JPH1044291A - Optical film and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film which can be easily released, causes no foaming or releasing and scarcely lowers its optical characteristics by providing an adhesive layer using acrylic polymer having specific functional group concentration as base polymer and having specific release adhesive force to a release side adherend on one or both side surfaces of an optical film material. SOLUTION: An adhesive layer 3 using acrylic polymer having a functional group concentration of 5×1/10<4> mol/g or less as base polymer and having 90 degrees release adhesive force to a release side adherend of 600g/20mm or less is provided on one side or both side surfaces of an optical film material 2. A protective film 1 is laminated on the material 2, and a separator 4 is laminated underneath the layer 3. The acrylic polymer uses one or more types of acrylic ester and methacrylic ester having a glass transition temperature of -10 deg.C or lower. The adhesive layer is attached, for example, by a type for directly attaching pressure sensitive adhesive liquid in which the adhesive is dissolved in solvent such as toluene or ethyl acetate, and has a thickness of 1 to 500μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be easily peeled off without damaging a liquid crystal cell at the time of bonding error and the like, and foaming and peeling off even in a heated and humidified atmosphere after adhering to a liquid crystal cell, resulting in deterioration of optical characteristics. The present invention relates to an optical film provided with an adhesive layer which is difficult and is suitable for a liquid crystal display device and the like.

[0002]

BACKGROUND OF THE INVENTION Optical film materials used in liquid crystal display devices (LCDs), such as polarizing films, retardation films, and elliptically polarizing films obtained by laminating them, are key devices of LCDs and prevent variations in quality and the efficiency of LCD assembly. For the purpose of conversion, etc., a method has been adopted in which a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive or the like is attached to a liquid crystal cell in a state of an optical film provided in advance.

For example, when the optical film is mounted on an LCD and subjected to a heating and humidifying process due to the expansion of the use of the LCD as a multimedia information terminal device or the like as well as higher performance and larger size due to the progress of the information society. Characteristics that do not cause foaming or peeling before and after the treatment (moisture and heat resistance), light transmittance and phase difference (retardation value:
Practical properties such as optical properties such as the product of the birefringence refractive index difference and the film thickness) (optical properties maintaining properties), optical properties are further enhanced, and durability is increased to withstand more severe conditions. Is required.

[0004] However, there has been a problem that it is difficult to achieve the above-mentioned requirement by the countermeasure method according to the related art. That is, the problem of foaming and peeling of the optical film under heating and humidification is due to the deformation of the optical film, so that the deformation of the optical film material and the cohesive strength of the adhesive layer have been the countermeasures so far. It is difficult to achieve difficult deformation while maintaining the optical characteristics, and there is no prospect of improving the moist heat resistance, and the increase in the amount of deformation due to the large area of the optical film due to the enlargement of LCD makes it more difficult to realize. It is a fact. In the latter case, due to the high cohesion of the adhesive layer, the heat and humidification treatment at the periphery and the center of the optical film causes unevenness in optical characteristics such as light transmittance and phase difference, causing a problem that the optical function retention is deteriorated. Then, the enlargement of the optical film makes the problem more remarkable.

[0005] Further, the above-mentioned high cohesive strength of the pressure-sensitive adhesive layer makes it easy to cause peeling of the edge of the optical film under humidification. When the optical film needs to be replaced due to a bonding error or the like, it takes a lot of time and labor for the peeling work, and the problem that the adhesive remains in the liquid crystal cell and it becomes a foreign substance easily occurs,
The thinning of the cell base made of a glass plate, a plastic film, or the like accompanying the thinning and lightening of the LCD also causes a problem that the cell cannot be reused because the peeling without damaging the cell becomes more difficult.

[0006]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal cell which can be easily separated without damaging the liquid crystal cell at the time of bonding error and the like, and can reuse the liquid crystal cell. It is an object of the present invention to develop an optical film that satisfies both the wet heat resistance and the optical function maintenance performance even if the size is large, and shows stable adhesive properties.

