JPH03255423A - Light control material - Google Patents

Abstract

PURPOSE:To allow the long maintenance of the function of the light control material by adding a means for averting the influence of light to the light control material. CONSTITUTION:Transparent electrode layers 2 are formed on both front and rear surfaces of a liquid crystal layer formed by dispersing a liquid crystal 12 into a cured epoxy resin matrix 11. The liquid crystal layer 1 contains a UV absorbent. The UV rays with which the light control material is irradiated are, therefore, absorbed by the UV absorbent and the reaction, such as decomposition and recombination, of the epoxy resin, is suppressed. The formation of such a material which immobilizes the liquid crystal is thereby suppressed and the impairment of the function of the light control material by the irradiation with the light is obviated. The light control material responds precisely to the on and off of the impressed voltage in this way, by which the clearing or clouding is arbitrarily executed. The function is thus maintained over a long period of time.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a light control material used for blinds, domes, lighting materials, displays, partition materials, etc. This invention relates to an improvement of a light control material that can be made optionally.

(Prior art) As a light control material containing liquid crystal in a resin matrix, 1. Nematic liquid crystal is emulsified and dispersed in an aqueous polyvinyl alcohol solution, encapsulated, coated on a transparent electrode substrate, dried, and then encapsulated. Another transparent electrode plate is glued onto the coating film to serve as a counter electrode. ■Liquid crystal is mixed into a photocurable resin such as acrylic resin, sealed between two transparent electrodes, and light is applied to it. Two types of liquid crystals are known: one in which liquid crystal is mixed into a thermosetting resin such as an epoxy resin, the liquid crystal is sealed between two transparent electrodes, and the mixture is thermoset.

(Problems to be Solved by the Invention) Among the above light control materials, (1) requires time and effort to remove moisture after application in the manufacturing process, and the particle size of the encapsulated liquid crystal Variations are likely to occur, and the amount of liquid crystal used is as large as 50% by weight or more of the entire liquid crystal layer, resulting in high costs. In addition, (2) requires a large area of the resin sheet to be uniformly irradiated with light, which is technically difficult, and the amount of liquid crystal used is large at 50% by weight or more, resulting in high costs. Compared to these, ■ uses less liquid crystal (30% of the entire liquid crystal layer).
In addition, since it is a thermosetting resin, uniform conditions can be obtained with simple manufacturing equipment, so the cost is low.Moreover, the liquid crystal phase separates in the hardened epoxy resin matrix and forms droplets. It is dispersed, and the variation in particle size is much smaller than in case ①, and the initial optical characteristics (i.e., the on-off response function that becomes highly turbid when the voltage is off and becomes transparent at low voltage when the voltage is on) are good. .

As described above, the light control material (3) has many advantages over other light control materials and is expected to be put into practical use, but the following problems still remain to be solved.

That is, if a voltage is applied between both electrodes to align the liquid crystal in one direction and make it transparent, then irradiation with light will cause the liquid crystal to remain oriented in one direction and remain transparent even if the current is stopped after a short period of irradiation. Furthermore, if light is irradiated without electricity being applied, the liquid crystal will not be aligned and will not become transparent unless the driving voltage is increased. Although the cause of this decline in the functionality of light control materials is not clear, the thermoset epoxy resin undergoes some kind of reaction (decomposition and recombination, etc.) when exposed to light, producing new substances. The generated substance entangles with the liquid crystal molecules and fixes them, so if the liquid crystal is oriented in one direction and becomes transparent, it remains transparent, and if the liquid crystal is randomly oriented and becomes cloudy, electricity is not applied. It is presumed that it becomes difficult to become transparent even if especially,
When trimethylolpropane tris-thiopropionate (hereinafter abbreviated as TMTP) is used as a curing agent,
Acrylic acid compound (CH
,=CH2COOR...R is an alkyl group),
These react with each other under the action of light, or with reactive residues (epoxy groups) in the resin matrix.

It is presumed that this is because an unknown compound is generated by reacting with a catalyst (such as a catalyst), and it becomes entangled with liquid crystal molecules and becomes immobilized. Note that such problems occur not only with ultraviolet rays but also with visible light.

