JP2007133091A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element which has memory property and is high in display performance. <P>SOLUTION: The liquid crystal display element has a liquid crystal layer including at least one dichroic dye and a bistable nematic liquid crystal whose alignment states in a homeotropic state and a planer state are stable between a pair of electrodes at least one of which is a transparent electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element, particularly a liquid crystal display element suitable for a guest-host system.

Many liquid crystal elements (liquid crystal display elements) have already been proposed. Among them, the guest-host liquid crystal element is capable of bright display and is expected as a liquid crystal element suitable for a reflection type. In a guest-host type liquid crystal device, a liquid crystal composition in which a dichroic dye is dissolved in a nematic liquid crystal is enclosed in a cell, and an electric field is applied to the liquid crystal composition. In this method, the orientation is changed and the light absorption state of the cell is changed.
In this guest-host type liquid crystal element, a brighter display is expected because a driving method that does not require a polarizing plate is possible as compared with a conventional liquid crystal display method.

  Further, the conventional guest-host method using nematic liquid crystal is a method that does not have display maintenance after the electric field is cut off, that is, a so-called memory property. When considering application as electronic paper, memory performance is important, and although guest host systems with memory performance have been proposed so far, the reality is that they have not reached a sufficient level. (For example, refer to Patent Document 1).

Several proposals have been made for a liquid crystal display element having a memory property using a nematic liquid crystal (see, for example, Non-Patent Document 1). However, these systems use a polarizing plate, so the reflectance is low. Therefore, it is desired to provide a liquid crystal display element having a memory property and a high display performance.
JP 7-278549 A Applied Physics Letters, 82, 4215, 2003

  An object of the present invention is to provide a liquid crystal display element having a memory property and high display performance.

  In a guest-host system using ordinary nematic liquid crystals, it is difficult to impart memory properties to the liquid crystals. Therefore, it is conceivable to combine a bistable nematic liquid crystal with a guest-host system. For example, as a bistable nematic liquid crystal, a bistable state of a focal conic state and a planar state by a chiral nematic liquid crystal is known, but in a guest-host method in which a dichroic dye is simply added to this liquid crystal composition, Even in the focal conic state, half of the dichroic dye absorbs light, resulting in a problem that display performance deteriorates. On the other hand, a simple combination of a liquid crystal composition obtained by adding a dichroic dye to a chiral nematic liquid crystal and a conventionally known liquid crystal system that exhibits a horizontal alignment state or a vertical alignment state can impart a memory property to the guest-host system. I found it difficult.

Therefore, the present inventor conducted extensive research on the above problem, and obtained the knowledge that the memory property can be imparted to the guest-host system by combining with a specific orientation state and the display performance does not deteriorate. Further studies were made based on this finding, and the present invention was completed.
As the bistable nematic liquid crystal according to the present invention, a chiral nematic liquid crystal is preferably used. However, in order to form a bistable state, the helix angle of the helix cannot be increased so much. However, in the present invention, the problem is obtained by obtaining the knowledge that display performance is improved by using in combination with a dichroic dye having a specific substituent. It came to solve the point.

  Means for solving the above-mentioned problems are as follows.

<1> A liquid crystal layer comprising at least one dichroic dye and a bistable nematic liquid crystal in which each alignment state is stable in a homeotropic state and a planar state between a pair of electrodes, at least one of which is a transparent electrode It is a liquid crystal display element which has.

According to the invention <1>, the liquid crystal layer according to the present invention comprises a dichroic dye and a bistable nematic liquid crystal in which the alignment state is stable in the homeotropic state and the planar state, respectively. Compared with the conventional focal conic state, the light absorption by the dichroic dye in the homeotropic state is small, that is, the reflectance in white display is high, and the display performance is high.
The “bistable nematic liquid crystal” of the present invention means a nematic liquid crystal in which two states, a homeotropic state and a planar state, are stable, and the liquid crystal layer of the present invention exhibits a memory property.

<2> The liquid crystal display element according to <1>, wherein the liquid crystal layer contains at least one chiral agent.

<3> The liquid crystal display element according to <1> or <2>, wherein the bistable nematic liquid crystal is a chiral nematic phase.

  According to the above inventions <2> and <3>, since the liquid crystal layer is a chiral nematic layer, the balance between the torsional force and the anchoring force received from the interface in the chiral nematic liquid crystal is balanced, and the homeotropic state and planar In the state, the nematic liquid crystal can be in a bistable state. In addition, by adding a chiral agent, a helical structure is formed, so that absorption independent of polarized light is possible and display performance is improved.

<4> The liquid crystal display element according to any one of <1> to <3>, wherein the liquid crystal display element has at least one kind of alignment film.

<5> The liquid crystal display element according to <4>, wherein the alignment film is at least one polyimide alignment film.

<6> The liquid crystal display element according to <5>, wherein the alignment film is at least one type of vertical polyimide alignment film.

<7> The liquid crystal display element according to any one of <1> to <6>, wherein the bistable nematic liquid crystal has a pretilt angle in a range of 90 to 75 °.

<8> The liquid crystal display element according to any one of <4> to <7>, wherein the alignment film is an alignment film subjected to at least one rubbing treatment.

According to the inventions <4> to <8> above, the liquid crystal layer is aligned by the alignment film, so that the balance between the twisting force and the anchoring force received from the interface in the chiral nematic liquid crystal is in an equilibrium state and exhibits memory properties. Can do.
In particular, when the alignment film stabilizes the alignment state in a substantially horizontal direction and a substantially vertical direction with respect to the substrate, the alignment state in the homeotropic state and the planar state is stabilized, and the display performance is improved.

<9> The liquid crystal display element according to any one of <1> to <8>, wherein the bistable nematic liquid crystal exhibits dual-frequency drivability.

    According to the above invention <9>, the liquid crystal layer is driven at two frequencies, whereby the change between the two alignment states becomes faster, and the suitability of the display element for moving images is improved.

<10> The liquid crystal display element according to any one of claims 1 to 9, wherein the dichroic dye has a substituent represented by the following general formula (1).
Formula ^{_{(1): - (Het)}} j - {(B 1) p - (Q 1) q - (B 2) r} n -C 1
[In the formula, Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group or a divalent cyclic aliphatic hydrocarbon group, and Q ¹ represents a divalent group. Represents a linking group, C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, p, q and r each independently represents 0 to 1; 5 represents an integer of 5, n represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q, and r are each 2 or more, 2 or more B ¹ , Q ¹ And B ² may be the same or different. When n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } are the same or different. May be. ]

〔式中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７及びＲ^８の少なくとも一つは、−（Ｈｅｔ）_ｊ−｛（Ｂ^１）_ｐ−（Ｑ^１）_ｑ−（Ｂ^２）_ｒ｝_ｎ−Ｃ^１であり、他は各々独立に水素原子又は置換基である。Ｈｅｔは酸素原子又は硫黄原子であり、Ｂ^１及びＢ^２は、各々独立に、アリーレン基、ヘテロアリーレン基又は２価の環状脂肪族炭化水素基を表し、Ｑ^１は２価の連結基を表し、Ｃ^１はアルキル基、シクロアルキル基、アルコキシ基、アルコキシカルボニル基、アシル基又はアシルオキシ基を表し、ｊは０又は１を表し、ｐ、ｑ及びｒは、各々独立に０〜５の整数を表し、ｎは１〜３の整数を表し、（ｐ＋ｒ）×ｎは３〜１０の整数であり、ｐ、ｑ及びｒがそれぞれ２以上の時、２以上のＢ^１、Ｑ^１及びＢ^２はそれぞれ同一でも異なっていてもよく、ｎが２以上の時、２以上の｛（Ｂ^１）_ｐ−（Ｑ^１）_ｑ−（Ｂ^２）_ｒ｝は同一でも異なっていてもよい。〕 <11> The liquid crystal display element according to any one of <1> to <10>, wherein at least one of the dichroic dyes is a compound represented by the following general formula (2).

