JP7197983B2 - double-sided adhesive sheet - Google Patents

Description

The present invention relates to a double-sided pressure-sensitive adhesive sheet. More specifically, it relates to a double-sided pressure-sensitive adhesive sheet comprising a foam substrate.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; hereinafter the same) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of easily adhering to adherends under pressure. Taking advantage of such properties, pressure-sensitive adhesives are widely used in various fields in the form of a double-sided pressure-sensitive adhesive sheet with a substrate having pressure-sensitive adhesive layers on both sides of the substrate for purposes such as joining and fixing.

The double-sided pressure-sensitive adhesive sheet with a base material using a foam having a cell structure as the base material (double-sided pressure-sensitive adhesive sheet with a foam base material) has a It can be advantageous in terms of impact absorption, surface shape followability (for example, step followability), and the like. Therefore, the double-sided pressure-sensitive adhesive sheet with a foam substrate can be preferably applied to bonding and fixing of parts in electronic devices such as mobile phones. Patent document 1 is mentioned as technical literature regarding the double-sided adhesive sheet with a foam base material.

Japanese Patent No. 5537613

BACKGROUND ART In recent years, as the performance of electronic devices such as mobile phones and smartphones has improved, the weight of members (adherends) such as lenses fixed by double-sided pressure-sensitive adhesive sheets has become heavier. For this reason, double-faced pressure-sensitive adhesive sheets used in electronic devices are required to have the ability to firmly fix and hold members without peeling off even when the electronic device is subjected to a strong impact such as being dropped. ing. On the other hand, in the manufacture of products using double-sided adhesive sheets, if defects are found during manufacturing or post-manufacturing inspections, the double-sided adhesive sheets are peeled off (re-peeled) from the parts in order to reuse the parts in the product. ), so-called “rework” may be implemented. Moreover, when dismantling a used product or collecting members from the product, the double-sided pressure-sensitive adhesive sheet may be peeled off from the member.

However, in general, a double-sided pressure-sensitive adhesive sheet that can more firmly fix an adherend tends to be more difficult to separate from the adherend. In particular, in a double-faced PSA sheet using a foam base material, if the bonding strength to the adherend is increased, the foam base material may be torn off during the peeling operation, or delamination of the foam base material may occur. (Peeling form in which the foam base material is torn within its thickness) tends to occur. Regarding this point, in the technique described in Patent Document 1, the ability to firmly fix members in a double-sided pressure-sensitive adhesive sheet with a foam base material is achieved by selecting the structure of the foam base material and the degree of cross-linking, suppressing the increase in adhesive strength over time, and the like. and releasability from the member. However, from the viewpoint of improving productivity and recycling efficiency, there is a demand for further improvement in releasability from adherends (for example, reworkability). The present invention has been made in view of such circumstances.

A double-sided pressure-sensitive adhesive sheet provided by this specification comprises a first surface and a second surface. Both sides of the double-sided pressure-sensitive adhesive sheet, that is, the first surface and the second surface are adhesive surfaces. The double-sided pressure-sensitive adhesive sheet includes a sheet-like foam base material, a first covering part arranged on the first surface side of the foam base material, and a second covering part arranged on the second surface side of the foam base material. and two coatings. The first covering portion includes an adhesive layer exposed on the first surface and a reinforcing layer provided by bonding the adhesive layer. The second covering part includes an adhesive layer exposed on the second surface. The double-sided pressure-sensitive adhesive sheet having such a structure has the reinforcing layer, so that the double-sided pressure-sensitive adhesive sheet can be prevented from tearing or tearing when peeled from the adherend, and the peelability (for example, reworkability) can be improved. It can be an indication of gender). In addition, the double-sided pressure-sensitive adhesive sheet can exhibit good shock absorbability and step absorbability by including a foam base material.

The reinforcing layer preferably has voids. As a constituent material of such a reinforcing layer, a sheet material having voids, such as non-woven fabric such as paper, can be preferably used. It is preferable that the adhesive constituting the adhesive layer is impregnated into the voids. As a result, it is possible to increase the bond between the reinforcing layer and the adhesive layer, and suitably prevent the occurrence of adhesive residue, that is, the occurrence of adhesive residue on the surface of the adherend after peeling. Hereinafter, the property of not easily causing adhesive residue is also referred to as "non-adhesive residue".

In some preferred embodiments, the reinforcing layer can be a fibrous sheet. The fibrous sheet is highly deformable and highly adaptable to winding and bending of the double-sided pressure-sensitive adhesive sheet. Therefore, it can be suitably used as the reinforcing layer disclosed herein.

In some aspects, the thickness of the reinforcing layer may be, for example, 20 μm or more and 150 μm or less. Within this range, tearing and tearing of the double-faced pressure-sensitive adhesive sheet tend to be favorably prevented without significantly impairing the surface conformability of the double-faced pressure-sensitive adhesive sheet.

In some aspects, the pressure-sensitive adhesive layer exposed on the first surface may be composed of a pressure-sensitive adhesive formed from an active energy ray-polymerizable pressure-sensitive adhesive composition. The use of the active energy ray-polymerizable pressure-sensitive adhesive composition facilitates formation of the first covering portion with high adhesion between the pressure-sensitive adhesive layer and the reinforcing layer. In particular, it is preferable to allow the polymerization reaction of the active energy ray-polymerizable pressure-sensitive adhesive composition to proceed while the reinforcing layer is in contact with (for example, impregnated with) the active energy ray-polymerizable pressure-sensitive adhesive composition.

In some embodiments, the adhesive layer exposed on the first surface preferably has a gel content of 70% or more. Such a pressure-sensitive adhesive layer tends to have high cohesiveness and excellent non-adhesive residue properties.

In the double-sided pressure-sensitive adhesive sheet disclosed herein, the outer surface of the reinforcing layer is preferably covered with a pressure-sensitive adhesive layer exposed on the first surface. Here, the outer surface of the reinforcing layer refers to the surface farther from the foam base material, and refers to the surface closer to the first surface of the double-sided pressure-sensitive adhesive sheet in the reinforcing layer constituting the first covering portion. Further, the inner surface of the reinforcing layer refers to the surface opposite to the outer surface, that is, the surface closer to the foam substrate. The thickness of the pressure-sensitive adhesive layer exposed on the first surface covering the outer surface of the reinforcing layer may be, for example, 10 μm or more and 200 μm or less. When the thickness is within this range, there is a tendency to achieve both high adhesive strength to an adherend and non-adhesive residue when peeled from the adherend at a higher level.

In the following description, the thickness of the pressure-sensitive adhesive layer covering the outer surface of the reinforcing layer may be referred to as "outer surface coating thickness". Further, when the inner surface of the reinforcing layer is covered with an adhesive layer, the thickness of the adhesive layer covering the inner surface of the reinforcing layer may be referred to as the "inner surface coating thickness". In some preferred embodiments, the first covering portion may include a reinforcing layer having voids, and an adhesive layer that impregnates the voids in the reinforcing layer and covers the outer and inner surfaces of the reinforcing layer.

In some aspects, a polyolefin-based foam base material can be preferably employed as the foam base material. The double-sided pressure-sensitive adhesive sheet having a polyolefin foam substrate can exhibit the effect of applying the present invention particularly well.

In some aspects, the thickness of the foam substrate is 200 μm or greater. While increasing the thickness of the foam substrate improves impact resistance, conventional constructions tend to make the foam substrate more susceptible to tearing (delamination). Therefore, according to the aspect in which the thickness of the foam substrate is 200 μm or more, the effect of application of the present invention can be exhibited particularly well.

In some embodiments, the foam substrate has a 25% compressive strength of 30 kPa or greater. By using a foam base material having such a compressive strength, a double-sided pressure-sensitive adhesive sheet that exhibits good impact absorption and unevenness absorption, and achieves both the ability to firmly fix a member and the peelability at a high level. tends to be favorably realized.

1 is a schematic cross-sectional view showing the configuration of a double-sided pressure-sensitive adhesive sheet according to one embodiment; FIG.

Preferred embodiments of the present invention are described below. Matters other than those specifically referred to in this specification that are necessary for the implementation of the present invention are applicable based on the teaching of the implementation of the invention described in this specification and the common general knowledge at the time of filing. understandable to traders. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.
In the drawings below, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified.

As used herein, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of adhering to an adherend under pressure, as described above. Further, the "base polymer" of the pressure-sensitive adhesive refers to the main component of the rubber-like polymer contained in the pressure-sensitive adhesive, that is, the polymer exhibiting rubber elasticity in a temperature range around room temperature. As used herein, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

The double-sided pressure-sensitive adhesive sheet disclosed herein comprises a first covering portion having an adhesive layer exposed on the first surface, a second covering portion having an adhesive layer exposed on the second surface, and the first covering portion. and a foam base material arranged between the second covering part, and the first surface and the second surface are configured to be adhesive surfaces. The first covering portion and the second covering portion, respectively. It is arranged on the first surface side and the second surface side of the foam substrate. The first covering part further includes a reinforcing layer provided in combination with the adhesive layer exposed on the first surface (first adhesive surface). The second covering portion may or may not include a reinforcing layer provided in association with the adhesive layer exposed on the second surface (second adhesive surface). In addition, the concept of the pressure-sensitive adhesive sheet as used herein may include those having various external shapes such as tape-like elongated shapes.

One structural example of the double-sided pressure-sensitive adhesive sheet disclosed herein is schematically shown in FIG. The double-sided pressure-sensitive adhesive sheet 10 according to this embodiment includes a foam substrate 15 and first coatings fixedly provided (without intention to peel off) on the first surface 15A and the second surface 15B of the foam substrate 15, respectively. It has a portion 11 and a second covering portion 12 .

The first covering portion 11 includes a first pressure-sensitive adhesive layer 112 exposed on the first surface 10A of the double-sided pressure-sensitive adhesive sheet 10 . That is, the outer surface 112A of the first pressure-sensitive adhesive layer 112 also serves as the first surface (first pressure-sensitive adhesive surface) 10A of the double-sided pressure-sensitive adhesive sheet 10 . The inner surface 112B of the first adhesive layer 112 is bonded (bonded) to the first surface 15A of the foam base material 15 . The first covering part 11 further includes a reinforcing layer 114 that is attached to the first adhesive layer 112 . In this embodiment, the reinforcing layer 114 is embedded within the thickness of the first adhesive layer 112 . In other words, reinforcing layer 114 is disposed between outer surface 112A and inner surface 112B of first adhesive layer 112 . In this embodiment, a sheet material having voids (for example, a fibrous sheet such as non-woven fabric) is used as the reinforcing layer 114, and the adhesive forming the first adhesive layer 112 is impregnated into the voids. In addition to covering the outer surface 114A and the inner surface 114B of the reinforcing layer 114 with the adhesive that constitutes the first adhesive layer 112, the reinforcing layer 114 is impregnated with the adhesive in the voids. It is bonded with the adhesive that constitutes the adhesive layer. Hereinafter, impregnation of the reinforcing layer with the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer may be simply expressed as impregnation of the reinforcing layer with the pressure-sensitive adhesive layer.

The second covering portion 12 includes a second pressure-sensitive adhesive layer 122 exposed on the second surface 10B of the double-sided pressure-sensitive adhesive sheet 10 . That is, the outer surface 122A of the second pressure-sensitive adhesive layer 122 also serves as the second surface (second pressure-sensitive adhesive surface) 10B of the double-sided pressure-sensitive adhesive sheet 10 . The inner surface 122B of the second adhesive layer 122 is bonded (bonded) to the second surface 15B of the foam base material 15 . The second covering portion 12 may further include a reinforcing layer 124 that is attached to the second adhesive layer 122 as shown in FIG. The configuration and arrangement of the reinforcing layer 124 may be the same as or different from the configuration and arrangement of the reinforcing layer 114 in the first covering portion 11 . Alternatively, reinforcing layer 124 may be omitted. That is, the second covering portion 12 does not have to include the reinforcing layer. In the example shown in FIG. 1 , the second covering portion 12 is configured in the same manner as the first covering portion 11 and arranged symmetrically with the first covering portion 11 with the foam substrate 15 interposed therebetween. That is, in the reinforcing layer 124, the adhesive constituting the second adhesive layer 122 covers the outer surface 124A and the inner surface 124B of the reinforcing layer 124, and the voids of the reinforcing layer 124 are impregnated with the adhesive. It is bonded with the adhesive by means of

The double-sided PSA sheet 10 before use (before being attached to an adherend) may be in the form of a PSA sheet roll 1 spirally wound as shown in FIG. In this pressure-sensitive adhesive sheet roll 1, a double-sided pressure-sensitive adhesive sheet 10 is wound while being superimposed on a double-sided release liner 20. As shown in FIG. As a result, the first adhesive surface 10A and the second adhesive surface 10B of the double-sided pressure-sensitive adhesive sheet 10 are attached to the first surface (first release surface) 20A and the second surface (second release surface) 20B of the single release liner 20. They are protected by abutting each other.

In the example shown in FIG. 1, the double-sided pressure-sensitive adhesive sheet 10 is wound so that the first covering portion 11 is on the inner peripheral side. It may be wound in a side facing direction. Further, in the example shown in FIG. 1, the first adhesive surface 10A and the second adhesive surface 10B of the double-sided pressure-sensitive adhesive sheet 10 are protected by a single release liner 20. The second adhesive surface 10B may be protected by two separate release liners. That is, the first release surface in contact with the first adhesive surface and the second release surface in contact with the second adhesive surface may be in contact with the release surfaces of two different release liners. The form of the double-sided pressure-sensitive adhesive sheet before use is not limited to the roll form shown in FIG. 1, and may be sheet form. For example, two or more double-sided pressure-sensitive adhesive sheets and two or more double-sided peelable release liners may be alternately laminated.

The release liner includes, for example, a release liner having a release-treated layer on the surface of a liner substrate such as a plastic film or paper (which may be resin-impregnated paper or resin-laminated paper); fluorine-based polymer (polytetrafluoroethylene, etc.); or a release liner made of a low-adhesive material such as polyolefin resin (polyethylene, polypropylene, etc.); and the like can be used. The release treated layer may be formed by surface-treating the liner substrate with a release agent. Examples of release agents include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and molybdenum (IV) sulfide. In one embodiment, a release liner having a release treatment layer with a release treatment agent (for example, a silicone-based release treatment agent) on one or both sides of a plastic film such as polyethylene terephthalate (PET) can be preferably employed.

<Foam base material>
The foam base material in the double-sided pressure-sensitive adhesive sheet disclosed herein is not particularly limited as long as it has a cell structure. The foam substrate may have the form of a single layer, or may have the form of multiple layers (multilayers) of two or more layers. Here, in the present specification, multilayer means two or more layers unless otherwise specified. The double-sided pressure-sensitive adhesive sheet disclosed herein has the advantage of being excellent in impact absorption and surface conformability (for example, step conformability) due to the foam base material. From the viewpoint of preventing delamination and improving flexibility, in some embodiments, a foam base material composed of a single (one layer) foam layer can be preferably employed.

The material of the foam substrate is not particularly limited. A foam substrate comprising a foam layer formed by a foam of plastic material (plastic foam) is usually preferred. The plastic material (which is meant to include rubber materials) for forming the plastic foam is not particularly limited, and can be appropriately selected from known plastic materials. The plastic material can be used singly or in appropriate combination of two or more.

Specific examples of plastic foams include polyolefin resin foams such as polyethylene foams and polypropylene foams; Resin foam; Polyvinyl chloride resin foam such as polyvinyl chloride foam; Vinyl acetate resin foam; Polyphenylene sulfide resin foam; Aliphatic polyamide (nylon)
Amide resin foams such as resin foams and wholly aromatic polyamide (aramid) resin foams; polyimide resin foams; polyether ether ketone (PEEK) foams; styrene such as polystyrene foams urethane-based resin foams; urethane-based resin foams such as polyurethane resin foams; and the like. As the plastic foam, a foam made of rubber-based resin such as a foam made of polychloroprene rubber may be used.

A preferred foam for the double-sided pressure-sensitive adhesive sheet disclosed herein is a polyolefin resin foam (hereinafter also referred to as "polyolefin foam"). As the polyolefin-based resin constituting the polyolefin-based foam substrate, a known or commonly used polyolefin-based resin can be used, and is not particularly limited. For example, polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), metallocene catalyst-based linear low density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene- Examples include vinyl acetate copolymers. Examples of LLDPE include Ziegler-Natta catalyst linear low density polyethylene, metallocene catalyst linear low density polyethylene and the like. Such polyolefin-based resins can be used singly or in combination of two or more.

