JP2012031384A - Dichroic dye, liquid crystal composition containing the same, and liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a guest-host type liquid crystal composition having a high dichroic ratio over a wavelength range of 400-650 nm, and to provide a dichroic dye composition used therefor.SOLUTION: The dichroic dye composition contains at least one kind of a dichroic dye from each group, shown by (I)-(IV) groups: (I) a dichroic azo dye is a monoazo dye formed by connecting two benzene rings by an azo group, and having an amino group; (II) a dichroic azo dye is a disazo dye formed by connecting a benzene ring to a naphthalene ring by an azo group, and having an amino group in the benzene ring; (III) a dichroic azo dye is a disazo dye formed by connecting a benzene ring to a naphthalene ring by an azo group, and having an amino group in the benzene ring; and (IV) a dichroic azo dye is a trisazo dye formed by connecting one benzene ring to three naphthalene rings by an azo group, and having a structure in which naphthalene rings on both terminals have each an amino group.

Description

  The present invention relates to a dichroic dye composition and a guest-host type liquid crystal composition used for a liquid crystal element used for a display element, a light control element and the like.

A liquid crystal device with a liquid crystal composition sandwiched between electrodes is a display device such as a notebook personal computer or a personal digital assistant (PDA), a camera finder whose view can be switched, etc. Are widely used, and its application range is expanding year by year.
Most of the liquid crystal elements currently used are TN type and STN type. However, since these elements use polarizing plates, there is a drawback that the light utilization efficiency is low. On the other hand, a liquid crystal element to which a guest-host type liquid crystal composition using a dichroic dye applies absorption anisotropy of the dichroic dye has a high light utilization efficiency without using a polarizing plate. In the case of a reflective display element that does not use a backlight, bright display is possible.

Dichroic dyes exhibit various absorption characteristics depending on the dye structure, but many of them absorb specific wavelengths such as red, blue, and yellow. Therefore, in order to obtain a composition that absorbs light in a wide wavelength region, it is usually necessary to mix a plurality of dichroic dyes.
As a dichroic dye composition exhibiting high dichroism in a wide wavelength range, for example, Patent Document 1 discloses a dichroic dye composition containing at least two kinds of disazo dyes having a specific structure and a tetrakisazo dye having a specific structure. Has been proposed.

JP 2008-179670 A

However, the guest-host type liquid crystal composition including the dichroic dye composition proposed in Patent Document 1 is not yet a sufficient value for the dichroic ratio according to the evaluation by the present inventors. It was causing a decline. In particular, according to the study by the present inventors, the dichroic dye is required to be further improved in terms of the dichroic ratio in the particularly important visible light wavelength region of 500 to 650 nm. .
The present invention has been made in view of the above circumstances, and an object thereof is to provide a dichroic dye composition capable of providing a guest-host type liquid crystal composition exhibiting a high dichroic ratio in a wide wavelength region. And Especially, it aims at providing the dichroic dye composition which can provide the guest host type liquid crystal composition excellent in the dichroic ratio in 500-650 nm which is an important visible light wavelength range. Furthermore, it aims at providing the liquid crystal composition containing this dichroic dye composition, and a liquid crystal.

  As a result of intensive studies to provide a dichroic dye composition used in a guest-host type liquid crystal composition exhibiting a high dichroic ratio in a wide wavelength region, in particular, the present inventors have provided a contrast ratio of a guest-host type display element. The inventors have found that the dichroic ratio of the guest-host type liquid crystal composition is improved by using at least four kinds of dichroic dyes having a specific molecular structure, and the present invention has been achieved. Above all, by combining a dichroic dye composition containing at least four kinds of dichroic dyes having the specific molecular structure with a fluorine-based liquid crystal material, the dichroic ratio of the guest-host type liquid crystal composition is improved I found.

That is, the gist of the present invention is as follows.
[1] A dichroic dye composition comprising at least one dichroic dye represented by the following groups (I) to (IV) from each group.

(In the formulas [I] to [IV], X ^{1 to} X ⁸ each independently represent a group represented by the following formula [a]. Represented by the general formula [a] of X ^{1 to} X ^8. The groups may be the same or different from one another.
Moreover, the benzene ring and / or naphthalene ring connected by an azo group may further have a substituent.

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, and ring A and ring B may each independently have a substituent 1,4. -A phenylene group or an optionally substituted cyclohexane-1,4-diyl group, L is a divalent linking group, p is 0, 1 or 2, and q and r are each independently Is 0 or 1. When p is 2, the two rings A may be the same or different, and the 1,4-phenylene group and cyclohexane-1, which are included in the formula [a] The total number of 4-diyl groups is 1
Or when 2 and q = 0, both 1,4-phenylene group and cyclohexane-1,4-diyl group are regarded as ring A. ))
[2] The dichroic dye composition according to the above [1], wherein p is 1 or 2.
[3] The dichroic dye composition as described in [1] and [2] above, wherein in formula [a], ring A to which R is linked is a cyclohexane-1,4-diyl group.
[4] The dichroic dye composition as described in any one of [1] to [3], wherein in the formula [a], R is a linear alkyl group having 2 to 8 carbon atoms.
[5] The dichroic dye composition according to any one of [1] to [4], further comprising at least one dye represented by the following group (V):

(In Formula [V], X < ⁹ > -X < ¹⁰ > shows group represented by the following formula [a] each independently, and A shows a hydrogen bond substituent substituent.
Moreover, the benzene ring and / or naphthalene ring connected by an azo group may further have a substituent.

