Adhesive sheet and portable electronic device

Abstract

To provide an adhesive sheet that can deliver excellent bonding reliability in a sufficiently stable manner, and a portable electronic device equipped with the adhesive sheet.SOLUTION: An adhesive sheet comprises an adhesive layer including a cured product of an adhesive composition containing a hydroxyl group-terminated urethane prepolymer and a polyisocyanate compound, wherein the adhesive force of the adhesive layer to a phenolic resin is 2.5 N / 15 mm or more, the adhesive force of the adhesive layer to skin is 5.0 N / 15 mm or less, and the 90-degree peel strength of the adhesive layer after ethanol immersion is 50% or more of the 90-degree peel strength before ethanol immersion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive sheet and an electronic device, and particularly to an adhesive sheet capable of sufficiently and stably exhibiting good adhesion reliability, and a portable electronic device including the adhesive sheet.

Background Art

[0002] Generally, an adhesive exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such a property, adhesives are widely used, for example, in the form of an adhesive sheet with a substrate having an adhesive layer on a support substrate or a substrate-free adhesive sheet, for the purpose of joining, fixing, protecting, etc. of members in portable electronic devices such as mobile phones.

[0003] Since portable electronic devices are used while being carried, they are likely to be attached with secretions such as sebum and dirt, chemicals such as cosmetics, hair styling products, moisturizing creams, and sunscreens, and oil components contained in foods. In particular, a touch panel type portable electronic device includes a display unit / input unit in which the display unit also functions as an input unit, and the surface of the display unit / input unit is operated by a user directly touching it with a fingertip, so there are many opportunities for oil components to adhere through the fingertip. In addition, among wearable devices, there are those that are worn and used in contact with the skin, and in such a usage form, there are many opportunities to be exposed to oil components such as sebum and chemicals applied to the skin. For example, when an oil component (sebum, cosmetics, etc.) comes into contact with the adhesive layer of an adhesive sheet fixing a member, inconveniences such as a decrease in adhesive force and extrusion of the adhesive may occur. In this regard, for example, Patent Document 1 examines a polyester-based adhesive sheet. In addition, in recent years, higher levels of chemical resistance have been required for adhesive sheets used in portable electronic devices. Specifically, not only oil components but also perfumes, insect repellent sprays, hand washing detergents, antibacterial sheets, etc. can come into contact with portable electronic devices through human operations. Many cosmetics and chemicals contain alcohols such as ethanol as solvents and dispersion media.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2020-79372 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, there is still no pressure-sensitive adhesive sheet that can sufficiently exhibit good adhesive reliability even when exposed to cosmetics, chemicals, etc. containing polar components, and there is a strong demand for the development of a pressure-sensitive adhesive sheet that can sufficiently and stably exhibit good adhesive reliability.

[0006] In view of the above problems, an object of the present invention is to provide a pressure-sensitive adhesive sheet that can sufficiently and stably exhibit good adhesive reliability, and an electronic device including the pressure-sensitive adhesive sheet. [Means for Solving the Problems]

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that by using a predetermined pressure-sensitive adhesive composition, the "adhesive strength (to phenolic resin)" and the "adhesive strength (to skin)" are appropriate, and the adhesive strength retention rate after ethanol immersion is improved. That is, a pressure-sensitive adhesive sheet that can sufficiently and stably exhibit good adhesive reliability is obtained, and the present invention has been completed. That is, the present invention is as follows. [1] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing a cured product of a pressure-sensitive adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound, wherein the adhesive strength of the pressure-sensitive adhesive layer to a phenolic resin is 2.5 N / 15 mm or more, the adhesive strength of the pressure-sensitive adhesive layer to skin is 5.0 N / 15 mm or less, and the 90-degree peel strength of the pressure-sensitive adhesive layer after ethanol immersion is 50% or more of the 90-degree peel strength before ethanol immersion. [2] The pressure-sensitive adhesive sheet according to the above [1], wherein the average content of structural units based on ethylene oxide in the pressure-sensitive adhesive layer is 60% by mass or less. [3] The pressure-sensitive adhesive composition further contains a tackifier resin, and the content of the tackifier resin is 10 to 70% by mass based on the solid content of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive sheet according to [1] or [2] above. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the tackifier resin is a styrene-based tackifier resin. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4] above, wherein the average content of the structural unit based on ethylene oxide in the pressure-sensitive adhesive composition is 60% by mass or less. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5] above, wherein the hydroxyl-terminated urethane prepolymer is a reaction product in the presence of a tin-free catalyst of an oxyalkylene polymer and a diisocyanate compound. [7] The pressure-sensitive adhesive sheet according to [6] above, wherein the tin-free catalyst contains at least one of zinc and bismuth. [8] The pressure-sensitive adhesive sheet according to [6] or [7] above, wherein the oxyalkylene polymer has an average content of the structural unit based on ethylene oxide of 60% by mass or less. [9] The pressure-sensitive adhesive sheet according to any one of [6] to [8] above, wherein the oxyalkylene polymer has an average number of hydroxyl groups per molecule of 1.5 to 3.0.

[10] The pressure-sensitive adhesive sheet according to any one of [6] to [9] above, wherein the oxyalkylene polymer contains an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2.0 or more and an oxyalkylene polymer B having one hydroxyl group per molecule.

[11] The pressure-sensitive adhesive sheet according to

[10] above, wherein the oxyalkylene polymer A contains an oxyalkylene polymer A1 having three hydroxyl groups per molecule and an oxyalkylene polymer A2 having two hydroxyl groups per molecule.

[12] A portable electronic device comprising the pressure-sensitive adhesive sheet according to any one of [1] to

[11] above.

[0008] According to the present specification, there is provided an adhesive sheet including a cured product of an adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound. This adhesive sheet has an adhesive force of the adhesive layer to a phenolic resin of 2.5 N / 15 mm or more, an adhesive force of the adhesive layer to the skin of 5.0 N / 15 mm or less, and a 90-degree peel strength after ethanol immersion of the adhesive layer of 50% or more of the 90-degree peel strength before ethanol immersion. Further, in the above adhesive sheet, the adhesive force of the adhesive layer to the phenolic resin is a predetermined value or more, the adhesive force of the adhesive layer to the skin is a predetermined value or less, and the 90-degree peel strength after ethanol immersion of the adhesive layer is a predetermined value or more of the 90-degree peel strength before ethanol immersion. Therefore, even when exposed to cosmetics, chemicals, etc. containing polar components such as ethanol (hereinafter also referred to as "polar chemicals, etc."), good adhesive reliability can be sufficiently exhibited. This is particularly significant in applications for portable electronic devices that are likely to come into contact with oil components (low-polarity components) such as sebum, cosmetics, and sunscreen creams, and can also be exposed to perfumes, insect repellent sprays, hand washing detergents, antibacterial sheets, etc. containing a polar solvent (typically ethanol).

Effects of the Invention

[0009] According to the present invention, it is possible to provide an adhesive sheet that can sufficiently and stably exhibit good adhesive reliability, and a portable electronic device including the adhesive sheet.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[0012] In this specification, the regulations that are considered preferable can be arbitrarily adopted, and a combination of preferable ones can be said to be more preferable. In this specification, the description “XX to YY” means “XX or more and YY or less”. In this specification, for preferable numerical ranges (for example, ranges such as content), the lower limit value and the upper limit value described stepwise can be combined independently of each other. For example, from the description “preferably 10 to 90, more preferably 30 to 60”, it is also possible to combine the “preferred lower limit value (10)” and the “more preferred upper limit value (60)” to obtain “10 to 60”. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In this specification, “the skin of the human body” may sometimes be simply referred to as “skin”. The number average molecular weight (Mn) and the weight average molecular weight (Mw) are the molecular weights in terms of polystyrene determined by measurement by gel permeation chromatography (GPC) based on a calibration curve prepared using a standard polystyrene sample. The isocyanate index is the equivalent ratio ([isocyanate group] / [active hydrogen-containing group]) of the isocyanate group to be reacted and the active hydrogen-containing group (for example, a hydroxyl group), and is expressed as a percentage. For example, an isocyanate index of 85 indicates that the equivalent ratio of the isocyanate group to the active hydrogen-containing group (for example, a hydroxyl group) is 85%. In this specification, as described above, the "adhesive" refers to a material that exhibits a soft solid (viscoelastic body) state in the temperature range near room temperature and has the property of easily adhering to an adherend under pressure. In this specification, the "solid content" refers to the non-volatile component excluding volatile substances such as solvents. When the adhesive composition is dried, it indicates the components that remain without volatilizing, including those that are liquid, syrup-like, and wax-like at room temperature. Note that the total solid content can also be calculated from the charged amount.

[0013] [Adhesive sheet] The adhesive sheet in an embodiment of the present invention (hereinafter, may also be simply referred to as "this embodiment") includes an adhesive layer and, if necessary, further includes a base material, a release liner, and other layers. The adhesive sheet of this embodiment may include a base material, a release liner, other layers, etc. in addition to the adhesive layer as long as the effects of the present invention can be achieved.

[0014] [Configuration of adhesive sheet] The adhesive sheet in this embodiment may be an adhesive sheet with a base material having an adhesive layer on one or both sides of the base material (support), or may be a base material-free adhesive sheet in which the adhesive layer is held by a release liner. The concept of "adhesive sheet" may include those referred to as adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet in this embodiment may be in a roll form, may be in a single-sheet form, or may be in a form processed into various shapes.

[0015] The adhesive sheet in this embodiment has, for example, a cross-sectional structure schematically shown in FIGS. 1 to 6. FIGS. 1 and 2 are configuration examples of a double-sided adhesive type adhesive sheet with a base material. In FIG. 1, the adhesive sheet 10 includes a base material 100, adhesive layers 210 and 220 provided on each surface (both non-peeling surfaces) of the base material 100, and release liners 310 and 320 with at least the sides of the adhesive layers 210 and 220 being the release surfaces. The adhesive layers 210 and 220 are each protected by the release liners 310 and 320. In FIG. 2, the adhesive sheet 20 includes a base material 100, adhesive layers 210 and 220 provided on each surface (both non-peeling surfaces) of the base material 100, and a release liner 310 with both sides being the release surfaces. The adhesive layer 210 is protected by the release liner 310. By winding the adhesive sheet 20 and bringing the adhesive layer 220 into contact with the back surface of the release liner 310, the adhesive layer 220 can be configured to be protected by the release liner 310.

[0016] FIGS. 3 and 4 are configuration examples of a double-sided adhesive sheet without a base material. In FIG. 3, the adhesive sheet 30 includes an adhesive layer 210 and release liners 310 and 320 with at least the side of the adhesive layer 210 being the release surface. Both surfaces 210A and 210B of the adhesive layer 210 are each protected by the release liners 310 and 320. In FIG. 4, the adhesive sheet 40 includes an adhesive layer 210 and a release liner 310 with both sides being the release surfaces. One surface (adhesive surface) 210A of the adhesive layer 210 is protected by the release liner 310. By winding the adhesive sheet 40 and bringing the other surface (adhesive surface) 210B of the adhesive layer 210 into contact with the back surface of the release liner 310, the other surface (adhesive surface) 210B can also be configured to be protected by the release liner 310.

[0017] FIGS. 5 and 6 are configuration examples of a single-sided adhesive sheet with a base material. In FIG. 5, the adhesive sheet 50 includes a base material 100, an adhesive layer 210 provided on one surface 100A (non-peeling surface) of the base material 100, and a release liner 310 with the side of the adhesive layer 210 serving as the release surface. The surface (adhesive surface) 210A of the adhesive layer 210 is protected by the release liner 310. In FIG. 6, the adhesive sheet 60 includes a base material 100 and an adhesive layer 210 provided on one surface 100A (non-peeling surface) side of the base material 100. The other surface 100B of the base material 100 serves as the release surface. By winding the adhesive sheet 60 and bringing the adhesive layer 210 into contact with the other surface 100B of the base material 100 that serves as the release surface, the surface (adhesive surface) 210B of the adhesive layer 210 can be protected by the other surface 100B of the base material.

