JP2018044164A - Photocurable adhesive sheet, adhesive sheet and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocurable adhesive sheet which can fill every corner by following step portions of a stuck surface, does not lower adhesive reliability even when irradiated with light for a long period of time, and can easily perform a sticking operation.SOLUTION: A photocurable adhesive sheet is an adhesive sheet before photocuring which is formed of a resin composition containing a (meth)acrylic copolymer (A), a crosslinking agent (B) and a photopolymerization initiator (C), has photocurability, has the following (1) and (2) characteristics and has the following (3) characteristics after photocuring. (1) The adhesive sheet can keep the shape at 0-40°C and exhibits self-adhesiveness; (2) the adhesive sheet exhibits viscosity at 70-100°C of 100-3,000 Pa s; and (3) the adhesive sheet has viscosity at 70-100°C of 3,000-50,000 Pa s.SELECTED DRAWING: None

Description

  The present invention relates to a photocurable pressure-sensitive adhesive sheet before photocuring and a pressure-sensitive adhesive sheet obtained by photocuring the same. Specifically, an image display device such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, a pen tablet, and the like, and a photocurable pressure-sensitive adhesive sheet that can be suitably used as a constituent member thereof, The present invention relates to a pressure-sensitive adhesive sheet obtained by photocuring this.

  In recent years, in order to improve the visibility of an image display device, an image display panel such as a liquid crystal display (LCD), a plasma display (PDP) or an electroluminescence display (ELD), and a protection disposed on the front side (viewing side) thereof. A space between the panel and the touch panel member is filled with an adhesive sheet, a liquid adhesive, or the like to suppress reflection of incident light or outgoing light from a display image at the air layer interface.

  As a method of filling the gap between the constituent members for an image display device with an adhesive, a method of filling the gap with a liquid adhesive resin composition containing an ultraviolet curable resin and then curing it by irradiating with ultraviolet rays. Is known (Patent Document 1).

  In addition, a method of filling a gap between constituent members for an image display device using an adhesive sheet is also known. For example, Patent Document 2 discloses an image of a pressure-sensitive adhesive sheet that has been primarily cross-linked with ultraviolet rays as a method for producing a laminate for constituting an image display device having a structure in which image display device constituent members are laminated on at least one side of the pressure-sensitive adhesive sheet. A method is disclosed in which, after bonding to a display device constituent member, the pressure-sensitive adhesive sheet is irradiated with ultraviolet rays through the image display device constituent member and subjected to secondary curing.

  Patent Document 3 discloses a sheet using a hot melt type adhesive composition having a loss tangent at 25 ° C. of less than 1 based on urethane (meth) acrylate having a weight average molecular weight of 20,000 to 100,000. Is disclosed.

  Further, Patent Document 4 discloses a touch panel comprising a (meth) acrylic polymer obtained by copolymerizing a monomer containing a (meth) acrylic monomer having a crosslinkable functional group and a specific macromer, and a crosslinking agent. A pressure-sensitive adhesive layer suitable for pasting is disclosed.

International Publication No. 2010/027041 International Publication No. 2012/032995 International Publication No. 2010/038366 JP 2013-18227 A JP 2012-184423 A

  In the field of image display devices centering on mobile phones and mobile terminals, in addition to thinning and high precision, design diversification has progressed, and new problems have arisen accordingly. For example, a black concealment portion is generally printed in a frame shape on the peripheral edge portion of the surface protection panel. Therefore, the pressure-sensitive adhesive sheet for bonding the constituent members having such a printing unit is required to have a printing level followability that can be filled to every corner following the printing level difference.

  In addition, image display devices such as touch panels have come to be used in a wide range, and accordingly, pressure-sensitive adhesive sheets used for image display device configuration laminates are exposed to light such as illumination and sunlight for a long time. However, there is a demand for adhesion reliability that does not degrade the performance.

  Therefore, the present invention can fill up every corner following the stepped portion of the bonding surface in the state before photocuring, and in the state after photocuring, the adhesive reliability does not decrease even if light is irradiated for a long time. It is a photocurable pressure-sensitive adhesive sheet, and a new photocurable pressure-sensitive adhesive sheet that can be easily bonded is provided.

The present invention is a pressure-sensitive adhesive sheet before photocuring, which is formed from a resin composition containing a (meth) acrylic copolymer (A), a crosslinking agent (B), and a photopolymerization initiator (C). And the photocurable adhesive sheet characterized by having the following characteristics (1) and (2) is proposed.
(1) In a room temperature state of 0 to 40 ° C., the sheet shape can be maintained and self-adhesion is exhibited.
(2) When heated to 70 to 100 ° C., the viscosity becomes 100 to 3000 Pa · s and exhibits fluidity.

  The photocurable pressure-sensitive adhesive sheet proposed by the present invention can maintain the sheet shape in a room temperature state, that is, a normal state, and can exhibit self-adhesiveness. It is possible to perform the bonding operation efficiently, such as easy positioning. Further, when heated to 70 to 100 ° C., the viscosity becomes 100 to 3000 Pa · s and exhibits hot melt properties, and therefore, for example, the pressure-sensitive adhesive can be filled by following an uneven portion such as a printing step. Furthermore, it exhibits a high cohesive force after photocuring, exhibits excellent foaming resistance even after long-time light irradiation, for example, and does not deteriorate the adhesion reliability even when light-irradiated for a long time. Therefore, the photocurable pressure-sensitive adhesive sheet proposed by the present invention is suitably used as a constituent member of an image display device such as a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, a touch panel, and a pen tablet. can do.

  Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment.

<This adhesive sheet>
A photocurable pressure-sensitive adhesive sheet (referred to as “this pressure-sensitive adhesive sheet”) according to an embodiment of the present invention includes a (meth) acrylic copolymer (A), a crosslinking agent (B), a photopolymerization initiator ( C), a pressure-sensitive adhesive sheet before photocuring formed from a resin composition (referred to as “the present pressure-sensitive adhesive composition”), and having the following characteristics (1) and (2): It is a photocurable pressure-sensitive adhesive sheet.
(1) In a room temperature state of 0 to 40 ° C., the sheet shape can be maintained and self-adhesion is exhibited.
(2) When heated to 70 to 100 ° C., the viscosity becomes 100 to 3000 Pa · s and exhibits fluidity.
Here, the "pressure-sensitive adhesive sheet before photocuring" is sufficient if it is a pressure-sensitive adhesive sheet, and does not mean only a pressure-sensitive adhesive sheet that has not undergone any photocuring process. That is, for example, any pressure-sensitive adhesive sheet that has undergone a photo-curing process, that can be further photo-cured, and that exhibits the effects of the present invention is included in the present invention.

  Since this pressure-sensitive adhesive sheet has the above-mentioned properties (1) and (2) before being photocured, it can maintain a sheet shape in a room temperature state of 0 to 40 ° C., in other words, in a normal state. Self-adhesive, that is, the property of exhibiting adhesive strength as it is. Furthermore, it exhibits a hot melt property that melts or flows when heated, exhibits an excellent cohesive force after photocuring, and can exhibit foam resistance after, for example, light irradiation for a long time.

<Characteristics at room temperature>
This pressure-sensitive adhesive sheet has the characteristics that (1) in the state before photocuring, the sheet shape can be maintained at room temperature of 0 to 40 ° C. and exhibits self-adhesion.
Thus, if it can hold | maintain a sheet form in a room temperature state, ie, a normal state, it will be easy to handle and it is especially excellent in productivity of a bonding member. Furthermore, in a normal state, if self-adhesiveness is shown, for example, it is easy to perform positioning when sticking, and the bonding work is very convenient.
In order to obtain such characteristics, for example, the present pressure-sensitive adhesive sheet may be produced from the pressure-sensitive adhesive composition (I) or (II) described later. However, the present invention is not limited to this.

(180 ° peeling force at 23 ° C and 40% RH)
The pressure-sensitive adhesive sheet can have the following feature (6). That is, (6) 180 ° to the glass when the pressure-sensitive adhesive sheet is peeled off from the soda lime glass at 23 ° C. and 40% RH at a peeling angle of 180 ° and a peeling speed of 60 mm / min. The peeling force can be 3 N / cm or more. A 180 ° peeling force at 23 ° C. of 3 N / cm or more is preferable because it has appropriate adhesion to an adherend at room temperature and is excellent in bonding workability.
From this point of view, the 180 ° peel strength of the pressure-sensitive adhesive sheet at 23 ° C. and 40% RH is preferably 3 N / cm or more, more preferably 20 N / cm or less, particularly 4 N / cm or more, or 15 N / cm or less. Is particularly preferred.
In order to adjust the 180 ° peel strength at 23 ° C. and 40% RH in the present adhesive sheet, for example, the present adhesive sheet is produced from the adhesive composition (I) or (II) described later, and further, a crosslinking agent or light What is necessary is just to adjust the kind and composition ratio of a polymerization initiator, or to adjust the heating / pressurization conditions at the time of bonding, and the light irradiation conditions after bonding. However, it is not limited to such a method.

<Characteristics when heated at 70 to 100 ° C.>
The pressure-sensitive adhesive sheet (2) has a characteristic that when heated to 70 to 100 ° C. before photocuring, the viscosity becomes 100 to 3000 Pa · s and exhibits fluidity.
If this pressure-sensitive adhesive sheet has such hot melt properties, it can be filled with the pressure-sensitive adhesive by following heating and softening or fluidizing to follow uneven portions such as printing steps. It can be filled without occurring.
In order to obtain such characteristics, for example, the present pressure-sensitive adhesive sheet may be produced from the pressure-sensitive adhesive composition (I) or (II) described later. However, the present invention is not limited to this.

