JP2017179230A - Optical transparent adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical transparent adhesive sheet having suppressed generation of gas and excellent step followability.SOLUTION: An optical transparent adhesive sheet has at least one or more pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains polyrotaxane of 0.5 to 3 pts.wt. based on 100 pts.wt. of a meth(acryl) acid ester copolymer, and 15 pts.wt. or more of monomer constituting the meth(acryl) acid ester copolymer is a monomer containing a hydroxyl group.SELECTED DRAWING: None

Description

  The present invention relates to an optical transparent adhesive sheet.

  In recent years, optical transparent adhesive sheets (OCA) for touch panels are not limited to glass as the forefront of the panel, and various resin (plastic) sheets may be used for the purpose of reducing the weight or securing safety when broken. The resin sheet generates more outgas from the resin in an environment such as a high temperature than the glass, and foaming occurs in the panel. Furthermore, these panels are generally printed, and OCA is required to be able to follow the steps. The former is generally expected to be improved by crosslinking the resin, while the latter requires the resin to be flexible.

  In Patent Document 1, when applied to an optical member such as a polarizing plate or a retardation plate, the optical properties such as total light transmittance are sufficiently satisfied, while stress relaxation, light leakage prevention, and durability are satisfied. Although an excellent pressure-sensitive adhesive layer sheet containing polyrotaxane is described, it does not deal with the problem of coexistence of gas generation suppression and level difference tracking, not the content related to an optically transparent pressure-sensitive adhesive sheet for a touch panel.

WO2010 / 067745

  An object of the present invention is to provide an optical transparent pressure-sensitive adhesive sheet in which whitening is suppressed even under high temperature and high humidity, generation of gas is suppressed, and excellent step following ability.

  In order to achieve the above object, the present inventors have found that by using a polyrotaxane, the cross-linking point of the resin can be slid, and both cross-linking and flexibility can be achieved, and the present invention has been completed. I arrived.

  That is, the present invention is as follows.

Item 1. An optical transparent adhesive sheet having at least one pressure-sensitive adhesive layer,
The pressure-sensitive pressure-sensitive adhesive layer contains a meta (acrylic acid) ester copolymer and 0.5 to 3 parts by weight of a polyrotaxane with respect to 100 parts by weight of the meta (acrylic acid) ester copolymer. A transparent adhesive sheet for optics, wherein 15 parts by weight or more of monomers constituting the (acrylic) acid ester copolymer is a monomer containing a hydroxyl group.

  Item 2. Item 2. The transparent adhesive sheet for optics according to item 1, wherein the pressure-sensitive adhesive layer has a gel fraction of 50% to 95%.

  Item 3. Item 3. The optical transparent pressure-sensitive adhesive sheet according to Item 1 or 2, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer has a difference between the initial hardness at 23 ° C. based on JISK 6253-3 and the hardness after 60 seconds larger than 10.

Item 4. The optically transparent adhesive sheet obtained using the optical adhesive composition of any one of claim | item 1-3,
A first adherend laminated on a first surface of the optical transparent adhesive sheet;
A second adherend laminated on a second surface opposite to the first surface of the optical transparent adhesive sheet,
The first adherend is a cover panel, a metal or metal oxide thin film, or a touch panel module,
The optical laminated body whose said 2nd to-be-adhered body is a film with a metal or metal oxide thin film, glass with a metal or metal oxide thin film, a polarizing plate, a touch panel module, or a display panel module.

  ADVANTAGE OF THE INVENTION According to this invention, whitening is suppressed under high temperature and high humidity, generation | occurrence | production of gas is suppressed, and the optical transparent adhesive sheet which has the outstanding level | step following ability is obtained.

The schematic diagram of a meta (acrylic) acid ester copolymer (I) and a polyrotaxane (II). (A) It is a perspective view which shows an image display apparatus provided with the optical laminated body which concerns on one Embodiment of this invention, (B) It is a disassembled perspective view of the part 2B in the dotted line of FIG. 2 (A).

  Details of the present invention will be described below.

  In the present invention, “(meth) acrylate” means acrylate and methacrylate.

  The optical transparent pressure-sensitive adhesive sheet of the present invention has at least one pressure-sensitive pressure-sensitive adhesive layer, and the pressure-sensitive pressure-sensitive adhesive layer comprises a meta (acrylic acid) ester copolymer and a meta (acrylic acid) ester copolymer 100. The adhesion which contains 0.5-3 weight part polyrotaxane with respect to a weight part, and 15 weight part or more of the monomers which comprise a meth (acrylic acid) ester copolymer is a monomer containing a hydroxyl group. Formed from the agent composition.

The meth (acrylic acid) ester copolymer (referred to as component (I), see FIG. 1) is obtained by polymerizing a plurality of types of monomer components. The meth (acrylic) acid ester copolymer ((I) has a reactive group R ₁ .

  The monomer component constituting the meth (acrylic acid) ester copolymer includes an alkyl (meth) acrylate having an alkyl group (component (A)) and a monomer having a hydroxyl group (component (B)). .

