JP7632515B2 - Adhesive tapes and articles - Google Patents

Description

The present invention relates to an adhesive tape that can be used in the manufacturing process of various products, including electronic devices.

Adhesive tapes are widely used in the manufacturing of a variety of products, including electronic devices and automobiles.

The adhesive tape generally has basic properties such as adhesive strength (peel strength) and tack (adhesiveness) (for example, Patent Documents 1 to 3), but depending on the application of the adhesive tape, other properties may be required. For example, when used for a large desktop display, the display is made frameless, and the tape application area is small, so a small area of tape must support a heavy display such as a liquid crystal module, and high shear adhesive strength is required. An example of a tape with high shear adhesive strength is thermal adhesive tape, but it is difficult to use because an additional heat application process is required and heat or excessive pressure cannot be applied depending on the location or part. Although Patent Documents 1 to 3 have basic properties such as adhesive strength and tack at a practical level, they do not yet demonstrate sufficient performance in terms of shear adhesive strength.

Furthermore, in recent years, as interest in environmental issues such as global warming has increased, there has been strong social demand, particularly for chemical manufacturers, to use plant-derived materials as an alternative to conventional petroleum-derived materials.

JP2005-307063 Patent Publication 2006-206624 Patent Publication 2009-102467

The problem that this invention aims to solve is to provide an adhesive tape that simultaneously exhibits excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness, and is also environmentally friendly.

The inventors have found that the above problem can be solved by an adhesive tape that contains a specific ratio of tackifier resin, has an adhesive layer with a temperature that shows a peak value of loss tangent (tan δ) within a specific range, and has a biomass degree of a specific value or more.

That is, the present invention relates to an adhesive tape that contains 50 to 150 parts by mass of a tackifier resin per 100 parts by mass of adhesive resin solids, has an adhesive layer with a temperature at which the loss tangent (tan δ) at a frequency of 1 Hz shows a peak value of -10°C to 50°C, and has a biomass degree of 45% or more.

The adhesive tape of the present invention simultaneously exhibits excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness, and is also environmentally friendly.

The adhesive tape of the present invention is characterized in that it contains 50 to 150 parts by mass of a tackifier resin per 100 parts by mass of adhesive resin solids, has an adhesive layer with a temperature at which the loss tangent (tan δ) at a frequency of 1 Hz shows a peak value of -10°C to 50°C, and has a biomass degree of 45% or more.

The embodiment of the pressure-sensitive adhesive tape includes, for example, a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer directly or through another layer on one or both sides of a substrate, and a so-called substrate-less pressure-sensitive adhesive tape composed only of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer may be a single layer or multiple layers made of the same or different compositions. When the tape of the present invention is used to fix two or more adherends that constitute, for example, electronic devices, it is preferable to use it in the embodiment of a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both sides of the substrate. When the tape is used for labels, it is preferable to use it in the embodiment of a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one side of the substrate.
The pressure-sensitive adhesive tape of the present invention may be stored with a release film laminated on the surface of the pressure-sensitive adhesive layer.

The adhesive tape of the present invention has a biomass ratio of 45% or more. In the present invention, the biomass ratio refers to the content (mass%) of carbon originating from biomass in the total carbon, calculated by measurement according to ASTM-D6866-18.

The thickness of the adhesive tape of the present invention is preferably in the range of 5 μm to 500 μm, more preferably in the range of 7 μm to 350 μm, more preferably in the range of 10 μm to 200 μm, more preferably in the range of 15 μm to 100 μm, and even more preferably in the range of 20 μm to 60 μm, in order to simultaneously satisfy excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness, and to contribute to the thinning of electronic devices, etc.

(Adhesive Layer)
The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive tape of the present invention preferably has a thickness in the range of 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 20 μm to 50 μm, in order to simultaneously satisfy excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness, and to contribute to the thinning of electronic devices and the like.

The adhesive layer constituting the adhesive tape of the present invention is formed from an adhesive composed of an adhesive resin and a tackifier resin. The adhesive layer preferably has a biomass ratio of 45% or more.
The temperature at which the adhesive resin exhibits a peak value of loss tangent (tan δ) at a frequency of 1 Hz is preferably low so that a large amount of the tackifier resin can be added, and specifically, is preferably −50° C. to 20° C., more preferably −45° C. to 15° C., and even more preferably −40° C. to 10° C. Examples of the adhesive include (meth)acrylic adhesives, urethane adhesives, synthetic rubber adhesives, natural rubber adhesives, and silicone adhesives. In terms of weather resistance and heat resistance, however, (meth)acrylic adhesives are preferred, in which an acrylic copolymer consisting of (meth)acrylate alone or a copolymer of (meth)acrylate and other monomers is used as a base polymer, and a tackifier resin and, if necessary, additives such as a crosslinking agent are blended.