  When the pressure-sensitive adhesive sheet is heated to 70 to 100 ° C., the viscosity becomes 100 to 3000 Pa · s, preferably 150 Pa · s or more or 2700 Pa · s or less, more preferably 200 Pa · s or more or 2500 Pa · s or less.

(180 ° peeling force at 80 ° C and 10% RH)
This pressure-sensitive adhesive sheet can have the following feature (7). That is, (7) The pressure mode is agglomerated when the pressure-sensitive adhesive sheet is peeled off from the soda lime glass at 80 ° C. and 10% RH at a peeling angle of 180 ° and a peeling speed of 60 mm / min. It is destruction, and the 180 ° peeling force for glass can be set to 1 N / cm or less.
A 180 ° peeling force at 80 ° C. of 1 N / cm or less is preferable because high wettability to the adherend can be obtained.
From this point of view, the 180 ° peel strength of this pressure-sensitive adhesive sheet at 80 ° C. and 10% RH is preferably 1 N / cm or less, particularly 0.8 N / cm or less, and more preferably 0.5 N / cm or less. Is particularly preferred.
In order to adjust the 180 ° peeling force at 80 ° C. and 10% RH in this pressure-sensitive adhesive sheet, for example, the pressure-sensitive adhesive sheet is produced from the pressure-sensitive adhesive composition (I) or (II) described later, and further a crosslinking agent or light. What is necessary is just to adjust the kind and composition ratio of a polymerization initiator, or to adjust the heating / pressurization conditions at the time of bonding, and the light irradiation conditions after bonding. However, it is not limited to such a method.

<Characteristic after photocuring>
This pressure-sensitive adhesive sheet can be photocured, and (3) after photocuring, the viscosity at 70 to 100 ° C. is 3000 to 50000 Pa · s.

  The pressure-sensitive adhesive sheet preferably has a viscosity at 70 to 100 ° C. of 3000 to 50000 Pa · s after photocuring from the viewpoint of obtaining a high cohesive force, among which 3500 Pa · s or more or 48000 Pa · s or less, of which 4000 Pa · s. More preferably, it is s or more or 45000 Pa · s or less.

(180 ° peel strength at 23 ° C and 40% RH after photocuring)
This pressure-sensitive adhesive sheet can have the following feature (4) after photocuring. That is, (4) a pressure-sensitive adhesive sheet that has been pressure-bonded to soda-lime glass and cured by light irradiation at 23 ° C. and 40% RH at a peeling angle of 180 ° and a peeling speed of 60 mm / min. The 180 ° peeling force to the glass when the adhesive sheet is peeled off from the glass can be 3 N / cm or more.
If the 180 ° peeling force at 23 ° C. after photocuring is 3 N / cm or more, it is preferable because adherends can be firmly bonded to each other.
From such a viewpoint, the 180 ° peeling force at 23 ° C. after photocuring of the pressure-sensitive adhesive sheet is preferably 3 N / cm or more, particularly 4 N / cm or more, and more preferably 5 N / cm or more, or 30 N / cm or less. Is particularly preferred.

(180 ° peel strength at 80 ° C and 10% RH after photocuring)
This pressure-sensitive adhesive sheet can have the following feature (5) after photocuring. That is, (5) a pressure-sensitive adhesive sheet that has been pressure-bonded to soda-lime glass and cured by irradiation with light at 80 ° C. and 10% RH at a peeling angle of 180 ° and a peeling speed of 60 mm / min. When the adhesive sheet is peeled off from the glass, the 180 ° peeling force with respect to the glass can be 3 N / cm or more.
If the 180 ° peel strength at 80 ° C. after photocuring is 3 N / cm or more, it is preferable because the foam resistance in a high temperature environment is excellent.
From this point of view, the 180 ° peeling force at 80 ° C. after photocuring of the pressure-sensitive adhesive sheet is preferably 3 N / cm or more, particularly 4 N / cm or more, and more preferably 5 N / cm or more or 20 N / cm or less. Is particularly preferred.

  In this pressure-sensitive adhesive sheet, in order to adjust the 180 ° peel strength at 23 ° C. or 80 ° C. after photocuring, for example, the pressure-sensitive adhesive composition (I) or (II) to be described later is produced and further crosslinked. What is necessary is just to adjust the kind and composition ratio of an agent and a photoinitiator, and to adjust the heating and pressurization conditions at the time of bonding, and the light irradiation conditions after bonding. However, it is not limited to such a method.

<Outgas generation amount>
This photo-cured adhesive sheet has an outgas generation amount of 40000 ppm or more in terms of hexadecane after light irradiation for 24 hours with a xenon arc lamp type light resistance tester defined in JIS K7350-2 (ISO 4892-2). preferable.
If the outgas generation amount is 40000 ppm or more in terms of hexadecane, the tackiness of the pressure-sensitive adhesive sheet and the wettability to the adherend are improved, which is preferable.
Therefore, from this point of view, the amount of outgas generated in the pressure-sensitive adhesive sheet is preferably 40000 ppm or more in terms of hexadecane, more preferably 45000 ppm or more, and particularly preferably 50000 ppm or more.
In addition, what is necessary is just to manufacture this adhesive sheet from adhesive composition (I) or (II) mentioned later, for example in order to make the said outgas generation amount into the said range in this adhesive sheet. However, the present invention is not limited to this.

<Foam resistance>
It is preferable that this pressure-sensitive adhesive sheet after photocuring exhibits foam resistance such that the diameter of the bubbles is 5 mm or less in the following foam resistance test.
Foam resistance test: A laminate was prepared by sandwiching an adhesive sheet between two glass plates having a diagonal length of 5 inches or more and a thickness of 1 mm or less, in accordance with JIS K7350-2 (ISO 4822-2). When the light is irradiated for 24 hours with a xenon arc lamp light resistance tester, the diameter of bubbles generated in the pressure-sensitive adhesive sheet is measured.

Since this adhesive sheet has the characteristic that the viscosity in 70-100 degreeC will be 3000-50000Pa * s after photocuring, it can show such foaming resistance after photocuring. Therefore, since it exhibits the property that reliability does not decrease even if light is irradiated for a long time, for example, it can be used for various image display devices, and adhesion reliability that does not decrease performance even if exposed to light such as illumination or sunlight for a long time. Can be obtained.
In order to obtain such characteristics, for example, the present pressure-sensitive adhesive sheet may be produced from the pressure-sensitive adhesive composition (I) or (II) described later. However, the present invention is not limited to this.

<This pressure-sensitive adhesive composition>
As a suitable example of this pressure-sensitive adhesive composition used for the production of this pressure-sensitive adhesive sheet, an acrylic copolymer (A1) comprising a graft copolymer having a macromonomer as a branch component, a crosslinking agent (B1), light Mention may be made of a pressure-sensitive adhesive composition (I) containing a polymerization initiator (C1).
Moreover, as another example of this adhesive composition, the monomer a1 whose glass transition temperature (Tg) is less than 0 degreeC, the monomer a2 whose glass transition temperature (Tg) is 0 degreeC or more and less than 80 degreeC, and a glass transition temperature ( The monomer a3 having a Tg) of 80 ° C. or higher is copolymerized at a molar ratio of a1: a2: a3 = 10-40: 90-35: 0-25, and the weight average molecular weight is 50,000- An adhesive composition (II) containing a (meth) acrylic copolymer (A2) that is 400,000, a crosslinking agent (B2), and a photopolymerization initiator (C2) can be mentioned.
However, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive sheet is not limited to the pressure-sensitive adhesive composition (I) or (II).
For the number average molecular weight and the weight average molecular weight, gel permeation chromatography (GPC) is used, and converted values using polystyrene as a standard substance are adopted.

  If this pressure-sensitive adhesive sheet is prepared from the pressure-sensitive adhesive composition (I) or (II) prepared by a known method, it can exhibit self-adhesion while maintaining the sheet shape at room temperature, and can be heated in an uncrosslinked state. Then, it has a hot melt property that melts or flows, and can be photocured, and exhibits excellent cohesive force after photocuring.

<Adhesive composition (I)>
As an adhesive composition (I), an acrylic copolymer (A1) comprising a graft copolymer having a macromonomer as a branch component, a crosslinking agent (B1), and a photopolymerization initiator (C1) are contained. And an adhesive composition.

(Acrylic copolymer (A1))
The acrylic copolymer (A1) as the base polymer may be a graft copolymer provided with a macromonomer as a branch component.

(Stem component)
The trunk component of the acrylic copolymer (A1) is preferably composed of a copolymer component containing a repeating unit derived from a (meth) acrylic acid ester.

