4-218044. More specifically, aldehyde hardeners (eg, formaldehyde), aziridine hardeners, epoxy hardeners, vinyl sulfone hardeners (eg, N, N′-ethylene-bis (vinylsulfonyl) Acetamide) ethane), N-methylol hardeners (for example, dimethylolurea, etc.), boric acid, metaboric acid, or polymer hardeners (for example, compounds described in JP-A-62-2234157). Can be mentioned. Among these hardeners, it is preferable to use a vinyl sulfone type hardener or a chlorotriazine type hardener alone or in combination.

  Examples of the vinyl sulfone hardener used in the present invention include aromatic compounds such as those described in German Patent No. 1,100,942 and US Pat. No. 3,490,911. Alkyl compounds bonded with hetero atoms as described in 44-29622, 47-25373 and 47-24259, sulfonamides and ester compounds as described in JP-B 47-8736, etc. 1,3,5-tris [β- (vinylsulfonyl) -propionyl] -hexahydro-s-triazine or JP-B-50-35807, JP-A-51-51, as described in JP-A-49-24435, etc. And alkyl compounds such as those described in JP-A No. 44164 and compounds described in JP-A No. 59-18944.

  These vinyl sulfone-based hardeners are dissolved in water or an organic solvent and have a mass ratio of 0.001 to 0.200, particularly preferably 0.001 to 0.050, with respect to the binder that can react with the hardener. Used.

  Among the vinyl sulfone hardeners according to the present invention, use of a vinyl sulfone hardener having a hydroxyl group in the molecule is preferred. In the present invention, aldehyde hardeners (formaldehyde, etc.), aziridine hardeners, epoxy hardeners, N-methylol hardeners (dimethylol urea, etc.) hardeners are vinylsulfone hardeners. It can be used in combination with a film agent.

  These hardeners are used in an amount of 0.001 to 1 g, preferably 0.005 to 0.5 g, per 1 g of binder.

(Chiral nematic liquid crystal)
The liquid crystal dispersion forming the chiral nematic liquid crystal dispersion layer according to the present invention is a chiral nematic liquid crystal dispersion having a cholesteric phase.

  A chiral nematic liquid crystal is a typical liquid crystal exhibiting a cholesteric phase, and is obtained by adding a predetermined amount of a chiral material (also referred to as a chiral dopant) to the nematic liquid crystal. This chiral nematic liquid crystal generally has a twisted arrangement of rod-like liquid crystal molecules and exhibits a cholesteric phase. When light is incident on this liquid crystal, when light is incident from a direction parallel to the helical axis, light having a wavelength represented by λ = np is selectively reflected (planar state). Here, λ is the wavelength, n is the average refractive index of the liquid crystal molecules, and p is the distance at which the liquid crystal molecules are twisted 360 °. On the other hand, when light is incident from a direction perpendicular to the helical axis, the light is transmitted without being reflected (focal conic state). Display is performed using this selective reflection and transmission.

  The operation mode of the reflective liquid crystal display element having memory characteristics is disclosed in Technical Paper SID International Symposium Technical Paper Vol. 29, page 897. This operation mode is a method of performing display by switching the alignment state of the chiral nematic liquid crystal to either a planar state (light selective reflection state) or a focal conic state (light transmission state). Since the planar state and the focal conic state are stable states, once the liquid crystal is set to any state, the state is maintained semipermanently unless an external force is applied. That is, it is useful as a reflective liquid crystal display element having a memory property that once an image is displayed, the displayed image is maintained as it is even when the power is turned off.

  The reflective liquid crystal display element described in the above document has a structure in which a chiral nematic liquid crystal is sandwiched between a pair of substrates each provided with an electrode. The liquid crystal is changed to a predetermined state (planar state and focal conic state) by controlling the intensity of the electric field and / or the application time.

  When a voltage equal to or higher than a threshold voltage for untwisting the liquid crystal is applied to the liquid crystal for a sufficient time, the liquid crystal is all in a homeotropic state (the long axis direction of the liquid crystal molecules is perpendicular to the substrate). In this state, since there is no memory property, when the electric field is erased, the liquid crystal is twisted. From the homeotropic state, when the electric field is suddenly erased, it becomes a planar state, and when the electric field is gradually erased, it becomes a focal conic state.

  In addition, when a pulse voltage higher than the threshold voltage for solving the twist is applied to the liquid crystal in the focal conic state (a voltage having a pulse width at which some liquid crystals are in a homeotropic state), the liquid crystal in the homeotropic state is The planar state is established after the application of the pulse voltage. By controlling the width of the pulse voltage and / or the height of the voltage, it is possible to adjust the ratio of the liquid crystal in the planar state (display halftone).

  In the liquid crystal-polymer composite film using chiral nematic liquid crystal, the amount of chiral dopant added to the nematic liquid crystal is adjusted, and the helical pitch of the chiral nematic liquid crystal is selected, and the selective reflection wavelengths are, for example, blue light, green light, red, respectively. By adjusting to light and yellow light, the liquid crystal is in a selective reflection state colored in red, green, blue and yellow in the case of the planar arrangement, and a colorless and transparent light transmission state in the case of the focal conic arrangement. -A polymer composite membrane is obtained. A color liquid crystal display device is obtained by sandwiching the liquid crystal-polymer composite film thus obtained between transparent electrodes. In the display element of the present invention, the chiral nematic liquid crystal composition is preferably composed of a liquid crystal composition that selectively reflects at least one light selected from blue light, green light, red light, and yellow light.

