CN106967380B

CN106967380B - Solvent-free adhesive composition, adhesive sheet, and display

Info

Publication number: CN106967380B
Application number: CN201610956187.1A
Authority: CN
Inventors: 吉延毅朗; 小泽祐树; 荒井隆行; 所司悟
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2015-11-04
Filing date: 2016-11-03
Publication date: 2020-12-22
Anticipated expiration: 2036-11-03
Also published as: JP2017088663A; TWI715654B; TW201723115A; KR102569065B1; KR20170052491A; JP6660710B2; CN106967380A

Abstract

The invention provides a solvent-free adhesive composition, an adhesive sheet and a display body, which can exert excellent blistering resistance. The solvent-free adhesive composition of the present invention is characterized by containing: at least one polymerization component selected from the group consisting of polymerizable vinyl monomers, polymerizable vinyl prepolymers, multifunctional (meth) acrylate monomers and multifunctional (meth) acrylate oligomers; and an organoalkoxysilane having a linear structure and alkoxysilyl groups at both ends thereof, wherein at least a part of the polymerization component contains an active hydrogen group.

Description

Solvent-free adhesive composition, adhesive sheet, and display

Technical Field

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.

Background

In recent years, various mobile electronic devices such as smartphones and tablet terminals include displays using a display module having a liquid crystal element, a light emitting diode (LED element), an organic electroluminescence (organic EL) element, and the like, and the displays are often touch panels.

In the display device as described above, a protective panel is generally provided on the front surface side of the display body module. Here, a gap is provided between the protective panel and the display body module to prevent the deformed protective panel from colliding with the display body module when the protective panel is deformed by an external force.

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

On the other hand, with the reduction in thickness and weight of electronic devices, it has been studied to change the protective panel from a conventional glass plate to a plastic plate such as an acrylic plate or a polycarbonate plate. Here, in the case of a method of filling the gap between the protective panel and the display module with an adhesive layer, when the protective panel is changed to a plastic plate, a new problem occurs in that air leaks from the plastic plate under high-temperature and high-humidity conditions, and foaming such as bubbling, floating, and peeling occurs. Therefore, an adhesive agent or the like filling up the gap between the display module and the protective panel is often required to have blister resistance.

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

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-544931

Patent document 2: japanese patent laid-open publication No. 2014-133812

Disclosure of Invention

Technical problem to be solved by the invention

Here, in the adhesive composition containing an epoxy silane coupling agent as disclosed in patent document 1, it is important to efficiently perform a ring-opening reaction of an epoxy group in order to effectively exhibit a coupling action. Thus, in general, the adhesive composition contains a monomer or polymer having an acidic group. However, an adhesive used for a touch panel is required to be free from acid so as not to deteriorate a transparent conductive film to be an adherend. Therefore, the adhesive composition disclosed in patent document 1 cannot sufficiently obtain the effect of the epoxy coupling agent without acid. As a result, the effect of improving the adhesion force of the obtained adhesive to an adherend becomes insufficient. Therefore, it is difficult to obtain an acid-free adhesive that can exhibit sufficient blister resistance from the adhesive composition disclosed in patent document 1.

In patent document 2, a specific example of the (meth) acryloyloxy group-containing silane coupling agent includes a compound having a (meth) acryloyloxy group at one end and an alkoxysilyl group at the other end (paragraph 0038 of patent document 2). The adhesive composition disclosed in patent document 2 contains a (meth) acrylate polymer and a (meth) acrylate monomer in addition to the coupling agent. When the adhesive composition is cured, it is presumed that the (meth) acryloyloxy group of the coupling agent also participates in the radical polymerization reaction between the polymer and the monomer, and as a result, the coupling agent is mixed in a state of being uniformly dispersed in the adhesive. Therefore, it is inferred that in the adhesive composition disclosed in patent document 2, the silane coupling agent is present in the vicinity of the surface of the adhesive layer, and the effect of improving the adhesion force cannot be obtained. As a result, the adhesive obtained from the adhesive composition disclosed in patent document 2 cannot exhibit sufficient blister resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a solvent-free adhesive composition, an adhesive sheet, and a display body, which can exhibit excellent blister resistance.

Means for solving the problems

In order to achieve the above object, the present invention provides a solvent-free adhesive composition comprising: at least one polymerization component selected from the group consisting of polymerizable vinyl monomers, polymerizable vinyl prepolymers, multifunctional (meth) acrylate monomers and multifunctional (meth) acrylate oligomers; and an organoalkoxysilane having a linear structure and alkoxysilyl groups at both ends thereof, wherein at least a part of the polymerization component contains an active hydrogen group (invention 1).

It is presumed that the solvent-free adhesive composition of the invention (invention 1) causes a hydrolytic condensation reaction between the polymerization component and the organoalkoxysilane in addition to a radical polymerization reaction between the polymerization components during curing. It is also presumed that the hydrolytic condensation reaction occurs mainly in the vicinity of the surface of the adhesive agent layer, and the proportion of the organoalkoxysilane present in the vicinity of the surface of the adhesive agent layer increases. Thus, the adhesive layer obtained from the adhesive composition has excellent cohesive force and excellent adhesion to an adherend. As a result, the adhesive can exhibit excellent blister resistance.

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

In the above-described 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 component (invention 3).

In the above-mentioned inventions (inventions 1 to 3), it is preferable that the solvent-free adhesive composition further contains a photopolymerization initiator (invention 4).

In the above-described inventions (inventions 1 to 4), the content of the organoalkoxysilane in the solvent-free adhesive composition is preferably 0.01 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the polymerization component (invention 5).

Secondly, the present invention provides an adhesive obtained by curing the solvent-free adhesive composition (invention 1 to 5) (invention 6).

In the above invention (invention 6), the adhesive preferably has a gel fraction of 50% or more and 100% or less (invention 7).

The third aspect of the present invention provides an adhesive sheet having an adhesive layer (invention 8) formed from the adhesive (inventions 6 and 7).

