JP7255628B2 - Light-curing adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photocurable pressure-sensitive adhesive sheet having the ability to be cured by irradiation with light, ie, photocurability.

In recent years, in order to improve the visibility of image display devices, image display panels such as liquid crystal displays (LCD), plasma displays (PDP), electroluminescence displays (ELD), and protection placed on the front side (visible side) By filling the gap between the panel and the touch panel member with an adhesive, the reflection of the incident light and the emitted light from the display image at the interface of the air layer is suppressed.

As a method of filling the gaps between the constituent members of the image display device with an adhesive, a method of filling the gaps between the constituent members of the image display device with an adhesive sheet is known.

The image display device constituent members as described above often have uneven portions on the adherend surface, such as a printed portion being formed on the adherend surface. It is necessary to have the property (also referred to as step absorbability) that the adhesive is filled even in the irregularities.

In order to fill such uneven portions with an adhesive, the adhesive sheet is required to be as flexible as that.
However, if the pressure-sensitive adhesive sheet is flexible, it lacks cohesive force sufficient to withstand pressure such as outgassing generated from the constituent members of the image display device, resulting in a problem of poor anti-foaming reliability.

In order to address such a problem, for example, in Patent Document 1, after bonding an adhesive sheet that has been primarily cured (temporarily cured) with ultraviolet light to a constituent member of an image display device, an ultraviolet ray is applied to the adhesive sheet through the constituent member of the image display device. A method of irradiation and secondary curing (main curing) is disclosed.
Such a pressure-sensitive adhesive sheet leaves room for further curing at the stage of primary curing (temporary curing), and because it is so flexible, the surface of the adherend may have unevenness, or foreign matter may be present at the adhesive interface. Even if it does, it can fully follow these unevenness and get used to it.
By subjecting the primarily cured pressure-sensitive adhesive sheet to secondary curing (main curing), it is possible to impart adhesive strength and cohesive strength sufficient to withstand the gas pressure of outgassing.

In recent years, with the diversification of designs, it has begun to form the frame-like concealing portion provided on the peripheral portion of the surface protection panel in a color other than black. When the concealed portion is formed in a color other than black, the concealed portion, that is, the printed portion tends to be higher than that of black because the concealability of the color other than black is low. Therefore, a pressure-sensitive adhesive is required for bonding components having such a large printed portion. It is required to have excellent conformability to print unevenness that can be filled up to the bottom.

In order for the pressure-sensitive adhesive sheet to follow a large print level difference and fill all the corners, the pressure-sensitive adhesive sheet is required to have higher flexibility and fluidity at the stage of bonding to the constituent members of the image display device.
On the other hand, however, this causes a problem that the adhesive layer flows and deforms during storage and transportation.

Therefore, for example, in Patent Document 2, 5 to 100 laminates including a semi-cured adhesive layer and a pair of base layers laminated so as to sandwich the semi-cured adhesive layer are stacked and stacked. A method for producing a pressure-sensitive adhesive sheet for an image display device is disclosed, in which light with a wavelength of 360 nm or less is irradiated from the lateral side with respect to a direction.

According to such a manufacturing method, since the laminate in which 5 to 100 sheets are stacked is irradiated with a specific light on the side surface side and only the end portion of the adhesive layer is cured, the adhesive layer during storage and transportation There is no risk of deformation due to flow.
However, by stacking 5 to 100 adhesive sheets and irradiating light from the side surface in the direction of stacking to cure the side surface portion, the adhesive layer is prevented from sticking out, and the adhesive layer is formed. After being cured, there is a problem that it is extremely complicated because it has a step of curing from the side surface side.

Patent No. 4971529 Patent No. 5991531

The present invention can be stored for a long period of time while retaining step absorbability capable of deforming following a step and filling a gap between constituent members for an image display device. To provide a new pressure-sensitive adhesive sheet which maintains the shape of the pressure-sensitive adhesive sheet and is excellent in storage stability without protruding of the pressure-sensitive adhesive.

The present invention provides a photocurable pressure-sensitive adhesive sheet containing a (meth)acrylic acid ester (co)polymer (a) as a main component resin,
The pressure-sensitive adhesive sheet has a weight average molecular weight (Mw) of 200,000 or more and 500,000 or less, and a molecular weight distribution (Mw/Mn) of 4 or more and 15 or less, and
In the polystyrene-equivalent molecular weight distribution curve, the maximum peak exists in the molecular weight region of 50,000 or more and less than 400,000, and one or more peaks or shoulders exist in the molecular weight region of 400,000 or more and less than 2,000,000. We propose a photocurable pressure-sensitive adhesive sheet that

The photocurable pressure-sensitive adhesive sheet proposed by the present invention has a weight average molecular weight (Mw) of 200,000 or more and 500,000 or less, a molecular weight distribution (Mw/Mn) of 4 or more and 15 or less, and has a specific molecular weight. It has a maximum peak in the region, and particularly has one or more peaks or shoulders in the region with a molecular weight of 400,000 or more and less than 2,000,000, so that it has high step absorption and excellent storage stability. can be
In addition, since the photocurable pressure-sensitive adhesive sheet proposed by the present invention is photocurable, it is possible to obtain high cohesive strength by irradiating light after lamination to the adherend, and excellent foaming resistance reliability. can have sex.

1 shows the molecular weight distribution curve of the pressure-sensitive adhesive sheet of Example 1 measured by gel permeation chromatography.

An example of an embodiment of the present invention will be described in detail below. However, the embodiment described here is just a representative example of the embodiment of the invention.

<This adhesive sheet>
A photocurable pressure-sensitive adhesive sheet (hereinafter referred to as "the present pressure-sensitive adhesive sheet") as an example of an embodiment of the present invention is a photocurable pressure-sensitive adhesive sheet that is cured by irradiation with light, It contains a (meth)acrylic acid ester (co)polymer (a) as a main component resin.
Here, the "main component resin" means a resin having the largest mass ratio among the resins constituting the present pressure-sensitive adhesive sheet, and is 50% by mass or more, especially 70% by mass or more of the resin constituting the present pressure-sensitive adhesive sheet. Among them, the resin accounts for 80% by mass or more, and more preferably 90% by mass or more (including 100% by mass).

(Gel fraction)
The pressure-sensitive adhesive sheet preferably does not form a three-dimensional network structure, and preferably has a gel fraction of 10% or less.
If the gel fraction of the pressure-sensitive adhesive sheet is 10% or less, it is easy to deform the pressure-sensitive adhesive sheet according to the shape of the adherend when it is attached to the adherend while applying pressure or temperature. , sufficient step absorbability can be obtained.
From this point of view, the gel fraction of the adhesive sheet is preferably 10% or less, more preferably 5% or less, more preferably 1% or less (including 0%).

This pressure-sensitive adhesive sheet is preferably photocurable. In other words, it may be in an uncured state as long as it has the property of being cured by light, and it is preferable that there is room for curing by light. At this time, the pressure-sensitive adhesive sheet may be photo-cured or heat-cured (also referred to as “temporary curing”) in a state in which a room for photo-curing is left. Such a pressure-sensitive adhesive sheet can be photo-cured (also referred to as “main curing”) after being attached to an adherend.
The gel fraction after the main curing of the adhesive sheet is preferably 30% or more, particularly preferably 40% or more. By curing the present pressure-sensitive adhesive sheet to such a range, the present pressure-sensitive adhesive sheet has a high cohesive strength even in a severe high-temperature and high-humidity environment, etc., and can improve foam resistance reliability.
In addition, "photocurable" means having reactivity or curability to general radiation, and among them, it is preferable to have reactivity or curability to ultraviolet rays and / or visible light. , and preferably has reactivity or curability with respect to light in the wavelength range of 200 nm to 780 nm.

