JP6786221B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet.

In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the adhesive is preferably used in the form of an adhesive sheet for fixing parts in portable electronic devices such as mobile phones, smartphones, and tablet personal computers. Patent documents 1 and 2 are examples of prior art documents relating to the adhesive sheet. Both Patent Documents 1 and 2 disclose prior arts including a base material having extensibility. Patent Document 2 relates to a medical adhesive sheet to be attached to the skin.

Japanese Unexamined Patent Publication No. 6-346032. Special Table 2005-500133

The adhesive sheet attached to the adherend can be removed from the adherend after the purpose of use such as fixing is completed. For example, an adhesive sheet used as a means for fixing a component of a portable electronic device can be removed from an adherend when the member is repaired, replaced, inspected, recycled, or the like. Since some of the adherends are easily deformed, it is desirable that the adhesive sheet used for such an application is configured so that the adherend can be removed without being deformed or damaged. Specifically, for example, it is desirable that the pressure-sensitive adhesive sheet can be removed from the surface of the adherend by grasping and pulling a part of the pressure-sensitive adhesive sheet.

Further, from the viewpoint of miniaturization and high integration of portable electronic devices, the adhesive sheet used as a means for fixing the constituent members should have a configuration suitable for heat dissipation of the constituent members (adhesive body). Is meaningful. However, in the pressure-sensitive adhesive sheet intended for tension removal from the adherend, the heat dissipation of the adherend has not yet been sufficiently considered.

The present invention has been created in view of the above circumstances, and an object of the present invention is to provide an adhesive sheet suitable for a usage mode in which heat dissipation of an adherend is assisted and the adherend is pulled out from the adherend.

According to the present invention, an stretchable pressure-sensitive adhesive sheet used in a portable electronic device is provided. This stretchable pressure-sensitive adhesive sheet (hereinafter, may be abbreviated as "sticky sheet") includes a filler-containing pressure-sensitive adhesive layer containing a thermally conductive filler. Since the pressure-sensitive adhesive sheet having such a structure includes the filler-containing pressure-sensitive adhesive layer, it has good thermal conductivity and is advantageous from the viewpoint of heat dissipation of the adherend. Moreover, since it has extensibility, it has good tensile removability. Therefore, it is suitable for fixing members (for example, fixing batteries) and other applications in portable electronic devices.

The pressure-sensitive adhesive sheet according to a preferred embodiment has a thermal resistance value of less than 12 cm ² · K / W. According to the stretchable adhesive sheet exhibiting such thermal characteristics, it is possible to achieve both heat dissipation of the adherend and tensile removability at a higher level.

The pressure-sensitive adhesive sheet according to a preferred embodiment includes a film-like base material that supports the filler-containing pressure-sensitive adhesive layer. According to the structure including the film-like base material as described above, an adhesive sheet having good tensile removal property can be preferably realized.

The pressure-sensitive adhesive sheet disclosed herein preferably has the filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more. According to the adhesive sheet having such a structure, good thermal conductivity and adhesive reliability can be suitably compatible with each other. For example, a pressure-sensitive adhesive sheet having a structure in which pressure-sensitive adhesive layers are provided on both sides of a film-like substrate and at least one (more preferably both) of the pressure-sensitive adhesive layers is a filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more is preferable.

The pressure-sensitive adhesive sheet according to a preferred embodiment has the filler-containing pressure-sensitive adhesive layer having a thickness of 35% or more of the total thickness of the pressure-sensitive adhesive sheet. According to the adhesive sheet having such a structure, good thermal conductivity and adhesive reliability can be suitably compatible with each other. For example, a pressure-sensitive adhesive sheet having filler-containing pressure-sensitive adhesive layers on both sides of a film-like base material and having a total thickness of 35% or more of the total thickness of the filler-containing pressure-sensitive adhesive layers is preferable.

In the pressure-sensitive adhesive sheet disclosed herein, the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is preferably 5% or more and 40% or less. According to the adhesive sheet having such a structure, good thermal conductivity and adhesive reliability can be suitably compatible with each other.

In a preferred embodiment of the technique disclosed herein, the pressure-sensitive adhesive sheet has an elongated portion that is at least stretchable in its longitudinal direction. The adhesive sheet having the above configuration is stretched by pulling in the longitudinal direction when the adhesive sheet is removed. By deforming the pressure-sensitive adhesive sheet due to this stretching, the pressure-sensitive adhesive sheet can be peeled off from the adherend without imposing an excessive load on the adherend. The adhesive sheet disclosed herein is preferably released from being attached to the adherend by pulling from one end of the elongated portion while being attached to the adherend. Furthermore, it may be preferably removed from the adherend. By adopting such a method of releasing the pasted state (typically, a removing method), the adhesive sheet disclosed here can be efficiently removed from the adherend without deforming or damaging the adherend. Can be done.

In the pressure-sensitive adhesive sheet disclosed herein, the average particle size of the thermally conductive filler is preferably greater than 15% and less than 50% of the thickness of the filler-containing pressure-sensitive adhesive layer containing the thermally conductive filler. .. According to such a configuration, the deterioration of the surface smoothness of the pressure-sensitive adhesive layer due to the blending of the heat conductive filler is suppressed, and the pressure-sensitive adhesive sheet and the adherend are in good contact with each other during use to efficiently transfer heat. Can be done. Further, according to the above configuration, when the pressure-sensitive adhesive sheet is deformed by stretching, the heat conductive filler can effectively contribute to a decrease in peeling force. Therefore, an adhesive sheet having good thermal conductivity and excellent tensile removal property can be realized.

The techniques disclosed herein can be preferably performed in embodiments where the total thickness of the pressure-sensitive adhesive sheet is greater than 100 μm. According to such a configuration, in an adhesive sheet having good thermal conductivity, both adhesive reliability and tensile removability can be suitably compatible.

The pressure-sensitive adhesive sheet disclosed herein is preferably used for portable electronic devices. In particular, the pressure-sensitive adhesive sheet disclosed herein has good thermal conductivity, so that it helps heat dissipation of the adherend during use, and is excellent in tensile removability when it is removed from the adherend. Utilizing this feature, it is desirable to efficiently dissipate heat generated during charging, etc., and for applications that fix batteries that are often removed during repair or replacement of parts that make up the product, product inspection, etc. It is particularly preferably used as an adhesive sheet of. According to the techniques disclosed herein, an adhesive sheet preferably used for fixing a battery is provided.

It is sectional drawing which shows one structural example of the adhesive sheet schematically. It is explanatory drawing which shows typically the method of measuring the tensile peeling stress B. 3 (a), 3 (b) and 3 (c) are schematic side views for explaining one aspect of tensile removal. 4 (a), 4 (b) and 4 (c) are schematic top views for explaining one aspect of tensile removal. 5 (a) is a front schematic view of the thermal characteristic evaluation device used for measuring the thermal resistance value in the embodiment, and FIG. 5 (b) is a side schematic view of the device shown in FIG. 5 (a).

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings regarding the implementation of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art. It should be noted that the embodiments described in the drawings are modeled for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the adhesive sheet of the present invention actually provided as a product. ..

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

<Structure of stretchable adhesive sheet>
The stretchable pressure-sensitive adhesive sheet disclosed herein has at least one filler-containing pressure-sensitive adhesive layer containing a thermally conductive filler. The pressure-sensitive adhesive sheet is typically a base-based pressure-sensitive adhesive sheet further comprising a base material that supports a filler-containing pressure-sensitive adhesive layer. As the base material (support), a film-like base material can be preferably adopted. As a preferred form of the pressure-sensitive adhesive sheet disclosed herein, a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer are provided on the first surface and the second side of the film-like base material, respectively, and the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are provided. The form of a double-sided pressure-sensitive adhesive sheet with a base material in which at least one (preferably both) of the pressure-sensitive adhesive layers is a filler-containing pressure-sensitive adhesive layer is exemplified. As another form, a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side of a film-like base material and the pressure-sensitive adhesive sheet being a filler-containing pressure-sensitive adhesive layer, or a base material supporting the filler-containing pressure-sensitive adhesive layer can be used. An example is a form of a double-sided pressure-sensitive adhesive sheet without a base material. The concept of an adhesive sheet here may include what is called an adhesive tape, an adhesive label, an adhesive film, or the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or in the form of a single leaf. Alternatively, it may be an adhesive sheet in a form further processed into various shapes.

The stretchable pressure-sensitive adhesive sheet disclosed herein may have, for example, the cross-sectional structure schematically shown in FIG. In the stretchable pressure-sensitive adhesive sheet 1 shown in FIG. 1, pressure-sensitive adhesive layers 21 and 22 are provided on each surface (both non-peelable) of the film-like base material 10. The pressure-sensitive adhesive sheet 1 before use has a structure in which each surface (each pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layers 21 and 22 is protected by a release liner (not shown). At least one of the pressure-sensitive adhesive layers 21 and 22 is a filler-containing pressure-sensitive adhesive layer, and preferably both of the pressure-sensitive adhesive layers 21 and 22 are filler-containing pressure-sensitive adhesive layers. Alternatively, although not shown, the pressure-sensitive adhesive sheet disclosed herein may be a base-less double-sided pressure-sensitive adhesive sheet consisting of only a pressure-sensitive adhesive layer.

Further, the stretchable pressure-sensitive adhesive sheet disclosed herein preferably has a long portion from the viewpoint of tensile removability. Thereby, in the adhesive sheet attached to the adherend, the adhesive sheet can be preferably removed from the adherend by grasping and pulling one end of the elongated portion in the longitudinal direction. The shape of the elongated portion is typically strip-shaped. From the viewpoint of tensile removability, the elongated portion may have a shape that tapers toward one end in the longitudinal direction. In a more preferred embodiment, the adhesive sheet is formed in an elongated shape as a whole. From the viewpoint of tensile removal workability, it is preferable that a tab (grip portion) is provided at one end of the pressure-sensitive adhesive sheet in the longitudinal direction. The shape of the tab is not particularly limited, but it is preferably a shape that can be gripped by a finger (for example, a rectangular shape).

<Characteristics of stretchable adhesive sheet>
The stretchable pressure-sensitive adhesive sheets disclosed herein typically have a thermal resistance value of approximately 12 cm ² · K / W or less. The pressure-sensitive adhesive sheet having such thermal characteristics has good thermal conductivity and can advantageously contribute to heat dissipation of the adherend to which the pressure-sensitive adhesive sheet is attached. Further, since the adhesive sheet has extensibility, it has good tensile removal property. Therefore, it is useful as an adhesive sheet used in portable electronic devices. For example, it is suitable as an adhesive sheet for fixing a member (battery or the like) of a portable electronic device.

From the viewpoint of enhancing the heat dissipation effect from the adherend, the thermal resistance value (steady heat flow method) of the adhesive sheet is preferably about 11 cm ² · K / W or less, more preferably about 10 cm ² · K / W or less (for example, about 10 cm 2.K / W or less). It can be 9.5 cm ^2. K / W or less). The lower limit of the thermal resistance value of the adhesive sheet is not particularly limited, but from the viewpoint of facilitating compatibility with good tensile removability, it is typically about 3 cm ² · K / W or more, and usually about 4 cm ² ·. K / W or more is appropriate, and preferably about 5 cm ² · K / W or more (for example, about 5.5 cm ² · K / W or more). The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented, for example, in a manner in which the thermal resistance value is approximately 5.5 cm ² · K / W or more and approximately 10 cm ² · K / W or less.

The thermal conductivity of the adhesive sheet is not particularly limited. From the viewpoint of facilitating both good thermal conductivity and suitable tensile removability, it is usually appropriate that the thermal conductivity (steady heat flow method) of the pressure-sensitive adhesive sheet is higher than about 0.12 W / m · K. It is preferably higher than about 0.13 W / m · K, and more preferably about 0.15 W / m · K or more (for example, about 0.17 W / m · K or more). The upper limit of the thermal conductivity of the adhesive sheet is not particularly limited, but from the viewpoint of ease of manufacture and the like, it is usually appropriate to set it to about 0.5 W / m · K or less, and typically about 0.4 W / K / K. It is m · K or less, for example, about 0.3 W / m · K or less.

The thermal resistance value and thermal conductivity of the pressure-sensitive adhesive sheet can be evaluated by, for example, the method described in Examples described later (steady heat flow method).

Although not particularly limited, the pressure-sensitive adhesive sheet disclosed herein preferably has an initial adhesive strength A to polycarbonate (PC) of about 1N / 20 mm or more (for example, 3N / 20 mm or more). As a result, a sufficient adhesive function can be exhibited on the adherend formed from various materials such as PC. Further, when the pressure-sensitive adhesive sheet having the initial adhesive strength A is applied to, for example, a portable electronic device, the fixed arrangement of the adherend member can be maintained even when the portable electronic device is dropped. The upper limit of the initial adhesive strength A is not particularly limited, but it is set to less than about 15 N / 20 mm (for example, less than about 12 N / 20 mm, typically less than about 10 N / 20 mm) in consideration of tensile removal property and adhesive residue prevention property. It is preferable to do so.

The initial adhesive strength A can be measured by the following method. Prepare an adhesive sheet cut to a size of 20 mm in width and 100 mm in length. The adhesive surface of the adhesive sheet (typically a double-sided adhesive sheet) is exposed in an environment of 23 ° C. and 50% RH, and the adhesive surface is pressure-bonded to the surface of the PC plate by reciprocating a 2 kg roller once. To do. After leaving this in the same environment for 30 minutes, using a tensile tester, the peel strength [N / 20 mm width] under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees according to JIS Z 0237: 2000. To measure. When the adhesive sheet is a double-sided adhesive sheet, a polyethylene terephthalate (PET) film having a thickness of 25 μm may be attached to the other adhesive surface, and then the adhesive surface to be measured may be pressure-bonded to a PC plate for measurement. As the tensile tester, a universal tensile compression tester (product name "TG-1kN", manufactured by Minebea) can be used. The same method is adopted for the examples described later.

Although not particularly limited, the pressure-sensitive adhesive sheet disclosed herein preferably has a tensile peeling stress B with respect to a PC of about 25 N / 20 mm or less. When the tensile peeling stress B is equal to or less than a predetermined value, the direction of action in the 0 degree direction (shearing direction) with respect to the adhesive surface (typically, the direction of -90 degrees to +90 degrees with respect to the adhesive surface. Hereinafter, the adhesive sheet can be smoothly removed from various adherends by simply pulling the adhesive sheet in the "tensile peeling direction"). The tensile peel stress B is preferably about 20 N / 20 mm or less, more preferably about 18 N / 20 mm or less, for example, about 15 N / 20 mm or less. The lower limit of the tensile peeling stress B is not particularly limited, but it is usually appropriate to set it to about 2N / 20 mm or more (for example, 5N / 20 mm or more) from the relationship with the initial adhesive force A.

