JPH06264060A - Ferroelectric liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition having good alignability (the easiness of being aligned), a good contrast ratio and rapid response to a change in the electric field near room temperature by combining a specified methyl- substituted dimethylsiloxane copolymer with a low-molecular-weight smectic liquid crystal compound. CONSTITUTION:The objecting composition comprises a methyl-substituted dimethylsiloxane copolymer having substituents each having an asymmetric carbon atom and aromatic or heterocyclic rings and a low-molecular-weight smectic liquid crystal compound. A desirable example of the copolymer is a siloxane copolymer of formula I (wherein X is a group of formula II, Y is a single bond or COO, (m) is an integer of 6-20; (n) is an integer of 1-8; *represents asymmetry; and (x) is a number representing a comonomer ratio of 0.1-0.7).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel ferroelectric liquid crystal composition. More specifically, the present invention relates to the field of optoelectronics, in particular, digital display devices such as calculators and watches, dot matrix type display devices, room temperature switching devices, electro-optical shutters, electro-optical diaphragms, optical modulators, optical communication optical path switching switches, The present invention relates to a novel ferroelectric liquid crystal composition suitably used as a material for a liquid crystal element used in a memory, a liquid crystal printer head, a variable focal length lens, and the like.

[0002]

2. Description of the Related Art Conventionally, a display device using a low molecular weight liquid crystal compound has been widely used for digital display of calculators, watches and the like. In these fields of use, conventional low molecular weight liquid crystal compounds are usually used by sandwiching them between two glass substrates whose spacing is controlled in the order of microns. However,
Such adjustment of the interval cannot be realized on a large screen or a curved screen.

As a means for solving this difficulty, it has been attempted to polymerize the liquid crystal so that the liquid crystal itself can be molded [J. Polym. Sci. , Polym. L
ett. , Ed. 13 , 243 (1975), Poly
m. Bull. 6 , 309 (1982), JP-A-56-
21479, etc.]. However, these conventional polymer liquid crystal compounds have the drawback that the polymer itself does not exhibit the properties as a liquid crystal at room temperature and must be heated to a liquid crystal at a temperature range not lower than the glass transition temperature and lower than the clearing temperature. is doing.

Further, Japanese Patent Application Laid-Open No. 63-99204 reports the synthesis of a polyacrylate-based ferroelectric polymer liquid crystal compound, and the ferroelectric polymer liquid crystal compound is prepared from the above polymer liquid crystal compound. Has also been shown to exhibit excellent performance. However, even in this conventional side chain type ferroelectric polymer liquid crystal compound, the response speed,
There is a problem with the usable temperature range.

Further, in JP-A-63-254529, a polyether-based ferroelectric polymer liquid crystal compound obtained by polymerizing an epoxy monomer having an optically active group [for example, represented by the general formula (1)] A repeating unit obtained by polymerizing an epoxy compound and represented by the general formula (1 ′) {in the formulas (1) and (1 ′), u represents an integer of 1 to 30. } The polymeric liquid crystal compound consisting of] is disclosed.

[0006]

[Chemical 3]

Further, WO 92/01731 discloses a repeating unit having an aromatic ring in the side chain and a chain hydrocarbon skeleton and a siloxane skeleton in the main chain, for example, in the following formula (2): The polymeric liquid crystal compounds shown are disclosed.

[0008]

[Chemical 4]

However, although these conventional side-chain type ferroelectric polymer liquid crystal compounds have the advantage of responding to an external electric field stimulus in a wide temperature range including around room temperature, their response speed is slow and they are practically used. It is still insufficient to serve.

On the other hand, as a liquid crystal composition, a polymer liquid crystal composition comprising a polymer liquid crystal compound having asymmetric carbon and a low molecular weight liquid crystal compound has been proposed (Japanese Patent Laid-Open No. 63-284291).
Issue). However, since the side chain type polymer liquid crystal compounds exemplified are those having a normal acrylate or siloxane chain as the main chain, the side chain spacing is not sufficient, and if the molecular weight is increased, a low molecular weight liquid crystal compound can be sufficiently mixed. It becomes difficult to speed up because it disappears. Therefore, while maintaining the conventional high polymer,
There is a problem that it is difficult to obtain a composition having high-speed response.

