JP3365707B2 - Antiferroelectric liquid crystal composition with small spontaneous polarization - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an antiferroelectric liquid crystal composition having a small spontaneous polarization.

[0002]

2. Description of the Related Art Liquid crystal display devices have 1) low voltage operability and 2)
It has excellent features such as low power consumption, 3) thin display, 4) light receiving type, etc., so far, TN method, STN method,
A guest-host method has been developed and put to practical use. However, a nematic liquid crystal that is widely used at present has a response speed of several mse.
It has a drawback of being slow from c to several tens of msec, and is subject to various restrictions in application.

In order to solve these problems, an STN method and an active matrix method using a thin layer transistor have been developed. However, the STN type display element has excellent display quality such as display contrast and viewing angle. However, problems such as high precision required for control of the cell gap and tilt angle and a rather slow response have become problems. Therefore, there has been a demand for the development of a new liquid crystal display system having excellent responsiveness, and an attempt has been made to develop a ferroelectric liquid crystal that enables an ultra-high-speed device having an optical response time of the order of μsec and extremely short.

Ferroelectric liquid crystals were first described in 1975 by Meyer.
DOBAMBC (p-decyloxybenzylidene-p-amino-2-methylbutyl cinnamate) was first synthesized by et al. (Le Journal de Phy).
sique, vol. 36, 1975, L-69). Furthermore, 1
DOB by Clark and Lagwall 980
Ferroelectric liquid crystal has been receiving a lot of attention since the characteristics of display devices such as submicrosecond high-speed response of AMBC and memory characteristics have been reported [N. A. Cla
rk, et al. , Appl. Phys. Lett. Three
6.899 (1980)].

However, their method has many technical problems for practical use. Especially, there is no material exhibiting a ferroelectric liquid crystal at room temperature, and it is effective in controlling the alignment of liquid crystal molecules which is indispensable for a display. No practical method was established. Since this report, various attempts have been made from both sides of liquid crystal materials / devices, prototype display devices utilizing switching between twisted two states have been produced, and high-speed electro-optical devices using the same have been disclosed, for example, in JP-A-56-107216. However, high contrast and proper threshold characteristics have not been obtained.

From this point of view, other switching methods have been searched and a transient scattering method has been proposed.
Then, in 1988, the inventors of the present invention reported a three-state switching method for a liquid crystal having three stable states [A.
D. L. Chandani, T .; Hagiwara,
Y. Suzuki et al. , Japan. J. of
Appl. Phys. , 27, (5), L729-L7
32 (1988)].

Thus, the "anti" ferroelectric liquid crystal has 1)
It can be said that it is a very useful liquid crystal compound capable of high-speed response, 2) high contrast and wide viewing angle, and 3) good alignment characteristics and memory effect.

Regarding the liquid crystal phase showing the tristable state of the "anti" ferroelectric liquid crystal, 1) A. D. L. Chandani
et al., Japan J. Appl. Phys., 2
8 , L-1265 (1989), 2) H.M. Orihar
a et al., Japan J. Appl. Phys.,
29 , L-333 (1990),
S * CA phase (Antifer)
roelectricSlectic C * phase). The present inventors defined this liquid crystal phase as the S * (3) phase because it switches between tristable states.

"Anti" ferroelectric phase S * (3) showing tri-stable state
Liquid crystal compounds having a phase sequence of are disclosed in Japanese Patent Application Laid-Open Nos. 1-331667, 1-316372,
There are JP-A-1-316339, JP-A-2-28128, and JP-A-1-213390, such as Ichihashi, and as a liquid crystal electro-optical device utilizing a tristable state, the present applicant has JP-A-2-40625. JP-A-2-153322
And Japanese Patent Application Laid-Open No. 2-173724.

When the "anti" ferroelectric liquid crystal is applied to a liquid crystal display, 1) operating temperature range, 2) response speed, 3)
It is difficult to satisfy all the spontaneous polarization, 4) hysteresis characteristics, etc. with a single liquid crystal, and it is usually prepared as a mixed liquid crystal of ten or more kinds.

Among the currently known antiferroelectric liquid crystals, those having a spontaneous polarization value of more than 100 nC / cm ² at a temperature 20 ° C. lower than the phase transition to the antiferroelectric phase are considerable. There are several, some of which are 150 nC /
There are also those that exceed the ones and 200nC / cm ^2, which exceeds the cm ^2. Although there is an advantage that the response speed is increased when the spontaneous polarization is large, the polarization reversal current becomes large and the driver IC is burdened (power consumption).
Is large, and as the dot matrix display screen becomes large (the number of pixels becomes large) due to the voltage drop due to the polarization reversal current, there arises a problem that display unevenness occurs. One way to solve this is the driver I
Although higher output of C can be considered, this causes an increase in power consumption, which is disadvantageous for application to a portable type such as a laptop computer.