The tensile peeling stress B can be measured by the following method. A measurement sample is prepared by cutting the adhesive sheet into a size of 20 mm in width and 120 mm in length. In an environment of 23 ° C. and 50% RH, each adhesive surface of the above measurement sample (typically a double-sided adhesive sheet) is overlapped on the surface of two PC plates (30 mm × 100 mm × 2 mm thickness) to obtain 2 kg. The roller is reciprocated once and crimped. 70 mm (that is, 20 mm × 70 mm) from one end of the measurement sample in the longitudinal direction is crimped to each PC plate. After leaving this in the same environment for 30 minutes, two PC plates were fixed to each other using a tensile tester, and the peel strength [N / 20 mm width] was obtained under the conditions of a tensile speed of 300 mm / min and a peeling angle of 0 degrees. ] Is measured. Specifically, as shown in FIG. 2, the adhesive surfaces 100A and 100B of the adhesive sheet measurement sample 100 are bonded to and crimped to two PC plates 111 and 112, respectively. This is pulled in the direction of the arrow in FIG. 2 (that is, the tensile peeling direction) at the above speed, and the peeling strength [N / 20 mm width] is measured. In the case of a single-sided adhesive sheet (single-sided adhesive sheet), the peel strength [N / 20 mm width] may be measured in the same manner as above except that one adhesive surface is fixed to one PC plate. As the tensile tester, a universal tensile compression tester (product name "TG-1kN", manufactured by Minebea) can be used. The same method is adopted for the examples described later.

In a preferred embodiment, the ratio (B / A) of the tensile peeling stress B [N / 20 mm] to the initial adhesive force A [N / 20 mm] is 3.0 or less. When the ratio (B / A) is small, it means that the tensile peeling stress B is reduced in a relative relationship with the initial adhesive force A in the configuration having the initial adhesive force A equal to or higher than a predetermined value. .. As a result, it is possible to preferably achieve both a sufficient adhesive function at the time of use and excellent tensile removability at the time of removal. The above ratio (B / A) is preferably about 2.8 or less (for example, about 2.6 or less, typically about 2.4 or less). Ideally, the lower the ratio (B / A), the better, and it may be, for example, about 1.0 or less. On the other hand, from a practical point of view, the above ratio (B / A) may be, for example, about 0.5 or more, or about 1.2 or more (typically about 1.5 or more). ..

In a preferred embodiment, the pressure-sensitive adhesive sheet exhibits a breaking strength of approximately 8 MPa or more. As a result, in a configuration exhibiting an adhesive strength equal to or higher than a predetermined value, damage such as tearing is unlikely to occur when the adhesive sheet is removed. It also tends to be excellent in workability. The breaking strength is more preferably about 10 MPa or more, and even more preferably about 15 MPa or more (for example, about 20 MPa or more). Although not particularly limited, the breaking strength is usually preferably about 100 MPa or less (for example, 80 MPa or less, typically 70 MPa or less), and 60 MPa or less (for example, from the viewpoint of elasticity and extensibility of the pressure-sensitive adhesive sheet). For example, it may be about 50 MPa or less, typically 40 MPa or less).

The breaking strength is measured according to the method for measuring "tensile strength" described in JIS K 7311: 1995. More specifically, the breaking strength can be measured under the condition of a tensile speed of 300 mm / min using a No. 3 dumbbell-shaped test piece (width 5 mm). As the tensile tester, the product name "Autograph AG-10G type tensile tester" manufactured by Shimadzu Corporation can be used. In the test, it is preferable to apply powder to the adhesive surface to remove the influence of the sticky adhesive. The tensile direction in the above test is not particularly limited, but when the adhesive sheet has a long shape, it is preferable to match the tensile direction with the longitudinal direction thereof. The breaking strength can be adjusted, for example, by selecting a base material.

The pressure-sensitive adhesive sheet disclosed herein preferably has extensibility. As a result, the adhesive sheet can be stretched and deformed and peeled off when the tension is removed. In this specification, "having extensibility" is defined as having an elongation at break of 20% or more. The elongation at break of the pressure-sensitive adhesive sheet can be about 50% or more (for example, 100% or more, typically 200% or more). In a preferred embodiment, the pressure-sensitive adhesive sheet exhibits an elongation at break of approximately 300% or more. As a result, the tension and the elongation deformation of the pressure-sensitive adhesive sheet interact with each other, and better tensile removal property is realized. The pressure-sensitive adhesive sheet exhibiting the above characteristics is also preferable in that it prevents deformation of the adherend during removal. The elongation at break is more preferably about 400% or more (for example, 450% or more, typically 500% or more). The upper limit of the elongation at break is not particularly limited, but may be, for example, about 1000% or less (typically 900% or less) from the viewpoint of removal workability and the like.

The elongation at break is measured according to the "elongation" measuring method described in JIS K 7311: 1995. More specifically, the elongation at break can be measured under the condition of a tensile speed of 300 mm / min using a No. 3 dumbbell-shaped test piece (width 5 mm, marked line spacing 20 mm). The tensile tester and others are basically the same as in the case of the above-mentioned breaking strength. The tensile direction in the above test is not particularly limited, but when the adhesive sheet has a long shape, it is preferable to match the tensile direction with the longitudinal direction thereof. The elongation at break can be adjusted, for example, by selecting a base material.

The pressure-sensitive adhesive sheet disclosed herein preferably exhibits 100% modulus of less than 10 MPa. By setting the 100% modulus of the pressure-sensitive adhesive sheet to less than a predetermined value, when the pressure-sensitive adhesive sheet is pulled and stretched and deformed to be removed from the adherend, the resistance at the start of pulling is reduced and the tensile removability tends to be excellent. The 100% modulus is more preferably less than 5 MPa. The lower limit of the 100% modulus is not particularly limited, but from the viewpoint of sticking workability of the pressure-sensitive adhesive sheet, it is usually appropriate to set it to 0.5 MPa or more (for example, 1 MPa or more). 100% modulus is measured according to the method of measuring "tensile stress" described in JIS K 7311: 1995. More specifically, the stress [MPa] when the No. 3 dumbbell-shaped test piece (width 5 mm, marked line spacing 20 mm) is pulled under the condition of a tensile speed of 300 mm / min and the marked line distance is extended by 100%. ] Is 100% modulus. As the tensile tester, the product name "Autograph AG-10G type tensile tester" manufactured by Shimadzu Corporation can be used. The 100% modulus of the pressure-sensitive adhesive sheet can be adjusted, for example, by selecting the base material type (selecting the blending ratio of the hard component and the soft component, etc.), the molding method, and the like.

In a preferred embodiment, the pressure-sensitive adhesive sheet is suitable to exhibit a tensile recovery rate of more than about 50%. It is more preferable that the tensile recovery rate is about 70% or more. The tensile recovery rate is more preferably about 80% or more (for example, 90% or more, typically 93% or more and 100% or less). Thereby, damage such as tearing at the time of removing the adhesive sheet can be prevented more highly. This point will be described. For example, when the adhesive sheet is pulled in the shearing direction to remove it, it usually takes a certain amount of time depending on the adhesive area and the like. Therefore, the removal work may be interrupted in the middle. In such a case, if the tensile recovery rate of the pressure-sensitive adhesive sheet is not more than a predetermined value, the removal work may be restarted from a state in which the mechanical properties (strength, elasticity, etc.) are lowered due to the tension before the work is interrupted. At that time, the adhesive sheet cannot withstand the tension at the time of resuming the removal work, and is liable to be damaged such as torn. Even when the pressure-sensitive adhesive sheet showing the tensile recovery rate is removed in such a manner that it is interrupted once as described above, the recovery after tension suppresses the deterioration of mechanical properties, so that the damage is more severe. Can be prevented.

The tensile recovery rate is measured by the following method.
[Measurement of tensile recovery rate]
For the adhesive sheet, a tensile test is performed in which the specific section distance L ₀ of the adhesive sheet is stretched by 100%. When the length of the specific section is L ₁ after 5 minutes have passed since the adhesive sheet was stretched 100% and released, the formula: tensile recovery rate (%) = L ₀ / L ₁ × 100; Obtain the tensile recovery rate.
More specifically, in accordance with JIS K 7311: 1995, a No. 3 dumbbell-shaped test piece (width 5 mm, marked line spacing 20 mm) is used to stretch 100% under the condition of a tensile speed of 300 mm / min. In other words, pull until the marked line spacing extends by 20 mm. Then, the length L ₁ (marked line interval: mm) after 5 minutes have passed after being released from tension is measured, and the tensile recovery rate is obtained from the formula: tensile recovery rate (%) = L ₀ / L ₁ × 100; .. In this method, L ₀ is the initial marked line spacing of 20 mm. The tensile tester and others are basically the same as in the case of elongation at break described above. The tensile direction in the above test is not particularly limited, but it is preferable to match the tensile direction with the longitudinal direction of the pressure-sensitive adhesive sheet or its long portion. The tensile recovery rate can be adjusted, for example, by selecting a base material.

<Adhesive layer>
(Base polymer)
The pressure-sensitive adhesive layer disclosed herein (in the case of a double-sided pressure-sensitive adhesive sheet with a base material, includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer; the same applies hereinafter) is an acrylic polymer known in the field of pressure-sensitive adhesives. , Rubber-based polymer, polyester-based polymer, urethane-based polymer, polyether-based polymer, silicone-based polymer, polyamide-based polymer, fluorine-based polymer, and other various rubber-like polymers are included as a base polymer. obtain. As will be described in detail later, the pressure-sensitive adhesive layer disclosed herein is preferably an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, a rubber-based pressure-sensitive adhesive layer containing a rubber-based polymer as a base polymer, and a urethane-based polymer. Is a urethane-based pressure-sensitive adhesive layer containing the above as a base polymer. Alternatively, the pressure-sensitive adhesive layer may be a combination of an acrylic polymer and a rubber-based polymer as the base polymer.

(Acrylic polymer)
In a preferred embodiment, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer from the viewpoints of adhesive properties (typically, adhesive strength), molecular design, stability over time, and the like. In addition, in this specification, a "base polymer" of a pressure-sensitive adhesive means a main component (typically, a component contained in excess of 50% by weight) of a polymer component contained in the pressure-sensitive adhesive.

As the acrylic polymer, for example, a polymer of a monomer raw material containing an alkyl (meth) acrylate as a main monomer and further containing a submonomer having copolymerizability with the main monomer is preferable. Here, the main monomer means a component that accounts for more than 50% by weight of all the monomer components in the monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as “C _1-20 ”). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, alkyl (meth) acrylate in which R ² is a chain alkyl group of C _1-14 (for example, C _2-10 , typically C _4-8 ) is preferable, and R Alkyl acrylates in which ¹ is a hydrogen atom and R ² is a chain alkyl group of C _4-8 are more preferable.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (Meta) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Octyl (meth) acrylate, Isooctyl (meth) acrylate, Nonyl (meth) acrylate, Isononyl (meth) acrylate, Decyl (meth) acrylate, Isodecyl (meth) acrylate, Undecyl (meth) acrylate, Lauryl (meth) acrylate, Tridecyl Examples thereof include (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecil (meth) acrylate, and ecocil (meth) acrylate. .. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). BA is more preferable from the viewpoint of adhesive properties and prevention of adhesive residue.

The blending ratio of the main monomer in all the monomer components is preferably about 70% by weight or more (for example, 85% by weight or more, typically 90% by weight or more). The upper limit of the blending ratio of the main monomer is not particularly limited, but is preferably about 99.5% by weight or less (for example, 99% by weight or less). When C _4-8 alkyl acrylate is used as the monomer component, the proportion of C _4-8 alkyl acrylate in the alkyl (meth) acrylate contained in the monomer component is preferably 70% by weight or more. It is more preferably 90% by weight or more, and further preferably about 95% by weight or more (typically 99% by weight or more and 100% by weight or less). The technique disclosed herein can be preferably carried out in an embodiment in which approximately 50% by weight or more (for example, approximately 60% by weight or more) of all monomer components is BA. In a preferred embodiment, the total monomer component may further contain 2EHA in a smaller proportion than BA.

A sub-monomer having copolymerizability with the main monomer, alkyl (meth) acrylate, can be useful for introducing cross-linking points into the acrylic polymer and enhancing the cohesive force of the acrylic polymer. Examples of the sub-monomer include a carboxy group-containing monomer, a hydroxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a keto group-containing monomer, a monomer having a nitrogen atom-containing ring, and an alkoxysilyl group-containing monomer. One or more functional group-containing monomers such as an imide group-containing monomer and an epoxy group-containing monomer can be used. For example, from the viewpoint of improving the cohesive force, an acrylic polymer in which a carboxy group-containing monomer and / or a hydroxyl group-containing monomer is copolymerized as the submonomer is preferable. Preferable examples of the carboxy group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA). Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth). Examples thereof include hydroxyalkyl (meth) acrylates such as acrylates and unsaturated alcohols. Of these, hydroxyalkyl (meth) acrylate is preferable, and 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are more preferable.

The amount of the submonomer may be appropriately selected so as to achieve a desired cohesive force, and is not particularly limited. Usually, from the viewpoint of achieving both adhesive force and cohesive force in a well-balanced manner, it is appropriate that the amount of submonomers is about 0.5% by weight or more in the total monomer components of the acrylic polymer, preferably 1. Weight% or more. The amount of the submonomer is appropriately about 30% by weight or less, preferably about 10% by weight or less (for example, about 5% by weight or less) in the total monomer components. When the carboxy group-containing monomer is copolymerized with the acrylic polymer, the content of the carboxy group-containing monomer is determined from the viewpoint of achieving both adhesive strength and cohesive strength in all the monomer components used for the synthesis of the acrylic polymer. It is preferably about 0.1% by weight or more (for example, about 0.2% by weight or more, typically about 0.5% by weight or more), and about 10% by weight or less (for example, about 8% by weight or less, Typically, it is preferably about 5% by weight or less). When the hydroxyl group-containing monomer is copolymerized with the acrylic polymer, the content of the hydroxyl group-containing monomer is approximately 0 in all the monomer components used for the synthesis of the acrylic polymer from the viewpoint of achieving both adhesive strength and cohesive force. It is preferably .001% by weight or more (for example, about 0.01% by weight or more, typically about 0.02% by weight or more), and about 10% by weight or less (for example, about 2% by weight or less). Is preferable.

The acrylic polymer disclosed herein may be copolymerized with a monomer (other monomer) other than the above as long as the effect of the present invention is not significantly impaired. The other monomers can be used, for example, for the purpose of adjusting the glass transition temperature of the acrylic polymer, adjusting the adhesive performance (for example, peelability), and the like. For example, examples of the monomer capable of improving the cohesive force of the pressure-sensitive adhesive include a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, vinyl esters, and an aromatic vinyl compound. As the above-mentioned other monomers, one kind may be used alone, or two or more kinds may be used in combination. Among them, vinyl esters are mentioned as a preferable example. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Of these, VAc is preferable. The content of the other monomers is preferably about 30% by weight or less (for example, about 10% by weight or less), and for example, about 0.01% by weight or more, based on all the monomer components used for the synthesis of the acrylic polymer. (Typically, it can be about 0.1% by weight or more).

