JP2006098907A - Display medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium improved in optical characteristics, especially a contrast ratio. <P>SOLUTION: In the display medium comprising a base body and constitutional layers including at least one liquid crystal layer containing a liquid crystal composition dispersed into a binder, D>1.20 is satisfied when it is defined that the absorbance of maximum absorption appearing in the infrared absorption spectra 2200 to 2250 cm<SP>-1</SP>of at least one liquid crystal layer is Da, the absorbance of maximum absorption appearing in 2830 to 2900 cm<SP>-1</SP>is Db and the absorbance ratio of respective absorbance values is Da/Db = D. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a display medium having a liquid crystal layer containing a liquid crystal composition dispersed in a substrate and a binder.

  In recent years, with the increase in the operating speed of personal computers, the spread of network infrastructure, the increase in capacity and price of data storage, information such as documents and images provided on printed paper on paper has become easier to use electronic information. Opportunities to obtain and browse electronic information are increasingly increasing.

  As a means for browsing such electronic information, a light emitting type such as a conventional liquid crystal display, a CRT, or a new organic EL display is mainly used. However, particularly when the electronic information is document information, it is used for a relatively long time. It is necessary to watch the browsing means, and these actions are not necessarily human-friendly means. In general, light-emitting displays have the disadvantages of flickering eyes, inconvenient to carry, limited reading posture, need to focus on a static screen, and increased power consumption when viewed over a long period of time. ing.

As a display means that compensates for these disadvantages, a reflection type display that uses external light and does not consume power for image retention (memory type) is known. Among reflection type displays, a method in which a liquid crystal composition is made into oil droplets and dispersed and held in a binder is called a polymer dispersion type liquid crystal or a scattering type liquid crystal, and various methods are known. (For example, see Patent Documents 1 to 4.)
As a result of examining the techniques disclosed in the above patent documents in detail, the present inventor can certainly display an image using the light scattering state and the light transmission state of the liquid crystal. It was found that the liquid crystal composition dispersed in the liquid crystal composition changed in response to the external field, the molecular alignment state of the liquid crystal was inhomogeneous and not stable, so the contrast ratio was low and the optical characteristics were problematic.
JP 2003-302625 A JP 7-287214 A JP-A-9-218421 JP 2000-98326 A

  The present invention has been made in view of the above problems, and an object thereof is to provide a display medium having improved optical characteristics, particularly a contrast ratio.

  The above problem could be solved by the following configuration.

(Claim 1)
A display medium having a constituent layer including at least one liquid crystal layer containing a liquid crystal composition dispersed in a substrate and a binder, wherein the infrared absorption spectrum of at least one liquid crystal layer is 2200-2250 cm ⁻¹ . When the absorbance of the maximum absorption that appears is Da, the absorbance of the maximum absorption that appears at 2830-2900 cm ⁻¹ is Db, and the absorbance ratio thereof is Da / Db = D,
D> 1.20
A display medium characterized by satisfying

(Claim 2)
2. The display medium according to claim 1, wherein at least one of the liquid crystal layers contains a surfactant composed of an alkylnaphthalenesulfonic acid represented by the following general formula (I) and a salt thereof.

(In the formula, R represents a C1-8 linear or branched alkyl group. M represents hydrogen, alkali metal, alkaline earth metal, ammonium or amine. M represents an integer of 1 to 3, and n represents 1 to 2. Represents an integer.)
(Claim 3)
The display medium according to claim 1, wherein the liquid crystal composition has a dielectric anisotropy (Δε) of 30 or more.

(Claim 4)
The display medium according to any one of claims 1 to 3, wherein the liquid crystal composition is a chiral nematic liquid crystal composition having a cholesteric phase.

(Claim 5)
5. The display medium according to claim 4, wherein the chiral nematic liquid crystal composition is a liquid crystal composition that selectively reflects at least one kind of light selected from blue light, green light, red light, and yellow light.

(Claim 6)
The display medium according to claim 4, wherein the chiral nematic liquid crystal composition is a liquid crystal composition that provides dextrorotatory or levorotatory selective reflection.

(Claim 7)
The display medium according to claim 1, wherein a plurality of liquid crystal compositions are included in the same liquid crystal layer.

(Claim 8)
The display medium according to claim 1, comprising a plurality of liquid crystal layers.

(Claim 9)
The display medium according to claim 1, wherein a liquid crystal layer is disposed between the pair of electrodes.

(Claim 10)
The display medium according to claim 1, further comprising a light shielding layer.

(Claim 11)
The display medium according to claim 10, wherein the light shielding layer is provided between a pair of electrodes.

(Claim 12)
12. The display medium according to claim 9, wherein at least one of the pair of electrodes is formed using an electrostatic induction ink jet method having a nozzle diameter of 30 μm or less. .

  ADVANTAGE OF THE INVENTION According to this invention, the display medium which improved the optical characteristic, especially contrast ratio can be provided.