[Wherein, at least one of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _q - ^(B _{2) r}} n -C ^1, and others are each independently a hydrogen atom or a substituent. Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group, or a divalent cyclic aliphatic hydrocarbon group, and Q ¹ represents a divalent linking group. , C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, and p, q and r each independently represents an integer of 0 to 5. N represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q and r are each 2 or more, 2 or more B ¹ , Q ¹ and B ² are Each may be the same or different, and when n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } may be the same or different. ]

〔式中、Ｒ^１１、Ｒ^１２、Ｒ^１３、Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７の少なくとも一つは、−（Ｈｅｔ）_ｊ−｛（Ｂ^１）_ｐ−（Ｑ^１）_ｑ−（Ｂ^２）_ｒ｝_ｎ−Ｃ^１であり、他は各々独立に水素原子又は置換基である。Ｈｅｔは酸素原子又は硫黄原子であり、Ｂ^１及びＢ^２は各々独立にアリーレン基、ヘテロアリーレン基又は２価の環状脂肪族炭化水素基を表し、Ｑ^１は２価の連結基を表し、Ｃ^１はアルキル基、シクロアルキル基、アルコキシ基、アルコキシカルボニル基、アシル基又はアシルオキシ基を表し、ｊは０又は１を表し、ｐ、ｑ及びｒは、各々独立に０〜５の整数を表し、ｎは１〜３の整数を表し、（ｐ＋ｒ）×ｎは３〜１０の整数であり、ｐ、ｑ及びｒがそれぞれ２以上の時、２以上のＢ^１、Ｑ^１及びＢ^２はそれぞれ同一でも異なっていてもよく、ｎが２以上の時、２以上の｛（Ｂ^１）_ｐ−（Ｑ^１）_ｑ−（Ｂ^２）_ｒ｝は同一でも異なっていてもよい。〕 <12> The liquid crystal display element according to any one of <1> to <11>, wherein at least one of the dichroic dyes is a compound represented by the following general formula (3).

[In the formula, at least one of R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _q- ( B ²⁾ _{r} n} -C ^1, and others are each independently a hydrogen atom or a substituent. Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group, or a divalent cyclic aliphatic hydrocarbon group, Q ¹ represents a divalent linking group, and C 1 ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, p, q and r each independently represents an integer of 0 to 5; n represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q and r are each 2 or more, 2 or more B ¹ , Q ¹ and B ² are the same However, when n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } may be the same or different. ]

  According to the inventions <10> to <12> above, by combining a dichroic dye having a specific structure with a bistable nematic liquid crystal, the reflectance in white background is increased and the contrast ratio in display is improved.

  According to the present invention, it is possible to provide a liquid crystal display element having memory properties and high display performance.

  Hereinafter, the present invention will be described in detail. In the present specification, “to” indicates a range including the numerical values described before and after the minimum and maximum values, respectively.

  The liquid crystal display element of the present invention has a liquid crystal layer containing at least one dichroic dye and a bistable nematic liquid crystal between a pair of electrodes, at least one of which is a transparent electrode. Hereinafter, various materials used in the present invention will be described.

(Liquid crystal layer)
The liquid crystal layer of the present invention contains at least a dichroic dye and a bistable nematic liquid crystal.
<Dichroic dye>
In the present invention, the dichroic dye is defined as a compound that dissolves in the host liquid crystal and has a function of absorbing light. The dichroic dye of the present invention may have any absorption maximum and absorption band, but has an absorption maximum in the yellow region (Y), magenta region (M), or cyan region (C). The case is preferred. Two or more dichroic dyes may be used, and it is preferable to use a mixture of dichroic dyes having absorption maxima in Y, M, and C. A method for performing full color display by mixing a yellow dye, a magenta dye and a cyan dye is detailed in “Color Chemistry” (written by Sumio Tokita, Maruzen, 1982). Here, the yellow region is a range of 430 to 490 nm, the magenta region is a range of 500 to 580 nm, and the cyan region is a range of 600 to 700 nm.

Next, the chromophore used for the dichroic dye of the present invention will be described.
The chromophore of the dichroic dye may be any, for example, azo dye, anthraquinone dye, perylene dye, merocyanine dye, azomethine dye, phthaloperylene dye, indigo dye, azulene dye, dioxazine dye, polythiophene dye, Examples include phenoxazine dyes. Preferred are azo dyes, anthraquinone dyes, and phenoxazine dyes, and particularly preferred are anthraquinone dyes and phenoxazone dyes (phenoxazin-3-one).

The azo dye may be any one such as a monoazo dye, a bisazo dye, a trisazo dye, a tetrakisazo dye, and a pentakisazo dye, but is preferably a monoazo dye, a bisazo dye, or a trisazo dye.
The ring structure contained in the azo dye includes aromatic groups (benzene ring, naphthalene ring, etc.) as well as heterocyclic rings (quinoline ring, pyridine ring, thiazole ring, benzothiazole ring, oxazole ring, benzoxazole ring, imidazole ring, Benzimidazole ring, pyrimidine ring, etc.).

  As the substituent of the anthraquinone dye, those containing an oxygen atom, a sulfur atom or a nitrogen atom are preferable, and examples thereof include an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group and an arylamino group. The substitution number of the substituent may be any number, but di-substitution, tri-substitution, and tetrakis substitution are preferred, and di-substitution and tri-substitution are particularly preferred. The substitution position of the substituent may be any place, but preferably 1,4-position disubstitution, 1,5-position disubstitution, 1,4,5-position trisubstitution, 1,2,4-position trisubstitution, They are 1,2,5-trisubstituted, 1,2,4,5-tetrasubstituted, 1,2,5,6-tetrasubstituted structures.

  The substituent of the phenoxazone dye (phenoxazin-3-one) preferably includes an oxygen atom, a sulfur atom or a nitrogen atom, and examples thereof include an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group and an arylamino group.

The dichroic dye used in the present invention preferably has a substituent represented by the following general formula (1).
Formula ^{_{(1): - (Het)}} j - {(B 1) p - (Q 1) q - (B 2) r} n -C 1

In the formula, Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group, or a divalent cyclic aliphatic hydrocarbon group, and Q ¹ is a divalent linkage. Represents a group, and C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group. j represents 0 or 1, p, q and r each independently represent an integer of 0 to 5, n represents an integer of 1 to 3, and (p + r) × n is an integer of 3 to 10, When p, q and r are each 2 or more, 2 or more B ¹ , Q ¹ and B ² may be the same or different. When n is 2 or more, 2 or more {(B ¹ ) _p − (Q ¹ ) _q- (B ² ) _r } may be the same or different.

Het is an oxygen atom or a sulfur atom, particularly preferably a sulfur atom.
B ¹ and B ² each independently represent an arylene group, a heteroarylene group or a divalent cyclic aliphatic hydrocarbon group, and any of them may or may not have a substituent.

