JP2024041042A - double-sided adhesive sheet - Google Patents

Abstract

[Problem] To provide a double-sided pressure-sensitive adhesive sheet that can have high adhesive strength, and can achieve both ease of microscopic uneven deformation and processability. [Solution] The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer that contains an acrylic polymer. The acrylic polymer is a polymer of a monomer component that contains heptyl acrylate and a carboxyl group-containing monomer. The monomer component contains 3% by weight or more of the carboxyl group-containing monomer. Furthermore, the pressure-sensitive adhesive layer has a gel fraction of more than 40%. The pressure-sensitive adhesive layer has a storage modulus of 0.04 MPa or more at 23°C and a tan δ of 0.46 or more at 23°C. [Selected Figure] Figure 1

Description

The present invention relates to a double-sided adhesive sheet.

Generally, adhesives (also referred to as pressure-sensitive adhesives, hereinafter the same) exhibit a soft solid state (viscoelastic body) in a temperature range around room temperature, and have the property of adhering to an adherend under pressure. Taking advantage of these properties, adhesives are used in various industrial fields, from mobile electronic devices such as smartphones and home appliances to automobiles and OA equipment, and are typically used in the form of adhesive sheets containing an adhesive layer to bond parts together. It is widely used for purposes such as surface protection. Technical documents regarding pressure-sensitive adhesive sheets include Patent Documents 1 and 2. Patent Documents 1 and 2 describe adhesives containing acrylic polymers polymerized using heptyl acrylate as a monomer component.

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

Adhesive sheets are required to have various performances depending on the location of application and usage mode. For example, when fixing members inside a portable electronic device using a double-sided adhesive sheet, the adhesion area is usually small due to limitations such as size and weight. The double-sided adhesive sheet used for this purpose needs to have adhesive strength that can achieve good fixation even on a small area, and the required performance has become higher due to the demand for weight reduction and miniaturization. It has become.

Further, the double-sided pressure-sensitive adhesive sheet used for bonding and fixing can be used in such a manner that it is applied to an adherend after being processed into a predetermined shape (outline) to match the shape of the adhesively fixed portion. For example, in fixing members of portable electronic devices, a double-sided adhesive sheet is processed into the shape of the adhesively fixed portion, such as a band shape or a frame shape, by cutting processing such as punching, and then used for fixing the members. In double-sided adhesive sheets used in this manner, if the adhesive is too soft, the adhesive may protrude during cutting, which may impair the stability of adhesive performance, reduce processing accuracy, and cause problems. . Therefore, it is desirable that the adhesive of a double-sided pressure-sensitive adhesive sheet that is used after being subjected to cutting processing such as punching is designed to have sufficient hardness to cope with the above-mentioned processing.

By the way, double-sided adhesive sheets are usually double-sided sheets with a release liner, each adhesive side of which is protected by a release liner, from the viewpoint of productivity and handling before use (that is, before being attached to an adherend). It is handled in the form of an adhesive sheet. By protecting the adhesive surface of the double-sided adhesive sheet with a release liner, the adhesive surface is kept smooth and adheres well to the surface of the adherend to exhibit the desired adhesive properties. In addition, the adhesive sheet having the adhesive surface protected by a release liner and held smooth can be uniformly applied to an adherend and provide a good appearance when the adherend surface is visually recognized. . The above-mentioned double-sided adhesive sheet is, for example, formed into a roll body (double-sided adhesive sheet roll with release liner), which is a roll of a double-sided adhesive sheet with a release liner, each adhesive side of which is protected by two release liners, for distribution and storage. and processed.

However, in the production of the above-mentioned double-sided adhesive sheet, for example, in the process of winding up a double-sided adhesive sheet with a release liner onto a roll, minute foreign matter gets mixed in between the two release liners, and due to the pressure inside the roll, the foreign matter This may cause dents in the double-sided adhesive sheet. Such dents remain as minute dents and are visible even after the double-sided pressure-sensitive adhesive sheet is attached to the adherend, and there is concern that this may cause deterioration in appearance quality. Such visible unevenness deformation cannot be eliminated once it is affixed to an adherend and stabilized. Particularly in recent years, there has been a tendency for higher appearance quality to be required depending on the area where double-sided adhesive sheets are applied, such as the display part of electronic devices, and double-sided adhesive sheets that suppress minute deformation of irregularities to a level that was not considered a problem in the past. It is assumed that this will be required. It is thought that if the adhesive is designed to be soft, the above-mentioned fine unevenness deformation will be alleviated to some extent, but on the other hand, there is a concern that workability during processing such as punching may be reduced. Since there is a trade-off relationship between suppressing the above-mentioned fine uneven deformation and workability, it is difficult to achieve both.

As a result of intensive studies, the present inventors found that a structure using an acrylic polymer containing heptyl acrylate as a monomer component can have high adhesive strength suitable for bonding and fixing applications, and has the ability to alleviate the above-mentioned fine uneven deformation. The present invention has been completed by creating a double-sided pressure-sensitive adhesive sheet that can achieve both the above-mentioned properties and the workability in punching and the like. That is, an object of the present invention is to provide a double-sided pressure-sensitive adhesive sheet that is capable of having high adhesive strength and is capable of achieving both ease of deformation of minute irregularities and workability.

According to this specification, a double-sided adhesive sheet is provided. This double-sided adhesive sheet has an adhesive layer containing an acrylic polymer. The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer. Further, the monomer component contains 3% by weight or more of the carboxy group-containing monomer. Furthermore, the gel fraction of the adhesive layer is higher than 40%. The adhesive layer has a storage modulus of 0.04 MPa or more at 23°C and a tan δ of 0.46 or more at 23°C. Here, tan δ refers to the ratio (G''/G') of the loss elastic modulus G'' to the storage elastic modulus G' of the adhesive layer.

By using an acrylic polymer containing heptyl acrylate as a monomer component and further containing 3% by weight or more of a carboxyl group-containing monomer, the adhesive can have high adhesive strength. In addition, the adhesive layer has a composition containing the above-mentioned acrylic polymer, has a gel fraction higher than 40%, and has a storage modulus of 0.04 MPa or higher at 23°C, so it can be easily used in cutting processes such as punching. Good workability. Furthermore, the adhesive layer has a tan δ of 0.46 or more at 23°C, so it has good relaxation properties, and minute uneven deformations that occur in the adhesive layer, such as dents on the adhesive surface, can be eliminated by the relaxation effect of the adhesive. Or it can be softened. The above-mentioned storage modulus at 23° C. of 0.04 MPa or more and tan δ at 23° C. of 0.46 or more can be preferably achieved by using an acrylic polymer containing heptyl acrylate as a monomer component. In short, according to the above configuration, it is possible to have high adhesive strength, and it is possible to achieve both relaxation of minute uneven deformation and workability.

In some preferred embodiments, the adhesive layer further includes a tackifying resin. By including a tackifying resin, adhesive strength can be improved. As the tackifying resin, at least one selected from rosin-based tackifying resins and terpene-based tackifying resins is preferably used.

In some preferred embodiments, the adhesive layer further includes an acrylic oligomer. Adhesive strength can be improved by including an acrylic oligomer. Among these, it is more preferable to use a tackifier resin and an acrylic oligomer together. Higher adhesive strength can be achieved by using appropriate amounts of tackifying resin and acrylic oligomer. The technology disclosed herein is a mode in which a tackifier resin and an acrylic oligomer are used in combination, and it is possible to achieve both relaxation of fine uneven deformation and workability while achieving excellent adhesive strength. In some embodiments, the ratio of the content C _T of the tackifying resin to the content C _O of the acrylic oligomer (C _T /C _O ) is preferably 1 or more and 10 or less.

In some preferred embodiments, the adhesive composition for forming the adhesive layer contains at least an isocyanate-based crosslinking agent. By using an isocyanate-based crosslinking agent, the cohesive force of the adhesive can be appropriately increased.

In some preferred embodiments, the thickness of the adhesive layer is greater than 5 μm and less than 50 μm. An adhesive layer whose thickness is limited to 50 μm or less can meet the demands for thinning and weight reduction. Moreover, by making the thickness of the adhesive layer larger than 5 μm, fine uneven deformation can be easily eliminated due to the relaxation effect of the adhesive layer. Furthermore, the adhesive force tends to improve as the adhesive layer thickness increases.

The double-sided adhesive sheet according to some preferred embodiments has a 180 degree peel strength against a stainless steel plate (adhesive strength against SUS) of 10 N/25 mm or more. The above-mentioned double-sided adhesive sheet having adhesive strength against SUS can exhibit high adhesive strength.

The double-sided pressure-sensitive adhesive sheet disclosed herein has high adhesive strength and has good workability in punching and the like, so it is preferably used in applications where it is processed into a predetermined external shape and long-term adhesion reliability is required. 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 double-sided adhesive sheets disclosed herein, in other words, an electronic device including the double-sided adhesive sheet.

FIG. 1 is a cross-sectional view schematically showing the structure of a double-sided pressure-sensitive adhesive sheet according to an embodiment. FIG. 3 is a cross-sectional view schematically showing the structure of a double-sided pressure-sensitive adhesive sheet according to another embodiment. FIG. 2 is a cross-sectional view schematically showing one configuration example of a laminate. FIG. 1 is an exploded perspective view schematically showing a configuration example of a display device.

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 "CA 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 double-sided adhesive sheet>
The double-sided pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer. The double-sided pressure-sensitive adhesive sheet is, for example, a base-less double-sided pressure-sensitive adhesive sheet that includes 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 double-sided pressure-sensitive adhesive sheet may be in the form of a double-sided pressure-sensitive adhesive sheet with a base material, in which the pressure-sensitive adhesive layer is laminated on each side 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 double-sided pressure-sensitive adhesive sheet according to one embodiment is schematically shown in FIG. This double-sided adhesive sheet 1 is configured as a base material-less double-sided adhesive sheet consisting of an adhesive layer 21. The double-sided adhesive sheet 1 has a first adhesive surface 21A composed of one surface (first surface) of the adhesive layer 21 and a second adhesive surface composed of the other surface (second surface) of the adhesive layer 21. The surface 21B is used by being 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 double-sided 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, at least on the side facing the adhesive layer 21, respectively. It may be a component of the double-sided pressure-sensitive adhesive sheet 100 with a release liner that is protected by release liners 31 and 32 that serve as release 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 double-sided adhesive sheet 1 may be overlapped and spirally wound so that the second adhesive surface 21B is the release liner. A double-sided pressure-sensitive adhesive sheet with a release liner may be configured in a form (roll form) in which it is in contact with the back side of 31 and protected.

Further, the double-sided adhesive sheet with a release liner 100 may be in the form of a roll body (a double-sided adhesive sheet roll with a release liner) 300 as shown in FIG. Such a double-sided adhesive sheet roll 300 has a double-sided adhesive sheet 100 with a release liner wound around a core (winding core) 150.

FIG. 2 schematically shows the structure of a double-sided pressure-sensitive adhesive sheet according to another embodiment. This double-sided adhesive sheet 2 includes a sheet-like support base material (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and a first adhesive layer fixedly provided on the first surface 10A side. 21 and a second adhesive layer 22 fixedly provided on the second surface 10B side. As shown in FIG. 2, the double-sided adhesive sheet 2 before use has a release liner on the surface 21A of the first adhesive layer 21 (first adhesive surface) and the surface 22A of the second adhesive layer 22 (second adhesive surface). 31 and 32 may be a component of the double-sided pressure-sensitive adhesive sheet 200 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 double-sided adhesive sheet 2 may be overlapped and spirally wound so that the second adhesive surface 22A is the release liner. A double-sided pressure-sensitive adhesive sheet with a release liner may be configured in a form (roll form) in which it is in contact with the back side of 31 and protected. Such a double-sided pressure-sensitive adhesive sheet with a base material is preferable because it has excellent processability, handleability, and the like.