In the above invention (invention 8), it is preferable that the adhesive sheet comprises two release sheets, and the adhesive layer is sandwiched between the release sheets so as to be in contact with release surfaces of the two release sheets (invention 9).

A third aspect of the present invention provides a display device, including: a display body constituting member having a step at least on the surface of the side to be bonded; another display body constituting member; and an adhesive layer which bonds the one display component and the other display component to each other, wherein the adhesive layer is the adhesive layer of the pressure-sensitive adhesive sheet (inventions 8 and 9).

Effects of the invention

The solvent-free adhesive composition, the adhesive sheet and the display of the present invention can exhibit excellent blister resistance.

Drawings

FIG. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.

Fig. 2 is a sectional view of a laminate according to an embodiment of the present invention.

Description of the reference numerals

1: an adhesive sheet; 11: an adhesive layer; 12a, 12 b: a release sheet; 2: a display body; 21: a first display body constituting member; 22: a second display body constituting member; 3: printing layer

Detailed Description

Hereinafter, embodiments of the present invention will be described.

[ solvent-free adhesive composition ]

The solvent-free adhesive composition of the present embodiment (hereinafter, sometimes referred to as "solvent-free adhesive composition P") contains: at least one polymerization component selected from the group consisting of polymerizable vinyl monomers, polymerizable vinyl prepolymers, multifunctional (meth) acrylate monomers and multifunctional (meth) acrylate oligomers; and an organoalkoxysilane having a linear structure and having alkoxysilyl groups at both ends thereof. Here, at least a part of the polymerization components contains an active hydrogen group. In the present specification, the term (meth) acrylate refers to both acrylate and methacrylate. Other similar terms are also the same.

It is estimated that the solvent-free adhesive composition P of the present embodiment causes radical polymerization of the polymerization components during curing and hydrolysis condensation of the active hydrogen groups of the polymerization components and the alkoxysilyl groups of the organoalkoxysilane. Since the hydrolytic condensation reaction proceeds more slowly than the radical polymerization reaction, it is presumed that the hydrolytic condensation reaction occurs after the radical polymerization reaction proceeds to some extent. Therefore, it is presumed that the proportion of the organoalkoxysilane present in the vicinity of the surface of the adhesive agent layer is increased. Further, the hydrolytic condensation reaction occurs in the alkoxysilyl groups present at both ends of the organoalkoxysilane, and thus a structure is formed in which the organoalkoxysilane is crosslinked between the polymerization components. It is inferred that this structure is effective in increasing the cohesive force in reinforcing the adhesive in a manner different from the structure formed by radical polymerization of the polymerization components with each other, and therefore the resulting adhesive has a very high cohesive force. The above results show that the adhesive layer obtained from the solvent-free adhesive composition P of the present embodiment has excellent cohesive strength and excellent adhesion to an adherend.

As can be seen from the above, the adhesive obtained using the solventless adhesive composition P of the present embodiment can exhibit excellent blister resistance. For example, even when a display obtained using the solvent-free adhesive composition P of the present embodiment is left under high-temperature and high-humidity conditions (for example, 85 ℃ and 85% RH) and outgassing occurs from a display component formed of a plastic plate or the like, foaming such as bubbling, floating, and peeling can be suppressed at the interface between the adhesive layer and the display component.

The above reaction or structure formed when curing the solventless adhesive composition P of the present embodiment is inferred, and other reactions or structures may occur. For example, it is not necessary that the alkoxysilyl groups at both ends of the organoalkoxysilane are bonded to the active hydrogen group, and the alkoxysilyl group at one end may remain unreacted. Further, in addition to the organoalkoxysilane repeating structure formed by hydrolysis condensation reaction of the organoalkoxysilanes, the alkoxysilyl group at both or one end may be bonded to the active hydrogen group of the polymer component. Further, the organoalkoxysilane may be present not only in the vicinity of the surface of the adhesive agent layer but also inside.

(1) Polymeric component

The solvent-free adhesive composition P of the present embodiment contains at least one polymerization component selected from the group consisting of a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, a polyfunctional (meth) acrylate monomer, and a polyfunctional (meth) acrylate oligomer.

In the solvent-free adhesive composition P of 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 hydroxyl group and a carboxyl group, and is particularly preferably a hydroxyl group from the viewpoints that the difference in the rates of the radical polymerization reaction and the hydrolytic condensation reaction as described above is clear, and the organoalkoxysilane is easily present in the vicinity of the surface of the adhesive agent layer. In general, when a touch panel or the like is placed in a high-temperature and high-humidity environment, moisture enters into the adhesive layer, and when the touch panel or the like returns to normal temperature, the adhesive layer may whiten and a problem of "wet heat whitening" in which transparency is lowered may occur. Here, the active hydrogen group is contained in the polymerization component, so that the group is present in the obtained adhesive. Since this group has good compatibility with moisture entering the adhesive, whitening of the adhesive layer can be suppressed as a result, and the adhesive becomes an adhesive having excellent resistance to wet heat whitening.

Of the 4 types, the polymerizable component preferably contains at least a polymerizable vinyl monomer and a polyfunctional (meth) acrylate oligomer. When the polymerization component contains these compounds, the cohesive force of the obtained adhesive is improved, and an 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 polymerizable vinyl monomers can be suitably used. The polymerizable vinyl monomer in the present embodiment is a polymerizable vinyl monomer having one vinyl-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, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylates having no functional group other than a vinyl group-containing group in the molecule, such as lauryl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, lauryl (meth) acrylate, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and polyoxyalkylene-modified (meth) acrylate. Among them, 2-ethylhexyl acrylate or isobornyl acrylate is preferably used.

The polymerizable vinyl monomer may have a functional group other than the vinyl group in the molecule. Examples of the functional group include the above-mentioned active hydrogen group, that is, a hydroxyl group, a carboxyl group, a thiol group, and a primary amino group or a secondary amino group. Specific examples of the polymerizable vinyl monomer having such a functional group include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; hydroxyl group-containing acrylamides such as N-methylolacrylamide and N-methylolmethacrylamide; and ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, 2-hydroxyethyl acrylate is preferably used.

