JP7346898B2 - adhesive film - Google Patents

Description

The present invention relates to an adhesive film that can be suitably used, for example, for transporting optical films, protecting surfaces, and other uses.

Liquid crystal displays (LCDs) installed in electronic terminals such as smartphones and tablet computers incorporate optical films such as polarizing plates and retardation plates.

The optical film undergoes various processing and assembly processes, and during these processes, an adhesive film is usually attached to transport the optical film and to prevent scratches, dirt, etc. from adhering to the surface. be done. The adhesive film is used only in the liquid crystal display manufacturing process and the optical film manufacturing and processing process, and is peeled off and removed from the optical film when the optical film is incorporated into the liquid crystal display. Due to the method of using the adhesive film, the adhesive film is generally called a protective film or a process film.
As the adhesive film, a surface protection film in which an adhesive containing an acrylic polymer, an antistatic agent, and a crosslinking agent is formed on one or both sides of a resin film is known (see, for example, Patent Document 1).
In recent years, a heating step of heating to a high temperature of about 100°C to 150°C is sometimes provided during the processing process, and an adhesive film that reliably transports and protects the optical film even during the heating process has become necessary. There is.

However, with conventional adhesive films, the adhesive strength is often insufficient at the initial stage and at high temperatures.For example, when transporting roll-to-roll, stress during processing and passing through support rolls may occur during the heating process. In some cases, the optical film peeled off from the adhesive film, causing trouble in subsequent steps.
Furthermore, when the optical film is peeled off from the adhesive film after the heating step, the adhesive remains on the surface of the optical film, which may contaminate the optical film.

Japanese Patent Application Publication No. 2013-216738

The problem to be solved by the present invention is to provide an adhesive film that has both excellent easy peelability and peel resistance.

The present invention is an adhesive tape having an adhesive layer (B) on at least one surface of a base material (A), either directly or via another layer, in an environment of a temperature of 23° C. and a relative humidity of 50% RH. 180° pull at a peeling speed of 300 mm/min. The peel adhesive force is 0.5 to 4.0 N/25 mm, and the optical film is pressed with a 2 kg roller in one round trip in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. The 180° peeling adhesive strength at a peeling speed of 300 mm/min after standing for 30 seconds in an environment of 120°C is 0.5 to 4.0 N/25 mm, and the loss tangent (Tan δ ₁₂₀ ) at 120°C and 1 Hz is The above problem is solved by setting the value to 1.0 or less.

Since the adhesive film of the present invention has excellent easy peelability and peeling resistance, it is particularly suitable for use as a process film for transportation or temporary protection in the processing process of optical films such as polarizing plates and retardation films. Can be used as a protective film.

As the adhesive film of the present invention, it is preferable to use a thin one from the viewpoint of use as a carrier film or a protective film. Specifically, the adhesive film preferably has a total thickness of 100 μm or less, more preferably 60 μm or less. Further, the lower limit of the total thickness of the adhesive film is not particularly limited, but is preferably 40 μm or more, more preferably 50 μm or more. The adhesive film of the present invention can have both excellent easy peelability and peel resistance by adopting the above-mentioned specific laminated structure.

[Base material (A)]
The base material (A) constituting the adhesive film of the present invention preferably has a thickness of 12 μm to 250 μm, more preferably a thickness of 25 μm to 100 μm, and has a thickness of 12 μm to 250 μm. It is more preferable to use a material with a thickness of 38 μm to 50 μm in order to achieve both excellent peelability and peeling resistance.

As the base material (A), it is preferable to use a resin film with excellent optical properties, such as polyethylene terephthalate film, polybutylene terephthalate film, polyethylene naphthalate film, polyethylene film, polypropylene film, cellophane film, diacetyl cellulose film. , triacetylcellulose film, acetylcellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, Ether ether ketone film, polyether sulfone film, polyetherimide film, polyimide film, fluorine resin film, nylon film, acrylic resin film, norbornene resin film (for example, Arton manufactured by JSR Corporation), cyclic olefin polymer film ( For example, Zeonor Film (manufactured by Nippon Zeon Co., Ltd.), etc. can be used.

