JP2003193012A - Pressure sensitive adhesive composition, pressure sensitive adhesive sheet and optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensitive adhesive sheet having a pressure sensitive adhesive layer which reduces total reflection of light at the interface between an optical film or an optical material and the pressure sensitive adhesive layer and does not reduce visibility even when plastic material is used as the optical material. <P>SOLUTION: The subject pressure sensitive adhesive composition mainly comprises an acrylic polymer containing an aromatic ring-containing copolymerizable monomer and a tertiary-amino group-containing copolymerization monomer as monomer units and has 1.49-1.60 refractivity after drying and/or curing. The tertiary-amino group-containing copolymerizable monomer may be a tertiary-amino group-containing (meth)acrylate. The pressure sensitive adhesive sheet is used for sticking and fixing the optical film on a display panel of a display and prepared by forming the pressure sensitive adhesive layer of the pressure sensitive adhesive composition on a release liner. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and an optical film which are used for laminating optical films such as by sticking and fixing the optical films on a display panel of a liquid crystal display device or the like. Regarding

[0002]

2. Description of the Related Art Conventionally, acrylic adhesives have been used as pressure-sensitive adhesive compositions for bonding various optical films such as antireflection films and conductive films (ITO films) to display panels such as liquid crystal display devices. Adhesive compositions consisting of polymers have been used.

Display panels to which these optical films are attached are widely used for mobile communication terminals (mobile phone terminals such as mobile phones and PHS machines, PDA terminals, etc.).

In recent years, there has been a demand for weight reduction and thickness reduction of devices, especially mobile communication terminals. A film light guide plate has been attracting attention as an optical film aiming at such weight reduction and thickness reduction. The "film light guide plate" is used in liquid crystal display devices and has the function of emitting transmission light that is transmitted laterally inside the liquid crystal panel to the upper or lower surface side, and a light source is arranged on the side surface of the liquid crystal display device. It is an optical film that can be easily illuminated when it is used. Since the film light guide plate is thinner than the conventional light guide plate, it is considered effective in reducing the weight and thickness of the device.

Further, the sophistication of required characteristics such as effective utilization of light and suppression or reduction of power consumption is progressing. For example, a display panel of a liquid crystal display device has a structure in which a plurality of optical members such as a glass substrate, a polarizing plate (film), and a retardation film (film) are laminated together with liquid crystal. Further, since the optical film is also used by being bonded to the optical member constituting these display panels, from the viewpoint of effective use of light, the optical film / pressure-sensitive adhesive layer /
It is required to prevent total reflection at each interface of the optical member.

Generally, the refractive index of materials used for optical films and optical members is, for example, about 1.52 in the case of glass, about 1.51 in the case of methacrylic resin, and about 1.51 in the case of polycarbonate. It is about 1.54. However, the conventional pressure-sensitive adhesive composition has a refractive index of about 1.47 after being dried and / or cured, and thus has a refractive index of 1.49.
It does not have the above high refractive index. Therefore, a difference in refractive index occurs at the interface between the optical film / pressure-sensitive adhesive layer or the interface between the pressure-sensitive adhesive layer / optical member, and total reflection occurs at a shallow angle, which hinders effective use of light. Has become.

Further, in order to prevent the visibility from being impaired under any environment where visual recognition is assumed, it is required that defects (for example, foaming or peeling) that impair the visibility do not occur. In the pressure-sensitive adhesive composition containing a conventional acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit as a main component, the refractive index can be set to a desired value, but polycarbonate or polymethyl ester can be used. When used as a plastic such as methacrylate or as an optical member, under severe environmental tests, for example, 80 ℃
It has been known that foaming and peeling may occur under the environmental conditions such as the high temperature environment of 60 ° C. and the environment of 60 ° C. and 95% RH, thereby hindering the visibility.

[0008]

Therefore, an object of the present invention is to provide an optical film / feel when various optical films are bonded to various optical members constituting a display device by using a pressure sensitive adhesive. It is possible to reduce the total reflection of light at each interface of the pressure-sensitive adhesive layer / optical member, and even if a plastic member is used as the optical member, the visibility is improved under any environment where visual recognition is assumed. It is intended to provide a pressure-sensitive adhesive composition that does not decrease, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition, and an optical film.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventor has found that when a specific monomer component is used as a monomer unit of a pressure-sensitive adhesive composition, after drying and / or Alternatively, the refractive index after curing becomes high, and a pressure-sensitive adhesive composition close to the refractive index of an optical film or an optical member is obtained, and when the pressure-sensitive adhesive composition is applied to an optical member, The present invention has been completed by finding that even if a plastic member is used as an optical member, it is possible to prevent the occurrence of foaming or peeling and prevent a decrease in visibility under any environment where visual recognition is assumed. did.

