JPH1135941A - Antiferroelectric liquid crystal composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable setting a response speed II freely to some extent while maintaining an antiferroelectric phase over a broad range of temperatures without causing a detrimental effect to a response speed I by adding a swallowtail compound to one or more antiferroelectric liquid crystal compounds and a mixture of phenylester compounds. SOLUTION: A response speed I refers to a response speed from an antiferroelectric state to a ferroelectric state and a response speed II refers to a response speed from a ferroelectric state to an antiferroelectric state. A swallowtail compound is represented by formula I (wherein R<1> is a 4-10C linear alkyl; X is H or F; and (m) is 2 or 3) and an antiferroelectric liquid crystal compound is represented by formula II (wherein R<2> is a 6-12C linear alkyl; Y is H or F; A is -CH3 or -CF3 ; (r) is 0 or 1; and when A is -CH3 , (r) is 0 and (p) is 4-10, when A is -CF3 and (r) is 0, (p) is 6-8, and when A is -CF3 and (r) is 1, S is 5-8 and (p) is 2 or 4) and a phenylester compound is represented by formula III (wherein R<3> is a 5-10C linear alkyl; Z is H or F; and (n) is 5-10).

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 containing a swallow-tail type compound and a liquid crystal display device using the same.

[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 information, the application of liquid crystal display elements to the OA related equipment field, or the television field, and the expansion of applications, the CR
The demand for a high-performance large-sized liquid crystal display device having a display capacity and display quality higher than that of a T display device has been rapidly increasing.

However, as long as the current nematic liquid crystal is used, even an active matrix drive liquid crystal display element used for a liquid crystal television has a large size and a low cost due to the complexity of the manufacturing process and low yield. Is not easy. ST of simple matrix drive
Even with N-type liquid crystal display elements, large-capacity driving is not always easy, and the response time is limited, making it difficult to display moving images. Further, a narrow viewing angle of a display element using a nematic liquid crystal has become a serious problem. Therefore, the nematic liquid crystal display element cannot satisfy the demand for the above-mentioned high performance large liquid crystal display element.

In such a situation, a liquid crystal display element using a ferroelectric liquid crystal has attracted attention as a high-speed liquid crystal display element. The surface-stabilized ferroelectric liquid crystal (SSFLC) device, announced by Clark and Lagabar, has been noted for its unprecedented fast response speed and wide viewing angle, and its switching characteristics have been studied in detail. Many ferroelectric liquid crystals have been synthesized in order to optimize various physical constants. However, the threshold characteristics are insufficient, the layer structure has a chevron structure, the contrast is poor, the high-speed response has not been realized, the orientation control is difficult, and one of the biggest features of SSFLC is However, there are problems such as difficulty in realizing bistability, which is difficult, and difficulty in recovering the orientation due to mechanical shock, and it is necessary to overcome these problems for practical use.

[0005] Apart from this, the development of elements having a switching mechanism different from that of SSFLC is also proceeding at the same time. Switching between the tristable states of a liquid crystal material having an antiferroelectric phase (hereinafter referred to as “antiferroelectric liquid crystal”) is one of these new switching mechanisms (Japanese Journal of A).
pplied Physics, Vol. 27, pp. L729, (1988)). The antiferroelectric liquid crystal device has three stable states. That is,
Two uniform states seen in ferroelectric liquid crystal devices
(Ur, Ul) and the third state. Chandani et al. Report that this third state is an antiferroelectric phase (Japanese Jo
urnal of Applied Physics, Vol. 28, pp. L1261, (198
9), Japanese Journal of Applied Physics, Vol. 28, p.
p.L1265, (1989)).

[0006] 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 Physics, Vol.28, pp.L
119, (1989), Japanese Journal of Applied Physics, V
ol.29, pp.L111, (1990)). 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 to realize a liquid crystal element having excellent contrast. Furthermore, it has been demonstrated that voltage gradation that is almost impossible with ferroelectric liquid crystal is possible with antiferroelectric liquid crystal, opening the way to full color, and the importance of antiferroelectric liquid crystal is further increasing. (Proceedings of the 4th International Conference on Ferroelectric Liquid Crystals, p. 77, (1993)).