The technology disclosed herein can be preferably implemented in the form of a base material-less double-sided pressure-sensitive adhesive sheet. Since the base material-less double-sided pressure-sensitive adhesive sheet does not have a supporting base material, it is easy to form a thin layer, and is also advantageous in that it can maximize adhesive properties such as adhesive strength and impact resistance. Further, the base material-less double-sided adhesive sheet can make full use of the thickness of the adhesive layer to alleviate minute irregularities that occur in the adhesive layer. On the other hand, double-sided pressure-sensitive adhesive sheets without a base material are disadvantageous in terms of processability compared to double-sided pressure-sensitive adhesive sheets with a base material because they are substantially composed only of a viscoelastic material. In addition, the adhesive layer can have good processability due to its viscoelastic properties and gel fraction properties.

<Adhesive layer>
(Viscoelastic properties)
The adhesive layer disclosed herein (in an embodiment including a first adhesive layer and a second adhesive layer, at least one of the first adhesive layer and the second adhesive layer. The same applies hereinafter unless otherwise specified) has a storage modulus at 23°C (23°C storage modulus) of 0.04 MPa or more. An adhesive layer that satisfies the above-mentioned 23° C. storage modulus tends to have excellent workability because extrusion of the adhesive is suppressed during cutting such as punching. In some preferred embodiments, the 23°C storage modulus is approximately 0.06 MPa or more, may be 0.08 MPa or more, or may be 0.10 MPa or more. The adhesive layer having the above-mentioned 23°C storage modulus has an appropriate cohesive force, so it tends to have high adhesion reliability to the adherend, and also causes visible uneven deformation of the size. It tends to be difficult. In some embodiments, the 23°C storage modulus of the adhesive layer is approximately 0.60 MPa or less, may be approximately 0.40 MPa or less, or may be approximately 0.20 MPa or less. An adhesive layer having a storage modulus at 23° C. of a predetermined value or less tends to have adhesive properties to an adherend. In some preferred embodiments, it is approximately 0.18 MPa or less, more preferably 0.15 MPa or less, still more preferably 0.13 MPa or less, may be 0.11 MPa or less, and may be less than 0.10 MPa, It may be 0.08 MPa or less, or it may be 0.06 MPa or less.

In addition, the adhesive layer disclosed herein is characterized by the above-mentioned 23°C storage modulus of 0.04 MPa or more and tan δ at 23°C (23°C tan δ) of 0.46 or more. Can be attached. The above tan δ (loss tangent) refers to the ratio (G''/G') of the loss elastic modulus G'' to the storage elastic modulus G' of the adhesive layer. An adhesive layer with a tan δ of 0.46 or more at 23°C has good relaxation properties, so minute deformations in the adhesive layer, such as dents on the adhesive surface, can be easily resolved in a short time due to the relaxation effect of the adhesive. Alleviated, resolved or softened. In some embodiments, the 23°C tan δ is 0.50 or more, and may be 0.55 or more. In some preferred embodiments, the 23°C tan δ is 0.60 or more, more preferably 0.65 or more, even more preferably 0.70 or more, particularly preferably 0.75 or more (for example, 0.78 or more). It is. The above 23°C tan δ usually tends to decrease as the 23°C storage modulus increases, so the upper limit of the 23°C tan δ is preferably set in an appropriate range that is compatible with the 23°C storage modulus. . In some embodiments, the 23° C. tan δ is 3 or less, may be 1.5 or less, may be 1.2 or less, or may be 1.0 or less. In some preferred embodiments, from the viewpoint of achieving both unevenness deformation relaxation and workability based on the 23°C storage modulus, the 23°C tan δ is less than 1.0 and less than 0.95. It may be less than 0.90, less than 0.85, less than 0.80, or less than 0.75. In some other embodiments, the 23°C tan δ may be 0.70 or less, 0.65 or less, 0.60 or less, or 0.55 or less.

In the technology disclosed herein, the 23°C storage elastic modulus and 23°C tan δ of the adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, a pressure-sensitive adhesive layer with a thickness of about 2 mm is produced by stacking a plurality of pressure-sensitive adhesive layers to be measured (in the case of a double-sided pressure-sensitive adhesive sheet without a base material, double-sided pressure-sensitive adhesive sheets). A sample of this adhesive layer was punched into a disk shape with a diameter of 7.9 mm, which was sandwiched and fixed between parallel plates. Dynamic viscoelasticity measurement is performed under the following conditions to determine the 23°C storage modulus and the 23°C tan δ.
・Measurement mode: Shear mode ・Temperature range: -70℃~150℃
・Heating rate: 5℃/min
・Measurement frequency: 1Hz
The above-mentioned method is also used in the Examples described below. Note that the adhesive layer to be measured may be formed by applying a corresponding adhesive composition in a layered manner and drying or curing it.

(acrylic polymer)
The adhesive layer constituting the double-sided 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.

As the acrylic polymer used in the technique disclosed herein, a polymer of monomer components containing heptyl acrylate is used. Acrylic polymers polymerized using monomer components containing heptyl acrylate are more flexible than polymers of other alkyl acrylates such as n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). An adhesive containing a polymer can have a high 23°C tan δ value, and can easily achieve both the 23°C storage modulus in the above range and the 23°C tan δ in the above range. Heptyl acrylate is considered to be one of the most suitable monomer components for achieving both the above 23°C storage modulus and the above 23°C tan δ. The reason why polymers of heptyl acrylate have excellent flexibility is not particularly limited, but polymers containing heptyl acrylate as a monomer unit have a low glass transition temperature and a This is thought to be because the space between them is relatively large. Among heptyl acrylates, n-heptyl acrylate is preferred from the viewpoint of flexibility. Acrylic polymers synthesized containing n-heptyl acrylate as a monomer component are considered to have relatively long linear side chains, and therefore tend to have larger spaces between main chains.

For example, in some embodiments, the proportion of 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 (for example, more than 90% by weight), 92% by weight or more, 94% by weight or more, 95% by weight or more, 96% by weight. The above is fine. By increasing the amount of heptyl acrylate used, the effects of its use (for example, improvement in the 23° C. tan δ of the adhesive and improvement in the relaxation of uneven deformation) can be effectively exhibited. On the other hand, from the viewpoint of copolymerizing the carboxyl group-containing monomer, the proportion of heptyl acrylate in the monomer component is 97% by weight or less. In some preferred embodiments, the proportion of heptyl acrylate in the monomer component is 96% by weight or less, may be 95% by weight or less, and may be 94% by weight or less. Limiting the proportion of heptyl acrylate within the above range is preferable in terms of improving storage modulus, and may be advantageous in terms of improving processability.

The acrylic polymer may be copolymerized with an alkyl (meth)acrylate (hereinafter also referred to as "optional alkyl (meth)acrylate") other than 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 (however, when R ¹ is a hydrogen atom, a heptyl group is excluded).

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.

In some embodiments, the proportion of heptyl acrylate in the total amount of alkyl (meth)acrylates contained in the monomer component is, for example, 50% by weight or more (specifically 50 to 100% by weight, for example, more than 50% by weight). Preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, particularly preferably 95% by weight or more, may be 99% by weight or more, and may be 100% by weight. . By employing such a monomer composition, the effects of using heptyl acrylate can be effectively exhibited. According to the technology disclosed herein, an adhesive that achieves a good balance of high adhesive strength, workability, and unevenness deformation relaxation properties is achieved based on the action of heptyl acrylate without relying on arbitrary alkyl (meth)acrylates such as 2EHA and BA. can be formed. Therefore, the technology disclosed herein can be preferably practiced 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 arbitrary 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 an 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 heptyl acrylate (biomass heptyl acrylate) is used as the heptyl acrylate. By using biomass heptyl acrylate, the effects of the technology disclosed herein can be achieved while reducing dependence on fossil resource materials. The biomass 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 heptyl groups are derived from biomass. As the biomass-derived heptyl acrylate, it is preferable to use biomass-derived n-heptyl acrylate (biomass n-heptyl acrylate).

In some embodiments, the proportion of biomass alkyl (meth)acrylate (preferably biomass 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), 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 or more. good. Further, the proportion of biomass alkyl (meth)acrylate (preferably biomass heptyl acrylate) among the monomer components is less than 97% by weight, and in some embodiments may be 95% by weight or less, and may be 93% by weight or less. It may be 91% by weight or less.

Moreover, it is preferable that the monomer component of the acrylic polymer contains a carboxy group-containing monomer. Carboxy group-containing monomers can improve cohesive force 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 a carboxyl group-containing monomer, the 23°C storage modulus of the adhesive layer can be improved, and excellent processability tends to be obtained. Further, by using a carboxy group-containing monomer, better adhesion can be exhibited, for example, to an adherend such as a highly polar material.

Carboxy group-containing monomers include, for example, acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, isocrotonic acid, and other ethylenically unsaturated monocarboxylic acids; maleic acid; acid, ethylenically unsaturated dicarboxylic acids such as itaconic acid and citraconic acid. Further, the carboxy group-containing monomer may be a monomer having a metal salt (for example, an alkali metal salt) of a carboxy group. Carboxy group-containing monomers can be used alone or in combination of two or more. Among these, preferred carboxy group-containing monomers include AA and MAA. AA is particularly preferred. When one or more carboxy group-containing monomers are used, the proportion of AA in the carboxy group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. It is. In a particularly preferred embodiment, the carboxy group-containing monomer consists essentially of AA. AA has a combination of functions such as polarity based on its carboxyl group, role as a crosslinking point, and Tg (106°C), so AA exerts adhesive properties such as adhesive force and cohesive force in the carboxyl group-containing monomer disclosed herein. It is considered to be one of the best monomer materials to achieve a good balance.

The proportion of the carboxy group-containing monomer in the monomer component of the acrylic polymer is 3% by weight or more (for example, more than 3.0% by weight), preferably 4.0% by weight or more, more preferably 4.5% 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, 6.5% by weight or more. It may be 7.0% by weight or more. By increasing the amount of the carboxy group-containing monomer used, the cohesive force of the adhesive layer is improved based on the action of the carboxy group-containing monomer, so the 23°C storage modulus and gel fraction of the adhesive can be improved. , it is easy to obtain adhesives with excellent processability. Further, the amount of the carboxyl group-containing monomer is, for example, suitably 20% by weight or less of the monomer components, preferably 15% by weight or less, and more preferably 12% by weight or less. In some preferred embodiments, the amount of the carboxy group-containing monomer may be 10% by weight or less, 8% by weight or less, 6% by weight or less, or 5% by weight or less. By appropriately adjusting the amount of the carboxy group-containing monomer used within the above range, a pressure-sensitive adhesive having good adhesive properties can be easily obtained.

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. For example, in an embodiment in which the monomer component of the acrylic polymer includes heptyl acrylate and a monomer containing a carboxy group, from the viewpoint of making it easier to balance the adhesive performance in relation to these monomer components, the optional functional group-containing monomer in the monomer component The content of is suitably 40% by weight or less, 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.

Furthermore, a hydroxyl group-containing monomer may be used as the optional functional group-containing monomer. In that case, the content of the hydroxyl group-containing monomer in the monomer components is suitably about 10% by weight or less (for example, 0.001 to 10% by weight), preferably about 5% by weight or less, more preferably about 5% by weight or less. It is 2% by weight or less. 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. In the technology disclosed herein, desired characteristics and effects can be preferably achieved with a composition in which the amount of the hydroxyl group-containing monomer used is limited or is not used.