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, and ring A and ring B may each independently have a substituent 1,4. -A phenylene group or an optionally substituted cyclohexane-1,4-diyl group, L is a divalent linking group not containing a cyclic structure, p is 0, 1 or 2, q And r are each independently 0 or 1. When p is 2, the two rings A may be the same or different, and the 1,4-phenylene group included in the formula [a] And the cyclohexane-1,4-diyl group is 1 or 2, and q = 0, the 1,4-phenylene group and the cyclohexane-1,4-diyl group are both ring A and I reckon.))
[6] A guest-host type liquid crystal composition comprising the dichroic dye composition according to any one of [1] to [5] above and a host liquid crystal.
[7] The liquid crystal composition as described in [6] above, wherein the host liquid crystal is a fluorine-based liquid crystal.
[8] A liquid crystal device, wherein the guest-host type liquid crystal composition according to [6] or [7] is sandwiched between a pair of electrode substrates, at least one of which is transparent.

According to the present invention, a dichroic dye composition capable of providing a guest-host type liquid crystal composition having a high dichroic ratio in a wavelength region of 450 to 600 nm, further 400 to 650 nm, and the dichroic dye composition A guest-host liquid crystal composition and a liquid crystal are provided. In particular, the dichroic dye composition of the present invention has an effect of being excellent in the dichroic ratio in an important visible light wavelength region of 500 to 650 nm.

Embodiments of the present invention will be specifically described below, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.
The liquid crystal composition of the present invention is effective by a combination of the dichroic dyes represented by the groups (I) to (IV) or the groups (I) to (V).
[I. Dichroic dye composition]
[I-1: Dichroic dye]
Dichroic dyes (I) to (IV) included in the dichroic dye composition of the present invention, and dichroic dyes of the present invention including dichroic dyes (I) to (IV) Preferred dichroic dye groups (V) contained in the dye composition are represented by the following formulas [I] to [V], respectively.

(In the formulas [I] to [V], X ^{1 to} X ¹⁰ each independently represent a group represented by the following formula [a], and A represents a hydrogen bonding substituent.
Moreover, the benzene ring and / or naphthalene ring connected by an azo group may further have a substituent.

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, and ring A and ring B may each independently have a substituent 1,4. -A phenylene group or an optionally substituted cyclohexane-1,4-diyl group, L is a divalent linking group, p is 0, 1 or 2, and q and r are each independently Is 0 or 1. When p is 2, the two rings A may be the same or different, and the 1,4-phenylene group and cyclohexane-1, which are included in the formula [a] When the total number of 4-diyl groups is 0, 1 or 2, and q = 0, both 1,4-phenylene groups and cyclohexane-1,4-diyl groups are regarded as ring A.)

<Basic structure of general formula [I]>
The dichroic azo dye represented by the general formula [I] is usually a yellow color when the two benzene rings are linked by an azo group and is a monoazo dye having the above skeleton having an amino group.
<Basic structure of general formula [II]>
The dichroic azo dye of the general formula [II] is a disazo dye having the above structure in which a benzene ring and a naphthalene ring are connected by an azo group and the benzene ring has an amino group, and thus usually exhibits a yellow color. .

<Basic structure of general formula [III]>
The dichroic azo dye represented by the general formula [III] is a disazo dye having the above structure in which a benzene ring and a naphthalene ring are connected by an azo group and the benzene ring has an amino group, and usually exhibits a yellow color. .
<Basic structure of general formula [IV]>
The dichroic azo dye of the general formula [IV] is a trisazo dye having the above structure in which one benzene ring and three naphthalene rings are connected by an azo group, and both naphthalene rings at both ends have an amino group, Usually, it exhibits a blue color.

<Basic structure of general formula [V]>
The dichroic azo dye of the general formula [V] has one benzene ring, a sulfur atom and a nitrogen atom.
The dissociative dye having the above structure in which a fused heterocyclic ring and one naphthalene ring are connected by an azo group, and the terminal naphthalene ring has an amino group, usually exhibits a blue color.
<For ^X 1 ^{~X 10>}
In the general formulas [I] to [IV], X ^{1 to} X ¹⁰ each independently represent a group represented by the following formula [a].

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, and ring A and ring B may each independently have a substituent 1,4. -A phenylene group or an optionally substituted cyclohexane-1,4-diyl group, L is a divalent linking group not containing a cyclic structure, p is 0, 1 or 2, q And r are each independently 0 or 1. When p is 2, the two rings A may be the same or different, and the 1,4-phenylene group included in the formula [a] And cyclohexane-1,4-diyl group is 0, 1 or 2, and q = 0, both 1,4-phenylene group and cyclohexane-1,4-diyl group are ring Considered A.)

(About R)
In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms.
Examples of the alkyl group having 1 to 12 carbon atoms include linear or branched groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an octyl group, and a dodecyl group.
As an example of a C1-C12 alkoxy group, linear or branched things, such as a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, an octoxy group, are mentioned.
From the viewpoint of the dichroic ratio, a linear alkyl group having 2 to 8 carbon atoms or a linear alkoxy group having 2 to 8 carbon atoms is preferable, and a linear alkyl group having 3 to 8 carbon atoms or 3 carbon atoms is more preferable. A linear alkoxy group having 8 to 8 carbon atoms, and a linear alkyl group having 3 to 8 carbon atoms is particularly preferable.

