JPS594674A - Liquid crystal composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a guest-host liquid crystal composition used in a liquid crystal display device capable of color display.

The guest-host liquid crystal composition is a liquid crystal composition in which a pleochroic dye as a guest substance is dissolved in a host liquid crystal as a matrix. This pleochroic dye requires a high order φ parameter in the host liquid crystal.

The order parameter (hereinafter referred to as S) is expressed by the formula ('I
), and is determined experimentally using formula (II).

In the formula, the term cOs1θ is statistically averaged, θ is the angle between the absorption axis of the guest dye molecule and the alignment direction of the host liquid crystal molecules, and A/sA is the angle between the absorption axis of the guest dye molecule and the alignment direction of the host liquid crystal molecules. It is the absorbance of a dye molecule for light polarized parallel and perpendicular to the opposite direction.

f3=(3cosRθ−1)/2 −・−・・
(I) 8 units (A, -A work)/(2A work + A/)...(
The old S represents the degree of parallelism of the dye molecule absorption axis to the alignment direction of the host liquid crystal molecules, and is a quantity that controls the display contrast in a guest-host type liquid crystal display element. In the case of pleochroic dyes with parallel dichroism, the closer the value approaches the theoretical fan value of 1', the less residual color remains in the white areas, resulting in a brighter, clearer display with greater contrast. It becomes possible.

The relationship between the molecular structure of pleochroic pigments and their properties has not yet been fully clarified. Selecting a pleochroic dye having a high S value in a desired hue is a difficult task, and it is also difficult to make an analogy from known materials.

As described above, the most important quantity that characterizes a pleochroic dye is the S value, but among other characteristics, high solubility in the host liquid crystal is the next most important in practical terms.

In dye molecules, a dialkylamino group (R represents a straight-chain alkyl group) is often introduced into the molecule as a so-called auxochrome to obtain a coloring effect. There are many cases.

However, when the group in the dialkylamino group is a lower alkyl group such as a methyl group or an ethyl group, the solubility of the pleochroic dye having such a dialkylamino group in the molecule in the host liquid crystal is not necessarily high enough. Sometimes I don't reach it.

In such cases, it is known that if the linear alkyl group pore on the dialkylamino group is made longer than, for example, the butyl group, the solubility of the dye in the host liquid crystal may be increased. However, in most cases, when the straight-chain alkyl group R on the dialkylamino group becomes longer than, for example, a butyl group, in pleochroic dyes containing such a group, there is almost no change in hue, but the 8 value is This is significantly lower than when R is a lower alkyl group such as a methyl group or an ethyl group.

An object of the present invention is to solve the above problems in pleochroic dyes having dialkylamino groups.

That is, the present invention provides a liquid crystal composition containing a dialkylamino-type pleochroic dye whose hue and S value are not significantly different from those of conventional type dyes, but whose solubility in host liquid crystals is greater than that of conventional type dyes. This is the purpose of

As a result of intensive studies, the present inventors found that the general formula CHm (wherein R' is a hydrogen atom, an alkyl group, an alkoxy group,
Represents a cycloalkyl group or dialkylamino group.

) The present invention was completed by discovering that the introduction of a group represented by Ta.

The liquid crystal composition of the present invention is characterized in that the above general formula CI) is used as a pleochroic dye component and is dissolved in a host liquid crystal.

Below, some examples of pleochroic dyes with improved solubility due to the introduction of groups represented by general formula [I] are shown.

Example 1 Solubility: 2.6ωt% (25C) Order parameter: 0.72 (2511 solubility =
5ωt% or more (25tS') Order parameter: Q, 70 (25C) Example 2 Solubility = 3.4ωt% (25C) Order-1 parameter: 0.79 (251Z') Solubility = 5ωt% or more (25C') Order・Parameters: o, 7a (2sc) Example 3 Solubility: 0.6ωt% (25C) Solubility = 24ωt% (25tr) Order parameter: 0.61 (25C) Example 4 NHs Solubility: 0.4ωt% (2511:' ) Order parameter: 0.75 (25C) ONHs Solubility = 3.1ωt% (2sC) Order parameter: 0.76 Example 6 Solubility: 1.6ωt% (25C) Order parameter: 0.69 Solubility; 3. 8ωt% (25C) Order parameter: 0.69 In the above five examples, the terminal group is dimethylamine. Note that the solubility value of each dye in the above five examples is based on ZLI, which is a commercially available phenylcyclohexane mixed liquid crystal described later. -1132
(manufactured by Merck & Co., Ltd.) is used as the host liquid crystal.