  Also, by adjusting the amount of chiral dopant added and adjusting the helical pitch of the chiral nematic liquid crystal so that the selective reflection wavelength is infrared light, the planar arrangement is colorless and transparent, the focal conic arrangement is the same, etc. A liquid crystal-binder composite film showing a light scattering state that appears white due to side scattering is obtained. A white display device is obtained by sandwiching the liquid crystal-binder composite film thus obtained between the transparent electrodes.

  The relationship between the helical pitch p (nm) and the selective reflection wavelength λ (nm) is expressed by the following formula (1).

Formula (1)
λ = n × p
In the formula, n represents an average refractive index, and n = (n1 ² + n2 ² ) ^1/2 . n1 represents a refractive index when light is incident in the major axis direction of the liquid crystal molecule, and n2 represents a refractive index when light is incident in a direction perpendicular to the major axis direction of the liquid crystal molecule.

  In order to produce a white display device or a color display device of each color, for example, a method in which a mixture of liquid crystal and a binder is sandwiched between substrates and then cured with a hardener or the like to phase separate the liquid crystal and the binder. can do. At this time, if the spacer is sandwiched between the substrates together with the mixture, the thickness of the liquid crystal-binder composite film can be easily controlled.

  As a chiral dopant to be added to the nematic liquid crystal, a plurality of kinds of chiral dopants may be mixed and used. The use of multiple types of chiral dopants increases the phase transition temperature of liquid crystals, improves the transparency of the composite film in the transparent state, and particularly speeds up the display switching between the transparent state and the selective reflection state of the color display device. It is effective to do.

  A first display device having a composite film using a left-handed chiral nematic liquid crystal as a color display device of a specific color, and a right-handed chiral hand that selectively reflects light having the same wavelength as that of the left-handed chiral nematic liquid crystal It is also one of preferred embodiments of the present invention to use a laminate of a second display device having a composite film using a nematic liquid crystal. By doing so, the reflectance can be increased and a better color display can be performed. In particular, when blue and red, whose relative visibility is lower than that of green, are strongly displayed, the overall color balance is improved. Therefore, such a multilayer structure is effective in a blue display device or a red display device.

  A smectic liquid crystal may be added to the liquid crystal-binder composite film used in the white display device. By adding the smectic liquid crystal, the transparency of the liquid crystal-binder composite film is improved, and the contrast between the colorless and transparent state and the white state can be increased.

  The film thickness of the liquid crystal-binder composite film used for each color display device is not particularly limited, but the film thickness of the liquid crystal-binder composite film used for the white display device is the film of the liquid crystal-binder composite film used for the color display device. It is desirable to make it larger than the thickness.

  Specific examples of the liquid crystal composition exhibiting a cholesteric phase include compounds described in US Pat. No. 5,695,682.

  Other scattering-type liquid crystal compositions used in the present invention include 4-substituted benzoic acid 4'-substituted phenyl esters, 2- (4-substituted phenyl) -5-substituted pyrimidines, 4-substituted cyclohexanecarboxylic acid 4'-substituted. Biphenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4'-substituted phenyl ester, 4-substituted biphenyl 4'-substituted cyclohexane, 4- (4-substituted cyclohexane) Carbonyloxy) benzoic acid 4'-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4 "-substituted terphenyl, 4-substituted 4'-substituted biphenyl, 4- Substituted phenyl-4'-substituted cyclohexane and the like, and further JP-A-2001-51260 JP-A-8-43846, JP-A-7-4950, JP-A-2000-147476, JP-A-8-160470, JP-A-10-54996, JP-A-2002-221709, JP-A-2001-92383, JP-A-2003-131234, JP-A-2004-77754, JP-A-2004-2771, etc., polymer network liquid crystal (PNLC), polymer-dispersed liquid crystal A liquid crystal composition called (PDLC) can be given.

  In the display element of the present invention, the liquid crystal composition according to the present invention is present in a state dispersed in a binder. For example, after mixing the liquid crystal and the chiral agent according to the present invention, the mixture can be prepared by adding the mixture to a gelatin solution containing a surfactant and dispersing the mixture using a known disperser.

(Surfactant)
Examples of the surfactant used for the dispersion include ionic surfactants such as aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like. Can be mentioned.

  Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, acylated peptide, alkyl sulfonic acid Salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate, secondary Higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkylphenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphate, alkyl phosphate D Stealth salt, lignin sulfonate, formalin condensate of naphthalene sulfonate, formalin condensate of alkyl naphthalene sulfonate, formalin condensate of special aromatic sulfonate (eg Mohr C) creosote oil sulfonate Formalin condensate and the like can be mentioned.

  Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic activators include, for example, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester , Polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, poly Oxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide Acetylene glycol, block copolymers with acetylene alcohol, ethylene oxide and propylene oxide, and ethylene oxide adduct of alkylphenol.

  For the dispersion, for example, a shearing stirrer, ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used.

(Micro capsule)
The liquid crystal composition of the present invention can be used in a state of being encapsulated in microcapsules.

  As a method for producing a microcapsule that can be used in the present invention, a known method such as a coacervation method, an interfacial polymerization method, or an in-situ method can be used. Among these, the production method by the coacervation method can be preferably used with little chemical influence on the liquid crystal composition which is an oil phase.

