JP6626125B2 - Adhesive composition and adhesive tape - Google Patents

Description

  The present invention, for example, in the adhesive tape used in the manufacturing process of electrical and electronic parts, etc., excellent in the fixing force of the parts, can be peeled without adhesive residue even when used in a high-temperature environment, and repeated adhesion-peeling The present invention also relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive composition has little change in adhesive force.

  The silicone pressure-sensitive adhesive composition is excellent in heat resistance, cold resistance, weather resistance, electrical insulation, chemical resistance, and adhesion to various adherends. Furthermore, an adhesive tape having a silicone adhesive layer is less likely to have an adhesive residue after peeling, especially when used in a high-temperature environment. Therefore, such an adhesive tape is widely used in applications such as protection of components, masking, temporary fixing, and fixing for transportation in a manufacturing process of various components such as electric and electronic components.

  Conventional adhesive tapes do not have stable adhesive properties when used repeatedly, and need to be replaced after each use. Specifically, the adhesive force may be increased due to repeated adhesion and the adhesive surface may be roughened to make the adherence easier to adhere to, and the tape may not be peeled off. In addition, when the adhesive force is reduced due to, for example, a low molecular component in the adhesive or a component contributing to the development of adhesiveness being transferred to the adherend due to repeated peeling, the fixing force to the component is insufficient. Parts may come off during the process. In addition, the adhesive may deteriorate during repeated use in a high temperature environment, and adhesive may remain on parts.

  In the past, many silicone pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes that have little adhesive residue after peeling have been studied (for example, Patent Documents 1 to 4). However, the problem of stability of adhesive force after peeling has not been studied at all.

  Patent Document 5 discloses a double-sided pressure-sensitive adhesive tape for attaching a transparent protective cover to an information display screen such as a display panel, in which an adsorption layer mainly composed of a silicone resin is laminated on one surface of a base film, There is disclosed an adhesive tape in which an adhesive layer made of an acrylic adhesive is laminated on the other surface. This silicone adsorbing layer is premised on reattachment, but this document does not mention the basic adhesive properties such as adhesive strength as well as the stability of adhesive strength after repeated peeling. In addition, since this adsorbing layer is made of silicone resin, the purpose of the adsorbing layer is to obtain a slight adsorbing force that does not cause the protective cover to fall off the display panel. This is fundamentally different from an adhesive tape used for an application in which some external force or a force for fixing another component (that is, a fixing force) is applied.

  Patent Literatures 6 to 8 disclose a jig for holding and transporting a printed wiring board in which a weak adhesive resin is applied to a jig base formed of a plate body. These patent documents do not mention the basic adhesive properties such as adhesive strength, as well as the stability of adhesive strength when peeling is repeated, and cannot be said to have been sufficiently verified. In the patent document, a weakly tacky adhesive is used, but if the tackiness is weak, the adhesive force after repeated peeling is not always stable. In addition, the fixing force to the parts and the adhesive residue have not been verified.

JP 2002-275450 A JP 2003-96429 A JP 2003-193226 A JP 2004-168808 A JP 2015-199878 A JP 2001-144430 A JP-A-2003-332795 JP 2004-359270 A

  The present inventors have paid attention to the problem of stability of adhesive force after peeling, and have developed a pressure-sensitive adhesive tape that can be used repeatedly for the purpose of reducing costs in the manufacturing process of various components such as electric and electronic components. . That is, an object of the present invention is to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape which are excellent in fixing force of parts, can be peeled without remaining adhesive even when used in a high-temperature environment, and have a small change in adhesive force even after repeated adhesion-peeling. Is to provide.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, the balance between the gel fraction and the degree of swelling of the silicone pressure-sensitive adhesive layer is related to changes in adhesive strength and other various properties when repeatedly used. This led to the completion of the present invention.