Examples of the 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 monomers such as styrene and alpha-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; amide monomers such as acrylamide, methacrylamide, N-methylmethacrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, and N-vinylpyrrolidone; and tertiary amino group-containing monomers such as N, N-diethylaminoethyl (meth) acrylate and N- (meth) acryloylmorpholine.

(1-2) polymerizable vinyl prepolymer

The polymerizable vinyl prepolymer is not particularly limited, and conventionally known polymerizable vinyl prepolymers can be suitably used, but a polymerizable vinyl prepolymer obtained by polymerizing the polymerizable vinyl monomer is preferably used. In the present specification, the prepolymer refers to a compound obtained by polymerizing a monomer, and refers to a compound capable of forming a polymer by further polymerization.

When the polymerizable vinyl monomer is polymerized to obtain a polymerizable vinyl prepolymer, one of the monomers may be polymerized alone or a plurality of the monomers may be copolymerized.

The polymerizable vinyl prepolymer may be obtained by radical Polymerization or living Polymerization, and may particularly be a polymer having a terminal of Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT).

The weight average molecular weight of the polymerizable vinyl prepolymer is preferably 6,000 or more, particularly preferably 7,500 or more, and more preferably 10,000 or more. The weight average molecular weight is preferably 1,500,000 or less, particularly preferably 1,000,000 or less, and more preferably 100,000 or less. When the weight average molecular weight is within the above range, the viscosity of the solventless adhesive composition P can be easily brought 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 polyfunctional (meth) acrylate monomers can be suitably used.

In particular, as the polyfunctional (meth) acrylate monomer, a monomer having two or more (meth) acryloyl groups in one molecule can be preferably used. 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, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and mixtures thereof, Propylene oxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloyloxyethyl) isocyanurate, bis (acryloyloxyethyl) hydroxyethyl isocyanurate, isocyanuric acid ethylene oxide-modified diacrylate, isocyanuric acid ethylene oxide-modified triacrylate, -caprolactone-modified tris (acryloyloxyethyl) isocyanurate, diglycerin tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, and the like.

(1-4) polyfunctional (meth) acrylate oligomer

The polyfunctional (meth) acrylate oligomer is not particularly limited, and conventionally known polyfunctional (meth) acrylate oligomers can be suitably used, but polyfunctional (meth) acrylate oligomers having two or more (meth) acryloyl groups in one molecule are preferably used. Examples of such oligomers include oligomers such as urethane acrylates, polyester acrylates, epoxy acrylates, polyether acrylates, polybutadiene acrylates, and silicone acrylates.

The urethane acrylate oligomer can be obtained, for example, by esterifying a urethane oligomer obtained by the reaction of a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, hydrogenated isoprene having a hydroxyl terminal, hydrogenated butadiene having a hydroxyl terminal, or the like with (meth) acrylic acid or a (meth) acrylic acid derivative, and a polyisocyanate.

Examples of the polyalkylene polyol used for producing the urethane acrylate oligomer include polypropylene glycol, polyethylene glycol, polybutylene glycol, and polyhexamethylene glycol, and polypropylene glycol is preferably used. When the number of functional groups of the obtained urethane acrylate oligomer is three or more, glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose, and the like may be appropriately combined.

Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, and diphenyl diisocyanate; and alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate, among which aliphatic diisocyanates are preferably used, and hexamethylene diisocyanate is particularly preferably used. The polyisocyanate is not limited to a bifunctional polyisocyanate, and a trifunctional or higher polyisocyanate may be used.

Examples of the (meth) acrylic acid derivative include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, ethyl 2-isocyanatoacrylate, ethyl 2-isocyanatomethacrylate, and 1, 1-bis (acryloyloxymethyl) ethyl isocyanate, with ethyl 2-isocyanatoacrylate being particularly preferably used.

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

The polyester acrylate oligomer can be obtained, for example, as follows: esterifying hydroxyl groups of a polyester oligomer having hydroxyl groups at both ends, which is obtained by condensation of a polyvalent carboxylic acid and a polyvalent alcohol, with (meth) acrylic acid; or the hydroxyl group at the end of an oligomer obtained by adding an alkylene oxide to a polycarboxylic acid is esterified with (meth) acrylic acid.

The epoxy acrylate oligomer can be obtained, for example, by esterification of (meth) acrylic acid by reacting with epoxy rings of a bisphenol epoxy resin or a novolac epoxy resin having a relatively low molecular weight. In addition, carboxyl-modified epoxy acrylate oligomers obtained by partially modifying epoxy acrylate oligomers with dicarboxylic acid anhydrides may also be used.

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

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

(1-5) addition ratio

When both of the polymerizable vinyl monomer and the polyfunctional (meth) acrylate oligomer are used as the polymerization component, the ratio of the mass of the polymerizable vinyl monomer divided by the mass of the polyfunctional (meth) acrylate oligomer is preferably 0.18 or more, particularly preferably 1 or more, and more preferably 1.5 or more. The ratio is preferably 999 or less, particularly preferably 19 or less, and further preferably 9 or less.

(2) Organoalkoxysilanes

The solvent-free adhesive composition P of the present embodiment contains an organoalkoxysilane having a linear structure and alkoxysilyl groups at both ends thereof. Here, "linear" of the "linear structure" substantially means "linear". That is, the linear structure may have a branch or may contain a cyclic structure as long as the effect of crosslinking the polymerization components by the organoalkoxysilane is exhibited well. The term "having alkoxysilyl groups at both ends" means that the linear structure has alkoxysilyl groups at both ends.

The organoalkoxysilane preferably has a plurality of alkoxysilyl groups at least one terminal end. That is, the organoalkoxysilane preferably has two alkoxysilyl groups or three alkoxysilyl groups at least one terminal end, and particularly preferably has three alkoxysilyl groups. When the organoalkoxysilane contains a plurality of alkoxysilyl groups at least one terminal, the bonding with the active hydrogen group of the polymerization component is facilitated, and as a result, the cohesive force of the obtained adhesive is increased.