(About ring A and ring B)
Ring A and ring B are each independently a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent.
The substituent that the 1,4-phenylene group or the cyclohexane-1,4-diyl group of ring A and ring B may have is not particularly limited as long as it does not decrease the dichroic ratio. A methoxy group; a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom; and a fluoromethyl group such as a monofluoromethyl group, a difluoromethyl group or a trifluoromethyl group. From the viewpoint of the dichroic ratio, a methyl group, a methoxy group, and a fluoromethyl group are preferable, and a methyl group, a methoxy group, and a trifluoromethyl group are more preferable.
Of the rings A, the ring A to which the substituent R is linked is preferably a cyclohexane-1,4-diyl group from the viewpoint of solubility in the host liquid crystal.

(About L)
L is a divalent linking group and does not contain a cyclic structure. The divalent linking group for L is not particularly limited as long as it does not decrease the dichroic ratio, and any one can be used, but the number of constituent atoms in the linking direction is preferably 1 to 4.
Specifically, an alkylene group, alkenylene group, alkynylene group, alkyleneoxy group (-alkylene-O-), oxyalkylene group (-O-alkylene-), ester group (carbonyloxy group (provided that the oxy group is ring B) Oxycarbonyl group (wherein the oxy group is bonded to ring A)), or a combination thereof. As the alkylene group, a linear or branched alkylene group having 1 to 4 carbon atoms such as a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, and a tert-butylene group. As the alkenylene group, a linear or branched chain having 2 to 4 carbon atoms such as vinylene group, propenylene group, isopropenylene group, butenylene group, isobutenylene group, sec-butenylene group, tert-butenylene group, etc. An alkenylene group is exemplified, and examples of the alkynylene group include a linear or branched chain having 2 to 4 carbon atoms such as an ethynylene group, a propynylene group, an isopropynylene group, a butynylene group, an isobutynylene group, a sec-butynylene group, and a tert-butynylene group. The alkynylene group is an alkyleneoxy group. An alkyleneoxy group having 1 to 4 carbon atoms of an Si group or an ethyleneoxy group, and examples of the oxyalkylene group include an oxyalkylene group having 1 to 4 carbon atoms such as an oxymethylene group and an oxyethylene group. , An oxycarbonyl group, a methyleneoxycarbonyl group, an ethyleneoxycarbonyl group, a propyleneoxycarbonyl group, an isopropyleneoxycarbonyl group, an oxycarbonyl group optionally substituted with an alkylene group such as a tert-butyleneoxycarbonyl group, and a carbonyloxy group And a carbonyloxy group which may be substituted with an alkylene group such as a methylenecarbonyloxy group.
Among these, those having 2 constituent atoms in the connecting direction are more preferable, and for example, an ethylene group, a vinylene group, an ethynylene group, an oxycarbonyl group, a carbonyloxy group, a methyleneoxy group, or an oxymethylene group is preferable. Most preferred is a —CH ₂ O— group, a —OCH ₂ — group or a —C≡C— group.

(About p, q, r)
p is 0, 1 or 2, and 1 or 2 is preferable from the viewpoint of high contrast and solubility in liquid crystals. However, when the dye is a general formula [V], p is preferably 0 or 1.
q and r are each independently 0 or 1. When p is 2, the two rings A may be the same or different.
In addition, when the total number (p + r) of the 1,4-phenylene group and cyclohexane-1,4-diyl group included in the formula [a] is 1 or 2, and q = 0, 1,4- Both the phenylene group and the cyclohexane-1,4-diyl group are regarded as ring A.
(Example of preferred structure of X ^{1 to} X ¹⁰ )
^Hereinafter, examples of the preferred structure of X 1 ^{to X 10.}

In the above structure, R ^{1 to} R ¹⁴ each independently represents an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. Specific examples of the alkyl group having 1 to 12 carbon atoms or the alkoxy group having 1 to 12 carbon atoms include those described above as specific examples of R. R ^{1 to} R ¹⁴ are preferably a linear alkyl group having 3 to 8 carbon atoms or a linear alkoxy group having 3 to 8 carbon atoms, and more preferably a linear alkyl group having 3 to 8 carbon atoms. The 1,4-cyclohexylidene group in the formula may be a cis isomer, a trans isomer or a mixture thereof, but a trans isomer is preferred.

Hereinafter, among the preferred structure of the ^X 1 ^{to X 10,} showing the structure particularly suitably used in the X 1 ^{to X 10} each.
The substituent X ^{1 in} the general formula [I] is p = 1 or 2 and q = r = 0 from the viewpoint of the production method of the compound, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Among them, the following substituents are preferable.

The substituent X ^{2 in} the general formula [I] is p = 2 or 3 and q = r = 0 from the viewpoint of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Or those having p = 2 and q = r = 1 are preferable, and the following substituents are particularly preferable.

The substituent X ^{3 in} the general formula [II] is p = 1 or 2 and q = r = 0 from the viewpoint of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Among them, the following substituents are preferable.

As the substituent X ^{4 in} the general formula [II], p = 1, 2 or 3 and q = r = 0 from the viewpoint of the production method of the compound, stability, dichroic ratio, solubility in the host liquid crystal and the like. In particular, the following substituents are preferable.