That is, the present invention comprises a crosslinked silicone structure, the gel fraction measured by the following method is 45% or more and less than 70%, and the degree of swelling with respect to toluene measured by the following method is 290% or less. Which is a silicone-based pressure-sensitive adhesive composition.
(Gel fraction)
The gel fraction is obtained by the following formula, which is the ratio of the insoluble component when the silicone-based pressure-sensitive adhesive composition is immersed in toluene at room temperature for one day.
Gel fraction (%) = (C / A) × 100
A: Initial mass of silicone-based pressure-sensitive adhesive composition C: Dry mass of silicone-based pressure-sensitive adhesive composition after immersion in toluene (drying condition: 130 ° C., 2 hours)
(Swelling degree)
The degree of swelling is obtained by the following equation, which is the swelling ratio due to toluene absorption when the silicone-based pressure-sensitive adhesive composition is immersed in toluene at room temperature for one day.
Swelling degree (%) = ((BA) / A) × 100%
A: Initial mass of silicone-based pressure-sensitive adhesive composition B: Swelling mass of silicone-based pressure-sensitive adhesive composition after immersion in toluene

  Furthermore, the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising the above-mentioned pressure-sensitive adhesive composition on at least one surface of a substrate.

  According to the present invention, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape which are excellent in fixing force of components, can be peeled without leaving adhesive even when used in a high-temperature environment, and have a small change in adhesive force even after repeated adhesion-peeling are obtained. Provided. In particular, since the pressure-sensitive adhesive tape of the present invention has the above-mentioned specific pressure-sensitive adhesive layer, for example, in the process of manufacturing various components such as electric and electronic components at a high temperature, the components do not peel off during the process, It is hard to remain, and the change in the adhesive force is small even when the bonding and peeling are repeated. Therefore, the adhesive can be used repeatedly, which is very useful in terms of cost reduction.

It is the graph which put together the comprehensive evaluation of the Example and the comparative example in the correlation of a gel fraction and a swelling degree. It is a schematic diagram for demonstrating the fixing force test in an Example and a comparative example.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a silicone-based pressure-sensitive adhesive as a main component. The gel fraction of the pressure-sensitive adhesive composition of the present invention is 45% or more and less than 70%, preferably 48 to 65%, more preferably 50 to 60%. The pressure-sensitive adhesive composition of the present invention has a degree of swelling in toluene of 290% or less, preferably 260% or less, more preferably 230% or less. Specific methods for measuring the gel fraction and the degree of swelling are described in the Examples section below. Generally, the degree of swelling depends on the crosslink density of the pressure-sensitive adhesive composition. When the crosslink density is high, the three-dimensionally crosslinked polymer chains constituting the adhesive are less likely to spread even when immersed in toluene, and the degree of swelling is reduced. On the other hand, when the crosslink density is low, the polymer chains easily spread, and the degree of swelling increases.

  When the gel fraction and the degree of swelling are in the specific ranges of the present invention, sufficient fixing force, adhesive residue preventing property, and stability of adhesive strength when used repeatedly can be obtained. If the gel fraction is less than 45%, the fixing force becomes stronger, but adhesive residue is likely to occur due to insufficient cohesive force, and the adhesive force after repeated use is not stable. On the other hand, if the gel fraction exceeds 70%, a sufficient fixing force cannot be obtained. Also, even if the gel fraction is in the range of 45% or more and less than 70%, if the degree of swelling exceeds 290%, adhesive residue easily occurs due to insufficient cohesive force due to low crosslink density, and repeated Adhesive strength when used is not stable.