Further, as an attempt to obtain a composition having a high-speed response while maintaining a high molecular weight with a composition comprising a non-liquid crystalline polymer compound and a low molecular weight liquid crystal compound, Japanese Patent Laid-Open No. 61-
Japanese Patent No. 47427 describes a composition in which a non-liquid crystalline polymer is blended with a low molecular weight liquid crystal compound to impart self-shape retention ability. In this composition, there is a liquid crystal region that is dispersed in the polymer compound (resin) matrix, so it may separate when left for a long time, and since the liquid crystal is dispersed in islands, the contrast It is difficult to control the orientation because it is a dispersion system. JP-A-62-260859, JP-A-62-260841
In the publication, a ferroelectric composite film containing a thermoplastic resin and a low-molecular liquid crystal compound is described, and a thermoplastic resin that is compatible is used. However, a low-molecular compound that is compatible with the thermoplastic resin is used. It is difficult to combine liquid crystal compounds, and it is difficult to control the alignment. Further, there is a problem that the low molecular weight liquid crystal compound used is limited to the ferroelectric liquid crystal. JP-A-1-19868
No. 3 discloses a polymer having a proton donor (or a proton acceptor) and a proton acceptor (or a proton donor).
Although a composition comprising a low molecular weight liquid crystal compound having is described, since both the polymer and the low molecular weight liquid crystal compound must have a proton donor (or a proton acceptor),
The problem is that both structures are quite limited.

[0012]

DISCLOSURE OF THE INVENTION The present invention has a novel ferroelectric property which has good orientation (orientation can be performed easily), has a good contrast ratio, and has a fast response to an electric field change near room temperature. It is an object to provide a liquid crystal composition.

[0013]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a composition comprising a specific methyl-substituted-dimethylsiloxane copolymer and a low-molecular smectic liquid crystal compound. Has a good orientation property (the orientation can be easily performed), has a good contrast ratio, and has a high-speed response to an electric field change near room temperature, and based on these findings, the present invention is completed. I arrived.

That is, the present invention provides a ferroelectric liquid crystal composition comprising a methyl-substituted dimethylsiloxane copolymer having a substituent having an asymmetric carbon atom and an aromatic ring or a heterocycle and a low molecular weight smectic liquid crystal compound. To do.

Since the methyl-substituted-dimethylsiloxane copolymer of the present invention has a dimethylsiloxane copolymerized portion in the main chain and has a portion with a wide side chain interval, it can be mixed with a low molecular weight smectic liquid crystal compound. Since the low molecular weight smectic liquid crystal compound enters between the side chains, the mixture becomes a compatible system and phase separation does not occur.

Further, in the ferroelectric liquid crystal composition of the present invention, the transition temperature of the composition can be easily adjusted only by changing the copolymerization ratio of the methylhydrogeno-dimethylsiloxane copolymer used for the synthesis of the copolymer. Is.

Since the siloxane copolymer used in the present invention functions as a chiral dopant and plays a role of imparting moldability and orientation to the composition, it necessarily has a chiral smectic C phase itself. It doesn't have to be. When the low molecular weight smectic liquid crystal compound is contained, the liquid crystal composition easily exhibits the chiral smectic C phase even if the copolymer does not exhibit the liquid crystal phase.

Further, since the siloxane copolymer used in the present invention functions as a chiral dopant, even if a low molecular weight smectic liquid crystal having no asymmetric carbon and therefore not showing ferroelectricity is used, A dielectric liquid crystal composition can be obtained. When using a low-molecular-weight smectic liquid crystal that does not exhibit ferroelectricity, it is not necessary to select a low-molecular-weight smectic liquid crystal compound in consideration of the spontaneous polarization of the copolymer and the direction of the helix. be able to.

The weight average molecular weight (Mw) of the siloxane copolymer used in the composition of the present invention is usually 1,000.
~ 1,000,000, preferably 1,000 ~
It is 100,000. If the Mw is less than 1,000, moldability as a film or coating film of the composition containing the siloxane copolymer may be impaired.
If it exceeds 1,000,000, unfavorable effects such as a long response time may be exhibited.

As the methyl-substituted dimethyl siloxane copolymer of the present invention, a siloxane copolymer represented by the following general formula [I] is preferably used.

[0021]

[Chemical 5] (Where X is

[0022]

[Chemical 6]

Represents a single bond or --COO--, m represents an integer of 6 to 20, n represents an integer of 1 to 8, * represents an asymmetric carbon atom, and x represents 0.1. It is a number representing a copolymerization ratio of 0.7. ) When the copolymerization ratio x is less than 0.1 or exceeds 0.7, the compatibility with the low molecular weight liquid crystal compound is lowered. The preferable range of x is 0.3 to 0.6.

Specific examples of the siloxane copolymer represented by the general formula [I] include copolymers A to F shown in Examples described later, and X is the following formula.

[0025]

[Chemical 7] And Y is a single bond, m = 10, n = 2, x =
Those which are 0.3 and the like can be mentioned.

