JP2006257343A - Nematic liquid crystal composition and liquid crystal display element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition having an improved speed of response when a liquid crystal display element is composed and having high heat and light stability. <P>SOLUTION: The liquid crystal composition comprises one or more kinds of compounds represented by general formulas (I), one or more kinds of compounds represented by general formula (II) and a UV absorber. The liquid display element is obtained by using the liquid crystal composition. The liquid crystal composition reduces viscosity when the liquid crystal display element is composed and has effects on enhancement of heat and light stability. Thereby, high reliability and the excellent speed of response can be achieved when used as a constituent member of the liquid crystal display element. As a result, the liquid crystal composition is useful as the liquid crystal display element such as a TN-LCD (twisted nematic liquid crystal display element) or an STN-LCD (supertwisted nematic liquid crystal display element). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention satisfies various characteristics of an electro-optic display element, has a wide nematic temperature range, low viscosity, excellent high-speed response, good display contrast, and excellent thermal and light stability. And a liquid crystal display element using the same.

A typical liquid crystal display element is a TN-LCD (twisted nematic liquid crystal display element), which is used in watches, calculators, electronic notebooks, and the like. On the other hand, with the expansion of display capacity, '' STN (Super Twisted Nematic) -LCD has been developed and is widely used in displays for high information processing such as personal computers and mobile phones.
Recently, in portable terminal displays (Personal Digital Assistance) and the like, good display characteristics in a wider temperature range are required. Such a liquid crystal material is required to have a low viscosity, a low driving voltage, a constant value over a wide temperature range, and a driving voltage that does not fluctuate in a frequency range corresponding to various time divisions. ing.

Liquid crystal compositions with good display contrast, temperature dependence of driving voltage, and fast response speed have been developed (see Patent Document 1), but the specific resistance of the liquid crystal composition decreases when heated. However, there is a problem that a phenomenon that adversely affects display characteristics such as a decrease in contrast occurs.
On the other hand, it is already known to add UV absorbers to liquid crystal compositions to reduce deterioration due to light irradiation (Patent Document 2), but in combination with specific liquid crystal compositions, the thermal stability is greatly increased. The point which can be improved is not known, and development of a liquid crystal composition excellent in display contrast, fast response speed and high thermal stability has been desired.

JP-A-14-38155 (page 2) JP-A-8-176549 (2 pages)

  The problem to be solved by the present invention is to provide a nematic liquid crystal composition excellent in display contrast, fast in response speed, excellent in heat and light stability, and a liquid crystal display element using the same.

As a result of studying liquid crystal compositions using various liquid crystal compounds in order to solve the above-mentioned problems, the present invention has been completed.
That is, the general formula (I)

（式中、R¹は、炭素数1〜12のアルキル基、炭素数1〜12のアルコキシル基、炭素数2〜12のアルケニル基又は炭素数2〜12のアルケニルオキシ基を表し、
A¹は、1,4-フェニレン基、3-フルオロ-1,4-フェニレン、3,5-ジフルオロ-1,4-フェニレン、トランス-1,4-シクロヘキシレン基、ピリジン-2,5-ジイル基又はピリミジン-2,5-ジイル基を表し、
sは0又は1を表し、
L¹及びL³はそれぞれ独立して、-H、-F又は-Clを表し、L²は、-F、-Cl、-CN、-CF₃、-OCH₂F、-OCHF₂、-OCF₃又は-CH₂CF₃を表す。）
で表される化合物1種以上を、3から30%含有し、
一般式(II)

(In the formula, R ¹ represents an alkyl group having 1 to 12 carbon atoms, an alkoxyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms,
A ¹ is 1,4-phenylene group, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl Group or pyrimidine-2,5-diyl group,
s represents 0 or 1,
L ¹ and L ³ each independently represent -H, -F or -Cl, and L ² represents -F, -Cl, -CN, -CF ₃ , -OCH ₂ F, -OCHF ₂ or -OCF ₃ or an -CH ₂ CF _3. )
Containing 1 to 3% of one or more compounds represented by
Formula (II)

