JP2002088367A - Antiferroelectric liquid crystal composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new antiferroelectric liquid crystal composition having excellent contrast. SOLUTION: This antiferroelectric liquid crystal composition is composed of antiferroelectric liquid crystals expressed by formulas (1) and (2) and phenyl triester compounds expressed by formula (3) and (4) (R1, R2, R3 and R4 are each an 8-10C straight-chain alkyl; X1, X2, X3 and X4 are each H or F; (i) is 5 or 7; (k) is an integer of 1-3; (m) is an integer of 5-8; (p) and (q) are each 1 or 2; and (r) is 8 or 10). The obtained antiferroelectric liquid crystal composition has improved orientation state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel antiferroelectric liquid crystal composition having excellent contrast.

[0002]

2. Description of the Related Art Liquid crystal display devices have been used in various small display devices to date because of their low voltage operation, low power consumption, and thin display. However, with the recent expansion of information and application of liquid crystal display elements to the OA related equipment field or the television field, demands for high performance large liquid crystal display elements having display capacity and display quality higher than those of conventional CRT display elements. But it has grown rapidly.

However, as long as the current nematic liquid crystal is used, it is not easy to increase the size of an active matrix drive liquid crystal display device (TFT). Even with a simple matrix drive STN-type liquid crystal display element (STN), large-capacity drive is more difficult than TFT drive. In addition, the response time is limited, and it is difficult to display a clear moving image. Therefore, it is difficult for a nematic liquid crystal display device to satisfy the demand for the above-described high performance large liquid crystal display device.

Further, in terms of display quality, narrowing of the viewing angle has been a serious problem in both TFTs and STN display elements using nematic liquid crystals. Although various improvement measures have been proposed and results have been obtained, disadvantages such as an increase in power consumption, a decrease in response speed, and a decrease in productivity occur. Moreover, it is fundamentally difficult to improve the viewing angle with STN. As long as a nematic liquid crystal is used, it is difficult to find a drastic improvement.

In such a situation, a liquid crystal display device using a ferroelectric liquid crystal has attracted attention as a high speed, wide viewing angle liquid crystal display device. Surface-stabilized ferroelectric liquid crystal (SSFLC) presented by Clark and Lagabar
The device has been noted for its unprecedented fast response speed and wide viewing angle, its switching characteristics have been studied in detail, and many ferroelectric liquid crystals have been synthesized to optimize various physical constants. Was. However, in order to obtain a practically satisfactory contrast due to an insufficient threshold voltage characteristic and a layer structure having a chevron structure, special measures must be taken with respect to the orientation of the liquid crystal. Further, it is extremely difficult to control the alignment of liquid crystal molecules, and it is not easy to realize bistability, which is one of the greatest features of SSFLC, with good reproducibility. In addition, there is a problem that the orientation is destroyed by mechanical impact and it is difficult to recover the orientation, and it is necessary to overcome these problems in order to put the device into practical use.

[0006]

As described above, various efforts have been made to increase the size and the definition of a liquid crystal element, including the development of a new mode. At the same time, the development of an element with a completely different switching mechanism is under way. Switching between the three stable states of a liquid crystal material having an antiferroelectric phase (hereinafter referred to as “antiferroelectric liquid crystal”) is one of these new switching mechanisms.
Tsuna (Japanese Journal of Applied Physics, Vol.
27, pp. L729, (1988)).

The antiferroelectric liquid crystal device has three stable states. That is, there are two uniform states (Ur, Ul) and a third state which are observed in the ferroelectric liquid crystal element. Chandani et al. Report that this third state is an antiferroelectric phase (Japanese Journal of Applied Physics, Vol. 28, p.
p.L1261, (1989), pp.L1265). Such switching between the three stable states is the first feature of the antiferroelectric liquid crystal device. A second feature of the antiferroelectric liquid crystal element is that there is a clear threshold value for an applied voltage.

Further, it has a memory property, which is the third feature of the antiferroelectric liquid crystal element. By utilizing these excellent features, a liquid crystal display device having a high response speed and good contrast can be realized. Another major feature is that the layer structure is easily switched by an electric field (Japanese Journal of Applied Physi
cs, Vol.28, pp.L119, (1989), Vol.29, pp.L111, (1
990)). This makes it possible to manufacture a liquid crystal display element having a very small number of defects and a self-healing ability for alignment, and a liquid crystal element having relatively excellent contrast can be realized. However, most of the antiferroelectric liquid crystal undergoes a phase transition from the isotropic phase to the smectic A phase. Was inferior.

