JP2011042785A - Pressure-sensitive adhesive tape or sheet and optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive tape or sheet reducing the total reflection of light in each interface of an optical film/a pressure-sensitive adhesive tape or sheet/an optical member. <P>SOLUTION: The pressure-sensitive adhesive tape or sheet 1 has constitution in which two or more layers of pressure-sensitive adhesive layers 2 and 3 are laminated in the thickness direction. In the pressure-sensitive adhesive tape or sheet 1, the pressure-sensitive adhesive forming the two or more layers of the pressure-sensitive adhesive layers 2 and 3 is an acrylic pressure-sensitive adhesive; the pressure-sensitive adhesive layers 2 and 3 are pressure-sensitive adhesive layers changed into a crosslinked structure; and the difference in refractive index of the two pressure-sensitive adhesive layers 2 and 3 located on at least both the surface sides is ≥0.02. In the pressure-sensitive adhesive tape or sheet 1, the pressure-sensitive adhesive layers 2 and 3 may be changed into the crosslinked structure with at least one compound selected from among multifunctional melamine compounds, multifunctional epoxy compounds and multifunctional isocyanate compounds. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive tape or sheet suitable for fixing and adhering an optical film, and an optical film in which the pressure-sensitive adhesive tape or sheet is used.

  In recent years, an electronic device having a display using various display panels has become widespread, and as a display panel in the display, a display panel in a touch panel or various displays (for example, a liquid crystal panel, a display panel of a cathode ray tube, a plasma display, etc. Display panels, EL display panels, and the like). In such an electronic device, in order to improve visibility and brightness, studies on a backlight, a reflector, and the like, and studies on an optical functional film have been made.

  The optical functional film is adhered and fixed to the display panel with a pressure-sensitive adhesive, and the pressure-sensitive adhesive is considered to adhere mainly to glass and various plastic materials, and therefore peels off. Investigations have been made on floating, weather resistance, etc. However, optical studies have not been made, and there is a problem that optical properties cannot be satisfied, such as a decrease in transmittance, depending on the combination of a certain transparent substrate and a pressure-sensitive adhesive. It was.

  In addition, advancement of required characteristics such as effective use of light and suppression or reduction of power consumption is progressing. For example, a display panel of a liquid crystal display device includes a liquid crystal, a glass substrate, a polarizing plate (film), a retardation, and the like. It is the structure which laminated | stacked several optical members, such as a board (film). Since an optical film (optical functional film) is also used by being bonded to an optical member constituting these display panels, from the viewpoint of effective use of light, an optical film / pressure-sensitive adhesive layer / optical It is required to prevent total reflection at each interface of the structural member.

  In general, the refractive index of materials used for optical films and optical members is, for example, about 1.52 for glass, about 1.51 for methacrylic resin, and 1.54 for polycarbonate. Degree. On the other hand, the refractive index (the refractive index of the pressure-sensitive adhesive layer) after drying or curing a conventional pressure-sensitive adhesive is about 1.47. Therefore, a refractive index difference is generated at the interface of the optical film / pressure-sensitive adhesive layer or the interface of the pressure-sensitive adhesive layer / optical member, and total reflection occurs at a shallow angle, thereby preventing effective use of light. It is a problem.

  Various pressure-sensitive adhesives that can prevent total reflection as described above have been proposed (see Patent Documents 1 and 2).

JP 2002-173656 A JP 2003-13029 A

  However, in Japanese Patent Application Laid-Open No. 2002-173656 and Japanese Patent Application Laid-Open No. 2003-13029, a pressure-sensitive adhesive having a specific refractive index is used, but the pressure-sensitive adhesive layer using the pressure-sensitive adhesive is The use of a single layer is being considered. Therefore, for example, the refractive index difference at each interface of the optical film / pressure-sensitive adhesive layer / optical member may still not be sufficient, and the total reflection at each interface is more effectively prevented and minimized. There is a need to suppress it.

Accordingly, an object of the present invention is to use an optical film / pressure-sensitive adhesive tape or sheet / optical when a pressure-sensitive adhesive tape or sheet is used to bond various optical films to various optical members constituting a display device. An object of the present invention is to provide a pressure-sensitive adhesive tape or sheet that can reduce the total reflection of light at each interface of the structural member.
Another object of the present invention is to provide an optical film capable of effectively utilizing light by reducing total reflection at each interface of the optical film / pressure-sensitive adhesive tape or sheet / optical member.

  As a result of intensive studies to achieve the above object, the present inventors bonded the optical film and the optical member using a pressure-sensitive adhesive tape or sheet having a specific layer structure. It was found that the total reflection of light at each interface of the optical film / pressure-sensitive adhesive tape or sheet / optical member could be reduced, and the present invention was completed.

  That is, the present invention is a pressure-sensitive adhesive tape or sheet having a structure in which two or more pressure-sensitive adhesive layers are laminated in the thickness direction, and forms the two or more pressure-sensitive adhesive layers. The adhesive is an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer having a cross-linked structure, and at least the difference in refractive index between the two pressure-sensitive adhesive layers located on both surface sides The pressure-sensitive adhesive tape or sheet for optical members is provided, wherein is 0.02 or more.

  In the present invention, the pressure-sensitive adhesive layer may be cross-linked with at least one compound selected from a polyfunctional melamine compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound. Moreover, it is preferable that the refractive indexes of the two pressure-sensitive adhesive layers located on both surface sides are 1.40 to 1.60, respectively, and two pressure-sensitive adhesive layers located on both surface sides. The refractive index of the pressure-sensitive adhesive layer on the low refractive index side is 1.40 to 1.50, and the refractive index of the pressure-sensitive adhesive layer on the high refractive index side is 1.45 to 1.55. preferable. Moreover, you may have the structure by which the pressure sensitive adhesive layer of two or more layers was laminated | stacked on the single side | surface of the release liner.

  The pressure-sensitive adhesive tape or sheet for optical members of the present invention can be suitably used as a pressure-sensitive adhesive tape or sheet for adhering and fixing an optical film to a display panel of a display device.

  The present invention also provides the optical film for an optical member, wherein the pressure-sensitive adhesive tape or sheet is adhered to one surface of the optical film that is adhered and fixed to the display panel of the display device. I will provide a. A liquid crystal panel is suitable as the display panel.

  According to the present invention, two or more pressure-sensitive adhesive layers are provided, and among the two or more pressure-sensitive adhesive layers, at least two pressure-sensitive adhesive layers located on both surface sides are provided. Since the refractive index of the film is different by 0.02 or more, the refractive index difference at each interface of the optical film / pressure-sensitive adhesive tape or sheet / optical member can be reduced, and total reflection is minimized. Can do. Accordingly, when an optical film using the pressure-sensitive adhesive tape or sheet is used, light can be effectively used.

It is a schematic sectional drawing which shows partially the example of the pressure sensitive adhesive tape or sheet | seat of this invention. It is a schematic sectional drawing which shows partially the example of the pressure sensitive adhesive tape or sheet | seat of this invention. It is a schematic sectional drawing which shows partially an example of the optical film of this invention.

[Pressure-sensitive adhesive tape or sheet]
The pressure-sensitive adhesive tape or sheet of the present invention (sometimes referred to as “laminated pressure-sensitive adhesive tape”) has a configuration in which two or more pressure-sensitive adhesive layers (adhesive layers) are laminated in the thickness direction. Further, among the two or more pressure-sensitive adhesive layers, at least two pressure-sensitive adhesive layers located on both surface sides have a refractive index difference of 0.02 or more (at least 0.02). It has a configuration. The refractive index difference between the two pressure-sensitive adhesive layers located on both surface sides is not particularly limited as long as it is 0.02 or more (preferably 0.03 or more, more preferably 0.04 or more). If the rate difference is too large, interfacial reflection occurs. Therefore, it is desirable that the difference is 0.2 or less (preferably 0.15 or less, more preferably 0.1 or less). Accordingly, the difference in refractive index between the two pressure-sensitive adhesive layers located on both surface sides is, for example, 0.02 to 0.2 (preferably 0.03 to 0.15, more preferably 0.04 to 0). .1) can be selected from the range. In addition, the effect of the effective use of light will fall that the refractive index difference of the two pressure sensitive adhesive layers located in both surface side is less than 0.02.

  The size of each refractive index of the two pressure-sensitive adhesive layers located on both surface sides is not particularly limited as long as the difference in refractive index is 0.02 or more, and the type of application and adherend. It can adjust suitably according to etc. For example, when the laminated pressure-sensitive adhesive tape is used for attaching an optical film to an optical member, the refractive indices of the two pressure-sensitive adhesive layers located on both surface sides are, for example, 1. It can be selected from the range of 40 to 1.60 (preferably 1.40 to 1.55). More specifically, the refractive index of the pressure-sensitive adhesive layer on the low refractive index side of the two pressure-sensitive adhesive layers located on both surface sides is, for example, 1.40 to 1.50 (preferably 1 .42 to 1.48, more preferably 1.43 to 1.46). On the other hand, the refractive index of the pressure-sensitive adhesive layer on the high refractive index side among the two pressure-sensitive adhesive layers located on both surface sides is, for example, 1.45 to 1.55 (preferably 1.47 to 1). .53, more preferably from 1.49 to 1.52).

