JP2018039928A - Adhesive sheet - Google Patents

Abstract

Provided is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive having a composition in which a tackifier resin is blended with an unsaturated rubber, and having excellent long-term quality stability. A pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifier resin. The pressure-sensitive adhesive has a weight average molecular weight MwH calculated from a molecular weight distribution curve based on GPC measurement for a region where the molecular weight in terms of polystyrene is 10,000 g / mol or more, and a retention rate of 70% or more in an aging test at 80 ° C. for 4 weeks. It is. [Selection diagram] Fig. 1

Description

  The present invention relates to an adhesive sheet.

  Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same shall apply hereinafter) is in the form of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is typically in the form of a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive, and is used as a bonding means with good workability and high adhesion reliability. It is widely used in various industrial fields such as OA equipment. As the base polymer of the pressure-sensitive adhesive, a polymer exhibiting rubber elasticity at normal temperature is preferably employed. An example of such a polymer is a polymer having a monomer unit containing a carbon-carbon unsaturated bond (for example, a polymer having a monomer unit based on a conjugated diene compound). Patent Document 1 describes an adhesive composition containing a partially hydrogenated block copolymer (such as a partially hydrogenated styrene butadiene block copolymer) having a vinyl aromatic monomer unit and a conjugated diene monomer unit. Has been.

JP-A-2006-35039

  With the spread of the application field and use mode of pressure-sensitive adhesive sheets, the required level for long-term quality stability (hereinafter also simply referred to as “quality stability”) of the pressure-sensitive adhesive sheet after manufacture is increasing. In this respect, the pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive using unsaturated rubber (particularly a pressure-sensitive adhesive having a relatively high content of unsaturated rubber) still has room for improvement. In particular, when a tackifying resin is blended with an unsaturated rubber, deterioration such as a decrease in cohesive force (cohesiveness) tends to proceed, and the quality stability of the pressure-sensitive adhesive sheet tends to decrease.

  Then, this invention aims at providing the adhesive sheet excellent in long-term quality stability in the structure provided with the adhesive of the composition with which tackifying resin was mix | blended with unsaturated rubber.

The pressure-sensitive adhesive sheet provided by this specification includes a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifying resin. The pressure-sensitive adhesive is aged for 4 weeks at 80 ° C. with a weight average molecular weight Mw _H calculated from a molecular weight distribution curve based on gel permeation chromatograph (GPC) measurement in a region where the molecular weight in terms of polystyrene is 10,000 g / mol or more. In the test, the maintenance rate is 70% or more. According to the art disclosed herein, by an indicator the weight average molecular weight Mw _H, it is possible to accurately grasp the degree of degradation of the adhesive. The pressure-sensitive adhesive sheet having a Mw _H maintenance rate (hereinafter also referred to as “Mw _H maintenance rate”) of 70% or more in the aging test can be excellent in quality stability. Moreover, since it is allowed to mix a tackifying resin with unsaturated rubber, according to the above-mentioned pressure-sensitive adhesive sheet, both excellent adhesive properties (for example, tack and peel strength) and long-term quality stability can be achieved. Can do.

  In some embodiments, the content of the unsaturated rubber in the pressure-sensitive adhesive may be 30% by weight or more of the pressure-sensitive adhesive. As described above, the pressure-sensitive adhesive containing a relatively large amount of unsaturated rubber is advantageous for improving the pressure-sensitive adhesive properties, but tends to easily deteriorate due to the unsaturated bond in the unsaturated rubber. According to the technology disclosed herein, a pressure-sensitive adhesive sheet with good quality stability can be provided even in such a configuration.

  In some embodiments, the content of the tackifying resin may be 10 parts by weight or more and 120 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber. According to the pressure-sensitive adhesive having such a composition, it is easy to obtain excellent pressure-sensitive adhesive properties (for example, tack and peel strength). According to the technology disclosed herein, a pressure-sensitive adhesive sheet with good quality stability can be provided even in a configuration using a pressure-sensitive adhesive having such a composition.

  In some embodiments, the tackifying resin can include a phenolic tackifying resin. The phenolic tackifier resin can contribute to the improvement of the adhesive property, but tends to be a factor for promoting the deterioration of the adhesive. According to the technology disclosed herein, a pressure-sensitive adhesive sheet with good quality stability can be provided even in a configuration including a phenolic tackifier resin. The content of the phenolic tackifying resin can be, for example, 5 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber. In such a composition, the improvement effect of the adhesion characteristic by use of a phenol type tackifying resin can be exhibited suitably. As the phenolic tackifier resin, for example, a terpene phenol resin can be preferably used.

  The technique disclosed here can be preferably implemented in an embodiment in which the tackifying resin includes a phenol tackifying resin and the phenol-based tackifying resin includes a terpene phenol resin having a hydroxyl value of 20 mgKOH / g or more. According to such a configuration, it is possible to suitably achieve both excellent adhesive properties and quality stability.

The pressure-sensitive adhesive may further contain an anti-aging agent in addition to the unsaturated rubber and the tackifier resin. By using an anti-aging agent, the Mw _H maintenance rate of the pressure-sensitive adhesive containing a combination of unsaturated rubber and tackifying resin is effectively increased, and the long-term quality stability (long life) of the pressure-sensitive adhesive sheet is improved. be able to. As an anti-aging agent, for example, it is effective to use a combination of a radical scavenger and a sulfur-based antioxidant. Moreover, you may use phosphorus antioxidant as anti-aging agent. By using a radical scavenger (for example, a phenol-based antioxidant), a sulfur-based antioxidant, and a phosphorus-based antioxidant in combination, a higher effect can be exhibited.

In some embodiments, the pressure-sensitive adhesive preferably has a phenolic tackifying resin content of 30 parts by weight or less based on 100 parts by weight of the unsaturated rubber. The content of the phenolic tackifying resin may be 0 parts by weight, that is, a pressure sensitive adhesive that does not include the phenolic tackifying resin. Thus, by focusing on the amount of the phenolic tackifier resin among the tackifier resins and limiting the upper limit of the content, the Mw _H retention rate of the adhesive is effectively increased, and the quality stability is good. A (long-life) pressure-sensitive adhesive sheet can be provided.

  In some embodiments, the unsaturated rubber has a monomer composition including a conjugated diene compound, and the proportion of the conjugated diene compound in the monomer composition may be 70% by weight or more. Thus, the pressure-sensitive adhesive containing an unsaturated rubber in which many conjugated diene compounds are used can exhibit excellent pressure-sensitive adhesive properties in a composition containing a tackifier resin, but tends to easily deteriorate. According to the technology disclosed herein, a pressure-sensitive adhesive sheet with good quality stability can be provided even in such a configuration.

  In some embodiments, the unsaturated rubber may include a block copolymer of a monovinyl substituted aromatic compound and a conjugated diene compound. A pressure-sensitive adhesive containing such a block copolymer and a tackifier resin can exhibit excellent pressure-sensitive adhesive properties. Therefore, according to the pressure-sensitive adhesive sheet provided with such a pressure-sensitive adhesive, it is possible to suitably achieve both excellent pressure-sensitive adhesive properties and quality stability. As the block copolymer, those having a diblock ratio of 60% by weight or more can be preferably employed from the viewpoints of tack and low temperature characteristics.

  In some embodiments, the pressure-sensitive adhesive layer may have a thickness of 30 μm or more. As the pressure-sensitive adhesive layer becomes thicker, the peel strength of the pressure-sensitive adhesive sheet tends to be improved, while structural destruction (cohesive failure) may easily occur inside the pressure-sensitive adhesive layer. Therefore, it is particularly meaningful to apply the technology disclosed herein to suppress the decrease in cohesiveness.

  The technology disclosed herein is a double-sided pressure-sensitive adhesive sheet comprising a base material, and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer as the pressure-sensitive adhesive layer supported on both surfaces of the base material, respectively. It can be preferably implemented in the form. The double-sided pressure-sensitive adhesive sheet, that is, the double-sided pressure-sensitive adhesive sheet is suitable for use for fixing a member. In fixing the member, it is preferable to suppress a decrease in cohesiveness of the adhesive over a long period of time after the adhesive sheet is pasted, from the viewpoint of preventing positional displacement and dropping (dissolution of the fixed state) of the member. Therefore, it is particularly meaningful to apply the technique disclosed herein to suppress the decrease in cohesiveness of the pressure-sensitive adhesive.

It is typical sectional drawing which shows the structure of the adhesive sheet (double-sided adhesive sheet with a base material) which concerns on one Embodiment. It is typical sectional drawing which shows the structure of the adhesive sheet (base-material-less double-sided adhesive sheet) which concerns on other embodiment. It is typical sectional drawing which shows the structure of the adhesive sheet (single-sided adhesive sheet with a base material) which concerns on other embodiment.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. It can be understood by a trader. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
In the following drawings, members / parts having the same action may be described with the same reference numerals, and redundant descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly describe the present invention, and do not accurately represent the size and scale of a product actually provided.

  In this specification, the “pressure-sensitive adhesive” refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure as described above. . The pressure-sensitive adhesive in the technology disclosed herein can be grasped as a solid component of the pressure-sensitive adhesive composition or a constituent component of the pressure-sensitive adhesive layer.

  In this specification, “unsaturated rubber” refers to a polymer having a monomer unit containing a carbon-carbon unsaturated bond and exhibiting rubber elasticity at room temperature (for example, 23 ° C.). A typical unsaturated rubber contains a carbon-carbon unsaturated bond in the main chain.

  In this specification, “a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound” refers to a monovinyl-substituted aromatic compound as a main monomer (more than 50% by weight of a copolymerization component; the same applies hereinafter). A polymer having at least one segment (hereinafter also referred to as “A segment”) and at least one segment having a conjugated diene compound as a main monomer (hereinafter also referred to as “B segment”). In general, the glass transition temperature of the A segment is higher than the glass transition temperature of the B segment. As a typical structure of such a polymer, a triblock copolymer (ABA structure triblock) having A segments (hard segments) at both ends of a B segment (soft segment), one A Examples thereof include a diblock structure copolymer (A-B structure diblock body) composed of a segment and one B segment.

  In this specification, the “styrene block copolymer” means a polymer having at least one styrene block. The styrene block refers to a segment having styrene as a main monomer. A segment consisting essentially of styrene is a typical example of a styrene block as used herein. The “styrene isoprene block copolymer” refers to a polymer having at least one styrene block and at least one isoprene block (a segment having isoprene as a main monomer). Typical examples of styrene isoprene block copolymers are triblock copolymer (triblock body) having styrene blocks (hard segment) at both ends of isoprene block (soft segment), one isoprene block and one styrene. Examples thereof include a diblock copolymer (diblock body) composed of blocks. The “styrene butadiene block copolymer” refers to a polymer having at least one styrene block and at least one butadiene block (a segment containing butadiene as a main monomer).

In this specification, the “styrene content” of the styrenic block copolymer refers to the weight ratio of the styrene component to the total weight of the block copolymer. The styrene content can be measured by NMR (nuclear ceramic resonance spectrum method).
Further, the ratio of the diblock body in the styrene block copolymer (hereinafter sometimes referred to as “diblock body ratio” or “diblock ratio”) is determined by the following method. That is, a styrene block copolymer is dissolved in tetrahydrofuran (THF), and GS5000H and G4000H liquid chromatograph columns manufactured by Tosoh Corporation are connected in two stages, for a total of four stages, and THF is used as the mobile phase. Then, high performance liquid chromatography is performed under conditions of a temperature of 40 ° C. and a flow rate of 1 mL / min. The peak area corresponding to the diblock body is measured from the obtained chart. And the diblock body ratio is calculated | required by calculating the percentage of the peak area corresponding to the said diblock body with respect to the whole peak area.

  In this specification, a numerical value representing a molecular weight or a weight average molecular weight is understood as a numerical value with a unit of “g / mol” unless otherwise specified. Moreover, the molecular weight relevant to GPC measurement shall mean the molecular weight of polystyrene conversion, unless it mentions specially.

