WO2016047435A1 - Adhesive sheet - Google Patents

Abstract

Provided is an adhesive sheet sufficiently exhibiting an adhesive function during use and having excellent tension-removal properties during removal. This invention provides an adhesive sheet comprising an adhesive agent layer. This adhesive sheet has an initial adhesive force A relative to polycarbonate of at least 3 N/20 mm and has a tension-peeling stress B relative to polycarbonate of no more than 22 N/20 mm. The adhesive agent layer includes filler particles. At least 50 wt% of the filler particles included in the adhesive agent layer have a particle diameter that is smaller than the thickness of the adhesive agent layer.

Description

Adhesive sheet

The present invention relates to an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2014-193749 filed on September 24, 2014 and Japanese Patent Application No. 2015-139003 filed on July 10, 2015. The entire contents of these applications are hereby incorporated by reference.

Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) is in a soft solid (viscoelastic body) state in the temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is preferably used in the form of a pressure-sensitive adhesive sheet, for example, for fixing components in portable electronic devices such as mobile phones, smartphones, and tablet computers. It is also preferably used as a pressure-sensitive adhesive sheet that is re-peeled after pasting. Patent documents 1 and 2 are mentioned as literature which discloses this kind of conventional technology. Both patent documents 1 and 2 are disclosing the prior art provided with the base material which has a stretching property. Patent document 2 is related with the medical adhesive sheet affixed on skin.

Japanese Patent Application Publication No. 6-346032 Japanese published patent publication 2005-500133

¡Adhesive sheets are required to have no adhesion failure such as peeling or misalignment during the period of use. Therefore, the pressure-sensitive adhesive sheet needs to have a predetermined or higher adhesive strength. 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, the pressure-sensitive adhesive sheet used as the fixing means for the constituent members of the portable electronic device can be removed from the adherend when the member is repaired, replaced, inspected, recycled, or the like. Since some adherends are easily deformed, it is desirable that the pressure-sensitive adhesive sheet used in this application is configured to be removed without causing deformation or damage of the adherend. Specifically, for example, a configuration in which a part of the pressure-sensitive adhesive sheet is exposed to the outside, and the pressure-sensitive adhesive sheet can be removed from the adherend surface by grasping and pulling the part is desirable. Such an adhesive sheet preferably has a small peeling stress at the time of removal in consideration of removal workability. However, if the adhesive force is designed to be greater than a predetermined value in order to ensure a sufficient adhesive function, the peeling stress when pulling and removing the adhesive sheet tends to increase. For this reason, the present situation is that a pressure-sensitive adhesive sheet that achieves both an adhesion function and a tensile removability at the practical level has not been realized yet.

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 when used and is excellent in tensile removability when removed.

According to the present invention, an adhesive sheet provided with an adhesive layer is provided. This pressure-sensitive adhesive sheet has an initial adhesive strength A for polycarbonate of 3 N / 20 mm or more, and a tensile peel stress B for polycarbonate of 22 N / 20 mm or less. The pressure-sensitive adhesive layer contains filler particles. And 50 weight% or more of the filler particle contained in the said adhesive layer has a particle diameter smaller than the thickness of this adhesive layer. A pressure-sensitive adhesive sheet according to a preferred embodiment includes a pressure-sensitive adhesive layer and a film-like substrate that supports the pressure-sensitive adhesive layer.

When the initial adhesive strength A is not less than a predetermined value, a sufficient adhesion function can be exerted on an adherend formed from various materials such as polycarbonate (PC). In addition, 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 adhesion surface (typically −90 degrees to +90 degrees with respect to the adhesion surface). The pressure-sensitive adhesive sheet can be smoothly removed from the various adherends by simply pulling the pressure-sensitive adhesive sheet in the direction (hereinafter also referred to as “tension peeling direction”). In short, according to the present invention, there is provided a pressure-sensitive adhesive sheet having both a sufficient adhesion function at the time of use and excellent tensile removability at the time of removal. Both the maintenance of the initial adhesive force A and the reduction of the tensile peeling stress B are realized by including filler particles in the adhesive layer. And by making the particle diameter of the filler particles of a predetermined ratio relatively small with respect to the thickness of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive surface is maintained in a good surface state, and the desired pressure-sensitive adhesive properties (for example, pressure-sensitive adhesive force) are obtained. It can be demonstrated. The appearance of the pressure-sensitive adhesive layer surface (adhesive surface) is also maintained well.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, a ratio (B / A) of the tensile peeling stress B [N / 20 mm] to the initial pressure-sensitive adhesive force A [N / 20 mm] is 3.0 or less. When the ratio (B / A) is small, it means that the tensile peeling stress B is reduced relative to the initial adhesive force A in the configuration having the initial adhesive force A of a predetermined value or more. . By comprising in this way, sufficient adhesive function at the time of use and the outstanding tension | pulling removability at the time of removal can be preferably made compatible.

In a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive sheet has an elongated portion and has extensibility at least in the longitudinal direction thereof. The pressure-sensitive adhesive sheet having the above configuration is elongated by pulling in the longitudinal direction when the pressure-sensitive adhesive sheet is removed, and the pressure-sensitive adhesive sheet can be deformed and peeled off from the adherend by this elongation. In the pressure-sensitive adhesive sheet having the above-described extensibility, the tensile removability is excellent due to the interaction between the tension as described above and the expansion deformation of the pressure-sensitive adhesive sheet, and in addition, the tensile peeling stress reducing action of the filler particles contained in the pressure-sensitive adhesive layer. Is preferably realized. In addition, the adhesive sheet disclosed herein is preferably released from being attached to the adherend by pulling from one end of the elongated portion while being attached to the adherend. Furthermore, it can be preferably removed from the adherend. By adopting such a sticking state release method (typically a removal 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 embodiment of the pressure-sensitive adhesive sheet disclosed herein, the filler particles contained in the pressure-sensitive adhesive layer contain 50% by weight or less of particles having a particle diameter of less than 1 μm. Thus, the tensile peeling stress B can be preferably reduced by limiting the proportion of fine particles having a particle diameter of less than 1 μm. Moreover, 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 embodiment 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, the tensile peeling stress B can be preferably reduced while suppressing a decrease in the initial pressure-sensitive adhesive force A.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the film-like 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 embodiment 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-like substrate and a second surface of the film-like substrate are provided. A second pressure-sensitive adhesive layer. Such a double-sided PSA sheet with a substrate can be preferably used as a highly reliable fixing means (typically, a joining means for two adherends).

The pressure-sensitive adhesive sheet disclosed herein is preferably used in such a manner that it is used for joining two adherends and then removed from the two adherends by pulling out between the two adherends. Can be done. Further, the pressure-sensitive adhesive sheet disclosed herein is used to join two adherends, and in a state where the two adherends are joined, a pressure-sensitive adhesive sheet positioned between the two adherends is used. By pulling, the attached state to 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 adherend.

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 adhesion function when used, and has excellent tensile removability when removed. Utilizing this feature, it is particularly preferably used as a pressure-sensitive adhesive sheet for battery fixing, which is frequently removed when repairing or exchanging members constituting a product, product inspection, or 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 typically the measuring method of the tensile peeling stress B. FIG. It is a typical side view for explaining one mode of tension removal. It is a schematic top view for demonstrating one aspect | mode of tension removal.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and common 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 accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. .

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

<Configuration 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-like substrate (support). The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a single sheet. Or the adhesive sheet of the form processed into various shapes may be sufficient. In addition, there may not be a film-form base material.

For example, the pressure-sensitive adhesive sheet disclosed herein may have a cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 is provided with pressure-sensitive adhesive layers 21 and 22 on each surface of the film-like substrate 10 (both are non-peelable). The adhesive sheet 1 before use has a configuration in which each surface (each adhesive surface) of the adhesive layers 21 and 22 is protected by a release liner (not shown). Alternatively, the pressure-sensitive adhesive sheet disclosed herein is not particularly illustrated, but may be a baseless double-sided pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer.

In addition, the pressure-sensitive adhesive sheet preferably has a long portion from the viewpoint of tensile removability. Thereby, in the adhesive sheet affixed on the adherend, the 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 elongate portion is typically a band 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 preferred embodiment, the entire pressure-sensitive adhesive sheet is formed in a long shape. From the viewpoint of workability for removing the tension, it is preferable that a tab (gripping part) is provided at one end in the longitudinal direction of the pressure-sensitive adhesive sheet. Although the shape of a tab is not specifically limited, It is preferable that it is a shape (for example, rectangular shape) which can be hold | gripped with a finger.

<Characteristics of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein is characterized by an initial pressure-sensitive adhesive force A for PC of 3 N / 20 mm or more. Thereby, sufficient adhesion function can be exhibited to the adherend formed from various materials such as PC. When the pressure-sensitive adhesive sheet having the initial adhesive strength A is applied to, for example, a portable electronic device, the fixed arrangement of the adherent member can be maintained even when the portable electronic device falls. The initial adhesive strength 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 strength A is not particularly limited, but may be less than 15 N / 20 mm (for example, less than 12 N / 20 mm, typically less than 10 N / 20 mm) in consideration of tensile removability and adhesive residue prevention. preferable.

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

The pressure-sensitive adhesive sheet disclosed herein is characterized by a tensile peeling stress B against PC of 22 N / 20 mm or less in addition to the initial pressure A. Thereby, when pulling the adhesive sheet in the tensile peeling direction and removing it from the adherend, the adhesive sheet can be smoothly removed from the adherend. The tensile peeling 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). Although the lower limit of the tensile peeling stress B is not particularly limited, it is appropriate to set it to 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 strength A. .

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

In a preferred embodiment, the ratio (B / A) of the tensile peel stress B [N / 20 mm] to the initial adhesive strength A [N / 20 mm] is 3.0 or less. Thereby, it is possible to preferably achieve both a sufficient adhesion function at the time of use and excellent tensile removability at the time of removal. The ratio (B / A) is preferably 2.8 or less (for example, 2.6 or less, typically 2.4 or less). The ratio (B / A) is ideally as low as possible, but practically, the lower limit may be, for example, about 1.2 or more (typically 1.5 or more).

