WO2022054788A1

WO2022054788A1 - Adhesive sheet

Info

Publication number: WO2022054788A1
Application number: PCT/JP2021/032809
Authority: WO
Inventors: 直宏加藤; 匡崇西脇; 康武蔵島
Original assignee: 日東電工株式会社
Priority date: 2020-09-14
Filing date: 2021-09-07
Publication date: 2022-03-17
Also published as: JP2022047827A; CN116075570A; KR20230066444A

Abstract

The present invention provides an adhesive sheet exhibiting excellent deformation resistance to a sustained load in the thickness direction (Z-axis direction) thereof. This adhesive sheet is provided with an adhesive layer including: an acrylic polymer as a base polymer; a tackifier resin; a (meth)acrylic oligomer; and an azole compound. In a preferred embodiment, the acrylic polymer is obtained by polymerizing, at a ratio of at least 50 wt%, an alkyl (meth)acrylate having a C1-6 alkyl group at an ester end thereof.

Description

Adhesive sheet

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

Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid state (viscous elastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is, for example, in the form of a pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on a support base material, or in the form of a base material-less pressure-sensitive adhesive sheet without a support base material, such as a smartphone or the like. It is widely used for the purpose of joining, fixing, and protecting members in portable electronic devices.

Patent Documents

1 and 2 are mentioned as technical documents relating to an adhesive tape used for fixing a member of a portable electronic device.

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

The adhesive area for fixing members in portable electronic devices with an adhesive sheet is usually small due to restrictions on size, weight, etc. The adhesive sheet used for this purpose needs to have an adhesive force that can realize good fixing even in a small area, and its required performance has become higher level due to the demand for weight reduction and miniaturization. ing. In particular, mobile electronic devices equipped with a touch panel display, such as smartphones, are becoming smaller and thinner, while the screens are becoming larger from the viewpoint of display visibility and operability. Therefore, the pressure-sensitive adhesive used is required to have adhesive fixing performance under more severe conditions. Specifically, in this application, the adhesive area is of course limited, and for example, an elastic member such as a flexible printed wiring board (FPC) is bent and accommodated in a limited internal space in a portable electronic device. , The measures are taken to accurately position it with an adhesive sheet and fix it stably. 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 above-mentioned weight reduction and miniaturization, the development of portable electronic device products having curved surface shapes such as three-dimensional shapes has progressed, and the surface shape tends to become more complicated. An adhesive sheet that can be attached to a complicated shape is required to have the ability to follow the shape well and adhere to it. For example, in the above-mentioned 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 surface shape) tends to be subjected to a continuous peeling load larger than that in the past. Adhesive sheets used in such applications are required to have higher levels of sustained peeling load resistance to deformation. Therefore, it would be very meaningful if a pressure-sensitive adhesive sheet that is not easily deformed by the continuous peeling load in the thickness direction (has deformation resistance against the continuous load in the Z-axis direction) is provided.

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 deformation resistance to a continuous load in the Z-axis direction.

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

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

In a preferred embodiment of the technique disclosed herein, the acrylic polymer is polymerized with an alkyl (meth) acrylate having an alkyl group having 1 or more and 6 or less carbon atoms at the ester terminal in a proportion of 50% by weight or more. .. By using such an acrylic polymer in combination with a tackifier resin, a (meth) acrylic oligomer and an azole compound, it is easy to obtain a pressure-sensitive adhesive sheet having excellent deformation resistance to a continuous load in the Z-axis direction.

In a preferred embodiment of the technique disclosed herein, the tackifier resin is contained in a proportion of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. By using a predetermined amount of the tackifier resin, the acrylic polymer as the base polymer can preferably improve the initial adhesiveness while ensuring the deformation resistance against a continuous load in the Z-axis direction.

In a preferred embodiment of the technique disclosed herein, the (meth) acrylic oligomer is contained in a proportion of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. By using a predetermined amount of the (meth) acrylic oligomer, excellent deformation resistance to a continuous load in the Z-axis direction can be exhibited even in a usage mode exposed to harsh conditions such as strong repulsion.

In a preferred embodiment of the technique disclosed herein, the content _CO [% by weight] of the (meth) acrylic oligomer and the content _CT [% by weight] of the tackifier resin in the pressure-sensitive adhesive layer are such. The ratio ( _CT / _CO ) of the content _CT [% by weight] to the content _CO [% by weight] satisfies 0.25 or more and 4 or less. By using the tackifier resin and the (meth) acrylic oligomer in combination in the above range, excellent initial adhesiveness is obtained, and the adhesiveness is sustained in the Z-axis direction even in a usage mode exposed to harsh conditions such as strong repulsion. It can exhibit highly excellent deformation resistance against a load.

In a preferred embodiment of the technique disclosed herein, 50% by weight or more of the tackifier resin is a phenolic tackifier resin having a hydroxyl value of 30 mgKOH / g or more. When such an adhesive resin is used, the adhesive strength is likely to be improved.

In a preferred embodiment of the technique disclosed herein, the azole compound is contained in a proportion 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 compound, excellent deformation resistance to a continuous load in the Z-axis direction can be exhibited.

A preferred embodiment of the technique disclosed herein includes a triazole-based compound as the azole-based compound. In a system using an acrylic polymer as a base polymer, when a triazole-based compound is used, it can exhibit highly excellent deformation resistance against a continuous load in the Z-axis direction.

In some preferred embodiments, the pressure-sensitive adhesive sheet is a substrate-less double-sided adhesive pressure-sensitive adhesive sheet composed of the above-mentioned pressure-sensitive adhesive layer. The base material-less double-sided adhesive sheet can be made thinner because 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. Further, according to the base material-less adhesive sheet, the action of the adhesive layer such as adhesive force and deformation resistance to a continuous load in the Z-axis direction can be maximized.

The adhesive sheet disclosed herein can be preferably used for joining members of a portable electronic device. The pressure-sensitive adhesive sheet disclosed herein has deformation resistance to a continuous load in the Z-axis direction, and is therefore preferably used for fixing an elastic adherend such as an FPC. According to the pressure-sensitive adhesive sheet, the elastic adherend can be fixed in a bent state, and the fixed state can be continuously maintained. Further, 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 surface shape) in a portable electronic device.

It is sectional drawing which shows typically one structural example of the pressure-sensitive adhesive sheet. It is sectional drawing which shows the other structural example of the pressure-sensitive adhesive sheet schematically. It is sectional drawing which shows the other structural example of the pressure-sensitive adhesive sheet schematically. It is sectional drawing which shows the other structural example of the adhesive sheet schematically. It is sectional drawing which shows the other structural example of the pressure-sensitive adhesive sheet schematically. It is sectional drawing which shows the other structural example of the pressure-sensitive adhesive sheet schematically. It is an exploded perspective view which shows the structural example of a display device schematically. It is a schematic diagram explaining the method of the Z-axis direction deformation resistance test.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings regarding the implementation of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in the present specification and the common general technical knowledge in the art. Further, in the following drawings, members / parts having the same function may be described with the same reference numerals, and duplicate description may be omitted or simplified. Further, the embodiments described in the drawings are schematically modeled for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product. ..

As described above, the term "adhesive" as used herein refers to a material that exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure. .. As defined in "C. A. Dahlquist," Adhesion: Fundamentals and Practice ", McLaren & Sons, (1966) P. 143", the pressure-sensitive adhesive here is generally a complex tensile modulus E ^* (1 Hz). It can be a material having a property of satisfying < ¹⁰⁷ dyne / cm ² (typically, a material having the above-mentioned property at 25 ° C.).

In this specification, "(meth) acryloyl" means acryloyl and methacryloyl comprehensively. Similarly, "(meth) acrylate" means acrylate and methacrylate, and "(meth) acrylic" means acrylic and methacrylic, respectively.

As used herein, the term "acrylic polymer" refers to a polymer containing 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”. Acrylic polymers in the present specification are defined as polymers containing monomer units derived from acrylic monomers.

The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet with a base material having the pressure-sensitive adhesive layer on one side or both sides of the base material (support), and the pressure-sensitive adhesive layer is held by a release liner. It may be a base material-less adhesive sheet such as a form. The concept of the pressure-sensitive adhesive sheet as used herein may include what is called an pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film, or the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or may be in the form of a single leaf. Alternatively, the pressure-sensitive adhesive sheet may be further processed into various shapes.

The pressure-sensitive adhesive sheet disclosed herein may have, for example, the cross-sectional structure schematically shown in FIGS. 1 to 6. Of these, FIGS. 1 and 2 are configuration examples of a double-sided adhesive type adhesive sheet with a base material. In the pressure-sensitive adhesive sheet 1 shown in FIG. 1, pressure-sensitive adhesive layers 21 and 22 are provided on each surface (both non-peelable) of the base material 10, and the pressure-sensitive adhesive layer has at least the peeling surface on the pressure-sensitive adhesive layer side. It has a structure protected by the

peeling liners

31 and 32, respectively. The pressure-sensitive adhesive sheet 2 shown in FIG. 2 is provided with pressure-sensitive adhesive layers 21 and 22 on each surface (both non-peelable) of the base material 10, and one of the pressure-sensitive adhesive layers 21 has both sides as peel-off surfaces. It has a structure protected by a peeling liner 31 which is made of. The pressure-sensitive adhesive sheet 2 of this type has a structure in which the pressure-sensitive adhesive layer 22 is also protected by the release liner 31 by winding the pressure-sensitive adhesive sheet and bringing the other pressure-sensitive adhesive layer 22 into contact with the back surface of the release liner 31. be able to.

FIGS. 3 and 4 are configuration examples of a double-sided adhesive sheet without a base material. The pressure-sensitive adhesive sheet 3 shown in FIG. 3 has a structure in which both

sides

21A and 21B of the base-less pressure-sensitive adhesive layer 21 are protected by at least the

release liners

31 and 32 having the pressure-sensitive adhesive layer side as a peel-off surface. The adhesive sheet 4 shown in FIG. 4 has a structure in which one surface (adhesive surface) 21A of the adhesive layer 21 without a base material is protected by a release liner 31 having both sides as release surfaces. When wound, 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 can also be protected by the release liner 31.

5 and 6 are configuration examples of a single-sided adhesive type adhesive sheet with a base material. In the pressure-sensitive adhesive sheet 5 shown in FIG. 5, the pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the base material 10, and the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is peeled off at least on the pressure-sensitive adhesive layer side. It has a structure protected by a peeling liner 31 which is a surface. The pressure-sensitive adhesive sheet 6 shown in FIG. 6 has a structure in which the pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the base material 10. The other surface 10B of the base material 10 is a peeling surface, and when the pressure-sensitive adhesive sheet 6 is wound, the pressure-sensitive adhesive layer 21 comes into contact with the other side surface 10B, and the surface (adhesive surface) 21B of the pressure-sensitive adhesive layer becomes the base material. The other side is protected by 10B.

<Adhesive layer>
In the technique disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. For example, acrylic adhesives, rubber adhesives (natural rubber adhesives, synthetic rubber adhesives, mixed systems, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, etc. The pressure-sensitive adhesive layer may be composed of one or more types of pressure-sensitive adhesives selected from various known pressure-sensitive adhesives such as pressure-sensitive adhesives and fluorine-based pressure-sensitive adhesives. Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive containing a (meth) acrylic polymer as a base polymer (a main component among polymer components, that is, a component contained in an amount of more than 50% by mass). The same meaning applies to rubber-based pressure-sensitive adhesives and other pressure-sensitive adhesives. As a preferable pressure-sensitive adhesive layer from the viewpoint of transparency, weather resistance and the like, 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 can be mentioned. Be done. The content ratio of the acrylic pressure-sensitive adhesive may be more than 98% by weight, or the pressure-sensitive adhesive layer may be substantially composed of the acrylic-based pressure-sensitive adhesive.

(Acrylic polymer)
Although not particularly limited, in a preferred embodiment of the technique disclosed herein, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive are acrylic polymers as a base polymer. including. The acrylic polymer is preferably a polymer of a monomer raw material containing an alkyl (meth) acrylate as a main monomer and further containing a submonomer having copolymerizability with the main monomer. Here, the main monomer means a component contained in the monomer raw material in an amount of more than 50% by weight.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as “C _1-20 ”). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, an alkyl (meth) acrylate in which R ² is a C _1-14 chain alkyl group is preferable, and an alkyl (meth) acrylate in which R ² is a C _1-10 chain alkyl group is preferable. ) Acrylate is more preferred, and alkyl (meth) acrylate in which R ² is a butyl group or a 2-ethylhexyl group is particularly preferred.

Examples of the alkyl (meth) acrylate 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, and n-butyl. (Meta) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) 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 Examples thereof include (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, and ecocil (meth) acrylate. .. These alkyl (meth) acrylates can be used alone or in combination of two or more. Particularly preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technique 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 weight by weight. It can be preferably carried out in an embodiment of% or more (usually 85% by weight or more, for example, 90% by weight or more, further 95% by weight or more). The technique disclosed herein can be carried out, for example, in a mode in which the alkyl (meth) acrylate contained in the above-mentioned monomer component is BA alone, a mode in which 2EHA is alone, a mode in which BA and 2EHA are contained, and the like.

When the monomer component contains BA and 2EHA, the weight ratio of BA to 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 can be 60/40 or higher (eg 60/40 or higher and 99/1 or lower), 80/20 or higher, and 90/10 or higher (eg 90/10 or higher). It may be 99/1 or less).

The technique disclosed herein can be preferably carried out in an embodiment 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. By using C _1-6 alkyl (meth) acrylate as the main monomer in this way, it is possible to preferably design an acrylic polymer capable of achieving deformation resistance against a continuous load in the Z-axis direction. The ratio of C _1-6 alkyl (meth) acrylate to the monomer component (in other words, the polymerization ratio) is more preferably larger than 50% by weight, still more preferably 60% by weight or more, and particularly preferably 70% by weight or more (for example). 80% by weight or more, and further 85% by weight or more). The upper limit of the ratio of C _1-6 alkyl (meth) acrylate to the monomer component is not particularly limited, and is usually 99% by weight or less, and 97% by weight or less in relation to the ratio of other copolymerizable monomers used. It is appropriate that there is, and it is preferable that it is 95% by weight or less. The C _1-6 alkyl (meth) acrylate may be used alone or in combination of two or more. As the 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 further preferable. In another aspect, the C _1-6 alkyl (meth) acrylate is preferably C _1-4 alkyl acrylate, more preferably C _2-4 alkyl acrylate. BA is mentioned as a preferable example of C _1-6 alkyl (meth) acrylate.

In the embodiment in which BA is used as the main monomer, the copolymerization ratio of BA in the acrylic polymer is preferably 50% by weight or more, more preferably larger than 50% by weight, still more preferably 60% by weight or more, and particularly preferably 60% by weight or more. It is 70% by weight or more (for example, 80% by weight or more, further 85% by weight or more), and more preferably 90% by weight or more (for example, more than 90% by weight). By copolymerizing with BA as the main monomer, the pressure-sensitive adhesive can be satisfactorily adhered to the adherend. The copolymerization ratio of BA in the acrylic polymer is not particularly limited, and is usually 99% by weight or less, which is 97% by weight in relation to the copolymerization ratio of other copolymerizable monomers (for example, an acidic group-containing monomer). % Or less is appropriate, and 95% by weight or less is preferable.

In a preferred embodiment of the technique disclosed herein, an acidic group-containing monomer is used as a monomer copolymerizable with the alkyl (meth) acrylate which is the main monomer. The acidic group-containing monomer can exhibit an improvement in cohesiveness based on its polarity and a good binding force to a polar adherend. When a cross-linking agent such as an isocyanate-based or epoxy-based cross-linking agent is used, the acidic group (typically, a carboxyl group) serves as a cross-linking point of the acrylic polymer. Due to these actions, deformation resistance to a continuous load in the Z-axis direction can be suitably realized. By using the acidic group-containing monomer in a predetermined ratio or more, it is possible to preferably design an acrylic polymer capable of achieving initial adhesiveness and deformation resistance to a continuous load in the Z-axis direction.