  When gelatin is used as one of the binders, coacervates can be produced by hydrophobic interaction with gum arabic, sodium alginate, carrageenan, carboxymethylcellulose, agar, polyvinylbenzenesulfonic acid, maleic anhydride copolymer, and other surfactants. Thereafter, by performing a gelatin hardening reaction using formaldehyde or the above-described gelatin hardener, the coacervated gelatin composite film can be hardened, and the strength of the microcapsule wall can be improved.

  The interfacial polymerization method can form a microcapsule wall by polymerizing polyamine, polyhydric phenol and the like with a polybasic acid halide, polyisocyanate and the like at the interface between the aqueous phase and the oil phase.

  As an in-situ polymerization method, microcapsules can be formed by crosslinking amide resin, phenol resin alone or a copolymer thereof used for urea-melamine or the like with formaldehyde or glutaraldehyde.

  For the microcapsule wall, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyvinyl alcohol, polyethylene oxide, polypropylene oxide, ethylene-vinyl alcohol copolymer, polyacetal , Acrylic resin, methylcellulose, ethylcellulose, phenolic resin, fluororesin, silicone resin, diene resin, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyphenylene ether, polyphenylene sulfide, Polyethersulfone, polyetherketone, polyarylate, aramid, polyimide, poly- -Microcapsule wall strength is improved by coexisting -phenylene, poly-p-xylene, poly-p-phenylene vinylene, polyhydantoin, polyparabanic acid, polybenzimidazole, polybenzothiazole, polybenzoxadiazole, polyquinoxaline, etc. Can be improved.

  The microcapsules according to the present invention can be dried and classified after being prepared in a solution system. Examples of the classification method include a spray dryer, a rotary dryer, and a band dryer.

(Antioxidant)
An antioxidant can be used in the liquid crystal dispersion layer of the present invention as necessary. Antioxidants include phenolic antioxidants, monophenolic antioxidants, polyphenolic and polymeric phenolic compounds, hindered phenolic antioxidants, phosphoric acid antioxidants, sulfur antioxidants, amines System antioxidants, hydroquinone derivatives and the like.

  Of these antioxidants, preferred compounds are phenolic antioxidants and amine antioxidants.

  The usage-amount of a preferable antioxidant is 0.1-100 g with respect to 1 kg of binders, More preferably, it is 1-10 g.

(Natural polymer polysaccharide derived from red algae)
The display element of the present invention can contain at least one compound of natural polymer polysaccharides derived from red algae in the constituent layers.

  Natural polymer polysaccharides derived from red algae used in the present invention are all polysaccharides extracted and purified from red algae, and are described in detail in “Food Industry” Vol. 31 (1988), p. 21. Has been. Specific examples of natural high molecular weight polysaccharides derived from red algae include gellan gum, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, and far selelaen. In the present invention, in particular, κ Carrageenan, λ-carrageenan and ι-carrageenan are preferred. Of these, ι-carrageenan and κ-carrageenan are particularly preferable, and ι-carrageenan is most preferable.

  The natural polymeric polysaccharide derived from the red algae may be used alone in a single coating solution, or two or more kinds may be used in combination. In particular, when κ-carrageenan is used, it is preferable to use λ-carrageenan from the viewpoint of film properties of the display medium.

  In this case, the ratio of κ-carrageenan to λ-carrageenan is in the range of 2: 8 to 9: 1 by mass ratio, preferably 4: 6 to 8: 2, particularly preferably 5: 5 to 7: 3. It is.

  Gellan gum is a polysaccharide composed of sugars of glucose, glucuronic acid and rhamnose. Available types include gellan gum K9A50, a kercogel for food and industrial products, a culture medium for microorganisms, plant tissue culture and gellan gum for confectionery. GELLITE is known.

  The concentration of these natural polymer polysaccharides in the coating solution is generally 0.02 to 5%, preferably 0.05 to 2%, particularly preferably 0.1 to 1%. This preferred range varies depending on the type and concentration of gelatin and other water-soluble polymers in the coating solution to be used and is not unambiguous, but the coating solution is a natural polymer substantially derived from gelatin and red algae. In the case where only the polysaccharide is used as a binder, the range is preferably used when the gelatin concentration is usually 1 to 6%.

  The binder of the present invention includes xanthan gum, konjac mannan, locust bean gum, guar gum, pectin, gum arabic, tamarind gum, sodium alginate, karaya gum, tragacanth gum, farsellan, Polysaccharides such as pullulan can be used in combination.

(High boiling point organic solvent)
The display element of this invention can contain the at least 1 sort (s) of high boiling point organic solvent in a structural layer.

  The high-boiling organic solvent used in the display element of the present invention can be any organic solvent as long as the boiling point is an organic solvent having a boiling point of 80 ° C. or higher, but is preferably a hydrophobic high-boiling organic solvent. Examples of high boiling point organic solvents include chlorinated paraffin, liquid paraffin, tricresyl phosphate, dibutyl phthalate, dioctyl phthalate, tri (2-ethyl-hexyloxy) phosphate, diethyl-lauroylamide, dinonylphenol, etc. For example, there can be mentioned exemplified compounds described in JP-A Nos. 1-196048, 1-209446 and JP-A-62-253943. Of these, the compounds preferably used are paraffinic compounds.

  The high-boiling organic solvent of the present invention is preferably contained in a binder of a display element by forming a dispersion using a known oil-in-water dispersion method together with a binder and a surfactant.

