JP5517716B2 - Pressure-sensitive adhesive composition for conductive film, pressure-sensitive adhesive sheet, and conductive film - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and an optical film that are used for bonding optical films, such as attaching and fixing an optical film to a display panel such as a liquid crystal display device.

  Conventionally, as a pressure-sensitive adhesive composition used when bonding various optical films such as an antireflection film and a conductive film (ITO film) to a display panel such as a liquid crystal display device, an adhesive made of an acrylic polymer is used. A composition is used.

  Display panels having these optical films attached thereto are widely used in mobile communication terminals (mobile phone terminals such as mobile phones and PHS machines, PDA terminals, and the like).

  In recent years, there has been a demand for weight reduction and thinning of devices, mainly mobile communication terminals. A film light guide plate has attracted attention as an optical film for the purpose of reducing the weight and thickness. "Film light guide plate" is used in liquid crystal display devices and has the function of emitting transmission light that transmits the inside of the liquid crystal panel in the horizontal direction to the upper or lower surface, and a light source is arranged on the side of the liquid crystal display device In this case, the optical film can be easily illuminated. The film light guide plate is considered to be effective for reducing the weight and thickness of the device because it is thinner than the conventional light guide plate.

  In addition, sophistication 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 has a configuration in which a plurality of optical members such as a glass substrate, a polarizing plate (film), a retardation plate (film), and the like are laminated together with liquid crystals. 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, each interface of the optical film / pressure-sensitive adhesive layer / optical member In this case, it is required to prevent total reflection.

  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. However, the conventional pressure-sensitive adhesive composition has a refractive index of about 1.47 after drying and / or curing, and does not have a high refractive index of 1.49 or more. Therefore, there is a problem that a refractive index difference occurs at the interface of the optical film / pressure-sensitive adhesive layer or the interface of the pressure-sensitive adhesive layer / optical member, total reflection occurs at a shallow angle, and hinders effective use of light. It has become.

Accordingly, an object of the present invention is to provide an optical film / pressure-sensitive adhesive layer / optical member in a case where various optical films are bonded to various optical members constituting a display device using a pressure-sensitive adhesive. An object of the present invention is to provide a pressure-sensitive adhesive composition capable of reducing total reflection of light at each interface and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition.
Another object of the present invention is to provide a pressure-sensitive adhesive composition having a refractive index after drying and / or curing that is equivalent to that of an optical film or an optical member, and the sensitivity of the pressure-sensitive adhesive composition. The object is to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer.
Still 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 layer / optical member.

  As a result of intensive studies to achieve the above object, the present inventor has a high refractive index after drying and / or curing when a specific monomer component is used as the monomer unit of the pressure-sensitive adhesive composition. Thus, it was found that a pressure-sensitive adhesive composition close to the refractive index of an optical film or optical member was obtained, and the present invention was completed.

That is, the present invention is a pressure-sensitive adhesive composition for a conductive optical film containing, as a main component, an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit, and can be dried and / or dried. Provided is a pressure-sensitive adhesive composition for fixing a conductive optical film to a liquid crystal panel of a display device having a refractive index after curing of 1.49 or more and 1.60 or less.

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

（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。）
また、前記芳香族環含有共重合性モノマーの配合割合は、モノマー成分全量に対して４０〜８０重量％であることが好ましい。
さらに、前記アクリル系重合体は、単量体単位として、さらに、ヒドロキシル基含有共重合性単量体を含むことが好ましい。 In the present invention, the aromatic ring-containing acrylic monomer is preferably an aromatic ring-containing (meth) acrylic acid alkyl ester represented by the following formula (1).

(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.)
Moreover, it is preferable that the mixture ratio of the said aromatic ring containing copolymerizable monomer is 40 to 80 weight% with respect to the monomer component whole quantity.
Furthermore, it is preferable that the acrylic polymer further contains a hydroxyl group-containing copolymerizable monomer as a monomer unit.

The present invention also provides a conductive optical film for pressure-sensitive adhesive sheet for a sticking fixed conductive optical film to the liquid crystal panel of the display device, on a release liner, conductive to the liquid crystal panel of the display device Provided is a pressure-sensitive adhesive sheet for a conductive optical film in which a pressure-sensitive adhesive layer is formed by a pressure-sensitive adhesive composition for fixing and fixing an optical optical film. Further, on one surface of the conductive optical film to stick and fix the liquid crystal panel of the display device, a pressure-sensitive adhesive by the conductive optical film sticking fixing pressure-sensitive adhesive composition to the liquid crystal panel of the display device Provided is a conductive optical film in which an agent layer is formed.