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

As a result of intensive studies in view of the above problems, the inventor is a display medium having at least one constituent layer including a substrate and a liquid crystal layer containing a liquid crystal composition dispersed in a binder. When the absorbance of the maximum absorption appearing at 2200 to 2250 cm ⁻¹ of the infrared absorption spectrum of the liquid crystal layer is Da, the absorbance of the maximum absorption appearing at 2830 to 2900 cm ⁻¹ is Db, and the absorbance ratio is Da / Db = D And D> 1.20, the liquid crystal composition dispersed in the binder has a uniform and stable alignment of liquid crystal molecules, and a display medium having a high contrast ratio can be realized. is there.

  That is, in the present invention, since the liquid crystal composition is dispersed in an aqueous binder, the polar group of the liquid crystal molecules is affected by the polarity of the binder in the vicinity of the interface, so that the alignment stability is lost. It has been found that the alignment state of the polar groups and hydrophobic groups of the liquid crystal molecules affected by the binder makes the molecular alignment state of the liquid crystals changing according to the external field uniform and stable even in the binder, and the contrast ratio can be improved. .

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

  The display medium of the present invention is formed of at least one constituent layer including a substrate and a liquid crystal layer containing a liquid crystal composition dispersed in a binder. The constituent layers include a liquid crystal layer containing a dispersed liquid crystal composition, an intermediate layer containing only a binder, a protective layer, a filter layer containing a dye or a pigment, a light shielding layer, and other layers.

〔binder〕
As the binder of the display medium 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.

  Also suitable binders for the present invention are transparent or translucent and generally colorless, natural polymers, synthetic polymers and copolymers, and other media forming films such as 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-anhydrous maleic acid) Acid), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (urethanes) The phenoxy tree , Poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and polyamides. Although it may be hydrophilic or hydrophobic, a hydrophobic transparent binder can be used in the present invention 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 ensuring the film strength of the liquid crystal layer, particularly when the counter electrode is used. In order to make the film thickness constant together with the binder, it is also possible to use resin pillar structures and spacer particles. However, 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 heating, dissolution, coating, cooling setting, and drying. Other examples of gelatin include, for example, polyvinyl alcohols. By using a thickening polysaccharide such as carrageenan or gellan gum in combination, it is possible to take steps similar to those of gelatin, 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.

  The binder may be hardened. When the binder is hardened, the mechanical strength of the binder can be improved without chemically interacting with the liquid crystal composition dispersed in the binder, so that the toughness of the display medium can be further improved.

  When gelatin is used as the binder, examples of preferable hardeners include US Pat. No. 4,678,739, column 41, 4,791,042, JP-A-59-116655, and 62-245261. , 61-18942, 61-249054, 61-245153, JP-A-4-218044, and the like. 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. 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.

[Microcapsule]
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 an amide resin, a phenol resin alone or a copolymer thereof used for urea-melamine or the like with formaldehyde, glutaraldehyde or the like.

  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.

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

[Substrate]
Examples of the substrate 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 acetal. Synthetic plastic films such as 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, a metal substrate such as stainless steel, a paper support such as baryta paper and resin coated paper, and a support provided with a reflective layer on the plastic film, supported by JP-A-62-253195 (pages 29-31) The thing described as a body is mentioned. 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.

[Liquid crystal composition]
The liquid crystal composition according to the present invention is preferably a chiral nematic liquid crystal composition having a cholesteric phase.

  A chiral nematic liquid crystal is a typical liquid crystal exhibiting a cholesteric phase, and can be obtained by adding a predetermined amount of a chiral material to a 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 having a memory property 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. In other words, it is useful as a reflective liquid crystal display medium having a memory property that once displayed, the displayed image is maintained as it is even when the power is turned off.

  The reflective liquid crystal display medium 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).

  The chiral nematic liquid crystal composition of the present embodiment (hereinafter sometimes simply referred to as “liquid crystal composition”) has a dielectric anisotropy (Δε) of 10 to 50, preferably 30 or more, and a refractive index anisotropy (Δn). Is 0.13-0.32, preferably 0.15-0.20, viscosity (η) is 0.02-0.12 Pa · s, preferably 0.02-0.1 Pa · s, and isotropic phase The transition temperature (Tc) is 50 to 130 ° C, preferably 60 to 95 ° C.

  In the present specification, the viscosity uses a value measured by a RheoStress RS50 parallel plate 20 (manufactured by HAAKE) at 20 ° C., but it does not have to be measured by the apparatus. The measurement may be performed by any device as long as it can be measured by the same principle as the above device. Further, by setting the dielectric anisotropy within the above range, it is possible to achieve both a uniform molecular arrangement of the liquid crystal composition dispersed in the binder and a reduced driving voltage. The dielectric anisotropy (Δε) is a value (25 ° C.) obtained by subtracting the dielectric constant in the direction perpendicular to the symmetry axis from the dielectric constant in the symmetry axis direction in a liquid crystal sample having uniaxial symmetry. In this specification, the dielectric anisotropy uses a value measured at room temperature using an LCR meter 4192A (manufactured by HP), but it does not necessarily have to be measured by the above apparatus. As long as the dielectric anisotropy can be measured, it may be measured using any apparatus. The refractive index anisotropy (Δn) is a value (25 ° C.) obtained by subtracting the refractive index in the direction perpendicular to the symmetry axis from the refractive index in the direction of the symmetry axis in a liquid crystal sample having uniaxial symmetry.

