JPH035720A - Liquid crystal actuator device - Google Patents

Abstract

PURPOSE:To obtain a small-sized, high(large)-output actuator device of simple system constitution which has extremely excellent fast response by using high molecule liquid crystal where mechanical energy is led out reversibly with an electric field and/or liquid crystal elastomer as a principal material for an output medium. CONSTITUTION:The liquid crystal actuator device 10 is provided while liquid crystal actuators 2A - 2D are sandwiched by five electrode plates 1A - 1E, and the laminate structure of them is covered with an elastic insulating cover 3 on the whole. The liquid crystal actuators 2A - 2D vary reversibly in elastic modulus principally in the laminating direction (vertically in figure) by applying and removing a voltage. Consequently, the high(large)-output liquid crystal actuator device of small-sized, simple constitution which have fast response is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal actuator/device, and is particularly suitable for use as an actuator/device for small machines such as medical welfare equipment and robots. This invention relates to a liquid crystal actuator device.

[Prior Art] Among various fffi liquid crystal materials, low-molecular liquid crystals have been used industrially as display elements for digital clocks, calculators, televisions, word processors, and the like. There have also been attempts to utilize polymer liquid crystals as memory elements, nonlinear optical elements, etc., but they have been put into practical use industrially as materials with high elastic modulus and high strength. In the case of low-molecular liquid crystals, high-molecular liquid crystals, mixed systems thereof, or mixed systems of these and other substances, the liquid crystal material can be used as an actuator.
Currently, no example of application as a device has been proposed.

Recently, Yoshihito Nagata and colleagues at Ibaraki University have developed a polymer oil-based gel with hydrophobic side chains (exhibiting thermotropic liquid crystallinity).
Taking advantage of the fact that gel rapidly hardens and softens at the transition point, the gel was heated in dimethyl sulfoxide (DMSO) to make it soft, then tension was applied to stretch it approximately three times, and it was cooled and hardened. It has been reported that when it is heated again, it rapidly shrinks to its original length at the inversion point (Hideke Yasunaga,
Yoshihito Nagata, "Second Polymer Gel Research Discussion Group" Lecture Abstracts, p. 73 (1989)). However, this is driven by temperature changes, and when considering its control, it is not possible to construct a practical actuator device.

[Problem to be solved by the invention] As described above, there have been no reports on the use of liquid crystal materials as actuator/device constituent materials, and there have been no reports suggesting that liquid crystal materials can be used as practical actuator/device components. The current situation is that nothing has been done.

The present invention has been made in view of the above circumstances, and is a compact high (large) output actuator device that has a simple system configuration and exhibits extremely excellent high-speed response.
An object of the present invention is to provide a liquid crystal actuator device composed of a reversibly stretchable, reversibly deformable or reversibly hardening/softening polymer liquid crystal, that is, a liquid crystal actuator device.

[Means and effects for solving the problem] The liquid crystal actuator device of the present invention uses a polymer liquid crystal and/or a polymer liquid crystal that reversibly extracts mechanical energy by an electric field as an output medium.
Alternatively, it is a device using a liquid crystal actuator whose main constituent material is liquid crystal elastomer.

The liquid crystal actuator device of the present invention further includes a structural unit (hereinafter referred to as "rLC cell") formed by holding a liquid crystal actuator directly or indirectly through a spacer such as an insulating film between at least one pair of electrodes. , means for applying a voltage between the pair of electrodes.

In the present invention, such LC cells include two or three
The above may be arranged in parallel or in series (stacked type), or in a composite type of parallel and series. By arranging a plurality of LC cells in this manner, the output of mechanical energy extracted from the liquid crystal actuator can be expanded. That is, for example, by stacking LC cells equipped with liquid crystal actuators whose elastic modulus changes reversibly by applying or removing a voltage in a direction perpendicular to the direction of elastic modulus displacement of the liquid crystal actuators, the output due to the change in elastic modulus can be obtained. Changes can be amplified. Further, by stacking LC cells including liquid crystal actuators that reversibly expand and contract by applying and removing voltage in the direction of expansion and contraction of the liquid crystal actuators, it is possible to increase the expansion and contraction displacement.

Such an LC cell or an array group of LC cells may be partially or entirely covered with a cover made of a stretchable or flexible insulating material such as a rubber composition.

Note that there are no particular limitations on the electrode material, and any commonly used materials can be used.

There are no particular restrictions on the material of the liquid crystal actuator, but it should be one that has been conventionally synthesized as a polymer liquid crystal, preferably a side chain type polymer liquid crystal with a structure containing a mesogen group with strong electroconductivity in the side chain. Polysiloxane, polybutadiene in the main chain,
Polymer liquid crystals having a polyethylene structure or the like and/or liquid crystal elastomers obtained by crosslinking them into elastomers can be used.