According to the present invention, since a 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 high. The refractive index of the optical member such as an antireflection film, a conductive film (ITO film), a film light guide plate, or an optical member such as a glass substrate constituting the liquid crystal panel is almost the same.
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 used effectively and power consumption can be greatly suppressed.

It is a graph which shows the relationship between the compounding quantity of the phenoxyethyl acrylate of a monomer component, and the refractive index after drying and / or after hardening of a pressure sensitive adhesive composition. It is a schematic sectional drawing which shows the pressure sensitive adhesive sheet of this invention. It is a schematic sectional drawing which shows the optical film of this invention. It is the schematic sectional drawing which showed the state which bonded together the liquid crystal panel using the optical film glass substrate of this invention. It is the schematic which shows the bonding state of the adhesive sheet in the evaluation method of a total reflection angle and emitted light intensity ratio.

  The aromatic ring-containing copolymerizable monomer used as the monomer in the pressure-sensitive adhesive composition of the present invention 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.

  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. As such an aromatic ring-containing acrylic monomer, an aromatic ring-containing (meth) acrylic acid ester is preferable. Aromatic ring-containing (meth) acrylic acid esters include, for example, aromatic ring-containing (meth) acrylic acid alkyl esters, (meth) acrylic acid aryl esters (such as (meth) acrylic acid phenyl esters). 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, for the aromatic ring-containing (meth) acrylic acid alkyl ester, 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.

  Aromatic ring-containing acrylic monomers can be used alone or in combination of two or more.

  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. Styrenic monomers can be used alone or in admixture of two or more.

  In the acrylic polymer contained as a main component in the pressure-sensitive adhesive composition of the present invention, the monomer is an aromatic ring-containing copolymerizable monomer comprising an aromatic ring-containing acrylic monomer and / or a styrene monomer. May be used, but aromatic ring-containing copolymerizable monomers (such as aromatic ring-containing acrylic monomers and styrene monomers) may be copolymerized with the aromatic ring-containing copolymerizable monomers. A monomer may be used in combination. As the copolymerizable monomer, an aromatic ring-free copolymerizable monomer (an aromatic ring-free ethylenically unsaturated monomer) can be used. The aromatic ring-free copolymerizable monomers can be used alone or in admixture of two or more.

  Although it does not restrict | limit especially as said aromatic ring non-containing copolymerizable monomer, The (meth) acrylic-acid alkylester which does not contain an aromatic ring and C1-C18 of an alkyl group is suitable. Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, ( Alkyl (meth) acrylates such as 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate Examples include esters. These (meth) acrylic acid alkyl esters can be used alone or in admixture of two or more.

  In addition, 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-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, Hydroxyl group-containing copolymerizable monomers such as 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate; Epoxy group-containing copolymers such as glycidyl (meth) acrylate Monomer-containing copolymerizable monomer such as N, N-dimethylaminoethyl (meth) acrylic acid alkyl ester; (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, etc. Examples thereof include a carboxyl group-containing copolymerizable monomer. The modifying monomers can be used alone or in admixture of two or more.

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

  A polar group-containing copolymerizable monomer such as a carboxyl group-containing copolymerizable monomer is an important component for causing a crosslinkage in an acrylic polymer.

  The pressure-sensitive adhesive composition of the present invention comprises an acrylic polymer containing the monomer component (aromatic ring-containing copolymerizable monomer, aromatic ring-free copolymerizable monomer, modifying monomer, etc.) as a monomer unit. A polymer, that is, an acrylic polymer obtained by polymerizing the monomer components is contained as a main component. 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. 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 employed. In such radical polymerization, a polymerization initiator used for normal radical polymerization can be used. For example, peroxides such as dibenzoyl peroxide and tert-butyl permaleate, and azo compounds such as 2,2′-azobisisobutyronitrile and azobisisovaleronitrile are used.

  In radical polymerization, the polymerization initiator may be used in an amount usually used in the polymerization of acrylic monomers, for example, about 0.005 to 10 parts by weight, preferably 100 parts by weight of the total amount of the monomers. Is about 0.1 to 5 parts by weight.

