KR20230066444A - adhesive sheet - Google Patents

Abstract

The present invention provides a pressure-sensitive adhesive sheet having excellent deformation resistance against continuous load in the thickness direction (Z-axis direction).
This PSA sheet includes an acrylic polymer as a base polymer, a tackifying resin, a (meth)acrylic oligomer, and a PSA layer containing an azole compound. In a preferred aspect, the acrylic polymer is polymerized with an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at an ester terminal in an amount of 50% by weight or more.

Description

adhesive sheet

The present invention relates to an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2020-153822 filed on September 14, 2020, the entire contents of which are incorporated herein by reference.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives. The same applies hereinafter) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive can be used, for example, in the form of a pressure-sensitive adhesive sheet with a base material including a pressure-sensitive adhesive layer on a support base material, or in the form of a substrate-less pressure-sensitive adhesive sheet without a support base material, for smartphones and other portable devices. It is widely used for purposes such as joining, fixing, and protecting members in electronic devices. Patent Literatures 1 and 2 can be cited as technical documents relating to adhesive tapes used for fixing members of portable electronic devices.

Japanese Unexamined Patent Publication No. 2019-70102 Japanese Unexamined Patent Publication No. 2018-28051

[0003] A member fixing in a portable electronic device by means of an adhesive sheet usually has a small bonding area due to restrictions such as size and weight. The pressure-sensitive adhesive sheet used for this purpose needs to have adhesive strength capable of achieving good fixation even in a small area, and its required performance is on a higher level due to the demand for weight reduction and miniaturization. In particular, portable electronic devices equipped with a touch panel type display, represented by smartphones, are miniaturized and thinned, and large screens are progressing from the viewpoint of visibility and operability of the display. Due to the unique situation, adhesive fixing performance under more severe conditions is required for the adhesive used. Specifically, in this application, the bonding area is limited, and, for example, an elastic member such as a flexible printed circuit board (FPC) is bent, accommodated in a limited internal space in a portable electronic device, and precisely positioned with an adhesive sheet. Therefore, measures such as stable fixation are being taken. In the pressure-sensitive adhesive sheet used for fixing such a member, a continuous peeling deformation load is applied in the thickness direction (also referred to as the Z-axis direction) of the pressure-sensitive adhesive sheet.

In recent years, in addition to the weight reduction and miniaturization described above, development of portable electronic devices products having curved surfaces such as three-dimensional shapes has been progressing, and their surface shapes tend to become more complicated. [0003] A pressure-sensitive adhesive sheet to be adhered to a complex shape is required to have the ability to closely follow and adhere to the shape. For example, in the portable electronic device, an adhesive sheet for fixing a member such as a cover glass having a complicated surface shape (which may be a curved shape) tends to be subjected to a continuous peeling load that is greater than before, and is used for this purpose. The pressure-sensitive adhesive sheet is required to have resistance to deformation against continuous peeling load at a higher level. Therefore, it is very meaningful to provide an adhesive sheet that is difficult to deform against a continuous peeling load in the thickness direction (having resistance to deformation against a continuous load in the Z-axis direction).

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an adhesive sheet capable of improving resistance to deformation against a sustained load in the Z-axis direction.

According to the present specification, a pressure-sensitive adhesive sheet comprising an acrylic polymer as a base polymer, a tackifier resin, a (meth)acrylic oligomer, and a pressure-sensitive adhesive layer containing an azole-based compound is provided.

In a system using an acrylic polymer as a base polymer, a tackifying resin, and a (meth)acrylic oligomer, by further using an azole-based compound, an adhesive sheet having excellent resistance to deformation against a continuous load in the Z-axis direction can be realized. . The pressure-sensitive adhesive sheet can fix the elastic adherend in a bent state and continuously maintain the fixed state. In addition, the pressure-sensitive adhesive sheet can fix a member having a complex shape and continuously maintain the fixed state.

In a preferred aspect of the technology disclosed herein, the acrylic polymer is polymerized in an amount of 50% by weight or more of an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at an ester terminal. By using such an acrylic polymer together with a tackifying resin, a (meth)acrylic oligomer, and an azole-based compound, an adhesive sheet having excellent resistance to deformation against sustained load in the Z-axis direction can be easily obtained.

In a preferred aspect of the technology disclosed herein, the tackifying resin is included in an amount of less than 30 parts by weight based on 100 parts by weight of the acrylic and polymer. By using a predetermined amount of the tackifying resin, the initial adhesiveness can be preferably improved while ensuring resistance to deformation against a continuous load in the Z-axis direction by the acrylic polymer as the base polymer.

In a preferred aspect of the technology disclosed herein, the (meth)acrylic oligomer is included in an amount of less than 30 parts by weight based on 100 parts by weight of the acrylic polymer. By using a predetermined amount of (meth)acrylic oligomer, excellent resistance to deformation against a continuous load in the Z-axis direction can be exhibited even in a use mode exposed to severe conditions such as strong repulsion.

In a preferred aspect of the technology disclosed herein, the content C _O [wt%] of the (meth)acrylic oligomer and the content C _T [wt%] of the tackifying resin in the pressure-sensitive adhesive layer are the content C _O [ The ratio (C _T /C _O ) of the corresponding content C _T [wt %] to [wt %] satisfies 0.25 or more and 4 or less. By using the tackifying resin and the (meth)acrylic oligomer in the above range, while obtaining excellent initial adhesiveness, it is possible to exhibit highly excellent resistance to deformation against continuous load in the Z-axis direction even in a use mode exposed to severe conditions such as strong repulsion. can

In a preferred aspect of the technology disclosed herein, 50% by weight or more of the tackifying resin is a phenolic tackifying resin having a hydroxyl value of 30 mgKOH/g or more. If such a tackifying resin is used, the adhesive force is likely to be improved.

In a preferred aspect of the technology disclosed herein, the azole-based compound is contained in an amount of 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. By using a predetermined amount of the azole-based compound, excellent resistance to deformation against a continuous load in the Z-axis direction can be exhibited.

In a preferable aspect of the technology disclosed herein, a triazole-based compound is included as the azole-based compound. In a system using an acrylic polymer as a base polymer, when a triazole-based compound is used, highly excellent resistance to deformation against a continuous load in the Z-axis direction can be exhibited.

In some preferred embodiments, the pressure-sensitive adhesive sheet is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer. A base material-free double-sided pressure sensitive adhesive sheet can be reduced in thickness to the extent that it does not have a base material, and can contribute to miniaturization and space saving of products to which the double-sided pressure sensitive adhesive sheet is applied. In addition, according to the substrate-free pressure-sensitive adhesive sheet, the effects of the pressure-sensitive adhesive layer, such as adhesion and deformation resistance against a continuous load in the Z-axis direction, can be expressed to the maximum extent.

The adhesive sheet disclosed herein can be preferably used for bonding members of portable electronic devices. Since the adhesive sheet disclosed herein has deformation resistance against a continuous load in the Z-axis direction, it is preferably used for fixing an elastic adherend such as an FPC. According to the adhesive sheet, the elastic adherend can be fixed in a bent state, and the fixed state can be continuously maintained. In addition, the pressure-sensitive adhesive sheet disclosed herein is also preferably used for fixing a member such as a cover glass having a complicated surface shape (which may be a curved shape) in a portable electronic device.

1 is a cross-sectional view schematically showing a configuration example of an adhesive sheet.
Fig. 2 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
Fig. 3 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
Fig. 4 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
Fig. 5 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
Fig. 6 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
7 is an exploded perspective view schematically illustrating a configuration example of a display device.
8 is a schematic view illustrating a method for testing resistance to strain in the Z-axis direction.

Preferred embodiments of the present invention will be described below. In addition, matters necessary for the practice of the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for the practice of the invention described in this specification and common technical knowledge at the time of filing. The present invention can be practiced based on the content disclosed herein and common knowledge in the art. In addition, in the following drawings, members and parts exhibiting the same action may be described with the same reference numerals, and overlapping explanations may be omitted or simplified. In addition, the embodiments described in the drawings are modeled for clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the PSA sheet of the present invention actually provided as a product.

In this specification, the 'adhesive', as described above, refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure. The adhesive referred to here is <Mr. no way. As defined in CA Dahlquist, 'Adhesion: Fundamentals and Practice', McLaren & Sons, (1966) P.143>, generally the complex tensile modulus E ^* (1 Hz) < 10 ⁷ dyne/cm 2 It may be a material having satisfactory properties (typically a material having the above properties at 25°C).

In this specification, '(meth)acryloyl' is meant to comprehensively indicate acryloyl and methacryloyl. Similarly, '(meth)acrylate' is meant to comprehensively indicate acrylate and methacrylate, and '(meth)acryl' to acryl and methacryl, respectively.

In this specification, "acrylic polymer" refers to a polymer comprising a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an 'acrylic monomer'. An acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer.

The PSA sheet disclosed herein may be a PSA sheet with a base material having the PSA layer on one side or both sides of a base material (support), or may be a PSA sheet without a base material such as a type in which the PSA layer is held by a release liner. do. The concept of the pressure-sensitive adhesive sheet herein may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. In addition, the PSA sheet disclosed herein may be in the form of a roll or sheet. Alternatively, it may be a pressure-sensitive adhesive sheet processed into more diverse shapes.

The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIGS. 1 to 6 . Among these, FIG. 1 and FIG. 2 are structural examples of the double-sided adhesive type adhesive sheet with a base material. In the PSA sheet 1 shown in FIG. 1 , PSA layers 21 and 22 are provided on each surface of a substrate 10 (both non-peelable), and at least the PSA layer side of these PSA layers is a peelable surface. It has a structure protected by peeling liners 31 and 32, respectively. In the PSA sheet 2 shown in FIG. 2 , PSA layers 21 and 22 are provided on each surface of a substrate 10 (both non-peelable), and one PSA layer 21 of them is a peelable surface on both sides. It has a structure protected by the peeling liner 31 which has become. In this type of PSA sheet 2, by winding the PSA sheet and bringing the other PSA layer 22 into contact with the back surface of the release liner 31, the PSA layer 22 is also protected by the release liner 31. configuration can be done.

3 and 4 are structural examples of a base-free double-sided pressure-sensitive adhesive sheet. In the PSA sheet 3 shown in FIG. 3, both surfaces 21A and 21B of the non-substrate PSA layer 21 are protected by release liners 31 and 32, respectively, in which at least the PSA layer side is a release surface. has a configuration The PSA sheet 4 shown in FIG. 4 has a configuration in which one surface (adhesive surface) 21A of the non-substrate PSA layer 21 is protected by a release liner 31 in which both surfaces are release surfaces. When this is rolled, the other surface (adhesive surface) 21B of the pressure-sensitive adhesive layer 21 comes into contact with the back surface of the release liner 31, so that the other surface 21B is also protected by the release liner 31. it is possible to do

5 and 6 are structural examples of a single-sided adhesive sheet with a base material. In the PSA sheet 5 shown in FIG. 5 , a PSA layer 21 is provided on one surface 10A (non-peelable) of a substrate 10, and the surface (adhesive surface) 21A of the PSA layer 21 is at least The side of the pressure-sensitive adhesive layer is protected by a release liner 31 serving as a release surface. The PSA sheet 6 shown in FIG. 6 has a configuration in which an PSA layer 21 is provided on one surface 10A (non-peelable) of a base material 10 . The other surface 10B of the base material 10 is a release surface, and when the pressure-sensitive adhesive sheet 6 is wound, the pressure-sensitive adhesive layer 21 comes into contact with the other surface 10B, and the surface of the pressure-sensitive adhesive layer (adhesive surface) ( 21B) is protected by the other side 10B of the substrate.

<Adhesive layer>

In the technology disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. For example, known various adhesives such as acrylic adhesives, rubber-based adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone-based adhesives, polyester-based adhesives, urethane-based adhesives, polyether-based adhesives, polyamide-based adhesives, fluorine-based adhesives, etc. It may be a pressure-sensitive adhesive layer comprising one or two or more types of pressure-sensitive adhesives selected from Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive containing a (meth)acrylic polymer as a base polymer (a main component in the polymer component, that is, a component contained in excess of 50% by mass). The same is true for the rubber-based pressure-sensitive adhesive and other pressure-sensitive adhesives. As a preferable pressure-sensitive adhesive layer from the viewpoints of transparency, weather resistance, etc., a pressure-sensitive adhesive layer having an acrylic pressure-sensitive adhesive content of 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more is mentioned. The content of the acrylic pressure-sensitive adhesive may be more than 98% by weight, or the pressure-sensitive adhesive layer substantially containing the acrylic pressure-sensitive adhesive may be used.

(Acrylic polymer)

Although not particularly limited, in a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive include an acrylic polymer as a base polymer. The acrylic polymer is preferably a polymer of monomer raw materials that includes an alkyl (meth)acrylate as a main monomer and may further include an auxiliary monomer copolymerizable with the main monomer. Here, the main monomer refers to a component included in more than 50% by weight in the monomer raw material.

As an alkyl (meth)acrylate, the compound represented by following formula (1) can be used suitably, for example.

CH ₂ =C(R ¹ )COOR ² (1)

Here, R ¹ in the formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereafter, the range of the number of carbon atoms is sometimes referred to as “C _1-20 ”). From the viewpoint of the storage modulus of the pressure-sensitive adhesive, etc., alkyl (meth)acrylates in which R ² is a C _1-14 chain alkyl group are preferable, and alkyl (meth)acrylates in which R ² is a C _1-10 chain alkyl group are more preferable, , Alkyl (meth)acrylates in which R ² is a butyl group or a 2-ethylhexyl group are particularly preferred.

Examples of alkyl (meth)acrylates in which R ² is a C _1-20 chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n -Butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate )Acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate , isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexa Decyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. are mentioned. These alkyl (meth)acrylates can be used individually by 1 type or in combination of 2 or more types. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technology disclosed herein, the monomer component constituting the acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA among the alkyl (meth)acrylates contained in the monomer component is 75% by weight or more (typically 85% by weight or more, for example, 90% by weight or more, further 95% by weight or more) may be preferably carried out in an aspect that occupies. The technique disclosed herein can be carried out, for example, in an aspect in which the alkyl (meth)acrylate contained in the monomer component is only BA, an aspect in which 2EHA is alone, or an aspect in which BA and 2EHA are included.

When the monomer component includes BA and 2EHA, the weight ratio of BA and 2EHA (BA/2EHA) is not particularly limited, and may be, for example, 1/99 or more and 99/1 or less. In a preferred embodiment, BA/2EHA may be 60/40 or higher (eg, 60/40 or higher and 99/1 or lower), may be 80/20 or higher, or 90/10 or higher (eg, 90/10 or higher and 99/1 or lower). 1 or less).

The technique disclosed herein can be preferably carried out in an aspect in which the monomer component constituting the acrylic polymer contains 50% by weight or more of C _1-6 alkyl (meth)acrylate. In other words, the polymerization ratio of C _1-6 alkyl (meth)acrylate in the acrylic polymer is preferably 50% by weight or more. In this way, by using C _1-6 alkyl (meth)acrylate as a main monomer, an acrylic polymer capable of realizing resistance to deformation against a sustained load in the Z-axis direction can be preferably designed. The proportion of C _1-6 alkyl (meth)acrylate in the monomer component (in other words, the polymerization ratio) is more preferably greater than 50% by weight, even more preferably 60% by weight or more, particularly preferably 70% by weight. or more (for example, 80% by weight or more, further 85% by weight or more). The upper limit of the ratio of C _1-6 alkyl (meth)acrylate in the monomer component is not particularly limited, and is usually 99% by weight or less, and from the relationship with the use ratio of other copolymerizable monomers, 97% by weight or less is appropriate. And, it is preferable to set it to 95% by weight or less. C _1-6 alkyl (meth)acrylate can be used individually by 1 type or in combination of 2 or more types. As C _1-6 alkyl (meth)acrylate, C _1-6 alkyl acrylate is preferable, C _2-6 alkyl acrylate is more preferable, and C _4-6 alkyl acrylate is still more preferable. In another aspect, C _1-6 alkyl (meth)acrylate is preferably C _1-4 alkylacrylate, more preferably C _2-4 alkylacrylate. A suitable example of C _1-6 alkyl (meth)acrylate is BA.

In the aspect using BA as the main monomer, the copolymerization ratio of BA in the acrylic polymer is preferably 50% by weight or more, more preferably greater than 50% by weight, even more preferably 60% by weight or more, particularly preferably 70% by weight or more (eg 80% by weight or more, even 85% by weight or more), more particularly preferably 90% by weight or more (eg more than 90% by weight). By copolymerizing BA as the main monomer, the pressure-sensitive adhesive can adhere well to the adherend. In addition, the copolymerization ratio of BA in the acrylic polymer is not particularly limited, and is usually 99% by weight or less, and is preferably 97% by weight or less in relation to the copolymerization ratio of other copolymerizable monomers (eg, acid group-containing monomers). And, it is preferable to set it to 95% by weight or less.

In a preferable aspect of the technology disclosed herein, an acidic group-containing monomer is used as a monomer having copolymerizability with an alkyl (meth)acrylate as a main monomer. An acidic group-containing monomer can improve cohesiveness based on its polarity and exhibit good binding force to a polar adherend. In the case of using a crosslinking agent such as an isocyanate or epoxy crosslinking agent, the acidic group (typically a carboxy group) serves as a crosslinking point for the acrylic polymer. Due to these actions, deformation resistance to a continuous load in the Z-axis direction can be suitably realized. An acrylic polymer capable of realizing initial adhesiveness and resistance to deformation against a sustained load in the Z-axis direction can be preferably designed by using an acidic group-containing monomer in a ratio higher than or equal to a predetermined ratio.

