JPH09105814A - Optical film and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film in which bubbles or peeling is not caused in heating and moisturizing treatment and optical characteristics such as transmittance and phase difference are hardly decreased even in an high temp. atmosphere, and which has excellent reworking property, cutting property, storage property, resistance against humidity and heat and maintaining property of optical functions, and moreover, has an excellent preventing effect against warpage of a liquid crystal cell. SOLUTION: This optical film consists of an optical film material (2) and an adhesive layer (3) on the one or both surfaces of the film material (2). The adhesive layer (3) has <=0.1wt.% saturation water absorption at 50 deg.C and 90%R.H. and <=15×10<5> dyn/cm<2> relaxation elastic modulus at 23 deg.C standard temp. and 10<5> sec relaxation time. Thereby, a liquid crystal display device having high quality and excellent durability can be obtd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention has excellent removability, cutting workability, storability, etc., and is excellent in moist heat resistance and optical function maintainability, and is unlikely to cause foaming, peeling, or deterioration of optical characteristics even in a heated and humidified atmosphere. Further, the present invention relates to an optical film having a pressure-sensitive adhesive layer, which is suitable for a liquid crystal display device and the like, which is excellent in warp prevention property of liquid crystal cells.

[0002]

BACKGROUND OF THE INVENTION Conventionally, various pressure-sensitive adhesive layers such as an acrylic pressure-sensitive adhesive layer are provided on an optical film material for sticking to a liquid crystal cell, for example, a polarizing film or a retardation film, or an elliptically polarizing film obtained by laminating them. An optical film for a liquid crystal display (LCD) has been proposed. In such an optical film, a pressure-sensitive adhesive layer for adhering a liquid crystal cell is preliminarily attached to an optical film material for the purpose of improving the efficiency of LCD assembly and preventing variations in quality.

In the above optical film for LCD,
Rework (remanufacturing work) even after sticking to the liquid crystal cell
In addition to excellent heat resistance, cutting workability during product processing, storage stability, etc., it has excellent moist-heat resistance that does not cause foaming or peeling before and after heat-humidification treatment when mounted on an LCD, and even when placed in a high-temperature atmosphere The optical properties such as transmittance and retardation (retardation value: product of refractive index difference Δn of birefringence and film thickness d) are not deteriorated, and excellent optical function maintenance is required. With the increasing size and size, the required performance is becoming more sophisticated, and it is required to improve the durability performance to withstand even more severe conditions.

However, in the conventional optical film, there is a problem that it is difficult to make the wet heat resistance and the optical function maintaining property compatible with each other. That is, in the conventional optical film, when it is a moisture-heat resistant optical film that does not cause foaming or peeling by heating and humidifying treatment, the optical function maintenance such that the optical characteristics such as light transmittance and phase difference are lowered by the heating treatment. Since the liquid crystal cell has poor properties, the liquid crystal cell is likely to warp. On the other hand, when the optical function maintaining property is excellent or the warp preventing property of the liquid crystal cell is enhanced, there is a problem that the moist heat resistance which causes foaming or peeling due to heating and humidifying is poor.

[0005]

DISCLOSURE OF THE INVENTION The present invention is to prevent foaming and peeling by heating and humidification, and to prevent deterioration of optical characteristics such as light transmittance and phase difference even in a high temperature atmosphere, reworkability and cutting workability. It is an object of the present invention to develop an optical film which is excellent not only in storage stability and the like but also in moist heat resistance and optical function maintenance, and which is also excellent in warp prevention of liquid crystal cells.

[0006]

SUMMARY OF THE INVENTION The present invention is based on 50 ° C., 90 ° C.
% Saturated humidity is 1.0 wt% or less, and relaxation elastic modulus is 1 at a standard temperature of 23 ° C. and a relaxation time of 10 ⁵ seconds.
The present invention provides an optical film characterized in that an adhesive layer having a density of 5 × 10 ⁵ dyn / cm ² or less is provided on one side or both sides of an optical film material.