Among them, the polyolefin-based resin is preferably a polyethylene-based resin or a polypropylene-based resin, and more preferably a polyethylene-based resin. That is, the foam base material in the technology disclosed herein is preferably a polyethylene-based foam base material or a polypropylene-based foam base material, and more preferably a polyethylene-based foam base material. Here, the polyethylene-based resin refers to a resin having ethylene as the main monomer (that is, the main component in the monomer), and in addition to HDPE, LDPE, LLDPE, etc., ethylene- Propylene copolymers, ethylene-vinyl acetate copolymers, and the like may be included. Similarly, a polypropylene-based resin refers to a resin containing propylene as a main monomer.

The average cell diameter of the foam substrate is not particularly limited, but it is usually suitable to be in the range of 10 μm to 1000 μm. As the average cell diameter increases, the impact resistance tends to improve. From this point of view, in some aspects, the average cell diameter may be, for example, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, 100 μm or more, or 150 μm or more. In addition, when the average cell diameter is small, the strength of the double-sided PSA sheet (particularly, delamination strength) tends to be improved. From this point of view, in some aspects, the average cell diameter may be, for example, 700 μm or less, 600 μm or less, 500 μm or less, or 400 μm or less. The average cell diameter here is obtained by observing a cross section of the foam substrate cut along a straight line extending in the flow direction at a magnification of 200 using a microscope (KEYENCE, Digital Microscope VHX-1000). It is obtained by measuring the length in the direction of flow of bubbles observed within a measurement range of 1 mm in length along the direction of flow of the body substrate, and calculating the average thereof. In addition, the flow direction (MD) of the foam substrate generally matches the longitudinal direction of the foam substrate in the case of a long foam substrate.

The density (apparent density) of the foam substrate is not particularly limited, and can be, for example, 0.02 to 0.5 g/cm ³ . When the density is 0.02 g/cm ³ or more, the strength of the double-sided pressure-sensitive adhesive sheet (especially, delamination strength) tends to improve, and the impact resistance and removability tend to improve. From this point of view, in some embodiments, the density of the foam substrate may be, for example, 0.05 g/cm ³ or higher, 0.07 g/cm ³ or higher, or 0.1 g/cm ³ or higher. , 0.2 g/cm ³ or more, 0.25 g/cm ³ or more, or 0.3 g/cm ³ or more. On the other hand, when the density is 0.5 g/cm ³ or less, there is a tendency that the conformability to irregularities is improved without excessively deteriorating the flexibility. When the double-sided pressure-sensitive adhesive sheet has good step conformability, generally, even when it is attached to an adherend having a step, it is difficult for a gap to form between it and the surface of the adherend, and bonding reliability and sealability are improved. . From this perspective, in some embodiments, the density of the foam substrate may be, for example, 0.45 g/cm ³ or less, or 0.40 g/cm ³ or less. The density (apparent density) can be measured, for example, by a method conforming to JIS K6767.

The expansion ratio of the foam substrate is not particularly limited, but is preferably 2 to 50 cc/g, more preferably 2.5 to 30 cc/g. When the foaming ratio is 2 cc/g or more, there is a tendency that flexibility is improved and conformability to unevenness is improved. On the other hand, when the expansion ratio is 50 cc/g or less, the strength of the double-sided PSA sheet (especially, delamination strength) tends to improve, and the impact resistance and removability tend to improve. In this specification, the expansion ratio of the foam substrate is defined as the reciprocal of the apparent density measured according to JIS K6767.

The foam base material (e.g., polyolefin-based foam base material) used for the double-sided pressure-sensitive adhesive sheet disclosed herein can be formed using a known or commonly used forming method (e.g., forming method using a foaming agent, etc.). can be done. Such forming methods may include, for example, plastic material molding, foaming, and cross-linking steps as described above. In addition, a stretching step may be included as necessary. The foaming step may serve as the molding step. Examples of the method for cross-linking the plastic foam include a chemical cross-linking method using an organic peroxide, an ionizing radiation cross-linking method using ionizing radiation, and the like, and these methods can be used in combination. Examples of the ionizing radiation include electron beams, α-rays, β-rays, and γ-rays. The dose of ionizing radiation is not particularly limited, and can be set to an appropriate irradiation dose in consideration of the target physical properties (for example, the degree of cross-linking) of the foam substrate. As the foam base material, a commercially available product may be used, or a commercially available product subjected to post-treatment or post-processing may be used. Alternatively, it is also possible to obtain a desired foam base material by informing a manufacturer of a commercial product of a desired composition, physical properties, structure, shape, etc., and placing an order.

As the foam substrate used for the double-sided pressure-sensitive adhesive sheet disclosed herein, one having a surface layer formed on its surface can be preferably employed. The surface layer is understood as a layer with a higher density than the interior of the foam substrate, and can be a dense layer (eg, a layer that has substantially no cells). Having a surface layer on the foam substrate makes it easier to increase the bonding strength between the first covering portion and/or the second covering portion and the foam substrate. This tends to suppress tearing of the double-sided pressure-sensitive adhesive sheet at the bonding interface. From the viewpoint of ease of production of the foam base material and prevention of tearing at the boundary between the inside of the foam base material and the surface layer, the surface layer is composed of the plastic material itself that constitutes the foam base material. is preferred. A skin layer formed by pressing the plastic material against the surface of a mold or the like when foaming the plastic material is a typical example included in the concept of the surface layer.

Fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, flame retardants, interfacial Various additives such as activators may be blended.

A known surface treatment may be applied to the surface of the foam base material. For example, chemical or physical surface treatments such as undercoating, corona discharge treatment, and plasma treatment may be applied. More specifically, in order to increase the adhesion with the adhesive layer, etc., chemical treatment such as conventional surface treatment, such as corona discharge treatment, chromic acid treatment, ozone exposure, flame exposure, high voltage shock exposure, ionizing radiation treatment, etc. Alternatively, it may be subjected to oxidation treatment or the like by a physical method, or may be subjected to coating treatment or the like using an undercoat agent, a release agent, or the like.

The thickness of the foam base material is not particularly limited, and can be appropriately selected according to the purpose and mode of use of the double-sided pressure-sensitive adhesive sheet. From the viewpoint of appropriately exhibiting the impact absorption and surface shape properties expected of the foam substrate, it is usually appropriate to use a foam substrate having a thickness of 30 μm or more or 50 μm or more. From the standpoint of handleability of the double-sided pressure-sensitive adhesive sheet (for example, workability into narrow tape shape, windability, punching workability), etc., the thickness of the foam substrate is usually 4000 μm or less. Yes, it may be 3000 μm or less, 2000 μm or less, 1500 μm or less, or 1200 μm or less.

In some aspects, the thickness of the foam substrate can be, for example, 200 μm or greater, 250 μm or greater, or 300 μm or greater. As the foam substrate becomes thicker, the strength tends to improve, and the impact absorption and removability tend to improve. When the double-sided pressure-sensitive adhesive sheet disclosed herein is applied to heavy products or large products, such as large flat panel displays such as personal computers and televisions, such a relatively thick foam substrate is used. It is particularly meaningful to use In such aspects, the thickness of the foam substrate can be, for example, 4000 μm or less, 3000 μm or less, or 2000 μm or less.

In some embodiments, the thickness of the foam substrate may be, for example, 1000 μm or less, 700 μm or less, 400 μm or less, 300 μm or less, less than 300 μm, less than 250 μm, less than 200 μm. It's okay. When the double-sided pressure-sensitive adhesive sheet disclosed herein is used for applications such as portable electronic devices such as mobile phones and smart phones, reducing the thickness of the foam substrate improves the handleability of the double-sided pressure-sensitive adhesive sheet. Also, from the viewpoint of miniaturization and weight reduction of products, it is particularly significant to use such a relatively thin foam base material. In such aspects, the thickness of the foam substrate can be, for example, 30 μm or greater, 50 μm or greater, 70 μm or greater, 100 μm or greater, or 125 μm or greater.

The 25% compressive hardness (25% compressive strength) of the foam substrate is not particularly limited, and may be, for example, in the range of 10 kPa or more and 300 kPa or less. Here, the 25% compressive strength of the foam base material means that the foam base material to be measured is cut into squares of 30 mm square and stacked to a thickness of about 2 mm. It is the load when it is compressed by a thickness corresponding to 25% of the initial thickness (load at a compression rate of 25%). That is, it refers to the load when the measurement sample is compressed to a thickness corresponding to 75% of the initial thickness. In addition, when the thickness of the foam base material to be measured is larger than about 2 mm, the foam base material cut into a square shape of 30 mm square may be used as a measurement sample as it is. By setting the 25% compressive strength (hereinafter also simply referred to as "compressive strength") to 10 kPa or more, there is a tendency for the impact absorption and drop characteristics to improve. From this point of view, in some aspects, the compressive strength may be, for example, 30 kPa or more, 35 kPa or more, 40 kPa or more, 50 kPa or more, 60 kPa or more, or 70 kPa or more. Further, by setting the compressive strength to 300 kPa or less, there is a tendency that the surface conformability is improved. From this point of view, in some aspects, the compressive strength may be, for example, 200 kPa or less, 150 kPa or less, or 100 kPa or less.

The 25% compressive strength of the foam substrate is measured according to JIS K6767. A similar measurement method is used in the examples described later. The compressive strength of the foam substrate can be controlled, for example, by selecting the type of plastic material forming the foam substrate, the degree of cross-linking, the expansion ratio, and the like.

The longitudinal (MD) elongation of the foam substrate is not particularly limited, but is usually preferably 200% to 800%, more preferably 400% to 600%. By setting the MD elongation to 200% or more, there is a tendency that impact resistance and followability to unevenness are improved. By setting the MD elongation to 800% or less, the strength of the foam substrate tends to improve, and the drop properties (for example, the ability to suppress damage to the foam substrate due to drop impact, etc.) tend to improve.

Although the elongation in the width direction (TD) of the foam substrate is not particularly limited, it is usually preferably 50% to 800%, more preferably 100% to 600%. By setting the TD elongation to 50% or more, there is a tendency that impact resistance and followability to unevenness are improved. By setting the TD elongation to 800% or less, the strength of the foam base material tends to improve, and the drop property tends to improve.

The elongation (MD elongation, TD elongation) of the foam substrate is measured according to JIS K6767. The elongation of the foam substrate can be controlled, for example, by selecting the type of plastic material forming the foam substrate, the expansion ratio, the degree of cross-linking, and the like.

The longitudinal (MD) tensile strength (MD tensile strength) of the foam substrate is not particularly limited, but is usually preferably 0.5 MPa to 20 MPa, more preferably 1 MPa to 15 MPa. By setting the MD tensile strength to 0.5 MPa or more, removability tends to be improved. By setting the MD tensile strength to 20 MPa or less, there is a tendency to improve impact absorption and surface conformability.

The tensile strength in the width direction (TD) of the foam substrate (TD tensile strength) is not particularly limited, but is usually preferably 0.2 MPa to 20 MPa, more preferably 0.5 MPa to 15 MPa. Removability tends to be improved by setting the TD tensile strength to 0.2 MPa or more. By setting the TD tensile strength to 20 MPa or less, there is a tendency that impact absorption and surface conformability are improved.

The tensile strength (MD tensile strength, TD tensile strength) of the foam substrate is measured according to JIS K6767. The tensile strength of the foam substrate can be controlled, for example, by selecting the type of plastic material that constitutes the foam substrate, the expansion ratio, the degree of cross-linking, and the like.

In some embodiments, a foam substrate having a closed cell rate of 70% or more can be preferably used. As used herein, the term "closed cell content" refers to a value measured by the following method. In principle, the upper limit of the closed cell content is 100%.

(Closed cell rate measurement method)
First, a test piece having a square shape with a side of 5 cm and a constant thickness is cut out from the foam substrate. The thickness of the test piece is measured to calculate the apparent volume V ₁ (cm ³ ) of the test piece, and the weight W ₁ (g) of the test piece is measured.
Next, the apparent volume V ₂ (cm ³ ) of the test piece occupied by air bubbles is calculated based on the following formula. The density of the resin constituting the test piece is calculated assuming that the density is 1 g/cm ³ .
Apparent volume occupied by bubbles V ₂ = V ₁ - W ₁
Subsequently, the test piece is submerged in distilled water at 23° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa is applied to the test piece for 3 minutes. After that, the test piece is taken out from the water, the water adhering to the surface of the test piece is removed, and the weight W ₂ (g) of the test piece is measured. Then, the closed cell ratio is calculated based on the following formula.
Closed cell ratio (%) = 100 - {100 x (W ₂ - W ₁ )/V ₂ }

Foam substrates may generally have closed cells (closed cell structure) and/or open cells (open cell structure). The closed cell ratio is a value that serves as an index representing the ratio of closed cells among the cells (cell structure) present in the foam base material. The term "independent cells" refers to cells that are surrounded by walls and are not connected to other cells. On the other hand, "interconnected cells" refer to cells that are connected to other cells. In the double-sided pressure-sensitive adhesive sheet disclosed herein, when the foam base material has a closed cell content of 70% or more, the strength and drop characteristics tend to be improved. More preferably, the closed cell ratio is 80% or more. The closed cell ratio can be controlled by selecting the type of plastic material that constitutes the foam substrate, expansion ratio, stretching conditions, and the like.

The degree of cross-linking of the foam substrate (eg, polyolefin-based foam substrate) can be, for example, 3-60% by weight. Here, "crosslinking degree" refers to a value measured by the following method.

(Method for measuring degree of cross-linking)
First, a test piece weighing about 100 mg is taken from the foam substrate, and the weight A (mg) of the test piece is accurately weighed. Next, this test piece was immersed in 30 cm ³ of xylene at 120° C. and allowed to stand for 24 hours, filtered through a 200-mesh wire mesh to collect the undissolved components on the wire mesh, and vacuum-dried to remove the undissolved components. Accurately weigh the weight B (mg). Based on the obtained weight A and weight B, the degree of cross-linking (unit: weight %) of the foam substrate is calculated according to the following formula.
Degree of cross-linking (% by weight) = 100 x (B/A)

The degree of cross-linking is a value that serves as an index representing the degree of cross-linking of the polymer (for example, polyolefin-based resin in the case of polyolefin-based foam) that constitutes the base material of the foam. That is, the larger the degree of cross-linking of the foam base material, the denser the cross-linking structure of the plastic material constituting the base material. As the degree of cross-linking increases, the strength and drop properties of the foam substrate tend to improve. When the degree of cross-linking is low, there is a tendency that impact absorption and surface conformability are improved. From the viewpoint of achieving both of these in a well-balanced manner, in some embodiments, the degree of crosslinking of the foam substrate is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and still more preferably 15 to 35% by weight. could be. The degree of cross-linking can be controlled by selecting the kind of plastic material that constitutes the foam substrate, the expansion ratio, the conditions of the cross-linking process, and the like.

The foam substrate may be colored in order to develop design properties and optical properties (light-shielding properties, light-reflecting properties, etc.) in the double-sided pressure-sensitive adhesive sheet disclosed herein.

For example, when the double-sided pressure-sensitive adhesive sheet disclosed herein is used for light shielding purposes, the visible light transmittance of the foam substrate is not particularly limited, but is 15% or less, similar to the visible light transmittance of the double-sided pressure-sensitive adhesive sheet described later. (eg, 0 to 15%), more preferably 10% or less (eg, 0 to 10%).

A coloring agent is used for coloring the foam base material. In addition, the said coloring agent can be used individually by 1 type or in combination of 2 or more types.

When the double-sided pressure-sensitive adhesive sheet of the present invention is used for light shielding purposes, the foam substrate is preferably colored black. For black, L ^* (lightness) defined by the L ^* a ^* b ^* color system is preferably 35 or less (eg, 0 to 35), more preferably 30 or less (eg, 0 to 30). . Note that a ^* and b ^* defined by the L ^* a ^* b ^* color system can be appropriately selected according to the value of L ^* . Although a ^* and b ^* are not particularly limited, both are preferably in the range of -10 to 10 (more preferably -5 to 5, still more preferably -2.5 to 2.5). Both are preferably zero or nearly zero.

In the present specification, L ^* , a ^* , and b ^* defined by the L ^* a ^* b ^* color system are measured using a color difference meter (trade name “CR-200” manufactured by Minolta Co., Ltd.; color difference meter). It is obtained by measuring using The L ^* a ^* b ^* color system is a color space recommended by the Commission Internationale de l'Eclairage (CIE) in 1976, and is called the CIE 1976 (L ^* a ^* b ^* ) color space. means that The L ^* a ^* b ^* color system is specified in JIS Z8729 in Japanese Industrial Standards.

