CN108300342B

CN108300342B - Adhesive sheet

Info

Publication number: CN108300342B
Application number: CN201710680576.0A
Authority: CN
Inventors: 冈原快; 大竹宏尚
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2016-09-08
Filing date: 2017-08-10
Publication date: 2021-10-29
Anticipated expiration: 2037-08-10
Also published as: CN108300342A; JP2018039928A; JP6830332B2

Abstract

The present invention relates to an adhesive sheet. The invention provides an adhesive sheet which has a composition in which a tackifier resin is blended into an unsaturated rubber and has excellent long-term quality stability. The present invention provides an adhesive sheet comprising an adhesive layer. The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifier resin. A weight average molecular weight Mw of the adhesive calculated from a molecular weight distribution curve based on GPC measurement and calculated in a range of 10,000g/mol or more in terms of polystyrene equivalent molecular weight in an aging test at 80 ℃ for four weeks_HThe retention rate is 70% or more.

Description

Adhesive sheet

Technical Field

This application claims priority based on japanese patent application 2016-.

The present invention relates to an adhesive sheet.

Background

Generally, an adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid (viscoelastic body) state in a temperature range around room temperature and has a property of being simply adhered to an adherend by pressure. By utilizing this property, adhesives are widely used in various industrial fields, such as home electric appliances, automobiles, and Office Automation (OA) equipment, as bonding means having good workability and high adhesion reliability, typically in the form of an adhesive sheet including an adhesive layer made of the adhesive. As the base polymer of the adhesive, a polymer exhibiting rubber elasticity at normal temperature is preferably used. Examples of such a polymer include a polymer having a monomer unit having a carbon-carbon unsaturated bond (for example, a polymer having a monomer unit based on a conjugated diene compound). Japanese patent application laid-open No. 2016-35039 discloses an adhesive composition containing a partially hydrogenated block copolymer (partially hydrogenated styrene-butadiene block copolymer, etc.) having a vinyl aromatic monomer unit and a conjugated diene monomer unit.

Disclosure of Invention

As the field of use and the manner of use of adhesive sheets expand, the level required for long-term quality stability (hereinafter also simply referred to as "quality stability") of the adhesive sheets after production increases. In this respect, there is still room for improvement in pressure-sensitive adhesive sheets including pressure-sensitive adhesives using unsaturated rubbers (particularly pressure-sensitive adhesives containing a large amount of unsaturated rubber). In particular, when a tackifier resin is blended with an unsaturated rubber, deterioration such as a decrease in cohesive force (cohesiveness) tends to be easily progressed, and the quality stability of the adhesive sheet tends to be lowered.

Accordingly, an object of the present invention is to provide an adhesive sheet having excellent long-term quality stability when the adhesive sheet has a composition in which a tackifier resin is blended with an unsaturated rubber.

The pressure-sensitive adhesive sheet provided by the present specification includes a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive containing an unsaturated rubber and a tackifier resin. A weight average molecular weight Mw of the adhesive calculated from a molecular weight distribution curve measured by Gel Permeation Chromatography (GPC) and calculated from a molecular weight of the adhesive in terms of polystyrene in a range of 10,000g/mol or more in an aging test at 80 ℃ for four weeks_HThe retention of (2) is 70% or more. According to the technique disclosed herein, by mixing the above weight average molecular weight Mw_HAs an index, the degree of deterioration of the binder can be accurately grasped. Mw in the above aging test_HRetention ratio (hereinafter also referred to as "Mw")_HRetention ratio) of 70% or more, can be a pressure-sensitive adhesive sheet with excellent quality stability. In addition, since it is allowable to mix a tackifier resin into the unsaturated rubber, the adhesive sheet can achieve both excellent adhesive properties (e.g., tackiness and peel strength) and long-term quality stability.

In some embodiments, the content of the unsaturated rubber in the adhesive may be 30% by weight or more of the adhesive. Such a pressure-sensitive adhesive containing a large amount of unsaturated rubber is advantageous in improving the adhesive properties, while deterioration tends to be facilitated due to the unsaturated bond in the unsaturated rubber. According to the technology disclosed herein, a pressure-sensitive adhesive sheet having good quality stability even with such a configuration can be provided.

In some embodiments, the content of the tackifier 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. With the adhesive of this composition, excellent adhesive properties (e.g., tack and peel strength) can be easily obtained. According to the technology disclosed herein, a pressure-sensitive adhesive sheet having good quality stability even when a pressure-sensitive adhesive having such a composition is used can be provided.

In some embodiments, the tackifying resin may contain a phenolic tackifying resin. Phenolic tackifying resins can contribute to improving adhesive properties, but on the other hand tend to be a factor that promotes deterioration of the adhesive. According to the technology disclosed herein, it is possible to provide a pressure-sensitive adhesive sheet having good quality stability even in the case of a configuration containing a phenolic tackifier resin. The content of the phenolic tackifier resin may be set to, 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. Such a composition can suitably exhibit an effect of improving the adhesive properties by using a phenolic tackifier resin. As the phenolic tackifying resin, for example, a terpene-phenol resin can be preferably used.

The technique disclosed herein can be preferably implemented in such a manner that the above-mentioned tackifier resin contains a phenolic tackifier resin and the phenolic tackifier resin contains a terpene-phenol resin having a hydroxyl value of 20mgKOH/g or more. With such a configuration, excellent adhesion characteristics and quality stability can be appropriately achieved at the same time.

The adhesive may contain an antioxidant in addition to the unsaturated rubber and the tackifier resin. By using the antioxidant, the Mw of the adhesive containing the unsaturated rubber and the tackifying resin in combination can be effectively improved_HThe retention rate can improve the long-term quality stability of the adhesive sheet (increase in lifetime). As the antioxidant, for example, a combination of a radical scavenger and a sulfurous antioxidant is effective. In addition, antioxidants containing phosphorus can also be used as antioxidantsAn oxidizing agent. By using a radical scavenger (for example, a phenolic antioxidant), a sulfur-containing antioxidant and a phosphorus-containing antioxidant in combination, higher effects can be exerted.

In some embodiments, the content of the adhesive is preferably 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 part by weight, that is, the adhesive may not contain the phenolic tackifying resin. In this way, by focusing attention on the amount of the phenolic tackifier resin in the tackifier resin and limiting the upper limit of the content thereof, the Mw of the adhesive can be effectively increased_HThe retention rate can provide a pressure-sensitive adhesive sheet having good quality stability (long life).

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

In some embodiments, the unsaturated rubber may comprise a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound. An adhesive containing such a block copolymer and a tackifier resin can exhibit excellent adhesive properties. Therefore, according to the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive, excellent adhesive properties and quality stability can be suitably achieved at the same time. The block copolymer may preferably have a diblock content of 60% by weight or more, from the viewpoint of improving the viscosity, low-temperature characteristics, and the like.

In some embodiments, the adhesive layer may have a thickness of 30 μm or more. When the pressure-sensitive adhesive layer is thickened, the peel strength of the pressure-sensitive adhesive sheet tends to be improved, but structural failure (cohesive failure) in the pressure-sensitive adhesive layer may easily occur. Therefore, it is particularly significant to apply the techniques disclosed herein to suppress the decrease in the cohesiveness.

The technique disclosed herein can be preferably implemented in the form of a pressure-sensitive adhesive sheet having double-sided pressure-sensitive adhesiveness including a substrate and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer supported on both sides of the substrate as the pressure-sensitive adhesive layers. The double-sided pressure-sensitive adhesive sheet, i.e., the double-sided pressure-sensitive adhesive sheet, is suitable for use in fixing members. In fixing the member, it is preferable to suppress a decrease in cohesive property of the adhesive agent over a long period of time after the adhesive sheet is attached, from the viewpoint of preventing the member from being positionally displaced or detached (release of the fixed state). Therefore, it is particularly significant to apply the techniques disclosed herein to suppress a decrease in cohesiveness of the adhesive.

Drawings

Fig. 1 is a schematic cross-sectional view showing the structure of an adhesive sheet (double-sided adhesive sheet with substrate) according to one embodiment.

Fig. 2 is a schematic cross-sectional view showing the structure of an adhesive sheet (double-sided adhesive sheet without a substrate) according to another embodiment.

Fig. 3 is a schematic cross-sectional view showing the structure of an adhesive sheet (substrate-attached single-sided adhesive sheet) according to another embodiment.

Reference numerals

1. 2, 3 pressure-sensitive adhesive sheet

11 first adhesive layer

12 second adhesive layer

15 base material

21. 22 Release liner

Detailed Description

Preferred embodiments of the present invention will be described below. Matters essential to the practice of the present invention other than those specifically mentioned in the present specification will be understood by those skilled in the art based on the technical common general knowledge about the teaching and application of the present invention described in the present specification. The present invention can be implemented based on the contents disclosed in the present specification and the common general knowledge in the art.

In the following drawings, members and portions that exhibit the same function are sometimes denoted by the same reference numerals, and redundant descriptions may be omitted or simplified. In addition, the embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not accurately indicate the size or scale of the product to be actually provided.

In the present specification, as described above, the "pressure-sensitive adhesive" refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range around room temperature and has a property of being easily adhered to an adherend by pressure. The adhesive in the art disclosed herein may also be understood as a solid component of the adhesive composition or a constituent component of the adhesive layer.

In the present specification, "unsaturated rubber" means a polymer having a monomer unit containing a carbon-carbon unsaturated bond and exhibiting rubber elasticity at room temperature (for example, 23 ℃). Typical unsaturated rubbers contain carbon-carbon unsaturation in the backbone.

In the present specification, the phrase "block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound" refers to a polymer having at least one segment (hereinafter, also referred to as "A segment") containing a monovinyl-substituted aromatic compound as a main monomer (more than 50% by mass of the copolymer component; the same applies hereinafter) and at least one segment (hereinafter, also referred to as "B segment") containing a conjugated diene compound as a main monomer. Generally, the glass transition temperature of the A segment is higher than the glass transition temperature of the B segment. Representative structures of the polymer include: a triblock copolymer (a-B-a triblock) having a triblock structure in which a segment (hard segment) is provided at each end of a B segment (soft segment), a diblock copolymer (a-B diblock structure) having a diblock structure comprising one a segment and one B segment, and the like.

In the present specification, "styrenic block copolymer" refers to a polymer having at least one styrene block. The styrene block means a segment having styrene as a main monomer. Segments substantially comprising only styrene are typical examples of styrene blocks as described herein. In addition, "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). As representative examples of the styrene-isoprene block copolymer, there can be mentioned: a triblock copolymer (triblock material) having a styrene block (hard segment) at each end of an isoprene block (soft segment), a diblock copolymer (diblock material) having a diblock structure comprising one isoprene block and one styrene block, and the like. "styrene-butadiene block copolymer" means a polymer having at least one styrene block and at least one butadiene block (a segment having butadiene as a main monomer).

In the present specification, the "styrene content" of the styrenic block copolymer means a weight ratio of the styrene component to the total weight of the block copolymer. The styrene content can be measured by NMR (nuclear magnetic resonance spectroscopy).

The ratio of the diblock compound to the styrenic block copolymer (hereinafter, sometimes referred to as "diblock compound ratio" or "diblock ratio") can be determined by the following method. That is, a styrene-based block copolymer was dissolved in Tetrahydrofuran (THF), and a total of 4 columns of GS5000H and G4000H, manufactured by Tosoh corporation, were connected in series by 2 columns, and high performance liquid chromatography was performed at a temperature of 40 ℃ and a flow rate of 1 mL/min using THF as a mobile phase. The peak area corresponding to the diblock was determined from the obtained graph. Then, the diblock ratio was determined by calculating the percentage of the peak area corresponding to the diblock compound with respect to the total peak area.

In the present specification, unless otherwise specified, a numerical value indicating a molecular weight or a weight average molecular weight is understood as a numerical value with a unit of "g/mol". Unless otherwise specified, the molecular weight in terms of GPC measurement is a molecular weight in terms of polystyrene.