[0007]

According to the present invention, it is excellent in reworkability, cutting workability, storability, etc., does not cause foaming or peeling due to heating and humidification, and has light transmittance, phase difference, etc. even when placed in a high temperature atmosphere. It is possible to obtain an optical film that is excellent in both wet heat resistance and optical function maintenance that does not easily deteriorate the optical characteristics of the liquid crystal, and is also excellent in warp prevention of the liquid crystal cell, and obtain a liquid crystal display device with high quality and excellent durability. be able to.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The optical film of the present invention comprises 50
A pressure-sensitive adhesive having a saturated water absorption rate of 1.0% by weight or less at 90 ° C. and 90% RH and a relaxation elastic modulus of 15 × 10 ⁵ dyn / cm ² or less at a standard temperature of 23 ° C. and a relaxation time of 10 ⁵ seconds. A layer is provided on one side or both sides of an optical film material.

An example of the optical film of the present invention is shown in FIGS. 2 is an optical film material, and 3 is an adhesive layer.
In FIG. 2, 21 is a polarizing film, 22 is a retardation film, and these are laminated through the pressure-sensitive adhesive layer 3 to form an elliptical polarizing film as the optical film material 2. In addition, 1 is a protective film and 4 is a separator.

As the optical film material, for example, a liquid crystal display such as a polarizing film, a retardation film, an elliptically polarizing film obtained by laminating a polarizing film and a retardation film, a reflective polarizing film or the elliptically polarizing film using the same. What is used for forming an apparatus or the like is used, and there is no particular limitation on its type. In the case of a laminated type optical film material such as the elliptically polarizing film, the pressure-sensitive adhesive layer in the present invention is preferable as the adhesive means used for laminating, from the viewpoints of wet heat resistance and optical function maintainability.

Specific examples of the polarizing film include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene / vinyl acetate copolymer partially saponified film, and iodine and / or dichroic film. Examples thereof include those stretched by adsorbing a reactive dye, polyene oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. The thickness of the polarizing film is usually 5 to 80 μm, but is not limited thereto.

The reflective polarizing film is for forming a liquid crystal display device of the type that reflects and displays incident light from the viewing side (display side), and has a built-in light source such as a backlight. It has an advantage that it can be omitted and the liquid crystal display device can be easily thinned.

The reflective polarizing film can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one side of the polarizing film via a transparent resin layer or the like, if necessary. The transparent resin layer provided as necessary can also serve as the protective film 1 as shown in the figure, and therefore the polarizing film has a transparent protective layer provided on one side or both sides thereof. Good.

As a specific example of the reflective polarizing film, a reflective layer is formed by providing a foil or a vapor-deposited film made of a reflective metal such as aluminum on one side of a transparent resin layer such as a protective film or the like which is matted as required. And the like.
Further, the transparent resin layer may be made to contain fine particles to form a surface fine uneven structure, and a reflective layer having a fine uneven structure may be provided thereon. The reflective layer has a reflective surface covered with a transparent resin layer or a polarizing film, and is used to prevent a decrease in reflectance due to oxidation, and to maintain the initial reflectance over a long period of time. Is more preferable.

The reflective layer having the fine uneven structure described above has an advantage that the incident light is diffused by irregular reflection to prevent directivity and glaring appearance, and that unevenness in brightness can be suppressed.
Further, the transparent resin layer containing fine particles has an advantage that incident light and reflected light thereof can be diffused when passing therethrough to further suppress uneven brightness. The reflective layer having a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent resin layer can be formed by transparentizing a metal by an appropriate method such as a vacuum evaporation method, an ion plating method, a sputtering method, or another vapor deposition method or a plating method. It can be performed by a method of directly attaching to the surface of the resin layer.

For the formation of the protective film and the transparent protective layer, plastics and the like which are excellent in transparency, mechanical strength, heat stability, moisture shielding property and the like are preferably used. Examples thereof include polyester resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, acrylic resin, urethane resin, acrylic urethane resin. Examples thereof include thermosetting or ultraviolet curable resins such as epoxy resins and silicone resins.

