JP2002256031A - Liquid crystal material, its production method, liquid crystal film, its production method and method of use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal material having photo-response characteristics which deform by a specific light irradiation, a production method of the material, a liquid crystal film having the characteristics, a production method and a method of use thereof. SOLUTION: The material which comprises a copolymer of a monofunctional monomer having an azobenzene structure and a polyfunctional monomer is obtained by photopolymerizing the monomers in a liquid crystal state. The liquid crystal film comprises an oriented copolymer molecule obtained by the production method. A photo-responsing film which comprises the liquid crystal film deforms in response to a light. In the production method of the liquid crystal film, a copolymer molecule obtained by the photopolymerization is oriented. The liquid crystal film is used by deforming the film through the first radiation irradiation and restoring the shape through the second radiation irradiation. The deformation and restoration of the film is preferably carried out in a swelling state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystalline substance and a method for producing the same, a liquid crystalline film, and a method for producing and using the same.

[0002]

2. Description of the Related Art Light-responsive properties that change their form in response to light are found, for example, in certain biological systems in nature. For example, periwinkle has the property of closing leaves by irradiation with red light and opening leaves by irradiation with near-infrared light.
In addition, it is known that a certain compound or substance absorbs light to change its molecular structure, and that irradiation of specific light changes the state of expression of certain characteristics. Conventionally, however, a substance or substance system which is easy to manufacture and use industrially and has a specific form, but has a light-responsive property or a light-deformation property whose form changes when irradiated with light. Is not known.

[0003]

According to the present invention, as a result of studying the light response characteristics of various compounds, the appearance of a certain liquid crystal substance is changed by irradiation with light. It has been found that it has a light-responsive characteristic and has been completed thereby. That is, a first object of the present invention is to provide a liquid crystalline material having a light-responsive property whose form changes when irradiated with specific light. A second object of the present invention is to provide a method for producing a liquid crystalline material having light-responsive characteristics. A third object of the present invention is to provide a liquid crystal film having light-responsive characteristics and a method for producing the same. A fourth object of the present invention is to provide a method for using a liquid crystalline film having light-responsive characteristics.

[0004]

The liquid crystalline substance of the present invention comprises:
It is characterized by comprising a copolymer obtained from a monofunctional polymerizable monomer having an azobenzene structure and a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer. The method for producing a liquid crystal material of the present invention comprises mixing a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer,
Photopolymerization is performed in a liquid crystal state of the monomer mixture.

[0005] The liquid crystalline film of the present invention is prepared by mixing a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer and subjecting the monomer mixture to photopolymerization in a liquid crystal state. And characterized in that it is composed of oriented copolymer molecules obtained by the above. The light-responsive film of the present invention comprises the liquid crystal film described above, and has a characteristic of being deformed in response to light in a swelling state with a liquid.

The method for producing a liquid crystal film according to the present invention comprises the steps of: mixing a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer; Wherein photopolymerization is performed and the produced copolymer molecules are oriented.

The method of using the liquid crystal film of the present invention is characterized in that the liquid crystal film is irradiated with radiation of a first wavelength to deform the film, and is irradiated with radiation of a second wavelength to irradiate the film. Is restored. Here, the deformation of the film by irradiating the radiation of the first wavelength and the restoration of the form of the film by irradiating the radiation of the second wavelength are performed in a state where the liquid crystalline film is swollen by the swelling liquid. Preferably.

[0008]

The liquid crystalline substance composed of a cross-linked copolymer obtained by reacting a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer has a monofunctional polymerizable monomer. As a result of the change of the azobenzene structure of the monomer by irradiation of light, an object made of the liquid crystalline substance is changed in the external structure or morphology due to a change in the tissue structure constituting the object. This property has been found by the inventor of the present invention.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal substance of the present invention is a polyfunctional polymer which copolymerizes a monofunctional polymerizable monomer having an azobenzene structure in a molecule (hereinafter referred to as "azobenzene-containing monomer") with the azobenzene-containing monomer. It is a gel-like substance obtained by copolymerizing with a crosslinkable monomer composed of a hydrophilic monomer while maintaining a liquid crystal state.

Specific examples of the azobenzene-containing monomer suitably used for obtaining the liquid crystalline substance of the present invention include:
For example, 6- [4- (4-hexyloxyphenylazo)
[Phenoxy] hexyl acrylate. Specific examples of the crosslinkable monomer that forms a copolymer with the azobenzene-containing monomer include, for example, 4,
4'-bis [6- (acryloyloxy) hexyloxy] azobenzene can be mentioned.

