JP6691748B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet.

  Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid (viscoelastic body) state in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is preferably used in the form of a pressure-sensitive adhesive sheet, for example, for fixing components in mobile electronic devices such as mobile phones, smartphones, and tablet PCs. It is also preferably used as a pressure-sensitive adhesive sheet that is peeled off again after being attached. Patent documents 1 and 2 are mentioned as documents which disclose this kind of prior art. Both Patent Documents 1 and 2 disclose conventional techniques including a base material having stretchability. Patent Document 2 relates to a medical adhesive sheet that is attached to the skin.

JP, 6-346032, A Japanese Patent Publication No. 2005-500133

  The pressure-sensitive adhesive sheet is required to be free from adhesion defects such as peeling and displacement during the period of use. Therefore, the pressure-sensitive adhesive sheet needs to have a predetermined adhesive force or more. On the other hand, the pressure-sensitive adhesive sheet attached to the adherend can be removed from the adherend after the purpose of use such as fixing is finished. For example, an adhesive sheet used as a fixing means for a component of a portable electronic device can be removed from an adherend when the component is repaired, replaced, inspected, recycled, or the like. Since some adherends are easily deformed, it is desirable that the pressure-sensitive adhesive sheet used for this purpose be configured so that it can be removed without causing deformation or damage to the adherend. Specifically, for example, it is desirable that a part of the adhesive sheet is exposed to the outside, and the adhesive sheet can be removed from the surface of the adherend by gripping and pulling the part. In consideration of removal workability, such a pressure-sensitive adhesive sheet preferably has a small peel stress at the time of removal. However, if the adhesive force is designed to be a predetermined value or more in order to secure a sufficient adhesive function, the peeling stress when pulling and removing the adhesive sheet tends to increase. Therefore, the present situation is that a pressure-sensitive adhesive sheet that has both an adhesive function during use and a tensile removability at a practical level has not yet been realized.

  The present invention was created in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet that exhibits a sufficient adhesive function during use and is excellent in tensile removability during removal.

  According to the present invention, an adhesive sheet provided with an adhesive layer is provided. This pressure-sensitive adhesive sheet has an initial adhesive force A for polycarbonate of 3 N / 20 mm or more and a tensile peeling stress B for polycarbonate of 22 N / 20 mm or less. Further, the pressure-sensitive adhesive layer contains filler particles. Then, 50% by weight or more of the filler particles contained in the pressure-sensitive adhesive layer has a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer. A pressure-sensitive adhesive sheet according to a preferred aspect includes a pressure-sensitive adhesive layer and a film-shaped substrate that supports the pressure-sensitive adhesive layer.

  When the initial adhesive force A is not less than a predetermined value, a sufficient adhesive function can be exerted on an adherend formed of various materials such as polycarbonate (PC). Further, when the tensile peeling stress B is equal to or less than a predetermined value, the direction acting in the 0 degree direction (shear direction) with respect to the adhesive surface (typically, −90 degrees to +90 degrees with respect to the adhesive surface). The direction of the pressure-sensitive adhesive sheet can be smoothly removed from various adherends by pulling the pressure-sensitive adhesive sheet in the following direction. In short, according to the present invention, there is provided a pressure-sensitive adhesive sheet that has both a sufficient adhesive function during use and excellent tensile removability during removal. The maintenance of the initial adhesive force A and the reduction of the tensile peeling stress B are both realized by including filler particles in the adhesive layer. Then, by making the particle size of the filler particles in a predetermined ratio relatively small with respect to the thickness of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive surface maintains a good surface state, and the desired pressure-sensitive adhesive property (for example, adhesive strength) is obtained. Can be demonstrated. The appearance of the surface of the pressure-sensitive adhesive layer (adhesive surface) is also kept good.

  In a preferred aspect of the PSA sheet disclosed herein, the ratio (B / A) of the tensile peel stress B [N / 20 mm] to the initial adhesive force A [N / 20 mm] is 3.0 or less. That the ratio (B / A) is small means that the tensile peeling stress B is reduced due to the relative relationship with the initial adhesive force A in the structure having the initial adhesive force A of a predetermined value or more. .. With such a configuration, it is possible to preferably achieve both a sufficient adhesive function during use and an excellent tensile removability during removal.

  In a preferred aspect of the technology disclosed herein, the pressure-sensitive adhesive sheet has an elongated portion and has extensibility in at least its longitudinal direction. When the pressure-sensitive adhesive sheet is removed, the pressure-sensitive adhesive sheet having the above-described structure is stretched by pulling in the longitudinal direction, and the pressure-sensitive adhesive sheet is deformed by this stretching and can be peeled off from the adherend. In the pressure-sensitive adhesive sheet having the above-mentioned extensibility, due to the interaction between the tension and the elongation deformation of the pressure-sensitive adhesive sheet as described above, in addition, the tensile peeling stress reducing action of the filler particles contained in the pressure-sensitive adhesive layer provides excellent tensile removability. Is preferably realized. Further, the pressure-sensitive adhesive sheet disclosed herein can be preferably released from the adhered state to the adherend by pulling from one end of the elongated portion in the state of being adhered to the adherend. And may be preferably removed from the adherend. By adopting such a method of releasing the adhered state (typically, a removing method), the pressure-sensitive adhesive sheet disclosed herein is efficiently removed from the adherend without deforming or damaging the adherend. Can be done.

  In a preferred aspect of the PSA sheet disclosed herein, the proportion of particles having a particle size of less than 1 μm in the filler particles contained in the PSA layer is 50% by weight or less. In this way, the tensile peeling stress B can be preferably reduced by limiting the proportion of the fine particles having a particle diameter of less than 1 μm. Further, it is preferable that the amount of the fine particles is limited in terms of productivity (more specifically, preparation of the pressure-sensitive adhesive composition).

  In a preferred aspect of the pressure-sensitive adhesive sheet disclosed herein, the content C of the filler particles in the pressure-sensitive adhesive layer is 30% by volume or less. By appropriately adjusting the content of the filler particles in the pressure-sensitive adhesive layer, it is possible to preferably reduce the tensile peel stress B while suppressing the decrease in the initial pressure-sensitive adhesive force A.

  In a preferred aspect of the pressure-sensitive adhesive sheet disclosed herein, the film-shaped substrate is a non-foamed resin film substrate. By using a non-foamed resin film as a base material, excellent tensile removability can be preferably realized.

  In a preferred aspect of the pressure-sensitive adhesive sheet disclosed herein, as the pressure-sensitive adhesive layer, a first pressure-sensitive adhesive layer provided on the first surface of the film-shaped substrate and a second surface of the film-shaped substrate are provided. And a second pressure-sensitive adhesive layer that has been formed. Such a double-sided pressure-sensitive adhesive sheet with a substrate can be preferably used as a highly reliable fixing means (typically, a means for joining two adherends).

  The pressure-sensitive adhesive sheet disclosed herein is preferably used in a mode in which it is used for joining two adherends and then removed from the two adherends by being pulled out from between the two adherends. Can be done. Further, the pressure-sensitive adhesive sheet disclosed herein is used for bonding two adherends, and in the state where the two adherends are bonded, a pressure-sensitive adhesive sheet positioned between the two adherends is used. By pulling, the pasted state on the two adherends can be preferably released. By pulling the pressure-sensitive adhesive sheet in a state where the two adherends are joined, the pressure-sensitive adhesive sheet can be smoothly pulled out and removed from the two adherends without deforming or damaging the adherends.

  The pressure-sensitive adhesive sheet disclosed herein is preferably used for portable electronic devices. In particular, the pressure-sensitive adhesive sheet disclosed herein exhibits a sufficient adhesive function when used and is excellent in tensile removability when removed. Utilizing this feature, it is particularly preferably used as a pressure-sensitive adhesive sheet for fixing a battery, which is often removed during repair or replacement of members constituting a product, product inspection and the like. According to the technology disclosed herein, an adhesive sheet that is preferably used for fixing a battery is provided.

It is sectional drawing which shows one structural example of an adhesive sheet typically. It is explanatory drawing which shows the measuring method of the tensile peeling stress B typically. It is a typical side view for explaining one mode of pulling and removing. It is a typical top view for explaining one mode of pulling and removing.

  Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters particularly referred to in the present specification and matters necessary for carrying out the present invention are based on the teachings for carrying out the invention described in the present specification and the common general knowledge at the time of application. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field. In addition, the embodiment described in the drawings is schematically illustrated for clearly explaining the present invention, and does not necessarily represent an accurate size or scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product. ..

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

<Structure of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein is typically a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on at least one surface (preferably both surfaces) of a film-shaped substrate (support). The concept of the pressure-sensitive adhesive sheet here may include what is called a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film or the like. The pressure-sensitive adhesive sheet disclosed herein may be in a roll shape or a sheet shape. Alternatively, it may be a pressure-sensitive adhesive sheet further processed into various shapes. In addition, the film-shaped base material may be omitted.

  The pressure-sensitive adhesive sheet disclosed herein can have, for example, a cross-sectional structure schematically shown in FIG. In the pressure-sensitive adhesive sheet 1 shown in FIG. 1, pressure-sensitive adhesive layers 21 and 22 are provided on each surface of the film-shaped substrate 10 (both of which are non-peeling). 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). Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be a double-sided pressure-sensitive adhesive sheet without a substrate, which is composed of only a pressure-sensitive adhesive layer, although not particularly shown.

  In addition, the pressure-sensitive adhesive sheet preferably has a long portion from the viewpoint of tensile removability. Accordingly, in the pressure-sensitive adhesive sheet attached to the adherend, the pressure-sensitive adhesive sheet can be preferably removed from the adherend by grasping and pulling one end in the longitudinal direction of the elongated portion. The shape of the elongated portion is typically a strip shape. 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 preferable aspect, the entire pressure-sensitive adhesive sheet is formed in a long shape. From the viewpoint of pulling and removing workability, it is preferable that a tab (holding portion) is provided at one end in the longitudinal direction of the adhesive sheet. Although the shape of the tab is not particularly limited, it is preferably a shape (for example, a rectangular shape) that can be held by a finger.

<Characteristics of adhesive sheet>
The PSA sheet disclosed herein is characterized by having an initial adhesive force A to PC of 3 N / 20 mm or more. As a result, a sufficient adhesive function can be exerted on the adherend formed of various materials such as PC. Further, when the adhesive sheet having the initial adhesive force A is applied to, for example, a portable electronic device, the fixed arrangement of the adherend can be maintained even when the portable electronic device falls. The initial adhesive force A is preferably 5 N / 20 mm or more (for example, 6 N / 20 mm or more, typically 6.5 N / 20 mm or more). The upper limit of the initial adhesive force A is not particularly limited, but in consideration of the tensile removability and the adhesive residue prevention property, it may be less than 15 N / 20 mm (for example, less than 12 N / 20 mm, typically less than 10 N / 20 mm). preferable.

  The initial adhesive force A can be measured by the following method. An adhesive sheet cut into a size with a width of 20 mm and a length of 100 mm is prepared. Under an environment of 23 ° C. and 50% RH, the adhesive surface of the adhesive sheet (typically a double-sided adhesive sheet) is exposed, and the adhesive surface is pressure-bonded to the surface of the PC board by reciprocating a 2 kg roller once. To do. After leaving this for 30 minutes in the same environment, using a tensile tester, according to JIS Z 0237: 2000, the peeling strength [N / 20 mm width] under the conditions of a pulling speed of 300 mm / min and a peeling angle of 180 degrees. To measure. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, a polyethylene terephthalate (PET) film having a thickness of 25 μm is attached to the other pressure-sensitive adhesive surface, and the pressure-sensitive 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.

