JP2016222916A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo crosslinkable adhesive sheet having adhesiveness even before photo crosslinking, without protruding or collapsing an adhesive resin composition due to too much flowing of an adhesive material during bonding and further capable of providing sufficient hardness after photo crosslinking.SOLUTION: There is proposed a double-sided adhesive sheet composed of an adhesive resin composition containing a (meth)acrylic copolymer (A) of 100 pts.mass, a crosslinking agent (B) of 0.5 to 20 pts.mass and a photoinitiator (C) of 0.1 to 5 pts.mass, and having a ratio (X/X) of tensile elasticity modulus before photo crosslinking (X) and a tensile elasticity modulus after photo crosslinking (X) of 3 or more in terms of tensile elasticity modulus.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive sheet. Specifically, the present invention relates to 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 an adhesive sheet that can be suitably used as a constituent member thereof.

  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).

  Patent Document 2 discloses a sheet using a hot-melt 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. It is disclosed.

  Patent Document 3 discloses a polymer / monomer mixture containing a polymer obtained by partially polymerizing an acrylic monomer, a monomer activated by a short-wavelength radiation shorter than the first wavelength, and radiation having a wavelength longer than the first wavelength. A radiation curable pressure-sensitive adhesive sheet containing a photoinitiator for initiating polymerization is disclosed.

Patent Document 4 discloses a method for manufacturing a laminate for constituting an image display device having a constitution in which image display device constituting members are laminated via a transparent double-sided pressure-sensitive adhesive sheet, and includes at least the following (1) and (2 The manufacturing method of the laminated body for image display apparatus structure characterized by having the process of) is disclosed.
(1) A step of forming a transparent double-sided pressure-sensitive adhesive sheet before secondary curing by forming the pressure-sensitive adhesive resin composition into a single-layer or multilayer sheet, followed by UV crosslinking and primary curing.
(2) After the two image display device constituent members are laminated via the transparent double-sided adhesive sheet before secondary curing, ultraviolet rays are irradiated from at least one image display device constituent member side, and the secondary material is passed through this member. A step of subjecting the transparent double-sided PSA sheet before curing to UV-curing by secondary crosslinking.

International Publication 2010/027041 Pamphlet International Publication No. 2010/038366 Pamphlet JP 2014-213572 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.
At this time, the pressure-sensitive adhesive disclosed in Patent Document 2 and the like has almost no adhesiveness (tackiness) before photocrosslinking, and thus the bonding operation was not easy.

  Therefore, the present invention is a photocrosslinkable pressure-sensitive adhesive sheet, which has adhesiveness even before photocrosslinking, and the pressure-sensitive adhesive resin composition protrudes or is crushed because the pressure-sensitive adhesive material flows too much at the time of bonding. Furthermore, the present invention is intended to provide a pressure-sensitive adhesive sheet that can obtain sufficient hardness after photocrosslinking.

In the present invention, (meth) acrylic copolymer (A) 100 parts by mass, crosslinking agent (B) 0.5-20 parts by mass, and photopolymerization initiator (C) 0.1-5 parts by mass. a double-sided pressure-sensitive adhesive sheet including the pressure-sensitive adhesive resin composition containing, tensile elastic modulus, the ratio of the tensile modulus before photocrosslinking (X ₁₎ and the tensile elastic modulus after photocrosslinking (X ₂₎ (X ₁ A pressure-sensitive adhesive sheet characterized by / X ₂ ) of 3 or more is proposed.

The pressure-sensitive adhesive sheet proposed by the present invention has a feature that the difference in tensile elastic modulus (X ₁ ) before and after photocrosslinking is remarkably large, has adhesiveness even before photocrosslinking, and is bonded at the time of bonding. The pressure-sensitive adhesive material does not flow too much and the pressure-sensitive adhesive resin composition does not protrude or is crushed, and sufficient hardness can be obtained after photocrosslinking.

  Next, an example for carrying out the present invention will be described. However, the present invention is not limited to an example of this embodiment.

<This adhesive sheet>
The double-sided pressure-sensitive adhesive sheet (hereinafter referred to as “the pressure-sensitive adhesive sheet”) according to an embodiment of the present invention includes a (meth) acrylic copolymer (A), a crosslinking agent (B), and a photopolymerization initiator (C ) Containing a pressure-sensitive adhesive resin composition (hereinafter referred to as “the present pressure-sensitive adhesive resin composition”).

<This adhesive resin composition>
As described above, the pressure-sensitive adhesive resin composition is a resin composition containing the (meth) acrylic copolymer (A), the crosslinking agent (B), and the photopolymerization initiator (C).

<(Meth) acrylic copolymer (A)>
The (meth) acrylic copolymer (A) as the base polymer is preferably a graft copolymer (A1) having a macromonomer as a branch component.

  Here, the “base polymer” means a resin constituting the main component of the present adhesive resin composition. Although the specific content of the base polymer is not specified, as a guideline, as a guideline, it is 50% by mass or more of the resin contained in the present adhesive resin composition, particularly 80% by mass or more, of which 90% by mass or more (100 (Including mass%). In addition, when two or more types of base polymers are used, the total amount thereof corresponds to the content.

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

The glass transition temperature of the copolymer constituting the trunk component of the graft 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 a polymer obtained by copolymerizing only the monomer component constituting the trunk component of the graft 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 graft copolymer (A1) is the flexibility of the pressure-sensitive adhesive resin composition at room temperature and the pressure-sensitive adhesive resin composition to the adherend. The glass transition temperature is −70 ° C. to 0 ° C. in order for the present pressure-sensitive adhesive resin composition to obtain appropriate adhesiveness (tackiness) at room temperature. Of these, −65 ° C. or higher or −5 ° C. or lower, particularly preferably −60 ° C. or higher or −10 ° C. or lower is particularly preferable.