The proportion of the component of the crosslinkable monomer in the copolymer constituting the liquid crystal material varies depending on the type of the azobenzene-containing monomer and the crosslinkable monomer, but is, for example, 5 to 30 mol%, preferably 10 to 10 mol%.
25 mol%. When the proportion of the crosslinkable monomer component is out of this range, the resulting liquid crystalline material of the copolymer may not exhibit sufficient morphological change due to light-responsive properties.

In order for a liquid crystalline substance composed of a copolymer obtained by copolymerizing an azobenzene-containing monomer and a crosslinkable monomer to exhibit suitable photoresponsive characteristics, it is necessary that the azobenzene-containing monomer be used in the copolymer. It is necessary that a long-chain polymer segment is formed to some extent, and a cross-linked structure in which the long-chain polymer segment is further cross-linked at an appropriate density by a cross-linkable monomer is required. It is necessary that the formed fibrous molecules are oriented in a specific direction.

In order to produce a copolymer in which such molecules are oriented, in practice, a monomer mixture of an azobenzene-containing monomer and a crosslinkable monomer is formed under the condition that the copolymer molecules to be produced are oriented. It is convenient to use the method of copolymerization below, and it is advantageous in that the desired orientation state can be reliably obtained.

Specifically, for example, a reaction vessel having an oriented surface formed on the inner surface is used as a reaction vessel, and the monomer mixture is subjected to photo-polymerization using, for example, an in-situ polymerization method. It is preferable to carry out a copolymerization reaction depending on the method of polymerization. According to this method, the copolymer molecules are generated in a state of being oriented in a specific direction determined by the oriented surface by the action of the oriented surface.
Here, the orientation treatment can be performed, for example, by forming a polyimide layer on the inner surface of the reaction vessel and rubbing the polyimide layer in a specific direction, or by applying an electric or magnetic field.

In order for the liquid crystal material of the present invention to have a practically practical change in form as a result of exhibiting light-responsive characteristics, the liquid crystal material must have a specific form. It is necessary to be. Specifically, the liquid crystalline substance may be formed by appropriate means. However, since the copolymer constituting the liquid crystal substance has a crosslinked structure, it is almost impossible to mold the resulting copolymer after the copolymerization reaction between the azobenzene-containing monomer and the crosslinkable monomer. Have difficulty. Therefore, a method in which the copolymerization reaction is carried out by using a so-called casting polymerization method using a reaction vessel also serving as a mold, and the resulting copolymer is simultaneously molded is advantageously used. Moreover, according to such a casting polymerization method, it is extremely easy to apply the above-mentioned preferred orientation treatment method.

The form in which the characteristics of the liquid crystalline substance of the present invention are most remarkably exhibited is a film form or a sheet form. This liquid crystalline film is light of a first specific wavelength (hereinafter referred to as “first light”).
"Specific wavelength light". ) Bends or bends, for example, to be folded when irradiated, and retains the bent state even when the irradiation of the first specific wavelength light is stopped;
Moreover, in this state, the liquid crystal film in the original form is irradiated with light of a second specific wavelength (hereinafter, referred to as “second specific wavelength light”) having a different wavelength from the first specific wavelength light. It has a light deformation characteristic for restoring.

The change in morphology due to the light-responsive properties of the liquid crystalline substance usually occurs more suitably when the liquid crystalline substance is swollen by an appropriate liquid.
This is considered to be because the swelling state secures a free space necessary for the molecules of the liquid crystalline substance to be isomerized. The swelling liquid is not particularly limited, and also varies depending on the composition of the copolymer constituting the liquid crystal substance, that is, the type of the azobenzene-containing monomer and the crosslinkable monomer. It can be suitably used.

The liquid crystal film is bent or curved in a direction in which one area of the film is folded along a straight bending line with respect to the other area by irradiation of the first specific wavelength light. . Here, the direction of the bending line is a direction perpendicular to the alignment direction in which the copolymer molecules oriented in the liquid crystalline film extend.

More specifically, as shown in FIG. 1A, in the liquid crystal film 10, the copolymer molecules M shown in a cylindrical shape are actually oriented in one direction as described later. When it is fibrous and the orientation direction is the X direction, irradiation of the first specific wavelength light causes
As shown in the figure, a bending line F extending in the Y direction perpendicular to the X direction
Is deformed so as to be bent around, and further folded in two. Also, the liquid crystal film 1 thus deformed
0 maintains the deformed form even after the irradiation of the first specific wavelength light is stopped. When the second specific wavelength light is applied, the deformed form is restored to the original normal film form.

