Adhesive composition and adhesive sheet

Abstract

To provide an adhesive composition capable of forming an adhesive which achieves adhesiveness to a rough surface and high-temperature holding power and has good shelf life.SOLUTION: There is provided an adhesive composition which contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifier resin and a softening agent. In the adhesive composition, the tackifier resin includes a natural product-based tackifier resin (A) which has a softening point of more than 80°C and includes no aromatic ring and a petroleum-based tackifier resin (B) which has a softening point of more than 100°C and includes an aromatic ring. In addition, the content of the tackifier resin (A) is 40 to 120 pts.wt. based on 100 pts.wt. of the block copolymer. The content of the tackifier resin (B) is 5 to 40 pts.wt. based on 100 pts.wt. of the block copolymer. The total amount of the tackifier resins is 60 to 160 pts.wt based on 100 pts.wt. of the block copolymer. And, the content of the softening agent is 5 to 40 pts.wt. based on 100 pts.wt. of the block copolymer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition comprising a block copolymer (e.g., a styrene-based block copolymer) of a monovinyl-substituted aromatic compound and a conjugated diene compound. The present invention also relates to an adhesive sheet comprising an adhesive layer containing the above block copolymer. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) exhibit a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to a substrate under pressure. Taking advantage of this property, adhesives are widely used in various industrial fields, from home appliances to automobiles and office automation equipment, as a bonding method that is easy to work with and has high adhesive reliability. Typical compositions of such adhesives include compositions containing a polymer that exhibits rubber elasticity at room temperature and a tackifying resin. For example, Patent Documents 1 to 3 describe adhesives containing styrene-based block copolymers such as styrene-isoprene-styrene block copolymer and styrene-butadiene-styrene block copolymer, and a tackifying resin. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-164845 [Patent Document 2] Patent No. 3994510 [Patent Document 3] Patent No. 5864195 [Overview of the project] [Problems that the invention aims to solve]

[0004] Adhesives containing styrene-based block copolymers as described above generally tend to exhibit reduced properties at high temperatures (especially cohesiveness) compared to their adhesive properties at room temperature. For example, Patent Document 1 attempts to improve adhesive strength at high temperatures by combining a specific styrene-based elastomer with a specific tackifying resin, but does not consider high-temperature retention. Patent Document 2 evaluates heat resistance and retention using an adhesive containing styrene-isoprene-styrene block copolymer (SIS) and a C5 petroleum-based tackifying resin, but since the softening point of C5 petroleum-based tackifying resins is generally less than 110°C (Patent Document 2 uses a resin with a softening point of about 100°C), it is difficult to obtain sufficient high-temperature retention. Patent Document 3 also only considers compositions containing styrene-butadiene-styrene block copolymer (SBS) and a C5 petroleum-based tackifying resin, and, like Patent Document 2, sufficient high-temperature retention cannot be expected. The compositions proposed in Patent Documents 1 to 3 do not provide sufficient high-temperature retention, as shown in the comparative examples described later.

[0005] In adhesives containing styrene-based block copolymers, if the goal is to improve high-temperature retention, a relatively hard adhesive capable of exhibiting cohesive force even at high temperatures can be designed. However, such adhesives typically have weak tack, and their adhesion to rough surfaces, for example, tends to decrease. In other words, there is a trade-off between rough surface adhesion and high-temperature retention. Furthermore, among adhesive materials that can improve adhesion and retention in styrene-based block copolymers, some affect storage stability, thus limiting the selection of adhesive compositions.

[0006] The present invention was created in view of the above circumstances, and aims to provide an adhesive composition that can form an adhesive that achieves both rough surface adhesion and high temperature retention, as well as good storage properties. Another related objective is to provide an adhesive sheet that has a good balance of rough surface adhesion, high temperature retention, and storage properties. [Means for solving the problem]

[0007] This specification provides an adhesive composition comprising a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softening agent. In this adhesive composition, the tackifying resin comprises a natural product-based tackifying resin (A) having a softening point exceeding 80°C and not containing aromatic rings, and a petroleum-based tackifying resin (B) having a softening point exceeding 100°C and containing aromatic rings. The content of the tackifying resin (A) is 40 to 120 parts by weight per 100 parts by weight of the block copolymer. The content of the tackifying resin (B) is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. Furthermore, the total amount of the tackifying resin is 60 to 160 parts by weight per 100 parts by weight of the block copolymer. The content of the softening agent is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. According to the above adhesive composition, a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound can be formed that achieves both rough surface adhesion and high-temperature retention, as well as good storage properties.

[0008] In some preferred embodiments, the tackifying resin (A) includes a terpene resin as the tackifying resin (A1) and a rosin-based resin as the tackifying resin (A2). By using a combination of the terpene resin and the rosin-based resin as the tackifying resin (A), the effects of the technology disclosed herein are preferably realized.

[0009] In some preferred embodiments, the tackifying resin (A2) includes a rosin-based resin having a softening point of 150°C or higher. By using a rosin-based resin with a high softening point as the tackifying resin (A2), better high-temperature retention can be obtained.

[0010] In some preferred embodiments of the adhesive composition, the content of the phenolic tackifying resin is less than 1 part by weight per 100 parts by weight of the block copolymer. By limiting the amount of phenolic tackifying resin used as described above, an adhesive with good storage properties and excellent quality stability, such as adhesive properties, can be preferably obtained.

[0011] In some embodiments, a styrene-based block copolymer is preferably used as the block copolymer. The effects of the techniques disclosed herein are preferably realized in adhesives containing the styrene-based block copolymer. In particular, the effects of the techniques disclosed herein can be preferably exhibited in adhesives containing a styrene-isoprene block copolymer.

[0012] In some preferred embodiments, the styrene content of the styrene-based block copolymer is 10 to 22% by weight. By setting the styrene content of the styrene-based block copolymer within this range, an adhesive that balances both tackiness and high-temperature retention is easily obtained.

[0013] Furthermore, this specification provides an adhesive sheet having an adhesive layer formed from any of the adhesive compositions disclosed herein. In the above adhesive sheet, the structure including an adhesive layer comprising a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound achieves both rough surface adhesion and high-temperature retention. Moreover, since the above adhesive sheet has good storage properties, it exhibits excellent quality stability, such as adhesive properties, even when stored for a long period of time. The adhesive sheet provided by this specification includes an adhesive layer having an adhesive layer, the adhesive layer containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softener, wherein the tackifying resin includes a natural product-based tackifying resin (A) having a softening point above 80°C and not containing aromatic rings, and a petroleum-based tackifying resin (B) having a softening point above 100°C and containing aromatic rings, the content of tackifying resin (A) is 40 to 120 parts by weight per 100 parts by weight of the block copolymer, the content of tackifying resin (B) is 5 to 40 parts by weight per 100 parts by weight of the block copolymer, the total amount of tackifying resin is 60 to 160 parts by weight per 100 parts by weight of the block copolymer, and the content of the softener is 5 to 40 parts by weight per 100 parts by weight of the block copolymer.

[0014] In addition, the adhesive sheet provided by this specification has an adhesive layer containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, and a tackifier resin, and the content of the phenolic tackifier resin in the adhesive layer is less than 1 part by weight with respect to 100 parts by weight of the block copolymer. This adhesive sheet includes the following characteristics: the adhesive force to a soft polyurethane foam measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees in an environment of 23°C and 50% RH is 3 N / 10 mm or more; and it does not fall in the holding force test for a stainless steel plate measured under the conditions of a temperature of 70°C, an adhesion area of 10 mm × 30 mm, a load of 500 g, and a holding time of 1 hour.

[0015] In addition, combinations of the respective elements described in this specification as appropriate may also be included in the scope of the invention for which patent protection is sought by this patent application.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic cross-sectional view showing the configuration of an adhesive sheet (double-sided adhesive sheet with a base material) according to one embodiment. [Figure 2] It is a schematic cross-sectional view showing the configuration of an adhesive sheet (double-sided adhesive sheet without a base material) according to another embodiment. [Figure 3] It is a schematic cross-sectional view showing the configuration of an adhesive sheet (single-sided adhesive sheet with a base material) according to another embodiment. [Figure 4] It is an explanatory diagram showing the method of a constant-load peeling test. <00​​​​​​​​In the following drawings, components and parts that perform the same function may be denoted by the same reference numeral and described accordingly, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic representations for the purpose of clearly illustrating the present invention and do not accurately represent the size or scale of the actual product provided.

[0018] In this specification, "adhesive" refers to a material that, as described above, exhibits a soft solid (viscoelastic) state at temperatures near room temperature and readily adheres to an adherend under pressure. The adhesive in the technology disclosed herein can also be understood as the solid component of an adhesive composition or a component of an adhesive layer.

[0019] In this specification, "block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound" refers to a polymer having at least one segment (hereinafter also referred to as "A segment") in which the monovinyl-substituted aromatic compound is the main monomer (meaning a copolymer component exceeding 50% by weight; the same applies hereinafter) and at least one segment (hereinafter also referred to as "B segment") in which the conjugated diene compound is the main monomer. Generally, the glass transition temperature of the A segment is higher than that of the B segment. Typical structures of such polymers include a triblock copolymer (ABA triblock) having A segments (hard segments) at both ends of a B segment (soft segment), and a diblock copolymer (AB diblock) consisting of one A segment and one B segment.

