JP2003329838A - Pressure-sensitive adhesive optical film, pressure- sensitive adhesive composition for optical film and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive optical film which has a pressure-sensitive adhesive layer to stick the optical film to a glass substrate of a liquid crystal panel or the like, which is excellent in a rework property and durability and which hardly leaves a glue on the panel surface. <P>SOLUTION: The pressure-sensitive adhesive optical film has a pressure- sensitive adhesive layer deposited on one surface of an optical film. The pressure-sensitive adhesive layer is made of a crosslinked product of a composition containing an acrylic polymer having (A) alkyl(meth)acrylate, (B) N- substituted (meth)acrylamide and/or N,N-substituted (meth)acrylamide by 1 to 12 wt.%, and (C) a hydroxyl group-containing (meth)acrylic monomer by 0.01 to 3 wt.% as the polymerization components and having no carboxyl group. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive optical film having an adhesive layer laminated on one surface of an optical film. Moreover, it is related with the adhesive composition for optical films used for adhesive optical films. Furthermore, a liquid crystal display device, an organic EL display device, and a P using the adhesive optical film
The present invention relates to an image display device such as a DP. Examples of the optical film include a polarizing film or a film obtained by laminating a retardation film, an optical compensation film, a brightness enhancement film, an antiglare sheet and the like on the polarizing film.

[0002]

2. Description of the Related Art In a liquid crystal display, it is essential to dispose polarizing elements on both sides of a glass substrate forming the outermost surface of the liquid crystal panel because of its image forming system. It is attached to the surface. In addition to the polarizing film on the outermost surface of the liquid crystal panel,
Various optical elements have been used to improve the display quality of a display. For example, a retardation film for preventing coloration, a viewing angle widening film for improving the viewing angle of a liquid crystal display, and a brightness enhancement film for enhancing the contrast of the display are used. These films are collectively called optical films.

When the optical film is attached to the outermost surface of a liquid crystal panel, an adhesive is usually used. In addition, since the optical film can be instantly fixed on the outermost surface of the liquid crystal panel, and since it has advantages such as not requiring a drying step to fix the optical film, the pressure-sensitive adhesive is preliminarily attached to one surface of the optical film. Is provided as.
That is, an adhesive optical film is generally used to attach the optical film to the outermost surface of the liquid crystal panel.

The adhesive optical film is attached to the outermost surface of the liquid crystal panel. At this time, if the bonding position is wrong or foreign matter is caught in the bonding surface, the optical film is peeled from the outermost surface of the liquid crystal panel and reused.
However, if peeling is heavy when peeling the optical film, the liquid crystal panel may be damaged such as a cell gap, or adhesive residue may be left on the liquid crystal panel surface. Also,
Usually, the adhesiveness of the adhesive layer of the adhesive optical film bonded to the liquid crystal panel increases with time. In addition, the panel manufacturer has a condition that a temperature is applied in each process, and the liquid crystal panel to which the optical film is attached is not always placed at a constant temperature place. Therefore, the adhesive optical film can be easily peeled off and re-bonded (rework) even after passing through each process and a long time after being bonded to the liquid crystal panel. Is required.

On the other hand, the pressure-sensitive adhesive type optical film bonded to the outermost surface of the liquid crystal panel is required to have durability so as not to be foamed or peeled off even in a use condition under heating and humidifying conditions. In this way, the adhesive optical film has durability and
It is required to satisfy the contradictory characteristics of performance (reworkability) such as easy peeling.

Conventionally, there is a method of reducing the adhesive area of the adhesive layer as a means for improving the reworkability of the adhesive optical film. As a means for this, for example, there is a method of reducing the adhesion area by forming a pressure-sensitive adhesive layer such that a pressure-sensitive adhesive layer and a non-pressure-sensitive layer are alternately applied in stripes. When the adhesion area is reduced in this way, reworking becomes good. However, the decrease in the adhesive area of the adhesive layer is disadvantageous in terms of durability related to foaming and peeling during heating and humidification. Therefore, if the reworkability is improved by the above method, peeling occurs during heating and humidification. This foaming and peeling,
When heated and humidified, the optical film deforms such as expansion and contraction,
It is considered that the stress generated by the deformation occurs because it acts on the interface between the adhesive and the liquid crystal cell.

JP-A-6-108025 discloses an adhesive containing a (meth) acrylic monomer containing an amino group and / or an amide group as a copolymerization component.

Further, in JP-A-9-59580,
Contains an acrylic acid-based alkyl ester, a polymerizable monomer having a carboxyl group in the molecule, a polymerizable monomer having a hydroxyl group in the molecule, and an acrylic resin copolymer whose essential component is a polymerizable monomer having an amide group in the molecule It is published about adhesives.

Further, Japanese Patent Application Laid-Open No. 9-176603 discloses a pressure-sensitive adhesive composed of a copolymer whose base polymer contains an acrylamide derivative as a monomer component.

However, these adhesives have a very strong adhesive force to the liquid crystal panel surface and may damage the liquid crystal panel at the time of peeling.

