JP2632929B2 - Liquid crystal dispersion film and device using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal dispersion film and a liquid crystal device using the same as a liquid crystal layer.

[Problems to be solved by conventional technologies and inventions]

Devices using liquid crystals are used as information display devices as well as filters for freely adjusting the amount of light.

These devices use a liquid crystal with fluidity of several μm to several tens μm.
It is necessary to keep the liquid crystal layer in a uniform thickness in order to keep it in a very narrow and uniform gap of about m and drive it by applying a voltage or the like to it. A spacer and a gap adjusting material, and a hard substrate such as glass are required.

However, in order to manufacture a large-area device using liquid crystal by this method, a gap having a uniform thickness must be formed over a large area, but this is not easy to achieve. In particular, it is not easy to change the orientation of the liquid crystal as well as to change the orientation of the liquid crystal and to accurately display a target object, as in a liquid crystal display device. In addition, the use of glass increases the weight and decreases the strength, which is one of the factors that hinders the wide application of the liquid crystal device.

In order to solve these drawbacks, a method has been proposed in which a liquid crystal encapsulated in a capsule is used in the presence of a capsule medium (JP-A-62-48789). In addition, there are disadvantages that the optical characteristics are affected and the driving voltage is increased.

In addition, a liquid crystal composition consisting of a thermoplastic amorphous polymer having no optical anisotropy such as polystyrene and polycarbonate and a low-molecular liquid crystal is made into a filter state by a casting method in a solution state, and is contained in a matrix polymer. It is disclosed that, when a low molecular liquid crystal is manufactured in a state of being finely dispersed in an island shape, it can be optically driven at a voltage of ± 18 V at 93 to 94 ° C. (Japanese Patent Application Laid-Open No. 61-47427). ), The driving voltage is high, and the adhesion between the film and the transparent conductive film is not sufficient, so that the film is liable to peel off, and a highly reliable liquid crystal display device cannot be obtained. Because it is difficult to substantially increase the liquid crystal density, it is difficult to obtain sharpness of the image,
When exposed to sunlight, there is a defect that the resin is liable to be deteriorated or discolored.

[Means for solving the problem]

The present invention has been made in order to improve the disadvantages in configuring the above-described large-area liquid crystal using device, and to obtain a liquid crystal using device which is easy, inexpensive, highly reliable, can have a large area, and has flexibility. A sponge-like polymer component consisting of 50 to 100% (meth) acrylic acid ester-based polymer (weight%, the same applies hereinafter) and 0 to 50% of an amorphous polymer which does not impair the transparency of the film. The present invention relates to a liquid crystal dispersion film in which liquid crystal is dispersed and a liquid crystal display device using the liquid crystal dispersion film as a liquid crystal layer of a liquid crystal display device.

[Examples] In the liquid crystal dispersion film of the present invention, as the polymer component, a (meth) acrylate polymer 50 to 100%
And a non-crystalline polymer 0 which does not impair the transparency of the film
Since a component consisting of up to 50% is used, a liquid crystal dispersion film having excellent transparency, light resistance (weather), flexibility and the like can be obtained.

The term “(meth) acrylate” as used herein means an acrylate and / or a methacrylate.

As the (meth) acrylate polymer,
For example, butyl acrylate, ethyl acrylate, methyl acrylate, propyl acrylate, alkyl acrylate alkyl esters and methoxyethyl acrylate having 1 to 8 carbon atoms such as octyl acrylate,
Polymerization or copolymerization of monomers such as hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, alkyl methacrylate having 1 to 4 carbon atoms such as butyl methacrylate, methoxyethyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, etc. Polymers or copolymers obtained by such a method are mentioned. These may be used alone or in combination of two or more.

In the (meth) acrylate polymer, an ethylene monomer copolymerizable with the monomer may be copolymerized in the polymer within a range of not more than 20%.