[0020] In this specification, "styrene-based block copolymer" means a polymer having at least one styrene block. The styrene block refers to a segment whose main monomer is styrene. A segment consisting substantially only of styrene is a typical example of a styrene block as used herein. Furthermore, "styrene-isoprene block copolymer" means a polymer having at least one styrene block and at least one isoprene block (a segment whose main monomer is isoprene). Representative examples of styrene-isoprene block copolymers include triblock copolymers (triblock bodies) having styrene blocks (hard segments) at both ends of an isoprene block (soft segment), and diblock copolymers (diblock bodies) consisting of one isoprene block and one styrene block. "Styrene-butadiene block copolymer" means a polymer having at least one styrene block and at least one butadiene block (a segment whose main monomer is butadiene).

[0021] In this specification, "styrene content" of a styrene-based block copolymer refers to the weight ratio of the styrene component to the total weight of the block copolymer. The above styrene content can be measured by NMR (nuclear magnetic resonance spectroscopy). Furthermore, the proportion of diblocks in a styrene-based block copolymer (hereinafter sometimes referred to as "diblock ratio" or "diblock ratio") can be determined by the following method. Specifically, the styrene-based block copolymer is dissolved in tetrahydrofuran (THF), and high-performance liquid chromatography is performed using THF as the mobile phase under conditions of 40°C and a flow rate of 1 mL / min, with two stages each of Tosoh Corporation's GS5000H and G4000H liquid chromatography columns connected in series. The peak area corresponding to the diblock is measured from the resulting chart. The diblock ratio is then determined by calculating the percentage of the peak area corresponding to the diblock to the total peak area.

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

[0023] <Adhesive composition> (Block copolymer of monovinyl-substituted aromatic compound and conjugated diene compound) The adhesive composition disclosed herein contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound. The monovinyl-substituted aromatic compound refers to a compound in which one functional group having a vinyl group is bonded to an aromatic ring. A typical example of the aromatic ring is a benzene ring (which may be a benzene ring substituted with a functional group that does not have a vinyl group (e.g., an alkyl group)). Specific examples of the monovinyl-substituted aromatic compound include styrene, α-methylstyrene, vinyltoluene, vinylxylene, etc. Specific examples of the conjugated diene compound include 1,3-butadiene, isoprene, etc. Such block copolymers can be used individually or in combination of two or more.

[0024] Furthermore, block copolymers of monovinyl-substituted aromatic compounds and conjugated diene compounds are components that can be used as base polymers for adhesives. The "base polymer" of an adhesive refers to the main component (i.e., the component that accounts for more than 50% by weight of the rubbery polymer) contained in the adhesive (a polymer that exhibits rubber elasticity in the temperature range around room temperature).

[0025] In the block copolymer described above, the A segment (hard segment) preferably has a copolymerization ratio of 70% by weight or more (more preferably 90% by weight or more, and may be substantially 100% by weight) of the monovinyl-substituted aromatic compound (two or more may be used in combination). In the block copolymer described above, the B segment (soft segment) preferably has a copolymerization ratio of 70% by weight or more (more preferably 90% by weight or more, and may be substantially 100% by weight) of the conjugated diene compound (two or more may be used in combination). Such a block copolymer can realize an adhesive sheet with higher performance.

[0026] The block copolymer described above may take the form of a diblock, a triblock, a radial, or a mixture thereof. In the triblock and radial forms, it is preferable that A segments (e.g., styrene blocks) are arranged at the ends of the polymer chains. This is because A segments arranged at the ends of polymer chains readily aggregate to form domains, thereby creating a pseudo-crosslinked structure that improves the cohesiveness of the adhesive. In the technologies disclosed herein, block copolymers with a diblock ratio of 30% by weight or more (more preferably 40% by weight or more, even more preferably 50% by weight or more, particularly preferably 60% by weight or more, typically 65% ​​by weight or more) are preferably used from the viewpoint of adhesion to the adherend (peel strength). From the viewpoint of peel strength, block copolymers with a diblock ratio of 70% by weight or more are particularly preferred. Furthermore, from the viewpoint of cohesiveness, etc., block copolymers with a diblock ratio of 90% by weight or less (more preferably 85% by weight or less, for example 80% by weight or less) are preferably used. For example, block copolymers with a diblock ratio of 60 to 85% by weight are preferred, and those with a diblock ratio of 70 to 85% by weight (for example 70 to 80% by weight) are more preferred.

[0027] (Styrene-based block copolymer) In some embodiments, the block copolymer is a styrene-based block copolymer. For example, it is preferable that the block copolymer comprises at least one of a styrene-isoprene block copolymer and a styrene-butadiene block copolymer. The styrene-based block copolymer may also contain a hydride, which is a hydrogenated product (with added hydrogen atoms) of at least a portion thereof. The styrene-based block copolymer can be used alone or in combination of two or more. It is preferable that the proportion of styrene-isoprene block copolymer in the adhesive is 70% by weight or more, or that the proportion of styrene-butadiene block copolymer is 70% by weight or more, or that the total proportion of styrene-isoprene block copolymer and styrene-butadiene block copolymer is 70% by weight or more. In some preferred embodiments, substantially all (e.g., 95-100% by weight) of the styrene-based block copolymer is a styrene-isoprene block copolymer. In some other preferred embodiments, substantially all (e.g., 95-100% by weight) of the styrene-based block copolymer is a styrene-butadiene block copolymer. Such compositions allow for better performance of the effects of applying the techniques disclosed herein.

[0028] The styrene-based block copolymer described above may be in the form of a diblock, a triblock, a radial, or a mixture thereof. In the triblock and radial forms, it is preferable that styrene blocks are arranged at the ends of the polymer chains. This is because styrene blocks arranged at the ends of polymer chains readily aggregate to form styrene domains, thereby forming a pseudo-crosslinked structure and improving the cohesiveness of the adhesive. As the styrene-based block copolymer used in the art disclosed herein, from the viewpoint of adhesive strength (peel strength) to the adherend, it is preferable to use one with a diblock ratio of 30% by weight or more (more preferably 40% by weight or more, even more preferably 50% by weight or more, particularly preferably 60% by weight or more, typically 65% ​​by weight or more). A styrene-based block copolymer with a diblock ratio of 70% by weight or more (e.g., 75% by weight or more) may also be used. Furthermore, from the viewpoint of cohesiveness, etc., a styrene-based block copolymer with a diblock ratio of 90% by weight or less (more preferably 85% by weight or less, e.g., 80% by weight or less) is preferable. From the viewpoint of achieving a good balance between rough surface adhesion and high-temperature retention by applying the technology disclosed herein, a styrene-based block copolymer with a diblock ratio of 60 to 85% by weight is preferred, and a styrene-based block copolymer with a diblock ratio of 70 to 85% by weight (e.g., 70 to 80% by weight) is more preferred.

[0029] The styrene content of the above-mentioned styrene-based block copolymer may be, for example, 5 to 40% by weight. From the viewpoint of cohesiveness, a styrene-based block copolymer with a styrene content of 10% by weight or more (more preferably more than 10% by weight, for example 12% by weight or more) is generally preferred. Furthermore, from the viewpoint of peel strength, a styrene content of 35% by weight or less (typically 30% by weight or less, more preferably 25% by weight or less) is preferred, and 22% by weight or less (typically less than 20% by weight, for example 18% by weight or less) is particularly preferred. From the viewpoint of better demonstrating the effects of applying the technology disclosed herein (the effect of achieving both rough surface adhesion and high-temperature retention), a styrene-based block copolymer with a styrene content of 10 to 22% by weight can be preferably used.

[0030] (Adhesive-granting resin) The adhesive composition disclosed herein includes a tackifying resin in addition to the block copolymer. Two or more tackifying resins can be used in combination. The tackifying resin is not particularly limited, and for example, petroleum-based tackifying resins and natural product-based tackifying resins can both be used. Here, petroleum-based tackifying resins are compounds derived from petroleum resources, have a chemical structure derived from petroleum resources, and impart adhesive properties based on their compatibility with adhesives and chemical properties. Natural product-based tackifying resins are compounds containing components derived from natural products, have a chemical structure derived from natural products, and impart adhesive properties based on their compatibility with adhesives and chemical properties. In the technology disclosed herein, one or more of the petroleum-based tackifying resins and natural product-based tackifying resins are appropriately selected based on their chemical structures to design an adhesive with a good balance of rough surface adhesion, high-temperature retention, and storage properties.

[0031] Examples of petroleum-based tackifiers include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, styrene resins, and their hydrogenated derivatives (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins). Other examples of petroleum-based tackifiers include coumarone-indene resins and dicyclopentadiene resins. Petroleum-based tackifiers can be used individually or in combination of two or more types.

[0032] Examples of styrene-based resins include those mainly composed of a styrene homopolymer, a α-methylstyrene homopolymer, a vinyltoluene homopolymer, and copolymers mainly composed of two or more of styrene, α-methylstyrene, and vinyltoluene in their monomer composition (for example, α-methylstyrene / styrene copolymer resins mainly composed of α-methylstyrene / styrene copolymer).

[0033] As a coumarone-indene resin, a resin containing coumarone and indene as monomer components that constitute the resin's backbone (main chain) can be used. Examples of monomer components that may be included in the resin's backbone other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0034] Examples of natural-based tackifying resins include terpene resins and rosin-based resins. Terpene resins include unmodified terpene resins and modified terpene resins. Rosin-based resins include rosin derivative resins. Natural-based tackifying resins can be used individually or in combination of two or more types.

[0035] Examples of terpene resins (unmodified terpene resins) include α-pinene polymers, β-pinene polymers, and dipentene polymers. Examples of modified terpene resins include those obtained by modifying the above terpene resins (phenol modification, aromatic modification (e.g., styrene modification), hydrogenation modification, hydrocarbon modification, etc.). Specifically, examples include terpene phenol resins, aromatically modified (e.g., styrene modified) terpene resins, and hydrogenated terpene resins. The above terpene phenol resins may include hydrogenated terpene phenol resins.