  In this specification, the refractive index anisotropy is a value measured at 25 ° C. using an Abbe refractometer type 1 manufactured by Atago Co., Ltd., but does not necessarily have to be measured by the above apparatus. As long as refractive index anisotropy can be measured, it may be measured using any apparatus. The isotropic phase transition temperature (Tc) is a temperature at which the liquid crystal phase of the sample transitions to the isotropic phase when the liquid crystal sample is heated. In the present specification, the isotropic phase transition temperature was measured by a liquid crystal evaluation device composed of a controller FP90 (manufactured by METLER), a hot stage FP82HT (manufactured by METTLER), and a polarizing microscope BX50 (manufactured by Olympus Optical Co., Ltd.). Although the values are used, they do not have to be measured by the device. Any apparatus may be used as long as the isotropic phase transition temperature can be measured.

  In a 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 medium of the present invention, the chiral nematic liquid crystal composition is composed of a plurality of liquid crystal compositions that selectively reflect at least one kind of light selected from blue light, green light, red light, and yellow light. preferable.

  In addition, 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, it is colorless and transparent in the planar arrangement, in the focal conic arrangement, 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 ² = (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 fabricate a white display device or a color display device of each color, for example, a liquid crystal and binder mixture is sandwiched between a pair of transparent electrodes and then cured with a hardener or the like to separate the liquid crystal and the binder. The method to do can be adopted. At this time, if the spacer is sandwiched between the transparent electrodes 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 mixture of plural kinds of chiral dopants may be 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 medium 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.

  As the surfactant used for the dispersion, alkylnaphthalenesulfonic acids represented by the general formula (I) are preferable.

  In the alkylnaphthalenesulfonic acids, the alkyl group R bonded to the aromatic ring has 1 to 8 carbon atoms, preferably 3 to 5 carbon atoms. Therefore, the naphthalene sulfonic acids are specifically n-propyl naphthalene sulfonic acid, n-butyl naphthalene disulfonic acid, isopentyl naphthalene sulfonic acid, diisopropyl naphthalene disulfonic acid, di-t-butyl naphthalene disulfonic acid, di-n. -Butylnaphthalenesulfonic acid, di-n-pentylnaphthalenesulfonic acid, tri-n-propylnaphthalenedisulfonic acid, triisobutylnaphthalenedisulfonic acid, tri-t-pentylnaphthalenesulfonic acid, and their sodium, potassium, and calcium salts Ammonium salts, dimethylamine salts, triethylamine salts, and the like.

  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.

  In addition, an infrared absorption spectrum of a liquid crystal layer in which a liquid crystal composition is dispersed in a binder is measured using an infrared spectrophotometer (HITACHI Spectrophotometer U-320) with KRS-5 [thallium iodide (TlI) and bromide. An aqueous binder solution in which a liquid crystal composition before film formation was dispersed was applied to a mixed crystal of thallium (TlBr)] and dried.

  Next, the configuration of the display medium of the present invention will be described.

[Transparent electrode]
The display medium of the present invention displays an image by arranging a liquid crystal layer between a pair of electrodes (also referred to as counter electrodes) and applying an electric field. A transparent electrode can be used for at least a part of the counter electrode. 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 medium of the present invention, at least one of the counter 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; It is preferably formed using a liquid discharge apparatus provided with discharge voltage application 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 ink jet, an electrode excellent in on-demand production, having little waste material and excellent in dimensional accuracy can be advantageously obtained.

[Light shielding layer]
The display medium of the present invention can be provided with a light shielding layer. The light shielding may be performed by any method, for example, by applying a metal reflector, a scattering plate, a colored paint on the substrate, or providing a binder constituting layer containing a colored material such as a pigment or a dye. In the present invention, it is preferable to provide this light-shielding layer between a pair of opposing electrodes. In this case, for example, a layer in which carbon black or the like is dispersed is provided in an adjacent layer close to the liquid crystal layer, thereby further absorbing light. Good black display with improved efficiency can be achieved. Moreover, when using the resin substrate with a transparent electrode for a counter electrode, a colored body can be provided on the surface opposite to the liquid crystal layer of the substrate. The color of the light to be blocked may be black for black display, or may be a filter color that compensates for the reflected color of the liquid crystal.

[Display medium drive method]
In the display medium 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 medium 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.

  Next, specific configuration examples of the display medium of the present invention will be described with reference to the drawings. However, the present invention is not limited to the exemplified configurations.

  The display medium of the present invention preferably has a configuration in which a binder and a liquid crystal composition dispersed in the binder are disposed between a pair of electrodes.

  FIG. 1 is a cross-sectional view showing an example of the configuration of a color display medium having a plurality of constituent layers containing dispersed liquid crystal compounds.