<Structural example of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein (which may be in a long form such as a tape) may be, for example, in the form of a double-sided pressure-sensitive adhesive sheet having the cross-sectional structure shown in FIG. The double-sided pressure-sensitive adhesive sheet 1 includes a base material (for example, a plastic film or a non-woven fabric) 15, and a first pressure-sensitive adhesive layer 11 and a second pressure-sensitive adhesive layer 12 that are respectively supported on both surfaces of the base material 15. More specifically, the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the base material 15, respectively. As shown in FIG. 1, the double-sided pressure-sensitive adhesive sheet 1 before use (before being attached to an adherend) is wound in a spiral shape with the front surface 21A and the back surface 21B overlapped with a release liner 21 which is a release surface. It can be in the form of In the double-sided pressure-sensitive adhesive sheet 1 in this form, the surface of the second pressure-sensitive adhesive layer 12 (second pressure-sensitive adhesive surface 12A) is peeled off by the front surface 21A of the release liner 21, and the surface of the first pressure-sensitive adhesive layer 11 (first pressure-sensitive adhesive surface 11A) is peeled off. The liner 21 is protected by the back surface 21B. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be protected by two independent release liners.

  The technique disclosed here is preferably applied to a double-sided pressure-sensitive adhesive sheet with a substrate as shown in FIG. 1, and also a double-sided pressure-sensitive adhesive sheet 2 having no base material (that is, having no base material) as shown in FIG. It can also be applied to. For example, as shown in FIG. 2, the double-sided pressure-sensitive adhesive sheet 2 before use is such that the first pressure-sensitive adhesive surface 11A and the second pressure-sensitive adhesive surface 11B of the substrate-less pressure-sensitive adhesive layer 11 are at least the surface (front surface) on the pressure-sensitive adhesive layer side. May be protected by release liners 21 and 22 that are release surfaces. Alternatively, the release liner 22 is omitted, and the release liner 21 having both sides of the release surface is used, and this and the adhesive layer 11 are overlapped and wound into a spiral shape, whereby the second adhesive surface 11B is released into the release liner. 21 may be in contact with the back surface of 21 and protected.

  As shown in FIG. 3, the technology disclosed herein is also a single-sided adhesive type base including a base material 15 and a pressure-sensitive adhesive layer 11 supported on the first surface (non-peeling surface) 15 </ b> A of the base material. It can be applied to the pressure-sensitive adhesive sheet 3 with material. For example, as shown in FIG. 3, the pressure-sensitive adhesive sheet 3 before use is a release liner in which the surface (adhesive surface) 11 </ b> A of the pressure-sensitive adhesive layer 11 is at least the surface (front surface) on the pressure-sensitive adhesive layer side. 21 may be the protected form. Alternatively, the release liner 21 is omitted, and the first adhesive surface 11A is the second of the substrate 15 by winding the adhesive sheet 3 with the substrate using the substrate 15 having the second surface 15B as the release surface. It may be in a form protected against the surface 15B.

The pressure-sensitive adhesive sheet disclosed herein is characterized by including a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifying resin, and having a Mw _H maintenance rate of the pressure-sensitive adhesive of 70% or more. . The Mw _H maintenance rate of the pressure-sensitive adhesive is the weight average molecular weight Mw _H of the pressure-sensitive adhesive after the aging test at 80 ° C. for 4 weeks (Mw _H after aging), and the weight average molecular weight Mw _H of the pressure-sensitive adhesive before the aging test. is defined as the ratio to aging before Mw _H). The aging test is performed by storing a pressure-sensitive adhesive sheet having a release liner bonded to the surface (pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layer in an air atmosphere at 80 ° C. for 4 weeks. As the release liner, release paper (for example, release-treated polylamination paper) can be preferably used. The thickness of the release liner is not particularly limited, and a release liner having a thickness of about 20 μm to 150 μm (typically about 25 μm to 100 μm) can be appropriately selected and used. More specifically, the aging test can be performed by the method described in Examples described later.

<Mw _H maintenance rate>
In this specification, the weight average molecular weight Mw _H of the pressure-sensitive adhesive (sometimes simply expressed as “Mw _H ”) means that the molecular weight in terms of polystyrene is 10,000 or more from the molecular weight distribution curve obtained by GPC measurement. Refers to the weight average molecular weight calculated for a region. In contrast, the entire of the molecular weight distribution curve (i.e., molecular weight in terms of polystyrene, including an area of less than 10,000) weight average molecular weight to be calculated, may be referred to the weight average molecular weight Mw _T. As a sample for GPC measurement, the pressure-sensitive adhesive collected from the pressure-sensitive adhesive sheet was dissolved in tetrahydrofuran (THF) to give a 0.1% by weight solution, which was allowed to stand overnight, and then filtered through a 0.45 μm membrane filter. Use the filtrate. The GPC measurement can be performed under the following conditions or conditions that can obtain results equivalent to the following conditions. A similar method is used in the embodiments described later.
・ Analyzer: HLC-8120GPC manufactured by Tosoh Corporation
Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000
Column size: 6.0 mmI. D. × 150mm
・ Eluent: THF
・ Flow rate: 0.6mL / min
・ Detector: Differential refractometer (RI)
-Column temperature: 40 ° C
・ Injection volume: 20μL
Standard sample: polystyrene

In the pressure-sensitive adhesive containing the unsaturated rubber and the tackifying resin, as the tackifying resin, one having a weight average molecular weight Mw _T lower than that of the unsaturated rubber is usually used. In the molecular weight distribution curve obtained by GPC measurement of such a pressure-sensitive adhesive, the peak corresponding to the tackifying resin typically appears in a region having a molecular weight of about several hundred to several thousand. According to the art disclosed herein (specifically, the molecular weight of 10,000 or more regions) high molecular weight region excluding such areas by focusing on the weight average molecular weight Mw _H for the molecular weight distribution curve of pressure-sensitive adhesive sheet It is possible to accurately grasp the deterioration and deterioration of the unsaturated rubber that can cause the quality of the rubber to deteriorate. According to the pressure-sensitive adhesive sheet having a maintenance rate (Mw _H maintenance rate) of 70% or more after the aging test of the weight average molecular weight Mw _H , excellent adhesive properties and long-term quality stability (for example, decrease in cohesiveness with time) Can be achieved at the same time.

In some embodiments, the Mw _H retention may be about 75% or more, about 80% or more, or about 85% or more. The technique disclosed here can be suitably implemented even in an aspect in which the Mw _H maintenance rate is approximately 87% or more, or in an aspect in which approximately 90% or more. The closer the Mw _H retention rate is to 100%, the higher the quality stability of the pressure-sensitive adhesive sheet. Therefore, in the technique disclosed here, the upper limit of the Mw _H maintenance rate may be 100%. Alternatively, the Mw _H maintenance rate may be less than 100% (for example, 99% or less) from a practical viewpoint in consideration of balance with other adhesive properties and economy. The Mw _H retention rate can be adjusted, for example, by selecting an unsaturated rubber, an amount of unsaturated rubber used, a selection of tackifying resin, an amount of tackifying resin used, and the like. Moreover, in the composition in which the pressure-sensitive adhesive contains an anti-aging agent, the Mw _H maintenance rate can be adjusted by the selection of the anti-aging agent and the amount of the anti-aging agent used.

Although not particularly limited, it is appropriate that the Mw _H (that is, Mw _H before aging) of the pressure-sensitive adhesive sheet disclosed herein is usually about 80,000 or more, and about 100,000 or more. It may be about 130,000 or more, or about 150,000 or more. As the Mw _{H of the} pressure-sensitive adhesive sheet increases, the cohesiveness generally tends to improve. The Mw _H of the pressure-sensitive adhesive sheet may be, for example, about 1,000,000 or less, may be about 800,000 or less, and may be about 600,000 or less. When the Mw _{H of the} pressure-sensitive adhesive sheet is lowered, tack and peel strength (especially, these characteristics at low temperatures, that is, low-temperature characteristics) generally tend to be improved. From such a viewpoint, in some embodiments, the Mw _H of the pressure-sensitive adhesive sheet may be approximately 400,000 or less, may be approximately 300,000 or less, may be approximately 250,000 or less, and may be approximately It may be 200,000 or less. Art disclosed herein, for example, can be preferably implemented in the form of a pressure-sensitive adhesive sheet Mw _H is about 130,000 about 200,000. The Mw _H of the pressure-sensitive adhesive sheet can be adjusted by selecting an unsaturated rubber. Moreover, in the composition containing a crosslinking agent, it can adjust also with the kind of crosslinking agent, and the usage-amount of a crosslinking agent.

Although not particularly limited, it is appropriate that the pressure-sensitive adhesive sheet disclosed herein has an Mw _H after aging test (that is, Mw _H after aging) of about 70,000 or more, and about 90,000 or more. And more preferably about 100,000 or more (for example, about 120,000 or more). When Mw _H increases after aging, better adhesive properties (for example, cohesiveness) tend to be exhibited even after a long period of time.

<Unsaturated rubber>
As the unsaturated rubber, various rubber-like polymers having a monomer unit containing a carbon-carbon unsaturated bond can be used. In some embodiments, the unsaturated rubber can be a homopolymer or copolymer of a conjugated diene compound. Specific examples of the conjugated diene compound include 1,3-butadiene and isoprene. The copolymer here may be a random copolymer, a block copolymer or a graft copolymer. Non-limiting examples of such unsaturated rubbers include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isobutene-isoprene rubber (IIR), acrylonitrile-butadiene rubber (NBR), Examples include chloroprene rubber (CR), styrene isoprene block copolymer, and styrene butadiene block copolymer. In some embodiments, an unsaturated rubber with a monomer composition comprising isoprene may be preferably employed. Since the unsaturated rubber having such a monomer composition tends to easily undergo an auto-oxidation reaction due to the presence of an isoprene structure, it is significant to apply the technique disclosed herein.

  In the unsaturated rubber having a monomer composition containing a conjugated diene compound, the proportion of the conjugated diene compound in the monomer composition is not particularly limited. From the viewpoint of improving the adhesive properties, the ratio of the conjugated diene compound can be, for example, 60% by weight or more, usually 65% by weight or more is suitable, and preferably 70% by weight or more, and 75% by weight. It may be 80% by weight or more (typically more than 80% by weight, for example, 82% by weight or more). According to the technique disclosed herein, a pressure-sensitive adhesive sheet with good quality stability can be provided even in a pressure-sensitive adhesive using a monomer composition unsaturated rubber containing a large amount of a conjugated diene compound.

(Block copolymer of monovinyl-substituted aromatic compound and conjugated diene compound)
In some embodiments, the unsaturated rubber may contain 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 having no vinyl group (for example, an alkyl group)). Specific examples of the monovinyl-substituted aromatic compound include styrene, α-methylstyrene, vinyl toluene, vinyl xylene and the like. Specific examples of the conjugated diene compound include 1,3-butadiene and isoprene. Such a block copolymer can be used as an unsaturated rubber in the technology disclosed herein, alone or in combination of two or more.

  The A segment (hard segment) in the block copolymer has a copolymerization ratio of the monovinyl-substituted aromatic compound (two or more can be used in combination) of 70% by weight or more (more preferably 90% by weight or more). It may be substantially 100% by weight). The B segment (soft segment) in the block copolymer has a copolymerization ratio of the conjugated diene compound (two or more can be used in combination) of 70% by weight or more (more preferably 90% by weight or more). It may be 100% by weight). According to such a block copolymer, a higher performance pressure-sensitive adhesive sheet can be realized.

The block copolymer may be in the form of a diblock body, a triblock body, a radial body, a mixture thereof, and the like. In the triblock body or radial body, it is preferable that an A segment (for example, a styrene block) is arranged at the end of the polymer chain. This is because the A segments arranged at the ends of the polymer chains are likely to gather to form a domain, thereby forming a pseudo cross-linked structure and improving the cohesiveness of the pressure-sensitive adhesive.
The block copolymer in the technique disclosed herein has a diblock ratio of 30% by weight or more (more preferably 40% by weight or more, more preferably 50%) from the viewpoint of adhesive strength (peel strength) to the adherend. % By weight or more, particularly preferably 60% by weight or more, typically 65% by weight or more) can be preferably used. From the viewpoint of peel strength, a block copolymer having a diblock body ratio of 70% by weight or more is particularly preferable. From the viewpoint of cohesiveness and the like, a block copolymer having a diblock body ratio of 90% by weight or less (more preferably 85% by weight or less, for example, 80% by weight or less) can be preferably used. For example, a block copolymer having a diblock ratio of 60 to 85% by weight is preferable, and a block copolymer having a ratio of 70 to 85% by weight (for example, 70 to 80% by weight) is more preferable.