[0018] <Properties of the Adhesive Sheet> In the adhesive sheet of the present embodiment, the adhesive force of the adhesive layer to the phenolic resin is 2.5 N / 15 mm or more, the adhesive force of the adhesive layer to the skin is 5.0 N / 15 mm or less, and the 90-degree peel strength of the adhesive layer after ethanol immersion is 50% or more of the 90-degree peel strength before ethanol immersion. An adhesive sheet satisfying such properties can sufficiently exhibit good adhesion reliability even when exposed to polar chemicals or the like.

[0019] Regarding the adhesive force of the adhesive layer of the adhesive sheet in the present embodiment to the phenolic resin, there is no particular limitation as long as it is 2.5 N / 15 mm or more, but preferably it is 3.0 to 20.0 N / 15 mm, more preferably 4.0 to 15.0 N / 15 mm, and particularly preferably 5.0 to 10.0 N / 15 mm. When the adhesive force of the adhesive layer to the phenolic substrate is at or above the lower limit value, the adhesion of the adhesive sheet to the phenolic substrate becomes good, so it is excellent for fixing the wearable device. On the other hand, when the adhesive force of the adhesive layer to the phenolic substrate is at or below the upper limit value, it is possible to easily peel off the adhesive sheet when the wearable device is repeatedly used, which is excellent in convenience. Note that the adhesive force to the phenolic resin is measured by the method described in the examples below.

[0020] The adhesive strength of the adhesive layer of the pressure-sensitive adhesive sheet in this embodiment to the skin (initial 90-degree peel strength) is not particularly limited as long as it is 5.0 N / 15 mm or less, but is preferably 1.0 to 5.0 N / 15 mm, more preferably 2.0 to 4.9 N / 15 mm, and particularly preferably 3.0 to 4.8 N / 15 mm. When the adhesive strength of the adhesive layer to the skin is equal to or higher than the lower limit value, the adhesion of the pressure-sensitive adhesive sheet to the skin becomes good. When the adhesive strength of the adhesive layer to the skin is equal to or lower than the upper limit value, the state of the skin after peeling the pressure-sensitive adhesive sheet from the skin becomes good, so it is excellent in gentleness to the human skin. Note that the adhesive strength to the skin is measured by the method described in the examples below.

[0021] The 90-degree peel strength after ethanol immersion with respect to the 90-degree peel strength (initial 90-degree peel strength) before ethanol immersion of the adhesive layer of the pressure-sensitive adhesive sheet in this embodiment is not particularly limited as long as it is 50% or more. From the viewpoint of stable adhesion reliability, it is preferably 60 to 100%, more preferably 61 to 100%, and particularly preferably 62 to 100%. Note that the 90-degree peel strength (initial 90-degree peel strength) before ethanol immersion and the 90-degree peel strength after ethanol immersion are measured by the method described in the examples below.

[0022] The 90-degree peel strength after oleic acid immersion with respect to the 90-degree peel strength (initial 90-degree peel strength) before oleic acid immersion of the adhesive layer of the pressure-sensitive adhesive sheet in this embodiment is not particularly limited. From the viewpoint of stable adhesion reliability, it is preferably 70 to 100%, more preferably 80 to 100%, and particularly preferably 90 to 100%. Note that the 90-degree peel strength (initial 90-degree peel strength) before oleic acid immersion and the 90-degree peel strength after oleic acid immersion are measured by the method described in the examples below.

[0023] (Adhesive layer) The adhesive layer is an adhesive layer containing a cured product of an adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound, that is, there is no particular limitation as long as it is an adhesive layer containing a urethane-based adhesive. For example, it may further contain an acrylic-based adhesive, a silicone-based adhesive, a rubber-based adhesive (natural rubber-based, synthetic rubber-based, a mixed system thereof, etc.), a polyester-based adhesive, a polyether-based adhesive, a polyamide-based adhesive, a fluorine-based adhesive, etc. The total content of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound (urethane-based adhesive) in the adhesive layer is not particularly limited, but is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 45% by mass or more.

[0024] The content of the structural unit based on ethylene oxide (hereinafter abbreviated as "EO unit") in the adhesive layer is not particularly limited. From the viewpoint of obtaining an adhesive that is gentle to the skin and has a good balance between the adhesive force to the skin and the adhesive force to the device, it is preferably 60% by mass or less, more preferably 8 to 55% by mass, still more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. The EO unit content of the adhesive layer is derived from the EO units constituting the oxyalkylene chain of the oxyalkylene polymer in the hydroxyl-terminated urethane prepolymer, and of the adhesive layer 13 It is determined by analyzing the monomer composition of the oxyalkylene chain of the adhesive layer by C-NMR (nuclear magnetic resonance) measurement.

[0025] The thickness of the above-mentioned adhesive sheet is not particularly limited, but is preferably 10 to 500 μm, more preferably 20 to 350 μm, still more preferably 30 to 250 μm, still more preferably 40 to 200 μm, still more preferably 50 to 150 μm, and particularly preferably 60 to 100 μm. When the thickness of the adhesive sheet is within the above range, the adhesion to the adherend can be improved.

[0026] The above adhesive layer may be a single layer or a multi-layer. The plurality of adhesive layers provided in the above adhesive sheet may be the same adhesive layer, or may be adhesive layers with different compositions, thicknesses, physical properties, etc.

[0027] The thickness of the above adhesive layer is not particularly limited, but preferably 4 to 100 μm, more preferably 6 to 70 μm, still more preferably 10 to 50 μm, and particularly preferably 15 to 50 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit value, the adhesion to the adherend can be improved, and the intrusion of polar chemicals, oil components, etc. from the interface with the adherend can be suppressed. When the thickness of the adhesive layer is equal to or less than the upper limit value, it is possible to avoid the adhesive sheet becoming excessively thick.

[0028] <Adhesive composition> The adhesive composition contains, for example, a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound, and may contain, if necessary, an adhesion-imparting resin and other components.

[0029] The content of EO units in the adhesive composition is not particularly limited, but from the viewpoint of obtaining an adhesive that is gentle to the skin and has a good balance between the adhesive force to the skin and the adhesive force to the device, it is preferably 60% by mass or less, more preferably 8 to 55% by mass, still more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. The content of EO units in the adhesive composition is derived from the EO units that constitute the oxyalkylene chain of the oxyalkylene polymer in the hydroxyl-terminated urethane prepolymer. In the adhesive composition, 13 It is determined by analyzing the monomer composition of the oxyalkylene chain in the adhesive composition by C-NMR (nuclear magnetic resonance) measurement.

[0030] <<Hydroxyl-terminated urethane prepolymer>> The hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer and a diisocyanate compound. The hydroxyl-terminated urethane prepolymer is preferably a reaction product obtained by reacting an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst.

[0031] The content of EO units in the hydroxyl-terminated urethane prepolymer is not particularly limited, but is preferably 60% by mass or less, more preferably 5 to 55% by mass, still more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. When the content of EO units in the hydroxyl-terminated urethane prepolymer is within the above range, an adhesive that is gentle to the skin and has a good balance between the adhesive force to the skin and the adhesive force to the device can be easily obtained. The EO units in the hydroxyl-terminated urethane prepolymer were taken as the weighted average value of the EO unit contents in each component of the raw materials. Note that the EO units in the hydroxyl-terminated urethane prepolymer can also be determined by 13 C-NMR measurement in the same manner as the EO unit content in the adhesive composition.

[0032] -Oxyalkylene polymer- The average content of EO units in the oxyalkylene polymer is not particularly limited, but is preferably 60% by mass or less, more preferably 8 to 55% by mass, still more preferably 10 to 50% by mass, still more preferably 12 to 40% by mass, and particularly preferably 15 to 25% by mass. When a plurality of oxyalkylene polymers are used in the synthesis of the hydroxyl-terminated urethane prepolymer, the average content of EO units in the oxyalkylene polymer means a value obtained by weighted-averaging the EO unit contents in each of these plurality of oxyalkylene polymers based on the blending amounts thereof. The EO unit content in each oxyalkylene polymer is a value calculated based on the EO blending amount of the raw materials in the synthesis of the oxyalkylene polymer. Note that the EO unit content in the oxyalkylene polymer can also be determined by 13 C-NMR measurement in the same manner as the EO unit content in the adhesive composition. When the average content of EO units in the oxyalkylene polymer is within the above range, an adhesive that is gentle to the skin and has a good balance between the adhesive force to the skin and the adhesive force to the device can be easily obtained.

[0033] The average number of hydroxyl groups per molecule of the oxyalkylene polymer is not particularly limited. However, from the viewpoint of obtaining an adhesive that is gentle to the skin and has a good balance between the adhesive force to the skin and the adhesive force to the device, it is preferably 1.5 to 3.0, more preferably 1.7 to 2.8, and particularly preferably 1.9 to 2.6. The average number of hydroxyl groups per molecule of the oxyalkylene polymer means a value obtained by weighted-averaging the number of hydroxyl groups per molecule of the oxyalkylene polymer based on the blending amounts of a plurality of oxyalkylene polymers used in the synthesis of the hydroxyl-terminated urethane prepolymer. The oxyalkylene polymer may be a single type of oxyalkylene polymer or two or more types of oxyalkylene polymers.

[0034] As the oxyalkylene polymer, it preferably includes an oxyalkylene polymer A having 2 or more hydroxyl groups per molecule (hereinafter, may be simply referred to as "polymer A"), and an oxyalkylene polymer B having 1 hydroxyl group per molecule (hereinafter, may be simply referred to as "polymer B"). The hydroxyl groups of polymer A and polymer B react with the isocyanate groups of the diisocyanate compound to form urethane bonds, thereby generating a hydroxyl-terminated urethane prepolymer. It is preferable that the unreacted hydroxyl groups in the hydroxyl groups of polymer A and polymer B are the terminal hydroxyl groups of the molecular chain of the hydroxyl-terminated urethane prepolymer.

[0035] The total content of polymer A and polymer B in the oxyalkylene polymer is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass. Although there are no particular restrictions on the content ratios of polymer A and polymer B in the oxyalkylene polymer, from the perspective of obtaining an adhesive with a good balance between the adhesiveness to the skin and the adhesiveness to the device, the mass ratio is preferably 10 / 90 to 95 / 5, more preferably 30 / 70 to 90 / 10, still more preferably 50 / 50 to 85 / 15, and particularly preferably 60 / 40 to 85 / 15.

[0036] --Oxyalkylene polymer A-- Polymer A has 2 or more hydroxyl groups per molecule, preferably 2 to 6. Polymer A may be a single type of oxyalkylene polymer or may be two or more types of oxyalkylene polymers. When polymer A is composed of two or more types of oxyalkylene polymers, it is easy to adjust the adhesiveness of the adhesive. When polymer A is composed of two or more types of oxyalkylene polymers, although there are no particular restrictions on the average number of hydroxyl groups per molecule of polymer A, it is preferably 2.1 to 3.0, more preferably 2.2 to 2.9, and particularly preferably 2.3 to 2.8. When the average number of hydroxyl groups of polymer A is within the above range, the load on the skin to which the device is fixed is suppressed, and an adhesive that is less likely to leave residue on the skin can be obtained. The average number of hydroxyl groups per molecule of polymer A can be calculated by the formula of hydroxyl value × Mn / 56100 from the measured values of the hydroxyl value and Mn of polymer A. The hydroxyl value can be measured by the method described in the examples.

[0037] When polymer A is composed of two or more types of oxyalkylene polymers, examples of polymer A include those containing an oxyalkylene polymer A1 having 3 hydroxyl groups per molecule (hereinafter, sometimes simply referred to as "polymer A1") and an oxyalkylene polymer A2 having 2 hydroxyl groups per molecule (hereinafter, sometimes simply referred to as "polymer A2"). Polymer A1 may be a single type or two or more types. Similarly, polymer A2 may be a single type or two or more types. The polymer A may contain an oxyalkylene polymer having 4 or more hydroxyl groups per molecule. When the polymer A consists of the polymer A1 and the polymer A2, the weighted average value of the number of hydroxyl groups per molecule of the polymer A1 being 3 and the number of hydroxyl groups per molecule of the polymer A2 being 2, based on the composition ratio (blending amount) of the polymer A1 and the polymer A2, can be regarded as the average number of hydroxyl groups of the polymer A.