  FIG. 1a shows a substrate A having a first electrode 1 and a second electrode 6 as a pair of electrodes, and the second electrode 6 located in the lower observation direction is transparent. An electrode is preferred.

  Between the first electrode 1 and the second electrode 6 at the opposite positions, there are three constituent layers 5, and each constituent layer is independently red light dispersed in a binder. A reflective liquid crystal composition 2, a green light reflective liquid crystal composition 3, and a blue light reflective liquid crystal composition 4 are contained. These color light reflecting liquid crystal compositions can perform color display by appropriately adjusting the amount of chiral dopant added to the nematic liquid crystal and the threshold voltage applied between the first electrode 1 and the second electrode 6. it can. Further, in order to remove illegal absorption of each color light reflecting liquid crystal composition and realize optimum color reproduction, it is also preferable to provide a filter layer for color correction between each constituent layer as shown in FIG. .

  In the display medium of the present invention, it is one of preferred embodiments to include a plurality of types of liquid crystal compositions in the same constituent layer.

  FIG. 2 is a cross-sectional view showing an example of a configuration of a display medium including a light reflecting liquid crystal composition of three colors in a single constituent layer.

  In FIG. 2 a), one constituent layer 5 is provided between the first electrode 1 and the second electrode 6, which are one electrode, and the constituent layer 5 has a red color dispersed in a binder. The light reflection liquid crystal composition 2, the green light reflection liquid crystal composition 3, and the blue light reflection liquid crystal composition 4 are included.

  FIG. 2 b) is a mode in which a black light-shielding layer 8 is provided as a constituent layer between a liquid crystal layer containing each color light-reflecting liquid crystal composition and the first electrode 1. By taking this configuration, Good black display with higher light absorption efficiency can be achieved. FIG. 2 c) shows a mode in which a black light shielding layer 8 is provided between the first electrode 1 and the base A ′.

  FIG. 3 is a cross-sectional view illustrating an example of the configuration of a color display medium that includes two or more pairs of electrodes and includes a plurality of liquid crystal layers containing a liquid crystal compound.

  3A, a new electrode 9 is provided between the liquid crystal layer 5 containing the green light reflecting liquid crystal composition 3 and the liquid crystal layer 5 containing the blue light reflecting liquid crystal composition 4 with respect to the structure of FIG. 3B is an example of a display medium having a configuration in which each constituent layer is sandwiched between a pair of electrodes.

  Although the structure of the display medium shown in FIGS. 1 to 3 described above can be displayed in black and white, it is preferably applied mainly for color display.

  FIG. 4 is a configuration diagram illustrating an example of a configuration of a display medium for monochrome display.

  4A, two liquid crystal layers 5 are provided between the first electrode 1 and the second electrode 6 which are one electrode, and the blue light reflecting liquid crystal composition 4 is included in one layer. The other component layer 5 includes a yellow light reflecting liquid crystal composition 11 having a complementary color relationship with the blue light reflecting liquid crystal composition 4 and displays white and black. In addition, a black light-shielding layer 8 is provided between the first electrode 1 and the liquid crystal layer 5, and by adopting this configuration, a good black display with higher light absorption efficiency can be performed. In FIG. 4 a), an example of black display by the blue light reflective liquid crystal composition 4 and the yellow light reflective liquid crystal composition 11 is shown. For example, a combination of a green light reflective liquid crystal composition and a magenta light reflective liquid crystal composition, Alternatively, a combination of a red light reflection liquid crystal composition and a cyan light reflection liquid crystal composition may be used.

  FIG. 4B shows a form in which the blue light reflection liquid crystal composition 4 and the yellow light reflection liquid crystal composition 11 are simultaneously present in a single layer.

  In the display medium of the present invention, the chiral nematic liquid crystal composition preferably includes a liquid crystal composition that provides dextrorotatory or levorotatory selective reflection.

  FIG. 5 is a cross-sectional view showing an example of the configuration of a black-and-white display medium including a liquid crystal composition providing dextrorotatory or levorotatory selective reflection.

  FIG. 5 a) is an example in which the left-handed liquid crystal composition 12 or the right-handed liquid crystal composition is included in each independent liquid crystal layer 5, and FIG. Is an example including a levorotatory liquid crystal composition 12 and a dextrorotatory liquid crystal composition, both of which are one form that can be applied for monochrome display.

  FIG. 6 is a cross-sectional view showing an example of the configuration of a color display medium including a liquid crystal composition that provides dextrorotatory or levorotatory selective reflection.