  In the present invention, the acrylic polymer obtained by polymerization using the monomer components (aromatic ring-containing copolymerizable monomer, aromatic ring-free copolymerizable monomer, modifying monomer, etc.) is dried as it is. Can be used. Further, the polymer can be used by being cured by crosslinking. By cross-linking the polymer, the cohesive force as a pressure-sensitive adhesive can be further increased.

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

  Conventionally known cross-linking agents are widely included. Especially as a crosslinking agent, a polyfunctional melamine compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound are preferable. 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, in the range of 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight with respect to 100 parts by weight of the polymer. is there.

  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 polymers, for example, Preferably it is the range of 0.05-15 weight part.

  The pressure-sensitive adhesive composition of the present invention may be used as it is, but various additives may be added as necessary for use. For example, in order to adjust the adhesive properties of a pressure-sensitive adhesive composition containing the polymer (especially acrylic polymer) as a main adhesive component, a known or commonly used tackifier resin (for example, rosin resin, terpene resin) Petroleum resin, coumarone / indene resin, styrene resin, etc.) may be blended. As additives other than the tackifying resin, various known additives such as a plasticizer, a filler such as fine powder silica, a colorant, and an ultraviolet absorber can be blended. The amount of these additives used may be a normal amount applied to an acrylic pressure sensitive adhesive.

  As described above, the pressure-sensitive adhesive composition (pressure-sensitive adhesive composition) of the present invention contains an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit as a main component. The pressure-sensitive adhesive composition can be used as a pressure-sensitive adhesive (adhesive) by drying and cross-linking the polymer using a cross-linking agent as necessary. It is important that the refractive index after drying and / or curing of the pressure-sensitive adhesive composition is 1.49 or more. As described above, the refractive index of the material used for the optical member such as the film light guide plate and the optical member such as the glass substrate is about 1.51 to 1.54, and is a pressure sensitive adhesive. If the refractive index after drying and / or curing the composition is less than 1.49, the difference in refractive index from the optical film or the optical member increases. Therefore, for example, when the layer made of the pressure-sensitive adhesive composition is provided on a film light guide plate which is a kind of optical film, total reflection occurs at a shallow angle, and the effective utilization of light may decrease. is there. In order to reduce the difference in refractive index from the optical film or optical member, it is also important that the refractive index after drying and / or curing of the pressure-sensitive adhesive composition of the present invention is 1.60 or less. is there.

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

  In the present invention, the refractive index after drying and / or curing of the pressure-sensitive adhesive composition is determined depending on the type of aromatic ring-containing copolymerizable monomer (aromatic ring-containing acrylic monomer, styrene monomer, etc.) and its blending. It is possible to adjust according to the ratio. The refractive index tends to increase as the blending ratio of the aromatic ring-containing copolymerizable monomer increases.

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

From FIG. 1, within the measurement range, the rate of increase in the refractive index with respect to the blending amount of phenoxyethyl acrylate is defined as follows.
y = 0.0009x + 1.4658
It can be expressed as. In addition, a measurement range is a range whose blending quantity of phenoxyethyl acrylate is 5-70 weight% with respect to all the monomer components.

  In addition, butyl acrylate and 3-hydroxypropyl acrylate are used as monomers other than phenoxyethyl acrylate. 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 all monomer components is 50% by weight. . Further, the blending ratio of butyl acrylate is increased or decreased by the amount by which the blending ratio of phenoxyethyl acrylate with respect to all monomer components is increased or decreased.

  Further, trimethylolpropane tolylene diisocyanate is blended as a crosslinking agent. That is, the acrylic polymer is crosslinked and cured. In addition, the compounding quantity of this crosslinking agent is 0.8 weight part with respect to 100 weight part of said polymers.

  Accordingly, the blending ratio of the aromatic ring-containing acrylic monomer is 30% by weight or more (for example, 30 to 100% by weight), preferably with respect to the total amount of the monomer components, although it depends on the type of the aromatic ring-containing copolymerizable monomer. Is preferably 40 to 80% by weight. 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 reduced to less than 1.49. There is.

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

  The pressure-sensitive adhesive sheet which is such a base-less pressure-sensitive adhesive sheet is, for example, the pressure-sensitive adhesive of the present invention on a release liner made of a base material such as a plastic film (polyethylene terephthalate film or the like) having a release layer. It can be obtained by applying an agent composition, drying it, and crosslinking and curing as necessary. Of course, in the release liner, the surface on which the pressure-sensitive adhesive composition is applied may be a surface on the release layer side. In the release liner, the release layer can be provided on one side or both sides of the substrate.