(Styrene block copolymer)
In a preferred embodiment of the technology disclosed herein, the unsaturated rubber is a styrenic block copolymer. For example, an embodiment in which the unsaturated rubber includes at least one of a styrene isoprene block copolymer and a styrene butadiene block copolymer is preferable. Among the styrene block copolymers contained in the pressure-sensitive adhesive, the proportion of styrene isoprene block copolymer is 70% by weight or more, the proportion of styrene butadiene block copolymer is 70% by weight or more, or styrene The total proportion of the isoprene block copolymer and the styrene butadiene block copolymer is preferably 70% by weight or more. In a preferred embodiment, substantially all (for example, 95 to 100% by weight) of the styrenic block copolymer is a styrene isoprene block copolymer. In another preferred embodiment, substantially all (for example, 95 to 100% by weight) of the styrenic block copolymer is a styrene butadiene block copolymer. According to such a composition, the effect of applying the technique disclosed here can be better exhibited.

  The styrenic block copolymer may be in the form of a diblock body, a triblock body, a radial body, a mixture thereof, and the like. In a triblock body and a radial body, it is preferable that the styrene block is arranged at the terminal of the polymer chain. This is because the styrene blocks arranged at the end of the polymer chain are likely to gather to form a styrene domain, thereby forming a pseudo cross-linked structure and improving the cohesiveness of the pressure-sensitive adhesive. As the styrenic block copolymer used in the technology disclosed herein, the diblock ratio is 30% by weight or more (more preferably 40% by weight or more) from the viewpoint of adhesive strength (peeling strength) to the adherend. More preferably 50% by weight or more, particularly preferably 60% by weight or more, typically 65% by weight or more) can be preferably used. A styrenic block copolymer having a diblock ratio of 70% by weight or more (for example, 75% by weight or more) may be used. From the viewpoint of cohesion and the like, a styrenic block copolymer having a diblock ratio of 90% by weight or less (more preferably 85% by weight or less, for example, 80% by weight or less) can be preferably used. From the viewpoint of achieving a good balance between adhesive properties and cohesiveness, a styrene block copolymer having a diblock ratio of 60 to 85% by weight is preferable, and a styrene type having a ratio of 70 to 85% by weight (for example, 70 to 80% by weight). A block copolymer is more preferred.

  The styrene content of the styrenic block copolymer may be, for example, 5 to 40% by weight. From the viewpoint of cohesiveness, a styrene block copolymer having a styrene content of 10% by weight or more (more preferably more than 10% by weight, for example, 12% by weight or more) is preferable. From the viewpoint of peel strength, the styrene content is preferably 35% by weight or less (typically 30% by weight or less, more preferably 25% by weight or less), and 20% by weight or less (typically less than 20% by weight). For example, 18% by weight or less) is particularly preferable. A styrene block copolymer having a styrene content of 12% by weight or more and less than 20% by weight can be preferably employed from the viewpoint of better exerting the effect of applying the technology disclosed herein.

(Unsaturated rubber content)
In the pressure-sensitive adhesive disclosed herein, the content of the unsaturated rubber (for example, styrene isoprene block copolymer) as described above may be, for example, about 10% by weight or more of the total pressure-sensitive adhesive, and about 20%. It may be not less than wt%. In some embodiments, the content of unsaturated rubber in the pressure-sensitive adhesive may be about 30% by weight or more, about 40% by weight or more, about 50% by weight or more. Also good. This makes it easier to form a pressure-sensitive adhesive sheet with better adhesive properties. Further, since the deterioration of the pressure-sensitive adhesive tends to easily progress as the content of unsaturated rubber in the pressure-sensitive adhesive increases, the effect of applying the technology disclosed herein can be better exhibited. From this point of view, the content of the unsaturated rubber may be about 55% by weight or more, or about 60% by weight or more. On the other hand, from the viewpoint of suitably exhibiting the use effect of the tackifier resin, the content of the unsaturated rubber in the pressure-sensitive adhesive is usually suitably about 95% by weight or less, and about 90% by weight or less. It may be about 80% by weight or less, about 75% by weight or less, or about 70% by weight or less. The technique disclosed herein can be preferably implemented in an embodiment in which the content of the unsaturated rubber is about 65% by weight or less (for example, about 60% by weight or less).

<Tackifying resin>
The pressure-sensitive adhesive layer disclosed herein contains a tackifying resin in addition to the unsaturated rubber. The tackifying resin is selected from various known tackifying resins such as phenolic tackifying resins, terpene resins, modified terpene resins, rosin tackifying resins, petroleum resins, styrene resins, coumarone / indene resins, and ketone resins. 1 type, or 2 or more types can be used. Although it does not specifically limit as tackifying resin, For example, a softening point can use a 40 degreeC or more, and a softening point has a 60 degreeC or more or 80 degreeC or more. The softening point of the tackifying resin can be, for example, 200 ° C. or lower (typically 180 ° C. or lower).

The term “phenolic tackifier resin” as used herein means a tackifier resin having a molecular structure including a phenol skeleton, and includes a terpene phenol resin, a hydrogenated terpene phenol resin, a phenol resin, a rosin phenol resin, and the like.
The terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue. A terpene-phenol copolymer (terpene-phenol copolymer resin) and a terpene homopolymer or copolymer This is a concept that includes both phenol-modified products (phenol-modified terpene resins). Preferable examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene and limonene (including d-form, l-form and d / l-form (dipentene)). Is mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. Sometimes referred to as hydrogenated terpene phenol resin. Examples of the phenols include phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin and the like.
The phenolic resin is typically a resin obtained from various phenols and formaldehyde as described above. Specifically, the phenol resin includes, for example, an alkylphenol resin, a xylene-formaldehyde resin, and the like. Examples of the phenolic resin include a resol type obtained by addition reaction of the above phenols and formaldehyde with an alkali catalyst, and a novolak type obtained by condensation reaction of the above phenols and formaldehyde with an acid catalyst. included.
The rosin phenolic resin is typically a phenol-modified product of rosins or rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include a rosin phenol resin obtained by a method of adding a phenol as described above to a rosin or a rosin derivative with an acid catalyst and performing thermal polymerization.

  Examples of terpene resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one terpene or a copolymer of two or more terpenes. Examples of the homopolymer of one kind of terpene include an α-pinene polymer, a β-pinene polymer, a dipentene polymer, and the like.

  Examples of the modified terpene resin include those obtained by modifying the terpene resin. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

The concept of rosin-based tackifying resin here includes both rosins and rosin derivative resins.
Examples of rosins include unmodified rosins such as gum rosin, wood rosin, tall oil rosin (raw rosin); modified rosins modified with hydrogenation, disproportionation, polymerization, etc. Averaged rosin, polymerized rosin, other chemically modified rosins, etc.).
The rosin derivative resin is typically a derivative of rosins as described above. The concept of the rosin resin here includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). For example, rosin esters such as an unmodified rosin ester that is an ester of an unmodified rosin and an alcohol, and a modified rosin ester that is an ester of a modified rosin and an alcohol; for example, an rosin modified with an unsaturated fatty acid. Saturated fatty acid-modified rosins; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosins or various rosin derivatives described above (rosin esters, unsaturated fatty acid-modified rosins and unsaturated Rosin alcohols obtained by reducing the carboxy group of fatty acid-modified rosin esters); for example, rosins or metal salts of the various rosin derivatives described above. Specific examples of rosin esters include unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) methyl ester, triethylene glycol ester, glycerin ester, pentaerythritol ester and the like.

  Examples of petroleum resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic / aromatic copolymer (C5 / C9) petroleum resins, and hydrogenated products thereof ( Examples thereof include alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins.

  Examples of styrene resins include those based on homopolymers of styrene, those based on homopolymers of α-methylstyrene, those based on homopolymers of vinyltoluene, styrene, α -Methylstyrene or vinyltoluene having a copolymer containing two or more monomers as the main component (for example, α-methylstyrene / styrene copolymer having α-methylstyrene / styrene copolymer as the main component) Coalesced resin) and the like.

  As the coumarone-indene resin, a resin containing coumarone and indene as a monomer component constituting the resin skeleton (main chain) can be used. Examples of monomer components that can be contained in the resin skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

  Examples of the ketone resin include condensates of formaldehyde with ketones such as methyl ethyl ketone, methyl isobutyl ketone, acetophenone, cyclohexanone, and methylcyclohexanone.

As a preferable aspect, the aspect in which an adhesive layer contains 1 type, or 2 or more types of phenol-type tackifying resin (for example, terpene phenol resin) is mentioned. By blending a phenolic tackifier resin with an unsaturated rubber (for example, a styrene block copolymer), the adhesive properties can be effectively improved. As a result, an adhesive sheet having excellent adhesive properties and long-term quality stability (long life) can be realized.
When the pressure-sensitive adhesive layer contains a phenolic tackifier resin, the content is not particularly limited. The content of the phenolic tackifying resin can be, for example, 1 part by weight or more with respect to 100 parts by weight of the unsaturated rubber, usually 5 parts by weight or more is appropriate, and even if it is 10 parts by weight or more. It may be 15 parts by weight or more. In some embodiments, the content of the phenolic tackifying resin with respect to 100 parts by weight of the unsaturated rubber may be 20 parts by weight or more, or 30 parts by weight or more (for example, 35 parts by weight or more). In addition, from the viewpoint of low-temperature characteristics and compatibility of the pressure-sensitive adhesive, the content of the phenolic tackifying resin with respect to 100 parts by weight of the unsaturated rubber is usually suitably 60 parts by weight or less, and 50 parts by weight or less. There may be. From the viewpoint of placing more emphasis on quality stability, in some embodiments, the content of the phenolic tackifier resin relative to 100 parts by weight of the unsaturated rubber may be, for example, less than 40 parts by weight, and 35 parts by weight or less. It may be 30 parts by weight or less, or 25 parts by weight or less.

  When using a phenolic tackifying resin, the phenolic tackifying resin amount in the entire tackifying resin may be, for example, 25% by weight or more, 30% by weight or more, and 50% by weight or more. It may be 80% by weight or more, or 90% by weight or more. Substantially all of the tackifying resin (for example, 95 to 100% by weight, or even 99 to 100% by weight) may be a phenolic tackifying resin. In such a configuration, the effect of using the phenol-based tackifier resin can be suitably exhibited. In some embodiments, the amount of the phenolic tackifying resin in the entire tackifying resin may be, for example, 70% by weight or less and 60% by weight or less from the viewpoint of improving low temperature characteristics and quality stability. It may be 45% by weight or less.

  In some embodiments, the amount of terpene phenolic resin in the total phenolic tackifying resin used can be, for example, 50% by weight or more, 70% by weight or more, and 85% by weight or more. It may be 90% by weight or more. Substantially all of the phenolic tackifying resin (for example, 95 to 100% by weight, or even 99 to 100% by weight) may be a terpene phenol resin. The technology disclosed herein can be suitably implemented in such a manner, and can provide a pressure-sensitive adhesive sheet having good adhesive properties and a long life.

(Tackifying resin _TH )
PSA layer disclosed herein, as the tackifying resin, a softening point contains a tackifier resin T _H than 100 ° C.. From the viewpoint of aggregation property, the softening point of the tackifier resin _{T H,} preferably at least 120 ° C., more preferably at least 125 ° C., more preferably above 130 ° C., 135 ° C. or higher (e.g., 140 ° C. or higher) is especially preferred. Further, from the viewpoint of peel strength to the adherend, the softening point of the tackifier resin T _H, is suitably 200 ° C. or less, preferably 180 ° C. or less, more preferably 170 ° C. or less (e.g., 160 ° C. or less) is there.

  Here, in this specification, the softening point of the tackifier resin is defined as a value measured based on a softening point test method (ring ball method) defined in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible, and is carefully filled so that no bubbles are formed in the ring placed on a flat metal plate. After cooling, cut off the raised part from the plane including the top of the ring with a slightly heated sword. Next, a supporter (ring stand) is put in a glass container (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth becomes 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in glycerin so as not to contact each other, and the temperature of glycerin is maintained at 20 ° C. plus or minus 5 ° C. for 15 minutes. . Next, a steel ball is placed on the center of the surface of the sample in the ring, and this is placed in a fixed position on the support. Next, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed, the center of the mercury bulb of the thermometer is set to the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is placed between the center and the edge of the bottom of the container so that the heating is even. It should be noted that the rate at which the bath temperature rises after reaching 40 ° C. after heating has started must be 5.0 plus or minus 0.5 ° C. per minute. The temperature at the time when the sample gradually softens and flows down from the ring and finally comes into contact with the bottom plate is read and used as the softening point. Two or more softening points are measured simultaneously, and the average value is adopted.