[0036] The term "terpene-phenol resin" above refers to a polymer containing terpene residues and phenol residues, and is a concept that encompasses both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and phenol-modified homopolymers or copolymers of terpenes (terpene resins, typically unmodified terpene resins) (phenol-modified terpene resins).

[0037] Specific examples of rosin-based resins include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosin) obtained by hydrogenation, disproportionation, polymerization, etc., of these unmodified rosin; and rosin derivative resins such as rosin esters obtained by esterifying unmodified rosin with alcohols (i.e., rosin esters), and modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with alcohols (i.e., modified rosin esters); unsaturated fatty acid modified rosin obtained by modifying unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with unsaturated fatty acids; and unsaturated fatty acid modified rosin obtained by modifying rosin esters with unsaturated fatty acids. Examples include rosin esters; unmodified rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), unsaturated fatty acid modified rosin, or rosin alcohols obtained by reducing the carboxyl groups of unsaturated fatty acid modified rosin esters; metal salts of rosins (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; and rosinphenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and then thermally polymerizing them.

[0038] The softening point of the tackifying resin used in the technologies disclosed herein is usually higher than 40°C and may be 60°C or higher. In some embodiments, the softening point of the tackifying resin is 80°C or higher (e.g., above 80°C), preferably 100°C or higher (e.g., above 100°C). The upper limit of the softening point of the tackifying resin is not particularly limited, and is usually suitable at 200°C or lower, preferably 180°C or lower, more preferably 170°C or lower (e.g., 160°C or lower) from the viewpoint of rough surface adhesion, etc., and may also be 140°C or lower, or 120°C or lower.

[0039] Here, in this specification, the softening point of the tackifying resin is defined as the value measured based on the softening point test method (ring-ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, taking care not to create bubbles. After cooling, the portion raised from the plane including the upper end of the ring is cut off with a slightly heated knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured in until it reaches a depth of 90 mm or more. Next, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin so that they do not come into contact with each other, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in a fixed position on the support. Next, maintain a distance of 50 mm from the top of the ring to the glycerin surface, place a thermometer, and position the center of the thermometer's mercury bulb at the same height as the center of the ring, then heat the container. The flame of the Bunsen burner used for heating should be positioned midway between the center and edge of the container's bottom to ensure even heating. After heating begins and the bath temperature reaches 40°C, the rate of increase must be 5.0 ± 0.5°C per minute. Read the temperature when the sample gradually softens, flows out of the ring, and finally contacts the bottom plate; this is defined as the softening point. Two or more softening point measurements should be taken simultaneously, and the average value should be used.

[0040] (Natural tackifying resin (A)) In some embodiments, a natural tackifying resin (A) having a softening point above 80°C and not containing aromatic rings is used as the tackifying resin. A natural tackifying resin with a molecular structure not containing aromatic rings and a softening point above 80°C is well compatible with the adhesive containing the block copolymer, and its additive effect can be suitably exhibited. By using the natural tackifying resin (A), sufficient high-temperature retention can be easily obtained based on its softening point. Furthermore, by using a compound that does not contain aromatic rings, it is easier to obtain good adhesion to rough surfaces and good storage properties.

[0041] The above-mentioned natural product-based tackifying resin (A) can be any natural product-based tackifying resin that has a softening point exceeding 80°C and a molecular structure that does not contain aromatic rings, without any particular limitations. For example, terpene resins, modified terpene resins, rosin-based resins, rosin derivative resins, etc., with a softening point exceeding 80°C can be used. The natural product-based tackifying resin (A) can be used alone or in combination of two or more types.

[0042] The softening point of the above-mentioned natural product-based tackifying resin (A) is greater than 80°C. From the viewpoint of high-temperature retention, the softening point of the natural product-based tackifying resin (A) is preferably 90°C or higher, more preferably 100°C or higher (e.g., above 100°C), even more preferably 110°C or higher (e.g., above 110°C), and particularly preferably 115°C or higher. In some embodiments, the softening point of the natural product-based tackifying resin (A) may be 120°C or higher, 140°C or higher, or 150°C or higher. The upper limit of the softening point of the above-mentioned natural product-based tackifying resin (A) is not particularly limited, and is usually suitable at 200°C or lower. From the viewpoint of rough surface adhesion, etc., it is preferably 180°C or lower, more preferably 170°C or lower (e.g., 160°C or lower), may be 140°C or lower, or 120°C or lower.

[0043] In some preferred embodiments, a terpene resin is used as the natural tackifying resin (A). The terpene resin is well compatible with the adhesive containing the block copolymer, and its additive effect can be suitably exhibited. Although not particularly limited, the terpene resin is well compatible with the soft segment (the segment mainly composed of a conjugated diene compound) of the block copolymer, and based on its softening point, it is thought to impart appropriate cohesive force to the soft segment, thereby contributing to improved high-temperature retention. For example, by using an appropriate amount of the terpene resin, a good balance between rough surface adhesion and high-temperature retention can be achieved.

[0044] The softening point of the above terpene resin is greater than 80°C and is not particularly limited otherwise. From the viewpoint of high-temperature retention, the softening point of the above terpene resin is preferably 90°C or higher, more preferably 95°C or higher, even more preferably 100°C or higher (e.g., above 100°C), particularly preferably 110°C or higher (e.g., above 110°C), and particularly preferably 115°C or higher. The upper limit of the softening point of the above terpene resin is usually suitable to be 200°C or lower, and from the viewpoint of rough surface adhesion, it is preferably 160°C or lower, more preferably 140°C or lower, and may also be 120°C or lower.

[0045] In embodiments where a terpene resin is used as the natural tackifying resin (A), the content of the terpene resin in the adhesive composition may be, for example, 1 part by weight or more, or 10 parts by weight or more, per 100 parts by weight of the block copolymer. In some preferred embodiments, from the viewpoint of effectively exhibiting the effect of adding the terpene resin, the content of the terpene resin per 100 parts by weight of the block copolymer is 20 parts by weight or more, may be 30 parts by weight or more, may be 40 parts by weight or more, or may be 50 parts by weight or more. In some embodiments, the content of the terpene resin per 100 parts by weight of the block copolymer is appropriate to be less than 120 parts by weight, and from the viewpoint of achieving both rough surface adhesion and high temperature retention, it is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, may be 70 parts by weight or less, or may be 50 parts by weight or less.

[0046] While not particularly limited, in embodiments where a terpene resin is used as the natural product-based tackifying resin (A), the amount of the terpene resin per 1 part by weight of the B segment (a segment mainly composed of a conjugated diene compound) in the block copolymer is, for example, 0.1 parts by weight or more, preferably 0.2 parts by weight or more, and may also be 0.4 parts by weight or more, 0.5 parts by weight or more, or 0.6 parts by weight or more. In some embodiments, the amount of the terpene resin per 1 part by weight of the B segment of the block copolymer is suitable to be 1.5 parts by weight or less, and from the viewpoint of achieving both rough surface adhesion and high-temperature retention, it is preferably 1.2 parts by weight or less, more preferably 1 part by weight or less, and may also be 0.8 parts by weight or less, or 0.6 parts by weight or less. By using a terpene resin amount within the above range, the effect of adding the terpene resin can be effectively exerted based on the compatibility of the terpene resin with the soft segment.

[0047] In some preferred embodiments, a rosin-based resin is used as the natural tackifying resin (A). The rosin-based resin is well compatible with the adhesive containing the block copolymer, and its additive effect can be suitably exhibited. Although not particularly limited, the rosin-based resin typically has a high-polarity region and a low-polarity region within a single molecule, is compatible with each segment (hard segment and soft segment) of the block copolymer, and is thought to contribute to achieving both rough surface adhesion and high-temperature holding power based on a different compatibility mechanism than that of the terpene resin. Furthermore, the use of a rosin-based resin is also advantageous in that it can improve adhesion to polar substrates such as metals.

[0048] The softening point of the above rosin-based resin is greater than 80°C and is not particularly limited otherwise. From the viewpoint of high-temperature retention, the softening point of the above rosin-based resin is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 130°C or higher, and particularly preferably 150°C or higher. The upper limit of the softening point of the above rosin-based resin is usually suitable to be 200°C or lower, and from the viewpoint of rough surface adhesion, it is preferably 180°C or lower, and may also be 170°C or lower.

[0049] In embodiments where a rosin-based resin is used as the natural product-based tackifying resin (A), the content of the rosin-based resin in the adhesive composition may be, for example, 1 part by weight or more, or 10 parts by weight or more, per 100 parts by weight of the block copolymer. In some preferred embodiments, from the viewpoint of effectively exhibiting the additive effect of the rosin-based resin, the content of the rosin-based resin per 100 parts by weight of the block copolymer is 20 parts by weight or more, may be 30 parts by weight or more, may be 40 parts by weight or more, or may be 50 parts by weight or more. In some embodiments, the content of the rosin-based resin per 100 parts by weight of the block copolymer is suitable to be 120 parts by weight or less, and from the viewpoint of achieving both rough surface adhesion and high-temperature holding power, it is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, may be 70 parts by weight or less, may be 50 parts by weight or less, or may be 30 parts by weight or less.