As the acidic group-containing monomer, a carboxy group-containing monomer is preferably used. Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, crotonic acid and isocrotonic acid; maleic acid, itaconic acid and citraconic acid. Such as ethylenically unsaturated dicarboxylic acid and its anhydride (maleic anhydride, itaconic anhydride, etc.) can be mentioned. Further, the acidic group-containing monomer may be a monomer having a metal salt of a carboxy group (for example, an alkali metal salt). Among them, AA and MAA are preferable, and AA is more preferable. When one or more kinds of acidic group-containing monomers are used, the ratio of AA to the acidic group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more. Is. In a particularly preferred embodiment, the acidic group-containing monomer consists substantially only of AA. AA has a polarity based on its carboxy group, a role as a cross-linking point, a combined action such as Tg (106 ° C.), and therefore, in the acidic group-containing monomer disclosed herein, initial adhesiveness and persistence in the Z-axis direction It is considered to be the most suitable monomer material for achieving a balance with deformation resistance against load.

In the technique disclosed herein, the content of the acidic group-containing monomer (typically the carboxy 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 determined. It is 3% by weight or more, and it is appropriate that it is 5% by weight or more. By using an acidic group-containing monomer in a predetermined amount or more, an acrylic polymer capable of achieving both initial adhesiveness and deformation resistance against a continuous load in the Z-axis direction is preferably realized based on its cohesiveness improving action and the like. be able to. 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 20% by weight or less, and is preferably 18% by weight or less from the viewpoint of maintaining the characteristics of the main monomer. The copolymerization ratio may be 15% by weight or less, for example, 13% by weight or less. In a more preferable aspect, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is about 12% by weight or less, more preferably about 10% by weight or less, and particularly preferably about 8% by weight or less. In an acrylic polymer having a monomer composition rich in C _1-6 alkyl (meth) acrylate (typically BA), the content of the acidic group-containing monomer (for example, AA) in the monomer component is particularly in the above range. It is effective.

In the technique disclosed herein, a copolymerizable monomer other than the carboxy group-containing monomer can be used as the auxiliary monomer having copolymerizability with the alkyl (meth) acrylate which is the main monomer. As such a sub-monomer, for example, the following functional group-containing monomers can be used.
Hydroxyl-containing monomers: Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; Unsaturated alcohols such as vinyl alcohol and allyl alcohol; polypropylene glycol mono (meth) acrylate.
Amide group-containing monomers: For example, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N-methoxymethyl. (Meta) acrylamide, N-butoxymethyl (meth) acrylamide.
Amino group-containing monomer: For example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile.
Keto group-containing monomer: For example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinylmethyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl. Pyrol, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolactam, N- (meth) acryloylmorpholin.
Alkoxysilyl group-containing monomers: for example 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane.

As the functional group-containing monomer (secondary monomer) other than the acidic group-containing monomer, one type can be used alone or two or more types can be used in combination. When the monomer component constituting the acrylic polymer contains a functional group-containing monomer, the ratio of the functional group-containing monomer to the monomer component depends on the adhesive force, the deformation resistance to a continuous load in the Z-axis direction, and other required performance. Will be decided as appropriate. It is appropriate that the ratio (copolymerization ratio) of the functional group-containing monomer is about 0.01% by weight or more (for example, 0.02% by weight or more, usually 0.03% by weight or more) in the monomer component. Further, it may be about 0.1% by weight or more (for example, 0.5% by weight or more, usually 1% by weight or more). 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 monomer other than the acidic group-containing monomer is preferably, for example, 10% by weight or less, further 5% by weight or less, and can be 1% by weight or less. .. In a more preferable aspect, the ratio of the functional group-containing monomer (for example, a hydroxyl group-containing monomer) other than the acidic group-containing monomer is about 0.5% by weight or less (for example, about 0.2% by weight or less). The monomer component constituting the acrylic polymer may be substantially free of a functional group-containing monomer other than the acidic group-containing monomer.

In a preferred embodiment of the technique disclosed herein, a hydroxyl group-containing monomer is used as the submonomer. In a system using a hydroxyl group-containing monomer as the sub-monomer, when a cross-linking agent such as an isocyanate-based or epoxy-based cross-linking agent is used, the hydroxyl group in the hydroxyl group-containing monomer can be a cross-linking point of the acrylic polymer. Therefore, when a hydroxyl group-containing monomer is used as the sub-monomer, the occurrence of cross-linking inhibition of the acrylic polymer by the azole compound is suitably suppressed even when the azole compound is used in combination, and the cross-linking of the acrylic polymer is preferable. Easy to progress to. As a result, deformation resistance to a continuous load in the Z-axis direction can be suitably realized. By using the hydroxyl group-containing monomer in a predetermined ratio or more, it is possible to preferably design an acrylic polymer capable of realizing excellent deformation resistance to a continuous load in the Z-axis direction in a system to which an azole compound is added. ..

In the technique 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, 0.005. It is appropriate to make it by weight% or more. By using a hydroxyl group-containing monomer in a predetermined amount or more, it is possible to preferably realize an acrylic polymer capable of improving the deformation resistance to a continuous load in the Z-axis direction. 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, or 0.03% by weight or more. It may be 0.04% by weight or more. The copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer is usually preferably 1% by weight or less, and more preferably 0.5% by weight or less from the viewpoint of maintaining the characteristics of the main monomer. Is 0.1% by weight or less, more preferably 0.08% by weight or less. In the acrylic polymer having a monomer composition rich in C _1-6 alkyl (meth) acrylate (typically BA), the content of the hydroxyl group-containing monomer (for example, 4-hydroxybutyl (meth) acrylate) in the monomer component is described above. The range is particularly effective.

As the monomer component constituting the acrylic polymer, a copolymerization component other than the above-mentioned acidic group-containing monomer and other submonomers can be used for the purpose of enhancing the cohesive force of the acrylic polymer. Examples of such copolymerization components include vinyl ester-based monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; cyclohexyl (meth). ) Cycloalkyl (meth) acrylates such as acrylates, cyclopentyl (meth) acrylates, isobornyl (meth) acrylates; aryl (meth) acrylates (eg phenyl (meth) acrylates), aryloxyalkyl (meth) acrylates (eg phenoxyethyl (meth)). ) Acrylate), aromatic ring-containing (meth) acrylates such as arylalkyl (meth) acrylates (eg, benzyl (meth) acrylates); olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; vinyl chloride, vinylidene chloride. Chlorine-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate; isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether. System monomers; and the like.
The amount of the other copolymerization component may be appropriately selected depending on the purpose and use, and is not particularly limited, but is usually preferably 10% by weight or less of the monomer component. For example, when a vinyl ester-based monomer (for example, vinyl acetate) is used as the other copolymerization component, the content thereof is, for example, about 0.1% by weight or more (usually about 0.5% by weight or more) of the monomer component. It is also appropriate that the content is about 20% by weight or less (usually about 10% by weight or less).

Acrylic polymers have polyfunctionality having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth) acryloyl group and vinyl group as other monomer components. It may contain a monomer. By using a polyfunctional monomer as the monomer component, the cohesive force of the pressure-sensitive adhesive layer can be enhanced. The polyfunctional monomer can be used as a cross-linking agent.

Examples of polyfunctional monomers include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and penta. Elythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1, Polyhydric alcohols and (meth) acrylics such as 6-hexanediol di (meth) acrylates, 1,12-dodecanediol di (meth) acrylates, trimethylol propanetri (meth) acrylates, tetramethylol methanetri (meth) acrylates. Esters with acids; examples include allyl (meth) acrylates, vinyl (meth) acrylates, divinylbenzenes, epoxy acrylates, polyester acrylates, urethane acrylates and the like. Preferable examples of these include trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate and dipentaerythritol hexa (meth) acrylate. Among them, 1,6-hexanediol di (meth) acrylate is mentioned as a preferable example. The polyfunctional monomer may be used alone or in combination of two or more. From the viewpoint of reactivity and the like, a polyfunctional monomer having two or more acryloyl groups is usually preferable.

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 achieving a good balance between the preferable storage elasticity disclosed herein and other adhesive performance or other properties, the amount of the polyfunctional monomer used can be approximately 3% by weight or less of the above-mentioned monomer component. Approximately 2% by weight or less is preferable, and approximately 1% by weight or less (for example, approximately 0.5% by weight or less) is more preferable. When the polyfunctional monomer is used, the lower limit of the amount used may be larger than 0% by weight and is not particularly limited. Usually, by setting the amount of the polyfunctional monomer to be used in an amount of about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exhibited.

The composition of the monomer components constituting the acrylic polymer shall be designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately −15 ° C. or lower (for example, approximately −70 ° C. or higher and −15 ° C. or lower). Is appropriate. Here, the Tg of the acrylic polymer means the Tg obtained by the Fox formula based on the composition of the above-mentioned monomer component. As shown below, the Fox formula is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the above Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for calculating Tg, the value described in the publicly known material shall be 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-Ethylhexyl acrylate -70 ° C
n-Butyl acrylate -55 ° C
Ethyl acrylate-22 ° C
Methyl acrylate 8 ℃
Methyl methacrylate 105 ° C
2-Hydroxyethyl acrylate -15 ° C
4-Hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

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

For monomers for which the glass transition temperature of the homopolymer is not described in the above document, the value obtained by the following measurement method shall be used.
Specifically, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by weight of a monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and acetic acid as a polymerization solvent. Add 200 parts by weight of ethyl and stir for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain with a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES"). The viscoelasticity is measured in a shear mode at a temperature range of −70 ° C. to 150 ° C. and a temperature rise rate of 5 ° C./min, and the temperature corresponding to the peak top temperature of tan δ is defined as Tg of the homopolymer.

Although not particularly limited, from the viewpoint of adhesiveness, it is advantageous that the Tg of the acrylic polymer is about −25 ° C. or lower, preferably about −35 ° C. or lower, and more preferably about −40 ° C. or lower. More preferably, it may be −45 ° C. or lower, for example, −50 ° C. or lower, or −55 ° C. or lower. Further, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is usually about −75 ° C. or higher, preferably about −70 ° C. or higher. The technique disclosed herein can be preferably carried out in an embodiment in which the Tg of the acrylic polymer is approximately −65 ° C. or higher and approximately −40 ° C. or lower (for example, approximately −65 ° C. or higher and approximately −45 ° C. or lower). In a preferred embodiment, the Tg of the acrylic polymer can be approximately −55 ° C. or higher and approximately −45 ° C. or lower. In another embodiment, the Tg of the acrylic polymer can 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 (that is, the type and amount ratio of the monomers used for synthesizing 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 × 104 or more, and it is appropriate that it is about ⁴⁵ × 10 ⁴ or more (for example, about 65 × ¹⁰⁴ or more). In a preferred embodiment, the Mw of the acrylic polymer is 70 × ¹⁰⁴ or more. Further, in a typical aspect of the technique disclosed herein, it is appropriate that the Mw of the acrylic polymer is larger than 70 × ¹⁰⁴ . By using an acrylic polymer having an Mw of more than 70 × ¹⁰⁴ , excellent deformation resistance to a continuous deformation load can be obtained based on its cohesiveness. The Mw of the acrylic polymer is more preferably about 75 × ¹⁰⁴ or more, further preferably about 90 × ¹⁰⁴ or more, and particularly preferably about 95 × ¹⁰⁴ or more. In a more particularly preferable aspect, the Mw is approximately 100 × 10 ⁴ or more (for example, approximately 110 × 10 ⁴ or more), and typically 120 × ¹⁰⁴ or more (for example, 130 × ¹⁰⁴ or more). Further, it is appropriate that the Mw is usually 300 × ¹⁰⁴ or less (more preferably about 200 × ¹⁰⁴ or less, for example, about 150 × ¹⁰⁴ or less). The Mw of the acrylic polymer may be approximately 140 × ¹⁰⁴ or less. For example, in an acrylic polymer obtained by a solution polymerization method or an emulsion polymerization method, Mw in the above range is preferable.

The dispersity (Mw / Mn) of the acrylic polymer disclosed here is not particularly limited. The degree of dispersion (Mw / Mn) here means 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 embodiment, the dispersity (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 a considerable amount of the low molecular weight body and the high molecular weight body is contained. The low molecular weight body contributes to the development of initial adhesiveness due to its good wettability to the adherend, and the high molecular weight body exhibits resistance (deformation resistance) to a continuous deformation load due to its cohesiveness. When the Mw / Mn is 8 or more, the initial adhesiveness is preferably exhibited. Further, when the Mw / Mn is 40 or less, the molecular weight distribution is preferably limited within an appropriate range, and stable characteristics (initial adhesiveness and deformation resistance) can be obtained. The Mw / Mn may be 10 or more, 12 or more, or 15 or more. The Mw / Mn is preferably 35 or less, more preferably 30 or less, still more preferably 25 or less.

In a preferred embodiment, the dispersity (Mw / Mn) of the acrylic polymer is less than 15. For example, in the case of an acrylic polymer having a relatively high molecular weight (typically Mw of more than 700,000) obtained by a solution polymerization method or an emulsion polymerization method, Mw / Mn in the above range is preferable. The Mw / Mn is preferably less than 12, more preferably less than 10, and even more preferably less than 8 (for example, 7.5 or less). Further, the Mw / Mn is theoretically 1 or more, for example, 2 or more, 3 or more, or 4 or more (typically 5 or more).

Note that Mw, Mn and Mw / Mn can be adjusted by the polymerization conditions (time, temperature, etc.), the use of a chain transfer agent, the selection of the polymerization solvent based on the chain transfer constant, and the like. Further, Mw and Mn are obtained from the standard polystyrene-equivalent values obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used.

<Adhesive composition>
The pressure-sensitive adhesive layer disclosed herein contains a monomer component having a composition as described above in the form of a polymer, an unpolymerized product (that is, a form in which a polymerizable functional group is unreacted), or a mixture thereof. It can be formed using an agent composition. The pressure-sensitive adhesive composition is a composition in which a pressure-sensitive adhesive (adhesive component) is contained in an organic solvent (solvent-type pressure-sensitive adhesive composition) and a composition in which the pressure-sensitive adhesive is dispersed in an aqueous solvent (water-dispersed pressure-sensitive adhesive). Composition), a composition prepared to be cured by active energy rays such as ultraviolet rays and radiation to form a pressure-sensitive adhesive (active energy ray-curable pressure-sensitive adhesive composition), coated in a heat-melted state, and near room temperature. It can be in various forms such as a hot melt type pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive when cooled to. The technique disclosed herein can be particularly preferably carried out in an embodiment including a pressure-sensitive adhesive layer formed of a solvent-type pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition from the viewpoint of pressure-sensitive adhesive properties and the like.

Here, the "active energy ray" in the present specification refers to an energy ray having energy that can cause a chemical reaction such as a polymerization reaction, a cross-linking reaction, and decomposition of an initiator. Examples of active energy rays referred to here include light such as ultraviolet rays, visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron rays, neutron rays, and X-rays.

The pressure-sensitive adhesive composition typically comprises at least a portion of the monomer component of the composition (which may be part of the type of monomer or part of the amount). Included in the form of. The polymerization method for forming the above-mentioned polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiating light such as ultraviolet rays (typically). Radiation polymerization carried out by irradiating radiation such as β-rays and γ-rays; which is carried out in the presence of a photopolymerization initiator; and the like can be appropriately adopted. Of these, solution polymerization and photopolymerization are preferable. In these polymerization methods, the mode of polymerization is not particularly limited, and conventionally known monomer supply methods, polymerization conditions (temperature, time, pressure, light irradiation amount, radiation irradiation amount, etc.), materials used other than monomers (polymerization initiator). , Surfactant, etc.) and the like can be appropriately selected.

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

As a monomer supply method for solution polymerization, a batch charging method, a continuous supply (drop) method, a split supply (drop) method, etc., in which all the monomer raw materials are supplied at once, can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of the monomer and solvent used, the type of the 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 embodiment, the polymerization temperature can be set to about 75 ° C. or lower (more preferably about 65 ° C. or lower, for example, about 45 ° C. to 65 ° C.).