As a result, the phenomenon of increasing solubility in liquid crystals is observed not only in the above example but also in almost all pleochroic dyes known to date.

Prior to the present invention, facts such as those discovered in the present invention had not been disclosed in the field of guest-host liquid crystal displays.

The reason why solubility is improved when a group such as CI) is included in a pleochroic dye molecule is not clear at present;
One reason is presumed to be that the inclusion of a group such as [I] causes the dye molecule to have a structure that is difficult to crystallize.

Specific examples of R1 in general formula CI) include hydrogen atom methyl groups, ethyl groups, linear or branched propyl groups, butyl groups, heptyl groups, octyl groups, dodecyl groups, alkyl groups such as octadecyl groups; Cycloalkyl groups such as cyclohexyl group, propylcyclohexyl group, Pterocycetate hexyl group, heptylcyclohexyl group; methoxy group, propoxy group, pentoxy group, octoxy group,
Examples include a flukoxy group such as an octadecyloxy group, a dialkylamino group such as a dimethylamino group, a diethylamino group, and a dibutylamino group.

The nematic liquid crystal used in the present invention can be selected from a wide range as long as it exhibits a nematic state within the operating temperature range. Further, by adding an optically active substance to be described later to such a nematic liquid crystal, it can be made to take a cholesteric state. Examples of nematic liquid crystals include the substances shown in Table 1 or derivatives thereof.

Table 1 In the above table, R' is an alkyl group or an alkoxy group,
represents a nitro group, a cyan group, or a halogen atom.

All of the liquid crystals in Table 1 have positive dielectric anisotropy, but the known ester-based, azoxy-based, azo-based liquid crystals, which have negative dielectric anisotropy,
A Schiff-based, pyrimidine-based, diester-based, or biphenyl ester-based liquid crystal can also be mixed with a liquid crystal having positive dielectric anisotropy to form a positive liquid crystal as a whole.

Furthermore, it goes without saying that even a liquid crystal with negative dielectric anisotropy can be used as is if an appropriate element configuration and driving method are used.

The host liquid crystal substance used in the present invention may be any of the liquid crystal compounds shown in Table 1 or a mixture thereof, but the following four
A liquid crystal substance sold by Merck & Co. under the trade name ZLI-x1a2 as a mixture of 9.3% by weight of liquid crystal compounds of various types, and Br1tish Drug House as a mixture of the following four types of liquid crystal compounds.
A liquid crystal material sold by E Company under the trade name E-7 has been found to be particularly useful in the present invention.

Examples of the optically active substance used in the present invention include chiral nematic compounds such as 2-methylbutyl group, 3-methylbutoxy group, 3-methylpentyl group, 3-methylpentoxy group, 4-methylhexyl group, 4-methylhexyl group, and 4-methylhexyl group. There are compounds in which an optically active group such as a nematic liquid crystal compound is introduced into a nematic liquid crystal compound. Also, alcohol derivatives such as t-menthol and d-borneol shown in JP-A No. 51-45546, d
- ketone derivatives such as camphor, 3-methylcyclohexane, carboxylic acid derivatives such as d-citronenedic acid and t-camporic acid, aldehyde derivatives such as d-citronellal, alkene derivatives such as d-linonene, other amines,
Of course, optically active substances such as amide and nitrile derivatives can be used.

As the element used in the present invention, a known liquid crystal display element can be used. That is, generally, transparent electrodes in an arbitrary pattern are provided on two glass substrates, at least one of which is transparent, and the element is placed so that the two glass substrates are parallel to each other with an appropriate spacer interposed so that the electrode surfaces face each other. A configuration consisting of the following is used.

In this case, the gap between the elements is determined by the spacer. The element gap is 3 to 100 μm.

In particular, 5 to 50 μm is preferable from a practical standpoint.

Examples of dyes used in the display of the present invention and liquid crystal compositions using these dyes will be specifically described below with reference to Examples.

Example 1 First, examples of pleochroic dyes used in the present invention are shown in Table 2 along with their hues and order parameters.

The characteristics of each dye listed in Table 2 were investigated as follows. That is, any of the dyes shown in Table 2 was added as a pleochroic dye to the above-mentioned phenylcyclohexane mixed liquid crystal ZLI-1132, and the dye was dissolved by stirring at room temperature without heating.