[0007]

According to the present invention, an acrylic film having a functional group concentration of 5 × 1/10 ⁴ mol / g or less is used as a base polymer on one or both surfaces of an optical film material, and the surface of the optical film material is adhered to a release-side adherend. Another object of the present invention is to provide an optical film having an adhesive layer having a peel strength of 600 g / 20 mm or less.

[0008]

According to the present invention, even if a liquid crystal cell is thin or large, it can be easily peeled without damaging the liquid crystal cell in the event of an adhesion error, etc. Can,
In addition, an optical film that does not generate foaming or peeling even in a heating and humidifying atmosphere, does not easily reduce optical properties such as light transmittance and phase difference, and has excellent moisture-heat resistance and optical function maintenance properties and exhibits stable adhesive properties. Thus, a liquid crystal display device having high quality and excellent durability can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical film of the present invention has a functional group concentration of 5 × 1/1 on one or both sides of an optical film material.
0 ⁴ mol / g or less of acrylic polymer as a base polymer, 90 degree peel adhesion to peel side adherend 600
g / 20 mm or less. Examples thereof are shown in FIGS. 2 is an optical film material and 3 is an adhesive layer. In FIG. 2, reference numeral 21 denotes a polarizing film;
Are retardation films, which are laminated via an adhesive layer 3 to form an elliptically 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 above-mentioned elliptically polarizing film, the adhesive layer in the present invention is preferable as an adhesive means used for lamination from the viewpoint of wet heat resistance, optical function retention and the like.

[0011] Specific examples of the above polarizing film include:
A film obtained by adsorbing iodine and / or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, and polyvinyl alcohol And a polyene-oriented film such as a polyvinyl chloride dehydrochlorinated product. The thickness of the polarizing film is usually 5 to 80 μm
But is not limited to this.

The reflective polarizing film is used to form a liquid crystal display device or the like that reflects and reflects incident light from the viewing side (display side), and has a built-in light source such as a backlight. It has advantages that it can be omitted and the thickness of the liquid crystal display device can be easily reduced.

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 drawings. Therefore, the above-mentioned polarizing film may have a transparent protective layer on one 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, there may be mentioned, for example, those in which fine particles are contained in the transparent resin layer to form a fine surface unevenness structure, and a reflective layer having a fine unevenness structure is 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 also has an advantage that the incident light and the reflected light thereof are diffused when transmitting the light and the unevenness of brightness can be further suppressed. The reflection layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent resin layer is formed by, for example, making the metal transparent by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method, or a plating method. It can be carried out 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 resins and acetate resins, polyethersulfone resins and polycarbonate resins, polyamide resins and polyimide resins, polyolefin resins and acrylic resins, or acrylic, urethane and acrylic urethane resins. And thermosetting resins such as epoxy resins and silicone resins, and ultraviolet curing 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. In general, the thickness is 5 mm or less, especially 1 mm or less, particularly 1 to 500 μm. The fine particles to be contained in the formation of the transparent resin layer having the fine surface irregularity structure are, for example, those having an average particle size of 0.5 to 5 μm.
Transparent resin such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, etc., inorganic fine particles that may be conductive, organic fine particles such as crosslinked or uncrosslinked polymer, etc. Those showing transparency in the layer are used. The use amount of the fine particles is generally 2 to 25 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the transparent resin.

As a specific example of the above-mentioned retardation film which is an optical film material, a film made of a suitable plastic such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate or polyamide is stretched. And a birefringent film obtained by the treatment. The retardation film can be formed by laminating two or more kinds of retardation films and controlling optical properties such as retardation.