  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 stem component of the graft copolymer (A1) include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-butyl acrylate, ethyl acrylate, methyl methacrylate, And methyl acrylate. These include hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, acrylic acid, methacrylic acid, glycidyl acrylate, acrylamide, N, N-dimethylacrylamide, acrylonitrile, methacrylate having hydrophilic groups and organic functional groups. Ronitrile and the like can also be used.
Various vinyl monomers such as vinyl acetate, alkyl vinyl ether, and hydroxyalkyl vinyl ether that can be copolymerized with the acrylic monomer or methacryl monomer can also be used as appropriate.

Further, the trunk component of the graft copolymer (A1) preferably contains a hydrophobic (meth) acrylate monomer and a hydrophilic (meth) acrylate monomer as structural units.
When the trunk component of the graft copolymer (A1) is composed of only 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 trunk component of the graft copolymer (A1), a hydrophobic (meth) acrylate monomer, a hydrophilic (meth) acrylate monomer, and a polymerizable functional group at the end of the macromonomer are randomly selected. The copolymer component formed by copolymerization can be mentioned.

  Here, the hydrophobic (meth) acrylate monomer is preferably an alkyl ester having no polar group (excluding methyl acrylate), such as n-butyl (meth) acrylate or n-hexyl (meth). Acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-methylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (Meth) acrylate, isodecyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, isobornyl (meth) a Examples include acrylate, cyclohexyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, methyl methacrylate, and vinyl acetate.

  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, 2-hydroxyethyl (meth) acrylate , Methoxypolyethylene glycol (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxypropyl hexahydrophthalic acid, N, N -Dimethylacrylamide, hydroxyethylacrylamide, etc. can be mentioned.

(Branch component: macromonomer)
As a branching component of the graft copolymer (A1), it is preferable to introduce a macromonomer and contain a repeating unit derived from the macromonomer.
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 graft copolymer (A1).
Specifically, since the glass transition temperature (Tg) of the macromonomer affects the heating and melting temperature (hot melt temperature) of the present adhesive resin composition, the glass transition temperature (Tg) of the macromonomer is 30 ° C. to 120 ° C. Preferably, the temperature is 40 ° C. or higher or 110 ° C. or lower, more preferably 50 ° C. or higher or 100 ° C. or lower.
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).

  Moreover, in the room temperature state, the branch components are attracted to each other and can maintain a state where the present adhesive resin composition is physically cross-linked, and the physical cross-linking can be achieved by heating to an appropriate temperature. It is also preferable to adjust the molecular weight and content of the macromonomer so that the fluidity can be obtained.

  From such a viewpoint, the macromonomer is preferably contained in the graft 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 or more. Or it is preferable that it is 20 mass% or less.

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 a copolymer of polystyrene, styrene and acrylonitrile, poly (t-butylstyrene), poly (α-methylstyrene), polyvinyltoluene, and polymethylmethacrylate. it can.

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

(Physical properties of (meth) acrylic copolymer (A))
The (meth) acrylic copolymer (A) preferably has a complex viscosity of 100 to 800 Pa · s, more preferably 150 to 700 Pa · s, and more preferably 170 to 600 Pa · s at a temperature of 130 ° C. and a frequency of 0.02 Hz. s is more preferable.
The complex viscosity at a temperature of 130 ° C. of the (meth) acrylic copolymer (A) affects the fluidity of the pressure-sensitive adhesive resin composition when the transparent double-sided pressure-sensitive adhesive material is used by hot-melting. If the viscosity is 100 to 800 Pa · s, excellent hot melt aptitude can be imparted.

  In order to adjust the complex viscosity of the (meth) acrylic copolymer (A) to the above range, for example, the glass transition temperature of the copolymer component constituting the trunk component of the graft copolymer (A1) is adjusted. Is mentioned. Preferably, it is adjusted to −70 ° C. to 0 ° C., particularly −65 ° C. or more or −5 ° C. or less, and particularly, −60 ° C. or more or −10 ° C. or less, and the molecular weight of the copolymer component is adjusted to adjust viscoelasticity. The method of adjusting can be mentioned. However, it is not limited to this method.

<Crosslinking agent (B)>
As the crosslinking agent (B), 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. Among them, from the viewpoint of reactivity and the strength of the cured product to be obtained, it has a polyfunctional (meth) acrylate having 2 or more (meth) acryloyl groups, especially 3 or more, an epoxy group, an isocyanate group, or a silanol group (meta ) Acrylate is preferred.

  Examples of such polyfunctional (meth) acrylates include 1,4-butanediol di (meth) acrylate, glycerin di (meth) acrylate, glycerin glycidyl ether di (meth) acrylate, and 1,6-hexanediol di (meth) acrylate. ) 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, trimethylolpropane 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, dipentaerythritol 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, di (meth) acrylate of ε-caprolactone adduct of hydroxybivalinate neopentglycol, trimethylolpropane tri (meta ) Acrylates, trimethylolpropane polyethoxytri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate and other UV curable polyfunctional monomers, as well as polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meta ) Polyfunctional acrylic oligomers such as acrylate and polyether (meth) acrylate, isocyanate (meth) acrylate, 1,1- (bis (meth) acryloyloxymethyl) Examples include ethyl isocyanate, 2- (2- (meth) acryloyloxyethyloxy) ethyl isocyanate, glycidyl (meth) acrylate, hydroxyethyl acrylate glycidyl ether, hydroxypropyl (meth) acrylate glycidyl ether, and hydroxybutyl (meth) acrylate glycidyl ether. be able to.

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 polyfunctional (meth) acrylic acid ester having a hydroxyl 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 the trunk component of the graft copolymer (A1). As B), it is preferable to use a polyfunctional (meth) acrylic acid ester having a hydroxyl group.