The inventors of the present invention, as a result of earnestly searching for solutions to the above-mentioned problem (①) in the light control material, have found that by adding a means to avoid the influence of light on the light control material, the original function of the light control material can be improved. The present invention has been made based on the findings that this can be maintained for a long period of time.

(Means for Solving the Problems) The light control material of the present invention, which is distantly related to the above object, will be explained based on the accompanying drawings. There are four aspects of the light control material of the present invention, and FIG.
The figure is a schematic vertical cross-sectional view of the light control material according to the third embodiment, and FIGS. 3 and 4 are schematic longitudinal cross-sectional views illustrating the action of the light control material of the present invention when a voltage is applied and when no voltage is applied. .

That is, the light control material of the first embodiment is a light control material in which transparent electrode layers 2.2 are formed on both upper and lower surfaces of a liquid crystal layer 1 in which liquid crystals 12 are dispersed in a hardened epoxy resin matrix 11, It is characterized in that the liquid crystal layer contains an ultraviolet absorber. The light control material of the second aspect is a light control material in which transparent electrode layers are formed on both upper and lower surfaces of a liquid crystal layer in which liquid crystal is dispersed in a hardened epoxy resin matrix, and the liquid crystal layer contains a radical scavenger. It is characterized by:

Further, the light control material of the third aspect is a light control material in which transparent electrode layers 2.2 are formed on both upper and lower surfaces of a liquid crystal layer 1 in which liquid crystals 12 are dispersed in a hardened epoxy resin matrix 11, A transparent resin layer 4 containing an ultraviolet absorber is integrally formed on at least one side of the light control material.

Furthermore, the light control material of the fourth aspect is a light control material in which transparent electrodes 2.2 are formed on both upper and lower surfaces of a liquid crystal layer 1 in which liquid crystals 12 are dispersed in a hardened epoxy resin matrix 11,
The liquid crystal layer 1 is salicylate-based.

It is characterized by containing benzophenone-based, benzotriazole-based, benzoate-based, hydroquinone-based, cyanoacrylate-based, thiodipropionic acid-based, hindered phenol-based, and hindered amine-based compounds, either alone or in appropriate combinations. And especially the fourth a
m also includes cases where the epoxy resin matrix is cured by TMTP.

Although it is possible to form the transparent electrode layer 2.2 directly on the surface of the liquid crystal layer 1, it is also possible to form the transparent electrode layer 2.2 on one side of transparent base materials 3, 3 made of transparent resin or glass by vapor deposition or the like as shown in the figure. However, it is also possible to integrally laminate this on both sides of the liquid crystal layer 1 so that the transparent electrode layer 2.2 is sandwiched therebetween. In this case, the combination of the transparent base material and the electrode layer can also be referred to as a transparent electrode layer.

The epoxy resin is preferably an aliphatic epoxy resin, and glycidyl ester epoxy resins, glycidyl ether epoxy resins, glycidyl amine epoxy resins, etc. are used.

Aromatic epoxy resins such as bisphenol-type epoxy resins and fluorinated bisphenol-type epoxy resins are appropriately mixed and used as the aliphatic epoxy resin. In order to form a matrix of these epoxy resins, a curing agent and an appropriate catalyst are added. As the curing agent, various curing agents such as amine type, acid anhydride type, and mercaptan type can be used, and the above-mentioned TMTP is particularly preferably employed.

In addition, the liquid crystals to be dispersed include cyanobiphenyl,
Various liquid crystal formulations such as pyrimidine-based, Schiff-base-based, ester-based, etc. can be used.

The above-mentioned ultraviolet absorber is a salicylate type.

Cyanoacrylate-based, benzotriazole-based, benzophenone-based compounds, etc. are used.

As the transparent electrode layer 2, polyethylene terephthalate,
It is possible to use a transparent resin base material such as polycarbonate or polysulfonate, or a glass base material in which ITO2 indium oxide, tin oxide, etc. is deposited on the surface by vapor deposition, and the conductive surface of this transparent electrode layer 2 is the liquid crystal layer 1. Both sides of the liquid crystal layer 1 are integrally laminated by laminating or the like so as to be in contact with the liquid crystal layer 1.