From the viewpoint of impact resistance and the like, the copolymer composition of the acrylic polymer has a glass transition temperature (Tg) of the polymer of about -15 ° C or lower (typically -25 ° C or lower, for example, -40 ° C or lower). It is appropriate that it is designed to be. The Tg of the acrylic polymer is usually about −70 ° C. or higher, for example, about −60 ° C. or higher. The Tg of the acrylic polymer is typically about −70 ° C. or higher and about −15 ° C. or lower, preferably about −60 ° C. or higher and about −25 ° C. or lower, for example, about −60 ° C. or higher and about −40 ° C. It is as follows.

The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of the monomers used in the synthesis of the polymer). Here, the Tg of the acrylic polymer is Fox based on the Tg of the homopolymer of each monomer constituting the polymer and the weight fraction (copolymerization ratio based on the weight) of the monomer. The value obtained from the formula of. As shown below, the Fox formula is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer. As the Tg of the homopolymer, the value described in the publicly known material shall be adopted.

In the technique disclosed herein, the following values are specifically used as the Tg of the homopolymer.
2-Ethylhexyl acrylate-70 ° C
Butyl acrylate -55 ° C
Vinyl acetate 32 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C
2-Hydroxyethyl acrylate -15 ° C
4-Hydroxybutyl acrylate-40 ° C
For Tg of homopolymers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. If it is not described in the Polymer Handbook, the value obtained by the measurement method described in JP-A-2007-51271 shall be used.

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthetic methods for the acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a massive polymerization method, and a suspension polymerization method, are appropriately adopted. be able to. For example, a solution polymerization method can be preferably used. As a monomer supply method for solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided feeding (dropping) method, or the like in which all the monomer raw materials are supplied at once can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of the monomer and solvent used, the type of the polymerization initiator, and the like, and can be, for example, about 20 ° C. or higher (typically 40 ° C. or higher). The temperature can be about 170 ° C. or lower (typically 140 ° C. or lower). Alternatively, photopolymerization performed by irradiating light such as UV (typically performed in the presence of a photopolymerization initiator), radiation polymerization performed by irradiating radiation such as β-rays and γ-rays, etc. Active energy ray irradiation polymerization may be adopted.

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons), acetate esters such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane are preferably used.

The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds. ; Etc. can be mentioned. Yet another example of the polymerization initiator is a redox-based initiator in which a peroxide and a reducing agent are combined. Such a polymerization initiator can be used alone or in combination of two or more. The amount of the polymerization initiator used may be a normal amount, for example, 0.005 part by weight or more and 1 part by weight or less (typically 0.01 part by weight or more 1) with respect to 100 parts by weight of all the monomer components. It can be selected from a range of about (part by weight or less).

The weight average molecular weight of the base polymer (preferably an acrylic polymer) disclosed herein (Mw) of, is not, it may be in the range, for example 10 × 10 ⁴ or more 500 × 10 ⁴ or less particularly limited. From the viewpoint of balancing the cohesive force and the adhesive force at a high level, the Mw of the base polymer (preferably an acrylic polymer) is preferably 10 × 10 ⁴ or more, more preferably 20 × 10 ⁴ or more, and further preferably 35. × 10 ⁴ or more, preferably 150 × 10 ⁴ or less, more preferably 110 × 10 ⁴ or less, still more preferably 90 × 10 ⁴ or less (typically 75 × 10 ⁴ or less, for example 65 × 10 ^4). Below). In one embodiment, the Mw of the base polymer is preferably 10 × 10 ⁴ or more and 150 × 10 ⁴ or less, more preferably 20 × 10 ⁴ or more and 110 × 10 ⁴ or less (for example, 20 × 10 ⁴ or more and 75 × 10 ⁴ or less). More preferably, it can be 35 × 10 ⁴ or more and 90 × 10 ⁴ or less (for example, 35 × 10 ⁴ or more and 65 × 10 ⁴ or less). Here, Mw refers to a standard polystyrene-equivalent value obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, the model name "HLC-8320GPC" (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) may be used. The same applies to the examples described later.

(Rubber polymer)
In another preferred embodiment, the pressure-sensitive adhesive layer is made of a rubber-based pressure-sensitive adhesive. The rubber-based pressure-sensitive adhesive according to a more preferred embodiment contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer. The monovinyl-substituted aromatic compound refers to a compound in which one functional group having a vinyl group is bonded to an aromatic ring. A typical example of the aromatic ring is a benzene ring (which may be a benzene ring substituted with a functional group having no vinyl group (for example, an alkyl group)). Specific examples of the monovinyl-substituted aromatic compound include styrene, α-methylstyrene, vinyltoluene, vinylxylene and the like. Specific examples of the conjugated diene compound include 1,3-butadiene, isoprene and the like. Such block copolymers can be used alone or in combination of two or more as a base polymer.

In the A segment (hard segment) of the block copolymer, the copolymerization ratio of the monovinyl-substituted aromatic compound (two or more thereof can be used in combination) is 70% by weight or more (more preferably 90% by weight or more). It may be substantially 100% by weight.). In the B segment (soft segment) of the block copolymer, the copolymerization ratio of the conjugated diene compound (two or more thereof can be used in combination) is 70% by weight or more (more preferably 90% by weight or more), which is substantially the same. It may be 100% by weight.). According to such a block copolymer, a higher performance pressure-sensitive adhesive sheet can be realized.

The block copolymer may be in the form of a diblock body, a triblock body, a radial body, a mixture thereof, or the like. In the triblock body and the radial body, it is preferable that the A segment (for example, styrene block) is arranged at the end of the polymer chain. This is because the A segments arranged at the ends of the polymer chains are likely to gather to form a domain, thereby forming a pseudo crosslinked structure and improving the cohesiveness of the pressure-sensitive adhesive. The block copolymer in the technique disclosed herein has, for example, a diblock body ratio of 30% by weight or more (more preferably 40% by weight) from the viewpoint of adhesive strength (peeling strength) and repulsion resistance to the adherend. As described above, more preferably 50% by weight or more, particularly preferably 60% by weight or more, typically 65% by weight or more, for example 70% by weight or more) can be preferably used. Further, from the viewpoint of resistance to continuously applied stress, those having a diblock body ratio of 90% by weight or less (more preferably 85% by weight or less, for example, 80% by weight or less) can be preferably used. For example, it is preferable to use a block copolymer having a diblock ratio of 60% by weight or more and 85% by weight or less.

(Styrene block copolymer)
In a preferred embodiment of the technique disclosed herein, the base polymer is a styrene-based block copolymer. For example, it can be preferably carried out in an embodiment in which the base polymer contains at least one of a styrene isoprene block copolymer and a styrene butadiene block copolymer. Of the styrene-based block copolymers contained in the pressure-sensitive adhesive, the proportion of styrene-isoprene block copolymer is 70% by weight or more, the proportion of styrene-butadiene block copolymer is 70% by weight or more, or styrene. The total ratio of the isoprene block copolymer and the styrene-butadiene block copolymer is preferably 70% by weight or more. In a preferred embodiment, substantially all of the styrene-based block copolymers (for example, 95% by weight or more and 100% by weight or less) are styrene isoprene block copolymers. In another preferred embodiment, substantially all of the styrene-based block copolymers (eg, 95% by weight or more and 100% by weight or less) are styrene-butadiene block copolymers. According to such a composition, an adhesive sheet having excellent repulsion resistance and a good balance with other adhesive properties can be preferably realized.

The styrene-based block copolymer may be in the form of a diblock body, a triblock body, a radial body, a mixture thereof, or the like. In the triblock body and the radial body, it is preferable that the styrene block is arranged at the end of the polymer chain. This is because the styrene blocks arranged at the ends of the polymer chains are likely to gather to form a styrene domain, thereby forming a pseudo-crosslinked structure and improving the cohesiveness of the pressure-sensitive adhesive. As the styrene-based block copolymer used in the technique disclosed herein, for example, the diblock ratio is 30% by weight or more (more preferably) from the viewpoint of adhesive strength (peeling strength) to the adherend and repulsion resistance. 40% by weight or more, more preferably 50% by weight or more, particularly preferably 60% by weight or more, typically 65% by weight or more) can be preferably used. A styrene-based block copolymer having a diblock ratio of 70% by weight or more (for example, 75% by weight or more) may be used. Further, from the viewpoint of holding power and the like, a styrene-based block copolymer having a diblock compound ratio of 90% by weight or less (more preferably 85% by weight or less, for example, 80% by weight or less) can be preferably used. For example, a styrene-based block copolymer having a diblock ratio of 60% by weight or more and 85% by weight or less can be preferably adopted.

The styrene content of the styrene-based block copolymer can be, for example, 5% by weight or more and 40% by weight or less. From the viewpoint of repulsion resistance and holding power, a styrene-based block copolymer having a styrene content of 10% by weight or more (more preferably larger than 10% by weight, for example, 12% by weight or more) is usually preferable. Further, from the viewpoint of adhesive strength to the adherend, the copolymer weight of the styrene-based block having a styrene content of 35% by weight or less (typically 30% by weight or less, more preferably 25% by weight or less, for example, less than 20% by weight). Coalescence is preferred. For example, a styrene-based block copolymer having a styrene content of 12% by weight or more and less than 20% by weight can be preferably adopted.

(Urethane polymer)
In still another preferred embodiment, the pressure-sensitive adhesive layer is made of a urethane-based pressure-sensitive adhesive. Here, the urethane-based pressure-sensitive adhesive (layer) refers to a pressure-sensitive adhesive (layer) containing a urethane-based polymer as a base polymer. The urethane-based pressure-sensitive adhesive is typically made of a urethane-based resin containing a urethane-based polymer obtained by reacting a polyol with a polyisocyanate compound as a base polymer. The urethane-based polymer is not particularly limited, and an appropriate urethane-based polymer (ether-based polyurethane, ester-based polyurethane, carbonate-based polyurethane, etc.) that can function as an adhesive can be adopted. Examples of the polyol include polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol and the like. Examples of the polyisocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate and the like.

(Thermal conductive filler)
The pressure-sensitive adhesive sheet disclosed herein is characterized by having a filler-containing pressure-sensitive adhesive layer containing a thermally conductive filler. By having such a filler-containing pressure-sensitive adhesive layer, good thermal conductivity (typically, a thermal resistance value of 12 cm ² · K / W or less) is suitably realized in the stretchable pressure-sensitive adhesive sheet. obtain.

The heat conductive filler (hereinafter, may be abbreviated as "filler") is not particularly limited, and a material that can improve the heat conductivity of the pressure-sensitive adhesive sheet by being contained in the pressure-sensitive adhesive layer can be used. it can. For example, particulate or fibrous fillers can be used.
The constituent materials of the filler (typically particulate filler) are metals such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, stainless steel; aluminum oxide, silicon oxide (silicon dioxide), titanium oxide. , Metal oxides such as zirconium oxide, zinc oxide, tin oxide, copper oxide, nickel oxide; aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, water Metal hydroxides and hydrated metal compounds such as barium oxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dowsonite, borosand, zinc borate; silicon carbide, boron carbide, carbonized Carbide such as nitrogen and calcium hydroxide; Nitride such as aluminum hydroxide, silicon nitride, boron nitride and gallium nitride; Carbonate such as calcium carbonate; Titanate such as barium titanate and potassium titanate; Carbon black, carbon tube ( It can be a carbon-based substance such as carbon nanotube), carbon fiber, diamond; an inorganic material such as glass; and the like. Alternatively, natural raw material particles such as volcanic shirasu, clay, and sand may be used. As the fibrous filler, various synthetic fiber materials and natural fiber materials can be used. These can be used alone or in combination of two or more. Usually, even if the content in the pressure-sensitive adhesive layer is relatively large, the smoothness of the pressure-sensitive adhesive surface is not easily impaired, and it can efficiently contribute to the improvement of tensile removability. Therefore, a particulate filler can be preferably adopted. Of these, it is preferable to use a particulate filler composed of an inorganic material (for example, a metal hydroxide such as aluminum hydroxide or a hydrated metal compound).

The average particle size of the filler is preferably less than 50% of the thickness of the pressure-sensitive adhesive layer containing the filler. In this specification, the average particle size of the filler means the particle size (50% median diameter) at which the cumulative particle size based on the weight is 50% in the particle size distribution obtained by the measurement based on the sieving method. .. If the average particle size of the filler contained in the pressure-sensitive adhesive layer is less than 50% of the pressure-sensitive adhesive layer, 50% by weight or more of the filler contained in the pressure-sensitive adhesive layer has a particle size smaller than the thickness of the pressure-sensitive adhesive layer. It can be said that. Since 50% by weight or more of the filler contained in the pressure-sensitive adhesive layer has a particle size smaller than the thickness of the pressure-sensitive adhesive layer, a good surface condition (for example, smoothness) is maintained on the surface (adhesive surface) of the pressure-sensitive adhesive layer. The tendency to be done increases. This is preferable from the viewpoint of improving the thermal conductivity and the adhesiveness (for example, the initial adhesive force A) by improving the adhesion to the adherend. In addition, the appearance of the surface of the pressure-sensitive adhesive layer can be well maintained.

The average particle size of the filler is preferably larger than 15% of the thickness of the pressure-sensitive adhesive layer containing the filler. According to the pressure-sensitive adhesive layer (filler-containing pressure-sensitive adhesive layer) containing a filler having such an average particle size, the tensile removability of the stretchable pressure-sensitive adhesive sheet tends to be effectively improved. From the viewpoint of obtaining a higher effect, the average particle size of the filler can be 20% or more of the thickness of the pressure-sensitive adhesive layer containing the filler, 25% or more, and further 30% or more. (For example, 35% or more) may be used.

This point will be described. The filler contained in the pressure-sensitive adhesive layer may exist in a state of being exposed on the pressure-sensitive adhesive surface or in a state of being encapsulated in the pressure-sensitive adhesive layer. The filler exposed on the adhesive surface reduces the area of the adhesive on the adhesive surface and improves the slipperiness of the adhesive interface in the shear direction. As a result, the tensile peeling stress B is reduced, but the decrease in the pressure-sensitive adhesive area on the adhesive surface also brings about a decrease in the initial adhesive force A. On the other hand, the filler existing inside the pressure-sensitive adhesive layer is considered to greatly contribute to the reduction of the tensile peeling stress B without lowering the initial pressure-sensitive adhesive force A. The main reason for this is not particularly limited, but a change in the state of the pressure-sensitive adhesive layer due to deformation of the pressure-sensitive adhesive sheet can be considered. Specifically, since the tensile peeling is a mode in which the adhesive is peeled off in a direction parallel to the adhesive surface (tension peeling direction, also referred to as a shearing direction), the adhesive sheet is deformed in that direction during the tensile peeling. .. The extensible pressure-sensitive adhesive sheet stretches with respect to the above tension, and the pressure-sensitive adhesive layer is deformed accordingly. For example, when the film-like base material that supports the pressure-sensitive adhesive layer has stretchability with respect to tension, the pressure-sensitive adhesive layer is also significantly deformed as the base material is stretched. It is considered that the deformation of the pressure-sensitive adhesive layer increases the amount of exposure of the filler contained in the pressure-sensitive adhesive layer to the pressure-sensitive adhesive surface and improves the slipperiness in the shearing direction at the bonding interface. It is also considered that the pressure-sensitive adhesive (adhesive component) is deformed by tensile peeling in the pressure-sensitive adhesive layer, whereas the filler behaves differently from the pressure-sensitive adhesive in the pressure-sensitive adhesive layer. It is also considered that the difference in the behavior of the adhesive and the filler with respect to the tensile peeling contributes to the reduction of the tensile peeling stress. It is considered that the above-mentioned changes in the surface state of the pressure-sensitive adhesive layer and the behavior of the components of the pressure-sensitive adhesive layer do not become apparent or can be ignored by, for example, 90-degree peeling or 180-degree peeling due to the difference in the peeling mode. Be done. However, it is typically considered that the stress change is greatly affected during tensile peeling. As a result, it is considered that the filler contained in the pressure-sensitive adhesive layer greatly contributes to both the maintenance of the initial pressure-sensitive adhesive force A and the reduction of the tensile peeling stress B. The effect of containing the filler is particularly remarkable in the adhesive sheet having extensibility. Further, in an stretchable pressure-sensitive adhesive sheet having a base material, the mechanical properties of the base material can typically contribute significantly to the adhesive strength (typically 180-degree peel strength), so that the pressure-sensitive adhesive composition (for example, pressure-imparting) is applied. It is considered that the contribution of the agent, the additive component such as the cross-linking agent, etc.) to the adhesive strength is relatively small. In such a pressure-sensitive adhesive sheet, by incorporating a filler in the pressure-sensitive adhesive layer, an action of selectively reducing only the tensile peeling stress B while maintaining the initial pressure-sensitive adhesive force A is preferably realized.

