JP2003262729A - Adhesive optical film and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive optical film comprising an optical film with an adhesive layer laminated on a surface thereof and capable of suppressing generation of micro-air bubbles in sticking the adhesive optical film to a liquid crystal panel or the like. <P>SOLUTION: The adhesive optical film comprises the optical film with the adhesive layer laminated on a surface thereof and is characterized in that the adhesive layer is formed of a cross-linked product of a composition containing an acrylic polymer containing an alkyl (meth)acrylate (a) with a 7-18C alkyl group and a hydroxy group containing monomer (b) with (a):(b)=100:0.01-5 weight ratio as monomer units and a compound with two or more functional groups reacting with hydroxy groups and further having 75-97 wt.% gelation ratio of the cross-linked product. <P>COPYRIGHT: (C)2003,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. Further, the present invention relates to an image display device such as a liquid crystal display device, an organic EL display device and a PDP using the adhesive optical film. 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 a liquid crystal panel because of its image forming method. Generally, a polarizing film is attached to the outermost surface of the liquid crystal panel. It is worn. In addition to the polarizing film, various optical elements have been used on the outermost surface of the liquid crystal panel in order to improve the display quality of the 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 a liquid crystal panel, an adhesive is usually used. In addition, since the optical film can be instantly fixed to the liquid crystal panel, and since it has advantages such as not requiring a drying step to fix the optical film, the adhesive is preliminarily provided as an adhesive layer on one surface of the optical film. Has been. That is, an adhesive optical film is generally used to attach the optical film to the outermost surface of the liquid crystal panel.

The necessary properties required for the pressure-sensitive adhesive are as follows: (1) When an optical film is stuck to a liquid crystal panel, the sticking position is incorrect, or a foreign substance is caught in the sticking surface. The film can be peeled off from the outermost surface of the liquid crystal panel and re-bonded (rework), (2) it has stress relaxation property to prevent optical unevenness caused by dimensional change of the optical film, (3) environmental promotion There is no problem caused by the pressure-sensitive adhesive in a durability test such as heating and humidification that is usually performed as a test.

Recently, there has been a demand for an adhesive polarizing film in which a concave recess is unlikely to be formed on the adhesive layer / release sheet side of the adhesive optical film when the adhesive optical films are laminated and stored. It is rising. The concave depressions formed in the pressure-sensitive adhesive optical film are caused by foreign matters of about 5 to 1000 μm mixed between the layers when the pressure-sensitive adhesive optical film is laminated. The concave depressions generally have a depth of 0.
It refers to a depression having a diameter of about 5 to 30 μm and a diameter of about 20 to 2000 μm. If a concave recess exists on the optical film surface, when the optical film is attached to a liquid crystal panel or the like,
Micro bubbles with a diameter of 20 to 2000 μm are generated, which significantly reduces the visibility of the liquid crystal display. Conventional adhesive optical films have not been able to solve this problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention is an adhesive optical film having an adhesive layer laminated on one surface of an optical film, which is obtained when the adhesive optical film is attached to a liquid crystal panel or the like. An object of the present invention is to provide an adhesive optical film capable of reducing the generation of micro bubbles. Furthermore, it aims at providing the image display apparatus using the said adhesive type optical film.

[0007]

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 type optical film comprising a pressure-sensitive adhesive layer laminated on one surface of an optical film, wherein the pressure-sensitive adhesive layer has an alkyl group having 7 to 18 carbon atoms.
Alkyl (meth) acrylate (a) and hydroxyl group-containing monomer (b) as monomer units (a): (b)
= 100: 0.01 to 5 (weight ratio), and a crosslinked product of a composition containing an acrylic polymer and a compound having two or more functional groups that react with hydroxyl groups, and the crosslinked product. The present invention relates to an adhesive optical film having a gel fraction of 75 to 97% by weight.