The above siloxane copolymer is not particularly limited in its production method and may be produced by any method. For example, the following general formula [II] is used.
The methylhydrogeno-dimethylsiloxane copolymer (compound II) represented by the formula (I) and the side chain component (compound III) having a double bond at the terminal represented by the following general formula [III] are almost combined with hydrosilane. At a ratio of equimolar,
It can be suitably produced by carrying out the hydrosilylation reaction in a solvent in the presence of a catalyst. The reaction proceeds as follows, for example.

[0027]

[Chemical 8] (In the formula, X, Y, m, n, *, and x have the same meanings as above)

Examples of the solvent used in the synthesis reaction of the siloxane copolymer I include inert aromatic hydrocarbons such as benzene, toluene and xylene, and inert ether solvents such as tetrahydrofuran (THF) and diisopropyl ether. Are preferably used. The solvent may be a single solvent or a mixed solvent, but normally, one having a boiling point of 70 ° C. or higher is preferably used in view of the reaction temperature. Further, as the catalyst, one having hydrosilylation activity is used, and specifically, for example, a platinum-based catalyst such as chloroplatinic acid, platinum (II) acetylacetonate, dicyclopentadienylplatinum chloride is preferably used. To be

There are no particular restrictions on the order and system of addition of the respective components when carrying out the synthetic reaction, but for example, a mixture of a methylhydrogeno-dimethylsiloxane copolymer and a side chain component in a predetermined ratio may be added. A preferred example is a method of adding a solvent such as toluene or THF, and then adding an appropriate amount of a catalyst such as chloroplatinic acid.
Regarding the method of adding the catalyst, the catalyst may be added alone or may be dissolved in a solvent such as isopropyl alcohol and added.

The above synthesis reaction can be suitably carried out, for example, in an inert atmosphere such as nitrogen gas or argon, usually in a temperature range of 60 to 100 ° C., preferably 80 to 100 ° C. The reaction time is usually about 3 to 30 hours.

The desired siloxane copolymer can be synthesized as described above. The siloxane copolymer thus obtained can be separated and recovered from the reaction mixture by a known method or the like to obtain a siloxane copolymer having a desired degree of purification. The highly purified siloxane copolymer of the present invention can be obtained by, for example, filtering the reaction mixture after completion of the synthesis reaction and distilling the solvent from the filtrate to obtain a residue, which is dissolved in a suitable solvent such as methylene chloride. And purified by column chromatography using, for example, silica gel as a packing material.

The low molecular weight smectic liquid crystal compound used in the present invention is not particularly limited, and any one or more kinds of conventionally known compounds can be selected and used. Examples of the liquid crystal compound include:

[0033]

[Chemical 9]

[0034]

[Chemical 10]

(In the formula, R ¹ and R ² are each a carbon number 1
To 12 linear or branched alkyl groups, alkoxy groups, acyloxy groups or alkoxycarbonyl groups, which may be the same or different from each other) and the like.

Further, the general formula

[0037]

[Chemical 11]

A compound represented by the following can also be used. R ³ in the general formula (IV) has 7 to 12 carbon atoms.
Alkyl group having 6 to 11 carbon atoms, an acyloxy group having 6 to 12 carbon atoms or an alkoxycarbonyl group having 6 to 12 carbon atoms, and R ⁴ is an alkyl group having 7 to 12 carbon atoms or 6 to 11 carbon atoms. It is an alkoxy group. R ⁵ and R ⁶ in the general formula (V) each have 4 to 1 carbon atoms.
4 alkyl groups or alkoxy groups, which may be the same or different from each other. on the other hand,
In the general formula (VI), R ⁷ is an alkyl group having 4 to 14 carbon atoms, and R ⁸ is an alkyl group having 5 to 14 carbon atoms or 4 carbon atoms.
To 14 alkoxy groups.

Furthermore,

[0040]

[Chemical 12] (In the formula, a and b are integers of 0 to 3, c is an integer of 8 to 12,
d represents an integer of 1 to 8. ).

Specific examples of these low molecular weight smectic liquid crystal compounds include:

[0042]

[Chemical 13]

[0043]

[Chemical 14] And so on.

The method of mixing the siloxane copolymer and the low molecular weight smectic liquid crystal compound is not particularly limited and may be direct mixing or solution mixing. For example, as a solution mixing method, a method in which a predetermined amount of a siloxane copolymer and a low molecular weight smectic liquid crystal compound are placed in a container, dissolved in a solvent such as dichloromethane and mixed, and the solvent is evaporated is preferable.