[0050] In some preferred embodiments, the natural product-based tackifying resin (A) comprises the terpene resin as the tackifying resin (A1) and the rosin-based resin as the tackifying resin (A2). By using a terpene resin and a rosin-based resin in combination as the tackifying resin (A), a better balance between rough surface adhesion and high-temperature retention can be achieved. In embodiments in which the tackifying resin (A1) and the tackifying resin (A2) are used in combination, the ratio of their use is not particularly limited. In some embodiments, the ratio (A1 / A2) of the content of tackifying resin (A1) to the content of tackifying resin (A2) is, for example, 1 / 10 or more, may be 1 / 5 or more, may be 1 / 3 or more, may be 1 / 2 or more, may be 2 / 3 or more, or may be 1 or more. The above ratio (A1 / A2) may be 10 or less, may be 5 or less, may be 3 or less, or may be 2 or less.

[0051] In embodiments using a natural product-based tackifying resin (A), the content of the natural product-based tackifying resin (A) in the adhesive composition (the total amount if two or more types are included) is not particularly limited, and an appropriate amount may be adopted to achieve the desired effect. In some embodiments, the content of the natural product-based tackifying resin (A) is more than 30 parts by weight and less than 140 parts by weight, and may be 35 to 130 parts by weight, per 100 parts by weight of the block copolymer. In some preferred embodiments, the content of the natural product-based tackifying resin (A) is 40 to 120 parts by weight per 100 parts by weight of the block copolymer. This allows for a good balance between rough surface adhesion and high-temperature holding power. The content of the natural product-based tackifying resin (A) per 100 parts by weight of the block copolymer may be 50 parts by weight or more, 70 parts by weight or more, 90 parts by weight or more, or 100 parts by weight or more. Furthermore, the content of the natural product-based tackifying resin (A) per 100 parts by weight of the block copolymer is preferably 110 parts by weight or less, but may be 90 parts by weight or less, 80 parts by weight or less, or 60 parts by weight or less.

[0052] (Petroleum-based tackifying resin (B)) In some embodiments, the tackifying resin includes a petroleum-based tackifying resin (B) having a softening point above 100°C and containing an aromatic ring. A petroleum-based tackifying resin with a softening point above 100°C and a molecular structure containing an aromatic ring is well compatible with the adhesive containing the block copolymer, and its additive effect can be suitably exhibited. By using the petroleum-based tackifying resin (B), sufficient high-temperature retention can be easily obtained based on the structure containing an aromatic ring and the softening point. Although not particularly limited in interpretation, the petroleum-based tackifying resin (B), having an aromatic ring, is well compatible with domains formed by the aggregation of hard segments (segments mainly composed of monovinyl-substituted aromatic compounds) of the block copolymer (hereinafter also referred to as "hard domains"; for example, styrene domains in styrene-based block copolymers). It is believed that the compatibility of the high-softening-point petroleum-based tackifying resin (B) with hard domains improves the heat resistance of the pseudo-crosslinking by the hard domains, contributing to the improvement of the high-temperature retention of the adhesive.

[0053] The above-mentioned petroleum-based tackifying resin (B) can be any petroleum-based tackifying resin that has a softening point exceeding 100°C and a molecular structure containing an aromatic ring, without any particular limitations. For example, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, styrene resins, coumarone-indene resins, etc., with a softening point exceeding 100°C can be used. Among these, aromatic petroleum resins and styrene resins are preferred. The petroleum-based tackifying resin (B) can be used alone or in combination of two or more types.

[0054] The softening point of the above petroleum-based tackifying resin (B) is greater than 100°C. From the viewpoint of high-temperature holding power, a softening point of 110°C or higher is appropriate for the petroleum-based tackifying resin (B), preferably 125°C or higher, more preferably 135°C or higher, and even more preferably 150°C or higher. The upper limit of the softening point of the above petroleum-based tackifying resin (B) is not particularly limited, and is usually appropriate to be 200°C or lower, preferably 180°C or lower, more preferably 170°C or lower (for example, 160°C or lower) from the viewpoint of rough surface adhesion, etc., and may also be 150°C or lower, or even 140°C or lower.

[0055] In embodiments using petroleum-based tackifying resin (B), the content of the petroleum-based tackifying resin (B) in the adhesive composition (the total amount if two or more types are included) is not particularly limited, and an appropriate amount may be adopted to achieve the desired effect. In some embodiments, the content of petroleum-based tackifying resin (B) is greater than 0 parts by weight, less than 50 parts by weight, and between 1 and 45 parts by weight, per 100 parts by weight of the block copolymer. In some preferred embodiments, the content of petroleum-based tackifying resin (B) is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. This allows for a good balance between rough surface adhesion and high-temperature holding power. The content of petroleum-based tackifying resin (B) per 100 parts by weight of the block copolymer may be 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, or 30 parts by weight or more (for example, 35 parts by weight or more). Furthermore, the content of the petroleum-based tackifying resin (B) per 100 parts by weight of the block copolymer may be 35 parts by weight or less, or 25 parts by weight or less, from the viewpoint of rough surface adhesion.

[0056] Although not particularly limited, in embodiments using petroleum-based tackifying resin (B), the amount of petroleum-based tackifying resin (B) per 1 part by weight of segment A in the block copolymer (a segment mainly composed of a monovinyl-substituted aromatic compound; in embodiments where the block copolymer is a styrene-based block copolymer, the styrene component) is, for example, 0.3 parts by weight or more, may be 0.6 parts by weight or more, may be 1 part by weight or more, may be 1.3 parts by weight or more, or may be 2 parts by weight or more. In some embodiments, the amount of petroleum-based tackifying resin (B) per 1 part by weight of segment A of the block copolymer (e.g., the styrene component) is appropriate to be 2.7 parts by weight or less, and from the viewpoint of rough surface adhesion, it may be 2.4 parts by weight or less, may be 1.8 parts by weight or less, or may be 1.5 parts by weight or less. By using a petroleum-based tackifying resin (B) within the above range, the petroleum-based tackifying resin (B) is well compatible with domains formed by the aggregation of hard segments of the block copolymer (for example, styrene domains in a styrene-based block copolymer), and the additive effect of the petroleum-based tackifying resin (B) can be effectively exerted.

[0057] In some preferred embodiments, the natural product-based tackifying resin (A) and the petroleum-based tackifying resin (B) are used in combination as the tackifying resin. By using the natural product-based tackifying resin (A) and the petroleum-based tackifying resin (B) in combination, it is easy to form an adhesive that has both rough surface adhesion and high-temperature retention, and good storage properties, by utilizing the effect on the block copolymer based on the difference in the chemical structure of each tackifying resin. In embodiments in which the natural product-based tackifying resin (A) and the petroleum-based tackifying resin (B) are used in combination, the ratio of their use is not particularly limited. In some embodiments, the ratio (A / B) of the content of natural product-based tackifying resin (A) to the content of petroleum-based tackifying resin (B) is, for example, 1 or more by weight, preferably 2 or more, and may be 3 or more, 4 or more, 5 or more, or 6 or more. The above ratio (A / B) is, for example, 20 or less, 16 or less is appropriate, and may be 12 or less, or 10 or less.

[0058] (Other tackifying resins) The adhesive composition may contain tackifying resins other than the natural product-based tackifying resin (A) and the petroleum-based tackifying resin (B), to the extent that it does not impair the effects of the present invention. Examples of tackifying resins other than the natural product-based tackifying resin (A) and the petroleum-based tackifying resin (B) include natural product-based tackifying resins with a softening point of 80°C or less, natural product-based tackifying resins containing aromatic rings, petroleum-based tackifying resins with a softening point of 100°C or less, and petroleum-based tackifying resins without aromatic rings. Examples of natural product-based tackifying resins containing aromatic rings include aromatically modified terpene resins, terpene phenol resins, and rosin phenol resins. Examples of petroleum-based tackifying resins without aromatic rings include aliphatic (C5) petroleum resins and alicyclic petroleum resins.

[0059] The technology disclosed herein makes it possible to form an adhesive with a good balance of rough surface adhesion, high-temperature retention, and shelf life without relying on (in other words, without making essential components of) tackifying resins other than natural product-based tackifying resin (A) and petroleum-based tackifying resin (B). Therefore, it is possible to adopt compositions in which the amount of tackifying resins other than natural product-based tackifying resin (A) and petroleum-based tackifying resin (B) is limited, or compositions that substantially do not contain such tackifying resins. For example, the content of tackifying resins other than natural product-based tackifying resin (A) and petroleum-based tackifying resin (B) can be less than 30% by weight, less than 10% by weight, less than 3% by weight, or less than 1% by weight of the total amount of tackifying resins contained in the adhesive composition. The technology disclosed herein can be implemented in a manner in which the adhesive composition substantially does not contain tackifying resins other than natural product-based tackifying resin (A) and petroleum-based tackifying resin (B).

[0060] Furthermore, according to the technology disclosed herein, both rough surface adhesion and high-temperature retention can be achieved based on the type and amount of tackifying resin other than phenolic tackifying resin used, without relying on phenolic tackifying resin (e.g., terpene phenolic resin). While phenolic tackifying resin can contribute to improving adhesive properties, it tends to accelerate the degradation of the adhesive. Therefore, achieving both rough surface adhesion and high-temperature retention without making phenolic tackifying resin an essential component is significant in terms of obtaining excellent shelf life. With such a configuration, an adhesive having the desired adhesive properties can be realized in a form with long-term quality stability. From this viewpoint, the content of phenolic tackifying resin can be less than 30% by weight of the total amount of tackifying resin contained in the adhesive composition, may be less than 10% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can be implemented in a manner in which the adhesive composition substantially does not contain phenolic tackifying resin. Furthermore, the content of the phenolic tackifying resin in the adhesive composition is preferably less than 30 parts by weight, more preferably less than 10 parts by weight, even more preferably less than 3 parts by weight, and particularly preferably less than 1 part by weight, per 100 parts by weight of the block copolymer. By limiting the amount of phenolic tackifying resin used as described above, an adhesive with good storage properties and excellent quality stability, such as adhesive properties, can be preferably obtained. Here, the term "phenolic tackifying resin" refers to a tackifying resin having a molecular structure containing a phenol skeleton, and is a concept that includes terpene phenol resins, hydrogenated terpene phenol resins, phenol resins (alkylphenol resins, xylene-formaldehyde resins, etc.), rosin phenol resins, etc.