The content of the crosslinking agent (B) is preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). More preferably, it is a ratio of 2 parts by mass or less, or 10 parts by mass or less.
By containing a crosslinking agent (B) 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 (C)>
The photopolymerization initiator (C) serves as a reaction initiation assistant in the crosslinking reaction of the aforementioned crosslinking agent (B).
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 (C) is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). More preferably, it is contained in a proportion of 1 part by mass or more, or 3 parts by mass or less.
By setting the content of the photopolymerization initiator (C) in the above range, an appropriate reaction sensitivity with respect to the active energy ray can be obtained.

<Other ingredients>
This adhesive resin composition may contain the well-known component mix | blended with the normal adhesive resin composition as components other than the 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.

<Features of this adhesive sheet>
This pressure-sensitive adhesive sheet can normally maintain a sheet shape, has a hot-melt property that melts or flows when heated in an uncrosslinked state, and has a photo-curable pressure-sensitive adhesive sheet that can be photo-cured. It can be.
If the sheet shape can be maintained in a normal state, it is easy to handle as compared with the liquid adhesive, and the work of filling the liquid can be omitted, so that the productivity is particularly excellent. At this time, if it has a property of adhering to an adherend in a short time in a normal state, that is, near room temperature, that is, a light adhesive force (referred to as “tackiness”), positioning at the time of sticking It is preferable to have tackiness in the normal state, that is, around room temperature, and more preferable to have tackiness even in a relatively low temperature range of -5 ° C to 20 ° C. By using the graft copolymer (A1) as the (meth) acrylic copolymer (A), such tackiness can be obtained.
Also, if it has a hot melt property that melts or flows when heated, it can be softened or fluidized by heating so that it can be filled with the adhesive following the uneven portions such as a printing step. It can be filled without causing such as.
Furthermore, if it has photocurability, it can adhere | attach firmly by carrying out photocuring finally.

As described above, in order to produce a pressure-sensitive adhesive sheet that can normally maintain a sheet shape, has a hot melt property that melts or flows when heated in an uncrosslinked state, and can be photocured. For example, in the case of a single-layer adhesive sheet, a single-layer adhesive sheet may be produced from the present adhesive resin composition. On the other hand, when a multilayer adhesive sheet is used, for example, a two-layer two-layer configuration in which an adhesive layer made of the present adhesive resin composition and an adhesive layer made of another adhesive resin composition are laminated, or an intermediate resin layer is used. 2 types and 3 layers configuration in which an adhesive layer made of the present adhesive resin composition is arranged on both sides, an adhesive layer made of the present adhesive resin composition, an intermediate layer made of an intermediate resin composition, and other adhesives 3 type | mold 3 layer structure formed by laminating | stacking the adhesion layer which consists of an agent resin composition in this order can be mentioned.
However, the pressure-sensitive adhesive resin composition for forming the pressure-sensitive adhesive sheet is not limited to the pressure-sensitive adhesive resin composition.

(Gel fraction)
The pressure-sensitive adhesive sheet has a gel fraction (a) before photocuring of 5% or less, particularly 4% or less, particularly 2% or less from the viewpoint that it can exhibit hot melt properties before photocuring. Is particularly preferred.
In addition, the pressure-sensitive adhesive sheet can obtain a high cohesive force after photocuring, and the gel fraction (b) after photocuring is 50% or more from the viewpoint of obtaining foaming reliability in a wet heat environment. Of these, 60% or more or 90% or less is preferable, and 65% or more or 80% or less is particularly preferable.

  In order to adjust the gel fraction (a) before photocuring and the gel fraction (b) after photocuring as described above, for example, as a (meth) acrylic copolymer (A), as a branch component, macro While using the graft copolymer (A1) provided with the monomer, the composition ratio of the crosslinking agent and the photopolymerization initiator may be adjusted, or the processing temperature and light irradiation amount may be adjusted. However, it is not limited to such a method.

(Tensile modulus)
If the ratio (X ₁ / X ₂ ) between the tensile modulus (X ₁ ) before photocrosslinking and the tensile modulus (X ₂ ) after photocrosslinking of the present pressure-sensitive adhesive sheet is 3 or more, good step absorbability And high foaming reliability.
From this viewpoint, the ratio (X ₁ / X ₂ ) between the tensile elastic modulus (X ₁ ) before photocrosslinking and the tensile elastic modulus (X ₂ ) after photocrosslinking is preferably 3 or more. 30 or less, more preferably 10 or more and 27 or less.

The tensile elastic modulus (X ₁ ) before photocrosslinking is preferably 0.01 MPa or more and 0.2 MPa or less, and more preferably 0.05 MPa or more or 0.1 MPa or less.
On the other hand, the tensile elastic modulus (X ₂ ) after photocrosslinking is preferably 0.8 MPa or more and 2.0 MPa or less, and more preferably 1.0 MPa or more or 1.8 MPa or less.

(Tensile maximum stress (Y))
If the ratio (Y ₁ / Y ₂ ) between the maximum tensile stress (Y ₁ ) before photocrosslinking and the maximum tensile stress (Y ₂ ) after photocrosslinking is 5 or more and 20 or less for this pressure-sensitive adhesive sheet, a good level difference is obtained. Absorbability and foaming reliability can be obtained.
From this viewpoint, the pressure-sensitive adhesive sheet has a ratio (Y ₁ / Y ₂ ) between the maximum tensile stress (Y ₁ ) before photocrosslinking and the maximum tensile stress (Y ₂ ) after photocrosslinking of 5 or more and 20 or less. Of these, 8 or more or 15 or less is more preferable.