Such a morphological change is caused by a photoisomerization reaction of the azobenzene structure of the copolymer molecule. That is, as shown in the following structural formula (1), azobenzene can transfer between a trans isomer and a cis isomer, and isomerization from the trans isomer to the cis isomer and the reverse All the isomerization phenomena are caused by irradiating radiation such as light of a specific wavelength.

Here, the first specific wavelength light at which the isomerization from the trans-isomer to the cis isomer is ultraviolet light having a wavelength of less than 400 nm, and the second specific wavelength light at which the opposite isomerization occurs is a wavelength of 400 nm. 550 nm visible light,
The molecular length a of the trans form is 9.0 angstroms, whereas the molecular length b of the cis form is 5.5 angstroms, which is greatly different.

[0022]

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As a result of such an isomerization reaction, the oriented copolymer molecules are reduced in length at each of them by the irradiation of the first specific wavelength light, and a large distortion is caused in the whole film, so that the film becomes Direction (Y direction) perpendicular to the orientation direction of copolymer molecules (X direction in FIG. 1)
And bends along the bending line F extending to, for example, a state in which the whole is folded into two, a state in which the whole is curved, or a state in which the curved shape is continuous in a wavy manner, It is considered that the liquid crystal film is deformed.

The deformed state is stably preserved while the tissue state of the liquid crystalline substance is not subjected to a force that causes a further structural change. As a result, the distortion in the copolymer molecules of the liquid crystal film 10 is alleviated, or such distortion is completely removed, so that the deformed form returns to the original film shape.

The film of a liquid crystalline substance having the above-mentioned light-responsive characteristics can be used as a light-deformable member in various fields by utilizing the fact that the film is deformed by irradiation with light. For example, in a case where a large number of small pieces of the liquid crystalline film are filled together with the swelling liquid in an appropriate transparent cell, when irradiated with the first specific wavelength light, deformation occurs in each of the small pieces of the liquid crystalline film. In the system inside the cell, the overall optical characteristics such as the light reflection performance or the light transmission performance change, or the brightness and the coloration state change. Therefore, an optical element or an optical device such as a light control type filter utilizing such a phenomenon, a display element or a display device, an illumination device,
It can be applied as a toy or the like, and further as a shape memory film, a switching element, a memory element, or the like.

Further, the above-mentioned liquid crystalline film has a double-flexibility as a characteristic of itself, and thus is useful as a double-flexibility film in applications utilizing the characteristics.

The above liquid crystalline substance is obtained by copolymerizing an azobenzene-containing monomer and a crosslinkable monomer, and thus can be industrially produced.

Hereinafter, embodiments of the present invention will be described. [Example 1] In this example, as an azobenzene-containing monomer, a 6- [4- (4-
Hexyloxyphenylazo) phenoxy] hexyl acrylate was used, and 4,4′-bis [6- (acryloyloxy) hexyloxy] azobenzene represented by the following structural formula (3) was used as a crosslinkable monomer.

[0029]

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Here, the azobenzene-containing monomer is used to synthesize (1) 4-hexyloxynitrobenzene by reacting 4-nitrophenol, 1-bromohexane and potassium carbonate, and (2) obtaining the obtained reaction. Sodium borohydride was added to the solution of the product in the presence of a palladium catalyst and reacted to obtain 4-hexyloxyaniline. (3) Sodium nitrite was added to a hydrogen chloride solution of the obtained reaction product. And react
Further, by adding a solution obtained by adding phenol to an aqueous sodium hydroxide solution and reacting, 4'-hydroxy-
4-hexyloxyazobenzene was obtained, and (4) the resulting reaction product, 6-chlorohexanol and potassium carbonate were dissolved in dimethylformamide and heated to obtain 4 '-(6-hydroxyhexyloxy) -4-. Hexyloxyazobenzene is obtained, and (5) it can be prepared by adding triethylamine and anhydrous tetrahydrofuran to the obtained reaction product, further adding hydroquinone, and dropping and reacting with diluted acrylic chloride.

