JP2022052802A - Pressure sensitive adhesive sheet - Google Patents

Abstract

To provide a pressure sensitive adhesive sheet excellent in impact resistance, flex resistance and glare protection properties.SOLUTION: A pressure sensitive adhesive sheet 1 includes a foam substrate 11 and an adhesive layer 12 formed at least on one side of the foam substrate 11. The foam substrate 11 has density of 0.40 g/cm3 or more and thickness of 300 μm or less. The pressure sensitive adhesive sheet 1 has an impact absorption rate of 20% or more at a falling ball impact test, and a compression set of 10% or less when compressed to 25% of initial thickness in a condition of 50°C for 24 hours.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive sheet.

Conventionally, image display members fixed to image display devices such as liquid crystal displays, electroluminescence displays, plasma displays, display members attached to so-called "mobile phones", "smartphones", "portable information terminals", cameras, etc. A foam material is used when an optical member such as a lens is fixed to a predetermined portion (for example, a housing or the like).

In recent years, with the thinning of electronic devices such as personal computers (PCs), tablet PCs, personal digital assistants (PDAs), and mobile phones, fixing optical members to prevent damage to liquid crystal panels and organic EL panels. And on the back of the panel, an adhesive sheet with shock absorption is used. As such an adhesive sheet, one in which an adhesive layer is provided on a foam base material is known (see, for example, Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 2018-150501 International Publication No. 2016/093110 Japanese Unexamined Patent Publication No. 2009-242541

In recent years, an organic EL panel using a foldable substrate (flexible substrate) such as a resin film has been put into practical use, and a foldable flexible display has been proposed. In a flexible display, in addition to the display panel such as an organic EL panel being foldable, the constituent members are also foldable, and these members are bonded via an adhesive sheet. In a foldable flexible display (foldable display), bending is repeated at the same place. At the bent part, compressive stress is applied to the inside and tensile stress is applied to the outside, and strain occurs in and around the bent part, so that there is a concern that the device may be destroyed. Therefore, the adhesive sheet used for the foldable display is also required to have bending resistance in addition to impact resistance.

As a method for improving the bending resistance of the pressure-sensitive adhesive sheet, it is conceivable to reduce the thickness of the pressure-sensitive adhesive layer and reduce the density of the foam used for the pressure-sensitive adhesive sheet. However, if the thickness of the pressure-sensitive adhesive layer is reduced, the impact resistance is lowered. In addition, when the density of the foam is reduced, the light-shielding property of the adhesive sheet is lowered, and the appearance tends to be inferior, such as light being transmitted through the adhesive sheet and light easily entering the housing from the outside, and the display is difficult to see. There is.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an adhesive sheet having excellent impact resistance, bending resistance, and light shielding property.

As a result of diligent studies to achieve the above object, the present inventors have provided a foam base material and an adhesive layer, and the density and thickness of the foam base material are within a specific range. It was found that the pressure-sensitive adhesive sheet having an impact absorption rate of 20% or more and a compression set of 10% or less under specific conditions is excellent in impact resistance, bending resistance, and light-shielding property. The present invention has been completed based on these findings.

As one embodiment of the present invention, the pressure-sensitive adhesive sheet includes a foam base material and a pressure-sensitive adhesive layer provided on at least one surface of the foam base material.
The foam substrate has a density of 0.40 g / cm ³ or more and a thickness of 300 μm or less.
Provided is an adhesive sheet having an impact absorption rate of 20% or more by a falling ball impact test and a compression set of 10% or less when compressed to 25% of the initial thickness under the condition of 50 ° C. for 24 hours. ..

Since the foam base material has a density of 0.40 g / cm ³ or more and a thickness of 300 μm or less, the pressure-sensitive adhesive sheet is excellent in both bending resistance and light-shielding property. Further, the pressure-sensitive adhesive sheet is excellent in impact resistance because the impact absorption rate by the falling ball impact test is 20% or more and the compression set is 10% or less.

The foam base material is preferably a urethane-based foam or an acrylic-based foam. As a result, the bending resistance and impact resistance of the adhesive sheet are more excellent.

The pressure-sensitive adhesive layer preferably has an elastic modulus of 200 kPa or less at 23 ° C. As a result, the adhesive layer has high flexibility at room temperature, and the adhesive sheet has better bending resistance.

The pressure-sensitive adhesive sheet preferably has a visible light transmittance of 4.0% or less. As a result, the light-shielding property of the adhesive sheet is more excellent.

The density of the foam base material is preferably 0.40 to 0.60 g / cm ³ . As a result, the impact resistance of the adhesive sheet is more excellent.

The adhesive sheet is preferably used by being bonded to an internal member of an electric / electronic device (preferably a portable electronic device).

According to the pressure-sensitive adhesive sheet in the present invention, it is excellent in impact resistance, bending resistance, and light-shielding property. Therefore, when the adhesive sheet is used at a bent portion of a foldable display, it is not easily damaged even if it is repeatedly bent and used, and the appearance of the display is also excellent.

It is a schematic diagram (front sectional view) which shows one Embodiment of the pressure-sensitive adhesive sheet in this invention.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention includes at least a foam base material and a pressure-sensitive adhesive layer provided on at least one surface of the foam base material. The pressure-sensitive adhesive sheet may be a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side of the foam base material, or a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the foam base material. In the case of a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layers on both sides may be the same pressure-sensitive adhesive layer, or may be a pressure-sensitive adhesive layer having different compositions, thicknesses, physical properties, and the like.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the pressure-sensitive adhesive sheet in the present invention. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 includes a foam base material 11, a pressure-sensitive adhesive layer 12 provided on one surface of the foam base material 11, and a release liner provided on the surface of the pressure-sensitive adhesive layer 12. 13 and.

The pressure-sensitive adhesive sheet has an impact absorption rate of 20% or more, preferably 40% or more, more preferably 55% or more, still more preferably 60% or more in the falling ball impact test. Since the falling ball impact test is a test in which a point impact is applied to the adhesive sheet, it is an impact test under harsher conditions than a test in which a surface impact is applied. Since the impact absorption rate in such a falling ball impact test is 20% or more, the adhesive sheet is excellent in impact resistance. The impact absorption rate by the above-mentioned falling ball impact test is a value obtained by the following falling ball impact test. When the pressure-sensitive adhesive sheet is provided with a release liner, the falling ball impact test is carried out without the release liner.
<Drop impact test>
The peak load Ref when a 40 g steel ball is freely dropped from a height of 30 cm on a measuring table maintained horizontally, and the steel ball is similarly attached to the measuring table with the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet. The peak load G when the product is freely dropped is measured. Then, the impact absorption rate is calculated by the following formula.
Impact absorption rate (%) = (Ref-G) / Ref × 100

The pressure-sensitive adhesive sheet has a compression set of 10% or less, preferably 6% or less, more preferably 5% or less, still more preferably 4 when compressed to 25% of the initial thickness under the condition of 50 ° C. for 24 hours. % Or less. When the compression set is 10% or less, the thickness recovery speed of the pressure-sensitive adhesive sheet is fast, and the bending resistance and the impact resistance are excellent. The compression set is a value obtained based on JIS K6262, and specifically, a value obtained by the following compression set test. When the pressure-sensitive adhesive sheet is provided with a release liner, the compression set test is carried out without the release liner.
<Compression set test>
The thickness of the adhesive sheet when compressed to a thickness of 25% of the initial thickness t ₀ , allowed to stand at 50 ° C. for 24 hours in the compressed state, then decompressed, and left for 1 hour in a room temperature environment. Measure t ₁ . Then, the compression set is calculated by the following formula.
Compression set (%) = (t ₀ − t ₁ ) / t ₀ × 100

The pressure-sensitive adhesive sheet preferably has a visible light transmittance of 4.0% or less, more preferably 3.0% or less, and further preferably 1.0% or less. When the visible light transmittance is 4.0% or less, the light-shielding property of the adhesive sheet is excellent, and the appearance of the applied optical member is excellent. The visible light transmittance is a value measured based on JIS K7136. When the pressure-sensitive adhesive sheet is provided with a release liner, the visible light transmittance is a value in a state without the release liner.

The impact absorption rate, the permanent compression strain, and the visible light transmittance of the adhesive sheet are comprehensively designed in addition to the density and thickness of the foam substrate, the type and composition of the resin constituting the foam, and the like. It can be adjusted by doing.

(Foam base material)
The foam substrate has a density of 0.40 g / cm ³ or more, preferably 0.42 g / cm ³ or more. When the density is 0.40 g / cm ³ or more, the foam base material and the pressure-sensitive adhesive sheet are excellent in light-shielding property. The density is preferably 0.60 g / cm ³ or less, more preferably 0.55 g / cm ³ or less. When the density is 0.60 g / cm ³ or less, the impact resistance of the adhesive sheet is more excellent.

The thickness of the foam substrate is 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, and further preferably 100 μm or less. When the thickness is 300 μm or less, the foam base material and the pressure-sensitive adhesive sheet have excellent bending resistance. The thickness is preferably 40 μm or more, more preferably 60 μm or more. When the thickness is 40 μm or more, bubbles can be uniformly contained and more excellent shock absorption can be exhibited.

The foam base material may be a single layer or may be a plurality of layers composed of the same or different layers. In the case of a plurality of layers, it is preferable that all the foam base materials satisfy the above densities. Further, in the case of a multi-layer, the thickness of the foam base material is the total thickness of the multi-layer.

The composition, bubble structure, and the like of the foam base material are not particularly limited as long as they have the above-mentioned characteristics. The bubble structure may be any of an open cell structure, a closed cell structure, and a semi-continuous semi-closed cell structure. From the viewpoint of further excellent bending resistance, a continuous cell structure and a semi-continuous semi-closed cell structure are preferable, and a semi-continuous semi-closed cell structure is more preferable.