(Molecular weight distribution)
The adhesive sheet preferably has the following molecular weight distribution characteristics (1) to (3) measured by Gel Permeation Chromatography.
(1) Weight average molecular weight (Mw) is 200,000 or more and 500,000 or less.
(2) The molecular weight distribution (Mw/Mn) is 4 or more and 15 or less.
(3) In the molecular weight distribution curve in terms of polystyrene, the maximum peak exists in the molecular weight region of 50,000 or more and less than 400,000, and one or more peaks or shoulders exist in the molecular weight region of 400,000 or more and less than 2,000,000. .

As described above, the present pressure-sensitive adhesive sheet has a weight average molecular weight (Mw) of 200,000 or more and 500,000 or less in the molecular weight distribution characteristics, and has a maximum peak in a region of 50,000 or more and less than 400,000. While being flexible enough to follow steps, it further contains a slightly high molecular weight component of 400,000 or more and less than 2,000,000 with a molecular weight distribution (Mw/Mn) in the range of 4 or more and 15 or less, It does not deform or flow even in a storage atmosphere of room temperature to about 40°C.
Therefore, it is possible to have high step absorbability while being excellent in storage stability.

From the above point of view, the weight average molecular weight (Mw) of the pressure-sensitive adhesive sheet is preferably 200,000 or more and 500,000 or less, more preferably 220,000 or more or 450,000 or less, and more preferably 250,000 or more or 400,000 or less. preferable.

From the same viewpoint as above, the molecular weight distribution (Mw/Mn) of the pressure-sensitive adhesive sheet is preferably 4 or more and 15 or less, more preferably 5 or more or 12 or less, and more preferably 6 or more or 10 or less.

Also, from the above point of view, in the molecular weight distribution curve in terms of polystyrene, the maximum A peak is present and one or more peaks or shoulders are present in the molecular weight region of 400,000 or more and less than 2,000,000, especially the molecular weight region of 600,000 or more and less than 1,800,000, especially the molecular weight region of 800,000 or more and less than 1,600,000. is preferred.

Here, the "peak" is a point where the sign of curvature (plus or minus) changes on the molecular weight distribution curve.
The above-mentioned "shoulder" refers to an inflection point or a stationary point of a portion of a molecular weight distribution curve that bulges upward with respect to a gentle curved slope.

Furthermore, in the above molecular weight distribution curve in terms of polystyrene, the ratio of the maximum peak intensity in the molecular weight region of 400,000 or more and less than 2,000,000 to the maximum peak intensity in the molecular weight region of 50,000 or more and less than 400,000 is 1.1 to 10. It is preferably 1.5 or more or 5.0 or less, and more preferably 2.0 or more or 4.0 or less.

The following methods 1 and 2 can be mentioned as methods for imparting the molecular weight distribution characteristics (1) to (3) to the pressure-sensitive adhesive sheet.
For example, as described later, the present resin composition containing a (meth)acrylate (co)polymer (a), a predetermined cross-linking agent (b), and a photoinitiator (c) is irradiated with a slight amount of light. Then, a high-molecular-weight reaction product that is slightly temporarily cured to the extent that it does not three-dimensionally crosslink is generated, and the above characteristics (1) to (3) are satisfied, and the (a) to (c) and the A method (Method 1) of forming a sheet by preparing the present resin composition in which the blending amount of the reaction product is adjusted can be mentioned.
According to such method 1, the molecular weight distribution characteristics (1) to ( 3) can be satisfied.
In addition to the (meth)acrylic acid ester (co)polymer (a) having a weight average molecular weight (Mw) within the range of (1), a low molecular weight A method (Method 2) of forming a sheet by preparing the present resin composition containing a mixture of these components or a high-molecular-weight polymer appropriately selected so as to satisfy the above properties (1) to (3) is given. be able to.
Methods other than these methods 1 and 2 can also provide the molecular weight distribution characteristics (1) to (3).

In the photocurable pressure-sensitive adhesive sheet obtained by the above method 1, the peaks or shoulders present in the molecular weight region of 400,000 or more and less than 2,000,000 are the cross-linking agent and the photoinitiator, and the cross-linking agent and (meth)acrylic acid. It can be considered that the ester (co)polymer (a) is formed by reacting to such an extent that a three-dimensional network structure is not formed and the molecular weight increases. Therefore, it can be considered that the peak or shoulder molecular weight and maximum peak intensity existing in the molecular weight region of 400,000 or more and less than 2,000,000 are greatly affected by the molecular weight, the number of functional groups, and the content of the cross-linking agent.

(thickness)
The thickness of the adhesive sheet is preferably 0.02 mm to 1 mm.
When the thickness of the present pressure-sensitive adhesive sheet is 0.02 mm or more, it can follow irregularities such as printed steps on an adherend or the like. Moreover, from the viewpoint of meeting the demand for thinning, the thickness is preferably 1 mm or less.
From this point of view, the thickness of the adhesive sheet is preferably 0.02 mm to 1 mm, more preferably 0.05 mm or more or 0.8 mm or less, and more preferably 0.1 mm or more or 0.5 mm or less. Among them, it is more preferably 0.075 mm or more or 0.25 mm or less.

(Viscoelastic properties)
The pressure-sensitive adhesive sheet preferably has the following viscoelastic properties (I) and (II).
(I) The storage elastic modulus G′ at a frequency of 10 ⁻⁵ Hz and a reference temperature of 20° C. is 1×10 ² Pa or more.
(II) The storage elastic modulus G' at a frequency of 10 ^-3 Hz and a reference temperature of 80°C is 5 x 10 ² Pa or less.
By having such viscoelastic properties, the present pressure-sensitive adhesive sheet can simultaneously have two properties that tend to be contradictory, ie, shape stability during storage and level difference absorption performance during lamination.
In order for this pressure-sensitive adhesive sheet to have such viscoelastic properties, it is necessary, for example, to adjust the composition of the (meth)acrylic acid ester (co)polymer, or to adjust the amount of additives such as the amount of cross-linking agent and photoinitiator. Alternatively, the molecular weight and molecular weight distribution of the pressure-sensitive adhesive composition may be adjusted. However, it is not limited to this method.

From this point of view, the storage modulus G′ of (I) is preferably 1×10 ² Pa or more, more preferably 2×10 ² Pa or more or 1×10 ⁵ Pa or less. Above all, it is more preferably 5×10 ² Pa or more or 1×10 ⁴ Pa or less.
From the same point of view, the storage modulus G′ of (II) above is preferably 5×10 ² Pa or less, more preferably 1×10 ⁻¹ Pa or more or 3×10 ² Pa or less. More preferably, it is more preferably 1×10 ¹ Pa or more or 2×10 ² Pa or less.

This adhesive sheet is attached to a stainless steel plate with an adhesive area of 25 mm × 20 mm, and a holding force test in which a load of 500 gf (4.9 N) is applied in the vertical direction at a temperature of 40 ° C. for 30 minutes The deviation length is 1.0 mm or less. is preferably
By having such a deviation length, the present pressure-sensitive adhesive sheet has sufficient shape stability in a generally conceivable storage environment for pressure-sensitive adhesive sheets, so that it is possible to suppress shape change during storage.

From this point of view, the deviation length is more preferably 1.0 mm or less, and further preferably 0.8 mm or less.
The length of deviation is a value obtained by a method described in Examples to be described later.

<Present resin composition>
The present pressure-sensitive adhesive sheet is a photo-curing obtained by temporarily curing a resin composition (referred to as "this resin composition") containing a (meth)acrylic acid ester (co)polymer (a) as a main component resin by light irradiation. It is preferably an object.
That is, the present pressure-sensitive adhesive sheet can be obtained by irradiating the present resin composition with light to temporarily cure the present resin composition to such an extent that the present resin composition does not form a three-dimensional network structure. However, it is not limited to the forming method.

The present resin composition is preferably a resin composition containing a (meth)acrylate (co)polymer (a), a cross-linking agent (b) and a photoinitiator (c).