The glass transition temperature of the copolymer constituting the trunk component of the acrylic copolymer (A1) is preferably −70 to 0 ° C.
In this case, the glass transition temperature of the copolymer component constituting the trunk component refers to the glass transition temperature of the polymer obtained by copolymerizing only the monomer component constituting the trunk component of the acrylic copolymer (A1). . Specifically, it means a value calculated by the Fox formula from the glass transition temperature and the composition ratio of the polymer obtained from the homopolymer of each component of the copolymer.
In addition, the calculation formula of Fox is a calculation value calculated | required by the following formula | equation, Polymer handbook [Polymer HandBook, J.M. Brandrup, Interscience, 1989].
1 / (273 + Tg) = Σ (Wi / (273 + Tgi))
[Wherein Wi represents the weight fraction of monomer i, and Tgi represents Tg (° C.) of the homopolymer of monomer i. ]

The glass transition temperature of the copolymer component constituting the trunk component of the acrylic copolymer (A1) is the flexibility of the pressure-sensitive adhesive composition (I) at room temperature and the pressure-sensitive adhesive composition to the adherend. Since the wettability of (I), that is, adhesiveness is affected, in order for the pressure-sensitive adhesive composition (I) to obtain appropriate adhesiveness (tackiness) at room temperature, the glass transition temperature is from −80 ° C. to It is preferably 0 ° C., more preferably −75 ° C. or higher or −5 ° C. or lower, and particularly preferably −70 ° C. or higher or −10 ° C. or lower.
However, even if the glass transition temperature of the copolymer component is the same temperature, the viscoelasticity can be adjusted by adjusting the molecular weight. For example, it can be made more flexible by reducing the molecular weight of the copolymer component.

Examples of the (meth) acrylic acid ester monomer contained in the main component of the acrylic copolymer (A1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meta Acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl ( (Meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO-modified (meth) acrylate, dicyclopenta Nyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, benzyl (meth) acrylate, etc. . These include hydroxyl-containing (meth) acrylates such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and glycerol (meth) acrylate having a hydrophilic group or an organic functional group, ) Acrylic acid, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (meth) acryloyloxypropylhexahydrophthalic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxypropylphthalate Acid, 2- (meth) acryloyloxyethylmaleic acid, 2- (meth) acryloyloxypropylmaleic acid, 2- (meth) acryloyloxyethylsuccinic acid, 2- (meth) acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid Carboxyl group-containing monomers such as maleic acid, itaconic acid, monomethyl maleate and monomethyl itaconic acid, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride, glycidyl (meth) acrylate, glycidyl α-ethyl acrylate , Epoxy group-containing monomers such as (meth) acrylic acid 3,4-epoxybutyl, amino group-containing (meth) acrylic acid ester monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate, (meth) Acrylamide, Nt-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, diacetone acrylamide, maleic acid amide, maleimide, etc. Monomers containing amide groups, vinylpyrrolidone, vinylpyridine, heterocyclic basic monomers such as vinyl carbazole, etc. can also be used.
In addition, styrene, t-butylstyrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, alkyl vinyl ether, hydroxyalkyl vinyl ether, alkyl, which can be copolymerized with the above acrylic monomers and methacrylic monomers. Various vinyl monomers such as vinyl monomers can also be used as appropriate.

Moreover, it is preferable that the trunk component of the acrylic copolymer (A1) contains a hydrophobic (meth) acrylate monomer and a hydrophilic (meth) acrylate monomer as constituent units.
If the trunk component of the acrylic copolymer (A1) is composed only of a hydrophobic monomer, a tendency to wet-heat whitening is recognized. Therefore, it is preferable to introduce a hydrophilic monomer into the trunk component to prevent wet-heat whitening. .
Specifically, as the main component of the acrylic copolymer (A1), a hydrophobic (meth) acrylate monomer, a hydrophilic (meth) acrylate monomer, and a polymerizable functional group at the terminal of the macromonomer are included. The copolymer component formed by random copolymerization can be mentioned.

Here, as said hydrophobic (meth) acrylate monomer, the alkyl ester which does not have a polar group (however, except methyl acrylate) is preferable, for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) Acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth Acrylate), isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, isobornyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and methyl methacrylate.
Examples of the hydrophobic vinyl monomer include vinyl acetate, styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, and alkyl vinyl monomers.

  As the hydrophilic (meth) acrylate monomer, methyl acrylate or an ester having a polar group is preferable. For example, methyl acrylate, (meth) acrylic acid, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, Hydroxyl-containing (meth) acrylates such as hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and glycerol (meth) acrylate, (meth) acrylic acid, 2- (meth) acryloyloxyethylhexahydrophthalic acid, 2- (Meth) acryloyloxypropylhexahydrophthalic acid, 2- (meth) acryloyloxyethylphthalic acid, 2- (meth) acryloyloxypropylphthalic acid, 2- (meth) acryloyloxyethylmaleic acid, 2 (Meth) acryloyloxypropyl maleic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate Carboxyl group-containing monomers such as maleic anhydride, acid anhydride group-containing monomers such as itaconic anhydride, glycidyl (meth) acrylate, glycidyl α-ethyl acrylate, 3,4-epoxybutyl (meth) acrylate, etc. Mention may be made of epoxy group-containing monomers, alkoxypolyalkylene glycol (meth) acrylates such as methoxypolyethylene glycol (meth) acrylate, N, N-dimethylacrylamide, hydroxyethylacrylamide and the like.

(Branch component: macromonomer)
The acrylic copolymer (A1) preferably contains a macromonomer-derived repeating unit by introducing a macromonomer as a branch component of the graft copolymer.
The macromonomer is a polymer monomer having a terminal polymerizable functional group and a high molecular weight skeleton component.

The glass transition temperature (Tg) of the macromonomer is preferably higher than the glass transition temperature of the copolymer component constituting the acrylic copolymer (A1).
Specifically, since the glass transition temperature (Tg) of the macromonomer affects the heating and melting temperature (hot melt temperature) of the pressure-sensitive adhesive composition (I), the glass transition temperature (Tg) of the macromonomer is 30 ° C. to It is preferably 120 ° C., more preferably 40 ° C. or more and 110 ° C. or less, and particularly preferably 50 ° C. or more or 100 ° C. or less.
With such a glass transition temperature (Tg), by adjusting the molecular weight, it is possible to maintain excellent processability and storage stability, and to adjust so as to hot-melt near 80 ° C.
The glass transition temperature of a macromonomer refers to the glass transition temperature of the macromonomer itself, and can be measured with a differential scanning calorimeter (DSC) (heating rate: 5 ° C./min, inflection of baseline shift) Tg is measured from the point).

Further, at room temperature, the branch components are attracted to each other and can maintain a state where they are physically cross-linked as a pressure-sensitive adhesive composition, and the physical cross-linking is released by heating to an appropriate temperature. In order to obtain fluidity, it is also preferable to adjust the molecular weight and content of the macromonomer.
From such a viewpoint, the macromonomer is preferably contained in the acrylic copolymer (A1) in a proportion of 5% by mass to 30% by mass, particularly 6% by mass or more and 25% by mass or less, and more preferably 8% by mass. It is preferable that the amount is 20% by mass or more.
The number average molecular weight of the macromonomer is preferably 500 or more and less than 8000, more preferably 800 or more and less than 7500, and particularly preferably 1000 or more and less than 7000.
As the macromonomer, a generally produced one (for example, a macromonomer manufactured by Toa Gosei Co., Ltd.) can be appropriately used.

The high molecular weight skeleton component of the macromonomer is preferably composed of an acrylic polymer or a vinyl polymer.
Examples of the high molecular weight skeleton component of the macromonomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) Acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (medium Acrylate), decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) ) Acrylate, isobornyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO modified (meth) acrylate, dicyclopentanyl (meth) acrylate, di Cyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, (meth) acrylic acid, group (Meth) acrylate monomers such as sidyl (meth) acrylate, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (meth) acrylonitrile, alkoxyalkyl (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylate, , Styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, alkyl vinyl monomer, vinyl acetate, alkyl vinyl ether, hydroxyalkyl vinyl ether, and other various vinyl monomers. These may be used alone or in combination of two or more. Can be used.

  Examples of the terminal polymerizable functional group of the macromonomer include a methacryloyl group, an acryloyl group, and a vinyl group.

(Crosslinking agent (B1))
As the crosslinking agent (B1), for example, a crosslinking agent having two or more crosslinking groups such as an epoxy group, an isocyanate group, an oxetane group, a silanol group, and a (meth) acryloyl group can be appropriately selected. Above all, in terms of reactivity and the strength of the cured product to be obtained, polyfunctional (meth) acrylates having 2 or more (meth) acryloyl groups, especially 3 or more, (meth) acrylates having epoxy groups or isocyanate groups, etc. Is preferred.

  After the image display device constituent members are bonded and integrated, the cross-linking agent (B1) is cross-linked in the adhesive material, so that the sheet exhibits high cohesive force in a high temperature environment instead of losing hot melt properties. Excellent foaming reliability can be obtained.

  Examples of such (meth) acrylate include 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin glycidyl ether di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, bisphenol A polyethoxydi (meth) acrylate, bisphenol A polyalkoxydi (meth) acrylate Bisphenol F polyalkoxy di (meth) acrylate, polyalkylene glycol di (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, ε-caprolactone modified tris ( -Hydroxyethyl) isocyanurate tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propoxylated pentaerythritol tri (meth) acrylate, ethoxylated pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, propoxylated Pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) acrylate, tris (acryloxyethyl) isocyanurate, pentaerythritol tetra (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) a Relate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol penta (meth) acrylate, hydroxypentylglycol dipentaglycol di (meth) acrylate, dicarboxyl of ε-caprolactone adduct of hydroxybivalic acid neopenglycol ) In addition to UV-curable polyfunctional monomers such as acrylate, trimethylolpropane tri (meth) acrylate, alkoxylated trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, polyester (meth) acrylate, Polyfunctional acrylic oligomers such as epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, isocyanate (meth) acrylate, 1,1- (bis (meth) acryloyloxymethyl) ethyl isocyanate, 2- (2- (meth) acryloyloxyethyloxy) ethyl isocyanate, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate glycidyl ether, hydroxypropyl ( A meth) acrylate glycidyl ether, a hydroxybutyl (meth) acrylate glycidyl ether, etc. can be mentioned.