The maximum tensile stress (Y ₁ ) before photocrosslinking is preferably 0.5 N or more and 5 N or less, and particularly preferably 0.8 N or more or 2 N or less.
On the other hand, the tensile maximum stress (Y ₂ ) after photocrosslinking is preferably 7N or more and 15N or less, and particularly preferably 9N or more and 12N or less.

(Tensile breaking stress (Z))
If the ratio (Z ₁ / Z ₂ ) between the tensile breaking stress (Z ₁ ) before photocrosslinking and the tensile breaking stress (Z ₂ ) after photocrosslinking is 10 or more and 50 or less, a good level difference is obtained. Absorbability and foaming reliability can be obtained.
From this viewpoint, the pressure-sensitive adhesive sheet has a ratio (Z ₁ / Z ₂ ) of the tensile breaking stress (Z ₁ ) before photocrosslinking to the tensile breaking stress (Z ₂ ) after photocrosslinking of 10 or more and 50 or less. Of these, it is particularly preferably 15 or more and 40 or less.

The tensile breaking stress (Z ₁ ) before photocrosslinking is preferably 0.1 N or more and 2 N or less, particularly preferably 0.2 N or more or 0.6 N or less.
On the other hand, the tensile breaking stress (Z ₂ ) after photocrosslinking is preferably 7N or more and 16N or less, and particularly preferably 9N or more and 12N or less.

In this pressure-sensitive adhesive sheet, in order to adjust the tensile elastic modulus, the maximum tensile stress and the tensile breaking stress to the above ranges, for example, as a (meth) acrylic copolymer (A), a graft having a macromonomer as a branch component While using a copolymer (A1), what is necessary is just to adjust the kind and number of parts of this macromonomer. However, it is not limited to this method.
When a graft copolymer (A1) having a macromonomer as a branch component is used as the (meth) acrylic copolymer (A), the sheet shape can be maintained even in a normal state, and it can be flowed by heating. It is possible to satisfy the steps and satisfy the step followability, and by performing the ultraviolet crosslinking, the curing reaction proceeds and excellent adhesion reliability can be obtained.

<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 adhesive sheet is a multi-layer transparent double-sided adhesive material, the outermost layer preferably has both uneven followability and foam resistance reliability as in the case of the single layer. It is preferable to mold using an adhesive resin composition.

On the other hand, since the intermediate layer does not contribute to adhesion with the image display device constituent member, it does not impair the transparency, and has a light transmittance that does not hinder the secondary curing reaction of the outermost layer, and has a cutting property. In addition, it preferably has a property of improving handling properties.
If the kind of base polymer which forms an intermediate | middle layer is transparent resin, it will not specifically limit. The base polymer forming the intermediate layer may be the same resin as the base polymer of the outermost layer or a different resin. Among these, it is preferable to use the same acrylic resin as the base polymer of the outermost layer from the viewpoints of ensuring transparency and ease of production, and preventing light refraction at the lamination boundary surface.

The intermediate layer and other resin layers may or may not have active energy ray curability. For example, it may be formed so as to be cured by ultraviolet crosslinking or may be formed so as to be cured by heat. Further, it may be formed so as not to be post-cured. However, considering the adhesiveness with the outermost layer, it is preferably formed so as to be post-cured, and particularly preferably formed so as to be UV-crosslinked.
In that case, since light transmittance will fall, if content of a crosslinking initiator increases, it is preferable to contain a ultraviolet-ray crosslinking agent by the content rate lower than the content rate in the outer layer of the crosslinking initiator in an intermediate | middle layer.

When this pressure-sensitive adhesive sheet is a multilayer transparent double-sided pressure-sensitive adhesive material, as a laminated structure, specifically, a two-type two-layer structure in which the present pressure-sensitive adhesive resin composition and another pressure-sensitive adhesive resin composition are laminated, Two kinds of three-layer structure in which the present adhesive resin composition is arranged on the front and back through an intermediate resin layer, the present adhesive resin composition, an intermediate resin composition, and another adhesive resin composition are laminated in this order. 3 types, 3 layers structure etc. which are formed can be mentioned.
Further, the present pressure-sensitive adhesive resin composition and another pressure-sensitive adhesive resin composition are formed into a sheet shape on different release films or image display device constituent members, and both pressure-sensitive adhesive surfaces are laminated to obtain the present pressure-sensitive adhesive sheet. Alternatively, the pressure-sensitive adhesive resin composition, the intermediate resin composition, and the pressure-sensitive adhesive resin composition may be co-extruded in this order to obtain a two-layer / three-layer pressure-sensitive adhesive sheet. Alternatively, the pressure-sensitive adhesive sheet may be obtained by laminating the pressure-sensitive adhesive resin composition or another pressure-sensitive adhesive resin composition on the front and back surfaces of the intermediate resin layer.
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>
The thickness of the pressure-sensitive adhesive sheet, that is, the total thickness, is preferably 50 μm to 1 mm from the viewpoint of not preventing thinning of the image display device and the step absorbability, and more preferably 75 μm or more or 500 μm or less. preferable.
If the total thickness of the pressure-sensitive adhesive sheet is 50 μm or more, it is possible to follow unevenness such as a high printing step, and if it is 1 mm or less, the demand for thinning can be met.
Furthermore, the printing thickness of the peripheral concealing layer in the conventional image display device is higher, specifically, from the viewpoint of filling up to a step of about 80 μm, the total thickness of the pressure-sensitive adhesive sheet is more preferably 75 μm or more. More preferably, it is 100 μm or more. On the other hand, from the viewpoint of meeting the demand for thinning, it is preferably 500 μm or less, more preferably 350 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.