A liquid crystal actuator whose main constituent material is a polymeric liquid crystal or a liquid crystal elastomer suitable for the liquid crystal actuator device of the present invention will be described below.

In this specification, unless otherwise specified, "liquid crystal" refers to low-molecular and high-molecular liquid crystals such as nematic liquid crystal, smectic liquid crystal, and ferroelectric liquid crystal that respond to an electric field.

Polymer liquid crystals can be roughly classified into main chain type, side chain type, and main chain side mixed type depending on the method of addition of mesogenic groups, that is, liquid crystal low molecular components. In the case of a side chain type, the bent chain portion that connects the mesogenic group and the main chain is called a spacer. The polymer liquid crystal used in the present invention is preferably a side chain type polymer liquid crystal.

In general, among polymer liquid crystals, crystalline polymer liquid crystals take three states from the low temperature side: crystalline state, liquid crystal state, and isotropic liquid state, whereas non-quality polymer liquid crystals take a glassy state from the low temperature side. It is known that it takes three states: a liquid crystal structure region, a liquid crystal state, and an isotropic liquid state, or two states: a glassy liquid crystal structure region and an isotropic liquid state.

The liquid crystal actuator according to the present invention is a liquid crystal actuator for extracting mechanical energy by stimulation of voltage application/removal, and the liquid crystal actuator is made of a polymer liquid crystal, preferably a side chain type polymer liquid crystal, or a liquid crystal elastomer obtained by elastomizing it. used as

In addition, in order to make polymer liquid crystal into an elastomer, ■ High molecular weight.

■ Incorporating a cross-linked structure.

(2) The glass transition temperature is below room temperature, preferably below -20°C.

■Having no or almost no crystal structure.

etc. are necessary conditions. However, in this case, especially in the cases of (1) and (2), the viscosity increases, which may result in a decrease in electric field responsiveness.

Furthermore, in order to improve the electric field responsiveness of the liquid crystal actuator, the number of nematic, preferably elastic, mesogenic groups in the polymer may be increased. However, in this case, an increase in the glass transition temperature is inevitable, and as a result, the liquid crystal region (
In other words, the movable temperature range of the liquid crystal actuator becomes narrower.

On the other hand, from the viewpoint of practicality of the liquid crystal actuator, it is essential to realize the above-mentioned liquid crystal state in a wide temperature range including room temperature.

Based on the above, in order to realize a high-strength polymer liquid crystal with a wide liquid crystal area while maintaining high-speed electric field response, the following constituent materials are used for the liquid crystal actuator according to the present invention. This is effective.

■ Adopt a main chain with a low glass transition temperature (Tg).

In polymer liquid crystal, in order to secure a wide liquid crystal area,
It is desirable to have a glass transition temperature as low as possible below room temperature. For this purpose, the main chain must have a low glass transition temperature, specifically, the main chain must have polysiloxane (T
g=-123℃), polyethylene (Tg=-102℃)
, polybutadiene (Tg=-t 20°C), and the like.

(2) Introducing a mesogenic group that has high electric field responsiveness and preferably has little effect on glass transition temperature and viscosity.

As described above, in general, the glass transition temperature tends to increase as more mesogenic groups are introduced. Therefore, it is preferable to introduce a mesogenic group having high electric field responsiveness and having little influence on the glass transition temperature and viscosity in a proportion that does not significantly increase the glass transition temperature.

The mesogenic group can be introduced by chemical methods, such as copolymerization of a liquid crystalline monomer constituting the mesogenic part and 100% monomer constituting the main chain, or 5i-H of polysiloxane.
A dynamic vulcanization method using a polymer reaction (chemical modification, modification) in which a terminal vinyl mesogenic group is added by a hydrosilylation reaction or a radical polymerization reaction using a peroxide can be used. In addition, physical methods such as mixing low-molecular liquid crystals described below are also suitable for introducing mesogenic groups.

■ Mixed use with low molecular liquid crystal.

In the case of low-molecular liquid crystals, it is necessary to mix other types of single substances (medium-temperature liquid crystals, high-temperature liquid crystals, thinners) to obtain a liquid crystal material that exhibits a liquid crystal phase over the temperature range required for practical use. . Similarly, in the case of polymer liquid crystals that have mesogenic groups in their side chains or main chains, it is known that when other types of low-molecular liquid crystals are mixed with the polymer liquid crystals, the orientation by electric field may be improved. It is being Therefore, the combined use of an appropriate amount of low-molecular-weight liquid crystal is extremely effective in improving electric field responsiveness.

■ Turn polymer liquid crystal into an elastomer.

