Adhesive sheet and method for dismantling joined body

Abstract

Provided are: an adhesive sheet capable of forming a joined body that can be dismantled by a simple operation; and a method for dismantling a joined body formed by using the adhesive sheet. The adhesive sheet has an adhesive surface that can be attached to an adherend. The adhesive surface is a surface of an adhesive layer containing a rubber component and an oil component. The oil component contains a low-temperature exudative oil that can exude out from the adhesive surface when the temperature drops to a predetermined value or less. The content of the oil component in the adhesive layer is at least 35 wt%.

Description

Method for dismantling adhesive sheet and joint

[0001] The present invention relates to a method for dismantling a pressure-sensitive adhesive sheet and a bonded structure including the pressure-sensitive adhesive sheet. This application claims priority to Japanese Patent Application No. 2023-214235, filed on December 19, 2023, the entire contents of which are incorporated herein by reference.

[0002] Generally, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Taking advantage of this property, pressure-sensitive adhesives are widely used in a variety of fields in the form of supported pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer on a support, or in the form of support-less pressure-sensitive adhesive sheets having no support. After use, the pressure-sensitive adhesive can be peeled off from the adherend by appropriate means, if necessary.

[0003] Japanese Patent Application Publication No. 2013-117004 Japanese Patent Application Publication No. 2014-003199

[0004] In recent years, from the viewpoint of reducing environmental impact and saving resources, it has become common to separate components bonded using adhesives from products after use and reuse them (recycle, reuse, etc.). For example, display devices built into products with display functions, such as smartphones, personal computers (desktop, notebook, tablet, etc.), and televisions, have multilayer structures containing multiple and different functional components, such as liquid crystal display devices, organic electroluminescence (EL) display devices, and plasma display panels (PDPs), and each component contains different materials, so there are significant advantages to reusing them through recycling, reuse, etc. Furthermore, a technology is known in which a surface protection sheet is adhered to the surface of glass, metal, or organic materials (e.g., PET, PI, etc.) to protect the surface from damage and dirt during processing, transportation, storage, etc., and such a surface protection sheet is removed from the adherend at an appropriate time after the protective purpose has been achieved.

[0005] However, there is a trade-off between the bonding reliability and ease of disassembly of adhesives, and disassembly of assembled structures requiring high bonding reliability generally tends to be difficult. Therefore, as methods for facilitating disassembly of assembled structures using adhesives, for example, a method of immersing an adhesive sheet assembly in water to peel it off, as described in Patent Document 1, and a method of curing the adhesive by ultraviolet light irradiation to reduce the adhesive strength, as described in Patent Document 2, have been proposed. However, the water immersion peeling method has limitations, such as requiring equipment such as a water tank depending on the size of the assembled structure and being inapplicable to water-sensitive adherends (e.g., adherends that deform, dissolve, or lose strength upon contact with water). Furthermore, the method of reducing adhesive strength by ultraviolet light irradiation cannot be applied to assembled structures configured to prevent ultraviolet light from reaching the adhesive. It would be useful to provide a method for disassembling assembled structures using adhesives that can be applied regardless of the water resistance or ultraviolet light transmittance of the adherends.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a pressure-sensitive adhesive sheet that can form a dismantled assembly by a simple operation. Another related object is to provide a method for dismantling an assembly using the pressure-sensitive adhesive sheet.

[0007] The pressure-sensitive adhesive sheet provided by this specification has an adhesive surface that can be attached to an adherend. The adhesive surface is the surface of a pressure-sensitive adhesive layer containing a rubber component and an oil component. The oil component contains a low-temperature exudable oil that can exude from the adhesive surface when the temperature drops below a predetermined value. By cooling the pressure-sensitive adhesive sheet to a temperature below a predetermined value, at least a portion of the oil component can be exuded (bleed) from the adhesive surface, thereby weakening the adhesion to the adherend. Therefore, a bonded structure using the pressure-sensitive adhesive sheet can be easily disassembled by the simple operation of cooling to a temperature below a predetermined value. From the viewpoint of making it easier to preferably exert such effects, in some embodiments, the content W of the oil component in the pressure-sensitive adhesive layer is Ｏ The weight percentage is preferably, for example, 35 weight percent or more.

[0008] In some preferred embodiments, the content W of the oil component in the pressure-sensitive adhesive layer Ｏ [wt%] is the content W of the rubber component Ｐ A PSA sheet having a PSA layer with such a composition can more suitably exhibit the effect of facilitating separation from the adherend by exuding the oil component upon cooling.

[0009] In some embodiments, the SP value of the rubber component (SP Ｐ ) and the SP value of the oil component (SP Ｏ ) is 1.0 (cal / cm ３ ) １／２ It is preferable that |SP Ｐ -SP Ｏ | is 1.0 (cal / cm ３ ) １／２ This makes it easier to obtain good compatibility between the rubber component and the oil component in the temperature range in which the PSA sheet is normally used, improving performance stability during normal use (when it is expected that bonding to the adherend will be maintained).

[0010] In some preferred embodiments, the oil component is an oil O having a relatively large difference in SP value from the rubber component. Ｌ and the SP value of the rubber component is relatively small. Ｓ Oil O Ｌ and oil O Ｓ By using the oil O in combination, it becomes easier to adjust the balance between the stability of performance in the temperature range in which the PSA sheet is normally used and the function of the oil component bleeding out during cooling to weaken the bond with the adherend. Ｌ and oil O Ｓ The difference in SP value between ３ ) １／２ It could be more than that.

[0011] In some embodiments, the rubber component is preferably a rubber containing an olefin-based rubber as a main component, and the pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in an embodiment in which the pressure-sensitive adhesive layer contains a rubber containing an olefin-based rubber as a main component as the rubber component.

[0012] In some preferred embodiments, the PSA layer further comprises a tackifier resin. By incorporating a tackifier resin into the PSA layer, good adhesiveness is more likely to be obtained in the temperature range in which the PSA sheet is normally used. The content of the tackifier resin in the PSA layer can be, for example, 0.5 to 2 times the content of the rubber component.

[0013] In some embodiments, the oil component preferably includes silicone oil. By incorporating silicone oil into the pressure-sensitive adhesive layer, the oil component can be advantageously bled upon cooling to weaken the bond to the adherend.

[0014] This specification also provides a method for dismantling an assembly including a pressure-sensitive adhesive sheet and a member bonded to the adhesive surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be any of the pressure-sensitive adhesive sheets disclosed herein. The dismantling method includes cooling the assembly to exude the low-temperature exudable oil from the adhesive surface, and separating the member from the pressure-sensitive adhesive sheet. According to the dismantling method, the assembly can be easily dismantled by the simple operation of cooling the assembly to a temperature below a predetermined value.

[0015] Appropriate combinations of the elements described in this specification may also be included within the scope of the invention for which patent protection is sought by this patent application.

[0016] 1 is a schematic cross-sectional view showing a configuration of a pressure-sensitive adhesive sheet according to one embodiment; 2 is a schematic cross-sectional view showing a configuration example of a bonded body including the pressure-sensitive adhesive sheet;

[0017] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for the purpose of clearly explaining the present invention, and do not necessarily accurately represent the size or scale of the actual product provided.

[0018] As used herein, the term "adhesive" refers to a material that, as described above, is in a soft solid (viscoelastic) state at temperatures near room temperature and easily adheres to an adherend under pressure. Furthermore, the term "adhesive surface" refers to a surface that is adhesive enough to be attached to an adherend. For example, in the shear adhesive strength measurement described in the Examples below, a surface that does not adhere to an aluminum plate is a typical example of a surface that does not fall under the category of an adhesive surface.

[0019] In this specification, the term "normally used temperature range" or "normally used temperature range" typically refers to a temperature of 10° C. or higher and 80° C. or lower, for example, 10° C. or higher and 60° C. In addition, in this specification, the term "room temperature range" or "temperature range near room temperature" refers to a temperature of approximately 20° C. to 30° C. (typically 23° C.).