The tackifier resin T _H, the above-mentioned phenol-based tackifying resins, terpene resins, modified terpene resins, rosin-based tackifying resins, petroleum resins, styrene resins, coumarone-indene resin, one or two of such ketone resin The above can be used. Of these, terpene phenol resins, rosin phenol resins, terpene resins, polymerized rosins, and esterified products of polymerized rosins are preferred.

As a preferable embodiment, there is an embodiment in which one or two or more terpene phenol resins are used as the tackifier resin _TH1 . For example, more than 25% by weight of the tackifier resin _{T H} (more preferably 30 wt% or more) is a preferred embodiment terpene phenol resin (tackifier resin _{T H1).} Furthermore, terpene phenol resin amount in the tackifier resin T _H is 70 wt% or less approximately (e.g. 60 wt% or less, typically 50 wt% or less) may be. Alternatively, the tackifier resin _T less than 50% by weight of _H is may be a terpene phenol resin (tackifier resin _{T H1),} 80 wt% or more (e.g. 90 wt% or more) terpene phenol resin (tackifier resin _{T H1} ) is a also good, substantially all of the tackifier resin _{T H} (e.g. 95 to 100 wt%, more 99-100% by weight) may be a terpene phenol resin (tackifier resin _{T H1).} A terpene phenol resin having a softening point of 120 ° C. or higher and 200 ° C. or lower (typically 130 ° C. or higher and 180 ° C. or lower, eg, 135 ° C. or higher and 170 ° C. or lower) can be preferably used.

The ratio for which tackifying resin _TH1 accounts among all the tackifying resin contained in the adhesive layer disclosed here is not specifically limited. The ratio can be, for example, 30% by weight or more (typically 40% by weight or more), and can be, for example, 70% by weight or less (typically 60% by weight or less). Alternatively, substantially all of the total tackifying resin (e.g., 95 to 100 wt%, more 99-100% by weight) may be a tackifier resin _{T H1.}

Furthermore, the art disclosed herein, as the tackifier resin T _{H, (typically} terpene phenolic resin) tackifier resin T _H1 may be preferably implemented in a manner that includes a different tackifier resin T _H2 and. The softening point of the tackifier resin T _H2 is lower it is preferable than the softening point of the tackifier resin T _H1, about 10 ° C. or higher (e.g., 20 ° C. or higher) than the softening point of the tackifier resin T _H1 is more preferably lower . According to such an embodiment, for example, a pressure-sensitive adhesive sheet with better peel strength can be realized. From the viewpoint of making cohesion and peel strength compatible at a high level, a tackifying resin TH ₂ having a softening point of 100 ° C. or higher and lower than 120 ° C. can be preferably used. Especially, use of tackifying resin _TH2 whose softening point is 110 degreeC or more and less than 120 _degreeC is preferable.

Examples of the tackifying resin _TH2 include the above-described various tackifying resins (phenolic tackifying resin, terpene resin, modified terpene resin, rosin tackifying resin, petroleum resin, styrene resin, coumarone / indene resin, ketone resin, etc. ) Can be appropriately selected and used. The technique disclosed here can be preferably implemented in a mode in which the pressure-sensitive adhesive contains at least one of a petroleum resin and a terpene resin as the tackifying resin _TH2 . For example, a composition in which the main component of the tackifying resin TH ₂ (that is, a component occupying more than 50% by weight of the tackifying resin TH ₂ ) is a petroleum resin, a composition that is a terpene resin, a petroleum resin and a terpene resin A composition that is a combination, etc. can be preferably employed. From the viewpoint of adhesive strength and compatibility, an embodiment in which the main component of the tackifying resin _TH2 is a terpene resin (for example, an α-pinene polymer or a β-pinene polymer) is preferable. A terpene resin may be used for substantially all of the tackifying resin _TH2 (for example, 95% by weight or more).

As the adhesive layer tackifier resin _{T H} disclosed herein, if it contains a tackifier resin _{T H1} and the tackifier resin _{T H2,} the relationship between their _usage, T _H1: weight ratio of _{T H2} 25 : 75 to 70:30 (more preferably 30:70 to 60:40). The technique disclosed here can be preferably implemented in an embodiment in which the pressure-sensitive adhesive contains more T _H1 than T _H2 as a tackifier resin. According to this aspect, a higher performance pressure-sensitive adhesive sheet can be realized.

Art disclosed herein, for example, as a tackifier resin _{T H,} the hydroxyl value may be preferably carried out in a manner containing 80 mg KOH / g or more (e.g. 90 mgKOH / g or higher) tackifying resin _{(T HO1).} The hydroxyl value of the tackifying resin _THO1 is typically 200 mgKOH / g or less, preferably 180 mgKOH / g or less (for example, 160 mgKOH / g or less). According to the pressure-sensitive adhesive containing the tackifying resin _THO1 , a higher-performance pressure-sensitive adhesive sheet can be realized. A pressure-sensitive adhesive sheet that achieves a higher level of cohesion and other properties (for example, low temperature initial back adhesion) can be realized.

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method defined in JIS K0070: 1992 can be adopted. The specific measurement method is as follows.
[Measurement method of hydroxyl value]
1. Reagent (1) As an acetylating reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, and pyridine is added thereto to make a total volume of 50 mL, and the mixture is sufficiently stirred. Alternatively, about 25 g (about 23.5 mL) of acetic anhydride is taken, and pyridine is added thereto to make a total volume of 100 mL, and the mixture is sufficiently stirred.
(2) As a measuring reagent, a 0.5 mol / L potassium hydroxide ethanol solution is used.
(3) Prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) About 2 g of a sample is accurately weighed in a flat bottom flask, 5 mL of an acetylating reagent and 10 mL of pyridine are added, and an air cooling tube is attached.
(2) The flask was heated in a bath at 100 ° C. for 70 minutes, allowed to cool, and 35 mL of toluene was added as a solvent from the top of the condenser and stirred, and then 1 mL of distilled water was added and stirred to acetic anhydride. Disassemble. Heat again in the bath for 10 minutes to complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Next, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole pipette.
(5) Potentiometric titration with 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is the end point.
(6) In the blank test, the above (1) to (5) are performed without putting a sample.
3. Calculation The hydroxyl value is calculated by the following formula.
Hydroxyl value (mgKOH / g) = [(BC) × f × 28.05] / S + D
here,
B: Amount of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test (mL),
C: The amount of 0.5 mol / L potassium hydroxide ethanol solution used for the sample (mL),
f: factor of 0.5 mol / L potassium hydroxide ethanol solution,
S: weight of the sample (g),
D: Acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide 56.11,
It is.

As the tackifier resin _THO1 , those having a hydroxyl value of a predetermined value or more among the above-described various tackifier resins can be used alone or in appropriate combination. In a preferred embodiment, at least a terpene phenol resin is used as the tackifier resin _THO1 . The terpene phenol resin is preferable because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol. The proportion of terpene phenol resin occupying in the tackifier resin T _HO1 is approximately 50 wt% or more (e.g. 80 wt% or more, and typically 90% by weight or more), more preferably, substantially the tackifier resin T _HO1 It is more preferable that all (for example, 95 to 100% by weight, more preferably 99 to 100% by weight) is a terpene phenol resin.

Art disclosed herein is, when implemented in a manner of using a pressure-sensitive adhesive layer containing a tackifier resin T _HO1, the proportion of the tackifier resin T _HO1 of the total tackifying resin is not particularly limited. The said ratio can be 10 weight% or more (typically 20 weight% or more), for example, for example, can be 70 weight% or less (typically 60 weight% or less). Alternatively, substantially all of the tackifying resin (for example, 95 to 100% by weight, or even 99 to 100% by weight) may be the tackifying resin _THO1 .

PSA layer disclosed herein is as a tackifier resin _{T H,} a hydroxyl value of 0 or 80 mg KOH / g of less than tackifier resin _{(T HO2)} may contain. Tackifier resin _{T HO2} may be used in place of the tackifier resin _{T HO1,} it may be used in combination with a tackifier resin _{T HO1.} As a preferred embodiment, the hydroxyl value is a tackifier resin _{T HO1} above 80 mg KOH / g, it includes embodiments comprising a tackifier resin _{T HO2.}

As the tackifier resin _THO2 , those having a hydroxyl value in the above range among the various tackifier resins described above can be used alone or in appropriate combination. For example, a phenolic tackifier resin (for example, terpene phenol resin or rosin phenol resin) having a hydroxyl value of 0 or more and less than 80 mgKOH / g, petroleum resin (for example, C5 petroleum resin), terpene resin (for example, β-pinene polymer) ), Rosins (for example, polymerized rosin), rosin derivative resins (for example, esterified products of polymerized rosin), and the like. In a preferred embodiment, at least a terpene phenol resin is used as the tackifying resin _THO2 . The terpene phenol resin is preferable because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol. The proportion of terpene phenol resin occupying in the tackifier resin T _HO2 is approximately 50 wt% or more (e.g. 80 wt% or more, and typically 90% by weight or more) may be substantially the tackifier resin T _HO2 All (for example, 95 to 100% by weight, further 99 to 100% by weight) may be a terpene phenol resin.

Art disclosed herein is, when implemented in a manner of using a pressure-sensitive adhesive layer containing a tackifier resin T _HO2, the proportion of the tackifier resin T _HO2 of the total tackifying resin is not particularly limited. The said ratio can be 10 weight% or more (typically 20 weight% or more), for example, for example, can be 70 weight% or less (typically 60 weight% or less). Alternatively, substantially all of the total tackifying resin (e.g., 95 to 100 wt%, more 99-100% by weight) may be a tackifier resin _{T HO2.}

The art disclosed herein, the PSA layer has a hydroxyl value 80 mg KOH / g or more (typically 80~160mgKOH / g, for example 80~140mgKOH / g) and a tackifier resin _{T HO1} of, hydroxyl value 40 mg KOH / g It can be preferably implemented in an embodiment containing a combination of tackifying resin _{THO2 of} less than 80 mgKOH / g. In this _case, the relationship between the amount of _{T HO1} and _{T HO2,} for example, the weight ratio _{(T HO1:} T _HO2) is 1: 5 to 5: can be set to be 1, and 1: It is appropriate to set it in the range of 3 to 3: 1 (for example, 1: 2 to 2: 1). As a preferred _{embodiment, T HO1,} T _HO2 is mentioned embodiment each a terpene phenol resin.

In one embodiment of the art disclosed herein, the tackifier resin _{T H} is as different tackifying resins and tackifying resin _{T HO1, T HO2,} has an aromatic ring and hydroxyl value is less than 30 mgKOH / g It may further contain a tackifying resin _THR1 . Examples of tackifying resins having an aromatic ring include the above-mentioned aromatic petroleum resins, aliphatic / aromatic copolymer petroleum resins, styrene resins, coumarone-indene resins, styrene-modified terpene resins, terpene-phenol copolymers Examples thereof include resins, phenol-modified terpene resins, and rosin phenol resins. Among these, those having a softening point of 120 ° C. or higher (preferably 130 ° C. or higher, eg 135 ° C. or higher) and a hydroxyl value of 30 mgKOH / g or lower (preferably less than 5 mgKOH / g, eg less than 1 mgKOH / g) It can be employed as _THR1 . Particularly preferred tackifying resins _THR1 include aromatic petroleum resins and styrene resins (for example, α-methylstyrene / styrene copolymer resins). In addition, the technique disclosed here can be implemented also in the aspect in which an adhesive layer does not contain tackifying resin _THR1 substantially.

In another embodiment of the PSA disclosed herein, the tackifier resin T _H as tackifier resin T _HO1, different tackifying resins and T _HO2, has an aromatic ring and isoprene units, terpene skeleton and It may contain a tackifier resin _THR2 substantially free of rosin skeleton. Here, the tackifying resin _THR2 substantially does not contain an isoprene unit, a terpene skeleton, and a rosin skeleton. The proportion of these structural parts (that is, the isoprene unit, the terpene skeleton, and the rosin skeleton) in the tackifying resin _THR2. Is less than 10% by weight in total (more preferably less than 8% by weight, even more preferably less than 5% by weight, for example, less than 3% by weight). The above ratio may be 0% by weight. In addition, the ratio of the isoprene unit, the terpene skeleton, and the rosin skeleton in the tackifying resin _THR2 can be measured by, for example, NMR (nuclear ceramic resonance spectrum method).