In a preferred embodiment, 60% by weight or more (for example, 70% by weight or more, typically 80% by weight or more) of the filler contained in the pressure-sensitive adhesive layer has a particle size smaller than the thickness of the pressure-sensitive adhesive layer. It is more preferable that substantially the entire amount (typically 99% by weight or more and 100% by weight or less) of the filler contained in the pressure-sensitive adhesive layer has a particle size smaller than the thickness of the pressure-sensitive adhesive layer. In another preferred embodiment, 40% by weight or more (for example, 50% by weight or more, typically 55% by weight or more) of the filler contained in the pressure-sensitive adhesive layer is used from the viewpoint of improving the surface condition of the pressure-sensitive adhesive surface. , The particle size is smaller than 2/3 (that is, 2/3 T, more preferably 1/2, that is, 1 / 2T) of the thickness T of the pressure-sensitive adhesive layer. In addition, when X% by weight or more of the filler has a particle size smaller than Y, the cumulative particle size (weight standard) up to the particle size Y (μm) in the particle size distribution obtained by the measurement based on the sieving method is X (weight basis). %) Less than. The proportion (% by weight) of the filler having a predetermined particle size can be determined based on the particle size distribution.

In a preferred embodiment, the filler contained in the pressure-sensitive adhesive layer is composed of particles having a particle size of less than 30 μm in an amount of 50% by weight or more (for example, 70% by weight or more). In the pressure-sensitive adhesive layer containing such a filler, the smoothness of the pressure-sensitive adhesive surface is not easily impaired even if the content of the filler is relatively large. Therefore, it is suitable for improving thermal conductivity. Further, as the filler contained in the pressure-sensitive adhesive layer, particles having a particle size of 20 μm or more account for 10% by weight or more (preferably 25% by weight or more, for example 40% by weight or more, typically 70% by weight or less). May be good. As a result, the action of lowering the tensile peeling stress B can be efficiently exhibited.

In a preferred embodiment, the proportion of particles having a particle size of less than 1 μm in the filler contained in the pressure-sensitive adhesive layer is 50% by weight or less. From the viewpoint of reducing tensile peel stress, it is desirable that the particle size of the filler has a certain size. Further, it is preferable that the amount of fine particles is limited from the viewpoint of productivity, for example, an excessive increase in viscosity does not occur in the preparation of the pressure-sensitive adhesive composition. Of the fillers contained in the pressure-sensitive adhesive layer, the proportion of particles having a particle size of less than 1 μm (for example, less than 2 μm, typically less than 5 μm) is 30% by weight or less (for example, 10% by weight or less, typically 3). Weight% or less) is more preferable.

The average particle size of the filler contained in the pressure-sensitive adhesive layer is usually 1 μm or more, preferably 3 μm or more (typically 5 μm or more, for example, 10 μm or more). As the average particle size increases, the effect of reducing tensile peel stress tends to improve. It is also preferable to make the average particle size more than a predetermined value from the viewpoint of maintaining good viscosity and dispersibility of the composition. The upper limit of the average particle size is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, for example 25 μm or less. A filler having a small average particle size does not easily impair the smoothness of the adhesive surface even if the content in the adhesive layer is relatively large. Therefore, it is suitable for reducing the thermal resistance of the stretchable adhesive sheet.

The shape of the filler is not particularly limited, and may be, for example, bulk shape, needle shape, plate shape (for example, hexagonal plate shape), layered shape, fibrous shape, or the like. The concept of bulk shape includes, for example, spherical shape, rectangular parallelepiped shape, crushed shape or a variant shape thereof. The shape of the filler is preferably a bulk shape, and more preferably a spherical shape.

The average aspect ratio of the filler is not particularly limited. From the viewpoint of reducing tensile peel stress, less than about 100 is suitable, preferably less than 50, more preferably less than 10 (for example, less than 5, typically less than 2). Here, the average aspect ratio of the filler is obtained as an average value of the aspect ratio represented by the ratio of the major axis to the minor axis (major axis / minor axis) of each particle constituting the filler. The major axis typically refers to the maximum transfer length of the particles to be measured, and the minor axis typically refers to the minimum transfer length of the particles to be measured. The average aspect ratio can be grasped through transmission electron microscope observation.

The content of the filler (for example, inorganic material particles, typically metal oxide or metal hydroxide) in the pressure-sensitive adhesive layer is not particularly limited, and the pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer has appropriate thermal conductivity (for example, for example). It can be set so that a thermal resistance value (less than or equal to a predetermined value) is realized. The content of the filler can be, for example, 10% by weight or more of the entire pressure-sensitive adhesive layer on a weight basis. From the viewpoint of achieving both thermal conductivity and good tensile removability, it is usually appropriate that the content of the filler is 15% by weight or more of the entire pressure-sensitive adhesive layer, and preferably 18% by weight or more. , 20% by weight or more is more preferable. The content of the filler in the pressure-sensitive adhesive layer is preferably set so that appropriate pressure-sensitive adhesive properties can be obtained in the pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer. From this point of view, it is usually appropriate that the content of the filler is 60% by weight or less of the pressure-sensitive adhesive layer, and 50% by weight or less (more preferably 40% by weight or less, still more preferably 35% by weight or less, for example. 32% by weight or less) is preferable.

Further, from the viewpoint of improving thermal conductivity, the content of the filler in the pressure-sensitive adhesive layer is preferably 20 parts by weight or more, preferably 25 parts by weight or more, based on 100 parts by weight of the base polymer. , More preferably 30 parts by weight or more, further preferably 40 parts by weight or more, and for example, 45 parts by weight or more. By appropriately adjusting the particle size and content of the filler, it is possible to preferably improve the thermal conductivity while maintaining the smoothness of the adhesive surface. The content of the filler in the pressure-sensitive adhesive layer is usually 200 parts by weight or less with respect to 100 parts by weight of the base polymer, and may be 150 parts by weight or less, for example, 100 parts by weight or less.
The pressure-sensitive adhesive layer (pressure-sensitive adhesive composition) in the technique disclosed herein may substantially not contain a component (dispersant) that improves the dispersibility of the filler, or may contain the above-mentioned dispersant. ..

It is appropriate that the filler content C (volume-based content) in the pressure-sensitive adhesive layer is 50% by volume or less. By appropriately adjusting the particle size and the content of the filler, the tensile peeling stress B can be preferably reduced while suppressing the decrease in the initial adhesive force A. The filler content C in the pressure-sensitive adhesive layer can be 45% by volume or less, preferably 40% by volume or less, and more preferably 30% by volume or less (for example, 25% by volume or less). From the viewpoint of reducing tensile peel stress, the content C is preferably 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and 12% by volume. It may be the above, and further, it may be 15% by volume or more. The filler content C [volume%] is determined based on the weight ratio and density of components other than the filler (typically, the pressure-sensitive component) in the pressure-sensitive adhesive layer and the weight ratio and density of the filler. For example, in the examples described later, 2.42 g / cm ³ is adopted as the density of aluminum hydroxide, and the filler content C [volume%] in the pressure-sensitive adhesive layer can be determined.

(Acrylic oligomer)
The pressure-sensitive adhesive composition disclosed herein may contain an acrylic oligomer. By adopting an acrylic oligomer, impact resistance and repulsion resistance can be improved in a well-balanced manner. Further, in the case where the pressure-sensitive adhesive composition is cured by active energy ray irradiation (for example, UV irradiation), the acrylic oligomer is more curing-inhibited (for example, not yet) than the tack-imparting resin such as rosin-based or terpene-based. It has the advantage that it does not easily cause polymerization inhibition of the reaction monomer. The acrylic oligomer is a polymer containing an acrylic monomer as a constituent monomer component thereof, and is defined as a polymer having a smaller Mw than the acrylic polymer.

The ratio of the acrylic monomer to all the monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, and more preferably 70% by weight or more (for example, 80% by weight). More than 90% by weight or more). In a preferred embodiment, the acrylic oligomer has a monomer composition consisting substantially only of the acrylic monomer.

As the constituent monomer component of the acrylic oligomer, a chain alkyl (meth) acrylate exemplified as a monomer that can be used for the acrylic polymer, a functional group-containing monomer, and other monomers can be used. Further, the constituent monomer may contain an alicyclic hydrocarbon group-containing (meth) acrylate. As the monomer component constituting the acrylic oligomer, one or more of the various monomers exemplified above can be used.

As the chain alkyl (meth) acrylate, an alkyl (meth) acrylate in which R ² is C _1-12 (for example, C _1-8 ) in the above formula (1) is preferably used. Preferable examples thereof include methyl methacrylate (MMA), ethyl acrylate, n-butyl acrylate (BA), isobutyl methacrylate, t-butyl acrylate, and 2-ethylhexyl acrylate (2EHA). Of these, MMA is more preferable.

A preferred example of the functional group-containing monomer is a monomer having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholin; N, N-dimethylamino. Examples thereof include amino group-containing monomers such as ethyl (meth) acrylate; amide group-containing monomers such as N, N-diethyl (meth) acrylamide; carboxy group-containing monomers such as AA and MAA; and hydroxyl group-containing monomers such as HEA.

The alicyclic hydrocarbon group-containing (meth) acrylate is, for example, one of the alicyclic hydrocarbon group-containing (meth) acrylates in which the number of carbon atoms of the alicyclic hydrocarbon group is in the range of 4 or more and 20 or less. Species or two or more species can be used. The alicyclic hydrocarbon group preferably has 5 or more carbon atoms (for example, 6 or more, typically 8 or more), and preferably 16 or less (for example, 12 or less, typically 10 or less). is there. Preferable examples of the alicyclic hydrocarbon group-containing (meth) acrylate include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Of these, dicyclopentanyl methacrylate (DCPMA) is more preferred.

The ratio of the alicyclic hydrocarbon group-containing (meth) acrylate to all the monomer components constituting the acrylic oligomer (that is, the copolymerization ratio) is about 30% by weight or more (for example, from the viewpoint of adhesiveness and cohesiveness). It is preferably 50% by weight or more, typically 55% by weight or more, and 90% by weight or less (for example, 80% by weight or less, typically 70% by weight or less).

In a preferred embodiment, the acrylic oligomer comprises a chain alkyl (meth) acrylate and / or an alicyclic hydrocarbon group-containing (meth) acrylate as its constituent monomer components. In this embodiment, the ratio of the chain alkyl group-containing and alicyclic hydrocarbon group-containing (meth) acrylic acid ester to all the monomer components constituting the acrylic oligomer is approximately 80% by weight or more (for example, 90% by weight). More than 100% by weight or less, typically 95% by weight or more and 100% by weight or less). It is more preferable that the monomer component constituting the acrylic oligomer is substantially composed of a chain alkyl (meth) acrylate and / or an alicyclic hydrocarbon group-containing (meth) acrylate.

When the acrylic oligomer is a copolymer of a monomer mixture containing a chain alkyl (meth) acrylate and an alicyclic hydrocarbon group-containing (meth) acrylate, the chain alkyl (meth) acrylate and the alicyclic hydrocarbon The ratio with the group-containing (meth) acrylate is not particularly limited. In one preferred embodiment, the weight ratio of the weight percentage of the chain alkyl (meth) weight ratio of acrylate (W _A) and the alicyclic hydrocarbon group-containing (meth) acrylate in the constituent monomer components of the acrylic oligomer (W _{B) (W} a: _{W B)} is usually 1: 9 or more, preferably 2: 8 or more, for example 3: 7 or more, and typically 3: 7 is greater, and usually 9: 1 or less, preferably 7 : 3 or less, for example 6: 4 or less, typically 5: 5 or less. The weight ratio _(W A: _{W B)} is usually 1: 9 to 9: 1, preferably 2: 8 or more 7: 3 or less (e.g., 3: 7 or 6: 4 or less, typically 3: 7 or more and 5: 5 or less).

Although not particularly limited, the composition of the constituent monomer components of the acrylic oligomer (that is, the polymerization composition) can be set so that the Tg of the acrylic oligomer is 10 ° C. or higher and 300 ° C. or lower. Here, the Tg of the acrylic oligomer means a value obtained in the same manner as the Tg based on the constituent monomer composition of the acrylic polymer based on the composition of the constituent monomer components of the acrylic oligomer. The Tg of the acrylic oligomer is preferably 180 ° C. or lower (for example, 160 ° C. or lower) from the viewpoint of initial adhesiveness. Further, the Tg is preferably 60 ° C. or higher (for example, 100 ° C. or higher, typically 120 ° C. or higher) from the viewpoint of cohesiveness of the pressure-sensitive adhesive.

Mw of the acrylic oligomer is not particularly limited, is typically on the order 0.1 × 10 ⁴ or more 3 × 10 ⁴ or less. From the viewpoint of improving the adhesive properties (e.g., adhesive strength and repulsion resistance), Mw of the acrylic oligomer is preferably 1.5 × 10 ⁴ or less, more preferably 1 × 10 ⁴ or less, 0.8 × 10 ⁴ or less (e.g. 0.6 × 10 ⁴ or less) are more preferred. From the viewpoint of cohesiveness, etc. of the adhesive, the Mw is, 0.2 × 10 ⁴ or more (e.g., 0.3 × 10 ⁴ or more) are preferred. The molecular weight of the acrylic oligomer can be adjusted by using a chain transfer agent or the like, if necessary, during polymerization.

Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be adopted in an appropriate manner. Since the types and amounts of polymerization initiators (for example, azo-based polymerization initiators such as AIBN) that can be used as needed are generally as described above, the description will not be repeated here.