The present resin composition may be a solvent-based resin composition containing a solvent, or may be a non-solvent-based resin composition containing no solvent.
In the case of a solvent-based resin composition, since the viscosity during coating can be controlled by the solvent, even a composition containing a high-molecular-weight polymer can be easily handled.
On the other hand, non-solvent-based resin compositions increase in viscosity and become difficult to handle when a composition containing a high-molecular-weight polymer is used. After that, it is effective to photo-cure to such an extent that a three-dimensional network structure is not formed.

[(Meth) acrylic acid ester (co) polymer (a)]
Examples of the (meth)acrylic acid ester (co)polymer (a) include, for example, an alkyl (meth)acrylate homopolymer and a copolymer obtained by polymerizing a monomer component copolymerizable therewith. can be mentioned. Examples thereof include homopolymers of alkyl (meth)acrylates and copolymers obtained by polymerizing monomer components copolymerizable therewith.

More specifically, an alkyl (meth)acrylate, (a) a carboxyl group-containing monomer copolymerizable therewith (hereinafter also referred to as “copolymerizable monomer A”), (b) a hydroxyl group-containing monomer (hereinafter “copolymerizable (hereinafter also referred to as "polymerizable monomer B"), (c) amino group-containing monomer (hereinafter also referred to as "copolymerizable monomer C"), (d) epoxy group-containing monomer (hereinafter also referred to as "copolymerizable monomer D"). ), (e) an amide group-containing monomer (hereinafter also referred to as "copolymerizable monomer E"), (f) a vinyl monomer (hereinafter also referred to as "copolymerizable monomer F"), (g) the number of carbon atoms in the side chain is 1 to 3 (meth) acrylate monomer (hereinafter also referred to as "copolymerizable monomer G") and (h) macromonomer (hereinafter also referred to as "copolymerizable monomer H") Any one selected from Copolymers of monomer components containing the above monomers can be mentioned.

The above alkyl (meth)acrylate is preferably a linear or branched alkyl (meth)acrylate having a side chain of 4 to 18 carbon atoms, and a linear or branched alkyl (meth)acrylate having a side chain of 4 to 18 carbon atoms. Examples include 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 (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl ( meth)acrylate, t-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, 3,5,5-trimethylcyclohexane (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl ( meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate and the like. These may be used singly or in combination of two or more.

Examples of the copolymerizable monomer A include (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl Phthalic acid, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-( Meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid may be mentioned. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer B include hydroxyalkyls such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. Meth)acrylates may be mentioned. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer C include aminoalkyl (meth)acrylates such as aminomethyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, aminoisopropyl (meth)acrylate, N-alkylamino Examples include N,N-dialkylaminoalkyl (meth)acrylates such as alkyl (meth)acrylates, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer D include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate glycidyl ether. . These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer E include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, Mention may be made of N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone(meth)acrylamide, maleic acid amide and maleimide. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer F include compounds having a vinyl group in the molecule. Examples of such compounds include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms, functional monomers having functional groups such as hydroxyl group, amide group and alkoxyalkyl group in the molecule, and Polyalkylene glycol di(meth)acrylates and vinyl ester monomers such as vinyl acetate, vinyl propionate and vinyl laurate and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes can be exemplified. These may be used alone or in combination of two or more.

Examples of the copolymerizable monomer G include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate and the like. These may be used alone or in combination of two or more.

The copolymerizable monomer H is a macromonomer having a side chain with 20 or more carbon atoms when polymerized to form a (meth)acrylic (co)polymer.
By using a macromonomer as a copolymerizable monomer, a (meth)acrylic (co)polymer can be made into a graft copolymer.
Therefore, the properties of the main chain and the side chains of the graft copolymer can be changed by selecting the copolymerizable monomer H and the other monomers and their mixing ratio.

The copolymerizable monomer H preferably has a skeleton component composed of an acrylic polymer or a vinyl polymer.
The skeleton component of the macromonomer includes, for example, the linear or branched alkyl (meth)acrylate having 4 to 18 carbon atoms in the side chain, the copolymerizable monomer A, the copolymerizable monomer B, and the copolymerizable monomer G. and the like, and these can be used alone or in combination of two or more.

A macromonomer has a functional group such as a radically polymerizable group, a hydroxyl group, an isocyanate group, an epoxy group, a carboxyl group, an amino group, an amide group, or a thiol group. As the macromonomer, one having a radically polymerizable group copolymerizable with other monomers is preferred. One or two or more radically polymerizable groups may be contained, and one group is particularly preferable. When the macromonomer has a functional group, it may contain one or two or more functional groups, with one being particularly preferred.
Either one or both of the radically polymerizable group and the functional group may be contained. When both a radically polymerizable group and a functional group are contained, a functional group other than either a functional group that is added to a polymer unit composed of another monomer, or a radically polymerizable group that is copolymerized with another monomer, or There may be two or more radically polymerizable groups.
Therefore, the terminal functional groups of the macromonomer include, for example, radically polymerizable groups such as methacryloyl groups, acryloyl groups, and vinyl groups, as well as hydroxyl groups, isocyanate groups, epoxy groups, carboxyl groups, amino groups, amide groups, and thiol groups. functional groups such as
Among them, those having a radically polymerizable group copolymerizable with other monomers are preferred. One or two or more radically polymerizable groups may be contained, and one group is particularly preferable. Even when the macromonomer has a functional group, it may contain one or two or more functional groups, with one being particularly preferred.
Either one or both of the radically polymerizable group and the functional group may be contained. When both a radically polymerizable group and a functional group are contained, a functional group other than either a functional group that is added to a polymer unit composed of another monomer, or a radically polymerizable group that is copolymerized with another monomer, or There may be two or more radically polymerizable groups.

The number average molecular weight of the copolymerizable monomer H is preferably 500 to 20,000, more preferably 800 or more or 8,000 or less, and more preferably 1,000 or more or 7,000 or less.
Commonly produced macromonomers (for example, macromonomers manufactured by Toagosei Co., Ltd.) can be used as appropriate.

<More preferred composition>
As a preferred example of the present resin composition, a (meth)acrylic acid ester copolymer (a-1) comprising a graft copolymer having a macromonomer as a branch component, a cross-linking agent (b) and a photoinitiator (c ) can be mentioned.

By using such a (meth)acrylic acid ester copolymer (a-1) and photocuring it to the extent that it does not form a three-dimensional network structure, it exhibits self-adhesiveness while maintaining a sheet shape at room temperature. It has hot-melt properties such that it melts or flows when heated, and can be photo-cured.
Therefore, if the (meth)acrylic acid ester copolymer (a-1) is used, it exhibits adhesiveness at room temperature (20° C.) even in an uncrosslinked state, and is preferably 50 to 100° C. can have the property of softening or fluidizing when heated to a temperature of 60° C. or higher or 90° C. or lower.
In addition, such a (meth)acrylic acid ester copolymer (a-1) has high melting or fluidity with respect to temperature, and thus has poor storage stability during transportation, for example. By slightly cross-linking this, the storage stability can be improved without impairing the original adhesive properties.

The glass transition temperature of the copolymer component constituting the trunk component of the (meth)acrylic acid ester copolymer (a-1) is determined by the flexibility of the adhesive sheet at room temperature and the adhesion to the adherend. Since it affects the wettability of the sheet, that is, the adhesiveness, the glass transition temperature should be -70°C to 0°C in order for the pressure-sensitive adhesive sheet to obtain appropriate adhesiveness (tackiness) at room temperature. The temperature is preferably −65° C. or higher or −5° C. or lower, and particularly preferably −60° C. or higher or −10° C. or lower.
However, even if the copolymer component has the same glass transition temperature, the viscoelasticity can be adjusted by adjusting the molecular weight. For example, by reducing the molecular weight of the copolymer component, it can be made more flexible.