  The pressure-sensitive adhesive composition can be applied using 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.

  Although the thickness of a pressure sensitive adhesive layer can be suitably set in the range which does not impair handling property etc., generally it is 5-500 micrometers, Preferably it is about 10-100 micrometers.

  The pressure-sensitive adhesive layer may be composed of a plurality of layers with or without other layers as long as 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.

  As the base material of the release liner, a plastic film is preferably used, but paper, a foamed body, a metal foil or the like may be used. Although the thickness of a base material can be suitably selected according to the objective, generally it is about 10-500 micrometers.

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

  Moreover, as a peeling layer, the peeling layer (for example, silicone type peeling layer etc.) currently used as a peeling layer in a conventional release liner 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.

  An optical film having such a pressure-sensitive adhesive layer can be used by producing a display device by sticking and fixing to a 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, and by releasing the release liner, the surface of the optical film on the pressure-sensitive adhesive layer side is exposed, and the display panel It can be fixed by sticking.

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

  FIG. 3 is a schematic cross-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.

  An optical film in which such a pressure-sensitive adhesive layer is formed on one surface is obtained by optically applying the pressure-sensitive adhesive composition using a conventional coating apparatus (roll coater, reverse coater, gravure coater, bar coater, etc.). An optical film using a pressure-sensitive adhesive sheet made of the pressure-sensitive adhesive composition, a method of coating and drying on a film, a method of heat-crosslinking if necessary, a method of curing with light such as ultraviolet rays, and the like. It can obtain by the method of sticking together. That is, the optical film may be transferred using a pressure-sensitive adhesive sheet or may be directly copied.

  In the optical film of the present invention, examples of the film light guide plate include a film imparted with a light guide function by forming a fine uneven shape on one surface of a polycarbonate film. In addition, the refractive index of the film material used for these film light guide plates is 1.49 or more, 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 a film light-guide plate can be suitably selected from the range of about 10-200 micrometers according to a use, for example.

  In addition, examples of the optical film include an antireflection film, a conductive film, and the like. The material constituting them is preferably one having the above refractive index.

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

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

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

  Thus, a display device can be manufactured by attaching an optical film to a display panel. Note that the display device illustrated 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 bonded 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, 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. As a substrate of such a liquid crystal panel, 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.

  In the pressure-sensitive adhesive composition of the present invention, the refractive index after drying and / or curing is 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. Therefore, there is little difference in the 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. Total reflection at each interface of / pressure-sensitive adhesive layer / optical member can be minimized. Therefore, the optical film using the pressure-sensitive adhesive composition of the present invention can exhibit excellent optical performance, and can effectively use light.

  Of course, since an acrylic polymer is used, adhesion performance is also excellent.

  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. 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.

Example 2
Pressure-sensitive adhesive sheet in the same manner as 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. Got.

Comparative Example 1
Sensitive in the same manner as in Example 1 except that phenoxyethyl acrylate: 25 parts, butyl acrylate: 74 parts, acrylic acid: 1 part, and 3-hydroxypropyl acrylate: 0.1 part are used as monomer components. A pressure-sensitive adhesive sheet was obtained.

The refractive index, total reflection angle, and outgoing light intensity ratio of the layer of the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheet according to Example 1 or 2 and Comparative Example 1 are as follows. It measured by the evaluation method of a radiant intensity ratio. The results of measurement or evaluation are shown in Table 1. And from these measurements or evaluation results, the effect of the optical performance is determined for the pressure-sensitive adhesive compositions according to Examples and Comparative Examples, ○ that has excellent optical performance, × that is normal or not so good As shown in Table 1.
Moreover, evaluation as an optical film was also performed by the following method.

(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 of total reflection angle / output light intensity ratio)
As shown in FIG. 5, the right-angle prism (material BK-7: nD1.517) and the glass substrate (material BK-7: nD1.517) are bonded to each other through the adhesive sheets obtained in Examples and Comparative Examples. Then, light is incident from the edge of the glass substrate, the incident angle and the presence or absence of light that passes through the adhesive sheet and the prism are examined, and the angle θ at which light is no longer emitted is evaluated as the total reflection angle (°). did.
The upper and lower surfaces of the glass substrate are processed in parallel, and the upper and lower surfaces and end surfaces (side surfaces) are processed in a vertical direction. Further, a single mode He—Ne laser was used as the light source, and the polarization direction was 45 ° with respect to the end face.

