JP7260033B2 - PSA SHEET, LAYER FOR CONSTRUCTION OF IMAGE DISPLAY DEVICE, AND IMAGE DISPLAY DEVICE - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing an ultraviolet absorber and a photoinitiator, and particularly to a pressure-sensitive adhesive sheet having ultraviolet foam resistance.

Image display devices such as personal computers, mobile terminals (PDA), game machines, televisions (TV), car navigation systems, touch panels, and pen tablets, such as plasma displays (PDP), liquid crystal displays (LCD), organic EL displays (OLED), electrophoresis In an image display device using a flat or curved image display panel such as a display (EPD) or an interferometric modulation display (IMOD), in order to ensure visibility and prevent damage, no gaps are provided between each component. , the components are integrated by sticking them together with an adhesive sheet or a liquid adhesive.

For example, in an image display device having a configuration in which a touch panel is interposed between the viewing side of a liquid crystal module and a surface protection panel, a liquid adhesive or adhesive sheet is applied between the surface protection panel and the viewing side of the liquid crystal module. The touch panel and other components, for example, the touch panel and the liquid crystal module, or the touch panel and the surface protection panel, are bonded together to be integrated.

As a method for filling the gaps between such constituent members for an image display device with an adhesive, Patent Document 1 discloses that the gaps are filled with a liquid adhesive resin composition containing an ultraviolet curable resin, and then irradiated with ultraviolet rays. A method of photocuring is disclosed.

Also known is a method of filling gaps between constituent members for an image display device using an adhesive sheet. For example, Patent Literature 2 discloses a method in which an adhesive sheet that has been primarily crosslinked with ultraviolet light is attached to a constituent member of an image display device, and then the adhesive sheet is irradiated with ultraviolet rays through the constituent member of the image display device for secondary curing. there is

By the way, some optical members used in image display devices may be deteriorated by ultraviolet rays, and in order to prevent deterioration, adhesive sheets may be required to absorb ultraviolet rays.
For example, as such a pressure-sensitive adhesive sheet, Patent Documents 3 and 4 propose a transparent pressure-sensitive adhesive sheet containing an ultraviolet absorber in the pressure-sensitive adhesive layer.

International Publication 2010/027041 Japanese Patent No. 4971529 Japanese Patent No. 5945393 JP 2015-229759 A

There are various purposes for imparting ultraviolet absorbency to the pressure-sensitive adhesive sheet.
For example, the purpose is to prevent optical members adjacent to the pressure-sensitive adhesive sheet from deteriorating due to long-term exposure to ultraviolet rays.
However, for this purpose, not only is it necessary to contain a relatively large amount of ultraviolet absorber, but also the ability to block light in a wide wavelength range of 380 nm or longer is required.
Therefore, when this type of UV absorber is included in a photocurable pressure-sensitive adhesive sheet, a photoinitiator having reactivity in a wide range of ultraviolet to visible light is used so that its photocurability is not hindered by the action of the UV absorber. It is conceivable to use a drug.
However, when such a photoinitiator is used, for example, when the photocurable pressure-sensitive adhesive sheet is stored under a fluorescent lamp, photocuring progresses gradually.

On the other hand, ultraviolet rays not only degrade the optical member, but also degrade the adhesive sheet itself, and decomposed products (outgassing) generated by the deterioration of the adhesive sheet may cause foaming and peeling. Therefore, there is a demand for a performance that can withstand foaming in the pressure-sensitive adhesive sheet due to exposure to ultraviolet light (referred to as "ultraviolet foaming resistance").

In order for the pressure-sensitive adhesive sheet to have such ultraviolet foaming resistance, the pressure-sensitive adhesive sheet after photocuring must have sufficient cohesion to withstand outgassing.
However, when the UV absorber is included in the photocurable adhesive sheet, simply increasing the content of the UV absorber in order to reduce the effects of UV rays will not allow the UV absorber to act as a plasticizer and cause the adhesive sheet to absorb the light. Since there is a possibility of inhibiting curability, it is necessary to examine from a completely different point of view from such a way of thinking.

Accordingly, the present invention relates to a photocurable pressure-sensitive adhesive sheet containing an ultraviolet absorber, and an object thereof is to provide a new pressure-sensitive adhesive sheet having ultraviolet foam resistance without impairing photocuring performance.

The present invention has a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing an ultraviolet absorber and a photoinitiator, wherein the ultraviolet absorber has an absorption coefficient of 1×10 ³ mL/(g cm) or more, and the absorption coefficient at a wavelength of 380 nm is less than 1 × 10 ³ mL / (g cm), and the pressure-sensitive adhesive composition has a total mass of the pressure-sensitive adhesive composition Proposed is a pressure-sensitive adhesive sheet characterized by containing the above-described ultraviolet absorber at a rate of 0.1 to 1.6% by mass.

The pressure-sensitive adhesive sheet proposed by the present invention uses an ultraviolet absorber having a specific absorption coefficient in a specific wavelength region, and by defining the content ratio of the ultraviolet absorber, it is possible to enjoy the desired effect. That is, since the ultraviolet absorber blocks transmission of short-wavelength ultraviolet rays, outgassing from the adhesive sheet can be reduced even when the adhesive sheet is exposed to ultraviolet rays. At this time, by specifying the content of the ultraviolet absorber, it is possible to prevent the ultraviolet absorber from acting as a plasticizer by itself and lowering the cohesive force of the adhesive sheet, and also obtain heat-resistant foaming properties at high temperatures. be able to.

Furthermore, by using a photoinitiator with an absorption coefficient of less than 10 mL/(g cm) at a wavelength of 405 nm, the photoinitiator is not activated in the visible light wavelength range, so It is possible to prevent photocuring even when stored in an environment exposed to visible light such as.
In addition, by specifying the content ratio of the ultraviolet absorber and the metal corrosion inhibitor, and by using a specific metal corrosion inhibitor in particular, it is possible to obtain anti-metal corrosion resistance without inhibiting the photocurability of the photoinitiator. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an evaluation test method for silver corrosion resistance reliability in Examples described later, (A) is a top view of a sample for silver corrosion resistance reliability evaluation, and (B) is a silver corrosion resistance reliability evaluation. FIG. 2 is a cross-sectional view of a sample for use;

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

<This adhesive sheet>
A pressure-sensitive adhesive sheet (hereinafter referred to as "this pressure-sensitive adhesive sheet") according to an example of an embodiment of the present invention is a pressure-sensitive adhesive composition (hereinafter referred to as "this pressure-sensitive adhesive composition") containing an ultraviolet absorber and a photoinitiator.
) has an adhesive layer formed from

The pressure-sensitive adhesive sheet may have at least one layer of the pressure-sensitive adhesive layer, and may have a multilayer structure of two or more layers. There may be intervening layers. In this case, all the pressure-sensitive adhesive layers may be formed from the present pressure-sensitive adhesive composition, or at least the outermost layer may be formed from the present pressure-sensitive adhesive composition.

(Thickness of this adhesive sheet)
The thickness of the adhesive sheet is preferably 10 μm or more and 500 μm or less.
By reducing the thickness of the sheet, it is possible to meet the demand for thinner thickness. It may become impossible.
Therefore, from such a viewpoint, the thickness of the pressure-sensitive adhesive sheet is preferably 10 μm or more and 500 μm or less, more preferably 15 μm or more or 400 μm or less, and more preferably 20 μm or more or 350 μm or less. preferable.

<Present adhesive composition>
The adhesive composition contains an ultraviolet absorber and a photoinitiator. In addition, if necessary, it may contain a (meth)acrylic acid ester (co)polymer, a cross-linking agent, a metal corrosion inhibitor and other components.
The term "(co)polymer" is meant to include homopolymers and copolymers, and the term "(meth)acrylate" is meant to include acrylates and methacrylates.

(Ultraviolet absorber)
The ultraviolet absorber has an absorption coefficient of 1×10 ³ mL/(g cm) or more at a wavelength of 340 nm, and an absorption coefficient of less than 1×10 ³ mL/(g cm) at a wavelength of 380 nm. is preferred.
The ultraviolet absorber has such a light absorption property, that is, the wavelength range of ultraviolet rays to be absorbed is narrow, or more specifically, the property of blocking only relatively short-wavelength ultraviolet rays. Inhibition of curing by the agent can be suppressed.
Moreover, even if the content of the ultraviolet absorber is reduced, the ultraviolet foaming resistance can be maintained.
From this point of view, the ultraviolet absorber more preferably has an absorption coefficient of 2×10 ³ mL/(g·cm) or more at a wavelength of 340 nm, and more preferably 3×10 ³ mL/(g·cm) or more. Among them, it is more preferably 3.5×10 ³ mL/(g·cm) or more.
In addition, the ultraviolet absorber more preferably has an absorption coefficient at a wavelength of 380 nm of less than 8 × 10 ² mL/(g cm), especially less than 7 × 10 ² mL/(g cm). More preferably less than 6×10 ² mL/(g·cm).