Examples of black colorants used for coloring the foam substrate black include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, etc.), graphite, copper oxide, manganese dioxide, and aniline. Black, perylene black, titanium black, cyanine black, activated carbon, ferrite (nonmagnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, composite oxide black pigment, anthraquinone organic black A dye or the like can be used. Among them, carbon black is preferable from the viewpoint of cost and availability.

The amount of the black colorant to be used is not particularly limited, and can be appropriately adjusted so as to impart desired optical properties to the double-sided pressure-sensitive adhesive sheet of the present invention.

On the other hand, when the double-sided pressure-sensitive adhesive sheet is used for light reflection purposes, the foam substrate is preferably colored white. As white, L ^* (lightness) defined by the L ^* a ^* b ^* color system is preferably 87 or more (eg, 87 to 100), more preferably 90 or more (eg, 90 to 100). . Note that a ^* and b ^* defined by the L ^* a ^* b ^* color system can be appropriately selected according to the value of L ^* . Both a ^* and b ^* , for example, are preferably in the range of -10 to 10 (more preferably -5 to 5, still more preferably -2.5 to 2.5), especially both are 0 or preferably approximately zero.

White colorants used for coloring white include, for example, titanium oxide (titanium dioxide such as rutile-type titanium dioxide and anatase-type titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, oxide Calcium, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate (light calcium carbonate, ground calcium carbonate, etc.), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, water Zinc oxide, aluminum silicate, magnesium silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, Inorganic white colorants such as bentonite, lithopone, zeolite, sericite, hydrated halloysite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, Examples include organic white colorants such as urea-formalin resin particles and melamine resin particles.

The amount of the white colorant to be used is not particularly limited, and can be appropriately adjusted so as to impart desired optical properties to the double-sided pressure-sensitive adhesive sheet of the present invention.

<Adhesive>
In the double-sided pressure-sensitive adhesive sheet disclosed herein, the type of pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. Examples include acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures of these, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, and polyamide adhesives. The pressure-sensitive adhesive layer may be composed of one or more pressure-sensitive adhesives selected from various known pressure-sensitive adhesives such as pressure-sensitive adhesives and fluorine-based pressure-sensitive adhesives. Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive that uses an acrylic polymer as a base polymer (the main component in the polymer component, that is, the component contained in an amount exceeding 50% by weight). The same applies to rubber adhesives and other adhesives. As the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet disclosed herein, a pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive, that is, an acrylic pressure-sensitive adhesive layer can be preferably employed from the viewpoint of transparency, weather resistance, and the like.

In this specification, "(meth)acryl" is meant to comprehensively refer to acryl and methacryl. Similarly, "(meth)acryloyl" is a generic term for acryloyl and methacryloyl, and "(meth)acrylate" is a generic term for acrylate and methacrylate.

In this specification, an acrylic polymer refers to a polymer containing an acrylic monomer as a monomer component constituting the acrylic polymer. That is, it refers to a polymer containing monomer units (polymerized residues) derived from acrylic monomers. Here, the acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule.

Although not particularly limited, in some embodiments of the technology disclosed herein, the pressure-sensitive adhesive layer may be an acrylic pressure-sensitive adhesive layer formed using an acrylic pressure-sensitive adhesive composition. The acrylic pressure-sensitive adhesive composition means a pressure-sensitive adhesive composition containing a monomer component that constitutes an acrylic polymer. Here, "a monomer component that constitutes an acrylic polymer" refers to a monomer component that constitutes an acrylic polymer in a pressure-sensitive adhesive obtained from an acrylic pressure-sensitive adhesive composition. The monomer component may be contained in the acrylic pressure-sensitive adhesive composition in the form of an unreacted monomer (i.e., a raw material monomer in which the polymerizable functional group is unreacted), and may be a polymerization residue (i.e., an acrylic polymer It may be contained in the form of a structural unit (monomer unit)), or may be contained in both forms. Hereinafter, the present invention will be described in more detail, mainly taking as an example the case where the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, but the pressure-sensitive adhesive layer in the present invention is not limited to the acrylic pressure-sensitive adhesive layer.

(monomer component)
In one aspect of the technology disclosed herein, the pressure-sensitive adhesive layer can be formed using an acrylic pressure-sensitive adhesive composition containing the following component (A) as the monomer component. In a preferred embodiment, the pressure-sensitive adhesive layer can be suitably formed using an acrylic pressure-sensitive adhesive composition containing at least the following component (A) as the monomer component.

Component (A) is an alkyl (meth)acrylate having an alkyl group having 1 to 18 carbon atoms at the ester end. Hereinafter, an alkyl (meth)acrylate having an alkyl group having X or more and Y or less carbon atoms at the ester end may be referred to as "C _XY alkyl (meth)acrylate". The structure of the C _1-18 alkyl group in the C _1-18 alkyl (meth)acrylate is not particularly limited, and both linear and branched alkyl groups can be used. As the component (A), one type of such C _1-18 alkyl (meth)acrylates can be used alone or two or more types can be used in combination.

Examples of C _1-18 alkyl (meth)acrylates having a linear alkyl group at the ester end include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n - pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n- undecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-pentadecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-heptadecyl ( meth)acrylates and n-octadecyl (meth)acrylates. Linear C _2-18 alkyl (meth)acrylates are preferred.

C _3-18 alkyl (meth)acrylates having a branched alkyl group at the ester end include isopropyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, t-pentyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate , 2-propylheptyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isomystyryl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, Examples include isoheptadecyl (meth)acrylate and isostearyl (meth)acrylate.

The technology disclosed herein can be preferably practiced in a mode in which component (A) contains one or more selected from C _4-9 alkyl acrylates. Suitable examples of _C4-9 alkyl acrylates include n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isooctyl acrylate and isononyl acrylate. In some embodiments, component (A) may contain BA alone, 2EHA alone, or a combination of BA and 2EHA in any weight ratio. When component (A) contains a combination of BA and 2EHA, the weight ratio of BA/2EHA may be, for example, 5/95 to 95/5, or 20/80 to 80/20. In some embodiments, the BA/2EHA weight ratio may be from 5/95 to 60/40, or from 10/90 to 40/60.
The technology disclosed herein is, for example, that the proportion of C _6-9 alkyl acrylate (eg 2EHA) in the total component (A) is 50 to 100% by weight, 60 to 100% by weight, or 70 to 100% by weight. It can be preferably implemented in one aspect.

In addition to component (A), the monomer component may contain one or more alicyclic monomers as component (B), which is an optional component.

As the alicyclic monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having an alicyclic structure-containing group can be used without particular limitation. can. As the component (B), one kind of such alicyclic monomers can be used alone or two or more kinds can be used in combination. Here, the term "alicyclic structure-containing group" refers to a moiety containing at least one alicyclic structure. In addition, "alicyclic structure" refers to a saturated or unsaturated carbocyclic structure having no aromaticity. In this specification, an alicyclic structure-containing group may be simply referred to as an "alicyclic group". Suitable examples of alicyclic groups include hydrocarbon groups and hydrocarbonoxy groups containing an alicyclic structure.

Examples of preferred alicyclic monomers in the technology disclosed herein include alicyclic (meth)acrylates having an alicyclic group and a (meth)acryloyl group. Specific examples of alicyclic (meth)acrylates include cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate. In addition to acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate and the like, HPMPA, TMA-2, HCPA and the like shown in the following chemical formulas can be mentioned.

The number of carbon atoms in the alicyclic group (in the case of an alicyclic (meth)acrylate, the portion of the alicyclic (meth)acrylate excluding the (meth)acryloyl group) in the alicyclic monomer is not particularly limited. For example, alicyclic monomers having 4 to 24 (preferably 5 to 18, more preferably 5 to 12) carbon atoms in the alicyclic group can be used. Among them, cyclohexyl acrylate (CHA), cyclohexyl methacrylate, isobornyl acrylate (IBXA) and isobornyl methacrylate are preferred, CHA and IBXA are more preferred, and CHA is particularly preferred.

The monomer component constituting the acrylic polymer contains, in addition to the above component (A), one or more monomers having at least one of a hydroxy group and a carboxy group as an optional component (C). good too. Component (C) may contain only one or more hydroxy group-containing monomers, or may contain only one or more carboxy group-containing monomers.

The monomer having a hydroxy group, that is, the hydroxy group-containing monomer has a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and has a hydroxy group, without particular limitation. can be used. The hydroxy group-containing monomers may be used singly or in combination of two or more. Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl ( hydroxyalkyl (meth)acrylates such as meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate; and hydroxyalkylcycloalkane (meth)acrylates such as 4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Other examples include hydroxyethyl (meth)acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like. Among these, hydroxyalkyl (meth)acrylates are preferred. For example, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group with 2 to 6 carbon atoms can be preferably used. In a preferred embodiment, one or more selected from 2-hydroxyethyl acrylate (2HEA), 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate (4HBA) and 4-hydroxybutyl methacrylate is used as the hydroxy group-containing monomer. can be used. The hydroxy group-containing monomer used in preferred embodiments of the technology disclosed herein can be 4HBA alone, 2HEA alone, or a combination of 4HBA and 2HEA.

As the monomer having a carboxy group, that is, the carboxy group-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a carboxy group are not particularly limited. can be used. A carboxy group-containing monomer can be used individually by 1 type or in combination of 2 or more types. Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate; itaconic acid, maleic acid, fumaric acid, ethylenically unsaturated dicarboxylic acids such as citraconic acid; metal salts thereof (for example, alkali metal salts); anhydrides of the above ethylenically unsaturated dicarboxylic acids such as maleic anhydride and itaconic anhydride; Among these, acrylic acid and methacrylic acid are preferred, and acrylic acid is particularly preferred.

The technology disclosed herein can be preferably carried out in a mode in which component (C) contains a hydroxy group-containing monomer. That is, it is preferred that component (C) contains only hydroxyl group-containing monomers, or contains both hydroxyl group-containing monomers and carboxy group-containing monomers. When the component (C) contains a hydroxy group-containing monomer and a carboxy group-containing monomer, the proportion of the hydroxy group-containing monomer in the entire component (C) is preferably more than about 50% by weight, and about 80% by weight or more ( For example, approximately 90% by weight or more). It is preferable to increase the proportion of the hydroxy group-containing monomer in the component (C) from the viewpoint of reducing metal corrosion caused by the carboxy group. The technology disclosed herein can be preferably practiced in an aspect in which component (C) consists essentially of a hydroxy group-containing monomer, that is, in an aspect in which the monomer component does not substantially contain a carboxy group-containing monomer. For example, the proportion of the carboxy group-containing monomer in the monomer component can be less than about 1% by weight, preferably less than about 0.5% by weight, and more preferably less than about 0.2% by weight.

The technology disclosed herein can also be preferably carried out in a mode in which approximately 50% by weight or more of the entire component (C) is a carboxy group-containing monomer. More preferably, the ratio of the carboxy group-containing monomer to the entire component (C) is about 80% by weight or more (for example, about 90% by weight or more). Increasing the proportion of the carboxy group-containing monomer in component (C) can be effective when it is desired to increase the adhesive force by utilizing the hydrogen-bonding intermolecular force caused by the carboxy group. The technology disclosed herein can be preferably practiced in an aspect in which component (C) consists essentially of a carboxy group-containing monomer, that is, in an aspect in which the monomer component does not substantially contain a hydroxy group-containing monomer. For example, the proportion of hydroxy group-containing monomers in the monomer component can be less than about 1% by weight, preferably less than about 0.5% by weight, and more preferably less than about 0.2% by weight.

In addition to component (A), the monomer component constituting the acrylic polymer may contain one or more heterocyclic-containing monomers as component (D), which is an optional component. Examples of heterocyclic-containing monomers include cyclic nitrogen-containing monomers and cyclic ether group-containing monomers.

As the cyclic nitrogen-containing monomer, those having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group and having a cyclic nitrogen structure can be used without particular limitation. Examples of cyclic nitrogen-containing monomers include lactam vinyl monomers such as N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; 2-vinyl-2-oxazoline, 2-vinyl-5-methyl -Oxazoline group-containing monomers such as 2-oxazoline and 2-isopropenyl-2-oxazoline; nitrogen-containing heterocycles such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, and vinylmorpholine; N-vinyl-based monomers having Other examples of cyclic nitrogen-containing monomers include (meth)acrylic monomers containing nitrogen-containing heterocycles such as morpholine, piperidine, pyrrolidine, piperazine, and aziridine rings. Specific examples include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, N-acryloylaziridine and the like. Still other examples of cyclic nitrogen-containing monomers include maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide; Succinimide-based monomers such as N-(meth)acryloyl-6-oxyhexamethylenesuccinimide and N-(meth)acryloyl-8-oxyhexamethylenesuccinimide; be done. Among the above cyclic nitrogen-containing monomers, lactam-based vinyl monomers are preferred, and N-vinyl-2-pyrrolidone is more preferred, from the viewpoint of cohesiveness and the like.

As the monomer having a cyclic ether group, a monomer having a polymerizable functional group having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group, and a cyclic ether group such as an epoxy group, an oxetane group, an oxolane group, etc. It can be used without any particular limitation. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and the like. Examples of oxetane group-containing monomers include 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, and 3-butyl-oxetanylmethyl (meth)acrylate. , 3-hexyl-oxetanylmethyl (meth)acrylate, and the like. Examples of oxolane group-containing monomers include tetrahydrofurfuryl (meth)acrylate.

The ratio of the component (A) to the total monomer components is not particularly limited. Since it is easy to obtain a pressure-sensitive adhesive layer with a good balance between adhesive strength and cohesive strength, the proportion of component (A) is usually about 99% by weight or less, and may be about 97% by weight or less. It may be approximately 95% by weight or less. In some embodiments, the proportion of component (A) can be 90 wt% or less, 85 wt% or less, or 80 wt% or less. From the viewpoint of initial adhesion to adherends, etc., the proportion of component (A) is generally preferably about 30% by weight or more, more preferably about 50% by weight or more. In some embodiments, the proportion of component (A) to the total monomer components can be greater than 65 wt%, greater than 70 wt%, or greater than 75 wt%.

When the monomer component in the technology disclosed herein contains at least one of the component (B), the component (C) and the component (D) in addition to the component (A), the entire monomer component The ratio of the total amount of components (B), (C) and (D) to the total amount may be, for example, 0.5% by weight or more, usually 1% by weight or more is suitable, 3% by weight or more, or It may be 5% by weight or more. In some embodiments, the proportion of the total amount of components (B), (C), and (D) may be 10% by weight or more, 15% by weight or more, or 20% by weight or more. However, the proportion of the total amount of components (B), (C) and (D) in the total amount of monomer components is set so that the sum of the proportion of component (A) is 100% by weight or less.

When component (B) is used, the ratio of component (B) to the total monomer components is not particularly limited. From the viewpoint of improving the cohesion and bonding with the reinforcing layer, the proportion of the component (B) may be, for example, 3% by weight or more, 5% by weight or more, 8% by weight or more, 10% by weight or more, It may be 20% by weight or more, or 30% by weight or more. From the standpoint of initial adhesion to adherends, etc., the proportion of component (B) is generally 65% by weight or less. In some embodiments, the proportion of component (B) may be, for example, 40 wt% or less, 25 wt% or less, 15 wt% or less, or less than 5 wt%. The monomer component may be substantially free of component (B).

When using the component (C), the ratio of the component (C) to the total monomer components is not particularly limited. From the viewpoint of improving effectiveness as a cross-linking starting point, the proportion of component (C) may be, for example, 0.1% by weight or more, 0.2% by weight or more, or 0.5% by weight or more. From the viewpoint of improving cohesive force and improving bonding with the reinforcing layer, in some embodiments, the proportion of component (C) may be, for example, 1% by weight or more, 3% by weight or more, or 5% by weight. % or more, 10 wt % or more, or 15 wt % or more. Further, from the viewpoint of initial adhesion to the adherend, etc., in some embodiments, the proportion of the component (C) is suitably 35% by weight or less, may be 30% by weight or less, or may be 25% by weight or less. Well, no more than 20 wt%, less than 15 wt%, or less than 10 wt%. In some embodiments, the monomer component may be substantially free of component (C).

When component (D) is used, the ratio of component (D) to the total monomer components is not particularly limited. From the viewpoint of improving the cohesion and bonding with the reinforcing layer, the proportion of the component (D) may be, for example, 1% by weight or more, usually 3% by weight or more, and 5% by weight or more. , 10% by weight or more, 15% by weight or more, or 20% by weight or more. Further, from the viewpoint of initial adhesion to the adherend, etc., the proportion of the component (D) is suitably 35% by weight or less, may be 30% by weight or less, may be 25% by weight or less, or may be less than 20% by weight. , less than 15 wt%, less than 10 wt%, or less than 5 wt%. In some embodiments, the monomer component may be substantially free of component (D).