  In addition, FIG. 5 is a schematic diagram showing a bonding state of the pressure-sensitive adhesive sheet in the evaluation method of the total reflection angle / emitted light intensity ratio. The upper glass (square section) is a glass substrate (material BK-7: nD1.517), and the lower glass (triangle section) is a right-angle prism (material BK-7: nD1.517). An adhesive sheet is sandwiched between these glasses.

Measurement was performed by bonding the right-angle prism and the glass substrate in advance using matching oil adjusted to have a refractive index nD1.517, and changing the angle of the laser beam to which the emitted light intensity from the right-angle prism is incident every 5 °. And the sum total was taken as the incident light intensity.
On the other hand, when the right-angle prism and the glass substrate were bonded together using the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, the output light intensity was measured in the same manner, and the sum total was obtained, and the matching oil was used. The ratio of the incident light intensity to the incident light intensity was determined and used as the outgoing light intensity ratio. In addition, it is so favorable that emitted light intensity ratio is large.

  From Table 1, the pressure-sensitive adhesive compositions according to the examples have almost the same refractive index as that of the optical film and the optical member, the total reflection angle is small, the outgoing light intensity ratio is large, and the total reflection is suppressed low. ing.

(Evaluation as an optical film)
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. A surface where a film light guide plate having a 43 ° slope and a uniform prism with a pitch of 0.25 mm is pasted, a cold cathode tube is disposed on the end face of the PMMA plate facing the slope of the film light guide plate, and the film light guide plate is pasted When the light emitting state was observed from the surface facing the surface, the pressure-sensitive adhesive sheets according to Example 1 and Example 2 had good in-plane luminance uniformity and front luminance, but the pressure-sensitive adhesive sheet of Comparative Example 1 had a cold cathode. The farther away from the tube, the darker it was and the front brightness at the center was also clearly reduced.

DESCRIPTION OF SYMBOLS 1 Pressure sensitive adhesive sheet 2 Release liner 3 Pressure sensitive adhesive layer 4 Optical film which has a pressure sensitive adhesive layer 5 Optical film 6 Pressure sensitive adhesive layer 7 Liquid crystal panel

Claims (7)

A pressure-sensitive adhesive composition for a conductive optical film containing an acrylic polymer containing an aromatic ring-containing copolymerizable monomer as a monomer unit as a main component, and having a refractive index after drying and / or curing 1. A pressure-sensitive adhesive composition for adhering and fixing a conductive optical film to a liquid crystal panel of a display device that is 1.49 or more and 1.60 or less. The pressure-sensitive adhesive composition for fixing a conductive optical film to a liquid crystal panel of a display device according to claim 1, wherein the aromatic ring-containing copolymerizable monomer is an aromatic ring-containing acrylic monomer and / or styrene monomer. object. The conductive optical film sticking fixation to the liquid crystal panel of the display apparatus of Claim 2 whose aromatic ring containing acrylic monomer is an aromatic ring containing (meth) acrylic-acid alkylester represented by following formula (1). Pressure-sensitive adhesive composition for use.

(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.) 4. The conductive optics for a liquid crystal panel of a display device according to claim 1, wherein a blending ratio of the aromatic ring-containing copolymerizable monomer is 40 to 80 wt% with respect to the total amount of the monomer components. A pressure-sensitive adhesive composition for fixing films. The conductive optical film for a liquid crystal panel of a display device according to any one of claims 1 to 4, wherein the acrylic polymer further contains a hydroxyl group-containing copolymerizable monomer as a monomer unit. Pressure-sensitive adhesive composition for sticking and fixing. A pressure-sensitive adhesive sheet for a conductive optical film for attaching and fixing a conductive optical film to a liquid crystal panel of the display device, the display device according to claim 1 on a release liner. A pressure-sensitive adhesive sheet for a conductive optical film, in which a pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition for fixing and fixing a conductive optical film to a liquid crystal panel. On one surface of the conductive optical film to stick and fix the liquid crystal panel of the display device, the conductive optical film sticking fixed to the liquid crystal panel of the display device according to any one of claims 1 to 5 A conductive optical film having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition.

Images