The transparent protective layer may be formed by an appropriate method such as a plastic coating method or a film laminating method, and the thickness may be appropriately determined. Generally 5 mm
Hereafter, it is preferably 1 mm or less, particularly 1 to 500 μm. Examples of the fine particles to be contained in the formation of the transparent resin layer having the surface fine uneven structure include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide and antimony oxide having an average particle size of 0.5 to 5 μm. Inorganic fine particles that may be electrically conductive, organic fine particles such as crosslinked or uncrosslinked polymer, and the like that exhibit transparency in a transparent resin layer are used. The amount of the fine particles used is generally 2 to 25 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the transparent resin.

Specific examples of the retardation film which is the above-mentioned optical film material include a film made of a suitable plastic such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate and polyamide. Examples include a birefringent film obtained by treatment. The retardation film can be formed by laminating two or more kinds of retardation films and controlling optical properties such as retardation.

The elliptically polarizing film or the reflective elliptically polarizing film, which is the above-mentioned optical film material, is obtained by laminating the polarizing film or the reflective polarizing film and the retardation film in an appropriate combination. It can also be formed by sequentially laminating (reflective) polarizing film and retardation film separately in the process of manufacturing a liquid crystal display device so as to form a combination.
As described above, the elliptically polarizing film prepared beforehand has excellent quality stability and stacking workability, and can improve the manufacturing efficiency of the liquid crystal display device.

The optical film forming layers such as the polarizing film, the retardation film, the protective film and the transparent protective layer are, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds. It is also possible to impart ultraviolet absorption ability by a method of treating with an ultraviolet absorber such as.

The pressure-sensitive adhesive layer provided on one side or both sides of the optical film material has a saturated water absorption of 1.0% by weight or less at 50 ° C. and 90% RH, and a relaxation time at a standard temperature of 23 ° C. and a relaxation time of 10 ⁵ seconds. It is formed to have an elastic modulus of 15 × 10 ⁵ dyn / cm ² or less. Thereby, while satisfying reworkability, cutting processability, storage stability, etc., it is possible to obtain an optical film that is excellent in both wet heat resistance and optical function maintenance and that can suppress its warp when applied to a liquid crystal cell. it can. The preferred saturated water absorption is 0.8% by weight or less, especially 0.6% by weight or less, and the relaxation elastic modulus is 13%.
It is not more than × 10 ⁵ dyn / cm ² , especially not more than 10 × 10 ⁵ dyn / cm ² .

In the above, it is considered that the manifestation of such characteristics is caused by setting the relaxation elastic modulus and the saturated water absorption of the pressure-sensitive adhesive layer to be low. That is, in the conventional design concept of the optical film, measures have been taken to increase the elastic modulus of the pressure-sensitive adhesive layer in order to prevent foaming due to heating and humidification. However, in that case, an increase in the elastic modulus leads to an increase in stress of the optical film material caused by a difference in thermal expansion between the adherend such as a liquid crystal cell and the like, and a decrease in optical characteristics of the optical film due to heating can be increased. is expected. By the way, as a result of obtaining the stress generated due to the difference in thermal expansion between the optical film material, the pressure-sensitive adhesive layer and the liquid crystal cell during the heating and humidifying treatment, the reference temperature is 23 ° C.,
Relaxation elastic modulus at relaxation time of 10 ⁵ seconds is 15 × 10 ⁵ dyn / cm ²
If a higher pressure-sensitive adhesive layer is interposed between the optical film material and the liquid crystal cell, the stress cannot be sufficiently relaxed and the optical characteristics are deteriorated, and the liquid crystal cell warps due to the shrinkage of the optical film material. It turned out to occur. Therefore, it seems that it is difficult to achieve both the wet heat resistance and the optical function maintaining property by the conventional design concept of the optical film.

