JP6660710B2 - Solventless pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet and display - Google Patents

Description

  The present invention relates to a solvent-free adhesive composition, an adhesive and an adhesive sheet that can be used for a display such as a touch panel, and a display using the same.

  2. Description of the Related Art In recent years, various mobile electronic devices such as smartphones and tablet terminals include a display using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like. It is becoming more and more a touch panel.

  In such a display as described above, usually, a protective panel is provided on the front side of the display module. Here, a gap is provided between the protection panel and the display module so that the deformed protection panel does not hit the display module even when the protection panel is deformed by an external force.

  However, if the air gap as described above, that is, the air layer is present, the reflection loss of light caused by the difference in the refractive index between the protective panel and the air layer and the difference in the refractive index between the air layer and the display module is large. There is a problem that image quality is reduced. Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer.

  On the other hand, with the reduction in thickness and weight of electronic devices, a change in the protective panel from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate is being studied. Here, in a mode in which the gap between the protection panel and the display module is filled with an adhesive layer, when the protection panel is changed to a plastic plate, outgas is generated from the plastic plate under high-temperature and high-humidity conditions, and air bubbles are generated. There is a new problem that blisters such as floating, peeling and the like occur. For this reason, a pressure-sensitive adhesive or the like filling the space between the display module and the protection panel is often required to have blister resistance.

  As an example of the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, Patent Document 1 discloses a pressure-sensitive adhesive composition for a touch panel containing an epoxy-based silane coupling agent. Patent Document 2 discloses a pressure-sensitive adhesive composition containing a (meth) acryloxy group-containing silane coupling agent, which is mainly used for flat display panels such as plasma display panels and liquid crystal displays. .

JP 2013-54493 A JP 2014-133812 A

  Here, in the pressure-sensitive adhesive composition containing an epoxy-based silane coupling agent as disclosed in Patent Document 1, the ring-opening reaction of an epoxy group is effectively advanced in order to efficiently exhibit a coupling action. This is very important. For this reason, in general, the pressure-sensitive adhesive composition contains a monomer or polymer having an acidic group. However, the pressure-sensitive adhesive for a touch panel is required to be acid-free so as not to deteriorate the transparent conductive film serving as an adherend. Therefore, in the pressure-sensitive adhesive composition as disclosed in Patent Document 1, the effect of the epoxy-based coupling agent cannot be sufficiently obtained while satisfying the acid-free condition. As a result, the effect of improving the adhesion of the obtained pressure-sensitive adhesive to the adherend becomes insufficient. Therefore, it is difficult to obtain an adhesive which is acid-free and can exhibit sufficient blister resistance from the adhesive composition disclosed in Patent Document 1.

  Patent Document 2 discloses, as a specific example of a (meth) acryloxy group-containing silane coupling agent, a compound having a (meth) acryloxy group at one terminal and an alkoxysilyl group at the other terminal. (Paragraph 0038 of Patent Document 2). The pressure-sensitive adhesive composition disclosed in Patent Document 2 contains a (meth) acrylate-based polymer and a (meth) acrylate-based monomer in addition to the coupling agent. When such an adhesive composition is cured, the (meth) acryloxy group of the coupling agent is also added to the radical polymerization reaction between the polymer and the monomer. As a result, the coupling agent is uniformly dispersed in the adhesive. Is assumed to be incorporated in a dispersed state. Therefore, in the pressure-sensitive adhesive composition disclosed in Patent Literature 2, it is presumed that the silane coupling agent is not present near the surface of the pressure-sensitive adhesive layer and does not have the effect of improving the adhesion. As a result, the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition disclosed in Patent Document 2 cannot exhibit sufficient blister resistance.

  The present invention has been made in view of such circumstances, and has as its object to provide a solventless pressure-sensitive adhesive composition, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a display that can exhibit excellent blister resistance.

  In order to achieve the above object, first, the present invention relates to a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, a polyfunctional (meth) acrylate monomer and a polyfunctional (meth) acrylate oligomer. A non-solvent type comprising an organoalkoxysilane having a linear structure and having an alkoxysilyl group at both terminals, wherein at least a part of the polymerization component contains an active hydrogen group. An adhesive composition is provided (Invention 1).

  The solvent-free pressure-sensitive adhesive composition according to the above invention (Invention 1) is characterized in that upon curing, in addition to the radical polymerization reaction between the polymerization components, a hydrolysis-condensation reaction between the polymerization component and the organoalkoxysilane occurs. Presumed. Further, it is estimated that the hydrolysis-condensation reaction mainly occurs near the surface of the pressure-sensitive adhesive layer, and the proportion of the organoalkoxysilane present near the surface of the pressure-sensitive adhesive layer increases. Thus, the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition has excellent cohesion and excellent adhesion to an adherend. As a result, the pressure-sensitive adhesive can exhibit excellent blister resistance.

  In the above invention (Invention 1), the active hydrogen group is preferably a hydroxy group (Invention 2).

  In the above inventions (Inventions 1 and 2), the solvent-free adhesive composition preferably contains at least the polymerizable vinyl monomer and the polyfunctional (meth) acrylate oligomer as the polymerization components (Invention 3). .

  In the above inventions (Inventions 1 to 3), the solventless adhesive composition preferably further contains a photopolymerization initiator (Invention 4).

  In the above inventions (Inventions 1 to 4), the content of the organoalkoxysilane in the solventless adhesive composition is 0.01 part by mass or more and 20 parts by mass or less based on 100 parts by mass of the polymerization component. (Invention 5).

  Secondly, the present invention provides a pressure-sensitive adhesive obtained by curing the solventless pressure-sensitive adhesive composition (Inventions 1 to 5) (Invention 6).

  In the above invention (Invention 6), the gel fraction of the pressure-sensitive adhesive is preferably 50% or more and 100% or less (Invention 7).

  Thirdly, the present invention provides a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive (Invention 6, 7) (Invention 8).

  In the above invention (Invention 8), the pressure-sensitive adhesive sheet includes two release sheets, and the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. (Invention 9).

  Thirdly, the present invention provides one display element constituent member having a step at least on a surface to be bonded, another display element constituent member, the one display element constituent member and the other display member constituent member. And a pressure-sensitive adhesive layer for laminating the pressure-sensitive adhesive sheets to each other, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (Invention 8, 9). (Invention 10).

  The solventless pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet and display according to the present invention can exhibit excellent blister resistance.