  Examples of (A) alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , T-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethyloctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) Acrylate, isobornyl (meth) acrylate, and cyclohexyl (meth) acrylate, isodecyl (meth) acrylate, isomistyryl (meth) acrylate, isododecyl (meth) acrylate, isosteary (Meth) acrylate, and iso-pentadecyl (meth) acrylate. As the component (A), only one type may be used, or two or more types may be used in combination. (A) The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having an alkyl group having 3 to 9 carbon atoms, but a linear or branched alkyl (meth) acrylate having 10 to 20 carbon atoms is 3 carbon atoms. It may be included in combination with an alkyl (meth) acrylate having ˜9 alkyl groups.

  The lower limit of (A) alkyl (meth) acrylate is 35% by weight or more, preferably 50% by weight or more in 100% by weight of the monomer. The upper limit of the alkyl (meth) acrylate is 85% by weight or less, preferably 80% by weight or less in 100% by weight of the monomer. When the content of the component (A) is 35% or more, foaming is suppressed and the adhesive strength of the adhesive sheet is further increased. When the content of the component (A) is 85% by weight or less, the pressure-sensitive adhesive sheet becomes moderately soft at room temperature, and the level difference following property of the pressure-sensitive adhesive sheet is further enhanced.

  Examples of the monomer (B) component containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. And other hydroxy (meth) acrylates. (B) As for the monomer containing a hydroxyl group, only 1 type may be used and 2 or more types may be used together.

  (B) The lower limit of the monomer containing a hydroxyl group is 15% by weight or more, preferably 20% by weight or more in 100% by weight of the monomer. The upper limit of the monomer containing a hydroxyl group is 40% by weight or less, preferably 35% by weight or less in 100% by weight of the monomer. When the content of the component (B) is 15% by weight or more, a whitening phenomenon due to moisture absorption of the pressure-sensitive adhesive layer when exposed to heat and / or humidity can be prevented. When the content of the component (B) is 40% by weight or less, the adhesiveness of the adhesive sheet to the resin plate is good.

  As a monomer component constituting the meth (acrylic acid) ester copolymer, N, N-dimethylacrylamide, an olefin compound having a (meth) acryloyl group, a carboxyl group and / or a cyclic amide is further added. It may contain (meth) acrylate, benzyl (meth) acrylate, phenoxy (meth) acrylate, styrene or the like.

  As an olefin compound having a (meth) acryloyl group, for example, polybutadiene having an acryloyl group at both ends (“TEAI-1000” and “EA-3000” manufactured by Nippon Soda Co., Ltd., and “BAC-45” manufactured by Idemitsu Kosan Co., Ltd.) And polybutadiene having methacryloyl groups at both ends (“TE-2000” and “EMA-300” manufactured by Nippon Soda Co., Ltd.) and the like. Also, polypropylene having a methacryloyl group at both ends can be used. Moreover, as an olefin compound which has a (meth) acryloyl group at random in a molecule | numerator, the esterified product (Kuraray "UC-203") of a maleic anhydride adduct of polyisoprene and 2-hydroxyethyl methacrylate etc. Is mentioned.

  In addition, in this specification, the said (A) component is not contained in the olefin compound which has a (meth) acryloyl group.

The optical transparent adhesive sheet of the present invention also contains a polyrotaxane (referred to as component (II), see FIG. 1). Polyrotaxane (II) has a reactive group R _2.

  Referring to FIG. 1, in the polyrotaxane 1, the linear molecule 3 penetrates through the openings of two cyclic molecules 2, and the blocking groups 4 are bonded to both ends of the linear molecule 3, so that the cyclic molecule 2 It has a structure that prevents desorption from the linear molecule 3.

  The polyrotaxane can be obtained by a conventionally known method, or a commercially available product can be obtained.

  The linear molecule 3 of the polyrotaxane is a molecule or substance that is included in the cyclic molecule 2 and can be integrated by a mechanical bond instead of a chemical bond such as a covalent bond. There is no particular limitation. In the present specification, “linear” of “linear molecule” means substantially “linear”. That is, as long as the cyclic molecule 2 can move on the linear molecule 3, the linear molecule 3 may have a branched chain.

  As the linear molecule 3 of polyrotaxane, for example, polyethylene glycol, polypropylene glycol, polyisoprene, polyisobutylene, polybutadiene, polytetrahydrofuran, polyacrylic acid ester, polydimethylsiloxane, polyethylene, polypropylene and the like are preferable. Two or more kinds of molecules 3 may be mixed in the pressure-sensitive adhesive composition.

  The weight average molecular weight of the linear molecule 3 of the polyrotaxane is preferably 3,000 to 300,000, and particularly preferably 10,000 to 200,000. When the weight average molecular weight is 3,000 or more, the amount of movement of the cyclic molecule 2 on the linear molecule 3 is large, and the stress relaxation property of the pressure-sensitive adhesive layer can be sufficiently obtained. Further, when the weight average molecular weight is 300,000 or less, the solubility of the polyrotaxane in the solvent and the compatibility with the (meth) acrylic copolymer (I) are good.

  The cyclic molecule 2 of the polyrotaxane 1 is not particularly limited as long as it can be included in the linear molecule 3 and can move on the linear molecule 3. In the present specification, “cyclic” of “cyclic molecule” means substantially “cyclic”. That is, as long as it can move on the linear molecule 3, the cyclic molecule 2 may not be completely closed, and may be, for example, a helical structure.

