JP7014049B2 - Adhesive sheet - Google Patents

Description

The present disclosure relates to an adhesive sheet.

An adhesive sheet having an adhesive layer containing an acrylic polymer as a main component on at least one main surface of the elastic foam layer is highly convenient due to its instantaneous adhesion property, and is external due to the flexibility of the elastic foam layer. Since it can relieve stress when it receives a load from, it is widely used in the industrial world, for example, for manufacturing electronic parts, structural use, and automobiles.

As such an adhesive sheet, for example, in Patent Document 1, a pressure-sensitive adhesive tape (adhesive sheet) having a pressure-sensitive adhesive layer formed of a bubble-containing viscoelastic composition on one side or both sides of a bubble-containing base material is used. There are disclosed that the bubble-containing viscoelastic composition contains an acrylic polymer, bubbles, hollow microspheres, a coloring pigment and a surfactant.

Further, in Patent Document 2, a pressure-sensitive adhesive layer is provided on both main surfaces of the viscoelastic body layer, and the pressure-sensitive adhesive layer is a layer formed by polymerizing an acrylic pressure-sensitive adhesive composition with an active energy ray. The acrylic pressure-sensitive adhesive composition is a polyfunctional (meth) acrylic acid alkyl ester-based vinyl monomer mixture or a partial polymer thereof, an active energy ray polymerization initiator, and a specific functional group. It is disclosed that it contains a (meth) acrylate and a specific (meth) acrylic acid ester oligomer containing a rosin-modified (meth) acrylate as a monomer component.

Japanese Unexamined Patent Publication No. 2011-168793 Japanese Unexamined Patent Publication No. 2009-13322

The pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer containing an acrylic polymer as a main component on at least one main surface of the elastic foam layer is a cured product layer obtained by curing an acrylic pressure-sensitive adhesive composition with heat or light. In this case, since the adhesive layer has a high hardness, the adhesive layer cannot follow the flexibility of the elastic foam layer, and there is a problem that the stress relaxing property of the entire adhesive sheet is inferior. Further, the adhesive sheet has a problem that the adhesive durability is inferior depending on the usage environment conditions.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an adhesive sheet capable of exhibiting good adhesive durability and stress relaxation property.

As a result of diligent studies by the present inventors on the above problems, the main component of the adhesive layer is a crosslinked product of a vinyl acetate-acrylic copolymer, and a vinyl acetate monomer unit in the crosslinked product of a vinyl acetate-acrylic copolymer. It has been found that by increasing the ratio of the above, the flexibility of the elastic foam layer can be followed and the adhesive durability is higher than that of the adhesive layer containing an acrylic polymer as a main component. However, when a vinyl acetate-acrylic copolymer having a high ratio of vinyl acetate monomer units is used, the glass transition temperature becomes high, the tackiness is lowered, and it becomes difficult to form an adhesive layer.

Therefore, as a result of further studies, the present inventors have developed an adhesive layer containing a crosslinked product of a vinyl acetate-acrylic copolymer as a main component and a vinyl chloride-vinyl acetate copolymer as a main component to solve the above problem. I came to do. According to this adhesive layer, the ratio of the vinyl acetate monomer unit in the adhesive layer is increased by the vinyl chloride-vinyl acetate-based copolymer without increasing the ratio of the vinyl acetate monomer unit in the vinyl acetate-acrylic copolymer. Therefore, it is possible to follow the flexibility of the elastic foam layer, exhibit high adhesive durability, and exhibit further good tackiness.

That is, one embodiment of the present disclosure has an elastic foam layer and an adhesive layer arranged on at least one main surface side of the elastic foam layer, and the adhesive layer is a vinyl acetate-acrylic copolymer. Provided is a pressure-sensitive adhesive sheet containing a crosslinked product as a main component and further containing a vinyl chloride-vinyl acetate-based copolymer.

According to the adhesive sheet according to the embodiment of the present disclosure, there is an effect that good adhesive durability and stress relaxation property can be exhibited.

It is a schematic sectional drawing which shows an example of the pressure-sensitive adhesive sheet which is one Embodiment of this disclosure. It is a schematic sectional drawing which shows an example of the pressure-sensitive adhesive sheet which is one Embodiment of this disclosure. It is a schematic diagram explaining the test method of the hot water immersion durability test.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings and the like. However, the present disclosure can be implemented in many different embodiments and is not construed as being limited to the description of the embodiments exemplified below. Further, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the embodiment, but this is merely an example and the interpretation of the present disclosure is limited. It's not something to do. Further, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures may be designated by the same reference numerals, and detailed description thereof may be omitted as appropriate. Further, for convenience of explanation, the phrase "upper" or "lower" may be used for explanation, but the vertical direction may be reversed.

Further, in the present specification, there is no particular limitation when a certain structure such as a certain member or a certain area is "above (or below)" another structure such as another member or another area. As long as this includes not only the case of being directly above (or directly below) the other configuration, but also the case of being above (or below) the other configuration, that is, separately above (or below) the other configuration. Including the case where the components of are included.

Hereinafter, the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive composition according to the embodiment of the present disclosure will be described.

A. Adhesive Sheet The adhesive sheet according to the embodiment of the present disclosure (hereinafter referred to as the adhesive sheet of the present disclosure) is an elastic foam layer and an adhesive layer arranged on at least one main surface side of the elastic foam layer. The pressure-sensitive adhesive layer contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component, and further contains a vinyl chloride-vinyl acetate-based copolymer.

1 and 2 are schematic cross-sectional views showing an example of the pressure-sensitive adhesive sheet of the present disclosure. As illustrated in FIGS. 1 and 2, the pressure-sensitive adhesive sheet 10 of the present disclosure has a pressure-sensitive adhesive layer 1 arranged on at least one main surface of the elastic foam layer 2 and the elastic foam layer 2, and the pressure-sensitive adhesive layer 1 is provided. However, it contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component, and further contains a vinyl chloride-vinyl acetate-based copolymer. The pressure-sensitive adhesive sheet 10 exemplified in FIG. 1 shows an example of a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer 1 on one main surface of the elastic foam layer 2, and the pressure-sensitive adhesive sheet 10 exemplified in FIG. 2 is an elastic foam layer. An example of a double-sided adhesive sheet having an adhesive layer 1 on both main surfaces of 2 is shown.

The pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer containing an acrylic polymer as a main component on at least one main surface side of the elastic foam layer has adhesive durability under various usage environmental conditions, especially under harsh environmental conditions such as immersion in warm water. It is required to have good physical properties such as stress relaxation and stress relaxation. In order to obtain an adhesive sheet satisfying these physical properties, it is necessary that the adhesive layer of the adhesive sheet has good adhesive durability and that the adhesive layer can follow the flexibility of the elastic foam layer. it is conceivable that.

As a method for improving the adhesive durability of an adhesive layer containing an acrylic polymer as a main component, for example, it is known to introduce a polar group into an acrylic polymer. Among them, the carboxyl group has a high polarity, so that the adhesion to the adherend is improved and the adhesive durability tends to be improved. However, even with an adhesive layer containing an acrylic polymer having a carboxyl group as a main component, sufficient adhesive durability to an adherend may not be obtained depending on the conditions of use environment. In addition, the adhesive layer may be hard and may not sufficiently follow the flexibility of the elastic foam layer.

