JPH06324312A - Field effect liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain such a polymer gel system free from diffusion without causing by-reaction which consumes energy such as electrolysis of water and to improve responsibility for the electric field applied, by using a liquid crystal elastomer as a gellating material having compatibility with a low mol.wt. liquid crystal material. CONSTITUTION:This compsn. consists of a low mol.wt. liquid crystal material 3 and a liquid crystal elastomer 1 swollen with the low mol.wt. liquid crystal material 3. The liquid crystal elastomer 1 used has both properties of liquid crystal and rubber and is obtd. by polymn. of a polymerizable low mol.wt. liquid crystal material in the presence of a crosslinking agent. Before voltage is applied, the liquid crystal elastomer 1 is swollen in the low mol.wt. liquid crystal material having orientation of molecules shown in the figure (a). When voltage is applied under a condition of the mesogen 2 of the liquid crystal elastomer and dielectric anisotropy of the low mol.wt. liquid crystal molecules 3 positive, the compsn. is oriented as shown in the figure (b) in such a manner that the direction of the major axis of the liquid crystal molecules is parallel to the electric field.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel liquid crystal composition which responds rapidly in an electric field. More specifically, the present invention relates to a field-effect liquid crystal composition improved so that deformation of a low-molecular liquid crystal in an electric field can be amplified by a high-molecular liquid crystal and can respond quickly even when a slight voltage is applied.

[0002]

2. Description of the Related Art Liquid crystal materials such as nematic liquid crystal materials
When a direct current voltage is applied while maintaining the temperature in the liquid crystal region by filling the gap between the conductive glass sheets, light is scattered by the liquid crystal film, the liquid crystal film becomes cloudy like ground glass, and when the direct current voltage is cut, it returns to the original state. Since it exhibits a so-called electro-optical effect, it is used in various displays.

By the way, as the liquid crystal substance, low molecular weight organic compounds such as aliphatic and aromatic carboxylic acid derivatives, ether and ketone derivatives, azomethine compounds, azine and glyoxal derivatives and azo compounds are used. By applying a voltage of several tens of volts,
Responds on the order of tens of milliseconds or hundreds of milliseconds,
Depending on the purpose of use, a quicker response on the order of a few milliseconds is required.

On the other hand, as a result of active research on stimuli-responsive polymer gels in recent years, polymer hydrogels are
It has become known that it expands and contracts reversibly depending on ambient conditions such as H, salt concentration, solvent, electric field, and light. Since this expansion and contraction is caused by diffusion of the polymer network into the solvent, the response rate is governed by the diffusion constant, and the smaller the polymer gel, the shorter the time required for expansion and contraction.

Therefore, if a new polymer gel system which is not controlled by diffusion can be formed, a rapid response of expansion and contraction and deformation should be obtained regardless of the size of the gel. Applying this basic idea to liquid crystals. Thus, an actuator with improved responsiveness can be obtained.

However, a general polymer network structure substance such as polystyrene gel, which has been developed in recent years, is not compatible with a low molecular weight liquid crystal substance and cannot be used for improving the response of liquid crystal. A liquid crystal having improved response according to the above concept has not been realized yet.

Deformation due to voltage application is also known in a system using a polymer hydrogel, but since the deformation of this hydrogel occurs at a potential higher than the electric field potential of water, most of the energy is consumed. Is consumed in the electrolysis of water and is inefficient, and it is inappropriate to use it as an actuator.

[0008]

DISCLOSURE OF THE INVENTION The present invention realizes a polymer gel system which is not governed by diffusion, and which does not involve energy-consuming side reactions such as electrolysis of water for liquid crystals. The purpose is to improve responsiveness.

[0009]

Means for Solving the Problems The present inventors have conducted various studies to form a polymer gel system of liquid crystal that is not controlled by diffusion and improve its responsiveness. It was found that the object can be achieved by using a liquid crystal elastomer having compatibility with a molecular liquid crystal substance, and the present invention has been completed based on this finding.

That is, the present invention relates to a low molecular weight liquid crystal substance,
A field effect type liquid crystal composition comprising a liquid crystal elastomer swollen by the low molecular weight liquid crystal substance is provided.

The liquid crystal elastomer used in the present invention is
It is a substance having both properties of rubber and liquid crystal, which is obtained by polymerizing a polymerizable low-molecular liquid crystal substance in the presence of a crosslinking agent.

