WO2023188482A1

WO2023188482A1 - Adhesive sheet

Info

Publication number: WO2023188482A1
Application number: PCT/JP2022/038804
Authority: WO
Inventors: 圭吾下岡; 徹田上; 健一山元; 康武蔵島
Original assignee: 日東電工株式会社
Priority date: 2022-03-29
Filing date: 2022-10-18
Publication date: 2023-10-05
Also published as: JP7311695B1; JP2023147288A; JP2023147166A; TW202346513A

Abstract

Provided is an adhesive sheet capable of achieving a high level of adhesion to high-polarity materials, adhesion to low-polarity materials, and holding power. The adhesive sheet has an adhesive agent layer containing an acrylic polymer. The acrylic polymer is a polymer of a monomer component containing n-heptyl acrylate and a carboxy-group-containing monomer. The monomer component of the acrylic polymer contains more than 3 wt% of the carboxy-group-containing monomer. Furthermore, the gel fraction of the adhesive agent layer is less than 70%. The weight-average molecular weight of the acrylic polymer is greater than 600,000.

Description

adhesive sheet

The present invention relates to an adhesive sheet.
This application claims priority based on Japanese Patent Application No. 2022-54421 filed on March 29, 2022 and Japanese Patent Application No. 2022-164655 filed on October 13, 2022. , the entire contents of those applications are incorporated herein by reference.

In general, adhesives (also referred to as pressure-sensitive adhesives, hereinafter the same) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of adhering to adherends under pressure. Taking advantage of these properties, adhesives are widely used in various industrial fields such as home appliances, automobiles, and OA equipment, typically in the form of adhesive sheets containing an adhesive layer, for purposes such as bonding parts and protecting surfaces. It's being used. Technical documents related to adhesive sheets include

Patent Documents

1 and 2.

Patent Documents

1 and 2 describe adhesives containing acrylic polymers polymerized using n-heptyl acrylate as a monomer component.

International Publication No. 2021/125247 International Publication No. 2021/125278

In general, pressure-sensitive adhesive sheets are required to have good adhesion performance to various materials. For example, with adhesives used to fix components that make up electronic devices such as the above-mentioned home appliances, one of the objects to be bonded is made of a highly polar material such as a stainless steel plate, and the other is made of a low polar material such as polyolefin. The ability to reliably fix a member whose surface is composed of a highly polar material and a low polar material may be required. Generally, by using a soft adhesive whose storage modulus is limited to a predetermined value or less, adhesiveness to different types of materials such as high polarity materials and low polarity materials can be easily obtained. However, such adhesives generally tend to have reduced holding power. There is a trade-off relationship between adhesion and holding power to different materials. Particularly in recent years, the adhesive area of adhesives has tended to become smaller due to the demand for smaller, lighter, and more precise electronic devices. In such applications, it tends to be more difficult to achieve high levels of adhesion to highly polar materials, adhesion to low polar materials, and retention.

As a result of extensive studies, the present inventors found that a structure using an acrylic polymer containing n-heptyl acrylate as a monomer component exhibits high adhesion to both high and low polarity materials, and has a sufficient adhesive strength. The present inventors have discovered that it is possible to obtain a pressure-sensitive adhesive having a strong holding power, and have completed the present invention. That is, an object of the present invention is to provide a pressure-sensitive adhesive sheet that can achieve both high levels of adhesive strength for highly polar materials, adhesive strength for low polar materials, and holding power.

According to this specification, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an acrylic polymer is provided. The acrylic polymer is a polymer of monomer components including n-heptyl acrylate and a carboxyl group-containing monomer. Furthermore, the monomer component of the acrylic polymer contains more than 3% by weight of the carboxy group-containing monomer. Furthermore, the gel fraction of the adhesive layer is less than 70%. The weight average molecular weight of the acrylic polymer is greater than 600,000. By using an adhesive that contains an acrylic polymer containing n-heptyl acrylate as a monomer component and has a gel fraction of less than 70%, it exhibits sufficient adhesive strength not only for highly polar materials but also for low polar materials. be able to. In addition, by copolymerizing the above acrylic polymer with a monomer containing a carboxyl group at a ratio of more than 3% by weight and designing the weight average molecular weight (Mw) to be greater than 600,000, we have achieved high adhesive strength to different materials. It is possible to improve the holding force while having the following properties. The use of the carboxy group-containing monomer also improves adhesion to highly polar materials. That is, according to the above configuration, it is possible to achieve both high levels of adhesive force for high polar materials, adhesive force for low polar materials, and holding force. In addition, in Patent Document 1, the adhesive strength and holding power for polypropylene (40 ° C., adhesive area 25 mm × 25 mm, load 1 kg) are evaluated, and in Patent Document 2, the holding force (80 ° C., adhesive area 25 mm × 25 mm, However, all of the acrylic polymers used either have a low Mw or have a low copolymerization ratio of carboxyl group-containing monomers, so the retention will be evaluated in the examples below. (80° C., adhesion area 10 mm x 20 mm, load 1.5 kg) was not obtained, and the adhesion force to high polarity materials, the adhesion force to low polarity materials, and the holding force were not fully satisfied.

In some preferred embodiments, the adhesive composition for forming the adhesive layer includes a crosslinking agent. By using a crosslinking agent, the cohesive force of the adhesive increases, and sufficient holding power can be suitably achieved.

In some preferred embodiments, the adhesive layer includes a tackifying resin. By using a tackifying resin, the gel fraction of the adhesive layer can be adjusted to an appropriate range, and the adhesive strength to high polarity materials and low polarity materials can be improved.

In some preferred embodiments, the thickness of the adhesive layer is 0.1 to 500 μm. The technology disclosed herein can be implemented with a configuration including an adhesive layer having the above thickness.

In some preferred embodiments, the adhesive layer has a gel fraction of 20% or more and less than 70%. By setting the gel fraction of the pressure-sensitive adhesive layer within the above range, both adhesive strength and holding power can be suitably achieved.

The adhesive sheet according to some preferred embodiments has a 180 degree peel strength against a stainless steel plate (adhesive strength against SUS) of 15 N/25 mm or more. The pressure-sensitive adhesive sheet having the adhesive strength against SUS can exhibit excellent adhesive strength against highly polar materials.

Adhesive sheets according to some preferred embodiments have a 180 degree peel strength against polypropylene (adhesive strength against PP) of 10 N/25 mm or more. The pressure-sensitive adhesive sheet having the above-mentioned adhesive strength to PP can have sufficient adhesion reliability to low polarity materials.

Adhesive sheets according to some preferred embodiments have a 180 degree peel strength against polyethylene (adhesion strength against PE) of 5 N/25 mm or more. The pressure-sensitive adhesive sheet having the above-mentioned adhesive strength to PE can have sufficient adhesion reliability to low polarity materials.

Adhesive sheets according to some preferred embodiments have a displacement distance of 10 mm or less in a holding force test conducted at 80° C., adhesive area 10 mm x 20 mm, load 1.5 kg, and for 1 hour. A pressure-sensitive adhesive sheet that does not easily shift in the above-mentioned holding power test can have sufficient holding power (specifically, high temperature holding power).

The adhesive sheet disclosed herein has both adhesion and holding power to different materials, so it can be preferably used for adhesion to highly polar or low polar materials, or for applications that require long-term adhesion reliability. can be done. For example, it is suitable for fixing members in electronic devices including home appliances, office automation equipment, and portable electronic devices such as smartphones. As described above, this specification provides an electronic device using any of the adhesive sheets disclosed herein, in other words, an electronic device including the adhesive sheet.

FIG. 1 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to an embodiment. FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment. FIG. 3 is a cross-sectional view schematically showing the configuration of a pressure-sensitive adhesive sheet according to another embodiment. FIG. 1 is a front view schematically showing an example of a portable electronic device including an adhesive sheet.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention are based on the teachings regarding carrying out the invention described in this 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 implemented based on the content disclosed in this specification and the common general knowledge in the field. Furthermore, in the following drawings, members and portions that have the same function may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the adhesive sheet of the present invention that is actually provided as a product. .

As mentioned above, the term "adhesive" as used herein refers to a material that exhibits a soft solid (viscoelastic) state in the temperature range around room temperature and has the property of easily adhering to an adherend under pressure. . The adhesive referred to here generally has a complex tensile modulus E ^* (1Hz) as defined in "C. A. Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P. 143". <10 ⁷ dyne/cm ² (typically, a material having the above properties at 25° C.).

In this specification, biomass-derived carbon means carbon derived from biomass materials, that is, materials derived from renewable organic resources (renewable carbon). The above-mentioned biomass materials are typically materials derived from biological resources (typically plants that perform photosynthesis) that can be reproduced sustainably in the presence of sunlight, water, and carbon dioxide. means. Therefore, materials derived from fossil resources that are depleted through use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The biomass carbon ratio of the adhesive layer and the adhesive sheet, that is, the proportion of biomass-derived carbon in the total carbon contained in the adhesive layer and the adhesive sheet, is the carbon isotope content with a mass number of 14 measured in accordance with ASTM D6866. It can be estimated from the amount.

<Configuration of adhesive sheet>
The adhesive sheet disclosed herein includes an adhesive layer. The above-mentioned pressure-sensitive adhesive sheet is, for example, a base material-less double-sided pressure-sensitive adhesive sheet comprising a first pressure-sensitive adhesive surface formed by one surface of the pressure-sensitive adhesive layer, and a second pressure-sensitive adhesive surface formed by the other surface of the pressure-sensitive adhesive layer. It can be in the form of Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a pressure-sensitive adhesive sheet with a base material, in which the pressure-sensitive adhesive layer is laminated on one or both sides of a support base material. Hereinafter, the supporting base material may be simply referred to as "base material". Note that the concept of adhesive sheet here may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. Note that the pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, the adhesive sheet may be further processed into various shapes.

The structure of a pressure-sensitive adhesive sheet according to one embodiment is schematically shown in FIG. This adhesive sheet 1 is configured as a double-sided adhesive sheet without a base material, which includes an adhesive layer 21. The adhesive sheet 1 has a first adhesive surface 21A constituted by one surface (first surface) of the adhesive layer 21 and a second adhesive surface constituted by the other surface (second surface) of the adhesive layer 21. 21B are attached to different parts of the adherend. The locations on which the

adhesive surfaces

21A and 21B are attached may be on different members, or may be on different locations within a single member. As shown in FIG. 1, the adhesive sheet 1 before use (that is, before being attached to an adherend) has a first adhesive surface 21A and a second adhesive surface 21B that are peeled off at least on the side facing the adhesive layer 21. It may be a component of the adhesive sheet 100 with a release liner that is protected by the

release liners

31 and 32 serving as surfaces. As the

release liners

31 and 32, it is preferable to use, for example, a sheet-like base material (liner base material) that is constructed by providing a release layer made of a release treatment agent on one side so that one side becomes a release surface. obtain. Alternatively, the release liner 32 may be omitted and a release liner 31 having release surfaces on both sides may be used, and this and the adhesive sheet 1 may be overlapped and spirally wound so that the second adhesive surface 21B is on the release liner 31. The pressure-sensitive adhesive sheet with a release liner may be in a protected form (roll form) in contact with the back surface of the adhesive sheet.

The structure of a pressure-sensitive adhesive sheet according to another embodiment is schematically shown in FIG. 2. This adhesive sheet 2 is a base material comprising a sheet-shaped support base material (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. It is constructed as a single-sided adhesive sheet. The adhesive layer 21 is fixedly provided on the first surface 10A side of the support base material 10, that is, without the intention of separating the adhesive layer 21 from the support base material 10. As shown in FIG. 2, the pressure-sensitive adhesive sheet 2 before use has a surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 protected by a release liner 31 having a release surface at least on the side facing the pressure-sensitive adhesive layer 21. It may be a component of the pressure-sensitive adhesive sheet 200 with a release liner. Alternatively, the release liner 31 may be omitted, the second surface 10B may be the release surface, and the adhesive sheet 2 may be wound so that the adhesive surface 21A is the second surface (back surface) of the support substrate 10. ) 10B may be in a protected form (roll form).

