JPS63287820A - Optical modulation substance and application, production thereof - Google Patents

Abstract

PURPOSE:To obtain the title substance capable of optical modulation by dispersing droplets of a liquid crystal into a cured substance composed of a thermosetting one-pack epoxide resin. CONSTITUTION:The title substance is formed by interposing the cured substance 1 which is composed of the thermosetting one-pack epoxide resin and is dispersed the droplets of the liquid crystal 2, between sheets 5 which are composed of a glass and a plastics, etc., and mounted two sheets of the electrically transparent conductive film 4 thereon respectively. The cured substance is reversibly changed between an opaque and a transparent states by combining a temp. and an electric field, thereby holding the opaque or the transparent state in a room temp. and a nonelectric field state. As the upper limit of the clearing point of a conventional liquid crystal is 80-130 deg.C, the thermosetting one-pack epoxy resin is preferably cured at a temp. (especially and preferably 40-200 deg.C) lower than the clearing point of the liquid crystal, and for this purpose, a latent curing agent is incorporated in said resin. Thus, the resin becomes transparent at the time of impressing the electric field, and opaque at the time of un- impressing the electric field.

Description

[Detailed Description of the Invention] り粟↓Ω■■也■ The present invention relates to liquid crystal technology, and in particular to a novel light modulating material containing a liquid crystal dispersed in a thermosetting one-component epoxy resin cured matrix; A light modulation device using the same, a light modulation substance thereof, and a method for manufacturing the light modulation device will be described.

A light modulating material in which liquid crystal droplets are dispersed in a polymer matrix and processed into a sheet or film has been proposed by Ferguson et al., and has come to be used in some outdoor signboards. (US Patent Application No. 4,435,047) It has been proposed to use gelatin, gum arabic, polyvinyl alcohol, polyurethane, etc. as the polymer.

Meanwhile, a group at the University of Kent has developed an encapsulated liquid crystal light modulator using epoxy resin, a more environmentally resistant polymer.

(International Publication No. WO35104262) By using an epoxy resin, the step of bonding the electrodes and the encapsulated liquid crystal light modulating substance can be omitted because the epoxy resin itself is an adhesive, and the encapsulated liquid crystal light modulating element can be obtained more easily. Now you can.

・B ゛ ゛ 7□・ When producing an encapsulated liquid crystal light modulating material using epoxy resin, a two-component epoxy resin could be used. When using a two-component epoxy resin, the epoxy resin,
The hardening agent and liquid crystal are first mixed and stirred, then stretched into a sheet or sealed between two transparent electrodes, and waited for curing.

However, when attempting to manufacture an encapsulated liquid crystal light modulating material using a two-component epoxy resin, the curing reaction begins the moment the epoxy resin, curing agent, and liquid crystal are mixed, so the mixture gradually changes. The viscosity changes and workability is poor.
There are many problems in production management.

In reality, it is necessary to strictly control the mixing order of the epoxy resin, curing agent, and liquid crystal, mixing method, stirring intensity, working temperature, working time, etc., making industrialization very difficult.

W The inventors of the present invention have arrived at the present invention as a result of various studies to solve the above-mentioned problems.

The present inventors have discovered that a material capable of modulating light can be provided by dispersing liquid crystal droplets in a cured thermosetting one-component epoxy resin, and based on this discovery, the present invention has been developed. It was completed. The present inventors have also found that workability can be improved by using a latent curing agent as a curing agent.

That is, the present invention is a thermosetting one-component epoxy resin cured product containing dispersed liquid crystal droplets capable of modulating light, a light modulation element using the material, and a method for manufacturing the same. . When manufacturing and obtaining the above light modulating substance and light modulating element, the thermosetting one-component epoxy resin is preferably cured at a temperature lower than the clearing point of the liquid crystal (particularly preferably 40°C to 200°C) for the following reasons. is desirable.

The solubility of a liquid crystal substance is high at a temperature such that the liquid crystal substance exhibits an isotropic phase, and low at a temperature such that the liquid crystal substance exhibits a liquid crystal phase.

This is because, in addition to the general effect that the higher the temperature, the higher the solubility of a substance, at a temperature where a liquid crystalline substance exhibits a liquid crystalline phase, interactions that attempt to solvate the substance and phase separation occur, resulting in liquid crystallization. This is thought to be because the interaction that attempts to form the effect acts as a contradictory effect. Further, when the solvent is a reactive prepolymer such as an epoxy resin, the solubility of the liquid crystal substance generally decreases as polymerization and curing progress. This has also been observed when a two-component epoxy resin is used as a solvent depending on the system.

