JP2021042276A - Pressure sensitive adhesive sheet - Google Patents

Abstract

To provide a pressure sensitive adhesive sheet exhibiting low adhesiveness at an initial stage of adhesion onto an adherend, capable of largely increasing an adhesive force by heating, whereas having a function of facilitating re-peeling.SOLUTION: A pressure sensitive adhesive sheet 1 includes an adhesive layer 21. The adhesive layer includes a polymer A as a base polymer and a heat-expandable microsphere having an expansion start temperature T1. An adhesive force N2 measured at 23°C after heated at a temperature lower than the expansion start temperature T1 by 20°C for 5 minutes being bonded on a stainless steel plate is 3.0 times an adhesive force N1 measured after held at 23°C for 30 minutes being bonded on a stainless steel plate.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive sheet.

In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is widely used in various fields in the form of a pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on the base material or in the form of a base-less pressure-sensitive adhesive sheet having no base material. It's being used.

Adhesives are required to have various properties depending on the application. Among these characteristics, there are some that are difficult to achieve at a high level, such as an attempt to improve one characteristic tends to reduce the other characteristic. As an example of such characteristics that are difficult to achieve at the same time, there are adhesive force to the adherend and reworkability. The above-mentioned rework is, for example, when the adhesive sheet is attached to the adherend due to failure (positional deviation, wrinkles, bubbles, foreign matter, etc.), or after the adhesive sheet is attached to the adherend. When a defect is found, the adhesive sheet is peeled off from the adherend and reattached. In response to such a request, Patent Document 1 proposes an adhesive sheet that exhibits low adhesive strength at the initial stage of attachment to an adherend and can greatly increase the adhesive strength thereafter.

Japanese Patent No. 6355874

According to the adhesive sheet described in Patent Document 1, by performing steps such as positioning and inspection before the adhesive strength increases, good reattachability (reworkability) can be exhibited in the steps and the members can be reused. And, after increasing the adhesive strength by heating or the like, strong adhesiveness can be exhibited. On the other hand, Patent Document 1 does not consider facilitating the re-peeling of the pressure-sensitive adhesive sheet whose adhesive strength has been increased. Improving the peelability of the adhesive sheet is beneficial in situations such as repair, collection, and disposal of the member to which the adhesive sheet is attached.

Therefore, the present invention provides an adhesive sheet that exhibits low adhesiveness at the initial stage of attachment to an adherend, can greatly increase the adhesive force by heating, and has a function of facilitating re-peeling. The purpose.

This specification provides a pressure-sensitive adhesive sheet that includes a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer contains polymer A as a base polymer and thermally expandable microspheres having an expansion start temperature T1. The pressure-sensitive adhesive sheet is attached to a stainless steel (SUS) steel plate and heated at a temperature 20 ° C. lower than the expansion start temperature T1 for 5 minutes, and then measured at 23 ° C. ) Is 3.0 times or more the adhesive strength N1 (hereinafter, also referred to as “initial adhesive strength”) measured after being bonded to a SUS plate and held at 23 ° C. for 30 minutes.

Since the pressure-sensitive adhesive sheet having such a structure has a large ratio of the post-heating adhesive force (N2) to the initial adhesive force (N1) (hereinafter, also referred to as “adhesive force increase ratio”), the heat expandability blended in the pressure-sensitive adhesive layer. The adhesive strength can be greatly increased without expanding the microspheres. Further, by heating to a temperature equal to or higher than the expansion start temperature T1, the thermally expandable microspheres can be expanded to reduce the adhesive force and improve the peelability of the adhesive sheet from the adherend.

The polymer A has a storage elastic modulus G'(hereinafter, also referred to as "storage elastic modulus G'(T1)") at the expansion start temperature T1 in the range of ^{approximately 1 × 10 4} Pa to 1 × 10 ^{6 Pa.} It is preferable to have. The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer using the polymer A as the base polymer has good adhesion to the adherend when the heat-expandable microspheres are not expanded, and has a peelability by expanding the heat-expandable microspheres. Easy to develop.

_{The polymer A preferably has a glass transition temperature Tg A} calculated by the Fox formula based on the composition of the monomer components constituting the polymer A of −65 ° C. or higher and lower than 0 ° C. The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer using the polymer A as the base polymer has good adhesion to the surface of the adherend when the heat-expandable microspheres are not expanded, and is peelable by expanding the heat-expandable microspheres. Is easy to express.

The content of the heat-expandable microspheres in the pressure-sensitive adhesive layer can be in the range of, for example, 10 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the polymer A. According to the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer having such a composition, the strong adhesiveness after the increase in the adhesive strength and the peelability by expanding the heat-expandable microspheres can be suitably compatible with each other.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer may further comprise polymer B, which is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer. By using the polymer B, an adhesive sheet having an adhesive strength increase ratio of 3.0 or more can be preferably realized.

_{The polymer B has a glass transition temperature Tg B} (hereinafter, may be simply referred to as “Tg _B ”) calculated by the Fox formula based on the composition of the (meth) acrylic monomer at 30 ° C. or higher and 120. It is preferably ℃ or less. The pressure-sensitive adhesive sheet disclosed herein can be preferably carried out using a polymer B having _{Tg B in the above range.}

In some embodiments, the polymer B preferably has a glass transition temperature Tg _B lower than the expansion start temperature T1 by 20 ° C. or more. According to the polymer B having Tg _B , a pressure-sensitive adhesive sheet having high adhesive strength after heating and good peelability due to expansion of heat-expandable microspheres can be preferably realized.

In some embodiments, the content of the polymer B in the pressure-sensitive adhesive layer can be, for example, in the range of 0.5 parts by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the polymer A. According to the content in the above range, it is possible to preferably achieve both the initial low adhesiveness and the strong adhesiveness after the increase in adhesive strength.

The pressure-sensitive adhesive sheet disclosed herein includes a support base material having a first surface and a second surface, and the pressure-sensitive adhesive layer is laminated on at least the first surface side of the support base material, that is, a base material. It can be carried out in the form of an adhesive sheet with. Such a pressure-sensitive adhesive sheet with a base material can be easy to handle and process.

The pressure-sensitive adhesive layer may be directly laminated on the first surface side of the support base material, or may be laminated via another layer (intermediate layer). In a preferred embodiment, an elastic intermediate layer is arranged between the pressure-sensitive adhesive layer and the first surface of the supporting substrate. As a result, the effect of reducing the adhesive force due to the expansion of the heat-expandable microspheres contained in the pressure-sensitive adhesive layer is effectively exerted on the adherend, and the pressure-sensitive adhesive layer is a supporting base material via the elastic intermediate layer. It is possible to preferably maintain the laminated form.

In addition, an appropriate combination of the above-mentioned elements may be included in the scope of the invention for which protection by the patent is sought by the present patent application.

It is sectional drawing which shows typically the structure of the pressure-sensitive adhesive sheet which concerns on one Embodiment. It is sectional drawing which shows typically the structure of the pressure-sensitive adhesive sheet which concerns on another embodiment. It is sectional drawing which shows typically the structure of the pressure-sensitive adhesive sheet which concerns on another embodiment.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the practice of the present invention are based on the teachings regarding the practice of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by a person skilled in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art.
In the following drawings, members / parts having the same function may be described with the same reference numerals, and duplicate description may be omitted or simplified. In addition, the embodiments described in the drawings are schematicized for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the actually provided product.

Further, in the present specification, the "acrylic polymer" refers to a polymer containing a monomer unit derived from a (meth) acrylic monomer in a polymer structure, and is typically a monomer derived from a (meth) acrylic monomer. A polymer containing a unit of more than 50% by weight. The (meth) acrylic monomer means a monomer having at least one (meth) acryloyl group in one molecule. Here, the "(meth) acryloyl group" means a comprehensive term for an acryloyl group and a methacryloyl group. Therefore, the concept of the (meth) acrylic monomer here may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth) acrylic acid" means acrylic acid and methacrylic acid, and "(meth) acrylate" means acrylate and methacrylate, respectively.

<Structural example of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein is configured to include a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a base-attached pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on one side or both sides of a support base material, and is a base material-less pressure-sensitive adhesive sheet having no support base material. It may be in the form. Hereinafter, the supporting base material may be simply referred to as a "base material".

The structure of the pressure-sensitive adhesive sheet according to one embodiment is schematically shown in FIG. The pressure-sensitive adhesive sheet 1 is a single-sided pressure-sensitive adhesive sheet with a base material having a sheet-shaped support base material 10 having a first surface 10A and a second surface 10B and an adhesive layer 21 provided on the first surface 10A side thereof. It is configured. In the configuration shown in FIG. 1, the elastic intermediate layer 50 is arranged between the first surface 10A of the support base material 10 and the pressure-sensitive adhesive layer 21. That is, the pressure-sensitive adhesive layer 21 is laminated on the first surface 10A of the support base material 10 via the elastic intermediate layer 50, and is preferably fixed. The elastic intermediate layer 50 is an arbitrary component and may be omitted. For example, the pressure-sensitive adhesive layer 21 may be directly laminated on the first surface 10A side of the support base material 10 and preferably adhered.
The pressure-sensitive adhesive sheet 1 is used by attaching the pressure-sensitive adhesive layer 21 to the adherend. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 before use (that is, before being attached to the adherend) has peelability on the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 at least on the side facing the pressure-sensitive adhesive layer 21. It may be a component of the pressure-sensitive adhesive sheet 100 with a release liner in a form of being in contact with the release liner 31 which is the surface (release surface). As the release liner 31, for example, a sheet-like base material (liner base material) having a release layer provided with a release treatment agent on one side thereof so that one side becomes a release surface can be preferably used. Alternatively, the release liner 31 is omitted, the support base material 10 having the second surface 10B as the release surface is used, and the adhesive sheet 1 is wound around to make the adhesive surface 21A into the second surface 10B of the support base material 10. It may be in contact with each other (roll form). When the adhesive sheet 1 is attached to the adherend, the release liner 31 or the second surface 10B of the support base material 10 is peeled off from the adhesive surface 21A, and the exposed adhesive surface 21A is pressure-bonded to the adherend.

The structure of the pressure-sensitive adhesive sheet according to the other embodiment is schematically shown in FIG. The pressure-sensitive adhesive sheet 2 is provided on a sheet-shaped support base material 10 having a first surface 10A and a second surface 10B, an adhesive layer 21 provided on the first surface 10A side thereof, and a second surface 10B side. It is configured as a double-sided pressure-sensitive adhesive sheet with a base material, which comprises the pressure-sensitive adhesive layer 22. In the configuration shown in FIG. 2, the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 21 is on the first surface 10A of the support base material 10, and the pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) 22 is on the second surface of the support base material 10. Each is directly laminated on 10B and preferably fixed. Alternatively, in the configuration shown in FIG. 2, on one or both of the first surface 10A of the support base material 10 and the pressure-sensitive adhesive layer 21 and between the second surface 10B of the support base material 10 and the pressure-sensitive adhesive layer 22. The elastic intermediate layer may be arranged as in FIG.
The pressure-sensitive adhesive sheet 2 is used by attaching the pressure-sensitive adhesive layers 21 and 22 to different parts of the adherend. The locations to which the pressure-sensitive adhesive layers 21 and 22 are attached may be individual locations of different members, or may be different locations within a single member. In the pressure-sensitive adhesive sheet 2 before use, as shown in FIG. 2, the surface (first adhesive surface) 21A of the pressure-sensitive adhesive layer 21 and the surface (second adhesive surface) 22A of the pressure-sensitive adhesive layer 22 are at least the pressure-sensitive adhesive layer 21, It can be a component of the pressure-sensitive adhesive sheet 200 with a release liner in a form of contacting the release liners 31 and 32 whose sides facing the 22 are the release surfaces, respectively. As the release liners 31 and 32, for example, those configured by providing a release layer with a release treatment agent on one side of a sheet-shaped base material (liner base material) so that one side becomes a release surface are preferably used. obtain. Alternatively, the release liner 32 is omitted, a release liner 31 having both sides as release surfaces is used, and the adhesive sheet 2 is overlapped with the release liner 31 and wound in a spiral shape so that the second adhesive surface 22A becomes the release liner 31. An adhesive sheet with a release liner in a form (roll form) in contact with the back surface of the surface may be configured.

The structure of the pressure-sensitive adhesive sheet according to still another embodiment is schematically shown in FIG. The pressure-sensitive adhesive sheet 3 is configured as a base-less double-sided pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer 21. The pressure-sensitive adhesive sheet 3 has a first pressure-sensitive adhesive surface 21A composed of one surface (first surface) of the pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive surface composed of the other surface (second surface) of the pressure-sensitive adhesive layer 21. 21B and 21B are attached to different parts of the adherend and used. As shown in FIG. 3, the adhesive sheet 3 before use has release liners 31 and 32 in which the first adhesive surface 21A and the second adhesive surface) 21B have at least the side facing the adhesive layer 21 as the release surface, respectively. It can be a component of the pressure-sensitive adhesive sheet 300 with a release liner in contact with the surface. Alternatively, the release liner 32 is omitted, a release liner 31 having both sides as release surfaces is used, and the adhesive sheet 3 is overlapped with the release liner 31 and wound in a spiral shape so that the second adhesive surface 21B becomes the release liner 31. An adhesive sheet with a release liner in a form (roll form) in contact with the back surface of the surface may be configured.

The pressure-sensitive adhesive sheet disclosed herein includes, if necessary, an intermediate layer other than the elastic intermediate layer, such as an undercoat layer, an adhesive layer, and an antistatic layer, between the supporting base material and the pressure-sensitive adhesive layer. May be good. In the case of a pressure-sensitive adhesive sheet having an elastic intermediate layer between the supporting base material and the pressure-sensitive adhesive layer, such an intermediate layer may be arranged between the supporting base material and the elastic intermediate layer, and may be arranged between the supporting base material and the elastic intermediate layer. It may be arranged between the layers and the pressure-sensitive adhesive layer.

The concept of the pressure-sensitive adhesive sheet here may include what is called an pressure-sensitive adhesive tape, a pressure-sensitive adhesive film, a pressure-sensitive adhesive label, or the like. The pressure-sensitive adhesive sheet may be in a roll form, a single-wafer form, or may be cut or punched into an appropriate shape according to the intended use and usage mode. The pressure-sensitive adhesive layer in the technique disclosed herein is typically formed continuously, but is not limited to this, even if it is formed in a regular or random pattern such as a dot shape or a striped shape. Good.

<Characteristics of adhesive sheet>
(Adhesive strength increase ratio)
The pressure-sensitive adhesive sheet disclosed herein is an adhesive strength increase ratio defined as the ratio of the post-heated adhesive strength (N2) [N / 20 mm] to the initial adhesive strength (N1) [N / 20 mm] (that is, N2 / N1). Is preferably 3.0 or more. An adhesive sheet having a large adhesive force increase ratio is initially heated at a temperature sufficiently lower than the expansion start temperature T1 of the inflatable microsphere (for example, a temperature 20 ° C. lower than the expansion start temperature T1) for a relatively short time. The adhesive strength can be greatly increased. Therefore, according to the pressure-sensitive adhesive sheet having a large adhesive strength increase ratio, it is possible to preferably achieve both the initial low adhesiveness and the strong adhesiveness at the time of use. Further, since the pressure-sensitive adhesive sheet after the increase in adhesive strength contains unexpanded heat-expandable microspheres, it is possible to improve the peelability of the pressure-sensitive adhesive sheet whose adhesive strength has once increased by expanding it at an arbitrary timing.

From the viewpoint of achieving both the initial low adhesiveness and the strong adhesiveness at the time of use at a higher level, the adhesive strength increase ratio is preferably 4.0 or more, preferably 5.0 or more, in some embodiments. More preferably, it may be 6.0 or more, 7.5 or more, 10 or more, 15 or more, or 18 or more. The upper limit of the adhesive strength increase ratio is not particularly limited, but may be, for example, 150 or less, 100 or less, or 80 or less, from the viewpoint of facilitating the suitable development of the peelability due to the expansion of the heat-expandable microspheres. It may be 50 or less, 40 or less, or 30 or less. The pressure-sensitive adhesive sheet disclosed herein can also be preferably carried out in an embodiment in which the pressure-increasing ratio is 20 or less, 14 or less, or 9 or less.

(Initial adhesive strength)
The initial adhesive strength of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. The initial adhesive strength can be set so as to exhibit the desired reworkability according to the purpose of use and the mode of use of the pressure-sensitive adhesive sheet. In some embodiments, the initial adhesive strength may be, for example, less than 2.5N / 20mm, usually less than 2.3N / 20mm, and may be less than 2.0N / 20mm. It may be less than 5N / 20mm and may be less than 1.0N / 20mm. The lower limit of the initial adhesive strength is not particularly limited and may be, for example, 0.001N / 20mm or more. From the viewpoint of sticking workability to the adherend and prevention of positional deviation before the adhesive strength increases, it is usually appropriate that the initial adhesive strength is 0.01 N / 20 mm or more, and the strength after the adhesive strength increases. From the viewpoint of facilitating compatibility with adhesiveness, it may be, for example, 0.1 N / 20 mm or more. In some embodiments, the initial adhesive strength may be, for example, 0.3N / 20mm or higher, 0.5N / 20mm or higher, 0.8N / 20mm or higher, or 1.2N / 20mm or higher.

(Adhesive force after heating)
In the pressure-sensitive adhesive sheet disclosed herein, the adhesive strength after heating is not particularly limited, and can be set according to the purpose and mode of use of the pressure-sensitive adhesive sheet. From the viewpoint of joining reliability, in some embodiments, the adhesive strength after heating may be, for example, 2.5 N / 20 mm or more, and usually 3.0 N / 20 mm or more, preferably 4.0 N / 20 mm or more. The above is more preferable, and it may be 5.0 N / 20 mm or more, 7.0 N / 20 mm or more, 10 N / 20 mm or more, or 12 N / 20 mm or more. The upper limit of the adhesive force after heating is not particularly limited, but from the viewpoint of ease of manufacturing and economic efficiency of the adhesive sheet, for example, it may be 50 N / 20 mm or less, 40 N / 20 mm or less, 30 N / 20 mm or less, 25 N. It may be 20 mm or less. In some embodiments, the post-heating adhesive force N2 may be, for example, 20 N / 20 mm or less, 17 N / 20 mm or less, or 13 N / 20 mm or less, from the viewpoint of enhancing the peelability due to the expansion of the heat-expandable microspheres. It can also be carried out in an embodiment of 9N / 20 mm or less.

