JP7563890B2 - Adhesive sheet and method for manufacturing the adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet and a method for manufacturing the adhesive sheet.

2. Description of the Related Art Metal film-attached pressure-sensitive adhesive sheets having a metal film such as aluminum are used for a variety of applications, such as decorative labels and display labels for various products, and conductive sheets for imparting electrical conductivity.
For example, Patent Document 1 discloses a conductive adhesive sheet having a conductive layer formed from a thin metal film having conductivity in the surface direction and formed on one surface of a supporting substrate, a conductive adhesive layer having conductivity in the thickness direction and covering the surface of the conductive layer, and an insulating adhesive layer covering the other surface of the supporting substrate.

JP 2013-216749 A

Such metal film-attached adhesive sheets are attached to a variety of adherends depending on their intended use. There is a demand for adhesive sheets that are suitable for attachment to a variety of adherends.

The present invention provides an adhesive sheet for attachment to soda glass, which comprises a substrate, a metal film, and an adhesive layer laminated on the surface of the metal film, the adhesive layer having a predetermined thickness and being a layer formed from an adhesive composition containing an acrylic copolymer having predetermined structural units, and a method for producing the adhesive sheet.
Specific aspects of the present invention are as follows [1] to [9].
[1] A pressure-sensitive adhesive sheet having a substrate, a metal film, and a pressure-sensitive adhesive layer laminated on a surface of the metal film,
the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive composition containing an acrylic copolymer (A) having a structural unit (a1) derived from an alkyl(meth)acrylate and a structural unit (a2) derived from a carboxy group-containing monomer,
The thickness of the pressure-sensitive adhesive layer is 20 μm or less,
An adhesive sheet used for attaching to soda glass.
[2] The pressure-sensitive adhesive sheet according to the above-mentioned [1], wherein the metal film is colored.
[3] The pressure-sensitive adhesive sheet described in [2] above, wherein the metal film contains a metal or metal compound selected from aluminum, chromium, nickel, gold, platinum, silver, tin, copper, iron, palladium, titanium oxide, and titanium nitride.
[4] The pressure-sensitive adhesive sheet according to any one of the above-mentioned [1] to [3], wherein the content of the structural unit (a2) is 0.1 mass% or more, based on the total amount of structural units of the acrylic copolymer (A).
[5] The pressure-sensitive adhesive sheet according to any one of the above-mentioned [1] to [4], wherein the pressure-sensitive adhesive composition further contains a crosslinking agent (B).
[6] The pressure-sensitive adhesive sheet according to the above-mentioned [5], wherein the content of the crosslinking agent (B) is 0.01 to 20.0 parts by mass per 100 parts by mass of the total amount of the acrylic copolymer (A).
[7] The pressure-sensitive adhesive sheet according to any one of [1] to [6] above, wherein the content of the metal deactivator in the pressure-sensitive adhesive composition is less than 1 part by mass per 100 parts by mass of the total amount of the acrylic polymer (A).
[8] The pressure-sensitive adhesive sheet according to any one of the above [1] to [7], which is used for attachment to a non-tin surface of soda glass.
[9] A method for producing the pressure-sensitive adhesive sheet according to any one of the above-mentioned [1] to [8],
A method for producing a pressure-sensitive adhesive sheet, comprising the following steps (1) and (2):
Step (1): A step of applying the pressure-sensitive adhesive composition to the surface of a metal film provided on a substrate to form a coating film.
Step (2): A step of drying the coating film.

The adhesive sheet of a preferred embodiment of the present invention is suitable for application to soda glass, and can effectively prevent so-called "evaporation skipping," in which at least a portion of the metal film is oxidized and altered by moisture in the air.

FIG. 1 is a schematic cross-sectional view of an example of the configuration of a pressure-sensitive adhesive sheet according to one embodiment of the present invention.

In this specification, for example, "(meth)acrylate" is used as a term indicating both "acrylate" and "methacrylate", and the same applies to other similar terms.
Moreover, the "active ingredient" of the pressure-sensitive adhesive composition means the ingredients contained in the pressure-sensitive adhesive composition excluding diluent solvents such as organic solvents.

[Configuration of the Adhesive Sheet]
The pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it has a configuration including a substrate, a metal film, and a pressure-sensitive adhesive layer laminated on the surface of the metal film, and may have layers other than these.
For example, FIG. 1 is a schematic cross-sectional view of an example of the configuration of a pressure-sensitive adhesive sheet according to one embodiment of the present invention.

A specific configuration of the adhesive sheet of one embodiment of the present invention is, as in adhesive sheet 1a in FIG. 1(a), a configuration in which a metal film 12 is laminated on one surface of a substrate 11, and an adhesive layer 13 is further laminated on the surface of the metal film 12, but is not limited to this.
For example, as in the adhesive sheet 1b of FIG. 1(b), a configuration may be used in which metal films 12a, 12b are laminated on both surfaces of a substrate 11, and an adhesive layer 13a is laminated on the surface of the metal film 12a, and an adhesive layer 13b is laminated on the surface of the metal film 12b.

Furthermore, the adhesive sheet of one embodiment of the present invention may be configured in such a manner that a release sheet 14 is further laminated on the surface of the adhesive layer 13 of the adhesive sheet 1a of FIG. 1(a), as in the adhesive sheet 1c of FIG. 1(c).
Similarly, as in adhesive sheet 1d in FIG. 1(d), the adhesive sheet 1b in FIG. 1(b) may have a release sheet 14a laminated on the surface of adhesive layer 13a, and a release sheet 14b laminated on the surface of adhesive layer 13b.
The materials of the two release sheets 14a, 14b of this adhesive sheet 1d may be the same or different, but it is preferable that the materials are adjusted so that the release strengths of release sheets 14a and 14b are different.

Alternatively, the adhesive sheet may have the configuration of the adhesive sheet 1a in FIG. 1(a), in which a peeling treatment is applied to the surface of the substrate 11 opposite to the surface on which the metal film 12 is laminated, and the resulting surface is wound into a roll.
In the pressure-sensitive adhesive sheet of one embodiment of the present invention, the substrate and the metal film may be directly laminated together, such as in the pressure-sensitive adhesive sheet 1a shown in FIG. 1, or another layer may be present between the substrate and the metal film.

Generally, when a pressure-sensitive adhesive sheet with a metal film is left attached to an adherend for a long period of time, moisture in the air can cause at least a part of the metal film to oxidize and deteriorate, which is called "vapor deposition skipping." Note that "vapor deposition skipping" is a phenomenon that can occur not only in metal vapor deposition films formed by vapor deposition, but also in metal films formed by methods other than vapor deposition. In this specification, "vapor deposition skipping" refers to a phenomenon in which at least a part of a metal film formed by a vapor deposition method or a method other than vapor deposition is oxidized and deteriorated.
For example, when deposition skipping occurs in at least a part of a colored metal film having metallic luster, the part where deposition skipping occurs discolors, resulting in an adhesive sheet with an appearance of having holes. In this case, when the adhesive sheet is used as a decorative label or a display label, the appearance of these labels is impaired.
Furthermore, even in the case of a transparent metal film such as indium tin oxide (ITO), if evaporation skipping occurs, there is concern that the properties required of the metal film, such as electrical conductivity, may be reduced.