（式中、R²及びR³はそれぞれ独立して、一般式(I)におけるR¹と同じ意味を表し、B¹、B²及びB³はそれぞれ独立して、1,4-フェニレン基、2-フルオロ-1,4-フェニレン、3-フルオロ-1,4-フェニレン、2-メチル-1,4-フェニレン、3-メチル-1,4-フェニレン、2,6-ジフルオロ-1,4-フェニレン、3,5-ジフルオロ-1,4-フェニレン、トランス-1,4-シクロヘキシレン基、ピリジン-2,5-ジイル基又はピリミジン-2,5-ジイル基を表し、
Z¹、Z²及びZ³はそれぞれ独立して、-CH₂CH₂-、-CH=CH-、-CF₂CF₂-、-CF=CF-、-CH₂O-、-OCH₂-、-(CH₂)₄-、-(CH₂)₃O-、-O(CH₂)₃-、-C≡C-、-CF₂O-、-OCF₂-、-COO-、-OCO-、-CH=N-N=CH-又は単結合を表す。)で表される化合物1種以上を、5から70%含有し、
UV吸収剤1種以上を、0.001から5%含有す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。

(In the formula, R ² and R ³ each independently represent the same meaning as R ¹ in the general formula (I), B ¹ , B ² and B ³ each independently represent a 1,4-phenylene group, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, 2,6-difluoro-1,4- Represents phenylene, 3,5-difluoro-1,4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl group or pyrimidine-2,5-diyl group;
Z ¹ , Z ² and Z ³ are each independently -CH ₂ CH _2- , -CH = CH-, -CF ₂ CF _2- , -CF = CF-, -CH ₂ O-, -OCH _2- ,-(CH ₂ ) ₄ -,-(CH ₂ ) ₃ O-, -O (CH ₂ ) _3- , -C≡C-, -CF ₂ O-, -OCF _2- , -COO-, -OCO -, -CH = NN = CH- or a single bond. ) Containing one or more compounds represented by 5 to 70%,
Provided is a nematic liquid crystal composition containing 0.001 to 5% of one or more UV absorbers, and a liquid crystal display device using the same.

  The nematic liquid crystal composition of the present invention has good temperature dependency, low viscosity, and excellent heat and light stability. Therefore, when used as a constituent member of a liquid crystal display element, the display contrast is good, the response speed is fast, and the reliability is high, so that it is useful for liquid crystal display elements such as TN and STN.

An example of the present invention will be described below.
In the present invention, the compound represented by the general formula (I) is contained in an amount of 3 to 30% by mass as the first component, and the content is particularly preferably in the range of 3 to 20% by mass.
Specifically, the compounds represented by the general formula (I) are particularly preferably compounds represented by the following general formulas (Ia) to (If).

(In the formula, R ¹ represents an alkoxyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms,
A ¹ is 1,4-phenylene group, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro-1 , 4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl group or pyrimidine-2,5-diyl group,
s represents 0 or 1. )

In the general formula (I), R ¹ represents an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms. Preferably, it represents a straight-chain alkyl group having 1 to 8 carbon atoms or a straight-chain alkenyl group having 2 to 8 carbon atoms, and when it represents an alkenyl group, the following formulas (a) to (e)

(構造式は右端で環に連結しているものとする。)で表される構造を表すことが好ましい。
A¹は具体的にはそれぞれ独立して以下の式で表される構造が好ましい。

(The structural formula is assumed to be connected to the ring at the right end).
Specifically, A ¹ is preferably a structure independently represented by the following formula.

これらの中でも以下の式で表される構造がより好ましい。

Among these, a structure represented by the following formula is more preferable.

The second component contains a compound selected from general formula (II), preferably 1 to 20 types, more preferably 1 to 15 types. The content of the general formula (II) is preferably in the range of 5 to 70% by mass, more preferably in the range of 10 to 70% by mass, and particularly preferably in the range of 25 to 70% by mass.
Specifically, the compounds represented by the general formula (II) are particularly preferably compounds represented by the following general formulas (Ia) to (If).

