JP2009040942A - Nematic liquid crystal composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition for active matrix type liquid crystal display elements, having a wide liquid crystal phase temperature range, low viscosity and negative dielectric anisotropy, and to provide active matrix type liquid crystal display elements using the composition. <P>SOLUTION: A nematic liquid crystal composition comprising a compound represented by general formula (1) as the first ingredient and a compound represented by general formula (2) as the second ingredient and having negative dielectric anisotropy is provided. <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 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).

  Today, there is a demand for a liquid crystal composition having a reduced viscosity in order to increase the response speed. 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. 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.

  On the other hand, as liquid crystal materials having a negative dielectric anisotropy, specific examples of a liquid crystal compound having a 2,3-difluorophenylene skeleton as described below and a liquid crystal composition having a relatively low viscosity using the same are disclosed. (See Patent Document 3).

  Further, specific examples of the following liquid crystal compound having a 2,3-difluorophenylene skeleton and a liquid crystal composition having a relatively low viscosity using the same are disclosed (see Patent Documents 4 and 5). However, the viscosity of these compositions was not sufficiently low.

  Furthermore, the following liquid crystal compounds having a 2,3-difluorophenylene skeleton are disclosed as liquid crystal materials having negative dielectric anisotropy (see Patent Documents 6 and 7).

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 is difficult to obtain a liquid crystal composition having a wide liquid crystal phase temperature range and low viscosity anisotropy, and development of a liquid crystal composition capable of solving these problems is desired. It was rare.

JP-A-2-233626 Special Publication 4-501575 Publication JP 2007-39642 A JP 2006-233182 A JP 2007-39639 A JP-A-60-199840 Japanese Patent Laid-Open No. 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 device having a wide liquid crystal phase temperature range, low viscosity, and negative dielectric anisotropy, and using the same An object is to provide an active matrix liquid crystal display element.

As a result of intensive studies to solve the above problems, the present inventors have found the usefulness of a liquid crystal composition containing a compound having two characteristic structures, and have completed the present invention.
The present invention is a general formula (1) as a first component,

（式中、R¹は炭素数1〜15のアルキル基または炭素数2〜15のアルケニル基を表し、mは0または1を表す。）で表される化合物を含有し、第二成分として一般式(2)

(Wherein R ¹ represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and m represents 0 or 1). Formula (2)

（式中、R²は炭素数1〜15のアルキル基または炭素数2〜15のアルケニル基を表す。）で表される化合物を含有し、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これを用いた液晶表示素子を提供する。

(Wherein R ² represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms), and has a negative dielectric anisotropy, A nematic liquid crystal composition and a liquid crystal display device using the same are provided.

  The combination of the liquid crystal compounds of the present invention has a nematic phase having a lower viscosity and stable at low temperatures, a wide liquid crystal phase temperature range, and a refractive index anisotropy (Δn = 0.05 to 0.15) can be adjusted over a wide range, and A liquid crystal composition for an active matrix type liquid crystal display element excellent in reliability was obtained. By using this composition, an active matrix type liquid crystal display device having a high response speed and a wide operating temperature range is provided, and is very useful as a liquid crystal display such as VA mode, IPS mode or ECB mode.

  The liquid crystal composition in the present invention is characterized by containing the general formulas (1) and (2) at the same time, and the content thereof is 5 to 60% of the compound represented by the general formula (1), It is preferable to contain 5 to 60% of the compound represented by the general formula (2), 10 to 50% of the compound represented by the general formula (1), and a compound represented by the general formula (2) It is more preferable to contain 10 to 30%.

In the general formula (1), R ¹ represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms or an alkenyl group having 2 to 7 carbon atoms. Preferably, an alkyl group having 2 to 5 carbon atoms is particularly preferable.
In the general formula (2), R ² represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms or an alkenyl group having 2 to 7 carbon atoms. An alkenyl group having 2 to 5 carbon atoms is preferable.
The liquid crystal composition of the present invention has the general formula (3) as the third component.