More preferably, the ultraviolet absorber has an absorption coefficient of less than 1×10 ² mL/(g·cm) at a wavelength of 405 nm.
When the absorption coefficient of the ultraviolet absorber at a wavelength of 405 nm is within the range, it is possible to suppress the hue of the pressure-sensitive adhesive sheet, specifically yellowishness. In addition, hue change can be suppressed.
From this point of view, the ultraviolet absorber preferably has an absorption coefficient of less than 1×10 ² mL/(g cm) at a wavelength of 405 nm, especially less than 8× ¹⁰ mL/(g cm). Among them, it is more preferably less than 5×10 ¹ mL/(g·cm).

Further, it is preferable that the ultraviolet absorber has a melting point of 100° C. or less.
When the melting point of the ultraviolet absorber is 100° C. or lower, it is excellent in dispersibility when mixed in the pressure-sensitive adhesive composition, and can be easily mixed uniformly.
Therefore, the melting point of the ultraviolet absorber is preferably 100° C. or lower, more preferably -50° C. or higher or 50° C. or lower.

Examples of the ultraviolet absorber include those having one or more structures selected from the group consisting of a benzotriazole structure, a benzophenone structure, a triazine structure, a benzoate structure, an oxalanilide structure, a salicylate structure and a cyanoacrylate structure. Among these, one having a predetermined absorption coefficient may be selected.
Among them, it is preferable to select one having a benzophenone structure from the viewpoint of adjustment of the absorption coefficient, compatibility with the pressure-sensitive adhesive, stability when added simultaneously with other various additives, and the like.

The absorption coefficient at the measurement wavelength of 340 nm can be measured by, for example, placing a solution diluted with a solvent (acetonitrile, acetone) that does not absorb light at the measurement wavelength into a quartz cell and measuring the absorbance. The extinction coefficient can be calculated by the following formula.
α340=A340×d/c
α340: extinction coefficient at wavelength 340 nm [mL/(g cm)]
A340: absorbance at wavelength 340 nm c: solution concentration [g/mL]
d: Optical path length (of quartz cell) [cm]

Also, when calculating the extinction coefficient, the absorbance converted from the measurement result of the transmittance may be used.
A340=-Log(T340/100)
T340: Light transmittance [%] at a wavelength of 340 nm

The absorption coefficient at a wavelength of 380 nm or 405 nm can also be obtained by the same method as above.

The pressure-sensitive adhesive composition preferably contains the ultraviolet absorber in a proportion of 0.1 to 1.6% by weight with respect to the total weight of the pressure-sensitive adhesive composition.
By containing the ultraviolet absorber in such a ratio, there is no risk of curing inhibition when the present pressure-sensitive adhesive sheet is photocured, and the ultraviolet absorber does not plasticize the pressure-sensitive adhesive more than necessary. Since cohesive force can be imparted, the pressure-sensitive adhesive sheet can have excellent ultraviolet foam resistance.
From such a point of view, the ultraviolet absorber is preferably contained in a proportion of 0.1 to 1.6% by mass with respect to the total mass (100% by mass) of the pressure-sensitive adhesive composition, especially 0.2% by mass. or more or 1.4% by mass or less, among them 0.3% by mass or more or 1.0% by mass or less, and further among them, 0.4% by mass or more or 0.9% by mass or less preferable.
From the above, the ultraviolet absorber is 0.1 to 1.4% by mass, 0.1 to 1.0% by mass, or 0.1 to 0.1% by mass with respect to the total mass (100% by mass) of the adhesive composition. It is preferably contained at a rate of .9% by mass, 0.2 to 1.6% by mass, 0.2 to 1.4% by mass, 0.2 to 1.0% by mass, or 0.2 to 0.9% by mass. More preferably, it is contained in a proportion of 0.3 to 1.6% by mass, 0.3 to 1.4% by mass, 0.3 to 1.0% by mass, or 0.3 to 0.9% by mass %, 0.4 to 1.6% by mass, 0.4 to 1.4% by mass, 0.4 to 1.0% by mass, or 0.4 to 0.9% by mass is most preferably contained in a ratio of

From the same point of view, in the present pressure-sensitive adhesive composition, the ultraviolet absorber is preferably contained in a proportion of 30 to 100 parts by mass with respect to 100 parts by mass of the photoinitiator, especially 40 parts by mass or more or 95 parts by mass. In the following, it is more preferable to contain at a ratio of 50 parts by mass or more or 90 parts by mass or less.

(photoinitiator)
As the photoinitiator, a photoinitiator having an absorption coefficient of less than 10 mL/(g·cm) at a wavelength of 405 nm is particularly preferred.
A photoinitiator having such an absorption coefficient has a low activity in the visible light region, so that it is unlikely that photocuring will proceed even when stored under a fluorescent lamp, resulting in a PSA sheet with excellent storage stability. Obtainable.
From this point of view, it is more preferable to use a photoinitiator with an absorption coefficient of less than 8 mL/(g cm) at a wavelength of 405 nm, and a photoinitiator with an absorption coefficient of 5 mL/(g cm) or less at a wavelength of 405 nm. It is particularly preferred to use

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 initiator capable of forming an exciplex with a hydrogen donor and transferring hydrogen of the hydrogen donor.
Among them, a hydrogen abstraction type initiator is preferable as the photoinitiator contained in the present pressure-sensitive adhesive composition.
The hydrogen abstraction type is more likely to obtain cohesion after photocuring, and is superior in durability such as heat-resistant foamability.
In addition, unlike the cleavage type, there is no fear that decomposition products will adversely affect corrosion, so it is not only easy to balance with metal corrosion resistance, but it is also possible to photo-cure in a state where photo-curability remains. .

Among these, cleavage-type photoinitiators include, for example, 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), phenylgly Methyl oxylic acid, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane- 1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl )-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide and derivatives thereof.
Among these, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are particularly preferred.

Examples of hydrogen abstraction type photoinitiators include benzophenone, Michler's ketone, 2-ethylanthraquinone, thioxanthone and derivatives thereof.

Among the above photoinitiators, a hydrogen abstraction type photoinitiator having an absorption coefficient of less than 10 mL/(g cm) at a wavelength of 405 nm because cohesive force is easily obtained after photocuring compared to the cleavage type photoinitiator. is particularly preferred.

<(Meth)acrylate (co)polymer>
The pressure-sensitive adhesive composition may contain a (meth)acrylate (co)polymer.

Examples of the (meth)acrylic acid ester (co)polymer include, for example, an alkyl (meth)acrylate homopolymer and a copolymer obtained by polymerizing this with a monomer component having copolymerizability. can be done.

More preferred (meth)acrylate (co)polymers include alkyl (meth)acrylates, hydroxyl group-containing monomers copolymerizable therewith, amino group-containing monomers, epoxy group-containing monomers, amide group-containing monomers and other A copolymer containing as a structural unit any one or more monomers selected from vinyl monomers can be mentioned.
In particular, when a highly polar component such as a carboxyl group is used as a copolymer component, the oxidizing action of the copolymer causes the adherend, particularly the conductive member such as an ITO film or an IGZO film, to be oxidized and deteriorated. is preferably a (meth)acrylate (co)polymer containing no carboxyl group-containing monomer as a structural unit.
The pressure-sensitive adhesive layer formed from the present pressure-sensitive adhesive composition containing such a (meth)acrylic acid ester (co)polymer is preferably photocurable by light irradiation.
The phrase "does not contain a carboxyl group-containing monomer as a structural unit" means "substantially does not contain", that is, "does not contain intentionally". However, since it may be unavoidably included, not only when it is completely absent, but also when the (meth)acrylic acid ester (co)polymer contains less than 0.5% by mass of the copolymerizable monomer A, preferably 0 .Includes cases where it is contained in an amount of less than 1% by mass.

The (meth)acrylic acid ester (co)polymer can be produced by a conventional method using the monomers exemplified below, if necessary, and a polymerization initiator.

A more specific example of the (meth)acrylic acid ester (co)polymer is a linear or branched alkyl (meth)acrylate having 4 to 18 carbon atoms in the side chain (hereinafter also referred to as “copolymerizable monomer A”). ) and any one or more monomer components copolymerizable therewith selected from the group consisting of B to E below.

- Macromonomer (hereinafter also referred to as "copolymerizable monomer B")
- (Meth)acrylate having 1 to 3 carbon atoms in the side chain (hereinafter also referred to as "copolymerizable monomer C")
- Hydroxyl group-containing monomer (hereinafter also referred to as "copolymerizable monomer D")
- Other vinyl monomers (hereinafter also referred to as "copolymerizable monomer E")

Among them, examples of the (meth)acrylic acid ester (co)polymer include (a) a copolymer composed of a monomer component containing a copolymerizable monomer A and a copolymerizable monomer B, and (b) a copolymer A preferred example is a copolymer composed of a monomer component containing a polar monomer A, a copolymerizable monomer C, and a copolymerizable monomer D and/or a copolymerizable monomer E.

(Copolymerizable monomer A)
Examples of linear or branched alkyl (meth)acrylates (copolymerizable monomer A) having 4 to 18 carbon atoms in the side chain include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, 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, behenyl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, benzyl (meth)acrylate Acrylate and the like can be mentioned. These may be used singly or in combination of two or more.

The copolymerizable monomer A is preferably contained in the total monomer components of the copolymer in an amount of 30% by mass or more and 90% by mass or less, especially 35% by mass or more or 88% by mass or less, especially 40% by mass. More preferably, it is contained in the range of more than or equal to 85% by mass or less.

