JPH034212A - Liquid crystal light control and display material and production thereof - Google Patents

Abstract

PURPOSE:To enhance the adhesive property between substrates treated with a specific coupling agent and a liquid crystal-contg. thin-film layer and to facilitate the production of a liquid crystal device having a large area and resilience by providing the above-mentioned thin-film layer between the substrates. CONSTITUTION:This material is produced by using the conductive substrates which are previously treated with the silane-coupling agent, more preferably gamma-(2-aminoethyl)aminoprophyl methyl dimethoxysilane or titanate coupling agent and forming the liquid crystal-contg. thin-film layer contg. a liquid crystal material as a continuous phase in a high-polymer material having a three-dimensional network structure between the substrates. After the electrode surfaces of the substrates consisting of a transparent conductive film, etc., are treated with the above-mentioned coupling agent, a soln. consisting of the liquid crystal material and a photosetting compsn. is packed between the substrates and is cured by photoirradiation under the conditions under which the soln. maintains an isotropic liquid state. The above-mentioned material is thus thereby produced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a thin film containing a liquid crystal that can be formed over a large area. , blocking, and transmitting can be controlled electrically, and are used in building windows, show windows, viewing-obstructing screens, and curtains for lighting control, as well as displaying text and graphics and providing high-speed response. Therefore, by electrically switching the display, it can be used as a display device such as an advertising board, a guide board, or a decorative display board.

(Prior Art) As liquid crystal display elements, TN type and STN type devices using nematic liquid crystal have conventionally been put into practical use. Also, devices using ferroelectric liquid crystals have been proposed.

These require polarizing plates and alignment processing, and require precise gap control to maintain screen characteristics, making it difficult to increase the screen size.

On the other hand, as a method to solve these problems, a method is known in which liquid crystal is microencapsulated, liquid crystal droplets are dispersed in a polymer, and the polymer is formed into a film. Here, gelatin, gum arabic, polyvinyl, alcohol, etc. have been proposed as the encapsulating substance (Japanese Patent Laid-Open No. 58-5
No. 01631, USP No. 4435047).

In the technology disclosed in the above specification, if the encapsulated liquid crystal molecules have positive dielectric constant anisotropy in the thin layer, in the presence of an electric field, the liquid crystal molecules will move in the direction of the electric field. The refractive index n0 of the liquid crystal and the refractive index n of the polymer
When the numbers 9 are equal, transparency occurs. When the electric field is removed, the liquid crystal molecules return to their random alignment and the refractive index of the liquid crystal droplet deviates from no, so that the liquid crystal droplet scatters light at its interface and the thin layer becomes cloudy.

In addition to the above, there are many other known technologies in which liquid crystal fine particles are dispersed in a polymer matrix using encapsulation technology or dispersion technology.

For example, JP-A No. 61-502128 discloses a liquid crystal dispersed in an epoxy resin, JP-A No. 62-2231 discloses a liquid crystal dispersed in a special ultraviolet curing resin, and JP-A No. 63-271233 discloses a liquid crystal dispersed in a special ultraviolet curing resin. , No. 63-278035, 63-
No. 278036 discloses a combination of a photocurable vinyl compound and a liquid crystal.

On the other hand, apart from these technologies, there is a similar liquid crystal light control/display material that has unprecedented features such as being able to be driven by electrical current and contains liquid crystal as a continuous phase in a polymer network structure. Patent application 1986-2 shows what can be achieved by making it into a form
64533.

However, when trying to use a flexible material such as a transparent conductive film as a conductive substrate, the adhesion to the substrate is poor, which was not a problem when the liquid crystal was dispersed in a polymer in the form of fine particles. , highly reliable LCD dimming/
The drawback was that display materials could not be made.

(Problem B to be Solved by the Invention) As described above, it is possible to fully satisfy the requirements (i) for the liquid crystal-containing thin film layer to be in close contact with the substrate, which is required in the practical application of large-sized liquid crystal devices, and yet to be used as a display device. A liquid crystal device that does not require a polarizing plate, which also satisfies the characteristics of (ii) being able to be driven at a low voltage and (ij) having sufficient contrast, cannot be manufactured using current processes.

As a result of intensive studies, the present inventors succeeded in producing a liquid crystal device that satisfies the properties (i) to (ij).

(Means for Solving the Problems) The present invention provides a light control/display material containing a liquid crystal material as a continuous phase in a polymeric material having a three-dimensional network structure between two conductive substrates, at least one of which is transparent. Yes, in dimming/display materials made by dissolving liquid crystal in a photocurable composition and then photocuring, the conductive substrate is treated in advance with a silane coupling agent or a titanium coupling agent. The present invention relates to a liquid crystal light control/display material characterized by the following.