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, even more 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 other copolymerization components other than the functional group-containing monomers described above for the purpose of improving cohesive strength, etc. 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 (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)acrylates (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylates (e.g., benzyl (meth)acrylate); olefin monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components 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 component 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 to be 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.

In a particularly preferred embodiment, the acrylic polymer is an acrylic polymer synthesized using a monomer component consisting essentially of heptyl acrylate (preferably n-heptyl acrylate) and a carboxy group-containing monomer (preferably acrylic acid). It will be done. According to the above monomer composition, the effects of heptyl acrylate and the carboxy group-containing monomer are effectively exhibited, achieving both the prescribed 23°C storage modulus and 23°C tan δ, obtaining high adhesive strength, and alleviating uneven deformation. It is possible to preferably achieve both properties and workability. From such a viewpoint, the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the monomer components is suitably 90% by weight or more (90 to 100% by weight), preferably 95% by weight or more, more preferably 99% by weight or more. % by weight or more, more preferably more than 99.5% by weight, particularly preferably more than 99.9% by weight (for example, more than 99.99% by weight), and the total proportion of heptyl acrylate and the carboxy group-containing monomer in the monomer components may be 100% by weight.

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 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 may 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 in solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) such as toluene; 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).

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and an acrylic polymer having an appropriate Mw that can satisfy both the above-mentioned 23° C. storage modulus and 23° C. tan δ is used. For example, the Mw of the acrylic polymer can range from approximately 10×10 ⁴ to 500×10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer may be about 20×10 ⁴ or more, about 30×10 ⁴ or more, about 40×10 ⁴ or more, or about 50×10 ⁴ or more. In some embodiments, the Mw of the acrylic polymer may be greater than 600,000, greater than 650,000, suitably greater than 700,000, and may be greater than 750,000. The larger the Mw of the acrylic polymer, the easier it is to obtain a pressure-sensitive adhesive that exhibits good cohesive force, and the processability tends to improve. In some preferred embodiments, the Mw of the acrylic polymer is 800,000 or more, may be 850,000 or more, may be 900,000 or more, may be 1 million or more (for example, more than 1 million), or may be 1.2 million or more. good. According to the monomer composition containing heptyl acrylate, the viscosity can be easily maintained at a low level, so the synthesis of the polymer is good, and an acrylic polymer having the above Mw can be easily obtained. In addition, by using an acrylic polymer that contains heptyl acrylate as a monomer unit and has an Mw of a predetermined value or more, the above-mentioned viscoelastic properties ( Specifically, it is easy to satisfy the storage modulus at 23° C. and tan δ at 23° C., and it is possible to preferably achieve both unevenness deformation relaxation and workability. On the other hand, from the viewpoint of impact resistance, adhesive strength, ease of synthesis, etc., the Mw of the acrylic polymer is usually approximately 3 million or less, preferably 2.5 million or less, and more preferably 2 million or less. , more preferably 1.8 million or less, may be 1.5 million or less, or may be 1.3 million or less. In some preferred embodiments, the Mw of the acrylic polymer may be 1.1 million or less, 1 million or less, 950,000 or less, or 900,000 or less. In some other preferred embodiments, the Mw of the acrylic polymer is 800,000 or less, may be 600,000 or less, may be less than 500,000, or may be 450,000 or less. By appropriately limiting the Mw of the acrylic polymer, the 23° C. tan δ tends to improve and the uneven deformation relaxation properties tend to improve.

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 below.
[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

(tackifier resin)
In some preferred embodiments, the adhesive layer includes a tackifying resin. By using a tackifying resin, high adhesive strength can be obtained. According to the technology disclosed herein, the adhesive layer has a composition containing a tackifying resin and has predetermined viscoelastic properties (specifically, 23°C storage modulus and 23°C tan δ) and gel fraction. , it is possible to achieve both unevenness deformation relaxation and workability. Although not particularly limited, the effect of using a tackifying resin can be effectively exhibited in a composition containing a high molecular weight acrylic polymer. 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 these, 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; and the like. 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. Adhesive strength can be improved by incorporating a rosin-based tackifier resin and/or a terpene-based tackifier resin into the acrylic adhesive. 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.

Some preferred embodiments include embodiments in which the tackifying resin contains one or more terpene phenol resins. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of tackifying resin is a terpene phenol resin. The proportion of the terpene phenol resin in the total amount of tackifying resin may be approximately 50% by weight or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more. Substantially all of the tackifying resin (for example, about 95% to 100% by weight, and even about 99% to 100% by weight) may be a terpene phenol resin.

The content of the terpene phenol resin in the adhesive layer is not particularly limited as long as it satisfies the desired properties (viscoelastic properties, etc.). In some embodiments, the content of the terpene phenol resin is usually about 1 part by weight or more, and suitably about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. The amount is preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). The greater the amount of terpene phenol resin used, the higher the 23°C storage modulus tends to be. In some embodiments, the content of the terpene phenol resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, and may be 50 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be less than 40 parts by weight, or less than 30 parts by weight. In some preferred embodiments, the content of the terpene phenol resin is less than 30 parts by weight, more preferably 25 parts by weight or less, and even more preferably 22 parts by weight, from the viewpoint of improving the uneven deformation relaxation property of the adhesive. or less, and may be 20 parts by weight or less.

The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifier resin having a softening point (softening temperature) of about 80° C. or higher can be preferably used. The softening point of the tackifying resin may be approximately 100°C or higher, or approximately 110°C or higher. Further, from the viewpoint of adhesion to the adherend, a tackifier resin having a softening point of approximately 200° C. or lower (more preferably approximately 180° C. or lower) may be preferably used. In some embodiments, the softening point of the tackifying resin may be less than 160°C, and may be less than 150°C.

Note that the softening point of the tackifying 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, 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 adhesive strength can be obtained. In some preferred embodiments, the softening point of the tackifier resin T _L is less than 140°C, more preferably less than 130°C, even more preferably less than 120°C, and may be 110°C or less, and has a softening point of 100°C or less. The temperature may be lower than or equal to 90°C. 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, 60°C or higher, 70°C or higher, or 80°C from the viewpoint of exhibiting appropriate cohesive force. or higher, 90°C or higher, 100°C or higher, or 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. 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. Further, the tackifying resin T _L may contain one type of terpene-based tackifying resin (eg, terpene phenol resin) alone, or may contain a combination of two or more types of terpene-based tackifying resin.

In some embodiments, the proportion of the terpene-based tackifying resin (e.g., terpene phenol resin) in the entire tackifying resin T _L can be, for example, more than about 50% by weight, and may be about 65% by weight or more, The content may be approximately 75% by weight or more, 85% by weight or more, or 95% by weight or more. 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 terpene-based tackifier resin. It can be preferably carried out.

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 some embodiments, the tackifying resin T _L may include a hydrogenated rosin ester. Also, for example, the tackifying resin T _L may 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. In some embodiments, only one or more hydrogenated rosin esters may be used as the rosin esters contained in the tackifier resin T _L.

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 tackifier resin T _L is not particularly limited, but in some embodiments, it is appropriate to set it to about 70 parts by weight or less based on 100 parts by weight of the acrylic polymer, and even if it is 60 parts by weight or less. Generally, the amount may be 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less. In some preferred embodiments, the content of the tackifying resin T _L is less than 30 parts by weight, more preferably 25 parts by weight or less, even more preferably 22 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be 20 parts by weight or less. In some embodiments, from the viewpoint of improving adhesive strength, the content of the tackifier resin T _L is, for example, 1 part by weight or more, preferably 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer. The amount is preferably 8 parts by weight or more, more preferably 10 parts by weight or more, still more preferably 12 parts by weight or more, and may be 15 parts by weight or more. The 23°C storage modulus tends to increase as the amount of the tackifying resin T _L having an appropriate softening point increases. The acrylic polymer containing heptyl acrylate as a monomer unit used in the technology disclosed herein has good compatibility with the tackifying resin, so it is possible to achieve desired characteristics by incorporating an appropriate amount of the tackifying resin. can.

In some embodiments, the adhesive layer combines a tackifying resin T _L and a tackifying resin T _H having a softening point of 150° C. or higher (for example, 150° C. to 200° C.) within a range that does not impair the effects of the invention. may also be included. 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.

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 (eg, a terpene phenol resin) having a hydroxyl value higher than 20 mg KOH/g. Among these, tackifying resins having a hydroxyl value of 30 mgKOH/g or more are preferred. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as a "high hydroxyl value resin". According to the tackifier resin containing such a high hydroxyl value resin, in addition to adhesive strength, an adhesive layer with high cohesive strength can be realized by interacting with a crosslinking agent such as an isocyanate-based crosslinking agent. In some embodiments, the tackifier resin may include a high hydroxyl value resin having a hydroxyl value of 60 mgKOH/g or more (for example, 70 mgKOH/g or more). Further, the above-mentioned high hydroxyl value resin (for example, terpene phenol resin) is preferably used in combination with, for example, an acrylic polymer containing heptyl acrylate as a monomer component, and can achieve both adhesive strength and cohesive strength.

The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer, the hydroxyl value of the high hydroxyl value resin is usually about 300 mgKOH/g or less, suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, or more. Preferably it is about 160 mgKOH/g or less, more preferably about 140 mgKOH/g or less, it may be 120 mgKOH/g or less, it may be 100 mgKOH/g or less, it may be 80 mgKOH/g or less (for example, 65 mgKOH/g or less). The technology disclosed herein can be preferably practiced in an embodiment in which the tackifier resin includes a high hydroxyl value resin (for example, a terpene-based tackifier resin, preferably a terpene phenol resin) with a hydroxyl value of 30 to 160 mgKOH/g. In some embodiments, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mgKOH/g (for example, 30 to 65 mgKOH/g) can be preferably employed.

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.

As the high hydroxyl value resin, one having a hydroxyl value of a predetermined value or more among the various tackifying resins mentioned above can be used. The high hydroxyl value resins can be used alone or in combination of two or more. For example, as the high hydroxyl value resin, a terpene phenol resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. Terpene phenol resin is advantageous because the hydroxyl value can be arbitrarily controlled by adjusting the copolymerization ratio of phenol.

Although not particularly limited, when using a high hydroxyl value resin, the proportion of the high hydroxyl value resin (for example, terpene phenol resin) to the entire tackifying resin contained in the adhesive layer should be approximately 5% by weight or more. The content may be 10% by weight or more, 15% by weight or more, or 20% by weight or more. In some embodiments, the proportion of the high hydroxyl value resin in the entire tackifying resin is preferably about 30% by weight or more, for example. Thereby, the effect of using the high hydroxyl value resin is preferably exhibited. In some preferred embodiments, the proportion of the high hydroxyl value resin in the entire tackifying resin is about 40% by weight or more, and may be about 50% by weight or more (for example, more than 50% by weight), and about 60% by weight. % or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more. Substantially all of the tackifying resin (for example, about 95 to 100% by weight, or even about 99 to 100% by weight) may be a high hydroxyl value resin.

The softening point of the high hydroxyl value resin is not particularly limited. The softening point of the high hydroxyl value resin may be, for example, approximately 50°C or higher, and from the viewpoint of improving cohesive force, a high hydroxyl value resin having a softening point (softening temperature) of approximately 80°C or higher may be preferably employed. For example, a terpene phenol resin having such a softening point can be preferably used. The softening point of the high hydroxyl value resin may be approximately 100°C or higher, or approximately 110°C or higher. The upper limit of the softening point of the high hydroxyl value resin is not particularly limited. From the viewpoint of adhesion to the adherend, a high hydroxyl value resin having a softening point of approximately 200° C. or lower (more preferably approximately 180° C. or lower) may be preferably used. In some embodiments, the softening point of the high hydroxyl value resin may be less than 160°C, may be less than 150°C, may be less than 145°C, may be less than 140°C, may be less than 130°C, may be less than 120°C. But that's fine.