（式中、R^a及びR^bはそれぞれ独立して炭素数1〜15のアルキル基または炭素数2〜15のアルケニル基を表す。）で表される化合物を含有することがより好ましい。この場合の含有量は、一般式(1)で表される化合物を5〜60%含有し、一般式(2)で表される化合物を5〜60%含有し、一般式(3)で表される化合物を5〜60％含有することが好ましく、一般式(1)で表される化合物を10〜50％含有し、一般式(2)で表される化合物を10〜30％含有し、一般式(3)で表される化合物を10〜40％含有することがより好ましい。
一般式(3)において、R^a及びR^bはそれぞれ独立して炭素数1〜5のアルキル基または炭素数2〜5のアルケニル基が好ましく、R^aまたはR^bの一方がアルキル基を表し、もう一方がアルケニル基を表すことがより好ましく、
具体的な構造としては、式(3-1)

(In the formula, R ^a and R ^b each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms). The content in this case is 5 to 60% of the compound represented by the general formula (1), 5 to 60% of the compound represented by the general formula (2), and represented by the general formula (3). It is preferable to contain 5 to 60% of the compound, 10 to 50% of the compound represented by the general formula (1), 10 to 30% of the compound represented by the general formula (2), It is more preferable to contain 10 to 40% of the compound represented by the general formula (3).
In the general formula (3), R ^a and R ^b are each independently preferably an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, and one of R ^a or R ^b represents an alkyl group, More preferably, the other represents an alkenyl group,
As a specific structure, the formula (3-1)

で現される化合物が特に好ましい。
本発明の液晶組成物の物性値を調整するために、一般式(4)及び一般式(5)

Are particularly preferred.
In order to adjust the physical properties of the liquid crystal composition of the present invention, the general formula (4) and the general formula (5)

（式中、R³〜R⁴はそれぞれ独立して炭素数1〜10のアルキル基、アルコキシル基または炭素数2〜10のアルケニル基を表し、R⁵〜R⁶はそれぞれ独立して炭素数1〜10のアルキル基またはアルコキシル基を表し、A〜Eはそれぞれ独立的してトランス-1,4-シクロへキシレン基または1,4-フェニレン基を表すが、これらの基中の水素原子はそれぞれ独立して-CH₃、-Fまたは-Clで置換されていても良く、L¹〜L⁴はそれぞれ独立して単結合、-CH₂CH₂-、-(CH₂)₄-、-CH=CH-、-COO-、-OCH₂-、-CH₂O-、-OCF₂-または-CF₂O-を表し、n及びoはそれぞれ独立して0〜2を表し、X¹〜X²はそれぞれ独立して-H、-Fまたは-Clを表す。）で表される化合物群から選ばれる1種または2種以上の化合物を含有することが好ましい。但し、該化合物群から一般式(2)、一般式(3)及び式(3-1)で表される化合物は除かれる。

(In the formula, R ^{3 to} R ⁴ each independently represents an alkyl group having 1 to 10 carbon atoms, an alkoxyl group, or an alkenyl group having 2 to 10 carbon atoms, and R ^{5 to} R ⁶ each independently represents 1 carbon atom. Represents an alkyl group or an alkoxyl group of -10, and A to E each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group, and the hydrogen atoms in these groups are independently -CH _3, may be substituted by -F or -Cl, L ¹ ~L ⁴ each independently represent a single _{bond, -CH 2 CH 2 -, -} (CH 2) 4 -, - CH = CH-, -COO-, -OCH _2- , -CH ₂ O-, -OCF ₂ -or -CF ₂ O-, n and o each independently represent 0 to 2, X ^{1 to} X ² each independently represents —H, —F or —Cl.) It is preferable to contain one or more compounds selected from the group of compounds represented by: However, compounds represented by general formula (2), general formula (3), and formula (3-1) are excluded from the compound group.

When the compound selected from the compound group represented by the general formula (4) and the general formula (5) is contained, it is preferably contained 1 to 15 types, more preferably 1 to 5 types.
The compound selected from the compound group represented by the general formula (4) and the general formula (5) is preferably contained in an amount of 5 to 40%, particularly preferably 5 to 25%.
In the general formula (5), X ^{1 to} X ² each independently represent —H, —F or —Cl, more preferably —H or —F, and particularly preferably X ¹ = X ² = −F.
More specifically, the following compounds are preferred as specific structures of the general formula (4).

（式中R⁷及びR⁸はそれぞれ独立して、炭素数1〜5のアルキル基、アルコキシル基、炭素数2〜5のアルケニル基または炭素数2〜5のアルケニルオキシ基を表し、フェニル基中のH原子はF原子で置換されていても良い。）
一般式(5)の具体的な構造として以下の化合物が好ましい。

(Wherein R ⁷ and R ⁸ each independently represents an alkyl group having 1 to 5 carbon atoms, an alkoxyl group, an alkenyl group having 2 to 5 carbon atoms or an alkenyloxy group having 2 to 5 carbon atoms, H atom of may be substituted with F atom.)
The following compounds are preferred as the specific structure of the general formula (5).