Examples of the (meth)acrylic acid ester monomer contained in the trunk component of the (meth)acrylic acid ester copolymer (a-1) 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 (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, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, benzyl (meth)acrylate and the like. These include hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate having hydrophilic groups and organic functional groups, and (meth)acrylates. ) acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate acid, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, crotonic acid, fumaric acid Acids, maleic acid, itaconic acid, monomethyl maleate, carboxyl group-containing monomers such as monomethyl itaconate, maleic anhydride, acid anhydride group-containing monomers such as itaconic anhydride, glycidyl (meth)acrylate, α-ethyl acrylic acid epoxy group-containing monomers such as glycidyl and 3,4-epoxybutyl (meth)acrylate; amino group-containing (meth)acrylate monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; ) acrylamide, Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetoneacrylamide, maleic acid amide, maleimide, etc. Monomers containing an amide group, heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine, vinylcarbazole, and the like can also be used.
In addition, styrene, t-butylstyrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitonyl, vinyl acetate, vinyl propionate, alkyl vinyl ether, hydroxyalkyl vinyl ether, and alkyl copolymerizable with the above acrylic monomers and methacrylic monomers. Various vinyl monomers such as vinyl monomers can also be used as appropriate.

Further, the trunk component of the (meth)acrylate (co)polymer (a-1) preferably contains a hydrophobic monomer and a hydrophilic monomer as structural units.
If the trunk component of the (meth)acrylic acid ester (co)polymer (a-1) is composed only of hydrophobic monomers, it tends to whiten under wet heat. It is preferred to prevent wet heat whitening.

Specifically, as the trunk component of the (meth)acrylic acid ester (co)polymer (a-1), a hydrophobic (meth)acrylate monomer, a hydrophilic (meth)acrylate monomer, and a macromonomer A copolymer component obtained by random copolymerization with a terminal polymerizable functional group can be mentioned.

Here, the hydrophobic (meth)acrylate monomers include, for example, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and 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 ) 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, di Cyclopentenyloxyethyl (meth)acrylate and methyl methacrylate can be mentioned.
Examples of hydrophobic vinyl monomers include alkyl vinyl esters such as vinyl acetate, styrene, t-butyl styrene, α-methyl styrene, vinyl toluene, and alkyl vinyl monomers.

Among them, the number of carbon atoms is 5 or more, especially 8 or more, especially 9 or more, from the viewpoint of easily forming an appropriate phase separation structure with the phase formed by the branch component described later and from the viewpoint of imparting appropriate adhesiveness (tackiness). , particularly preferably 10 or more alkyl (meth)acrylates.

When the present pressure-sensitive adhesive sheet is used for a member having a touch sensor function, for example, a photocurable composition with a low dielectric constant is required in order to absorb changes in touch detection sensitivity and suppress noise generation in detection signals. There is At this time, from the viewpoint of adjusting the dielectric constant of the cured product obtained by curing the resin composition to a low level, the hydrophobic monomer has 5 or more carbon atoms, especially 8 or more, especially 9 or more, especially 10 or more alkyl ( Preference is given to using meth)acrylates.

Examples of alkyl (meth)acrylates having 8 or more carbon atoms include 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, Examples include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate and the like.

Examples of the hydrophilic monomers include methyl acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, glycerol (meth) acrylate, and the like. Hydroxyl group-containing (meth)acrylate, (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid , 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth) Carboxyl group-containing monomers such as acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, and monomethyl itaconate; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; ) epoxy group-containing monomers such as glycidyl acrylate, glycidyl α-ethyl acrylate, and 3,4-epoxybutyl (meth)acrylate; alkoxypolyalkylene glycol (meth)acrylates such as methoxypolyethylene glycol (meth)acrylate; (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, (meth)acryloylmorpholine, hydroxyethyl (meth)acrylamide, isopropyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, phenyl (meth)acrylamide, (Meth)acrylamide-based monomers such as Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and diacetone (meth)acrylamide can be used.

Among the above, from the viewpoint of improving the adhesion to the adherend while preventing wet heat whitening of the composition, the above hydrophilic monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, and acid anhydride group-containing monomers. It is preferable to use a monomer, a (meth)acrylamide-based monomer.

On the other hand, when the pressure-sensitive adhesive sheet is used for a corrosive member such as a metal or metal oxide, a hydrophilic component that does not contain a highly acidic carboxyl group or an acid anhydride is used in order to prevent corrosion deterioration of the adherend. is preferably used. From this point of view, the above hydrophilic monomers include, for example, hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate, (meth)acrylamide, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, (meth)acryloylmorpholine, hydroxyethyl (meth)acrylamide, isopropyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, phenyl (meth)acrylamide, (Meth)acrylamide-based monomers such as Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and diacetone (meth)acrylamide is preferably used.

The (meth)acrylate (co)polymer (a-1) preferably contains a macromonomer as a structural unit by introducing a macromonomer as a branch component of the graft copolymer. A macromonomer is a macromonomer having terminal functional groups and a high molecular weight backbone component.

The glass transition temperature (Tg) of the macromonomer is preferably higher than the glass transition temperature of the copolymer component constituting the (meth)acrylate (co)polymer (a-1).
Specifically, the glass transition temperature (Tg) of the macromonomer affects the heating and melting temperature (hot melt temperature) of the adhesive sheet, so it is preferably 30 ° C. to 120 ° C., especially 40 ° C. or higher or 110 ° C. °C or below, more preferably 50°C or above or 100°C or below.

If the macromonomer has such a glass transition temperature (Tg), by adjusting the molecular weight, it is possible to maintain excellent workability and storage stability, and it is adjusted so that it hot melts at around 50 to 80 ° C. be able to.
The glass transition temperature of the macromonomer means the glass transition temperature of the macromonomer itself, which can be measured with a differential scanning calorimeter (DSC).

In addition, at room temperature, the branch components attract each other to maintain a state of physical cross-linking as a resin composition. It is also preferable to adjust the molecular weight and content of the macromonomer so that the properties can be obtained.

From this point of view, the macromonomer is preferably contained in the (meth)acrylic acid ester (co)polymer (a-1) at a rate of 5% by mass to 30% by mass, especially 6% by mass or more or 25% by mass. % or less, preferably 8% by mass or more or 20% by mass or less.
The number average molecular weight of the macromonomer is preferably 500 to 100,000, preferably less than 8,000, more preferably 800 or more or less than 7,500, more preferably 1,000 or more or less than 7,000.

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 backbone 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 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, 2-phenoxyethyl (meth)acrylate , 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO-modified (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, (Meth)acrylate monomers such as benzyl (meth)acrylate, hydroxyalkyl (meth)acrylate, (meth)acrylic acid, glycidyl (meth)acrylate, alkoxyalkyl (meth)acrylate, alkoxypolyalkylene glycol (meth)acrylate, and styrene , t-butyl styrene, α-methyl styrene, vinyl toluene, alkyl vinyl monomers, alkyl vinyl esters, alkyl vinyl ethers, hydroxyalkyl vinyl ethers, (meth)acrylonitrile, (meth)acrylamides, N-substituted (meth)acrylamides, and other vinyl monomers, which can be used alone or in combination of two or more.

[Crosslinking agent (b)]
As the cross-linking agent (b), a cross-linking agent having at least double bond cross-linking is preferable. At least one crosslinkable functional group selected from, for example, (meth)acryloyl groups, epoxy groups, isocyanate groups, carboxyl groups, hydroxyl groups, carbodiimide groups, oxazoline groups, aziridine groups, vinyl groups, amino groups, imino groups, and amide groups and may be used alone or in combination of two or more.
Also included is a mode in which the cross-linking agent (b) is chemically bonded to the (meth)acrylate (co)polymer (a).