It is appropriate that the content of the acrylic oligomer in the pressure-sensitive adhesive composition disclosed herein is, for example, 0.5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of better exerting the effect of the acrylic oligomer, the content of the acrylic oligomer is preferably 1 part by weight or more (for example, 1.5 parts by weight or more, typically 2 parts by weight or more). .. Further, from the viewpoint of curability of the pressure-sensitive adhesive composition, compatibility with the acrylic polymer, and the like, it is appropriate that the content of the acrylic oligomer is less than 50 parts by weight (for example, less than 10 parts by weight). It is preferably less than 8 parts by weight (for example, less than 7 parts by weight, typically 5 parts by weight or less). Even with such a small amount of addition, improvement in impact resistance and repulsion resistance by using an acrylic oligomer can be realized.

(Adhesive imparting agent)
The pressure-sensitive adhesive layer disclosed herein may have a composition containing a pressure-sensitive adhesive. The tackifier is not particularly limited, and for example, a rosin-based tackifier resin, a terpene-based tackifier resin, a hydrocarbon-based tackifier resin, an epoxy-based tackifier resin, a polyamide-based tackifier resin, and an elastomer-based tackifier resin, Various tackifier resins such as phenol-based tackifier resins and ketone-based tackifier resins can be used. As such a tackifier resin, one type can be used alone or two or more types can be used in combination.

Specific examples of the rosin-based tackifier resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc. The same shall apply hereinafter); Other various rosin derivatives; etc. Examples of the above-mentioned rosin derivatives include rosins obtained by esterifying unmodified rosin with alcohols (that is, esterified rosin) and esterifying modified rosin with alcohols (that is, esterified rosin). Esters; Unmodified rosins and unsaturated fatty acid-modified rosins obtained by modifying modified rosins with unsaturated fatty acids; Unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; Unmodified rosins, modified rosins, unsaturated Rosin alcohols obtained by reducing the carboxy group in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosins, modified rosins, and various rosin derivatives; rosins. Examples thereof include a rosin phenol resin obtained by adding phenol to (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and thermally polymerizing the mixture. When an acrylic polymer is used as the base polymer, it is preferable to use a rosin-based tackifier resin. From the viewpoint of improving adhesive properties such as adhesive strength, one of the above rosin-based tackifying resins may be selected alone, or two or three or more having different types and characteristics (for example, softening points) may be used in combination. It is more preferable to do so.

Examples of terpene-based tackifier resins are terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer; these terpene resins are modified (phenolic modification, aromatic modification, hydrogenation modification, hydrocarbons). Modified terpene resin (modified, etc.); etc. Examples of the modified terpene resin include terpene-modified phenolic resin, styrene-modified terpene resin, aromatic-modified terpene resin, hydrogenated terpene resin and the like. When an acrylic polymer is used as the base polymer, it is preferable to use a terpene-based tackifier resin (for example, a terpene-modified phenolic resin). In particular, from the viewpoint of improving adhesive properties such as adhesive strength, one or more of the above terpene-based tackifying resins (for example, terpene-modified phenolic resins) having different types and characteristics (for example, softening points) are used in combination. Is preferable.

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

In the technique disclosed herein, as the tackifier resin, a resin having a softening point (softening temperature) of about 70 ° C. or higher (preferably about 100 ° C. or higher, more preferably about 110 ° C. or higher) can be preferably used. According to the pressure-sensitive adhesive containing the pressure-sensitive adhesive resin having a softening point equal to or higher than the above-mentioned lower limit value, a pressure-sensitive adhesive sheet having more excellent adhesive strength can be realized. Among the tackifier resins exemplified above, terpene-based tackifier resins having the above softening points (for example, terpene-modified phenolic resin), rosin-based tackifier resins (for example, esterified products of polymerized rosin) and the like can be preferably used. The upper limit of the softening point of the tackifier resin is not particularly limited, and can be, for example, about 200 ° C. or lower (typically about 180 ° C. or lower). The softening point of the tackifier resin referred to here is defined as a value measured by the softening point test method (ring ball method) specified in any of JIS K 5902 and JIS K 2207.

The amount of the tackifier used is not particularly limited, and can be appropriately set according to the desired adhesive performance (adhesive strength, etc.). For example, based on the solid content, about 10 parts by weight or more (more preferably 20 parts by weight or more, still more preferably 30 parts by weight or more) and 100 parts by weight or less (more preferably) of the tackifier with respect to 100 parts by weight of the acrylic polymer. It is preferably used in a proportion of 80 parts by weight or less, more preferably 60 parts by weight or less). The amount of the tackifier to be used with respect to 100 parts by weight of the acrylic polymer is, for example, about 10 parts by weight or more and 100 parts by weight or less (more preferably 20 parts by weight or more and 80 parts by weight or less, still more preferably 30 parts by weight or more and 60 parts by weight or less. ) Can be. The technique disclosed herein may be carried out in a manner including a pressure-sensitive adhesive layer substantially free of the pressure-sensitive adhesive.

When the pressure-sensitive adhesive layer is composed of a rubber-based pressure-sensitive adhesive, the rubber-based pressure-sensitive adhesive preferably contains a high-softening point resin having a softening point of 120 ° C. or higher as the tackifying resin. The pressure-sensitive adhesive sheet of this aspect is preferable from the viewpoint of repulsion resistance, holding power and the like. In a preferred embodiment, the high softening point resin may include a tackifier resin having a softening point of 125 ° C. or higher (more preferably 130 ° C. or higher, still more preferably 135 ° C. or higher, for example 140 ° C. or higher). From the viewpoint of adhesive strength to the adherend, the softening point of the high softening point resin is usually 200 ° C. or lower, preferably 180 ° C. or lower, more preferably 170 ° C. or lower (for example, 160 ° C. or lower). ).

As the high softening point resin, a terpene phenol resin, a polymerized rosin, an esterified product of a polymerized rosin, or the like can be preferably adopted. As these high softening point resins, one type can be used alone, or two or more types can be used in combination as appropriate. As a preferred embodiment, there is an embodiment in which the high softening point resin contains one kind or two or more kinds of terpene phenol resins. The softening point of the terpene phenol resin is not particularly limited, but usually, those having a softening point of 120 ° C. or higher (for example, 125 ° C. or higher) and 200 ° C. or lower (typically 180 ° C. or lower, for example 170 ° C. or lower) are used. Is appropriate. For example, a terpene phenol resin having a softening point of 120 ° C. or higher and 200 ° C. or lower (typically 120 ° C. or higher and 180 ° C. or lower, for example, 125 ° C. or higher and 170 ° C. or lower) can be preferably adopted.

The terpene phenol resin has a softening point of 120 ° C. or higher and a hydroxyl value (OH value) of 40 mgKOH / g or more (typically 40 mgKOH / g or more and 200 mgKOH / g or less, for example, 40 mgKOH / g or more and 160 mgKOH / g). The following) can be preferably adopted. According to the terpene phenol resin having such a hydroxyl value, a higher performance pressure-sensitive adhesive sheet can be realized. As the value of the hydroxyl value in this specification, a value measured by the potentiometric titration method specified in JIS K 0070: 1992 can be adopted. As a specific measurement method, the method described in JP-A-2014-55235 is adopted.

The techniques disclosed herein include, for example, that the rubber-based pressure-sensitive adhesive has a high softening point resin (H1) having a hydroxyl value of 40 mgKOH / g or more and less than 80 mgKOH / g, and a hydroxyl value of 80 mgKOH / g or more (typically 80 mgKOH / g). It can be preferably carried out in a embodiment containing a high softening point resin (H2) of g or more and 160 mgKOH / g or less, for example, 80 mgKOH / g or more and 140 mgKOH / g or less) in combination. In this case, the relationship between the amount of the high softening point resin (H1) and the high softening point resin (H2) used is usually such that the weight ratio (H1: H2) is 1: 5 or more, typically 1: 3. As mentioned above, it is appropriate to set it to be, for example, 1: 2 or more, and 5: 1 or less, typically 3: 1 or less, for example, 2: 1 or less. For example, the weight ratio (H1: H2) can be set to be in the range of 1: 5 or more and 5: 1 or less, and is usually 1: 3 or more and 3: 1 or less (for example, 1: 2 or more and 2: 1 or less). It is appropriate to set it so that it is in the range of). As a preferred embodiment, there is an embodiment in which both the high softening point resin (H1) and the high softening point resin (H2) are terpene phenolic resins.

From the viewpoint of repulsion resistance, holding power, etc., the content of the high softening point resin can be, for example, 20 parts by weight or more, and 30 parts by weight or more (for example, 35 parts by weight or more) with respect to 100 parts by weight of the base polymer. ) Is preferable. From the viewpoint of adhesive strength, low temperature characteristics, etc., the content of the high softening point resin with respect to 100 parts by weight of the base polymer is usually preferably 100 parts by weight or less, preferably 80 parts by weight or less, more preferably. Is 70 parts by weight or less. The content of the high softening point resin may be 60 parts by weight or less (for example, 50 parts by weight or less).

The technique disclosed herein is an embodiment in which the rubber-based pressure-sensitive adhesive contains a low softening point resin having a softening point of less than 120 ° C. in place of the high softening point resin or in addition to the high softening point resin. Can be carried out. As a preferred embodiment, the rubber-based pressure-sensitive adhesive contains a high softening point resin having a softening point of 120 ° C. or higher and a low softening point resin having a softening point of less than 120 ° C.

As the low softening point resin, those having a softening point of, for example, 40 ° C. or higher (typically 60 ° C. or higher) can be used. From the viewpoint of repulsion resistance, holding power and the like, those having a softening point of 80 ° C. or higher (more preferably 100 ° C. or higher) and lower than 120 ° C. can be preferably adopted. A low softening point resin having a softening point of 110 ° C. or higher and lower than 120 ° C. may be used.

The technique disclosed herein can be preferably carried out in a manner in which the rubber-based pressure-sensitive adhesive contains at least one of a petroleum resin and a terpene resin (typically an unmodified terpene resin) as the low softening point resin. For example, the main component of the low softening point resin (that is, the component accounting for more than 50% by weight of the low softening point resin) is a composition of petroleum resin, a composition of terpene resin, or a combination of petroleum resin and terpene resin. A certain composition, etc. can be preferably adopted. From the viewpoint of adhesive strength and compatibility, it is preferable that the main component of the low softening point resin is a terpene resin (for example, β-pinene polymer). Substantially all of the low softening point resin (for example, 95% by weight or more) may be a terpene resin.

In a preferred embodiment, the low softening point resin may be a tackifier resin having a hydroxyl value of 0 or more and less than 80 mgKOH / g (low hydroxyl value tackifier resin). As the low hydroxyl value tackifier resin, among the various tackifier resins described above, those having a hydroxyl value in the above range can be used alone or in combination as appropriate. For example, a terpene phenol resin having a hydroxyl value of 0 or more and less than 80 mgKOH / g, a petroleum resin (for example, C5-based petroleum resin), a terpene resin (for example, β-pinene polymer), a rosin-based resin (for example, polymerized rosin), and rosin. A derivative resin (for example, an esterified product of polymerized rosin) or the like can be used.

From the viewpoint of adhesive strength to the adherend, the content of the low softening point resin can be, for example, 10 parts by weight or more, and usually 15 parts by weight or more (for example, 20 parts by weight) with respect to 100 parts by weight of the base polymer. (Above) is appropriate. From the viewpoint of repulsion resistance and the like, it is usually appropriate that the content of the low softening point resin is 120 parts by weight or less, preferably 90 parts by weight or less, and more preferably 70 parts by weight or less (for example, 60 parts by weight). (By weight or less). The content of the low softening point resin may be 50 parts by weight or less (for example, 40 parts by weight or less).

When the tackifier resin contains a low softening point resin and a high softening point resin, the relationship between the amounts used thereof is such that the weight ratio of the low softening point resin: the high softening point resin is 1: 5 or more and 3: 1 or less (more than that). It is preferable to set it to be 1: 5 or more and 2: 1 or less). The technique disclosed herein is an embodiment in which the rubber-based pressure-sensitive adhesive contains a larger amount of a high softening point resin as a tackifier resin than a low softening point resin (for example, a weight ratio of a low softening point resin: a high softening point resin is 1). : 1.2 or more and 1: 5 or less) can be preferably carried out. According to such an aspect, a higher performance adhesive sheet can be realized.

In the technique disclosed herein, the content of the tackifier resin with respect to 100 parts by weight of the base polymer (typically a rubber-based polymer) is usually 20 parts by weight or more, preferably 30 parts by weight. As mentioned above, it is more preferably 40 parts by weight or more (for example, 50 parts by weight or more). Further, from the viewpoint of low temperature characteristics (for example, adhesive strength and impact resistance under low temperature conditions), it is usually appropriate that the content of the tackifier resin with respect to 100 parts by weight of the base polymer is 200 parts by weight or less. It is preferably 150 parts by weight or less. The content of the tackifier resin with respect to 100 parts by weight of the base polymer may be 100 parts by weight or less (for example, 80 parts by weight or less).

(Crosslinking agent)
The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer disclosed herein may contain a cross-linking agent, if necessary. The type of the cross-linking agent is not particularly limited, and a conventionally known cross-linking agent can be appropriately selected and used. Examples of such a cross-linking agent include 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, metal chelate-based cross-linking agents, and the like. Be done. The cross-linking agent may be used alone or in combination of two or more. Among them, from the viewpoint of improving the cohesive force, it is preferable to use an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent, and an isocyanate-based cross-linking agent is more preferable.

The amount of the cross-linking agent used is not particularly limited, and is, for example, about 10 parts by weight or less (for example, about 0.005 parts by weight or more, preferably about 0.01 parts by weight) with respect to 100 parts by weight of the base polymer (for example, acrylic polymer). As described above, it can be typically selected from the range of 5 parts by weight or less). Since the technique disclosed herein can achieve the desired tensile peeling stress B without reducing the amount of the cross-linking agent used, the amount of the cross-linking agent used is approximately 0 with respect to 100 parts by weight of the acrylic polymer. .1 parts by weight or more (for example, 0.8 parts by weight or more, typically 1.2 parts by weight or more) may be used. Further, from the viewpoint of limiting the cohesive force and reducing the tensile peeling stress B, the amount of the cross-linking agent used is about 5 parts by weight or less (for example, 3 parts by weight or less, typically 3 parts by weight or less) with respect to 100 parts by weight of the acrylic polymer. May be 2 parts by weight or less).

(Other ingredients)
The pressure-sensitive adhesive composition may be a leveling agent, a cross-linking aid, a plasticizer, a softening agent, a coloring agent (dye, pigment), an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, and light, if necessary. It may contain various additives that are common in the field of pressure-sensitive adhesive compositions, such as stabilizers and dispersants. Further, for example, an adhesive force adjusting agent such as a silicone-based oligomer may be added to the pressure-sensitive adhesive composition (typically an acrylic pressure-sensitive adhesive composition). As for such various additives, conventionally known ones can be used by a conventional method and do not particularly characterize the present invention, and thus detailed description thereof will be omitted.
Further, the pressure-sensitive adhesive composition may contain solid particles other than the thermally conductive filler for the purpose of improving the tensile removability and the like. Examples of such solid particles include polystyrene, acrylic resin (for example, polymethylmethacrylate), phenol resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide (for example, nylon), polyimide, and the like. Polymer particles such as polyvinylidene chloride can be used. The particle size and particle size distribution of the solid particles can be, for example, substantially the same as those of the heat conductive filler described above. It is appropriate that the amount of solid particles other than the heat conductive filler used is 1/2 or less (typically 1/100 or more and 1/2 or less) of the amount of the heat conductive filler used on a weight basis. It is preferably 1/4 or less (typically 1/100 or more and 1/4 or less). The technique disclosed herein can be preferably carried out in a configuration that does not substantially contain solid particles other than the thermally conductive filler.

