JPH0461035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a guest-host type liquid crystal composition used in a liquid crystal display element capable of color display. A guest-host type 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 high order parameters in the host liquid crystal. The order parameter (hereinafter referred to as S) is defined by equation (), and is experimentally determined using equation (). In the formula, the term cos ² θ 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〓 and A⊥ are the angles formed by the alignment direction of the liquid crystal molecules, respectively. It is the absorbance of a dye molecule for light polarized parallel and perpendicular to the opposite direction. S=(3 ² -1)/2...() S=(A-A⊥)/(2A⊥+A)
...() S represents the degree of parallelism of the dye molecule absorption axis to the orientation direction of the host liquid crystal molecules, and is an amount that controls the display contrast in a guest-host type liquid crystal display element. In the case of pleochroic dyes with parallel dichroism, as the value approaches the theoretical maximum value of 1, the degree of residual color in the white areas decreases, making it possible to display brightly and clearly with high contrast. Become. The relationship between the molecular structure of pleochroic pigments and their various properties has not yet been fully clarified. Selecting a pleochroic dye with a higher S value in a desired hue is a difficult task, and making analogies from known materials is also a difficult task. 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, dialkylamino groups are used as so-called auxochromes to obtain coloring effects. (R represents a straight-chain alkyl group) are often introduced into the molecule. Specifically, R is often a methyl group, an ethyl group, etc. However, when R 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 a case, it is known that if the linear alkyl group R on the dialkylamino group is made longer than, for example, a 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, the S value increases, although there is almost no change in hue. is significantly lower than that of lower alkyl groups such as methyl and ethyl groups. An object of the present invention is to solve the above problems in pleochroic dyes having dialkylamino groups. That is, it is an object of the present invention to provide 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 The gist of the present invention is to provide a guest solution in which a pleochroic dye as a guest material is dissolved in a host liquid crystal.
In the host type liquid crystal composition, the pleochroic dye has the general formula D-W [wherein W is the general formula] (However, R ¹ represents a hydrogen atom, an alkyl group, or an alkoxy group.) D represents any one of the following formulas (a) to (p). ] A guest-host type liquid crystal composition characterized by containing a dye represented by the following. [However, Y ¹ is a hydrogen atom, an alkyl group, an alkoxy group, an alkoxyalkyl group, an alkoxyalkoxy group, a nitro group, a cyano group, a halogen atom,
Represents either a W group or _-CF3 , and ^B0 is -
OOC−, −CONH−, O ₂ S−,

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[expression] or

Represents one of [formula], B ¹ is

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[expression] or

[Formula], Z ¹ to ^{Z 3} are hydrogen atoms or methyl groups, Z ⁴ to ^{Z 6} are hydrogen atoms, halogen atoms, methyl groups or methoxy groups,
^Z7 to ^Z9 are hydrogen atoms, halogen atoms or methyl groups, ^Z10 to ^Z12 are hydrogen atoms, hydroxyl groups, methyl groups or methoxy groups, ^Z1 and ^Z2 , ^Z4 and ^Z5 , ^Z7
and Z ⁸ , Z ¹⁰ and Z ¹¹ may be linked to each other to form a naphthalene ring or a quinoline ring. n ₀ to n ₄ represent 0 or 1, and n ₁ , n ₂ , and n ₄ are not 0 at the same time. ] [However, B ⁴ is −COO−, −COS−, −OCH ₂ −,
SCH ₂ −, −CH ₂ O−, −CH ₂ CH ₂ −, −CH ₂ −, −
Represents either COCH ₂ − or −CH ₂ CO−,
Y ² to ^{Y 5} are a hydrogen atom, an amino group, a hydroxy group, or a chlorine atom, and when one of them is a chlorine atom, at least one of them is an amino group or a hydroxy group. Y ⁶ is a hydrogen atom, a methoxy group, or

[Formula] (R ² is a W group or an alkoxy group), X ¹ is a hydrogen atom or a cyano group, and n ₈ is 0 or 1. ] [However, X ² and X ³ represent an amino group or a hydroxy group, and Y ⁷ represents a hydrogen atom, a chlorine atom, or a methoxy group. ] [However, Y ⁹ and Y ¹¹ are amino groups, hydroxy groups, or hydrogen atoms, Y ¹⁰ is hydrogen atoms, hydroxy groups,
amino group or