  The refractive index of the pressure-sensitive adhesive layer or the like can be measured by irradiating sodium D-line in an atmosphere at 25 ° C. with an Abbe refractometer.

  As a laminated pressure-sensitive adhesive tape, a pressure-sensitive adhesive from one surface side (high refractive index side or low refractive index side) to the other surface side (low refractive index side or high refractive index side) It is preferable that each layer has a structure in which each refractive index of two or more pressure-sensitive adhesive layers changes gradually or stepwise, and particularly changes gradually or stepwise in one direction ( Preferably, it has a (decreasing or increasing) configuration. By adopting such a configuration (for example, a configuration in which the refractive index difference gradually decreases from the pressure-sensitive adhesive layer on the high refractive index side to the pressure-sensitive adhesive layer on the low refractive index side), Even if the difference in refractive index between the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer on the low refractive index side is large, the refractive index gradually increases from one pressure-sensitive adhesive layer to the other pressure-sensitive adhesive layer. Or since it changes in one direction step by step, total reflection inside the laminated pressure-sensitive adhesive tape can be effectively prevented. For example, when the laminated pressure-sensitive adhesive tape has two pressure-sensitive adhesive layers, one step is performed from the pressure-sensitive adhesive layer on the high refractive index side to the pressure-sensitive adhesive layer on the low refractive index side. Thus, the refractive index of the pressure-sensitive adhesive layer is reduced. In the case of having three or more pressure-sensitive adhesive layers, the pressure-sensitive adhesive layer on the high refractive index side is changed to the pressure-sensitive adhesive layer on the low refractive index side in two or more stages. It is preferable to have a configuration in which the refractive index of the pressure-sensitive adhesive layer gradually decreases.

  Two or more pressure-sensitive adhesives so that the refractive index of the pressure-sensitive adhesive layer changes gradually or stepwise in one direction from one pressure-sensitive adhesive layer to the other pressure-sensitive adhesive layer. In the case of laminating the layers, in the laminate of the pressure-sensitive adhesive layers in which two or more layers are laminated, the refractive index difference between the two pressure-sensitive adhesive layers in contact with each other is not particularly limited. 2 or less (for example, 0.02-0.2, preferably 0.03-0.15, more preferably 0.04-0.1).

  The laminated pressure-sensitive adhesive tape has at least two layers of pressure-sensitive adhesive as long as the refractive indexes of the two pressure-sensitive adhesive layers located on both surface sides are different by 0.02 or more. The configuration in which the agent layer is laminated is not particularly limited. For example, as shown in FIG. 1, a configuration in which two pressure-sensitive adhesive layers are directly laminated, as shown in FIG. 2, two pressure-sensitive properties are used. Examples include a configuration in which the adhesive layer is laminated via another layer (such as a base material or another pressure-sensitive adhesive layer). As the laminated pressure-sensitive adhesive tape, a substrate-less type pressure-sensitive adhesive tape or sheet is suitable.

  In the present invention, the laminated pressure-sensitive adhesive tape can be suitably used for attaching an optical film to an optical member, and thus is a double-sided adhesive tape or sheet in which both surfaces are adhesive surfaces (adhesive surfaces). It is important to be. In this case, each surface of the two pressure-sensitive adhesive layers having a refractive index different by 0.02 or more and positioned on both surface sides can be used as an adhesive surface.

  1 and 2 are schematic sectional views partially showing examples of the pressure-sensitive adhesive tape or sheet of the present invention. 1-2, 1 and 11 are pressure-sensitive adhesive tapes or sheets (laminated pressure-sensitive adhesive tape), 2 is a pressure-sensitive adhesive layer, 3 is a pressure-sensitive adhesive layer, 4 is a pressure-sensitive adhesive layer, 5 is Release liner. A laminated pressure-sensitive adhesive tape 1 shown in FIG. 1 has a configuration in which a pressure-sensitive adhesive layer 3 is formed on a release liner 5 and a pressure-sensitive adhesive layer 2 is further laminated on the pressure-sensitive adhesive layer 3. The double-sided adhesive tape or sheet of the base material-less type. Also, the laminated pressure-sensitive adhesive tape 11 shown in FIG. 2 has a pressure-sensitive adhesive layer 3 formed on a release liner 5, and a pressure-sensitive adhesive layer 4 and a pressure-sensitive adhesive layer 3 on the pressure-sensitive adhesive layer 3. The adhesive layer 2 is a base-less double-sided adhesive tape or sheet having a configuration in which the adhesive layer 2 is laminated in this order. In these laminated pressure-sensitive adhesive tape 1 and laminated pressure-sensitive adhesive tape 11, the pressure-sensitive adhesive layer 2 and the pressure-sensitive adhesive layer 3 have different refractive indexes, specifically, pressure-sensitive. The adhesive layer 2 has a refractive index higher by 0.02 or more than the pressure-sensitive adhesive layer 3. Accordingly, relatively, the pressure-sensitive adhesive layer 2 is a pressure-sensitive adhesive layer on the high refractive index side, and the pressure-sensitive adhesive layer 3 is a pressure-sensitive adhesive layer on the low refractive index side.

  In the laminated pressure-sensitive adhesive tape 11 shown in FIG. 2, the pressure-sensitive adhesive layer 4 has a refractive index that is smaller than the refractive index of the pressure-sensitive adhesive layer 2 and larger than the refractive index of the pressure-sensitive adhesive layer 3. have. Therefore, the refractive index decreases in the order of the pressure-sensitive adhesive layer 2, the pressure-sensitive adhesive layer 4, and the pressure-sensitive adhesive layer 3.

  Note that the release liner 5 has a release surface on both sides, and the surface of the release liner 5 (the surface opposite to the pressure-sensitive adhesive layer 3) is superposed on the surface of the pressure-sensitive adhesive layer 2 and rolled. It can be produced as a pressure-sensitive adhesive tape or sheet in a form wound in a roll shape.

[Pressure-sensitive adhesive layer]
In FIGS. 1 and 2, two pressure-sensitive adhesive layers located on both surface sides are pressure-sensitive adhesive layers on the high refractive index side (sometimes referred to as “high refractive index pressure-sensitive adhesive layers”). It has a pressure-sensitive adhesive layer 2 and a pressure-sensitive adhesive layer 3 which is a pressure-sensitive adhesive layer on the low refractive index side (sometimes referred to as a “low refractive index pressure-sensitive adhesive layer”). Moreover, in FIG. 2, as a pressure sensitive adhesive layer (it may be called an "intermediate pressure sensitive adhesive layer") located between two pressure sensitive adhesive layers located on both surface sides, a pressure sensitive adhesive is used. Only one pressure-sensitive adhesive layer 4 having a refractive index smaller than the refractive index of the layer 2 and larger than the refractive index of the pressure-sensitive adhesive layer 3 is provided. Of course, only one intermediate pressure-sensitive adhesive layer may be provided, or two or more layers may be provided. As the pressure-sensitive adhesive forming such a pressure-sensitive adhesive layer, conventionally known ones such as a rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive can be used. As described above, since the pressure-sensitive adhesive layer having a different refractive index is used as the pressure-sensitive adhesive layer, an acrylic pressure-sensitive adhesive is preferably used from the viewpoint of easily controlling the refractive index. Can do. The pressure-sensitive adhesives forming each pressure-sensitive adhesive layer can be used alone or in combination of two or more.

  The acrylic pressure-sensitive adhesive forming each pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive base polymer for controlling the refractive index to a desired refractive index as shown below. As the monomer component (monomer component) of the polymer, an aromatic ring-containing copolymerizable monomer or a fluorine atom-containing copolymerizable monomer can be used. Specifically, in a normal acrylic pressure-sensitive adhesive, (meth) acrylic acid alkyl ester is used as a monomer main component, but the refractive index of the pressure-sensitive adhesive layer by the acrylic pressure-sensitive adhesive is changed. In the case of increasing, an aromatic ring-containing copolymerizable monomer is used as the monomer component, while in the case of reducing the refractive index of the pressure-sensitive adhesive layer, a fluorine atom-containing copolymerizable monomer is used as the monomer component, and Adjust the refractive index of the pressure-sensitive adhesive layer to the desired refractive index by adjusting the ratio (upper limit: 100% by weight) of the aromatic ring-containing copolymerizable monomer and fluorine atom-containing copolymerizable monomer to the total amount of monomer components. Can be controlled. Note that the refractive index of the pressure-sensitive adhesive layer by the acrylic pressure-sensitive adhesive tends to increase as the blending ratio of the aromatic ring-containing copolymerizable monomer increases, while the fluorine atom-containing acrylic monomer has a higher refractive index. As the blending ratio increases, it tends to decrease.