Here, the initial adhesive force [N / 20 mm] is applied by crimping to a stainless steel (SUS) plate as an adherend and leaving it in an environment of 23 ° C. and 50% RH for 30 minutes, and then in the same environment (that is, 23). (At ° C), the peeling angle is 180 degrees, and the tensile speed is 300 mm / min.
The adhesive strength [N / 20 mm] after heating is 20 ° C. from the expansion start temperature T1 [° C.] of the heat-expandable microspheres contained in the adhesive layer of the adhesive sheet to be evaluated by being pressure-bonded to the SUS plate as an adherend. After heating at a low temperature (hereinafter, also referred to as “heat treatment temperature T2”) for 5 minutes and then leaving it in an environment of 23 ° C. and 50% RH for 30 minutes, the peeling angle is 180 degrees and the tensile speed is 300 mm / It is grasped by measuring the adhesive strength of 180 ° peeling under the condition of minutes.
As the adherend, a SUS304BA plate is used in any of the measurements of the initial adhesive strength, the adhesive strength after heating, and the peel strength N3 after the expansion treatment described later. In the measurement, if necessary, an appropriate backing material (for example, a PET film having a thickness of about 25 μm) can be attached to the adhesive sheet to be measured to reinforce it. More specifically, these adhesive strengths can be measured according to the method described in Examples described later.

The adhesive strength after heating of the pressure-sensitive adhesive sheet disclosed herein represents one characteristic of the pressure-sensitive adhesive sheet, and does not limit the usage mode of the pressure-sensitive adhesive sheet. In other words, the mode of use of the pressure-sensitive adhesive sheet disclosed herein is not limited to a mode in which the pressure-sensitive adhesive strength is increased by heating at the heat treatment temperature T2 for 5 minutes after being attached to the adherend, for example, in the room temperature range (usually). Can also be used in an embodiment in which the treatment of heating to 20 ° C. to 30 ° C., typically 23 ° C. to 25 ° C. or higher is not particularly performed. Even in such a usage mode, the adhesive strength is increased in the long term, and a strong bond can be realized. Further, the pressure-sensitive adhesive sheet disclosed here can promote an increase in adhesive strength by performing heat treatment at an arbitrary timing after sticking at a temperature higher than 30 ° C. and lower than the expansion start temperature T1. The heating temperature T3 in such a heat treatment is not particularly limited, and can be set in consideration of workability, economy, heat resistance of the base material of the pressure-sensitive adhesive sheet and the adherend, and the like. The heating temperature T3 is not particularly limited as long as it is lower than the expansion start temperature T1, and can be, for example, less than 170 ° C., 150 ° C. or lower, 120 ° C. or lower, or 100 ° C. or lower. It may be 80 ° C. or lower, 70 ° C. or lower, and the heating temperature T3 may be, for example, 40 ° C. or higher, 50 ° C. or higher, 60 ° C. or higher, 70 ° C. or higher. The temperature may be 80 ° C. or higher, or 100 ° C. or higher. The heating time is not particularly limited, and may be, for example, 1 hour or less, 30 minutes or less, 10 minutes or less, or 5 minutes or less. The heating time may be, for example, 1 minute or longer, 3 minutes or longer, 7 minutes or longer, or 15 minutes or longer. Alternatively, the heat treatment may be performed for a longer period of time as long as the pressure-sensitive adhesive sheet and the adherend are not significantly deteriorated by heat. The heat treatment may be performed at one time or may be divided into a plurality of times.

In some embodiments, the heating temperature T3 [° C.] is preferably 5 ° C. or higher lower than the expansion start temperature T1 [° C.], more preferably 10 ° C. or higher, and 15 ° C. or higher or The temperature may be as low as 20 ° C. or higher. By increasing the temperature difference (T1-T3), it is possible to better suppress the phenomenon that the thermally expandable microspheres unintentionally expand due to temperature non-uniformity during heat treatment for increasing the adhesive force. Can be done. The upper limit of the temperature difference (T1-T3) is not particularly limited and can be, for example, 150 ° C. or lower, 125 ° C. or lower, 100 ° C. or lower, or 80 ° C. or lower from the viewpoint of heat treatment efficiency. It may be 50 ° C. or lower.

(Expansion processing)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is formed from the adherend by performing a treatment (expansion treatment) for expanding the heat-expandable microspheres contained in the pressure-sensitive adhesive layer after being attached to the adherend. Can enhance the peelability of. For example, when the heat-expandable microspheres expand, the pressure-sensitive adhesive layer containing the heat-expandable microspheres expands and deforms, and the adhesion to the adherend decreases and the adhesive strength decreases. The heating temperature in the expansion treatment is usually a temperature equal to or higher than the expansion start temperature T1 of the thermally expandable microsphere (for example, a temperature 5 ° C. or higher, 10 ° C. or higher or 15 ° C. or higher higher than the expansion start temperature T1). Is appropriate. The upper limit of the heating temperature in the expansion treatment is not particularly limited, but from the viewpoint of heat resistance of the adherend or the adhesive sheet, energy cost, etc., it is usually appropriate to set it to 250 ° C, and it may be set to 200 ° C or less. Preferably, it may be 180 ° C. or lower. The heating means used in the expansion treatment is not particularly limited, and one or more of the known heating means can be applied simultaneously or stepwise. Non-limiting examples of the heating means may include hot plates, hot air dryers, infrared lamps, hot water supplies and the like. The heating time in the thermal expansion treatment can be set so that the expansion of the thermal expansion microspheres proceeds appropriately. In some embodiments, the heating time can be selected from, for example, about 1 second to 30 minutes, preferably about 10 seconds to 15 minutes, from the viewpoint of ease of process control and productivity.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet has a post-expansion-treated adhesive force N3 measured by the following procedures (1) to (5) of less than 1.0 N / 20 mm. It is preferably less than 0.5 N / 20 mm, more preferably less than 0.5 N / 20 mm. Here, the post-expansion treatment adhesive force N3 [N / 20 mm] is a value of the 180 ° peeling adhesive force measured in the following procedure (5) per width of 20 mm of the measurement sample, for example, the following procedure (4). ), Even if a part of the area of the measurement sample is peeled off from the adherend and lifted up, it is not converted into the value per 20 mm width of the portion where the measurement sample is in close contact with the adherend. Further, in the following procedure (5), when the tensile test cannot be appropriately performed because the measurement sample is extremely easily peeled off from the adherend (for example, most of the area of the measurement sample is obtained by the expansion treatment of the above (4). Is peeled off from the adherend and floated up), it can be evaluated that the peelability at the expansion start temperature T1 is good.
[Measurement procedure of peel strength N3 after expansion treatment]
(1) The pressure-sensitive adhesive sheet to be evaluated is pressure-bonded to a SUS plate as an adherend to prepare a measurement sample.
(2) The measurement sample is heated for 5 minutes at a temperature 20 ° C. lower than the expansion start temperature T1 [° C.] of the heat-expandable microspheres contained in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (heat treatment temperature T2).
(3) The measurement sample is left in an environment of 23 ° C. and 50% RH for 30 minutes.
(4) Next, the measurement sample is heated at the expansion start temperature T1 [° C.] for 5 minutes.
(5) The measurement sample is left in an environment of 23 ° C. and 50% RH for 30 minutes, and then peeled off by 180 ° in the same environment (that is, at 23 ° C.) under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm / min. Measure the adhesive strength.

<Adhesive layer>
The pressure-sensitive adhesive layer in the technique disclosed herein contains polymer A as a base polymer and thermally expandable microspheres. The polymer A is a polymer of the monomer raw material A. The pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing a complete polymer or a partial polymer of the monomer raw material A and a heat-expandable microsphere. The form of the pressure-sensitive adhesive composition is not particularly limited, and may be various forms such as a solvent type, an aqueous dispersion type, a hot melt type, and an active energy ray-curable type (for example, a photocurable type).

(Thermal expansion microsphere)
The heat-expandable microspheres are not particularly limited, and can be appropriately selected from known heat-expandable microspheres (various inorganic heat-expandable microspheres, organic heat-expandable microspheres, and the like). As the heat-expandable microspheres, a microencapsulated foaming agent can be preferably used from the viewpoint of easy mixing operation. Examples of such heat-expandable microspheres include microspheres in which a substance that easily gasifies and expands by heating, such as isobutane, propane, and pentane, is encapsulated in an elastic shell. The shell is often formed of a hot-meltable substance or a substance that is destroyed by thermal expansion. Examples of the substance forming the shell include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethylmethacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone and the like.

The heat-expandable microspheres can be produced by a conventional method, for example, a core selvation method, an interfacial polymerization method, or the like. For the heat-expandable microspheres, for example, a series of the product name "Matsumoto Microsphere" manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. "301D", "Matsumoto Microsphere F-50D", "Matsumoto Microsphere F-501D", "Matsumoto Microsphere F-80SD", "Matsumoto Microsphere F-80VSD", etc.) , Product name "051DU", "053DU", "551DU", "551-20DU", "551-80DU", Sekisui Chemical Co., Ltd. Commercial products such as can be used.

The average particle size D of the heat-expandable microspheres can be appropriately selected depending on the thickness Ta and the like of the pressure-sensitive adhesive layer containing the heat-expandable microspheres. From the viewpoint of smoothness of the surface (adhesive surface) of the pressure-sensitive adhesive layer attached to the adherend and avoiding cohesive destruction of the pressure-sensitive adhesive layer due to expansion of the heat-expandable microspheres, in some embodiments, the heat-expandable microspheres The average particle size of the above may be, for example, 100 μm or less, 80 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 13 μm or less. Further, from the viewpoint of the handleability of the heat-expandable microspheres and the peeling effect due to expansion, in some embodiments, the average particle size of the heat-expandable microspheres may be, for example, 1 μm or more, 3 μm or more, or 5 μm. It may be more than or equal to 8 μm or more. Here, the average particle size means the particle size (50% volume average particle size) at an integrated value of 50% in the volume-based particle size distribution obtained by a measuring device based on the laser diffraction / scattering method. The particle size of the heat-expandable microspheres may be adjusted in the process of producing the heat-expandable microspheres, or may be performed by means such as classification after the formation. In some embodiments, the heat-expandable microspheres may be those having a uniform particle size by means such as classification.

The expansion start temperature T1 of the heat-expandable microspheres is not particularly limited, but is usually 60 ° C. from the viewpoint of avoiding a situation in which the heat-expandable microspheres inadvertently expand at a timing when the adhesive sheet is not intended to be peeled off. It is appropriate, preferably 70 ° C. or higher, 80 ° C. or higher, 90 ° C. or higher, 100 ° C. or higher, 120 ° C. or higher, 140 ° C. or higher, 160 ° C. or higher. .. From the viewpoint of heat resistance of the adherend and energy cost, the expansion start temperature T1 of the thermally expandable microsphere is usually preferably 230 ° C., preferably 210 ° C. or lower, and preferably 200 ° C. It is more preferably 180 ° C. or lower, 150 ° C. or lower, 130 ° C. or lower, or 100 ° C. or lower.

In the present specification, the expansion start temperature T1 of the thermally expandable microspheres starts to increase in volume of the microcapsules when measured at a heating rate of 10 ° C./min using a thermomechanical analyzer. It refers to the temperature at which it was made.

From the viewpoint of efficiently and stably reducing the adhesive force to the adherend by the expansion of the thermally expandable microspheres, the volume expansion rate is moderately not bursting until it becomes 5 times or more, especially 7 times or more, especially 10 times or more. Thermally expanding microspheres having a high strength are preferable.

The blending amount of the heat-expandable microspheres in the pressure-sensitive adhesive layer is not particularly limited, and can be set so that the effect of improving the peelability (decreasing the adhesive strength) by expanding the heat-expandable microspheres is appropriately exhibited. .. In some embodiments, the content of the heat-expandable microspheres relative to 100 parts by weight of the base polymer (ie, polymer A) of the pressure-sensitive adhesive layer can be, for example, 1 part by weight or more, typically 10 parts by weight or more. It may be 25 parts by weight or more, 35 parts by weight or more, 50 parts by weight or more, 70 parts by weight or more, or 85 parts by weight or more. Further, from the viewpoint of adhesion of the pressure-sensitive adhesive layer to the adherend before expanding the heat-expandable microspheres, the content of the heat-expandable microspheres with respect to 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer is usually 200. It is appropriate that the amount is 50 parts by weight or less, preferably 150 parts by weight or less, and more preferably 120 parts by weight or less.

(Foaming agent)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein may further contain a known foaming agent (a concept that does not contain heat-expandable microspheres) in addition to the heat-expandable microspheres. As the foaming agent, various foaming agents such as various inorganic foaming agents and organic foaming agents can be appropriately selected and used. The foaming agent may be used alone or in combination of two or more. Typical examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogencarbonate, sodium hydrogencarbonate, ammonium nitrite, sodium boron hydroxide, and various azides. Typical examples of organic foaming agents include water; alkane-fluorinated compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azobisisobutyronitrile, azodicarboxylicamide, and barium azodicarboxylate. Azo compounds such as paratoluenesulfonyl hydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 4,4'-oxybis (benzenesulfonylhydrazide), hydrazine compounds such as allylbis (sulfonylhydrazide); p-toluylene Semicarbazide compounds such as sulfonyl semicarbazide, 4,4'-oxybis (benzenesulfonyl semicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; N, N'-dinitrosopentamethylene terrorism Examples thereof include -nitroso compounds such as lamin, N, N'-dimethyl-N, N'-dinitrosoterephthalamide.

When such a foaming agent is used, the amount used can be, for example, in the range of 0.01 parts by weight to 25 parts by weight with respect to 100 parts by weight of the base polymer (that is, polymer A) of the pressure-sensitive adhesive layer. .. From the viewpoint of ease of controlling the timing of increasing or decreasing the adhesive strength, the amount of the foaming agent used with respect to 100 parts by weight of the base polymer is usually preferably 20 parts by weight or less, and preferably 10 parts by weight or less. More preferably, it may be 5 parts by weight or less, or 1 part by weight or less. It is preferable not to use a foaming agent.

(Polymer A)
Polymer A is the base polymer of the pressure-sensitive adhesive layer containing the heat-expandable microspheres. Here, in the present specification, the base polymer of the pressure-sensitive adhesive layer is typically a main component of a polymer component contained in the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, that is, a component occupying more than 50% by weight, for example. It can be a component that accounts for 75% by weight or more of the above polymer components. In some embodiments, the polymer A is a component that occupies more than 50% by weight of the entire pressure-sensitive adhesive layer, and may be a component that occupies 70% by weight or more.
In the pressure-sensitive adhesive sheet disclosed herein, the polymer A includes acrylic polymers, rubber-based polymers, polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, and polyamide-based polymers known in the field of pressure-sensitive adhesives. , Fluorine-based polymers, and one or more of various polymers that exhibit rubber elasticity in the room temperature range can be used.

Glass transition temperature Tg _A of the polymer A may be not particularly limited, the preferred characteristics in the PSA sheet disclosed herein is selected to obtain. In some embodiments, _{polymer A having a Tg A} of less than 0 ° C. may be preferably employed. Since such a pressure-sensitive adhesive containing the polymer A exhibits appropriate fluidity (for example, the motility of the polymer chains contained in the pressure-sensitive adhesive), the pressure-sensitive adhesive strength is efficiently increased without expanding the heat-expandable microspheres. Suitable for realizing an adhesive sheet that can be raised. The pressure-sensitive adhesive sheet disclosed herein can be _{preferably implemented using a polymer A having a Tg A} of less than −10 ° C., less than −20 ° C., less than −30 ° C. or less than −35 ° C. In some embodiments, Tg _A may be below −40 ° C. or below −45 ° C. The lower limit of Tg _A is not particularly limited. From the viewpoint of availability of the material and improvement of the cohesive force of the pressure-sensitive adhesive layer _{, polymer A having a Tg A} of −80 ° C. or higher, −70 ° C. or higher, or −65 ° C. or higher can be preferably adopted. In some embodiments, Tg _A may be, for example, −63 ° C. or higher, −55 ° C. or higher, −50 ° C. or higher, or −45 ° C. or higher.

Here, in this specification, the glass transition temperature (Tg) of a polymer is a nominal value described in literature, catalogs, etc., or by the Fox formula based on the composition of the monomer raw material used for the preparation of the polymer. The required Tg. As shown below, the Fox formula is a relational expression between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer in which each of the monomers constituting the copolymer is homopolymerized.
1 / Tg = Σ (Wi / Tgi)
In the Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the homopolymer of the monomer i. Represents the glass transition temperature (unit: K) of. When the target polymer for specifying Tg is a homopolymer, the Tg of the homopolymer and the Tg of the target polymer match.

As the glass transition temperature of the homopolymer used for calculating Tg, the value described in publicly known materials shall be used. Specifically, the figures are listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). For the monomers whose multiple types of values are described in the Polymer Handbook, the highest value is adopted.

As the glass transition temperature of the homopolymer of the monomer not described in the Polymer Handbook, the value obtained by the following measurement method shall be used.
Specifically, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by weight of a monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and acetic acid as a polymerization solvent. Add 200 parts by weight of ethyl and stir for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain with a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES"). The viscoelasticity is measured in a shear mode at a temperature range of −70 ° C. to 150 ° C. and a temperature rising rate of 5 ° C./min, and the temperature corresponding to the peak top temperature of tan δ is defined as Tg of the homopolymer.