  The cyclic molecule 2 of the polyrotaxane 1 is preferably a cyclic polymer such as cyclic polyether, cyclic polyester, cyclic polyetheramine, or cyclic polyamine, or a cyclodextrin such as α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin. Can be mentioned. Specific examples of the cyclic polymer include crown ether or a derivative thereof, calixarene or a derivative thereof, cyclophane or a derivative thereof, cryptand or a derivative thereof.

  As the cyclic molecule 2, among the above, since it is relatively easily available and many types of the blocking group 4 can be selected, cyclodextrins such as α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, etc. Are preferable, and α-cyclodextrin is more preferable. Two or more kinds of these cyclic molecules 2 may be mixed in the polyrotaxane or the pressure-sensitive adhesive composition.

  When cyclodextrin is used as the cyclic molecule 2, the cyclodextrin may have a functional group capable of improving the solubility of the polyrotaxane. Preferable functional groups include, for example, acetyl group, alkyl group, trityl group, tosyl group, trimethylsilane group, phenyl group, polyester chain, oxyethylene chain, alkyl chain, acrylate chain, and the like. The weight average molecular weight of the functional group is preferably 100 to 10,000, and particularly preferably 400 to 2,000.

  The blocking group 4 of the polyrotaxane 1 is not particularly limited as long as the cyclic molecule 2 can maintain a form skewered by the linear molecule 3. Examples of such groups include bulky groups and ionic groups.

  Specifically, the block group 4 of the polyrotaxane 1 is a dinitrophenyl group, a cyclodextrin, an adamantane group, a trityl group, a fluorescein, a pyrene, an anthracene, or the like, or a weight average molecular weight of 1,000 to 1 The main chain or side chain of a polymer of 1,000,000 is preferable, and these blocking groups 4 may be mixed in the polyrotaxane 1 or in the pressure-sensitive adhesive composition.

  Examples of the polymer having a weight average molecular weight of 1,000 to 1,000,000 include polyamide, polyimide, polyurethane, polydimethylsiloxane, and polyacrylate.

  The cyclic molecule 2 is preferably 0.1 to 60% when the amount of the cyclic molecule 2 included in the skewered form by the linear molecule 3 is 100%. More preferably, the linear molecules 3 are included in a skewered manner in an amount of 1 to 50%, particularly preferably 5 to 40%.

  The maximum inclusion amount of the cyclic molecule 2 can be determined by the length of the linear molecule and the thickness of the cyclic molecule. For example, when the linear molecule is polyethylene glycol and the cyclic molecule is an α-cyclodextrin molecule, the maximum inclusion amount is experimentally determined (see Macromolecules 1993, 26, 5698-5703).

  A polyrotaxane is 0.5-3 weight part with respect to 100 weight part of the said meth (acrylic acid) ester copolymer. When it is 0.5 part by weight or more, the initial hardness of the pressure-sensitive adhesive sheet and the hardness after aging are appropriately maintained and the foam resistance is good. When the amount is 3 parts by weight or less, high step following ability is obtained.

Meta (acrylic) acid ester copolymer (I) and the polyrotaxane (II), meta with the reactive group R ₁ of the (acrylic) acid ester copolymer (I), the reactive group R ₂ of the polyrotaxane (II) Are bound by direct binding to each other or indirectly through a cross-linking agent. Examples of the cross-linking agent include, but are not limited to, isocyanate compounds. Examples of the reactive group R ₁ of the meth (acrylic acid) ester copolymer (I) include a hydroxyl group, a carboxyl group, an amine group, and a double bond. Examples of the reactive group R ₂ of the polyrotaxane (II) include a hydroxyl group, a carboxyl group, an isocyanate group, an epoxy group, an amine group, a double bond and the like. As an example of the combination of the reactive group R ₁ and the reactive group R ₂ , when R ₁ and R ₂ are the same or different UV-reactive double bonds (C═C), R ₁ is a hydroxyl group (—OH And R ₂ is an isocyanate group (—NCO), R ₁ is a carboxyl group (—COOH), and R ₂ is an epoxy group or an amine group.

  As a method for producing the pressure-sensitive adhesive composition, for example, the monomer component constituting the meth (acrylic acid) ester copolymer (I) is radically polymerized in the presence of a polymerization initiator to form a methacrylic acid ester copolymer. Polymer (I) is further prepared, and polyrotaxane (II) and optionally other components are added to meth (acrylic acid) ester copolymer (I), and meth (acrylic) acid ester copolymer (I) and Examples thereof include a method for obtaining a pressure-sensitive adhesive composition by bonding polyrotaxane (II).

  As the polymerization of the monomer component constituting the meth (acrylic) acid ester copolymer (I), known polymerization reactions such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization can be appropriately selected.

  Examples of the solvent that can be used in the solution polymerization include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, and diethyl ether. As for the said solvent, only 1 type may be used and 2 or more types may be used together.

  In order to obtain the meth (acrylic acid) ester copolymer, a polymerization initiator can be used. The polymerization initiator is not particularly limited, and can be appropriately selected and used. The polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator. As for the said polymerization initiator, only 1 type may be used and 2 or more types may be used together.

  The thermal polymerization initiator that can be used in the solution polymerization is not particularly limited, and examples thereof include an azo polymerization initiator and a peroxide polymerization initiator. As for the said thermal-polymerization initiator, only 1 type may be used and 2 or more types may be used together.