  Accordingly, the pressure sensitive adhesive forming the high refractive index pressure sensitive adhesive layer (sometimes referred to as “high refractive index pressure sensitive adhesive”) is an acrylic heavy polymer that is the base polymer of the acrylic pressure sensitive adhesive. It is preferable to use a pressure-sensitive adhesive in which an aromatic ring-containing copolymerizable monomer is used as the monomer component of the coalescence (monomer component). Further, as a pressure-sensitive adhesive for forming a low-refractive index pressure-sensitive adhesive layer (sometimes referred to as “low-refractive index pressure-sensitive adhesive”), an acrylic heavy polymer that is a base polymer of an acrylic pressure-sensitive adhesive is used. It is preferable to use a pressure-sensitive adhesive in which a fluorine atom-containing copolymerizable monomer is used as a monomer component (monomer component) of the coalescence. Furthermore, as a pressure-sensitive adhesive forming the intermediate pressure-sensitive adhesive layer (sometimes referred to as “intermediate pressure-sensitive adhesive”), an acrylic polymer that is a base polymer of the acrylic pressure-sensitive adhesive is used. As the monomer component (monomer component), it is preferable to use a pressure-sensitive adhesive in which an aromatic ring-containing copolymerizable monomer or a fluorine atom-containing copolymerizable monomer is used.

(High refractive index pressure sensitive adhesive)
As described above, an acrylic pressure-sensitive adhesive can be preferably used as the high-refractive index pressure-sensitive adhesive from the viewpoint of controlling the refractive index, and in particular, the refractive index of the high-refractive index pressure-sensitive adhesive layer. In order to control the refractive index to a desired size, an aromatic ring-containing copolymer is used as a monomer component (monomer component) of an acrylic polymer that is a base polymer of an acrylic pressure-sensitive adhesive. A pressure-sensitive adhesive using a functional monomer is preferred. That is, as the high refractive index pressure-sensitive adhesive, a pressure-sensitive adhesive composition containing an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit as a base polymer or a main component is preferably used. Can do.

  The aromatic ring-containing copolymerizable monomer is not particularly limited as long as it is a copolymerizable monomer having an aromatic ring in the molecule. As the aromatic ring-containing copolymerizable monomer, for example, an aromatic ring-containing ethylenically unsaturated monomer can be suitably used. Aromatic ring-containing copolymerizable monomers can be used alone or in admixture of two or more.

  As such an aromatic ring-containing copolymerizable monomer, for example, an aromatic ring-containing copolymerizable monomer or an aromatic ring-containing monomer described in JP-A-2002-173656 and JP-A-2003-13029 is used. be able to. Specifically, examples of the aromatic ring-containing copolymerizable monomer include aromatic ring-containing acrylic monomers and styrene 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, but an aromatic ring-containing (meth) acrylic ester is preferable. Examples of the aromatic ring-containing (meth) acrylic acid ester include an aromatic ring-containing (meth) acrylic acid alkyl ester, (meth) acrylic acid aryl ester [(meth) acrylic acid phenyl ester and the like] and the like. Among the aromatic ring-containing (meth) acrylic acid esters, aromatic ring-containing (meth) acrylic acid alkyl esters are particularly preferable.

（式（１）中、Ｒ¹は水素原子又はメチル基である。Ｒ²はアルキレン基、または−Ｒ³−（ＯＲ³）_n−である。ここでＲ³はアルキレン基であり、ｎは正の整数である。また、Ｘはアリール基又はアリールオキシ基である。） As the aromatic ring-containing (meth) acrylic acid alkyl ester, a compound represented by the following formula (1) is preferable.

(In the formula (1), R ¹ is a hydrogen atom or a methyl group. R ² is an alkylene group, or —R ³ — (OR ³ ) _n —, where R ³ is an alkylene group, and n is (It 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 a methylene group, an ethylene group, a propylene group, an isopropylene group, and a butylene group. Preferred alkylene groups include those having 1 to 4 carbon atoms, and a methylene group and an ethylene group are particularly suitable.

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

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

  The aryl group for X includes a phenyl group, a naphthyl group, and the like. The aryloxy group includes a phenyloxy group, a naphthyloxy group, and the like. The aryl group and aryloxy group of X may contain 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 for the aryl group and aryloxy group of X, an alkyl group and an alkoxy group are preferable. A substituent can be used individually or in combination of 2 or more types.

Specifically, as the aromatic ring-containing (meth) acrylic acid alkyl ester represented by the formula (1), aryl C _1-18 alkyl (meth) acrylate, aryloxy C _1-18 alkyl (meth) acrylate, Aryloxypoly C _1-6 alkylene glycol (meth) acrylate and the like can be mentioned. More specifically, the aromatic ring-containing (meth) acrylic acid alkyl ester includes, for example, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide (EO) modified cresol ( And (meth) acrylate, ethylene oxide (EO) -modified nonylphenol (meth) acrylate, and the like.

  Examples of the styrene monomer in the aromatic ring-containing copolymerizable monomer include styrene, vinyltoluene, α-methylstyrene, and the like. Styrene is optimal as the styrenic monomer.

  In the high refractive index pressure-sensitive adhesive, the monomer component of the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive is an aromatic ring comprising an aromatic ring-containing acrylic monomer and / or a styrene monomer. Although only the containing copolymerizable monomer may be used, the aromatic ring-containing copolymerizable monomer (such as an aromatic ring-containing acrylic monomer or styrene monomer) and the aromatic ring-containing copolymerizable monomer are copolymerized. You may use together with the other monomer which can superpose | polymerize. As the copolymerizable monomer (copolymerizable monomer), an aromatic ring-free copolymerizable monomer (such as an aromatic ring-free ethylenically unsaturated monomer) can be used. The copolymerizable monomers can be used alone or in admixture of two or more.

In such a copolymerizable monomer, the aromatic ring-free copolymerizable monomer is not particularly limited, but does not contain an aromatic ring, and is a (meth) acryl having 1 to 18 carbon atoms in the alkyl group. An acid alkyl ester (sometimes referred to as “aromatic ring-free (meth) acrylic acid alkyl ester”) can be preferably used. Specifically, as the aromatic ring-free (meth) acrylic acid alkyl ester, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, Butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, (me ) Heptadecyl acrylate, and (meth) acrylic acid C _1-18 alkyl esters such as (meth) octadecyl acrylate.

  Moreover, as the copolymerizable monomer, various monomers known as monomers for modifying acrylic pressure-sensitive adhesives can be used. Examples of such modifying monomers include hydroxyl groups such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. Group-containing copolymerizable monomers; carboxyl group-containing copolymerizable monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; vinyl esters such as vinyl acetate; (meth) acrylonitrile Amide group-containing copolymerizable monomers such as (meth) acrylamide; epoxy group-containing copolymerizable monomers such as glycidyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylic acid alkyl ester, etc. Examples include amino group-containing copolymerizable monomers. As such a modifying monomer, a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymerizable monomer are suitable. Among the carboxyl group-containing copolymerizable monomers, acrylic acid is particularly suitable. The polar group-containing copolymerizable monomer such as a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymerizable monomer is an important component for causing a crosslink in the acrylic polymer.

  In the acrylic pressure-sensitive adhesive as a high refractive index pressure-sensitive adhesive, the blending ratio of the aromatic ring-containing copolymerizable monomer is not the type of the aromatic ring-containing copolymerizable monomer, but the aromatic ring-free copolymer Although it varies depending on the type of the monomer used for modification and the monomer for modification, it is 30% by weight or more (for example, 30 to 100% by weight), preferably 40 to 80% by weight based on the total amount of the monomer components. As described above, the refractive index of the high-refractive index pressure-sensitive adhesive layer can be adjusted by the type and blending ratio of the aromatic ring-containing copolymerizable monomer.

  In the high refractive index pressure-sensitive adhesive, the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive is the monomer component (aromatic ring-containing copolymerizable monomer; aromatic ring-free (meth) acrylic). It can be prepared by polymerizing (copolymerizing) an aromatic ring-free copolymerizable monomer such as an acid alkyl ester or a copolymerizable monomer such as a modifying monomer. Examples of the polymerization method include a solution polymerization method performed using a polymerization initiator such as an azo compound or a peroxide, an emulsion polymerization method or a bulk polymerization method, a polymerization method performed by irradiating light or radiation using a photoinitiator, and the like. These polymerization methods can be employed, and a method of polymerizing using a polymerization initiator that decomposes to generate radicals (radical polymerization method) can be suitably employed. In such radical polymerization, polymerization initiators used in ordinary radical polymerization (for example, peroxides such as dibenzoyl peroxide and tert-butyl permaleate; 2,2′-azobisisobutyronitrile, azobis) An azo compound such as isovaleronitrile) can be used. In radical polymerization, the polymerization initiator may be used in an amount usually used in the polymerization of acrylic monomers, for example, 0.005 to 10 with respect to 100 parts by weight of the total amount of the monomer components. About 0.1 parts by weight, preferably about 0.1-5 parts by weight.

  The acrylic polymer obtained by polymerization using the monomer components (aromatic ring-containing copolymerizable monomer, non-aromatic ring-containing copolymerizable monomer, modifying monomer, etc.) is dried as it is. Can be used. Further, the polymer can be used by being cured by crosslinking. That is, the high refractive index pressure-sensitive adhesive can be prepared by obtaining an acrylic polymer by the polymerization and then drying, and if necessary, crosslinking the acrylic polymer with a crosslinking agent. it can. In addition, the cohesion force as a pressure-sensitive adhesive can be further increased by crosslinking the polymer. In such curing by crosslinking, a crosslinking agent can be used. For crosslinking of the polymer, a heat crosslinking method is preferably used.

