JP2007119672A - Nematic liquid crystal composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition for active matrix liquid crystal display element having broad liquid crystal phase temperature range and low viscosity and provide an active matrix liquid crystal display element produced by using the liquid crystal composition and having broad working temperature range. <P>SOLUTION: The nematic liquid crystal composition contains a compound expressed by structural formula (1) in an amount of 35-65% as the first component and a compound expressed by general formula (2) as the second component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nematic crystal composition 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. Also, in order to obtain a wider viewing angle characteristic, a TFT display combined with IPS and OCB modes and a reflection type of 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 phenyl bicyclohexyl 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, a liquid crystal composition in which a liquid crystal temperature range is adjusted using a tetracyclic compound is already known, and a specific example of a preferable compound is disclosed (Patent Document 5). However, this composition was also not sufficiently low in viscosity to accommodate a high-speed response.

  From the above, it has been difficult to obtain a liquid crystal composition having a wide liquid crystal phase temperature range and low viscosity.

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) Japanese Unexamined Patent Publication No. 2000-26860 (21 on page 23)

  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 and low viscosity, and an active temperature range using this liquid crystal composition is wide. It is to provide a matrix type liquid crystal display element.

  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35〜65%含有し、第二成分としてとして一般式(2)

Containing 35 to 65% of a compound represented by the general formula (2) as a second component

(式中、R¹は炭素数1〜15のアルキル基又は炭素数2〜15のアルケニル基であり、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、B²、B³はそれぞれ独立的に
(a) trans-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、
L¹、L²、L³はそれぞれ独立的に単結合、-CH₂CH₂-、-(CH₂)₄-、-COO-、-OCH₂-、-CH₂O-、-OCF₂-、-CF₂O-又は-C≡C-を表し、
Q¹は-OCH₂-、-OCF₂-、-OCHF-、-CF₂-、または単結合であり、
X¹〜X³はそれぞれ独立してH、F又はClである。) で表される化合物群から選ばれる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。

Wherein R ¹ is 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 halogen group as a substituent. And one or more CH ₂ groups present in these groups are each independently replaced by -O-, -S-, -CO- as O atoms are not directly bonded to each other. Well,
B ¹ , B ² and B ³ 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 above group (a), the group (b) may be substituted with CH ₃ or halogen,
L ¹ , L ² and L ³ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — , -CF ₂ O- or -C≡C-
Q ¹ is —OCH ₂ —, —OCF ₂ —, —OCHF—, —CF ₂ —, or a single bond,
X ^{1 to} X ³ are each independently H, F or Cl. A liquid crystal composition for an active matrix type liquid crystal display element comprising one or more compounds selected from the group of compounds represented by formula (1) and a liquid crystal display element comprising the liquid crystal composition as a constituent member provide.

  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 30 to 65%, but is preferably in the range of 40 to 60% by mass.

It contains 1 or 2 or more types from the compound group represented by the general formula (2) as the second component, preferably 1 to 10 types, more preferably 1 to 7 types, more preferably 2 to 5 types. Further preferred.

The content of one or more compounds selected from the compound group represented by the general formula (2) as the second component is preferably in the range of 5 to 30% by mass, and 10 to 20% by mass. More preferably, it is the range. R ¹ is an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or one CH ₂ group present in an alkyl group having 2 to 10 carbon atoms replaced by —O—. Preferably, 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 represented by —O—. The substituted group is more preferable, and the structure of the following formulas (a) to (e) is more preferable 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 , B ² and B ³ are trans-1,4-cyclohexylene group, 1,4-phenylene group, 3-fluoro-1,4-phenylene group or 3,5-difluoro-1,4-phenylene group 1,4-phenylene group or trans-1,4-cyclohexylene group is more preferable. L ¹ , L ² and L ³ are 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- , -OCF _2- , -CF ₂ O- or a single bond is preferred, -CH ₂ CH _2- , -CF ₂ O- or single A bond is more preferable, and —CH ₂ CH ₂ — or a single bond is particularly preferable.