< construction example of pressure-sensitive adhesive sheet >

The pressure-sensitive adhesive sheet disclosed herein (which may be in the form of a tape or the like having a long dimension) may be in the form of a double-sided pressure-sensitive adhesive sheet having a cross-sectional structure as shown in fig. 1, for example. The double-sided adhesive sheet 1 includes a substrate (e.g., plastic film, nonwoven fabric) 15, and a first adhesive layer 11 and a second adhesive layer 12 supported on both sides of the substrate 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-releasable) of the substrate 15, respectively. The double-sided adhesive sheet 1 before use (before being attached to an adherend) may be wound spirally while being overlapped with the release liner 21 having both the front surface 21A and the back surface 21B as shown in fig. 1. In the double-sided adhesive sheet 1 of this embodiment, the front surface (second adhesive surface 12A) of the second adhesive layer 12 is protected by the front surface 21A of the release liner 21, and the front surface (first adhesive surface 11A) of the first adhesive layer 11 is protected by the back surface 21B of the release liner 21. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be protected by two separate release liners.

The technique disclosed herein is preferably applied to a double-sided adhesive sheet with a substrate as shown in fig. 1, and may be applied to a double-sided adhesive sheet 2 without a substrate (i.e., without a substrate) as shown in fig. 2, in addition to this. The double-sided psa sheet 2 before use may be in the form of a substrate-free psa layer 11 in which the first psa surface 11A and the second psa surface 11B are protected by

release liners

21, 22, respectively, at least on the psa layer side (front side). Alternatively, the following embodiments are possible: the release liner 22 is omitted, and the release liner 21 having both surfaces as release surfaces is used, and the second adhesive surface 11B is wound in a spiral shape while being overlapped with the adhesive layer 11, and is thereby protected by being in contact with the back surface of the release liner 21.

The technique disclosed herein can also be applied to a substrate-attached pressure-sensitive adhesive sheet 3 of a one-sided pressure-sensitive adhesive type having a substrate 15 and a pressure-sensitive adhesive layer 11 supported by a first surface (non-release surface) 15A of the substrate as shown in fig. 3. As shown in fig. 3, for example, the psa sheet 3 before use may be in a form in which the surface (psa surface) 11A of the psa layer 11 is protected by a release liner 21 having a release surface at least on the psa layer side (front surface). Alternatively, the following embodiments are possible: the release liner 21 is omitted and the base material 15 having the second surface 15B as the release surface is used, and the adhesive sheet 3 with the base material is wound, whereby the first adhesive surface 11A is in contact with the second surface 15B of the base material 15 and protected.

Of the adhesive sheets disclosed hereinCharacterized in that it comprises an adhesive layer composed of an adhesive containing an unsaturated rubber and a tackifier resin, and the Mw of the adhesive_HThe retention rate is 70% or more. Mw of the adhesive_HThe retention is defined as the weight-average molecular weight Mw of the adhesive after an aging test at 80 ℃ for four weeks_H(Mw after aging)_H) Relative to the weight-average molecular weight Mw of the adhesive before the aging test_H(Mw before aging)_H) The ratio of. The aging test was performed by keeping the pressure-sensitive adhesive sheet with the release liner bonded to the surface (pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layer at 80 ℃ in an atmospheric air atmosphere for four weeks. As a release liner, a release paper (e.g., a polyethylene laminated paper (ポリラミ) with release treatment) may be preferably used. The thickness of the release liner is not particularly limited, and a release liner having a thickness of, for example, about 20 μm to about 150 μm (typically about 25 μm to about 100 μm) can be appropriately selected for use. More specifically, the aging test can be performed by the method described in the examples described later.

<Mw_HRetention rate>

In the present specification, the weight average molecular weight Mw of the adhesive_H(sometimes abbreviated as "Mw_H") means a weight average molecular weight calculated for a molecular weight in terms of polystyrene in a range of 10,000 or more in a molecular weight distribution curve obtained by GPC measurement. In contrast, the weight average molecular weight calculated for the entire molecular weight distribution curve (i.e., including the range in which the molecular weight in terms of polystyrene is less than 10,000) may be referred to as the weight average molecular weight Mw_T. As a sample for GPC measurement, a 0.1 wt% solution prepared by dissolving a pressure-sensitive adhesive collected from a pressure-sensitive adhesive sheet in Tetrahydrofuran (THF) was used, and the filtrate was left overnight and then filtered through a 0.45 μm membrane filter. The GPC measurement can be performed under the following conditions or under conditions that can obtain results equivalent thereto. The same method is used in the examples described later.

An analysis device: HLC-8120GPC, manufactured by Tosoh corporation

Column: TSKgel SuperHZM-H/HZ 4000/HZ 3000/HZ 2000

Column size: 6.0mmI.D. x 150mm

Eluent: THF (tetrahydrofuran)

Flow rate: 0.6 mL/min

The detector: differential Refractometer (RI)

Column temperature: 40 deg.C

Sample size: 20 μ L

Standard sample: polystyrene

In adhesives containing unsaturated rubbers and tackifying resins, the tackifying resin is generally used in a form that has a weight average molecular weight Mw_TA tackifying resin lower than the unsaturated rubber. In the molecular weight distribution curve of such an adhesive obtained by GPC measurement, a peak corresponding to the above-mentioned tackifier resin typically appears in a range of about several hundred to about several thousand in molecular weight. By the technique disclosed herein, the weight average molecular weight Mw of the molecular weight distribution curve in a high molecular weight range (specifically, a range of molecular weight of 10,000 or more) other than the above range is focused on_HThe deterioration and deterioration of the unsaturated rubber, which can cause the quality of the adhesive sheet to deteriorate, can be accurately determined. According to the weight average molecular weight Mw_HRetention after aging test (Mw)_HRetention ratio) of 70% or more, and can achieve both excellent adhesive properties and long-term quality stability (e.g., a property of causing little decrease in cohesiveness with time).

In some forms, Mw_HThe retention rate may be about 75% or more, may be about 80% or more, and may be about 85% or more. The techniques disclosed herein may also preferably be applied at Mw_HThe retention ratio is about 87% or more, and about 90% or more. Mw_HThe closer the retention rate is to 100%, the more the quality stability of the adhesive sheet tends to increase. Thus, in the technique disclosed herein, Mw_HThe upper limit of the retention rate may be 100%. Alternatively, the Mw may be determined from the practical viewpoint of balance with other adhesive properties and economy_HThe retention may be less than 100% (e.g., 99% or less). Mw_HThe retention rate can be adjusted by, for example, selecting the unsaturated rubber, the amount of the unsaturated rubber used, selecting the tackifier resin, the amount of the tackifier resin used, and the like. In additionIn addition, in the case of a composition in which the adhesive contains an antioxidant, the Mw may be adjusted by selecting the antioxidant and the amount of the antioxidant used_HRetention rate.

Although not particularly limited, the Mw of the adhesive sheet disclosed herein_H(i.e., Mw before aging)_H) Usually, about 80,000 or more is suitable, and may be about 100,000 or more, about 130,000 or more, or about 150,000 or more. Mw of adhesive sheet_HAt elevated temperatures, the cohesion generally tends to increase. Further, Mw of the pressure-sensitive adhesive sheet_HFor example, the content may be about 1,000,000 or less, about 800,000 or less, or about 600,000 or less. Mw of adhesive sheet_HWhen the viscosity and peel strength (particularly, these properties at low temperatures, that is, low-temperature properties) are decreased, the viscosity and peel strength tend to be generally increased. From this point of view, in some embodiments, the Mw of the adhesive sheet_HMay be about 400,000 or less, may be about 300,000 or less, may be about 250,000 or less, and may be about 200,000 or less. The techniques disclosed herein may be preferably performed at Mw, for example_HThe pressure-sensitive adhesive sheet is in the form of about 130,000 or more and about 200,000 or less. Mw of adhesive sheet_HCan be adjusted by selection of the unsaturated rubber, etc. In the composition containing the crosslinking agent, the kind of the crosslinking agent and the amount of the crosslinking agent may be adjusted.

Although not particularly limited, Mw after aging test of the adhesive sheet disclosed herein_H(i.e., Mw after aging)_H) Suitably about 70,000 or more, preferably about 90,000 or more, more preferably about 100,000 or more (e.g., about 120,000 or more). Mw after aging_HWhen the amount is increased, more excellent adhesive properties (for example, cohesiveness) tend to be exhibited even after a long period of time.

< unsaturated rubber >

As the unsaturated rubber, various rubbery polymers having a monomer unit containing a carbon-carbon unsaturated bond can be used. In some embodiments, the unsaturated rubber may be a homopolymer or a copolymer of a conjugated diene compound. Specific examples of the conjugated diene compound include 1, 3-butadiene and isoprene. The copolymer referred to herein may be a random copolymer, or may be 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), isobutylene-isoprene rubber (IIR), nitrile-butadiene rubber (NBR), Chloroprene Rubber (CR), styrene-isoprene block copolymer, styrene-butadiene block copolymer, and the like. In some embodiments, it may be preferable to use an unsaturated rubber composed of isoprene-containing monomers. The unsaturated rubber composed of such a monomer tends to facilitate the autoxidation reaction due to the presence of an isoprene structure, and therefore, the application of the technology disclosed herein is of great significance.

In the unsaturated rubber composed of a monomer 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 proportion of the conjugated diene compound may be, for example, 60% by weight or more, and usually 65% by weight or more is suitable, and preferably 70% by weight or more, and may be 75% by weight or more, or may be 80% by weight or more (typically more than 80% by weight, for example, 82% by weight or more). According to the technology disclosed herein, an adhesive sheet having good quality stability even when the adhesive is provided with an adhesive using an unsaturated rubber having such a monomer composition containing a conjugated diene compound in a large amount can be provided.

(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 is a compound in which one functional group having a vinyl group is bonded to an aromatic ring. Typical examples of the aromatic ring include a benzene ring (which may be substituted with a functional group having no vinyl group (e.g., an alkyl group)). Specific examples of the monovinyl-substituted aromatic compound include: styrene, alpha-methylstyrene, vinyltoluene, vinylxylene, and the like. Specific examples of the conjugated diene compound include 1, 3-butadiene and isoprene. Such block copolymers may be used alone or in combination of two or more as the unsaturated rubber in the art disclosed herein.

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

The block copolymer may be in the form of a diblock copolymer, a triblock copolymer, a radial copolymer, a mixture thereof, or the like. In the triblock polymer and the radial polymer, an a segment (for example, a styrene block) is preferably arranged at the end of the polymer chain. This is because: the a segments disposed at the ends of the polymer chain are easily aggregated to form domains, thereby forming pseudo-crosslinked structures, and improving the cohesive property of the binder.

As the block copolymer in the technique disclosed herein, a block copolymer having a diblock content of 30 wt% or more (more preferably 40 wt% or more, further preferably 50 wt% or more, particularly preferably 60 wt% or more, and typically 65 wt% or more) can be preferably used from the viewpoint of the adhesive force (peel strength) to an adherend. From the viewpoint of peel strength, a block copolymer having a diblock content of 70% by weight or more is particularly preferable. In addition, from the viewpoint of cohesiveness and the like, a block copolymer having a diblock content of 90 wt% or less (more preferably 85 wt% or less, for example 80 wt% or less) can be preferably used. For example, a block copolymer having a diblock fraction of 60 to 85 wt% is preferable, and a block copolymer having a diblock fraction of 70 to 85 wt% (for example, 70 to 80 wt%) is more preferable.

(styrenic block copolymer)

In a preferred embodiment of the technology disclosed herein, the unsaturated rubber is a styrene-based block copolymer. For example, the unsaturated rubber preferably contains at least one of a styrene-isoprene block copolymer and a styrene-butadiene block copolymer. Among the styrene-based block copolymers contained in the adhesive, it is preferable that the proportion of the styrene-isoprene block copolymer is 70% by weight or more, or the proportion of the styrene-butadiene block copolymer is 70% by weight or more, or the total proportion of the styrene-isoprene block copolymer and the styrene-butadiene block copolymer is 70% by weight or more. In a preferred embodiment, substantially all (for example, 95 to 100% by weight) of the styrene-based block copolymer is a styrene-isoprene block copolymer. In another preferred embodiment, substantially all (for example, 95 to 100% by weight) of the styrene-based block copolymer is a styrene-butadiene block copolymer. With such a composition, the effects of the technique disclosed herein can be more effectively exerted.