Due to the physical properties of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive optical film of the present invention has a concave-shaped dent even when minute foreign substances are mixed in between the layers to form a concave-shaped dent. It is designed to be easy to recover, and can be significantly recovered within 300 seconds after removing foreign matter. Therefore, even if a concave recess is generated due to the inclusion of foreign matter between the layers when the adhesive optical film is laminated, when the adhesive optical film is actually attached to a glass substrate such as a liquid crystal panel, microscopic bubbles are generated. The occurrence can be greatly reduced and the deterioration of the visibility of the liquid crystal display can be suppressed.

In order to obtain the physical properties of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is based on an acrylic polymer containing an alkyl (meth) acrylate (a) having a long-chain alkyl group having 7 to 18 carbon atoms as a main component. The gel fraction used as a polymer and showing the degree of crosslinking of the pressure-sensitive adhesive layer is adjusted to 75 to 97%. More preferably, the long-chain alkyl group has 7 to 14 carbon atoms. The gel fraction is preferably 85-95%.

The acrylic polymer is a copolymer containing an alkyl (meth) acrylate (a) and a hydroxyl group-containing monomer (b). The hydroxyl group-containing monomer (b) participates in crosslinking with a compound having two or more functional groups that react with hydroxyl groups. In order to prevent problems such as peeling and foaming caused by an adhesive when a reliability test is performed on the liquid crystal panel, the monomer unit (a):
The weight ratio of (b) is adjusted to 100: 0.01-5. The weight ratio of the monomer units (a) :( b) is
More preferably, it is 100: 0.05 to 0.3.

The adhesive optical film has an adhesive area of 10 mm × 10 m through the adhesive layer of the adhesive optical film.
The amount of strain of the pressure-sensitive adhesive layer after 1 hour obtained from the creep test in which the sample is fixed to the substrate at m and a load of 500 g is applied (A: μ
m) and the strain amount (B: μm) of the pressure-sensitive adhesive layer when 300 seconds have passed after removing the load is expressed by the formula (1): {(A−B) / A} × 100 ≧ 80 ( %),
And it is preferable that the formula (2): B ≦ 40 is satisfied.

The strain amounts (A) and (B) are values measured in detail by the method described in Examples. The left term value of the equation (1) represents the recovery rate of the concave depression after 300 seconds, and the value of the equation (1) is 80% or more, and further 90% or more is a liquid crystal panel or the like. It is preferable in preventing fine bubbles generated when the optical film is attached. The strain amount (B) is the depth of the concave depression after 300 seconds. The smaller the strain, the faster the recovery of the concave depression, and as shown in equation (2), is 40 μm or less, and further 25 μm or less. preferable.

Further, the present invention relates to an image display device using the pressure-sensitive adhesive type 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.

[0015]

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 an alkyl (meth) acrylate (a) having an alkyl group having 7 to 18 carbon atoms and a hydroxyl group-containing monomer (b) as a monomer unit ( a): (b) = 10
Formed by a crosslinked product of a pressure-sensitive adhesive composition in which an acrylic polymer contained in an amount of 0: 0.01 to 5 (weight ratio) is used as a base polymer, and a compound having two or more functional groups that react with hydroxyl groups is added to the base polymer. There is.

The alkyl group of the alkyl (meth) acrylate (a) may be linear or branched as long as it has 7 to 18 carbon atoms. For example, heptyl group, octyl group, 2
-Ethylhexyl group, isooctyl group, nonyl group, decyl group, isodecyl group, undecyl group, dodecyl group, tridecyl group, isomistyryl group, octadecyl group and the like. The alkyl (meth) acrylate means alkyl acrylate and / or alkyl methacrylate, and has the same meaning as (meth) in the present invention.

As the hydroxyl group-containing monomer (b), 2-
Examples thereof include hydroxyl group-containing (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and hydroxyhexyl (meth) acrylate, and N-methylol (meth) acrylamide.