Among these, as the base material (A), it is preferable to use a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, an acrylic resin film, a triacetyl cellulose film, etc., and it is more preferable to use a polyethylene terephthalate film. The use of a polyethylene terephthalate film having a heat shrinkage rate at 120° C. of 1.0% or less, more preferably 0.5% or less, even more preferably 0.1% or less provides even better easy peelability. This is preferable for producing an adhesive tape with peel resistance. Note that the heat shrinkage rate at 120° C. of the base material (A) refers to a value measured by the method described in Examples.

Further, as the base material (A), one having an easily adhesive layer on the surface can be used for the purpose of improving the adhesiveness with the adhesive layer (B). In addition, for the purpose of further improving the adhesion, the base material (A) may be subjected to surface roughening treatment by sandblasting, solvent treatment, etc., corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment. , ozone treatment, ultraviolet irradiation treatment, and other oxidation treatments can be used.

[Adhesive layer (B)]
The adhesive layer (B) constituting the protective film of the present invention preferably has a thickness of 50 μm or less, more preferably a range of 1 μm to 30 μm, and even more preferably a range of 5 μm to 15 μm. By providing the adhesive layer (B) with the above-mentioned thickness, a protective film having both excellent easy peelability and heat resistance can be obtained.

As the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer (B), a pressure-sensitive adhesive composition used for ordinary pressure-sensitive adhesive films can be used. Examples of the adhesive composition include (meth)acrylic adhesives, urethane adhesives, synthetic rubber adhesives, natural rubber adhesives, silicone adhesives, etc., but (meth)acrylate alone or The base polymer is an acrylic copolymer consisting of a copolymer of (meth)acrylate and other monomers, and additives such as tackifying resins and crosslinking agents are added to this as necessary. Adhesive compositions can be preferably used.

As the acrylic copolymer, an acrylic copolymer whose main monomer component is a (meth)acrylate monomer having 1 to 12 carbon atoms can be preferably used, and as the (meth)acrylate having 1 to 12 carbon atoms, for example, 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, Examples include monomers such as isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and one or more of these may be used. Among these, (meth)acrylates in which the alkyl group has 4 to 12 carbon atoms are preferred, and (meth)acrylates in which the alkyl group has a linear or branched structure and 4 to 9 carbon atoms are more preferred. Among these, acrylates having a linear or branched structure having 4 to 9 carbon atoms are more preferred.

The content of (meth)acrylate having 1 to 12 carbon atoms in the acrylic copolymer is preferably 80 to 98.5% by mass, and 90 to 98.5% by mass of the monomer components constituting the acrylic copolymer. More preferably, it is .5% by mass.

Further, the acrylic copolymer used in the present invention may be copolymerized with a highly polar monomer, and examples of the highly polar monomer include a monomer having a hydroxyl group, a monomer having a carboxyl group, a monomer having an amide group, etc. , one or more of these may be used.

Examples of monomers having hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, etc. Meta)acrylates can be used.

As the monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide modified succinic acid acrylate, etc. can be used, and among them, acrylic acid is copolymerized. Preferably used as a component.

Furthermore, examples of monomers having an amide group include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N,N-dimethylacrylamide, and the like.

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, 2-methoxyethyl (meth)acrylate, 2-phenoxyethyl ( Examples include terminal alkoxy-modified (meth)acrylates such as meth)acrylates.

The content of the highly polar vinyl monomer is preferably 0.2 to 15% by mass, more preferably 2 to 10% by mass, and 4 to 8% by mass in the monomer components constituting the acrylic copolymer. % is more preferable. By containing it within this range, the cohesive force, holding power, and adhesiveness of the adhesive can be easily adjusted to a suitable range.

The adhesive layer (B) uses an acrylic copolymer made of a copolymer of (meth)acrylate and a hydroxyl group-containing monomer as a base polymer, and additives such as a tackifying resin and a crosslinking agent are added to this as necessary. A (meth)acrylic adhesive containing the following can be used.
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 is preferred due to the water resistance of the adhesive. or bulk polymerization method is preferred. Polymerization initiation methods include thermal initiation using peroxide-based thermal polymerization initiators such as benzoyl peroxide and lauroyl peroxide, azo-based thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based, benzoin ether-based, benzyl An initiation method using ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based, or benzophenone-based photoinitiator or a method using electron beam irradiation can be arbitrarily selected.