[0009]

Means for Solving the Problems That is, the following general formula:
Antiferroelectric liquid crystal represented by (1) and (2) and general formula
An antiferroelectric liquid crystal composition comprising the phenyl triester compound represented by (3) or (4). In the general formula (1), j is 5 and k is an antiferroelectric liquid crystal compound of 2; in the general formula (2), m is 5 an antiferroelectric liquid crystal compound; It is preferable to use a phenyltriester compound in which p is 2 in the formula (3) and r is 8 in the general formula (4).

[0010]

Embedded image (Wherein R ¹ , R ² , R ³ and R ⁴ are each a straight-chain alkyl group having 8 to 10 carbon atoms, X ¹ , X ² , X ³ and X ⁴ are each a hydrogen atom or a fluorine atom, j is 5 Or 7, k is an integer of 1 to 3, m is an integer of 5 to 8, p and q are 1 or 2, respectively, and r is 8 or 10.)

The antiferroelectric liquid crystal represented by the general formulas (1) and (2) comprises 40 to 80 mol% of the liquid crystal composition,
The triphenyl ester compound represented by (3) is 30 to 50 mol% of the liquid crystal composition, and the triphenyl ester compound represented by the general formula (4) is 1 to 50 mol% of the liquid crystal composition. This is a preferred embodiment. The liquid crystal composition of the present invention has at least a smectic A phase on the higher temperature side than the antiferroelectric phase, and the temperature range of the antiferroelectric phase is at least 0.
Desirably, it is -40C. The antiferroelectric liquid crystal composition is a simple matrix liquid crystal display device in which a scanning electrode and a signal electrode are arranged in a matrix between a pair of electrode substrates.

The antiferroelectric liquid crystal compound represented by the general formula (1) used in the present invention is disclosed in the earlier application of the present inventors (Japanese Unexamined Patent Publication No.
198155). For example,
When m = 5, n = 2, it is manufactured by the following method. (1) AcO-Ph (X) -COOH + SOCl ₂ → AcO-Ph (X) -COCl (2) (1) + HOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ → AcO-Ph (X) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (3) (2) + Ph-CH ₂ NH ₂ → HO-Ph (X) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (4) R ¹ O-Ph-Ph-COOH + SOCl ₂ → R ¹ O-Ph-Ph-COCl (5) (3) + (4) → Antiferroelectric liquid crystal compound Formula In, -Ph- is a 1,4-phenylene group, -Ph (X)-is a 1,4-phenylene group which may be substituted by fluorine, Ph- is a phenyl group,
C * indicates an asymmetric carbon.

The above-mentioned manufacturing method is briefly described below. (1) is a chlorination reaction of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride. (2) is esterification by the reaction of chlorinated product (1) with alcohol. (3) is the deacetylation of ester (2). (4) is a chlorination reaction of alkyloxybiphenylcarboxylic acid. (5) is the formation of liquid crystal by the reaction between phenol (3) and acid chloride (4).

The phenyl triester compounds represented by the general formulas (3) and (4) used in the present invention can be produced by a known method. An example is as follows. (B) AcO-Ph (F) -COOH + SOCl ₂ → AcO-Ph (F) -COCl (b) (b) + R'-OH → AcO-Ph (F) -COO-R '(c) ( B) + (CH ₃ NH ₂ ) → HO-Ph (F) -COO-R '(d) R "-COCl + HO-Ph-COOH → R" -COO-Ph-COOH (d) (d) + SOCl ₂ → R "-COO-Ph-COCl (f) (e) + (c) → R" -COO-Ph-COO-Ph (F) -COO-R 'where -Ph- is 1,4 -Phenylene group, -Ph (F)-is a 1,4-phenylene group substituted with fluorine at the 3-position, AcO- is an acetyl group, R ',
R "represents a corresponding alcohol residue.

(A) Chlorination of 4-acetoxybenzoic acid with thionyl chloride. (B) is the reaction between acid chloride (a) and alcohol. (C) is a deacetylation reaction of the ester (b). (D) shows the reaction between acid chloride and p-hydroxybenzoic acid. (E) is a chlorination reaction of the carboxylic acid compound (d) with thionyl chloride. (F) is the reaction for obtaining the desired product.