That is, the present invention is a pressure-sensitive adhesive composition containing, as a main component, an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit. Provided is a pressure-sensitive adhesive composition which further contains a tertiary amino group-containing copolymerizable monomer as a monomer unit and has a refractive index after drying and / or curing of 1.49 or more and 1.60 or less.

The tertiary amino group-containing copolymerizable monomer is preferably a tertiary amino group-containing (meth) acrylate. Examples of the tertiary amino group-containing (meth) acrylate include N, N-dialkylamino-alkyl (meth)
Acrylate can be preferably used.

Further, in the present invention, the aromatic ring-containing copolymerizable monomer is preferably an aromatic ring-containing acrylic monomer and / or styrene monomer.

The present invention is also a pressure-sensitive adhesive sheet for adhering and fixing an optical film to a display panel of a display device, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition on a release liner. There is provided a pressure-sensitive adhesive sheet in which is formed. Further provided is an optical film in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is formed on one surface of an optical film for sticking and fixing to a display panel of a display device.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic ring-containing copolymerizable monomer used as the monomer unit of the acrylic polymer in the pressure-sensitive adhesive composition of the present invention has an aromatic ring in the molecule. There is no particular limitation as long as it is a copolymerizable monomer. As the aromatic ring-containing copolymerizable monomer, for example, an aromatic ring-containing ethylenically unsaturated monomer can be preferably used. The aromatic ring-containing copolymerizable monomers can be used alone or in combination of two or more.

Specific examples of the aromatic ring-containing copolymerizable monomer include aromatic ring-containing acrylic type monomers and styrene type monomers.

The aromatic ring-containing acrylic monomer is not particularly limited as long as it is an acrylic monomer having an aromatic ring in the molecule. As such an aromatic ring-containing acrylic monomer, an aromatic ring-containing (meth) acrylic acid ester is preferable. The aromatic ring-containing (meth) acrylic acid ester includes, for example, an aromatic ring-containing (meth) acrylic acid alkyl ester, (meth) acrylic acid aryl ester ((meth) acrylic acid phenyl ester, etc.) and the like. Among the aromatic ring-containing (meth) acrylic acid ester, the aromatic ring-containing (meth) acrylic acid alkyl ester is particularly preferable.

As the aromatic ring-containing (meth) acrylic acid alkyl ester, a compound represented by the following formula (1) is preferable.

[Chemical 1] (In the formula (1), R ¹ is a hydrogen atom or a methyl group. R ²
The alkylene group or ^{-R 3, - (OR 3)} n - is.
Here, R ³ is an alkylene group, and n is a positive integer. X is an aryl group or an aryloxy group. )

Examples of the alkylene group for R ² include alkylene groups having 1 to 18 carbon atoms such as methylene group, ethylene group, propylene group, isopropylene group and butylene group. The preferred alkylene group has 1 to 4 carbon atoms.
The alkylene group is included, and a methylene group and an ethylene group are particularly suitable.

Examples of the alkylene group for R ³ include a methylene group, an ethylene group, a trimethylene group, a methylethylene group,
Examples thereof include alkylene groups having 1 to 6 carbon atoms such as a tetramethylene group. The preferred alkylene group has 1 to 4 carbon atoms.
The alkylene group is included, and a methylene group and an ethylene group are particularly suitable.

N is a positive integer, for example, an integer of 1-10. Preferred n includes an integer of about 1 to 6.

The aryl group of X includes a phenyl group and a naphthyl group. Further, the aryloxy group includes a phenyloxy group, a naphthyloxy group and the like. X
The aryl group and aryloxy group of may have a substituent. Such a substituent is not particularly limited, and examples thereof include an alkyl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a nitro group, a cyano group, a halogen atom and a sulfo group. As the substituent of the aryl group and aryloxy group of X, an alkyl group and an alkoxy group are preferable. The substituents may be used alone or in combination of two or more.

Specifically, the aromatic ring-containing (meth) acrylic acid alkyl ester represented by the formula (1) includes aryl C _1-18 alkyl (meth) acrylate and aryloxy C _1-18 alkyl (meth). ) Acrylate, aryloxy poly C _1-6 alkylene glycol (meth) acrylate and the like. More specifically, examples of the aromatic ring-containing (meth) acrylic acid alkyl ester include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxydiethylene glycol (meth).
Acrylate, ethylene oxide (EO) modified cresol (meth) acrylate, ethylene oxide (E
O) modified nonylphenol (meth) acrylate and the like are included.

The aromatic ring-containing acrylic monomer may be used alone or in combination of two or more kinds.

Examples of the styrene-based monomer in the aromatic ring-containing copolymerizable monomer include styrene and
Examples include vinyltoluene and α-methylstyrene. Styrene is the most suitable styrene monomer. The styrenic monomers can be used alone or in admixture of two or more.