As the acid group-containing monomer, a carboxy group-containing monomer is preferably used. Examples of the carboxy group-containing monomer include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid, isocrotonic acid, and the like. ethylenically unsaturated monocarboxylic acids; Ethylenically unsaturated dicarboxylic acids, such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.) are mentioned. In addition, the acidic group-containing monomer may be a monomer having a metal salt (for example, an alkali metal salt) of a carboxyl group. Among them, AA and MAA are preferred, and AA is more preferred. When one or two or more acidic group-containing monomers are used, the proportion of AA in the acidic group-containing monomer is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight. More than that. In one particularly preferred aspect, the acidic group-containing monomer contains substantially only AA. AA balances initial adhesion and resistance to deformation against sustained load in the Z-axis direction in the acidic group-containing monomers disclosed herein from complex actions such as polarity based on its carboxyl group, role as a crosslinking point, and Tg (106 ° C). It is considered to be an optimal monomer material for realization.

In the technique disclosed herein, the content of the acidic group-containing monomer (typically, the carboxyl group-containing monomer) in the monomer component (in other words, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer) is usually 3% by weight or more, , it is appropriate to set it as 5% by weight or more. By using a monomer containing a predetermined amount or more of an acidic group, an acrylic polymer capable of achieving both initial adhesion and resistance to deformation against a sustained load in the Z-axis direction can be preferably realized based on its cohesion enhancing action and the like. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer may be, for example, 6% by weight or more. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is usually suitably 20% by weight or less, and preferably 18% by weight or less from the viewpoint of maintaining the properties of the main monomer. The copolymerization ratio may be 15% by weight or less, for example, 13% by weight or less. In a more preferred aspect, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is approximately 12% by weight or less, more preferably approximately 10% by weight or less, and particularly preferably approximately 8% by weight or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth)acrylate (typically BA), it is particularly effective to set the content of the acid group-containing monomer (eg, AA) in the monomer component within the above range. am.

In the technique disclosed herein, a copolymerizable monomer other than a carboxy group-containing monomer may be used as a secondary monomer having copolymerizability with alkyl (meth)acrylate as the main monomer. As such an auxiliary monomer, the following functional group-containing monomers can be used, for example.

Hydroxyl group-containing monomers: e.g., 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. hydroxyalkyl (meth) acrylates; unsaturated alcohols such as vinyl alcohol and allyl alcohol; Polypropylene glycol mono(meth)acrylate.

Amide group-containing monomers: e.g., (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane (meth)acrylamide ) Acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide.

Amino group-containing monomers: eg aminoethyl (meth)acrylate, N,N-dimethyl aminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.

Monomers having an epoxy group: eg, glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allylglycidyl ether.

Cyano group-containing monomers: eg acrylonitrile, methacrylonitrile.

Keto group-containing monomers: eg diacetone (meth)acrylamide, diacetone (meth)acrylate, vinylmethyl ketone, vinylethyl ketone, allylacetoacetate, vinylacetoacetate.

Monomers having nitrogen atom-containing rings: e.g. N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine , N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine.

Alkoxysilyl group-containing monomers: e.g., 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-( meth)acryloxypropylmethyldiethoxysilane.

Functional group-containing monomers (sub-monomers) other than the acidic group-containing monomers may be used singly or in combination of two or more. When the monomer component constituting the acrylic polymer includes a functional group-containing monomer, the proportion of the functional group-containing monomer in the monomer component is appropriately determined depending on adhesive strength, resistance to deformation against sustained load in the Z-axis direction, and other required performance. The ratio (copolymerization ratio) of the functional group-containing monomer is suitably about 0.01% by weight or more (eg, 0.02% by weight or more, usually 0.03% by weight or more) of the monomer component, and furthermore, 0.1% by weight or more (eg, 0.5% by weight or more). % or more, typically 1% by weight or more). Further, the upper limit thereof is preferably about 40% by weight or less (for example, 30% by weight or less, usually 20% by weight or less). In a more preferable aspect, the ratio of the functional group-containing monomers other than the acidic group-containing monomer is, for example, 10% by weight or less, preferably 5% by weight or less, and can be 1% by weight or less. Further, in a preferred embodiment, the ratio of functional group-containing monomers (eg, hydroxyl group-containing monomers) other than the acidic group-containing monomer is approximately 0.5% by weight or less (eg, approximately 0.2% by weight or less). The monomer component constituting the acrylic polymer may be one that does not substantially contain a functional group-containing monomer other than the acidic group-containing monomer.

In a preferable aspect of the technology disclosed herein, a hydroxyl group-containing monomer is used as the secondary monomer. In a system using a hydroxyl group-containing monomer as the secondary monomer, when a crosslinking agent such as an isocyanate or epoxy crosslinking agent is used, the hydroxyl group in the hydroxyl group-containing monomer can serve as a crosslinking point for the acrylic polymer. Therefore, when a hydroxyl group-containing monomer is used as the secondary monomer, even when an azole compound is used in combination, the occurrence of inhibition of crosslinking of the acrylic polymer by the azole compound is appropriately suppressed, and crosslinking of the acrylic polymer proceeds appropriately. easy. Thereby, deformation resistance to a continuous load in the Z-axis direction can be suitably realized. By using a hydroxyl group-containing monomer in a ratio higher than or equal to a predetermined ratio, it is possible to preferably design an acrylic polymer capable of realizing excellent resistance to deformation against sustained load in the Z-axis direction in a system in which an azole-based compound is added.

In the technology disclosed herein, the content of the hydroxyl group-containing monomer in the monomer component (in other words, the copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer) is usually 0.001% by weight or more, and it is appropriate to set it to 0.005% by weight or more. do. By using a hydroxyl group-containing monomer of a predetermined amount or more, an acrylic polymer capable of improving resistance to deformation against a sustained load in the Z-axis direction can be preferably realized. The copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer may be, for example, 0.01% by weight or more, 0.02% by weight or more, 0.03% by weight or more, or 0.04% by weight or more. The copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer is usually suitably 1% by weight or less, and from the viewpoint of maintaining the properties of the main monomer, it is preferably 0.5% by weight or less, and more preferably 0.1% by weight. % or less, more preferably 0.08% by weight or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth)acrylate (typically BA), the content of the hydroxyl group-containing monomer (eg 4-hydroxybutyl (meth)acrylate) in the monomer component is It is particularly effective to set it as said range.

As the monomer component constituting the acrylic polymer, other copolymerization components other than the acidic group-containing monomer and other auxiliary monomers described above can be used for the purpose of enhancing the cohesive force of the acrylic polymer. Examples of such a copolymerization component include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; Aromatic vinyl compounds, such as styrene, substituted styrene ((alpha)-methylstyrene etc.), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; Aryl(meth)acrylates (e.g. phenyl(meth)acrylate), aryloxyalkyl(meth)acrylates (e.g. phenoxyethyl(meth)acrylate), arylalkyl(meth)acrylates (e.g. benzyl( aromatic ring-containing (meth)acrylates such as meth)acrylate; olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; Vinyl ether type monomers, such as methyl vinyl ether and ethyl vinyl ether, etc. are mentioned.

The amount of these other copolymerization components may be appropriately selected according to the purpose and application and is not particularly limited, but is usually preferably 10% by weight or less of the monomer components. For example, when using a vinyl ester monomer (eg, vinyl acetate) as the other copolymerizable component, its content can be, for example, about 0.1% by weight or more (usually about 0.5% by weight or more) of the monomer component, and , It is appropriate to set it as about 20 weight% or less (usually about 10 weight% or less).

As another monomer component, the acrylic polymer may contain a polyfunctional monomer having at least two polymerizable functional groups (typically radical polymerizable functional groups) having unsaturated double bonds such as a (meth)acryloyl group or a vinyl group. By using a polyfunctional monomer as the monomer component, the cohesive force of the pressure-sensitive adhesive layer can be increased. A polyfunctional monomer can be used as a crosslinking agent.

Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. Acrylates, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,4 -Butanedioldi(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetri esters of polyhydric alcohols such as (meth)acrylate and (meth)acrylic acid; Allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, etc. are mentioned. Preferable examples among these include trimethylolpropane tri(meth)acrylate, 1,6-hexanedioldi(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Among them, 1,6-hexanediol di(meth)acrylate is exemplified as a preferred example. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types. From viewpoints of reactivity and the like, polyfunctional monomers having two or more acryloyl groups are usually preferred.

The amount of the polyfunctional monomer used is not particularly limited and can be appropriately set so that the purpose of use of the polyfunctional monomer is achieved. From the viewpoint of balancing the preferred storage modulus disclosed herein with other adhesive performance or other characteristics in a well-balanced manner, the amount of the polyfunctional monomer may be approximately 3% by weight or less, preferably approximately 2% by weight or less, More preferably about 1% by weight or less (eg, about 0.5% by weight or less). The lower limit of the usage amount in the case of using a polyfunctional monomer should just be larger than 0 weight%, and is not specifically limited. Usually, the effect of using the polyfunctional monomer can be exhibited appropriately by setting the usage amount of the polyfunctional monomer to about 0.001% by weight or more (eg, about 0.01% by weight or more) of the monomer component.

It is appropriate that the composition of the monomer component constituting the acrylic polymer is designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately -15°C or lower (eg, approximately -70°C or higher and -15°C or lower). Here, the Tg of the acrylic polymer refers to Tg obtained by Fox's formula based on the composition of the monomer component. As shown below, Fox's formula is a relational expression between the Tg of the copolymer and the glass transition temperature (Tgi) of a homopolymer obtained by homopolymerization of each of the monomers constituting the copolymer.

1/Tg = Σ(Wi/Tgi)

In addition, in Fox's formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of monomer (i) in the copolymer (copolymerization ratio based on weight), and Tgi is the amount of monomer (i) It represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for calculating Tg, a value described in known materials is used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.

2-Ethylhexylacrylate -70℃

N-butyl acrylate -55℃

Ethyl acrylate -22℃

Methyl acrylate 8℃

Methyl methacrylate 105℃

2-hydroxyethyl acrylate -15℃

4-Hydroxybutylacrylate -40℃

Vinyl acetate 32℃

Styrene 100℃

Acrylic acid 106℃

Methacrylic acid 228℃

Regarding the glass transition temperature of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For a monomer for which a plurality of types of values are described in this document, the highest value is adopted.

For a monomer whose glass transition temperature is not described in the above literature as well, the value obtained by the following measuring method shall be used.

Specifically, 100 parts by weight of monomer, 0.2 part by weight of 2,2'-azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, stirrer, nitrogen inlet pipe and reflux condenser, It stirs for 1 hour while passing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Next, this homopolymer solution was applied by casting on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample was punched into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name 'ARES') While, the viscoelasticity is measured in the shear mode at a temperature range of -70 ° C to 150 ° C and a heating rate of 5 ° C / min, and the temperature corresponding to the peak top temperature of tan δ is taken as the Tg of the homopolymer.

Although not particularly limited, from the viewpoint of adhesiveness, it is advantageous that the acrylic polymer has a Tg of approximately -25°C or lower, preferably approximately -35°C or lower, more preferably approximately -40°C or lower, still more preferably -45°C. or less, for example, -50°C or less, or -55°C or less. Also, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is usually approximately -75°C or higher, and preferably approximately -70°C or higher. The technology disclosed herein can be preferably implemented in an aspect in which the Tg of the acrylic polymer is approximately -65°C or higher and approximately -40°C or lower (eg, approximately -65°C or higher and approximately -45°C or lower). In a preferred aspect, the Tg of the acrylic polymer may be approximately -55°C or higher and approximately -45°C or lower. In another aspect, the Tg of the acrylic polymer may be approximately -65°C or higher and approximately -55°C or lower. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (ie, the type or usage ratio of monomers used in the synthesis of the polymer).

The Mw of the acrylic polymer is not particularly limited, and may be, for example, approximately 10×10 ⁴ or more and 500×10 ⁴ or less. From the viewpoint of cohesiveness, the Mw is usually about 30×10 ⁴ or more, and it is appropriate to set it to about 45×10 ⁴ or more (eg, about 65×10 ⁴ or more). In a preferred aspect, Mw of the acrylic polymer is 70×10 ⁴ or more. Further, in one typical aspect of the technology disclosed herein, it is appropriate that the Mw of the acrylic polymer is greater than 70×10 ⁴ . By using an acrylic polymer having a Mw of greater than 70×10 ⁴ , excellent resistance to deformation against a continuous deformation load is obtained based on its cohesiveness. The Mw of the acrylic polymer is more preferably approximately 75×10 ⁴ or greater, even more preferably approximately 90×10 ⁴ or greater, and particularly preferably approximately 95×10 ⁴ or greater. Further, in a particularly preferred aspect, the Mw is approximately 100×10 ⁴ or greater (eg, approximately 110×10 ⁴ or greater), and typically greater than or equal to 120×10 ⁴ (eg, 130×10 ⁴ or greater). In addition, the Mw is usually 300 × 10 ⁴ or less (more preferably about 200 × 10 ⁴ or less, for example, about 150 × 10 ⁴ or less). Mw of the acrylic polymer may be approximately 140×10 ⁴ or less. For example, in the case of an acrylic polymer obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to set the Mw within the above range.

The degree of dispersion (Mw/Mn) of the acrylic polymer disclosed herein is not particularly limited. The degree of dispersion (Mw/Mn) as used herein refers to the degree of dispersion (Mw/Mn) expressed by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In a preferred aspect, the degree of dispersion (Mw/Mn) of the acrylic polymer is 8 or more and 40 or less. The fact that the Mw/Mn of the acrylic polymer is 8 or more and 40 or less may mean that the molecular weight distribution is wide and includes a significant amount of a low molecular weight material and a high molecular weight material. The low molecular weight material contributes to the development of initial adhesion by virtue of good wettability to the adherend, and the high molecular weight material exhibits resistance to a continuous deformation load (resistance to deformation) due to its cohesive property. When the Mw/Mn is 8 or more, the initial adhesiveness is favorably expressed. In addition, when the Mw/Mn is 40 or less, the molecular weight distribution is preferably restricted within an appropriate range, and stable properties (initial adhesion and deformation resistance) are obtained. The Mw/Mn may be 10 or more, 12 or more, or 15 or more. Further, the Mw/Mn is preferably 35 or less, more preferably 30 or less, still more preferably 25 or less.

In one preferred aspect, the acrylic polymer has a degree of dispersion (Mw/Mn) of less than 15. For example, in the case of an acrylic polymer having a relatively high molecular weight (typically more than 700,000 Mw) obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to set the Mw/Mn within the above range. The Mw/Mn is preferably less than 12, more preferably less than 10, still more preferably less than 8 (eg, 7.5 or less). In addition, Mw/Mn is theoretically 1 or more, for example, may be 2 or more, 3 or more, or 4 or more (typically 5 or more).

In addition, Mw, Mn, and Mw/Mn can be controlled by polymerization conditions (time, temperature, etc.), use of a chain transfer agent, selection of a polymerization solvent based on chain transfer constant, and the like. In addition, Mw and Mn can be obtained from standard polystyrene conversion values obtained by GPC (Gel Permeation Chromatography). As the GPC device, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

<Adhesive composition>

The pressure-sensitive adhesive layer disclosed herein may be formed using a pressure-sensitive adhesive composition including a monomer component having the above-described composition in the form of a polymer, an unpolymerized material (ie, a form in which a polymerizable functional group is unreacted), or a mixture thereof. there is. The pressure-sensitive adhesive composition includes a composition containing an adhesive (adhesive component) in an organic solvent (solvent-type pressure-sensitive adhesive composition), a composition in which the pressure-sensitive adhesive is dispersed in an aqueous solvent (water-dispersible pressure-sensitive adhesive composition), and an active energy ray such as ultraviolet rays or radiation. It may be in various forms, such as a composition prepared to form an adhesive by curing (active energy ray-curable pressure-sensitive adhesive composition), a hot-melt pressure-sensitive adhesive composition that is applied in a heated melt state and forms an adhesive when cooled to around room temperature. The technique disclosed herein can be particularly preferably carried out in terms of adhesive properties and the like, in an aspect provided with a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition.

Here, in the present specification, 'active energy ray' refers to an energy ray having energy capable of causing a chemical reaction such as a polymerization reaction, a crosslinking reaction, and decomposition of an initiator. Examples of active energy rays here include light such as ultraviolet rays, visible rays, and infrared rays, and radiations such as α rays, β rays, γ rays, electron rays, neutron rays, and X rays.

The pressure-sensitive adhesive composition typically contains at least a part of the monomer components of the composition (may be a part of the type of monomer or a part of the amount) in the form of a polymer. The polymerization method at the time of forming the above polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately employed. thermal polymerization (typically carried out in the presence of a thermal polymerization initiator) such as, for example, solution polymerization, emulsion polymerization, bulk polymerization; photopolymerization carried out by irradiation with light such as ultraviolet rays (typically carried out in the presence of a photopolymerization initiator); Radiation polymerization performed by irradiation with radiation such as β-rays and γ-rays can be suitably employed. Among them, solution polymerization and photopolymerization are preferred. In these polymerization methods, the polymerization mode is not particularly limited, and a conventionally known monomer supply method, polymerization conditions (temperature, time, pressure, light dose, radiation dose, etc.), materials used other than monomers (polymerization initiator, surfactant, etc.) ), etc. can be selected appropriately.