The loss tangent (tan δ) at a frequency of 1 Hz is calculated from the storage modulus (G') and loss modulus (G") obtained by dynamic viscoelasticity measurement using temperature dispersion, using the formula tan δ = G" / G'. In measuring dynamic viscoelasticity, a viscoelasticity tester (manufactured by TA Instruments Japan, product name: ARES G2) is used to sandwich a test piece of an adhesive layer formed to a thickness of approximately 2 mm between parallel disks with a diameter of 8 mm, which is the measuring section of the tester, and the storage modulus (G') and loss modulus (G") are measured at a frequency of 1 Hz from -50°C to 150°C.

As the acrylic copolymer, an acrylic copolymer having an alkyl (meth)acrylate monomer as a main monomer component can be preferably used, and the alkyl group of the alkyl (meth)acrylate monomer may be linear or branched. Examples of the alkyl (meth)acrylate monomer include alkyl (meth)acrylates having an alkyl group with 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, and cyclohexyl (meth)acrylate. One or more of these can be used, but it is preferable to use two or more. Among these, (meth)acrylate monomers in which the alkyl group has 2 to 16 carbon atoms are preferred, and (meth)acrylate monomers in which the alkyl group has 3 to 14 carbon atoms are more preferred. The use of the above monomers is preferred because it simultaneously exhibits excellent shear adhesive strength and excellent initial tackiness, and also makes it easy to add a tackifier.

The content of one or more types selected from the group consisting of alkyl (meth)acrylate monomers relative to the total amount of acrylic monomers that can be used in producing the acrylic copolymer is preferably 70% by mass or more, more preferably 75 to 99% by mass, and even more preferably 80 to 96% by mass.

The acrylic copolymer is also preferably copolymerized with a highly polar vinyl monomer. Examples of the highly polar vinyl monomer include carboxyl group-containing vinyl monomers, hydroxyl group-containing vinyl monomers, and amide group-containing vinyl monomers, and one or more of these are used. Among these, carboxyl group-containing monomers and hydroxyl group-containing vinyl monomers are preferably used because they make it easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

The carboxyl group-containing vinyl monomer may be acrylic acid, methacrylic acid, itaconic acid, maleic acid, β-carboxyethyl acrylic acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide modified succinic acid acrylate, etc., and among these, it is preferable to use acrylic acid as a copolymerization component in order to achieve excellent initial tackiness.

The content of the carboxyl group-containing vinyl monomer relative to the total amount of acrylic monomers used in producing the acrylic copolymer is 1 to 30% by mass, more preferably 2 to 20% by mass, and more preferably 3 to 15% by mass in order to simultaneously achieve excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness.

Examples of the hydroxyl group-containing vinyl monomer that can be used include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, etc., and among these, 4-hydroxybutyl (meth)acrylate is preferred because it simultaneously exhibits excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness.

The content of the hydroxyl group-containing vinyl monomer relative to the total amount of acrylic monomers that can be used in producing the acrylic copolymer is 1.0% by mass or less, but is preferably 0.01 to 0.85% by mass, more preferably 0.02 to 0.7% by mass, more preferably 0.03 to 0.5% by mass, and even more preferably 0.04 to 0.3% by mass, and is preferably 0.05 to 0.2% by mass in order to simultaneously exhibit excellent shear adhesive strength and excellent initial tackiness.

Examples of amide group-containing vinyl monomers include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

Other highly polar vinyl monomers include vinyl acetate, ethylene oxide modified succinic acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid, and terminal alkoxy modified (meth)acrylates such as 2-methoxyethyl (meth)acrylate and 2-phenoxyethyl (meth)acrylate.

The content of the highly polar vinyl monomer relative to the total amount of acrylic monomers that can be used in producing the acrylic copolymer is preferably 0.2 to 15% by mass, more preferably 0.4 to 10% by mass, and is preferably 0.5 to 6% by mass in order to simultaneously achieve excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness.