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

On the other hand, as another aspect of the technique disclosed herein, when an active energy ray-curable pressure-sensitive adhesive composition (typically a photocurable pressure-sensitive adhesive composition) is adopted, the above-mentioned active energy ray-curable pressure-sensitive adhesive is used. The composition preferably contains substantially no organic solvent from the viewpoint of environmental hygiene and the like. 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. Further, as will be described later, since it is suitable for forming a pressure-sensitive adhesive layer in a form in which the liquid film of the pressure-sensitive adhesive composition is cured between the peeling surfaces of a pair of release films, it means that a solvent (organic solvent and aqueous solvent are included). A pressure-sensitive adhesive composition that does not substantially contain (there is)) is preferable. 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. Here, the solvent means 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 constituent component of the pressure-sensitive adhesive layer finally formed.

In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator may be used depending on the polymerization method, polymerization mode and the like. Such a polymerization initiator may be used alone or in combination of two or more.

The thermal polymerization initiator is not particularly limited, but is, for example, an azo-based polymerization initiator, a peroxide-based initiator, a redox-based initiator by a combination of a peroxide and a reducing agent, and a substituted ethane-based initiator. Etc. can be used. More specifically, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (2-amidinopropane). ) Dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutyramidine), 2 , 2'-Azobis [N- (2-carboxyethyl) -2-methylpropionamidine] Azo-based initiators such as hydrate; persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide (BPO), Peroxide-based initiators such as t-butyl hydroperoxide and hydrogen peroxide; for example, substituted ethane-based initiators such as phenyl-substituted ethane; for example, a combination of persulfate and sodium hydrogen sulfite, peroxide and sodium ascorbate. Examples include, but are not limited to, redox-based initiators in combination with and the like. The thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100 ° C. (typically 40 to 80 ° C.).

The photopolymerization initiator is not particularly limited, but is, for example, a ketal-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, α-. Ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, thioxanthone-based light A polymerization initiator or the like can be used.

Specific examples of the ketal-based photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, trade name "Irgacure 651" manufactured by BASF Corporation) and the like.
Specific examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl-phenyl-ketone (for example, trade name "Irgacure 184" manufactured by BASF), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, and the like. 1- [4- (2-Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one (for example, trade name "Irgacure 2959" manufactured by BASF), 2-hydroxy-2. -Methyl-1-phenyl-propane-1-one (for example, trade name "Darocure 1173" manufactured by BASF), methoxyacetophenone and the like are included.
Specific examples of the benzoin ether-based photopolymerization initiator include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acylphosphine oxide-based photopolymerization initiator include bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (for example, trade name "Irgacure 819" manufactured by BASF) and bis (2,4,6). -Trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (for example, brand name "Lucillin TPO" manufactured by BASF), bis (2,6-- Dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like are included.
Specific examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropane-1-one and the like. Is done. Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl 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. Specific examples of the benzoin-based photopolymerization initiator include benzoin and the like. 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-hydroxycyclohexylphenylketone and the like.
Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-dichlorothioxanthone, and isopropylthioxanthone. , 2,4-Diisopropylthioxanthone, dodecylthioxanthone and the like.

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

(Adhesive composition containing a monomer component in the form of a complete polymer)
The pressure-sensitive adhesive composition according to a preferred embodiment contains the monomer component of the agent composition in the form of a complete polymer. Such a pressure-sensitive adhesive composition is, for example, a solvent-type pressure-sensitive adhesive composition containing an acrylic polymer which is a complete polymer of a monomer component in an organic solvent, or an aqueous dispersion-type pressure-sensitive adhesive in which the acrylic polymer is dispersed in an aqueous solvent. It can be in the form of a composition, etc. In the present specification, the term "complete polymer" means that the polymerization conversion rate is more than 95% by weight.

(Adhesive composition containing polymerized and unpolymerized monomer components)
The pressure-sensitive adhesive composition according to another preferred embodiment contains a polymer of a monomer mixture containing at least a part of the monomer component (raw material monomer) of the composition. Typically, a part of the above-mentioned monomer component is contained in the form of a polymer, and the rest is contained in the form of an unpolymerized product (unreacted monomer). The polymer of the monomer mixture can be prepared by polymerizing the monomer mixture at least partially.
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-mentioned monomer mixture and an unreacted monomer, and typically exhibits a syrup-like (viscous liquid) form. Hereinafter, the partial polymer having such properties may be referred to as "monomer syrup" or simply "syrup".

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

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

The pressure-sensitive adhesive composition containing a partial polymer of the above-mentioned 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 (for example, a photopolymerization method). The pressure-sensitive adhesive composition containing the partial polymer contains other components used as necessary (for example, a photopolymerization initiator, a polyfunctional monomer, a cross-linking agent, a (meth) acrylic oligomer described later, etc.). obtain. The method of blending such other components is not particularly limited, and may be contained in the monomer mixture in advance or added to the partial polymer, for example.

Further, in the pressure-sensitive adhesive composition disclosed herein, a complete polymer of a monomer mixture containing some types of monomers among the monomer components (raw material monomers) is dissolved in the remaining types of monomers or a partial polymer thereof. It may be in the form. Such a form of the pressure-sensitive adhesive composition is also included in the example of the pressure-sensitive adhesive composition containing the polymer of the monomer component and the unpolymerized product.

As described above, a photopolymerization method can be preferably adopted as a curing method (polymerization method) for forming a pressure-sensitive adhesive from a pressure-sensitive adhesive composition containing a polymer and a non-polymer component of a monomer component. In the pressure-sensitive adhesive composition containing the polymer prepared by the photopolymerization method, it is particularly preferable to adopt the photopolymerization method as the curing method. Since the polymer obtained by the photopolymerization method already contains a photopolymerization initiator, a new photopolymerization initiator is added when the pressure-sensitive adhesive composition containing this polymer is further cured to form a pressure-sensitive adhesive. Can be photocured without it. Alternatively, it may be a pressure-sensitive adhesive composition having a composition in which a photopolymerization initiator is added, if necessary, to the polymer prepared by the photopolymerization method. The photopolymerization initiator to be added may be the same as or different from the photopolymerization initiator used to prepare the polymer. The pressure-sensitive adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. The photocurable pressure-sensitive adhesive composition has an advantage that even a thick pressure-sensitive adhesive layer can be easily formed. In a preferred embodiment, the photopolymerization when forming the pressure-sensitive adhesive from the pressure-sensitive adhesive composition can be carried out by irradiation with ultraviolet rays. A known high-pressure mercury lamp, low-pressure mercury lamp, metal halide lamp, or the like can be used for ultraviolet irradiation.

(Crosslinking agent)
The pressure-sensitive adhesive composition (preferably a solvent-type pressure-sensitive adhesive composition) used for forming the pressure-sensitive adhesive layer preferably contains a cross-linking agent as an optional component. By including a cross-linking agent, the viscoelastic properties disclosed herein can be preferably realized. The pressure-sensitive adhesive layer in the technique disclosed herein contains the above-mentioned cross-linking agent in a form after the cross-linking reaction, a form before the cross-linking reaction, a form partially cross-linked, an intermediate or a composite form thereof, and the like. obtain. The cross-linking agent is usually contained in the pressure-sensitive adhesive layer exclusively in the form after the cross-linking reaction.

The type of the cross-linking agent is not particularly limited, and a conventionally known cross-linking agent can be appropriately selected and used. Examples of such a cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, a melamine-based cross-linking agent, a carbodiimide-based cross-linking agent, a hydrazine-based cross-linking agent, and an amine-based cross-linking agent. Examples thereof include a peroxide-based cross-linking agent, a metal chelate-based cross-linking agent, a metal alkoxide-based cross-linking agent, and a metal salt-based cross-linking agent. The cross-linking agent may be used alone or in combination of two or more. Examples of the cross-linking agent that can be preferably used in the technique disclosed herein include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, and an oxazoline-based cross-linking agent.

As the epoxy-based cross-linking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferable. The epoxy-based cross-linking agent may be used alone or in combination of two or more.

Although not particularly limited, specific examples of the epoxy-based cross-linking agent include, for example, N, N, N', N'-tetraglycidyl-m-xylenediolamine, 1,3-bis (N, N-diglycidylaminomethyl). ) Cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like can be mentioned. Commercially available epoxy-based cross-linking agents include Mitsubishi Gas Chemical's product name "TETRAD-C" and product name "TETRAD-X", DIC's product name "Epicron CR-5L", and Nagase ChemteX's product. The product name "Denacol EX-512", the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like can be mentioned.

In the embodiment in which the epoxy-based cross-linking agent is used, the amount used thereof is not particularly limited. The amount of the epoxy-based cross-linking agent used may be, for example, more than 0 parts by weight and about 1 part by weight or less (preferably about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the acrylic polymer. can. From the viewpoint of preferably exerting the effect of improving the cohesive force, it is usually appropriate that the amount of the epoxy-based cross-linking agent used is approximately 0.002 parts by weight or more with respect to 100 parts by weight of the acrylic polymer, and it is preferable. It may be about 0.005 parts by weight or more, for example, about 0.01 parts by weight or more, about 0.02 parts by weight or more, or about 0.03 parts by weight or more. Further, from the viewpoint of avoiding insufficient adhesiveness due to excessive cross-linking, it is usually appropriate that the amount of the epoxy-based cross-linking agent used is about 0.2 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. It is preferably 0.1 parts by weight or less (for example, 0.05 parts by weight or less).

As the isocyanate-based cross-linking agent, polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, including one having an isocyanurate structure) can be preferably used. The isocyanate-based cross-linking agent may be used alone or in combination of two or more.

As a preferable polyfunctional isocyanate, a polyfunctional isocyanate having an average of 3 or more isocyanate groups per molecule is exemplified. Such trifunctional or higher functional isocyanates are addition reactions of bifunctional or trifunctional or higher functional isocyanate multimers (eg, dimers or trimers), derivatives (eg, polyhydric alcohols and two or more molecules of polyfunctional isocyanates). Product), polymer, etc. For example, diphenylmethane diisocyanate dimer or trimer, hexamethylene diisocyanate isocyanurate (isocyanurate structure trimer adduct), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa. Examples thereof include reaction products with methylene diisocyanate, polyfunctional isocyanates such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanates include the trade name "Duranate TPA-100" manufactured by Asahi Kasei Chemicals, the trade name "Coronate L", the same "Coronate HL", the same "Coronate HK", and the same "Coronate" manufactured by Tosoh Corporation. "HX", "Coronate 2096" and the like can be mentioned.

In the embodiment in which the isocyanate-based cross-linking agent is used, the amount used thereof is not particularly limited. The amount of the isocyanate-based cross-linking agent used can 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 viewpoint of cohesiveness, it is usually appropriate that the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the acrylic polymer is about 0.1 parts by weight or more, and about 0.3 parts by weight or more (for example, 0. 5 parts by weight or more) is preferable. In a more preferable aspect, the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the acrylic polymer is about 1 part by weight or more, and may be about 1.5 parts by weight or more. Further, the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the acrylic polymer is usually appropriately set to about 8 parts by weight or less, and may be set to about 5 parts by weight or less (for example, less than about 4 parts by weight). preferable. In a more preferred embodiment, the amount of the isocyanate-based cross-linking agent used with respect to 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 cross-linking agent, an oxazoline-based cross-linking agent having one or more oxazoline groups in one molecule can be used without particular limitation. The oxazoline-based cross-linking agent may be used alone or in combination of two or more. The oxazoline group may be any of a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group. Usually, an oxazoline-based cross-linking 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 an oxazoline-based cross-linking 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-iso. Examples include propenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of the oxazoline-based cross-linking agent include the cross-linking agent exemplified in Japanese Patent Application Publication No. 2009-001673. Specific examples include compounds containing a main chain consisting of an acrylic skeleton or a styrene skeleton and having an oxazoline group in the side chain of the main chain. Preferable examples include an oxazoline group-containing acrylic polymer containing a main chain composed of an acrylic skeleton and having an oxazoline group in the side chain of the main chain. Commercially available oxazoline-based cross-linking agents include, for example, the trade names "Epocross WS-500", "Epocross WS-700", "Epocross K-2010E", "Epocross K-2020E", and "Epocross K-" manufactured by Nippon Shokubai. 2030E ”and the like.

In the embodiment in which the oxazoline-based cross-linking agent is used, the amount used thereof is not particularly limited. The amount of the oxazoline-based cross-linking agent used can 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 with respect to 100 parts by weight of the acrylic polymer. In some embodiments, the amount of the oxazoline-based cross-linking agent used per 100 parts by weight of the acrylic polymer may be 1 part by weight or more, or 1.5 parts by weight or more. Increasing the amount of oxazoline-based cross-linking agent used tends to make it easier to obtain higher cohesive force. The amount of the oxazoline-based cross-linking agent used can be usually, 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 with respect to 100 parts by weight of the acrylic polymer.

The technique disclosed herein can be preferably carried out in an embodiment in which at least an isocyanate-based cross-linking agent is used as the cross-linking agent. The isocyanate group of the isocyanate-based cross-linking agent can react with a cross-linking reaction point such as an acidic group that can be introduced into the acrylic polymer to construct a cross-linked structure. By this cross-linking reaction, the cohesiveness of the pressure-sensitive adhesive is increased, and the deformation resistance to a continuous load in the Z-axis direction is more preferably exhibited. Examples of such embodiments include an embodiment in which the isocyanate-based cross-linking agent is used alone, and an embodiment in which the isocyanate-based cross-linking agent and another cross-linking agent are used in combination. In one aspect, the pressure-sensitive adhesive composition contains an isocyanate-based cross-linking agent as a cross-linking agent, but substantially does not contain an epoxy-based cross-linking agent. In a 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 cross-linking agent from the viewpoint of improving anchoring property with respect to the base film.

In another aspect, the pressure-sensitive adhesive composition contains an epoxy-based cross-linking agent as a cross-linking agent. The epoxy group of the epoxy-based cross-linking 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 cross-linking agent to construct a cross-linked structure.

In a particularly preferred embodiment, the pressure-sensitive adhesive composition contains both an epoxy-based cross-linking agent and an isocyanate-based cross-linking agent as the cross-linking agent. For example, by using an epoxy-based cross-linking agent and an isocyanate-based cross-linking agent in combination with an acrylic polymer having an acidic group, the deformation resistance to a continuous load in the Z-axis direction can be further improved without impairing the adhesiveness. .. Specifically, it is possible to maintain the deformation resistance in the Z-axis direction for a long period of time even under the strong repulsion high temperature and high humidity conditions as discussed in the examples described later. The ratio of the content _CI of the isocyanate-based cross-linking agent to the content _CE of the epoxy-based cross-linking agent ( _CI / _CE ) is not particularly limited, and deformation resistance to a continuous load in the Z-axis direction can be obtained. Set properly. It is appropriate that the above ratio ( _CI / _CE ) is, for example, larger than 1, and is about 5 or more, preferably about 15 or more, more preferably about 30 or more, still more preferably about 60 or more, and particularly preferably. Is about 80 or more (for example, about 100 or more). Further, the above ratio ( _CI / _CE ) is, for example, about 1000 or less, and it is appropriate that it is about 500 or less, preferably about 200 or less, more preferably about 150 or less, and further preferably about 120 or less. (For example, about 80 or less).

The content of the cross-linking agent (total amount of the cross-linking agent) in the pressure-sensitive adhesive composition disclosed here is not particularly limited. From the viewpoint of cohesiveness, the content of the cross-linking agent is usually about 0.001 part by weight or more with respect to 100 parts by weight of the acrylic polymer, and it is appropriate that the content is about 0.002 part by weight or more. It is preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, still more preferably about 0.02 parts by weight or more, and particularly preferably about 0.03 parts by weight or more. Further, from the viewpoint of avoiding insufficient adhesive strength, the content of the cross-linking agent in the pressure-sensitive adhesive composition is usually about 20 parts by weight or less with respect to 100 parts by weight of the acrylic polymer, and may be about 15 parts by weight or less. It is suitable, and is preferably about 10 parts by weight or less (for example, about 5 parts by weight or less).