Therefore, the present inventors have investigated the composition of the adhesive layer so as to exhibit high adhesive durability regardless of the usage environment conditions and sufficiently follow the flexibility of the elastic foam layer. As a result, the following results have been investigated. For this reason, a crosslinked product of a vinyl acetate-acrylic copolymer has been selected as the main component of the adhesive layer. That is, since the vinyl acetate-acrylic copolymer contains a structural unit derived from vinyl acetate (vinyl acetate monomer unit), the main component of the adhesive layer is a crosslinked product of the vinyl acetate-acrylic copolymer, so that the adhesive can be adhered. It is presumed that the polarity of the layer is increased and the adhesive retention to the adherend is enhanced.

However, the present inventors have increased the ratio of vinyl acetate monomer units in the crosslinked product of the vinyl acetate-acrylic copolymer in order to enhance the effect exhibited by the vinyl acetate in the crosslinked product. I learned that problems will arise. That is, in order to increase the ratio of the vinyl acetate monomer unit in the crosslinked product of the vinyl acetate-acrylic copolymer, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive has a high ratio of the vinyl acetate monomer unit. It is necessary to contain an acrylic copolymer as a main agent. However, when a vinyl acetate-acrylic copolymer having a high ratio of vinyl acetate monomer units is used, the glass transition temperature becomes high, the tackiness is lowered, and it becomes difficult to form an adhesive layer.

Therefore, as a result of further diligent studies on a method for adjusting the content of the vinyl acetate component including the vinyl acetate monomer unit in the pressure-sensitive adhesive layer, the present inventors have conducted a further diligent study, and as a result, the vinyl acetate-acrylic copolymer is contained in the pressure-sensitive adhesive layer. The above-mentioned problems have been solved by including the crosslinked product of the above and a vinyl chloride-vinyl acetate-based copolymer. That is, by further containing the vinyl chloride-vinyl acetate-based copolymer in the adhesive layer, the content of the vinyl acetate component in the adhesive layer is increased by the amount of the vinyl acetate monomer unit in the vinyl chloride-vinyl acetate-based copolymer. As a result, it becomes possible to fully exert the effect of the vinyl acetate described above. Further, in the pressure-sensitive adhesive composition containing a vinyl acetate-acrylic acetate copolymer, a vinyl chloride-vinyl acetate-based copolymer and a curing agent, the vinyl chloride-vinyl acetate-based copolymer is completely incorporated into the adhesive main skeleton. Since it is possible to add an arbitrary amount of the adhesive layer, it is possible to adjust the viscosity when forming the adhesive layer.

As described above, according to the pressure-sensitive adhesive sheet of the present disclosure, the composition of the pressure-sensitive adhesive layer contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component, and further contains a specific composition containing a vinyl chloride-vinyl acetate-based copolymer. Therefore, a desired amount of the vinyl acetate component is present in the adhesive layer, so that good adhesive durability and stress relaxation property can be exhibited.

Hereinafter, each configuration of the adhesive sheet of the present disclosure will be described.

1. 1. Adhesive layer The adhesive layer in the present disclosure contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component, and further contains a vinyl chloride-vinyl acetate-based copolymer. Here, the main component refers to the component having the highest content in the composition of the pressure-sensitive adhesive layer.

The adhesive layer is arranged on at least one main surface side of the elastic foam layer, but may be arranged on both main surface sides of the elastic foam layer.

The pressure-sensitive adhesive layer contains a crosslinked product of a vinyl acetate-acrylic copolymer and a vinyl chloride-vinyl acetate-based copolymer, so that a desired amount of vinyl acetate component is present in the pressure-sensitive adhesive layer, and as a result. , The above-mentioned effects can be exhibited. Here, the vinyl acetate component in the adhesive layer includes the vinyl acetate portion contained in the vinyl acetate-acrylic copolymer, the vinyl acetate portion contained in the vinyl chloride-vinyl acetate-based copolymer, and the vinyl acetate-acrylic. It also contains unreacted vinyl acetate contained in the crosslinked polymer and unreacted vinyl acetate contained in the vinyl chloride-vinyl acetate-based copolymer.

(1) Crosslinked product of vinyl acetate-acrylic copolymer The crosslinked product of vinyl acetate-acrylic copolymer is a compound containing a repeating unit derived from a vinyl acetate-acrylic copolymer. The vinyl acetate-acrylic copolymer has a carboxyl group or a hydroxyl group in the molecule.

The vinyl acetate-acrylic copolymer contains a vinyl acetate monomer unit and an acrylic monomer unit. The vinyl acetate monomer unit means a structural unit derived from vinyl acetate, and the acrylic monomer unit means a structural unit derived from (meth) acrylic acid or (meth) acrylic acid ester. The (meth) acrylic acid ester is not particularly limited, and is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl. Examples thereof include (meth) acrylate, isooctyl (meth) acrylate, n-amyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, and n-decyl methacrylate. In addition, (meth) acrylic refers to either acrylic or methacrylic, or both, and (meth) acrylate refers to either one or both of an acrylate group or methacrylate.

The copolymerization form of vinyl acetate-acrylic copolymer is not particularly limited, such as random copolymerization, block copolymerization, and graft copolymerization.

The vinyl acetate-acrylic copolymer may contain a third monomer unit in addition to the above-mentioned monomer unit. Examples of the third monomer unit include α, β-unsaturated carboxylic acid, polyfunctional monomer, copolymerizable monomer, ethylenically unsaturated monomer and the like. Examples of the α, β-unsaturated carboxylic acid include (meth) acrylic acid. Examples of the polyfunctional monomer include those having two or more polymerizable double bonds in one molecule such as ethylene glycol di (meth) acrylate and triethylene glycol di (meth) acrylate. Examples of the copolymerizable monomer include N-vinylpyrrolidone and N-isopropylacrylamide. Examples of the ethylenically unsaturated monomer include 2-hydroxyethyl (meth) acrylate and styrene.

The crosslinked product of the vinyl acetate-acrylic copolymer has a self-crosslinked structure in which the same functional groups of the vinyl acetate-acrylic copolymer or different functional groups are bonded between the repeating units of the vinyl acetate-acrylic copolymer. It may be a crosslinked structure in which a curing agent is used between the repeating units of the vinyl acetate-acrylic copolymer. The former can be formed, for example, by a photocuring reaction using a photopolymerization initiator, and the latter can be formed, for example, by a thermosetting reaction using a curing agent. Above all, the crosslinked product of the vinyl acetate-acrylic copolymer preferably has a crosslinked structure in which a curing agent is used between the repeating units of the vinyl acetate-acrylic copolymer. This is because the crosslinked product of the vinyl acetate-acrylic copolymer has such a structure, so that the amount of unreacted monomer residue in the adhesive layer is smaller than that in the case of the self-crosslinked structure. In this way, when the amount of unreacted monomer residue in the adhesive layer is small, the adverse effect on the adhesive performance due to the reaction of the unreacted monomer is reduced, it is stable over time, it has a low odor, and it has few volatile components and is good for the environment. It has advantages such as. Further, since it is not a photopolymerization system, it can be colored, and it is also possible to impart a function such as UV cut to the adhesive layer.