  In a) of FIG. 6, a first electrode 1 and a second electrode 6 are provided as a pair of electrodes on a base A, and the first electrode 1 and the second electrode 6 located at opposite positions are disposed between the first electrode 1 and the second electrode 6. The liquid crystal layer 5 has three layers, and each component layer independently includes a levorotatory red light reflective liquid crystal composition 12 dispersed in a binder and a dextrorotatory red light reflective liquid crystal. A red reflective layer 14 containing the composition 13, a green reflective layer 18 composed of a levorotatory green light reflective liquid crystal composition 16 and a dextrorotatory green light reflective liquid crystal composition 17 dispersed in a binder, And a blue reflective layer 21 composed of a levorotatory blue light reflective liquid crystal composition 19 and a dextrorotatory blue light reflective liquid crystal composition 20 dispersed in a binder. FIG. 6 b) shows an example in which each levorotatory liquid crystal composition and dextrorotatory liquid crystal composition dispersed in a binder are contained in independent liquid crystal layers.

[Application field of display medium of the present invention]
The display medium of the present invention can be used in ID card related fields, public related fields, transportation related fields, broadcast related fields, payment related fields, distribution and 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.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
[Preparation of Display Medium 1: Comparative Example]
(Preparation of transparent electrode 1)
An ITO (indium tin oxide) film is formed on the entire surface of polyethylene terephthalate having a thickness of 100 μm by a known sputtering method, and then has an electrode pattern with an electrode interval of 50 μm and an electrode width of 2 mm using a photolithographic method. A transparent electrode 1 was produced.

(Preparation of liquid crystal layer coating solution 1)
Nematic liquid crystal BL006 (manufactured by Merck) having a positive dielectric anisotropy of 78.7% by mass, 9.2% by mass of dextrorotatory chiral agent CB15 (manufactured by Merck), 4.2% by mass A dextrorotatory green reflective liquid crystal composition 1 prepared by thoroughly mixing dextrorotatory chiral agent R1011 (manufactured by Merck) and 7.9% by mass of dextrorotatory chiral agent R811 (manufactured by Merck). (Δε: 13) was prepared. Next, gelatin was added in an amount of 8% by mass with respect to ion-exchanged water, stirred at room temperature, allowed to stand for 30 minutes to sufficiently swell the gelatin, and then the temperature was raised to 42 ° C. to dissolve the gelatin. To this solution, 12% by mass of isopropyl alcohol containing 10% by mass of sodium dodecyl sulfate (manufactured by Wako Pure Chemical Industries) as a surfactant is added to water, and then the dextrorotatory green reflective liquid crystal composition 1 is added to water. On the other hand, 12% by mass was added. While this mixed solution was kept at 42 ° C., it was stirred with a comb-type disperser to obtain a liquid crystal layer coating solution 1 having an average dispersed particle size of 5 μm. When this liquid crystal layer coating solution 1 was applied and dried on KRS-5 and measured with an infrared spectrophotometer (HITACHI Spectrophotometer U-320), the absorbance ratio Da / Db = D = 1.14.

(Preparation of display medium)
The liquid crystal layer coating liquid 1 heated to 42 ° C. is applied on the transparent electrode 1 so as to have a film thickness of 35 μm, and immediately after the coating, the sample is left in an environment of 10 ° C. to form the liquid crystal layer coating liquid in a jelly form. After solidifying, water was dried while maintaining the jelly-like shape. Similarly, an aqueous solution containing 5% by weight of gelatin is applied onto the sample and water is dried, and further, an aqueous solution containing 20% by weight of carbon black and containing 5% by weight of gelatin is applied to remove water. Dried. A silver paste ink (DW-250H-5 manufactured by Toyobo Co., Ltd.) is used for the sample, and an electrode pattern perpendicular to the electrode pattern of the transparent electrode 1 is formed by a screen printing method with an electrode interval of 50 μm and an electrode width of 2 mm. Medium 1 was obtained.

[Preparation of Display Medium 2: Comparative Example]
In the production of the display medium 1, the display medium 2 was produced in the same manner except that the surfactant was changed to EMAL 10 needle (manufactured by Kao Corporation, sodium lauryl sulfate). At this time, D = 1.10.

[Preparation of Display Medium 3: Present Invention]
In the production of the display medium 1, the display medium 3 was produced in the same manner except that the surfactant was changed to sodium triisopropyl naphthalene sulfonate. At this time, D = 1.67.

[Preparation of Display Medium 4: Present Invention]
In the production of the display medium 1, the display medium 4 was produced in the same manner except that the surfactant was changed to sodium di-n-butylnaphthalenedisulfonate. At this time, D = 1.72.

[Production of Display Medium 5: Comparative Example]
In the production of the display medium 3, the liquid crystal composition 1 was divided into a nematic liquid crystal ZLI1565 (manufactured by Merck & Co.) showing a positive dielectric anisotropy of 71.0% by mass and a right-handed chiral agent CB15 of 10.0% by mass. (Merck) 4.0 wt% dextrorotal chiral agent MLC6248 (Merck) 15.0 wt% dextrorotal chiral agent R811 (Merck) was prepared by thoroughly mixing. A liquid crystal layer coating solution 2 was prepared in the same manner except that the dextrorotatory green reflective liquid crystal composition 2 (Δε: 6) was used, and a display medium 5 was prepared. At this time, D of the liquid crystal layer coating liquid 2 was 0.75.