In view of the above, the inventors of the present invention have been earnestly researching to achieve both wet heat resistance and optical function maintenance,
The relationship between the relaxation elastic modulus and the saturated water absorption of the pressure-sensitive adhesive layer and the foaming due to the heating and humidifying treatment was examined, and the results illustrated in FIG. 3 were obtained. From FIG. 3, it can be seen that the conventional measure for increasing the elastic modulus of the pressure-sensitive adhesive layer to prevent foaming due to the heating and humidifying treatment is effective. On the other hand, it can be seen that foaming can be prevented even when the saturated water absorption is low even in the low elastic modulus region, and thus foaming by the conventional heating / humidification treatment is caused by vaporization and expansion of water in the adhesive layer. Expected to be.

Therefore, from the above, it is expected that both moist-heat resistance and optical function maintenance are compatible in the region where the relaxation elastic modulus and the saturated water absorption of the pressure-sensitive adhesive layer are low, and the present invention realizes it with the above-mentioned constitution. It was done. That is, in order to suppress the deterioration of the optical characteristics during the heating and humidifying process and suppress the warp of the liquid crystal cell, the relaxation elastic modulus at the standard temperature of 23 ° C. and the relaxation time of 10 ⁵ seconds is 15 × 10 ⁵ dyn / cm ² The following pressure-sensitive adhesive layers are required. At the same time, in order to suppress foaming during the heating and humidifying treatment, the saturated water absorption rate is 1.
It is necessary that the pressure-sensitive adhesive layer is 0% by weight or less.

In the present invention, the pressure-sensitive adhesive layer is preferably such that the saturated water absorption is low, and that when the relaxation elastic modulus is low, the saturated water absorption is low. For forming the pressure-sensitive adhesive layer, it has excellent optical transparency and exhibits appropriate wettability, cohesiveness, and adhesive property of adhesion, for example, acrylic copolymer, silicone polymer, polyester, polyurethane, polyether or synthetic. Polymers such as rubber can be used, and acrylic copolymers are particularly preferable because they are excellent in transparency, weather resistance and heat resistance.

Specific examples of the acrylic copolymer include a monomer as a main component which exhibits appropriate wettability and flexibility, such as ethyl group, n-propyl group, isopropyl group and n-butyl group. , Isobutyl and isoamyl groups,
Acrylic ester or methacrylic acid ester having an organic group such as a hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl group, isooctyl group, isononyl group, lauryl group or dodecyl group and an alkyl group having 2 to 14 carbon atoms. And the like using one kind or two or more kinds thereof.

The above-mentioned acrylic copolymer contains as a copolymer component a monomer for imparting cohesiveness, adhesiveness and crosslinking reactivity as a pressure-sensitive adhesive. The copolymerization monomer is not particularly limited as long as it can be copolymerized with the above-mentioned main component monomer. In general, such a copolymer component tends to increase the relaxation elastic modulus of the acrylic copolymer, and when it has a functional group, it also tends to increase the saturated water absorption, so that it is often preferable to use the minimum amount. In the present invention, an appropriate amount of various monomers can be copolymerized within a range satisfying the above-mentioned predetermined relaxation elastic modulus and saturated water absorption.

Specific examples of the copolymerization monomer include:
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate,
12-hydroxylauryl (meth) acrylate and (4-
Hydroxylcyclohexyl) -methyl acrylate-containing hydroxyl group-containing monomer, acrylic acid or methacrylic acid, carboxyethyl acrylate or carboxypentyl acrylate, itaconic acid, maleic acid, crotonic acid-containing monomer, maleic anhydride And acid anhydride monomers such as itaconic anhydride, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. To be

Further, amide-based monomers such as (meth) acrylamide and N-substituted (meth) acrylamide, maleimide-based monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide, and N-laurylmaleimide and N-phenylmaleimide. Body, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc. Monomers, succinimide-based single monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, and N- (meth) acryloyl-8-oxyoctamethylenesuccinimide. Body like may be mentioned as co-monomers.