(Copolymerizable monomer B)
The macromonomer (copolymerizable monomer B) is a monomer having a side chain with 20 or more carbon atoms when polymerized to form a (meth)acrylate (co)polymer. By using the copolymerizable monomer B, the (meth)acrylate (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 B and the other monomers and their mixing ratio.

As for the macromonomer (copolymerizable monomer B), the skeleton component is preferably composed of an acrylic acid ester copolymer or a vinyl polymer.
Examples of the skeleton component of the macromonomer include those exemplified by the copolymerizable monomer A described above, the copolymerizable monomer C described later, the copolymerizable monomer D described later, and the like. Can be used in combination.

A macromonomer has a radically polymerizable group or a functional group such as 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.

The number average molecular weight of the copolymerizable monomer B 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.
Macromonomers that are generally produced (eg, macromonomers manufactured by Toagosei Co., Ltd.) can be appropriately used.
The copolymerizable monomer B is 5% by mass or more and 30% by mass or less, especially 6% by mass or more and 25% by mass or less, especially 8% by mass or more and 20% by mass or less in the total monomer components of the copolymer. It is preferably contained within the range.

A (meth)acrylic ester (co)polymer composed of a copolymerizable monomer B is a (meth)acrylic ester copolymer (a-1) composed of a graft copolymer having a macromonomer as a branch component. can be mentioned.

When a pressure-sensitive adhesive layer is formed using such a (meth)acrylic acid ester copolymer (a-1), the pressure-sensitive adhesive layer can exhibit 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.

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 layer at room temperature and the adhesion of the adhesive to the adherend. Since it affects the wettability of the layer, that is, the adhesiveness, the glass transition temperature is -70°C to 0°C in order for the pressure-sensitive adhesive sheet 1 to obtain appropriate adhesiveness (tackiness) at room temperature. Among them, -65°C or higher or -5°C or lower, especially -60°C or higher or -10°C or lower is particularly preferred.
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.

(Copolymerizable monomer C)
Examples of the (meth)acrylate (copolymerizable monomer C) having 1 to 3 carbon atoms in the side chain include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl ( meth)acrylates and the like can be mentioned. These may be used alone or in combination of two or more.

The copolymerizable monomer C is preferably contained in the total monomer components of the copolymer in an amount of 0% by mass or more and 70% by mass or less, especially 3% by mass or more or 65% by mass or less, especially 5% by mass or more. Alternatively, it is more preferably contained in the range of 60% by mass or less.

(Copolymerizable monomer D)
Examples of the hydroxyl group-containing monomer (copolymerizable monomer D) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. Hydroxyalkyl (meth)acrylates such as These may be used alone or in combination of two or more.

The copolymerizable monomer D is preferably contained in the total monomer components of the copolymer in an amount of 0% by mass or more and 30% by mass or less, especially 0% by mass or more or 25% by mass or less, especially 0% by mass or more. Alternatively, it is more preferably contained in the range of 20% by mass or less.

(Copolymerizable monomer E)
Examples of the other vinyl monomer (copolymerizable monomer E) include compounds having a vinyl group in the molecule, excluding copolymerizable monomers A to D.
Such compounds include functional monomers having functional groups such as amide groups and alkoxylalkyl groups in the molecule, polyalkylene glycol di(meth)acrylates, vinyl acetate, vinyl propionate and vinyl laurate. Ester monomers and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes may be mentioned. These may be used alone or in combination of two or more.

The copolymerizable monomer E is preferably contained in the total monomer components of the copolymer in an amount of 0% by mass or more and 30% by mass or less, especially 0% by mass or more or 25% by mass or less, especially 0% by mass or more. Alternatively, it is more preferably contained in the range of 20% by mass or less.

In addition to those listed above, epoxy group-containing monomers such as glycidyl (meth)acrylate, glycidyl α-ethylacrylate, and 3,4-epoxybutyl (meth)acrylate; dimethylaminoethyl (meth)acrylate, diethylaminoethyl ( Amino group-containing (meth)acrylic acid ester-based monomers such as meth)acrylate; (meth)acrylamide, Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N -monomers containing an amide group or imide group such as butoxymethyl (meth)acrylamide, diacetone (meth)acrylamide, maleic acid amide and maleimide; heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine and vinylcarbazole; It can be used appropriately as needed.

Among the above, preferred examples of (meth)acrylate (co)polymers include 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isostearyl (meth)acrylate, lauryl any one or more monomer components (a) selected from the group consisting of (meth)acrylate, tridecyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, and methyl (meth)acrylate; Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, glycerol (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile, fluorinated ( A (meth)acrylic acid ester copolymer obtained by copolymerizing a monomer component (b) containing any one or more monomer components (b) selected from the group consisting of meth)acrylates and silicone (meth)acrylates can be mentioned.
Further, as an example of a preferable (meth)acrylic acid ester (co)polymer, a chemical bond is formed by a combination of functional groups such as a hydroxyl group and an isocyanate group or an amino group and an isocyanate group, or Mention may be made of those that are graft copolymers with macromonomers as branching components.

The (meth)acrylic acid ester (co)polymer preferably has a mass average molecular weight of 100,000 to 1,500,000, more preferably 150,000 to 1,300,000, more preferably 200,000 to 1,200,000.
When it is desired to obtain an adhesive composition with high cohesive strength, the weight average molecular weight of the (meth)acrylic acid ester (co)polymer is 700,000 or more and 150 from the viewpoint that the higher the molecular weight, the greater the cohesive strength due to the entanglement of the molecular chains. 10,000 or less, particularly preferably 800,000 or more or 1,300,000 or less.
On the other hand, when it is desired to obtain a pressure-sensitive adhesive composition having high fluidity and stress relaxation properties, the weight average molecular weight is preferably 100,000 or more and 700,000 or less, particularly 150,000 or more or 600,000 or less.
On the other hand, it is difficult to use a polymer with a large molecular weight when a solvent is not used when molding an adhesive sheet or the like.
Therefore, the (meth)acrylate (co)polymer has a mass average molecular weight of 100,000 to 700,000, more preferably 150,000 to 600,000, more preferably 200,000 to 500,000.

(crosslinking agent)
The pressure-sensitive adhesive composition may contain a cross-linking agent as necessary.
By adding a cross-linking agent, the degree of cross-linking, in other words, the gel fraction can be increased, and the cohesive force can be increased.
For example, as a method of cross-linking the (meth)acrylic acid ester (co)polymer described above, chemically bonding with reactive groups such as hydroxyl groups and carboxyl groups introduced into the (meth)acrylic acid ester (co)polymer. A method of adding a cross-linking agent and reacting by heating or curing, or adding a reaction initiator such as a polyfunctional (meth) acrylate having two or more (meth) acryloyl groups as a cross-linking agent and a photoinitiator, and ultraviolet light A method of cross-linking by irradiation or the like can be mentioned.
Among them, the cross-linking method by irradiation with light such as ultraviolet rays is preferable from the viewpoint of not consuming the polar functional groups in the present pressure-sensitive adhesive composition by reaction and maintaining high cohesion and adhesive physical properties derived from the polar components.

Examples of the cross-linking agent include (meth)acryloyl group, epoxy group, isocyanate group, carboxyl group, hydroxyl group, carbodiimide group, oxazoline group, aziridine group, vinyl group, amino group, imino group, amide group, N-substituted ( A cross-linking agent having at least one cross-linkable functional group selected from a meth)acrylamide group and an alkoxysilyl group may be mentioned, and may be used alone or in combination of two or more.
The crosslinkable functional group may be protected with a deprotectable protecting group.

Among them, polyfunctional (meth)acrylates are preferable from the viewpoint of ease of control of the cross-linking reaction.
Examples of such polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, poly Alkylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri In addition to UV-curable polyfunctional monomers such as pentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, polyester (meth)acrylate, epoxy (meth)acrylate, Examples include polyfunctional acrylic oligomers such as urethane (meth)acrylate and polyether (meth)acrylate, and polyfunctional acrylamide.

Examples of cross-linking agents having two or more cross-linkable functional groups include glycidyl (meth)acrylate, glycidyl α-ethylacrylate, 3,4-epoxybutyl (meth)acrylate, 4-hydroxybutyl ( Epoxy group-containing monomers such as meth) acrylate glycidyl ether; 2-isocyanatoethyl (meth) acrylate, 2-(2-(meth) acryloyloxyethyloxy) ethyl isocyanate, (meth) acrylic acid 2-(0-[ Monomers containing isocyanate groups or blocked isocyanate groups such as 1′-methylpropylideneamino]carboxyamino)ethyl, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl (meth)acrylate; vinyltrimethoxysilane, Vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-2-(aminoethyl)-3 Various silane coupling agents such as -aminopropylmethyldimethoxysilane and 3-isocyanatopropyltriethoxysilane can be mentioned.

A cross-linking agent having two or more cross-linkable functional groups has a structure in which one functional group is reacted with a (meth)acrylic acid ester (co)polymer and bonded to the (meth)acrylic acid ester (co)polymer. may be taken. By adopting such a structure, the (meth)acrylic acid ester (co)polymer can be chemically bonded with a double bond crosslinkable functional group such as a (meth)acryloyl group or a vinyl group.
In addition, by bonding the cross-linking agent to the (meth)acrylic acid ester (co)polymer, there is a tendency that bleeding out of the cross-linking agent and unexpected plasticization of the pressure-sensitive adhesive sheet can be suppressed.
In addition, by bonding the cross-linking agent to the (meth)acrylic acid ester (co)polymer, the reaction efficiency of the photocrosslinking reaction is promoted, so there is a tendency to obtain a cured product with higher cohesion. be.

