JP5286631B2 - Liquid crystal composition and liquid crystal display element - Google Patents

Description

  The present invention relates to a nematic liquid crystal composition useful as an electro-optical liquid crystal display material and a liquid crystal display element using the same.

  The liquid crystal display (LCD) has been used as a calculator display, and it has been the same as the development of computers to support the expansion of display capacity from TN-LCD (twisted nematic liquid crystal display) to STN-LCD. I have done it. STN-LCD was developed by Scheffer et al. [SID ''85 Digest, 120 pages (1985)] or Kinugawa et al. [SID' '86 Digest, pages 122 (1986)]. Word processors, personal computers, etc. It has been widely used for high information processing displays. Recently, however, the rise of TFT-LCDs has made STN-LCDs more commonly used for small and medium-sized LCDs such as mobile phones, PDAs, and automotive applications. For STN-LCDs, in order to achieve low cost, designs that do not incorporate temperature compensation circuits for operating voltages and only simple compensation are common, and there is an increasing demand for improved temperature characteristics for liquid crystals. In particular, portable terminals (Personal Digital Assistance) centering on mobile phones are required to achieve high-speed response without losing contrast and to obtain good display characteristics in a wider temperature range. Such liquid crystal materials can maintain the steepness of the rising characteristics of nematic liquid crystal, maintain a constant value for a low viscosity and a wide temperature range, or drive voltage in a frequency range corresponding to various time divisions. Is required not to fluctuate. One of the causes of LCD display quality degradation due to ambient temperature changes is a change in operating voltage due to a change in twist pitch temperature, an increase in viscosity due to the addition of a chiral agent, and a deterioration in response speed. As a method for keeping the operating voltage of the pitch constant over a wide temperature range, there is known a method of controlling the temperature dependence of the twist pitch by using two kinds of chiral agents having different temperature dependence of the twist pitch (Patent Literature). 1), there are problems such as an increase in cost due to the use of two types of chiral agents, an increase in viscosity due to an increase in the amount added, and a deterioration in response speed. As a representative chiral agent, cholesteryl nonate, a cholesterol derivative, is known, but the temperature dependence of the operating voltage has been desired to be improved.

International Publication No. 97/29167 Pamphlet

  The problem to be solved by the present invention is to provide a liquid crystal composition in which the temperature dependency of the operating voltage is improved without deteriorating the display characteristics of the liquid crystal display element represented by the steepness-response relationship. An object of the present invention is to provide a liquid crystal display device using the liquid crystal composition.

In order to solve the above-mentioned problems, the present invention has studied the combination of various chiral additives and liquid crystal compounds. As a result, the compound represented by the general formula (III) (4′-But-2-enyloxy-biphenyl-4carboxylic acid) It has been found that the use of (acid 1-phenyl-ethyl ester) as a pitch adjusting agent improves the temperature dependence of the operating voltage without deteriorating the display characteristics of the liquid crystal display element.
That is, the present invention provides the following nematic liquid crystal.
General formula (I) and general formula (II)

(Wherein R ¹ , R ² , and R ³ are each independently a fluorine-substituted alkyl group or alkoxyl group, an alkenyl group having 2 to 8 carbon atoms, or a carbon atom, which may be optionally substituted with fluorine. Represents an alkenyloxy group of formula 3-8, and A, B, C, D and E are each independently 1,4-phenylene group, 2-methyl-1,4-phenylene group, 3-methyl-1,4 -Phenylene group, naphthalene-2,6-diyl group, phenanthrene-2,7-diyl group, fluorene-2,7-diyl group, trans-1,4-cyclohexylene group, 1,2,3,4-tetrahydro Naphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, trans-1,3 dioxane-2,5-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl Group Represents a gin-2,5-diyl group or a pyridazine-2,5-diyl group, and these rings may be further substituted with 1 to 3 fluorine atoms, and l and m are each independently 0, 1 or 2 , Z ¹ and Z ² are each independently a single bond, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —COO—, —C≡C— or —CH═. N—N═CH— , wherein Z ³ and Z ⁴ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, — COO—, —C≡C— or —CH═N—N═CH—, wherein X ² is a cyano group, fluorine atom, chlorine atom, trifluoromethoxy group, trifluoromethyl group, difluoromethoxy group, hydrogen atom or It represents 3,3,3-trifluoroethoxy group, ^{X 1} and ^{X 3} is Atom, contain a fluorine atom or a chlorine atom.) In represented compound together 5 or more, the general formula (III)

（式中、Ｒは炭素原子数１から３のアルキル基又は水素原子を表し、*は不斉炭素を表す。）
で表される化合物を０．０２５％〜３．０％含有する液晶組成物であって、ネマティック相―等方性液体相転移温度が６０〜１５０℃でΔｎが０．０７〜０．３０でありｄ／ｐが０．２〜０．６であることを特徴とする液晶組成物。また当該液晶組成物を用いた液晶表示素子を提供する。

(In the formula, R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and * represents an asymmetric carbon.)
A liquid crystal composition containing 0.025% to 3.0% of a compound represented by the formula: a nematic phase-isotropic liquid phase transition temperature of 60 to 150 ° C. and Δn of 0.07 to 0.30. A liquid crystal composition having a d / p of 0.2 to 0.6 . In addition, a liquid crystal display element using the liquid crystal composition is provided.