[Formula] group, X ⁴ represents a hydrogen atom or a chlorine atom, B ⁵ is -COO-,
-OCO-, _-OCH2- or _-CH2O- , and _n9 represents 0 or 1. ] [X ⁵ represents an oxygen atom or a sulfur atom. ] [However, X ⁷ is a hydrogen atom or a halogen atom,
^X8 represents a hydrogen atom, an alkyl group or an alkoxy group, and ^B6 represents -COO-, -OCO-, _-OCH2- or -CONH-. ] [However, X ⁷ is a hydrogen atom or a halogen atom,
X ⁸ represents a hydrogen atom, an alkyl group or an alkoxy group. ] [However, X ⁹ and X ¹⁰ are hydrogen atoms,

[Formula] base,

[Formula] represents a group, R ⁴ represents an alkyl group, B ⁸ represents -COO-, -OCO-, -COS-,
-OCH ₂ -, -CONH- or -CON(CH ₃ )-. ] [However, R ⁵ is an alkyl group or

Represents [formula]. ] [However, R ⁶ represents an alkyl group. ] [However, R ⁷ represents a hydrogen atom, a halogen atom, or an alkoxy group. ] [However, B ⁹ and B ¹¹ are -OCO- or -CH ₂ O-
, B ¹⁰ and B ¹² represent -COO- or -OCH ₂ -. ] Below, some examples of pleochroic dyes whose solubility has been improved by introducing a group represented by the general formula [ ] are shown. Example 1 Conventional dye Solubility: 2.6ωt% (25℃) Order parameter: 0.72 (25℃) Dye of the present invention Solubility: 5ωt% or more (25℃) Order parameter: 0.70 (25℃) Example 2 Conventional dye Solubility: 3.4ωt% (25℃) Order parameter: 0.79 (25℃) Dye of the present invention Solubility: 5ωt% or more (25℃) Order parameter: 0.76 (25℃) Example 3 Conventional dye Solubility: 0.6ωt% (25℃) Order parameter: 0.59 (25℃) Dye of the invention Solubility: 2.4ωt% (25℃) Order parameter: 0.61 (25℃) Example 4 Conventional dye Solubility: 0.4ωt% (25℃) Order parameter: 0.75 (25℃) Dye of the present invention Solubility: 3.1ωt% (25℃) Order parameter: 0.76 Example 6 Conventional dye Solubility: 1.6ωt% (25℃) Order parameter: 0.69 Dye of the present invention Solubility: 3.8ωt% (25℃) Order parameter: 0.69 In the above five examples, the dimethylamino group as the terminal group is

It can be seen that the solubility of the dye is improved by changing to the [Formula] group. The solubility values of the respective dyes in the above five examples are the values when ZLI-1132 (manufactured by Merck & Co., Ltd.), which is a commercially available phenylcyclohexane-based mixed liquid crystal described later, is used as the host liquid crystal. to dye molecules

It has been found that the phenomenon that the solubility in liquid crystals improves when the formula [Formula] is introduced is not limited to the above examples, but is observed in almost all pleochroic dyes known to date. Prior to the present invention, the findings of the present invention had not been made clear in the field of guest-host liquid crystal displays. The reason why the solubility is improved when a group like the formula [] is included in the pleochroic dye molecule is not clear to date, but one reason is that the inclusion of a group like the [] makes the dye more soluble. This is presumed to be due to the structure of the molecule making it difficult to crystallize. Specific examples of R ¹ in the general formula [] include a hydrogen atom; an alkyl group such as a methyl group, an ethyl group, a linear or branched propyl group, a butyl group, a heptyl group, an octyl group, a dodecyl group, and an octadecyl group. ; Cycloalkyl groups such as cyclohexyl group, propylcyclohexyl group, butylcyclohexyl group, heptylcyclohexyl group; alkoxy groups such as methoxy group, propoxy group, pentoxy group, octoxy group, octadecyloxy group;
Examples include dialkylamino groups such as dimethylamino group, diethylamino group, and dibutylamino group. The nematic liquid crystal used in the present invention may be one that exhibits a nematic state within the operating temperature range.
You can choose from a fairly wide 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. The first example of a nematic liquid crystal is
Examples include the substances shown in the table or their derivatives.

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[Table] In the above table, R' represents an alkyl group or an alkoxy group, and X represents a nitro group, a cyano group, or a halogen atom. All of the liquid crystals listed in Table 1 have positive dielectric anisotropy. LCD also
It can 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 types of liquid crystal compounds may be used.