The styrenic block copolymer may be in the form of diblock copolymer, triblock copolymer, radial copolymer, or a mixture thereof. In the triblock and radial, a styrene block is preferably arranged at the end of the polymer chain. This is because: the styrene blocks disposed at the ends of the polymer chains are easily aggregated to form styrene domains, thereby forming pseudo-crosslinked structures and improving the cohesive property of the adhesive. As the styrenic block copolymer used in the technique disclosed herein, a block copolymer having a diblock content of 30% by weight or more (more preferably 40% by weight or more, further preferably 50% by weight or more, particularly preferably 60% by weight or more, and typically 65% by weight or more) can be preferably used from the viewpoint of the adhesive strength (peel strength) to an adherend. The styrene-based block copolymer may have a diblock content of 70 wt% or more (for example, 75 wt% or more). In addition, from the viewpoint of cohesiveness and the like, a styrene-based block copolymer having a diblock content of 90 wt% or less (more preferably 85 wt% or less, for example 80 wt% or less) can be preferably used. From the viewpoint of achieving both the adhesive property and the cohesive property in a balanced manner, a styrene-based block copolymer having a diblock content of preferably 60 to 85% by weight, and more preferably 70 to 85% by weight (for example, 70 to 80% by weight) is used.

The styrene content of the styrene-based block copolymer may be, for example, 5 to 40% by weight. From the viewpoint of cohesiveness, a styrene-based 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 preferred. From the viewpoint of peel strength, the styrene content is preferably 35 wt% or less (typically 30 wt% or less, more preferably 25 wt% or less), and particularly preferably 20 wt% or less (typically less than 20 wt%, for example 18 wt% or less). From the viewpoint of more effectively exerting the effects of the application of the technology disclosed herein, a styrene-based block copolymer having a styrene content of 12 wt% or more and less than 20 wt% can be preferably used.

(content of unsaturated rubber)

In the adhesive disclosed herein, the content of the unsaturated rubber (e.g., styrene-isoprene block copolymer) may be, for example, about 10 wt% or more, or about 20 wt% or more of the entire adhesive. In some embodiments, the unsaturated rubber may be present in the adhesive in an amount of about 30% by weight or more, or about 40% by weight or more, or about 50% by weight or more of the adhesive. This makes it easy to form a pressure-sensitive adhesive sheet having more excellent adhesive properties. In addition, as the content of the unsaturated rubber in the adhesive increases, the deterioration of the adhesive tends to proceed easily, and therefore, the effects of applying the technology disclosed herein can be more effectively exhibited. From this viewpoint, 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 properly exerting the effect of using the tackifier resin, the content of the unsaturated rubber in the pressure-sensitive adhesive is usually set to about 95% by weight or less as appropriate, and may be about 90% by weight or less, or may be about 80% by weight or less, or may be about 75% by weight or less, or may be about 70% by weight or less. The technique disclosed herein can also be preferably carried out in such a manner that the content of the above-mentioned unsaturated rubber is about 65% by weight or less (e.g., about 60% by weight or less).

< tackifying resin >

The adhesive layer disclosed herein contains a tackifying resin in addition to the unsaturated rubber. As the tackifier resin, one or two or more kinds of publicly known various tackifier resins selected from a phenol-based tackifier resin, a terpene resin, a modified terpene resin, a rosin-based tackifier resin, a petroleum resin, a styrene resin, a coumarone-indene resin, a ketone-based resin, and the like can be used. The tackifier resin is not particularly limited, and for example, a tackifier resin having a softening point of 40 ℃ or higher, preferably 60 ℃ or higher or 80 ℃ or higher can be used. The softening point of the tackifier resin may be, for example, 200 ℃ or lower (typically 180 ℃ or lower).

The phenolic tackifying resin referred to herein is a tackifying resin having a molecular structure containing a phenol skeleton, and is a concept including terpene phenol resins, hydrogenated terpene phenol resins, rosin phenol resins, and the like.

The terpene-phenol resin is a polymer containing a terpene residue and a phenol residue, and is a concept including both a copolymer of a terpene and a phenol (terpene-phenol copolymer resin) and a substance obtained by phenol-modifying a homopolymer or a copolymer of a terpene (phenol-modified terpene resin). Preferred examples of terpenes constituting such a terpene-phenol resin include: monoterpenes such as α -pinene, β -pinene, limonene (including d form, l form, and d/l form (terpineol)). The hydrogenated terpene phenol resin is a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. Sometimes also referred to as hydrogenated terpene phenol resins. The phenols include, for example: phenol, m-cresol, 3, 5-xylenol, p-alkylphenol, resorcinol, and the like.

Phenolic resins are typically resins derived 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 phenol resin include a resol type resin obtained by addition reaction of the above phenol and formaldehyde in the presence of a base catalyst, and a novolac type resin obtained by condensation reaction of the above phenol and formaldehyde in the presence of an acid catalyst.

The rosin phenol 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 rosin phenol resins obtained by a method of polymerizing a phenol and a rosin or a rosin derivative in the presence of an acid catalyst and the like.

Examples of terpene resins include polymers of terpenes (typically monoterpenes), such as alpha-pinene, beta-pinene, d-limonene, l-limonene, terpineol, and the like. The terpene may be a homopolymer of one kind, or a copolymer of two or more kinds. Examples of homopolymers of terpenes include α -pinene polymers, β -pinene polymers, and terpineol polymers.

Examples of the modified terpene resin include resins obtained by modifying the above terpene resins. Specifically, a styrene-modified terpene resin, a hydrogenated terpene resin, and the like can be exemplified.

The concept of the rosin-based tackifying resin as referred to herein includes both rosin-based and rosin derivative resins.

Examples of the rosin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, tall oil rosin and the like; modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, other chemically modified rosins, etc.) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc.

Rosin derivative resins are typically derivatives of rosins as described above. The rosin-based resin referred to herein includes derivatives of unmodified rosins and derivatives of modified rosins (including hydrogenated rosins, disproportionated rosins and polymerized rosins). Examples thereof include rosin esters such as an unmodified rosin ester which is an ester of an unmodified rosin and an alcohol, and a modified rosin ester which is an ester of a modified rosin and an alcohol; for example, unsaturated fatty acid-modified rosins obtained by modifying rosins with unsaturated fatty acids; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosin alcohols obtained by reducing carboxyl groups of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters); for example, metal salts of rosins or of the various rosin derivatives mentioned above; and the like. Specific examples of the rosin esters include: methyl esters of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.), triethylene glycol esters, glycerol esters, pentaerythritol esters, and the like.

Examples of petroleum resins include: aliphatic (C5 type) petroleum resins, aromatic (C9 type) petroleum resins, aliphatic/aromatic (C5/C9 type) petroleum resins, hydrogenated products thereof (for example, alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), and the like.

As examples of the styrene resin, there can be mentioned: a resin containing a homopolymer of styrene as a main component, a resin containing a homopolymer of α -methylstyrene as a main component, a resin containing a homopolymer of vinyltoluene as a main component, a resin containing a copolymer of two or more of styrene, α -methylstyrene and vinyltoluene as a main component in a monomer composition (for example, an α -methylstyrene/styrene copolymer resin containing an α -methylstyrene/styrene copolymer as a main component), and the like.

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

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

As a preferable embodiment, a mode in which the adhesive layer contains one or two or more kinds of phenolic tackifying resins (for example, terpene phenol resins) can be cited. By blending a phenolic tackifier resin with an unsaturated rubber (for example, a styrenic block copolymer), the adhesive properties can be effectively improved. This makes it possible to realize a pressure-sensitive adhesive sheet having excellent adhesive properties and good long-term quality stability (long-life).

When the pressure-sensitive adhesive layer contains a phenolic tackifier resin, the content thereof is not particularly limited. The content of the phenolic tackifier resin may be set to, for example, 1 part by weight or more, usually 5 parts by weight or more is appropriate, and may be 10 parts by weight or more, and may be 15 parts by weight or more, relative to 100 parts by weight of the unsaturated rubber. In some embodiments, the content of the phenolic tackifier resin may be 20 parts by weight or more, or may be 30 parts by weight or more (for example, 35 parts by weight or more) with respect to 100 parts by weight of the unsaturated rubber. From the viewpoint of low-temperature properties and compatibility of the adhesive, the content of the phenolic tackifier resin is usually preferably 60 parts by weight or less, and may be 50 parts by weight or less, based on 100 parts by weight of the unsaturated rubber. From the viewpoint of more importance on quality stability, in some embodiments, the content of the phenolic tackifier resin may be, for example, less than 40 parts by weight, or 35 parts by weight or less, or 30 parts by weight or less, or 25 parts by weight or less, with respect to 100 parts by weight of the unsaturated rubber.

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

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

(tackifying resin T)_H)

The pressure-sensitive adhesive layer disclosed herein contains a tackifier resin T having a softening point of 100 ℃ or higher_HAs the above tackifying resin. From the viewpoint of cohesiveness, tackifier resin T_HThe softening point of (A) is preferably 120 ℃ or higher, more preferably 125 ℃ or higher, still more preferably 130 ℃ or higher, and particularly preferably 135 ℃ or higher (for example, 140 ℃ or higher). In addition, the tackifier resin T is used from the viewpoint of peel strength and the like of the adherend_HThe softening point of (A) is preferably 200 ℃ or lower, more preferably 180 ℃ or lower, and still more preferably 170 ℃ or lower (for example, 160 ℃ or lower).

Herein, the softening point of the tackifier resin in the present specification is defined as a value measured based on a softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted rapidly at as low a temperature as possible, the melted sample is filled in a ring placed on a flat metal plate and care is taken not to blister. After cooling, the portion protruding from the plane containing the upper end of the ring was cut off with a slightly heated knife. Next, the holder (ring holder) was placed in a glass vessel (heating bath) having a diameter of 85mm or more and a height of 127mm or more, and glycerin was injected to a depth of 90mm or more. Next, a steel ball (diameter 9.5mm, weight 3.5g) and a ring filled with the sample were immersed in glycerin without contacting each other, and the temperature of the glycerin was maintained at 20 ℃. + -. 5 ℃ for 15 minutes. Next, a steel ball is placed in the center of the surface of the sample in the ring, and placed in a fixed position on the holder. Then, the container was heated while keeping the distance from the upper end of the ring to the glycerin surface at 50mm, placing a thermometer, and adjusting the position of the center of the mercury bulb of the thermometer to the same height as the center of the ring. The flame of the bunsen burner used in heating is adjusted to be located in the middle of the center and the edge of the bottom of the container, thereby making the heating uniform. Note that the ratio of increase in bath temperature from the start of heating to 40 ℃ must be 5.0 ℃ ± 0.5 ℃ per minute. The sample gradually softened and flowed down the loop, and the temperature at which the sample finally contacted the bottom plate was read as the softening point. The softening point was measured at the same time twice or more, and the average value was used.

As tackifying resins T_HOne or more kinds of the above-mentioned phenolic tackifying resin, terpene resin, modified terpene resin, rosin-based tackifying resin, petroleum resin, styrene resin, coumarone-indene resin, ketone resin and the like can be used. Among them, terpene phenol resins, rosin phenol resins, terpene resins, polymerized rosins, and esterified products of polymerized rosins are preferable.

As a preferable embodiment, one or more terpene-phenol resins are used as the tackifier resin T_H1The method (1). For example, a tackifier resin T is preferable_H25% by weight or more (more preferably 30% by weight or more) of (A) is a terpene-phenol resin (tackifier resin T)_H1) The method (1). Further, a tackifier resin T_HThe terpene-phenol resin in (b) may be present in an amount of about 70 wt% or less (e.g., 60 wt% or less, typically 50 wt% or less). Alternatively, it may be a tackifier resin T_H50% by weight or more of (B) is a terpene-phenol resin (tackifying resin T)_H1) The terpene-phenol resin (tackifier resin T) may be 80 wt% or more (for example, 90 wt% or more)_H1) The tackifier resin T may be used_HSubstantially all (e.g., 95 to 100 wt%, further 99 to 100 wt%) of the terpene-phenol resin (tackifier resin T)_H1). Terpenes having a softening point of 120 ℃ or higher and 200 ℃ or lower (typically 130 ℃ or higher and 180 ℃ or lower, for example 135 ℃ or higher and 170 ℃ or lower) can be preferably usedAn alkenylphenol resin.

