TW201343866A - Double-faced pressure-sensitive adhesive sheet - Google Patents

Abstract

The present invention provides a double-faced pressure-sensitive adhesive sheet comprising a foam substrate, pressure-sensitive adhesive layers provided on a first face and a second face of the foam substrate, and having an overall thickness t of 400 &mgr;m or smaller. At least one of the pressure-sensitive adhesive layers is constituted with a rubber-based pressure-sensitive adhesive comprising, as a base polymer, a block copolymer of a mono-vinyl-substituted aromatic compound and a conjugated diene compound.

Description

Double-sided adhesive sheet

The present invention relates to a double-sided adhesive sheet having a foam substrate.

Japanese Patent Application Nos. 2012-060664 and 2012- 060665, filed on March 16, 2012, and Japanese Patent Applications Nos. 2012-177534 and 2012-177535, filed on August 9, 2012, and The priority of Japanese Patent Application No. 2012-200907, filed on Sep. 12, the entire disclosure of which is hereby incorporated by reference.

In general, an adhesive (also known as a pressure-sensitive adhesive; the same below) has a soft solid (viscoelastic) state in a temperature region near room temperature, and the pressure is simply followed by the property of the adherend. . With such a property, the adhesive, for example, a double-sided adhesive sheet having a base material provided with an adhesive layer on both sides of a substrate is widely used for bonding or fixing in various fields. A double-sided adhesive sheet using a foam as a substrate (a double-sided adhesive sheet with a foamed base material) and a double-sided adhesive sheet having a plastic film having no bubble structure as a base material, impact absorption or It is more advantageous in terms of ladder followability and the like. Further, it is more advantageous in terms of water repellency, sealing property, and the like as compared with a double-sided adhesive sheet having a nonwoven fabric as a base material. As a technical document relating to the double-sided adhesive sheet with a foam base material, Japanese Patent Application Laid-Open No. 2010-155959 is incorporated.

In recent years, from the viewpoint of weight reduction, miniaturization, and thinning of a product, it is required to achieve a desired performance with a smaller total thickness for a double-sided adhesive tape with a substrate. example For example, regarding a double-sided adhesive sheet with a foam substrate used in a mobile device such as a mobile phone or a smart phone, a double-sided adhesive sheet having a small total thickness and high performance is particularly required.

On the other hand, with the increase in screen size and high functionality of the mobile device, for example, the performance required for the double-sided adhesive sheet for fixing the frontmost display panel (glass lens or the like) to the casing is further improved. The reason for this is that if the area of the display panel is increased, the quality of the display panel is increased. In addition, in a display panel having a touch function such as a smart phone, the back surface of the glass lens has various layers, thereby displaying The overall quality of the panel is increased. For the double-sided adhesive sheet to which such a display panel is fixed, it is required to further improve the resilience resistance, the extrusion adhesion force, the constant load peeling property, and the like.

However, it is difficult to reduce the total thickness of the double-sided adhesive sheet to which the foamed base material is attached, and to improve the rebound resistance of the double-sided adhesive sheet. The reason for this is that, in order to reduce the total thickness of the double-sided adhesive sheet attached to the foam substrate, the smaller the thickness of the foam substrate, the more advantageous, but if the thickness of the foam substrate becomes small, the The ability of the foam substrate to disperse stress is lowered, whereby the resistance to rebound is lowered.

Accordingly, an object of the present invention is to provide a double-sided adhesive sheet which is provided with a foam base material and which has a small total thickness and is excellent in rebound resilience.

The double-sided adhesive sheet disclosed herein comprises: a foam substrate, a first adhesive layer disposed on the first surface of the foam substrate, and a second surface disposed on the foam substrate Second adhesive layer. The adhesive constituting at least one of the first adhesive layer and the second adhesive layer is a rubber-based adhesive containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer. Agent. The total thickness of the double-sided adhesive sheet is 400 μm or less. The double-sided adhesive sheet (the double-sided adhesive sheet with a foam base material) having such a configuration can have a good resilience even if the total thickness is small by having an adhesive layer composed of the rubber-based adhesive. Double-sided adhesive sheet. As the foam base material, for example, a foam base material having a thickness of 60 μm or more and 300 μm or less can be preferably used.

In a preferred aspect of the double-sided adhesive sheet disclosed herein, the rubber is adhered The agent contains a tackifying resin. For example, the tackifier resin preferably contains a high softening point resin having a softening point of 120 ° C or higher. A preferred example of such a high softening point resin is a terpene phenol resin.

The technique disclosed herein may preferably be carried out in such a manner that the tackifying resin contains a low softening point resin having a softening point of less than 120 ° C and a high softening point resin having a softening point of 120 ° C or higher. According to this aspect, a double-sided adhesive sheet of higher performance can be realized. The above high softening point resin preferably contains a terpene phenol resin.

The technique disclosed herein is preferably carried out in such a manner that the rubber-based adhesive contains a tackifying resin having a hydroxyl value of 80 mgKOH/g or more. According to this aspect, a double-sided adhesive sheet of higher performance can be realized.

1‧‧‧Double adhesive tape

2, 3, 4‧‧‧ window frame double-sided adhesive sheet

5,6‧‧‧Double-sided adhesive sheet

5A‧‧‧Adhesive surface of double-sided adhesive sheet 5

5B‧‧‧The other adhesive side of the test piece 54

11‧‧‧First adhesive layer

11A‧‧‧First adhesive surface

12‧‧‧Second Adhesive Layer

12A‧‧‧Second Adhesive Surface

15‧‧‧Flaked foam substrate

15A‧‧‧The first side of the substrate 15

15B‧‧‧The second side of the substrate 15

17‧‧‧Release liner

17A‧‧‧Before the release liner

17B‧‧‧The back of the release liner

21, 31, 41, 62‧‧‧ PC boards

21A‧‧‧through holes provided on the PC board 21

22, 32, 61‧‧‧ glass plates

23‧‧‧ round stick

24‧‧‧Support table

42‧‧‧step belt

43‧‧‧Acrylic board

44‧‧‧ Non-woven

52‧‧‧ Polycarbonate film

54‧‧‧Test strips

54A, 54B‧‧‧ Both ends of the length of the test piece 54

56‧‧‧Exposed body

62A‧‧‧through hole

63‧‧‧ weights

64‧‧‧Support table

T‧‧‧ total thickness

Fig. 1 is a schematic cross-sectional view showing the configuration of a double-sided adhesive sheet according to an embodiment.

Fig. 2 (a) and Fig. 2 (b) are explanatory views showing a sample for evaluation used for measuring the pressing force.

Fig. 3 is an explanatory view showing a method of measuring the pressing force.

4(a) and 4(b) are explanatory views showing samples for evaluation used for evaluating impact resistance.

5(a) and 5(b) are explanatory views showing samples for evaluation used for evaluating water repellency.

Fig. 6 is an explanatory view showing a method of evaluating the rebound resilience.

Fig. 7 is an explanatory view showing a method of evaluating constant load peeling characteristics.

Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters based on those skilled in the art. The present invention can be implemented based on the contents disclosed in the present specification and common knowledge in the art.

In the following drawings, members and portions that perform the same functions are denoted by the same reference numerals, and the repeated description may be omitted or simplified. Further, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and do not accurately represent the size or scale of the adhesive sheet of the present invention actually provided as a product.

In the present specification, the term "adhesive" means a material having a soft solid (viscoelastic) state in a temperature region near room temperature as described above, and a property simply by pressure with a member to be bonded. The term "adhesive" as defined herein, "CADahlquist, "Adhesion: Fundamental and Practice", McLaren & Sons, (1966) p. 143", generally has a complex tensile modulus E*(1 Hz) < A material having a properties of 10 ⁷ dynes/cm ² (typically, a material having the above properties at 25 ° C). In addition, the "base polymer" of the adhesive means a main component (i.e., the rubbery form) of the rubbery polymer (polymer which exhibits rubber elasticity in a temperature range near room temperature) contained in the adhesive. 50% by mass or more of the polymer).

In the present specification, the "block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound" means that at least one aromatic compound substituted with a monovinyl group is a main monomer (more than 50% by mass) a polymer of a copolymer component; the same) segment (hereinafter also referred to as "A segment") and at least one segment having a conjugated diene compound as a main monomer (hereinafter also referred to as "B segment") . In general, the glass transition temperature of the A segment is higher than the glass transition temperature of the B segment. As a representative structure of the polymer, a copolymer having a triblock structure of an A segment (hard segment) at both ends of a B segment (soft segment) (a triblock copolymer of an ABA structure) can be exemplified. A copolymer comprising a diblock structure of an A segment and a B segment (diblock copolymer of AB structure) and the like.

In the present specification, "styrene block copolymer" means a polymer having at least one styrene block. The above styrene block means a segment having styrene as a main monomer. A segment substantially containing only styrene is a typical example of a styrene block as referred to herein. In addition, "styrene isoprene block copolymer" means having at least one styrene block and A polymer of at least one isoprene block (in the form of isoprene as the main monomer). A typical example of the styrene isoprene block copolymer is a copolymerization of a triblock structure in which each end of the isoprene block (soft segment) has a styrene block (hard segment). (triblock copolymer), a copolymer (diblock copolymer) comprising a diblock structure of 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 (small segment having butadiene as a main monomer).

In the present specification, the "styrene content" of the styrenic block copolymer means the mass ratio of the styrene component to the overall mass of the block copolymer. The above styrene content can be determined by NMR (nuclear magnetic resonance spectroscopy).

Further, the ratio of the diblock copolymer to the styrene block copolymer (hereinafter sometimes referred to as "diblock copolymer ratio" or "diblock ratio") can be obtained by the following method . In other words, the styrene block copolymer was dissolved in tetrahydrofuran (THF), and the two columns of the liquid chromatography column of GS5000H and G4000H manufactured by Tosoh Corporation were connected in series in four stages, and THF was used as the mobile phase. High performance liquid chromatography was carried out at a temperature of 40 ° C and a flow rate of 1 mL/min. The peak area corresponding to the diblock copolymer was determined from the obtained chart. Further, the diblock copolymer ratio was determined by calculating the percentage of the peak area corresponding to the diblock copolymer with respect to the total peak area.