The content of the high hydroxyl value resin in the adhesive layer is not particularly limited as long as it satisfies the desired properties (viscoelastic properties, etc.). In some embodiments, the content of the high hydroxyl value resin is usually about 1 part by weight or more, and can be about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. It is suitable, preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, still more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In some embodiments, the content of the high hydroxyl value resin in the adhesive layer is, for example, 70 parts by weight or less, and may be 60 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less. In some preferred embodiments, the content of the high hydroxyl value resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, even if it is 20 parts by weight or less. good.

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 in the adhesive layer is not particularly limited as long as it satisfies the desired properties (viscoelastic properties, etc.). In some embodiments, the content of the tackifying resin is usually about 1 part by weight or more, and suitably about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. The amount is preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). The larger the amount of tackifying resin used, the higher the 23°C storage modulus tends to be. In some embodiments, the content of the tackifier resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, and may be 50 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be less than 40 parts by weight, or less than 30 parts by weight. In some preferred embodiments, the content of the tackifying resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, from the viewpoint of ease of uneven deformation and processability. , 20 parts by weight or less. The acrylic polymer containing heptyl acrylate as a monomer unit used in the technology disclosed herein has good compatibility with the tackifier resin, so it is possible to achieve desired characteristics by incorporating an appropriate amount of the tackifier resin. can.

(acrylic oligomer)
In some preferred embodiments, the adhesive layer contains an acrylic oligomer. By containing an acrylic oligomer, the adhesive force of the pressure-sensitive adhesive can be improved. According to the technology disclosed herein, the pressure-sensitive adhesive layer with a composition containing an acrylic oligomer can have high adhesive strength while achieving both unevenness deformation relaxation and processability. Although not particularly limited, the effect of using an acrylic oligomer can be effectively exhibited in a composition containing a high molecular weight acrylic polymer. Acrylic oligomers can be used singly or in combination of two or more.

It is desirable that the acrylic oligomer has a Tg of about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and more preferably about 40°C or more and about 300°C or less. When Tg is within the above range, adhesive strength can be suitably improved. In some preferred embodiments, the Tg of the acrylic oligomer is about 30°C or higher, more preferably about 50°C or higher (for example, about 60°C or higher), from the viewpoint of adhesive cohesiveness, and From this point of view, the temperature is preferably about 200°C or less, more preferably about 150°C or less, and even more preferably about 100°C or less (for example, about 80°C or less).

In this specification, the Tg of the acrylic oligomer refers to the Tg determined by the Fox equation based on the composition of the monomer components. The Fox equation, as shown below, is a relational equation between Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1/Tg=Σ(Wi/Tgi)
In the above Fox equation, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the weight fraction of monomer i in the copolymer. Represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used to calculate Tg, the value described in a known document shall be used. For example, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used. For monomers for which multiple types of values are described in this document, the highest value is adopted.

For monomers whose homopolymer glass transition temperature is not described in the above literature, the value obtained by the following measurement method shall be used.
Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and acetic acid as a polymerization solvent were placed in a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser. Add 200 parts by weight of ethyl and stir for 1 hour while passing nitrogen gas. After removing oxygen in the polymerization system in this manner, the temperature was raised to 63° C. and the reaction was allowed to proceed for 10 hours. Next, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Next, this homopolymer solution is cast onto a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity testing machine (manufactured by TA Instruments Japan, model name "ARES"). The viscoelasticity is measured in the shear mode at a temperature range of -70° C. to 150° C. and a heating rate of 5° C./min while giving the same temperature, and the temperature corresponding to the peak top temperature of tan δ is taken as the Tg of the homopolymer.

The weight average molecular weight (Mw) of the acrylic oligomer is typically about 1,000 or more and less than about 30,000, preferably about 1,500 or more and less than about 20,000, and more preferably about 2,000 or more and less than about 10,000. When Mw is within the above range, good adhesive strength is likely to be obtained. In some preferred embodiments, the Mw of the acrylic oligomer is about 2,500 or more (for example, about 3,000 or more), and from the viewpoint of adhesiveness, it is preferably about 7,000 or less, more preferably about 5,000 or less (for example, about 4,500 or less). , typically about 4000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and determined as a value in terms of standard polystyrene. Specifically, the measurement is performed using HPLC8020 manufactured by Tosoh Corporation with two columns of TSKgelGMH-H (20) at a flow rate of about 0.5 mL/min using tetrahydrofuran solvent.

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

Examples of acrylic oligomers include alkyl (meth)acrylates in which the alkyl group has a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentaacrylate; Esters of (meth)acrylic acid and alicyclic alcohol such as nyl (meth)acrylate (alicyclic hydrocarbon group-containing (meth)acrylate); aryl such as phenyl (meth)acrylate and benzyl (meth)acrylate Containing as a monomer unit an acrylic monomer having a relatively bulky structure, such as (meth)acrylate having a cyclic structure, further improves the adhesiveness of the adhesive layer. It is preferable from the viewpoint that In addition, when using ultraviolet rays when synthesizing acrylic oligomers or preparing adhesive layers, it is preferable to use ultraviolet rays that have saturated bonds because they are less likely to inhibit polymerization, and those that have alkyl groups with a branched structure are preferable. Alkyl (meth)acrylates or esters with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) can be suitably used as monomers constituting the acrylic oligomer. In addition, all of the above-mentioned branched alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates correspond to (meth)acrylate monomers in the technology disclosed herein. The cycloaliphatic hydrocarbon group can be a saturated or unsaturated cycloaliphatic hydrocarbon group.

The proportion of (meth)acrylate monomer (for example, alicyclic hydrocarbon group-containing (meth)acrylate) in the monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight. The content is more than 70% by weight, more preferably 70% by weight or more (for example, 80% by weight or more, and even 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially of (meth)acrylate monomers.

In addition to the above-mentioned (meth)acrylate monomers, functional group-containing monomers can be used as constituent monomer components of the acrylic oligomer. Suitable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; N,N-dimethylamino Amino group-containing monomers such as ethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate Monomers; These functional group-containing monomers can be used alone or in combination of two or more. Among these, carboxy group-containing monomers are preferred, and AA is particularly preferred. For example, by using a carboxy group-containing monomer as the functional group-containing monomer, the adhesive strength to a highly polar adherend can be easily improved.

When the monomer component constituting the acrylic oligomer includes a functional group-containing monomer, the proportion of the functional group-containing monomer (for example, a carboxy group-containing monomer such as AA) in the monomer component can be approximately 1% by weight or more. It is appropriate, preferably 2% by weight or more, more preferably 3% by weight or more, and approximately 15% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. be.

Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. The types of polymerization initiators (for example, azo polymerization initiators such as AIBN) that can be used as necessary are generally the same as those exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiators and the amount used arbitrarily may vary. The amount of the chain transfer agent such as n-dodecyl mercaptan is appropriately determined based on common technical knowledge so as to obtain a desired molecular weight, and therefore detailed explanation will be omitted here.

From the above viewpoint, suitable acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl In addition to each homopolymer of acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), a copolymer of CHMA and isobutyl methacrylate (IBMA), a copolymer of CHMA and IBXMA, Copolymer of CHMA and acryloylmorpholine (ACMO), copolymer of CHMA and diethylacrylamide (DEAA), copolymer of CHMA and AA, copolymer of ADA and methyl methacrylate (MMA), DCPMA and IBXMA copolymers of DCPMA and MMA, and copolymers of DCPMA and MMA.

When the adhesive layer disclosed herein contains an acrylic oligomer, the content is preferably, for example, 0.1 part by weight or more (for example, 1 part by weight or more) based on 100 parts by weight of the acrylic polymer. It is. From the viewpoint of better exhibiting the effects of the acrylic oligomer, the content of the acrylic oligomer is preferably about 3 parts by weight or more, more preferably about 5 parts by weight or more, and about 8 parts by weight or more. The amount may be approximately 10 parts by weight or more. Further, from the viewpoint of compatibility with the acrylic polymer, in some embodiments, the content of the acrylic oligomer is less than 50 parts by weight (for example, less than 40 parts by weight) based on 100 parts by weight of the acrylic polymer. The amount is preferably less than 30 parts by weight, more preferably about 25 parts by weight or less, even more preferably about 20 parts by weight or less. In some preferred embodiments, the content of the acrylic oligomer is less than 20 parts by weight, may be 15 parts by weight or less, may be 12 parts by weight or less, and may be 10 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be less than 8 parts by weight, or less than 6 parts by weight. By limiting the amount of acrylic oligomer used in this manner, the effects of the technology disclosed herein can be preferably exhibited.

In some preferred embodiments, the adhesive layer contains one or more of the above-mentioned tackifier resins and one or more acrylic oligomers. In a composition containing an acrylic polymer containing heptyl acrylate as a monomer component, by using a tackifier resin and an acrylic oligomer together, it has excellent adhesive strength while achieving a high level of unevenness deformation relaxation and processability. Compatible adhesives may preferably be formed. Although not particularly limited, in a composition containing a high molecular weight acrylic polymer, the effect of using a tackifier resin and an acrylic oligomer in combination can be effectively exhibited. The ratio (C _T /C _O ) of the tackifying resin content C _T [wt%] to the acrylic oligomer content C _O [wt %] in the adhesive layer is not particularly limited, and is, for example, 0.1. It is appropriate to set the value to 10 or less. In some embodiments, the ratio (C _T /C _O ) is greater than or equal to 0.25, may be greater than or equal to 0.4, may be greater than or equal to 0.7, and may be greater than or equal to 0.8. The higher the ratio (C _T /C _O ) is, the more effectively the effect of adding the tackifier resin can be exhibited. In some preferred embodiments, the ratio (C _T /C _O ) is approximately 1 or more (for example, more than 1.0), more preferably 1.5 or more, still more preferably 2.0 or more, and 2. It may be 5 or more, 3.0 or more, or 3.5 or more. Further, from the viewpoint of obtaining the effect of adding the acrylic oligomer, in some embodiments, the above ratio (C _T /C _O ) is approximately 9 or less, preferably 7 or less, and may be 5 or less, It may be 3 or less. In some other embodiments, the ratio (C _T /C _O ) may be 2 or less, 1.5 or less, or 1.2 or less.

In some preferred embodiments, the total amount (total amount) of the tackifier resin and acrylic oligomer contained in the adhesive layer is 100 parts by weight of the acrylic polymer, from the viewpoint of preferably exhibiting the effects of the technology disclosed herein. It is appropriate for the amount to be about 1 part by weight or more, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, still more preferably 20 parts by weight or more, particularly preferably 25 parts by weight or more. In addition, it is appropriate to use less than 120 parts by weight (for example, about 80 parts by weight or less), preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, even more preferably about 40 parts by weight or less, and particularly preferably about 40 parts by weight or less. The amount may be 35 parts by weight or less, 30 parts by weight or less, 28 parts by weight or less, or 26 parts by weight or less.