It is a sectional view of an adhesive sheet concerning one embodiment of the present invention. It is a sectional view of a layered product concerning one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.
(Solvent-free adhesive composition)
The solvent-free pressure-sensitive adhesive composition according to the present embodiment (hereinafter sometimes referred to as “solvent-free pressure-sensitive adhesive composition P”) may be a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, or a polyfunctional (meth) acrylate monomer. And at least one polymerization component selected from polyfunctional (meth) acrylate oligomers and an organoalkoxysilane having a linear structure and having alkoxysilyl groups at both terminals. Here, at least a part of the polymerization component contains an active hydrogen group. In addition, in this specification, (meth) acrylate means both acrylate and methacrylate. The same applies to other similar terms.

  In the solventless pressure-sensitive adhesive composition P according to the present embodiment, at the time of curing, the radical polymerization reaction between the polymerization components progresses, and the active hydrogen group of the polymerization component and the alkoxysilyl group of the organoalkoxysilane. It is presumed that the hydrolysis-condensation reaction proceeds during the reaction. Since the hydrolysis / condensation reaction proceeds more slowly than the radical polymerization reaction, it is presumed that the hydrolysis / condensation reaction mainly occurs after the radical polymerization reaction has progressed to some extent. Therefore, it is presumed that the ratio of the organoalkoxysilane existing near the surface of the pressure-sensitive adhesive layer increases. Further, since the hydrolysis-condensation reaction occurs at the alkoxysilyl groups present at both ends of the organoalkoxysilane, a structure in which the organoalkoxysilane is crosslinked between the polymerization components is formed. Since the structure is supposed to reinforce the pressure-sensitive adhesive in a different manner from the structure formed by the radical polymerization reaction between the polymerization components and effectively improve the cohesive force, the obtained pressure-sensitive adhesive is extremely Has high cohesion. As a result, the pressure-sensitive adhesive layer obtained from the solvent-free pressure-sensitive adhesive composition P according to the present embodiment has excellent cohesion and excellent adhesion to an adherend.

  From the above, the pressure-sensitive adhesive obtained by using the solvent-free pressure-sensitive adhesive composition P according to the present embodiment can exhibit excellent blister resistance. For example, a display obtained by using the solvent-free pressure-sensitive adhesive composition P according to the present embodiment is placed under a high-temperature and high-humidity condition (for example, 85 ° C., 85% RH), and a display body composed of a plastic plate or the like is used. Even when outgassing occurs from the member, generation of blisters such as bubbles, floating, and peeling at the interface between the pressure-sensitive adhesive layer and the display member is suppressed.

  The above-described reaction and the structure to be formed when the solvent-free pressure-sensitive adhesive composition P according to the present embodiment is cured are presumed, and other reactions occur or other structures are formed. May be done. For example, in the organoalkoxysilane, the alkoxysilyl groups at both ends need not necessarily be bonded to an active hydrogen group, and the alkoxysilyl group at one end may remain without reacting. Further, a hydrolysis-condensation reaction between organoalkoxysilanes occurs to form an organoalkoxysilane repeating structure, and the alkoxysilyl groups at both ends or one end thereof and the active hydrogen group of the polymerization component are bonded. Is also good. Further, the organoalkoxysilane may be present not only in the vicinity of the surface of the pressure-sensitive adhesive layer but also in the inside thereof.

(1) Polymerization component The solvent-free adhesive composition P according to the present embodiment is at least selected from a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, a polyfunctional (meth) acrylate monomer, and a polyfunctional (meth) acrylate oligomer. Contains one polymerization component.

  In the solventless pressure-sensitive adhesive composition P according to the present embodiment, at least a part of the polymerization component has an active hydrogen group. The active hydrogen group is preferably at least one of a hydroxy group and a carboxy group, and the difference in rate between the radical polymerization reaction and the hydrolysis-condensation reaction becomes clear, and the organoalkoxysilane is coated on the surface of the pressure-sensitive adhesive layer. It is particularly preferable that it is a hydroxy group from the viewpoint that it is more likely to be present in the vicinity. Generally, when a touch panel or the like is placed in a high-temperature and high-humidity environment, moisture penetrates into the adhesive layer, and when the touch panel or the like returns to room temperature, the adhesive layer is whitened and the transparency is reduced. The problem of "wet heat whitening" may occur. Here, when the polymerization component contains the active hydrogen group, the group will be present in the obtained pressure-sensitive adhesive. Since the group has good compatibility with the infiltrated water, as a result, the whitening of the pressure-sensitive adhesive layer is suppressed, and the pressure-sensitive adhesive has excellent wet heat whitening resistance.

  The polymerization component preferably contains at least a polymerizable vinyl monomer and a polyfunctional (meth) acrylate oligomer among the above four types. When the polymerization component contains these compounds, the cohesive force of the obtained pressure-sensitive adhesive is improved, and a pressure-sensitive adhesive having more excellent blister resistance can be obtained.

(1-1) Polymerizable vinyl monomer The polymerizable vinyl monomer is not particularly limited as long as it has a vinyl group-containing group, and conventionally known ones can be appropriately used. In addition, the polymerizable vinyl monomer in this embodiment means a polymerizable vinyl monomer having one vinyl group-containing group, and does not overlap with a polyfunctional (meth) acrylate monomer described later.

  Specific examples of the polymerizable vinyl monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and cyclohexyl (meth). Acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) Acrylate, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, polyoxyalkylene-modified (meth) acrylate No functional group other than Le group-containing group (meth) acrylate. Among these, it is preferable to use 2-ethylhexyl acrylate or isobornyl acrylate.

  Further, the polymerizable vinyl monomer may further have a functional group other than a vinyl group-containing group in the molecule. Examples of the functional group include the active hydrogen groups described above, that is, a hydroxy group, a carboxy group, a thiol group, and a primary or secondary amino group. Specific examples of the polymerizable vinyl monomer having such a functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth). A) hydroxyalkyl (meth) acrylates such as acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; hydroxy-containing acrylamides such as N-methylolacrylamide and N-methylolmethacrylamide; Examples thereof include ethylenically unsaturated carboxylic acids such as methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, it is preferable to use 2-hydroxyethyl acrylate.

  Other polymerizable vinyl monomers include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene and α-methylstyrene. Styrene monomers such as butadiene, isoprene, chloroprene and the like; nitrile monomers such as acrylonitrile and methacrylonitrile; acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, Amide monomers such as N-N-dimethyl (meth) acrylamide, N-N-diethyl (meth) acrylamide, N-vinylpyrrolidone; N-N-diethylaminoethyl (meth) acrylate, N- (meth) acryloyl 3 such as morpholine Amino group-containing monomer, and the like.

(1-2) Polymerizable vinyl prepolymer The polymerizable vinyl prepolymer is not particularly limited, and a conventionally known polymer can be appropriately used, and is obtained by polymerizing the polymerizable vinyl monomer described above. It is preferred to use a polymerizable vinyl prepolymer. In addition, in this specification, a prepolymer is a compound obtained by polymerizing a monomer, and means a compound capable of forming a polymer by performing further polymerization.