The cross-linked product of the vinyl acetate-acrylic copolymer has a cross-linked structure in which a curing agent is used between the repeating units of the vinyl acetate-acrylic copolymer. The cross-linked product of the vinyl acetate-acrylic copolymer is vinyl acetate-. It can be said that the compound has the following bonds between the repeating units of the acrylic copolymer. That is, the crosslinked vinyl acetate-acrylic copolymer can have at least one bond selected from the group consisting of urethane bonds, epoxy bonds and metal chelate bonds, and has two or more kinds of bonds. You may. The fact that the crosslinked product of the vinyl acetate-acrylic copolymer has a urethane bond means that a urethane bond is formed between the repeating units derived from the vinyl acetate-acrylic copolymer. Similarly, when the crosslinked product of the vinyl acetate-acrylic copolymer has an epoxy bond or a metal chelate, an epoxy bond or a urethane bond is formed between the repeating units derived from the vinyl acetate-acrylic copolymer. Say that.

Further, the cross-linked product of the vinyl acetate-acrylic copolymer has a cross-linked structure in which a curing agent is used between the repeating units of the vinyl acetate-acrylic copolymer. It can be said that the vinyl-acrylic copolymer is a cured product obtained by cross-linking a vinyl-acrylic copolymer with at least one curing agent selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent and a metal chelate-based curing agent. Details of the isocyanate-based curing agent, the epoxy-based curing agent, and the metal chelate-based curing agent that react with the vinyl acetate-acrylic copolymer will be described in the section “B. Adhesive Composition” described later.

The crosslinked product of the vinyl acetate-acrylic copolymer may contain a structural unit derived from the vinyl chloride-vinyl acetate-based copolymer as a part in addition to the repeating unit derived from the vinyl acetate-acrylic copolymer.

(2) Vinyl Chloride-Vinyl Acetate Copolymer The pressure-sensitive adhesive layer in the present disclosure further contains a vinyl chloride-vinyl acetate-based copolymer in addition to the crosslinked product of the vinyl acetate-acrylic copolymer as the main component. It is characterized by. As described above, the content of the vinyl acetate component in the adhesive layer is the ratio of the vinyl acetate monomer unit of the crosslinked vinyl acetate-acrylic copolymer and the vinyl acetate monomer unit of the vinyl chloride-vinyl acetate-based copolymer. This is because it can be adjusted with the ratio.

Further, since the vinyl chloride monomer unit in the vinyl chloride-vinyl acetate copolymer has high water resistance, even when the pressure-sensitive adhesive sheet is used under harsh environmental conditions such as a hot water immersion environment, the pressure-sensitive adhesive layer is formed. It is presumed that it is less likely to deteriorate and can exhibit high adhesive durability. Further, the adhesive layer has a high affinity with an adherend of a difficult-to-adhere material such as vinyl chloride depending on the ratio and content of the vinyl chloride monomer unit, and has good adhesive durability even under harsh environmental conditions. It is presumed that it is possible to show sex.

The vinyl chloride-vinyl acetate-based copolymer contains a vinyl chloride monomer unit and a vinyl acetate monomer unit. The vinyl chloride monomer unit means a structural unit derived from a vinyl chloride monomer.

The vinyl chloride-vinyl acetate-based copolymer may contain a third monomer unit in addition to the above-mentioned monomer unit. Examples of the third monomer unit include carboxylic acid, dicarboxylic acid, acrylic acid, vinyl alcohol, hydroxyacrylic acrylate and the like.

The copolymerization form of the vinyl chloride-vinyl acetate copolymer is not particularly limited, such as random copolymerization, block copolymerization, and graft copolymerization.

The vinyl chloride-vinyl acetate-based copolymer preferably contains vinyl acetate in an amount of 1% by mass or more, particularly preferably 5% by mass or more, and particularly preferably 10% by mass or more.
The upper limit of the content of vinyl acetate in the vinyl chloride-vinyl acetate-based copolymer is not particularly limited, but can be 50% by mass.

The vinyl chloride-vinyl acetate-based copolymer preferably has a number average molecular weight (Mn) of 3,000 or more and 100,000 or less, particularly preferably 5,000 or more and 80,000 or less, and particularly preferably 10,000 or more and 60,000 or less. The number average molecular weight is a value measured by the same method as the method for measuring the weight average molecular weight described later.

The content of the vinyl chloride-vinyl acetate-based copolymer in the adhesive layer is preferably 0.5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the crosslinked product of the vinyl acetate-acrylic copolymer. Above all, it is preferably 1 part by mass or more and 20 parts by mass or less, and particularly preferably 2 parts by mass or more and 15 parts by mass or less. When the content of the vinyl chloride-vinyl acetate-based copolymer in the pressure-sensitive adhesive layer is within the above range, the vinyl acetate content in the pressure-sensitive adhesive layer can be made to have an adhesive holding power in a warm water immersion environment. It is presumed that the amount can be adjusted to an amount that can be established as an adhesive layer.

In the adhesive layer, the vinyl chloride-vinyl acetate-based copolymer is compatible with the crosslinked product of the vinyl acetate-acrylic copolymer. "Vinyl chloride-vinyl acetate-based copolymer is compatible with the crosslinked product of vinyl acetate-acrylic copolymer" means that when the adhesive layer is observed with a scanning electron microscope, the vinyl acetate-acrylic copolymer It means that vinyl chloride-vinyl acetate copolymers are scattered on the crosslinked product.

(3) Adhesive-imparting resin The adhesive layer may contain a tackifier resin in addition to a crosslinked product of a vinyl acetate-acrylic copolymer and a vinyl chloride-vinyl acetate-based copolymer. This is because the adhesive layer can be imparted with adhesiveness, and the adhesive durability of the adhesive layer can be further enhanced.

The weight average molecular weight of the tackifier resin is, for example, preferably 200 or more and 8000 or less, particularly preferably 500 or more and 6000 or less, and particularly preferably 800 or more and 4000 or less. This is because when the weight average molecular weight of the tackifier resin is within the above range, it is possible to achieve both compatibility with the vinyl acetate-acrylic copolymer and adhesiveness.

The weight average molecular weight is determined by impregnating the adhesive layer with acetone, stirring for 3 days, taking it out, filtering it with a 0.45 μm mesh filter, volatilizing acetone with a nitrogen blower in the extract, and zero THF in the dry solid content. Add 5 wt% to dissolve, and use the filtrate filtered through a 0.45 μm mesh filter as the polystyrene-equivalent value measured by gel permeation chromatography (GPC) under the following conditions.
(GPC measurement conditions)
-Gel permeation chromatography device: manufactured by Waters, trade name "Waters 2695"
-Column: GPC LF-804 (manufactured by Shodex), 3 bottles-Eluent: THF
・ Flow velocity: 1 mL / min,
-Sample concentration: 0.5% by mass
-Sample injection volume: 50 μL
・ Measurement temperature: 40 ° C
・ Detector: RI
・ Standard material: Polystyrene

The tackifier resin preferably has a high softening point. By including the adhesive resin having a high softening point, the thermal stability of the entire adhesive layer is improved, and the adhesive layer can have a certain degree of hardness even under harsh environmental conditions such as under warm water immersion environment. This is because it is presumed that the component that inhibits the adhesiveness is less likely to invade from the outside and the adhesive durability is improved. The softening point of the tackifier resin is preferably 60 ° C. or higher and 200 ° C. or lower, particularly preferably 70 ° C. or higher and 180 ° C. or lower, and particularly preferably 80 ° C. or higher and 150 ° C. or lower. The softening point of the tackifier resin is a value measured by a thermomechanical analysis method (TMA) after separating the tackifier resin from the tacky layer by the same method as the method for measuring the weight average molecular weight.