As described above, the superiority of the antiferroelectric liquid crystal is becoming more certain, but the driving temperature range is expanded and the response speed is further improved. The development of ferroelectric liquid crystals is desired. Regarding the response speed, in the case of the antiferroelectric liquid crystal, there are two switchings from the antiferroelectric state to the ferroelectric state and from the ferroelectric state to the antiferroelectric state. The two switching speeds by this voltage, ie, the response speed, are important factors that determine the display quality of the display element.

The response speed from the antiferroelectric state to the ferroelectric state (hereinafter referred to as "response speed I") is, for example, the writing speed per scanning line in a simple matrix drive in which line-sequential scanning is performed. It is important to determine the number of scanning lines constituting the screen. As the response speed I increases, the number of scanning lines can be increased, and a high-definition element can be realized.

The required response speed from the ferroelectric state to the antiferroelectric state (hereinafter referred to as "response speed II") varies depending on the design of the element driving method. For example, it changes depending on the set voltage of the offset voltage. But,
If the response speed II is too fast, the ferroelectric state cannot be maintained (maintaining a bright or dark state), and a constant luminance cannot be maintained, which causes a problem in contrast. vice versa,
If the response speed II is too slow, no change from the ferroelectric state to the antiferroelectric state (rewriting from a bright or dark state to a dark or bright state) occurs and driving becomes impossible. If the change to the ferroelectric state is not completely completed within the above, the change is carried over to the next frame, and as a result of accumulating such states, a sufficient dark state cannot be obtained and the contrast decreases. Therefore, the response speed II has a considerable effect on display quality. The response speed II is set to an optimum value after the drive method is determined. For this purpose, it is desirable that the response speed II can be freely changed to some extent. After considering various driving methods, response time II is 1 ~
It is desirable to set within 5 milliseconds.

[0011]

In practice, the antiferroelectric liquid crystal has a further improved response speed and an appropriate response speed, has a wider temperature range of the antiferroelectric phase, and has a smectic A phase. Things are desirable. The response speed I is M. N
According to Akagawa, antiferroelectric liquid crystals depend on the rotational viscosity of liquid crystal molecules (Masahiro Nakaga
wa, Japanese Journal of Applied Physics, 30, 1759
(1991)). That is, the lower the viscosity, the faster the response speed.
Looking at the change of the response speed with respect to the temperature, the response speed decreases exponentially at a temperature lower than the room temperature and below. The antiferroelectric liquid crystal is considered to have a high viscosity because the liquid crystal phase is a smectic phase, so that the viscosity increases rapidly at low temperatures and the response speed decreases rapidly due to the viscous resistance. ing.

As one of concrete measures for solving this problem, a compound having a relatively low viscosity is added to a liquid crystal composition to lower the viscosity of the whole composition and thereby to improve the response speed I. An attempt to do so is conceivable. Although this method seems to be the most realistic solution at present, it tends to lower the maximum temperature of the antiferroelectric phase,
Even if the response speed is improved, a problem occurs in the temperature range of the antiferroelectric phase.

In general, when considering an antiferroelectric liquid crystal device as a display, it is considered that the temperature of the device becomes at least about 40 ° C. due to the backlight. Therefore, the upper limit temperature of the antiferroelectric phase needs to be at least 40 ° C. or higher for normal operation of the device. On the low-temperature side, it is necessary that the element can be driven at least at 10 ° C. Therefore,
The lower limit temperature of the antiferroelectric phase is desirably at least 0 ° C. Therefore, the response speed I must be improved while paying attention to the temperature range of the antiferroelectric phase.

On the other hand, there is almost no knowledge about the control of the response speed II. Although the response speed II seems to have viscosity dependency similarly to the response speed I, the dependency is considered to be small. Conventional control of response speed II
It is common to mix antiferroelectric liquid crystals having the following characteristics, but it is difficult to balance with characteristics other than response speed II, and it is difficult to set response speed II with a certain degree of freedom. The present invention has been made from such a viewpoint, and when a specific swallow tail type compound is added to a specific antiferroelectric liquid crystal mixture, an antiferroelectric phase can be secured in a wide temperature range, and the response speed can be improved. It has been found that the response speed II can be freely set to some extent without adversely affecting I, and the present invention has been completed.