  When a polymerizable vinyl prepolymer is obtained by polymerizing the above-described polymerizable vinyl monomer, one type of the monomer may be polymerized alone or a plurality of types may be copolymerized.

  Further, the polymerizable vinyl prepolymer may be one obtained by free radical polymerization or one obtained by living polymerization, and in particular, has left RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) terminal. It may be a polymer.

  The weight average molecular weight of the polymerizable vinyl prepolymer is preferably at least 6,000, more preferably at least 7,500, and even more preferably at least 10,000. In addition, the weight average molecular weight is preferably 1,500,000 or less, particularly preferably 1,000,000 or less, and further preferably 100,000 or less. When the weight average molecular weight is within the above range, the viscosity of the solventless pressure-sensitive adhesive composition P can be easily adjusted to a desired range. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

(1-3) Polyfunctional (meth) acrylate monomer The polyfunctional (meth) acrylate monomer is not particularly limited, and conventionally known ones can be appropriately used.

  In particular, as the polyfunctional (meth) acrylate monomer, a monomer having two or more (meth) acryloyl groups in one molecule can be preferably exemplified. Examples of such monomers include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Neopentyl glycol adipate di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified di (meth) acrylate ) Acrylate, di (acryloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acyl , Propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, bis (acryloxyethyl) hydroxy Ethyl isocyanurate, isocyanuric acid ethylene oxide modified diacrylate, isocyanuric acid ethylene oxide modified triacrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate, diglycerin tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, propion Acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acryle And caprolactone-modified dipentaerythritol hexa (meth) acrylate.

(1-4) Polyfunctional (meth) acrylate oligomer The polyfunctional (meth) acrylate oligomer is not particularly limited, and conventionally known ones can be appropriately used, but two or more in one molecule. It is preferable to use a polyfunctional (meth) acrylate oligomer having a (meth) acryloyl group. Examples of such oligomers include urethane acrylate, polyester acrylate, epoxy acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate oligomers.

  Urethane acrylate oligomers include, for example, polyurethane oligomers obtained by reacting a compound such as polyalkylene polyol, polyether polyol, polyester polyol, hydrogenated isoprene having a hydroxy group end, hydrogenated butadiene having a hydroxy group end with polyisocyanate Can be obtained by esterification with (meth) acrylic acid or a (meth) acrylic acid derivative.

  Here, examples of the polyalkylene polyol used in the production of the urethane acrylate oligomer include polypropylene glycol, polyethylene glycol, polybutylene glycol, polyhexylene glycol, and the like, and it is particularly preferable to use polypropylene glycol. When the number of functional groups of the obtained urethane acrylate oligomer is 3 or more, glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose, and the like may be appropriately combined.

  Examples of polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, and diphenyl diisocyanate; alicyclic diisocyanates such as dicyclohexyl methane diisocyanate and isophorone diisocyanate. Among them, it is preferable to use an aliphatic diisocyanate, and particularly preferable to use hexamethylene diisocyanate. The polyisocyanate is not limited to difunctional ones, and trifunctional or more functional ones can be used.

  Examples of the (meth) acrylic acid derivative include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, 2-isocyanatoethyl acrylate, 2-isocyanatoethyl methacrylate, and 1,1-bis (acrylic acid). (Roxymethyl) ethyl isocyanate and the like, and it is particularly preferable to use 2-isocyanate ethyl acrylate.

  As another method for producing a urethane acrylate oligomer, a hydroxy group of a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, a hydrogenated isoprene having a hydroxy group terminal, a hydrogenated butadiene having a hydroxy group terminal, and an isocyanate alkyl ( A urethane acrylate oligomer can also be obtained by a reaction between the -N = C = O moiety of the (meth) acrylate. In this case, as the isocyanate alkyl (meth) acrylate, the above-mentioned 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, 1,1-bis (acryloxymethyl) ethyl isocyanate, or the like can be used.

  The polyester acrylate-based oligomer is obtained, for example, by esterifying a hydroxy group of a polyester oligomer having hydroxy groups at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid, or It can be obtained by esterifying the terminal hydroxy group of an oligomer obtained by adding an alkylene oxide to a carboxylic acid with (meth) acrylic acid.

  The epoxy acrylate oligomer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a bisphenol-type epoxy resin or a novolak-type epoxy resin having a relatively low molecular weight and esterifying it. A carboxyl-modified epoxy acrylate oligomer obtained by partially modifying an epoxy acrylate oligomer with a dibasic carboxylic anhydride can also be used.

  The polyether acrylate oligomer can be obtained, for example, by esterifying a hydroxy group of a polyether polyol with (meth) acrylic acid.

  The weight average molecular weight of the polyfunctional (meth) acrylate oligomer is preferably 10,000 or more, particularly preferably 20,000 or more. In addition, the weight average molecular weight is preferably 350,000 or less, particularly preferably 200,000 or less.

(1-5) Mixing ratio When two kinds of a polymerizable vinyl monomer and a polyfunctional (meth) acrylate oligomer are used as a polymerization component, the mass of the polymerizable vinyl monomer is divided by the mass of the polyfunctional (meth) acrylate oligomer. The obtained ratio is preferably 0.18 or more, particularly preferably 1 or more, and more preferably 1.5 or more. Further, the ratio is preferably 999 or less, particularly preferably 19 or less, and more preferably 9 or less.

(2) Organoalkoxysilane The solventless adhesive composition P according to the present embodiment has a linear structure and contains an organoalkoxysilane having an alkoxysilyl group at both terminals. Here, “straight-chain” in “straight-chain structure” means substantially “straight-chain”. That is, the linear structure may have a branched chain or may have a cyclic structure, as long as the effect of crosslinking between the polymerization components by the organoalkoxysilane is sufficiently exhibited. Further, having an alkoxysilyl group at both ends means having an alkoxysilyl group at each of both ends of the linear structure.

  The organoalkoxysilane preferably contains a plurality of alkoxysilyl groups at at least one end. That is, the organoalkoxysilane preferably contains two alkoxysilyl groups or three alkoxysilyl groups at at least one end, and particularly preferably contains three alkoxysilyl groups. Organoalkoxysilane, at least one terminal, by containing a plurality of alkoxysilyl groups, as a result of easy bonding with the active hydrogen group that the polymerization component has, as a result, the cohesive force of the resulting adhesive is higher. Become.

  Examples of the alkoxysilyl group include methoxysilyl, ethoxysilyl, n-propoxysilyl, isopropoxysilyl, n-butoxysilyl, s-butoxysilyl, isobutoxysilyl, t-butoxysilyl and the like. Is mentioned. Among these, a methoxysilyl group is preferable from the viewpoint of obtaining excellent blister resistance.