In a preferred embodiment, the pressure-sensitive adhesive sheet exhibits a breaking strength of 10 MPa or more. Thereby, in the structure which shows the adhesive force more than predetermined, it can become a structure which is hard to produce damage, such as a piece, at the time of removal of an adhesive sheet. Moreover, there exists a tendency which is excellent also in workability. The breaking strength is more preferably 20 MPa or more, and further preferably 30 MPa or more (for example, 45 MPa or more, typically 60 MPa or more). From the viewpoint of the 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 above breaking strength is measured in accordance with 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 a powder to the adhesive surface to remove the influence of stickiness of the adhesive. In addition, although the tension direction in the said test is not specifically limited, When an adhesive sheet is elongate, it is preferable to make it correspond with the longitudinal direction. The breaking strength can be adjusted, for example, by selecting a base material.

The pressure-sensitive adhesive sheet disclosed here preferably has extensibility. Thereby, the adhesive sheet can be extended and deformed and peeled off when the tension is removed. In this specification, “having extensibility” is defined as an elongation at break of 20% or more. The elongation at break of the pressure-sensitive adhesive sheet can be 50% or more (for example, 100% or more, typically 200% or more). In a preferred embodiment, the pressure-sensitive adhesive sheet exhibits an elongation at break of 300% or more. Thereby, tension | pulling and the expansion | extension deformation of an adhesive sheet interact, and the more excellent tension | pulling removability is implement | achieved. The pressure-sensitive adhesive sheet exhibiting the above characteristics is also preferable in terms of preventing deformation of the adherend during 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 removal workability.

The elongation at break is measured according to the “elongation” measuring method described in JIS K 7311: 1995. More specifically, the elongation at break can be measured using a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm) under the condition of a tensile speed of 300 mm / min. The tensile tester and others are basically the same as in the case of the above-described breaking strength. In addition, although the tension direction in the said test is not specifically limited, When an adhesive sheet is elongate, it is preferable to make it correspond with the longitudinal direction. The elongation at break can be adjusted, for example, by selecting a base material.

The pressure-sensitive adhesive 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 resistance at the start of pulling tends to decrease 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 it is usually suitably 0.5 MPa or more (for example, 1 MPa or more) from the viewpoint of the workability of attaching the adhesive sheet. The 100% modulus is measured according to the “tensile stress” measurement method described in JIS K 7311: 1995. More specifically, using a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm), the tensile stress was 300 mm / min, and the stress [MPa when the marked line distance was increased by 100%. ] Is taken as 100% modulus. As the tensile tester, a product name “Autograph AG-10G type tensile tester” manufactured by Shimadzu Corporation can be used. The same method can be adopted for the embodiments described later. The 100% modulus of the pressure-sensitive adhesive sheet can be adjusted by, for example, selection of a base material type (selection of a mixing ratio of a hard component and a soft component), a molding method, and the like.

In a preferred embodiment, it is appropriate that the pressure-sensitive adhesive sheet exhibits a tensile recovery rate exceeding 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%). Thereby, damages, such as tearing at the time of adhesive sheet removal, can be prevented more highly. This point will be described. For example, when removing the pressure-sensitive adhesive sheet by pulling in the shear direction, a certain amount of time is usually required depending on the adhesion area and the like. Therefore, the removal operation may be interrupted halfway. 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 operation can be resumed from a state in which the mechanical properties (strength, elasticity, etc.) have decreased due to the tension before the operation is interrupted. At that time, the pressure-sensitive adhesive sheet cannot withstand the tension when the removal operation is resumed, and is easily damaged. Even when the pressure-sensitive adhesive sheet showing the tensile recovery rate is removed in such a manner as to be interrupted once as described above, the deterioration after mechanical pulling is suppressed by the recovery after pulling, so that the damage is more severe. Can be prevented.

The tensile recovery rate is measured by the following method.
[Measurement of tensile recovery rate]
Per adhesive sheet, performing a tensile test stretching specific section distance L ₀ of the adhesive sheet 100%. From the formula: Tensile recovery rate (%) = L ₀ / L ₁ × 100, where L ₁ is the length of the specific section after the adhesive sheet has been stretched 100% and released after 5 minutes. Obtain the tensile recovery rate.
More specifically, in accordance with JIS K 7311: 1995, a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm) is stretched 100% under the condition of a tensile speed of 300 mm / min. In other words, it is pulled until the marked line interval extends 20 mm. Then, the length L ₁ (mark line interval: mm) after 5 minutes from the release of the tension is measured, and the tensile recovery rate is obtained from the formula: Tensile recovery rate (%) = L ₀ / L ₁ × 100; . In this method, L ₀ is an initial marked line interval of 20 mm. The tensile tester and others are basically the same as in the case of the elongation at break described above. In addition, the tensile direction in the said test is although it does not specifically limit, It is preferable to make it correspond with the longitudinal direction of an adhesive sheet or its elongate part. The tensile recovery rate can be adjusted, for example, by selecting a base material.

<Adhesive layer>
(Base polymer)
The pressure-sensitive adhesive layer disclosed herein (in the case of a double-sided pressure-sensitive adhesive sheet with a base material includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer; the same shall apply hereinafter) is an acrylic polymer known in the field of pressure-sensitive adhesives. The base polymer includes one or more of various rubber-like polymers such as rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers. obtain. As will be described in detail later, the pressure-sensitive adhesive layer disclosed herein is preferably an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, a rubber pressure-sensitive adhesive layer containing a rubber-based polymer as a base polymer, and a urethane-based polymer. It is a urethane type adhesive layer which contains as a base polymer. Alternatively, a pressure-sensitive adhesive layer in which an acrylic polymer and a rubber polymer are used in combination as the base polymer may be used.

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

As the acrylic polymer, for example, a polymer of a monomer raw material that includes alkyl (meth) acrylate as a main monomer and may further include a submonomer copolymerizable with the main monomer is preferable. Here, the main monomer means a component occupying more than 50% by weight of all monomer components in the monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. 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 represented 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 chain alkyl group of C _1-14 (for example, C _2-10 , typically C _4-8 ) is preferable. Alkyl acrylates in which ¹ is a hydrogen atom and R ² is a C _4-8 chain alkyl group are more preferred.

Examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl. (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, And eicosyl (meth) acrylate. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). BA is more preferable from the viewpoints of adhesive properties and prevention of adhesive residue.

The blending ratio of the main monomer in all 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 mixing 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 implemented in an embodiment in which 50% by weight or more (for example, 60% by weight or more) of all monomer components is BA. In a preferred embodiment, the total monomer component may further comprise 2EHA in a proportion less than BA.

The secondary monomer copolymerizable with the main monomer, alkyl (meth) acrylate, can be useful for introducing a crosslinking point into the acrylic polymer or increasing the cohesive strength of the acrylic polymer. As a secondary 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 type or two or more types of 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 obtained by copolymerizing a carboxy group-containing monomer and / or a hydroxyl group-containing monomer as the submonomer is preferable. Preferable examples of the carboxy group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA). Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth). Examples thereof include hydroxyalkyl (meth) acrylates such as acrylates and unsaturated alcohols. Of these, hydroxyalkyl (meth) acrylate is preferable, and 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are more preferable.

The amount of the submonomer is not particularly limited as long as it is appropriately selected so as to realize a desired cohesive force. Usually, from the viewpoint of achieving a good balance between adhesive force and cohesive force, the amount of the secondary monomer is suitably 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 submonomer is suitably 30% by weight or less, preferably 10% by weight or less (for example, 5% by weight or less) in the total monomer components. When the carboxy group-containing monomer is copolymerized with the acrylic polymer, the content of the carboxy group-containing monomer is, among all monomer components used for the synthesis of the acrylic polymer, from the viewpoint of coexistence of adhesive force and cohesive force. It is preferably in the range of about 0.1 to 10% by weight (eg 0.2 to 8% by weight, typically 0.5 to 5% by weight). When a hydroxyl group-containing monomer is copolymerized with an acrylic polymer, the content of the hydroxyl group-containing monomer is approximately 0 out of all monomer components used for the synthesis of the acrylic polymer from the viewpoint of achieving both adhesive strength and cohesive strength. 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 other monomers can be used for the purpose of adjusting the glass transition temperature of the acrylic polymer, adjusting the adhesive performance (for example, peelability), and the like. Examples of the monomer that can improve the cohesive strength of the pressure-sensitive adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, and aromatic vinyl compounds. The said other monomer may be used individually by 1 type, and may be used in combination of 2 or more type. Of these, vinyl esters are preferred examples. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Of these, VAc is preferable. The content of the other monomer is about 30% by weight or less (typically 0.01 to 30% by weight, for example, 0.1 to 10% by weight) in all monomer components used for the synthesis of the acrylic polymer. It is preferable.

The copolymer composition of the acrylic polymer is such that the glass transition temperature (Tg) of the polymer is −15 ° C. or lower (typically −70 ° C. or higher and −15 ° C. or lower) from the viewpoint of impact resistance and the like. It is appropriate that it is designed, and is preferably −25 ° C. or lower (eg, −60 ° C. or higher and −25 ° C. or lower), more preferably −40 ° C. or lower (eg, −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 and amount ratio of monomers used for the synthesis of the polymer). Here, the Tg of the acrylic polymer refers to a fox based on the Tg of the homopolymer (homopolymer) of each monomer constituting the polymer and the weight fraction (copolymerization ratio based on weight) of the monomer. The value obtained from the formula. The formula of Fox is a relational expression between Tg of a copolymer and 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 (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer. As the Tg of the homopolymer, the value described in known materials is adopted.