In the technology disclosed herein, the total amount (total amount) of the acrylic polymer, tackifier resin, and acrylic oligomer in the adhesive layer is appropriately set so that the effect of the technology disclosed herein is exhibited, It is not limited to a specific range. In some preferred embodiments, the total amount (total amount) of the acrylic polymer, tackifier resin, and acrylic oligomer in the entire adhesive layer is 50% by weight from the viewpoint of preferably exhibiting the effects of the technology disclosed herein. Suitably, it is about 70% by weight or more, more preferably about 90% by weight or more, and still 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). It may be 98% 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 an appropriate cohesive force and form a pressure-sensitive adhesive with a good balance between adhesive force and cohesive force. Furthermore, by increasing the amount of crosslinking agent used, the gel fraction and 23° C. storage modulus can be increased and processability can be improved. 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.

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 technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as the crosslinking agent. The amount of the isocyanate crosslinking agent used is not particularly limited. The amount of the isocyanate crosslinking agent used can be, for example, about 0.1 part by weight or more based on 100 parts by weight of the acrylic polymer. From the perspective of achieving both cohesive force and adhesion, the amount of isocyanate crosslinking agent used per 100 parts by weight of the acrylic polymer should usually be approximately 0.3 parts by weight or more (for example, 0.5 parts by weight or more). is preferred. In some preferred embodiments, the amount of the isocyanate crosslinking agent used per 100 parts by weight of the acrylic polymer is about 1.0 parts by weight or more, more preferably about 1.5 parts by weight or more, and still more preferably about 2.0 parts by weight. The amount is at least 2.5 parts by weight, particularly preferably at least 2.5 parts by weight, and may be at least 2.8 parts by weight. By increasing the amount of the isocyanate crosslinking agent used, the gel fraction and 23°C storage modulus can be improved. In addition, from the viewpoint of improving adhesion to the adherend, the amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less, preferably 8 parts by weight or less, per 100 parts by weight of the acrylic polymer. , more preferably 6 parts by weight or less, still more preferably 5 parts by weight or less, particularly preferably 4 parts by weight or less, may be 3.5 parts by weight or less, and may be 3.2 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 usually appropriate to use the epoxy crosslinking agent in an amount of about 0.002 parts by weight or more per 100 parts by weight of the acrylic polymer, preferably The amount may be approximately 0.005 part by weight or more, for example, approximately 0.01 part by weight or more, or approximately 0.02 part by weight or more. By increasing the amount of epoxy crosslinking agent used, the gel fraction and 23°C storage modulus can be improved. Further, from the viewpoint of improving adhesion to the adherend, in some embodiments, the amount of the epoxy crosslinking agent used can be approximately 0.7 parts by weight or less per 100 parts by weight of the acrylic polymer, It is suitably about 0.5 parts by weight or less, preferably about 0.2 parts by weight or less, more preferably about 0.1 parts by weight or less (for example, less than 0.1 parts by weight), and about 0.07 parts by weight or less. The amount may be 0.04 parts by weight or less, or may be 0.03 parts by weight or less. By limiting the amount of epoxy crosslinking agent used within a predetermined range, sufficient adhesive strength can be easily maintained.

In some preferred embodiments, as the crosslinking agent, an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the isocyanate crosslinking agent are used in combination. The technology disclosed herein uses a crosslinking agent other than an isocyanate crosslinking agent (i.e., a crosslinking agent with a different type of crosslinkable reactive group from an isocyanate crosslinking agent; hereinafter also referred to as a "non-isocyanate crosslinking agent") and an isocyanate. It can be preferably carried out in an embodiment in which the method is used in combination with a crosslinking agent.

The type of non-isocyanate crosslinking agent that can be used in combination with the isocyanate crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. The non-isocyanate crosslinking agents can be used alone or in combination of two or more. In some preferred embodiments, an epoxy crosslinker can be employed as the non-isocyanate crosslinker. For example, better adhesive properties can be achieved by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination.

The relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (preferably the epoxy crosslinking agent) is not particularly limited, and may be determined appropriately within a range that satisfies predetermined viscoelastic properties and gel fraction. Set. The content of the isocyanate crosslinking agent is, for example, greater than 1 time, may be approximately 5 times or more, or approximately 10 times the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent). or more, preferably about 50 times or more, more preferably about 80 times or more, still more preferably about 100 times or more (for example, more than 100 times), particularly preferably about 120 times or more (for example, about 140 times). above). In addition, from the viewpoint of suitably exhibiting the effect of using an isocyanate crosslinking agent and a non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) in combination, a non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) is usually used. The content of the isocyanate crosslinking agent relative to the content of the crosslinking agent (crosslinking agent) is, for example, approximately 1000 times or less, suitably approximately 500 times or less, preferably approximately 300 times or less, and more preferably approximately 200 times or less. , more preferably about 180 times or less (for example, about 160 times or less).

The content of crosslinking agent (total amount of crosslinking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesion, the content of the crosslinking agent is usually about 0.001 parts by weight or more, and preferably about 0.01 parts by weight or more, based on 100 parts by weight of the acrylic polymer. Preferably it is about 0.1 part by weight or more, more preferably about 1 part by weight or more, still more preferably about 2 parts by weight or more, particularly preferably about 2.5 parts by weight or more. The content of the crosslinking agent in the adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and about 10 parts by weight, based on 100 parts by weight of the acrylic polymer. The following is preferable. In some preferred embodiments, the content of the crosslinking agent per 100 parts by weight of the acrylic polymer is 5.0 parts by weight or less, may be 4.0 parts by weight or less, or may be 3.5 parts by weight or less.

(Coloring Agent)
The adhesive layer disclosed herein may or may not contain a colorant for the purpose of adjusting optical properties (light transmittance, etc.) and imparting hiding power, design, color, etc. The colorant may be, for example, a black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, or other colorant. The above colorant may typically be contained in the adhesive layer in a state dispersed (or dissolved) in the constituent material of the adhesive layer. As the colorant, a conventionally known pigment or dye may be used. As the pigment, an inorganic pigment or an organic pigment may be used. The colorant may be used alone or in combination of two or more types.

The coloring agent is not particularly limited, and for example, a black coloring agent can be preferably used because it can efficiently adjust hiding properties and light blocking properties by using a small amount. Specific examples of the black colorant include carbon black, graphite, aniline black, perylene black, cyanine black, titanium black, inorganic pigment hematite, activated carbon, molybdenum disulfide, chromium complex, anthraquinone colorant, and the like. The black coloring agent can be used alone or in an appropriate combination of two or more.

Furthermore, as the colorant, a non-black colorant that can be selected from, for example, a white colorant or a gray colorant may also be preferably used. Such coloring agents may be one or more selected from inorganic materials (eg, metals, metal compounds), organic materials, and organic-inorganic composites. Specific examples of the above coloring agents include titanium oxide (titanium dioxide such as rutile titanium dioxide and anatase titanium dioxide), zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, and tin oxide. , metal oxides such as barium oxide, cesium oxide, yttrium oxide; carbonate compounds such as magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate; aluminum hydroxide, calcium hydroxide, Hydroxides such as magnesium hydroxide and zinc hydroxide; silicate compounds such as aluminum silicate, magnesium silicate, and calcium silicate; barium sulfate, calcium sulfate, barium stearate, zinc white, zinc sulfide, talc, clay, kaolin, titanium phosphate , mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, hydrated halloysite, etc.; acrylic resin, polystyrene resin, polyurethane resin, amide resin, polycarbonate resin, silicone Examples include organic materials such as urea-formalin resins, urea-formalin resins, and melamine resins.

In some embodiments, the content of the colorant in the adhesive layer (if two or more types of colorants are included, the total amount of the two or more types, the total content) is, for example, about 0.1% by weight or more, Approximately 0.5% by weight or more is suitable, it may be about 1% by weight or more, it may be about 2% by weight or more, and it may be about 3% by weight or more. Further, in some embodiments, the content of the colorant in the adhesive layer can be approximately 30% by weight or less from the viewpoint of compatibility with the adhesive component and maintenance of adhesive properties such as adhesive strength. Usually, it is suitable to be about 20% by weight or less, it may be about 15% by weight or less, it may be about 10% by weight or less, and it may be about 5% by weight or less. In some preferred embodiments, the content of the colorant in the adhesive layer may be approximately 3% by weight or less, approximately 1% by weight or less, approximately 0.1% by weight or less, and approximately 0.1% by weight or less. It may be less than 0.01% by weight. The technology disclosed herein can be preferably implemented in an embodiment in which the adhesive layer does not substantially contain a colorant.

(Other additives)
In addition to the above-mentioned components, the adhesive composition may optionally contain a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, Various additives common in the adhesive field, such as rust preventives and light stabilizers, may be included. 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.

(Method for forming adhesive layer)
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 double-sided adhesive sheets having a base material, for example, a method (direct method) is adopted in which an adhesive composition is directly applied to the base material (typically by coating) and dried to form an adhesive layer. can do. In addition, a method (transfer method) of forming an adhesive layer on the surface by applying an adhesive composition to a surface having releasability (releasable surface) and drying the adhesive composition, and then transferring the adhesive layer 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.

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.

The adhesive layer may have a single layer structure or a multilayer structure of two or more layers. From the viewpoint of productivity etc., it is preferable that the adhesive layer has a single layer structure.

(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 double-sided 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, and more preferably approximately 60 μm or less. , more preferably about 50 μm or less, and may be about 40 μm or less. The thickness of the adhesive layer can be approximately 35 μm or less, for example, approximately 30 μm or less, or 20 μm or less (for example, 15 μm or less). An adhesive layer with a limited thickness can meet the demands for thinning and weight reduction. Furthermore, by limiting the thickness of the adhesive layer, the adhesive is less likely to protrude during processing such as punching, and processability can be improved. 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. It is advantageous to do so. In some preferred embodiments, the thickness of the adhesive layer is greater than 5 μm, more preferably about 10 μm or more, even more preferably about 12 μm or more (e.g., greater than 12 μm), even more preferably about 15 μm or more, e.g. It may be 18 μm or more. By making the thickness of the adhesive layer larger than 5 μm, fine uneven deformation can be easily eliminated due to the relaxation effect of the adhesive layer. Furthermore, as the thickness of the adhesive layer increases, the adhesive strength tends to improve as well. In more preferred embodiments, the thickness of the adhesive layer may be more than 20 μm, 24 μm or more, 27 μm or more, about 30 μm or more, or about 32 μm or more. 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 gel fraction (by weight) of the adhesive layer disclosed herein is higher than 40%. The pressure-sensitive adhesive layer having the above-mentioned gel fraction tends to have excellent workability, with the pressure-sensitive adhesive being suppressed from extruding during cutting such as punching. Further, since the adhesive layer having the above-mentioned gel fraction has appropriate hardness, it tends to be difficult to cause visible uneven deformation. In some preferred embodiments, the gel fraction is 45% or more, more preferably 50% or more, even more preferably 55% or more, may be 60% or more, may be 65% or more, and may be 70% or more. % or more, or 75% or more. In addition, from the viewpoint of adhesive strength, the upper limit of the gel fraction of the adhesive layer is usually suitably less than 90%, may be less than 85%, may be less than 80%, and may be less than 75%. It may be less than In some preferred embodiments, the gel fraction of the adhesive layer is less than 70%, more preferably less than 65%, even more preferably less than 60%, and may be less than 55%, less than 50%. But that's fine. By limiting the gel fraction of the adhesive layer to a predetermined value or less, the adhesiveness to the adherend tends to improve.

The gel fraction of the adhesive layer is measured by the following method. That is, approximately 0.1 g of an adhesive sample (weight Wg ₁ ) was wrapped in a purse-like shape with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) with an average pore diameter of 0.2 μm, and the opening was wrapped with an octopus thread (weight Wg ₃ ). tie up 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
The above-mentioned method is also used in the Examples described 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 double-sided pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet with a base material, the base material supporting the pressure-sensitive adhesive layer may include a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, Complexes of these, etc. can be used. 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 blends. 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 the rubber sheet include natural rubber sheet, butyl rubber sheet, 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. In addition, a base material is also called a base material layer in a double-sided 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 double-sided pressure-sensitive adhesive sheet that takes into account the suppression of dependence on fossil resource-based materials, biomass-derived base materials (typically resin films) are preferably used.