(In the formula, R ⁴ and R ⁵ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, and an alkenyloxy group having 2 to 12 carbon atoms. Y ¹ , Y ² , Y ³ , Y ⁴ , Y ⁵ , Y ⁶ and Y ⁷ each independently represent —H, —F or a methyl group, and Z ⁴ represents —CH ₂ CH ₂ —, —CH═CH—, —COO—, —OCO—, or a single bond, and Z ⁵ represents —C≡C—, —COO—, or —OCO—.
In the general formula (II), R ⁴ and R ⁵ preferably represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms, More preferably, it represents a straight-chain alkyl group having 1 to 8 carbon atoms or a straight-chain alkenyl group having 2 to 8 carbon atoms, and when it represents an alkenyl group, it is represented by the aforementioned formulas (a) to (e). It is preferable to represent the structure.
Specifically, B ¹ , B ² and B ³ are each preferably independently represented by the following formula.

これらの中でも、以下の式で表される構造がより好ましい。

Among these, the structure represented by the following formula is more preferable.

第3成分として、UV吸収剤、1種以上を0.001から5質量%含有するが、0.001から2質量%の範囲であることが好ましく、0.01から1質量%であることが特に好ましい。
UV吸収剤としては一般式(III)

As the third component, one or more UV absorbers are contained in an amount of 0.001 to 5% by mass, preferably in the range of 0.001 to 2% by mass, particularly preferably 0.01 to 1% by mass.
General formula (III) as UV absorber

(式中、Y¹及びY²はそれぞれ独立的に水素原子、炭素数1〜20のアルキル基、少なくとも一つのハロゲンにより置換された炭素数1〜20のアルキル基、炭素数2〜20のアルケニル基又は少なくとも一つのハロゲンにより置換された炭素数2〜20のアルケニル基を表し、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-、-N-、-S-、-CO-、-COO-、-OCO-又は-OCO-O-により置き換えられてもよく、X¹は水素原子、フッ素原子又は塩素原子を表す。)
で表される化合物が好ましく、具体的には以下の一般式(III-a)から一般式(III-h)で表される化合物が特に好ましい。

Wherein Y ¹ and Y ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms substituted with at least one halogen, or an alkenyl having 2 to 20 carbon atoms. Represents an alkenyl group having 2 to 20 carbon atoms substituted by a group or at least one halogen, and one or two or more CH ₂ groups present in these groups each independently have an O atom directly bonded to each other May be replaced by -O-, -N-, -S-, -CO-, -COO-, -OCO- or -OCO-O-, and X ¹ is a hydrogen atom, a fluorine atom or a chlorine atom Represents.)
A compound represented by the following general formula (III-a) to general formula (III-h) is particularly preferable.

(Wherein X ² represents a hydrogen atom, a fluorine atom or a chlorine atom)
The liquid crystal composition of the present invention is excellent in heat and light stability in the case of constituting a liquid crystal display element, and excellent in electro-optical characteristics such as low viscosity, temperature dependency and frequency dependency of threshold voltage. Features. After heating at 150 ° C. for 1 hour, it preferably has a specific resistance value of 1.0E10 Ω · cm or more. The dielectric anisotropy (Δε) is preferably 5 or more and 35 or less, and particularly preferably 10 or more and 30 or less. The frequency dependency ΔV / Δf (Vth [5000 Hz] −Vth [64 Hz] / Vth [64 Hz] × 100% of the threshold voltage is preferably 5% or less.

  The liquid crystal composition of the present invention can provide a liquid crystal composition having excellent properties other than those described above, but the nematic phase upper limit temperature is preferably 60 ° C or higher, more preferably 80 ° C or higher. 90 ° C. or higher is particularly preferable. Δn is preferably in the range of 0.10 to 0.25, more preferably in the range of 0.10 to 0.20, the range of 0.10 to 0.16 is particularly preferred for TN-LCD cell thickness design, and the range of 0.12 to 0.18 is the STN-LCD. Particularly preferred for cell thickness designs of

  The liquid crystal composition of the present invention may contain a nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, a dichroic dye and the like in addition to the above compounds. Further, a chiral agent may be added to prevent the reverse twist domain of TN-LCD or to induce the helical structure of STN-LCD. As the chiral agent, commercially available products can be used. Examples thereof include cholesteryl nonanoate (CN), S-811, R-811, CB-15, and C-15 manufactured by Merck. It is known that the induced helical pitch becomes longer and shorter as the temperature rises, but one of these may be used alone or in combination of two or more, or both may be used in combination of one or more. good. For example, in the TN-LCD, STN-LCD, and TFT-LCD, the quotient d / p of the thickness d between the substrates and the induced spiral pitch p can be selected from the range of 0.001 to 24, but the range of 0.01 to 12 The range of 0.1 to 2 is more preferable, the range of 0.1 to 1.5 is still more preferable, the range of 0.1 to 1 is still more preferable, and the range of 0.1 to 0.8 is particularly preferable.