Therefore, as shown in the examples, when the one-component epoxy resin is cured at a temperature at which the liquid crystal material exhibits an isotropic phase, that is, in a state where the solubility of the liquid crystal material is very high, the liquid crystal material Because curing proceeds in a homogeneous system in which the particles are dissolved in unreacted prepolymers or polymers with a low degree of polymerization, phase separation or encapsulation beyond microphase separation on the order of micrometers or less does not occur, and the particles have a size appropriate for optical modulation. liquid crystal capsule (several micrometers)
~several tens of μ) becomes difficult to obtain.

Therefore, the inventors of the present invention have conducted various studies as described above in order to solve the above-mentioned problems, and have found that it is possible to modulate light having favorable properties by curing the liquid crystal at a temperature lower than the clearing point of the liquid crystal. It was possible to produce a thermosetting one-component epoxy resin cured product containing dispersed liquid crystal droplets.

Examples of the structure, luminous intensity, display or storage principle of the substance and the element using the substance are as shown below.

・A solid film or sheet-like material that can be reversibly switched between an opaque state and a transparent state by an electric field, and when an electric field is applied, liquid crystal molecules aligned by the electric field in the thickness direction A transparent state occurs when the optical refractive index and the optical refractive index of the cured epoxy resin become almost equal, and when no electric field is applied, the average optical refractive index in the thickness direction of the liquid crystal and the optical refractive index of the cured epoxy resin are equal to each other. A substance that becomes opaque due to light scattering due to different light scattering, and an element using the substance that can be reversibly switched between an opaque state and a transparent state by an electric field. An element in which a cured thermosetting one-component epoxy resin in which liquid crystal droplets are dispersed is sandwiched between sheets of glass, plastic, etc., each having a conductive film.

A solid film or sheet-like material that can be reversibly switched between an opaque state and a transparent state by an electric field, and when an electric field is applied, liquid crystal molecules aligned by the electric field are A transparent state occurs when the optical refractive index and the optical refractive index of the cured epoxy resin become almost equal, and when no electric field is applied, the average optical refractive index in the thickness direction of the liquid crystal and the optical refractive index of the cured epoxy resin are equal to each other. A substance that becomes opaque due to light scattering due to different effects, and an element using the substance that can be reversibly switched between an opaque state and a transparent state by an electric field. The device consists of a cured thermosetting one-component epoxy resin in which droplets of liquid crystal are dispersed between two sheets of glass, plastic, etc., each having a transparent conductive film.

・A solid film or sheet-like material that can be reversibly switched between an opaque state and a transparent state by an electric field, and when an electric field is applied, liquid crystal molecules aligned by the electric field in the thickness direction It becomes transparent when the optical refractive index and the optical refractive index of the cured epoxy resin become almost equal, and when no electric field is applied, it becomes opaque due to light scattering due to the unaligned or spiral state of the liquid crystal within the liquid crystal droplet. Such a material and an element using the material that can be reversibly switched between an opaque state and a transparent state by an electric field. The device consists of a cured thermosetting one-component epoxy resin in which droplets of liquid crystal are dispersed between two sheets of glass, plastic, etc., each having a transparent conductive film.

φ It has the above display principle, and the diameter of the liquid crystal droplets that mainly scatter light is 10 times or more the helical pitch length of the liquid crystal, and the liquid crystal used is chiral smectic C liquid crystal or chiral smectic C liquid crystal with a dichroic dye added. A doped liquid crystal material and a device using the material that can be reversibly switched between an opaque state and a transparent state by an electric field. The device consists of a cured thermosetting one-component epoxy resin in which droplets of liquid crystal are dispersed between two sheets of glass, plastic, etc., each having a transparent conductive film.

A solid film or sheet of material that can be reversibly switched between an opaque and transparent state depending on temperature; in the hot isotropic phase, the light refraction of the liquid in the droplet A transparent state occurs when the optical refractive index of the cured epoxy resin and the liquid crystal are almost equal, and in a low-temperature liquid crystal state, the optical refractive index of the average liquid crystal in the thickness direction differs from the optical refractive index of the cured epoxy resin. 1. A substance that becomes opaque due to light scattering, and an element using the substance that can be reversibly switched between an opaque state and a transparent state depending on temperature. The structure consists of a small drop of liquid crystal between two sheets of glass, plastic, etc., which may or may not have (Joule thermal addressing type) or not (thermal, laser writing type) transparent conductive films. An element sandwiched with a cured thermosetting one-component epoxy resin in which is dispersed.