The arylene group represented by B ¹ and B ² is preferably an arylene group having 6 to 20 carbon atoms, and more preferably an arylene group having 6 to 10 carbon atoms. Specific examples of preferable arylene groups include benzene ring, naphthalene ring and anthracene ring groups. Particularly preferred are benzene ring and substituted benzene ring groups, and more preferred is a 1,4-phenylene group.
The heteroarylene group represented by B ¹ and B ² is preferably a heteroarylene group having 1 to 20 carbon atoms, and more preferably a heteroarylene group having 2 to 9 carbon atoms. Specific examples of preferred heteroarylene groups include pyridine ring, quinoline ring, isoquinoline ring, pyrimidine ring, pyrazine ring, thiophene ring, furan ring, oxazole ring, thiazole ring, imidazole ring, pyrazole ring, oxadiazole ring, thiadiazole ring and A group consisting of a triazole ring, and a condensed heteroarylene group formed by condensation of these groups.
The divalent cyclic aliphatic hydrocarbon group represented by B ¹ and B ² is preferably a divalent cyclic aliphatic hydrocarbon group having 3 to 20 carbon atoms, more preferably 4 to 10 carbon atoms. Preferred divalent cycloaliphatic hydrocarbon groups are cyclohexanediyl and cyclopentanediyl, more preferably cyclohexane-1,2-diyl group, cyclohexane-1,3-diyl group, cyclohexane-1,4-diyl. Group, cyclopentane-1,3-diyl group, particularly preferably (E) -cyclohexane-1,4-diyl group.

The divalent arylene group, heteroarylene group and divalent cyclic aliphatic hydrocarbon group represented by B ¹ and B ² may further have a substituent, and examples of the substituent include the following substituent group V Is mentioned.

(Substituent group V)
Halogen atom (for example, chlorine, bromine, iodine, fluorine), mercapto group, cyano group, carboxyl group, phosphate group, sulfo group, hydroxy group, 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms, more preferably carbon A carbamoyl group having 2 to 5 carbon atoms (for example, methylcarbamoyl, ethylcarbamoyl, morpholinocarbonyl), a sulfamoyl group having 0 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 5 carbon atoms (for example, methylsulfamoyl group) , Ethylsulfamoyl, piperidinosulfonyl), a nitro group, an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms (for example, methoxy, ethoxy, 2-methoxyethoxy). , 2-phenylethoxy), carbon number 6-20, preferably carbon number 6-12, more preferably carbon number -10 aryloxy groups (for example, phenoxy, p-methylphenoxy, p-chlorophenoxy, naphthoxy), C1-20, preferably C2-12, more preferably C2-8 acyl groups (for example, Acetyl, benzoyl, trichloroacetyl), C1-20, preferably C2-12, more preferably C2-8 acyloxy groups (for example, acetyloxy, benzoyloxy), C1-20, preferably C2-C12, more preferably C2-C8 acylamino group (for example, acetylamino), C1-C20, preferably C1-C10, more preferably C1-C8 sulfonyl group (for example, Methanesulfonyl, ethanesulfonyl, benzenesulfonyl), 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, Preferably, the sulfinyl group having 1 to 8 carbon atoms (for example, methanesulfinyl, ethanesulfinyl, benzenesulfinyl), 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms substituted or unsubstituted Amino groups such as amino, methylamino, dimethylamino, benzylamino, anilino, diphenylamino, 4-methylphenylamino, 4-ethylphenylamino, 3-n-propylphenylamino, 4-n-propylphenylamino, 3 -N-butylphenylamino, 4-n-butylphenylamino, 3-n-pentylphenylamino, 4-n-pentylphenylamino, 3-trifluoromethylphenylamino, 4-trifluoromethylphenylamino, 2-pyridylamino , 3-pyridylamino, 2-thiazolylami , 2-oxazolylamino, N, N-methylphenylamino, N, N-ethylphenylamino), ammonium having 0 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 6 carbon atoms. A group (eg trimethylammonium, triethylammonium), 0-15 carbon atoms, preferably 1-10 carbon atoms, more preferably a hydrazino group having 1-6 carbon atoms (eg trimethylhydrazino group), 1-15 carbon atoms, preferably Is a ureido group having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms (eg ureido group, N, N-dimethylureido group), 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably carbon. An imide group having 1 to 6 carbon atoms (for example, a succinimide group), an alkylthio having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, and more preferably 1 to 8 carbon atoms. (For example, methylthio, ethylthio, propylthio), an arylthio group having 6 to 80 carbon atoms, preferably 6 to 40 carbon atoms, and more preferably 6 to 30 carbon atoms (for example, phenylthio, p-methylphenylthio, p-chlorophenylthio, 2 -Pyridylthio, 1-naphthylthio, 2-naphthylthio, 4-propylcyclohexyl-4'-biphenylthio, 4-butylcyclohexyl-4'-biphenylthio, 4-pentylcyclohexyl-4'-biphenylthio, 4-propylphenyl-2 -Ethynyl-4′-biphenylthio), a heteroarylthio group having 1 to 80 carbon atoms, preferably 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms (for example, 2-pyridylthio, 3-pyridylthio, 4-pyridylthio). , 2-quinolylthio, 2-furylthio, 2-pyrrolylthio An alkoxycarbonyl group having 2 to 20 carbon atoms, preferably 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms (for example, methoxycarbonyl, ethoxycarbonyl, 2-benzyloxycarbonyl), 6 to 20 carbon atoms, preferably An aryloxycarbonyl group having 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms (for example, phenoxycarbonyl), 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms unsubstituted. An alkyl group (eg, methyl, ethyl, propyl, butyl), a substituted alkyl group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms {eg, hydroxymethyl, trifluoromethyl, benzyl, Carboxyethyl, ethoxycarbonylmethyl, acetylaminomethyl, and here 2 to 18 carbon atoms Preferably, an unsaturated hydrocarbon group having 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms (for example, vinyl group, ethynyl group 1-cyclohexenyl group, benzylidine group, benzylidene group) is also included in the substituted alkyl group. A substituted or unsubstituted aryl group having 6 to 20 carbon atoms, preferably 6 to 15 carbon atoms, more preferably 6 to 10 carbon atoms (for example, phenyl, naphthyl, p-carboxyphenyl, p-nitrophenyl, 3 , 5-dichlorophenyl, p-cyanophenyl, m-fluorophenyl, p-tolyl, 4-propylcyclohexyl-4′-biphenyl, 4-butylcyclohexyl-4′-biphenyl, 4-pentylcyclohexyl-4′-biphenyl, 4, -Propylphenyl-2-ethynyl-4′-biphenyl), 1 to 20 carbon atoms, preferably 2 carbon atoms 10, further preferably a substituted or unsubstituted heteroaryl group having 4 to 6 carbon atoms (such as pyridyl, 5-methylpyridyl, thienyl, furyl, morpholino, tetrahydrofurfuryl).

  These substituent groups V can have a structure in which a benzene ring or a naphthalene ring is condensed. Furthermore, the substituent shown in the explanation of V explained so far may be further substituted on these substituents.

  Preferred as the substituent group V are the aforementioned alkyl group, aryl group, alkoxy group, aryloxy group, halogen atom, amino group, substituted amino group, hydroxy group, alkylthio group, and arylthio group, and more preferably alkyl group. A group, an aryl group, and a halogen atom.