Examples of the alkoxysilyl group include a methoxysilyl group, an ethoxysilyl group, a n-propoxysilyl group, an isopropoxysilyl group, a n-butoxysilyl group, a sec-butoxysilyl group, an isobutoxysilyl group, and a tert-butoxysilyl group. Among them, a methoxysilyl group is preferable from the viewpoint of obtaining excellent blister resistance.

The organoalkoxysilane preferably has no group reactive with the polymerization component other than the alkoxysilyl group. Examples of the group capable of performing this reaction other than the alkoxysilyl group include a (meth) acryloyloxy group, a vinyloxy group, an allyloxy group and the like. By not having such a group, the organoalkoxysilane described above can be inhibited from being uniformly absorbed into the polymerization components. Thus, the ratio of the organoalkoxysilane present in the vicinity of the surface of the obtained adhesive layer becomes higher, and the adhesion of the adhesive layer to an adherend is further improved. Further, by the absence of a group other than the alkoxysilyl group, the reaction of the alkoxysilyl group with the active hydrogen group in the polymerization component proceeds unhindered. In this way, a structure in which the organoalkoxysilane crosslinks the polymerization components is favorably formed in the obtained adhesive layer, and the cohesive force on the surface of the adhesive layer is further improved. As a result, the obtained adhesive layer was excellent in blistering resistance.

Examples of the organoalkoxysilane contained in the solventless adhesive composition P of the present embodiment include bis (alkoxysilyl) alkane; aromatic compounds such as 1, 4-bis (alkoxysilyl) benzene and 1, 4-bis (alkoxysilylalkyl) benzene; alkylene oxide compounds such as 1, 2-bis (alkoxysilyl) ethylene oxide and 1, 3-bis (alkoxysilyl) propylene oxide; alicyclic compounds such as 1, 3-bis (alkoxysilyl) cyclobutane, 1, 3-bis (alkoxysilylalkyl) cyclobutane, 1, 4-bis (alkoxysilyl) cyclohexane, and 1, 4-bis (alkoxysilylalkyl) cyclohexane. Among these, bis (alkoxysilyl) alkanes are particularly preferable from the viewpoint of small molecular volume and easy bond formation with active hydrogen groups of the adhesive.

The number of carbon atoms of the alkane of the bis (alkoxysilyl) alkane is 1 or more, particularly preferably 3 or more, and more preferably 5 or more. The number of carbon atoms of the alkane is preferably 20 or less, particularly preferably 10 or less, and further preferably 7 or less.

Preferable examples of the bis (alkoxysilyl) alkane include 1, 6-bis (trimethoxysilyl) hexane, 1, 7-bis (trimethoxysilyl) heptane, 1, 8-bis (trimethoxysilyl) octane, and the like. Among them, 1, 6-bis (trimethoxysilyl) hexane and 1, 8-bis (trimethoxysilyl) octane are preferably used from the viewpoint of obtaining excellent blister resistance.

The content of the organoalkoxysilane in the solventless adhesive composition P is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, based on 100 parts by mass of the polymerization component. 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 within the above range, the above effects of the organoalkoxysilane can be sufficiently obtained.

(3) Polymerization initiator

The solventless adhesive composition P of the present embodiment preferably further contains a polymerization initiator. The solvent-free adhesive composition P can be effectively cured by containing a polymerization initiator.

The polymerization initiator is not particularly limited, and conventionally known polymerization initiators can be used, but is preferably selected according to the curing method of the solventless adhesive composition P. That is, when the solvent-free adhesive composition P is cured by irradiation with ultraviolet rays as active energy rays, a photopolymerization initiator is preferably used as the polymerization initiator. In addition, when the solvent-free type adhesive composition P is cured by heating, a thermal polymerization initiator is preferably used. The photopolymerization initiator and the thermal polymerization initiator may be used together.

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-dimethoxy-2-phenylacetophenone, 2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinyl-1-propanone, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, p-phenylene-isopropyl ether, and the like, 4, 4' -diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, benzyldimethylketal, acetophenone dimethylketal, p-dimethylaminobenzoate, oligo [ 2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl ] acetone ], 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 lauroyl peroxide; azo compounds such as azobisisobutyronitrile and the like. 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 0.1 part by mass or more, particularly preferably 0.3 part by mass or more, and further preferably 0.5 part by mass or more, relative to 100 parts by mass of the polymerization component. The content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, based on 100 parts by mass of the polymerization component. By setting the content to 0.1 part by mass or more, the solvent-free adhesive composition P can be effectively cured. On the other hand, when the content is 10 parts by mass or less, the polymerization initiator which remains unreacted during curing can be eliminated or reduced, and the resulting adhesive can be easily set to desired physical properties.

(4) Various additives

The solvent-free adhesive composition P may contain various additives, such as a silane coupling agent, an ultraviolet absorber, an antistatic agent, an adhesion promoter, an antioxidant, a light stabilizer, a softening agent, a filler, and a refractive index adjuster, as required. The polymerization solvent described later is not included in the additives constituting the solvent-free adhesive composition P.

Here, when the solvent-free adhesive composition P contains a silane coupling agent, the adhesion between the obtained adhesive and the glass member or the plastic plate is improved. This makes the resultant adhesive more excellent in blister resistance.

The silane coupling agent is an organosilicon compound having at least one alkoxysilyl group in the molecule, other than the organoalkoxysilane, and is preferably a silane coupling agent having good compatibility with the polymerization component and the organoalkoxysilane and light transmittance.

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

When the solvent-free adhesive composition P contains a silane coupling agent, the content thereof is preferably 0.01 parts by mass or more, particularly preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, based on 100 parts by mass of the polymerization component. The content is preferably 1 part by mass or less, particularly preferably 0.5 part by mass or less, and further preferably 0.3 part by mass or less, per 100 parts by mass of the polymerization component.

(5) Production of solvent-free adhesive composition

The solventless adhesive composition P can be produced by mixing the polymerization component and the organoalkoxysilane, and adding an additive as needed.