Further, vinyl-based monomers such as vinyl acetate, N-vinylpyrrolidone, N-vinylcarboxylic acid amides and styrene, divinyl-based monomers such as divinylbenzene, 1,4-butyl diacrylate and 1, Diacrylate-based monomers such as 6-hexyl diacrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, polyethylene glycol (meth) acrylate and polypropylene glycol (meth)
Ester group different from acrylic ester type monomers such as acrylate, fluorine (meth) acrylate and silicone (meth) acrylate, and the above-mentioned main component monomers such as methyl (meth) acrylate and octadecyl (meth) acrylate (Meth) acrylic acid ester having a is also mentioned as a monomer for copolymerization.

Among the above-mentioned copolymerization monomers, the maleimide-based monomer and the itacone-imide-based monomer exhibit the property of hardly increasing the saturated water absorption rate of the resulting acrylic copolymer, and the adhesiveness improving agent. Can be preferably used as Further, a monomer having a functional group capable of reacting with an intermolecular crosslinking agent and participating in intermolecular crosslinking of the acrylic copolymer, for example, the above-mentioned carboxyl group-containing monomer or acid anhydride monomer, ( Glycidyl (meth) acrylate and hydroxyl group-containing monomers can also be preferably used. In particular, a monomer having a high crosslinking reactivity such as carboxyethyl acrylate or 6-hydroxyhexyl (meth) acrylic acid can impart the necessary crosslinking property with a small amount of copolymerization, so that the obtained acrylic copolymer It is difficult to increase the relaxation elastic modulus and the saturated water absorption of the coalescence, and it can be used particularly preferably.

On the other hand, a polyfunctional acrylate-based monomer or the like may also be used for copolymerization, if necessary, for example, in the case where a crosslinking treatment is performed by post-crosslinking operation without adding a crosslinking agent by irradiation with radiation such as an electron beam. It can be used as a monomer. Examples of the polyfunctional acrylate-based monomer include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and neopentyl glycol di (meth) acrylate. , Pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate and the like.

For the preparation of the acrylic copolymer, for example, a suitable method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method or a suspension polymerization method is added to one or a mixture of two or more respective monomers. It can be done by applying. In the case of the bulk polymerization method, a polymerization method using ultraviolet irradiation can be preferably applied.
The acrylic copolymer preferably used in the present invention has a weight average molecular weight of 100,000 or more from the viewpoint of wet heat resistance and the like, especially 200,000 or more, particularly 400,000 to 2,000,000.

When preparing the acrylic copolymer, a polymerization initiator may be used if necessary. The amount used can be appropriately determined, but is generally 0.001 to 0.01% of the total amount of the monomer.
5% by weight. As the polymerization initiator, an appropriate one such as a thermal polymerization initiator or a photopolymerization initiator can be used according to the polymerization method.

Incidentally, examples of the thermal polymerization initiator include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate and di (2-ethoxy). Ethyl) peroxydicarbonate,
Organic peroxides such as t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide and diacetyl peroxide.

Further, 2,2'-azobisisobutyronitrile and 2,2'-azobis (2-methylbutyronitrile), 1,2'-azobis (isobutyronitrile)
1'-azobis (cyclohexane 1-carbonitrile)
And 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile) and dimethyl 2,2′-azobis (2
-Methylpropionate), 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2-
An azo compound such as (2-imidazolin-2-yl) propane] can also be used as the thermal polymerization initiator.

On the other hand, examples of the photopolymerization initiator include 4-
(2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone or α-hydroxy-α, α′-
Dimethylacetophenone, methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone,
Acetophenone-based initiators such as -hydroxycyclohexylphenyl ketone and 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1, and benzoin ether-based initiators such as benzoin ethyl ether and benzoin isopropyl ether; can give.

Further, a ketal-based initiator such as benzyldimethyl ketal, benzophenone or benzoylbenzoic acid,
Benzophenone-based initiators such as 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone and 2,4-
Thioxanthone-based initiators such as dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone and 2,4-diisopropylthioxanthone, camphorquinone and halogenated compounds Ketones, acylphosphinoxides, acylphosphonates, and the like are also examples of the photopolymerization initiator.