Acrylic copolymers can be obtained by copolymerization using known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization, but solution polymerization and bulk polymerization are preferred due to the water resistance of the adhesive. The polymerization can be initiated by any of the following: thermal initiation using a peroxide-based thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, or an azo-based thermal polymerization initiator such as azobisisobutylnitrile; ultraviolet irradiation initiation using an acetophenone-based, benzoin ether-based, benzil ketal-based, acylphosphine oxide-based, benzoin-based, or benzophenone-based photopolymerization initiator; and electron beam irradiation.

The molecular weight of the acrylic copolymer is preferably 400,000 or more, more preferably 420,000 to 1,500,000, in terms of standard polystyrene, as measured by gel permeation chromatography (GPC), and is preferably 450,000 to 1,200,000 in order to simultaneously achieve excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness.

Here, the molecular weight measured by the GPC method is a standard polystyrene equivalent value measured using a GPC device (HLC-8329GPC) manufactured by Tosoh Corporation, and the measurement conditions are as follows:

Sample concentration: 0.5% by mass (THF solution)
Sample injection volume: 100 μL
Eluent: THF
Flow rate: 1.0mL/min Measurement temperature: 40℃
Main column: TSKgel GMHXL 4 pieces Guard column: TSKgel HXL-H
Detector: Differential refractometer Standard polystyrene molecular weight: 10,000 to 20,000,000 (manufactured by Tosoh Corporation)

The adhesive used in the adhesive tape of the present invention preferably forms a three-dimensional cross-linked structure to improve cohesive strength. As an indicator of the formation of a cross-linked structure, the gel fraction, which is expressed as the insoluble matter after immersion for 24 hours in toluene, which is a good solvent for (meth)acrylic adhesives, is used. In this case, it is preferably 10 to 50 mass%, and more preferably 15 to 40 mass%. If the gel fraction is less than 10 mass%, the cohesive strength in the shear direction is insufficient, and if it exceeds 50 mass%, the initial tackiness decreases.

The gel fraction is calculated by the following formula.
Gel fraction (mass %)={(mass of adhesive after immersion in toluene)/(mass of adhesive before immersion in toluene)}×100

The adhesive layer of the adhesive tape of the present invention contains 50 to 150 parts by mass of tackifier resin per 100 parts by mass of adhesive resin solids, preferably 60 to 125 parts by mass, and more preferably 80 to 110 parts by mass.

Examples of the tackifier resin include rosin-based tackifier resins, which are plant-derived tackifier resins, terpene-based tackifier resins, and terpene phenol-based tackifier resins. The tackifier resins can be used alone or in combination of two or more.

Examples of rosin-based tackifying resins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, modified rosins obtained by modifying these unmodified rosins through polymerization, disproportionation, hydrogenation, etc. (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and other chemically modified rosins), as well as various rosin derivatives. Examples of the rosin derivatives include rosin phenol-based resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and thermally polymerizing the resulting mixture; rosin ester-based resins such as rosin ester compounds (unmodified rosin esters) obtained by esterifying unmodified rosin with alcohols, and modified rosin ester compounds (polymerized rosin ester, stabilized rosin ester, disproportionated rosin ester, fully hydrogenated rosin ester, partially hydrogenated rosin ester, etc.) obtained by esterifying modified rosins such as polymerized rosin, stabilized rosin ester, disproportionated rosin ester, fully hydrogenated rosin ester, partially hydrogenated rosin ester, etc.) with alcohols; unsaturated fatty acid modified rosin-based resins obtained by modifying rosin or modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.) with unsaturated fatty acid; unsaturated fatty acid modified rosin ester-based resins obtained by modifying rosin ester-based resins with unsaturated fatty acid; rosin alcohol-based resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid modified rosin-based resins, and unsaturated fatty acid modified rosin ester-based resins; metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin, modified rosin, and various rosin derivatives.

Examples of terpene-based tackifying resins include terpene-based resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, and modified terpene-based resins obtained by modifying these terpene-based resins (such as phenol-modified, aromatic-modified, hydrogen-modified, and hydrocarbon-modified) (for example, terpene-phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins).
As the tackifier resin, a rosin-based tackifier resin or a terpene-based tackifier resin can be suitably used.