The above-mentioned elliptically polarizing film or reflection type elliptically polarizing film as an optical film material is obtained by laminating a polarizing film or a reflection type polarizing film and a retardation film in an appropriate combination. Such an elliptically polarizing film or the like can also be formed by sequentially and separately laminating a (reflection type) polarizing film and a retardation film in a manufacturing process of a liquid crystal display device so as to form a combination. A polarizing film or the like has an advantage that it is excellent in quality stability, laminating workability, and the like, and can improve the manufacturing efficiency of a liquid crystal display device.

The layers forming an optical film such as a polarizing film, a retardation film, a protective film and a transparent protective layer are made of, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salts. Ultraviolet absorbing ability can be provided by a method of treating with an ultraviolet absorbent such as a system compound.

The adhesive layer provided on one side or both sides of the optical film material is made of an acrylic polymer having a functional group concentration of 5 × 1 × 10 ⁴ mol / g or less as a base polymer, and is bonded at 90 ° to the release side adherend. It is formed with a force of 600 g / 20 mm or less.

As described above, both the heat and humidity resistance and the optical function maintaining property are excellent, the cell warpage can be suppressed even when applied to a thin or large liquid crystal cell, and the peeling process by manual work at the time of bonding error or the like can be performed. An optical film that can be easily and efficiently formed can be obtained. The functional group concentration is 5 × 1
If it exceeds / 10 ⁴ mol / g, it is necessary to provide an adhesive layer having a high cohesive force in order to impart moisture and heat resistance for preventing foaming and peeling, and it is difficult to achieve characteristics other than moisture and heat resistance as described above. Becomes

That is, in the above, the prevention of foaming and peeling due to the heating and humidifying treatment is performed by setting the concentration of the functional group in the adhesive layer to be low. Such a design concept is that the foaming problem is that the moisture in the pressure-sensitive adhesive layer is vaporized and expanded at a high temperature over the cohesive force of the pressure-sensitive adhesive, and the bubbles are expanded to such an extent that the bubbles are visually recognized by deformation of the optical film. Peeling, especially peeling (floating) of the end portion, is based on the finding that the adhesive strength at the cell / adhesive layer interface is reduced due to moisture absorption.

Therefore, it can be seen that in order to prevent the foaming, it is effective to increase the cohesive force of the adhesive layer according to the conventional design concept. However, in this case, as described above, the improvement of the cohesive force causes a large stress to be generated in the optical film material due to a difference in thermal expansion or the like, thereby causing a decrease in optical characteristics. Of the optical film, especially the end portions are easily peeled off under the humidifying condition as described above, and it is not possible to achieve both moisture heat resistance and optical function retention.

In the above, the conventional design concept of changing the composition or adding a chemical to improve the adhesive strength is that the adhesive layer has a high hygroscopicity and a large decrease in the adhesive strength when humidified.
In this case, if the adhesive strength is set so as not to cause moisture-absorbing peeling in anticipation of a decrease in the adhesive strength due to moisture absorption, the adhesive strength will be high, which is difficult to peel off at the time of bonding error, etc. It is difficult to use.

On the other hand, in the present invention, the adhesive strength at the interface between the liquid crystal cell (optical film material) and the adhesive layer is reduced by using a low functional group concentration adhesive layer, and moisture absorption is suppressed. As a result, moisture absorption due to foaming is suppressed, the initial adhesive strength is maintained well, foaming and peeling are prevented, and a low adhesive strength that enables peeling at the time of bonding error or the like can be set. And optical function maintenance are compatible. Further, from the point of peeling of the optical film at the time of bonding error, etc., the adhesive force is preferably as low as possible within a range where peeling at the film edge does not occur, but the adhesive force is reduced due to the reduction of the water absorption of the adhesive layer. Due to the suppression effect, the adhesive force at normal time can be set low, which is advantageous for peeling.