Among all the tackifier resins contained in the pressure-sensitive adhesive layer disclosed herein, tackifier resin T_H1The ratio occupied is not particularly limited. The above ratio may be set to, for example, 30 wt% or more (typically 40 wt% or more), or may be set to, for example, 70 wt% or less (typically 60 wt% or less). Alternatively, substantially all (for example, 95 to 100% by weight, and more preferably 99 to 100% by weight) of all the tackifier resins may be the tackifier resin T_H1。

In addition, the technology disclosed herein may preferably contain a tackifier resin T_H1(typically terpene phenol resins) different tackifying resins T_H2As tackifying resins T_HThe method (2) is implemented. Tackifying resin T_H2Preferably lower than the tackifying resin T_H1More preferably, the softening point of (2) is higher than that of the tackifier resin T_H1Is lower by about 10 ℃ or higher (e.g., 20 ℃ or higher). According to this embodiment, for example, a pressure-sensitive adhesive sheet having more excellent peel strength can be realized. From the viewpoint of achieving both of the cohesiveness and the peel strength at a high level, it is preferable to use a tackifier resin T having a softening point of 100 ℃ or higher and lower than 120 ℃_H2. Among them, it is preferable to use a tackifier resin T having a softening point of 110 ℃ or higher and lower than 120 ℃_H2。

As tackifying resins T_H2The various tackifier resins (phenolic tackifier resin, terpene resin, modified terpene resin, rosin tackifier resin, petroleum resin, styrene resin, coumarone-indene resin, ketone resin, etc.) described above can be appropriately selected and used. In the technique disclosed herein, it is preferable that the tackifier resin T is at least one of a petroleum resin and a terpene resin contained in the adhesive_H2The method (2) is implemented. For example, a tackifier resin T may be preferably used_H2Main component (i.e., tackifying resin T)_H2The component (b) accounts for more than 50 wt%) of a petroleum resin, a terpene resin, a combination of a petroleum resin and a terpene resin, and the like. From the viewpoint of adhesion and compatibility, the tackifier resin T is preferable_H2Is a terpene resin (e.g., alpha-pinene polymer)β -pinene polymer). May be a tackifying resin T_H2Substantially all (e.g., 95 wt% or more) of (a) is a terpene resin.

The adhesive layer disclosed herein contains a tackifying resin T_H1And a tackifying resin T_H2As tackifying resins T_HIn the case of (3), the relationship between the amounts of their use is preferably such that T_H1:T_H2The weight ratio of (a) to (b) is set to 25:75 to 70:30 (more preferably 30:70 to 60: 40). The technique disclosed herein may preferably be such that the binder content ratio T is set to be higher than the binder content ratio T_H2Multiple T_H1The resin composition is used as a tackifier resin. According to this embodiment, a higher performance adhesive sheet can be realized.

The technique disclosed herein can be preferably used, for example, with a tackifier resin (T) having a hydroxyl value of 80mgKOH/g or more (e.g., 90mgKOH/g or more)_HO1) As tackifying resins T_HThe method (2) is implemented. Tackifying resin T_HO1The hydroxyl value of (B) is typically 200mgKOH/g or less, preferably 180mgKOH/g or less (for example, 160mgKOH/g or less). According to the presence of a tackifying resin T_HO1The adhesive of (3) can realize a higher performance adhesive sheet. It is possible to realize an adhesive sheet that can achieve both of the cohesion and other characteristics (e.g., low-temperature initial adhesiveness and the like) at a higher level.

Here, the hydroxyl value may be a value determined by JIS K0070: 1992, the values determined by potentiometric titration. Specific measurement methods are shown below.

[ method for measuring hydroxyl value ]

1. Reagent

(1) As the acetylation reagent, a reagent obtained by: about 12.5g (about 11.8mL) of acetic anhydride was taken, pyridine was added thereto so that the total amount was 50mL, and stirring was sufficiently performed. Or using a reagent obtained by: about 25g (about 23.5mL) of acetic anhydride was taken, and pyridine was added thereto so as to make the total amount to be 100mL, and sufficiently stirred.

(2) As a measuring reagent, 0.5mol/L ethanol solution of potassium hydroxide was used.

(3) In addition, toluene, pyridine, ethanol, and distilled water were prepared.

2. Operation of

(1) About 2g of the sample was accurately weighed in a flat bottom flask, 5mL of the acetylating agent and 10mL of pyridine were added, and an air condenser tube was installed.

(2) The flask was heated in a bath at 100 ℃ for 70 minutes, then cooled naturally, and 35mL of toluene as a solvent was added from the top of the condenser tube and stirred, and then 1mL of distilled water was added and stirred, thereby decomposing acetic anhydride. To complete the decomposition, the bath was again heated for 10 minutes and allowed to cool naturally.

(3) The condenser tube was cleaned with 5mL ethanol and removed. Subsequently, 50mL of pyridine was added as a solvent and stirred.

(4) 25mL of 0.5mol/L ethanolic potassium hydroxide solution were added using a full pipette.

(5) Potentiometric titration was carried out using 0.5mol/L ethanolic potassium hydroxide solution. The inflection point of the resulting titration curve was taken as the endpoint.

(6) The blank test was conducted without placing a sample in the above (1) to (5).

3. Computing

The hydroxyl number was calculated by the following formula.

Hydroxyl value (mgKOH/g) [ (B-C) × f × 28.05]/S + D

Wherein the content of the first and second substances,

b: the amount (mL) of 0.5mol/L KOH/ethanol solution used in the blank test,

C: the amount (mL) of 0.5mol/L ethanolic potassium hydroxide solution used in the sample,

f: factor of 0.5mol/L potassium hydroxide ethanol solution,

S: the weight (g) of the sample,

D: acid value, acid value,

28.05: 1/2 for potassium hydroxide having a molecular weight of 56.11.

As tackifying resins T_HO1Among the various tackifying resins described above, tackifying resins having a hydroxyl value of at least a predetermined value can be used alone or in appropriate combination. In a preferred embodiment, at least a terpene-phenol resin is used as the tackifier resin T_HO1. The terpene-phenol resin may be arbitrarily selected by copolymerization ratio of phenolThe hydroxyl value is preferably controlled. Terpene phenol resin in tackifying resin T_HO1More preferably about 50% by weight or more (for example, 80% by weight or more, typically 90% by weight or more), and still more preferably tackifier resin T_HO1Substantially all (for example, 95 to 100% by weight, and more preferably 99 to 100% by weight) of (a) the terpene-phenol resin (b) is a terpene-phenol resin.

The technique disclosed herein to use a composition containing a tackifying resin T_HO1In the case of embodiment (2) of the pressure-sensitive adhesive layer, the tackifier resin T_HO1The proportion of the tackifier resin in the whole is not particularly limited. The above ratio may be set to, for example, 10 wt% or more (typically 20 wt% or more), or may be set to, for example, 70 wt% or less (typically 60 wt% or less). Alternatively, substantially all (for example, 95 to 100% by weight, and more preferably 99 to 100% by weight) of all the tackifier resins may be the tackifier resin T_HO1。

The pressure-sensitive adhesive layer disclosed herein may contain a tackifier resin (T) having a hydroxyl value of 0 or more and less than 80mgKOH/g_HO2) As tackifying resins T_H. Tackifying resin T_HO2Can replace tackifying resin T_HO1Can also be used with tackifying resin T_HO1Are used in combination. As a preferred embodiment, a tackifier resin T having a hydroxyl value of 80mgKOH/g or more is mentioned_HO1And a tackifying resin T_HO2The method (1).

As tackifying resins T_HO2Among the various tackifying resins described above, tackifying resins having a hydroxyl value within the above range can be used alone or in appropriate combination. For example, a phenolic tackifying resin (e.g., terpene phenol resin, rosin phenol resin), a petroleum resin (e.g., C5-based petroleum resin), a terpene resin (e.g., β -pinene polymer), a rosin (e.g., polymerized rosin), a rosin derivative resin (e.g., esterified product of polymerized rosin), and the like having a hydroxyl value of 0 or more and less than 80mgKOH/g can be used. In a preferred embodiment, at least a terpene-phenol resin is used as the tackifier resin T_HO2. The terpene-phenol resin is preferable because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol. Terpene phenol resin in tackifying resinT_HO2The amount of the tackifier resin T may be about 50% by weight or more (for example, 80% by weight or more, typically 90% by weight or more), or may be the amount of the tackifier resin T_HO2Substantially all (for example, 95 to 100% by weight, and more preferably 99 to 100% by weight) of (a) the terpene-phenol resin (b) is a terpene-phenol resin.

The technique disclosed herein to use a composition containing a tackifying resin T_HO2In the case of embodiment (2) of the pressure-sensitive adhesive layer, the tackifier resin T_HO2The proportion of the tackifier resin in the whole is not particularly limited. The above ratio may be set to, for example, 10 wt% or more (typically 20 wt% or more), or may be set to, for example, 70 wt% or less (typically 60 wt% or less). Alternatively, substantially all (for example, 95 to 100% by weight, and more preferably 99 to 100% by weight) of all the tackifier resins may be the tackifier resin T_HO2。

The technique disclosed herein can preferably combine the tackifier resin T having a hydroxyl value of 80mgKOH/g or more (typically 80mgKOH/g to 160mgKOH/g, for example 80mgKOH/g to 140mgKOH/g) with the above-mentioned pressure-sensitive adhesive layer_HO1And a tackifier resin T having a hydroxyl value of 40mgKOH/g or more and less than 80mgKOH/g_HO2The method (2) is implemented. In this case, T_HO1And T_HO2The amount of (A) may be, for example, such that the weight ratio (T) is_HO1:T_HO2) The weight ratio is set in the range of 1:5 to 5:1, and is preferably set in the range of 1:3 to 3:1 (for example, 1:2 to 2: 1). As a preferred embodiment, T is mentioned_HO1、T_HO2All are terpene phenol resins.

In one embodiment of the technology disclosed herein, the tackifier resin T is_HMay further contain a tackifier resin T having an aromatic ring and a hydroxyl value of 30mgKOH/g or less_HR1As a tackifying resin T_HO1、T_HO2Different tackifying resins. Examples of the tackifier resin having an aromatic ring include the above aromatic petroleum resin, aliphatic/aromatic copolymerized petroleum resin, styrene resin, coumarone-indene resin, styrene-modified terpene resin, and terpene-phenol copolymer resinPhenol-modified terpene resins, rosin phenol resins, and the like. Of these, a tackifier resin having a softening point of 120 ℃ or higher (preferably 130 ℃ or higher, for example, 135 ℃ or higher) and a hydroxyl value of 30mgKOH/g or lower (preferably less than 5mgKOH/g, for example, less than 1mgKOH/g) can be used as the tackifier resin T_HR1. Among these, preferable tackifier resin T_HR1Aromatic petroleum resins and styrene resins (for example, α -methylstyrene/styrene copolymer resins) can be mentioned. In the technique disclosed herein, the adhesive layer may be substantially free of the tackifier resin T_HR1The method (2) is implemented.

In another embodiment of the adhesive disclosed herein, the tackifier resin T is_HA tackifier resin T which may contain an aromatic ring and which is substantially free of an isoprene unit, a terpene skeleton and a rosin skeleton_HR2As a tackifying resin T_HO1、T_HO2Different tackifying resins. Here, the tackifier resin T_HR2The fact that they are substantially free of isoprene unit, terpene skeleton and rosin skeleton means that these structural parts (i.e., isoprene unit, terpene skeleton and rosin skeleton) are present in the tackifier resin T_HR2The ratio of the total amount of (a) to (b) is less than 10% by weight (more preferably less than 8% by weight, still more preferably less than 5% by weight, for example less than 3% by weight). The above proportion may be 0% by weight. The isoprene unit, the terpene skeleton and the rosin skeleton are present in the tackifier resin T_HR2The ratio of (b) can be measured by NMR (nuclear magnetic resonance spectroscopy), for example.

Examples of the tackifier resin having an aromatic ring and substantially not containing an isoprene unit, a terpene skeleton and a rosin skeleton include the above aromatic petroleum resin, aliphatic/aromatic copolymerized petroleum resin, styrene resin, coumarone-indene resin and the like. Of these, a tackifier resin having a softening point of 120 ℃ or higher (preferably 130 ℃ or higher, for example, 135 ℃ or higher) may be used as the tackifier resin T_HR2. Among these, preferable tackifier resin T_HR2Aromatic petroleum resins and styrene resins (for example, α -methylstyrene/styrene copolymer resins) can be mentioned. Although not particularly limitedBut as a tackifier resin T_HR2The tackifier resin T_HR1For the same reason, a tackifier resin having a hydroxyl value of 30mgKOH/g or less (preferably less than 5mgKOH/g, for example, less than 1mgKOH/g) can be preferably used. Therefore, the tackifier resin T is used in the art disclosed herein_HR2For example, a tackifier resin T which is also compatible with the tackifier resin T may be preferably used_HR1The tackifying resin of (1). Similarly, the tackifier resin T in the art disclosed herein_HR1It is preferable to use a tackifier resin T which also satisfies the requirements of_HR2The tackifying resin of (1). In the technique disclosed herein, the adhesive layer may be substantially free of the tackifier resin T_HR2The method (2) is implemented.