  The organoalkoxysilane preferably has no group other than the alkoxysilyl group that can react with the polymerization component. Examples of the reactive group other than the alkoxysilyl group include a (meth) acryloxy group, a vinyloxy group and an allyloxy group. Since the organoalkoxysilane does not have such a group, it is possible to suppress the organoalkoxysilane from being uniformly incorporated into the polymerization component. Thereby, the ratio of the organoalkoxysilane present in the vicinity of the surface of the obtained pressure-sensitive adhesive layer becomes higher, and the adhesion of the pressure-sensitive adhesive layer to the adherend is further improved. Further, the absence of any group other than the alkoxysilyl group allows the reaction between the alkoxysilyl group and the active hydrogen group in the polymerization component to proceed without hindrance. Thereby, the structure in which the organoalkoxysilane is crosslinked between the polymerization components in the obtained pressure-sensitive adhesive layer is favorably formed, and the cohesive force on the pressure-sensitive adhesive layer surface is further improved. As a result, the resulting pressure-sensitive adhesive layer has excellent blister resistance.

  Examples of the organoalkoxysilane contained in the solvent-free adhesive composition P according to the present embodiment include bis (alkoxysilyl) alkane; 1,4-bis (alkoxysilyl) benzene, and 1,4-bis (alkoxy). Aromatic compounds such as silylalkyl) benzene; alkylene oxide compounds such as 1,2-bis (alkoxysilyl) ethylene oxide and 1,3-bis (alkoxysilyl) propylene oxide; 1,3-bis (alkoxysilyl) cyclobutane; And alicyclic compounds such as 1,3-bis (alkoxysilylalkyl) cyclobutane, 1,4-bis (alkoxysilyl) cyclohexane, and 1,4-bis (alkoxysilylalkyl) cyclohexane. Among these, bis (alkoxysilyl) alkane is particularly preferred from the viewpoint that the molecule is not bulky and easily forms a bond with the active hydrogen group of the pressure-sensitive adhesive.

  The alkane of the bis (alkoxysilyl) alkane preferably has one or more carbon atoms, particularly preferably three or more carbon atoms, and more preferably five or more carbon atoms. The alkane preferably has 20 or less carbon atoms, more preferably 10 or less carbon atoms, and further preferably 7 or less carbon atoms.

  Preferred examples of the bis (alkoxysilyl) alkane include 1,6-bis (trimethoxysilyl) hexane, 1,7-bis (trimethoxysilyl) heptane, and 1,8-bis (trimethoxysilyl) octane. Can be Among these, it is preferable to use 1,6-bis (trimethoxysilyl) hexane or 1,8-bis (trimethoxysilyl) octane from the viewpoint of obtaining excellent blister resistance.

  The content of the organoalkoxysilane in the solvent-free pressure-sensitive adhesive composition P is preferably at least 0.01 part by mass, particularly preferably at least 0.05 part by mass with respect to 100 parts by mass of the polymerization component. Preferably, it is more preferably at least 0.1 part by mass. Further, the content is preferably 20 parts by mass or less, particularly preferably 10 parts by mass or less, and further preferably 3 parts by mass or less based on 100 parts by mass of the polymerization component. When the content is in the above range, the above-described effects of the organoalkoxysilane can be sufficiently obtained.

(3) Polymerization initiator It is preferable that the solventless adhesive composition P according to the present embodiment further contains a polymerization initiator. By containing the polymerization initiator, it becomes possible to efficiently cure the solventless adhesive composition P.

  The polymerization initiator is not particularly limited, and a conventionally known one can be used. However, it is preferable to select the polymerization initiator according to the curing mode of the non-solvent type adhesive composition P. That is, when the solventless pressure-sensitive adhesive composition P is cured by irradiation with ultraviolet rays as active energy rays, it is preferable to use a photopolymerization initiator as the polymerization initiator. When the solventless pressure-sensitive adhesive composition P is cured by heating, it is preferable to use a thermal polymerization initiator. A photopolymerization initiator and a thermal polymerization initiator may be used in combination.

  Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylamino Zophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2 , 4-Diethylthioxanthone, benzyldimethylketal, acetophenonedimethylketal, p-dimethylaminobenzoate, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2,4 , 6-trimethylbenzoyl-diphenyl-phosphine oxide and the like. These may be used alone or in combination of two or more.

  Examples of the thermal polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, peroxides such as benzoyl peroxide and laurium peroxide, and azo compounds such as azobisisobutyronitrile. These may be used alone or in combination of two or more.

  The content of the polymerization initiator in the solventless adhesive composition P is preferably at least 0.1 part by mass, particularly preferably at least 0.3 part by mass with respect to 100 parts by mass of the polymerization component. Preferably, it is more preferably at least 0.5 part by mass. Further, the content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 3 parts by mass or less based on 100 parts by mass of the polymerization component. When the content is 0.1 part by mass or more, the curing of the solvent-free pressure-sensitive adhesive composition P can be efficiently advanced. On the other hand, when the content is 10 parts by mass or less, it becomes possible to eliminate or reduce the polymerization initiator that remains unreacted during curing, and it is easy to set the obtained pressure-sensitive adhesive to desired physical properties.

(4) Various additives In the solvent-free adhesive composition P, various additives such as a silane coupling agent, an ultraviolet absorber, an antistatic agent, a tackifier, an antioxidant, a light stabilizer, A softener, a filler, a refractive index adjuster, and the like can be added. In addition, the below-mentioned polymerization solvent shall not be contained in the additive which comprises the solventless adhesive composition P.

  Here, when the solventless pressure-sensitive adhesive composition P contains a silane coupling agent, the obtained pressure-sensitive adhesive has improved adhesion to a glass member or a plastic plate. Thereby, the obtained adhesive becomes more excellent in blister resistance.

  The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in a molecule, excluding the above-mentioned organoalkoxysilane, and has good compatibility with the above-mentioned polymerization component and organoalkoxysilane, and Those having properties are preferred.

  Examples of such a silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 2- ( Silicon compounds having an epoxy structure such as 3,4-epoxycyclohexyl) ethyltrimethoxysilane, and silicon compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane , 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of these and an alkyl group-containing silicon such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, etc. Condensates with compounds are mentioned. These may be used alone or in combination of two or more.

  When the solvent-free pressure-sensitive adhesive composition P contains a silane coupling agent, its content is preferably at least 0.01 part by mass, particularly preferably 0.05 part by mass, based on 100 parts by mass of the polymerization component. It is preferably at least 0.1 parts by mass, and more preferably 0.1 parts by mass or more. Further, the content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and more preferably 0.3 part by mass or less based on 100 parts by mass of the polymerization component. Is preferred.