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

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

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 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 includes a redox initiator based on a combination of a peroxide and a reducing agent. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The polymerization initiator may be used in a normal amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) with respect to 100 parts by weight of the total 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 to} 500 × 10 ⁴ . From the viewpoint of balancing cohesion and adhesive strength at a high level, the Mw of the base polymer (preferably an acrylic polymer) is preferably 10 × 10 ⁴ to 150 × 10 ⁴ , more preferably 20 × 10 ⁴ to 110. × 10 ⁴ (for example, 20 × 10 ⁴ to 75 × 10 ⁴ ), more preferably 35 × 10 ⁴ to 90 × 10 ⁴ (for example, 35 × 10 ⁴ to 65 × 10 ⁴ ). Here, Mw refers to a value in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) may be used. The same applies to the embodiments described later.

(Rubber polymer)
In another preferred embodiment, the pressure-sensitive adhesive layer is composed of a rubber-based pressure-sensitive adhesive. Further, the rubber-based pressure-sensitive adhesive according to one 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, vinyl toluene, vinyl xylene and the like. Specific examples of the conjugated diene compound include 1,3-butadiene and isoprene. Such a block copolymer can be used for a base polymer individually by 1 type or in combination of 2 or more types.

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

The block copolymer may be in the form of a diblock body, a triblock body, a radial body, a mixture thereof, or the like. In the triblock body and the radial body, it is preferable that 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 gather to form a domain, thereby forming a pseudo cross-linked structure and improving the cohesiveness of the pressure-sensitive adhesive. As the block copolymer in the technique disclosed herein, for example, a diblock ratio is 30% by weight or more (more preferably 40% by weight) from the viewpoint of adhesive strength (peeling strength) to the adherend and repulsion resistance. 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. From the viewpoint of resistance to continuously applied stress, 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 embodiment of the technology disclosed herein, the base polymer is a styrenic block copolymer. For example, it can be preferably implemented in an embodiment in which the base polymer contains at least one of a styrene isoprene block copolymer and a styrene butadiene block copolymer. Among the styrene block copolymers contained in the pressure-sensitive adhesive, the proportion of styrene isoprene block copolymer is 70% by weight or more, the proportion of styrene butadiene block copolymer is 70% by weight or more, or styrene The total 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 styrenic block copolymer is a styrene isoprene block copolymer. In another preferred embodiment, substantially all (for example, 95 to 100% by weight) of the styrenic block copolymer is a styrene butadiene block copolymer. According to such a composition, an adhesive sheet that is excellent in repulsion resistance and well balanced with other adhesive properties can be suitably 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 a triblock body and a radial body, it is preferable that the styrene block is arranged at the terminal of the polymer chain. This is because the styrene blocks arranged at the end of the polymer chain are likely to gather to form a styrene domain, thereby forming a pseudo cross-linked structure and improving the cohesiveness of the pressure-sensitive adhesive. The styrenic block copolymer used in the technology disclosed herein is, for example, a diblock ratio of 30% by weight or more (more preferably) from the viewpoint of adhesive strength (peeling strength) to the adherend and repulsion resistance. Is preferably 40% by weight or more, more preferably 50% by weight or more, particularly preferably 60% by weight or more, and typically 65% by weight or more. A styrenic 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 and the like, a styrenic 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 styrenic block copolymer having a diblock ratio of 60 to 85% by weight can be preferably used.

The styrene content of the styrenic block copolymer can be, for example, 5 to 40% by weight. From the viewpoint of repulsion resistance and holding power, a styrene block copolymer having a styrene content of usually 10% by weight or more (more preferably more than 10% by weight, for example, 12% by weight or more) is preferred. Further, from the viewpoint of the adhesive strength to the adherend, the 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 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 embodiment, 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 composed of a urethane-based resin containing, as a base polymer, a urethane-based polymer obtained by reacting a polyol and a polyisocyanate compound. The urethane polymer is not particularly limited, and any appropriate urethane polymer (ether polyurethane, ester polyurethane, carbonate polyurethane, etc.) that can function as an adhesive can be adopted. Examples of the polyol include polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, and the like. Examples of the polyisocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and the like.

(Filler particles)
The pressure-sensitive adhesive layer disclosed herein is characterized by containing filler particles. Thereby, both the maintenance of the initial adhesive strength A and the reduction of the tensile peeling stress B are realized. This point will be described. The filler particles contained in the pressure-sensitive adhesive layer may exist in a state exposed on the pressure-sensitive adhesive surface or in a state of being included in the pressure-sensitive adhesive layer. The filler particles exposed on the pressure-sensitive adhesive surface reduce the area of the pressure-sensitive adhesive on the pressure-sensitive adhesive surface and improve the slip property in the shear direction of the adhesive interface. As a result, the tensile peel stress B is reduced, but the reduction of the adhesive area on the adhesive surface also causes a decrease in the initial adhesive force A. On the other hand, it is considered that the filler particles present in the pressure-sensitive adhesive layer greatly contribute to the reduction of the tensile peeling stress B without reducing the initial adhesive force A. The main reason for this is not particularly limited and can be interpreted as a change in the state of the pressure-sensitive adhesive layer accompanying the deformation of the pressure-sensitive adhesive sheet. Specifically, tensile peeling is an aspect in which the pressure-sensitive adhesive is peeled in a direction parallel to the adhesive surface (tensile peeling direction, also referred to as shear direction), and thus the pressure-sensitive adhesive sheet is deformed in the direction at the time of tensile peeling. . The extensible pressure-sensitive adhesive sheet stretches with respect to the above tension, and the pressure-sensitive adhesive layer is deformed accordingly. For example, when the film-like base material that supports the pressure-sensitive adhesive layer has extensibility with respect to tension, the pressure-sensitive adhesive layer is also greatly deformed as the base material is extended. It is considered that the 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 shear direction at the adhesion interface. It is also considered that the pressure-sensitive adhesive (adhesive component) is deformed by tensile peeling in the pressure-sensitive adhesive layer, whereas the filler particles behave differently from the pressure-sensitive adhesive in the pressure-sensitive adhesive layer. It is also conceivable that the difference in behavior between the pressure-sensitive adhesive and the filler particles with respect to the tensile peeling contributes to the reduction of the tensile peeling stress. The above-described change in the surface state of the pressure-sensitive adhesive layer and the behavior of the pressure-sensitive adhesive layer components are considered to be such that they are not manifested by, for example, 90-degree peeling or 180-degree peeling, or can be ignored from the difference in the peeling mode. It is done. However, it is considered that the stress change is greatly affected at the time of tensile peeling. As a result, it is considered that the filler particles contained in the pressure-sensitive adhesive layer greatly contribute to both the maintenance of the initial adhesive strength A and the reduction of the tensile peeling stress B. The effect of containing the filler particles is particularly noticeable in the pressure-sensitive adhesive sheet having extensibility. In an extensible adhesive sheet having a substrate, typically, the mechanical properties of the substrate can greatly contribute to the adhesive strength (typically 180 degree peel strength), so that an adhesive composition (for example, tackifying) It is thought that the contribution to the adhesive strength of additives such as an agent and a crosslinking agent is relatively small. In such a pressure-sensitive adhesive sheet, an effect of selectively reducing only the tensile peeling stress B while maintaining the initial pressure-sensitive adhesive force A is preferably realized by including filler particles in the pressure-sensitive adhesive layer.

The type of filler particles used is not particularly limited. For example, a particulate or fibrous filler can be used. The constituent material of filler particles (typically particulate filler) is, for example, metals 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, dowsonite, borax, zinc borate; silicon carbide, boron carbide, Carbides such as nitrogen carbide and calcium carbide; nitriding such as aluminum nitride, silicon nitride, boron nitride and gallium nitride Carbonates such as calcium carbonate; titanates such as barium titanate and potassium titanate; carbonaceous materials such as carbon black, carbon tubes (carbon nanotubes), carbon fibers and diamond; glass; inorganic materials such as polystyrene; Acrylic resin (for example, polymethyl methacrylate), phenol resin, benzoguanamine resin, urea resin, silicone resin, polyester, polyurethane, polyethylene, polypropylene, polyamide (for example, nylon), polyimide, polymer such as polyvinylidene chloride, and the like. Alternatively, natural raw material particles such as volcanic shirasu, clay, and sand may be used. Various synthetic fiber materials and natural fiber materials can be used as the fibrous filler. These can be used alone or in combination of two or more. Among these, a particulate filler is preferable from the viewpoint of reducing tensile peeling stress, and among these, the use of a particulate filler composed of an inorganic material (for example, aluminum hydroxide) is preferable.

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. Thereby, the tendency for an adhesive surface to maintain a favorable surface state becomes large, and it can exhibit a desired adhesive characteristic (for example, initial stage adhesive force A). In addition, the appearance of the pressure-sensitive adhesive layer surface 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 the entire amount (typically 99 to 100% by weight) 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. In another preferred embodiment, 40% by weight or more (for example, 50% by weight or more, typically 55% by weight or more) of the filler particles contained in the pressure-sensitive adhesive layer from the viewpoint of improving the surface state of the pressure-sensitive adhesive surface. However, it has a particle size smaller than 2/3 (that is, 2 / 3T, more preferably 1/2, that is, 1 / 2T) of the thickness T of the pressure-sensitive adhesive layer. Note that X weight% or more of filler particles has a particle size smaller than Y means that the cumulative particle size (weight basis) up to the particle size Y (μm) in the particle size distribution obtained by measurement based on the sieving method is X ( % By weight). The proportion (% by weight) of filler particles having a predetermined particle diameter can be determined based on the 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 diameter of less than 30 μm. Such a pressure-sensitive adhesive layer containing filler particles is advantageous in terms of maintaining adhesive strength and appearance, since the smoothness of the pressure-sensitive adhesive surface is hardly impaired even if the filler particle content is relatively increased. The filler particles contained in the pressure-sensitive adhesive layer have a particle size of less than 20 μm (for example, less than 15 μm, typically less than 10 μm), 50% by weight or more (for example, 70% by weight or more, typically 80% by weight or more). More preferably.

