JP2008308581A - Liquid crystal composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition having a broad liquid crystal phase temperature range, low viscosity and negative dielectric anisotropy and useful for an active matrix liquid crystal display element. <P>SOLUTION: The invention provides a nematic liquid crystal composition containing 20-65% compound expressed by structural formula (1) as the first component, and having a nematic-isotropic transition temperature of 68-120°C, a crystal or smectic-nematic transition temperature of -80 to -20°C, a refractive index anisotropy Δn of 0.05-0.15 and a dielectric anisotropy Δε of -2.0 to -8.0. An active matrix liquid crystal display element having a broad operation temperature range is provided by the liquid crystal composition of the invention and the element is extremely practical as a liquid crystal display of a reflection mode, a semi-transmission mode, etc. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nematic crystal composition having a negative dielectric anisotropy useful as an electro-optical liquid crystal display material, and a liquid crystal display device using the same.

  Due to the excellent display quality, active matrix liquid crystal display devices are put on the market for portable terminals, liquid crystal televisions, projectors, computers and the like. In the active matrix display method, TFT (thin film transistor) or MIM (metal insulator metal) is used for each pixel, and high voltage holding ratio is regarded as important in this method. In order to obtain a wider viewing angle characteristic, a TFT display combined with VA, IPS, and OCB modes and a reflection type in ECB mode have been proposed to obtain a brighter display. In order to cope with such display elements, new liquid crystal compounds or liquid crystal compositions have been proposed (Patent Document 1 and Patent Document 2).

  In twisted nematic liquid crystal display elements (TN-LCDs) and super twisted nematic liquid crystal display elements (STN-LCDs), there is a strong demand for liquid crystal compositions with reduced viscosity in order to increase the response speed of displays. Yes. In addition, in order to enable a wide operating temperature range from a low temperature region to a high temperature region, a liquid crystal composition having a wide nematic temperature range is required.

  The low viscosity liquid crystal composition can be obtained by increasing the content of a bicyclohexane derivative composed of a cyclohexane ring having a small Δn value. However, these compounds have high smectic properties, and it is difficult to lower the nematic phase lower limit temperature (Tn) when the content of the bicyclohexane compound is increased, and a liquid crystal composition having a wide nematic temperature range is obtained. It was difficult.

Liquid crystal compositions having a relatively low viscosity are already known, and specific examples of preferred compounds are disclosed (Patent Document 3). A liquid crystal composition having a small refractive index anisotropy in which a bicyclohexane derivative and a phenylbicyclohexane derivative are combined is already known, and a specific example of a preferable compound is disclosed (Patent Document 4). However, the viscosity of these compositions was not sufficiently low. A liquid crystal composition using vinyl or propylbicyclohexane has already been disclosed (see Patent Document 5). However, the liquid crystal composition described in the cited document has a positive dielectric anisotropy, and there is no disclosure about a liquid crystal composition having a completely different dielectric anisotropy.
On the other hand, liquid crystal compounds having a 2,3-difluorophenylene skeleton as described below (see Patent Documents 6 and 7) are disclosed as liquid crystal materials having negative dielectric anisotropy.

(In the formula, R and R ′ represent an alkyl group having 1 to 10 carbon atoms or an alkoxy group.)
However, a liquid crystal composition having a negative dielectric anisotropy composed only of the compounds described in the cited document achieves a sufficiently low viscosity in a liquid crystal composition that requires a high-speed response such as a liquid crystal television. It has not reached.
From the above, it has been difficult to obtain a liquid crystal composition having a wide liquid crystal phase temperature range and low viscosity and negative dielectric anisotropy.

JP-A-2-233626 Special Publication 4-501575 Publication Japanese Patent No. 2882577 (Example 28 on page 32) JP-A-10-259377 (Examples A to D on page 17) JP 2006-328399 A JP-A-60-199840 JP-A-2-4725

  The problem to be solved by the present invention is to provide a liquid crystal composition for an active matrix liquid crystal display element having a wide liquid crystal phase temperature range, a low viscosity, and a negative dielectric anisotropy, and the liquid crystal composition It is an object to provide an active matrix type liquid crystal display element having a wide operating temperature range.