For example, in a preferred aspect, a solution polymerization method may be employed for synthesizing the acrylic polymer. According to the solution polymerization, a polymerization reaction solution in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technique disclosed herein may be formed from a pressure-sensitive adhesive composition containing an acrylic polymer solution obtained by subjecting the polymerization reaction solution or a suitable post-treatment to the reaction solution. As the acrylic polymer solution, one obtained by preparing the polymerization reaction solution to an appropriate viscosity (concentration) as necessary can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (e.g., emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used.

As a method for supplying monomers in the case of solution polymerization, a batch input method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like can be appropriately employed. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (usually about 40°C to 140°C). In a preferred aspect, the polymerization temperature can be set to about 75°C or less (more preferably about 65°C or less, such as about 45°C to about 65°C).

A solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (eg, aromatic hydrocarbons) such as toluene and xylene; Acetate esters, such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; Any one type of solvent selected from ketones, such as methyl ethyl ketone and acetone, or a mixed solvent of two or more types can be used.

On the other hand, as another aspect of the technology disclosed herein, when an active energy ray-curable pressure-sensitive adhesive composition (typically a photocurable pressure-sensitive adhesive composition) is employed, as the active energy ray-curable pressure-sensitive adhesive composition, from the viewpoint of environmental hygiene, etc., an organic solvent It is preferable to not contain substantially. For example, a pressure-sensitive adhesive composition having an organic solvent content of about 5% by weight or less (more preferably about 3% by weight or less, for example, about 0.5% by weight or less) is preferable. In addition, since it is suitable for forming the pressure-sensitive adhesive layer in the form of curing the liquid film of the pressure-sensitive adhesive composition between the peeling surfaces of a pair of peeling films as described later, the solvent (meaning including an organic solvent and an aqueous solvent) is substantially A pressure-sensitive adhesive composition that does not contain is preferred. For example, a pressure-sensitive adhesive composition having a solvent content of about 5% by weight or less (more preferably about 3% by weight or less, for example, about 0.5% by weight or less) is preferable. In addition, the solvent herein refers to a volatile component to be removed in the process of forming the pressure-sensitive adhesive layer, that is, a volatile component that is not intended to be a component of the finally formed pressure-sensitive adhesive layer.

In the polymerization, a known or conventional thermal polymerization initiator or photopolymerization initiator can be used depending on the polymerization method or polymerization mode. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types suitably.

The thermal polymerization initiator is not particularly limited, but examples thereof include an azo polymerization initiator, a peroxide-based initiator, a redox-based initiator obtained by combining a peroxide and a reducing agent, and a substituted ethane-based initiator. More specifically, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (2-ami Dinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(N,N' azo initiators such as -dimethyleneisobutylamidine) and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxide-based initiators such as benzoyl peroxide (BPO), t-butyl hydroperoxide, and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; Examples include, but are not limited to, redox initiators such as combinations of persulfates and sodium bisulfite and combinations of peroxides and sodium ascorbate. In addition, thermal polymerization may be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C).

Examples of the photopolymerization initiator include, but are not particularly limited to, ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, Aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and the like can be used.

Specific examples of the ketal-based photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one (eg, trade name “Irgacure 651” manufactured by BASF) and the like.

Specific examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl-phenyl-ketone (eg, trade name "Irgacure 184" manufactured by BASF), 4-phenoxydichloroacetophenone, 4-t-butyl- Dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (e.g., trade name 'Irgacure 2959' manufactured by BASF) '), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (eg, trade name 'Darocur 1173' manufactured by BASF), methoxyacetophenone, and the like.

Specific examples of the benzoin ether photopolymerization initiator include benzoin ether such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and substitution of anisole methyl ether. Benzoin ether is included.

Specific examples of the acylphosphine oxide-based photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (e.g., trade name “Irgacure 819” manufactured by BASF), bis(2,4, 6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (e.g., trade name 'Lucirin TPO' manufactured by BASF), bis (2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and the like are included.

Specific examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like. do. Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride and the like. Specific examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime and the like. Benzoin etc. are contained in the specific example of a benzoin type photoinitiator. Specific examples of the benzyl-based photopolymerization initiator include benzyl and the like.

Specific examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like.

Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothio oxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like are included.

The amount of such a thermal polymerization initiator or photopolymerization initiator may be a conventional amount depending on the polymerization method or polymerization mode, and is not particularly limited. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) of the polymerization initiator can be used with respect to 100 parts by weight of the monomer to be polymerized.

(Adhesive composition containing a monomer component in the form of a complete polymer)

The pressure-sensitive adhesive composition according to one preferred aspect includes the monomer component of the pressure-sensitive adhesive composition in the form of a complete polymer. Such a pressure-sensitive adhesive composition may be, for example, a solvent-type pressure-sensitive adhesive composition containing an acrylic polymer, which is a complete polymer of monomer components, in an organic solvent, or a water dispersion-type pressure-sensitive adhesive composition in which the acrylic polymer is dispersed in an aqueous solvent. In addition, in the present specification, 'completely polymerized material' refers to a material having a polymerization conversion rate of more than 95% by weight.

(Adhesive Composition Containing Polymers and Unpolymers of Monomer Components)

A pressure-sensitive adhesive composition according to another preferable aspect includes a polymer of a monomer mixture containing at least a part of the monomer components (raw monomers) of the composition. Typically, a part of the monomer component is included in the form of a polymer, and the remainder is included in the form of an unpolymer (unreacted monomer). The polymer of the monomer mixture can be prepared by at least partially polymerizing the monomer mixture.

The polymer is preferably a partial polymer of the monomer mixture. Such a partial polymer is a mixture of a polymer derived from the above monomer mixture and an unreacted monomer, and typically exhibits a syrupy (viscous liquid) state. Hereinafter, partial polymers having such properties may be referred to as 'monomer syrup' or simply 'syrup'.

The polymerization method for obtaining the polymer is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. From the viewpoint of efficiency or simplicity, a photopolymerization method can be preferably employed. According to photopolymerization, the polymerization conversion of the monomer mixture can be easily controlled by polymerization conditions such as light irradiation amount (light amount).

The polymerization conversion (monomer conversion) of the monomer mixture in the partial polymerization is not particularly limited. The polymerization conversion rate can be, for example, approximately 70% by weight or less, and is preferably approximately 60% by weight or less. From the viewpoint of the ease of preparation or coatability of the pressure-sensitive adhesive composition containing the partially polymerized product, the polymerization conversion ratio is usually about 50% by weight or less, and about 40% by weight or less (eg, about 35% by weight or less) is preferable. . The lower limit of the polymerization conversion ratio is not particularly limited, but is typically about 1% by weight or more, and usually about 5% by weight or more.

A pressure-sensitive adhesive composition containing a partially polymerized product of the above monomer mixture can be easily obtained, for example, by partially polymerizing a monomer mixture containing all of the raw material monomers by an appropriate polymerization method (eg, photopolymerization method). Other components (eg, a photopolymerization initiator, a multifunctional monomer, a crosslinking agent, a (meth)acrylic oligomer to be described later, etc.) may be mixed with the pressure-sensitive adhesive composition containing the partially polymerized product, if necessary. The method of blending such other components is not particularly limited, and for example, they may be previously contained in the monomer mixture or added to the partial polymer.

In addition, the PSA composition disclosed herein may be a form in which a complete polymer of a monomer mixture containing one type of monomer among monomer components (raw monomers) is dissolved in the other type of monomer or a partial polymer thereof. A pressure-sensitive adhesive composition of this type is also included as an example of a pressure-sensitive adhesive composition containing a polymer and an unpolymerized material of monomer components.

Thus, as a curing method (polymerization method) at the time of forming an adhesive from an adhesive composition containing a polymer and an unpolymerized substance of monomer components, a photopolymerization method is preferably employable. In the case of an adhesive composition containing a polymer prepared by a photopolymerization method, it is particularly suitable to employ a photopolymerization method as a curing method thereof. Since the polymer obtained by the photopolymerization method already contains a photopolymerization initiator, when forming an adhesive by further curing an adhesive composition containing this polymer, it can be photocured without adding a new photopolymerization initiator. Alternatively, it may be a pressure-sensitive adhesive composition having a composition in which a photopolymerization initiator is added as needed to a polymer prepared by a photopolymerization method. The photopolymerization initiator to be added may be the same as or different from the photopolymerization initiator used for preparation of the polymer. A pressure-sensitive adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. A photocurable pressure-sensitive adhesive composition has the advantage of being easily formed even if it is a thick pressure-sensitive adhesive layer. In a preferable aspect, photopolymerization when forming the pressure-sensitive adhesive from the pressure-sensitive adhesive composition can be performed by ultraviolet irradiation. For ultraviolet irradiation, a known high-pressure mercury lamp, low-pressure mercury lamp, metal halide lamp, or the like can be used.

(crosslinking agent)

It is preferable that the adhesive composition (preferably solvent-type adhesive composition) used for formation of an adhesive layer contains a crosslinking agent as an arbitrary component. By including a crosslinking agent, the viscoelastic properties disclosed herein can be preferably realized. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the cross-linking agent in a form after cross-linking reaction, before cross-linking reaction, in a partially cross-linked form, or in an intermediate or complex form thereof. The crosslinking agent is usually included in the pressure-sensitive adhesive layer only in the form after the crosslinking reaction.

The type of crosslinking agent is not particularly limited, and can be appropriately selected and used from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, peroxide crosslinking agents, and metal chelate crosslinking agents. , a metal alkoxide-based crosslinking agent, a metal salt-based crosslinking agent, and the like. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. As the crosslinking agent that can be preferably used in the technology disclosed herein, an isocyanate crosslinking agent, an epoxy crosslinking agent, and an oxazoline crosslinking agent are exemplified.

As the epoxy-based crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based crosslinking agent having 3 to 5 epoxy groups per molecule is preferable. An epoxy-type crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

Although not particularly limited, specific examples of the epoxy-based crosslinking agent include, for example, N,N,N'N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl) Cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. are mentioned. Examples of commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" manufactured by Mitsubishi Gas Chemical Co., Ltd., "Epiclon CR-5L" manufactured by DIC, and "Dena" manufactured by Nagase Chemtex. Cole EX-512', trade name 'TEPIC-G' manufactured by Nissan Chemical Industries, Ltd., and the like are exemplified.

In the aspect of using an epoxy-based crosslinking agent, the amount used is not particularly limited. The amount of the epoxy-based crosslinking agent may be, for example, greater than 0 parts by weight and approximately 1 part by weight or less (preferably approximately 0.001 to 0.5 parts by weight) based on 100 parts by weight of the acrylic polymer. From the viewpoint of suitably exhibiting the effect of improving the cohesive force, the amount of the epoxy-based crosslinking agent is usually appropriately about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, based on 100 parts by weight of the acrylic polymer. For example, Approximately 0.01 part by weight or more may be sufficient, approximately 0.02 part by weight or more may be sufficient, and approximately 0.03 part by weight or more may be sufficient. In addition, from the viewpoint of avoiding insufficient adhesiveness due to excessive crosslinking, it is generally appropriate that the amount of epoxy-based crosslinking agent used is approximately 0.2 parts by weight or less, and approximately 0.1 parts by weight or less (e.g., 0.05 parts by weight) based on 100 parts by weight of the acrylic polymer. below) is preferred.

As the isocyanate-based crosslinking agent, polyfunctional isocyanates (referring to compounds having an average of two or more isocyanate groups per molecule, including those containing an isocyanurate structure) can be preferably used. Isocyanate-type crosslinking agents can be used individually by 1 type or in combination of 2 or more types.

As a preferable polyfunctional isocyanate, the polyfunctional isocyanate which has 3 or more isocyanate groups on average per molecule is illustrated. Such trifunctional or higher functional isocyanate may be a multimer (e.g., dimer or trimer), a derivative (e.g., an addition reaction product of a polyhydric alcohol and a bifunctional or higher molecular isocyanate), a polymer, or the like of a bifunctional or trifunctional or higher functional isocyanate. there is. For example, dimer or trimer of diphenylmethane diisocyanate, isocyanurate compound of hexamethylene diisocyanate (trimeric adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylol and polyfunctional isocyanates such as reaction products of propane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanate include "Duranate TPA-100", a trade name manufactured by Asahi Kasei Chemicals, and "Colonate L", "Colonate HL", "Colonate HK", and "Colonate HK", manufactured by Tosoh Corporation. Colonate HX', the same 'Colonate 2096', etc. are mentioned.

In the aspect of using an isocyanate-based crosslinking agent, the amount of the isocyanate-based crosslinking agent is not particularly limited. The amount of the isocyanate-based crosslinking agent may be, for example, approximately 0.5 parts by weight or more and approximately 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. From the standpoint of cohesiveness, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is usually suitably about 0.1 parts by weight or more, and preferably about 0.3 parts by weight or more (for example, 0.5 parts by weight or more). In a more preferable aspect, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is approximately 1 part by weight or more, and may be approximately 1.5 parts by weight or more. In addition, the amount of isocyanate-based crosslinking agent based on 100 parts by weight of the acrylic polymer is usually suitably set to approximately 8 parts by weight or less, and preferably set to approximately 5 parts by weight or less (for example, less than approximately 4 parts by weight). In a more preferable aspect, the amount of the isocyanate-based crosslinking agent based on 100 parts by weight of the acrylic polymer is approximately 3 parts by weight or less, for example, 2 parts by weight or less.

As the oxazoline-based crosslinking agent, one having at least one oxazoline group in one molecule can be used without particular limitation. An oxazoline-type crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Any of 2-oxazoline group, 3-oxazoline group, and 4-oxazoline group may be sufficient as an oxazoline group. Usually, an oxazoline-based crosslinking agent having a 2-oxazoline group can be preferably used. For example, a copolymer obtained by copolymerizing addition polymerizable oxazoline with another monomer can be used as the oxazoline-based crosslinking agent. Non-limiting examples of such addition polymerizable oxazolines include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of the oxazoline-based crosslinking agent include the crosslinking agent exemplified in Japanese Unexamined Patent Publication No. 2009-001673. Specific examples include compounds having a main chain containing an acrylic skeleton or a styrene skeleton and having an oxazoline group in the side chain of the main chain. As a suitable example, an oxazoline group-containing acrylic polymer having a main chain containing an acrylic skeleton and having an oxazoline group in the side chain of the main chain is exemplified. Examples of commercially available products of the oxazoline-based crosslinking agent include "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E" and "Epoque" manufactured by Nippon Shokubai Co., Ltd. Ross K-2030E' and the like.

In the aspect of using the oxazoline-based crosslinking agent, the usage amount thereof is not particularly limited. The amount of the oxazoline-based crosslinking agent may be, for example, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight or more based on 100 parts by weight of the acrylic polymer. In some embodiments, the amount of the oxazoline-based crosslinking agent used per 100 parts by weight of the acrylic polymer may be 1 part by weight or more, and may be 1.5 parts by weight or more. It tends to become easier to obtain higher cohesive force by increasing the usage-amount of an oxazoline-type crosslinking agent. The amount of the oxazoline-based crosslinking agent may be, for example, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, or 3 parts by weight or less based on 100 parts by weight of the acrylic polymer.

The technique disclosed herein can be preferably carried out in an aspect using at least an isocyanate-based crosslinking agent as a crosslinking agent. The isocyanate group of the isocyanate-based crosslinking agent may react with a crosslinking reaction site such as an acidic group that may be introduced into the acrylic polymer to form a crosslinked structure. Due to this crosslinking reaction, the cohesiveness of the pressure-sensitive adhesive is increased, and the resistance to deformation against a continuous load in the Z-axis direction is exhibited more favorably. Examples of such an embodiment include an embodiment in which an isocyanate-based crosslinking agent is used alone and an embodiment in which an isocyanate-based crosslinking agent and another crosslinking agent are used in combination. In one aspect, the pressure-sensitive adhesive composition includes an isocyanate-based crosslinking agent as a crosslinking agent, but does not substantially include an epoxy-based crosslinking agent. In the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one surface of the base film, it is meaningful to use an isocyanate-based crosslinking agent from the viewpoint of improving anchoring properties of the base film.

In another aspect, the pressure-sensitive adhesive composition contains an epoxy-based crosslinking agent as a crosslinking agent. The epoxy group of the epoxy-based crosslinking agent can react with an acidic group that can be introduced into the acrylic polymer in a reaction form different from that of the isocyanate-based crosslinking agent to build a crosslinked structure.