The monomer component in the technology disclosed herein may contain monomers other than the components (A) to (D) described above (hereinafter also referred to as “other monomers”).

Examples of the other monomers include alkyl (meth)acrylates not belonging to component (A), that is, alkyl (meth)acrylates having 1 or 19 or more (for example, 19 to 24) carbon atoms in the alkyl group. Specific examples of such alkyl (meth)acrylates include methyl (meth)acrylate, n-nonadecyl (meth)acrylate, isononadecyl (meth)acrylate, n-eicosyl (meth)acrylate, isoeicosyl (meth)acrylate, and the like. . These can be used individually by 1 type or in combination of 2 or more types.

Other examples of the other monomers include monomers containing functional groups other than hydroxy groups and carboxy groups and not belonging to components (B) and (D). Such functional group-containing monomers can be used for the purposes of introducing cross-linking points into the acrylic polymer, improving cohesive strength, improving bonding with the reinforcing layer, and the like. Examples of functional group-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N - amide group-containing monomers such as methylol (meth)acrylamide, N-methylolpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide; for example aminoethyl (meth)acrylate, N, amino group-containing monomers such as N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile for example styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, vinyl sulfone sulfonic acid group-containing monomers such as sodium acid; Monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; alkoxysilyl group-containing monomers such as methoxysilane and 3-(meth)acryloxypropyltriethoxysilane; These can be used individually by 1 type or in combination of 2 or more types.

The monomer component in the technique disclosed herein is copolymerizable with the component (A) as the other monomer for the purpose of adjusting the Tg of the (meth)acrylic polymer and improving the cohesive force. Monomers other than those exemplified may be included. Examples of such monomers include carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.) and vinyltoluene; aromatic ring-containing (meth)acrylates such as phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylates (e.g. benzyl (meth)acrylate); For example, olefin-based monomers such as ethylene, propylene, isoprene, butadiene and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; Glycol-based monomers such as meth)polypropylene glycol acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; These can be used singly or in combination of two or more.

Although not particularly limited, the ratio of the total amount of components (A) to (D) to the total amount of the above monomer components is typically more than about 50% by weight, preferably about 70% by weight or more, and more It is preferably about 80% by weight or more, more preferably about 90% by weight or more. The technique disclosed herein can be preferably implemented in a mode in which the ratio of the total amount is approximately 95% by weight or more (for example, approximately 99% by weight or more). The proportion of the above total amount may be 100% by weight. The technique disclosed herein can be preferably implemented in a mode in which the ratio of the total amount to the entire monomer component is 99.999% by weight or less (eg, 99.99% by weight or less).

Although not particularly limited, the glass transition temperature (Tg) of the copolymer corresponding to the composition of the monomer component is preferably −20° C. or less from the viewpoint of adhesion to the reinforcing layer, etc. It may be 30° C. or lower, −40° C. or lower, or −45° C. or lower. The Tg of the copolymer may be, for example, -70°C or higher, -65°C or higher, -60°C or higher, or -55°C or higher.

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

As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in the known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
n-butyl acrylate -55°C
2-ethylhexyl acrylate -70°C
Cyclohexyl acrylate 15°C
Isobornyl acrylate 94°C
2-hydroxyethyl acrylate -15°C
4-hydroxybutyl acrylate -40°C
Acrylic acid 106°C
Methacrylic acid 228°C

For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used. For monomers for which multiple values are listed in the above Polymer Handbook, the highest value is adopted. For monomers for which the glass transition temperature of homopolymers is not described in the above Polymer Handbook, the value obtained by the measurement method described in JP-A-2007-51271 shall be used.

<Adhesive composition>
The pressure-sensitive adhesive layer disclosed herein is a pressure-sensitive adhesive layer containing a monomer component having the composition as described above in the form of a polymer, an unpolymerized product (that is, a form in which the polymerizable functional group is unreacted), or a mixture thereof. can be formed using the agent composition. The pressure-sensitive adhesive composition includes a composition containing a pressure-sensitive adhesive (adhesive component) in an organic solvent (solvent-type pressure-sensitive adhesive composition), and a composition in which the pressure-sensitive adhesive is dispersed in an aqueous solvent (water-dispersed pressure-sensitive adhesive composition), a composition prepared to form an adhesive by curing with active energy rays such as ultraviolet rays and radiation (active energy ray-curable adhesive composition), applied in a heat-melted state, near room temperature It can be in various forms, such as a hot melt adhesive composition that forms an adhesive when cooled to a temperature.

As used herein, the term "active energy ray" refers to an energy ray having energy capable of causing chemical reactions such as polymerization reaction, cross-linking reaction, and initiator decomposition. Examples of active energy rays here include light such as ultraviolet rays, visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron beams, neutron rays, and X rays. In addition, the concept of the active energy ray-curable pressure-sensitive adhesive composition is that it is fluid before irradiation with an active energy ray, and a viscoelastic body (adhesive) is formed by proceeding with a polymerization reaction by irradiation with an active energy ray. After forming a pressure-sensitive adhesive layer by removing the solvent or the like from the active energy ray-polymerizable pressure-sensitive adhesive composition configured to be able to form the adhesive layer, the pressure-sensitive adhesive layer is irradiated with an active energy ray to promote a cross-linking reaction. and an active energy cross-linkable pressure-sensitive adhesive composition configured to change the pressure-sensitive adhesive physical properties. From the viewpoint of impregnating properties into the reinforcing layer, an active energy ray-polymerizable pressure-sensitive adhesive composition is more preferable.

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

In the polymerization, a known or commonly used photopolymerization initiator or thermal polymerization initiator can be used depending on the polymerization method, polymerization mode, and the like. Such polymerization initiators can be used singly or in combination of two or more. Although the photopolymerization initiator is not particularly limited, for example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acylphosphine oxide photopolymerization initiator, α- Ketol photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators, benzoin photoinitiators, benzyl photoinitiators, benzophenone photoinitiators, thioxanthone photoinitiators A polymerization initiator or the like can be used. Although the thermal polymerization initiator is not particularly limited, for example, an azo polymerization initiator, a peroxide initiator, a redox initiator obtained by combining a peroxide and a reducing agent, and a substituted ethane initiator. etc. can be used. Thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C). The amount of such a thermal polymerization initiator or photopolymerization initiator to be used is not particularly limited, and can be a normal amount to be used according to the polymerization method, polymerization mode, and the like. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) of a polymerization initiator is used with respect to 100 parts by weight of the monomer to be polymerized. can be done.

The adhesive composition in the technology disclosed herein may contain a polymerization reaction product of a monomer mixture containing at least part of the monomer components (raw material monomers) of the composition. The monomer mixture may contain all of the monomer components. The polymerization reaction product of the monomer mixture can be prepared by at least partially polymerizing the monomer mixture. The adhesive composition in the technology disclosed herein may contain a partial polymer or a complete polymer of a monomer mixture containing some or all of the above monomer components.

(Adhesive Composition Containing Polymerized and Unpolymerized Monomer Components)
In some aspects, the adhesive composition in the technology disclosed herein contains a monomer mixture containing a part of the monomer components (raw material monomers) in the form of a polymerization reaction product (partially polymerized product or fully polymerized product). , contains the remainder of the monomer component in the form of an unpolymerized product (unreacted monomer). Thus, the pressure-sensitive adhesive composition containing unreacted monomers can be a low-viscosity pressure-sensitive adhesive composition even if it contains substantially no solvent or dispersion medium or contains a relatively small amount of solvent or dispersion medium, and the unreacted monomers can form a pressure-sensitive adhesive layer exhibiting good pressure-sensitive adhesive performance. It is preferable that the pressure-sensitive adhesive composition has a low viscosity from the viewpoint of promoting impregnation of the reinforcing layer with the pressure-sensitive adhesive composition.

Further, in the pressure-sensitive adhesive composition disclosed herein, the complete polymer of the monomer mixture containing some types of monomers among the monomer components (raw material monomers) is dissolved in the remaining types of monomers or partial polymerizations thereof. may be in the form Such a form of pressure-sensitive adhesive composition is also included in examples of pressure-sensitive adhesive compositions containing polymerized and unpolymerized monomer components.
In the present specification, the term "completely polymerized product" means that the polymerization conversion rate is over 95% by weight. The polymerization conversion rate of the complete polymer may be, for example, 97% by weight or more, 99% by weight or more, or substantially 100% by weight.

In some preferred embodiments, the pressure-sensitive adhesive composition may contain a partial polymer of a monomer mixture containing part of the monomer components. Such a partially polymerized product is a mixture of a polymer derived from the above-mentioned monomer component and an unreacted monomer among the above-mentioned monomer components, and typically presents a syrup (viscous liquid). Hereinafter, the partial polymer having such properties is sometimes referred to as "polymer syrup" or simply "syrup".

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

The polymerization conversion rate (monomer conversion) of the monomer mixture in the partially polymerized product is not particularly limited. From the viewpoint of suppressing the viscosity of the pressure-sensitive adhesive composition and enhancing the impregnation of the reinforcing layer, the polymerization conversion rate can be, for example, approximately 70% by weight or less, preferably approximately 60% by weight or less, and approximately It may be 50% by weight or less, approximately 40% by weight or less, or approximately 35% by weight or less. The lower limit of the polymerization conversion rate is not particularly limited, but from the viewpoint of coating properties and adhesive properties after curing (after polymerization reaction), it is usually appropriate to be about 1% by weight or more, preferably about 5% by weight or more, and about It may be 10% by weight or more.

A pressure-sensitive adhesive composition containing a partially polymerized product of the above-mentioned monomer mixture can be obtained, for example, by partially polymerizing a monomer mixture containing part or all of the above-mentioned monomer components (raw material monomers) by an appropriate polymerization method (e.g., photopolymerization method). can be easily obtained by In addition to the partial polymer, the pressure-sensitive adhesive composition containing the above partial polymer contains other components that are used as necessary (for example, photopolymerization initiators, polyfunctional monomers, acrylic oligomers, silane coupling agents, raw materials monomer balance, cross-linking agents, tackifying resins, etc.). The method of containing such other components is not particularly limited. For example, a method of pre-mixing other components with a part of the monomer mixture, a method of adding other components to a partially polymerized product of the monomer mixture, or the like can be employed. These methods can be combined as appropriate.

A polyfunctional monomer is a monomer having at least two polymerizable functional groups (typically, radically polymerizable functional groups) having unsaturated double bonds such as (meth)acryloyl groups and vinyl groups. A crosslinked structure can be introduced into the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition by using a polyfunctional monomer. Therefore, the use of multifunctional monomers can help control the gel content, as described below. Moreover, by appropriately using a polyfunctional monomer, it is possible to moderately increase the cohesiveness of the pressure-sensitive adhesive layer and increase the bondability between the pressure-sensitive adhesive layer and the reinforcing layer.

Examples of multifunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, penta Erythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1, Polyhydric alcohols such as 6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and (meth)acryl Esters with acids; allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, and the like. Preferred examples of these include trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate and dipentaerythritol hexa(meth)acrylate. A particularly preferred example is 1,6-hexanediol di(meth)acrylate. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of reactivity and the like, polyfunctional monomers having two or more acryloyl groups are usually preferred.

The amount of the polyfunctional monomer to be used is not particularly limited, and can be appropriately set so as to achieve the intended use of the polyfunctional monomer. From the viewpoint of achieving a good balance between the preferred storage modulus disclosed herein and other adhesive properties or other properties, in some embodiments, the amount of the polyfunctional monomer used is about 100 parts by weight of the monomer component. It may be 3 parts by weight or less, preferably about 2 parts by weight or less, may be about 1 part by weight or less, may be about 0.5 parts by weight or less, or may be 0.3 parts by weight or less. The lower limit of the amount used in the case of using a polyfunctional monomer is not particularly limited as long as it is greater than 0 parts by weight with respect to 100 parts by weight of the monomer component. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of the polyfunctional monomer used to about 0.001 part by weight or more based on 100 parts by weight of the monomer component. In some aspects, the amount of polyfunctional monomer used relative to 100 parts by weight of the monomer component may be, for example, approximately 0.01 parts by weight or more, or may be 0.05 parts by weight or more.

At least part of the amount of the polyfunctional monomer used is preferably added to the partially polymerized product of the monomer mixture so that the polymerizable functional groups of the polyfunctional monomer are contained in the pressure-sensitive adhesive composition in an unreacted state. . As a result, the increase in the viscosity of the pressure-sensitive adhesive composition is suppressed, the impregnation of the pressure-sensitive adhesive composition into the reinforcing layer is enhanced, and the polymerizable functional groups of the polyfunctional monomer are reacted to form a highly cohesive pressure-sensitive adhesive. It can form layers. The entire amount of polyfunctional monomer used may be added to the partially polymerized monomer mixture.

The adhesive composition disclosed herein may contain an acrylic oligomer from the viewpoint of improving adhesive strength. As the acrylic oligomer, the Tg of the copolymer corresponding to the composition of the above monomer components (typically, roughly corresponding to the Tg of the base polymer contained in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition). In comparison, it is preferable to use a polymer with a higher Tg. The use of an acrylic oligomer can also contribute to improving bonding between the pressure-sensitive adhesive layer and the reinforcing layer.

The above acrylic oligomer preferably has a Tg of about 0°C to about 300°C, preferably about 20°C to about 300°C, more preferably about 40°C to about 300°C. When the Tg is within the above range, the adhesive strength and the bondability with the reinforcing layer can be favorably improved. The Tg of the acrylic oligomer is a value calculated based on the Fox formula, like the Tg of the copolymer corresponding to the composition of the monomer components.

The weight average molecular weight (Mw) of the acrylic oligomer can typically be from about 1000 to less than about 30000, preferably from about 1500 to less than about 20000, more preferably from about 2000 to less than about 10000. When Mw is not too low, it tends to be easier to obtain good adhesive strength. In addition, since the Mw is not too high, it becomes easier to improve the bond between the reinforcing layer and the pressure-sensitive adhesive layer. For example, an increase in viscosity of the pressure-sensitive adhesive composition due to blending of the oligomer can be suppressed, and the voids of the reinforcing layer can be easily impregnated with the pressure-sensitive adhesive composition. The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and calculated as a value converted to standard polystyrene. Specifically, it is measured using HPLC8020 manufactured by Tosoh Corporation, using two columns of TSKgelGMH-H(20), and using tetrahydrofuran as a solvent at a flow rate of about 0.5 ml/min.

Examples of monomers constituting acrylic oligomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate Alkyl (meth)acrylates such as , 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 alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate aryl (meth)acrylates such as; (meth)acrylates obtained from terpene compound derivative alcohols; and the like. Such (meth)acrylates can be used singly or in combination of two or more.

Examples of acrylic oligomers include alkyl (meth)acrylates having branched alkyl groups such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopenta Esters of (meth)acrylic acid and alicyclic alcohols such as nyl (meth)acrylate; (meth) having a cyclic structure such as aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate From the viewpoint of further improving the adhesiveness of the pressure-sensitive adhesive layer, it is preferable that an acrylic monomer having a relatively bulky structure, typified by acrylate, is included as a monomer unit. In addition, when ultraviolet rays are used when synthesizing an acrylic oligomer or when producing a pressure-sensitive adhesive layer, those having saturated bonds are preferable, and the alkyl groups have a branched structure, in that they are less likely to cause polymerization inhibition. Alkyl (meth)acrylates or esters with alicyclic alcohols can be suitably used as monomers constituting acrylic oligomers.

From this point of view, suitable acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopenta In addition to homopolymers of nil acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), copolymers of CHMA and isobutyl methacrylate (IBMA), and copolymers of CHMA and IBXMA , copolymer of CHMA and acryloylmorpholine (ACMO), copolymer of CHMA and diethylacrylamide (DEAA), copolymer of ADA and methyl methacrylate (MMA), copolymer of DCPMA and IBXMA, DCPMA and copolymers of MMA, and the like. In each copolymer described above, the amount of the monomer species described later may be, for example, 0.1 times or more and 10 times or less on a weight basis with respect to the amount of the monomer species described above. 0.2 times or more and 5 times or less, 0.3 times or more and 3 times or less, or 0.5 times or more and 2 times or less, but are not limited to these examples.

When the pressure-sensitive adhesive composition disclosed herein contains an acrylic oligomer, the content is not particularly limited. From the viewpoint of favorably enjoying the effects of using the acrylic oligomer, in some embodiments, the content of the acrylic oligomer relative to 100 parts by weight of the monomer component may be, for example, 3 parts by weight or more, or even 5 parts by weight or more. Well, it may be 7 parts by weight or more. In addition, from the viewpoint of initial adhesion to the adherend or foam base material and adhesion to the reinforcing layer, the content of the acrylic oligomer with respect to 100 parts by weight of the monomer component is usually 50 parts by weight or less. and may be 30 parts by weight or less, or may be 20 parts by weight or less.