FIG. 3 schematically shows the structure of a pressure-sensitive adhesive sheet according to yet another embodiment. This adhesive sheet 3 includes a sheet-shaped support base material (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and a first adhesive layer 21 fixedly provided on the first surface 10A side. and a second adhesive layer 22 fixedly provided on the second surface 10B side. In the adhesive sheet 3 before use, as shown in FIG. , 32 may be a component of the adhesive sheet 300 with a release liner. Alternatively, the release liner 32 may be omitted and a release liner 31 having release surfaces on both sides may be used, and this and the adhesive sheet 3 may be overlapped and spirally wound so that the second adhesive surface 22A is on the release liner 31. The pressure-sensitive adhesive sheet with a release liner may be in a protected form (roll form) in contact with the back surface of the adhesive sheet.

In addition, in the double-sided pressure-sensitive adhesive sheet with a base material, at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer (for example, the first pressure-sensitive adhesive layer) may be the pressure-sensitive adhesive layer described below. The other adhesive layer (for example, the second adhesive layer) may be the adhesive layer disclosed herein, and the adhesive layer disclosed herein (specifically, the one adhesive layer described above) may be the adhesive layer disclosed herein. The adhesive layer may have a composition different from that of the adhesive layer (for example, the first adhesive layer). The other pressure-sensitive adhesive layer may be formed from a known or commonly used pressure-sensitive adhesive, for example.

<Adhesive layer>
The adhesive layer constituting the adhesive sheet disclosed herein contains an acrylic polymer. The pressure-sensitive adhesive layer is typically a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. Note that the base polymer refers to the main component of a rubbery polymer (a polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the adhesive layer. Furthermore, in this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight, unless otherwise specified. Further, the following description regarding the adhesive and the components that can be included in the adhesive layer is also applicable to the adhesive composition used to form the adhesive (layer) unless otherwise specified.

In addition, as used herein, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule, as monomer units constituting the polymer. . Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer." Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. In addition, in this specification, "(meth)acryloyl" refers comprehensively to acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to acrylic and methacrylic.

(acrylic polymer)
As the acrylic polymer used in the technique disclosed herein, a polymer of monomer components containing n-heptyl acrylate is used. Acrylic polymers polymerized using monomer components containing n-heptyl acrylate have superior flexibility than polymers of other alkyl acrylates such as n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). It can exhibit superior adhesive strength to both high polarity materials and low polarity materials. The reason for this is not particularly limited, but is because polymers containing n-heptyl acrylate as a monomer unit have relatively long linear side chains in addition to having a low glass transition temperature. This is thought to be due to the relatively large space between the main chains within the adhesive.

For example, in some embodiments, the proportion of n-heptyl acrylate in the monomer components of the acrylic polymer is 50% by weight or more (for example, more than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight. % or more, more preferably 85% by weight or more, particularly preferably 90% by weight or more, may be 92% by weight or more, may be 94% by weight or more, or may be 96% by weight or more. By increasing the amount of n-heptyl acrylate used, the effects of its use can be effectively expressed. On the other hand, from the viewpoint of copolymerizing carboxyl group-containing monomers and other monomers, the proportion of n-heptyl acrylate in the monomer components is less than 97% by weight, and in some embodiments is 95% by weight or less. The content may be 93% by weight or less, or may be 91% by weight or less.

The acrylic polymer may be copolymerized with an alkyl (meth)acrylate (hereinafter also referred to as "optional alkyl (meth)acrylate") other than n-heptyl acrylate. As the optional alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably 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 (excluding n-heptyl group).

Examples of the above-mentioned optional alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s -Butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl methacrylate, 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, lauryl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate Acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and the like. These optional alkyl (meth)acrylates can be used alone or in combination of two or more. Optional alkyl (meth)acrylates that may be preferably used include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

The proportion of optional alkyl (meth)acrylate included in the monomer component is, for example, in some embodiments less than 47% by weight, may be less than 45% by weight, may be less than 30% by weight, and may be less than 10% by weight. It may be less than 5% by weight, or less than 1% by weight. The technology disclosed herein can be preferably carried out in an embodiment in which the monomer component does not substantially contain any alkyl (meth)acrylate.

In addition, in this specification, when the monomer component does not substantially contain monomer A (for example, the above-mentioned optional alkyl (meth)acrylate), it means that the monomer A is not used, at least intentionally, and the monomer component is For example, unintentional inclusion of about 0.01% by weight or less is acceptable.

In some embodiments, the monomer component may include an alkyl (meth)acrylate having a biomass-derived alkyl group at the ester end (hereinafter also referred to as "biomass alkyl (meth)acrylate"). In recent years, environmental issues such as global warming have become more important, and it is desired to reduce the amount of fossil resource-based materials such as petroleum used. Under these circumstances, there is a need to reduce the amount of fossil resource-based materials used in the adhesive field as well. By using biomass alkyl (meth)acrylate, it is possible to suitably realize an acrylic pressure-sensitive adhesive that is designed to reduce dependence on fossil resource-based materials.

The biomass alkyl (meth)acrylate is not particularly limited, and is, for example, an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived (meth)acrylic acid. Examples of alkanols derived from biomass include biomass ethanol, alkanols derived from plant materials such as palm oil, palm kernel oil, coconut oil, and castor oil. When the biomass-derived alkanol has three or more carbon atoms, the alkanol may be linear or branched. In some embodiments, an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate used in the synthesis of the acrylic polymer. In such a biomass alkyl (meth)acrylate, the greater the number of carbon atoms in the alkanol, the greater the number ratio of biomass-derived carbon to the total number of carbons contained in the biomass alkyl (meth)acrylate, that is, the biomass carbon ratio of the alkyl (meth)acrylate. becomes higher. Therefore, in the above-mentioned biomass alkyl (meth)acrylate, it is desirable that the alkyl group derived from biomass has a large number of carbon atoms in order to reduce dependence on fossil resource materials. On the other hand, if the number of carbon atoms in the alkyl group constituting the alkyl (meth)acrylate is too large, it tends to be difficult to obtain adhesive properties such as adhesive strength, and it also has a negative impact on productivity such as synthesis, ease of handling, and cost. It can be disadvantageous. In an embodiment in which an ester of biomass-derived alkanol and non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate, adhesive properties and reduced dependence on fossil resource materials (more specifically, It is desirable to use a material that is compatible with the above-mentioned alkyl (meth)acrylate biomass carbon ratio) in a well-balanced manner.

In some preferred embodiments, biomass-derived n-heptyl acrylate (biomass n-heptyl acrylate) is used as n-heptyl acrylate. By using biomass n-heptyl acrylate, the effects of the technology disclosed herein can be achieved while reducing dependence on fossil resource materials. The biomass n-heptyl acrylate is an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived acrylic acid. For example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used. In such compounds, only the linear heptyl groups are derived from biomass.

The proportion of biomass alkyl (meth)acrylate (preferably biomass n-heptyl acrylate) in the monomer components of the acrylic polymer is, for example, 50% by weight or more (for example, more than 50% by weight) in some embodiments, Preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, may be 92% by weight or more, may be 94% by weight or more, and may be 96% by weight. The above is fine. Further, the proportion of biomass alkyl (meth)acrylate (preferably biomass n-heptyl acrylate) among the monomer components is less than 97% by weight, and in some embodiments may be 95% by weight or less, and in some embodiments may be 93% by weight or less. % or less, or 91% by weight or less. In some other embodiments, the proportion of biomass alkyl (meth)acrylate in the monomer component may be 90% by weight or less, 70% by weight or less, 50% by weight or less, 30% by weight or less, It may be 10% by weight or less, or 1% by weight or less.

Furthermore, the monomer component of the acrylic polymer contains more than 3% by weight of a carboxyl group-containing monomer. Carboxy group-containing monomers can exhibit improved cohesiveness based on their polarity. Further, when using a crosslinking agent such as an isocyanate type crosslinking agent or an epoxy type crosslinking agent, the carboxy group can serve as a crosslinking point of the acrylic polymer. By using more than 3% by weight of the carboxy group-containing monomer, it is possible to obtain sufficient holding power while having high adhesive strength to different materials. Further, by using a carboxy group-containing monomer, better adhesion to highly polar materials can be obtained.

Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. be done. Among these, preferred carboxy group-containing monomers include AA and MAA. AA is particularly preferred. Carboxy group-containing monomers can be used singly or in combination of two or more.

The proportion of the carboxy group-containing monomer in the monomer component of the acrylic polymer is more than 3% by weight (specifically more than 3.0% by weight), preferably 4.0% by weight or more, more preferably 4% by weight or more. The content is .5% by weight or more, more preferably 5.0% by weight or more (for example, more than 5.0% by weight), particularly preferably 5.5% by weight or more, and may be 6.0% by weight or more. In some embodiments, the proportion of the carboxy group-containing monomer in the monomer component may be 7.0% by weight or more, 8.0% by weight or more (for example, more than 8.0% by weight), and 9. It may be 0% by weight or more. By increasing the amount of the carboxyl group-containing monomer used, the cohesive force of the adhesive layer will improve based on the action of the carboxyl group-containing monomer, so it is possible to design the Mw of the acrylic polymer to be appropriately low and increase the adhesive force. It becomes possible. Further, the amount of the carboxy group-containing monomer is, for example, suitably 20% by weight or less of the total monomer components, preferably 15% by weight or less, and more preferably 12% by weight or less. In some embodiments, the amount of the carboxy group-containing monomer may be less than 10% by weight, may be less than 8% by weight, may be less than 6% by weight, and may be less than 5% by weight. By appropriately adjusting the amount of the carboxyl group-containing monomer within the above range, it is possible to achieve a good balance between adhesion to highly polar materials, adhesion to low polar materials, and holding power.

The acrylic polymer may be copolymerized with a functional group-containing monomer (any functional group-containing monomer) other than the carboxy group-containing monomer. Examples of optional functional group-containing monomers that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or contribute to improving adhesive strength include hydroxyl group (OH group)-containing monomers (2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- Hydroxyalkyl (meth)acrylates such as hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate, etc. ), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers with nitrogen atom-containing rings (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl Examples include group-containing monomers, imide group-containing monomers, and the like. The above arbitrary functional group-containing monomers can be used alone or in combination of two or more.

When the monomer component constituting the acrylic polymer contains the above-mentioned optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting the effect of using the optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, and 0.5% by weight or more. It is appropriate that the amount is 1% by weight or more. In addition, from the viewpoint of making it easier to balance the adhesive performance in relation to n-heptyl acrylate and the carboxyl group-containing monomer, it is appropriate that the content of the arbitrary functional group-containing monomer in the monomer component is 40% by weight or less. , is preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less). In some embodiments, the content of optional functional group-containing monomers in the monomer component is, for example, less than 3% by weight, may be less than 1% by weight, may be less than 0.5% by weight, and may be less than 0.3% by weight. % or less than 0.1% by weight. The technique disclosed herein can be preferably carried out in an embodiment in which the monomer component of the acrylic polymer does not substantially contain any functional group-containing monomer.

Further, when a hydroxyl group-containing monomer is used as the above-mentioned optional functional group-containing monomer, the content thereof may generally be approximately 0.001% by weight or more of the total monomer components, or approximately 0.01% by weight or more, It may be approximately 0.02% by weight or more. The content of the hydroxyl group-containing monomer is suitably about 10% by weight or less, preferably about 5% by weight or less, more preferably about 2% by weight or less, based on the total monomer components. In some embodiments, the content of hydroxyl group-containing monomer in the monomer component may be less than 1% by weight, may be less than 0.5% by weight, may be less than 0.3% by weight, and may be less than 0.1% by weight. % or less than 0.01% by weight. The monomer component of the acrylic polymer may be substantially free of hydroxyl group-containing monomers. According to the technology disclosed herein, desired effects can be achieved without relying on hydroxyl group-containing monomers.