[0020] In this specification, the "SP value" refers to the Hildebrand solubility parameter. The SP value can be calculated from the Hansen solubility parameter. The Hansen solubility parameter consists of a dispersion term δD, a polar term δP, and a hydrogen bonding term δH. The relationship between the Hildebrand solubility parameter (SP value) and the Hansen solubility parameter is expressed by the following formula (1): SP value = (δD ２ +δP ２ +δH ２ ) １／２(1) Here, the units of the SP value, δD, δP, and δH in the above formula (1) are all (J / cm ３ ) １／２ The Hansen solubility parameters of each substance contained in the adhesive can be calculated by examining the types and molar ratios of the molecular units that make up the molecular structure of the substance and then calculating a weighted average of the Hansen solubility parameters of each molecular unit type by molar ratio. The Hansen solubility parameters of each molecular unit type can be determined using the molecular group contribution method using the software "HSPiP, Hansen Solubility Parameters in Practice ver. 4," available from the link (https: / / hansen-solubility.com / ). Specifically, by entering each constituent unit of the target substance in SMILES notation, the HSP values ​​(δd, δp, δh) for each unit can be calculated.

[0021] For materials for which the nominal SP value is provided by the manufacturer, etc., this nominal value can be used instead of the SP value calculated from the Hansen solubility parameter. When the nominal SP value of a material is expressed as a numerical range, when performing calculations using this SP value (for example, calculating the difference in SP value between the material and another material), the arithmetic mean value of the upper and lower end values ​​of the numerical range (i.e., the value calculated by (upper end value + lower end value) / 2) is used. The SP value is also expressed as "(J / cm ３ ) １／２ It is sometimes expressed in units of "(cal / cm ３ ) １／２ These can be converted into each other, and are expressed in units of 1 (J / cm ３ ) １／２ is approximately 2.045 (cal / cm ３ ) １／２ is equivalent to

[0022] In this specification, "weight" may be read as "mass." For example, "% by weight" may be read as "% by mass," and "parts by weight" may be read as "parts by mass."

[0023] <Adhesive Layer> (Rubber Component) The adhesive sheet disclosed herein has an adhesive layer composed of an adhesive containing a rubber component and an oil component. As the rubber component, various polymers exhibiting rubber elasticity at room temperature (typically 23°C) can be used. Examples of such polymers include, but are not limited to, rubber-based polymers, silicone-based polymers, acrylic polymers, polyester-based polymers, urethane-based polymers, urethane-acrylic polymers, polyether-based polymers, polyamide-based polymers, etc. The above polymers can be used alone or in combination of two or more.

[0024] In some embodiments, one or more rubber-based polymers are preferably used as the main component of the rubber component. For example, it is preferred that more than 50 wt %, more preferably 70 wt % or more, and even more preferably 90 wt % or more of the rubber component contained in the PSA be rubber-based polymers. Substantially the entire rubber component may be rubber-based polymers.

[0025] Examples of rubber-based polymers contained in the rubber component include olefin-based rubber; block copolymer rubber and hydrogenated products thereof, such as styrene-butadiene-styrene block copolymer rubber (SBS), styrene-isoprene-styrene block copolymer rubber (SIS), styrene-isobutylene-styrene block copolymer rubber (SIBS), styrene-vinyl-isoprene-styrene block copolymer rubber (SVIS), styrene-ethylene-butylene-styrene block copolymer rubber (SEBS), which is a hydrogenated product of SBS, and styrene-ethylene-propylene-styrene block copolymer rubber (SEBS), which is a hydrogenated product of SIS. One or more selected from the following can be used: styrene-based block copolymers such as styrene block copolymer rubber (SEPS) and styrene-isoprene-propylene-styrene block copolymer (SIPS); natural rubber; butadiene rubber (BR); styrene-butadiene rubber (SBR); chloroprene rubber (CR); polyisoprene; butene-based polymers having butene (1-butene, and cis- or trans-2-butene) and / or 2-methylpropene (isobutylene) as the main monomer; modified products of these rubbers (e.g., acid-modified products and acrylic-modified products); etc. The technology disclosed herein can be implemented, for example, in an embodiment in which the main component of the rubber component is olefin-based rubber, natural rubber, BR, SBR, or CR.

[0026] The technology disclosed herein can be preferably implemented, for example, in an embodiment in which the main component of the rubber component is an olefin-based rubber. Examples of the olefin-based rubber include ethylene-α-olefin copolymers such as ethylene-propylene copolymer (EPM) and ethylene-α-olefin-non-conjugated polyene (typically non-conjugated diene) copolymers such as ethylene-propylene-diene copolymer (EPDM).

[0027] The SP value (unit: (cal / cm) of the rubber component contained in the adhesive layer ３ ) １／２ Hereinafter, when the unit of the numerical value indicating the SP value is omitted, it is (cal / cm) unless otherwise specified. ３ ) １／２) may be, for example, 7.0 or more and 10.0 or less, preferably 7.5 or more and 9.5 or less, and more preferably 8.0 or more and 9.0 or less (e.g., 8.2 or more and 8.7 or less, 8.4 or more and 8.6 or less). When the rubber component contains two or more polymers with different SP values, the SP value of the rubber component (i.e., the SP value of the entire rubber component) is the sum of the products of the weight fraction of each polymer in the entire rubber component and the SP value of the polymer. The SP value of a rubber component consisting of one type of polymer is the SP value of the polymer, and the SP value of a rubber component consisting of two or more polymers with substantially the same SP value is the SP value of those polymers. The same applies to the SP value of the oil component described below.

[0028] In an embodiment in which the rubber component contains two or more polymers with different SP values, the SP value of each polymer is not particularly limited and can be appropriately selected so that the SP value of the entire rubber component is within any of the above-mentioned ranges. In some embodiments, the SP value of each polymer is suitably approximately 7.0 to 13, preferably 7.0 to 12, or may be 7.0 to 11, 7.5 to 10, 8.0 to 9.5, or 8.2 to 9.2.

[0029] As the polymer having an SP value within any of the above ranges, one having the corresponding SP value can be selected from various polymers that exhibit rubber elasticity at room temperature (typically 23° C.) Non-limiting examples of polymers that can be considered as options include olefin rubber, natural rubber, BR, SBR, CR, SEBR, modified products thereof, and the like.

[0030] In embodiments in which the main rubber component is an olefin-based rubber, the olefin-based rubber may be used in combination with another polymer having a higher SP value, for example, to improve the cohesion of the PSA or to improve compatibility with other components. The difference in SP value between the olefin-based rubber and the other polymer may be, for example, 0.2 or more. From the viewpoint of achieving the desired effect with a smaller amount of use, it may be 0.3 or more, or may be 0.4 or more, 0.5 or more, or 0.6 or more. Furthermore, from the viewpoint of compatibility between the rubber components during normal use of the PSA sheet, the difference in SP value between the olefin-based rubber and the other polymer is suitably 1.5 or less, preferably 1.2 or less, and may be 1.0 or less, 0.9 or less, 0.8 or less, or 0.7 or less. The other polymer may be, for example, an acrylic-modified or acid-modified product of any of the rubber-based polymers described above. In some embodiments, an acid-modified styrene-based block copolymer such as acid-modified SEBS may be preferably used as the other polymer. The ratio of the amount of the olefin rubber to the other polymer used (olefin rubber:other polymer) by weight may be, for example, about 60:40 to 99.5:0.5, preferably about 70:30 to 99.5:0.5, more preferably about 80:20 to 99.5:0.5, and may be 85:15 to 99:1, or may be 90:10 to 99:1.

[0031] Rubber component content W in the adhesive layer Ｐ The weight percent may be, for example, in the range of about 12 weight percent to 90 weight percent. Ｐ From the viewpoint of bonding reliability with the adherend during normal use, it is advantageous that the content W is 15% by weight or more, and preferably 18% by weight or more. Ｐ The rubber content W of the adhesive layer may be 20% by weight or more, 23% by weight or more, or 25% by weight or more. ＰIn order to broaden the range in which the content of the oil component and other optional components can be selected, the content W may be, for example, 80% by weight or less, 70% by weight or less, or 60% by weight or less. Ｐ is, for example, less than 50% by weight, and may be less than 40% by weight, less than 35% by weight, less than 33% by weight, or less than 30% by weight.