The solvent-free adhesive composition P of the present embodiment is a solvent-free type, and therefore has an appropriate viscosity mainly due to the polymerization component. Therefore, the solvent-free adhesive composition P of the present embodiment can be used as a coating solution without adding a diluent or the like.

[ adhesive agent ]

The adhesive of the present embodiment is obtained by curing the solvent-free adhesive composition P. The solvent-free adhesive composition P may be cured by irradiation with active energy rays or by heat treatment depending on the material contained in the composition P. As such, "curing" in the present specification includes both curing based on irradiation of an active energy ray and curing based on heat treatment, unless specifically mentioned.

The solvent-free adhesive composition P is preferably cured by irradiation with active energy rays. This makes it possible to prevent thermal deterioration, thermal shrinkage, and the like of the resin film or the like to be coated with the solvent-free adhesive composition P without applying heat during curing. Further, since heating is not performed, it is possible to suppress the volatile components in the solvent-free adhesive composition P from being lost by heating.

The active energy ray is an active energy ray having an energy quantum in an electromagnetic wave or a charged particle beam, and specifically, an ultraviolet ray, an electron beam, or the like can be mentioned. Among the active energy rays, ultraviolet rays which are easy to handle are particularly preferable.

The irradiation of ultraviolet rays can be performed by a high-pressure mercury lamp, fusion H lamp (fusion H lamp), xenon lamp, or the like, and the illuminance is preferably 50mW/cm with respect to the irradiation amount of ultraviolet rays²Above 1000mW/cm²The following. The light amount is preferably 50mJ/cm²Above, more preferably 80mJ/cm²Above, 200mJ/cm is particularly preferable²The above. Further, the light amount is preferably 10000mJ/cm²More preferably 5000mJ/cm or less²Hereinafter, the concentration is particularly preferably 2000mJ/cm²The following. On the other hand, the electron beam irradiation can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably 10krad or more and 1000krad or less.

The heating temperature of the heat treatment is preferably 50 ℃ or higher, and particularly preferably 70 ℃ or higher. The heating temperature is preferably 150 ℃ or lower, and particularly preferably 120 ℃ or lower. The heating time of the heat treatment is preferably 10 seconds or more, and particularly preferably 50 seconds or more. The heating time is preferably 10 minutes or less, and particularly preferably 90 seconds or less. The drying treatment after the solvent-free adhesive composition P is applied can also be used as the heating treatment.

In addition, when the adhesive of the present embodiment is produced, the heating treatment may be performed and then the irradiation with the active energy ray may be performed, or both the treatments may be performed simultaneously. Further, it is preferable that the curing period is set at room temperature (for example, 23 ℃ C., 50% RH) for about 1 to 2 weeks after the heat treatment or after the irradiation with the active energy ray.

The gel fraction of the adhesive of the present embodiment is preferably 50% or more, particularly preferably 55% or more, and more preferably 60% or more. The gel fraction is preferably 100% or less, particularly preferably 80% or less, and more preferably 70% or less. When the gel fraction of the adhesive is within the above range, the cohesive force of the adhesive increases and the blister resistance becomes more excellent. Here, the method of measuring the gel fraction of the adhesive is shown in the test examples described later.

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

[ adhesive sheet ]

The adhesive sheet of the present embodiment has an adhesive layer for bonding one display constituent member and another display constituent member, and the adhesive layer is formed of the adhesive.

Fig. 1 shows a specific structure of an example of the pressure-sensitive adhesive sheet of the present embodiment. As shown in fig. 1, an adhesive sheet 1 according to an embodiment is configured as follows: two

release sheets

12a, 12 b; and an adhesive layer 11 sandwiched between the two

release sheets

12a, 12b so as to be in contact with the release surfaces of the two

release sheets

12a, 12 b. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes both a surface subjected to a release treatment and a surface showing releasability even if the release treatment is not performed.

(1) Adhesive layer

The adhesive layer 11 is composed of the above adhesive, that is, an adhesive obtained by curing the solvent-free adhesive composition P.

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

When the thickness of the adhesive layer 11 is 10 μm or more, a desired adhesive force can be easily exhibited. Further, the adhesive layer 11 has good workability when the thickness is 1000 μm or less.

(2) Release sheet

The

release sheets

12a and 12b protect the adhesive layer 11 before the adhesive sheet 1 is used, and are released when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of 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 a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene- (meth) acrylic acid copolymer film, an ethylene- (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, and a fluororesin film. In addition, these crosslinked films may also be used. Further, a laminated film of these may be used.

The release surfaces (particularly, the surfaces in contact with the adhesive agent layer 11) of the

release sheets

12a and 12b 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. Of the

release sheets

12a and 12b, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is preferably 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 sheet 1 of the present embodiment has an adhesive force to soda-lime glass of preferably 5N/25mm or more, particularly preferably 10N/25mm or more, and more preferably 15N/25mm or more. The adhesive force is preferably 50N/25mm or less, particularly preferably 40N/25mm or less, and more preferably 35N/25mm or less. When the adhesive force of the adhesive sheet 1 is 5N/25mm or more, the blister resistance becomes more excellent. Further, when the adhesive force of the adhesive sheet 1 is 50N/25mm or less, good reworkability can be obtained, and if mis-bonding occurs, expensive display member components can be reused. Here, the adhesion in the present specification means substantially an adhesion obtained by a method according to JIS Z0237: the specific method of measuring the adhesive force measured by the 180-degree peel method of 2009 is shown in the test examples described later.

(3-2) haze value

The haze value of the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is preferably 5% or less, particularly preferably 1% or less, and more preferably 0.5% or less. When the haze value of the adhesive layer 11 is 5% or less, the transparency is high, and the adhesive layer is suitably used for optical applications (for displays). The haze value in the present specification is defined as follows according to JIS K7136: 2000 measured values.

(3-3) Total light transmittance

The total light transmittance of the adhesive layer 11 of the adhesive sheet 1 of the present embodiment is preferably 90% or more, particularly preferably 95% or more, and more preferably 98% or more. When the total light transmittance is 98% or more, the transparency is very high, and the optical film is suitable for optical use. The total light transmittance in the present specification is defined as follows according to JIS K7361-1: 1997 measured values.