(5) Production of Solvent-Free Adhesive Composition The solvent-free adhesive composition P can be produced by mixing a polymerization component and an organoalkoxysilane and optionally adding an additive.

  In addition, since the solventless adhesive composition P according to the present embodiment is a solventless type, it has an appropriate viscosity mainly due to a polymerization component. Therefore, the solvent-free adhesive composition P according to the present embodiment can be used as it is as a coating solution without adding a diluent or the like.

(Adhesive)
The pressure-sensitive adhesive according to the present embodiment is obtained by curing a solventless pressure-sensitive adhesive composition P. Curing of the solvent-free adhesive composition P can be performed by irradiation with active energy rays, or can be performed by heat treatment, depending on the material contained in the composition P. As described above, “curing” in this specification includes both curing by irradiation with active energy rays and curing by heat treatment, unless otherwise specified.

  The curing of the solvent-free adhesive composition P is preferably performed by irradiation with active energy rays. This eliminates the need to apply heat during curing, and can prevent heat deterioration, heat shrinkage, and the like of the resin film or the like to which the solventless adhesive composition P is applied. In addition, by not heating, it is possible to suppress the disappearance of the volatile components in the solventless adhesive composition P by heating.

  The active energy beam refers to a beam having an energy quantum among electromagnetic waves or charged particle beams, and specific examples include ultraviolet rays and electron beams. Among the active energy rays, ultraviolet rays which are easy to handle are particularly preferable.

Irradiation of ultraviolet rays, a high-pressure mercury lamp, a fusion H lamp, can be carried out by a xenon lamp or the like, the dose of ultraviolet ray is illuminance 50 mW / cm ² or more, and preferably 1000 mW / cm ² or less. Amount is preferably at 50 mJ / cm ² or more, more preferably 80 mJ / cm ² or more, and particularly preferably 200 mJ / cm ² or more. Further, the light amount is preferably at 10000 mJ / cm ² or less, more preferably 5000 mJ / cm ² or less, particularly preferably 2000 mJ / cm ² or less. On the other hand, electron beam irradiation can be performed by an electron beam accelerator or the like, and the electron beam irradiation amount is preferably 10 krad or more and 1000 krad or less.

  The heating temperature of the heat treatment is preferably at least 50 ° C, particularly preferably at least 70 ° C. Further, the heating temperature is preferably 150 ° C. or lower, particularly preferably 120 ° C. or lower. The heating time of the heat treatment is preferably at least 10 seconds, particularly preferably at least 50 seconds. In addition, the heating time is preferably 10 minutes or less, and particularly preferably 90 seconds or less. This heat treatment can also serve as a drying treatment after the application of the solventless pressure-sensitive adhesive composition P.

  In the production of the pressure-sensitive adhesive according to the present embodiment, after performing a heat treatment, active energy ray irradiation may be performed, or both treatments may be performed simultaneously. It is also preferable to provide a curing period of about 1 to 2 weeks at normal temperature (for example, 23 ° C., 50% RH) after the heat treatment or the irradiation with the active energy ray.

  The gel fraction of the pressure-sensitive adhesive according to the present embodiment is preferably 50% or more, particularly preferably 55% or more, and further preferably 60% or more. In addition, the gel fraction is preferably 100% or less, particularly preferably 80% or less, and further preferably 70% or less. When the gel fraction of the pressure-sensitive adhesive is in the above range, the cohesive force of the pressure-sensitive adhesive is increased, and the blister resistance is further improved. Here, the method of measuring the gel fraction of the pressure-sensitive adhesive is as shown in Test Examples described later.

  The pressure-sensitive adhesive according to the present embodiment is obtained by curing the solventless pressure-sensitive adhesive composition P described above. Therefore, at the time of the curing, the condensation reaction between the organoalkoxysilane and the active hydrogen group proceeds mainly in the vicinity of the surface together with the polymerization reaction between the polymerization components, so that a strong crosslinked structure is formed in the adhesive. . As a result, the pressure-sensitive adhesive according to the present embodiment has a very high cohesive force. That is, the pressure-sensitive adhesive according to the present embodiment has high flexibility as a whole while locally increasing the cohesive force of the surface in contact with the adherend. Thus, the pressure-sensitive adhesive according to the present embodiment can exhibit excellent blister resistance while having sufficient step-following properties.

(Adhesive sheet)
The pressure-sensitive adhesive sheet according to the present embodiment has a pressure-sensitive adhesive layer for laminating one display member and another display member, and the pressure-sensitive adhesive layer is formed of the above-described pressure-sensitive adhesive. is there.

  FIG. 1 shows a specific configuration as an example of the pressure-sensitive adhesive sheet according to the present embodiment. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to one embodiment includes two release sheets 12a and 12b and the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. , 12b. In addition, the release surface of the release sheet in this specification refers to a surface having releasability in the release sheet, and includes both the surface subjected to the release treatment and the surface exhibiting the releasability even without performing the release treatment. .

(1) Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer 11 is composed of the above-mentioned pressure-sensitive adhesive, that is, composed of a pressure-sensitive adhesive obtained by curing the solventless pressure-sensitive adhesive composition P.

  The thickness (the value measured according to JIS K7130: 1999) of the pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 10 μm or more, more preferably 25 μm or more, and particularly preferably 50 μm or more. Is more preferable, and more preferably 75 μm or more. Further, the thickness is preferably 1000 μm or less, more preferably 400 μm or less, and particularly preferably 300 μm or less. The pressure-sensitive adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

  When the thickness of the pressure-sensitive adhesive layer 11 is 10 μm or more, a desired pressure-sensitive adhesive force is easily exerted. In addition, when the thickness of the pressure-sensitive adhesive layer 11 is 1000 μm or less, workability is improved.

(2) Release Sheet The release sheets 12a and 12b protect the pressure-sensitive adhesive layer 11 until the pressure-sensitive adhesive sheet 1 is used, and are released when the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 11) is used. In the pressure-sensitive adhesive sheet 1 according to the present embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

  Examples of the release sheets 12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene. Terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine A resin film or the like is used. These crosslinked films are also used. Further, these laminated films may be used.

  The release surfaces of the release sheets 12a and 12b (particularly, the surfaces in contact with the adhesive layer 11) are preferably subjected to a release treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. It is preferable that one of the release sheets 12a and 12b is a heavy release type release sheet having a large release force, and the other release sheet is a light release type release sheet having a small release force.

  The thickness of the release sheets 12a and 12b is not particularly limited, but is usually 20 μm or more and 150 μm or less.