Q ¹ represents a divalent linking group. Preferably, it is a linking group comprising an atomic group composed of at least one atom selected from a carbon atom, a nitrogen atom, a sulfur atom and an oxygen atom. The divalent linking group represented by Q ¹ is preferably an alkylene group having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms (for example, methylene, ethylene, propylene, butylene, pentylene, cyclohexyl-1,4- Diyl), preferably an alkenylene group having 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms (for example, ethenylene), preferably 2 to 20 carbon atoms, more preferably an alkynylene group having 2 to 10 carbon atoms (for example, Ethynylene), amide group, ether group, ertel group, sulfoamide group, sulfonic acid ester group, ureido group, sulfonyl group, sulfinyl group, thioether group, carbonyl group, -NR- group (where R is a hydrogen atom, alkyl group) Or an aryl group, and the alkyl group represented by R is preferably 1 to 20 carbon atoms, and more preferably Or an aryl group represented by R is preferably an aryl group having 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms), an azo group, an azoxy group, a complex group. One or more ring divalent groups (preferably a divalent heterocyclic group having 2 to 20 carbon atoms, more preferably 4 to 10 carbon atoms, such as a piperazine-1,4-diyl group). Examples thereof include a divalent linking group having 0 to 60 carbon atoms configured in combination.

The divalent linking group represented by Q ¹ is preferably an alkylene group, an alkenylene group, an alkynylene group, an ether group, a thioether group, an amide group, an ester group, a carbonyl group, or a combination thereof.
Q ¹ may further have a substituent, and examples of the substituent include the substituent group V described above.

C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group. The alkyl group, cycloalkyl group, alkoxy group, alkoxycarbonyl group, acyl group or acyloxy group represented by C ¹ includes each group having a substituent.
C ¹ is preferably an alkyl or cycloalkyl group having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, still more preferably 1 to 8 carbon atoms (for example, methyl, ethyl, propyl, butyl, t-butyl, i -Butyl, sec-butyl, pentyl, t-pentyl, hexyl, heptyl, octyl, cyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-propylcyclohexyl, 4-butylcyclohexyl, 4-pentylcyclohexyl, hydroxymethyl, tri Fluoromethyl, benzyl), an alkoxy group having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 8 carbon atoms (for example, methoxy, ethoxy, 2-methoxyethoxy, 2-phenylethoxy), carbon 1-20, more preferably 2-12 carbons, even more preferred Or an acyloxy group having 2 to 8 carbon atoms (for example, acetyloxy, benzoyloxy), 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and still more preferably an acyl group having 1 to 8 carbon atoms (for example, acetyl, formyl). Group, pivaloyl, 2-chloroacetyl, stearoyl, benzoyl, pn-octyloxyphenylcarbonyl), or alkoxycarbonyl having 2 to 20, more preferably 2 to 12, more preferably 2 to 8 carbon atoms. Represents a group (eg methoxycarbonyl, ethoxycarbonyl, 2-benzyloxycarbonyl).

C ¹ is particularly preferably an alkyl group or an alkoxy group, and more preferably an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group or a trifluoromethoxy group.

C ¹ may further have a substituent, and examples of the substituent include the substituent group V.

Examples of the substituent of the alkyl group represented by C ^1, among the substituent group V, a halogen atom, a cyano group, a hydroxy group, a carbamoyl group, an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, an acylamino group, an amino Group, alkylthio group, arylthio group, heteroarylthio group, alkoxycarbonyl group, and aryloxycarbonyl group are preferable.

The substituent of the cycloalkyl group represented by C ¹ includes, among the substituent group V, a halogen atom, a cyano group, a hydroxy group, a carbamoyl group, an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, an acylamino group, an amino group. Group, alkylthio group, arylthio group, heteroarylthio group, alkoxycarbonyl group, aryloxycarbonyl group, and alkyl group are preferable.

The substituent of the alkoxy group represented by C ¹ is, among the substituent group V, a halogen atom (particularly a fluorine atom), a cyano group, a hydroxy group, a carbamoyl group, an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, An acylamino group, an amino group, an alkylthio group, an arylthio group, a heteroarylthio group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferable.

The substituent of the alkoxycarbonyl group represented by C ¹ is, among substituent group V, halogen atom, cyano group, hydroxy group, carbamoyl group, alkoxy group, aryloxy group, acyl group, acyloxy group, acylamino group, amino group Group, alkylthio group, arylthio group, heteroarylthio group, alkoxycarbonyl group, and aryloxycarbonyl group are preferable.

The substituent of the acyl group represented by C ¹ is a halogen atom, a cyano group, a hydroxy group, a carbamoyl group, an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, an acylamino group, an alkylthio group in the substituent group V. , Arylthio group, heteroarylthio group, alkoxycarbonyl group, and aryloxycarbonyl group are preferable.

The substituent of the acyloxy group represented by C ¹ is, among substituent group V, a halogen atom, a cyano group, a hydroxy group, a carbamoyl group, an alkoxy group, an aryloxy group, an acyl group, an acyloxy group, an acylamino group, and an amino group. , An alkylthio group, an arylthio group, a heteroarylthio group, an alkoxycarbonyl group, and an aryloxycarbonyl group are preferable.

j represents 0 or 1, preferably 0.
p, q and r each represent a number of 0 to 5, n represents a number of 1 to 3, and the total number of groups represented by B ¹ and B ² , that is, (p + r) × n is 3 to 10 It is an integer, more preferably an integer of 3 to 5. When p, q, or r is 2 or more, 2 or more B ¹ , Q ^1, and B ² may be the same or different, and when n is 2 or more, 2 or more {( _{^{B 1) p - (Q 1}} ) q - (B 2) r} may each be the same or different.

Preferred combinations of p, q, r and n are described below.
(I) p = 3, q = 0, r = 0, n = 1
(Ii) p = 4, q = 0, r = 0, n = 1
(Iii) p = 5, q = 0, r = 0, n = 1
(Iv) p = 2, q = 0, r = 1, n = 1
(V) p = 2, q = 1, r = 1, n = 1
(Vi) p = 1, q = 1, r = 2, n = 1
(Vii) p = 3, q = 1, r = 1, n = 1
(Viii) p = 2, q = 0, r = 2, n = 1
(Ix) p = 1, q = 1, r = 1, n = 2
(X) p = 2, q = 1, r = 1, n = 2

  Particularly preferably, (i) p = 3, q = 0, r = 0, n = 1; (iv) p = 2, q = 0, r = 1, n = 1; and (v) p = 2, The combination is q = 1, r = 1, n = 1.

Note that it is preferable that-{(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } _n -C ¹ includes a partial structure exhibiting liquid crystallinity. The liquid crystal herein may be in any phase, but is preferably a nematic liquid crystal, a smectic liquid crystal, or a discotic liquid crystal, and particularly preferably a nematic liquid crystal.

Specific examples of-{(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } _n -C ¹ are shown below, but the present invention is not limited thereto (in the following chemical formula, wavy lines Represents the connection position).

The dichroic dye used in the present ^invention, - that has a substituent 1 or more represented by _{^{{(B 1) p - -}} (Q 1) q (B 2) r} n -C 1 Preferably, 1 to 8 is more preferable, 1 to 4 is more preferable, and 1 or 2 is particularly preferable.