Further, 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 double-sided pressure-sensitive adhesive sheet with a base material, 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 containing a resin material as a main component (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 base material may be transparent, or may have light-blocking or light-attenuating properties. In some embodiments, the substrate (eg, resin film) can contain a colorant. Thereby, the light transmittance (light-shielding property) of the base material can be adjusted. Adjusting the light transmittance (for example, vertical light transmittance) of the base material can be useful for adjusting the light transmittance of the base material and further the light transmittance of the double-sided pressure-sensitive adhesive sheet containing the base material.

As the colorant, conventionally known pigments and dyes can be used as well as colorants that can be included in the adhesive layer. The colorant is not particularly limited, and may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, or the like.

In some embodiments, a black coloring agent can be preferably used as the coloring agent for the substrate because light blocking properties (for example, vertical light transmittance) can be efficiently adjusted with a small amount of the coloring agent. Specific black colorants include those exemplified as colorants that can be included in the adhesive layer. In some preferred embodiments, pigments (eg, particulate black colorants such as carbon black) with an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm, can be used.

The amount of colorant used in the base material (eg, resin film) is not particularly limited, and can be adjusted as appropriate so as to impart desired optical properties. The amount of coloring agent used is suitably about 0.1 to 30% by weight of the base material, for example 0.1 to 25% by weight (typically 0.1 to 20% by weight). can do.

The base material (for example, resin film) may contain fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, Various additives such as antistatic agents, lubricants, and plasticizers 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 producing 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 base material may be colored with a colored layer disposed on the surface of the base film (preferably a resin film). In the base material having such a structure including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be arranged on either one surface or both surfaces of the base film. In a configuration in which colored layers are arranged on both surfaces of the base film, the configurations of the colored layers may be the same or different.

Such a colored layer can typically be formed by applying a colored layer forming composition containing a colorant and a binder to a base film. As the colorant, conventionally known pigments and dyes can be used, as well as colorants that can be contained in the adhesive layer or resin film. As the binder, materials known in the paint or printing fields can be used without particular limitation. Examples include polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate, and the like. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. The colored layer can be formed by any means conventionally used for forming colored layers without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably employed.

The colored layer may have a single layer structure consisting of one layer as a whole, or may have a multilayer structure including two, three or more sub-colored layers. A colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) a colored layer-forming composition. The color and amount of the colorant contained in each sub-colored layer may be the same or different. In the colored layer for imparting light-shielding properties, it is particularly meaningful to have a multilayer structure from the viewpoint of preventing the generation of pinholes and increasing the reliability of preventing light leakage.

The thickness of the entire colored layer is suitably about 1 μm to 10 μm, preferably about 1 μm to 7 μm, and can be, for example, about 1 μm to 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to 2 μm.

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.

In the double-sided pressure-sensitive adhesive sheet of the embodiment including a base material, the thickness of the base material is not particularly limited. From the viewpoint of preventing the double-sided pressure-sensitive adhesive sheet from becoming excessively 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 (eg, approximately 25 μm or less) depending on the purpose and manner of use of the double-sided adhesive sheet. In some embodiments, the thickness of the substrate can 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 double-sided adhesive sheet is the same, which improves the adhesion to the adherend and base material. It can be advantageous from this point of view. In addition, a base material with a limited thickness can meet the demands for thinning and weight reduction. 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, from the viewpoint of handleability and processability of the double-sided adhesive sheet. . In some embodiments, the thickness of the substrate can be about 8 μm or more, and can be about 10 μm or more.

<Total thickness of double-sided adhesive sheet>
The total thickness of the double-sided pressure-sensitive adhesive sheet disclosed herein (which includes a pressure-sensitive 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 double-sided 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. The thickness may be less than 100 μm (for example, approximately 100 μm or less). In some preferred embodiments, the thickness of the double-sided 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 double-sided 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. , more preferably about 20 μm or more, may be about 30 μm or more, and may be about 50 μm or more. A double-sided 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 a double-sided adhesive sheet without a base material, the thickness of the adhesive layer is the total thickness of the double-sided adhesive sheet.

<Release liner>
In the technology disclosed herein, a release liner can be used during formation of the adhesive layer, production of the double-sided adhesive sheet, storage of the double-sided 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 double-sided pressure-sensitive adhesive sheet described above, one formed using a biomass-derived material or a recycled material (recycled film, etc.) can be preferably used.

The release liner disclosed herein (in an embodiment in which the double-sided pressure-sensitive adhesive sheet with a release liner includes two release liners, at least one of the two release liners; the same applies hereinafter unless otherwise specified) may include a release liner base. A material having a release treatment layer on the material can be preferably used. The release treatment layer may be formed by surface treating a release liner base material with a release treatment agent. The release agent may be a known release agent such as a silicone release agent, a long chain alkyl release agent, a fluorine release agent, or molybdenum (IV) sulfide. In some embodiments, a release liner having a release layer formed of a silicone release agent may be preferably employed. The thickness and formation method of the release treatment layer are not particularly limited, and can be set so that appropriate release properties are exhibited on the adhesive side surface of the release liner.

Various plastic films can be used as the release liner base material. In this specification, a plastic film is typically a non-porous sheet, and is a concept that is distinguished from, for example, nonwoven fabric (that is, it does not include nonwoven fabric). As the release liner substrate, a resin film having a non-porous structure and typically substantially free of air bubbles (voidless) may preferably be used. The resin film may have a single layer structure or a multilayer structure of two or more layers (for example, a three layer structure).

Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer. Polyolefin resins such as ethylene-butene copolymers, cellulose resins such as triacetylcellulose, acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, norbornene resins Cyclic polyolefin resins such as resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymers Examples include coalescent resins, polyarylate resins, polyphenylene sulfide resins, and the like. A release liner base material formed from any one type or a mixture of two or more of these resins can be used. Among them, a preferred release liner base material is a polyester resin film (for example, a PET film) formed from a polyester resin.

The plastic film used as the above-mentioned release liner base material may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Further, the plastic film may have a single layer structure or a multilayer structure including two or more sublayers. The above plastic film contains antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, slip agents, anti-blocking agents, Known additives that can be used in release liner base materials, such as nucleating agents, may be blended. In a plastic film with a multilayer structure, each additive may be blended in all sublayers, or may be blended only in some sublayers.

The thickness of the release liner is not particularly limited, and may be, for example, about 10 μm to 500 μm. From the viewpoint of strength and dimensional stability of the release liner, the thickness of the release liner is suitably 20 μm or more, preferably 25 μm or more, may be 30 μm or more, and may be 35 μm or more. By protecting the adhesive surface with a release liner having sufficient thickness, the smoothness of the adhesive surface is easily maintained. For example, uneven deformation of the adhesive layer is less likely to occur due to external force from the back surface of the release liner or foreign matter present on the back surface of the release liner. Such an event may be caused by, for example, foreign matter mixed between the release liners when the double-sided pressure-sensitive adhesive sheet with a release liner is wound onto a roll. In addition, from the viewpoint of handleability of the release liner (for example, ease of winding), the thickness of the release liner is suitably 300 μm or less, preferably 200 μm or less, and may be 150 μm or less. It may be 100 μm or less. By setting the thickness of the release liner to a predetermined value or less, removal from the double-sided pressure-sensitive adhesive sheet tends to be smooth. In some embodiments, the thickness of the release liner may be 75 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less. According to the technology disclosed herein, even if minute unevenness deformation such as dents occurs in the adhesive layer due to external force or foreign matter from the back of the release liner, the adhesive layer has excellent ability to alleviate unevenness deformation. , the above-mentioned fine unevenness deformation can be eliminated or softened, and good appearance quality can be imparted. Note that when the double-sided pressure-sensitive adhesive sheet with a release liner disclosed herein includes two release liners, that is, a first release liner and a second release liner, the thicknesses of the first release liner and the second release liner are the same. There may be one or different. From the viewpoint of release workability, etc., it is preferable that the first release liner and the second release liner have different thicknesses, and the thickness of the thicker release liner is approximately 1/2 the thickness of the thinner release liner. It is preferable to have a thickness of .1 times or more, for example, approximately 1.25 times or more.

<Roll body>
Further, according to this specification, a roll body (a double-sided adhesive sheet roll with a release liner) including the double-sided adhesive sheet with a release liner disclosed herein in a wound form is provided. One of the effects of the technology disclosed herein is unevenness deformation mitigation, which is caused by the adhesion caused by minute foreign matter mixed between two release liners when the double-sided pressure-sensitive adhesive sheet with a release liner is wound into a roll. It is effective against fine unevenness deformation of the agent layer. The technology disclosed herein is suitable for double-sided pressure-sensitive adhesive sheets that are stored in a roll form before use. The roll body as described above typically includes a core and a double-sided pressure-sensitive adhesive sheet with a release liner wound around the core. The shape of the core is not particularly limited, and may be, for example, a solid cylinder, a hollow cylinder (ie, cylindrical shape), a hollow or solid polygonal cylinder, or the like. From the viewpoint of improving the handling properties of the roll body, a hollow cylindrical or hollow polygonal column core can be preferably employed. A cylindrical core is particularly preferred.

<Characteristics of double-sided adhesive sheet>
(Adhesive strength to SUS)
In some embodiments, the double-sided adhesive sheet preferably has a 180 degree peel strength against a stainless steel plate (adhesive strength against SUS) of about 10 N/25 mm or more. The above-mentioned double-sided adhesive sheet having adhesive strength against SUS can exhibit high adhesive strength. The adhesive strength to SUS is more preferably about 15 N/25 mm or more, still more preferably about 18 N/25 mm or more, particularly preferably 20 N/25 mm or more (for example, 22 N/25 mm or more). The upper limit of the adhesive force to SUS is not particularly limited, but from the viewpoint of compatibility with workability etc., it may normally be, for example, about 50 N/25 mm or less, and in some embodiments, it may be about 30 N/25 mm or less. . The adhesive strength to SUS is measured using a 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.

(Biomass carbon ratio)
In some embodiments, the double-sided adhesive sheet may contain 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 double-sided 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 double-sided adhesive sheet means that the amount of fossil resource-based materials typified by petroleum etc. used is small. From this point of view, the higher the biomass carbon ratio of the double-sided pressure-sensitive adhesive sheet, the more preferable it is. For example, the biomass carbon ratio of the double-sided adhesive sheet 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, the biomass carbon ratio of the double-sided adhesive sheet may be, for example, 90% or less, 85% or less, or 80% or less, from the viewpoint of facilitating good adhesive performance.

<Application>
The use of the double-sided pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and can be used for various purposes. The double-sided pressure-sensitive adhesive sheet disclosed herein is suitable for adhesively fixing members in applications that require high adhesive strength and can be processed into a predetermined shape (outline). For example, it can be preferably used for fixing members in various types of portable equipment. In addition, the double-sided adhesive sheet disclosed herein is highly suppressed from uneven deformation of the adhesive layer such as dents on the surface of the adhesive layer, so it is used in applications where the double-sided adhesive sheet attached to the surface of an adherend is visually recognized. It is suitable for applications where appearance quality is required, such as. For example, there is a tendency for higher appearance quality to be required depending on the area where the double-sided adhesive sheet is applied, such as the display part of electronic equipment. The double-sided pressure-sensitive adhesive sheet disclosed herein is suitable for fixing a member in a display section of an electronic device such as the above-mentioned portable electronic device.