[0038] In 100 parts by mass in total of the polymer A, the total amount of the polymer A1 and the polymer A2 is not particularly limited, but from the viewpoint of ease of adjusting the adhesive strength of the adhesive, etc., it is preferably 85 parts by mass or more, more preferably 90 parts by mass or more, and particularly preferably 95 parts by mass or more. In 100 parts by mass in total of the polymer A, it is particularly preferable that the total amount of the polymer A1 and the polymer A2 is 100 parts by mass, that is, the polymer A consists of the polymer A1 and the polymer A2.

[0039] The content of the polymer A1 is not particularly limited, but from the viewpoints of good adhesive strength of the adhesive and suppression of adhesive residue, etc., in 100 parts by mass in total of the polymer A1 and the polymer A2, it is preferably 20 parts by mass or more, more preferably 25 to 95 parts by mass, and particularly preferably 30 to 90 parts by mass. The content of the polymer A2 is not particularly limited, but from the same viewpoints, in 100 parts by mass in total of the polymer A1 and the polymer A2, it is preferably 80 parts by mass or less, more preferably 5 to 75 parts by mass, and particularly preferably 10 to 70 parts by mass.

[0040] When the polymer A consists of, for example, the polymer A1 and the polymer A2, the content of the polymer A1 is not particularly limited, but from the viewpoint of obtaining an adhesive having a good balance between the adhesive strength to the skin and the adhesive strength to the device, in 100 parts by mass in total of the polymer A1, the polymer A2, and the polymer B in the oxyalkylene polymer, it is preferably 10 to 45 parts by mass, more preferably 15 to 40 parts by mass, and particularly preferably 30 to 40 parts by mass. The content of polymer A2 is not particularly limited, but from the same perspective, in 100 parts by mass in total of polymer A1, polymer A2 and polymer B in the oxyalkylene polymer, it is preferably 15 to 50 parts by mass, more preferably 30 to 50 parts by mass, and particularly preferably 40 to 50 parts by mass. The content ratios of polymer A1, polymer A2 and polymer B are preferably, in descending order, polymer A2, polymer A1, polymer B.

[0041] The average content of EO units in polymer A is not particularly limited, but is preferably 0 to 80% by mass, more preferably 0 to 70% by mass, still more preferably 0 to 60% by mass, and particularly preferably 0 to 50% by mass. The average content of EO units in polymer A 13 can be determined by analyzing the monomer composition of the oxyalkylene chain in polymer A by C-NMR measurement. For example, when the oxyalkylene chain in polymer A consists of EO units and structural units based on propylene oxide (also referred to as "PO units"), the EO unit content can be calculated based on the area of the peak indicating the methylene group of the EO unit and the area of the peak indicating the methyl group of the PO unit. When polymer A consists of, for example, polymer A1 and polymer A2, the EO unit content for each of polymer A1 and polymer A2 is the same. Note that the average content of EO units in polymer A can be regarded as the value calculated from the blending amount of EO in the synthesis raw materials of polymer A. When polymer A consists of, for example, polymer A1 and polymer A2, the value obtained by weight-averaging the EO unit content of polymer A1 and the EO unit content of polymer A2 based on the composition ratio (blending amount) of polymer A1 and polymer A2 can be regarded as the EO unit content of polymer A.

[0042] The Mn of polymer A is not particularly limited, but from the viewpoints of good adhesiveness of the adhesive, suppression of adhesive residue, and formation of an adhesive layer having good flexibility, etc., it is preferably 1000 to 50000, more preferably 5000 to 30000, and particularly preferably 8000 to 25000. Although there is no particular limitation on the Mw / Mn (molecular weight distribution) of the polymer A, it is preferably close to 1, and a narrower molecular weight distribution is preferred from the viewpoint that the hydroxyl-terminated urethane prepolymer is less likely to have a high viscosity and the synthesis efficiency can be improved. Specifically, it is preferably 1.25 or less, more preferably 1.22 or less, and particularly preferably 1.20 or less. Although there is no particular limitation on the degree of unsaturation of the polymer A, from the viewpoints of good curability of the hydroxyl-terminated urethane prepolymer and suppression of adhesive residue, etc., it is preferably as close to 0 meq / g as possible, preferably 0.020 meq / g or less, more preferably 0.018 meq / g or less, and particularly preferably 0.015 meq / g or less. When the polymer A is composed of two or more oxyalkylene polymers, each oxyalkylene polymer preferably has an Mn, Mw / Mn, and degree of unsaturation within the above ranges.

[0043] There is no particular limitation on the method for synthesizing the polymer A. For example, it can be obtained by subjecting a initiator having two or more active hydrogens to ring-opening addition polymerization with a compound having a cyclic ether structure, preferably an alkylene oxide, in the presence of a catalyst. When the polymer A is composed of the polymer A1 and the polymer A2, a method can also be used in which a initiator having three active hydrogens and a initiator having two active hydrogens are used in combination to perform ring-opening addition polymerization of a compound having a cyclic ether structure to simultaneously produce the polymer A1 and the polymer A2. From the viewpoint of more accurately adjusting the blending amounts of the polymer A1 and the polymer A2, a method in which the polymer A1 obtained by subjecting a initiator having three active hydrogens to ring-opening addition polymerization with a compound having a cyclic ether structure and the polymer A2 obtained by subjecting a initiator having two active hydrogens to ring-opening addition polymerization with a compound having a cyclic ether structure are separately synthesized and then mixed is preferred.

[0044] The compound having a cyclic ether structure may be linear or branched. Although there is no particular limitation on the number of carbon atoms of the compound having a cyclic ether structure, it is preferably 2 to 14, more preferably 2 to 10, and particularly preferably 2 to 4. The compounds having a cyclic ether structure are not particularly limited, and examples thereof include ethylene oxide (EO), propylene oxide (PO), 1,2-butylene oxide, 2,3-butylene oxide, methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, hexyl glycidyl ether, and tetrahydrofuran. These may be used alone or in combination of two or more. Among these, EO and PO are preferred.

[0045] When two or more compounds having a cyclic ether structure are used in combination, in the polymer A, the sequences of oxyalkylene groups derived from each compound may be random or block.

[0046] Examples of the group having active hydrogen in the initiator include a hydroxyl group, a carboxy group, and an amino group having a hydrogen atom bonded to a nitrogen atom. These may be used alone or in combination of two or more. Among these, a hydroxyl group is preferred, and an alcoholic hydroxyl group is more preferred. Examples of the initiator having three hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol. These may be used alone or in combination of two or more. Examples of the initiator having two hydroxyl groups include ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. These may be used alone or in combination of two or more.

[0047] The number of active hydrogens in the initiator usually corresponds to the number of hydroxyl groups per molecule of the oxyalkylene polymer. The polymer A1 can be synthesized, for example, using glycerin as an initiator. Also, the polymer A2 can be synthesized, for example, using propylene glycol as an initiator. Note that the initiator as a synthesis raw material of the oxyalkylene polymer is 13By means of ¹³C-NMR measurement, the type and amount can be specified. When polymer A consists of polymer A1 and polymer A2, from the information on the type and amount of the initiator by ¹³C-NMR measurement of polymer A, the content ratio of oxyalkylene groups such as EO units and PO units bonded to each initiator is determined, and the ratio of polymer A1 and polymer A2 is determined. 13 From the information on the type and amount of the initiator by ¹³C-NMR measurement, the content ratio of oxyalkylene groups such as EO units and PO units bonded to each initiator is determined, and the ratio of polymer A1 and polymer A2 is determined.

[0048] Ring-opening addition polymerization can be carried out using known catalysts such as alkali catalysts such as potassium hydroxide, transition metal compound-porphyrin complex catalysts such as complexes obtained by reacting an organoaluminum compound and porphyrin, double metal cyanide complex catalysts, and catalysts composed of phosphazene compounds. Among these catalysts, a double metal cyanide complex (DMC) catalyst is preferred because an oxyalkylene polymer having a narrow molecular weight distribution and a relatively low viscosity is easily obtained. As the double metal cyanide complex, known compounds can be used, and for example, a zinc hexacyanocobaltate complex having tert-butanol as a ligand can be mentioned. The synthesis of an oxyalkylene polymer by ring-opening addition polymerization using a DMC catalyst can be carried out by a known method. For example, the production methods described in International Publication No. 2003 / 062301, International Publication No. 2004 / 067633, JP-A No. 2004-269776, JP-A No. 2005-15786, International Publication No. 2013 / 065802, JP-A No. 2015-10162, etc. can be applied.

[0049] --Oxyalkylene polymer B-- The oxyalkylene polymer B has one hydroxyl group per molecule. As the polymer B, one type of oxyalkylene polymer may be used alone, or two or more types of oxyalkylene polymers may be used. When the polymer B consists of two or more types of oxyalkylene polymers, the average number of hydroxyl groups per molecule of the polymer B is not particularly limited, but is preferably 0.1 to 1.0, more preferably 0.5 to 1.0, and particularly preferably 0.8 to 1.0. The number of hydroxyl groups of the polymer B is the same as that of the polymer A, 13It can be confirmed by specifying the type and amount of the initiator of the synthetic raw material through 13C-NMR measurement.

[0050] There is no particular limitation on the Mn of polymer B, but from the viewpoints of forming an adhesive layer having good flexibility, good adhesiveness of the adhesive, and suppression of glue residue, etc., it is preferably 4000 to 30000, more preferably 4500 to 25000, and particularly preferably 5000 to 20000. There is no particular limitation on the Mw / Mn of polymer B, but being close to 1 and having a narrow molecular weight distribution is preferable from the viewpoint that the hydroxyl-terminated urethane prepolymer is less likely to have a high viscosity and the synthesis efficiency can be improved. It is preferably less than 1.20, more preferably less than 1.13, and particularly preferably less than 1.10. Also, there is no particular limitation on the unsaturation of polymer B, but from the viewpoints of good curability of the hydroxyl-terminated urethane prepolymer and suppression of glue residue in the adhesive layer, etc., it is preferably 0.015 meq / g or less, more preferably 0.013 meq / g or less, and particularly preferably 0.010 meq / g or less, and the closer to 0 meq / g, the more preferable. When polymer B is composed of two or more oxyalkylene polymers, each oxyalkylene polymer preferably has an Mn, Mw / Mn, and unsaturation within the above ranges.

[0051] There is no particular limitation on the synthesis method of polymer B. For example, it can be obtained by subjecting an initiator having one active hydrogen to ring-opening addition polymerization with a compound having a cyclic ether structure, preferably an alkylene oxide, in the presence of a catalyst. The compound having a cyclic ether structure is the same as the description for polymer A. It is preferably PO alone or a combination of EO and PO.

[0052] There is no particular limitation on the average content of the EO unit of polymer B, but from the viewpoint of good balance between the adhesiveness to the skin and the adhesiveness to the device, and obtaining an adhesive with suppressed crystallinity, it is preferably 0 to 80% by mass, more preferably 0 to 60% by mass, and particularly preferably 0 to 50% by mass. The average content of EO units in polymer B is determined in the same manner as in the case of polymer A.

[0053] Examples of the group having active hydrogen in the initiator include the same ones as in the case of polymer A. These may be used alone or in combination of two or more. Among these, a hydroxyl group is preferable, and an alcoholic hydroxyl group is more preferable. As the initiator having one hydroxyl group, from the viewpoint of easy availability, etc., for example, monohydric alcohols having 2 to 4 carbon atoms such as n-propanol, isopropanol, n-butanol, sec-butanol, isobutanol, tert-butanol, etc. are preferably mentioned. These may be used alone or in combination of two or more. Among these, n-butanol, sec-butanol, isobutanol, and tert-butanol are preferable. The ring-opening addition polymerization can be carried out by a known method in the same manner as in the case of polymer A.

[0054] The content of polymer B is not particularly limited, but from the same viewpoint, in 100 parts by mass in total of polymer A1, polymer A2, and polymer B in the oxyalkylene polymer, it is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and particularly preferably 10 to 20 parts by mass.