The tertiary amino group-containing copolymerizable monomer used as the monomer unit of the acrylic polymer in the pressure-sensitive adhesive composition of the present invention has a tertiary amino group in its molecule. The copolymerizable monomer is not particularly limited. The tertiary amino group-containing copolymerizable monomer can be used alone or in combination of two or more kinds.

Specifically, as the tertiary amino group-containing copolymerizable monomer, for example, a tertiary amino group-containing (meth) acrylate can be preferably used. As the tertiary amino group-containing (meth) acrylate, for example,
A compound represented by the following formula (2) is preferable.

[Chemical 2] (In the formula (2), R ⁴ is a hydrogen atom or a methyl group. R ⁵
Is an alkylene group. R ⁶ and R ⁷ are the same or different and each is a hydrocarbon group. )

Examples of the alkylene group for R ⁵ include alkylene groups having 1 to 18 carbon atoms such as methylene group, ethylene group, propylene group, isopropylene group and butylene group. The preferred alkylene group has 2 to 1 carbon atoms.
0 alkylene groups are included, and more preferable alkylene groups include alkylene groups having 2 to 6 carbon atoms,
Particularly, an alkylene group having 2 to 4 carbon atoms is most suitable.

The hydrocarbon group for R ⁶ and R ⁷ is, for example,
Examples thereof include an alkyl group, an aryl group and a cycloalkyl group. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, a hexyl group and the like. An alkyl group of about 10 is mentioned. A preferred alkyl group has 1 carbon atom
A C6 alkyl group (more preferably a C1-4 alkyl group) is included, and a C1-3 alkyl group is particularly suitable.

Further, examples of the aryl group as the hydrocarbon group of R ⁶ and R ⁷ include a phenyl group and a naphthyl group, and examples of the cycloalkyl group include a cyclohexyl group.

R ⁶ and R ⁷ may be the same or different, but are often the same. The hydrocarbon group for R ⁶ and R ⁷ is preferably an alkyl group.

Specifically, as the tertiary amino group-containing (meth) acrylate represented by the formula (2), for example,
N, N- _{DiC 1-10} alkylamino-C _1-18 alkyl (meth) acrylate, N, N-diarylamino-C _{1-18
Examples} thereof include alkyl (meth) acrylate and N, N- _{dicycloalkylamino} -C _1-18 alkyl (meth) acrylate. More specifically, as the tertiary amino group-containing (meth) acrylate, N, N-dialkylamino-ethyl (meth) acrylate [for example, N, N-
Dimethylamino-ethyl (meth) acrylate, N, N
-Diethylamino-ethyl (meth) acrylate, N,
N-dipropylamino-ethyl (meth) acrylate,
N, N-dibutylamino-ethyl (meth) acrylate and the like], N, N-dialkylamino-propyl (meth)
Acrylate [eg, N, N-dimethylamino-propyl (meth) acrylate, N, N-diethylamino-
Propyl (meth) acrylate, N, N-dipropylamino-propyl (meth) acrylate, N, N-dibutylamino-propyl (meth) acrylate, etc.], N,
N-dialkylamino-butyl (meth) acrylate [eg, N, N-dimethylamino-butyl (meth) acrylate, N, N-diethylamino-butyl (meth) acrylate]
Acrylate, N, N-dipropylamino-butyl (meth) acrylate, N, N-dibutylamino-butyl (meth) acrylate and the like], and the like.

In the acrylic polymer contained as the main component in the pressure-sensitive adhesive composition of the present invention, the monomer is an aromatic ring-containing copolymer composed of an aromatic ring-containing acrylic monomer and / or a styrene monomer. Although only the polymerizable monomer and the tertiary amino group-containing copolymerizable monomer may be used, an aromatic ring-containing copolymerizable monomer (such as an aromatic ring-containing acrylic monomer or styrene monomer) and a tertiary amino group The group-containing copolymerizable monomer may be used in combination with the aromatic ring-containing copolymerizable monomer and / or another monomer copolymerizable with the tertiary amino group-containing copolymerizable monomer. As the copolymerizable monomer,
A copolymerizable monomer that does not contain an aromatic ring and a tertiary amino group (may be referred to as “aromatic ring-non-tertiary amino group-containing copolymerizable monomer”) can be used. The aromatic ring / tertiary amino group-free copolymerizable monomer may be used alone or in combination of two or more.

The aromatic ring / tertiary amino group-free copolymerizable monomer is not particularly limited, but does not contain an aromatic ring or a tertiary amino group, and the alkyl group has 1 to 18 carbon atoms. (Meth) acrylic acid alkyl ester which is Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, ( (Meth) 2-ethylhexyl acrylate, (meth)
Examples thereof include alkyl (meth) acrylates such as octyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, and dodecyl (meth) acrylate. These (meth) acrylic acid alkyl esters may be used alone or in admixture of two or more.