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. Furthermore, examples of the electronic devices include personal computers (desktop type, notebook type, tablet type, etc.), televisions, and the like. These may include a built-in display device such as a liquid crystal or organic EL.

In some embodiments, the double-sided adhesive sheet can be used, for example, for the purpose of fixing a pressure-sensitive sensor and other members in a portable electronic device including a pressure-sensitive sensor among the above-mentioned portable electronic devices. In some embodiments, the double-sided adhesive sheet includes a device for indicating a position on the screen (typically a pen-shaped or mouse-shaped device) and a device for detecting the position, and a plate corresponding to the screen. For fixing a pressure-sensitive sensor and other components in an electronic device (typically a portable electronic device) that has a function that allows specifying an absolute position on a touch panel (typically a touch panel). can be used.

In some preferred embodiments, the double-sided adhesive sheet is suitable for use in applications where it is placed on the back side of a display screen (display section) such as a touch panel display in a portable electronic device. By arranging the double-sided adhesive sheet according to some preferred embodiments on the back surface of the display screen (display section), it is possible to prevent the visibility of the display screen from decreasing regardless of how the portable electronic device is used.

The material (adherend material) to which the double-sided adhesive sheet disclosed herein is attached is not particularly limited, but includes, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, Metal materials such as chromium, zinc, etc., or alloys containing two or more of these, such as polyimide resin, acrylic resin, polyether nitrile resin, polyether sulfone resin, polyester resin (PET resin, polyethylene various resins such as naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyetheretherketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, liquid crystal polymers, etc. Examples include materials (typically plastic materials), inorganic materials such as alumina, zirconia, soda glass, quartz glass, and carbon. Among these, metal materials such as copper, aluminum, and stainless steel, and resin materials (typically plastic materials) such as polyester resins such as PET, polyimide resins, aramid resins, and polyphenylene sulfide resins are widely used. ing. The above-mentioned material may be a material of a member constituting a product such as an electronic device. The double-sided pressure-sensitive adhesive sheet disclosed herein can be used by being attached to a member made of the above material. Moreover, the above-mentioned material may be a material constituting the fixed object (for example, a back member such as an electromagnetic wave shield or a reinforcing plate) such as the pressure-sensitive sensor and the display section. Note that the object to be fixed refers to an object to which the double-sided pressure-sensitive adhesive sheet is attached, that is, an adherend. In addition, the back surface member refers to a member disposed on the opposite side of the pressure-sensitive sensor and the front surface (viewing side) of the display section in, for example, a portable electronic device, and for example, the display device shown in FIG. 4 described later. It may be a member constituting the support portion 540 disposed on the back surface of the device 500 . Further, the object to be fixed may have either a single-layer structure or a multi-layer structure, and the surface to which the double-sided pressure-sensitive adhesive sheet is attached (attached surface) may be subjected to various surface treatments. Although not particularly limited, an example of the object to be fixed is a back member with a thickness of 1 μm or more (typically 5 μm or more, e.g. 60 μm or more, even 120 μm or more) and 1500 μm or less (e.g. 800 μm or less). Can be mentioned.

In some embodiments, the member or material to which the double-sided pressure-sensitive adhesive sheet is attached may be light-transparent (light-transparent adherend). Since the adhesive surface of a double-sided adhesive sheet attached to a light-transparent adherend can be visually recognized through the light-transparent adherend, it is desirable to have an adhesive surface with good appearance quality. The light transmittance of the light-transmitting adherend may be, for example, greater than 50%, and may be 70% or more. In some preferred embodiments, the light transmittance of the adherend is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). Such a material may be a resin film (for example, a polyester resin film such as a PET film) placed on the back surface of an image display section of various devices such as portable electronic devices. The double-sided pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode where it is attached to an adherend (for example, a member) having a light transmittance of a predetermined value or more as described above. The above-mentioned light transmittance refers to light transmittance at a wavelength of 550 nm.

Moreover, in some embodiments, the double-sided pressure-sensitive adhesive sheet is used in a mode in which it is attached to a metal member. Examples of the material of the metal member include the metal materials exemplified as the adherend material. Such a metal member is, for example, a member or article having a surface (adhesive sheet pasting surface) made of a metal material such as aluminum or stainless steel, and a preferable example is a metal member such as a stainless steel member or an aluminum member. Examples include members. The double-sided adhesive sheet may cover the entire surface of the metal member, or may cover a portion of the surface (for example, a partial area where concealment is required). The metal member may be, for example, a member that constitutes a support portion 540 of a display device 500 shown in FIG. 4, which will be described later. The metal member is preferably one adherend of the double-sided pressure-sensitive adhesive sheet.

As described above, according to the technology disclosed herein, a laminate including a double-sided adhesive sheet and a member to which the double-sided adhesive sheet is attached is provided. In some embodiments, a laminate including a double-sided adhesive sheet is a laminate including the double-sided adhesive sheet and a metal member (first member). Such a laminate may include a metal member and a double-sided adhesive sheet covering at least a portion of the surface of the metal member. The double-sided adhesive sheet may cover the entire surface of the metal member, or may cover a portion of the surface (for example, a partial area where concealment is required). Typically, one surface (adhesive surface) of the double-sided adhesive sheet is attached to the metal member. In some embodiments, the member to which the double-sided pressure-sensitive adhesive sheet is attached may have the light transmittance of the adherend material described above. In this embodiment, the laminate including the double-sided adhesive sheet is a laminate including the double-sided adhesive sheet and a light-transmitting member (second member). In some preferred embodiments, the laminate includes a metal member (first member), a double-sided adhesive sheet, and a light-transmitting member (second member) in this order. Note that the base material-less double-sided adhesive sheet is also referred to as an adhesive layer in the laminate.

An example of the structure of the laminate is shown in FIG. 3. The laminate 50 shown in FIG. 3 includes a first member 41, a double-sided adhesive sheet 1 without a base material, and a second member 42 in this order. Specifically, in the laminate 50, one adhesive surface (first adhesive surface) 1A of the base material-less double-sided adhesive sheet 1 is adhered to the first member 41, and the other adhesive surface of the double-sided adhesive sheet 1 is adhered to the first member 41. The surface (second adhesive surface) 1B is adhered to the second member 42. In this embodiment, both the first member 41 and the second member 42 have a sheet-like or plate-like shape, and the laminate 50 has a multilayer structure. Further, in this embodiment, the first member 41 is a metal member, and the second member 42 is a light-transmitting member. The details of the members constituting the laminate are the same as those described above for the members, materials, and adherends, so duplicate explanations will not be repeated.

Further, in some embodiments, the double-sided pressure-sensitive adhesive sheet is preferably used in electronic devices that include various light sources such as LEDs (light emitting diodes) and light emitting elements such as self-luminous organic EL. For example, it can be preferably used in electronic equipment (typically portable electronic equipment) that includes an organic EL display device or a liquid crystal display device that requires predetermined optical characteristics.

FIG. 4 is an exploded perspective view schematically showing a configuration example of a display device. As shown in FIG. 4, the display device 500 included in the portable electronic device 400 includes a display section 520 including a cover member, an organic EL unit, etc., and a support section 540. The display device 500 is configured to further include a double-sided adhesive sheet 530. In this configuration example, the double-sided adhesive sheet 530 fixes the members that constitute the display section 520 and the support section 540. Note that the support portion 540 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate), and the like. The double-sided pressure-sensitive adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

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

The matters disclosed by this specification include the following.
[1] A portable electronic device,
A double-sided adhesive sheet is bonded to the member constituting the portable electronic device,
The double-sided adhesive sheet has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. Portable electronic equipment, which refers to the ratio (G''/G') of loss elastic modulus G'' to modulus G'.
[2] The portable electronic device according to [1] above, wherein the adhesive layer further includes a tackifier resin.
[3] The portable electronic device according to [1] or [2] above, wherein the tackifier resin is at least one selected from rosin-based tackifier resins and terpene-based tackifier resins.
[4] The portable electronic device according to any one of [1] to [3] above, wherein the adhesive layer further contains an acrylic oligomer.
[5] The portable electronic device according to any one of [1] to [4] above, wherein the adhesive layer contains a tackifying resin and an acrylic oligomer.
[6] The portable electronic device according to [5] above, wherein the ratio of the content C _T of the tackifying resin to the content C _O of the acrylic oligomer (C _T /C _O ) is 1 or more and 10 or less.
[7] The portable electronic device according to any one of [1] to [6] above, wherein the adhesive composition for forming the adhesive layer contains at least an isocyanate-based crosslinking agent.
[8] The portable electronic device according to any one of [1] to [7] above, wherein the adhesive layer has a thickness of more than 5 μm and 50 μm or less.
[9] The portable electronic device according to any one of [1] to [8] above, wherein the double-sided adhesive sheet has a 180 degree peel strength of 10 N/25 mm or more against a stainless steel plate.

[11] A double-sided adhesive sheet having an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. A double-sided adhesive sheet, which refers to the ratio (G''/G') of loss elastic modulus G'' to modulus G'.
[12] The double-sided pressure-sensitive adhesive sheet according to [11] above, wherein the pressure-sensitive adhesive layer further contains a tackifying resin.
[13] The double-sided pressure-sensitive adhesive sheet according to [11] or [12] above, wherein the tackifying resin is at least one selected from rosin-based tackifying resins and terpene-based tackifying resins.
[14] The double-sided pressure-sensitive adhesive sheet according to any one of [11] to [13] above, wherein the pressure-sensitive adhesive layer further contains an acrylic oligomer.
[15] The double-sided pressure-sensitive adhesive sheet according to any one of [11] to [14] above, wherein the pressure-sensitive adhesive layer contains a tackifier resin and an acrylic oligomer.
[16] The double-sided pressure-sensitive adhesive sheet according to [15] above, wherein the ratio of the content C _T of the tackifying resin to the content C _O of the acrylic oligomer (C _T /C _O ) is 1 or more and 10 or less.
[17] The double-sided pressure-sensitive adhesive sheet according to any one of [11] to [16] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains at least an isocyanate-based crosslinking agent.
[18] The double-sided pressure-sensitive adhesive sheet according to any one of [11] to [17] above, wherein the pressure-sensitive adhesive layer has a thickness of more than 5 μm and not more than 50 μm.
[19] The double-sided adhesive sheet according to any one of [11] to [18] above, which has a 180 degree peel strength against a stainless steel plate of 10 N/25 mm or more.
[20] The double-sided adhesive sheet according to any one of [11] to [19] above, which is used for fixing members in electronic devices.
[21] An electronic device comprising the double-sided adhesive sheet according to any one of [11] to [20] above.
[22] A double-sided adhesive sheet with a release liner, comprising the double-sided adhesive sheet according to any one of [11] to [20] above, and a release liner laminated on the adhesive surface of the double-sided adhesive sheet.
[23] A double-sided adhesive sheet roll with a release liner, which is wound with the double-sided adhesive sheet with a release liner according to [22] above.

[31] A laminate comprising a metal member (first member) and a double-sided adhesive sheet,
The double-sided adhesive sheet has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. A laminate, which refers to the ratio of the loss modulus G'' to the modulus G'(G''/G').
[32] A laminate comprising a light-transmitting member (second member) and a double-sided adhesive sheet,
The double-sided adhesive sheet has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. A laminate, which refers to the ratio of the loss modulus G'' to the modulus G'(G''/G').
[33] A laminate comprising, in this order, a metal member (first member), a double-sided adhesive sheet, and a light-transmitting member (second member),
The double-sided adhesive sheet has an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. A laminate, which refers to the ratio of the loss modulus G'' to the modulus G'(G''/G').
[34] The laminate according to [31] or [33] above, wherein the metal member is an aluminum member or a stainless steel member.
[35] The laminate according to [32] or [33] above, wherein the light transmittance of the light transmitting member is greater than 50%.
[36] The laminate according to [32], [33], or [35] above, wherein the light-transmitting member is made of a resin film.
[37] The laminate according to any one of [31] to [35] above, which is used for electronic equipment.