The substituent X ^{5 in} the general formula [III] is p = 1 to 3 and q = r = 0 from the viewpoint of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Or those having p = 2 and q = r = 1 are preferable, and the following substituents are particularly preferable.

The substituent X ⁶ of the general formula [III] is p = 1 to 3 and q = r = 0 from the viewpoint of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Among them, the following substituents are preferable.

The substituents X ⁷ and X ^{8 in} the general formula [IV] include p = 2 or 3 and q = r from the viewpoint of the production method of the compound, stability, dichroic ratio, solubility in the host liquid crystal, and the like. = 0 or p = 2 and q = r = 1 are preferable, and the following substituents are particularly preferable. X ⁷ and X ⁸ may be the same or different, but the same is preferable because the synthesis is easy.

As the substituents X ⁹ and X ^{10 in} the general formula [V], p = 1 or 2, q = 0 or from the viewpoint of the production method, stability, dichroic ratio, solubility in the host liquid crystal and the like of the compound 1 and r = 0 or p = q = r = 0 are preferable, and the following substituents are particularly preferable. X ⁹ and X ¹⁰ may be the same or different.

Incidentally, ^R 1 ^{to R 14} in the above illustration of preferred substituents ^X 1 ^{to X 10} is a Arukoshikishi for the alkyl group or 2 to 8 carbon atoms having 2 to 8 carbon atoms.

<Substituent which the benzene ring and / or naphthalene ring linked by an azo group may have>
In the general formulas [I] to [V], the benzene ring and / or naphthalene ring connected by an azo group may further have a substituent. Such a substituent is not particularly limited as long as it does not interfere with the performance of the dichroic dye. For example, a methyl group; a methoxy group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom; and a monofluoromethyl group And fluoromethyl groups such as a difluoromethyl group and a trifluoromethyl group. From the viewpoint of the dichroic ratio, a methyl group, a methoxy group, and a trifluoromethyl group are preferable.

<About A in General Formula [V]>
A represents a hydrogen bonding substituent. The hydrogen-bonding substituent is not particularly limited as long as it is a substituent that can form a hydrogen bond between molecules or within a molecule. For example, hydrogen that can form a hydrogen bond with nitrogen, oxygen, sulfur, halogen, etc. is at least 1 And the hydrogen is usually
The electron density is lower than that of a hydrogen atom bonded to aliphatic carbon. Examples of such a hydrogen bonding substituent represented by A having hydrogen include —NH ₂ , an alkylamino group,
-SH, -OH, carboamide group, -NH-C (= R) NH 2 (R represents an oxygen atom or an imino _{group.), - NH-COCF 3} , such as a sulfonamide group, and among them -OH
The group is particularly preferred.

<Specific examples of dichroic dye>
Although the example of the pigment | dye of each group which can be used by this invention is shown collectively below, unless it exceeds the summary of this invention, it is not limited to these.
(I) Group In order from the left, an arbitrary partial structure represented by formula [b] described later, an arbitrary partial structure represented by formula [d] described later, and a formula [c] described later All structures in which three partial structures of an arbitrary partial structure are combined in an arbitrary combination (II) group A partial structure represented by formula [b] and an arbitrary partial structure represented by formula [e] in order from the left And any structure in which three partial structures of an arbitrary partial structure represented by the formula [c] are combined in an arbitrary combination. (III) group An arbitrary partial structure represented by the formula [b] described later in order from the left And any structure in which three partial structures of an arbitrary partial structure represented by formula [f] to be described later and an arbitrary partial structure represented by formula [c] to be described later are combined in any combination (IV) Arbitrary partial structure represented by the formula [c] described later in order from the group left and an arbitrary portion represented by the formula [g] described later All structures in which a structure and three partial structures of an arbitrary partial structure represented by the formula [c] described later are combined in an arbitrary combination (V) group An arbitrary represented by the formula [b] described later in order from the left All the structures in which the three partial structures of the partial structure represented by formula [h], which will be described later, and the arbitrary partial structure represented by formula [b], which will be described later, are combined in any combination. Partial structure [b]

(In the formula, each R is independently methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl. Group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, s-butoxy group, t-butoxy group , Pentyloxy group, isopentyloxy group, neopentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, undecyloxy group, dodecyloxy group)
Partial structure [c]

(In the formula, each R is independently methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl. Group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group, methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, s-butoxy group, t-butoxy group , Pentyloxy group, isopentyloxy group, neopentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, nonyloxy group, decyloxy group, undecyloxy group, dodecyloxy group)
Partial structure [d]

Partial structure [e]

Partial structure [f]

Partial structure [g]

部分構造〔ｈ〕

Partial structure [h]

<Method of synthesizing dichroic dye>
The azo dichroic dyes represented by the general formulas [I] to [V] can be produced by a known method. For example, the following documents are helpful.
"Dicroic Dies for Liquid Crystal Display" (A. V. Ivashchenko, CRC, 1994)
And the literature cited in this article, “Review Review Synthetic Dyes” (Horiguchi Hiroshi, Sankyo Publishing, 1968)
JP-A-2009-007485, JP-A-2009-007486, JP-A-2000-239664 (a method for synthesizing the left side of the dye of the general formula (V))
US Pat. No. 2,365,345 (Right-side synthesis method of dye of general formula (V))

Of the azo dichroic dyes represented by the general formulas [I] to [V] described above, the dye represented by the general formula [I] is usually yellow, and the dye represented by the general formula [II] Is usually yellow, the dye represented by the general formula [III] is usually red, and the dye represented by the general formulas [IV] and [V] is usually blue.
[I-2: Dichroic dye composition]
The dichroic dye composition of the present invention contains at least one dichroic dye from each of the groups (I) to (IV) represented by the general formulas [I] to [IV]. Preferably, it further contains at least one dichroic dye of group (V) represented by the general formula [V].