[0032] (Oil Component) In the technology disclosed herein, the oil component contained in the adhesive layer can be appropriately selected from various oils, such as silicone oil, hydrocarbon oil, mineral oil, vegetable oil (e.g., castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, etc.), fluorine oil, polyether oil, ester oil, phosphorus compound oil, etc. The oil component may contain only one type of oil, or may contain two or more types of oil. In the technology disclosed herein, the low-temperature exudable oil that can exude from the adhesive surface when the temperature drops below a predetermined value is that oil in the case of an adhesive layer containing only one type of oil as an oil component, or may be at least one of those oils in the case of an adhesive layer containing two or more types of oil.

[0033] Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil, and modified silicone oil (e.g., modified dimethyl silicone oil). The "modified" in the modified silicone oil may be, for example, aralkyl-modified, long-chain alkyl-modified, polyether-modified, epoxy-modified, carboxy-modified, carbinol-modified, etc. Silicone oils may be used alone or in combination of two or more. The technology disclosed herein is preferably implemented in an embodiment in which the pressure-sensitive adhesive layer contains silicone oil as the oil component. Silicone oil may be used in combination with other oils. In some embodiments, linear silicone oils are preferred from the viewpoint of mobility in the pressure-sensitive adhesive layer (e.g., exudation from the adhesive surface at low temperatures). The silicone oil may be, for example, an aromatic ring-containing silicone oil such as methylphenyl silicone oil.

[0034] Commercially available silicone oils include silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. (e.g., KF56A, KF96L series, KF96 series, KF69 series, KF99 series, KF50 series, KF54 series, KF410 series, KF412 series, KF414 series, FL series, KF-6000, KF-6001, KF-6002, KF-6003, etc.); Momentive Silicone oils manufactured by Toray Dow Corning Co., Ltd. (e.g., Element14*PDMS series, TSF404 series, TSF410 series, TSF4300 series, TSF431 series, TSF433 series, TSF437 series, TSF4420 series, TSF4421 series, etc.); silicone oils manufactured by Toray Dow Corning Co., Ltd. (e.g., BY16-846 series, SF8416 series, SH200 series, SH203 series, SH230 series, SF8419 series, FS1265 series, SH510 series, SH550 series, SH710 series, FZ-2110 series, FZ-2203 series, etc.); silicone oils manufactured by Wacker Asahi Kasei Silicone Co., Ltd. (WACKER (registered trademark) SILICONE FLUID AK series, WACKER (registered trademark) SILICONE LUID AP series, WACKER (registered trademark) SILICONE FLUID AR series, WACKER (registered trademark) SILICONE FLUID AS series, WACKER (registered trademark) TN series, WACKER (registered trademark) L series, WACKER (registered trademark) AF series, etc.);

[0035] Examples of hydrocarbon oils include paraffinic process oils such as paraffin oil, naphthenic process oils such as naphthenic oil, aromatic process oils such as aromatic oil, and liquid paraffin. When derived from petroleum, such hydrocarbon oils can also be recognized as mineral oils. The hydrocarbon oils can be used alone or in combination of two or more. The technology disclosed herein can be preferably implemented in an embodiment in which the PSA layer contains a hydrocarbon oil as the oil component. A hydrocarbon oil may be used in combination with another oil. A preferred example is a combination of a hydrocarbon oil and a silicone oil.

[0036] SP value of the oil component contained in the PSA layer (in an embodiment containing two or more oils as the oil component, the SP value of the entire oil component) (SP Ｏ ) may be, for example, 7.0 or more and 10 or less, preferably 7.5 or more and 9.5 or less, and more preferably 8.0 or more and 9.0 or less (e.g., 8.2 or more and 8.7 or less, 8.4 or more and 8.6 or less, etc.).

[0037] In an embodiment in which the oil component contains two or more oils with different SP values, the SP value of each oil is not particularly limited, and for example, the SP value of the entire oil component (SP Ｏ In some embodiments, the SP value of each oil is suitably about 7.0 or more and 13 or less, preferably 7.2 or more and 12 or less, or may be 7.5 or more and 11 or less, 8.0 or more and 10 or less, or 8.2 or more and 9.5 or less.

[0038] In some embodiments, the SP value of the rubber component (SP Ｐ ) and the SP value of the oil component (SP Ｏ ) (i.e., |SP Ｐ -SP ＯFrom the viewpoint of compatibility and performance stability in the temperature range in which the PSA sheet is normally used, |SP is suitably 1.0 or less, preferably 0.5 or less, more preferably 0.3 or less, may be 0.2 or less, may be 0.1 or less (for example, less than 0.1), may be 0.07 or less, or may be 0.05 or less. Ｐ -SP Ｏ | may be 0 or greater than 0.

[0039] In some embodiments, the oil component contained in the PSA layer preferably contains at least one oil (e.g., silicone oil) whose SP value difference with the rubber component is a predetermined value or more. Such oils can function suitably as low-temperature exuding oils that can exude from the PSA surface when the temperature drops below a predetermined value. The low-temperature exuding oil in the technology disclosed herein can be an oil whose SP value difference with the rubber component is 0.1 or more (preferably 0.15 or more, more preferably 0.2 or more). In some embodiments, the SP value difference between the rubber component and the low-temperature exuding oil may be 0.25 or more, or may be 0.3 or more. Furthermore, from the viewpoint of easily achieving good compatibility and performance stability in the normal temperature range of use, in some embodiments, the SP value difference between the rubber component and the low-temperature exuding oil is suitably 6.0 or less, preferably 4.0 or less, more preferably 2.0 or less, and may be 1.0 or less, 0.8 or less, 0.7 or less, or 0.6 or less.

[0040] In some embodiments, from the viewpoint of the flexibility of the PSA layer and compatibility at room temperature, the oil used as the oil component suitably has a pour point of 50°C or less, preferably 40°C or less, more preferably 30°C or less, and even more preferably 25°C or less. Furthermore, at least one of the oils constituting the oil component preferably has a pour point of -5°C or less, more preferably -10°C or less, and even more preferably -15°C or less, and may be -20°C or less, or may be -25°C or less, -30°C or less, or -35°C or less. Oils with such low pour points can preferably function as low-temperature exuding oils that can exude from the PSA surface when the temperature drops below a predetermined value. The low pour point oil may be, for example, a silicone oil. The low pour point oil (e.g., an oil with a pour point of -5°C or less) may be used in combination with an oil with no pour point restriction. The oil with no pour point restriction may have a pour point, for example, above -10°C, or above -5°C, or may be 0°C or higher, 5°C or higher, or 10°C or higher.

[0041] In some embodiments, the oil component contained in the PSA layer has an SP value (SP Ｐ ) and oil O Ｌ and the SP value of the rubber component (SP Ｐ ) and oil O Ｓ That is, oil O Ｌ SP value of SP ＯＬ , Oil O Ｓ SP value of SP ＯＳ When expressed as |SP Ｐ -SP ＯＬ |>|SP Ｐ -SP ＯＳ | Oil O Ｌ and oil O ＳBy using these in combination, it becomes easier to adjust the balance between the performance stability in the temperature range in which the PSA sheet is normally used and the function of the oil component bleeding out during cooling to weaken the bond to the adherend. More specifically, when a PSA layer containing at least a rubber component and an oil component and optionally further containing other components (such as a tackifier resin described below) is designed so that these components show good compatibility in the normal temperature range of use, and when the temperature drops below a predetermined value, the compatibility decreases and at least a part of the oil component bleeds to the adhesive surface, the oil component is used. Ｌ and oil O Ｓ According to a composition containing a combination of the above, the temperature at which the bleeding occurs (predetermined value) and the degree of bleeding can be adjusted by selecting the type and amount of the oil O. Ｌ and oil O Ｓ In the pressure-sensitive adhesive layer containing the above in combination, when the temperature drops below a predetermined value, the amount of oil O Ｌ tends to ooze out from the adhesive surface.