As described above, the peaks or shoulders present in the molecular weight region of 400,000 or more and less than 2,000,000 are the three-dimensional network structure of the cross-linking agent and the photoinitiator, and the cross-linking agent and the (meth)acrylic acid ester copolymer. It can be considered that this is formed due to the increase in molecular weight due to the reaction to the extent that does not form Therefore, the molecular weight, the number of functional groups and the content of the cross-linking agent affect the molecular weight and peak intensity of the peak or shoulder present in the molecular weight range of 400,000 or more and less than 2,000,000 in the molecular weight distribution of the adhesive sheet.

From this point of view, it is preferable to use a polyfunctional (meth)acrylate as the cross-linking agent (b). Here, polyfunctional refers to having two or more crosslinkable functional groups.
In addition, you may have 3 or more and 4 or more crosslinkable functional groups as needed.
Moreover, the crosslinkable functional group may be protected with a deprotectable protecting group.

Examples of the polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1, 6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecane dimethacrylate, tricyclodecanedimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A poly Propoxy di (meth) acrylate, bisphenol F polyethoxy di (meth) acrylate, ethylene glycol di (meth) acrylate, neopentyl 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 Acrylates, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentylglycol hydroxybivalate di(meth)acrylate , di(meth)acrylate of ε-caprolactone adduct of neopentene glycol hydroxybivalate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, etc. In addition to UV-curable polyfunctional (meth)acrylic monomers, polyfunctional (meth)acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyether (meth)acrylate, etc. can be mentioned. These may be used singly or in combination of two or more.

From the above viewpoint, the molecular weight of the cross-linking agent is preferably 100 to 1000, especially 200 or more or 600 or less, and the number of functional groups is 2 to 6, especially 2 or more or 4 or less. .

Also from the above viewpoint, the content of the cross-linking agent (b) is 0.5 to 50 parts by mass, preferably 1 part by mass or more, relative to 100 parts by mass of the (meth)acrylate (co)polymer (a) 40 parts by mass or less, preferably 5 parts by mass or more or 30 parts by mass or less.

[Photoinitiator (c)]
The photoinitiator (c) functions as a reaction initiation aid in the cross-linking reaction of the above-described cross-linking agent (b). Among the photoinitiators (c), photoinitiators sensitive to ultraviolet rays having a wavelength of 380 nm or less are preferable from the viewpoint of ease of control of the cross-linking reaction.
On the other hand, a photoinitiator sensitive to light with a wavelength longer than 380 nm is preferable in that high photoreactivity can be obtained and sensitive light can easily reach deep into the pressure-sensitive adhesive sheet.

Photoinitiators are broadly classified into two groups according to the radical generation mechanism: cleavage-type photoinitiators that can generate radicals by cleaving and decomposing the single bond of the photoinitiator itself; and a hydrogen abstraction type photoinitiator capable of forming an exciplex with a hydrogen donor and transferring hydrogen of the hydrogen donor.

Among these, the cleavable photoinitiator decomposes into another compound when radicals are generated by light irradiation, and once excited, it loses its function as an initiator. Therefore, it is preferable because it does not remain as an active species in the adhesive after the cross-linking reaction is completed, and there is no possibility that the adhesive will be unexpectedly deteriorated by light.

On the other hand, hydrogen abstraction type photoinitiators do not produce decomposed products like cleavage type photoinitiators during the radical generation reaction caused by irradiation with active energy rays such as ultraviolet rays, so they are less likely to become volatile components after the reaction is completed, and they do not adhere to adherends. It is useful in that it can reduce the damage of

In the present invention, it is preferable to use a hydrogen abstraction type initiator as the photoinitiator (c) from the viewpoint of reducing damage to the adherend.
Further, for example, when a high-molecular-weight reaction product is generated by irradiating a small amount of light for temporary curing, the photoinitiator is not deactivated in the temporary curing step, which is preferable.

Examples of the cleavage-type photoinitiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenylketone, 2-hydroxy-2-methyl-1-phenyl-propane-1- one, 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-(4-methylbenzyl)-2-dimethylamino-1-(4-morpholinophenyl) butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]- 1-[4-(4-morpholinyl)phenyl]-1-butanone, 1,2-octanedione, 1-(4-(phenylthio),2-(o-benzoyloxime)), 1-[9-ethyl- 6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone 1-(O-acetyloxime), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6 -trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide, derivatives thereof, etc. can be mentioned.

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, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, methyl 2-benzoylbenzoate, methyl benzoylformate, bis(2-phenyl) -2-oxoacetic acid)oxybisethylene, 4-(1,3-acryloyl-1,4,7,10,13-pentoxotridecyl)benzophenone, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2, Examples include 4-dimethylthioxanthone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, camphorquinone and derivatives thereof.
However, the photoinitiator (c) is not limited to the substances listed above. Any one of the photoinitiators (c) listed above or a derivative thereof may be used, or two or more thereof may be used in combination.

Among these, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine are preferred in terms of high sensitivity to light and discoloration as decomposition products after reaction. Acylphosphine oxide photoinitiators such as oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide are preferred.
Further, from the viewpoint of ease of reaction control, the photoinitiator (c) may be benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3′-dimethyl-4- Methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, methyl 2-benzoylbenzoate, benzoyl It is preferable to use methyl formate and the like.

The content of the photoinitiator (c) is not particularly limited. As a guideline, 0.1 to 10 parts by mass, especially 0.5 parts by mass or more or 5 parts by mass or less, especially 1 part by mass per 100 parts by mass of the (meth)acrylic acid ester (co)polymer (a) It is preferably contained in a proportion of 3 parts by mass or more.
By setting the content of the photoinitiator (c) within the above range, appropriate reaction sensitivity to light can be obtained.

Furthermore, it is also possible to use a sensitizer in addition to the photoinitiator (c) component. The sensitizer is not particularly limited, and any sensitizer used for photoinitiators can be used without any problem. Examples include aromatic amines, anthracene derivatives, anthraquinone derivatives, coumarin derivatives, thioxanthone derivatives, phthalocyanine derivatives, aromatic ketones such as benzophenone, xanthone, thioxanthone, Michler's ketone, 9,10-phenanthraquinone, and derivatives thereof. be able to.

[Other ingredients]
The present resin composition is blended in a normal adhesive composition in addition to the (meth)acrylic acid ester (co)polymer (a), the cross-linking agent (b) and the photoinitiator (c) described above. may contain known ingredients. For example, tackifying resins, antioxidants, light stabilizers, metal deactivators, rust inhibitors, anti-aging agents, moisture absorbers, anti-hydrolysis agents, anti-static agents, anti-foaming agents, inorganic particles, etc. It is possible to appropriately contain the additive of.

(Rust inhibitor (d))
The present resin composition preferably contains a rust inhibitor (d) in order to prevent corrosion of metals such as silver and copper.
Examples of specific antirust agents include benzotriazole compounds, benzimidazole compounds, benzothiazole compounds, other triazole derivatives, and the like.
Among these, one or more selected from benzotriazole compounds, 1,2,3-triazole and 1,2,4-triazole are preferred.

Triazole derivatives such as 1,2,3-triazole and 1,2,4-triazole are preferred, particularly 1,2,3 - triazole is preferred. The reason for this is presumed that corrosion can be prevented by forming a protective film in which copper atoms and triazole molecules are chemically bonded to the surface of the conductor pattern formed of a metal material containing copper. It is from. In addition, the effect of the protective film of triazole can be similarly obtained in a conductive member having a conductor pattern formed of a metal material containing silver.

<Structure of double-sided adhesive sheet with release film>
The pressure-sensitive adhesive sheet can also be a double-sided pressure-sensitive adhesive sheet with a release film.
For example, a release film-attached double-sided pressure-sensitive adhesive sheet can be obtained by molding a single-layer or multi-layer sheet-like main pressure-sensitive adhesive sheet (main pressure-sensitive adhesive sheet after curing) on a release film.