[0061] (Total amount of tackifying resin) The total amount of tackifying resin in the adhesive composition is not particularly limited, and an appropriate amount may be used to achieve the desired effect. In some embodiments, the total amount of tackifying resin is more than 35 parts by weight and less than 180 parts by weight, and may be 45 to 170 parts by weight, per 100 parts by weight of the block copolymer. In some preferred embodiments, the total amount of tackifying resin is 60 to 160 parts by weight per 100 parts by weight of the block copolymer. This allows for a good balance between rough surface adhesion and high-temperature retention. The total amount of tackifying resin per 100 parts by weight of the block copolymer may be 80 parts by weight or more, 100 parts by weight or more, or 110 parts by weight or more. Furthermore, the total amount of tackifying resin per 100 parts by weight of the block copolymer is preferably 140 parts by weight or less, but may be 130 parts by weight or less, 120 parts by weight or less, or 110 parts by weight or less. In some embodiments, the total amount of tackifying resin per 100 parts by weight of the block copolymer may be less than 100 parts by weight, less than 90 parts by weight, or less than 80 parts by weight. Even with a configuration in which the total amount of tackifying resin is limited in this way, the desired effect can be achieved according to the technology disclosed herein.

[0062] (Softener) The adhesive compositions disclosed herein preferably contain a softening agent. By including a softening agent in the adhesive, adhesion to the adherend can be improved, and rough surface adhesion can be enhanced. For example, by including a softening agent in a composition with high high-temperature cohesiveness, it is easy to form an adhesive that balances rough surface adhesion and high-temperature holding power. Herein, a softening agent as used herein refers to a material that is a liquid or a viscous fluid at room temperature (e.g., 25°C), or a material with a softening point of 40°C or lower. The above softening point can be measured by the same method as the method for measuring the softening point of the tackifying resin described above.

[0063] The type of softener is not particularly limited, and an appropriate one is selected depending on the adhesive composition (type of block copolymer, type of tackifying resin, etc.). Examples of softeners include liquid rubbers such as polybutene and polyisoprene, and process oils such as paraffinic oils and naphthenic oils. Liquid resins such as liquid terpene resins and liquid rosinic resins may also be used as softeners. Other examples of softeners include esters of higher fatty acids such as stearic acid and palmitic acid (higher fatty acid esters), and fatty acid amides. Among these, liquid terpene resins and process oils are preferred. Softeners can be used individually or in combination of two or more types.

[0064] The content of the softener in the adhesive composition is not particularly limited, and an appropriate amount may be used to achieve the desired effect. In some embodiments, the content of the softener is greater than 0 parts by weight and less than 50 parts by weight, and may be 1 to 45 parts by weight, per 100 parts by weight of the block copolymer. In some preferred embodiments, the content of the softener is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. This makes it easier to form an adhesive in which rough surface adhesion and high temperature holding power are improved in a well-balanced manner. The content of the softener per 100 parts by weight of the block copolymer may be 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more. Also, the content of the softener per 100 parts by weight of the block copolymer may be 35 parts by weight or less, or 30 parts by weight or less.

[0065] (Isocyanate compounds) The adhesive compositions disclosed herein may further contain an isocyanate compound. The cohesive force of the adhesive can be improved by using an isocyanate compound. A polyfunctional isocyanate (meaning a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used as the isocyanate compound. As such a polyfunctional isocyanate, one or more can be selected from various isocyanate compounds (polyisocyanates) having two or more isocyanate groups per molecule. Examples of such polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.

[0066] When using an isocyanate compound, the amount used is not particularly limited, but for example, it can be more than 0 parts by weight and 10 parts by weight or less (typically 0.01 to 10 parts by weight) per 100 parts by weight of the block copolymer. Usually, it is appropriate to use 0.1 to 10 parts by weight of the isocyanate compound per 100 parts by weight of the block copolymer, and it is preferable to use 0.1 to 5 parts by weight (typically 0.3 to 3 parts by weight, for example 0.5 to 1 part by weight). In some embodiments, the adhesive composition may be substantially free of isocyanate compounds. According to the technology disclosed herein, high-temperature holding power and constant-load peeling properties can be improved without using an isocyanate compound. Note that a substantially free adhesive composition means that the isocyanate compound content in the adhesive composition is less than 0.1% by weight (for example 0 to 0.05% by weight).

[0067] (Anti-aging agent) The adhesive composition disclosed herein may optionally contain an antioxidant. The use of an antioxidant can improve the quality stability of the adhesive. The antioxidant may be used alone or in combination of two or more. Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants (such as hindered phenol-based antioxidants), hindered amine-based antioxidants, aromatic amine-based antioxidants, sulfur-based antioxidants, etc. Although not particularly limited, the amount of antioxidant contained in the adhesive composition disclosed herein can be, for example, approximately 20 parts by weight or less per 100 parts by weight of the block copolymer, and is usually appropriate to be 10 parts by weight or less, and may also be 5 parts by weight or less. Furthermore, the amount of the antioxidant can be, for example, 0.1 parts by weight or more per 100 parts by weight of the block copolymer, may be 0.5 parts by weight or more, or 1 part by weight or more.

[0068] (Other ingredients) The adhesive compositions disclosed herein may, as necessary, contain various additives common in the field of adhesives, such as leveling agents, crosslinking agents, crosslinking aids, plasticizers, fillers, colorants (pigments, dyes, etc.), antistatic agents, ultraviolet absorbers, and light stabilizers. Such additives can be conventionally used by conventional methods. Furthermore, the adhesive compositions disclosed herein may contain one or more rubbery polymers other than block copolymers of monovinyl-substituted aromatic compounds and conjugated diene compounds, to the extent that they do not impair the effects of the present invention. The techniques disclosed herein can preferably be implemented in a manner in which the adhesive composition substantially does not contain rubbery polymers other than the block copolymer (for example, in a manner in which the content of the block copolymer is 0 to 1 part by weight per 100 parts by weight).

[0069] In some embodiments, the adhesive composition may be substantially free of chelating compounds. Here, the chelating compound refers, for example, to a chelating compound of an alkaline earth metal oxide and a resin (such as an alkylphenol resin) having a functional group (such as a hydroxyl group or a methylol group) to which the oxide can coordinate. The technology disclosed herein can preferably be implemented in which the adhesive composition does not contain any such chelating compounds at all, or the content of such chelating compounds is 1% by weight or less. According to such embodiments, an adhesive sheet with superior adhesive strength can be realized.

[0070] In some preferred embodiments, the adhesive composition may be composed such that the total amount of the block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softener accounts for 90% by weight or more of the total weight of the adhesive (i.e., the weight of the adhesive layer composed of this adhesive). For example, an embodiment in which the total amount is 90 to 99.8% by weight (typically, for example, 95 to 99.5% by weight) of the total weight of the adhesive can be preferably adopted.

[0071] The form of the adhesive composition disclosed herein is not particularly limited, and may include, for example, an adhesive composition containing an adhesive (adhesive component) of the above-described composition in an organic solvent (solvent type), an adhesive composition in which the adhesive is dispersed in an aqueous solvent (water-dispersible type, typically aqueous emulsion type), a hot-melt type adhesive composition, and the like. From the viewpoint of coatability and freedom of substrate selection, solvent-type or water-dispersible adhesive compositions can be preferably used. From the viewpoint of achieving higher adhesive performance, solvent-type adhesive compositions are particularly preferred. Furthermore, hot-melt types can be applied in a heated and molten state that substantially does not contain organic solvents, so they are preferred from the viewpoint of productivity and reduction of environmental impact.

[0072] Solvent-type adhesive compositions are typically prepared in the form of a solution containing each of the above-mentioned components in an organic solvent. The organic solvent can be appropriately selected from known or conventional organic solvents. For example, one solvent or a mixture of two or more solvents can be used, selected from aromatic compounds such as toluene and xylene (typically aromatic hydrocarbons); acetic acid esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; halide alkanes such as 1,2-dichloroethane; ketones such as methyl ethyl ketone and acetylacetone; etc. Although not particularly limited, it is usually appropriate to prepare the above solvent-type adhesive composition to have a non-volatile content (NV) of 30 to 65% by weight (e.g., 40 to 55% by weight).

[0073] Various conventionally known methods can be applied to obtain an adhesive sheet from an adhesive composition. For example, a method in which an adhesive layer is formed by directly applying (typically coating) the adhesive composition to a substrate and drying it (direct method) can be preferably employed. Alternatively, an adhesive layer may be formed on a surface with good release properties (e.g., the surface of a release liner, the back surface of a release-treated support substrate, etc.) by applying the adhesive composition to the surface and drying it, or a method in which the formed adhesive layer is transferred to the substrate (transfer method) can be employed. The adhesive composition can be applied using known or conventional coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, and spray coaters. From the viewpoint of promoting the crosslinking reaction and improving manufacturing efficiency, it is preferable to dry the adhesive composition under heat. Typically, a drying temperature of approximately 40°C to 150°C (typically 40°C to 120°C, e.g., 50°C to 120°C, and even 70°C to 100°C) can be preferably used. The drying time is not particularly limited, but it should be from several tens of seconds to several minutes (e.g., within approximately 5 minutes, preferably 30 seconds to 2 minutes). After that, an additional drying step may be provided as needed. The adhesive layer is typically formed continuously, but depending on the purpose and application, it may be formed in regular or random patterns such as dots or stripes.

