JP5233226B2 - Nematic liquid crystal composition - Google Patents

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 for 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 display response speed. Yes. In addition, a liquid crystal composition having a wide nematic temperature range is required to enable a wide operating temperature range from a low temperature region to a high temperature region.

  A 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 when the content of the bicyclohexane compound is increased, it is difficult to lower the nematic phase lower limit temperature (Tn), 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 compound 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.

  On the other hand, liquid crystal compounds having a 2,3-difluorophenylene skeleton as described below (see Patent Documents 5 and 6) 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.
In addition, when the compound having a negative dielectric anisotropy is composed only of a liquid crystal compound having a 2,3-difluorophenylene skeleton as described above, there are two polar groups that can be laterally introduced into the liquid crystal molecule long axis. However, liquid crystal compositions that are required to be driven at a low voltage, such as mobile phones, have not achieved a sufficiently low voltage.
A trifluoronaphthalene compound has been developed as a compound having a negative dielectric anisotropy advantageous for low voltage driving, and a trifluoronaphthalene compound having oxygen atoms at the 2nd and 6th positions constituting the present invention has already been disclosed. (See Patent Document 7). However, according to the cited document, the naphthalene compound is advantageous in terms of low voltage driving and viscosity, but it is difficult to sufficiently reduce the liquid crystal phase lower limit temperature (solid phase or smectic phase-nematic phase transition temperature). there were.
In addition, although there are already disclosures on difluorochroman compounds (see Patent Documents 8 and 9), liquid crystal compositions using such compounds are disadvantageous in terms of viscosity. There is no disclosure of a specific composition that can solve the problem.

  From the above, it is difficult to obtain a liquid crystal composition for an active matrix liquid crystal display element having a low liquid crystal phase lower limit temperature and a negative dielectric anisotropy while maintaining physical properties such as refractive index anisotropy and viscosity. Met.

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-A-60-199840 JP-A-2-4725 JP 2006-267083 A JP 2006-199941 A JP 2006-151864 A

  The problem to be solved by the present invention is an active matrix liquid crystal having a low dielectric constant anisotropy having a low solid phase or smectic phase-nematic phase transition temperature while maintaining physical properties such as refractive index anisotropy and viscosity. It is an object of the present invention to provide a liquid crystal composition for display elements and to provide an active matrix liquid crystal display element having a wide operating temperature range using the liquid crystal composition.

  The present invention, as a result of extensive studies to solve the above problems, as a first component general formula (1) and general formula (2)

(式中、R¹〜R⁴はそれぞれ独立的に炭素数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、
Z¹は単結合、-CH₂CH₂-、-(CH₂)₄-、-COO-、-OCH₂-、-CH₂O-、-OCF₂-又は-CF₂O-を表す。)で表される化合物からなる群から選ばれる化合物を1種もしくは2種以上含有し、第二成分として一般式(3)及び一般式(4)

(Wherein R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms,
Z ¹ represents a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — or —CF ₂ O—. ) Containing one or more compounds selected from the group consisting of compounds represented by general formula (3) and general formula (4) as the second component

(式中、R⁵〜R⁸はそれぞれ独立的に炭素数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、
Z²は単結合、-CH₂CH₂-、-(CH₂)₄-、-COO-、-OCH₂-、-CH₂O-、-OCF₂-又は-CF₂O-を表す。)で表される化合物からなる群から選ばれる化合物を1種もしくは2種以上含有し、第三成分として構造式(5)

(Wherein R ^{5 to} R ⁸ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms,
Z ² represents a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — or —CF ₂ O—. ) Containing one or more compounds selected from the group consisting of compounds represented by the structural formula (5)

で表される化合物を10〜50質量%含有し、誘電率異方性が負であることを特徴とするネマチック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。

And a liquid crystal display element comprising the liquid crystal composition as a constituent member. The nematic liquid crystal composition has a negative dielectric anisotropy.

  The combination of the liquid crystal compounds of the present invention has low viscosity, has a solid phase or smectic phase-nematic phase transition temperature, can adjust the refractive index anisotropy (Δn = 0.05 to 0.15) in a wide range, and is reliable. An excellent liquid crystal composition for an active matrix liquid crystal display device 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 transmissive or transflective mode.