The inventors have found through their research that the thinner the adhesive layer of the adhesive sheet, the more likely this problem of vapor deposition skipping occurs, and that it is also likely to occur when the adhesive sheet is attached to soda glass (particularly when the adhesive sheet is attached to the non-tin surface of the soda glass). In other words, an adhesive sheet with a thinner adhesive layer used for application to be attached to soda glass has the problem that vapor deposition skipping is likely to occur.
On the other hand, the pressure-sensitive adhesive sheet of one embodiment of the present invention has a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing an acrylic copolymer (A) having a predetermined structural unit, as described below, and therefore has the characteristic of being excellent in the effect of suppressing deposition skipping. Therefore, the pressure-sensitive adhesive sheet of one embodiment of the present invention has a high effect of suppressing deposition skipping even when the pressure-sensitive adhesive layer is thinned to a thickness of 20 μm or less and is further attached to soda glass.
Due to the above-mentioned characteristics, the adhesive sheet of one embodiment of the present invention can be suitably used in areas where the clearance is narrow and the thickness of the adhesive sheet to be used is limited, such as when it is applied to soda glass, and is particularly suitable for application to the non-tin surface of soda glass, an environment in which deposition splash is more likely to occur.
The configuration of each layer of the pressure-sensitive adhesive sheet according to one embodiment of the present invention will be described below.

<Substrate>
The substrate of the pressure-sensitive adhesive sheet of one embodiment of the present invention is appropriately selected depending on the application, and examples thereof include paper substrates, porous substrates such as nonwoven fabrics, and resin films.

Examples of paper materials that make up the paper base material include thin paper, medium-quality paper, fine paper, impregnated paper, coated paper, art paper, parchment paper, glassine paper, etc.

Examples of resins that make up the resin film include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resins such as polyethylene and polypropylene; vinyl-based resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide-based resins such as polyetherimide and polyimide; polyamide-based resins; acrylic resins; and fluorine-based resins.

These resin films may be made of only one type of resin, or may be made of two or more types of resins.
The resin film used in one embodiment of the present invention may contain various additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, and a colorant, in addition to the above-mentioned resin.

The resin film may be unstretched or may be stretched uniaxially, e.g., longitudinally or transversely, or biaxially.
The resin film may be a resin film having a void-containing layer containing voids therein. The resin film may be a resin film having a void-free resin layer laminated on at least one surface side of the void-containing layer.

The substrate used in one embodiment of the present invention may be a single-layer substrate made of the above-mentioned paper substrate or resin film, or a multilayer substrate made by laminating two or more types selected from the paper substrate and the resin film.
Examples of multilayer substrates include laminated resin films formed by laminating two or more types of resin films, and laminate substrates formed by laminating a paper substrate with a thermoplastic resin such as polyethylene.

When the substrate used in one embodiment of the present invention is a resin film or a laminate substrate, the surface of the substrate may be subjected to a surface treatment such as an oxidation method or a roughening method, or a primer treatment.
The oxidation method is not particularly limited, and examples thereof include corona discharge treatment, plasma treatment, chromic acid oxidation (wet), flame treatment, hot air treatment, and ozone/ultraviolet light irradiation treatment.
The method for forming the irregularities is not particularly limited, and examples thereof include sandblasting and solvent treatment.

The thickness of the substrate used in one embodiment of the present invention is preferably 1 to 1000 μm, more preferably 5 to 500 μm, even more preferably 10 to 300 μm, even more preferably 15 to 150 μm, and particularly preferably 20 to 120 μm.

<Metal Film>
The metal film of the pressure-sensitive adhesive sheet of one embodiment of the present invention is a film containing a metal or a metal compound.
The metal or metal compound constituting the metal film is appropriately selected depending on the application, and examples thereof include aluminum, chromium, nickel, gold, platinum, silver, tin, copper, iron, palladium, titanium oxide, titanium nitride, indium tin oxide (ITO), and the like.
The metal film in the pressure-sensitive adhesive sheet of one embodiment of the present invention may be a metal film containing only one metal selected from the above metals, or may be a metal film containing two or more metals selected from the above metals.

Moreover, the metal film may be colored or transparent (colorless).
For example, when the pressure-sensitive adhesive sheet according to an embodiment of the present invention is used as a decorative label or a display label, the metal film is colored. The pressure-sensitive adhesive sheet according to an embodiment of the present invention has a property of being excellent in suppressing vapor deposition skipping, and is less likely to cause the adverse effect of impairing the appearance of the label due to the occurrence of vapor deposition skipping.
In addition, when the metal film is colored, the metal film preferably contains a metal or a metal compound selected from aluminum, chromium, nickel, gold, platinum, silver, tin, copper, iron, palladium, titanium oxide, and titanium nitride.

Examples of methods for forming the metal film include a method of depositing the above-mentioned metal or metal compound by a PVD (physical vapor deposition) method such as vacuum deposition, sputtering, or ion plating, and a method of attaching a film (metal foil) made of the above-mentioned metal or metal compound using a general adhesive.
In addition, when the metal film is a metal vapor deposition film formed by vapor deposition, it is generally more likely to cause vapor deposition skipping. However, the pressure-sensitive adhesive sheet of one embodiment of the present invention has a characteristic of having an excellent effect of suppressing vapor deposition skipping. Therefore, even when the pressure-sensitive adhesive sheet of one embodiment of the present invention has a metal vapor deposition film as the metal film, it can effectively suppress vapor deposition skipping that may occur in the metal vapor deposition film.

The thickness of the metal film of the adhesive sheet of one embodiment of the present invention is preferably 1 to 5,000 nm, more preferably 5 to 1,000 nm, even more preferably 10 to 500 nm, and even more preferably 20 to 300 nm.

<Adhesive Layer, Adhesive Composition>
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is a layer formed from a pressure-sensitive adhesive composition containing an acrylic copolymer (A) having a structural unit (a1) derived from an alkyl (meth)acrylate and a structural unit (a2) derived from a carboxy group-containing monomer.

The thickness of the adhesive layer of the adhesive sheet of the present invention is 20 μm or less, but may be 18 μm or less, 15 μm or less, 12 μm or less, 10 μm or less, 8 μm or less, 5 μm or less, 4 μm or less, or 3 μm or less, depending on the application of the adhesive sheet.
The thickness of the pressure-sensitive adhesive layer may be 1 μm or more, 2 μm or more, 3 μm or more, or 5 μm or more, depending on the application of the pressure-sensitive adhesive sheet.
Regarding the thickness of the pressure-sensitive adhesive layer, the lower limit and the upper limit can be arbitrarily selected and combined.