[0074] (Thickness of the adhesive layer) While not particularly limited, the thickness of the adhesive layer is appropriately about 4 μm or more (e.g., 20 μm or more), and also appropriately about 150 μm or less (typically 120 μm or less, for example, 100 μm or less). In some embodiments, the thickness of the adhesive layer may preferably be 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more (e.g., 60 μm or more). An adhesive sheet having an adhesive layer of such thickness can exhibit excellent adhesive performance (typically, a balance between rough surface adhesion and high-temperature retention). In the case of a double-sided adhesive sheet with a substrate, it is preferable to have an adhesive layer of the above thickness on each side of the substrate. The thickness of each adhesive layer may be the same or different.

[0075] <Example of adhesive sheet structure> The adhesive sheet disclosed herein (which may be in the form of a long strip such as a tape) may be, for example, a double-sided adhesive sheet having the cross-sectional structure shown in Figure 1. This double-sided adhesive sheet 1 comprises a base material (e.g., a plastic film) 15 and a first adhesive layer 11 and a second adhesive layer 12 supported on both sides of the base material 15, respectively. More specifically, the first adhesive layer 11 and the second adhesive layer 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the base material 15, respectively. Before use (before being attached to an object), the double-sided adhesive sheet 1 may be in a spiral shape, as shown in Figure 1, with a release liner 21 whose front surface 21A and back surface 21B are both release surfaces. In this form of double-sided adhesive sheet 1, the surface of the second adhesive layer 12 (second adhesive surface 12A) is protected by the front surface 21A of the release liner 21, and the surface of the first adhesive layer 11 (first adhesive surface 11A) is protected by the back surface 21B of the release liner 21. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be protected by two separate release liners.

[0076] The technology disclosed herein is preferably applied to a double-sided adhesive sheet with a substrate as shown in Figure 1, and can also be applied to a substrate-less (i.e., without a substrate) double-sided adhesive sheet 2 as shown in Figure 2. Before use, the double-sided adhesive sheet 2 may be in a configuration where the first adhesive surface 11A and the second adhesive surface 11B of the substrate-less adhesive layer 11 are protected by release liners 21 and 22, each having a release surface on at least the surface (front) facing the adhesive layer. Alternatively, the release liner 22 may be omitted, and a release liner 21 with release surfaces on both sides may be used, with the adhesive layer 11 overlapping and wound in a spiral shape so that the second adhesive surface 11B is in contact with and protected by the back surface of the release liner 21.

[0077] The technology disclosed herein can also be applied to a single-sided adhesive sheet 3 with a substrate, comprising a substrate 15 and an adhesive layer 11 supported on the first surface (non-peel surface) 15A of the substrate, as shown in Figure 3. Before use, the adhesive sheet 3 may be in a form in which the surface (adhesive surface) 11A of the adhesive layer 11 is protected by a release liner 21, at least on the adhesive layer side (front surface), which is a release surface, as shown in Figure 3. Alternatively, the release liner 21 may be omitted, and a substrate 15 with a second surface 15B as the release surface may be used, and the adhesive sheet 3 with the substrate may be wound so that the first adhesive surface 11A abuts against the second surface 15B of the substrate 15 and is protected.

[0078] <Base material> When applying the technologies disclosed herein to a double-sided adhesive sheet with a substrate or a single-sided adhesive sheet with a substrate, the substrate can be appropriately selected and used depending on the application of the adhesive sheet. Examples of substrates include plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, and polyvinyl chloride film; foam sheets made from foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics (including paper such as Japanese paper and fine paper) made from various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) either alone or in blends; and metal foils such as aluminum foil and copper foil. The above-mentioned plastic films (typically referring to non-porous plastic films, a concept distinct from woven and nonwoven fabrics) can be either unoriented films or oriented (uniaxially oriented or biaxially oriented) films. Furthermore, the surface of the substrate on which the adhesive layer is provided may be subjected to surface treatments such as the application of a primer or corona discharge treatment.

[0079] Examples of the non-woven fabric used as the base material include non-woven fabrics composed of pulps such as wood pulp, and natural fibers such as cotton and hemp; non-woven fabrics composed of chemical fibers (synthetic fibers) such as polyester fibers like polyethylene terephthalate (PET) fibers, rayon, vinylon, acetate fibers, polyvinyl alcohol (PVA) fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers; non-woven fabrics composed of two or more kinds of fibers with different materials; and the like. Among these, from the viewpoints of impregnation property of the adhesive and water repellency resistance, non-woven fabrics composed of pulp or hemp (e.g., hemp pulp), non-woven fabrics composed of PET fibers, and the like are preferable. The use of the non-woven fabric base material also contributes to improving the flexibility and tearability of the adhesive sheet.

[0080] As the non-woven fabric (non-woven fabric base material), those with a basis weight of approximately 30 g / m 2 or less (e.g., 25 g / m 2 or less, typically 20 g / m 2 or less) can be preferably adopted. Such non-woven fabrics with this basis weight are suitable for producing a lightweight and highly adhesive adhesive sheet. From the viewpoint of water repellency resistance, non-woven fabrics with a basis weight of less than 18 g / m 2 (e.g., 16 g / m 2 or less, typically 15 g / m 2 or less) are preferable. From the viewpoint of improving the strength of the base material itself, the above basis weight is preferably 10 g / m 2 or more (e.g., 12 g / m 2 or more, typically 13 g / m 2 or more).

[0081] [[ID=2B]] The bulk density of the non-woven fabric base material (which can be calculated by dividing the basis weight by the thickness) is suitably approximately 0.20 g / cm 3 or more, preferably 0.25 g / cm 3 or more (e.g., 0.30 g / cm 3 or more), and is suitably approximately 0.50 g / cm 3 or less, preferably 0.40 g / cm 3 or less (e.g., 0.35 g / cm 3The following is preferable. By having a bulk density within the above range, the substrate itself has appropriate strength and good adhesive impregnation is obtained. From the viewpoint of rebound resistance, a bulk density of 0.25 to 0.40 g / cm³ is preferable. 3 (For example, 0.30~0.35 g / cm³) 3 The use of a nonwoven fabric base material of a certain degree is particularly preferable.

[0082] In addition to the constituent fibers described above, the nonwoven fabric substrate may contain resin components such as starch (e.g., cationized starch), polyacrylamide, viscose, polyvinyl alcohol, urea-formaldehyde resin, melamine-formaldehyde resin, and polyamide-polyamine epichlorohydrin. These resin components may function as paper strength enhancers for the nonwoven fabric substrate. The strength of the nonwoven fabric substrate can be adjusted by using such resin components as needed. The nonwoven fabric substrate may also contain other additives common in the field of nonwoven fabric manufacturing, such as yield improvers, water filter agents, viscosity modifiers, and dispersants, as needed.

[0083] The thickness of the substrate can be appropriately selected depending on the purpose, but generally it is appropriate to have a thickness of approximately 2 μm or more (typically 10 μm or more), and it is preferable to have a thickness of 500 μm or less (typically 200 μm or less). When a nonwoven fabric is used as the substrate, the thickness of the nonwoven fabric substrate is appropriate to be approximately 150 μm or less. From the viewpoint of sufficiently impregnating the entire substrate with adhesive, the above thickness is preferable to be 100 μm or less (for example, 70 μm or less). Also, considering the ease of handling when manufacturing adhesive sheets, the above thickness is preferable to be 10 μm or more (for example, 25 μm or more). From the viewpoint of resistance to repulsion, the above thickness is preferable to be 30 μm or more (for example, 35 μm or more, typically 40 μm or more), and it is preferable to have a thickness of 60 μm or less (for example, 50 μm or less, typically 45 μm or less).

[0084] <Thickness of adhesive sheet> The total thickness of the adhesive sheet disclosed herein (including the thickness of the adhesive layer and substrate, but not the thickness of the release liner) is not particularly limited, but from the viewpoint of thinning, weight reduction, and resource conservation, it is preferably about 1000 μm or less (for example, 500 μm or less, typically 300 μm or less), and may be 150 μm or less. Furthermore, from the viewpoint of ensuring good adhesive properties, it is appropriate to have a thickness of 50 μm or more (for example, 70 μm or more, typically 100 μm or more).

[0085] <Removable Liner> Conventional release paper or the like can be used as the release liner, and is not particularly limited. For example, a release liner having a release treatment layer on the surface of a substrate such as a plastic film or paper, or a release liner made of a low-adhesion material such as a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.) can be used. The release treatment layer may be formed by surface-treating the substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

[0086] <Characteristics of adhesive sheets> The adhesive sheet disclosed herein preferably has an adhesive strength (foam-to-adhesion strength) of 3 N / 10 mm or more to a flexible urethane foam, measured under conditions of 23°C, 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180 degrees. Since the foam surface is rough, the adhesive sheet exhibiting the above foam-to-adhesion strength can exhibit sufficient adhesion to the rough surface. From the viewpoint of rough surface adhesion, the foam-to-adhesion strength is more preferably 4 N / 10 mm or more, even more preferably 5 N / 10 mm or more, and particularly preferably 6 N / 10 mm or more. The upper limit of the foam-to-adhesion strength is not particularly limited and may be, for example, around 10 N / 10 mm or less. The foam-to-adhesion strength is measured in accordance with JIS Z 0237, after pressing a 2 kg roller back and forth once onto the surface of the flexible urethane foam as the adherend, leaving it for 30 minutes, and then measuring under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. The adherend (flexible polyurethane foam) used is Color Foam (product name "ECS" (gray)) manufactured by Inoac Corporation or an equivalent product. The above-mentioned flexible polyurethane foam (product name "ECS" (gray)) has a density of 22 ± 2 kg / m³. 3 It is a polyether urethane foam with a hardness of 107.9 ± 22.6 N (measured by Method D as specified in JIS K 6400-2 (2004)). The adhesion to the foam is measured more specifically by the method described in the examples below.