In the present invention, the concentration of the functional group in the adhesive layer is set to 5 × 1/10 ⁴ mol / g or less as described above from the viewpoint of preventing foaming, peeling and deterioration of the optical characteristics. Is 3 × 1/10 ⁴ mol / g or less, especially 1
× 1/10 ⁴ mol / g or less. Functional group concentration 5 × 1
If it exceeds / 10 ⁴ mol / g, it becomes difficult to achieve both the adhesive strength required for preventing peeling at the end and the like and the adhesive strength required for peeling at the time of bonding error or the like.

On the other hand, the peeling adhesive force differs depending on the peeling conditions such as the speed and the angle, and it is preferable to set the adhesive force in consideration of the peeling work from the viewpoint of work efficiency and prevention of cell damage. 90 ° peeling adhesive force (peeling speed 100
(g / min, 25 ° C), the adhesive strength is 600g / 20mm or less, so the repeatability (fatigue) of the peeling process by hand, smooth workability, work efficiency and low labor burden, prevention of cell damage Excellent in properties. Preferred 90 degree peel adhesion is 50 to 500 g / 20 mm, especially 100 to 400 g.
g / 20 mm.

The pressure-sensitive adhesive layer can be formed of an acrylic pressure-sensitive adhesive having an acrylic polymer having a predetermined functional group concentration as a base polymer as described above. Such an acrylic pressure-sensitive adhesive can be preferably used because it is excellent in transparency, weather resistance, heat resistance and the like. As the acrylic polymer, one or two types of acrylates or methacrylates having a glass transition temperature of −10 ° C. or lower are used as monomers as main components that exhibit appropriate wettability and flexibility. Those using the above are exemplified.

Examples of the above-mentioned ester include, for example, n-butyl group, isobutyl group, isoamyl group and hexyl group, heptyl group and cyclohexyl group, 2-ethylhexyl group, isooctyl group and isononyl group from the viewpoint of lowering adhesive strength. An acrylate or a methacrylate having an organic group having 4 or more carbon atoms, especially an alkyl group having 4 to 24 carbon atoms, such as a thiol, lauryl group, dodecyl group, isomyristyl group, and octadecyl group can be preferably used.

The above-mentioned low adhesiveness is particularly prominent on a glass plate, and the reason is not clear, but the present inventors have found that:
It is thought that the ratio of ester groups having a large contribution to the adhesive force to the glass per unit volume is relatively decreased by increasing the number of carbon atoms. An acrylate or a methacrylate having an organic group having three or less carbon layers such as a methyl group, an ethyl group, and a propyl group can be used as a combined system.

The acrylic polymer may contain, as a copolymer component, a monomer for improving the cohesiveness or adhesiveness of the pressure-sensitive adhesive or for imparting crosslinking reactivity. There is no particular limitation on the copolymerization monomer,
Any material can be used as long as it can be copolymerized with the monomer constituting the main component. In such a case, the copolymer component having a functional group such as a carboxyl group, a hydroxyl group, an epoxy group, an amide group, an imide group, a sulfonic acid group, and a phosphoric acid group increases the functional group concentration. It can be used within a satisfactory range.

Examples of the functional group-containing copolymerizable monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, and carboxyl group-containing monomers such as itaconic acid, maleic acid and crotonic acid. 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate or 6-hydroxyhexyl (meth) acrylate, 8- (meth) acrylic acid
Hydroxyl group-containing monomers such as hydroxyoctyl and 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate, and glycidyl (meth) acrylate And epoxy group-containing monomers.

Amide monomers such as (meth) acrylamide and N-acryloylmorpholine, N-substituted (meth) acrylamide and N-vinylpyrrolidone, N-cyclohexylmaleimide and N-isopropylmaleimide;
Maleimide monomers such as N-laurylmaleimide and N-phenylmaleimide; N-methylitaconimide and N-methylitaconimide;
-Ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide and N-cyclohexyl itaconimide,
Itaconic imide monomers such as N-lauryl itaconimide, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide A succinimide monomer such as sulfonic acid group-containing monomer such as 2-acrylamido-2-methylpropanesulfonic acid;
Phosphoric acid group-containing monomers such as -hydroxyethylacryloyl phosphate are also exemplified as functional group-containing monomers for copolymerization.