(3) Physical Properties (3-1) Adhesive Force The adhesive force of the pressure-sensitive adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 5 N / 25 mm or more, particularly preferably 10 N / 25 mm or more. Is preferably 15 N / 25 mm or more. In addition, the adhesive strength is preferably 50 N / 25 mm or less, particularly preferably 40 N / 25 mm or less, and further preferably 35 N / 25 mm or less. When the adhesive force of the adhesive sheet 1 is 5 N / 25 mm or more, the blister resistance becomes more excellent. In addition, when the adhesive force of the adhesive sheet 1 is 50 N / 25 mm or less, good reworkability is obtained, and in the event of a bonding error, an expensive display member can be reused. Here, the adhesive force in the present specification basically refers to the adhesive force measured by a 180-degree peeling method according to JIS Z0237: 2009, and a specific measuring method is as shown in a test example described later. is there.

(3-2) Haze value The haze value of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 5% or less, particularly preferably 1% or less, and more preferably 0.5% or less. % Is preferable. When the haze value of the pressure-sensitive adhesive layer 11 is 5% or less, the transparency is high, which is suitable for optical use (for display). The haze value in the present specification is a value measured according to JIS K7136: 2000.

(3-3) Total light transmittance The total light transmittance of the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 according to the present embodiment is preferably 90% or more, particularly preferably 95% or more, and further preferably. It is preferably 98% or more. When the total light transmittance is 98% or more, the transparency is extremely high, which makes it suitable for optical use. In addition, the total light transmittance in this specification is a value measured according to JIS K7361-1: 1997.

(4) Production of pressure-sensitive adhesive sheet As one production example of the pressure-sensitive adhesive sheet 1, a coating layer is formed by applying the solventless pressure-sensitive adhesive composition P to the release surface of one release sheet 12a (or 12b). After superposing the release surface of the other release sheet 12b (or 12a) on the coating layer, the adhesive layer 11 is formed by irradiating the application layer with active energy rays and / or heating.

  As another production example of the pressure-sensitive adhesive sheet 1, the solvent-free pressure-sensitive adhesive composition P is applied to the release surface of one of the release sheets 12a (or 12b), and is subjected to active energy ray irradiation and / or heat treatment. After the non-solvent type pressure-sensitive adhesive composition P is cured to form the pressure-sensitive adhesive layer 11, the release surface of the other release sheet 12b (or 12a) is superimposed on the pressure-sensitive adhesive layer 11.

  As a method for applying the coating solution of the solventless pressure-sensitive adhesive composition P, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

  In the pressure-sensitive adhesive sheet 1 according to the present embodiment manufactured as described above, the pressure-sensitive adhesive layer 11 is formed of a pressure-sensitive adhesive obtained by curing the solventless pressure-sensitive adhesive composition P described above. Have power. Further, when forming a coating film of the solvent-free pressure-sensitive adhesive composition P, a large amount of organoalkoxysilane having polarity is unevenly distributed near the surface of the coating film, and the condensation reaction is presumed to proceed more near the surface. . As a result, in the pressure-sensitive adhesive sheet 1 according to the present embodiment, it is estimated that the closer to the surface of the pressure-sensitive adhesive layer 11, the higher the cohesive force. Thus, according to the pressure-sensitive adhesive sheet 1 according to the present embodiment, excellent blister resistance is exhibited.

(Display body)
As shown in FIG. 2, the display body 2 according to the present embodiment includes a first display body constituent member 21 (one display body constituent member) having a step on at least a surface to be bonded, and a second display body constituent member. The display member 22 (another display member) and the pressure-sensitive adhesive layer 11 that is located therebetween and bonds the first display member 21 and the second display member 22 to each other. It is configured with. In the display 2 according to the present embodiment, the first display component 21 has a step on the surface on the side of the pressure-sensitive adhesive layer 11, and specifically has a step due to the print layer 3. .

  The pressure-sensitive adhesive layer 11 of the display body 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 described above.

  Examples of the display 2 include a liquid crystal (LCD) display, a light emitting diode (LED) display, an organic electroluminescence (organic EL) display, electronic paper, and the like, and may be a touch panel. Further, the display 2 may be a member constituting a part of them.

  The first display member 21 is preferably a protective panel made of a glass plate, a plastic plate, or the like, or a laminate including them. In this case, the printing layer 3 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the first display member 21.

  The glass plate is not particularly limited, for example, chemically strengthened glass, non-alkali glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate Glass etc. are mentioned. The thickness of the glass plate is not particularly limited, but is usually 0.1 mm or more, preferably 0.2 mm or more. The thickness is usually 5 mm or less, preferably 2 mm or less.

  The plastic plate is not particularly limited, and examples thereof include an acrylic plate and a polycarbonate plate. The thickness of the plastic plate is not particularly limited, but is usually 0.2 mm or more, preferably 0.4 mm or more. The thickness is usually 5 mm or less, preferably 3 mm or less.

  Various functional layers (a transparent conductive film, a metal layer, a silica layer, a hard coat layer, an antiglare layer, etc.) may be provided on one or both surfaces of the glass plate or the plastic plate, and an optical member may be provided. May be laminated. Further, the transparent conductive film and the metal layer may be patterned.

  The second display member 22 includes an optical member to be attached to the first display member 21, a display module (for example, a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic). EL) module), an optical member as a part of the display module, or a laminate including the display module.

  Examples of the optical member include a scattering prevention film, a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, and a diffusion film. , A transflective film, a transparent conductive film, and the like. Examples of the shatterproof film include a hard coat film in which a hard coat layer is formed on one surface of a base film.

  The material constituting the print layer 3 is not particularly limited, and a known material for printing is used. The thickness of the printing layer 3, that is, the height of the step is preferably at least 3 μm, particularly preferably at least 5 μm, further preferably at least 7 μm, most preferably at least 10 μm. In addition, the height is preferably 50 μm or less, and particularly preferably 35 μm or less.

  In order to manufacture the display body 2, as an example, one of the release sheets 12 a of the pressure-sensitive adhesive sheet 1 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1 is replaced with the printing layer of the first display member 21. 3 is attached to the surface on the side where there is. Thereafter, the other release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 and the second display member 22 are bonded. Further, as another example, the bonding order of the first display member 21 and the second display member 22 may be changed.

  In the display body 2 described above, since the pressure-sensitive adhesive layer 11 is made of a pressure-sensitive adhesive obtained by curing the above-described solventless pressure-sensitive adhesive composition P, it has a very high cohesive force as described above, In particular, it is presumed that this cohesive force is higher as it is closer to the surface of the adhesive layer 11. For this reason, even if the display body 2 is placed under high-temperature and high-humidity conditions and outgas is generated from the first display body constituent member 21 or the second display body constituent member 22, blisters such as bubbles, floating, and peeling may occur. Generation is suppressed.