The tackifier resin preferably exhibits polarity, and among the tackifier resins, those having high polarity are preferable. This is because the balance between the hydrophobicity and the compatibility with the vinyl acetate-acrylic copolymer is good.

The content of the tackifier resin in the pressure-sensitive adhesive layer can be an amount capable of exhibiting a desired function, but is 3 parts by mass with respect to 100 parts by mass of the crosslinked body of the vinyl acetate-acrylic copolymer. It is preferably 60 parts by mass or less, more preferably 5 parts by mass or more and 50 parts by mass or less, and particularly preferably 8 parts by mass or more and 45 parts by mass or less. If the content of the tackifier resin is excessive, the tackifier resin may bleed out from the tacky layer.

The tackifying resin may be any resin that can impart tackiness to the pressure-sensitive adhesive layer, and known pressure-sensitive adhesive resins can be used. Among them, styrene-based resins, rosin-based resins, terpene-based resins and It is preferably at least one selected from the group consisting of hydrocarbons made of petroleum-based resins. This is because the compatibility with the crosslinked product of the vinyl acetate-acrylic copolymer and the vinyl acetate-vinyl acetate-based copolymer is good, and the above-mentioned physical properties are easily satisfied. The adhesive layer may contain these individually by 1 type or in combination of 2 or more types. Details of the styrene-based resin, the rosin-based resin, and the terpene-based resin will be described in "(4) At least selected from the group consisting of hydrocarbons consisting of the styrene-based resin, the rosin-based resin, the terpene-based resin, and the petroleum-based resin". Since it will be described in the section of "One kind of resin", the description here will be omitted. Above all, the pressure-sensitive adhesive layer preferably contains at least one of a styrene-based resin and a rosin-based resin. This is because these resins have high compatibility with the vinyl acetate-acrylic copolymer and have good thermal stability. Among the styrene resins, a copolymer of a styrene monomer and an aliphatic monomer is preferable.

(4) At least one resin selected from the group consisting of hydrocarbons consisting of styrene resin, rosin resin, terpene resin and petroleum resin The adhesive layer is a crosslinked product of vinyl acetate-acrylic copolymer and In addition to the vinyl chloride-vinyl acetate-based copolymer, at least one resin selected from the group consisting of hydrocarbons consisting of styrene-based resin, rosin-based resin, terpene-based resin and petroleum-based resin can be further contained. .. When the adhesive layer further contains these resins, it is possible to exhibit good adhesive durability and stress relaxation property even in an adherend having a low polarity on the adherend surface in a warm water immersion environment. Further, since these resins have a higher glass transition temperature than the vinyl acetate-acrylic copolymer and can improve the glass transition temperature of the entire adhesive layer, for example, the adhesive layer can be softened in a warm water immersion environment. It can be suppressed, and even when the component of the adherend bleeds out, it is presumed that the bleed-out component does not easily enter the adhesive layer and the deterioration of the performance of the adhesive layer can be suppressed. Furthermore, since these resins are hydrophobic, it is presumed that water can be made difficult to attract to the adhesive layer in a warm water immersion environment, and as a result, deterioration of the adhesive layer can be suppressed.

The styrene-based resin may be a styrene-based polymer, or may be a mixture of a styrene-based monomer and a styrene-based polymer. Of these, styrene-based polymers are preferable.

The styrene-based polymer may be a homopolymer or a copolymer of one or more kinds of styrene-based monomers, and may be a copolymer of one or more kinds of styrene-based monomers and other monomers other than the styrene-based monomers. May be good. Examples of the styrene-based monomer include styrene; alkyl-substituted styrenes such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-t-butylstyrene, and 2,4-dimethylstyrene; α-. Examples thereof include α-alkyl substituted styrenes such as methylstyrene and α-methyl-4-methylstyrene; and substituted styrenes such as substituted styrenes such as 2-chlorostyrene, 4-chlorostyrene, hydroxystyrene and vinylbenzoic acid. Examples of the monomer other than the styrene-based monomer include an aliphatic monomer and an aromatic monomer. Examples of the aliphatic monomer include aliphatic hydrocarbons. Examples of the aromatic monomer include aromatic hydrocarbons other than those exemplified for the styrene-based monomer.

Specific examples of the styrene-based polymer include polystyrene, poly-α-methylstyrene, a copolymer of α-methylstyrene and styrene, a copolymer of a styrene-based monomer and an aliphatic monomer, and a styrene-based monomer and an aromatic-based polymer. Polymers with monomers, copolymers of styrene-based monomers other than α-methylstyrene and α-methylstyrene and aliphatic monomers, styrene-based monomers other than α-methylstyrene and α-methylstyrene and aromatics Examples thereof include a copolymer with a monomer. The adhesive layer may contain these individually by 1 type or in combination of 2 or more types. The copolymerization form of the styrene-based polymer is not particularly limited, such as random copolymerization, block copolymerization, and graft copolymerization.

Examples of the rosin-based resin include rosins such as gum rosin, wood rosin, and tall oil rosin; and rosin derivatives such as polymerized rosin, disproportionated rosin, hydride rosin, reinforced rosin, rosin ester, polymerized rosin ester, and rosin phenol. The adhesive layer may contain these individually by 1 type or in combination of 2 or more types.

Examples of the terpene-based resin include a terpene polymer, a β-pinene polymer, a terpene phenol resin, and an aromatic-modified terpene polymer. The adhesive layer may contain these individually by 1 type or in combination of 2 or more types.

Examples of hydrocarbons made of petroleum-based resins include C5-based petroleum resins and C9-based petroleum resins. The adhesive layer may contain these individually by 1 type or in combination of 2 or more types.

Above all, it is preferable that at least one resin selected from the above group is at least one of a styrene resin and a rosin resin. In other words, the pressure-sensitive adhesive layer preferably contains at least one of a styrene-based resin and a rosin-based resin. This is because these resins have high compatibility with the crosslinked product of the vinyl acetate-acrylic copolymer and have good thermal stability. Among the styrene-based resins, a copolymer of a styrene-based monomer and an aliphatic monomer is more preferable.

The weight average molecular weight and softening point of at least one resin selected from the above group may be the same as the weight average molecular weight and softening point of the tackifier resin described in the above section "(3) Adhesive-imparting resin". can.

Further, the content of at least one resin selected from the above group in the pressure-sensitive adhesive layer with respect to 100 parts by mass of the crosslinked vinyl acetate-acrylic copolymer is an amount capable of exhibiting a desired function. It can be the same as the content of the tackifier resin with respect to 100 parts by mass of the crosslinked body of the vinyl acetate-acrylic copolymer described in the above section “(3) Tacket-imparting resin”.