The tackifier resin preferably has a biomass degree of 50% or more, more preferably 60% or more, more preferably 70% or more, more preferably 80% or more, more preferably 90% or more, and most preferably 95% to 100%. The use of the above tackifier resin is preferable in that it simultaneously exhibits excellent peel strength, excellent shear adhesive strength, and excellent initial tackiness, and also improves the biomass degree.

The softening point of the tackifier resin is not particularly specified, but is 20 to 180°C, preferably 25°C to 140°C. Two or more types of the tackifier resin may be used in combination.

The adhesive layer used in the adhesive tape of the present invention, which is composed of the adhesive resin and the tackifier resin, preferably has a temperature at which the loss tangent (tan δ) peaks at a frequency of 1 Hz is -10°C to 50°C. By setting the peak loss tangent of the adhesive layer within this range, it becomes easier to impart good adhesion to the adherend at room temperature. Furthermore, from the viewpoint of improving the shear adhesive strength, it is more preferable that the temperature is -5°C to 45°C, and even more preferable that the temperature is 5°C to 40°C.

The adhesive constituting the adhesive layer may contain additives such as plasticizers, softeners, antioxidants, flame retardants, glass or plastic fibers/balloons, beads, fillers such as metals, metal oxides, metal nitrides, colorants such as pigments and dyes, leveling agents, thickeners, water repellents, and defoamers.

The adhesive constituting the adhesive layer preferably contains a solvent in order to maintain good coating workability. Examples of the solvent that can be used include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. In addition, when preparing a water-based adhesive composition, water or an aqueous solvent mainly composed of water can be used.

(Substrate)
The pressure-sensitive adhesive tape of the present invention may be provided with a substrate. As the substrate, for example, a nonwoven fabric substrate or a resin film may be used.
Examples of the nonwoven fabric substrate include nonwoven fabrics obtained using chemical fibers such as Manila hemp, wood pulp, rayon, acetate fiber, polyester fiber, vinylon fiber (polyvinyl alcohol fiber), polyamide fiber, and mixtures thereof. Among these, it is more preferable to use a nonwoven fabric produced using 50% or more of raw materials derived from plants.

In addition, sheets or films obtained using polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polyethylene furanoate, polyolefins, polyacrylates, polyvinyl chloride, polyethylene, polypropylene ethylene vinyl alcohol, polyurethane, polyamide, and polyimide, and non-foamed film substrates such as glass can be used. The surfaces of these substrates may be subjected to antistatic treatment, corona treatment, and the like.
In addition, a foam substrate may be used as the substrate. For example, polyolefin foam, polyurethane foam, acrylic foam, other rubber foam, etc. may be used as the foam substrate. The surface of the foam substrate may be subjected to antistatic treatment, corona treatment, etc. Among them, it is more preferable to use the resin film produced using 20% or more of raw materials derived from plants.

(Production method)
Examples of manufacturing methods for the pressure-sensitive adhesive tape of the present invention, in the case of a pressure-sensitive adhesive tape having a substrate (core), include a manufacturing method (direct method) in which the pressure-sensitive adhesive composition is applied to one or both sides of the substrate and dried or the like to produce the tape; or a manufacturing method (transfer method) in which the pressure-sensitive adhesive composition is applied to the surface of a release liner and dried or the like to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer is transferred to one or both sides of the substrate to produce the tape.
Examples of a method for producing the substrate-less pressure-sensitive adhesive tape include a method in which a pressure-sensitive adhesive composition is applied to the surface of a release liner and then dried to form a pressure-sensitive adhesive layer.

Examples of the method for applying the pressure-sensitive adhesive composition to the substrate or release liner include methods using an applicator, roll coater, gravure coater, reverse coater, spray coater, air knife coater, die coater, and the like.
The pressure-sensitive adhesive composition may be dried for 30 seconds to 10 minutes at 50° C. to 140° C. After drying, the composition may be further aged at a temperature in the range of 30° C. to 50° C. in order to promote the curing reaction.

The present invention will be explained in more detail below using examples.

[Preparation Example 1]
A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 59.9 parts by mass of n-butyl acrylate, 36 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then held at 75°C for 5 hours.

Next, 2 parts by mass of a solution of 2,2'-azobis(2-methylbutyronitrile) previously dissolved in ethyl acetate (solid content 0.1% by mass) was added to the mixture, and the mixture was held at 72°C for 4 hours under stirring, and then held at 75°C for 5 hours.
Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire screen to obtain a solution of an acrylic copolymer (A-1) having a weight average molecular weight of 1,040,000.