(Antidepressant)
The display element of this invention can contain the at least 1 sort (s) of antifungal agent in a structural layer. It is possible to prevent deterioration of the binder contained in the constituent layer due to wrinkles at high temperature and high humidity, and to improve durability as a display element.

  Specific examples of antifungal agents include thiazolylbenzimidazole compounds, isothiazolone compounds, chlorophenol compounds, bromophenol compounds, thiocyanate and isothiocyanate compounds, acid azide compounds, diazine and triazine compounds. Active halogen compounds such as thiourea compounds, alkyl guanidine compounds, quaternary ammonium salts, organic tin and organic zinc compounds, cyclohexyl phenol compounds, imidazole and benzimidazole compounds, sulfamide compounds, sodium chlorinated isocyanurate, There are various antibacterial and antifungal agents such as chelating agents, sulfite compounds, and antibiotics represented by penicillin. In addition, other L. E. West, “Water Quality Criteria”, Photo. Sci. and Eng. , Vol. 9, no. 6 (1965); various antifungal agents described in JP-A-57-8542, 58-105145, 59-126533, 55-111942, and 57-157244; Use of compounds such as those described in “History of antibacterial and antifungal” by Hiroshi Horiguchi, Sankyo Publishing (Sho 57), “Handbook of Antibacterial and Antifungal Technology”, Japanese Society of Antibacterial and Antifungal Society, Gihodo (Akira 61) Can do.

  The addition amount of the antifungal agent is about 0.1 to 50 mg, preferably 1 to 20 mg per 1 g of binder.

(Black image forming layer)
The position of the black image forming layer suitable in the present invention is most preferably the uppermost layer. By bringing the black image forming layer as the uppermost layer, it is possible to perform display with the least deterioration in character quality.

  The black image referred to in the present invention is an image having absorption in substantially the entire wavelength range of visible light, and the visual color tone can include a color tone such as dark blue, dark green, and dark brown.

  A suitable method for the black image forming layer of the present invention is an electrolytic deposition method. An example is disclosed in Japanese Patent Application Laid-Open No. 2004-177756, but in the present invention, since the lower color image needs to be seen through, titanium oxide or the like as a filler is unnecessary.

  Another preferred black image forming layer is based on an electrochromic method. There is an example in JP-A-2002-328401, but also in this case, titanium oxide or the like as a filler is unnecessary.

  Another preferred black image forming layer is a liquid crystal dispersion layer in which a cholesteric liquid crystal in which a black dichroic dye is dispersed or dissolved is dispersed in a binder. As the black dichroic dye dispersed or dissolved in the cholesteric liquid crystal, an anthraquinone type or azo type which is a dichroic dye mixed well with the liquid crystal can be used. More preferably, it is preferable to exhibit black dichroism alone. Examples of such a dye include Black-1, Black-2, Black-3, Black-4, Black-5, and Black-6 manufactured by Mitsubishi Chemical Corporation.

  Next, other components of the display element of the present invention will be described.

[Support]
Examples of the support that can be used in the present invention include polyolefins such as polyethylene and polypropylene, polycarbonates, cellulose acetate, polyethylene terephthalate, polyethylene dinaphthalene dicarboxylate, polyethylene naphthalates, polyvinyl chloride, polyimide, and polyvinyl. Synthetic plastic films such as acetals and polystyrene can also be preferably used. Syndiotactic polystyrenes are also preferred. These can be obtained, for example, by the methods described in JP-A Nos. 62-117708, 1-46912 and 1-178505. Further, as a support in JP-A-62-253195 (pages 29 to 31), which is provided with a metal base such as stainless steel, a paper support such as baryta paper and resin coated paper, and a reflection layer on the plastic film. What has been described. RDNo. 17643, page 28, ibid. No. 18716, page 647, right column to page 648, left column, and No. 307105, page 879 can also be preferably used. As these supports, those having resistance to curling due to heat treatment of Tg or less as in US Pat. No. 4,141,735 can be used. Further, the surface of these supports may be subjected to surface treatment for the purpose of improving the adhesion between the support and other constituent layers. In the present invention, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, and flame treatment can be used as the surface treatment. Furthermore, the support body described in pages 44 to 149 of publicly known technology No. 5 (issued by Aztec Co., Ltd. on March 22, 1991) can also be used. Furthermore, RDNo. 308119, page 1009, Product Licensing Index, Volume 92, P108, “Supports”, and the like. In addition, a glass substrate or an epoxy resin kneaded with glass can be used.

(Light absorption layer)
The light absorption layer essential for the chiral nematic liquid crystal display element may be used together with the black image forming layer of the present invention or may not be provided.

  The light absorbing layer may be any method, for example, applying a metallic reflector, a scattering plate, a colored paint on the substrate, or providing a binder constituent layer containing a colored material such as a pigment or dye. In the present invention, by providing, for example, a layer in which carbon black or the like is dispersed in an adjacent layer close to the liquid crystal layer, good black display with higher light absorption efficiency can be performed. Moreover, when using the resin substrate with a transparent electrode for a counter electrode, a light absorption layer can be provided in the surface on the opposite side to the liquid crystal layer of a board | substrate. The color of light to be absorbed may be black for black display, or may be a filter color that compensates for the reflected color of the liquid crystal.