(Adhesive-imparting resin)
In a preferred embodiment, the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) comprises a tack-imparting resin. Examples of the pressure-sensitive adhesive resin that can be contained in the pressure-sensitive adhesive composition include a phenol-based pressure-sensitive adhesive resin, a terpene-based pressure-sensitive adhesive resin, a modified terpen-based pressure-sensitive adhesive resin, a rosin-based pressure-sensitive adhesive resin, a hydrocarbon-based pressure-sensitive adhesive resin, and an epoxy-based pressure-sensitive adhesive. One or more selected from various known tackifier resins such as a imparting resin, a polyamide-based tackifier resin, an elastomer-based tackifier resin, and a ketone-based tackifier resin can be used. Adhesive strength is improved by using the adhesive resin.

Examples of phenol-based tackifier resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins and rosinphenolic resins.
The terpene phenolic resin refers to a polymer containing a terpene residue and a phenol residue, and a copolymer of terpene and a phenol compound (terpene-phenole copolymer resin) and terpene or a homopolymer thereof or a copolymer thereof. It is a concept that includes both phenol-modified products (phenol-modified terpene resin). Preferable examples of terpenes constituting such a terpene phenolic resin are monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form, and d / l-form (dipentene)). Can be mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is also called hydrogenated terpene phenolic resin.
The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include novolak type and resol type.
The rosin phenolic resin is typically a phenolic variant of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid modified rosins and unsaturated fatty acid modified rosin esters). Examples of the rosin phenol resin include a rosin phenol resin obtained by adding phenol to rosins or the above-mentioned various rosin derivatives with an acid catalyst and thermally polymerizing the resin.
Among these phenol-based tackifier resins, terpenephenol resins, hydrogenated terpenephenol resins and alkylphenol resins are preferable, terpenephenol resins and hydrogenated terpenephenol resins are more preferable, and terpenephenol resins are particularly preferable.

Examples of terpene-based tackifier resins 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 kind of terpenes or a copolymer of two or more kinds of terpenes. Examples of the homopolymer of one kind of terpenes include α-pinene polymer, β-pinene polymer, dipentene polymer and the like.
Examples of the modified terpene resin include modified terpene resins. Specific examples thereof include styrene-modified terpene resin and hydrogenated terpene resin.

The concept of rosin-based tackifier resin here includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosins, wood rosins, and tall oil rosins; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. (hydrogen-added rosins, non-modified rosins). Normalized rosins, polymerized rosins, other chemically modified rosins, etc.);

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

Examples of hydrocarbon-based tackifier resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.). ), Various hydrocarbon-based resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, kumaron-based resins, and kumaron-inden-based resins.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesive force, a tackifier resin having a softening point (softening temperature) of about 80 ° C. or higher (preferably about 100 ° C. or higher) can be preferably adopted. For example, a phenol-based tackifier resin (terpene phenol resin or the like) having such a softening point can be preferably used. In a preferred embodiment, a terpene phenol resin having a softening point of about 135 ° C. or higher (further, about 140 ° C. or higher) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of adhesion to the adherend and the base film, a tackifier resin having a softening point of about 200 ° C. or lower (more preferably about 180 ° C. or lower) can be preferably used. The softening point of the tackifier resin can be measured based on the softening point test method (ring ball method) specified in JIS K2207.

As a preferred embodiment, there is an embodiment in which the tackifier resin contains one or more phenol-based tackifier resins (for example, terpene phenol resin). The technique disclosed herein can be preferably carried out, for example, in an embodiment in which about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of the tackifier resin is a terpene phenol resin. Approximately 50% by weight or more of the total amount of the tackifier resin may be terpene phenol resin, and approximately 80% by weight or more (for example, approximately 90% by weight or more) may be terpene phenol resin. Substantially all of the tackifier resin (for example, about 95% by weight or more and 100% by weight or less, and further, about 99% by weight or more and 100% by weight or less) may be a terpene phenol resin.

The content of the phenol-based tackifier resin (for example, terpene phenol resin) is not particularly limited as long as it satisfies the desired viscoelastic properties. From the viewpoint of adhesive strength, the content of the phenol-based tackifier resin (for example, terpene phenol resin) is usually about 1 part by weight or more, and may be about 5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. It is suitable, preferably about 8 parts by weight or more (typically 10 parts by weight or more), and more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). Further, from the viewpoint of deformation resistance and the like, it is appropriate that the content of the phenolic tackifier resin is about 45 parts by weight or less with respect to 100 parts by weight of the acrylic polymer, preferably about 35 parts by weight. Hereinafter, it is more preferably about 30 parts by weight or less, still more preferably less than 30 parts by weight (for example, 25 parts by weight or less, typically 20 parts by weight or less).

Although not particularly limited, in one aspect of the technique disclosed herein, the tackifier resin may include a tackifier resin having a hydroxyl value higher than 20 mgKOH / g. Of these, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more is preferable. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more may be referred to as a “high hydroxyl value resin”. According to the tackifier resin containing such a high hydroxyl value resin, a pressure-sensitive adhesive layer having a high cohesive power can be realized by interacting with a cross-linking agent such as an isocyanate-based cross-linking agent in addition to the pressure-sensitive adhesive power. In one embodiment, the tackifier resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH / g or more (more preferably 70 mgKOH / g or more). Further, the high hydroxyl value resin (for example, terpene phenol resin) as described above is preferably used in combination with an acrylic polymer containing C _1-6 alkyl (meth) acrylate as a main monomer, for example, with respect to an adherend. Can exhibit good adhesive strength.

The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer, the hydroxyl value of the high hydroxyl value resin is usually about 300 mgKOH / g or less, and about 200 mgKOH / g or less is suitable, preferably about 180 mgKOH / g or less. It is preferably about 160 mgKOH / g or less, and more preferably about 140 mgKOH / g or less. The technique disclosed herein can be preferably carried out in an embodiment in which the tackifier resin contains a high hydroxyl value resin having a hydroxyl value of 30 to 160 mgKOH / g (for example, a phenol-based tackifier resin, preferably a terpene phenol resin). In one embodiment, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mgKOH / g (for example, 30 to 65 mgKOH / g) can be preferably adopted. In another embodiment, a high hydroxyl value resin having a hydroxyl value of 70 to 140 mgKOH / g can be preferably adopted.

Here, as the value of the hydroxyl value, the value measured by the potentiometric titration method specified in JIS K0070: 1992 can be adopted. The specific measurement method is as shown below.
[Measurement method of hydroxyl value]
1. 1. Reagent (1) As the acetylation reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, pyridine is added thereto to make the total volume 50 mL, and the reagent is sufficiently stirred. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to this to make the total volume 100 mL, and use the one that has been sufficiently stirred.
(2) As a measurement reagent, a 0.5 mol / L potassium hydroxide ethanol solution is used.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. 2. Operation (1) Weigh about 2 g of a sample into a flat-bottomed flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air cooling tube.
(2) The flask is heated in a bath at 100 ° C. for 70 minutes, allowed to cool, 35 mL of toluene is added as a solvent from the upper part of the cooling tube and stirred, and then 1 mL of distilled water is added and stirred to obtain acetic anhydride. Disassemble. Heat again in the bath for 10 minutes to complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Then, 50 mL of pyridine as a solvent is added and stirred.
(4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole 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 used as the end point.
(6) In the blank test, perform the above (1) to (5) without inserting a sample.
3. 3. Calculation Calculate the hydroxyl value by the following formula.
Hydroxy group value (mgKOH / g) = [(BC) x f x 28.05] / S + D
here,
B: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the 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: Sample weight (g),
D: Acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide 56.11,
Is.

As the high hydroxyl value resin, among the various tackifier resins described above, those having a hydroxyl value of a predetermined value or higher can be used. As the high hydroxyl value resin, one type can be used alone or two or more types can be used in combination. For example, as the high hydroxyl value resin, a phenolic tackifier resin having a hydroxyl value of 30 mgKOH / g or more can be preferably adopted. The terpene phenol resin is convenient because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol.

Although not particularly limited, as the tackifier resin in the technique disclosed herein, a tackifier resin having a hydroxyl value of less than 30 mgKOH / g (for example, less than 20 mgKOH / g) can be used. Hereinafter, the tackifier resin having a hydroxyl value of less than 30 mgKOH / g may be referred to as "low hydroxyl value resin". The hydroxyl value of the low hydroxyl value resin may be approximately 15 mgKOH / g or less, or may be 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 value resin (for example, a terpene phenol resin) is preferably used in combination with an acrylic polymer containing C _7-10 alkyl (meth) acrylate as a main monomer, for example, to improve adhesion to an adherend. It can be demonstrated well.

Although not particularly limited, when a high hydroxyl value resin is used, the ratio of the high hydroxyl value resin (for example, terpene phenol resin) to the entire tackifier resin contained in the pressure-sensitive adhesive layer is, for example, about 25% by weight or more. It is preferably about 30% by weight or more, and more preferably about 50% by weight or more (for example, about 80% by weight or more, typically about 90% by weight or more). Substantially all of the tackifier resin (for example, about 95 to 100% by weight, more preferably about 99 to 100% by weight) may be a high hydroxyl value resin.

In the embodiment in which the tackifier resin is used, the content of the tackifier resin is not particularly limited. The content of the tackifier resin is usually 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, and can be about 5 parts by weight or more, and is about 8 parts by weight or more (for example, about 10 parts by weight or more). ) Is appropriate. The technique disclosed herein can be preferably carried out in an embodiment in which the content of the tackifier resin with respect to 100 parts by weight of the acrylic polymer is about 12 parts by weight or more (for example, about 15 parts by weight or more). The upper limit of the content of the tackifying resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer and deformation resistance, it is appropriate that the content of the tackifier resin with respect to 100 parts by weight of the acrylic polymer is about 70 parts by weight or less, preferably about 55 parts by weight or less. More preferably, it is about 45 parts by weight or less (for example, about 40 parts by weight or less, typically about 30 parts by weight or less). In a preferred embodiment, the content of the tackifier resin with respect to 100 parts by weight of the acrylic polymer is less than 30 parts by weight, more preferably about 25 parts by weight or less, still more preferably about 20 parts by weight or less.

((Meta) acrylic oligomer)
In a preferred embodiment, the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) disclosed herein contains a (meth) acrylic oligomer from the viewpoint of improving adhesive strength and the like. The (meth) acrylic oligomer includes Tg of the copolymer corresponding to the composition of the above-mentioned monomer component (typically, Tg of the (meth) acrylic polymer contained in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition. It is preferable to use a polymer having a Tg higher than that of). By containing a (meth) acrylic oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved.

It is desirable that the Tg of the (meth) acrylic oligomer is about 0 ° C. or higher and about 300 ° C. or lower, preferably about 20 ° C. or higher and about 300 ° C. or lower, and more preferably about 40 ° C. or higher and about 300 ° C. or lower. When Tg is within the above range, the adhesive strength can be suitably improved. In a preferred embodiment, the Tg of the (meth) acrylic oligomer is about 30 ° C. or higher, more preferably about 50 ° C. or higher (for example, about 60 ° C. or higher), and adhesiveness from the viewpoint of cohesiveness of the pressure-sensitive adhesive. From the viewpoint of the above, it is preferably about 200 ° C. or lower, more preferably about 150 ° C. or lower, still more preferably about 100 ° C. or lower (for example, about 80 ° C. or lower). The Tg of the (meth) acrylic oligomer is a value calculated based on the Fox formula, like the Tg of the copolymer corresponding to the composition of the above-mentioned monomer component.

The weight average molecular weight (Mw) of the (meth) acrylic oligomer can typically be about 1000 or more and less than about 30,000, preferably about 1500 or more and less than about 20,000, and more preferably about 2,000 or more and less than about 10,000. When Mw is within the above range, good adhesive strength and holding characteristics can be obtained, which is preferable. In a preferred embodiment, the Mw of the (meth) acrylic oligomer is about 2500 or more (for example, about 3000 or more) from the viewpoint of deformation resistance to a continuous load in the Z-axis direction, and is preferable from the viewpoint of adhesiveness. Is about 7000 or less, more preferably about 5000 or less (for example, 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 determined as a value in terms of standard polystyrene. Specifically, the measurement is carried out using TSKgelGMH-H (20) × 2 as a column on HPLC8020 manufactured by Tosoh Co., Ltd. under the condition of a flow rate of about 0.5 ml / min in a tetrahydrofuran solvent.

Examples of the monomers constituting the (meth) acrylic oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth) acrylate. s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) Alkyl (meth) acrylates, isooctyl (meth) acrylates, nonyl (meth) acrylates, isononyl (meth) acrylates, decyl (meth) acrylates, isodecyl (meth) acrylates, undecyl (meth) acrylates, dodecyl (meth) acrylates. Meta) acrylates; esters of (meth) acrylic acids such as cyclohexyl (meth) acrylates, isobornyl (meth) acrylates, and dicyclopentanyl (meth) acrylates with alicyclic alcohols (containing alicyclic hydrocarbon groups (meth)). ) Acrylate); aryl (meth) acrylate such as phenyl (meth) acrylate, benzyl (meth) acrylate; (meth) acrylate obtained from terpene compound derivative alcohol; and the like. Such (meth) acrylates can be used alone or in combination of two or more.

Examples of the (meth) acrylic oligomer include alkyl (meth) acrylates in which an alkyl group has a branched structure such as isobutyl (meth) acrylate and t-butyl (meth) acrylate; cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. Esters of (meth) acrylic acids such as dicyclopentanyl (meth) acrylates with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth) acrylates); of phenyl (meth) acrylates and benzyl (meth) acrylates. The inclusion of an acrylic monomer having a relatively bulky structure as a monomer unit, typified by a (meth) acrylate having a cyclic structure such as an aryl (meth) acrylate, further enhances the adhesiveness of the pressure-sensitive adhesive layer. It is preferable from the viewpoint that it can be improved. Further, when ultraviolet rays are used in the synthesis of the (meth) acrylic oligomer or in the preparation of the pressure-sensitive adhesive layer, those having a saturated bond are preferable in that polymerization inhibition is unlikely to occur, and the alkyl group is branched. An alkyl (meth) acrylate having a structure or an ester with an alicyclic alcohol (an alicyclic hydrocarbon group-containing (meth) acrylate) can be suitably used as a monomer constituting a (meth) acrylic oligomer. The above-mentioned branched chain alkyl (meth) acrylate, alicyclic hydrocarbon group (meth) acrylate, and aryl (meth) acrylate all correspond to the (meth) acrylate monomer in the technique disclosed herein. The alicyclic hydrocarbon group can be a saturated or unsaturated alicyclic hydrocarbon group.

The ratio of the (meth) acrylate monomer (for example, the alicyclic hydrocarbon group-containing (meth) acrylate) to all the monomer components constituting the (meth) acrylic oligomer is typically more than 50% by weight, preferably more than 50% by weight. Is 60% by weight or more, more preferably 70% by weight or more (for example, 80% by weight or more, further 90% by weight or more). In a preferred embodiment, the (meth) acrylic oligomer has a monomer composition consisting substantially only of the (meth) acrylate monomer.

As the constituent monomer component of the (meth) acrylic oligomer, a functional group-containing monomer can be used in addition to the above (meth) acrylate monomer. Preferable examples of the functional group-containing monomer are monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholin; N, N-dimethylamino. Amino group-containing monomer such as ethyl (meth) acrylate; Amide group-containing monomer such as N, N-diethyl (meth) acrylamide; carboxyl group-containing monomer such as AA and MAA; hydroxyl group-containing such as 2-hydroxyethyl (meth) acrylate Monomer; These functional group-containing monomers may be used alone or in combination of two or more. Of these, a carboxyl group-containing monomer is preferable, and AA is particularly preferable.