[Formula] 38.4% by weight

[Formula] 34.2% by weight

[Formula] 18.1% by weight A liquid crystal material sold by Merck under the trade name ZLI-1132 as a mixture of 9.3% by weight and the following 4
types of liquid crystal compounds

[Formula] 51% by weight

[Formula] 25% by weight

[Formula] 16% by weight E from British Drug House as an 8% by weight mixture.
A liquid crystal material sold under the tradename -7 has been found to be particularly useful in the present invention. As the optically active substance used in the present invention, chiral nematic compounds such as 2-methylbutyl group,
3-methylbutoxy group, 3-methylpentyl group,
There are compounds in which optically active groups such as 3-methylpentoxy, 4-methylhexyl, and 4-methylhexyl groups are introduced into nematic liquid crystal compounds.
Also, l-menthol shown in Japanese Patent Application Laid-open No. 51-45546,
Alcohol derivatives such as d-borneol, ketone derivatives such as d-syndrome, 3-methylcyclohexane, carboxylic acid derivatives such as d-citronellaic acid and l-cyonolic acid, aldehyde derivatives such as d-citronellal, alkenes such as d-linonene, etc. Of course, optically active substances such as derivatives and other amine, 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 of the element is determined by the spacer. The element gap is 3 to 100μm,
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 as follows:
The second one along with its hue and order parameters
Shown in the table.

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[Table] The characteristics of each dye listed in Table 2 were investigated as follows. That is, in the above-mentioned phenylcyclohexane mixed liquid crystal Z-1132, as a pleochroic dye,
Any of the dyes shown in Table 2 was added and stirred at room temperature without particular heating to dissolve the dye. The above-mentioned liquid crystal composition prepared in this manner was applied to an intersubstrate gap consisting of two glass substrates having transparent electrodes and a homogeneous alignment treatment performed by applying polyamide resin on the surface in contact with the liquid crystal, applying hardening, and then rubbing. 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 assumes a homogeneous alignment state in which the liquid crystal molecules and dye molecules are aligned in a constant direction parallel to the electrode surface, and the dye molecules also follow the host liquid crystal. Take a similar orientation. The absorption spectrum of the guest-host device thus prepared was measured using light polarized parallel to and perpendicular to the alignment direction of the liquid crystal molecules, and the absorbance of the dye for each polarized light was measured. A 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 obtained, the value of the order parameter S was calculated from the above formula S=A−A⊥/2A⊥+A. Example 2 A liquid crystal composition obtained by adding 0.53 weight percent of dye No. 26 in Table 2 to the liquid crystal used in Example 1 was used to create an element exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm). The absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve indicates A, and the curve indicates A⊥. A in the visible region is 0.972, A⊥ is
It was 0.122. Therefore, the order 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 A liquid crystal composition obtained by adding 0.53 weight percent of dye No. 34 in Table 2 to the liquid crystal used in Example 1 was used to create an element exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm). The absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve indicates A, and the curve indicates A⊥. A in the visible region is 1.031, A⊥ is
It 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 A liquid crystal composition obtained by adding 0.52 weight percent of dye No. 36 in Table 2 to the liquid crystal used in Example 1 was used to create an element exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm). The absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve indicates A, and the curve indicates A⊥. A in the visible region is 0.816, A⊥
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 A liquid crystal composition obtained by adding 0.84 weight percent of dye No. 39 in Table 2 to the liquid crystal used in Example 1 was used to create an element exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm). The absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve indicates A, and the curve indicates A⊥. A in the visible region is 1.236, A⊥
was 0.105. Therefore, the order parameter of the dye of this example is 0.78. The maximum absorption wavelength of the dye of this example in ZLI-1132 was 506 nm. Example 6 A liquid crystal composition obtained by adding 0.71 weight percent of dye No. 42 in Table 2 to the liquid crystal used in Example 1 was used to create a device exactly the same as in Example 1 (however, the gap between the substrates was approximately 10 μm). The absorption spectrum was measured in the same manner as in Example 1. The spectrum is shown in FIG. The curve indicates A, and the curve indicates A⊥. A in the visible region is 1.009, A⊥
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 Dye No. 175 in Table 2 was added to the liquid crystal used in Example 1.
A liquid crystal composition to which 0.7 weight percent of the dye was added was encapsulated in the same device as in Example 1 (however, the gap between the base liquid was approximately 10 μm), and the absorption spectrum was measured in the same manner as in Example 1. A in the visible range
was 1.432, and A⊥ was 0.132. 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 565 nm.