[0087] The adhesive sheets disclosed herein preferably do not fall off in a holding force test on a stainless steel plate measured under the conditions of a temperature of 70°C, a bonding area of ​​10 mm × 30 mm, a load of 500 g, and a holding time of 1 hour. Adhesive sheets satisfying these characteristics have excellent high-temperature holding power, are less prone to peeling or shifting even when used in a manner exposed to high temperatures, and easily achieve excellent adhesive reliability. In some embodiments of the adhesive sheets, the displacement distance from the initial position in the above holding force test is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1.5 mm or less. The above holding force test is specifically carried out by the method described in the examples below.

[0088] In some embodiments, the adhesive sheet preferably has a peel distance of 5 mm or less in both the initial and after-aging tests in the constant-load peel test measured by the method described in the examples below. Adhesive sheets satisfying this characteristic have sufficient resistance to continuous peel loads even when stored for a long period of time, thus enabling highly reliable bonding and fixing. The peel distance in the constant-load peel test is more preferably 3 mm or less, even more preferably 2 mm or less, and particularly preferably 1 mm or less (e.g., 0.5 mm or less).

[0089] Furthermore, it is preferable that the adhesive sheet disclosed herein has a rate of decrease in constant-load peeling properties after aging (rate of decrease after aging test), which can be determined from the method described in the examples below, of 50% or less. Adhesive sheets that satisfy the above properties have excellent long-term quality stability and sufficient storage properties. It is particularly preferable that the adhesive sheet disclosed herein has a rate of decrease after aging test of 20% or less.

[0090] <Application> The adhesive compositions or adhesive sheets disclosed herein are useful for joining components in various types of office automation equipment (e.g., PCs), home appliances (e.g., rice cookers, refrigerators), automobiles, building materials (e.g., housing materials), etc. (for example, for fixing various parts in such products). [Examples]

[0091] The following describes several embodiments of the present invention, but it is not intended to limit the present invention to those shown in these embodiments. In the following description, "parts" and "%" are based on weight unless otherwise specified. In addition, unless otherwise specified, the amounts used for each material are based on amounts that do not include solvents.

[0092] <Example 1> (Preparation of adhesive composition) A 50% NV adhesive composition was prepared by stirring and mixing 100 parts of styrene-isoprene block copolymer (manufactured by Zeon Corporation, product name "Quintac 3520", styrene content 15%, diblock ratio 78%), 60 parts of terpene resin as a natural tackifying resin (A1) (manufactured by Yasuhara Chemical Co., Ltd., product name "YS Resin PX1150N"), 20 parts of rosin resin as a natural tackifying resin (A2) (manufactured by Arakawa Chemical Industries, Ltd., product name "Pensel D160"), 5 parts of styrene resin as a petroleum-based tackifying resin (B) (manufactured by Kraton Co., Ltd., product name "SA140"), 10 parts of liquid terpene resin as a softener (C) (manufactured by Yasuhara Chemical Co., Ltd., product name "YS Resin PX300N"), 3 parts of an antioxidant, and toluene as a solvent. As an anti-aging agent, we used BASF's product name "IRGANOX CB612" (a 2:1 blend of BASF's product names "IRGAFOS 168" and "IRGANOX 565").

[0093] (Making adhesive sheets) The above adhesive composition was applied to the release-treated surface of a 75 μm thick silicone-based release agent-treated PET film, and dried at 120°C for 3 minutes to form a 70 μm thick adhesive layer. A release liner, which had been released using a silicone-based release agent, was then bonded to the surface of the adhesive layer. In this way, the adhesive sheet (substrate-less double-sided adhesive sheet with release liner) according to this example was prepared.

[0094] <Examples 2-10 and Comparative Examples 1-12> The adhesive compositions for each example were prepared in the same manner as in Example 1, except that the type and amount of tackifying resin and the type and amount of softener were changed as shown in Tables 1 and 2. Adhesive sheets for each example were then prepared using each adhesive composition in the same manner as in Example 1.

[0095] The materials used, as shown in the table, are as follows: (Natural tackifying resin that does not contain aromatic rings) "PX1150N": Product name "YS Resin PX1150N" manufactured by Yasuhara Chemical Co., Ltd., a terpene resin with a softening point of 115°C. "PX1000": Product name "YS Resin PX1000" manufactured by Yasuhara Chemical Co., Ltd., a terpene resin with a softening point of 100°C. "PX800": Product name "YS Resin PX800" manufactured by Yasuhara Chemical Co., Ltd., a terpene resin with a softening point of 80°C. "D160": Product name "Pensel D160" manufactured by Arakawa Chemical Industries, Ltd., a rosin-based resin with a softening point of 157°C. "A115": Product name "Super Ester A115" manufactured by Arakawa Chemical Industries, Ltd., a rosin-based resin with a softening point of 120°C. "A75": Product name "Super Ester A75" manufactured by Arakawa Chemical Industries, Ltd., a rosin-based resin with a softening point of 80°C. (Petroleum-based tackifying resin containing aromatic rings) "SA140": A product name "SA140" manufactured by Kraton, a styrene-based resin with a softening point of 137°C. "Kristalex 5140": A product name "Kristalex 5140" manufactured by Eastman Chemical Company, an aromatic petroleum resin with a softening point of 140°C. "Neopolymer 150": A product manufactured by JXTG Energy Corporation, named "Nisseki Neopolymer 150," an aromatic petroleum resin with a softening point of 155°C. "FTR2120": A product name "FTR2120" manufactured by Mitsui Chemicals, Inc., an aromatic petroleum resin with a softening point of 125°C. "SX100": Product name "YS Resin SX100" manufactured by Yasuhara Chemical Co., Ltd., a styrene-based resin with a softening point of 100°C. (Natural tackifying resin containing aromatic rings) "T145": Product name "YS Polystar T145" manufactured by Yasuhara Chemical Co., Ltd., a terpene phenol resin with a softening point of 145°C. "TO105": Product name "YS Resin TO105" manufactured by Yasuhara Chemical Co., Ltd., an aromatic modified terpene resin with a softening point of 100°C. (Alicyclic / aliphatic petroleum resin) "M100": Product name "Alcon M100" manufactured by Arakawa Chemical Industries, Ltd., an alicyclic petroleum resin with a softening point of 100°C. "P100": Product name "Alcon P100" manufactured by Arakawa Chemical Industries, Ltd., an aliphatic petroleum resin with a softening point of 100°C. (Softener) "PX300N": Product name "YS Resin PX300N" manufactured by Yasuhara Chemical Co., Ltd., a liquid terpene resin with a softening point of 30°C. "PW-90": Product name "Diana Process Oil PW-90" manufactured by Idemitsu Kosan Co., Ltd., paraffin-based oil.

[0096] <Evaluation Method> (Adhesion to foam) The release liner covering one side of an adhesive sheet (double-sided adhesive sheet) was peeled off and attached to a 50 μm thick PET film for backing. This backed adhesive sheet was cut to a size of 10 mm wide and 100 mm long to prepare test specimens. As the adherend, a 10mm thick flexible polyurethane foam (color foam manufactured by Inoac Corporation (product name "ECS" (gray)) was cut to a size of 30mm in width and 100mm in length) and used as the adherend. Under conditions of 23°C and 50% RH, the other adhesive surface (measurement target surface) of the test piece was exposed, and the exposed adhesive surface of the test piece was pressed onto the adherend surface by rolling a 2kg roller back and forth once. After leaving it in the same conditions for 30 minutes, the 180° peel adhesion strength (adhesion strength against foam) [N / 10mm] was measured using a tensile testing machine at a tensile speed of 300mm / min in accordance with JIS Z 0237. If the adhesion strength against foam is 3.0N / 10mm or higher, it is judged that it has sufficient adhesion to rough surfaces. Note that when using a single-sided adhesive sheet as a test specimen for measurement, the PET film backing mentioned above is not mandatory.

[0097] (70℃ holding power) The release liner covering one side of the adhesive sheet (double-sided adhesive sheet) was peeled off and the sheet was backed by attaching it to a 50 μm thick PET film. This backed adhesive sheet was cut into strips 10 mm wide to prepare test specimens. In an environment of 23°C and 50% RH, the other adhesive side (measurement target surface) of the test specimen was exposed, and the exposed adhesive side of the test specimen was pressed onto a stainless steel plate (SUS304) as the adherend, with a 2 kg roller applied over an area of ​​10 mm wide and 30 mm long, by one back-and-forth motion. After leaving the test specimen attached to the adherend in the same environment for 30 minutes, the adherend was suspended so that the length direction of the test specimen was vertical, and a load of 500 g was applied to the free end of the test specimen. In accordance with JIS Z 0237, the specimen was left in an environment of 70°C for 1 hour with the load applied. For the test specimens after being left unattended, the distance they had shifted from their initial placement (slip distance) [mm] was measured. Measurements were performed using three test specimens for each adhesive sheet (i.e., n=3), and the arithmetic mean of the slip distances [mm] for these specimens was defined as the "70°C holding strength." If even one test specimen fell, it was recorded as "fallen." If a specimen did not fall after one hour in the 70°C holding strength test, it was judged to have sufficient high-temperature holding strength. Note that when using a single-sided adhesive sheet as a test specimen for measurement, the PET film backing mentioned above is not mandatory.