When all the monomer components constituting the (meth) acrylic oligomer contain a functional group-containing monomer, the ratio of the functional group-containing monomer (for example, a carboxyl group-containing monomer such as AA) to the total monomer component is approximately 1% by weight. The above is appropriate, preferably 2% by weight or more, more preferably 3% by weight or more, and about 15% by weight or less, preferably 10% by weight or less, more preferably. It is 7% by weight or less.

The (meth) acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization and the like) can be adopted in an appropriate manner. The types of polymerization initiators (for example, azo-based polymerization initiators such as AIBN) that can be used as needed are generally as exemplified in the synthesis of acrylic polymers, and the amount of the polymerization initiator and arbitrarily used. Since the amount of the chain transfer agent such as n-dodecyl mercaptan is appropriately set based on the common technical knowledge so as to have a desired molecular weight, detailed description thereof will be omitted here.

From the above viewpoint, suitable (meth) acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), and di. In addition to each homopolymer of cyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADAM), 1-adamantyl acrylate (ADA), a copolymer of CHMA and isobutyl methacrylate (IBMA), and a combination of CHMA and IBXMA. Polymers, polymers of CHMA and acryloylmorpholin (ACMO), polymers of CHMA and diethylacrylamide (DEAA), polymers of CHMA and AA, polymers of ADA and methylmethacrylate (MMA), Examples thereof include a polymer of DCPMA and IBXMA, a polymer of DCPMA and MMA, and the like.

When the pressure-sensitive adhesive composition disclosed herein contains a (meth) acrylic oligomer, the content thereof is, for example, 0.1 part by weight or more (for example, 1 part by weight or more) with respect to 100 parts by weight of the acrylic polymer. It is appropriate to do. From the viewpoint of better exerting the effect of the (meth) acrylic oligomer, 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, and further preferably about about 8 parts by weight. It is 10 parts by weight or more, particularly preferably about 12 parts by weight or more. Further, from the viewpoint of compatibility with the acrylic polymer, the content of the (meth) acrylic oligomer is preferably less than 50 parts by weight (for example, less than 40 parts by weight), preferably 30 parts by weight. Less than, more preferably about 25 parts by weight or less, still more preferably about 20 parts by weight or less.

In a preferred embodiment, the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) comprises one or more of the above-mentioned tack-imparting resins and one or more of the (meth) acrylic oligomers. In a composition containing a high molecular weight acrylic polymer, by using a tackifier resin and a (meth) acrylic oligomer in combination, an embodiment of use that is exposed to harsh conditions such as strong repulsion while obtaining excellent initial adhesiveness. Also, it can exhibit highly excellent deformation resistance against a continuous load in the Z-axis direction. The ratio ( _CT / _CO ) of the content _CT [% by weight] of the tackifier resin to the content _CO [% by weight] of the (meth) acrylic oligomer in the pressure-sensitive adhesive layer is not particularly limited. The above ( _CT / _CO ) is appropriately set to, 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, and further preferably 0.7. It is 1.5 or less.

The total amount (total amount) of the tackifier resin and the (meth) acrylic oligomer contained in the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) according to a preferred embodiment is from the viewpoint of preferably exerting the effect of the technique disclosed herein. It is appropriate that the amount is about 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, still more preferably 20 parts by weight or more, and particularly preferably. Is 25 parts by weight or more, and it is appropriate that it is 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. It is less than the weight part.

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

Here, the "azole compound" in the present specification refers to a five-membered ring aromatic compound containing one or more heteroatoms, in which at least one of the heteroatoms is a nitrogen atom. .. As an example of an azole compound that can be suitably used in the techniques disclosed herein, a five-membered ring aromatic compound containing two or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom. Can be mentioned.

The reason why such an azole compound exhibits excellent deformation resistance against a continuous load in the Z-axis direction is not particularly limited, but for example, the following reasons can be considered. .. Azole compounds contain nitrogen atoms with unpaired electrons. When the pressure-sensitive adhesive layer contains an azole compound, the unpaired electrons contained in the nitrogen atom contained in the azole compound electrically interact with each other on the surface of the adherend (which may be a metal, a resin, etc.). This improves the adhesive performance at the interface between the adhesive sheet and the adherend. It is considered that the deformation resistance of the adhesive sheet to a continuous load in the Z-axis direction is improved through such improvement of the adhesive performance.

Examples of azole compounds that can be suitably used in the techniques disclosed herein include imidazole, pyrazole, oxazole, isooxazole, thiadiazole, 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, 1,3,4-thiadiazole, tetrazole, 1, Examples thereof include azoles such as 2,3,4-thiatriazole; derivatives thereof; amine salts thereof; metal salts thereof; and the like. Examples of derivatives of azoles include compounds having a structure containing a fused ring of an azole ring and another ring, for example, a benzene ring. Specific examples include indazole, benzoimidazole, benzotriazole (that is, 1,2,3-benzotriazole having a structure in which the azole ring and benzene ring of 1,2,3-triazole are condensed), benzothiazole and the like, and Further, these derivatives are alkylbenzotriazole (eg, 5-methylbenzotriazole, 5-ethylbenzotriazole, 5-n-propylbenzotriazole, 5-isobutylbenzotriazole, 4-methylbenzotriazole), alkoxybenzotriazole (eg, 5-methylbenzotriazole). 5-methoxybenzotriazole), alkylaminobenzotriazole, alkylaminosulfonylbenzotriazole, mercaptobenzotriazole, hydroxybenzotriazole, nitrobenzotriazole (eg 4-nitrobenzotriazole), halobenzotriazole (eg 5-chlorobenzotriazole), Hydroxyalkylbenzotriazole, hydrobenzotriazole, aminobenzotriazole, (substituted aminomethyl) -tolyltriazole, carboxybenzotriazole, N-alkylbenzotriazole, bisbenzotriazole, naphthotriazole, mercaptobenzothiazole, aminobenzothiazole, etc. Examples thereof include amine salts and metal salts thereof. As another example of the azole derivative, an azole derivative having a non-condensed ring structure, for example, on a non-condensed azole ring such as 3-amino-1,2,4-triazole, 5-phenyl-1H-tetrazole, etc. Examples thereof include compounds having a structure having a substituent. As the azole compound, one kind may be used alone or two or more kinds may be used in combination.

In a preferred embodiment, the pressure-sensitive adhesive layer contains a triazole-based compound as an azole-based compound. Here, the "triazole-based compound" as used herein refers to a five-membered ring aromatic compound containing three or more heteroatoms, in which three 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 deformation resistance can be exhibited with respect to a continuous load in the Z-axis direction.

A preferred embodiment of such a triazole-based compound is a triazole-based compound having a non-condensation ring structure. Examples of the triazole-based compound having a non-condensation ring structure include compounds having a structure represented by the following formula (2a) or (2b).

Here, in the above formulas (2a) and (2b), R ³ is a substituent on a hydrogen atom or an azole ring, for example, an alkyl group having 1 to 6 carbon atoms and an alkoxy having 1 to 6 carbon atoms. Group, aryl group with 6 to 14 carbon atoms, carboxy group, carboxyalkyl group with 2 to 6 carbon atoms, amino group, mono or di-C _1-10 alkylamino group, amino-C _1-6 alkyl group, It can be selected from substituents such as mono or di-C _1-10 alkylamino-C _1-6 alkyl groups, mercapto groups, alkoxycarbonyl groups with 1-6 carbon atoms, and the like. ^R4 in the above formulas (2a) and (2b) is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, and a mono. Or di-carboxy-C _1-6 alkyl group, amino group, mono or di-C _1-10 alkyl amino group, amino-C _1-6 alkyl group, mono or di-C _1-10 alkyl amino-C _1- It can be selected from substituents such as ₆ alkyl groups, mercapto groups, alkoxycarbonyl groups having 1 to 12 carbon atoms, and the like. R ³ and R ⁴ may be the same or different. Preferable examples of the triazole-based compound represented by the formula (2a) include 1,2,3-triazole. Moreover, 1,2,4-triazole is mentioned as a preferable example of the triazole-based compound represented by the formula (2b). Of these, 1,2,4-triazole is preferable.

Further, as another preferable example of the above-mentioned triazole-based compound, a benzotriazole-based compound can be mentioned. The benzotriazole-based compound is not particularly limited as long as it is a compound having a benzotriazole skeleton, but having a structure represented by the following formula (3) is from the viewpoint that more excellent deformation resistance can be obtained. preferable.

Here, in the above formula (3), R ⁵ is a substituent on a hydrogen atom or a benzene ring, for example, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a carbon atom number. 6-14 aryl groups, carboxy groups, carboxyalkyl groups with 2-6 carbon atoms, amino groups, mono or di-C _1-10 alkyl amino groups, amino-C _1-6 alkyl groups, mono or di-C It can be selected from substituents such as _1-10 alkylamino-C _1-6 alkyl groups, mercapto groups, alkoxycarbonyl groups with 1-6 carbon atoms, and the like. When n in the above formula (3) is an integer of 0 to 4, and n is 2 or more, the n ^R5s contained in the above formula (3) may be the same or different from each other. May be good. R ⁶ in the above formula (3) is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 14 carbon atoms, a mono or di-carboxy-. C _1-6 Alkyl Group, Amino Group, Mono or Di-C _1-10 Alkyl Amino Group, Amino-C _1-6 Alkyl Group, Mono or Di-C _1-10 Alkyl Amino-C _1-6 Alkyl Group, Alkoxy It can be selected from substituents such as groups, alkoxycarbonyl groups with 1-12 carbon atoms, and the like. R ⁵ and R ⁶ may be the same or different. Preferable examples of the benzotriazole-based compound represented by the formula (3) are 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, 1- (1', 2'-dicarboxyethyl). Examples thereof include benzotriazole.

The content of the azole compound (for example, triazole compound) (when a plurality of kinds of azole compounds are used in combination, the total amount) is not particularly limited, and is, for example, 0.01 part by weight with respect to 100 parts by weight of the base polymer. The above (typically 0.05 parts by weight or more) can be obtained. From the viewpoint of obtaining better deformation resistance, the content of the azole compound with respect to 100 parts by weight of the base polymer is preferably 0.1 part by weight or more, and may be 0.3 part by weight or more, and is 0. It may be 0.5 parts by weight or more, 0.6 parts by weight or more, or 0.7 parts by weight or more. On the other hand, from the viewpoint of increasing the cohesive force (for example, heat-resistant cohesive force) of the pressure-sensitive adhesive, it is usually appropriate that the content of the azole compound is 10 parts by weight or less with respect to 100 parts by weight of the base polymer, and 8 weight by weight. It may be less than 6 parts by weight, less than 6 parts by weight, or less than 5 parts by weight.

(Other additives)
In addition to the above-mentioned components, the pressure-sensitive adhesive composition includes a leveling agent, a cross-linking aid, a plasticizer, a softener, an antistatic agent, an antioxidant, an ultraviolet absorber, an antioxidant, and a light stabilizer, if necessary. Various additives that are common in the field of adhesives such as these may be contained. As for such various additives, conventionally known additives can be used by a conventional method and do not particularly characterize the present invention, and therefore detailed description thereof will be omitted.

The pressure-sensitive adhesive layer disclosed here can be formed by a conventionally known method. For example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to a non-peelable base material and drying or curing the pressure-sensitive adhesive composition can be adopted. Further, by applying a pressure-sensitive adhesive composition to a peelable surface (peeling surface) and drying or curing the pressure-sensitive adhesive layer to form a pressure-sensitive adhesive layer on the surface, a base-less adhesive consisting of only the pressure-sensitive adhesive layer can be adhered. Sheets can be made. Further, a method (transfer method) of transferring the pressure-sensitive adhesive layer formed on the peeled surface to a non-peeling substrate may be adopted. As the peeling surface, the surface of the peeling liner, the back surface of the base material that has been peeled off, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may have a regular or random pattern such as a dot shape or a striped shape. It may be a formed pressure-sensitive adhesive layer.

As a method for applying the pressure-sensitive adhesive composition, various conventionally known methods can be used. Specifically, for example, 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 coater, etc. Examples include the extrusion coating method.

In one aspect of the technique disclosed herein, it is preferable to dry the pressure-sensitive adhesive composition under heating from the viewpoint of promoting the crosslinking reaction, improving the production efficiency, and the like. The drying temperature can be, for example, about 40 to 150 ° C., and is usually preferably about 60 to 130 ° C. After the pressure-sensitive adhesive composition is dried, further aging is performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, advancing the cross-linking reaction, alleviating the strain that may exist in the base film or the pressure-sensitive adhesive layer, and the like. May be good.

In another aspect, in the pressure-sensitive adhesive sheet disclosed herein, the surface obtained by drying or curing the liquid film of the pressure-sensitive adhesive composition on the peel-off surface of the release film and curing on the peel-off surface is the first pressure-sensitive adhesive surface. It can be suitably produced by a method including forming a pressure-sensitive adhesive layer. According to this method, when the pressure-sensitive adhesive composition (liquid film) in a fluid state is in contact with the peeled surface and dried or cured, the smoothness of the surface of the pressure-sensitive adhesive layer formed in contact with the peeled surface is improved. It can be controlled with high accuracy. For example, by using a release film having a release surface having appropriate smoothness, it is possible to stably (with good reproducibility) produce a first adhesive surface having desired smoothness.

The pressure-sensitive adhesive sheet disclosed herein can be preferably produced by a method including forming a pressure-sensitive adhesive layer by drying or curing a liquid film of the pressure-sensitive adhesive composition between the peeling surfaces of a pair of release films. This method is suitable as a method for producing a base material-less double-sided pressure-sensitive adhesive sheet. Further, by adhering the base material-less double-sided pressure-sensitive adhesive sheet thus obtained to the non-peeling surface of the supporting base material, it can be preferably applied to the production of a single-sided pressure-sensitive adhesive sheet with a base material and a double-sided pressure-sensitive adhesive sheet with a base material. .. As a method of arranging the liquid film of the pressure-sensitive adhesive composition between the peel-off surfaces of the pair of release films, a liquid pressure-sensitive adhesive composition is applied to the peel-off surfaces of the first release film, and then the liquid of the pressure-sensitive adhesive composition is applied. A method of covering the film with the second release film can be adopted. As another method, a first release film and a second release film are supplied between a pair of rolls with the release surfaces facing each other, and a liquid pressure-sensitive adhesive composition is supplied between the release surfaces. Can be mentioned.

The thickness of the adhesive layer is not particularly limited. The thickness of the pressure-sensitive adhesive layer is usually preferably 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 a preferred embodiment, the thickness of the pressure-sensitive adhesive layer is about 70 μm or less (usually 60 μm or less), and may be, for example, about 50 μm or less, or about 40 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesiveness and adherend followability, it is advantageous to set it to about 3 μm or more, preferably about 6 μm or more, and more preferably about 10 μm or more. (For example, 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 carried out, for example, in the form of a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer having a thickness of about 10 μm or more and about 150 μm or less (preferably about 15 μm or more and about 50 μm or less). A preferred example is a base-less double-sided adhesive pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer having the above-mentioned thickness.

(Gel fraction)
Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein can be, for example, 20% or more on a weight basis, and usually 30% or more is appropriate, 35. % Or more is preferable. By increasing the gel fraction of the pressure-sensitive adhesive layer in an appropriate range, it tends to be easy to obtain deformation resistance against a continuous load in the Z-axis direction. 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, and particularly preferably 48% or more. The gel fraction may be, for example, 50% or more. On the other hand, if the gel fraction is too high, the initial adhesiveness may tend to be 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, still more preferably 70% or less (for example, 65% or less).