In a preferred embodiment, the proportion of particles having a particle diameter of less than 1 μm in the filler particles contained in the pressure-sensitive adhesive layer is 50% by weight or less. From the viewpoint of reducing the tensile peeling stress, it is desirable that the filler particles have a certain size. Moreover, it is preferable in terms of productivity that the amount of fine particles is limited, 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% by weight or less (eg, 10% by weight or less, typically 5% or less) is more preferable.

The average particle diameter of the entire filler particles contained in the pressure-sensitive adhesive layer is usually suitably 0.5 μm or more, preferably 0.8 μm or more (for example, 3 μm or more, typically 5 μm or more). When the average particle size is increased, the tensile peeling stress reduction effect tends to be improved, and the tensile peeling 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 in terms of maintaining good viscosity and dispersibility of the composition. The upper limit of the average particle diameter is usually suitably 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 15 μm or less. When the average particle size is small, a decrease in the adhesive performance tends to be suppressed. It is desirable that the average particle size is small in terms of the appearance of the adhesive surface. In this specification, the average particle size of the filler particles refers to a particle size (50% median diameter) at which the cumulative particle size based on weight is 50% in the particle size distribution obtained by 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 a deformed shape thereof. The shape of the filler particles is preferably a bulk shape, and more preferably a spherical shape.

The average aspect ratio of the filler particles is not particularly limited, and is preferably less than about 100 from the viewpoint of reducing tensile peeling stress, preferably less than 50, more preferably less than 10 (for example, less than 5, typically less than 2). It 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 major axis / minor axis in the filler particles. The major axis typically refers to the maximum difference length of the particles to be measured, and the minor axis typically refers to the minimum difference length of the particles to be measured. The average aspect ratio can be grasped through transmission electron microscope observation.

The filler particle content C in the pressure-sensitive adhesive layer is suitably 30% by volume or less. By appropriately adjusting the particle diameter and content of the filler particles, the tensile peeling stress B can be preferably reduced while suppressing a decrease in the initial adhesive strength A. The filler particle content C 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). Further, from the viewpoint of reducing 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) substantially contains a component (dispersant) that improves the dispersibility of the filler particles. However, it may not be included, or the dispersant may be included. The filler particle content C [% by volume] is determined based on the weight ratio and density of components other than the filler particles in the pressure-sensitive adhesive layer (typically, the pressure-sensitive adhesive component), and the weight ratio and density of the filler particles. For example, in Examples described later, 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 obtained.

Further, the content of filler particles (for example, inorganic material particles, typically metal oxide or metal hydroxide) in the pressure-sensitive adhesive layer is less than 100 parts by weight with respect to 100 parts by weight of the base polymer on a weight basis. Is appropriate. By appropriately adjusting the particle diameter and content of the filler particles, the tensile peeling stress B can be preferably reduced while suppressing a decrease in the initial adhesive strength A. The content of 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. ). Further, from the viewpoint of reducing 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). As described above, typically 25 parts by weight or more).

(Acrylic oligomer)
The pressure-sensitive adhesive composition disclosed herein may contain an acrylic oligomer. By adopting an acrylic oligomer, impact resistance and repulsion resistance can be improved in a well-balanced manner. Further, in the case of curing the pressure-sensitive adhesive composition by active energy ray irradiation (for example, UV irradiation), the acrylic oligomer is harder to inhibit curing (for example, unreacted than, for example, a rosin-based or terpene-based tackifier resin). It has the advantage of hardly causing polymerization inhibition of the reactive monomer). The acrylic oligomer is a polymer containing an acrylic monomer as a constituent monomer component, and is defined as a polymer having a smaller Mw than the acrylic polymer.

The proportion of the acrylic monomer in the total 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 (for example, 80% by weight). Or more and 90% by weight or more). In a preferred embodiment, the acrylic oligomer has a monomer composition consisting essentially only 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 monomers that can be used in the acrylic polymer can be used. Moreover, the said structural monomer may also contain alicyclic hydrocarbon group containing (meth) acrylate. As a monomer component which comprises an acryl-type oligomer, the 1 type (s) or 2 or more types of the various monomers illustrated above can be used.

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

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

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 Or 2 or more types can be used. The number of carbon atoms of the alicyclic hydrocarbon group is preferably 5 or more (for example, 6 or more, typically 8 or more), and preferably 16 or less (for example, 12 or less, typically 10 or less). is there. Preferable examples of the alicyclic hydrocarbon group-containing (meth) acrylate include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentanyl (meth) acrylate. Of these, dicyclopentanyl methacrylate (DCPMA) is more preferable.

The ratio of the alicyclic hydrocarbon group-containing (meth) acrylate to the total monomer components constituting the acrylic oligomer (that is, the copolymerization ratio) is about 30 to 90% by weight (from the viewpoint of tackiness and cohesion) ( 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 a constituent monomer component. In this embodiment, the proportion of the chain alkyl group-containing and alicyclic hydrocarbon group-containing (meth) acrylic acid ester in the total monomer components constituting the acrylic oligomer is about 80% by weight or more (for example, 90 to 100). % By weight, typically 95-100% by weight). The monomer component constituting the acrylic oligomer is more preferably 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 to 7: 3 (eg, 3: 7 to 6: 4, typically 3: 7 to 5: 5). It is.

Although not particularly limited, the composition (that is, the polymerization composition) of the constituent monomer component of the acrylic oligomer can be set so that the Tg of the acrylic oligomer is 10 ° C. or more and 300 ° C. or less. 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 component of the acrylic oligomer. The Tg of the acrylic oligomer is preferably 180 ° C. or lower (for example, 160 ° C. or lower) from the viewpoint of initial adhesiveness. Moreover, it is preferable that said Tg is 60 degreeC or more (for example, 100 degreeC or more typically 120 degreeC or more) from a cohesive viewpoint of an 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), 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. Further, from the viewpoint of 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 by using a chain transfer agent as necessary during the 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 employed in an appropriate mode. Since the types and amounts of polymerization initiators that can be used as needed (for example, azo polymerization initiators such as AIBN) are generally as described above, the description thereof will not be repeated here.

It is appropriate that the content of the acrylic oligomer in the pressure-sensitive adhesive composition disclosed herein is, for example, 0.5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of better exerting the effect of the acrylic oligomer, the content of the acrylic oligomer is preferably 1 part by weight or more (eg, 1.5 parts by weight or more, typically 2 parts by weight or more). . Further, 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 suitably less than 50 parts by weight (for example, less than 10 parts by weight), The amount is preferably less than 8 parts by weight (for example, less than 7 parts by weight, typically 5 parts by weight or less). Even with such a small amount of addition, an improvement in impact resistance and repulsion resistance can be realized by using an 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 a phenolic tackifying resin and a ketone tackifying resin can be used. Such tackifier resin can be used individually by 1 type or in combination of 2 or more types.

Specific examples of rosin-based tackifying resins include unmodified rosins such as gum rosin, wood rosin, tall oil rosin (raw rosin); modified rosins modified by hydrogenation, disproportionation, polymerization, etc. Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same shall apply hereinafter.); Other various rosin derivatives; Examples of the rosin derivative include rosins such as those obtained by esterifying an unmodified rosin with an alcohol (that is, an esterified product of rosin) and those obtained by esterifying a modified rosin with an alcohol (that is, an esterified product of a modified rosin). Esters: Unmodified rosins and modified rosins modified with unsaturated fatty acids Unsaturated fatty acid modified rosins; Unmodified rosins, modified rosins, unsaturated rosin esters modified with unsaturated fatty acids Rosin alcohols obtained by reducing carboxyl groups 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 employed as the base polymer, it is preferable to use a rosin tackifier resin. From the viewpoint of improving adhesive properties such as adhesive strength, one of these rosin-based tackifying resins can be selected alone, or two or more of different types and properties (for example, softening point) can 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) and the like. Examples of the modified terpene resin include terpene-modified phenol resin, styrene-modified terpene resin, aromatic modified terpene resin, hydrogenated terpene resin, and the like. When an acrylic polymer is employed as the base polymer, it is preferable to use a terpene 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 terpene-based tackifier resins (for example, terpene-modified phenol resins) having different types and properties (for example, softening point) are used in combination. It is preferable.

Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc. ), Various hydrocarbon resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone indene resins, and the like.

In the technology disclosed herein, as the tackifier resin, those having a softening point (softening temperature) of about 70 ° C. or higher (preferably about 100 ° C. or higher, more preferably about 110 ° C. or higher) can be preferably used. According to the pressure-sensitive adhesive containing the tackifying resin having the softening point equal to or higher than the lower limit value described above, a pressure-sensitive adhesive sheet with more excellent adhesive force can be realized. Of the tackifying resins exemplified above, a terpene tackifying resin having a softening point (for example, a terpene-modified phenol resin), a rosin tackifying resin (for example, an esterified product of polymerized rosin), or 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). In addition, the softening point of the tackifier resin here is defined as a value measured by a softening point test method (ring and ball method) defined in either JIS K 5902 or JIS K 2207.

The amount of the tackifier used is not particularly limited, and can be appropriately set according to the target tack performance (adhesive strength, etc.). For example, the tackifier is used at a ratio of about 10 to 100 parts by weight (more preferably 20 to 80 parts by weight, more preferably 30 to 60 parts by weight) based on 100 parts by weight of the acrylic polymer on a solid basis. It is preferable to do. You may implement the technique disclosed here in the aspect provided with the adhesive layer which does not contain a tackifier substantially.

When the pressure-sensitive adhesive layer is composed of a rubber-based pressure-sensitive adhesive, the rubber-based pressure-sensitive adhesive preferably contains a high softening point resin having a softening point of 120 ° C. or higher as a tackifier resin. The pressure-sensitive adhesive sheet of this embodiment 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, more preferably 135 ° C. or higher, for example, 140 ° C. or higher). Further, from the viewpoint of adhesive strength to the adherend, the softening point of the high softening point resin is usually appropriately 200 ° C. or lower, preferably 180 ° C. or lower, more preferably 170 ° C. or lower (eg 160 ° C. or lower). ).