[Brief explanation of the drawing]

1 to 5 are spectral characteristic diagrams of displays of Examples 2 to 6 using the liquid crystal compositions of the present invention.

Claims (1)

[Scope of Claims] 1. In a guest-host type liquid crystal composition in which a pleochroic dye as a guest substance is dissolved in a host liquid crystal serving as a matrix, the pleochroic dye has the general formula D-W.
[In the formula, W is a general formula [] (However, R ¹ represents a hydrogen atom, an alkyl group, or an alkoxy group.) D represents any one of the following formulas (a) to (p). ] A guest-host type liquid crystal composition characterized by containing a dye represented by the following. [However, Y ¹ is a hydrogen atom, an alkyl group, an alkoxy group, an alkoxyalkyl group, an alkoxyalkoxy group, a nitro group, a cyano group, a halogen atom,
Represents either a W group or _-CF3 , and ^B0 is -
OOC−, −CONH−, O ₂ S−, [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] [formula] Represents either [Formula] or [Formula], B ¹ represents either [Formula] [Formula] or [Formula], Z ¹ to ^{Z 3} are hydrogen atoms or methyl groups, and Z ⁴ to ^{Z 6} are hydrogen atom, halogen atom, methyl group or methoxy group,
^Z7 to ^Z9 are hydrogen atoms, halogen atoms or methyl groups, ^Z10 to ^Z12 are hydrogen atoms, hydroxyl groups, methyl groups or methoxy groups, ^Z1 and ^Z2 , ^Z4 and ^Z5 , ^Z7
and Z ⁸ , Z ¹⁰ to ^{Z 11} may be linked to each other to form a naphthalene ring or a quinoline ring. n ₀ to n ₄ represent 0 or 1, and n ₁ , n ₂ , and n ₄ are not 0 at the same time. ] [However, B ⁴ is −COO−, −COS−, −OCH ₂ −,
SCH ₂ −, −CH ₂ O−, −CH ₂ CH ₂ −, −CH ₂ −, −
Represents either COCH ₂ − or −CH ₂ CO−,
Y ² to ^{Y 5} are a hydrogen atom, an amino group, a hydroxy group, or a chlorine atom, and when one of them is a chlorine atom, at least one of them is an amino group or a hydroxy group. Y ⁶ represents a hydrogen atom, a methoxy group or [Formula] (R ² is a W group or an alkoxy group), X ¹ represents a hydrogen atom or a cyano group, and n ₈ represents 0 or 1. ] [However, X ² and X ³ represent an amino group or a hydroxy group, and Y ⁷ represents a hydrogen atom, a chlorine atom, or a methoxy group. ] [However, Y ⁹ and Y ¹¹ are amino groups, hydroxy groups, or hydrogen atoms, Y ¹⁰ is hydrogen atoms, hydroxy groups,
Amino group or [Formula] group, X ⁴ represents a hydrogen atom or a chlorine atom, B ⁵ represents -COO-,
-OCO-, _-OCH2- or _-CH2O- , and _n9 represents 0 or 1. ] [X ⁵ represents an oxygen atom or a sulfur atom. ] [However, X ⁷ is a hydrogen atom or a halogen atom,
^X8 represents a hydrogen atom, an alkyl group or an alkoxy group, and ^B6 represents -COO-, -OCO-, _-OCH2- or -CONH-. ] [However, X ⁷ is a hydrogen atom or a halogen atom,
X ⁸ represents a hydrogen atom, an alkyl group or an alkoxy group. ] [However, X ⁹ and X ¹⁰ represent a hydrogen atom, a group of [Formula], a group of [Formula], R ⁴ represents an alkyl group, and B ⁸ represents -COO-, -OCO-, -OCS-,
-OCH ₂ -, -CONH- or -CON(CH ₃ )-. ] [However, R ⁵ represents an alkyl group or [Formula]. ] [However, R ⁶ represents an alkyl group. ] [However, R ⁷ represents a hydrogen atom, a halogen atom, or an alkoxy group. ] [However, B ⁹ and B ¹¹ are -OCO- or -CH ₂ O-
, B ¹⁰ and B ¹² represent -COO- or -OCH ₂ -. ]