Examples of such a structure include the general formula

[Chemical 1] (Wherein R1 is a hydrogen atom or a methyl group, n is an integer of 2 to 12) is represented by the general formula

[Chemical 2] In the presence of a bis (acrylic acid or methacrylic acid) ester represented by the formula (R2 is a hydrogen atom or a methyl group, m is an integer of 2 to 12), a radical polymerization initiator such as an azobis compound or a peroxide is used. Examples thereof include those obtained by polymerization.

In the liquid crystal composition of the present invention, the liquid crystal elastomer is prepared by using a low molecular weight liquid crystal substance such as a compound represented by the general formula:

[Chemical 3] It is prepared by adding it to the biphenyl compound represented by the formula (R3 in the formula is an alkyl group) and allowing it to swell sufficiently. Since this swelling ratio is usually about 2 to 20 times, the low molecular weight liquid crystal substance is used in a ratio of 2 times or more, preferably 10 times or more that of the liquid crystal elastomer.

[0014]

Next, the operation of the liquid crystal composition of the present invention will be schematically described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing changes in the alignment state of liquid crystal molecules before and after applying a voltage when a side chain type liquid crystal elastomer is used, and the white ellipses 2, 2 ... In the figure are mesogens of the liquid crystal elastomer 1. , And the black ellipses 3, 3 ... Show the molecules of the low-molecular liquid crystal substance.

Before the voltage is applied, the liquid crystal elastomer 1 is swollen in the low molecular weight liquid crystal substance 3, and the molecular orientation at that time is as shown in (a). When a voltage is applied when the mesogen of the liquid crystal elastomer and the induced anisotropy of the low molecular weight liquid crystal substance molecules are negative, the long axis direction of the liquid crystal molecules and the direction of the electric field become parallel as shown in (b). Orient. FIG. 2 is a schematic diagram in the case of using the main chain type liquid crystal elastomer, and the state is also oriented from the state of (a) to the state of (b).

This change in orientation is transmitted as a change in the polymer network structure of the liquid crystal elastomer, and the entire structure changes. Next, when the voltage is turned off, each liquid crystal molecule is restored to the state (a) before the voltage is applied, and the entire structure returns to the original state.

On the other hand, even if a voltage is applied to the liquid crystal elastomer that is not swollen with the low molecular weight liquid crystal substance, the liquid crystal elastomer does not have fluidity and thus does not deform.

Here, an example in which the induced anisotropy of the liquid crystal elastomer and the low molecular weight liquid crystal is both negative is shown, but in the present invention, both are positive, or one is positive and the other is negative. The case is also included. Then, it is possible to generate different response behaviors by changing the combination in this way.

[0019]

The present invention will be described in more detail with reference to Examples.

Example 4'-Cyano-4-biphenyloxyhexyl acrylate 1.00 g (2.86 mmol), crosslinking agent 1,6-
Diacrylate hexane 66.0 mg (0.292 mm
ol) and 5.2 mg (0.032 mmol) of the polymerization initiator 2,2′-azobis (isobutyronitrile) are mixed with toluene-dimethyl sulfoxide (DMSO) mixed solvent 3.5 m.
It was dissolved in 1 (toluene: 2 ml, DMSO: 1.5 ml) and degassed under reduced pressure. This reaction solution was kept at 60 ° C. for 30 hours for radical copolymerization. An uncrosslinked liquid crystal polymer was also prepared without adding a crosslinking agent for comparison of thermal properties such as transition temperature. The polymerization reaction occurred efficiently in the toluene-DMSO mixed liquid, and a relatively high molecular weight liquid crystal polymer and a homogeneous gel liquid crystal elastomer were obtained.
The obtained elastomer was repeatedly washed in methylene chloride and then dried under reduced pressure.

The liquid crystal polymer, liquid crystal elastomer, and low molecular weight liquid crystal material 4-cyano-4'-hexyloxybiphenyl used herein all showed a nematic phase.
Table 1 shows the transition temperatures of the liquid crystal polymer (LCP), the liquid crystal elastomer (LCE), and the low molecular weight liquid crystal substance [LLC (III)] determined by DSC measurement and polarization microscope observation. The liquid crystal phase formation temperature range of the liquid crystal elastomer was reduced compared to the liquid crystal polymer. It is considered that Tg (glass transition point) increased and TN → I (nematic phase-isotropic phase transition temperature) decreased due to crosslinking.