Among the examples mentioned above, a polyfunctional monomer or oligomer containing a polar functional group such as a hydroxyl group is preferable from the viewpoint of improving the adhesion to the adherend and the effect of suppressing the heat and whitening.
Among these, it is preferable to use a polyfunctional (meth) acrylic acid ester having a hydroxyl group or a carboxyl group.
Therefore, from the viewpoint of preventing wet heat whitening, it is preferable to contain a hydrophobic acrylate monomer and a hydrophilic acrylate monomer as a backbone component of the acrylic copolymer (A1), that is, the graft copolymer. Furthermore, it is preferable to use a polyfunctional (meth) acrylic acid ester having a hydroxyl group as the crosslinking agent (B).

The content of the crosslinking agent (B1) is not particularly limited. As a standard, 0.5 to 20 parts by mass, especially 1 part or more or 15 parts by mass or less, and 2 parts or more or 10 parts by mass or less, relative to 100 parts by mass of the acrylic copolymer (A1). Is preferred.
By containing a crosslinking agent (B1) in the said range, the shape stability of this pressure-sensitive adhesive sheet in an uncrosslinked state and the foaming reliability in the pressure-sensitive adhesive material after crosslinking can be made compatible. However, this range may be exceeded in balance with other elements.

(Photopolymerization initiator (C1))
The photopolymerization initiator (C1) serves as a reaction initiation assistant in the crosslinking reaction of the aforementioned crosslinking agent (B1).
As the photopolymerization initiator, those currently known can be used as appropriate. Among these, a photopolymerization initiator that is sensitive to ultraviolet rays having a wavelength of 380 nm or less is preferable from the viewpoint of easy control of the crosslinking reaction.
On the other hand, a photopolymerization initiator that is sensitive to light having a wavelength longer than 380 nm is preferable in that the sensitive light can easily reach the deep part of the pressure-sensitive adhesive sheet.

  Photopolymerization initiators are roughly classified into two types depending on the radical generation mechanism, a cleavage type photopolymerization initiator that can cleave and decompose a single bond of the photopolymerization initiator itself, and a photoexcited initiator. And a hydrogen donor in the system form an exciplex and can be roughly classified into a hydrogen abstraction type photopolymerization initiator that can transfer hydrogen of the hydrogen donor.

Among these, the cleavage type photopolymerization initiator is decomposed when a radical is generated by light irradiation to be another compound, and once excited, it does not function as a reaction initiator. For this reason, it does not remain as an active species in the pressure-sensitive adhesive after the crosslinking reaction is completed, and it is not likely to cause unexpected light degradation or the like in the pressure-sensitive adhesive, which is preferable.
On the other hand, a hydrogen abstraction type photopolymerization initiator does not generate a decomposition product such as a cleavage type photopolymerization initiator during radical generation reaction by irradiation of active energy rays such as ultraviolet rays, so that it is difficult to become a volatile component after completion of the reaction. This is useful in that damage to the body can be reduced.

  Examples of the cleavage type photoinitiator include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1- ON, 1- (4- (2-hydroxyethoxy) phenyl) -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- [4- {4- (2-hydroxy-2 -Methyl-propionyl) benzyl} phenyl] -2-methyl-propan-1-one, oligo (2-hydroxy-2-methyl-1- (4- (1-methylvinyl) phenyl) propanone), phenylglyoxylic Methyl acid, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1- ON, 2- (dimethylamino) -2-[(4 -Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl Examples thereof include phosphine oxide and derivatives thereof.

Examples of the hydrogen abstraction type photoinitiator include benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3′-dimethyl-4-methoxybenzophenone, 4- (meth). Acryloyloxybenzophenone, methyl 2-benzoylbenzoate, methyl benzoylformate, bis (2-phenyl-2-oxoacetic acid) oxybisethylene, 4- (1,3-acryloyl-1,4,7,10,13- Pentaoxotridecyl) benzophenone, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone and their derivatives And so on.
However, the photopolymerization initiator is not limited to the substances listed above. Any one of the above-mentioned cleavage type photopolymerization initiator and hydrogen abstraction type photopolymerization initiator may be used, or two or more kinds may be used in combination.

The content of the photopolymerization initiator (C1) is not particularly limited. As a guideline, 0.1 to 10 parts by weight, especially 0.5 parts by weight or more and 5 parts by weight or less, and 1 part by weight or more or 3 parts by weight or less based on 100 parts by weight of the acrylic copolymer (A1). It is preferable to contain in the ratio.
By setting the content of the photopolymerization initiator (C1) in the above range, an appropriate reaction sensitivity with respect to the active energy ray can be obtained.

(Other ingredients)
The pressure-sensitive adhesive composition (I) may contain known components blended in a normal pressure-sensitive adhesive composition as components other than those described above. For example, if necessary, tackifier resin, antioxidant, light stabilizer, metal deactivator, anti-aging agent, hygroscopic agent, polymerization inhibitor, ultraviolet absorber, rust inhibitor, silane coupling agent Various additives such as inorganic particles can be appropriately contained.
Moreover, you may contain reaction catalyst (A tertiary amine type compound, a quaternary ammonium type compound, a lauric acid tin compound, etc.) suitably as needed.

<Adhesive composition (II)>
As the pressure-sensitive adhesive composition (II), a monomer a1 having a glass transition temperature (Tg) of less than 0 ° C., a monomer a2 having a glass transition temperature (Tg) of from 0 ° C. to less than 80 ° C., and a glass transition temperature (Tg) of 80 (Meth) acrylic acid ester copolymer having a weight average molecular weight of 50,000 to 400,000, which is copolymerized at a molar ratio of a1: a2: a3 = 10-40: 90-35: 0-25 Mention may be made of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer (A2) containing a coalescence or vinyl copolymer, a crosslinking agent (B2), and a photopolymerization initiator (C2).

((Meth) acrylic copolymer (A2))
The (meth) acrylic copolymer (A2) as the base polymer is preferably a (meth) acrylic acid ester copolymer or a vinyl copolymer.

  The above (meth) acrylic acid ester copolymer or vinyl copolymer preferably has a weight average molecular weight of 50,000 to 500,000, particularly 60000 from the viewpoint of achieving both shape retention at room temperature and hot melt properties. It is more preferably 450,000 or less, more preferably 70000 or more and 400000 or less.

Acrylic acid ester-based copolymers have physical properties such as glass transition temperature (Tg) and molecular weight by appropriately selecting the types, composition ratios, and polymerization conditions of acrylic monomers and methacrylic monomers used to adjust them. Can be adjusted as appropriate.
In this case, examples of the acrylic monomer constituting the acrylic ester copolymer include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, and the like as main raw materials.
In addition to these, a (meth) acrylic monomer having various functional groups may be copolymerized with the acrylic monomer according to the purpose of imparting cohesive force or imparting polarity.
Examples of the (meth) acrylic monomer having the functional group include methyl methacrylate, methyl acrylate, hydroxyethyl acrylate, acrylic acid, glycidyl acrylate, N-substituted acrylamide, acrylonitrile, methacrylonitrile, fluorine-containing alkyl acrylate, and organosiloxy group. An acrylate etc. can be mentioned.

  On the other hand, examples of the vinyl copolymer include vinyl copolymers obtained by appropriately polymerizing vinyl acetate copolymerizable with the above acrylic monomer and methacrylic monomer, and various vinyl monomers such as alkyl vinyl ether and hydroxyalkyl vinyl ether. .

As the (meth) acrylic copolymer (A2) of the present adhesive sheet, a monomer a1 having a glass transition temperature (Tg) of less than 0 ° C., a monomer a2 having a glass transition temperature (Tg) of from 0 ° C. to less than 80 ° C. (Meth) acrylic acid ester copolymer formed by copolymerization with a monomer a3 having a glass transition temperature (Tg) of 80 ° C. or more in a molar ratio of a1: a2: a3 = 10-40: 90-35: 0-25 A polymer or vinyl copolymer is preferred.
At this time, the glass transition temperatures (Tg) of the monomers a1, a2, and a3 are the meanings of the glass transition temperatures (Tg) when a polymer is produced from the monomer (homogenization).

The monomer a1 is preferably a (meth) acrylic acid ester monomer having an alkyl group structure having a side chain having 4 or more carbon atoms, for example.
In this case, the side chain having 4 or more carbon atoms may be a straight chain or a branched carbon chain.
More specifically, the monomer a1 is a (meth) acrylic acid ester monomer having a linear alkyl group structure having 4 to 10 carbon atoms, or a branched alkyl group structure having 6 to 18 carbon atoms ( It is preferably a (meth) acrylic acid ester monomer.

Here, as “a (meth) acrylic acid ester monomer having a linear alkyl group structure having 4 to 10 carbon atoms”, n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n- A decyl acrylate etc. can be mentioned.
On the other hand, as the “(meth) acrylic acid ester monomer having a branched alkyl group structure having 6 to 18 carbon atoms”, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-methylhexyl acrylate, isooctyl acrylate, isononyl acrylate, Examples include isodecyl acrylate and isodecyl methacrylate.