The foam base material can be made of a resin composition containing a resin material (polymer). It should be noted that the loss, which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the unfoamed resin composition [resin composition (solid substance) when not foamed]. The peak top of the positive contact (tan δ) is preferably in the range of −30 ° C. or higher and 30 ° C. or lower. The lower limit of the temperature range in which the peak top of the loss tangent is present is preferably -25 ° C, more preferably -20 ° C, still more preferably -10 ° C, and the upper limit is preferably 20 ° C, more preferably 10 ° C. Is. In the case of a material having two or more peak tops of loss tangent, it is desirable that at least one of them falls within the above range. Peak top strength of loss tangent (tan δ) in the range of -30 ° C or higher and 30 ° C or lower of the resin composition (solid material) (this value is in the range of -30 ° C or higher and lower than 30 ° C in the foam substrate). It is preferable that the peak top strength of the loss tangent (tan δ) is high from the viewpoint of shock absorption (corresponding to the value obtained by dividing the peak top strength of the foam base material by the density (g / cm ³ )). For example, the peak top strength of the loss tangent (tan δ) of the above resin composition (solid material) in the range of −30 ° C. or higher and 30 ° C. or lower is preferably 0.9 (g / cm ³ ) ^-1 or higher. The upper limit is, for example, about 3.

Further, the initial elastic modulus (23 ° C., tensile speed 300 mm / min) of the unfoamed resin composition (solid matter) is preferably low, preferably 50 N / mm ² or less, and more preferably 30 N / mm ² . It is as follows. The lower limit of the initial elastic modulus is, for example, 0.3 N / mm ² .

The resin material (polymer) constituting the foam base material is not particularly limited, and a known or well-known resin material constituting the foam can be used. Examples of the resin material include acrylic polymers, rubbers, urethane polymers, ethylene-vinyl acetate copolymers and the like. Among these, urethane-based polymers and acrylic-based polymers are preferable. That is, the foam base material is preferably a urethane-based foam containing a urethane-based polymer or an acrylic-based foam containing an acrylic polymer. The resin material (polymer) constituting the foam base material may be only one kind or two or more kinds.

The peak top of the loss tangent (tan δ), which is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement of the foam substrate, is −30 ° C. or higher and 30 ° C. or lower. In order to make it within the range, the Tg of the resin material can be used as an index or a guideline. For example, as the resin material, Tg is in the range of −50 ° C. or higher and lower than 50 ° C. (the lower limit is preferably −40 ° C., more preferably −30 ° C., and the upper limit is preferably 40 ° C., more preferably 30 ° C.). You can choose from certain resin materials.

As the acrylic polymer, an acrylic polymer formed by a monomer having a homopolymer Tg of −10 ° C. or higher and a monomer having a homopolymer Tg of less than −10 ° C. as essential monomer components is preferable. By adjusting the quantitative ratio of the former monomer and the latter monomer using such an acrylic polymer, it is the ratio of the storage elastic modulus and the loss elastic modulus at an angular frequency of 1 rad / s in the dynamic viscoelasticity measurement. A foamed sheet having a peak top of loss tangent (tan δ) of −30 ° C. or higher and 30 ° C. or lower can be obtained relatively easily.

In addition, in this specification, "the glass transition temperature (Tg) at the time of forming a homopolymer" (sometimes simply referred to as "the Tg of a homopolymer") is "the glass transition temperature of the homopolymer of the said monomer (the glass transition temperature (Tg)". It means "Tg)", and specifically, the numerical value is given in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc, 1987). The Tg of the homopolymer of the monomer not described in the above document refers to, for example, a value obtained by the following measuring method (see JP-A-2007-51271). That is, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser, 100 parts by mass of a monomer, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and ethyl acetate as a polymerization solvent. Add 200 parts by mass and stir for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by mass. Next, this homopolymer solution is cast-coated on a separator and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. Then, this test sample is punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Leometrics) in the temperature range of -70 to. The viscoelasticity is measured in a shear mode at a heating rate of 150 ° C. and 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer. The Tg of the resin material (polymer) can also be measured by this method.

In a monomer having a homopolymer Tg of −10 ° C. or higher, the Tg is, for example, −10 ° C. to 250 ° C., preferably 10 to 230 ° C., more preferably 50 to 200 ° C., and particularly preferably 100 to 200 ° C. ..

Examples of the monomer having a Tg of −10 ° C. or higher in the above homopolymer include (meth) acrylonitrile; an amide group-containing monomer such as (meth) acrylamide and N-hydroxyethyl (meth) acrylamide; and homozygous acid such as (meth) acrylic acid. Carboxy group-containing (meth) acrylic acid ester with Tg of polymer at -10 ° C or higher; (meth) acrylic acid alkyl ester with Tg of -10 ° C or higher for homopolymers such as methyl methacrylate and ethyl methacrylate; (meth) acrylic (Meta) acrylic acid alicyclic ester having a Tg of -10 ° C or higher for homopolymers such as isobornyl acid and cyclohexyl (meth) acrylic acid; (meth) acrylic having a Tg of -10 ° C or higher such as benzyl (meth) acrylate. Examples thereof include acid aromatic esters; heterocyclic-containing vinyl monomers such as N-vinyl-2-pyrrolidone and acroylmorpholin; and hydroxy group-containing monomers such as 2-hydroxyethylmethacrylate. Only one kind of these may be used, or two or more kinds may be used. Among them, monomers having a functional group such as a nitrogen atom-containing group such as a carboxy group, a hydroxy group and a nitrile group (particularly (meth) acrylonitrile, (meth) acrylic acid and 2-hydroxyethyl (meth) acrylate) are preferable. Acrylonitrile and acrylic acid are preferred. When a monomer having a Tg of −10 ° C. or higher of the homopolymer is used, the peak top strength of the loss tangent (tan δ) of the foam base material can be increased probably because the intramolecular interaction is strong.

In a monomer having a homopolymer Tg of less than −10 ° C., the Tg is, for example, −70 ° C. or higher and lower than −10 ° C., preferably −70 ° C. to −12 ° C., more preferably −65 ° C. to −15 ° C. ..

Examples of the monomer having a Tg of less than -10 ° C. for the above homopolymer include (meth) acrylic acid alkyl esters having a Tg of less than -10 ° C. for homopolymers such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate. Can be mentioned. Only one kind of these may be used, or two or more kinds may be used. Of these, acrylic acid C _2-8 alkyl ester is preferable.

The content of the monomer having a Tg of −10 ° C. or higher in the homopolymer is, for example, 2 to 30% by mass with respect to the total amount of the monomer components forming the acrylic polymer (total amount of the monomer components), and the lower limit is preferably 3% by mass. %, More preferably 4% by mass, and the upper limit is preferably 25% by mass, more preferably 20% by mass. Further, the content of the monomer having a Tg of less than −10 ° C. of the homopolymer with respect to all the monomer components (total amount of the monomer components) forming the acrylic polymer is, for example, 70 to 98% by mass, and the lower limit is preferably. It is 75% by mass, more preferably 80% by mass, and the upper limit is preferably 97% by mass, more preferably 96% by mass.

As the acrylic polymer, in particular, as a monomer component forming the acrylic polymer, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 2 to 4 carbon atoms is used for all the monomer components. 50% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more), and the Tg of the homopolymer is 10 ° C. or more, and a nitrogen atom-containing group such as a carboxy group, a hydroxy group, or a nitrile group, etc. It is preferable to contain 2 to 20% by mass (preferably 3 to 15% by mass, more preferably 5 to 10% by mass) of the monomer having a functional group.

The rubber may be either natural rubber or synthetic rubber. Examples of the rubber include nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), styrene-butadiene rubber (SBR), acrylic rubber (ACM, ANM), urethane rubber (AU), and silicone rubber. Among these, nitrile rubber (NBR), methyl methacrylate-butadiene rubber (MBR), and silicone rubber are preferable.

Examples of the polyurethane-based polymer include those obtained by reacting a polyisocyanate, a long-chain polyol, a chain extender, and, if necessary, another isocyanate-reactive compound.

The polyisocyanate is a compound having two or more isocyanate groups in the molecule. Examples of the polyisocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and aromatic aliphatic polyisocyanates. The polyisocyanate may also be a dimer or trimer, a reaction product or a polymer of the aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic polyisocyanate, and / or an aromatic aliphatic polyisocyanate. For example, diphenylmethane diisocyanate dimer or trimer, reaction product of trimethylol propane and tolylene diisocyanate, reaction product of trimethylol propane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, etc. (Polyester polyisocyanate, etc.) and the like. As the polyisocyanate, only one kind may be used, or two or more kinds may be used.

Examples of the long-chain polyol include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polyacrylic polyols and the like. The number average molecular weight of the long-chain polyol is usually 500 or more, preferably 500 to 10000, more preferably 600 to 6000, and even more preferably 800 to 4000. As the long-chain polyol, only one kind may be used, or two or more kinds may be used.

As the chain extender, a chain extender usually used for producing a urethane-based polymer can be used, and examples thereof include low molecular weight polyols and polyamines. The molecular weight of the chain extender is usually less than 500, preferably 300 or less. As the chain extender, only one kind may be used, or two or more kinds may be used.

Examples of the urethane-based polymer include polycarbonate-based polyurethane, polyester-based polyurethane, and polyether-based polyurethane.

As the ethylene-vinyl acetate copolymer, a known or well-known ethylene-vinyl acetate copolymer can be used.

In addition to the resin material, the foam substrate may contain a surfactant, a cross-linking agent, a thickener, a rust preventive, a silicone compound, and other additives, if necessary.

For example, any surfactant may be contained for the purpose of reducing the bubble diameter and stabilizing the foamed foam. The surfactant is not particularly limited, and any of anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like may be used, but the bubble diameter may be reduced and foaming may occur. From the viewpoint of the stability of the foam, an anionic surfactant is preferable, and a fatty acid ammonium-based surfactant such as ammonium stearate is more preferable. Only one type of surfactant may be used, or two or more types may be used. Further, different kinds of surfactants may be used in combination, and for example, an anionic surfactant and a nonionic surfactant, or an anionic surfactant and an amphoteric surfactant may be used in combination.

When a surfactant is contained, the amount of the surfactant added [solid content (nonvolatile content)] is, for example, 10 parts by mass exceeding 0 part by mass with respect to 100 parts by mass of the resin material [solid content (nonvolatile content)]. The lower limit is preferably 0.5 parts by mass, and the upper limit is preferably 8 parts by mass.