The pressure-sensitive adhesive composition may further contain a monofunctional monomer that reacts with the crosslinkable functional group of the crosslinker. Such monofunctional monomers include alkyl (meth)acrylates such as methyl acrylate; hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, polyalkylene glycol (meth)acrylate, hydroxyl group-containing (meth) acrylates; ether group-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate and methoxypolyethylene glycol (meth) acrylate; (meth) acrylamide, dimethyl (meth) acrylamide, diethyl (meth) acrylamide, ( (Meth)acrylamide-based monomers such as meth)acryloylmorpholine, isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, phenyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide etc. can be mentioned.
Among them, it is preferable to use hydroxyl group-containing (meth)acrylates and (meth)acrylamide monomers from the viewpoint of improving the adhesion to the adherend and the effect of suppressing wet heat whitening.

The content of the cross-linking agent is 0.01 or more and 10 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester (co)polymer from the viewpoint of balancing the flexibility and cohesion of the adhesive composition. It is preferably blended in the following proportions, among which 0.05 parts by mass or more and 8 parts by mass or less, among which 0.1 parts by mass or more and 5 parts by mass or less is particularly preferable.

When the pressure-sensitive adhesive sheet is multi-layered, among the layers constituting the pressure-sensitive adhesive sheet, the content of the cross-linking agent in the intermediate layer or the layer serving as the substrate may exceed the above range.
The content of the cross-linking agent in the intermediate layer or the layer serving as the base material is preferably blended at a ratio of 0.01 to 40 parts by mass with respect to 100 parts by mass of the (meth)acrylic acid ester (co)polymer. It is preferably 1 part by mass or more and 30 parts by mass or less, and particularly preferably 2 parts by mass or more and 25 parts by mass or less.

(other ingredients)
In addition to the (meth)acrylic acid ester (co)polymer, UV absorber, photoinitiator, and cross-linking agent, the pressure-sensitive adhesive composition may contain other components as necessary.
Other components include, for example, light stabilizers, metal deactivators, metal corrosion inhibitors, anti-aging agents, antistatic agents, moisture absorbers, foaming agents, antifoaming agents, inorganic particles, viscosity modifiers, and tackifiers. Various additives such as resins, photosensitizers and fluorescent agents, and reaction catalysts (tertiary amine compounds, quaternary ammonium compounds, tin laurate compounds, etc.) can be used. In addition, it may appropriately contain known components that are blended in ordinary pressure-sensitive adhesive compositions.
Moreover, you may use together 2 or more types of each component.

Among the above, it is particularly preferable to contain a light stabilizer.
Combined use of the light stabilizer and the ultraviolet absorber described above can further improve the resistance to ultraviolet foaming. Hindered amine compounds (HALS) are particularly preferred as the light stabilizer.

(Method for producing the present pressure-sensitive adhesive composition)
The pressure-sensitive adhesive composition can be obtained by mixing predetermined amounts of a photoinitiator, an ultraviolet absorber and other components.

The mixing method at this time is not particularly limited, and the mixing order of each component is not particularly limited.
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. Also, the present pressure-sensitive adhesive composition can be used as a solvent-free 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.

In addition, a heat treatment step may be added during the production of the pressure-sensitive adhesive composition, and in this case, it is desirable to mix the components of the pressure-sensitive adhesive composition in advance and then perform the heat treatment. A masterbatch obtained by concentrating various mixed components may be used.

<Adhesive layer>
The present pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer formed from the present pressure-sensitive adhesive composition, and even if the pressure-sensitive adhesive layer has been cured, there is room for curing or in an uncured state. There may be. Among these, the pressure-sensitive adhesive layer preferably has the property of being photo-cured by light irradiation.
In addition, the pressure-sensitive adhesive layer does not contain a carboxyl group-containing monomer selected from the above-mentioned (meth)acrylic acid ester (co)polymers in addition to the ultraviolet absorber and the photoinitiator as the present pressure-sensitive adhesive composition. It preferably contains a (meth)acrylate (co)polymer.
By doing so, the pressure-sensitive adhesive sheet can be suitably used for laminating constituent members for an image display device provided with various conductive members such as a conductive member having a conductive pattern formed of a metal material.

<This light-curable adhesive sheet>
Among the present pressure-sensitive adhesive sheets, an embodiment having a property of photocuring by light irradiation, that is, a light-curing pressure-sensitive adhesive sheet (hereinafter referred to as "the present light-curing pressure-sensitive adhesive sheet") is subjected to light irradiation after lamination of adherends. It is possible to photo-cure it. With such a photocurable pressure-sensitive adhesive sheet, it is possible to achieve both step absorbability at the time of adhering an adherend member and foaming resistance reliability after adhering an adherend member.

As the present photocurable pressure-sensitive adhesive sheet, a pressure-sensitive adhesive formed from the present pressure-sensitive adhesive composition containing an ultraviolet absorber, a photoinitiator, and a (meth)acrylic acid ester (co)polymer that does not contain a carboxyl group-containing monomer The ultraviolet absorber has an absorption coefficient of 1×10 ³ mL/(g cm) or more at a wavelength of 340 nm, and an absorption coefficient of 1×10 ³ mL/(g cm) or more at a wavelength of 380 nm. (g cm), the adhesive composition contains an ultraviolet absorber in a proportion of 30 to 100 parts by mass with respect to 100 parts by mass of the photoinitiator, and the adhesive layer is irradiated with light. It preferably has the property of being photocured.

The photocurable pressure-sensitive adhesive sheet may be cured (also referred to as "precured") in a state in which there is room for photocuring, or may be completely unprecured. good.
In this case, the gel fraction of the present photocurable pressure-sensitive adhesive sheet that has not been precured at all is preferably 5% or less.
On the other hand, the precured photocurable pressure-sensitive adhesive sheet preferably has a gel fraction of 80% or less, more preferably 5% or more or 70% or less, and more preferably 10% or more or 60% or less. .
The gel fraction after final photocuring (simply referred to as “photocuring” or “main curing”) of the present photocurable pressure-sensitive adhesive sheet is 30% or more, particularly 40% or more, particularly 50% or more. is preferred. By photocuring the present photocurable pressure-sensitive adhesive sheet in such a range, the present photocurable pressure-sensitive adhesive sheet can have high cohesive strength even in a severe high-temperature and high-humidity environment, etc., and can improve foam resistance reliability.

The following (1) or (2) can be mentioned as a preferred method for forming the pressure-sensitive adhesive layer of the present photocurable pressure-sensitive adhesive sheet.

(1) During the production of the present photocurable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer is formed in a state in which the sheet shape is maintained in a precured (primary crosslinked) state and is provided with photocurability (photoactivity). .
(2) During the production of the present photocurable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer is formed in a state in which the sheet shape is maintained in an uncured (crosslinked) state and is provided with photocurability (photoactivation).

Specific examples of the above (1) include, for example, a photopolymerization initiator, a (meth)acrylic acid ester (co)polymer having a functional group (i), and a functional group (ii) that reacts with the functional group (i). ) and, in addition, a composition (adhesive) containing a polyfunctional (meth) acrylate having two or more (meth) acryloyl groups, if necessary, is heated or cured to form an adhesive layer. The method of forming can be mentioned.
According to this method, the functional group (i) in the (meth)acrylic acid ester (co)polymer reacts with the functional group (ii) in the compound to form a chemical bond for curing. (crosslinking) to form an adhesive layer. By forming the pressure-sensitive adhesive layer in this way, the photopolymerization initiator can exist in the pressure-sensitive adhesive layer while maintaining its activity.
In this case, as the photopolymerization initiator, either of the cleavage type photoinitiator and the hydrogen abstraction type photoinitiator may be used.

The combination of the functional group (i) and the functional group (ii) is preferably, for example, a carboxyl group and an epoxy group, a carboxyl group and an aziridyl group, a carboxyl group and an isocyanate group, a hydroxyl group and an isocyanate group, or an amino group and an isocyanate group. . Among these, a combination of a hydroxyl group (functional group (i)) and an isocyanate group (functional group (ii)) or an amino group (functional group (i)) and an isocyanate group (functional group (ii)) is particularly preferred. More specifically, the (meth)acrylic acid ester copolymer has a hydroxyl group, for example, a (meth)acrylic acid ester as a copolymer of a monomer component containing the above-described hydroxyl group-containing monomer (copolymerizable monomer D) A particularly preferred example is when a copolymer is used and the compound has an isocyanate group.

Moreover, the compound having the functional group (ii) may further have a radically polymerizable functional group such as a (meth)acryloyl group. As a result, the pressure-sensitive adhesive layer can be formed while maintaining the photocurability (crosslinking) of the (meth)acrylic acid ester (co)polymer due to the radically polymerizable functional group. More specifically, the (meth)acrylic acid ester (co)polymer has a hydroxyl group, and for example, a (meth)acrylic acid ester copolymer as a copolymer of a monomer component containing the above-described hydroxyl group-containing monomer is used. and when the compound has a (meth)acryloyl group, for example, the compound is 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, or the like. is a particularly suitable example.
Thus, by utilizing the cross-linking reaction between (meth)acrylic acid ester (co)polymers due to the radically polymerizable functional group, a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups can be used. Even if it is not, it is more preferable because it has the advantage that the cohesive force after photocuring (crosslinking) is likely to be efficiently increased and the reliability is excellent.