The double-sided adhesive sheet (which may be in the form of a strip or the like) disclosed herein comprises a foam substrate and a first adhesive layer respectively disposed on the first side and the second side of the foam substrate The agent layer and the second adhesive layer are formed. For example, it may be a double-sided adhesive sheet having the form of the cross-sectional structure shown in Fig. 1. The double-sided adhesive sheet 1 includes a sheet-shaped foam substrate 15 and a first adhesive layer 11 and a second adhesive layer 12 which are supported by both surfaces of the substrate 15. More specifically, the first adhesive layer 11 and the second adhesive layer 12 are provided on the first surface 15A and the second surface 15B of the substrate 15 (both non-releasable). The double-sided adhesive sheet 1 before use (before being adhered to the adherend) can be peeled off from the front surface 17A and the back surface 17B as shown in FIG. The spacers 17 are overlapped and wound in a spiral shape. In the double-sided adhesive sheet 1 of this form, the surface (second adhesive surface 12A) of the second adhesive layer 12 is protected by the front surface 17A of the release liner 17, and the surface of the first adhesive layer 11 (first adhesive surface 11A) ) is protected by the back surface 17B of the release liner 17. Alternatively, the first adhesive surface 11A and the second adhesive surface 12A may be protected by two separate release liners.

As the release liner, a conventional release paper or the like can be used, and it is not particularly limited. For example, a release liner for a surface of a substrate such as a plastic film or paper having a release-treated layer, a fluorine-containing polymer (such as polytetrafluoroethylene) or a polyolefin resin (polyethylene, polypropylene, etc.) can be used. A release liner of a material, and the like. The release treatment layer may be, for example, a release treatment layer formed by surface-treating the base material using a release treatment agent such as polyfluorene-based, long-chain alkyl-based, fluorine-based or molybdenum sulfide.

The double-sided adhesive sheet disclosed herein has a total thickness of 400 μm or less (typically 350 μm or less). From the viewpoint of thin film formation, miniaturization, weight reduction, and resource saving, a double-sided adhesive sheet having a total thickness of 300 μm or less (more preferably 250 μm or less, for example, 230 μm or less) is preferable. The lower limit of the total thickness of the double-sided adhesive sheet is not particularly limited. In general, the total thickness of the double-sided adhesive sheet is preferably 50 μm or more, more preferably 70 μm or more (more preferably 100 μm or more, further preferably 150 μm or more, for example, 190 μm), from the viewpoints of impact resistance and water repellency. the above).

Here, the total thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other adhesive surface. In the example shown in FIG. 1, the thickness from the first adhesive surface 11A to the second adhesive surface 12A is t. . Therefore, for example, even if it is a double-sided adhesive sheet in a form in which the front adhesive surface is adhered to the adherend by a release liner, the thickness of the release liner is not included in the thickness of the double-sided adhesive sheet herein.

<Rubber adhesive>

In the technique disclosed herein, at least one of the first adhesive layer and the second adhesive layer is composed of a specific rubber-based adhesive. The first adhesive layer and the first adhesive layer Both of the second adhesive layers are composed of a specific rubber-based adhesive.

(base polymer)

The rubber-based adhesive contains a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer. The above monovinyl-substituted aromatic compound means a compound having a functional group having a vinyl group bonded to an aromatic ring. A typical example of the above aromatic ring is a benzene ring (which may be a benzene ring substituted with a functional group having no vinyl group (for example, an alkyl group)). Specific examples of the monovinyl-substituted aromatic compound include styrene, α-methylstyrene, vinyltoluene, and vinylxylene. Specific examples of the conjugated diene compound include 1,3-butadiene and isoprene. Such a block copolymer may be used alone or in combination of two or more for the base polymer.

In the above-mentioned block copolymer, the A segment (hard segment) is preferably a copolymerization ratio of the above monovinyl-substituted aromatic compound (which may be used in combination of two or more) of 70% by mass or more (more preferably 90% by mass). % or more may be substantially 100% by mass). In the B-chain segment (soft segment) of the block copolymer, the copolymerization ratio of the conjugated diene compound (which may be used in combination of two or more kinds) is preferably 70% by mass or more (more preferably 90% by mass or more). It is substantially 100% by mass). According to the block copolymer, a double-sided adhesive sheet of higher performance can be realized.

The block copolymer may be in the form of a diblock copolymer, a triblock copolymer, a radial body, or the like. In the triblock copolymer and the radial body, it is preferred to arrange an A segment (for example, a styrene block) at the end of the polymer chain. The reason for this is that the A segment disposed at the end of the polymer chain is easily concentrated to form a domain, whereby a pseudo crosslinked structure can be formed, thereby improving the cohesiveness of the adhesive. As the block copolymer in the technique disclosed herein, it is preferable to use, for example, a diblock copolymer ratio of 30% by mass or more from the viewpoint of adhesion to the adherend (peel strength) or rebound resilience ( It is more preferably 40% by mass or more, further preferably 50% by mass or more, particularly preferably 60% by mass or more, and typically 65% by mass or more, for example, 70% by mass or more. In addition, according to the pair The diblock copolymer ratio is preferably 90% by mass or less (more preferably 85% by mass or less, for example, 80% by mass or less) from the viewpoint of the stress resistance to be continuously applied (for example, the constant load peeling property described below). Block copolymer. For example, a block copolymer having a diblock copolymer ratio of 60 to 85% by mass can be preferably used.

(styrene block copolymer)

In a preferred aspect of the techniques disclosed herein, the base polymer is a styrenic block copolymer. For example, it is preferred to carry out the aspect in which the base polymer contains at least one of a styrene isoprene block copolymer and a styrene butadiene block copolymer. Among the styrene block copolymers contained in the adhesive, the proportion of the styrene isoprene block copolymer is preferably 70% by mass or more, or the ratio of the styrene butadiene block copolymer is 70% by mass or more, or the total ratio of the styrene isoprene block copolymer and the styrene butadiene block copolymer is 70% by mass or more. In a preferred embodiment, substantially all (for example, 95 to 100% by mass) of the styrene block copolymer is a styrene isoprene block copolymer. In another preferred embodiment, substantially all (for example, 95 to 100% by mass) of the styrene block copolymer is a styrene butadiene block copolymer. With such a composition, a double-sided adhesive sheet excellent in rebound resilience and good in balance with other adhesive properties (for example, constant load peeling characteristics) can be suitably obtained.

The styrene block copolymer may be in the form of a diblock copolymer, a triblock copolymer, a radial body, or the like. In the triblock copolymer and the radial body, it is preferred to arrange a styrene block at the end of the polymer chain. The reason for this is that the styrene block disposed at the end of the polymer chain is easily concentrated to form a domain, whereby a pseudo crosslinked structure can be formed, thereby improving the cohesiveness of the adhesive. As the styrene block copolymer used in the technique disclosed herein, it is preferable to use, for example, a diblock copolymer ratio from the viewpoint of adhesion to the adherend (peel strength) or rebound resilience. 30% by mass or more (more preferably 40% by mass or more, further preferably 50% by mass or more, particularly preferably 60% by mass or more, and typically 65% by mass or more) of the styrene block copolymer. Can also be two The block copolymer ratio is 70% by mass or more (for example, 75% by mass or more) of the styrene block copolymer. Further, from the viewpoint of constant load peeling characteristics and the like, a styrenic block copolymer having a diblock copolymer ratio of 90% by mass or less (more preferably 85% by mass or less, for example, 80% by mass or less) can be preferably used. . For example, a styrenic block copolymer having a diblock copolymer ratio of 60 to 85% by mass can be preferably used.

The styrene content of the styrene block copolymer may be, for example, 5 to 40% by mass. From the viewpoint of the resilience-resistance or the constant-load peeling property, a styrene-based block copolymer having a styrene content of 10% by mass or more (more preferably, more than 10% by mass, for example, 12% by mass or more) is usually preferable. Further, from the viewpoint of adhesion to the adherend, the styrene content is preferably 35 mass% or less (typically 30 mass% or less, more preferably 25 mass% or less, for example, less than 20 mass%). a styrenic block copolymer. For example, a styrenic block copolymer having a styrene content of 12% by mass or more and less than 20% by mass can be preferably used.

(tackifying resin)

In a preferred aspect of the technology disclosed herein, the rubber-based adhesive further contains a tackifying resin in addition to a base polymer (for example, a styrenic block copolymer). As the tackifier resin, one or two or more kinds of various known tackifier resins selected from the group consisting of petroleum resins, terpene resins, rosin resins, rosin derivative resins, and ketone resins can be used.

Examples of the petroleum resin include an aliphatic (C5-based) petroleum resin, an aromatic (C9-based) petroleum resin, a C5/C9 copolymerized petroleum resin, an alicyclic petroleum resin, and the like.

Examples of the terpene resin include terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer (hereinafter, in order to clearly distinguish from the modified terpene resin described below, The term "unmodified terpene resin"); a modified terpene resin obtained by modifying the terpene resin (phenol modification, styrene modification, hydrogenation modification, hydrocarbon modification, etc.); Wait. Examples of the modified terpene resin include terpene phenol resin and styrene-modified decene. Resin, hydrogenated terpene resin, and the like.

The above "terpene phenol resin" means a polymer containing a terpene residue and a phenol residue, and includes a copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin) and a homopolymer of terpene or The concept of a resin (a phenol-modified terpene resin) in which a copolymer (a terpene resin, typically an unmodified terpene resin) is subjected to phenol modification. Preferred examples of the terpene constituting the terpene phenol resin include α-pinene, β-pinene, and limonene (including d-form, l-form, and d/l (dipentene)). .

Specific examples of the rosin-based resin include unmodified rosin (raw rosin) such as rosin gum, wood rosin, and tall oil rosin; and the unmodified rosin is modified by hydrogenation, disproportionation, polymerization, or the like. Modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc.);

Examples of the rosin derivative resin include those obtained by esterifying an unmodified rosin with an alcohol (that is, an esterified product of rosin), and a modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.). a rosin ester such as an ester obtained by esterification of an alcohol (ie, an esterified product of modified rosin); an unmodified rosin or a modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) is modified with an unsaturated fatty acid. Unsaturated fatty acid modified rosin; unsaturated fatty acid modified rosin ester obtained by modifying rosin ester with unsaturated fatty acid; unmodified rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerization) Rosin alcohols obtained by reduction of rosin, etc., unsaturated fatty acid-modified rosins or carboxyl groups in unsaturated fatty acid-modified rosin esters; rosins such as unmodified rosins, modified rosins, and various rosin derivatives ( a metal salt of a rosin ester; a rosin phenol resin obtained by adding and thermally polymerizing rosin (unmodified rosin, modified rosin, various rosin derivatives, etc.) with phenol in an acid catalyst; Wait.