The foam base material may contain an arbitrary cross-linking agent in order to improve the strength, heat resistance and moisture resistance of the foam base material. The cross-linking agent is not particularly limited, and either oil-soluble or water-soluble may be used. Examples of the cross-linking agent include epoxy-based, oxazoline-based, isocyanate-based, carbodiimide-based, melamine-based, silicone-based (for example, silane coupling agent, etc.), metal oxide-based, and the like. As the cross-linking agent, only one kind may be used, or two or more kinds may be used. Above all, it is preferable to contain at least an oxazoline-based cross-linking agent.

When a cross-linking agent is contained, the amount of the cross-linking agent added [solid content (nonvolatile content)] is, for example, more than 0 parts by mass and 10 parts by mass or less with respect to 100 parts by mass of the resin material [solid content (nonvolatile content)]. The lower limit is preferably 0.01 parts by mass, and the upper limit is preferably 9 parts by mass.

Further, any thickener may be contained in order to improve the stability of the foamed foam and the film forming property. The thickener is not particularly limited, and examples thereof include acrylic acid-based, urethane-based, and polyvinyl alcohol-based. Of these, polyacrylic acid-based thickeners and urethane-based thickeners are preferable.

When a thickener is contained, the amount of the thickener added [solid content (nonvolatile content)] is, for example, 10 parts by mass exceeding 0 parts by mass with respect to 100 parts by mass of the resin material [solid content (nonvolatile content)]. The lower limit is preferably 0.1 parts by mass, and the upper limit is preferably 5 parts by mass.

Further, any rust preventive may be contained in order to prevent corrosion of the metal member adjacent to the adhesive sheet. As the rust preventive, an azole ring-containing compound is preferable. When the azole ring-containing compound is used, it is possible to achieve both corrosion resistance to metals and adhesion to adherends at a high level. As the rust preventive agent, only one kind may be used, or two or more kinds may be used.

The azole ring-containing compound may be a compound having a 5-membered ring containing one or more nitrogen atoms in the ring, and is, for example, a diazole (imidazole, pyrazole) ring, a triazole ring, a tetrazole ring, an oxazole ring, or an isoxazole. Examples thereof include a ring, a thiazole ring, a compound having an isothazole ring, and the like. These rings may be condensed with an aromatic ring such as a benzene ring to form a fused ring. Examples of the compound having such a fused ring include a compound having a benzimidazole ring, a benzopyrazole ring, a benzotriazole ring, a benzoxazole ring, a benzoisoxazole ring, a benzothiazole ring, or a benzoisothiazole ring.

The azole ring and the condensed ring (benzotriazole ring, benzothiazole ring, etc.) may each have a substituent. Examples of the substituent include an alkyl group having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms) such as a methyl group, an ethyl group, a propyl group, an isopropyl group and a butyl group; a methoxy group, an ethoxy group and an isopropyloxy group. An alkoxy group having 1 to 12 carbon atoms (preferably 1 to 3 carbon atoms) such as a group and a butoxy group; an aryl group having 6 to 10 carbon atoms such as a phenyl group, a trill group and a naphthyl group; an amino group; a methylamino group, (Mono or di) C _1-10 alkylamino group such as dimethylamino group; amino-C _1-6 alkyl group such as aminomethyl group and 2-aminoethyl group; N, N-diethylaminomethyl group, N, N- Mono or di (C _1-10 alkyl) amino-C _1-6 alkyl group such as bis (2-ethylhexyl) aminomethyl group; mercapto group; alkoxycarbonyl with 1 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group Group; carboxy group; carboxy-C _1-6 alkyl group such as carboxymethyl group; carboxy-C _1-6 alkylthio group such as 2-carboxyethylthio group; N, N-bis (hydroxymethyl) aminomethyl group and the like N, N-bis (hydroxy-C _1-4 alkyl) amino-C _1-4 alkyl group; sulfo group and the like can be mentioned. Further, the azole ring-containing compound may form a salt such as a sodium salt or a potassium salt.

From the viewpoint of rust-preventive action against metals, compounds in which the azole ring forms a fused ring with an aromatic ring such as a benzene ring are preferable, and among them, benzotriazole-based compounds (compounds having a benzotriazole ring) and benzothiazole-based compounds (compounds having a benzotriazole ring). Compounds having a benzothiazole ring) are particularly preferred.

Examples of the benzotriazole-based compound include 1,2,3-benzotriazole, methylbenzotriazole, carboxybenzotriazole, carboxymethylbenzotriazole, and 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole. , 1- [N, N-bis (2-ethylhexyl) aminomethyl] methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl) methyl] imino] bisethanol, or these Examples include sodium salts.

Examples of the benzothiazole-based compound include 2-mercaptobenzothiazole, 3- (2- (benzothiazolyl) thio) propionic acid, and sodium salts thereof.

When a rust preventive is contained, the amount of the rust preventive (for example, the above-mentioned azole ring-containing compound) [solid content (nonvolatile content)] added [solid content (nonvolatile content)] is within a range that does not impair the original characteristics of the foam. However, for example, 0.2 to 5 parts by mass is preferable with respect to 100 parts by mass of the resin material [solid content (nonvolatile content)]. The lower limit is more preferably 0.3 parts by mass, still more preferably 0.4 parts by mass, and the upper limit is more preferably 3 parts by mass, still more preferably 2 parts by mass.

The foam substrate preferably contains a colorant such as a pigment or a dye. Examples of the colorant include a black colorant. When a black colorant is included, the light-shielding property of the adhesive sheet is further improved. Examples of the black colorant include carbon black (furness black, channel black, acetylene black, thermal black, lamp black, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, and activated carbon. , Ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, composite oxide-based black dye, and the like.

The foam base material has an L ^* (brightness) defined by the L ^* a ^* b ^* color system, preferably 35 or less (0 to 35), and more preferably 30 or less (from the viewpoint of excellent light-shielding property). 0 to 30). It should be noted that a ^* and b ^* defined by the L ^* a ^* b ^* color system can be appropriately selected according to the value of L ^* , respectively. For a ^* and b ^* , for example, both are preferably in the range of -10 to 10 (particularly -5 to 5), and both are 0 or almost 0 (particularly -2.5 to 2.5). Range) is more preferable.

In the present specification, L ^* , a ^* , and b ^* defined by the L ^* a ^* b ^* color system are, for example, a color difference meter (trade name "CR-200", manufactured by Minolta Co., Ltd .; color difference). It is obtained by measuring using a meter). The L ^* a ^* b ^* color system is a color space recommended by the International Commission on Illumination (CIE) in 1976, and is a color space called the CIE1976 (L ^* a ^* b ^* ) color system. It means that. The L ^* a ^* b ^* color system is defined in JIS Z8729 in the Japanese Industrial Standards.

The foam substrate may contain any suitable other component as long as the shock absorption is not impaired. As such other components, only one kind may be used, or two or more kinds may be used. Examples of the other components include polymer components other than the above, softeners, antioxidants, antioxidants, gelling agents, curing agents, plasticizers, fillers, reinforcing agents, foaming agents, flame retardants, and photostabilizing agents. Examples thereof include agents, ultraviolet absorbers, pH adjusters, solvents (organic solvents), thermal polymerization initiators, photopolymerization initiators and the like.

The foam base material can be produced by subjecting a resin composition containing a constituent resin material to foam molding. As the foaming method (method for forming bubbles), a method usually used for foam molding such as a physical method and a chemical method can be adopted. That is, the foam base material may be a foam (physical foam) formed by foaming by a physical method, or a foam (chemical foam) formed by foaming by a chemical method. May be. Generally, the physical method is one in which a gas component such as air or nitrogen is dispersed in a polymer solution to form bubbles by mechanical mixing (mechanical foam). Further, the chemical method is a method of forming a cell by a gas generated by thermal decomposition of a foaming agent added to a polymer base to obtain a foam. From the viewpoint of environmental problems, the physical method is preferable. Bubbles formed by physical methods are often open bubbles.

As the resin composition containing the resin material to be subjected to foam molding, a resin solution in which the resin material is dissolved in a solvent may be used, but from the viewpoint of air bubble property, an emulsion containing the resin material is preferably used. That is, the foam base material is preferably a foam of an emulsion resin composition. As the emulsion, two or more kinds of emulsions may be blended and used. Further, the resin composition may be stored as a resin composition containing no cross-linking agent and may be mixed with the cross-linking agent immediately before being subjected to foam molding.

The solid content concentration of the emulsion is preferably high from the viewpoint of film forming property. The solid content concentration of the emulsion is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more.

The foam base material is preferably one in which a foam is produced through a step of mechanically foaming the emulsion resin composition to foam it. That is, the foam base material is preferably a mechanical foam of an emulsion resin composition. The foaming device is not particularly limited, and examples thereof include devices such as a high-speed shearing method, a vibration method, and a pressurized gas discharge method. Among these, the high-speed shearing method is preferable from the viewpoint of miniaturizing the bubble diameter and producing a large capacity.

The bubbles when foamed by mechanical stirring are those in which a gas is incorporated into the emulsion. The gas is not particularly limited as long as it is inert to the emulsion, and examples thereof include air, nitrogen, and carbon dioxide. Above all, air is preferable from the viewpoint of economy.

The foam base material can be obtained by subjecting the emulsion resin composition foamed by the above method to a base material and drying the base material. The base material is not particularly limited, and examples thereof include a peel-treated plastic film (peeling-treated polyethylene terephthalate film and the like), a plastic film (polyethylene terephthalate film and the like), a heat conductive layer and the like.

The foam base material may have a surface layer formed by heat-melting the surface. The surface layer is a layer (bulk) having no bubbles, and is integrally formed with the layer having bubbles. The surface layer can be formed by foaming the resin composition to obtain a foam (sheet-like foam) and then heat-melting the surface of the foam. By melting the surface in the thickness direction in this way, the thickness of the foam base material can be adjusted to be thin and the density can be adjusted, the impact absorption rate can be increased, and the compression set can be reduced. can. Furthermore, the surface roughness (thickness error) is reduced, and the thickness accuracy is improved.