In a particularly preferred aspect, the pressure-sensitive adhesive composition includes both an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent as a crosslinking agent. For example, by using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination with an acrylic polymer having an acidic group, it is possible to further improve resistance to deformation against a sustained load in the Z-axis direction without damaging adhesiveness. Specifically, the resistance to deformation in the Z-axis direction can be maintained for a long period of time even under conditions of high repulsion, high temperature, and high humidity as examined in examples described later. The ratio (C _I /C _E ) of the content (C _I ) of the isocyanate-based cross-linking agent to the content (C _E ) of the epoxy-based cross-linking agent is not particularly limited, and is appropriately selected so as to obtain resistance to deformation against a continuous load in the Z-axis direction. is set The ratio (C _I /C _E ) is, for example, greater than 1, preferably about 5 or more, preferably about 15 or more, more preferably about 30 or more, still more preferably about 60 or more, particularly preferably about 80 or more (eg, about 100 or more). In addition, the ratio (C _I /C _E ) is, for example, about 1000 or less, preferably about 500 or less, preferably about 200 or less, more preferably about 150 or less, still more preferably about 120 or less. (e.g., less than or equal to about 80).

The content of the crosslinking agent (total amount of crosslinking agent) in the pressure-sensitive adhesive composition disclosed herein is not particularly limited. From the standpoint of cohesiveness, the content of the crosslinking agent is usually about 0.001 part by weight or more, preferably about 0.002 part by weight or more, preferably about 0.005 part by weight or more, more preferably about 0.005 part by weight or more with respect to 100 parts by weight of the acrylic polymer. Approximately 0.01 parts by weight or more, more preferably approximately 0.02 parts by weight or more, particularly preferably approximately 0.03 parts by weight or more. In addition, from the viewpoint of avoiding insufficient adhesive strength, the content of the crosslinking agent in the pressure-sensitive adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and about 10 parts by weight or less (e.g., It is preferable to set it as about 5 parts by weight or less).

(tackifying resin)

In a preferred aspect, the pressure-sensitive adhesive composition (and furthermore, the pressure-sensitive adhesive layer) contains a tackifying resin. Examples of the tackifying resin that may be included in the pressure-sensitive adhesive composition include phenol-based tackifying resins, terpene-based tackifying resins, modified terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, and polyamides. One or two or more kinds selected from various known tackifying resins such as tackifier-based tackifying resins, elastomer-based tackifying resins, and ketone-based tackifying resins can be used. Adhesion is improved by the use of tackifying resin.

Examples of phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkyl phenol resins, and rosin phenol resins.

Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and includes a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin) and a phenol-modified terpene or homopolymer or copolymer thereof. It is a concept including both (phenol-modified terpene resin). Suitable examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l- and d/l-forms (dipentene)). there is. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It may be called hydrogenated terpene phenol resin.

Alkyl phenol resin is a resin (oil-based phenol resin) obtained from an alkyl phenol and formaldehyde. Examples of the alkylphenol resin include novolak type and resol type.

The rosin phenol resin is typically a phenol-modified product of rosin or various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosin and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include rosin phenol resins obtained by adding phenol to rosin or various rosin derivatives described above using an acid catalyst and subjecting them to thermal polymerization, or the like.

Among these phenolic tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins, and alkylphenol resins are preferred, terpene phenol resins and hydrogenated terpene phenol resins are more preferred, and terpene phenol resins are particularly preferred.

Examples of the terpene-based tackifying resin include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one type of terpenes or a copolymer of two or more types of terpenes. Examples of homopolymers of one type of terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers.

As an example of a modified terpene resin, what modified|denatured the said terpene resin is mentioned. Specifically, styrene-modified terpene resins and hydrogenated terpene resins are exemplified.

The concept of the rosin-based tackifying resin as used herein includes both rosin and rosin derivative resin. Examples of rosins include unmodified rosins such as gum rosin, wood rosin, and tall oil rosin (raw rosin); Modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc.) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. is included.

The rosin derivative resin is typically a derivative of the above rosins. The concept of the rosin-based resin herein includes derivatives of unmodified rosin and modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). For example, rosin esters such as unmodified rosin esters that are esters of unmodified rosin and alcohols and modified rosin esters that are esters of modified rosin and alcohols; For example, rosins modified with unsaturated fatty acids obtained by modifying rosins with unsaturated fatty acids; For example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; For example, rosin alcohols obtained by reducing the carboxy group of rosin or various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosin and unsaturated fatty acid-modified rosin esters); Examples thereof include metal salts of rosin or various rosin derivatives described above. Specific examples of rosin esters include methyl esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), triethylene glycol esters, glycerin esters, and pentaerythritol esters.

Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic/alicyclic petroleum resins, and hydrogenated hydrocarbons. Resin, various hydrocarbon-type resins, such as a coumarone-type resin and a coumarone-indene-type resin, are mentioned.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifying resin having a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher) can be preferably employed. For example, a phenolic tackifying resin (such as terpene phenol resin) having such a softening point can be preferably used. In one preferred aspect, a terpenephenol resin having a softening point of about 135° C. or higher (and even about 140° C. or higher) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. A tackifying resin having a softening point of about 200°C or less (more preferably about 180°C or less) can be preferably used from the viewpoint of adhesion to the adherend or base film. In addition, the softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

As one preferable aspect, the aspect in which the said tackifying resin contains 1 type, or 2 or more types of phenolic tackifying resin (eg, terpene phenol resin) is mentioned. The technique disclosed herein can be preferably carried out in an aspect in which, for example, about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of the tackifying resin is a terpene phenol resin. Approximately 50% by weight or more of the total amount of the tackifying resin may be a terpene phenol resin, and approximately 80% by weight or more (eg, approximately 90% by weight or more) may be a terpene phenol resin. Substantially all of the tackifying resin (for example, approximately 95% by weight or more and 100% by weight or less, further approximately 99% by weight or more and 100% by weight or less) may be a terpene phenol resin.

The content of the phenol-based tackifying resin (eg, terpene phenol resin) is not particularly limited as long as the desired viscoelastic properties are satisfied. The content of the phenol-based tackifying resin (eg, terpene phenol resin) is usually about 1 part by weight or more, and it is appropriate to make it about 5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer from the viewpoint of adhesive strength. Preferably It is about 8 parts by weight or more (typically 10 parts by weight or more), more preferably about 12 parts by weight or more (eg 15 parts by weight or more). In addition, from the viewpoint of deformation resistance, etc., the content of the phenolic tackifying resin is suitably about 45 parts by weight or less, preferably about 35 parts by weight or less, more preferably about 30 parts by weight based on 100 parts by weight of the acrylic polymer. less than 30 parts by weight, more preferably less than 30 parts by weight (eg, less than 25 parts by weight, typically less than 20 parts by weight).

Although not particularly limited, in one aspect of the technology disclosed herein, the tackifying resin may include a tackifying resin having a hydroxyl value greater than 20 mgKOH/g. Especially, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more is preferable. Hereinafter, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as a "high hydroxyl value resin". According to the tackifying resin in which such a high acid group contains a resin, a pressure-sensitive adhesive layer having high cohesive strength can be realized by interacting with a crosslinking agent such as an isocyanate-based crosslinking agent in addition to the adhesive strength. In one aspect, the tackifying resin may contain resin having a high hydroxyl value of 50 mgKOH/g or more (more preferably 70 mgKOH/g or more). In addition, the above-described high-hydroxyl group resin (eg, terpene phenol resin) is preferably used in combination with, for example, an acrylic polymer having C _1-6 alkyl (meth)acrylate as a main monomer, and has good adhesion to an adherend. can exert

The upper limit of the hydroxyl value of the resin having a high hydroxyl value is not particularly limited. From the viewpoint of compatibility with acrylic polymers, etc., the hydroxyl value of the resin with a high hydroxyl value is usually about 300 mgKOH/g or less, suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, and more preferably about 180 mgKOH/g or less. 160 mgKOH/g or less, more preferably approximately 140 mgKOH/g or less. The technique disclosed herein may be preferably carried out in an aspect in which the tackifying resin includes a resin having a high hydroxyl value of 30 to 160 mgKOH/g (eg, a phenolic tackifying resin, preferably a terpene phenol resin). In one aspect, a resin having a high hydroxyl value of 30 to 80 mgKOH/g (eg, 30 to 65 mgKOH/g) may be preferably employed. In another aspect, a resin having a high hydroxyl value of 70 to 140 mgKOH/g can be preferably employed.

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method stipulated in JIS K0070:1992 can be employed. The specific measuring method is as showing below.

[Method for measuring hydroxyl value]

1. Reagents

(1) As an acetylation reagent, take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine to make a total amount of 50 mL, and sufficiently stir. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to make the total amount to 100 mL, and use what was sufficiently stirred.

(2) As a measuring reagent, a 0.5 mol/L potassium hydroxide ethanol solution is used.

(3) In addition, prepare toluene, pyridine, ethanol and distilled water.

2. Manipulation

(1) Precisely weigh and collect about 2 g of sample in a flat bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and install an air cooling tube.

(2) After heating the flask in a bath at 100 ° C. for 70 minutes, the flask is allowed to cool, and 35 mL of toluene is added as a solvent from the top of the cooling tube and stirred, and then 1 mL of distilled water is added and stirred to decompose acetic anhydride. In order to completely decompose, it is heated again in a bath for 10 minutes and allowed to cool.

(3) The cooling tube was washed with 5 mL of ethanol and separated. Subsequently, 50 mL of pyridine was added as a solvent and stirred.

(4) 25 mL of 0.5 mol/L potassium hydroxide ethanol solution is added using a hole pipette.

(5) Potentiometric titration is performed with a 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is made the end point.

(6) In the blank test, the above (1) to (5) are performed without adding a sample.

3. Calculation

A hydroxyl value is computed by the following formula.

Hydroxyl value (mgKOH/g)=[(B-C)×f×28.05]/S+D

From here,

B: amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used for blank test,

C: amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used for the sample,

f: factor of 0.5 mol/L potassium hydroxide ethanol solution,

S: weight of sample (g),

D: acid value,

28.05: 1/2 of the molecular weight of potassium hydroxide, 56.11;

am.

As the resin with a high hydroxyl value, among the various tackifying resins described above, one having a hydroxyl value of a predetermined value or higher can be used. High acid value resin can be used individually by 1 type or in combination of 2 or more types. For example, as a resin with a high hydroxyl value, a phenolic tackifying resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. The terpene phenol resin is suitable because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol.

Although not particularly limited, a tackifying resin having a hydroxyl value of less than 30 mgKOH/g (eg, less than 20 mgKOH/g) may be used as the tackifying resin in the technology disclosed herein. Hereinafter, a tackifying resin having a hydroxyl value of less than 30 mgKOH/g may be referred to as a "low hydroxyl value resin". The low hydroxyl value of the resin may be approximately 15 mgKOH/g or less, or approximately 10 mgKOH/g or less. The lower limit of the hydroxyl value of the low hydroxyl value resin is not particularly limited, and may be substantially 0 mgKOH/g. Such a low hydroxyl resin (eg, terpene phenol resin) is preferably used in combination with, for example, an acrylic polymer containing C _7-10 alkyl (meth)acrylate as a main monomer, and has good adhesion to adherends can exert

Although not particularly limited, when a resin with a high acid group is used, the ratio of the resin with a high acid group (eg, terpene phenol resin) to the total tackifying resin included in the pressure-sensitive adhesive layer may be, for example, about 25% by weight or more , preferably about 30% by weight or more, and more preferably about 50% by weight or more (eg, about 80% by weight or more, typically about 90% by weight or more). Substantially all of the tackifying resin (for example, approximately 95 to 100% by weight, further approximately 99 to 100% by weight) may be a resin with a high acid group.

In the aspect using the tackifying resin, the content of the tackifying resin is not particularly limited. The content of the tackifying resin is usually 1 part by weight or more, and can be about 5 parts by weight or more, about 8 parts by weight or more (for example, about 10 parts by weight or more) with respect to 100 parts by weight of the acrylic polymer. It is suitable. The technique disclosed herein can be preferably carried out in an aspect in which the content of the tackifying resin relative to 100 parts by weight of the acrylic polymer is about 12 parts by weight or more (eg, about 15 parts by weight or more). The upper limit of content of tackifying resin is not specifically limited. From the viewpoint of compatibility with the acrylic polymer and resistance to deformation, the content of the tackifying resin with respect to 100 parts by weight of the acrylic polymer is suitably about 70 parts by weight or less, preferably about 55 parts by weight or less, more preferably about 55 parts by weight or less. about 45 parts by weight or less (eg, about 40 parts by weight or less, typically about 30 parts by weight or less). In one preferred aspect, the content of the tackifying resin relative to 100 parts by weight of the acrylic polymer is less than 30 parts by weight, more preferably approximately 25 parts by weight or less, still more preferably approximately 20 parts by weight or less.

((meth)acrylic oligomer)

In a preferred aspect, the pressure-sensitive adhesive composition disclosed herein (and furthermore, the pressure-sensitive adhesive layer) contains a (meth)acrylic oligomer from the viewpoint of improving adhesion and the like. As the (meth)acrylic oligomer, it is preferable to use a polymer having a higher Tg than the Tg of the copolymer corresponding to the composition of the monomer component (typically corresponding to the Tg of the (meth)acrylic polymer contained in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition). desirable. By containing a (meth)acrylic oligomer, the adhesive force of an adhesive can be improved.

The (meth)acrylic oligomer preferably has a Tg of about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and more preferably about 40°C or more and about 300°C or less. When the Tg is within the above range, the adhesive strength can be suitably improved. In a preferred aspect, the Tg of the (meth)acrylic oligomer is about 30 ° C. or higher, more preferably about 50 ° C. or higher (eg, about 60 ° C. or higher), from the viewpoint of cohesiveness of the pressure-sensitive adhesive. is about 200°C or less, more preferably about 150°C or less, even more preferably about 100°C or less (eg, about 80°C or less). In addition, the Tg of the (meth)acrylic oligomer is the same as the Tg of the copolymer corresponding to the composition of the monomer component, and is a value calculated based on Fox's formula.

The weight average molecular weight (Mw) of the (meth)acrylic oligomer may be typically about 1000 or more and less than about 30000, preferably about 1500 or more and less than about 20000, and more preferably about 2000 or more and less than about 10000. When Mw is within the above range, it is preferable because good adhesion and holding properties can be obtained. In a preferred aspect, the Mw of the (meth)acrylic oligomer is about 2500 or more (eg, about 3000 or more) from the standpoint of resistance to deformation against sustained load in the Z-axis direction, and preferably about 7000 or less from the viewpoint of adhesiveness, More preferably, it is about 5000 or less (eg, about 4500 or less, typically about 4000 or less). The Mw of the (meth)acrylic oligomer can be measured by gel permeation chromatography (GPC) and obtained as a value in terms of standard polystyrene. Specifically, it is measured under conditions of a flow rate of about 0.5 ml/min in a tetrahydrofuran solvent using HPLC8020 manufactured by Tosoh Corporation using TSKgelGMH-H (20) x 2 columns as columns.

As a monomer constituting the (meth)acrylic oligomer, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, iso Butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethyl Hexyl(meth)acrylate, heptyl(meth)acrylate, octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate , alkyl (meth)acrylates such as isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene compound derivative alcohols; and the like. Such (meth)acrylates can be used individually by 1 type or in combination of 2 or more types.

Examples of (meth)acrylic oligomers include alkyl (meth)acrylates in which an alkyl group has a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; Esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and dicyclopentanyl(meth)acrylate ((meth)acrylate containing an alicyclic hydrocarbon group) ; Contains as a monomer unit an acrylic monomer having a structure with relatively high steric hindrance, represented by (meth)acrylate having a cyclic structure such as phenyl (meth)acrylate or aryl (meth)acrylate such as benzyl (meth)acrylate It is preferable from the viewpoint of further improving the adhesiveness of the pressure-sensitive adhesive layer. In addition, in the case of employing ultraviolet rays at the time of synthesizing (meth)acrylic oligomers or at the time of preparing the pressure-sensitive adhesive layer, it is preferable to have a saturated bond from the viewpoint of not causing inhibition of polymerization, and the alkyl group has a branched alkyl (meth)acrylic group. An ester ((meth)acrylate containing an alicyclic hydrocarbon group) or an ester with an alicyclic alcohol can be suitably used as a monomer constituting the (meth)acrylic oligomer. All of the above branched chain alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates correspond to (meth)acrylate monomers in the art disclosed herein. The alicyclic hydrocarbon group may be a saturated or unsaturated alicyclic hydrocarbon group.

The proportion of the (meth)acrylate monomer (eg, alicyclic hydrocarbon group-containing (meth)acrylate) in all monomer components constituting the (meth)acrylic oligomer is typically greater than 50% by weight, preferably is 60% by weight or more, more preferably 70% by weight or more (eg, 80% by weight or more, further 90% by weight or more). In one preferred aspect, the (meth)acrylic oligomer has a monomer composition comprising substantially only (meth)acrylate monomers.

As the constituent monomer component of the (meth)acrylic oligomer, a functional group-containing monomer can be used in addition to the above-mentioned (meth)acrylate monomer. Preferable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as AA and MAA; and hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group containing monomers can be used individually by 1 type or in combination of 2 or more types. Among them, carboxy group-containing monomers are preferred, and AA is particularly preferred.

When all the monomer components constituting the (meth)acrylic oligomer include a functional group-containing monomer, the proportion of the functional group-containing monomer (eg, a carboxyl group-containing monomer such as AA) in all the monomer components is about 1% by weight or more It is appropriate, preferably 2% by weight or more, more preferably 3% by weight or more, and suitably about 15% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. am.