As another specific example of (1) above, for example, a method using the above-described hydrogen abstraction type initiator as a photopolymerization initiator can be mentioned. Since the hydrogen abstraction initiator returns to the ground state even if it is excited once, it can be reused as a photopolymerization initiator. Thus, by using a hydrogen-abstracting photoinitiator, it is possible to maintain the photocuring (crosslinking) property of the photopolymerization initiator even after the pressure-sensitive adhesive sheet is produced.

As a specific example of the above (2), for example, a method using the above-described macromonomer as a monomer component constituting the (meth)acrylic acid ester copolymer can be mentioned. More specifically, mention may be made of methods utilizing graft copolymers with macromonomers as branching components. By using such a macromonomer, it is possible to maintain a state in which the branch components are attracted to each other and physically crosslinked as a composition (adhesive) at room temperature.
Therefore, it is possible to produce a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a photoinitiator that generates radicals when light is received and that can maintain the sheet state in an uncured (crosslinked) state. In this case, as the photopolymerization initiator, either of the cleavage type photoinitiator and the hydrogen abstraction type photoinitiator may be used.

The present photocurable pressure-sensitive adhesive sheet preferably has the following spectral characteristics.
That is, the photocurable pressure-sensitive adhesive sheet preferably has a light transmittance of 10% or less at a wavelength of 320 nm, more preferably 5% or less, more preferably 3% or less. The light transmittance at a wavelength of 340 nm is preferably 20% or less, more preferably 10% or less, more preferably 5% or less.
By having the above light transmittance, it is possible to suppress the occurrence of foaming, peeling, etc. due to deterioration of the adhesive sheet itself.

The light transmittance of the present photocurable pressure-sensitive adhesive sheet at a wavelength of 365 nm is preferably 10% or more, more preferably 15% or more or 90% or less, and more preferably 20% or more and 80% or less. is more preferred.
The light transmittance of the present photocurable pressure-sensitive adhesive sheet at a wavelength of 380 nm is preferably 20% or more, more preferably 30% or more or 95% or less, and more preferably 40% or more and 90% or less. is more preferred.
The light transmittance of the present photocurable pressure-sensitive adhesive sheet at a wavelength of 395 nm is preferably 50% or more, more preferably 70% or more, more preferably 80% or more.
Having the above light transmittance makes it easier to activate the photoinitiator, so that the cohesive force of the adhesive after photocuring can be sufficiently obtained, and reliability can be easily obtained.

Preferred embodiments of the present photocurable pressure-sensitive adhesive sheet are the same as the present pressure-sensitive adhesive sheet described above, and can be appropriately selected and applied. The preferred embodiments of the seat are interchangeable.

(metal corrosion inhibitor)
By the way, when the present photocurable pressure-sensitive adhesive sheet is formed from the present pressure-sensitive adhesive composition whose main component is a (co)polymer of a monomer component that does not contain a carboxyl group-containing monomer, corrosion resistance to metal Good properties.
However, as a result of researching the corrosion of the metal material when a photocurable adhesive sheet is attached to a conductive member made of a metal material containing a specific metal, such as silver, and then photocured, it has been found that the light contained in the adhesive sheet It has been found that the initiator is activated by light to generate radicals, and the radicals react with silver in the metal material, which may promote corrosion of metal materials containing silver.
In order to solve this problem, the present photocurable pressure-sensitive adhesive sheet contains a metal corrosion inhibitor, and a protective film is formed on the silver of the conductive member, so that the radicals generated from the photoinitiator by the light irradiation are transferred to the conductive member. It is proposed to suppress the reaction with silver of
From the above viewpoints, the present photocurable pressure-sensitive adhesive sheet preferably has a pressure-sensitive adhesive layer formed from the present pressure-sensitive adhesive composition containing a metal corrosion inhibitor.

In the pressure-sensitive adhesive composition, the metal corrosion inhibitor is preferably contained in a proportion of 0.05 to 2.0% by weight with respect to the total weight of the pressure-sensitive adhesive composition.
Further, in the adhesive composition, the metal corrosion inhibitor is preferably contained in a proportion of 10 to 200 parts by weight with respect to 100 parts by weight of the photoinitiator.
By containing in such a compounding ratio, the effect of the metal corrosion inhibitor can be maximized without inhibiting the curing by the photoinitiator.
From such a point of view, the metal corrosion inhibitor is preferably contained in a proportion of 10 to 200 parts by weight with respect to 100 parts by weight of the photoinitiator. parts or more or 70 parts by mass or less, more preferably 20 parts by mass or more or 50 parts by mass or less.

The metal corrosion inhibitor has an absorption coefficient at 365 nm of 20 mL/(g cm) or less, especially 10 mL/(g cm), from the viewpoint that the contained metal corrosion inhibitor does not inhibit the photoreaction of the adhesive composition. Below, among them, 5 mL/(g·cm) or less, among these, 1 mL/(g·cm) or less is particularly preferable.
As a metal corrosion inhibitor having such properties, a metal corrosion inhibitor having no skeleton selected from a naphthalene skeleton, anthracene skeleton, a thiazole skeleton and a thiadiazole skeleton is preferred. By not having such a skeleton, the metal corrosion inhibitor can have an absorption coefficient within the above range.

Also, the metal corrosion inhibitor is preferably a hydrophilic compound.
If the metal corrosion inhibitor is hydrophilic, it will easily move in the pressure-sensitive adhesive layer based on a (meth)acrylic (co)polymer, which is also hydrophilic. A film can be formed, and the attack (reaction) of radicals generated from the photoinitiator by light irradiation to metal members, particularly silver, can be suppressed.
From this point of view, the water solubility of the metal corrosion inhibitor at 25° C. is preferably 20 g/L or more, particularly 50 g/L or more, and more preferably 100 g/L or more.

From the above viewpoints, the metal corrosion inhibitor has an absorption coefficient at 365 nm of 20 mL/(g cm) or less and is a triazole compound among metal corrosion inhibitors composed of hydrophilic compounds. Among them, one or a mixture of two or more selected from benzotriazole, 1,2,3-triazole and 1,2,4-triazole is particularly preferred.
The benzotriazole may be either substituted or unsubstituted benzotriazole, such as 1,2,3-benzotriazole, alkylbenzotriazole such as methyl-1H-benzotriazole, carboxybenzotriazole, 1 -halogenobenzotriazoles such as hydroxybenzotriazole, 5-aminobenzotriazole, 5-phenylthiolbenzotriazole, 5-methoxybenzotriazole, nitrobenzotriazole, chlorobenzotriazole, bromobenzotriazole, fluorobenzotriazole, copper benzotriazole, silver Examples include benzotriazole, benzotriazole silane compounds, and the like. Among these, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl, and 1-[N,N-bis(2-ethylhexyl)aminomethyl ]benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2′-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol Any one or a mixture of two or more selected from the group consisting of is preferable.
Furthermore, 1,2,4-triazole is a solid with a melting point of about 120°C, while 1,2,3-triazole has a melting point of about 20°C and is almost liquid at room temperature. Therefore, 1,2,3-triazole has excellent dispersibility when mixed in the pressure-sensitive adhesive composition, can be uniformly mixed, and has excellent advantages such as easy masterbatch.

<Physical properties of this adhesive sheet>
The adhesive sheet is preferably optically transparent. That is, it is preferably a transparent adhesive sheet. Here, "optically transparent" means that the total light transmittance is 80% or more, preferably 85% or more, more preferably 90% or more.

<Usage form of this adhesive sheet>
The pressure-sensitive adhesive sheet can be used by directly applying the pressure-sensitive adhesive composition to an adherend and forming it into a sheet, or by forming a single-layer or multi-layer sheet on a release film with a release film. An adhesive sheet can also be used. That is, a release film sheet-attached pressure-sensitive adhesive sheet can be obtained by laminating a release film on at least one of the front and back sides of the present pressure-sensitive adhesive sheet.

Examples of materials for the release film include polyester films, polyolefin films, polycarbonate films, polystyrene films, acrylic films, triacetylcellulose films, and fluororesin films. Among these, polyester films and polyolefin films are particularly preferred.

The release film preferably has a light transmittance of 40% or less at a wavelength of 410 nm or less.
By laminating a release film having a light transmittance of 40% or less at a wavelength of 410 nm or less on at least one surface of the adhesive sheet, a photoinitiator having activity in the visible light wavelength range is used. Even if there is, it is possible to effectively prevent the progress of photopolymerization due to the irradiation of visible light.
From this point of view, the release film laminated on one or both sides of the pressure-sensitive adhesive sheet preferably has a light transmittance of 40% or less at a wavelength of 410 nm or less, especially 30% or less, and especially 20% or less. is more preferable.