  With the combination of the present invention, the temperature dependence of the threshold voltage and the response speed could be improved at the same time without greatly deteriorating the steepness (γ) important for increasing the contrast. This liquid crystal composition is effective for an LCD having a twist orientation twisted by 90 ° to 250 °, and is particularly effective for a narrow gap LCD of 5.0 μm or less.

  In the present invention, it contains 5 or more compounds represented by general formula (I) and general formula (II) together, preferably 5 to 25 types, more preferably 7 to 25 types, and particularly preferably 9 to 20 types. The content of the general formula (III) is preferably such that the d / p is in the range of 0.05 to 0.8, and the content is generally preferably 0.1 to 0.7, more preferably 0.2 to 0.6.

In general formula (III), R is preferably a methyl group.
R ¹ , R ² and R ³ are each independently independently fluorine-substituted alkyl group or alkoxyl group having 1 to 8 carbon atoms, alkenyl group having 2 to 8 carbon atoms, or 3 to 8 carbon atoms. An alkyl group having 1 to 6 carbon atoms or an alkoxyl group, an alkenyl group having 2 to 6 carbon atoms or an alkenyloxy group having 3 to 6 carbon atoms is preferable, and an alkyl group having 1 to 6 carbon atoms or an alkoxyl group. A group or an alkenyl group having 2 to 6 carbon atoms is more preferable, and the following structure is preferable as the alkenyl group.

Z¹、Z²、Z³及びZ⁴はそれぞれ独立的に単結合、−CH₂CH₂−、−（CH₂）₄−、−OCH₂−、−CH₂O−、−COO−、−C≡C−又は−CH=N-N=CH−を表すが単結合、−COO−、−C≡C−、−CH=N-N=CH−が特に好ましい。

Z ¹ , Z ² , Z ³ and Z ⁴ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —COO—, — C≡C— or —CH═NN═CH— is represented, but a single bond, —COO—, —C≡C—, —CH═NN═CH— are particularly preferred.

X ^{2 represents a} cyano group, a fluorine atom, a chlorine atom, a trifluoromethoxy group, a trifluoromethyl group, a difluoromethoxy group, a hydrogen atom or a 3,3,3-trifluoroethoxy group. Preferred is a cyano group.
X ¹ and X ^{3 each} represents a hydrogen atom, a fluorine atom or a chlorine atom, preferably a hydrogen atom or a fluorine atom.
As specific compounds of the compounds represented by the general formula (I) and the general formula (II), the following general formula

Wherein R ⁴ and R ⁵ are each independently an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or 3 to 6 carbon atoms. Of the compounds represented by general formula (I-1) to general formula (I-54) among the compounds represented by general formula (I-1, I-3, I-4, I-8, I-10, I-11, I-13, I-14, I-22, I-25, I-26, I-28, I-29, I-31, I- 33, I-36, I-38, I-41, I-45, I-46, I-47) host liquid crystal whose operating voltage, refractive index anisotropy, liquid crystal phase transition temperature and the like are adjusted by a compound selected from Is preferable for realizing a higher contrast and a higher speed response while keeping the operating voltage constant. I-4, I-10, I-11, I-13, I-14, I-22, I-33, I-36, I-45, I-46, I-47) preferable.

  The liquid crystal composition of the present invention preferably has a liquid crystal phase transition temperature of 70 to 150 ° C, particularly preferably 80 to 130 ° C. Δn is preferably 0.07 to 0.30, and particularly preferably 0.13 to 0.25.

  In the 90 ° to 250 ° twist cell, the second component is compared to the first component, and the ratio (d / P value) of the cell thickness d (μm) to the twist pitch length P (μm) is low-dimensional domain, stripe domain, A liquid crystal composition containing a necessary amount in a range of 0.05 to 0.8 in which no high twist domain is generated.

  Hereinafter, the present invention will be described in more detail with reference to Examples * 29167, but the present invention is not limited to these Examples. Further, “%” in the compositions of the following Examples and Comparative Examples means “% by weight”.