[0015]

That is, the present invention provides a swallow-tail type compound represented by the following general formula (1) and one or more antiferroelectric liquid crystal compounds represented by the following general formula (2). An antiferroelectric liquid crystal composition obtained by adding to a mixture of two or more phenyl ester compounds represented by the following general formula (3).

[0016]

Embedded image (In the formula (1), R ¹ is a linear alkyl group having 4 to 10 carbon atoms, X is a hydrogen atom or a fluorine atom, m is an integer of 2 or 3. In the formula (2), R ² is a carbon atom. 6 to 12 linear alkyl groups, Y is a hydrogen atom or a fluorine atom, A is -CH ₃
Or -CF ₃ , r is 0 or 1, and when A is -CH ₃ ,
When r is 0 and p is an integer of 4 to 10, A is -CF ₃ and r is 0,
p is an integer of 6 to 8, or when A is -CF ₃ and r is 1, s
Is an integer of 5 to 8, and p is an integer of 2 or 4. formula
In (3), R ³ is a linear alkyl group having 5 to 10 carbon atoms, Z
Is a hydrogen atom or a fluorine atom, and n is an integer of 5 to 10.)

In the present invention, in the general formula (1), a swallow-tail type compound in which R ¹ is a straight-chain alkyl group having 9 carbon atoms, m is 2, and X is a fluorine atom is a preferable antiferroelectric liquid crystal composition. Give things. As the antiferroelectric liquid crystal or a mixture thereof, in the general formula (2), A is -CF ₃ , r is 1, Y is
Is a fluorine atom, or A is —CH ₃ , and p is 4 to
It is preferable that the integer of 6 and Y be a fluorine atom, and a mixture of both is particularly preferable in view of the balance of various physical properties. In the general formula (3),
It is preferable to select a phenyl ester compound in which R ³ is a straight-chain alkyl group having 9 carbon atoms, n is 8, and Z is a fluorine atom.

In the antiferroelectric liquid crystal composition of the present invention,
The swallow tail type compound represented by the general formula (1) is used in an amount of 1 to 60 mol%, more preferably 10 to 60 mol% of the antiferroelectric liquid crystal composition.
The general formula (2) is 30 to 80 mol%, more preferably 40 to 70 mol%, and the general formula (3) is 1 to 30 mol%, more preferably 5 to 20 mol%. It is selected from the range of mol%. The obtained antiferroelectric liquid crystal composition has at least a smectic A phase on a higher temperature side than the antiferroelectric phase, and the upper limit temperature of the antiferroelectric phase is 40 ° C or higher and the lower limit temperature is 0 ° C or lower. Is practically preferable. Then, the antiferroelectric liquid crystal composition was prepared by disposing a scanning electrode and a signal electrode in a matrix.
It is a simple matrix liquid crystal display element arranged between a pair of electrode substrates.

The swallowtail type compound represented by the general formula (1) used in the present invention can be easily produced by the method shown by the present inventors (Japanese Patent Application No. 8-243393). For example, when m = 2, it is manufactured by the following method. (B) R ¹ COCl + HO-Ph-COOH → R ¹ COO
-Ph-COOH (b) (b) + SOCl ₂ → R ¹ COO
-Ph-COCl (c) (C ₂ H ₅ ) ₂ CHOH + HO-Ph (X) -COCl → HO-Ph
(X) -COOCH (C ₂ H ₅ ) ₂ (d) (b) + (c) → target compound In the formula, -Ph- is a 1,4-phenylene group, -Ph (X)-is a 2-position F It represents a 1,4-phenylene group which may be substituted.

The above-mentioned manufacturing method is briefly described as follows. (A) shows the reaction between fatty acid chloride and p-hydroxybenzoic acid. (B) is the production of acid chloride. (C) is a reaction between an aliphatic alcohol and p-hydroxybenzoic acid chloride. (D) is a reaction for producing the target substance.