Specific examples of the silicone-based pressure-sensitive adhesive used in the present invention include silicone raw rubber (a long-chain polymer of polydimethylsiloxane composed of D units [(CH ₃ ) ₂ SiO]) and MQ resin (M units [(CH ₃ ) An adhesive comprising a silicone resin having a three-dimensional structure composed of ₃ SiO _1/2 ] and a Q unit [SiO ₂ ]. Such a pressure-sensitive adhesive composed of silicone raw rubber and MQ resin is excellent in adhesiveness as compared with silicone raw rubber alone. Also, by changing the ratio of the silicone raw rubber and the MQ resin in the adhesive, basic adhesive properties such as adhesive strength, holding power, and tack can be controlled. Silicone-based pressure-sensitive adhesives are roughly classified into addition-curable type and peroxide-curable type according to their curing mechanism. The addition-curable silicone pressure-sensitive adhesive is cured by a crosslinking reaction of a main agent composed of an alkenyl group-containing silicone raw rubber and a crosslinking agent composed of a polyorganosiloxane containing an SiH group, for example, by heating under a platinum catalyst. At this time, it is possible to change the crosslinking density by appropriately adjusting the amount of the crosslinking agent. Further, the peroxide-curable silicone pressure-sensitive adhesive is cured by adding a peroxide such as benzoyl peroxide as a curing agent, removing the solvent, and then heating at a high temperature, for example. At this time, it is possible to change the crosslinking density of the pressure-sensitive adhesive by appropriately adjusting the amount of the peroxide to be added. Two or more silicone adhesives may be used in combination. In particular, the pressure-sensitive adhesive composition of the present invention preferably contains an addition-curable silicone pressure-sensitive adhesive that has been cross-linked and cured.

  The pressure-sensitive adhesive composition of the present invention can be obtained using a commercially available product. For example, a pressure-sensitive adhesive composition having desired physical properties can be obtained by crosslinking and curing a commercially available silicone-based pressure-sensitive adhesive. Specifically, by crosslinking and curing the silicone-based pressure-sensitive adhesive exemplified above, the pressure-sensitive adhesive composition of the present invention containing a crosslinked silicone structure can be obtained. The cross-linking curing reaction is usually performed by heating, but depending on the type of the adhesive or the curing agent, the cross-linking curing can be performed by a condensation reaction or ultraviolet irradiation.

  The pressure-sensitive adhesive composition having a specific gel fraction and swelling degree of the present invention can be obtained, for example, using a mixture of two or more commercially available silicone-based pressure-sensitive adhesives. Specifically, for example, a silicone adhesive having a relatively high gel fraction and swelling degree, and a silicone adhesive having a relatively low gel fraction and swelling degree are mixed at an appropriate ratio and crosslinked and cured. An adhesive composition having a gel fraction and a degree of swelling within the range of the present invention can be obtained. However, the pressure-sensitive adhesive composition of the present invention is not limited to one obtained by such a method.

  An additive may be added to the pressure-sensitive adhesive composition of the present invention for the purpose of improving various properties. Specific examples of additives include inorganic fillers such as carbon black and silica; polyorganosiloxanes such as silicone resin, polydimethylsiloxane and polydimethylphenylsiloxane; antioxidants such as phenolic antioxidants and amine antioxidants. Agents; silane coupling agents; However, it is necessary to appropriately select the type and amount of the additive so as not to impair the effects of the invention.

<Adhesive tape>
The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention described above on at least one surface of a substrate, and typically, the pressure-sensitive adhesive film is adhered to one or both surfaces of a substrate film. It is an adhesive tape having an agent layer. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 2 to 150 μm, more preferably 5 to 100 μm, and particularly preferably 10 to 75 μm.

  The pressure-sensitive adhesive layer can be formed by causing a cross-linking and curing reaction of the pressure-sensitive adhesive composition. For example, a pressure-sensitive adhesive composition can be applied on a substrate and crosslinked and cured by heating or condensation reaction or ultraviolet irradiation to form a pressure-sensitive adhesive layer on the substrate. Further, the pressure-sensitive adhesive composition is coated on release paper or other film, and crosslinked and cured by heating or condensation reaction or ultraviolet irradiation to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is adhered to one or both surfaces of the substrate. You can also match.