(5) Others The adhesive layer may contain an unreacted vinyl acetate-acrylic copolymer, vinyl acetate resin, or the like that does not form a crosslinked product.

The adhesive layer may contain additives such as a leveling agent, a plasticizer, a softener, a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, an antioxidant, and a light stabilizer. As the additive contained in the pressure-sensitive adhesive layer, a conventionally known material contained in a general pressure-sensitive adhesive layer can be used by a conventional method.

Further, the pressure-sensitive adhesive layer may contain a colorant. The pressure-sensitive adhesive layer can exhibit a desired color by containing a colorant, and can enhance the design of the pressure-sensitive adhesive sheet. As the colorant, for example, an organic colorant such as an organic pigment or a dye, or a general-purpose material such as an inorganic pigment can be used. Of these, organic colorants are preferable.

The thickness of the adhesive layer can be appropriately set so as to be large enough to exhibit the desired physical properties, and is not particularly limited, but can be, for example, 3 μm or more and 200 μm or less, preferably 5 μm or more and 100 μm. ..

The pressure-sensitive adhesive layer may be substantially free of a photopolymerization initiator, depending on the crosslinked structure of the crosslinked product of the vinyl acetate-acrylic copolymer. Substantially free of photopolymerization initiator means that the photopolymerization initiator cannot be detected when the pressure-sensitive adhesive layer is measured by a gas chromatograph mass spectrometer (GCMS).

Examples of the photopolymerization initiator include general-purpose materials used for photocuring acrylic pressure-sensitive adhesives. For example, benzoin, benzoin methyl ether, benzoin isopropyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexyl. Phenyl Ketone, Benzophenone, p-Phenylbenzophenone, Dichlorobenzophenone, 2-Methylanthraquinone, 2-Ethylanthraquinone, 2-Aminoanthraquinone, 2-Methylthioxanthone, 2-Ethylthioxanthone, 2-Chlorothioxanthone, benzyldimethylketal, Acetphenone dimethylketal , P-Dimethylaminobenzoic acid ester and the like.

The pressure-sensitive adhesive layer is a cured product layer of a pressure-sensitive adhesive composition containing at least a vinyl acetate-acrylic copolymer, a vinyl chloride-vinyl acetate-based copolymer, and a curing agent. The pressure-sensitive adhesive composition will be described later in the section “B. Pressure-sensitive adhesive composition”.

2. 2. Elastic Foam Layer The elastic foam layer in the pressure-sensitive adhesive sheet of the present disclosure has a function of supporting the pressure-sensitive adhesive layer and enhancing the followability and shock absorption of the pressure-sensitive adhesive sheet to the adherend.

The material of the elastic foam layer is not particularly limited, and examples thereof include acrylic resin foam (acrylic foam); polyethylene foam; polyurethane resin foam; rubber foam containing acrylic rubber and other elastomers. Can be mentioned.

The elastic foam layer has a bubble structure (cell structure). The cell structure (cell structure) is not particularly limited, and may be a closed cell structure or an open cell structure, and is a semi-continuous semi-closed cell structure in which a closed cell structure and an open cell structure are mixed. There may be. Above all, an elastic foam layer having a closed cell structure is preferable because it has good followability to the shape of the adherend surface of the adherend and stress relaxation property. The average bubble diameter and density of the elastic foam layer can be appropriately set according to the strength and flexibility of the pressure-sensitive adhesive sheet of the present disclosure, the purpose of use, and the like.

The elastic foam layer is a colorant, a filler (inorganic filler, organic filler, etc.), an antioxidant, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, a flame retardant, and a surfactant. Various additives such as may be blended. Further, the elastic foam layer may have a primer layer formed on one or both main surfaces, or may be surface-treated. When the primer layer is formed on the main surface of the elastic foam layer, the adhesive layer is provided via the primer layer.

The elastic foam layer may be composed of a single layer, or may be composed of a plurality of layers composed of the same or different elastic foams.

The thickness of the elastic foam layer is not particularly limited, and can be appropriately set according to the strength and flexibility of the pressure-sensitive adhesive sheet of the present disclosure, the purpose of use, and the like. The thickness of the elastic foam layer can be, for example, 200 μm or more and 5000 μm.

The elastic foam layer can be produced by a known method. For example, it can be produced by a method including a molding step, a cross-linking step and a foaming step of a resin material or a resin foam, and if necessary, a stretching step. Examples of the method for cross-linking the elastic foam layer include a chemical cross-linking method using an organic peroxide or the like, a radiation cross-linking method for irradiating ultraviolet rays, electron beams, or the like, and these methods may be used alone or. Two or more types can be used in combination.

3. 3. Peeling layer The pressure-sensitive adhesive sheet of the present disclosure may have a peeling layer on a main surface opposite to the surface of the pressure-sensitive adhesive layer in contact with the elastic foam layer. As the release layer, a general-purpose material can be appropriately selected and used in the field of adhesive sheets, for example, various resin films, papers, cloths, rubber sheets, foam sheets, metal foils, and the like. These composites (for example, a sheet having a laminated structure in which an olefin resin is laminated on both sides of paper) and the like can be appropriately selected and used. The peeling layer may have a peeling treatment film containing a peeling treatment agent such as a silicone-based peeling treatment agent, a fluorine-based peeling treatment agent, and a long-chain alkyl-based peeling treatment agent on the surface.

4. Others The pressure-sensitive adhesive sheet of the present disclosure preferably has a tensile elastic modulus of 0.10 MPa or more and 3.00 MPa or less, particularly preferably 0.15 MPa or more and 2.00 MPa or less, and particularly 0.20 MPa or more and 1.00 MPa or less. The following is preferable.
It is presumed that when the tensile elastic modulus of the adhesive sheet is within the above range, the followability to the adherend is good, stress relaxation property is exhibited, and the adhesive holding state can be maintained for a long time. be.
The tensile elastic modulus is a value measured by a measuring method based on JIS Z0237 (test piece size: 10 mm × 50 mm, distance between chucks: 25 mm, tensile speed: 500 mm / min). The tensile elastic modulus of the pressure-sensitive adhesive sheet is the tensile elastic modulus of the pressure-sensitive adhesive sheet excluding the release layer.
The method for producing the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited, but for example, at least a vinyl acetate-acrylic copolymer, a vinyl chloride-vinyl acetate-based copolymer, and a curing agent are applied to the surface of the release layer or the elastic foam layer. It can be obtained by applying a solution of the pressure-sensitive adhesive composition containing the coating material and heat-curing the coating film to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive composition used for producing the pressure-sensitive adhesive sheet of the present disclosure will be described in the section "B. Adhesive composition" described later.

Since the adhesive sheet of the present disclosure has excellent adhesive durability and stress relaxation even in harsh environments, for example, automobiles, aircraft, ships, electronic devices, electronic device housings, home appliances, infrastructure structures, lifelines. It can be used in fields such as building materials and general building materials. Above all, it can be suitably used as an adhesive sheet for automobiles such as an adhesive sheet for automobile exteriors and an adhesive sheet for automobile interiors, and an adhesive sheet for vinyl chloride.