Examples of the ethylene monomer include vinyl chloride compounds such as vinyl chloride and vinyl bromide, vinyl cyanide compounds such as acrylonitrile and methacrylonitrile, vinyl acetate compounds such as vinyl acetate and vinyl propionate, Aromatic vinyl compounds such as styrene, α-methylstyrene, o-chlorostyrene, m-chlorostyrene and sulfonated styrene, aromatic vinyl derivatives such as sulfonated α-methylstyrene, vinylidene chloride, vinylidene fluoride, etc. Of vinylidene halide compounds, acrylic acid and its salts such as acrylic acid and sodium acrylate, acrylamide and acrylamide derivatives, methacrylic acid and its salts such as methacrylic acid and sodium methacrylate, and methacrylamide and methacrylamide Derivative And so on.

There is no particular limitation on the molecular weight of the (meth) acrylic acid ester-based polymer and the like, and those having a molecular weight of several thousands to several hundred thousand are usually used, and the larger the molecular weight is, the more preferable.

Among the (meth) acrylic acid ester-based polymers as described above, 1 to 70% of acrylic acid alkyl ester and 30 to 98% of methacrylic acid alkyl ester are used from the viewpoint of film flexibility and handleability during production of the copolymer. % Is preferred.

When the content of the alkyl acrylate exceeds 70%, the softening point of the copolymer decreases and the copolymer tends to stick, and industrial productivity decreases. When the content is less than 2%, the copolymer becomes hard and the flexibility decreases. Tend to.

In the (meth) acrylate polymer, (a) 60 to 100% of an alkyl acrylate having 1 to 8 carbon atoms and an alkyl group having 1 to 8 carbon atoms.
Emulsifying a monomer mixture consisting of 100 parts of a monomer consisting of 0 to 40% of a methacrylic acid alkyl ester 4 and 0.1 to 20 parts of a crosslinkable monomer having two or more (preferably three or less) polymerized bonds. (B) 0 to 40% of an alkyl acrylate having 1 to 8 carbon atoms and 1 to 4 carbon atoms of an alkyl group in 10 to 50 parts of a crosslinked acrylate-based elastic material obtained by polymerization;
A mixture of 100 parts of a monomer comprising 60 to 100% of a methacrylic acid alkyl ester and 0 to 5 parts of a chain transfer agent;
A two-layer polymer having a total of 100 parts of the component (a) and the component (b) obtained by dropping and polymerizing 0 to 90 parts is preferable.

Examples of the compound having two or more double bonds include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, divinylbenzene,
Diallyl phthalate, allyl methacrylate, allyl acrylate, triallyl cyanurate and the like,
Examples of the chain transfer agent include alkyl mercaptans having 2 to 30 carbon atoms, mercapto acids, thiophenol, and solvents such as carbon tetrachloride.

When the proportion of the alkyl acrylate in the elastic body (a) is less than 60%, the softening point of the crosslinked elastic body increases, and the flexibility and mechanical properties of the (meth) acrylic ester polymer decrease. If the amount of the crosslinkable monomer is out of the above range, rubber elasticity tends to be hardly exhibited, or rubber elasticity tends to be reduced due to excessive crosslinking.

The average particle size of the elastic body (a) is preferably adjusted to 300 to 3000 ° by adjusting the amount of the surfactant used and the amount of the aqueous dispersion medium. If the particle size is less than 300 mm, the mechanical strength of the two-layer polymer tends to be insufficient,
If it exceeds 3000 °, the transparency of the copolymer tends to decrease.

When the proportion of the alkyl methacrylate in the mixture of (b) is less than 60% or when the amount of the chain transfer agent exceeds 5 parts, the obtained (meth) acrylate polymer ( The two-layer copolymer) tends to be easily oxidized, and the solvent resistance, the light (weather) resistance, the handleability during the production of the copolymer, and the like tend to be reduced.

Further, in the two-layer copolymer, when the amount of the elastic body (a) used is less than 10 parts, the copolymer tends to be hard and brittle, and when the amount exceeds 50 parts, it tends to be too soft. Occurs.