Other polymerization initiators include potassium persulfate, ammonium persulfate, hydrogen peroxide and the like, and redox type initiators in which they are used in combination with a reducing agent.

In the present invention, the pressure-sensitive adhesive layer may be crosslinked as described above. In this case, the crosslinking treatment with the intermolecular cross-linking agent can be performed by, for example, a method of mixing the intermolecular cross-linking agent with the liquid of the pressure-sensitive adhesive. As the intermolecular crosslinking agent, an appropriate one can be used depending on the type of functional group in the pressure-sensitive adhesive polymer involved in intermolecular crosslinking, and is not particularly limited. Therefore, any of the known materials can be used.

Incidentally, examples of the intermolecular cross-linking agent include polyfunctional isocyanate cross-linking agents such as tolylene diisocyanate, trimethylol propane tolylene diisocyanate and diphenyl methane triisocyanate, polyethylene glycol diglycidyl ether and diglycidyl ether, trimethylol propane tri Other examples include epoxy crosslinking agents such as glycidyl ether, melamine resin crosslinking agents, metal salt crosslinking agents, metal chelate crosslinking agents and amino resin crosslinking agents.

The blending amount of the intermolecular cross-linking agent can be appropriately determined depending on the content of the functional group in the pressure-sensitive adhesive polymer, etc. within a range satisfying the above-mentioned predetermined relaxation elastic modulus and saturated water absorption. Generally, 0.01 to 20 parts by weight, especially 0.1 to 15 parts by weight, and especially 0.2 to 10 parts by weight of the intermolecular crosslinking agent are used per 100 parts by weight of the adhesive polymer.

If necessary, the pressure-sensitive adhesive layer may include, for example, natural or synthetic resins, glass fibers or glass beads, metal powder or other materials in a range satisfying the above-mentioned predetermined relaxation elastic modulus and saturated water absorption. Appropriate additives that may be added to the pressure-sensitive adhesive layer, such as fillers and pigments made of inorganic powder, colorants and antioxidants, may also be added. It is also possible to incorporate fine particles to form a pressure-sensitive adhesive layer having a light diffusing property.

The adhesive layer may be attached to one side or both sides of the optical film material by an appropriate method. As an example thereof, for example, an adhesive is dissolved or dispersed in a solvent composed of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate to prepare an adhesive liquid of about 10 to 40% by weight, which is cast. A method of directly attaching on the optical film material by an appropriate developing method such as a method or coating method, or a method of forming an adhesive layer on the separator and transferring it onto the optical film material according to the above. To be

The pressure-sensitive adhesive layer may be provided on one side or both sides of the optical film material as a superposed layer of different compositions or types. Further, when it is provided on both sides, pressure-sensitive adhesive layers having different compositions or types may be provided on the front and back of the optical film material. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use and the like, and is generally 1 to 500 μm. When the adhesive layer is exposed on the surface, it is preferable to protect the surface with a separator or the like until practical use.

In forming the optical film of the present invention, various film materials such as a protective film may be laminated by
It is preferable to use a material that conforms to the pressure-sensitive adhesive layer attached to the above-mentioned optical film material, from the viewpoints of resistance to moist heat and optical function maintenance.

The optical film of the present invention can be used for appropriate applications such as formation of a liquid crystal display device. The liquid crystal display device can be formed by adhering the optical film of the present invention to one side or both sides of the liquid crystal cell via the adhesive layer. At the time of sticking, the polarizing film, the retardation film and the like are placed at a predetermined position, and the position can be the same as the conventional position.

Incidentally, FIG. 4 and FIG. 5 show examples of the arrangement of the optical film in the liquid crystal display device. Reference numeral 5 is a liquid crystal cell, and other reference numerals are the same as above. The device illustrated in FIG. 4 is of a reflective type in which the polarizing film 21 is provided with the reflective layer 23, and thus the reflective layer is arranged on the outer side of one side of the liquid crystal cell.