In the case of a multilayer structure, the ratio of the thickness of each outermost layer to the thickness of the intermediate layer is preferably 1: 1 to 1:20, and more preferably 1: 2 to 1:10.
If the thickness of the intermediate layer is within the above range, the contribution of the thickness of the pressure-sensitive adhesive layer in the laminate is not too large, and it is preferable that the workability relating to cutting and handling is not deteriorated because it is too flexible.
In addition, if the outermost layer is in the above range, it is preferable because the adhesion to the adherend and the wettability can be maintained without being inferior in conformity to unevenness and a bent surface.

  Moreover, it is preferable that the thickness of the maximum thickness part of this adhesive sheet is 250 micrometers or less. 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.

<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.

(Adhesive sheet laminate)
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)
As an example of the application of the present adhesive sheet, an image display apparatus configuration laminate (hereinafter referred to as “this image display apparatus configuration”) having a configuration in which two image display device constituent members are laminated via the present adhesive sheet. Referred to as a “laminated body”).

The image display device configuration laminate includes, for example, at least two image display device components facing each other, and at least one of the image display device components includes a light-impermeable portion and a light-transmitting portion on the bonding surface. An image display device configuration laminate having a configuration in which a space between the two image display device configuration members is filled with the present adhesive sheet, the image display device configuration laminate having the image display device configuration There can be mentioned a laminate for constituting an image display device having a constitution in which the pressure-sensitive adhesive sheet is irradiated with light via a device constituent member and the pressure-sensitive adhesive sheet is partially photocured.
Under the present circumstances, the gel fraction of the position which touches the said light transmissive part of the said adhesive sheet is 50% or more, and the gel fraction of the position which contact | connects the said light impermeable part can be made into less than 5%.

  Here, examples of the constituent member for an image display device include a laminate composed of any one of a group consisting of a touch panel, an image display panel, a surface protection panel, and a polarizing film, or a combination of two or more kinds.

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.

The laminate for constituting an image display device can be manufactured, for example, through the following steps (1) to (3).
However, since the manufacturing method of the laminate for constituting an image display device only needs to include at least the following steps (1) to (3), other steps are added or other steps are performed between the steps. It is possible to insert.

(1) A pressure-sensitive adhesive resin composition containing a (meth) acrylic copolymer (A), a crosslinking agent (B), and a photopolymerization initiator (C) is prepared, and the pressure-sensitive adhesive resin composition is prepared. The process of producing this pressure-sensitive adhesive sheet by forming it into a single-layer or multilayer sheet.
(2) The process of sticking and laminating two image display apparatus constituent members via this adhesive sheet.
(3) A step of irradiating the adhesive sheet with active energy rays from the outside of at least one of the image display apparatus constituent members, crosslinking the adhesive sheet, and bonding the two image display apparatus constituent members.

(Process (1))
In step (1), the present pressure-sensitive adhesive resin composition is prepared by a known method, and is formed into a single-layer or multi-layer uncrosslinked sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive resin composition. This pressure-sensitive adhesive sheet is prepared.
As a method for forming the pressure-sensitive adhesive resin composition into a sheet, a currently known method can be arbitrarily adopted.
At this time, the pressure-sensitive adhesive resin composition is formed into a single-layer or multilayer sheet on the release film to produce a single-layer or multilayer transparent double-sided pressure-sensitive adhesive material having an adhesive layer. Good.
Further, the pressure-sensitive adhesive resin composition is molded into a single-layer or multilayer sheet on the image display device constituent member, and the single-layer or multi-layer transparent provided with the adhesive layer on the image display device constituent member. You may make it produce a double-sided adhesive material.

(Process (2))
In the step (2), two image display device constituent members can be adhered and laminated via the present adhesive sheet.
At this time, when the graft copolymer (A1) is used as the base polymer of the present pressure-sensitive adhesive sheet, the macromonomer aggregates in a normal state, that is, a room temperature state, to form a physical cross-linked structure. Excellent storage stability and cutting processability can be imparted.
In addition, when the (meth) acrylic copolymer (A) has a complex viscosity of 100 to 800 Pa · s at a temperature of 130 ° C. and a frequency of 0.02 Hz, excellent workability when used as a hot melt sheet at the time of bonding. Can be enjoyed.

Thus, at a process (2), two image display apparatus structural members can be stuck and laminated | stacked through this adhesive sheet. In this way, it is possible to obtain a degree of adhesiveness that can be easily attached by simply pressing the pressure-sensitive adhesive sheet against the adherend. Therefore, it is easy to position the adhesive material and it is very convenient in terms of work.
In addition, since this pressure-sensitive adhesive sheet is excellent in shape retention and can be processed into an arbitrary shape in advance, an image display device constituent member for laminating the pressure-sensitive adhesive sheet molded on a release film It can also be cut in advance according to the dimensions.
The cutting method at this time is generally punched with a Thomson blade, cut with a super cutter or laser, and half-cuts leaving either the front or back release film in a frame shape so that the release film can be easily peeled off. Is more preferable.
Also in the step (2), the present pressure-sensitive adhesive sheet, that is, the transparent double-sided pressure-sensitive adhesive material is in an uncrosslinked state.

(Process (3))
In step (3), the adhesive layer of the present adhesive sheet is irradiated with active energy rays from the outside of at least one of the image display device constituent members, the adhesive layer is crosslinked, and the two image display device constituent members are bonded. Thus, the laminate for constituting the image display device can be manufactured.