In addition, from the viewpoint of improving the cohesiveness, the tackifier resin T is added to 100 parts by weight of the unsaturated rubber_HThe total amount of (a) (i.e., the total amount of the tackifier resin having a softening point of 100 ℃ or higher) is preferably 10 parts by weight or more, and more preferably 20 parts by weight or more (e.g., 25 parts by weight or more). Further, a tackifier resin T is added to 100 parts by weight of the unsaturated rubber_HThe content of (b) may be set to 60 parts by weight, for example. From the viewpoint of tackiness and low-temperature characteristics, the tackifier resin T is added to 100 parts by weight of the unsaturated rubber_HThe content of (b) is preferably 50 parts by weight or less, more preferably 45 parts by weight or less (for example, 40 parts by weight or less).

The tackifier resin T has a good balance between the cohesiveness and the low-temperature characteristics (for example, low-temperature initial tackiness)_HThe proportion of the tackifier resin in the total amount of the tackifier resin is preferably about 50% by weight or more, and preferably 80% by weight or more (for example, 90% by weight or more). The technique disclosed herein can preferably use substantially all (for example, 95 to 100 wt%, and more preferably 99 to 100 wt%) of the tackifier resin as the tackifier resin T_HThe method (2) is implemented.

(tackifying resin T)_L)

The adhesive layers disclosed herein may contain a tackifying resin T having a softening point of less than 100 ℃_L. Tackifying resin T_LThe lower limit of the softening point of (2) is not particularly limited. Softening points above 40 ℃ (typically 6 ℃) may be used0 ℃ or higher). Tackifying resin T_LThe hydroxyl value and structure (for example, presence or absence of an aromatic ring, presence or absence of an isoprene unit, presence or absence of a terpene skeleton, presence or absence of a rosin skeleton, etc.) of (a) is not particularly limited. The above-mentioned various tackifying resins (phenolic tackifying resins, terpene resins, modified terpene resins, rosin tackifying resins, petroleum resins, styrene resins, coumarone-indene resins, ketone resins, etc.) having a softening point of less than 100 ℃ are appropriately selected and used.

(content of tackifying resin)

In the technique disclosed herein, the total amount (total content) of the tackifier resin is not particularly limited, and may be set so that desired performance can be obtained according to the purpose and use. The total amount of the tackifier resin may be set to, for example, 1 part by weight or more, 5 parts by weight or more, or 10 parts by weight or more, based on 100 parts by weight of the unsaturated rubber. From the viewpoint of obtaining higher adhesive performance (for example, adhesive force), the total amount of the tackifier resin may be 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, or 30 parts by weight or more, relative to 100 parts by weight of the unsaturated rubber. In some embodiments, the total amount of the tackifier resin may be 40 parts by weight or more, or 55 parts by weight or more, based on 100 parts by weight of the unsaturated rubber. From the viewpoint of easily realizing an adhesive exhibiting good tackiness and low-temperature performance (for example, initial tackiness at low temperature), the total amount of the tackifier resin is usually preferably 120 parts by weight or less, more preferably 100 parts by weight or less, and still more preferably 80 parts by weight or less, based on 100 parts by weight of the unsaturated rubber. In some embodiments, the total amount of the tackifier resin may be 60 parts by weight or less, 50 parts by weight or less, or 45 parts by weight or less (for example, 40 parts by weight or less) with respect to 100 parts by weight of the unsaturated rubber.

< antiaging agent >

The adhesive disclosed herein may contain an antioxidant as needed. By using the antioxidant, the Mw of the adhesive containing the unsaturated rubber and the tackifying resin in combination can be improved_HRetention rate, can be achievedThe long-term quality stability of the pressure-sensitive adhesive sheet is improved (long life). The antioxidant may be used alone, two or more kinds may be used in combination, or three or more kinds may be used in combination.

(radical scavenger)

In some embodiments, the aging resistor may include a radical scavenger (radical scavenger). Examples of the radical scavenger include known radical scavengers that can be used in the field of unsaturated rubbers, such as phenol antioxidants, hindered amine antioxidants, and aromatic amine antioxidants. The radical scavenger may be used alone or in combination of two or more.

Examples of the radical scavenger that can be preferably used in the technology disclosed herein include phenolic antioxidants. As non-limiting examples of phenolic antioxidants, mention may be made of: monophenolic antioxidants such as 2, 6-di-tert-butyl-4-methylphenol and 2, 6-di-tert-butyl-4-ethylphenol; bisphenol antioxidants such as 2,2 '-methylenebis (4-methyl-6-tert-butylphenol), 2' -methylenebis (4-ethyl-6-tert-butylphenol), 4 '-butylidenebis (3-methyl-6-tert-butylphenol), and 4, 4' -thiobis (3-methyl-6-tert-butylphenol); high molecular weight phenolic antioxidants such as 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, tetrakis [ methylene-3- (3 ', 5 ' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] methane, 1, 3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane and the like; and the like.

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

The amount of the radical scavenger (for example, a phenol antioxidant) to be used may be, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, and may be 0.1 parts by weight or more (for example, 0.5 parts by weight or more) based on 100 parts by weight of the unsaturated rubber. By increasing the amount of radical scavenger used, the Mw tends to be higher_HThe retention rate is increased and the quality stability of the adhesive sheet is improved. From the viewpoint of suppressing adverse effects on the adhesion performance (for example, a decrease in the cohesive property of the adhesive before aging), the amount of the radical scavenger used is preferably set to usually 10 parts by weight or less, and preferably 5 parts by weight or less (for example, 3 parts by weight or less), relative to 100 parts by weight of the unsaturated rubber.

(Sulfur-containing antioxidant)

In some embodiments, the aging resistor may comprise a sulfur-containing antioxidant. The sulfur-containing antioxidant continuously acts as a peroxide decomposer that decomposes and/or converts a peroxide capable of being generated in the adhesive into a stable compound, and thus can contribute to an increase in Mw_HRetention (and further, improvement of quality stability of the adhesive sheet). The use of sulfur-containing antioxidants is particularly effective in adhesives containing unsaturated rubbers and phenolic tackifying resins (e.g., terpene-phenolic resins).

As the sulfur-containing antioxidant, for example, a thioether-based antioxidant having a thioether structure in the molecule can be used. As non-limiting examples of sulfurous antioxidants, mention may be made of: 2, 2-bis ({ [3- (dodecylthio) propanoyl)]Oxy } methyl) propanediyl-bis [3- (dodecylthio) propionate]Bis [ 2-methyl-4- (3-n-dodecyl thiopropionyloxy) -5-tert-butylphenyl]Thioether, 3-dodecylthiopropionic acid-2-tert-butyl-4- [ (5-tert-butyl-4-hydroxy-2-methylphenyl) thio group]5-methylphenyl ester, dilauryl 3,3 '-thiodipropionate, ditridecyl 3, 3' -thiodipropionate, dimyristyl 3,3 '-thiodipropionate, distearyl 3, 3' -thiodipropionate, pentaerythritol tetrakis (laurylthiopropionate), and the like. The sulfur-containing antioxidant may be used singly or in combination of two or more. In some embodiments, it may be preferable to use a sulfur-containing antioxidant (typically a thioether-based antioxidant) having a structure without an aromatic ring. In addition, it may be preferable to employ one or more (e.g., three or four) "CH(s)" within one molecule₂-OC(O)-CH₂CH₂-S-CH₂- "thioether antioxidants of structure.

The number of the thioetheric sulfur atoms contained in one molecule of the thioetheric antioxidant may be one, or two or more. From the viewpoint of the persistence of the effect, a thioether antioxidant containing two or more (typically, two or more and four or less) thioether sulfur atoms in one molecule is preferable. In some embodiments, by using a thioether-based antioxidant having a thioether equivalent weight (molecular weight corresponding to one thioether sulfur atom) of 1000 or less (preferably 700 or less, more preferably 500 or less, for example 350 or less), it is possible to effectively increase Mw while suppressing the influence on the adhesive property_HRetention rate. In addition, the thioether equivalent is preferably 150 or more, more preferably 200 or more, from the viewpoint of the effect persistence. The thioether equivalent weight can be calculated by dividing the molecular weight by the number of thioether sulfur atoms.

The molecular weight of the sulfurous antioxidant is suitably 2000 or less, preferably 1500 or less (for example 1250 or less). By using the sulfur-containing antioxidant, the Mw can be effectively increased while suppressing the influence on the adhesive properties (e.g., tackiness, low-temperature initial tackiness)_HRetention rate. From the viewpoint of the persistence of the effect, the molecular weight of the sulfurous antioxidant is preferably 150 or more, more preferably 200 or more, and still more preferably 350 or more.

The amount of the sulfur-containing antioxidant to be used relative to the amount of the unsaturated rubber may be set, for example, such that the number of moles of the sulfur sulfide (S) contained in the sulfur-containing antioxidant is 0.01mmol or more relative to 100g of the unsaturated rubber. Hereinafter, the number of moles of the thioetheric sulfur per 100g of the unsaturated rubber is sometimes referred to as "S number of moles" and is expressed in units of mmol/100 g. The molar number of S is preferably 0.05mmol/100g or more, more preferably 0.1mmol/100g or more, and may be setIt is 0.2mmol/100g or more, and may be set to 0.5mmol/100g or more (for example, 0.8mmol/100g or more). By increasing the S mole number of the sulfur-containing antioxidant, has Mw_HThe retention rate tends to be high and the quality stability tends to be improved. The technique disclosed herein can also be preferably carried out so that the S mol number is 1mmol/100g or more (for example, 2mmol/100g or more), or so that the S mol number is 4mmol/100g or more (for example, 5mmol/100g or more). The number of moles of S is, for example, 100mmol/100g or less, but is preferably 50mmol/100g or less, and more preferably 30mmol/100g or less, from the viewpoint of suppressing adverse effects on the adhesive performance (for example, reduction in tackiness and initial tackiness at low temperature). The technique disclosed herein can be preferably performed so that the S mol number is 20mmol/100g or less, or so that the S mol number is 15mmol/100g or less (for example, 10mmol/100g or less).

The amount of the sulfur-containing antioxidant to be used may be, for example, 0.01 part by weight or more, usually 0.01 part by weight or more is appropriate, and may be 0.05 part by weight or more (for example, 0.1 part by weight or more) based on 100 parts by weight of the unsaturated rubber. By increasing the amount of sulfur-containing antioxidant used, has Mw_HThe retention tends to be high. From the viewpoint of suppressing adverse effects on the adhesion performance (for example, reduction in tackiness and initial tackiness at low temperature), the amount of the sulfur-containing antioxidant used is usually suitably 10 parts by weight or less, preferably 7 parts by weight or less, and more preferably 5 parts by weight or less (for example, 3 parts by weight or less) per 100 parts by weight of the unsaturated rubber.

The amount of the sulfur-containing antioxidant to be used may be, for example, 0.01 or more, usually 0.05 or more, preferably 0.1 or more (for example, 0.5 or more) in terms of S molar ratio relative to 100 parts by weight of the unsaturated rubber. By increasing the S molar ratio of the sulfurous antioxidant, has Mw_HThe retention rate tends to be high and the quality stability tends to be improved. From the viewpoint of suppressing adverse effects on the adhesion performance (for example, reduction in tackiness and initial tackiness at low temperature), the amount of the sulfur-containing antioxidant used is usually 15 or less in S molar ratio, preferably 10 or less, per 100 parts by weight of the unsaturated rubberPreferably, 7 or less (for example, 6 or less). From the viewpoint of suppressing coloring (for example, yellowing) of the binder due to aging, it may be advantageous to decrease the S molar ratio. Here, the S molar ratio is a value obtained by multiplying the number of thioetheric sulfur contained in one molecule of the sulfur-containing antioxidant by the weight part of the amount of the sulfur-containing antioxidant used per 100 parts by weight of the unsaturated rubber. For example, in the case where 1 part by weight of a sulfur-containing antioxidant is contained with respect to 100 parts by weight of an unsaturated rubber, and the sulfur-containing antioxidant contains two thioether sulfur in one molecule, the S molar ratio of the above-mentioned sulfur-containing antioxidant in the composition is calculated to be 2.