The adhesive layer of the adhesive sheet of one embodiment of the present invention has a thickness of 20 μm or less, which reduces the amount of adhesive remaining on the adherend when peeled off, and also makes it difficult for the adhesive to protrude from the edge of the adhesive sheet. In addition, since the absolute value of the thickness is small, it is advantageous in terms of cost and productivity. Furthermore, since the thickness is highly accurate, it can be suitably used even in application locations with narrow clearances.
However, as described above, the adhesive sheet with the metal film having the thinned adhesive layer is prone to the problem of vapor deposition skipping. However, the adhesive layer of the adhesive sheet of one embodiment of the present invention is a layer formed from an adhesive composition containing an acrylic copolymer (A) having a structural unit (a2), even though it is thinned to a thickness of 20 μm or less, so that the effect of suppressing vapor deposition skipping can be improved. In particular, when the adhesive sheet is attached to soda glass, and further, when the adhesive sheet is attached to the non-tin surface of soda glass, the effect of suppressing vapor deposition skipping can be more effectively expressed.

In the course of various investigations, the present inventors have found that when a metal-film-attached adhesive sheet is attached to soda glass, particularly when the sheet is attached to the non-tin surface of the soda glass, deposition skipping is likely to occur. It has also been found that the thinner the adhesive layer of the adhesive sheet, the more likely deposition skipping is to occur. The reasons for this are considered to be as follows.
Soda lime glass is manufactured by mixing and melting metal salts such as sodium carbonate (Na ₂ CO ₃ ), calcium carbonate (CaCO ₃ ) and magnesium carbonate (CaCO ₃ ) together with silica sand (SiO ₂ ). Therefore, soda lime glass contains metal oxides derived from metal salts, such as sodium oxide (Na ₂ O), calcium oxide (CaO) and magnesium oxide (MgO). It is presumed that metal ions derived from these metal oxides migrate to the adhesive layer and metal film of the metal film-attached adhesive sheet attached to the surface of the soda lime glass, promoting the oxidation of the metal film, resulting in deposition skipping. From this presumption, it can be imagined that the thinner the thickness of the adhesive layer interposed between the soda lime glass and the metal film, the easier it is for metal ions generated from the soda lime glass to migrate to the metal film.
The inventors have found that when a pressure-sensitive adhesive sheet with a metal film is applied to the non-tin surface of soda glass, deposition skipping is more likely to occur than when the sheet is applied to the tin surface. Therefore, it is believed that metal ions derived from the above-mentioned metal oxides are more likely to migrate to the metal film of the pressure-sensitive adhesive sheet on the non-tin surface.

The inventors therefore attempted to suppress the migration of metal ions derived from metal oxides contained in soda glass to the metal film by including an acrylic copolymer (A) having a structural unit (a2) derived from a carboxyl group-containing monomer in the adhesive composition forming the adhesive layer. In other words, they speculated that the carboxy group (-COOH) of the structural unit (a2) of the acrylic copolymer (A) captures metal ions derived from metal oxides contained in soda glass at the adhesive surface of the adhesive layer with the soda glass, thereby suppressing the migration of the metal ions to the metal film. Based on this speculation, they found that by using an acrylic copolymer (A) having a structural unit (a2) containing a carboxy group to form the adhesive layer, an adhesive sheet that can effectively suppress deposition skipping can be obtained even if the thickness of the adhesive layer is reduced to 20 μm or less, and the adhesive sheet of the present invention was completed based on this knowledge.

The pressure-sensitive adhesive composition which is a material for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of one embodiment of the present invention contains an acrylic copolymer (A), and preferably further contains a crosslinking agent (B).
In the pressure-sensitive adhesive composition used in one embodiment of the present invention, the total content of components (A) and (B) is preferably 30 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 60 to 100 mass%, still more preferably 65 to 100 mass%, and particularly preferably 70 to 100 mass%, relative to the total amount (100 mass%) of the active ingredients in the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition used in one embodiment of the present invention may further contain a tackifier (C), and may contain pressure-sensitive adhesive additives other than the components (A) to (C).
Hereinafter, each component contained in the pressure-sensitive adhesive composition used in one embodiment of the present invention will be described.

<Component (A): Acrylic Copolymer>
The acrylic copolymer (A) used in one embodiment of the present invention has a structural unit (a1) derived from an alkyl (meth)acrylate (hereinafter also referred to as "monomer (a1')") and a structural unit (a2) derived from a carboxy group-containing monomer (hereinafter also referred to as "monomer (a2')").
The acrylic copolymer (A) may be used alone or in combination of two or more kinds.
The acrylic copolymer (A) used in one embodiment of the present invention may be either an emulsion type polymer or a non-emulsion type polymer, but is preferably a non-emulsion type polymer.
Furthermore, the copolymerization form of the acrylic copolymer (A) is not particularly limited, and may be any of a random copolymer, a block copolymer, and a graft copolymer.

The mass average molecular weight (Mw) of the acrylic copolymer (A) used in one embodiment of the present invention is preferably 50,000 to 2,000,000, more preferably 100,000 to 1,800,000, even more preferably 200,000 to 1,500,000, still more preferably 250,000 to 1,200,000, and particularly preferably 300,000 to 1,000,000.
In this specification, the mass average molecular weight (Mw) is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC), specifically, a value measured based on the method described in the examples.

In the pressure-sensitive adhesive composition used in one embodiment of the present invention, the content of the acrylic copolymer (A) is preferably 30 mass % or more, more preferably 40 mass % or more, even more preferably 50 mass % or more, still more preferably 60 mass % or more, and particularly preferably 70 mass % or more, relative to the total amount (100 mass %) of active ingredients in the pressure-sensitive adhesive composition.
In addition, the content of the acrylic copolymer (A) may be 100% by mass or less based on the total amount (100% by mass) of the active ingredients of the pressure-sensitive adhesive composition. In the case where the crosslinking agent (B) is contained, the content is preferably 99.95% by mass or less, more preferably 99.9% by mass or less, even more preferably 99.5% by mass or less, still more preferably 99.0% by mass or less, and particularly preferably 98.5% by mass or less.
That is, the content of the acrylic copolymer (A) relative to the total amount (100 mass%) of the active ingredients of the pressure-sensitive adhesive composition is preferably 30 to 99.99 mass%, more preferably 40 to 99.95 mass%, even more preferably 50 to 99.90 mass%, still more preferably 60 to 99.50 mass%, and particularly preferably 70 to 99.00 mass%.

The acrylic copolymer (A) used in one embodiment of the present invention may be a copolymer having a structural unit (a3) derived from a functional group-containing monomer other than a carboxy group (hereinafter also referred to as "monomer (a3')"), and may further be a copolymer having a structural unit (a4) derived from a monomer other than the monomers (a1'), (a2') and (a3') (hereinafter also referred to as "monomer (a4')").