  The pressure-sensitive adhesive sheet disclosed herein is characterized in that, in addition to the initial pressure-sensitive adhesive force A, the tensile peeling stress B with respect to PC is 22 N / 20 mm or less. Accordingly, when the adhesive sheet is pulled in the pulling and peeling direction to be removed from the adherend, the adhesive sheet can be smoothly removed from the adherend. The tensile peel stress B is preferably 20 N / 20 mm or less (for example, 19 N / 20 mm or less, typically 18 N / 20 mm or less). The lower limit of the tensile peeling stress B is not particularly limited, but it is suitable to be about 5 N / 20 mm or more (for example, 8 N / 20 mm or more, typically 10 N / 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 pressure-sensitive adhesive sheet is cut into a size of 20 mm in width and 120 mm in length to prepare a measurement sample. Under an environment of 23 ° C. and 50% RH, the adhesive surface of each of the measurement samples (typically the double-sided adhesive sheet) is superposed on the surfaces of two PC plates (30 mm × 100 mm × 2 mm thickness) and 2 kg of weight is applied. Press the roller back and forth once. 70 mm (that is, 20 mm × 70 mm) from one end of the measurement sample in the longitudinal direction is pressure-bonded to each PC plate. After leaving this for 30 minutes in the same environment, using a tensile tester, each of the two PC plates was fixed, and the peeling strength [N / 20 mm width under the conditions of a pulling speed of 300 mm / min and a peeling angle of 0 degree. ] Is measured. Specifically, as shown in FIG. 2, the adhesive surfaces 100A and 100B of the adhesive sheet measurement sample 100 are bonded to the two PC plates 111 and 112, respectively, and pressure bonded. This is pulled in the direction of the arrow in FIG. 2 (that is, the pulling peeling direction) at the above speed, and the peeling strength [N / 20 mm width] is measured. In the case of a single-sided adhesive pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet), the peel strength [N / 20 mm width] may be measured in the same manner as described above except that one pressure-sensitive 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 peel stress B [N / 20 mm] to the initial adhesive force A [N / 20 mm] is 3.0 or less. As a result, it is possible to favorably achieve both a sufficient adhesive function during use and excellent tensile removability during removal. The above ratio (B / A) is preferably 2.8 or less (for example, 2.6 or less, typically 2.4 or less). Ideally, the lower the ratio (B / A), the better. However, in practice, the lower limit may be, for example, 1.2 or more (typically 1.5 or more).

  In a preferred aspect, the pressure-sensitive adhesive sheet exhibits a breaking strength of 10 MPa or more. Thereby, in a structure showing an adhesive force of a predetermined value or more, damage such as tearing can be less likely to occur when the adhesive sheet is removed. In addition, workability tends to be excellent. The breaking strength is more preferably 20 MPa or more, further preferably 30 MPa or more (for example, 45 MPa or more, typically 60 MPa or more). From the viewpoint of elasticity and extensibility of the pressure-sensitive adhesive sheet, the breaking strength is preferably about 100 MPa or less (for example, 80 MPa or less, typically 70 MPa or less).

  The breaking strength is measured according to the “tensile strength” measuring method described in JIS K 7311: 1995. More specifically, the breaking strength can be measured using a No. 3 dumbbell-shaped test piece (width: 5 mm) under the condition of a tensile speed of 300 mm / min. As the tensile tester, a 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 stickiness of the adhesive. The pulling direction in the above test is not particularly limited, but when the pressure-sensitive adhesive sheet has a long shape, it is preferable to match the lengthwise direction. The breaking strength can be adjusted, for example, by selecting the base material.

  The pressure-sensitive adhesive sheet disclosed herein preferably has stretchability. As a result, the adhesive sheet can be stretched and deformed and peeled off when pulled off. In this specification, “having extensibility” is defined to have an elongation at break of 20% or more. The elongation at break of the pressure-sensitive adhesive sheet can be 50% or more (eg, 100% or more, typically 200% or more). In a preferred embodiment, the pressure-sensitive adhesive sheet exhibits an elongation at break of 300% or more. As a result, the tensile force and the extensional deformation of the pressure-sensitive adhesive sheet interact with each other, and more excellent tensile removability is realized. The pressure-sensitive adhesive sheet having the above characteristics is also preferable in that the adherend is prevented from being deformed at the time of removal. 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 workability for removal and the like.

  The elongation at break is measured in accordance with the “elongation” measuring method described in JIS K 7311: 1995. More specifically, the elongation at break can be measured using a No. 3 dumbbell-shaped test piece (width: 5 mm, marked line interval: 20 mm) at a tension rate of 300 mm / min. The tensile tester and the like are basically the same as in the case of the breaking strength described above. The pulling direction in the above test is not particularly limited, but when the pressure-sensitive adhesive sheet has a long shape, it is preferable to match the lengthwise direction. The elongation at break can be adjusted, for example, by selecting the base material.

  The PSA sheet disclosed herein preferably exhibits a 100% modulus of less than 10 MPa. By setting the 100% modulus of the pressure-sensitive adhesive sheet to be less than a predetermined value, when the pressure-sensitive adhesive sheet is removed from the adherend by stretching and deforming the pressure-sensitive adhesive sheet, the resistance at the beginning of pulling tends to be small 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 the workability of sticking the pressure-sensitive adhesive sheet, it is usually suitable to set it to 0.5 MPa or more (for example, 1 MPa or more). The 100% modulus is measured according to the measuring method of "tensile stress" described in JIS K 7311: 1995. More specifically, a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm) was used to pull at a pulling speed of 300 mm / min, and the stress [MPa when the marked line distance was extended by 100%] ] Is 100% modulus. As the tensile tester, a product name “Autograph AG-10G type tensile tester” manufactured by Shimadzu Corporation can be used. A similar method can be adopted for the examples described below. The 100% modulus of the pressure-sensitive adhesive sheet can be adjusted by, for example, selection of the type of base material (selection of compounding ratio of hard component and soft component, etc.), molding method and the like.

  In one preferable aspect, the pressure-sensitive adhesive sheet suitably exhibits a tensile recovery rate of more than 50%. The tensile recovery rate is more preferably 70% or more. The tensile recovery rate is more preferably 80% or more (for example, 90% or more, typically 93% to 100%). As a result, damage such as tearing at the time of removing the adhesive sheet can be more highly prevented. This point will be described. For example, when removing the adhesive sheet by pulling it in the shearing direction, it usually takes some time depending on the adhesion area and the like. Therefore, the removal work may be interrupted midway. In such a case, if the tensile recovery rate of the pressure-sensitive adhesive sheet is less than or equal to a predetermined value, the removal work may be restarted from the state in which the mechanical properties (strength, elasticity, etc.) have decreased due to the pulling before the work was interrupted. At that time, the pressure-sensitive adhesive sheet cannot withstand pulling when the removing operation is restarted, and is easily damaged such as tearing. The pressure-sensitive adhesive sheet exhibiting the above-mentioned tensile recovery rate, even when removed in such a manner that an interruption occurs once as described above, since deterioration in mechanical properties is suppressed by recovery after tensile, damage is more severe. Can be prevented.

The tensile recovery rate is measured by the following method.
[Measurement of tensile recovery rate]
With respect to the pressure-sensitive adhesive sheet, a tensile test is performed in which the specific section distance L ₀ of the pressure-sensitive adhesive sheet is stretched by 100%. When the length of the specific section after 5 minutes has elapsed since the pressure-sensitive adhesive sheet was stretched 100% and released was defined as L ₁ , the formula: tensile recovery rate (%) = L ₀ / L ₁ × 100; Obtain the tensile recovery rate.
More specifically, according to JIS K 7311: 1995, a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm) is used to stretch 100% under a condition of a pulling speed of 300 mm / min. In other words, pull until the marked line interval extends by 20 mm. Then, the length L ₁ (mark line interval: mm) after 5 minutes from release from tension is measured, and the tension recovery rate is calculated from the formula: tensile recovery rate (%) = L ₀ / L ₁ × 100. .. In this method, L ₀ is the initial mark spacing of 20 mm. The tensile tester and others are basically the same as those for the above-described elongation at break. The pulling direction in the above test is not particularly limited, but it is preferable to match it with the longitudinal direction of the pressure-sensitive adhesive sheet or the long portion thereof. The tensile recovery rate can be adjusted, for example, by selecting the 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 substrate, 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. , A rubber-based polymer, a polyester-based polymer, a urethane-based polymer, a polyether-based polymer, a silicone-based polymer, a polyamide-based polymer, a fluorine-based polymer, or the like, which contains one or more kinds of various rubber-like polymers as a base polymer. obtain. Although described in detail below, 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 pressure-sensitive adhesive layer containing a rubber polymer as a base polymer, and a urethane polymer. Is a urethane-based pressure-sensitive adhesive layer containing as a base polymer. Alternatively, it may be a pressure-sensitive adhesive layer in which an acrylic polymer and a rubber polymer are used together as a 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 pressure-sensitive adhesive properties (typically pressure-sensitive adhesive strength), molecular design, temporal stability, and the like. In this specification, the "base polymer" of the pressure-sensitive adhesive refers to the main component of the polymer component contained in the pressure-sensitive adhesive (typically, a component contained in an amount exceeding 50% by weight).

  As the acrylic polymer, for example, a polymer of a monomer raw material that contains an alkyl (meth) acrylate as a main monomer and further can contain a sub-monomer having copolymerizability with the main monomer is preferable. Here, the main monomer means a component which accounts for more than 50% by weight of all the monomer components in the above-mentioned 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. R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of the number of carbon atoms may be referred to as “C _1-20 ”). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, an alkyl (meth) acrylate in which R ² is a C _1-14 (for example, C _2-10 , typically C _4-8 ) chain alkyl group is preferable, and R is Alkyl acrylate in which ¹ is a hydrogen atom and R ² is a C _4-8 chain alkyl group is more preferable.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl. (Meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (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 (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, Eicosyl (meth) acrylate etc. are mentioned. These alkyl (meth) acrylates may 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 mixing ratio of the main monomer in all the monomer components is preferably 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 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 95% by weight or more (typically 99 to 100% by weight). The technique disclosed herein can be preferably carried out in an embodiment in which 50% by weight or more (eg, 60% by weight or more) of all monomer components is BA. In a preferred embodiment, the total monomer component may further include 2EHA in a proportion smaller than BA.

  The sub-monomer having a copolymerizability with the main monomer, alkyl (meth) acrylate, can be useful for introducing a cross-linking point into the acrylic polymer and for enhancing the cohesive force of the acrylic polymer. As the auxiliary monomer, for example, 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, an alkoxysilyl group-containing monomer, One or more functional group-containing monomers such as imide group-containing monomers and epoxy group-containing monomers can be used. For example, from the viewpoint of improving cohesive strength, an acrylic polymer in which a carboxy group-containing monomer and / or a hydroxyl group-containing monomer is copolymerized as the sub-monomer is preferable. Preferred 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. Among them, hydroxyalkyl (meth) acrylate is preferable, and 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are more preferable.

  The amount of the sub-monomer may be appropriately selected so that a desired cohesive force is realized, and is not particularly limited. Usually, from the viewpoint of achieving a good balance between the adhesive force and the cohesive force, the amount of the auxiliary monomer is appropriately 0.5% by weight or more, preferably 1% by weight, based on the total monomer components of the acrylic polymer. % Or more. Further, the amount of the sub-monomer is appropriately 30% by weight or less, preferably 10% by weight or less (for example, 5% by weight or less) based on the total monomer components. When the carboxy group-containing monomer is copolymerized to the acrylic polymer, the content of the carboxy group-containing monomer is, from the viewpoint of compatibility between the adhesive force and the cohesive force, in all the monomer components used for the synthesis of the acrylic polymer, It is preferably in the range of approximately 0.1 to 10% by weight (for example, 0.2 to 8% by weight, typically 0.5 to 5% by weight). When the hydroxyl group-containing monomer is copolymerized with the acrylic polymer, the content of the hydroxyl group-containing monomer is about 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 in the range of 0.001 to 10% by weight (for example, 0.01 to 5% by weight, typically 0.02 to 2% by weight).