(Adhesive composition)
The pressure-sensitive adhesive layer disclosed herein may be a pressure-sensitive adhesive layer formed from a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt type pressure-sensitive adhesive composition, and an active energy ray-curable pressure-sensitive adhesive composition. .. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in which a pressure-sensitive adhesive (sticking agent layer-forming component) is contained in a solvent containing water as a main component (water-based solvent), and is typically water-dispersed. A type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like are included. Further, the solvent-type pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of containing a pressure-sensitive adhesive in an organic solvent. The technique disclosed herein is preferably carried out in a mode in which a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition is provided from the viewpoint of preferably realizing adhesive properties such as adhesive strength.

(Method of forming the adhesive layer)
The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition to a peelable surface (peeling surface) and drying it can be adopted. Alternatively, a method (direct method) of forming the pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the film-like substrate and drying it can be adopted. Further, a method (transfer) in which a pressure-sensitive adhesive composition is applied to a peelable surface (peeling surface) and dried to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to a film-like substrate (transfer). Law) may be adopted. As the peeling surface, the surface of the peeling liner, the back surface of the peeling-treated base material, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may have a regular or random pattern such as a dot shape or a striped shape. It may be a formed pressure-sensitive adhesive layer.

The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, a curtain coating method, or the like. Further, the drying of the pressure-sensitive adhesive composition is preferably carried out under heating from the viewpoint of promoting the cross-linking reaction and improving the production efficiency. The drying temperature can be, for example, about 40 ° C. or higher (preferably about 60 ° C. or higher) and about 150 ° C. or lower (preferably about 130 ° C. or lower). After the pressure-sensitive adhesive composition is dried, even if aging is performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, proceeding with the cross-linking reaction, alleviating the strain that may exist in the base material or the pressure-sensitive adhesive layer, etc. Good.

(Thickness of adhesive layer)
The thickness of the pressure-sensitive adhesive layer disclosed herein is not particularly limited, and can be appropriately selected depending on the intended purpose. Usually, the thickness of the pressure-sensitive adhesive layer is preferably about 5 μm or more (more preferably about 12 μm or more, still more preferably about 18 μm or more) from the viewpoint of productivity such as drying efficiency and adhesive performance. , The thickness may be more than about 25 μm. The thickness of the pressure-sensitive adhesive layer is usually about 200 μm or less (preferably about 150 μm or less, more preferably about 100 μm or less), and may be about 90 μm or less. In the case of a double-sided pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first surface and the second surface of the film-like substrate, the thickness of the pressure-sensitive adhesive layers may be the same. It may be different.

The pressure-sensitive adhesive sheet disclosed herein can be preferably carried out in a mode containing at least one filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more. Examples of such an embodiment include a single-sided pressure-sensitive adhesive sheet with a base material having a filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more on one surface of the base material, and a filler containing a filler having a thickness of 30 μm or more on at least one surface of the base material. Double-sided pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer (The pressure-sensitive adhesive layer on the other surface of the base material may be a filler-containing pressure-sensitive adhesive layer having a thickness of less than 30 μm, and may be of any thickness without filler. A pressure-sensitive adhesive layer may be used), and a base-less double-sided pressure-sensitive adhesive sheet having a filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more is included. As described above, according to the configuration including at least one filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more (more preferably 35 μm or more, typically 40 μm or more, for example 42 μm or more), thermal conductivity is good and tensile removal is performed. A pressure-sensitive adhesive sheet having good properties can be preferably realized. Of these, a pressure-sensitive adhesive sheet having a filler-containing pressure-sensitive adhesive layer having the above thickness on both sides of the film-like base material is preferable.

The total thickness of the filler-containing pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive sheet (in the case of a pressure-sensitive adhesive sheet containing only one filler-containing pressure-sensitive adhesive layer, the thickness of the filler-containing pressure-sensitive adhesive layer) can be, for example, more than 25 μm. Usually, 30 μm or more is suitable, preferably more than 50 μm, more preferably 60 μm or more, and 70 μm or more (for example, 80 μm or more) may be used. Further, from the viewpoint of tensile removability and the like, the upper limit of the total thickness of the filler-containing pressure-sensitive adhesive layer is usually preferably 400 μm or less, preferably 300 μm or less, and more preferably 250 μm or less (for example, 200 μm or less).

<Film-like base material>
The film-like base material disclosed herein preferably exhibits a breaking strength of 8 MPa or more. By using the film-like base material exhibiting the above-mentioned breaking strength, the pressure-sensitive adhesive sheet is less likely to be torn and can exhibit excellent tensile removability. According to the film-like substrate exhibiting the breaking strength, the workability tends to be improved. The breaking strength is typically 10 MPa or more, more preferably 15 MPa or more (for example, 20 MPa or more). From the viewpoint of elasticity and extensibility of the film-like base material, the breaking strength is preferably about 100 MPa or less (for example, 90 MPa or less, typically 80 MPa or less). The breaking strength is measured by the same method as in the case of the adhesive sheet. The breaking strength of the base material can be adjusted, for example, by selecting the base material type (selecting the blending ratio of the hard component and the soft component, etc.), the molding method, and the like.

The film-like substrate disclosed herein preferably has extensibility. By using an extensible base material, an extensible pressure-sensitive adhesive sheet is preferably realized. By using an extensible base material, the shape of the film can be deformed with a relatively low stress due to its flexibility. The elongation at break of the film-like substrate can be 50% or more (for example, 100% or more, typically 200% or more). In a preferred embodiment, the film-like substrate exhibits 300% or more elongation at break. The base material exhibiting elongation at break stretches with respect to tension when the pressure-sensitive adhesive sheet is removed. Due to this elongation, the adhesive sheet is deformed and peeled off from the adherend. In this way, the tension and the deformation of the base material interact with each other to further improve the tensile removability of the pressure-sensitive adhesive sheet. The elongation at break is more preferably 400% or more (for example, 450% or more, typically 500% or more). The upper limit of the elongation at break is not particularly limited, but may be, for example, about 1000% or less (typically 900% or less) from the viewpoint of removal workability and the like. The elongation at break is measured by the same method as in the case of the adhesive sheet. The elongation at break of the base material can be adjusted by, for example, the selection of the base material type (selection of the blending ratio of the hard component and the soft component, etc.), the molding method, and the like.

It is appropriate that the film-like substrate disclosed here exhibits a tensile recovery rate of more than 50%, and the tensile recovery rate is preferably 70% or more. The tensile recovery rate is more preferably 80% or more (for example, 90% or more, typically 93% or more and 100% or less). Thereby, damage such as tearing at the time of removing the adhesive sheet can be prevented more highly. The tensile recovery rate is measured by the same method as the method for measuring the tensile recovery rate of the pressure-sensitive adhesive sheet. The tensile recovery rate of the base material can be adjusted, for example, by selecting the base material type (selection of the blending ratio of the hard component and the soft component, etc.), the molding method, and the like.

The film-like substrate disclosed herein preferably exhibits 100% modulus of less than 10 MPa. By setting the 100% modulus of the film-like base material to less than a predetermined value, when the pressure-sensitive adhesive sheet is pulled and stretched and deformed to be removed from the adherend, the resistance at the start of pulling is reduced and the tensile removability tends to be excellent. is there. The 100% modulus is more preferably less than 5 MPa. The lower limit of the 100% modulus is not particularly limited, but from the viewpoint of sticking workability of the pressure-sensitive adhesive sheet, it is usually appropriate to set it to 0.5 MPa or more (for example, 1 MPa or more). The 100% modulus is measured by the same method as for the adhesive sheet. The 100% modulus of the base material can be adjusted, for example, by selecting the base material type (selection of the blending ratio of the hard component and the soft component, etc.), the molding method, and the like.

As the film-like base material (supporting base material) for supporting (lining) the pressure-sensitive adhesive layer, various film-like base materials can be used. As the base material, for example, a woven fabric film, a non-woven fabric film, or a resin film can be used. Of these, a resin film is preferable. The resin film may be a non-foaming resin film, a rubber-like film, a foam film, or the like. Of these, non-foaming resin films and rubber-like films are preferable, and non-foaming resin films are more preferable. The non-foamed resin film has substantially no bubbles (voids) that can be a weak point in terms of mechanical strength, and tends to be superior in mechanical strength such as tensile strength as compared with a foam. The non-foamed resin film is also excellent in terms of workability, dimensional stability, thickness accuracy, economy (cost), and the like. Therefore, by using a non-foamed resin film as a base material, excellent tensile removability can be preferably realized.
The "resin film" in the present specification is a substantially non-porous film, and is a concept that is distinguished from so-called non-woven fabrics and woven fabrics (that is, a concept excluding non-woven fabrics and woven fabrics). Further, the non-foamed resin film refers to a resin film that has not been intentionally treated to form a foam. Specifically, the non-foaming resin film can be a resin film having a foaming ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times). The non-foamed resin film includes, for example, a soft resin film called soft polyolefin, soft polyurethane, soft polyester, soft polyvinyl chloride and the like.

Preferable examples of the resin material constituting the resin film disclosed herein include polyurethanes such as ether-based polyurethanes, ester-based polyurethanes, and carbonate-based polyurethanes; urethane (meth) acrylate-based polymers; polyethylene (PE) and polypropylene (PP). , Polyesters such as ethylene-propylene copolymers and ethylene-butene copolymers; polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate and polybutylene naphthalate; polycarbonates; and the like. As the polyester, polybutylene terephthalate (PBT), polyethylene naphthalate, and polybutylene naphthalate are more preferable. The resin material is a styrene-based copolymer such as a styrene butadiene copolymer, a styrene isoprene copolymer, a styrene ethylene butylene copolymer, a styrene ethylene propylene copolymer, a styrene butadiene styrene copolymer, and a styrene isoprene styrene copolymer. It may be a coalescence (typically a styrene-based elastomer), an acrylic-based copolymer called acrylic rubber, or a vinyl chloride-based resin (PVC) such as soft polyvinyl chloride. Good. The above resin materials may be used alone or in combination of two or more. The resin material includes what is generally called rubber or thermoplastic elastomer.

In a preferred embodiment, the film-like substrate is a polyurethane-based resin film. Here, the polyurethane-based resin film refers to a resin film containing polyurethane as the main component of the resin component (the component having the highest blending ratio, typically a component contained in excess of 50% by weight; the same applies hereinafter). .. A polyurethane-based resin film is typically composed of a material that does not substantially exhibit a yield point, and is a film material that easily realizes an adhesive sheet that exhibits a predetermined breaking strength and elongation, and if necessary, a tensile recovery rate. Is. The polyurethane-based resin film can also realize good physical properties without adding an additive component such as a plasticizer, and thus is also a preferable group in the technique disclosed herein in terms of preventing bleeding out of the additive component. Can be a material.

The proportion of polyurethane in the resin component contained in the polyurethane-based resin film is preferably 70% by weight or more (for example, 80% by weight or more, typically 90% by weight or more and 100% by weight or less). The polyurethane-based resin film disclosed herein may be a film made of a polymer blend of polyurethane and other resins. The other resin may be one or more, for example, an acrylic resin, a polyolefin, a polyester, a polycarbonate, or the like. Alternatively, the technique disclosed herein can also be carried out in an embodiment using a base material that substantially does not contain a resin component other than polyurethane.

The polyurethane is a polymer compound synthesized by subjecting a polyol (for example, diol) and a polyisocyanate (for example, diisocyanate) to a polyaddition reaction at a predetermined ratio. The NCO / OH ratio of polyurethane may be appropriately set based on the common general technical knowledge of those skilled in the art so as to obtain desired mechanical properties (for example, breaking strength, elongation at break, tensile recovery rate).

Examples of the polyol that can be used in the synthesis of the polyurethane include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexane. Diols, 1,8-octanediols, polyoxytetramethylene glycols, diethylene glycols, polyethylene glycols, polypropylene glycols and other diols; polyesters that are polycondensates of the above diols and dicarboxylic acids (eg, adipic acid, azelaic acid, sebacic acid). Polyols; carbonate diols such as polyalkylene carbonate diols; and the like. These can be used alone or in combination of two or more.

Examples of the polyisocyanate that can be used for synthesizing the polyurethane include aromatic, aliphatic, and alicyclic diisocyanates, and multimers (for example, dimersions and trimers) of these diisocyanates. Examples of the diisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, and 1,3-phenylenedi isocyanate. , 1,4-phenylenediocyanate, butane-1,4-diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4 , 4-Diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, methylcyclohexanediisocyanate, m-tetramethylxylylene diisocyanate and the like. These can be used alone or in combination of two or more. Of these, aromatic diisocyanates are preferable.

In addition to the polyol and polyisocyanate, other copolymerization components may be introduced into the polyurethane. As the other copolymerization component, one or more of monocarboxylic acid, dicarboxylic acid, trifunctional or higher polycarboxylic acid, hydroxycarboxylic acid, alkoxycarboxylic acid, derivatives thereof and the like can be used. It is appropriate that the ratio of these other copolymerization components is less than 30% by weight (for example, less than 10% by weight, typically less than 5% by weight) in polyurethane. The technique disclosed herein can also be preferably carried out in an embodiment including a polyurethane-based resin film base material containing a polyurethane as a main component which does not contain other copolymerization components.

In another preferred embodiment, the film-like substrate is a resin film containing a urethane (meth) acrylate-based polymer. As the urethane (meth) acrylate-based polymer disclosed herein, a polymer containing a structural unit derived from urethane (meth) acrylate can be used. Here, the urethane (meth) acrylate refers to a compound having a urethane bond and a (meth) acryloyl group in one molecule, and such a compound can be used without particular limitation. Urethane (meth) acrylate may be used alone or in combination of two or more. Urethane (meth) acrylates preferably have two or more urethane bonds and two or more (meth) acryloyl groups. The number of (meth) acryloyl groups contained in the urethane (meth) acrylate is preferably 2 or more and 5 or less, and more preferably 2 or more and 3 or less. For example, urethane (meth) acrylate having two (meth) acryloyl groups may be preferably used. Further, the urethane (meth) acrylate is preferably urethane acrylate. Here, the term "urethane acrylate" means that the number ratio of acryloyl groups among the (meth) acryloyl groups contained in the urethane (meth) acrylate exceeds 50%.

As the urethane (meth) acrylate, various commercially available urethane (meth) acrylates can be used. For example, the product name "UV-3300B" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., the product name "Beam Set 505A-6" manufactured by Arakawa Chemical Industry Co., Ltd., and the like can be preferably used.