[0042] In some embodiments, oil O Ｌ SP value (SP ＯＬ ) and oil O Ｓ SP value (SP ＯＳ ) (i.e., |SP ＯＬ -SP ＯＳ |SP is suitably 0.05 or more, advantageously 0.1 or more, preferably 0.15 or more, and more preferably 0.2 or more. ＯＬ -SP ＯＳ As the value of | increases, it tends to be easier to control the change from a state showing good compatibility in the normal use temperature range to a state in which the low-temperature exudable oil bleeds onto the adhesive surface when the temperature drops below a predetermined value. ＯＬ -SP ＯＳ may be 0.25 or more, 0.3 or more, 0.35 or more, or 0.4 or more. In order to easily obtain good compatibility and performance stability in the normal temperature range of use, in some embodiments, |SP ＯＬ -SPＯＳ is suitably 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less, and may be 1.5 or less, 1.0 or less, 0.8 or less, 0.7 or less, or 0.6 or less. ＯＬ and SP ＯＳ The magnitude relationship between SP and ＯＳ <SP ＯＬ SP ＯＬ <SP ＯＳ The technology disclosed herein may be, for example, Ｌ SP value of oil O Ｓ The SP value is higher than the SP value of ＯＳ <SP ＯＬ The SP value of the rubber component (SP Ｐ ) and SP ＯＬ and SP ＯＳ The relationship is SP ＯＬ <SP ＯＳ <SP Ｐ SP Ｐ <SP ＯＳ <SP ＯＬ SP ＯＬ <SP Ｐ ≦SP ＯＳ SP ＯＳ ≦SP Ｐ <SP ＯＬ In some embodiments, the SP ＯＬ <SP Ｐ <SP ＯＳ or SP ＯＳ <SP Ｐ <SP ＯＬ According to this embodiment, it is preferable that |SP Ｐ -SP Ｏ It is easy to reduce the value of |. ＯＳ <SP Ｐ <SP ＯＬ It is preferable that:

[0043] Oil O Ｌ and oil O Ｓ The combination with, for example, oil O Ｌ is silicone oil, and oil OＳ may be a hydrocarbon oil, and oil O Ｌ , O Ｓ may be silicone oil, and oil O Ｌ , O Ｓ All of the oils may be hydrocarbon oils, or other combinations may be used. Ｌ is a silicone oil (for example, a silicone oil having a pour point of −20° C. or less), and oil O Ｓ is a hydrocarbon oil.

[0044] Oil content W in the adhesive layer Ｏ [% by weight] may be, for example, in the range of about 10% by weight or more and 88% by weight or less. In some embodiments, the content W Ｏ is suitably, for example, 20% by weight or more, advantageously 25% by weight or more, preferably 30% by weight or more, more preferably 35% by weight or more, and may be 40% by weight or more or 45% by weight or more. Ｏ From the viewpoint of bonding reliability with the adherend during normal use, it is appropriate to set the content W to, for example, 80% by weight or less, and advantageously to set it to 75% by weight or less. Ｏ is preferably 70% by weight or less, more preferably 66% by weight or less (e.g., 65% by weight or less), and may be 60% by weight or less, 55% by weight or less, or 53% by weight or less.

[0045] The oil component is Oil O Ｌ and Oil O Ｓ In an embodiment comprising the above, the oil O Ｌ content of oil (i.e., the weight of the entire adhesive layer) Ｌ The weight percentage of oil O may be, for example, 3% by weight or more, 5% by weight or more, or 10% by weight or more. Ｌ In order to better exhibit the function of the oil (for example, the function as a low-temperature exuding oil), the oil O in the adhesive layer isＬ The content of oil O in the pressure-sensitive adhesive layer is advantageously 12% by weight or more, preferably 14% by weight or more, and may be 16% by weight or more, or may be 18% by weight or more. Ｌ The content of may be, for example, 40% by weight or less, and in some embodiments, from the viewpoints of compatibility, bonding reliability, and the like in a normal temperature range of use, is preferably 35% by weight or less, more preferably 30% by weight or less, may be 27% by weight or less, 25% by weight or less, 23% by weight or less, or 21% by weight or less, or may be less than 20% by weight.

[0046] The oil component is Oil O Ｌ and Oil O Ｓ In an embodiment comprising the above, the oil O Ｓ The content of oil O may be, for example, 5% by weight or more, 10% by weight or more, or 15% by weight or more. Ｓ function (for example, oil O in the normal operating temperature range) Ｌ When the adhesive surface is cooled to a temperature below a predetermined value, the oil O Ｌ In order to better exhibit the function of allowing the oil O to ooze out of the adhesive surface, Ｓ The content of oil O in the PSA layer is advantageously more than 20% by weight, preferably 23% by weight or more, may be 25% by weight or more, or may be 27% by weight or more. Ｌ The content may be, for example, less than 50% by weight, and in some embodiments, from the viewpoint of the handleability of the PSA sheet (e.g., processability, ease of manufacture, etc.) and bonding reliability in the normal temperature range of use, it is preferably 45% by weight or less, more preferably 40% by weight or less, and may be 37% by weight or less, 35% by weight or less, 33% by weight or less, or 30% by weight or less.

[0047] The oil component is Oil O Ｌ and Oil O Ｓ In an embodiment comprising oil O Ｌ and oil O ＳThe relationship between the content of oil O and the content of oil O is not particularly limited and can be appropriately set so as to obtain the desired effect of use. Ｌ and oil O Ｓ The ratio of the oil content to Ｌ : Oil O Ｓ ) may be, for example, 5:95 to 95:5, 10:90 to 80:20, 20:80 to 60:40, or 30:70 to 50:50 by weight. Ｓ The content [wt%] of oil O Ｌ The content [wt %] of is, for example, preferably less than 1.0 times, 0.9 times or less, 0.8 times or less, or 0.7 times or less, and is preferably 0.2 times or more, 0.3 times or more, 0.4 times or more, or 0.5 times or more.

[0048] In the pressure-sensitive adhesive layer disclosed herein, the content W of the rubber component Ｐ Oil component content W relative to [wt%] Ｏ The ratio of [wt %], i.e., the ratio (W Ｏ / W Ｐ ) can be, for example, in the range of about 0.5 to 5.0. In some embodiments, from the viewpoint of more suitably exhibiting the function of weakening the bond with the adherend by bleeding of the oil component during cooling, the above ratio (W Ｏ / W Ｐ ) is suitably 0.7 or more or 0.9 or more, preferably more than 1.0, and may be 1.2 or more, 1.4 or more, or 1.5 or more. From the viewpoint of easily suppressing bleeding of oil components in the normal temperature range of use, in some embodiments, the above ratio (W Ｏ / W Ｐ ) is suitably 4.0 or less, preferably 3.5 or less, and may be 3.0 or less, 2.7 or less, or 2.5 or less.

[0049] (Tackifier Resin) In some preferred embodiments, the PSA layer preferably further contains a tackifier resin in addition to the rubber component and the oil component. In the technology disclosed herein, incorporating a tackifier resin into the PSA layer can be useful for improving the adhesion of the PSA sheet to an adherend in the normal temperature range of use, improving bonding reliability (e.g., improving shear adhesive strength, as described below), and the like. The tackifier resin is not particularly limited, and various known tackifier resins, such as terpene resins, rosin resins, rosin derivative resins, petroleum resins, and ketone resins, can be appropriately selected and used. One tackifier resin may be used alone, or two or more tackifier resins may be used in combination. When two or more tackifier resins are used, the tackifier resins may be selected from the same type of resin (e.g., rosin derivative resins) or different types of resins (e.g., terpene resins and rosin derivative resins).