[Preparation of Display Medium 6: Present Invention]
In the production of the display medium 3, the liquid crystal composition 1 is divided into a nematic liquid crystal ZLI-4814-000 (manufactured by Merck & Co.) exhibiting a positive dielectric anisotropy of 81.0% by mass, and a dextrorotatory property of 14.0% by mass. Of CB15 (manufactured by Merck & Co., Inc.) and 5.0% by mass of dextrorotatory chiral agent R1011 (manufactured by Merck & Co., Inc.) are sufficiently mixed to prepare a dextrorotatory green reflective liquid crystal composition 3 (Δε: A liquid crystal layer coating solution 3 was prepared in the same manner except that it was changed to 33), and a display medium 6 was prepared. At this time, D of the liquid crystal layer coating solution 3 was 1.44.

<< Evaluation of display medium >>
An AC voltage of 50 Hz and 250 msec was applied to both electrodes of each obtained display medium while changing the voltage value, and a spectral reflectance (Y value) was measured using a spectrophotometer CM-3700d manufactured by Konica Minolta Sensing. Was measured. The smaller the Y value, the more transparent. The contrast is given by “Y value in high reflectivity state / Y value in low reflectivity state”. In the display medium in each experimental example described below, when the liquid crystal layer is in a planar state, it is in a high reflectance state (colored), and when it is in a focal conic state, it is in a low reflectance state (transparent).

  The results obtained as described above are shown in Table 1.

  As is clear from the results shown in Table 1, it was confirmed that the display medium satisfying the configuration of the present invention has an increased contrast ratio and improved optical characteristics.

Example 2
<< Preparation of liquid crystal layer coating liquid >>
(Preparation of liquid crystal layer coating solution 4)
In the preparation of the liquid crystal layer coating liquid 1 described in Example 1, 52.0% by mass of nematic liquid crystal ZLI1565 (manufactured by Merck) and 22.0% by mass of nematic liquid crystal E44 (manufactured by Merck) 6.0% by mass Of dextrorotatory chiral agent CB15 (manufactured by Merck), 6.0% by mass of dextrorotatory chiral agent MLC6248 (manufactured by Merck), 14.0% by mass of dextrorotatory chiral agent R811 (manufactured by Merck) A liquid crystal layer coating solution 4 was prepared in the same manner except that the mixture was changed to dextrorotatory yellow reflective liquid crystal composition 2 (Δε: 12) prepared by thoroughly mixing. At this time, D of the liquid crystal layer coating solution 4 was 1.12.

(Preparation of liquid crystal layer coating solution 5)
33.0% by mass of nematic liquid crystal ZLI1565 (manufactured by Merck), 33.0% by mass of nematic liquid crystal E44 (manufactured by Merck), 7.0% by mass of right-handed chiral agent CB15 (manufactured by Merck), 7 0.0% by mass of dextrorotatory chiral agent MLC6248 (Merck), 20.0% by mass of dextrorotatory chiral agent R811 (Merck) was mixed thoroughly, and dextrorotatory blue reflectance A dextrorotatory blue light reflective liquid crystal coating solution 5 was prepared in the same manner except that the liquid crystal composition 6 (Δε: 12) was changed.

(Preparation of liquid crystal layer coating solution 6)
The liquid crystal layer coating solution 4 and the liquid crystal layer coating solution 5 prepared above were mixed at a mass ratio of 1: 1.3 to prepare a liquid crystal layer coating solution 6.

(Preparation of liquid crystal layer coating solution 7)
In the preparation of the liquid crystal layer coating liquid 2 described in Example 1, nematic liquid crystal ZLI1565 (manufactured by Merck & Co.) showing a positive dielectric anisotropy of 74.0% by mass and a dextrorotatory property of 3.5% by mass. Chiral agent CB15 (manufactured by Merck & Co., Inc.), 9.0% by mass of dextrorotary chiral agent MLC6248 (manufactured by Merck & Co., Ltd.), 13.5% by mass of dextrorotatory chiral agent R811 (manufactured by Merck & Co., Ltd.) are sufficiently mixed. Thus, a dextrorotatory yellow light reflective liquid crystal coating solution 7 (Δε: 4) was prepared.

(Preparation of liquid crystal layer coating solution 8)
Nematic liquid crystal ZLI1565 (manufactured by Merck) having a positive dielectric anisotropy of 66.5% by mass, 7.9% by mass of dextrorotatory chiral agent CB15 (manufactured by Merck), 8.6% by mass A dextrorotatory chiral agent MLC6248 (manufactured by Merck) and 17.0% by mass of dextrorotatory chiral agent R811 (manufactured by Merck) were sufficiently mixed to prepare a dextrorotatory blue reflective liquid crystal composition 8 ( Δε: 4) was prepared.

(Preparation of liquid crystal layer coating solution 9)
The liquid crystal layer coating solution 9 and the liquid crystal layer coating solution 8 prepared above were mixed at a mass ratio of 1: 1.3 to prepare a liquid crystal layer coating solution 9.