As a material for such a release film, a known release film can be appropriately used. For example, polyester film, polyolefin film, polycarbonate film, polystyrene film, acrylic film, triacetyl cellulose film, fluororesin film, etc., coated with silicone resin for release treatment, release paper, etc. can be selected as appropriate. can be used.

When a release film is laminated on both sides of the pressure-sensitive adhesive sheet, one release film may have the same lamination structure or material as the other release film, or may have a different lamination structure or material. good.
Also, they may have the same thickness or different thicknesses.
In addition, release films with different peel strengths and release films with different thicknesses can be laminated on both sides of the pressure-sensitive adhesive sheet.

The thickness of the release film is not particularly limited. Among them, the thickness is preferably 25 μm to 500 μm, more preferably 38 μm or more or 250 μm or less, and more preferably 50 μm or more or 200 μm or less, from the viewpoint of workability and handleability.

The pressure-sensitive adhesive sheet employs a method of directly extruding the pressure-sensitive adhesive composition or a method of molding by injecting into a mold without using an adherend or release film as described above. You can also
Furthermore, the present pressure-sensitive adhesive sheet can be formed by directly filling the pressure-sensitive adhesive composition between constituent members for an image display device, which are adherends.

<Manufacturing method of this adhesive sheet>
In addition to the (meth)acrylic acid ester (co)polymer (a), the resin composition may optionally contain a cross-linking agent (b), a photoinitiator (c), a rust inhibitor (d), and other obtained by mixing predetermined amounts of each of the components.
The mixing method of these components is not particularly limited, and the mixing order of each component is also not particularly limited. Further, a heat treatment step may be added during the production of the composition, and in this case, it is desirable to mix the components of the present resin composition in advance and then perform the heat treatment.
Also, a masterbatch obtained by concentrating various mixed components may be used.

The device for mixing is not particularly limited, and for example, a universal kneader, a planetary mixer, a Banbury mixer, a kneader, a gate mixer, a pressure kneader, three rolls or two rolls can be used. You may mix using a solvent as needed.
In addition, the present resin composition can be used as a solventless system containing no solvent. When used as a solvent-free system, no solvent remains and the advantage of improved heat resistance and light resistance can be provided.
From this point of view as well, the present resin composition preferably contains a (meth)acrylate (co)polymer (a), a cross-linking agent (b), and a photoinitiator (c).

The pressure-sensitive adhesive sheet can be produced by applying (coating) the resin composition prepared as described above on a base sheet or a release sheet in a melted state by heat, and then cooling.
Further, for example, the present pressure-sensitive adhesive sheet having a laminated structure is obtained by applying (coating) the present resin composition on a base sheet or a release sheet in a state of being melted by heat, and then cooling to form the first layer. is formed, the present resin composition is applied (coated) on the formed first layer, and then cooled to form a second layer. is melted by heating, the first and second layers are formed in the same manner as described above, and then the respective coated (coated) surfaces are bonded together, or the present resin composition is It can be manufactured by a method of melting by heating and simultaneously forming the first layer and the second layer by co-extrusion molding.

The coating (coating) method is not particularly limited as long as it is a general coating method, and examples thereof include roll coating, die coating, gravure coating, comma coating, screen printing and the like.

<Laminate for configuring image display device>
The laminate for constituting an image display device of the present invention (hereinafter also referred to as "this laminate") has a structure in which two constituent members for an image display device are laminated via the present pressure-sensitive adhesive sheet. .

Examples of constituent members for image display devices include image display panels, surface protection panels, touch sensors, and optical films, and more specifically, combinations of two or more thereof.

Examples of the image display panel include liquid crystal displays, organic EL displays, electronic paper displays, plasma displays, and quantum dot displays. or equipment.

Examples of the surface protection panel include a bendable or bendable member that is made of a material such as thin plate glass or plastic and is positioned on the outermost layer side to protect against external impact, such as a cover film. be able to. Alternatively, a touch panel function may be integrated, such as a touch-on-lens (TOL) type or a one glass solution (OGS) type.
Further, the surface protection panel may have a printed stepped portion printed in a frame shape on the peripheral portion thereof.

Examples of the touch sensor include a bendable or bendable member having a sensor function and having a touch sensor mounted on a base material such as thin plate glass or plastic.
Further, an in-cell type image display panel having a built-in touch function in the image display panel and an on-cell type image display panel having a touch panel function built in between the polarizing plate and the image display panel are also included in the touch sensor.

As the optical film, for example, a polarizing film, a retardation film, an optical filter, an antireflection film, a near-infrared cut film, an electromagnetic wave shielding film, etc., which is mounted inside a flexible display and exhibits an optical function and can be bent or bent. can be mentioned.

Further, the composition of the laminate is as follows: image display panel/adhesive sheet/touch sensor, image display panel/adhesive sheet/surface protection panel, touch sensor/adhesive sheet/surface protection panel, image display panel/adhesive Sheet/touch sensor/this pressure-sensitive adhesive sheet/surface protection panel, optical film/this pressure-sensitive adhesive sheet/touch sensor, or optical film/this pressure-sensitive adhesive sheet/touch sensor/this pressure-sensitive adhesive sheet/surface protection panel are preferable.

<Method for producing a laminate for constituting an image display device>
After laminating two constituent members for an image display device through the pressure-sensitive adhesive sheet, the laminated body is obtained by irradiating light from at least one of the constituent members of the image display device, through the constituent members of the image display device. The adhesive sheet can be produced by photocuring.
At this time, photocuring is preferably performed so that the gel fraction of the pressure-sensitive adhesive sheet becomes 30% or more.

<Image display device>
The image display device of the present invention (hereinafter also referred to as "this device") is an image display device having this laminate, and includes, for example, a personal computer, a mobile terminal (PDA), a game machine, a television (TV), a car navigation system, and a touch panel. , an image display device such as a pen tablet.

<Explanation of terms, etc.>
In the present invention, "(meth)acrylic" means acrylic and methacrylic, "(meth)acryloyl" means acryloyl and methacryloyl, and "(meth)acrylate" means acrylate and methacrylate, respectively. .

In the present invention, the term "film" includes the "sheet", and the term "sheet" includes the "film".
In addition, the expression "panel" such as an image display panel, a protective panel, etc. includes a plate, a sheet and a film.

In the present invention, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" or "preferably Y It also includes the meaning of "less than".
In addition, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably greater than X" unless otherwise specified, and is described as "Y or less" (Y is an arbitrary number). If not otherwise specified, it also includes the meaning of "preferably smaller than Y".

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is by no means limited to the following examples.

<Example 1>
(Meth)acrylic acid ester (co)polymer (a): 15 parts by mass of macromonomer (number average molecular weight: 2500, Tg: 105°C) consisting of methyl methacrylate as branch component, 81 parts by mass of n-butyl acrylate as trunk component/acrylic 1 kg of a copolymer (A-1, weight average molecular weight of 300,000) consisting of 4 parts by mass of acid, 100 g of propoxylated pentaerythritol triacrylate (“B-1”, molecular weight of 530 g/mol) as a cross-linking agent (b), light As an initiator (c), 15 g of a mixture (c-1) of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone was uniformly melted and kneaded to prepare a resin composition 1.
The resin composition 1 was sandwiched between two peel-treated polyethylene terephthalate films (Diafoil MRF manufactured by Mitsubishi Chemical Corporation, thickness 75 μm / Diafoil MRT manufactured by Mitsubishi Chemical Corporation, thickness 38 μm), and the thickness was 150 μm. It was shaped into a sheet at a temperature of 80° C. so that
A transparent double-sided pressure-sensitive adhesive sheet 1 was prepared by irradiating light from one side of the polyethylene terephthalate film with a high-pressure mercury lamp so that the integrated amount of light at a wavelength of 365 nm would be 100 mJ/cm ² .
The transparent double-sided pressure-sensitive adhesive sheet 1 is in a temporarily cured state, in other words, photocurable, and leaves room for curing by light irradiation.