[0050] The concept of terpene resin as used herein encompasses both terpene resins and modified terpene resins. Examples of terpene resins (unmodified terpene resins) include α-pinene polymers, β-pinene polymers, dipentene polymers, and the like. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins. The modifications can be, for example, phenol-modified, aromatic-modified, hydrogenated, hydrocarbon-modified, and the like. Specific examples of modified terpene resins include terpene phenolic resins, hydrogenated terpene phenolic resins, aromatic-modified (e.g., styrene-modified) terpene resins, hydrogenated terpene resins, and the like. The term "terpene phenolic resin" refers to a polymer containing a terpene residue and a phenol residue, and encompasses both a copolymer of a terpene and a phenolic compound (terpene-phenol copolymer resin) and a phenol-modified terpene homopolymer or copolymer (terpene resin, typically an unmodified terpene resin) of terpene (phenol-modified terpene resin).

[0051] Specific examples of rosin-based resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins obtained by modifying these unmodified rosins through hydrogenation (hydrogenation), disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.).

[0052] Examples of rosin derivative resins include rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin) and those obtained by esterifying modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with alcohols (i.e., esterified products of modified rosin, for example, hydrogenated rosin ester); unsaturated fatty acid modified rosins obtained by modifying unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with unsaturated fatty acid; and unsaturated fatty acid modified rosins obtained by modifying rosin esters with unsaturated fatty acid. Examples include fatty acid modified rosin esters; rosin alcohols obtained by reducing the carboxyl groups of unmodified rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), unsaturated fatty acid modified rosins, or unsaturated fatty acid modified rosin esters; metal salts of rosins (particularly rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; and rosin phenolic resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and then thermally polymerizing the resulting mixture.

[0053] Examples of petroleum-based resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, styrene-based resins, and hydrogenated products thereof (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), etc. Other examples of petroleum-based resins include coumarone-indene resins and dicyclopentadiene resins.

[0054] Examples of styrene-based resins include those containing a homopolymer of styrene as the main component, those containing a homopolymer of α-methylstyrene as the main component, those containing a homopolymer of vinyltoluene as the main component, and those containing a copolymer containing two or more of styrene, α-methylstyrene, and vinyltoluene as the main component in the monomer composition (for example, an α-methylstyrene / styrene copolymer resin containing an α-methylstyrene / styrene copolymer as the main component).

[0055] The coumarone-indene resin may be a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain). Examples of monomer components that may be contained in the resin skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0056] In the technology disclosed herein, the softening point of the tackifier resin used as a constituent of the PSA layer is not particularly limited and can be appropriately set taking into consideration compatibility with other components and the effect on adhesive properties. In some embodiments, the softening point of the tackifier resin may be, for example, 45°C or higher. From the viewpoint of easily achieving a PSA layer that exhibits adequate cohesion and bonding reliability in a normal use temperature range, it is appropriate to be 55°C or higher, preferably 60°C or higher, or may be 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, or 110°C or higher. In some embodiments, the softening point of the tackifier resin may be, for example, 180°C or lower. From the viewpoint of easily achieving good compatibility with other components in a normal use temperature range, it is advantageous to be 160°C or lower, preferably 145°C or lower, or may be 135°C or lower, 125°C or lower, 115°C or lower, or 105°C or lower.

[0057] The softening point of a tackifying resin is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, avoiding the formation of bubbles. After cooling, the raised portion of the ring, including the top edge, is cut off with a slightly heated knife. Next, a holder (ring stand) is placed in a glass container (heating bath) with a diameter of at least 85 mm and a height of at least 127 mm, and glycerin is poured in to a depth of at least 90 mm. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin without touching each other, and the glycerin temperature is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in its fixed position on the holder. Next, maintain a distance of 50 mm from the top of the ring to the glycerin surface, place a thermometer, and heat the container with the center of the thermometer's mercury bulb at the same height as the center of the ring. The flame of the Bunsen burner used for heating should be aimed midway between the center of the bottom and the edge of the container, ensuring uniform heating. After heating begins and the temperature reaches 40°C, the rate of increase in the bath temperature must be 5.0 ± 0.5°C per minute. The sample gradually softens, flows down the ring, and finally touches the bottom plate, at which point the temperature is read and considered the softening point. Two or more samples should be measured at the same time, and the average value should be used.

[0058] In some embodiments, the tackifier resin used as a component of the PSA layer can preferably be one that achieves a score of 2 or higher (more preferably 3) in the following compatibility test. [Compatibility Test] 100 parts by weight of a rubber component used as a component of the PSA layer, 100 parts by weight of the tackifier resin to be evaluated, and an appropriate amount of solvent are mixed to prepare a mixture (preferably a solution) containing the rubber component and the tackifier resin in the solvent. The mixing can be performed under heated conditions (e.g., heating to approximately 35°C to 80°C) as needed. It is appropriate to select a solvent capable of dissolving at least the rubber component, and it is preferable to select a solvent capable of dissolving both the rubber component and the tackifier resin. For example, when the rubber component is EPDM, toluene can be used as the solvent. The amount of the solvent used is not particularly limited and can be set so as to dissolve the tackifier resin, for example, and can be appropriately selected from a range of approximately 1 to 10 times the total amount of the rubber component and the tackifier resin. The resulting mixture (preferably a solution) is applied to the release surface of a polyester film release liner, one side of which is treated with a silicone release agent, and dried at 120°C for 3 minutes to form a 30 μm thick film. The appearance and adhesiveness of this film are evaluated using the following four criteria. Here, "exhibiting adhesiveness" means that the film adheres to the aluminum plate when lightly pressed against the surface with a fingertip. 3 points: Both one and the other surfaces of the film exhibit adhesiveness, and the film's haze value is 10% or less. 2 points: Both one and the other surfaces of the film exhibit adhesiveness, but the film's haze value is greater than 10%. 1 point: Only one of the two surfaces of the film exhibits adhesiveness. 0 point: Neither one nor the other surface of the film exhibits adhesiveness.

[0059] Content W of tackifier resin in adhesive layer ＴＦ The [wt %] is not particularly limited and can be appropriately set so as to obtain the desired effect of use.ＴＦ may be, for example, 1% by weight or more or 3% by weight or more, and from the viewpoint of easily obtaining a higher effect of use, in some embodiments, it is appropriate that it is 5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, may be 20% by weight or more, or may be 25% by weight or more. ＴＦ From the viewpoint of the flexibility and compatibility of the adhesive during normal use, it is appropriate that the content is, for example, 65% by weight or less, and preferably 50% by weight or less (e.g., less than 50% by weight), and may be 45% by weight or less, 40% by weight or less, 35% by weight or less, or 32% by weight or less.

[0060] In the pressure-sensitive adhesive layer disclosed herein, the content W of the rubber component Ｐ Tackifier resin content W relative to [wt%] ＴＦ The ratio of [wt %], i.e., the ratio (W ＴＦ / W Ｐ ) may be, for example, 0.1 or more, and from the viewpoint of better exerting the effect of using the tackifier resin, it is appropriate to be 0.2 or more, preferably 0.3 or more, more preferably 0.5 or more, may be 0.7 or more, may be 0.9 or more, may be 1.0 or more, or may be 1.2 or more. Furthermore, from the viewpoint of the flexibility and compatibility of the PSA during normal use, in some embodiments, the above ratio (W ＴＦ / W Ｐ ) is suitably, for example, 5.0 or less, preferably 3.0 or less, more preferably 2.0 or less, and may be 1.8 or less or 1.6 or less.

[0061] (Other Components) The pressure-sensitive adhesive layer disclosed herein may contain, as other optional components, various additives commonly used in the field of pressure-sensitive adhesives, such as crosslinking agents, crosslinking aids, vulcanizing agents, vulcanization accelerators, leveling agents, fillers, colorants such as pigments and dyes, antistatic agents, light stabilizers, preservatives, antioxidants, etc. As for such various additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed description thereof will be omitted.