Examples of tackifying resins having an aromatic ring and substantially free of isoprene units, terpene skeleton and rosin skeleton include the above-described aromatic petroleum resins, aliphatic / aromatic copolymer petroleum resins, styrene resins, Coumarone-indene resin and the like can be mentioned. Among these, those having a softening point of 120 ° C. or higher (preferably 130 ° C. or higher, eg, 135 ° C. or higher) can be adopted as the tackifying resin _THR2 . Particularly preferred tackifying resins _THR2 include aromatic petroleum resins and styrene resins (for example, α-methylstyrene / styrene copolymer resins). Although not particularly limited, as the tackifier resin _{T HR2,} for the same reason as the tackifier resin _{T HR1,} hydroxyl value 30 mgKOH / g or less (preferably less than 5 mgKOH / g, for example less than 1 mgKOH / g) of those Can be preferably employed. Therefore, as the tackifying resin _THR2 in the technology disclosed herein, those corresponding to the tackifying resin _THR1 can be preferably used. Similarly, as tackifying resin _THR1 in the technique disclosed here, what corresponds also to tackifying resin _THR2 can be used preferably. In addition, the technique disclosed here can be implemented also in the aspect in which an adhesive layer does not contain tackifying resin _THR2 substantially.

Further, the total amount of tackifier resin T _H to unsaturated rubber 100 parts by weight (i.e., the total amount of softening point 100 ° C. or more tackifier resins), from the viewpoint of aggregation enhancing, suitable to be 10 parts by weight or more Yes, 20 parts by weight or more (for example, 25 parts by weight or more) is preferable. The content of the tackifier resin T _H to unsaturated rubber 100 parts by weight, for example, may be 60 parts by weight. From the viewpoint of tack and low temperature characteristics, the content of the tackifier resin T _H to unsaturated rubber 100 parts by weight, preferably 50 parts by weight or less, more preferably 45 parts by weight or less (for example, 40 parts by weight or less).

Ratio of tackifier resin T _H relative to the total amount of tackifying resin, from the viewpoint of achieving both good balance and cohesion and low temperature properties (e.g., low temperature initial adhesiveness) is suitably about 50 wt% or more, Preferably it is 80 weight% or more (for example, 90 weight% or more). The art disclosed herein, substantially all of the tackifying resin (e.g., 95 to 100 wt%, more 99-100% by weight) may be preferably carried out in a manner which is tackifier resin _{T H.}

(Tackifying resin T _L )
The pressure-sensitive adhesive layer disclosed herein may include a tackifying resin _TL having a softening point of less than 100 ° C. The lower limit of the softening point of the tackifier resin _TL is not particularly limited. A softening point of 40 ° C. or higher (typically 60 ° C. or higher) can be used. The hydroxyl value and structure of the tackifier resin _TL (for example, the presence or absence of an aromatic ring, the presence or absence of an isoprene unit, the presence or absence of a terpene skeleton, the presence or absence of a rosin skeleton) are not particularly limited. The above-mentioned various tackifier resins (phenolic tackifier resins, terpene resins, modified terpene resins, rosin tackifier resins, petroleum resins, styrene resins, coumarone / indene resins, ketone resins, etc.) What has a point less than 100 degreeC should just be selected suitably.

(Content of tackifying resin)
In the technology disclosed herein, the total amount (total content) of the tackifying resin is not particularly limited, and can be set so as to obtain desired performance according to the purpose and application. The total amount of tackifying resin can be, for example, 1 part by weight or more with respect to 100 parts by weight of the unsaturated rubber, and may be 5 parts by weight or more, or 10 parts by weight or more. From the viewpoint of obtaining higher adhesive performance (for example, adhesive strength), the total amount of the tackifying resin relative to 100 parts by weight of the unsaturated rubber may be 15 parts by weight or more, may be 20 parts by weight or more, and is 25% by weight. May be 30 parts by weight or more. In some embodiments, the total amount of tackifying resin relative to 100 parts by weight of the unsaturated rubber may be 40 parts by weight or more, or 55 parts by weight or more. Further, from the viewpoint of easily realizing a pressure-sensitive adhesive exhibiting good tack and low-temperature performance (for example, initial adhesiveness at low temperature), the total amount of tackifying resin with respect to 100 parts by weight of the unsaturated rubber is usually 120 parts by weight or less. Is suitably 100 parts by weight or less, more preferably 80 parts by weight or less. In some embodiments, the total amount of tackifying resin relative to 100 parts by weight of unsaturated rubber may be 60 parts by weight or less, may be 50 parts by weight or less, and is 45 parts by weight or less (eg, 40 parts by weight or less). It may be.

<Anti-aging agent>
The pressure-sensitive adhesive disclosed herein can contain an anti-aging agent as necessary. By using an anti-aging agent, it is possible to increase the Mw _H maintenance rate of the pressure-sensitive adhesive containing a combination of unsaturated rubber and tackifying resin, and to improve the long-term quality stability (long life) of the pressure-sensitive adhesive sheet. . Antiaging agent may be used individually by 1 type, may be used in combination of 2 or more type, and may be used in combination of 3 or more type.

(Radical scavenger)
In some embodiments, the anti-aging agent may include a radical scavenger (radical trap agent). Examples of the radical scavenger include known radical scavengers that can be used in the field of unsaturated rubbers, such as phenolic antioxidants, hindered amine antioxidants, and aromatic amine antioxidants. A radical scavenger can be used individually by 1 type or in combination of 2 or more types.

  Examples of radical scavengers that can be preferably used in the technology disclosed herein include phenolic antioxidants. Non-limiting examples of phenolic antioxidants include monophenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6) -T-butylphenol), 4,4'-thiobis (3-methyl-6-t-butylphenol) and other bisphenol antioxidants; 1,3,5-trimethyl-2,4,6-tris (3,5 -Di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, 1, , 3- tris (2-methyl-4-hydroxy -5-t-butylphenyl) polymer phenolic antioxidant such as butane; and the like.

  The phenolic antioxidant may be a hindered phenolic antioxidant. Non-limiting examples of the hindered phenol antioxidant include pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 4,6-bis (dodecylthiomethyl) -o-cresol, 4-[[4,6-bis (octylthio) -1,3,5-triazine -2-yl] amino] -2,6-di-t-butylphenol, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate, bis (2,2, 6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine Polycondensates of Nord (dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate), and the like.

The amount of radical scavenger (for example, phenolic antioxidant) used can be, for example, 0.01 parts by weight or more with respect to 100 parts by weight of the unsaturated rubber, and usually 0.05 parts by weight or more. Is suitable, and may be 0.1 parts by weight or more (for example, 0.5 parts by weight or more). Due to the increase in the amount of radical scavenger used, the Mw _H retention rate increases, and the quality stability of the pressure-sensitive adhesive sheet tends to improve. From the viewpoint of suppressing an unfavorable influence on the adhesive performance (for example, decrease in cohesiveness of the adhesive before aging), the amount of the radical scavenger used relative to 100 parts by weight of the unsaturated rubber is usually 10 parts by weight or less. Is preferably 5 parts by weight or less (eg, 3 parts by weight or less).

(Sulfur-based antioxidant)
In some embodiments, the anti-aging agent can include a sulfur-based antioxidant. The sulfur-based antioxidant continuously functions as a peroxide decomposing agent that decomposes and / or converts a peroxide that can be generated in the pressure-sensitive adhesive into a stable compound, thereby improving the Mw _H maintenance rate (and eventually This can contribute to improvement in the quality stability of the pressure-sensitive adhesive sheet. In the pressure-sensitive adhesive containing an unsaturated rubber and a phenol-based tackifier resin (for example, terpene phenol resin), it is particularly effective to use a sulfur-based antioxidant.

As the sulfur-based antioxidant, for example, a thioether-based antioxidant having a thioether structure in the molecule can be used. Non-limiting examples of sulfur-based antioxidants include 2,2-bis ({[3- (dodecylthio) propionyl] oxy} methyl) propanediyl = bis [3- (dodecylthio) propionate, bis [2-methyl. -4- (3-n-dodecylthiopropionyloxy) -5-t-butylphenyl] sulfide, 3-dodecylsulfanylpropanoic acid = 2-t-butyl-4-[(5-t-butyl-4-hydroxy- 2-methylphenyl) sulfanyl] -5-methylphenyl, dilauryl-3,3′-thiodipropionate, ditridecyl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, di Examples include stearyl-3,3′-thiodipropionate, pentaerythritol tetralauryl thiopropionate, and the like. A sulfur type antioxidant can be used individually by 1 type or in combination of 2 or more types. In some embodiments, a sulfur-based antioxidant having a structure not containing an aromatic ring (typically a thioether-based antioxidant) may be preferably employed. Further, a thioether-based antioxidant having one or more (for example, three or four) “—CH ₂ —OC (O) —CH ₂ CH ₂ —S—CH ₂ —” structures in one molecule. Can be preferably employed.

The number of thioetheric sulfur atoms contained in one molecule of thioether-based antioxidant may be one, or two or more. From the viewpoint of durability of the effect, a thioether-based antioxidant containing two or more (typically two or more and four or less) thioetheric sulfur atoms in one molecule is preferable. In some embodiments, by using a thioether-based antioxidant having a thioether equivalent (molecular weight per thioetheric sulfur atom) of 1000 or less (preferably 700 or less, more preferably 500 or less, such as 350 or less), adhesion performance is improved. effect can be effectively improved the Mw _H maintenance rate while suppressing. Further, from the viewpoint of sustaining the effect, the thioether equivalent is preferably 150 or more, and more preferably 200 or more. The thioether equivalent can be calculated by dividing the molecular weight by the number of thioetheric sulfur atoms.

The molecular weight of the sulfur-based antioxidant is suitably 2000 or less, and preferably 1500 or less (for example, 1250 or less). By using such a sulfur-based antioxidant, it is possible to effectively improve the Mw _H retention rate while suppressing the influence on the adhesive performance (for example, tack and low temperature initial adhesiveness). Further, the molecular weight of the sulfur-based antioxidant from the viewpoint of sustaining the effect is suitably 150 or more, preferably 200 or more, and more preferably 350 or more.

The amount of the sulfur-based antioxidant used relative to the amount of the unsaturated rubber is, for example, such that the number of moles of thioether sulfur (S) contained in the sulfur-based antioxidant is 0.01 mmol or more per 100 g of the unsaturated rubber. Can be set as follows. Hereinafter, the number of moles of thioetheric sulfur per 100 g of unsaturated rubber is referred to as “number of moles of S” and is sometimes expressed in units of mmol / 100 g. The S mole number is usually suitably 0.05 mmol / 100 g or more, preferably 0.1 mmol / 100 g or more, may be 0.2 mmol / 100 g or more, 0.5 mmol / 100 g or more ( For example, it may be 0.8 mmol / 100 g or more). Due to the increase in the number of S moles of the sulfur-based antioxidant, the Mw _H retention rate is increased and the quality stability tends to be improved. The technique disclosed here can be suitably implemented even in an embodiment in which the number of S moles is 1 mmol / 100 g or more (for example, 2 mmol / 100 g or more) or an embodiment in which the number of S moles is 4 mmol / 100 g or more (for example, 5 mmol / 100 g or more). Further, the number of S moles can be set to, for example, 100 mmol / 100 g or less, and is usually 50 mmol / 100 g or less from the viewpoint of suppressing an unfavorable influence on the adhesive performance (for example, tack and low-temperature initial adhesion deterioration). It is suitable to do, and it is preferable to set it as 30 mmol / 100g or less. The technique disclosed here can also be suitably implemented in an embodiment where the number of S moles is 20 mmol / 100 g or less, or an embodiment where the number of S moles is 15 mmol / 100 g or less (for example, 10 mmol / 100 g or less).