In the light control/display material of the present invention, the substrate may be made of a rigid material such as glass or metal, but it is best to use a flexible material such as a plastic film. Two substrates are provided facing each other with an appropriate distance between them. In addition, at least one of them has transparency,
The light control layer supported between the two substrates must be visible from the outside world. However, complete transparency is not required. If this liquid crystal device is to be used to act on light passing from one side of the device to the other, both substrates must have adequate transparency. This substrate is made into a conductive substrate by forming appropriate transparent or opaque electrodes on the entire surface or part of the substrate depending on the purpose.

Examples of the silane coupling agent used in the present invention include vinyl silanes such as γ-methacryloxypropyltrimethoxysilane and vinylmethoxysilane, aminosilanes such as r-(2-aminoethyl)aminopropylmethyldimethoxysilane, T - Epoxysilanes such as glycidoxypropyltrimethoxysilane can be mentioned. Further, examples of the titanium coupling agent include (meth)acrylic titanates such as isopropyl dimethacrylic isostearoyl titanate.

Among these, surface treatment with γ-(2-aminoethyl)aminopropylmethyldimethoxysilane is preferred from the viewpoint of wettability and adhesiveness of the material constituting the light control layer.

The electrode can be treated by dissolving a silane coupling agent or a titanium coupling agent in an organic solvent to prepare a solution, and applying the solution to the electrode of the substrate.

A liquid crystal material and a transparent solid component are interposed between the two substrates. Incidentally, it is desirable to interpose a spacer for maintaining the distance between the two substrates according to a conventional method, similarly to a well-known liquid crystal device.

Of course, the liquid crystal material does not need to be a single liquid crystal compound, and may be a mixture containing two or more types of liquid crystal compounds or substances other than liquid crystal compounds, and is usually used as a liquid crystal material in this technical field. Any recognized material may be used, and any material having positive dielectric anisotropy may be used. The liquid crystal used is preferably nematic liquid crystal, smectic liquid crystal, or cholesteric liquid crystal.

Examples of liquid crystal materials include 4-substituted benzoic acid 4°-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4''-substituted phenyl ester, 4-substituted cyclohexane-41-substituted biphenyl ester, and 4-(4-substituted cyclohexanecarbonyl). oxy)benzoic acid 4'-substituted phenyl ester, 4-(4-substituted cyclohexyl)benzoic acid 4''-substituted phenyl ester, 4-(4-f-substituted cyclohexyl)benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4 '-f-substituted biphenyl, 4-substituted phenyl-4'-substituted cyclohexane, 4-substituted-4''-substituted terphenyl, 4-substituted biphenyl 4'-substituted cyclohexane, 2-(4-substituted phenyl)-5-substituted pyrimidine etc. can be mentioned.

Liquid crystal materials require the formation of a continuous phase between two substrates. If the ratio of liquid crystal material components is low, it is difficult to form a continuous phase. Furthermore, if the ratio of the liquid crystal component is high, the adhesion between the liquid crystal enclosing thin film layer and the substrate decreases, making it impossible to apply the method to a flexible substrate. The proportion of the liquid crystal material in the light control layer components is preferably 45% to 70% by weight, more preferably 50% to 70% by weight.
It is 60% by weight (hereinafter % means % by weight).

If the transparent solid component present in the continuous phase of this liquid crystal material is dispersed in the form of particles, it is possible to achieve satisfactory display characteristics, but the adhesion between the liquid crystal containing thin film layer and the substrate is low, making it difficult to put it to practical use as a device. I don't get it.

Therefore, the transparent solid component must have a three-dimensional network structure.

Preferably, these liquid crystal light control/display materials can be manufactured as follows. That is, (1) after the surface of the substrate having the electrode layer is treated with a silane coupling agent or a titanium coupling agent, (2) a liquid crystal material and a polyfunctional (meth)acrylate monomer or oligomer, A solution consisting of a photocurable composition containing a polymerization initiator and optional components as necessary is interposed, and then (3) the photocurable composition is cured by irradiating ultraviolet rays through a transparent substrate. to let

However, the curing temperature range is preferably the isotropic liquid transition temperature of the solution or higher, and more effectively, the curing temperature is between the isotropic liquid transition temperature of the solution and a temperature about 10°C higher than that transition temperature. It is preferable to carry out the operation within the range of .