  A solvent may be added to lower the viscosity of the pressure-sensitive adhesive composition during application. Specific examples of the solvent include aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, octane and isoparaffin; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and isobutyl acetate. Ether solvents such as diisopropyl ether and 1,4-dioxane;

  The coating method is not particularly limited, and a known method may be used. Specific examples include coating using a comma coater, lip coater, roll coater, die coater, knife coater, blade coater, rod coater, kiss coater or gravure coater; screen coating; dip coating; cast coating. Can be

  The substrate is not particularly limited, but a film-like substrate is preferable. In particular, a resin film having high heat resistance that can be processed at a high temperature is preferable. Specific examples thereof include, for example, polyimide (PI), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyamide imide (PAI), and polyether sulfone (PES). ), Polytetrafluoroethylene (PTFE) and the like. These films can be used as a single layer or a laminated film of two or more layers. Among them, a polyimide film is preferable. The thickness of the substrate is not particularly limited, but is preferably 2 to 180 μm, more preferably 5 to 100 μm, and particularly preferably 12 to 75 μm.

  Further, the surface of the base material on which the pressure-sensitive adhesive layer is provided may be subjected to an easy adhesion treatment as required. Examples of the easy adhesion treatment include a primer treatment, a corona treatment, an etching treatment, a plasma treatment, and a sandblast treatment.

  The adhesive tape of the present invention may be provided with a release liner. The release liner is used to protect the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape, and is peeled off immediately before sticking, exposing the pressure-sensitive adhesive and sticking the pressure-sensitive adhesive tape to the adherend. The type of the release liner is not particularly limited, and a known release liner can be used. Specific examples thereof include those obtained by subjecting a surface of a base material such as high quality paper, glassine paper, synthetic resin film or the like to a release agent treatment. For the release agent treatment, a release agent such as a fluorine-substituted alkyl-modified silicone resin may be used. In particular, as the release liner to be laminated on the silicone-based pressure-sensitive adhesive layer, a release liner obtained by releasing the surface of a polyethylene terephthalate film with a fluorine-substituted alkyl-modified silicone resin is preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the following description, “parts” means “parts by mass”.

<Example 1>
70 parts of an addition-curable silicone pressure-sensitive adhesive stock solution (trade name: SD-4560, manufactured by Dow Corning Toray Co., Ltd.) having a solid content concentration of 60% by mass; 30 parts of -4587L, manufactured by Dow Corning Toray Co., Ltd., 54 parts of toluene as a diluting solvent, and 0.3 part of a platinum catalyst (trade name: NC-25, manufactured by Dow Corning Toray) as a curing catalyst were uniformly mixed. Thus, an adhesive liquid (1) was obtained.

  Next, the pressure-sensitive adhesive liquid (1) is applied to one side of a primer-treated polyimide (PI) film having a thickness of 25 μm so that the thickness of the pressure-sensitive adhesive layer after drying becomes 30 μm. After curing and drying in 2 minutes, an adhesive layer was formed. Then, a release liner (a 50 μm-thick PET film subjected to a release treatment with a fluorine-substituted alkyl-modified silicone resin) was bonded to the pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive tape.

<Example 2>
50 parts of an addition-curable silicone pressure-sensitive adhesive stock solution (trade name: SD-4560, manufactured by Dow Corning Toray Co., Ltd.) having a solid content concentration of 60% by mass, and an addition-curable silicone pressure-sensitive adhesive stock solution (trade name: SD) having a solid content concentration of 40% by mass -4587L, 50 parts of Dow Corning Toray Co., Ltd.), 43 parts of toluene as a diluting solvent, and 0.3 part of a platinum catalyst (trade name: NC-25, manufactured by Dow Corning Toray) as a curing catalyst are uniformly mixed. Thus, an adhesive liquid (2) was obtained. Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (2) was used.

<Example 3>
20 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4560, manufactured by Dow Corning Toray Co., Ltd.) having a solid content concentration of 60% by mass, and an addition-curable silicone pressure-sensitive adhesive stock solution (trade name: SD) having a solid content concentration of 40% by mass -4587L, 80 parts of Toray Dow Corning Co., Ltd.), 26 parts of toluene as a diluting solvent, and 0.3 part of a platinum catalyst (trade name: NC-25, manufactured by Dow Corning Toray) as a curing catalyst are uniformly mixed. Thus, an adhesive liquid (3) was obtained. Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (3) was used.