<Composition>
The amount of each dye group represented by the (I) group, (II) group, (III) group, (IV) group and (V) group is appropriately selected depending on the hue to be obtained. When trying to obtain flat absorption in a wavelength region of ˜650 nm, when the total amount of dye is 100 parts by weight, (I) group dye 5 to 35 parts by weight, (II) group dye 5 to 35 parts by weight 5 to 35 parts by weight of (III) group dye, 5 to 50 parts by weight of (IV) group dye, and 5 to
It is preferably used in a proportion of 25 parts by weight, more preferably 10-25 parts by weight of (I) group dye, 10-25 parts by weight of group II dye, 10-25 parts by weight of (III) group dye, IV) When 20 to 45 parts by weight of the group dye and (V) group dye are used, they are used at a ratio of 10 to 20 parts by weight. In addition, 0.2 to 5 parts by weight of the (II) group dye, 0.1 to 3 parts by weight of the (III) group dye, and 0.3 of the (IV) group dye per 1 part by weight of the (I) group dye -7 parts by weight, (V) group dyes are preferably 0.2-5 parts by weight, and (II) group dyes are 0.5-3 parts by weight with respect to 1 part by weight of (I) group dyes. III) The group dye is preferably 0.2 to 2 parts by weight, the (IV) group dye is preferably 1 to 4 parts by weight, and the (V) group dye is preferably 0.5 to 2 parts by weight.

<Other ingredients>
The dichroic dye composition of the present invention may contain other components as long as the effects of the present invention are not impaired.
As such a dye, a dichroic dye having a high dichroic ratio is preferable, and examples thereof include dyes represented by the following group (VI) or (VII).
((VI) group: azo dichroic dye represented by formula [VI])

(In the formula, X ¹¹ and X ¹² each independently represent a substituent represented by the general formula [a]. The benzene ring and / or naphthalene ring linked by an azo group further has a substituent. May be.)
In the formula [VI], the substituents of X ¹¹ and X ¹² can be selected from the viewpoints of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like. Specific examples of X ¹¹ and X ¹² include the substituents defined by X ^{1 to} X ¹⁰ in the above formulas [I] to [V].
In the formula [VI], the benzene ring and / or naphthalene ring linked by an azo group may further have a substituent which is linked by an azo group in the above formulas [I] to [V]. Examples of the substituent that the benzene ring and / or naphthalene ring may have are exemplified.
Specific examples of (VI) group dyes are listed below.

((VII) group: azo dichroic dye represented by formula [VII])

(In the formula, X ¹³ and X ¹⁴ represent a substituent represented by the general formula [a]. The benzene ring and / or naphthalene ring connected by an azo group may further have a substituent. Good.)
In the formula [VII], the substituents for X ¹³ and X ¹⁴ can be selected from the viewpoints of the compound production method, stability, dichroic ratio, solubility in the host liquid crystal, and the like.
Specific examples of X ¹³ and X ¹⁴ include the substituents defined by X ¹ -X ¹⁰ in the aforementioned formulas [I] to [V].
In the formula [VII], the benzene ring and / or naphthalene ring linked by an azo group may further have a substituent which is linked by an azo group in the above formulas [I] to [V]. Examples of the substituent that the benzene ring and / or naphthalene ring may have are exemplified.
Specific examples of (VII) group dyes are listed below.

In order not to impair the effects of the present invention, the total amount of the dichroic dyes in the groups (I) to (V) is two colors including other dyes such as the (VI) group and the (VII) group. Is preferably 10% by weight or more, and more preferably 50% by weight or more, based on the total amount of the active dye composition.
[II. Liquid crystal composition]
The liquid crystal composition of the present invention is a guest-host type liquid crystal composition comprising the above-described dichroic dye composition of the present invention and a host liquid crystal material.
[II-1: Host liquid crystal]
As a host liquid crystal material used for the guest-host type liquid crystal composition of the present invention, an Np-type liquid crystal material mainly composed of a liquid crystal compound represented by the following general formulas [VIII] to [XII], an Nn-type liquid crystal Materials.

(In each formula, ring G represents a cyclohexane ring, a benzene ring, a dioxane ring, or a pyrimidine ring, and n represents an integer of 1 to _3. -Z- represents a single bond, —COO—, —CH ₂ CH _{2 —.} , -CH = CH-, or -C≡C-.

R ²¹ represents a halogen atom such as a fluorine atom or a chlorine atom; a substituted alkyl group having 1 to 7 carbon atoms, a substituted alkoxy group having 1 to 7 carbon atoms, a substituted alkenyl group having 1 to 7 carbon atoms; or the substituted alkyl group, A substituted cyclohexyl group or substituted phenyl group having a substituted alkoxy group and the substituted alkenyl group as a substituent is represented. The substituted alkyl group, the substituted alkoxy group and the substituted alkenyl group have a halogen atom such as a fluorine atom or a chlorine atom.
R ²² and R ²³ each independently represents a hydrogen atom; a halogen atom such as a fluorine atom or a chlorine atom.
R ²⁵ and R ²⁶ each independently represent a cyano group; a halogen atom such as a fluorine atom or a chlorine atom.
R ²⁰ , R ²⁴ , R ²⁷ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. An alkoxyalkyl group and an alkenyl group having 1 to 10 carbon atoms are represented. )
The host liquid crystal material used for the guest-host type liquid crystal composition of the present invention preferably has the following characteristics.