Although not particularly limited, the weight-average molecular weight of the polymer A (Mw) is usually suitably be at about 20 × 10 ⁴ or more. According to the polymer A of Mw, a pressure-sensitive adhesive showing good cohesiveness can be easily obtained. The Mw of the polymer A may be, for example, 30 × 10 ⁴ or more, 40 × 10 ⁴ or more, or 50 × 10 ⁴ or more. From the viewpoint of obtaining a higher cohesive force, in some embodiments, Mw of the polymer A may be a 60 × 10 ⁴ or more, may be 80 × 10 ⁴ or more. Also, Mw of the polymer A is generally suitably be at about 500 × 10 ⁴ or less. Since the polymer A of Mw easily forms an adhesive exhibiting appropriate fluidity (movability of polymer chains), the adhesive sheet having a low adhesive strength at the initial stage of application and a high adhesive strength after the increase in adhesive strength is used. Suitable for realization. In some embodiments, Mw of the polymer A is, for example may be a 250 × 10 ⁴ or less, may be a 200 × 10 ⁴ or less, may be 0.99 × 10 ⁴ or less.

In this specification, Mw of polymer A and polymer B described later can be determined by gel permeation chromatography (GPC) in terms of polystyrene. More specifically, Mw can be measured according to the methods and conditions described in the examples described later.

The storage elastic modulus G'(storage elastic modulus G'(T1)) of the polymer A at the expansion start temperature T1 of the thermally expandable microspheres is not particularly limited, and is, for example, about 1 × 10 ³ Pa to 1 × 10 ^{6 Pa.} Can be. Since the storage elastic modulus G'at the expansion start temperature T1 is not too low, the function of deforming the pressure-sensitive adhesive layer by the expansion of the heat-expandable microspheres to improve the peelability (decrease the adhesive strength) can be preferably exhibited. .. From this point of view, the storage elastic modulus G'(T1) is ^{preferably 10 kPa (10 × 10 3} Pa) or more, more preferably 15 kPa or more, 20 kPa or more, 40 kPa or more, and 60 kPa or more. It may be. Further, from the viewpoint of adhesion to the adherend before expanding the heat-expandable microspheres, the storage elastic modulus G'(T1) is usually preferably 500 kPa or less, and is 300 kPa or less. Is preferable, and it is more preferably 150 kPa or less, 100 kPa or less, 80 kPa or less, or 50 kPa or less.

As the polymer A in the pressure-sensitive adhesive sheet disclosed herein, an acrylic polymer can be preferably adopted. In particular, in the embodiment in which the pressure-sensitive adhesive layer contains the polymer B described later in addition to the polymer A, when an acrylic polymer is used as the polymer A, good compatibility with the polymer B tends to be easily obtained. Good compatibility between the polymer A and the polymer B is preferable because it can contribute to the reduction of the initial adhesive force and the improvement of the adhesive force after heating through the improvement of the mobility of the polymer B in the pressure-sensitive adhesive layer.

The acrylic polymer is, for example, a polymer containing 50% by weight or more of a monomer unit derived from (meth) acrylic acid alkyl ester, that is, 50 out of the total amount of the monomer component (monomer raw material A) for preparing the acrylic polymer. It can be a polymer in which% by weight or more is a (meth) acrylic acid alkyl ester. As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms (that is, C _{1-20) can be preferably used.} Since it is easy to balance the characteristics, _{the ratio of the (meth) acrylic acid C 1-20} alkyl ester in the monomer raw material A may be, for example, 50% by weight or more, 60% by weight or more, or 70% by weight or more. But it may be. For the same reason, the proportion of the (meth) acrylic acid C _1-20 alkyl ester in the monomer raw material A may be, for example, 99.9% by weight or less, 98% by weight or less, or 95% by weight or less. .. In some embodiments, the proportion of the (meth) acrylic acid C _1-20 alkyl ester in the monomer raw material A may be, for example, 90% by weight or less, 85% by weight or less, or 80% by weight or less.

Non-limiting specific examples of (meth) acrylic acid C _1-20 alkyl ester include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, ( N-butyl acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) Hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth) ) Decyl acrylate, Isodecyl (meth) acrylate, Undecyl (meth) acrylate, Dodecyl (meth) acrylate, Tridecyl (meth) acrylate, Tetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, (meth) Hexadecyl acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, nonadecil (meth) acrylate, eicosyl (meth) acrylate and the like can be mentioned.

Of these, it is preferable to use at least (meth) acrylic acid C _1-18 alkyl ester, and it is more preferable to use at least (meth) acrylic acid C _{1-14 alkyl ester.} In some embodiments, the acrylic polymer is at least one selected from _{(meth) acrylic acid C 4-12} alkyl esters (preferably acrylic acid C _4-10 alkyl esters, eg acrylic acid C _{6-10 alkyl esters).} Can be contained as a monomer unit. For example, an acrylic polymer containing one or both of n-butyl (BA) acrylate and 2-ethylhexyl acrylate (2EHA) is preferable, and an acrylic polymer containing at least 2 EHA is particularly preferable. Examples of other (meth) acrylic acid C _1-18 alkyl esters that may be preferably used are methyl acrylate, methyl methacrylate (MMA), n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA). , Isostearyl acrylate (ISTA) and the like.

The monomer raw material A may contain, if necessary, another monomer (copolymerizable monomer) copolymerizable with the (meth) acrylic acid alkyl ester as well as the (meth) acrylic acid alkyl ester as the main component. .. As the copolymerizable monomer, a monomer having a polar group (for example, a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) can be preferably used. Monomers having polar groups can be useful for introducing cross-linking points into acrylic polymers and increasing the cohesive force of acrylic polymers. The copolymerizable monomer may be used alone or in combination of two or more.

Non-limiting specific examples of the copolymerizable monomer include the following.
Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic. 4-Hydroxybutyl acid, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxy) Hydroxyalkyl (meth) acrylates such as methylcyclohexyl) methyl (meth) acrylate.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N- Vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloyl piperidine, N- (meth) acryloylpyrrolidin, N-vinylmorpholin, N-vinyl-3 -Morholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxadin-2-one, N-vinyl-3,5-morpholindione, N-vinylpyrazole, N-vinylisoxazole, N-vinyl Thiazol, N-vinylisothiazole, N-vinylpyridazine, etc .;
Monomers having a succinimide skeleton, such as N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyhexamethylene succinimide;
Maleimides such as, for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide; and
For example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc. Itaconimides.
Carboxy group-containing monomer: For example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and the like.
Acid anhydride group-containing monomer: For example, maleic anhydride, itaconic anhydride.
Epoxy group-containing monomer: For example, an epoxy group-containing acrylate such as glycidyl (meth) acrylate or -2-ethyl glycidyl ether (meth) acrylate, allyl glycidyl ether, glycidyl ether (meth) acrylate and the like.
Cyanide-containing monomer: For example, acrylonitrile, methacrylonitrile, etc.
Isocyanate group-containing monomer: For example, 2-isocyanate ethyl (meth) acrylate and the like.
Amide group-containing monomers: For example, (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth). N, N-dialkyl (meth) acrylamide, such as acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide; N-ethyl (meth) N-alkyl (meth) acrylamide such as acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, Nn-butyl (meth) acrylamide; N-vinylcarboxylic acid amide such as N-vinylacetamide Classes; monomers having a hydroxyl group and an amide group, for example, N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth). Acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) ( N-Hydroxyalkyl (meth) acrylamide, such as meta) acrylamide; monomers with an alkoxy group and an amide group, such as N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-butoxymethyl ( N-alkoxyalkyl (meth) acrylamide such as meta) acrylamide; In addition, N, N-dimethylaminopropyl (meth) acrylamide, N- (meth) acryloylmorpholine and the like.
Aminoalkyl (meth) acrylates: For example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, t (meth) acrylate. -Butylaminoethyl.
Alkoxy group-containing monomers: for example, 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, (meth) acrylate. Alkoxyalkyls (meth) acrylate, such as butoxyethyl, ethoxypropyl (meth) acrylate; Alkoxyalkylene glycol (meth) acrylate, such as methoxyethylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, etc. Kind.
Monomers containing sulfonic acid groups or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfo. Propyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid, 2-hydroxyethylacryloyl phosphate, etc.
(Meta) acrylic acid ester having an alicyclic hydrocarbon group: For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate and the like.
(Meta) acrylic acid ester having an aromatic hydrocarbon group: For example, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate and the like.
Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Vinyl esters: For example, vinyl acetate, vinyl propionate and the like.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene and the like.
In addition, heterocyclic-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, halogen atom-containing (meth) acrylates such as vinyl chloride and fluorine atom-containing (meth) acrylates, and silicon atom-containing silicone (meth) acrylates. (Meta) acrylate, (meth) acrylic acid ester obtained from terpene compound derivative alcohol, etc.

When such a copolymerizable monomer is used, the amount used is not particularly limited, but it is usually appropriate to use 0.01% by weight or more of the monomer raw material A. From the viewpoint of better exerting the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1% by weight or more of the monomer raw material A or 1% by weight or more. The amount of the copolymerizable monomer used can be 50% by weight or less of the monomer raw material A, and preferably 45% by weight or less. As a result, it is possible to prevent the cohesive force of the adhesive from becoming too high and improve the tack feeling at room temperature (25 ° C.). In some embodiments, the amount of the copolymerizable monomer used may be 40% by weight or less or 35% by weight or less of the monomer raw material A.

In some embodiments, the monomer raw material A may comprise a monomer having a nitrogen atom-containing ring. By using a monomer having a nitrogen atom-containing ring, the cohesive force and polarity of the adhesive can be adjusted, and the adhesive force after heating can be suitably improved. By including the monomer having a nitrogen atom-containing ring in the monomer raw material A, the compatibility between the polymer A formed from the monomer raw material A and the polymer B tends to be improved. As a result, it becomes easy to obtain an adhesive sheet capable of greatly increasing the adhesive force at a temperature lower than the expansion start temperature T1.

The monomer having a nitrogen atom-containing ring can be appropriately selected from, for example, the above-mentioned examples, and one type can be used alone or two or more types can be used in combination. In some embodiments, the monomer raw material A may contain, as a monomer having a nitrogen atom-containing ring, at least one monomer selected from the group consisting of N-vinyl cyclic amide represented by the following general formula (M1). preferable. The monomer raw material A may contain only one or more of such N-vinyl cyclic amides as a monomer having a nitrogen atom-containing ring.

ここで、上記一般式（Ｍ１）中のＲ^１は、２価の有機基である。

^{Here, R 1} in the above general formula (M1) is a divalent organic group.

Specific examples of N-vinyl cyclic amide include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, and N-vinyl-1,3. -Oxazine-2-one, N-vinyl-3,5-morpholindione and the like can be mentioned. Particularly preferred are N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactam.

The amount of the monomer having a nitrogen atom-containing ring is not particularly limited, and is usually 0.01% by weight or more (preferably 0.1% by weight or more, for example 0.5% by weight or more) of the monomer raw material A. Is appropriate. In some embodiments, the amount of the monomer having a nitrogen atom-containing ring used may be 1% by weight or more, 5% by weight or more, 10% by weight or more, or 12% by weight or more of the monomer raw material A. May be. Further, from the viewpoint of improving the tack feeling at room temperature (25 ° C.) and improving the flexibility at low temperature, it is usually appropriate that the amount of the monomer having a nitrogen atom-containing ring used is 40% by weight or less of the monomer raw material A. Yes, it may be 30% by weight or less, 20% by weight or less, or 18% by weight or less.

In some preferred embodiments, the monomer raw material A comprises a hydroxyl group-containing monomer. By using the hydroxyl group-containing monomer, the cohesive force and polarity of the adhesive can be adjusted, and the adhesive force after heating can be suitably improved. Further, the hydroxyl group-containing monomer provides a reaction point with a cross-linking agent (for example, an isocyanate-based cross-linking agent) described later, and the cohesive force of the pressure-sensitive adhesive can be enhanced by the cross-linking reaction.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and N- (2-hydroxyethyl) (meth) acrylamide. It can be preferably used. Of these, preferred examples include 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA), and N- (2-hydroxyethyl) acrylamide (HEAA).

The amount of the hydroxyl group-containing monomer used is not particularly limited, and is usually preferably 0.01% by weight or more (preferably 0.1% by weight or more, for example 0.5% by weight or more) of the monomer raw material A. .. In some embodiments, the amount of the hydroxyl group-containing monomer used may be 1% by weight or more, 5% by weight or more, or 10% by weight or more of the monomer raw material A. Further, from the viewpoint of the mobility of the polymer B in the pressure-sensitive adhesive layer, the improvement of the tack feeling at room temperature (25 ° C.), and the improvement of the flexibility at low temperature, the amount of the hydroxyl group-containing monomer used is usually 40 of the monomer raw material A. It is appropriate that the weight is 30% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less.

In some embodiments, as the copolymerizable monomer, a monomer having a nitrogen atom-containing ring (for example, N-vinyl cyclic amide) and a hydroxyl group-containing monomer can be used in combination. In this case, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 0.1% by weight or more of the monomer raw material A, 1% by weight or more, and 5% by weight or more. It may be 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more. The total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 50% by weight or less of the monomer raw material A, and preferably 40% by weight or less.

In an embodiment in which the monomer raw material A contains a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer in combination, the content (W _N ) of the monomer having a nitrogen atom-containing ring and the content of the hydroxyl group-containing monomer in the monomer raw material A (W N). W _OH) relationship with (by weight) is not particularly limited. W _N / W _OH may be, for example, 0.01 or more, usually 0.05 or more, 0.1 or more, 0.2 or more, 0.5 or more, 0. It may be 0.7 or more. Further, W _N / W _OH may be, for example, 100 or less, usually 20 or less, 10 or less, 5 or less, 2 or less, or 1.5 or less.

In some embodiments, the monomer raw material A does not contain a monomer having a polyorganosiloxane skeleton (monomer S1) which is preferably used as a constituent component of the monomer raw material B described later, or the content of the monomer is the monomer raw material A. It is preferably less than 10% by weight (more preferably less than 5% by weight, for example, less than 2% by weight). According to the monomer raw material A having such a composition, a pressure-sensitive adhesive sheet that preferably achieves both initial reworkability and strong adhesiveness after an increase in adhesive strength can be preferably realized. For the same reason, in some other embodiments, the monomer raw material A does not contain the monomer S1, or if it contains the monomer S1, its content (weight basis) is higher than the content of the monomer S1 in the monomer raw material B. It is preferably low.

The method for obtaining the polymer A is not particularly limited, and various polymerization methods such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method can be appropriately adopted. In some embodiments, the solution polymerization method may be preferably employed. The polymerization temperature at the time of solution polymerization can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.). ℃).

The initiator used for the polymerization can be appropriately selected from conventionally known thermal polymerization initiators, photopolymerization initiators and the like, depending on the polymerization method. The polymerization initiator may be used alone or in combination of two or more.

Examples of the thermal polymerization initiator include azo-based polymerization initiators (for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis (for example). 2-Methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovalerian acid, azobisisobutyvaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2 -(5-Methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethylene) Isobutylamidin) dihydrochloride, etc.); Persulfate such as potassium persulfate; Peroxide-based polymerization initiator (for example, dibenzoylperoxide, t-butylpermalate, lauroyl peroxide, etc.); Redox-based polymerization initiator, etc. Can be mentioned. The amount of the thermal polymerization initiator used is not particularly limited, but is, for example, 0.01 parts by weight to 5 parts by weight, preferably 0, based on 100 parts by weight of the monomer component (monomer raw material A) used for preparing the acrylic polymer. The amount can be in the range of 0.05 parts by weight to 3 parts by weight.

The photopolymerization initiator is not particularly limited, and is, for example, a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, and photoactivity. Oxim-based photopolymerization initiator, benzoin-based photopolymerization initiator, benzyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, Ketal-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, acylphosphine oxide-based photopolymerization initiator Agents and the like can be used. The amount of the photopolymerization initiator used is not particularly limited, but is, for example, an amount in the range of 0.01 parts by weight to 5 parts by weight, preferably 0.05 parts by weight to 3 parts by weight with respect to 100 parts by weight of the monomer raw material A. Can be.

In some embodiments, the polymer A is a partial polymer (polymer syrup) obtained by irradiating a mixture of the above-mentioned monomer raw material A with a polymerization initiator with ultraviolet rays (UV) to polymerize a part of the monomer components. ) Can be included in the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer. A pressure-sensitive adhesive composition containing such a polymer syrup can be applied to a predetermined object to be coated and irradiated with ultraviolet rays to complete the polymerization. That is, the polymer syrup can be grasped as a precursor of polymer A. The pressure-sensitive adhesive layer disclosed herein can be formed, for example, by using a pressure-sensitive adhesive composition containing the above-mentioned polymer syrup and polymer B.

(Polymer B)
The pressure-sensitive adhesive sheet disclosed herein comprises a polymer A (for example, an acrylic polymer) as described above, and a polymer B which is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer. It can be preferably realized by using a pressure-sensitive adhesive layer containing. Such a pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing the polymer A in the form of a complete polymer or a partial polymer of the monomer raw material A and the polymer B. The form of the pressure-sensitive adhesive composition is not particularly limited, and may be various forms such as a solvent type, an aqueous dispersion type, a hot melt type, and an active energy ray-curable type (for example, a photocurable type).

The polymer B in the technique disclosed herein is a copolymer of a monomer having a polyorganosiloxane skeleton (hereinafter, also referred to as “monomer S1”) and a (meth) acrylic monomer. The polymer B has a low polarity and motility of a polyorganosiloxane structure derived from the monomer S1 to suppress the adhesive force at the initial stage of attachment to the adherend, and the adhesive force to increase the adhesive force to the adherend by heating. Can function as a rise retarder. The monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. Monomer S1 promotes uneven distribution of polymer B on the surface of the pressure-sensitive adhesive layer on the pressure-sensitive adhesive sheet before use (before sticking to the adherend) due to its low polarity due to its structure, and light peeling at the initial stage of bonding. Expresses sex (low adhesiveness). As the monomer S1, a monomer having a structure having a polymerizable reactive group at one end can be preferably used. By copolymerization of the monomer S1 with the (meth) acrylic monomer, a polymer B having a polyorganosiloxane skeleton in the side chain is formed. The polymer B having such a structure tends to have a low initial adhesive strength and a high adhesive strength after heating due to the motility and mobility of the side chains.