  The azo initiator is not particularly limited. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4′-azobis (4 -Cyanopentanoic acid), 2,2'-azobis (2-methylbutyronitrile), azobiscyclohexanecarbonitrile and the like.

  The peroxide-based polymerization initiator is not particularly limited. For example, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxide Oxypivalate, lauroyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butyl Examples include peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxy-3,5,5-trimethylhexanoate, and t-butyl peroxylaurate.

  The compounding quantity of the said polymerization initiator is not specifically limited, What is necessary is just in the range which can be utilized as an initiator.

    The pressure-sensitive adhesive composition may contain other known additives. The above-mentioned pressure-sensitive adhesive composition includes, for example, a silane coupling agent, a tackifier, a leveling agent, an antioxidant, a rust inhibitor, a light stabilizer, an ultraviolet absorber, and a polymerization inhibitor as necessary. May be included.

  Examples of the tackifying resin include a xylene resin, a phenol resin, a rosin resin, and a terpene resin. As for the said tackifier resin, only 1 type may be used and 2 or more types may be used together. Of these, a xylene resin is preferable, and an alkylphenol reaction product of the xylene resin is more preferable.

  Moreover, as said tackifying resin, the hydrogenated resin is preferable and the transparency of an adhesive sheet increases by using such a hydrogenated resin.

  The pressure-sensitive adhesive composition preferably further contains a silane coupling agent. Normally, when an acrylic adhesive is used when a metal thin film formed of metal or a metal oxide such as ITO is an adherend, the adhesive sheet peels from the metal or metal oxide thin film under high temperature and high humidity. It may be easier. When the said adhesive composition contains a silane coupling agent, the adhesiveness with respect to the adherend of an adhesive sheet becomes still higher.

  Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γglycol. Sidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-aminopropyltrimethoxysilane , Γ-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrime Kishishiran, .gamma.-mercaptopropyl triethoxy silane, mercaptopropyl butyl trimethoxy silane, and .gamma.-mercaptopropyl methyl dimethoxy silane, and the like. As for the said silane coupling agent, only 1 type may be used and 2 or more types may be used together. Of these, a silane coupling agent having an epoxy group is preferable.

  In the pressure-sensitive adhesive composition, the content of the silane coupling agent is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight with respect to 100 parts by weight of the meth (acrylic acid) ester copolymer. Above, preferably 5 parts by weight or less, more preferably 3 parts by weight or less. When the content of the silane coupling agent is not less than the above lower limit, the adhesiveness of the pressure-sensitive adhesive sheet to the adherend is further increased, and peeling is more unlikely to occur. When the content of the silane coupling agent is not more than the above upper limit, the release paper or the release film can be easily peeled off from the pressure-sensitive adhesive sheet, and the surface roughness of the pressure-sensitive adhesive sheet is less likely to occur after peeling.

  As a method for preparing the pressure-sensitive adhesive composition, for example, the copolymer and the tackifying resin to be added as necessary, the silane coupling agent and other additives, a solvent, and the like are mixed and stirred. The method of doing is mentioned.

  Since the pressure-sensitive adhesive composition according to the present invention contains the above-mentioned specific components meth (acrylic acid) ester copolymer (I) and polyrotaxane (II), generation of gas is suppressed, and excellent step tracking Have sex. For this reason, an adhesive composition is used suitably for manufacture of the transparent adhesive sheet for optics (henceforth abbreviated as an adhesive sheet).

  The manufacturing method of the said adhesive sheet is not specifically limited. As a method for producing a non-support type pressure-sensitive adhesive sheet, for example, a coating film is formed by coating the pressure-sensitive adhesive composition on the release-treated surface of the release sheet, and the solvent is removed by drying. On top of the coated film, a newly prepared release paper or release film is laminated so that the release treatment surface is in contact with the coated film to obtain a laminated body, and then the obtained laminated body is removed with a rubber roller or the like. The method of pressurizing is mentioned. The release sheet is not particularly limited. The release sheet may be a release paper or a release resin sheet.

  A conventionally well-known method can be used as a coating method of the said adhesive composition. Examples of the method for applying the pressure-sensitive adhesive composition include a method using a roll coater, a gravure coater, a reverse coater, a lip coater, a curtain coater, and a slit die coater.

  As a method for producing the pressure-sensitive adhesive sheet, a method in which the monomer component as a raw material of the copolymer is radically polymerized by bulk polymerization and the copolymer is produced and simultaneously formed into a sheet is also suitable. The bulk polymerization is preferably photopolymerization because the polymerization heat can be easily removed and the reaction can be easily controlled.

  The following method is mentioned as a preferable example of the manufacturing method of the said adhesive sheet. Using a mixture of the above monomer component with a photopolymerization initiator or a thermal polymerization initiator, the monomer component is partially polymerized by ultraviolet irradiation, heating, etc., and thickened to a viscosity suitable for coating, to obtain a polymer precursor. Get the body. If necessary, a photopolymerization initiator, an additive, and the like are added to the polymer precursor and mixed to obtain a polymer precursor composition. This polymer precursor composition is applied to a release treatment surface of a transparent synthetic resin film on which one surface has been release treatment to form a polymer precursor composition layer. On this polymer precursor composition layer, a release treatment surface of another transparent synthetic resin film having a release treatment on one surface is superposed. The polymer precursor composition layer is subjected to light irradiation such as ultraviolet irradiation through a synthetic resin film, whereby the polymer precursor is radically polymerized to form an optical transparent adhesive sheet.