[0016]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is of course not limited thereto. Example 1 An antiferroelectric liquid crystal composition was prepared using the following compounds (A1, A2, B, C) as compounds corresponding to general formulas (1), (2), (3) and (4). did. A1: C ₉ H ₁₉ O-Ph-Ph-COO-Ph (F) -COO-C * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ 37.5 mol% A2: C ₉ H ₁₉ O-Ph- Ph-COO-Ph (F) -COO-C * H (CH ₃ ) C ₅ H ₁₁ 22.5 〃 B: C ₉ H ₁₉ COO-Ph-COO-Ph (F) -COO- (CH ₂ ) ₂ CH ( CH _{3) 2} 35 〃 _{C: C 9 H 19 COO-} Ph-COO-Ph (F) -COO-C 8 H 17 5 〃

The physical properties of the prepared antiferroelectric liquid crystal composition were measured. The phase series was determined by texture observation using a polarizing microscope and DSC measurement. The test cell was prepared as follows. Rubbed polyimide thin film (30nm)
The above liquid crystal composition was filled in an isotropic phase into a liquid crystal cell (cell thickness: 2 μm) with an ITO electrode having the following formula: This cell is
The liquid crystal was aligned by gradually cooling at 1.0 ° C./min. The cell was placed between orthogonal polarizing plates so that the layer direction of the liquid crystal was parallel to the analyzer or the polarizer. The contrast is as follows: at 30 ° C., the light transmittance at 0 applied voltage and 35 V, 1
It was determined from the ratio of the maximum light transmittance when a 0 Hz triangular wave voltage was applied. The results are shown in Table 1.

Comparative Example 1 An antiferroelectric liquid crystal composition was prepared in the same manner as in Example 1 except that the compound C was not used and B was changed to 40 mol%, and the physical properties were measured. Indicated.

Table 2 Phase Series Column Contrast Example 1 Cr (<-20) SCA * (72) SA (95) I 48 Comparative Example 1 Cr (<-20) SCA * (73) SA (95) I 29 phase In the description of the series, () indicates the phase transition temperature (° C.), Cr indicates a crystalline phase, SCA * indicates an anti-strong dielectric phase, SA indicates a smectic A phase, and I indicates an isotropic phase.

[0020]

According to the antiferroelectric liquid crystal composition of the present invention, a liquid crystal display device having a higher contrast ratio can be realized because the alignment property is improved.

Continuation of the front page (72) Inventor Tomoyuki Yui F-term (reference) 4H027 BA07 BD02 BD12 BD20 CC03 CC05 CF08 in the Tokyo Plant in Mitsubishi Gas Chemical Co., Ltd., 6-1, 1-1 Shinjuku, Katsushika-ku, Tokyo

Claims (10)

[Claims] An antiferroelectric liquid crystal composition comprising an antiferroelectric liquid crystal represented by the following general formulas (1) and (2) and a phenyltriester compound represented by the following general formulas (3) and (4): . Embedded image (Wherein R ¹ , R ² , R ³ and R ⁴ are each a straight-chain alkyl group having 8 to 10 carbon atoms, X ¹ , X ² , X ³ and X ⁴ are each a hydrogen atom or a fluorine atom, j is 5 Or 7, k is an integer of 1 to 3, m is an integer of 5 to 8, p and q are 1 or 2, respectively, and r is 8 or 10.) 2. In the general formula (1), j is 5 and k is 2
2. The antiferroelectric liquid crystal composition according to claim 1, wherein 3. The antiferroelectric liquid crystal composition according to claim 1, wherein m is 5 in the general formula (2). 4. The antiferroelectric liquid crystal composition according to claim 1, wherein p is 2 in the general formula (3). 5. The antiferroelectric liquid crystal composition according to claim 1, wherein in the general formula (4), r is 8. 6. The antiferroelectric liquid crystal composition according to claim 1, wherein the antiferroelectric liquid crystal represented by the general formulas (1) and (2) accounts for 40 to 80 mol% of the liquid crystal composition. 7. The antiferroelectric liquid crystal composition according to claim 1, wherein the triphenylester compound represented by the general formula (3) accounts for 30 to 50 mol% of the liquid crystal composition. 8. The antiferroelectric liquid crystal composition according to claim 1, wherein the triphenylester compound represented by the general formula (4) accounts for 1 to 50 mol% of the liquid crystal composition. 9. The antiferroelectric liquid crystal composition according to claim 1, which has at least a smectic A phase on a higher temperature side than the antiferroelectric phase, and the temperature range of the antiferroelectric phase is at least 0 to 40 ° C. 10. An antiferroelectric liquid crystal display device comprising the antiferroelectric liquid crystal composition according to claim 1 disposed between a pair of electrode substrates.