Since this pressure-sensitive adhesive sheet contains a crosslinking agent (B) and a photopolymerization initiator (C), the adhesive layer of this pressure-sensitive adhesive sheet is irradiated with active energy rays to crosslink and cure the pressure-sensitive adhesive layer. The two image display device constituent members can be firmly attached.
In this case, as the active energy ray, an energy ray that sensitizes the polymerization initiator, such as a heat ray, an X-ray, an electron beam, an ultraviolet ray, or a visible ray, may be irradiated. Among them, it is preferable to irradiate ultraviolet rays, particularly ultraviolet rays having a wavelength of 380 nm or less, from the viewpoints of suppressing damage to the image display device constituent members and facilitating reaction control.
There are no particular restrictions on the UV irradiation conditions. For example, it is preferable to irradiate so that the integrated light quantity of the ultraviolet rays that reach the adhesive material is 500 to 5000 mJ / cm ^{2 at} a wavelength of 365 nm. This is from the viewpoint of sufficiently promoting the crosslinking reaction while maintaining workability.
However, when the constituent elements of the image display device that are interposed when irradiating ultraviolet rays block the light beam having the above wavelength, the type of energy rays to which the adhesive material is sensitive in accordance with the interposed member is the type of polymerization initiator. It is preferable to adjust as appropriate.

(Other processes)
Between the step (2) and the step (3), a step of heating and melting the pressure-sensitive adhesive layer of the transparent double-sided pressure-sensitive adhesive material by heating the laminate obtained in the step (2) may be inserted. . That is, the laminate stuck in the step (2) may be heated to melt (hot melt) the adhesive layer of the present adhesive sheet.

When this pressure-sensitive adhesive sheet is heated, the aggregation of the macromonomers is released, the physical cross-linked structure is eliminated, and high fluidity can be expressed. Therefore, when there are irregularities such as printing steps on the wearing surface, the adhesive sheet is heated and flowed (hot melted) when laminating the two components of the image display device, thereby following the irregularities of the adhesive material. And wettability to the adherend are increased, and the members can be more firmly integrated without leaving any distortion.
Under the present circumstances, it is preferable to heat to 60-100 degreeC and to make it hot-melt. If it is 60 degreeC or more, the fluidity | liquidity of an adhesive material can fully be provided and an adhesive resin composition can fully be filled to an uneven | corrugated | grooved part. On the other hand, if it is 100 ° C. or less, not only can the thermal damage to the image display device constituting member to be adhered be suppressed, but also the adhesive material flows too much and the adhesive resin composition is protruded and crushed. Can also be prevented.
From such a viewpoint, the hot melt temperature is preferably 60 to 100 ° C., more preferably 62 ° C. or more and 95 ° C. or less, and particularly preferably 65 ° C. or more and 90 ° C. or less.

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

  For example, the image display device includes at least two image display device components facing each other, and at least one of the image display device components has a light non-transmission portion and a light transmission portion on the bonding surface. And an image display device having a configuration in which a space between the two image display device components is filled with an adhesive sheet. Under the present circumstances, the gel fraction of the position which touches the said light transmissive part of the said adhesive sheet is 50% or more, and the gel fraction of the position which contact | connects the said light impermeable part can be made into less than 5%.

  In the image display device configuration laminate and the image display device, a portion that does not transmit light having a wavelength necessary for photocuring, such as a printed portion around the screen (referred to as a “light-impermeable portion” in the present invention), An image display device constituent member having a portion that transmits light having a wavelength necessary for photocuring (referred to as a “light transmission portion” in the present invention) on the bonding surface, and another image display device constituent member When pasting, the gel fraction at the position in contact with the light opaque portion is less than 1%, and the gel fraction at the position in contact with the light transparent portion is set to 40% or more, thereby being compressed by the light opaque portion. Thus, the stress received can be relaxed, the strain generated in this portion can be reduced, and the adherends can be firmly bonded with high cohesive force.

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 a component for an image display device having a printing part, that is, a light-opaque part, and a component for an image display device 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. Then, since the printing unit shields the light, the light does not reach the portion in contact with the printing unit, or the reaching light is remarkably limited, while the light contacts the light transmitting unit without the printing unit. It can be sufficiently reached, the cross-linking reaction of this part 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 phrases>
“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), polymethyl methacrylate macromonomer (Tg: 105 ° C, number average molecular weight is 2400) 15 parts by mass (18 mol%) and butyl acrylate (Tg: -55 ° C) 81 parts by mass The graft copolymer (A1) formed by random copolymerization of parts (75 mol%) and acrylic acid (Tg: 106 ° C.) 4 parts by mass (7 mol%) was used.
In this graft copolymer (A1), the glass transition temperature of the copolymer constituting the trunk component is −60 ° C., the content of the macromonomer in the graft copolymer (A1) is 15% by mass, and the temperature is 130. The complex viscosity at 260 ° C. and a frequency of 0.02 Hz was 260 Pa · s.

1 kg of this graft copolymer (A1), 90 g of glycerol dimethacrylate (manufactured by NOF Corporation, product name: GMR) as a crosslinking agent (B), and 2,4,6- as a photopolymerization initiator (C) 15 g of a mixture of trimethylbenzophenone and 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) was uniformly mixed to prepare an adhesive resin composition 1.
The pressure-sensitive adhesive resin composition 1 was divided into two release films, that is, two peeled polyethylene terephthalate films (“Diafoil MRV-V06” manufactured by Mitsubishi Plastics, Inc., thickness 100 μm / “Diafoil manufactured by Mitsubishi Plastics, Inc.). MRQ ”(thickness: 75 μm) and formed into a sheet shape using a laminator to a thickness of 150 μm, thereby producing an adhesive sheet 1 (thickness: 150 μm).

[Example 2]
A pressure-sensitive adhesive resin composition 2 was prepared in the same manner as in Example 1 except that 90 g of glycerin dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK ester 701) (B-1) was used as the crosslinking agent (B). did.
Using the pressure-sensitive adhesive resin composition 2, a pressure-sensitive adhesive sheet 2 (thickness 150 μm) was prepared in the same manner as in Example 1.