A monomer having a functional group is often copolymerized because it is useful for intermolecular crosslinking via the functional group and an intermolecular crosslinking agent. In the pressure-sensitive adhesive layer according to the present invention, an appropriate amount can be used within a range satisfying a predetermined functional group concentration. In general, depending on the type of the above-mentioned main component monomer, the concentration of the functional group in the obtained copolymer is usually 4% by weight or less, especially 2% by weight or less, particularly 1% by weight or less. It can be a predetermined range.

It should be noted the while enabling crosslinking treatment through a functional group, preferred low concentration of the functional group from the viewpoint of such compatibility wet heat resistance and the optical functional maintainability, for example 1 × 1/10 ⁴ mol /
Those that efficiently function as a crosslinking reaction point even at a lower functional group concentration than the point of achieving a concentration of not more than g are preferably used. Incidentally, at the end of a relatively long methylene chain such as the above-mentioned 5-carboxypentyl acrylate, (meth) acrylic acid 4-hydroxybutyl and 6-hydroxyhexyl, 8-hydroxyoctyl, 10-hydroxydecyl and 12-hydroxylauryl. A monomer having a functional group has a high degree of freedom in the movement of the functional group in the copolymer, and is rich in crosslinking reactivity. A small amount of about 0.5% by weight of the copolymer can provide a sufficient crosslinking effect. Exerts almost no increase in the functional group concentration of the resulting copolymer.

Other copolymerizable monomers used for the purpose of controlling the cohesiveness and adhesiveness of the pressure-sensitive adhesive include, for example, vinyl monomers such as vinyl acetate and styrene, and divinyl monomers such as divinylbenzene. Monomer, diacrylate monomers such as 1,4-butyldiacrylate and 1,6-hexyldiacrylate, tetrahydrofurfuryl (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, (Meth) acrylates, acrylic acid-based monomers such as silicone (meth) acrylate, alkoxy group-containing monomers such as trimethoxysilylpropyl acrylate, and acid anhydride monomers such as maleic anhydride and itaconic anhydride And so on. Since the acid anhydride monomer may generate a carboxyl group by hydrolysis in the copolymer, it must be taken into consideration from the viewpoint of controlling the functional group concentration.

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

For the preparation of the acrylic polymer, for example, an appropriate system such as a solution polymerization system, an emulsion polymerization system, a bulk polymerization system or a suspension polymerization system is applied to one or a mixture of two or more monomers. You can do it. In the case of the bulk polymerization method, a polymerization method using ultraviolet irradiation can be preferably applied.
In this case, it is necessary to control the amount of the functional group-containing copolymerizing monomer used in order to achieve a predetermined functional group concentration of the acrylic polymer obtained as described above.

The acrylic polymer which can be preferably used in the present invention has a weight average molecular weight of 40 from the viewpoint of wet heat resistance and the like.
More than 10,000, especially 800,000 to 4 million, especially 10
10,000 to 3 million. In addition, by forming an adhesive layer having a weight average molecular weight in such a range, the optical film is cut into a predetermined size or the like, and when the punching or punching is performed, it is possible to prevent the adhesive layer from sticking out or contaminating a punching blade. Thus, it is possible to obtain an optical film having excellent practicability such as cutting workability and preservability.

In preparing the acrylic polymer,
If necessary, a polymerization initiator can be used. 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.

Also, 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-methylbutyronitrile),
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 photopolymerization initiators 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.

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

Examples of other polymerization initiators include potassium persulfate, ammonium persulfate, hydrogen peroxide and the like, or a redox initiator using them in combination with a reducing agent.

In the present invention, the pressure-sensitive adhesive layer may be subjected to a crosslinking treatment 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 the functional group in the base polymer involved in the intermolecular crosslinking, and the like.
There is no particular limitation. Therefore, any of the known materials can be used.