The content of the tackifier resin per 100 parts by mass of the base polymer is usually 20 parts by mass or more, preferably 30 parts by mass or more, and more preferably 40 mass, from the viewpoint of the repulsion resistance or the constant load peeling property. Parts or more (for example, 50 parts by mass) on). In addition, it is preferable to set the content of the tackifier resin to 100 parts by mass or less based on 100 parts by mass of the base polymer, based on the low-temperature characteristics (for example, adhesion under low-temperature conditions). 150 parts by mass or less. The content of the tackifier resin per 100 parts by mass of the base polymer may be 100 parts by mass or less (for example, 80 parts by mass or less).

(high softening point resin)

The technique disclosed herein is preferably carried out in such a manner that the rubber-based adhesive contains a high-softening point resin having a softening point of 120 ° C or higher as the tackifying resin. The double-sided adhesive sheet of this aspect is preferred from the viewpoint of resistance to resilience or constant load peeling. In a preferred aspect, the high-softening point resin may have a tackifying resin having a softening point of 125 ° C or higher (more preferably 130 ° C or higher, further preferably 135 ° C or higher, for example, 140 ° C or higher). Further, the softening point of the high-softening point resin is usually 200 ° C or less, preferably 180 ° C or less, more preferably 170 ° C or less (for example, 160 ° C or less), from the viewpoint of adhesion to the adherend. .

The softening point of the tackifying resin herein is defined by a value measured by a softening point test method (ring and ball method) prescribed in JIS K5902 and JIS K2207. Specifically, the sample is rapidly melted at a temperature as low as possible, and the melt is filled in a ring placed on a flat metal plate, taking care not to cause foaming. After cooling, a slightly heated knife is used to cut the protruding portion from the plane containing the upper end of the ring. Next, the support (ring table) was placed in a glass vessel (heating bath) having a diameter of 85 mm or more and a height of 127 mm or more, and glycerin was injected until the depth reached 90 mm or more. Next, the steel ball (diameter: 9.5 mm, weight: 3.5 g) and the ring of the filled sample were immersed in glycerin so as not to contact each other, and the temperature of the glycerin was maintained at 20 ° C ± 5 ° C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring and placed in a constant position on the support. Next, the distance from the upper end of the ring to the glycerin surface was kept at 50 mm, a thermometer was placed, the center position of the mercury ball of the thermometer was set to the same height as the center of the ring, and the container was heated. The flame of the Bunsen burner used for heating, located at the center and edge of the bottom of the container Between, to evenly heat. Further, the ratio of the bath temperature rise after reaching 40 ° C after the start of heating must be 5.0 ± 0.5 ° C per minute. The sample gradually softens and flows down from the ring, and the temperature at which the final substrate is contacted is read as a softening point. The measurement of the softening point was carried out twice or more at the same time, and the average value thereof was taken.

As the high-softening point resin, a terpene phenol resin, a polymerized rosin, an esterified product of a polymerized rosin, or the like can be preferably used. These high-softening point resins may be used alone or in combination of two or more.

As a preferred aspect, the above high-softening point resin may contain one or two or more kinds of terpene phenol resins. For example, it is preferably 25 mass% or more (more preferably 30 mass% or more) of the entire high softening point resin as a terpene phenol resin. 50% by mass or more (more preferably 70% by mass or more, further preferably 80% by mass or more, for example, 90% by mass or more) of the high softening point resin may be substantially all of the terpene phenol resin and the high softening point resin ( For example, it is 95% by mass or more) and it may be a terpene phenol resin. A terpene phenol resin having a softening point of 120 ° C or more and 200 ° C or less (typically 120 ° C or more and 180 ° C or less, for example, 125 ° C or more and 170 ° C or less) can be preferably used.

The terpene phenol resin preferably has a hydroxyl value (OH value) of 40 mgKOH/g or more (typically 40 to 200 mgKOH/g, for example, 40 to 160 mgKOH/g) and a softening point of 120 ° C or more. Enphenol resin. According to the terpene phenol resin having the hydroxyl value, a double-sided adhesive sheet having higher performance can be realized.

As the value of the above hydroxyl value, a value measured by a potentiometric titration method prescribed in JIS K0070:1992 can be employed. The specific measurement method is as follows.

[Method for measuring hydroxyl value] Reagent

(1) As the acetamidine reagent, a reagent obtained by adding about 12.5 g (about 11.8 ml) of acetic anhydride, adding pyridine to the total amount to 50 mL, and sufficiently stirring the mixture was used. In addition, about 25 g (about 23.5 ml) of acetic anhydride was used, and pyridine was added thereto to adjust the total amount to 100 mL. The reagent is fully stirred.

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

(3) Others, prepare toluene, pyridine, ethanol, and distilled water.

2. Operation

(1) Accurately weigh about 2 g of the sample into a flat-bottomed flask, add 5 mL of acetamidine reagent and 10 mL of pyridine, and install an air cooling tube.

(2) The flask was heated in a bath at 100 ° C for 70 minutes, then left to cool, and 35 mL of toluene was added as a solvent from the upper portion of the cooling tube and stirred, and then 1 mL of distilled water was added and stirred, whereby acetic anhydride was decomposed. To complete the decomposition, heat again in the bath for 10 minutes and let it cool.

(3) The cooling tube was washed with 5 ml of ethanol and removed. Then, 50 mL of pyridine was added as a solvent and stirred.

(4) A 25 mL 0.5 mol/L potassium hydroxide ethanol solution was added using a full pipette.

(5) Potentiometric titration was carried out using a 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve was taken as the end point.

(6) The above (1) to (5) were carried out in the blank test without adding a sample.

3. Calculation

The hydroxyl value was calculated from the following formula: hydroxyl value (mgKOH/g) = [(B-C) × f × 28.05] / S + D

Here, B: the amount of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test (mL), C: the amount of 0.5 mol/L potassium hydroxide ethanol solution used in the sample (mL), f: 0.5 mol/ L factor of potassium hydroxide ethanol solution, S: mass of sample (g), D: acid value, 28.05: 1/2 of molecular weight of potassium hydroxide 56.11.

In the technique disclosed herein, for example, the rubber-based adhesive may preferably contain a high-softening point resin (H1) having a hydroxyl group of 40 mgKOH/g or more and less than 80 mgKOH/g, and a hydroxyl value of 80 mgKOH/g or more (typically The state of the high softening point resin (H2) of 80 to 160 mgKOH/g, for example, 80 to 140 mgKOH/g) is carried out. In this case, the relationship between the amount of use of the high-softening point resin (H1) and the high-softening point resin (H2) is set, for example, such that the mass ratio (H1:H2) is in the range of 1:5 to 5:1. It is usually appropriate to set the mass ratio (H1:H2) to a range of 1:3 to 3:1 (for example, 1:2 to 2:1). As a preferred aspect, the high softening point resin (H1) and the high softening point resin (H2) are all examples of terpene phenol resins.

The content of the high-softening point resin can be, for example, 20 parts by mass or more, preferably 30 parts by mass or more (for example, 35 parts by mass), based on 100 parts by mass of the base polymer. the above). In addition, it is preferable to set the content of the high-softening point resin to 100 parts by mass of the base polymer to 100 parts by mass or less, preferably from the viewpoint of the adhesive strength and the low-temperature property (for example, the impact resistance under low-temperature conditions). 80 parts by mass or less, more preferably 70 parts by mass or less. The content of the high softening point resin may be 60 parts by mass or less (for example, 50 parts by mass or less).

(low softening point resin)

The technique disclosed herein may be carried out in such a manner that the rubber-based adhesive contains a low-softening point resin having a softening point of less than 120 ° C in place of or in addition to the high-softening point resin. In a preferred embodiment, the rubber-based pressure-sensitive adhesive contains a high-softening point resin having a softening point of 120 ° C or higher and a low-softening point resin having a softening point of less than 120 ° C.

As the low-softening point resin, a resin having a softening point of, for example, 40 ° C or higher (typically 60 ° C or higher) can be used. From the viewpoints of resistance to resilience or constant load peeling, etc., a resin having a softening point of 80 ° C or higher (more preferably 100 ° C or higher) and less than 120 ° C is usually preferably used. For example, it is preferred that the softening point is 110 ° C or more and less than 120 ° C low softness. Resin resin.

In the technique disclosed herein, at least one of the rubber-based adhesive containing a petroleum resin and a terpene resin (typically, an unmodified terpene resin) is preferably used as the low-softening point resin. For example, it is preferable to use a main component of a low-softening point resin (that is, a component which accounts for more than 50% by mass in a low-softening point resin) as a composition of a petroleum resin, a composition of a terpene resin, or a petroleum resin and a terpene resin. The composition of the combination, etc. From the viewpoints of adhesion and compatibility, etc., it is preferred that the main component of the low-softening point resin is a terpene resin (for example, a β-pinene polymer). Substantially all of the low-softening point resin (for example, 95% by mass or more) may be a terpene resin.

The content of the low-softening point resin can be, for example, 10 parts by mass or more, and usually 15 parts by mass or more (for example, 20 parts by mass or more), based on 100 parts by mass of the base polymer, from the viewpoint of the adhesion to the adherend. More appropriate. In addition, the content of the low-softening point resin is usually 120 parts by mass or less, preferably 90 parts by mass or less, more preferably 70 parts by mass or less (for example, 60 parts by mass or less). . The content of the low-softening point resin may be set to 50 parts by mass or less (for example, 40 parts by mass or less).