[0062] (Formation of Pressure-Sensitive Adhesive Layer) The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein can be formed using a pressure-sensitive adhesive composition having a corresponding composition. The pressure-sensitive adhesive composition can be in various forms, such as a water-dispersed pressure-sensitive adhesive composition in which a pressure-sensitive adhesive (adhesive component) is dispersed in water, a solvent-based pressure-sensitive adhesive composition in which a pressure-sensitive adhesive is contained in an organic solvent, an active energy ray-curable pressure-sensitive adhesive composition prepared to form a pressure-sensitive adhesive upon curing with active energy rays such as ultraviolet light or radiation, or a hot-melt pressure-sensitive adhesive composition that is applied in a heated and molten state and forms a pressure-sensitive adhesive upon cooling to around room temperature. When a solvent-based pressure-sensitive adhesive composition is used, the solvent contained in the composition can be appropriately selected from conventionally known organic solvents. For example, any one solvent selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; and ketones such as methyl ethyl ketone; or a mixed solvent of two or more thereof can be used.

[0063] The pressure-sensitive adhesive composition can be applied using a known or commonly used coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a die coater, a bar coater, a knife coater, a spray coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, curtain coating, or the like.

[0064] (Thickness of Pressure-Sensitive Adhesive Layer) The thickness of the pressure-sensitive adhesive layer is not particularly limited and may be, for example, about 3 μm to 2000 μm. From the viewpoint of adhesion to the adherend, such as conformability to unevenness, in some embodiments, the thickness of the pressure-sensitive adhesive layer is advantageously 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. Furthermore, from the viewpoint of preventing the occurrence of adhesive residue due to cohesive failure of the pressure-sensitive adhesive layer, in some embodiments, the thickness of the pressure-sensitive adhesive layer is usually 500 μm or less, preferably 200 μm or less, more preferably 100 μm or less, and may be 50 μm or less, or may be 30 μm or less.

[0065] <Adhesive Sheet> The adhesive sheet disclosed herein has an adhesive surface that can be attached to an adherend. The adhesive sheet may be in the form of a substrate-less double-sided adhesive sheet having, for example, a first adhesive surface constituted by one surface of an adhesive layer and a second adhesive surface constituted by the other surface of the adhesive layer. Alternatively, the adhesive sheet may be a substrate-attached adhesive sheet in the form of a non-releasable substrate (layer) having the adhesive layer on one or both sides. The concept of adhesive sheet here may include what are called adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, the adhesive sheet may be in the form of an adhesive sheet processed into various shapes.

[0066] The structure of a pressure-sensitive adhesive sheet according to one embodiment is shown schematically in FIG. 1 . This pressure-sensitive adhesive sheet 1 is configured as a substrate-less double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer 21. The pressure-sensitive adhesive sheet 1 is used by attaching a first adhesive surface 21A, which is configured as one surface (first surface) of the pressure-sensitive adhesive layer 21, and a second adhesive surface 21B, which is configured as the other surface (second surface) of the pressure-sensitive adhesive layer 21, to different locations on an adherend. The locations to which the adhesive surfaces 21A and 21B are attached may be locations on different members, or may be different locations within a single member. For example, as shown in FIG. 2 , the pressure-sensitive adhesive sheet can be configured as a bonded structure 100 in which a first member 61 and a second member 62 are bonded via the pressure-sensitive adhesive sheet 1 by bonding the first adhesive surface 21A of the pressure-sensitive adhesive sheet 1 (pressure-sensitive adhesive layer 21) to a first member 61 and bonding the second adhesive surface 21B to a second member 62.

[0067]

[0033] Before use (i.e., before attachment to an adherend), the PSA sheet 1 may be a component of a release-liner PSA sheet 50 in a form in which the first adhesive surface 21A and the second adhesive surface 21B are protected by release liners 31, 32, each of which serves as a release surface on at least the side facing the PSA layer 21, as shown in Figure 1. The release liners 31, 32 may preferably be, for example, a sheet-like substrate (liner substrate) configured such that one side serves as a release surface by providing a release layer made of a release treatment agent on that surface. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used, which may then be superimposed on the PSA sheet 1 and wound into a spiral shape to form a release-liner PSA sheet in a form in which the second adhesive surface 21B is protected by contacting the back surface of the release liner 31 (roll form).

[0068] The release liner is not particularly limited, and examples thereof include release liners in which the surface of a liner substrate such as a resin film or paper has been release-treated, and release liners made of low-adhesion materials such as fluorine-based polymers (e.g., polytetrafluoroethylene) and polyolefin-based resins (e.g., polyethylene and polypropylene). For the release treatment, for example, a silicone-based or long-chain alkyl-based release treating agent can be used. In some embodiments, a release-treated resin film can be preferably used as the release liner.

[0069] (Substrate) The pressure-sensitive adhesive sheet disclosed herein may include a substrate layer. Various sheet-like substrates can be used as the substrate (layer) supporting (backing) the pressure-sensitive adhesive layer. Various sheet-like substrates can be used as the substrate, such as resin films, paper, cloth, rubber sheets, foam sheets, metal foils, and composites thereof. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluororesin films; cellophane; and the like. Other examples of resin films include resin films formed from one or more engineering plastics (which may be super engineering plastics) such as polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyarylate resins, polyamideimide resins, and polyimide resins. The use of engineering plastics is preferred from the standpoint of heat resistance. Examples of paper include Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, and top-coated paper. Examples of cloth include woven fabrics and nonwoven fabrics made from various fibrous materials, either alone or in combination. Examples of the fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets and butyl rubber sheets. Examples of foam sheets include foamed polyurethane sheets and foamed polychloroprene rubber sheets. Examples of metal foils include aluminum foil and copper foil.

[0070] The thickness of the substrate layer is not particularly limited and can be selected appropriately depending on the purpose, but can generally be 1 to 500 μm. From the viewpoints of processability, handleability, workability, etc., the thickness of the substrate layer is suitably 2 μm or more (for example, 3 μm or more, typically 5 μm or more), and may be approximately 7 μm or more, or may be 10 μm or more. Furthermore, the thickness of the substrate layer is suitably approximately 200 μm or less, and from the viewpoints of weight reduction and thinning, it is preferably approximately 100 μm or less, more preferably approximately 50 μm or less, and may be 30 μm or less, 20 μm or less, or 15 μm or less.

[0071] The surface of the substrate layer facing the pressure-sensitive adhesive layer may be subjected to a conventionally known surface treatment, such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer, as necessary. Such a surface treatment may be a treatment for improving the adhesion between the substrate layer and the pressure-sensitive adhesive layer, in other words, the anchoring ability of the pressure-sensitive adhesive layer to the substrate layer. The composition of the primer is not particularly limited and can be appropriately selected from known primers.

[0072] (Shear Adhesion Strength) The PSA sheet disclosed herein suitably has a shear adhesion strength of approximately 0.05 MPa or more, measured at 23°C using an aluminum plate as an adherend. PSA sheets exhibiting such a shear adhesion strength exhibit good adhesion to adherends and can be preferably used, for example, in constructing bonded structures including the PSA sheet. In some embodiments, from the viewpoint of improving bonding reliability, the shear adhesion strength is preferably 0.1 MPa or more, more preferably 0.3 MPa or more, and may be 0.5 MPa or more, 0.6 MPa or more, or 0.7 MPa or more. The upper limit of the shear adhesion strength is not particularly limited, and a higher value is preferable from the viewpoint of bonding reliability. On the other hand, from the viewpoint of practical aspects such as the productivity and cost of the PSA sheet, in some embodiments, the shear adhesion strength may be, for example, 30 MPa or less, 20 MPa or less, 10 MPa or less, or 5 MPa or less. The shear adhesion strength of the PSA sheet is measured by the method described in the Examples below.

[0073] (Cooling Temperature) The PSA sheet disclosed herein has an adhesive surface that can be attached to an adherend, and the oil component contained in the PSA layer constituting the adhesive surface contains a low-temperature exudable oil that can exude from the adhesive surface when the temperature drops below a predetermined value. The oil component exuded from the adhesive surface forms a localized or continuous oil film between the adhesive surface and the adherend, thereby weakening the adhesion between the PSA layer and the adherend. To avoid this effect being exerted unnecessarily during normal use of the PSA sheet (when it is expected to maintain adhesion to the adherend), the predetermined value is suitably a temperature significantly lower than the temperature range in which the PSA sheet is normally used. In some embodiments, the predetermined value is suitably a temperature below 0°C, and may be, for example, -5°C, -10°C, or -15°C.