・A solid film or sheet material that can be reversibly switched between an opaque state and a transparent state by a combination of temperature and electric field, and maintains the opaque state or transparent state in the absence of an electric field at room temperature. By heating the liquid crystal to a high-temperature isotropic phase with no electric field applied and then rapidly cooling it, the liquid crystal inside the liquid crystal droplet becomes unaligned, and light scattering by the droplet becomes opaque, and the high-temperature isotropic phase After heating the liquid crystal to a temperature of 100°C, the liquid crystal is slowly cooled while applying an electric field, so that the optical refractive index in the thickness direction of the liquid crystal molecules aligned by the electric field and the optical refractive index of the cured epoxy resin become almost equal, resulting in a transparent state. substance and using the substance;
A rewritable type, a write-once type, or a read type, which has the property of being reversibly switched between an opaque state and a transparent state by a combination of temperature and electric field, and maintaining the opaque state or transparent state in the absence of an electric field at room temperature. 0nly type memory element. The device consists of a cured thermosetting one-component epoxy resin in which droplets of liquid crystal are dispersed between two sheets of glass, plastic, etc., each having a transparent conductive film.

It is possible to change between an opaque state and a transparent state by a combination of temperature and electric field using a material that has the above-mentioned principle and in which the liquid crystal used is a liquid crystal having both a nematic phase and a smectic A phase. A rewritable type, write-once type, or Rea that is reversibly switched and has the property of maintaining an opaque state or a transparent state at room temperature and without an electric field.
d 0nty type memory element. The device consists of a cured thermosetting one-component epoxy resin in which droplets of liquid crystal are dispersed between two sheets of glass, plastic, etc., each having a transparent conductive film.

The upper limit of the clearing point of commercially available normal liquid crystals is 80℃~1
Since the temperature is about 30°C, when carrying out the present invention,
A one-component epoxy resin formulation that cures at low temperatures is required.

In order to obtain a low-temperature curing liquid epoxy resin composition, the present inventors have developed a latent curing agent "Amicure" manufactured by Ajinomoto Co., Ltd. (Ajinomoto Co., Ltd.), which has excellent low-temperature curing performance and has been previously developed by the present inventors. ) trademark) series, it was possible to obtain a light modulation element having particularly excellent features in terms of workability, productivity, etc.

EXAMPLES The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to these Examples.

Example 1 Epoxy resin "Epicoat" (oiled shell epoxy)
(Trademark) 828 100 parts, Ajinomoto Co., Inc. latent curing agent "Amicure" (Trademark of Ajinomoto Co., Inc.) PN-23
Mix and stir 20 parts of cyanobiphenyl and 60 parts of cyanoterphenyl-based nematic mixed liquid crystal, and after degassing under vacuum,
Using a 25μm PET film as a spacer as shown in Figure 1, IT
It was inserted between two cells made of O glass. This cell was heated in an oven at 90° C. to heat-cure the epoxy resin and obtain a light modulation element.

The clearing point of the liquid crystal used was 110°C, and the minimum heating curing temperature of the -liquid epoxy resin composition was 90°C.

By applying a 35V AC or DC electric field to the obtained light modulation element, it was confirmed that it became transparent when an electric field was applied and opaque when no electric field was applied.

In addition, microscopic observation of the obtained light modulation element confirmed that the liquid crystal was dispersed in the cured epoxy resin in the form of spherical droplets of several micrometers to several tens of micrometers.

Comparative Example] The formulation was prepared in exactly the same manner as in Example 1, mixed and stirred,
An attempt was made to obtain a light modulating material by curing in an oven at 120°C.

Even when a 35 V AC or DC electric field was applied to the obtained light modulation element, no clear contrast response could be confirmed.

In addition, microscopic and mirror observation of the obtained light modulation element revealed that the liquid crystal was in the form of spherical droplets of several μm to several tens of μm and was not dispersed in the cured epoxy resin, and the temperature was higher than the clearing point of the liquid crystal. Curing at 120° C. was found to be unsuitable for preparing the materials of the invention.