The foam base material preferably has the surface layer on at least one surface, and more preferably on both sides. It is preferable that the surface layer is provided on the entire surface of the foam base material on which it is formed, that is, the entire surface is heat-melted. The heat melting treatment may be performed twice or more on the same surface. The heat-melting treatment may be performed on the surface of the foam substrate on which the pressure-sensitive adhesive layer is not provided, after the pressure-sensitive adhesive layer is provided.

Examples of the heat-melting treatment include a pressing treatment using a hot roll, a laser irradiation treatment, a contact melting treatment on a heated roll, and a frame treatment. In the case of a press process using a heat roll, the process can be performed using a heat laminator or the like. Examples of the material of the thermal roll include rubber, metal, and a fluororesin. The temperature during the heat-melting treatment is not particularly limited, but is preferably a temperature 15 ° C. lower (more preferably 12 ° C. lower) than the softening point or melting point of the resin constituting the foam substrate, and is also preferable. It is preferably 20 ° C. higher (more preferably 10 ° C. higher) or lower than the softening point or melting point of the resin constituting the foam substrate. Further, when the heat-melting treatment is performed in a state where the pressure-sensitive adhesive layers are laminated, the temperature at the time of the heat-melting treatment may be 40 ° C. or higher than the softening point or the melting point of the resin constituting the foam substrate. preferable. The treatment time of the heat-melting treatment depends on the treatment temperature, but is preferably about 0.1 seconds to 10 seconds, preferably about 0.5 seconds to 7 seconds, for example.

Examples of the device for performing the heat melting treatment include a continuous treatment device in which a heating roll and a cooling roll are provided so that the roll surfaces face each other and the gap between the two rolls can be adjusted. For example, the foam unwound from the feeding roll is passed through the gap between the heating roll and the cooling roll by the continuous processing apparatus, and the contact melting treatment is performed by the heating roll, and one surface of the foam is heat-melted while being heat-melted. By cooling the other surface, the foam base material having the surface layer formed on the one surface is wound by a take-up roll. When a foam base material having the surface layers on both sides is obtained, the other surface of the foam base material can also be subjected to the heat melting treatment in the same manner as described above.

The surface of the foam base material on the side provided with the pressure-sensitive adhesive layer is, for example, corona discharge treatment, plasma treatment, sand mat processing treatment, ozone exposure treatment, for the purpose of improving adhesion and retention with the pressure-sensitive adhesive layer. Physical treatments such as flame exposure treatment, high piezoelectric shock exposure treatment, ionizing radiation treatment; chemical treatments such as chromium acid treatment; surface treatments such as easy adhesion treatment with a coating agent (undercoating agent) may be performed. It is preferable that the surface treatment for enhancing the adhesion is applied to the entire surface of the foam base material on the pressure-sensitive adhesive layer side.

(Adhesive layer)
The elastic modulus of the pressure-sensitive adhesive layer at 23 ° C. is preferably 200 kPa or less, more preferably 150 kPa or less, still more preferably 100 kPa or less. The elastic modulus may be, for example, 10 kPa or more, 30 kPa or more, or 40 kPa or more. When the elastic modulus is 200 kPa or less, the pressure-sensitive adhesive layer has sufficient flexibility, and the bending resistance of the pressure-sensitive adhesive sheet is further excellent. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, the elastic modulus of each of the pressure-sensitive adhesive layers on both sides is preferably within the above range from the viewpoint of better bending resistance of the pressure-sensitive adhesive sheet. The elastic modulus is obtained by the following elastic modulus measurement test.
<Elastic modulus measurement test>
The adhesive layers are superposed to a thickness of about 2 mm to prepare a sheet-shaped test sample. Then, this test sample is punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and while applying shear strain at a frequency of 1 Hz using a viscoelasticity tester, the temperature range is −70 to 150 ° C., 5 ° C./min. The viscoelasticity is measured in the shear mode at the rate of temperature rise, and the elastic modulus at 23 ° C. is obtained.

The pressure-sensitive adhesive layer (the pressure-sensitive adhesive layer provided on one side of the foam base material) may be a single layer or may be a plurality of layers composed of the same or different layers. In the case of a plurality of layers, it is preferable that all the pressure-sensitive adhesive layers satisfy the above elastic modulus.

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive (natural rubber-based, synthetic rubber-based, a mixture thereof, etc.), a silicone-based pressure-sensitive adhesive, and a polyester. Examples thereof include based adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluoroadhesives. Among them, as the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, an acrylic pressure-sensitive adhesive is preferable from the viewpoints of adhesion, weather resistance, cost, and ease of designing the pressure-sensitive adhesive. The pressure-sensitive adhesive layer is preferably an acrylic pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive. As the above-mentioned adhesive, only one kind may be used, or two or more kinds may be used.

The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth) acryloyl group in the molecule) as a monomer component constituting the polymer. That is, the acrylic polymer contains a structural unit derived from the acrylic monomer. The acrylic polymer is preferably a polymer containing a (meth) acrylic acid alkyl ester as a monomer component constituting the polymer. As the acrylic polymer, only one kind may be used, or two or more kinds may be used.

In addition, in this specification, a base polymer means a main component in the polymer component used for a pressure-sensitive adhesive layer, for example, a polymer component contained in excess of 50% by mass. The content ratio of the acrylic polymer in the acrylic pressure-sensitive adhesive layer is preferably 60% by mass or more, more preferably 70% by mass or more, based on 100% by mass of the total amount of the acrylic pressure-sensitive adhesive layer.

The acrylic polymer is preferably a polymer composed (formed) of a (meth) acrylic acid alkyl ester as an essential monomer component. That is, the acrylic polymer preferably contains (meth) acrylic acid alkyl ester as a constituent unit. In addition, in this specification, "(meth) acrylic" means "acrylic" and / or "methacrylic" (one or both of "acrylic" and "methacrylic"), and the same applies to the others. ..

As the above-mentioned (meth) acrylic acid alkyl ester as an essential monomer component, a (meth) acrylic acid alkyl ester having a linear or branched-chain alkyl group is preferably mentioned. As the (meth) acrylic acid alkyl ester, only one kind may be used, or two or more kinds may be used.

The (meth) acrylic acid alkyl ester having a linear or branched alkyl group is not particularly limited, and for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (. Isopropyl acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, (meth) Isopentyl acrylate, (meth) hexyl acrylate, (meth) heptyl acrylate, (meth) octyl acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, (meth) ) Isononyl acrylate, (meth) decyl acrylate, (meth) isodecyl acrylate, (meth) undecyl acrylate, dodecyl (meth) acrylate (lauryl (meth) acrylate), (meth) tridecyl acrylate, (meth) Tetradecyl acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (stearyl (meth) acrylate), isostearyl (meth) acrylate, (meth) acrylic Examples thereof include (meth) acrylic acid alkyl esters having a linear or branched alkyl group having 1 to 20 carbon atoms, such as nonadesyl acid and eicosyl (meth) acrylic acid. Among them, the (meth) acrylic acid alkyl ester having a linear or branched alkyl group has a linear or branched alkyl group having 1 to 18 carbon atoms (preferably 4 to 12) (meth). ) Acrylic acid alkyl ester is preferable.

The proportion of the (meth) acrylic acid alkyl ester in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is not particularly limited, but is 50% by mass or more (for example, 50 to 100% by mass). It is preferable, more preferably 70% by mass or more, still more preferably 85% by mass or more, and particularly preferably 90% by mass or more. The above ratio is preferably less than 100% by mass, more preferably 99.5% by mass or less, still more preferably 98% by mass or less, and particularly preferably 97% by mass or less. When the above ratio is within the above range, a pressure-sensitive adhesive layer having a good quantitative balance with the copolymerizable monomer and having good adhesion even if it is thin can be formed.

The acrylic polymer may contain a copolymerizable monomer together with the (meth) acrylic acid alkyl ester as a monomer component constituting the polymer. That is, the acrylic polymer may contain a copolymerizable monomer as a constituent unit. As the copolymerizable monomer, only one kind may be used, or two or more kinds may be used.

As the copolymerizable monomer, a carboxy group-containing monomer and / or an acid anhydride monomer is preferable from the viewpoint of being able to form a pressure-sensitive adhesive layer having good adhesion even if it is thin. Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomer include maleic anhydride and itaconic anhydride.

The ratio of the carboxy group-containing monomer and / or the acid anhydride monomer to the total amount of 100% by mass of the total monomer components constituting the acrylic polymer is not particularly limited, but is preferably 0.2% by mass or more. , More preferably 0.5% by mass or more, still more preferably 1% by mass or more, and particularly preferably 2% by mass or more. The above ratio is preferably 15% by mass or less, more preferably 12% by mass or less, still more preferably 10% by mass or less, and particularly preferably 7% by mass or less. When the above ratio is within the above range, a pressure-sensitive adhesive layer having a good quantitative balance with the (meth) acrylic acid alkyl ester and having good adhesion even if it is thin can be formed.

The copolymerizable monomer may further contain a functional group-containing monomer for the purpose of introducing a cross-linking point into the acrylic polymer or enhancing the cohesive force of the acrylic polymer. Examples of the functional group-containing monomer include a hydroxy group-containing monomer, an epoxy group-containing monomer, a nitrogen atom-containing monomer, a keto group-containing monomer, an alkoxysilyl group-containing monomer, a sulfonic acid group-containing monomer, and a phosphoric acid group-containing monomer. Of these, hydroxy group-containing monomers and nitrogen atom-containing monomers are preferable. As the functional group-containing monomer, only one kind may be used, or two or more kinds may be used.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. 6-Hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, methyl (4-hydroxymethylcyclohexyl) methyl (meth) ) Hydroxyalkyl (meth) acrylates such as acrylates; unsaturated alcohols such as vinyl alcohols and allyl alcohols; polypropylene glycol mono (meth) acrylates and the like.

Examples of the epoxy group-containing monomer include glycidyl group-containing monomers such as (meth) glycidyl acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether.