Examples of polyfunctional (meth)acrylate monomers include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1.3
- Poly(meth)acrylates such as butylene glycol, tetramethylene glycol, hexamethylene glycol, trimethylolpropane, glycerin, and pentaerythritol, obtained by adding 2 moles or more of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol. Di(meth)acrylate of diol,
Triol di- or tri(meth)acrylate obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane, and diol di- or tri(meth)acrylate obtained by adding 2 moles or more of ethylene oxide to 1 mole of bisphenol A. Examples include (meth)acrylate, poly(meth)acrylate of dipentaerythol, etc., but trimethylpropane triacrylate, tricyclodecane dimethylol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, hexanediol diacrylate, etc. , neopentyl glycol diacrylate,
Tris(acryloxyethyl)isocyanurate is
This is preferable in terms of compatibility with liquid crystal materials.

Examples of oligomers include: ■ Urethane acrylates with urethane bonds synthesized by polyaddition reactions of polyols, polyisocyanates, and 2-hydroxyalkyl (meth)acrylates; ■ Urethane acrylates containing urethane bonds synthesized by addition reactions between epoxy resins and (meth)acrylic acid. Epoxy acrylate ■ Polyol,
Polyester acrylate synthesized by polycondensation reaction with polybasic acid and (meth)acrylic acid ■ Polyester synthesized by polycondensation reaction of polyol and polybasic acid, and further polyisocyanate and 2-
Polyester urethane acrylate obtained by polyaddition of hydroxyalkyl (meth)acrylate (2) Examples include polyether acrylate synthesized by a condensation reaction of a polyol having an ether bond in the polymer chain and (meth)acrylic acid.

Polyester urethane acrylate is preferred from the viewpoint of adhesion to the substrate. As a polymerization initiator, for example, 2-hydroxy-2-methyl-1-phenylpropan-1-one (manufactured by Merck & Co., Ltd. "Darocure 1173J"), 1-hydroxycyclohexycyclohexylphenyl ketone (manufactured by Ciba Geigy Co., Ltd. "Irgacure 184J") , 1-
(4-isopropylphenyl)-2-hydroxy-2-
Methylpropane 1-one (Merck & Co., Ltd. “Darocur 11
16J), benzyldimethylkecur (manufactured by Ciba Geigy “Irgacure 651J”), 2-methyl-1-(
4-(Methylthio)phenyl]-2-morpholinopropanone-1 (manufactured by Ciba Geigy “Irgacure 907J”)
, 2.4-diethylthioxanthone (Kayacure Df! A mixture of "Cantercure ITXJ" and ethyl p-dimethylaminobenzoate, acylphosphine oxide ("Lucirin LR8728J" manufactured by BASP)
) etc. From the viewpoint of adhesion between the liquid crystal containing thin film layer and the substrate, acylphosphine oxide, which is a crystal powder,
Benzyldimethylketanol and the like are preferred.

Optional components include photosensitizers, chain transfer agents, antioxidants, thermal polymerization inhibitors, dyes, etc., and are appropriately selected according to the types of monomers, oligomers, etc. and the desired performance of the liquid crystal vice. be able to. In particular, the combined use of a chain transfer agent is extremely effective depending on the type of monomer or oligomer, and prevents the degree of cross-linking from becoming too high, thereby making the liquid crystal material more responsive to electric fields and lowering the voltage Drivability is demonstrated. Good examples of chain transfer agents are butanediol dithiopropionate, pentaerythol tetrakis (β-thiopropionate), triethylene glycol dimercaptan, and the like.

The amount of chain transfer agent added varies depending on the type of monomer and oligomer used, but if it is too small, the effect will be weak, and if it is too large, the opacity of the liquid crystal dimming/display material will decrease, and the This is not preferable because the contrast tends to deteriorate.

The effective amount is 0.05-30 for the photocurable composition.
% by weight is preferred, and 0.1 to 20% by weight is particularly preferred.

In order to support a solution containing each of these components between two substrates, this solution may be injected between the substrates, but it is also possible to inject the solution between the two substrates, but it is also possible to apply it onto one substrate using a coating machine such as a gravure coater. The substrate may be coated and then the other substrate may be placed on top of the other substrate.

Curing of the solution can be accomplished by irradiating a suitable dose of ultraviolet light through the transparent substrate.

The thickness of the light control layer is usually adjusted to a range of 5 to 50 microns.

The liquid crystal dimming/display material configured in this manner enables time-division driving, which was not possible with conventional droplet dispersion type liquid crystal devices, and also has a lower driving voltage than conventional droplet dispersion type liquid crystal devices. low contrast, high contrast, and fast response speed. Further, the liquid crystal-containing thin film layer can be brought into sufficient contact with the substrate. Therefore, the liquid crystal device configured in this way is ideal for manufacturing flexible liquid crystal devices using transparent plastic films such as polyethylene terephthalate as substrates, and is suitable for manufacturing flexible liquid crystal devices using transparent plastic films such as polyethylene terephthalate as substrates. , it is also possible to create robust liquid crystal devices.