ここで、上記一般式（１），（２）中のＲ^３は水素またはメチルであり、Ｒ^４はメチル基または１価の有機基であり、ｍおよびｎは０以上の整数である。 As the monomer S1, for example, a compound represented by the following general formula (1) or (2) can be used. More specifically, examples of the one-ended reactive silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. include X-22-174ASX, X-22-2426, X-22-2475, and KF-2012. Monomer S1 can be used alone or in combination of two or more.

^{Here, R 3} in the above general formulas (1) and (2) is hydrogen or methyl, R ⁴ is a methyl group or a monovalent organic group, and m and n are integers of 0 or more.

The functional group equivalent of the monomer S1 can be an appropriate value within a range in which the desired effect is exhibited by using the monomer S1, and is not limited to a specific range. From the viewpoint of sufficiently suppressing the initial adhesive force, the functional group equivalent may be, for example, 140 g / mol or more, 200 g / mol or more, and usually 300 g / mol or more (for example, 500 g / mol or more). Is suitable, preferably 700 g / mol or more, 800 g / mol or more, 850 g / mol or more, 1000 g / mol or more, or 1500 g / mol or more. In some embodiments, the functional group equivalent may be 2500 g / mol or more, 3000 g / mol or more, or 4500 g / mol, from the viewpoint of achieving both low adhesiveness at the initial stage of application and adhesive strength increase with time. It may be 6000 g / mol or more, 9000 g / mol or more, 12000 g / mol or more, or 15000 g / mol or more (for example, 16000 g / mol or more). The functional group equivalent of the monomer S1 can be, for example, 50,000 g / mol or less. From the viewpoint of increasing the adhesive strength with time, the functional group equivalent is preferably, for example, 30,000 g / mol or less, and more preferably 20,000 g / mol or less. In some embodiments, the functional group equivalent of the monomer S1 may be less than 18000 g / mol, less than 15000 g / mol, less than 10000 g / mol, less than 6000 g / mol, less than 5000 g / mol. .. When the functional group equivalent of the monomer S1 is within the above range, the compatibility (for example, compatibility with the base polymer) and mobility in the pressure-sensitive adhesive layer can be easily adjusted within an appropriate range, and the pressure-sensitive adhesive strength increase ratio is high. It becomes easier to realize the agent layer.

Non-limiting examples of the preferred range of the functional group equivalent of the monomer S1 include 700 g / mol or more and 50,000 g / mol or less, 700 g / mol or more and 30,000 g / mol or less, 700 g / mol or more and 20,000 g / mol or less, 700 g / mol or more and 18,000 g. It includes less than / mol, 700 g / mol or more and less than 15000 g / mol, 800 g / mol or more and less than 10000 g / mol, 850 g / mol or more and less than 6000 g / mol, 1500 g / mol or more and less than 5000 g / mol. In some embodiments, the preferred range of functional group equivalents of monomer S1 is 3000 g / mol or more and 50,000 g / mol or less, 6000 g / mol or more and 50,000 g / mol or less, 12000 g / mol or more and 50,000 g / mol or less, 15,000 g / mol or more and 50,000 g / mol or less. It can be less than or equal to mol.

Here, the "functional group equivalent" means the weight of the main skeleton (for example, polydimethylsiloxane) bonded to each functional group. The title unit g / mol is converted to 1 mol of functional group. The functional group equivalent of the monomer S1 ^{can be calculated, for example, from the spectral intensity of 1} H-NMR (proton NMR) based on nuclear magnetic resonance (NMR). ¹ The calculation of the functional group equivalent (g / mol) of the monomer S1 based on the spectral intensity of ^{1 H-NMR is based on the general structural analysis method according to 1 1} H-NMR spectrum analysis, and if necessary, Patent No. 5591153. This can be done with reference to the description in the publication.

When two or more kinds of monomers having different functional group equivalents are used as the monomer S1, an arithmetic mean value can be used as the functional group equivalent of the monomer S1. That is, the functional group equivalent of the monomer S1 composed of n kinds of monomers having different functional group equivalents (monomer S1 _{1 , monomer S1 2} ... Monomer S1 _n ) can be calculated by the following formula.
Functional group equivalent of the monomer S1 (g / mol) = (monomer S1 ₁ functional group equivalent × monomer S1 ₁ of the amount + monomer S1 ₂ functional group equivalent × monomer S1 ₂ of the amount + ... + monomer S1 _n Functional group equivalent amount × amount of monomer S1 _n ) / (amount of monomer S1 ₁ + amount of monomer S1 ₂ + ... + amount of monomer S1 _n )

The content of the monomer S1 may be, for example, 5% by weight or more of the total amount of the monomer component (monomer raw material B) for preparing the polymer B, from the viewpoint of better exerting the effect as an adhesive strength increase retarder. It is preferably 10% by weight or more, 15% by weight or more, or 20% by weight or more. Further, the content of the monomer S1 in the monomer raw material B is preferably 60% by weight or less, may be 50% by weight or less, or may be 40% by weight or less from the viewpoint of polymerization reactivity and compatibility. , 30% by weight or less. If the content of the monomer S1 is less than 5% by weight, the initial adhesive strength may not be sufficiently suppressed. If the content of the monomer S1 is more than 60% by weight, the increase in adhesive strength may be insufficient.

The monomer raw material B contains, in addition to the monomer S1, a (meth) acrylic monomer copolymerizable with the monomer S1. By copolymerizing one or more (meth) acrylic monomers with the monomer S1, the mobility of the polymer B in the pressure-sensitive adhesive layer can be suitably adjusted. Copolymerizing the monomer S1 with the (meth) acrylic monomer can also help improve the compatibility between the polymer B and the polymer A (for example, the acrylic polymer).

Examples of the (meth) acrylic monomer that can be used for the monomer raw material B include (meth) acrylic acid alkyl esters. For example, one or more of the monomers exemplified above as the (meth) acrylic acid alkyl ester that can be used when the polymer A is an acrylic polymer can be used as a constituent component of the monomer raw material B. In some embodiments, the monomer raw material B is a (meth) acrylic acid C _4-12 alkyl ester (preferably a (meth) acrylic acid C _4-10 alkyl ester, eg, a (meth) acrylic acid C _6-10 alkyl ester). Can contain at least one of. In some other embodiments, the monomer raw material B may contain at least one of _{a methacrylic acid C 1-18} alkyl ester (preferably a methacrylic acid C _1-14 alkyl ester, such as a methacrylic acid C _{1-10 alkyl ester).} .. The monomer raw material B may contain, for example, one or more selected from MMA, BMA and 2EHMA as the (meth) acrylic monomer.

Another example of the above (meth) acrylic monomer is a (meth) acrylic acid ester having an alicyclic hydrocarbon group. For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate and the like can be used. In some embodiments, the monomer raw material B may contain at least one selected from dicyclopentanyl methacrylate, isobornyl methacrylate and cyclohexyl methacrylate as the (meth) acrylic monomer.

The content of the (meth) acrylic acid alkyl ester and the (meth) acrylic acid ester having an alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10% by weight or more and 95% by weight or less, and 20% by weight. It may be 95% by weight or less, 30% by weight or more and 90% by weight or less, 40% by weight or more and 90% by weight or less, and 50% by weight or more and 85% by weight or less. May be good. The use of (meth) acrylic acid alkyl ester may be advantageous from the viewpoint of ease of control of the increased adhesive strength behavior. In some embodiments, the content of the (meth) acrylic acid ester having an alicyclic hydrocarbon group may be less than 50% by weight, less than 30% by weight, or less than 15% by weight of the monomer raw material B. It may be less than 10% by weight and less than 5% by weight. It is not necessary to use a (meth) acrylic acid ester having an alicyclic hydrocarbon group.

In some preferred embodiments, the (meth) acrylic monomer, which is a constituent of the monomer raw material B, may contain a monomer M2 having a homopolymer Tg of 50 ° C. or higher. By copolymerizing the monomer S1 and the monomer M2 in the polymer B, the motility and mobility of the polyorganosiloxane structural portion with increasing temperature are suitably controlled, and it is easy to obtain an adhesive sheet having a high adhesive force increase ratio. Become. In some embodiments, the Tg of the homopolymer of the monomer M2 may be 60 ° C. or higher, 70 ° C. or higher, 80 ° C. or higher, or 90 ° C. or higher. The upper limit of Tg of the homopolymer of the monomer M2 is not particularly limited, but it is usually appropriate to be 200 ° C. or lower from the viewpoint of easiness of synthesizing the polymer B and the like. In some embodiments, the Tg of the homopolymer of the monomer M2 may be, for example, 180 ° C. or lower, 150 ° C. or lower, or 120 ° C. or lower.

As the monomer M2, for example, among the (meth) acrylic monomers exemplified above, those in which the Tg of the homopolymer satisfies the condition can be used. For example, one or more monomers selected from the group consisting of (meth) acrylic acid alkyl esters and (meth) acrylic acid esters having alicyclic hydrocarbon groups can be used. As the (meth) acrylic acid alkyl ester, a methacrylic acid alkyl ester in which the number of carbon atoms of the alkyl group is in the range of 1 to 4 can be preferably adopted.

In the embodiment in which the monomer raw material B contains the monomer M2, the content of the monomer M2 may be, for example, 5% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more of the monomer raw material B. However, it may be 25% by weight or more, or 30% by weight or more. In some embodiments, the content of the monomer M2 may be 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more of the monomer raw material B. But it may be. Further, the content of the monomer M2 may be, for example, 90% by weight or less, and usually 80% by weight or less is appropriate. In the polymer B, when the copolymerization ratio of the monomer M2 having a Tg of 50 ° C. or higher is limited to a predetermined value or less, it becomes easy to exhibit a good adhesive force increasing property at a temperature lower than the expansion start temperature T1. In some embodiments, the content of the monomer M2 is preferably 75% by weight or less, preferably 70% by weight or less, 65% by weight or less, 60% by weight or less, 50% by weight or less, 45% by weight. It may be less than%.

The content of the monomer M2 is, for example, one or more monomers selected from the group consisting of the (meth) acrylic acid alkyl ester and the (meth) acrylic acid ester in which the monomer M2 has an alicyclic hydrocarbon group. It can be preferably applied in an embodiment consisting of one or more monomers in which the monomer M2 is selected from a (meth) acrylic acid alkyl ester (for example, a methacrylate alkyl ester). A preferred example of such an embodiment is an embodiment in which the monomer M2 is composed of MMA.

In some embodiments, the (meth) acrylic monomer may comprise a monomer M3 in which the Tg of the homopolymer is less than 50 ° C. (typically −20 ° C. or higher and lower than 50 ° C.). By using the monomer M3, it becomes easy to obtain an adhesive sheet having both adhesive force and cohesive force in a well-balanced manner after the adhesive force is increased. From the viewpoint of facilitating the exertion of such an effect, the monomer M3 is preferably used in combination with the monomer M2.

As the monomer M3, for example, among the (meth) acrylic monomers exemplified above, those in which the Tg of the homopolymer satisfies the condition can be used. For example, one or more monomers selected from the group consisting of (meth) acrylic acid alkyl esters can be used.

In the embodiment in which the monomer raw material B contains the monomer M3, the content of the monomer M3 may be, for example, 5% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more of the monomer raw material B. It may be 25% by weight or more, 30% by weight or more, or 35% by weight or more. The content of the monomer M3 is usually 70% by weight or less of the monomer raw material B, 60% by weight or less, or 50% by weight or less. The content of the monomer M3 can be preferably applied, for example, in an embodiment in which the monomer M3 consists of one or more monomers selected from (meth) acrylic acid alkyl esters (eg, methacrylic acid alkyl esters).

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the monomer raw material B preferably has a monomer content of a homopolymer having a Tg higher than 170 ° C. of 30% by weight or less. Here, the term "monomer content of X% by weight or less" in the present specification includes a mode in which the monomer content is 0% by weight, that is, a mode in which the monomer is substantially not contained, unless otherwise specified. It is a concept. Further, "substantially free" means that the above-mentioned monomer is not used at least intentionally. By limiting the copolymerization ratio of the monomer having a Tg of the homopolymer higher than 170 ° C., it becomes easy to exhibit good adhesive strength increasing property at a temperature lower than the expansion start temperature T1. In some embodiments, the content of the monomer having a Tg of the homopolymer higher than 170 ° C. may be 20% by weight or less, 10% by weight or less, 5% by weight or less, or 2% by weight or less.

In some embodiments, the monomer raw material B preferably contains at least MMA as the (meth) acrylic monomer. When MMA According to the copolymerized polymer B, a large pressure-sensitive adhesive sheet can be easily obtained in N _50. The ratio of MMA to the total amount of the (meth) acrylic monomer contained in the monomer raw material B may be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, and 30% by weight or more. However, it may be 40% by weight or more. In some embodiments, the proportion of MMA in the total amount of the (meth) acrylic monomers may be, for example, greater than 50% by weight, greater than 55% by weight, greater than 60% by weight, or 65% by weight. It may be more than 70% by weight. The ratio of MMA to the total amount of the (meth) acrylic monomer is usually 95% by weight or less, 90% by weight or less, or 85% by weight or less. In some preferred embodiments, the proportion of MMA in the total amount of the (meth) acrylic monomers may be 75% by weight or less, 65% by weight, from the viewpoint of increasing adhesive strength at temperatures lower than the expansion start temperature T1. % Or less, 60% by weight or less, 55% by weight or less (for example, 50% by weight or less).

As another example of the monomer that can be contained together with the monomer S1 as the monomer unit constituting the polymer B, the carboxyl group-containing monomer and the acid anhydride group-containing monomer exemplified above as the monomer that can be used when the polymer A is an acrylic polymer. Monomer, hydroxyl group-containing monomer, epoxy group-containing monomer, cyano group-containing monomer, isocyanate group-containing monomer, amide group-containing monomer, monomer having nitrogen atom-containing ring (N-vinyl cyclic amide, monomer having succinimide skeleton, maleimides, itaconimide (Class, etc.), (meth) acrylic acid aminoalkyls, vinyl esters, vinyl ethers, olefins, (meth) acrylic acid esters having aromatic hydrocarbon groups, heterocyclic-containing (meth) acrylates, halogen atom-containing (meth) ) Acrylic, (meth) acrylic acid ester obtained from a terpen compound derivative alcohol, and the like.

As yet another example of the monomer that can be contained together with the monomer S1 as the monomer unit constituting the polymer B, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di ( Oxyalkylene di (meth) acrylates such as meta) acrylates, propylene glycol di (meth) acrylates, dipropylene glycol di (meth) acrylates, and tripropylene glycol di (meth) acrylates; monomers having a polyoxyalkylene skeleton, such as polyethylene glycol. It has a polymerizable functional group such as a (meth) acryloyl group, a vinyl group, or an allyl group at one end of a polyoxyalkylene chain such as or polypropylene glycol, and an ether structure (alkyl ether, aryl ether, aryl alkyl) at the other end. Polymerizable polyoxyalkylene ether having (ether, etc.); methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxy (meth) acrylate Alkoxyalkyl (meth) acrylic acid such as propyl; Salts such as alkali metal salt of (meth) acrylic acid; Polyvalent (meth) acrylates such as trimethylpropantri (meth) acrylic acid ester: vinylidene chloride, (meth) acrylic acid Vinyl halide compounds such as -2-chloroethyl; oxazoline group-containing monomers such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline; (meth) acryloyl Acryloyl group-containing monomers such as acryloyl, -2-aziridinyl ethyl (meth) acrylate; -2-hydroxyethyl (meth) acrylate, -2-hydroxypropyl (meth) acrylate, lactones and (meth) acrylic. A hydroxyl group-containing vinyl monomer such as an adduct with -2-hydroxyethyl acid; a fluorine-containing vinyl monomer such as a fluorine-substituted (meth) acrylic acid alkyl ester; a reactive halogen-containing vinyl monomer such as 2-chloroethyl vinyl ether and vinyl monochloroacetate. Organic silicon-containing vinyl such as vinyl trimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, 2-methoxyethoxytrimethoxysilane Lumonomer; In addition, macromonomers having a radically polymerizable vinyl group at the terminal of a monomer polymerized with a vinyl group; and the like can be mentioned. These can be copolymerized with the monomer S1 alone or in combination of two or more.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the composition of the (meth) acrylic monomer contained in the monomer raw material B has a glass transition temperature Tg _B [° C.] based on the composition of the (meth) acrylic monomer. , It is preferable to set the expansion start temperature to be lower than T1 [° C.]. That is, _{it is preferable that T1-Tg B} is 0 ° C. or higher. According to such a polymer B, the adhesive force can be greatly increased without expanding the heat-expandable microspheres through the mobility of the polymer B in a temperature range lower than the expansion start temperature T1.

The glass transition temperature Tg _B is usually preferably 30 ° C. or higher, more preferably 40 ° C. or higher, 45 ° C. or higher, or 50 ° C. or higher. According to the polymer B having a high Tg _B , heat generated by the operation of the device used in the manufacturing process, exhaust heat from a nearby device, etc. within the period when the adhesive sheet attached to the adherend is required to have reworkability, etc. Therefore, even if a temperature of room temperature or higher is applied to the pressure-sensitive adhesive sheet, the reworkability can be appropriately maintained. This is because the Tg _B of the polymer B is appropriately increased to improve the motility and mobility of the polyorganosiloxane structural portion with increasing temperature, which is a monomer unit derived from the (meth) acrylic monomer contained in the polymer B. It is considered that the low adhesiveness due to the presence of the polyorganosiloxane structural portion can be better maintained. In some embodiments, Tg _B may be 55 ° C. or higher, 60 ° C. or higher, 65 ° C. or higher, or 70 ° C. or higher. Further, from the viewpoint of heat resistance of the adherend or the adhesive sheet, energy cost for heat treatment, etc., Tg _B is usually preferably 150 ° C. or lower, preferably 120 ° C. or lower. It is more preferably 100 ° C. or lower, 90 ° C. or lower, 85 ° C. or lower, 80 ° C. or lower, 70 ° C. or lower, 60 ° C. or lower, or 50 ° C. or lower.