Here, as a release film having a light transmittance of 40% or less at a wavelength of 410 nm or less, that is, a film having an effect of partially blocking the transmission of visible light and ultraviolet light, polyester-based, polypropylene-based , A laminated film with an ultraviolet absorbing layer, which is made by applying a slightly adhesive resin with removability to one surface of a polyethylene-based cast film or stretched film, and applying a paint containing an ultraviolet absorber to the other surface. can be mentioned.
In addition, a cast film or stretched film of polypropylene or polyethylene may be coated with a removably slightly tacky resin containing an ultraviolet absorber on one side thereof.
In addition, cast films and stretched films made of polyester, polypropylene or polyethylene resins containing an ultraviolet absorber are coated with releasable, slightly tacky resins.
In addition, a multilayer cast film or stretched film formed by molding a layer made of a resin that does not contain an ultraviolet absorber on one or both sides of a layer made of a polyester, polypropylene, or polyethylene resin containing an ultraviolet absorber. One surface may be coated with a slightly adhesive resin having removability.
In addition, a coating containing an ultraviolet absorber is applied to one surface of a cast film or stretched film made of polyester-, polypropylene-, or polyethylene-based resin to form an ultraviolet-absorbing layer, and the ultraviolet-absorbing layer is re-peeled. For example, a resin coated with a slightly sticky resin having properties can be mentioned.
In addition, a cast film or stretched film made of polyester, polypropylene, or polyethylene resin is coated with a paint containing an ultraviolet absorber on one side to form an ultraviolet absorbing layer, and the other surface is a microscopic layer with removability. Examples include those coated with an adhesive resin. In addition, the other side of a resin film made of polyester, polypropylene, or polyethylene resin coated with a slightly adhesive resin having removability on one side and a separately prepared resin film are bonded together with an ultraviolet absorber. Examples include those laminated via a layer or an adhesive layer.
The above film may have other layers such as an antistatic layer, a hard coat layer, an anchor layer, and the like, if necessary.

The thickness of the release film is not particularly limited. Among them, for example, from the viewpoint of workability and handleability, 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.

The present pressure-sensitive adhesive sheet employs a method of directly extruding the present pressure-sensitive adhesive composition without using an adherend or release film as described above, or a method of molding by injecting into a mold. can also Furthermore, a pressure-sensitive adhesive sheet can be obtained by directly filling the present pressure-sensitive adhesive composition between members such as conductive members.

<Application of this adhesive sheet>
This pressure-sensitive adhesive sheet can be used for image display devices such as personal computers, mobile terminals (PDA), game machines, televisions (TV), car navigation systems, touch panels, pen tablets, plasma displays (PDP), liquid crystal displays (LCD), In image display devices using image display panels such as organic EL displays (OLED), inorganic EL displays, electrophoretic displays (EPD), and interferometric modulation displays (IMOD), the constituent members for image display devices that make up these are pasted. Suitable for matching.
Moreover, among others, it is suitable for bonding a conductive member including a transparent conductive layer formed of a metal material containing silver. At this time, the conductive member may have an insulating protective film (passivation film).

This pressure-sensitive adhesive sheet can be used by being attached to a conductive member comprising a metal material containing silver, for example, the conductive layer surface of a transparent conductive layer.
In this case, any adhesive layer surface of the pressure-sensitive adhesive sheet and the conductive layer surface of the transparent conductive layer may be adhered to each other.
When the present pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, the laminate may have a structure in which both pressure-sensitive adhesive layer surfaces of the present pressure-sensitive adhesive sheet and the conductive layer surface of the transparent conductive layer are bonded together.

<Laminate for constituting the present image display device>
This pressure-sensitive adhesive sheet can be laminated with one or more constituent members of an image display device to form a laminate for constituting an image display device. Among them, an image display device configuration by laminating an image display device component provided with a conductive member formed of a metal material containing silver and another image display device component with the present pressure-sensitive adhesive sheet interposed therebetween. (hereinafter referred to as "laminate for constituting the present image display device").

When producing the image display device constituting laminate using the present photocurable adhesive sheet, after laminating the two image display device constituent members via the present photocurable adhesive sheet, at least one By irradiating light from the image display device constituent member side and photocuring the photocurable pressure-sensitive adhesive sheet, the present image display device constituent laminate can be produced.

Specific examples of the laminate for constituting the image display device include release film/adhesive sheet/touch panel, image display panel/adhesive sheet/touch panel, image display panel/adhesive sheet/touch panel/adhesive sheet/protection. Configurations such as a panel, polarizing film/this pressure-sensitive adhesive sheet/touch panel, and polarizing film/this pressure-sensitive adhesive sheet/touch panel/this pressure-sensitive adhesive sheet/protective panel can be mentioned.

Further, the touch panel includes a structure in which a touch panel function is included in a protection panel, and a structure in which a touch panel function is included in an image display panel.
Therefore, the laminate for constituting the image display device has a configuration such as release film/adhesive sheet/protective panel, release film/adhesive sheet/image display panel, image display panel/adhesive sheet/protective panel, and the like. There may be.
Moreover, in the above-described configurations, all configurations in which the above-described conductive layer is interposed between the present pressure-sensitive adhesive sheet and members such as a touch panel, a protective panel, an image display panel, and a polarizing film adjacent thereto can be mentioned. However, it is not limited to these lamination examples.

Examples of the touch panel include a resistive film type, a capacitive type, an electromagnetic induction type, and the like. Among them, the capacitive method is preferable.

Materials for the surface protection panel include glass, acrylic resin, polycarbonate resin, alicyclic polyolefin resin such as cycloolefin polymer, styrene resin, polyvinyl chloride resin, phenol resin, melamine resin, Plastic such as epoxy resin may be used.
Materials for the surface protection panel include glass, acrylic resin, polycarbonate resin, alicyclic polyolefin resin such as cycloolefin polymer, styrene resin, polyvinyl chloride resin, phenol resin, melamine resin, Plastic such as epoxy resin may be used.

The image display panel is composed of other optical films such as polarizing films and other retardation films, liquid crystal materials, and backlight systems (usually, the surface of the adhesive composition or adhesive article attached to the image display panel is an optical film. ), and there are an STN method, a VA method, an IPS method, etc. depending on the control method of the liquid crystal material, and any method may be used.

The laminate for constituting an image display device can be used as a constituent member of an image display device such as a liquid crystal display, an organic EL display, an inorganic EL display, electronic paper, a plasma display, and a microelectromechanical system (MEMS) display. .
The image display panel is composed of other optical films such as polarizing films and other retardation films, liquid crystal materials, and backlight systems (usually, the surface of the adhesive composition or adhesive article attached to the image display panel is an optical film. ), and there are an STN method, a VA method, an IPS method, etc. depending on the control method of the liquid crystal material, and any method may be used.

<Explanation of terms>
In this specification, when expressed 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 expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), "preferably larger than X" or "preferably less than Y" It also includes intent.

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

<Example 1>
(Meth)acrylic acid ester (co)polymer (a): 15 parts by mass of macromonomer (number average molecular weight: 2,500) with methyl methacrylate as branch component, 81 parts by mass of n-butyl acrylate as trunk component/4 parts of acrylic acid 1 kg of graft copolymer (A-1, mass average molecular weight of 300,000, Tg-12° C.) consisting of parts by mass, 2-hydroxy-4-n-octyloxybenzophenone (B-1, 5 g of a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (C-1) as a photoinitiator (c), propoxylated as a cross-linking agent (d). Pentaerythritol triacrylate (D-1) 100 g, light stabilizer (e), decanedioate bis (2,2,6,6-tetramethyl-1-octyloxy-4-piperidin-4-yl) (E 2 g of F-1) and 2 g of 1,2,3-triazole (F-1) as a metal corrosion inhibitor (f) were uniformly melt-kneaded to prepare a resin composition 1.
1,2,3-triazole (F-1) as a metal corrosion inhibitor has an absorption coefficient of 0.3 mL/(g cm) at 365 nm and a water solubility of >1000 g/L at 25°C. Met.

The resin composition 1 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 1 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 1 is in an uncured state and has the property of being photo-cured by light irradiation.

<Example 2>
(Meth)acrylic acid ester (co)polymer (a), 13.5 parts by mass of branch component isobornyl methacrylate:methyl methacrylate=1:1 macromonomer (number average molecular weight 3,000), stem component is a copolymer (A-2, mass average molecular weight of 160,000) consisting of 43.7 parts by mass of lauryl acrylate / 40 parts by mass of 2-ethylhexyl acrylate / 2.8 parts by mass of acrylamide; B-1) 5 g, (C-1) 10 g as a photoinitiator (c), (D-1) 100 g as a cross-linking agent (d), and (E-1) 2 g as a light stabilizer (e). The resin composition 2 was prepared by uniform melt-kneading.
The resin composition 2 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 2 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 2 is in an uncured state and has the property of being photo-cured by light irradiation.

<Example 3>
(Meth)acrylic acid ester (co)polymer (a) is a copolymer (A-3, mass average molecular weight of 400,000 ) 1 kg, (B-1) 5 g as an ultraviolet absorber (b), (C-1) 8 g as a photoinitiator (c), (D-1) 30 g as a cross-linking agent (d), light stabilizer As (e), 2 g of (E-1) was uniformly melt-kneaded to prepare a resin composition 3.
The resin composition 3 is 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 is It is formed into a sheet at a temperature of 60°C so as to have a thickness of 100 µm, and from one side of the polyethylene terephthalate film, it is irradiated with light from a high-pressure mercury lamp so that the integrated light quantity at a wavelength of 365 nm becomes 1500 mJ/cm ² , and precured. Then, a transparent double-sided pressure-sensitive adhesive sheet 3 was produced.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 3 leaves room for photocuring by light irradiation.