[0055] -Diisocyanate compound- The diisocyanate compound used for the synthesis of the hydroxyl-terminated urethane prepolymer is an organic compound having two isocyanate groups in one molecule. The diisocyanate compound is not particularly limited, and examples include aliphatic diisocyanate compounds, alicyclic diisocyanate compounds, aromatic diisocyanate compounds, araliphatic diisocyanate compounds, etc. These may be used alone or in combination of two or more.

[0056] The aliphatic diisocyanate compound may be either linear or branched. There is no particular limitation on the aliphatic diisocyanate compound. For example, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate can be mentioned. These may be used alone or in combination of two or more. There is no particular limitation on the alicyclic diisocyanate compound. For example, isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane can be mentioned. These may be used alone or in combination of two or more. There is no particular limitation on the aromatic diisocyanate compound. For example, tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate can be mentioned. These may be used alone or in combination of two or more. There is no particular limitation on the aromatic aliphatic diisocyanate compound. For example, xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI) can be mentioned. These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining a good curability of the hydroxyl group-terminated urethane prepolymer and an adhesive layer having good flexibility, HDI, IPDI, HMDI, and TMXDI are preferable, and HDI is more preferable.

[0057] Further, as the diisocyanate compound, a bifunctional isocyanate-terminated urethane prepolymer obtained by previously reacting the above-described diisocyanate compound with a diol (for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, etc.) can also be used.

[0058] -Tin-free catalyst- A tin-free catalyst is a urethanization catalyst that does not contain tin. From the viewpoint of obtaining an adhesive with low toxicity and being gentle to the skin, it is preferable that the adhesive does not contain tin and tin compounds.

[0059] The tin-free catalyst is not particularly limited, and examples thereof include a tertiary amine catalyst and an organometallic catalyst containing a metal other than tin. These may be used alone or in combination of two or more. Among these, from the viewpoint of a better reaction promoting effect, an organometallic catalyst is preferable. The metal contained in the organometallic catalyst containing a metal other than tin is not particularly limited, and examples thereof include zinc, bismuth, titanium, lead, iron, cobalt, and zirconium. These may be used alone or in combination of two or more. Among these, from the viewpoints of low toxicity to the skin and ease of handling, zinc and bismuth are preferable, and zinc is more preferable.

[0060] The tertiary amine catalyst is not particularly limited, and examples thereof include triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), etc. These may be used alone or in combination of two or more. The organometallic catalysts containing metals other than tin are not particularly limited. For example, zinc carboxylates such as zinc naphthenate and zinc 2-ethylhexanoate, zinc compounds such as zinc acetylacetonate; bismuth compounds such as bismuth 2-ethylhexanoate and bismuth neodecanoate; titanium compounds such as dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zirconium compounds such as zirconium naphthenate. These may be used alone or in combination of two or more.

[0061] The amount of the tin-free catalyst used in the reaction of the oxyalkylene polymer and the diisocyanate compound is not particularly limited. However, from the viewpoints of good reaction acceleration effect and reduction of the residual amount of the metal component, it is preferably more than 0.001 part by mass and less than 0.05 part by mass, more preferably 0.005 to 0.045 part by mass, and particularly preferably 0.01 to 0.04 part by mass with respect to 100 parts by mass of the oxyalkylene polymer.

[0062] The method for producing the hydroxyl-terminated urethane prepolymer is not particularly limited. For example, there are a method of charging the oxyalkylene polymer, the diisocyanate compound, the catalyst, and the solvent into the reaction vessel all at once; a method of post-adding the diisocyanate compound to the reaction vessel charged with the oxyalkylene polymer, the catalyst, and the solvent by dropping or the like; and the like. From the viewpoint of easy control of the molecular weight distribution of the hydroxyl-terminated urethane prepolymer by the preferential reaction of the low-molecular components in the synthesis raw materials, the method of post-adding the diisocyanate compound is preferred as the method for producing the hydroxyl-terminated urethane prepolymer.

[0063] The solvent used for producing the hydroxyl-terminated urethane prepolymer is not particularly limited, and examples thereof include ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; aromatic hydrocarbons such as toluene and xylene; and the like. These may be used alone or in combination of two or more. When a solvent is used in the production of the hydroxyl-terminated urethane prepolymer, the amount used is not particularly limited. However, from the viewpoints of the uniformity of the reaction system and the synthesis efficiency, it is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and particularly preferably 80 to 300 parts by mass with respect to 100 parts by mass in total of the oxyalkylene polymer.

[0064] The isocyanate index in the production of the hydroxyl-terminated urethane prepolymer (reaction of the oxyalkylene polymer and the diisocyanate compound) is not particularly limited. However, from the viewpoint of efficiently obtaining a hydroxyl-terminated urethane prepolymer with an appropriate molecular chain length, it is preferably less than 100, more preferably 30 to 95, and particularly preferably 50 to 95.

[0065] The reaction temperature in the production of the hydroxyl-terminated urethane prepolymer is not particularly limited. However, from the viewpoints of promoting the urethanization reaction and suppressing side reactions, it is preferably less than 100 °C, more preferably 70 to 95 °C, and particularly preferably 75 to 90 °C. After completion of the reaction, a reaction terminator such as acetylacetone may be added to deactivate the catalyst.

[0066] The average number of hydroxyl groups per molecule of the hydroxyl-terminated urethane prepolymer is not particularly limited. However, from the viewpoint of obtaining an adhesive having a good balance between the adhesion to the skin and the adhesion to the device, it is preferably less than 3.0, more preferably 1.7 to 2.9, and particularly preferably 1.8 to 2.5.

[0067] <<Polyisocyanate Compound>> The polyisocyanate compound is a curing agent for the hydroxyl-terminated urethane prepolymer. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and may be used alone or in combination of two or more kinds. From the viewpoints of easy availability and reactivity, etc., diisocyanate compounds are preferred as the polyisocyanate compound. Also, from the viewpoints of good adhesive strength of the adhesive and suppression of adhesive residue, etc., polyisocyanate compounds having three or more isocyanate groups in one molecule are preferred.

[0068] Specific examples of the diisocyanate compound include the same ones as the specific examples of the diisocyanate compound constituting the above-mentioned hydroxyl group-terminated urethane prepolymer. These may be used alone or in combination of two or more kinds. Examples of the polyisocyanate compound having three or more isocyanate groups in one molecule include, for example, isocyanurate-modified products, biuret-modified products, allophanate-modified products which are derivatives of the above-mentioned diisocyanate compounds, and trifunctional or higher-functional isocyanate group-terminated urethane prepolymers (adducts) which are reaction products of a diisocyanate compound and a polyol having three or more hydroxyl groups in one molecule (for example, trimethylolpropane). These may be used alone or in combination of two or more kinds.

[0069] <<Adhesion-imparting resin>> There is no particular limitation on the adhesion-imparting resin, and examples thereof include rosin-based adhesion-imparting resins, terpene-based adhesion-imparting resins, alicyclic saturated hydrocarbon-based adhesion-imparting resins, styrene-based adhesion-imparting resins, acrylic-based adhesion-imparting resins, etc. These may be used alone or in combination of two or more kinds. Among these, styrene-based adhesion-imparting resins are preferred from the viewpoint of less coloring of the adhesive.

[0070] In the tackifier resin, it may contain one or both of a tackifier resin having a softening point of 70°C or higher and a tackifier resin having a softening point of less than 70°C, but it is preferably contained a tackifier resin having a softening point of 70°C or higher, and it is also preferable that it is a tackifier resin having a softening point of 70°C or higher. By containing a tackifier resin having a softening point of 70°C or higher, an adhesive having sufficient adhesive force and being suppressed from remaining on the skin when peeled off from the skin can be easily obtained.

[0071] Also, in the adhesive composition, either a tackifier resin having a hydroxyl group or a tackifier resin having no hydroxyl group can be preferably contained, but from the viewpoint of moderately suppressing the adhesive force to the skin and further improving the water resistance, a tackifier resin having no hydroxyl group can be preferably used. The adhesive composition may not contain a tackifier resin having no hydroxyl group.

[0072] -Rosin-based tackifier resin- The rosin-based tackifier resin is not particularly limited. For example, unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; modified rosin obtained by hydrogenating, disproportionating, polymerizing, etc. these unmodified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same applies hereinafter); other various rosin derivatives; and the like. These may be used alone or in combination of two or more. The rosin derivative is not particularly limited. For example, rosin esters such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin), those obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxy groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins such as unmodified rosin, modified rosin, various rosin derivatives (especially rosin esters); rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) in the presence of an acid catalyst and subjecting them to thermal polymerization; and the like. These may be used alone or in combination of two or more. Among these, rosin esters are preferred.

[0073] For rosin-based tackifying resins, commercially available products can be used. For example, "HARIESTER TF", "HARIESTER S", "NEOTALL G2", "NEOTALL 101N", "NEOTALL 125HK", "HARITACK 8LJA", "HARITACK ER95", "HARITACK SE10", "HARITACK PH", "HARITACK F85", "HARITACK F105", "HARITACK FK100", "HARITACK FK125", "HARITACK PCJ" manufactured by Harima Kasei Co., Ltd.; "Foral 105-E", "Foral 85-E", "Foral AX-E" manufactured by Eastman Chemical Company; "Super Ester A-75", "Super Ester A-100", "Super Ester A-115", "Super Ester A-125", "Pencil A", "Pencil AZ", "Pencil C", "Pencil D-125", "Pink Crystal KE-100", "Pink Crystal KE-311", "Pink Crystal KE-359", "Pink Crystal KE-604", "Pink Crystal KR-140" manufactured by Arakawa Chemical Industries, Ltd.; "KF382S", "KF392S", "KF364", "KF384S", "KF394S", "KF398S", "KF399S", "KF452S", "KF462S", "KF454S", "KF464S", "KP120", "KP130", "KP140", "KP150", "K107", "K108", etc. manufactured by GUANGDONG KOMO Co., Ltd. can be mentioned.

[0074] -Terpene-based tackifying resin- There are no particular restrictions on terpene-based tackifying resins. For example, terpene resins such as α-pinene polymers, β-pinene polymers, dipentene polymers; modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.); and the like can be mentioned. The above-mentioned modified terpene resin is not particularly limited. For example, terpene-modified phenol resin, aromatic-modified terpene resin (such as styrene-modified terpene resin, etc.), hydrogenated terpene resin, etc. may be mentioned. These may be used alone or in combination of two or more. Among these, aromatic-modified terpene resin is preferred.

[0075] As the terpene-based tackifying resin, commercially available products can be used. For example, YS Resin TO125 (manufactured by Yasuhara Chemical Co., Ltd.), YS Resin TH130 (manufactured by Yasuhara Chemical Co., Ltd.), Alcon M115 (manufactured by Arakawa Chemical Industries, Ltd.), etc. may be mentioned.

[0076] -Hydrocarbon-based tackifying resin- The hydrocarbon-based tackifying resin is not particularly limited. For example, aliphatic (C5-based) petroleum resin, aromatic (C9-based) petroleum resin, aliphatic / aromatic copolymer (C5 / C9-based) petroleum resin, hydrogenated products thereof (for example, alicyclic petroleum resin (alicyclic saturated hydrocarbon resin) obtained by hydrogenating aromatic petroleum resin), various modified products thereof (for example, maleic anhydride-modified product), coumarone resin, coumarone-indene resin, etc., various hydrocarbon-based resins may be mentioned. These may be used alone or in combination of two or more. Among these, alicyclic saturated hydrocarbon resin is preferred.

[0077] -Styrene-based tackifying resin- The styrene-based tackifying resin is not particularly limited. For example, styrene homopolymer, α-methylstyrene homopolymer, α-methylstyrene / styrene copolymer, styrene / aliphatic copolymer, α-methylstyrene / styrene / aliphatic copolymer, C9-based petroleum resin, C5 / C9-based petroleum resin, phenol-modified styrene resin, and hydrogenated products thereof, etc. may be mentioned. These may be used alone or in combination of two or more.