In the acrylic copolymer (A) used in one embodiment of the present invention, the total content of the structural units (a1) and (a2) is preferably 35 to 100 mass%, more preferably 45 to 100 mass%, more preferably 55 to 100 mass%, even more preferably 65 to 100 mass%, still more preferably 75 to 100 mass%, still more preferably 85 to 100 mass%, and particularly preferably 90 to 100 mass%, based on the total amount (100 mass%) of the structural units of the acrylic copolymer (A).
The monomers and constituent units constituting the acrylic copolymer (A) will be described below.

[Monomer (a1′), Structural Unit (a1)]
The alkyl group in the monomer (a1') preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, even more preferably 1 to 16 carbon atoms, still more preferably 1 to 12 carbon atoms, and particularly preferably 4 to 8 carbon atoms.
The alkyl group contained in the monomer (a1') may be a linear alkyl group or a branched alkyl group.

Examples of the monomer (a1') include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate (n-propyl (meth)acrylate, i-propyl (meth)acrylate), butyl (meth)acrylate (n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate), pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate.
These monomers (a1') may be used alone or in combination of two or more kinds.

In addition, the acrylic copolymer (A) used in one embodiment of the present invention preferably has, as the structural unit (a1), a structural unit (a11) derived from an alkyl (meth)acrylate having an alkyl group having 4 to 8 carbon atoms (hereinafter also referred to as "monomer (a11')").

The monomer (a11') preferably contains at least one selected from butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, more preferably contains butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate, and even more preferably contains butyl (meth)acrylate.

The content of the structural unit (a11) is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, and particularly preferably 95 to 100% by mass, relative to the total amount (100% by mass) of the structural unit (a1) contained in the acrylic copolymer (A).

In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a1) is, relative to the total amount (100 mass%) of the structural units of the acrylic copolymer (A), preferably 30 mass% or more, more preferably 40 mass% or more, even more preferably 50 mass% or more, still more preferably 60 mass% or more, particularly preferably 70 mass% or more, and is preferably 99.9 mass% or less, more preferably 99.5 mass% or less, even more preferably 99.0 mass% or less, still more preferably 98.0 mass% or less, and particularly preferably 97.0 mass% or less.
In other words, the content of the structural unit (a1) relative to the total amount (100 mass%) of the structural units of the acrylic copolymer (A) is preferably 30 to 99.9 mass%, more preferably 40 to 99.5 mass%, even more preferably 50 to 99.0 mass%, still more preferably 60 to 98.0 mass%, and particularly preferably 70 to 97.0 mass%.

[Monomer (a2′), Structural Unit (a2)]
Examples of the monomer (a2') include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and citraconic acid; and 2-carboxyethyl (meth)acrylate.
These monomers (a2') may be used alone or in combination of two or more kinds.

The monomer (a2') used in one embodiment of the present invention preferably contains an ethylenically unsaturated monocarboxylic acid, and more preferably contains (meth)acrylic acid.
The content of the structural unit (a2) is adjusted so as to satisfy the above requirement (I), and the preferred range is as described above.

In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a2) relative to the total amount (100 mass%) of the structural units of the acrylic copolymer (A) is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, more preferably 1.0 mass% or more, even more preferably 1.5 mass% or more, still more preferably 2.0 mass% or more, still more preferably 2.5 mass% or more, and particularly preferably 3.0 mass% or more.
Furthermore, from the viewpoint of obtaining a pressure-sensitive adhesive sheet having excellent adhesive strength, the content of the structural unit (a2) is preferably 50 mass% or less, more preferably 40 mass% or less, more preferably 35 mass% or less, even more preferably 30 mass% or less, still more preferably 25 mass% or less, and particularly preferably 20 mass% or less, relative to the total amount of the structural units of the acrylic copolymer (A).
In other words, in one embodiment of the present invention, the content of the structural unit (a2) is preferably 0.1 to 50 mass%, more preferably 0.5 to 40 mass%, more preferably 1.0 to 35 mass%, even more preferably 1.5 to 30 mass%, still more preferably 2.0 to 25 mass%, and particularly preferably 3.0 to 20 mass%, relative to the total amount of structural units of the acrylic copolymer (A).

[Monomer (a3′), Structural Unit (a3)]
The acrylic copolymer (A) used in one embodiment of the present invention may be a copolymer having a structural unit (a3) derived from a monomer (monomer (a3')) containing a functional group other than a carboxy group.
Examples of the monomer (a3') include a hydroxy group-containing monomer and an epoxy group-containing monomer.
These monomers (a3') may be used alone or in combination of two or more kinds.

Examples of hydroxy-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.
The number of carbon atoms in the alkyl group of the hydroxyalkyl (meth)acrylates is preferably 1 to 10, more preferably 1 to 8, even more preferably 1 to 6, and still more preferably 2 to 4. The alkyl group may be a linear alkyl group or a branched alkyl group.

Examples of epoxy-containing monomers include epoxy group-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth)acrylate; glycidyl crotonate, and allyl glycidyl ether.

In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a3) is, relative to the total amount (100 mass%) of the structural units of the acrylic copolymer (A), preferably 50 mass% or less, more preferably 40 mass% or less, even more preferably 30 mass% or less, still more preferably 20 mass% or less, and particularly preferably 10 mass% or less.
In addition, there is no particular lower limit on the content of the structural unit (a3), and it may be 0 mass% or more, 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.2 mass% or more, 0.3 mass% or more, 0.4 mass% or more, or 0.5 mass% or more, relative to the total amount (100 mass%) of the structural units of the acrylic copolymer (A).
Furthermore, with regard to the amount of the structural unit (a3), the above-mentioned lower limit and upper limit can be combined arbitrarily.

[Monomer (a4'), Structural Unit (a4)]
The acrylic copolymer (A) used in one embodiment of the present invention may be a copolymer having a structural unit (a4) derived from a monomer (monomer (a4')) other than the monomers (a1'), (a2'), and (a3').
The monomer (a4') is not particularly limited, and examples thereof include olefins such as ethylene, propylene, isobutylene, etc., halogenated olefins such as vinyl chloride, vinylidene chloride, etc., diene monomers such as butadiene, isoprene, chloroprene, etc., styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, N-vinylpyrrolidone, etc.
These monomers (a4') may be used alone or in combination of two or more kinds.

In the acrylic copolymer (A) used in one embodiment of the present invention, the content of the structural unit (a4) is preferably 0 to 40% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, still more preferably 0 to 10% by mass, and particularly preferably 0 to 5% by mass, relative to the total amount (100% by mass) of the structural units of the acrylic copolymer (A).

<Other adhesive resins>
The pressure-sensitive adhesive composition used in one embodiment of the present invention may further contain a pressure-sensitive adhesive resin other than component (A) within a range that does not impair the effects of the present invention.
Such other adhesive resins may be any resin that has adhesiveness by itself, and examples thereof include urethane-based resins, rubber-based resins, olefin-based resins, silicone-based resins, and curable resins in which polymerizable groups have been introduced into these resins.
These other adhesive resins may be used alone or in combination of two or more kinds.
The other adhesive resin may be an emulsion type resin or a non-emulsion type resin, but is preferably a non-emulsion type resin.