(phosphorus-containing antioxidant)

In some embodiments, the aging resistor may comprise a phosphorus-containing antioxidant. The phosphorus-containing antioxidant can contribute to an increase in Mw by functioning as a peroxide decomposer that decomposes or converts a peroxide that can be generated in the adhesive into a stable compound_HRetention (and further, improvement of quality stability of the adhesive sheet). As non-limiting examples of antioxidants containing phosphorus, mention may be made of: tris (2, 4-di-t-butylphenyl) phosphite, tris (nonylphenyl) phosphite, triphenyl phosphite, distearyl pentaerythritol diphosphite, and the like.

The amount of the phosphorus-containing antioxidant to be used may be, for example, 0.05 parts by weight or more, usually 0.1 parts by weight or more is suitable, and may be 0.5 parts by weight or more (for example, 1 part by weight or more) based on 100 parts by weight of the unsaturated rubber. By increasing the amount of phosphorus-containing antioxidant used, has Mw_HThe retention tends to be high. From the viewpoint of suppressing adverse effects on the adhesion performance (for example, reduction in tackiness and initial tackiness at low temperature), the amount of the phosphorus-containing antioxidant to be used is usually 15 parts by weight or less, preferably 10 parts by weight or less, and more preferably 7 parts by weight or less (for example, 5 parts by weight or less) with respect to 100 parts by weight of the unsaturated rubber.

In some embodiments, as the age resistor, a sulfur-containing antioxidant (e.g., a thioether-based antioxidant) and a phosphorus-containing antioxidant may be used in combination. According to this mode, canTo suppress adverse effects on adhesive properties and thereby effectively increase Mw_HRetention rate. The reason is not particularly limited, and may be considered as follows. That is, phosphorus-containing antioxidants generally tend to react with peroxides more rapidly than do sulfur-containing antioxidants. On the other hand, the phosphorus-containing antioxidant is irreversibly consumed by the reaction with the peroxide, and therefore, there is a possibility that the durability of its effect tends to be insufficient in a severe aging test at 80 ℃ for four weeks. By using both the peroxide decomposer containing a sulfur antioxidant and a phosphorus antioxidant, it is possible to continuously exert a good peroxide decomposition function while suppressing the influence on the adhesive property. In addition, by using a sulfur-containing antioxidant and a phosphorus-containing antioxidant in combination, the amount of the sulfur-containing antioxidant used can be reduced, which can contribute to the suppression of the secular coloring of the adhesive. More desirable results can be achieved by using a combination of a sulfur-containing antioxidant, a phosphorus-containing antioxidant, and a phenolic antioxidant.

Although not particularly limited, when the phosphorus-containing antioxidant and the thioether antioxidant are used in combination, the amount A of the thioether antioxidant to be used is not particularly limited, and is not limited to 100 parts by weight of the unsaturated rubber_S[ molar ratio of S]With the amount A of the phosphorus-containing antioxidant per 100 parts by weight of the unsaturated rubber_P[ parts by weight]Ratio of (A)_S/A_PFor example, the range of 0.1 to 10 can be set. By setting the range, the effect of using both the sulfur-containing antioxidant and the phosphorus-containing antioxidant tends to be exhibited appropriately. In some embodiments, a is used from the viewpoint of obtaining a more favorable effect_S/A_PMay be 0.2 or more, or may be 0.5 or more. In addition, A_S/A_PMay be 5 or less, or may be 3 or less. In addition, A is_PAnd A_SEach means a numerical value representing the amount of the unsaturated rubber used in terms of the molar ratio of parts by weight to S, A_PAnd A_SThe value of (a) is itself a dimensionless number.

The radical scavenger disclosed herein may be combined with one or both of the phosphorus-containing antioxidant and the thioether-based antioxidant, or may contain other antioxidants capable of functioning as peroxide decomposers in place of these antioxidants. Examples of such other antioxidants include: amine antioxidants (phenyl-alpha-naphthylamine, diphenylamine, etc.), benzimidazole antioxidants, and the like. The other antioxidants mentioned above may be used alone, but are generally preferably used in combination with a radical scavenger (e.g., a phenolic antioxidant).

(content of antioxidant)

Although not particularly limited, the total amount of the antioxidant contained in the adhesive disclosed herein may be set to, for example, about 20 parts by weight or less, and is preferably set to 15 parts by weight or less, and may be set to 10 parts by weight or less, based on 100 parts by weight of the unsaturated rubber. The technique disclosed herein can be preferably performed in such a manner that the total amount of the antioxidant used is 7 parts by weight or less (for example, 5 parts by weight or less, or 4 parts by weight or less) with respect to 100 parts by weight of the unsaturated rubber. The total amount of the antioxidant may be set to, for example, 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more, based on 100 parts by weight of the unsaturated rubber.

< isocyanate Compound >

The pressure-sensitive adhesive layer disclosed herein may be a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing an isocyanate-based compound in addition to an unsaturated rubber and a tackifying resin. According to the adhesive composition, an adhesive sheet having more excellent long-term quality stability (for example, suppressed decrease in cohesiveness) can be realized. As the isocyanate compound, a polyfunctional isocyanate (which means a compound having an average of two or more isocyanate groups per molecule and includes a compound having an isocyanurate structure) can be preferably used. As the polyfunctional isocyanate, one or two or more selected from various isocyanate compounds (polyisocyanates) having two or more isocyanate groups in one molecule can be used. Examples of such polyfunctional isocyanates include: aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.

Specific examples of the aliphatic polyisocyanate include: 1, 2-ethylene diisocyanate; butylene diisocyanates such as 1, 2-butylene diisocyanate, 1, 3-butylene diisocyanate, and 1, 4-butylene diisocyanate; hexamethylene diisocyanate such as 1, 2-hexamethylene diisocyanate, 1, 3-hexamethylene diisocyanate, 1, 4-hexamethylene diisocyanate, 1, 5-hexamethylene diisocyanate, 1, 6-hexamethylene diisocyanate, 2, 5-hexamethylene diisocyanate, etc.; 2-methyl-1, 5-pentanediisocyanate, 3-methyl-1, 5-pentanediisocyanate, lysine diisocyanate, and the like.

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

Specific examples of the aromatic polyisocyanate include: 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2' -diphenylmethane diisocyanate, 4 '-diphenyl ether diisocyanate, 2-nitrobiphenyl-4, 4' -diisocyanate, 2 '-diphenylpropane-4, 4' -diisocyanate, 3 '-dimethyldiphenylmethane-4, 4' -diisocyanate, 4 '-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 1, 4-naphthalene diisocyanate, 1, 5-naphthalene diisocyanate, 3' -dimethoxybiphenyl-4, 4' -diisocyanate, 1, 4-xylylene diisocyanate, 1, 3-xylylene diisocyanate, and the like.

As a preferred isocyanate compound, a polyfunctional isocyanate having an average of three or more isocyanate groups per molecule can be exemplified. The trifunctional or higher isocyanate may be a polymer (typically a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (for example, an addition reaction product of a polyol and two or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples thereof include polyfunctional isocyanates such as dimer or trimer of diphenylmethane diisocyanate, isocyanurate form of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of the polyfunctional isocyanate include: the trade name "DURANATE TPA-100" manufactured by Asahi chemical Co., Ltd, the trade name "CORONATE L", "CORONATE HL", "CORONATE HK", "CORONATE HX", or "CORONATE 2096" manufactured by Tosoh chemical Co., Ltd.

In the case of using the isocyanate compound, the amount thereof to be used is not particularly limited, and may be set to more than 0 part by weight and 10 parts by weight or less (typically 0.01 part by weight to 10 parts by weight) relative to 100 parts by weight of the unsaturated rubber, for example. The amount of the isocyanate compound used is preferably 0.1 part by weight or more (typically 0.3 part by weight or more, for example, 0.5 part by weight or more) and preferably 10 parts by weight or less, and preferably 5 parts by weight or less (typically 3 parts by weight or less, for example, 1 part by weight or less) with respect to 100 parts by weight of the unsaturated rubber. By using the isocyanate compound within the above range, an adhesive sheet particularly excellent in balance of properties can be realized.

< other ingredients >

The pressure-sensitive adhesive layer disclosed herein may contain one or two or more rubbery polymers other than the unsaturated rubber as necessary within limits not detrimental to the effects of the present invention. The rubber-like polymer may be any of various polymers known in the field of adhesives, such as rubbers, acrylics, polyesters, polyurethanes, polyethers, silicones, polyamides, and fluorine-containing polymers. The technique disclosed herein can be preferably carried out in such a manner that the pressure-sensitive adhesive layer does not substantially contain a rubbery polymer other than the unsaturated rubber (for example, in a manner that the content is 0 to 1 part by weight with respect to 100 parts by weight of the unsaturated rubber).

The pressure-sensitive adhesive composition (or the pressure-sensitive adhesive layer) disclosed herein may contain, as required, various additives that are common in the field of pressure-sensitive adhesives such as leveling agents, crosslinking aids, plasticizers, softening agents, fillers, colorants (pigments, dyes, etc.), antistatic agents, ultraviolet absorbers, and light stabilizers. With respect to such various additives, conventionally known additives can be used by a conventional method.

The pressure-sensitive adhesive disclosed herein can be preferably applied so as not to substantially contain a liquid rubber such as polybutene (for example, the content may be 1 part by weight or less, or 0 part by weight, based on 100 parts by weight of the unsaturated rubber). This mode can be advantageous from the viewpoint of improving the peel strength and the cohesive property.

In some embodiments, the 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 oxide of an alkaline earth metal and a resin (e.g., an alkylphenol resin) having a functional group (e.g., a hydroxyl group, a hydroxymethyl group, etc.) capable of coordinating with the oxide. The technique disclosed herein can be preferably carried out in such a manner that the above-mentioned pressure-sensitive adhesive composition does not contain such a chelate compound at all or the content ratio of the chelate compound is 1% by weight or less. According to this embodiment, a pressure-sensitive adhesive sheet having more excellent adhesive strength can be realized.

In some embodiments, the adhesive may have a composition in which the total amount of the unsaturated rubber and the tackifier resin is 75% by weight or more of the total weight of the adhesive (i.e., the weight of the adhesive layer composed of the adhesive). For example, the total amount of the unsaturated rubber and the tackifier resin may be preferably 80% by weight or more (for example, 85% by weight or more, or 90% by weight or more) and 99.8% by weight or less (typically, 99.5% by weight or less) of the total weight of the adhesive.

< adhesive composition >

The adhesive layer disclosed herein may be a layer formed of an adhesive composition containing a component corresponding to the adhesive layer. The form of the pressure-sensitive adhesive composition is not particularly limited, and examples thereof include a form (solvent type) of a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive (pressure-sensitive adhesive component) having the above-described composition in an organic solvent, a form (water dispersion type, typically aqueous emulsion type) of a pressure-sensitive adhesive composition in which a pressure-sensitive adhesive is dispersed in an aqueous solvent, and a hot-melt type pressure-sensitive adhesive composition. From the viewpoints of coatability, freedom of choice of substrate, and the like, a solvent-based or water-dispersed adhesive composition can be preferably used. From the viewpoint of achieving higher adhesive performance, a solvent-based adhesive composition is particularly preferable.

The solvent-based adhesive composition is typically prepared in the form of a solution containing the above-mentioned components in an organic solvent. The organic solvent may be appropriately selected from known or commonly used organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) selected from toluene, xylene, and the like; acetates such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; halogenated alkanes such as 1, 2-dichloroethane; ketones such as methyl ethyl ketone and acetylacetone; and the like, or a mixed solvent of two or more thereof. Although not particularly limited, it is appropriate to prepare the above-described solvent-based adhesive composition so that the nonvolatile content (NV) is 30 wt% or more (for example, 40 wt% or more), and to prepare the solvent-based adhesive composition so that the NV is 65 wt% or less (for example, 55 wt% or less). When the NV is too low, the production cost tends to increase, and when the NV is too high, workability such as coatability may decrease.

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 of forming an adhesive layer by directly applying (typically coating) an adhesive composition on a substrate and drying it (direct method) can be preferably employed. In addition, a method (transfer method) of applying the above-described pressure-sensitive adhesive composition to a surface having good releasability (for example, a surface of a release liner, a back surface of a support substrate subjected to release treatment, or the like) and drying the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer on the surface and transferring the pressure-sensitive adhesive layer to a substrate can be employed.