The (meth) acrylic ester polymer has a two-layer structure of a crosslinked acrylic ester elastic material (a) and a layer made of a mixture (b) copolymerized with the crosslinked elastic material. It is preferably produced by a legal method. For example, aqueous dispersion medium 6 per 100 parts of monomer
Using 0 to 400 parts, a nonionic, anionic or amphoteric surfactant, a radical generation initiator such as potassium persulfate, cumene hydroperoxide, azobisisobutyronitrile, sodium sulfite, sodium formaldehyde sulfoxylate, ascorbin It is preferably produced using an acid or a reducing agent such as ferrous sulfate.

The copolymer obtained by the emulsion polymerization method can be separated and dried from the aqueous dispersion medium in a usual manner to obtain a powder, and the obtained product can be used as it is, for example, hydrolysis. May be used after introducing a functional group by introducing a hydroxyl group by a halogenation or by introducing a halogen group by halogenation such as chlorination. Further, when a halogen group, mercaptan, sulfide, or the like is contained, treatment with fuming sulfuric acid may be performed to introduce a sulfone group to improve adhesion to a transparent electrode or the like.

For non-crystalline polymers that can be used together with (meth) acrylate polymers as polymer components of liquid crystal dispersion films, the transparency of the film obtained when mixed with (meth) acrylate polymers has been put to practical use. There is no particular limitation as long as it does not impair so much that it cannot be provided (it is preferably used as a matrix of an optical film and has a light transmittance of 50% or more, and more preferably 80% or more). Is used. Such non-crystalline polymer adjusts the balance of physical properties of the film,
It is a component used for adjusting the sponge-like structure of the liquid crystal dispersion film, adjusting the refractive index, adjusting the alignment performance of liquid crystal, and the like. It is preferable that the refractive indices of the liquid crystal and the polymer component are close to each other, and the difference is 0.5 or less, preferably 0.3 or less.

Specific examples of the amorphous polymer, for example, vinyl chloride resin, vinylidene chloride resin, acrylic resin, methacrylic resin, AS resin, MS resin, ABS resin, MBS resin, nitrile resin, polyvinyl acetate, polyvinyl alcohol, polyvinyl Butyral, polyvinyl formal, cellulosic resin, linear polyester resin, polycarbonate,
Examples include polyamide, polyimide, polyamideimide, polystyrene, halogenated polystyrene, and sulfonated polystyrene. They may also be modified. These may be used alone or in combination of two or more.

The amount of the non-crystalline polymer used is 0 to 50%, preferably 0 to 30%, of the polymer component constituting the liquid crystal dispersion film, and when the used amount exceeds 50%, light resistance (weather) decreases,
Deterioration and yellowing of the polymer are likely to occur, and the display function also deteriorates.

The polymer component may contain a heat stabilizer, a light stabilizer, an antioxidant, a lubricant, a surfactant, a trace amount of an inorganic filler, and the like, if necessary.

There is no particular limitation on the liquid crystal dispersed in the liquid crystal dispersion film, and when a polymer component and a liquid crystal are mixed during the production of the film, a polymer component phase and a liquid crystal phase are present as different phases, Are present in a state where they are mixed with each other, and exhibit a nematic arrangement, a cholesteric arrangement, and a smectic arrangement at a use temperature of, for example, -20 to + 80 ° C, and are used as a liquid crystal for a liquid crystal device. Can be used as long as it is possible.

Specific examples of the liquid crystal component include, for example, azoxy compounds such as p-alkoxy-p'-alkylazoxybenzene and p-azoxyphenetol, p-alkoxy-p'-alkylbenzylideneaniline, p-alkoxybenzylidene- Schiff base compounds such as p'-aminocinnamic acid alkyl ester, p-alkoxybenzylidene-p'-alkylaniline, p-alkyl-p'-
Phenyl ester compounds such as cyanophenylbenzoic acid, p-alkoxy-p'-alkoxyphenylbenzoic acid and cholesterylbenzoic acid, p-alkoxy-p'-cyanobiphenyl, p-alkyl-p'-cyanobiphenyl, p-alkoxy Biphenyl-based compounds such as -p'-carboxylic acid biphenylalkyl ester, pyrimidine-based compounds such as 2-alkoxyphenyl-5-alkylpyrimidine, 2-alkoxyphenyl-5-alkoxypyrimidine, and further phenylcyclohexane-based compounds;
Examples thereof include cyclohexylcyclohexane compounds, cyclohexylphenylethane compounds, dioxane compounds, methyleneoxy compounds, and oleic compounds. These may be used alone or in combination of two or more.