In the liquid crystal composition of the present invention, the compound represented by the general formula (1) or the general formula (2) is preferably selected as the first component, but one or more compounds are preferably selected, but represented by the structural formula (1). Preferably, one or more compounds are selected from each of the compound represented by the structural formula (2) and the compound represented by the structural formula (2). The compound represented by the compound (2) is a compound in which Z ¹ is a single bond, and —CH ₂ —. More preferably, one or more of each of the compounds that are CH ₂ — are selected.
Further, the content of the first component is preferably in the range of 10 to 50% by mass, more preferably 20 to 35% by mass, and in the case of obtaining a higher speed response, the range of 10 to 35% by mass. More preferably, in the case where lower voltage driving is desired, it is more preferably in the range of 35 to 50% by mass.

  As the second component, the compound represented by the general formula (3) or the general formula (4) is preferably selected from one or more. The content of the second component is preferably in the range of 3 to 20% by mass, but more preferably 10 to 20% by mass when a lower refractive index anisotropy is desired.

The content of one or more compounds selected from the compound group represented by Structural Formula (5) as the third component is in the range of 10 to 50% by mass, but in the range of 15 to 45% by mass. More preferably, the content is in the range of 20 to 40% by mass.
General formula (6) as the fourth component

(式中、R⁹、R¹⁰は一般式(1)におけるR¹と同じ意味を表し、
B¹、B²はそれぞれ独立的に
(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- 及び又は -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であり、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、
Z³はそれぞれ独立的に一般式(2)におけるZ¹と同じ意味を表し、
nは1、2又は3であるが、
構造式(5)で表される化合物は除く。)で表される化合物を1種又は2種以上含有するが、n=1である化合物とn=2である化合物をそれぞれ1種又は2種以上含有することがより好ましく、2種以上含有することがさらに好ましい。
第5成分として一般式(7)

(In the formula, R ⁹ and R ¹⁰ represent the same meaning as R ¹ in the general formula (1),
B ¹ and B ² 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- and / or -S- (May be)
(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-)
A group selected from the group consisting of: the group (a), the group (b) may be substituted with CH ₃ or halogen,
Z ³ each independently represents the same meaning as Z ¹ in the general formula (2),
n is 1, 2 or 3,
Excludes compounds represented by structural formula (5). 1 or 2 or more compounds, more preferably 1 or 2 or more compounds each containing n = 1 and n = 2, more preferably 2 or more compounds. More preferably.
General formula (7) as the fifth component

(式中、R¹¹、R¹²は一般式(1)におけるR¹と同じ意味を表し、
B³、B⁴はそれぞれ独立的に一般式(6)におけるB¹と同じ意味を表し、
Z⁴、Z⁵は一般式(6)におけるZ¹と同じ意味を表し、
k、lはそれぞれ独立的に0、1又は2であるがk+lは1又は2であり、
X¹はF、Cl、CF₃又はHである。)
で表される化合物を1種又は2種以上含有するが、2種以上含有することが好ましい。
また、R¹〜R¹²は炭素数1〜10のアルキル基又は炭素数2〜10のアルケニル基、炭素数2〜10のアルキル基中に存在する1個のCH₂基が-O-により置き換えられたものが好ましく、未置換の直鎖状炭素数1〜8のアルキル基又は炭素数2〜8のアルケニル基、炭素数2〜8のアルキル基中に存在する1個のCH₂基が-O-により置き換えられたものがより好ましく、アルケニル基では以下の式(a)〜(e)の構造が好ましく、(b)〜(d)がより好ましく、(b)又は(d)がさらに好ましい。

(Wherein R ¹¹ and R ¹² represent the same meaning as R ¹ in the general formula (1),
B ³ and B ⁴ each independently represent the same meaning as B ¹ in the general formula (6),
Z ⁴ and Z ⁵ represent the same meaning as Z ¹ in the general formula (6),
k and l are each independently 0, 1 or 2, but k + l is 1 or 2,
X ¹ is F, Cl, CF ₃ or H. )
1 type or 2 types or more, but preferably 2 types or more are contained.
R ^{1 to} R ¹² are alkyl groups having 1 to 10 carbon atoms or alkenyl groups having 2 to 10 carbon atoms, and one CH ₂ group present in the alkyl group having 2 to 10 carbon atoms is replaced by —O—. In which an unsubstituted linear alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms and one CH ₂ group present in the alkyl group having 2 to 8 carbon atoms is- More preferred are those substituted by O-, and alkenyl groups preferably have the structures of the following formulas (a) to (e), more preferably (b) to (d), and still more preferably (b) or (d) .