Q ¹ is —OCH 2 —, —OCF 2 —, —OCHF—, —CF 2 —, or a single bond, preferably —OCF 2 —, —CF 2 —, or a single bond, and more preferably a single bond. X ^{1 to} X ³ are each independently H, F or Cl, but —H and —F are preferred, and X ² is preferably F.

  More specifically, the following compounds are preferred as the specific structure of the general formula (2).

（式中R¹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す。）

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

  The general formula (3) is used as the third component to adjust the physical properties of the composition and to achieve lower viscosity and lower voltage.

(式中、R²はR¹と同じ意味を表し、
B⁴はB¹と同じ意味を表し、
L⁴、L¹と同じ意味を表し、
B⁴及びL⁴が複数存在する場合はそれらは同一でも良く異なっていても良く、
mは 0、1又は2であり、
nは0又は1であり、
Q²は-OCH2-、-OCF2-、-OCHF-、-CF2-、または単結合であり、
X⁴〜X⁸はそれぞれ独立してH、F又はClである。) で表される化合物群から選ばれる1種もしくは2種以上の化合物含有することが好ましい。

(Wherein R ² represents the same meaning as R ¹ ,
B ⁴ has the same meaning as B ¹
L ^{4 has} the same meaning as L ¹ ,
When there are a plurality of B ⁴ and L ^4, they may be the same or different,
m is 0, 1 or 2;
n is 0 or 1,
Q ² is -OCH2-, -OCF2-, -OCHF-, -CF2-, or a single bond,
X ^{4 to} X ⁸ are each independently H, F, or Cl. It is preferable to contain one or more compounds selected from the group of compounds represented by:

  It is preferable to contain 2-15 types of compound groups represented by General formula (3) as a 3rd component, 2-10 types are more preferable, and 4-7 types are more preferable.

The content of one or more compounds selected from the compound group represented by the general formula (3) as the third component is more preferably in the range of 5 to 30% by mass, and 10 to 30% by mass. More preferably, it is the range. R ^{3 to} R ⁵ are preferably an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, an unsubstituted linear alkyl group having 1 to 8 carbon atoms or an alkyl group having 2 to 8 carbon atoms. Alkenyl groups are more preferred, and structures of formulas (a) to (e) are more preferred for alkenyl groups.

B ⁴ is preferably trans-1,4-cyclohexylene group, 1,4-phenylene group, 3-fluoro-1,4-phenylene group or 3,5-difluoro-1,4-phenylene group, A -phenylene group or a trans-1,4-cyclohexylene group is more preferable. L ⁴ is a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —OCF ₂ —, —CF ₂ O— or —C≡C—. -CH ₂ CH _2- , -OCF _2- , -CF ₂ O- or a single bond is preferable, -CH ₂ CH _2- , -CF ₂ O- or a single bond is more preferable, -CH ₂ CH ₂ -Or a single bond is particularly preferred. m is 0, 1 or 2, and n is 0 or 1, but m + n is preferably 1 or 2.

Q ² is —OCH ² —, —OCF ² —, —OCHF—, —CF ² —, or a single bond, preferably —OCF 2 —, —CF 2 —, or a single bond, and more preferably a single bond. X ^{4 to} X ⁸ are each independently H, F or Cl, but —H and —F are preferred, and X ⁸ is preferably F.

  More specifically, the general formula (3) is preferably a compound represented by the following general formula as a specific structure.

（式中、R²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す。）

(In the formula, each R ² independently represents an alkyl group having 1 to 15 carbon atoms 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 2.5 to 7.0, and 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 γ1: Rotational viscosity
HR: Retention rate at 60 ° C (%) (Injected into TN-LCD with 6μm cell thickness, 5V applied, flame
Between the measured voltage and the initial applied voltage when measured at 200 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-
On -OC _n H _{2n + 1}
F -F
CFFF -CF ₃
OCFFF -OCF ₃
ndm- C _n H _{2n + 1} -C = C- (CH ₂ ) _m-1-
nOm- C _n H _{2n + 1} -O- (CH ₂ ) _m-1-
-E- -COO-
-T- -C≡C-

(1-3) Synthesis of liquid crystal composition adjustment Nematic liquid crystal compositions (No. 1), (No. 2) and (No. 3) shown below were prepared and their physical properties were measured. Shown in 1.