The ratio of the carboxy group-containing monomer to the total functional group-containing monomers (total functional group-containing monomers including the carboxy group-containing monomer) used as a copolymerization component of the acrylic polymer is determined by the effect of copolymerizing the carboxy group-containing monomer. From the viewpoint of achieving the desired performance, the content is suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, such as It may be 95% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99.9% by weight or more). The upper limit of the proportion of the carboxy group-containing monomer to the total of the functional group-containing monomers is 100% by weight, and may be, for example, 95% by weight or less.

The monomer components constituting the acrylic polymer may contain copolymerization components other than the above-mentioned functional group-containing monomers for the purpose of improving cohesive force and the like. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl ) acrylates; aryl (meth)acrylates (e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylates (e.g. benzyl (meth)acrylate), etc. Aromatic ring-containing (meth)acrylate; Olefinic monomer; Chlorine-containing monomer; Isocyanate group-containing monomer such as 2-(meth)acryloyloxyethyl isocyanate; Alkoxy such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate Group-containing monomers; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components mentioned above can be used alone or in combination of two or more.

The amount of such other copolymerized components is not particularly limited as long as it can be selected as appropriate depending on the purpose and use, but from the viewpoint of appropriately exhibiting the effects of use, it is appropriate to set it to 0.05% by weight or more. , 0.5% by weight or more. In addition, from the viewpoint of making it easier to balance the adhesive performance, it is appropriate that the content of other copolymer components in the monomer components is 20% by weight or less, so that the adhesive properties based on the essential monomer components can be suitably exhibited. From this point of view, it is preferably 10% by weight or less, more preferably 8% by weight or less, still more preferably less than 5% by weight, for example, it may be less than 3% by weight, and may be less than 1% by weight. The technology disclosed herein can also be preferably practiced in an embodiment in which the monomer component does not substantially contain other copolymer components.

Acrylic polymers are polyfunctional polymers that have at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds, such as (meth)acryloyl groups and vinyl groups, as other monomer components. It may also contain monomers. By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased. Polyfunctional monomers can be used as crosslinking agents. The polyfunctional monomer is not particularly limited, and includes, for example, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopentyl glycol di(meth)acrylate. etc. One type of polyfunctional monomer can be used alone or two or more types can be used in combination.

The amount of the polyfunctional monomer used is not particularly limited, and can be appropriately set so that the intended use of the polyfunctional monomer is achieved. The amount of the polyfunctional monomer used can be about 3% by weight or less of the monomer components, preferably about 2% by weight or less, and more preferably about 1% by weight or less (for example, about 0.5% by weight or less). The lower limit of the amount used when using a polyfunctional monomer is not particularly limited, as long as it is greater than 0% by weight. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of the polyfunctional monomer to be approximately 0.001% by weight or more (for example, approximately 0.01% by weight or more) of the monomer components.

The biomass carbon ratio of the monomer component constituting the acrylic polymer (biomass carbon ratio of the acrylic polymer) may be, for example, 1% or more, suitably 10% or more, preferably 30% or more, and more preferably is 50% or more (for example, more than 50%), may be 70% or more, may be 80% or more, or may be 90% to 100%. By designing in this way, an acrylic pressure-sensitive adhesive can be obtained that takes into account the suppression of dependence on fossil resource-based materials.

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be used. may be adopted as appropriate. For example, a solution polymerization method can be preferably employed. As a monomer supply method when performing solution polymerization, a batch charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The polymerization temperature can be selected as appropriate depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is, for example, about 20°C to 170°C (typically about 40°C to 140°C). I can do it.

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

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide (BPO) and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. Still another example of the polymerization initiator is a redox initiator using a combination of a peroxide and a reducing agent. Such polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used may be any normal amount, for example, approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) per 100 parts by weight of all monomer components. degree).

As the acrylic polymer, an acrylic polymer having a weight average molecular weight (Mw) of more than 600,000 is used. As a result, a pressure-sensitive adhesive exhibiting good cohesive force can be obtained, and sufficient holding power can be obtained while having high adhesive strength to different materials. The Mw of the acrylic polymer is preferably 650,000 or more. In some embodiments, the Mw of the acrylic polymer is suitably 700,000 or more, preferably 750,000 or more, more preferably 800,000 or more, even more preferably 850,000 or more, particularly preferably 900,000 or more (e.g. (over 900,000). By setting the Mw of the acrylic polymer high to increase the cohesive force of the adhesive, it is possible to adopt, for example, a monomer composition that emphasizes adhesive force to different materials. In addition, from the viewpoint of adhesive strength to different materials, ease of synthesis, etc., it is appropriate that the Mw of the acrylic polymer is usually about 3 million or less, preferably 2 million or less, more preferably 1.5 million or less, More preferably, it is 1.2 million or less, particularly preferably 1,000,000 or less. In some embodiments, from the viewpoint of improving adhesive strength to different materials, the Mw of the acrylic polymer may be 900,000 or less, 850,000 or less, 800,000 or less, 750,000 or less, 700,000 or less, It may be less than 10,000.

The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and determined as a value in terms of standard polystyrene. Specifically, it can be determined by measuring under the following conditions using a GPC measurement device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation). The same applies to the embodiments described later.
[GPC measurement conditions]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: 1 piece of product name “TSKgel SuperH-RC” (manufactured by Tosoh Corporation)
Detector: Differential refractometer (RI)
Standard sample: polystyrene

(tackifying resin)
In some preferred embodiments, the adhesive layer includes a tackifying resin. By using a tackifying resin, it is possible to improve adhesion to high polarity materials and low polarity materials. Furthermore, by using an appropriate amount of tackifier resin, the gel fraction of the adhesive layer can be adjusted to an appropriate range. The tackifier resin is not particularly limited and includes, for example, rosin-based tackifier resin, terpene-based tackifier resin, hydrocarbon-based tackifier resin, epoxy-based tackifier resin, polyamide-based tackifier resin, elastomer-based tackifier resin, Various tackifying resins such as phenolic tackifying resins and ketone tackifying resins can be used. Such tackifying resins can be used alone or in combination of two or more.

Specific examples of rosin-based tackifying resins include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc. (the same applies hereinafter); and other various rosin derivatives. Examples of the above-mentioned rosin derivatives include rosins such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin), and those obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin). Esters: Unsaturated fatty acid-modified rosins, which are unmodified rosin or modified rosin modified with unsaturated fatty acids; Unsaturated fatty acid-modified rosin esters, which are rosin esters modified with unsaturated fatty acids; Unmodified rosin, modified rosin, unsaturated Rosin alcohols obtained by reducing the carboxyl group in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; rosins; Examples include rosin phenol resins obtained by adding phenol to (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and thermally polymerizing them. Among them, rosin ester is preferred.

Although not particularly limited, specific examples of rosin esters include esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl ester, triethylene glycol ester, glycerin ester. , pentaerythritol ester and the like.

Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer; Modified terpene resins (modified etc.); etc. An example of the above-mentioned modified terpene resin is terpene phenol resin.

Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and includes copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins), and homopolymers or copolymers of terpenes. This concept includes both phenol-modified products (phenol-modified terpene resins). Specific examples of terpenes constituting such terpene phenol resin include 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. Sometimes called hydrogenated terpene phenolic resin.

Examples of hydrocarbon-based tackifying resins include aliphatic (C5-based) petroleum resins, aromatic (C9-based) petroleum resins, aliphatic/aromatic copolymerized (C5/C9-based) petroleum resins, and Hydrogenated substances (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified products thereof (e.g., maleic anhydride modified products), coumaron-based resins, coumaron-indene-based resins Examples include various hydrocarbon resins such as.

In some embodiments, it is preferable to use at least one selected from rosin-based tackifying resins and terpene-based tackifying resins as the tackifying resin. Examples of embodiments using at least one selected from rosin-based tackifying resins and terpene-based tackifying resins include embodiments in which the tackifying resin contains only rosin-based tackifying resins, and embodiments in which the tackifying resin contains terpene-based tackifying resins (e.g., terpene-based tackifying resins). Examples include embodiments in which the tackifying resin contains only a phenolic resin) and embodiments in which the tackifying resin includes a rosin-based tackifying resin and a terpene-based tackifying resin. By incorporating a rosin-based tackifying resin and/or a terpene-based tackifying resin into an acrylic adhesive, excellent adhesive properties such as adhesive strength can be easily obtained. In some preferred embodiments, the total proportion of the rosin-based tackifying resin and the terpene-based tackifying resin in the entire tackifying resin contained in the adhesive layer is, for example, approximately more than 50% by weight (more than 50% by weight and not more than 100% by weight). ), and may be about 70% by weight or more, about 80% by weight or more, about 90% by weight or more, about 95% by weight or more, or about 99% by weight or more.

In some embodiments, it is more preferable to use a rosin-based tackifier resin as the tackifier resin. By containing a rosin-based tackifying resin in the adhesive, the adhesive strength to high polarity materials and low polarity materials can be preferably improved. Among them, rosin ester is preferred. The proportion of the rosin-based tackifying resin in the entire tackifying resin contained in the adhesive layer can be, for example, about 50% by weight or more, about 70% by weight or more, or about 80% by weight or more. . The technology disclosed herein is preferably in an embodiment in which substantially all of the tackifier resin (for example, approximately 97% by weight or more, or 99% by weight or more, and may be 100% by weight) is a rosin-based tackifier resin. can be implemented.

When a rosin-based tackifying resin is used as the tackifying resin, the content ratio of the tackifying resin other than the rosin-based tackifying resin (non-rosin-based tackifying resin) in the adhesive layer is, for example, based on 100 parts by weight of the acrylic polymer. It is appropriate that the amount is 40 parts by weight or less. Thereby, the effect of including rosin ester is suitably exhibited. The amount of the non-rosin tackifier resin used is preferably about 20 parts by weight or less (for example, less than 20 parts by weight), and may be about 10 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be 5 parts by weight or less, or approximately 1 part by weight or less.

In some preferred embodiments, the content of the terpene phenol resin as the tackifier resin in the adhesive layer is, for example, 40 parts by weight or less, and 35 parts by weight or less, based on 100 parts by weight of the acrylic polymer. It may be 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less. By employing such an amount of terpene phenol resin, it is easy to obtain an effect of improving adhesive strength to low polarity materials. Here, the content of the terpene phenol resin being X parts by weight or less based on 100 parts by weight of the acrylic polymer means that the adhesive layer does not contain the terpene phenol resin and that the terpene phenol resin is not contained in the acrylic polymer. The term is used to include both the inclusion of X parts by weight or less per 100 parts by weight. In some embodiments, the content of the terpene phenol resin in the adhesive layer may be 3 parts by weight or less, and 1 part by weight or less (for example, 0 to 0.1 parts by weight) based on 100 parts by weight of the acrylic polymer. It may be within the range of In some other embodiments, the content of the terpene phenol resin in the adhesive layer may be, for example, 1 part by weight or more, 3 parts by weight or more, 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer. It may be at least 7 parts by weight, or at least 9 parts by weight. By using an appropriate amount of terpene phenol resin within the above range, the effects of the technology disclosed herein can be preferably achieved. In some other preferred embodiments using a terpene phenol resin, the content of the terpene phenol resin in the adhesive layer is 10 parts by weight or more, and 12 parts by weight or more based on 100 parts by weight of the acrylic polymer. The amount may be 14 parts by weight or more. By using an appropriate amount of terpene phenol resin, it is possible to improve the adhesive strength to high polarity materials while maintaining the adhesive strength to low polarity materials. The amount of terpene phenol resin used in the above range applies to either the embodiment in which only terpene phenol resin is used as the tackifier resin, or the embodiment in which terpene phenol resin and non-terpene phenol resin (preferably rosin-based tackifier resin) are used in combination. is also applicable. In some embodiments, the amount of terpene phenol resin used within the above range may be preferably employed, for example, in embodiments in which the terpene phenol resin is used in combination with a non-terpene phenol resin (preferably a rosin-based tackifying resin).