The pressure-sensitive adhesive composition disclosed herein may be obtained by blending a partial polymer of a monomer mixture containing a part of the monomer components (raw material monomers) with the rest of the monomer raw materials. The remainder of the monomer component may be a partial type or a partial amount of the monomers included in the monomer component. For example, one type of monomer belonging to any one of components (B) to (D) among a plurality of types of monomers constituting the monomer component is excluded from the above monomer mixture in part or in whole, and the monomer mixture is partially The monomers excluded above can be added to the polymer. The amount of the monomer components excluded from the monomer mixture is not particularly limited, and may be, for example, about 1 to 50% by weight or about 5 to 20% by weight of the total monomer components.

A known silane coupling agent can be blended into the adhesive composition disclosed herein, if necessary. The silane coupling agent can help improve bonding between the reinforcing layer and the pressure-sensitive adhesive layer and between the foam substrate and the pressure-sensitive adhesive layer. Silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane. Epoxy group-containing silane coupling agents such as silane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl Amino group-containing silane coupling agents such as butylidene)propylamine and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acryls such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; group-containing silane coupling agents; isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane; The amount of the silane coupling agent used is appropriately 1 part by weight or less, preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.6 part by weight, per 100 parts by weight of the monomer component. .

A photopolymerization method can be preferably employed as a curing method (polymerization method) for forming an adhesive from the adhesive composition containing polymerized and unpolymerized monomer components. Such a pressure-sensitive adhesive composition can be grasped as a photocurable (polymerizable) pressure-sensitive adhesive composition. Adopting a photopolymerization method as a curing method is particularly suitable for a pressure-sensitive adhesive composition containing a polymerization reaction product prepared by a photopolymerization method. Since the polymerization reaction product obtained by the photopolymerization method already contains a photopolymerization initiator, a new photopolymerization initiator is added when the pressure-sensitive adhesive composition containing this polymerization reaction product is further cured to form a pressure-sensitive adhesive. Can be light cured without addition. Alternatively, it may be a pressure-sensitive adhesive composition having a composition obtained by adding a photopolymerization initiator to a polymerization reaction product prepared by a photopolymerization method, if necessary. The additional photoinitiator may be the same as or different from the photoinitiator used to prepare the polymerization reactants. A pressure-sensitive adhesive composition prepared by a method other than photopolymerization can be made photocurable by adding a photopolymerization initiator. A photocurable pressure-sensitive adhesive composition has the advantage that even a thick pressure-sensitive adhesive layer can be easily formed. In a preferred embodiment, photopolymerization when forming the adhesive from the adhesive composition can be performed by UV irradiation. A known high-pressure mercury lamp, low-pressure mercury lamp, metal halide lamp, black light lamp, or the like can be used for ultraviolet irradiation.

(Adhesive composition containing a monomer component in the form of a complete polymer)
The pressure-sensitive adhesive composition according to some other embodiments may contain the monomer components of the pressure-sensitive adhesive composition in the form of a complete polymer. Such adhesive compositions include, for example, a solvent-based adhesive composition containing an acrylic polymer, which is a complete polymerization product of monomer components, in an organic solvent, and water in which the acrylic polymer is dispersed in an aqueous solvent (dispersion medium). It may be in the form of a dispersed pressure-sensitive adhesive composition, or the like.

The adhesive composition disclosed herein can contain a cross-linking agent. As the cross-linking agent, a known or commonly used cross-linking agent in the field of adhesives can be used. Examples of cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, metal alkoxide-based cross-linking agents, A metal chelate-based cross-linking agent, a metal salt-based cross-linking agent, a carbodiimide-based cross-linking agent, an amine-based cross-linking agent, and the like can be mentioned. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The content of the cross-linking agent (the total amount thereof when two or more cross-linking agents are included) is not particularly limited. From the viewpoint of realizing a pressure-sensitive adhesive that exhibits adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, the content of the cross-linking agent is usually about 5 parts by weight with respect to 100 parts by weight of the monomer component contained in the pressure-sensitive adhesive composition. part or less, preferably about 0.001 to 5 parts by weight, more preferably about 0.001 to 4 parts by weight, and about 0.001 to 3 parts by weight. is more preferred. Alternatively, it may be a PSA composition that does not substantially contain a cross-linking agent as described above.

In some aspects, as the cross-linking agent, an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent can be used in combination. In this embodiment, the relationship between the content of the isocyanate-based cross-linking agent and the content of the epoxy-based cross-linking agent is not particularly limited. From the viewpoint of achieving both adhesion and cohesiveness to the reinforcing layer in a well-balanced manner, the content of the isocyanate-based cross-linking agent may be, for example, more than 1 times the content of the epoxy-based cross-linking agent, or even 2 times or more. Well, it may be 5 times or more, or 7 times or more. In addition, from the viewpoint of effectively increasing the cohesion of the pressure-sensitive adhesive layer, the content of the isocyanate cross-linking agent is, for example, 200 times or less the content of the epoxy cross-linking agent, and may be 100 times or less. It may be twice or less, or may be 20 times or less.

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

Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.
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; - hexamethylene diisocyanates such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; 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, 1,3 - cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

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

Examples of preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such tri- or more functional isocyanates are polymers (typically dimers or trimers) of di- or tri- or more functional isocyanates, derivatives (for example, polyhydric alcohols and two or more molecules of polyfunctional isocyanates). addition reaction products), polymers, and the like. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa Polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and the like can be mentioned. Commercially available polyfunctional isocyanates include "Duranate TPA-100" (trade name) manufactured by Asahi Kasei Chemicals, "Coronate L" (trade name), "Coronate HL" and "Coronate HK" (trade names) manufactured by Nippon Polyurethane Industry Co., Ltd. "Coronate HX", "Coronate 2096" and the like.

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

Specific examples of epoxy-based cross-linking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy-based cross-linking agents include Mitsubishi Gas Chemical Company's trade name "TETRAD-C" and trade name "TETRAD-X", DIC's trade name "Epiclon CR-5L", and Nagase ChemteX Corp.'s trade name. and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd. under the trade name of "Denacol EX-512".

The pressure-sensitive adhesive composition can contain a tackifying resin as necessary. Tackifying resins can help improve adhesion to adherends and improve adhesion to foam substrates. The tackifying resin is not particularly limited, and includes phenolic tackifying resins, terpene resins, modified terpene resins (terpene phenolic resins, etc.), rosin-based tackifying resins (unmodified rosin, rosin esters, hydrogenated products thereof, unmodified Homogenized products, polymers, etc.), petroleum resins, styrene resins, coumarone-indene resins, ketone-based resins, and the like can be used. Suitable examples include rosin-based tackifying resins such as polymerized rosin esters and terpene phenolic resins.

In the technology disclosed herein, a tackifying resin having a softening point (softening temperature) of about 100° C. or higher (preferably about 120° C. or higher, more preferably about 135° C. or higher) can be preferably used. A pressure-sensitive adhesive containing a tackifying resin having a softening point equal to or higher than the above-described lower limit value can realize a pressure-sensitive adhesive sheet with more excellent repulsion resistance. Among the tackifying resins exemplified above, terpene-based tackifying resins (e.g., terpene phenolic resins) and rosin-based tackifying resins (e.g., esterified products of polymerized rosin) having such softening points can be preferably used. . The tackifier resin can be preferably used in a mode containing, for example, a terpene phenol resin having a softening point of 135° C. or higher. Moreover, a pressure-sensitive adhesive containing a tackifying resin having a softening point of 140° C. or higher can achieve particularly excellent repulsion resistance. For example, a terpene phenol resin having a softening point of 140°C or higher can be preferably used. The upper limit of the softening point of the tackifier resin is not particularly limited, and can be, for example, approximately 200° C. or lower (typically approximately 180° C. or lower). The softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) defined in JIS K2207.

The amount of the tackifier resin used is desirably set within a range in which the pressure-sensitive adhesive layer does not become too hard. preferably. The technique disclosed herein can be preferably carried out in a mode in which the amount of tackifying resin used is 5 parts by weight or less with respect to 100 parts by weight of the base polymer, or in which the tackifying resin is not substantially contained. This makes it easier to obtain a low-viscosity pressure-sensitive adhesive composition that does not substantially contain a solvent or a dispersion medium, or even if the content thereof is relatively small.

In addition, the adhesive composition in the technique disclosed herein can contain various additives known in the field of adhesives, if necessary. For example, coloring agents such as dyes and pigments, antistatic agents, surfactants, plasticizers, softeners, cross-linking aids, leveling agents, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors etc., can be added as appropriate depending on the application. As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

In some preferred embodiments, an active energy ray (typically light) curable pressure-sensitive adhesive composition can be preferably employed as the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer. Among the active energy ray-curable pressure-sensitive adhesive composition, the active energy ray-polymerizable pressure-sensitive adhesive composition is particularly preferable. The active energy ray-polymerizable pressure-sensitive adhesive composition can be a low-viscosity pressure-sensitive adhesive composition even if it contains substantially no solvent or dispersion medium or contains a relatively small amount of solvent or dispersion medium, and the unreacted monomer is polymerized. It is possible to form a pressure-sensitive adhesive layer exhibiting good pressure-sensitive adhesive performance. The low viscosity of the pressure-sensitive adhesive composition is significant from the viewpoint of enhancing the bond between the pressure-sensitive adhesive and the reinforcing layer. In particular, after applying the active energy ray-curable pressure-sensitive adhesive composition to a reinforcing layer having voids such as a non-woven fabric, the reinforcing layer is well impregnated by curing (preferably polymerizing) the pressure-sensitive adhesive composition. and a pressure-sensitive adhesive layer having excellent cohesive force can be formed. The double-faced pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed in this manner can be prevented from tearing or tearing when peeled from the adherend, and can be excellent in non-adhesive residue properties. .

In some other embodiments, a pressure-sensitive adhesive composition in which a completely polymerized product of monomer components is dissolved or dispersed in a solvent may be used as the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer. In this type of pressure-sensitive adhesive composition, the solvent content is not particularly limited. In some embodiments, the solvent content may be 70% or less, 55% or less, or 45% or less by weight of the total pressure-sensitive adhesive composition. The solvent contained in the pressure-sensitive adhesive composition is a component that should be removed by drying or the like during the process of forming the pressure-sensitive adhesive layer from the pressure-sensitive adhesive composition. Therefore, suppressing the content of the solvent is preferable from the viewpoints of improving the productivity of the double-sided PSA sheet and reducing material costs and energy costs. In addition, it is preferable to reduce the amount of organic solvent used from the viewpoint of reducing the environmental load. Furthermore, by reducing the solvent content, it tends to be easier to suppress the phenomenon of foaming in the pressure-sensitive adhesive layer when the solvent is removed. This can be advantageous from the viewpoint of improving the uniformity of adhesive performance and improving non-residual property.

Although the viscosity of the pressure-sensitive adhesive composition is not particularly limited, it is usually suitable to be 50 Pa·s or less, preferably 25 Pa·s or less. When the viscosity of the pressure-sensitive adhesive composition becomes low, applying the pressure-sensitive adhesive composition to the reinforcing layer tends to form a pressure-sensitive adhesive layer having good bonding properties with the reinforcing layer. When using a reinforcing layer having voids (for example, non-woven fabric), it is particularly significant to lower the viscosity of the pressure-sensitive adhesive composition to improve impregnation. From this point of view, in some aspects, the viscosity of the pressure-sensitive adhesive composition may be, for example, 20 Pa·s or less, 15 Pa·s or less, 10 Pa·s or less, or 8 Pa·s or less. The lower limit of the viscosity of the adhesive composition is not particularly limited. From the viewpoint of improving the leveling property and the ease of thickness control of the pressure-sensitive adhesive composition, in some embodiments, the viscosity of the pressure-sensitive adhesive composition may be, for example, 1 Pa·s or more, or may be 2 Pa·s or more. , 3 Pa·s or more.
The viscosity of the pressure-sensitive adhesive composition is measured using a BH viscometer under conditions of a measurement temperature of 30° C. and a rotation speed of 10 rpm. A similar measurement method is used in the examples described later. The viscosity of the pressure-sensitive adhesive composition is determined by, for example, the weight-average molecular weight of the polymer contained in the pressure-sensitive adhesive composition, the types and amounts of unpolymerized substances and solvents, and other components (eg, acrylic oligomers, tackifying resins, etc.). can be adjusted by the type and amount of

<Reinforcing layer>
The double-sided pressure-sensitive adhesive sheet disclosed herein includes a reinforcing layer attached to the pressure-sensitive adhesive layer exposed on the first pressure-sensitive adhesive surface. Although the reinforcing layer is not particularly limited, a layer that can be arranged between the first adhesive surface and the foam base material can be preferably used. The reinforcing layer is composed of, for example, natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, inorganic fibers such as glass fibers and carbon fibers, and fibrous substances such as metal fibers. fiber sheet; porous polyolefin film such as porous polyethylene film, porous polyvinyl alcohol film, porous resin film such as porous polyamide film; polyethylene (PE) film, polypropylene (PP) film, ethylene-propylene copolymer Polyolefin films such as coalesced films, polyester films such as polyethylene terephthalate (PET) films, plastic films such as polyvinyl chloride films, metal foils such as aluminum foils and copper foils, and the like can be used. The reinforcing layer may be subjected to a treatment for strengthening the bond between the pressure-sensitive adhesive and the reinforcing layer, such as application of a primer or corona discharge treatment.

The concept of the fibrous sheet includes woven fabrics, non-woven fabrics, knitted fabrics, nets, etc., made by spinning various fibrous materials alone or blended as described above. Here, the nonwoven fabric is a concept that includes nonwoven fabrics that are produced using a general paper machine, for example papers such as Japanese paper and woodfree paper. Felt is also included in the above concept of nonwoven fabric. The plastic film typically refers to a non-porous plastic film, and is a concept distinguished from the above-mentioned fibrous sheets such as woven fabrics and non-woven fabrics, and the above-mentioned porous resin film. As the plastic film, both a non-stretched film and a stretched (uniaxially stretched or biaxially stretched) film can be used.

The thickness of the reinforcing layer is preferably set so as not to significantly impair the flexibility of the double-sided pressure-sensitive adhesive sheet. In some aspects, the thickness of the reinforcing layer can be, for example, 150 μm or less, 100 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less. From the viewpoint of strength and handleability, the thickness is preferably 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more. From the viewpoint of achieving both repulsion resistance and strength in a well-balanced manner, in some preferred embodiments, the thickness of the reinforcing layer may be, for example, 30 μm to 60 μm, 35 μm to 55 μm, or 40 μm to 50 μm. may

As the reinforcing layer, it is preferable to use a layer having voids. The voids in the reinforcing layer may typically be voids that are open to the surface of the reinforcing layer, in other words, voids that are open to the outside of the reinforcing layer. A reinforcing layer having such voids tends to improve the bondability between the reinforcing layer and the pressure-sensitive adhesive layer. In some preferred embodiments, part of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer enters the voids. That is, the adhesive layer impregnates the reinforcing layer. Thereby, the bonding between the reinforcing layer and the pressure-sensitive adhesive layer can be enhanced, and the non-adhesive property can be improved.

As the reinforcing layer having voids, the above-described fibrous sheet or porous resin film can be used. Among them, the use of fibrous sheets is preferred. By impregnating the fibrous sheet as a reinforcing layer with an adhesive, the adhesive functions as a binder for the fibers forming the fibrous sheet, and the strength of the fibrous sheet can be improved. Impregnating the fibrous sheet with the adhesive that constitutes the adhesive layer can also help strengthen the adhesive layer. Therefore, by impregnating the fibrous sheet with the adhesive layer exposed on the surface of the double-sided pressure-sensitive adhesive sheet in the covering portion, tearing or tearing when the double-sided pressure-sensitive adhesive sheet is peeled off is suppressed, and good non-adhesive residue is obtained. can demonstrate their sexuality. As a result, the releasability of the double-sided PSA sheet can be effectively improved.

In addition, the fibrous sheet is excellent in ease of deformation (for example, ease of expansion and contraction), and has high adaptability to winding and bending of the double-faced pressure-sensitive adhesive sheet. When the double-sided pressure-sensitive adhesive sheet is spirally wound before use, or when the double-sided pressure-sensitive adhesive sheet is passed through conveying rolls during the manufacturing or use process, each part of the double-sided pressure-sensitive adhesive sheet is This is advantageous from the viewpoint of suppressing the occurrence of wrinkles and floats between layers. Suppressing the occurrence of wrinkles and lifting can help improve the non-adhesive residue property and appearance quality.