The apparatus illustrated in FIG. 5 uses the retardation film 22. The retardation film is used for compensating for the retardation of the liquid crystal cell for the purpose of preventing coloring, expanding the viewing angle range, and the like. In that case, it can also be used as an elliptically polarizing film laminated with a polarizing film.

The optical film of the present invention has flexibility and can be easily applied to a curved surface, a large area surface, or the like, and any liquid crystal cell, for example, an active matrix driving type represented by a thin film transistor type, Various liquid crystal display devices can be formed by applying to a liquid crystal cell of an appropriate type such as a simple matrix drive type represented by a twist nematic type or a super twist nematic type.

[0051]

【Example】

Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer, 99.8 parts of butyl acrylate (parts by weight, hereinafter the same), 0.2 part of 6-hydroxyhexyl acrylate,
And 2,2′-azobisisobutyronitrile 0.3 were added together with 120 parts of ethyl acetate and reacted at 60 ° C. for 4 hours and then at 70 ° C. for 2 hours under a nitrogen gas stream to complete the reaction, 114 parts of ethyl acetate was added to the reaction solution to obtain an acrylic copolymer solution having a solid content of 30% by weight, and 0.3 part of trimethylolpropane tolylene diisocyanate was added to 100 parts of the solid content of the acrylic copolymer solution. A system adhesive was obtained.

Next, the above-mentioned acrylic pressure-sensitive adhesive was applied to a separator made of a polyester film and heat-treated at 150 ° C. for 5 minutes to obtain a pressure-sensitive adhesive layer having a thickness of 1 mm. In addition, after a pressure-sensitive adhesive layer having a thickness of 23 μm was provided by the same operation, a polarizing film (manufactured by Nitto Denko Corporation, NPF-G1225DUNA) was used.
GS1) and a polycarbonate film having a thickness of 70 μm are attached to one surface of a retardation film uniaxially stretched at 160 ° C., respectively, and then the separator on the polarizing film side is peeled off to separate the polarizing film through the adhesive layer. An optical film made of an elliptically polarizing film was obtained by laminating the absorption axis and the slow axis of the retardation film so as to intersect each other at 45 degrees.

Example 2 In addition to using 99.5 parts of butyl acrylate, 0.5 part of 6-hydroxyhexyl acrylate, and 0.7 part of trimethylolpropane tolylene diisocyanate. An acrylic pressure-sensitive adhesive was prepared according to Example 1 to obtain an optical film.

Example 3 Acrylic resin was prepared in the same manner as in Example 1 except that 99.8 parts of 2-ethylhexyl acrylate was used in place of butyl acrylate and the amount of trimethylolpropane tolylene diisocyanate used was 0.1 part. An adhesive was prepared to obtain an optical film.

Comparative Example 1 94.9 parts of butyl acrylate, 5 parts of acrylic acid, and 0.1 of 2-hydroxyethyl acrylate were used as monomers, and the amount of trimethylolpropane tolylene diisocyanate used was 1 part. Otherwise, an acrylic pressure-sensitive adhesive was prepared according to Example 1 to obtain an optical film.

Comparative Example 2 Acrylic adhesive according to Example 1 except that 95 parts of butyl acrylate and 5 parts of acrylic acid were used as monomers, and the amount of trimethylolpropane tolylene diisocyanate used was 1 part. The agent was prepared to obtain an optical film.

Evaluation Test Saturated Water Absorption Rate 1 mm thick adhesive layer (5 mm × 5 m) obtained in Examples and Comparative Examples
m) in an atmosphere of 50 ° C. and 90% RH,
The water absorption was determined while measuring the weight change using an electronic balance capable of measuring 001 mg order, and the value when the water absorption was saturated was taken as the saturated water absorption.