The mass average molecular weight (Mw) of the other adhesive resin used in one embodiment of the present invention is preferably 10,000 to 2,000,000, more preferably 20,000 to 1,800,000, and even more preferably 30,000 to 1,500,000.

In the adhesive composition used in one embodiment of the present invention, the content of the adhesive resin other than component (A) is preferably 0 to 100 parts by mass, more preferably 0 to 50 parts by mass, more preferably 0 to 30 parts by mass, even more preferably 0 to 10 parts by mass, even more preferably 0 to 5 parts by mass, still more preferably 0 to 1 part by mass, and particularly preferably 0 to 0.1 parts by mass, relative to 100 parts by mass of the total amount of component (A) contained in the adhesive composition.

<Component (B): Crosslinking Agent>
The pressure-sensitive adhesive composition used in one embodiment of the present invention preferably further contains a crosslinking agent (B).
By preparing a pressure-sensitive adhesive composition containing the crosslinking agent (B) together with the component (A), the cohesive strength in the pressure-sensitive adhesive layer can be increased to obtain a pressure-sensitive adhesive sheet having high adhesive strength. Furthermore, even when the sheet is left standing for a long period of time in a high-temperature, high-humidity environment in which deposition skipping is more likely to occur while attached to soda glass, deposition skipping can be more effectively suppressed.

Examples of the crosslinking agent (B) used in one embodiment of the present invention include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and metal chelate-based crosslinking agents.
These crosslinking agents (B) may be used alone or in combination of two or more kinds.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate; diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate.
In addition, trimers of these organic polyisocyanate compounds, and isocyanate-terminated urethane prepolymers obtained by reacting these organic polyisocyanate compounds with polyol compounds can also be used.

Examples of epoxy crosslinking agents include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 1,3-bis(N,N-diglycidylaminomethyl)toluene, and N,N,N',N'-tetraglycidyl-4,4-diaminodiphenylmethane.

Examples of imine-based crosslinking agents include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β-aziridinyl propionate, N,N'-toluene-2,4-bis(1-aziridinecarboxamide)triethylenemelamine, etc.

Examples of metal chelate crosslinking agents include coordination compounds of polyvalent metals such as aluminum chelate compounds such as trisethylacetoacetate aluminum, ethylacetoacetate aluminum diisopropylate, and trisacetylacetonate aluminum.

The crosslinking agent (B) used in one embodiment of the present invention preferably contains at least one selected from an isocyanate-based crosslinking agent and a metal chelate-based crosslinking agent, more preferably contains at least an isocyanate-based crosslinking agent, and even more preferably contains at least a tolylene diisocyanate-based compound.

When the pressure-sensitive adhesive composition used in one embodiment of the present invention contains a crosslinking agent (B), the content of the crosslinking agent (B) is, relative to 100 parts by mass of the total amount of the acrylic copolymer (A), preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, even more preferably 0.50 parts by mass or more, still more preferably 0.70 parts by mass or more, particularly preferably 1.00 parts by mass or more, and is also preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, more preferably 10.0 parts by mass or less, even more preferably 8.0 parts by mass or less, still more preferably 6.0 parts by mass or less, and particularly preferably 4.5 parts by mass or less.
That is, in one embodiment of the present invention, the content of the crosslinking agent (B) is preferably 0.01 to 20.0 parts by mass, more preferably 0.05 to 15.0 parts by mass, more preferably 0.10 to 10.0 parts by mass, even more preferably 0.50 to 8.0 parts by mass, still more preferably 0.70 to 6.0 parts by mass, and particularly preferably 1.00 to 4.5 parts by mass, relative to 100 parts by mass of the total amount of the acrylic copolymer (A).

<Tackifier (C)>
The pressure-sensitive adhesive composition used in one embodiment of the present invention may further contain a tackifier (C).
In this specification, the tackifier refers to a component that auxiliaryally improves the adhesiveness of the acrylic copolymer (A), which is an adhesive resin, and is an oligomer usually having a mass average molecular weight (Mw) of less than 10,000, and is distinguished from the adhesive resin containing the above-mentioned acrylic copolymer (A).
The mass average molecular weight (Mw) of the tackifier (C) used in one embodiment of the present invention is preferably 400 to 4,000, more preferably 800 to 1,500.

Examples of the tackifier (C) used in one embodiment of the present invention include rosin-based resins, terpene-based resins, styrene-based resins, hydrocarbon-based resins, and hydrogenated resins obtained by hydrogenating these resins.
These tackifiers (C) may be used alone or in combination of two or more kinds.

Examples of the rosin resin include rosin resin, rosin ester resin, and rosin phenol resin, and may be hydrogenated rosin resins obtained by hydrogenating these resins.
The terpene resin may be any compound having a structural unit derived from isoprene, and examples thereof include terpene resins, aromatic modified terpene resins, and terpene phenol resins, and may be hydrogenated terpene resins obtained by hydrogenating these resins.
Examples of the styrene-based resin include resins obtained by copolymerizing a styrene-based monomer such as α-methylstyrene or β-methylstyrene with an aliphatic monomer, and hydrogenated styrene-based resins obtained by hydrogenating such resins may also be used.
Examples of the hydrocarbon resin include C5 hydrocarbon resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine, and 1.3-pentadiene produced by thermal decomposition of petroleum naphtha; C9 hydrocarbon resins obtained by copolymerizing C9 fractions such as indene and vinyltoluene produced by thermal decomposition of petroleum naphtha; and hydrogenated hydrocarbon resins obtained by hydrogenating these.

The softening point of the tackifier (C) used in one embodiment of the present invention is preferably 70 to 170°C, more preferably 80 to 160°C, even more preferably 85 to 150°C, and still more preferably 90 to 140°C.
In this specification, the softening point of the tackifier (C) means a value measured in accordance with JIS K2531.
When two or more tackifiers are used in combination, it is preferable that the weighted average value calculated from the softening points and blend ratios of the respective tackifiers is within the above range.

When the pressure-sensitive adhesive composition used in one embodiment of the present invention contains a tackifier (C), the content of the tackifier (C) is preferably 5 to 300 parts by mass, more preferably 10 to 200 parts by mass, even more preferably 20 to 180 parts by mass, and even more preferably 30 to 150 parts by mass, relative to 100 parts by mass of the total amount of the acrylic copolymer (A) contained in the pressure-sensitive adhesive composition.

<Additives for adhesives>
The pressure-sensitive adhesive composition used in one embodiment of the present invention may further contain pressure-sensitive adhesive additives other than the crosslinking agent (B) and the tackifier (C) to the extent that the effects of the present invention are not impaired.
Examples of such adhesive additives include plasticizers (liquid resins, liquid paraffin, etc.), compatibilizers, wetting agents, thickeners, defoamers, UV absorbers, antioxidants, fillers, rust inhibitors, antibacterial agents, insect repellents, fragrances, pigments, dyes, curing agents, curing assistants, catalysts, etc.
Each of these additives may be used alone or in combination of two or more kinds.