When a plastic film is used as a substrate, large-area liquid crystal devices can be easily mass-produced by commonly known coating and laminating methods, which has a great industrial advantage.

Furthermore, the liquid crystal device of the present invention changes to a transparent state when the temperature reaches a temperature above which the liquid crystal material undergoes a phase transition to an isotropic liquid phase without applying a voltage, so a liquid crystal material having an appropriate phase transition temperature is selected. By doing so, it can also be used as a temperature-sensitive (temperature-responsive) light control device in a desired temperature range.

(Examples) Hereinafter, the present invention will be described in more detail by showing examples of the present invention, but the present invention is not limited by these examples.

Example 1 Teijin Aji A-125 was used as a transparent conductive film (ITO/PET), and after applying a 5% by weight isopropyl alcohol solution of T-(2-aminoethyl)aminopropylmethyldimethoxysilane to the ITO surface. , 100
Heat treatment was performed in an oven at °C for 5 minutes. The wettability of the surface obtained was 44 dyne/cm. (J
IS K6768) Using this treated film, the following solution was sandwiched at a temperature of 75°C and cured using a high pressure mercury lamp. The energy given is approximately 1.5 J/ctl
It is.

"Art Resin tlN-250ON" (polyester urethane acrylate manufactured by 11 Kyo Kogyo ■) 38 parts by weight "
Aloe Nkust 5700. (Acrylate monomer manufactured by Toagosei ■ 10 parts by weight 1-hydroxycyclohexylphenyl ketone 2 parts by weight rPN-002J (Dainippon Ink & Chemicals ■ Nematic liquid crystal) 50 parts by weight r1
5AAJ (Glass spacer manufactured by Sumita Optical Glass)
A small amount of the obtained liquid crystal device was cut into widths of 10 mm, and the T-peel strength was measured using a tensile tester to evaluate the adhesion between the liquid crystal encapsulating thin film and the film, which was 18 g/10 mm.

The obtained liquid crystal device became completely transparent at a driving voltage of 100 V (50 Hz AC). The light transmittance ratio between the opaque state and the transparent state was 1:3. When the cross section of the light control layer was observed using a scanning electron microscope, a tertiary polymer network was observed.

The properties of the liquid crystal material rPN-002 used are as follows.

TN, 85.0°CV
1.26 V birefringence △n
0.269 Dielectric constant anisotropy Δε 24.0 Comparative example 1 The T-peel strength was measured in the same manner as in Example 1 except that the transparent conductive film surface treatment was not performed.
It was 9g/10m+.

In addition, the wettability of the ITO surface of the film is 34 dyne/1.
Met.

In this way, surface treatment improves adhesive strength by 20 times,
A significant effect was observed.

(Effects of the Invention) Since the liquid crystal device of the present invention has excellent adhesion between the liquid crystal containing thin film layer and the substrate, it is possible to easily manufacture a liquid crystal device having a large area and flexibility.

Claims (1)

[Claims] A light control/display material containing a liquid crystal material as a continuous phase in a polymeric substance having a three-dimensional network structure between one or two conductive substrates, at least one of which is transparent, and which is photocurable. A light control/display material produced by dissolving liquid crystal in a composition and photocuring the composition, characterized in that the conductive substrate is treated in advance with a silane coupling agent or a titanium coupling agent. Liquid crystal dimming and display materials. 2. A patent characterized in that the photocurable composition consists of a) a (meth)acrylate oligomer having a difunctional or higher reactive functional group, b) a reactive monomer that acts as a diluent, and c) a polymerization initiator A liquid crystal light control/display material according to claim 1. 3. The ratio of liquid crystal substance to photocurable composition is 45: by weight.
The liquid crystal light control/display material according to claim 1 or 2, characterized in that the ratio is in the range of 55 to 70:30. 4. The liquid crystal light control/display material according to claim 1, wherein the light control layer has a thickness of 5 to 50 microns. 5. Claim 1, characterized in that the liquid crystal material is a mixture of one or more types selected from the group consisting of nematic liquid crystal, smectic liquid crystal, and cholesteric liquid crystal.
The liquid crystal light control/display material according to item 2, item 3, or item 4. 6. A step of treating the electrode surface of a conductive substrate with a silane coupling agent or a titanium-based coupling agent, a step of interposing a solution consisting of a liquid crystal material and a photocurable composition between two substrates, and the solution A liquid crystal dimming device characterized by being cured by light irradiation under conditions that maintain an isotropic liquid state.
Method of manufacturing display materials. 7. The liquid crystal light control/display material according to claim 6, wherein the surface treatment agent for the electrode surface of the conductive substrate is γ-(2-aminoethyl)aminopropylmethyldimethoxysilane. Production method.