The application of the adhesive composition can be performed using a known or commonly used coater such as a gravure roll coater, a reverse roll coater, a roll-lick coater, a dip roll coater, a bar coater, a knife coater, or a spray coater. From the viewpoint of accelerating the crosslinking reaction, improving the production efficiency, and the like, the drying of the adhesive composition is preferably performed under heating. For example, a drying temperature of about 40 ℃ or higher (for example, about 50 ℃ or higher, further about 70 ℃ or higher) and about 150 ℃ or lower (typically, about 120 ℃ or lower, further about 100 ℃ or lower) may be preferably used. The drying time is not particularly limited, and may be set to about several tens of seconds to about several minutes (for example, within about 5 minutes, preferably about 30 seconds to about 2 minutes). Then, an additional drying process may be provided as necessary. The adhesive layer is typically formed continuously, but may be formed in a regular or irregular pattern such as dots or stripes depending on the purpose and application.

(thickness of adhesive layer)

Although not particularly limited, the thickness of the adhesive layer is suitably about 4 μm or more (typically about 20 μm or more, for example, about 30 μm or more), and is suitably about 150 μm or less (typically about 120 μm or less, for example, about 100 μm or less). In some embodiments, the thickness of the adhesive layer may be preferably 30 μm or more, more preferably 40 μm or more, and further preferably 50 μm or more (for example, 60 μm or more). The pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with such a thickness can exhibit excellent pressure-sensitive adhesive performance (e.g., peel strength) when the pressure-sensitive adhesive layer is configured to contain an unsaturated rubber and a tackifier resin. Therefore, it is possible to provide an adhesive sheet having both high adhesion performance and high quality stability (long life). In the case of a double-sided pressure-sensitive adhesive sheet with a substrate, a configuration may be adopted in which pressure-sensitive adhesive layers having the above thicknesses are provided on both sides of the substrate. The thickness of each adhesive layer may be the same or different.

< pressure-sensitive adhesive sheet >

(substrate)

When the technique disclosed herein is applied to a double-sided adhesive sheet with a substrate or a single-sided adhesive sheet with a substrate, the substrate may be selected and used as appropriate according to the use of the adhesive sheet, for example, as follows: plastic films such as polypropylene films, ethylene-propylene copolymer films, polyester films, and polyvinyl chloride films; foam sheets including foams such as polyurethane foam, polyethylene foam, polychloroprene foam, and the like; woven and nonwoven fabrics (including papers such as japanese paper and taffy (fermented flour)) obtained by weaving or blending various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate fiber) alone or together; metal foils such as aluminum foil and copper foil; and the like. As the plastic film (typically, a non-porous plastic film, which is a concept different from woven fabric or nonwoven fabric), any of an unstretched film and a stretched (uniaxially stretched or biaxially stretched) film may be used. Further, the surface of the substrate on which the pressure-sensitive adhesive layer is to be provided may be subjected to surface treatment such as coating with a primer or corona discharge treatment.

In a preferred embodiment, a nonwoven fabric (nonwoven fabric substrate) is used as the substrate. By using a nonwoven fabric substrate, the initial tackiness at low temperature and the cohesiveness (for example, the property of being able to withstand without dropping in the holding power test) tend to be improved. As the nonwoven fabric used as the base material, for example, a nonwoven fabric composed of pulp such as wood pulp, natural fibers such as cotton and hemp; nonwoven fabrics composed of polyester fibers such as polyethylene terephthalate (PET) fibers, rayon, vinylon, acetate fibers, polyvinyl alcohol (PVA) fibers, polyamide fibers, polyolefin fibers, and chemical fibers (synthetic fibers) such as polyurethane fibers; a nonwoven fabric composed of two or more kinds of fibers of different materials; and the like. Among them, from the viewpoint of impregnation with a binder and repulsion resistance (follow-up property on curved surfaces), a nonwoven fabric made of pulp or hemp (for example, hemp pulp), a nonwoven fabric made of PET fibers, and the like are preferable. The use of the nonwoven fabric substrate also contributes to improvement in flexibility and hand-tearability of the adhesive sheet.

As the nonwoven fabric (nonwoven fabric substrate), a nonwoven fabric having a basis weight (basis weight) of about 30g/m or so can be preferably used²The following (e.g., about 25 g/m)²Below, typically about 20g/m²Below). The nonwoven fabric of the basis weightIs suitable for producing a light-weight pressure-sensitive adhesive sheet having excellent adhesive properties. From the viewpoint of resilience resistance, the basis weight is preferably less than 18g/m²(e.g., 16 g/m)²Below, typically 15g/m²Below). The basis weight is preferably 10g/m from the viewpoint of improving the strength of the base material itself²Above (e.g., 12 g/m)²Above, typically 13g/m²Above).

The bulk density (calculated by dividing the basis weight by the thickness) of the nonwoven fabric substrate was about 0.20g/cm³The above is appropriate, and preferably 0.25g/cm³Above (e.g., 0.30 g/cm)³Above) and about 0.50g/cm³The following are appropriate, and 0.40g/cm is preferable³Below (e.g., 0.35 g/cm)³Below). When the bulk density is within the above range, the base material itself has appropriate strength, and good adhesive impregnation properties can be obtained. From the viewpoint of rebound resistance, it is particularly preferable to use a bulk density of about 0.25g/cm³About 0.40g/cm³(e.g., about 0.30 g/cm)³About 0.35g/cm³) The nonwoven fabric substrate of (1).

The nonwoven fabric base material may contain a resin component such as starch (e.g., cationic starch), polyacrylamide, viscose, polyvinyl alcohol, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide-polyamine epichlorohydrin, in addition to the above-described constituent fibers. The resin component can function as a paper strength enhancer for the nonwoven fabric substrate. The strength of the nonwoven fabric substrate can be adjusted by using the resin component as needed. The nonwoven fabric substrate in the technology disclosed herein may contain, as necessary, additives that are common in the field related to the production of nonwoven fabrics, such as a yield improver, a water filtration agent, a viscosity modifier, and a dispersant.

The thickness of the base material can be appropriately selected according to the purpose, and is usually set to about 2 μm or more (typically about 10 μm or more) as appropriate, and is preferably set to 500 μm or less (typically 200 μm or less). When a nonwoven fabric is used as the substrate, the thickness of the nonwoven fabric substrate is preferably about 150 μm or less. The thickness is preferably 100 μm or less (for example, 70 μm or less) from the viewpoint of sufficiently impregnating the entire substrate with the binder. In view of workability in the production of the pressure-sensitive adhesive sheet, the thickness is preferably 10 μm or more (for example, 25 μm or more). From the viewpoint of rebound resistance, the thickness is preferably 30 μm or more (for example, 35 μm or more, typically 40 μm or more), and preferably 60 μm or less (for example, 50 μm or less, typically 45 μm or less). The nonwoven fabric substrate disclosed herein preferably satisfies two or more of the above preferred ranges of basis weight, thickness and bulk density (for example, basis weight and thickness, more preferably, all of basis weight, thickness and bulk density). This makes it possible to realize an adhesive sheet having a highly balanced variety of adhesive properties (e.g., rebound resistance, cohesion, peel strength, etc.).

(Release liner)

The release liner is not particularly limited, and may be any commonly used release paper. For example, a release liner having a release treatment layer on the surface of a base material such as a plastic film or paper, a release liner containing a low-adhesive material such as a fluoropolymer (polytetrafluoroethylene or the like) or a polyolefin resin (polyethylene, polypropylene or the like), or the like can be used. The release-treated layer can be formed by surface-treating the substrate with a release-treating agent such as silicone, long-chain alkyl, fluorine-containing, or molybdenum sulfide.

(thickness of adhesive sheet)

The total thickness of the psa sheet disclosed herein is not particularly limited, but is preferably set to about 1000 μm or less (e.g., 500 μm or less, typically 300 μm or less) from the viewpoint of thinning, weight reduction, resource saving, and the like. From the viewpoint of ensuring good adhesive properties, it is preferable to set the thickness to 50 μm or more (for example, 70 μm or more, typically 100 μm or more).

(characteristics)

In the adhesive sheet disclosed herein, it is preferable that the test piece does not fall off in the holding force test of the adhesive sheet after the aging test. That is, it is preferable that the adhesive layer after the aging test retains the cohesive property at a level that exhibits the above-described retention force. The pressure-sensitive adhesive sheet satisfying the above characteristics is excellent in long-term quality stability. The pressure-sensitive adhesive sheet disclosed herein is more preferably such that the offset distance from the initial position in the holding force test after the aging test is 1mm or less, and still more preferably 0.5mm or less.

The pressure-sensitive adhesive sheet disclosed herein preferably exhibits a level of cohesiveness such that the test piece does not fall off in the holding power test of the pressure-sensitive adhesive sheet before the aging test. The offset distance from the initial position in the holding force test is more preferably 1mm or less, and still more preferably 0.5mm or less.

The retention test after the aging test and before the aging test was performed by the method described in the examples described later. When the holding force test is performed using the single-sided pressure-sensitive adhesive sheet as a test piece, it is not necessary to bond a PET film to the first pressure-sensitive adhesive surface of the test piece.

< use >

The adhesive sheet disclosed herein is useful for joining members in various Office Automation (OA) devices (e.g., Personal Computers (PCs)), home electric appliances (e.g., rice cookers, refrigerators), automobiles, building materials (e.g., building materials), and the like (e.g., fixing applications of various parts in the products, labels, and the like). The pressure-sensitive adhesive sheet disclosed herein can be preferably used for applications in which a decorative sheet used for decorating the inner wall of a building is fixed to the position (inner wall) to which the decorative sheet is attached, because of its excellent long-term quality stability.

The matters disclosed in the present specification include the following.

(1) An adhesive sheet comprising an adhesive layer, wherein,

the adhesive layer is composed of an adhesive containing an unsaturated rubber and a tackifier resin, and

the weight average molecular weight Mw of the adhesive is calculated in a molecular weight distribution curve based on GPC measurement in a four-week aging test at 80 ℃ in a range of 10,000g/mol or more_HThe retention ratio of (b) is 70% or more (for example, 70% to 100%).

(2) The pressure-sensitive adhesive sheet according to the item (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 tackifier resin is about 10 parts by weight or more and about 120 parts by weight or less based on 100 parts by weight of the unsaturated rubber.

(4) The adhesive sheet according to any one of (1) to (3), wherein the tackifier resin contains at least one selected from the group consisting of a phenolic tackifier resin, a terpene resin, a modified terpene resin, a rosin tackifier resin, a petroleum resin, a styrene resin, a coumarone-indene resin and a ketone resin.

(5) The adhesive sheet according to any one of (1) to (4), wherein the tackifier resin comprises a phenolic tackifier resin, and a content of the phenolic tackifier resin is about 5 parts by weight or more and about 60 parts by weight or less based on 100 parts by weight of the unsaturated rubber.

(6) The adhesive sheet according to any one of (1) to (5), wherein the tackifier resin comprises a phenolic tackifier resin comprising a terpene-phenol resin having a hydroxyl value of 20mgKOH/g or more.

(7) The adhesive sheet according to any one of (1) to (6), wherein the tackifier resin comprises a phenolic tackifier resin comprising a terpene-phenol resin having a hydroxyl value of 80mgKOH/g or more.

(8) The adhesive sheet according to any one of (1) to (7), wherein the softening point of the tackifier resin is 40 ℃ or higher (e.g., 60 ℃ or higher).

(9) The adhesive sheet according to any one of (1) to (8), wherein the adhesive contains an antioxidant agent comprising a radical scavenger and a sulfurous antioxidant.

(10) The adhesive sheet according to any one of (1) to (9), wherein the adhesive contains an antioxidant agent containing a phosphorus-containing antioxidant.

(11) The adhesive sheet according to any one of (1) to (10) above, wherein the adhesive contains an antioxidant agent comprising a thioether antioxidant and a phosphorus-containing antioxidant as sulfur-containing antioxidants,

for the above-mentioned unsaturationAnd 100 parts by weight of rubber, A_S[ molar ratio of S]And the amount A of the antioxidant containing phosphorus per 100 parts by weight of the unsaturated rubber_P[ parts by weight]Ratio of (A)_S/A_P) 0.1 to 10.

(12) The adhesive sheet according to any one of (8) to (11), wherein the total amount of the antioxidant is 1.5 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the unsaturated rubber.