[0011]

SUMMARY OF THE INVENTION The present invention is a pressure-sensitive adhesive optical film provided with a pressure-sensitive adhesive layer for bonding the optical film to a glass substrate such as a liquid crystal panel, which has both reworkability and durability. It is an object of the present invention to provide a material that is excellent in adhesiveness and is less likely to cause adhesive residue on the panel surface. Moreover, it aims at providing the adhesive composition for optical films used for the said adhesive optical film, and also providing the image display apparatus using the said adhesive optical film.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and found that the adhesive optical film described below can achieve the above object, and completed the present invention.

That is, the present invention is a pressure-sensitive adhesive optical film in which a pressure-sensitive adhesive layer is laminated on one surface of an optical film, wherein the pressure-sensitive adhesive layer comprises (A) alkyl (meth) acrylate and (B) N-. 1-12% by weight of substituted (meth) acrylamide and / or N, N-substituted (meth) acrylamide,
(C) Hydroxyl group-containing (meth) acrylic monomer 0.01
The present invention relates to a pressure-sensitive adhesive optical film, which is formed by a cross-linked product of a composition containing a (meth) acrylic polymer having no carboxyl group and containing 3% by weight as a polymerization component.

In the pressure-sensitive adhesive optical film of the present invention, the pressure-sensitive adhesive layer has a carboxyl containing an alkyl (meth) acrylate, the specific (meth) acrylamide, and the specific (meth) acrylic monomer as polymerization components. Adhesion that is formed from a crosslinked product of a composition containing a (meth) acrylic polymer that does not have a group, and uses the pressure-sensitive adhesive layer so that the adhesive does not peel off from the adherend when fixed to the adherend. It has a force, and the adhesive force hardly increases with time, and it can be easily peeled without contaminating the adherend when re-peeling from the adherend.

In the present invention, said (B) is N, N
-Substituted (meth) acrylamide is preferably 1 to 12% by weight.

The N-substituent of N-substituted (meth) acrylamide and the N, N-substituent of N, N-substituted (meth) acrylamide are preferably alkyl groups. In the pressure-sensitive adhesive optical film of the present invention, the pressure-sensitive adhesive layer has a room temperature atmosphere of 25 ° C. with respect to alkali-free glass.
The adhesive force based on 90 ° peeling at a speed of 00 mm / min is preferably 10 N / 25 mm or less. When the adhesive force under the above conditions is 10 N / 25 mm or less,
The adhesive force (peeling force) for peeling is small, peeling can be easily performed, and reworkability is good.

The present invention also provides (A) alkyl (meth).
Acrylate, (B) N-substituted (meth) acrylamide and / or N, N-substituted (meth) acrylamide 1-1
2% by weight, (C) a hydroxyl group-containing (meth) acrylic monomer (0.01 to 3% by weight) as a polymerization component and having no carboxyl group (meth) acrylic polymer,
And a pressure-sensitive adhesive composition for an optical film, which contains a polyfunctional compound. The polyfunctional compound is preferably an aliphatic isocyanate cross-linking agent.

Further, the present invention relates to an image display device using the pressure-sensitive adhesive optical film. The pressure-sensitive adhesive optical film of the present invention is used by being attached to a glass substrate such as a liquid crystal panel according to the usage of various image display devices such as liquid crystal display devices.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The pressure-sensitive adhesive layer of the pressure-sensitive adhesive type optical film of the present invention comprises (A) alkyl (meth) acrylate,
(B) N-substituted (meth) acrylamide and / or N,
1 to 12% by weight of N-substituted (meth) acrylamide,
(C) Hydroxyl group-containing (meth) acrylic monomer 0.01
It is formed by a crosslinked product of a composition containing a (meth) acrylic polymer having no carboxyl group and containing 3% by weight as a polymerization component. The acrylic polymer does not contain a carboxyl group-containing monomer component.
When the acrylic polymer contains a carboxyl group-containing monomer component, the adhesive strength becomes strong and the reworkability becomes poor. In addition, adhesive residue is likely to occur.

The (meth) acrylic polymer is
The monomer unit of (A) alkyl (meth) acrylate has a main skeleton. In addition, the (meth) acrylate of (A) alkyl (meth) acrylate means an acrylate and / or a methacrylate, and the (meth) of the present invention has the same meaning. Examples of the alkyl (meth) acrylate include alkyl acrylates having about 2 to 12 carbon atoms and alkyl methacrylates having about 4 to 12 carbon atoms, and specifically, ethyl acrylate, propyl acrylate, butyl (meth) acrylate. , 2-
Examples thereof include ethylhexyl (meth) acrylate and isooctyl (meth) acrylate, which can be used alone or in combination. Among these, alkyl acrylates having 2 to 8 carbon atoms and alkyl methacrylates having 4 to 8 carbon atoms are preferable.

N of the N-substituted (meth) acrylamide
The substituent is not particularly limited as long as it is a commonly used substituent as long as the performance of the pressure-sensitive adhesive is not impaired, but in the present invention, an alkyl group is particularly preferable. For example, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide,
N, N-dimethylaminopropyl (meth) acrylamide etc. are mentioned.