[0098] (Constant load peel test) Referring to Figure 4, one adhesive surface 5A of the adhesive sheet (double-sided adhesive sheet) 5 before (initial) and after the aging test described below was attached to a PET film 52 with a thickness of 75 μm to create a backing. This backed adhesive sheet 5 was cut to a size of 10 mm in width and 100 mm in length to prepare a test piece 54. Under conditions of 23°C and 50% RH, the other adhesive surface 5B of the test piece 54 was pressed onto the surface of the adherend 56 by passing a 2 kg roller back and forth once. This was left in the same conditions for 30 minutes. A stainless steel plate (SUS304) was used as the adherend. After that, under conditions of 23°C and 50% RH, the adherend 56 was held horizontally with the side to which the test piece 54 was attached facing downwards, as shown in Figure 4. A load 58 of 100 g (1.0 N) was applied to one end of the test piece 54 so that the peeling angle was 90 degrees, and the peeling distance [mm] after 24 hours was measured. Measurements were performed using two test specimens each for the adhesive sheets before (initial) and after the aging test (i.e., n=2), and the arithmetic mean of the peel distance [mm] for these test specimens was used as the evaluation result for "constant load peeling". If even one test specimen fell, it was indicated as "fallen". Note that when using a single-sided adhesive sheet as a test specimen for measurement, the PET film backing mentioned above is not mandatory.

[0099] (Aging test) A sample for aging testing was prepared by cutting the adhesive sheet, including the release liner covering the adhesive surface, into a rectangle measuring 30 cm vertically and 20 cm horizontally. The sample was stored for 10 days in a dryer maintained at 85°C in an air atmosphere. The samples were stored suspended in the dryer, ensuring they did not overlap.

[0100] (Storability) The shelf life was evaluated based on the peel distance [mm] of the constant-load peel test measured on the adhesive sheets before and after the aging test described above. Specifically, the rate of decrease in constant-load peel characteristics after the aging test (decrease rate after aging test) was calculated using the following formula: The percentage decrease after the aging test [%] = (detachment distance after the aging test - detachment distance before the aging test) / detachment distance before the aging test × 100; I wanted more. If the degradation rate after aging testing is 50% or less, it is judged to have sufficient preservation properties. If the degradation rate after aging testing is 20% or less, it is judged to have excellent preservation properties.

[0101] Tables 1 and 2 show an overview of each case and its evaluation results.

[0102] [Table 1]

[0103] [Table 2]

[0104] As shown in Tables 1-2, the adhesive sheets in Examples 1-10 had a foam adhesion strength of 3.0 N / 10 mm or more, did not fall off in the 70°C holding strength test, and the rate of deterioration of constant load peel characteristics after the aging test was 50% or less. All of them had sufficient rough surface adhesion, high temperature holding strength, and storage properties. On the other hand, Comparative Examples 1-12 were inferior in at least one of the foam adhesion strength, 70°C holding strength, and storage properties.

[0105] Specifically, Examples 1 and 2 show the results of studies on the content of aromatic petroleum-based tackifying resin (B) with a softening point exceeding 100°C. Comparing the results of Example 1 with the results of Comparative Examples 6 and 8, which do not use tackifying resin (B), it can be seen that by increasing the content of tackifying resin (B) to 5 parts or more, rough surface adhesion and high-temperature retention can be improved. Furthermore, comparing the results of Example 2 with the results of Comparative Examples 9 and 10, it can be seen that by keeping the content of tackifying resin (B) at 40 parts by weight or less, excellent rough surface adhesion can be obtained. Comparative Example 6 is modeled after the composition of Example 8 in Patent Document 1, and Comparative Example 8 is modeled after the composition of Example 2 in Patent Document 2. Comparative Example 7 is modeled after the composition of Example 2 in Patent Document 3. Comparative Example 9 is an example in which the amount of aromatic petroleum resin (B) is increased from the composition of Example 4, and Comparative Example 10 is an example in which the amount of aromatic petroleum resin (B) is increased from the composition of Example 3.

[0106] Furthermore, a comparison of the results of Examples 3-4 with the results of Comparative Examples 9, 11, and 12 shows that sufficient rough surface adhesion can be obtained when the content of natural tackifying resin (A) is in the range of 40-120 parts and the total amount of tackifying resin is in the range of 60-160 parts. In addition, the results of Comparative Example 11 show that if the content of natural tackifying resin (A) is too high, the high-temperature holding power decreases. Comparative Example 11 is an example in which the amount of natural tackifying resin (A) is increased from the composition of Example 10, and Comparative Example 12 is an example in which the amount of natural tackifying resin (A) is decreased from the composition of Example 2.

[0107] Examples 5-6 and Comparative Example 5 show the results of studies on the softening point of aromatic petroleum-based tackifier (B). From these comparisons, it can be seen that the high-temperature holding power is improved when the softening point of aromatic petroleum-based tackifier (B) is above 100°C. Examples 7-8 and Comparative Example 4 show the results of studies on the softening point of natural product-based tackifier (A). It can be seen that by using natural product-based tackifier (A) with a softening point above 80°C, both rough surface adhesion and high-temperature holding power can be achieved. Examples 9-10 and Comparative Examples 1-2 show the results of studies on the amount of softener. It can be seen that both rough surface adhesion and high-temperature holding power can be achieved by using a softener within the range of 5-40 parts. Comparative Example 5 is an example in which aromatic petroleum-based tackifier (B) is replaced with one with a low softening point in the composition of Example 2. Comparative Example 4 is an example in which natural product-based tackifier (A) is replaced with one with a low softening point in the composition of Example 5. Comparative Examples 1 and 2 are examples in which the amount of softener used was changed from the composition of Example 2.

[0108] In Comparative Example 3, although the initial constant-load peel test results were good, the constant-load peel characteristics deteriorated after the aging test, and storage stability was not achieved. Comparative Example 3 is an example in which a terpene phenol resin was used instead of the natural product-based tackifying resin (A) in the composition of Example 7, and it is thought that the adhesive deteriorated due to the use of the terpene phenol resin.

[0109] From the above results, it can be seen that an adhesive composition containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softener, comprising a natural product-based tackifying resin (A) having a softening point exceeding 80°C and not containing aromatic rings, and a petroleum-based tackifying resin (B) having a softening point exceeding 100°C and containing aromatic rings, wherein the content of tackifying resin (A) is 40 to 120 parts by weight per 100 parts by weight of block copolymer, the content of tackifying resin (B) is 5 to 40 parts by weight per 100 parts by weight of block copolymer, the total amount of tackifying resin is 60 to 160 parts by weight per 100 parts by weight of block copolymer, and the content of softener is 5 to 40 parts by weight per 100 parts by weight of block copolymer can form an adhesive that achieves both rough surface adhesion and high-temperature retention, as well as good storage properties.

[0110] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. [Explanation of symbols]

[0111] 1, 2, 3 Adhesive sheets 11 First adhesive layer 12 Second adhesive layer 15 Base material 21,22 Release Liner

Claims

1. It contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softening agent. The tackifying resin is A natural tackifying resin (A) having a softening point exceeding 80°C and not containing aromatic rings, A petroleum-based tackifying resin (B) having a softening point exceeding 100°C and containing an aromatic ring, Includes, The tackifying resin (A) includes a terpene resin as the tackifying resin (A1) and a rosin-based resin as the tackifying resin (A2). The content of the tackifying resin (A) is 40 to 120 parts by weight per 100 parts by weight of the block copolymer. The content of the tackifying resin (B) is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. The total amount of the tackifying resin is 60 to 160 parts by weight per 100 parts by weight of the block copolymer. The adhesive composition wherein the content of the softening agent is 5 to 40 parts by weight per 100 parts by weight of the block copolymer.

2. The adhesive composition according to claim 1, wherein the tackifying resin (A2) comprises a rosin-based resin having a softening point of 150°C or higher.

3. The adhesive composition according to claim 1 or 2, wherein the content of the phenolic tackifying resin is less than 1 part by weight per 100 parts by weight of the block copolymer.

4. The adhesive composition according to claim 1 or 2, wherein the block copolymer is a styrene-based block copolymer.

5. The adhesive composition according to claim 1 or 2, wherein the block copolymer is a styrene-isoprene block copolymer.

6. The adhesive composition according to claim 4, wherein the styrene content of the styrene-based block copolymer is 10 to 22% by weight.

7. An adhesive sheet having an adhesive layer formed from the adhesive composition according to claim 1 or 2.

8. An adhesive sheet having an adhesive layer, The adhesive layer contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, a tackifying resin, and a softening agent. The tackifying resin is A natural tackifying resin (A) having a softening point exceeding 80°C and not containing aromatic rings, A petroleum-based tackifying resin (B) having a softening point exceeding 100°C and containing an aromatic ring, Includes, The tackifying resin (A) includes a terpene resin as the tackifying resin (A1) and a rosin-based resin as the tackifying resin (A2). The content of the softening agent in the adhesive layer is 5 to 40 parts by weight per 100 parts by weight of the block copolymer. The content of the phenolic tackifying resin in the adhesive layer is less than 1 part by weight per 100 parts by weight of the block copolymer. Here, the adhesive sheet has the following characteristics: The adhesive strength to the flexible polyurethane foam, measured under conditions of 23°C, 50% RH, tensile speed of 300 mm / min, and peel angle of 180 degrees, is 3 N / 10 mm or more; and In a holding strength test on a stainless steel plate measured under the conditions of a temperature of 70°C, a bonding area of ​​10 mm x 30 mm, a load of 500 g, and a holding time of 1 hour, the object does not fall off; An adhesive sheet that satisfies the requirements.

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