The monomer a2 has a (meth) acrylic acid ester monomer having 4 or less carbon atoms, a (meth) acrylic acid ester monomer having a cyclic skeleton in the side chain, a vinyl monomer having 4 or less carbon atoms, or a cyclic skeleton in the side chain. A vinyl monomer is preferred.
Among these, the monomer a2 is particularly preferably a vinyl monomer having 4 or less carbon atoms in the side chain.

Here, as "(meth) acrylic acid ester monomer having 4 or less carbon atoms", methyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl methacrylate, t- Examples thereof include butyl acrylate, isobutyl acrylate, and isobutyl methacrylate.
“(Meth) acrylic acid ester monomer having a cyclic skeleton in the side chain” includes isobornyl acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, tetrahydrofurfuryl methacrylate, benzyl acrylate, benzyl methacrylate , Phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, 3,3,5-trimethylcyclohexanol acrylate, cyclic trimethylolpropane formal acrylate, 4-ethoxylated cumylphenol acrylate, dicyclopentenyl Oxyethyl acrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentenyl acrylate - it can be mentioned, such as theft.
Examples of the “vinyl monomer having 4 or less carbon atoms” include vinyl acetate, vinyl propionate, vinyl butyrate, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, and isobutyl vinyl ether.
Examples of the “vinyl monomer having a cyclic skeleton in the side chain” include styrene, cyclohexyl vinyl ether, norbornyl vinyl ether, norbornenyl vinyl ether and the like. Among these, a vinyl monomer having 4 or less carbon atoms in the side chain or an acrylate monomer having 4 or less carbon atoms in the side chain is particularly suitable.

The monomer a3 is preferably a (meth) acrylic acid ester monomer having a side chain having 1 or less carbon atoms or a (meth) acrylic acid ester monomer having a cyclic skeleton in the side chain.
Here, examples of the “(meth) acrylic acid ester monomer having a side chain having 1 or less carbon atoms” include methyl methacrylate, acrylic acid, and methacrylic acid.
Examples of the “(meth) acrylic acid ester monomer having a cyclic skeleton in the side chain” include isobornyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, Examples thereof include cyclopentenyl methacrylate.

The (meth) acrylic copolymer (A2) is copolymerized with a monomer a1, a monomer a2, and a monomer a3 at a molar ratio of a1: a2: a3 = 10-40: 90-35: 0-25. The tan δ peak can be adjusted to 0 to 20 ° C. in the normal state, that is, the room temperature state, if the (meth) acrylic acid ester copolymer or vinyl copolymer formed is contained. Can be held. In addition, the property of adhering to the adherend in a short time with a light force (referred to as “tackiness”) can be developed. Moreover, when it heats to the temperature which can be hot-melted, fluidity will be expressed and it can be filled to every corner following the level | step-difference part of a bonding surface.
Therefore, from such a viewpoint, the molar ratio of the monomer a1, the monomer a2, and the monomer a3 in the (meth) acrylic ester copolymer or vinyl copolymer constituting the (meth) acrylic copolymer (A2) is A1: a2: a3 = 10 to 40:90 to 35: 0 to 25, preferably 13 to 40:87 to 35: 0 to 23, of which 15 to 40:85 to 38: 2 to 20 Is preferred.
From the same viewpoint as described above, the monomer a1, the monomer a2, and the monomer a3 in the (meth) acrylic ester copolymer or vinyl copolymer constituting the (meth) acrylic copolymer (A2) The molar ratio is preferably a2>a1> a3.

(Crosslinking agent (B2))
When the crosslinking agent (B2) is crosslinked in the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet exhibits a high cohesive force in a high-temperature environment and can obtain excellent foaming reliability.

  As such a crosslinking agent (B2), for example, a crosslinking agent having two or more crosslinking groups such as an epoxy group, an isocyanate group, an oxetane group, a silanol group, and a (meth) acryloyl group can be appropriately selected. Above all, in terms of reactivity and the strength of the cured product to be obtained, polyfunctional (meth) acrylates having 2 or more (meth) acryloyl groups, especially 3 or more, (meth) acrylates having epoxy groups or isocyanate groups, etc. Is preferred.

  As such (meth) acrylate, for example, 1,4-butanediol di (meth) acrylate, glycerin di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di ( (Meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, bisphenol A polyethoxydi (meth) acrylate, bisphenol A polypropoxy di (meth) acrylate, bisphenol F polyethoxydi (meth) acrylate, ethylene glycol di (meth) acrylate, tri Methylolpropane trioxyethyl (meth) acrylate, ε-caprolactone modified tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, pentaerythritol tri (meth) acrylate , Propoxylated pentaerythritol tri (meth) acrylate, ethoxylated pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, di Pentaerythritol hexa (meth) acrylate, polyethylene glycol di (meth) acrylate, tris (acryloxyethyl) isocyanurate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate , Tripentaerythritol hexa (meth) acrylate, tripentaerythritol penta (meth) acrylate , Hydroxybivalate neopentyl glycol di (meth) acrylate, ε-caprolactone adduct of hydroxybivalate neopentglycol, di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane polyethoxytri In addition to UV-curable polyfunctional monomers such as (meth) acrylate and ditrimethylolpropane tetra (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, and polyether (meth) acrylate Polyfunctional acrylic oligomers such as isocyanate (meth) acrylate, 1,1- (bis (meth) acryloyloxymethyl) ethyl isocyanate, 2- (2- (meth) acryloyloxy Examples thereof include ethyloxy) ethyl isocyanate, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate glycidyl ether, hydroxypropyl (meth) acrylate glycidyl ether, and hydroxybutyl (meth) acrylate glycidyl ether.

  Among the examples mentioned above, a polyfunctional monomer or oligomer containing a polar functional group is preferable from the viewpoint of improving the adhesion to the adherend, heat resistance, and wet heat whitening suppression effect. Among these, it is preferable to use polyfunctional (meth) acrylic acid ester having an isocyanuric ring skeleton.

The content of the crosslinking agent (B2) is not particularly limited. As a standard, 0.5 to 20 parts by weight, particularly 1 part or more or 15 parts by weight or less, and 2 parts or more or 10 parts by weight per 100 parts by weight of the (meth) acrylic copolymer (A2). The following ratio is preferable.
By containing the crosslinking agent (B2) in the above range, both the shape stability of the present pressure-sensitive adhesive sheet in an uncrosslinked state and the anti-foaming reliability of the pressure-sensitive adhesive sheet after crosslinking can be achieved. However, this range may be exceeded in balance with other elements.

(Photopolymerization initiator (C2))
The photopolymerization initiator (C2) serves as a reaction initiation assistant in the cross-linking reaction of the above-described cross-linking agent (B2), and those described in the photo-polymerization initiator (C1) are appropriately used. Can be used.

The content of the photopolymerization initiator (C2) is not particularly limited. As a standard, 0.1 to 10 parts by weight, particularly 0.5 parts by weight or more or 5 parts by weight or less, and 1 part by weight or more or 3 parts per 100 parts by weight of the (meth) acrylic copolymer (A2). It is preferable to contain it in the ratio below the mass part.
By setting the content of the photopolymerization initiator (C2) in the above range, an appropriate reaction sensitivity with respect to active energy rays can be obtained.

(Other ingredients)
The pressure-sensitive adhesive composition (II) may contain known components blended in a normal pressure-sensitive adhesive composition as components other than those described above. For example, if necessary, tackifier resin, antioxidant, light stabilizer, metal deactivator, anti-aging agent, hygroscopic agent, polymerization inhibitor, ultraviolet absorber, rust inhibitor, silane coupling agent Various additives such as inorganic particles can be appropriately contained.
Moreover, you may contain reaction catalyst (A tertiary amine type compound, a quaternary ammonium type compound, a lauric acid tin compound, etc.) suitably as needed.

<Laminated structure>
The pressure-sensitive adhesive sheet may be a single-layer sheet or a multilayer sheet in which two or more layers are laminated.
When the pressure-sensitive adhesive sheet is a multi-layer pressure-sensitive adhesive sheet, it may be provided with a pressure-sensitive adhesive layer (referred to as “the present pressure-sensitive adhesive layer”) formed from the pressure-sensitive adhesive composition, for example, an intermediate layer and an outermost layer. In the case of forming a laminated pressure-sensitive adhesive sheet, the outermost layer is preferably formed from the present pressure-sensitive adhesive composition, and among them, the pressure-sensitive adhesive composition (I) (II).

  The pressure-sensitive adhesive sheet may have a structure formed by forming a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition on a release film, and an adherend, for example, as described later. It may be provided with a configuration in which the present adhesive layer is formed on a constituent member for an image display device. In addition, for example, it may be a pressure-sensitive adhesive sheet with a base material having a configuration in which the main pressure-sensitive adhesive layer is formed on a base material, or a base-less pressure-sensitive adhesive sheet having no base material. Furthermore, it may be a double-sided pressure-sensitive adhesive sheet having the main pressure-sensitive adhesive layer on both upper and lower sides, or may be a single-sided pressure-sensitive adhesive sheet having the main pressure-sensitive adhesive layer only on the upper and lower sides.

<Thickness>
As for the thickness of the present pressure-sensitive adhesive sheet, it is preferable that the thickness of the maximum thickness portion is 250 μm or less from the viewpoint of not preventing thinning of the image display device. In other words, the pressure-sensitive adhesive sheet may be a sheet having a uniform thickness or a non-uniform sheet having a partially different thickness. The thickness of the large portion is preferably 250 μm or less.
Further, from the viewpoint of not hindering the adhesion strength and impact absorption with the adherend, the thickness of the maximum thickness portion is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more.