Example 2 In Example 1, instead of Ajinomoto Co.'s latent curing agent "Amicure" (Trademark of Ajinomoto Co., Inc.) PN-23, the latent curing agent "Amicure" (trademark of Ajinomoto Co., Inc.) was used. ) A light modulation element was obtained in exactly the same manner except that MY-24 (Trademark) was used.

By applying a 35V AC or DC electric field to the obtained light modulation element, it was confirmed that it became transparent when an electric field was applied and opaque when no electric field was applied.

Furthermore, microscopic observation of the obtained light modulation element confirmed that the liquid crystal was dispersed in the cured epoxy resin in the form of spherical droplets of several micrometers to several tens of micrometers.

[Brief explanation of drawings]

FIG. 1 shows an example of a light modulation element composed of two sheets of ITO glass and a PET film as a spacer. In the figure, ■■■■■ has the following meanings. ■Thermosetting one-component epoxy resin cured product ■Liquid crystal ■PET
Film spacer ■ITO■Glass

Claims (11)

[Claims] (1) A thermosetting one-component epoxy resin cured product containing dispersed liquid crystal droplets capable of modulating light. (2) The material according to claim (1), which is cured at a temperature lower than the clearing point of liquid crystal. (3) The material according to claim (2), which has a curing temperature of 40°C to 200°C. (4) A solid film or sheet material that can be reversibly switched between an opaque state and a transparent state by an electric field, and when an electric field is applied, the thickness of liquid crystal molecules aligned by the electric field. A transparent state is achieved when the optical refractive index in the direction and the optical refractive index of the cured epoxy resin are almost equal, and when no electric field is applied, the average optical refractive index in the thickness direction of the liquid crystal and the optical refraction of the cured epoxy resin are the same. A material according to claim 1, which becomes opaque due to light scattering due to the different ratios. (5) The substance according to claim (1), wherein the liquid crystal used is a nematic liquid crystal. (6) A solid film or sheet material that can be reversibly switched between an opaque state and a transparent state by an electric field, and when an electric field is applied, the thickness of liquid crystal molecules aligned by the electric field. A transparent state occurs when the optical refractive index of the direction and the optical refractive index of the cured epoxy resin become almost equal, and when no electric field is applied, an opaque state occurs due to light scattering due to the unaligned or spiral state of the liquid crystal within the liquid crystal droplet. The substance according to claim (1), which is such that: (7) A patent claim in which the liquid crystal is a chiral smectic C liquid crystal or a chiral smectic C liquid crystal to which a dichroic dye is added, and the diameter of the liquid crystal droplets that mainly scatter light is 10 times or more the helical pitch length of the liquid crystal. Substances listed in scope (1). (8) A solid film or sheet of material that can be reversibly switched between an opaque state and a transparent state depending on temperature, such that in the hot isotropic phase, the liquid in the droplet A transparent state occurs when the optical refractive index and the optical refractive index of the cured epoxy resin become almost equal, and in a low-temperature liquid crystal state, the optical refractive index of the average liquid crystal in the thickness direction and the optical refractive index of the cured epoxy resin are equal to each other. Claims (
Substances listed in section 1). (9) A solid film or sheet material that can be reversibly switched between an opaque state and a transparent state by a combination of temperature and electric field, and maintains the opaque state or transparent state in the absence of an electric field at room temperature. By heating the liquid crystal to a high-temperature isotropic phase and then rapidly cooling it when no electric field is applied, a non-aligned state of the liquid crystal within the liquid crystal droplet is created, and light scattering by the droplet results in an opaque state. After heating the liquid crystal until it reaches the square phase, it is slowly cooled while applying an electric field, so that the optical refractive index in the thickness direction of the liquid crystal molecules aligned by the electric field and the optical refractive index of the cured epoxy resin become almost equal, resulting in a transparent state. Claim (1)
Substances listed in section. (10) Claim (1) in which the liquid crystal used is a liquid crystal having both a nematic phase and a smectic A phase.
Substances listed in section. (11) A method for producing a thermosetting one-component epoxy resin cured product containing dispersed liquid crystal droplets capable of modulating light, characterized by curing at a temperature lower than the clearing point of the liquid crystal. . (12) Contains a thermosetting one-component epoxy resin cured product containing dispersed liquid crystal droplets capable of modulating light, which can be changed between an opaque state and a transparent state by at least one of an electric field or temperature. An element that can be reversibly switched between