(Function) When using the above light control material, as shown in FIGS. 3 and 4, lead wires 21 for applying voltage to the upper and lower transparent electrode layers 2.2
．． 21 is bound. Transparent electrode layer 2.
When a driving voltage is applied between 2, all of the liquid crystal molecules 12b in the liquid crystal layer 12a dispersed in a phase-separated state in the epoxy resin matrix 11 of the liquid crystal M1 are aligned in one direction, as shown in FIG. However, due to its optical effect, the light control material becomes transparent.

On the other hand, when the application of the driving voltage is stopped, the liquid crystal molecules 12b in the liquid crystal layer 12a are randomly oriented as shown in FIG. 4, and due to the light scattering effect, the light control material becomes cloudy (ground glass). becomes.

In the present invention, a means for avoiding the influence of light on the liquid crystal layer 1 is added, and thereby the liquid crystal (molecules) 12b .
Random orientation functionality is maintained.

That is, in the first embodiment, since the epoxy resin matrix 11 of the liquid crystal layer 1 contains an ultraviolet absorber, the ultraviolet rays irradiated to the light control material are absorbed by the ultraviolet absorber, and the epoxy resin is decomposed by the light. It is assumed that reactions such as recombination and recombination are suppressed, and as a result, the generation of new substances due to the irradiation light as described above is suppressed, and immobilization of the liquid crystal molecules 12b does not occur.

In addition, in the second embodiment, even if a new substance that immobilizes liquid crystal molecules is created by the irradiation light, the new substance is captured by the capture agent before immobilizing the liquid crystal, causing immobilization of the liquid crystal molecules 12b... It is assumed that this will disappear.

Moreover, in the case of the third aspect, since the transparent resin layer 4 containing the ultraviolet absorber is integrally formed on at least one side of the light control material, if the transparent resin layer 4 is used to irradiate the side on which the transparent resin layer 4 is formed, , epoxy resin matrix 11 in liquid crystal layer 1
becomes less susceptible to the influence of ultraviolet rays, and therefore, as described above, the progress of fixation of the liquid crystal molecules 12b is delayed, and the durability of the function as a light control material is improved.

Furthermore, in the case of the fourth embodiment, the liquid crystal layer 1 contains a salicylate-based, benzophenone-based, benzotriazole-based, benzoate-based, hydroquinone-based, cyanoacrylate-based, thiodipropionic acid-based, hindered phenol-based, or hindered amine-based compound. By containing each alone or in appropriate combination, light (e.g. sunlight) to this light control material can be reduced.
Reactions such as decomposition and recombination of epoxy resin caused by irradiation are suppressed, and new substances that fix liquid crystal molecules are not generated, or some kind of reaction progresses in the epoxy system due to light irradiation, and new substances that adversely affect liquid crystal molecules are generated. Even if a substance is produced, it is assumed that the liquid crystal molecules 12b... will not be immobilized because the generated new substance will be captured by the above-mentioned compound before immobilizing the liquid crystal.

The above-mentioned compound used in the fourth embodiment is preferably one that has good compatibility with the materials constituting the liquid crystal layer, such as epoxy resin, curing agent, and liquid crystal, in consideration of uniform dispersion in the liquid crystal layer. is desirable.

Further, it is not preferable to use a material that affects the reaction between the epoxy resin and the curing agent and inhibits curing.

In addition, in the case of the fourth embodiment, TM as a curing agent for the epoxy resin
When TP is used, the acrylic acid compound is generated in the resin matrix, but the radicals generated by light irradiation are captured by the additive compound, the acrylic acid compound is stabilized, and the liquid crystal molecules 12b... are immobilized. becomes less likely to occur.

(Example) Next, examples will be described.

Preparation of light control material raw materials> YH300 manufactured by Tobu Kasei as an epoxy resin, TMTP manufactured by Yodo Kagaku as a hardening agent, and 1,8 as a catalyst.
-diazabicyclo[5,4,O]undec-7ene,
BDH E43 as a liquid crystal (epoxy resin)
The weight ratio of pair (curing agent + catalyst) to (liquid crystal) is 1:0.7:
0.85, mix uniformly, and add a small amount of acrylic resin microbeads (particle size 12 μm).
The material was prepared by adding and mixing. This preparation material was used as the common material below.