The liquid crystal composition thus prepared has a transparent electrode, and a polyamide resin is coated on the surface in contact with the liquid crystal, cured, and rubbed to homogeneously align the substrate. It was encapsulated in an element of 10 to 100 μm. When no voltage is applied in the element subjected to the alignment treatment, the liquid crystal composition maintains a homogeneous alignment state in which the liquid crystal molecules and dye molecules are aligned parallel to the electrode surface and in a fixed direction, and the dye molecules also follow the host liquid crystal. take the orientation.

The absorption spectra of the guest and host devices thus prepared were measured using light polarized parallel to and perpendicular to the alignment direction of the liquid crystal molecules, and The absorbance AI and A and the maximum absorption wavelength were determined.

In determining the absorbance of the dye, corrections were made for absorption by the host liquid crystal and glass substrate and reflection loss of the element. Using the absorbance values A/ and A of the dye for each of the polarized lights thus determined, the value of order parameter 8 was calculated from the above formula.

Example 2 A liquid crystal exactly the same as that used in Example 1 was added to the liquid crystal shown in Table 2.
A liquid crystal composition to which 0.53 weight percent of dye No. 26 was added was used in a device completely similar to that of Example 1 (however, the gap between the substrates was approximately 10 μm).
m), and the absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. Curve 1 indicates AI, and curve 11 indicates artificial. A in the visible range
I was 0.972 and A soil was 0.122. Therefore, the o-dar parameter of the dye of this example is 0.70.

The maximum absorption wavelength of the dye of this example in ZLI-1132 was 481 nm.

Example 3 Table 2 A3 was added to the same liquid crystal as used in Example 1.
A liquid crystal composition containing 0.53 weight percent of the dye No. 4 was used in a device completely similar to that of Example 1 (however, the gap between the substrates was approximately 10 μm).
m), and the absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve lit is A
Curve I and Curve 1■ indicate Af, respectively. AI in visible region is 1.031. A was 0.132. Therefore, the order parameter of the dye of this example is 0.69.

The maximum absorption wavelength of the dye of this example in ZLI-1132 was 486 nm.

Example 4 The same liquid crystal as that used in Example 1 was coated with
A liquid crystal composition to which 0.52 weight percent of the dye No. 636 was added was used in a device exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm).
m), and the absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. Curve V shows AI, and curve v1 shows Al. A in the visible region was 40.816, and Al was 0.095. Therefore, the order parameter of the dye of this example is 0.72.

The maximum absorption wavelength of the dye of this example in ZLI-1132 was 520 nm.

Example 5 The same liquid crystal as that used in Example 1 was coated with a liquid crystal of 0.8
A liquid crystal composition containing 4% by weight was encapsulated in a device exactly the same as in Example 1 (however, the inter-substrate gap was approximately 10 μm), and the absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. Curve Vll represents AI, and curve v111 represents Al. The AI in the visible region is 1,236, the Al is o;1os, and therefore the order parameter of the dye of this example is 0.78.

The maximum absorption wavelength of the dye of this example in ZLr-1132 was 506 nm.

Example 6 A liquid crystal completely similar to that used in Example 1 was coated with a liquid crystal of 0.7
A liquid crystal composition containing 1% by weight was encapsulated in the same device as in Example 1 (however, the inter-substrate gap was approximately IO μm), and the absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. Curve Ix represents AI, and curve x represents Al. AI in visible range is 1
,009, and Al was 0.095. Therefore, the order parameter of the dye of this example is 0.76.

The maximum absorption wavelength of the dye of this example in ZLI-1132 was 546 nm.

Example 7 A second surface plate 1 was added to the same liquid crystal as that used in Example 1.
A liquid crystal composition containing 0.7 weight percent of dye No. 75 was used in an element completely similar to that of Example 1 (however, the gap between the base liquid was approximately 10 μm).
m), and the absorption spectrum was measured in the same manner as in Example 1. AI in visible region is 1.432. Al is 0.
It was 132. Therefore, the order parameter of the dye of this example is 0.77.

The maximum absorption wavelength of the dye of this example in ZLI-1132 was 555 nm.