[0078] Among these, from the viewpoint of excellent compatibility with (meth)acrylic block copolymers, styrene homopolymer, α-methylstyrene homopolymer, α-methylstyrene / styrene copolymer, styrene / aliphatic polymer, α-methylstyrene / styrene / aliphatic copolymer, phenol-modified styrene resin, and their partially hydrogenated products are preferred, styrene homopolymer, α-methylstyrene homopolymer, α-methylstyrene / styrene copolymer, and their partially hydrogenated products are more preferred, and styrene homopolymer is particularly preferred.

[0079] As the styrene-based tackifying resin, commercially available products can be used. For example, "SYLVARES SA-85", "SYLVARES SA-100", "SYLVARES SA-120", "SYLVARES SA-140", "SYLVARES 520" manufactured by Arizona Chemical; "Escorez ECR-213", "Escorez ECR-807" manufactured by ExxonMobil; "YS Resin SX100" manufactured by Yasuhara Chemical; "FTR0100", "FTR2120", "FTR2140", "FTR6100", "FTR6110", "FTR6125", "FTR7100", "FTR8100", "FTR8120", "FMR0150" manufactured by Mitsui Chemicals; "Kristalex F85", "Kristalex F100", "Kristalex F115", "Kristalex 1120", "Kristalex 3070", "Kristalex 3085", "Kristalex 3100", "Kristalex 5140", etc. manufactured by Eastman Chemical.

[0080] -Acrylic tackifying resin- The acrylic tackifying resin is not particularly limited. For example, acrylic tackifying resins based on acrylic polymers (homopolymers or copolymers) using one or more of (meth)acrylic acid alkyl esters as monomer components can be mentioned. These may be used alone or in combination of two or more. Specific examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid methyl, (meth)acrylic acid ethyl, (meth)acrylic acid propyl, (meth)acrylic acid isopropyl, (meth)acrylic acid butyl, (meth)acrylic acid isobutyl, (meth)acrylic acid s-butyl, (meth)acrylic acid t-butyl, (meth)acrylic acid pentyl, (meth)acrylic acid hexyl, (meth)acrylic acid heptyl, (meth)acrylic acid octyl, (meth)acrylic acid 2-ethylhexyl, (meth)acrylic acid isooctyl, (meth)acrylic acid nonyl, (meth)acrylic acid isononyl, (meth)acrylic acid decyl, (meth)acrylic acid isodecyl, (meth)acrylic acid undecyl, (meth)acrylic acid dodecyl, (meth)acrylic acid tridecyl, (meth)acrylic acid tetradecyl, (meth)acrylic acid pentadecyl, (meth)acrylic acid hexadecyl, (meth)acrylic acid heptadecyl, (meth)acrylic acid octadecyl, (meth)acrylic acid nonadecyl, (meth)acrylic acid eicosyl, and other (meth)acrylic acid C1-20 alkyl esters. These may be used alone or in combination of two or more. Among these, (meth)acrylic acid alkyl esters having a linear or branched alkyl group with 4 to 18 carbon atoms can be preferably used.

[0081] The above acrylic polymer may contain, if necessary, units corresponding to other monomer components copolymerizable with the above (meth)acrylic acid alkyl ester.

[0082] The content of the tackifier resin with respect to the solid content of the adhesive composition is not particularly limited, but is preferably 10 to 70% by mass, more preferably 10 to 65% by mass, and particularly preferably 15 to 60% by mass. When the content of the tackifier resin with respect to the solid content of the adhesive composition is at least the lower limit value, the adhesive force to the adherend can be increased. When the content of the tackifier resin with respect to the solid content of the adhesive composition is at most the upper limit value, the damage to the skin can be reduced.

[0083] The content of the tackifier resin with respect to 100 parts by mass of the hydroxyl-terminated urethane prepolymer is not particularly limited. However, from the viewpoint of obtaining an adhesive having sufficient adhesive strength to the device and the encapsulant and sufficient long-term water resistance, it is preferably 0.5 to 150 parts by mass, more preferably 1.0 to 120 parts by mass, still more preferably 3.0 to 100 parts by mass, and particularly preferably 5.0 to 80 parts by mass.

[0084] The softening point of the tackifier resin is not particularly limited. However, from the viewpoint of improving the cohesive force and the adhesion to the adherend, it is preferably 80 to 200 °C, more preferably 100 to 180 °C, still more preferably 135 to 180 °C, and particularly preferably 140 to 180 °C. The softening point of the tackifier resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207:2006.

[0085] As the tackifier resin, a "low hydroxyl value resin" which is a tackifier resin having a hydroxyl value of less than 30 mgKOH / g can be used. The hydroxyl value of the low hydroxyl value resin is not particularly limited, and it may be 20 mgKOH / g or less, 15 mgKOH / g or less, 10 mgKOH / g or less, or substantially 0 mgKOH / g.

[0086] As the tackifier resin, a "high hydroxyl value resin" which is a tackifier resin having a hydroxyl value of 30 mgKOH / g or more can be used. The hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoints of compatibility with polyester-based polymers and durability against low-polarity components, etc., it is preferably 50 to 200 mgKOH / g, more preferably 60 to 180 mgKOH / g, still more preferably 60 to 160 mgKOH / g or less, and particularly preferably 60 to 140 mgKOH / g or less.

[0087] As the value of the above hydroxyl value, the value measured by the potentiometric titration method specified in JIS K0070:1992 can be adopted. The specific measurement method is as shown below. - Method for Measuring Hydroxyl Value - 1. Reagents (1) As the acetylation reagent, take 12.5 g (11.8 mL) of acetic anhydride, add pyridine to it to make the total volume 50 mL, and use the well-stirred one. Or, take 25 g (23.5 mL) of acetic anhydride, add pyridine to it to make the total volume 100 mL, and use the well-stirred one. (2) As the measurement reagent, use 0.5 mol / L potassium hydroxide ethanol solution. (3) In addition, prepare toluene, pyridine, ethanol and distilled water. 2. Operations (1) Weigh 2 g of the sample accurately and collect it in a flat-bottomed flask, add 5 mL of the acetylation reagent and 10 mL of pyridine, and attach an air-cooling tube. (2) After heating the above flask in a 100 °C bath for 70 minutes, let it cool, add 35 mL of toluene as a solvent from the upper part of the cooling tube, stir, then add 1 mL of distilled water and stir to decompose acetic anhydride. Heat it in the bath again for 10 minutes to complete the decomposition, and let it cool. (3) Wash the cooling tube with 5 mL of ethanol and remove it. Then, add 50 mL of pyridine as a solvent and stir. (4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole pipette. (5) Perform potentiometric titration with 0.5 mol / L potassium hydroxide ethanol solution. Take the inflection point of the obtained titration curve as the end point. (6) For the blank test, perform the above (1) - (5) without adding the sample. 3. Calculation Calculate the hydroxyl value according to the following formula. Hydroxyl value (mgKOH / g) = [(B - C) × f × 28.05] / S + D Here, B: The amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test, C: The amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the sample, f: The factor of 0.5 mol / L potassium hydroxide ethanol solution, S: The mass (g) of the sample, D: Acid value, 28.05: Half of the molecular weight of potassium hydroxide, which is 56.11, is as follows.

[0088] As the low hydroxyl value resin and the high hydroxyl value resin, those having the corresponding hydroxyl value among the various tackifier resins described above can be used. The low hydroxyl value resin and the high hydroxyl value resin can each be used alone or in combination of two or more.

[0089] <<Other Components>> The pressure-sensitive adhesive composition may contain other components in addition to the hydroxyl-terminated urethane prepolymer, the polyisocyanate compound, and the tackifier resin. Examples of other components include various additives such as plasticizers, antioxidants, antistatic agents, fillers, ultraviolet absorbers, light stabilizers, conductivity-imparting agents, and leveling agents. A solvent may also be included. The other components may be used alone or in combination of two or more, and can be blended in a content within a range that does not impair the effects of the present invention.

[0090] In the pressure-sensitive adhesive composition (excluding the solvent), the total content of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound is not particularly limited, but from the viewpoint of sufficiently exhibiting the effects of the present invention, it is preferably 30% by mass or more, more preferably 40% by mass or more, and particularly preferably 45% by mass or more.

[0091] In the pressure-sensitive adhesive composition (excluding the solvent), the total content of the hydroxyl-terminated urethane prepolymer, the polyisocyanate compound, and the optional tackifier resin is not particularly limited, but from the viewpoint of sufficiently exhibiting the effects of the present invention, it is preferably 85% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, and it is also preferable that it is 100% by mass.

[0092] Although there is no particular limitation on the content of the hydroxyl-terminated urethane prepolymer relative to the total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, from the viewpoint of fully exerting the effects of the present invention, it is preferably 70 to 98% by mass, more preferably 80 to 95% by mass, and particularly preferably 85 to 92% by mass.

[0093] Although there is no particular limitation on the content of the hydroxyl-terminated urethane prepolymer relative to the total of the hydroxyl-terminated urethane prepolymer, the polyisocyanate compound, and the optional tackifier resin, from the viewpoint of fully exerting the effects of the present invention, it is preferably 20 to 90% by mass, more preferably 30 to 85% by mass, and particularly preferably 40 to 80% by mass.

[0094] Although there is no particular limitation on the content of the polyisocyanate compound relative to the total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, from the viewpoint of fully exerting the effects of the present invention, it is preferably 2 to 30% by mass, more preferably 5 to 20% by mass, and particularly preferably 8 to 15% by mass.

[0095] Although there is no particular limitation on the content of the polyisocyanate compound relative to the total of the hydroxyl-terminated urethane prepolymer, the polyisocyanate compound, and the optional tackifier resin, from the viewpoint of fully exerting the effects of the present invention, it is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and particularly preferably 5 to 10% by mass.

[0096] Although there is no particular limitation on the content of the tackifier resin relative to the total of the hydroxyl-terminated urethane prepolymer, the polyisocyanate compound, and the optional tackifier resin, from the viewpoint of fully exerting the effects of the present invention, it is preferably 10 to 70% by mass, more preferably 10 to 65% by mass, and particularly preferably 15 to 60% by mass.

[0097] The plasticizer is not particularly limited and can be selected from the viewpoints of compatibility with other contained components and wettability of the adhesive layer to the adherend, etc. For example, fatty acid esters having 8 to 30 carbon atoms and phosphate esters can be mentioned. These may be used alone or in combination of two or more. The antioxidant is not particularly limited. For example, those contributing to suppression of thermal deterioration of the adhesive layer such as phenolic, amine-based, sulfur-based, and phosphorus-based antioxidants can be mentioned. These may be used alone or in combination of two or more. Among these, from the viewpoint of low toxicity to the skin, phenolic antioxidants are preferred. The antistatic agent is not particularly limited. For example, inorganic salts; ionic liquids containing imidazolium ions, pyridinium ions, ammonium ions, etc.; surfactants; etc., which contribute to suppression of damage to the circuit pattern due to electrostatic discharge can be mentioned. These may be used alone or in combination of two or more. The filler is not particularly limited. For example, talc, calcium carbonate, and titanium oxide can be mentioned. These may be used alone or in combination of two or more. The ultraviolet absorber is not particularly limited. For example, ultraviolet absorbers such as benzophenone-based, benzotriazole-based, salicylic acid-based, oxalic acid anilide-based, cyanoacrylate-based, and triazine-based ultraviolet absorbers can be mentioned. These may be used alone or in combination of two or more. The light stabilizer is not particularly limited. For example, hindered amine-based light stabilizers and ultraviolet stabilizers can be mentioned. These may be used alone or in combination of two or more. The conductivity-imparting agent is not particularly limited. For example, metal fine particles such as silver nanoparticles can be mentioned. These may be used alone or in combination of two or more. The leveling agent is not particularly limited. For example, polymer-based leveling agents such as acrylic-based, vinyl-based, silicone-based, and fluorine-based leveling agents can be mentioned. These may be used alone or in combination of two or more.