In another preferred embodiment, the film-like substrate is a PVC-based resin film. The PVC-based resin film is produced by molding a PVC-based resin composition (molding material) containing a PVC-based resin into a film. Here, the PVC-based resin composition refers to a resin composition in which the main component (that is, 50% by weight or more) of the resin component (polymer component) is a PVC-based resin (typically PVC). It is preferable that about 80% by weight or more (more preferably about 90% by weight or more) of the total amount of the resin component contained in the PVC-based resin composition is the PVC-based resin. Substantially the total amount of the resin component may be PVC. According to such a PVC-based resin composition, a PVC-based resin film exhibiting physical properties suitable as a base material for an adhesive sheet can be formed.

For film-like base materials (for example, resin film base materials), fillers (inorganic fillers, organic fillers, etc.), colorants (pigments, dyes), antioxidants, antioxidants, and ultraviolet absorbers are used, if necessary. Various additives such as agents, antistatic agents, lubricants, plasticizers, stabilizers and the like may be blended. For example, when a soft PVC resin film is used as the film-like base material, the amount of the plasticizer blended is about 20 parts by weight or more (more preferably about 30 parts by weight or more) or 100 parts by weight per 100 parts by weight of the PVC resin. It is appropriate to set the following (more preferably, about 70 parts by weight or less). The blending ratio of the various additives is usually less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The surface of the film-like base material may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat agent. Such a surface treatment may be a treatment for improving the adhesion between the film-like base material and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer on the base material. When the film-like base material is a polyurethane-based resin film, good anchoring property can be obtained even if the above-mentioned surface treatment is not applied due to its high surface energy.

The film-like base material may have a single-layer structure, or may have a multi-layer structure of two layers, three layers or more. In the case of a multi-layer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the resin (more preferably polyurethane). The method for producing the film-like base material is not particularly limited as long as a conventionally known method may be appropriately adopted. When a resin film base material is used as the film-like base material, it is produced by appropriately adopting a conventionally known general film molding method such as extrusion molding, inflation molding, T die casting molding, or calender roll molding. A resin film base material can be used.

The thickness of the film-like base material is not particularly limited, and can be appropriately selected depending on the intended purpose. For example, the thickness of the film-like base material can be 1 mm or less. From the viewpoint of facilitating the reduction of the thermal resistance of the pressure-sensitive adhesive sheet, it is usually advantageous that the thickness of the film-like substrate is 300 μm or less, and 150 μm or less (typically less than 100 μm, for example, less than 80 μm). Is more preferable. From the viewpoint of tensile removability, the thickness of the film-like substrate is usually preferably 10 μm or more, and preferably about 20 μm or more (typically 30 μm or more, for example 40 μm or more). .. For example, the above thickness is preferably applied to a non-foamed resin film base material.

<Peeling liner>
As the release liner, a conventional release paper or the like can be used, and the release liner is not particularly limited. For example, it is made of a release liner having a release treatment layer on the surface of a liner base material such as a resin film or paper, or a low adhesive material of a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.). A release liner or the like can be used. The peeling treatment layer may be formed by surface-treating the liner base material with a peeling treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Size of stretchable adhesive sheet, etc.>
When the stretchable pressure-sensitive adhesive sheet disclosed herein has an elongated shape, its width can be configured to be about 30 mm or less (for example, 20 mm or less, typically 15 mm or less). For example, when the pressure-sensitive adhesive sheet is used in a portable electronic device, the above width can be preferably adopted. From the viewpoint of preventing damage such as tearing during tensile removal, the width of the adhesive sheet is preferably 1 mm or more (for example, 3 mm or more, typically 5 mm or more). In one aspect, the width of the pressure-sensitive adhesive sheet may be 8 mm or more, or 10 mm or more (for example, 12 mm or more). When the entire adhesive sheet is elongated, the above width is the width of the adhesive sheet.

When the stretchable adhesive sheet disclosed herein has an elongated shape, the length thereof is preferably 1 cm or more (for example, 3 cm or more, typically 5 cm or more) from the viewpoint of removal workability by tension. .. From the viewpoint of removal workability, the length of the adhesive sheet is preferably 30 cm or less (for example, 15 cm or less). In one aspect, the length of the pressure-sensitive adhesive sheet may be 10 cm or less, or 6 cm or less.

The ratio (L / W) of the length L to the width W of the extensible pressure-sensitive adhesive sheet is preferably 1 or more. The stretchable adhesive sheet having such a shape can exhibit a good adhesive function to a rectangular adherend (for example, a battery or the like). Further, it is more preferable that the stretchable pressure-sensitive adhesive sheet has a band shape (typically a rectangular shape) as in the above embodiment. In that case, although it depends on the shape and size of the adherend and the place where the adherend is attached, the stretchable adhesive sheet having the above ratio (L / W) of about 2 or more (typically 3 or more, for example, 5 or more) is removed. It tends to be excellent in property and handleability. The upper limit of the ratio (L / W) is not particularly limited, but the ratio (L / W) can be about 50 or less (for example, 30 or less, typically 20 or less) from the viewpoint of strength, handleability, and the like. ..

The total thickness of the stretchable pressure-sensitive adhesive sheet (including the pressure-sensitive adhesive layer and the base material, but not the release liner) disclosed herein is not particularly limited. Usually, it is appropriate that the total thickness is in the range of about 20 μm or more and 1.5 mm or less (for example, 30 μm or more and 600 μm or less). The total thickness of the pressure-sensitive adhesive sheet is preferably about 50 μm or more (for example, 70 μm or more) in consideration of adhesive characteristics and the like, and preferably about 300 μm or less (for example, 200 μm or less) from the viewpoint of reducing thermal resistance. When the total thickness of the adhesive sheet is set to a predetermined value or less, it may be advantageous in terms of thinning, downsizing, weight reduction, resource saving, and the like of the product. In another preferred embodiment, the total thickness of the pressure-sensitive adhesive sheet may be 80 μm or greater (eg, 100 μm or greater, typically 130 μm or greater) and greater than 150 μm (eg, greater than 300 μm, typically greater than 500 μm). May be good. The adhesive sheet having such a total thickness can be preferably used for fixing an adherend to be reattached after being attached to, for example, a wall surface or the like and used for a predetermined period of time.

In the pressure-sensitive adhesive sheet according to a preferred embodiment, a thickness of 35% or more of the total thickness of the pressure-sensitive adhesive sheet is composed of a filler-containing pressure-sensitive adhesive layer. According to the pressure-sensitive adhesive sheet having such a structure, both adhesion reliability and good thermal conductivity can be suitably compatible. Here, the fact that the adhesive sheet is composed of a filler-containing pressure-sensitive adhesive layer having a thickness of 35% or more of the total thickness of the pressure-sensitive adhesive sheet means that, for example, the filler-containing pressure-sensitive adhesive layers (first pressure-sensitive adhesive layer, second In the double-sided pressure-sensitive adhesive sheet with a base material having the pressure-sensitive adhesive layer), the total thickness of the filler-containing pressure-sensitive adhesive layers is 35% or more of the total thickness of the pressure-sensitive adhesive sheet. Further, in the base material-less double-sided pressure-sensitive adhesive sheet composed of the filler-containing pressure-sensitive adhesive layer, the thickness of the filler-containing pressure-sensitive adhesive layer is 100% of the total thickness of the pressure-sensitive adhesive sheet.

In the aspect of the pressure-sensitive adhesive sheet with a base material (typically, a double-sided pressure-sensitive adhesive sheet with a base material), the thickness of the filler-containing pressure-sensitive adhesive layer out of the total thickness of the pressure-sensitive adhesive sheet from the viewpoint of making it easier to improve the thermal conductivity. Can be 40% or more, and may be 50% or more (for example, 55% or more). Further, in the above aspect, from the viewpoint of tensile removability, it is usually appropriate that the thickness of the filler-containing pressure-sensitive adhesive layer is 90% or less of the total thickness of the pressure-sensitive adhesive sheet, and is 80% or less (for example, 70% or less). ) Is preferable.

Although not particularly limited, the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet disclosed herein can be, for example, 1% or more, and is usually used from the viewpoint of obtaining higher heat conductivity. Is suitable to be 3% or more (for example, 5% or more), and preferably 10% or more (for example, 15% or more). Further, from the viewpoint of adhesive reliability, the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is usually 50% or less, and 40% or less (for example, 35% or less). Is preferable, and for example, it may be 30% or less. In the pressure-sensitive adhesive sheet disclosed herein, the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is 3% or more and 50% or less (more preferably 5% or more and 40% or less, for example, 10% or more and 35% or less). It can be preferably carried out in the above embodiment.

The technique disclosed herein can be preferably carried out in an embodiment in which the weight of the thermally conductive filler contained in the 1 m ² stretchable pressure-sensitive adhesive sheet is 6 g or more. That is, a pressure-sensitive adhesive sheet in which the content of the thermally conductive filler per area of the pressure-sensitive adhesive is 6 g / m ² or more is preferable. With such a configuration, a stretchable pressure-sensitive adhesive sheet having excellent thermal conductivity can be preferably realized. From the viewpoint of obtaining higher thermal conductivity, the content of the thermally conductive filler can be, for example, 8 g / m ² or more, preferably 10 g / m ² or more, and 12 g / m ² or more (for example,). It is more preferably 15 g / m ² or more, more preferably 20 g / m ² or more). Further, from the viewpoint of making it easy to achieve both thermal conductivity and tensile workability at a high level, it is usually appropriate that the content of the thermal conductive filler is 100 g / m ² or less, and 80 g / m ² or less. Is preferable.

The pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and is, for example, a metal material such as stainless steel (SUS) and aluminum; an inorganic material such as glass and ceramics; nylon, polycarbonate (PC), polymethyl methacrylate (PMMA), and the like. Resin materials such as polypropylene, polyethylene terephthalate (PET), acrylic nitrile butadiene styrene copolymer resin (ABS), impact resistant polystyrene (HIPS), PC-ABS blend resin, PC-HIPS blend resin; rubber such as natural rubber and butyl rubber It can be used by being attached to an adherend having a surface made of a material; and a composite material thereof or the like.

<Use>
Since the stretchable pressure-sensitive adhesive sheet disclosed herein has a filler-containing pressure-sensitive adhesive layer, it has good thermal conductivity, exhibits a sufficient adhesive function during use, and is excellent in tensile removability during removal. Taking advantage of this feature, it is preferably used as an adhesive sheet for various purposes that can be peeled off again after being attached. For example, for fixing a protective panel (lens) that protects the display part of electronic devices, for fixing a decoration panel of a display (for example, a TV display), for fixing a battery pack of a personal computer, for waterproofing a lens of a digital video camera, etc. The pressure-sensitive adhesive sheet disclosed herein can be applied. Among them, it can be preferably used as an adhesive sheet for portable electronic devices, which is required to have an adhesive strength equal to or higher than a predetermined value at the time of use, and is required to be smoothly removed at the time of repair, replacement, inspection, recycling, etc. of constituent members. For example, mobile phones, smartphones, tablet PCs, laptop PCs, various wearable devices (for example, wristwatch type that is worn on the wrist like a wristwatch, modular type that is worn on a part of the body with a clip or strap, glasses type) (Monocular type and binocular type. Including head mount type. Eyewear type, clothes type attached to shirts, socks, hats, etc. in the form of accessories, earwear type attached to ears like earphones, etc.), Digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), computers (computers, etc.), portable game equipment, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable TVs, mobile phones In portable electronic devices such as printers, portable scanners, and portable modems, protective panel (lens) fixing to protect the display, key module member fixing, rim sheet fixing, decoration panel fixing, battery fixing, and various other members (circuit board, various types) Preferable for fixing panel members, buttons, lighting equipment members, internal camera members, heat dissipation materials, graphite sheets), fixing display objects (including various marks) such as logos (design letters) and various designs. Can be applied. In addition, in this specification, "portable" means that it is not enough to be portable, but that an individual (standard adult) has a level of portability that is relatively easy to carry. It shall mean.

Further, the stretchable adhesive sheet (typically, a double-sided adhesive sheet) disclosed herein is excellent in performance (pull-out removability) of removing the adhesive sheet by pulling it out from between objects. Here, the pull-out removability means that the tab of the adhesive sheet is exposed from two objects fixed by sandwiching the stretchable adhesive sheet, and the object is fixed by pulling the exposed tab and pulling out the stretchable adhesive sheet. It refers to the ease of removal, such as releasing (typically joining). The above two objects may be two places of one member. Further, the above two objects can be two of three or more objects bonded via one stretchable adhesive sheet. Hereinafter, a more specific description will be given with reference to FIGS. 3 and 4.

FIG. 3 is a schematic side view for explaining one aspect of tensile removal (typically pull-out removal), and FIG. 3A is a view showing a state in which tensile removal of an extensible adhesive sheet is started. , (B) is a diagram showing a state in which the tab is pulled to remove the tab, and (c) is a diagram showing a state in which the tensile removal of the extensible adhesive sheet is completed. FIG. 4 is a schematic top view for explaining one aspect of tensile removal (typically pull-out removal), and FIGS. 4A to 4C are shown in FIGS. 3A to 3C, respectively. It is a corresponding figure.

As shown in FIGS. 3A and 4A, the stretchable adhesive sheet (double-sided adhesive sheet) 200 is provided with a tab T that is exposed to the outside when the objects A and B are joined. There is. The object B is joined to the object A by using the stretchable adhesive sheet 200. Then, when it is desired to release the joint state between the object A and the object B for the purpose of repair, replacement, etc., the stretchable adhesive sheet 200 is pulled out from between the object A and the object B. Specifically, the extensible adhesive sheet 200 is pulled so as to pinch the tab T with fingers and pull it out from between the objects A and B. Then, the stretchable adhesive sheet 200 begins to stretch, contracts in the direction orthogonal to the pulling direction, and begins to peel off from the objects A and B (see (b) in FIG. 3 and (b) in FIG. 4). Finally, the entire adhesive region of the extensible adhesive sheet 200 is peeled off, and the drawing of the extensible adhesive sheet 200 from between the objects A and B is completed (see (c) of FIG. 3 and (c) of FIG. 4). ). The removal of the object B joined to the object A is also completed at the same time.

The adhesive sheet having excellent tensile removability as described above is suitable as an adhesive sheet used for the purpose of fixing a battery (including a primary battery and a secondary battery, for example, a polymer battery) in a portable electronic device. The battery generates heat during charging (particularly, quick charging), and it is beneficial to efficiently release the heat in order to suppress deterioration (extend the life of the battery). For batteries that are expected to be charged quickly and that it is difficult to secure sufficient heat dissipation space (air passage, etc.) around them, such as batteries built into portable electronic devices, use the adhesive sheet disclosed here. It is particularly meaningful to fix the battery (for example, to fix it in the housing of a portable electronic device).