[0012]

The object of the present invention is to reduce the power consumption as a result of the antiferroelectric liquid crystal compound and its composition having unnecessarily high spontaneous polarization in the temperature range in which the antiferroelectric liquid crystal phase is exhibited. Is large, and the problem that the display unevenness of the screen occurs is solved, the power consumption is low in the operating temperature range, and the result that the display unevenness of the screen is greatly improved,
The present invention relates to a novel antiferroelectric liquid crystal composition that can be applied to a large screen.

[0013]

According to the present invention, the antiferroelectric liquid crystal phase to the ferroelectric liquid crystal phase (or the liquid crystal phase on the higher temperature side including smectic A) at 50 ° C. or higher and 120 ° C. or lower in the temperature rising process. Has a phase transition temperature to
The response speed τr at 4 ° C. is 42.1 μs or less,
The value of spontaneous polarization at 30 ° C. is 10 nC / cm ² or more,
An antiferroelectric liquid crystal composition having an antiferroelectric liquid crystal composition of 118 nC / cm ² or less, which is a racemate of a compound which can be an antiferroelectric liquid crystal compound when optically resolved into an optically active compound. 1.0 wt% or more in composition, 90 wt
% Or less, the present invention relates to an antiferroelectric liquid crystal composition having a small spontaneous polarization.

In the present invention, a part of the conventional antiferroelectric liquid crystal compound having a high spontaneous polarization is used in the form of a racemate, so that the other properties of the antiferroelectric liquid crystal are not adversely affected. The inventors have succeeded in obtaining the antiferroelectric liquid crystal composition according to claim 1 by reducing the spontaneous polarization of the antiferroelectric liquid crystal composition.

That is, in order to obtain the antiferroelectric liquid crystal composition of the present invention having a small spontaneous polarization, one or two of the antiferroelectric liquid crystal compounds having a function of expressing the antiferroelectric liquid crystal are used.
This can be achieved by adding 1.0 to 90.0% by weight of a racemate of a compound which can be an antiferroelectric liquid crystal compound when optically resolved into a mixture of one or more kinds of compounds in the form of an optically active compound. .

The racemic body is preferably a racemic body of a compound which acts as an antiferroelectric liquid crystal compound in the antiferroelectric liquid crystal composition, but it is not necessarily limited thereto, and the point is that the racemic body is essential. It may be a racemate of a compound which, when divided into an optically active compound, exhibits an action as an antiferroelectric liquid crystal compound.

One of the racemates is represented by the following general formula (I)

[Chemical 5] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1, X ₁ , X ₂ , X ₃ , X ₄ , X ₅ and X ₆ are elements independently selected from the elements consisting of H and F, and Cf is CH ₃ , CF ₃ , CClF ₂ and C ₂
It is a group selected from the group consisting of H ₅ . ) Is a racemate.

This racemic body is contained in the antiferroelectric liquid crystal composition in an amount of 1.0 to 80.0% by weight, preferably 5.0 to 50.
The composition of the present invention can be obtained by mixing at a ratio of 0% by weight.

Another preferred racemate as the racemate is the following general formula (II)

[Chemical 6] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1, and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , and X ₆ are elements independently selected from the elements consisting of H and F. ) Is a racemate.

This racemic body is contained in the antiferroelectric liquid crystal composition in an amount of 1.0 to 70.0% by weight, preferably 5.0 to 50.
The composition of the present invention can be obtained by mixing at a ratio of 0% by weight.

Another one of the racemates is represented by the following general formula (III)

[Chemical 7] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1, and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ , and X ₆ are elements independently selected from the elements consisting of H and F. ) Is a racemate.

This racemic body is contained in the antiferroelectric liquid crystal composition in an amount of 1.0 to 70.0% by weight, preferably 5.0 to 50.
The composition of the present invention can be obtained by mixing at a ratio of 0% by weight.

Another one of the racemates is represented by the following general formula (IV)

[Chemical 8] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, Y
Is a group selected from the group consisting of —O—, —COO— and a single bond, and X ₁ , X ₂ , X ₃ , and X ₄ are elements independently selected from the elements consisting of H and F. Yes, Cf
Is a group selected from the group consisting of CH ₃ , CF ₃ , CClF ₂ and C ₂ H ₅ . ) Can be mentioned.

This racemic body is contained in the antiferroelectric liquid crystal composition in an amount of 1.0 to 70.0% by weight, preferably 5.0 to 50.
The composition of the present invention can be obtained by mixing at a ratio of 0% by weight.