A preferable structure of the substituent represented by the general formula (1) is the following combination.
[1] Het is a sulfur atom, B ¹ represents an aryl group or a heteroaryl group, B ² represents a cyclohexane-1,4-diyl group, C ¹ represents an alkyl group, j = 1, p = 2, q = 0, r = 1 and n = 1.
[2] Het is a sulfur atom, B ¹ represents an aryl group or a heteroaryl group, B ² represents a cyclohexane-1,4-diyl group, C ¹ represents an alkyl group, j = 1, p = 1, q = 0, r = 2 and n = 1.

A particularly preferred structure is
[I] Het represents a sulfur atom, B ¹ represents a 1,4-phenylene group, B ² represents a trans-cyclohexyl group, and C ¹ represents an alkyl group (preferably a methyl group, an ethyl group, a propyl group, a butyl group). Group, pentyl group or hexyl group), j = 1, p = 2, q = 0, r = 1 and n = 1, the structure represented by the following general formula (a-1),
[2] Het represents a sulfur atom, B ¹ represents a 1,4-phenylene group, B ² represents a trans-cyclohexane-1,4-diyl group, and C ¹ represents an alkyl group (preferably a methyl group or an ethyl group). Group, propyl group, butyl group, pentyl group or hexyl group) and represented by the following general formula (a-2) wherein j = 1, p = 1, q = 0, r = 2 and n = 1. Construction,
It is.

In the general formulas (a-1) and (a-2), R ^{a1 to} R ^a12 each independently represent a hydrogen atom or a substituent. Examples of the substituent include a substituent selected from the aforementioned substituent group V.
R ^{a1 to} R ^a12 are preferably each independently a hydrogen atom, a halogen atom (particularly a fluorine atom), an alkyl group, an aryl group, or an alkoxy group. Among the alkyl groups, aryl groups, and alkoxy groups represented by R ^{a1 to} R ^a12 , preferable ones have the same ^meanings as the alkyl groups, aryl groups, and alkoxy groups described in Substituent Group V above.

In the general formulas (a-1) and (a-2), C ^a1 and C ^a2 each independently represent an alkyl group, preferably an alkyl group having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms. It is. Particularly preferably, it represents a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group or a hexyl group.

The azo dye may be any one such as a monoazo dye, a bisazo dye, a trisazo dye, a tetrakisazo dye, and a pentakisazo dye, but is preferably a monoazo dye, a bisazo dye, or a trisazo dye.
As ring structures contained in azo dyes, aromatic rings (benzene ring, naphthalene ring, etc.) as well as hetero rings (quinoline ring, pyridine ring, thiazole ring, benzothiazole ring, oxazole ring, benzoxazole ring, imidazole ring, benzimidazole) Ring, pyrimidine ring, etc.).

As the substituent of the anthraquinone dye, those containing an oxygen atom, a sulfur atom or a nitrogen atom are preferable, and examples thereof include an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group and an arylamino group.
The substitution number of the substituent may be any number, but di-substitution, tri-substitution, and tetrakis substitution are preferred, and di-substitution and tri-substitution are particularly preferred. The substitution position of the substituent may be any place, but preferably 1,4-position disubstitution, 1,5-position disubstitution, 1,4,5-position trisubstitution, 1,2,4-position trisubstitution, They are 1,2,5-trisubstituted, 1,2,4,5-tetrasubstituted, 1,2,5,6-tetrasubstituted structures.

  The anthraquinone dye is more preferably a compound represented by the following general formula (2), and the phenoxazone dye is more preferably a compound represented by the following general formula (3).

In general formula (2), at least one of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ is-(Het) _j -{(B ¹ ) _p- ( _{^{Q 1) q - (B 2}} ) r} n -C ^1, and others are each independently a hydrogen atom or a substituent.

一般式（３）中、Ｒ^１１、Ｒ^１２、Ｒ^１３、Ｒ^１４、Ｒ^１５、Ｒ^１６及びＲ^１７の少なくとも一つ以上は、−（Ｈｅｔ）_ｊ−｛（Ｂ^１）_ｐ−（Ｑ^１）_ｑ−（Ｂ^２）_ｒ｝_ｎ−Ｃ^１であり、他はそれぞれ水素原子又は置換基である。
ここで、Ｈｅｔ、Ｂ^１、Ｂ^２、Ｑ^１、ｐ、ｑ、ｒ、ｎ、及びＣ^１は、一般式（１）におけるＨｅｔ、Ｂ^１、Ｂ^２、Ｑ^１、ｐ、ｑ、ｒ、ｎ、及びＣ^１と同定義である。

In the general formula (3), at least one of R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _Q- (B ² ) _r } _n -C ¹ , and the others are each a hydrogen atom or a substituent.
Here, Het, B ¹ , B ² , Q ¹ , p, q, r, n, and C ¹ are Het, B ¹ , B ² , Q ¹ , p, q, r, in the general formula (1). n, and a ^{C 1} the same definition.

In the general formula (2), examples of the substituent represented by R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ include the substituent group V described above. An arylthio group having 6 to 80 carbon atoms, more preferably 6 to 40 carbon atoms, still more preferably 6 to 30 carbon atoms (for example, phenylthio, p-methylphenylthio, p-chlorophenylthio, 4-methylphenylthio, 4-ethyl Phenylthio, 4-n-propylphenylthio, 2-n-butylphenylthio, 3-n-butylphenylthio, 4-n-butylphenylthio, 2-t-butylphenylthio, 3-t-butylphenylthio 4-t-butylphenylthio, 3-n-pentylphenylthio, 4-n-pentylphenylthio, 4-amylpentylphenylthio, 4-hexylphenylthio, 4- Ptylphenylthio, 4-octylphenylthio, 4-trifluoromethylphenylthio, 3-trifluoromethylphenylthio, 2-pyridylthio, 1-naphthylthio, 2-naphthylthio, 4-propylcyclohexyl-4′-biphenylthio, 4 -Butylcyclohexyl-4′-biphenylthio, 4-pentylcyclohexyl-4′-biphenylthio, 4-propylphenyl-2-ethynyl-4′-biphenylthio), 1 to 80 carbon atoms, more preferably 1 to 1 carbon atoms. 40, more preferably a heteroarylthio group having 1 to 30 carbon atoms (for example, 2-pyridylthio, 3-pyridylthio, 4-pyridylthio, 2-quinolylthio, 2-furylthio, 2-pyrrolylthio), a substituted or unsubstituted alkylthio group ( For example, methylthio, ethylthio, butylthio Phenethylthio), a substituted or unsubstituted amino group (for example, amino, methylamino, dimethylamino, benzylamino, anilino, diphenylamino, 4-methylphenylamino, 4-ethylphenylamino, 3-n-propylphenylamino, 4-n-propylphenylamino, 3-n-butylphenylamino, 4-n-butylphenylamino, 3-n-pentylphenylamino, 4-n-pentylphenylamino, 3-trifluoromethylphenylamino, 4- Trifluoromethylphenylamino, 2-pyridylamino, 3-pyridylamino, 2-thiazolylamino, 2-oxazolylamino, N, N-methylphenylamino, N, N-ethylphenylamino), a halogen atom (for example, a fluorine atom, Chlorine atom), substituted or not Alkyl group (for example, methyl, trifluoromethyl), substituted or unsubstituted alkoxy group (for example, methoxy, trifluoromethoxy), substituted or unsubstituted aryl group (for example, phenyl), substituted or unsubstituted heteroaryl Groups (eg, 2-pyridyl), substituted or unsubstituted aryloxy groups (eg, phenoxy), substituted or unsubstituted heteroaryloxy groups (eg, 3-thienyloxy), and the like.