The alkyl (meth) acrylate (a) and the hydroxyl group-containing monomer (b) have a weight ratio of monomer unit (a) :( b) in the copolymer of 100: 0.0.
It is adjusted so as to be 1 to 5, but a monomer unit having a carboxyl group, a monomer unit having an N element, a monomer unit having an epoxy group and the like can be introduced as long as the object of the present invention is not impaired. Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, fumaric acid, maleic acid and itaconic acid. Examples of the N element-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide,
Examples thereof include N, N-diethyl (meth) acrylamide, (meth) acryloylmorpholine, (meth) acetonitrile, vinylpyrrolidone, N-cyclohexylmaleimide, itacone imide and N, N-dimethylaminoethyl (meth) acrylamide. Examples of the monomer having an epoxy group include a monomer having a functional group such as glycidyl (meth) acrylate. Furthermore, vinyl acetate, styrene, etc. can also be used. These monomers can be used alone or in combination of two or more.

The average molecular weight of the acrylic polymer is not particularly limited, but the weight average molecular weight is preferably about 300,000 to 2,500,000. The acrylic polymer can be produced by various known methods, and 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. Among 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 the solvent for the acrylic polymer. The solution concentration is usually about 20 to 80% by weight.

The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains a functional group which reacts with the acrylic polymer and the hydroxyl group.
Contains compounds with three or more. The compounding amount of the compound having two or more functional groups that react with the hydroxyl group with respect to the acrylic polymer is appropriately adjusted so that the gel fraction of the crosslinked product formed by the composition is 75 to 97% by weight. 2 functional groups that react with acrylic polymers and hydroxyl groups
The compounding ratio of the compound having three or more is usually 0.01 (compound) having two or more functional groups capable of reacting with a hydroxyl group with respect to 100 parts by weight of the acrylic polymer (solid content).
It is about 6 parts by weight, preferably about 0.1 to 3 parts by weight.

Examples of the compound having two or more functional groups that react with hydroxyl groups include polyfunctional isocyanate compounds, polyfunctional metal chelate compounds (metal chelate compounds such as Al and Ti), polyfunctional alkoxysilanes, and polyfunctional epoxy compounds. , Polyfunctional acid halides (eg, acid chlorides), and the like. Among these, polyfunctional isocyanate compounds are preferable.

Further, if necessary, the pressure-sensitive adhesive composition may include a filler, a pigment, a colorant, etc. made of a tackifier, a plasticizer, glass fibers, glass beads, metal powder, other inorganic powder, or the like. Fillers, antioxidants, ultraviolet absorbers, silane coupling agents, and the like, and various additives may be appropriately used within a range not departing from the object of the present invention. Further, it may be a pressure-sensitive adhesive layer containing fine particles and exhibiting light diffusion property.

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

The polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching is produced, for example, by soaking the 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) is 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 cured 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 obstructing 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 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 of 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 that 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 as 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 or the like 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.

A 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 those for the purpose of compensating for the viewing angle and 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 described above are obtained by laminating a polarizing plate or a reflection type polarizing plate and a 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 compensating 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 direction slightly oblique 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.

From the standpoint of achieving a wide viewing angle for good visibility, an optically anisotropic layer comprising a liquid crystal polymer alignment layer, particularly a discotic liquid crystal polymer tilt alignment layer, was supported by a triacetyl cellulose film. An optical compensation retardation plate can be preferably used.

A polarizing plate in which a polarizing plate and a brightness enhancement film are bonded together is usually used by being provided on the back side of a 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 diffuser 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.

The above-mentioned brightness enhancement film is, for example, a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies, transmits linearly polarized light of a predetermined polarization axis and reflects other light. 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 having the predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby suppressing 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 phase difference for a 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 in which the optical layer is laminated on the polarizing plate can be formed by a method of sequentially laminating separately 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 coating the pressure-sensitive adhesive composition (solution) and drying it, a release sheet 3 provided with the pressure-sensitive adhesive layer 2 are used. And the like. Adhesive layer 2
(Dry film thickness) is not particularly limited, but is 10 to 40
It is preferably about μm.