The (meth)acrylic oligomer can be formed by polymerizing its constituting monomer components. The polymerization method or polymerization mode is not particularly limited, and various conventionally known polymerization methods (eg, solution polymerization, emulsion polymerization, bulk polymerization, photo polymerization, radiation polymerization, etc.) can be employed as appropriate. The type of polymerization initiator (eg, azo-based polymerization initiator such as AIBN) that can be used as needed is generally the same as exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiator or chain transfer agent such as n-dodecylmercaptan optionally used Since the amount is appropriately set based on common technical knowledge so as to achieve a desired molecular weight, detailed explanations are omitted here.

Examples of (meth)acrylic oligomers suitable from the above viewpoint include dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), and isobornyl acrylate (IBXA). In addition to homopolymers of dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), copolymers of CHMA and isobutyl methacrylate (IBMA) , copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), copolymers of CHMA and AA, copolymers of ADA and methyl methacrylate (MMA) ), a copolymer of DCPMA and IBXMA, a copolymer of DCPMA and MMA, and the like.

When the (meth)acrylic oligomer is contained in the pressure-sensitive adhesive composition disclosed herein, it is appropriate to set the content to, for example, 0.1 part by weight or more (eg, 1 part by weight or more) with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of exhibiting the effect of the (meth)acrylic oligomer better, the content of the (meth)acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably about 10 parts by weight or more. Part by weight or more, particularly preferably about 12 parts by weight or more. Further, from the viewpoint of compatibility with the acrylic polymer, etc., the content of the (meth)acrylic oligomer is suitably less than 50 parts by weight (for example, less than 40 parts by weight), preferably less than 30 parts by weight, more preferably Preferably it is about 25 parts by weight or less, more preferably about 20 parts by weight or less.

In a preferred aspect, the pressure-sensitive adhesive composition (and furthermore, the pressure-sensitive adhesive layer) contains one or two or more types of tackifying resins and one or two or more types of (meth)acrylic oligomers. In a composition containing a high molecular weight acrylic polymer, excellent initial adhesion is obtained by using a combination of a tackifying resin and a (meth)acrylic oligomer, while being exposed to severe conditions such as strong repulsion. It can exhibit highly excellent resistance against deformation. The ratio (C _T /C O ₎ of the content (C T ) [wt %] of the tackifying resin to the content (C _O ) [wt %] of the (meth)acrylic oligomer in the pressure _- sensitive adhesive layer is not particularly limited. The above (C _T /C _O ) is suitably, for example, 0.1 or more and 9 or less, preferably 0.25 or more and 4 or less, more preferably 0.4 or more and 2 or less, still more preferably 0.7 or more and 1.5 or less.

The content (total amount) of the tackifying resin and the (meth)acrylic oligomer contained in the pressure-sensitive adhesive composition (and furthermore, the pressure-sensitive adhesive layer) according to a preferred aspect is, from the viewpoint of preferably exhibiting the effect of the technique disclosed herein, acrylic polymer 100 It is appropriate to set it as about 1 part by weight or more, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, still more preferably about 20 parts by weight or more, particularly preferably about 25 parts by weight with respect to parts by weight. or more, and suitably less than 120 parts by weight (for example, about 80 parts by weight or less), preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, still more preferably about 40 parts by weight or less. am.

(Azole compound)

The pressure-sensitive adhesive layer in the technology disclosed herein contains an azole-based compound. In a system using an acrylic polymer, a tackifying resin, and a (meth)acrylic oligomer as the base polymer, when an azole-based compound is further used, excellent resistance to deformation against a sustained load in the Z-axis direction can be exhibited.

Here, the 'azole-based compound' in the present specification refers to a five-membered aromatic compound containing one or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom. Examples of azole-based compounds that can be suitably used in the technology disclosed herein include 5-membered aromatic compounds containing two or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom.

The reason why excellent resistance to deformation against a sustained load in the Z-axis direction is exhibited by using such an azole-based compound is not particularly limited, but the following reasons are considered, for example. The azole-based compound includes a nitrogen atom having an unpaired electron. When an azole-based compound is contained in the pressure-sensitive adhesive layer, the unpaired electrons of the nitrogen atoms contained in the azole-based compound conduct electrical interaction on the surface of the adherend (which may be metal, resin, etc.), thereby causing the pressure-sensitive adhesive sheet to adhere to the adherend. The adhesion performance at the interface of is improved. It is thought that the deformation resistance of the pressure-sensitive adhesive sheet against a continuous load in the Z-axis direction is improved through such improvement in adhesive performance.

Examples of azole-based compounds that can be suitably used in the technology disclosed herein include imidazole, pyrazole, oxazole, isoxazole, thiazole, isothiazole, selenazole, 1,2,3-triazole, 1,2,4-triazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1 azoles such as 3,4-thiadiazole, tetrazole, and 1,2,3,4-thiatriazole; derivatives thereof; amine salts thereof; These metal salts, etc. are mentioned. Examples of azole derivatives include compounds having a structure including a condensed ring of an azole ring and another ring, such as a benzene ring. Specific examples include indazole, benzoimidazole, benzotriazole (ie, 1,2,3-benzotriazole having a structure in which the azole ring of 1,2,3-triazole and the benzene ring are condensed), benzothiazole, etc., and further Alkylbenzotriazole derivatives thereof (e.g., 5-methylbenzotriazole, 5-ethylbenzotriazole, 5-n-propylbenzotriazole, 5-isobutylbenzotriazole, 4-methylbenzotriazole); Alkoxybenzotriazoles (e.g. 5-methoxybenzotriazole), alkylaminobenzotriazoles, alkylaminosulfonylbenzotriazoles, mercaptobenzotriazoles, hydroxybenzotriazoles, nitrobenzotriazoles (e.g. 4 -nitrobenzotriazole), halobenzotriazole (eg 5-chlorobenzotriazole), hydroxyalkylbenzotriazole, hydroxybenzotriazole, aminobenzotriazole, (substituted aminomethyl) -tolyltriazole, amine salts thereof, such as carboxybenzotriazole, N-alkylbenzotriazole, bisbenzotriazole, naphthotriazole, mercaptobenzothiazole, and aminobenzothiazole; and metal salts thereof. As another example of an azole derivative, a substituent is placed on a non-condensed azole ring, such as 3-amino-1,2,4-triazole or 5-phenyl-1H-tetrazole. Compounds having a structure are exemplified. An azole compound can be used individually by 1 type or in combination of 2 or more types.

In a preferred aspect, the pressure-sensitive adhesive layer includes a triazole-based compound as an azole-based compound. Here, the 'triazole-based compound' in the present specification refers to a 5-membered aromatic compound containing 3 or more heteroatoms, wherein 3 of the heteroatoms are nitrogen atoms. In a system using an acrylic polymer as a base polymer, according to a configuration using a triazole-based compound, highly excellent resistance to deformation against a sustained load in the Z-axis direction can be exhibited.

As a preferred aspect of such a triazole-based compound, a triazole-based compound having a non-condensed ring structure is exemplified. As a triazole type compound of non-condensed ring structure, the compound which has a structure represented by the following formula (2a) or (2b) is mentioned, for example.

Here, in the formulas (2a) and (2b), R ³ is a hydrogen atom or a substituent on an azole ring, such as an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a carbon atom number. Aryl group of 6 to 14, carboxy group, carboxyalkyl group of 2 to 6 carbon atoms, amino group, mono- or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, mono- or di-C _1-10 alkyl It may be selected from substituents such as an amino-C _1-6 alkyl group, a mercapto group, and an alkoxycarbonyl group having 1 to 6 carbon atoms. R ⁴ in the formulas (2a) and (2b) is a hydrogen atom, an alkyl group of 1 to 12 carbon atoms, an alkoxy group of 1 to 12 carbon atoms, an aryl group of 6 to 14 carbon atoms, mono- or di- Carboxy-C _1-6 alkyl group, amino group, mono or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, mono or di-C _1-10 alkylamino-C _1-6 alkyl group, mercapto group, carbon It may be selected from substituents such as an alkoxycarbonyl group having 1 to 12 atoms. R ³ and R ⁴ may be the same or different. 1,2,3-triazole is mentioned as a suitable example of the triazole type compound represented by Formula (2a). Moreover, 1,2,4-triazole is mentioned as a suitable example of the triazole type compound represented by Formula (2b). Especially, 1,2,4-triazole is preferable.

In addition, another suitable example of the triazole-based compound is a benzotriazole-based compound. The benzotriazole-based compound is not particularly limited as long as it is a compound having a benzotriazole skeleton, but one having a structure represented by the following formula (3) is preferable from the viewpoint of obtaining more excellent resistance to deformation.

Here, in the formula (3), R ⁵ is a hydrogen atom or a substituent on a benzene ring, such as an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl having 6 to 14 carbon atoms. group, carboxy group, carboxyalkyl group having 2 to 6 carbon atoms, amino group, mono or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, mono or di-C _1-10 alkylamino-C _{1- 6} It may be selected from substituents such as an alkyl group, a mercapto group, and an alkoxycarbonyl group having 1 to 6 carbon atoms. In the formula (3), n is an integer of 0 to 4, and when n is 2 or more, n pieces of R ⁵ contained in the formula (3) may be the same as or different from each other. R ⁶ in the formula (3) is a hydrogen atom, an alkyl group of 1 to 12 carbon atoms, an alkoxy group of 1 to 12 carbon atoms, an aryl group of 6 to 14 carbon atoms, mono- or di-carboxy-C _{1- 6} Alkyl group, amino group, mono or di-C _1-10 Alkylamino group, amino-C _1-6 Alkyl group, mono or di-C _1-10 Alkylamino-C _1-6 Alkyl group, mercapto group, 1 to 12 carbon atoms It may be selected from substituents such as an alkoxycarbonyl group of R ⁵ and R ⁶ may be the same or different. Suitable examples of the benzotriazole-based compound represented by Formula (3) include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, and 1-(1',2'-dicarboxy Ethyl) benzotriazole etc. are mentioned.

The content of the azole-based compound (e.g., triazole-based compound) (the total amount when a plurality of azole-based compounds are used in combination) is not particularly limited, and is, for example, 0.01 part by weight or more (typically 0.01 part by weight or more with respect to 100 parts by weight of the base polymer). 0.05 parts by weight or more). From the viewpoint of obtaining better resistance to deformation, the content of the azole-based compound relative to 100 parts by weight of the base polymer is preferably 0.1 part by weight or more, may be 0.3 parts by weight or more, may be 0.5 parts by weight or more, or may be 0.6 parts by weight or more. , 0.7 parts by weight or more may be sufficient. On the other hand, from the viewpoint of increasing the cohesive force (eg, heat-resistant cohesion) of the pressure-sensitive adhesive, the content of the azole compound is usually suitably 10 parts by weight or less, and 8 parts by weight or less based on 100 parts by weight of the base polymer. It may be 6 parts by weight or less, and may be 5 parts by weight or less.

(other additives)

The pressure-sensitive adhesive composition contains various additives common in the field of pressure-sensitive adhesives, such as leveling agents, crosslinking aids, plasticizers, softeners, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, and light stabilizers, as needed, in addition to the components described above. There may be. Regarding these various additives, conventionally known ones can be used by conventional methods, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method (direct method) of forming an adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to a non-peelable base material and drying or curing it can be employed. In addition, by applying a pressure-sensitive adhesive composition to a peelable surface (release surface) and drying or curing to form a pressure-sensitive adhesive layer on the surface, a substrate-free pressure-sensitive adhesive sheet containing only the pressure-sensitive adhesive layer can be produced. Alternatively, a method (transfer method) of transferring the pressure-sensitive adhesive layer formed on the peeling surface to a non-peelable substrate may be employed. As the peeling surface, the surface of a peeling liner, the back surface of a base material subjected to peeling treatment, and the like can be used. In addition, although the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, it is not limited to such a form, and may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a dot shape or a stripe shape, for example.

As a method of applying the pressure-sensitive adhesive composition, conventionally known various methods can be used. Specifically, for example, extrusion by roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coat, etc. Methods, such as a coating method, are mentioned.

In one aspect of the technique disclosed herein, it is preferable to dry the pressure-sensitive adhesive composition under heating from the viewpoints of accelerating the crosslinking reaction and improving production efficiency. The drying temperature can be, for example, about 40 to 150°C, and is usually preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be further performed for the purpose of adjusting migration of components within the pressure-sensitive adhesive layer, progressing the crosslinking reaction, and relieving strain that may exist within the base film or pressure-sensitive adhesive layer.

In another aspect, the pressure-sensitive adhesive sheet disclosed herein is a method comprising drying or curing a liquid film of a pressure-sensitive adhesive composition on a release surface of a release film to form a pressure-sensitive adhesive layer wherein the cured surface on the release surface is a first adhesive surface. can be suitably prepared. According to this method, the smoothness of the surface of the pressure-sensitive adhesive layer formed in contact with the release surface can be precisely controlled by drying or curing the pressure-sensitive adhesive composition (liquid film) in a fluid state in contact with the release surface. For example, by using a release film having a release surface having appropriate smoothness, it is possible to stably (with good reproducibility) manufacture the first adhesive surface having desired smoothness.

The pressure-sensitive adhesive sheet disclosed herein may be preferably prepared by a method comprising forming a pressure-sensitive adhesive layer by drying or curing a liquid film of the pressure-sensitive adhesive composition between release surfaces of a pair of release films. This method is suitable as a method for producing a substrate-free double-sided pressure-sensitive adhesive sheet. In addition, by bonding the substrate-free double-sided adhesive sheet obtained in this way to the non-peelable surface of the supporting substrate, it can be suitably applied to the production of a single-sided adhesive sheet with a substrate or a double-sided adhesive sheet with a substrate. As a method of arranging a liquid film of an adhesive composition between the release surfaces of a pair of release films, a liquid adhesive composition is applied to the release surfaces of a first release film, and then the liquid film of the adhesive composition is covered with a second release film. can be employed. As another method, while supplying a 1st peeling film and a 2nd peeling film between a pair of rolls facing a peeling surface, the method of supplying a liquid adhesive composition between those peeling surfaces is mentioned.

The thickness of the pressure-sensitive adhesive layer is not particularly limited. The thickness of the pressure-sensitive adhesive layer is usually about 300 μm or less, preferably about 200 μm or less, more preferably about 150 μm or less, still more preferably about 100 μm or less. In the pressure-sensitive adhesive sheet according to one preferred aspect, the thickness of the pressure-sensitive adhesive layer is about 70 μm or less (usually 60 μm or less), for example, about 50 μm or less, or about 40 μm. Although the lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, it is advantageous to set it to about 3 μm or more, preferably about 6 μm or more, more preferably about 10 μm or more (e.g., about 15 μm or more), more preferably about 25 μm or more, for example, about 35 μm or more, or about 45 μm or more. The technique disclosed herein can be suitably implemented in the form of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of, for example, about 10 μm or more and about 150 μm or less (preferably about 15 μm or more and about 50 μm or less). As a suitable example, a substrate-free double-sided adhesive pressure-sensitive adhesive sheet containing only a pressure-sensitive adhesive layer having the above thickness is exemplified.

(gel fraction)

Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein may be, for example, 20% or more by weight, usually 30% or more is appropriate, and 35% or more is preferable. By increasing the gel fraction of the pressure-sensitive adhesive layer within an appropriate range, resistance to deformation against continuous load in the Z-axis direction tends to be easily obtained. In the technique disclosed herein, it is more preferable to use a pressure-sensitive adhesive layer having a gel fraction of 40% or more. The gel fraction is more preferably 45% or more, particularly preferably 48% or more. The gel fraction may be, for example, 50% or more. On the other hand, when the gel fraction is too high, initial adhesiveness may be easily insufficient. From this point of view, the gel fraction of the pressure-sensitive adhesive layer is preferably 90% or less, more preferably 80% or less, and still more preferably 70% or less (eg, 65% or less).

Here, the 'gel fraction of the pressure-sensitive adhesive layer' refers to a value measured by the following method. The gel fraction can be understood as a weight ratio of the ethyl acetate insoluble content in the pressure-sensitive adhesive layer.

[Method for measuring gel fraction]

A pressure-sensitive adhesive sample of about 0.1 g (weight Wg ₁ ) is wrapped in a pouch shape with a porous polytetrafluoroethylene film (weight Wg ₂ ) having an average pore diameter of 0.2 μm, and the inlet is tied with a twine (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, a trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko (average pore diameter: 0.2 µm, porosity: 75%, thickness: 85 µm) or an equivalent thereof is used. do.

The bundle is immersed in 50 mL of ethyl acetate, maintained at room temperature (typically 23°C) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer to the outside of the membrane, and then the bundle is taken out and the ethyl acetate adhered to the outer surface. is wiped off, and the bundle is dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the bundle is measured. The gel fraction (F _G ) of the pressure-sensitive adhesive layer can be obtained by substituting each value into the following formula. The same method is employed in the examples described later.

Gel fraction (F _G ) (%) = [(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

(viscoelastic properties)

The storage elastic modulus G' (25°C) at 25°C of the pressure-sensitive adhesive layer disclosed herein is not particularly limited. In a preferred aspect, the G'(25°C) is 0.15 MPa or more. According to the pressure-sensitive adhesive having G' (25°C), good deformation resistance can be preferably exhibited from an early stage after being applied to an adherend. The G' (25°C) is preferably 0.17 MPa or more, more preferably 0.2 MPa or more, still more preferably 0.23 MPa or more. The G' (25°C) is particularly preferably 0.25 MPa or more, and may be, for example, 0.3 MPa or more. The G' (25°C) is usually suitably 1.0 MPa or less, and is preferably 0.6 MPa or less, more preferably 0.4 MPa or less, and even more preferably 0.4 MPa or less from the viewpoint of coexistence of initial adhesion and deformation resistance. Preferably, it is 0.35 MPa or less. The G' (25°C) may be, for example, 0.3 MPa or less, 0.25 MPa or less, or 0.2 MPa or less.