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.

<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, 93 parts of n-heptyl acrylate (n-HpA) and 7 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. An acrylic polymer solution was obtained. The weight average molecular weight (Mw) of this acrylic polymer was 900,000. Mw was adjusted by adjusting the concentration of monomer components during polymerization. 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)
To the solution of the acrylic polymer obtained above, terpene phenol resin (trade name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd.) was added as a tackifying resin to 100 parts of the acrylic polymer contained in the solution. 20 parts of resin, softening point approximately 115°C, hydroxyl value 30 to 60 mgKOH/g), 5 parts of acrylic oligomer, and isocyanate crosslinking agent A (trade name "Coronate L", trimethylolpropane/tolylene diisocyanate trimer) 75% ethyl acetate solution of adduct, manufactured by Tosoh Corporation) 3 parts (solid content basis) and epoxy crosslinking agent (trade name "TETRAD-C", 1,3-bis(N,N-diglycidylaminomethyl)) 0.02 part of cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added and mixed with stirring to prepare a pressure-sensitive adhesive composition according to this example.
As the acrylic oligomer, one prepared by the following method was used. Specifically, in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser, and a dropping funnel, 95 parts of cyclohexyl methacrylate (CHMA) and 5 parts of AA, and 10 parts of AIBN as a polymerization initiator, After charging ethyl acetate as a polymerization solvent and stirring in a nitrogen stream for 1 hour to remove oxygen from the polymerization system, the temperature was raised to 85°C and reacted for 5 hours to form an acrylic oligomer with a solid content concentration of 50%. Obtained. The Mw of the obtained acrylic oligomer was 3,600.

(Preparation of double-sided adhesive sheet)
The obtained adhesive composition was applied to the release surface of a 38 μm thick polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) and dried at 100° C. for 2 minutes to form a 35 μm thick polyester release liner. An adhesive layer was formed. A release surface of a polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) having a thickness of 25 μm was attached to this adhesive layer. In this way, a base material-less double-sided pressure-sensitive adhesive sheet with a release liner was obtained, both sides of which were protected by the two polyester release liners.

<Examples 2 to 9 and Comparative Examples 1 to 3>
Example is basically the same except that the monomer composition of the acrylic polymer, Mw, the amount of tackifier resin, the amount of acrylic oligomer, the type and amount of crosslinking agent, and the thickness of the adhesive layer were changed as shown in Table 1. A pressure-sensitive adhesive composition according to each example was prepared in the same manner as in Example 1, and using the obtained pressure-sensitive adhesive composition, a base material-less double-sided adhesive with a release liner according to each example was prepared in the same manner as in Example 1. A sheet was produced. The Mw of the acrylic polymer was adjusted by adjusting the concentration of monomer components during polymerization.
In Table 1, BA represents n-butyl acrylate. Further, in Table 1, isocyanate-based crosslinking agent B represents an isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX", 1% ethyl acetate solution of a trifunctional isocyanate compound), and is shown in Table 1. The content shown represents the content of solid content (non-volatile content).

<Example 10>
An adhesive composition prepared by the method described in Example 1 was prepared, and the adhesive composition was applied to one side of a 2 μm thick PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) as a base layer. It was applied to the surface (first side) and dried at 100° C. for 2 minutes to form a first adhesive layer with a thickness of 35 μm. A release surface of a polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) having a thickness of 25 μm was attached to the first adhesive layer. In addition, a polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Chemical Corporation) with a thickness of 38 μm was prepared, the above adhesive composition was applied to the release surface of the release liner, and the adhesive composition was dried at 100°C for 2 minutes. In this way, a second adhesive layer having a thickness of 35 μm was formed. This second adhesive layer was transferred to the adhesive layer-free surface of the base layer on which the first adhesive layer was formed. In this way, a double-sided adhesive sheet with a release liner (a double-sided adhesive sheet with a base material) according to this example was produced.

<Evaluation method>
(Adhesive strength to SUS)
Under a measurement environment of 23°C and 50% RH, a 50 μm thick PET film was pasted on one adhesive side of a double-sided adhesive sheet to back it, and the measurement sample was cut to a size of 25 mm in width and 100 mm in length. did. In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample was pressed onto the surface of a stainless steel plate (SUS304BA plate) that had 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/25 mm] was measured. In the above peel strength measurement, the universal tensile compression tester used is Minebea's "Tensile Compression Tester, TG-1kN" or its equivalent.

(Punching workability)
A double-sided adhesive sheet with a release liner cut into a predetermined size was used as a sample for evaluation. Insert the processing blade from one release liner (light release liner) side of the evaluation sample and process (cutting) until the other release liner (heavy release side release liner) on the opposite side is half-cut. It was processed into a frame shape with an external size of 25 mm x 25 mm and a width of 2 mm, and the parts other than the frame-shaped adhesive sheet were removed. After 60 seconds had elapsed, one of the release liners was removed from the double-sided adhesive sheet, and the degree of protrusion of the adhesive on the exposed processed end surface of the double-sided adhesive sheet was observed using a microscope. Those in which adhesive protrusion of 0.1 mm or more was observed were evaluated as "x", and those in which adhesive protrusion was less than 0.1 mm were evaluated as "○". For each example, 10 evaluation samples were prepared and the evaluation test was performed 10 times (N=10), and the number of evaluation tests evaluated as ○ (/10) was taken as the evaluation result of punching workability. If the number of evaluation tests evaluated as ○ is 5 or more (that is, 5/10 or more), it is determined that the test has passed.

(Evaluation of unevenness deformation)
The double-sided adhesive sheet with a release liner according to each example (a laminate of a release liner on a light release side/a double-sided adhesive sheet/a release liner on a heavy release side) is wound in the same environment and under the same conditions to form a roll body, After a predetermined period of time had elapsed, what was unwound from the roll body was cut into a size of 500 mm x 1000 mm to obtain a sample for evaluation. In a clean room environment, the back side of the release liner on the heavy release side was wiped with Kimwipe (manufactured by Nippon Paper Crecia Co., Ltd.) to remove foreign matter, and then the release liner on the light release side was peeled from the evaluation sample. After 1 hour, the evaluation sample was held in a flat shape at the midpoint between the point light source and the projection screen, which were arranged at a distance of about 100 cm (a position at a distance of about 50 cm from the point light source), The evaluation sample was arranged so that the angle of the exposed pressure-sensitive adhesive layer surface to the light beam from the point light source was about 90 degrees. In the evaluation sample, the surface of the adhesive layer from which the release liner on the easy-release side was peeled off was placed on the point light source side. In a dark room at 23°C and 50% RH, the point light source was turned on and the image projected onto the screen through the evaluation sample was visually observed to determine the uneven deformation (specifically, The presence or absence of uneven deformation on the surface of the adhesive layer was evaluated. As a point light source, for example, "xenon lamp C2577" manufactured by Hamamatsu Photonics Co., Ltd. can be used. For each example, 10 evaluation samples were prepared and the evaluation test was performed 10 times (N=10), and the number of evaluation tests (passed) in which no unevenness deformation was observed was calculated as the result of the unevenness deformation evaluation. It was used as If the number of passes is 6 or more (that is, 6/10 or more), it is determined that the fine uneven deformation has been alleviated.

Table 1 shows the outline and evaluation results of each example.

As shown in Table 1, the adhesives according to Examples 1 to 10 contain heptyl acrylate as a monomer component, further contain an acrylic polymer containing 3% or more of a carboxyl group-containing monomer, and have a gel fraction of 40%. , the storage modulus at 23°C is 0.04 MPa or more, and the tan δ at 23°C is 0.46 or more, and the double-sided adhesive sheet containing the above adhesive has high adhesive strength to SUS, good punching workability, and fine It was also excellent in alleviating unevenness deformation. On the other hand, in Comparative Examples 1 and 2 using BA-based polymers, the 23° C. tan δ was less than 0.46, and the uneven deformation relaxation properties were poor. Furthermore, although Comparative Example 1 had high adhesion to SUS, the gel fraction was 40%, and the evaluation results of punching workability were poor. Comparative Example 2 had higher gel fraction and 23° C. storage modulus than Comparative Example 1, and improved punching processability, but resulted in lower adhesive strength. In addition, in Comparative Example 3, an acrylic polymer containing heptyl acrylate as a monomer component was used as in the above-mentioned example, but it was inferior to the above-mentioned example in terms of adhesive strength, punching workability, and uneven deformation relaxation properties. . In Comparative Example 3, the amount of carboxyl group-containing monomer used in the acrylic polymer was less than 3%, high adhesive strength was not obtained, and the 23°C storage modulus was low at less than 0.04 MPa, resulting in good punching workability. was not obtained, and the 23° C. tan δ was low at less than 0.46, which is considered to be the reason for the poor unevenness deformation relaxation properties.
From the above, it has an adhesive layer containing heptyl acrylate as a monomer component and an acrylic polymer further containing 3% by weight or more of a carboxyl group-containing monomer, and the gel fraction of the adhesive layer is higher than 40%, 23 A double-sided pressure-sensitive adhesive sheet having a storage modulus of 0.04 MPa or more at 23°C and a tan δ of 0.46 or more at 23°C can have high adhesive strength, as well as ease of deformation of minute irregularities and workability. It can be seen that both can be achieved.

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

1, 2, 530 Double-sided adhesive sheet 1A First adhesive surface 1B Second adhesive surface 10 Support base material 10A First surface 10B Second surface 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 41 First member 42 Second member 50 Laminated body 100, 200 Double-sided adhesive sheet with release liner 150 Core 300 Double-sided adhesive sheet roll with release liner 400 Portable electronic device 500 Display device 520 Display section 540 Support section

Claims (10)

A double-sided adhesive sheet having an adhesive layer containing an acrylic polymer,
The acrylic polymer is a polymer of monomer components including heptyl acrylate and a carboxyl group-containing monomer,
The monomer component contains 3% by weight or more of the carboxy group-containing monomer,
The gel fraction of the adhesive layer is higher than 40%,
The adhesive layer has a storage elastic modulus of 0.04 MPa or more at 23°C, and a tan δ of 0.46 or more at 23°C, where the tan δ is the storage elasticity of the adhesive layer. A double-sided adhesive sheet, which refers to the ratio (G''/G') of loss elastic modulus G'' to modulus G'. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer further contains a tackifying resin. The double-sided pressure-sensitive adhesive sheet according to claim 2, wherein the tackifying resin is at least one selected from rosin-based tackifying resins and terpene-based tackifying resins. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer further contains an acrylic oligomer. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer contains a tackifying resin and an acrylic oligomer. The double-sided pressure-sensitive adhesive sheet according to claim 5, wherein the ratio (C _T /C _O ) of the content C _T of the tackifying resin to the content C _O of the acrylic oligomer is 1 or more and 10 or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains at least an isocyanate-based crosslinking agent. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the thickness of the pressure-sensitive adhesive layer is more than 5 μm and not more than 50 μm. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which has a 180 degree peel strength of 10 N/25 mm or more against a stainless steel plate. The double-sided adhesive sheet according to any one of claims 1 to 3, which is used for fixing members in electronic equipment.

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