When the adhesive composition used in one embodiment of the present invention contains these adhesive additives, the content of each of the adhesive additives is appropriately set depending on the type of additive, but is preferably 0.01 to 40 parts by mass, more preferably 0.05 to 30 parts by mass, even more preferably 0.1 to 20 parts by mass, and even more preferably 0.2 to 10 parts by mass, relative to 100 parts by mass of the total amount of the acrylic copolymer (A).

The pressure-sensitive adhesive composition of one embodiment of the present invention may contain a metal deactivator. However, since the metal deactivator itself is a persistent substance, from an environmental perspective, the smaller the content of the metal deactivator, the more preferable it is.
The specific content of the metal deactivator is, relative to 100 parts by mass of the total amount of the acrylic copolymer (A), preferably less than 1 part by mass, more preferably less than 0.1 part by mass, even more preferably less than 0.01 part by mass, still more preferably less than 0.001 part by mass, and particularly preferably less than 0.0001 part by mass or 0 part by mass (i.e., no metal deactivator is contained).

Examples of the metal deactivators include benzotriazole, 4-methylbenzotriazole, 5-methylbenzotriazole, 5-chlorobenzotriazole, tolyltriazole, potassium salt of tolyltriazole, 3-(N-salicyloyl)amino-1,2,4-triazole, and 2-(2'-hydroxy-5-methylphenyl)benzotriazole.

<Organic solvent>
The pressure-sensitive adhesive composition used in one embodiment of the present invention may be further diluted with an organic solvent to form a solution, from the viewpoints of facilitating the formation of a coating film and improving workability.
Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.
These organic solvents may be used alone or in combination of two or more kinds.
As for these organic solvents, the organic solvents used in the synthesis of the acrylic copolymer (A) may be used as they are, or one or more organic solvents other than the organic solvents used in the synthesis of the acrylic copolymer (A) may be added.

The active ingredient concentration of the adhesive composition used in one embodiment of the present invention is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and even more preferably 15 to 60% by mass, relative to the total amount (100% by mass) of the adhesive composition.

<Release sheet>
The pressure-sensitive adhesive sheet of one embodiment of the present invention may further have a release sheet on the surface of the pressure-sensitive adhesive layer.
The release sheet used in one embodiment of the present invention may be, for example, a sheet having a release agent layer formed from a release agent on one or both sides of a release sheet substrate.

Examples of substrates for release sheets include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; resin films such as polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymers, polyurethane, ethylene-vinyl acetate copolymers, ionomer resins, ethylene (meth)acrylic acid copolymers, polystyrene, polycarbonate, fluororesins, low-density polyethylene, linear low-density polyethylene, and triacetyl cellulose; paper substrates such as fine paper, coated paper, and glassine paper; and laminated paper in which these paper substrates are laminated with a thermoplastic resin such as polyethylene.

Examples of release agents that form the release agent layer include silicone resins, olefin resins, long-chain alkyl resins, alkyd resins, fluorine resins, and rubber elastomers such as isoprene resins and butadiene resins.

There are no particular limitations on the thickness of the release sheet, but it is preferably 5 to 300 μm, more preferably 7 to 200 μm, and even more preferably 10 to 150 μm. If a resin film is used as the substrate for the release sheet, it is even more preferably 10 to 100 μm.

[Method for producing pressure-sensitive adhesive sheet]
The method for producing the pressure-sensitive adhesive sheet of one embodiment of the present invention is not particularly limited, but from the viewpoint of producing a pressure-sensitive adhesive sheet having an excellent effect of suppressing deposition skipping, a method having the following steps (1) and (2) is preferred.
Step (1): A step of applying the pressure-sensitive adhesive composition to the surface of a metal film provided on a substrate to form a coating film.
Step (2): A step of drying the coating film.

As in step (1), by applying the adhesive composition directly to the surface of the metal film to form a coating film, an adhesive sheet can be obtained in which the carboxyl groups (-COOH) of the acrylic copolymer (A) in the adhesive layer are more unevenly distributed on the surface of the adhesive layer facing the metal film. As a result, when the adhesive sheet obtained is attached to soda glass, metal ions that may be generated from metal oxides contained in the soda glass react with the carboxyl groups (-COOH) in the adhesive layer before migrating to the metal film, making it possible to suppress the migration of metal ions to the metal film. And even when the thickness of the adhesive layer is reduced to 20 μm or less, the migration of metal ions to the metal film can be sufficiently suppressed.

In the step (1), it is necessary to form a metal film on a substrate in advance.
The metal film may be formed on the substrate by vapor deposition, or may be formed by attaching the substrate and the metal film via an adhesive. Alternatively, a commercially available substrate with a metal film formed thereon may be used.

In step (1), methods for applying the adhesive composition onto the surface of the metal film include, for example, spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

Step (2) is a step of drying the coating film formed in step (1). As drying conditions, it is preferable to heat and dry the coating film at a temperature of 80° C. to 150° C. for 30 seconds to 5 minutes (preferably 40 seconds to 3 minutes, and more preferably 45 seconds to 2 minutes).
Through step (2), a pressure-sensitive adhesive layer can be formed on the surface of the metal film.
In order to complete the crosslinking in the pressure-sensitive adhesive layer, it is preferable to carry out a seasoning step in which the pressure-sensitive adhesive layer is held for a certain period of time (for example, about 1 to 14 days).

Through the above steps, a pressure-sensitive adhesive sheet having a configuration like that of the pressure-sensitive adhesive sheet 1a shown in FIG. 1(a) can be manufactured.
Furthermore, after that, the release-treated surface of a release sheet may be further laminated on the surface of the formed adhesive layer to form an adhesive sheet having a structure like that of adhesive sheet 1c shown in FIG. 1(c).

A double-sided adhesive sheet having a structure like adhesive sheet 1b shown in FIG. 1(b) can be produced by forming an adhesive layer on one metal film through steps (1) and (2) above, and then forming an adhesive layer on the other metal film in the same manner. When an adhesive layer is formed on the metal film, a release-treated surface of a release sheet can be further laminated on the surface of the adhesive layer, thereby producing a double-sided adhesive sheet having a structure like adhesive sheet 1d shown in FIG. 1(d).

The pressure-sensitive adhesive sheet of one embodiment of the present invention can also be produced by a method other than the method including the above-mentioned steps (1) and (2).
For example, the pressure-sensitive adhesive layer can also be produced by applying a pressure-sensitive adhesive composition onto the release-treated surface of a release sheet to form a coating film, drying the coating film to form a pressure-sensitive adhesive layer, and then attaching the surface of the pressure-sensitive adhesive layer to a metal film of a substrate having a metal film formed thereon.
In this production method, the coating method and the drying conditions for the coating film are as described above.