  In addition, although it does not specifically limit as said transparent synthetic resin film, For example, a polyethylene terephthalate film, a polyethylene film, a polypropylene film etc. are mentioned.

  Examples of the photopolymerization initiator that can be used in the polymer precursor composition include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (“Darocur (registered trademark) 2959” manufactured by BASF). ) And other ketone photopolymerization initiators, α-hydroxy-α, α′-dimethyl-acetophenone (“Darocur (registered trademark) 1173” manufactured by BASF), methoxyacetophene, 2,2-dimethoxy-2-phenylacetate Acephenone photopolymerization initiators such as phen ("IRGACURE (registered trademark) 651" manufactured by BASF), 2-hydroxy-2-cyclohexylacetophenone ("IRGACURE (registered trademark) 184" manufactured by BASF), benzyldimethyl ketal, etc. Ketal photopolymerization initiator, halogenated ketone, acylphosphinoxide, line Acyl phosphodiesterase diisocyanate, and the like.

  When the polymer precursor composition contains the photopolymerization initiator, the content of the photopolymerization initiator is preferably 0.01 parts by weight or more, more preferably, with respect to 100 parts by weight of the polymer precursor. It is 0.03 parts by weight or more, preferably 5 parts by weight or less, more preferably 1 part by weight or less. When the content of the photopolymerization initiator is not less than the above lower limit, the polymer precursor is sufficiently polymerized and the cohesive force of the pressure-sensitive adhesive sheet is further increased. When the content of the photopolymerization initiator is not more than the above upper limit, the amount of radicals generated becomes moderate at the time of light irradiation, the number average molecular weight of the polymer after photopolymerization becomes moderately high, and the gel fraction of the pressure-sensitive adhesive sheet is moderate. When the pressure-sensitive adhesive sheet is bonded to an adherend such as a resin cover panel, foaming due to outgas is less likely to occur at the interface between the pressure-sensitive adhesive sheet and the cover panel at high temperature or high temperature and high humidity.

  Examples of the lamp used for light irradiation include a lamp having a light emission distribution at a wavelength of 400 nm or less.

  Examples of the lamp having an emission distribution at a wavelength of 400 nm or less include, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp. Is mentioned. Among them, the polymer precursor composition efficiently emits light in the active wavelength region of the photopolymerization initiator and has little absorption of components other than the photopolymerization initiator contained in the polymer precursor composition layer. A chemical lamp is preferable because light sufficiently reaches the inside of the physical layer and the polymer precursor composition layer can be effectively polymerized.

The light irradiation intensity in the light irradiation is a factor that affects the degree of polymerization of the polymer precursor composition layer. Therefore, depending on the degree of polymerization of the target polymer after light irradiation, the performance of the pressure-sensitive adhesive sheet, etc. Adjusted. For example, when an acetophenone photopolymerization initiator is used as the photopolymerization initiator, the light irradiation intensity in the wavelength region effective for photolysis of the acetophenone photopolymerization initiator is preferably 0.1 mW / cm ² or more. It is preferably 100 mW / cm ² or less.
The effective wavelength region for the photodecomposition of the acetophenone photopolymerization initiator is usually about 365 nm to 420 nm, although it varies depending on the photopolymerization initiator.

  The lower limit of the weight average molecular weight of the polymer after the light irradiation is preferably 400,000 or more, more preferably 600,000 or more. The upper limit of the weight average molecular weight is preferably 3 million or less, more preferably 2.5 million or less. When the weight average molecular weight is not less than the above lower limit, the cohesive force of the pressure-sensitive adhesive sheet is further increased, and when the pressure-sensitive adhesive sheet is bonded to an adherend such as a cover panel, the pressure-sensitive adhesive sheet is at a high temperature or high temperature and high humidity. Foaming due to outgas is further less likely to occur at the interface between the substrate and the adherend. When the weight average molecular weight is not more than the above upper limit, the adhesive strength of the adhesive sheet is further increased.

  The said weight average molecular weight shows the weight average molecular weight in polystyrene conversion measured by gel permeation chromatography.

  The transparent adhesive sheet for optics which concerns on this invention is equipped with the pressure sensitive adhesive layer obtained using the said adhesive composition. The transparent adhesive sheet for optics according to the present invention is excellent in level difference followability and foam resistance.

  The gel fraction of the pressure-sensitive adhesive layer of the optical transparent pressure-sensitive adhesive sheet according to the present invention is preferably 50 to 95%, more preferably 70 to 95%, and still more preferably 80 to 90%. When it is 50% or more, the meth (acrylic acid) ester copolymer (I) and the polyrotaxane (II) are sufficiently bonded, and foaming at the interface between the pressure-sensitive adhesive sheet and the adherend is suppressed. Such foaming is more effectively suppressed when it is 70% or more. If it is 95% or less, the step following ability is ensured.