In some embodiments, the tackifying resin is a tackifying resin T _L having a softening point of less than 150°C. By using the tackifier resin T _L , higher adhesion strength can be obtained for both high and low polarity materials. The softening point of the tackifier resin T _L may be lower than 140°C or lower than 130°C from the viewpoint of improving adhesive strength to high polarity materials and low polarity materials. In some preferred embodiments, the softening point of the tackifier resin T _L is less than 120°C, suitably less than 110°C, preferably about 105°C or less, more preferably about 100°C or less, More preferably, the temperature is about 95°C or less (for example, less than 95°C), particularly preferably about 90°C or less (for example, about 85°C or less). The lower limit of the softening point of the tackifier resin T _L is not particularly limited. In some embodiments, the softening point of the tackifier resin T _L may be approximately 50° C. or higher, approximately 60° C. or higher, or approximately 65° C. or higher, for example, from the viewpoint of exhibiting appropriate cohesive force. The temperature may be approximately 70°C or higher. In some other embodiments, the softening point of the tackifier resin T _L may be, for example, about 80°C or higher, about 90°C or higher, about 100°C or higher, or about 110°C or higher.

As the tackifier resin T _L , one type suitably selected from among the tackifier resins exemplified above having a softening point of less than 150°C can be used alone or in combination of two or more types. In some embodiments, the tackifying resin T _L preferably includes at least one selected from rosin-based tackifying resins and terpene-based tackifying resins, and more preferably includes rosin-based tackifying resins. The tackifying resin T _L may contain one type of rosin-based tackifying resin alone, or may contain a combination of two or more types of rosin-based tackifying resin.

Although not particularly limited, examples of rosin-based tackifier resins that can be preferably employed as the tackifier resin T _L include rosin esters such as unmodified rosin esters and modified rosin esters. A suitable example of the modified rosin ester is a hydrogenated rosin ester. For example, esters of unmodified rosin or modified rosin (eg, hydrogenated rosin), such as rosin esters such as methyl ester, glycerin ester, etc., can be used as the tackifying resin T _L.

In the adhesive layer according to some preferred embodiments, the tackifier resin T _L includes a hydrogenated rosin ester. The tackifier resin T _L may also include a non-hydrogenated rosin ester. Here, the term "non-hydrogenated rosin ester" is a concept that comprehensively refers to rosin esters other than hydrogenated rosin esters mentioned above. Examples of non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters and polymerized rosin esters. The tackifier resin T _L may contain a combination of a hydrogenated rosin ester and a non-hydrogenated rosin ester as rosin esters, or may contain only one or more hydrogenated rosin esters. It may contain only one species or two or more non-hydrogenated rosin esters. The adhesive layer according to some preferred embodiments contains only one or more hydrogenated rosin esters as the rosin esters contained in the tackifier resin T _L.

The tackifying resin T _L may contain other tackifying resins in addition to the rosin-based tackifying resin. As the other tackifier resin, one type suitably selected from the tackifier resins exemplified above having a softening point of less than 150°C can be used alone or in combination of two or more types.

In some embodiments, the proportion of the rosin-based tackifier resin in the entire tackifier resin T _L can be, for example, more than about 50% by weight, may be about 65% by weight or more, and may be about 75% by weight or more. Good too. The technology disclosed herein is an embodiment in which substantially all of the tackifier resin T _L (for example, approximately 97% by weight or more, or 99% by weight or more, and may be 100% by weight) is a rosin-based tackifier resin. It can be preferably carried out.

In addition, as the tackifying resin T _L , for example, a tackifying resin having a softening point of less than 50°C, more preferably approximately 40°C or less (typically a rosin-based, terpene-based, hydrocarbon-based, etc. tackifying resin, e.g. Hydrogenated rosin methyl ester, etc.) may or may not be included. Such a low softening point tackifier resin may be a liquid tackifier resin that exhibits a liquid state at 30°C. The liquid tackifying resin can be used alone or in combination of two or more. The content of the liquid tackifying resin can be approximately 30% by weight or less of the entire tackifier resin T _L from the viewpoint of cohesive force etc., and should be approximately 10% by weight or less (for example, 0 to 10% by weight). is suitable, and may be approximately 2% by weight or less (0.5 to 2% by weight), and may be less than 1% by weight.

The content of the tackifying resin T _L (the total amount when two or more types of tackifying resin T _L are included) is not particularly limited, but is about 100 parts by weight or less (for example, 100 parts by weight) based on 100 parts by weight of the acrylic polymer. It is appropriate to set it as less than By limiting the amount of the tackifying resin T _L used to a predetermined amount or less, it is possible to improve adhesive strength to high polarity materials and low polarity materials while maintaining sufficient holding power. In some preferred embodiments, the amount of the tackifier resin T _L used is suitably 90 parts by weight or less, preferably 80 parts by weight, based on 100 parts by weight of the acrylic polymer, from the viewpoint of holding power etc. 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, or 45 parts by weight or less. In some other embodiments, the amount of the tackifier resin T _L to be used may be 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less based on 100 parts by weight of the acrylic polymer. In most cases, the amount may be 20 parts by weight or less (for example, less than 20 parts by weight). In some embodiments, from the viewpoint of improving adhesive strength, the amount of the tackifying resin T _L used is, for example, more than 10 parts by weight, and not less than 12 parts by weight, based on 100 parts by weight of the acrylic polymer. The amount may be 14 parts by weight or more, it may be more than 15 parts by weight, suitably 20 parts by weight or more, preferably 30 parts by weight or more, more preferably 35 parts by weight or more, still more preferably 38 parts by weight or more. , may be 45 parts by weight or more, 50 parts by weight or more (for example, more than 50 parts by weight), 55 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more. Often, the amount may be 75 parts by weight or more. The acrylic polymer containing n-heptyl acrylate as a monomer unit used in the technology disclosed herein has good compatibility with the tackifier resin, so it can be used to maintain retention power by incorporating a larger amount of the tackifier resin. , it is possible to improve adhesion to different materials.

In some embodiments, the adhesive layer may include a combination of a tackifying resin T _L and a tackifying resin T _H having a softening point of 150° C. or higher (eg, 150° C. to 200° C.). As the tackifier resin T _H , one kind or a combination of two or more kinds of tackifier resins having a softening point of 150° C. or more among the tackifier resins exemplified above can be used.

Note that the softening point of the tackifier resin in this specification is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature, and the sample is carefully filled into a ring placed on a flat metal plate, taking care not to form bubbles. After it has cooled down, use a slightly heated knife to cut off the raised part from the plane including the top of the ring. Next, a supporter (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured into the container to a depth of 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample were immersed in glycerin without coming into contact with each other, and the temperature of the glycerin was maintained at 20°C plus or minus 5°C for 15 minutes. . A steel ball is then placed in the center of the surface of the sample in the ring and placed in position on the support. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, set the center of the mercury bulb of the thermometer at the same height as the center of the ring, and heat the container. The flame of the Bunsen burner used for heating should be halfway between the center of the bottom of the container and the edge to ensure even heating. Note that the rate at which the bath temperature increases after heating starts and reaches 40°C must be 5.0 plus or minus 0.5°C per minute. The sample gradually softens and flows down from the ring, and the temperature at which it finally touches the bottom plate is read, and this is taken as the softening point. The softening point is measured at two or more points at the same time, and the average value is used.

In some embodiments, it is preferred that the tackifier resin T _L accounts for more than 50% by weight of the total amount of tackifier resins included in the adhesive layer. Thereby, the effect of containing the tackifying resin _TL tends to be effectively expressed. The proportion of the tackifying resin T _L in the total amount of the tackifying resin contained in the adhesive layer is _preferably 60% by weight or more, more preferably The content is 70% by weight or more, more preferably 80% by weight or more, particularly preferably 90% by weight or more, may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifier resin contained in the adhesive layer consists essentially only of tackifier resin _TL . In this embodiment, the proportion of the tackifying resin T _L in the total amount of tackifying resin contained in the adhesive layer is in the range of 99 to 100% by weight.

Although not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin having a hydroxyl value of less than 70 mgKOH/g. Among these, tackifier resins with a hydroxyl value of less than 60 mgKOH/g (more preferably less than 50 mgKOH/g, still more preferably less than 45 mgKOH/g) are preferred. Hereinafter, a tackifier resin having a hydroxyl value of less than 70 mgKOH/g may be referred to as a "low hydroxyl value resin". According to the tackifying resin containing such a low hydroxyl value resin, an adhesive layer having high adhesive strength to both high polarity materials and low polarity materials can be preferably realized. The lower limit of the hydroxyl value of the low hydroxyl value resin is 0 mgKOH/g or more, may be about 10 mgKOH/g or more, or may be about 15 mgKOH/g or more. One type of low hydroxyl value resin can be used alone or two or more types can be used in combination. As the low hydroxyl value resin, one type suitably selected from the tackifying resins exemplified above having a hydroxyl value of less than 70 mgKOH/g can be used alone or in combination of two or more types. In some embodiments, the low hydroxyl value resin preferably includes at least one selected from rosin-based tackifier resins and terpene-based tackifier resins, and more preferably includes rosin-based tackifier resins. The low hydroxyl value resin may contain one type of rosin-based tackifier resin alone, or may contain a combination of two or more types of rosin-based tackifier resin. Moreover, the low hydroxyl value resin may be the above-mentioned tackifier resin T _L or tackifier resin T _H , and it is preferable that the tackifier resin T _L is a low hydroxyl value resin.

In some embodiments, the low hydroxyl value resin preferably accounts for more than 50% by weight of the total amount of tackifying resin contained in the adhesive layer. Thereby, it is possible to preferably improve the adhesion strength to low polarity materials. In some preferred embodiments, the proportion of the low hydroxyl value resin in the total amount of tackifier resin contained in the adhesive layer is preferably 60% by weight from the viewpoint of more effectively exhibiting the effect of using the low hydroxyl value resin. The content is more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifying resin contained in the adhesive layer consists essentially of a low hydroxyl value resin. In this embodiment, the proportion of the low hydroxyl value resin in the total amount of tackifier resin contained in the adhesive layer is in the range of 99 to 100% by weight.

Although not particularly limited, the adhesive layer disclosed herein has a content of a tackifying resin having a hydroxyl value of 70 mgKOH/g or more (hereinafter also referred to as "high hydroxyl value resin") as a tackifying resin. is preferably less than 5 parts by weight based on 100 parts by weight of the acrylic polymer. By limiting the amount of high hydroxyl value resin used in this way, the effect of improving adhesive strength to low polarity materials can be easily obtained. Here, the content of the high hydroxyl value resin being less than 5 parts by weight based on 100 parts by weight of the acrylic polymer means that the adhesive layer does not contain the high hydroxyl value resin and that the adhesive layer does not contain the high hydroxyl value resin. It is used in the sense that it is included in a proportion of less than 5 parts by weight based on 100 parts by weight of the acrylic polymer. The content of the high hydroxyl value resin in the adhesive layer is preferably less than 3 parts by weight based on 100 parts by weight of the acrylic polymer, and is in the range of 1 part by weight or less (for example, 0 to 0.1 parts by weight). It is more preferable that there be.