[Characteristics and uses of adhesive sheets]
The pressure-sensitive adhesive sheet according to one embodiment of the present invention is suitable for application to soda glass, and can effectively suppress the so-called "evaporation skipping" that occurs when at least a portion of a metal film is oxidized and altered by moisture in the air. This characteristic can be fully exhibited even when the pressure-sensitive adhesive layer is thinned to a thickness of 20 μm or less.
When the pressure-sensitive adhesive sheet of one embodiment of the present invention is attached to the non-tin side or the tin side of a float glass plate conforming to the JIS R3202:2011 standard and allowed to stand in a high-temperature and high-humidity environment of 85°C and a relative humidity of 85%, it is preferable that no deposition skipping occurs even after 96 hours, and more preferably no deposition skipping occurs even after 168 hours.

The pressure-sensitive adhesive sheet of the present invention is used for application to soda-lime glass, but in view of the above-mentioned characteristics of the present invention, it is preferable to apply it to the non-tin surface of the soda-lime glass. In addition, the pressure-sensitive adhesive sheet of one embodiment of the present invention can also be used in application locations with narrow clearances.
The adhesive sheet of one embodiment of the present invention is not particularly limited in its use, and can be used, for example, as a decorative label or display label to be attached to the surface of soda glass, a tamper-proof sheet, a conductive sheet for imparting conductivity, and the like.

The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples in any way.
The physical properties were measured by the methods described below.

[Mass average molecular weight (Mw)]
Measurements were carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the conditions below, and the values measured were converted into standard polystyrene equivalent values.
(Measurement conditions)
Column: "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL" and "TSK gel G1000HXL" connected in sequence (all manufactured by Tosoh Corporation)
Column temperature: 40°C
Developing solvent: tetrahydrofuran Flow rate: 1.0 mL/min

[Softening point]
Measurement was performed in accordance with JIS K2531.

Production Example 1
(Preparation of Pressure-Sensitive Adhesive Composition (1))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (1) having an active ingredient concentration of 30 mass %.
"Acrylic copolymer (A-i)" (a copolymer in which the content ratio of the structural units is n-butyl acrylate (BA)/acrylic acid (AAc)=90.0/10.0 (mass%), Mw=470,000): 100 parts by mass (effective component ratio)
"Tolylene diisocyanate (TDI)" (product name "Coronate L", manufactured by Tosoh Corporation): 2.0 parts by mass (active ingredient ratio)

Production Example 2
(Preparation of Pressure-Sensitive Adhesive Composition (2))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (2) having an active ingredient concentration of 35 mass %.
"Acrylic copolymer (A-ii)" (a copolymer having a content ratio of structural units of n-butyl acrylate (BA)/vinyl acetate (VAc)/acrylic acid (AAc) = 90.0/5.0/5.0 (mass%), Mw = 350,000): 100 parts by mass (effective component ratio)
"Tolylene diisocyanate (TDI)" (product name "Coronate L", manufactured by Tosoh Corporation): 1.0 part by mass (active ingredient ratio)

Production Example 3
(Preparation of Pressure-Sensitive Adhesive Composition (3))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (3) having an active ingredient concentration of 35 mass %.
"Acrylic copolymer (A-iii)" (a copolymer having a content ratio of structural units of n-butyl acrylate (BA)/2-ethylhexyl acrylate (2EHA)/acrylic acid (AAc)/2-hydroxyethyl acrylate (2HEA) = 56.0/40.0/3.5/0.5 (mass%), Mw = 480,000): 100 parts by mass (effective component ratio)
"Tolylene diisocyanate (TDI)" (product name "Coronate L", manufactured by Tosoh Corporation): 1.0 part by mass (active ingredient ratio)

Production Example 4
(Preparation of Pressure-Sensitive Adhesive Composition (4))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (4) having an active ingredient concentration of 40 mass %.
"Acrylic copolymer (A-iv)" (a copolymer having a content ratio of structural units of 2-ethylhexyl acrylate (2EHA)/n-butyl acrylate (BA)/ethyl acrylate (EA)/acrylic acid (AAc)/2-hydroxyethyl acrylate (2HEA) = 60.0/22.5/15.0/2.0/0.5 (mass%), Mw = 680,000): 100 parts by mass (effective component ratio)
"Tolylene diisocyanate (TDI)" (product name "Coronate L", manufactured by Tosoh Corporation): 0.75 parts by mass (active ingredient ratio)
"Hydrogenated rosin resin" (product name "KE-359", manufactured by Arakawa Chemical Industries, Ltd., softening point = 94 to 104 ° C.): 25 parts by mass (effective ingredient ratio)
- "Aromatic terpene resin" (product name "YS Resin TO105", manufactured by Yasuhara Chemical Co., Ltd., softening point = 100 to 110 ° C.): 15 parts by mass (effective ingredient ratio)

Production Example 5
(Preparation of Pressure-Sensitive Adhesive Composition (5))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (5) having an active ingredient concentration of 30 mass %.
"Acrylic copolymer (A-v)": a copolymer of 2-ethylhexyl acrylate (2EHA)/methyl acrylate (MA)/glycidyl methacrylate (GMA)/acrylic acid (AAc) = 60.0/38.0/0.5/1.5 (mass%), Mw = 580,000: 100 parts by mass (effective component ratio)
"Aziridine-based crosslinking agent (aziridine)" (product name "BXX5134", manufactured by Toyochem Co., Ltd.): 0.24 parts by mass (effective ingredient ratio)

Production Example 6
(1) Synthesis of Linear Urethane Prepolymer (Ure) In a reaction vessel under a nitrogen atmosphere, 100 parts by mass (effective component ratio) of polycarbonate diol having a mass average molecular weight (Mw) of 1,000 was mixed with isophorone diisocyanate such that the equivalent ratio of the hydroxyl groups of the polycarbonate diol to the isocyanate groups of isophorone diisocyanate was 1/1, and 160 parts by mass of toluene was further added. The mixture was stirred under a nitrogen atmosphere and reacted at 80° C. for 6 hours or more until the isocyanate group concentration reached the theoretical amount.
Next, a solution prepared by diluting 1.44 parts by mass (effective component ratio) of 2-hydroxyethyl methacrylate (HEMA) with 30 parts by mass of toluene was added, and the mixture was allowed to react at 80° C. for a further 6 hours until the isocyanate groups at both ends had disappeared, thereby obtaining a linear urethane prepolymer (Ure) having a mass average molecular weight (Mw) of 29,000.
(2) Synthesis of acrylic urethane resin (i) In a reaction vessel under a nitrogen atmosphere, 45.0 parts by mass (effective component ratio) of the linear urethane prepolymer (Ure) obtained in (1) above, 53.2 parts by mass (effective component ratio) of methyl methacrylate (MMA), 1.8 parts by mass (effective component ratio) of 2-hydroxyethyl methacrylate (HEMA) and 22.5 parts by mass of toluene were added, and the mixture was heated to 105 ° C. while stirring. Then, in the reaction vessel, a solution obtained by diluting 1.0 part by mass (effective component ratio) of a radical initiator (manufactured by Nippon Finechem Co., Ltd., product name "ABN-E") with 94.5 parts by mass of toluene was dripped over 4 hours while maintaining the temperature at 105 ° C. After completion of dripping of the solution, the mixture was reacted at 105 ° C. for 6 hours to obtain a solution of acrylic urethane resin (i) having a mass average molecular weight (Mw) of 105,000.
(3) Preparation of Pressure-Sensitive Adhesive Composition (6) The components shown below were added in the amounts shown below and diluted with toluene to prepare a pressure-sensitive adhesive composition (6) having an active ingredient concentration of 25 mass %.
"Acrylic urethane resin (i)" (a resin obtained through the above (1) and (2), a copolymer having a content ratio of structural units of Ure/MMA/HEMA=45.0/53.2/1.8 (mass%), Mw=105,000): 100 parts by mass (effective component ratio)
"Hexamethylene diisocyanate (HMDI)" (product name "Coronate HL", manufactured by Tosoh Corporation): 2.0 parts by mass (active ingredient ratio)