As these racemates, only racemates having the same chemical formula can be used, but a plurality of racemates having different chemical formulas can be used in combination.

Examples of the antiferroelectric liquid crystal compound include all antiferroelectric liquid crystal compounds known before this application. The antiferroelectric liquid crystal compound is exemplified by the general formula (V)

Embedded image A-skeleton structure-D (V) (In the formula, A is R-, RO-, RCOO-, ROCO-
And ^{RCO-, R 3 -O-R 4} - and R ⁵ -CH = C
It is a group selected from the group consisting of H—R ⁶ —, and R is an alkyl group having 2 to 20 carbon atoms. However, in the case of R-, a part of hydrogen in the alkyl group may be halogen-substituted, R ³ is a linear alkyl group having 1 to 8 carbon atoms, and R ⁴ is 1 to 10 carbon atoms. A linear alkylene group, R ⁵ is hydrogen or a linear or branched alkyl group having 1 to 5 carbon atoms, and R ⁶ is a linear or branched alkyl group having 2 to 14 carbon atoms,

[Chemical 10] An independent Barre radicals from the group consisting of, E is, -CF _3,
Is a group selected from the group consisting of —C ₂ F ₅ , —C ₃ F ₇ , CClF ₂ , CH ₃ and C ₂ H ₅ , * is an asymmetric carbon, G is a straight chain having 2 to 20 carbon atoms or It is a branched alkyl group, and the branched portion is a methyl group, and a part of the straight chain alkyl may contain one carbon-carbon double bond,

[Chemical 11] The skeletal structure is the following formula group

[Chemical 12]

[Chemical 13]

[Chemical 14]

[Chemical 15]

[Chemical 16]

[Chemical 17]

[Chemical 18]

[Chemical 19]

[Chemical 20]

[Chemical 21]

[Chemical formula 22]

[Chemical formula 23]

[Chemical formula 24]

[Chemical 25] Is selected from the group consisting of ).

Specific examples of the antiferroelectric liquid crystal compound include compounds represented by the following general formula groups (1) to (138). (In the formula, R ¹ and R
² is an alkyl group independently selected from the group consisting of alkyl groups having 4 to 20 carbon atoms, Z is CF ₃ , C
It is a group selected from the group consisting of ₂ F ₅ , CH ₃ and C ₂ H ₅ . )

[Chemical formula 26]

[Chemical 27]

[Chemical 28]

[Chemical 29]

[Chemical 30]

[Chemical 31]

[Chemical 32]

[Chemical 33]

[Chemical 34]

[Chemical 35]

[Chemical 36]

[Chemical 37]

[Chemical 38]

[Chemical Formula 39]

[Chemical 40]

[Chemical 41]

[Chemical 42]

[Chemical 43]

[Chemical 44]

[Chemical formula 45]

[Chemical formula 46]

[Chemical 47]

[Chemical 48]

[Chemical 49]

[Chemical 50]

Particularly preferred antiferroelectric liquid crystal compounds are:

[Chemical 51] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, *
Represents an asymmetric carbon) and

[Chemical 52] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, *
Represents an asymmetric carbon).

Further, as the antiferroelectric liquid crystal compound, the following general formula is used.

[Chemical 53] (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, *
Is asymmetric carbon), the spontaneous polarization of the compound itself is relatively low, and therefore the feature is that the compounding amount of the racemate is small.

[0030]

The present invention will be described below with reference to examples of the present invention, but the present invention is not limited thereto.

Example 1 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 54]

The phase transition temperature of the composition is

[Table 1] Is. Spontaneous polarization measured by the triangular wave method at 20 Hz and ± 50 V is 108 nC / cm ² at 40 ° C. and 30 ° C.
Is 116 nC / cm ² .

The response speed and tilt angle of the above composition were as follows.

[Table 2]

[Table 3]

Example 2 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 55]

The phase transition temperature of the composition is

[Table 4] Is. When the magnitude of spontaneous polarization was measured by the same method as in Example 1, it was 93 nC / cm ² at 40 ° C. and 1 at 30 ° C.
It was 01 nC / cm ² .

The response speed and tilt angle were as follows.

[Table 5]

[Table 6]

Example 3 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 56]

The phase transition temperature of the composition is

[Table 7] Is. When the magnitude of spontaneous polarization was measured by the same method as in Example 1, it was 93 nC / cm ² at 40 ° C. and 1 at 30 ° C.
It was 02 nC / cm ² .

The response speed and tilt angle were as follows.

[Table 8]

[Table 9]

Example 4 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 57]

The phase transition temperature of the composition is

[Table 10] Is. When the magnitude of spontaneous polarization was measured in the same manner as in Example 1, it was 95 nC / cm ² at 40 ° C. and 1 at 30 ° C.
It was 03 nC / cm ² .