From the viewpoint of efficiently increasing the adhesive strength without expanding the thermally expandable microspheres, the composition of the monomer raw material B usually has Tg _B [° C.] lower than the expansion start temperature T1 [° C.] by 5 ° C. or more. Therefore, it is appropriate to adjust so that T1-Tg _B is 5 ° C. or higher. In some embodiments, T1-Tg _B may be 10 ° C. or higher, 15 ° C. or higher, preferably 20 ° C. or higher, more preferably 30 ° C. or higher, 40 ° C. or higher, 60. It may be ℃ or higher, and may be 70 ℃ or higher. Further, T1-Tg _B is usually preferably 250 ° C. or lower, may be 200 ° C. or lower, 150 ° C. or lower, 100 ° C. or lower, or 80 ° C. or lower.

Here, the glass transition temperature Tg _B based on the composition of the (meth) acrylic monomer is based on the composition of only the (meth) acrylic monomer among the monomer components used in the preparation of the polymer B, according to the Fox formula. The required Tg. For Tg _B , the Fox formula described above was applied only to the (meth) acrylic monomer among the monomer components used in the preparation of the polymer B, and the glass transition temperature of the homopolymer of each (meth) acrylic monomer was used. , Can be calculated from the weight fraction of each (meth) acrylic monomer in the total amount of the (meth) acrylic monomer. From the viewpoint of facilitating the effect by appropriately setting Tg _B , the total amount of the monomer S1 and the (meth) acrylic monomer in the total monomer components for preparing the polymer B is, for example, 50% by weight or more. It may be 70% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or substantially 100% by weight.

From the viewpoint of facilitating control of the mobility of the polymer B in the pressure-sensitive adhesive layer, in some embodiments, the composition of the monomer raw material B is such that the TTg _B is higher than the _{Tg A in relation to the glass transition temperature Tg A of the polymer A.} It can be set to be 20 ° C. or higher, that is, Tg _{B −} Tg _{A to} be 20 ° C. or higher. In some embodiments, Tg _{B −} Tg _A may be, for example, 50 ° C. or higher, 60 ° C. or higher, 70 ° C. or higher, or 80 ° C. or higher. Further, in some embodiments, Tg _{B −} Tg _A may be, for example, 150 ° C. or lower, 140 ° C. or lower, 130 ° C. or lower, or 120 ° C. or lower.

When heat treatment is performed to promote an increase in adhesive strength, the heating temperature T3 [° C.] in the heat treatment is equal to or higher than the _{glass transition temperature Tg B [° C.] from the viewpoint of the mobility of the polymer B in the pressure-sensitive adhesive layer.} It is preferable that the temperature is _{higher than the glass transition temperature Tg B} [° C.] (that is, (T3-Tg _B )> 0). From the viewpoint of enhancing the effect of promoting the increase in adhesive strength, the temperature difference (T3-Tg _{B ) between the heating temperature T3 [° C.] and the glass transition temperature Tg B} [° C.] is set to, for example, 5 ° C. or higher in some embodiments. The temperature may be 10 ° C. or higher, 20 ° C. or higher, 40 ° C. or higher, or 60 ° C. or higher. The upper limit of the temperature difference (T3-Tg _B ) is not particularly limited and may be, for example, 150 ° C. or less. In consideration of workability, economy, heat resistance of the base material of the adhesive sheet and the adherend, etc., the temperature difference (T3-Tg _B ) may be, for example, 100 ° C. or less in some embodiments, and is 70. It may be ℃ or less, 50 ℃ or less, and 35 ℃ or less.

The glass transition temperature of the polymer B (that is, the glass transition temperature Tg _Ball based on the composition of the monomer raw material B) is not particularly limited and can be selected so as to obtain preferable properties in the pressure-sensitive adhesive sheet disclosed herein. The Tg _Ball may be, for example, less than 50 ° C., 30 ° C. or lower, 20 ° C. or lower, 15 ° C. or lower, or 10 ° C. or lower. When the Tg _{Ball of the} polymer B becomes low, the mobility of the polymer B is improved, and the adhesive strength tends to be easily increased by heating in a temperature range lower than the expansion start temperature T1. Further, in some embodiments, the Tg _Ball may be, for example, −40 ° C. or higher, −30 ° C. or higher, −20 ° C. or higher, or −10 ° C. or higher. When the Tg _Ball is high, the reworkability tends to be easily maintained even if a temperature higher than room temperature is applied after the adhesive sheet is attached.

In some embodiments, the polymer B may preferably be one that does not have a functional group that causes a cross-linking reaction with the polymer A. In other words, the polymer B is preferably contained in the pressure-sensitive adhesive layer in a form that is not chemically bonded to the polymer A. The pressure-sensitive adhesive layer containing the polymer B in such a form has good mobility of the polymer B during heating and is suitable for improving the adhesive strength increase ratio. The functional group that causes a cross-linking reaction with the polymer A may differ depending on the type of the functional group contained in the polymer A, and may be, for example, an epoxy group, an isocyanate group, a carboxy group, an alkoxysilyl group, an amino group, or the like.

The Mw of the polymer B is not particularly limited. The Mw of the polymer B may be, for example, 1000 or more, and may be 5000 or more. From the viewpoint of preferably exhibiting an increase in adhesive strength at a temperature lower than the expansion start temperature T1, the Mw of the polymer B may be, for example, 10,000 or more, 12,000 or more, 15,000 or more, 20, It may be 000 or more. In some embodiments, the Mw of Polymer B may be 50,000 or greater, 80,000 or higher, 100,000 or higher, or 120,000 or higher (eg, 150,000 or higher). The upper limit of Mw of the polymer B is, for example, 500,000 or less, may be 350,000 or less, may be 350,000 or less, or may be less than 100,000. The Mw of the polymer B may be less than 80,000, and 70,000, from the viewpoint of adjusting the compatibility and mobility in the pressure-sensitive adhesive layer to an appropriate range and increasing the adhesive strength at a temperature lower than the expansion start temperature T1. It may be less than 50,000, less than 40,000, less than 20,000, or even less than 10,000.

In some preferred embodiments, the Mw of the polymer B is preferably lower than the Mw of the polymer A. This makes it easier to realize an adhesive sheet that has both good reworkability at the initial stage of application and adhesive strength increasing property at a temperature lower than the expansion start temperature T1. The Mw of the polymer B may be, for example, 0.8 times or less of the Mw of the polymer A, 0.75 times or less, 0.5 times or less, 0.3 times or less, 0.1. It may be double or less, 0.05 times or less, 0.03 times or less (for example, 0.02 times or less).

Polymer B can be produced, for example, by polymerizing the above-mentioned monomers by a known method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, or a photopolymerization method.

Chain transfer agents can be used as needed to adjust the molecular weight of Polymer B. Examples of chain transfer agents used include compounds having a mercapto group such as octyl mercaptan, lauryl mercaptan, t-nonyl mercaptan, t-dodecyl mercaptan, mercaptoethanol, α-thioglycerol; thioglycolic acid, methyl thioglycolate, etc. Ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, ethylene Thioglycolic acid esters such as thioglycolic acid ester of glycol, thioglycolic acid ester of neopentyl glycol, and thioglycolic acid ester of pentaerythritol; α-methylstyrene dimer; and the like can be mentioned.

The amount of the chain transfer agent used is not particularly limited, but usually 0.05 parts by weight to 20 parts by weight, preferably 0.1 parts by weight to 15 parts by weight of the chain transfer agent with respect to 100 parts by weight of the monomer. , More preferably 0.2 parts by weight to 10 parts by weight. By adjusting the amount of the chain transfer agent added in this way, the polymer B having a suitable molecular weight can be obtained. The chain transfer agent may be used alone or in combination of two or more.

As a means for adjusting the molecular weight of the polymer B, various conventionally known means including the use of the chain transfer agent can be used alone or in combination as appropriate. The same applies to the molecular weight of polymer A. Non-limiting examples of such means include selection of polymerization method, selection of type and amount of polymerization initiator, selection of polymerization temperature, selection of type and amount of polymerization solvent in solution polymerization method, light weight. Legal selection of light irradiation intensity, etc. are included. A person skilled in the art can understand how to obtain a polymer having a desired molecular weight based on the description of the present specification including specific examples described later and the common general technical knowledge at the time of filing the application of the present application.

In the pressure-sensitive adhesive sheet disclosed herein, the amount of polymer B used may be, for example, 0.1 part by weight or more with respect to 100 parts by weight of polymer A used, and 0.5 parts by weight from the viewpoint of obtaining a higher effect. It may be 1 part by weight or more, or 2 parts by weight or more. In some embodiments, from the viewpoint of improving reworkability, the amount of the polymer B used may be, for example, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more. The amount of polymer B used with respect to 100 parts by weight of polymer A may be, for example, 75 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less. From the viewpoint of avoiding an excessive decrease in the cohesive force of the pressure-sensitive adhesive layer, in some embodiments, the amount of polymer B used with respect to 100 parts by weight of polymer A can be, for example, 40 parts by weight or less, and 35 parts by weight or less. , 30 parts by weight or less, or 25 parts by weight or less. From the viewpoint of obtaining higher adhesive strength after heating, in some embodiments, the amount of the polymer B used may be 20 parts by weight or less, 17 parts by weight or less, 15 parts by weight or less, or 12 parts by weight. It may be 10 parts by weight or less, 8 parts by weight or less, 6 parts by weight or less, or 4 parts by weight or less (for example, 3 parts by weight or less).

The pressure-sensitive adhesive layer may contain a polymer (arbitrary polymer) other than the polymer A and the polymer B, if necessary, as long as the performance of the pressure-sensitive adhesive sheet disclosed herein is not significantly impaired. Generally, the amount of such an arbitrary polymer used is appropriately 20% by weight or less of the total polymer component contained in the pressure-sensitive adhesive layer, and may be 15% by weight or less, or 10% by weight or less. In some embodiments, the amount of the optional polymer used may be 5% by weight or less of the total polymer component, 3% by weight or less, or 1% by weight or less. The pressure-sensitive adhesive layer may be substantially free of polymers other than Polymer A and Polymer B.

(Crosslinking agent)
A cross-linking agent may be used for the pressure-sensitive adhesive layer, if necessary, for the purpose of adjusting the cohesive force or the like. As the cross-linking agent, a cross-linking agent known in the field of pressure-sensitive adhesives can be used. Examples thereof include a cross-linking agent, an alkyl etherified melamine-based cross-linking agent, and a metal chelate-based cross-linking agent. In particular, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, and a metal chelate-based cross-linking agent can be preferably used. The cross-linking agent may be used alone or in combination of two or more.

Specifically, examples of isocyanate-based cross-linking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, and naphthaline. Examples thereof include diisocyanates, triphenylmethane triisocyanates, polymethylene polyphenyl isocyanates, and adducts of these with polyols such as trimethylolpropane. Alternatively, a compound having at least one or more isocyanate groups and one or more unsaturated bonds in one molecule, specifically, 2-isocyanatoethyl (meth) acrylate or the like may also be used as the isocyanate-based cross-linking agent. Can be done. These can be used alone or in combination of two or more.

Examples of the epoxy-based cross-linking agent include bisphenol A, epichlorohydrin-type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, and trimethyl propantri. Examples include glycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N', N'-tetraglycidyl-m-xylylene diamine and 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane. Can be done. These can be used alone or in combination of two or more.

Examples of the metal chelate compound include aluminum, iron, tin, titanium, nickel and the like as metal components, and acetylene, methyl acetoacetate, ethyl lactate and the like as chelate components. These can be used alone or in combination of two or more.

The amount used when the cross-linking agent is used is not particularly limited, and may be, for example, an amount exceeding 0 parts by weight with respect to 100 parts by weight of the polymer A. The amount of the cross-linking agent used can be, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, based on 100 parts by weight of the polymer A. As the amount of the cross-linking agent used increases, the adhesive strength at the initial stage of application is suppressed, and the reworkability tends to be improved. From the viewpoint of suppressing the cohesive destruction of the pressure-sensitive adhesive layer due to the expansion of the heat-expandable microspheres, in some embodiments, the amount of the cross-linking agent used with respect to 100 parts by weight of the polymer A may be 0.1 part by weight or more. It may be 0.5 parts by weight or more, 0.8 parts by weight or more, 1 part by weight or more, or 2 parts by weight or more. On the other hand, from the viewpoint of appropriately allowing the mobility of the polymer B and increasing the adhesive strength increase ratio, the amount of the cross-linking agent used with respect to 100 parts by weight of the polymer A is usually preferably 15 parts by weight or less, and 10 parts by weight. It may be less than or equal to 5 parts by weight.

The technique disclosed herein can be preferably carried out in an embodiment using at least an isocyanate-based cross-linking agent as the cross-linking agent. From the viewpoint of achieving both good reworkability at the initial stage of application and an increase in adhesive strength at a temperature lower than the expansion start temperature T1, in some embodiments, the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the polymer A is, for example, 0. It can be 01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, 0.5 parts by weight or more. Alternatively, it may be 0.8 parts by weight or more, 1 part by weight or more, or 2 parts by weight or more. The amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the polymer A is usually 15 parts by weight or less, preferably 10 parts by weight or less, and may be 7 parts by weight or less, and 5 parts by weight. It may be 3 parts or less, or 3 parts by weight or less.

Although not particularly limited, if the pressure-sensitive adhesive layer is used isocyanate crosslinking agent in a configuration that includes a hydroxyl group-containing monomer as a monomer unit, the amount W _OH of the hydroxyl group-containing monomer to the amount W _NCO of isocyanate crosslinking agent, by _weight, it can be an amount that W OH _{/ W NCO} is 2 or more. By increasing the amount of the hydroxyl group-containing monomer used for the isocyanate-based cross-linking agent in this way, a cross-linked structure suitable for greatly increasing the adhesive force at a temperature lower than the expansion start temperature T1 with respect to the adhesive force at the initial stage of application is formed. Can be done. In some embodiments, the _WOH / W _NCO may be 3 or greater, 5 or greater, 10 or greater, 20 or greater, or 30 or greater. It may be 50 or more. The upper limit of W _OH / W _{NCO is not particularly limited, and the W OH} / W _NCO is, for example, 500 or less from the viewpoint of allowing an appropriate degree of cross-linking of the polymer B by heating at a temperature lower than the expansion start temperature T1. It may be 200 or less, 100 or less, or 50 or less.

A cross-linking catalyst may be used in order to allow any of the above-mentioned cross-linking reactions to proceed more effectively. As the cross-linking catalyst, for example, a tin-based catalyst (particularly dioctyltin dilaurate) can be preferably used. The amount of the cross-linking catalyst used is not particularly limited, but can be, for example, approximately 0.0001 parts by weight to 1 part by weight with respect to 100 parts by weight of the polymer A.

A polyfunctional monomer can be used for the pressure-sensitive adhesive layer, if necessary. The polyfunctional monomer can be useful for purposes such as adjusting the cohesive force by being used in place of the above-mentioned cross-linking agent or in combination with the cross-linking agent. For example, a polyfunctional monomer may be preferably used in a pressure-sensitive adhesive layer formed from a photocurable pressure-sensitive adhesive composition.
Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like. Pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecane Didioldi (meth) acrylate, trimethylolpropantri (meth) acrylate, tetramethylolmethanetri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl Examples thereof include diol (meth) acrylate and hexyldiol di (meth) acrylate. Of these, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate can be preferably used. The polyfunctional monomer may be used alone or in combination of two or more.

The amount of the polyfunctional monomer used varies depending on its molecular weight, the number of functional groups, and the like, but it is usually appropriate to use it in the range of 0.01 parts by weight to 3.0 parts by weight with respect to 100 parts by weight of the polymer A. .. In some embodiments, the amount of the polyfunctional monomer used may be, for example, 0.02 parts by weight or more, or 0.03 parts by weight or more, based on 100 parts by weight of the polymer A. As the amount of the polyfunctional monomer used increases, the adhesive strength at the initial stage of application is suppressed, and the reworkability tends to be improved. On the other hand, from the viewpoint of ensuring the mobility of the polymer B and controlling the movement by a cross-linking network to control the increase in adhesive force after heating at a temperature lower than the expansion start temperature T1, the amount of the polyfunctional monomer used is , 2.0 parts by weight or less, 1.0 parts by weight or less, or 0.5 parts by weight or less with respect to 100 parts by weight of the polymer A.

(Adhesive-imparting resin)
The pressure-sensitive adhesive layer may contain a pressure-imparting resin, if necessary. The tackifier resin is not particularly limited, and for example, a rosin-based tackifier resin, a terpene-based tackifier resin, a phenol-based tackifier resin, a hydrocarbon-based tackifier resin, a ketone-based tackifier resin, a polyamide-based tackifier resin, and the like. Examples thereof include epoxy-based tackifier resins and elastomer-based tackifier resins. The tackifier resin may be used alone or in combination of two or more.

Examples of the rosin-based tackifier resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, and modified rosins (raw rosins) obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, or the like. Polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, partially hydrogenated rosins and other chemically modified rosins), as well as various rosin derivatives.
Examples of the rosin derivative include
A rosin phenolic resin obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and thermally polymerizing them;
Alcohols include ester compounds of rosins obtained by esterifying unmodified rosins with alcohols (unmodified rosin esters), and modified rosins such as polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, and partially hydrogenated rosins. Resin ester-based resins such as ester compounds of modified rosins esterified with (polymerized rosin ester, stabilized rosin ester, disproportionated rosin ester, fully hydrogenated rosin ester, partially hydrogenated rosin ester, etc.);
Unsaturated fatty acid-modified rosin-based resins obtained by modifying unmodified rosins and modified rosins (polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, partially hydrogenated rosins, etc.) with unsaturated fatty acids;
An unsaturated fatty acid-modified rosin ester resin obtained by modifying a rosin ester resin with an unsaturated fatty acid;
Carboxyl group in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid modified rosin resin and unsaturated fatty acid modified rosin ester resin Rosin alcohol-based resin that has been reduced
Examples thereof include unmodified rosin, modified rosin, and metal salts of rosin-based resins (particularly rosin ester-based resins) such as various rosin derivatives.

Examples of the terpene-based tackifier resin include terpene-based resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer, and modification of these terpene-based resins (phenol modification, aromatic modification, hydrogenation modification). , Carbone-modified, etc.) modified terpene-based resin (for example, terpene phenol-based resin, styrene-modified terpene-based resin, aromatic-modified terpene-based resin, hydrogenated terpene-based resin, etc.) and the like.