  The optical transparent pressure-sensitive adhesive sheet according to the present invention may be a non-support type that does not have a base material sheet, or may be a support type in which pressure-sensitive adhesive sheets are arranged on both surfaces of the base material sheet. . In the non-support type adhesive sheet, the adhesive sheet itself is an adhesive layer. The support-type pressure-sensitive adhesive sheet includes a base material sheet, a first pressure-sensitive adhesive layer disposed on the first surface of the base material sheet, and a second opposite to the first surface of the base material sheet. It is preferable to provide the 2nd adhesive layer arrange | positioned on the surface of this.

  The base sheet preferably has transparency. The base sheet is not particularly limited, and for example, a sheet formed of an acrylic compound, an olefin compound, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), nylon, urethane, polyimide, or the like, or a network structure And a sheet having a hole and the like.

  The thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, and still more preferably 300 μm or less. The adhesive force with respect to the adherend of an adhesive sheet becomes high enough that the thickness of the said adhesive sheet is more than the said minimum. The handleability of an adhesive sheet becomes it high that the thickness of the said adhesive sheet is below the said upper limit. The thickness of the pressure-sensitive adhesive layer indicates the total thickness of all pressure-sensitive adhesive layers in a support-type pressure-sensitive adhesive sheet including a plurality of pressure-sensitive adhesive layers such as the first and second pressure-sensitive adhesive layers.

  The thickness of the substrate sheet is preferably 2 μm or more, more preferably 5 μm or more, preferably 200 μm or less, more preferably 100 μm or less. When the thickness of the substrate sheet is equal to or more than the lower limit, the strength of the pressure-sensitive adhesive sheet is increased, it is difficult to break, and the handleability is further enhanced. When the thickness of the base sheet is equal to or less than the above upper limit, the influence of the hardness of the base sheet portion is reduced, and the level difference followability of the pressure-sensitive adhesive sheet is further enhanced.

  The application of the pressure-sensitive adhesive sheet is not particularly limited as long as it is an optical application. The transparent adhesive sheet for optics according to the present invention has sufficient step following ability for a cover panel such as a cover glass having a step by printing, a resin cover panel having a step by printing, or a transparent conductive substrate having a step by wiring. And has anti-foaming resistance against outgas. For this reason, the adhesive sheet which concerns on this invention can be used suitably for a touchscreen. Moreover, the adhesive sheet which concerns on this invention can be used suitably for adhesion | attachment of the to-be-adhered body which is easy to generate | occur | produce outgas. For example, the above adhesive sheet adheres a cover panel and a touch panel module for protecting the surface when manufacturing image display devices such as mobile phones, smartphones, personal computers, electronic paper, tablet personal computers and game machines. Or a cover panel and a display panel module, or a touch panel module and a display panel module.

  The optical laminate according to the present invention includes the optical transparent adhesive sheet, the first adherend laminated on the first surface of the optical transparent adhesive sheet, and the first optical transparent adhesive sheet. A second adherend laminated on a second surface opposite to the first surface. The first adherend is preferably a cover panel, a metal or metal oxide thin film, or a touch panel module. The second adherend is preferably a film with a metal or metal oxide thin film, a glass with a metal or metal oxide thin film, a polarizing plate, a touch panel module, or a display panel module.

  The cover panel is a cover glass, a polycarbonate plate or a polymethyl methacrylate plate, and the first adherend is the cover glass, the polycarbonate plate, the polymethyl methacrylate plate, the metal or metal oxide thin film. The attached film or the touch panel module is preferable.

  Specific examples of the optical laminate include a cover panel-touch panel module laminate in which a cover panel and a touch panel module are bonded via an optical transparent adhesive sheet, and a cover panel and a display panel via an optical transparent adhesive sheet. Examples include a cover panel-display panel module laminate in which the module is bonded, a touch panel module display panel module laminate in which the touch panel module and the display panel module are bonded via an optical transparent adhesive sheet, and the like. As the cover panel, a glass plate or a resin plate is preferably used. The optical transparent adhesive sheet is particularly suitable when the cover panel is a polycarbonate plate or an acrylic plate.

  A film laminate with a transparent electrode layer in which two films with a transparent electrode layer formed of a metal or metal oxide are laminated through the optical transparent adhesive sheet is also preferable as the optical laminate.

  The optical laminate is suitably used for an image display device including the optical laminate and an image display unit.

  FIG. 2A is a perspective view showing an image display device 1 including an optical laminate according to an embodiment of the present invention, and FIG. 2B is a partial exploded perspective view thereof.

  The image display device 10 has a structure in which a cover panel 13 for protecting the surface is bonded onto a touch panel module 14 via an optical transparent adhesive sheet 12. The touch panel module 14 has a structure in which a film 16 with a metal thin film, an optical transparent adhesive sheet 17, a film 16 with a metal thin film, an optical transparent adhesive sheet 17, and a support 18 are laminated in this order. A portion where the optical transparent adhesive sheet 12, the film 16 with a metal thin film, the optical transparent adhesive sheet 17 and the film 16 with a metal thin film are laminated in this order is a film laminate 19 with a metal thin film. A portion in which the film laminate 19 with a metal thin film, the optical transparent adhesive sheet 17 and the support 18 are laminated in this order is a touch panel module 20.

  In FIG. 2B, the touch panel module is bonded to the display panel module via the optical transparent adhesive sheet 17, and in that case, the touch panel module is bonded in a state where the support 18 is peeled off from the touch panel module.