(13) The adhesive sheet according to any one of (1) to (12) above, wherein the adhesive contains 30 parts by weight or less of a phenolic tackifier resin per 100 parts by weight of the unsaturated rubber.

(14) The adhesive sheet according to any one of (1) to (13), wherein the adhesive composition for forming the adhesive layer contains an isocyanate compound.

(15) The pressure-sensitive adhesive sheet according to any one of (1) to (14), wherein the total amount of the unsaturated rubber and the tackifier resin in the pressure-sensitive adhesive is about 85% by weight or more and about 99.8% by weight or less based on the total weight of the pressure-sensitive adhesive.

(16) The adhesive sheet according to any one of (1) to (15), wherein the unsaturated rubber is a homopolymer or a copolymer of a conjugated diene compound.

(17) The adhesive sheet according to any one of (1) to (16), wherein the unsaturated rubber is a homopolymer or a copolymer of isoprene.

(18) The adhesive sheet according to any one of (1) to (17), 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.

(19) The adhesive sheet according to any one of (1) to (18) above, wherein the unsaturated rubber contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound.

(20) The adhesive sheet according to (19) above, wherein the diblock fraction of the block copolymer is about 60% by weight or more.

(21) The adhesive sheet according to any one of (1) to (20), wherein the thickness of the adhesive layer is about 30 μm or more.

(22) The pressure-sensitive adhesive sheet according to any one of (1) to (21) above, wherein the pressure-sensitive adhesive sheet is configured as a double-sided pressure-sensitive adhesive sheet having a substrate and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer supported on both sides of the substrate as the pressure-sensitive adhesive layers.

(23) An adhesive sheet comprising an adhesive layer, wherein,

the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer contains an unsaturated rubber and a tackifier resin having a softening point of 60 ℃ or higher,

the unsaturated rubber contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, wherein the conjugated diene compound accounts for 70 wt% or more of the monomer composition and the diblock fraction is about 60 wt% or more,

the content of the unsaturated rubber is about 30 wt% or more of the adhesive,

the tackifier resin contains at least one selected from the group consisting of a phenolic tackifier resin, a terpene resin, a modified terpene resin, a rosin tackifier resin, a petroleum resin, and a coumarone-indene resin,

the total amount of the tackifier resin is about 10 parts by weight or more and about 120 parts by weight or less based on 100 parts by weight of the unsaturated rubber,

(24) The pressure-sensitive adhesive sheet according to item (23) above, wherein the pressure-sensitive adhesive contains an antioxidant agent comprising a radical scavenger and a sulfur-containing antioxidant.

Examples

Some examples related to the present invention will be described below, but the present invention is not intended to be limited to the examples shown. In the following description, "part" and "%" are based on weight unless otherwise specified. Unless otherwise specified, the description of the amount of each material used and the like is based on the amount without considering the solvent, unless otherwise specified.

< preparation of double-sided adhesive sheet >

(example 1)

100 parts of a styrene-isoprene block copolymer (product name "Quindac 3520", styrene content 15%, diblock ratio 78%, manufactured by Nippon Raynaud Co.), 40 parts of a terpene phenol resin, 30 parts of a terpene resin, 0.75 part of an isocyanate compound (product name "CORONATE L" manufactured by Tosoh Co.), 1 part of a hindered phenol antioxidant (product name "EUNOX AO-565" manufactured by Eutec Chemical Co., 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-t-butylphenol) as a radical scavenger, 2 parts of a phosphorus-containing antioxidant (product name "IRGAFOS 168" manufactured by BASF Co., Ltd., tris (2, 4-di-t-butylphenyl) phosphite), 2 parts of a thioether-based antioxidant (product name "ADK STAB-503" manufactured by Adeka company of Adeka (ADEKA), Ditridecyl 3, 3' -thiodipropionate) and toluene as a solvent were mixed with stirring to prepare an adhesive composition having NV 50%.

Here, as the terpene phenol resins, two kinds of terpene phenol resins were used so that the trade name "YS Polymer S145" (softening point 145 ℃ C., hydroxyl value 100mgKOH/g) manufactured by Yasuhara Chemical company and the trade name "YS Polymer T145" (softening point 145 ℃ C., hydroxyl value 60mgKOH/g) manufactured by the company were in a weight ratio of 1:1 and the total amount thereof was 40 parts. As the terpene Resin, a product name "YS Resin PX 1150N" (softening point 115 ℃ C., hydroxyl value less than 1mgKOH/g) manufactured by Anyuan chemical company was used.

The adhesive composition obtained above was applied to a release liner, and dried at 120 ℃ for 3 minutes to be bonded to a PET film (product name "Lumirror S10" manufactured by toray) having a thickness of 12 μm, thereby forming an adhesive layer (first adhesive layer) having a thickness of 64 μm. Next, an adhesive layer (second adhesive layer) having a thickness of 64 μm was formed on the second surface (the surface opposite to the first surface) of the PET film in the same manner as the first surface. Thus, a double-sided pressure-sensitive adhesive sheet of this example was produced. As the release liner, release paper having a thickness of about 89 μm after release treatment with a silicone release agent on one side (the side on the adhesive layer side) (polyethylene laminated paper obtained by laminating polyethylene on one side of a backing paper, manufactured by prince F-TEX corporation, product name "Separator 75eps (m) grow (modified)") was used on both the first surface side and the second surface side.

(example 2)

A double-sided adhesive sheet of this example was produced in the same manner as in example 1 except that the thioether-based antioxidant was changed to 2 parts by the product name "ADK STAB AO-412S" (2, 2-bis ({ [3- (dodecylthio) propanoyl ] oxy } methyl) propanediyl-bis [3- (dodecylthio) propanoate ] manufactured by adiaceae.

(example 3)

A double-sided adhesive sheet of example 3 was produced in the same manner as in example 1 except that the usage amounts of the respective terpene phenol resins and terpene resins were changed to those shown in table 1.

(example 4)

A double-sided adhesive sheet of example 4 was produced in the same manner as in example 1 except that the thioether-based antioxidant was not used.

< aging test >

The pressure-sensitive adhesive sheets of each example were cut into a rectangular shape having a length of 30cm and a width of 20cm together with a release liner covering both pressure-sensitive adhesive surfaces, to prepare samples for aging test. The above samples were stored for four weeks in a desiccator maintained at 80 ℃ in an atmospheric atmosphere. The samples were suspended in the above-mentioned desiccator and stored so as not to overlap each other.

<Mw_HRetention rate>

GPC measurement was performed on the adhesive agent constituting the second adhesive layer of the adhesive sheet before and after aging test by the above-described method, and Mw before aging was calculated by using analysis software attached to a GPC measurement apparatus_HAnd Mw after aging_H. Further, by the following formula: (Mw after aging)_HMw before aging_H) X 100; determination of Mw_HRetention ratio (%). The results are shown in table 1.

< holding force test >

For each of the pressure-sensitive adhesive sheets before and after the aging test, a PET film (trade name "Lumirror S10", manufactured by dongli corporation) having a thickness of 25 μm was bonded to the first pressure-sensitive adhesive surface (the pressure-sensitive adhesive surface of the first pressure-sensitive adhesive layer) of the pressure-sensitive adhesive sheet, and the resultant was cut into a strip having a width of 10mm, thereby producing a test piece. The second adhesive surface (adhesive surface of the second adhesive layer) of the test piece was exposed, and the test piece was pressure-bonded to an adherend, i.e., an bakelite board (phenolic resin board), by reciprocating a 2kg roller once at 23 ℃ and 50% RH, with a bonding area of 10mm in width and 20mm in length. The test piece attached to the adherend in this manner was left to stand in the same environment for 30 minutes, and then the adherend was hung down so that the longitudinal direction of the test piece was perpendicular, and a load of 500g was applied to the free end of the test piece, and the test piece was left to stand in an environment of 40 ℃ for 30 minutes with the load applied thereto in accordance with JIS Z0237. The distance (offset distance) of the test piece after the placement from the first attachment position was measured. The measurement was performed using three test pieces (i.e., n is 3) for each adhesive sheet, and the arithmetic average of the offset distances of these test pieces is shown in the column of "holding force" in table 1. Note that, even when one test piece is dropped, the test piece is expressed as "dropped".

As shown in Table 1, Mw even after a severe aging test of four weeks at 80 ℃ was_HThe adhesive sheets of examples 1 to 3 having a retention rate of 70% or more also maintained good cohesiveness at a level that did not fall off in the above holding force test. In contrast, Mw_HThe adhesive sheet of example 4 having a retention of less than 70% had the same initial cohesion (before aging test) as those of examples 1 and 2, but the cohesion was significantly improved by the aging testSignificantly reduced and failed to withstand the retention test after aging test. Specifically, all three test pieces dropped before 30 minutes had elapsed. Note that, in the pressure-sensitive adhesive sheet of example 1, slight coloring was observed in the pressure-sensitive adhesive after the aging test.

Specific examples of the present invention have been described above in detail, but these examples are merely illustrative and do not limit the claims. The techniques described in the claims include those obtained by variously changing or modifying the specific examples illustrated above.

Claims

1. An adhesive sheet comprising an adhesive layer, wherein,

the adhesive layer is composed of an adhesive containing an unsaturated rubber and a tackifying resin,

the content of the unsaturated rubber is more than 40 wt% of the adhesive,

the unsaturated rubber contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound, the proportion of diblock material of the block copolymer being 60% by weight or more,

the tackifier resin contains a phenolic tackifier resin, the content of the phenolic tackifier resin is 5 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the unsaturated rubber,

the adhesive contains an aging inhibitor comprising a radical scavenger, a sulfur-containing antioxidant and a phosphorus-containing antioxidant, and

a weight average molecular weight Mw of the adhesive calculated in a molecular weight distribution curve based on gel permeation chromatography measurement and having a molecular weight of 10,000g/mol or more in terms of polystyrene in an aging test at 80 ℃ for four weeks_HThe retention of (2) is 70% or more.

2. The adhesive sheet according to claim 1, wherein the content of the tackifier 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.

3. The adhesive sheet according to claim 1 or 2, wherein the softening point of the tackifier resin is 40 ℃ or higher.

4. The adhesive sheet according to claim 1 or 2,

the tackifying resin comprises a phenolic tackifying resin,

the phenolic tackifying resin comprises a terpene phenol resin having a hydroxyl value of 20mgKOH/g or more.

5. The adhesive sheet according to claim 1 or 2, wherein the content of the phenolic tackifier resin in the adhesive is 30 parts by weight or less based on 100 parts by weight of the unsaturated rubber.

6. The adhesive sheet according to claim 1 or 2, wherein the unsaturated rubber has a monomer composition containing a conjugated diene compound, and the proportion of the conjugated diene compound in the monomer composition is 70% by weight or more.

7. The adhesive sheet according to claim 1 or 2, wherein the thickness of the adhesive layer is 30 μm or more.

8. The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet is configured as an adhesive sheet having double-sided adhesiveness including a substrate and a first adhesive layer and a second adhesive layer as the adhesive layers supported on both sides of the substrate.

9. The adhesive sheet according to claim 1, wherein,

the content of the tackifier resin is 10 to 120 parts by weight based on 100 parts by weight of the unsaturated rubber,

the softening point of the tackifying resin is above 40 ℃,

the tackifying resin comprises a phenolic tackifying resin,

the content of the phenolic tackifying resin is 5 to 30 parts by weight based on 100 parts by weight of the unsaturated rubber,

the phenolic tackifying resin comprises a terpene phenol resin with a hydroxyl value of more than 20mgKOH/g,

the adhesive contains an anti-aging agent,

the anti-aging agent comprises a free radical scavenger, a sulfur-containing antioxidant and a phosphorus-containing antioxidant,

the unsaturated rubber has a monomer composition containing a conjugated diene compound, the conjugated diene compound being present in an amount of 70 wt% or more based on the monomer composition,

the unsaturated rubber contains a block copolymer of a monovinyl-substituted aromatic compound and the conjugated diene compound, the proportion of diblock material of the block copolymer being 60% by weight or more,

the adhesive layer has a thickness of 30 [ mu ] m or more, and

the pressure-sensitive adhesive sheet is configured as a pressure-sensitive adhesive sheet having double-sided pressure-sensitive adhesive properties including a substrate and a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer supported on both sides of the substrate as the pressure-sensitive adhesive layers.