(Wherein R ⁹ and R ¹¹ represent an alkyl group having 1 to 5 carbon atoms, and R ¹⁰ represents an alkyl group or alkoxyl group having 1 to 5 carbon atoms.)
In addition to the above compounds, normal nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, and the like may be contained.

In the present invention, the nematic phase-isotropic liquid phase transition temperature (T _NI ) is 68 to 120 ° C, more preferably 70 to 105 ° C, and particularly preferably 70 to 95 ° C. The solid phase or smectic phase-nematic phase transition temperature (T _{→ N} ) is -80 to -20 ° C, more preferably -30 ° C or less, and particularly preferably -40 ° C or less. The refractive index anisotropy (Δn) at 25 ° C. is 0.05 to 0.15, more preferably 0.07 to 0.13, and particularly preferably 0.08 to 0.11. The dielectric anisotropy (Δε) at 25 ° C. is −1.5 to −8.0, more preferably −1.5 to −6.0, and particularly preferably −1.5 to −5.5.

  The nematic liquid crystal composition of the present invention is useful for a liquid crystal display device, but is particularly useful for a liquid crystal display device for active matrix driving, and can be used for a liquid crystal display device for VA mode, IPS mode or ECB mode. Moreover, it can be used in any of the transmission mode, the reflection mode, and the semi-transmission mode.

Hereinafter, although an example is given and the present invention is explained in full detail, the present invention is not limited by these. “%” Means “% by mass”.
T _NI : Nematic phase-isotropic liquid phase transition temperature (℃) is the upper limit temperature of liquid crystal phase
T _{→ N} : Solid phase or smectic phase-nematic phase transition temperature (° C) is the liquid crystal phase lower limit temperature
And
Δε: dielectric anisotropy at 25 ° C. Δn: refractive index anisotropy at 25 ° C. η: viscosity at 20 ° C.
VHR: Retention rate at 60 ° C (%)
(The value is expressed in% as the ratio of the measured voltage to the initial applied voltage when injected into a VA-LCD with a cell thickness of 3.5 μm and measured with 5 V applied, frame time 16.7 ms, and pulse width 64 μs.)

The following abbreviations are used in the description of compounds.
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-

本発明のネマチック液晶組成物として実施例1(No.1)及び比較例1(R1)の組成と物性値を表1に示す。

Table 1 shows the compositions and physical property values of Example 1 (No. 1) and Comparative Example 1 (R1) as the nematic liquid crystal composition of the present invention.

The physical property value of Example 1 (No. 1) is T _{→ N} sufficiently lower than that of Comparative Example 1 (R1), η is also greatly reduced, and other physical property values are equal or higher. The value is shown. From the above, it can be seen that Example 1 (No. 1), which is the liquid crystal composition of the present invention, is very useful because it has a wide liquid crystal phase temperature range and low viscosity.
Next, Table 2 shows compositions and physical property values of Example 2 (No. 2), Comparative Example 2 (R2), and Comparative Example 3 (R3).

Comparative Example 2 (R2), which is a liquid crystal composition described in Patent Document 3, does not contain the compound represented by General Formula (2), which is an essential component of the present invention. Therefore, Comparative Example 2 (R2) has a higher viscosity η and higher T _{→ N} (° C) than Example 2 (No. 2), so the response speed is slow, leaving problems in low-temperature stability. there were. Since Comparative Example 3 (R3) does not contain the general formula (1), which is an essential component of the present invention, the response speed was slow and the low temperature stability remained as in Comparative Example 2 (R2). From the above, it can be seen that Example 2 (No. 2) according to the present invention is an excellent liquid crystal that greatly improves the low-temperature stability and has a very low viscosity η related to the response speed.

Claims (7)

General formula (1) as the first component,

(Wherein R ¹ represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and m represents 0 or 1). Formula (2)

(Wherein R ² represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms), and has a negative dielectric anisotropy, Nematic liquid crystal composition. General formula (3)

2. The nematic according to claim 1, comprising a compound represented by the formula: wherein R ^a and R ^b each independently represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms. Liquid crystal composition. Formula (3-1)

3. The nematic liquid crystal composition according to claim 2, comprising a compound represented by: 2. The nematic liquid crystal composition according to claim 1, wherein R ² in formula (2) is an alkenyl group having 2 to 5 carbon atoms. 5. A liquid crystal display device using the nematic composition according to claim 1. 5. An active matrix driving liquid crystal display device using the nematic composition according to claim 1. 5. A VA mode, IPS mode or ECB mode liquid crystal display element using the nematic composition according to claim 1.