The general formula used in the present invention
The antiferroelectric liquid crystal compound represented by the formula (2) can be easily produced by the method shown by the present inventors (JP-A-4-198155). For example, A = -CF ₃ , r = 1, s
= 5, p = 2, it is manufactured by the following method. (1) AcO-Ph (Y) -COOH + SOCl ₂ → AcO-Ph (Y)
-COCl (2) (1) + HOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ → AcO-Ph (Y) -CO
OC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (3) (2) + Ph-CH ₂ NH ₂ → HO-Ph (Y) -CO
OC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (4) R ² O-Ph-Ph-COOH + SOCl ₂ → R ² O-Ph-P
h-COCl (5) (3) + (4) → antiferroelectric liquid crystal compound, wherein -Ph- is a 1,4-phenylene group, and -Ph (Y)-is a fluorine-substituted 1, 4-phenylene group, Ph- is phenyl group,
C * represents an asymmetric carbon atom.

The above manufacturing method will be briefly described below. (1) is a chlorination reaction of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride. (2)
Is esterification by 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).

[0023]

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 The following compounds corresponding to the general formulas (1), (2) and (3) of the present invention were mixed in the following proportions, respectively, to prepare an antiferroelectric liquid crystal composition. Formula (1): C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO-CH (C ₂ H ₅ ) ₂ 30 mol% Formula (2): C ₉ H ₁₉ -O-Ph-Ph- COO-Ph (3F) -COO-C * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ 37.5 Formula (2): C ₈ H ₁₇ -O-Ph-Ph-COO-Ph (3F) -COO -C * H (CH ₃ ) C ₅ H ₁₁ 22.5 Formula (3): C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO-C ₈ H ₁₇ 10 where -Ph- is 1, 4-phenylene group, -Ph (3F)-is a 1,4-phenylene group substituted with fluorine at the 3-position, and C * is an asymmetric carbon.

The phase sequence of the prepared composition is shown in Table 1.
Table 1 shows the results of measuring the response time at 30 ° C. of the liquid crystal composition. The response time was obtained as follows. I with rubbed polyimide thin film (30nm) I
A liquid crystal cell with a TO electrode (cell thickness 2 μm) was filled with the above compound in an isotropic phase. The cell was gradually cooled at 1.0 ° C./min to align the liquid crystal. The cell was placed between the orthogonal polarizing plates so that the layer direction of the liquid crystal was parallel to the analyzer or the polarizer. The minimum response of light transmittance is 0% and the maximum response is 100%. Response time I is the time required to change the light transmittance from 10% to 90% by applying a voltage of 50V and 10Hz at 30 ° C. II was defined as the time required for the light transmittance to change from 90% to 10%.

Comparative Example 1 Table 1 shows the same results as in Example 1, except that the following racemic compound was used instead of the compound corresponding to the general formula (1). C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO-CH (CH ₃ ) C ₈ H ₁₇ (racemic) As is clear from the results of Example 1 and Comparative Example 1 in Table 1,
Response time I by using swallow tail type compound
The response time II can be set to a desired speed without deteriorating the characteristics of the above. Comparative Example 2 Table 1 shows the same results as in Example 1 except that the compound corresponding to the general formula (1) was set to 40 mol% and the compound corresponding to the general formula (3) was not used.

Example 2 The following compounds corresponding to the general formulas (1), (2) and (3) of the present invention were mixed in the following proportions, respectively, to prepare an antiferroelectric liquid crystal composition. The results obtained in the same manner as in Example 1 are shown in Table 1. Formula (1): C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO-CH (C ₂ H ₅ ) ₂ 15 mol% Formula (2): C ₉ H ₁₉ -O-Ph-Ph- COO-Ph (3F) -COO-C * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ 52.5 mol% Formula (2): C ₈ H ₁₇ -O-Ph-Ph-COO-Ph (3F) -COO-C * H (CH ₃ ) C ₅ H ₁₁ 22.5 mol% Formula (3): C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO-C ₈ H ₁₇ 10 mol% -Ph- represents a 1,4-phenylene group, -Ph (3F)-represents a 1,4-phenylene group substituted by fluorine at the 3-position, and C * represents an asymmetric carbon.