The response speed and tilt angle were as follows.

[Table 11]

[Table 12]

Example 5 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 58]

The phase transition temperature of the composition is

[Table 13] Is. When the magnitude of spontaneous polarization was measured by the same method as in Example 1, it was 93 nC / cm ² at 40 ° C. and 1 at 30 ° C.
It was 05 nC / cm ² .

The response speed and tilt angle were as follows.

[Table 14]

[Table 15]

Example 6 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 59]

The phase transition temperature of the composition is

[Table 16] Is. Measurement of the magnitude of spontaneous polarization in the same manner as in Example 1, was 116nC / cm ² at 105nC / cm ^2, 30 ℃ at 40 ° C..

The response speed and tilt angle were as follows.

[Table 17]

[Table 18]

Example 7 An antiferroelectric liquid crystal composition having the following composition was prepared. In the table,
Those with R indicate the R form, and those with ± indicate the racemate.

[Chemical 60]

The phase transition temperature of the composition is

[Table 19] Is. Measurement of the magnitude of spontaneous polarization in the same manner as in Example 1, was 118nC / cm ² at 110nC / cm ^2, 30 ℃ at 40 ° C..

The response speed and tilt angle were as follows.

[Table 20]

[Table 21]

[0052]

According to the present invention, the power consumption is reduced and the display unevenness on the screen is improved in the practical temperature range, and it can be used as an antiferroelectric liquid crystal material for a larger screen.

[Brief description of drawings]

FIG. 1 shows a model of a hysteresis curve of relative transmittance with respect to a triangular wave applied voltage.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuyoshi Yoshida Kasumigaseki 3-chome 3-5 Tokyo Chiyoda-ku Tokyo Showa Shell Sekiyu Co., Ltd. (72) Inventor Noriko Yamakawa Kasumigaseki 3-chome 5 Chiyoda-ku Tokyo Showa Shell Petroleum Co., Ltd. (72) Inventor Osamu Nonaka 3-5 Kasumigaseki, Chiyoda-ku, Tokyo Showa Shell Petroleum Co., Ltd. (56) Reference JP-A-3-223390 (JP, A) JP-A-6- 25153 (JP, A) JP-A-5-271658 (JP, A) JP-A-4-305555 (JP, A) JP-A-8-3556 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09K 19 / 02,19 / 42 C09K 19 / 46,19 / 20

Claims (5)

(57) [Claims] 1. A temperature of 50 ° C. or higher and 120 ° C. during the temperature rising process.
It has a phase transition temperature at which it transforms from an antiferroelectric liquid crystal phase to a ferroelectric liquid crystal phase (or a liquid crystal phase on the higher temperature side including smectic A), and the response speed τr at 30 ° C. is 42.1 μs or less. And an antiferroelectric liquid crystal composition having a spontaneous polarization value of 10 nC / cm ² or more and 118 nC / cm ² or less at 30 ° C. and having an optical resolution in the form of an optically active compound. An antiferroelectric liquid crystal composition having a small spontaneous polarization, characterized in that the antiferroelectric liquid crystal composition contains a racemate of a compound capable of becoming a dielectric liquid crystal compound in an amount of 1.0 wt% or more and 90 wt% or less. 2. The following general formula (I): (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1 and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ ,
X ₆ is an element independently selected from the elements consisting of H and F, and Cf is CH ₃ , CF ₃ , CClF ₂
And a group selected from the group consisting of C ₂ H ₅ . The antiferroelectric liquid crystal composition according to claim 1, which contains a racemate represented by 3. The racemic body of the general formula (I) is represented by the following general formula (II): (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1 and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ ,
X ₆ is an element independently selected from the elements consisting of H and F. The antiferroelectric liquid crystal composition according to claim 1, which is a racemic body represented by: 4. The racemic body of the general formula (I) is represented by the following general formula (III): (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, p
Is 0 or 1 and X ₁ , X ₂ , X ₃ , X ₄ , X ₅ ,
X ₆ is an element independently selected from the elements consisting of H and F. The antiferroelectric liquid crystal composition according to claim 1, which is a racemic body represented by: 5. The following general formula (IV): (In the formula, m is an integer of 6 to 14, n is an integer of 3 to 10, Y
Is a group selected from the group consisting of —O—, —COO— and a single bond, and X ₁ , X ₂ , X ₃ and X ₄ are elements independently selected from the elements consisting of H and F. Yes, Cf is CH ₃ , CF ₃ , CC
It is a group selected from the group consisting of IF ₂ and C ₂ H ₅ . ) A racemate represented by
The antiferroelectric liquid crystal composition described.