Further, in the present invention, the N-substituent is preferably an alkyl group containing no amino group.
When the N-substituent is an alkyl group containing no amino group, reworkability is further improved.

The N, N-substituent of the N, N-substituted (meth) acrylamide is also preferably an alkyl group as described above. For example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide,
N, N-dipropyl (meth) acrylamide, (meth)
Acryloyl morpholine etc. are mentioned.

For the same reason as above, the N, N-substituent is preferably an alkyl group containing no amino group.

The amount of N-substituted (meth) acrylamide and / or N, N-substituted (meth) acrylamide used is 1 to
It is 12% by weight, and particularly preferably 2 to 7% by weight.

In the present invention, it is particularly preferable to use N, N-substituted (meth) acrylamide.

Examples of the (C) hydroxyl group-containing (meth) acrylic monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy. Hexyl (meth) acrylate and the like can be mentioned.

The amount of the hydroxyl group-containing (meth) acrylic monomer used is 0.01 to 3% by weight, particularly 0.05 to
It is preferably 0.3% by weight.

Further, a monomer unit such as vinyl acetate or styrene can be introduced into the (meth) acrylic polymer as long as the performance of the pressure-sensitive adhesive is not impaired.

The weight average molecular weight of the (meth) acrylic polymer is not particularly limited as long as it does not impair the performance of the pressure-sensitive adhesive, but it is preferably about 700 to 2,000,000.

The (meth) acrylic polymer can be produced by various known methods. For example, a radical polymerization method such as a bulk polymerization method, a solution polymerization method or a suspension polymerization method can be appropriately selected. As the radical polymerization initiator, various known azo and peroxide type initiators can be used, and the reaction temperature is usually about 50 to 85 ° C. and the reaction time is about 1 to 8 hours. Of the above-mentioned production methods, the solution polymerization method is preferable, and a polar solvent such as ethyl acetate or toluene is generally used as a solvent for the (meth) acrylic polymer. The solution concentration is usually about 20 to 80% by weight. The Tg of the (meth) acrylic polymer is preferably -50 to -20 ° C.

The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains a polyfunctional compound. Examples of the polyfunctional compound include organic crosslinking agents and polyfunctional metal chelates. Examples of the organic crosslinking agent include epoxy crosslinking agents, isocyanate crosslinking agents, imine crosslinking agents and the like.
The polyfunctional metal chelate is one in which a polyvalent metal is covalently or coordinately bonded to an organic compound. As the polyvalent metal atom, Al, Cr, Zr, Co, Cu, Fe, N
i, V, Zn, In, Ca, Mg, Mn, Y, Ce, S
Examples thereof include r, Ba, Mo, La, Sn and Ti. Examples of the atom in the organic compound that forms a covalent bond or a coordinate bond include an oxygen atom, and examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound.

In the present invention, the polyfunctional compound is preferably an aliphatic isocyanate cross-linking agent. By using an aliphatic isocyanate cross-linking agent, it is possible to increase the anchoring property to the glass substrate, further accelerate the crosslinking reaction, and suppress the reaction between the residual isocyanate group and the hydroxyl group on the glass substrate surface. You can

Examples of the aliphatic isocyanate include, for example,
Hexamethylene diisocyanate, dimer acid diisocyanate, norbornene diisocyanate, Takenate D110N (Mitsui Takeda Chemical Co., Ltd.), Coronate L
(Japan Polyurethane Industry Co., Ltd.) and the like.

The amount of the polyfunctional compound used is not particularly limited, but is usually preferably about 0.01 to 6% by weight, and more preferably about 0.1 to 3% by weight.

The degree of crosslinking of the adhesive layer is 20 to 80 in terms of gel fraction.
%, More preferably 30 to 60%. The gel fraction is calculated by the following formula from the initial weight and the weight after immersion drying when the pressure-sensitive adhesive layer is immersed in ethyl acetate at 25 ° C for 7 days.

Gel fraction = {(weight after immersion drying) / (initial weight)} × 100 (%) Further, the pressure-sensitive adhesive composition may contain a tackifier, a plasticizer, a glass fiber, if necessary. A filler such as glass beads, metal powder or other inorganic powder, a pigment, a colorant, an antioxidant, an ultraviolet absorber, etc., and various additives are appropriately used without departing from the object of the present invention. You can also
Particularly, it is preferable to use a silane coupling agent in order to improve durability during humidification. Further, it may be a pressure-sensitive adhesive layer containing fine particles and exhibiting light diffusivity.

In the pressure-sensitive adhesive optical film of the present invention, as shown in FIG. 1, one surface of the optical film 1 is provided with a pressure-sensitive adhesive layer 2 for sticking to a liquid crystal panel or the like. Further, a release sheet 3 can be provided on the pressure-sensitive adhesive layer 2.

As the optical film 1, one used for forming a liquid crystal display device or the like is used, and the kind thereof is not particularly limited. For example, the optical film may be a polarizing film (polarizing plate). A polarizing film having a transparent protective film on one side or both sides of a polarizer is generally used.