[Transparent electrode]
In the present invention, it is preferable to use a transparent electrode for at least one of the pair of electrodes. The transparent electrode is not particularly limited as long as it is transparent and can conduct electricity. For example, Indium Tin Oxide (ITO: Indium Tin Oxide), Indium Zinc Oxide (IZO: Indium Zinc Oxide), Tin Oxide (FTO) ), Indium oxide, zinc oxide, platinum, gold, silver, rhodium, copper, chromium, carbon, aluminum, silicon, amorphous silicon, magnesium, BSO (Bismuth Silicon Oxide), or a mixture thereof. In the mixture, for example, an ITO layer having a thickness of about 50 nm and a silver layer having a thickness of about 50 nm may have a laminated structure.

  Further, a conductive polymer such as a polythiophene-based, polypyrrole-based, polyaniline-based, polyacetylene-based, polyparaphenylene-based, polyselenophenylene-based polymer, or a mixture thereof can be used as the transparent electrode.

  Further, a transparent electrode is produced by applying a liquid in which ITO fine powder fired at 350 ° C. to 800 ° C. is dispersed in a solution containing a solvent or a polymer material to a substrate and volatilizing the solvent or curing the polymer. It is also possible. In this case, the solidification temperature after coating is preferably 40 ° C. or higher and 200 ° C. or lower. ITO fine powder, for example, by mixing tin chloride aqueous solution and indium chloride aqueous solution, adding ammonia etc. to cause coprecipitation reaction while keeping pH at 9, fractionate and wash the resulting hydroxide precipitate Thus, it can be produced by baking at 500 ° C. for 2 hours. By changing the mixing ratio of tin chloride and indium chloride, a fine powder having an arbitrary mixing ratio can be formed. The shape of the fine powder may be any of a granular shape, a needle shape, a plate shape, and a flake shape, and a mixture of a needle shape and a granular shape may be used.

  In addition, a coating liquid in which about 10% of organic indium and organic tin are mixed in a xylol at a mass ratio of 97: 3 is applied on the substrate, and the solvent is volatilized and baked at 100 ° C. or higher and 150 ° C. or lower. A solidifying method can also be preferably used.

  For the purpose of improving the mechanical strength of the electrode, a polymer compound such as a compound species capable of forming a polyurethane resin containing blocked isocyanate or a compound species capable of forming an epoxy resin may be mixed in the coating solution.

  The surface resistance value of the transparent electrode is preferably 500Ω / □ or less, particularly preferably 300Ω / □ or less. The film thickness is preferably 0.2 μm or more and 50 μm or less.

[Production method of electrode]
In order to form a transparent electrode and a metal electrode, a known method can be used. For example, mask deposition may be performed on the substrate by sputtering or the like, or patterning may be performed by photolithography after the entire surface is formed. Electrodes can also be formed by electrolytic plating, electroless plating, printing methods, and ink jet methods.

  After forming an electrode pattern including a catalyst layer having a monomer polymerization ability on a substrate using an inkjet method, a monomer component that is polymerized by the catalyst and becomes a conductive polymer layer after polymerization is added, It is also possible to form a metal electrode pattern by polymerizing and further performing metal plating such as silver on the conductive polymer layer, and the process is greatly reduced because no photoresist or mask pattern is used. It can be simplified.

  When the electrode material is formed by coating, known methods such as a dipping method, a spinner method, a spray method, a roll coater method, a flexographic printing method, and a screen printing method can be used.

[Electrostatic inkjet method]
In the display element of the present invention, at least one of the pair of electrodes has a liquid discharge head having a nozzle with an internal diameter of 30 μm or less for discharging a charged liquid, and a supply means for supplying a solution into the nozzle And a liquid discharge apparatus including discharge voltage applying means for applying a discharge voltage to the solution in the nozzle.

  Furthermore, it is preferable that the solution in the nozzle is formed using a discharge device provided with a convex meniscus forming means for forming a state where the solution rises in a convex shape from the nozzle tip.

  In addition, an operation control unit that controls application of a drive voltage for driving the convex meniscus forming unit and application of a discharge voltage by the discharge voltage application unit is provided, and the operation control unit applies the discharge voltage by the discharge voltage application unit. It is also preferable to use a liquid ejection apparatus having a first ejection control unit that applies a driving voltage to the convex meniscus forming means when ejecting liquid droplets while performing the above.

  In addition, an operation control unit that controls driving of the convex meniscus forming unit and voltage application by the discharge voltage applying unit is provided, and the operation control unit is configured to swell the solution by the convex meniscus forming unit and apply the discharge voltage. And a second discharge control unit that performs the operation in synchronization with the liquid discharge device. It is also a preferred form to use a liquid ejection apparatus having a liquid level stabilization control unit that performs operation control for drawing the liquid level inward.

  By producing an electrode pattern using such an electrostatic inkjet, it is advantageous that an electrode having excellent on-demand characteristics, little waste material, and excellent dimensional accuracy can be obtained.

[Display element drive method]
In the display element of the present invention, it is preferable that the driving operation of the counter electrode described above is simple matrix driving.

  The simple matrix driving in the present invention is a driving method in which a current is sequentially applied to a circuit in which a positive line including a plurality of positive electrodes and a negative electrode line including a plurality of negative electrodes are opposed to each other in a vertical direction. Say that. By using simple matrix driving, there is an advantage that the circuit configuration and driving IC can be simplified and manufactured at low cost.

  The display element of the present invention may use active matrix driving. The active matrix drive is a system in which scanning lines, data lines, and current supply lines are formed in a grid pattern, and are driven by TFT circuits provided in each grid pattern. Since switching can be performed for each pixel, there are advantages such as gradation and memory function.