Examples of the phenol-based tackifier resin include a condensate of various phenols (eg, phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin, etc.) and formaldehyde (eg, alkylphenol-based resin, xyleneformaldehyde). Examples thereof include resol obtained by adding and reacting the above-mentioned phenols and formaldehyde with an alkali catalyst, and novolac obtained by subjecting the above-mentioned phenols and formaldehyde to a condensation reaction with an acid catalyst.

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

Commercially available products of polymerized rosin ester that can be preferably used include trade names "Pencel D-125", "Pencel D-135", "Pencel D-160", "Pencel KK", and "Pencel" manufactured by Arakawa Chemical Industry Co., Ltd. Examples thereof include, but are not limited to these.

Commercially available terpene phenolic resins that can be preferably used include the trade names "YS Polystar S-145", "YS Polystar G-125", "YS Polystar N125", and "YS Polystar U-115" manufactured by Yasuhara Chemical Co., Ltd. , Product names "Tamanor 803L" and "Tamanor 901" manufactured by Arakawa Chemical Industry Co., Ltd., and product names "Sumilite Resin PR-12603" manufactured by Sumitomo Bakelite Co., Ltd. are exemplified, but not limited thereto.

The content of the tackifying resin is not particularly limited, and can be set so as to exhibit appropriate adhesive performance according to the purpose and application. The content of the tackifier resin with respect to 100 parts by weight of the polymer A (when two or more kinds of tackifier resins are included, the total amount thereof) can be, for example, about 5 to 500 parts by weight.

As the tackifier resin, a resin having a softening point (softening temperature) of about 80 ° C. or higher (preferably about 100 ° C. or higher, for example, about 120 ° C. or higher) can be preferably used. According to the pressure-sensitive adhesive resin having a softening point equal to or higher than the above-mentioned lower limit value, a pressure-sensitive adhesive sheet having a high pressure-sensitive adhesive force can be easily obtained after heating. The upper limit of the softening point is not particularly limited, and may be, for example, about 200 ° C. or lower (typically 180 ° C. or lower). The softening point of the tackifier resin can be measured based on the softening point test method (ring ball method) specified in JIS K2207.

In addition, the pressure-sensitive adhesive layer in the technique disclosed herein is a leveling agent, a plasticizer, a softening agent, a colorant (dye, pigment, etc.), a filler, and an antioxidant, as long as the effects of the present invention are not significantly impaired. , Antioxidants, UV absorbers, Antioxidants, Light Stabilizers, Preservatives, and other known additives that can be used in adhesives may be included, if necessary.

The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein can be a cured layer of the pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer is formed by applying (for example, coating) a pressure-sensitive adhesive composition such as an aqueous dispersion type, a solvent type, a photocurable type, or a hot melt type to an appropriate surface, and then appropriately performing a curing treatment. obtain. When performing two or more types of curing treatments (drying, cross-linking, polymerization, cooling, etc.), these can be performed simultaneously or in multiple steps. In a pressure-sensitive adhesive composition using a partial polymer (polymer syrup) of a monomer raw material, a final copolymerization reaction is typically carried out as the above-mentioned curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, in the case of a photocurable pressure-sensitive adhesive composition, light irradiation is performed. If necessary, a hardening treatment such as cross-linking and drying may be carried out. For example, when it is necessary to dry with a photocurable pressure-sensitive adhesive composition, it is preferable to perform photocuring after drying. In the pressure-sensitive adhesive composition using a complete polymer, typically, as the curing treatment, treatments such as drying (heat drying) and cross-linking are carried out as necessary.

The application of the pressure-sensitive adhesive composition can be carried out using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be, for example, 3 μm or more. From the viewpoint of suppressing deterioration of the smoothness of the adhesive surface due to the inclusion of the heat-expandable microspheres, the thickness of the pressure-sensitive adhesive layer is usually preferably 7 μm or more, preferably more than 10 μm. It may be more than 15 μm, more than 25 μm, or more than 35 μm. The upper limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but is usually 300 μm or less, and may be 200 μm or less, 150 μm or less, 100 μm or less, or 70 μm or less. It may be advantageous that the thickness of the pressure-sensitive adhesive layer is not too large from the viewpoint of avoiding cohesive failure of the pressure-sensitive adhesive layer due to expansion of the heat-expandable microspheres. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be 60 μm or less, 50 μm or less, or 45 μm or less.

The thickness Ta of the pressure-sensitive adhesive layer is preferably larger than the average particle size D of the heat-expandable microspheres. That is, it is preferable that Ta / D is larger than 1.0. From the viewpoint of the smoothness of the adhesive surface, in some embodiments, the Ta / D is preferably 2.0 or more, and may be 3.0 or more, or 4.0 or more. Further, from the viewpoint of facilitating the peeling effect due to the expansion of the heat-expandable microspheres, the Ta / D is usually preferably 50 or less, preferably 20 or less, and may be 15 or less. It may be 10 or less.

In the case of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first and second surfaces of the base material, the thickness of the pressure-sensitive adhesive layer described above is at least the thickness of the first pressure-sensitive adhesive layer. Can be applied to. The thickness of the second pressure-sensitive adhesive layer can be selected from the same range. Further, in the case of a base material-less pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive sheet matches the thickness of the pressure-sensitive adhesive layer.
Further, in the pressure-sensitive adhesive sheet disclosed herein, a pressure-sensitive adhesive layer containing heat-expandable microspheres (adhesive having first and second pressure-sensitive adhesive layers containing heat-expandable microspheres on the first and second surfaces of the base material). In the sheet, each pressure-sensitive adhesive layer) may have a single-layer structure or a multi-layer structure having two or more layers. From the viewpoint of controllability of the adhesive force of the heat-expandable microspheres before expansion, in some embodiments, the pressure-sensitive adhesive layer preferably has a single-layer structure.

<Supporting base material>
The pressure-sensitive adhesive sheet according to some aspects may be in the form of a base-based pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer on one or both sides of a supporting base material. The material of the supporting base material is not particularly limited, and can be appropriately selected depending on the purpose and mode of use of the pressure-sensitive adhesive sheet. Non-limiting examples of base materials that can be used include a polyolefin film containing a polyolefin such as polypropylene or an ethylene-propylene copolymer as a main component, a polyester film containing a polyester such as polyethylene terephthalate or polybutylene terephthalate as a main component, and the like. Plastic film such as polyvinyl chloride film containing polyvinyl chloride as the main component; foam sheet made of foam such as polyurethane foam, polyethylene foam, polychloroprene foam; various fibrous substances (natural fibers such as hemp and cotton, Woven fabrics and non-woven fabrics made of synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) alone or by blending; papers such as Japanese paper, high-quality paper, kraft paper, crepe paper; aluminum foil, Metal foils such as copper foil; and the like. A base material having a composite structure thereof may be used. Examples of such a composite base material include a base material having a structure in which a metal foil and the plastic film are laminated, a plastic base material reinforced with an inorganic fiber such as glass cloth, and the like.

As the base material of the pressure-sensitive adhesive sheet disclosed herein, various film base materials can be preferably used. The film base material may be a porous base material such as a foam film or a non-woven fabric sheet, or may be a non-porous base material, and may be a porous layer and a non-porous layer. May be a base material having a laminated structure. In some embodiments, as the film base material, a film containing an independently shape-maintainable (self-supporting or independent) resin film as a base film can be preferably used. As used herein, the term "resin film" means a resin film (of voidless) having a non-porous structure and typically containing substantially no bubbles. Therefore, the resin film is a concept that is distinguished from a foam film and a non-woven fabric. As the resin film, one that can independently maintain its shape (self-supporting or independent) can be preferably used. The resin film may have a single-layer structure or a multi-layer structure having two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polyamide (PA), polyimide (PI), polyamideimide (PAI), and polyetheretherketone (PEEK) such as polyester, polyolefin, nylon 6, nylon 66, and partially aromatic polyamide. ), Polyethersulfone (PES), Polyphenylene sulfide (PPS), Polycarbonate (PC), Polyurethane (PU), Ethylene-vinyl acetate copolymer (EVA), Polytetrafluoroethylene (PTFE) and other fluororesins, acrylic resins , Polyacrylate, polystyrene, polyvinyl chloride, polyvinylidene chloride and other resins can be used. The resin film may be formed by using a resin material containing one kind of such a resin alone, or may be formed by using a resin material in which two or more kinds are blended. Good. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

Preferable examples of the resin material constituting the resin film include polyester-based resin, PPS resin, and polyolefin-based resin. Here, the polyester-based resin refers to a resin containing polyester in a proportion of more than 50% by weight. Similarly, the PPS resin refers to a resin containing PPS in a proportion of more than 50% by weight, and the polyolefin-based resin refers to a resin containing polyolefin in a proportion of more than 50% by weight.

As the polyester-based resin, a polyester-based resin containing a polyester obtained by polycondensing a dicarboxylic acid and a diol as a main component is typically used. Specific examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate and the like.

As the polyolefin resin, one kind of polyolefin can be used alone, or two or more kinds of polyolefins can be used in combination. The polyolefin can be, for example, a homopolymer of an α-olefin, a copolymer of two or more kinds of α-olefins, a copolymer of one or more kinds of α-olefins and another vinyl monomer, and the like. Specific examples include ethylene-propylene copolymers such as polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, and ethylene propylene rubber (EPR), and ethylene-propylene-. Examples thereof include a butene copolymer, an ethylene-butene copolymer, an ethylene-vinyl alcohol copolymer, and an ethylene-ethyl acrylate copolymer. Both low density (LD) polyolefin and high density (HD) polyolefin can be used. Examples of polyolefin resin films include unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, medium density polyethylene (MDPE). Examples thereof include a film, a high-density polyethylene (HDPE) film, a polyethylene (PE) film in which two or more types of polyethylene (PE) are blended, a PP / PE blend film in which polypropylene (PP) and polyethylene (PE) are blended.

Specific examples of the resin film that can be preferably used as the base film of the pressure-sensitive adhesive sheet disclosed herein include PET film, PEN film, PPS film, PEEK film, CPP film and OPP film. Examples of preferable base films from the viewpoint of strength and dimensional stability include PET film, PEN film, PPS film and PEEK film. From the viewpoint of availability of the base material, PET film and PPS film are particularly preferable, and PET film is particularly preferable.

Known resin films include light stabilizers, antioxidants, antistatic agents, colorants (dyees, pigments, etc.), fillers, slip agents, antiblocking agents, etc., as long as the effects of the present invention are not significantly impaired. Additives can be blended as needed. The blending amount of the additive is not particularly limited, and can be appropriately set according to the use of the pressure-sensitive adhesive sheet and the like.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film molding methods such as extrusion molding, inflation molding, T-die casting molding, and calender roll molding can be appropriately adopted.

The base material may be substantially composed of such a base film. Alternatively, the base material may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an optical property adjusting layer (for example, a coloring layer and an antireflection layer), a printing layer or a laminating layer for imparting a desired appearance to a base material, an antistatic layer, an undercoat layer, and a peeling layer. Such as a surface treatment layer.

The thickness of the base material is not particularly limited, and can be selected according to the purpose and mode of use of the pressure-sensitive adhesive sheet. The thickness of the base material can be, for example, 1000 μm or less. In some embodiments, from the viewpoint of handleability and processability of the pressure-sensitive adhesive sheet, the thickness of the base material may be, for example, 500 μm or less, 300 μm or less, 250 μm or less, or 200 μm. It may be as follows. From the viewpoint of miniaturization and weight reduction of the product to which the adhesive sheet is applied, in some embodiments, the thickness of the base material may be, for example, 160 μm or less, 130 μm or less, or 100 μm or less. It may be 90 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. As the thickness of the base material becomes smaller, the flexibility of the pressure-sensitive adhesive sheet and the ability to follow the surface shape of the adherend tend to improve. Further, from the viewpoint of handleability, processability and the like, the thickness of the base material may be, for example, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 25 μm or more, or 25 μm or more. In some embodiments, the thickness of the substrate may be, for example, 30 μm or more, 35 μm or more, 55 μm or more, 70 μm or more, 75 μm or more, 90 μm or more, 120 μm or more. .. For example, in an adhesive sheet that can be used for the purpose of reinforcing, supporting, impact mitigating, or the like of an adherend, a base material having a thickness of 30 μm or more can be preferably adopted.

A conventionally known surface such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and formation of an undercoat layer by applying an undercoat agent (primer) is performed on the first surface of the base material, if necessary. It may be treated. Such a surface treatment is performed by anchoring the pressure-sensitive adhesive layer to the base material (direct anchoring property of the pressure-sensitive adhesive layer directly laminated on the base material to the base material and other layers such as an elastic intermediate layer. It is a treatment for improving the indirect anchoring property of the pressure-sensitive adhesive layer laminated on the base material through the base material. The same shall apply hereinafter). For example, in an adhesive sheet provided with a base material containing a resin film as a base film, a base material subjected to such anchoring property improving treatment can be preferably adopted. The above surface treatments can be applied alone or in combination. The composition of the primer used for forming the undercoat layer is not particularly limited, and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, but is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. Other treatments that can be applied to the first surface of the substrate as needed include antistatic layer forming treatments, colored layer forming treatments, printing treatments and the like.

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer only on the first side surface of the base material, the second side surface of the base material may be subjected to peeling treatment or antistatic treatment, if necessary. Conventionally known surface treatments such as treatments may be applied. For example, by surface-treating the back surface of the base material with a release treatment agent (typically, by providing a release layer with a release treatment agent), the unwinding force of the adhesive sheet in the form of being wound in a roll shape is increased. Can be lightened. As the stripping agent, a silicone-based stripping agent, a long-chain alkyl-based stripping agent, an olefin-based stripping agent, a fluorine-based stripping agent, a fatty acid amide-based stripping agent, molybdenum sulfide, silica powder, or the like can be used. .. In addition, for the purpose of improving printability, reducing light reflectivity, improving layering property, etc., the second surface of the base material is subjected to treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, and alkali treatment. It may have been done. Further, in the case of the double-sided adhesive sheet, the second surface of the base material is subjected to the same surface treatment as those exemplified above as the surface treatment that can be applied to the first surface of the base material, if necessary. May be good. The surface treatment applied to the first surface of the base material and the surface treatment applied to the second surface may be the same or different.

<Elastic intermediate layer>
The pressure-sensitive adhesive sheet disclosed herein may include an elastic intermediate layer arranged between the base material and the pressure-sensitive adhesive layer. This elastic intermediate layer is a layer provided as needed, and is not necessarily provided. By interposing an elastic intermediate layer between the base material and the pressure-sensitive adhesive layer, the anchoring property of the pressure-sensitive adhesive layer on the base material can be improved. For example, when the heat-expandable microspheres in the pressure-sensitive adhesive layer are expanded by heating to improve the peelability of the pressure-sensitive adhesive sheet from the adherend, the effect of reducing the adhesive force due to the expansion is effective on the adherend. It is possible to preferably maintain the form in which the pressure-sensitive adhesive layer is bonded to the supporting base material via the elastic intermediate layer. Providing the elastic intermediate layer on the back surface side (the side opposite to the surface to be attached to the adherend) of the pressure-sensitive adhesive layer can also contribute to the improvement of the peelability by heat-expanding the heat-expandable microspheres. For example, when the pressure-sensitive adhesive layer expands with the expansion of the heat-expandable microspheres, the shape of the pressure-sensitive adhesive layer changes three-dimensionally by reducing the restraint of expansion in the surface direction of the pressure-sensitive adhesive sheet. It is possible to promote the formation of a structure (for example, the occurrence of warpage) and promote the peeling (lifting) of the adhesive sheet from the adherend. Further, when the pressure-sensitive adhesive sheet is attached to the adherend, the adhesiveness of the surface of the pressure-sensitive adhesive layer to the surface of the adherend can be improved due to the deformability of the elastic intermediate layer.

In some embodiments, the hardness of the elastic intermediate layer is preferably, for example, 50 or less, more preferably 40 or less, as the hardness by a Type D durometer (Shore D) based on ASTM D-2240.

In some embodiments, a pressure-sensitive adhesive can be preferably used as the constituent material of the elastic intermediate layer. The pressure-sensitive adhesive constituting the elastic intermediate layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive using an acrylic polymer as a base polymer, a rubber-based pressure-sensitive adhesive using a rubber such as natural rubber or synthetic rubber as a base polymer, and a vinyl alkyl ether. Known adhesives such as adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, styrene-diene block copolymer adhesives, creep property improved adhesives, radiation curable adhesives, etc. It can be appropriately selected from the various adhesives of. Further, the pressure-sensitive adhesive component that can be used for the pressure-sensitive adhesive layer described above can be preferably used as a constituent material of the elastic intermediate layer.

When the base polymer of the pressure-sensitive adhesive used for the elastic intermediate layer (hereinafter, also referred to as “polymer I”) is an acrylic polymer, the acrylic polymer may be, for example, a methyl group, an ethyl group, a propyl group, a butyl group, or the like. Alkyl with 20 or less carbon atoms such as 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, dodecyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecil group, eicosyl group, etc. It can be a polymer of a monomer raw material containing a (meth) acrylic acid alkyl ester having a group as a main monomer (a component accounting for 50% by weight or more of the monomer raw material for preparing the acrylic polymer). Monomer raw materials used for the preparation of Polymer I are, if necessary, acrylate, methacrylic acid, itaconic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, N-methylolacrylamide, It may further contain one or more submonomers selected from acrylonitrile, methacrylic acid, glycidyl acrylate, glycidyl methacrylate, vinyl acetate, styrene, isoprene, butadiene, isobutylene, vinyl ether and the like.

When the base polymer (polymer A) of the pressure-sensitive adhesive layer containing the heat-expandable microspheres is an acrylic polymer, the base polymer (polymer I) of the elastic intermediate layer is considered from the viewpoint of affinity between the pressure-sensitive adhesive layer and the elastic intermediate layer. Acrylic polymers can be preferably used as the above. The polymer I can be selected from the same acrylic polymers that can be used as the polymer A.