Formation into an elastomer can be carried out by a normal crosslinking reaction, etc., but by forming it into an elastomer, it is possible to obtain a liquid crystal actuator that has no fluidity even at high temperatures and has high strength. Therefore, it is preferable to use an elastomer as long as the electric field response is not impaired.

In view of the above, the following materials are suitable for forming the liquid crystal actuator according to the present invention.

The polymeric liquid crystal or liquid crystal elastomer contains a siloxane, ethylene, or butadiene structure in its main chain, and has a general formula such as a mesogenic group (m is an integer of 0 or 1 or more) -A -: -(:H-N- 1 C -0- ↑ -N-N-, N-N- (trans) etc. in the side chain, the introduction ratio of such mesogenic groups is 20 to 50% by weight, and the molecular weight is 103 to 106
A liquid crystal elastomer obtained by crosslinking a liquid crystal polymer of about 100 ml or more is preferable.

In addition, in the above general formula, -R-, etc. indicate the following.

-R-: →CH2→ , →CH2 publication -〇- (trans)
etc. 1:0 or 1 n:0, 1.2 or 3 Specifically, mesogen The following liquid crystal monomer is introduced as a base using 20 to 95% by weight of a platinum catalyst at 5 to 75 ppm, or the following crosslinking agent such as
Examples include those made into an elastomer using up to 30% by weight in the presence of a catalyst.

(Tetramethyldivinyldisiloxane) (n≧0) (Bis(vinyldimethylsilyl)benzene) These polymeric liquid crystals or liquid crystal elastomers may be used alone or in combination of two or more.

Further, as a low molecular liquid crystal suitable for use in combination with such a polymeric liquid crystal or a liquid crystal elastomer, the low molecular liquid crystal used for introducing the mesogenic group described above can be used.

These low molecular liquid crystals may be used alone or in combination of two or more.

If the mixing ratio of the low-molecular liquid crystal to the polymeric liquid crystal or liquid crystal elastomer is too small, the effect of improving electric field response by using the low-molecular liquid crystal in combination will be low, and if it is too large, the fluidity will increase and the strength will decrease.

Therefore, it is preferable that the mixing ratio of the polymeric liquid crystal or liquid crystal elastomer and the low-molecular liquid crystal is 0.1 to 1 by weight.

The liquid crystal actuator according to the present invention can be composed of the above-mentioned polymeric liquid crystal and/or liquid crystal elastomer, or if necessary, further composed of low molecular liquid crystal, but in order to further improve the strength, various reinforcing agents and fillers may be added. Alternatively, additives such as low-molecular liquid crystals may be mixed and used for the purpose of widening the operating temperature range.

The driving force behind the reversible stretchability of the liquid crystal actuator used in the liquid crystal actuator according to the present invention is the application and removal of voltage. Therefore, in order to efficiently exhibit reversible stretchability, it is preferable that the shape or mode of use of the liquid crystal actuator used be a laminated thin film type.

The liquid crystal actuator according to the present invention can be produced by adding various main chain constituent substances, mesogenic group-introducing substances, cross-linking agents, and various additives as necessary, and reacting and molding them according to conventional methods, or by further adding to the reactants. It can be easily manufactured by mixing and molding low-molecular liquid crystals.

The liquid crystal actuator device of the present invention, which includes such a liquid crystal actuator, is a high-output device with excellent high-speed response that reversibly outputs mechanical energy according to the voltage applied and removed between the electrodes. .

[Examples] The liquid crystal actuator device of the present invention will be described in more detail below with reference to the drawings, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Example of vibration isolator (laminated type) Referring to FIG. 1 (longitudinal sectional view) and FIG. 2 (perspective view),
A liquid crystal actuator device according to a first embodiment of the present invention will be described.

The liquid crystal actuator device 10 of this embodiment has liquid crystal actuators 2A, 2B, and 2C between five electrode plates IA, IB, IC, ID, and IE.

2D are sandwiched between each other, and the entire laminated structure is covered with a stretchable insulating cover 3.

Conductive wires 5a and 5b from the battery 4 are buried inside the cover 3, and among the electrode plates IA to IE, IA and IC
A conductor 5a from the positive pole of the battery 4 is connected to IB and ID, and a conductor 5b from the negative pole of the battery 4 is connected to IB and ID.
are connected to each other.

As a result, the liquid crystal actuator 2A between electrode plates IA and IB, the liquid crystal actuator 2B between electrode plate IB and IC,
A voltage is applied to each of the liquid crystal actuator 2C between the electrode plates IC and 10, and the liquid crystal actuator 2D between the electrode plates ID and IE. In the figure, 6
is a switch.

The elastic modulus of the liquid crystal actuators 2A to 2D reversibly changes mainly in the stacking direction (in the vertical direction in the figure) by applying or removing a voltage. Therefore, the liquid crystal actuator device 10 of this embodiment provides a vibration isolator whose elastic modulus changes reversibly by turning the switch 6 on and off, thereby absorbing external vibrations.