In some preferred embodiments, a nonwoven fabric can be used as the reinforcing layer. Nonwoven fabrics include, for example, pulps such as wood pulp and hemp pulp; nonwoven fabrics composed of natural fibers such as cotton and hemp (for example, Manila hemp); polyester fibers such as polyethylene terephthalate (PET) fibers; rayon, vinylon, and acetate fibers. , polyvinyl alcohol (PVA) fiber, polyamide fiber, polyolefin fiber, polyurethane fiber, and other chemical fibers (synthetic fibers); can do. Among them, from the viewpoint of the impregnability and strength of the adhesive, nonwoven fabrics made of paper pulp such as wood pulp and hemp pulp (for example, hemp pulp made from Manila hemp), nonwoven fabrics made of PET fibers, etc. preferable.

In addition to the constituent fibers as described above, the nonwoven fabric may contain resin components such as starch (e.g., cationic starch), polyacrylamide, viscose, polyvinyl alcohol, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide polyamine epichlorohydrin. . The resin component may function as a paper strength enhancer for the nonwoven fabric substrate. By using such a resin component as needed, the strength of the nonwoven fabric substrate can be adjusted. The nonwoven fabric substrate in the technique disclosed herein may optionally contain other general additives in the field related to the production of nonwoven fabrics, such as retention aids, drainage agents, viscosity modifiers, and dispersants. .

The thickness of the fibrous sheet (for example, nonwoven fabric) is usually about 150 μm or less. From the viewpoint of facilitating sufficient impregnation of the pressure sensitive adhesive into the inside of the fibrous sheet, the thickness may be, for example, 100 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less. From the viewpoint of strength and handleability, the thickness is usually 10 μm or more, preferably 15 μm or more, and may be 20 μm or more, 25 μm or more, 30 μm or more, or 40 μm or more. .

The basis weight of the fibrous sheet (for example, non-woven fabric) is usually about 4 g/m ² or more. In some embodiments, fibrous sheets having a basis weight of about 5 g/m ² or greater, about 7 g/m ² or greater, about 10 g/m ² or greater, or about 12 g/m ² or greater may be preferably used. A higher basis weight tends to improve the strength and handleability of the fibrous sheet. On the other hand, from the viewpoint of facilitating sufficient impregnation of the pressure-sensitive adhesive to the inside of the fibrous sheet, the basis weight is usually about 30 g/m ² or less, preferably about 25 g/m ² or less, and about 20 g/m 2 or less. m ² or less, approximately 18 g/m ² or less, or approximately 16 g/m ² or less.

The bulk density of the fibrous sheet (for example, non-woven fabric) is usually about 0.1 g/cm ³ or more, about 0.2 g/cm ³ or more, for example about 0.25 g/cm ³ or more. is preferred. A higher bulk density tends to improve the strength and handleability of the fibrous sheet. On the other hand, the bulk density may be, for example, about 1.1 g/cm ³ or less, or about 0.8 g/cm ³ or less. From the viewpoint of facilitating impregnation of the pressure-sensitive adhesive into the inside of the fibrous sheet, the bulk density is usually about 0.6 g/cm ³ or less, preferably about 0.5 g/cm ³ or less. In some aspects, a fibrous sheet having a bulk density of about 0.4 g/cm ³ or less, further about 0.35 g/cm ³ or less, for example about 0.3 g/cm ³ or less can be preferably used.

Although not particularly limited, the tensile strength (MD tensile strength) of the reinforcing layer in the longitudinal direction (MD) may be, for example, 1 N/15 mm or more. When the MD tensile strength of the reinforcing layer increases, tearing and tearing of the double-sided adhesive tape tend to be better prevented when peeled off. From this point of view, in some aspects, the reinforcing layer may have an MD tensile strength of, for example, 2 N/15 mm or more, or 3 N/15 mm or more. The MD tensile strength of the reinforcing layer is usually preferably 50 N/15 mm or less, and may be, for example, 30 N/15 mm or less, 20 N/15 mm or less, or 10 N/15 mm or less. When the MD tensile strength is lowered, the impregnability of the pressure-sensitive adhesive and the ease of deformation of the reinforcing layer tend to be improved.

Although not particularly limited, the tensile strength (TD tensile strength) in the width direction (TD) of the reinforcing layer is, for the same reason as the MD tensile strength, for example 1 N/15 mm or more, 2 N/15 mm or more, or 3 N/ It can be 15mm or more. For the same reason as the MD tensile strength, the TD tensile strength may be, for example, 50 N/15 mm or less, 30 N/15 mm or less, 20 N/15 mm or less, or 10 N/15 mm or less.

The tensile strength (MD tensile strength, TD tensile strength) of the reinforcing layer is measured as a value per width of 15 mm according to JIS P8113. That is, the sheet-like material (for example, non-woven fabric) used as the reinforcing layer is cut into strips with a width of 15 mm, which is used as a test piece for measurement. A similar measurement method is used in the examples described later. The tensile strength of the reinforcing layer can be controlled by the constituent material of the reinforcing layer (for example, the material of fibers constituting the fibrous sheet), bulk density, thickness, and the like.

In embodiments using a reinforcing layer having voids (for example, a fibrous sheet such as a nonwoven fabric), the reinforcing layer preferably has a permeation time of 1000 seconds or less in a liquid permeability test performed by the following method.

(Liquid permeability test)
A cylinder with an inner diameter of 20 mm and a height of 75 mm is made. A test piece is prepared by cutting a sheet material (for example, nonwoven fabric) used as a reinforcing layer into a size (for example, a 50 mm square) that can sufficiently cover the opening of the cylinder. This test piece covers the opening at one end of the cylinder from the outside, and the part protruding outside the opening is fixed to the outer periphery of the cylinder with a tetrafluoroethylene packing. The end of the side covered with the sheet-like material is placed on the bottom side, and the cylinder is vertically held so that the bottom side is suspended in the air. Then, 10 g of the test liquid (acrylic polymer solution, which will be described later) is gently introduced from the upper end opening of the cylinder, and the time until the test liquid permeates the test piece and drips for the first time is measured. A similar method is used in the examples described later.
As the test liquid, an acrylic polymer solution (viscosity 6.0 Pa·s) prepared under the following conditions is used.
[Method for preparing test solution]
A monomer mixture composed of 2-ethylhexyl acrylate (90 parts by weight) and acrylic acid (10 parts by weight) was added with a photopolymerization initiator (trade name "Irgacure 651" manufactured by BASF, 0.05 parts by weight) and photopolymerization initiation. agent (trade name “Irgacure 184” manufactured by BASF, 0.05 parts by weight). This formulation is irradiated with ultraviolet rays containing a wavelength of 460 nm or less, and the viscosity of the formulation (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) is 6.0 Pa s. An acrylic polymer solution obtained by partially polymerizing a monomer mixture is used as a test liquid for the liquid permeability test.

When the liquid permeability of the reinforcing layer is high (permeation time is short), the pressure-sensitive adhesive composition applied to the reinforcing layer tends to permeate (impregnate) into the reinforcing layer more easily. From this point of view, in some aspects, the permeation time may be, for example, 800 seconds or less, 600 seconds or less, 400 seconds or less, or 200 seconds or less. The lower limit of the permeation time is not particularly limited, but from the viewpoint of the strength and handleability of the reinforcing layer, 10 seconds or more is usually suitable, and it may be 20 seconds or more, or 30 seconds or more. In some aspects, the permeation time of the reinforcing layer may be 50 seconds or more, or 70 seconds or more.

<First covering part>
In the double-sided pressure-sensitive adhesive sheet disclosed herein, at least the first covering portion out of the first covering portion and the second covering portion is provided with the adhesive layer exposed on the first adhesive surface and bonded with the adhesive layer. It is configured including a reinforcing layer. It is preferable that the reinforcing layer is a reinforcing layer having voids (for example, nonwoven fabric), and the reinforcing layer is impregnated with the pressure-sensitive adhesive layer.

In some embodiments, the pressure-sensitive adhesive layer includes an outer layer forming the outer surface of the first covering portion (which also serves as the first pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet) and an inner layer forming the inner surface of the first covering portion. obtain. The outer layer typically includes a portion that covers the outer surface of the reinforcement layer. The inner layer typically includes a portion covering the inner surface of the reinforcing layer. In an embodiment in which a reinforcing layer (for example, nonwoven fabric) having voids is impregnated with an adhesive layer, and the adhesive layer includes the outer layer and the inner layer, the adhesive layer impregnated in the reinforcing layer is It can be an outer layer, an inner layer, or both an outer layer and an inner layer. When both the outer layer and the inner layer are impregnated with the reinforcing layer, the degree of impregnation of the reinforcing layer may be the same or different between the outer layer and the inner layer. From the viewpoint of effectively improving the non-sticky property, it is preferable that at least the outer layer is impregnated with the reinforcing layer.

Various conventionally known methods can be applied as a method for forming the pressure-sensitive adhesive layer to be bonded to the reinforcing layer. For example, a method of directly applying a pressure-sensitive adhesive composition to a reinforcing layer (direct method), a method of applying a pressure-sensitive adhesive composition onto a suitable release surface to form a pressure-sensitive adhesive layer on the release surface, and removing the pressure-sensitive adhesive layer A method of bonding to a reinforcing layer and transferring (transfer method) and the like can be mentioned. A combination of these methods may also be used. In the configuration in which the pressure-sensitive adhesive layer includes an outer layer and an inner layer as described above, one of the outer layer and the inner layer may be formed by a transfer method, and the other may be formed by a direct method. For example, the outer layer may be formed by transferring the inner layer to the inner surface of the reinforcing layer and then applying the adhesive composition to the outer surface of the reinforcing layer. Application of the pressure-sensitive adhesive composition can be performed using known or commonly used coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, and spray coaters.

In some aspects of the double-sided pressure-sensitive adhesive sheet provided with a reinforcing layer, the reinforcing layer (for example, a fibrous sheet such as nonwoven fabric) is impregnated with the pressure-sensitive adhesive layer so that the void area is 500 μm ² /400 μm or less. is preferred.
Here, the "void area" means that the double-sided pressure-sensitive adhesive sheet is stretched in the thickness direction along a cutting line perpendicular to the flow direction (MD direction, typically the longitudinal direction of the sheet) of the nonwoven fabric base material constituting the double-sided pressure-sensitive adhesive sheet. In the cut cross section (longitudinal cross section), the length of the cross section (typically corresponds to the length in the width direction of the nonwoven fabric substrate.) The area of voids observed per 400 μm (area of opening to the cross section ). The void area can be understood by analyzing an image (SEM image) obtained by observing the cross section with a scanning electron microscope (SEM) at a magnification of about 100 to 1000 (eg, 300). can. More specifically, the void area can be determined according to the method described in the examples below. The void area is determined for at least 3 cross sections (more preferably 5 or more, for example 5 to 10) by varying the cutting position in the longitudinal direction (MD) of the sheet material used as the reinforcing layer, and the average value thereof is calculated. It is preferable to adopt

A smaller void area means that the reinforcing layer is better impregnated with the adhesive. Therefore, by configuring the first covering portion so as to reduce the void area, the bonding between the reinforcing layer and the pressure-sensitive adhesive layer can be enhanced, and the non-adhesive property can be effectively improved. In some embodiments, the void area may be, for example, 300 μm ² /400 μm or less, 200 μm ² /400 μm or less, or 100 μm ² /400 μm or less. The lower limit of the void area is not particularly limited, and may be substantially 0 μm ² /400 μm or less. In some embodiments, the void area may be, for example, 10 μm ² /400 μm or more, or 30 μm ² /400 μm or more, in consideration of productivity and material costs. The void area can be adjusted by selection of the reinforcing layer, viscosity of the pressure-sensitive adhesive composition, method of forming the pressure-sensitive adhesive layer, and the like.

In the first covering part according to some aspects, the outer surface of the reinforcing layer is preferably covered with an adhesive layer. The thickness of the pressure-sensitive adhesive layer covering the outer surface of the reinforcing layer (outer surface coating thickness) may be, for example, 10 μm or more. From the viewpoint of increasing the adhesiveness to the adherend, the outer surface coating thickness may be 20 μm or more, 25 μm or more, 30 μm or more, or 40 μm or more. Moreover, from the viewpoint of suitably exhibiting the non-adhesive property improvement effect of the reinforcing layer, it is appropriate that the thickness of the outer surface coating is usually 200 μm or less. In some aspects, the outer surface coating thickness can be 150 μm or less, 100 μm or less, or 75 μm or less.

In the first covering part according to some aspects, the inner layer of the reinforcing layer is preferably covered with an adhesive layer. The thickness of the pressure-sensitive adhesive layer covering the inner surface of the reinforcing layer (inner surface coating thickness) may be, for example, 3 μm or more. When the adhesive layer that covers the inner layer is used to attach the first covering portion to the foam base material, from the viewpoint of preventing the first covering portion from peeling off from the foam base material, the thickness of the inner surface coating is It is preferably 10 μm or more, and may be 15 μm or more or 20 μm or more. In addition, from the viewpoint of preventing breakage (cohesive failure) of the pressure-sensitive adhesive layer covering the inner surface of the reinforcing layer, the thickness of the inner surface coating is usually 200 μm or less, preferably 150 μm or less, 100 μm or less, or 75 μm. It may be below.

The relationship between the outer surface coating thickness and the inner surface coating thickness is not particularly limited. In some preferred embodiments, the outer coating thickness can be equal to or greater than the inner coating thickness, and the outer coating thickness can be greater than the inner coating thickness. As a result, the total thickness of the double-sided pressure-sensitive adhesive sheet is suppressed, and the first pressure-sensitive adhesive surface tends to exert good adhesion to the adherend. In this embodiment, a reinforcing layer having voids (for example, a fibrous sheet such as a nonwoven fabric) and an adhesive layer including an outer layer and an inner layer are employed, and the reinforcing layer is impregnated with an adhesive that constitutes at least the outer layer. is particularly significant. The thickness of the outer surface coating thickness can be, for example, 1.0 times the inner surface coating thickness, and may be greater than 1.0 times, greater than or equal to 1.2 times, or greater than or equal to 1.5 times.

The thickness of the first covering portion (that is, the distance between the outer surface and the inner surface of the first covering portion) is not particularly limited, and may be, for example, 20 μm or more. From the viewpoint of enhancing the adhesiveness to the adherend and suitably exhibiting the effect of providing the reinforcing layer, in some embodiments, the thickness of the first covering portion may be, for example, 30 μm or more, or 50 μm or more. , 70 μm or more, or 100 μm or more. Moreover, from the viewpoint of suppressing the total thickness of the double-sided pressure-sensitive adhesive sheet, in some embodiments, the thickness of the first covering portion may be, for example, 500 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less. .

<Second covering part>
The second covering part in the technique disclosed here includes an adhesive layer exposed on the second adhesive surface. The material, structure, manufacturing method, etc. of the pressure-sensitive adhesive layer of the second covering portion can be appropriately selected from those exemplified above as applicable to the pressure-sensitive adhesive layer of the first covering portion. The material, structure, manufacturing method, etc. of the pressure-sensitive adhesive layer of the second covering portion may be the same as or different from those of the pressure-sensitive adhesive layer of the first covering portion. In some embodiments, the same PSA composition can be used to form the first PSA layer and the second PSA layer from the viewpoint of improving productivity and usability of the double-sided PSA tape.

<Double-sided adhesive sheet>
The double-sided PSA sheet disclosed herein has a configuration in which a first covering portion and a second covering portion are arranged on the first surface side and the second surface side of a foam substrate, respectively. A method for producing a double-sided pressure-sensitive adhesive sheet having such a configuration is not particularly limited. For example, the first covering portion may be arranged by bonding the inner surface of the first covering portion prepared in advance to the first surface of the foam substrate, and the first covering portion may be disposed on the first surface of the foam substrate. You may arrange|position by forming a part. As a method for forming the first covering portion on the first surface of the foam base material, for example, a pressure-sensitive adhesive layer (inner layer) is placed on the first surface by a transfer method or a direct method, and the inner layer is A method of bonding a reinforcing layer to the outer surface and applying an adhesive composition to the outer surface of the reinforcing layer to form an adhesive layer (outer layer) can be used. Similarly, the second coating portion may be arranged by bonding the inner surface of the second coating portion prepared in advance to the second surface of the foam substrate, and the second coating may be formed on the second surface of the foam substrate. You may arrange|position by forming a part. In the case of the second covering portion that does not include a reinforcing layer, the pressure-sensitive adhesive layer that constitutes the second covering portion can be provided on the foam substrate by a direct method or a transfer method.