[0074] <Disassembly Method> The pressure-sensitive adhesive sheet disclosed herein has an adhesive surface that can be attached to an adherend. Therefore, by attaching the adhesive surface to a desired adherend, a bonded body including the pressure-sensitive adhesive sheet can be preferably constructed. Such a bonded body (which can also be understood as a member with a pressure-sensitive adhesive sheet) can be easily disassembled by cooling it at a desired timing, since cooling can cause oil to exude from the adhesive surface, weakening the bond with the adherend. Therefore, this specification provides a method for disassembling a bonded body including any of the pressure-sensitive adhesive sheets disclosed herein and a member to which the adhesive surface of the pressure-sensitive adhesive sheet is attached, the method comprising: cooling the bonded body to exude the low-temperature exudable oil from the adhesive surface; and separating the member from the pressure-sensitive adhesive sheet.

[0075] The shape and material of the adherend to which the adhesive surface is bonded are not particularly limited. Preferred adherends include those having a non-porous, smooth surface to which the adhesive sheet is attached. The material constituting at least the surface of the adherend may be, for example, a metal material such as stainless steel (SUS) or aluminum; glass such as an alkali glass plate or alkali-free glass; or a resin material such as an acrylic resin, an ABS resin, a polycarbonate resin, or a polystyrene resin. The surface of the adherend may be a painted surface made of an acrylic, polyester, alkyd, melamine, urethane, acid-epoxy crosslinked, or composite of these (e.g., an acrylic-melamine, an alkyd-melamine), or a plated surface such as a zinc-plated steel plate.

[0076] In the disassembly method disclosed herein, the temperature to which the bonded body is cooled is suitably significantly lower than the temperature range at which PSA sheets are typically used. In some embodiments, the cooling temperature is suitably less than 0°C, and may be, for example, −5°C, −10°C, −15°C, −20°C or lower, or −25°C or lower. On the other hand, if the cooling temperature is excessively low, the mobility of the oil component contained in the PSA layer may decrease (e.g., the mobility of the polymer constituting the rubber component may decrease, or the low-temperature exudative oil may solidify), making it difficult for the oil to bleed from the adhesive surface. From this perspective, in some embodiments, the cooling temperature is suitably, for example, −60°C or higher, −50°C or higher, or −40°C or higher, and may be −30°C or higher, −25°C or higher, −20°C or higher, or −15°C or higher.

[0077] In the disassembly method, the cooling time for the bonded body can be appropriately set so that the bonded body can be appropriately disassembled (preferably in a manner that avoids damage or deformation of the components). From the viewpoint of shortening the time required for disassembly, in some embodiments, the cooling time is suitably 3 hours or less, preferably 1 hour or less, more preferably 30 minutes or less, and may be 20 minutes or less or 15 minutes or less. In some embodiments, the immersion time can be, for example, 30 seconds or more, or may be 1 minute or more, 3 minutes or more, or 5 minutes or more.

[0078] <Applications> The pressure-sensitive adhesive sheets disclosed herein can be used in a variety of applications, taking advantage of the feature that the bond to the adherend can be easily weakened by the simple operation of cooling to a temperature below a predetermined value. They are adhered to an adherend and then removed from the adherend after their intended purpose has been achieved. While not particularly limited, the pressure-sensitive adhesive sheets disclosed herein can be preferably used in situations where it is difficult to apply methods such as immersion in water for peeling or ultraviolet irradiation to reduce adhesive strength for peeling, such as when attaching to light-impermeable adherends or water-sensitive adherends. Furthermore, the pressure-sensitive adhesive sheets disclosed herein can easily release the bond between rigid bodies, making them suitable for applications using rigid bodies as adherends. For example, they can be used as pressure-sensitive adhesive sheets for masking, temporary fixation, or protection.

[0079] The pressure-sensitive adhesive sheet disclosed herein can also be preferably used as a processing material that is fixed to an adherend and peeled off in the manufacturing process of electronic devices and electronic components, for example. A suitable application of the pressure-sensitive adhesive sheet disclosed herein can also be used in the manufacturing of semiconductor elements. For example, the pressure-sensitive adhesive sheet disclosed herein can be preferably used as a wafer fixing sheet that fixes the wafer to a fixing plate in semiconductor wafer processing (typically silicon wafer processing). The pressure-sensitive adhesive sheet disclosed herein can also be preferably used as a protective sheet that protects the wafer during the wafer processing.

[0080] The thermosetting adhesive and adhesive sheet disclosed herein can also be applied to optical applications. More specifically, the present invention can be preferably implemented as an optical adhesive sheet used for bonding optical members (for bonding optical members) or for manufacturing products using the optical members (optical products), and as a method for dismantling a bonded structure including the adhesive sheet.

[0081] The optical member refers to a member having optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.). The optical member is not particularly limited as long as it is a member having optical properties, but examples thereof include components constituting devices (optical devices) such as display devices (image display devices) and input devices, or components used in these devices, such as polarizing plates, wavelength plates, retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, hard coat (HC) films, impact absorbing films, antifouling films, photochromic films, light control films, transparent conductive films (ITO films), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and further components in which these are laminated (these may be collectively referred to as "functional films"). The above "plate" and "film" respectively include plate-like, film-like, sheet-like and other forms. For example, "polarizing film" includes "polarizing plate", "polarizing sheet", and the like.

[0082] Examples of the display device include a liquid crystal display device, an organic EL display device, a PDP, and electronic paper. The technology disclosed herein is particularly suitable for devices that include expensive components, such as foldable display devices and in-vehicle display devices. The display device also includes a display device that allows input, such as a touch panel. Since there is a strong demand for the display device to be recyclable and reusable, applying the technology disclosed herein is particularly beneficial.

[0083] The optical member is not particularly limited, and examples thereof include members (e.g., sheet-like, film-like, or plate-like members) made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin film, etc. In this specification, the term "optical member" also includes members (such as design films, decorative films, and surface protection films) that serve to decorate or protect a display device or input device while maintaining its visibility.

[0084] As an example of another application, the adhesive sheets disclosed herein and joined bodies such as products, devices, and structures comprising the adhesive sheets can be components of electronic devices (preferably portable electronic devices) that require desired adhesive performance during normal use, while also requiring smooth removal during repair, replacement, inspection, recycling, etc. of constituent parts. For example, they can be components of portable electronic devices such as mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear types worn on the wrist like a wristwatch, modular types worn on a part of the body with a clip or strap, eyewear types including glasses (monocular and binocular types, including head-mounted types), clothing types attached to shirts, socks, hats, etc. as accessories, earwear types attached to the ears like earphones), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems. The display device may be a component of an electronic device such as a desktop computer, a display, a television (liquid crystal, plasma, organic electroluminescence, etc.), etc. In this specification, "portable" does not simply mean being portable, but means having a level of portability that allows an individual (average adult) to carry it relatively easily.

[0085] The matters disclosed in this specification include the following. [1] A pressure-sensitive adhesive sheet having an adhesive surface that can be attached to an adherend, wherein the adhesive surface is the surface of a pressure-sensitive adhesive layer containing a rubber component and an oil component, and the oil component contains a low-temperature exudable oil that can exude from the adhesive surface when the temperature drops below a predetermined value. [2] The pressure-sensitive adhesive sheet according to [1] above, wherein the content of the oil component in the pressure-sensitive adhesive layer is 35 wt % or more. [3] The content W of the oil component in the pressure-sensitive adhesive layer is 35 wt % or more. Ｏ [wt%] is the content W of the rubber component Ｐ [4] The pressure-sensitive adhesive sheet according to the above item [1] or [2], wherein the content W of the oil component in the pressure-sensitive adhesive layer is more than 1.0 times the content W of the oil component in the pressure-sensitive adhesive layer. Ｏ (B) the content W of the oil component in the pressure-sensitive adhesive layer is 35% by weight or more; and Ｏ [wt%] is the content W of the rubber component Ｐ [5] The pressure-sensitive adhesive sheet according to the above [1], wherein the difference between the SP value of the rubber component and the SP value of the oil component is 1.0 (cal / cm ３ ) １／２ [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the oil component comprises silicone oil. [7] The oil component is an oil O having a relatively large difference in SP value from the rubber component. Ｌ and the SP value of the rubber component is relatively small. Ｓ and the oil O Ｌ SP value and the above oil O Ｓ The difference between the SP value and ３ ) １／２[8] The pressure-sensitive adhesive sheet according to any one of [1] to [6] above, wherein the rubber component is a rubber containing an olefin-based rubber as a main component. [9] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above, wherein the pressure-sensitive adhesive layer further comprises a tackifier resin.