Also, the loss modulus G" (25° C.) of the pressure-sensitive adhesive layer disclosed herein at 25° C. is not particularly limited. In a preferred embodiment, the G" (25° C.) is 2.0 MPa or less. The G" (25 ° C.) is preferably 1.5 MPa or less, more preferably 1.0 MPa or less, and even more preferably 0.5 MPa or less. The G" (25 ° C.) is 0.3 MPa or less (eg, 0.25 MPa or less) may be continued In addition, the G" (25 ° C.) is usually suitably 0.01 MPa or more, and from the viewpoint of wettability to the surface of the adherend and further initial adhesion, etc., it is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, More preferably, it is 0.2 MPa or more, and for example, 0.25 MPa or more may be sufficient.

In addition, the tan δ (25° C.) at 25° C. of the pressure-sensitive adhesive layer disclosed herein may be appropriately set in consideration of initial adhesion and deformation resistance at room temperature, and is not particularly limited. Here, tanδ (loss tangent) of the pressure-sensitive adhesive (layer) refers to the ratio of the loss modulus G" to the storage modulus G' of the pressure-sensitive adhesive (layer). That is, tanδ = G"/G'. Tan δ (25°C) is suitably, for example, about 0.3 or more, and from the viewpoint of deformation resistance, it is preferably about 0.5 or more, more preferably about 0.7 or more, even more preferably about 0.8 or more, particularly preferably about 0.8 or more. 0.9 or more (eg, about 1 or more). Further, tan δ (25°C) is suitably, for example, approximately 3 or less, and is preferably approximately 2 or less, more preferably approximately 1.5 or less, and even more preferably approximately 1.2 or less from the viewpoint of initial adhesiveness.

The storage elastic modulus G' (85°C) at 85°C of the pressure-sensitive adhesive layer disclosed herein is not particularly limited. In a preferred aspect, the G'(85°C) is 0.02 MPa or more. By having the above G' (85 ° C.), continuous deformation resistance can be preferably obtained. The G '(85 ℃) may be specifically 0.022MPa or more. Further, the G' (85°C) is preferably 0.025 MPa or more, more preferably 0.027 MPa or more. The G'(85°C) is more preferably approximately 0.03 MPa or greater (eg, 0.035 MPa or greater), particularly preferably 0.04 MPa or greater, and still more particularly preferably 0.045 MPa or greater. In addition, the G' (85 ° C.) is usually suitably 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The said G' (85 degreeC) may be 0.06 MPa or less.

In addition, the loss elastic modulus G" (85°C) at 85°C of the pressure-sensitive adhesive layer disclosed herein is not particularly limited. In a preferred embodiment, the G" (85°C) is 0.5 MPa or less. The G" (85°C) is preferably 0.3 MPa or less, more preferably 0.1 MPa or less, and even more preferably 0.05 MPa or less. The G" (85° C.) may be 0.03 MPa or less (eg 0.02 MPa or less). do. The G" (85°C) is usually suitably 0.001 MPa or more, and from the viewpoint of adhesiveness, etc., it is preferably 0.002 MPa or more, more preferably 0.005 MPa or more, still more preferably 0.008 MPa or more. and may be, for example, 0.01 MPa or more.

In addition, tan δ (85° C.) at 85° C. of the pressure-sensitive adhesive layer disclosed herein may be appropriately set in consideration of continuous deformation resistance, and is not particularly limited. Tan δ (85° C.) is suitably, for example, about 0.1 or more, preferably about 0.12 or more, more preferably about 0.15 or more, still more preferably about 0.2 or more (eg, 0.22 or more). Also, tan δ (85°C) is suitably, for example, approximately 2 or less, preferably approximately 1 or less, and more preferably approximately 0.5 or less (eg, approximately 0.3 or less).

The pressure-sensitive adhesive layer disclosed herein preferably has a storage modulus G' (apply) of 0.6 MPa or less at a temperature at which the pressure-sensitive adhesive sheet is pressed to an adherend (compression temperature). The pressure-sensitive adhesive having G' (apply) may well wet the surface of an adherend and exhibit excellent initial adhesiveness. The above G' (apply) is more preferably 0.4 MPa or less, still more preferably 0.35 MPa or less, and may be, for example, 0.3 MPa or less, or 0.25 MPa or less. The G' (apply) may be, for example, 0.2 MPa or less. Further, from the viewpoint of coexistence of initial adhesion and deformation resistance, the G' (apply) is suitably larger than 0.12 MPa, preferably 0.15 MPa or more, more preferably 0.17 MPa or more (eg, 0.2 MPa or more), and even more. Preferably it is 0.25 MPa or more, and may be, for example, 0.3 MPa or more. The compression temperature is selected from the range of more than 0 ° C and less than 60 ° C from the viewpoint of compression workability or temperature management. In the case of a pressure-sensitive adhesive sheet used for portable electronic devices, it is preferable to select the pressing temperature in the range of 20°C to 45°C (typically 25°C or 40°C, preferably 25°C) from the temperature limit for the application. desirable. Pressing in the above temperature range is different from conventional thermal bonding performed at about 100° C., and is thermal bonding applicable to electronic devices and the like.

In the technology disclosed herein, the storage modulus G' (25 ° C), G' (85 ° C), G' (apply), loss modulus G "(25 ° C), G" (85 ° C), tanδ ( 25°C) and tanδ (85°C) can be obtained by dynamic viscoelasticity measurement. Specifically, a pressure-sensitive adhesive layer having a thickness of about 2 mm is prepared by overlapping a plurality of pressure-sensitive adhesive layers to be measured (pressure-sensitive adhesive sheets in the case of a base-free pressure-sensitive adhesive sheet). A sample obtained by punching this pressure-sensitive adhesive layer into a disk shape with a diameter of 7.9 mm was sandwiched between parallel plates and fixed, and subjected to dynamic test under the following conditions by a viscoelasticity tester (eg, ARES or its equivalent manufactured by TA Instruments). Viscoelasticity measurements were performed to determine storage modulus G' (25 ° C), G' (85 ° C), G' (apply), loss modulus G "(25 ° C), G" (85 ° C), tanδ (25 ° C) and tanδ ( 85 ℃) is obtained.

・Measurement Mode: Shear Mode

・Temperature range: -70℃~150℃

・Temperature increase rate: 5℃/min

・Measurement frequency: 1Hz

In Examples to be described later, it is also measured by the above method. In addition, the pressure-sensitive adhesive layer to be measured can be formed by applying a corresponding pressure-sensitive adhesive composition in a layered form and drying or curing it.

<Description>

In the aspect in which the PSA sheet disclosed herein is in the form of a single-sided or double-sided PSA sheet with a base material, the base material for supporting (backing) the PSA layer is a resin film, a foam film (foam base material), paper, cloth, Metal foils, composites thereof, and the like can be used.

The technique disclosed herein can be implemented in the form of a pressure-sensitive adhesive sheet with a base material including the pressure-sensitive adhesive layer on at least one surface of a base film (support). For example, it may be implemented in the form of a double-sided pressure-sensitive adhesive sheet attached to a base material including the pressure-sensitive adhesive layer on one surface and the other surface of the base film.

As a base film, what contains a resin film as a base film can be used preferably. The base film is typically a (independent) member capable of independently maintaining its shape. The base film in the technology disclosed herein may be substantially constituted from such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, and a coloring layer provided on the surface of the base film.

The said resin film is a film which has a resin material as a main component (component contained in the said resin film in excess of 50 weight%). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymers; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); Vinyl chloride-based resin film; vinyl acetate-based resin film; polyimide-based resin film; polyamide-based resin film; fluororesin film; Cellophane etc. are mentioned. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoints of handleability and workability, a polyester film is preferred, and among these, a PET film is particularly preferred. In this specification, a 'resin film' is typically a non-porous sheet, and is a concept distinct from so-called nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics).

The resin film may have a single-layer structure or may have a two-layer, three-layer or higher multilayer structure. From the viewpoint of shape stability, the resin film preferably has a single-layer structure. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the resin (eg, polyester-based resin). The manufacturing method of a resin film should just employ|adopt a conventionally well-known method suitably, and it is not specifically limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die cast molding, and calender roll molding can be appropriately employed.

In another aspect, paper, cloth, or metal is used as the substrate material. Examples of paper that can be used for the base film include Japanese paper, kraft paper, glassine paper, quality paper, synthetic paper, and top-coated paper. Examples of fabrics include woven fabrics and non-woven fabrics obtained by single or mixed spinning of various fibrous materials. Examples of the fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of the metal foil that can be used for the base film include aluminum foil and copper foil.

In addition, the nonwoven fabric referred to herein is a concept indicating a nonwoven fabric for adhesive sheets used mainly in the field of adhesive sheets other than adhesive tapes, and is a nonwoven fabric typically produced using a general paper machine (so-called 'paper'). in some cases). In addition, a resin film here is typically a non-porous resin sheet, and is a concept different from, for example, a nonwoven fabric (ie, does not include a nonwoven fabric). Any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film may be sufficient as the said resin film. In addition, surface treatment such as application of an undercoat agent, corona discharge treatment, plasma treatment, or the like may be performed on the surface of the base material on which the pressure-sensitive adhesive layer is provided.

The resin film (eg, PET film) may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, etc., as needed. Additives may be blended. The blending ratio of various additives is usually less than about 30% by weight (for example, less than about 20% by weight, preferably less than about 10% by weight).

Conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat may be applied to the surface of the base film. Such surface treatment may be a treatment for improving the adhesion between the base film and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the base film.

The thickness of the base film disclosed herein is not particularly limited. From the viewpoint of avoiding excessive thickness of the adhesive sheet, the thickness of the base film (eg, resin film) may be, for example, about 200 μm or less, preferably about 150 μm or less, and more preferably about 100 μm or less. The thickness of the base film may be approximately 70 μm or less, may be approximately 50 μm or less, or may be approximately 30 μm or less (eg, approximately 25 μm or less) depending on the purpose of use or usage mode of the adhesive sheet. In one aspect, the thickness of the base film may be approximately 20 μm or less, may be approximately 15 μm or less, or may be approximately 10 μm or less (eg, approximately 5 μm or less). By reducing the thickness of the base film, the thickness of the pressure-sensitive adhesive layer can be further increased even when the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous from the viewpoint of improving adhesion to the substrate. The lower limit of the thickness of the base film is not particularly limited. From the standpoint of handling (handling) and processability of the adhesive sheet, the thickness of the base film is usually about 0.5 μm or more (eg, 1 μm or more), preferably about 2 μm or more, for example, about 4 μm or more. . In one aspect, the thickness of the base film may be approximately 6 μm or more, may be approximately 8 μm or more, or may be approximately 10 μm or more (eg, greater than 10 μm).

<Foam Substrate>

In another preferred aspect, a foam substrate is used as the substrate. The foam base material disclosed herein is a base material having a portion having cells (cell structure), and typically includes at least one layer of layered foam (foam layer). The foam substrate may be a substrate composed of one layer or two or more foam layers. The foam substrate may be, for example, a substrate substantially constituted by only one or two or more foam layers. Although not particularly limited, one suitable example of the foam substrate in the technology disclosed herein is a foam substrate comprising a single (one layer) foam layer.

The thickness of the foam substrate is not particularly limited and can be appropriately set depending on the strength and flexibility of the pressure-sensitive adhesive sheet and the purpose of use. From the viewpoint of thinning, the thickness of the foam substrate is usually 1 mm or less, preferably 0.70 mm or less, preferably 0.40 mm or less, and more preferably 0.30 mm or less. The technology disclosed herein can be preferably implemented in an aspect in which the thickness of the foam substrate is 0.25 mm or less (typically 0.18 mm or less, for example, 0.16 mm or less) from the viewpoint of processability and the like. In view of the impact resistance of the pressure-sensitive adhesive sheet, the thickness of the foam substrate is usually 0.04 mm or more, preferably 0.05 mm or more, preferably 0.06 mm or more, and more preferably 0.07 mm or more (eg, 0.08 mm or more). desirable. The technology disclosed herein can be preferably practiced in an aspect where the thickness of the foam substrate is greater than 0.10 mm (typically greater than 0.10 mm, preferably greater than 0.12 mm, such as greater than 0.13 mm). As the thickness of the foam substrate increases, the impact resistance tends to improve.

The density (refers to the apparent density. Hereinafter, the same unless otherwise specified) of the foam substrate is not particularly limited, and may be, for example, 0.1 to 0.9 g/cm ³ . From the viewpoint of impact resistance, the density of the foam substrate is suitably 0.8 g/cm ³ or less, and preferably 0.7 g/cm ³ or less (eg, 0.6 g/cm ³ or less). In one aspect, the density of the foam substrate may be less than 0.5 g/cm ³ , and may be less than 0.4 g/cm ³ (eg, 0.5 g/cm ³ or less). Further, from the viewpoint of impact resistance, the density of the foam substrate is preferably 0.12 g/cm ³ or more, more preferably 0.15 g/cm ³ or more, and even more preferably 0.2 g/cm ³ or more (eg, 0.3 g/cm ³ or more). desirable. In one aspect, the foam substrate may have a density of 0.4 g/cm ³ or higher, 0.5 g/cm ³ or higher (eg, greater than 0.5 g/cm ³ ), or even 0.55 g/cm ³ or higher. In addition, the density (apparent density) of the foam substrate can be measured based on JIS K 6767.

The average cell diameter of the foam substrate is not particularly limited, but is preferably 300 µm or less, more preferably 200 µm or less, and even more preferably 150 µm or less from the viewpoint of stress distribution. The lower limit of the average cell diameter is not particularly limited, but from the viewpoint of conformability to steps, 10 μm or more is usually appropriate, 20 μm or more is preferable, 30 μm or more is more preferable, and 40 μm or more (e.g., 50 μm or more) ) is more preferred. In one aspect, the average cell diameter may be 55 μm or more or 60 μm or more. In addition, the average cell diameter here refers to the average cell diameter in terms of a true sphere obtained by observing a cross section of a foam base material with an electron microscope.

The cell structure of the foam constituting the foam substrate disclosed herein is not particularly limited. As the cell structure, any of an open cell structure, a closed cell structure, and a semi-open semi-closed cell structure may be used. From the viewpoint of shock absorbency, a closed-cell structure or a semi-continuous semi-closed-cell structure is preferable.

The 25% compressive strength C ₂₅ of the foam substrate is not particularly limited, and may be, for example, 20 kPa or more (typically 30 kPa or more, and further 40 kPa or more). C ₂₅ is usually 250 kPa or more, preferably 300 kPa or more (eg, 400 kPa or more). A pressure-sensitive adhesive sheet having such a foam base material can exhibit good durability against impact such as falling. For example, tearing of the pressure-sensitive adhesive sheet due to impact can be better prevented. The upper limit of C ₂₅ is not particularly limited, but usually 1300 kPa or less (eg, 1200 kPa or less) is appropriate. In one aspect, C ₂₅ may be 1000 kPa or less, 800 kPa or less, further 600 kPa or less (eg 500 kPa or less), or 360 kPa or less. In another preferred aspect, the C ₂₅ of the foam substrate may be 20 kPa to 200 kPa (typically 30 kPa to 150 kPa, eg 40 kPa to 120 kPa). A pressure-sensitive adhesive sheet having such a foam base material may have excellent cushioning properties. For example, peeling of the pressure-sensitive adhesive sheet can be better prevented when the foam base material absorbs the impact of falling.

The 25% compressive strength C ₂₅ of the foam substrate is obtained by stacking the foam substrate cut into a square shape of 30 mm square and sandwiching a measurement sample with a thickness of about 2 mm between a pair of flat plates, 25% of the original thickness It refers to the load when compressed by the thickness corresponding to (load at 25% compression ratio). That is, it refers to the load when the measurement sample is compressed to a thickness corresponding to 75% of the original thickness. The said compressive strength is measured based on JIS K 6767. As a specific measurement procedure, the measurement sample is set at the center of the pair of flat plates, and the flat plates are continuously compressed to a predetermined compression rate by narrowing the interval between the flat plates, and the flat plates are stopped there to measure the load after 10 seconds. The compressive strength of the foam substrate can be controlled by, for example, the degree of crosslinking and density of the material constituting the foam substrate, the size and shape of cells, and the like.

The tensile elongation of the foam substrate is not particularly limited. For example, a foam substrate having a tensile elongation in the flow direction (MD) of 200% to 800% (more preferably 400% to 600%) can be suitably employed. Further, a foam substrate having a tensile elongation in the transverse direction (TD) of 50% to 800% (more preferably 200% to 500%) is preferable. The elongation of the foam substrate is measured in accordance with JIS K 6767. The elongation of the foam substrate can be controlled by, for example, the degree of crosslinking or the apparent density (expanding ratio).