  The acrylic polymer disclosed herein may be copolymerized with a monomer (other monomer) other than those described above, as long as the effects of the present invention are not significantly impaired. The above-mentioned 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, releasability), and the like. Examples of the monomer capable of improving the cohesive force of the pressure-sensitive adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, aromatic vinyl compounds and the like. The above-mentioned other monomers may be used alone or in combination of two or more. Of these, vinyl esters are preferred examples. Specific examples of the vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate and the like. Among them, VAc is preferable. The content of the above-mentioned other monomers is about 30% by weight or less (typically 0.01 to 30% by weight, for example 0.1 to 10% by weight) based on all monomer components used for the synthesis of the acrylic polymer. Preferably.

  From the viewpoint of impact resistance and the like, the copolymer composition of the acrylic polymer has a glass transition temperature (Tg) of −15 ° C. or lower (typically −70 ° C. or higher and −15 ° C. or lower). It is appropriately designed, preferably -25 ° C or lower (for example, -60 ° C or higher and -25 ° C or lower), more preferably -40 ° C or lower (for example, -60 ° C or higher and -40 ° C or lower).

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

In the technology 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
Regarding the Tg of homopolymers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. When it is not described in the above Polymer Handbook, the value obtained by the measuring method described in JP-A-2007-51271 is used.

  The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as a synthetic method of the acrylic polymer such as a solution polymerization method, an emulsion polymerization method, a bulk 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 method for supplying the monomers when carrying out the solution polymerization, a batch charging method for supplying all the monomer raw materials at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.). it can. 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-ray, γ-ray, etc. Active energy ray irradiation polymerization may be adopted.

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

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

The weight average molecular weight (Mw) of the base polymer (preferably acrylic polymer) disclosed herein is not particularly limited and may be, for example, in the range of 10 × 10 ⁴ or more and 500 × 10 ⁴ or less. From the viewpoint of balancing the cohesive force and the adhesive force at a high level, the Mw of the base polymer (suitably an acrylic polymer) is preferably 10 × 10 ^{4 to} 150 × 10 ⁴ , and more preferably 20 × 10 ^{4 to} 110. It is in the range of × 10 ⁴ (for example, 20 × 10 ⁴ to 75 × 10 ⁴ ), and more preferably 35 × 10 ^{4 to} 90 × 10 ⁴ (for example, 35 × 10 ^{4 to} 65 × 10 ⁴ ). Here, Mw refers to a standard polystyrene conversion value obtained by gel permeation chromatography (GPC). As the GPC device, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) may be used. The same applies to the examples described below.

(Rubber polymer)
In another preferable aspect, the pressure-sensitive adhesive layer is made of a rubber-based pressure-sensitive adhesive. The rubber-based pressure-sensitive adhesive according to a further 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 and isoprene. Such block copolymers can be used alone or in combination of two or more as the base polymer.

  The A segment (hard segment) in the block copolymer has a copolymerization ratio of the monovinyl-substituted aromatic compound (two or more kinds thereof can be used in combination) of 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) in the block copolymer, the copolymerization ratio of the conjugated diene compound (two or more kinds can be used in combination) is 70% by weight or more (more preferably 90% by weight or more), and It may be 100% by weight). With such a block copolymer, a higher performance 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 an A segment (for example, a 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 be aggregated to form a domain, thereby forming a pseudo crosslinked structure and improving the cohesiveness of the pressure-sensitive adhesive. The block copolymer in the technology disclosed herein has, for example, a diblock ratio of 30% by weight or more (more preferably 40% by weight) from the viewpoint of adhesion (peeling strength) to an adherend and repulsion resistance. 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 stress continuously applied, 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 to 85% by weight.

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

  The styrenic 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, a styrene block is preferably arranged at the end of the polymer chain. This is because the styrene blocks arranged at the ends of the polymer chains easily aggregate to form a styrene domain, which forms a pseudo cross-linked structure and improves the cohesiveness of the pressure-sensitive adhesive. The styrene block copolymer used in the technique disclosed herein has, for example, a diblock ratio of 30% by weight or more (more preferably, from the viewpoint of adhesive strength (peeling strength) to an 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 block copolymer having a diblock ratio of 70% by weight or more (for example, 75% by weight or more) may be used. From the viewpoint of holding power, etc., a styrene block copolymer having a diblock 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 to 85% by weight can be preferably used.

  The styrene content of the styrene block copolymer may be, for example, 5 to 40% by weight. 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 more than 10% by weight, for example, 12% by weight or more) is usually preferable. Further, from the viewpoint of adhesive strength to an adherend, a styrene block copolymer 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 used.

(Urethane polymer)
In still another preferred aspect, the pressure-sensitive adhesive layer is composed 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 and a polyisocyanate compound as a base polymer. The urethane-based polymer is not particularly limited, and an appropriate urethane-based polymer can be adopted from various urethane-based polymers that can function as an adhesive (ether-based polyurethane, ester-based polyurethane, carbonate-based polyurethane, etc.). 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.

(Filler particles)
The adhesive layer disclosed herein is characterized by including filler particles. This makes it possible to maintain the initial adhesive force A and reduce the tensile peeling stress B at the same time. This point will be described. The filler particles contained in the pressure-sensitive adhesive layer may be present in a state of being exposed on the pressure-sensitive adhesive surface or being encapsulated in the pressure-sensitive adhesive layer. The filler particles exposed on the adhesive surface reduce the area of the adhesive on the adhesive surface and improve the slip property of the adhesive interface in the shear direction. As a result, the tensile peeling stress B is reduced, but the reduction of the pressure-sensitive adhesive area on this pressure-sensitive adhesive surface also causes the reduction of the initial pressure-sensitive adhesive force A. On the other hand, it is considered that the filler particles present inside the pressure-sensitive adhesive layer 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 to interpretation, but it is considered that the state of the pressure-sensitive adhesive layer changes with the deformation of the pressure-sensitive adhesive sheet. Specifically, tensile peeling is a mode in which the pressure-sensitive adhesive is peeled off in a direction parallel to the adhesive surface (pulling peeling direction. Also referred to as shearing direction), and therefore the pressure-sensitive adhesive sheet is deformed in that direction during pulling peeling. .. The stretchable pressure-sensitive adhesive sheet is stretched by the above-mentioned tension, and the pressure-sensitive adhesive layer is also deformed accordingly. For example, when the film-shaped substrate that supports the pressure-sensitive adhesive layer is stretchable with respect to tension, the pressure-sensitive adhesive layer is also largely deformed as the substrate is stretched. It is considered that this deformation of the pressure-sensitive adhesive layer increases the exposure amount of the filler particles contained in the pressure-sensitive adhesive layer to the pressure-sensitive adhesive surface, and improves the slip property in the shearing direction at the bonding interface. It is also considered that the pressure-sensitive adhesive (pressure-sensitive adhesive component) in the pressure-sensitive adhesive layer is deformed by tensile peeling, while the filler particles behave 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 particles with respect to the tensile peeling contributes to the reduction of the tensile peel stress. And, it is considered that the change in the surface state of the pressure-sensitive adhesive layer and the behavior of the pressure-sensitive adhesive layer constituents do not become apparent in, for example, 90 degree peeling or 180 degree peeling, or are negligible due to the difference in peeling mode. Be done. However, it is considered that the stress change is typically greatly affected during tensile peeling. As a result, it is considered that the filler particles contained in the pressure-sensitive adhesive layer greatly contribute to both maintaining the initial pressure-sensitive adhesive force A and reducing the tensile peeling stress B. The effect of including the filler particles is particularly remarkable in the pressure-sensitive adhesive sheet having stretchability. Further, in an extensible pressure-sensitive adhesive sheet having a base material, typically, the mechanical properties of the base material can greatly contribute to the adhesive force (typically, 180-degree peel strength), so that the pressure-sensitive adhesive composition (for example, tackifying It is considered that the contribution of adhesive agents, cross-linking agents and other added components) to the adhesive strength is relatively small. In such a pressure-sensitive adhesive sheet, by including filler particles in the pressure-sensitive adhesive layer, the effect of selectively reducing only the tensile peeling stress B while maintaining the initial pressure-sensitive adhesive force A is realized.

  The type of filler particles used is not particularly limited. For example, a particulate or fibrous filler can be used. The constituent material of the filler particles (typically particulate filler) is, for example, a metal such as copper, silver, gold, platinum, nickel, aluminum, chromium, iron, stainless steel; aluminum oxide, silicon oxide (silicon dioxide), oxidation Metal oxides such as titanium, 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, Metal hydroxides and hydrated metal compounds such as barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dawsonite, borax, zinc borate; silicon carbide, boron carbide, Carbides such as nitrogen carbide and calcium carbide; nitriding of aluminum nitride, silicon nitride, boron nitride, gallium nitride, etc. Carbonates such as calcium carbonate; titanates such as barium titanate and potassium titanate; carbon-based substances such as carbon black, carbon tubes (carbon nanotubes), carbon fibers, diamonds; inorganic materials such as glass; polystyrene; It may be an acrylic resin (for example, polymethylmethacrylate), a phenol resin, a benzoguanamine resin, a urea resin, a silicone resin, a polyester, a polyurethane, a polyethylene, a polypropylene, a polyamide (for example, nylon), a polyimide, a polymer such as polyvinylidene chloride, 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 may be used alone or in combination of two or more. Among them, the particulate filler is preferable from the viewpoint of reducing the tensile peeling stress, and among them, the particulate filler composed of an inorganic material (for example, aluminum hydroxide) is preferably used.

  50% by weight or more of the filler particles contained in the pressure-sensitive adhesive layer has a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer. As a result, the adhesive surface has a greater tendency to maintain a good surface state and can exhibit desired adhesive properties (for example, initial adhesive force A). In addition, the appearance of the surface of the pressure-sensitive adhesive layer is maintained well. 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 particles contained in the pressure-sensitive adhesive layer has a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer. .. It is more preferable that substantially all (typically 99 to 100% by weight) of the filler particles contained in the pressure-sensitive adhesive layer have a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer. In another preferred embodiment, from the viewpoint of improving the surface state of the adhesive surface, 40% by weight or more of the filler particles contained in the adhesive layer (for example, 50% by weight or more, typically 55% by weight or more). Has a particle diameter smaller than ⅔ (that is, ⅔T, more preferably ½, that is, ½T) of the thickness T of the pressure-sensitive adhesive layer. It should be noted that that X wt% or more of the filler particles have a particle size smaller than Y means that the cumulative particle size (weight basis) up to the particle size Y (μm) is X (in the particle size distribution obtained by the measurement based on the sieving method. Less than 100% by weight). The proportion (% by weight) of filler particles having a predetermined particle diameter can be determined based on the above particle size distribution.

  In a preferred embodiment, the filler particles contained in the pressure-sensitive adhesive layer account for 50% by weight or more (for example, 70% by weight or more, typically 90% by weight or more) of particles having a particle size of less than 30 μm. The pressure-sensitive adhesive layer containing such filler particles is advantageous in that the smoothness of the pressure-sensitive adhesive surface is not easily impaired even if the content of the filler particles is relatively large, and the adhesive strength is maintained and the appearance is improved. The filler particles contained in the pressure-sensitive adhesive layer have 50% by weight or more (eg 70% by weight or more, typically 80% by weight or more) of particles having a particle size of less than 20 μm (eg less than 15 μm, typically less than 10 μm). More preferably.

  Further, in a preferred aspect, the proportion of particles having a particle diameter of less than 1 μm is 50% by weight or less among the filler particles contained in the pressure-sensitive adhesive layer. From the viewpoint of reducing the tensile peeling stress, it is desirable that the filler particles have a certain size. Further, it is preferable that the amount of the 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 filler particles contained in the pressure-sensitive adhesive layer, the proportion of particles having a particle size of less than 1 μm (eg, less than 2 μm, typically less than 5 μm) is 30 wt% or less (eg, 10 wt% or less, typically 5% by weight or less) is more preferable.