Here, as the value of the hydroxyl value, a value measured by the potentiometric titration method specified in JIS K0070:1992 can be adopted. The specific measurement method is as shown below.
[Method for measuring hydroxyl value]
1. Reagent (1) As the acetylation reagent, take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine to make a total volume of 50 mL, and stir thoroughly. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to make a total volume of 100 mL, stir thoroughly, and use.
(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as the measurement reagent.
(3) Additionally, prepare toluene, pyridine, ethanol, and distilled water.
2. Procedure (1) Accurately weigh about 2 g of sample into a flat bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air cooling tube.
(2) After heating the above flask in a bath at 100°C for 70 minutes, let it cool, add 35 mL of toluene as a solvent from the upper part of the cooling tube and stir, and then add 1 mL of distilled water and stir to remove acetic anhydride. Disassemble. To complete decomposition, heat again in the bath for 10 minutes and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Next, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol/L potassium hydroxide ethanol solution using a whole pipette.
(5) Perform potentiometric titration with a 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is defined as the end point.
(6) For a blank test, perform (1) to (5) above without adding a sample.
3. Calculation Calculate the hydroxyl value using the following formula.
Hydroxyl value (mgKOH/g)=[(B-C)×f×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 in the sample,
f: factor of 0.5 mol/L potassium hydroxide ethanol solution,
S: weight of sample (g),
D: acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide, 56.11,
It is.

When the adhesive layer disclosed herein includes a tackifier resin, from the viewpoint of improving the biomass carbon ratio of the adhesive layer, a tackifier resin derived from plants (vegetable tackifier resin) is preferably used as the tackifier resin. It can work. Examples of the vegetable tackifier resin include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin. The vegetable tackifying resins can be used alone or in combination of two or more. When the adhesive layer disclosed herein includes a tackifying resin, the proportion of the vegetable tackifying resin in the total amount of the tackifying resin is 30% by weight or more (for example, 50% by weight or more, typically 80% by weight). above) is preferable. In some embodiments, the proportion of vegetable tackifying resin in the total amount of tackifying resin is 90% by weight or more (eg, 95% by weight or more, typically 99-100% by weight). The technology disclosed herein can be preferably implemented in an embodiment that does not substantially contain tackifying resins other than vegetable tackifying resins.

The content of the tackifying resin (the total amount when two or more tackifying resins are included) is not particularly limited, but is about 100 parts by weight or less (for example, less than 100 parts by weight) based on 100 parts by weight of the acrylic polymer. It is appropriate to do so. By limiting the amount of tackifying resin used to a predetermined amount or less, it is possible to improve adhesive strength to high polarity materials and low polarity materials while maintaining sufficient holding power. In some preferred embodiments, the amount of the tackifying resin used is suitably 90 parts by weight or less, preferably 80 parts by weight or less, based on 100 parts by weight of the acrylic polymer, from the viewpoint of holding power etc. The amount may be 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, or 45 parts by weight or less. In some other embodiments, the amount of the tackifying resin used may be 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less, based on 100 parts by weight of the acrylic polymer. It may be 20 parts by weight or less (for example, less than 20 parts by weight). Further, in some embodiments, from the viewpoint of improving adhesive strength, the amount of the tackifying resin used is, for example, more than 10 parts by weight, and may be 12 parts by weight or more, based on 100 parts by weight of the acrylic polymer. , may be 14 parts by weight or more, may be more than 15 parts by weight, suitably 20 parts by weight or more, preferably 30 parts by weight or more, more preferably 35 parts by weight or more, still more preferably 38 parts by weight or more, 45 parts by weight or more. It may be at least 50 parts by weight (for example, more than 50 parts by weight), at least 55 parts by weight, at least 60 parts by weight, at least 65 parts by weight, at least 70 parts by weight, The amount may be 75 parts by weight or more. The acrylic polymer containing n-heptyl acrylate as a monomer unit used in the technology disclosed herein has good compatibility with the tackifier resin, so it can be used to maintain retention power by incorporating a larger amount of the tackifier resin. , it is possible to improve adhesion to different materials.

In the technology disclosed herein, the total content of the acrylic polymer and tackifying resin in the adhesive layer is appropriately set and limited to a specific range so that the effects of the technology disclosed herein are exhibited. It's not something you can do. The total amount (total amount) of the acrylic polymer and tackifier resin contained in the adhesive layer according to some preferred embodiments is more than 50% by weight from the viewpoint of preferably exhibiting the effects of the technology disclosed herein. is appropriate, preferably about 70% by weight or more, more preferably about 90% by weight or more, even more preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less, or less than 100% by weight), and 97% by weight. % or more.

(Crosslinking agent)
In the technology disclosed herein, the adhesive composition used to form the adhesive layer may contain a crosslinking agent as necessary. The type of crosslinking agent is not particularly limited, and examples include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, and metals. Examples include alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, and silane coupling agents. One type of crosslinking agent can be used alone or two or more types can be used in combination. Among these, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and melamine crosslinking agents are preferred, and isocyanate crosslinking agents and epoxy crosslinking agents are more preferred. By appropriately selecting and using a crosslinking agent, the pressure-sensitive adhesive layer can obtain cohesive force, and can preferably achieve both adhesion and holding power to different materials. The adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after a crosslinking reaction, a form before a crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, etc. May contain. The crosslinking agent is typically contained in the adhesive layer exclusively in the form after crosslinking reaction.

As the isocyanate-based crosslinking agent, polyfunctional isocyanates (referring to compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate crosslinking agents can be used alone or in combination of two or more.

Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.
Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; 1,2-tetramethylene diisocyanate; - hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; Examples include 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, and the like.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; 1,2-cyclopentyl diisocyanate, and 1,3-cyclohexyl diisocyanate; -Cyclopentyl diisocyanates such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate. , 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate , 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate , xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

Examples of preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of three or more isocyanate groups per molecule. Such trifunctional or higher functional isocyanates are polymers (typically dimers or trimers) of bifunctional or trifunctional or higher functional isocyanates, derivatives (for example, a combination of a polyhydric alcohol and two or more molecules of polyfunctional isocyanate). addition reaction products), polymers, etc. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, and products of the reaction between trimethylolpropane and hexamethylene diisocyanate. Examples include polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenylisocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercial products of such polyfunctional isocyanates include "Duranate TPA-100" manufactured by Asahi Kasei Chemicals, "Coronate L", "Coronate HL", "Coronate HK", and "Coronate HL" manufactured by Tosoh Corporation. Examples include "Coronate 2096" and "Coronate 2096".

The amount of the isocyanate crosslinking agent used is not particularly limited. For example, the amount can be approximately 0.1 part by weight or more per 100 parts by weight of the acrylic polymer. From the viewpoint of achieving both cohesive force and adhesion, the amount of the isocyanate crosslinking agent to be used per 100 parts by weight of the acrylic polymer can be, for example, 0.5 parts by weight or more, and preferably 1.0 parts by weight or more. and preferably 1.5 parts by weight or more. Further, the amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less per 100 parts by weight of the acrylic polymer, preferably less than 5 parts by weight, more preferably less than 4.0 parts by weight, More preferably, it is less than 3.0 parts by weight (for example, 2.5 parts by weight or less).

As the epoxy crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. The epoxy crosslinking agents can be used alone or in combination of two or more.

Although not particularly limited, specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy crosslinking agents include Mitsubishi Gas Chemical's product names "TETRAD-C" and "TETRAD-X", DIC's product name "Epicron CR-5L", and Nagase ChemteX's product name Examples include the product name "Denacol EX-512" manufactured by Nissan Chemical Industries, Ltd. and the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

The amount of the epoxy crosslinking agent used is not particularly limited. The amount of the epoxy crosslinking agent used may be, for example, more than 0 parts by weight and no more than about 1 part by weight (typically about 0.001 to 1 part by weight) per 100 parts by weight of the acrylic polymer. can. From the viewpoint of suitably exhibiting the effect of improving cohesive force, it is appropriate that the amount of the epoxy crosslinking agent used is approximately 0.005 parts by weight or more, and approximately 0.01 parts by weight, based on 100 parts by weight of the acrylic polymer. The amount is preferably at least 0.02 parts by weight, more preferably about 0.02 parts by weight or more. In addition, from the viewpoint of improving adhesion to the adherend, the amount of the epoxy crosslinking agent used is approximately 0.5 parts by weight or less per 100 parts by weight of the acrylic polymer, and approximately 0.2 parts by weight. It is preferably at most 0.1 part by weight (for example less than 0.1 part by weight), more preferably at most 0.07 part by weight, and may be at most 0.04 part by weight.

In some preferred embodiments, as the crosslinking agent, an epoxy crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the epoxy crosslinking agent are used in combination. According to the technology disclosed herein, a crosslinking agent other than an epoxy crosslinking agent (that is, a crosslinking agent having a different type of crosslinkable reactive group from an epoxy crosslinking agent; hereinafter also referred to as a "non-epoxy crosslinking agent") By using it in combination with an epoxy crosslinking agent, it is possible to suitably achieve both adhesion to different materials and high holding power.

The type of non-epoxy crosslinking agent that can be used in combination with the epoxy crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. The non-epoxy crosslinking agents can be used alone or in combination of two or more.

In some preferred embodiments, an isocyanate crosslinking agent can be employed as the non-epoxy crosslinking agent. For example, by using an epoxy crosslinking agent and an isocyanate crosslinking agent in combination, better adhesive properties can be achieved. The relationship between the content of the epoxy crosslinking agent and the content of the non-epoxy crosslinking agent (preferably an isocyanate crosslinking agent) is not particularly limited. The content of the epoxy crosslinking agent can be, for example, about 1/10 or less of the content of the non-epoxy crosslinking agent (preferably an isocyanate crosslinking agent). From the viewpoint of achieving both adhesion to the adherend and cohesive force, it is appropriate that the content of the epoxy crosslinking agent is approximately 1/30 or less of the content of the non-epoxy crosslinking agent, It is preferably about 1/50 or less, more preferably about 1/75 or less, and may be about 1/90 or less. In addition, from the viewpoint of suitably exhibiting the effect of using an epoxy crosslinking agent and a non-epoxy crosslinking agent (preferably an isocyanate crosslinking agent) in combination, the content of the epoxy crosslinking agent is usually adjusted to It is appropriate to set the content to about 1/1000 or more, for example about 1/500 or more, preferably about 1/300 or more, more preferably 1/150 or more, still more preferably 1/120 or more of the content of the system crosslinking agent. It is.

The total amount of the crosslinking agent used is not particularly limited, and for example, approximately 0.005 parts by weight or more (for example, 0.01 parts by weight or more, typically 0.1 parts by weight or more) based on 100 parts by weight of the acrylic polymer. The amount can be selected from a range of about 10 parts by weight or less (for example, about 8 parts by weight or less, preferably about 5 parts by weight or less).

(Other additives)
In addition to the above-mentioned components, the adhesive composition may contain a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, a coloring agent (pigment, dye, etc.), an antistatic agent, and an antiaging agent, as necessary. , ultraviolet absorbers, antioxidants, light stabilizers, and other additives commonly used in the adhesive field. Regarding such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed explanations will be omitted.

The adhesive layer (layer consisting of an adhesive) disclosed herein is formed from a water-based adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition. It may be an adhesive layer. The aqueous adhesive composition refers to an adhesive composition containing an adhesive (adhesive layer forming component) in a water-based solvent (aqueous solvent), and is typically a water-based adhesive composition. This includes what is called a type adhesive composition (a composition in which at least a portion of an adhesive is dispersed in water). Moreover, a solvent-based adhesive composition refers to an adhesive composition containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of the organic solvents (toluene, ethyl acetate, etc.) that can be used in the above-mentioned solution polymerization can be used without particular limitation. The technology disclosed herein can be preferably implemented in an embodiment including an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method can be adopted in which a pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition to a surface having peelability (peelability surface) or a non-peelability surface and drying it. For an adhesive sheet having a base material, for example, a method (direct method) of forming an adhesive layer by directly applying (typically coating) an adhesive composition to the base material and drying is adopted. be able to. In addition, a method (transfer method) in which an adhesive composition is applied to a surface that has releasability (release surface) and dried to form an adhesive layer on the surface, and the adhesive layer is transferred to a base material. may be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of a release liner, the back surface of a release-treated base material, etc. can be used. Note that although the adhesive layer disclosed herein is typically formed continuously, it is not limited to this form, and may be formed, for example, in a regular or random pattern such as dots or stripes. It may also be a formed adhesive layer.

The adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, die coater, or bar coater. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.
From the viewpoint of promoting crosslinking reaction, improving production efficiency, etc., it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, about 40 to 150°C, and usually preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be performed for the purpose of adjusting component migration within the pressure-sensitive adhesive layer, progressing the crosslinking reaction, alleviating distortion that may exist within the pressure-sensitive adhesive layer, and the like.

(thickness)
The thickness of the adhesive layer is not particularly limited, and a configuration having an adhesive layer having an appropriate thickness in the range of, for example, 0.1 to 500 μm may be adopted depending on the use and purpose of use. In some embodiments, from the viewpoint of preventing the adhesive sheet from becoming excessively thick, the thickness of the adhesive layer is usually approximately 100 μm or less, preferably approximately 70 μm or less, more preferably approximately 60 μm or less, More preferably, it is approximately 50 μm or less. The thickness of the adhesive layer can be approximately 35 μm or less, and may be approximately 30 μm or less, for example. An adhesive layer with a limited thickness can meet the demands for thinning and weight reduction. Additionally, in general, as the thickness of the adhesive layer becomes smaller, the adhesion to the adherend tends to decrease, but according to the technology disclosed herein, it is possible to , it is possible to achieve sufficient adhesion to both high-polar and low-polar materials. In some embodiments, the lower limit of the thickness of the adhesive layer is suitably about 0.5 μm or more, from the viewpoint of adhesion to the adherend, it may be about 1 μm or more, and it may be about 3 μm or more. Advantageously, it is approximately 10 μm or more, more preferably approximately 12 μm or more (eg greater than 12 μm), still more preferably approximately 15 μm or more, and may for example be approximately 18 μm or more. In some preferred embodiments, the thickness of the adhesive layer is greater than 20 μm, may be greater than or equal to 24 μm, and may be greater than or equal to 27 μm. The thicker the adhesive layer is, the easier it is to achieve the target adhesive force. The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers having the above-mentioned thickness on both sides of a base material. In addition, in a double-sided adhesive sheet with a base material that has a first adhesive layer and a second adhesive layer on each side of the base material, the first adhesive layer and the second adhesive layer have the same thickness. They may have different thicknesses.

(gel fraction)
The adhesive layer disclosed herein has a gel fraction of less than 70% (by weight). By using an adhesive with a gel fraction of less than 70%, it is possible to exhibit sufficient adhesive strength not only for highly polar materials but also for low polar materials. In some embodiments, the gel fraction of the adhesive layer is preferably less than 65%, may be less than 60%, may be less than 55%, may be less than 50%, may be less than 45%, may be less than 40%. It may be less than 35%. Further, from the viewpoint of obtaining sufficient holding power, in some preferred embodiments, the gel fraction of the adhesive layer is 20% or more, more preferably 25% or more, still more preferably 30% or more, and 35% or more. It may be more than 40%, it may be more than 45%, it may be more than 50%, it may be more than 55%, it may be more than 60%. By adjusting the gel fraction of the adhesive layer within the above range depending on the monomer composition of the acrylic polymer, Mw, and adhesive composition, both adhesive strength and holding power can be suitably achieved. Specifically, the gel fraction is measured by the method described in Examples below.

(Biomass carbon ratio)
In some embodiments, the adhesive layer may include a biomass-derived material, and the biomass carbon ratio may be greater than or equal to a predetermined value. The biomass carbon ratio of the adhesive layer is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio in the adhesive means that less fossil resource-based materials, such as petroleum, are used. From this point of view, the higher the biomass carbon ratio of the adhesive, the more preferable. For example, the biomass carbon ratio of the adhesive layer may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. good. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of material availability, it may be 95% or less, or 90% or less. In some embodiments, from the viewpoint of facilitating good adhesive performance, the biomass carbon ratio of the adhesive layer may be, for example, 90% or less, 85% or less, or 80% or less.

<Base material>
In an embodiment in which the adhesive sheet disclosed herein is in the form of a single-sided adhesive type or double-sided adhesive type adhesive sheet with a base material, the base material that supports (backs) the adhesive layer may be a resin film, paper, cloth, or rubber. Sheets, foam sheets, metal foils, composites thereof, etc. can be used. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; polyimide Examples include resin film; polyamide resin film; fluororesin film; cellophane, and the like. Examples of paper include Japanese paper, kraft paper, glassine paper, high quality paper, synthetic paper, top coated paper, and the like. Examples of the fabric include woven fabrics and nonwoven fabrics made of various fibrous substances alone or in combination. Examples of the above-mentioned fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets, butyl rubber sheets, and the like. Examples of foam sheets include foamed polyolefin sheets, foamed polyurethane sheets, foamed polychloroprene rubber sheets, and the like. Examples of metal foil include aluminum foil, copper foil, and the like. Note that the base material that supports the adhesive layer is also referred to as a base material layer in the adhesive sheet.

The base material may be formed from a biomass-derived material or a non-biomass-derived material. From the viewpoint of producing a pressure-sensitive adhesive sheet in consideration of reducing dependence on fossil resource-based materials, biomass-derived base materials (typically resin films) are preferably used.

Furthermore, the base material may be formed using a recyclable material or a recycled material (also referred to as recycled material). As such a recycled material, a resin film is preferably used. Resin films (for example, polyester films such as PET films) can be recycled, so whether or not they are made from plant-based materials, reusing the used resin film allows for sustainable reproduction. It is possible to reduce the environmental burden. Such a recyclable resin film or a recycled resin film is also referred to as a recycled film. The recycled material (for example, recycled film) may be formed from a biomass-derived material or a non-biomass-derived material.

As the base material constituting the base material-attached pressure-sensitive adhesive sheet, one containing a resin film as a base film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The base material in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the base material may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc. provided on the surface of the base film.

The resin film is a film whose main component is a resin material (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. Examples include polyester 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 film such as a natural rubber film or a butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and among these, PET films are particularly preferred.

In addition, in this specification, "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 be an unstretched film, a uniaxially stretched film, or a biaxially stretched film. Also, such resin films may be non-foamed. Here, the term "non-foamed resin film" refers to a resin film that has not been intentionally processed to form a foam. Specifically, the non-foamed resin film may be a resin film with an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

The above base material (e.g. resin film) may contain fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet rays, etc., as necessary. Various additives such as an absorbent, an antistatic agent, a lubricant, and a plasticizer may be blended. The blending ratio of various additives is about less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The base material (for example, a resin film) may have a single layer structure, or may have a multilayer structure of two layers, three layers, or more. From the viewpoint of shape stability, the base material preferably has a single-layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the above resin (for example, polyester resin). The method for manufacturing the base material (typically a resin film) is not particularly limited, and any conventionally known method may be appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calender roll molding can be appropriately employed.

The surface of the base material 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. Such surface treatment may be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the ability of the adhesive layer to anchor to the base material.

Furthermore, when the technology disclosed herein is implemented in the form of a single-sided pressure-sensitive adhesive sheet with a base material, the back surface of the base material may be subjected to a peeling treatment as necessary. For example, the peeling treatment is performed by applying a general silicone-based, long-chain alkyl-based, or fluorine-based peeling agent to a thin film, typically about 0.01 μm to 1 μm (for example, 0.01 μm to 0.1 μm). It can be a process to add. By performing such a peeling treatment, effects such as facilitating the unwinding of a roll-shaped adhesive sheet can be obtained.

In the pressure-sensitive adhesive sheet including a base material, the thickness of the base material is not particularly limited. From the viewpoint of preventing the pressure-sensitive adhesive sheet from becoming too thick, the thickness of the base material can be, for example, approximately 200 μm or less, preferably approximately 150 μm or less, and more preferably approximately 100 μm or less. The thickness of the base material may be approximately 70 μm or less, approximately 50 μm or less, or approximately 30 μm or less (for example, approximately 25 μm or less) depending on the purpose and manner of use of the adhesive sheet. In some embodiments, the thickness of the base film layer may be about 20 μm or less, about 15 μm or less, about 10 μm or less (eg, about 5 μm or less). By reducing the thickness of the base material, the thickness of the adhesive layer can be increased even if the total thickness of the adhesive sheet is the same. This can be advantageous from the viewpoint of improving adhesion to adherends and base materials. The lower limit of the base material is not particularly limited. From the viewpoint of handleability and processability of the pressure-sensitive adhesive sheet, the thickness of the base material is usually about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example about 6 μm or more. In some embodiments, the thickness of the substrate can be about 15 μm or more, and can be about 25 μm or more.

<Release liner>
In the technology disclosed herein, a release liner can be used during formation of the adhesive layer, production of the adhesive sheet, storage of the adhesive sheet before use, distribution, shape processing, etc. 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 release liner made of a fluorine-based polymer (polytetrafluoroethylene, etc.), etc. may be used. be able to. The release treatment layer may be formed by surface-treating the liner base material with a release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide release agent. As the liner base material, like the base material of the above-mentioned adhesive sheet, one formed using a biomass-derived material or a recycled material (recycled film, etc.) can be preferably used.

<Total thickness of adhesive sheet>
The total thickness of the adhesive sheet disclosed herein (which includes an adhesive layer and may further include a base layer, but does not include a release liner) is not particularly limited. The total thickness of the adhesive sheet is, for example, approximately 1 mm or less, may be approximately 500 μm or less, and may be approximately 300 μm or less, and from the viewpoint of thinning, approximately 200 μm or less is appropriate, and approximately 150 μm or less. (For example, approximately 100 μm or less). In some preferred embodiments, the thickness of the pressure-sensitive adhesive sheet can be approximately 50 μm or less, for example, approximately 35 μm or less. The lower limit of the thickness of the adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), suitably about 3 μm or more, preferably about 10 μm or more, more preferably about 15 μm or more, It may be about 50 μm or more, or about 100 μm or more. A pressure-sensitive adhesive sheet having a thickness of a predetermined value or more tends to have good adhesion to an adherend and also tends to have excellent handling properties. In addition, in the adhesive sheet without a base material, the thickness of the adhesive layer becomes the total thickness of the adhesive sheet.

<Characteristics of adhesive sheet>
In some embodiments, the adhesive sheet preferably has a 180 degree peel strength against a stainless steel plate (adhesive strength against SUS) of approximately 15 N/25 mm or more (for example, 17 N/25 mm or more). A pressure-sensitive adhesive sheet exhibiting such adhesive strength to SUS can exhibit excellent adhesive strength to highly polar materials. The adhesive force to SUS is more preferably about 20 N/25 mm or more, still more preferably about 25 N/25 mm or more, particularly preferably 30 N/25 mm or more, and may be 32 N/25 mm or more. The upper limit of the adhesive strength to SUS is not particularly limited, but from the viewpoint of coexistence with other adhesive properties such as holding power, it may usually be about 50 N/25 mm or less, for example. The adhesive strength to SUS is measured using an SUS plate as an adherend under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees in a measurement environment of 23° C. and 50% RH. More specifically, it is measured by the method described in Examples below.

The adhesive sheet disclosed herein preferably has a 180 degree peel strength against polypropylene (adhesive strength against PP) of about 10 N/25 mm or more. A pressure-sensitive adhesive sheet exhibiting such adhesion to PP can adhere well to low polarity materials and exhibit high adhesion reliability to the above-mentioned adherends. The adhesive force to PP is more preferably about 12 N/25 mm or more, still more preferably about 14 N/25 mm or more, particularly preferably about 16 N/25 mm or more, and about 18 N/25 mm or more (for example, about 20 N/25 mm or more). There may be. The upper limit of the adhesive force to PP is not particularly limited, but from the viewpoint of coexistence with other adhesive properties such as holding power, it is usually about 40 N/25 mm or less, and may be 30 N/25 mm or less. The adhesive strength to PP is measured using PP as an adherend in a measurement environment of 23° C. and 50% RH at a tensile rate of 300 mm/min and a peel angle of 180 degrees. More specifically, it is measured by the method described in Examples below.