  As a result of intensive studies to solve the above problems, the present invention has the structural formula (1) as the first component,

で表される化合物を20〜65%含有し、ネマチック−アイソトロピック転移温度が68℃〜120℃であり、クリスタル又はスメクチック−ネマチック転移温度が-80℃〜-20℃であり、屈折率異方性Δnが0.05〜0.15であり、誘電率異方性Δεが-2.0〜-8.0であることを特徴とするアクティブマトリクス型液晶表示素子用液晶組成物及び当該液晶組成物を構成部材とする液晶表示素子を提供する。

20 to 65% of the compound represented by the formula, the nematic-isotropic transition temperature is 68 ° C to 120 ° C, the crystal or smectic-nematic transition temperature is -80 ° C to -20 ° C, and the refractive index is anisotropic. A liquid crystal composition for an active matrix liquid crystal display device, having a property Δn of 0.05 to 0.15 and a dielectric anisotropy Δε of −2.0 to −8.0, and a liquid crystal display comprising the liquid crystal composition as a constituent member An element is provided.

  The combination of the liquid crystal compounds of the present invention has a nematic phase that is very low in viscosity and stable at low temperatures, has a wide liquid crystal phase temperature range, and can adjust the refractive index anisotropy (Δn = 0.05 to 0.15) over a wide range. In addition, a liquid crystal composition for an active matrix liquid crystal display element having excellent reliability was obtained. By using this composition, an active matrix liquid crystal display element having a wide operating temperature range is provided, which is very practical as a liquid crystal display in a reflective or transflective mode.

  In the liquid crystal composition of the present invention, the content of the compound represented by the structural formula (1) as the first component is 20 to 65%, but is preferably in the range of 25 to 50% by mass.

  General formula (2), general formula (3) and general formula (4) as the second component to adjust the physical properties of the composition

(式中、R¹〜R⁶はそれぞれ独立して炭素数1〜15のアルキル基又は炭素数2〜15のアルケニル基を表し、この基は非置換であるか、あるいは置換基として少なくとも1個のハロゲン基を有しており、そしてこれらの基中に存在する1個又は2個以上のCH₂基はそれぞれ独立してO原子が相互に直接結合しないものとして-O-、-S-、-CO-により置き換えられても良く、
B¹〜B⁷はそれぞれ独立して
(a) トランス-1,4-シクロへキシレン基(この基中に存在する1個のCH₂基又は隣接していない2個以上のCH₂基は -O- 又は -S- に置き換えられてもよい。)
(b) 1,4-フェニレン基(この基中に存在する1個のCH₂基又は隣接していない2個以上のCH₂基は -N- に置き換えられてもよい。)
からなる群より選ばれる基を表し、上記の基(a)、基(b)はCH₃又はハロゲンで置換されていても良く、
L¹〜L⁷はそれぞれ独立して単結合、-CH₂CH₂-、-(CH₂)₄-、-COO-、-OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-又は-C≡C-を表し、
m、n、o、p、q及びrはそれぞれ独立して0、1又は2を表し、m+nは0、1又は2を表し、o+p、及びq+rはそれぞれ独立して0、1、2又は3を表し、
X¹〜X⁷はそれぞれ独立してH、F又はClを表す。) で表される化合物からなる群から選ばれる1種もしくは2種以上の化合物を含有することが好ましい。これらの化合物を含有する場合、1種〜15種が好ましく、3種〜10種がより好ましく、5種〜10種がさらに好ましい。又、これらの化合物からなる群の含有率は、20〜70質量％の範囲であることが好まく、30〜60質量％の範囲であることがより好ましい。

(Wherein R ^{1 to} R ⁶ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and this group is unsubstituted or has at least one substituent. And one or two or more CH ₂ groups present in these groups are each independently -O-, -S-, May be replaced by -CO-
B ^{1 to} B ⁷ are each independently
(a) trans-1,4-cyclohexylene group (one CH ₂ group present in this group or two or more non-adjacent CH ₂ groups are replaced by -O- or -S- May be good.)
(b) 1,4-phenylene group (one CH ₂ group present in this group or two or more non-adjacent CH ₂ groups may be replaced by —N—)
Represents a group selected from the group consisting of the above group (a), the group (b) may be substituted with CH ₃ or halogen,
L ^{1 to} L ⁷ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ —, —CF ₂ represents O- or -C≡C-
m, n, o, p, q and r each independently represents 0, 1 or 2, m + n represents 0, 1 or 2, and o + p and q + r each independently represents 0. , 1, 2 or 3,
X ^{1 to} X ⁷ each independently represent H, F or Cl. It is preferable to contain one or more compounds selected from the group consisting of compounds represented by When these compounds are contained, 1 to 15 types are preferable, 3 to 10 types are more preferable, and 5 to 10 types are more preferable. Further, the content of the group consisting of these compounds is preferably in the range of 20 to 70% by mass, and more preferably in the range of 30 to 60% by mass.