The acrylic copolymer (A-1) solution was mixed with 15 parts by mass of "Haritac PCJ" (biomass content: 95%) manufactured by Harima Chemical Industries, Ltd., 85 parts by mass of "Super Ester A-100" (biomass content: 100%) manufactured by Arakawa Chemical Industries, Ltd., and an adduct of tolylene diisocyanate and trimethylolpropane ("Burnoc D-40" manufactured by DIC Corporation, hereafter abbreviated as "D-40") to obtain an adhesive (P-1) (biomass content: 49.6%) with a gel fraction of 39.9%.

[Preparation Example 2]
The acrylic copolymer (A-1) was blended with 15 parts of Arakawa Chemical Industries'"Super Ester L" (biomass degree: 90.7%), 45 parts of Arakawa Chemical Industries'"Super Ester A-75" (biomass degree: 91%), 30 parts of Super Ester A-100, 10 parts of Haritac PCJ, and D-40 to obtain a pressure-sensitive adhesive (P-2) (biomass degree: 47.0%) with a gel fraction of 29.1%.

[Preparation Example 3]
An acrylic copolymer (A-2) solution having a weight average molecular weight of 500,000 was obtained in the same manner as in Preparation Example 1, except that the amounts of 2-ethylhexyl acrylate, acrylic acid, and β-carboxyethyl acrylate were changed to 96.4 parts by mass, 1.2 parts by mass, and 2.4 parts by mass, respectively.
The acrylic copolymer (A-2) solution was mixed with 85 parts by mass of Super Ester A-100, 15 parts by mass of Haritac PCJ, and a 2% ethyl acetate solution of an epoxy crosslinker (Tetrad C manufactured by Mitsubishi Gas Chemical Company, Inc.) to obtain a pressure sensitive adhesive (P-3) (biomass content: 49.6%) with a gel fraction of 37.8%.

[Preparation Example 4]
An acrylic copolymer (A-3) solution having a weight average molecular weight of 510,000 was obtained in the same manner as in Preparation Example 1, except that the amounts of n-butyl acrylate, 2-ethylhexyl acrylate, acrylic acid, and 4 parts by mass were changed to 59 parts by mass, 36 parts by mass, 4 parts by mass, and 4-hydroxybutyl acrylate were changed to 0.1 parts by mass.
The acrylic copolymer (A-3) solution was mixed with 85 parts by mass of Super Ester A-100, 15 parts by mass of Haritac PCJ, and D-40 to obtain a pressure-sensitive adhesive (P-4) (biomass content: 49.6%) with a gel fraction of 30.6%.

[Preparation Example 5]
An acrylic copolymer (A-4) solution having a weight average molecular weight of 660,000 was obtained in the same manner as in Preparation Example 1, except that the components were changed to 54.9 parts by mass of n-butyl acrylate, 44 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of acrylic acid, and 0.1 parts by mass of 4-hydroxybutyl acrylate.
The acrylic copolymer (A-4) solution was mixed with 85 parts by mass of Super Ester A-100, 15 parts by mass of Haritac PCJ, and D-40 to obtain a pressure-sensitive adhesive (P-5) (biomass content: 49.6%) with a gel fraction of 25.5%.

[Example 1]
The pressure-sensitive adhesive (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side being release-treated) and dried at 80° C. for 5 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 50 μm.
Thereafter, the mixture was aged in an environment of 40° C. for 48 hours to obtain a double-sided adhesive tape (T-1).

[Example 2]
A double-sided adhesive tape (T-2) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the adhesive (P-2) was used instead of the adhesive (P-1).

[Example 3]
A double-sided adhesive tape (T-3) having a thickness of 50 μm was obtained in the same manner as in Example 1, except that the adhesive (P-3) was used instead of the adhesive (P-1).

[Example 4]
A double-sided adhesive tape (T-4) having a thickness of 50 μm was obtained in the same manner as in Example 3, except that the adhesive (P-4) was used instead of the adhesive (P-1).

[Example 5]
A double-sided adhesive tape (T-5) having a thickness of 50 μm was obtained in the same manner as in Example 3, except that the adhesive (P-5) was used instead of the adhesive (P-1).