[0098] The method for producing the adhesive composition is a method in which an oxyalkylene polymer and a diisocyanate compound are reacted in the presence of a tin-free catalyst to obtain a hydroxyl-terminated urethane prepolymer, and the hydroxyl-terminated urethane prepolymer and a polyisocyanate compound are mixed to produce the adhesive composition. By reacting the hydroxyl-terminated urethane prepolymer with a polyisocyanate compound, a urethane-based adhesive can be suitably obtained. When mixing the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, an adhesion-imparting resin and other components that may be contained in the above-described adhesive composition may be mixed.

[0099] <Method for producing an adhesive layer> As one embodiment of the pressure-sensitive adhesive sheet of the present invention, as the pressure-sensitive adhesive layer, a urethane-based pressure-sensitive adhesive obtained by curing the above-described pressure-sensitive adhesive composition can be used. A urethane-based pressure-sensitive adhesive is obtained as a reaction product of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound in the pressure-sensitive adhesive composition. As will be described later, for example, by applying the pressure-sensitive adhesive composition onto a substrate and curing it, the urethane-based pressure-sensitive adhesive can be formed as a pressure-sensitive adhesive layer.

[0100] The above-described pressure-sensitive adhesive composition may be a one-component type in which the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound as a curing agent are premixed according to the usage mode of the pressure-sensitive adhesive layer, etc., or a two-component type composed of a first agent containing the hydroxyl-terminated urethane prepolymer and a second agent containing the polyisocyanate compound as a curing agent.

[0101] In the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, a catalyst and a solvent may be used as necessary. When using a catalyst, a urethanization catalyst which is the above-described tin-free catalyst can be used. It may be the same as or different from the one used in the synthesis of the hydroxyl-terminated urethane prepolymer. When the catalyst used in the synthesis of the hydroxyl-terminated urethane prepolymer remains, the remaining catalyst can also exhibit a catalytic action in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound. When adding a catalyst during the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound, the addition amount is not particularly limited, but is preferably more than 0.001 part by mass and less than 0.05 part by mass, more preferably 0.005 to 0.045 part by mass, and particularly preferably 0.01 to 0.04 part by mass, based on 100 parts by mass in total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound. When a catalyst is added, it is preferable to add a reaction terminator after the reaction is completed to deactivate the catalyst.

[0102] Examples of the solvent used in the reaction between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound include the same ones as those in the synthesis of the above-described hydroxyl-terminated urethane prepolymer. It may be the same as or different from the one used in the synthesis of the hydroxyl-terminated urethane prepolymer. When the solvent used in the synthesis of the hydroxyl-terminated urethane prepolymer remains, it may be used as it is. When using a solvent, the usage amount is not particularly limited, but is preferably 50 to 500 parts by mass, more preferably 70 to 400 parts by mass, and particularly preferably 80 to 300 parts by mass, based on 100 parts by mass in total of the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound.

[0103] The reaction temperature between the hydroxyl-terminated urethane prepolymer and the polyisocyanate compound is not particularly limited, but from the viewpoints of promoting the urethanization reaction and suppressing side reactions, it is preferably less than 120 °C, more preferably 40 to 110 °C, and particularly preferably 50 to 100 °C.

[0104] The isocyanate index of the polyisocyanate compound to be reacted with the hydroxyl-terminated urethane prepolymer is not particularly limited, but is preferably more than 100, more preferably 101 to 1500, and particularly preferably 105 to 1000.

[0105] The formation of the pressure-sensitive adhesive layer is not particularly limited and can be carried out using known methods. For example, a method of applying a pressure-sensitive adhesive composition on a release liner, curing it to form a pressure-sensitive adhesive layer, and laminating a substrate; a method of applying a pressure-sensitive adhesive composition on a substrate, curing it to form a pressure-sensitive adhesive layer, and laminating a release liner; etc. can be mentioned. These may be used alone or in combination of two or more. A method (direct method) of directly applying (for example, coating) a pressure-sensitive adhesive composition to a non-peelable substrate and drying it to form a pressure-sensitive adhesive layer can be adopted. Also, a method (transfer method) of applying a pressure-sensitive adhesive composition to a surface having peelability (peel surface), drying it to form a pressure-sensitive adhesive layer on the surface (peel surface), and transferring the pressure-sensitive adhesive layer to a non-peelable substrate may be adopted. From the viewpoint of productivity, the transfer method is preferred. In the configuration of a substrate-free type, a pressure-sensitive adhesive composition is applied to a surface having peelability (peel surface) and dried, and if necessary, a release liner is placed on the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer. As the above peel surface, the surface of a release liner, the back surface of a substrate subjected to peeling treatment, etc. can be used. The pressure-sensitive adhesive layer disclosed here is typically formed continuously, but is not limited to such a form, and may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a stripe shape. The coating method of the pressure-sensitive adhesive composition is not particularly limited, and for example, known methods such as bar coating, knife coating, roll coating, blade coating, die coating, microgravure coating, comma coating, slot die coating, lip coating, and cast coating can be applied. These may be used alone or in combination of two or more. After coating, in order to sufficiently volatilize the solvent contained in the pressure-sensitive adhesive composition, for example, it is preferable to form the pressure-sensitive adhesive layer by drying with hot air at 40 to 80°C and curing.

[0106] It is preferable to perform a crosslinking treatment on the pressure-sensitive adhesive layer in order to impart appropriate cohesive force. As the crosslinking treatment, there are physical crosslinking by irradiation with ionizing radiation such as electron beams, γ-rays, and X-rays, and chemical crosslinking with a crosslinking agent. However, from the viewpoint of performing crosslinking with good handleability and reproducibility, it is preferable to perform chemical crosslinking treatment with a crosslinking agent. For example, a crosslinking agent is added to the pressure-sensitive adhesive composition containing the material constituting the pressure-sensitive adhesive layer, and crosslinking treatment is performed by heat treatment. As such a crosslinking agent, a crosslinking agent used in crosslinking treatment such as an isocyanate-based crosslinking agent, a peroxide-based crosslinking agent, and a metal chelate-based crosslinking agent can be used.

[0107] The pressure-sensitive adhesive layer subjected to the crosslinking treatment as described above maintains an appropriate balance between skin adhesiveness and cohesiveness depending on the degree of crosslinking. However, the molecular weight and molecular weight distribution of the urethane-based pressure-sensitive adhesive also affect these adjustments.

[0108] <Base material> In the aspect where the adhesive sheet is an adhesive sheet with a base material of single-sided adhesive type or double-sided adhesive type, the base material that supports (backs) the pressure-sensitive adhesive layer is not particularly limited. For example, resin films, papers, cloths, rubber sheets, foam sheets, metal foils, composites thereof, etc. may be mentioned. These may be used alone or in combination of two or more.

[0109] The surface of the base material (the surface on the pressure-sensitive adhesive layer side) may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer. The surface treatment can improve the adhesion between the base material and the pressure-sensitive adhesive layer (that is, the anchoring property of the pressure-sensitive adhesive layer to the base material).

[0110] The thickness of the base material is not particularly limited, but is preferably 2 to 1000 μm, more preferably 10 to 500 μm, and particularly preferably 20 to 200 μm.

[0111] The above resin film is a film mainly composed of a resin material (a component contained in the resin film in an amount exceeding 50% by mass). There is no particular limitation on the resin film. For example, polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; rubber films such as natural rubber film and butyl rubber film; etc. may be mentioned. These may be used alone or in combination of two or more. Among these, from the viewpoints of handleability and processability, polyester resin films are preferred, and PET films are more preferred. In this specification, the "resin film" is usually a non-porous sheet, which is a concept distinguished from so-called non-woven fabrics and woven fabrics (that is, a concept excluding non-woven fabrics and woven fabrics).

[0112] Various additives such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and plasticizers may be blended in the above resin film as necessary. There is no particular limitation on the blending ratio of the various additives, but it is preferably less than 30% by mass, more preferably less than 20% by mass, and particularly preferably less than 10% by mass.

[0113] The above resin film may have a single-layer structure or a multi-layer structure having two, three, or more layers. However, from the viewpoint of shape stability, the resin film preferably has a single-layer structure. When the above resin film has a multi-layer structure, at least one layer (preferably all layers) preferably has a continuous structure of the above resin (for example, a polyester resin). The manufacturing method of the resin film may appropriately adopt a conventionally known method. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, calendar roll molding, etc. can be appropriately adopted.

[0114] There is no particular limitation on the paper. For example, Japanese paper, kraft paper, glassine paper, high-quality paper, synthetic paper, top-coated paper, etc. can be mentioned. These may be used alone or in combination of two or more.

[0115] There is no particular limitation on the cloth. For example, woven fabrics, non-woven fabrics, etc. made of single or blended various fibrous substances can be mentioned. These may be used alone or in combination of two or more. There is no particular limitation on the fibrous substance. For example, cotton, silk, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. can be mentioned. These may be used alone or in combination of two or more. The non-woven fabric refers to a concept of non-woven fabric for adhesive sheets mainly used in the fields of adhesive tapes and other adhesive sheets, and refers to a non-woven fabric (sometimes also referred to as "paper") produced using a general paper-making machine.

[0116] There is no particular limitation on the rubber sheet. For example, natural rubber sheet, butyl rubber sheet, etc. can be mentioned. These may be used alone or in combination of two or more.

[0117] There is no particular limitation on the foam sheet. For example, foamed polyurethane sheet, foamed polychloroprene rubber sheet, etc. can be mentioned. These may be used alone or in combination of two or more.

[0118] There is no particular limitation on the metal foil. For example, aluminum foil, copper foil, etc. can be mentioned. These may be used alone or in combination of two or more.

[0119] <Release Liner> When forming the adhesive layer, producing the adhesive sheet, storing, distributing, and shaping the adhesive sheet before use, etc., a release liner can be used. Before using the adhesive sheet, the surface of the adhesive layer of the adhesive sheet is preferably covered with a release liner for protecting the surface of the adhesive layer. The release liner is appropriately peeled from the surface of the adhesive layer when the adhesive sheet is used. There is no particular limitation on the release liner. For example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper; a release liner made of a low-adhesion material such as a fluoropolymer (such as polytetrafluoroethylene) or a polyolefin resin (such as polyethylene or polypropylene); high-quality paper or glassine paper with a release agent such as a silicone resin or a fluororesin coated on the surface; parchment paper; a material obtained by coating a release agent such as a silicone resin or a fluororesin on the surface of high-quality paper with an anchor coat or polyethylene laminate by resin; a resin film having transparency such as a polyester film; etc. These may be used alone or in combination of two or more. There is no particular limitation on the thickness of the release liner. From the viewpoint of being able to protect the adhesive layer and being easily peeled off during use, it is preferably 5 to 200 μm, more preferably 10 to 100 μm, and particularly preferably 20 to 50 μm. There is no particular limitation on the release treatment layer. For example, it may be formed by surface-treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

[0120] Also, when the adhesive layer is formed only on one side of the substrate, the surface of the substrate where the adhesive layer is not formed is subjected to a release treatment, and the adhesive sheet is wound so that the adhesive layer is bonded to the surface of the substrate where the adhesive layer is not formed to protect the adhesive layer. Further, when the adhesive layer is formed on both sides of the substrate, after bonding one release treatment surface of a release liner having release treatment surfaces on both sides to one adhesive layer, the adhesive sheet may be wound so that the other release treatment surface of the release liner contacts the other adhesive layer to protect both adhesive layers.

[0121] [Portable electronic device] By attaching the above adhesive sheet to a portable electronic device, a portable electronic device equipped with the above adhesive sheet can be obtained. The portable electronic device is not particularly limited. For example, mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear type worn on the wrist like a wristwatch, modular type worn on a part of the body with a clip or strap, etc., eyewear type including glasses type (monocular or binocular, including head-mounted type), clothing type attached to a shirt, socks, hat, etc. in the form of an accessory, earwear type attached to the ear like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), computers (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. These may be used alone or in combination of two or more. The portable devices other than portable electronic devices are not particularly limited. For example, mechanical wristwatches or pocket watches, pocket lights, hand mirrors, pill cases, etc. These may be used alone or in combination of two or more. The adhesive sheet of the present invention may be applied to portable devices other than portable electronic devices. In this specification, "portable" does not simply mean that it can be carried, but means having a level of portability that an individual (standard adult) can relatively easily carry. [Examples]

[0122] Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited by the following examples, and various modifications are possible without departing from the gist of the present invention. In the following, "parts" and "%" mean "parts by mass" and "mass%", respectively.