Production Example 7
(Preparation of Pressure-Sensitive Adhesive Composition (7))
The components shown below were added in the amounts shown below and diluted with ethyl acetate to prepare a pressure-sensitive adhesive composition (7) having an active ingredient concentration of 30 mass %.
Acrylic copolymer (ii) (a copolymer having a content ratio of structural units of n-butyl acrylate (BA)/methyl methacrylate (MMA)/vinyl acetate (VAc)/2-hydroxyethyl acrylate (2HEA)=80.0/10.0/9.0/1.0 (mass%), Mw=600,000): 100 parts by mass (effective component ratio)
"Trimethylolpropane xylene diisocyanate (XDI)" (product name "Takenate D-110N", manufactured by Mitsui Chemicals, Inc.): 1.6 parts by mass (active ingredient ratio)
"Hydrogenated rosin resin" (product name "KE-359", manufactured by Arakawa Chemical Industries, Ltd., softening point = 94 to 104 ° C.): 25 parts by mass (effective ingredient ratio)

Examples 1 to 5, Comparative Examples 1 to 2
(Preparation of adhesive sheet)
A pressure-sensitive adhesive composition of the type shown in Table 1 was applied onto the aluminum-vapor-deposited surface of a PET film with an aluminum vapor-deposited film (manufactured by Toray Advanced Film Co., Ltd., product name "Metal Me", thickness: 50 μm, a laminate in which an aluminum film, which is a metal film, is formed to a thickness of 30 to 50 nm by vapor deposition on a PET film substrate) to form a coating film, and the coating film was dried at 100° C. (110° C. only for Comparative Example 1) for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 10 μm.
Then, the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031", thickness: 38 μm, polyethylene terephthalate (PET) film with a silicone release treatment on the surface) was laminated on the exposed surface of the formed adhesive layer to produce an adhesive sheet having the same configuration as the adhesive sheet 1c shown in FIG. 1(c).

The pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were evaluated for their effect of suppressing deposition skipping based on the following method. The evaluation results are shown in Table 2.
[Evaluation of the effect of suppressing deposition skipping]
The pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples were cut into squares with sides of 25 mm to prepare test samples. The release sheet of the test sample was removed, and the exposed surface of the pressure-sensitive adhesive layer was attached to the non-tin or tin side of a float glass plate conforming to the standard of JIS R3202:2011. The state of the aluminum film of the test sample after 24 hours, 96 hours, and 168 hours in a high-temperature and high-humidity environment of 85°C and 85% relative humidity was visually observed through the float glass plate, and the presence or absence of deposition skipping was evaluated according to the following criteria.
A: No deposition scattering was observed.
F: Vapor deposition skipping was observed.

As can be seen from Table 2, the adhesive sheets produced in Examples 1 to 5 were highly effective in suppressing deposition skipping even when left unattended in a high-temperature, high-humidity environment for 168 hours. On the other hand, the adhesive sheets produced in Comparative Examples 1 and 2 showed deposition skipping after being left unattended in a high-temperature, high-humidity environment for 96 hours.

Reference symbols 1a, 1b, 1c, 1d: adhesive sheet 11; substrate 12, 12a, 12b; metal film 13, 13a, 13b; adhesive layer 14, 14a, 14b; release sheet

Claims (9)

A pressure-sensitive adhesive sheet having a substrate, a metal film, and a pressure-sensitive adhesive layer laminated on a surface of the metal film,
the pressure-sensitive adhesive layer is a layer formed from a pressure-sensitive adhesive composition comprising an acrylic copolymer (A) having a structural unit (a1) derived from an alkyl (meth)acrylate and a structural unit (a2) derived from a carboxy group-containing monomer (however, excluding removable pressure-sensitive adhesive compositions comprising a (meth)acrylic acid ester copolymer having a weight-average molecular weight of 300,000 to 900,000 obtained by polymerizing a monomer mixture containing at least 0.1 to 2.0% by weight of a vinyl monomer having a secondary hydroxyl group, and aqueous pressure-sensitive adhesive compositions comprising a water-dispersible acrylic copolymer having a weight-average molecular weight of 100,000 to 600,000 that contains an acidic phosphate ester group);
The content of the structural unit (a2) is 0.5% by mass or more based on the total amount of the structural units of the acrylic copolymer (A),
The thickness of the pressure-sensitive adhesive layer is 20 μm or less,
An adhesive sheet used for attaching to soda glass. The adhesive sheet according to claim 1, wherein the metal film is colored. The adhesive sheet according to claim 2, wherein the metal film contains a metal or a metal compound selected from aluminum, chromium, nickel, gold, platinum, silver, tin, copper, iron, palladium, titanium oxide, and titanium nitride. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the content of the structural unit (a2) is 1.0 mass % or more based on the total amount of structural units of the acrylic copolymer (A). The adhesive sheet according to any one of claims 1 to 4, wherein the adhesive composition further contains a crosslinking agent (B). The pressure-sensitive adhesive sheet according to claim 5, wherein the content of the crosslinking agent (B) is 0.01 to 20.0 parts by mass per 100 parts by mass of the total amount of the acrylic copolymer (A). The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the content of the metal deactivator contained in the pressure-sensitive adhesive composition is less than 1 part by mass per 100 parts by mass of the total amount of the acrylic polymer (A). The adhesive sheet according to any one of claims 1 to 7, which is used for attachment to the non-tin surface of soda glass. A method for producing the pressure-sensitive adhesive sheet according to any one of claims 1 to 8, comprising the steps of:
A method for producing a pressure-sensitive adhesive sheet, comprising the following steps (1) and (2):
Step (1): A step of applying the pressure-sensitive adhesive composition to the surface of a metal film provided on a substrate to form a coating film.
Step (2): A step of drying the coating film.