In the liquid crystal dispersed in the polymer component, most of the liquid crystal, preferably 60% or more, more preferably 70% or more communicates with at least one of the front and back of the liquid crystal dispersion film, and the polymer component has a sponge-like structure. Liquid crystals are dispersed in the gaps as shown. When the ratio of the liquid crystal communicating with the front surface and / or the back surface of the liquid crystal dispersion film is less than 60%, uniform alignment of the liquid crystal is difficult to be performed, and it is difficult to perform a display with good contrast. A drive voltage tends to be required.

The sponge-like structure refers to a state in which a matrix substance forms a continuous phase by forming a network, and a liquid crystal is present in a space (a hole or an independent space). Normally, the gap communicates from the front to the back of the liquid crystal film, or communicates with one of the front and back surfaces. However, a partially independent island-like (capsule-like) is used. It can be included.

The mixing ratio of the polymer component and the liquid crystal component is within a range in which the polymer component and the liquid crystal component are phase-separated, and the polymer component / liquid crystal component is 1 / 0.3 to 1/5, preferably 1 / 0.5 to 1 in weight ratio.
It is about / 3.

When the ratio is larger than 1 / 0.3, most of the liquid crystal components are dissolved in the polymer component, or even if they are dispersed as a liquid crystal component phase, they often exist as independent dispersed particles, and the liquid crystal used in the present invention It is difficult to obtain a film in which a polymer component and a liquid crystal component each form a continuous layer, such as a dispersion film. On the other hand, if it is smaller than 1/5, it becomes difficult to form a liquid crystal dispersion film,
It is difficult to achieve the object of the present invention.

The thickness of the liquid crystal dispersion film is usually 2 to 1000 μm,
Preferably it is 5 to 100 μm. When the thickness exceeds 1000 μm, the driving voltage increases, and the material cost also increases. On the other hand, when the thickness is less than 2 μm, the influence of thickness variation tends to increase.

Voids formed in the film-like polymer component by dispersing the liquid crystal (ie, liquid crystal)
Includes some encapsulated parts, but it is difficult to define the size because many of them communicate internally, but for convenience, the short axis of the hole seen in the cut surface of the film is When the length is defined as the average diameter, it is preferably not more than 500 μm, more preferably 5 to 100 μm.
The preferred range of the average diameter also varies depending on the thickness of the liquid crystal dispersion film. Generally speaking, the smaller the thickness, the smaller the average diameter. The average diameter does not need to be a uniform size, but may have a wide distribution.
It may have a plurality of distributions such as medium and small diameter.

Such a liquid crystal dispersion film is cast using a composition prepared by adding a solvent and various additives for adjusting the viscosity and handleability of the composition to a composition comprising a polymer component and liquid crystal, if necessary. It can be formed by a method such as a water surface spreading method and a coating method.

For example, in the case of using a casting method, a solution or dispersion of a polymer component is prepared using a solvent, and a liquid crystal dispersion film is formed by casting a solution in which the liquid crystal is dispersed or dissolved in the solution. .

In the case of using the water surface development method, a liquid crystal dispersion film having a desired film thickness can be formed by developing a solution or dispersion containing a polymer component and liquid crystal on a non-solvent surface.

Examples of the additive to be added to the composition comprising the polymer component and the liquid crystal include dichroic dyes such as azo, methine, merocyanine, and anthraquinone, which are added to enable color display; And a dopant liquid crystal added for lowering the driving voltage and lowering the viscosity; and a life improving agent for improving the life of the liquid crystal display element.