The polarizer is not particularly limited and various kinds can be used. Examples of the polarizer 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 a dichroic dye such as iodine or a dichroic dye. Examples include polyene oriented films, such as those obtained by adsorbing a volatile substance and uniaxially stretched, polyvinyl alcohol dehydration products, polyvinyl chloride dehydrochlorination products, and the like. Among these, a polarizer made of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching is produced by, for example, immersing polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and stretching it to 3 to 7 times its original length. You can If necessary, it can be immersed in an aqueous solution of potassium iodide, which may contain boric acid, zinc sulfate, zinc chloride or the like. If necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, it is possible to wash the stains and anti-blocking agents on the surface of the polyvinyl alcohol-based film, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing is also obtained. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. It can be stretched in an aqueous solution of boric acid or potassium iodide, or in a water bath.

As a material for forming the transparent protective film provided on one side or both sides of the above-mentioned polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like is preferable. For example, polyester-based polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose, acrylic-based polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Examples thereof include a polymer and a polycarbonate polymer.
Further, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers. , Polyethersulfone polymer, polyetheretherketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer,
An arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, a blend of the above polymers, and the like are also examples of the polymer forming the transparent protective film. The transparent protective film can also be formed as a cured layer of an acrylic, urethane-based, acrylic urethane-based, epoxy-based, silicone-based, etc. thermosetting or ultraviolet curable resin. Of these, cellulosic polymers are preferred. The thickness of the transparent protective film is not particularly limited, but is generally 500 μm or less,
1 to 300 μm is preferable. In particular, the thickness is preferably 5 to 200 μm.

The surface of the transparent protective film on which the polarizer is not adhered (the surface on which the coating layer is not provided) has been subjected to a treatment for the purpose of hard coat layer, antireflection treatment, sticking prevention, diffusion or antiglare. May be

The hard coat treatment is carried out for the purpose of preventing scratches on the surface of the polarizing plate. For example, a hardened film excellent in hardness and sliding characteristics made of an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the transparent protective film.
The antireflection treatment is carried out for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to conventional methods. Further, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer.

The anti-glare treatment is carried out for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visual recognition of the light transmitted through the polarizing plate. For example, a sand blasting method or an embossing method is used. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a surface-rendering method or a method of blending transparent fine particles. The fine particles to be contained in the formation of the surface fine uneven structure are, for example, conductive particles made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles and organic fine particles made of a crosslinked or uncrosslinked polymer are used. When forming the surface fine uneven structure, the amount of the fine particles used is generally about 2 to 50 parts by weight based on 100 parts by weight of the transparent resin forming the surface fine uneven structure.
25 parts by weight is preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle enlarging function) for diffusing the light transmitted through the polarizing plate and enlarging the viewing angle.

The antireflection layer, the sticking prevention layer, the diffusion layer, the antiglare layer and the like can be provided on the transparent protective film itself, or as an optical layer separately from the transparent protective film. it can.

An isocyanate adhesive, a polyvinyl alcohol adhesive, a gelatin adhesive, a vinyl latex adhesive, an aqueous polyester, or the like is used for the adhesion treatment between the polarizer and the transparent protective film.

The optical film of the present invention comprises:
In practical use, other optical layers can be laminated and used. Although the optical layer is not particularly limited, for example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as 1/2 or 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on a polarizing plate, an elliptically polarizing plate or a circular polarizing plate in which a retardation plate is further laminated on a polarizing plate, a polarizing plate A wide viewing angle polarizing plate in which a viewing angle compensation film is further laminated on the plate, or a polarizing plate in which a brightness improving film is further laminated on the polarizing plate is preferable.

The reflective polarizing plate is a polarizing plate provided with a reflective layer, and is for forming a liquid crystal display device of the type which reflects incident light from the viewing side (display side) to display. Further, there is an advantage that it is possible to omit the incorporation of a light source such as a backlight and to easily reduce the thickness of the liquid crystal display device. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like, if necessary.

Specific examples of the reflection type polarizing plate include a transparent protective film which is mat-treated if necessary, and one side of which is provided with a foil or a vapor deposition film made of a reflective metal such as aluminum to form a reflective layer. can give. Further, by incorporating fine particles into the transparent protective film to form a surface fine uneven structure,
There is also one having a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has the advantage that diffused incident light is diffused to prevent directivity and glare, and uneven brightness can be suppressed. Further, the transparent protective film containing fine particles also has an advantage that incident light and reflected light thereof are diffused when they pass 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 protective film is formed by, for example, a vacuum deposition method, an ion plating method,
It can be performed by a method of directly attaching a metal to the surface of the transparent protective layer by an appropriate method such as a vapor deposition method such as a sputtering method or a plating method.

The reflection plate may be used as a reflection sheet in which a reflection layer is provided on an appropriate film according to the transparent film, instead of the method of directly applying to the transparent protective film of the polarizing plate. Since the reflective layer is usually made of a metal, the use form in which the reflective surface is covered with a transparent protective film, a polarizing plate, or the like prevents the reduction of the reflectance due to oxidation, and thus the long-lasting initial reflectance. It is more preferable from the viewpoint of avoiding the additional provision of the protective layer.