The elastic intermediate layer is not limited to the one constructed by using the adhesive as described above. For example, natural rubber; synthetic rubber such as nitrile-based, diene-based, and acrylic resin-based; thermoplastic elastomer such as polyolefin-based and polyester-based; rubber such as ethylene-vinyl acetate copolymer, polyurethane, polybutadiene, and soft polyvinyl chloride. An elastic intermediate layer may be formed by using one or more kinds of elastic materials selected from synthetic resins having elasticity and the like.

The pressure-sensitive adhesive or the above-mentioned elastic material constituting the elastic intermediate layer is a cross-linking agent, a pressure-imparting resin, a leveling agent, a plasticizer, a softening agent, a coloring agent (dye, pigment, etc.), a filler, an antioxidant, an antiaging agent. , Known additives such as UV absorbers, antioxidants, light stabilizers, preservatives and the like may be included, if necessary. The cross-linking agent can be appropriately selected and used from the cross-linking agents exemplified above as an optional component of the pressure-sensitive adhesive layer, for example. The amount of the cross-linking agent used in the elastic intermediate layer can be selected from the range exemplified above as the amount of the cross-linking agent used in the pressure-sensitive adhesive layer. The tackifier resin can be appropriately selected and used from the tackifier resins exemplified above as an optional component of the pressure-sensitive adhesive layer, for example. The amount of the tackifier resin used in the elastic intermediate layer can be selected from the range exemplified above as the amount of the tackifier resin used in the pressure-sensitive adhesive layer.

In some embodiments, the elastic intermediate layer may have a composition that does not contain or has a limited content of thermally expandable microspheres. In such an embodiment, the weight ratio of the heat-expandable microspheres to the entire elastic intermediate layer is usually preferably less than 5% by weight, preferably less than 1% by weight, and less than 0.5% by weight. Is more preferable. For example, an elastic intermediate layer containing no heat-expandable microspheres can be preferably adopted.

The method of forming the elastic intermediate layer is not particularly limited, and for example, a method of applying a coating liquid containing an elastic intermediate layer forming material to the base material (coating method), or whether a film made of the elastic intermediate layer forming material is adhered to the base material. , Or a method of adhering a laminated film having a layer made of an elastic intermediate layer forming material on the back surface of the adhesive layer (the surface opposite to the surface to be attached to the adherend) to the base material (dry laminating method). An appropriate method can be adopted from a method of co-extruding the base material forming material and the elastic intermediate layer forming material (co-extrusion method) and the like.

The elastic intermediate layer may be made of a foam film (for example, polyethylene foam, polyurethane foam, etc.). Foaming is a conventional method, for example, a method by mechanical stirring, a method using a reaction-producing gas, a method using a foaming agent, a method for removing soluble substances, a method by spraying, a method for forming syntactic foam, etc. It can be carried out by a sintering method or the like.

The thickness of the elastic intermediate layer is not particularly limited, and it can be set so as to exert a desired effect by providing the elastic intermediate layer. The thickness of the elastic intermediate layer can be, for example, 0.1 μm or more, and may be 1 μm or more or 5 μm or more. From the viewpoint of better exerting the effect of providing the elastic intermediate layer, it is usually appropriate that the thickness of the elastic intermediate layer is 10 μm or more, and from the viewpoint of reducing the restraint of expansion of the pressure-sensitive adhesive sheet in the surface direction. It is advantageous that it is 25 μm or more, for example, it may be 50 μm or more, 75 μm or more, 100 μm or more, 100 μm or more, 125 μm or more, or 150 μm or more. Further, the thickness of the elastic intermediate layer is usually preferably 1000 μm or less, preferably 500 μm or less, 300 μm or less, or 200 μm or less from the viewpoint of handleability and processability of the pressure-sensitive adhesive sheet. Good.

The elastic intermediate layer may have a single-layer structure or a multi-layer structure including two or more sublayers. The thickness of each sub-layer may be, for example, 0.1 μm or more, usually 5 μm or more, 10 μm or more, 25 μm or more, 40 μm or more, or 60 μm or more. The thickness of each sub-layer may be, for example, 300 μm or less, preferably 200 μm or less, and more preferably 100 μm or less, from the viewpoint of suppressing cohesive failure of the elastic intermediate layer.

The multi-layered elastic intermediate layer may have a support sheet between adjacent sublayers. The support sheet can be useful for suppressing cohesive failure of the elastic intermediate layer, improving the workability of the adhesive sheet, and the like. For example, when the elastic intermediate layer is relatively thick (for example, when the thickness is 50 μm or more, 100 μm or more, or 125 μm or more), an elastic intermediate layer having a multi-layer structure including at least one support sheet between the sub-layers is preferably adopted. obtain. Similar to the above-mentioned support base material, the support sheet can be appropriately selected from various plastic films, foam sheets, woven fabrics, non-woven fabrics, papers, metal foils, sheets having a composite structure thereof, and the like. .. Examples of support sheets that can be preferably adopted include non-woven fabrics and plastic films. The thickness of the non-woven fabric may be, for example, 10 μm or more, 20 μm or more, 50 μm or more, and usually 120 μm or less, 100 μm or less, or 80 μm or less. The thickness of the plastic film is usually preferably 20 μm or less, preferably 15 μm or less from the viewpoint of the flexibility of the elastic intermediate layer, 10 μm or less, 5 μm or less, and usually. It is appropriate that is 2 μm or more.

<Adhesive sheet with base material>
When the pressure-sensitive adhesive sheet disclosed herein is in the form of a pressure-sensitive adhesive sheet with a base material, the thickness of the pressure-sensitive adhesive sheet may be, for example, 1000 μm or less, 600 μm or less, 350 μm or less, or 300 μm or less. However, it may be 250 μm or less. From the viewpoint of miniaturization, weight reduction, thinning, etc. of the product to which the pressure-sensitive adhesive sheet is applied, in some embodiments, the thickness of the pressure-sensitive adhesive sheet may be, for example, 200 μm or less, or 175 μm or less. It may be 140 μm or less, 120 μm or less, or 100 μm or less (for example, less than 100 μm). Further, from the viewpoint of handleability and the like, the thickness of the pressure-sensitive adhesive sheet may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more. In some embodiments, the thickness of the pressure-sensitive adhesive sheet may be, for example, 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, 120 μm or more, 150 μm or more, or 200 μm or more. .. The upper limit of the thickness of the adhesive sheet is not particularly limited.
The thickness of the adhesive sheet means the thickness of the portion to be attached to the adherend. For example, in the pressure-sensitive adhesive sheet 1 having the configuration shown in FIG. 1, it refers to the thickness from the pressure-sensitive adhesive surface 21A of the pressure-sensitive adhesive sheet 1 to the second surface 10B of the base material 10, and does not include the thickness of the release liner 31.

The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented, for example, in a mode in which the thickness Ts of the supporting base material is larger than the thickness Ta of the pressure-sensitive adhesive layer, that is, a mode in which Ts / Ta is larger than 1. Although not particularly limited, Ts / Ta may be, for example, 1.1 or more, 1.2 or more, 1.5 or more, or 1.7 or more. May be good. For example, in an adhesive sheet that can be used for the purpose of reinforcing, supporting, impact mitigating, or the like of an adherend, an increase in Ts / Ta tends to make it easier for a good effect to be exhibited even if the adhesive sheet is made thinner. In some embodiments, Ts / Ta may be 2 or greater (eg, greater than 2), 2.5 or greater, or 2.8 or greater. Further, Ts / Ta may be, for example, 50 or less, or 20 or less. The Ts / Ta may be, for example, 10 or less, 8 or less, or 5 or less, from the viewpoint of facilitating the high adhesive force after heating even if the pressure-sensitive adhesive sheet is thinned.

The pressure-sensitive adhesive layer is preferably adhered to the supporting base material directly or via an elastic intermediate layer. Here, "adhesion" means that in an adhesive sheet whose adhesive strength has increased after being attached to an adherend, the adhesive layer is formed to such an extent that the adhesive layer does not separate from the supporting base material when the adhesive sheet is peeled off from the adherend. It means that it exhibits sufficient anchoring property with respect to the supporting base material (it may be anchoring property via an elastic intermediate layer). According to the pressure-sensitive adhesive sheet with a base material in which the pressure-sensitive adhesive layer is fixed to the support base material, the adherend and the support base material can be firmly integrated. As a preferable example of the pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is adhered to the base material, adhesion that does not cause peeling (anchor failure) between the pressure-sensitive adhesive layer and the supporting base material during the above-mentioned measurement of the pressure-sensitive adhesive force after heating. The sheet can be mentioned. An adhesive sheet having an adhesive force after heating of 10 N / 20 mm or more and which does not cause anchoring failure when measuring the adhesive force after heating is a preferred example corresponding to an adhesive sheet in which the adhesive layer is adhered to a substrate. Is.

In the pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is directly adhered to the supporting base material, for example, a liquid pressure-sensitive adhesive composition is brought into contact with the first surface of the base material, and the pressure-sensitive adhesive composition is placed on the first surface. It can be preferably produced by a method including curing to form a pressure-sensitive adhesive layer in this order. Curing of the pressure-sensitive adhesive composition may involve one or more of drying, cross-linking, polymerization, cooling, etc. of the pressure-sensitive adhesive composition. According to the method of forming the pressure-sensitive adhesive layer by curing the liquid pressure-sensitive adhesive composition on the first surface of the base material, the cured pressure-sensitive adhesive layer is bonded to the first surface of the base material. Compared with the method of arranging the pressure-sensitive adhesive layer on the first surface, the anchoring property of the pressure-sensitive adhesive layer on the base material can be improved. Utilizing this, a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is adhered to a base material can be suitably manufactured.

In some embodiments, as a method of bringing the liquid pressure-sensitive adhesive composition into contact with the first surface of the base material, a method of directly applying the pressure-sensitive adhesive composition to the first surface of the base material can be adopted. By bringing the first surface (adhesive surface) of the pressure-sensitive adhesive layer cured on the first surface of the base material into contact with the peeled surface, the second surface of the pressure-sensitive adhesive layer is fixed to the first surface of the base material. Moreover, it is possible to obtain a pressure-sensitive adhesive sheet having a structure in which the first surface of the pressure-sensitive adhesive layer is in contact with the peeled surface. As the peeling surface, the surface of the peeling liner, the back surface of the base material that has been peeled off, or the like can be used.

Further, for example, in the case of a photocurable pressure-sensitive adhesive composition using a partial polymer (polymer syrup) of a monomer raw material, for example, the pressure-sensitive adhesive composition is applied to a peeling surface, and then the applied pressure-sensitive adhesive composition is applied. By covering the object with the first surface of the base material, the uncured adhesive composition is brought into contact with the first surface of the base material, and in that state, it is sandwiched between the first surface of the base material and the peeled surface. The pressure-sensitive adhesive layer may be formed by irradiating the pressure-sensitive adhesive composition with light and curing the pressure-sensitive adhesive composition.

The method exemplified above does not limit the method for producing the pressure-sensitive adhesive sheet disclosed herein. In the production of the pressure-sensitive adhesive sheet disclosed herein, an appropriate method capable of fixing the pressure-sensitive adhesive layer to the first surface of the base material can be used alone or in combination of two or more types. Examples of such a method include a method of curing a liquid pressure-sensitive adhesive composition on the first surface of a base material to form a pressure-sensitive adhesive layer as described above, and a method of forming a pressure-sensitive adhesive layer on the first surface of a base material. Examples thereof include a method of applying a surface treatment for enhancing the anchoring property, a method of providing an undercoat layer on the first surface of the base material, a method of interposing an elastic intermediate layer between the first surface of the base material and the pressure-sensitive adhesive layer, and the like. For example, a method of adhering a cured adhesive layer to the first surface of a surface-treated base material that enhances anchoring property, or a method of adhering after curing to an elastic intermediate layer provided on the first surface of the base material. The pressure-sensitive adhesive sheet may be manufactured by a method such as laminating agent layers. In addition, the anchoring property of the pressure-sensitive adhesive layer on the base material can be improved by selecting the material of the base material and the composition of the pressure-sensitive adhesive. Further, by applying a temperature higher than room temperature to the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on the first surface of the base material, the anchoring property of the pressure-sensitive adhesive layer on the base material can be enhanced. The temperature applied to enhance the anchoring property is selected from a temperature lower than the expansion start temperature T1 of the thermally expandable microsphere (preferably 5 ° C. or higher, more preferably 10 ° C. or higher), for example, 35 ° C. to 80 ° C. It may be about 40 ° C. to 70 ° C., and may be about 45 ° C. to 60 ° C.

The pressure-sensitive adhesive sheet disclosed herein is a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer provided on the first surface side of the base material and a second pressure-sensitive adhesive layer provided on the second surface side of the base material (that is, In the form of a double-sided adhesive base-attached pressure-sensitive adhesive sheet), the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same structure or different structures. When the configurations of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer are different, the difference may be, for example, a difference in composition or a difference in structure (thickness, surface roughness, formation range, formation pattern, etc.). For example, the second pressure-sensitive adhesive layer may be a layer that does not have a function of facilitating re-peeling, and may be, for example, a pressure-sensitive adhesive layer that does not contain heat-expandable microspheres. Further, the surface of the second pressure-sensitive adhesive layer (second pressure-sensitive adhesive surface) may be a surface that is not intended to have both initial low adhesiveness and strong adhesiveness at the time of use.

<Adhesive sheet with release liner>
The pressure-sensitive adhesive sheet disclosed herein may take the form of a pressure-sensitive adhesive product in which the surface (adhesive surface) of the pressure-sensitive adhesive layer is brought into contact with the peel-off surface of the release liner. Therefore, the present specification provides an adhesive sheet (adhesive product) with a release liner including any of the adhesive sheets disclosed herein and a release liner having a release surface that abuts on the adhesive surface of the adhesive sheet. obtain.

The thickness of the release liner is not particularly limited, but is usually about 5 μm to 200 μm. When the thickness of the release liner is within the above range, the workability of bonding to the pressure-sensitive adhesive layer and the workability of peeling from the pressure-sensitive adhesive layer are excellent, which is preferable. In some embodiments, the thickness of the release liner may be, for example, 10 μm or greater, 20 μm or greater, 30 μm or greater, or 40 μm or greater. The thickness of the release liner may be, for example, 100 μm or less, or 80 μm or less, from the viewpoint of facilitating the release from the pressure-sensitive adhesive layer. If necessary, the release liner may be subjected to a known antistatic treatment such as a coating type, a kneading type, or a vapor deposition type.

The release liner is not particularly limited, and for example, a release liner having a release layer on the surface of a liner base material such as a resin film or paper (paper on which a resin such as polyethylene is laminated) or a fluoropolymer. A release liner made of a resin film formed of a low adhesive material such as (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.) can be used. Since the surface smoothness is excellent, a release liner having a release layer on the surface of the resin film as the liner base material or a release liner made of a resin film formed of a low adhesive material can be preferably adopted. The resin film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and is, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, or a vinyl chloride copolymer. Examples thereof include films, polyester films (PET film, PBT film, etc.), polyurethane films, ethylene-vinyl acetate copolymer films, and the like. For forming the release layer, for example, a silicone-based release treatment agent, a long-chain alkyl-based release treatment agent, an olefin-based release treatment agent, a fluorine-based release treatment agent, a fatty acid amide-based release treatment agent, molybdenum sulfide, silica powder, etc. , A known stripping agent can be used. The use of a silicone-based stripping agent is particularly preferred.

The thickness of the release layer is not particularly limited, but is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. The method for forming the release layer is not particularly limited, and a known method according to the type of the release treatment agent to be used can be appropriately adopted.

<Use>
The adhesive sheet provided by this specification can exhibit good reworkability at the initial stage of being attached to an adherend, for example, so that a decrease in yield can be suppressed and the quality of the product containing the adhesive sheet can be improved. Can contribute to. The adhesive force of the pressure-sensitive adhesive sheet can be greatly increased by aging (heating at a temperature lower than the expansion start temperature T1, aging, a combination thereof, etc.). For example, the adhesive sheet can be firmly adhered to the adherend by heating at a desired timing. Further, the pressure-sensitive adhesive sheet can be heated to a temperature equal to or higher than the expansion start temperature T1 to expand the heat-expandable microspheres to improve the peelability from the adherend and easily peel off from the adherend. it can. Taking advantage of these characteristics, the adhesive sheet disclosed herein is used in various fields for the purpose of fixing, joining, molding, decorating, protecting, reinforcing, supporting, shock absorbing, etc. of members contained in various products. If desired (for example, when repairing a member or collecting a member when disposing of a product), it is preferable as an adhesive sheet that can be easily peeled off from the member by heating to a temperature of T1 or higher, which is the expansion start temperature. Can be used. Therefore, the adhesive sheet disclosed herein can be useful for improving convenience in repairing the product, improving the recyclability of the members contained in the product, and the like. Further, the pressure-sensitive adhesive sheet disclosed herein can have both initial reworkability, strong adhesiveness after an increase in adhesive strength, and re-peelability by heating to a temperature of expansion start temperature T1 or higher. Therefore, it is also useful as a highly reliable temporary fixing means.

The pressure-sensitive adhesive sheet disclosed herein is, for example, an adherend in the form of a base-attached pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on at least the first side of a film-like base material having a first surface and a second surface. It can be preferably used as a reinforcing film that is attached to and reinforces the adherend. In such a reinforcing film, as the film base material, one containing a resin film as a base film can be preferably used. Further, from the viewpoint of enhancing the reinforcing performance, it is preferable that the pressure-sensitive adhesive layer is adhered to the first surface of the film-like base material.
For example, optical members used in optical products and electronic members used in electronic products are becoming highly integrated, smaller and lighter, and thinner, and a plurality of thin optical members having different linear expansion coefficients and thicknesses / Electronic members can be stacked. By attaching the reinforcing film as described above to such a member, it is possible to impart appropriate rigidity to the optical member / electronic member. As a result, in the manufacturing process and / or the product after manufacturing, curling and bending due to stress that may occur between the plurality of members having different linear expansion coefficients and thicknesses can be suppressed.
Further, in the manufacturing process of an optical product / electronic product, when a shape processing process such as a cutting process is performed on a thin optical member / electronic member as described above, the processing is performed by attaching a reinforcing film to the member. It is possible to alleviate the local stress concentration on the optical member / electronic member and reduce the risk of cracks, cracks, peeling of laminated members, and the like. The handling of the reinforcing member attached to the optical member / electronic member also reduces local stress concentration during transportation, lamination, rotation, etc. of the member, and suppresses bending or bending due to the weight of the member. Can be useful.
Furthermore, devices such as optical products and electronic products containing the above-mentioned reinforcing film collide with flying objects when the device is dropped or placed under a heavy object at the stage of being used by consumers in the market. Even when unintentional stress is applied, such as in the case, the stress applied to the device can be relieved by including the reinforcing film in the device. Therefore, the durability of the device can be improved by including the reinforcing film in the device.