The adhesive sheet disclosed herein preferably has a 180 degree peel strength against polyethylene (adhesive strength against PE) of approximately 5 N/25 mm or more. A pressure-sensitive adhesive sheet exhibiting such adhesive strength to PE can exhibit sufficient adhesion reliability to low polarity materials. The adhesive strength to PE is more preferably about 7 N/25 mm or more, still more preferably about 10 N/25 mm or more, particularly preferably about 12 N/25 mm or more, and 14 N/25 mm or more (for example, about 15 N/25 mm or more). It's okay. The upper limit of the adhesive force to PE is not particularly limited, but from the viewpoint of coexistence with other adhesive properties such as holding power, it is usually about 30 N/25 mm or less, and may be 25 N/25 mm or less. The above-mentioned adhesive strength to PE is measured using PE as an adherend in a measurement environment of 23° C. and 50% RH at a tensile rate of 300 mm/min and a peel angle of 180 degrees. More specifically, it is measured by the method described in Examples below.

As mentioned above, the adhesive sheet disclosed herein may exhibit adhesive strength of a predetermined value or more to PP and PE. Adhesive sheets exhibiting the above-mentioned adhesive strength to PP and adhesive strength to PE can have stable and sufficient adhesion reliability to different materials including various low polarity materials, and therefore are useful in a wide range of applications. .

The pressure-sensitive adhesive sheet disclosed herein has a holding power test conducted under the conditions of 80° C., adhesion area 10 mm x 20 mm, load 1.5 kg, and 1 hour. The deviation distance may be 10 mm or less. Such a pressure-sensitive adhesive sheet has high cohesive force and sufficient holding power. The displacement distance in the holding force test is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1 mm or less (0 to 0.1 mm). More specifically, the above-mentioned holding power test is carried out by the method described in the Examples below.

In some embodiments, the adhesive sheet may include a biomass-derived material, and the biomass carbon ratio may be greater than or equal to a predetermined value. The biomass carbon ratio of the adhesive sheet is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio in the adhesive sheet means that less fossil resource-based materials, such as petroleum, are used. From this point of view, the higher the biomass carbon ratio of the pressure-sensitive adhesive sheet, the more preferable it is. For example, the biomass carbon ratio of the adhesive sheet may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. . The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of material availability, it may be 95% or less, or 90% or less. In some embodiments, from the viewpoint of facilitating good adhesive performance, the biomass carbon ratio of the adhesive sheet may be, for example, 90% or less, 85% or less, or 80% or less.

<Application>
The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and can be used for various purposes. The pressure-sensitive adhesive sheet disclosed herein exhibits high adhesion to both high-polar and low-polar materials, and has sufficient holding power, so it is suitable for use with members made of high-polar materials including metal members, , suitable for adhesively fixing members made of low polarity materials. For example, it is suitable for applications where the component to be bonded has a high polarity surface or a low polarity surface and long-term bonding reliability is required. Examples of materials constituting such a highly polar surface include metal materials such as stainless steel, glass materials, and polyester resin members such as PET. In addition, materials constituting the low polarity surface include polyolefin resins such as polyethylene (PE) and polypropylene (PP), which are generally known as materials with low surface free energy, fluorine-based polymers (such as polytetrafluoroethylene), Examples include polystyrene, polyoxymethylene, polyvinyl acetate, and the like. Among these, the pressure-sensitive adhesive sheet disclosed herein is preferably used for adhesively fixing an adherend having a surface made of a material containing a polyolefin such as PE or PP, or a fluorine-based polymer.

Suitable applications for the adhesive sheet disclosed herein include fixing members in electronic devices such as home appliances, office automation equipment, and portable electronic devices. The members constituting the above-mentioned electronic devices can be made of highly polar materials such as metals, or low polar materials such as PE, PP, or fluororesin. It is meaningful to realize adhesive fixation with excellent adhesive reliability for various dissimilar materials including those with low polarity. Examples of the electronic devices include various home appliances, personal computers (desktop type, notebook type, tablet type, etc.), and the like. Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, and various wearable devices (e.g., wrist-wear type that is worn on the wrist like a wristwatch, and Modular type that is attached to a part of the body, eyewear type that includes glasses type (monocular type and binocular type, including head-mounted type), clothing type that is attached to shirts, socks, hats, etc. in the form of accessories, and earphones. digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, and in-vehicle devices. This includes information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. Note that in this specification, "portable" does not mean that it is sufficient to simply be able to carry it; it also means that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. shall mean.

FIG. 4 is an example schematically showing a portable electronic device (smartphone) using the adhesive sheet disclosed herein. As shown in FIG. 4, a battery (heat generating element) 540 is built inside the casing 520 of the portable electronic device 500. Moreover, the portable electronic device 500 is configured to include an adhesive sheet 550. In this configuration example, the adhesive sheet 550 has the form of a double-sided adhesive sheet (double-sided adhesive sheet) that fixes members constituting the portable electronic device 500. Note that the portable electronic device 500 includes a touch panel 570 whose display section also functions as an input section. The adhesive sheet disclosed herein is preferably used as a component (member joining means) of the above-mentioned portable electronic devices.

Furthermore, since the adhesive sheet disclosed herein may have an adhesive layer containing an acrylic polymer with a high biomass carbon ratio in some embodiments, conventional general acrylic adhesives (i.e. By being used as a substitute for acrylic adhesives in various applications where acrylic adhesives (acrylic adhesives with a low biomass carbon ratio) are used, it can contribute to reducing dependence on fossil resource-based materials. The adhesive sheet disclosed herein can be preferably used as an adhesive sheet with reduced dependence on fossil resource materials.

The matters disclosed by this specification include the following.
[1] Electronic equipment,
An adhesive sheet is bonded to the member constituting the electronic device,
The adhesive sheet has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including n-heptyl acrylate and a carboxyl group-containing monomer,
The monomer component of the acrylic polymer contains more than 3% by weight of the carboxy group-containing monomer,
The adhesive layer has a gel fraction of less than 70%,
The weight average molecular weight of the acrylic polymer is greater than 600,000, an electronic device.
[2] The electronic device according to [1] above, wherein the surface of the member is made of a material selected from metal, polyolefin resin, and fluororesin.
[3] The electronic device according to [1] or [2] above, wherein the electronic device is a home appliance.
[4] The electronic device according to [1] or [2] above, wherein the electronic device is a portable electronic device.
[5] The electronic device according to any one of [1] to [4] above, wherein the adhesive composition for forming the adhesive layer contains a crosslinking agent.
[6] The electronic device according to any one of [1] to [5] above, wherein the adhesive layer contains a tackifier resin.
[7] The electronic device according to any one of [1] to [6] above, wherein the adhesive layer has a thickness of 0.1 to 500 μm.
[8] The electronic device according to any one of [1] to [7] above, wherein the adhesive layer has a gel fraction of 20% or more and less than 70%.
[9] The electronic device according to any one of [1] to [8] above, wherein the adhesive sheet is a base material-less double-sided adhesive sheet consisting only of the adhesive layer.
[10] The electronic device according to any one of [1] to [8] above, wherein the adhesive sheet has a base material and the adhesive layer provided on at least one surface of the base material.

[11] Has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including n-heptyl acrylate and a carboxyl group-containing monomer,
The monomer component of the acrylic polymer contains more than 3% by weight of the carboxy group-containing monomer,
The adhesive layer has a gel fraction of less than 70%,
A pressure-sensitive adhesive sheet, wherein the acrylic polymer has a weight average molecular weight of more than 600,000.
[12] The pressure-sensitive adhesive sheet according to [11] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a crosslinking agent.
[13] The pressure-sensitive adhesive sheet according to [11] or [12] above, wherein the pressure-sensitive adhesive layer contains a tackifying resin.
[14] The pressure-sensitive adhesive sheet according to any one of [11] to [13] above, wherein the pressure-sensitive adhesive layer has a thickness of 0.1 to 500 μm.
[15] The adhesive sheet according to any one of [11] to [14] above, wherein the adhesive layer has a gel fraction of 20% or more and less than 70%.
[16] The adhesive sheet according to any one of [11] to [15] above, which has a 180 degree peel strength against a stainless steel plate of 15 N/25 mm or more.
[17] The adhesive sheet according to any one of [11] to [16] above, which has a 180 degree peel strength against polypropylene of 10 N/25 mm or more.
[18] The adhesive sheet according to any one of [11] to [17] above, which has a 180 degree peel strength against polyethylene of 5 N/25 mm or more.
[19] Any one of [11] to [18] above, wherein the displacement distance in a holding force test conducted at 80° C., adhesive area 10 mm x 20 mm, load 1.5 kg, and 1 hour is 10 mm or less. adhesive sheet.
[20] The pressure-sensitive adhesive sheet according to any one of [11] to [19] above, which is a base material-less double-sided pressure-sensitive adhesive sheet consisting only of the pressure-sensitive adhesive layer.
[21] The pressure-sensitive adhesive sheet according to any one of [11] to [19] above, comprising a base material and the pressure-sensitive adhesive layer provided on at least one surface of the base material.
[22] The adhesive sheet according to any one of [11] to [21] above, which is used for fixing members in electronic devices.
[23] An electronic device comprising the adhesive sheet according to any one of [11] to [21] above.

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

<Evaluation method>
[Gel fraction]
Approximately 0.1 g of an adhesive sample (weight Wg ₁ ) is wrapped in a purse-like shape with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore diameter of 0.2 μm, and the opening is tied with an octopus string (weight Wg ₃ ). The above-mentioned porous polytetrafluoroethylene (PTFE) membrane is available from Nitto Denko under the trade name "Nitoflon (registered trademark) NTF1122" (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) or its equivalent. use the product.
This package was immersed in 50 mL of ethyl acetate and kept at room temperature (approximately 23°C) for 7 days to allow only the sol component in the adhesive layer to elute out of the membrane.The package was then taken out and attached to the outer surface. The remaining ethyl acetate is wiped off, the package is dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the package is measured. The gel fraction of the adhesive layer is determined by substituting each value into the following formula.
Gel fraction (%) = [(Wg ₄ - Wg ₂ - Wg ₃ )/Wg ₁ ] x 100

[Adhesive strength to SUS]
Under a measurement environment of 23°C and 50% RH, one adhesive side of an adhesive sheet (double-sided adhesive sheet) was lined with a PET film with a thickness of 50 μm, and cut into a size of 25 mm in width and 100 mm in length. Prepare a measurement sample. In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample is pressed onto the surface of a stainless steel plate (SUS304BA plate) that has been cleaned with ethyl acetate by making one reciprocation with a 2 kg roller. After leaving it in the same environment for 72 hours, using a universal tensile compression tester, the peel strength (relative to SUS Adhesive force) [N/25mm] is measured.

[Adhesion to PP]
Under a measurement environment of 23°C and 50% RH, one adhesive side of an adhesive sheet (double-sided adhesive sheet) was lined with a PET film with a thickness of 50 μm, and cut into a size of 25 mm in width and 100 mm in length. Prepare a measurement sample. In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample was pressed onto the surface of a polypropylene plate (PP plate) washed with ethanol by making one reciprocation with a 2 kg roller. After leaving it in the same environment for 72 hours, the peel strength (relative to PP Adhesive force) [N/25mm] is measured. As the PP board, for example, the product name "Kobe Polysheet PP-N-AN" (thickness: 2 mm) manufactured by Showa Denko Materials Co., Ltd. is used.