In some preferred embodiments, the gel content of the adhesive constituting the adhesive layer can be about 70% or more. As the gel content of the pressure-sensitive adhesive increases, the non-adhesive residue tends to improve. In addition, by increasing the gel content in a structure in which a reinforcing layer (for example, a fibrous sheet such as a nonwoven fabric) is impregnated with an adhesive, the bonding between the adhesive and the reinforcing layer tends to be improved, and reinforcement by the adhesive The effect of improving the strength of the layer also tends to increase. From this point of view, in some aspects, the gel content of the adhesive may be, for example, greater than 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, or greater than or equal to 87%. The upper limit of the gel content is not particularly limited, but from the viewpoint of enhancing the adhesiveness to the adherend, 99% or less is usually suitable, and 97% or less is also acceptable. The gel content can be adjusted by selecting the composition of the monomer components, selecting the polymerization method and polymerization conditions, using polyfunctional monomers, using cross-linking agents, and the like. The gel content of the adhesive is measured by the following method. A similar method is used in the examples described later. The gel component can be applied to both the pressure-sensitive adhesive forming the first pressure-sensitive adhesive surface and the pressure-sensitive adhesive forming the second pressure-sensitive adhesive surface. It is preferable that at least the pressure-sensitive adhesive constituting the first pressure-sensitive adhesive surface has the gel component.

(Gel content measurement method)
About 0.1 g of adhesive sample (weight Wg ₁ ) collected from the adhesive layer is wrapped in a porous polytetrafluoroethylene membrane (weight Wg ₂ ) with an average pore size of 0.2 μm in a purse-like shape, and the opening is wrapped with octopus thread ( Tie with weight Wg ₃ ). As the porous polytetrafluoroethylene membrane, trade name "Nitoflon (registered trademark) NTF1122" (Nitto Denko Co., Ltd., average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) or its equivalent is used. The package is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute the sol (ethyl acetate soluble matter) in the sample from the membrane. Next, the package is taken out, ethyl acetate adhering to the outer surface is wiped off, the package is dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the package is measured. Each value is substituted into the following _formula to calculate the gel content GC of the adhesive.
Gel content G _C (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

The total thickness (that is, the distance from the first adhesive surface to the second adhesive surface) of the double-sided PSA sheet disclosed here is not particularly limited. From the viewpoint of utilizing the properties of the foam base material and exhibiting good adhesion to the adherend, the total thickness of the double-sided PSA sheet may be, for example, 50 μm or more, 75 μm or more, or 100 μm or more. It may be 150 μm or more. In addition, from the viewpoint of handleability of the double-sided pressure-sensitive adhesive sheet (for example, workability into a narrow tape shape, windability, punching workability), etc., the thickness of the double-sided pressure-sensitive adhesive sheet is usually 5000 μm or less. Yes, it may be 4000 μm or less, 3000 μm or less, 2500 μm or less, 2000 μm or less, or 1500 μm or less. Reducing the thickness of the double-sided pressure-sensitive adhesive sheet is also preferable from the viewpoint of miniaturization and weight reduction of products to which the double-sided pressure-sensitive adhesive tape is applied.

In addition, the double-sided pressure-sensitive adhesive sheet disclosed herein has a function of layers other than the foam base material, the first coating layer and the second coating layer (undercoat layer, antistatic layer, etc.) within a range that does not significantly impair the effects of the present invention. a layer, a decorative layer such as a printed layer, etc. (hereinafter also referred to as "another layer"). Said other layer may, for example, be between the foam substrate and the first coating layer and/or between the second coating layer. Also, the other layer may be included in the first coating layer and/or the second coating layer.

<Application>
The object (adherend) to which the double-sided pressure-sensitive adhesive sheet disclosed herein is attached is not particularly limited. The double-sided pressure-sensitive adhesive sheet disclosed herein includes, for example, metal materials such as stainless steel (SUS) and aluminum; inorganic materials such as glass and ceramics; polycarbonate (PC), polymethylmethacrylate (PMMA), polypropylene, polyethylene terephthalate (PET); ), acrylonitrile-butadiene-styrene copolymer resin (ABS), high-impact polystyrene (HIPS), PC-ABS blend resin, PC-HIPS blend resin, and other resin materials; rubber materials such as natural rubber and butyl rubber; and composites thereof It can be used in a mode in which it is attached to an adherend made of a material or the like.

Since the double-sided pressure-sensitive adhesive sheet disclosed herein contains a foam base material, it can be excellent in shock absorption, waterproofness, dustproofness, and the like. Taking advantage of these features, it can be used for electronic device applications, such as fixing the display part of mobile electronic devices, fixing display protection members of mobile electronic devices, fixing key module members of mobile phones, fixing TV decoration panels, etc. It can be preferably applied to applications such as fixing battery packs of personal computers and waterproofing lenses of digital video cameras. A particularly preferred use is for portable electronic devices. In particular, it can be preferably used for portable electronic equipment having a liquid crystal display device. For example, in such a portable electronic device, it is suitable for joining a display section (which may be a display section of a liquid crystal display device) or a display section protection member to a housing.

The display protection member is typically a member having a region exhibiting optical transparency in the thickness direction (hereinafter also referred to as a “light transmissive member”), and is sometimes referred to as a lens. . Here, the term "lens" as used herein is a concept that includes both a lens that exhibits light refraction and a lens that does not exhibit light refraction. In other words, the term "lens" in this specification also includes a light-transmissive member that does not have a refraction function, such as a protective panel that merely protects the display section of a portable electronic device. The protection panel can also be understood as a light-transmissive display protection member or display cover member. When the material of the protective panel is glass, the protective panel can also be called "cover glass". However, the material of the protective panel or the lens is not limited to glass, and may be any material that can exhibit light transmittance.

In addition, the term "portable electronic device" as used herein refers to general electronic devices that are used while being carried, and is not particularly limited. Here, “portable” means not only being able to be carried but having a level of portability that allows an individual (typical adult) to carry it relatively easily. do. Examples of the "portable electronic device" here include mobile phones, smart phones, tablet PCs, notebook PCs, and the like. Such a mobile electronic device may be a so-called wearable terminal (for example, a wristband type such as a wristwatch type, a head mount type such as a glasses type, etc.). The portable electronic devices include, for example, telephones, clocks, cameras, glasses, personal computers and other information terminals, health management tools such as sphygmomanometers, pulse monitors, and pedometers, music players, video players, sound recorders, video recorders, etc. 1 or 2 It may have the above functions.

Matters disclosed by this specification include the following.
(1) A double-sided pressure-sensitive adhesive sheet having both a first surface and a second surface serving as adhesive surfaces,
a sheet-like foam base material;
a first coating portion disposed on the first surface side of the foam substrate;
and a second coating portion disposed on the second surface side of the foam base material,
The first covering part includes a pressure-sensitive adhesive layer exposed on the first surface and a reinforcing layer provided in combination with the pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet, wherein the second covering portion includes a pressure-sensitive adhesive layer exposed on the second surface.
(2) The double-sided pressure-sensitive adhesive sheet according to (1) above, wherein the reinforcing layer has voids, and the voids are impregnated with the adhesive constituting the adhesive layer exposed on the first surface.
(3) The double-sided pressure-sensitive adhesive sheet according to (1) or (2) above, wherein the reinforcing layer is a fibrous sheet.
(4) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (3) above, wherein the reinforcing layer has a thickness of approximately 20 μm or more and approximately 150 μm or less.
(5) The pressure-sensitive adhesive layer exposed on the first surface is composed of a pressure-sensitive adhesive formed from an active energy ray-polymerizable pressure-sensitive adhesive composition, according to any one of (1) to (4) above. Double-sided adhesive sheet.
(6) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the pressure-sensitive adhesive layer exposed on the first surface has a gel content of about 70% or more.
(7) The outer surface of the reinforcing layer is covered with the adhesive layer exposed on the first surface, and the thickness of the adhesive surface covering the outer surface is about 10 μm or more and about 200 μm or less, above (1) to (6) The double-sided pressure-sensitive adhesive sheet according to any one of (6).
(8) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (7) above, wherein the foam substrate is a polyolefin foam substrate.
(9) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (8) above, wherein the foam substrate has a thickness of about 200 μm or more.
(10) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (9) above, wherein the 25% compressive strength of the foam substrate is approximately 30 kPa, approximately 35 kPa, or approximately 40 kPa or more.
(11) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (10) above, wherein the reinforcing layer has a permeation time of about 30 seconds or more and about 1000 seconds or less in the liquid permeability test described above.
(12) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (11) above, wherein the reinforcing layer is a nonwoven fabric (preferably paper).
(13) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (12) above, wherein the reinforcing layer is a nonwoven fabric (preferably paper) made of hemp pulp.
(14) The double-sided pressure-sensitive adhesive sheet according to (13) above, wherein substantially 100% by weight (typically 98% by weight or more, for example 99% by weight or more) of the constituent fibers is hemp.
(15) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (14) above, wherein the reinforcing layer has an MD tensile strength of approximately 1 N/15 mm or more and approximately 50 N/15 mm or less.
(16) The pressure-sensitive adhesive layer exposed on the first surface is composed of a pressure-sensitive adhesive formed from an active energy ray-polymerizable pressure-sensitive adhesive composition, and the pressure-sensitive adhesive composition constitutes the pressure-sensitive adhesive composition. The double-sided pressure-sensitive adhesive sheet according to any one of the above (1) to (15), containing about 0.05 parts by weight or more and about 1 part by weight or less of a polyfunctional monomer with respect to 100 parts by weight of the monomer component.
(17) Any one of (1) to (16) above, wherein the pressure-sensitive adhesive layer exposed on the first surface is formed from a pressure-sensitive adhesive composition having a viscosity of about 3 Pa s or more and about 50 Pa s. The double-sided adhesive sheet described in .
(18) Any one of (1) to (17) above, wherein the second covering portion includes an adhesive layer exposed on the second surface and a reinforcing layer provided in combination with the adhesive layer. The double-sided adhesive sheet described in crab.
(19) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (18) above, wherein the foam substrate is a foam substrate having a surface layer formed on its surface.
(20) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (19) above, wherein the pressure-sensitive adhesive layer exposed on the first surface is an acrylic pressure-sensitive adhesive layer.
(21) The acrylic pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive composition,
The acrylic pressure-sensitive adhesive composition contains the following component (A) as a monomer component, and further contains at least one of the following component (B), component (C) and component (D), above (20) The double-sided adhesive sheet described in .
Component (A): Alkyl (meth)acrylate having an alkyl group having 1 to 18 carbon atoms at the ester end.
Component (B): an alicyclic monomer.
Component (C): a monomer selected from hydroxy and carboxy groups.
Component (D): heterocycle-containing monomer.
(22) The proportion of C _6-9 alkyl acrylate (e.g., 2EHA) in the total component (A) is approximately 50% by weight or more and 100% by weight or less, approximately 60% by weight or more and 100% by weight or less, or approximately 70% by weight. The double-sided pressure-sensitive adhesive sheet according to (21) above, which is 100% by weight or less.

Several examples relating to the present invention are described below, but the present invention is not intended to be limited to those shown in such examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Example 1>
(Preparation of polymer syrup 1 (2EHA/AA=90/10))
A monomer mixture composed of 2-ethylhexyl acrylate (2EHA, 90 parts) and acrylic acid (AA, 10 parts) was blended with a photoinitiator (0.1 part), and then under a nitrogen atmosphere, the viscosity (BH Viscometer, No. 5 rotor, 10 rpm, measurement temperature: 30° C.) was irradiated with ultraviolet light including a wavelength of 460 nm or less until the temperature reached 6.0 Pa·s to obtain a partially polymerized product (polymer syrup 1). As the photopolymerization initiator, a product name "Irgacure 651" manufactured by BASF and a product name "Irgacure 184" manufactured by the same company were used at a weight ratio of 1:1.

(Preparation of adhesive composition UV-A)
1,6-Hexanediol diacrylate (HDDA, 0.1 part) is blended with the acrylic polymer syrup 1 (100 parts) described above, and an ultraviolet curable adhesive composition that does not substantially contain an organic solvent. A compound UV-A was prepared. The viscosity of this adhesive composition UV-A was 6.0 Pa·s. The viscosity of the adhesive composition UV-A was measured using a BH viscometer. Measured under conditions of 5 rotors, 10 rpm, measurement temperature: 30°C. The viscosity of each pressure-sensitive adhesive composition described below was also measured under the same conditions.

(Preparation of covering portion)
The pressure-sensitive adhesive composition UV-A was applied to a thickness of 25 μm on the release-treated surface of a 38 μm-thick polyester film (polyester release liner A) having one surface subjected to a release treatment. On the surface (open surface) of the pressure-sensitive adhesive composition UV-A applied on the release liner A, a polyester release liner B of the same type as the release liner A (however, the release property is higher than that of the release liner A). By stacking the release-treated surfaces, a laminate having a structure in which the adhesive composition UV-A was sandwiched between the release-treated surfaces of the two release liners A and B was formed. Both sides of this laminate (outside of both release liners) were irradiated with ultraviolet rays for 3 minutes from a black light lamp with an illumination intensity of 5 mW/cm ² . Thus, a pressure-sensitive adhesive layer having a thickness of 25 μm was produced.
By peeling off the release liner B from the adhesive layer to expose one side of the adhesive layer and attaching it to the second side of the nonwoven fabric as the reinforcing layer (the side facing the foam base material), the adhesive layer is transferred to the second side. A pressure-sensitive adhesive layer (inner pressure-sensitive adhesive layer) was provided according to the method. After the lamination, the release liner A was used continuously to protect the pressure-sensitive adhesive layer. As the nonwoven fabric, paper A (basis weight: 14.2 g/m ² , nonwoven fabric available from Nippon Paper Papylia Co., Ltd.) containing hemp pulp as a constituent fiber was used.

Next, the adhesive composition UV-A was directly applied to the first surface of the paper A (the surface facing the first adhesive surface of the double-sided adhesive sheet). The coating amount of the pressure-sensitive adhesive composition UV-A is about It was adjusted to be 50 μm. The surface (open surface) of the pressure-sensitive adhesive composition UV-A applied to the outer surface of paper A is subjected to a release treatment with a polyester release liner C of the same type as release liner A (however, the release property is lower than that of release liner A). An outer pressure-sensitive adhesive layer was formed by a direct method by overlapping the surfaces and irradiating ultraviolet rays from the outside of the release liner C with a black light lamp having an illumination of 5 mW/cm ² for 3 minutes.
In this way, the first covering portion comprising the pressure-sensitive adhesive layer in which the inner pressure-sensitive adhesive layer and the outer pressure-sensitive adhesive layer are integrated (fused) and the reinforcing layer impregnated with the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive layer. The inner and outer surfaces were protected by release liners A and C, respectively. Two pieces of the first covering portion were produced, and one of them was used as the second covering portion.

(Production of double-sided adhesive sheet)
The release liner A covering the inner surfaces of the first and second coating parts obtained above was peeled off, and a crosslinked polyethylene foam sheet A (product name: "Volara", thickness 0.30 mm, thickness 0.30 mm, Density of 0.20 g/cm ³ , compressive strength of 80 kPa, available from Sekisui Chemical Co., Ltd.). Then, the sheet was passed once through a laminator at 50° C. under conditions of a pressure of 0.5 MPa and a speed of 10 m/min, and then cured in an oven at 40° C. for 24 hours to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Example 2>
(Preparation of adhesive composition Sol-A)
A reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel was charged with 2EHA (95 parts) and AA (5 parts) and a mixed solvent of ethyl acetate and toluene (212 parts, ethyl acetate /toluene weight ratio = 70/30), and stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, 0.4 part of benzoyl peroxide was added as a polymerization initiator, and solution polymerization was carried out at 60° C. for 6 hours to obtain an acrylic polymer solution. Mw of this acrylic polymer was about 120×10 ⁴ .
To the acrylic polymer solution, 0.4 parts of an isocyanate cross-linking agent (0.4 parts, manufactured by Tosoh Corporation, product name "Coronate L", trimethylolpropane / tolylene diisocyanate 3 75% ethyl acetate solution of the polymer adduct) and an epoxy-based cross-linking agent (0.05 parts, manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD-C") are added and stirred to form a solvent-type adhesive composition. Product Sol-A was prepared.