In addition, the pressure-sensitive adhesive sheet disclosed herein can be preferably used, for example, in a manner of being attached to a member constituting various portable devices (portable devices). Here, "portable" means that it is not enough to be portable, but that an individual (standard adult) has a level of portability that is relatively easy to carry. To do. Examples of portable devices here include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices, digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), and computers (computers (portable music players, IC recorders, etc.)). Calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, mobile radios, mobile TVs, mobile printers, mobile scanners, mobile modems, and other portable electronic devices, as well as mechanical watches and pockets. Clocks, flashlights, hand mirrors, etc. may be included. Examples of the members constituting the portable electronic device may include an optical film, a display panel, and the like used in an image display device such as a thin layer display such as a liquid crystal display and a film type display. The adhesive sheet disclosed herein can also be preferably used in a mode of being attached to various members in automobiles, home appliances and the like.

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

<Preparation of polymer A>
(Polymer A1)
100 parts of n-butyl acrylate (BA), 5 parts of vinyl acetate (VAc), 3 parts of acrylic acid (AA), 2-hydroxyethyl acrylate in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube and a cooler. 0.1 part of (HEA), 0.3 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and toluene as a polymerization solvent were charged, and the reaction was carried out at 60 ° C. for 6 hours to carry out the polymer. A solution of A1 was obtained. The weight average molecular weight of the polymer A1 (Mw) was 55 × 10 ^4.

(Polymer A2)
60 parts of 2-ethylhexyl acrylate (2EHA), 15 parts of N-vinyl-2-pyrrolidone (NVP), 10 parts of methyl methacrylate (MMA) in a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube and a cooler. , HEA (15 parts), AIBN (0.2 parts), and ethyl acetate (200 parts) as a polymerization solvent were charged and reacted at 60 ° C. for 6 hours to obtain a solution of polymer A2. Mw of polymer A2 was 110 × 10 ^4.

(Polymer A3)
In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube and a cooler, 100 parts of 2EHA, 2 parts of AA, 0.2 part of AIBN, and 200 parts by mass of ethyl acetate as a polymerization solvent were charged, and the reaction was carried out at 60 ° C. for 6 hours. To obtain a solution of polymer A3. Mw of polymer A3 was 110 × 10 ^4.

<Preparation of polymer B>
(Polymer B1)
In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube and a cooler, 60 parts of MMA, 10 parts of n-butyl methacrylate (BMA), 10 parts of 2-ethylhexyl methacrylate (2EHMA), and a functional group equivalent of 900 g / mol. Polyorganosiloxane skeleton-containing methacrylate monomer (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) 8.7 parts, polyorganosiloxane skeleton-containing methacrylate monomer having a functional group equivalent of 4600 g / mol (trade name: KF) -2012, manufactured by Shin-Etsu Chemical Industry Co., Ltd.) 11.3 parts, 100 parts of ethyl acetate, and 0.8 parts of α-thioglycerol as a chain transfer agent were added, and the mixture was stirred at 70 ° C. in a nitrogen atmosphere for 1 hour. , 0.2 part of AIBN was added and reacted at 70 ° C. for 2 hours, then 0.1 part by weight of AIBN was added and then reacted at 80 ° C. for 5 hours. In this way, a solution of polymer B1 was obtained. Mw of the polymer B1 is was 2.0 × 10 ^4.

(Polymer B2)
The composition of the monomer component is 40 parts of MMA, 20 parts of BMA, 20 parts of 2EHMA, 8.7 parts of polyorganosiloxane skeleton-containing methacrylate monomer (X-22-174ASX) having a functional group equivalent of 900 g / mol, and poly having a functional group equivalent of 4600 g / mol. Polymer B2 was prepared in the same manner as in the preparation of polymer B1, except that 11.3 parts of the organosiloxane skeleton-containing methacrylate monomer (KF-2012) was changed. Mw of polymer B2 was 2.2 × 10 ^4.

The weight average molecular weight of each of the above-mentioned polymers was measured under the following conditions using a GPC device (manufactured by Tosoh Corporation, HLC-8220 GPC), and was determined by polystyrene conversion.
[GPC conditions]
-Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution)
-Sample injection volume: 10 μL
-Eluent: THF-Flow velocity: 0.6 mL / min
・ Measurement temperature: 40 ° C
·column:
Sample column; TSKguardcolumn SuperHZ-H (1) + TSKgel SuperHZM-H (2)
Reference column; TSKgel SuperH-RC (1)
・ Detector: Differential refractometer (RI)

<Preparation of elastic intermediate layer>
(Elastic intermediate layer F1)
In the solution of the polymer A1, 40 parts of the tackifier resin and the isocyanate-based cross-linking agent X1 (manufactured by Toso Co., Ltd., trade name "Coronate L", trimethylolpropane / tolylene diisocyanate) are added to 100 parts of the acrylic polymer contained in the solution. Two parts (75% ethyl acetate solution) of the trimer adduct were added and mixed by stirring to prepare a pressure-sensitive adhesive composition f1 for forming an elastic intermediate layer. The tackifying resin includes 10 parts of a polymerized rosin ester (trade name "Haritac PCJ", manufactured by Harima Chemicals, Inc.) having a softening point of about 125 ° C., and a stabilized rosin ester (trade name "Haritac SE10") having a softening point of about 80 ° C. 10 parts of Harima Chemicals, 5 parts of hydrogenated rosin methyl ester (trade name "M-HDR", manufactured by Guangxi Richeng Linchan Chemical Industry Co., Ltd., liquid), and terpenphenol resin (commodity) with a softening point of about 133 ° C. The name "Sumilite Resin PR-12603", manufactured by Sumitomo Bakelite Co., Ltd.) 15 copies were used.

Two polyester release films were prepared, one of which was a release surface made of a silicone-based release treatment agent. The pressure-sensitive adhesive composition f1 was applied to the peeled surface of these release films and dried to form a pressure-sensitive adhesive layer having the same thickness on each release film. These adhesive layers are bonded to the first and second surfaces of a non-woven fabric having a thickness of 75 μm (a non-woven fabric in which 99% Manila hemp and 1% vinylon are mixed. Density 0.30 g / cm ³ ) to obtain the above-mentioned non-woven fabric. A double-sided pressure-sensitive adhesive sheet with a base material having a total thickness of 160 μm having pressure-sensitive adhesive layers on both sides was produced. This double-sided adhesive sheet was used as the elastic intermediate layer F1.

(Elastic intermediate layer F2)
To a solution of the polymer A2, 2.5 parts of an isocyanate-based cross-linking agent X2 (manufactured by Mitsui Chemicals, trade name: Takenate D110N, trimethylolpropane xylylene diisocyanate) was added to 100 parts of the acrylic polymer contained in the solution. The pressure-sensitive adhesive composition f2 for forming an elastic intermediate layer was prepared by stirring and mixing.
The pressure-sensitive adhesive composition f2 was applied to the peel-off surface of a polyester peel-off film, one side of which is a peel-off surface made of a silicone-based release treatment agent, and dried to prepare a base-less double-sided pressure-sensitive adhesive sheet having a thickness of 30 μm. This base material-less double-sided adhesive sheet was used as the elastic intermediate layer F2.

<Making an adhesive sheet>
(Example 1)
In a solution of polymer A1, 5 parts of polymer B1, 5 parts of isocyanate-based cross-linking agent X1 (coronate L) based on solid content, and heat-expandable microspheres C1 (Matsumoto oil and fat) per 100 parts of polymer A1 contained in the solution. 100 parts of "Matsumoto Microsphere F-501D" manufactured by Pharmaceutical Co., Ltd., expansion start temperature 120 ° C., average particle size 10 μm) was added and mixed uniformly to prepare a pressure-sensitive adhesive composition D1.
The pressure-sensitive adhesive composition D1 is applied to the peeling surface of the peeling liner R1 (MRQ25T100, thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) in which one side of the polyester film is a peeling surface with a silicone-based peeling agent, and the pressure is 5 at 70 ° C. It was dried for 1 minute to form a heat-expandable pressure-sensitive adhesive layer E1 having a thickness of 40 μm.
One adhesive surface of the elastic intermediate layer F1 was bonded to the first surface of a polyethylene terephthalate (PET) film (manufactured by Toray Industries, Inc., trade name "Lumirror") having a thickness of 50 μm as a supporting base material. Next, the heat-expandable pressure-sensitive adhesive layer E1 was attached to the other adhesive surface of the elastic intermediate layer F1. In this way, the adhesive sheet according to Example 1 was obtained in the form of an adhesive sheet with a release liner in which the release surface of the release liner R1 was in contact with the adhesive surface.

(Example 2)
In a solution of polymer A1, 5 parts of polymer B2, 5 parts of isocyanate-based cross-linking agent X1 (coronate L) based on solid content, and heat-expandable microspheres C2 (Matsumoto oil and fat) per 100 parts of polymer A1 contained in the solution. 100 parts of "Matsumoto Microsphere F-100VSD" manufactured by Pharmaceutical Co., Ltd., expansion start temperature 170 ° C., average particle size 10 μm) was added and mixed uniformly to prepare a pressure-sensitive adhesive composition D2.
The pressure-sensitive adhesive sheet according to Example 2 was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive composition D2 was used instead of the pressure-sensitive adhesive composition D1.

(Example 3)
In a solution of polymer A2, 2.5 parts of polymer B2, 2.5 parts of isocyanate-based cross-linking agent X2 (Takenate D110N) based on solid content, and heat-expandable microspheres per 100 parts of polymer A2 contained in the solution. 50 parts of C1 (Matsumoto Microsphere F-501D) was added and mixed uniformly to prepare a pressure-sensitive adhesive composition D3.
The pressure-sensitive adhesive sheet according to Example 3 was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive composition D3 was used instead of the pressure-sensitive adhesive composition D1.

(Example 4)
In a solution of polymer A3, 2.5 parts of polymer B1, 2 parts of isocyanate-based cross-linking agent X1 (coronate L) based on solid content, and thermally expandable microspheres C3 (2 parts) per 100 parts of polymer A3 contained in the solution. 30 parts of Matsumoto Yushi Seiyaku Co., Ltd., trade name "Matsumoto Microsphere F-301SD", expansion start temperature 90 ° C., average particle size 15 μm) was added and mixed uniformly to prepare a pressure-sensitive adhesive composition D4.
The pressure-sensitive adhesive sheet according to Example 4 was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition D4 was used instead of the pressure-sensitive adhesive composition D1 and the elastic intermediate layer F2 was used instead of the elastic intermediate layer F1. did.

<Measurement and evaluation>
(Storage modulus G'(T1))
The storage elastic modulus G'(T1) of the polymer A1 contained in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to Example 1 was determined by dynamic viscoelasticity measurement. Specifically, the pressure-sensitive adhesive layer is formed under basically the same conditions as in Example 1 except that the pressure-sensitive adhesive composition is applied to the peel-off surface of the release liner instead of the PET film, and the thickness is increased by stacking a plurality of the pressure-sensitive adhesive layers. A pressure-sensitive adhesive layer of about 2 mm was formed. A measurement sample prepared by punching this pressure-sensitive adhesive layer into a disk shape having a diameter of 7.9 mm is sandwiched between parallel plates and fixed, and a viscoelasticity tester (“ARES” manufactured by TA Instruments) is used under the following conditions. The dynamic viscoelasticity was measured in 1 and the storage elastic modulus G'at the expansion start temperature T1 (that is, 120 ° C.) of the heat-expandable microsphere C1 was determined.
-Measurement mode: Shear mode-Temperature range: -50 ° C to 200 ° C
・ Temperature rise rate: 5 ° C / min
・ Measurement frequency: 1Hz

Similarly, for the polymer A contained in the pressure-sensitive adhesive layer according to Examples 2 to 4, the storage elastic modulus G'at the expansion start temperature T1 of the heat-expandable microspheres contained in the pressure-sensitive adhesive layer was determined.

(Measurement of adhesive strength N1)
The pressure-sensitive adhesive sheet according to each example was cut to a width of 20 mm together with the release liner to prepare a test piece.
Under a standard environment of 23 ° C. and 50% RH, the peeling liner covering the adhesive surface of the test piece is peeled off, and the exposed adhesive surface is reciprocated once on a stainless steel plate (SUS304BA plate) as an adherend. And crimped. After leaving this in the above standard environment for 30 minutes, a universal tensile compression tester (device name "tensile compression tester, TCM-1kNB" manufactured by Minebea) is used, and the peeling angle is 180 degrees according to JIS Z0237. The 180 ° peeling adhesive strength (resistance to the above tension) was measured under the condition of a tensile speed of 300 mm / min. The measurement was performed three times, and the average value thereof is shown in Table 1 as the initial adhesive strength (N1) [N / 20 mm].

(Measurement of adhesive strength N2)
The test piece pressure-bonded to the adherend in the same manner as in the measurement of the adhesive force N1 is placed at a temperature 20 ° C. lower than the expansion start temperature T1 of the heat-expandable microspheres contained in the pressure-sensitive adhesive layer of the test piece (heat treatment temperature T2). ) For 5 minutes, then left in the above standard environment for 30 minutes, and then the 180 ° peeling adhesive strength was measured in the same manner. The measurement was performed three times, and the average value thereof is shown in Table 1 as the adhesive strength (N2) [N / 20 mm] after heating.

(Evaluation of peelability at expansion start temperature T1)
The test piece crimped to the adherend in the same manner as in the measurement of the adhesive force N1 is heated at the heat treatment temperature T2 for 5 minutes, left in the standard environment for 30 minutes, and then heated at the expansion start temperature T1 for 5 minutes. Then, after leaving it in the above standard environment for 30 minutes, the adhesive strength was measured by peeling it off by 180 ° in the same manner. The measurement was performed three times, and the average value thereof was taken as the adhesive strength (N3) after the expansion treatment. Based on the obtained results, the peelability was evaluated in the following three stages. The results are shown in Table 1. By heating the adhesive sheets of Examples 1 to 3 at the expansion start temperature T1 for 5 minutes, most of the test pieces from both sides in the width direction to the vicinity of the center of the width are peeled off from the adherend and lifted up. Was extremely easily peeled off from the adherend.
E: Adhesive strength after expansion treatment is less than 0.5N / 20mm (excellent in peelability)
G: Adhesive strength after expansion treatment is 0.5 N / 20 mm or more and less than 1.0 N / 20 mm (good peelability)
P: Adhesive strength after expansion treatment is 1.0 N / 20 mm or more (poor peelability)

As shown in Table 1, all of the adhesive sheets according to Examples 1 to 3 have an adhesive force increase ratio (N2 / N1) of 3.0 or more, which is sufficiently lower than the expansion start temperature T1 (heat treatment temperature T2). ) For 5 minutes, the initial adhesive strength was greatly increased. Further, the adhesive sheets of Examples 1 to 3 could be easily peeled off from the adherend by heating at the expansion start temperature T1 after increasing the adhesive force by heating at the heat treatment temperature T2.

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

1,2,3 Adhesive sheet 10 Supporting base material 10A First surface 10B Second surface 21 Adhesive layer (first adhesive layer)
21A Adhesive surface (first adhesive surface)
21B adhesive surface (second adhesive surface)
22 Adhesive layer (second adhesive layer)
22A Adhesive surface (second adhesive surface)
31,32 Release liner 50 Elastic intermediate layer 100, 200, 300 Adhesive sheet with release liner (adhesive product)

Claims (10)

An adhesive sheet containing an adhesive layer,
The pressure-sensitive adhesive layer contains polymer A as a base polymer and thermally expandable microspheres having an expansion start temperature T1.
The adhesive force N2 measured at 23 ° C. after being bonded to a stainless steel sheet and heated at a temperature 20 ° C. lower than the expansion start temperature T1 for 5 minutes is measured after being bonded to a stainless steel sheet and held at 23 ° C. for 30 minutes. An adhesive sheet that has an adhesive strength of 3.0 times or more that of N1. The pressure-sensitive adhesive sheet according to claim 1, wherein the polymer A has a storage elastic modulus ^{G'at 1 × 10 4} Pa to 1 × 10 ^{6 Pa at the expansion start temperature T1.} The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the _{glass transition temperature Tg A} calculated by the Fox formula based on the composition of the monomer components constituting the polymer A is −65 ° C. or higher and lower than 0 ° C. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer contains 10 parts by weight or more and 200 parts by weight or less of the heat-expandable microspheres with respect to 100 parts by weight of the polymer A. The pressure-sensitive adhesive layer further contains polymer B and contains
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the polymer B is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer. _{The pressure-sensitive adhesive sheet according to claim 5, wherein the polymer B has a glass transition temperature Tg B} calculated by the Fox formula based on the composition of the (meth) acrylic monomer, which is 30 ° C. or higher and 120 ° C. or lower. The pressure-sensitive adhesive sheet according to claim 6, wherein the glass transition temperature Tg _B is 20 ° C. or more lower than the expansion start temperature T1. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the content of the polymer B in the pressure-sensitive adhesive layer is 0.5 parts by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the polymer A. The invention according to any one of claims 1 to 8, wherein the support base material having the first surface and the second surface is provided, and the pressure-sensitive adhesive layer is laminated on at least the first surface side of the support base material. Adhesive sheet. The pressure-sensitive adhesive sheet according to claim 9, wherein an elastic intermediate layer is arranged between the pressure-sensitive adhesive layer and the first surface of the support base material.

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