The amount of the sulfur-based antioxidant used may be, for example, 0.01 parts by weight or more with respect to 100 parts by weight of the unsaturated rubber. Part or more (for example, 0.1 part by weight or more). Mw _H maintenance rate tends to be improved by increasing the amount of sulfur-based antioxidant used. In addition, from the viewpoint of suppressing an unfavorable influence on the adhesive performance (for example, tack and lowering of low temperature initial adhesiveness), the use amount of the sulfur-based antioxidant with respect to 100 parts by weight of the unsaturated rubber is usually 10 parts by weight or less. Is preferably 7 parts by weight or less, more preferably 5 parts by weight or less (eg, 3 parts by weight or less).

The amount of the sulfur-based antioxidant used may be, for example, 0.01 or more as an S molar ratio with respect to 100 parts by weight of the unsaturated rubber, and usually 0.05 or more is appropriate, and 0.1 or more (for example, 0.5 or more). By increasing the S molar ratio of the sulfur-based antioxidant, the Mw _H retention rate is increased, and the quality stability tends to be improved. Further, from the viewpoint of suppressing an unfavorable influence on the adhesive performance (for example, tack and lowering of low temperature initial adhesiveness), the use amount of the sulfur-based antioxidant with respect to 100 parts by weight of the unsaturated rubber is usually as S molar ratio. 15 or less is appropriate, 10 or less is preferable, and 7 or less (for example, 6 or less) is preferable. Decreasing the S molar ratio can be advantageous from the viewpoint of suppressing coloration (for example, yellowing) of the pressure-sensitive adhesive due to aging. Here, the S molar ratio is a value obtained by multiplying the number of parts by weight of the sulfur-based antioxidant used with respect to 100 parts by weight of the unsaturated rubber by the number of thioether-based sulfur contained in one molecule of the sulfur-based antioxidant. Say. For example, when 1 part by weight of a sulfur-based antioxidant is included per 100 parts by weight of an unsaturated rubber, and the sulfur-based antioxidant contains two thioether sulfur in one molecule, the sulfur system in the composition The S molar ratio of the antioxidant is calculated as 2.

(Phosphorus antioxidant)
In some embodiments, the anti-aging agent may include a phosphorus antioxidant. The phosphorus-based antioxidant functions as a peroxide decomposer that decomposes or converts a peroxide that can be generated in the pressure-sensitive adhesive into a stable compound, thereby improving the Mw _H retention rate (and thus stabilizing the quality of the pressure-sensitive adhesive sheet). Improvement of the property). Non-limiting examples of phosphorus antioxidants include tris (2,4-di-t-butylphenyl) phosphite, tris (nonylphenyl) phosphite, triphenyl phosphite, distearyl pentaerythritol diphosphite. , Etc.

The amount of the phosphorus-based antioxidant used can be, for example, 0.05 parts by weight or more with respect to 100 parts by weight of the unsaturated rubber. Part or more (for example, 1 part by weight or more). Mw _H maintenance rate tends to be improved by increasing the amount of sulfur-based antioxidant used. In addition, from the viewpoint of suppressing an unfavorable influence on the adhesive performance (for example, tack and lowering of low temperature initial adhesiveness), the amount of the phosphorus antioxidant used relative to 100 parts by weight of the unsaturated rubber is usually 15 parts by weight or less. Is preferably 10 parts by weight or less, more preferably 7 parts by weight or less (for example, 5 parts by weight or less).

In some embodiments, the antioxidant may be a combination of a sulfur-based antioxidant (eg, a thioether-based antioxidant) and a phosphorus-based antioxidant. According to this aspect, it is possible to effectively improve the Mw _H maintenance rate while suppressing an undesirable influence on the adhesive performance. The reason for this is not particularly limited, but is considered as follows, for example. That is, phosphorus antioxidants generally tend to react with peroxides more quickly than sulfur antioxidants. On the other hand, since phosphorus antioxidants are irreversibly consumed by reaction with peroxides, the durability of the effect may be insufficient in a severe aging test of 4 weeks at 80 ° C. Combined use of two types of peroxide decomposing agents, sulfur-based antioxidants and phosphorus-based antioxidants, can exert a good peroxide-decomposing function while suppressing the effect on adhesive properties. it can. Further, by using a sulfur-based antioxidant and a phosphorus-based antioxidant in combination, the amount of the sulfur-based antioxidant used can be reduced, which can contribute to the suppression of coloration of the adhesive over time. By using a combination of a sulfur-based antioxidant, a phosphorus-based antioxidant, and a phenol-based antioxidant, a more favorable result can be realized.

Although not particularly limited, when a phosphorus antioxidant and a thioether antioxidant are used in combination, the use amount A _S [S molar ratio] of the thioether antioxidant to 100 parts by weight of the unsaturated rubber The ratio of the phosphorus antioxidant to the amount A _P [parts by weight] of 100 parts by weight of the unsaturated rubber, that is, A _S / A _P can be set in the range of 0.1 to 10, for example. By setting it as this range, it exists in the tendency for the effect of using a sulfur type antioxidant and phosphorus antioxidant together to be exhibited suitably. From the viewpoint of obtaining a better effect, in some embodiments, A _S / A _P may be 0.2 or more, and may be 0.5 or more. Further, A _S / A _P may be 5 or less, or 3 or less. Incidentally, A _P and A _S are respectively meant numeric portion when the amount expressed in parts by weight S molar ratio to unsaturated rubber 100 parts by weight, A _P and A values themselves dimensionless number of _S Suppose that

  Other radical scavengers disclosed herein may function as peroxide decomposers in combination with one or both of phosphorus-based antioxidants and thioether-based antioxidants, or instead of these antioxidants. An antioxidant may be included. Examples of such other antioxidants include amine antioxidants (phenyl-α-naphthylamine, diphenylamine, etc.), benzimidazole antioxidants, and the like. The other antioxidants can be used alone, but it is usually preferable to use them in combination with a radical scavenger (for example, a phenolic antioxidant).

(Content of anti-aging agent)
Although not particularly limited, the total amount of the anti-aging agent contained in the pressure-sensitive adhesive disclosed herein can be, for example, about 20 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber. It is suitable that the amount is not more than parts by weight, and may be not more than 10 parts by weight. The technique disclosed here is also suitably implemented in an embodiment in which the total amount of the anti-aging agent used for 100 parts by weight of the unsaturated rubber is 7 parts by weight or less (for example, 5 parts by weight or less, or 4 parts by weight or less). obtain. Further, the total amount of the anti-aging agent can be, for example, 0.5 parts by weight or more with respect to 100 parts by weight of the unsaturated rubber, and can be 1 part by weight or more, or 1.5 parts by weight or more. It may be 2 parts by weight or more.

<Isocyanate compound>
The pressure-sensitive adhesive layer disclosed herein may be formed from a pressure-sensitive adhesive composition containing an isocyanate compound in addition to the unsaturated rubber and the tackifier resin. According to the pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet excellent in longer-term quality stability (for example, in which a decrease in cohesiveness is suppressed) can be realized. As the isocyanate compound, polyfunctional isocyanate (refers to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. As this polyfunctional isocyanate, 1 type (s) or 2 or more types selected from the various isocyanate compounds (polyisocyanate) which have a 2 or more isocyanate group in 1 molecule can be used. Examples of such polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates and the like.

  Specific examples of the aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanate such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, 1,4-tetramethylene diisocyanate; -Hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; Examples include 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

  Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate; 1,2-cyclopentyl diisocyanate, 1,3 -Cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

  Specific examples of the aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and 2,2′-diphenylmethane diisocyanate. 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxy Diphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate.

  Examples of preferred isocyanate compounds include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such a trifunctional or higher functional isocyanate is a difunctional or trifunctional or higher polymer (typically a dimer or trimer), a derivative (for example, a polyhydric alcohol and two or more polyfunctional isocyanates). Addition reaction product), polymer and the like. For example, diphenylmethane diisocyanate dimer or trimer, hexamethylene diisocyanate isocyanurate (trimer adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexamer Examples of the reaction product with methylene diisocyanate include polyfunctional isocyanates such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. As commercial products of such polyfunctional isocyanates, trade names “Duranate TPA-100” manufactured by Asahi Kasei Chemicals Corporation, trade names “Coronate L”, “Coronate HL”, “Coronate HK”, “Coronate HK” manufactured by Tosoh Corporation HX ”,“ Coronate 2096 ”and the like.

  When an isocyanate compound is used, the amount used is not particularly limited. For example, the amount is more than 0 parts by weight and 10 parts by weight or less (typically 0.01 to 10 parts by weight) with respect to 100 parts by weight of the unsaturated rubber. be able to. The amount of the isocyanate compound used relative to 100 parts by weight of the unsaturated rubber is preferably 0.1 parts by weight or more (typically 0.3 parts by weight or more, for example 0.5 parts by weight or more), and 10 parts by weight or less. It is suitable to be 5 parts by weight or less (typically 3 parts by weight or less, for example, 1 part by weight or less). By using an isocyanate compound within such a range, a pressure-sensitive adhesive sheet having an excellent performance balance can be realized.

<Other ingredients>
The pressure-sensitive adhesive layer disclosed herein may contain one or more rubbery polymers other than the unsaturated rubber as required, as long as the effects of the present invention are not impaired. Such rubber-like polymers may be various polymers such as rubber-based, acrylic-based, polyester-based, urethane-based, polyether-based, silicone-based, polyamide-based, and fluorine-based polymers known in the field of pressure-sensitive adhesives. The technology disclosed herein is an embodiment in which the pressure-sensitive adhesive layer does not substantially contain a rubbery polymer other than the unsaturated rubber (for example, an embodiment in which the content per 100 parts by weight of the unsaturated rubber is 0 to 1 part by weight. ).

  The pressure-sensitive adhesive composition disclosed herein (which may also be a pressure-sensitive adhesive layer) is optionally provided with a leveling agent, a crosslinking agent, a crosslinking aid, a plasticizer, a softening agent, a filler, and a colorant (pigment, dye). Etc.), an antistatic agent, an ultraviolet absorber, a light stabilizer and the like, and various additives generally used in the field of pressure-sensitive adhesives. About such various additives, a conventionally well-known thing can be used by a conventional method.

The pressure-sensitive adhesive disclosed herein contains substantially no liquid rubber such as polybutene (for example, the content per 100 parts by weight of the unsaturated rubber is 1 part by weight or less, and may be 0 part by weight). ) Embodiment. Such an embodiment can be advantageous from the viewpoint of improving peel strength and cohesiveness.
In some embodiments, the pressure-sensitive adhesive composition may be a composition that is substantially free of a chelate compound. Here, the chelate compound is, for example, a chelate compound of an alkaline earth metal oxide and a resin (alkylphenol resin or the like) having a functional group (hydroxyl group, methylol group or the like) capable of coordinating the oxide. Point to. The technology disclosed herein can be preferably implemented in such a manner that the pressure-sensitive adhesive composition does not contain such a chelate compound at all or the content of the chelate compound is 1% by weight or less. According to such an embodiment, a pressure-sensitive adhesive sheet with more excellent adhesive strength can be realized.

  In some embodiments, the pressure-sensitive adhesive is such that the total amount of unsaturated rubber and tackifying resin is 75% by weight of the total weight of the pressure-sensitive adhesive (that is, the weight of the pressure-sensitive adhesive layer constituted by the pressure-sensitive adhesive). The composition may occupy the above. For example, the total amount of unsaturated rubber and tackifying resin is 80% by weight or more (for example, 85% by weight or 90% by weight or more) of the total weight of the pressure-sensitive adhesive, and 99.8% by weight or less (typically Specifically, for example, an embodiment that is, for example, 99.5% by weight or less can be preferably employed.

<Adhesive composition>
The pressure-sensitive adhesive layer disclosed herein may be formed from a pressure-sensitive adhesive composition containing a component corresponding to the pressure-sensitive adhesive layer. The form of the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition in a form (solvent type) containing the pressure-sensitive adhesive (adhesive component) having the above-described composition in an organic solvent, the pressure-sensitive adhesive is dispersed in an aqueous solvent. It may be a pressure-sensitive adhesive composition in the form (water-dispersed type, typically an aqueous emulsion type), a hot-melt type pressure-sensitive adhesive composition, or the like. From the viewpoints of coating properties and the degree of freedom in selecting a substrate, a solvent-type or water-dispersed pressure-sensitive adhesive composition can be preferably employed. From the viewpoint of realizing higher adhesive performance, a solvent-type adhesive composition is particularly preferable.