  The crosslinking agent can be appropriately selected from conventionally known crosslinking agents. Specifically, the cross-linking agent is particularly preferably a polyfunctional melamine compound, a polyfunctional epoxy compound, or a polyfunctional isocyanate compound. A crosslinking agent can be used individually or in mixture of 2 or more types.

  Examples of the polyfunctional melamine compound include methylated trimethylol melamine and butylated hexamethylol melamine. Moreover, as a polyfunctional epoxy compound, diglycidyl aniline, glycerol diglycidyl ether, etc. are mentioned, for example. The amount of the polyfunctional melamine compound and / or polyfunctional epoxy compound used is, for example, 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer. It is a range.

  Examples of the polyfunctional isocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, diphenylmethane diisocyanate duplex, reaction product of trimethylolpropane and tolylene diisocyanate, and trimethylol. A reaction product of propane and hexamethylene diisocyanate, polyether polyisocyanate, polyester polyisocyanate and the like can be mentioned. The usage-amount of a polyfunctional isocyanate compound is 0.01-20 weight part with respect to 100 weight part of said acrylic polymers, for example, Preferably it is the range of 0.05-15 weight part.

  In addition to the acrylic polymer, various additives may be added to the acrylic pressure-sensitive adhesive as the high refractive index pressure-sensitive adhesive as necessary. Such additives are not particularly limited, and are known or commonly used additives for acrylic pressure-sensitive adhesives [for example, tackifying resins (for example, rosin resins, terpene resins, petroleum resins, coumarones). Indene resin, styrene resin, etc.), plasticizer, filler (fine powder silica, etc.), colorant, ultraviolet absorber, antioxidant, emulsifier, surfactant, antistatic agent, etc.] can be used. The amount of the additive used may be a normal amount applied to the acrylic pressure-sensitive adhesive.

(Low refractive index pressure sensitive adhesive)
As described above, an acrylic pressure-sensitive adhesive can be preferably used as the low-refractive index pressure-sensitive adhesive from the viewpoint of controlling the refractive index, and in particular, the refractive index of the low-refractive index pressure-sensitive adhesive layer. In order to control the refractive index to a desired size, as a monomer component of the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive (monomer component) A pressure-sensitive adhesive using a monomer is preferred. That is, as the low refractive index pressure-sensitive adhesive, a pressure-sensitive adhesive composition containing an acrylic polymer containing a fluorine atom-containing copolymerizable monomer as a monomer unit as a base polymer or a main component is preferably used. it can.

  The fluorine atom-containing copolymerizable monomer is not particularly limited as long as it is a copolymerizable monomer having at least one fluorine atom in the molecule. As the fluorine atom-containing copolymerizable monomer, for example, a fluorine atom-containing ethylenically unsaturated monomer can be suitably used. A fluorine atom containing copolymerizable monomer can be used individually or in mixture of 2 or more types.

（式（２）中、Ｒ⁴は水素原子又はメチル基であり、Ｒ⁵はフッ素化炭化水素基である） As the fluorine atom-containing copolymerizable monomer, a fluorine atom-containing acrylic monomer can be suitably used. The fluorine atom-containing acrylic monomer is not particularly limited as long as it is an acrylic monomer having at least one fluorine atom in the molecule. Specifically, fluorine atom-containing (meth) acrylic acid ester can be suitably used as the fluorine atom-containing acrylic monomer. Such a fluorine atom-containing (meth) acrylic acid ester is preferably a fluorine atom-containing (meth) acrylic acid ester, and the fluorine atom-containing (meth) acrylic acid ester is represented, for example, by the following formula (2). A fluorine atom-containing (meth) acrylic acid ester can be suitably used.

(In Formula (2), R ⁴ is a hydrogen atom or a methyl group, and R ⁵ is a fluorinated hydrocarbon group)

Examples of the fluorinated hydrocarbon group for R ⁵ include a fluorinated aliphatic hydrocarbon group, a fluorinated alicyclic hydrocarbon group, and a fluorinated aromatic hydrocarbon group. As the fluorinated hydrocarbon group, a fluorinated aliphatic hydrocarbon group is preferred. Examples of the fluorinated aliphatic hydrocarbon group include a fluorinated alkyl group. In the fluorinated aliphatic hydrocarbon group, the aliphatic hydrocarbon moiety may be linear or branched. In the fluorinated aliphatic hydrocarbon group, the fluorine atom may be bonded to any carbon atom in the aliphatic hydrocarbon group site. The fluorine atom bonded to one carbon atom may be singular or plural. Of course, the number of carbon atoms to which fluorine atoms are bonded is not particularly limited.

Accordingly, in the fluorinated aliphatic hydrocarbon group, as the fluorinated alkyl group, -C _a H _b F _{2a + 1-b} (wherein, a represents a positive integer and b is a positive number less than 0 or 2a + 1). An integer is shown).

  In the fluorinated aliphatic hydrocarbon group (in particular, the fluorinated alkyl group), the carbon number of the hydrocarbon group site is not particularly limited, and is selected from, for example, a range of about 1 to 18 (preferably 1 to 12). can do. When the number of carbon atoms is too large, compatibility with other copolymerizable monomers decreases. For example, in the fluorinated alkyl group, examples of the alkyl group moiety include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, octyl, nonyl, decyl, undecyl, dodecyl, Examples of the alkyl group moiety include about 1 to 18 carbon atoms such as tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl group.

  More specifically, when the alkyl group moiety is a methyl group moiety, examples of the fluorinated alkyl group include trifluoromethyl, difluoromethyl, and monofluoromethyl groups. When the alkyl group site is an ethyl group site, examples of the fluorinated alkyl group include pentafluoroethyl, 1,1,2,2-tetrafluoroethyl, 1,2,2,2-tetrafluoroethyl, 1,1,2-trifluoroethyl, 1,2,2-trifluoroethyl, 2,2,2-trifluoroethyl, 1,1-difluoroethyl, 1,2-difluoroethyl, 2,2-difluoroethyl , 1-monofluoroethyl, 2-monofluoroethyl group and the like. As the fluorinated alkyl group having 3 or more carbon atoms, as in the above-exemplified fluorinated methyl group and fluorinated ethyl group, one or more carbon atoms at one or more of the carbon atoms in the alkyl group moiety may be used. Various fluorinated alkyl groups to which a fluorine atom is bonded can be exemplified.

Examples of the fluorinated alicyclic hydrocarbon group include a fluorinated cycloalkyl group. Similarly to the fluorinated aliphatic hydrocarbon group, in the fluorinated alicyclic hydrocarbon group, the fluorine atom may be bonded to any carbon atom of the alicyclic hydrocarbon group. The linking fluorine atom may be either singular or plural. Furthermore, the number of carbon atoms to which fluorine atoms are bonded is not particularly limited. Accordingly, the fluorine cycloaliphatic hydrocarbon group, for example, the fluorinated cycloalkyl groups, -C _s in _{H t F 2s-1-t} ( wherein, s represents an positive integer of 3 or more, t is 0 or a positive integer less than 2 s −1 (in which an alicyclic ring is formed by carbon atoms). In such a fluorinated alicyclic hydrocarbon group, examples of the alicyclic hydrocarbon group site include cycloheptyl, cyclohexyl group sites and the like. More specifically, when the alicyclic hydrocarbon group moiety is a cyclohexyl group moiety, examples of the fluorinated alicyclic hydrocarbon group include 2-fluorocyclohexyl group, 3-fluorocyclohexyl group, 4-fluorocyclohexyl group. A cyclohexyl group having one fluorine atom such as a group; a cyclohexyl group having two fluorine atoms such as a 2,4-difluorocyclohexyl group and a 2,6-difluorocyclohexyl group; a 2,4,6-trifluorocyclohexyl group and the like A cyclohexyl group having three fluorine atoms and the like are included.

The fluorinated hydrocarbon group for R ⁵ may be substituted with a substituent. Such a substituent is not particularly limited, and examples thereof include a hydrocarbon group such as an alkyl group, an alkoxy group, a hydroxy group, a carboxy group, an amino group, a nitro group, a cyano group, and a halogen atom. A substituent can be used individually or in combination of 2 or more types.

Accordingly, the fluorine atom-containing (meth) acrylic acid ester [fluorinated (meth) acrylate] represented by the formula (2) includes, for example, a fluorine atom-containing (meth) acrylic acid alkyl ester [fluorinated alkyl (meth) Acrylate], fluorine atom-containing (meth) acrylic acid cycloalkyl ester [fluorinated cycloalkyl (meth) acrylate], fluorine atom-containing (meth) acrylic acid aryl ester [fluorinated aryl (meth) acrylate] and the like. As the fluorine atom-containing (meth) acrylic acid ester, a fluorinated alkyl (meth) acrylate (particularly a fluorinated alkyl acrylate) is suitable. Examples of the fluorinated alkyl (meth) acrylate include 2,2,2-trifluoroethyl acrylate (CH ₂ = CHCOOCH ₂ CF ₃ , trade name “Biscoat 3F” manufactured by Osaka Organic Chemical Co., Ltd.), 2,2,3, and the like. , 3,4,4,5,5-octafluoropentyl acrylate (CH ₂ = CHCOOCH ₂ (CF ₂ ) ₄ H, trade name “Biscoat 8F” manufactured by Osaka Organic Chemical Co., Ltd.), 2- (heptadecafluorononyl) And ethyl acrylate (CH ₂ = CHCOOCH ₂ CH ₂ C ₈ F ₁₇ , trade name “FA-108” manufactured by Kyoeisha Chemical Co., Ltd.) and the like.