Any of various monomers known as modifying monomers for acrylic pressure-sensitive adhesives can be used. The modifying monomer can also be used as an aromatic ring / tertiary amino group-free copolymerizable monomer. Examples of such modifying monomers include vinyl esters such as vinyl acetate; (meth) acrylonitrile; amide group-containing copolymerizable monomers such as (meth) acrylamide; 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4
Hydroxyl group-containing copolymerizable monomers such as -hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate; Epoxy group-containing copolymerizable monomers such as glycidyl (meth) acrylate; (meth) acrylic acid And a carboxyl group-containing copolymerizable monomer such as crotonic acid, itaconic acid, maleic acid and fumaric acid. The modifying monomers may be used alone or in combination of two or more.

As the modifying monomer, a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymerizable monomer are preferably used. Among the carboxyl group-containing copolymerizable monomers, acrylic acid is particularly preferable.

The polar group-containing copolymerizable monomer such as the carboxyl group-containing copolymerizable monomer is an important component for causing cross-linking in the acrylic polymer.

The pressure-sensitive adhesive composition of the present invention comprises the above-mentioned monomer components (aromatic ring-containing copolymerizable monomer, tertiary amino group-containing copolymerizable monomer, aromatic ring / tertiary amino group-free copolymerizable monomer). An acrylic polymer containing a polymerizable monomer, a modifying monomer or the like) as a monomer unit, that is, an acrylic polymer obtained by polymerizing the monomer component is contained as a main component. Examples of the polymerization method include a solution polymerization method using a polymerization initiator such as an azo compound or a peroxide, an emulsion polymerization method or a bulk polymerization method, and a polymerization method performed by irradiating light or radiation with a photoinitiator. Can be adopted.

In the present invention, a method of polymerizing using a polymerization initiator that decomposes to generate radicals (radical polymerization method) can be suitably adopted. In such radical polymerization, a polymerization initiator used in ordinary radical polymerization can be used. Examples thereof include peroxides such as dibenzoyl peroxide and tert-butyl permaleate, and azo compounds such as 2,2'-azobisisobutyronitrile and azobisisovaleronitrile.

In the radical polymerization, the amount of the polymerization initiator used may be the amount usually used in the polymerization of acrylic monomers, for example, 0.005 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers. Degree, preferably 0.
It is about 1 to 5 parts by weight.

In the present invention, the above monomer components (aromatic ring-containing copolymerizable monomer, tertiary amino group-containing copolymerizable monomer, aromatic ring / tertiary amino group-free copolymerizable monomer, and modifying monomer) are used. The acrylic polymer obtained by polymerization using a monomer or the like) can be dried and used as it is. It is also possible to use the polymer after curing it by crosslinking. By crosslinking the polymer, the cohesive force of the pressure-sensitive adhesive can be further increased.

A crosslinking agent can be used in the curing by such crosslinking. That is, the pressure-sensitive adhesive composition of the present invention may contain a crosslinking agent. A heat crosslinking method is preferably used for crosslinking the polymer.

The cross-linking agent widely includes conventionally known ones. As the crosslinking agent, a polyfunctional melamine compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound are particularly preferable. The cross-linking agents can be used alone or in admixture of two or more.

Examples of the polyfunctional melamine compound include methylated trimethylolmelamine and butylated hexamethylolmelamine. Examples of polyfunctional epoxy compounds include diglycidyl aniline and glycerin diglycidyl ether. The amount of the polyfunctional melamine compound and / or the polyfunctional epoxy compound used is, for example, 0.001 to 10 parts by weight, preferably 0.01, relative to 100 parts by weight of the polymer.
Is in the range of 5 parts by weight.

As the polyfunctional isocyanate compound, for example, tolylene diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, a dimer of diphenylmethane diisocyanate, a reaction product of trimethylolpropane and tolylene diisocyanate is used. , A reaction product of trimethylolpropane and hexamethylene diisocyanate, polyether polyisocyanate, polyester polyisocyanate and the like. The amount of the polyfunctional isocyanate compound used is, for example, 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight, based on 100 parts by weight of the polymer.

The pressure-sensitive adhesive composition of the present invention may be used as it is, but may be used by adding various additives as required. For example, in order to adjust the adhesive properties of a pressure-sensitive adhesive composition containing the polymer (particularly an acrylic polymer) as a main adhesive component, a known or commonly used tackifying resin (eg, rosin resin, terpene resin) , Petroleum resin,
Coumarone / indene resin, styrene resin, etc.) may be blended. Further, as an additive other than the tackifying resin,
Various known additives such as a plasticizer, a filler such as finely divided silica, a colorant, and an ultraviolet absorber can also be blended. The amounts of these additives used may be the usual amounts applied to acrylic pressure-sensitive adhesives.