  In order to drive the display element of the present invention, for example, the driving circuit and driving described in JP-A Nos. 2003-5222, 2003-228045, 2002-14323, 2003-29301, and 2002-287175 Waveforms can be used.

  The display element of the present invention preferably has a configuration in which a liquid crystal layer containing a binder and a liquid crystal composition dispersed in the binder is disposed between a pair of counter electrodes.

(Black image data)
In the present invention, since there is a black image forming layer, it is necessary to put black image data in the output data, but this can be done by a known method.

(Application field of the display element of the present invention)
The display element of the present invention can be used in ID card related fields, public related fields, transportation related fields, broadcasting related fields, payment related fields, distribution logistics related fields, and the like. Specifically, keys for doors, student ID cards, employee ID cards, various membership cards, convenience store cards, department store cards, vending machine cards, gas station cards, subway and railway cards, bus cards, Examples include cash cards, credit cards, highway cards, driver's licenses, hospital examination cards, health insurance cards, Basic Resident Registers, passports, electronic book terminals, document viewers, signboards and bulletin boards.

Example 1
[Production of Display Element 1]
(Preparation of electrolyte solution)
In 2.5 g of dimethyl sulfoxide, 90 mg of sodium iodide and 75 mg of silver iodide were added and completely dissolved, and then 150 mg of polyethylene glycol (average molecular weight of 500,000) was added and stirred for 1 hour while heating to 120 ° C. An electrolyte solution was obtained.

(Preparation of transparent electrode 1)
A stripe-shaped ITO film having a pitch of 145 μm and an electrode width of 130 μm was formed on a glass substrate 1 having a thickness of 1.5 mm according to a known method, whereby a transparent electrode 1 was obtained.

(Preparation of black image forming layer 1)
A solution obtained by adding polyacrylic spherical beads having an average particle diameter of 20 μm to the electrolyte solution so as to have a volume fraction of 10% and applying the solution onto the transparent electrode 1 of the substrate 1 is applied to the electrolyte solution. The two transparent electrodes 1 are stacked so that the stripes are orthogonal to each other so as to be in contact with the electrolyte solution, pressed with a pressure of 9.8 kPa, and the periphery is sealed with an olefin-based sealant to obtain a black image forming layer 1 It was.

(Preparation of liquid crystal composition 1)
Nematic liquid crystal BL012 (manufactured by Merck & Co.) exhibiting positive dielectric anisotropy 60.0% by mass, right-handed chiral agent CB15 (manufactured by Merck & Co.) 20.0% by weight, right-handed chiral agent CE2 (Merck) 20.0% by mass was sufficiently mixed to prepare a dextrorotatory green light reflective liquid crystal composition 1.

(Preparation of liquid crystal composition 2)
Nematic liquid crystal BL011 (manufactured by Merck) showing positive dielectric anisotropy as well as 35.4% by mass of nematic liquid crystal E44 (manufactured by Merck) showing positive dielectric anisotropy of 35.4% by mass, dextrorotatory property 49.5% by mass of the chiral agent CB15 (manufactured by Merck & Co., Inc.) was sufficiently mixed to obtain a dextrorotatory blue light reflective liquid crystal composition 2.

(Preparation of liquid crystal composition 3)
Nematic liquid crystal BL012 (manufactured by Merck) having a positive dielectric anisotropy 69.0% by mass, right-handed chiral agent CB15 (manufactured by Merck) 15.5% by weight, right-handed chiral agent CE2 (Merck) 15.5% by mass was sufficiently mixed to obtain a dextrorotatory red light reflective liquid crystal composition 3.

(Preparation of liquid crystal dispersion)
8% by mass of photographic gelatin was added to ion-exchanged water, stirred at room temperature and allowed to stand for 30 minutes to fully swell the gelatin, and then the temperature was raised to 42 ° C. to completely dissolve the gelatin. To this solution, 12% by mass of an isopropyl alcohol solution containing 10% by mass of alkanol XC (alkyl naphthalene sulfonic acid, manufactured by Merck & Co., Inc.) as a surfactant was added to the water component of the gelatin solution, and then liquid crystal composition 1 was obtained. 12% by mass was added to the water of the gelatin solution. While this mixed solution was kept at 42 ° C., it was stirred with a comb-type disperser to obtain a liquid crystal layer coating liquid 1 containing a liquid crystal dispersion having an average dispersed particle diameter of 5 μm.

  Liquid crystal layer coating solutions 2 and 3 were prepared in the same manner as the liquid crystal layer coating solution 1 except that the liquid crystal compositions 2 and 3 were used.

(Preparation of substrate 2 having transparent electrode 2)
A substrate 2 having a transparent electrode 2 having an electrode pattern with a pitch of 145 μm and an electrode width of 130 μm using a photolithographic method after an ITO film is formed on one surface of a polyethylene terephthalate film having a thickness of 100 μm by a known sputtering method. Was made.

(Preparation of substrate 3 having transparent electrode 3)
A substrate 3 having transparent electrodes 3 having an electrode pattern with a pitch of 145 μm and an electrode width of 130 μm was obtained in the same manner as the transparent electrode 2 on both surfaces of a polyethylene terephthalate film having a thickness of 100 μm. At this time, the electrodes were made to have orthogonal patterns.