  The average particle size of all the filler particles contained in the pressure-sensitive adhesive layer is usually 0.5 μm or more, and preferably 0.8 μm or more (for example, 3 μm or more, typically 5 μm or more). When the average particle size is large, the effect of reducing the tensile peel stress tends to be improved, and the tensile peel stress B can be efficiently reduced by adding a small amount of filler particles. Setting the average particle size to a predetermined value or more is also preferable 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 30 μm or less, more preferably 25 μm or less, still more preferably 15 μm or less. When the average particle size is small, the decrease in adhesive performance tends to be suppressed. It is desirable that the average particle size is also small in terms of the appearance of the adhesive surface. In this specification, the average particle size of the filler particles means a particle size (50% median size) at which the weight-based cumulative particle size is 50% in the particle size distribution obtained by the measurement based on the sieving method. ..

  The shape of the filler particles is not particularly limited, and may be, for example, a bulk shape, a needle shape, a plate shape (for example, a hexagonal plate shape), a layer shape, or the like. The concept of the bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, or an irregular shape thereof. The shape of the filler particles is preferably a bulk shape, and among them, a spherical shape is more preferable.

  The average aspect ratio of the filler particles is not particularly limited, and from the viewpoint of reducing the tensile peeling stress, it is suitable that it is less than about 100, preferably less than 50, more preferably less than 10 (eg less than 5, typically less than 2). Can be Here, the average aspect ratio of the filler particles is obtained as an average value of the aspect ratios of the respective particles represented by the long diameter / short diameter in the filler particles. The major axis typically refers to the maximum differential length of the particles to be measured, and the minor axis typically refers to the minimum differential length of the particles to be measured. The average aspect ratio can be ascertained through transmission electron microscope observation.

The content C of the filler particles in the pressure-sensitive adhesive layer is appropriately 30% by volume or less. By appropriately adjusting the particle size and content of the filler particles, it is possible to preferably reduce the tensile peeling stress B while suppressing the decrease in the initial adhesive force A. The content C of the filler particles in the pressure-sensitive adhesive layer is preferably 25% by volume or less, more preferably 20% by volume or less (for example, 16% by volume or less, typically 14% by volume or less). From the viewpoint of reducing the tensile peeling stress, the content C is suitably 0.3% by volume or more, preferably 2% by volume or more, more preferably 3% by volume or more (for example, 5% by volume). % Or more, typically 10% by volume or more). Since the technology disclosed herein can exhibit a desired effect by adding a small amount of filler particles, the pressure-sensitive adhesive layer (pressure-sensitive adhesive composition) contains a component (dispersant) that improves the dispersibility of the filler particles. May not be included, or the above dispersant may be included. The content C [volume%] of the filler particles is determined based on the weight ratio and density of components (typically the adhesive component) other than the filler particles in the pressure-sensitive adhesive layer, and the weight ratio and density of the filler particles. For example, in the examples described below, 2.42 g / cm ³ is adopted as the density of aluminum hydroxide, and the content C [volume%] of the filler particles in the pressure-sensitive adhesive layer can be determined.

  Further, the content of the filler particles (for example, inorganic material particles, typically a metal oxide or a metal hydroxide) in the pressure-sensitive adhesive layer is less than 100 parts by weight based on 100 parts by weight of the base polymer. Is appropriate. By appropriately adjusting the particle size and content of the filler particles, it is possible to preferably reduce the tensile peeling stress B while suppressing the decrease in the initial adhesive force A. The content of the filler particles in the pressure-sensitive adhesive layer is preferably 80 parts by weight or less, more preferably 60 parts by weight or less (for example, 45 parts by weight or less, typically 35 parts by weight or less) with respect to 100 parts by weight of the base polymer. ). From the viewpoint of reducing the tensile peeling stress, the content is suitably 0.5 parts by weight or more, preferably 3 parts by weight or more, more preferably 8 parts by weight or more (for example, 12 parts by weight). Above, typically 25 parts by weight or more).

(Acrylic oligomer)
The PSA composition disclosed herein may include 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 of a mode in which the pressure-sensitive adhesive composition is cured by irradiation with active energy rays (for example, UV irradiation), the acrylic-based oligomer inhibits curing (for example, It has an advantage of being less likely to cause (polymerization inhibition of a reaction monomer). The acrylic oligomer is a polymer containing an acrylic monomer as its constituent monomer component, and is defined as a polymer having a smaller Mw than the acrylic polymer.

  The proportion of the acrylic monomer in all the monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (eg 80% by weight). Above, further 90% by weight or more). In a preferred embodiment, the acrylic oligomer has a monomer composition consisting essentially of acrylic monomers.

  As the constituent monomer component of the acrylic oligomer, the chain alkyl (meth) acrylate, the functional group-containing monomer, and other monomers exemplified as the monomer that can be used in the acrylic polymer can be used. Further, the above-mentioned constituent monomer may contain an alicyclic hydrocarbon group-containing (meth) acrylate. As the monomer component constituting the acrylic oligomer, one kind or two or more kinds 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, 2-ethylhexyl acrylate (2EHA). Among them, MMA is more preferable.

  Preferred examples of the functional group-containing monomer include N-vinyl-2-pyrrolidone, N-acryloylmorpholine, and other monomers having a nitrogen atom-containing ring (typically, a nitrogen atom-containing heterocycle); 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; hydroxyl group-containing monomers such as HEA.

  As the alicyclic hydrocarbon group-containing (meth) acrylate, for example, one type of alicyclic hydrocarbon group-containing (meth) acrylate in which the alicyclic hydrocarbon group has 4 to 20 carbon atoms. Alternatively, two or more kinds can be used. The number of carbon atoms in the alicyclic hydrocarbon group is preferably 5 or more (eg 6 or more, typically 8 or more), and preferably 16 or less (eg 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. Among them, dicyclopentanyl methacrylate (DCPMA) is more preferable.

  From the viewpoint of adhesiveness and cohesiveness, the proportion of the alicyclic hydrocarbon group-containing (meth) acrylate in all the monomer components constituting the acrylic oligomer (that is, the copolymerization proportion) is about 30 to 90% by weight ( For example, it is preferably 50 to 80% by weight, typically 55 to 70% by weight).

  In a preferred embodiment, the acrylic oligomer contains a chain alkyl (meth) acrylate and / or an alicyclic hydrocarbon group-containing (meth) acrylate as its constituent monomer component. In this aspect, the proportion of the chain alkyl group-containing and alicyclic hydrocarbon group-containing (meth) acrylic acid ester in all the monomer components constituting the acrylic oligomer is approximately 80% by weight or more (for example, 90 to 100). % By weight, typically 95-100% by weight). 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 1: 9 to 9: 1, preferably 2: 8-7: 3 (e.g., 3: 7-6: 4, typically 3: 7-5: 5) Is.

  Although not particularly limited, the composition (that is, the polymerization composition) of the constituent monomer components of the acrylic oligomer 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 refers to 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 (eg 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.

The Mw of the acrylic oligomer is not particularly limited, but is typically about 0.1 × 10 ^{4 to} 3 × 10 ⁴ . From the viewpoint of improving adhesive properties (for example, adhesive strength and repulsion resistance), the Mw of the acrylic oligomer is preferably 1.5 × 10 ⁴ or less, more preferably 1 × 10 ⁴ or less, and 0.8 × 10 ⁴ or less. (For example, 0.6 × 10 ⁴ or less) is more preferable. From the viewpoint of the cohesiveness of the pressure-sensitive adhesive, the Mw is preferably 0.2 × 10 ⁴ or more (for example, 0.3 × 10 ⁴ or more). The molecular weight of the acrylic oligomer can be adjusted, for example, by using a chain transfer agent at the time of polymerization.

  The acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be adopted in an appropriate mode. The types and the amounts of the polymerization initiators (for example, azo polymerization initiators such as AIBN) that can be used as necessary are also approximately as described above, and therefore the description thereof will not be repeated here.

  The content of the acrylic oligomer in the pressure-sensitive adhesive composition disclosed herein is appropriately 0.5 parts by weight or more based on 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). .. From the viewpoint of the curability of the pressure-sensitive adhesive composition and the compatibility with the acrylic polymer, the content of the acrylic oligomer is appropriately less than 50 parts by weight (eg 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 if such a small amount is added, the impact resistance and the repulsion resistance can be improved by using the acrylic oligomer.

(Tackifier)
The pressure-sensitive adhesive layer disclosed herein may be a composition containing a tackifier. The tackifier is not particularly limited, for example, rosin tackifier resin, terpene tackifier resin, hydrocarbon tackifier resin, epoxy tackifier resin, polyamide tackifier resin, elastomer tackifier resin, Various tackifying resins such as phenol-based tackifying resins and ketone-based tackifying resins can be used. Such tackifier resins may be used alone or in combination of two or more.

  Specific examples of the rosin-based tackifying resin include unmodified rosins such as gum rosin, wood rosin and tall oil rosin (raw rosin); modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization or the like ( Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc. (the same applies hereinafter); various other rosin derivatives; and the like. Examples of the rosin derivative include rosin such as unmodified rosin esterified with alcohols (that is, rosin esterification product) and modified rosin esterified with alcohols (that is, modified rosin esterification product). Esters: Unmodified rosin or unsaturated fatty acid modified rosin obtained by modifying modified rosin with unsaturated fatty acid; Unsaturated fatty acid modified rosin ester obtained by modifying rosin ester with unsaturated fatty acid; Unmodified rosin, modified rosin, 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 rosin, modified rosin, and various rosin derivatives; rosins (Unmodified rosin, modified rosin, various rosin derivatives, etc.) Rosin phenol resins obtained by thermal polymerization by adding Lumpur acid catalyst; and the like. When an acrylic polymer is used as the base polymer, it is preferable to use a rosin-based tackifying 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 more of them having different types and properties (eg, softening point) may be used in combination. More preferably.

  Examples of terpene-based tackifier resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; modification of these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbons). Modified terpene resin; Examples of the modified terpene resin include terpene modified phenol resin, styrene modified terpene resin, aromatic modified terpene resin and hydrogenated terpene resin. When an acrylic polymer is used as the base polymer, it is preferable to use a terpene-based tackifying resin (for example, a terpene-modified phenol 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 phenol resin) having different types and properties (for example, softening point) are used in combination. Preferably.

  Examples of the hydrocarbon-based tackifying resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc. ), Aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone-indene-based resins, and various other hydrocarbon-based resins.

  In the technology disclosed herein, as the tackifying resin, one 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. With the pressure-sensitive adhesive containing the tackifying resin having a softening point equal to or higher than the lower limit value described above, a pressure-sensitive adhesive sheet having more excellent adhesive force can be realized. Among the tackifying resins exemplified above, terpene-based tackifying resins having the above softening point (for example, terpene-modified phenol resin), rosin-based tackifying resins (for example, esterified products of polymerized rosin) and the like can be preferably used. The upper limit of the softening point of the tackifying 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 tackifying resin here is defined as a value measured by the softening point test method (ring and ball method) defined in either JIS K5902 or JIS K2207.

  The amount of the tackifier used is not particularly limited and can be appropriately set according to the desired tacking performance (adhesive strength, etc.). For example, the tackifier is used in an amount of about 10 to 100 parts by weight (more preferably 20 to 80 parts by weight, further preferably 30 to 60 parts by weight) based on 100 parts by weight of the acrylic polymer based on the solid content. Preferably. The technique disclosed herein may be implemented in an aspect including a pressure-sensitive adhesive layer that does not substantially contain a tackifier.

  When the pressure-sensitive adhesive layer is made 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 a tackifying resin. The pressure-sensitive adhesive sheet of this aspect is preferable from the viewpoint of repulsion resistance and holding power. In a preferred embodiment, the high softening point resin may include a tackifying resin having a softening point of 125 ° C or higher (more preferably 130 ° C or higher, further preferably 135 ° C or higher, for example 140 ° C or higher). In addition, from the viewpoint of the adhesive strength to the adherend, etc., the softening point of the above high softening point resin is usually 200 ° C. or lower, preferably 180 ° C. or lower, more preferably 170 ° C. or lower (eg 160 ° C. or lower). ).

  As the high softening point resin, terpene phenol resin, polymerized rosin, esterified product of polymerized rosin and the like can be preferably adopted. These high softening point resins can be used alone or in appropriate combination of two or more kinds. As a preferable embodiment, an embodiment in which the high softening point resin contains one or more kinds of terpene phenol resins can be mentioned. 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 used.