As the above high softening point resin, terpene phenol resin, polymerized rosin, esterified polymerized rosin and the like can be preferably employed. These high softening point resins can be used singly or in appropriate combination of two or more. As a preferable embodiment, there is an embodiment in which the high softening point resin contains one or more terpene phenol resins. 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, eg, 125 ° C. or higher and 170 ° C. or lower) can be preferably used.

As the terpene phenol resin, those having 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) are preferable. Can be adopted. According to the terpene phenol resin having such a hydroxyl value, a higher performance pressure-sensitive adhesive sheet can be realized. As the value of the hydroxyl value in this specification, a value measured by a potentiometric titration method defined in JIS K 0070: 1992 can be adopted. As a specific measuring method, a method described in JP 2014-55235 A is employed.

For example, the technology disclosed herein includes a rubber softener having 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 mg KOH / g (for example, 80 to 140 mg KOH / g) of a high softening point resin (H2) may be preferably used in combination. In this case, the relationship between the amounts used of the high softening point resin (H1) and the high softening point resin (H2) is such that, for example, the weight ratio (H1: H2) is in the range of 1: 5 to 5: 1. In general, it is appropriate to set the range of 1: 3 to 3: 1 (for example, 1: 2 to 2: 1). A preferred embodiment 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 and holding power, the content of the high softening point resin can be, for example, 20 parts by weight or more with respect to 100 parts by weight of the base polymer, 30 parts by weight or more (for example, 35 parts by weight or more). ) Is preferable. From the viewpoint of adhesive strength, low temperature characteristics, etc., the content of the high softening point resin relative to 100 parts by weight of the base polymer is usually suitably 100 parts by weight or less, preferably 80 parts by weight or less, more preferably Is 70 parts by weight or less. The content of the high softening point resin may be 60 parts by weight or less (for example, 50 parts by weight or less).

The technology disclosed herein is an embodiment in which the rubber-based pressure-sensitive adhesive contains a low softening point resin having a softening point of less than 120 ° C. instead of or in addition to the high softening point resin. Can be implemented. As a preferable embodiment, an embodiment in which the rubber-based pressure-sensitive adhesive includes a high softening point resin having a softening point of 120 ° C. or more 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, for example, 40 ° C. or higher (typically 60 ° C. or higher) can be used. From the viewpoint of repulsion resistance, holding power, etc., usually, those having a softening point of 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 implemented in a mode in which the rubber-based adhesive includes 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 occupying 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 can be preferably employed. 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 of the low softening point resin (for example, 95% by weight or more) may be a terpene resin.

In a preferred embodiment, the low softening point resin may be a tackifying resin (low hydroxyl value tackifying resin) having a hydroxyl value of 0 or more and less than 80 mgKOH / g. As the low hydroxyl value tackifier resin, those having a hydroxyl value in the above range among the above-mentioned various tackifier resins can be used alone or in appropriate 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, a polymerized rosin), a rosin A derivative resin (for example, esterified product of polymerized rosin) or the like can be used.

From the viewpoint of adhesive strength to the adherend, the content of the low softening point resin can be, for example, 10 parts by weight or more, and usually 15 parts by weight or more (for example, 20 parts by weight) with respect to 100 parts by weight of the base polymer. 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). 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 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 be 1: 5 to 2: 1). In the technology disclosed herein, the rubber-based pressure-sensitive adhesive includes an aspect in which a higher softening point resin is included as a tackifier resin than a low softening point resin (for example, a weight ratio of a low softening point resin to a high softening point resin is 1). : 1.2 to 1: 5). According to this aspect, a higher performance pressure-sensitive adhesive sheet can be realized.

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

(Crosslinking agent)
The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer disclosed herein may contain a crosslinking agent as necessary. The kind in particular of a crosslinking agent is not restrict | limited, It can select from a conventionally well-known crosslinking agent suitably and can be used. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, metal chelate crosslinking agents, and the like. It is done. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Among these, from the viewpoint of improving cohesive strength, it is preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent, and an isocyanate-based crosslinking agent is more preferable.

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

(Other ingredients)
The pressure-sensitive adhesive composition can be used as required by leveling agents, crosslinking aids, plasticizers, softeners, colorants (dyes, pigments), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light It may contain various additives generally used in the field of pressure-sensitive adhesive compositions, such as stabilizers and dispersants. Further, for example, an adhesive strength adjusting agent such as a silicone oligomer may be added to the pressure-sensitive adhesive composition (typically an acrylic pressure-sensitive adhesive composition). About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | 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-type pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. . The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer forming component) in a water-based solvent (water-based solvent), and is typically dispersed in water. What is called a type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like are included. Moreover, a solvent-type adhesive composition means the adhesive composition of the form which contains an adhesive in an organic solvent. The technique disclosed here is preferably implemented 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 strength.

(Method for 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 peelable surface (peeling surface) and drying it can be employed. Alternatively, a method (direct method) of forming the pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the film-like substrate and drying it can be employed. Also, a method of transferring a pressure-sensitive adhesive layer to a film-like substrate (transfer) by forming a pressure-sensitive adhesive layer on the surface by applying a pressure-sensitive adhesive composition to a peelable surface (peeling surface) and drying it (transfer) Method). As the release surface, the surface of the release liner, the back surface of the substrate after the release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, for example, a regular or random pattern such as a dot or stripe. The formed adhesive layer may be sufficient.

Application of the pressure-sensitive adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. Moreover, it is preferable to perform drying of an adhesive composition under heating from viewpoints, such as acceleration | stimulation of a crosslinking reaction and a manufacturing efficiency improvement. The drying temperature can be, for example, about 40 to 150 ° C. (preferably about 60 to 130 ° C.). After drying the pressure-sensitive adhesive composition, it may be further aged for the purpose of adjusting component migration in the pressure-sensitive adhesive layer, progress of the crosslinking reaction, relaxation of strain that may exist in the base material or pressure-sensitive adhesive layer, etc. Good.

(Adhesive layer thickness)
The thickness of the pressure-sensitive adhesive layer disclosed herein is not particularly limited and can be appropriately selected depending on the purpose. Usually, the thickness of the pressure-sensitive adhesive layer is suitably about 3 to 200 μm, preferably about 5 to 150 μm, more preferably 8 to 100 μm from the viewpoint of productivity such as drying efficiency and pressure-sensitive adhesive performance. More preferably, it is 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-like substrate, the thickness of each pressure-sensitive adhesive layer may be the same or different.

<Film substrate>
It is preferable that the film-like base material disclosed here exhibits a breaking strength of 10 MPa or more. By using the film-like base material exhibiting the above breaking strength, the pressure-sensitive adhesive sheet is more difficult to tear and can exhibit excellent tensile removability. According to the film-like base material exhibiting the breaking strength, 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). Further, from the viewpoint of elasticity and extensibility of the film-like substrate, the breaking strength is preferably about 100 MPa or less (for example, 90 MPa or less, typically 80 MPa or less). The said breaking strength is measured by the method similar to the case of an adhesive sheet. The same method is adopted for the embodiments described later. The breaking strength of the base material can be adjusted by, for example, selecting the base material type (selecting the blending ratio of the hard component and the soft component), the molding method, and the like.

The film-like substrate disclosed here preferably has extensibility. By using an extensible substrate, an extensible adhesive sheet is preferably realized. By using an 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-like substrate can be 50% or more (for example, 100% or more, typically 200% or more). In a preferred embodiment, the film-like substrate exhibits an elongation at break of 300% or more. The base material exhibiting the elongation at break extends with respect to the tension when the pressure-sensitive adhesive sheet is removed. By this extension, the adhesive sheet is deformed and peeled off from the adherend. In this way, the tension and the deformation of the base material interact with each other, and the tensile removability of the 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 removal workability. 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 embodiments described later. The elongation at break of the base material can be adjusted, for example, by selecting the base material type (selecting the mixing ratio of the hard component and the soft component), the molding method, and the like.

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

It is preferable that the film-like substrate disclosed here exhibits a 5% modulus of less than 10 MPa. When the 5% modulus of the film-like substrate is less than the predetermined value, when removing from the adherend by stretching and deforming the pressure-sensitive adhesive sheet, the resistance at the beginning of pulling tends to decrease and the tensile removability tends to be excellent. is there. The 5% modulus is more preferably less than 5 MPa (for example, less than 3 MPa, typically less than 2 MPa). Although the lower limit of the 5% modulus is not particularly limited, it is usually appropriate to set it to 0.5 MPa or more (for example, 1 MPa or more) from the viewpoint of workability for attaching the adhesive sheet. The 5% modulus is measured in accordance with the “tensile stress” measurement method described in JIS K 7311: 1995. More specifically, using a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm), the tensile stress was 300 mm / min, and the stress when the marked line distance was extended by 5% [MPa ] Is 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 embodiments described later. The 5% modulus of the base material can be adjusted, for example, by selecting the base material type (selecting the mixing ratio of the hard component and the soft component), the molding method, and the like.

It is preferable that the film-like substrate disclosed here exhibits a 100% modulus of less than 10 MPa. By making the 100% modulus of the film-like substrate less than the predetermined value, when removing from the adherend by pulling and stretching the pressure-sensitive adhesive sheet, the resistance at the beginning of pulling tends to decrease and the tensile removability tends to be excellent. is there. The 100% modulus is more preferably less than 5 MPa. The lower limit of the 100% modulus is not particularly limited, but it is usually suitably 0.5 MPa or more (for example, 1 MPa or more) from the viewpoint of the workability of attaching the adhesive sheet. The 100% modulus is measured by the same method as that for the pressure-sensitive adhesive sheet. The same method can be adopted for the embodiments described later.