(Example-1) Ultraviolet absorber TINU manufactured by Ciba Geigy was added to the above preparation material.
Two sheets of polyethylene terephthalate resin (P E
T) Interposed between films to make the total thickness 0.265
m, and this was heated and cured in an oven at 70° C. for 1 hour to obtain a light control material.

Connect the lead wire to the electrode layer of the obtained light control material.

When voltage was applied, the light control material became transparent, and when voltage application was stopped, it became cloudy (cloudy). In addition, when similar performance tests were conducted on light control materials exposed to ultraviolet light for long periods of time, even samples exposed for 200 hours showed that the applied voltage could not be turned on or off.
It responded accurately to off-state and repeated transparent and cloudy states, and its responsiveness was good.

(Example 2) The above prepared material containing no ultraviolet absorber was interposed between two PET resin films on which IT○ transparent electrodes were formed in the same manner as above and heat treated to obtain a similar light control material. . An acrylic film (thickness: 0, 1 m) containing an ultraviolet absorber was laminated on at least one side of this light control material via an adhesive.

When the above response test was carried out on a sample of this light control material exposed to ultraviolet light for a long time, even the sample exposed for 500 hours showed good response.

(Example 3) A polycarbonate resin sheet containing an ultraviolet absorber (thickness 0
．． 5+am) was laminated with adhesive and the same responsiveness test as above was conducted.
It showed good responsiveness even after time exposure.

(Example-4) A glass plate (3-thickness) was integrally laminated on at least one side of the light control material prepared in Example-2 with a resin layer containing an ultraviolet absorber (hot melt adhesive layer) interposed therebetween. When the above-mentioned responsiveness test was conducted on the product, it showed good responsiveness even after 700 hours of exposure.

(Example-5) The above preparation material was added to benzotriazole-based methyl-3-(
3-t-butyl-5-(2H-benzotriazole-2
-yl)-4-hydroxyphenyl]propionate and polyethylene glycol in an amount of 5% by weight,
A light control material was obtained by interposing the TO transparent electrode between two polyethylene terephthalate resin (PET) films and heating and curing this in an oven at 70° C. for 1 hour.

When a lead wire was attached to the electrode layer of the obtained light control material and a voltage was applied, the light control material became transparent, and when the voltage application was stopped, it became cloudy. In addition, when similar performance tests were conducted on light control materials that were exposed to sunlight for long periods of time while voltage was applied, even samples exposed for 2500 hours responded appropriately to the on/off of the applied voltage, becoming transparent and becoming cloudy. The condition was repeated and the response was good.

(Example-6) Add binder amine-based bis(1°2.2
,6,6. -Pentamethyl-4-piperidyl) sebacate was added in an amount of 1% by weight, and it was placed between two polyethylene terephthalate resin (PET) films on which IT○ transparent electrodes were formed, and then heated in an oven at 70°C for 1 hour. A light control material was obtained by heating and curing for a period of time.

When a lead wire was attached to the electrode layer of the obtained light control material and a voltage was applied, the light control material became transparent, and when the voltage application was stopped, it became cloudy. In addition, when similar performance tests were conducted on light control materials that were exposed to sunlight for long periods of time while voltage was applied, even samples exposed for 1000 hours responded accurately to the on/off of the applied voltage and remained transparent and cloudy. The condition was repeated and the response was good.

(Example-7) Bindered amine-based dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2 succinate was added to the above am material.
, 2,6,6-titramethylbiperidine polymer.
5% by weight was added, interposed between two polyethylene terephthalate resin (PET) films on which ITO transparent electrodes were formed, and heated and cured in an oven at 70° C. for 1 hour to obtain a light control material.

When a lead wire was attached to the electrode layer of the obtained light control material and a voltage was applied, the light control material became transparent, and when the voltage application was stopped, it became cloudy. In addition, when similar performance tests were conducted on light control materials that had been exposed to sunlight for long periods of time while voltage was applied, even samples exposed for 400 hours responded accurately to the on/off of the applied voltage and remained transparent and cloudy. The condition was repeated and the response was good.