(Preparation of liquid crystal layer coating solution 10)
In the preparation of the liquid crystal layer coating liquid 3 described in Example 1, the liquid crystal composition 3 was nematic liquid crystal ZLI-4814-000 (manufactured by Merck & Co.) showing a positive dielectric anisotropy of 84.5% by mass, 10.5% by mass of dextrorotary chiral agent MLC6248 (Merck) and 5.0% by mass of dextrorotal chiral agent R1011 (Merck) were mixed thoroughly to obtain a dextrorotatory yellow color. The reflective liquid crystal composition 10 (Δε: 34) was adjusted.

(Preparation of liquid crystal layer coating solution 11)
6. Nematic liquid crystal ZLI-4814-000 (manufactured by Merck) showing positive dielectric anisotropy of 87.0% by mass, 6.0% by mass of dextrorotatory chiral agent CB15 (manufactured by Merck), and 0% by mass of dextrorotatory chiral agent R1011 (manufactured by Merck & Co., Inc.) was sufficiently mixed to prepare dextrorotatory blue reflective liquid crystal composition 11 (Δε: 34).

(Preparation of liquid crystal layer coating solution 12)
The liquid crystal layer coating solution 10 and the liquid crystal layer coating solution 11 prepared above were mixed at a mass ratio of 1: 1.3 to prepare a liquid crystal layer coating solution 12.

<< Production and Evaluation of Display Medium >>
In the production of the display media 1 to 7 described in Example 1, the liquid crystal layer coating liquids 1 to 3 were similarly changed to the liquid crystal layer coating liquids 6, 9, and 12 prepared above, respectively. 12 were prepared, and the same evaluations as in Example 1 were performed. The results obtained are shown in Table 2.

  As is clear from the results shown in Table 2, it was confirmed that the display medium satisfying the configuration of the present invention had an increased contrast ratio and improved optical characteristics. Further, instead of applying the liquid crystal layer coating liquids 6, 9, and 12, samples prepared by laminating the liquid crystal layer coating liquids 4, 5, 7, 8, 10, and 11 in separate layers were prepared. It was possible to confirm the same effect as the result described in.

Example 3
<< Preparation of liquid crystal layer coating liquid >>
(Preparation of liquid crystal layer coating solution 15)
In the preparation of the liquid crystal layer coating liquid 1 described in Example 1, the liquid crystal composition 1 was mixed with 85.0% by mass of nematic liquid crystal BL006 (manufactured by Merck) having positive dielectric anisotropy, and dextrorotatory. A right-rotating green light-reflecting liquid crystal layer coating solution 13 was prepared in the same manner except that the liquid crystal composition 13 was composed of 15.0% by mass of the chiral agent CNL-611R (manufactured by Merck). Prepared.

  Next, it is composed of 85.0% by mass of nematic liquid crystal BL006 (manufactured by Merck) exhibiting positive dielectric anisotropy and 15.0% by mass of levorotatory chiral agent CNL-617L (manufactured by Merck). A liquid crystal composition 14 was prepared.

  The liquid crystal layer coating liquids 15 and 14 prepared above were mixed at a mass ratio of 1: 1 to prepare a liquid crystal layer coating liquid 15.

(Preparation of liquid crystal layer coating solution 18)
In the preparation of the liquid crystal layer coating solution 2 described in Example 1, the liquid crystal composition 2 was mixed with 71.0% by mass of nematic liquid crystal ZLI1565 (manufactured by Merck & Co.) exhibiting positive dielectric anisotropy, and dextrorotatory. A right-rotating green light-reflecting liquid crystal layer coating solution 16 was prepared in the same manner except that the liquid crystal composition 16 was composed of 29.0% by mass of chiral agent R811 (manufactured by Merck). .

  Next, a liquid crystal composed of 71.0% by mass of nematic liquid crystal ZLI1565 (manufactured by Merck) exhibiting positive dielectric anisotropy and 29.0% by mass of levorotatory chiral agent S811 (manufactured by Merck). Composition 17 was prepared.

  The liquid crystal layer coating liquids 16 and 17 prepared above were mixed at a mass ratio of 1: 1 to prepare a liquid crystal layer coating liquid 18.

(Preparation of liquid crystal layer coating solution 21)
In the preparation of the liquid crystal layer coating solution 3 described in Example 1, 93.5% by mass of the liquid crystal composition 3 of ZLI-4814-000 (manufactured by Merck) and a dextrorotatory chiral agent R1011 (manufactured by Merck) A right-handed green light-reflecting liquid crystal layer coating solution 19 was prepared in the same manner except that the liquid crystal composition 19 was composed of 6.5% by mass of

  Next, a liquid crystal composition 20 composed of 93.5% by mass of ZLI-4814-000 (manufactured by Merck) and 6.5% by mass of levorotatory chiral agent S1011 (manufactured by Merck) was prepared.

  The liquid crystal layer coating liquids 19 and 20 prepared above were mixed at a mass ratio of 1: 1 to prepare a liquid crystal layer coating liquid 21.