The tensile strength (tensile strength) of the foam substrate is not particularly limited. For example, a foam substrate having a tensile strength in the flow direction (MD) of 5 MPa to 35 MPa (preferably 10 MPa to 30 MPa) can be suitably employed. Further, a foam substrate having a tensile strength in the transverse direction (TD) of 1 MPa to 25 MPa (more preferably 5 MPa to 20 MPa) is preferable. The tensile strength of the foam substrate is measured in accordance with JIS K 6767. The tensile strength of the foam base material can be controlled by, for example, the degree of crosslinking or the apparent density (expanding ratio).

The material of the foam substrate is not particularly limited. Usually, a foam substrate comprising a foam layer formed of a foam of plastic material (plastic foam) is preferred. The plastic material (meaning including rubber material) for forming the plastic foam body is not particularly limited and can be appropriately selected from known plastic materials. Plastic materials can be used individually by 1 type or in appropriate combination of 2 or more types.

Specific examples of the plastic foam include foams made of polyolefin resins such as foams made of PE and foams made of PP; foams made of polyester resins such as foams made of PET, foams made of PEN, and foams made of PBT; foams made of polyvinyl chloride-based resins such as foams made of polyvinyl chloride; polyvinyl acetate-based resin foams; polyphenylene sulfide resin foams; amide-based resin foams such as aliphatic polyamide (nylon) resin foams and wholly aromatic polyamide (aramid) resin foams; polyimide-based resin foams; foams made of polyether ether ketone (PEEK); foams made of styrenic resins such as foams made of polystyrene; Foams made of urethane resins, such as foams made of polyurethane resin, etc. are mentioned. Further, as the plastic foam, a foam made of rubber-based resin such as a foam made of polychloroprene rubber may be used.

As a preferred foam, a polyolefin-based resin foam (hereinafter also referred to as a 'polyolefin-based foam') is exemplified. As the plastic material constituting the polyolefin-based foam (that is, the polyolefin-based resin), various known or commonly used polyolefin-based resins can be used without particular limitation. For example, PE, PP, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, etc., such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE), etc. are mentioned. Examples of LLDPE include Ziegler-Natta catalyst-based linear low-density polyethylene, metallocene-catalyzed linear low-density polyethylene, and the like. Such polyolefin-type resins can be used individually by 1 type or in combination of 2 or more types suitably.

Preferred examples of the foam substrate in the technology disclosed herein include a PE-based foam substrate substantially composed of a foam of a PE-based resin, and a PP-based substantially composed of a foam of a PP-based resin from the viewpoint of impact resistance, waterproofness, dustproofness, and the like. and polyolefin-based foam substrates such as foam substrates. Here, the PE-based resin refers to a resin containing ethylene as a main monomer (ie, a main component in the monomer), and in addition to HDPE, LDPE, LLDPE, etc., an ethylene-propylene copolymer having an ethylene copolymerization ratio of more than 50% by weight or ethylene -A vinyl acetate copolymer may be included. Similarly, the PP-based resin refers to a resin containing propylene as a main monomer. As the foam substrate in the technology disclosed herein, a PE-based foam substrate can be preferably employed.

The method for producing the plastic foam (typically polyolefin foam) is not particularly limited, and various known methods can be appropriately employed. For example, it can be produced by a method including a molding process, a crosslinking process, and a foaming process of the plastic material or the plastic foam. In addition, a stretching process may be included as needed.

As a method of crosslinking the plastic foam, for example, a chemical crosslinking method using an organic peroxide or the like or an ionizing radiation crosslinking method by irradiating ionizing radiation may be used, and these methods may be used in combination. Examples of the ionizing radiation include electron beams, α-rays, β-rays, and γ-rays. The dose of ionizing radiation is not particularly limited, and can be set to an appropriate dose in consideration of target physical properties (eg, degree of crosslinking) of the foam base material.

Various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, flame retardants, and surfactants may be incorporated into the foam base material as necessary.

The foam base material in the technology disclosed herein may be colored black, white, etc. in order to express desired design properties and optical properties (eg, light blocking property, light reflectivity, etc.) in the pressure-sensitive adhesive sheet provided with the foam base material. . For this coloration, known organic or inorganic colorants can be used alone or in appropriate combination of two or more.

Appropriate surface treatment may be given to the surface of a foam base material as needed. This surface treatment may be, for example, a chemical or physical treatment to increase adhesion to an adjacent material (eg, an adhesive layer). Examples of such surface treatment include corona discharge treatment, chromic acid treatment, ozone exposure, flame exposure, ultraviolet irradiation treatment, plasma treatment, application of an undercoat agent (primer), and the like.

<Releasable liner>

In the technique disclosed herein, the release liner can be used for forming the pressure-sensitive adhesive layer, manufacturing the pressure-sensitive adhesive sheet, preserving the pressure-sensitive adhesive sheet before use, distributing, and processing the shape. The release liner is not particularly limited, and examples thereof include a release liner comprising a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (PE, PP, etc.) ) can be used. The release treatment layer may be formed by surface treatment of the liner substrate with a release treatment agent such as silicon, long-chain alkyl, fluorine, or molybdenum sulfide.

<Adhesive Sheet>

The pressure-sensitive adhesive sheet disclosed herein is compressed to a stainless steel plate under conditions of 23° C. and a compression load of 0.1 kg, and the 180 degree peel strength (initial adhesive force to the stainless steel plate) measured within 1 minute after compression is preferably 5 N/10 mm or more. . By satisfying this characteristic, it is possible to exhibit excellent initial adhesion to various adherends (for example, materials used as members of portable electronic devices). In addition, the pressure-sensitive adhesive sheet having excellent initial adhesion is advantageous in that it is easy to adhere to fragile adherends that may be damaged by normal pressure bonding. The initial adhesion to the stainless steel sheet is more preferably 10 N/10 mm or more, still more preferably 14 N/10 mm or more, and particularly preferably 14.5 N/10 mm or more. The upper limit of the initial adhesive strength to the SUS plate is not particularly limited, but is usually about 25 N/10 mm or less (eg, about 20 N/10 mm or less).

Initial adhesion to the stainless steel sheet can be measured as follows. First, a sample piece is produced by cutting an adhesive sheet to a size of 10 mm in width and 100 mm in length. A PET film having a thickness of 50 µm is attached to one adhesive surface of the pressure-sensitive adhesive sheet for backing. In addition, in the measurement of the single-sided pressure-sensitive adhesive sheet with a substrate, the above-mentioned backing film is unnecessary. In an environment of 23° C. and 50% RH, the adhesive face of the sample piece was pressed against a stainless steel plate (SUS304BA plate) to prepare a measurement sample. The crimping is performed by reciprocating a 0.1 kg roller once. The peel strength [N/10 mm] of the measurement sample is measured using a tensile tester under conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees in an environment of 23° C. and 50% RH. The measurement of the peel strength is performed within less than 1 minute from the application to the stainless steel sheet. In addition, as a tensile tester, "Precision Universal Testing Machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or an equivalent product thereof can be used.

In addition, the adhesive sheet disclosed herein is attached to a PET plate under the conditions of 23 ° C. and a compression load of 2 kg, and 180 degree peel strength (PET It is preferable that the adhesive strength after curing for 30 minutes to the plate) is 4 N/10 mm or more. By satisfying this characteristic, it is possible to exhibit excellent initial adhesion to various adherends (for example, materials used as members of portable electronic devices). The pressure-sensitive adhesive sheet having the adhesive strength tends to exhibit good adhesion to resin materials used in electronic devices, such as polycarbonate (PC) and polyimide (PI). Further, a pressure-sensitive adhesive sheet having excellent initial adhesiveness is also advantageous in that it is easy to adhere to fragile adherends that may be damaged by normal pressure bonding. The adhesive strength after curing for 30 minutes to the PET plate is more preferably 5 N/10 mm or more, still more preferably 6 N/10 mm or more, and particularly preferably 8 N/10 mm or more. The upper limit of the adhesive force after curing for 30 minutes to the PET plate is not particularly limited, but is usually about 20 N/10 mm or less (eg, about 15 N/10 mm or less).

Adhesion to the PET plate after curing for 30 minutes may be measured according to JIS Z 0237:2000. For example, a sample piece is produced by cutting an adhesive sheet to a size of 10 mm in width and 100 mm in length. A PET film having a thickness of 50 µm is attached to one adhesive surface of the pressure-sensitive adhesive sheet for backing. In addition, in the measurement of the single-sided adhesive sheet with a base material, the above-mentioned backing film is unnecessary. Under an environment of 23 ° C. and 50% RH, the adhesive side of the sample piece was pressed to a PET plate (a PET film #25 fixed on a stainless steel plate (SUS304BA) using double-sided adhesive tape NO.5000NS manufactured by Nitto Denko), Produce measurement samples. The crimping is performed by reciprocating a 2 kg roller once. The measurement sample was subjected to a curing time of 30 minutes in an environment of 23 ° C. and 50% RH, and then, using a tensile tester, under an environment of 23 ° C. and 50% RH, a tensile speed of 300 mm / min and a peel angle Under the condition of 180 degrees, the peel strength [N/10 mm] is measured. The measurement of the peel strength is performed within less than 1 minute from the end of the curing time. In addition, as a tensile tester, "Precision Universal Testing Machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or an equivalent product thereof can be used.

In addition, the pressure-sensitive adhesive sheet disclosed herein is measured in the Z-axis direction deformation resistance test, which is measured under conditions of 65° C. and 90% RH for 72 hours using a PET film having a length of 70 mm, a width of 10 mm, and a thickness of 125 μm, in an example to be described later. The lifting height at the end may be less than 1500 μm. A PSA sheet satisfying the above characteristics has particularly excellent resistance to deformation against a peeling load substantially only in the thickness direction (Z-axis direction) of the PSA sheet, and is particularly difficult to deform against a continuous peeling load in that direction. In addition, stable deformation resistance can be exhibited even when an adhesive sheet attached to an adherend (for example, a portable electronic device or a module that is a component thereof) is exposed to high temperature and high humidity conditions during storage or the like. The lifting height is preferably less than 1000 μm, more preferably less than 800 μm, still more preferably less than 400 μm, and particularly preferably less than 200 μm (eg, less than 150 μm). In addition, the lifting height is the height including the thickness of the pressure-sensitive adhesive sheet (50 μm in an embodiment to be described later).

In addition, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially including only the PSA layer, the storage elastic modulus G′ (25° C.) of the PSA sheet at 25° C. may be 0.15 MPa or more. The pressure-sensitive adhesive sheet having the storage modulus G' (25°C) can preferably exhibit good resistance to deformation from an early stage after being applied to an adherend. The G' (25°C) is preferably 0.17 MPa or more, more preferably 0.2 MPa or more, still more preferably 0.23 MPa or more. The above G' (25°C) is particularly preferably 0.25 MPa or more, and may be, for example, 0.3 MPa or more. The G' (25°C) is usually suitably 1.0 MPa or less, and is preferably 0.6 MPa or less, more preferably 0.4 MPa or less, and even more preferably 0.4 MPa or less from the viewpoint of coexistence of initial adhesion and deformation resistance. Preferably, it is 0.35 MPa or less. The G' (25°C) may be, for example, 0.3 MPa or less, 0.25 MPa or less, or 0.2 MPa or less.

Further, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only a PSA layer, the storage elastic modulus G' (85°C) of the PSA sheet at 85°C may be 0.02 MPa or more. In this way, a pressure-sensitive adhesive sheet having continuous resistance to deformation can be preferably obtained. The G '(85 ℃) may be specifically 0.022MPa or more. The G' (85°C) is preferably 0.025 MPa or more, more preferably 0.027 MPa or more. The G'(85°C) is more preferably approximately 0.03 MPa or greater (eg, 0.035 MPa or greater), particularly preferably 0.04 MPa or greater, and still more particularly preferably 0.045 MPa or greater. In addition, the G' (85 ° C.) is usually suitably 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The said G' (85 degreeC) may be 0.06 MPa or less.

Further, in the case where the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only a PSA layer, the PSA sheet is at a temperature at which the PSA sheet is pressed to an adherend (compression temperature) from the viewpoint of initial adhesiveness. The storage elastic modulus G '(apply) of may be 0.6 MPa or less. The G'(apply) is preferably 0.4 MPa or less, more preferably 0.35 MPa or less, and may be, for example, 0.3 MPa or less, or 0.25 MPa or less. The G' (apply) may be, for example, 0.2 MPa or less. Further, from the viewpoint of coexistence of initial adhesion and deformation resistance, the G' (apply) is suitably larger than 0.12 MPa, preferably 0.15 MPa or more, more preferably 0.17 MPa or more (e.g., 0.2 MPa or more). ), more preferably 0.25 MPa or more, for example, 0.3 MPa or more may be sufficient. The compression temperature is selected from the range of more than 0 ° C and less than 60 ° C from the viewpoint of compression workability or temperature management. In the case of a pressure-sensitive adhesive sheet used for portable electronic devices, it is preferable to select the compression temperature in the range of 20°C to 45°C (typically 25°C or 40°C) from the temperature limit for the application.

In addition, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only a PSA layer, it is appropriate that the PSA sheet has a loss elastic modulus G" (25°C) of 2.0 MPa or less at 25°C. The G" (25°C) is preferably 1.5 MPa or less, more preferably 1.0 MPa or less, still more preferably 0.5 MPa or less. The G" (25°C) may be 0.3 MPa or less (for example, 0.25 MPa or less). The G" (25°C) is usually suitably 0.01 MPa or more, and the wettability to the surface of the adherend, furthermore, the initial stage From the standpoint of adhesiveness, etc., it is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.2 MPa or more, and may be, for example, 0.25 MPa or more.

Further, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only a PSA layer, it is appropriate that the loss modulus G" (85°C) of the PSA sheet at 85°C is usually 0.5 MPa or less. The G" (85°C) is preferably 0.3 MPa or less, more preferably 0.1 MPa or less, still more preferably 0.05 MPa or less. The G" (85°C) may be 0.03 MPa or less (for example, 0.02 MPa or less). The G" (85°C) is usually suitably 0.001 MPa or more, and from the viewpoint of adhesiveness, etc., it is preferable. is 0.002 MPa or more, more preferably 0.005 MPa or more, still more preferably 0.008 MPa or more, and may be, for example, 0.01 MPa or more.

In addition, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only an PSA layer, the tanδ (25°C) at 25°C of the PSA sheet is, for example, about 0.3 or more in terms of deformation resistance. From the standpoint of resistance to deformation, it is preferably about 0.5 or more, more preferably about 0.7 or more, still more preferably about 0.8 or more, and particularly preferably about 0.9 or more (eg, about 1 or more). In addition, tan δ (25°C) is suitably, for example, about 3 or more, and is preferably about 2 or less, more preferably about 1.5 or less, still more preferably about 1.2 or less from the viewpoint of initial adhesiveness.

Further, when the PSA sheet disclosed herein is a substrate-free PSA sheet substantially containing only an PSA layer, the tanδ (85°C) of the PSA sheet at 85°C is suitably, for example, about 0.1 or more, and is preferable. It is preferably about 0.12 or more, more preferably about 0.15 or more, still more preferably about 0.2 or more (eg, 0.22 or more). Further, tan δ (85°C) is suitably, for example, approximately 2 or less, preferably approximately 1 or less, and more preferably approximately 0.5 or less (eg, approximately 0.3 or less).

Storage modulus G'(25°C), G'(85°C), G'(apply), loss modulus G"(25°C), G"(85°C), tanδ(25°C) and tanδ( 85 ° C.) can be obtained in the same way as the dynamic viscoelasticity measurement for the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive sheet according to one preferred aspect is a substrate-free double-sided adhesive pressure-sensitive adhesive sheet (substrate-free double-sided pressure-sensitive adhesive sheet) substantially containing only a pressure-sensitive adhesive layer. Since such a substrate-free pressure-sensitive adhesive sheet is excellent in followability, it adheres well to an adherend having a step, for example, and can exhibit excellent adhesive performance. In addition, when fixing rigid materials to each other, compression unevenness is unlikely to occur, and good adhesive fixation is easy to be realized. Therefore, a rigid member capable of having a level difference, such as a wiring board or a housing, can be preferably used for joining members of an electronic device disposed therein. Since the substrate-free double-sided pressure-sensitive adhesive sheet is composed of a pressure-sensitive adhesive layer in its entire thickness, it can exhibit stronger adhesive strength (eg, light compression adhesiveness) in a limited thickness space. Therefore, it can be particularly preferably used for joining members of portable electronic devices.

The total thickness of the pressure-sensitive adhesive sheet (not including the release liner) disclosed herein is not particularly limited. The total thickness of the adhesive sheet can be, for example, about 500 μm or less, usually about 350 μm or less, and preferably about 250 μm or less (for example, about 200 μm or less). The technology disclosed herein is a pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) having a total thickness of about 150 μm or less (more preferably about 100 μm or less, still more preferably about 60 μm or less, for example, about 55 μm or less). It can be preferably carried out in the form of. The lower limit of the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, but is usually about 10 μm or more, preferably about 20 μm or more, and more preferably about 30 μm or more. When the PSA sheet includes a foam base material, the upper limit of the total thickness of the PSA sheet is usually suitably 1.5 mm or less, preferably 1 mm or less, and more preferably 0.5 mm or less.