[Brief explanation of the drawing]

Figures 1 to 5 show Example 2 using the liquid crystal composition of the present invention.
- It is a spectral characteristic diagram of the display body of Example 6.乍/Figure j Skin surface (η7n) Figure 2 Wavelength (omitted Figure 3, 'Skin surface (6,)

Claims (1)

[Scope of Claims] 1. In a liquid crystal composition in which a pleochroic dye as a guest substance is dissolved in a host liquid crystal as a matrix, the pleochroic dye has the general formula CI) (wherein R1 is a hydrogen atom) , alkyl group, alkoxy group,
Represents a cycloalkyl group or dialkylamino group. ) A liquid crystal composition comprising a dye having a group represented by: 2. The dyes having the group represented by the general formula CI] include azo dyes, azomethine dyes, anthra-non-based dyes,
Claim 1, characterized in that the dye is a quinophthalone dye, a perylene dye, a perinone dye, a thioindigo dye, a naphthalimide dye, an oxazine dye, a coumarin dye, a naphthoquinone dye, or a merocyanine dye. The liquid crystal composition described. 3. The dye having a group represented by the general formula (CI) is a dye having a group represented by the general formula (If) (wherein, W is the general formula CI), BO, B
l, Bl, Bl are -N=N+. -N=CH+, -CH=N+, -coo+. -0CO-, -cos+, -5co+. 0CRs, CHIO, S, CH2. -CH5S, NHCO, -CONH+. Elementary atoms, alkyl groups, cycloalkyl groups, alkoxy groups, nitro groups, cyano groups, carboxylic acid ester groups, acyloxy groups, alkylsulfonyl groups, aryol groups, heterocyclic residues, halogen atoms, W groups, They may be an alkyl group or may be linked together to form a nitrogen-containing ring such as a pyrrolidine ring or a morpholine ring. zl, zl, za represent a hydrogen atom, a halogen atom, a methyl group, a hydroxy group, a methoxy group, a cyano group, and R
" , R" may be linked to form a part of a ζ nitrogen-containing ring, or Zl and zt may be linked to each other to form a part of an aromatic ring. nl is 0,1, nl is 0,1.2,
"2 e"4 # n6 is 0,1゜2, "8 #
The liquid crystal composition according to claim 1, characterized in that it is represented by "5e" (7 represents 0 and 1, respectively). 4. The dye having a group represented by the general formula CI) has the general formula [■] (wherein, W is a group represented by the general formula (I), and B4 is -
coo+, -0CO+, -CO8-. -8CO+, -CH*O+, -OCH-9-CHm
8, 8CHs, NHCO. The group k shows L, Y", Y", Y', Y' is 711
[Indicates child, amino group, hydroxy group% Y” s Y
" * Either one of y4 and yl represents an amino group or a hydroxy group. Y6 represents a hydrogen atom or a halogen atom. Xl represents a hydrogen atom, a halogen atom, or a cyano group. n8 and n9 are 0, 1 , m indicates 112°3.)
The liquid crystal composition according to claim 1, characterized in that it is represented by: 5. The dye having a group represented by the general formula CI) has the general formula (IV) (wherein, W is a group represented by the general formula [1), Y'',
Y'' represents a hydrogen atom, an amine group, or a hydroxyl group.Yl
o represents a hydrogen atom, an amino group, a hydroxyl group, or an alkoxy group. ) The liquid crystal composition according to claim 1, characterized in that it is represented by: 6. A dye having a group represented by the general formula CI) has the general formula (V) (wherein, Xl represents an oxygen atom or a sulfur atom; W represents a group represented by the general formula [■]). The liquid crystal composition according to claim 1, characterized in that: 7. The dye having a group represented by the general formula [I] is a group represented by the general formula CM) CVI) (wherein W is a general formula CI), X6 is a hydrogen atom, a hydroxy group, XY is a hydrogen atom, and range 1
The liquid crystal composition described in . 8. The dye having a group represented by the general formula (1) has the general formula [■] (wherein, W is a group represented by the general formula (I), X11 is a hydrogen atom, a hydroxy group, and XY is a hydrogen atom. ).
The liquid crystal composition according to claim 1, characterized in that it is represented by: 9. Claim 1, characterized in that the dye having a group represented by the general formula CII is represented by a group represented by the general formula [■] (wherein W is the general formula CI) liquid crystal composition. 10. The liquid crystal composition according to item 1, wherein the dye having a group represented by the general formula (1) is a group represented by the general formula (IX) (wherein W is the general formula CI). 11. The liquid crystal composition according to claim 1, wherein the dye having a group represented by the general formula CI] is a group represented by the general formula [''X] (wherein W is the general formula CI) 12. The dye having a group represented by the general formula CI) has the general formula [XI) 1 (wherein W is a group represented by the general formula [I], and Xls is a hydrogen atom, an alkyl group, or an alkoxy group). A liquid crystal composition according to x14.
2. The liquid crystal composition according to claim 1, wherein x'' is a hydrogen atom or a halogen atom, and X1@ is water.