In the case where the above-mentioned tackifying resin contains a low-softening point resin and a high-softening point resin, the relationship between the amounts used is preferably a ratio of a low softening point resin: a high softening point resin of 1:5 to 3:1. (More preferably 1:5~2:1) to set. In the technique disclosed herein, it is preferable that the above rubber-based adhesive contains a resin having a lower softening point and a higher softening point resin as a tackifying resin (for example, a low softening point resin: a high softening point resin mass ratio of 1) : 1.2~1:5) implementation of the pattern. According to this aspect, a double-sided adhesive sheet of higher performance can be realized.

(high hydroxyl value tackifying resin)

In the technique disclosed herein, the rubber-based pressure-sensitive adhesive preferably has a viscosity-increasing resin having a hydroxyl value of 80 mgKOH/g or more (for example, 90 mgKOH/g or more). on The hydroxyl value of the high hydroxyl value tackifying resin is typically 200 mgKOH/g or less, preferably 180 mgKOH/g or less (for example, 160 mgKOH/g or less). As the hydroxyl value, the value measured by the potentiometric titration method specified in JIS K0070:1992 can be used, and specifically, the value of the above-described method for measuring the hydroxyl value is applied. According to the adhesive containing such a high hydroxyl value tackifying resin, a double-sided adhesive sheet having higher performance can be realized. For example, a double-sided adhesive sheet having a higher degree of resistance to resilience or constant load peeling and other adhesive properties can be realized.

As the high hydroxyl value tackifying resin, a tackifier resin having a hydroxyl value of a specific value or more among the above various tackifier resins may be used singly or in combination as appropriate. In a preferred embodiment, at least a terpene phenol resin is used as the above high hydroxyl value tackifying resin. The terpene phenol resin is preferably controlled by arbitrarily controlling the hydroxyl value depending on the copolymerization ratio of the phenol. 50% by mass or more (more preferably 70% by mass or more, for example, 90% by mass or more) of the high hydroxyl value tackifying resin contained in the adhesive is preferably a terpene phenol resin, or substantially all (for example, 95 to 100% by mass, and more preferably 99 to 100% by mass, is a terpene phenol resin.

The content of the high hydroxyl value tackifying resin can be set to, for example, 5 parts by mass or more, and usually preferably 10 parts by mass or more, based on the repulsion resistance or the constant load peeling property, etc., for example, 15 parts by mass or more). In addition, the content of the high hydroxyl value tackifying resin based on 100 parts by mass of the base polymer is usually 100 parts by mass or less, preferably 80 parts by mass or less, more preferably 60 parts by mass. the following. The content of the high hydroxyl value tackifying resin may be 50 parts by mass or less (for example, 30 parts by mass or less).

The softening point of the high hydroxyl value tackifying resin is not particularly limited. That is, any of a high hydroxyl value tackifying resin corresponding to the above high softening point resin and a high hydroxyl value tackifying resin corresponding to a low softening point resin can be used.

For example, a high hydroxyl value tackifying resin having a softening point of 100 ° C or more (typically more than 100 ° C, for example, 110 ° C or more) can be preferably used. It is particularly preferable to use a softening point of 120 ° C or higher (typically more than 120 ° C, preferably 125 ° C or higher, for example, 130 ° C or higher). Hydroxyl value tackifying resin. According to such a high hydroxyl value and high softening point tackifying resin, a double-sided adhesive sheet of higher performance can be realized. Further, from the viewpoint of the low-temperature characteristics of the double-sided adhesive sheet, a high hydroxyl value tackifying resin having a softening point of 200 ° C or less (for example, 100 ° C or more and 200 ° C or less) is usually preferably used. More preferably, it is a high hydroxyl value tackifying resin having a softening point of 120 ° C or more and 180 ° C or less (for example, 125 ° C or more and 170 ° C or less).

In the technique disclosed herein, the rubber-based adhesive preferably contains a tackifying resin (high-softening point resin) having a softening point of 120 ° C or more, and the high-softening point resin is 25 mass% or more (more preferably 30 mass). % or more, for example, 40% by mass or more, is carried out in the form of a high hydroxyl value tackifying resin such as a terpene phenol resin. 50% by mass or more of the high softening point resin (more preferably 70% by mass or more, further preferably 80% by mass or more, for example, 90% by mass or more) may be a high hydroxyl value tackifying resin, and the high softening point resin is substantially all (for example, 95 to 100% by mass) may be a high hydroxyl value tackifying resin.

(low hydroxyl value tackifying resin)

The rubber-based adhesive may contain a tackifying resin (low hydroxyl value tackifying resin) having a hydroxyl group of 0 mgKOH/g or more and less than 80 mgKOH/g instead of the above high hydroxyl value tackifying resin or may be contained together with the above high hydroxyl tackifying resin. . In a preferred embodiment, the rubber-based pressure-sensitive adhesive contains a high hydroxyl value tackifying resin having a hydroxyl value of 80 mgKOH/g or more and a low hydroxyl value tackifying resin having a hydroxyl value of 0 mgKOH/g or more and less than 80 mgKOH/g. Aspect. As the low hydroxyl value tackifying resin, the tackifying resins having a hydroxyl value within the above range among the above various tackifying resins may be used singly or in combination as appropriate. For example, a terpene phenol resin having a hydroxyl value of 0 mgKOH/g or more and less than 80 mgKOH/g, a petroleum resin (for example, a C5-based petroleum resin), a terpene resin (for example, a β-pinene polymer), or a rosin-based resin can be used. For example, a polymerized rosin), a rosin derivative resin (for example, an esterified product of a polymerized rosin), and the like.

The softening point of the low hydroxyl value tackifying resin is not particularly limited. That is, any of a low hydroxyl value tackifying resin corresponding to the above high softening point resin and a low hydroxyl value tackifying resin corresponding to a low softening point resin can be used.

In a preferred aspect, the rubber-based adhesive has a softening point of less than 120 ° C (typically 80 ° C or more and less than 120 ° C, more preferably 100 ° C or more and less than 120 ° C, for example, 110 ° C The tackifying resin above and below 120 ° C) is used as the above low hydroxyl value tackifying resin. According to the adhesive of this composition, a double-sided adhesive sheet having high adhesion and excellent constant-load peeling characteristics can be realized. As the low hydroxyl value tackifying resin, it may be an adhesive which combines a low hydroxyl value tackifying resin (S1) having a softening point of less than 120 ° C and a low hydroxyl value tackifying resin (S2) having a softening point of 120 ° C or more. . The relationship between the usage amounts can be set, for example, such that the mass ratio (S1: S2) is in the range of 1:5 to 5:1, and usually the mass ratio (S1:S2) is 1:3 to 3:1 ( For example, the range of 1:2~2:1) is more appropriate.

In the case where the rubber-based adhesive contains a high hydroxyl value tackifying resin and a low hydroxyl value tackifying resin, the relationship between the amounts of use is preferably a low hydroxyl value tackifying resin: a high hydroxyl value tackifying resin quality. Set the ratio to 1:5~5:1 (more preferably 1:3~3:1). According to this method, a double-sided adhesive sheet of higher performance can be realized.

(isocyanate compound)

The above rubber-based adhesive in the technique disclosed herein may further contain an isocyanate compound. According to the rubber-based adhesive of this composition, a double-sided adhesive sheet which is resistant to resilience or constant load peeling property and which is improved can be realized. As the isocyanate compound, a polyfunctional isocyanate (a compound having two or more isocyanate groups per molecule, including a compound having an isocyanurate structure) can be preferably used. As the polyfunctional isocyanate, one type or two or more types selected from various isocyanate compounds (polyisocyanates) having two or more isocyanate groups in one molecule can be used. Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Specific examples of the aliphatic polyisocyanate include 1,2-ethanediisocyanate; butadiene diisocyanate such as 1,2-butyl diisocyanate, 1,3-butyl diisocyanate, and 1,4-butyl diisocyanate; , 2-hexamethylene diisocyanate, 1,3-hexadiisocyanate, 1,4-hexane diisocyanate Ethyl diisocyanate such as ester, 1,5-hexamethylene diisocyanate, hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1, 5-pentane diisocyanate, quaternary acid diisocyanate, and the like.

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

Specific examples of the aromatic polyisocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 2,4'-diphenylmethane. Diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrobiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane -4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, isophthalic diisocyanate, p-phenylene Isocyanate, naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, benzodimethyl-1,4-di Isocyanate, benzodimethyl-1,3-diisocyanate, and the like.

As the preferable 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 of a difunctional or trifunctional or higher isocyanate (typically a dimer or a trimer), a derivative (for example, a polyhydric alcohol and two or more polyfunctional isocyanates). Addition reaction product), polymer, and the like. For example, a dimer or a trimer of diphenylmethane diisocyanate, an isocyanurate body of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), trimethylolpropane A reaction product of toluene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, a polyfunctional polyisocyanate such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, or polyester polyisocyanate. As the polyfunctional isocyanate For the commercial products, the product name "Duranate TPA-100" manufactured by Asahi Kasei Chemical Co., Ltd., the trade name "Coronate L" manufactured by Japan Polyurethane Industry Co., Ltd., the trade name "Coronate HL" manufactured by Japan Polyurethane Industry Co., Ltd., and the Japanese polyurethane industry. The trade name "Coronate HK" manufactured by the company, the trade name "Coronate HX" manufactured by Japan Polyurethane Industry Co., Ltd., and the trade name "Coronate 2906" manufactured by Japan Polyurethane Industry Co., Ltd., etc.

In the case of using an isocyanate compound, the amount thereof to be used may be, for example, more than 0 parts by mass and 10 parts by mass or less (typically 0.01 to 10 parts by mass) based on 100 parts by mass of the base polymer. Usually, the amount of the isocyanate compound to be used is preferably 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the base polymer, and is usually 0.3 to 3 parts by mass, for example, 0.5 to 0.5 parts by mass. 1 part by mass). By using an isocyanate compound in this range, an adhesive sheet having particularly excellent balance of properties can be obtained.