The liquid crystal dispersion film may be produced as a single film, but since the required film thickness of the film is preferably 5 to 100 μm, there is a case where handling is hindered. In such a case, it may be formed directly on an electrode of a protective substrate having a thin film electrode or on an alignment film when manufacturing a liquid crystal device.

When the liquid crystal dispersion film thus formed is used in place of the liquid crystal layer of a liquid crystal device, compared to a polymer film in which liquid crystals are dispersed in the form of islands, the electrode and the alignment film and the liquid crystal disperse. Since the contact area is widened and the amount of liquid crystal used can be increased, it can be driven at a low voltage. Further, since the liquid crystal dispersion film used in the present invention has a constant thickness, it is used as a display layer having a uniform thickness over a wide area without using a spacer, similarly to a conventional liquid crystal dispersion film. sell.

Next, a liquid crystal device using the liquid crystal dispersion film used in the present invention will be described.

For liquid crystal devices, DS, TN, GH, PC
Any method such as a method and an ECB method may be used.

A general liquid crystal device includes, for example, a transparent conductive film and a transparent substrate provided on one side of a liquid crystal layer, and a transparent conductive film and a transparent substrate or a thin film electrode provided on one side of a liquid crystal layer. An alignment film and / or an insulating film may be formed between the thin film electrode and the liquid crystal layer. If necessary, a polarizing plate, a light reflection / diffusion plate, an ultraviolet cut filter, a color for color display, etc. Various filters such as a filter and a filter for preventing surface reflection may be attached.

As the alignment film, besides a film obtained by rubbing a commonly used plastic film such as polyester, polyamide, polyimide amide, or polyvinyl alcohol by an ordinary method, a film obtained by depositing silica obliquely on a transparent substrate can also be used. This alignment film has a great effect on the performance of the liquid crystal device, and is provided on both sides of the liquid crystal dispersion film or on one side, the material of the front and back alignment films is the same or different, and the rubbing direction is changed. It is preferable to appropriately select the method according to the material of the alignment film and the liquid crystal used, the polymer component, the balance of these alignment materials, and the like. In the meantime, it is advantageous to provide the same alignment direction on both sides of the liquid crystal dispersion film, and in the case of smectic alignment, change the material of the alignment film on both sides of the liquid crystal dispersion film,
In addition, rubbing to one side tends to be good, but it is not limited to this.

In the liquid crystal device of the present invention, a film in which liquid crystal is dispersed in a polymer component so as to be in a specific state is used instead of a conventional liquid crystal layer. Therefore, when a conventional liquid crystal layer is used, two substrates are indispensable for holding the same, and a spacer for holding the two substrates at a constant interval is indispensable. In addition, a liquid crystal display device can be obtained in which a problem that a display device having a large area is hardly obtained because a thickness is easily curled is obtained.

INDUSTRIAL APPLICABILITY The liquid crystal use device of the present invention can be suitably used for a large-area display device or a light control filter.

 Next, the device of the present invention will be described based on examples.

Example 1 As a (meth) acrylic ester copolymer, butyl acrylate / methyl methacrylate was 31/6 by weight.
75 parts of a copolymer of No. 9 (SD-001 manufactured by Kanegafuchi Chemical Co., Ltd.) and a copolymer of butyl acrylate / methyl acrylate in a weight ratio of 40/60 (Kanebiraku L manufactured by Kanegafuchi Chemical Co., Ltd.) -MH) using 50 parts of a toluene solution having a solid concentration of 50%, and mixing them with 125 parts of methyl ethyl ketone to obtain a homogeneous solution, and further adding 100 parts of p-ethoxy-p'-n-butylbenzylideneaniline (EBBA). Was.

The obtained solution was provided on a glass substrate having a thickness of 1 mm, provided with an ITO layer, and applied with a polyester having a thickness of 15 μm by spin coating, dried, and rubbed with a cotton cloth.
Next, the laminate was dried in a hot air circulation type dryer at a temperature of 130 ° C. or lower to obtain a laminate having a liquid crystal dispersion film having a thickness of 20 μm.