The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror which reflects and transmits light in the reflective layer. The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when the liquid crystal display device is used in a relatively bright atmosphere,
An image is displayed by reflecting incident light from the viewing side (display side), and in a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built into the back side of the semi-transmissive polarizing plate. It is possible to form a liquid crystal display device of the type that displays That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called ¼ wavelength plate (also called a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also called a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device, and is used for black and white display without the coloring. Used effectively. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed obliquely. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection.

Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. Although the thickness of the retardation plate is not particularly limited, it is generally about 20 to 150 μm.

Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate and poly. Ether sulfone, polyphenylene sulfide, polyphenylene oxide,
Examples thereof include polyallyl sulfone, polyvinyl alcohol, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulosic polymers, and various binary and ternary copolymers, graft copolymers, blends thereof, and the like. These polymer materials become oriented materials (stretched film) by stretching.

As the liquid crystalline polymer, for example, various kinds of main chain type or side chain type in which a conjugated linear atomic group (mesogen) for imparting liquid crystal orientation is introduced into the main chain or side chain of the polymer And so on. Specific examples of the main chain type liquid crystalline polymer include a structure in which a mesogenic group is bonded by a spacer portion that imparts flexibility, such as a nematic oriented polyester liquid crystalline polymer, a discotic polymer or a cholesteric polymer. . Specific examples of the side chain type liquid crystalline polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment imparting paraffin is provided through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogen moiety composed of a substituted cyclic compound unit. These liquid crystalline polymers are prepared by, for example, rubbing the surface of a thin film of polyimide or polyvinyl alcohol formed on a glass plate, or obliquely vapor-depositing silicon oxide to form a solution of the liquid crystalline polymer on the treated surface. It is performed by developing and heat treating.

The retardation plate may be one having an appropriate retardation according to the purpose of use, such as various wavelength plates or one for the purpose of compensating the viewing angle or the like due to birefringence of the liquid crystal layer. It may be one in which at least one type of retardation plate is laminated to control optical characteristics such as retardation.

The elliptically polarizing plate and the reflection type elliptically polarizing plate are obtained by laminating the polarizing plate or the reflection type polarizing plate and the retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can be formed by sequentially stacking them separately in the manufacturing process of a liquid crystal display device so as to form a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate is excellent in stability of quality, workability of lamination, and the like, and has an advantage that manufacturing efficiency of a liquid crystal display device can be improved.

The viewing angle compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction, not perpendicular to the screen. Such a viewing angle compensating retardation plate includes, for example, a retardation film, an orientation film of a liquid crystal polymer or the like, or a transparent substrate on which an orientation layer of a liquid crystal polymer or the like is supported. The ordinary retardation film is a birefringent polymer film uniaxially stretched in the plane direction, whereas the retardation plate used as the viewing angle compensation film is biaxially stretched in the plane direction. A polymer film having birefringence, or a bidirectionally stretched film such as a polymer or a tilt-oriented film having a birefringence in which the refractive index in the thickness direction stretched uniaxially in the plane direction and also stretched in the thickness direction is controlled. Used. Examples of the tilted oriented film include those obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to stretching treatment and / or shrinking treatment under the action of the shrinkage force caused by heating, and those obtained by obliquely orienting a liquid crystal polymer. Can be mentioned. The raw material polymer of the retardation plate is the same as the polymer explained in the previous retardation plate, which prevents coloration due to the change of the viewing angle due to the phase difference due to the liquid crystal cell and enlarges the viewing angle for good viewing. An appropriate one can be used for the purpose such as.

Further, from the viewpoint of achieving a wide viewing angle with good visibility, an optically anisotropic layer comprising an alignment layer of a liquid crystal polymer, particularly an inclined alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A compensation retardation plate can be preferably used.

The polarizing plate in which the polarizing plate and the brightness enhancement film are bonded together is usually used by being provided on the back side of the liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from a backlight of a liquid crystal display device or the back side, and transmits other light. A polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter and obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. It The light reflected by the surface of the brightness enhancement film is inverted through a reflection layer or the like provided on the rear side of the brightness enhancement film to be re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in a predetermined polarization state to achieve brightness. The brightness can be improved by increasing the amount of light transmitted through the improvement film and by supplying polarized light that is difficult to be absorbed by the polarizer to increase the amount of light that can be used for liquid crystal display image display and the like. That is,
When light is input from the back side of the liquid crystal cell through a polarizer without using a brightness enhancement film, almost all light with a polarization direction that does not match the polarization axis of the polarizer is reflected by the polarizer. It is absorbed and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display and the like is reduced accordingly, and the image becomes dark. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and then inverted through a reflection layer or the like provided behind it. The light-increasing film transmits only the polarized light whose polarization direction is such that the light reflected and inverted between the two can pass through the polarizer. Since the light is supplied to the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

A diffusing plate may be provided between the brightness enhancement film and the reflective layer or the like. The light in the polarization state reflected by the brightness enhancement film goes to the reflection layer and the like, but the installed diffusion plate uniformly diffuses the light passing therethrough, and at the same time, cancels the polarization state and becomes a non-polarization state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the light in the natural light state, is repeatedly directed to the reflection layer and the like, reflected through the reflection layer and the like, again passes through the diffuser plate, and is incident again on the brightness enhancement film. Thus, between the brightness enhancement film and the reflective layer, while maintaining the brightness of the display screen by providing a diffuser that returns the polarized light to the original natural light state, at the same time, reduce the unevenness of the brightness of the display screen, It is possible to provide a uniform and bright screen. It is considered that by providing such a diffusion plate, the number of repetitions of reflection of the first incident light is moderately increased, and it is possible to provide a uniform bright display screen in combination with the diffusion function of the diffusion plate.