As a mixing ratio, the siloxane copolymer fraction is preferably 5 to 99% by weight. When the fraction of the siloxane copolymer is less than 5% by weight, the film-forming property and orientation of the liquid crystal composition may deteriorate. In addition, when the low-molecular-weight smectic liquid crystal compound to be mixed is non-chiral, it may cause inconvenience such as not expressing a ferroelectric phase. If the fraction of the siloxane copolymer exceeds 99% by weight, the response time to changes in the electric field may be long. Further, the composition may contain a dye, an adhesive and the like.

[0046]

EXAMPLES Next, the present invention will be explained based on examples, but the present invention is not limited to these examples.

In the equation showing the phase transition behavior, each symbol is
It has the meaning described below. glass: glass phase, S_C ^*: Chiral smectic C
Phase, S_X ^*: S_C ^*Smectic phase higher than the phase, Iso:
Isotropic liquid phase, S_A: Smectic A phase, N : Nematic
C phase, Cryst: crystalline state The phase transition temperature was determined by observation with a polarizing microscope. The phase
In the formula showing the transition behavior, the numbers represent ° C.

Table 1 shows the structures and physical properties of the siloxane copolymers A to G used in the following Examples and Comparative Examples.
X, Y, m, n, and x are symbols in the formula [I].

[0049]

[Table 1]

Example 1 Copolymer A and the following low-molecular smectic liquid crystal compound a
Were mixed in the proportions shown in Table 2 to obtain a composition. Low molecular weight smectic liquid crystal compound a

[0051]

[Chemical 15]

Mixing method Each of them was weighed so as to have the ratio shown in Table 2, dissolved in 5 cc of a solvent (dichloromethane), mixed, and then mixed at about 100 ° C.
The solvent was evaporated at.

When the above composition was sandwiched between glass substrates with ITO electrodes and observed under a polarizing microscope, the island-like structure peculiar to the dispersion system was not observed, and the composition was uniformly a liquid crystal phase. I was able to confirm that it has become. Microscopic observation was carried out at a magnification of 400 times while changing the temperature between 100 ° C. and room temperature.

The above composition was sandwiched between glass substrates with an ITO electrode (electrode area 0.5 cm ² ), and subjected to orientation treatment by applying shearing stress between the upper and lower substrates several times at 80 ° C. (S _A phase) (cell thickness: Two
μm). A voltage of ± 10 V / μm was applied to this at 25 ° C., and the response time was measured. The values shown in Table 2 were obtained.

From the above results, it can be seen that the present composition exhibits ferroelectricity and has high-speed response.

[0056]

[Table 2] In addition, the cell used to measure the response speed is ± 10 V / μm
Voltage was applied and the contrast ratio was measured.
And good contrast was obtained.

Example 2 Copolymer B and the following low molecular weight smectic liquid crystal compound b manufactured by Midori Kagaku Co., Ltd. were mixed in the proportions shown in Table 3 to obtain a composition. Low molecular weight smectic liquid crystal compound b

[0058]

[Chemical 16]

[0059]

[Table 3]

The mixing method was the same as in Example 1. A glass substrate with an ITO electrode (electrode area of 0.
5 cm ² ) and the weight ratio of 40:60 is 50
_A composition having a weight ratio of 60:40 is applied at 50 ° C. (S
_{In the (C} ^* phase), while applying a rectangular voltage of ± 5 V and 10 Hz between the upper and lower electrodes, a shear stress was applied between the upper and lower substrates several times to perform orientation treatment (cell thickness 2 μm). It was cooled as it was, a voltage of ± 10 V / μm was applied at 25 ° C., and the response time was measured. From the above results, it was found that this composition has a high-speed response.

Example 3 Copolymer C and the following low molecular weight smectic liquid crystal compound c manufactured by Midori Kagaku Co., Ltd. were mixed in the proportions shown in Table 4 to obtain a composition. Low molecular weight smectic liquid crystal compound c

[0062]

[Chemical 17]

[0063]

[Table 4]

The mixing method and orientation method were the same as in Example 1. However, the orientation temperature was 60 ° C. When a voltage of ± 10 V / μm was applied at 25 ° C. and the response time was measured, the values shown in Table 4 were obtained. From the above results, it was found that this composition has a high-speed response. Further, a voltage of ± 10 V / μm was applied to the cell used for measuring the response speed, and the contrast ratio was measured to be 25, which was a good contrast.

Example 4 The copolymer D and the low molecular weight smectic liquid crystal compound b are shown in Table 5.
To obtain a composition. The mixing method was the same as in Example 1.