(other ingredients)

The rubber-based pressure-sensitive adhesive may contain one or two or more kinds of rubber-like polymers other than the base polymer, as needed. The rubbery polymer may be various polymers such as rubber-based, acrylic-based, polyester-based, urethane-based, polyether-based, polyfluorinated, polyamine-based, and fluorine-based polymers known in the adhesive field. Examples of the rubber-based rubber-like polymer include natural rubber, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), isoprene rubber, chloroprene rubber, and polyisobutylene. , butyl rubber, recycled rubber, etc. In the case where the rubber-based adhesive contains a rubber-like polymer other than the base polymer, the amount of the rubber-like polymer to be used is usually 50 parts by mass or less, preferably 30%, based on 100 parts by mass of the base polymer. The amount by mass or less is more preferably 10 parts by mass or less (for example, 5 parts by mass or less). In the technique disclosed herein, it is preferable that the rubber-based adhesive contains substantially no rubber-like polymer other than the base polymer (for example, the content is 0 to 1 by mass relative to 100 parts by mass of the base polymer). The status of the application).

The rubber-based adhesive may contain a leveling agent, a crosslinking agent, and a crosslinking aid as needed. Various additives generally used in the field of adhesives such as agents, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, and the like. Regarding such various additives, previously known additives can be used by a conventional method. In the technique disclosed herein, it is preferable that the rubber-based adhesive does not substantially contain a liquid rubber such as polybutene (for example, a content of 1 part by mass or less based on 100 parts by mass of the base polymer) Or it is implemented in the form of 0 parts by mass. According to the adhesive, a double-sided adhesive sheet which is more excellent in rebound resilience and/or constant load peeling characteristics can be realized.

In a preferred aspect, the rubber-based adhesive may be a total amount of the base polymer and the tackifying resin, and the total mass of the rubber-based adhesive (ie, the quality of the adhesive layer composed of the rubber-based adhesive). ) a composition of 90% by mass or more. For example, it is preferable to use a combination of the base polymer and the tackifying resin in an amount of from 90 to 99.8% by mass (typically from 95 to 99.5% by mass) based on the total mass of the rubber-based adhesive.

In a preferred aspect, the rubber-based adhesive may be a composition that does not substantially contain a chelating compound. Here, the chelate compound refers to, for example, a chelate compound of an oxide of an alkaline earth metal and a resin (such as an alkylphenol resin) having a functional group (hydroxyl group, hydroxymethyl group or the like) capable of coordinating the oxide. The technique disclosed herein is preferably carried out in such a manner that the rubber-based adhesive is completely free of such a chelating compound or the content ratio of the chelating compound is 1% by mass or less. According to this aspect, a double-sided adhesive sheet excellent in adhesion can be achieved.

<Foam base material>

In the technique disclosed herein, a foam substrate (typically a sheet-like foam substrate) refers to a substrate having a portion having a bubble (bubble structure), and typically refers to a layered layer. A foam (foam layer) is a base material of a constituent element. The foam base material may be a base material consisting essentially of only one or two or more foam layers, or may be a composite base material including a foam layer and a non-foam layer (for example, the above foam layer and a non-foamed layer of a substrate). Here, the non-foaming layer means a layer having no bubble structure. Foaming When the bulk substrate comprises two or more foam layers, the material or structure of the foam layers may be the same or different.

Hereinafter, a foam substrate having a structure substantially composed of a single layer of a foam layer will be described as a main example, but it is not intended to limit the structure of the foam substrate in the technology disclosed herein.

The thickness of the foam base material can be appropriately set in accordance with the strength, flexibility, use purpose, and the like of the double-sided adhesive sheet in a range in which the total thickness of the double-sided adhesive sheet is not more than 400 μm. The thickness of the foam base material is usually 350 μm or less (for example, 300 μm or less), and preferably 250 μm or less, more preferably from the viewpoint of easily ensuring the thickness of the adhesive layer which can exhibit the desired adhesive properties. It is 220 μm or less, for example, 200 μm or less. A foam substrate having a thickness of 180 μm or less can be used. In addition, the thickness of the foam base material is preferably 30 μm or more, more preferably 40 μm or more, and still more preferably 50 μm or more (for example, 60 μm or more) from the viewpoints of the rebound resistance and impact resistance of the double-sided adhesive sheet. ).

The material of the foam substrate is not particularly limited. In general, a foam base material containing a foam layer formed of a foam (plastic foam) of a plastic material is preferable. The plastic material (which is intended to include a rubber material) for forming a plastic foam is not particularly limited and may be appropriately selected from known plastic materials. The plastic materials may be used singly or in combination of two or more.

Specific examples of the plastic foam include polyolefin foams such as polyethylene foams and polypropylene foams; polyethylene terephthalate foams and polynaphthalenes. A foam made of a polyester resin such as a foam made of ethylene formate or a foam made of polybutylene terephthalate; a polyvinyl chloride resin foam such as a foam made of polyvinyl chloride; and vinyl acetate; A foam made of an ester resin; a foam made of a polyphenylene sulfide resin; a foam made of a polyamide (nylon) resin; a foam made of a wholly aromatic polyamine (Aramid) resin; Foam; polyimide resin foam; polyether ether ketone (PEEK) foam; polystyrene A foam made of a styrene resin such as a foam; a foam made of a urethane resin such as a foam made of a polyurethane resin; and the like. Further, as the plastic foam, a foam made of a rubber-based resin such as a foam made of a polychloroprene rubber may be used.

A polyolefin resin foam is exemplified as a preferred foam. As the plastic material (that is, the polyolefin resin) constituting the polyolefin-based foam, various known or conventional polyolefin-based resins can be used without particular limitation. For example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), metallocene catalyst type linear low density polyethylene, polyethylene, polypropylene, An ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer, or the like. Such a polyolefin-based resin may be used alone or in combination of two or more.

A preferred example of the foam base material in the technique disclosed herein is a polyethylene foam which is substantially composed of a foam of a polyethylene resin, from the viewpoints of impact resistance and water repellency. A base material or a polypropylene-based foam base material which is substantially composed of a foam of a polypropylene resin. Here, the polyethylene-based resin refers to a resin containing ethylene as a main monomer (ie, a main component in a monomer), and may include ethylene-propylene copolymerization of HDPE, LDPE, LLDPE, and the like, and a copolymerization ratio of ethylene of more than 50% by mass. Or ethylene-vinyl acetate copolymer or the like. Similarly, a polypropylene-based resin means a resin containing propylene as a main monomer. As the foam substrate in the technique disclosed herein, a polyethylene-based foam substrate can be preferably used.

The average cell diameter of the foam substrate is not particularly limited, but is usually preferably 10 μm to 1000 μm, and more preferably 20 μm to 600 μm. When the average cell diameter is set to 10 μm or more, the impact resistance tends to be improved. On the other hand, when the average cell diameter is set to 1000 μm or less, the water repellency (water repellency) tends to be improved. Further, the average cell diameter can be measured, for example, by an optical microscope.

The density (apparent density) of the foam substrate is not particularly limited, but is usually preferably 0.1 to 0.5 g/cm ³ , more preferably 0.2 to 0.4 g/cm ³ . When the density is set to 0.1 g/cm ³ or more, the strength of the foam base material (further, the strength of the double-sided adhesive sheet) is improved, and the impact resistance or workability tends to be improved. On the other hand, when the density is set to 0.5 g/cm ³ or less, the flexibility does not decrease excessively, and the step followability tends to be improved. When the step-following property of the double-sided adhesive sheet is good, even when it is adhered to the adherend having a step, it is not easy to form a gap with the surface of the adherend, and the water repellency is improved. Further, the density (apparent density) of the foam substrate can be measured, for example, by the method according to JIS K6767.

The expansion ratio of the foam substrate is not particularly limited, but is usually preferably 2 to 10 cm ³ /g, more preferably 2.5 to 5 cm ³ /g. When the expansion ratio is set to 2 cm ³ /g or more, the flexibility is improved and the step followability tends to be improved. On the other hand, when the expansion ratio is set to 10 cm ³ /g or less, the strength of the foam base material (and the strength of the double-sided adhesive sheet) is improved, and the impact resistance or workability tends to be improved. Further, in the present specification, the expansion ratio of the foam base material is defined by the reciprocal of the apparent density (g/cm ³ ) measured in accordance with JIS K6767.

The elongation of the foam substrate (for example, a polyolefin foam substrate) is not particularly limited. For example, the elongation in the longitudinal direction (MD) is preferably 200% to 800% (more preferably 400%). ~600%). Further, it is preferable that the elongation in the width direction (TD) is 50% to 800% (more preferably 100% to 600%). By setting the elongation to be equal to or higher than the above lower limit, impact resistance or step followability can be improved. On the other hand, by setting the elongation below the above upper limit, the strength of the foam base material can be improved and the impact resistance can be improved. The elongation of the foam substrate was measured in accordance with JIS K6767. The elongation of the foam substrate can be controlled, for example, according to the degree of crosslinking or the expansion ratio.

The tensile strength of the foam substrate (for example, a polyolefin foam substrate) is not particularly limited. For example, the tensile strength in the longitudinal direction (MD) is preferably from 0.5 to 20 MPa (more preferably from 1 to 15 MPa). Further, the tensile strength in the width direction (TD) is preferably 0.2 to 20 MPa (more preferably 0.5 to 15 MPa). By setting the tensile strength equal to or higher than the above lower limit value, the operability of the foam base material and the double-sided adhesive sheet can be improved. On the other hand, by setting it to the above The tensile strength below the upper limit can improve impact resistance or step followability. The tensile strength (tensile strength in the longitudinal direction and tensile strength in the width direction) of the foam substrate was measured in accordance with JIS K6767. The tensile strength of the above-mentioned foam base material can be controlled, for example, according to the degree of crosslinking, the expansion ratio, and the like.

The foam base material (for example, a polyolefin-based foam base material) preferably has a compression hardness in which the foam base material is stacked so as to have a thickness of about 25 mm, and is sandwiched by a flat plate, and the resultant is compressed to The load at 25% of the initial thickness is 10 to 300 kPa (more preferably 30 to 200 kPa). By setting the compression hardness to 10 kPa or more, the operability can be improved. On the other hand, by setting the compression hardness to 300 kPa or less, the step followability can be improved. The compression hardness of the foam substrate was measured in accordance with JIS K6767. The compression hardness of the above-mentioned foam base material can be controlled, for example, according to the degree of crosslinking, the expansion ratio, and the like.

In the above foam substrate, a filler (inorganic filler, organic filler, etc.), an anti-aging agent, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a plasticizer, a flame retardant may be optionally provided as needed. , various additives such as surfactants.