  The solvent-type pressure-sensitive adhesive composition is typically prepared in the form of a solution containing each component described above in an organic solvent. The organic solvent can be appropriately selected from known or commonly used organic solvents. For example, aromatic compounds such as toluene and xylene (typically aromatic hydrocarbons); acetates such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane Any one solvent selected from the group: halogenated alkanes such as 1,2-dichloroethane; ketones such as methyl ethyl ketone and acetylacetone; and a mixed solvent of two or more. Although not particularly limited, it is appropriate to prepare the above-mentioned solvent-type pressure-sensitive adhesive composition so as to have a nonvolatile content (NV) of 30% by weight or more (for example, 40% by weight or more), and 65% by weight or less (for example, 55% by weight). % Or less) is suitable. When NV is too low, the manufacturing cost tends to be high, and when NV is too high, handling properties such as coatability may be lowered.

As a method for obtaining a pressure-sensitive adhesive sheet from the pressure-sensitive adhesive composition, various conventionally known methods can be applied. For example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to a substrate and drying it can be preferably employed. Further, the pressure-sensitive adhesive composition is applied to a surface having good releasability (for example, the surface of a release liner, the back surface of a release support substrate, etc.) and dried to form a pressure-sensitive adhesive layer on the surface. Alternatively, a method (transfer method) of transferring the pressure-sensitive adhesive layer to the substrate may be employed.
Application of the pressure-sensitive adhesive composition can be carried out using a known or conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater and the like. From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. For example, a drying temperature of about 40 ° C. or higher (for example, 50 ° C. or higher, further 70 ° C. or higher) and about 150 ° C. or lower (typically 120 ° C. or lower, more preferably 100 ° C. or lower) is preferably employed. be able to. The drying time is not particularly limited, but may be about several tens of seconds to several minutes (for example, within about 5 minutes, preferably about 30 seconds to 2 minutes). Then, you may provide an additional drying process as needed. The pressure-sensitive adhesive layer is typically formed continuously, but may be formed in a regular or random pattern such as a dot or stripe depending on the purpose and application.

(Adhesive layer thickness)
Although not particularly limited, the thickness of the pressure-sensitive adhesive layer is suitably about 4 μm or more (typically 20 μm or more, for example, 30 μm or more), and about 150 μm or less (typically 120 μm or less, for example, for example, 100 μm or less) is appropriate. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more (for example, 60 μm or more). The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer having such a thickness can exhibit excellent pressure-sensitive adhesive performance (for example, peel strength) when the pressure-sensitive adhesive layer contains an unsaturated rubber and a tackifier resin. Therefore, a pressure-sensitive adhesive sheet that is highly compatible with pressure-sensitive adhesive performance and quality stability (long life) can be provided. In the case of a double-sided pressure-sensitive adhesive sheet with a substrate, it is preferable that a pressure-sensitive adhesive layer having the above thickness is provided on each side of the substrate. The thickness of each adhesive layer may be the same or different.

<Adhesive sheet>
(Base material)
When the technology disclosed herein is applied to a double-sided PSA sheet with a substrate or a single-sided PSA sheet with a substrate, examples of the substrate include a polypropylene film, an ethylene-propylene copolymer film, a polyester film, and a polyvinyl chloride film. Foam sheets made of foams such as polyurethane foam, polyethylene foam, polychloroprene foam; various fibrous materials (natural fibers such as hemp and cotton; synthetic fibers such as polyester and vinylon; semi-finished materials such as acetate A woven fabric and a non-woven fabric (meaning including papers such as Japanese paper and fine paper)); metal foils such as aluminum foil and copper foil; etc. It can be appropriately selected and used depending on the application of the pressure-sensitive adhesive sheet. As the plastic film (typically a non-porous plastic film, which is a concept distinguished from a woven fabric or a non-woven fabric), any of an unstretched film and a stretched (uniaxially stretched or biaxially stretched) film is used. Can also be used. Moreover, surface treatment, such as application | coating of a primer and corona discharge treatment, may be given to the surface in which an adhesive layer is provided among base materials.

  In a preferred embodiment, a nonwoven fabric (nonwoven fabric substrate) is used as the substrate. By using a nonwoven fabric base material, there is a tendency that low-temperature initial adhesiveness and cohesiveness (for example, performance to withstand without falling in a holding force test) are improved. Examples of the nonwoven fabric used for the base material include nonwoven fabrics composed of pulps such as wood pulp, natural fibers such as cotton and hemp; polyester fibers such as polyethylene terephthalate (PET) fibers, rayon, vinylon, acetate fibers, polyvinyl Use non-woven fabric composed of chemical fibers (synthetic fibers) such as alcohol (PVA) fiber, polyamide fiber, polyolefin fiber, polyurethane fiber; non-woven fabric composed of two or more kinds of different materials; Can do. Among these, from the viewpoint of the impregnation property of the adhesive and the repulsion resistance (curved surface followability), a nonwoven fabric composed of pulp and hemp (for example, hemp pulp), a nonwoven fabric composed of PET fibers, and the like are preferable. The use of the nonwoven fabric substrate also contributes to an improvement in the flexibility and hand cutting property of the pressure-sensitive adhesive sheet.

As the nonwoven fabric (nonwoven fabric substrate), those having a basis weight of about 30 g / m ² or less (for example, 25 g / m ² or less, typically 20 g / m ² or less) can be preferably used. Such a nonwoven fabric having a basis weight is suitable for producing a pressure-sensitive adhesive sheet that is lightweight and excellent in adhesive performance. From the viewpoint of repulsion resistance, a nonwoven fabric having a basis weight of less than 18 g / m ² (for example, 16 g / m ² or less, typically 15 g / m ² or less) is preferable. From the viewpoint of improving the strength of the substrate itself, the basis weight is preferably 10 g / m ² or more (for example, 12 g / m ² or more, typically 13 g / m ² or more).

The bulk density of the nonwoven fabric substrate (which can be calculated by dividing the basis weight by the thickness) is suitably about 0.20 g / cm ³ or more, and 0.25 g / cm ³ or more (for example, 0.30 g / cm). ³ or more), preferably about 0.50 g / cm ³ or less, and preferably 0.40 g / cm ³ or less (eg, 0.35 g / cm ³ or less). When the bulk density is within the above range, the substrate itself has an appropriate strength, and good pressure-sensitive adhesive impregnation is obtained. From the viewpoint of repulsion resistance, it is particularly preferable to use a nonwoven fabric substrate having a bulk density of about 0.25 to 0.40 g / cm ³ (for example, 0.30 to 0.35 g / cm ³ ).

  In addition to the constituent fibers as described above, the nonwoven fabric substrate contains resin components such as starch (eg, cationized starch), polyacrylamide, viscose, polyvinyl alcohol, urea formaldehyde resin, melamine formaldehyde resin, and polyamide polyamine epichlorohydrin. Can do. The resin component may function as a paper strength enhancer for the nonwoven fabric substrate. The strength of the nonwoven fabric substrate can be adjusted by using such a resin component as necessary. The nonwoven fabric substrate in the technology disclosed herein may contain other additives that are commonly used in the field of nonwoven fabric production, such as a yield improver, a drainage agent, a viscosity modifier, and a dispersant, as necessary. .

  The thickness of the substrate can be appropriately selected according to the purpose, but generally it is appropriate to set it to approximately 2 μm or more (typically 10 μm or more), and 500 μm or less (typically 200 μm or less). It is preferable that When a nonwoven fabric is used as the substrate, the thickness of the nonwoven fabric substrate is suitably about 150 μm or less. From the viewpoint of sufficiently impregnating the entire substrate with the pressure-sensitive adhesive, the thickness is preferably 100 μm or less (for example, 70 μm or less). Moreover, when the handleability at the time of adhesive sheet preparation is considered, it is preferable that the said thickness is 10 micrometers or more (for example, 25 micrometers or more). From the viewpoint of repulsion resistance, the thickness is preferably 30 μm or more (for example, 35 μm or more, typically 40 μm or more), and 60 μm or less (for example, 50 μm or less, typically 45 μm or less). Is preferred. The nonwoven fabric substrate disclosed herein has at least two of the basis weight, thickness and bulk density in the above preferred ranges (for example, basis weight and thickness, more preferably all of basis weight, thickness and bulk density). It is preferable to satisfy. Thereby, an adhesive sheet in which a plurality of adhesive properties (for example, repulsion resistance, cohesiveness, peel strength, etc.) are highly balanced can be realized.

(Release liner)
A 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 adhesive material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.) Etc. can be used. The release treatment layer may be formed, for example, by surface-treating the substrate with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

(Thickness of adhesive sheet)
The total thickness of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and should be about 1000 μm or less (for example, 500 μm or less, typically 300 μm or less) from the viewpoints of thinning, lightening, and resource saving. Is preferred. Further, from the viewpoint of ensuring good adhesive properties, it is appropriate that the thickness is 50 μm or more (for example, 70 μm or more, typically 100 μm or more).

(Characteristic)
In the pressure-sensitive adhesive sheet disclosed herein, it is preferable that the test piece does not fall in the holding power test of the pressure-sensitive adhesive sheet after the aging test. That is, in the pressure-sensitive adhesive layer after the aging test, it is preferable that the cohesiveness at a level showing the above-mentioned holding power is maintained. The pressure-sensitive adhesive sheet satisfying the above characteristics is excellent in long-term quality stability. In the holding power test after the aging test, the pressure-sensitive adhesive sheet disclosed herein is more preferably 1 mm or less, more preferably 0.5 mm or less from the initial position.

Moreover, it is preferable that the adhesive sheet disclosed here shows the cohesiveness of the level which a test piece does not fall in the holding power test of the adhesive sheet before using for the said aging test. In the holding force test, the displacement distance from the initial position is more preferably 1 mm or less, and further preferably 0.5 mm or less.
The holding power test after the aging test and before the aging test is performed by the method described in the examples described later. In addition, when implementing a holding power test by using a single-sided adhesive sheet as a test piece, it is not necessary to bond a PET film to the first adhesive surface of the test piece.

<Application>
The pressure-sensitive adhesive sheet disclosed herein is a joint between members in various OA devices (for example, PC), home appliances (for example, rice cookers, refrigerators), automobiles, building materials (for example, residential building materials), and the like (for example, various types in such products). Useful for fixing parts and nameplates). The pressure-sensitive adhesive sheet disclosed here utilizes, for example, the advantage of excellent long-term quality stability, and fixes, for example, a decorative sheet used for decorating the inner wall of a building to the application position (inner wall) of the decorative sheet. It can be preferably used for applications.

The matters disclosed by this specification include the following.
(1) An adhesive sheet including an adhesive layer,
The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifying resin,
The pressure-sensitive adhesive has a weight average molecular weight Mw _H calculated for a region having a molecular weight of 10,000 g / mol or higher from a molecular weight distribution curve based on GPC measurement, and a maintenance rate of 70% or higher in an aging test at 80 ° C. for 4 weeks (for example, 70% to 100%).
(2) The pressure-sensitive adhesive sheet according to (1), wherein the content of the unsaturated rubber is about 30% by weight or more of the pressure-sensitive adhesive.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the content of the tackifying resin is about 10 parts by weight or more and about 120 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber.
(4) The tackifying resin is at least selected from the group consisting of phenolic tackifying resins, terpene resins, modified terpene resins, rosin tackifying resins, petroleum resins, styrene resins, coumarone-indene resins, and ketone resins. The adhesive sheet in any one of said (1)-(3) containing 1 type.
(5) The tackifying resin includes a phenolic tackifying resin, and the content of the phenolic tackifying resin is about 5 parts by weight or more and about 60 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber. The pressure-sensitive adhesive sheet according to any one of (1) to (4) above.
(6) The tackifying resin includes a phenolic tackifying resin, and the phenolic tackifying resin includes a terpene phenol resin having a hydroxyl value of 20 mgKOH / g or more, according to any one of the above (1) to (5). Adhesive sheet.
(7) The tackifying resin includes a phenolic tackifying resin, and the phenolic tackifying resin includes a terpene phenol resin having a hydroxyl value of 80 mgKOH / g or more, according to any one of the above (1) to (6). Adhesive sheet.
(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7), wherein a softening point of the tackifying resin is 40 ° C. or higher (for example, 60 ° C. or higher).