B. Adhesive Composition The pressure-sensitive adhesive composition according to the embodiment of the present disclosure (hereinafter referred to as the pressure-sensitive adhesive composition of the present disclosure) is a vinyl acetate-acrylic copolymer, a vinyl chloride-vinyl acetate-based copolymer, and the like. And contains at least a hardener.

According to the pressure-sensitive adhesive composition of the present disclosure, a desired amount of vinyl acetate component is contained by containing at least a vinyl acetate-acrylic copolymer, a vinyl chloride-vinyl acetate-based copolymer, and a curing agent, and elastic foaming is performed. It is possible to form an adhesive layer that can follow the flexibility of the body layer and can exhibit high adhesive durability and good tackiness.

Hereinafter, the composition of the pressure-sensitive adhesive composition of the present disclosure will be described.

1. 1. Vinyl Acetate-Acrylic Copolymer The pressure-sensitive adhesive composition of the present disclosure contains a vinyl acetate-acrylic copolymer as a main component. Since the details of the vinyl acetate-acrylic copolymer have been described in the above section "A. Adhesive Sheet", the description thereof is omitted here.

2. 2. Vinyl Chloride-Vinyl Acetate Copolymer The pressure-sensitive adhesive composition of the present disclosure comprises a vinyl chloride-vinyl acetate-based copolymer. Since the details of the vinyl chloride-vinyl acetate-based copolymer and the effect of containing the copolymer have been described in the above section "A. Adhesive Sheet", the description thereof is omitted here.

The content of the vinyl chloride-vinyl acetate-based copolymer in the pressure-sensitive adhesive composition can be an amount capable of exerting the function of the vinyl chloride-vinyl acetate-based copolymer, for example, vinyl acetate-. The solid content of the acrylic polymer is preferably 0.5 parts by mass or more and 25 parts by mass or less, particularly preferably 1 part by mass or more and 20 parts by mass or less, and particularly 2 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the solid content. It is preferably less than or equal to parts by mass.

3. 3. Curing Agent The pressure-sensitive adhesive composition of the present disclosure comprises a curing agent. When the pressure-sensitive adhesive composition is heated, a thermosetting reaction occurs between the functional group of the vinyl acetate-acrylic copolymer and the curing agent, and desired cross-linking is performed between the repeating units of the vinyl acetate-acrylic copolymer. A crosslinked product of a vinyl acetate-acrylic copolymer having a bond is formed. The curing agent is not particularly limited as long as it is a material capable of obtaining a crosslinked product of a vinyl acetate-acrylic copolymer, and is derived from a known curing agent used for a pressure-sensitive adhesive containing a vinyl acetate-acrylic copolymer as a main component. It can be selected as appropriate. Examples of such a curing agent include at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and a metal chelate-based curing agent.

The isocyanate-based curing agent is not particularly limited, and is, for example, a polyisocyanate compound, a trimer of a polyisocyanate compound, a urethane prepolymer having an isocyanate group at the end obtained by reacting a polyisocyanate compound with a polyol compound, and the like. Examples thereof include a trimer of the urethane prepolymer. Examples of the polyisocyanate compound include aromatic polyisocyanate, aliphatic polyisocyanate, aromatic aliphatic polyisocyanate, alicyclic polyisocyanate and the like, and specific examples thereof include 2,4-tolylene diisocyanate and 2,5-tolylene diisocyanate. Isocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, Examples thereof include dicyclohexylmethane-2,4'-diisocyanate and lysine isocyanate. The isocyanate-based curing agent may be used alone or in combination of two or more.

The epoxy-based curing agent is not particularly limited, and for example, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and the like. Examples include polyfunctional epoxy compounds such as neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutadiene diglycidyl ether. Be done. The epoxy-based curing agent may be used alone or in combination of two or more.

The metal chelate-based curing agent is not particularly limited, and is, for example, a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, and acetylacetone or acetoacetate. Coordinating compounds with ethyl can be mentioned.

The content of the curing agent in the pressure-sensitive adhesive composition can be appropriately set depending on the type of the curing agent. For example, when the curing agent is an isocyanate-based curing agent, it is preferably 0.01 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the solid content of the vinyl acetate-acrylic copolymer. It is preferably 05 parts by mass or more and 5.0 parts by mass or less, and particularly preferably 0.10 parts by mass or more and 4.0 parts by mass or less.
Further, for example, when the curing agent is an epoxy-based curing agent, it is preferably 0.01 parts by mass or more and 10.00 parts by mass or less with respect to 100 parts by mass of the solid content of the vinyl acetate-acrylic copolymer. It is preferably 0.05 parts by mass or more and 5.00 parts by mass or less, and particularly preferably 0.10 parts by mass or more and 3.00 parts by mass or less.
For example, if the curing agent is a metal chelate-based curing agent, the solid content of the vinyl acetate-acrylic copolymer is preferably 0.01 parts by mass or more and 10.00 parts by mass or less, and particularly 0. It is preferably 0.05 parts by mass or more and 5.00 parts by mass or less, and particularly preferably 0.10 parts by mass or more and 3.00 parts by mass or less.

4. Adhesive-imparting resin The pressure-sensitive adhesive composition of the present disclosure may further contain a tack-imparting resin. Since the details of the tackifier resin and the effect of including the tackifier resin have been described in the above section "A. Adhesive sheet", the description thereof is omitted here.

The content of the tackifier resin in the pressure-sensitive adhesive composition can be an amount capable of exerting the function of the tackifier resin, for example, in 100 parts by mass of the solid content of the vinyl acetate-acrylic copolymer. On the other hand, it is preferably 3 parts by mass or more and 60 parts by mass or less, particularly preferably 5 parts by mass or more and 50 parts by mass or less, and particularly preferably 8 parts by mass or more and 45 parts by mass or less.

5. At least one resin selected from the group consisting of hydrocarbons consisting of styrene-based resin, rosin-based resin, terpene-based resin and petroleum-based resin The pressure-sensitive adhesive composition of the present disclosure includes styrene-based resin, rosin-based resin, and terpene-based resin. It may further comprise at least one resin selected from the group consisting of hydrocarbons consisting of resins and petroleum-based resins. Since the details of these resins and the effects of containing these resins have been described in the above section “A. Adhesive Sheet”, the description thereof is omitted here.

The content of at least one resin selected from the above group in the pressure-sensitive adhesive composition with respect to 100 parts by mass of the vinyl acetate-acrylic copolymer was described in the above section "3. Adhesive-imparting resin". The content of the tackifier resin with respect to 100 parts by mass of the vinyl acetate-acrylic copolymer can be the same.

6. Others The pressure-sensitive adhesive composition of the present disclosure includes leveling agents, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, and light stabilizers. And the like can be included. The blending amount of these additives can be appropriately set as long as the characteristics of the pressure-sensitive adhesive composition of the present disclosure are not impaired.
The pressure-sensitive adhesive composition of the present disclosure preferably has a vinyl acetate component content of 1.0% by mass or more and 50.0% by mass or less in 100% by mass of the total solid content of the pressure-sensitive adhesive composition. It is preferably 0% by mass or more and 45.0% by mass or less, and particularly preferably 10.0% by mass or more and 40.0% by mass or less.
The vinyl acetate component in the pressure-sensitive adhesive composition forms a vinyl acetate monomer unit contained in a vinyl acetate-acrylic copolymer, a vinyl acetate monomer unit contained in a vinyl chloride-vinyl acetate-based copolymer, and a copolymer. Unreacted vinyl acetate, etc. The content of the vinyl acetate component in the pressure-sensitive adhesive composition can be specified by the method for calculating the content of the vinyl acetate component in the pressure-sensitive adhesive layer described in the above section "A. Adhesive Sheet".