As the above-mentioned brightness enhancement film, for example, a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies is transmitted through linearly polarized light having a predetermined polarization axis and other light is reflected. Those that exhibit the characteristics of, such as an oriented film of a cholesteric liquid crystal polymer or an oriented liquid crystal layer supported on a film substrate, reflect either left-handed or right-handed circularly polarized light and transmit other light. Appropriate materials such as those exhibiting characteristics can be used.

Therefore, in the brightness enhancement film of the type which transmits the linearly polarized light of the above-mentioned predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned to suppress the absorption loss by the polarizing plate. It can be efficiently transmitted. On the other hand, in the case of a type of brightness enhancement film that drops circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on the polarizer, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. By using a ¼ wavelength plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

The retardation plate functioning as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer functioning as a quarter-wave plate and another retardation film for light color light having a wavelength of 550 nm. It can be obtained by a method of superposing a retardation layer exhibiting characteristics, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one layer or two or more retardation layers.

As for the cholesteric liquid crystal layer,
Two layers or three layers with different reflection wavelengths
By arranging the layers so as to overlap each other, it is possible to obtain an element that reflects circularly polarized light in a wide wavelength range such as a visible light region, and based on that, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-mentioned polarization separation type polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above reflective polarizing plate or semi-transmissive polarizing plate is combined with a retardation plate.

The optical film obtained by laminating the optical layer on a polarizing plate can be formed by a method of laminating sequentially in the manufacturing process of a liquid crystal display device or the like. Has an advantage that it is excellent in quality stability and assembling work and can improve the manufacturing process of a liquid crystal display device or the like. Appropriate adhesion means such as an adhesive layer may be used for lamination. When the above-mentioned polarizing plate and other optical layers are adhered, their optical axes can be arranged at appropriate angles depending on the intended retardation characteristics and the like.

The method of forming the pressure-sensitive adhesive layer 2 on the optical film 1 described above is not particularly limited, and a method of applying the pressure-sensitive adhesive composition (solution) and drying it, and a release sheet 3 provided with the pressure-sensitive adhesive layer 2 And the like. Adhesive layer 2
(Dry film thickness) is not particularly limited, but is 10 to 40
It is preferably about μm.

As the constituent material of the release sheet 3,
Paper, synthetic resin film such as polyethylene, polypropylene, polyethylene terephthalate, rubber sheet, paper,
Appropriate thin sheets such as cloth, non-woven fabric, net, foamed sheet, metal foil, and laminates thereof can be used. In order to enhance the releasability from the pressure-sensitive adhesive layer 2, the surface of the release sheet 3 may be treated with silicone, long-chain alkyl, or
It may be subjected to a peeling treatment such as a fluorine treatment.

The layers such as the optical film and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive optical film of the present invention include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds, etc. It may be one having an ultraviolet absorbing ability by a method such as a method of treating with the ultraviolet absorbent of 1.

The adhesive optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, an adhesive optical film, and a component such as an illumination system, if necessary, and incorporating a drive circuit. There is no particular limitation except that a polarizing plate or an optical film according to 1. Also for liquid crystal cells, for example, TN type or ST
Any type such as N type and π type may be used.

It is possible to form an appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive optical film is arranged on one side or both sides of a liquid crystal cell, or a device using a backlight or a reflector in an illumination system. In that case, the polarizing plate or the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When a polarizing plate or an optical film is provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, and other appropriate components are provided at appropriate positions in one layer or Two or more layers can be arranged.

Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitting body (organic electroluminescent light emitting body). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminated body of such a light emitting layer and an electron injection layer formed of a perylene derivative, or a laminated body of these hole injection layer, light emitting layer, and electron injection layer is known. Has been.

In the organic EL display device, holes and electrons are injected into the organic light emitting layer by applying a voltage to the transparent electrode and the metal electrode, and energy generated by the recombination of these holes and electrons is fluorescent. It emits light based on the principle that a substance is excited and the excited fluorescent substance emits light when returning to the ground state. The mechanism of recombination in the middle is similar to that of a general diode, and as can be expected from this, the current and the emission intensity show a strong nonlinearity with rectification with respect to the applied voltage.

In the organic EL display device, at least one of the electrodes must be transparent in order to extract light emitted from the organic light emitting layer.
A transparent electrode formed of a transparent conductor such as O) is used as an anode. On the other hand, it is important to use a substance having a small work function for the cathode in order to facilitate electron injection and increase the luminous efficiency, and a metal electrode such as Mg-Ag or Al-Li is usually used.