R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are preferably hydrogen atom, fluorine atom, chlorine atom, substituted or unsubstituted arylthio group, alkylthio group, amino group, alkylamino Group, arylamino group, alkyl group, aryl group, alkoxy group or aryloxy group, particularly preferably a hydrogen atom, a fluorine atom, a substituted or unsubstituted arylthio group, an alkylthio group, an amino group, an alkylamino group or an arylamino group It is a group.

More preferably, in the general formula (2), at least one of R ¹ , R ⁴ , R ⁵ , and R ⁸ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _q- ( B ²⁾ the case of _{r} n} -C ^1.

In the general formula (3), the substituents represented by R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ are halogen atoms, alkyl groups, aryl groups, alkylthio groups, arylthio groups. , Heterocyclic thio group, hydroxyl group, alkoxy group, aryloxy group, carbamoyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, amide group, particularly preferably a hydrogen atom, a halogen atom, an alkyl group, an arylthio group , An amide group.

R ¹⁶ is preferably an amino group (including alkylamino and arylamino groups), a hydroxyl group, a mercapto group, an alkylthio group, an arylthio group, an alkoxy group, or an aryloxy group, and particularly preferably an amino group.

  Although the specific example of the dichroic dye which can be used for this invention below is shown, this invention is not limited at all by the following specific examples.

  Specific examples of the azo dichroic dye that can be used in the present invention are shown below, but the present invention is not limited to the following specific examples.

  Specific examples of dioxazine dichroic dyes and merocyanine dichroic dyes that can be used in the present invention are shown below, but the present invention is not limited to the following specific examples.

  The dichroic dye having a substituent represented by the general formula (1) can be synthesized by combining known methods. For example, it can be synthesized according to the method described in JP-A No. 2003-192664.

<Bistable nematic liquid crystal>
In the liquid crystal display element of the present invention, a bistable nematic liquid crystal in which the alignment state is stable in the homeotropic state and the planar state is used. A bistable nematic liquid crystal is defined as a nematic liquid crystal in which at least two states exist stably. Bistability means that these states are stable under physical conditions such as temperature, pressure, and humidity. In the case of a nematic liquid crystal, a voltage required for changing the alignment state is lower than that of a cholesteric liquid crystal or a smectic liquid crystal. Further, when combined with a chiral agent, there is an advantage that a helical structure is easily formed and display performance is improved.

  As the bistable nematic liquid crystal state, in the present invention, a homeotropic state, that is, a vertical alignment state or a nearly vertical alignment state (hereinafter sometimes referred to as “substantially vertical alignment state”), a planar state, that is, a horizontal alignment or A nearly horizontal alignment state (hereinafter sometimes referred to as “substantially horizontal alignment state”) is bistable. When absorption of the dichroic dye is considered to be bistable between the substantially vertical alignment state and the substantially horizontal alignment state, the light is efficiently emitted because the substantially vertical alignment state corresponds to the white background state and the substantially horizontal alignment state corresponds to the colored state. It is preferable from the viewpoint of controlling the transmission and absorption of light and increasing the contrast ratio in display performance.

  The substantially vertical alignment state means that the director of the liquid crystal is in the range of 75 to 90 ° with respect to the substrate, preferably in the range of 80 to 90 °, more preferably 85 to 90 °. This is the case in the range of 90 °. The substantially horizontal alignment state means that the director of the liquid crystal is in the range of 0 to 15 ° with respect to the substrate, preferably in the range of 0 to 10 °, more preferably 0 to 0 °. This is the case in the range of 5 °. By applying a voltage, the angle of change when the state is changed between the substantially vertical alignment state and the substantially horizontal alignment state is increased, so that the contrast ratio is increased, which is a preferable mode.

In order to make the substantially vertical alignment state and the substantially horizontal alignment state bistable, specifically, the alignment film and the hydrophilicity / hydrophobicity of the liquid crystal are appropriately combined, the pretilt angle is optimized, the amount of chiral agent added It is preferable to optimize the torsional force of the chiral nematic liquid crystal by adjusting. The pretilt angle is preferably in the range of 75 to 90 °.
In the case of using an alignment film, for example, if an alignment film is provided so that nematic liquid crystal having positive dielectric anisotropy is aligned horizontally, the horizontal alignment state is stable when no voltage is applied, and Since the rate anisotropy is positive, the state in which the liquid crystal molecules are tilted vertically is stable. On the other hand, the host liquid crystal having a negative dielectric anisotropy has a stable state in which the liquid crystal molecules are horizontally inclined when a voltage is applied, and therefore includes an alignment film so that it is vertically aligned when no voltage is applied. As described above, it is preferable to provide an alignment film so that a stable alignment state can be obtained even when no voltage is applied to a stable alignment state when a voltage is applied.

  When the alignment film is used, in order for the substantially vertical alignment state and the substantially horizontal alignment state to be more bistable, it is preferable to optimize the so-called anchoring force that the alignment film regulates the alignment of the liquid crystal molecules. That is, a condition where the anchoring forces in the substantially vertical alignment state and the substantially horizontal alignment state are substantially balanced is preferable. As a means for optimizing the anchoring force, there is a method of optimizing according to the host liquid crystal using the hydrophilicity / hydrophobicity of the alignment film, the strength of rubbing treatment, and the like.

  In the liquid crystal display element of the present invention, it is preferable to form an alignment-treated layer (alignment film) on the surface where the support is in contact with the liquid crystal layer. Examples of the alignment treatment include a method of applying and aligning a quaternary ammonium salt, a method of applying polyimide and aligning by rubbing treatment, a method of aligning and depositing SiOx from an oblique direction, and further utilizing photoisomerization. And an alignment method by light irradiation. As the alignment film, for example, those described in pages 240 to 256 of “Liquid Crystal Device Handbook” (edited by Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989) are used.

  The alignment film is preferably a polyimide alignment film, a polyimide vertical alignment film, and more preferably a polyimide vertical alignment film subjected to rubbing treatment. In the case of a polyimide alignment film, the anchoring force is strong, it is easy to align liquid crystal molecules in a desired alignment, and it is preferable because it has a high insulating property and a long lifetime of the device. In addition, vertical alignment is preferable because the absorption by the dichroic dye in the transmissive state (white display) can be reduced, and the contrast ratio of the display can be increased. In particular, a polyimide vertical alignment film subjected to a rubbing treatment is suitable for the present invention because bistability in a substantially vertical alignment state and a substantially horizontal alignment state is increased. Specifically, as the polyimide vertical alignment film subjected to the rubbing treatment, a polyimide vertical alignment film manufactured by Nissan Chemical Co., a polyimide vertical alignment film manufactured by JSR, a polyimide vertical alignment film manufactured by Chisso, and the like are suitable. Regarding the rubbing treatment, it is preferable to suitably optimize the rubbing direction and the rubbing strength of the substrate so that the bistability in the substantially vertical alignment state and the substantially horizontal alignment state is enhanced.

  In order to drive the bistable nematic liquid crystal and the dichroic dye appropriately, it is preferable to use a dual frequency driving method.

In order to form a bistable state of a bistable nematic liquid crystal, it is preferable to use a chiral nematic liquid crystal formed from a chiral agent and a nematic liquid crystal. In the case of chiral nematic liquid crystal, the liquid crystal has a helical structure, and the torsional force and the anchoring force from the alignment film are balanced, so that bistability is increased and a bistable state can be formed.
Examples of the chiral agent include TN and STN chiral agents described on pages 199 to 202 of “Liquid Crystal Device Handbook” (edited by Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989).