When the pressure-sensitive adhesive layer is formed by using the pressure-sensitive adhesive composition of the present disclosure, the pressure-sensitive adhesive composition is usually used by adding a solvent. The solvent is preferably a solvent capable of dissolving each component of the pressure-sensitive adhesive composition, and can be appropriately selected from general adhesives or solvents used for pressure-sensitive adhesives. Preferred solvents include, for example, methyl ethyl ketone (MEK), ethyl acetate, butyl acetate, n-propyl acetate, toluene, n-hexane and the like. The solvent may be one kind or two or more kinds.

The present disclosure is not limited to the above embodiment. The above embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present disclosure and having the same effect and effect is the present invention. Included in the technical scope of the disclosure.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Examples 1 to 11, Comparative Examples 1 to 2]
The following materials were mixed at the blending ratios shown in Table 1 to prepare a coating liquid for the pressure-sensitive adhesive composition. The above coating liquid was applied to a resin film (peeling layer) that had been peeled off, and dried in an oven to remove the solvent to obtain an adhesive layer (thickness after drying: 40 μm). The above adhesive layer is attached to one surface of a double-sided adhesive acrylic foam tape (“Y-4180-12” manufactured by 3M Ltd.) having a thickness of 1.2 mm and cured at room temperature for one week. Adhesive layer / acrylic elastic foam An adhesive sheet having a laminated structure of layers was obtained. In the above laminated structure, "/" means a laminated interface.

<Adhesive>
-Adhesive A: Vinyl acetate-acrylic copolymer-containing solvent-type adhesive ("Cybinol AT-262" manufactured by Saiden Chemical Co., Ltd., solid content 43% by mass, vinyl acetate-acrylic copolymer 43% by mass and vinyl acetate 2. Contains 1% by mass)
-Adhesive B: Acrylic acid copolymer-containing solvent-type adhesive ("Cybinol AT-287K" manufactured by Saiden Chemical Co., Ltd., solid content 45% by mass, vinyl acetate-acrylic copolymer and vinyl acetate-free)
<Vinyl chloride-vinyl acetate copolymer-containing solution>
-Vinyl chloride-vinyl acetate copolymer-containing solution A: Vinyl chloride-vinyl acetate-dicarboxylic acid copolymer ("Solvine M5" manufactured by Nissin Chemical Industry Co., Ltd., number average molecular weight 32000, vinyl chloride: vinyl acetate: dicarboxylic acid = 85: 14: 1 (% by mass)) dissolved in methyl ethyl ketone (MEK) 25% by mass concentration solution-Vinyl chloride-vinyl acetate copolymer-containing solution B: Vinyl chloride-vinyl acetate-carboxylic acid copolymer (Kaneka Co., Ltd.) A 25% by mass concentration solution in which "Kanevinyl T5DA" manufactured by Kanevinyl T5DA, vinegar content 18%) is dissolved in methyl ethyl ketone (MEK) <styrene resin-containing solution>
A styrene-based resin-containing solution A: A styrene-based monomer / aliphatic monomer copolymer (“FTR6110” manufactured by Mitsui Chemicals, Inc., softening point 110 ° C., weight average molecular weight 1600, number average molecular weight 1100) is dissolved with methyl ethyl ketone (MEK). 50% by mass concentrated solution-styrene resin-containing solution B: styrene-based monomer / aliphatic monomer copolymer ("FTR6100" manufactured by Mitsui Chemicals, Inc., softening point 95 ° C., weight average molecular weight 1200, number average molecular weight 900). 50% by mass concentration solution dissolved in methyl ethyl ketone (MEK) <Rodin-based resin-containing solution>
-Rosin-based resin-containing solution A: A 50% by mass concentration solution in which a polymerized rosin-based ester resin ("PCJ" manufactured by Harima Chemicals, softening point 118 ° C to 128 ° C, weight average molecular weight 1500) is dissolved in methyl ethyl ketone (MEK) <curing. Agent>
-Isocyanate-based curing agent A ("Cybinol curing agent AL" manufactured by Saiden Chemical Co., Ltd., solid content: 45% by mass)

The composition of the obtained adhesive sheet in the adhesive layer is shown in Table 2 below. The content of each material in Table 2 below is a theoretical value of the content (%) in the total solid content of the adhesive layer.

[evaluation]
The adhesive sheets of Examples 1 to 11 and Comparative Examples 1 and 2 were evaluated as follows.

1. 1. Normal adhesive strength The adhesive sheet is cut into a length of 100 mm and a width of 10 mm, and the surface opposite to the adhesive layer side is made into a polyethylene terephthalate substrate with a thickness of 50 μm (trade name "Cosmo Shine A4100", manufactured by Toyobo Co., Ltd.). I pasted them together. Next, the surface of the pressure-sensitive adhesive sheet on the pressure-sensitive adhesive layer side was pressure-bonded to SUS430J1L (bright-annealed product) one-way with a 2 kg roller to obtain a test piece. After leaving at room temperature for 24 hours, the peel strength was measured at 180 degrees at a tensile speed of 50 mm / min. The measurement was performed using a tensile tester (manufactured by A & D Co., Ltd., product name "RTG-1250"), and the measurement atmosphere was a temperature of 23 ° C. and a humidity of 50% RH. The results are shown in Table 3 below.

2. 2. Hot water immersion durability (1) Hot water immersion durability evaluation 1
The surface of the adhesive sheet (10 mm x 50 mm) opposite to the adhesive layer side is one-way pressure-bonded to the duralumin plate (duralumin A2017, 15 mm x 75 mm) with a 2 kg roller, left at room temperature for 24 hours, and then the adhesive layer side of the adhesive sheet. The surface of No. 1 was pressure-bonded to the adherend A one-way with a 2 kg roller to obtain a test piece. After the obtained test piece was left at room temperature for 24 hours, the end of the test piece was forcibly pushed open by 2.0 mm as shown in FIGS. 3 (a) and 3 (b), and 100 in a constant temperature water bath at a temperature of 40 ° C. After leaving it for a while, it was confirmed whether or not it had peeled off. Those that did not come off were marked with "○", and those that did come off were marked with "×". A metal plate (SUS plate, SUS430J1L, bright annealed product) was used as the adherend A. 3A and 3B are schematic views illustrating a test method for a hot water immersion durability test, FIG. 3A is a plan view, and FIG. 3B is a cross-sectional view. Further, reference numerals 10 in FIGS. 3A and 3B indicate an adhesive sheet, reference numeral 51 indicates a duralumin plate, reference numeral 52 indicates an adherend, reference numeral 53 indicates a spacer, and reference numeral 54 indicates a screw. The thickness of the spacer 53 was the same as the thickness of the adhesive sheet 10. The results are shown in Table 3 below.