<Application>
The pressure-sensitive adhesive sheet can be used as it is, but can also be used as follows. However, the usage method of this adhesive sheet is not limited.

  This pressure-sensitive adhesive sheet can be provided as a pressure-sensitive adhesive sheet laminate having a configuration in which a release film is laminated on one surface or both surfaces of the pressure-sensitive adhesive sheet, for example.

(Laminated body for configuring the present image display device)
In addition, an image display device configuration laminate having a configuration in which two image display device components are laminated via the present adhesive sheet (hereinafter referred to as “the image display device configuration laminate”). Can be made and provided.

  In the laminate for constituting an image display device, for example, a constituent member for an image display device and another constituent member for an image display device are laminated via the adhesive sheet, and the former image display device constituting member is interposed. The pressure-sensitive adhesive sheet can be produced by irradiating the pressure-sensitive adhesive sheet with light and photocuring the pressure-sensitive adhesive sheet.

As an example of the laminate for constituting the present image display device, in addition to the laminate comprising the construction of the protective panel / the present adhesive sheet / polarizing film, for example, the image display panel / the present adhesive sheet / touch panel, the image display panel / the present adhesive sheet / protection. Examples of configuration of panel, image display panel / main adhesive sheet / touch panel / main adhesive sheet / protection panel, polarizing film / main adhesive sheet / touch panel, polarizing film / main adhesive sheet / touch panel / main adhesive sheet / protection panel, etc. Can do.
The protection panel and the image display panel may include a touch panel sensor incorporated in the protection panel or the image display panel itself.

(This image display device)
An image display device (hereinafter referred to as “the present image display device”) can also be formed using the present adhesive sheet or the laminate for constituting the present image display device.

An example of a preferable manufacturing method of the image display device will be described.
First, the pressure-sensitive adhesive sheet is heated and melted, and an image display device constituent member and another image display device constituent member are laminated via the pressure-sensitive adhesive sheet. At this stage, the present pressure-sensitive adhesive sheet is moderately soft, and can sufficiently follow the steps while maintaining storage stability.
Next, light such as ultraviolet rays is irradiated from the outside of the constituent member for an image display device. As a result, the crosslinking reaction proceeds and can be photocured, and excellent peel resistance and foam resistance can be realized.

  The two image display device components include, for example, personal computers, mobile terminals (PDAs), game machines, televisions (TVs), car navigation systems, touch panels, pen tablets, and other image display devices such as LCDs, PDPs, and ELs. Can be mentioned. More specifically, for example, any one of a group consisting of a touch panel, an image display panel, a surface protection panel, and a polarizing film, or a laminate composed of a combination of two or more types can be given.

(Explanation of words)
“Sheet” generally refers to a product that is thin by definition in JIS and has a thickness that is small and flat for the length and width. In general, “film” is thicker than the length and width. A thin flat product with an extremely small thickness and an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JISK6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish the two in terms of the present invention, in the present invention, even when the term “film” is used, the term “sheet” is included and the term “sheet” is used. In some cases, “film” is included.
In addition, the expression “panel” such as an image display panel and a protection panel includes a plate, a sheet and a film, or a laminate thereof.

In the present specification, when “X to Y” (X and Y are arbitrary numbers) is described, it means “preferably greater than X” or “preferably,” with the meaning of “X to Y” unless otherwise specified. The meaning of “smaller than Y” is also included.
Further, when described as “X or more” (X is an arbitrary number), it means “preferably larger than X” unless otherwise specified, and described as “Y or less” (Y is an arbitrary number). In the case of a case, it means “preferably smaller than Y” unless otherwise specified.

  Hereinafter, the embodiment will be described in more detail. However, the present invention is not limited by these.

[Example 1]
As a (meth) acrylic copolymer (A), a polymethyl methacrylate macromonomer having a number average molecular weight of 2400 (Tg: 105 ° C.) 15 parts by mass (18 mol%) and butyl acrylate (Tg: −55 ° C.) 81 parts by mass 1 kg of an acrylic copolymer (A-1) (weight average molecular weight: 230,000) obtained by random copolymerization of (75 mol%) and 4 parts by mass (7 mol%) of acrylic acid (Tg: 106 ° C.) and crosslinking As the agent (B), 75 g of glycerin dimethacrylate (manufactured by NOF Corporation, product name: GMR) (B-1), 2,4,6-trimethylbenzophenone and 4-methylbenzophenone as the photopolymerization initiator (C) Of the mixture (manufactured by Lanberti, product name: Ezacure TZT) (C-1) 15 g was uniformly mixed to prepare an adhesive composition 1.
The composition 1 was divided into two release films, that is, two polyethylene terephthalate films subjected to release treatment (“Diafoil MRV-V06” manufactured by Mitsubishi Plastics, Inc., thickness 100 μm / “Diafoil MRQ” manufactured by Mitsubishi Plastics, A pressure-sensitive adhesive sheet 1 (thickness 150 μm) was produced by sandwiching the film with a thickness of 75 μm and using a laminator to form a sheet having a thickness of 150 μm.

Printing step of 238 mm x 182 mm x 0.8 mm thick glass (long side 20 mm, short side 17 mm) that does not transmit ultraviolet light 60 μm thick and non-printed part is 198 mm x 148 mm An attached glass plate was prepared.
One release film of the pressure-sensitive adhesive sheet 1 was peeled off, and roll-bonded to soda lime glass having a thickness of 150 mm × 200 mm and a thickness of 1 mm.
Next, the remaining release film is peeled off, and after press-bonding to the printing surface of the glass plate with printing steps using a vacuum press so that the four sides of the adhesive surface are on the printing steps (absolute pressure 5 kPa, temperature 80 ° C., A press pressure of 0.04 MPa) and an autoclave treatment (80 ° C., gauge pressure of 0.2 MPa, 20 minutes) were applied and finished. From the printed glass side, ultraviolet rays were irradiated with a high-pressure mercury lamp so that ultraviolet rays having a wavelength of 365 nm reached the adhesive sheet at 2000 mJ / cm ² , and the adhesive sheet was cured to produce a laminate 1.

[Example 2]
As the (meth) acrylic copolymer (A), 2-ethylhexyl acrylate (Tg: -70 ° C) 55 parts by mass (36 mol%), vinyl acetate (Tg: 32 ° C) 40 parts by mass (56 mol%), 1 kg of acrylic copolymer (A-2) (weight average molecular weight: 170,000) obtained by random copolymerization with 5 parts by mass (8 mol%) of acrylic acid (Tg: 106 ° C.) is used as a crosslinking agent (B ), Ε-caprolactone-modified isocyanuric acid triacrylate (B-2) (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: A9300-1CL), and photopolymerization initiator (C) as Ezacure KTO46 (C-2) (Lamberti) The pressure-sensitive adhesive composition 2 was prepared by uniformly mixing 5 g.
The composition 2 was shaped into a sheet in the same manner as in Example 1 to prepare an adhesive sheet 2 (thickness 150 μm).
A laminate 2 was produced in the same manner as in Example 1 except that the adhesive sheet 2 was used.

[Example 3]
As a (meth) acrylic copolymer (A), a polymethyl methacrylate macromonomer having a number average molecular weight of 1400 (Tg: 105 ° C.) 10 parts by mass (17 mol%) and 2-ethylhexyl acrylate (Tg: −70 ° C.) 90 1 kg of an acrylic copolymer (A-3) (weight average molecular weight: 230,000) obtained by random copolymerization with parts by mass (83 mol%), and propoxylated pentaerythritol triacrylate (new) as a crosslinking agent (B) Nakamura Chemical Co., Ltd., product name: ATM-4PL) (B-3) 50 g and 4-methylbenzophenone (C-3) 15 g as a photopolymerization initiator (C) are uniformly mixed, and an adhesive composition 3 is obtained. Produced.
The composition 3 was shaped into a sheet in the same manner as in Example 1 to prepare an adhesive sheet 3 (thickness 150 μm).
A laminate 3 was produced in the same manner as in Example 1 except that the adhesive sheet 3 was used.

[Example 4]
As the (meth) acrylic copolymer (A), a polymethyl methacrylate macromonomer having a number average molecular weight of 2400 (Tg: 105 ° C.) 12 parts by mass (19 mol%) and 2-ethylhexyl acrylate (Tg: −70 ° C.) 85 1 kg of an acrylic copolymer (A-4) (weight average molecular weight: 80,000) formed by random copolymerization of 3 parts by mass (7 mol%) with part by mass (74 mol%) and acrylic acid (Tg: 106 ° C.) As a crosslinking agent (B), 90 g of glycerin dimethacrylate (manufactured by NOF Corporation, product name: GMR) (B-1) and Ezacure KTO46 (C-2) (manufactured by Lanberti) as a photopolymerization initiator (C) 5 g was uniformly mixed to prepare an adhesive composition 4.
The composition 4 was shaped into a sheet in the same manner as in Example 1 to prepare an adhesive sheet 4 (thickness 150 μm).
A laminate 4 was produced in the same manner as in Example 1 except that the adhesive sheet 4 was used.