  As a preferred embodiment of the present invention, a mode using a chiral nematic liquid crystal phase to which a chiral compound is added is used. As the chiral compound, for example, R-811, S-811, R-1082, S-1082 manufactured by Merck & Co., Inc. can be used. The ratio of the chiral compound is preferably 0.01 to 15% by mass, particularly preferably 0.5 to 6% by mass in the liquid crystal layer. The display performance is enhanced by using the chiral compound in combination.

  Furthermore, the bistable nematic liquid crystal of the present invention is preferably a liquid crystal exhibiting dual-frequency drive. Dual frequency drive liquid crystal indicates positive dielectric anisotropy when the frequency of the electric field applied to the liquid crystal is in the low frequency region, and the sign of the dielectric anisotropy is reversed negative in the high frequency region. It is a liquid crystal. By using the dual-frequency driving liquid crystal, it is possible to reversibly change two or more bistable states by switching the frequency. It is also preferable from the viewpoint of high-speed response.

  When a normal single-frequency driving liquid crystal is used, it is difficult to switch the bistable state, and thus a dual-frequency driving liquid crystal is preferable.

  The dual frequency drive liquid crystal is described in detail in the 142th Committee of the Japan Society for the Promotion of Science, Liquid Crystal Device Handbook, Nikkan Kogyo Shimbun, 1989, pages 189 to 192, and these can be appropriately applied in the present invention. As a specific example of the dual frequency drive liquid crystal, the following dual frequency drive liquid crystal 1 manufactured by Aldrich is shown.

Furthermore, examples of commercially available dual-frequency drive liquid crystal materials include DF-02XX, DF-05XX, FX-1001, FX-1002, and Merck MLC-2048 manufactured by Chisso.
Specific examples of the skeleton include azomethine compounds, cyanobiphenyl compounds, cyanophenyl esters, fluorine-substituted phenyl esters, cyclohexanecarboxylic acid phenyl esters, fluorine-substituted cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane, fluorine-substituted phenylcyclohexanes, cyano-substituted phenylpyrimidines, Fluorine-substituted phenylpyrimidine, alkoxy-substituted phenylpyrimidine, fluorine-substituted alkoxy-substituted phenylpyrimidine, phenyldioxane, tolan compounds, fluorine-substituted tolane compounds, alkenylcyclohexylbenzonitrile, and the like.

  The dual frequency drive liquid crystal used in the present invention may be a mixture of a plurality of liquid crystal compounds. Furthermore, a liquid crystal compound in which the sign of dielectric anisotropy is not reversed between the low frequency region and the high frequency region of the applied electric field may be included.

  The frequency region of the electric field applied to the liquid crystal is preferably in the range of 0.1 Hz to 10 MHz, and more preferably 1 Hz to 1 MHz. Here, 0.1 Hz to 100 kHz is used as the low frequency region, preferably 1 Hz to 10 kHz, and more preferably 10 Hz to 10 kHz. 100 Hz to 10 MHz, preferably 100 Hz to 1 MHz, and more preferably 1 kHz to 1 MHz is used as the high frequency region.

  In the present invention, for the purpose of changing the physical properties of the host liquid crystal (in this specification, the host liquid crystal means a bistable nematic liquid crystal unless otherwise specified) within a desired range (for example, the liquid crystal phase For the purpose of adjusting the temperature range to a desired range), a compound that does not exhibit liquid crystallinity may be added. Moreover, you may contain compounds, such as a ultraviolet absorber and antioxidant.

  Although there is no restriction | limiting in particular about content of a host liquid crystal and a dichroic dye in the liquid crystal element of this invention, Content of a dichroic dye is 0.1-15 mass% with respect to content of a host liquid crystal. It is preferably 0.5 to 6% by mass. In addition, the content of the host liquid crystal and the dichroic dye is adjusted to a liquid crystal composition including both, and the absorption spectrum of the liquid crystal cell in which the liquid crystal composition is sealed is measured to obtain a desired optical density as the liquid crystal cell. It is desirable to determine the dye concentration necessary to indicate.

(substrate)
As the electrode substrate, a substrate in which an electrode layer is formed on a substrate usually made of glass or plastic can be used. Examples of the plastic substrate include acrylic resin, polycarbonate resin, epoxy resin, PES, and PEN. As the substrate, for example, those described in pages 218 to 231 of “Liquid Crystal Device Handbook” (Japan Society for the Promotion of Science 142nd edition, Nikkan Kogyo Shimbun, 1989) can be used. The electrode layer formed on the substrate is preferably a transparent electrode layer. For example, it can be formed from indium oxide, indium tin oxide (ITO), tin oxide, or the like. As for the transparent electrode, for example, those described in pages 232 to 239 of “Liquid Crystal Device Handbook” (edited by the Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989) are used.

(Liquid crystal display element)
The liquid crystal display element of the present invention is produced, for example, by placing a pair of substrates facing each other at an interval of 1 to 50 μm via a spacer and arranging the liquid crystal composition of the present invention in a space formed between the substrates. Can do. As the spacer, for example, those described in pages 257 to 262 of “Liquid Crystal Device Handbook” (edited by Japan Society for the Promotion of Science 142nd Committee, Nikkan Kogyo Shimbun, 1989) can be used. The liquid crystal composition of the present invention can be disposed in a space between substrates by coating or printing on the substrates.

  The liquid crystal display element of the present invention can be driven by a simple matrix driving method or an active matrix driving method using a thin film transistor (TFT). The simple matrix driving method is preferable from the viewpoint of being able to manufacture at a low cost, and the active matrix driving method is preferable from the viewpoint of being able to perform high-quality display. The driving method is described in detail, for example, on pages 387 to 460 of “Liquid Crystal Device Handbook” (edited by the 142th Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, 1989). Available as a method. In particular, as a dual frequency driving method in a simple matrix, methods disclosed in Japanese Patent Laid-Open Nos. 54-84995, 61-16988, and 2002-149130 can be used.

  In the liquid crystal element of the present invention, a plurality of dichroic dyes may be mixed in one liquid crystal composition. The color of the liquid crystal composition may be anything.

  The liquid crystal display element of the present invention provides high display performance, is excellent in visibility, has a high response speed, and can be easily manufactured. In addition, it has low memory consumption due to its memory characteristics. Therefore, the liquid crystal display element of the present invention can be suitably used as a point card, a material used only temporarily, and a medium for displaying an image as a rewritable display medium.

  The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios, operations, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples. .

[Example 1]
<Production of display element>
1. Preparation of Dichroic Dye and Liquid Crystal The dichroic dyes (1-2) and (1-8) of the specific examples were synthesized according to the method described in JP-A No. 2003-192664. The dichroic dye (1-13) was synthesized according to the method described in JP-A-2005-120334. As the nematic liquid crystal exhibiting dual frequency, the dual-frequency driving liquid crystal 1 (commercially available, manufactured by Aldrich) of the above-described specific example compound was used. As the chiral agent R-811, a commercially available product (manufactured by Aldrich) was used.

2. Preparation of liquid crystal composition In the combinations shown in Table 1 below, the dichroic dye and the chiral agent R-811 were heated and dissolved in 1.0 g of the above-mentioned dichroic liquid crystal 1 for 1 day at room temperature. Liquid crystal compositions A, B, and C were prepared by allowing to stand. The chiral agent R-811 was added to 1.2% by mass in the liquid crystal composition, and each dichroic dye was added to the liquid crystal evaluation cell having a thickness of 8 μm. The absorbance was adjusted to 0.8 when injected.