(Preparation of liquid crystal display element A)
The liquid crystal layer coating solution 1 was applied onto the transparent electrode 2 using a wire bar, cooled, and then substantially dried, and the substrate 3 was stacked on the liquid crystal layer and completely dried. Further, on the other transparent electrode 3 of the substrate 3, the liquid crystal layer coating solution 2 was applied, cooled and substantially dried, and the substrate 3 was similarly stacked and completely dried. A liquid crystal layer coating solution 3 was further applied thereon and processed in the same manner. The stripe patterns of the transparent electrodes facing each other across the liquid crystal dispersion layers were arranged to be orthogonal. The liquid crystal display element A was produced as described above.

  Here, to substantially dry the applied liquid crystal layer means to dry the substrate so that the substrate can be adhered.

  As for the dry film thickness of each liquid crystal dispersion layer, the liquid crystal layer 1 was 12 μm, the liquid crystal layer 2 was 16 μm, and the liquid crystal layer 3 was 20 μm.

[Production of Display Element 1]
The black image forming layer 1 was stacked on the liquid crystal layer 1 side of the obtained liquid crystal display element A, and glass and a PET film of the transparent electrode 2 were adhered to obtain the display element 1.

Example 2
(Production of substrate 1)
An ITO thin film having a surface resistance of 10 Ω / cm ² obtained by dispersing a tin oxide fine particle doped with antimony (average particle size 0.5 μm) in a 0.5% isopropanol solution of indium (III) isopropoxide by spin coating. It apply | coated on the attached glass substrate. By performing heat treatment at 100 ° C. for 1 hour, a porous electrode having a thickness of 3 μm was formed on the ITO. A coating film of tungsten oxide was formed on the porous electrode by a sputtering method, and a tungsten oxide layer having a thickness of 100 nm was provided on the electrode surface.

(Production of substrate 2)
An iridium oxide layer having a thickness of 100 nm was formed by sputtering on a glass substrate with an ITO thin film on which a porous electrode was formed in the same manner as the substrate 1.

(Preparation of black image display layer 2)
Tomasan Co., Ltd. Neoceptor SA-2 (ionic conductive polymer) in a 20% by mass ethanol solution was mixed and dispersed with 0.1% by mass PMMA particles (particle size 5 μm, spherical). This solution was applied to the surfaces of the substrates 1 and 2 so as to have a dry film thickness of 5 μm and heated at 90 ° C. for 3 minutes, and then the substrates 1 and 2 were bonded and sealed to obtain a black image display layer 2.

(Preparation of display element 2)
The liquid crystal display element A obtained in Example 1 was used, and the black image display layer 2 was bonded thereto to obtain a display element 2.

Example 3
(Preparation of black image forming layer 3)
The liquid crystal composition prepared in Example 1 86.0% by mass and black dichroic dye Black-4 (manufactured by Mitsubishi Chemical Corporation) 4.0% by mass are mixed well, and the liquid crystal dispersion preparation method of Example 1 is prepared. In the same manner as above, a liquid crystal dispersion 4 for forming a black image forming layer 3 was obtained.

(Preparation of display element 3)
Similarly to the formation of the liquid crystal display element A of Example 1, the liquid crystal layer 3, the transparent electrode 3, the liquid crystal layer 2, the transparent electrode 3, and the liquid crystal layer 1 are applied on the transparent electrode 2, cooled, and substantially dried. The transparent electrodes 3 are stacked and dried. Further, the liquid crystal dispersion 4 for forming the black image forming layer 3 is applied on the transparent electrode 3, cooled and substantially dried, and the transparent electrode 2 is stacked so that the electrode surface is in close contact with the black image forming layer 3, dried and displayed. Element 3 was obtained.

  As for the dry film thickness of each liquid crystal dispersion layer, the liquid crystal layer 3 was 21 μm, the liquid crystal layer 2 was 16 μm, the liquid crystal layer 1 was 11 μm, and the black image forming layer was 9 μm.

Example 4
(Preparation of liquid crystal composition 4)
Nematic liquid crystal E48 (manufactured by Merck & Co., Inc.) 53 mass% and dextrorotatory chiral material CB15 (manufactured by Merck & Co., Inc.) 47 mass% were sufficiently mixed to prepare liquid crystal composition 4 having a selective reflection color of cyan.

(Preparation of liquid crystal composition 5)
A nematic liquid crystal E48 (manufactured by Merck & Co., Inc.) 50% by mass and dextrorotatory chiral material CB15 (manufactured by Merck & Co., Inc.) 50% by mass were sufficiently mixed to prepare a liquid crystal composition 5 having a selective reflection color of reddish purple.

(Preparation of liquid crystal composition 6)
Nematic liquid crystal E48 (manufactured by Merck & Co., Inc.) 70% by mass and dextrorotatory chiral material CB15 (manufactured by Merck & Co., Inc.) 30% by mass were sufficiently mixed to prepare liquid crystal composition 6 having a selective reflection color of red.

(Preparation of liquid crystal composition 7)
Nematic liquid crystal E44 (manufactured by Merck) having positive dielectric anisotropy and BL011 (manufactured by Merck) were 44.05% by mass and 19.05% by mass, respectively, and a right-rotating chiral agent CB15 (manufactured by Merck) 36.5% by mass was sufficiently mixed to obtain a liquid crystal composition 7 having yellow selective reflection.

(Preparation of liquid crystal dispersion)
In the same manner as in Example 1, gelatin dispersions of the respective liquid crystal compositions were obtained.