(NI point)
The nematic phase-isotropic liquid phase transition temperature (NI point) is 60 ° C. or higher, preferably 80 ° C. or higher, and 130 ° C. or lower, preferably 110 ° C. or lower. Generally, when the NI point is excessively low, the operating temperature range is narrowed. If it is excessively high, the viscosity of the host liquid crystal tends to increase, and the response performance decreases.

(Dielectric anisotropy Δε)
The absolute value of Δε is 2 or more, preferably 3 or more, and 20 or less, preferably 10 or less. In general, if Δε is excessively low, a high driving voltage is required. If it is excessively high, the viscosity of the host liquid crystal tends to increase, and the response performance decreases.
Further, the liquid crystal compound may contain additives such as an optically active substance such as cholesteryl nonanoate, an ultraviolet absorber, and an antioxidant.
Further, the dichroic dye composition of the present invention has a particularly good dichroic ratio in combination with a host material containing a fluorine compound.

[II-2: Composition]
The liquid crystal composition of the present invention comprises at least one dichroic dye selected from the groups (I), (II), (III) and (IV), preferably (V ) Group of at least one dichroic dye, or the dichroic dye composition of the present invention containing these can be easily prepared by dissolving them in the above-mentioned host liquid crystal compound according to a known method. .
Under the present circumstances, the dichroic dye composition of this invention may use 1 type, or may use 2 or more types.
The amount of each dye group represented by the group (I), the group (II), the group (III), the group (IV) and the group (V) is appropriately selected depending on the hue to be obtained, but is 400 to 600 nm. In particular, when obtaining flat absorption in the wavelength region of 500 nm to 650 nm, when the total amount of dye is 100 parts by weight, (I) group dye 5 to 35 parts by weight, (II) group dye 5 to 35 parts by weight, (III) group dyes 5 to 35 parts by weight, (IV) group dyes 5 to 50 parts by weight, (V) group dyes 5 to 25 parts by weight, preferably (I) group dyes (II) group dye is 0.2 to 5 parts by weight, (III) group dye is 0.1 to 3 parts by weight, (IV) group dye is 0.3 to 7 parts by weight with respect to 1 part by weight, (V ) Group dye is preferably 0.2 to 5 parts by weight.

The total amount of dichroic dye used is usually 0.1% by weight or more, preferably 0.2% by weight or more, and usually 15% by weight or less, preferably 5% by weight or less based on the host liquid crystal material. If the total amount of the dichroic dye used is excessively small relative to the host liquid crystal material, the color density at the time of coloring decreases, and if it is excessively large, the viscosity of the liquid crystal tends to be affected and drive characteristics tend to deteriorate.
When using 2 or more types of the dichroic dye composition of this invention, it is made for the total amount to be in the said range.

The guest-host type liquid crystal composition of the present invention can be easily obtained by mixing and dissolving the liquid crystal composition, the dichroic dye and various additives at such a ratio by an operation such as shaking. In addition, the liquid-crystal composition of this invention contains other dichroic dyes other than the dichroic dye of the said (I)-(V) group which concerns on this invention in the range which does not impair the effect of this invention. Also good. In this case, the total amount of the dichroic dyes of the groups (I) to (V) according to the present invention and the other dichroic dyes is set within the above range. Further, the ratio of the total amount of the dichroic dyes in the groups (I) to (V) to the total use amount of the dichroic dyes is 10% by weight or more, preferably 50% by weight or more.
Examples of the dye that the guest-host type liquid crystal composition of the present invention may contain in addition to the dichroic dyes of the groups (I) to (V) according to the present invention include dichroic dyes having a high dichroic ratio. Preferable examples include the dyes represented by the group (VI) or (VII).

[II-3: Characteristics]
(Dichroic ratio)
The guest-host type liquid crystal composition thus adjusted exhibits a high dichroic ratio in the wavelength range of 400 nm to 650 nm, and further in the range of 450 nm to 600 nm, particularly 500 nm to 650 nm. Here, the dichroic ratio means a ratio of absorbance when the liquid crystal composition is injected into the liquid crystal cell and then the orientation of the liquid crystal composition is changed by applying a voltage, and is calculated by the following equation.

Dichroic ratio = (A _// ) / (A _⊥ )
A _{吸 光} Absorbance in vertical orientation
The dichroic ratio of A _// guest-host type liquid crystal composition of the absorbance present invention during horizontal orientation is usually 13.5 or more, preferably 14.5 or more.

  The guest-host type liquid crystal composition of the present invention thus prepared is sandwiched between a pair of electrode substrates, at least one of which is transparent, for example, “Liquid Crystal Device Handbook, edited by Japan Society for the Promotion of Science, 142nd Committee” Various liquid crystal elements applying the guest host effect such as Heilmeier type guest host and phase transition type guest host described in Nikkan Kogyo Shimbun, page 315 to page 329, etc., can be configured.