As described above, the pressure-sensitive adhesive composition (adhesive composition) of the present invention comprises an aromatic ring-containing copolymerizable monomer and a tertiary amino group-containing copolymerizable monomer as monomer units. Acrylic polymer containing is included as the main component. The pressure-sensitive adhesive composition can be used as a pressure-sensitive adhesive (adhesive) by drying and optionally crosslinking the polymer with a crosslinking agent. It is important that the refractive index of the pressure-sensitive adhesive composition after drying and / or curing is 1.49 or more. As described above, the refractive index of the material used for the optical film such as the film light guide plate or the optical member such as the glass substrate is about 1.51 to 1.54. When the refractive index after drying and / or curing the composition is less than 1.49, the refractive index difference with the optical film or the optical member becomes large. Therefore, for example, when the layer made of the pressure-sensitive adhesive composition is provided on the film light guide plate which is a kind of optical film,
Total reflection can occur at shallow angles, reducing effective utilization of light. Further, in order to reduce the difference in refractive index from the optical film or optical member, it is important that the pressure-sensitive adhesive composition of the present invention has a refractive index of 1.60 or less after drying and / or curing. is there.

Therefore, the refractive index of the pressure-sensitive adhesive composition of the present invention after drying and / or curing is preferably 1.49 or more and 1.60 or less (1.49 to 1.60). . In particular, 1.50 or more and 1.55 or less (1.50
Is most preferably 1.55).

In the present invention, the refractive index of the pressure-sensitive adhesive composition after drying and / or curing is determined by the aromatic ring-containing copolymerizable monomer (aromatic ring-containing acrylic monomer, styrene monomer, etc.) It can be adjusted depending on the type of the tertiary amino group-containing copolymerizable monomer and the mixing ratio thereof. The refractive index tends to increase as the blending ratio of the aromatic ring-containing copolymerizable monomer increases.

FIG. 1 shows an acrylic polymer using phenoxyethyl acrylate as an aromatic ring-containing copolymerizable monomer, the compounding amount of phenoxyethyl acrylate as a monomer component, and after drying the pressure-sensitive adhesive composition and / or Alternatively, it is a graph showing the relationship with the refractive index after curing. As shown in FIG. 1, the refractive index increases as the compounding amount of phenoxyethyl acrylate increases.

From FIG. 1, the increase rate of the refractive index with respect to the blended amount of phenoxyethyl acrylate within the measurement range is y = 0.0009x + 1.4658, where x is the blended amount of phenoxyethyl acrylate and y is the refractive index. It can be expressed as. The measurement range was such that the compounding amount of phenoxyethyl acrylate was 5 with respect to all the monomer components.
Is in the range of up to 70% by weight.

The monomers other than phenoxyethyl acrylate include butyl acrylate and acrylic acid 3
-Hydroxypropyl is used. The proportion of these two component monomers is butyl acrylate: 3-hydroxypropyl acrylate = 50: 0.06 (parts by weight) when the blending ratio of phenoxyethyl acrylate to the total monomer components is 50% by weight. . Further, the proportion of butyl acrylate mixed is increased or decreased by the proportion of the proportion of phenoxyethyl acrylate to all monomer components increased or decreased.

Further, trimethylolpropane tolylene diisocyanate is blended as a crosslinking agent. That is, the acrylic polymer is crosslinked and cured. The blending amount of the crosslinking agent is 0.8 parts by weight with respect to 100 parts by weight of the polymer.

Therefore, although depending on the kind of the aromatic ring-containing copolymerizable monomer, the blending ratio of the aromatic ring-containing acrylic monomer is 30% by weight or more, preferably 40 to 80% by weight, based on the total amount of the monomer components. Is desirable. When the blending ratio of the aromatic ring-containing acrylic monomer is less than 30% by weight based on the total amount of the monomer components, the refractive index after drying and / or curing of the pressure-sensitive adhesive composition is 1.
It may fall below 49.

The proportion of the tertiary amino group-containing copolymerizable monomer is, for example, 0.5 to 15% by weight, preferably 1 to 10% by weight, based on the total amount of the monomer components. When the compounding ratio of the tertiary amino group-containing copolymerizable monomer is less than 0.5% by weight based on the total amount of the monomer components, the effect of preventing the occurrence of foaming or peeling is lowered, while it exceeds 15% by weight. In that case, yellowing becomes remarkable and it may not be suitable for this application.

FIG. 2 is a schematic sectional view showing the pressure-sensitive adhesive sheet of the present invention. In FIG. 2, 1 is a pressure sensitive adhesive sheet (adhesive sheet), 2 is a release liner, and 3 is a pressure sensitive adhesive layer (adhesive layer). The pressure sensitive adhesive sheet 1 is
A substrateless pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer 3 is provided on a release liner 2.