[0066]

[Table 5]

The above composition was sandwiched between glass substrates with ITO electrodes, and a shear stress was applied between the upper and lower substrates several times while applying a rectangular voltage of ± 5 V and 10 Hz between the upper and lower electrodes at 60 ° C. for orientation treatment. (Cell thickness is 2 μm). Cool as it is, 2
When a voltage of ± 10 V / μm was applied at 5 ° C. and the response time was measured, the values shown in Table 5 were obtained. From the above results, it can be seen that the present composition exhibits ferroelectricity and also has high-speed response. Further, a voltage of ± 10 V / μm was applied to the cell used for measuring the response speed, and the contrast ratio was measured to be 28, indicating that good contrast was obtained.

Example 5 The copolymer E and the low molecular weight smectic liquid crystal compound b are shown in Table 6.
To obtain a composition. The mixing method was the same as in Example 1.

[0069]

[Table 6]

A 20 wt% toluene solution of the above composition was formed into a film having a thickness of 3 μm by using a micro gravure coater on the electrode surface of a polyether sulfone (PES) substrate with an ITO electrode. Immediately after the solvent is dried, a substrate of the same type, to which nothing is applied, is laminated so that the liquid crystal layer and the electrode surface are in contact with each other.
0 mm and a length of 3 m) were produced.

Then, the unorientation element 2 was subjected to the bending and orienting treatment by using an orienting device composed of a group of four heating rolls as shown in FIG. Each heating roll 1 has a diameter of 80 mm
Was made of chrome-plated iron and had a width of 300 mm. Surface temperature is T ₁ = 90 ° C, T ₂ = 85 ° C, T
Control was performed at ₃ = 80 ° C. and T ₄ = 77 ° C., and the line speed was v = 8 m / min. By this aligning device, the liquid crystal of the non-aligned element 2 is cooled from the isotropic phase to the liquid crystal phase while being sheared by bending deformation, and finally is uniaxially horizontally aligned in the direction perpendicular to the substrate longitudinal direction, and the aligned element 3 was gotten.

Polarizing plates were arranged above and below the above device so that their polarization axes were orthogonal to each other, a voltage of ± 20 V was applied between the electrodes, and the contrast ratio was measured to be 30. Good contrast was obtained. It was

Therefore, it was demonstrated that this composition is suitable for continuous production of liquid crystal optical elements using the above-mentioned simple method.

Example 6 Copolymer F and the following low molecular weight smectic liquid crystal compound d
Were mixed in the ratio shown in Table 7 to obtain a composition. Low molecular weight smectic liquid crystal compound d

[0075]

[Chemical 18]

[0076]

[Table 7]

The mixing method was the same as in Example 1. The orientation method was the same as in Example 4. However, the orientation temperature is 80
Performed at ° C. When a voltage of ± 10 V / μm was applied at 25 ° C. and the response time was measured, the values shown in Table 7 were obtained. From the above results, it was found that this composition has a high-speed response.

Comparative Example Polymer G and low-molecular smectic liquid crystal compound c were mixed at a weight ratio of 60:40. The mixing method was the same as in Example 1.

When the composition was sandwiched between glass substrates with ITO electrodes and observed under a polarizing microscope, it was confirmed that, unlike in Examples 1 to 6, a uniform liquid crystal phase was not formed and phase separation occurred.

[0080]

EFFECT OF THE INVENTION The ferroelectric liquid crystal composition of the present invention has a good alignment property that allows easy alignment, has excellent contrast, and has a high-speed response to an electric field near room temperature.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an alignment device used in Examples.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Hachiya 1280 Kamizumi, Sodegaura-shi, Chiba Idemitsu Kosan Co., Ltd.

Claims (3)

[Claims] 1. A ferroelectric liquid crystal composition comprising a methyl-substituted-dimethylsiloxane copolymer having a substituent having an asymmetric carbon atom and an aromatic ring or a heterocycle and a low-molecular-weight smectic liquid crystal compound. 2. The ferroelectric liquid crystal composition according to claim 1, wherein the methyl-substituted-dimethylsiloxane copolymer is a siloxane copolymer represented by the following general formula [I]. [Chemical 1] (In the formula, X is Represents, Y represents a single bond or —COO—, and m represents 6
Is an integer from 20 to 20, n is an integer from 1 to 8, * is an asymmetric carbon atom, and x is a number representing a copolymerization ratio of 0.1 to 0.7. ) 3. The ferroelectric liquid crystal composition according to claim 1, wherein the low molecular weight smectic liquid crystal compound is a low molecular weight smectic liquid crystal compound having no asymmetric carbon atom.