<Example 4>
(Meth) acrylic acid ester (co) polymer (a), (A-2) 1 kg, ultraviolet absorber (b), (B-1) 5 g, photoinitiator (c), (C-1 ), 100 g of (D-1) as a cross-linking agent (d), and 2 g of (F-1) as a metal corrosion inhibitor (f) were uniformly melted and kneaded to prepare a resin composition 4.
The resin composition 4 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 4 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 4 is in an uncured state and has a property of being photo-cured by light irradiation.

<Example 5>
(Meth) acrylic acid ester (co) polymer (a) as (A-2) 1 kg, ultraviolet absorber (b) as (B-1) 8 g, photoinitiator (c) as (C-1 ) and 100 g of (D-1) as a cross-linking agent (d) were uniformly melt-kneaded to prepare a resin composition 5.
The resin composition 5 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 5 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 5 is in an uncured state and has a property of being photo-cured by light irradiation.

<Example 6>
(Meth) acrylic acid ester (co) polymer (a) as (A-2) 1 kg, ultraviolet absorber (b) as (B-1) 8 g, photoinitiator (c) as (2-hydroxy -2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) oligomer 50 parts by weight/2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide 46 parts by weight/2,4,6-trimethylbenzophenone 8 g of a mixture (C-2) of 3.2 parts by mass/0.8 parts by mass of 4-methylbenzophenone and 100 g of (D-1) as a cross-linking agent (d) are uniformly melt-kneaded to obtain a resin composition 6. made.
The resin composition 6 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 6 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 6 is in an uncured state and has the property of being photo-cured by light irradiation.

<Example 7>
(Meth) acrylic acid ester (co) polymer (a), (A-1) 1 kg, ultraviolet absorber (b), (B-1) 18 g, photoinitiator (c), (C-1 ) and 120 g of (D-1) as a cross-linking agent (d) were uniformly melt-kneaded to prepare a resin composition 7.
The resin composition 7 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 7 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The adhesive layer in the transparent double-sided adhesive sheet 7 is in an uncured state and has a property of being photocured by light irradiation.

<Comparative Example 1>
(A-2) 1 kg as the (meth)acrylic acid ester (co)polymer (a), 2,2-dihydroxy-4-methoxybenzophenone (B-2, molecular weight 244.2) as the ultraviolet absorber (b) , melting point 73 ° C.) 5 g, (C-1) 10 g as a photoinitiator (c), (D-1) 100 g as a cross-linking agent (d), (E-1) 2 g as a light stabilizer (e) were uniformly melted and kneaded to prepare a resin composition 8.
The resin composition 8 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 8 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The adhesive layer in the transparent double-sided adhesive sheet 8 is in an uncured state and has a property of being photocured by light irradiation.

<Comparative Example 2>
(Meth) acrylic acid ester (co) polymer (a) as (A-1) 1 kg, ultraviolet absorber (b) as (B-1) 20 g, photoinitiator (c) as (C-1 ) and 100 g of (D-1) as a cross-linking agent (d) were uniformly melt-kneaded to prepare a resin composition 9.
The resin composition 8 is 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 is A transparent double-sided pressure-sensitive adhesive sheet 9 was produced by shaping into a sheet at a temperature of 80° C. so as to have a thickness of 100 μm.
The adhesive layer in the transparent double-sided adhesive sheet 9 is in an uncured state and has a property of being photocured by light irradiation.

<Comparative Example 3>
(Meth) acrylic acid ester (co) polymer (a) as (A-3) 1 kg, photoinitiator (c) as (C-1) 8 g, cross-linking agent (d) as (D-1) A resin composition 10 was produced by uniformly melting and kneading 30 g. No UV absorber (b) was added.
The resin composition 10 is 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 is It is formed into a sheet at a temperature of 60°C so as to have a thickness of 100 µm, and from one side of the polyethylene terephthalate film, it is irradiated with light from a high-pressure mercury lamp so that the integrated light quantity at a wavelength of 365 nm becomes 1000 mJ/cm ² , and precured. Then, a transparent double-sided pressure-sensitive adhesive sheet 10 was produced.
The pressure-sensitive adhesive layer in the transparent double-sided pressure-sensitive adhesive sheet 10 leaves room for photocuring by light irradiation.

[Evaluation of the physical properties]
The physical properties of the transparent double-sided pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were measured as follows.

<Gel fraction>
The release films of the transparent double-sided pressure-sensitive adhesive sheets 1 to 10 are peeled off on both sides, and about 0.4 g of each of the transparent double-sided pressure-sensitive adhesive sheets 1 to 10 is collected and bagged with SUS mesh (#200) whose mass (X) is measured in advance. The bag was folded and closed, and the mass (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. , was obtained by substituting the obtained mass into the following formula.
Gel fraction [%] = [(ZX) / (YX)] × 100

Transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were used as measurement samples before photocuring (main curing). For the measurement samples after photocuring (main curing), the transparent double-sided adhesive sheets 1 to 10 were irradiated with light through the release film using a high-pressure mercury lamp so that the integrated light amount at 365 nm was 3000 mJ/cm ² . After that, the sample was cured at room temperature for 12 hours and used as a measurement sample.

<Spectral characteristics>
The transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were cut to 50×80 mm using a Thomson punching machine with the release film laminated. The release film on one side was peeled off, and the exposed adhesive surface was bonded to soda lime glass (54×82 mm, t 0.6 mm) with a hand roll. After that, it was pressure-bonded to another sheet of soda-lime glass (same as above) by vacuum press (23° C., press pressure 0.1 MPa, 1 minute). Next, autoclave treatment (60 ° C., gauge pressure 0.2 MPa, 20 minutes) is applied to finish adhesion, and from one glass side, a high pressure mercury lamp is used so that the integrated light amount at 365 nm becomes 3000 mJ / cm ² The pressure-sensitive adhesive sheet was photo-cured by irradiating light, and cured at room temperature for 12 hours to prepare a sample for spectral characteristic measurement. Using these, the spectral properties of transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were measured under the following conditions.
<Apparatus> UV-2450 (manufactured by Shimadzu Corporation)
<Wavelength> 300 to 400 nm (Measurement of light transmittance at wavelengths of 320 nm, 340 nm, 365 nm, 380 nm, and 395 nm)

<Storage stability>
The transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were cut to 50×50 mm using a Thomson punching machine with the release film laminated. These pressure-sensitive adhesive sheets were left standing with the diafoil MRT (release film) facing upward, and irradiated with light of 1100 Lx for 24 hours using a three-wavelength fluorescent lamp. The change in gel fraction before and after the storage test under strong fluorescent light was calculated.

Then, the storage stability was determined according to the following criteria.
After the test, the gel fraction of the adhesive sheet increased significantly, and the gel fraction change was 20% or more, "poor", and the gel fraction change was suppressed to 10% or more and less than 20%. Those in which the gel fraction change was suppressed to less than 10% were evaluated as "⊚ (very good)".

<Heat resistant foamability>
The transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were cut to 50×80 mm using a Thomson punching machine with the release film laminated. The release film on one side was peeled off, and the exposed adhesive surface was bonded to soda lime glass 1 (54×82 mm, t 0.6 mm) with a hand roll. Next, the release film on the adhesive side of the polarizing plate with adhesive (VLC2 manufactured by Sanritz Co., Ltd.) was peeled off, and the exposed adhesive surface was bonded to soda lime glass 2 (54 × 82 mm, t 0.6 mm) with a hand roll. . Further, the protective film on the polarizing plate side was peeled off, and 6 glass beads (40 μm in diameter) were arranged on the polarizing plate. On the side of this polarizing plate, the other release film of the transparent double-sided adhesive sheets 1 to 10 attached to the soda-lime glass 1 was peeled off, and the sheet was attached with a hand roll onto the polarizing plate on which the glass beads were arranged.
Next, autoclave treatment (60 ° C., gauge pressure 0.2 MPa, 20 minutes) is performed and the finish is attached, and from the soda lime glass 1 side, using a high pressure mercury lamp, the integrated light amount at 365 nm becomes 3000 mJ / cm ² . By irradiating light to photocure the adhesive sheet and curing it for 12 hours at room temperature, a sample for heat-resistant foaming evaluation (soda lime glass 1 / transparent double-sided adhesive sheet / polarizing plate with adhesive / soda lime glass 2) was obtained. made.

These were allowed to stand in an environment of 85° C. for 300 hours, and the presence or absence of foaming was visually observed.
A case where air bubbles were generated at the polarizing plate/transparent double-sided pressure-sensitive adhesive sheet interface or the like was evaluated as "poor", and a case where air bubbles were not generated and the appearance was good was evaluated as "good".