(Preparation of display element 4)
The black image forming layer 3 used in Example 3 is applied onto the transparent electrode 2 using a wire bar, cooled and substantially dried, and then the transparent electrode 3 is stacked and dried. Further, the liquid crystal layer 7 was applied on the electrode on the opposite surface of the transparent electrode 3, cooled and substantially dried, and then the transparent electrode 3 was stacked and dried. A liquid crystal layer 6 was applied thereon and cooled, and then a liquid crystal layer 5 was laminated. After cooling and substantially drying, the transparent electrode 3 was stacked and dried. The liquid crystal layer 4 was applied thereon, cooled, and substantially dried, and then stacked such that the electrode surface of the transparent electrode 2 was in contact with the liquid crystal layer 4 and dried to obtain the display element 4.

  The thickness of each liquid crystal layer after drying was 10 μm for the black image forming layer, 12 μm for the liquid crystal layer 7, 10 μm for the liquid crystal layer 6, 7 μm for the liquid crystal layer 5, and 22 μm for the liquid crystal layer 4.

Comparative Example 1
(Preparation of light absorbing layer coating solution)
20% by mass of carbon black was added to a 5% by mass aqueous solution of gelatin and mixed well to obtain a light absorbing layer coating solution.

  In the formation of the display element 3 of Example 3, the light absorbing layer coating solution was applied and dried in place of the black image forming layer 3 to form a light absorbing layer. Further, on this light absorbing layer, a silver paste ink (DW-250H-5 manufactured by Toyobo Co., Ltd.) is used to form an electrode pattern with a pitch of 145 μm, an electrode width of 130 μm, and orthogonal to the electrode pattern of the transparent electrode 3 by screen printing. The comparative display element 1 was obtained.

Comparative Example 2
The liquid crystal layer 7 was applied onto the transparent electrode 2 using a wire bar, cooled and substantially dried. The transparent electrode 3 was stacked thereon and dried. The liquid crystal layer 6 was applied thereon and cooled, and then the liquid crystal layer 5 was laminated, cooled and substantially dried, and the transparent electrode 3 was stacked and dried. On this, the liquid crystal layer 4 was applied, cooled and dried, and then the light absorption layer coating solution used in Comparative Example 1 was applied and dried to obtain a light absorption layer. Further, on this light absorbing layer, a silver paste ink (DW-250H-5 manufactured by Toyobo Co., Ltd.) is used to form an electrode pattern with a pitch of 145 μm, an electrode width of 130 μm, and orthogonal to the electrode pattern of the transparent electrode 3 by screen printing. The comparative display element 2 was obtained.

  The thickness of each liquid crystal layer after drying was 12 μm for the liquid crystal layer 7, 9 μm for the liquid crystal layer 6, 8 μm for the liquid crystal layer 5, and 20 μm for the liquid crystal layer 4.

  Each display element was connected to a drive circuit, and display performance was evaluated.

[Evaluation of color reproducibility]
For the display elements 1, 2, and 3 and the comparative display element 2, RGBK colors composed of RGBK and their mixed colors were output, and color reproducibility was measured with a CM3700d colorimeter manufactured by Konica Minolta Sensing. FIG. 1 shows a chromaticity diagram (a ^* , b ^* ) based on the CIE 1976 L ^* a ^* b ^* color space by calculation from measurement data. Since the display elements 1, 2, and 3 of the present invention all had the same result, the result of the display element 1 was displayed as a representative.

For the display element 4 and the comparative display element 2, CMYK colors composed of CMYK and their mixed colors were output, and color reproducibility was measured with a CM3700d colorimeter manufactured by Konica Minolta Sensing. FIG. 2 shows a chromaticity diagram (a ^* , b ^* ) based on the CIE1976L ^* a ^* b ^* color space by calculation from the measurement data.

[Evaluation of black line / character pattern reproducibility]
A black fine line / character pattern was displayed on each display element, and the visibility of the fine line was visually evaluated. The evaluation results are shown in Table 1.

  In addition, since it is difficult to indicate the black tightening numerically, a visual evaluation was performed by a skilled worker who is familiar with the printed matter. The evaluation results are shown in Table 2.

  From the results shown in Tables 1 and 2, it can be seen that the sample of the present invention is excellent in color reproducibility and also excellent in the reproducibility of black thin lines and character patterns.

It is a figure which shows the chromaticity diagram (a ^* b ^* ) of the display element 1 of this invention, and the comparison display element 1. FIG. It is a figure which shows the chromaticity diagram (a ^* b ^* ) of the display element 4 and the comparative display element 2 of this invention.

Claims (6)

In a display device having a liquid crystal dispersion layer in which chiral nematic liquid crystal that selectively reflects a desired wavelength range of visible light in a binder is dispersed, an image showing substantially black is formed separately from the liquid crystal dispersion layer A display element comprising a black image forming layer. A plurality of liquid crystal dispersion layers in which chiral nematic liquid crystals that selectively reflect the desired wavelength range of visible light are dispersed in a binder are laminated, and the wavelength peaks reflected by each liquid crystal dispersion layer are different. The display element according to claim 1. The display element according to claim 1, wherein the black image forming layer is provided closer to the image viewing side than the total liquid crystal dispersion layer. The display element according to claim 1, wherein the black image forming layer is a liquid crystal dispersion layer in which a chiral nematic liquid crystal in which a black dichroic dye is dispersed or dissolved is dispersed in a binder. The display element according to claim 1, wherein the black image forming layer is a layer that forms an image using an electrochromic method. The display element according to claim 1, wherein the black image forming layer is a layer that forms an image using an electrolytic deposition method.

Images