In General Formula (2), General Formula (3), or General Formula (4), R ^{1 to} R ⁶ are each an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkyl having 2 to 10 carbon atoms. A group in which one CH ₂ group present in the group is replaced by —O— is preferably an unsubstituted linear alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, carbon number 2 It is more preferred that one CH ₂ group present in the alkyl group of ˜8 is replaced by —O—, and the structure of the following formulas (a) to (e) is more preferred for the alkenyl group.

(構造式は右端で環に連結しているものとする。)

(The structural formula shall be connected to the ring at the right end.)

B ^{1 to} B ⁷ are preferably a trans-1,4-cyclohexylene group, a 1,4-phenylene group, a 3-fluoro-1,4-phenylene group or a 3,5-difluoro-1,4-phenylene group, L ^{1 to} L ⁷ are more preferably a 1,4-phenylene group or a trans-1,4-cyclohexylene group, a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, — _{OCH 2 -, - CH 2 O} -, - OCF 2 -, - CF 2 O- or -C≡C- in _{but, -CH 2 CH 2 -, -} OCH 2 -, - CH 2 O-, or single A bond is preferred, —CH ₂ CH ₂ —, —OCH ₂ —, —CH ₂ O— or a single bond is more preferred, —OCH ₂ —, —CH ₂ O— or a single bond is particularly preferred.

m, n, o, p, q and r each independently represent 0, 1 or 2, m + n represents 0, 1 or 2, and o + p and q + r each independently represent 0, 1, 2 or 3, m + n is preferably 1, o + p and q + r are preferably 2. X ^{1 to} X ⁷ each independently represent H, F or Cl, but —H or —F is preferred.
More specifically, the following compounds are preferred as the specific structure of the general formula (2).

（式中R¹及びR²はそれぞれ独立して、炭素数1〜15のアルキル基、アルコキシル基、炭素数2〜15のアルケニル基又は炭素数2〜15のアルケニルオキシ基を表す。）
一般式(3)の具体的な構造として以下の一般式で表される化合物が好ましい。

(In the formula, R ¹ and R ² each independently represent an alkyl group having 1 to 15 carbon atoms, an alkoxyl group, an alkenyl group having 2 to 15 carbon atoms, or an alkenyloxy group having 2 to 15 carbon atoms.)
As a specific structure of the general formula (3), a compound represented by the following general formula is preferable.

（式中R³及びR⁴はそれぞれ独立して、炭素数1〜15のアルキル基、アルコキシル基又は炭素数2〜15のアルケニル基を表す。）
一般式(4)の具体的な構造として以下の一般式で表される化合物が好ましい。

(In the formula, R ³ and R ⁴ each independently represent an alkyl group having 1 to 15 carbon atoms, an alkoxyl group, or an alkenyl group having 2 to 15 carbon atoms.)
As a specific structure of the general formula (4), a compound represented by the following general formula is preferable.

（式中R⁵及びR⁶はそれぞれ独立して、炭素数1〜15のアルキル基、アルコキシル基又は炭素数2〜15のアルケニル基を表す。）

(In the formula, R ⁵ and R ⁶ each independently represents an alkyl group having 1 to 15 carbon atoms, an alkoxyl group, or an alkenyl group having 2 to 15 carbon atoms.)

In the present invention, the nematic phase-isotropic liquid phase transition temperature (T _NI ) is more preferably 70 ° C. or higher. The solid phase or smectic phase-nematic phase transition temperature (T 1 _{→ N 2} ) is preferably −20 ° C. or lower. The dielectric anisotropy (Δε) at 25 ° C. is preferably −2.0 to −8.0, more preferably −3.0 to −5.0. The refractive index anisotropy (Δn) at 25 ° C. is preferably 0.08 to 0.13.