  The nematic liquid crystal composition is useful for TN-LCD, STN-LCD, OCB-LCD, polymer dispersion type liquid crystal display element, phase change type cholesteric liquid crystal display element, but is particularly useful for TN-LCD and STN-LCD. is there. Further, it can be used for a transmissive or reflective liquid crystal display element.

In the TN liquid crystal display element of the present invention, the twist angle can be selected in the range of 80 ° to 130 °, preferably 85 ° to 110 °, depending on the purpose. In the STN liquid crystal display element of the present invention, the twist angle can be selected in the range of 180 ° to 270 ° depending on the purpose, and 220 ° to 260 ° is preferable.
By using the liquid crystal composition of the present invention, in the display of 1/32 to 1/400 duty, more preferably 1/60 to 1/250 duty, the decrease in specific resistance value is reduced in heating and UV irradiation. Therefore, it is possible to provide a high-contrast liquid crystal display element that is improved in reliability and improved with respect to an increase in information amount and color display.

EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples. Further, “%” in the compositions of the following Examples and Comparative Examples means “% by mass”.
In the examples, the measured characteristics are as follows.
T _NI : Nematic phase-isotropic liquid phase transition temperature (° C)
Δε: Dielectric anisotropy (25 ° C)
Δn: Birefringence (25 ° C)
η: Viscosity (mPa · s) (25 ° C)
The STN-LCD display element was created as follows. A chiral substance “S-811” (manufactured by Merck & Co., Inc.) was added to the nematic liquid crystal composition to prepare a mixed liquid crystal, which was injected into a STN-LCD display cell having a twist angle of 240 degrees. The chiral material was added so that the intrinsic spiral pitch P of the mixed liquid crystal and the display cell thickness d by adding the chiral material were Δn · d = 0.90 and d / p = 0.50.
Vth (STN): Threshold voltage (V)
Vsat (STN): Saturation voltage (V)
γ: Steepness Vsat (STN) / Vth (STN)
τ: Responsiveness (msec)
SR (heat): The specific resistance value (Ω · cm ² ) after vacuum injection of liquid crystal composition into STN-LCD with twist of 240 degrees and heating at 150 ° C for 1 hour
The following abbreviations are used in compound descriptions.
-n number: -C _n H _{2n + 1} (the alkyl side chain is a number, and R is representative for representation)
-On: -OC _n H _{2n + 1
-ndm :-( C n H 2n + 1} -CH = CH- (CH 2) m-1)
ndm-: C _n H _{2n + 1} -CH = CH- (CH ₂ ) _m-1-
-Od (m) n: -O ( C n H 2n + 1 -CH = CH- (CH 2) m-2)
d (m) nO-: C _n H _{2n + 1} -CH = CH- (CH ₂ ) _m-2 O-
Linking group
-VO-: -COO- -T-: -C≡C-
-2-: -CH ₂ CH ₂ --Z-: -CH = NN = CH-
Substituent
-CN: -C≡N -F: -F
ring
Ph: 1,4-phenylene group Ph1: 3-fluoro-1,4-phenylene group
Ph2: 3,5-difluoro-1,4-phenylene group
Ma: Pyrimidine-2,5-diyl group Cy: 1,4-cyclohexylene group
The following structure (manufactured by JF-77 Johoku Chemical) was used as a UV absorber.

(Example 1, Comparative Example 1)
The nematic liquid crystal composition shown below was prepared, its physical properties were measured, and the results are shown in Table 1 together with Comparative Example 1.

As shown in Table 1, the liquid crystal composition of Example 1 has an equivalent threshold voltage as compared with Comparative Example 1, and in the temperature range of -20 ° C to 25 ° C, the steepness, the response speed, and the threshold voltage temperature. The thermal stability is also greatly improved while maintaining the characteristics of excellent dependency and frequency dependency.
(Example 2, comparative example 2)
Further, the nematic liquid crystal composition shown below was prepared, and its physical property values were measured. The results are shown in Table 2 together with Comparative Example 2.