As a 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 pressure-sensitive adhesive optical film of the present invention can be preferably used for forming various devices such as liquid crystal display devices. 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 disposed 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 a single 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 which 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, of 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.

[0068]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In addition, in each example, a part is a weight part.

Example 1 (Preparation of adhesive) 100 parts of isooctyl acrylate,
2-hydroxyethyl acrylate 0.12 parts, azobisisobutyronitrile 0.4 parts and ethyl acetate 150
While stirring the parts, reaction was carried out at about 60 ° C. for 6 hours to obtain an acrylic polymer solution having a weight average molecular weight of 1.2 million.
To the acrylic polymer solution, 1 part of a trifunctional isocyanate compound, Coronate L manufactured by Nippon Polyurethane Company, was added to 100 parts of the polymer solid content to prepare an adhesive solution.

(Preparation of adhesive optical film) Thickness 80 μ
The polyvinyl alcohol film of m was stretched 5 times in an aqueous iodine solution and then dried, and a triacetyl cellulose film was adhered to both sides via an adhesive to obtain a polarizing film. The pressure-sensitive adhesive solution prepared above was
Was coated on a release paper having a thickness of 20 μm so as to have a thickness after drying of 20 μm to obtain an adhesive bulk with a gel fraction of 91% by weight. This was laminated on the polarizing film prepared above to obtain an adhesive polarizing film.

Comparative Example 1 (Preparation of pressure-sensitive adhesive) 100 parts of butyl acrylate, 3 parts of acrylic acid, 0.4 parts of azobisisobutyronitrile and 50 parts of ethyl acetate were reacted with stirring at 60 ° C. for 6 hours. An acrylic polymer solution having a weight average molecular weight of 1.3 million was obtained. To the acrylic polymer solution, 0.7 part of a trifunctional isocyanate compound, Coronate L manufactured by Nippon Polyurethane Company, was added to 100 parts of the polymer solid content to prepare an adhesive solution.

(Production of Adhesive Optical Film) An adhesive bulk having a gel fraction of 65% by weight was obtained in the same manner as in Example 1 except that the above adhesive solution was used. Further, an adhesive polarizing film was produced in the same manner as in Example 1.

Comparative Example 2 (Preparation of adhesive) 100 parts of butyl acrylate, 5 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate
Parts, 0.4 parts of azobisisobutyronitrile and 150 parts of ethyl acetate were reacted with stirring at about 60 ° C. for 6 hours to obtain an acrylic polymer solution having a weight average molecular weight of 1.35 million. To the above acrylic polymer solution, 1.2 parts of a trifunctional isocyanate compound, Coronate L manufactured by Nippon Polyurethane Company, was added to 100 parts of the polymer solid content to prepare an adhesive solution.

(Preparation of adhesive optical film) An adhesive bulk having a gel fraction of 85% by weight was obtained in the same manner as in Example 1 except that the above adhesive solution was used. Further, an adhesive polarizing film was produced in the same manner as in Example 1.

The adhesive polarizing films obtained in the above Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1.

(Gel Fraction) The pressure-sensitive adhesive bulk was taken out, the weight (w1) was measured, and the mixture was allowed to stand in ethyl acetate for 7 days. Then, the polymer (gel component) that was insoluble in ethyl acetate was taken out, ethyl acetate was volatilized in a dryer, and the weight (w2) of the remaining solid content was measured and calculated from the following formula. Gel fraction (% by weight) = (w2 / w1) × 100.