[Comparative Example 1]
The laminated body 5 was produced as follows so that it might correspond to the Example of international publication 2012/032995 gazette.
As the (meth) acrylic copolymer (A), 2-ethylhexyl acrylate (Tg: -70 ° C) 75 parts by mass (57 mol%), vinyl acetate (Tg: 32 ° C) 20 parts by mass (33 mol%) and acrylic acid (Tg: 106 ° C.) 1 kg of an acrylic copolymer (A-5) obtained by random copolymerization with 5 parts by mass (10 mol%), trimethylolpropane triacrylate (B-4) as a crosslinking agent (B) ) 200 g and 10 g of 4-methylbenzophenone (C-3) as a photopolymerization initiator (C) were mixed and added to prepare an intermediate layer resin composition. The intermediate layer resin composition is sandwiched between two exfoliated polyethylene terephthalate films (manufactured by Panac, NP75Z01, thickness 75 μm / Toyobo, E7006, thickness 38 μm) so that the sheet has a thickness of 80 μm. The intermediate layer sheet (α) was produced.

Subsequently, 20 g of 4-methylbenzophenone (C-3) is added and mixed as a photopolymerization initiator (C) to 1 kg of the acrylic copolymer (A-5) to prepare a resin composition for an adhesive layer. did.
The adhesive layer resin composition was divided into two release films, that is, two peeled polyethylene terephthalate films (“Diafoil MRA” manufactured by Mitsubishi Plastics Co., Ltd., thickness 75 μm / “E7006” manufactured by Toyobo Co., Ltd.) 38 μm) and shaped into a sheet shape to a thickness of 35 μm to produce a resin sheet (β) for an adhesive layer.
Further, the adhesive layer resin composition was sandwiched between two exfoliated polyethylene terephthalate films (Mitsubishi Resin, Diafoil MRF, thickness 75 μm / Toyobo, E7006, thickness 38 μm). In this way, it was shaped into a sheet to produce an adhesive layer resin sheet (β ′).

The PET film on both sides of the intermediate layer sheet (α) is sequentially peeled and removed, and the PET film on one side of the adhesive layer resin sheets (β) and (β ′) is peeled off, and the exposed adhesive surface is used for the intermediate layer. A three-layer pressure-sensitive adhesive sheet composed of (β) / (α) / (β ′) was prepared by sequentially pasting on both surfaces of the sheet (α).
Through the PET film remaining on the surface of (β) and (β ′), ultraviolet light is irradiated with a high-pressure mercury lamp so that the integrated light quantity at a wavelength of 365 nm is 1000 mJ / cm ^2, and (α), (β) and ( β ′) was UV-crosslinked to prepare an adhesive sheet 5 (thickness 150 μm).
A laminate 5 was produced in the same manner as in Example 1 except that the adhesive sheet 5 was used.

[Comparative Example 2]
As a (meth) acrylic copolymer (A), 1 kg of a commercially available acrylic pressure-sensitive adhesive (A-6) (manufactured by Soken Chemical Co., Ltd., trade name “SK Dyne 1882”) is used as an isocyanate curing agent (Soken Chemical). A pressure-sensitive adhesive composition 6 was prepared by uniformly mixing 1.85 g (trade name “L-45”) manufactured by the company and 0.5 g epoxy curing agent (trade name “E-5XM” manufactured by Soken Chemical Co., Ltd.).
The composition 6 was applied to a release surface of a release film having a thickness of 50 μm, that is, a peeled polyethylene terephthalate film (“MRF75” manufactured by Mitsubishi Plastics Co., Ltd .: 75 μm) so that the thickness after drying becomes 75 μm. And the solvent was dried by heating to prepare a pressure-sensitive adhesive sheet having a thickness of 75 μm.
Further, the release film of the composition 6 is a release film, that is, a release surface of a polyethylene terephthalate film (“Diafoil MRV-V06” manufactured by Mitsubishi Plastics, 100 μm thick), and the thickness after drying becomes 75 μm. Then, the solvent was dried by heating to prepare a pressure-sensitive adhesive sheet having a thickness of 75 μm.
The two prepared adhesive sheets were attached to their respective adhesive surfaces and allowed to cure for one week to prepare an adhesive sheet 6 (thickness 150 μm).

Printing step of 238 mm x 182 mm x 0.8 mm thick glass (long side 20 mm, short side 17 mm) that does not transmit ultraviolet light 60 μm thick and non-printed part is 198 mm x 148 mm An attached glass plate was prepared.
One release film of the pressure-sensitive adhesive sheet 6 was peeled off, and roll-bonded to soda lime glass having a thickness of 150 mm × 200 mm and a thickness of 1 mm.
Next, the remaining release film is peeled off, and after press-bonding to the printing surface of the glass plate with printing steps using a vacuum press so that the four sides of the adhesive surface are on the printing steps (absolute pressure 5 kPa, temperature 80 ° C., A press body of 0.04 MPa) and an autoclave treatment (80 ° C., gauge pressure of 0.2 MPa, 20 minutes) were applied and finished to prepare a laminate 6.

[Comparative Example 3]
The laminated body 7 was produced as follows so that it might correspond to the Example of WO2010038366.
As an alternative to the (meth) acrylic copolymer (A), phenoxy resin (A-7) (InChem, PKHH, weight average molecular weight 52,000) 650 g, and as an alternative to the crosslinking agent (B), carbonate 1 kg of polyurethane acrylate (B-4) having a skeleton (manufactured by Negami Kogyo Co., Ltd., UN5500, weight average molecular weight 67,000), photopolymerization initiator (C), 1-cyclohexyl phenyl ketone (C-4) (BASF) Manufactured, Irgacure 184) 43 g of PSA composition 7 was prepared.
The composition 7 was shaped into a sheet in the same manner as in Example 1 to prepare an adhesive sheet 7 (thickness 150 μm).

Printing step of 238 mm x 182 mm x 0.8 mm thick glass (long side 20 mm, short side 17 mm) that does not transmit ultraviolet light 60 μm thick and non-printed part is 198 mm x 148 mm An attached glass plate was prepared.
One release film of the pressure-sensitive adhesive sheet 7 was peeled off, and roll-bonded to 150 mm × 200 mm 1 mm thick soda lime glass while heating at 80 ° C.
Next, the remaining release film is peeled off, and after press-bonding to the printing surface of the glass plate with printing steps using a vacuum press so that the four sides of the adhesive surface are on the printing steps (absolute pressure 5 kPa, temperature 80 ° C., A press pressure of 0.04 MPa) and an autoclave treatment (80 ° C., gauge pressure of 0.2 MPa, 20 minutes) were applied and finished. From the printed glass side, ultraviolet rays were irradiated with a high-pressure mercury lamp so that ultraviolet rays having a wavelength of 365 nm reached the adhesive sheet at 2000 mJ / cm ² , and the adhesive sheet was cured to produce a laminate 7.

[Evaluation]
About the adhesive sheet and laminated body which were created in the Example and the comparative example, it evaluated as follows.

(Viscosity measurement)
A plurality of pressure-sensitive adhesive sheets 1 to 7 prepared in Examples and Comparative Examples were used, laminated to have a thickness of 1 mm to 2 mm, and punched into a circle having a diameter of 20 mm.
Using a rheometer (“MARS” manufactured by Eiko Seiki Co., Ltd.), adhesive jig: Φ25 mm parallel plate, strain: 0.5%, frequency: 1 Hz, heating rate: 3 ° C./min, 70 ° C. to 120 ° C. The complex viscosity of the pressure-sensitive adhesive sheet before photocuring was measured.
For the pressure-sensitive adhesive sheets 1 to 5 and 7, the pressure-sensitive adhesive sheet was cured by irradiating the pressure-sensitive adhesive sheet with ultraviolet rays through a polyethylene terephthalate film so that the integrated light quantity at 365 nm was 2000 mJ / cm ² using a high-pressure mercury lamp. . The cured adhesive sheet was laminated so as to have a thickness of 1 mm to 2 mm, and punched into a circle having a diameter of 20 mm.
Using a rheometer (“MARS” manufactured by Eiko Seiki Co., Ltd.), adhesive jig: Φ25 mm parallel plate, strain: 0.5%, frequency: 1 Hz, heating rate: 3 ° C./min, 70 ° C. to 120 ° C. The complex viscosity of the pressure-sensitive adhesive sheet after photocuring was measured.

(Adhesive strength after curing)
One release film of the pressure-sensitive adhesive sheets 1 to 7 prepared in Examples and Comparative Examples is peeled off, and a 50 μm PET film (Mitsubishi Resin, Diafoil T100, thickness 50 μm) is laminated as a backing film to be a laminated product. Prepared.
After the laminated product was cut into a length of 150 mm and a width of 10 mm, the adhesive layer exposed by peeling off the remaining release film was roll-bonded to soda lime glass by reciprocating a 2 kg roll. After the autoclave treatment (80 ° C, gauge pressure 0.2MPa, 20 minutes) is applied to the bonded product, the adhesive sheet is cured by irradiating with ultraviolet light so that the integrated light quantity at 365nm is 2000mJ / cm ^2. , And cured for 15 hours to obtain a peel force measurement sample.
The peel force (N / cm) to the glass when the above peel force measurement sample was peeled off at 23 ° C. 40% RH and 80 ° C. 10% RH at a peel angle of 180 ° and a peel speed of 60 mm / min. Measured and determined the adhesive strength after curing.