  The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12a and / or 12b. Further, the first display member 21 may have a step other than the printing layer 3. Further, not only the first display member 21 but also the second display member 22 may have a step on the adhesive layer 11 side.

  Hereinafter, the present invention will be described more specifically with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Production Example 1]
1. Preparation of urethane acrylate oligomer 100 parts by mass of polypropylene glycol having a weight average molecular weight of 3000 (solid content converted value; the same applies hereinafter), 4 parts by mass of hexamethylene diisocyanate, and 0.02 parts by mass of dioctyltin dilaurate were mixed at 80 ° C. For 6 hours to obtain a reaction product. When the IR spectrum of the obtained reaction product was measured by infrared spectroscopy, it was confirmed that the isocyanate group had almost disappeared.

  Thereafter, 1 part by mass of 2-isocyanate ethyl acrylate was mixed with the entire amount of the obtained reaction product, and the mixture was stirred at 80 ° C. for 3 hours to obtain a urethane acrylate oligomer. The IR spectrum of the obtained urethane acrylate oligomer was measured by infrared spectroscopy. As a result, it was confirmed that the isocyanate group had almost disappeared. Moreover, the molecular weight of the obtained urethane acrylate oligomer was measured by the method described later, and was found to be a weight average molecular weight (Mw) of 25,000.

2. Preparation of liquid mixture 40 parts by mass of 2-ethylhexyl acrylate as a polymerizable vinyl monomer, 20 parts by mass of isobornyl acrylate as a polymerizable vinyl monomer, and 10 parts by mass of 2-hydroxyethyl acrylate as a polymerizable vinyl monomer, A liquid mixture was obtained by mixing and stirring 30 parts by mass of the urethane acrylate-based oligomer prepared as described above as a polyfunctional (meth) acrylate oligomer.

Here, the above-mentioned weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured (GPC measurement) using gel permeation chromatography (GPC) under the following conditions.
<Measurement conditions>
・ GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
-Measurement solvent: tetrahydrofuran-Measurement temperature: 40 ° C

[Production Example 2]
40 parts by mass of 2-ethylhexyl acrylate as a polymerizable vinyl monomer, 20 parts by mass of acryloyl morpholine as a polymerizable vinyl monomer, 10 parts by mass of 2-hydroxyethyl acrylate as a polymerizable vinyl monomer, A liquid mixture was obtained by mixing and stirring 30 parts by mass of the prepared urethane acrylate oligomer.

[Example 1]
1. Preparation of Solvent-Free Adhesive Composition 100 parts by mass of the liquid mixture prepared in Production Example 1 above (in terms of solid content; the same applies hereinafter) and 1,6-bis (trimethoxysilyl) hexane 0 as an organoalkoxysilane By mixing 0.3 parts by mass and 0.5 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerization initiator, a solventless adhesive composition was obtained.

2. Production of pressure-sensitive adhesive sheet The solvent-free pressure-sensitive adhesive composition obtained in the above step 1 was subjected to a release treatment on one side of a polyethylene terephthalate film with a silicone-based release agent (Lintech Co., Ltd., product name “SP-PET752150”). )) With a knife coater.

  Next, a light-peelable release sheet (product name “SP-PET382120” manufactured by Lintec Corporation) in which the coating layer on the heavy-peelable release sheet obtained above and one surface of the polyethylene terephthalate film were subjected to release treatment with a silicone-based release agent. Were bonded so that the release-treated surface of the light release type release sheet was in contact with the coating layer.

Thereafter, the coating layer is irradiated with ultraviolet rays through the heavy release type release sheet under the following conditions to form a heavy release type release sheet / adhesive layer (thickness: 100 μm) / light release type release sheet. An adhesive sheet was produced.
[UV irradiation conditions]
・ Light source: high pressure mercury lamp ・ Light intensity: 1000 mJ / cm ²
・ Illuminance: 100 mW / cm ²

[Examples 2 to 4, Comparative Examples 1 to 6]
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the type of the liquid mixture and the type and the amount of the organoalkoxysilane were changed as shown in Table 1. In Comparative Example 3, the tris- (trimethoxysilylpropyl) isocyanurate used as the organoalkoxysilane had a so-called isocyanurate ring as a main skeleton, and three trimethoxysilylpropyl groups were equidistant from the main skeleton. It is combined with Therefore, the organoalkoxysilane cannot be said to be the organoalkoxysilane having the above-mentioned linear structure, and does not correspond to the organoalkoxysilane according to the present embodiment.

[Test Example 1] (Measurement of gel fraction)
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the pressure-sensitive adhesive layer was wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. By subtracting the single mass, the mass of the pressure-sensitive adhesive alone was calculated. The mass at this time is defined as M1.

  Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 3 days. Thereafter, the adhesive was taken out and dried in an oven at 100 ° C. for 3 hours. After drying, the mixture was allowed to stand for 3 hours in an environment at a temperature of 23 ° C. and a relative humidity of 50%, and the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. . The mass at this time is defined as M2. The gel fraction (%) is represented by (M2 / M1) × 100. Table 1 shows the results.

[Test Example 2] (Evaluation of optical characteristics)
The light-peelable release sheet was peeled off from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) having a thickness of 1.1 mm. By peeling the release sheet, a sample for evaluation was obtained.

  Measurement light of a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name “NDH-2000”) is incident from the pressure-sensitive adhesive layer side of the evaluation sample, and the total light transmittance (%) and the haze value (%) are measured. It was measured. Each measurement was performed three times, and their average was calculated. Table 1 shows the results.

[Test Example 3] (Measurement of adhesive strength)
The light-peelable release sheet was peeled from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was replaced with a polyethylene terephthalate (PET) film (PET A4300, manufactured by Toyobo Co., Ltd.) having an easily adhesive layer. (Thickness: 100 μm) to obtain a laminate of a release sheet / adhesive layer / PET film. The obtained laminate was cut into a width of 25 mm and a length of 150 mm, and this was used as a sample.

  Under an environment of 23 ° C. and 50% RH, the heavy release type release sheet was peeled off from the sample, the exposed pressure-sensitive adhesive layer was adhered to soda lime glass (manufactured by Nippon Sheet Glass), and a 2 kg roller was moved back and forth once. It crimped by doing. Then, after leaving for 24 hours under the conditions of 23 ° C. and 50% RH, the adhesive force (N) was measured using a tensile tester (manufactured by Orientec, Tensilon) at a peeling speed of 300 mm / min and a peeling angle of 180 °. / 25 mm). The conditions other than those described here were measured in accordance with JIS Z0237: 2009. Table 1 shows the results.