(Measurement of strain due to load on adhesive layer on polarizing film) Adhesive polarizing film cut to 10 mm × 30 mm on a Bakelite plate having a size of 75 mm × 30 mm and a thickness of 2 mm has an adhesive area of 10 mm × 10 mm. The pieces were bonded together via an adhesive and left at 23 ° C./65% RH for 16 hours. This sample is fixed vertically,
A load of 500 g was applied to the end of the polarizing film for 1 hour.
The strain from the initial state at that time was defined as the strain amount (A) of the adhesive polarizing film. After that, the load is removed and 300
Left for a second. The strain from the initial state after standing for 300 seconds was defined as the strain amount (B) of the adhesive polarizing film. Table 1 shows the strain amounts (A) and (B) and the value of the left term value of the formula (1) calculated from them: {(A−B) / A} × 100 (%).

(Confirmation of Number of Minute Bubbles Generated by Bonding Adhesive Polarizing Film to Glass) Adhesive polarizing films were cut into a size of 280 mm × 210 mm, 50 sheets were laminated, and a load of 0.01 Mpa was applied thereon. It took 16 hours. Remove the load and put one polarizing film on the flat surface.
After standing for a minute, the pressure-sensitive adhesive layer of each pressure-sensitive adhesive type polarizing film was stuck on a Corning non-alkali glass plate # 1737 and left at 50 ° C. × 0.05 MPa atmosphere for 5 minutes. This sample was visually confirmed, and the number of samples in which visible microscopic bubbles were confirmed was counted. The results are shown in Table 1.

[0079]

[Table 1]

[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

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13363 G02F 1/13363 5G435 G09F 9/00 313 G09F 9/00 313 (72) Inventor Kunio Nagasaki Osaka No. 1-2 Shimohozumi, Ibaraki City, Ibaraki, Japan (72) Inventor Nobuaki Maruoka No. 1-2-2 Shimohozumi Shimohozumi, Ibaraki City, Osaka (72) Inventor Makoto Shodosawa Ibaraki, Osaka Prefecture Hozumi Ichishita 1-2, Nitto Denko Co., Ltd. (72) Inventor Mie Ota 1-21-2 Shihohozumi Ibaraki, Osaka Prefecture Nitto Denko Co., Ltd. (72) Masayuki Satake Shita, Ibaraki, Osaka Hozumi 1-2, Nitto Denko Corporation (72) Inventor Akiko Ogasawara 1-2-2 Shimohozumi, Ibaraki City, Osaka Nitto Denko Corporation Inner F-term (reference) 2H049 BA02 BA27 BB43 BB52 BB54 BC14 BC22 2H091 FA02 FA11 FA12 FA37X FB02 FD15 GA16 GA17 LA16 4F100 AK25B AK25K AT00A BA02 BA10A BA10B CA02B GB41 GB90 JL13B YY00B 4030801 A4A04A01 AB02A04A01A04A04A01A04A04A04A01 DF041 DF051 GA05 GA07 GA11 GA22 JA09 JB09 NA17 NA20 5G435 AA17 BB05 BB06 BB12 GG42 GG43

Claims (3)

[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 an alkyl (meth) acrylate having an alkyl group having 7 to 18 carbon atoms ( a) and a hydroxyl group-containing monomer (b) as monomer units (a) :( b) = 100: 0.
01 to 5 (weight ratio), which is formed by a crosslinked product of a composition containing an acrylic polymer and a compound having two or more functional groups that react with hydroxyl groups, and the crosslinked product has a gel fraction of 75. The adhesive optical film is characterized in that 2. An adhesive area of 10 mm × 10 mm is fixed to the substrate through the adhesive layer of the adhesive optical film, and 50
The strain amount (A: μm) of the pressure-sensitive adhesive layer after 1 hour obtained from the creep test in which a load of 0 g is applied, and the strain amount of the pressure-sensitive adhesive layer when 300 seconds have passed after the load was removed (B: μm) is expressed by the formula (1): {(A−B) / A} × 100 ≧ 80 (%),
And the formula (2): B ≦ 40, The pressure-sensitive adhesive optical film according to claim 1, wherein 3. An image display device using the pressure-sensitive adhesive optical film according to claim 1.