[Example 3]
1 kg of the same graft copolymer (A1) as in Example 1, 90 g of glycerin dimethacrylate (manufactured by NOF Corporation, product name: GMR) as a crosslinking agent (B), and 2, as a photopolymerization initiator (C) 15 g of a mixture of 4,6-trimethylbenzophenone and 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) and 50 g of an ultraviolet stabilizer (product name: TIN123) manufactured by Ciba Japan are mixed uniformly. Agent resin composition 3 was produced.
And the adhesive sheet 3 (thickness 150 micrometers) was created like Example 1 using this adhesive resin composition 3. FIG.

[Example 4]
As the (meth) acrylic copolymer (A), polymethyl methacrylate macromonomer (Tg: 105 ° C., number average molecular weight is 2500) 10 parts by mass (12 mol%) and butyl acrylate (Tg: −55 ° C.) 88 parts by mass A graft copolymer (A2) obtained by random copolymerization of parts (84 mol%) and 2 parts by mass (7 mol%) of acrylic acid (Tg: 106 ° C.) was used.
In this graft copolymer (A2), the glass transition temperature of the copolymer constituting the trunk component is −60 ° C., the content of the macromonomer in the graft copolymer (A2) is 10% by mass, and a temperature of 130 The complex viscosity at 240 ° C. and a frequency of 0.02 Hz was 240 Pa · s.

1 kg of this graft copolymer (A2), 50 g of trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: CLM400) as a crosslinking agent (B), and 2, as a photopolymerization initiator (C) A pressure-sensitive adhesive resin composition 4 was prepared by uniformly mixing 15 g of a mixture of 4,6-trimethylbenzophenone and 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT).
And the adhesive sheet 4 (150 micrometers in thickness) was created similarly to Example 1 using this adhesive resin composition 4. FIG.

[Example 5]
As the (meth) acrylic copolymer (A), polymethyl methacrylate macromonomer (Tg: 105 ° C, number average molecular weight is 2500) 8 parts by mass (10 mol%) and butyl acrylate (Tg: -55 ° C) 89 masses A graft copolymer (A3) obtained by random copolymerization of parts (85 mol%) and 3 parts by mass (5 mol%) of acrylic acid (Tg: 106 ° C.) was used.
In this graft copolymer (A3), the glass transition temperature of the copolymer constituting the trunk component is −40 ° C., the content of the macromonomer in the graft copolymer (A3) is 8% by mass, and the temperature is 130. The complex viscosity at 220 ° C. and a frequency of 0.02 Hz was 220 Pa · s.

1 kg of this graft copolymer (A3), 90 g of glycerin dimethacrylate (manufactured by NOF Corporation, product name: GMR) as a crosslinking agent (B), and 2,4,6- as a photopolymerization initiator (C) 15 g of a mixture of trimethylbenzophenone and 4-methylbenzophenone (manufactured by Lanberti, product name: Ezacure TZT) was uniformly mixed to prepare an adhesive resin composition 5.
And this adhesive resin composition 5 was used, and the adhesive sheet 5 (thickness 150 micrometers) was created similarly to Example 1. FIG.

[Comparative Example 1]
It produced so that it might correspond to the Example of international publication 2012/032995 gazette.
That is, as the (meth) acrylic copolymer (A), 2-ethylhexyl acrylate (Tg: -70 ° C) 75 parts by mass (57 mol%) and vinyl acetate (Tg: 32 ° C) 20 parts by mass (33 mol%) To 1 kg of an acrylic copolymer (A-5) obtained by random copolymerization with 5 parts by mass (10 mol%) of acrylic acid (Tg: 106 ° C.), trimethylolpropane triacrylate (B -4) 200 g of 4-methylbenzophenone (C-3) as a photopolymerization initiator (C) was mixed and added to prepare an intermediate layer resin composition.
The intermediate layer resin composition is sandwiched between two exfoliated polyethylene terephthalate films (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 prepared.

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 so as to have 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 shape to prepare a resin sheet for adhesive layer (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 6 (thickness 150 μm).

[Comparative Example 2]
A pressure-sensitive adhesive sheet was produced according to Example 6 of WO2010 / 038366.
That is, as an alternative to the (meth) acrylic copolymer (A), 650 g of a phenoxy resin (InChem, PKHH, weight average molecular weight 52,000) and a carbonate skeleton as an alternative to the crosslinking agent (B) 1 kg of polyurethane acrylate (manufactured by Negami Kogyo Co., Ltd., UN5500, weight average molecular weight 67,000), and pressure-sensitive adhesive obtained by uniformly mixing 43 g of 1-cyclohexyl phenyl ketone (manufactured by BASF, Irgacure 184) as a photopolymerization initiator (C) Resin composition 7 was produced.
For the composition 7, a pressure-sensitive adhesive sheet 7 (thickness 150 μm) was prepared in the same manner as in Example 1.

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

(Tensile modulus, breaking strength, breaking elongation)
The pressure-sensitive adhesive sheets 1 to 7 were cut into a width of 20 mm to obtain a tensile test measurement sample before photocrosslinking.
After the adhesive sheets 1 to 7 are cut into a width of 20 mm, the adhesive sheet is cured by irradiating with ultraviolet rays from the release PET side using a high-pressure mercury lamp so that the integrated light quantity at 365 nm is 2000 mJ / cm ^2. Curing was performed at 50 ° C. and 15% RH for 15 hours to obtain a tensile test measurement sample after photocrosslinking.
The tensile test measurement sample was measured for tensile modulus, tensile strength at break, and tensile elongation at tension at a test speed of 300 mm / min in an environment of 23 ° C. and 50% RH.
In addition, the measurement conditions of the tensile elasticity modulus set the displacement as 30-50 mm.

(Gel fraction)
The following measurements were carried out on the portions of the pressure-sensitive adhesive sheets 1 to 7 produced in Examples and Comparative Examples that were in contact with the light transmitting part, that is, the hard part and the part that was in contact with the light non-transmitting part, that is, the soft part. .