[Comparative Preparation Example 1]
The acrylic copolymer (A-4) was mixed with 85 parts by mass of "FTR6100" manufactured by Mitsui Chemicals, Inc., 15 parts by mass of "FTR6125" manufactured by Mitsui Chemicals, Inc., and D-40 to obtain a pressure-sensitive adhesive (Q-1) (biomass content: 0%) having a gel fraction of 39.1%.

[Comparative Preparation Example 2]
A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 61.9 parts by mass of 2-ethylhexyl acrylate, 26 parts by mass of isobornyl acrylate, 12 parts by mass of acrylic acid, 0.1 part by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then held at 75°C for 5 hours.

Next, 2 parts by mass of a solution of 2,2'-azobis(2-methylbutyronitrile) previously dissolved in ethyl acetate (solid content 0.1% by mass) was added to the mixture, and the mixture was held at 72°C for 4 hours under stirring, and then held at 75°C for 5 hours.
Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire screen to obtain a solution of an acrylic copolymer (B-1) having a weight average molecular weight of 300,000.
D-40 was added to the acrylic copolymer (B-1) solution to obtain a pressure sensitive adhesive (Q-2) (biomass content: 21%) having a gel fraction of 6.9%.

[Comparative Preparation Example 3]
A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 97.9 parts by mass of n-butyl acrylate, 2 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72° C. for 4 hours with stirring, and then held at 75° C. for 5 hours.

Next, 4 parts by mass of a solution of 2,2'-azobis(2-methylbutyronitrile) previously dissolved in ethyl acetate (solid content 0.1% by mass) was added to the mixture, and the mixture was held at 72°C for 4 hours under stirring, and then held at 75°C for 5 hours.

Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire screen to obtain a solution of an acrylic copolymer (B-2) having a weight average molecular weight of 1,060,000.
D-40 was added to the acrylic copolymer (B-2) solution to obtain a pressure-sensitive adhesive (Q-3) (biomass ratio: 19.8%) with a gel fraction of 42.8%.

[Comparative Preparation Example 4]
The acrylic copolymer (A-1) solution was mixed with 85 parts by mass of Super Ester L, 15 parts by mass of Haritac PCJ, and D-40 to obtain a pressure-sensitive adhesive (Q-4) (biomass content: 45.4%) with a gel fraction of 27.4%.

[Comparative Preparation Example 5]
The acrylic copolymer (A-1) solution was mixed with 85 parts by mass of Super Ester A-100, 65 parts by mass of Haritac PCJ, and D-40 to obtain a pressure-sensitive adhesive (Q-5) (biomass content: 58.7%) having a gel fraction of 15.0%.

[Comparative Example 1]
The pressure-sensitive adhesive (Q-1) obtained in Comparative Preparation Example 1 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side being release-treated) and dried at 80° C. for 5 minutes to prepare a pressure-sensitive adhesive layer having a thickness of 50 μm.
Thereafter, the mixture was aged in an environment of 40° C. for 48 hours to obtain a double-sided adhesive tape (U-1).

[Comparative Example 2]
A double-sided adhesive tape (U-2) having a thickness of 50 μm was obtained in the same manner as in Comparative Example 1, except that the adhesive (Q-2) was used instead of the adhesive (Q-1).

[Comparative Example 3]
A double-sided adhesive tape (U-3) having a thickness of 50 μm was obtained in the same manner as in Comparative Example 1, except that the adhesive (Q-3) was used instead of the adhesive (Q-1).

[Comparative Example 4]
A double-sided adhesive tape (U-4) having a thickness of 50 μm was obtained in the same manner as in Comparative Example 1, except that the adhesive (Q-4) was used instead of the adhesive (Q-1).

[Comparative Example 5]
A double-sided adhesive tape (U-5) having a thickness of 50 μm was obtained in the same manner as in Comparative Example 1, except that the adhesive (Q-5) was used instead of the adhesive (Q-1).

[Method for measuring peel strength]
The release liner on one side of each of the double-sided adhesive tapes obtained in the Examples and Comparative Examples was peeled off, the tape was backed with a 25 μm thick PET film, and cut to a width of 25 mm to prepare a test piece.
The release liner on the other side of the test piece was peeled off and the other side was attached to the surface of a 2 mm thick stainless steel (SUS) plate (adhesive area 25 mm x 80 mm), and then the upper surface was pressed against the plate by rolling a 2 kg roll back and forth once to obtain a patch.
The patch was left for 1 hour in an atmosphere of 23° C. and 50% RH.
Next, the 180 degree peel strength (N/25 mm) of the test piece constituting the adhesive was measured in an atmosphere of 23° C. and 50% RH in accordance with JIS Z0237.