  In the low refractive index pressure sensitive adhesive, as the monomer component of the acrylic polymer which is the base polymer of the acrylic pressure sensitive adhesive, only the fluorine atom-containing copolymerizable monomer may be used, but the fluorine atom containing You may use together a copolymerizable monomer and the other monomer copolymerizable with this fluorine atom containing copolymerizable monomer. As the copolymerizable monomer (copolymerizable monomer), for example, a fluorine atom-free copolymerizable monomer (such as a fluorine atom-free ethylenically unsaturated monomer) can be used. The copolymerizable monomers can be used alone or in admixture of two or more.

In such a copolymerizable monomer, the fluorine atom-free copolymerizable monomer is not particularly limited, but does not contain a fluorine atom, and an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl group. Esters (sometimes referred to as “fluorine atom-free (meth) acrylic acid alkyl esters”) can be suitably used. The fluorine atom-free (meth) acrylic acid alkyl ester is the same (meth) acrylic acid C as the aromatic ring-free (meth) acrylic acid alkyl ester as a copolymerizable monomer in the high refractive index pressure-sensitive adhesive. _Examples thereof include _1-18 alkyl esters.

  Moreover, as the copolymerizable monomer, various monomers known as monomers for modifying acrylic pressure-sensitive adhesives can be used. Examples of such a modifying monomer include monomers similar to the modifying monomer as a copolymerizable monomer in the high refractive index pressure-sensitive adhesive [hydroxyl group-containing copolymerizable monomer, carboxyl group-containing copolymerizable monomer. Monomer, vinyl ester, (meth) acrylonitrile, amide group-containing copolymerizable monomer, epoxy group-containing copolymerizable monomer, amino group-containing copolymerizable monomer, and the like. As such a modifying monomer, a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymerizable monomer are suitable. Among the carboxyl group-containing copolymerizable monomers, acrylic acid is particularly suitable. In addition, polar group-containing copolymerizable monomers such as hydroxyl group-containing copolymerizable monomers and carboxyl group-containing copolymerizable monomers are important for causing cross-linking in acrylic polymers as described above. Is an essential ingredient.

  In the acrylic pressure-sensitive adhesive as the low refractive index pressure-sensitive adhesive, the blending ratio of the fluorine atom-containing copolymerizable monomer is different from the fluorine atom-containing copolymerizable monomer, the fluorine atom-free copolymerizable monomer, Although it varies depending on the type of the modifying monomer, it is 15% by weight or more (for example, 15 to 90% by weight), preferably 15 to 50% by weight, based on the total amount of the monomer components. As described above, the refractive index of the low refractive index pressure-sensitive adhesive layer can be adjusted by the type and blending ratio of the fluorine atom-containing copolymerizable monomer.

In the acrylic pressure-sensitive adhesive as the low refractive index pressure-sensitive adhesive, when the fluorine atom-containing copolymerizable monomer is a fluorinated alkyl (meth) acrylate, the carbon at the alkyl group site in the fluorinated alkyl group As the number increases, compatibility with fluorine atom-free copolymerizable monomers such as (meth) acrylic acid alkyl esters and modified monomers decreases. From the viewpoint of compatibility, the type of fluorinated alkyl (meth) acrylate And the range of the blending ratio may be naturally limited. For example, in a system containing 2-ethylhexyl acrylate: 90 parts by weight and acrylic acid: 10 parts by weight as monomer components, the fluorinated alkyl (meth) acrylate is 2,2,2-trifluoroethyl acrylate [CH ₂ = CHCOOCH ₂ CF ₃ ], the limit is about 100 parts by weight, and in the case of tetra (difluoromethylene) methyl acrylate [CH ₂ ═CHCOOCH ₂ (CF ₂ ) ₄ H], the limit is about 40 parts by weight.

  In the low refractive index pressure-sensitive adhesive, the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive is the monomer component (fluorine atom-containing copolymerizable monomer; fluorine atom-free (meth) alkyl acrylate). It can be prepared by polymerizing (copolymerizing) a fluorine atom-free copolymerizable monomer such as an ester or a copolymerizable monomer such as a modifying monomer. As the polymerization method, similarly to the acrylic polymer in the high refractive index pressure-sensitive adhesive, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and the like performed using a polymerization initiator such as an azo compound or a peroxide, Various polymerization methods such as a polymerization method performed by irradiating light or radiation using a photoinitiator can be adopted, and a method of polymerizing using a polymerization initiator that decomposes to generate a radical (radical polymerization method) It can be suitably employed. In such radical polymerization, polymerization initiators used in ordinary radical polymerization (for example, peroxides such as dibenzoyl peroxide and tert-butyl permaleate; 2,2′-azobisisobutyronitrile, azobis) An azo compound such as isovaleronitrile) can be used. In radical polymerization, the polymerization initiator may be used in an amount usually used in the polymerization of acrylic monomers, for example, 0.005 to 10 with respect to 100 parts by weight of the total amount of the monomer components. About 0.1 parts by weight, preferably about 0.1-5 parts by weight.

  The acrylic polymer obtained by polymerization using the monomer component (fluorine atom-containing copolymerizable monomer, fluorine atom-free copolymerizable monomer, modifying monomer, etc.) should be used as it is dried. Can do. Further, the polymer can be used by being cured by crosslinking. That is, the low refractive index pressure-sensitive adhesive can be prepared by obtaining an acrylic polymer by the polymerization and then drying, and if necessary, crosslinking the acrylic polymer with a crosslinking agent. it can. In addition, the cohesion force as a pressure-sensitive adhesive can be further increased by crosslinking the polymer. In curing by such crosslinking, a crosslinking agent can be used in the same manner as the high refractive index pressure-sensitive adhesive. For the crosslinking of the polymer, a heat crosslinking method is preferably used.

  The crosslinking agent can be appropriately selected from conventionally known crosslinking agents. Specifically, the cross-linking agent is particularly preferably a polyfunctional melamine compound, a polyfunctional epoxy compound, or a polyfunctional isocyanate compound. A crosslinking agent can be used individually or in mixture of 2 or more types. Specific examples and amounts of use of the polyfunctional melamine compound, polyfunctional epoxy compound, polyfunctional isocyanate compound and the like are the same as described above.

  In addition to the acrylic polymer, various additives may be added to the acrylic pressure-sensitive adhesive as the low refractive index pressure-sensitive adhesive as necessary. Such additives are not particularly limited, and are known or commonly used additives for acrylic pressure-sensitive adhesives [for example, tackifying resins (for example, rosin resins, terpene resins, petroleum resins, coumarones). Indene resin, styrene resin, etc.), plasticizer, filler (fine powder silica, etc.), colorant, ultraviolet absorber, antioxidant, emulsifier, surfactant, antistatic agent, etc.] can be used. The amount of the additive used may be a normal amount applied to the acrylic pressure-sensitive adhesive.

(Intermediate pressure sensitive adhesive)
As described above, an acrylic pressure-sensitive adhesive can be preferably used as the intermediate pressure-sensitive adhesive from the viewpoint of controlling the refractive index, and in particular, the refractive index of the intermediate pressure-sensitive adhesive layer can be set to a desired value. Aromatic ring-containing copolymer as necessary as monomer component (monomer component) of acrylic polymer, which is the base polymer of acrylic pressure-sensitive adhesive, to control the refractive index of the size A pressure-sensitive adhesive using a polymerizable monomer or a fluorine atom-containing copolymerizable monomer is suitable. That is, the intermediate pressure-sensitive adhesive contains, as necessary, an acrylic polymer containing an aromatic ring-containing copolymerizable monomer or a fluorine atom-containing copolymerizable monomer as a monomer unit as a base polymer or a main component. A pressure-sensitive adhesive composition can be suitably used. Specifically, in the acrylic pressure-sensitive adhesive in the intermediate pressure-sensitive adhesive, the monomer component does not contain an aromatic ring and a fluorine atom, and the alkyl group has 1 to 18 carbon atoms (meth) acryl. Acid alkyl ester (sometimes referred to as “aromatic ring and fluorine atom-free (meth) acrylic acid alkyl ester”) and, if necessary, aromatic ring-containing copolymerizable monomer and fluorine atom-containing copolymerizable monomer In addition, if necessary, other monomers (copolymerizable monomers) copolymerizable with these monomer components can be used.

As the aromatic ring and fluorine atom-free (meth) acrylic acid alkyl ester, carbon of the alkyl group exemplified as the aromatic ring-free (meth) acrylic acid alkyl ester and fluorine atom-free (meth) acrylic acid alkyl ester (Meth) acrylic acid alkyl ester having a number of 1 to 18 [(meth) acrylic acid C _1-18 alkyl ester]. Specifically, examples of the aromatic ring and fluorine atom-free (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic. Isopropyl acid, butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylic acid 2-ethylhexyl, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, (meth) acrylic Tetradecyl acid, pentadecyl (meth) acrylate, (meth) acrylic acid hex Decyl, (meth) acrylate, heptadecyl and (meth) (meth) acrylic acid C _1-18 alkyl esters such as octadecyl acrylate.