It is preferable that the film-like substrate disclosed here exhibits a 150% modulus of less than 20 MPa. By making the 150% modulus of the film-like substrate less than a predetermined value, the resistance at the time of the tensile removal work tends to be small when the adhesive sheet is removed from the adherend by stretching and deforming. The 150% modulus is more preferably less than 15 MPa (for example, less than 12 MPa, typically less than 8 MPa). The lower limit of the 150% modulus is not particularly limited, but is usually 1 MPa or more (for example, 5 MPa or more) from the viewpoint of workability for attaching the adhesive sheet. The 150% modulus is measured according to the “tensile stress” measurement method described in JIS K 7311: 1995. More specifically, using a No. 3 dumbbell-shaped test piece (width 5 mm, marked line interval 20 mm), the tensile stress was 300 mm / min, and the stress [MPa when the marked line distance was increased by 150%] ] Is assumed to be 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 embodiments described later. The 150% modulus of the base material can be adjusted, for example, by selecting the base material type (selecting the mixing ratio of the hard component and the soft component), the molding method, and the like.

Various film-like substrates can be used as the film-like substrate (supporting substrate) for supporting (lining) the pressure-sensitive adhesive layer. As the substrate, for example, a woven fabric film, a nonwoven fabric film, or a resin film can be used. Among these, a resin film is preferable. The resin film may be a non-foamed resin film, a rubber-like film, a foam film, or the like. Of these, non-foamed resin films and rubber-like films are preferred, and non-foamed resin films are more preferred. The non-foamed resin film is substantially free of bubbles that can be a weak point in terms of mechanical strength, and tends to be superior in mechanical strength such as tensile strength as compared with a foam. Non-foamed resin films are also excellent in terms of processability, dimensional stability, thickness accuracy, economy (cost), and the like.
In addition, the “resin film” in this specification is a substantially non-porous film and is a concept that is distinguished from a so-called nonwoven fabric or woven fabric (ie, a concept that excludes nonwoven fabric or woven fabric). In addition, the non-foamed resin film refers to a resin film that has not been intentionally processed to form a foam. Specifically, the non-foamed resin film may be a resin film having an expansion 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.

Preferred examples of the resin material constituting the resin film disclosed herein include polyurethanes such as ether polyurethane, ester polyurethane and carbonate polyurethane; urethane (meth) acrylate polymers; polyethylene (PE), polypropylene (PP) And polyolefins such as ethylene-propylene copolymer and ethylene-butene copolymer; 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 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, or a styrene isoprene styrene copolymer. It may be a coalescence (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. In addition, what is generally called rubber | gum and a thermoplastic elastomer is included in the said resin material.

In a preferred embodiment, the film-like substrate is a polyurethane resin film. Here, the polyurethane-based resin film refers to a resin film containing polyurethane as a main component of a resin component (a component having the highest blending ratio, typically a component that exceeds 50% by weight; the same shall apply hereinafter). . A polyurethane-based resin film is typically made of a material that does not substantially exhibit a yield point, and is a film material that can easily realize a pressure-sensitive adhesive sheet that exhibits a predetermined breaking strength and elongation and, if necessary, a tensile recovery rate. It is. Since the polyurethane resin film can also realize good physical properties without adding an additive component such as a plasticizer, for example, it is a preferable group in the technology disclosed herein from the viewpoint of preventing the additive component from bleeding out. 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 (for example, 80% by weight or more, typically 90% by weight or more and 100% by weight or less). The polyurethane-based resin film disclosed herein may be a film made of a polymer blend of polyurethane and other resin. Said other resin may be 1 type (s) or 2 or more types, such as acrylic resin, polyolefin, polyester, a polycarbonate, for example. Or the technique disclosed here can be implemented also in the aspect using the base material which does not contain resin components other than a polyurethane substantially.

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

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

Examples of the polyisocyanate that can be used for the synthesis of 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 (isocyanatemethyl) cyclohexane, methylcyclohex Down diisocyanate, m- tetramethylxylylene diisocyanate, and the like. These can be used alone or in combination of two or more. Of these, aromatic diisocyanates are preferred.

In addition to polyol and polyisocyanate, other copolymer components may be introduced into the polyurethane. As other copolymerization components, one or more of monocarboxylic acid, dicarboxylic acid, trifunctional or higher polycarboxylic acid, hydroxycarboxylic acid, alkoxycarboxylic acid, and derivatives thereof can be used. The proportion of these other copolymerization components is suitably less than 30% by weight (for example, less than 10% by weight, typically less than 5% by weight) in the polyurethane. The technique disclosed here can also be preferably implemented in an embodiment including a polyurethane-based resin film base material mainly composed of polyurethane not containing other copolymerization components.

In another preferred embodiment, the film-like substrate is a resin film containing a urethane (meth) acrylate 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, 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 any 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. The number of (meth) acryloyl groups possessed by the urethane (meth) acrylate is preferably 2 to 5, and more preferably 2 to 3. For example, urethane (meth) acrylate having two (meth) acryloyl groups can be preferably used. The urethane (meth) acrylate is preferably urethane acrylate. Here, “urethane acrylate” refers to a (meth) acryloyl group contained in urethane (meth) acrylate in which the number ratio of acryloyl groups exceeds 50%.

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

In another preferred embodiment, the film-like substrate is a PVC resin film. The PVC-based resin film is produced by molding a PVC-based resin composition (molding material) containing a PVC-based resin into a film shape. 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). About 80% by weight or more (more preferably about 90% by weight or more) of the total resin component contained in the PVC-based resin composition is preferably a PVC-based resin. Substantially all of the resin component may be PVC. According to such a PVC-based resin composition, a PVC-based resin film having physical properties suitable as a base material for an adhesive sheet can be formed.

For film bases (for example, resin film bases), fillers (inorganic fillers, organic fillers, etc.), colorants (pigments, dyes), anti-aging agents, antioxidants, UV absorption, as necessary Various additives such as an agent, an antistatic agent, a lubricant, a plasticizer, and a stabilizer may be blended. For example, when a soft PVC-based resin film is used as the film-like substrate, the amount of 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-based resin. Is appropriate. The blending 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 conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and primer coating. Such a surface treatment may be a treatment for improving the adhesion between the film-like substrate and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the substrate. In addition, when a film-like base material is a polyurethane-type resin film, favorable anchoring property can be acquired even if the above surface treatments are not performed by the height of the surface energy.

The film-like substrate may have a single layer structure or a multilayer structure of 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 resin (more preferably polyurethane). The manufacturing method of a film-form base material should just employ a conventionally well-known method suitably, and is not specifically limited. When a resin film substrate is employed as the film substrate, for example, a conventionally known general film molding method such as extrusion molding, inflation molding, T-die casting molding, calendar roll molding, etc., is appropriately employed. A resin film substrate can be used.

The thickness of the film-like substrate is not particularly limited and can be appropriately selected according to the purpose. Usually, the thickness is suitably 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 thickness is difficult to break and can be excellent in tensile removability. The thickness of the film-like substrate is suitably 3 mm or less (for example, 2 mm or less, typically 1.5 mm or less). Further, the thickness of the film-like substrate is preferably 300 μm or less, more preferably 200 μm or less (for example, 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 technology disclosed herein, good tensile removability can be realized even in a configuration using a base material having a thickness equal to or less than the predetermined thickness. In addition, reducing the thickness of the film-like substrate is advantageous in terms of reducing the thickness, reducing the size, reducing the weight, and saving resources of the pressure-sensitive adhesive sheet.

<Release liner>
A conventional release paper or the like can be used as the release liner, and is not particularly limited. For example, it consists of 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 fluorine-based polymer (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, for example, by surface-treating the liner base material with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Size of adhesive sheet>
When the pressure-sensitive adhesive sheet disclosed herein has a long shape, the width thereof can be configured to be about 30 mm or less (for example, 20 mm or less, typically 15 mm or less). For example, when the pressure-sensitive adhesive sheet is used in a portable electronic device, the above width can be preferably adopted. From the viewpoint of preventing damage such as tearing during pulling, the width of the pressure-sensitive adhesive sheet is preferably 1 mm or more (eg, 3 mm or more, typically 5 mm or more), and is preferably 10 mm or more (eg, 12 mm or more). It is more preferable. In addition, when the whole adhesive sheet is elongate, the above-mentioned width | variety becomes a width | variety of an adhesive sheet.

When the pressure-sensitive adhesive sheet disclosed herein has a long shape, the length is preferably 1 cm or more (for example, 3 cm or more, typically 5 cm or more) from the viewpoint of removal workability by pulling. From the viewpoint of removal 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 here (including the pressure-sensitive adhesive layer and the base material, but not including the release liner) is not particularly limited, and is about 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 can be advantageous in terms of reducing the thickness of the product, reducing the size, reducing the weight, and saving resources. In another preferred embodiment, the total thickness of the pressure-sensitive adhesive sheet may be 80 μm or more (for example, 100 μm or more, typically 130 μm or more), and is more than 150 μm (for example, 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, for example, an application of fixing an adherend to be replaced after being attached to a wall surface or the like and used for a predetermined period.

Although the adhesive sheet disclosed here is not particularly limited, for example, metal materials such as stainless steel (SUS) and aluminum; inorganic materials such as glass and ceramics; nylon, polycarbonate (PC), polymethyl methacrylate (PMMA), It can be used by being attached to an adherend having a surface made of a resin material such as polypropylene or polyethylene terephthalate (PET); a rubber material such as natural rubber or butyl rubber; and a composite material thereof.