A: The peel strength was 25 N/25 mm or more.
B: The peel strength was 12.5 N/25 mm or more and less than 25 N/25 mm.
C: The peel strength was less than 12.5 N/mm.
D: Stick-slip (SS) occurred and measurement was not possible.

[Method for measuring shear adhesive strength]
The double-sided adhesive tapes obtained in the Examples and Comparative Examples were cut into 10 mm squares to prepare test pieces. The release liner on one side of the test piece was peeled off and the piece was attached to the surface of a 2 mm thick stainless steel (SUS) plate, and then the release liner on the other side was peeled off and a 25 mm wide, 80 mm long, 50 μm thick stainless steel foil was attached, and the piece was pressed against the plate by rolling it back and forth once with a 2 kg roll to obtain a patch.
The patch was left for 24 hours in an atmosphere of 23° C. and 50% RH.
Next, the stainless steel foil and stainless steel plate of the test piece constituting the adhesive were pulled at a speed of 10 mm/min in an atmosphere of 23° C. and 50% RH, and the strength at which the stainless steel foil peeled off was measured.

A: The shear adhesive strength was 2 MPa or more.
B: The shear adhesive strength was 1.5 MPa or more and less than 2.0 MPa.
C: The shear adhesive strength was 1.0 MPa or more and less than 1.5 MPa.
D: The shear adhesive strength was less than 1.0 MPa.

[Method for evaluating initial tackiness]
The adhesive surface of each of the double-sided adhesive tapes obtained in the Examples and Comparative Examples was evaluated for feel when touched with a finger according to the following criteria.
A: When you touch the adhesive surface of the tape, it feels very tacky.
B: There is a slight tackiness when you touch the adhesive surface of the tape.
C: There is almost no tackiness when the adhesive surface of the tape is touched.

The above results show that Examples 1 to 5 of the present invention have good properties in terms of peel strength, initial tackiness, and shear adhesive strength. On the other hand, Comparative Examples 1 to 5 show poor properties in one or more of the above properties.

Claims (8)

a pressure-sensitive adhesive layer containing 50 parts by mass to 150 parts by mass of a rosin-based tackifier resin relative to 100 parts by mass of a solid content of the pressure-sensitive adhesive resin, having a temperature showing a peak value of a loss tangent (tan δ) at a frequency of 1 Hz of -10°C to 25.5°C and a biomass degree of 45% or more;
the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is a (meth)acrylic pressure-sensitive adhesive containing an acrylic copolymer made of a (meth)acrylate alone or a copolymer of a (meth)acrylate and another monomer,
An adhesive tape having a biomass content of 45% or more. The pressure-sensitive adhesive layer contains a rosin-based tackifier resin in an amount of 50 parts by mass to 150 parts by mass relative to 100 parts by mass of the adhesive resin solid content, and has a temperature at which a loss tangent (tan δ) at a frequency of 1 Hz shows a peak value in a range of −10° C. to 50° C.;
the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer is a (meth)acrylic pressure-sensitive adhesive containing an acrylic copolymer made of a (meth)acrylate alone or a copolymer of a (meth)acrylate and another monomer,
An adhesive tape having a 180 degree peel strength from a stainless steel plate of 28.3 N/25 mm or more, as measured in accordance with JIS Z0237, and a biomass content of 45% or more. 3. The pressure-sensitive adhesive tape according to claim 1, wherein the (meth)acrylate is an alkyl (meth)acrylate, and the alkyl group of the alkyl (meth)acrylate has 1 to 18 carbon atoms. The pressure-sensitive adhesive tape according to any one of claims 1 to 3 , wherein the tackifier resin has a biomass ratio of 50% or more. The pressure-sensitive adhesive tape according to any one of claims 1 to 4 , wherein the tackifier resin comprises two or more types. The pressure-sensitive adhesive tape according to any one of claims 1 to 5 , wherein the acrylic copolymer has a weight average molecular weight of 400,000 or more. The pressure-sensitive adhesive tape according to any one of claims 1 to 6 , wherein the pressure-sensitive adhesive layer has a gel fraction of 10% to 50%. The pressure-sensitive adhesive tape according to any one of claims 1 to 7 , wherein the pressure-sensitive adhesive layer has a thickness of 5 to 200 µm.