Examples of the intermolecular crosslinking agent include polyfunctional isocyanate-based crosslinking agents such as tolylene diisocyanate, trimethylolpropane tolylene diisocyanate, diphenylmethane triisocyanate, polyethylene glycol diglycidyl ether, diglycidyl ether, and trimethylolpropane triisocyanate. Examples include epoxy-based crosslinking agents such as glycidyl ether, melamine resin-based crosslinking agents, metal salt-based crosslinking agents, metal chelate-based crosslinking agents, and amino resin-based crosslinking agents.

The amount of the intermolecular crosslinking agent can be appropriately determined according to the content of the functional group in the base polymer. Generally, 0.005 to 20 parts by weight, preferably 0.01 to 15 parts by weight, particularly 0.1 to 10 parts by weight of the intermolecular crosslinking agent is used per 100 parts by weight of the base polymer. The elastic modulus of the pressure-sensitive adhesive layer, which is preferable in terms of heat resistance such as foam prevention and moisture resistance, is 1 in a tensile test at 90 ° C.
1 g / mm ² or more based on 000% modulus, especially 2
g / mm ² or more, especially 4 g / mm ² or more.

The adhesive layer may include, if necessary, a filler or a pigment made of natural or synthetic resin, glass fiber, glass beads, metal powder, other inorganic powder, or the like as long as the transparency is not impaired. Also, an appropriate additive such as a coloring agent or an antioxidant which may be added to the adhesive layer may be blended. In addition, an adhesive layer exhibiting light diffusing properties can be formed by incorporating fine particles. The cohesive force of the pressure-sensitive adhesive layer can be determined by a conventional method such as the composition and molecular weight of the polymer, the crosslinking method and the degree of crosslinking, and the addition of optional components.

The attachment of the adhesive layer to one or both sides of the optical film material can be performed by an appropriate method. For example,
For example, by dissolving or dispersing the pressure-sensitive adhesive in a solvent consisting of an appropriate solvent alone or a mixture such as toluene and ethyl acetate,
A pressure-sensitive adhesive liquid of about 0 to 40% by weight is prepared, and the liquid is directly applied on an optical film material by an appropriate developing method such as a casting method or a coating method, or a pressure-sensitive adhesive layer is formed on a separator according to the above. A method of forming and transferring it onto an optical film material is exemplified.

The adhesive layer may be provided as a different layer on the superposed layer or on the front and back of the material, and its thickness may be appropriately determined according to the purpose of use. Although the thickness may be more than 1 mm, it is generally 1 to 5 in terms of optical characteristics and workability of attachment.
It has a thickness of 00 μm, especially 5 to 200 μm, especially 10 to 100 μm. When the adhesive layer is exposed on the surface, it is preferable to protect the surface with a separator or the like until it is practically used.

In forming the optical film of the present invention, the lamination of various film materials such as a protective film includes
It is preferable to use a material that conforms to the pressure-sensitive adhesive layer attached to the above-described optical film material from the viewpoints of wet heat resistance, optical function maintenance, and the like.

The optical film of the present invention can be used for appropriate applications such as formation of a liquid crystal display. The formation of the liquid crystal display device can be performed by attaching the optical film according to the present invention to one 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.

FIGS. 3 and 4 show examples of the arrangement of the optical films in the liquid crystal display device. Reference numeral 5 denotes a liquid crystal cell, and other symbols are the same as described above. The device illustrated in FIG. 3 is of a reflection type in which a reflection layer 23 is provided on a polarizing film 21, and the reflection layer is disposed outside one side of the liquid crystal cell.

The device illustrated in FIG. 4 uses a 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 can be 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 the present invention to an appropriate type of liquid crystal cell such as a simple matrix driving type represented by a twisted nematic type or a super twisted nematic type.