[Discussion 1]
From Table 1 above, the pressure-sensitive adhesive sheets of Examples 1 to 11 in which the pressure-sensitive adhesive layer contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component and further contains a vinyl chloride-vinyl acetate-based copolymer are immersed in warm water. It did not come off from the adherend A even when placed in an environment. This suggests that the pressure-sensitive adhesive sheets of Examples 1 to 11 have good adhesive durability and stress relaxation property to the adherend A in a warm water immersion environment. On the other hand, Comparative Example 1, which does not contain the crosslinked product of the vinyl acetate-acrylic copolymer as the main component, contains the crosslinked product of the vinyl acetate-acrylic copolymer as the main component, but does not contain the vinyl chloride-vinyl acetate-based copolymer. In the pressure-sensitive adhesive sheet of Comparative Example 2, peeling from the adherend A was confirmed in a warm water immersion environment, although the normal adhesive strength was about the same as that of the pressure-sensitive adhesive sheets of Examples 1 to 11. It is presumed that the adhesive sheets of Comparative Examples 1 and 2 had inferior adhesive durability and stress relaxation property to the adherend A even in a warm water immersion environment because the adhesive layer contained a small amount of vinyl acetate. To.

(2) Hot water immersion durability evaluation 2
A test piece was prepared in the same manner as in the above "(1) Hot water immersion durability evaluation 1" except that the adherend B was used instead of the adherend A, and the hot water immersion durability evaluation was performed. For the adherend B, a coated plate on which a resin coating film (solvent coloring base coating composition "Retan PG Ecoclear HX (Q)" manufactured by Kansai Paint Co., Ltd.) is formed on the surface of a steel plate is used, and the surface on the coating film side is covered. I made it to the surface. The results are shown in Table 4 below.

(3) Hot water immersion durability evaluation 3
A test piece was prepared in the same manner as in the above "(1) Hot water immersion durability evaluation 1" except that the adherend C was used instead of the adherend A, and the hot water immersion durability evaluation was performed. As the adherend C, a coating substitute film (“wrap film series 1080” manufactured by 3M Co., Ltd.) having a colored resin film layer made of a polyvinyl chloride material on the surface was used, and the surface on the side of the colored resin film layer was used as the adherend surface. The results are shown in Table 4 below.

[Discussion 2]
From Table 4 above, the pressure-sensitive adhesive sheets of Examples 3 to 11 in which the pressure-sensitive adhesive layer further contained a styrene-based resin or a rosin-based resin did not peel off from the adherend B and the adherend C even when placed in a warm water immersion environment. Since the material of the adherend surface of the adherend B and the adherend C is resin, it is considered that the adherend surface has a lower polarity than the adherend A in which the material of the adherend surface is metal. It was suggested that the pressure-sensitive adhesive sheets of Examples 3 to 11 had good adhesive durability and stress relaxation property even on a low-polarity adherend surface even in a hot water immersion environment.

1 ... Adhesive layer 2 ... Elastic foam layer 10 ... Adhesive sheet

Claims (25)

It has an elastic foam layer and an adhesive layer arranged on at least one main surface side of the elastic foam layer.
A pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer contains a crosslinked product of a vinyl acetate-acrylic copolymer as a main component and further contains a vinyl chloride-vinyl acetate-based copolymer. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is arranged on both main surface sides of the elastic foam layer. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the crosslinked product of the vinyl acetate-acrylic copolymer has a urethane bond. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the crosslinked product of the vinyl acetate-acrylic copolymer has an epoxy bond. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the crosslinked product of the vinyl acetate-acrylic copolymer has a metal chelate bond. The crosslinked product of the vinyl acetate-acrylic copolymer is a cured product obtained by cross-linking the vinyl acetate-acrylic copolymer with a curing agent.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the curing agent is an isocyanate-based curing agent. The crosslinked product of the vinyl acetate-acrylic copolymer is a cured product obtained by cross-linking the vinyl acetate-acrylic copolymer with a curing agent.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the curing agent is an epoxy-based curing agent. The crosslinked product of the vinyl acetate-acrylic copolymer is a cured product obtained by cross-linking the vinyl acetate-acrylic copolymer with a curing agent.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the curing agent is a metal chelate-based curing agent. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the vinyl chloride-vinyl acetate-based copolymer has a number average molecular weight of 3000 or more and 100,000 or less. The content of the vinyl chloride-vinyl acetate-based copolymer in the adhesive layer is 0.5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the crosslinked product of the vinyl acetate-acrylic copolymer. The adhesive sheet according to any one of claims 1 to 9. The pressure-sensitive adhesive sheet according to any one of claims 1 to 10, wherein the vinyl chloride-vinyl acetate-based copolymer is compatible with the crosslinked product of the vinyl acetate-acrylic copolymer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 11, wherein the pressure-sensitive adhesive layer further contains a pressure-sensitive adhesive resin. The pressure-sensitive adhesive sheet according to claim 12, wherein the pressure-sensitive adhesive resin has a weight average molecular weight of 200 or more and 8,000 or less. The pressure-sensitive adhesive sheet according to claim 12, wherein the softening point of the pressure-sensitive adhesive resin is 60 ° C. or higher and 200 ° C. or lower. The claim according to any one of claims 12 to 14, wherein the content of the tackifier resin with respect to 100 parts by mass of the crosslinked product of the vinyl acetate-acrylic copolymer is 3 parts by mass or more and 60 parts by mass or less. The described adhesive sheet. Any one of claims 12 to 15, wherein the tackifier resin is at least one selected from the group consisting of hydrocarbons consisting of styrene-based resin, rosin-based resin, terpene-based resin, and petroleum-based resin. The adhesive sheet according to the claim. The pressure-sensitive adhesive sheet according to any one of claims 12 to 16, wherein the pressure-sensitive adhesive resin is a copolymer of a styrene-based monomer and an aliphatic monomer. 13. The adhesive sheet described in the claim. The pressure-sensitive adhesive sheet according to claim 18, wherein the at least one resin selected from the above group is at least one of a styrene-based resin and a rosin-based resin. The pressure-sensitive adhesive sheet according to claim 18, wherein at least one resin selected from the above group is a copolymer of a styrene-based monomer and an aliphatic monomer. The pressure-sensitive adhesive sheet according to any one of claims 18 to 20, wherein the weight average molecular weight of at least one resin selected from the above group is 200 or more and 8000 or less. The pressure-sensitive adhesive sheet according to any one of claims 18 to 21, wherein the softening point of at least one resin selected from the above group is 60 ° C. or higher and 200 ° C. or lower. Claims 18 to 22 wherein the content of at least one resin selected from the above group with respect to 100 parts by mass of the crosslinked vinyl acetate-acrylic copolymer is 3 parts by mass or more and 60 parts by mass or less. The adhesive sheet according to any one of the claims. The pressure-sensitive adhesive sheet according to any one of claims 1 to 23, wherein the pressure-sensitive adhesive layer contains substantially no photopolymerization initiator. The pressure-sensitive adhesive sheet according to any one of claims 1 to 24, wherein the thickness of the pressure-sensitive adhesive layer is 3 μm or more and 200 μm or less.

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