Moreover, as an aromatic ring containing copolymerizable monomer, the thing similar to the aromatic ring containing copolymerizable monomer illustrated in the said high refractive index pressure sensitive adhesive can be used. Specifically, as the aromatic ring-containing copolymerizable monomer, an aromatic ring-containing acrylic monomer [for example, aromatic ring-containing (meth) acrylic acid ester, etc.], a styrene monomer (styrene, etc.) or the like is used. Can do. As the aromatic ring-containing copolymerizable monomer, an aromatic ring-containing (meth) acrylic acid alkyl ester [for example, aryl C _1-18 alkyl (meth) acrylate, aryloxy C _1-18 alkyl (meta ) Acrylates, aryloxypoly C _1-6 alkylene glycol (meth) acrylates, etc.] are preferred.

  Furthermore, as a fluorine atom containing copolymerizable monomer, the thing similar to the fluorine atom containing copolymerizable monomer illustrated in the said low refractive index pressure sensitive adhesive can be used. Specifically, as the fluorine atom-containing copolymerizable monomer, a fluorine atom-containing acrylic monomer [fluorine atom-containing (meth) acrylic acid ester or the like] can be used. As the fluorine atom-containing copolymerizable monomer, a fluorine atom-containing (meth) acrylic acid ester [for example, fluorinated alkyl (meth) acrylate, etc.] is suitable as described above.

  Furthermore, as the copolymerizable monomer, various monomers known as modifying monomers for acrylic pressure-sensitive adhesives can be used. Examples of such a modifying monomer include monomers similar to the modifying monomer as a copolymerizable monomer in the high refractive index pressure-sensitive adhesive and the low refractive index pressure-sensitive adhesive [hydroxyl group-containing copolymerizable monomer. Body, carboxyl group-containing copolymerizable monomer, vinyl ester, (meth) acrylonitrile, amide group-containing copolymerizable monomer, epoxy group-containing copolymerizable monomer, amino group-containing copolymerizable monomer Etc.]. As such a modifying monomer, a hydroxyl group-containing copolymerizable monomer and a carboxyl group-containing copolymerizable monomer are suitable. Among the carboxyl group-containing copolymerizable monomers, acrylic acid is particularly suitable. In addition, polar group-containing copolymerizable monomers such as hydroxyl group-containing copolymerizable monomers and carboxyl group-containing copolymerizable monomers are important for causing cross-linking in acrylic polymers as described above. Is an essential ingredient.

  In the acrylic pressure-sensitive adhesive as the intermediate pressure-sensitive adhesive, the blending ratio of the aromatic ring-containing copolymerizable monomer or the fluorine atom-containing copolymerizable monomer is the refractive index of the intermediate pressure-sensitive adhesive layer as described above. Is an important factor to adjust. For example, when the refractive index of the intermediate pressure-sensitive adhesive layer is increased by blending the aromatic ring-containing copolymerizable monomer, the blending ratio of the aromatic ring-containing copolymerizable monomer is the aromatic ring-containing copolymerizable monomer. Usually, the aromatic ring in the acrylic pressure-sensitive adhesive as the high refractive index pressure-sensitive adhesive layer is different depending on the type of the non-aromatic ring-containing copolymerizable monomer and the modifying monomer. The blending ratio is less than the blending ratio of the containing copolymerizable monomer. On the other hand, when the refractive index of the intermediate pressure-sensitive adhesive layer is lowered by blending the fluorine atom-containing copolymerizable monomer, the blending ratio of the fluorine atom-containing copolymerizable monomer is the kind of the fluorine atom-containing copolymerizable monomer. In addition, the fluorine atom-containing copolymerization property in the acrylic pressure-sensitive adhesive as the low refractive index pressure-sensitive adhesive layer is usually different depending on the type of the non-aromatic ring-containing copolymerizable monomer and the modifying monomer. The blending ratio is less than the blending ratio of the monomer. Of course, the aromatic ring-containing copolymerizable monomer or the fluorine atom-containing copolymerizable monomer may not be blended.

  In the intermediate pressure-sensitive adhesive, the acrylic polymer that is the base polymer of the acrylic pressure-sensitive adhesive contains the monomer component (aromatic ring and fluorine atom-free (meth) acrylic acid alkyl ester, aromatic ring-containing) It can be prepared by polymerizing (copolymerizing) a copolymerizable monomer, a fluorine atom-containing copolymerizable monomer, a modifying monomer, and the like. As the polymerization method, a solution polymerization method performed using a polymerization initiator such as an azo compound or a peroxide, as in the case of the acrylic polymer in the high refractive index pressure sensitive adhesive or the low refractive index pressure sensitive adhesive, Various polymerization methods such as an emulsion polymerization method, a bulk polymerization method, a polymerization method performed by irradiating light or radiation using a photoinitiator can be adopted, and polymerization is performed using a polymerization initiator that decomposes to generate radicals. The method (radical polymerization method) to be used can be preferably employed. In such radical polymerization, polymerization initiators used in ordinary radical polymerization (for example, peroxides such as dibenzoyl peroxide and tert-butyl permaleate; 2,2′-azobisisobutyronitrile, azobis) An azo compound such as isovaleronitrile) can be used. In radical polymerization, the polymerization initiator may be used in an amount usually used in the polymerization of acrylic monomers, for example, 0.005 to 10 with respect to 100 parts by weight of the total amount of the monomer components. About 0.1 parts by weight, preferably about 0.1-5 parts by weight.

  Polymerization using the monomer components (aromatic ring and fluorine atom-free (meth) acrylic acid alkyl ester, aromatic ring-containing copolymerizable monomer, fluorine atom-containing copolymerizable monomer, modifying monomer, etc.) The acrylic polymer thus obtained can be used after being dried as it is. Further, the polymer can be used by being cured by crosslinking. That is, the intermediate pressure-sensitive adhesive can be prepared by obtaining an acrylic polymer by the polymerization and then drying and crosslinking the acrylic polymer with a crosslinking agent as necessary. In addition, the cohesion force as a pressure-sensitive adhesive can be further increased by crosslinking the polymer. In curing by such crosslinking, a crosslinking agent can be used in the same manner as the high refractive index pressure sensitive adhesive and the low refractive index pressure sensitive adhesive. For the crosslinking of the polymer, a heat crosslinking method is preferably used.

  The crosslinking agent can be appropriately selected from conventionally known crosslinking agents. Specifically, the cross-linking agent is particularly preferably a polyfunctional melamine compound, a polyfunctional epoxy compound, or a polyfunctional isocyanate compound. A crosslinking agent can be used individually or in mixture of 2 or more types. Specific examples and amounts of use of the polyfunctional melamine compound, polyfunctional epoxy compound, polyfunctional isocyanate compound and the like are the same as described above.

  In addition to the acrylic polymer, various additives may be added to the acrylic pressure-sensitive adhesive as the intermediate pressure-sensitive adhesive as necessary. Such additives are not particularly limited, and are known or commonly used additives for acrylic pressure-sensitive adhesives [for example, tackifying resins (for example, rosin resins, terpene resins, petroleum resins, coumarones). Indene resin, styrene resin, etc.), plasticizer, filler (fine powder silica, etc.), colorant, ultraviolet absorber, antioxidant, emulsifier, surfactant, antistatic agent, etc.] can be used. The amount of the additive used may be a normal amount applied to the acrylic pressure-sensitive adhesive.

(Each pressure-sensitive adhesive layer)
Each pressure-sensitive adhesive layer (high refractive index pressure-sensitive adhesive layer, low refractive index pressure-sensitive adhesive layer, intermediate pressure-sensitive adhesive layer, etc.) is a pressure-sensitive adhesive for forming each pressure-sensitive adhesive layer. (High refractive index pressure sensitive adhesive, low refractive index pressure sensitive adhesive, intermediate pressure sensitive adhesive, etc.) a method of applying on a predetermined surface (the surface of other pressure sensitive adhesive layer or release liner), After forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive for forming each pressure-sensitive adhesive layer on a release liner, the method of transferring the pressure-sensitive adhesive layer to a predetermined surface, etc. Can be formed. In applying the pressure-sensitive adhesive, a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater can be used.

  The thickness of each pressure-sensitive adhesive layer such as a high refractive index pressure-sensitive adhesive layer, a low refractive index pressure-sensitive adhesive layer, or an intermediate pressure-sensitive adhesive layer can be appropriately set within a range that does not impair handleability. For example, the thickness of the high refractive index pressure-sensitive adhesive layer is generally about 5 to 500 μm (preferably 10 to 100 μm, more preferably 20 to 50 μm). The thickness of the low refractive index pressure-sensitive adhesive layer is generally about 5 to 500 μm (preferably 10 to 100 μm, more preferably 20 to 50 μm). Furthermore, the thickness of the intermediate pressure-sensitive adhesive layer can be selected from the range of 5 to 500 μm (preferably 10 to 100 μm, more preferably 20 to 50 μm) as the thickness of each pressure-sensitive adhesive layer.