(Preparation of covering part and double-sided pressure-sensitive adhesive sheet)
The pressure-sensitive adhesive composition Sol-A was applied to the release-treated surface of the release liner A described above and dried at 100° C. for 2 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 25 μm. By bonding this adhesive layer to the second surface of the nonwoven fabric (Paper A), an adhesive layer (inner adhesive layer) was provided on the second surface by a transfer method. The release liner A was subsequently used to protect the adhesive layer.
Next, the adhesive composition Sol-A is directly applied to the first surface of the paper A (the surface facing the first adhesive surface side of the double-sided adhesive sheet) and dried at 100 ° C. for 2 minutes, by a direct method. An outer adhesive layer was formed. The coating amount of the pressure-sensitive adhesive composition Sol-A was adjusted so that the outer surface coating thickness of the paper A was about 50 μm, considering the amount of the paper A impregnated. The release liner C described above was adhered to the surface of the outer pressure-sensitive adhesive layer for protection. In this way, the first covering portion comprising the pressure-sensitive adhesive layer in which the inner pressure-sensitive adhesive layer and the outer pressure-sensitive adhesive layer are integrated (fused) and the reinforcing layer impregnated with the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive layer. The inner and outer surfaces were protected by release liners A and C, respectively. Two pieces of the first covering portion were produced, and one of them was used as the second covering portion.
A double-sided pressure-sensitive adhesive sheet according to this example was obtained in the same manner as the double-sided pressure-sensitive adhesive sheet in Example 1, except that these covering portions were used.

<Example 3>
(Preparation of polymer syrup 2 (2EHA/NVP/HEA) = 78/18/4))
A photoinitiator (0.07 part), and then the partial polymer ( A polymer syrup 2) was obtained. As the photopolymerization initiator, a product name "Irgacure 651" manufactured by BASF and a product name "Irgacure 184" manufactured by the same company were used at a weight ratio of 1:1.

(Preparation of adhesive composition UV-B)
HEA (17.5 parts), HDDA (0.087 parts) and a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., 0.35) are added to the polymer syrup 2 (100 parts) described above. Part) was blended to prepare an ultraviolet curable pressure-sensitive adhesive composition UV-B containing substantially no organic solvent. The viscosity of this adhesive composition UV-B was 6.5 Pa·s.
A double-sided PSA sheet according to this example was obtained in the same manner as in Example 1, except that PSA composition UV-B was used instead of PSA composition UV-A.

<Example 4>
(Preparation of acrylic oligomer 1)
Methyl methacrylate (MMA, 38.7 parts) and dicyclopentanyl methacrylate (DCPMA, 57.7 parts) with 1-thioglycerol (3.3 parts) as a chain transfer agent and ethyl acetate (64 parts) as a solvent Part) was mixed, and dissolved oxygen was removed by blowing nitrogen gas. Next, 2,2'-azobisisobutyronitrile (0.30 parts) was added as a polymerization initiator and reacted at 70°C for 2 hours, followed by reaction at 80°C for 2 hours. Ethyl acetate and residual monomers were removed from the resulting reaction solution under vacuum drying conditions of 85° C. and 7.5 kPa to obtain acrylic oligomer 1 in powder form.

(Preparation of adhesive composition UV-C)
The powdery acrylic oligomer 1 and 2EHA obtained above were mixed at a weight ratio of 1:1, and dissolved by stirring for 30 minutes to obtain an oligomer/2EHA mixture.
To polymer syrup 2 described above (100 parts) was added the above oligomer/2EHA mixture (12 parts), HEA (17.5 parts), 1,6-hexanediol diacrylate (HDDA, 0.087 parts) and silane cup. A ring agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., 0.35 parts) was blended to prepare an ultraviolet-curable pressure-sensitive adhesive composition UV-C containing substantially no organic solvent. The viscosity of this adhesive composition UV-C was 5.4 Pa·s.
A double-sided PSA sheet according to this example was obtained in the same manner as in Example 1, except that PSA composition UV-C was used instead of PSA composition UV-A.

<Examples 5-7>
In the preparation of the adhesive composition UV-A used in Example 1, the amount of HDDA used relative to acrylic polymer syrup 1 (100 parts) was 0.05 parts (Example 5), 0.15 parts (Example 6), and By changing to 0.30 parts (Example 7), adhesive compositions UV-D, UV-E and UV-F were obtained. Double-sided PSA sheets according to Examples 5 to 7 were obtained in the same manner as in Example 1, except that the PSA compositions UV-D, UV-E, and UV-F were used instead of the PSA composition UV-A. .

<Examples 8 and 9>
As the reinforcing layer, instead of the paper A used in Example 1, in Example 8, paper B (basis weight 17.8 g/m ² , non-woven fabric available from Nippon Paper Papylia Co., Ltd.) containing hemp pulp as a constituent fiber, and Example 9 Paper C (basis weight: 17.2 g/m ² , non-woven fabric available from Nippon Paper Papylia Co., Ltd.) having paper pulp as a constituent fiber was used. Other points were the same as in Example 1, and double-faced pressure-sensitive adhesive sheets according to Examples 8 and 9 were obtained.

<Example 10>
Polymer syrup 3, which has a lower viscosity than polymer syrup 1, was prepared by shortening the UV irradiation time during the preparation of polymer syrup 1 to obtain a partially polymerized product. A pressure-sensitive adhesive composition UV-G (viscosity 3 Pa·s) containing substantially no organic solvent was prepared in the same manner as the pressure-sensitive adhesive composition UV-A except that this polymer syrup 3 was used. A double-sided PSA sheet according to this example was obtained in the same manner as in Example 1, except that PSA composition UV-G was used instead of PSA composition UV-A.

<Example 11>
Polymer syrup 4, which has a higher viscosity than polymer syrup 1, was prepared by extending the UV irradiation time during the preparation of polymer syrup 1 to obtain a partially polymerized product. A pressure-sensitive adhesive composition UV-H (viscosity 30 Pa·s) containing substantially no organic solvent was prepared in the same manner as the pressure-sensitive adhesive composition UV-A except that this polymer syrup 4 was used. A double-sided pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition UV-H was used instead of the pressure-sensitive adhesive composition UV-A.

<Examples 12 to 15>
The amount of adhesive composition UV-A applied directly to the first surface of paper A was adjusted so that the outer surface coating thickness shown in Table 2 was obtained. Other points were the same as in Example 1 to obtain double-sided pressure-sensitive adhesive sheets according to Examples 12 to 15.

<Example 16>
Instead of the foam sheet A, a crosslinked polyethylene foam sheet B (product name: “Volara”, thickness: 0.2 mm, density: 0.20 cm ³ , compressive strength: 45 kPa, subjected to corona discharge treatment on both sides) was used. available from the company) was used. Other points were the same as in Example 1 to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Example 17>
Instead of the foam sheet A, a crosslinked polyethylene foam sheet C (product name: “Volara”, thickness: 2.0 mm, density: 0.07 cm ³ , compressive strength: 45 kPa, Sekisui Chemical Co., Ltd. available from the company) was used. Other points were the same as in Example 1 to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Example 18>
Instead of the foam sheet A, a crosslinked polyolefin foam sheet D (thickness: 0.3 mm, density: 0.10 cm ³ , compressive strength: 37 kPa) with corona discharge treatment on both sides was used. Other points were the same as in Example 1 to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Example 19>
Instead of the foam sheet A, a crosslinked polyolefin foam sheet E (thickness: 0.3 mm, density: 0.08 cm ³ , compressive strength: 36 kPa) with corona discharge treatment on both sides was used. Other points were the same as in Example 1 to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Examples 20, 21>
As the reinforcing layer, instead of the paper A used in Example 1, in Example 18, paper D (basis weight 6.0 g/m ² , non-woven fabric available from Nippon Paper Papylia Co., Ltd.) containing paper pulp as a constituent fiber, Example 19 Paper E (basis weight: 23.0 g/m ² , non-woven fabric available from Nippon Paper Papylia Co., Ltd.) having paper pulp as a constituent fiber was used in each case. Other points were the same as in Example 1, and double-faced pressure-sensitive adhesive sheets according to Examples 20 and 21 were obtained.

<Example 22>
As a reinforcing layer, instead of the paper A used in Example 1, a polyethylene terephthalate (PET) film with a thickness of 0.012 mm was used. Other points were the same as in Example 1 to obtain a double-sided pressure-sensitive adhesive sheet according to this example.

<Example 23>
The pressure-sensitive adhesive composition UV-A was applied to a thickness of 75 μm on the release-treated surface of the release liner A, and the release liner B was layered on top of this and irradiated with ultraviolet rays for 3 minutes from both sides with a black light lamp having an illuminance of 5 mW/cm ² . As a result, a pressure-sensitive adhesive layer having a thickness of 75 μm and having both sides protected by the release liners A and B was obtained. The double-sided pressure-sensitive adhesive sheet according to this example was obtained by preparing two pressure-sensitive adhesive layers, peeling off the release liner A, and adhering them to the first and second surfaces of the foam sheet A. This double-sided pressure-sensitive adhesive sheet does not have a reinforcing layer attached to the pressure-sensitive adhesive layer on either the first surface side or the second surface side of the foam sheet A.

<Measurement and evaluation>
(Measurement of void area)
The first covering portion prepared in each example was cut in the thickness direction along a cutting line perpendicular to the MD of the reinforcing layer, and steam dyed with a 4% osmium (Os) aqueous solution at 50°C for 5 hours. After that, a sample for observation was cut out with a microtome, fixed on a sample table with a conductive adhesive tape, and subjected to Pt—Pd sputtering for 20 seconds. The cross section of the sample prepared in this manner was observed under the following conditions.
Apparatus: Hitachi High-Technologies Corporation product, field emission scanning electron microscope, model number "S-4800";
Measurement conditions: Secondary electron images were observed at an acceleration voltage of 3 kV (magnification of 300 times).
By analyzing the SEM image obtained in this way with commercially available image analysis software (a product of Asahi Kasei Engineering Co., Ltd., trade name "Azo-kun" was used.), observation was made per 400 μm in length of the cross section of the sample. The area of the void (μm ² /400 μm) was determined. The analysis mode in the above image analysis software was set to "particle analysis". In setting the analysis conditions, while looking at each SEM image, the threshold value for determining whether a void or not was manually set so that the portions that were actually voids would be properly picked up. In addition, parts that are clearly different from the voids that are the purpose of measurement (that is, voids that indicate the degree of impregnation of the nonwoven fabric) (for example, cracks in the adhesive layer that occurred during preparation of the observation sample) should not be included in the void area. made it The void areas were determined for three cross sections at different cutting positions in the machine direction of the nonwoven fabric substrate (that is, n=3), and the average value thereof was taken as the void area of the double-sided pressure-sensitive adhesive sheet.
Based on the value of the obtained void area, the degree of impregnation of the reinforcing layer with the pressure-sensitive adhesive was evaluated in the following four stages.
E: Void area of 100 μm ² /400 μm or less (excellent)
G: Void area exceeding 100 μm ² /400 μm and 200 μm ² /400 μm or less (good)
A: Void area exceeding 200 μm ² /400 μm and 500 μm ² /400 μm or less (practically acceptable)
P: Void area exceeds 500 μm ² /400 μm (poor impregnation)

(Rip and tear resistance)
The double-faced pressure-sensitive adhesive sheet according to each example was subjected to the following tear/tear resistance test.
Specifically, a test piece was prepared by cutting a double-sided pressure-sensitive adhesive sheet into a rectangular shape with a width of 10 mm and a length of 100 mm. The release liner covering the first adhesive surface of the test piece was peeled off, and the exposed first adhesive surface was press-bonded to a glass plate (width 30 mm, length 100 mm or more) by reciprocating a 2 kg roller once. After allowing this to stand at room temperature (about 25°C) for 30 minutes, the release liner on the second surface was peeled off, and a universal tensile/compression tester (TG-1kN, manufactured by Minebea Co., Ltd.) was used to test at a tensile speed of 1000mm/min. The test piece was peeled off from the glass plate at a peeling angle of 90 degrees, and the presence or absence of tearing or tearing at that time was observed. When the double-faced pressure-sensitive adhesive sheet was peeled off from the glass plate without being broken during the peeling, the resistance to tearing was evaluated as "G" (good). When the double-faced pressure-sensitive adhesive sheet was broken during the peeling, the resistance to tearing was evaluated as "P" (poor).

(No adhesive residue)
The release liner covering the second adhesive surface of the double-sided pressure-sensitive adhesive sheet according to each example was peeled off, a PET film having a thickness of 25 μm was adhered, and a test piece was prepared by cutting into a rectangular shape having a width of 25 mm and a length of 100 mm. The release liner covering the first adhesive surface of the test piece was peeled off, and the exposed first adhesive surface was press-bonded to a glass plate (width 30 mm, length 100 mm or more) by reciprocating a 2 kg roller once. After allowing this to stand at room temperature (about 25° C.) for 30 minutes, using a universal tension/compression tester (TG-1 kN, manufactured by Minebea Co., Ltd.), under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees, the above A test piece was peeled off from the glass plate. The image obtained by photographing the peeled glass plate surface with a digital camera (trade name “EXILIM EX-ZS12” manufactured by CASIO) was analyzed, and the percentage of adhesive residue was calculated according to the following formula.
Percentage of adhesive residue (%) = (area where adhesive remains on the glass plate) / (area where the double-sided adhesive sheet is attached to the glass plate) x 100
Based on the obtained values, the non-adhesive residue properties were evaluated according to the following four levels.
E: Percentage of adhesive residue is 0% or more and 1% or less (excellent non-adhesive residue property)
G: Percentage of adhesive residue is more than 1% and 5% or less (good non-adhesive residue property)
A: Percentage of adhesive residue is more than 5% and 15% or less (indicates practically acceptable non-adhesive residue property)
P: Percentage of adhesive residue is more than 15% (poor non-adhesive residue)

The results obtained are shown in Tables 1-3. In the table, "coating viscosity" indicates the viscosity of the pressure-sensitive adhesive composition used to prepare the double-sided pressure-sensitive adhesive sheet, and "tensile strength" of the reinforcing layer indicates MD tensile strength.

As shown in Tables 1 to 3, the test piece of the double-faced PSA sheet of Example 23, in which the covering portion did not have a reinforcing layer, was broken in the tearing test. On the other hand, the double-faced pressure-sensitive adhesive sheets of Examples 1 to 22, in which the covering part had a reinforcing layer, could be peeled off from the glass plate without being broken in the tearing test. Moreover, it was confirmed that the double-sided pressure-sensitive adhesive sheets of Examples 1 to 21 using a reinforcing layer having voids are clearly superior in non-adhesive residue property compared to the double-sided pressure-sensitive adhesive sheet of Example 22 using a PET film as a reinforcing layer. .

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

1 adhesive sheet roll 10 double-sided adhesive sheet 10A first surface (first adhesive surface)
10B second surface (second adhesive surface)
REFERENCE SIGNS LIST 11 first covering part 12 second covering part 15 foam substrate 15A first surface 15B second surface 112 first adhesive layer (adhesive layer)
112A Outer surface 112B Inner surface 114 Reinforcing layer 114A Outer surface 114B Inner surface 122 Second adhesive layer (adhesive layer)
122A Outer surface 122B Inner surface 124 Reinforcing layer 124A Outer surface 124B Inner surface

Claims (8)

A double-sided pressure-sensitive adhesive sheet in which both the first surface and the second surface are adhesive surfaces,
a sheet-like foam base material;
a first covering portion disposed on the first surface side of the foam substrate;
and a second coating portion disposed on the second surface side of the foam base material,
The foam base material is a polyolefin-based foam base material,
The first covering portion includes a pressure-sensitive adhesive layer exposed on the first surface and a reinforcing layer A provided in combination with the pressure-sensitive adhesive layer,
The tensile strength in the longitudinal direction of the reinforcement layer A is 1 N/15 mm or more and 50 N/15 mm or less,
The reinforcing layer A has voids, and the voids are impregnated with an adhesive constituting the adhesive layer exposed on the first surface,
The double-sided pressure-sensitive adhesive sheet, wherein the second covering portion includes a pressure-sensitive adhesive layer exposed on the second surface, and a reinforcing layer B provided in association with the pressure-sensitive adhesive layer. 2. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein said reinforcing layer A is a fibrous sheet. The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the reinforcing layer A has a thickness of 20 µm or more and 150 µm or less. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer exposed on the first surface is composed of a pressure-sensitive adhesive formed from an active energy ray-polymerizable pressure-sensitive adhesive composition. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer exposed on the first surface has a gel content of 70% or more. The outer surface of the reinforcing layer A is covered with an adhesive layer exposed on the first surface, and the adhesive layer exposed on the first surface covers the outer surface with a thickness of 10 μm or more and 200 μm or less. 6. The double-sided pressure-sensitive adhesive sheet according to any one of 1 to 5. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the foam substrate has a thickness of 200 µm or more. The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the foam substrate has a 25% compressive strength of 30 kPa or more.

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