A pressure-sensitive adhesive sheet which is such a pressure-sensitive adhesive sheet without a base material is, for example, a release liner made of a base material such as a plastic film having a release layer (such as a polyethylene terephthalate film) on the release liner. It can be obtained by applying a pressure-sensitive adhesive composition, drying, and optionally crosslinking and curing. Of course, in the release liner, the surface on which the pressure-sensitive adhesive composition is applied may be the surface on the release layer side. In the release liner, the release layer can be provided on one side or both sides of the base material.

The pressure-sensitive adhesive composition can be applied using a conventional coater, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater or the like. it can.

The thickness of the pressure-sensitive adhesive layer can be appropriately set within a range that does not impair handleability and the like, but is generally 5 to 500 μm.
m, preferably about 10 to 100 μm.

The pressure-sensitive adhesive layer may be composed of a plurality of layers with or without other layers provided that the effects of the present invention are not impaired. For example, the pressure-sensitive adhesive sheet may be a double-sided adhesive sheet in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention is provided on both surfaces of a transparent substrate.

A plastic film is preferably used as the base material of the release liner, but it may be paper, foam, metal foil or the like. The thickness of the base material can be appropriately selected according to the purpose, but is generally about 10 to 500 μm.

The material of the plastic film as the base material of the release liner is polyester such as polyethylene terephthalate, polypropylene, ethylene-
Examples include polyolefins such as propylene copolymers and thermoplastic resins such as polyvinyl chloride. The plastic film may be either a non-stretched film or a stretched (uniaxially stretched or biaxially stretched) film.

As the release layer, a release layer used as a release layer in a conventional release liner (for example, a silicone release layer) can be used.

Such a pressure-sensitive adhesive sheet can be bonded to an optical film such as a film light guide plate to produce an optical film having a pressure-sensitive adhesive layer.

The optical film having such a pressure-sensitive adhesive layer can be used by making a display device by sticking and fixing it to a display panel. Of course, the surface of the optical film to be attached to the display panel is the surface on the pressure sensitive adhesive layer side, and by peeling off the release liner, the surface on the pressure sensitive adhesive layer side of the optical film is exposed, and the display panel It can be attached and fixed to.

The pressure-sensitive adhesive sheet of the present invention may be used as a pressure-sensitive adhesive tape by cutting it into a suitable width and winding it into a roll.

FIG. 3 is a schematic sectional view showing the optical film of the present invention. In FIG. 3, 4 is an optical film having a pressure-sensitive adhesive layer, 5 is an optical film such as a film light guide plate, and 6 is a pressure-sensitive adhesive layer.

The optical film having such a pressure-sensitive adhesive layer formed on one surface thereof is prepared by using a conventional coating device (roll coater, reverse coater, gravure coater, bar coater, etc.). A method of coating the product on an optical film and drying, and a method of heating and crosslinking if necessary, or a method of curing with light such as ultraviolet rays,
Further, it can be obtained by a method of bonding to an optical film using the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive sheet may be used for transfer onto the optical film or may be directly copied.

In the optical film of the present invention, as the film light guide plate, for example, a film in which a light guide function is imparted by forming fine unevenness on one surface of a polycarbonate film is exemplified. The refractive index of the film material used for these film light guide plates is 1.49 or more,
It is preferably 1.50 or more, more preferably 1.51 or more, and most preferably 1.52 or more. The upper limit of the refractive index is preferably 1.60. The thickness of the film light guide plate can be appropriately selected from the range of, for example, about 10 to 200 μm according to the application.

Other examples of the optical film include an antireflection film and a conductive film, and the materials constituting them are preferably those having the above refractive index.

In the present invention, the optical film may have a release liner on the surface on the pressure sensitive adhesive layer side.

The optical film of the present invention is adhered and fixed to a display panel (for example, a liquid crystal panel having a structure in which a plurality of optical members such as a glass substrate, a polarizing plate and a retardation plate are laminated together with a liquid crystal). Can be used.

FIG. 4 is a schematic sectional view showing a state in which an optical film is attached to a liquid crystal panel. In FIG. 4, 4 is an optical film having a pressure-sensitive adhesive layer on one surface, 5 is an optical film, 6 is a pressure-sensitive adhesive layer, and 7 is a liquid crystal panel (the description of various optical members such as a glass substrate is omitted. It is). The surface of the optical film 4 on the pressure sensitive adhesive layer 6 side is bonded and fixed to the liquid crystal panel.

As described above, the display device can be manufactured by bonding the optical film to the display panel. In addition,
The display device shown in FIG. 4 uses a liquid crystal panel as a display panel. A display device (liquid crystal display device) in which an optical film is attached to the liquid crystal panel can be used as a transmissive liquid crystal display device.