Here, the "gel fraction of the pressure-sensitive adhesive layer" means a value measured by the following method. The gel fraction can be grasped as the weight ratio of the ethyl acetate insoluble content in the pressure-sensitive adhesive layer.
[Gel fraction measurement method]
About 0.1 g of the pressure-sensitive adhesive sample (weight Wg ₁ ) is wrapped in a porous polytetrafluoroethylene film (weight Wg ₂ ) having an average pore diameter of 0.2 μm in a purse-like shape, and the mouth is tied with octopus thread (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) film, the trade name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Co., Ltd. or its equivalent. Use the item.
This package is immersed in 50 mL of ethyl acetate and held at room temperature (typically 23 ° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer out of the film, and then the package is taken out and placed on the outer surface. The attached ethyl acetate is wiped off, the package is dried at 130 ° C. for 2 hours, and the weight of the package (Wg ₄ ) is measured. The gel fraction _FG of the pressure-sensitive adhesive layer can be obtained by substituting each value into the following equation. The same method is adopted in the examples described later.
Gel fraction _FG (%) = [(Wg ₄ -Wg ₂ -Wg ₃ ) / Wg ₁ ] x 100

(Viscoelastic property)
The storage elastic 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 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 attached to the 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 preferably 1.0 MPa or less, and is preferably 0.6 MPa or less, more preferably 0, from the viewpoint of achieving both initial adhesiveness and deformation resistance. It is 0.4 MPa or less, more preferably 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, the loss elastic 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, still more preferably 0.5 MPa or less. The G" (25 ° C.) is 0.3 MPa or less (for example, 0). It may be .25 MPa or less). The G "(25 ° C.) is usually preferably 0.01 MPa or more, and is preferably 0.05 MPa or more from the viewpoint of wettability to the surface of the adherend, and eventually initial adhesiveness. It is more preferably 0.1 MPa or more, further preferably 0.2 MPa or more, and may be, for example, 0.25 MPa or more.

Further, the tan δ (25 ° C.) of the pressure-sensitive adhesive layer disclosed here at 25 ° C. may be appropriately set in consideration of the initial adhesiveness and deformation resistance at room temperature, and is not particularly limited. Here, the tan δ (tangent loss) of the pressure-sensitive adhesive (layer) means the ratio of the loss elastic modulus G ″ to the storage elastic modulus G ′ of the pressure-sensitive adhesive (layer), that is, tan δ = G ″ / G ′. be. It is appropriate that tan δ (25 ° C.) is, 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, and further preferably about 0. It is 0.8 or more, particularly preferably about 0.9 or more (for example, about 1 or more). Further, the tan δ (25 ° C.) is suitable, for example, about 3 or less, preferably about 2 or less, more preferably about 1.5 or less, and further preferably about 1.2 or less from the viewpoint of initial adhesiveness. ..

The storage elastic modulus G'(85 ° C.) of the pressure-sensitive adhesive layer disclosed here at 85 ° C. is not particularly limited. In a preferred embodiment, the G'(85 ° C.) is 0.02 MPa or higher. By having the above G'(85 ° C.), continuous deformation resistance can be preferably obtained. Specifically, the G'(85 ° C.) can be 0.022 MPa 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 about 0.03 MPa or more (for example, 0.035 MPa or more), particularly preferably 0.04 MPa or more, still more preferably 0.045 MPa or more. Further, the G'(85 ° C.) is usually preferably 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The G'(85 ° C.) may be 0.06 MPa or less.

Further, the loss elastic modulus G "(85 ° C.) of the pressure-sensitive adhesive layer disclosed herein at 85 ° C. 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, still more preferably 0.05 MPa or less. The G ″ (85 ° C.) is 0.03 MPa or less (for example, 0). It may be .02 MPa or less). The G "(85 ° C.) is usually preferably 0.001 MPa or more, and is preferably 0.002 MPa or more, more preferably 0.005 MPa or more, still more preferably 0.005 MPa or more from the viewpoint of adhesiveness or the like. It is 0.008 MPa or more, and may be, for example, 0.01 MPa or more.

Further, the tan δ (85 ° C.) of the pressure-sensitive adhesive layer disclosed here at 85 ° C. may be appropriately set in consideration of sustained deformation resistance, and is not particularly limited. It is appropriate that the tan δ (85 ° C.) is, for example, about 0.1 or more, preferably about 0.12 or more, more preferably 0.15 or more, still more preferably 0.2 or more (for example, 0.22 or more). ). Further, the tan δ (85 ° C.) is preferably, for example, about 2 or less, preferably about 1 or less, and more preferably about 0.5 or less (for example, about 0.3 or less).

The pressure-sensitive adhesive layer disclosed here preferably has a storage elastic modulus G'(apply) of 0.6 MPa or less at the temperature (crimping temperature) when the pressure-sensitive adhesive sheet is pressure-bonded to the adherend. The pressure-sensitive adhesive having G'(apply) can wet well on the surface of the adherend and exhibit excellent initial adhesiveness. The G'(apply) is more preferably 0.4 MPa or less, further preferably 0.35 MPa or less, 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 achieving both initial adhesiveness and deformation resistance, it is appropriate that the G'(apply) is larger than 0.12 MPa, preferably 0.15 MPa or more, and more preferably 0.17 MPa or more. (For example, 0.2 MPa or more), more preferably 0.25 MPa or more, and for example, 0.3 MPa or more may be used. The crimping temperature is selected from a range of more than 0 ° C. and less than 60 ° C. from the viewpoint of crimping workability, temperature control, and the like. In the case of an adhesive sheet used for portable electronic devices, the crimping temperature is selected from the range of 20 ° C to 45 ° C (typically 25 ° C or 40 ° C, preferably 25 ° C) due to the temperature limitation in the application. It is desirable to do. The thermocompression bonding in the above temperature range is different from the conventional thermocompression bonding performed at about 100 ° C., and is a thermocompression bonding applicable to electronic devices and the like.

In the techniques disclosed herein, the storage elastic modulus of the pressure-sensitive adhesive layer is G'(25 ° C.), G'(85 ° C.), G'(apply), loss elastic modulus G "(25 ° C.), G" (85 ° C.). ), Tanδ (25 ° C.) and tanδ (85 ° C.) can be determined by dynamic viscoelasticity measurement. Specifically, a pressure-sensitive adhesive layer having a thickness of about 2 mm is produced by stacking a plurality of pressure-sensitive adhesive layers (adhesive sheets in the case of a base material-less pressure-sensitive adhesive sheet) to be measured. This adhesive layer was punched into a disk shape with a diameter of 7.9 mm, and the sample was sandwiched between parallel plates to fix it. Dynamic viscoelasticity measurement was performed under the conditions of, storage elastic modulus G'(25 ° C), G'(85 ° C), G'(apply), loss elastic modulus G "(25 ° C), G" (85 ° C). , Tan δ (25 ° C) and tan δ (85 ° C).
-Measurement mode: Shear mode-Temperature range: -70 ° C to 150 ° C
・ Temperature rise rate: 5 ° C / min
・ Measurement frequency: 1Hz
Also in the examples described later, the measurement is performed by the above method. The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in a layered manner and drying or curing the pressure-sensitive adhesive layer.

<Base material>
In the embodiment in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive type or double-sided pressure-sensitive adhesive sheet with a base material, the base material for supporting (lining) the pressure-sensitive adhesive layer is a resin film or a foam film (foaming). Body base material), paper, cloth, metal foil, composites thereof and the like can be used.

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

As the base film, a base film containing a resin film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The substrate film in the techniques disclosed herein may be substantially composed of 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, a colored layer and the like provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (a component contained in the resin film in an amount of more than 50% by weight). Examples of resin films include polyethylene (PE), polypropylene (PP), ethylene / propylene copolymer and other polyolefin resin films; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and the like. Polyethylene resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; cellophane; and the like. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, a polyester film is preferable from the viewpoint of handleability and processability, and a PET film is particularly preferable. In the present specification, the "resin film" is typically a non-porous sheet, and is a concept that is distinguished from so-called non-woven fabrics and woven fabrics (in other words, a concept excluding non-woven fabrics and woven fabrics). be.

The resin film may have a single-layer structure or may have a multi-layer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film preferably has a single-layer structure. In the case of a multi-layer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above resin (for example, a polyester resin). The method for producing the resin film may appropriately adopt a conventionally known method, and is not particularly limited. For example, conventionally known general film molding methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding can be appropriately adopted.

In another aspect, paper, cloth, or metal is used as the base material. Examples of paper that can be used as the base film include Japanese paper, kraft paper, glassin paper, high-quality paper, synthetic paper, top-coated paper and the like. Examples of the cloth include woven cloths and non-woven fabrics made by spinning various fibrous substances alone or by blending them. Examples of the fibrous material include cotton, sufu, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber and the like. Examples of the metal foil that can be used for the base film include aluminum foil, copper foil, and the like.

The non-woven fabric referred to here is a concept that mainly refers to a non-woven fabric for an adhesive sheet used in the field of adhesive tape and other adhesive sheets, and is typically a non-woven fabric produced by using a general paper machine. (Sometimes called "paper"). Further, the resin film referred to here is typically a non-porous resin sheet, and is a concept that is distinguished from, for example, a non-woven fabric (that is, does not include a non-woven fabric). The resin film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film. Further, the surface of the base material on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as application of an undercoat agent, corona discharge treatment, and plasma treatment.

The resin film (for example, PET film) may contain a filler (inorganic filler, organic filler, etc.), a colorant, a dispersant (surfactant, etc.), an antistatic agent, an antioxidant, an ultraviolet ray, if necessary. Various additives such as absorbents, antistatic agents, lubricants, and plasticizers may be blended. The blending ratio of the various additives is usually about less than about 30% by weight (for example, less than about 20% by weight, preferably less than about 10% by weight).

The surface of the base film may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat agent. Such a 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 on the base film.

The thickness of the base film disclosed here is not particularly limited. From the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the base film (for example, the resin film) can be, for example, about 200 μm or less, preferably about 150 μm or less, and more preferably about 100 μm or less. Depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the base film may be about 70 μm or less, about 50 μm or less, or about 30 μm or less (for example, about 25 μm or less). In one embodiment, the thickness of the base film may be about 20 μm or less, about 15 μm or less, or about 10 μm or less (for example, about 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 if the total thickness of the pressure-sensitive adhesive sheets is the same. This can be advantageous from the viewpoint of improving the adhesion to the base material. The lower limit of the thickness of the base film is not particularly limited. From the viewpoint of handleability (handleability) and processability of the pressure-sensitive adhesive sheet, the thickness of the base film is usually about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example, about 4 μm or more. .. In one embodiment, the thickness of the base film can be about 6 μm or more, may be about 8 μm or more, or may be about 10 μm or more (for example, more than 10 μm).

<Foam base material>
In another preferred embodiment, a foam substrate is used as the substrate. The foam base material disclosed herein is a base material provided with a portion having bubbles (bubble structure), and is typically a base material containing at least one layered foam (foam layer). be. The foam base material may be a base material composed of one layer or two or more foam layers. The foam base material may be, for example, a base material substantially composed of only one layer or two or more foam layers. Although not particularly limited, a preferable example of the foam base material in the technique disclosed herein is a foam base material composed of a single layer (one layer) of the foam base material.

The thickness of the foam base material is not particularly limited, and can be appropriately set according to the strength and flexibility of the adhesive sheet, the purpose of use, and the like. From the viewpoint of thinning, the thickness of the foam base material is usually 1 mm or less, 0.70 mm or less is appropriate, 0.40 mm or less is preferable, and 0.30 mm or less is more preferable. The technique disclosed herein is preferably carried out in an embodiment in which the thickness of the foam base material 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. obtain. Further, from the viewpoint of impact resistance of the pressure-sensitive adhesive sheet, the thickness of the foam base material is usually 0.04 mm or more, preferably 0.05 mm or more, preferably 0.06 mm or more, and preferably 0.07 mm. The above (for example, 0.08 mm or more) is more preferable. The technique disclosed herein is preferably carried out in an embodiment in which the thickness of the foam substrate is 0.10 mm or more (typically, more than 0.10 mm, preferably 0.12 mm or more, for example, 0.13 mm or more). obtain. As the thickness of the foam base material increases, the impact resistance tends to be improved.

The density of the foam base material (referred to as an apparent density; hereinafter the same unless otherwise specified) 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 base material is preferably 0.8 g / cm ³ or less, preferably 0.7 g / cm ³ or less (for example, 0.6 g / cm ³ or less). In one embodiment, 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). From the viewpoint of impact resistance, the density of the foam base material is preferably 0.12 g / cm ³ or more, more preferably 0.15 g / cm ³ or more, and 0.2 g / cm ³ or more (for example, 0.3 g). / Cm ³ or more) is more preferable. In one embodiment, the density of the foam substrate may be 0.4 g / cm ³ or higher, 0.5 g / cm ³ or higher (eg, more than 0.5 g / cm ³ ), and even 0. It may be .55 g / cm ³ or more. The density (apparent density) of the foam base material can be measured according to JIS K 6767.

The average bubble diameter of the foam base material is not particularly limited, but from the viewpoint of stress distribution, it is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less. The lower limit of the average bubble diameter is not particularly limited, but from the viewpoint of step followability, 10 μm or more is usually suitable, 20 μm or more is preferable, 30 μm or more is more preferable, and 40 μm or more (for example, 50 μm or more) is further preferable. In one embodiment, the average bubble diameter may be 55 μm or more, and may be 60 μm or more. The average bubble diameter referred to here is a true sphere-equivalent average bubble diameter obtained by observing the cross section of the foam substrate with an electron microscope.

The bubble structure of the foam constituting the foam base material disclosed here is not particularly limited. The bubble structure may be any of an open cell structure, a closed cell structure, and a semi-continuous semi-closed cell structure. From the viewpoint of shock absorption, 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, further 40 kPa or more). Usually, 250 kPa or more is suitable for C ₂₅ , and 300 kPa or more (for example, 400 kPa or more) is preferable. The pressure-sensitive adhesive sheet provided with such a foam base material can exhibit good durability against impacts such as dropping. For example, tearing of the 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 (for example, 1200 kPa or less) is appropriate. In one embodiment, C ₂₅ may be 1000 kPa or less, 800 kPa or less, further 600 kPa or less (for example, 500 kPa or less), or 360 kPa or less. In another preferred embodiment, the foam substrate C ₂₅ can be 20 kPa to 200 kPa (typically 30 kPa to 150 kPa, for example 40 kPa to 120 kPa). The pressure-sensitive adhesive sheet provided with such a foam base material can have excellent cushioning properties. For example, the foam base material absorbs the drop impact, so that the peeling of the adhesive sheet can be better prevented.

The 25% compressive strength C ₂₅ of the foam base material is obtained by sandwiching a measurement sample having a thickness of about 2 mm by stacking the foam base material cut into a square shape of 30 mm square between a pair of flat plates. It refers to the load when compressed by the thickness corresponding to 25% of the thickness (load at a compressive strength of 25%). That is, it refers to the load when the measurement sample is compressed to a thickness corresponding to 75% of the initial thickness. The compressive strength is measured according to JIS K 6767. As a specific measurement procedure, the measurement sample is set in 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 for 10 seconds. Measure the load after the lapse. The compressive strength of the foam base material can be controlled, for example, by the degree of cross-linking and density of the material constituting the foam base material, the size and shape of bubbles, and the like.

The tensile elongation of the foam base material is not particularly limited. For example, a foam base material having a tensile elongation in the flow direction (MD) of 200% to 800% (more preferably 400% to 600%) can be preferably adopted. Further, a foam base material having a tensile elongation in the width direction (TD) of 50% to 800% (more preferably 200% to 500%) is preferable. The elongation of the foam base material is measured according to JIS K 6767. The elongation of the foam base material can be controlled by, for example, the degree of cross-linking, the apparent density (foaming ratio), and the like.

The tensile strength (tensile strength) of the foam base material is not particularly limited. For example, a foam base material having a tensile strength in the flow direction (MD) of 5 MPa to 35 MPa (preferably 10 MPa to 30 MPa) can be preferably adopted. Further, a foam base material having a tensile strength in the width direction (TD) of 1 MPa to 25 MPa (more preferably 5 MPa to 20 MPa) is preferable. The tensile strength of the foam base material is measured according to JIS K 6767. The tensile strength of the foam base material can be controlled, for example, by the degree of cross-linking, the apparent density (foaming ratio), and the like.

The material of the foam base material is not particularly limited. Usually, a foam base material containing a foam layer formed of a foam (plastic foam) of a plastic material is preferable. The plastic material for forming the plastic foam (meaning including the rubber material) is not particularly limited, and can be appropriately selected from known plastic materials. As the plastic material, one kind may be used alone or two or more kinds may be used in combination as appropriate.