1) The pressure-sensitive adhesive resin composition is weighed (W1) and wrapped in a 200-mesh SUS mesh (W0) that has been weighed in advance.
2) The SUS mesh is immersed in 100 mL of ethyl acetate for 24 hours.
3) Take out the SUS mesh and dry at 75 ° C. for 4 and a half hours.
4) The weight (W2) after drying is calculated | required and the gel fraction of an adhesive resin composition is measured from a following formula.
Gel fraction (%) = 100 × (W2−W0) / W1

(Workability (storage))
A pressure-sensitive adhesive sheet 1 to 7 cut to 50 mm × 50 mm square was sandwiched between two glass plates having a thickness of 100 mm × 100 mm and a thickness of 2 mm to prepare a laminate. A weight of 500 g was placed on the laminate, and after standing for 24 hours in an environment at 60 ° C., visual observation was performed to determine whether the adhesive protruded from the laminate.
Visual observation of the prepared laminate, "X" indicates that the adhesive protruded as a whole, "△" indicates that the adhesive protruded only at the corner, and "○" indicates that the adhesive did not protrude Judged.

(Step absorbency)
The adhesive sheets 1-6 in the state before light irradiation produced in Examples 1-5 and the comparative example 1 were cut | judged to 50 mm x 80 mm, and the adhesive surface exposed by peeling one release film was used for the peripheral part 3mm. On the printing surface of soda lime glass (82 mm x 53 mm x 0.5 mm thickness) printed with a thickness of 80 µm, press-bonded using a vacuum press so that the four sides of the adhesive material are on the printing step (absolute pressure) 5 kPa, temperature 80 ° C., press pressure 0.04 MPa). Next, the remaining release film was peeled off, and a ZEONOR film (manufactured by Nippon Zeon Co., Ltd., 100 μm thickness) was press-bonded, followed by autoclaving (80 ° C., gauge pressure 0.2 MPa, 20 minutes) to finish and stick.
Next, from the printed soda lime glass side, ultraviolet rays with a wavelength of 365 nm are irradiated with ultraviolet rays with a high-pressure mercury lamp so that the sheet X reaches 2000 mJ / cm ² , and an unprinted opening, that is, light The laminated body 1-6 for evaluation was created by hardening the sheet | seat of the location which contact | connects a permeation | transmission part.

  About the adhesive sheet 7 created in Comparative Example 2, a laminate of soda lime glass and ZEONOR film (manufactured by ZEON Corporation, 100 μm thickness) printed in the same procedure as described above is prepared using the adhesive sheet 7. After that, autoclave treatment (80 ° C., gauge pressure 0.2 MPa, 20 minutes) was applied and finished and a laminate 7 for evaluation was obtained.

  Visual observation of the produced laminates 1 to 7, "X" indicates that the adhesive material does not follow in the vicinity of the printing step and air bubbles remain, and indicates that unevenness due to bending and distortion of the film is observed near the step. “B” and those smoothly bonded without bubbles were judged as “B”.

The pressure-sensitive adhesive sheets prepared in Examples 1 to 5 were greatly changed in tensile properties before and after photocuring. Since it has such characteristics, the pressure-sensitive adhesive sheets prepared in Examples 1 to 5 have excellent step absorbability before photocuring, and can have excellent foam resistance after photocuring. Was confirmed.
On the other hand, in the comparative example, the change in tensile properties was insufficient before and after photocuring, so in Comparative Example 1 the change after photocrosslinking was insufficient, resulting in a sheet with inferior reliability. The sheet was inferior in workability (storage property) before crosslinking.

Claims (9)

A pressure-sensitive adhesive containing 100 parts by weight of a (meth) acrylic copolymer (A), 0.5 to 20 parts by weight of a crosslinking agent (B), and 0.1 to 5 parts by weight of a photopolymerization initiator (C). A double-sided pressure-sensitive adhesive sheet comprising a resin composition,
About the tensile elastic modulus, the ratio (X ₁ / X ₂ ) between the tensile elastic modulus (X ₁ ) before photocrosslinking and the tensile elastic modulus (X ₂ ) after photocrosslinking is 3 or more. .   The (meth) acrylic copolymer (A) is a graft copolymer having a macromonomer as a branch component, and contains the macromonomer in a proportion of 5 to 30% by mass. The pressure-sensitive adhesive sheet according to claim 1. The maximum tensile stress (Y ₁ / Y ₂ ) between the maximum tensile stress (Y ₁ ) before photocrosslinking and the maximum tensile stress (Y ₂ ) after photocrosslinking is 10 times or more. The adhesive sheet as described. The tensile rupture stress has a ratio (Z ₁ / Z ₂ ) between the tensile rupture stress (Z ₁ ) before photocrosslinking and the tensile rupture stress (Z ₂ ) after photocrosslinking of 10 or more. The pressure-sensitive adhesive sheet according to crab.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the gel fraction before photocrosslinking is 5% or less and the gel fraction after photocrosslinking is 50% or more.   The adhesive sheet laminated body provided with the structure formed by laminating | stacking the adhesive sheet in any one of Claims 1-5, and a release film. At least two image display device constituent members that face each other, and at least one image display device constituent member has a light impermeable portion and a light transmissive portion on the bonding surface.
A laminate for an image display device configuration comprising a configuration filled with the adhesive sheet according to any one of claims 1 to 4 between the two image display device components.
An image display device configuration laminate comprising a configuration in which the pressure-sensitive adhesive sheet is irradiated with light through the image display device component and the pressure-sensitive adhesive sheet is partially photocured.   The two constituent members for an image display device are 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. Item 8. The image display device according to Item 7.   The image display apparatus comprised using the laminated body for image display apparatus structures of Claim 7 or 8.