In addition, the battery is usually placed in a place where it needs to be removed when repairing, replacing, or inspecting a component (including a battery) of a portable electronic device. Therefore, the adhesive sheet for fixing the battery often needs to be removed. However, removing the battery by using a remover, peeling it off by hand, heating, or other physical means may damage the battery and may not be preferable in terms of safety. Reducing the peeling force by photo-curing is also not effective because the irradiation is performed through the battery due to the application site of the adhesive sheet. The adhesive sheet disclosed herein exerts a function of fixing the battery well, and when removing the battery after the period of use, the above-mentioned tension removal (typically pull-out removal) method is used. , The removal can be done easily. The pressure-sensitive adhesive sheet is particularly preferable as a pressure-sensitive adhesive sheet used for the purpose of fixing a polymer battery. Polymer batteries tend to be more deformable than other types of batteries (typically batteries with metal cases), so traditional peeling methods can deform the battery and impair its functionality. there were. According to the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet can be satisfactorily removed while suppressing the deformation of the polymer battery by utilizing the above-mentioned tensile removal (typically pull-out removal) method.

Moreover, the adhesive sheet used for fixing the battery of a portable battery device is often unable to be pulled in parallel with the shearing direction when it is removed due to other parts existing around the battery and the arrangement of the battery. .. In such a case, the adhesive sheet is removed by pulling it at an angle non-parallel to the adhesive surface (for example, an angle of 45 degrees or more and 90 degrees or less, typically 70 degrees or more and less than 90 degrees). At the time of removal, there was a risk of damage due to contact with an adherend (battery) or an obstacle. According to the technique disclosed herein, the pressure-sensitive adhesive sheet can be preferably removed without damaging it even in such a removal mode.

Further, the adhesive sheet having excellent tensile removal property (typically pull-out removal property) is attached to a wall surface, a pillar, furniture, a home electric appliance, a glass surface, etc., and is attached after being used for a predetermined period of time. It is also suitable as an adhesive sheet (typically a double-sided adhesive sheet) used for the purpose of fixing a body (object to be fixed, object to be attached, etc.). Also in this application, the adhesive sheet exerts a good fixing function during fixing of the adherend, and when removing the adherend, the entire adhesive sheet is pulled out by grasping a tab or the like provided on the adhesive sheet. As a result, the pressure-sensitive adhesive sheet can be efficiently removed (for example, removal in the direction of the arrow in FIG. 3C).

Matters disclosed by this specification include:
(1) An extensible adhesive sheet used in portable electronic devices.
A pressure-sensitive adhesive sheet comprising a filler-containing pressure-sensitive adhesive layer containing a thermally conductive filler.
(2) The adhesive sheet according to (1) above, which has a thermal resistance value lower than 12 cm ² · K / W.
(3) The adhesive sheet according to (1) or (2) above, which has a thermal conductivity higher than 0.12 W / m · K.
(4) The pressure-sensitive adhesive sheet according to claim 1 or 2, which has the filler-containing pressure-sensitive adhesive layer having a thickness of about 30 μm or more.
(5) The above (1) to (4), wherein the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is about 3% or more and about 40% or less (for example, about 5% or more and 40% or less). Adhesive sheet described in any.
(6) The average particle size of the heat conductive filler is larger than about 15% and less than about 50% of the thickness of the filler-containing pressure-sensitive adhesive layer containing the heat conductive filler. The adhesive sheet according to any one of (5).
(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6) above, wherein the weight of the heat conductive filler contained in the pressure-sensitive adhesive sheet 1 m ² is about 6 g or more and about 100 g or less.
(8) The heat conductive filler is aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium hydrate, tin oxide. The pressure-sensitive adhesive sheet according to any one of (1) to (7) above, which is at least one selected from the group consisting of hydrate, basic magnesium carbonate, hydrotalcite, dosonite, borosand and zinc borate.
(9) The adhesive sheet according to any one of (1) to (8) above, wherein the total thickness is larger than about 100 μm.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9) above, wherein a thickness of about 35% or more of the total thickness of the pressure-sensitive adhesive sheet is composed of the filler-containing pressure-sensitive adhesive layer.

(11) The pressure-sensitive adhesive sheet according to any one of (1) to (10) above, comprising a film-like base material that supports the filler-containing pressure-sensitive adhesive layer.
(12) The pressure-sensitive adhesive sheet according to (11) above, wherein the film-like base material is a non-foamed resin film base material.
(13) The film-like base material contains polyurethane in a proportion of about 70% by weight or more.
The pressure-sensitive adhesive sheet according to (11) or (12) above, wherein the polyurethane is an ether-based polyurethane, an ester-based polyurethane, or a carbonate-based polyurethane.
(14) The first pressure-sensitive adhesive layer is provided with a first pressure-sensitive adhesive layer provided on the first surface of the film-like base material and a second pressure-sensitive adhesive layer provided on the second surface of the film-like base material. The pressure-sensitive adhesive sheet according to any one of (11) to (13) above, wherein at least one of the layer and the second pressure-sensitive adhesive layer is the filler-containing pressure-sensitive adhesive layer.
(15) The pressure-sensitive adhesive sheet according to (14) above, wherein both the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are the filler-containing pressure-sensitive adhesive layers.

(16) The adhesive sheet according to any one of (1) to (15) above, which has a long portion and has at least extensibility in the longitudinal direction thereof.
(17) The state described in (16) above, wherein the state of being attached to the adherend is released by pulling from one end of the elongated portion in the state of being attached to the adherend. Adhesive sheet.
(18) The above (1), which is used to join one object (adhesion) and another object (adhesion), and is removed from the object by pulling it out from between the objects. The adhesive sheet according to any one of (17).
(19) The adhesive sheet according to any one of (1) to (18) above, further provided with tabs.
(20) The adhesive sheet according to any one of (1) to (19) above, which is used for fixing a battery.

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

<Example 1>
(Preparation of acrylic pressure-sensitive adhesive composition)
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction pipe, a reflux cooler, and a dropping funnel, 100 parts of BA, 5 parts of VAc, 3 parts of AA, 0.1 part of HEA, and 0.2 part of AIBN as a polymerization initiator. , Toluene as a polymerization solvent was charged, and solution polymerization was carried out at 60 ° C. for 6 hours to obtain a toluene solution of acrylic polymer A. Mw of the acrylic polymer A was 55 × 10 ^4.
For 100 parts of the acrylic polymer A contained in the toluene solution, 40 parts of a polymerized rosin ester resin (manufactured by Arakawa Chemical Industry Co., Ltd., product name "Pencel D-125", softening point 125 ° C.) as a tackifier resin and an isocyanate type 2 parts of cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L") and 40 parts of aluminum hydroxide particles as a heat conductive filler (manufactured by Showa Denko Co., Ltd., product name "Heidilite H-31") The acrylic pressure-sensitive adhesive composition according to this example was prepared by adding and mixing. In the heat conductive filler used in this example, the ratio of particles having an average particle size of 18 μm and a particle size of less than 30 μm is 70% or more, and the ratio of particles having a particle size of less than 1 μm is 1%. Further, on a weight basis, the content of the thermally conductive filler in the solid content (adhesive layer forming component) contained in the acrylic pressure-sensitive adhesive composition is 22.0%.

(Making a double-sided adhesive sheet)
Two commercially available release liners (trade name "SLB-80W3D", manufactured by Sumika Kako Paper Co., Ltd.) were prepared. The pressure-sensitive adhesive composition was applied to one surface (peeling surface) of each of the release liners so as to have a thickness of 45 μm after drying, and dried at 100 ° C. for 2 minutes. In this way, a filler-containing pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer and second pressure-sensitive adhesive layer) was formed on the peel-off surfaces of the two release liners, respectively.
As a film-like base material, a non-foamed ether-based polyurethane resin film having a thickness of 60 μm (manufactured by Nihon Matai Co., Ltd., trade name “Esmer URS ET-N”) was prepared. Adhesive layers formed on the above two release liners were laminated on both sides of the film-like base material. The release liner was left as it was on the pressure-sensitive adhesive layer and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer. The obtained structure was passed once through a laminator (0.3 MPa, speed 0.5 m / min) at 80 ° C., and then aged in an oven at 50 ° C. for 1 day. In this way, a double-sided adhesive sheet according to this example was obtained. The total thickness of this double-sided pressure-sensitive adhesive sheet is 150 μm, and the ratio of the thickness of the filler-containing pressure-sensitive adhesive layer (total thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer) to the total thickness is 60%. The ratio of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is 13% by weight. The pressure-sensitive adhesive sheet contains 25 g of a thermally conductive filler per 1 m ^{2 of} the pressure-sensitive adhesive sheet.

<Example 2>
A commercially available double-sided pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer having a thickness of 150 μm was prepared. The total thickness of this double-sided adhesive sheet is 150 μm. The pressure-sensitive adhesive layer is a rubber-based pressure-sensitive adhesive layer that does not contain a filler.

<Evaluation>
For the pressure-sensitive adhesive sheet according to each example, the thermal conductivity in the thickness direction was carried out using the thermal characteristic evaluation apparatus shown in FIG. FIG. 5A is a front schematic view of the thermal characteristic evaluation device, and FIG. 5B is a side schematic view of the thermal characteristic evaluation device. The release liner was removed during the measurement.

Specifically, a pair of blocks (sometimes referred to as "rods") L made of aluminum (A5052, thermal conductivity: 140 W / m · K) formed so as to be a cube having a side of 20 mm. An adhesive sheet S (square shape having a length of 20 mm and a width of 20 mm) was sandwiched between the two blocks L, and a pair of blocks L were bonded to each other with the adhesive sheet S. Then, it was arranged between the heating element (heater block) H and the radiator (cooling base plate configured so that the cooling water circulates inside) C so that the pair of blocks L are up and down. Specifically, the heating element H was placed on the upper block L, and the heat radiating element C was placed under the lower block L.
At this time, the pair of blocks L bonded by the adhesive sheet S are located between the pair of pressure adjusting screws J penetrating the heating element H and the radiator C. A load cell R is arranged between the pressure adjusting screw J and the heating element H, and is configured to measure the pressure when the pressure adjusting screw J is tightened. This pressure was used as the pressure applied to the pressure-sensitive adhesive sheet S. Specifically, in this test, the pressure adjusting screw J was tightened so that the pressure applied to the pressure-sensitive adhesive sheet S was 25 N / cm ² (250 kPa).
Further, three probes P (diameter 1 mm) of the contact type displacement meter were installed so as to penetrate the lower block L and the adhesive sheet S from the radiator body C side. At this time, the upper end portion of the probe P is in contact with the lower surface of the upper block L, and the distance between the upper and lower blocks L (thickness of the adhesive sheet S) can be measured.
Temperature sensors D were attached to the heating element H and the upper and lower blocks L. Specifically, a temperature sensor D was attached to one location of the heating element H. Further, temperature sensors D were attached to five places of each block L at intervals of 5 mm in the vertical direction.
In the measurement, first, the pressure adjusting screw J was tightened to apply pressure to the adhesive sheet S, the temperature of the heating element H was set to 80 ° C., and cooling water at 20 ° C. was circulated through the heat radiating element C.
Then, after the temperatures of the heating element H and the upper and lower blocks L are stabilized, the temperatures of the upper and lower blocks L are measured by each temperature sensor D, and the thermal conductivity (W / m · K) and the temperature gradient of the upper and lower blocks L are measured. The heat flux passing through the pressure-sensitive adhesive sheet S was calculated from the above, and the temperature at the interface between the upper and lower blocks L and the pressure-sensitive adhesive sheet S was calculated. Then, using these, the thermal conductivity (W / m · K) and the thermal resistance value (cm ² · K / W) at the above pressure were calculated using the following thermal conductivity equation (Fourier's law).
Q = -λgradT
R = L / λ
Q: Heat flow velocity per unit area gradeT: Temperature gradient L: Sheet thickness λ: Thermal conductivity R: Thermal resistance

Further, for the double-sided adhesive sheets of Examples 1 and 2, the initial adhesive force A [N / 20 mm] and the tensile peeling stress B [N / 20 mm] were measured by the above-mentioned methods.
The results are shown in Table 1.

As shown in Table 1, the pressure-sensitive adhesive sheet of Example 1 having the filler-containing pressure-sensitive adhesive layer has a clearly higher thermal conductivity and significantly lower heat than the pressure-sensitive adhesive sheet of Example 2 having no filler-containing pressure-sensitive adhesive layer. The resistance value is shown. Further, from the results shown in Table 1, it can be seen that the pressure-sensitive adhesive sheet of Example 1 exhibits suitable performance (adhesive reliability and tensile removability) as an stretchable pressure-sensitive adhesive sheet. When the initial adhesive force A and the tensile peeling stress B of the double-sided adhesive sheet of Example 1 were measured by the above method, the initial adhesive force A was 12.0 N / 20 mm and the tensile peel stress B was 9.8 N / 20 mm. , It was confirmed that it exhibits properties suitable for pull-out removal.

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

1,200 Stretchable Adhesive Sheet 10 Film-like Base Material 21,22 Adhesive Layer (Filler-Containing Adhesive Layer)
100 measurement sample (extensible adhesive sheet)
100A, 100B Adhesive surface 111,112 Polycarbonate plate

Claims (10)

An extensible adhesive sheet used in portable electronic devices.
A filler-containing pressure-sensitive adhesive layer containing a thermally conductive filler and a film-like base material supporting the filler-containing pressure-sensitive adhesive layer are provided.
The average particle size of the thermally conductive filler is greater than 15% and less than 50% of the thickness of the filler-containing pressure-sensitive adhesive layer containing the thermally conductive filler.
The film-like base material is a non-foamed non-foamed material composed of at least one resin material selected from the group consisting of polyurethane, urethane (meth) acrylate-based polymer, polycarbonate, styrene-based elastomer, acrylic rubber and vinyl chloride-based resin. It is a resin film
The extensible adhesive sheet, the elongation at break is not less than 200%, and the thermal resistance 12cm ² · K / W from rather low,
The ratio (B / A) of the tensile peeling stress B [N / 20 mm] to the initial adhesive force A [N / 20 mm] of the stretchable adhesive sheet is 3.0 or less, and the initial adhesive force A has a tensile speed of 300 mm. It is the peel strength against polycarbonate measured under the condition of / min and the peeling angle of 180 degrees, and the tensile peeling stress B is the peeling strength with respect to the polycarbonate measured under the condition of a tensile speed of 300 mm / min and a peeling angle of 0 degrees . Adhesive sheet. The pressure-sensitive adhesive sheet according to claim 1, further comprising the filler-containing pressure-sensitive adhesive layer having a thickness of 30 μm or more. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein 35% or more of the total thickness of the pressure-sensitive adhesive sheet is composed of the filler-containing pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the ratio of the weight of the heat conductive filler to the weight of the pressure-sensitive adhesive sheet is 5% or more and 40% or less. The adhesive sheet according to any one of claims 1 to 4, which has an elongated portion and has at least extensibility in the longitudinal direction thereof. The adhesive sheet according to claim 5, wherein the state of being attached to the adherend is released by pulling from one end of the elongated portion in a state of being attached to the adherend. The adhesive sheet according to any one of claims 1 to 6 , which has a total thickness of more than 100 μm. The adhesive sheet according to any one of claims 1 to 7, which is used for joining two objects and is removed from the two objects by pulling out from between the two objects. The adhesive sheet according to any one of claims 1 to 8, which is used for fixing a battery. A portable electronic device comprising the adhesive sheet according to any one of claims 1 to 9.

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