Specific examples of the plastic foam include polyolefin resin foams such as PE foams and PP foams; polyester resin foams such as PET foams, PEN foams, and PBT foams; Polyvinyl chloride resin foam such as polyvinyl chloride resin; vinyl acetate resin foam; polyphenylene sulfide resin foam; aliphatic polyamide (nylon) resin foam, total aromatic polyamide (aramid) Amid-based resin foams such as resin foams; polyimide-based resin foams; polyetheretherketone (PEEK) foams; styrene-based resin foams such as polystyrene foams; polyurethane resin foams, etc. Urethane-based resin foam; and the like. Further, as the plastic foam, a rubber-based resin foam such as a polychloroprene rubber foam may be used.

As a preferable foam, a polyolefin-based resin foam (hereinafter, also referred to as “polyolefin-based foam”) is exemplified. As the plastic material (that is, the polyolefin-based resin) constituting the polyolefin-based foam, various known or commonly used polyolefin-based resins can be used without particular limitation. For example, PE such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), PP, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and the like can be mentioned. Examples of LLDPE include Ziegler-Natta catalytic linear low density polyethylene, metallocene catalytic linear low density polyethylene and the like. As such a polyolefin resin, one kind may be used alone or two or more kinds may be used in combination as appropriate.

As a preferable example of the foam base material in the technique disclosed herein, a PE-based foam base material substantially composed of a foam of a PE-based resin is used from the viewpoint of impact resistance, waterproofness, dust resistance, and the like. , Polyolefin-based foam base material such as PP-based foam base material substantially composed of foam of PP-based resin. Here, the PE-based resin refers to a resin containing ethylene as a main monomer (that is, the main component of the monomer), and in addition to HDPE, LDPE, LLDPE, etc., ethylene in which the copolymerization ratio of ethylene exceeds 50% by weight- It may include a propylene copolymer, an ethylene-vinyl acetate copolymer and the like. Similarly, the PP-based resin refers to a resin containing propylene as a main monomer. As the foam base material in the technique disclosed herein, a PE-based foam base material can be preferably adopted.

The method for producing the plastic foam (typically, a polyolefin-based foam) is not particularly limited, and various known methods can be appropriately adopted. For example, it can be produced by a method including the above-mentioned plastic material or the above-mentioned plastic foam molding step, cross-linking step and foaming step. In addition, a stretching step may be included if necessary.
Examples of the method for cross-linking the plastic foam include a chemical cross-linking method using an organic peroxide or the like, an ionizing radiation cross-linking method for irradiating ionizing radiation, and the like, and these methods can be used in combination. Examples of the ionizing radiation include electron beams, α rays, β rays, γ rays and the like. The dose of ionizing radiation is not particularly limited, and an appropriate irradiation dose can be set in consideration of the target physical properties (for example, the degree of cross-linking) of the foam base material.

The foam base material may contain, if necessary, fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, flame retardants, etc. Various additives such as a surfactant may be blended.

The foam base material in the technique disclosed herein is black or white in order to exhibit desired designability and optical properties (for example, light-shielding property, light reflectivity, etc.) in the pressure-sensitive adhesive sheet provided with the foam base material. Etc. may be colored. For this coloring, known organic or inorganic colorants can be used alone or in combination of two or more.

The surface of the foam base material may be appropriately surface-treated, if necessary. This surface treatment can be, for example, a chemical or physical treatment to enhance adhesion to adjacent materials (eg, a pressure-sensitive adhesive layer). Examples of such surface treatments 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.

<Peeling liner>
In the technique disclosed herein, a release liner can be used when forming an adhesive layer, producing an adhesive sheet, storing an adhesive sheet before use, distributing it, processing a shape, and the like. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner base material such as a resin film or paper, a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (PE, A release liner or the like made of a low adhesive material such as PP) can be used. The peeling treatment layer may be formed by surface-treating the liner base material with a peeling treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Adhesive sheet>
The adhesive sheet disclosed here is crimped to a stainless steel sheet under the conditions of 23 ° C. and a crimping load of 0.1 kg, and the 180-degree peel strength (initial adhesive force to the stainless steel sheet) measured within 1 minute after crimping is 5N. It is preferably / 10 mm or more. By satisfying this property, excellent initial adhesiveness can be exhibited to various adherends (for example, materials used as members of portable electronic devices). Further, the adhesive sheet having excellent initial adhesiveness is also advantageous in that it can be easily attached to a fragile adherend which may be damaged by ordinary crimping. The initial adhesive force to the stainless steel sheet is more preferably 10 N / 10 mm or more, further preferably 14 N / 10 mm or more, and particularly preferably 14.5 N / 10 mm or more. The upper limit of the initial adhesive force to the SUS plate is not particularly limited, but usually, about 25 N / 10 mm or less (for example, about 20 N / 10 mm or less) is appropriate.

The initial adhesive force to the above stainless steel sheet can be measured as follows. First, the adhesive sheet is cut into a size of 10 mm in width and 100 mm in length to prepare a sample piece. A PET film having a thickness of 50 μm is attached to one of the adhesive surfaces of the adhesive sheet for lining. The backing film is not required for the measurement of the single-sided adhesive sheet with a base material. In an environment of 23 ° C. and 50% RH, the adhesive surface of the sample piece is pressure-bonded to 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 above measurement sample is measured using a tensile tester in an environment of 23 ° C. and 50% RH under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees. The peel strength is measured within less than 1 minute after being attached to the stainless steel plate. As the tensile tester, "Precision universal testing machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or an equivalent product thereof can be used.

Further, the adhesive sheet disclosed here is attached to a PET plate under the conditions of 23 ° C. and a crimping load of 2 kg, and is measured within 1 minute after the lapse of 3 minutes of curing time in an environment of 23 ° C. and 50% RH. It is preferable that the 180-degree peel strength (adhesive strength after curing for 30 minutes with respect to the PET plate) is 4N / 10 mm or more. By satisfying this property, excellent initial adhesiveness can be exhibited to various adherends (for example, materials used as members of portable electronic devices). The adhesive sheet having the adhesive strength tends to show good adhesiveness to a resin material used for electronic devices such as polycarbonate (PC) and polyimide (PI). Further, the adhesive sheet having excellent initial adhesiveness is also advantageous in that it can be easily attached to a fragile adherend which may be damaged by ordinary crimping. The adhesive force after 30-minute curing to the PET plate is more preferably 5N / 10 mm or more, further preferably 6N / 10 mm or more, and particularly preferably 8N / 10 mm or more. The upper limit of the adhesive force after 30-minute curing with respect to the PET plate is not particularly limited, but usually, about 20 N / 10 mm or less (for example, about 15 N / 10 mm or less) is appropriate.

The adhesive strength after 30 minutes of curing to the PET plate can be measured according to JIS Z 0237: 2000. For example, a sample piece is prepared by cutting an adhesive sheet into 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 of the adhesive surfaces of the adhesive sheet for lining. The backing film is not required for the measurement of the single-sided adhesive sheet with a base material. In an environment of 23 ° C. and 50% RH, the adhesive surface of the sample piece was fixed on a PET plate (stainless steel plate (SUS304BA)) with PET film # 25 using double-sided adhesive tape NO.5000NS manufactured by Nitto Denko. A measurement sample is prepared by crimping it to the product). The crimping is performed by reciprocating a 2 kg roller once. The measurement sample is allowed to cure for 3 minutes in an environment of 23 ° C. and 50% RH, and then using a tensile tester, the tensile speed is 300 mm / in an environment of 23 ° C. and 50% RH. The peel strength [N / 10 mm] is measured under the condition that the peel angle is 180 degrees. The peel strength is measured within 1 minute from the end of the curing time. As the tensile tester, "Precision universal testing machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or an equivalent product thereof can be used.

Further, the pressure-sensitive adhesive sheet disclosed herein is a Z-axis direction deformation resistance measured under the conditions of 65 ° C. and 90% RH 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 embodiment described later. In the sex test, the floating height at the end of the measurement may be less than 1500 μm. An adhesive sheet satisfying the above characteristics has particularly excellent deformation resistance against a peeling load consisting substantially only in the thickness direction (Z-axis direction) of the adhesive sheet, and is sustainable in that direction. It is particularly difficult to deform due to the peeling load. In addition, even when the adhesive sheet attached to the 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, etc., it exhibits stable deformation resistance. Can be. The floating height is preferably less than 1000 μm, more preferably 800 μm or less, still more preferably 400 μm or less, and particularly preferably less than 200 μm (for example, less than 150 μm). The floating height is a height including the thickness of the pressure-sensitive adhesive sheet (50 μm in the examples described later).

Further, when the pressure-sensitive adhesive sheet disclosed herein is a base material-less pressure-sensitive adhesive sheet substantially consisting of only a pressure-sensitive adhesive layer, the storage elastic modulus G'(25 ° C.) of the pressure-sensitive adhesive sheet at 25 ° C. is 0. It can be 15 MPa or more. The pressure-sensitive adhesive sheet having a storage elastic modulus G'(25 ° C.) can preferably exhibit good deformation resistance from an early stage after being attached 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 preferably 1.0 MPa or less, and is preferably 0.6 MPa or less, more preferably 0, from the viewpoint of achieving both initial adhesiveness and deformation resistance. It is 0.4 MPa or less, more preferably 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 pressure-sensitive adhesive sheet disclosed here is a base material-less pressure-sensitive adhesive sheet substantially consisting of only a pressure-sensitive adhesive layer, the storage elastic modulus G'(85 ° C.) of the pressure-sensitive adhesive sheet at 85 ° C. is 0. It can be 02 MPa or more. Thereby, a pressure-sensitive adhesive sheet having continuous deformation resistance can be preferably obtained. Specifically, the G'(85 ° C.) can be 0.022 MPa 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 about 0.03 MPa or more (for example, 0.035 MPa or more), particularly preferably 0.04 MPa or more, still more preferably 0.045 MPa or more. Further, the G'(85 ° C.) is usually preferably 1.0 MPa or less, for example, 0.5 MPa or less, typically 0.1 MPa or less. The G'(85 ° C.) may be 0.06 MPa or less.

Further, when the pressure-sensitive adhesive sheet disclosed herein is a base material-less pressure-sensitive adhesive sheet consisting substantially only of a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet presses the pressure-sensitive adhesive sheet to an adherend from the viewpoint of initial adhesiveness. The storage elastic modulus G'(apply) at the temperature at which the adhesive is applied (crimping temperature) may be 0.6 MPa or less. The G'(apply) is preferably 0.4 MPa or less, more preferably 0.35 MPa or less, 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 achieving both initial adhesiveness and deformation resistance, it is appropriate that the G'(apply) is larger than 0.12 MPa, preferably 0.15 MPa or more, and more preferably 0.17 MPa or more. (For example, 0.2 MPa or more), more preferably 0.25 MPa or more, and for example, 0.3 MPa or more may be used. The crimping temperature is selected from a range of more than 0 ° C. and less than 60 ° C. from the viewpoint of crimping workability, temperature control, and the like. In the case of an adhesive sheet used for a portable electronic device application, it is desirable to select the crimping temperature from the range of 20 ° C. to 45 ° C. (typically 25 ° C. or 40 ° C.) due to the temperature limitation in the application.

Further, when the pressure-sensitive adhesive sheet disclosed herein is a base material-less pressure-sensitive adhesive sheet substantially consisting of only a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet usually has a loss elastic modulus G ″ (25 ° C.) at 25 ° C. It is suitable that it is 2.0 MPa or less. The above 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), and the G ″ (25 ° C.) is usually preferably 0.01 MPa or more. From the viewpoint of wettability to the surface of the adherend and, by extension, initial adhesiveness, it is preferably 0.05 MPa or more, more preferably 0.1 MPa or more, still more preferably 0.2 MPa or more, for example, 0.25 MPa or more. There may be.

Further, when the pressure-sensitive adhesive sheet disclosed herein is a base material-less pressure-sensitive adhesive sheet substantially consisting of only a pressure-sensitive adhesive layer, the loss elastic modulus G ″ (85 ° C.) of the pressure-sensitive adhesive sheet at 85 ° C. is usually set. It is appropriate that it is 0.5 MPa or less. The above 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), and the G" (85 ° C.) is usually 0.001 MPa or more. From the viewpoint of adhesiveness and the like, 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.

Further, when the pressure-sensitive adhesive sheet disclosed herein is a base material-less pressure-sensitive adhesive sheet consisting substantially only of a pressure-sensitive adhesive layer, the tan δ (25 ° C.) of the pressure-sensitive adhesive sheet at 25 ° C. is from the viewpoint of deformation resistance. For example, it is appropriate to set it to about 0.3 or more, preferably about 0.5 or more, more preferably about 0.7 or more, still more preferably about 0.8 or more, particularly preferably from the viewpoint of deformation resistance. Is about 0.9 or more (for example, about 1 or more). Further, the tan δ (25 ° C.) is suitable, for example, about 3 or less, preferably about 2 or less, more preferably about 1.5 or less, and further preferably about 1.2 or less from the viewpoint of initial adhesiveness. ..

Further, when the pressure-sensitive adhesive sheet disclosed here is a base material-less pressure-sensitive adhesive sheet substantially consisting of only a pressure-sensitive adhesive layer, the tan δ (85 ° C.) of the pressure-sensitive adhesive sheet at 85 ° C. is, for example, about 0.1 or more. It is appropriate, preferably about 0.12 or more, more preferably 0.15 or more, still more preferably 0.2 or more (for example, 0.22 or more). Further, the tan δ (85 ° C.) is preferably, for example, about 2 or less, preferably about 1 or less, and more preferably about 0.5 or less (for example, about 0.3 or less).

Storage elastic modulus G'(25 ° C), G'(85 ° C), G'(apply), loss elastic modulus G "(25 ° C), G" (85 ° C), tan δ (25 ° C) and tan δ (85 ° C.) can be determined by the same method as the dynamic viscoelasticity measurement for the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive sheet according to a preferred embodiment is a base-less double-sided adhesive pressure-sensitive adhesive sheet (base-less double-sided pressure-sensitive adhesive sheet) substantially composed of only a pressure-sensitive adhesive layer. Since such a base material-less adhesive sheet has excellent followability, it can adhere well to an adherend having a step, for example, and can exhibit excellent adhesive performance. Further, when the rigid materials are fixed to each other, uneven crimping is unlikely to occur, and it is easy to realize good adhesive fixing. Therefore, a rigid member having a step, such as a wiring board or a housing, can be preferably used for joining members of an electronic device arranged inside the rigid member. Since the entire thickness of the base material-less double-sided pressure-sensitive adhesive sheet is composed of a pressure-sensitive adhesive layer, it is possible to exhibit stronger adhesive force (for example, light pressure-bonding adhesiveness) in a limited thickness space. Therefore, it can be particularly preferably used for member joining applications of portable electronic devices.

The total thickness of the adhesive sheet (excluding the release liner) disclosed here is not particularly limited. The total thickness of the pressure-sensitive 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 technique disclosed herein is preferably in the form of an adhesive sheet (typically a double-sided adhesive sheet) having a total thickness of about 150 μm or less (more preferably about 100 μm or less, still more preferably less than about 60 μm, for example about 55 μm or less). Can be carried out. The lower limit of the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, but usually, about 10 μm or more is suitable, about 20 μm or more is preferable, and about 30 μm or more is more preferable. When the pressure-sensitive adhesive sheet comprises a foam base material, the upper limit of the total thickness of the pressure-sensitive adhesive sheet is usually preferably 1.5 mm or less, preferably 1 mm or less, and more preferably 0.5 mm or less. be.