In the organic EL display device having such a structure, the organic light emitting layer is formed of an extremely thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, when entering from the surface of the transparent substrate during non-light emission, the light transmitted through the transparent electrode and the organic light emitting layer and reflected by the metal electrode goes out to the surface side of the transparent substrate again, when viewed from the outside, The display surface of the organic EL display device looks like a mirror surface.

In an organic EL display device including an organic electroluminescent light-emitting body having a transparent electrode on the front surface side of an organic light-emitting layer that emits light when a voltage is applied and a metal electrode on the back surface side of the organic light-emitting layer, A polarizing plate can be provided on the surface side of the electrode, and a retardation plate can be provided between the transparent electrode and the polarizing plate.

Since the retardation plate and the polarizing plate have a function of polarizing the light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized from the outside by the polarization action. Especially, the phase difference plate is 1/4.
The mirror surface of the metal electrode can be completely shielded by using a wave plate and adjusting the angle between the polarization directions of the polarizing plate and the retardation plate to π / 4.

That is, as for the external light incident on the organic EL display device, only the linearly polarized light component is transmitted by the polarizing plate. This linearly polarized light is generally elliptically polarized by the retardation plate, but it is circularly polarized when the retardation plate is a 1/4 wavelength plate and the polarization direction between the polarizing plate and the retardation plate is π / 4. .

This circularly polarized light passes through the transparent substrate, the transparent electrode and the organic thin film, is reflected by the metal electrode, passes through the organic thin film, the transparent electrode and the transparent substrate again, and becomes linearly polarized light again on the retardation plate. . Since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate. as a result,
The mirror surface of the metal electrode can be completely shielded.

[0083]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Also, heating durability, humidification durability, adhesive strength,
The method for measuring the amount of adhesive residue is shown below.

Example 1 Butyl acrylate (95 parts by weight), N, N-dimethylacrylamide (5 parts by weight), 2-hydroxyethyl acrylate (0.8 parts by weight), and azobisisobutyronitrile (0.2 parts by weight). (Parts by weight) in an ethyl acetate solvent at 60 ° C.
At room temperature for 7 hours to obtain an acrylate polymer solution having a solid content of 30% by weight. To 100 parts by weight of the solid content of the acrylate-based polymer solution, 0.2 parts by weight of Takenate D110N (Mitsui Takeda Chemical Co., Ltd.) as a trifunctional isocyanate compound was added and mixed well to obtain an adhesive composition. It was This is polyethylene terephthalate (P
ET) After being coated on a separator to a thickness of 20 μm and dried, a polarizing film (a polyvinyl alcohol film was impregnated with iodine and stretched, and then a triacetyl cellulose film was adhered to both sides via an adhesive. To produce an adhesive polarizing film.

Example 2 An adhesive polarizing film was prepared in the same manner as in Example 1 except that N, N-diethylacrylamide was used instead of N, N-dimethylacrylamide.

Example 3 An adhesive polarizing film was prepared in the same manner as in Example 1 except that N-isopropylacrylamide was used instead of N, N-dimethylacrylamide.

Example 4 An adhesive polarizing film was prepared in the same manner as in Example 1 except that N, N-dimethylaminopropylacrylamide was used instead of N, N-dimethylacrylamide.

Comparative Example 1 An adhesive polarizing film was prepared in the same manner as in Example 1 except that acrylamide was used instead of N, N-dimethylacrylamide.

Comparative Example 2 Acrylic acid was used in place of N, N-dimethylacrylamide, and Takenate D110N (0.2 parts by weight) was used.
Instead of Coronate L (Japan Polyurethane Industry
An adhesive type polarizing film was prepared in the same manner as in Example 1 except that 0.6 part by weight of Co., Ltd.) was used.

Comparative Example 3 An adhesive polarizing film was prepared in the same manner as in Example 1 except that the amount of 2-hydroxyethyl acrylate used was changed to 10 parts by weight.

Comparative Example 4 The amount of butyl acrylate used was changed to 85 parts by weight,
An adhesive polarizing film was prepared in the same manner as in Example 1 except that the amount of N, N-dimethylacrylamide used was changed to 15 parts by weight.

Comparative Example 5 An adhesive polarizing film was prepared in the same manner as in Example 1 except that 5 parts by weight of acrylic acid was added to prepare an acrylate polymer solution.