(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 ⁴ are preferably a trans-1,4-cyclohexylene group or a 1,4-phenylene group. B ¹ .about.B ⁴ is a single _{bond, -CH 2 CH 2 -, -} (CH 2) 4 -, - COO -, - OCH 2 -, - CH 2 O -, - OCF 2 -, - CF 2 O- Or —C≡C—, but —CH ₂ CH ₂ —, —OCH ₂ —, —CH ₂ O—, or a single bond is preferred, —CH ₂ CH ₂ —, —OCH ₂ —, —CH ₂ O -Or a single bond is more preferable, -OCH _2- , -CH ₂ O- or a single bond is particularly preferable.

In the present invention, the nematic phase-isotropic liquid phase transition temperature (T _NI ) is more preferably 65 ° 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 −2.5 to −6.0. 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.

  Hereinafter, the present invention will be described in more detail with reference to examples, 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

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-
-On -OC _n H _{2n + 1}
ndm- C _n H _{2n + 1} -C = C- (CH ₂ ) _m-1-

  The following nematic liquid crystal compositions (No. 1) to (No. 4) 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. 4) of 1 to 4 have 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. Also, the viscosity was low and the panel response speed was good. For the nematic composition 1, the content of the third component represented by the structural formula (5) was 15% by mass, which was a sufficiently low solid phase or smectic phase-nematic phase transition temperature (T _{→ N} ) Is obtained. In the nematic composition 3, the content of the third component represented by the structural formula (5) is 37% by mass within the most preferable range as the content of the third component. Compared to R1, T _{→ N} , Δε, and all the viscosities showed significant advantages. In particular, nematic composition 2 prepared mainly for the purpose of lowering the driving voltage has a sufficiently low value of dielectric anisotropy, and nematic composition 4 prepared mainly for the purpose of increasing the response speed. Shows a sufficiently low viscosity and a good response speed.

  As comparative examples, nematic liquid crystal compositions (R1) to (R3) shown below were prepared and their physical properties were measured. Table 2 shows the results.

  Although R1 does not contain a third component, a sufficiently low solid phase or smectic phase-nematic phase transition temperature is not obtained as compared with the examples. Although R2 does not contain the second component, it has only a very high solid phase or smectic phase-nematic phase transition temperature although its viscosity is lower than in the examples. Although R3 does not contain the first component, it exhibits a very high solid phase or smectic phase-nematic phase transition temperature, and also exhibits a very high viscosity.

Claims (9)

General formula (1) and general formula (2) as the first component

(Wherein R ^{1 to} R ⁴ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms,
Z ¹ represents a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — or —CF ₂ O—. ) Containing one or more compounds selected from the group consisting of compounds represented by general formula (3) and general formula (4) as the second component

(Wherein R ^{5 to} R ⁸ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms,
Z ² represents a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — or —CF ₂ O—. ) Containing one or more compounds selected from the group consisting of compounds represented by the structural formula (5)

A nematic liquid crystal composition comprising 10 to 50% by mass of a compound represented by the formula and having a negative dielectric anisotropy. 2. The liquid crystal composition according to claim 1, comprising a compound represented by the general formula (1) and a compound represented by the general formula (2). 3. The liquid crystal composition according to claim 1, comprising a compound in which Z ¹ is a single bond in the general formula (2) and a compound in which Z ¹ is —CH ₂ CH ₂ —. 4. The liquid crystal composition according to claim 1, comprising a compound represented by the general formula (3) and a compound represented by the general formula (4). The liquid crystal composition according to any one of claims 1 to 4, wherein the content of the first component is 10 to 50% by mass and the content of the second component is 3 to 20% by mass. General formula (6) as the fourth component

(Wherein R ⁹ and R ¹⁰ each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms,
B ¹ and B ² each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted with halogen,
Z ³ represents a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — or —CF ₂ O—,
n represents 1, 2 or 3,
Excludes compounds represented by structural formula (5). 6. The liquid crystal composition according to any one of claims 1 to 5, comprising one or more compounds represented by formula (1). 7. The liquid crystal composition according to claim 6, comprising a compound in which n = 1 in the general formula (6) and a compound in which n = 2. 8. A vertical alignment liquid crystal display device using the liquid crystal composition according to claim 1 and having a pretilt angle of 80 to 90 °. 9. A liquid crystal display device using the liquid crystal display element according to claim 8.