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

  In the technology disclosed herein, for example, 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 to 160 mgKOH / g, for example, 80 to 140 mgKOH / g) can be preferably carried out in an embodiment including a combination with a high softening point resin (H2). In this case, the relationship between the amounts of the high softening point resin (H1) and the high softening point resin (H2) used is such that the weight ratio (H1: H2) is in the range of 1: 5 to 5: 1. Can be set to, and normally, it is suitable to set it in the range of 1: 3 to 3: 1 (for example, 1: 2 to 2: 1). As one preferable embodiment, there is an embodiment in which both the high softening point resin (H1) and the high softening point resin (H2) are terpene phenol resins.

  From the viewpoint of repulsion resistance, holding power, etc., the content of the high softening point resin may be, for example, 20 parts by weight or more, and 30 parts by weight or more (eg 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 and low temperature characteristics, the content of the high softening point resin is usually 100 parts by weight or less, preferably 80 parts by weight or less, and more preferably 100 parts by weight based on 100 parts by weight of the base polymer. 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).

  In the technology disclosed herein, the rubber-based pressure-sensitive adhesive contains a low softening point resin having a softening point of less than 120 ° C. instead of the high softening point resin or in addition to the high softening point resin. Can be implemented. In 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, one having a softening point of 40 ° C. or higher (typically 60 ° C. or higher) can be used. From the viewpoint of repulsion resistance, holding power, etc., a softening point of usually 80 ° C. or higher (more preferably 100 ° C. or higher) and lower than 120 ° C. can be preferably used. 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 mode in which the rubber 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 that accounts for more than 50% by weight of the low softening point resin) is a composition that is a petroleum resin, a composition that is a terpene resin, or a combination of a petroleum resin and a terpene resin. A certain composition or the like can be preferably adopted. From the viewpoint of adhesive strength and compatibility, an embodiment in which the main component of the low softening point resin is a terpene resin (for example, β-pinene polymer) is preferable. Substantially all (eg 95% by weight or more) of the low softening point resin may be a terpene resin.

  In a preferred embodiment, the low softening point resin may be a tackifying resin having a hydroxyl value of 0 or more and less than 80 mgKOH / g (low hydroxyl value tackifying resin). As the low hydroxyl value tackifying resin, those having a hydroxyl value in the above range among the above-mentioned various tackifying resins can be used alone or in combination. 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 petroleum resin), a terpene resin (for example, β-pinene polymer), a rosin resin (for example, polymerized rosin), 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 an 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 (eg 20 parts by weight) with respect to 100 parts by weight of the base polymer. The 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, more preferably 70 parts by weight or less (for example, 60 parts by weight or less). Parts 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 tackifying resin contains a low softening point resin and a high softening point resin, the relationship between the amounts of the resins used is that the weight ratio of low softening point resin: high softening point resin is 1: 5 to 3: 1 (more preferably Is preferably set to 1: 5 to 2: 1). In the technology disclosed herein, the rubber-based pressure-sensitive adhesive contains a large amount of a high softening point resin as a tackifying resin rather than a low softening point resin (for example, a weight ratio of low softening point resin: high softening point resin is 1). : 1.2 to 1: 5). According to such an aspect, a higher performance adhesive sheet can be realized.

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

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

  The amount of the crosslinking agent used is not particularly limited, and for example, is about 10 parts by weight or less (for example, about 0.005 to 10 parts by weight, preferably about 0.01 to about 100 parts by weight of the base polymer (for example, an acrylic polymer)). 5 parts by weight). Since the technology disclosed herein can realize a desired tensile peel stress B without reducing the amount of the crosslinking agent used, the amount of the crosslinking agent used is approximately 0 relative to 100 parts by weight of the acrylic polymer. 1 part by weight or more (for example, 0.8 parts by weight or more, typically 1.2 parts by weight or more). Further, from the viewpoint of limiting the cohesive force and reducing the tensile peeling stress B, the amount of the crosslinking 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 based on 100 parts by weight of the acrylic polymer. May be 2 parts by weight or less).

(Other ingredients)
The pressure-sensitive adhesive composition is, if necessary, a leveling agent, a crosslinking aid, a plasticizer, a softening agent, a colorant (dye, pigment), an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light agent. It may contain various additives commonly used in the field of pressure-sensitive adhesive compositions, such as stabilizers and dispersants. Further, for example, an adhesiveness adjusting agent such as a silicone-based oligomer may be added to the adhesive composition (typically an acrylic adhesive composition). As such various additives, conventionally known ones can be used by a conventional method, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

(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-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, an active energy ray-curable pressure-sensitive adhesive composition. .. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer-forming component) in a solvent containing water as a main component (water-based solvent), and typically, a water dispersion. Type adhesive compositions (compositions in which at least a part of the adhesive is dispersed in water) and the like are included. In addition, the solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in which an organic solvent contains a pressure-sensitive adhesive. The technology disclosed herein is preferably carried out in an aspect including a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition, from the viewpoint of suitably realizing pressure-sensitive adhesive properties such as pressure-sensitive adhesive force.

(Method of forming pressure-sensitive 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 surface having peelability (peeling surface) and drying the composition can be adopted. Alternatively, a method (direct method) in which the pressure-sensitive adhesive composition is directly applied (typically applied) to the film-shaped substrate and dried to form the pressure-sensitive adhesive layer can be employed. In addition, a method of forming a pressure-sensitive adhesive layer on the surface having peelability (release surface) by applying the pressure-sensitive adhesive composition and drying the surface, and transferring the pressure-sensitive adhesive layer to a film-shaped substrate (transfer Method) may be adopted. As the release surface, the surface of the release liner, the back surface of the release-treated substrate, or the like can be used. Note that the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and for example, in a regular or random pattern such as dots or stripes. It may be the 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, and a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, curtain coating, or the like. The pressure-sensitive adhesive composition is preferably dried under heating from the viewpoint of promoting the crosslinking reaction, improving production efficiency, and the like. The drying temperature can be, for example, about 40 to 150 ° C (preferably about 60 to 130 ° C). After the pressure-sensitive adhesive composition is dried, further aging may be performed for the purpose of adjusting the migration of components in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, and relaxing the strain that may be present in the substrate or pressure-sensitive adhesive layer. Good.

(Thickness of adhesive layer)
The thickness of the pressure-sensitive adhesive layer disclosed herein is not particularly limited and can be appropriately selected according to the purpose. Usually, the thickness of the pressure-sensitive adhesive layer is appropriately about 3 to 200 μm, preferably about 5 to 150 μm, and more preferably 8 to 100 μm from the viewpoint of productivity such as drying efficiency and adhesive performance. , And more preferably 15 to 80 μm. In the case of a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a film-shaped substrate, the thickness of each pressure-sensitive adhesive layer may be the same or different.

<Film base material>
The film-like substrate disclosed herein preferably exhibits a breaking strength of 10 MPa or more. By using the film-shaped substrate having the above breaking strength, the pressure-sensitive adhesive sheet becomes more difficult to be torn, and excellent tensile removability can be exhibited. According to the film-shaped substrate having the above breaking strength, the workability tends to be improved. The breaking strength is more preferably 30 MPa or more (for example, 45 MPa or more, typically 60 MPa or more). From the viewpoint of elasticity and extensibility of the film-shaped substrate, 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 that for the pressure-sensitive adhesive sheet. The same method is adopted for the examples described later. The breaking strength of the base material can be adjusted by, for example, selection of the base material type (selection of the mixing ratio of the hard component and the soft component), the molding method, and the like.

  The film-shaped substrate disclosed herein preferably has extensibility. A stretchable pressure-sensitive adhesive sheet is preferably realized by using a stretchable substrate. By using the extensible substrate, the shape of the film can be deformed with relatively low stress due to its flexibility. The elongation at break of the film substrate can be 50% or more (eg 100% or more, typically 200% or more). In a preferred embodiment, the film-like substrate exhibits an elongation at break of 300% or more. The substrate exhibiting the elongation at break stretches with respect to the tension when the pressure-sensitive adhesive sheet is removed. Due to this extension, the adhesive sheet is deformed and peeled off from the adherend. In this way, the tensile force and the deformation of the base material interact with each other, and the tensile removability of the pressure-sensitive adhesive sheet is further improved. 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 workability for removal and the like. The elongation at break is measured by the same method as that for the pressure-sensitive adhesive sheet. The same method is adopted for the examples described later. The elongation at break of the base material can be adjusted by, for example, selection of the base material type (selection of the mixing ratio of the hard component and the soft component), the molding method, and the like.

  The film substrate disclosed herein suitably 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% to 100%). As a result, damage such as tearing at the time of removing the adhesive sheet can be more highly prevented. The measurement of the tensile recovery rate is performed by the same method as the method for measuring the tensile recovery rate of the pressure-sensitive adhesive sheet. The same method is adopted for the examples described later. The tensile recovery rate of the base material can be adjusted, for example, by selecting the type of base material (selecting the mixing ratio of the hard component and the soft component) and the molding method.

  The filmy substrates disclosed herein preferably exhibit a 5% modulus of less than 10 MPa. By setting the 5% modulus of the film-shaped substrate to be less than the predetermined value, when the adhesive sheet is removed from the adherend by stretching and deforming the pressure-sensitive adhesive sheet, the resistance at the beginning of pulling tends to be small and the pulling removability tends to be excellent. is there. The 5% modulus is more preferably less than 5 MPa (eg less than 3 MPa, typically less than 2 MPa). The lower limit of the above-mentioned 5% modulus is not particularly limited, but from the viewpoint of workability of sticking the pressure-sensitive adhesive sheet, it is usually suitable to be 0.5 MPa or more (eg 1 MPa or more). The 5% modulus is measured according to the measuring method of "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 interval 20 mm) is pulled at a pulling speed of 300 mm / min and the marked line distance is extended by 5% [MPa] ] To be 5% modulus. As the tensile tester, a product name “Autograph AG-10G type tensile tester” manufactured by Shimadzu Corporation can be used. The same method is adopted for the examples described later. The 5% modulus of the base material can be adjusted by, for example, selection of the base material type (selection of the mixing ratio of the hard component and the soft component), the molding method and the like.

  The film-like substrate disclosed herein preferably exhibits a 100% modulus of less than 10 MPa. By setting the 100% modulus of the film-like substrate to be less than a predetermined value, when the adhesive sheet is removed from the adherend by stretching and deforming the adhesive sheet, the resistance at the beginning of pulling tends to be small and the pulling 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 the workability of sticking the pressure-sensitive adhesive sheet, it is usually suitable 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 in the pressure-sensitive adhesive sheet. A similar method can be adopted for the examples described below.

  The filmy substrates disclosed herein preferably exhibit a 150% modulus of less than 20 MPa. When the 150% modulus of the film-shaped substrate is less than a predetermined value, when the adhesive sheet is removed from the adherend by stretching and deforming the adhesive sheet, the resistance during pulling and removing work tends to be small. The 150% modulus is more preferably less than 15 MPa (eg less than 12 MPa, typically less than 8 MPa). The lower limit of the above 150% modulus is not particularly limited, but from the viewpoint of workability of sticking the pressure-sensitive adhesive sheet, it is usually appropriate to set it to 1 MPa or more (for example, 5 MPa or more). The 150% modulus is measured according to the “tensile stress” measuring method described in JIS K 7311: 1995. More specifically, a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm) was used to pull at a pulling speed of 300 mm / min, and the stress [MPa when the marked line distance was extended by 150%] ] Is a 150% modulus. As the tensile tester, a product name “Autograph AG-10G type tensile tester” manufactured by Shimadzu Corporation can be used. The same method is adopted for the examples described later. The 150% modulus of the base material can be adjusted by, for example, selection of the base material material (selection of the mixing ratio of the hard component and the soft component) and the molding method.