Further, the above-mentioned crosslinkable monomer is (1) 4
4- (6-hydroxyhexyloxy) nitrobenzene is synthesized by reacting -nitrophenol, 1-chlorohexanol and potassium carbonate, and (2) a solution of the obtained reaction product is added to a solution of the obtained reaction product in the presence of a palladium catalyst. 4- (6-Hydroxyhexyloxy) aniline was obtained by adding sodium borohydride and reacting. (3) Sodium nitrite was added to a hydrogen chloride solution of the obtained reaction product to cause a reaction, and further hydroxylation was performed. 4'-hydroxy-4- (6-hydroxyhexyloxy) azobenzene was obtained by adding phenol to an aqueous sodium solution and reacting. (4) The obtained reaction product was treated with 6-chlorohexanol and carbonic acid. Potassium is dissolved in dimethylformamide and heated to give 4 '-(6-hydrido). (Xyhexyloxy) -4-hexyloxyazobenzene was obtained, (5) triethylamine and tetrahydrofuran anhydride were added to the obtained reaction product, hydroquinone was further added, and a reaction was carried out by dropwise addition of diluted acrylic chloride. Can be prepared.

Using the above monomers, a liquid crystal film was prepared according to the following procedure. That is, an azobenzene-containing monomer in a ratio of 80 mol% in the entire monomer, a crosslinkable monomer in a ratio of 20 mol%, and
A photopolymerization initiator (trade name “Irgacure 784” (Ciba-
(Specialty Chemicals)) to prepare a liquid crystal monomer mixture. This liquid crystal monomer mixture exhibits an isotropic phase at 100 ° C. and a nematic phase at a temperature of 85 ° C.

On the other hand, as shown in FIG. 2, two flat glass substrates 21 are arranged in parallel so as to face each other with a gap G of 2.0 μm therebetween. The periphery is formed by sealing with a sealing material 22, and alignment films 24, 24 are formed on the inner surfaces of the glass substrates 21, 21 by rubbing the polyimide films so as to be antiparallel to each other. The cell 20 was used as a polymerization reaction vessel, and the above liquid crystal monomer mixture was filled in the cell at a temperature of 100 ° C. After that, 0.
The temperature was lowered to 85 ° C. at a rate of 5 ° C., and at this temperature, light of a wavelength of 545 nm from a high-pressure mercury lamp obtained through an appropriate filter was irradiated at an energy intensity of 4 mW / cm ² for 2 hours, whereby The liquid crystal film was taken out of the cell to obtain a sample.

The molecular structure of the liquid crystalline substance thus obtained is as shown in the following structural formula (4).

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When this liquid crystal film sample was observed with the naked eye, it had a black streak pattern extending in a specific direction. In addition, when the sample was observed with a polarizing microscope, when the sample was rotated with respect to the plane of polarization, a periodic change in the amount of transmitted light (change in brightness) was observed at intervals of 45 degrees in the rotation angle. From this, it was confirmed that the liquid crystalline film had birefringence and uniaxial orientation. Then, when the polarized light absorption spectrum of the sample was measured, dichroism of absorption was confirmed at a wavelength of around 360 nm, and it was confirmed that the azobenzene moiety was uniaxially oriented. The direction of the orientation was the same as the direction of the black streak pattern.

Further, when the above sample was observed in detail with a polarizing microscope, as shown in FIG. 3, it was an aggregate of polymer fibers which were elongated in one direction and the diameter of each fiber was It was found to be a few microns to a few tens of microns. When the surface of the sample was observed with an atomic force microscope, as shown in FIG. 4, wavy irregularities recognized as being derived from a fibrous body having a diameter of several tens of microns were confirmed.

When the above sample was immersed in an organic solvent, toluene, it swelled. When the sample was observed with a polarizing microscope in this swollen state, the same periodic change in the amount of transmitted light (change in light and darkness) as when the sample was not swollen was observed. From this, it was confirmed that the liquid crystal film had birefringence and uniaxial orientation even in the swollen state.

The sample in the swollen state is irradiated with ultraviolet light having a wavelength of 360 nm as the first specific wavelength light at 3 mW / cm ^2.
Irradiation at an intensity of, the sample immediately began to bend and was completely bent in about 30 seconds. This bending occurred in a direction perpendicular to the direction of the black streak pattern. This bent state did not change even after the irradiation of the first specific wavelength light was stopped.

Next, visible light having a wavelength of 450 nm, which is the second specific wavelength light, is applied to the bent sample.
Upon irradiation at an intensity of mW / cm ^2, the bent state immediately began to return to the original state, and was completely restored in about 30 seconds.
The process of the change of the restoration is substantially the reverse of the process of the bending by the irradiation of the first specific wavelength light.