<Example 2>
The resin composition 1 prepared in the same manner as in Example 1 was formed into a sheet having a thickness of 150 μm in the same manner as in Example 1, and from one side of the polyethylene terephthalate film, the integrated light amount at a wavelength of 365 nm was 250 mJ. A transparent double-sided pressure-sensitive adhesive sheet ² was produced by irradiating light from a high-pressure mercury lamp so as to have a density of 1/cm 2 and curing slightly.
The transparent double-sided pressure-sensitive adhesive sheet 2 is also in a temporarily cured state, in other words, photocurable, leaving room for curing by light irradiation.

<Comparative Example 1>
A resin composition 1 prepared in the same manner as in Example 1 was formed into a sheet having a thickness of 150 μm in the same manner as in Example 1, and a transparent double-sided pressure-sensitive adhesive sheet 3 was prepared without curing.

<Comparative Example 2>
The resin composition 1 prepared in the same manner as in Example 1 was formed into a sheet having a thickness of 150 μm in the same manner as in Example 1, and from one side of the polyethylene terephthalate film, the integrated light amount at a wavelength of 365 nm was 600 mJ. /cm ² by irradiating with light from a high-pressure mercury lamp and pre-curing, to produce a transparent double-sided pressure-sensitive adhesive sheet 4 before main curing.

<Comparative Example 3>
(Meth)acrylic acid ester (co)polymer (a), a copolymer (A-2, weight average molecular weight 400,000 ) 1 kg, 50 g of nonanediol diacrylate (b-2) as a cross-linking agent (b), and 15 g of 4-methylbenzophenone (c-2) as a photoinitiator (c) are uniformly melted and kneaded to form a resin composition. 2 was produced.
The resin composition 2 was sandwiched between two peel-treated polyethylene terephthalate films (Diafoil MRF manufactured by Mitsubishi Chemical Corporation, thickness 75 μm / Diafoil MRT manufactured by Mitsubishi Chemical Corporation, thickness 38 μm), and the thickness was 150 μm. It was shaped into a sheet at a temperature of 80° C. so that
From one polyethylene terephthalate film side, the transparent double-sided pressure-sensitive adhesive sheet 5 was cured by irradiating light from a high-pressure mercury lamp so that the integrated amount of light at a wavelength of 365 nm was 600 mJ/cm ² and allowed to stand at room temperature for 12 hours. was made.

"Evaluation of the physical properties"
The physical properties of the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 obtained in Examples and Comparative Examples were evaluated as follows.

<Molecular weight>
A measurement sample was prepared by dissolving 4 mg of the transparent double-sided adhesive sheets 1 to 5 using 12 mL of THF, and a gel permeation chromatography (GPC) analyzer (device name: HLC-8320GPC manufactured by Tosoh Corporation) was used. Using, measure the molecular weight distribution curve under the following conditions, weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), maximum peak molecular weight (Mp), molecular weight of 400,000 or more and less than 2 million region peak or shoulder The ratio of the peak or shoulder intensity in the molecular weight region of 400,000 or more and less than 2,000,000 to the peak intensity of the maximum peak molecular weight (Mp) was determined.
・Guard column: TSKguardcolumnH _XL
・Separation column:
TSKgelGMH _XL (4 pieces)
・Temperature: 40℃
・Injection volume: 100 μL
・Polystyrene equivalent ・Solvent: THF
・Flow rate: 1.0 mL/min

<Storage elastic modulus G'>
The storage elastic moduli G' of the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 were measured under the following conditions using a viscoelasticity measuring device Dynamic Analyzer RDA II manufactured by Rheometrics.
・Temperature: 20 to 150°C
・Angular frequency: ω = 0.005 to 500 rad/sec
・Parallel plate: 20mmφ
・Distortion amount: 3%

Using temperatures of 20° C. and 80° C. as reference temperatures, a temperature-time conversion master curve is created, the frequency f value is calculated from f (Hz) = ω / (2π), and the storage elastic modulus G 'at each frequency is calculated. read.

<Gel fraction>
The release films of the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 are peeled off on both sides, and about 0.4 g of each of the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 is collected, and the mass (X) is measured in advance with a SUS mesh (#200). The material was wrapped in a bag, the mouth of the bag was folded and closed, and the weight (Y) of this package was measured. After that, the package was immersed in 50 mL of ethyl acetate for 24 hours, then taken out and vacuum-dried at 70°C for 4.5 hours to evaporate the adhering ethyl acetate, and the mass (Z) of the dried package was measured. , the obtained mass was substituted into the following formula to obtain the gel fraction (before main curing).
Gel fraction [%] = [(ZX) / (YX)] × 100

Regarding the gel fraction after the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 were further cured (after the main curing), the integrated amount of light at a wavelength of 365 nm from one release film side of the transparent double-sided pressure-sensitive adhesive sheet was 4000 mJ/cm ² . After curing by irradiating light with a high-pressure mercury lamp so as to obtain the desired thickness, the sample was left to stand at room temperature for 12 hours and used for measurement.

<Holding force test>
The transparent double-sided adhesive sheets 1 to 5 with a thickness of 150 μm prepared in Examples and Comparative Examples were cut into 40 mm × 50 mm, the release film on one side was peeled off, and a polyethylene terephthalate film for backing (manufactured by Mitsubishi Chemical Corporation, Diafoil S-100, thickness 38 μm) was pasted on the back with a hand roller, and cut into strips of width 25 mm×length 100 mm to obtain test pieces.
Next, the remaining release film was peeled off and attached to a stainless steel plate (120 mm x 50 mm x 1.2 mm thick) with a hand roller so that the attachment area was 25 mm x 20 mm.
Then, after curing the test piece for 15 minutes in an atmosphere of 40 ° C., after hanging a weight of 500 gf (4.9 N) attached to the test piece in the vertical direction and leaving it to stand, the weight drop time (minutes) was measured. It was measured.
For those that did not fall within 30 minutes, the length (mm) by which the bonding position between the SUS and the test piece deviated downward, that is, the amount of deviation was measured.

<Storage stability>
The above transparent double-sided pressure-sensitive adhesive sheets 1 to 5 were cut to 50×50 mm using a Thomson punching machine with the release film still laminated. After peeling off the single-sided release film, only the adhesive is cut to 30 x 30 mm, and the peeled single-sided release film is pasted together with a roll, so that the double-sided release film is 50 x 50 mm and the adhesive is cut to 30 x 30 mm. A processed product was produced.
The cut products of these adhesive sheets 1 to 5 were laminated so as to be sandwiched between glass plates of 50 mm × 50 mm × 1 mm in thickness, and a weight of 500 g was placed on the top glass plate and left at 40 ° C. for 200 hours. .
If the adhesive sheet was significantly crushed after curing and the paste protruded from the edge by 0.1 mm or more, it was rated as "Poor". good)".

<Step absorption>
The above transparent double-sided pressure-sensitive adhesive sheets 1 to 5 were cut to 50×80 mm using a Thomson punching machine with the release film laminated. Peel off the release film on one side, and apply the exposed adhesive surface to the printed surface of soda lime glass (82 mm × 53 mm × 0.5 mm thick) printed with a thickness of 80 μm on the peripheral edge of 5 mm. It was press-bonded using a vacuum press machine so that the edge was on the printing step (temperature 80° C., press pressure 0.04 MPa). Next, the remaining release film was peeled off, and a cycloolefin polymer film (manufactured by Nippon Zeon Co., Ltd., thickness 100 μm) was press-bonded, followed by autoclave treatment (80 ° C., gauge pressure 0.2 MPa, 20 minutes) and finish bonding. to produce a laminate.
Visually observe the produced laminate, and if the adhesive sheet does not follow the printed steps and air bubbles remain, or if uneven unevenness due to the film bending and distorting near the steps is seen, "Poor", air bubbles A smooth lamination without unevenness was evaluated as "good".