The foam base material in the technique disclosed herein exhibits desired design properties or optical characteristics (for example, light blocking property, light reflectivity, etc.) in order to provide a double-sided adhesive sheet having the foam base material. Coloring is also possible. In the coloring, a known organic or inorganic coloring agent may be used singly or in combination of two or more kinds as appropriate.

For example, when the double-sided adhesive sheet disclosed herein is used for a light-shielding application, the visible light transmittance of the foam base material is not particularly limited, and is preferably similar to the visible light transmittance of the double-sided adhesive sheet described below. 0~15%, more preferably 0~10%. Further, when the double-sided adhesive sheet disclosed herein is used for light-reflecting use, the visible light reflectance of the foam base material is preferably 20~ as well as the visible light reflectance of the double-sided adhesive sheet described below. 100%, more preferably 25~100%.

The visible light transmittance of the foam substrate can be measured by a spectrophotometer (for example, a spectrophotometer manufactured by Hitachi High-Tech Co., Ltd., model "U-4100") at a wavelength of 550. The intensity of light irradiated from one surface side of the foam base material and transmitted to the other surface side was measured under the condition of nm. The visible light reflectance of the foam substrate can be determined by measuring the intensity of light that is irradiated onto one surface of the foam substrate and reflected at a wavelength of 550 nm using the spectrophotometer. Further, the visible light transmittance and the visible light reflectance of the double-sided adhesive sheet can also be obtained by the same method.

In the case where the double-sided adhesive sheet disclosed herein is used for a light-shielding application, the foam substrate is preferably colored black. As black, it is preferable that L* (lightness) defined by the L*a*b* color system is 35 or less (for example, 0 to 35), and more preferably 30 or less (for example, 0 to 30). Further, each of a* or b* defined by the L*a*b* color system can be appropriately selected according to the value of L*. The a* or b* is not particularly limited. For example, it is preferably both in the range of -10 to 10 (more preferably in the range of -5 to 5, and further preferably in the range of -2.5 to 2.5). For example, it is preferred that both a* and b* are 0 or substantially zero.

In addition, in the present specification, L*, a*, b* defined by the L*a*b* color system can be measured, for example, by a color difference meter (for example, manufactured by Minolta Co., Ltd., device name "CR-200"). . In addition, the L*a*b* color is the color space recommended by the International Commission on Illumination (CIE) in 1976, which means the color space called the CIE1976 (L*a*b*) color system. In addition, the L*a*b* color is defined by JIS Z8729 in Japanese Industrial Standards.

Examples of the black colorant used when the foam base material is colored black include carbon black (furnace black, chimney black, acetylene black, thermal black, lamp black, etc.), graphite, copper oxide, and manganese dioxide. , aniline black, black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium A compound, a composite oxide black pigment, an anthraquinone organic black pigment, or the like. Carbon black is exemplified as a black colorant which is preferable from the viewpoints of cost, availability, and the like. The amount of the black colorant to be used is not particularly limited, and can be appropriately adjusted to an amount capable of imparting desired optical characteristics.

When the double-sided adhesive sheet disclosed herein is used for the purpose of light reflection, the above-mentioned hair The bubble substrate is preferably colored white. As white, it is preferable that L* (lightness) defined by the L*a*b* color system is 87 or more (for example, 87 to 100), and more preferably 90 or more (for example, 90 to 100). Further, each of a* or b* defined by the L*a*b* color system can be appropriately selected according to the value of L*. As a* or b*, for example, it is preferred that both of them are in the range of -10 to 10 (more preferably in the range of -5 to 5, and further preferably in the range of -2.5 to 2.5). For example, it is preferred that both a* and b* are 0 or substantially zero.

Examples of the white colorant used when the foam base material is colored white include titanium oxide (titanium dioxide such as rutile type titanium dioxide or anatase titanium dioxide), zinc oxide, aluminum oxide, cerium oxide, and zirconia. , magnesium oxide, calcium oxide, tin oxide, antimony oxide, antimony oxide, antimony oxide, magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide , magnesium hydroxide, zinc hydroxide, aluminum citrate, magnesium citrate, calcium citrate, barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, ceria, alumina, clay, kaolin , inorganic white coloring agent such as titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, zinc lanthanum, zeolite, sericite, kaolin, acrylic resin particles, polystyrene resin particles, polyamine An organic white coloring agent such as a formate resin particle, a guanamine resin particle, a polycarbonate resin particle, a polyoxymethylene resin particle, a urea-formalin resin particle, or a melamine resin particle. The amount of the white colorant to be used is not particularly limited, and can be appropriately adjusted to an amount capable of imparting desired optical characteristics.

The surface of the foam substrate can be subjected to an appropriate surface treatment as needed. The surface treatment can be a chemical or physical treatment to increase the adhesion to adjacent materials, such as the adhesive layer. Examples of the surface treatment include corona discharge treatment, chromic acid treatment, ozone exposure, flame exposure, ultraviolet irradiation treatment, plasma treatment, and application of a primer (primer).

<double-sided adhesive sheet>

The double-sided adhesive sheet disclosed herein comprises the foam substrate and the first adhesive Layer and second adhesive layer. At least one of the first adhesive layer and the second adhesive layer is an adhesive layer composed of the rubber-based adhesive. The other adhesive layer may be an adhesive layer composed of the above rubber-based adhesive, or may be an adhesive layer composed of another adhesive. The "other adhesive" may be, for example, an adhesive such as an acrylic, a polyester, an urethane, a polyether, a polyoxyn, a polyamine or a fluorine as a base polymer. Agent. Further, it may be a rubber-based adhesive containing a polymer which is not a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer (for example, a natural rubber-based adhesive or a polyisobutylene-based adhesive) Adhesive, etc.).

In a preferred aspect, the adhesive constituting the first adhesive layer and the adhesive constituting the second adhesive layer are each a block copolymer containing a monovinyl-substituted aromatic compound and a conjugated diene compound. A rubber-based adhesive for base polymers. The adhesive constituting the first adhesive layer may be the same as or different from the adhesive constituting the second adhesive layer. From the viewpoints of productivity, cost, and the like, a double-sided adhesive sheet in which the first adhesive layer and the second adhesive layer are composed of a rubber-based adhesive of the same composition is preferable.

The above-mentioned adhesive layer is typically formed using a binder (adhesive component) containing the above composition, a liquid at normal temperature, or a composition (adhesive composition) which can be liquid at least by heating. For example, it may be an adhesive composition containing a form of an adhesive component in an organic solvent (solvent type), or an adhesive composition in which an adhesive is dispersed in an aqueous solvent (water-dispersible type, typically aqueous emulsion type), and heat. A flux adhesive composition or the like. A solvent-based or water-dispersible pressure-sensitive adhesive composition can be preferably used from the viewpoints of coatability and freedom of selection of the foam base material. In order to achieve higher adhesion properties, it is generally advantageous to use a solvent-based adhesive composition.

As a method of forming an adhesive layer on a foam substrate, various previously known methods can be applied. For example, a method of directly applying the above-mentioned pressure-sensitive adhesive composition to a foam substrate (direct method), applying the above-mentioned pressure-sensitive adhesive composition to a suitable release surface, and forming an adhesive on the release surface may be mentioned. Layer and bonding the adhesive layer to the foam substrate for transfer Printing method (transfer method), etc. These methods can be used in combination. In the case of using a solvent-containing adhesive composition, it is preferred to dry the adhesive composition under heating from the viewpoint of promoting the crosslinking reaction and improving the production efficiency.

The total thickness of the adhesive layer (the total thickness of the adhesive layers on both sides of the substrate) is not particularly limited as long as the total thickness of the double-sided adhesive sheet does not exceed 400 μm. For example, the total thickness of the adhesive layer can be set to 10 μm to 200 μm. The total thickness of the adhesive layer is usually 20 μm or more, preferably 30 μm or more, and more preferably 40 μm or more, from the viewpoint of adhesion performance. Moreover, it is preferable to set the total thickness of the adhesive layer to 170 μm or less, and preferably 150 μm or less, and more preferably 100 μm or less, from the viewpoint of easily securing the thickness of the foam base material capable of exhibiting desired characteristics (for example, It is 80 μm or less).

The thickness of the first adhesive layer may be the same as or different from the thickness of the second adhesive layer. In general, it is preferred to use a composition in which the thickness of the two adhesive layers is substantially the same. Further, the thickness of the adhesive layer formed of the above rubber-based adhesive (that is, a rubber-based adhesive containing a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer) The single side can be set, for example, from 5 μm to 100 μm, preferably from 10 μm to 75 μm, more preferably from 15 μm to 65 μm (for example, from 20 μm to 40 μm). Each of the adhesive layers may be in any form of a single layer or a plurality of layers.

The double-sided adhesive sheet disclosed herein may further contain a layer other than the foam base material and the adhesive layer (intermediate layer, undercoat layer, etc.; not limited to the following, insofar as the effect of the present invention is not significantly impaired) Floor"). For example, the other layers described above may be disposed between the foam substrate and either or both of the adhesive layers. In the double-sided adhesive sheet of such a configuration, the thickness of the other layers is included in the total thickness of the double-sided adhesive sheet (i.e., the thickness from one adhesive surface to the other adhesive surface).

According to a preferred aspect of the technology disclosed herein, it is possible to provide double-sided adhesion exhibiting a pressing force of 40 N/cm ² or more (more preferably 50 N/cm ² or more, for example, 55 N/cm ² or more). sheet. When the double-sided adhesive sheet having a high adhesive force is pressed in this manner, when the double-sided adhesive sheet adhesive member is used, peeling due to internal stress is less likely to occur, and the reliability is excellent, which is preferable.

The above-mentioned pressing force is defined as the maximum stress: a sash-shaped (also referred to as a frame-like) double-sided adhesive sheet having a width of 53 cm, a length of 116 cm, and a width of 1 mm is used to gather the roller of 5 kg in a round-trip condition. The carbonate plate was adhered to the glass plate to prepare a sample for evaluation. In the sample for evaluation, the glass plate was pressed from the inside to the outside in the thickness direction of the glass plate at a load speed of 10 mm/10 minutes until the glass plate was pressed. The maximum stress observed during the separation from the polycarbonate sheet. The above pressing force can be measured, for example, by the procedure described in the following examples.