<Comparative Example 1>
100 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4587L, manufactured by Dow Corning Toray Co., Ltd.) having a solid content of 40% by mass, 33 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: NC-25 as a curing catalyst) , Manufactured by Dow Corning Toray Co., Ltd.) was uniformly mixed to obtain a pressure-sensitive adhesive liquid (4). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (4) was used.

<Comparative Example 2>
100 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4580, manufactured by Dow Corning Toray Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: NC-25 as a curing catalyst) , Manufactured by Dow Corning Toray Co., Ltd.) was uniformly mixed to obtain a pressure-sensitive adhesive solution (5). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (5) was used.

<Comparative Example 3>
100 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4584, manufactured by Dow Corning Toray Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: NC-25 as a curing catalyst) , Manufactured by Dow Corning Toray Co., Ltd.) was uniformly mixed to obtain an adhesive liquid (6). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (6) was used.

<Comparative Example 4>
100 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4560, manufactured by Dow Corning Toray Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: NC-25 as a curing catalyst) , Manufactured by Dow Corning Toray Co., Ltd.) was uniformly mixed to obtain a pressure-sensitive adhesive liquid (7). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (7) was used.

<Comparative Example 5>
100 parts of an addition-curable silicone adhesive stock solution (trade name: SD-4570, manufactured by Dow Corning Toray Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: NC-25 as a curing catalyst) , Manufactured by Dow Corning Toray Co., Ltd.) was uniformly mixed to obtain an adhesive liquid (8). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (8) was used.

<Comparative Example 6>
100 parts of an addition-curable silicone adhesive stock solution (trade name: KR-3700, manufactured by Shin-Etsu Chemical Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: CAT-PL-) as a curing catalyst 0.5T (manufactured by Shin-Etsu Chemical Co., Ltd.) were uniformly mixed to obtain a pressure-sensitive adhesive liquid (9). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (9) was used.

<Comparative Example 7>
100 parts of an addition-curable silicone adhesive stock solution (trade name: KR-3701, manufactured by Shin-Etsu Chemical Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: CAT-PL-) as a curing catalyst 0.5T (50T, Shin-Etsu Chemical Co., Ltd.) were uniformly mixed to obtain a pressure-sensitive adhesive liquid (10). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (10) was used.

<Comparative Example 8>
100 parts of an addition-curable silicone pressure-sensitive adhesive stock solution (trade name: KR-3704, manufactured by Shin-Etsu Chemical Co., Ltd.) having a solid content of 60% by mass, 71 parts of toluene as a diluting solvent, and a platinum catalyst (trade name: CAT-PL-) as a curing catalyst 0.5T (50T, Shin-Etsu Chemical Co., Ltd.) were uniformly mixed to obtain a pressure-sensitive adhesive liquid (11). Then, an adhesive tape was obtained in the same manner as in Example 1 except that the adhesive liquid (11) was used and an untreated PET film having a thickness of 38 μm was used as a release liner.

<Comparative Example 9>
100 parts of a stock solution of a peroxide-curable silicone pressure-sensitive adhesive having a solid content of 60% by mass (product name: SH-4280, manufactured by Dow Corning Toray Co., Ltd.), 71 parts of toluene as a diluting solvent, and a curing agent (product name: Niiper (registered trademark)) ) 3.0 parts of BMT-40 (manufactured by NOF CORPORATION) were uniformly mixed to obtain an adhesive liquid (12).

  Next, an adhesive solution (12) was applied to one side of a primer-treated polyimide (PI) film having a thickness of 25 μm so that the dried adhesive layer had a thickness of 30 μm. The solvent was removed in a drying oven at 60 ° C. for 1 minute, and then cured and dried at 180 ° C. for 2 minutes to form an adhesive layer. Then, a release liner (a 50 μm-thick PET film subjected to a release treatment with a fluorine-substituted alkyl-modified silicone resin) was bonded to the pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive tape.