  Examples of the image display device 10 include a mobile phone and a portable information terminal. Examples of the support 18 include a release-treated polyethylene terephthalate film.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

Example 1
(1) Production of copolymer A reactor equipped with a thermometer, a stirrer and a cooling pipe was prepared. After adding 25 parts by weight of butyl acrylate, 55 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of 2-hydroxyethyl acrylate, and 0.01 parts by weight of lauryl mercaptan, the reactor is heated to start refluxing. did. Subsequently, 0.01 parts by weight of 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane was added as a polymerization initiator in the reactor, and polymerization was started under reflux. It was. Two hours after the start of polymerization, a partially polymerized acrylic copolymer having a polymerization conversion rate of 30% by weight and a weight average molecular weight of 1,000,000 was obtained.

  To 100 parts by weight of the obtained acrylic copolymer, 0.5 part by weight of polyrotaxane (SA1315P manufactured by Advanced Soft Material) is added as a curing agent, and a photopolymerization initiator is added to 100 parts by weight of the acrylic copolymer. 1 part by weight (Esacure One, manufactured by Nippon Shibel Hegner) was mixed to obtain an adhesive composition.

(2) Manufacture of optical pressure-sensitive adhesive laminate sheet The pressure-sensitive adhesive composition obtained above was dried on the surface of a 75 μm-thick transparent polyethylene terephthalate (PET) film (used as a separator) having a dry film thickness. The pressure-sensitive adhesive layer was obtained by applying with a doctor knife so that the thickness was 100 μm and irradiating with UV in a nitrogen atmosphere. The cured pressure-sensitive adhesive layer exhibited adhesiveness in a dry state. Next, a 75 μm-thick PET film (used as a separator) is attached to the other surface of the pressure-sensitive adhesive layer, and a transparent pressure-sensitive adhesive tape (total thickness of the laminate is 250 μm) having separators on both sides is obtained as an optical pressure-sensitive adhesive laminated sheet. It was.

(Examples 2 to 4 and Comparative Examples 1 to 4)
A copolymer solution was obtained in the same manner as in Example 1 except that the types and blending amounts of the monomer component and the curing agent constituting the copolymer were changed as shown in Table 1 below. A pressure-sensitive adhesive composition and an optical pressure-sensitive adhesive laminated sheet were obtained from the obtained copolymer solution in the same manner as in Example 1.

(Evaluation)
About the obtained optical adhesive lamination sheet, the following evaluation items were evaluated.

(1) Gelation fraction A 100 μm-thick transparent adhesive sheet obtained in each of Examples 1 to 4 and Comparative Examples 1 to 4 was cut into a flat rectangular shape of 50 mm × 25 mm to prepare a test piece. the weight W ₁ of the test piece was measured. After immersing the test piece in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate using a 200-mesh stainless steel mesh and dried at 110 ° C. for 1 hour. The weight W ₂ after drying the test piece was measured to calculate the gel fraction by the following equation.

Gel fraction (% by weight) = 100 × (W ₂ −W ₀ ) / (W ₁ −W ₀ )
In the formula, W ₀ represents the weight of the substrate, W ₁ represents the weight of the test piece before dipping, and W ₂ represents the weight of the test piece after dipping and drying. When the transparent adhesive sheet does not have a substrate, W ₀ = 0.

(2) Step-following property A 10-μm thick polyethylene terephthalate film was bonded to a substrate-less pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer thickness of 15 μm to produce a step sheet having a total thickness of 25 μm. The obtained stepped sheet was cut into a size of 50 mm × 50 mm, and a rectangular tape having a hole of 30 mm × 40 mm in the center part was produced. The obtained rectangular sheet was affixed on a 1 mm thick glass plate to obtain a 25 μm stepped glass substrate.

  The obtained optical adhesive laminate sheet was cut to have a planar shape of 50 mm × 50 mm, one release polyethylene terephthalate film of the adhesive laminate sheet was peeled off, and the release surface was pasted on a 75 μm thick transparent polyethylene terephthalate film Combined. Further, the other release polyethylene terephthalate film of the pressure-sensitive adhesive laminated sheet was peeled off, and the peeled surface was attached to the surface of the stepped glass substrate on which the stepped sheet was attached in a room temperature environment. After autoclaving (0.5 MPa, 23 ° C., 15 minutes), the step portion is observed with a microscope, and the separation of the optical transparent adhesive sheet from the edge portion of the step is observed (peel length) ) Was measured. The step following ability was judged according to the following criteria.

[Judgment criteria for step following ability]
○: Peeling length is less than 50 μm Δ: Peeling length is 50 μm or more and less than 200 μm X: Peeling length is 200 μm or more

(3) Foam resistance The obtained optical pressure-sensitive adhesive laminated sheet is cut so as to have a flat shape of 45 mm × 60 mm, one release polyethylene terephthalate film of the pressure-sensitive adhesive laminated sheet is peeled off, and the peeled surface is attached with an ITO layer. The film was laminated on the ITO surface of a polyethylene terephthalate film (thickness 0.125 mm, amorphous ITO film, manufactured by Sekisui Nanocoat Technology). Further, the other release polyethylene terephthalate film of the pressure-sensitive adhesive laminate sheet was peeled off, and the peeled surface was bonded onto a polycarbonate plate (thickness 1 mm) to obtain a test piece.