1 to 3 nematic liquid crystal compositions (No.1) to (No.3) 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. In addition, the viscosity was low, the response speed of the panel was good, and the retention after 1 hour of heating at 150 ° C. kept the initial value, and the reliability was good.

Comparative Examples 1 to 3 Preparation of Synthesis of Liquid Crystal Composition As comparative examples, nematic liquid crystal compositions (R1) to (R3) shown below were prepared and measured for physical properties. The results are shown in Table 2.

  In Comparative Examples 1 to 3, the content of the first component was 30%, but the viscosity was higher than that of Comparative Example 1 to Comparative Example 3.

(Comparative Example 4) Preparation of Synthesis of Liquid Crystal Composition As a comparative example, the nematic liquid crystal composition (R4) shown below was prepared and measured for physical properties. The results are shown in Table 3.

Comparative Example 4 The nematic liquid crystal composition (R4) had a higher viscosity than the panel and the panel response speed was not sufficiently high. Further, the nematic phase-isotropic liquid phase transition temperature (T _NI ) was as low as 65 ° C., and the temperature range of the liquid crystal phase was narrow, so that it could not be used as a practical liquid crystal composition.

(Comparative Examples 5 to 8) Synthesis of liquid crystal composition adjustment Nematic liquid crystal compositions (R5) to (R8) shown below were prepared as comparative examples, and their physical properties were measured. Table 4 shows the results.

The characteristics of the nematic liquid crystal compositions (R5) to (R8) in Comparative Examples 5 to 8 are high in nematic phase-isotropic liquid phase transition temperature (T _NI ) but higher in viscosity than the panel response. The speed was not fast enough.

Comparative Example 9 Preparation of Synthesis of Liquid Crystal Composition As a comparative example, the nematic liquid crystal composition (R9) shown below was prepared and measured for physical properties. The results are shown in Table 4.

The nematic liquid crystal composition (R9) of Comparative Example 9 has a high nematic phase-isotropic liquid phase transition temperature (T _NI ), but its viscosity is high compared to the panel, and the response speed of the panel is not sufficiently high. .

Claims (6)

Structural formula (1) as the first component,

Containing 35 to 65% of a compound represented by the general formula (2) as a second component

Wherein R ¹ is 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 halogen group as a substituent. And one or more CH ₂ groups present in these groups are each independently replaced by -O-, -S-, -CO- as O atoms are not directly bonded to each other. Well,
B ¹ , B ² and B ³ 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 above group (a), the group (b) may be substituted with CH ₃ or halogen,
L ¹ , L ² and L ³ are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —COO—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ — , -CF ₂ O- or -C≡C-
Q ¹ is -OCH2-, -OCF2-, -OCHF-, -CF2-, or a single bond,
X ^{1 to} X ³ are each independently H, F or Cl. A nematic liquid crystal composition comprising one or more compounds selected from the group of compounds represented by: General formula (3) as the third component

(Wherein R ² represents the same meaning as R ¹ ,
B ⁴ has the same meaning as B ¹
L ^{4 has} the same meaning as L ¹ ,
When there are a plurality of B ⁴ and L ^4, they may be the same or different,
m is 0, 1 or 2;
n is 0 or 1,
Q ² is -OCH2-, -OCF2-, -OCHF-, -CF2-, or a single bond,
X ^{4 to} X ⁸ are each independently H, F, or Cl. 2. The nematic liquid crystal composition according to claim 1, comprising one or more compounds selected from the group of compounds represented by formula (1): 3. The nematic liquid crystal composition according to claim 2, comprising 35 to 65% of a compound represented by the structural formula (1), a compound represented by the general formula (2), and a compound represented by the general formula (3). Nematic-isotropic transition temperature is 68 ° C to 120 ° C, crystal or smectic-nematic transition temperature is -80 ° C to -20 ° C, refractive index anisotropy Δn is 0.05 to 0.15, dielectric constant anisotropic The liquid crystal composition according to claim 1, wherein the property Δε is 2.5 to 10.0. A liquid crystal display device using the nematic liquid crystal composition according to claim 1. An active matrix liquid crystal display element using the nematic liquid crystal composition according to claim 1.