<Use>
The pressure-sensitive adhesive sheets disclosed herein may exhibit excellent deformation resistance to sustained loads in the Z-axis direction. Taking advantage of these characteristics, the pressure-sensitive adhesive sheet can be used in various applications where deformation resistance to a continuous load in the Z-axis direction is required. 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 above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, laptop computers, various wearable devices (for example, wristwatch-type wristwatches, clips, straps, etc.). Modular type to be attached to a part of, eyewear type including glasses type (monocular type and binocular type, including head mount type), clothes type to be attached to shirts, socks, hats, etc. in the form of accessories, earphones (Earwear type, etc. attached to the ear), digital camera, digital video camera, audio equipment (portable music player, IC recorder, etc.), computer (computer, etc.), portable game equipment, electronic dictionary, electronic notebook, electronic book, in-vehicle Includes information devices, mobile radios, mobile TVs, mobile printers, mobile scanners, mobile modems, etc. In addition, in this specification, "portable" means that it is not enough to be portable, but to have a level of portability that an individual (standard adult) can carry relatively easily. It shall mean.

The adhesive sheet disclosed here (typically a double-sided adhesive sheet) can be used for fixing a member constituting a portable electronic device as described above in the form of a bonding material processed into various outer shapes. Among them, it can be preferably used for a portable electronic device having a liquid crystal display device. For example, an electronic device (typically, a portable electronic device such as a smartphone) having a display unit (which may be a display unit of a liquid crystal display device) such as a touch panel display, for the purpose of increasing the screen size or the like. The pressure-sensitive adhesive sheet disclosed herein is preferably used for fixing an elastic adherend in an apparatus for bending and accommodating an elastic member such as an FPC in an internal space. 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. Thereby, the elastic member housed in the limited internal space in the portable electronic device in a bent state can be accurately positioned by the adhesive sheet disclosed herein and held in a stable fixed state. Further, examples of the material arranged inside the portable electronic device as described above include a material having polarity and rigidity such as polycarbonate and polyimide. For this type of material (polar and rigid resin material), the pressure-sensitive adhesive sheets disclosed herein can preferably exhibit deformation resistance to a sustained load in the Z-axis direction. Alternatively, the adhesive sheet disclosed herein is preferably used in a portable electronic device for fixing a member such as a cover glass having a three-dimensional shape (typically a curved surface shape) constituting the portable electronic device. .. The pressure-sensitive adhesive sheet used for fixing a member having such a three-dimensional surface shape tends to be subjected to a relatively large continuous load in the Z-axis direction. By using the pressure-sensitive adhesive sheet disclosed here, even a member having a three-dimensional shape as described above can be stably fixed.

The development of electronic devices (typically portable electronic devices such as smartphones and tablet personal computers) having a display unit (which may be a display unit of a liquid crystal display device) such as the touch panel type display has been particularly recent in recent years. It is being aimed at achieving both high functionality and high functionality. With regard to increasing the screen size, measures have been taken such as bending and accommodating an elastic member such as an FPC in the internal space as described above. On the other hand, with regard to higher functionality, new functions such as a pressure sensor with more accurate pressure sensing performance and a face recognition unlock function have been added to realize higher performance and higher quality products. In order to do so, it is indispensable to highly integrate circuits such as FPCs that carry it. Examples of the means for highly integrating the circuit include double-sided type FPC and multi-layer FPC, both of which are in the direction of increasing the rigidity of the FPC, and Z as evaluated in the Z-axis direction deformation resistance test described later. It is expected that the required characteristics will be the improvement of deformation resistance against continuous axial load. The pressure-sensitive adhesive sheet according to a preferred embodiment of the technique disclosed herein exhibits excellent deformation resistance under harsh high-temperature and high-humidity conditions (strong repulsion conditions) as in the Z-axis direction deformation resistance test described later. Therefore, it is more suitable for the above-mentioned next-generation touch panel display-mounted electronic device (typically, a touch panel display-mounted portable electronic device such as a smartphone), and can be preferably used.

For example, the pressure-sensitive adhesive sheet according to a preferred embodiment of the technique disclosed herein is preferably used for various light sources such as LEDs (light emission diodes) and electronic devices including light emitting elements such as self-luminous organic EL. For example, it can be preferably used for an electronic device (typically a portable electronic device) including an organic EL display device or a liquid crystal display device.

FIG. 7 is an exploded perspective view schematically showing a configuration example of the display device. As shown in FIG. 7, the display device 200 included in the portable electronic device 100 includes a display unit 220 composed of a cover member, an organic EL unit, and the like, and a support unit 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 portion 220 and the support portion 240. The support portion 240 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate) and the like. The pressure-sensitive adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

The matters disclosed herein include:
(1) A pressure-sensitive adhesive sheet comprising an pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, a tackifier resin, a (meth) acrylic oligomer, and an azole-based compound.
(2) The adhesive according to (1) above, wherein the acrylic polymer is polymerized with an alkyl (meth) acrylate having an alkyl group having 1 or more and 6 or less carbon atoms at the ester terminal at a ratio of 50% by weight or more. Sheet.
(3) The pressure-sensitive 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) above, wherein the copolymerization ratio of the hydroxyl group-containing monomer in the acrylic polymer is 0.01% by weight or more.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the pressure-sensitive adhesive resin is contained in a ratio 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) above, wherein the (meth) acrylic oligomer is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. ..
(8) The content _{CO [% by weight] of the (meth) acrylic oligomer in the pressure-sensitive adhesive layer and the content CT} [weight%] of the _tackifier resin are relative to the content _CO [% by weight]. The pressure-sensitive adhesive sheet according to any one of (1) to (7) above, wherein the ratio ( _CT / _CO ) of the content _CT [% by weight] satisfies 0.25 or more and 4 or less.
(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8) above, which contains the pressure-sensitive adhesive resin having a hydroxyl value of 30 mgKOH / g or more as the pressure-sensitive adhesive resin.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9) above, wherein 50% by weight or more of the pressure-sensitive adhesive resin is a phenol-based pressure-sensitive adhesive resin having a hydroxyl value of 30 mgKOH / g or more.
(11) The above-mentioned (1) to (10), wherein the azole compound is contained in a ratio 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. Adhesive sheet.
(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11) above, which contains a triazole-based compound as the azole-based compound.
(13) The pressure-sensitive adhesive sheet according to (12) above, wherein the triazole-based compound is a triazole-based compound having a non-condensation ring structure.
(14) The pressure-sensitive adhesive sheet according to (12) above, wherein the triazole-based compound is a benzotriazole-based compound.
(15) The pressure-sensitive adhesive sheet according to (1) to (14), wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent.
(16) The pressure-sensitive adhesive sheet according to any one of (1) to (15) above, which is a base material-less double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer.
(17) The adhesive sheet according to any one of (1) to (16) above, which is used for joining members in a portable electronic device.
(18) A portable electronic device comprising the adhesive sheet according to any one of (1) to (17) above and parts joined by the adhesive sheet.
(19) The portable electronic device according to (18) above, wherein the circuit board is bent and accommodated in the internal space of the portable electronic device, and the adhesive sheet is fixed in a bent state. ..
(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 surface shape.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

The azole compounds used in the following examples are as follows.
Azole-based compound A: 1,2,3-benzotriazole (trade name "BT-120", manufactured by Johoku Chemical Industry Co., Ltd.)
Azole-based compound B: 1- (1', 2'-dicarboxyethyl) benzotriazole (trade name "BT-M", manufactured by Johoku Chemical Industry Co., Ltd.)
Azole-based 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, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, 93 parts of BA, 7 parts of AA and 0.05 part of 4-hydroxybutyl acrylate (4HBA) as monomer components were used as a polymerization solvent. The mixture was charged with ethyl acetate and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this manner, 0.1 part of AIBN was added as a polymerization initiator and solution polymerization was carried out at 60 ° C. for 6 hours to obtain a solution of the acrylic polymer according to this example. The above-mentioned polymerization reaction was carried out by adjusting the amount of the polymerization solvent to control the concentration of the non-volatile component (monomer component). The Mw of this acrylic polymer was 132 × ¹⁰⁴ , and the Mw / Mn was 5.85.

(Preparation of adhesive composition)
In the solution of the acrylic polymer obtained above, 1.5 parts of an isocyanate-based cross-linking agent (trade name "Coronate L", 3 amounts of trimethylolpropane / tolylene diisocyanate) with respect to 100 parts of the acrylic polymer contained in the solution. 75% ethyl acetate solution of body adduct, manufactured by Toso Co., Ltd., 0.01 part of epoxy cross-linking agent (trade name "TETRAD-C", 1,3-bis (N, N-diglycidylaminomethyl) cyclo Hexan (manufactured by Mitsubishi Gas Chemicals, Inc.) and 15 parts of terpenphenol resin (trade name "YS Polymer S-145" manufactured by Yasuhara Chemical Co., Ltd., softening point of about 145 ° C., hydroxyl value 70-110 mgKOH / g), 15 parts. The (meth) acrylic oligomer and 0.8 parts of the azole compound A (1,2,3-benzotriazole) were added and mixed with stirring to prepare the pressure-sensitive adhesive composition according to this example.

As the (meth) acrylic oligomer, the one prepared by the following method was used. Specifically, in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser, and a dropping funnel, 95 parts of CHMA and 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent. Was charged and stirred in a nitrogen stream for 1 hour to remove oxygen in the polymerization system, then heated to 85 ° C. and reacted for 5 hours to obtain a (meth) acrylic oligomer having a solid content concentration of 50%. The Mw of the obtained (meth) acrylic oligomer was 3600.

(Making an adhesive sheet)
As the peeling liner A, a polyester peeling film (trade name "Diafoil MRV", thickness 75 μm, manufactured by Mitsubishi Polyester Co., Ltd.) whose one side is peeled and treated as a peeling surface is used as a peeling liner B and one side is peeled. A polyester peeling film (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) that has been peeled off was prepared. The pressure-sensitive adhesive composition obtained above was applied to the peel-off surface of the peel-off 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 placed on the exposed adhesive surface of the pressure-sensitive adhesive layer so that the peel-off surface was on the pressure-sensitive adhesive layer side to prepare a base-less double-sided adhesive pressure-sensitive adhesive sheet according to this example.

<Examples 2 to 5>
The pressure-sensitive adhesive composition according to this example was prepared by the same method as in Example 1 except that the types and addition amounts of the azole compounds were as shown in Table 1. Using the obtained pressure-sensitive adhesive composition, a base-less double-sided adhesive pressure-sensitive adhesive sheet (thickness 50 μm) according to this example was produced in the same manner as in Example 1.

<Example 6>
The pressure-sensitive adhesive composition according to this example was prepared by the same method as in Example 1 except that an epoxy-based cross-linking agent was not used. Using the obtained pressure-sensitive adhesive composition, a base-less double-sided adhesive pressure-sensitive adhesive sheet (thickness 50 μm) according to this example was produced in the same manner as in Example 1.

<Example 7>
The pressure-sensitive adhesive composition according to this example was prepared by the same method as in Example 1 except that an azole compound was not used. Using the obtained pressure-sensitive adhesive composition, a base-less double-sided adhesive pressure-sensitive adhesive sheet (thickness 50 μm) according to this example was produced in the same manner as in Example 1.

<Example 8>
The pressure-sensitive adhesive composition according to this example was prepared by the same method as in Example 1 except that the (meth) acrylic oligomer was not used. Using the obtained pressure-sensitive adhesive composition, a base-less double-sided adhesive pressure-sensitive adhesive sheet (thickness 50 μm) according to this example was produced in the same manner as in Example 1.

[Z-axis direction deformation resistance test (high temperature and high humidity conditions)]
As shown in FIG. 8A, 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 were prepared. The PC plate 50 and the PET film 60 were overlapped so as to align one end in the longitudinal direction, and the PC plate 50 and the PET film 60 were fixed in a state where the remaining portion of the PET film 60 protruded from the other end of the PC plate 50. .. A commercially available double-sided adhesive tape (manufactured by Nitto Denko, "No. 5000NS") was used for the above fixing.
An adhesive sheet sample piece 70 was prepared by cutting the adhesive sheet according to each example in which both adhesive surfaces were protected by two release liners into a size having a width of 3 mm and a length of 10 mm. The surface of the PC plate 50 opposite to the fixed surface of the PET film is placed on the upper side, and one release liner is peeled off from the pressure-sensitive adhesive sheet sample piece 70, so that the width direction of the PC plate 50 and the length of the pressure-sensitive adhesive sheet sample piece 70 are obtained. The adhesive sheet sample piece 70 is attached to the upper surface of the PC plate 50 so that both ends in the width direction of the adhesive sheet sample piece 70 are on lines 7 mm and 10 mm from the other end on the upper surface of the PC plate 50 in the same direction. Fixed. The above fixing was performed by reciprocating a 2 kg roller once on the upper surface of the pressure-sensitive adhesive sheet sample piece 70 protected by the other release liner.
Next, in an environment of 23 ° C. and 50% RH, the other release liner of the adhesive sheet sample piece 70 attached to the PC plate 50 was peeled off, and as shown in FIG. 8B, the PC plate 50 was used. The protruding portion (length 40 mm) of the PET film 60 fixed to the PC plate 50 is folded back toward the PC plate 50 so that the adhesive sheet sample piece 70 and the other end (free end) of the PET film 60 are aligned with each other. By reciprocating a 0.1 kg roller from the top of the PET film 60 once, the other end of the bent PET film 60 is fixed to the upper surface of the PC plate 50 via the adhesive sheet sample piece 70, and this is fixed at 65 ° C. and 90%. Exposed to the RH environment. After being exposed to the same environment for 72 hours, it was confirmed whether or not the adhesive state between the adhesive sheet sample piece 70 and the PET film 60 was maintained, and when the PET film 60 was peeled off as shown in FIG. 8 (c), " It was judged as "failure". When the PET film 60 was held, the floating height [μm] of the PET film 60 from the pressure-sensitive adhesive sheet sample piece 70 was measured using a microscope. The measurement was performed 3 times and the lowest value was recorded. The floating height is a height including the thickness of the pressure-sensitive adhesive sheet sample piece 70.
According to this evaluation method, unlike the conventional repulsion resistance evaluation, the deformation resistance to a peeling load substantially only in the thickness direction (Z-axis direction) of the adhesive sheet is high temperature and high humidity of 65 ° C. and 90% RH. It is possible to evaluate under the harsh conditions of, and it is possible to evaluate the continuous deformation resistance by observing over time.

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

As shown in Table 1, the pressure-sensitive adhesive sheets according to Examples 1 to 6 provided with a pressure-sensitive adhesive layer containing an acrylic polymer, a tackifier resin, a (meth) acrylic oligomer, and an azole-based compound are Z-axis. In the directional deformation resistance test, it had clearly excellent deformation resistance against a continuous load in the Z-axis direction. On the other hand, the pressure-sensitive adhesive sheet of Example 7 in which the azole compound was not used and the pressure-sensitive adhesive sheet of Example 8 in which the (meth) acrylic oligomer was not used were both sustained in the Z-axis direction in the above-mentioned Z-axis direction deformation resistance test. The deformation resistance to the target load was inferior.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples exemplified above.

1,2,3,4,5,6 Adhesive sheet 10

Base material

21,22

Adhesive layer

31,32 Release liner

Claims

A pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, a tackifier resin, a (meth) acrylic oligomer, and an azole compound.
The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic polymer is polymerized with an alkyl (meth) acrylate having an alkyl group having 1 or more and 6 or less carbon atoms at the ester terminal at a ratio of 50% by weight or more.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive resin is contained 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, wherein the (meth) acrylic oligomer is contained in a ratio of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer.
The content CO [% by weight] of the (meth) acrylic oligomer in the pressure-sensitive adhesive layer and the content CT [% by weight] of the tackifier resin are the contents relative to the content CO [ % by weight]. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the ratio of CT [% by weight] ( CT / CO ) satisfies 0.25 or more and 4 or less.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein 50% by weight or more of the pressure-sensitive adhesive resin is a phenol-based pressure-sensitive adhesive resin having a hydroxyl value of 30 mgKOH / g or more.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the azole compound is contained in a proportion 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.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which contains a triazole-based compound as the azole-based compound.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which is a base-less double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer.
The adhesive sheet according to any one of claims 1 to 9, which is used for joining members in a portable electronic device.