In addition, liquid crystal actuators can be used as such vibration isolators.
Preferred examples of the constituent material of the 7-night crystal actuator used in the device include the following polymeric liquid crystals and liquid crystal elastomers.

Example 2 Example of a vibrator (stacked type) A liquid crystal actuator that reversibly expands and contracts in the stacking direction in response to voltage application and removal is used as the liquid crystal actuator shown in FIGS. 1 and 2.
Configured the device.

According to such a liquid crystal actuator device 10, a vibrator that reversibly expands and contracts to apply vibrations to the outside is provided by turning on and off the switch 6.

In addition, a liquid crystal actuator as such an exciter
Preferred examples of the constituent material of the night crystal actuator used in the device include the following polymeric liquid crystals and liquid crystal elastomers.

Example 3 (unimorph type) Example Referring to FIG. 3 (cross-sectional view), FIG. 4 (perspective view), and FIG. 5 (perspective view), a liquid crystal actuator according to a third example of the present invention・Explain the device.

The liquid crystal actuator device 20 of this embodiment has a liquid crystal actuator 1 between a pair of stretchable electrodes 11A and 118.
2 is held, one electrode 11a is connected to a conductor 5a from the positive pole of the battery 4, and the other electrode 11b is connected to a conductor 5b from the negative pole of the battery 4. By closing the switch 6, the power is turned off. A voltage is applied between Jfuta and ttb. In addition, elastic electric 8i11
An elastic plate 7 is adhered to the outer surface of b.

The liquid crystal actuator 12 used in this example is
It contracts when a voltage is applied and returns to its original state when the voltage is removed. Therefore, by closing switch 6,
By applying a voltage between the stretchable electrodes 11a and 11b, the liquid crystal actuator 12 contracts, but the stretchability '2
Since the contraction of the ii pole 11a side is prevented by the elastic plate 7, as shown in FIG. 3, the electrode 11a side and fib
The differential contraction of the liquid crystal actuator 12 with respect to the sides causes the liquid crystal actuator device 20 to be in a curved state.

Such a liquid crystal actuator device 20 has a fourth
As shown in the figure and Figure 5, there are multiple
(book) can be placed side by side to serve as a pseudo finger. The pseudo finger shown in FIGS. 4 and 5 has three liquid crystal actuator devices 20 (20A, 20B, 20C) attached to a substrate 8, and the above-mentioned liquid crystal actuator devices can be activated by applying voltage. It uses curvature to perform work. That is, a voltage is applied to each of the liquid crystal actuator devices 20A, 20B, and 20C by closing the switch 6 of the circuit for energizing the liquid crystal actuator device 20 consisting of the battery 4 and the conductive wires 5a and 5b.
This is bent to grip the object 9 as shown in FIG. By opening switch 6, each liquid crystal actuator device 20A, 20B.

20C is expanded and returned to its original state, and releases the object 9 to be processed, as shown in FIG.

In addition, the liquid crystal actuator as a pseudo finger like this
Preferred examples of the constituent material of the night crystal actuator used in the device include the following polymeric liquid crystals or liquid crystal elastomers.

CH3 [Effects of the Invention] As detailed above, according to the liquid crystal actuator device of the present invention, a liquid crystal actuator device having a small size and simple configuration, high output and high speed response is provided.

Therefore, the liquid crystal actuator device of the present invention is extremely useful as a high-performance actuator device for small-sized mechanisms such as medical welfare equipment and robots.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a liquid crystal actuator device according to an embodiment of the present invention, FIG. 2 is a perspective view thereof, and FIG. 3 is a cross-sectional view of a liquid crystal actuator device according to another embodiment of the present invention. 4 and 5 are perspective views of a pseudo finger using the liquid crystal actuator device shown in FIG. 3. 10. I.A. 2A. 20...Liquid crystal actuator device, IB, IC
, ID, IE...electrode plate, 2B, 2C, 2D, 12...liquid crystal actuator, 11b...stretchable IE pole.

Claims (1)

[Claims] (1) A device using a liquid crystal actuator whose main constituent material is a polymeric liquid crystal and/or a liquid crystal elastomer that extracts mechanical energy reversibly from an electric field as the main medium, and which has at least a pair of electrodes directly or with a spacer between them. a structural unit that indirectly holds a liquid crystal actuator through a liquid crystal actuator, and a means for applying a voltage between the pair of electrodes, and the liquid crystal actuator is reversibly moved in accordance with the voltage applied between the pair of electrodes. A liquid crystal actuator device characterized by emitting mechanical energy such as expansion/contraction, deformation, hardening/softening, etc.