(4) Production of adhesive sheet

As one example of production of the adhesive sheet 1, the solvent-free adhesive composition P is applied to the release surface of one release sheet 12a (or 12b) to form a coating layer, and the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer, followed by irradiation with an active energy ray and/or heat treatment of the coating layer to form the adhesive layer 11.

As another production example of the adhesive sheet 1, the solvent-free adhesive composition P is applied to the release surface of one release sheet 12a (or 12b), and the solvent-free adhesive composition P is cured by irradiation with active energy rays and/or heat treatment to form the adhesive layer 11, and then the release surface of the other release sheet 12b (or 12a) is laminated on the adhesive layer 11.

Examples of the method for applying the coating liquid of the solvent-free adhesive composition P include a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method.

In the adhesive sheet 1 of the present embodiment produced as described above, the adhesive layer 11 is formed of an adhesive obtained by curing the solvent-free adhesive composition P described above, and therefore has a very high cohesive force as described above. It is also presumed that when a coating film of the solventless adhesive composition P is formed, organoalkoxysilane having polarity is often present in the vicinity of the surface of the coating film, and the condensation reaction proceeds more in the vicinity of the surface. As a result, it is estimated that the adhesive sheet 1 of the present embodiment has a higher cohesive force as it approaches the surface of the adhesive agent layer 11. Thus, the pressure-sensitive adhesive sheet 1 of the present embodiment can exhibit excellent blister resistance.

[ display body ]

As shown in fig. 2, the display 2 of the present embodiment has the following structure: a first display body constituting member 21 (a first display body constituting member) having a step at least on the surface on the bonded side; a second display body constituting member 22 (another display body constituting member); and an adhesive layer 11 interposed therebetween and bonding the first display element component 21 and the second display element component 22 to each other. In the display 2 of the present embodiment, the first display component 21 has a step on the surface on the adhesive layer 11 side, specifically, a step formed by the printed layer 3.

The adhesive layer 11 in the above display 2 is the adhesive layer 11 of the above adhesive sheet 1.

Examples of the display 2 include a Liquid Crystal Display (LCD) display, a Light Emitting Diode (LED) display, an organic electroluminescence (organic EL) display, and an electronic paper, and may be a touch panel. The display 2 may be a member that constitutes a part of them.

The first display element constituting member 21 is preferably a glass plate, a plastic plate, or the like, and is preferably a protective panel made of a laminate or the like including these. In this case, the printed layer 3 is generally formed in a frame shape on the adhesive layer 11 side in the first display component member 21.

The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium/strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass, and the like. The thickness of the glass plate is not particularly limited, but is usually 0.1mm or more, preferably 0.2mm or more. The thickness is usually 5mm or less, preferably 2mm 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 sheet is not particularly limited, but is usually 0.2mm or more, preferably 0.4mm or more. The thickness is usually 5mm or less, preferably 3mm or less.

Further, 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 surface or both surfaces of the glass plate or the plastic plate, and an optical member may be laminated. In addition, the transparent conductive film and the metal layer may be patterned.

The second display body constituting member 22 is preferably an optical member to be attached to the first display body constituting member 21, a display body module (for example, a Liquid Crystal (LCD) module, a Light Emitting Diode (LED) module, an organic electroluminescence (organic EL) module, or the like), an optical member which is a part of the display body module, or a laminated body including the display body module.

Examples of the optical member include a shatter prevention film, a polarizing plate (polarizing film), a polarizing plate, a retardation plate (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflective film, and a transparent conductive film. The chipping prevention film may be a hard coat film formed by forming a hard coat layer on one surface of a base film.

The material constituting the printed layer 3 is not particularly limited, and a known material for printing can be used. The thickness of the printed layer 3, i.e., the height of the step is preferably 3 μm or more, particularly preferably 5 μm or more, more preferably 7 μm or more, and most preferably 10 μm or more. The height is preferably 50 μm or less, and particularly preferably 35 μm or less.

In the production of the display 2, one release sheet 12a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the surface of the first display component member 21 on the side where the printed layer 3 is present, as an example. Then, the other release sheet 12b is peeled 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 component 22 are bonded. As another example, the order of attaching the first display body constituting member 21 and the second display body constituting member 22 may be replaced.

In the above display 2, it is presumed that the adhesive layer 11 is formed of an adhesive obtained by curing the solvent-free adhesive composition P, and therefore has a very high cohesive force as described above, and in particular, the cohesive force is higher as it is closer to the surface of the adhesive layer 11. Therefore, even when the display 2 is left under high-temperature and high-humidity conditions and the first display component member 21 or the second display component member 22 generates the exhaust gas, the generation of bubbles such as bubbles, floating, and peeling can be suppressed.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within 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 12 b. In addition, the first display body constituting member 21 may have a step other than the printed layer 3. Further, not only the first display element constituting member 21 but also the second display element constituting member 22 may have a step on the adhesive agent layer 11 side.

Examples

The present invention will be described in more detail 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 oligomers

100 parts by mass of polypropylene glycol having a weight average molecular weight of 3000 (a value converted into a solid content; the same applies hereinafter), 4 parts by mass of hexamethylene diisocyanate, and 0.02 part by mass of dioctyltin dilaurate were mixed and stirred at 80 ℃ for 6 hours, whereby a reaction product was obtained. With respect to the obtained reaction product, IR spectrum measurement by infrared spectroscopy confirmed that the isocyanate group was almost disappeared.

Then, 1 part by mass of 2-isocyanatoethyl acrylate was mixed with respect to the total amount of the obtained reactants, and stirred at 80 ℃ for 3 hours to obtain a urethane acrylate oligomer. The obtained urethane acrylate oligomer was measured for IR spectrum by infrared spectroscopy, and it was confirmed that the isocyanate group was almost disappeared. The molecular weight of the obtained urethane acrylate oligomer was measured by the method described later, and the weight average molecular weight (Mw) was 25,000.