Examples of the nitrogen atom-containing monomer include an amide group-containing monomer, an amino group-containing monomer, a cyano group-containing monomer, and a monomer having a nitrogen atom-containing ring. Examples of the amide group-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, and N. -Mestermethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide and the like can be mentioned. Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate. Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile. Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, and N-vinylpyrazine. , N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholin, N-vinylcaprolacttam, N- (meth) acryloylmorpholin and the like.

Examples of the keto group-containing monomer include diacetone (meth) acrylamide, diacetone (meth) acrylate, vinylmethyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate and the like.

Examples of the alkoxysilyl group-containing monomer include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, and 3-( Meta) Acryloxypropylmethyldiethoxysilane and the like can be mentioned.

Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methyl propane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth). ) Acryloyloxynaphthalene sulfonic acid and the like can be mentioned.

Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloyl phosphate and the like.

The proportion of the functional group-containing monomer in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer is, for example, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, and 5% by mass. % Or more, and may be 10% by mass or more. The above ratio may be, for example, 40% by mass or less, 20% by mass or less, or may not be substantially contained. In addition, in this specification, "substantially not contained" means that it is unintentionally contained, for example, when it is unavoidably mixed, rather than being positively blended, for example, 0.05% by mass or less. It is 0.01% by mass or less.

The copolymerizable monomer may further contain other monomers. Examples of the other monomers include vinyl ester-based monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; cyclohexyl (meth). ) Cycloalkyl (meth) acrylates such as acrylates, cyclopentyl (meth) acrylates, dicyclopentanyl (meth) acrylates, isobornyl (meth) acrylates; aryl (meth) acrylates (eg, phenyl (meth) acrylates), aryloxyalkyl ( Aromatic ring-containing (meth) acrylates such as meth) acrylates (eg phenoxyethyl (meth) acrylates), arylalkyl (meth) acrylates (eg benzyl (meth) acrylates); Olefin-based monomer; Chlorine-containing monomer such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomer such as 2- (meth) acryloyloxyethyl isocyanate; alkoxy group-containing monomer such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate. ; Examples include vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether.

The ratio of the other monomers in the total amount of 100% by mass of all the monomer components constituting the acrylic polymer may be, for example, 0.05% by mass or more and 0.5% by mass or more. The above ratio may be, for example, 20% by mass or less, 10% by mass or less, 5% by mass or less, and may not be substantially contained.

In order to form a crosslinked structure in the polymer skeleton, the acrylic polymer may contain a polyfunctional monomer copolymerizable with the monomer component forming the acrylic polymer as a monomer component constituting the polymer. .. Examples of the polyfunctional monomer include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and penta. Elythritol di (meth) acrylate, trimethylolpropantri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy (meth) acrylate (eg, polyglycidyl (meth) acrylate), polyester Examples thereof include monomers having a (meth) acryloyl group and other reactive functional groups in the molecule such as (meth) acrylate and urethane (meth) acrylate. As the polyfunctional monomer, only one kind may be used, or two or more kinds may be used. The polyfunctional monomer exerts the same function as the cross-linking agent described later, and may also correspond to the cross-linking agent.

The base polymer such as the acrylic polymer contained in the pressure-sensitive adhesive layer can be obtained by polymerizing a monomer component. The polymerization method is not particularly limited, and examples thereof include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a polymerization method by irradiation with active energy rays (active energy ray polymerization method). Among them, a solution polymerization method and an active energy ray polymerization method are preferable, and a solution polymerization method is more preferable, from the viewpoints of transparency and cost of the pressure-sensitive adhesive layer.

Further, various general solvents may be used for the polymerization of the above-mentioned monomer components. Examples of the solvent include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane, methylcyclohexane and the like. Hydrocarbons of the above; organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone can be mentioned. As the solvent, only one kind may be used, or two or more kinds may be used.

In the polymerization of the above-mentioned monomer components, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) may be used depending on the type of the polymerization reaction. As the polymerization initiator, only one kind may be used, or two or more kinds may be used.

The thermal polymerization initiator is not particularly limited, but is, for example, a persulfate such as an azo-based polymerization initiator, a peroxide-based polymerization initiator (for example, dibenzoyl peroxide, tert-butyl permalate, potassium persulfate, etc.). , Benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane-based initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox-based polymerization initiators, and the like. Of these, the azo-based polymerization initiator disclosed in JP-A-2002-69411 is preferable. Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile (hereinafter, may be referred to as "AIBN"), 2,2'-azobis-2-methylbutyronitrile, and 2,2. ′ -Azobis (2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovalerian acid and the like can be mentioned. The amount of the thermal polymerization initiator used may be a normal amount, and is selected from, for example, 0.005 to 1 part by mass, preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the monomer component. can do.

The photopolymerization initiator is not particularly limited, and is, for example, a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, and light. Examples thereof include an active oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. In addition, acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators can be mentioned. Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and the like. Anisole methyl ether and the like can be mentioned. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). ) Dichloroacetophenone and the like. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one, and the like. Be done. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalene sulfonyl chloride and the like. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (O-ethoxycarbonyl) -oxime. Examples of the benzoin-based photopolymerization initiator include benzoin and the like. Examples of the benzyl-based photopolymerization initiator include benzyl and the like. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenylketone and the like. Examples of the ketal-based photopolymerization initiator include benzyldimethyl ketal and the like. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphinoxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphin oxide and the like. .. Examples of the titanium-based photopolymerization initiator include bis (η ^5-2,4 -cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-yl) -phenyl. ) Titanium and the like. The amount of the photopolymerization initiator used may be a normal amount, for example, in the range of 0.01 to 3 parts by mass, preferably 0.1 to 1.5 parts by mass with respect to 100 parts by mass of the monomer component. You can choose from.

The pressure-sensitive adhesive layer may contain a pressure-sensitive adhesive resin. When the tackifier resin is included, the pressure-sensitive adhesive layer tends to have better adhesion even if it is thin. When the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer and a pressure-sensitive adhesive resin, it has excellent adhesion to an adherend and is more difficult to peel off.

Examples of the pressure-sensitive adhesive resin include phenol-based pressure-sensitive adhesive resin, terpene-based pressure-sensitive adhesive resin, rosin-based pressure-sensitive adhesive resin, hydrocarbon-based pressure-sensitive adhesive resin, epoxy-based pressure-sensitive adhesive resin, polyamide-based pressure-sensitive adhesive resin, and elastomer-based pressure-sensitive adhesive resin. Examples thereof include resins and ketone adhesive-imparting resins. In addition, examples of the tackifier resin include low polymers of (meth) acrylic acid alkyl esters such as low polymers of dicyclopentanyl methacrylate (DCPMA) and methyl methacrylate (MMA). As the tackifier resin, only one kind may be used, or two or more kinds may be used.

Examples of the phenol-based tackifier resin include terpene phenol resin, hydrogenated terpene phenol resin, alkylphenol resin, and rosin phenol resin. The terpene phenol resin is a polymer containing terpene residues and phenol residues, and can be a copolymer of terpene and a phenol compound (terpene-phenol copolymer resin), a homopolymer or a copolymer of terpene. Examples thereof include phenol-modified ones (phenol-modified terpene resin). Examples of terpenes constituting the terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (d-form, l-form, d / l-form (dipentene), etc.). The hydrogenated terpene phenol resin is a resin having a structure obtained by hydrogenating the terpene phenol resin. The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include novolak type and resol type. The above-mentioned rosin phenol resin is a phenol-modified product of rosins or various rosin derivatives described later. The rosin phenol resin can be obtained, for example, by adding phenol to rosins or various rosin derivatives described below with an acid catalyst and thermally polymerizing the resin.

Examples of the terpene-based tackifier resin include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. The polymer of the above terpenes may be a homopolymer of one kind of terpenes, or may be a copolymer of two or more kinds of terpenes. Examples of the homopolymer of a kind of terpenes include α-pinene polymer, β-pinene polymer, dipentene polymer and the like. The modified terpene-based tackifier resin is a modified version of the terpene resin (modified terpene resin). Examples of the modified terpene resin include styrene-modified terpene resin and hydrogenated terpene resin.

Examples of the rosin-based tackifier resin include rosins and rosin derivative resins. Examples of the rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosins, Disproportionate rosins, polymerized rosins, other chemically modified rosins, etc.) and the like. Examples of the rosin derivative resin include derivatives of the rosins. Examples of the rosin derivative resin include unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; rosin esters are unsaturated. Unsaturated fatty acid-modified rosins modified with fatty acids; unsaturated fatty acid-modified rosin esters modified with unsaturated fatty acids from rosin esters; rosin alcohols obtained by reducing the carboxy group of rosins or the above-mentioned various rosin derivatives; rosins Alternatively, metal salts of the above-mentioned various rosin derivatives can be mentioned. Specific examples of the above rosin esters include unmodified rosin or methyl ester of modified rosin, triethylene glycol ester, glycerin ester, pentaerythritol ester and the like.

Examples of the hydrocarbon-based tackifier resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, and aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.). , Aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, kumaron resins, kumaron inden resins and the like.

The content of the tackifier resin in the pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 part by mass or more (for example, 1 to 100 parts by mass) with respect to 100 parts by mass of the total amount of the base polymer. Is 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more. When the content is 1 part by mass or more, the pressure-sensitive adhesive layer has even better adhesion even if it is thin. The content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, from the viewpoint of excellent heat-resistant cohesive force.

The pressure-sensitive adhesive layer preferably contains a cross-linking agent. By including the cross-linking agent, for example, the acrylic polymer in the acrylic pressure-sensitive adhesive layer can be cross-linked and the gel fraction can be controlled. As the cross-linking agent, only one kind may be used, or two or more kinds may be used.

The cross-linking agent is not particularly limited, and is, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, a melamine-based cross-linking agent, a peroxide-based cross-linking agent, a urea-based cross-linking agent, a metal alkoxide-based cross-linking agent, and a metal chelate-based cross-linking agent. Agents, metal salt-based cross-linking agents, carbodiimide-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, amine-based cross-linking agents, hydrazine-based cross-linking agents, silicone-based cross-linking agents, silane-based cross-linking agents (silane coupling agents), etc. Can be mentioned.