Relaxation Elastic Modulus A pressure-sensitive adhesive layer having a thickness of 1 mm obtained in Examples and Comparative Examples (5 mm × 1.
1 mm), a storage elastic modulus G ′ at −100 to 200 ° C. was measured at a frequency of 1 Hz using a dynamic viscoelastic device (manufactured by Seiko Denshi KK), and the measured data was used as the following WLF.
Converted to dispersion data G '(ω) based on frequency ω with 23 ° C as the reference temperature using the time-temperature conversion rule consisting of
Then, the relaxation elastic modulus Gk and the relaxation time τk were estimated by the generalized Maxwell model, and the relaxation elastic modulus at the standard temperature of 23 ° C. and the relaxation time of 10 ⁵ seconds was obtained. loga _T = C ₁ (T−T _s ) / (C ₂ + T−T _s ) G ′ (ω) = ΣGk [(ω · τk) 2 / {1+ (ω · τk)
2}] τk = ηk / Gk where loga _T is the shift factor, T is the temperature,
Coefficient C ₁ = 8.86, coefficient C ₂ = 101.6, characteristic temperature T
_s = glass transition temperature T _g + 45 ° C. Further, ηk is a relaxation viscosity.

Heat resistance Optical films (200 mm × 150) obtained in Examples and Comparative Examples
mm, the same shall apply hereinafter) was attached to a glass plate via the pressure-sensitive adhesive layer, and the presence or absence of foaming was visually observed after heating for 1000 hours in an atmosphere at 110 ° C.

Moisture resistance The optical films obtained in Examples and Comparative Examples were adhered to a glass plate via the pressure-sensitive adhesive layer, and foaming and peeling after heating for 1000 hours in an atmosphere of 80 ° C. and 90% RH were observed. The presence or absence was visually observed.

Polarization Degree Maintaining Property The optical films obtained in Examples and Comparative Examples were adhered to both surfaces of a glass plate via the adhesive layer so that the absorption axes were orthogonal to each other in the front and back, and in an atmosphere of 110 ° C. After heating for 1000 hours, it was examined on the backlight whether or not there was a decrease in the degree of polarization that affects visibility.

Amount of Warpage Regarding the optical films obtained in Examples and Comparative Examples, a glass plate (200 mm × 150 mm, thickness 0.7) was formed through the adhesive layer.
mm) and heated in an atmosphere at 110 ° C. for 1000 hours, and the warp of the glass plate was examined. Regarding the warp, the glass plate with the optical film after the heat treatment was left still on the smooth surface with the optical film side facing upward, the floating amount at the four corners was measured, and the average value was evaluated as the warp amount.

The above results are shown in Table 1.

[Table 1]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an optical film.

FIG. 2 is a cross-sectional view of another example of an optical film.

FIG. 3 is a graph showing the relationship between saturated water absorption rate, relaxation elastic modulus, and presence or absence of foaming.

FIG. 4 is a cross-sectional view of an example of a liquid crystal display device.

FIG. 5 is a cross-sectional view of another example of a liquid crystal display device.

[Explanation of symbols]

 2: Optical film material 21: Polarizing film 22: Retardation film 23: Reflective layer 3: Adhesive layer 5: Liquid crystal cell

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Makoto Kojima 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Prefecture Nitto Denko Corporation (72) Kazuhiko Miyauchi 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Prefecture Nitto Denko Corporation (72) Inventor Naoshi Yamaoka 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (4)

[Claims] 1. A saturated water absorption at 50 ° C. and 90% RH is 1.0 wt% or less, and a relaxation elastic modulus at a standard temperature of 23 ° C. and a relaxation time of 10 ⁵ seconds is 15 × 10 ⁵ dyn / cm. ^An optical film having an adhesive layer of ² or less provided on one side or both sides of an optical film material. 2. The optical film according to claim 1, wherein the optical film material is a polarizing film, a reflective polarizing film or a retardation film. 3. The elliptically polarizing film according to claim 1, wherein the optical film material is a laminate of a polarizing film and a retardation film via the pressure-sensitive adhesive layer according to claim 1, or a reflective polarizing film and a retardation film. An optical film that is a laminated reflective elliptically polarizing film. 4. The liquid crystal cell according to claim 1, wherein one or both sides of the liquid crystal cell are provided.
A liquid crystal display device, wherein at least one of the optical films described in 1 above is adhered.