As shown in Table 2, the liquid crystal composition of Example 2 is superior to Comparative Example 2 in both temperature dependency and frequency dependency of the threshold voltage, and greatly improves thermal stability. It has improved.

Claims (8)

Formula (I)

(In the formula, R ¹ represents an alkyl group having 1 to 12 carbon atoms, an alkoxyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms,
A ¹ is 1,4-phenylene group, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl Group or pyrimidine-2,5-diyl group,
s represents 0 or 1,
L ¹ and L ³ each independently represent -H, -F or -Cl, and L ² represents -F, -Cl, -CN, -CF ₃ , -OCH ₂ F, -OCHF ₂ or -OCF ₃ or an -CH ₂ CF _3. )
Containing 1 to 3% of one or more compounds represented by
Formula (II)

(In the formula, R ² and R ³ each independently represent the same meaning as R ¹ in the general formula (I), B ¹ , B ² and B ³ each independently represent a 1,4-phenylene group, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2-methyl-1,4-phenylene, 3-methyl-1,4-phenylene, 2,6-difluoro-1,4- Represents phenylene, 3,5-difluoro-1,4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl group or pyrimidine-2,5-diyl group;
Z ¹ , Z ² and Z ³ are each independently -CH ₂ CH _2- , -CH = CH-, -CF ₂ CF _2- , -CF = CF-, -CH ₂ O-, -OCH _2- ,-(CH ₂ ) ₄ -,-(CH ₂ ) ₃ O-, -O (CH ₂ ) _3- , -C≡C-, -CF ₂ O-, -OCF _2- , -COO-, -OCO -, -CH = NN = CH- or a single bond. ) Containing one or more compounds represented by 5 to 70%,
A nematic liquid crystal composition containing 0.001 to 5% of one or more UV absorbers. UV absorber is general formula (III)

Wherein Y ¹ and Y ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms substituted with at least one halogen, or an alkenyl having 2 to 20 carbon atoms. Represents an alkenyl group having 2 to 20 carbon atoms substituted by a group or at least one halogen, and one or two or more CH ₂ groups present in these groups each independently have an O atom directly bonded to each other May be replaced by -O-, -N-, -S-, -CO-, -COO-, -OCO- or -OCO-O-, and X ¹ is a hydrogen atom, a fluorine atom or a chlorine atom Represents.)
2. The nematic liquid crystal composition according to claim 1, which is a compound represented by the formula: General Formula (I-1), General Formula (I-2), General Formula (I-3), General Formula (I-4), General Formula (I-5), and General Formula (I-6)

(In the formula, R ¹ represents an alkoxyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms,
A ¹ is 1,4-phenylene group, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro-1 , 4-phenylene, trans-1,4-cyclohexylene group, pyridine-2,5-diyl group or pyrimidine-2,5-diyl group,
s represents 0 or 1. 3. The nematic liquid crystal composition according to claim 1, comprising at least one compound selected from the group consisting of compounds represented by: General formula (II-1), general formula (II-2), general formula (II-3), general formula (II-4), general formula (II-5), general formula (II-6), general formula (II-7) and general formula (II-8)

(In the formula, R ⁴ and R ⁵ are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms. Y ¹ , Y ² , Y ³ , Y ⁴ , Y ⁵ , Y ⁶ and Y ⁷ each independently represent —H, —F or a methyl group, and Z ⁴ represents —CH ₂ CH ₂ —, -CH = CH -, - COO - , - OCO-, or a single bond, Z ⁵ is -C≡C -, - COO -, - . the OCO- representing a) selected from the group consisting of compounds represented by 4. The nematic liquid crystal composition according to any one of claims 1 to 3, which contains one or more compounds to be obtained. 5. The nematic liquid crystal composition according to claim 1, which has a specific resistance value of 1.0E10 Ω · cm or more after heating at 150 ° C. for 1 hour. 6. The nematic liquid crystal composition according to claim 1, wherein the dielectric anisotropy (Δε) is in the range of 5 to 35. 7. The nematic liquid crystal composition according to claim 1, wherein the refractive index anisotropy (Δn) is in the range of 0.10 to 0.25. 8. A liquid crystal display element using the liquid crystal composition according to claim 1.