[0058]

【Example】

Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer and a stirrer, 99.7 parts of isooctyl acrylate (parts by weight,
The same applies hereinafter), 6-hydroxyhexyl acrylate 0.
3 parts and 2,2′-azobisisobutyronitrile 0.3
Together with ethyl acetate and added at 60 ° C. under a stream of nitrogen gas.
After reacting for hours, ethyl acetate was added to the reaction solution,
An acrylic polymer solution having a solid content of 30% by weight was obtained, and 0.1 part of trimethylolpropane tolylene diisocyanate and 0.1 part of γ-glycidoxypropylmethoxysilane were mixed with 100 parts of the solid content. An acrylic adhesive was obtained. The weight average molecular weight of the acrylic polymer was 1.94 million in terms of polystyrene by gel permeation chromatography (the same applies hereinafter), and the functional group concentration was 0.17 × 1/10 ⁴ mol / g. .

Next, the acrylic pressure-sensitive adhesive was applied to a separator obtained by treating a polyester film with a release agent, and heated at 150 ° C. for 5 minutes to form a 23 μm-thick pressure-sensitive adhesive layer. Film (Nitto Denko Corporation, NPF
-G1225DUNAGS1) to give an optical film.

Example 2 99.8 parts of butyl acrylate and 0.2 part of 4-hydroxybutyl acrylate were used as monomers having a weight average molecular weight of 1.7 million and a functional group concentration of 0.14 × 1/10 ⁴ mol / g. An acrylic polymer was obtained, and 0.3 parts of trimethylolpropane tolylene diisocyanate was added thereto to prepare an acrylic pressure-sensitive adhesive, and an optical film was obtained in the same manner as in Example 1 except that an adhesive layer was formed using the pressure-sensitive adhesive. Was.

Example 3 Using 59.8 parts of isononyl acrylate, 39.8 parts of butyl acrylate and 0.4 part of 5-carboxypentyl acrylate as monomers, a weight average molecular weight of 1.5 million was obtained.
An acrylic polymer having a functional group concentration of 0.23 × 1/10 ⁴ mol / g was obtained, and 0.4 part of trimethylolpropane triglycidyl ale was added thereto to prepare an acrylic pressure-sensitive adhesive. An optical film was obtained in the same manner as in Example 1 except that was formed.

Comparative Example 1 95 parts of butyl acrylate and 5 parts of acrylic acid were used as monomers, and the weight average molecular weight was 1.45 million and the functional group concentration was 6.
Acrylic pressure-sensitive adhesive was prepared by adding 9 × 1/10 ⁴ mol / g of an acrylic polymer, and adding 0.8 parts of trimethylolpropane tolylene diisocyanate thereto, to form a pressure-sensitive adhesive layer. An optical film was obtained according to Example 1.

COMPARATIVE EXAMPLE 2 95 parts of butyl acrylate, 4.8 parts of acrylic acid and 0.2 part of 2-hydroxyethyl acrylate were used as monomers, and had a weight average molecular weight of 1.55 million and a functional group concentration of 6.8 × 1.
/ 10 ⁴ mol / g of an acrylic polymer, and trimethylolpropane tolylene diisocyanate was added to 1.2.
An optical film was obtained in the same manner as in Example 1, except that an acrylic pressure-sensitive adhesive was prepared and a pressure-sensitive adhesive layer was formed using the same.

Evaluation Test Peel Adhesion A pressure-sensitive adhesive layer having a thickness of 50 μm was applied to a thickness of 2 according to the examples and comparative examples.
Formed on a 5 μm polyester film, cut into a width of 20 mm, pressure-bonded to a glass plate by reciprocating a 2 kg rubber roller once, and left in an autoclave at 50 ° C. and 5 atm for 30 minutes to mature the bonded state. After that, the 90 ° peel adhesive strength (peel speed: 100 mm / min, 25 ° C.) was examined.