The nematic liquid crystal composition is useful for a liquid crystal display element, particularly useful for a liquid crystal display element for driving an active matrix, and can be used for a liquid crystal display element for a reflection mode or a transflective mode.
The nematic liquid crystal composition of the present invention may contain a normal nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal and the like in addition to the above compounds.

The present invention will be further described in detail below, but the present invention is not limited thereto. Further, “%” in the compositions of the following and comparative examples means “mass%”.
T _NI : Nematic phase-isotropic liquid phase transition temperature (° C) is the liquid crystal phase upper limit temperature
T _{→ N} : Solid phase or smectic phase-nematic phase transition temperature (° C) is the lower limit of liquid crystal phase temperature
And
Δε: Dielectric anisotropy Δn: Refractive index anisotropy η: Viscosity
HR: Retention rate at 70 ° C (%) (Injected into VA-LCD with cell thickness of 3.5μm, 5V applied, flame
Between the measured voltage and the initial applied voltage when measured at 16.7 ms and a pulse width of 64 μs.
Value expressed as a percentage. )
The following abbreviations are used in compound descriptions.
Terminal n (number) C _n H _{2n + 1-}
-2- -CH ₂ CH ₂ -
-1O- -CH ₂ O-
-O1- -OCH _2-
-On -OC _n H _{2n + 1}
ndm- C _n H _{2n + 1} -C = C- (CH ₂ ) _m-1-

(Examples 1 and 2) Adjustment of liquid crystal composition Nematic liquid crystal compositions (No. 1) and (No. 2) shown below were prepared and their physical properties were measured, and the results are shown in Table 1.

The nematic liquid crystal compositions (No. 1) to (No. 2) of 1-2 are characterized by nematic phase-isotropic liquid phase transition temperature (T _NI ), solid phase or smectic phase-nematic phase transition temperature (T _{→ N} ), dielectric anisotropy (Δε), and refractive index anisotropy (Δn) showed desired values. Moreover, the viscosity was low, the response speed of the panel was good, and the value of the voltage holding ratio was also good, indicating high reliability.

(Comparative Examples 1-2) Adjustment of liquid crystal composition As comparative examples, nematic liquid crystal compositions (R1)-(R2) shown below were prepared, their physical properties were measured, and the results are shown in Table 2.

  Comparative Examples 1 and 2 did not contain the first component, but were higher in viscosity than the Examples.

Claims (5)

Structural formula (1) as the first component,

20 to 65% of the compound represented by the formula, the nematic-isotropic transition temperature is 68 ° C to 120 ° C, the crystal or smectic-nematic transition temperature is -80 ° C to -20 ° C, and the refractive index is anisotropic. A nematic liquid crystal composition having a property Δn of 0.05 to 0.15 and a dielectric anisotropy Δε of −2.0 to −8.0. 2. The nematic liquid crystal composition according to claim 1, comprising 25 to 50% of the compound represented by the structural formula (1). General formula (2), general formula (3) and general formula (4) as the second component

(Wherein R ^{1 to} R ⁶ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and this group is unsubstituted or has at least one substituent. And one or two or more CH ₂ groups present in these groups are each independently -O-, -S-, May be replaced by -CO-
B ^{1 to} B ⁷ are each independently
(a) trans-1,4-cyclohexylene group (one CH ₂ group present in this group or two or more non-adjacent CH ₂ groups are replaced by -O- or -S- May be good.)
(b) 1,4-phenylene group (one CH ₂ group present in this group or two or more non-adjacent CH ₂ groups may be replaced by —N—)
Represents a group selected from the group consisting of the above group (a), the group (b) may be substituted with CH ₃ or halogen,
L ^{1 to} L ⁷ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ —, —CF ₂ represents O- or -C≡C-
m, n, o, p, q and r each independently represents 0, 1 or 2, m + n represents 0, 1 or 2, and o + p and q + r each independently represents 0. , 1, 2 or 3,
X ^{1 to} X ⁷ each independently represent H, F or Cl. 2. The nematic liquid crystal composition according to claim 1, comprising one or more compounds selected from the group consisting of compounds represented by the formula: 3. A liquid crystal display device using the nematic liquid crystal composition according to claim 1. 3. An active matrix liquid crystal display device using the nematic liquid crystal composition according to claim 1.