A liquid crystal panel is preferably used as the display panel. As the liquid crystal panel, it is possible to preferably use a liquid crystal panel used in a display screen section of a mobile phone (such as a mobile phone) in mobile communication. As a substrate of such a liquid crystal panel, a glass substrate, a plastic substrate (in particular, a glass substrate) or the like can be used. The refractive index thereof is 1.49 or more, preferably 1.50 or more, more preferably 1.51 or more, most preferably 1.52 or more, and the upper limit thereof is preferably 1.60.

Note that in the present invention, even if a plastic substrate (for example, a substrate made of a plastic member such as polycarbonate or polymethylmethacrylate) is used as a substrate for an optical member such as a display panel, the environment is assumed to be visible. In this case, the visibility is prevented from being deteriorated due to foaming or peeling under any environment, and the excellent visibility can be continuously exhibited.

The refractive index of the pressure-sensitive adhesive composition of the present invention after drying and / or curing is close to that of an optical film such as a film light guide plate or an optical member such as a glass substrate of a liquid crystal panel. Since it is a value, there is little difference in refractive index at the interface between the pressure-sensitive adhesive layer and the optical film by the pressure-sensitive adhesive composition, or at the interface between the pressure-sensitive adhesive layer and the optical member. Optical film / Pressure-sensitive adhesive layer /
It is possible to minimize the total reflection at each interface of the optical member. Therefore, the optical film using the pressure-sensitive adhesive composition of the present invention can exhibit excellent optical performance and can further effectively utilize light.

Of course, since the acrylic polymer is used, the adhesive performance is excellent.

[0078]

According to the present invention, since the specific monomer component is used as the monomer unit of the pressure-sensitive adhesive composition, the refractive index after drying and / or curing of the pressure-sensitive adhesive composition is Has a high refractive index, which is almost the same as the refractive index of an optical film such as an antireflection film, a conductive film (ITO film), a film light guide plate, or an optical member such as a glass substrate forming a liquid crystal panel. Therefore, the refractive index difference at each interface of the optical film / pressure-sensitive adhesive layer / optical member is reduced, and total reflection can be minimized.
Therefore, when an optical film using the pressure-sensitive adhesive composition is used, light can be effectively used and power consumption can be greatly suppressed.

Moreover, even if the plastic member is used as the optical member, the deterioration of the visibility is prevented under any environment where the visual recognition is supposed.

[0080]

EXAMPLES Examples of the present invention will be described below for more specific description. In the following, "parts" means "parts by weight" and "%" means "% by weight".

Example 1 Phenoxyethyl acrylate: 50 parts, Butyl acrylate: 46 parts, Acrylic acid: 1 part, N, N-Dimethylaminopropyl acrylate: 3 parts, 3-Hydroxypropyl acrylate: 0.06 Parts and 45 parts of ethyl acetate as a polymerization solvent were charged into a three-necked flask, and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, benzoyl peroxide: 0.2 part was added, and the temperature was raised to 60 ° C. and reacted for 10 hours, then to 75 ° C. and reacted for 2 hours. It was Ethyl acetate was added to the reaction solution to obtain an acrylic polymer solution having a solid content concentration of 25% by weight. To this acrylic polymer solution, trimethylolpropane tolylene diisocyanate as a cross-linking agent:
After adding 8 parts, a release liner made of a polyethylene terephthalate film having a thickness of 38 μm was cast-coated so that the thickness after drying was about 25 μm, and heat-dried at 130 ° C. for 3 minutes to form a release liner. Covers 5 more
Aging was performed at 0 ° C. for 72 hours to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a crosslinked structure.

Example 2 Phenoxyethyl acrylate: 6 as a monomer component
5 parts, isononyl acrylate: 27 parts, acrylic acid: 3
Parts, N, N-diethylaminoethyl acrylate: 5 parts,
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 0.1 part of 3-hydroxypropyl acrylate was used.

Comparative Example 1 Phenoxyethyl acrylate: 2 as a monomer component
5 parts, butyl acrylate: 71 parts, acrylic acid: 1 part,
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that N, N-dimethylaminopropyl acrylate: 3 parts and 3-hydroxypropyl acrylate: 0.1 part were used.

Comparative Example 2 Phenoxyethyl acrylate: 5 as a monomer component
0 parts, butyl acrylate: 49 parts, acrylic acid: 1 part,
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 3-hydroxypropyl acrylate: 0.06 part was used.