Peelability The 194 mm × 250 mm size optical film obtained in each of Examples and Comparative Examples was bonded to a 1.1 mm-thick glass plate via the adhesive layer, and then the optical film was peeled off to perform the work at that time. Sex was determined according to the following criteria. Good: When there was no particular problem in the peeling work. Bad: When a little stronger resistance was found in the peeling work. Inappropriate: When there was a remarkable resistance to the peeling work or when adhesive residue was observed on the glass plate.

Heat resistance A 194 mm × 250 mm size optical film obtained in each of the examples and comparative examples was placed on a 1.1 mm thick glass plate (each side 10 mm larger than the optical film through the adhesive layer). ), Left in an autoclave at 50 ° C. and 5 atm for 30 minutes to mature the bonded state, and then heated in an atmosphere at 90 ° C. for 1000 hours to visually observe the presence or absence of foaming and peeling. Was determined.

(1) Foaming: Good: No bubbles with a diameter of 20 μm or more are found. Bad: Bubbles with a diameter of 20 to 50 μm are found. Unsuitable: Bubbles with a diameter of 50 μm or more that affect visibility are found. (2) Peeling Good: No peeling is observed Bad: Peeling that does not affect visibility is unsuitable: Peeling that affects visibility is observed

Moisture resistance The presence or absence of foaming and peeling was determined in accordance with the above-mentioned heat resistance, except that the heating conditions were 1000 hours in an atmosphere of 60 ° C. and 95% RH.

Optical Property Maintaining Property The optical film of 194 mm × 250 mm size obtained in each of Examples and Comparative Examples was bonded to both sides of a 1.1 mm thick glass plate via its adhesive layer so that the absorption axes were perpendicular to each other. Then 50
After leaving it in an autoclave at 5 ° C. and 5 atm for 30 minutes to ripen the adhesive state, it was heated in an atmosphere at 90 ° C. for 1000 hours, and examined for a decrease in the degree of polarization affecting visibility on a backlight. Judgment was made based on the following criteria. Good: When there is no decrease in the degree of polarization that affects visibility as a whole Poor: When there is a slight decrease in the degree of polarization that affects visibility at the edges Unsuitable: Decrease in the degree of polarization that affects visibility Is approved

The above results are shown in Tables 1 and 2.

[Table 1]

[0071]

[Table 2]

As shown in Tables 1 and 2, after the optical film was adhered to the liquid crystal cell via the adhesive layer, the film could be easily peeled off without damaging the cell, and showed a stable adhesive force to the liquid crystal cell and was heated and humidified. It can be seen that foaming, peeling, and deterioration of optical characteristics do not occur even after the treatment.

[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 cross-sectional view of an example of a liquid crystal display device.

FIG. 4 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

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location G02F 1/1335 510 G02F 1/1335 510 (72) Inventor Yoshikazu Tanaka 1-chome Shimohozumi, Ibaraki-shi, Osaka 1-2 Nitto Denko Corporation (72) Kazuhiko Miyauchi 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nippon Denko Corporation (72) Naoshi Yamaoka 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Corporation

Claims (4)

[Claims] An acrylic film having a functional group concentration of 5 × 1 × 10 ⁴ mol / g or less is used as a base polymer on one or both sides of an optical film material, and the surface of the optical film material is 90% to the release side adherend.
An optical film having a pressure-sensitive adhesive layer having a peel strength of 600 g / 20 mm or less. 2. The optical film material according to claim 1, wherein the functional group is one or more of a carboxyl group, a hydroxyl group, an epoxy group, an amide group, an imide group, a sulfonic acid group or a phosphoric acid group. And an optical film which is a reflective polarizing film or a retardation film. 3. An elliptically polarizing film according to claim 1 or 2, wherein the optical film material is formed by laminating a polarizing film and a retardation film via the adhesive layer according to claim 1 or 2.
Alternatively, an optical film which is a reflective elliptically polarizing film obtained by laminating a reflective polarizing film and a retardation 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.