<Comparative Example 10>
100 parts of a stock solution of a peroxide-curable silicone pressure-sensitive adhesive having a solid content of 60% by mass (trade name: KR-100, manufactured by Shin-Etsu Chemical Co., Ltd.), 71 parts of toluene as a diluting solvent, a curing agent (trade name: Niiper (registered trademark)) 3.0 parts of BMT-40 (manufactured by NOF CORPORATION) were uniformly mixed to obtain a pressure-sensitive adhesive liquid (13). Then, an adhesive tape was obtained in the same manner as in Comparative Example 9 except that the adhesive liquid (13) was used.

<Gel fraction and swelling degree of pressure-sensitive adhesive composition>
The pressure-sensitive adhesive liquids (1) to (13) obtained in Examples and Comparative Examples were applied on a release liner such that the thickness after drying became 50 to 200 μm. Subsequently, the composition was heated in a drying oven, cured and dried to obtain an adhesive composition, which was used as a sample. The heating temperature at this time was the same as in each of the examples and comparative examples. That is, the pressure was set to 130 ° C. for 2 minutes for the pressure-sensitive adhesive liquids (1) to (11), and to 60 ° C., 1 minute and 180 ° C. for 2 minutes for the pressure-sensitive adhesive liquids (12) and (13).

The obtained sample was cut into a size of 50 mm x 50 mm, and the release liner was peeled off to obtain a measurement sample composed of a sheet-shaped pressure-sensitive adhesive composition. The initial mass (A) (= the mass of the pressure-sensitive adhesive composition before swelling) of the measurement sample was measured. Then, the measurement sample was immersed in toluene at 250 times or more the initial mass (A) at room temperature (23 ° C.) for one day to swell. After the immersion, the measurement sample was taken out and the swelling mass (B) (= the mass of the pressure-sensitive adhesive composition swollen with toluene) was measured. Further, this measurement sample was dried in a dryer at 130 ° C. for 2 hours to remove the absorbed solvent, and the dry mass (C) (= the mass of the dried pressure-sensitive adhesive composition) was measured. The gel fraction and the degree of swelling of the pressure-sensitive adhesive composition were obtained by the following equations.
Gel fraction (%) = (C / A) × 100
Swelling degree (%) = ((BA) / A) × 100%

<Adhesion to SUS at room temperature (23 ° C)>
An adhesive tape cut to a width of 20 mm was attached to a polished SUS plate, and was reciprocated once with a roller covered with a rubber layer weighing 2 kg, and left under a 23 ° C environment for 20 to 40 minutes. Thereafter, the force required to peel the tape at an angle of 180 ° at a speed of 300 mm / min was measured using a tensile tester.

<Repeating adhesion to SUS after heating (200 ° C and 230 ° C) and adhesive residue>
An adhesive tape cut to a width of 20 mm was adhered to a polished SUS plate, reciprocated once with a roller covered with a rubber layer having a weight of 2 kg, and left in a dryer at 200 ° C. and 230 ° C. for 30 minutes. This was taken out and allowed to cool at room temperature. Thereafter, the force required to peel the tape at an angle of 180 ° at a speed of 300 mm / min (adhesion after the first heating) was measured using a tensile tester. The pressure-sensitive adhesive tape after peeling was adhered to a polished SUS plate again, and the adhesive force after the second heating was measured in the same manner as in the first time. Thereafter, the measurement was repeated until the adhesive strength after the 10th heating. In addition, the adhesive remaining property at the time of peeling each time was visually confirmed, and evaluated according to the following criteria.
○: No adhesive residue ×: Adhesive residue

<Change rate of adhesive strength>
When the adhesive force was repeatedly measured 10 times after heating, the rate of change in adhesive force was calculated according to the following formula (Tables 1 and 2), and the maximum and minimum rates of change were described (Table 3).
Rate of change (%) = Adhesive strength after each heating / Adhesive strength after first heating × 100%

<Fixing force test>
As shown in FIG. 2, a weight 2 of 75 g is attached to the adhesive layer 1b side (lower side) of the adhesive tape 1 having both ends fixed (attachment area 20 mm × 25 mm), and left in a dryer at 200 ° C. for 1 hour. Then, the presence or absence of the weight 2 was confirmed, and the fixing force was evaluated based on the following criteria.
○: Weight did not drop ×: Weight dropped

  Tables 1 to 3 show the results of the above measurements. Further, FIG. 1 shows a graph summarizing the comprehensive evaluations of the examples and comparative examples in the correlation between the gel fraction and the degree of swelling.