(Example-8) 1.4% by weight of cyanoacrylate-based ethyl-2-cyano-3,3-diphenyl acrylate,
Hindered phenol pentaerythrityl-tetrakis(2-(3,5-di-t-butyl-4-hydroxyphenyl)propione-110.4% by weight, hindered amine bis(1,2,2,6, Add 0.4% by weight of 6-bentamethyl-4-piperidyl) sebacate, and
A light control material was obtained by interposing the To transparent electrode between two polyethylene terephthalate resin (PET) films and heating and curing the film at 70° C. for 1 hour in an oven.

When a lead wire was attached to the electrode layer of the obtained light control material and a voltage was applied, the light control material became transparent, and when the voltage application was stopped, it became cloudy. In addition, when similar performance tests were conducted on light control materials that were exposed to sunlight for long periods of time while voltage was applied, even samples exposed for 500 hours responded accurately to the on/off of the applied voltage and remained transparent and cloudy. The condition was repeated and the response was good.

In the above examples, the light control material was exposed to ultraviolet light or sunlight while a voltage was applied, but substantially the same effect was obtained even if the light control material was exposed in the same manner without any voltage applied.

(Comparative Example-1) Only the above preparation material was interposed between two polyethylene terephthalate resin (PET) films on which ITO transparent electrodes were formed, and this was heated and cured in an oven at 70°C for 1 hour. I got the light material.

When a lead wire was attached to the electrode layer of the obtained light control material and a voltage was applied, the light control material became transparent, and when the voltage application was stopped, it became cloudy. Furthermore, when exposed to ultraviolet light while applying voltage, it remained transparent even when no voltage was applied after 0.5 hour exposure.

(Comparative Example-2) When the light control material obtained in Comparative Example-1 was exposed to sunlight while voltage was applied, it remained transparent even when no voltage was applied after 5 hours of exposure. Became.

The above results are summarized in Table 1.

(The following is a blank space) (Effects of the invention) As described above, the light control material of the present invention is provided with a means for avoiding the influence of light on the epoxy resin matrix, so it is possible to prevent the formation of substances that fix liquid crystals. is suppressed,
The function of the light control material is not inhibited by light irradiation. Therefore, it responds appropriately to turning on and off the applied voltage, becomes transparent or cloudy at will, and maintains this function for a long period of time. Moreover, since the matrix of the liquid crystal layer is stronger than epoxy resin, the liquid crystal is evenly dispersed, and the amount of liquid crystal used is small, resulting in lower costs. The practical value of the present invention having such remarkable effects is extremely large.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of the light control material according to the first, second and fourth aspects, FIG. 2 is a schematic longitudinal sectional view of the light control material according to the third aspect, and FIGS. 3 and 4 FIG. 2 is a schematic vertical cross-sectional view illustrating the action of the light control material of the present invention when a voltage is applied and when no voltage is applied. (Explanation of symbols) 1...Liquid crystal layer, 11...Epoxy resin matrix, 12...Liquid crystal, 2...Transparent electrode, 3.
...Transparent base material, 4...Transparent resin layer. one or more one

Claims (1)

[Scope of Claims] 1. A light control material in which transparent electrode layers are formed on both upper and lower surfaces of a liquid crystal layer in which liquid crystal is dispersed in a hardened epoxy resin matrix, wherein the liquid crystal layer contains an ultraviolet absorber. Characteristic light control material. 2. A light control material in which transparent electrode layers are formed on both upper and lower surfaces of a liquid crystal layer in which liquid crystal is dispersed in a hardened epoxy resin matrix, wherein the liquid crystal layer contains a radical scavenger. . 3. A light control material in which transparent electrode layers are formed on both upper and lower surfaces of a liquid crystal layer in which liquid crystal is dispersed in a hardened epoxy resin matrix, the light control material having a transparent resin layer containing an ultraviolet absorber on at least one side. A light control material characterized by being integrally formed. 4. A light control material in which transparent electrode layers are laminated on both upper and lower surfaces of a liquid crystal layer in which liquid crystal is dispersed in a hardened epoxy resin matrix, and the liquid crystal layer is made of salicylate, benzophenone, benzotriazole, benzoate, or hydroquinone. 1. A light control material containing a cyanoacrylate-based, thiodipropionic acid-based, hindered phenol-based, or hindered amine-based compound, each singly or in an appropriate combination. 5. The light control material according to claim 4, wherein the epoxy resin matrix is cured by containing trimethylolpropane tris(β-thiopropionate) as a curing agent.