<Application>
The pressure-sensitive adhesive sheet disclosed herein exhibits a sufficient adhesion 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 applications that can be peeled off after being attached. For example, for fixing a protective panel (lens) that protects a display unit for electronic equipment, for fixing a decoration panel of a display (for example, a television display), for fixing a battery pack of a personal computer, and for waterproofing a lens of a digital video camera, The adhesive sheet disclosed here can be applied. Among them, it can be preferably used as a pressure-sensitive adhesive sheet for a portable electronic device that requires a predetermined or higher adhesive force during use, but requires smooth removal when repairing, exchanging, inspecting, or recycling components. For example, mobile phones, smartphones, tablet computers, laptop computers, various wearable devices (for example, wristwear devices that are worn on the wrist like wristwatches, modular devices that are worn on a part of the body with clips, straps, etc.) (Eyewear type including monocular type and binocular type, including head mounted type), clothing type attached to shirts, socks, hats, etc. in the form of accessories, earwear type attached to ears like earphones, etc.), Digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game machines, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information equipment, portable radios, portable TVs, mobile phones Protects display units in portable electronic devices such as printers, portable scanners, and portable modems Protection panel (lens) fixing, key module member fixing, rim sheet fixing, decoration panel fixing, battery fixing, and other various members (circuit boards, 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 logos, logos (design letters), and fixing of display objects (including various marks) such as various designs. The pressure-sensitive adhesive sheet disclosed herein exhibits a predetermined or higher pressure-sensitive adhesive force, so that when used in the portable electronic device, the adherent member can be fixed against an impact when the portable electronic device falls. The arrangement can be maintained. This is particularly advantageous in battery fixing applications. This is because the battery to be fixed can expand with use over time, so there is a gap around it, and poor fixing due to dropping impact etc. (peeling of the adhesive sheet) tends to be a significant defect. . In this specification, “carrying” means that it is not sufficient to be able to carry it alone, but that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. Shall mean.

Also, the pressure-sensitive adhesive sheet disclosed here (typically, a double-sided pressure-sensitive adhesive sheet) is excellent in the performance of being removed by being pulled out from between the adherends (drawing removal property). Here, the pull-out removal property means that a part (typically a tab) of the pressure-sensitive adhesive sheet is exposed from two adherends fixed via the pressure-sensitive adhesive sheet, and the exposed portion is pulled to form a pressure-sensitive adhesive sheet. It means the ease of removal such that the fixation (typically bonding) of the adherend is released by pulling out. Note that the two adherends may be two places of 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 tension removal (typically pull-out removal), and (a) is a diagram showing a state in which tension removal of the pressure-sensitive adhesive sheet is started, (b) is a figure which shows the state which is pulling and removing the adhesive sheet, (c) is a figure which shows the state which the tension removal of the adhesive sheet was completed. FIG. 4 is a schematic top view for explaining one aspect of tension removal (typically pull-out removal). (A) to (c) are respectively shown in (a) to (c) of FIG. It is a corresponding figure.

As shown in FIGS. 3A and 4A, the adhesive sheet (double-sided adhesive sheet) 200 is provided with a tab T that is exposed to the outside when the adherends A and B are joined. Yes. The adherend B is bonded to the adherend A using the adhesive sheet 200. And after achieving the said joining objective, the adhesive sheet 200 is pulled so that the tab T may be pinched with a finger and it may withdraw | drop from between the to-be-adhered bodies A and B. FIG. Then, the pressure-sensitive adhesive sheet 200 starts to expand, the direction orthogonal to the pulling direction contracts, and begins to peel off from the adherends A and B (see FIGS. 3B and 4B). Finally, the entire adhesion region of the pressure-sensitive adhesive sheet 200 is peeled off, and the pull-out of the pressure-sensitive adhesive sheet 200 from the adherends A and B is completed (see FIGS. 3C and 4C). Removal of the adherend B joined to the adherend A is also completed at the same time.

The pressure-sensitive adhesive sheet having excellent tensile removability 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 disposed at a place where it is necessary to remove the component (including the battery) of the portable electronic device when repairing, exchanging, or inspecting the component. Therefore, the adhesive sheet for fixing the battery is frequently required to be removed. However, removal of the battery by using physical means such as use of a removal tool, peeling off, or heating may damage the battery and may not be preferable in terms of safety. Reduction of peeling force by photocuring is not effective because it is irradiated through the battery due to the application site of the adhesive sheet. The pressure-sensitive adhesive sheet disclosed herein uses the above-described method of pulling out (typically pulling out) when removing the battery after the period of use while demonstrating the function of fixing the battery well. , 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. Because polymer batteries tend to be more easily deformed than other types of batteries (typically batteries with a metal case), conventional peeling methods can deform the battery and impair its function. there were. According to the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet can be satisfactorily removed while suppressing the deformation of the polymer battery by using the above-described pulling removal (typically, pull-out removal) method.

In addition, the adhesive sheet used to fix the battery of portable battery devices often cannot be pulled parallel to the shearing direction when it is removed due to other parts around the battery or the arrangement of the battery. . In such a case, the pressure-sensitive adhesive sheet is removed by pulling at an angle non-parallel to the adhesive surface (for example, an angle of 45 degrees or more and 90 degrees or less, typically an angle of 70 degrees or more and less than 90 degrees), During removal, there is a risk of damage due to contact with an adherend (battery) or an obstacle. According to the technique disclosed here, even in such a removal mode, the pressure-sensitive adhesive sheet can be preferably removed without being damaged.

Furthermore, the adhesive sheet having excellent tensile removability (typically pulling removability) is applied to a wall surface, pillar, furniture, home appliance, glass surface, etc. It is also suitable as an adhesive sheet (typically a double-sided adhesive sheet) used for the purpose of fixing a body (an object to be fixed, an object to be bonded, etc.). Also in this application, while fixing the adherend, the adhesive sheet exhibits a good fixing function, and when removing the adherend, grips a tab provided on the adhesive sheet and pulls out the entire adhesive sheet. Thus, the pressure-sensitive adhesive sheet can be efficiently removed (for example, removed in the direction of the arrow in FIG. 3C).

The matters disclosed by this specification include the following.
(1) It has an adhesive layer,
The initial adhesive strength A for polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B for polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains filler particles,
The adhesive sheet in which 50% by weight or more of the filler particles contained in the adhesive layer has a particle diameter smaller than the thickness of the adhesive layer.
(2) A pressure-sensitive adhesive layer, and a film-like substrate that supports the pressure-sensitive adhesive layer,
The initial adhesive strength A for polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B for polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains filler particles,
The adhesive sheet in which 50% by weight or more of the filler particles contained in the adhesive layer has a particle diameter smaller than the thickness of the adhesive layer.
(3) The ratio (B / A) of the tensile peel stress B [N / 20 mm] to the initial adhesive strength A [N / 20 mm] is 3.0 or less, as described in (1) or (2) above. Adhesive sheet.
(4) The pressure-sensitive adhesive sheet according to any one of the above (1) to (3), which has an elongated portion and has extensibility at least in the longitudinal direction thereof.
(5) The state according to (4) above, wherein the state of being attached to the adherend is released by pulling from one end of the elongated portion in the state of being attached to the adherend. Adhesive sheet.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the filler particles contained in the pressure-sensitive adhesive layer have a proportion of particles having a particle diameter of less than 1 μm of 50% by weight or less.
(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6), wherein a content C of the filler particles in the pressure-sensitive adhesive layer is 30% by volume or less.
(8) The pressure-sensitive adhesive according to any one of (1) to (7), further comprising a film-like substrate that supports the pressure-sensitive adhesive layer, wherein the film-like substrate is a non-foamed resin film substrate. Sheet.
(9) A film-like base material that supports 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-like base material, and the film-like base material A pressure-sensitive adhesive sheet according to any one of the above (1) to (8), comprising a second pressure-sensitive adhesive layer provided on the second surface.
(10) The pressure-sensitive adhesive sheet according to (9), which is used to join two adherends and is removed from the two adherends by being pulled out between the two adherends.
(11) The pressure-sensitive adhesive sheet according to any one of (1) to (10), further comprising a tab.
(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11), which is used for a portable electronic device.
(13) The pressure-sensitive adhesive sheet according to (12), which is used for fixing a battery.

(14) The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has a formula (1):
CH ₂ = C (R ¹ ) COOR ² (1)
(In the above formula (1), R ¹ is a hydrogen atom or a methyl group. 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 is contained at a ratio of 70% by weight or more.
(15) The alkyl (meth) acrylate includes 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 and eicosyl (meth) acrylate The pressure-sensitive adhesive sheet according to (14), which is at least one selected from the group consisting of:
(16) The acrylic polymer further includes a functional group-containing monomer as the monomer component,
The functional group-containing monomers include 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), which is at least one selected from the group consisting of hydroxybutyl (meth) acrylate.
(17) The pressure-sensitive adhesive layer contains a tackifier resin having a softening point of 100 ° C or higher,
The pressure-sensitive adhesive sheet according to any one of the above (14) to (16), wherein the tackifying resin contains at least one of a rosin-based tackifying resin and a terpene-based tackifying resin.
(18) The pressure-sensitive adhesive sheet according to any one 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 one of (14) to (18), wherein the pressure-sensitive adhesive layer contains an acrylic oligomer.

(20) The filler particles include 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, dosonite, 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) The filler particles have a ratio of particles having a particle diameter of less than 20 μm of 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, dowsonite, 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, (1) to (20) The adhesive sheet in any one of.
(22) The filler particles have an average particle size of 0.5 μm to 30 μm, particles having a particle size of less than 20 μm account for 50% by weight or more, and the proportion of particles having a particle size of less than 1 μm is 50% by weight. And
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 the above (1) to (21), which is at least one selected from the group consisting of basic magnesium carbonate, hydrotalcite, dowsonite, 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 the above (1) to (22), which is a polymer of

(24) It further comprises a film-like substrate that supports the pressure-sensitive adhesive layer, and the film-like substrate is a resin film substrate having an expansion ratio of less than 1.1 times.
Any of (1) to (23) above, wherein the film-like 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 pressure-sensitive adhesive sheet has a breaking strength of 10 MPa or more, an elongation at break of 300% or more, a 100% modulus of less than 10 MPa,
It further comprises a film-like substrate that supports the pressure-sensitive adhesive layer,
The film-like 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), wherein the polyurethane is an ether-based polyurethane, an ester-based polyurethane, or a carbonate-based polyurethane.