Example 2 The above Example 1 was repeated except that the ratio of the azobenzene-containing monomer was 95 mol% and the ratio of the crosslinkable monomer was 5 mol% in the monomer mixture.
In the same manner as in the above, a liquid crystal film was produced. This liquid crystal film also had birefringence and uniaxial orientation.

[0041]

According to the liquid crystalline substance of the present invention, by forming a molded article in which the copolymer molecules are oriented,
By utilizing the light response characteristics of the azobenzene structure, it is possible to provide an object having a light deformation characteristic whose outer shape changes with light.

According to the method for producing a liquid crystalline substance of the present invention,
It is possible to advantageously produce a liquid crystalline substance to be a material of an object having light deformation characteristics utilizing the light response characteristics of an azobenzene structure. Since the liquid crystal substance is obtained by copolymerizing an azobenzene-containing monomer and a crosslinkable monomer, it can be industrially manufactured stably and repeatedly with similar characteristics.

According to the liquid crystalline film of the present invention, a biflexible film is provided, and a film that bends and deforms by irradiation with light of the first specific wavelength and recovers its shape by irradiation of light of the second specific wavelength is provided. Is done. According to the method for producing a liquid crystalline film of the present invention, a liquid crystalline film having reversible light deformation characteristics can be produced by a simple process. According to the method of using the liquid crystal film of the present invention, the film-shaped object can be bent and deformed by irradiating the first specific wavelength light, and can restore its shape by irradiating the second specific wavelength light. it can.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing the orientation of copolymer molecules in a liquid crystalline film of the present invention, and FIG. 1B is an explanatory view showing a bent state of the liquid crystalline film.

FIG. 2 is an explanatory sectional view showing an example of a polymerization reaction vessel used in an example of the method for producing a liquid crystalline film of the present invention.

FIG. 3 is an explanatory view showing an image of a polarizing microscope photograph showing an orientation state of molecules of the liquid crystalline film according to Example 1.

FIG. 4 is an explanatory view showing an image of an atomic force microscope photograph showing the state of the surface of the liquid crystalline film according to Example 1.

[Explanation of symbols]

 Reference Signs List 10 liquid crystal film M copolymer molecule F bending line 20 cell 21 glass substrate 22 sealing material 24 alignment film G gap

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C08L 33:14 C08L 33:14 F term (reference) 4F071 AA33 AF29 BB12 BC01 4H027 BA13 BB06 BD24 4J011 QA03 QA15 QA33 QA38 QA46 SA90 UA01 VA02 WA10 4J100 AL08P AL66Q BA02P BA02Q BA45P BA45Q BC43P BC43Q BD13P BD13Q CA04

Claims (8)

[Claims] 1. A liquid crystalline substance comprising a copolymer obtained from a monofunctional polymerizable monomer having an azobenzene structure and a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer. 2. A copolymer obtained by mixing a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerizing with the monofunctional polymerizable monomer, and photopolymerizing the monomer mixture in a liquid crystal state. A liquid crystalline substance comprising a polymer. 3. A monofunctional polymerizable monomer having an azobenzene structure is mixed with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer, and photopolymerized in a liquid crystal state of the monomer mixture. A method for producing a liquid crystalline substance. 4. A monomer obtained by mixing a monofunctional polymerizable monomer having an azobenzene structure with a polyfunctional polymerizable monomer copolymerized with the monofunctional polymerizable monomer and subjecting the mixture to photopolymerization in a liquid crystal state of the monomer mixture. A liquid crystalline film comprising an oriented copolymer molecule. 5. A photoresponsive film comprising the liquid crystalline film according to claim 4, wherein the photoresponsive film is deformed in response to light when swollen by a liquid. 6. A monofunctional polymerizable monomer having an azobenzene structure is mixed with a polyfunctional polymerizable monomer which copolymerizes with the monofunctional polymerizable monomer, and is photopolymerized in a liquid crystal state of the monomer mixture, and the resulting copolymer is formed. A method for producing a liquid crystalline film, comprising: orienting polymer molecules. 7. The liquid crystal film according to claim 4, wherein
A method of using a liquid crystalline film, characterized in that the film is deformed by irradiating radiation of a second wavelength and the form of the film is restored by irradiating radiation of a second wavelength. 8. Deformation of the film by irradiating radiation of the first wavelength and restoration of the form of the film by irradiation of radiation of the second wavelength are obtained by swelling the liquid crystalline film with the swelling liquid. The method according to claim 7, wherein the method is carried out in the following manner.