The 90 ° peel strength of the liquid crystal dispersion film in the laminate was 7 g / cm. On the other hand, a liquid crystal dispersion film was produced in the same manner as in Example 1 except that polystyrene was used instead of the (meth) acrylate polymer as the polymer component of the liquid crystal dispersion film in Example 1. An attempt was made to measure the 90 ° peel strength of the liquid crystal dispersion film in the obtained laminate, but the liquid crystal dispersion film was easily peeled off at the time of preparing the measurement sample, and the measurement was not possible.

The 90 ° peel strength was measured according to the JIS C5016A method.

When a part of the obtained film was cut out and extracted with ethyl alcohol, 92% of the used ethyl was extracted. Microscopic observation of the surface of the film after extraction,
It was confirmed that there was a hole having a hole diameter of about 5 to 50 μm, and most of the holes were continuous from the front to the back.

Example 2 A sheet was obtained in which a patterned ITO layer was formed on a 500 μm-thick polyester sheet, and a rubbed polyester orientation film was formed thereon. The obtained sheet is superimposed on the laminate having the liquid crystal dispersion film obtained in Example 1 with the rubbed polyester alignment film face down, and hot-pressed under vacuum to form a 10 cm square. A flat device was manufactured.

When a voltage of 80 V was applied between both electrodes of the obtained device, only the patterned electrodes became transparent, and the pattern was displayed.

[Effects of the Invention] In the present invention, since a liquid crystal dispersion film is produced using a specific polymer compound, a liquid crystal dispersion film having good adhesion to a transparent conductive film, an insulating film, an alignment film and the like can be obtained. Since the liquid crystal dispersion film obtained in this way is used in place of the conventional liquid crystal layer to manufacture a liquid crystal device, not only a spacer is not required and a uniform gap between electrodes can be easily formed and maintained, but also a liquid crystal display device can be formed. In addition, it is possible to manufacture the liquid crystal display device of the present invention which has a large area, is light, and has a high reliability even if it has a curved surface. Furthermore, since it is a film mainly composed of a (meth) acrylic ester polymer having excellent light resistance (weather), discoloration and deterioration are suppressed, and it is suitable for outdoor use.

Claims (6)

(57) [Claims] (1) a (meth) acrylic ester polymer
A liquid crystal dispersion film in which a liquid crystal is dispersed such that a polymer component comprising 100% by weight and 0 to 50% by weight of an amorphous polymer which does not impair the transparency of the film forms a sponge. 2. The liquid crystal dispersion according to claim 1, wherein said (meth) acrylate polymer is a copolymer comprising 2 to 70% by weight of alkyl acrylate and 30 to 98% by weight of alkyl methacrylate. the film. 3. The (meth) acrylic ester-based polymer comprises: (a) 60 to 100% by weight of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group and 1 to 4 carbon atoms in the alkyl group. Crosslinking obtained by emulsion polymerization of a monomer mixture consisting of 100 parts by weight of a monomer comprising 0 to 40% by weight of an alkyl methacrylate and 0.1 to 20 parts by weight of a crosslinking monomer having two or more double bonds. (B) 0 to 40% by weight of an acrylate alkyl ester having 1 to 8 carbon atoms and 1 to 50 parts by weight of an acrylic acid ester-based elastic material;
(A) component obtained by dropping 100 parts by weight of a monomer consisting of 60 to 100% by weight of a methacrylic acid alkyl ester and 50 to 90 parts by weight of a mixture consisting of 0 to 5 parts by weight of a chain transfer agent. The total of the component (b) and the component (b) is 100 parts by weight of a two-layer copolymer.
The liquid crystal dispersion film as described in the above. 4. The liquid crystal dispersion film according to claim 1, wherein most of the liquid crystal communicates with at least one of the front and back of the film. 5. A liquid crystal device using the liquid crystal dispersion film according to claim 1 as a liquid crystal layer of the liquid crystal device. 6. The apparatus according to claim 5, wherein an insulating film and / or an alignment film for aligning the liquid crystal is provided between the liquid crystal dispersion film and the thin film electrode.