As the film-shaped substrate (supporting substrate) that supports (backs) the pressure-sensitive adhesive layer, various film-shaped substrates can be used. As the base material, for example, a woven film, a non-woven film, or a resin film can be used. Of these, a resin film is preferable. The resin film may be a non-foamed resin film, a rubber film, a foam film or the like. Of these, non-foamed resin films and rubber-like films are preferable, and non-foamed 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 have excellent mechanical strength such as tensile strength as compared with a foamed body. The non-foamed resin film is also excellent in processability, dimensional stability, thickness accuracy, economy (cost) and the like.
The "resin film" in this 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 foamed body. The non-foamed resin film may specifically 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). Non-foamed resin films include, for example, soft resin films 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 polyurethane such as ether polyurethane, ester polyurethane and carbonate polyurethane; urethane (meth) acrylate polymer; polyethylene (PE) and polypropylene (PP). , Ethylene-propylene copolymers, ethylene-butene copolymers, and other polyolefins; polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate, and polybutylene naphthalate; polycarbonates; 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 polymer (typically a styrene elastomer), an acrylic copolymer called acrylic rubber, or a vinyl chloride resin (PVC) such as soft polyvinyl chloride. Good. The said resin material can be used individually by 1 type or in combination of 2 or more types. The resin material includes what is generally called rubber or thermoplastic elastomer.

  In a preferred embodiment, the film-shaped substrate is a polyurethane resin film. Here, the polyurethane resin film refers to a resin film containing polyurethane as a main component of a resin component (a component with the highest compounding ratio, typically a component contained in excess of 50% by weight; the same applies hereinafter). .. Polyurethane-based resin film is typically composed of a material that does not substantially show a yield point, and is a film material that easily realizes a pressure-sensitive 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 therefore, in terms of preventing bleed-out of the additive component, a preferable group in the technology disclosed herein. It can be a material.

  The proportion of polyurethane in the resin component contained in the polyurethane resin film is preferably 70% by weight or more (eg 80% by weight or more, typically 90% by weight or more and 100% by weight or less). The polyurethane resin film disclosed herein may be a film made of a polymer blend of polyurethane and another resin. The above-mentioned other resin may be, for example, one kind or two or more kinds of acrylic resin, polyolefin, polyester, polycarbonate and the like. Alternatively, the technology disclosed herein can also be implemented in an embodiment using a substrate that does not substantially contain a resin component other than polyurethane.

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

  Examples of the polyol that can be used for the synthesis of the polyurethane include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexane. Diols such as diols, 1,8-octanediol, polyoxytetramethylene glycol, diethylene glycol, polyethylene glycol and polypropylene glycol; polyesters which are polycondensates of the above diols and dicarboxylic acids (eg adipic acid, azelaic acid, sebacic acid) Polyol; carbonate diol such as polyalkylene carbonate diol; and the like. These may 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, dimers 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, 1,3-phenylene diisocyanate. , 1,4-phenylene diisocyanate, 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 (isocyanatomethyl) cyclohexane, methylcyclohexyl Down diisocyanate, m- tetramethylxylylene diisocyanate, and the like. These may be used alone or in combination of two or more. Of these, aromatic diisocyanates are preferred.

  In addition to the polyol and the polyisocyanate, other copolymer components may be introduced into the polyurethane. As the other copolymerization component, one kind or two or more kinds of a monocarboxylic acid, a dicarboxylic acid, a trifunctional or higher functional polycarboxylic acid, a hydroxycarboxylic acid, an alkoxycarboxylic acid, a derivative thereof or the like can be used. The proportion of these other copolymerization components is suitably about 30% by weight (eg, less than 10% by weight, typically less than 5% by weight) in the polyurethane. The technique disclosed herein can also be preferably implemented in an aspect including a polyurethane-based resin film substrate containing polyurethane as a main component that does not contain other copolymerization components.

  In another preferable aspect, the film-shaped 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 can be used individually by 1 type or in combination of 2 or more types. The urethane (meth) acrylate preferably has two or more urethane bonds and two or more (meth) acryloyl groups. 2-5 are preferable and, as for the number of the (meth) acryloyl groups which urethane (meth) acrylate has, 2-3 are more preferable. For example, urethane (meth) acrylate having two (meth) acryloyl groups can be preferably used. Further, the urethane (meth) acrylate is preferably urethane acrylate. Here, "urethane acrylate" refers to one in which the number ratio of acryloyl groups among the (meth) acryloyl groups contained in urethane (meth) acrylate exceeds 50%.

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

  In another preferable embodiment, the film-shaped substrate is a PVC resin film. The PVC resin film is produced by molding a PVC resin composition (molding material) containing a PVC resin into a film. Here, the PVC 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 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 components contained in the PVC resin composition is the PVC resin. Substantially all of the resin component may be PVC. According to such a PVC resin composition, a PVC resin film having physical properties suitable as a base material for an adhesive sheet can be formed.

  For film-like substrates (eg resin film substrates), if necessary, fillers (inorganic fillers, organic fillers, etc.), colorants (pigments, dyes), antioxidants, antioxidants, ultraviolet absorbers Various additives such as agents, antistatic agents, lubricants, plasticizers and stabilizers may be blended. For example, when a soft PVC resin film is used as the film-shaped substrate, the compounding amount of the plasticizer is about 20 to 100 parts by weight (more preferably about 30 to 70 parts by weight) per 100 parts by weight of the PVC resin. Is appropriate. The mixing ratio of 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 substrate may be subjected to a conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoating agent. Such a surface treatment may be a treatment for improving the adhesion between the film-shaped substrate and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the substrate. When the film-shaped substrate is a polyurethane-based resin film, good anchorage can be obtained owing to its high surface energy even without the above-mentioned surface treatment.

  The film-shaped substrate may have a single-layer structure or a multi-layer structure having two layers, three layers or more. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the above resin (more preferably polyurethane). The method for producing the film-shaped substrate may be any conventionally known method, and is not particularly limited. When a resin film substrate is used as the film substrate, it is prepared by appropriately adopting a conventionally known general film forming method such as extrusion molding, inflation molding, T die cast molding, calender roll molding and the like. A resin film substrate can be used.

  The thickness of the film-shaped substrate is not particularly limited and can be appropriately selected depending on the purpose. Usually, it is suitable to be 10 μm or more, preferably about 30 μm or more (for example, 40 μm or more, typically 70 μm or more). The film-like base material having the above-mentioned thickness can be hard to be torn and can be excellent in tensile removability. It is suitable that the thickness of the film-shaped substrate is 3 mm or less (for example, 2 mm or less, typically 1.5 mm or less). The thickness of the film-shaped substrate is preferably 300 μm or less, more preferably 200 μm or less (eg 150 μm or less, typically 120 μm or less). For example, the above thickness is preferably applied to a non-foamed resin film substrate. According to the technique disclosed here, good tensile removability can be realized even in a configuration using a base material having a thickness not more than the above predetermined value. Further, reducing the thickness of the film-shaped substrate is advantageous in terms of thinning the pressure-sensitive adhesive sheet, downsizing, weight saving, resource saving, and the like.

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

<Adhesive sheet size, etc.>
When the pressure-sensitive adhesive sheet disclosed herein has a long 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. The width of the pressure-sensitive adhesive sheet is preferably 1 mm or more (for example, 3 mm or more, typically 5 mm or more), and is 10 mm or more (for example, 12 mm or more), from the viewpoint of preventing damage such as tearing during tensile removal. Is more preferable. In addition, when the whole adhesive sheet is elongate, the above-mentioned width becomes the width of the adhesive sheet.

  When the pressure-sensitive adhesive sheet disclosed herein has a long shape, the length thereof is preferably 1 cm or more (eg, 3 cm or more, typically 5 cm or more) from the viewpoint of workability of removing by pulling. From the viewpoint of removing workability, the length of the pressure-sensitive adhesive sheet is preferably 30 cm or less (for example, 15 cm or less, typically 5 cm or less).

  The total thickness of the pressure-sensitive adhesive sheet disclosed herein (including the pressure-sensitive adhesive layer and the base material, but not including the release liner) is not particularly limited and is in the range of approximately 20 μm to 5 mm (for example, 40 to 1000 μm). Is appropriate. The total thickness of the pressure-sensitive adhesive sheet is preferably about 50 to 300 μm (for example, 70 to 200 μm) in consideration of adhesive properties and the like. When the total thickness of the pressure-sensitive adhesive sheet is set to a predetermined value or less, it may be advantageous in terms of thinning the product, downsizing, weight saving, resource saving, and the like. In another preferred aspect, the total thickness of the pressure-sensitive adhesive sheet may be 80 μm or more (eg, 100 μm or more, typically 130 μm or more), and is more than 150 μm (eg, more than 300 μm, typically more than 500 μm). May be. The pressure-sensitive adhesive sheet having such a total thickness can be preferably used, for example, for fixing an adherend to be reattached after being attached to a wall surface or the like and used for a predetermined period.

  The pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and examples thereof include metallic materials such as stainless steel (SUS) and aluminum; inorganic materials such as glass and ceramics; nylon, polycarbonate (PC), polymethylmethacrylate (PMMA), A resin material such as polypropylene or polyethylene terephthalate (PET); a rubber material such as natural rubber or butyl rubber; and an adherend having a surface made of a composite material thereof can be used by being attached.

<Use>
The pressure-sensitive adhesive sheet disclosed herein exhibits a sufficient adhesive function when used, and has excellent tensile removability when removed. Taking advantage of this feature, it is preferably used as a pressure-sensitive adhesive sheet for various purposes that can be peeled off again after pasting. For example, for fixing a protection panel (lens) that protects the display unit for electronic devices, fixing a decoration panel of a display (for example, a TV display), fixing a battery pack of a personal computer, waterproofing a lens of a digital video camera, etc. The adhesive sheet disclosed here can be applied. Among them, it can be preferably used as a pressure-sensitive adhesive sheet for portable electronic devices, which requires a predetermined or more adhesive force at the time of use, but requires smooth removal at the time of repair, replacement, inspection, recycling, etc. of constituent members. For example, mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear type worn on the wrist like a wristwatch, modular type worn on a part of the body with clips or straps, glasses type) (Eyewear type including monocular type and binocular type, including head mounted 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 devices (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable televisions, portable phones Protects the display of portable electronic devices such as printers, portable scanners, and portable modems. Protective panel (lens) fixing, key module member fixing, rim sheet fixing, decoration panel fixing, battery fixing, various other members (circuit board, various panel members, buttons, lighting equipment members, internal camera members, heat dissipation materials, graphite sheets) It can be preferably applied to applications such as fixing of, and fixing of display objects (including various marks) such as logos (design characters) and various designs. Since the pressure-sensitive adhesive sheet disclosed herein exhibits a predetermined or higher pressure-sensitive adhesive force, when used in the portable electronic device, the adherend member is fixed against the impact when the portable electronic device falls. Can hold the configuration. This is particularly advantageous in battery fastening applications. This is because the battery to be fixed can expand over time, so there is a gap around it, and improper fixing (peeling of the adhesive sheet) due to drop impact or the like tends to cause a noticeable defect. .. In this specification, “portable” does not mean that it is simply portable, and that it has a level of portability that an individual (standard adult) can carry relatively easily. Shall mean.

  In addition, the pressure-sensitive adhesive sheet disclosed here (typically, a double-sided pressure-sensitive adhesive sheet) has excellent performance (pulling-out removability) of removing the adhesive sheet by pulling it from between the adherends. Here, the pull-out removability means that a part (typically a tab) of the adhesive sheet is exposed from two adherends fixed via the adhesive sheet, and the exposed portion is pulled to form an adhesive sheet. It means the ease of removal by releasing the fixation (typically joining) of the adherends. Note that the two adherends may be provided at two locations on one member. Hereinafter, a more specific description will be given with reference to FIGS.

  FIG. 3 is a schematic side view for explaining one aspect of pulling removal (typically pulling removal), and FIG. 3A is a diagram showing a state in which pulling removal of the adhesive sheet is started, (b) is a figure which shows the state which is pulling and removing an adhesive sheet, (c) is a figure which shows the state which the pulling removal of the adhesive sheet was completed. FIG. 4 is a schematic top view for explaining one aspect of pulling removal (typically pulling removal), and FIGS. 4A to 4C are respectively shown in FIGS. 3A to 3C. It is a corresponding figure.