(Adhesive strength before curing)
One release film of the pressure-sensitive adhesive sheets 1 to 7 prepared in Examples and Comparative Examples is peeled off, and a 50 μm PET film (Mitsubishi Resin, Diafoil T100, thickness 50 μm) is laminated as a backing film to be a laminated product. Prepared.
After the laminated product was cut into a length of 150 mm and a width of 10 mm, the adhesive sheet exposed by peeling off the remaining release film was reciprocated with a 2 kg roll on soda lime glass, and the pressure-sensitive adhesive sheet was roll-bonded.
The peel strength (N / cm) to the glass when this adhesive strength measurement sample was peeled off at 23 ° C. 40% RH and 80 ° C. 10% RH at a peel angle of 180 ° and a peel rate of 60 mm / min. Measured and determined the adhesive strength before curing.
In the table, the peeling mode when peeling in an 80 ° C. and 10% RH environment was described as “CF” for cohesive failure and “AF” for interfacial peeling.

(transparency)
After peeling off one release film of the pressure-sensitive adhesive sheets 1 to 7 prepared in Examples and Comparative Examples and roll bonding the exposed pressure-sensitive adhesive surface to two soda lime glasses (82 mm × 53 mm × 0.5 mm thickness) Then, autoclaving (80 ° C., gauge pressure 0.2 MPa, 20 minutes) was applied and finished and a laminated body for optical evaluation was produced.
About the said laminated body, the haze value according to JISK7136 and the total light transmittance (%) according to JISK7361-1 were calculated | required using the haze meter (the Nippon Denshoku Industries Co., Ltd. make, NDH5000).

(Bonding workability)
In the production of the laminate for optical evaluation, when the sheets prepared in Examples and Comparative Examples were bonded to soda lime glass, the sheets were roll-bonded in an environment of 23 ° C. and 40%, and could be closely fixed to the glass plate. The test piece was judged as “good (good)”, and the glass plate and the sheet did not adhere to each other in an environment of 23 ° C. and 40%, and those requiring heating at the time of roll bonding were judged as “x (poor)”.

(Outgas analysis)
The outgas after light irradiation according to the present invention is detected by the following analysis method.

(Outgas generation method)
The pressure-sensitive adhesive sheets 1 to 5 and 7 prepared in Examples and Comparative Examples were irradiated with ultraviolet rays through a polyethylene terephthalate film using a high-pressure mercury lamp so that the integrated light amount at 365 nm was 2000 mJ / cm ^2. A corresponding pressure-sensitive adhesive sheet was prepared after photocuring. The photocured adhesive sheet was cut into 1 cm × 3 cm and sealed in a 20 ml vial. This vial was placed in a xenon UV irradiation apparatus (Suntest CPS: manufactured by Toyo Seiki Co., Ltd.) and subjected to UV irradiation treatment at an illuminance of 765 W / m ² and a temperature of 60 ° C. for 24 hours.
The pressure-sensitive adhesive sheet 6 of Comparative Example 2 was cut into 1 cm × 3 cm, and sealed in a 20 ml vial. This vial was placed in a xenon UV irradiation apparatus (Suntest CPS: manufactured by Toyo Seiki Co., Ltd.) and subjected to UV irradiation treatment at an illuminance of 765 W / m ² and a temperature of 60 ° C. for 24 hours.

(Outgas analysis method)
The generated gas from the UV-treated resin composition as described above can be measured by a gas chromatography analysis method (HS-GC) equipped with a headspace sampler.

(1) Collection of analysis gas The gas generated from the pressure-sensitive adhesive sheet was collected under the following conditions.
1. HS sampler: TuboMatrix 40 (Perkin Elmer)
2. Heating temperature: 80 ° C
3. Heating time: 30 minutes Needle temperature: 110 ° C
5. Transfer temperature: 170 ° C
6). Injection time: 0.1 minutes Column pressure: 16.0 psi

(2) GC analysis The generated gas was analyzed by GC (manufactured by PerkinElmer: Claras 580), and the detected outgas generation amount was quantified in terms of hexadecane.

(Unevenness absorbability)
The laminates 1 to 7 created in the examples and comparative examples were visually observed, and “× (poor)” indicates that the adhesive did not follow in the vicinity of the printing step and the residual distortion of the adhesive sheet in the vicinity of the step. A sample where the unevenness of origin was seen was determined as “Δ”, and a sample smoothly bonded without bubbles was determined as “good”.

(Anti-foaming reliability)
After putting the laminated bodies 1-7 created in Examples and Comparative Examples into a xenon UV irradiation device (Suntest CPS: manufactured by Toyo Seiki Co., Ltd.), and performing UV irradiation treatment at an illuminance of 765 W / m ² and a temperature of 60 ° C. for 24 hours. The appearance of was observed.
“× (poor)” indicates that bubbles with a diameter of 5 mm or more are generated on the adhesive sheet, “△ (usual)” indicates bubbles with a diameter of 5 mm or less, and “○ (poor)” indicates that there is no foaming and no change in appearance. (Good) ”.

(Discussion)
The pressure-sensitive adhesive sheets produced in Examples 1 to 4 have excellent wettability to the adherend surface and excellent conformability to the uneven surface, as can be seen from the fact that the peeling mode at high temperature before photocuring is cohesive failure. In addition, the adhesive strength after photocuring was high. Therefore, using the pressure-sensitive adhesive sheets prepared in Examples 1 to 4, it is a highly reliable laminate that does not peel, foam, or deform even under severe environmental tests such as long-term ultraviolet irradiation at high temperatures. I was able to get a body.
Moreover, the adhesive sheet produced in Examples 1-4 was able to hold | maintain a shape in 0-40 degreeC, and showed self-adhesiveness.

In the pressure-sensitive adhesive sheet of Comparative Example 1, the pressure-sensitive adhesive resin composition is partially cross-linked by ultraviolet irradiation, that is, when laminated with glass with a printed step due to the state after photocuring, the residual distortion of the pressure-sensitive adhesive sheet is near the printed step. The unevenness by was seen and it was inferior to the pasting appearance. Moreover, after photocuring this again, since adhesive force was low and it was inferior to cohesive force, foaming was seen by the ultraviolet irradiation test, and it was also inferior to bonding reliability.
In Comparative Example 2, since the crosslinking reaction of the pressure-sensitive adhesive resin composition had already been completed at the stage before being bonded to the member, changes in viscosity and adhesive force appeared even when irradiated with ultraviolet rays. Moreover, when laminating | stacking with the glass with a printing level | step difference, it became a result that a part of adhesive could not be filled but the bubble remained in the corner vicinity where a printing level | step difference cross | intersects. In addition, growth of bubbles was observed in the ultraviolet irradiation test triggered by the distortion of the adhesive material near the step.
Comparative Example 3 is a hot melt type adhesive sheet that does not use a (meth) acrylic copolymer as a main component and uses an adhesive resin composition having a certain degree of rigidity in a room temperature region.
As can be seen from the low adhesive strength before photocuring, the sheet of Comparative Example 3 has a very low tack property near room temperature as compared with the pressure-sensitive adhesive sheet of Example, and self-adhesion at 0 to 40 ° C. Sex was insufficient. When the pressure-sensitive adhesive sheet of Comparative Example 3 was bonded, it was necessary to preheat the adherend from the positioning stage, and there was a problem that the work was complicated compared to a pressure-sensitive adhesive sheet that could be stuck at room temperature only by pressure bonding.

Claims (8)

A (meth) acrylic copolymer (A), a crosslinking agent (B), and a pressure-sensitive adhesive sheet before photocuring formed from a resin composition containing a photopolymerization initiator (C),
A photocurable pressure-sensitive adhesive sheet that has photocurability, has the following properties (1) and (2), and has the following property (3) after photocuring.
(1) The shape can be maintained at 0 to 40 ° C. and self-adhesiveness is exhibited.
(2) At 70 to 100 ° C., the viscosity is 100 to 3000 Pa · s.
(3) The viscosity at 70 to 100 ° C. is 3000 to 50000 Pa · s.   The (meth) acrylic copolymer (A) comprises a monomer a1 having a glass transition temperature (Tg) of less than 0 ° C., a monomer a2 having a glass transition temperature (Tg) of from 0 ° C. to less than 80 ° C., and a glass transition temperature. The monomer a3 having a (Tg) of 80 ° C. or higher is copolymerized at a molar ratio of a1: a2: a3 = 10-40: 90-35: 0-25, and the weight average molecular weight is 50,000. It is a (meth) acrylic-type copolymer which is -400,000, The photocurable adhesive sheet of Claim 1 characterized by the above-mentioned.   The photocurable pressure-sensitive adhesive sheet according to claim 2, wherein either of the monomers a2 and a3 is a (meth) acrylic acid ester monomer having a cyclic skeleton in a side chain.   The crosslinking agent (B) has two or more crosslinkable groups, and the crosslinkable group is any one of an epoxy group, an isocyanate group, an oxetane group, a silanol group, or a (meth) acryloyl group. The photocurable pressure-sensitive adhesive sheet according to claim 2 or 3, characterized in that   The photocurable adhesive sheet laminated body provided with the structure formed by laminating | stacking the photocurable adhesive sheet in any one of Claims 1-4, and a release film.   An image display apparatus constituent member is laminated on both surfaces of the photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 4, and the light-curable adhesive sheet is irradiated with light through at least one image display apparatus constituent member. Then, a laminate for constituting an image display device comprising a constitution obtained by partially photocuring the photocurable pressure-sensitive adhesive sheet.   The said image display apparatus structural member is a laminated body which consists of any 1 type in the group which consists of a touch panel, an image display panel, a surface protection panel, and a polarizing film, or a combination of 2 or more types. 2. A laminate for constituting an image display device according to 1.   The image display apparatus comprised using the laminated body for image display apparatus structures of Claim 6 or 7.