[0123] [Measurement method] The measurement methods of various physical properties in the following synthesis examples are as follows.

[0124] <Number-average molecular weight (Mn) and weight-average molecular weight (Mw)> Mn and Mw were measured by gel permeation chromatography (GPC) under the following measurement conditions (in terms of polystyrene conversion), and the molecular weight distribution (Mw / Mn) was calculated from these values. 〔Measurement conditions〕 · Equipment used: "HLC-8320GPC", manufactured by Tosoh Corporation · Column used: "TSKgel (registered trademark) SuperMultipore HZ-M", manufactured by Tosoh Corporation · Detector: Differential refractive index (RI) detector · Detection temperature: 40 °C · Eluent: Tetrahydrofuran · Flow rate: 0.350 mL / min · Sample concentration: 0.5 mass% · Sample injection volume: 10 μL · Standard sample: Polystyrene

[0125] <Ethylene oxide (EO) unit content> The EO unit content of each oxyalkylene polymer was regarded as the charged amount of EO in the oxyalkylene polymer based on the charged amounts of propylene oxide (PO) and EO used in the synthesis. The EO unit content of the hydroxyl-terminated urethane prepolymer was taken as the weighted average value of the EO unit contents in each component of the raw materials.

[0126] <Hydroxyl value> The hydroxyl value was determined in accordance with Method B (Potentiometric automatic titration method) of JIS K 1557-1:2007.

[0127] <Degree of unsaturation> The degree of unsaturation was measured in accordance with JIS K 1557-3:2007.

[0128] <Average number of hydroxyl groups per molecule of oxyalkylene polymer A> The value obtained by weight-averaging the number of hydroxyl groups per molecule of each of oxyalkylene polymers A1 and A2 used as oxyalkylene polymer A (the number of hydroxyl groups per molecule of the initiator used in the synthesis of each oxyalkylene polymer) based on the blending amount of each oxyalkylene polymer was defined as the average number of hydroxyl groups per molecule of oxyalkylene polymer A.

[0129] <Average number of hydroxyl groups per molecule of hydroxyl-terminated urethane prepolymer> The value obtained by weight-averaging the number of hydroxyl groups per molecule of each oxyalkylene polymer (oxyalkylene polymers A1, A2, and B) used in the synthesis of the hydroxyl-terminated urethane prepolymer based on the blending amount of each oxyalkylene polymer was regarded as the average number of hydroxyl groups per molecule of the hydroxyl-terminated urethane prepolymer.

[0130] [Substances used] Details of the substances used in the following synthesis examples and examples are shown below. · TBA-DMC catalyst: Zinc hexacyanocobaltate complex with tert-butanol as a ligand · Glycerin · Propylene glycol · n-Butanol · Propylene oxide (PO) · Ethylene oxide (EO) · Adsorbent: Synthetic magnesium silicate; "Kyoward (registered trademark) 600S", manufactured by Kyowa Chemical Industry Co., Ltd. · Urethanization catalyst: Zinc (Zn)-containing urethanization catalyst (zinc carboxylate); "K-KAT XK627", manufactured by KING INDUSTRIES · Diisocyanate compound: Hexamethylene diisocyanate (HDI), "Durate (registered trademark) 50M-HDI", manufactured by Asahi Kasei Corporation · Toluene · Ethyl acetate · Curing agent (polyisocyanate compound): HDI-based polyisocyanate, "Durate E402-80B", manufactured by Asahi Kasei Corporation; solid content 80% by mass · Adhesion-imparting resin: α-methylstyrene resin (manufactured by Arizona Chemical, trade name "SYLVARES SA-140", softening point 137°C)

[0131] [Synthesis of oxyalkylene polymer] (Synthesis Example 1-1) Into a pressure-resistant container, 1000 g of glycerin as an initiator and a TBA-DMC catalyst (metal concentration 46 mass ppm) were charged. After purging the inside of the container with nitrogen, while stirring the reaction solution, it was heated to 135°C, and 120 g of propylene oxide (PO) was added and reacted. After the temperature rise of the reaction solution stopped, it was cooled to 135°C. While stirring the reaction solution, 3782.4 g of PO and 945.6 g of ethylene oxide (EO) were added to the container. After confirming that the internal pressure change had disappeared, an adsorbent was added, and neutralization and removal of the catalyst were carried out to obtain oxyalkylene polymer 1-1, which is polymer A1.

[0132] (Synthesis Example 1-2) In Synthesis Example 1-1, the initiator was changed from glycerin to propylene glycol, and otherwise in the same manner as Synthesis Example 1-1, oxyalkylene polymer 1-2, which is polymer A2, was synthesized.

[0133] (Synthesis Example 1-3) In Synthesis Example 1-1, except for not adding EO, in the same manner as Synthesis Example 1-1, oxyalkylene polymer 1-3, which is polymer A1, was synthesized.

[0134] (Synthesis Example 1-4) In Synthesis Example 1-2, except for not adding EO, in the same manner as Synthesis Example 1-2, oxyalkylene polymer 1-4, which is polymer A2, was synthesized.

[0135] (Synthesis Example 1-5) In Synthesis Example 1-1, the initiator was changed from glycerin to n-butanol. After cooling the reaction solution, EO was not added, 2364 g of PO was added, and otherwise in the same manner as Synthesis Example 1-1, oxyalkylene polymer 1-5, which is polymer B, was synthesized. Table 1 shows various physical properties of oxyalkylene polymers 1-1 to 1-5.

[0136] [Table 1]

[0137] [Synthesis of Hydroxyl-Terminated Urethane Prepolymer] (Synthesis Example 2-1) Into a reaction vessel equipped with a thermometer, a stirrer, and a condenser, 36.0 parts by mass of oxyalkylene polymer 1-1, 48.0 parts by mass of oxyalkylene polymer 1-2, 16.0 parts by mass of oxyalkylene polymer 1-5, 50.6 parts by mass of toluene, and 50.6 parts by mass of ethyl acetate were charged. 0.038 parts by mass of a zinc (Zn)-containing urethanization catalyst was added, and the mixture was mixed at 40°C. Then, 1.7 parts by mass of HDI (isocyanate index 85) was added, and the reaction was carried out at 80°C. The average number of hydroxyl groups per molecule of the blended oxyalkylene polymer A (oxyalkylene polymers A1 and A2) was 2.4, and the average number of hydroxyl groups per molecule of the oxyalkylene polymer (oxyalkylene polymers A1, A2, and B) was 2.2. While appropriately diluting with ethyl acetate, the mixture was maintained at 80°C and reacted for 7 hours to obtain a 50% by mass transparent solution of hydroxyl-terminated urethane prepolymer U1 (average number of hydroxyl groups per molecule of the oxyalkylene polymer (oxyalkylene polymers A1, A2, and B): 2.2, EO unit content: 16.5% by mass).

[0138] (Synthesis Example 2-2) Using the composition shown in Table 2, a solution of hydroxyl-terminated urethane prepolymer U2 was produced in the same manner as in Synthesis Example 2-1. The average number of hydroxyl groups per molecule of the oxyalkylene polymer (oxyalkylene polymers A1, A2, and B) of hydroxyl-terminated urethane prepolymer U2 was 2.2, and the EO unit content was 7.0%.

[0139] Table 2 shows the composition of the oxyalkylene polymer, diisocyanate compound, and catalyst in Synthesis Examples 2-1 to 2-2.

[0140]

Table 2

[0141] [Manufacture of the Adhesive Sheet for Evaluation] (Example 1) To a liquid mixture of 90 parts by mass of a 50% by mass solution of a hydroxyl-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent, 10 parts by mass of an α-methylstyrene resin was added and stirred to prepare an adhesive composition according to each example. The adhesive composition was applied to the release surface of a 38-μm-thick polyester release film (trade name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 25 μm. To this adhesive layer, the release surface of a 25-μm-thick polyester release film (trade name "Diafoil MRF", thickness 25 μm, manufactured by Mitsubishi Polyester Co., Ltd.) was laminated. Then, aging was carried out at 50°C for 96 hours. In this way, a base material-less double-sided adhesive sheet with a thickness of 25 μm, whose both sides were protected by the above two release films, was obtained.

[0142] (Examples 2 to 4) Adhesive sheets of Examples 2 to 4 were produced in the same manner as in Example 1, except that the composition of the adhesive composition was changed to the composition shown in Table 3.

[0143] (Example 5) An adhesive sheet of Example 5 was produced in the same manner as in Example 1, except that the hydroxyl-terminated urethane prepolymer U1 was changed to a hydroxyl-terminated urethane prepolymer U2.

[0144] (Example 6) An adhesive sheet of Example 6 was produced in the same manner as in Example 3, except that a liquid mixture of 100 parts by mass of a 50% by mass solution of a hydroxyl-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent (urethane adhesive composition) was changed to an acrylic adhesive solution (acrylic adhesive composition) prepared as follows. To 100 parts by mass of an acrylic copolymer (a copolymer consisting of 65 parts by mass of isononyl acrylate, 30 parts by mass of 2-methoxyethyl acrylate, and 5 parts by mass of acrylic acid), 20 parts by mass of glyceryl tricaprylate, 10 parts by mass of rosin esters (trade name: Haritack PCJ, manufactured by Harima Kasei Co., Ltd.) as a tackifier, and 0.07 parts by mass of a trifunctional isocyanate compound (trade name: Coronate HL, manufactured by Tosoh Corporation) as a crosslinking agent were blended in toluene to prepare a uniform acrylic pressure-sensitive adhesive solution (solid content: 40% by mass). 100 parts by mass of the prepared acrylic pressure-sensitive adhesive solution was used as an acrylic pressure-sensitive adhesive composition.

[0145] (Example 7) A pressure-sensitive adhesive sheet of Example 7 was produced in the same manner as in Example 1, except that a liquid (urethane pressure-sensitive adhesive composition) obtained by mixing 100 parts by mass of a 50% by mass solution of a hydroxyl-terminated urethane prepolymer U1 and 5 parts by mass of a curing agent was changed to an acrylic pressure-sensitive adhesive solution (acrylic pressure-sensitive adhesive composition) prepared as follows. To 100 parts by mass of an acrylic copolymer (a copolymer consisting of 65 parts by mass of isononyl acrylate, 30 parts by mass of 2-methoxyethyl acrylate, and 5 parts by mass of acrylic acid), 20 parts by mass of glyceryl tricaprylate, 10 parts by mass of rosin esters (trade name: Haritack PCJ, manufactured by Harima Kasei Co., Ltd.) as a tackifier, and 0.07 parts by mass of a trifunctional isocyanate compound (trade name: Coronate HL, manufactured by Tosoh Corporation) as a crosslinking agent were blended in toluene to prepare a uniform acrylic pressure-sensitive adhesive solution (solid content: 40% by mass). 90 parts by mass of the prepared acrylic pressure-sensitive adhesive solution was used as an acrylic pressure-sensitive adhesive composition.

[0146] [Evaluation of Pressure-Sensitive Adhesive Sheet] For each of the pressure-sensitive adhesive sheets produced in the above examples, the following various evaluations were carried out. Table 3 shows the evaluation results. Examples 1 to 2 and 5 are examples, and Examples 3 to 4 and 6 to 7 are comparative examples.