<UV foam resistance>
The transparent double-sided pressure-sensitive adhesive sheets 1 to 10 were cut to 200×150 mm using a Thomson punching machine with the release film laminated. The release film on one side of the transparent double-sided pressure-sensitive adhesive sheet was peeled off, and the exposed pressure-sensitive adhesive surface was bonded to the entire surface of soda lime glass (200×150 mm, t 0.6 mm) with a hand roll. Next, the other release film was peeled off, and the exposed adhesive surface was vacuum press-bonded to another sheet of soda lime glass (200 × 150 mm, t 0.6 mm) (23 ° C., press pressure 0.1 MPa, 1 minutes). Next, autoclave treatment (60 ° C., gauge pressure 0.2 MPa, 20 minutes) is applied to finish adhesion, and from one glass side, a high pressure mercury lamp is used so that the integrated light amount at 365 nm becomes 3000 mJ / cm ² A sample for UV foam resistance evaluation was prepared by irradiating light to photo-cure the pressure-sensitive adhesive sheet and curing it at room temperature for 12 hours.
These were allowed to stand under the following environment for 8 hours/24 hours, and the presence or absence of foaming or microbubbles under a strong UV irradiation environment was visually observed over time.
<Apparatus> Suntest CPS+ (manufactured by Toyo Seiki Co., Ltd.)
<Light source> Xenon arc lamp (air-cooled, wavelength 270 nm cut filter)
<Irradiance> 765 W/m ² (wavelength 800 nm or less)
<Temperature> BST63°C

Then, the UV foam resistance was determined according to the following criteria.
"X (poor)" indicates that a large number of large bubbles or microbubbles were generated after standing still for 3 hours. △ (usual)", good appearance after standing for 8 hours, and foaming or microbubbles after standing for 24 hours; "○ (good)", good appearance after 24 hours It was determined to be "A (very good)".

<Silver Corrosion Resistance>
As a conductive member containing silver, a silver nanowire film (Activegrid Film manufactured by C3nano, base polyethylene terephthalate (thickness 50 μm), surface resistance value 50 Ω / □, with overcoat layer, total light transmittance > 91%, haze ≤ 0 .9%, b*≤1.3) were prepared.
As shown in FIG. 1, the silver nanowire film is cut into a length of 45 mm and a width of 80 mm, and silver paste (Dotite D-550 manufactured by Fujikura Kasei Co., Ltd.) is applied in the vertical direction so that the distance between the electrodes is 50 mm. After coating with a width and drying, the sheet was cut in the horizontal direction so as to have a vertical width of 9 mm. These 9 mm×80 mm×5 silver nanowire films with silver paste electrodes were arranged in parallel on soda lime glass.
On top of this, the single-sided release film of the double-sided adhesive sheet cut to a width of 50 mm was peeled off, and the adhesive sheet was laminated with a roll so that the adhesive sheet was positioned between the electrodes. After applying the adhesive sheet with release film, the adhesive sheet was irradiated with light from a high-pressure mercury lamp so that the integrated amount of light at a wavelength of 365 nm was 3000 mJ/cm ² for photocuring.

This sample was subjected to an environmental test under a wet heat environment of 65° C. 90% RH×300 hours to confirm an increase in the resistance value between the electrodes.
In the above environmental test, "△ (usual)" indicates that the resistance value increase exceeds 10%, "○ (good)" indicates that the resistance value increase is suppressed to 10% or less, and further increases the resistance value by 1. % or less was judged as "very good".

Table 1 shows the evaluation results of Examples and Comparative Examples.
In each example and comparative example in Table 1, the (meth)acrylic copolymer (A), the ultraviolet absorber (B), the photoinitiator (C), the cross-linking agent, the light stabilizer and the metal corrosion inhibitor The numerical value described in each item is parts by mass.

The transparent double-sided pressure-sensitive adhesive sheets of Examples 1 to 7 use an ultraviolet absorber and a photoinitiator having a specific absorption coefficient, and by controlling the amount of these additions, the photocuring is not inhibited, and the exposure environment Since it is possible to suppress the deterioration of the adhesive sheet itself in the UV irradiation environment, the deterioration of the adhesive sheet itself is suppressed particularly in the UV irradiation environment, and the ultraviolet foaming resistance is excellent.
In particular, in the transparent double-sided pressure-sensitive adhesive sheets of Examples 1 to 5 and 7, since the absorption coefficient of the photoinitiator at 405 nm is small, photocuring of the pressure-sensitive adhesive hardly progresses even when stored under a high-intensity fluorescent lamp. It was excellent in storage stability.
In addition, Examples 1 and 4, to which a metal corrosion inhibitor was added, were excellent in silver metal corrosion resistance. Among them, Example 4, in which the (meth)acrylic acid ester (co)polymer (a) does not contain a carboxylic acid, has extremely excellent silver corrosion resistance, and is laminated to a conductive member formed of a metal material containing silver. It was particularly suitable for use even when

On the other hand, the transparent double-sided pressure-sensitive adhesive sheet 7 of Comparative Example 1 uses an ultraviolet absorber with a high absorption coefficient at a wavelength of 380 nm. The adhesive sheet was not sufficiently photocured, and was inferior in heat resistance reliability and UV resistance reliability. In Comparative Example 2, in which a larger amount of the ultraviolet absorber is added to the photoinitiator, the ultraviolet absorber itself plasticizes the adhesive sheet and inhibits the activation of the photoinitiator to some extent, resulting in photocuring. Since the subsequent cohesive force becomes low, the heat resistance reliability and the UV resistance reliability are inferior.
A transparent double-sided pressure-sensitive adhesive sheet like Comparative Example 3, which does not contain an ultraviolet absorber, cannot suppress deterioration of the pressure-sensitive adhesive sheet itself when exposed to ultraviolet rays, and a large amount of decomposition products (outgassing) are generated from the pressure-sensitive adhesive sheet. Foaming and peeling occurred in the ultraviolet foaming test.

Since the pressure-sensitive adhesive sheet of the present invention is excellent in heat-resistant foaming property, ultraviolet-ray foaming resistance, storage stability, and corrosion resistance, it can be applied to optical applications, particularly image display device applications.

Claims (17)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing an ultraviolet absorber, a photoinitiator, a (meth)acrylate (co)polymer, and a cross-linking agent,
The ultraviolet absorber has an absorption coefficient of 1×10 ³ mL/(g cm) or more at a wavelength of 340 nm, and an absorption coefficient of less than 1×10 ³ mL/(g cm) at a wavelength of 380 nm. and
The pressure-sensitive adhesive composition contains the ultraviolet absorber in a proportion of 0.1 to 1.6% by weight with respect to the total weight of the pressure-sensitive adhesive composition, and 30 parts by weight per 100 parts by weight of the photoinitiator. Containing the ultraviolet absorber at a rate of ~100 parts by mass,
A pressure-sensitive adhesive sheet characterized in that the pressure-sensitive adhesive sheet has a property of being photo-cured by light irradiation and has a gel fraction of 57% to 80%. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive composition contains the ultraviolet absorber at a rate of 0.1 to 1.4% by mass with respect to the total weight of the pressure-sensitive adhesive composition. . The adhesive sheet according to claim 1 or 2, wherein the photoinitiator has an absorption coefficient of less than 10 mL/(g·cm) at a wavelength of 405 nm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the photoinitiator is a hydrogen abstraction type photoinitiator. 5. The (meth)acrylic acid ester (co)polymer according to any one of claims 1 to 4, wherein the (meth)acrylic acid ester (co)polymer is a (meth)acrylic acid ester (co)polymer containing no carboxyl group-containing monomer as a structural unit. adhesive sheet. Claims 1 to 3, wherein the (meth)acrylic acid ester (co)polymer has a chemical bond formed by a combination of functional groups such as a hydroxyl group and an isocyanate group, or an amino group and an isocyanate group. 6. The pressure-sensitive adhesive sheet according to any one of 5. The pressure-sensitive adhesive sheet according to claim 6, wherein the (meth)acrylate (co)polymer further has a radically polymerizable functional group. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the (meth)acrylate (co)polymer is a graft copolymer having a macromonomer as a branch component. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive composition further contains a metal corrosion inhibitor. The pressure-sensitive adhesive sheet according to claim 9, wherein the metal corrosion inhibitor has an absorption coefficient at 365 nm of 20 mL/(g·cm) or less. The pressure-sensitive adhesive sheet according to claim 9 or 10, wherein the metal corrosion inhibitor has a water solubility of 20 g/L or more at 25°C. The pressure-sensitive adhesive sheet according to any one of claims 9 to 11, wherein the metal corrosion inhibitor is a triazole compound. The adhesive composition according to any one of claims 9 to 12, wherein the metal corrosion inhibitor is contained in a proportion of 0.05 to 2.0% by mass with respect to the total mass of the adhesive composition. Adhesive sheet described. The pressure-sensitive adhesive sheet according to any one of claims 9 to 13, wherein the pressure-sensitive adhesive composition contains a metal corrosion inhibitor in a proportion of 10 to 200 parts by mass with respect to 100 parts by mass of the photoinitiator. The adhesive sheet according to any one of claims 1 to 14, and a release film laminated on at least one side of the adhesive sheet and having a light transmittance of 40% or less at a wavelength of 410 nm or less. Adhesive sheet with release film. A laminate for image display device construction, which is formed by using the pressure-sensitive adhesive sheet according to any one of claims 1 to 14 and one or more image display device constituent members. An image display device formed by using the laminate for constituting an image display device according to claim 16 .

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