  The obtained test piece was treated in an autoclave at 23 ° C. and 0.5 MPa for 15 minutes, and then allowed to stand at high temperature and high humidity of 85 ° C. and 85% RH for 240 hours. The state of generation of bubbles at the bonding interface was visually observed. The foam resistance was determined according to the following criteria.

[Criteria for foam resistance]
○: No bubbles of a size of 0.01 mm or more are observed at all Δ: 1 to 5 bubbles of a size of 0.01 mm or more are observed per test sample ×: Size of 0.01 mm or more More than 6 bubbles are observed per test sample

(4) Whitening resistance (Δhaze value after high temperature and high humidity test)
The obtained optical pressure-sensitive adhesive laminated sheet was cut to have a plane shape of 40 mm × 60 mm, one release polyethylene terephthalate film of the pressure-sensitive adhesive laminated sheet was peeled off, and the peeled surface was placed on a transparent polyethylene terephthalate film (thickness 75 μm). Pasted together. Further, the other release polyethylene terephthalate film of the pressure-sensitive adhesive laminated sheet was peeled off, and the peeled surface was bonded to a slide glass (“S-1214” manufactured by MATSANAMI) to obtain a test piece.
The obtained test piece was left under high temperature and high humidity of 85 ° C. and 85% RH. The haze value (%) of the test piece before starting to stand and after leaving for 240 hours was measured using a haze meter (manufactured by Tokyo Denshoku Co., Ltd., fully automatic haze meter TC-HIIIDPK), and the Δ haze value was calculated by the following formula. did.

ΔHaze value (%) = (Haze value after standing for 240 hours (%)) − (Haze value before starting to stand (%))
[Criteria for whitening resistance]
○: Δhaze value (%) = 1 or less ×: Δhaze value (%) = 1 or more

(5) Hardness Immediately after measurement at 23 ° C. (D / 50/1) and after 60 seconds (D / 50/1) of an optical pressure-sensitive adhesive laminated sheet (thickness is made by laminating a plurality of sheets to a thickness of 700 μm) according to JIS K 6253-3 / 50/60) surface hardness (D hardness) was measured.

  The difference between the surface hardness immediately after measurement (D / 50/1) and the surface hardness after 60 seconds (D / 50/60) reflects the degree of stress relaxation, and the greater the difference in surface hardness, the more stress relaxation. Means that the step following property is good.

The composition and results are shown in Table 1 below. The optical pressure-sensitive adhesive laminated sheet of Comparative Example 1 in which the proportion of the monomer containing a hydroxyl group was 10 parts by weight with respect to 100 parts by weight of the meth (acrylic acid) ester copolymer had poor whitening resistance. The optical pressure-sensitive adhesive laminated sheet of Comparative Example 2 in which the ratio of the polyrotaxane was 5 parts by weight with respect to 100 parts by weight of the meth (acrylic acid) ester copolymer was inferior in the step following ability. The optical pressure-sensitive adhesive laminated sheet of Comparative Example 3 containing no polyrotaxane as a curing agent had poor foam resistance. The optical pressure-sensitive adhesive laminated sheet of Comparative Example 4 containing hexanediol diacrylate as a curing agent has a smaller hardness difference and a step following ability than the optical pressure-sensitive adhesive laminated sheet of Example 3 in which only the type of curing agent is different. It was inferior.

DESCRIPTION OF SYMBOLS 10 ... Image display apparatus 12 ... Transparent adhesive sheet for optics 13 ... Cover panel 14 ... Touch panel module 15 ... Display panel module 16 ... Film with metal thin film 17 ... Transparent adhesive sheet for optics 18 ... Support body 19 ... Film laminated body with metal thin film 20 ... Touch panel module

Claims (4)

An optical transparent adhesive sheet having at least one pressure-sensitive adhesive layer,
The pressure-sensitive pressure-sensitive adhesive layer contains a meta (acrylic acid) ester copolymer and 0.5 to 3 parts by weight of a polyrotaxane with respect to 100 parts by weight of the meta (acrylic acid) ester copolymer. A transparent adhesive sheet for optics, wherein 15 parts by weight or more of monomers constituting the (acrylic) acid ester copolymer is a monomer containing a hydroxyl group.   The transparent adhesive sheet for optics according to claim 1 whose gel fraction of said adhesive layer is 50%-95%.   The optically transparent adhesive according to claim 1 or 2, wherein a difference between an initial hardness at 23 ° C and a hardness after 60 seconds in accordance with JIS K 6253-3 of the adhesive constituting the adhesive layer is larger than 10. Sheet. An optical transparent pressure-sensitive adhesive sheet obtained by using the optical pressure-sensitive adhesive composition according to any one of claims 1 to 3,
A first adherend laminated on a first surface of the optical transparent adhesive sheet;
A second adherend laminated on a second surface opposite to the first surface of the optical transparent adhesive sheet,
The first adherend is a cover panel, a metal or metal oxide thin film, or a touch panel module,
The optical laminated body whose said 2nd to-be-adhered body is a film with a metal or metal oxide thin film, glass with a metal or metal oxide thin film, a polarizing plate, a touch panel module, or a display panel module.

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