[Release liner]
The laminated pressure-sensitive adhesive tape (1, 11) shown in FIGS. 1 and 2 is a baseless type double-sided adhesive tape or sheet, and its adhesive surface is protected by a release liner 5. In addition, since both surfaces of the release liner 5 are release surfaces, the surface of the release liner 5 (the surface opposite to the pressure-sensitive adhesive layer 3) is superimposed on the surface of the pressure-sensitive adhesive layer 2. The pressure-sensitive adhesive layer 2 and the pressure-sensitive adhesive layer 3 are protected by winding in a roll shape. Further, as the release liner, a release liner in which only at least one surface (particularly one surface) is a release surface can be used. In this case, by using two release liners, the pressure-sensitive adhesive layer 2 and the sensitive liner can be used. The pressure-sensitive adhesive surface with the pressure-sensitive adhesive layer 3 can be protected.

  Such a release liner is not particularly limited, and can be appropriately selected from known release liners. Specifically, as the release liner, for example, a plastic film having high releasability itself [for example, ethylene such as polyethylene (low density polyethylene, linear low density polyethylene, etc.), polypropylene, ethylene-propylene copolymer, etc. -Alpha-olefin copolymer (block copolymer or random copolymer), polyolefin film made of a polyolefin resin made of a mixture thereof; a release liner made of Teflon (registered trademark) film, etc.] However, a release liner having a configuration in which a release treatment layer is formed on the surface (one side or both sides) of various supports (base materials) can be suitably used.

  As a base material of the release liner, a plastic film is preferably used, but a composite base material (for example, paper (for example, Japanese paper, western paper, glassine paper, etc.), non-woven fabric or cloth, foam, metal foil, various base materials (for example, It may be a metal-deposited plastic film or the like. Although the thickness of a base material can be suitably selected according to the objective, generally it is about 10-500 micrometers. In addition, as a raw material of the plastic film of the base material of the release liner, polyester such as polyethylene terephthalate; polyolefin such as polypropylene, polyethylene and ethylene-propylene copolymer; polyvinyl chloride; polyimide; thermoplastic resin such as polycarbonate, etc. Can be mentioned. The plastic film may be either an unstretched film or a stretched (uniaxially stretched or biaxially stretched) film.

  The release treatment layer is a known or commonly used release treatment agent for forming the release treatment layer in the release liner (for example, a silicone release agent, a fluorine release agent, a long-chain alkyl release agent, etc.). Can be formed. The release treatment layer is a polyolefin film made of a polyolefin resin such as an ethylene-α-olefin copolymer such as polyethylene, polypropylene, or an ethylene-propylene copolymer; a Teflon (registered trademark) film is formed on the support. Further, it may be formed by laminating or coating. In the release liner, the release treatment layer can be provided on one side or both sides of the substrate as described above.

  When the laminated pressure-sensitive adhesive tape of the present invention is, for example, a base-less type double-sided adhesive tape or sheet as shown in FIG. 1, a low refractive index pressure-sensitive adhesive is provided on one surface of the release liner. After coating and drying to form a low refractive index pressure sensitive adhesive layer, a high refractive index pressure sensitive adhesive is applied onto the low refractive index pressure sensitive adhesive layer and dried to obtain a high refractive index pressure sensitive adhesive. It can be produced by forming a layer and, if necessary, crosslinking and curing. In the case of a double-sided adhesive tape or sheet of the base material type as shown in FIG. 2, a low refractive index pressure sensitive adhesive is applied on one surface of the release liner and dried to reduce the low refractive index pressure sensitive property. After forming the adhesive layer, an intermediate pressure-sensitive adhesive is applied on the low refractive index pressure-sensitive adhesive layer and dried to form an intermediate pressure-sensitive adhesive layer, and then the intermediate pressure-sensitive adhesive layer is formed. Further, a high refractive index pressure-sensitive adhesive is applied and dried to form a high refractive index pressure-sensitive adhesive layer, which is then crosslinked and cured as necessary. As described above, the laminated pressure-sensitive adhesive tape is obtained by applying each pressure-sensitive adhesive on a predetermined surface of the release liner or the pressure-sensitive adhesive layer so that the pressure-sensitive adhesive layer has a predetermined layer configuration. By repeatedly forming each pressure-sensitive adhesive layer, it can be produced.

  The high-refractive index pressure-sensitive adhesive layer and the low-refractive index pressure-sensitive adhesive layer are laminated via a layer (such as a base material) other than the pressure-sensitive adhesive layer as long as the effects of the present invention are not impaired. You may have the structure made. For example, the laminated pressure-sensitive adhesive tape may be a double-sided adhesive tape or sheet in which a high refractive index pressure sensitive adhesive layer and a low refractive index pressure sensitive adhesive layer are provided on both sides of a transparent substrate.

  The laminated pressure-sensitive adhesive tape of the present invention can be used as a pressure-sensitive adhesive tape or sheet for adhering and fixing an optical film to a display panel of a display device. A film light guide plate can be suitably used as such an optical film. Moreover, as an optical film, a conductive film (ITO film) and an antireflection film can also be used.

[Optical film]
The optical film of the present invention, for example, by laminating the laminated pressure-sensitive adhesive tape to an optical film such as a film light guide plate, a high refractive index pressure sensitive adhesive layer and a low refractive index pressure sensitive adhesive layer, It can be produced as an optical film having a pressure-sensitive adhesive layer in a laminated form with or without other layers. The surface on which the laminated pressure-sensitive adhesive tape is bonded to the optical film is either the pressure-sensitive adhesive surface (adhesive surface) on the high refractive index pressure-sensitive adhesive layer side or the pressure-sensitive adhesive surface on the low refractive index pressure-sensitive adhesive layer side. It may be suitable and can be appropriately selected according to the refractive index of the optical film, the refractive index of the display panel to which the optical film is bonded, and the like. In many cases, the surface of the laminated pressure-sensitive adhesive tape on the low refractive index pressure-sensitive adhesive layer side is bonded to an optical film.

  In the optical film of the present invention, a pressure-sensitive adhesive layer such as a low-refractive index pressure-sensitive adhesive layer or a high-refractive index pressure-sensitive adhesive layer has a predetermined layer configuration on a predetermined surface of the optical film. Alternatively, each pressure-sensitive adhesive may be applied to repeat the formation of each pressure-sensitive adhesive layer.

  A specific example of such an optical film is shown in FIG. FIG. 3 is a schematic sectional view partially showing an example of the optical film of the present invention. In FIG. 3, 6 is an optical film having a pressure sensitive adhesive layer, 7 is an optical film such as a film light guide plate, 8a is a low refractive index pressure sensitive adhesive layer, and 8b is a high refractive index pressure sensitive adhesive layer. is there. For example, the optical film 6 shown in FIG. 3 is formed by using a conventional coating apparatus (roll coater, reverse coater, gravure coater, bar coater, etc.) to form a pressure-sensitive adhesive that forms each pressure-sensitive adhesive layer. On the film or pressure-sensitive adhesive layer, a method of applying and drying, and a method of crosslinking by heating as necessary, a method of curing by light such as ultraviolet rays, and each pressure-sensitive adhesive layer are formed. It can be produced by a method of bonding to an optical film using a laminated pressure-sensitive adhesive tape. That is, the optical film may be transferred using a pressure-sensitive adhesive sheet or may be directly copied.

  In addition, in an optical film, as a film light guide plate, the film which provided the light guide function by forming fine uneven | corrugated shape in the single side | surface of a polycarbonate film can be used, for example. The refractive index of the film material used for such a film light guide plate is 1.49 or more (preferably 1.50 or more, more preferably 1.51 or more, most preferably 1.52 or more). The upper limit of the refractive index is preferably 1.60. The thickness of a film light-guide plate can be suitably selected from the range of about 10-200 micrometers according to a use, for example. Further, the antireflective film and the conductive film as other optical films are preferably those having the refractive index as materials constituting them.

  A release liner may be provided on the surface (surface) on the pressure-sensitive adhesive layer side of the optical film having the pressure-sensitive adhesive layer.

  The optical film of the present invention (an optical film having a pressure-sensitive adhesive layer) is 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 after being stuck to each other. That is, the optical film having the pressure-sensitive adhesive layer described above can be used by producing a display device by sticking and fixing to the display panel. Of course, the surface of the optical film to be bonded to the display panel is the surface on the pressure-sensitive adhesive layer side. For example, the surface of the optical film on the pressure-sensitive adhesive layer side is exposed by peeling off the release liner. Can be fixed to the panel.

  A liquid crystal panel is preferably used as the display panel. As the liquid crystal panel, a liquid crystal panel used in a display screen section of a mobile phone (such as a mobile phone) in mobile communication can be suitably used. The substrate of such a liquid crystal panel is not particularly limited, and a glass substrate, a plastic substrate (particularly, a glass substrate), or the like can be used. The refractive index 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 is preferably 1.60.

  The laminated pressure-sensitive adhesive tape of the present invention has two or more pressure-sensitive adhesive layers, and among the two or more pressure-sensitive adhesive layers, at least two pressure-sensitive adhesive layers located on both surface sides are provided. Since the refractive index of the pressure-sensitive adhesive layer is different by 0.02 or more, one of the adhesive surfaces is a value close to the refractive index of an optical member such as a film light guide plate or an optical member such as a glass substrate of a liquid crystal panel. The difference in refractive index at the interface between the laminated pressure-sensitive adhesive tape and the optical film or at the interface between the laminated pressure-sensitive adhesive tape and the optical member is small, and these optical films / laminated pressure-sensitive adhesive tapes / Total reflection at each interface of the optical member can be minimized. Therefore, the optical film using the laminated pressure-sensitive adhesive tape of the present invention can exhibit excellent optical performance, and can effectively utilize light.