2. Preparation of liquid mixtures

A liquid mixture was obtained by mixing 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, 10 parts by mass of 2-hydroxyethyl acrylate as a polymerizable vinyl monomer, and 30 parts by mass of the urethane acrylate oligomer prepared as described above as a polyfunctional (meth) acrylate oligomer, and stirring them at 25785.

Here, the weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement Condition >

GPC measurement apparatus: HLC-8020 manufactured by TOSOH CORPORATION

GPC column (passage in the following order): TOSOH CORPORATION, Inc

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ production example 2 ]

A liquid mixture was obtained by mixing 40 parts by mass of 2-ethylhexyl acrylate as a polymerizable vinyl monomer, 20 parts by mass of acryloylmorpholine as a polymerizable vinyl monomer, 10 parts by mass of 2-hydroxyethyl acrylate as a polymerizable vinyl monomer, and 30 parts by mass of the urethane acrylate oligomer prepared in production example 1, and stirring them at room temperature of 25785.

[ example 1]

1. Preparation of solvent-free adhesive composition

A solvent-free adhesive composition was obtained by mixing 100 parts by mass (in terms of solid content; the same applies hereinafter) of the liquid mixture prepared in production example 1, 0.3 part by mass of 1, 6-bis (trimethoxysilyl) hexane as an organoalkoxysilane, and 0.5 part by mass of 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerization initiator.

2. Production of adhesive sheet

The solvent-free adhesive composition obtained in step 1 was coated on the release-treated surface of a heavy release type release sheet (product name "SP-PET 752150" manufactured by linec Corporation) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent, using a knife coater.

Next, the coating layer on the heavy release type release sheet obtained in the above was bonded to a light release type release sheet (product name "SP-PET 382120" manufactured by linec Corporation) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent, in such a manner that the release-treated surface of the light release type release sheet was in contact with the coating layer.

Then, the coating layer was irradiated with ultraviolet rays under the following conditions via the heavy release sheet, thereby producing an adhesive sheet having a structure of a heavy release sheet/an adhesive layer (thickness: 100 μm)/a light release sheet.

[ conditions for ultraviolet irradiation ]

Light source: high pressure mercury lamp

Light amount: 1000mJ/cm²

Illuminance: 100mW/cm²

[ examples 2 to 4, comparative examples 1 to 6 ]

Adhesive sheets were produced in the same manner as in example 1, except that the type of the liquid mixture and the type and amount of the organoalkoxysilane were changed as shown in table 1. In comparative example 3, tris (trimethoxysilylpropyl) isocyanurate used as the organoalkoxysilane has a so-called isocyanurate ring as a main skeleton, and three trimethoxysilylpropyl groups are bonded to the main skeleton at equal intervals. Therefore, the organoalkoxysilane cannot be said to be the above-mentioned organoalkoxysilane having a linear structure, and does not correspond to the organoalkoxysilane of the present embodiment.

[ test example 1] (measurement of gel fraction)

The adhesive sheets obtained in examples and comparative examples were cut into 80mm × 80mm sizes, the adhesive layers were wrapped in a polyester net (mesh size 200), the masses thereof were weighed by a precision balance, and the masses of the nets alone were subtracted to calculate the masses of the adhesives alone. The mass at this time was set to M1.

Subsequently, the adhesive coated in the polyester net 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 ℃ for 3 hours. After drying, the sheet was left to stand in an environment at a temperature of 23 ℃ and a relative humidity of 50% for 3 hours, and then the mass of the sheet was weighed by a precision balance, and the mass of the web alone was subtracted to calculate the mass of the adhesive alone. The mass at this time was set to M2. The gel fraction (%) is represented by (M2/M1). times.100. The results are shown in table 1.

[ test example 2 ] (evaluation of optical Properties)

The light-release type release Sheet was peeled from the adhesive sheets obtained in examples and comparative examples, and the exposed adhesive layer was attached to soda-lime Glass (manufactured by Nippon Sheet Glass Company, ltd.) having a thickness of 1.1mm, and then the heavy-release type release Sheet was peeled off, thereby obtaining a sample for evaluation.

The measurement light of a haze meter (NIPPON DENSHOKU INDUSTRIES co., ltd., product name "NDH-2000") was incident on the adhesive layer side of the evaluation sample, and the total light transmittance (%) and the haze value (%) were measured. The measurement was performed 3 times, and the average value thereof was calculated. The results are shown in table 1.

[ test example 3 ] (measurement of adhesive force)

The light release type release sheet was peeled from the adhesive sheets obtained in examples and comparative examples, and the exposed adhesive layer was bonded to an easy adhesive layer of a polyethylene terephthalate (PET) film (TOYOBO co., ltd., product name "PET a 4300" with a thickness of 100 μm) having an easy adhesive layer, thereby obtaining a release sheet/adhesive layer/PET film laminate. The obtained laminate was cut into a width of 25mm and a length of 150mm, and used as a sample.

A heavy release Sheet was peeled from the sample at 23 ℃ and 50% RH, and the exposed adhesive layer was adhered to soda-lime Glass (manufactured by Nippon Sheet Glass Company, ltd.), followed by pressure bonding by reciprocating a 2kg roller once. Then, after leaving at 23 ℃ and 50% RH for 24 hours, the adhesion (N/25mm) was measured under conditions of a peel speed of 300mm/min and a peel angle of 180 degrees using a tensile tester (ORIENTEC CO., LTD., manufactured by Tensilon). Conditions other than those described herein were as follows according to JIS Z0237: 2009 to perform the measurement. The results are shown in table 1.

[ test example 4 ] (evaluation of blister resistance)

The light-peeling-type release sheets obtained in examples and comparative examples were peeled off, and the exposed adhesive layer was attached to the surface provided with a transparent conductive film of tin-doped indium oxide (ITO) cut to 60mm × 60mm of a polyethylene terephthalate film (product name "ITO film", thickness: 125 μm, manufactured by OIKE & co., ltd.) provided with a transparent conductive film on one surface thereof. Then, the heavy-release type release sheet was peeled from the adhesive sheet, and the exposed adhesive layer was attached to the polycarbonate-side surface of a resin plate (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "MR-58", thickness: 785 μm) in which polymethyl methacrylate (PMMA) and Polycarbonate (PC) were laminated, thereby obtaining a test piece.