<< Production and Evaluation of Display Medium >>
In the production of the display media 1 to 7 described in Example 1, the same applies to Example 1 except that the liquid crystal layer coating liquids 1 to 3 were changed to the liquid crystal layer coating liquids 15, 18, and 21 prepared above, respectively. As a result of performing the same evaluations, it was confirmed that the display medium satisfying the configuration of the present invention has an increased contrast ratio and improved optical characteristics, similar to the result of Example 1.

Example 4
The liquid crystal composition 1 of Example 1 was changed to the liquid crystal composition described in paragraphs [0081] to [0082] of JP-A-5-273576, and the phase transition voltage of the liquid crystal was measured. As a result of the evaluation, it was confirmed that the display medium satisfying the configuration of the present invention has a small change ratio of the phase transition voltage, and that the effects of the present invention can be obtained with other than the cholesteric liquid crystal.

Example 5
Instead of screen printing the silver paste described in Example 1, a solution containing silver colloidal particles having an average particle diameter of 20 nm was applied to an electrode pattern similar to that in Example 1 using an electrostatic ink jet apparatus having a discharge tip nozzle diameter of 15 μm. When the same sample as that of Example 1 was evaluated, the effect of the present invention could be confirmed as in Example 1.

It is sectional drawing which shows an example of a structure of the color display medium which has multiple structure layers containing the liquid crystal compound disperse | distributed. It is sectional drawing which shows an example of a structure of the display medium containing the light reflection liquid crystal composition of 3 colors in a single structure layer. It is sectional drawing which shows an example of a structure of the color display medium comprised from two or more pairs of electrodes, and having two or more the structural layers containing a liquid crystal compound. It is a block diagram which shows an example of a structure of the display medium for a monochrome display. It is sectional drawing which shows an example of a structure of the black-and-white display medium containing the liquid crystal composition which gives dextrorotatory or levorotatory selective reflection. It is sectional drawing which shows an example of a structure of the color display medium containing the liquid crystal composition which gives dextrorotatory or levorotatory selective reflection.

Explanation of symbols

A, A ′ substrate 1 first electrode 2 red light reflective liquid crystal composition 3 green light reflective liquid crystal composition 4 blue light reflective liquid crystal composition 5 liquid crystal layer 6 second electrode (transparent electrode)
7 Filter layer 8 Black light shielding layer 9, 10 Transparent electrode 11 Yellow light reflecting liquid crystal composition 12 Left-handed liquid crystal composition 13 Right-handed liquid crystal composition 14 Left-handed red light-reflecting liquid crystal composition 15 Right handed 16 red reflective liquid crystal composition 16 red reflective layer 17 levorotatory green light reflective liquid crystal composition 18 dextrorotatory green light reflective liquid crystal composition 19 green reflective layer 20 levorotatory blue light reflective liquid crystal composition 21 right-handed blue light reflective liquid crystal composition 22 blue reflective layer

Claims (12)

A display medium having a constituent layer including at least one liquid crystal layer containing a liquid crystal composition dispersed in a substrate and a binder, wherein the infrared absorption spectrum of at least one liquid crystal layer is 2200-2250 cm ⁻¹ . When the absorbance of the maximum absorption that appears is Da, the absorbance of the maximum absorption that appears at 2830-2900 cm ⁻¹ is Db, and the absorbance ratio thereof is Da / Db = D,
D> 1.20
A display medium characterized by satisfying 2. The display medium according to claim 1, wherein at least one of the liquid crystal layers contains a surfactant composed of an alkylnaphthalenesulfonic acid represented by the following general formula (I) and a salt thereof.

(In the formula, R represents a C1-8 linear or branched alkyl group. M represents hydrogen, alkali metal, alkaline earth metal, ammonium or amine. M represents an integer of 1 to 3, and n represents 1 to 2. Represents an integer.) The display medium according to claim 1, wherein the liquid crystal composition has a dielectric anisotropy (Δε) of 30 or more. The display medium according to any one of claims 1 to 3, wherein the liquid crystal composition is a chiral nematic liquid crystal composition having a cholesteric phase. 5. The display medium according to claim 4, wherein the chiral nematic liquid crystal composition is a liquid crystal composition that selectively reflects at least one light selected from blue light, green light, red light, and yellow light. The display medium according to claim 4, wherein the chiral nematic liquid crystal composition is a liquid crystal composition that provides dextrorotatory or levorotatory selective reflection. The display medium according to claim 1, wherein a plurality of liquid crystal compositions are included in the same liquid crystal layer. The display medium according to claim 1, comprising a plurality of liquid crystal layers. The display medium according to claim 1, wherein a liquid crystal layer is disposed between the pair of electrodes. The display medium according to claim 1, further comprising a light shielding layer. The display medium according to claim 10, wherein the light shielding layer is provided between a pair of electrodes. 12. The display medium according to claim 9, wherein at least one of the pair of electrodes is formed using an electrostatic induction ink jet method having a nozzle diameter of 30 μm or less. .

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