Next, the liquid crystal elastomer thus obtained was dipped in a 20-fold volume of a low-molecular liquid crystal substance 4-cyano-4'-hexyloxybiphenyl to be swollen. As a result, it swelled at 76.0 ° C. about 8.8 times the dry weight. Liquid crystalline elastomer in gel state [LCE +
(III)] TN → I is low molecular liquid crystal (III) TN → I
77.8 ° C, which is slightly higher than the above.

[0023]

[Table 1]

The symbol g in the table means a glass state, K means a crystalline state, N means a nematic state, and I means an isotropic phase.

Reference Example A sandwich type cell prepared by using a transparent glass electrode was filled with a low molecular weight liquid crystal substance together with a liquid crystal elastomer cut to about 50 to 200 μm. The cell was kept at 76.0 ° C for several hours to allow the liquid crystal elastomer to swell, and
A direct current voltage of 0 to 100 V was applied. Although the liquid crystal elastomer was deformed in the order of milliseconds with the application of voltage, the original shape was quickly restored when the voltage was removed.
Upon deformation, a change in orientation of liquid crystal molecules was observed.

[0026]

According to the present invention, the deformation of a low molecular weight liquid crystal in an electric field can be amplified to the deformation of a high molecular weight liquid crystal, and a field effect type liquid crystal composition capable of responding quickly to a slight voltage application. A thing is provided and this can be used conveniently as various actuators, a display, etc.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing changes and deformations of an array state before and after applying a voltage when a side chain type liquid crystal elastomer is used.

FIG. 2 is a schematic diagram showing a change and deformation of an array state before and after applying a voltage when a main chain type liquid crystal elastomer is used.

[Explanation of symbols]

 1 Liquid crystal elastomer molecule 2 Mesogen of liquid crystal elastomer molecule 3 Low molecular liquid crystal substance molecule

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[Procedure amendment]

[Submission date] March 10, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007] Also, the deformation due to voltage application, but are also known in the system using a polymer hydrogel, deformation of the hydrogel for occurring at a higher potential than the electrolytic potential of water, energy Most of it is consumed in the electrolysis of water, which is inefficient, and it is inappropriate to use it as an actuator.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

In the liquid crystal composition of the present invention, the liquid crystal elastomer is prepared by using a low molecular weight liquid crystal substance such as a compound represented by the general formula:

[Chemical 3] It is prepared by adding it to the biphenyl compound represented by and allowing it to swell sufficiently. Usually this swelling factor is 2
Since approximately 20 times, the low molecular weight liquid crystal material, the liquid crystal elastomer twice Weight above, preferably used in a ratio of more than 10 times Weight.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Before the voltage is applied, the liquid crystal elastomer 1 is swollen in the low molecular weight liquid crystal substance 3, and the molecular orientation at that time is as shown in (a). When Yuden anisotropy of the mesogen and a low molecular liquid crystal material molecules of the liquid crystal elastomer applies a voltage for positive, so that the parallel axial direction and the electric field orientation of liquid crystal molecules as shown in (b) Orient to. FIG. 2 is a schematic diagram in the case of using the main chain type liquid crystal elastomer, and the state is also oriented from the state of (a) to the state of (b).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

[0018] Here, although an example where Yuden anisotropy of the liquid crystal elastomer and a low molecular liquid crystal are both positive, when both the negative and in the present invention, the other one is a positive negative The case of is also included. Then, it is possible to generate different response behaviors by changing the combination in this way.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022] Next, this way the liquid crystal elastomer obtained by immersing swelled 20 times weight of the low molecular weight liquid crystal material 4-cyano-4'-hexyloxy biphenyl. As a result, it swelled at 76.0 ° C. about 8.8 times the dry weight. Liquid crystalline elastomer in gel state [LCE +
(III)] TN → I is TN of low-molecular liquid crystal (III)
→ It was 77.8 ° C, which was slightly higher than I.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohiko Hirasa 1-1, Higashi 1-1 Tsukuba, Ibaraki Prefecture Institute of Industrial Science and Technology

Claims (2)

[Claims] 1. A field effect liquid crystal composition comprising a low molecular weight liquid crystal substance and a liquid crystal elastomer swollen with the low molecular weight liquid crystal substance. 2. The liquid crystal composition according to claim 1, wherein the low molecular weight liquid crystal substance and the liquid crystal elastomer exhibit a nematic phase.