(Heat Durability Test) The pressure-sensitive adhesive type polarizing film was cut into a size of 12 inches, attached to a non-alkali glass plate (Corning 1737, manufactured by Corning Incorporated), and autoclaved (50 ° C., 0.5 MPa, 15 min). To do. After that, evaluation was performed after standing in an atmosphere at a temperature of 90 ° C. for 500 hours. In addition, the evaluation of heating durability was confirmed visually by the occurrence of defects according to the following criteria. The evaluation results are shown in Table 1. ◯: No defects occurred ×: Defects such as foaming, fine peeling of the film, peeling and the like were observed (humidity durability test) The adhesive polarizing film was cut into 12-inch size, and a non-alkali glass plate (made by Corning Incorporated) ,
It is attached to Corning 1737) and subjected to autoclave treatment (50 ° C., 0.5 MPa, 15 min). After that, the temperature is 60 ° C, and the humidity is 90% in an atmosphere of 500.
After standing for a time, evaluation was performed. In addition, the evaluation of the humidification durability was performed by visually confirming the occurrence of defects according to the following criteria. The evaluation results are shown in Table 1. ○: No defects occurred ×: Problems such as foaming, fine peeling of the film, peeling and the like are seen (adhesion test) Adhesive polarizing film was cut into 25 mm width, non-alkali glass plate (Corning, Corning) 1737) and autoclave (50 ° C,
0.5 MPa, 15 min). Further normal pressure, 60
It was left for 17 hours in an atmosphere of ° C. Then, using a tensile tester (Minebea Co., Ltd., TCM-1KNB), 90
The measurement was performed under conditions of peeling, a pulling speed of 300 mm / min, and a room temperature atmosphere of 25 ° C. Adhesive force is 10N
When / 25 mm or less, the reworkability is good. The measurement results are shown in Table 1.

(Adhesive Residue Test) Adhesive polarizing film was applied to 12
It is cut into inch size, attached to a non-alkali glass plate (Corning 1737, manufactured by Corning), and autoclaved (50 ° C., 0.5 MPa, 15 min). Furthermore, it was left to stand in an atmosphere of normal pressure and 60 ° C. for 24 hours. Then, the adhesive polarizing film was peeled from the glass plate, and the state of adhesive residue on the glass surface was confirmed according to the following criteria. The evaluation results are shown in Table 1. ⊚: No adhesive residue was observed at all ○: Adhesive residue was observed at the beginning and / or at the end of peeling, but there was no problem in practical use Δ: Some adhesive residue was found at other than the beginning of peeling and / or the end of peeling It can be seen, but there is no problem in practical use ×: Adhesive residue occurs at some degree of practical problem

[Table 1] As shown in Table 1, the pressure-sensitive adhesive optical film of the present invention has good durability, almost no adhesive residue, and an adhesive force of 10 N /
The reworkability is excellent when it is 25 mm or less.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an adhesive optical film of the present invention.

[Explanation of symbols]

1 Optical film 2 Adhesive layer 3 Release sheet

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) C09J 133/24 C09J 133/24 175/04 175/04 G02F 1/1335 510 G02F 1/1335 510 1/13363 1/13363 (72) Inventor Akiko Ogasawara 1-2-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Katsuhiko Kamiya 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Akira Hirao 1-2 chome Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Co., Ltd. F-term (reference) 2H049 BA02 BA06 BB52 BC14 BC22 2H091 FA08X FA11X FA32X FA37X FB02 FD14 GA01 LA04 LA06 LA09 4F100 AK01A AK25B AK26B AK41A AK51H BA02 CA02B CB05B EJ05B JK06 JK06B JL13B JL14 JN10 YY00B 4J004 AA10 AA14 AA17 AB01 CC02 FA08 FA10 4J040 DF041 DF051 DF062 DF102 EF181 JA09 JB09 KA16 L A06 NA17

Claims (7)

[Claims] 1. A pressure-sensitive adhesive optical film comprising a pressure-sensitive adhesive layer laminated on one surface of an optical film, wherein the pressure-sensitive adhesive layer comprises (A) alkyl (meth) acrylate and (B) N-.
Carboxyl containing 1 to 12% by weight of substituted (meth) acrylamide and / or N, N-substituted (meth) acrylamide and 0.01 to 3% by weight of (C) hydroxyl group-containing (meth) acrylic monomer as a polymerization component. An adhesive optical film, which is formed by a cross-linked product of a composition containing a (meth) acrylic polymer having no group. 2. The pressure-sensitive adhesive optical film according to claim 1, wherein the (B) is 1 to 12% by weight of N, N-substituted (meth) acrylamide. 3. The N-substituent of the N-substituted (meth) acrylamide and the N, N-substituent of the N, N-substituted (meth) acrylamide are alkyl groups. The adhesive optical film according to item 2. 4. The adhesive force based on 90 ° peeling at a room temperature atmosphere of 25 ° C. at a speed of 300 mm / min to the alkali-free glass of the pressure-sensitive adhesive layer is 10 N / 25 mm or less. The pressure-sensitive adhesive optical film according to any one of claims. 5. (A) alkyl (meth) acrylate,
(B) N-substituted (meth) acrylamide and / or N,
1 to 12% by weight of N-substituted (meth) acrylamide,
(C) Hydroxyl group-containing (meth) acrylic monomer 0.01
A pressure-sensitive adhesive composition for an optical film, comprising a (meth) acrylic polymer having no carboxyl group and containing 3 to 3% by weight as a polymerization component, and a polyfunctional compound. 6. The pressure-sensitive adhesive composition for an optical film according to claim 5, wherein the polyfunctional compound is an aliphatic isocyanate cross-linking agent. 7. An image display device using the pressure-sensitive adhesive optical film according to claim 1.