[0027]

[Table 1] Phase sequence Response time I Response time II Example 1 Cr (<-20) SCA * (63) SA (84) I 14.9μs 1100μs Comparative Example 1 Cr (<-10) SCA * (65 ) SA (85) I 17.1 9900 Comparative Example 2 Cr (<-20) SCA * (72) SC * (74) SA (96) I 22 4800 Example 2 Cr (<-20) SCA * (72) SC * (77) SA (92) I 16.0 1800 In the description of the phase series, () indicates the phase transition temperature (° C.), Cr is the crystal phase, SCA * is the antiferroelectric phase, SA is the smectic A phase, I
Indicates an isotropic phase, respectively.

[0028]

The present invention provides a novel antiferroelectric liquid crystal composition. The novel antiferroelectric liquid crystal composition provided by the present invention has an antiferroelectric phase over a wide temperature range, and has a high response speed I when transitioning from an antiferroelectric state to a ferroelectric state, The response speed II at the time of transition from the dielectric state to the antiferroelectric state can have an appropriate speed, so that an antiferroelectric liquid crystal display device with high display quality can be realized.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Motoyama 22nd Wadai, Tsukuba, Ibaraki Pref. Mitsubishi Gas Chemical Company, Ltd.

Claims (8)

[Claims] 1. A swallow tail type compound represented by the following general formula (1) is replaced with one or more antiferroelectric liquid crystal compounds represented by the following general formula (2) and the following general formula (3) An antiferroelectric liquid crystal composition obtained by adding to a mixture of phenyl ester compounds represented by the formula: Embedded image (In the formula (1), R ¹ is a linear alkyl group having 4 to 10 carbon atoms, X is a hydrogen atom or a fluorine atom, m is an integer of 2 or 3. In the formula (2), R ² is a carbon atom. 6 to 12 linear alkyl groups, Y is a hydrogen atom or a fluorine atom, A is -CH ₃
Or -CF ₃ , r is 0 or 1, and when A is -CH ₃ ,
When r is 0 and p is an integer of 4 to 10, A is -CF ₃ and r is 0,
p is an integer of 6 to 8, or when A is -CF ₃ and r is 1, s
Is an integer of 5 to 8, and p is an integer of 2 or 4. formula
In (3), R ³ is a linear alkyl group having 5 to 10 carbon atoms, Z
Is a hydrogen atom or a fluorine atom, and n is an integer of 5 to 10.) 2. The antiferroelectric liquid crystal composition according to claim 1, wherein in the general formula (1), R ¹ is a straight-chain alkyl group having 9 carbon atoms, m is 2, and X is a fluorine atom. 3. The antiferroelectric liquid crystal composition according to claim 1, wherein in the general formula (2), A is —CF ₃ , r is 1, and Y is a fluorine atom. 4. The antiferroelectric liquid crystal composition according to claim 1, wherein in the general formula (2), A is —CH ₃ , p is an integer of 4 to 6, and Y is a fluorine atom. 5. The antiferroelectric liquid crystal composition according to claim 1, wherein in the general formula (3), R ³ is a straight-chain alkyl group having 9 carbon atoms, n is 8, and Z is a fluorine atom. 6. The antiferroelectric liquid crystal composition according to claim 1, wherein the swallow tail type compound represented by the general formula (1) is 1 to 60 mol% of the antiferroelectric liquid crystal composition. 7. The antiferroelectric material according to claim 1, wherein the antiferroelectric phase has at least a smectic A phase at a higher temperature than the antiferroelectric phase, and the upper limit temperature of the antiferroelectric phase is 40 ° C. or more and the lower limit temperature is 0 ° C. or less. Liquid crystal composition. 8. A simple matrix liquid crystal display device comprising the antiferroelectric liquid crystal composition according to claim 1 arranged between a pair of electrode substrates in which scanning electrodes and signal electrodes are arranged in a matrix.