(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8), wherein the pressure-sensitive adhesive includes an anti-aging agent, and the anti-aging agent includes a radical scavenger and a sulfur-based antioxidant.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9), wherein the pressure-sensitive adhesive contains an anti-aging agent, and the anti-aging agent contains a phosphorus-based antioxidant.
(11) The pressure-sensitive adhesive includes an anti-aging agent, and the anti-aging agent includes a thioether-based antioxidant as a sulfur-based antioxidant and a phosphorus-based antioxidant,
Ratio of the amount A _S [S molar ratio] of the thioether antioxidant to 100 parts by weight of the unsaturated rubber to the amount A _P [parts by weight] of the phosphorus antioxidant to 100 parts by weight of the unsaturated rubber ( The pressure-sensitive adhesive sheet according to any one of the above (1) to (10), wherein A _S / A _P ) is 0.1 to 10.
(12) The pressure-sensitive adhesive sheet according to any one of (8) to (11), wherein the total amount of the anti-aging agent is 1.5 to 10 parts by weight with respect to 100 parts by weight of the unsaturated rubber. .
(13) The pressure-sensitive adhesive sheet according to any one of (1) to (12), wherein the pressure-sensitive adhesive has a phenolic tackifying resin content of 30 parts by weight or less based on 100 parts by weight of the unsaturated rubber.
(14) The pressure-sensitive adhesive sheet according to any one of (1) to (13), wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate compound.
(15) In the above pressure-sensitive adhesive, the total amount of the unsaturated rubber and the tackifying resin is about 85% by weight to 99.8% by weight of the total weight of the pressure-sensitive adhesive. The pressure-sensitive adhesive sheet according to any one of 14).

(16) The pressure-sensitive adhesive sheet according to any one of (1) to (15), wherein the unsaturated rubber is a homopolymer or copolymer of a conjugated diene compound.
(17) The pressure-sensitive adhesive sheet according to any one of (1) to (16), wherein the unsaturated rubber is a homopolymer or copolymer of isoprene.
(18) Any of (1) to (17) above, wherein the unsaturated rubber has a monomer composition containing a conjugated diene compound, and a proportion of the conjugated diene compound in the monomer composition is about 70% by weight or more. The pressure-sensitive adhesive sheet described in 1.
(19) The pressure-sensitive adhesive sheet according to any one of (1) to (18), wherein the unsaturated rubber includes a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound.
(20) The pressure-sensitive adhesive sheet according to (19), wherein the block copolymer has a diblock ratio of about 60% by weight or more.
(21) The pressure-sensitive adhesive sheet according to any one of (1) to (20), wherein the pressure-sensitive adhesive layer has a thickness of about 30 μm or more.
(22) A double-sided pressure-sensitive adhesive sheet comprising a base material, and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer as the pressure-sensitive adhesive layer supported on both surfaces of the base material, The adhesive sheet in any one of said (1)-(21).

(23) An adhesive sheet including an adhesive layer,
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer contains an unsaturated rubber and a tackifying resin having a softening point of 60 ° C. or higher,
The unsaturated rubber includes a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, and the block copolymer has a conjugated diene compound content of 70% by weight or more in the monomer composition, and The block body ratio is about 60% by weight or more,
The content of the unsaturated rubber is about 30% by weight or more of the pressure-sensitive adhesive,
The tackifying resin includes at least one selected from the group consisting of phenolic tackifying resins, terpene resins, modified terpene resins, rosin tackifying resins, petroleum resins and coumarone / indene resins,
The total amount of the tackifying resin is about 10 parts by weight or more and about 120 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber;
The pressure-sensitive adhesive has a weight average molecular weight Mw _H calculated for a region having a molecular weight of 10,000 g / mol or higher from a molecular weight distribution curve based on GPC measurement, and a maintenance rate of 70% or higher in an aging test at 80 ° C. for 4 weeks (for example, 70% to 100%).
(24) The pressure-sensitive adhesive sheet according to (23), wherein the pressure-sensitive adhesive contains an anti-aging agent, and the anti-aging agent contains a radical scavenger and a sulfur-based antioxidant.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified. In addition, the description of the amount used of each material is based on the amount not considering the solvent unless otherwise specified.

<Production of double-sided PSA sheet>
(Example 1)
100 parts of styrene isoprene block copolymer (manufactured by Nippon Zeon Co., Ltd., product name “Quintac 3520”, styrene content 15%, diblock body ratio 78%), 40 parts of terpene phenol resin, and 30 parts of terpene resin Part, isocyanate compound (Tosoh Corporation product, product name “Coronate L”) 0.75 part, hindered phenolic antioxidant as a radical scavenger (product name “EUNOX AO-565” manufactured by Eutec Chemical) 1 part of 4-[[4,6-bis (octylthio) -1,3,5-triazin-2-yl] amino] -2,6-di-t-butylphenol) and phosphorus antioxidant (BASF) Product name “IRGAFOS 168”, 2 parts of tris (2,4-di-t-butylphenyl) phosphite), An ether antioxidant (product name "Adekastab AO-503" manufactured by ADEKA, 2 parts of ditridecyl-3,3'-thiodipropionate) and toluene as a solvent are mixed with stirring, and an adhesion of NV 50% An agent composition was prepared.
Here, as the terpene phenol resin, the product name “YS Polystar S145” (softening point 145 ° C., hydroxyl value 100 mgKOH / g) manufactured by Yashara Chemical Co., Ltd. and the product name “YS Polystar T145” (softening point 145 ° C. Two types with a hydroxyl value of 60 mgKOH / g) were used at a weight ratio of 1: 1 so that their total was 40 parts. As the terpene resin, a product name “YS Resin PX1150N” (softening point 115 ° C., hydroxyl value of less than 1 mgKOH / g) manufactured by Yasuhara Chemical Co., Ltd. was used.

  The pressure-sensitive adhesive composition obtained above was applied to a release liner, dried at 120 ° C. for 3 minutes, and bonded to a 12 μm thick PET film (trade name “Lumirror S10” manufactured by Toray Industries, Inc.). A 64 μm pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) was formed. Next, a pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) having a thickness of 64 μm was formed on the second surface (surface opposite to the first surface) of the PET film in the same manner as the first surface. Thus, the double-sided adhesive sheet which concerns on this example was produced. As the release liner, a release paper (Oji F-Tex Co., Ltd.) with a thickness of about 89 μm, on both the first and second sides, one side (the surface on the pressure-sensitive adhesive layer side) was peeled with a silicone release agent. Made of high-quality paper, polyethylene laminated on one side, product name “Separate 75 EPS (M) Cream Kai”).

(Example 2)
A product name “Adekastab AO-412S” (2,2-bis ({[3- (dodecylthio) propionyl] oxy} methyl) propanediyl = bis [3- (dodecylthio) propionate) manufactured by ADEKA Corporation is used as a thioether-based antioxidant. A double-sided PSA sheet according to this example was produced in the same manner as in Example 1 except that the amount was changed to 2 parts.

(Example 3)
A double-sided pressure-sensitive adhesive sheet according to Example 3 was produced in the same manner as in Example 1 except that the amounts of each terpene phenol resin and terpene resin used were changed to those shown in Table 1.

(Example 4)
A double-sided PSA sheet according to Example 4 was prepared in the same manner as Example 1 except that no thioether-based antioxidant was used.

<Aging test>
The pressure-sensitive adhesive sheet according to each example was cut into a rectangular shape having a length of 30 cm and a width of 20 cm together with the release liner covering both pressure-sensitive adhesive surfaces, and a sample for an aging test was produced. The sample was stored for 4 weeks in a drier in an air atmosphere maintained at 80 ° C. The samples were stored in a state suspended in the dryer so as not to overlap each other.

<Mw _H maintenance rate>
About the adhesive which comprises the 2nd adhesive layer of the adhesive sheet before an aging test and after an aging test, GPC measurement is performed by the method mentioned above, Mw _H before aging and after aging using an analysis software attached to a GPC measuring device Mw _H was calculated. Further, after the following equation :( aging Mw _H / aging before Mw _H) × 100; a calculated Mw _H maintenance rate (%). The results are shown in Table 1.

<Retention force test>
For each of the pressure-sensitive adhesive sheets before and after the aging test, a PET film having a thickness of 25 μm (trade name “Lumirror S10” manufactured by Toray Industries, Inc.) on the first pressure-sensitive adhesive surface (the pressure-sensitive adhesive surface of the first pressure-sensitive adhesive layer) of the pressure-sensitive adhesive sheet. ) Were bonded together, and this was cut into a strip shape having a width of 10 mm to prepare a test piece. The second adhesive surface of the test piece (adhesive surface of the second adhesive layer) is exposed, and the test piece is placed on a bakelite plate (phenol resin plate) as an adherend in an environment of 23 ° C. and 50% RH. Then, a 2 kg roller was reciprocated once in a pasting area having a width of 10 mm and a length of 20 mm for pressure bonding. After leaving the test piece attached to the adherend in this way for 30 minutes in the same environment, the adherend is suspended so that the length direction of the test piece is in the vertical direction, and the free end of the test piece is A load of 500 g was applied to the test piece, and allowed to stand in an environment of 40 ° C. for 30 minutes in accordance with JIS Z0237. About the test piece after the said leaving-to-stand, the distance (deviation distance) shifted | deviated from the first sticking position was measured. The measurement was performed using three test pieces for each pressure-sensitive adhesive sheet (that is, n = 3), and the arithmetic average value of the deviation distances related to these test pieces is shown in the column of “holding force” in Table 1. In addition, when even one test piece fell, it described as "falling".

As shown in Table 1, in the pressure-sensitive adhesive sheets of Examples 1 to 3 having an Mw _H maintenance rate of 70% or more, even after a severe aging test of 4 weeks at 80 ° C., a good level that does not drop in the holding power test Agglomeration was maintained. On the other hand, the pressure-sensitive adhesive sheet of Example 4 having an Mw _H maintenance rate of less than 70% was the same as in Examples 1 and 2 in the initial (before the aging test). It decreased significantly and could not withstand the holding power test after the aging test. Specifically, all three test pieces fell before 30 minutes. In the pressure-sensitive adhesive sheet according to Example 1, the pressure-sensitive adhesive was slightly colored after the aging test.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1, 2, 3 Adhesive sheet 11 First adhesive layer 12 Second adhesive layer 15 Base material 21, 22 Release liner

Claims (13)

An adhesive sheet including an adhesive layer,
The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifier resin,
The pressure-sensitive adhesive has a weight-average molecular weight Mw _H calculated for a region having a molecular weight in terms of polystyrene of 10,000 g / mol or more based on a molecular weight distribution curve based on gel permeation chromatography, maintained in an aging test at 80 ° C. for 4 weeks. A pressure-sensitive adhesive sheet having a rate of 70% or more.   The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the unsaturated rubber is 30% by weight or more of the pressure-sensitive adhesive.   The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the content of the tackifying resin is 10 parts by weight or more and 120 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein a softening point of the tackifying resin is 40 ° C or higher. The tackifying resin includes a phenolic tackifying resin,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the content of the phenolic tackifying resin is 5 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the unsaturated rubber. The tackifying resin includes a phenolic tackifying resin,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the phenol-based tackifying resin includes a terpene phenol resin having a hydroxyl value of 20 mgKOH / g or more. The pressure-sensitive adhesive contains an anti-aging agent,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the anti-aging agent includes a radical scavenger and a sulfur-based antioxidant. The pressure-sensitive adhesive contains an anti-aging agent,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the anti-aging agent contains a phosphorus-based antioxidant.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the pressure-sensitive adhesive has a phenolic tackifying resin content of 30 parts by weight or less based on 100 parts by weight of the unsaturated rubber.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the unsaturated rubber has a monomer composition including a conjugated diene compound, and a ratio of the conjugated diene compound to the monomer composition is 70% by weight or more. .   The said unsaturated rubber contains the block copolymer of a monovinyl substituted aromatic compound and a conjugated diene compound, The diblock body ratio of this block copolymer is 60 weight% or more, The any one of Claim 1 to 10 The pressure-sensitive adhesive sheet according to one item.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 11, wherein the pressure-sensitive adhesive layer has a thickness of 30 µm or more.   It is comprised as a double-sided adhesive adhesive sheet provided with a base material and the 1st adhesive layer and 2nd adhesive layer as said adhesive layer each supported by both surfaces of this base material. To 12. The pressure-sensitive adhesive sheet according to any one of 12 to 12.

Images