According to another preferred embodiment of the technology disclosed herein, in the evaluation of the rebound resistance by the method described in the following examples, after standing at room temperature for 24 hours and at 70 ° C for 24 hours, Under any of the evaluation conditions, a double-sided adhesive sheet showing the rebound resilience to the extent that the both ends of the test piece were not observed to be lifted could be realized.

According to another preferred embodiment of the technology disclosed herein, in the constant load peeling test conducted by the method described in the following examples, even when a load of 200 g is applied and maintained at 70 ° C, Also shown is a double-sided adhesive sheet having a constant load peeling property of not less than 7 days (more preferably 10 days or more) without peeling.

The double-sided adhesive sheet disclosed herein can have desired optical characteristics (transmittance, reflectance, etc.). For example, a double-sided adhesive sheet for light-shielding use preferably has a visible light transmittance of 0 to 15% (more preferably 0 to 10%). Further, the double-sided adhesive sheet for light reflection use preferably has a visible light reflectance of 20% to 100% (more preferably 25% to 100%). The optical characteristics of the double-sided adhesive sheet can be adjusted, for example, by coloring the foam substrate or the like as described above.

The double-sided adhesive sheet disclosed herein is preferably halogen-free in view of prevention of metal corrosion. The double-sided adhesive sheet is halogen-free, for example, in the case where the double-sided adhesive sheet can be used for fixing electrical and electronic components. In addition, it can suppress halogen-containing gas during combustion. This is also preferable from the viewpoint of reducing environmental load. The halogen-free double-sided adhesive sheet may be used alone or in a combination of intentionally not using a halogen compound as a raw material of a foam substrate or an adhesive, using a foam substrate intentionally unmixed with a halogen compound, and using an additive. In the case, it is obtained without using a method such as an additive derived from a halogen compound.

The double-sided adhesive sheet disclosed herein is not particularly limited and can be used for, for example, a metal material such as stainless steel (SUS) or aluminum; an inorganic material such as glass or ceramic; polycarbonate, polymethyl methacrylate (PMMA), A resin material such as polypropylene or polyethylene terephthalate (PET); a rubber material such as natural rubber or butyl rubber; and a adherend of the composite material or the like.

The double-sided adhesive sheet disclosed herein is excellent in impact resistance or step followability because it contains a foam base material, and excellent rebound resistance can be obtained even if the total thickness is small. Therefore, the effective use of such features can be preferably applied to electronic device applications, such as fixing of a mobile phone lens, fixing of a keyboard module component of a mobile phone, impact absorbing material of an electronic device, fixing of a decorative panel of a television, The battery pack protection use of the computer, the lens waterproofing of the digital camera, and the like. As a particularly preferred use, it can be preferably used for portable electronic devices, particularly portable electronic devices (for example, mobile phones, smart phones, etc.) with built-in liquid crystal display devices. For example, in such a portable electronic device, it can be suitably used for the bonding use of a display panel and a casing.

In the following, some embodiments of the invention are described, but are not intended to limit the invention to the embodiments. In addition, the "parts" and "%" in the following description are the quality standards unless otherwise specified. In addition, each characteristic in the following description was measured or evaluated as follows.

(1) 180 degree peel strength

A polyethylene terephthalate (PET) film having a thickness of 25 μm was adhered to one of the adhesive faces of the double-sided adhesive sheet, and the obtained product was cut into a size of 20 mm in width and 100 mm in length. Use the sample.

The other adhesive surface of the above-mentioned measurement sample was exposed in an environment of 23 ° C and 50% RH, and the other adhesive surface was pressure-bonded to the surface of the adherend under the condition that the 2 kg roller was reciprocated once. The resultant was placed in the environment for 30 minutes, and then a universal tensile compression tester (device name "tensile compression tester TG-1kN", manufactured by Meiya Co., Ltd.) was used, and the stretching speed was measured according to JIS Z0237. The peel strength (N/20 mm width) was measured under conditions of 300 mm/min and a peeling angle of 180 degrees.

Five kinds of adherends for stainless steel plate (SUS304BA plate), polycarbonate plate (PC plate), polymethyl methacrylate plate (PMMA plate), glass plate and polypropylene resin plate (PP plate), according to the above procedure 180 degree peel strength (adhesion).

(2) pressing the force

As shown in Fig. 2 (a) and Fig. 2 (b), the double-sided adhesive sheet was cut into a window frame shape (frame shape) of 53 mm in width, 116 mm in length, and 1 mm in width to obtain a double-sided adhesive sheet having a window frame shape. Using the sash-shaped double-sided adhesive sheet, a glass plate having a width of 53 mm, a length of 116 mm, and a thickness of 1 mm (using Gorilla glass manufactured by Corning Incorporated, the same below) and a PC plate having a through hole having a diameter of 15 mm at the center portion (horizontal: 70 mm, vertical: 130 mm, thickness: 2 mm), and crimped under a condition of a round trip of 5 kg, and a sample for evaluation was obtained.

2(a) and 2(b) are schematic views of the sample for evaluation, and Fig. 2(a) is a plan view, and Fig. 2(b) is a cross-sectional view taken along line A-A'. In Figs. 2(a) and 2(b), reference numeral 21 denotes a PC board, reference numeral 2 denotes a sash-shaped double-sided adhesive sheet, reference numeral 22 denotes a glass plate, and reference numeral 21A denotes a through hole provided in the PC board 21.

These evaluation samples were placed in the above-described universal tensile compression tester. Further, the round bar was passed through the through hole of the PC board, and the round bar was lowered at a speed of 10 mm/min to press the glass plate in a direction away from the PC board. Further, the maximum stress observed until the separation between the glass plate and the polyPC plate was measured as the pressing force. Further, the measurement was carried out in an environment of 23 ° C and 50% RH.

Fig. 3 is a schematic cross-sectional view showing a method of measuring a pressing force. Reference numeral 21 denotes a PC board, reference numeral 2 denotes a double-sided adhesive sheet in the form of a window frame, reference numeral 22 denotes a glass plate, reference numeral 23 denotes a round bar, and reference numeral 24 denotes a support table. As shown in FIG. 3, the sample for evaluation was fixed to the support stand 24 of the tensile compression tester, and the glass plate 22 of the sample for evaluation was pressed by the round bar 23 of the through-hole 21A of the PC board 21. Further, in the above-described pressing force measurement, the PC board 21 is not bent or broken by the load applied by the glass sheet 22 being pressed by the round bar 23.

(3) Impact resistance

As shown in Fig. 4 (a) and Fig. 4 (b), the double-sided adhesive sheet was cut into a window frame shape (frame shape) of a width of 53 mm, a length of 116 mm, and a width of 1 mm to obtain a sash-shaped double-sided adhesive tape. Using the sash-shaped double-sided adhesive sheet, a PC board (transverse 70 mm, vertical 130 mm, thickness 2 mm) and a glass plate (horizontal: 53 mm, vertical: 116 mm, thickness: 1 mm, mass 18 g) were placed on a roll of 5 kg. The pressure-bonding was carried out under the conditions, and the sample for evaluation was obtained (refer FIG. 4 (a), FIG. 4 (b)).

4(a) and 4(b) are schematic views of the sample for evaluation, and Fig. 4(a) is a plan view, and Fig. 4(b) is a cross-sectional view taken along line BB'. In Figs. 4(a) and 4(b), reference numeral 31 denotes a PC board, reference numeral 3 denotes a window frame double-sided adhesive sheet, and reference numeral 32 denotes a glass sheet.

A weight of 110 g was attached to the back surface of the PC board of the evaluation sample (the side opposite to the surface on which the glass sheet was adhered). For the evaluation sample of the above-mentioned attached code, a 60-time free fall from a height of 1.2 m to a drop test of a concrete slab was carried out at room temperature (about 23 ° C). At this time, the direction of the drop was adjusted so that the six faces of the above-mentioned evaluation sample were sequentially downward. That is, the drop mode of one time is performed for 10 cycles for each of the six faces.

Further, at the time of each drop, it was visually confirmed whether or not peeling occurred between the PC plate and the glass plate, and the number of drops until peeling occurred was evaluated as the impact resistance against the drop at normal temperature. After 60 falls, the situation of divestiture was not observed as "more than 60 times."

(4) Water resistance

The double-sided adhesive sheet is cut into a window frame of 53 mm in width, 116 mm in length, and 1 mm in width (side Frame-like), obtaining a double-sided adhesive sheet with a window frame. The sash-shaped double-sided adhesive sheet was adhered to the outer edge portion of the acrylic plate having a width of 53 mm, a length of 116 mm, and a thickness of 1 mm to prepare an acrylic plate with a sash-shaped double-sided adhesive sheet.

As shown in FIGS. 5(a) and 5(b), a step tape 42 having a width of 5 mm is adhered to the surface of the PC board 41. The step tape 42 is provided with irregularities on the surface of the PC board 41. Here, as the step tape 42, an adhesive sheet having an adhesive layer on one side of the film substrate is used. In order to easily observe the presence or absence of water seepage, the nonwoven fabric 44 is disposed on both sides of the step belt 42. Further, the acrylic plate with the sash-shaped double-sided adhesive sheet produced as described above is placed on the PC board 41 so as to cover the center portion of the long side of the sash-shaped double-sided adhesive sheet 4 and cross-cut in the width direction. 42, and the 5kg roller is reciprocated once and for all.

As the step tape 42, an adhesive tape having a thickness (the total thickness of the film base material and the adhesive layer) of 10 μm, 30 μm, 50 μm, or 70 μm is used, and the unevenness (step) corresponding to the thickness of each step tape 42 is produced. A total of four evaluation samples were adhered to the PC board 41 by the acrylic sheets of the sash-shaped double-sided adhesive sheets. Further, a stepless evaluation sample was produced by the same procedure as described above except that the step belt was not used.

5(a) and 5(b) are schematic views of a sample for evaluation used for evaluating waterproof characteristics, and Fig. 5(a) is a plan view, and Fig. 5(b) is a cross-sectional view taken along line C-C'. In Figs. 5(a) and 5(b), reference numeral 41 denotes a PC board, reference numeral 42 denotes a stepped tape, reference numeral 4 denotes a double-sided adhesive sheet in the form of a window frame, reference numeral 43 denotes an acrylic plate, and reference numeral 44 denotes a non-woven fabric.