The content of the cross-linking agent in the pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, based on 100 parts by mass of the total amount of the base polymer. Parts, particularly preferably 0.5 to 10 parts by mass.

The isocyanate-based cross-linking agent is a compound (polyfunctional isocyanate compound) having an average of two or more isocyanate groups per molecule. Examples of the isocyanate-based cross-linking agent include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Examples of the aliphatic polyisocyanates include 1,2-ethylene diisocyanate; 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, 1,4-tetramethylene diisocyanate and other tetramethylene diisocyanates; 1,2. -Hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; Examples thereof include 2-methyl-1,5-pentanediisocyanate, 3-methyl-1,5-pentanediisocyanate and lysine diisocyanate.

Examples of the alicyclic polyisocyanates include isophorone diisocyanates; 1,2-cyclohexyldiisocyanates, 1,3-cyclohexyldiisocyanates, 1,4-cyclohexyldiisocyanates and other cyclohexyldiisocyanates; 1,2-cyclopentyldiisocyanates, 1,3. -Cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and the like.

Examples of the aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate. , 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate , 4,4'-Diphenylpropane diisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate , Xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate and the like.

Examples of the isocyanate-based cross-linking agent include trimethylolpropane / tolylene diisocyanate adduct (trade name “Coronate L”, manufactured by Toso Co., Ltd.) and trimethylolpropane / hexamethylene diisocyanate adduct (trade name “Coronate HL”). , Tosoh Co., Ltd.), trimethylolpropane / xylylene diisocyanate adduct (trade name "Takenate D-110N", manufactured by Mitsui Chemicals Co., Ltd.) and the like.

The water dispersion of the modified acrylic polymer produced by emulsion polymerization does not need to use an isocyanate-based cross-linking agent, but if necessary, it easily reacts with water, so that it is blocked by isocyanate-based cross-linking. Agents can also be used.

When an isocyanate-based cross-linking agent is used as the cross-linking agent, the content of the isocyanate-based cross-linking agent is not particularly limited, but is preferably 0.5 parts by mass or more, more preferably 0.5 part by mass with respect to 100 parts by mass of the total amount of the base polymer. Is 1 part by mass or more, more preferably 1.5 parts by mass or more. The content is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass or less.

Examples of the epoxy-based cross-linking agent (polyfunctional epoxy compound) include N, N, N', N'-tetraglycidyl-m-xylene diamine, diglycidyl aniline, and 1,3-bis (N, N-diglycidyl). Aminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether , Gglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris (2) -Hydroxyethyl) isocyanurate, resorcin diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy-based resins having two or more epoxy groups in the molecule can be mentioned. Further, examples of the epoxy-based cross-linking agent include commercially available products such as the trade name "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.).

When an epoxy-based cross-linking agent is used as the cross-linking agent, the content of the epoxy-based cross-linking agent is not particularly limited, but is more than 0 parts by mass and 1 part by mass or less with respect to 100 parts by mass of the total amount of the base polymer. It is preferable, more preferably 0.001 to 0.5 part by mass, still more preferably 0.002 to 0.2 part by mass, still more preferably 0.005 to 0.1 part by mass, and particularly preferably 0.008 to 0 part. 05 parts by mass.

The peroxide-based cross-linking agent can be appropriately used as long as it generates radically active species by heat to promote cross-linking of the base polymer, but in consideration of workability and stability, it is halved for 1 minute. It is preferable to use a peroxide having a period temperature of 80 to 160 ° C, and more preferably to use a peroxide having a period temperature of 90 to 140 ° C.

Examples of the peroxide-based cross-linking agent include di (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature: 90.6 ° C.) and di (4-t-butylcyclohexyl) peroxydicarbonate (1). Minute half-life temperature: 92.1 ° C., di-sec-butylperoxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butylperoxyneodecanoate (1 minute half-life temperature: 103) .5 ° C), t-hexyl peroxypivalate (1 minute half-life temperature: 109.1 ° C), t-butyl peroxypivalate (1 minute half-life temperature: 110.3 ° C), dilauroyl peroxide (1 minute half-life temperature: 110.3 ° C) 1 minute half temperature: 116.4 ° C), di-n-octanoyl peroxide (1 minute half temperature: 117.4 ° C), 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanoate (1 minute half-life temperature: 124.3 ° C.), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C.), dibenzoyl peroxide (1 minute half-life temperature: 130. 0 ° C.), t-butyl peroxyisobutyrate (1 minute half-life temperature: 136.1 ° C.), 1,1-di (t-hexyl peroxy) cyclohexane (1 minute half-life temperature: 149.2 ° C.) And so on.

The half-life of the peroxide-based cross-linking agent is an index showing the decomposition rate of the peroxide, and means the time until the residual amount of the peroxide is halved. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in the manufacturer's catalog, etc. For example, "Organic Peroxide Catalog 9th Edition" of Nichiyu Co., Ltd. (May 2003) ”and so on. As a method for measuring the amount of peroxide decomposition remaining after the reaction treatment, for example, HPLC (high performance liquid chromatography) can be used. More specifically, for example, about 0.2 g of the pressure-sensitive adhesive after the reaction treatment is taken out, immersed in 10 ml of ethyl acetate, extracted by shaking at 120 rpm for 3 hours at 25 ° C. with a shaker, and then 3 at room temperature. Let stand for a day. Next, 10 ml of acetonitrile was added, and the mixture was shaken at 120 rpm for 30 minutes at 25 ° C., and about 10 μl of the extract obtained by filtering with a membrane filter (0.45 μm) was injected into HPLC for analysis. It can be the amount of peroxide.

When a peroxide-based cross-linking agent is used as the cross-linking agent, the content of the cross-linking agent is not particularly limited, but is preferably 2 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the acrylic polymer. Is 0.02 to 2 parts by mass, more preferably 0.05 to 1 part by mass.

Further, as the above-mentioned cross-linking agent, an organic cross-linking agent or a polyfunctional metal chelate may be used in combination. A polyfunctional metal chelate is one in which a polyvalent metal is covalently or coordinated to an organic compound. Examples of the polyvalent metal atom include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti and the like. Can be mentioned. Examples of the atom in the organic compound having a covalent bond or a coordination bond include an oxygen atom, and examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound.

The cross-linking agent preferably contains an isocyanate-based cross-linking agent. Further, it is more preferable to contain another cross-linking agent together with the isocyanate-based cross-linking agent. As the above-mentioned other cross-linking agent, an epoxy-based cross-linking agent is preferable. When such a cross-linking agent is used, a pressure-sensitive adhesive layer having a thinner but more excellent adhesion can be obtained by the combination with the above-mentioned acrylic polymer (particularly, the combination with the above-mentioned preferable acrylic-based polymer).

The pressure-sensitive adhesive layer may further include a cross-linking accelerator, an antioxidant, a filler (organic filler, inorganic filler, etc.), a colorant (pigment, dye, etc.), an antioxidant, a plasticizer, and the like. Additives such as softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, granules, foils, and rust preventives are the effects of the present invention. May be contained within a range that does not impair. As the above-mentioned additives, only one kind may be used, or two or more kinds may be used.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 to 90 μm, more preferably 3 to 50 μm. The thickness of the pressure-sensitive adhesive layer is the thickness of the pressure-sensitive adhesive layer on one side when the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet. When the thickness is 1 μm or more, the adhesiveness of the adhesive sheet becomes higher. When the thickness is 90 μm or less, the thickness of the adhesive sheet can be further reduced.

The method for producing the pressure-sensitive adhesive layer is not particularly limited, but is obtained by, for example, applying (coating) a pressure-sensitive adhesive (adhesive composition) containing the base polymer onto the foam base material or the release liner. The pressure-sensitive adhesive composition layer is dried and cured, or the pressure-sensitive adhesive composition is applied (coated) on a foam substrate or a release liner, and the obtained pressure-sensitive adhesive composition layer is irradiated with active energy rays. Curing is mentioned. Further, if necessary, it may be further heated and dried.

Examples of the active energy rays include ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, and electron beams, ultraviolet rays, and the like, and ultraviolet rays are particularly preferable. Further, the irradiation energy of the active energy ray, the irradiation time, the irradiation method, and the like are not particularly limited.

The pressure-sensitive adhesive composition can be produced by a known or conventional method. For example, a solvent-type pressure-sensitive adhesive composition can be prepared by mixing an additive with a solution containing the base polymer, if necessary. When the base polymer is an acrylic polymer, for example, an active energy ray-curable pressure-sensitive adhesive composition is added to a mixture of monomer components constituting the acrylic polymer or a partial polymer thereof, if necessary. It can be produced by mixing the agents.

A known coating method may be used for applying (coating) the pressure-sensitive adhesive composition. For example, a coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, or a direct coater may be used.

The heat-drying temperature of the solvent-type pressure-sensitive adhesive composition is preferably 40 to 200 ° C, more preferably 50 to 180 ° C, and even more preferably 70 to 170 ° C. As the drying time, an appropriate time may be adopted as appropriate, but it is, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

When the acrylic pressure-sensitive adhesive layer is formed by irradiation with active energy rays, the acrylic-based polymer can be produced from the monomer component and the pressure-sensitive adhesive layer can be formed. As the monomer component, a syrup can be used which is partially polymerized in advance for irradiation with active energy rays. A high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, or the like can be used for ultraviolet irradiation.

The pressure-sensitive adhesive sheet can be manufactured according to a known or conventional manufacturing method. The pressure-sensitive adhesive sheet may be obtained by directly forming the pressure-sensitive adhesive layer on the surface of the foam base material (direct copying method), or once the pressure-sensitive adhesive layer is formed on a release liner, the foam base material is formed. It may be obtained by providing the pressure-sensitive adhesive layer on the foam base material by transferring (bonding) to (transfer method).