<Use>

The pressure-sensitive adhesive sheet disclosed herein may exhibit excellent resistance to deformation against a continuous load in the Z-axis direction. Taking advantage of these characteristics, the pressure-sensitive adhesive sheet can be used in various applications requiring resistance to deformation against a continuous load in the Z-axis direction. For example, it can be preferably used for fixing members in various portable devices (portable devices). Further, for example, it can be preferably used for fixing various members of an electronic device (typically a portable electronic device). Non-limiting examples of the portable electronic device include mobile phones, smart phones, tablet PCs, notebook computers, and various wearable devices (e.g., a wrist-wear type worn on a wrist such as a wrist watch, attached to a part of the body by a clip or strap, etc.) Modular type, eyewear type including eyewear type (monocular type, binocular type, head mount type included), clothing type attached to shirts, socks, hats, etc. as accessories, earwear type worn on ears such as earphones, etc. ), digital cameras, digital video cameras, sound equipment (portable music players, IC recorders, etc.), calculators (electronic desk calculators, etc.), portable game equipment, electronic dictionaries, electronic notebooks, electronic books, vehicle information equipment, portable radios, portables This includes TVs, portable printers, portable scanners, and portable modems. In addition, in this specification, 'carrying' is not enough to be simply portable, and means having a level of portability that an individual (standard adult) can carry with relative ease.

The pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) disclosed herein is in the form of a bonding material processed into various shapes and can be used for fixing members constituting portable electronic devices as described above. Among them, it can be preferably used in a portable electronic device having a liquid crystal display device. For example, as an electronic device (typically a portable electronic device such as a smart phone) including a display unit such as a touch panel display (which may be a display unit of a liquid crystal display device), an elastic member such as an FPC is used to make the screen larger. In a device that is bent and accommodated in an internal space, the adhesive sheet disclosed herein is preferably used for fixing the elastic adherend. By using the pressure-sensitive adhesive sheet disclosed herein, the elastic adherend can be stably fixed in a bent state, and the fixed state can be continuously maintained. Accordingly, the elastic member accommodated in a bent state in the limited internal space of the portable electronic device can be accurately positioned and maintained in a stable fixed state by the adhesive sheet disclosed herein. In addition, materials disposed inside the portable electronic device as described above include polar and rigid materials such as polycarbonate and polyimide. For this kind of material (polar and rigid resin material), the pressure-sensitive adhesive sheet disclosed herein can preferably exhibit resistance to deformation against a continuous load in the Z-axis direction. Alternatively, the adhesive sheet disclosed herein is preferably used for fixing a member such as a cover glass having a three-dimensional shape (typically a curved shape) constituting the portable electronic device in a portable electronic device. A relatively large continuous load in the Z-axis direction tends to be applied to an adhesive sheet used for fixing a member having such a three-dimensional surface shape. By using the adhesive sheet disclosed herein, even a member having the above three-dimensional shape can be stably fixed.

The development of electronic devices (typically portable electronic devices such as smart phones and tablet PCs) including a display unit (which may be a display unit of a liquid crystal display device) such as the touch panel type display is especially in recent years due to the large screen and high functionality. It is oriented towards reconciliation. [0004] For the screen size, a countermeasure is taken such as bending and accommodating an elastic member such as an FPC as described above in an internal space. On the other hand, with respect to high functionality, new functions such as a pressure-sensitive sensor with higher precision pressure sensing performance and a face recognition unlocking function are being materialized. High integration is indispensable. Examples of means for high integration of circuits include double-sided type FPCs and multi-layer FPCs, but both are in the direction of increasing the rigidity of the FPC, and are resistant to continuous load in the Z-axis direction as evaluated in the Z-axis direction deformation resistance test described later. It is expected that the improvement of deformability will be a required characteristic. Since the adhesive sheet according to a preferred aspect of the technology disclosed herein may exhibit excellent deformation resistance under severe high temperature and high humidity conditions (strong repulsion condition), such as in the Z-axis direction deformation resistance test described later, the above-described next-generation touch panel It is more suitable and can be preferably used for type display-mounted electronic devices (typically, touch-panel display-mounted portable electronic devices such as smart phones).

For example, the pressure-sensitive adhesive sheet according to one preferred aspect of the technology disclosed herein is preferably used in electronic devices including various light sources such as light emitting diodes (LEDs) or light emitting elements such as self-emitting organic EL. For example, it can be suitably used for electronic equipment (typically portable electronic equipment) provided with an organic EL display device or a liquid crystal display device.

7 is an exploded perspective view schematically illustrating a configuration example of a display device. As shown in FIG. 7 , the display device 200 included in the portable electronic device 100 includes a display portion 220 composed of a cover member, an organic EL unit, or the like, and a support portion 240 . The display device 200 is configured to further include an adhesive sheet 230 . In this configuration example, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) for fixing the members constituting the display unit 220 and the support unit 240 . In addition, the support portion 240 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate) and the like. The adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

Matters disclosed by this specification include the following.

(1) An adhesive sheet comprising an acrylic polymer as a base polymer, a tackifying resin, a (meth)acrylic oligomer, and an adhesive layer containing an azole compound.

(2) The pressure-sensitive adhesive sheet according to (1) above, wherein the acrylic polymer is polymerized with an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at an ester terminal in an amount of 50% by weight or more.

(3) The adhesive sheet according to (1) or (2) above, wherein the acrylic polymer is copolymerized with an acidic group-containing monomer.

(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3) above, wherein the acrylic polymer is copolymerized with a hydroxyl group-containing monomer.

(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein the copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer is 0.01% by weight or more.

(6) The adhesive sheet according to any one of (1) to (5), wherein the tackifying resin is contained in an amount of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer.

(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6), wherein the (meth)acrylic oligomer is contained in an amount of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer.

(8) The content C _O [wt%] of the (meth)acrylic oligomer in the pressure-sensitive adhesive layer and the content C _T [wt%] of the tackifying resin are the corresponding content C relative to the content C _O [wt%] The PSA sheet according to any one of (1) to (7) above, wherein the ratio of _T [weight%] (C _T /C _O ) satisfies 0.25 or more and 4 or less.

(9) The adhesive sheet according to any one of (1) to (8) above, wherein the tackifying resin having a hydroxyl value of 30 mgKOH/g or more is included as the tackifying resin.

(10) The adhesive sheet according to any one of (1) to (9), wherein 50% by weight or more of the tackifying resin is a phenolic tackifying resin having a hydroxyl value of 30 mgKOH/g or more.

(11) The adhesive sheet according to any one of (1) to (10) above, wherein the azole compound is contained in an amount of 0.1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer.

(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11) above, wherein the azole compound includes a triazole compound.

(13) The pressure-sensitive adhesive sheet according to (12), wherein the triazole-based compound is a triazole-based compound having a non-condensed ring structure.

(14) The pressure-sensitive adhesive sheet according to (12), wherein the triazole-based compound is a benzotriazole-based compound.

(15) The PSA sheet according to (1) to (14), wherein the PSA composition for forming the PSA layer contains an isocyanate-based crosslinking agent.

(16) The PSA sheet according to any one of (1) to (15), which is a substrate-free double-sided adhesive PSA sheet containing the PSA layer.

(17) The adhesive sheet according to any one of (1) to (16) above, which is used for joining members in portable electronic devices.

(18) A portable electronic device comprising the adhesive sheet according to any one of (1) to (17) above, and parts bonded by the adhesive sheet.

(19) The portable electronic device according to (18) above, wherein a circuit board is bent and accommodated in an internal space of the portable electronic device, and the adhesive sheet is fixed while the circuit board is bent.

(20) The portable electronic device according to (18) above, wherein in the portable electronic device, the adhesive sheet is used for fixing a cover glass having a curved shape.

[Example]

Some embodiments of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these embodiments. In addition, in the following description, 'part' and '%' are based on weight unless otherwise specified.

The azole-based compounds used in the following Examples are as follows.

Azole compound A: 1,2,3-benzotriazole (trade name 'BT-120', manufactured by Johoku Chemical Industry Co., Ltd.)

Azole compound B: 1-(1',2'-dicarboxyethyl)benzotriazole (trade name 'BT-M', manufactured by Johoku Chemical Industry Co., Ltd.)

Azole compound C: 1,2,4-triazole (trade name "1,2,4-triazole", manufactured by Johoku Chemical Industry Co., Ltd.)

<Example 1>

(Preparation of acrylic polymer solution)

In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet pipe, reflux condenser and dropping funnel, 93 parts of BA, 7 parts of AA, and 0.05 part of 4-hydroxybutylacrylate (4HBA) as monomer components and ethyl acetate as a polymerization solvent were mixed. It injected|threw-in and stirred for 2 hours, introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.1 part of AIBN was added as a polymerization initiator and solution polymerization was performed at 60° C. for 6 hours to obtain an acrylic polymer solution according to this example. In addition, the polymerization reaction proceeded by controlling the concentration of the non-volatile matter (monomer component) by adjusting the amount of the polymerization solvent. Mw of this acrylic polymer was 132×10 ⁴ , and Mw/Mn was 5.85.

(Preparation of pressure-sensitive adhesive composition)

To the acrylic polymer solution obtained above, 1.5 parts of isocyanate-based crosslinking agent (trade name 'Colonate L', 75% ethyl acetate solution of trimethylolpropane/tolylene diisocyanate trimeric adduct, Tosoh based on 100 parts of acrylic polymer contained in the solution) company) and 0.01 part of an epoxy-based crosslinking agent (trade name 'TETRAD-C', 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, manufactured by Mitsubishi Gas Chemical Co.) and 15 parts of a terpene phenol resin (YAS Trade name 'YS Polystar-S-145' manufactured by Hara Chemical Co., Ltd., softening point of about 145 ° C, hydroxyl value of 70 to 110 mgKOH / g), 15 parts of (meth) acrylic oligomer, and 0.8 part of azole compound A (1,2, 3-benzotriazole) was added and stirred and mixed to prepare the pressure-sensitive adhesive composition according to the present example.

As the (meth)acrylic oligomer, one prepared by the following method was used. Specifically, 95 parts of CHMA, 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were introduced into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel. After removing oxygen in the polymerization system by stirring for a period of time, the temperature was raised to 85°C and reacted for 5 hours to obtain a (meth)acrylic oligomer having a solid content concentration of 50%. Mw of the obtained (meth)acrylic oligomer was 3600.

(Manufacture of adhesive sheet)

As the release liner (A), a polyester release film (trade name: Diafoil MRV, 75 μm thick, manufactured by Mitsubishi Polyester Co., Ltd.), which has been subjected to a release process on one side to become a release surface, is used as a release liner (B), A polyester release film (trade name "Diafoil MRF", thickness 38 µm, manufactured by Mitsubishi Polyester Co., Ltd.) was prepared after a release treatment to form a release surface. The adhesive composition obtained above was applied to the release surface of the release liner (A) and dried at 100° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 50 μm. A release liner (B) was covered on the exposed adhesive surface of the pressure-sensitive adhesive layer so that the release surface thereof was on the pressure-sensitive adhesive layer side to prepare a substrate-free double-sided adhesive pressure-sensitive adhesive sheet according to this example.

<Example 2~Example 5>

A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that the type and amount of the azole-based compound was changed as shown in Table 1. Using the obtained PSA composition, in the same manner as in Example 1, a substrate-free double-sided adhesive PSA sheet (thickness: 50 μm) according to this example was produced.

<Example 6>

A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1 except that the epoxy-based crosslinking agent was not used. Using the obtained PSA composition, in the same manner as in Example 1, a substrate-free double-sided adhesive PSA sheet (thickness: 50 μm) according to this example was produced.

<Example 7>

A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1 except that the azole-based compound was not used. Using the obtained PSA composition, in the same manner as in Example 1, a substrate-free double-sided adhesive PSA sheet (thickness: 50 μm) according to this example was produced.

<Example 8>

A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1 except that the (meth)acrylic oligomer was not used. Using the obtained PSA composition, in the same manner as in Example 1, a substrate-free double-sided adhesive PSA sheet (thickness: 50 μm) according to this example was produced.

[Strain resistance test in Z-axis direction (high temperature and high humidity conditions)]

As shown in (a) of FIG. 8, a polycarbonate (PC) plate 50 having a length of 30 mm, a width of 10 mm, and a thickness of 2 mm, and a PET film 60 having a length of 70 mm, a width of 10 mm, and a thickness of 75 μm are prepared, The PC plate 50 and the PET film are overlapped by aligning one end of the PC plate 50 and the PET film 60 in the longitudinal direction, and the remaining part of the PET film 60 protrudes from the other end of the PC plate 50. (60) was fixed. For the fixing, a commercially available double-sided adhesive tape ('No.5000NS' manufactured by Nitto Denko) was used.

PSA sheet sample pieces 70 were prepared by cutting the PSA sheet according to each example in which both adhesive surfaces were protected with two release liners to a size of 3 mm in width and 10 mm in length. The surface of the PC board 50 opposite to the fixing surface of the PET film is placed upward, and one release liner is removed from the PSA sheet sample piece 70, and the width direction of the PC board 50 and the PSA sheet are separated. The longitudinal direction of the sample piece 70 is matched, and both ends of the PSA sheet sample piece 70 in the width direction are aligned on a line 7 mm and 10 mm from the other end on the upper surface of the PC plate 50, so that the PSA sheet sample piece 70 was attached to the upper surface of the PC plate 50 and fixed. The fixing was performed by reciprocating the upper surface of the other side of the PSA sheet sample piece 70 protected by the release liner with a 2 kg roller once.

Next, in an environment of 23° C. and 50% RH, the other release liner of the PSA sheet sample piece 70 attached to the PC board 50 was removed, and as shown in FIG. 8(b), the PC board 50 The protruding portion (40 mm in length) from the PC plate 50 of the PET film 60 fixed to ) is folded toward the PC plate 50 side, and the other end (free end) of the PSA sheet sample piece 70 and the PET film 60 ), the other end of the bent PET film 60 is fixed to the upper surface of the PC board 50 via the adhesive sheet sample piece 70 by making a 0.1 kg roller reciprocate once on the PET film 60, , and exposed it to an environment of 65° C. 90% RH. After exposure to the same environment for 72 hours, it is checked whether or not the adhesive state between the adhesive sheet sample piece 70 and the PET film 60 is maintained, and as shown in FIG. 8(c), the PET film 60 is The peeling case was judged as 'failed'. When the PET film 60 was held, the lifting height [μm] of the PET film 60 from the PSA sheet sample piece 70 was measured using a microscope. The measurement was performed 3 times and the lowest value was recorded. In addition, the said lifting height is a height including the thickness of the adhesive sheet sample piece 70.

According to this evaluation method, unlike the conventional evaluation of repellency resistance, the resistance to peeling load substantially only in the thickness direction (Z-axis direction) of the adhesive sheet was evaluated under the severe conditions of high temperature and high humidity of 65°C and 90% RH. It is possible to do this, and furthermore, continuous resistance to deformation can be evaluated by performing observation over time.

G'(25℃)[MPa], G"(25℃)[MPa], tanδ(25℃), G'(85℃)[MPa], G"(85℃)[MPa] of the pressure-sensitive adhesive layer according to each example MPa], tan δ (85 ° C.), gel fraction (%), and the evaluation results of the Z-direction deformation resistance test (65 ° C. 90% RH) are shown in Table 1.

[Table 1]

As shown in Table 1, the PSA sheets according to Examples 1 to 6 including an acrylic polymer, a tackifying resin, a (meth)acrylic oligomer, and a pressure-sensitive adhesive layer containing an azole compound were tested for resistance to deformation in the Z-axis direction. , it clearly had excellent resistance to deformation against continuous load in the Z-axis direction. On the other hand, neither of the PSA sheet of Example 7 without using an azole-based compound and the PSA sheet of Example 8 without using a (meth)acrylic oligomer were resistant to a continuous load in the Z-axis direction in the Z-axis direction deformation resistance test. Transformability was off.

As mentioned above, although the specific example of this invention was demonstrated in detail, these are only examples and do not limit the claim. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

1, 2, 3, 4, 5, 6: adhesive sheet
10: registration
21, 22: adhesive layer
31, 32: release liner

Claims (10)

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, a tackifying resin, a (meth)acrylic oligomer, and an azole-based compound. According to claim 1,
The acrylic polymer is a pressure-sensitive adhesive sheet in which an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at an ester terminal is polymerized in a proportion of 50% by weight or more. According to claim 1 or 2,
The tackifying resin is included in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer, the pressure-sensitive adhesive sheet. According to any one of claims 1 to 3,
The (meth)acrylic oligomer is contained in an amount of less than 30 parts by weight based on 100 parts by weight of the acrylic polymer. According to any one of claims 1 to 4,
The content C _O [wt%] of the (meth)acrylic oligomer and the content C _T [wt%] of the tackifying resin in the pressure-sensitive _adhesive layer are the corresponding content C T [weight %] relative to the content C _O [weight %] %] ratio (C _T /C _O ) satisfies 0.25 or more and 4 or less. According to any one of claims 1 to 5,
50% by weight or more of the tackifying resin is a phenol-based tackifying resin having a hydroxyl value of 30 mgKOH/g or more. According to any one of claims 1 to 6,
The azole-based compound is included in a ratio of 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. According to any one of claims 1 to 7,
A pressure-sensitive adhesive sheet comprising a triazole-based compound as the azole-based compound. According to any one of claims 1 to 8,
A pressure-sensitive adhesive sheet that is a substrate-less double-sided adhesive pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer. According to any one of claims 1 to 9,
An adhesive sheet used for joining members in portable electronic devices.

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