<Adhesive strength>
One of the release films of the transparent double-sided pressure-sensitive adhesive sheets 1 to 5 was peeled off, and a 50 μm polyethylene terephthalate film (manufactured by Mitsubishi Chemical Corporation, Diafoil T100, thickness 50 μm) was laminated as a backing film. After the laminate was cut to a length of 150 mm and a width of 10 mm, the remaining release film was peeled off, and the exposed adhesive surface was roll-pressed to soda-lime glass.
After autoclave treatment (80° C., gauge pressure 0.2 MPa, 20 minutes) was applied to the laminated product, the adhesive sheet was cured by irradiating ultraviolet rays at 365 nm so that the integrated light amount was 4000 mJ/cm ² . , cured at room temperature for 12 hours to prepare a sample for peel strength measurement.
The peel force measurement sample was peeled off at a peel angle of 180° and a peel speed of 60 mm/min in an environment of 23°C and 40% RH, and the peel force (N/cm) against glass was measured.

<Reliability against foaming>
Among the stepped glass/adhesive sheet/COP laminates produced in the step absorption evaluation, the samples that were smoothly laminated without air bubbles or irregularities had an integrated amount of light at a wavelength of 365 nm from the COP side of 4000 mJ/cm ² . Light was irradiated from a high-pressure mercury lamp so as to obtain a final curing. After standing at room temperature for 12 hours, the appearance was visually evaluated after being stored in an environment of 65° C. and 90% RH for 500 hours.
Those in which deformation, foaming, or peeling of the adhesive sheet occurred after the environmental test were evaluated as "poor", and those in which no deformation, foaming, or peeling of the adhesive sheet occurred were evaluated as "good".

Table 1 shows the evaluation results of Examples and Comparative Examples.

The transparent double-sided pressure-sensitive adhesive sheets of Examples 1 and 2, in which the (meth)acrylic acid ester copolymer was slightly cured (temporarily cured) to such an extent that it did not form a three-dimensional network structure, to generate a reaction product with a high molecular weight, , showing high holding power and excellent storage stability.
Furthermore, even after pre-curing, fluidity due to heating is sufficiently maintained, and even if one of the adherends is a material with low rigidity, such as a film, there will be no bending near the steps, resulting in a smooth laminate. I was able to get
Furthermore, after forming a laminate, it is possible to further harden the adhesive sheet by irradiating it with light. A reliable laminate was obtained.

On the other hand, as in Comparative Example 1, the uncured transparent double-sided pressure-sensitive adhesive sheet 3 has a slightly low holding power, and a high level of storage stability cannot be obtained, assuming a harsh storage environment in summer. In the environment of 40° C. for a long time, the result was that the paste protruded remarkably.
In addition, as in Comparative Examples 2 and 3, the transparent double-sided pressure-sensitive adhesive sheets that were temporarily cured until the gel fraction reached 10% or more exhibited sufficient storage stability. Since the fluidity is impaired by the dimensional network structure, when producing a laminate, the adhesive may not be fully filled near the corners where the printing steps intersect, leaving air bubbles, or the film may bend near the printing steps. As a result, the smoothness was impaired, and the step absorbability and the reliability after lamination were inferior.

Therefore, from the above examples and the results of the tests conducted so far, the photocurable adhesive sheet containing the (meth)acrylic acid ester (co)polymer (a) as the main component resin, and the gel fraction of the adhesive sheet is 10% or less, the pressure-sensitive adhesive sheet has a weight average molecular weight (Mw) of 200,000 or more and 500,000 or less, and a molecular weight distribution (Mw/Mn) of 4 or more, as measured by gel permeation chromatography. 15 or less, and in the molecular weight distribution curve in terms of polystyrene, the maximum peak exists in the molecular weight region of 50,000 or more and less than 400,000, and the molecular weight region is 400,000 or more and less than 2,000,000 One or more peaks Alternatively, if it is a photocurable pressure-sensitive adhesive sheet characterized by the presence of a shoulder, it can be deformed following a step to fill the gap between the constituent members for the image display device. It can be considered that the shape of the pressure-sensitive adhesive sheet can be maintained and the pressure-sensitive adhesive will not protrude even after long-term storage.

The pressure-sensitive adhesive sheet of the present invention can have storage stability while maintaining various properties required for pressure-sensitive adhesive sheets, such as unevenness absorbability, adhesive strength, and anti-foaming reliability. It can also be applied to display devices.

Claims (16)

A photocurable pressure-sensitive adhesive sheet containing a (meth)acrylic acid ester (co)polymer (a) as a main component resin,
The pressure-sensitive adhesive sheet has a weight average molecular weight (Mw) of 200,000 or more and 500,000 or less, and a molecular weight distribution (Mw/Mn) of 4 or more and 15 or less, and
In the polystyrene-equivalent molecular weight distribution curve, the maximum peak exists in the molecular weight region of 50,000 or more and less than 400,000, and one or more peaks or shoulders exist in the molecular weight region of 400,000 or more and less than 2,000,000. A photo - curing pressure -sensitive adhesive sheet. 2. The photocurable pressure-sensitive adhesive sheet according to claim 1, comprising a (meth)acrylate (co)polymer (a), a cross-linking agent (b) and a photoinitiator (c). 3. The photocurable pressure-sensitive adhesive sheet according to claim 1, wherein the (meth)acrylate (co)polymer (a) is a graft copolymer using a macromonomer. 4. The photocurable polymer according to any one of claims 1 to 3, wherein the (meth)acrylic acid ester (co)polymer (a) has a weight average molecular weight (Mw) of 50,000 or more and 400,000 or less. adhesive sheet. The photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the photoinitiator (c) contains one or more hydrogen abstraction type photoinitiators. The photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which has the following viscoelastic properties of (I).
(I) Storage modulus G' of 1×10 ² Pa or more at a frequency of 10 ⁻⁵ Hz and a reference temperature of 20° C. The photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 6, which has the following viscoelastic properties of (II).
(II) Storage modulus G′ at a frequency of 10 ⁻³ Hz and a reference temperature of 80° C. is 5×10 ² Pa or less. It is attached to a stainless steel plate with an adhesion area of 25 mm × 20 mm, and the displacement length is 1.0 mm or less in a holding force test in which a load of 500 gf (4.9 N) is applied in the vertical direction at a temperature of 40 ° C. for 30 minutes. 8. The pressure- sensitive adhesive sheet having photocurability according to any one of 1 to 7. A pressure-sensitive adhesive sheet with a release film, which is obtained by laminating the photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 8 and a release film. A pressure-sensitive adhesive sheet as a photocured product of the photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive sheet has a gel fraction of 30% or more. 9. A laminate for constructing an image display device, comprising two constituent members for an image display device, which are laminated via the photocurable pressure-sensitive adhesive sheet according to any one of claims 1 to 8. 11. A laminate for image display device construction, comprising a configuration in which two constituent members for an image display device are laminated with the pressure-sensitive adhesive sheet according to claim 10 interposed therebetween. 3. The image display device constituent member is any one of the group consisting of a touch sensor, an image display panel, a surface protection panel, and a polarizing film, or a laminate composed of a combination of two or more. 13. The laminate for constituting an image display device according to 11 or 12. After laminating two image display device constituent members via the photocurable adhesive sheet according to any one of claims 1 to 8, light is irradiated from at least one image display device constituent member side, and the image A method for producing a laminate for constituting an image display device, comprising a step of photocuring the photocurable pressure-sensitive adhesive sheet through a display device constituting member. 15. The image according to claim 14, wherein when the adhesive sheet having photocurability is photocured, the photocuring is performed so that the gel fraction of the adhesive sheet after photocuring is 30% or more. A method for manufacturing a laminate for constituting a display device. An image display device comprising the laminate for image display device construction according to any one of claims 11 to 13.

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