[Adhesive strength to PE]
Under a measurement environment of 23°C and 50% RH, one adhesive side of an adhesive sheet (double-sided adhesive sheet) was lined with a PET film with a thickness of 50 μm, and cut into a size of 25 mm in width and 100 mm in length. Prepare a measurement sample. In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample was pressed onto the surface of a polyethylene board (PE board) washed with ethanol by making one reciprocation with a 2 kg roller. After leaving it in the same environment for 72 hours, the peel strength (relative to PE Adhesive force) [N/25mm] is measured. As the PE board, for example, the product name "Kobe Polysheet EL-N-AN" (thickness: 2 mm) manufactured by Showa Denko Materials Co., Ltd. is used.

In the above-mentioned peel strength measurements, the universal tensile compression tester used is Minebea's "Tensile Compression Tester, TG-1kN" or its equivalent. Note that when performing the above peel strength measurement on a single-sided adhesive sheet, backing with a PET film is not necessary. When the base material thickness is thin (for example, when the base material thickness is 25 μm or less), it may be lined with a PET film.

[Holding power]
Under an environment of 23°C and 50% RH, a 50 μm thick PET film is pasted on one adhesive side of an adhesive sheet (double-sided adhesive sheet) for lining, and a measurement sample is prepared by cutting it into a length of 10 mm in width. . The other adhesive side of the measurement sample was attached to a Bakelite plate (phenolic resin plate) as an adherend, with a pasting area of 10 mm width and 20 mm length (adhesion area 200 mm ² ), and a 2 kg roller was moved back and forth once. Crimp. After leaving the sample affixed to the adherend in this way in the same environment for 30 minutes, the adherend was hung so that the length direction of the sample was in the vertical direction, and 1. A load of 5 kg is applied to the product, and the product is left in an environment of 80° C. for 1 hour in accordance with JIS Z0237. After 1 hour has passed, the deviation distance [mm] of the upper end of the sample from the initial pasting position is measured (deviation distance after 1 hour). Measurements are performed using three samples for each adhesive sheet (ie, N=3), and their arithmetic mean value is determined. If the deviation distance is 10 mm or less, it is determined to pass, and if the deviation distance exceeds 10 mm or the sample falls within 1 hour, it is determined to be rejected.

<Example 1>
(Synthesis of acrylic polymer)
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel, 90 parts of n-heptyl acrylate (n-HpA) and 10 parts of acrylic acid (AA) as monomer components, and a polymerization solvent were added. and ethyl acetate were added thereto, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C to 70°C for 8 hours. A solution of acrylic polymer (A1) was obtained. The weight average molecular weight (Mw) of the acrylic polymer (A1) was 670,000. Note that the above n-HpA is a compound having a biomass-derived heptyl group at the ester end, which was synthesized using biomass-derived heptyl alcohol.

(Preparation of adhesive composition)
100 parts of the above acrylic polymer (A1), rosin tackifier resin (product name "Haritac SE10", manufactured by Harima Kasei Co., Ltd., hydrogenated rosin glycerin ester, softening point 75-85°C, hydroxyl value 25-40 mgKOH/g) 40 1 part, and 2 parts of an isocyanate crosslinking agent (trade name "Coronate L", 75% ethyl acetate solution of trimethylolpropane/tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation) were stirred and mixed to obtain the adhesive according to this example. A drug composition was prepared.

(Preparation of adhesive sheet)
The obtained adhesive composition was applied to the release surface of a polyester release film (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) with a thickness of 38 μm, and dried at 100° C. for 2 minutes to form a film with a thickness of 30 μm. An adhesive layer was formed. A release surface of a 25 μm thick polyester release film (trade name “Diafoil MRF”, 25 μm thick, manufactured by Mitsubishi Chemical Corporation) was attached to this adhesive layer. In this way, a substrate-less double-sided pressure-sensitive adhesive sheet having a thickness of 30 μm and having both sides protected by the two polyester release films was obtained.

<Example 2>
In the preparation of the adhesive composition in Example 1, an epoxy crosslinking agent (trade name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N , N-diglycidylaminomethyl)cyclohexane) was further added and mixed with stirring to prepare a pressure-sensitive adhesive composition according to this example. A substrate-less double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive composition was used.

<Examples 3 to 5>
A solution of acrylic polymer (A2) was obtained in the same manner as the synthesis of acrylic polymer (A1), except that the monomer composition was changed to 94 parts of n-HpA and 6 parts of AA, and the concentration of monomer components during polymerization was adjusted. . Using the above acrylic polymer (A2), adhesive compositions according to each example were prepared in the same manner as in Example 2 except that the composition was changed to that shown in Table 1. A base material-less double-sided adhesive sheet according to the example was produced.

<Example 6>
A solution of acrylic polymer (A3) was obtained in the same manner as in the synthesis of acrylic polymer (A1) except that the monomer composition was changed to 96 parts of n-HpA and 4 parts of AA. Adhesive compositions according to this example were prepared in the same manner as in Example 2 except that the above acrylic polymer (A3) was used, and the adhesive compositions were used to form a base material-less double-sided adhesive sheet according to this example. was created.

<Examples 7 to 9>
Adhesive compositions according to each example were prepared in the same manner as in Example 6, except that the type of tackifier resin was changed as shown in Table 1, and the adhesive composition was used to prepare a base material according to each example. A double-sided pressure-sensitive adhesive sheet was prepared. Specifically, in Example 7, 40 parts of the rosin-based tackifier resin of Example 6 was replaced with 25 parts of the rosin-based tackifier resin and a terpene-based tackifier resin (product name "YS In Example 8, the above rosin of Example 6 was used as the tackifying resin. In Example 9, the amount of the rosin tackifier resin used was changed from 40 parts in Example 6 to 15 parts.

<Comparative example 1>
A solution of an acrylic polymer (A4) having a lower molecular weight than the acrylic polymer (A3) was obtained in the same manner as the synthesis of the acrylic polymer (A3) except that the concentration of monomer components during polymerization was adjusted. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 6 except that the above acrylic polymer (A4) was used, and a base material-less double-sided pressure-sensitive adhesive sheet according to this example was prepared using the pressure-sensitive adhesive composition. Created.

<Comparative Examples 2-3>
A solution of acrylic polymer (A5) was obtained in the same manner as in the synthesis of acrylic polymer (A1) except that the monomer composition was changed to 97 parts of n-HpA and 3 parts of AA. Using the above acrylic polymer (A5), adhesive compositions according to each example were prepared in the same manner as in Example 2 except that the composition was changed to that shown in Table 1. A base material-less double-sided adhesive sheet according to the example was produced.

<Comparative Examples 4-5>
The acrylic polymer was synthesized basically in the same manner as the acrylic polymer (A1) except that the monomer composition was changed to 95 parts of n-butyl acrylate (BA) or 95 parts of 2-ethylhexyl acrylate (2EHA) and 5 parts of AA. Solutions of (A6) and (A7) were obtained. Adhesive compositions according to each example were prepared in the same manner as in Example 2 except that the above acrylic polymer (A6) or (A7) was used, and the adhesive composition was used to create a base material according to each example. A double-sided pressure-sensitive adhesive sheet was prepared.

Table 1 shows the outline and evaluation results of the pressure-sensitive adhesive sheets of each example.

As shown in Table 1, the adhesives according to Examples 1 to 9 contain n-heptyl acrylate as a monomer component, and contain an acrylic polymer having a Mw of more than 600,000 and containing more than 3% by weight of a carboxyl group-containing monomer, The gel fraction was less than 70%. The adhesives according to these examples have adhesive strength to SUS of 15 N/25 mm or more, PP adhesive strength of 10 N/25 mm or more, and PE adhesive strength of 5 N/25 mm or more, and also pass the holding power test (specifically In general, the deviation distance was 1 mm or less). More specifically, Examples 1 and 2, in which the amount of carboxyl group-containing monomer used was the largest, had high adhesive strength to low polar materials (PP and PE) and particularly excellent adhesive strength to SUS. was. Furthermore, the results of Examples 3 to 5 show that by increasing the amount of tackifier resin, the adhesive strength to SUS, the adhesive strength to PP, and the adhesive strength to PE can be improved. The results of these examples also show that as the amount of tackifier resin increases, the gel fraction of the adhesive layer tends to decrease and the adhesive strength tends to increase. On the other hand, in Comparative Example 1 in which an acrylic polymer having an Mw of 600,000 was used, the holding power test result was a failure. Furthermore, Comparative Example 2 in which an acrylic polymer with a copolymerization ratio of a carboxyl group-containing monomer (specifically, AA) was 3% also failed in the holding power test. In Comparative Example 3, in which the amount of crosslinking agent was increased compared to Comparative Example 2, the holding power was improved, but the adhesive strength to SUS, the adhesive strength to PP, and the adhesive strength to PE all decreased significantly. Furthermore, from the results of Comparative Examples 2 and 3, it can be seen that when the gel fraction becomes too high, it becomes difficult to satisfy the adhesive properties. Furthermore, in Comparative Examples 4 to 5 in which an alkyl acrylate (BA or 2EHA) other than n-heptyl acrylate was used, adhesive strength at the level of Examples 1 to 9 could not be obtained.

From the above results, we found that by using an adhesive that contains an acrylic polymer containing n-heptyl acrylate as a monomer component and has a gel fraction of less than 70%, it is effective against not only highly polar materials but also low polar materials. It can be seen that adhesive strength is obtained. In addition, by copolymerizing the above acrylic polymer with a carboxyl group-containing monomer at a ratio of more than 3% by weight and designing the Mw to be greater than 600,000, it has high adhesive strength to different materials. It can be seen that the holding force can be improved. It can be seen that the adhesion to highly polar materials can also be improved by using the above carboxy group-containing monomer. That is, as the acrylic polymer, a polymer of a monomer component containing n-heptyl acrylate and more than 3% by weight of a carboxyl group-containing monomer is used, the gel fraction of the adhesive layer is less than 70%, and the acrylic polymer It can be seen that adhesives with Mw greater than 600,000 can achieve both high levels of adhesion to highly polar materials, adhesion to low polar materials, and holding power.

Although specific examples of the present invention have been described above in detail, these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above.

1, 2, 3 Adhesive sheet 10 Supporting base material 10A First side 10B Second side (back side)
21 Adhesive layer (first adhesive layer)
21A Adhesive surface (first adhesive surface)
21B Second adhesive surface 22 Adhesive layer (second adhesive layer)
22A Adhesive surface (second adhesive surface)
31, 32

Release liner

100, 200, 300 Adhesive sheet with release liner

Claims

Has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including n-heptyl acrylate and a carboxyl group-containing monomer,
The monomer component of the acrylic polymer contains more than 3% by weight of the carboxy group-containing monomer,
The adhesive layer has a gel fraction of less than 70%,
A pressure-sensitive adhesive sheet, wherein the acrylic polymer has a weight average molecular weight of more than 600,000.
The adhesive sheet according to claim 1, wherein the adhesive composition for forming the adhesive layer contains a crosslinking agent.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a tackifying resin.
The adhesive sheet according to claim 1 or 2, wherein the adhesive layer has a thickness of 0.1 to 500 μm.
The adhesive sheet according to claim 1 or 2, wherein the adhesive layer has a gel fraction of 20% or more and less than 70%.
The adhesive sheet according to claim 1 or 2, having a 180 degree peel strength of 15 N/25 mm or more against a stainless steel plate.
The adhesive sheet according to claim 1 or 2, having a 180 degree peel strength against polypropylene of 10 N/25 mm or more.
The pressure-sensitive adhesive sheet according to claim 1 or 2, having a 180 degree peel strength against polyethylene of 5 N/25 mm or more.
The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet has a displacement distance of 10 mm or less in a holding force test conducted at 80° C., adhesive area 10 mm x 20 mm, load 1.5 kg, and for 1 hour.
The adhesive sheet according to claim 1 or 2, which is used for fixing members in electronic equipment.