  As described above, in the present invention, various modes of the liquid crystal element can be used, but in the phase transition mode obtained by adding an optically active substance to the nematic liquid crystal composition, a polarizing plate is not used. Since the contrast ratio is high and the display is bright, it is particularly preferable as a reflective liquid crystal display element.

Embodiments of the present invention will be described below by way of examples. However, the present invention is not limited to these examples as long as the gist thereof is not exceeded.
In the following, the guest-host type liquid crystal composition and the liquid crystal element were evaluated by the following methods.
<Production of liquid crystal element>
A guest-host type liquid crystal composition prepared at room temperature with the composition shown in the following examples and comparative examples was injected into a liquid crystal cell to prepare a liquid crystal element. The liquid crystal cell substrate used was a glass substrate (thickness 1.1 mm) on which an ITO transparent electrode layer was formed, with a cell gap of 12 μm, with an epoxy resin seal, and perpendicular to the opposing surfaces of the pair of substrates. A polyimide alignment film for alignment is formed.

<Evaluation of dichroic ratio>
In each of the above elements, the transmittances when no voltage was applied and when 20 V was applied were measured in Examples 1 to 4 using a spectrophotometer (U-3100, trade name, manufactured by Hitachi, Ltd.). 6 and Comparative Example 2 were measured using a spectrophotometer (U-4100, trade name, manufactured by Hitachi, Ltd.). The dichroic ratio at each wavelength (absorbance when voltage 20 V was applied / absorbance when no voltage was applied) was determined. In addition, in order to reduce the error of the measured value due to the individual difference caused by the alignment unevenness of the liquid crystal cell and the like, in Examples 5 and 6 and Comparative Example 2, three elements were prepared and measured. The voltage application was a 1 kHz rectangular wave.
Moreover, the molecular structure of the pigment | dyes 1-11 used in Examples 1-6 and Comparative Examples 1 and 2 is as follows.

The relationship between the dyes 1 to 12 and the general formulas [I] to [V] of the present invention, the substituents X ^{1 to} X ¹⁰ and the formula [
The relationship with a] is shown in Table A below.

[Example 1]
A dichroic dye composition 1 having the following composition is dissolved in 100 g of an Nn-type liquid crystal mixture containing a fluorine compound as a main component and having an NI point of 90 ° C. and Δε of −4.2. Prepared.
<Dye composition 1 blend>
Dye 1 ((I) group) 0.1301 g
Dye 2 ((VI) group) 0.0235 g
Dye 3 ((II) group) 0.1271 g
Dye 4 ((III) group) 0.083 g
Dye 6 ((IV) group) 0.1194 g
Dye 7 ((IV) group) 0.1271 g
Table 1 shows the result of producing a device by the above method using the liquid crystal composition 1 and obtaining the dichroic ratio.

[Example 2]
A dichroic dye composition 2 having the following composition is an Nn-type liquid crystal mixture mainly composed of a fluorine compound, dissolved in 100 g having an NI point of 90 ° C. and Δε of −4.2 to prepare a liquid crystal composition 2 did. <Dye composition 2 blend>
Dye 1 ((I) group) 0.134 g
Dye 2 ((VI) group) 0.024 g
Dye 3 ((II) group) 0.131 g
Dye 4 ((III) group) 0.0856 g
Dye 6 ((IV) group) 0.1113 g
Dye 7 ((IV) group) 0.1156 g
Dye 8 ((VII) group) 0.0248 g
Table 1 shows the results of producing a device by the above method using the liquid crystal composition 2 and obtaining the dichroic ratio.

[Example 3]
A dichroic dye composition 3 having the following composition is dissolved in 100 g of an Nn-type liquid crystal mixture containing a fluorine-based compound as a main component and having an NI point of 90 ° C. and Δε of −4.2 to prepare a liquid crystal composition 3 did. <Dye composition 3 blend>
Dye 1 ((I) group) 0.2 g
Dye 2 ((VI) group) 0.045 g
Dye 3 ((II) group) 0.245 g
Dye 4 ((III) group) 0.16 g
Dye 6 ((IV) group) 0.46 g
Table 1 shows the results obtained by fabricating a device by the above method using the liquid crystal composition 3 and obtaining the dichroic ratio.

[Example 4]
A dichroic dye composition 4 having the following composition is an Nn-type liquid crystal mixture mainly composed of a fluorine compound, dissolved in 100 g having an NI point of 90 ° C. and Δε of −4.2 to prepare a liquid crystal composition 4 did. <Dye composition 4 blend>
Dye 1 ((I) group) 0.25 g
Dye 2 ((VI) group) 0.045 g
Dye 3 ((II) group) 0.245 g
Dye 5 ((III) group) 0.28 g
Dye 7 ((IV) group) 0.45 g
Table 1 shows the results of producing an element by the above method using the liquid crystal composition 4 and obtaining the dichroic ratio.

[Comparative Example 1] Composition in Claims of Japanese Patent Application Laid-Open No. 2008-179670 A dichroic dye composition 5 having the following composition is an Nn-type liquid crystal mixture containing a fluorine-based compound as a main component and having an NI point of 90 ° C. Was dissolved in 100 g of -4.2 to prepare liquid crystal composition 5. <Dye composition 5 formulation>
Dye 9 0.0958g
Dye 3 ((II) group) 0.1277 g
Dye 10 0.1064g
Dye 11 0.1277 g
Dye 8 ((VII) group) 0.1702 g
Table 1 shows the result of producing a device by the above method using the liquid crystal composition 5 and obtaining the dichroic ratio.