The total thickness of the pressure-sensitive adhesive sheet is, for example, 50 to 1000 μm, preferably 70 to 500 μm, more preferably 100 to 350 μm, and further preferably 150 to 320 μm. In the present specification, the "total thickness of the pressure-sensitive adhesive sheet" means from the surface of the single-sided pressure-sensitive adhesive sheet on the side where the pressure-sensitive adhesive layer of the foam base material is not provided to the pressure-sensitive surface of the pressure-sensitive adhesive layer. The thickness refers to the thickness from the adhesive surface of one adhesive layer to the adhesive surface of the other adhesive layer beyond the foam substrate in the case of a double-sided adhesive sheet, which is the thickness of the release liner described later. Does not include.

The pressure-sensitive adhesive sheet may be provided with another layer (for example, an intermediate layer, an undercoat layer, etc.) as long as the effect of the present invention is not impaired. For example, another layer may be provided between the foam base material and the pressure-sensitive adhesive layer. However, from the viewpoint of excellent bending resistance of the pressure-sensitive adhesive sheet, it is preferable that no other resin layer is provided between the foam base material and the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive sheet may be provided with a release liner on the surface (adhesive surface) of the pressure-sensitive adhesive layer until use. When the adhesive sheet is a double-sided adhesive sheet, each adhesive surface may be protected by two release liners, or may be rolled by one release liner having both sides as release surfaces. It may be protected in a wound form (rolled body). The peeling liner is used as a protective material for the adhesive layer and is peeled off when it is attached to the adherend. The release liner does not necessarily have to be provided.

As the release liner, a conventional release paper or the like can be used, and the release liner is not particularly limited. And so on. Examples of the base material having the peeling treatment layer include a plastic film and paper surface-treated with a peeling treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, and molybdenum sulfide. Examples of the fluoropolymer in the low adhesive substrate made of the fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylfluorofluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chloro. Examples thereof include a fluoroethylene-vinylidene fluoride copolymer. In addition, examples of the non-polar polymer include olefin resins (for example, polyethylene, polypropylene, etc.). The release liner can be formed by a known or conventional method. Further, the thickness of the release liner is not particularly limited. Further, in the present specification, the release liner is not included in the pressure-sensitive adhesive sheet.

Since the adhesive sheet is excellent in impact resistance and light shielding property, it is used, for example, when attaching (attaching) various members or parts to a predetermined part (for example, a housing) in an optical member such as an electric / electronic device. It is preferable to be In addition, "electrical electronic device" means a device corresponding to at least one of an electric device or an electronic device. Examples of the electric / electronic device include an image display device such as a liquid crystal display, an electroluminescence display, and a plasma display, and a portable electronic device. It is particularly preferable that the adhesive sheet is used by being bonded to an internal member of an optical member (particularly, an electric / electronic device). When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the pressure-sensitive adhesive sheet is used for fixing an internal member of an optical member (particularly, an electric / electronic device). Examples of the image display device include an image display device in the portable electronic device, a display inside and outside a vehicle such as a train or a bus (roll display), and the like.

The portable electronic devices include, for example, mobile phones, smartphones, tablet personal computers, notebook personal computers, various wearable devices (for example, wristwear type worn on the wrist like a wristwatch, clips, straps, etc.) on a part of the body. Modular type to be worn, eyewear type including glasses type (monocular type and binocular type, including head mount type), clothes type to be attached to shirts, socks, hats, etc. in the form of accessories, ears like earphones (Earwear type, etc.), digital cameras, digital video cameras, acoustic devices (portable music players, IC recorders, etc.), computers (computers, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, etc. Examples include mobile radios, mobile TVs, mobile printers, mobile scanners, and mobile modems. In addition, in the present specification, "portable" means that it is not enough to be portable, but to have a level of portability that an individual (standard adult) can carry relatively easily. It shall mean. The pressure-sensitive adhesive sheet is used, for example, so that the pressure-sensitive adhesive layer adheres to the member of the portable electronic device.

Since the adhesive sheet has excellent bending resistance, it is preferably used in a portion where it is repeatedly bent and used. Further, since the pressure-sensitive adhesive sheet is excellent in shock absorption, it is preferable to use it in a portion where shock absorption is required. Therefore, the adhesive sheet is a member in an electric / electronic device that is used by being folded, for example, an electric / electronic device having a foldable image display device (flexible display) (particularly, a foldable image display device (foldable display)). It is preferably used for bonding (particularly between members). Examples of the usage mode of the adhesive sheet in the flexible display include bonding between members at bending points, a shock absorbing sheet arranged in a housing (for example, the back surface of the display), and the like. Further, since the adhesive sheet is also excellent in light-shielding property, it can be preferably applied to the back surface of the display when the display is an OLED display.

In the shock absorbing sheet arranged on the back surface of the display, for example, when the adhesive sheet is a double-sided adhesive sheet, one adhesive layer is on the inner surface of the housing (inner surface on the back side) and the other adhesive layer is on the back surface of the display. They are used by pasting them together. When the adhesive sheet is a single-sided adhesive sheet, the adhesive layer may be attached to either the inner surface of the housing or the back surface of the display, but it is preferable to attach the adhesive layer to the inner surface of the housing. Since the adhesive sheet is excellent in impact resistance, bending resistance, and light shielding property, when the adhesive sheet is used at a bent part of a flexible display (particularly, a foldable display), it is damaged even if it is repeatedly bent and used. It is difficult and the appearance of the display is excellent.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Production Example 1 (Preparation of Adhesive Layer A)
34.8 parts by mass of dicyclopentanyl methacrylate (DCPMA), 23.3 parts by mass of methyl methacrylate (MMA), 2 parts by mass of 1-thioglycerol as a chain transfer agent, and 38.7 parts by mass of ethyl acetate as a polymerization solvent. Was put into a four-necked flask, and these were stirred at 70 ° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by mass of AIBN as a polymerization initiator was put into a four-necked flask and reacted at 70 ° C. for 2 hours, and then at 80 ° C. for 2 hours. Then, the reaction solution was put into a temperature atmosphere of 130 ° C., and ethyl acetate, a chain transfer agent, and an unreacted monomer were dried and removed to obtain an acrylic oligomer. The acrylic oligomer was diluted equivalently with 2EHA to obtain an oligomer solution.
On the other hand, it is composed of 60 parts by mass of lauryl acrylate (LA), 22 parts by mass of 2-ethylhexyl acrylate (2EHA), 10 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 8 parts by mass of 4-hydroxybutyl acrylate (4HBA). 0.1 part by mass of a photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins B.V.) and a photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins B.V.) are added to the monomer mixture. After blending 0.1 parts by mass, UV irradiation is performed until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reaches about 7 Pa · s, and a part of the above monomer components. Obtained a polymerized prepolymer composition.
Next, in 100 parts by mass of the prepolymer composition, 37 parts by mass of 2EHA, 6 parts by mass of the oligomer solution, 0.08 part by mass of hexanediol diacrylate (HDDA), and a silane coupling agent (trade name "KBM-403"). , Shin-Etsu Chemical Industry Co., Ltd.) 0.3 parts by mass was added and mixed to obtain a pressure-sensitive adhesive composition (pre-curing composition).

The above pressure-sensitive adhesive composition is applied onto a polyethylene terephthalate (PET) -based release liner (trade name "MRF50", manufactured by Mitsubishi Chemical Corporation) so that the final thickness (thickness of the pressure-sensitive adhesive layer) is 25 μm. Then, a coating layer (adhesive composition layer) was formed. Next, a PET-based release liner (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) was provided on the coating layer to coat the coating layer and block oxygen. Then, a laminated body of MRF50 / coating layer (adhesive composition layer) / MRF38 was obtained.
Next, the laminated body was irradiated with ultraviolet rays having an illuminance of 5 mW / cm ² for 300 seconds from the upper surface (MRF38 side) of the laminated body with a black light (manufactured by Toshiba Corporation). Further, a drying treatment was carried out in a dryer at 130 ° C. for 2 minutes to volatilize the residual monomer to form an adhesive layer (adhesive layer A) having a thickness of 25 μm.

Production Example 2 (Preparation of Adhesive Layer B)
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, a dropping funnel, and a stirrer, 70 parts by mass of butyl acrylate, 30 parts by mass of 2-ethylhexyl acrylate, and 3 parts of acrylic acid using 150.9 parts by mass of toluene as a solvent. A part by mass of 4HBA and 0.08 part by mass of AIBN were added to the initiator, and polymerization was carried out at 60 ° C. for 6 hours in a nitrogen stream to obtain a solution of an acrylic polymer.
In this solution, 30 parts by mass of a polymerized rosin ester resin (trade name "Haritac SE10", manufactured by Harima Kasei Group Co., Ltd.) and an isocyanate-based cross-linking agent (trade name "Coronate") are added to 100 parts by mass of the polymer component in the solution. L ”, manufactured by Toso Co., Ltd.) was blended in 3 parts by mass (in terms of solid content) to prepare an acrylic pressure-sensitive adhesive composition.
This acrylic pressure-sensitive adhesive composition was applied onto a silicone-treated release paper using a bar coater and dried at 110 ° C. for 3 minutes to form a pressure-sensitive adhesive layer (adhesive layer B) having a thickness of 25 μm. ..

Production Example 3 (Preparation of Adhesive Layer C)
95 parts by mass of butyl acrylate (BA), 5 parts by mass of acrylic acid, and 233.8 parts by mass of ethyl acetate as a polymerization solvent are put into a four-necked flask, and these are stirred at 70 ° C. for 1 hour under a nitrogen atmosphere. bottom. Next, 0.2 parts by mass of AIBN as a polymerization initiator was put into a four-necked flask and reacted at 70 ° C. for 2 hours, and then reacted at 80 ° C. for 2 hours to obtain an acrylic polymer solution.
On the other hand, 95 parts by mass of cyclohexylmethacrylate (CHMA), 5 parts by mass of acrylic acid, 10 parts by mass of α-methylstyrene dimer as a chain transfer agent, and 118.75 parts by mass of toluene as a polymerization solvent were put into a four-necked flask. Then, these were stirred at 70 ° C. for 1 hour under a nitrogen atmosphere. Next, 10 parts by mass of AIBN as a polymerization initiator was put into a four-necked flask and reacted at 70 ° C. for 2 hours, and then at 80 ° C. for 2 hours. Then, the reaction solution was put into a temperature atmosphere of 130 ° C., and toluene, a chain transfer agent, and an unreacted monomer were dried and removed to obtain an acrylic oligomer.
Next, in the acrylic polymer solution, with respect to 100 parts by mass of the acrylic polymer, 20 parts by mass of the acrylic oligomer, 20 parts by mass of terpenephenol resin (trade name "YS Polystar S145", manufactured by Yasuhara Chemical Co., Ltd.), 3 parts by mass (solid content equivalent) of isocyanate-based cross-linking agent (trade name "Coronate L", manufactured by Toso Co., Ltd.) and epoxy-based cross-linking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemicals Co., Ltd.) are 0. 01 parts by mass (in terms of solid content) was blended to prepare an acrylic pressure-sensitive adhesive composition.
This acrylic pressure-sensitive adhesive composition was applied onto a silicone-treated release paper using a bar coater and dried at 110 ° C. for 3 minutes to form a pressure-sensitive adhesive layer (adhesive layer C) having a thickness of 25 μm. ..