          In the examples, the measured characteristics are as follows.

T _NI : Nematic phase-isotropic liquid phase transition temperature (℃)
Vth: Threshold voltage when injected into 240 ° STN-LCD (V) Static 1000Hz
γ: V90 / V10 (Vth) Static 1000Hz
τ: Response speed when injected into 240 ° STN-LCD (ms)
Δn: birefringence
The STN-LCD display element was manufactured as follows. A twisted angle of 240 degrees is obtained by adjusting the mixed liquid crystal by adding a chiral substance to the nematic liquid crystal composition, and rubbing the organic film of “Sunever 150” (manufactured by Nissan Chemical Co., Ltd.) on the opposing flat transparent electrode. Injected into STN-LCD display cell. The chiral material was added so that the intrinsic helical pitch P of the mixed liquid crystal and the cell thickness d of the display cell were Δn · d = 0.85 and d / p = 0.50 by adding the chiral material.
(Example 1 and Comparative Examples 1 to 3)
Nematic liquid crystal composition M1

T _{NI =} 100 Δn = 0.130 Vth = 1.9V
The liquid crystal composition of Example 1 was configured using a compound represented by the formula (III) as a chiral agent. In addition, liquid crystal compositions were prepared using the compounds represented by formula (IV), formula (V) and formula (VI), and the liquid crystal compositions of Comparative Examples 1 to 3 were prepared. These compositions and physical properties are shown in Table 1.

*; Formula (V): Formula (VI) = 2: 1
As shown in Table 1, the liquid crystal composition of Example 1 using the chiral agent represented by the formula (III) has a temperature dependency (mV / ° C.) of the operating voltage from the formula (IV) to the formula ( It is clear that the liquid crystal composition of the comparative example using the chiral agent represented by VI) is greatly improved.
Table 2 shows the response speeds (τr = τd) of the liquid crystal compositions of Example 1 and Comparative Examples 1 to 3 prepared.

As shown in Table 2, the liquid crystal composition of Example 1 using the chiral agent represented by the formula (III) has a response speed of the chiral agent represented by the formulas (IV) to (VI). It is apparent that the liquid crystal composition of the comparative example used is improved by 5% to 10%.

Claims (5)

General formula (I) and general formula (II)

(Wherein R ¹ , R ² , and R ³ are each independently a fluorine-substituted alkyl group or alkoxyl group, an alkenyl group having 2 to 8 carbon atoms, or a carbon atom, which may be optionally substituted with fluorine. Represents an alkenyloxy group of formula 3-8, and A, B, C, D and E are each independently 1,4-phenylene group, 2-methyl-1,4-phenylene group, 3-methyl-1,4 -Phenylene group, naphthalene-2,6-diyl group, phenanthrene-2,7-diyl group, fluorene-2,7-diyl group, trans-1,4-cyclohexylene group, 1,2,3,4-tetrahydro Naphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, trans-1,3 dioxane-2,5-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl Group Represents a gin-2,5-diyl group or a pyridazine-2,5-diyl group, and these rings may be further substituted with 1 to 3 fluorine atoms, and l and m are each independently 0, 1 or 2 and Z ¹ and Z ² are each independently a single bond, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —COO—, —C≡C— or —CH═. N—N═CH—, wherein Z ³ and Z ⁴ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, — COO—, —C≡C— or —CH═N—N═CH—, wherein X ² is a cyano group, fluorine atom, chlorine atom, trifluoromethoxy group, trifluoromethyl group, difluoromethoxy group, hydrogen atom or Represents a 3,3,3-trifluoroethoxy group, and X ¹ and X ³ are water Containing 5 or more compounds represented by the general formula (III).

(In the formula, R represents an alkyl group having 1 to 3 carbon atoms or a hydrogen atom, and * represents an asymmetric carbon.)
A liquid crystal composition containing 0.025% to 3.0% of a compound represented by the formula:
A liquid crystal composition having a nematic phase-isotropic liquid phase transition temperature of 60 to 150 ° C., Δn of 0.07 to 0.30, and d / p of 0.2 to 0.6. General formula (I-1) to general formula (I-54)

(Wherein R ⁴ and R ⁵ represent an alkyl group or alkoxyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms). The liquid crystal composition according to claim 1, comprising:   The liquid crystal composition according to claim 1 or 2, comprising 0.1 to 2% of the general formula (III).   5 to 95% of the compound represented by the general formula (I) is contained, 5 to 95% of the compound represented by the general formula (II) is contained, and 0.02 to 0.02 of the compound represented by the general formula (III) is contained. The liquid crystal composition according to claim 1, comprising 3%.   The liquid crystal display element comprised using the liquid-crystal composition of Claims 1-4.