<Evaluation results>
As shown in Table 3, in Examples 1 to 3, even after repeated use at 200 ° C. and 230 ° C. for 10 times, the change in the adhesive strength after heating was within ± 15% of the initial value, and the adhesion after repeated use was observed. The power was very stable. Also, there was no adhesive residue and the fixing force of the parts was sufficient.

  In Comparative Example 1, although the gel fraction was not low, but the swelling degree was high (that is, the crosslink density was low), there was no glue residue. However, when repeatedly used at 230 ° C., the adhesive strength was remarkably increased. The adhesion was unstable.

  In Comparative Examples 2 to 3 and Comparative Examples 6 and 7, since the gel fraction was low and the degree of swelling was high, glue residue occurred when repeatedly used at 230 ° C. In addition, the change in adhesive strength when used repeatedly was large.

  In Comparative Examples 4 and 5, there was no adhesive residue because the degree of swelling was not high, but the stability of adhesive strength when repeatedly used was poor because the gel fraction was low.

  In Comparative Example 8 (weakly tacky adhesive), since the gel fraction was high and the degree of swelling was high, glue residue was likely to occur, and the stability of the adhesive strength when repeatedly used was poor. In addition, due to the high gel fraction, the fixing power of the parts was inferior.

  In Comparative Examples 9 to 10 (peroxide-curable pressure-sensitive adhesives), since the gel fraction was low and the degree of swelling was high, adhesive residue was liable to occur, and the stability of adhesive strength when repeatedly used was poor. .

  The pressure-sensitive adhesive composition of the present invention is particularly useful, for example, as a material for forming a pressure-sensitive adhesive layer of a pressure-sensitive adhesive tape. INDUSTRIAL APPLICABILITY The adhesive tape of the present invention is very useful for applications such as protection of components, masking, temporary fixing, and fixing for transport in the manufacturing process of various components such as electric and electronic components.

DESCRIPTION OF SYMBOLS 1 Adhesive tape 1a Base material 1b Adhesive layer 2 Weight

Claims (7)

A silicone comprising a crosslinked silicone structure, wherein the gel fraction measured by the following method is 45% or more and less than 70%, and the degree of swelling with respect to toluene measured by the following method is 290% or less. -Based pressure-sensitive adhesive composition.
(Gel fraction)
The gel fraction is obtained by the following formula, which is the ratio of the insoluble component when the silicone-based pressure-sensitive adhesive composition is immersed in toluene at room temperature for one day.
Gel fraction (%) = (C / A) × 100
A: Initial mass of silicone-based pressure-sensitive adhesive composition C: Dry mass of silicone-based pressure-sensitive adhesive composition after immersion in toluene (drying condition: 130 ° C., 2 hours)
(Swelling degree)
The degree of swelling is obtained by the following equation, which is the swelling ratio due to toluene absorption when the silicone-based pressure-sensitive adhesive composition is immersed in toluene at room temperature for one day.
Swelling degree (%) = ((BA) / A) × 100%
A: Initial mass of silicone-based pressure-sensitive adhesive composition B: Swelling mass of silicone-based pressure-sensitive adhesive composition after immersion in toluene   The silicone pressure-sensitive adhesive composition according to claim 1, wherein the gel fraction is 48 to 65%.   The silicone pressure-sensitive adhesive composition according to claim 1, having a swelling degree of 260% or less.   The silicone-based pressure-sensitive adhesive composition according to claim 1, further comprising an addition-curable silicone pressure-sensitive adhesive that has been cross-linked and cured.   A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to claim 1 on at least one surface of a substrate.   The pressure-sensitive adhesive tape according to claim 5, wherein the substrate is a resin film.   The pressure-sensitive adhesive tape according to claim 6, wherein the resin film is a polyimide film.

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