[Test Example 4] (Evaluation of blister resistance)
The light-peelable release sheet of the pressure-sensitive adhesive sheet obtained in each of Examples and Comparative Examples was peeled off, and the exposed pressure-sensitive adhesive layer was replaced with a polyethylene terephthalate film (tail) provided with a transparent conductive film made of tin-doped indium oxide (ITO) on one surface. It was attached to the surface provided with a transparent conductive film (product name: “ITO film”, manufactured by Ike Kogyo Co., Ltd., thickness: 125 μm), and cut into 60 mm × 60 mm. Furthermore, the heavy release type release sheet was peeled off from the pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer was replaced with a resin plate (manufactured by Mitsubishi Gas Chemical Company, product name "Mitsubishi Gas Chemical Co., Ltd." A test piece was obtained by affixing it to the polycarbonate-side surface of “MR-58”, thickness: 785 μm).

The obtained test piece was autoclaved at 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure, 23 ° C. and 50% RH for 24 hours. Next, it was stored under high temperature and high humidity conditions of 85 ° C. and 85% RH for 72 hours. Thereafter, the peeling off at the interface between the pressure-sensitive adhesive layer and the adherend was visually confirmed, and the blister resistance was evaluated according to the following criteria. Table 1 shows the results.
：: Neither air bubbles nor peeling was observed.
Δ: Small bubbles were slightly observed, but no peeling was observed.
×: Large bubbles or peeling off can be confirmed.

[Test Example 5] (Evaluation of wet heat whitening resistance)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples or Comparative Examples was replaced with a polyethylene terephthalate film having a transparent conductive film made of tin-doped indium oxide (ITO) provided on one side (product name "ITO film" manufactured by Oike Industry Co., Ltd.) , Thickness: 125 μm) to obtain a laminate. At this time, the surface of the film on which the transparent conductive film was provided was attached to the pressure-sensitive adhesive layer. The obtained laminate was subjected to an autoclave treatment at 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure, 23 ° C. and 50% RH for 24 hours. Thereafter, the haze value (%) was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name “NDH2000”) according to JIS K7136: 2000.

  Next, the laminated body was stored for 120 hours under the moist heat condition of 85 ° C. and 85% RH (durability test). Thereafter, the temperature was returned to normal temperature and normal humidity of 23 ° C. and 50% RH, and the haze value (%) of the laminate was measured again. The haze value was measured within 30 minutes after returning the laminate to normal temperature and normal humidity.

From the increase in the haze value (%) after the durability test from the haze value (%) before the durability test, the wet heat whitening resistance was evaluated based on the following criteria. Table 1 shows the results.
：: The haze value (%) after the durability test is 0.90% or less.
：: The increase in the haze value (%) after the durability test exceeds 0.90% and is 1.50% or less.
X: The rise value of the haze value (%) after the durability test exceeds 1.50%.

[Test Example 6] (Evaluation of step followability)
A UV curable ink (manufactured by Teikoku Ink, product name "POS-911 Ink") is applied to the surface of a glass plate (manufactured by NSG Precision, product name "Corning Glass Eagle XG", 90 mm long x 50 mm wide x 0.5 mm thick). ) Was screen-printed in a frame shape (outer size: 90 mm long × 50 mm wide, 5 mm wide) so that the coating thickness was 30 μm. Next, ultraviolet rays are irradiated (80 W / cm ² , ^two metal halide lamps, lamp height 15 cm, belt speed 10 to 15 m / min) to cure the printed ultraviolet curable ink, and to form a step having a step by printing. A glass plate was produced.

  The light-peelable release sheet was peeled from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and the exposed pressure-sensitive adhesive layer was replaced with a polyethylene terephthalate film having an easily bonding layer (manufactured by Toyobo Co., Ltd., product name “PET A4300”, thickness: (100 μm). Next, the heavy release type release sheet was peeled off to expose the pressure-sensitive adhesive layer. Then, using a laminator (trade name “LPD3214”, manufactured by Fujipla Co., Ltd.), the exposed surface of the pressure-sensitive adhesive layer and the stepped surface of the stepped glass plate are combined with the entire surface of the frame-shaped printed pressure-sensitive adhesive layer. It was bonded so as to cover it and used as a sample for evaluation.

The obtained evaluation sample was autoclaved at 50 ° C. and 0.5 MPa for 30 minutes, and then left at normal pressure, 23 ° C. and 50% RH for 24 hours. Then, it was stored for 72 hours under a high temperature and high humidity condition of 85 ° C. and 85% RH (durability test). Followability was evaluated. Table 1 shows the results.
A: There is no peeling off near the step, and the adhesive follows without gap.
：: Slight peeling is seen near the step.
×: Large bubbles are mixed in the vicinity of the step.

  As can be seen from Table 1, the pressure-sensitive adhesive sheets obtained in the examples were excellent in blister resistance, and were also excellent in wet heat whitening resistance and step followability.

  The solvent-free pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for bonding a display component.

DESCRIPTION OF SYMBOLS 1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Peeling sheet 2 ... Display body 21 ... 1st display body constituent member 22 ... 2nd display body constituent member 3 ... Printing layer

Claims (10)

At least one polymerization component selected from a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, a polyfunctional (meth) acrylate monomer, and a polyfunctional (meth) acrylate oligomer;
Having a linear structure, containing an organoalkoxysilane having an alkoxysilyl group at both terminals,
At least a part of the polymerization component contains an active hydrogen group ,
The solvent-free adhesive composition , wherein the organoalkoxysilane has no group other than the alkoxysilyl group that can react with the polymerization component .   The solvent-free adhesive composition according to claim 1, wherein the active hydrogen group is a hydroxy group.   The solventless adhesive according to claim 1, wherein the solventless adhesive composition contains at least the polymerizable vinyl monomer and the polyfunctional (meth) acrylate oligomer as the polymerization component. 4. Composition.   The solventless pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the solventless pressure-sensitive adhesive composition further includes a photopolymerization initiator.   The content of the organoalkoxysilane in the solventless adhesive composition is 0.01 part by mass or more and 20 parts by mass or less based on 100 parts by mass of the polymerization component. The solventless pressure-sensitive adhesive composition according to any one of Items 4 to 4.   An adhesive obtained by curing the solvent-free adhesive composition according to claim 1.   The pressure-sensitive adhesive according to claim 6, wherein the gel fraction of the pressure-sensitive adhesive is 50% or more and 100% or less.   An adhesive sheet having an adhesive layer comprising the adhesive according to claim 6. The pressure-sensitive adhesive sheet includes two release sheets,
The pressure-sensitive adhesive sheet according to claim 8, wherein the pressure-sensitive adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. One display body constituent member having a step on at least the side to be bonded,
Other display member components,
A display body comprising an adhesive layer for bonding the one display body constituent member and the other display body constituent member to each other,
A display, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to claim 8.

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