3. Preparation of Liquid Crystal Display Element A polyimide vertical alignment film (JSR, JALS-2021) was attached on a glass substrate with ITO, which is a transparent electrode, by spin coating and baking. Next, the obtained glass substrate with a vertical alignment film was rubbed.
A small amount of an 8 μm spherical spacer (manufactured by Sekisui Chemical Co., Ltd.) is mixed with any one of the obtained liquid crystal compositions A to C, and the glass substrate with ITO is placed so that the alignment film side is in contact with the liquid crystal layer. Sealed with a photo-curing sealant (manufactured by Sekisui Chemical). The rubbing directions were parallel to each other.
As the scattering white layer, a coating liquid prepared by dispersing a white pigment made of titanium oxide whose surface activity has been eliminated by surface treatment together with 5% by mass of carboxycellulose is applied to the surface of the glass substrate that is not in contact with the liquid crystal. Thus, liquid crystal display elements-1 to 3 were produced.

4). Evaluation When a low frequency voltage (20 V, 60 Hz) is applied to each of the obtained liquid crystal display elements 1 to 3 of the present invention using a signal generator (manufactured by Tektronix), the liquid crystal layer is transparent, That is, it was confirmed that the white state was maintained and the white state was maintained even after the voltage application was stopped. Further, when a high frequency voltage (20 V, 100 kHz) was applied, the liquid crystal layer was in a colored state, and it was confirmed that the colored state was maintained even after the voltage application was stopped. This liquid crystal was confirmed to have a pretilt angle of 4 ° by a pretilt angle measuring device (PAS-301, manufactured by Toyo Technica). Both the homeotropic state (white state) and the planar state (colored state) were left at room temperature for one day. However, since it was confirmed that the display performance did not change visually, it was also confirmed to be bistable.

It was confirmed that the liquid crystal display element of the present invention produced in Example 1 gave a white background that was gentle to the eyes with small viewing angle dependence based on scattering.
Further, when the switching speed was measured with MCPD3000 manufactured by Otsuka Electronics, the process in both directions was 20 ms or less, and it was confirmed that a high-speed response was possible.

  From the above results, the liquid crystal display element of the present invention in the examples does not require a polarizing plate, has excellent visibility giving a scattered white background similar to paper, has high-speed response, and is in the previous state even when no voltage is applied. It has been confirmed that the display element has a very low power consumption because it has a memory property to maintain the above.

[Example 2]
1. Production of Plastic Substrate An undercoat layer and a back layer were produced for PEN (Dupont-Teijin Q65A) in the same manner as in the production of Sample A in Example 1 of JP-A-2000-105445. That is, 100 parts by weight of polyethylene-2,6-naphthalate polymer and Tinuvin P.I. 326 (manufactured by Ciba-Geigy Ciba-Geigy) was dried, melted at 300 ° C., extruded from a T-die, and stretched 3.3 times at 140 ° C., followed by 130 The plastic substrate (PEN) of the present invention having a thickness of 90 μm was obtained by performing transverse stretching 3.3 times at 250 ° C. and further heat-fixing at 250 ° C. for 6 seconds.

2. Production of Transparent Electrode Layer Conductive indium tin oxide was coated on one side of the plastic substrate obtained above, and a uniform thin film having a thickness of 200 nm was laminated. The surface resistance was about 20 Ω / cm ² , and the light transmittance (500 nm) was 85%. Next, the indium tin oxide thin film was patterned into a stripe shape (width 100 μm, interval 10 μm) by photolithography to form a transparent electrode layer.

(Preparation of guest-host type liquid crystal layer)
By the same operation as Example 1 using the said support body, the liquid crystal display elements -4-6 of this invention were produced using said liquid-crystal composition AC.

(Evaluation of display performance)
When the obtained liquid crystal display elements -4 to 6 of the present invention were evaluated in the same manner as in Example 1, the same results as in the liquid crystal display element produced in Example 1 were obtained.

Claims (12)

  A liquid crystal having a liquid crystal layer comprising at least one dichroic dye and a bistable nematic liquid crystal in which each alignment state is stable in a homeotropic state and a planar state between a pair of electrodes, at least one of which is a transparent electrode Display element.   The liquid crystal display element according to claim 1, wherein the liquid crystal layer contains at least one chiral agent.   The liquid crystal display element according to claim 1, wherein the bistable nematic liquid crystal is a chiral nematic phase.   The liquid crystal display element according to claim 1, wherein the liquid crystal display element has at least one kind of alignment film.   The liquid crystal display element according to claim 4, wherein the alignment film is at least one kind of polyimide alignment film.   The liquid crystal display element according to claim 5, wherein the alignment film is at least one kind of vertical polyimide alignment film.   The liquid crystal display element according to claim 1, wherein a pretilt angle of the bistable nematic liquid crystal is in a range of 75 ° to 90 °.   The liquid crystal display element according to claim 4, wherein the alignment film is at least one kind of rubbing-treated alignment film.   The liquid crystal display element according to any one of claims 1 to 8, wherein the bistable nematic liquid crystal exhibits dual-frequency drivability. The liquid crystal display element according to any one of claims 1 to 9, wherein the dichroic dye has a substituent represented by the following general formula (1).
Formula ^{_{(1): - (Het)}} j - {(B 1) p - (Q 1) q - (B 2) r} n -C 1
[In the formula, Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group or a divalent cyclic aliphatic hydrocarbon group, and Q ¹ represents a divalent group. Represents a linking group, C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, p, q and r each independently represents 0 to 1; 5 represents an integer of 5, n represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q, and r are each 2 or more, 2 or more B ¹ , Q ¹ And B ² may be the same or different. When n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } are the same or different. May be. ] The liquid crystal display element according to any one of claims 1 to 10, wherein at least one of the dichroic dyes is a compound represented by the following general formula (2).

[Wherein, at least one of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _q - ^(B _{2) r}} n -C ^1, and others are each independently a hydrogen atom or a substituent. Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group, or a divalent cyclic aliphatic hydrocarbon group, and Q ¹ represents a divalent linking group. , C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, and p, q and r each independently represents an integer of 0 to 5. N represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q and r are each 2 or more, 2 or more B ¹ , Q ¹ and B ² are Each may be the same or different, and when n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } may be the same or different. ] The liquid crystal display element according to claim 1, wherein at least one of the dichroic dyes is a compound represented by the following general formula (3).

[In the formula, at least one of R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ is-(Het) _j -{(B ¹ ) _p- (Q ¹ ) _q- ( B ²⁾ _{r} n} -C ^1, and others are each independently a hydrogen atom or a substituent. Het is an oxygen atom or a sulfur atom, B ¹ and B ² each independently represent an arylene group, a heteroarylene group, or a divalent cyclic aliphatic hydrocarbon group, Q ¹ represents a divalent linking group, and C 1 ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group, j represents 0 or 1, p, q and r each independently represents an integer of 0 to 5; n represents an integer of 1 to 3, (p + r) × n is an integer of 3 to 10, and when p, q and r are each 2 or more, 2 or more B ¹ , Q ¹ and B ² are the same However, when n is 2 or more, two or more {(B ¹ ) _p- (Q ¹ ) _q- (B ² ) _r } may be the same or different. ]