From Table 1, it was found that the dye compositions of Examples 1 to 4 exhibited a high dichroic ratio over the entire wavelength range of 450 nm to 600 nm. In particular, Examples 2 to 4 showed a dichroic ratio of 14.5 or more over the entire wavelength range.
On the other hand, the dye composition of Comparative Example 1 was found to have a clearly lower dichroic ratio in the wavelength range of 450 nm to 600 nm, particularly in the wavelength range of 500 nm to 600 nm, as compared with Examples 1 to 4.

[Example 5]
A liquid crystal composition 6 was prepared in the same manner as in Example 1 except that the dichroic dye composition 6 prepared at the same blending ratio as that of the dichroic dye composition 1 of Example 1 was used.
Three elements were produced by using the liquid crystal composition 6 by the above-described method, and the dichroic ratio was measured three times in total.

[Example 6]
A liquid crystal composition 7 was prepared in the same manner as in Example 1 except that the dichroic dye composition 7 having the following composition was used instead of the dichroic dye composition 1 <Dye composition 7 composition>
Dye 1 ((I) group) 0.204 g
Dye 2 ((VI) group) 0.037 g
Dye 3 ((II) group) 0.199 g
Dye 4 ((III) group) 0.16 g
Dye 6 ((IV) group) 0.19 g
Dye 7 ((IV) group) 0.15 g
Dye 12 ((V) group) 0.2 g
Three elements were produced by the above-described method using this liquid crystal composition 7, and the dichroic ratio was measured three times in total.

[Comparative Example 2]
A liquid crystal composition 8 was prepared in the same manner as in Example 1 except that the dichroic dye composition 8 prepared with the same blending ratio as the dichroic dye composition 5 of Comparative Example 1 was used. Using this liquid crystal composition 8 Three elements were manufactured by the above method, and the dichroic ratio was measured three times in total.

From Table-2, it was found that the dye compositions of Examples 5 and 6 exhibited a high dichroic ratio over a wavelength range of 400 nm to 650 nm. Among them, a high dichroic ratio of 15.5 or higher was exhibited in a particularly important visible light wavelength range of 500 nm to 650 nm. In addition, Example 6 shows a high dichroic ratio even at 700 nm, and shows a high dichroic ratio over the entire visible light wavelength range of 400 nm to 700 nm.
On the other hand, the dichroic composition of Comparative Example 2 was found to have a clearly lower dichroic ratio at 550 nm to 650 nm than Examples 5 and 6.

  The dichroic dye composition and guest-host type liquid crystal composition of the present invention can be suitably used for a liquid crystal element in which a liquid crystal composition is sandwiched between electrodes, for example, a display element or a light control element. Since it has a high dichroic ratio and a high contrast when a guest-host display device is used, it can be particularly suitably used for a reflective display device that does not use a backlight.

Claims (8)

A dichroic dye composition comprising at least one dichroic dye represented by the following groups (I) to (IV) from each group.

(In the formulas [I] to [IV], X ^{1 to} X ⁸ each independently represent a group represented by the following formula [a]. Further, a benzene ring and / or a naphthalene ring connected by an azo group is Furthermore, you may have a substituent.

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms,
Ring A and Ring B are each independently a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent,
L is a divalent linking group containing no cyclic structure, p is 0, 1 or 2, and q and r are each independently 0 or 1. When p is 2, the two rings A may be the same or different. In addition, when the total number of 1,4-phenylene groups and cyclohexane-1,4-diyl groups included in the formula [a] is 1 or 2, and q = 0, Any cyclohexane-1,4-diyl group is considered ring A. )   The dichroic dye composition according to claim 1, wherein p is 1 or 2.   The dichroic dye composition according to claim 1 or 2, wherein in formula [a], ring A to which R is linked is a cyclohexane-1,4-diyl group.   4. The dichroic dye composition according to claim 1, wherein in the formula [a], R is a linear alkyl group having 2 to 8 carbon atoms. The dichroic dye composition according to any one of claims 1 to 4, further comprising at least one dye represented by the following group (V):

(In Formula [V], X < ⁹ > -X < ¹⁰ > shows the group represented by the following formula [a] each independently, and A shows a hydrogen bond substituent substituent.
Moreover, the benzene ring and / or naphthalene ring connected by an azo group may further have a substituent.

(In the formula [a], R is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, and ring A and ring B may each independently have a substituent 1,4. -A phenylene group or an optionally substituted cyclohexane-1,4-diyl group, L is a divalent linking group not containing a cyclic structure, p is 0, 1 or 2, q And r are each independently 0 or 1. When p is 2, the two rings A may be the same or different, and the 1,4-phenylene group included in the formula [a] And the cyclohexane-1,4-diyl group is 1 or 2, and q = 0, the 1,4-phenylene group and the cyclohexane-1,4-diyl group are both ring A and I reckon.))   A guest-host type liquid crystal composition comprising the dichroic dye composition according to any one of claims 1 to 5 and a host liquid crystal.   The liquid crystal composition according to claim 6, wherein the host liquid crystal is a fluorine-based liquid crystal.   8. A liquid crystal element comprising the guest-host type liquid crystal composition according to claim 6 sandwiched between a pair of electrode substrates, at least one of which is transparent.