  Examples of the present invention will be described below in more detail. In the following, “part” means part by weight, and “%” means weight%.

Example 1
Phenoxyethyl acrylate: 50 parts, butyl acrylate: 49 parts, acrylic acid: 1 part, 3-hydroxypropyl acrylate: 0.06 part, and ethyl acetate: 45 parts as a polymerization solvent were put into a three-necked flask. The mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 parts of benzoyl peroxide was added, the temperature was raised to 60 ° C. and reacted for 10 hours, and then the temperature was raised 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 concentration of 25% by weight.
After adding 0.8 parts of trimethylolpropane tolylene diisocyanate as a crosslinking agent to this acrylic polymer solution, the thickness after drying is about 25 μm on a release liner made of a polyethylene terephthalate film with a thickness of 38 μm. The pressure-sensitive adhesive sheet having a cross-linked pressure-sensitive adhesive layer (“” is coated by casting, dried by heating at 130 ° C. for 3 minutes, covered with a release liner, and further aged at 50 ° C. for 72 hours. May be referred to as “pressure-sensitive adhesive sheet A1”). The refractive index of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet A1 was 1.508.

Further, 2-ethylhexyl acrylate: 70 parts, acrylic acid: 5 parts, trade name “FA-108” as a fluorine atom-containing acrylic monomer (manufactured by Kyoeisha Chemical Co., CH ₂ ═CHCOOCH ₂ CH ₂ C ₈ F ₁₇ ): 25 parts and 45 parts of ethyl acetate as a polymerization solvent were put into a three-necked flask and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 parts of benzoyl peroxide was added, the temperature was raised to 60 ° C. and reacted for 10 hours, and then the temperature was raised 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 concentration of 25% by weight.
After adding 0.8 parts of trimethylolpropane tolylene diisocyanate as a crosslinking agent to this acrylic polymer solution, the thickness after drying is about 25 μm on a release liner made of a polyethylene terephthalate film with a thickness of 38 μm. The pressure-sensitive adhesive sheet having a cross-linked pressure-sensitive adhesive layer (“” is coated by casting, dried by heating at 130 ° C. for 3 minutes, covered with a release liner, and further aged at 50 ° C. for 72 hours. May be referred to as “pressure-sensitive adhesive sheet B1”). The refractive index of the pressure sensitive adhesive layer in the pressure sensitive adhesive sheet B1 was 1.445.

  The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet A1 and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet B1 are bonded together to produce a pressure-sensitive adhesive sheet having a structure in which two pressure-sensitive adhesive layers are laminated. did.

(Example 2)
Similar to the pressure-sensitive adhesive sheet A1 in Example 1, except that styrene: 20 parts, benzyl acrylate: 25 parts, isononyl acrylate: 55 parts, and 3-hydroxypropyl acrylate: 0.1 part are used as monomer components. Thus, a pressure-sensitive adhesive sheet (sometimes referred to as “pressure-sensitive adhesive sheet A2”) was obtained. The refractive index of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet A2 was 1.506.

  A structure in which two pressure-sensitive adhesive layers are laminated by laminating the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet A2 and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet B1 obtained in Example 1. A pressure-sensitive adhesive sheet was prepared.

(Example 3)
As monomer components, isononyl acrylate: 47 parts, acrylic acid: 3 parts, trade name “Biscoat 8F” as a fluorine atom-containing acrylic monomer (manufactured by Osaka Organic Chemicals, CH ₂ = CHCOOCH ₂ (CF ₂ ) ₄ H): 50 Parts, 3-hydroxypropyl acrylate: A pressure-sensitive adhesive sheet (sometimes referred to as “pressure-sensitive adhesive sheet B2”) in the same manner as the pressure-sensitive adhesive sheet B1 in Example 1 except that 0.1 part is used. Got. The refractive index of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet B2 was 1.425.

  The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet A1 obtained in Example 1 and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet B2 are bonded together, and two pressure-sensitive adhesive layers are laminated. A pressure-sensitive adhesive sheet was prepared.

(Comparative Example 1)
Phenoxyethyl acrylate: 50 parts, butyl acrylate: 49 parts, acrylic acid: 1 part, 3-hydroxypropyl acrylate: 0.06 part, and ethyl acetate: 45 parts as a polymerization solvent were put into a three-necked flask. The mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 parts of benzoyl peroxide was added, the temperature was raised to 60 ° C. and reacted for 10 hours, and then the temperature was raised 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 concentration of 25% by weight.
After adding 0.8 parts of trimethylolpropane tolylene diisocyanate as a crosslinking agent to this acrylic polymer solution, the thickness after drying is about 50 μm on a release liner made of a polyethylene terephthalate film with a thickness of 38 μm. It was cast and coated at 130 ° C. for 3 minutes, covered with a release liner, and further aged at 50 ° C. for 72 hours to obtain a pressure-sensitive adhesive sheet having a cross-linked pressure-sensitive adhesive layer. It was. Therefore, this pressure-sensitive adhesive sheet corresponds to the pressure-sensitive adhesive sheet of Example 1 in which the pressure-sensitive adhesive layer has a thickness of 50 μm. The refractive index of the pressure-sensitive adhesive layer in this pressure-sensitive adhesive sheet was 1.508 as in the pressure-sensitive adhesive sheet A1 in Example 1.

(Evaluation)
The refractive index of the layer by the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheets according to Examples 1 to 3 and Comparative Example 1 is measured by the following refractive index measurement method, and color unevenness from the front of the panel is assembled. The optical performance is evaluated by the following evaluation method as an optical material, and the evaluation (effect) of the optical performance is judged from these measurements or evaluation results. Those not present are shown in Table 1 as “x”.

(Refractive index measurement method)
The refractive index of the layer (pressure-sensitive adhesive layer) of the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheet by irradiating sodium D rays in an atmosphere at 25 ° C. with an Abbe refractometer (that is, pressure-sensitive adhesive composition) The refractive index after drying and / or curing of the product was measured.

(Evaluation method as an optical material)
Using the pressure-sensitive adhesive sheets obtained in the examples and comparative examples, a polymethylmethacrylate plate (PMMA plate) having a thickness of 40 mm and a length of 25 mm processed to a length of 25 mm was previously applied to the film surface. The end face of the PMMA plate that has a 43 ° slope and is bonded so that the film light guide plate side having a uniform prism with a pitch of 0.25 mm is a pressure-sensitive adhesive layer on the low refractive index side and faces the slope of the film light guide plate A cold-cathode tube was placed on the surface, and the light emission state was observed from the surface opposite to the surface where the film light guide plate was bonded.

  From Table 1, it was confirmed that when the pressure-sensitive adhesive sheet according to the example was used, total reflection could be minimized and light could be used effectively.

1,11 Pressure-sensitive adhesive tape or sheet (laminated pressure-sensitive adhesive tape)
2 pressure sensitive adhesive layer 3 pressure sensitive adhesive layer 4 pressure sensitive adhesive layer 5 release liner 6 optical film having pressure sensitive adhesive layer 7 optical film such as film light guide plate 8a low refractive index pressure sensitive adhesive layer 8b high Refractive index pressure sensitive adhesive layer

Claims (8)

  A pressure-sensitive adhesive tape or sheet having a structure in which two or more pressure-sensitive adhesive layers are laminated in the thickness direction, wherein the pressure-sensitive adhesive forming the two or more pressure-sensitive adhesive layers is an acrylic-based feeling. The pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer having a crosslinked structure, and at least the difference in refractive index between the two pressure-sensitive adhesive layers located on both surfaces is 0.02 or more. A pressure-sensitive adhesive tape or sheet for optical members.   2. The optical member according to claim 1, wherein the pressure-sensitive adhesive layer is crosslinked with at least one compound selected from a polyfunctional melamine compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound. Pressure-sensitive adhesive tape or sheet for use.   The pressure-sensitive adhesive tape or sheet for optical members according to claim 1 or 2, wherein the refractive indexes of the two pressure-sensitive adhesive layers located on both surface sides are 1.40 to 1.60, respectively.   The refractive index of the pressure-sensitive adhesive layer on the low refractive index side in the two pressure-sensitive adhesive layers located on both surfaces is 1.40 to 1.50, and the refraction of the pressure-sensitive adhesive layer on the high refractive index side The pressure-sensitive adhesive tape or sheet for optical members according to claim 1 or 2, wherein the ratio is 1.45 to 1.55.   The pressure-sensitive adhesive tape or sheet for optical members according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer of two or more layers is laminated on one side of the release liner.   The pressure-sensitive adhesive tape or sheet for optical members according to any one of claims 1 to 5, which is a pressure-sensitive adhesive tape or sheet for sticking and fixing an optical film on a display panel of a display device.   The pressure-sensitive adhesive tape or sheet according to any one of claims 1 to 6 is stuck to one surface of an optical film for sticking and fixing to a display panel of a display device. Optical film for optical members.   The optical film for an optical member according to claim 7, wherein the display panel is a liquid crystal panel.

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