Example 1
By passing the product name "PureCell" (100 μm product, manufactured by Inoac Corporation) through the continuous processing device in which the temperature of the induction heating roll is set to 240 ° C., one side of each surface is sequentially melted by heat. A urethane-based foam sheet (foam base material A) having a semi-independent semi-continuous structure having a thickness of 80 μm and a density of 0.55 g / cm ³ was obtained by heat-melting treatment on both sides.

One of the release liners is peeled off from the pressure-sensitive adhesive layer A obtained in Production Example 1, and the foam base material A obtained above is attached to the exposed pressure-sensitive adhesive layer A. A single-sided pressure-sensitive adhesive sheet having a layer structure of the foam base material A] was produced. Next, one release liner is peeled off from another pressure-sensitive adhesive layer A obtained in Production Example 1, and the single-sided pressure-sensitive adhesive sheet is brought into contact with the exposed pressure-sensitive adhesive layer A, and the foam base material A and the pressure-sensitive adhesive layer A are in contact with each other. A double-sided pressure-sensitive adhesive sheet having a layer structure of [release liner / pressure-sensitive adhesive layer A / foam base material A / pressure-sensitive adhesive layer A / release liner] was produced.

Example 2
A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive layer B obtained in Production Example 2 was used instead of the two pressure-sensitive adhesive layers A.

Example 3
Acrylic emulsion solution (solid content 55%, ethyl acrylate-butyl acrylate-acrylic nitrile copolymer (weight ratio 45:48: 7)) 100 parts by mass, fatty acid ammonium-based surfactant (aqueous dispersion of ammonium stearate, Solid content 33%) 2 parts by mass, carboxybetaine type amphoteric surfactant ("Amogen CB-H", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts by mass, oxazoline-based cross-linking agent ("Epocross WS-500", Co., Ltd. Made by Nippon Catalyst, solid content 39%) 10 parts by mass, pigment (carbon black) ("NAF-5091", manufactured by Dainichi Seika Kogyo Co., Ltd.) 1 part by mass, polyacrylic acid-based thickener (ethyl-acrylic acid acrylate-acrylic acid) 0.6 parts by mass of an acid copolymer (20% by mass of acrylic acid) and 28.7% of solid content was stirred and mixed with a disper (“Robomix”, manufactured by Primix) to foam. This foaming composition was applied onto a peeling-treated PET-based peeling liner (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation), and dried at 70 ° C. for 4.5 minutes and 140 ° C. for 4.5 minutes. An acrylic foam sheet (foam base material B) having an open cell structure having a thickness of 100 μm and a density of 0.45 g / cm ³ was obtained.

A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the foam base material B obtained above was used instead of the foam base material A.

Example 4
A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 3 except that the pressure-sensitive adhesive layer B obtained in Production Example 2 was used instead of the two pressure-sensitive adhesive layers A.

Example 5
By passing the product name "PureCell" (80 μm product, manufactured by Inoac Corporation) through the continuous processing device in which the temperature of the induction heating roll is set to 240 ° C., one side of each surface is sequentially melted by heat. A urethane-based foam sheet (foam base material C) having a semi-independent semi-continuous structure having a thickness of 60 μm and a density of 0.48 g / cm ³ was obtained by heat-melting treatment on both sides.

A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the foam base material C obtained above was used instead of the foam base material A.

Example 6
By passing the product name "PureCell" (200 μm product, manufactured by Inoac Corporation) through the continuous processing device in which the temperature of the induction heating roll is set to 240 ° C., one side of each surface is sequentially melted by heat. A urethane-based foam sheet (foam base material D) having a semi-independent semi-continuous structure having a thickness of 160 μm and a density of 0.45 g / cm ³ was obtained by heat-melting treatment on both sides.

A double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the foam base material D obtained above was used instead of the foam base material A.

Comparative Example 1
Same as Example 1 except that a polyurethane film (trade name "Silklon ES-85", manufactured by Okura Industrial Co., Ltd., thickness 100 μm, density 1.2 g / cm ³ ) was used instead of the foam base material A. To prepare an adhesive sheet.

Comparative Example 2
Except for the fact that urethane foam (trade name "PureCell", manufactured by Inoac Corporation, thickness 80 μm, density 0.33 g / cm ³ ) (foam base material E) was used instead of the foam base material A. An adhesive sheet was produced in the same manner as in Example 1.

Comparative Example 3
As the foam base material, a polyethylene-based foam sheet (trade name “Borara IF # 08008”, manufactured by Sekisui Chemical Co., Ltd., thickness 800 μm, density 0.13 / cm ³ ) (foam base material F) was used. Then, one of the release liners is peeled off from the pressure-sensitive adhesive layer C obtained in Production Example 3, and the foam base material C is attached to the exposed pressure-sensitive adhesive layer C. A single-sided pressure-sensitive adhesive sheet having a layer structure of [base material C] was produced. Next, one release liner is peeled off from another pressure-sensitive adhesive layer C obtained in Production Example 2, and the single-sided pressure-sensitive adhesive sheet is brought into contact with the exposed pressure-sensitive adhesive layer C, and the foam base material F and the pressure-sensitive adhesive layer C are in contact with each other. A double-sided pressure-sensitive adhesive sheet having a layer structure of [release liner / pressure-sensitive adhesive layer C / foam base material F / pressure-sensitive adhesive layer C / release liner] was produced.

Comparative Example 4
The pressure-sensitive adhesive layer A was used as a double-sided pressure-sensitive adhesive sheet.

<Evaluation>
The following evaluations were made on the adhesive sheets obtained in Examples and Comparative Examples. The results are shown in Table 1.

(1) Bending test A release liner was peeled off from the adhesive sheet, and a PET film (thickness 100 μm) was attached to both adhesive surfaces to prepare a test piece. The test piece was repeatedly bent 100,000 times under the conditions of a bending radius of 3 mm and an angle of 180 °. Among the test pieces after bending 100,000 times, those without breaks, wrinkles, and bending marks were marked with "○".

(2) Drop impact test First, the peak load (kN) when a 40 g steel ball was freely dropped from a height of 30 cm on a measuring table maintained horizontally was measured and used as a reference value (Ref). Then, the peak load G when the steel ball is freely dropped is measured from the adhesive layer surface of the adhesive sheet (sample size: 20 mm square) from which the release liners on both sides have been peeled off attached to the measuring table. bottom. Then, the impact absorption rate was calculated by the following formula.
Impact absorption rate (%) = (Ref-G) / Ref × 100

(3) Visible light transmittance Peel off the peeling liners on both sides from the adhesive sheet to make a test piece, and use a haze meter (device name "HAZEMETER HM-150", manufactured by Murakami Color Technology Laboratory Co., Ltd.) to make the above test piece. The total light transmittance was obtained by irradiating from one surface side and measuring the intensity of the light transmitted to the other surface side, and used this as the visible light transmittance.

(4) Compression set A size of 30 mm × 30 mm was cut out from the pressure-sensitive adhesive sheet and used as a test piece. Then, the test piece is compressed in an atmosphere of 50 ° C. (compressed until the thickness of the compressed test piece becomes 25% of the original thickness), and the state is maintained for 24 hours before testing. The pieces were released from the compressed state, left at 23 ° C for 1 hour, and the thickness of the test pieces was measured at 23 ° C. Then, the compression set was calculated by the following formula. Those that could not be compressed to a thickness of 25% were regarded as "unmeasurable" and judged to be inferior in impact resistance.
Compression set (%) = (t ₀ − t ₁ ) / t ₀ × 100
t ₀ : Initial thickness (mm)
t ₁ : Remove the test piece from the compression device, and the thickness (mm) of the test piece after 1 hour has passed.

(5) Elastic modulus of the pressure-sensitive adhesive layer The pressure-sensitive adhesive layers were superposed until the thickness became about 2 mm to prepare a sheet-shaped test sample. Then, this test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (trade name "ARES", manufactured by Leometrics), and the temperature is increased. The viscoelasticity was measured in the shear mode at a heating rate of −70 to 150 ° C. and 5 ° C./min in the region, and the elastic modulus at 23 ° C. was determined.

1 Adhesive sheet 11 Foam base material 12 Adhesive layer 13 Peeling liner

Claims (6)

A pressure-sensitive adhesive sheet comprising a foam base material and an adhesive layer provided on at least one surface of the foam base material.
The foam substrate has a density of 0.40 g / cm ³ or more and a thickness of 300 μm or less.
An adhesive sheet having an impact absorption rate of 20% or more in a falling ball impact test and a compression set of 10% or less when compressed to 25% of the initial thickness under the conditions of 50 ° C. for 24 hours. The pressure-sensitive adhesive sheet according to claim 1, wherein the foam base material is a urethane-based foam or an acrylic-based foam. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has an elastic modulus of 200 kPa or less at 23 ° C. The adhesive sheet according to any one of claims 1 to 3, wherein the visible light transmittance is 4.0% or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the density of the foam base material is 0.40 to 0.60 g / cm ³ . The adhesive sheet according to any one of claims 1 to 5, which is used by being bonded to an internal member of an electric / electronic device.

Images