The test piece thus obtained was autoclaved at 50 ℃ and 0.5MPa for 30 minutes and then left to stand at normal pressure, 23 ℃ and 50% RH for 24 hours. Next, the resultant was stored at 85 ℃ and 85% RH for 72 hours under high-temperature and high-humidity conditions. Then, the peeling of the adhesive layer at the interface with the adherend was visually confirmed, and the blister resistance was evaluated by the following criteria. The results are shown in table 1.

O: no bubble or lift-off peeling could be observed.

And (delta): a small amount of small bubbles was observed, but no floating separation was observed.

X: large bubbles or floating separation were observed.

[ test example 5 ] (evaluation of resistance to Wet-Heat whitening)

The adhesive layer of the adhesive sheet obtained in example or comparative example was sandwiched between two polyethylene terephthalate films (manufactured by OIKE & co., ltd., product name "ITO film", thickness: 125 μm) each having a transparent conductive film formed of tin-doped indium oxide (ITO) provided on one surface thereof, to obtain a laminate. At this time, the surface of the film provided with the transparent conductive film was attached to an adhesive layer. The laminate thus obtained was autoclaved at 50 ℃ and 0.5MPa for 30 minutes and then left to stand at 23 ℃ and 50% RH for 24 hours under normal pressure. Then, using a haze meter (NIPPON DENSHOKU industies co., ltd., product name "NDH 2000"), the haze was measured in accordance with JIS K7136: haze value (%) was measured at 2000.

Subsequently, the laminate was stored under wet heat conditions of 85 ℃ and 85% RH for 120 hours (durability test). Then, the temperature and humidity were returned to 23 ℃ and 50% RH at normal temperature and normal humidity, and the haze value (%) of the laminate was measured again. The haze value is measured within 30 minutes after the laminate is returned to normal temperature and humidity.

The wet-heat whitening resistance was evaluated from the haze value (%) before the durability test to the increase value of the haze value (%) after the durability test according to the following criteria. The results are shown in table 1.

Very good: the haze value (%) after the durability test is 0.90% or less.

O: the haze value (%) after the durability test increased by more than 0.90% and 1.50% or less.

X: the haze value (%) after the durability test increased by more than 1.50%.

[ test example 6 ] (evaluation of tracking due to level difference)

Ultraviolet curable ink (Teiku Printing Inks Mfg. Co., Ltd., product name "POS-911 ink") was screen-printed on the surface of a glass plate (NSG Precision Co., Ltd., product name "Corning glass Eagle XG", 90mm in length X50 mm in width X0.5 mm in thickness) in a frame shape (outer shape: 90mm in length X50 mm in width, 5mm in width) so that the coating thickness became 30 μm. Then, ultraviolet rays (80W/cm) were irradiated²Two metal halide lamps with a height of 15cm and a speed of 10-15 mPer minute), the printed ultraviolet curable ink was cured to produce a glass plate having a step difference formed by printing.

The light release type release sheets were peeled from the adhesive sheets obtained in examples and comparative examples, and the exposed adhesive layer was bonded to an easy adhesive layer of a polyethylene terephthalate film (TOYOBO Co., Ltd., product name "PET A4300" thickness: 100 μm) having an easy adhesive layer. Subsequently, the heavy-release type release sheet is peeled off to expose the adhesive layer. The exposed surface of the adhesive layer and the surface having a step difference of the glass plate having a step difference were bonded to each other by using a laminator (product name "LPD 3214" manufactured by fujiapla inc.) so that the adhesive layer covered the entire frame-shaped printing surface, and the resultant was used as a sample for evaluation.

The obtained evaluation sample was autoclaved at 50 ℃ and 0.5MPa for 30 minutes and then left to stand at normal pressure, 23 ℃ and 50% RH for 24 hours. Next, the adhesive layer was stored under high temperature and high humidity conditions of 85 ℃ and 85% RH for 72 hours (durability test), and then the adhesive layer (particularly, the vicinity of the step difference generated by the printed layer) was visually confirmed, and the step difference following property was evaluated by the following criteria. The results are shown in table 1.

Very good: the vicinity of the level difference is not peeled off, and the adhesive follows the step without a gap.

O: slight lift-off was observed near the level difference.

X: large bubbles are mixed in the vicinity of the level difference.

[ Table 1]

As is clear from Table 1, the pressure-sensitive adhesive sheets obtained in the examples were excellent in blister resistance, and also excellent in resistance to wet-heat whitening and step-difference following properties.

Industrial applicability

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

Claims

1. A solvent-free adhesive composition characterized by comprising:

a polymeric component comprising a polymerizable vinyl monomer and a urethane acrylic oligomer; and

an organoalkoxysilane having a bis (alkoxysilyl group),

at least a part of the polymerization components contains active hydrogen groups,

the content of the organoalkoxysilane is 0.01 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the polymerization component.

2. The solventless adhesive composition of claim 1 wherein the active hydrogen groups are hydroxyl groups.

3. The solventless adhesive composition according to claim 1 further comprising a photopolymerization initiator.

4. An adhesive obtained by curing the solvent-free adhesive composition according to claim 1.

5. The adhesive according to claim 4, wherein the gel fraction of the adhesive is 50% or more and 100% or less.

6. An adhesive sheet having an adhesive layer formed from the adhesive described in claim 4.

7. The adhesive sheet according to claim 6,

the adhesive sheet is provided with two sheets of release sheets,

the adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the release sheets.

8. A display body, comprising:

a display body constituting member having a step at least on the surface of the side to be bonded;

another display body constituting member; and

an adhesive layer which bonds the one display component and the other display component to each other,

the display body is characterized in that,

the adhesive layer is the adhesive layer of the adhesive sheet according to claim 6.