  As shown in FIGS. 3A and 4A, the pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) 200 is provided with a tab T exposed to the outside when the adherends A and B are joined. There is. The adherend B is joined to the adherend A using this adhesive sheet 200. After the joining purpose is achieved, the tab T is pinched with a finger and the adhesive sheet 200 is pulled so as to be pulled out from between the adherends A and B. Then, the pressure-sensitive adhesive sheet 200 begins to expand, contracts in the direction orthogonal to the pulling direction, and begins to peel from the adherends A and B (see (b) of FIG. 3 and (b) of FIG. 4). Then, finally, the entire adhesive region of the pressure-sensitive adhesive sheet 200 is peeled off, and the pulling-out of the pressure-sensitive adhesive sheet 200 from between the adherends A and B is completed (see (c) of FIG. 3 and (c) of FIG. 4). The removal of the adherend B that has been joined to the adherend A is also completed at the same time.

  The pressure-sensitive adhesive sheet excellent in pullability as described above is suitable as a pressure-sensitive adhesive sheet used for fixing a battery (including a primary battery and a secondary battery; for example, a polymer battery) in a portable electronic device. In many cases, the battery is usually placed at a place that needs to be removed when repairing, replacing, inspecting, or the like of the components of the portable electronic device (including the battery). Therefore, the adhesive sheet for fixing the battery is frequently required to be removed. However, removing the battery by physical means such as using a removing tool, peeling it off by hand, and heating may damage the battery and may not be preferable in terms of safety. Reducing the peeling force by photo-curing is not effective because the irradiation is through the battery because of the application site of the adhesive sheet. The pressure-sensitive adhesive sheet disclosed here exhibits the function of fixing the battery well, and when removing the battery after the period of use, the above-described pull-out removal (typically pull-out removal) method is used. , It can be easily removed. The pressure-sensitive adhesive sheet is particularly preferable as a pressure-sensitive adhesive sheet used for fixing a polymer battery. Since polymer batteries tend to deform more easily than other types of batteries (typically batteries with a metal case), the conventional peeling method may deform the battery and impair its function. there were. According to the pressure-sensitive adhesive sheet disclosed herein, it is possible to satisfactorily remove the pressure-sensitive adhesive sheet while suppressing the deformation of the polymer battery by using the above-described pull-out removal (typically pull-out removal) method.

  In addition, the adhesive sheet used for fixing the battery of the portable battery device is often unable to be pulled parallel to the shearing direction at the time of removal due to other components existing around the battery and the arrangement of the battery. .. In such a case, the pressure-sensitive adhesive sheet is pulled and removed 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 the adherend (battery) or obstacles. According to the technique disclosed herein, even in such a removal mode, the pressure-sensitive adhesive sheet can be preferably removed without damaging it.

  Furthermore, the above-mentioned adhesive sheet having excellent tensile removability (typically pull-out removability) is attached to a wall surface, a pillar, furniture, home electric appliances, a glass surface, etc., and is used after being used for a predetermined period of time. It is also suitable as a pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) used for the purpose of fixing a body (object to be fixed, object to be stuck, etc.). Even in this application, while fixing the adherend, the pressure-sensitive adhesive sheet exerts a good fixing function, and at the time of detaching the adherend, the tab or the like provided on the pressure-sensitive adhesive sheet is grasped and the whole pressure-sensitive adhesive sheet is pulled out. Thereby, the removal of the pressure-sensitive adhesive sheet (for example, removal in the arrow direction in (c) of FIG. 3) can be efficiently performed.

The matters disclosed by this specification include the following.
(1) An adhesive layer is provided,
The initial adhesive force A to the polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B to the polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains filler particles,
A pressure-sensitive adhesive sheet, wherein 50% by weight or more of the filler particles contained in the pressure-sensitive adhesive layer has a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer.
(2) A pressure-sensitive adhesive layer, and a film substrate supporting the pressure-sensitive adhesive layer,
The initial adhesive force A to the polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B to the polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains filler particles,
A pressure-sensitive adhesive sheet, wherein 50% by weight or more of the filler particles contained in the pressure-sensitive adhesive layer has a particle diameter smaller than the thickness of the pressure-sensitive adhesive layer.
(3) 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, and the above (1) or (2) is described. Adhesive sheet.
(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3) above, which has a long portion and has extensibility in at least its longitudinal direction.
(5) The above-mentioned (4), wherein the state of being adhered to the adherend is released by pulling from one end of the elongated portion in the state of being adhered to the adherend. Adhesive sheet.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the filler particles contained in the pressure-sensitive adhesive layer have a proportion of particles having a particle size of less than 1 μm of 50% by weight or less.
(7) Content C of the said filler particle in the said adhesive layer is 30 volume% or less, The adhesive sheet in any one of said (1)-(6).
(8) The pressure-sensitive adhesive according to any one of (1) to (7) above, which further comprises a film-shaped substrate that supports the pressure-sensitive adhesive layer, and the film-shaped substrate is a non-foamed resin film substrate. Sheet.
(9) A film-shaped substrate supporting the pressure-sensitive adhesive layer is further provided, and as the pressure-sensitive adhesive layer, a first pressure-sensitive adhesive layer provided on the first surface of the film-shaped substrate, and a film-shaped substrate The pressure-sensitive adhesive sheet according to any one of (1) to (8) above, comprising a second pressure-sensitive adhesive layer provided on the second surface.
(10) The pressure-sensitive adhesive sheet according to (9) above, which is used for joining two adherends and is removed from the two adherends so as to be pulled out from between the two adherends.
(11) The pressure-sensitive adhesive sheet according to any one of (1) to (10), further including a tab.
(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11), which is used in a portable electronic device.
(13) The pressure-sensitive adhesive sheet according to (12) above, which is used for fixing a battery.

(14) The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion of more than 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has the formula (1):
CH ₂ = C (R ¹ ) COOR ² (1)
(R ¹ in the above formula (1) is a hydrogen atom or a methyl group, and R ² is a chain alkyl group having 1 to 20 carbon atoms.); The pressure-sensitive adhesive sheet according to any one of (1) to (13), which contains 70% by weight or more.
(15) The alkyl (meth) acrylate is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s. -Butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (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 From tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate and eicosyl (meth) acrylate The pressure-sensitive adhesive sheet according to (14) above, which is at least one selected from the group consisting of:
(16) The acrylic polymer further contains a functional group-containing monomer as the monomer component,
The functional group-containing monomer includes acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4 -The pressure-sensitive adhesive sheet according to (14) or (15) above, which is at least one selected from the group consisting of hydroxybutyl (meth) acrylate.
(17) The pressure-sensitive adhesive layer contains a tackifying resin having a softening point of 100 ° C. or higher,
The said tackifying resin is a pressure sensitive adhesive sheet in any one of said (14)-(16) containing at least 1 sort (s) of rosin type tackifying resin and terpene type tackifying resin.
(18) The pressure-sensitive adhesive sheet according to any of (14) to (17), wherein the pressure-sensitive adhesive layer contains 10 to 60 parts by weight of a tackifier with respect to 100 parts by weight of the acrylic polymer.
(19) The pressure-sensitive adhesive sheet according to any of (14) to (18), wherein the pressure-sensitive adhesive layer contains an acrylic oligomer.

(20) The filler particles are aluminum, chromium, iron, stainless steel, aluminum oxide, silicon oxide, titanium oxide, 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, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dawsonite, borax, zinc borate At least one selected from the group consisting of silicon carbide, boron carbide, nitrogen carbide, calcium carbide, aluminum nitride, silicon nitride, boron nitride, gallium nitride, calcium carbonate, barium titanate, and potassium titanate. The pressure-sensitive adhesive sheet according to any one of 1) to (19).
(21) In the filler particles, the proportion of particles having a particle diameter of less than 20 μm is 50% by weight or more,
The filler particles are aluminum, chromium, iron, stainless steel, aluminum oxide, silicon oxide, titanium oxide, 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, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dawsonite, borax, zinc borate, silicon carbide , Boron carbide, nitrogen carbide, calcium carbide, aluminum nitride, silicon nitride, boron nitride, gallium nitride, calcium carbonate, barium titanate, and potassium titanate. The pressure-sensitive adhesive sheet according to any one of (20).
(22) The filler particles have an average particle diameter of 0.5 μm to 30 μm, particles having a particle diameter of less than 20 μm account for 50% by weight or more, and the proportion of particles having a particle diameter of less than 1 μm is 50% by weight. Is less than
The filler particles are aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, base. The pressure-sensitive adhesive sheet according to any one of (1) to (21) above, which is at least one selected from the group consisting of soluble magnesium carbonate, hydrotalcite, dawsonite, borax, and zinc borate.
(23) The filler particles are at least one selected from the group consisting of polystyrene, acrylic resin, phenol resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide, polyimide and polyvinylidene chloride. The pressure-sensitive adhesive sheet according to any one of (1) to (22) above, which is a polymer of

(24) A film-shaped substrate supporting the pressure-sensitive adhesive layer is further provided, and the film-shaped substrate is a resin film substrate having an expansion ratio of less than 1.1 times,
Any of the above (1) to (23), wherein the film-shaped substrate contains at least one resin material selected from the group consisting of polyurethane, urethane (meth) acrylate-based polymer, polyolefin, polyester and polyvinyl chloride. The pressure-sensitive adhesive sheet according to crab.
(25) The adhesive sheet has a breaking strength of 10 MPa or more, an elongation at break of 300% or more, and a 100% modulus of less than 10 MPa.
Further comprising a film-like substrate supporting the pressure-sensitive adhesive layer,
The film-shaped substrate contains polyurethane in a proportion of 70% by weight or more,
The pressure-sensitive adhesive sheet according to any one of (1) to (24) above, wherein the polyurethane is an ether polyurethane, an ester polyurethane, or a carbonate polyurethane.

(26) In the above (1) to (25), the pressure-sensitive adhesive layer is composed of a rubber-based pressure-sensitive adhesive containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer. The pressure-sensitive adhesive sheet according to any one.
(27) The pressure-sensitive adhesive sheet according to (26), wherein the block copolymer has a diblock ratio of 30% by weight or more.
(28) The pressure-sensitive adhesive sheet according to the above (26) or (27), wherein the block copolymer is a styrene-based block copolymer having a styrene content of 5 to 40% by weight.
(29) The pressure-sensitive adhesive layer 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.,
The high softening point resin contains a terpene phenol resin A having a hydroxyl value of 40 mgKOH / g or more and less than 80 mgKOH / g and a terpene phenol resin B having a hydroxyl value of 80 mgKOH / g or more,
The pressure-sensitive adhesive sheet according to any of (26) to (28) above, wherein the low softening point resin is a terpene resin.

(30) A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer and a film-shaped substrate supporting the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive sheet has an elongated portion, and has extensibility in at least its longitudinal direction,
A tab is provided at one end in the longitudinal direction,
The initial adhesive force A to the polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B to the polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion of more than 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has the formula (1):
CH ₂ = C (R ¹ ) COOR ² (1)
(R ¹ in the above formula (1) is a hydrogen atom or a methyl group, and R ² is a chain alkyl group having 1 to 20 carbon atoms.); Included in a proportion of 70% by weight or more,
The alkyl (meth) acrylate may be methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl ( (Meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (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, tri Group consisting of sil (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate and eicosyl (meth) acrylate. Is at least one selected from
The acrylic polymer further contains a functional group-containing monomer as the monomer component,
The functional group-containing monomer includes acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4 -At least one selected from the group consisting of hydroxybutyl (meth) acrylate,
The pressure-sensitive adhesive layer contains filler particles,
The filler particles have an average particle diameter of 0.5 μm to 30 μm, particles having a particle diameter of less than 20 μm account for 50% by weight or more, and a proportion of particles having a particle diameter of less than 1 μm is 50% by weight or less. ,
The filler particles are aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, base. At least one selected from the group consisting of soluble magnesium carbonate, hydrotalcite, dawsonite, borax and zinc borate,
The content C of the filler particles in the pressure-sensitive adhesive layer is 30% by volume or less,
The pressure-sensitive adhesive layer contains a tackifying resin having a softening point of 100 ° C. or higher,
The tackifying resin contains at least one of a rosin-based tackifying resin and a terpene-based tackifying resin,
The pressure-sensitive adhesive layer contains 10 to 60 parts by weight of a tackifier with respect to 100 parts by weight of the acrylic polymer,
The film-shaped substrate is a resin film substrate having an expansion ratio of less than 1.1 times,
The adhesive sheet has a breaking strength of 10 MPa or more, an elongation at break of 300% or more, and a 100% modulus of less than 10 MPa,
The film-shaped substrate contains polyurethane in a proportion of 70% by weight or more,
The polyurethane is an ether polyurethane, an ester polyurethane or a carbonate polyurethane,
The pressure-sensitive adhesive sheet, wherein the ratio (B / A) of the tensile peel stress B [N / 20 mm] to the initial adhesive force A [N / 20 mm] is 3.0 or less.

  Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to 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 tube, a reflux condenser, a dropping funnel, 100 parts BA, 5 parts VAc, 3 parts AA, 0.1 parts HEA, and 0.2 parts AIBN as a polymerization initiator. Then, toluene as a polymerization solvent was charged, and solution polymerization was performed at 60 ° C. for 6 hours to obtain a toluene solution of acrylic polymer A. The Mw of this acrylic polymer A was 55 × 10 ⁴ .
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 tackifying resin with respect to 100 parts of the acrylic polymer A contained in the toluene solution 2 parts of a cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., product name “Coronate L”) and 1 part of aluminum hydroxide particles as filler particles (manufactured by Showa Denko KK, trade name “Hijilite H-21”) were added, By mixing, the acrylic pressure-sensitive adhesive composition according to this example was prepared. The filler particles used in this example have an average particle size of 27 μm and a particle size ratio of less than 25 μm is 40% or more and a particle size of less than 1 μm is 0%.

(Preparation of double-sided adhesive sheet)
Two commercially available release liners (trade name "SLB-80W3D", manufactured by Sumika Kako Kaisha, Ltd.) were prepared. The pressure-sensitive adhesive composition was applied onto one surface (release surface) of each of these release liners so that the thickness after drying was 25 μm, and dried at 100 ° C. for 2 minutes. In this way, pressure-sensitive adhesive layers (first pressure-sensitive adhesive layer and second pressure-sensitive adhesive layer) were respectively formed on the release surfaces of the two release liners.
As a film-like substrate, a non-foaming ether type polyurethane resin film having a thickness of 100 μm (manufactured by Nippon Matai Co., Ltd., trade name “ESMER URS ET-N”, breaking strength 73 to 74 MPa, elongation at break 506 to 507%, 5% modulus 1.6 MPa, 150% modulus 6.4 to 6.5 MPa) was prepared. The pressure-sensitive adhesive layers formed on the above two release liners were attached to both surfaces of this film-like substrate. The release liner was left as it was on the pressure-sensitive adhesive layer and used for protecting the surface (pressure-sensitive surface) of the pressure-sensitive adhesive layer. The obtained structure was passed once through a laminator at 80 ° C. (0.3 MPa, speed 0.5 m / min), and then aged in an oven at 50 ° C. for 1 day. Thus, the double-sided PSA sheet according to this example was obtained.

<Examples 2 to 7>
As shown in Table 1, the amount of filler particles added was 5 parts (Example 2), 10 parts (Example 3), 20 parts (Example 4), 30 parts (Example 5), relative to 100 parts of the acrylic polymer A. Double-sided PSA sheets according to Examples 2 to 7 were produced in the same manner as in Example 1 except that the amount was changed to 40 parts (Example 6) or 50 parts (Example 7).

<Examples 8 to 14>
Double-sided pressure-sensitive adhesive sheets according to Examples 8 to 14 were produced in the same manner as in Examples 1 to 7, except that the filler particles were changed to aluminum hydroxide particles (Showa Denko KK, trade name "Hijilite H-31"). The filler particles used in these examples have an average particle size of 18 μm and a particle size ratio of less than 25 μm is 54% or more and a particle size of less than 1 μm is 1%.

<Examples 15 to 21>
Double-sided pressure-sensitive adhesive sheets according to Examples 15 to 21 were produced in the same manner as in Examples 1 to 7, except that the filler particles were changed to aluminum hydroxide particles (Showa Denko KK, trade name "Hijilite H-32"). The filler particles used in these examples have an average particle size of 8 μm and a ratio of particles having a particle size of less than 25 μm is 85% or more and a ratio of particles having a particle size of less than 1 μm is 3%.

<Examples 22 to 28>
Double-sided pressure-sensitive adhesive sheets according to Examples 22 to 28 were produced in the same manner as in Examples 1 to 7, except that the filler particles were changed to aluminum hydroxide particles (manufactured by Showa Denko KK, trade name "Hijilite H-42"). The filler particles used in these examples have an average particle size of 1 μm, a ratio of particle sizes of less than 25 μm is 100%, and a ratio of particles having a particle size of less than 1 μm is 47%.

<Example 29>
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser, a dropping funnel, BA 70 parts, 2EHA 30 parts, AA 3 parts, 4HBA 0.05 part, and AIBN 0.2 part as a polymerization initiator, Toluene as a polymerization solvent was charged and solution polymerization was performed at 60 ° C. for 6 hours to obtain a toluene solution of acrylic polymer B. The Mw of this acrylic polymer B was 55 × 10 ⁴ .
30 parts of a polymerized rosin ester resin as a tackifying resin (manufactured by Arakawa Chemical Industry Co., Ltd., product name “Pencel D-125”, softening point 125 ° C.), and 100 parts of an acrylic polymer B contained in the toluene solution Add 3 parts of a cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L") and 30 parts of aluminum hydroxide particles as filler particles (Showa Denko KK, trade name "Hijilite H-32"), By mixing, the acrylic pressure-sensitive adhesive composition according to this example was prepared. A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 except that this acrylic pressure-sensitive adhesive composition was used.

<Example 30>
A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 29 except that the amount of the filler particles added was changed to 40 parts with respect to 100 parts of the acrylic polymer B.

<Example 31>
A toluene solution of acrylic polymer B was prepared in the same manner as in Example 29, and 1 part of an isocyanate cross-linking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., product name “Coronate L”) and a filler to 100 parts of the above acrylic polymer B were added. 30 parts of aluminum hydroxide particles (manufactured by Showa Denko KK, trade name "Hijilite H-32") as particles were added and mixed to prepare an acrylic pressure-sensitive adhesive composition according to this example. This adhesive composition does not contain a tackifier. A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 except that this acrylic pressure-sensitive adhesive composition was used.

<Example 32>
A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 31 except that the amount of the filler particles added was changed to 40 parts with respect to 100 parts of the acrylic polymer B.

<Example 33>
A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 except that filler particles were not added.

With respect to the double-sided pressure-sensitive adhesive sheets of Examples 1 to 33, the initial pressure-sensitive adhesive force A [N / 20 mm] and the tensile peel stress B [N / 20 mm] were measured by the methods described above. The appearance of the adhesive surface and the presence or absence of adhesive residue were also evaluated.
Regarding the appearance of the adhesive surface, visually observing the surface (adhesive surface) of the adhesive sheet of each example, and when it was smooth, it was evaluated as "○", and when streaks and irregularities were observed, it was evaluated as "X". did.
The presence or absence of adhesive residue was visually observed on the adherend after measuring the tensile peeling stress B, and when adhesive residue was not observed, it was evaluated as "○", and when adhesive residue was observed even in a small amount, It was evaluated as "x".
The results are shown in Tables 1-3. Table 3 also shows the outline and results of Examples 19 and 20 for comparison. In addition, in the table, in the measurement of the tensile peeling stress B, when there was almost no adhesion, it was described as "-".

  As shown in Tables 1 to 3, by including the filler particles in the pressure-sensitive adhesive layer, the tensile peeling stress B could be selectively reduced while suppressing the reduction of the initial adhesive force A. This is clear from the comparison between Example 33 in which filler particles were not added and Examples 19 and 20. Further, in the example where the tensile peeling stress B is a predetermined value or less, the adhesive residue was also prevented. Furthermore, the results of the above examples show that the optimum addition amount changes depending on the particle size of the filler particles. Specifically, it is desirable that the addition amount of filler particles having a large particle size be relatively small, and that the addition amount of filler particles having a small particle size be relatively large. However, as in Examples 1 to 7, when the particle diameter of the filler particles is a predetermined value or more in a relative relationship with the thickness of the pressure-sensitive adhesive layer, the surface state of the pressure-sensitive adhesive layer is adversely affected and the adhesive performance is improved. It can be seen that not only the deterioration of the adhesiveness but also the deterioration of the appearance of the adhesive surface can be remarkable.

  From the above results, the PSA sheets of Examples 8 to 11, 19 to 21 and 26 to 32 have an initial adhesive force A to PC of 3 N / 20 mm or more and a tensile peeling stress B to PC of 22 N / 20 mm or less. From this, it can be seen that it exhibits a sufficient adhesive function during use and has excellent tensile removability during removal. Among them, in Examples 19 to 21 and 26 to 30, the decrease in the initial adhesive force A to PC was suppressed to less than 10% as compared with Example 33 containing no filler particles, and nevertheless the tensile peel stress B was significantly increased. (For example, in Example 21, the tensile peeling stress B is reduced to about 37% of Example 33), and it can be seen that particularly excellent performance can be exhibited.

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

1 Adhesive Sheet 10 Film-Shaped Substrate 21, 22 Adhesive Layer

Claims (13)

Equipped with an adhesive layer,
The initial adhesive force A to the polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B to the polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains filler particles,
50% by weight or more of the filler particles contained in the pressure-sensitive adhesive layer has a particle size smaller than the thickness of the pressure-sensitive adhesive layer,
The filler particles have an average particle diameter of 0.5 μm to 30 μm, particles having a particle diameter of less than 20 μm account for 50% by weight or more, and a proportion of particles having a particle diameter of less than 1 μm is 50% by weight or less. ,
The filler particles are aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, base. A pressure-sensitive adhesive sheet , which is at least one selected from the group consisting of soluble magnesium carbonate, hydrotalcite, dawsonite, borax, and zinc borate .   The pressure-sensitive adhesive sheet according to claim 1, further comprising a film-shaped substrate that supports the pressure-sensitive adhesive layer.   The pressure-sensitive adhesive sheet according to claim 2, wherein the film-shaped substrate contains at least one resin material selected from polyurethane and urethane (meth) acrylate-based polymers. Wherein the ratio of the initial adhesion A the tensile peel stress to [N / 20mm] B [N / 20mm] (B / A) is 3.0 or less, according to any one of claims 1 to 3 Adhesive sheet. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5 , which has a long portion and has extensibility in at least its longitudinal direction. The pressure-sensitive 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 the state of being attached to the adherend.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the content C of the filler particles in the pressure-sensitive adhesive layer is 30% by volume or less.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, further comprising a film-shaped substrate that supports the pressure-sensitive adhesive layer, the film-shaped substrate being a non-foamed resin film substrate.   As the pressure-sensitive adhesive layer, a first pressure-sensitive adhesive layer provided on the first surface of the film-shaped substrate, and a second pressure-sensitive adhesive layer provided on the second surface of the film-shaped substrate, Item 8. The pressure-sensitive adhesive sheet according to item 8.   The pressure-sensitive adhesive sheet according to claim 9, which is used for joining two adherends and is removed from the two adherends so as to be pulled out from between the two adherends.   The pressure-sensitive adhesive sheet according to claim 1, further comprising a tab.   The pressure-sensitive adhesive sheet according to claim 1, which is used in a portable electronic device.   The pressure-sensitive adhesive sheet according to claim 12, which is used for fixing a battery.

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