[10] The pressure-sensitive adhesive sheet according to [9] above, wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 0.5 to 2 times the content of the rubber component.

[11] A pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to

[10] above.

[12] A method for dismantling a bonded body comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[10] above and members to which the adhesive surface of the pressure-sensitive adhesive sheet is bonded, the method comprising: cooling the bonded body to exude the low-temperature exudable oil from the adhesive surface; and separating the members from the pressure-sensitive adhesive sheet.

[0086] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0087] <Materials Used> The materials used are shown in Table 1 as follows. EPDM: Ethylene-propylene-diene rubber manufactured by Mitsui Chemicals, Inc., product name "3092M", ethylene content 65%, diene content 4.6%, diene type ENB, Mooney viscosity (ML(1+4), 125°C) 61. Modified SEBS: Maleic acid-modified SEBS manufactured by Kraton, product name "FT-1901GT", styrene content 30%, maleic anhydride graft amount 1.4 to 2.0%. Hydrocarbon oil: Liquid paraffin manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Silicone oil: Methylphenyl silicone oil manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-56A". Hydrogenated rosin ester: hydrogenated rosin ester manufactured by Arakawa Chemical Industries, Ltd., product name "PE-590". Terpene resin A: terpene resin manufactured by Yasuhara Chemical Co., Ltd., product name "YS Resin PX1150N", softening point 115°C. Terpene resin B: terpene resin manufactured by Yasuhara Chemical Co., Ltd., product name "YS Resin PX1000", softening point 100°C. Terpene resin C: terpene resin manufactured by Yasuhara Chemical Co., Ltd., product name "YS Resin PX800", softening point 80°C.

[0088] <Preparation of Pressure-Sensitive Adhesive Sheet> (Example 1) A pressure-sensitive adhesive composition was prepared by adding toluene as a solvent to the types and amounts of rubber components, oil components, and tackifying resin shown in Table 1, and mixing them uniformly. The pressure-sensitive adhesive composition was applied to the release surface of a polyester film release liner, one side of which had a release surface treated with a silicone-based release agent, and dried at 120°C for 3 minutes to prepare a substrate-less double-sided pressure-sensitive adhesive sheet consisting of a 30 μm-thick pressure-sensitive adhesive layer.

[0089] (Examples 2 to 11) PSA layers (substrate-less double-sided PSA sheets) according to each example were prepared in the same manner as in Example 1, except that the types and amounts of the rubber component, oil component, and tackifying resin were changed as shown in Table 1. Note that Example 10 did not use a tackifying resin, and Example 11 did not use an oil component. The resultant product obtained in Example 10 was a film that exhibited substantially no tackiness at 23°C.

[0090] <Evaluation> (Shear Adhesion Strength) Two aluminum plates (Standard Test Piece Co., Ltd., A5052P, size: length 100 mm, width 50 mm, thickness 0.3 mm) were prepared. The pressure-sensitive adhesive sheet according to each example was cut into a 20 mm square, and one adhesive surface was bonded to one longitudinal end of the first aluminum plate, and the other adhesive surface was bonded to the other longitudinal end of the second aluminum plate (bonding area 20 mm × 20 mm). The resulting bonded structure was then autoclaved (50°C, 0.5 MPa, 15 minutes) to obtain a bonded structure for shear adhesion strength measurement. The shear adhesion strength [MPa] of the resulting bonded structure was measured at a tension rate of 10 mm / min using a tensile tester (Minebea Co., Ltd., universal tension and compression tester, device name "Tension and Compression Tester, TCM-1kNB") under a measurement environment of 23°C and 50% RH. The results are shown in Table 1. The pressure-sensitive adhesive sheet of Example 10 was not bonded to an aluminum plate, and a bonded assembly for measurement could not be prepared, so the corresponding column was marked "Measurement not possible."

[0091] (Disassembly Test) Two aluminum plates (A5052P, manufactured by Standard Test Piece Co., Ltd., size: length 100 mm, width 50 mm, thickness 0.3 mm) were prepared. The pressure-sensitive adhesive sheet according to each example was cut into a 50 mm square. One adhesive surface was attached to the center of the first aluminum plate, and the other adhesive surface was attached to the longitudinal center of the second aluminum plate. The resulting assembly was then autoclaved (50°C, 0.5 MPa, 15 minutes) to obtain a bonded assembly for the disassembly test. This bonded assembly was placed in a thermostatic chamber at -10°C and cooled for 10 minutes. After removing the bonded assembly from the thermostatic chamber, if the bonded assembly could be easily disassembled by manually sliding one of the aluminum plates in the shear direction within 30 seconds, the assembly was evaluated as "Good" (good disassembly). If the aluminum plate could not be slid, the assembly was evaluated as "Poor" (poor disassembly). The results are shown in Table 1. The pressure-sensitive adhesive sheet of Example 10 did not adhere to the aluminum plate and a bonded body could not be formed, so the corresponding column was marked "Not applicable."

[0092]

[0093] As shown in Table 1, all of the PSA sheets according to Examples 1 to 8 exhibited good adhesiveness (shear adhesive strength) in an environment of 23° C. Furthermore, all of the joined structures produced using these PSA sheets could be easily disassembled by cooling to −10° C. On the other hand, the PSA sheets of Examples 9 and 11 were unable to fully demonstrate the effect of facilitating disassembly by cooling, and the resultant product obtained in Example 10 did not exhibit adhesiveness at 23° C. as described above.

[0094] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0095] REFERENCE SIGNS LIST 1 Pressure-sensitive adhesive sheet 21 Pressure-sensitive adhesive layer 31, 32 Release liner 50 Pressure-sensitive adhesive sheet with release liner 61 First member 62 Second member 100 Bonded body

Claims

1. A pressure-sensitive adhesive sheet having an adhesive surface that can be attached to an adherend, the adhesive surface being a surface of an adhesive layer containing a rubber component and an oil component, the oil component containing a low-temperature exudable oil that can exude from the adhesive surface when the temperature drops below a predetermined value, and the content W of the oil component in the pressure-sensitive adhesive layer Ｏ [Weight %] is 35 weight % or more.

2. The content W of the oil component in the pressure-sensitive adhesive layer Ｏ [wt%] is the content W of the rubber component Ｐ The pressure-sensitive adhesive sheet according to claim 1 , wherein the content is more than 1.0 times [wt %].

3. The difference between the SP value of the rubber component and the SP value of the oil component is 1.0 (cal / cm ３ ) １／２ The pressure-sensitive adhesive sheet according to claim 1 , wherein:

4. The oil component is an oil O having a relatively large difference in SP value from the rubber component. Ｌ and the SP value of the rubber component is relatively small. Ｓ The oil O Ｌ SP value of the oil O Ｓ The difference between the SP value and ３ ) １／２ The pressure-sensitive adhesive sheet according to claim 1 .

5. The pressure-sensitive adhesive sheet according to claim 1, wherein the rubber component is a rubber whose main component is an olefin-based rubber.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer further comprises a tackifier resin.

7. The pressure-sensitive adhesive sheet according to claim 6, wherein the content of the tackifier resin in the pressure-sensitive adhesive layer is 0.5 to 2 times the content of the rubber component.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the oil component includes silicone oil.

9. A method for dismantling an assembly comprising the adhesive sheet according to any one of claims 1 to 5 and a member to which the adhesive surface of the adhesive sheet is joined, the method comprising: cooling the assembly to cause the low-temperature exudable oil to exude from the adhesive surface; and separating the member and the adhesive sheet.

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