(26) 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 adhesive sheet in 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 (26) or (27), wherein the block copolymer is a styrene block copolymer having a styrene content of 5 to 40% by weight.
(29) The pressure-sensitive adhesive layer includes 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 includes 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 one of (26) to (28), 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-like substrate that supports the pressure-sensitive adhesive layer,
The pressure-sensitive adhesive sheet has a long portion and has extensibility at least in the longitudinal direction thereof,
A tab is provided at one end in the longitudinal direction,
The initial adhesive strength A for polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B for polycarbonate is 22 N / 20 mm or less,
The pressure-sensitive adhesive layer contains an acrylic polymer in a proportion exceeding 50% by weight of the polymer component contained in the pressure-sensitive adhesive layer,
The acrylic polymer has a formula (1):
CH ₂ = C (R ¹ ) COOR ² (1)
(In the above formula (1), R ¹ is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms.) In a proportion of 70% by weight or more,
The alkyl (meth) acrylate includes 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 syl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate and eicosyl (meth) acrylate At least one selected from
The acrylic polymer further includes a functional group-containing monomer as the monomer component,
The functional group-containing monomers include 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 size of 0.5 μm to 30 μm, particles having a particle size of less than 20 μm account for 50% by weight or more, and the proportion of particles having a particle size 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 basic magnesium carbonate, hydrotalcite, dowsonite, borax and zinc borate,
The filler particle content C in the pressure-sensitive adhesive layer is 30% by volume or less,
The pressure-sensitive adhesive layer includes a tackifier resin having a softening point of 100 ° C. or higher,
The tackifying resin includes 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-like substrate is a resin film substrate having an expansion ratio of less than 1.1 times,
The pressure-sensitive adhesive sheet has a breaking strength of 10 MPa or more, an elongation at break of 300% or more, a 100% modulus of less than 10 MPa,
The film-like substrate contains polyurethane in a proportion of 70% by weight or more,
The polyurethane is an ether polyurethane, ester polyurethane or carbonate polyurethane,
The pressure-sensitive adhesive sheet, wherein a ratio (B / A) of the tensile peeling stress B [N / 20 mm] to the initial pressure-sensitive adhesive force A [N / 20 mm] is 3.0 or less.

Hereinafter, some examples related to the present invention will be described, but the present invention is not intended to be limited to the examples shown in the examples. In the following description, “parts” 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 inlet tube, a reflux condenser, and a dropping funnel, 100 parts of BA, 5 parts of VAc, 3 parts of AA, 0.1 part of HEA, and 0.2 part of AIBN as a polymerization initiator 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 the acrylic polymer A was 55 × 10 ⁴ .
For 100 parts of acrylic polymer A contained in the toluene solution, 40 parts of polymerized rosin ester resin (product name “Pencel D-125”, softening point 125 ° C., manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier resin, and isocyanate type 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 (manufactured by Showa Denko Co., Ltd., trade name “Hijilite H-21”) as filler particles are added. By mixing, an 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, the proportion of particles having a particle size of less than 25 μm is 40% or more, and the proportion of particles having a particle size of less than 1 μm is 0%.

(Production of double-sided PSA sheet)
Two commercially available release liners (trade name “SLB-80W3D”, manufactured by Sumika Kogyo Co., Ltd.) were prepared. The pressure-sensitive adhesive composition was applied to 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 formed on the release surfaces of the two release liners.
Non-foamed ether polyurethane resin film with a thickness of 100 μm (made 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 as a film-like substrate 1.6 MPa, 150% modulus 6.4 to 6.5 MPa). The pressure-sensitive adhesive layers formed on the two release liners were bonded to both surfaces of the film-like substrate. The release liner was left on the pressure-sensitive adhesive layer as it was and used for protecting the surface (pressure-sensitive surface) of the pressure-sensitive adhesive layer. The obtained structure was passed through a laminator (0.3 MPa, speed 0.5 m / min) at 80 ° C. once and then aged in an oven at 50 ° C. for 1 day. Thus, the double-sided adhesive sheet which concerns on this example was obtained.

<Examples 2 to 7>
As shown in Table 1, the amount of filler particles added is 5 parts (Example 2), 10 parts (Example 3), 20 parts (Example 4), 30 parts (Example 5) with respect 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 PSA 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 (trade name “Hijilite H-31” manufactured by Showa Denko KK). The filler particles used in these examples have an average particle diameter of 18 μm, a ratio of particles having a particle diameter of less than 25 μm is 54% or more, and a ratio of particles having a particle diameter of less than 1 μm is 1%.

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

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

<Example 29>
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 70 parts of BA, 30 parts of 2EHA, 3 parts of AA, 0.05 part of 4HBA, 0.2 part of AIBN 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. Mw of this acrylic polymer B was 55 × 10 ⁴ .
For 100 parts of acrylic polymer B contained in the toluene solution, 30 parts of polymerized rosin ester resin (product name “Pencel D-125”, softening point 125 ° C., manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier resin, and isocyanate type 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 (manufactured by Showa Denko Co., Ltd., trade name “Hijilite H-32”) as filler particles are added. By mixing, an 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 filler particles added was changed to 40 parts with respect to 100 parts of the acrylic polymer B.

<Example 31>
In the same manner as in Example 29, a toluene solution of acrylic polymer B was prepared, and 1 part of an isocyanate-based crosslinking agent (product name “Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts of the acrylic polymer B. 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 pressure-sensitive 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 PSA sheet according to this example was prepared in the same manner as in Example 31 except that the amount of 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 the filler particles were not added.

With respect to the double-sided PSA sheets of Examples 1 to 33, the initial adhesive strength A [N / 20 mm] and the tensile peel stress B [N / 20 mm] were measured by the methods described above. Further, the appearance of the adhesive surface and the presence or absence of adhesive residue were also evaluated.
As for the appearance of the adhesive surface, the surface (adhesive surface) of the adhesive sheet of each example was visually observed, and when it was smooth, it was evaluated as “◯”, and when streaks or irregularities were observed, it was evaluated as “x”. did.
The presence or absence of glue residue is determined by visually observing the adherend after measuring the tensile peel stress B. If no glue residue is observed, it is evaluated as “◯”. Evaluated as “x”.
The results are shown in Tables 1 to 3. Table 3 also shows the outline and results of Examples 19 and 20 for comparison. In the table, in the measurement of the tensile peel stress B, “−” was shown when almost no adhesion occurred.

As shown in Tables 1 to 3, by including filler particles in the pressure-sensitive adhesive layer, it was possible to selectively reduce the tensile peeling stress B while suppressing a decrease in the initial adhesive strength A. This is clear from the comparison between Example 33 and Examples 19 and 20 in which no filler particles were added. Further, in the example where the tensile peeling stress B is equal to or less than a predetermined value, adhesive residue is also prevented. Furthermore, from the results of the above examples, it can be seen that the optimum addition amount varies depending on the particle size of the filler particles. Specifically, the filler particles having a large particle size are desirably added in a relatively small amount, and the filler particles having a small particle size are desirably formed in a relatively large amount. However, for example, as in Examples 1 to 7, when the particle size of the filler particles is equal to or greater than a predetermined value in relation to the thickness of the pressure-sensitive adhesive layer, the surface condition of the pressure-sensitive adhesive layer is adversely affected, and the pressure-sensitive adhesive performance It can be seen that not only the deterioration of the adhesive surface but also the deterioration of the appearance of the adhesive surface can be significant.

From the above results, the adhesive sheets of Examples 8 to 11, Examples 19 to 21, and 26 to 32 have an initial adhesive strength A to PC of 3 N / 20 mm or more and a tensile peel stress B to PC of 22 N / 20 mm or less. From this, it can be seen that a sufficient adhesive function is exhibited during use, and excellent tensile removability when removed. In particular, in Examples 19 to 21 and 26 to 30, the decrease in the initial adhesive strength A with respect to PC was suppressed to less than 10% as compared with Example 33 containing no filler particles, and the tensile peel stress B was nevertheless greatly increased. (For example, in Example 21, the tensile peel 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 in detail above, 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.

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 10 Film- like base material 21,22 Adhesive layer

Claims (13)

1. With an adhesive layer,
   The initial adhesive strength A for polycarbonate is 3 N / 20 mm or more, and the tensile peel stress B for polycarbonate is 22 N / 20 mm or less,
   The pressure-sensitive adhesive layer contains filler particles,
   The adhesive sheet in which 50% by weight or more of the filler particles contained in the adhesive layer has a particle diameter smaller than the thickness of the adhesive layer.
2. The pressure-sensitive adhesive sheet according to claim 1, further comprising a film-like substrate that supports the pressure-sensitive adhesive layer.
3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein a ratio (B / A) of the tensile peeling stress B [N / 20mm] to the initial pressure-sensitive adhesive force A [N / 20mm] is 3.0 or less.
4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which has an elongated portion and has extensibility at least in the longitudinal direction thereof.
5. The pressure-sensitive adhesive sheet according to claim 4, wherein the state of being attached to the adherend is released by pulling from one end of the elongated portion while being attached to the adherend.
6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the filler particles contained in the pressure-sensitive adhesive layer have a proportion of particles having a particle diameter of less than 1 µm of 50% by weight or less.
7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein a content C of the filler particles in the pressure-sensitive adhesive layer is 30% by volume or less.
8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, further comprising a film-like substrate that supports the pressure-sensitive adhesive layer, wherein the film-like substrate is a non-foamed resin film substrate.
9. The pressure-sensitive adhesive layer comprises a first pressure-sensitive adhesive layer provided on the first surface of the film-like substrate and a second pressure-sensitive adhesive layer provided on the second surface of the film-like substrate. Item 9. The pressure-sensitive adhesive sheet according to item 8.
10. 10. The pressure-sensitive adhesive sheet according to claim 9, wherein the pressure-sensitive adhesive sheet is used to join two adherends and is removed from the two adherends by being pulled out between the two adherends.
11. The pressure-sensitive adhesive sheet according to any one of claims 1 to 10, further comprising a tab.
12. The pressure-sensitive adhesive sheet according to any one of claims 1 to 11, which is used for a portable electronic device.
13. The pressure-sensitive adhesive sheet according to claim 12, which is used for fixing a battery.

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