The waterproof evaluation test is based on the IPX7 standard (JIS C0920/IEC60529), and the sample for evaluation of each uneven height is immersed in a water depth of 1 m in a standard state (23 ° C, 50% RH) for 30 minutes to confirm the presence or absence of internal The water seepage is carried out.

In addition, the above-described waterproof evaluation test was carried out by aging the sample for evaluation of each uneven height for 30 minutes in a standard state (temperature: 23 ° C, humidity: 50%). Further, for each step, evaluation was performed using eight evaluation samples (i.e., n = 8).

For samples without step evaluation, no water seepage was observed in 8 samples. Next, the evaluation result of the water repellency was expressed as "good". For the sample for evaluation with a step, the highest value of the step in the step in which no water was observed was expressed as "allowable step". The larger the allowable step, the higher the water repellency under the step condition. The water repellency evaluation result under the step condition can also be grasped as the step followability of the double-sided adhesive sheet.

(5) Resilience

A stainless steel cylinder having a diameter of 30 mm was used as the adherend, and the rebound resilience of the double-sided adhesive sheet was evaluated. That is, as shown in Fig. 6, one adhesive surface 5A of the double-sided adhesive sheet 5 is adhered to and lining the polycarbonate film 52 having a thickness of 400 μm, and the affixed adhesive sheet is cut into a width of 10 mm and a length of 50 mm. The size of the test piece 54 was produced. In the environment of 23 ° C and 50% RH, as shown in FIG. 6, the other adhesive surface 5B of the test piece 54 is such that the longitudinal direction of the test piece 54 is the circumferential direction of the adherend (stainless steel cylinder) 56. In this way, the 2kg roller is reciprocated once and for all. Further, the adherend 56 is used after being washed with ethanol in advance. After being left under (A) normal temperature (23 ° C, 50% RH) for 24 hours and (B) placed under an environment of 70 ° C for 24 hours, two lengthwise directions of the test piece 54 were observed. Whether the ends 54A and 54B are peeled off from the surface of the adherend 56 and lifted up, and the lift-up distance (the length of the portion of the test piece 54 which is lifted from the surface of the adherend 56) is measured in the case of lifting. In the case where both ends of the test piece were lifted, the average value of the lift distance of both ends was taken as the lift-off distance of the test piece. When no lift is observed at both ends, it is expressed as "no lift".

(6) Constant load peeling characteristics

The double-sided adhesive sheet was cut into a window frame shape (frame shape) of 53 mm in width, 116 mm in length, and 1 mm in width to obtain a double-sided adhesive sheet having a window frame shape. As shown in Fig. 7, a glass plate (glass lens) 61 having a width of 53 mm, a length of 116 mm, and a thickness of 1 mm and a PC plate having a through hole 62A at the center portion were used as shown in Fig. 7 (horizontal: 70 mm, vertical) : 130mm, thickness: 5mm) 62, crimped and adhered under the condition of a round trip of 5kg, for evaluation. sample. This is placed on the support table 64, and the outer edge portion of the PC board 62 is supported, and a weight 63 of a specific quality is placed on the glass plate 61 through the through hole 62A. The resultant was held at 70 ° C and counted until the number of days until the glass plate 61 was separated from the PC plate 62. The constant load peeling characteristics were evaluated by the above method with the weights of the weights of 90 g, 120 g, and 200 g.

<Experimental Example 1> (sample S1)

100 parts of styrene isoprene block copolymer (manufactured by Nippon Zeon Co., Ltd., product name "Quintac 3520", diblock copolymer ratio 78%, styrene content 15%), 40 parts terpene phenol resin 30 parts of terpene resin, 0.75 parts of isocyanate compound (product of Japan Polyurethane Industry Co., Ltd., product name "Coronate L") and toluene as a solvent were stirred and mixed to prepare an adhesive composition A1 having 50% NV. . As the terpene resin, the product name "YS Polystar S145" (softening point 145 ° C, hydroxyl value 100 mg KOH / g) manufactured by Anwara Chemical Co., Ltd. and the trade name "YS Polystar T145" manufactured by the company (softening point 145 ° C) The hydroxyl value of 60 mgKOH/g) was used in such a manner that the mass ratio of 1:1 was 40 parts in total. In addition, as the terpene resin, the trade name "YS Resin PX1150N" manufactured by Anwara Chemical Co., Ltd. (softening point: 115 ° C, a hydroxyl value of less than 1 mgKOH/g) was used.

The adhesive composition A1 was applied to one surface of a commercially available release liner (trade name "SLB-80W3D", manufactured by Sumitomo Chemical Co., Ltd.) so as to have a thickness of 25 μm after drying and at 100 ° C. It was dried for 2 minutes to form an adhesive layer. Then, the adhesive layer was adhered to one surface of a polyethylene resin foam sheet (hereinafter referred to as "base material No. 1") as a foam base material to obtain a single-sided adhesive sheet. The substrate No. 1 had a thickness of 150 μm, a tensile strength (tensile strength (MD)) in the longitudinal direction of 12.0 MPa, and a tensile strength (tensile strength (TD)) in the width direction of 10.0 MPa.

Then, the adhesive composition A1 is applied to one of the same release liners as described above. The surface was dried to a thickness of 25 μm and dried at 100 ° C for 2 minutes to form an adhesive layer. The adhesive layer is adhered to the other surface of the foam substrate in the single-sided adhesive sheet. Then, the obtained structure was passed through a laminator (0.3 MPa, speed 0.5 m/min) at 80 ° C in one pass, and then cured in an oven at 50 ° C for 1 day. Thus, a double-sided adhesive sheet sample S1 having a structure of "release liner/adhesive layer/foam substrate/adhesive layer/release liner" and a total thickness of 200 μm was obtained.

(sample S2)

In a reaction vessel having a cooling tube, a nitrogen introduction tube, a thermometer, a dropping funnel, and a stirring device, 69 parts of toluene, 163 parts of ethyl acetate as a solvent, 80 parts of butyl acrylate, and 20 parts of 2-ethyl acrylate were charged. Ester, 3 parts of acrylic acid, 5 parts of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, and 0.2 part of 2,2'-azobisisobutyronitrile as a starter, carried out in a nitrogen stream at 60 ° C Polymerization was carried out for 6 hours to obtain an acrylic polymer. In the solution, 30 parts of the polymerized rosin ester resin was blended with 100 parts of the polymer component in the solution, and 1.5 parts of an isocyanate compound (trade name "Coronate L") was blended in terms of solid content to prepare an acrylic adhesive composition. A2.

As the foam base material, a foam sheet (base material No. 2) made of a polyethylene resin having a thickness of 100 μm was used. The base material No. 2 had a tensile strength (MD) of 9.5 MPa and a tensile strength (TD) of 8.7 MPa.

Except that the adhesive composition A2 was used instead of the adhesive composition A1, the thickness of the adhesive layer adhered to one surface and the other surface of the substrate was 50 μm, and the substrate No. 2 was used instead of the substrate No. 1. A double-sided adhesive sheet sample S2 having a composition of "release liner/adhesive layer/foam substrate/adhesive layer/release liner" and a total thickness of 200 μm was obtained in the same manner as in the production of the sample S1. .

(sample S3)

As the foam base material, a foam sheet (base material No. 3) made of a polyethylene resin having a thickness of 150 μm was used. The substrate has a tensile strength (MD) of 11.0 MPa and a tensile strength (TD) of 9.5. MPa. In the same manner as in the production of the sample S2, except that the thickness of the adhesive layer adhered to one surface and the other surface of the substrate was 25 μm, and the substrate No. 3 was used instead of the substrate No. 2, A structure of "release liner/adhesive layer/foam substrate/adhesive layer/release liner" and a double-sided adhesive sheet sample S3 having a total thickness of 200 μm.

The total thickness of each of the double-sided adhesive sheets of the double-sided adhesive sheet samples S1 to S3 and the results of measurement or evaluation by the above method are shown in Table 1. In the table, # indicates the peel strength, which indicates the destruction of the foam substrate in the peel strength measurement.

As shown in the above table, a rubber-based adhesive comprising a block copolymer containing a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymer is provided on the first side and the second side of the foam substrate. The adhesive layer and the double-sided adhesive sheet sample S1 having a total thickness of 200 μm showed remarkably excellent resilience resistance as compared with the samples S2 and S3 in which both adhesives contained the acrylic adhesive. Further, the sample S1 was also excellent in constant load peeling characteristics and pressing adhesion. In addition, the peel strength of the polypropylene board is also high, and the polyolefin is issued. The foam substrate has good anchoring properties. In addition, the impact resistance and other characteristics are also equivalent to or better than the samples S2 and S3.

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

1‧‧‧Double adhesive tape

11‧‧‧First adhesive layer

11A‧‧‧First adhesive surface

12‧‧‧Second Adhesive Layer

12A‧‧‧Second Adhesive Surface

15‧‧‧Flaked foam substrate

15A‧‧‧The first side of the substrate 15

15B‧‧‧The second side of the substrate 15

17‧‧‧Release liner

17A‧‧‧Before the release liner

17B‧‧‧The back of the release liner

Claims (4)

A double-sided adhesive sheet comprising: a foam substrate; a first adhesive layer disposed on the first surface of the foam substrate; and a second surface disposed on the second surface of the foam substrate a second adhesive layer constituting at least one of the first adhesive layer and the second adhesive layer is a block copolymer containing a monovinyl-substituted aromatic compound and a conjugated diene compound as a base polymerization A rubber-based adhesive having a total thickness of 400 μm or less. The double-sided adhesive sheet of claim 1, wherein the thickness of the foam substrate is 60 μm or more and 300 μm or less. The double-sided adhesive sheet according to claim 1 or 2, wherein the rubber-based adhesive comprises a tackifying resin, and the tackifying resin comprises a low-softening point resin having a softening point of less than 120 ° C and a high softening point having a softening point of 120 ° C or higher. The resin, the above high softening point resin contains a terpene phenol resin. The double-sided adhesive sheet according to any one of claims 1 to 3, wherein the rubber-based adhesive comprises a tackifying resin having a hydroxyl value of 80 mgKOH/g or more.