[0147] [Adhesive Strength] (1) Against Phenolic Resin The surface side of the adhesive sheet (100 mm in length, 15 mm in width) from which the release film was peeled, on which the adhesive layer was formed, was overlapped with a phenolic resin plate ("Sumilite (registered trademark) PL-1102", manufactured by Sumitomo Bakelite Co., Ltd.; 125 mm in length, 30 mm in width, 2 mm in thickness). From the other surface side of the adhesive sheet on which the adhesive layer was formed and the release film was not peeled, it was reciprocated once with a rubber roller under a load of 2 kg and a speed of 300 mm / min to press-bond the adhesive layer to the phenolic resin plate. After standing for 20 minutes, the adhesive sheet was peeled off at a peeling angle of 90° and a speed of 300 mm / min, and the adhesive strength in the case where the adherend was a phenolic resin (against phenolic resin) was measured by a method according to JIS Z 0237:2009. Table 3 shows the average value of the three measurement values. Also, the measured adhesive strength was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3. <<Evaluation Criteria (against phenolic resin)>> A: 3.0 N / 15 mm or more B: 2.5 N / 15 mm or more and less than 3.0 N / 15 mm C: 2.0 N / 15 mm or more and less than 2.5 N / 15 mm D: Less than 2.0 N / 15 mm In the case of Evaluation A and B, it can be said that the adhesive strength against the phenolic resin plate, which is a typical material such as a sealing material for the circuit pattern of the wearable device, is sufficient. On the other hand, in the case of Evaluation C and D, the adhesive strength against the phenolic resin was insufficient.

[0148] (2) Against skin In the above (1) against phenolic resin, when the skin of the forearm of a human (3 subjects) was used as the adherend instead of the phenolic resin plate, the adhesive strength was measured in the same manner. The humans (3 subjects) were (1) gender: male, race: Japanese, age: in their 30s, (2) gender: male, race: Japanese, age: in their 20s, (3) gender: female, race: Japanese, age: in their 30s. Table 3 shows the average value of the three measurement values. Also, the measured adhesive strength was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3. <<Evaluation Criteria (against skin)>> A: 1.0 to 3.0 N / 15 mm B: More than 3.0 N / 15 mm and less than or equal to 5.0 N / 15 mm C: Less than 1.0 N / 15 mm D: More than 5.0 N / 15 mm In the case of Evaluation A, it can be said that the pain to the skin is less and the adhesion to the skin is more appropriate. In the case of Evaluation B, it can be said that the adhesion to the skin is appropriate and it is gentle to the skin. On the other hand, in the case of Evaluation C, the adhesion to the skin was insufficient. Also, in the case of Evaluation D, it was difficult to peel off from the skin and there was sometimes pain when peeling.

[0149] (3) Difference The difference (adhesion to phenolic resin - adhesion to skin) between the adhesion when the adherend is phenolic resin (against phenolic resin) and the adhesion when the adherend is the skin of the forearm of a human (3 subjects) (against skin) was calculated and shown in Table 3. Also, the calculated difference was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3. <<Evaluation Criteria (Difference)>> A: 2.5 N / 15 mm or more B: 1.8 N / 15 mm or more and less than 2.5 N / 15 mm C: 1.5 N / 15 mm or more and less than 1.8 N / 15 mm D: Less than 1.5 N / 15 mm In the case of Evaluations A and B, it can be said that the wearable device can be gently fixed to and removed from the skin. On the other hand, in the case of Evaluations C and D, it was difficult to stably fix the wearable device to the skin.

[0150] <Initial 90 - degree Peel Strength> Under the measurement environment of 23°C and 50% RH, a 50-μm-thick PET film is pasted on one adhesive layer of the substrate-free double-sided adhesive sheet for backing, and cut into a size of 5 mm in width and 100 mm in length to obtain an adhesive sheet test piece. Under the same environment, the other adhesive layer of the above adhesive sheet test piece is pressure-bonded to the surface of a stainless steel plate (SUS304BA plate) with a 2-kg roller for one round trip, and this is used as a measurement sample. The above measurement sample is cured for 30 minutes under the same environment. After further leaving it for 24 hours under the same environment, using a universal tensile-compression testing machine, in accordance with JIS Z 0237:2000, under the conditions of a tensile speed of 300 mm / min and a peeling angle of 90 degrees, the initial peeling strength [N / 5 mm] is measured. As the universal tensile-compression testing machine, the "Tensile-Compression Testing Machine, TG-1kN" manufactured by Minebea Co., Ltd. or its equivalent is used. In the case of a single-sided adhesive sheet, backing with a PET film is not required.

[0151] <Peeling strength after ethanol immersion> A measurement sample is obtained in the same manner as the measurement of the above initial 90-degree peeling strength, and this is cured for 30 minutes under the same environment. Next, under a room temperature (23°C) environment, the above measurement sample is immersed in a container containing ethanol for 24 hours. Then, the above measurement sample is taken out from the ethanol bath, and after gently wiping off the ethanol adhering to the surroundings with a dry cloth, the peeling strength [N / 5 mm] after ethanol immersion is measured in the same manner as the above initial 90-degree peeling strength measurement. The ratio (%) of the peeling strength [N / 5 mm] after ethanol immersion obtained to the above initial peeling strength [N / 5 mm] (peeling strength after ethanol immersion / initial peeling strength × 100) is calculated and evaluated according to the following evaluation criteria. <<Evaluation criteria>> A: 80% or more B: 60% or more and less than 80% C: 20% or more and less than 60% D: Less than 20% In the case of evaluation A and B, it can be said that the adhesion reliability after ethanol immersion is sufficient. On the other hand, in the case of evaluation C and D, the adhesion reliability after ethanol immersion was insufficient.

[0152] <Peeling strength after oleic acid immersion> A measurement sample is obtained by the same method as the measurement of the above-mentioned initial 90-degree peel strength, and this is cured for 30 minutes in the same environment. Then, in a room temperature (23°C) environment, the above measurement sample is immersed in a container containing oleic acid for 24 hours. Thereafter, the above measurement sample is taken out from the oleic acid bath, and the oleic acid adhering to the periphery is gently wiped off with a dry cloth, and then the peel strength [N / 5mm] after oleic acid immersion is measured by the same method as the above-mentioned initial 90-degree peel strength measurement. The ratio (%) of the peel strength [N / 5mm] after oleic acid immersion obtained to the above-mentioned initial peel strength [N / 5mm] (peel strength after oleic acid immersion / initial peel strength × 100) is calculated and evaluated according to the following evaluation criteria. <<Evaluation Criteria>> A: 80% or more B: 60% or more and less than 80% C: 20% or more and less than 60% D: Less than 20% In the case of evaluation A and B, it can be said that the adhesion reliability after oleic acid immersion is sufficient. On the other hand, in the case of evaluation C and D, the adhesion reliability after oleic acid immersion was insufficient.

[0153]

Table 3

[0154] As can be seen from the evaluation results shown in Table 3, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 2 and 5 had appropriate adhesiveness to the phenolic resin and adhesiveness to the skin. In addition, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 2 and 5 had a high adhesion retention rate after ethanol immersion. In addition, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 2 and 5 had a high adhesion retention rate after oleic acid immersion. Furthermore, Example 2 is more preferable than Examples 1 and 5 in that the "adhesion retention rate after ethanol immersion" is evaluated as "A".

Industrial Applicability

[0155] The pressure-sensitive adhesive sheet of the present invention can be preferably used, for example, for joining members of portable electronic devices. Portable electronic devices have many opportunities to come into contact with oils such as sebum, and may also come into contact with polar chemicals such as perfumes. Therefore, it is particularly meaningful to configure the sheet so that it can exhibit good durability not only against low-polarity components such as oils but also against polar chemicals.

[0156] The pressure-sensitive adhesive sheet of the present invention can sufficiently exhibit good adhesive reliability even when exposed to polar chemicals. The pressure-sensitive adhesive sheet of the present invention can be preferably used for fixing various members that can come into contact with oils. As a typical example of the use for fixing various members that can come into contact with oils, the use for fixing members in various portable electronic devices can be mentioned.

[0157] The pressure-sensitive adhesive sheet of the present invention is used for joining and fixing members of a portable electronic device with a touch panel. A portable electronic device with a touch panel includes a display unit / input unit (touch panel) in which the display unit also functions as an input unit, and the surface of the display unit / input unit is operated by the user directly touching it with a fingertip. Therefore, low-polarity components such as oils contained in secretions such as sebum and dirt on hands, chemicals such as cosmetics, hair styling products, moisturizing creams, and sunscreens, or foods are likely to adhere. In addition, it can also be exposed to polar chemicals containing a polar solvent (for example, ethanol) such as perfumes, insect repellent sprays, hand washing detergents, and antibacterial sheets. The effects of the pressure-sensitive adhesive sheet of the present invention can be preferably exhibited for portable electronic devices that have many opportunities to come into contact with low-polarity components and polar chemicals.

[0158] The pressure-sensitive adhesive sheet of the present invention (for example, a double-sided pressure-sensitive adhesive sheet) can be used for fixing members constituting a portable electronic device in the form of an adhesive material processed into various outer shapes. Among these, it can be preferably used for a portable electronic device having a liquid crystal display device. For example, in such a portable electronic device, it is suitable for uses such as joining a display unit (which may be the display unit of the liquid crystal display device) or a display unit protection member and a housing.

[0159] The bonding material preferably has a narrow-width portion with a width of 4.0 mm or less. Since the pressure-sensitive adhesive sheet of the present invention can be excellent not only in oil resistance but also in cohesive force, even when used as a bonding material having a shape (for example, a frame shape) including a narrow-width portion, the members can be fixed well.

[0160] The narrow-width portion is usually linear. Here, the term "linear" includes not only a straight line, a curve, a broken line (for example, an L-shape), etc., but also a concept including an annular shape such as a frame shape or a circular shape, and a composite or intermediate shape thereof. The above-mentioned annular shape is not limited to one formed by a curve, and includes, for example, an annular shape in which part or all is formed in a straight line, such as a shape along the outer periphery of a square (frame shape) or a shape along the outer periphery of a fan shape. The length of the narrow-width portion is not particularly limited. For example, when the length of the narrow-width portion is 10 mm or more, the effects of the present invention can be preferably exhibited.

Explanation of Reference Numerals

[0161] 10, 20, 30, 40, 50, 60 Pressure-sensitive adhesive sheet 100 Base material 100A One surface 100B The other surface 210, 220 Adhesive layer 210A Surface (adhesive surface) 210B Surface (adhesive surface) 310, 320 Release liner

Claims

1. An adhesive sheet comprising a cured product of an adhesive composition containing a hydroxyl-terminated urethane prepolymer and a polyisocyanate compound, wherein the adhesive force of the adhesive layer to the phenolic resin is 2.5 N / 15 mm or more, the adhesive force of the adhesive layer to the skin is 5.0 N / 15 mm or less, and the 90-degree peel strength of the adhesive layer after ethanol immersion is 50% or more of the 90-degree peel strength before ethanol immersion.

2. The adhesive sheet according to claim 1, wherein the adhesive layer has an average content of structural units based on ethylene oxide of 60% by mass or less.

3. The adhesive composition further contains an adhesion-imparting resin, and the content of the adhesion-imparting resin is 10 to 70% by mass based on the solid content of the adhesive composition. The adhesive sheet according to claim 1 or 2.

4. The adhesive sheet according to claim 1 or 2, wherein the adhesion-imparting resin is a styrene-based adhesion-imparting resin.

5. The adhesive sheet according to claim 1 or 2, wherein the adhesive composition has an average content of structural units based on ethylene oxide of 60% by mass or less.

6. The adhesive sheet according to claim 1 or 2, wherein the hydroxyl-terminated urethane prepolymer is a reaction product of an oxyalkylene polymer and a diisocyanate compound in the presence of a tin-free catalyst.

7. The adhesive sheet according to claim 6, wherein the tin-free catalyst contains at least one of zinc and bismuth.

8. The adhesive sheet according to claim 6, wherein the oxyalkylene polymer has an average content of structural units based on ethylene oxide of 60% by mass or less.

9. The adhesive sheet according to claim 6, wherein the oxyalkylene polymer has an average number of hydroxyl groups per molecule of 1.5 to 3.

0.

10. The adhesive sheet according to claim 6, wherein the oxyalkylene polymer contains an oxyalkylene polymer A having an average number of hydroxyl groups per molecule of 2.0 or more and an oxyalkylene polymer B having one hydroxyl group per molecule.

11. The adhesive sheet according to claim 10, wherein the oxyalkylene polymer A contains an oxyalkylene polymer A1 having three hydroxyl groups per molecule and an oxyalkylene polymer A2 having two hydroxyl groups per molecule.

12. A portable electronic device comprising the adhesive sheet according to claim 1 or 2.

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