With respect to the pressure-sensitive adhesive sheets according to Examples 1 and 2 and Comparative Examples 1 and 2, the foaming / peeling prevention property and the refractive index of the layer of the pressure-sensitive adhesive composition were evaluated by the following foaming / peeling prevention property. It was measured or evaluated by the method and the refractive index measuring method. The results of measurement or evaluation are shown in Table 1. Then, from these measurement or evaluation results, to determine the effect of the optical performance for the pressure-sensitive adhesive composition according to Examples and Comparative Examples,
Those having excellent optical performance are shown in Table 1, and those having normal or not so good are shown in Table 1. The evaluation as an optical film was also performed by the following method.

(Evaluation Method for Preventing Foaming / Peeling) A plate made of polymethylmethacrylate having a thickness of 1.2 mm (PMMA
A film made of polyethylene terephthalate (PET film) having a thickness of 125 μm was attached to a plate via the pressure-sensitive adhesive sheet (adhesive sheet) obtained in Examples and Comparative Examples, and aged at 23 ° C. for 3 days, 8
Put PMMA into a thermo-hygrostat at 0 ° C or 60 ° C and 95% RH for 500 hours.
By observing the appearance of the entire surface of the plate / adhesive sheet / PET film layered structure, foaming with a diameter (φ) of 0.1 mm or more, and / or peeling at the edges, " Those that “decreased” were judged as x, and those that did not show such a change were judged as o.

(Refractive Index Measuring Method) With an Abbe refractometer,
Irradiation with sodium D-rays in an atmosphere of 25 ° C., the refractive index of the layer (pressure-sensitive adhesive layer) of the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheet (that is, after drying the pressure-sensitive adhesive composition and / or The refractive index after curing) was measured.

Table 1 shows the presence / absence of the use of the tertiary amino group-containing copolymerizable monomer as the monomer component in the pressure-sensitive adhesive composition for the pressure-sensitive adhesive sheets according to Examples and Comparative Examples. It is also shown in the column of "presence or absence of amine".

[0089]

[Table 1]

From Table 1, the pressure-sensitive adhesive compositions according to the examples have almost the same refractive index as the optical film and the optical member. Moreover, even if a plastic member is used as the optical member, foaming does not occur between the optical member and the pressure-sensitive adhesive layer or in the pressure-sensitive adhesive layer even in a harsh environment, and the pressure-sensitive adhesive is also formed. The agent layer is not peeled off from the optical member, and the reduction in visibility is prevented.

(Evaluation as Optical Film) Using the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, 40 mm
A 1.2 mm thick polymethylmethacrylate plate (PMMA plate) processed into a width of 25 mm in advance
Has a slope of 43 ° to the film surface and a pitch of 0.25 m
A film light guide plate having a uniform prism of m is attached, a cold cathode tube is arranged on the end face of the PMMA plate facing the slope of the film light guide plate, and the light emission state is changed from the face opposite to the face where the film light guide plate is attached. As a result of observation, the adhesive sheets according to Examples 1 and 2 showed good in-plane uniformity of luminance and good front luminance, but the adhesive sheets of Comparative Example 1 became darker as the distance from the cold cathode tube increased, and the central portion The front brightness of the sample was also clearly reduced, and it was not so good.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of phenoxyethyl acrylate as a monomer component and the refractive index of a pressure-sensitive adhesive composition after drying and / or after curing.

FIG. 2 is a schematic sectional view showing a pressure-sensitive adhesive sheet of the present invention.

FIG. 3 is a schematic sectional view showing an optical film of the present invention.

FIG. 4 is a schematic cross-sectional view showing a state in which the optical film glass substrate of the present invention is attached to a liquid crystal panel.

[Explanation of symbols]

1 Pressure-sensitive adhesive sheet 2 Release liner 3 Pressure-sensitive adhesive layer 4 Optical film having pressure-sensitive adhesive layer 5 Optical film 6 Pressure-sensitive adhesive layer 7 LCD panel

Claims (6)

[Claims] 1. A pressure-sensitive adhesive composition containing, as a main component, an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit, which is used as a monomer unit of the acrylic polymer. Furthermore, it contains a tertiary amino group-containing copolymerizable monomer and has a refractive index of 1. after drying and / or curing.
A pressure-sensitive adhesive composition which is 49 or more and 1.60 or less. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the tertiary amino group-containing copolymerizable monomer is a tertiary amino group-containing (meth) acrylate. 3. The pressure-sensitive adhesive composition according to claim 2, wherein the tertiary amino group-containing (meth) acrylate is N, N-dialkylamino-alkyl (meth) acrylate. 4. The pressure-sensitive adhesive composition according to claim 1, wherein the aromatic ring-containing copolymerizable monomer is an aromatic ring-containing acrylic monomer and / or styrene monomer. 5. A pressure-sensitive adhesive sheet for adhering and fixing an optical film to a display panel of a display device, wherein the pressure-sensitive adhesive according to claim 1 is provided on a release liner. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed of the composition. 6. A pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 4 on one surface of an optical film for sticking and fixing to a display panel of a display device. An optical film on which is formed.