The molecular weight of the acrylic copolymer is preferably 500,000 or more, and preferably 500,000 to 1,500,000, as measured by gel permeation chromatography (GPC) in terms of standard polystyrene. This is preferable in terms of exhibiting even better peelability and peeling resistance.

Here, the molecular weight measurement by the GPC method is a standard polystyrene equivalent value measured using a GPC device manufactured by Tosoh Corporation (HLC-8329GPC), and the measurement conditions are as follows.
Sample concentration: 0.5% by mass (THF solution)
Sample injection volume: 100μL
Eluent: THF
Flow rate: 1.0mL/min Measurement temperature: 40℃
Main column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: Differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (manufactured by Tosoh Corporation)

As the adhesive that can be used in the present invention, one containing a tackifying resin can be used in order to obtain a pressure-sensitive adhesive sheet with even better peel adhesive strength.
Examples of the tackifying resin include rosin-based tackifying resin, polymerized rosin-based tackifying resin, polymerized rosin ester-based tackifying resin, rosin phenol-based tackifying resin, stabilized rosin ester-based tackifying resin, and disproportionated rosin ester. Typical tackifier resins, hydrogenated rosin ester tackifier resins, terpene tackifier resins, terpene phenol tackifier resins, petroleum resin tackifier resins, (meth)acrylate tackifier resins, etc. can be used. .
Further, as the adhesive, it is preferable to use one containing a crosslinking agent in order to form an adhesive layer with even better cohesive force.

As the crosslinking agent, for example, isocyanate crosslinking agents, epoxy crosslinking agents, metal chelate crosslinking agents, aziridine crosslinking agents, etc. can be used. Among these, as the crosslinking agent, it is preferable to use a crosslinking agent that is easy to mix and use with the pre-produced acrylic copolymer or its solution and that can quickly proceed with the crosslinking reaction. Specifically, it is more preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent.
As the isocyanate-based crosslinking agent, for example, tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, etc. can be used. , trimethylolpropane-modified tolylene diisocyanate is preferably used.

It is more preferable to select and use the crosslinking agent in an amount such that the gel fraction with respect to toluene in the adhesive layer is 40% by mass to 95% by mass, and the amount such that the gel fraction is 50% by mass to 90% by mass. It is more preferable to select and use them in order to obtain an adhesive film that has both excellent easy peelability and peel resistance. In addition, the said gel fraction refers to the value measured by the method shown below.

The above-mentioned adhesive was coated on the release-treated surface of the release liner so that the thickness after drying was 10 μm, and then dried in an environment of 100°C for 3 minutes, and then dried in an environment of 40°C. A pressure-sensitive adhesive layer was formed by aging for 2 days.
A test piece was prepared by cutting the adhesive layer into a square with a length of 50 mm and a width of 50 mm.
After measuring the mass (G1) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23°C.
After the immersion, the mixture of the test piece and toluene was filtered using a 300 mesh wire gauze to extract components insoluble in toluene. The mass (G2) of the insoluble component dried in a 110° C. environment for 1 hour was measured.
The gel fraction was calculated based on the mass (G1), mass (G2), and the following formula.
Gel fraction (mass%) = (G2/G1) x 100

The adhesive layer (B) has a loss tangent (Tan δ ₁₂₀ ) value at 120° C. of 1.0 or less, preferably 1.2 or less, more preferably 0.05 or more and 0.8 or less. and more preferably 0.2 or more and 0.6 or less in order to obtain an adhesive film that has both excellent easy peelability and peel resistance. Note that the loss tangent (Tan δ ₁₂₀ ) at 120° C. refers to a value measured by the method described in Examples.

Examples of the adhesive include plasticizers, softeners, antioxidants, flame retardants, glass and plastic fibers/balloons, beads, metals, fillers such as metal oxides and metal nitrides, pigments, dyes, etc. Those containing additives such as colorants, leveling agents, thickeners, water repellents, and antifoaming agents can be used.
As the adhesive, it is preferable to use one containing a solvent in order to maintain good coating workability. As the solvent, for example, toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, hexane, etc. can be used. Furthermore, in the case of forming an aqueous pressure-sensitive adhesive composition, water or an aqueous solvent mainly composed of water can be used.

[Adhesive film]
The adhesive film of the present invention can be prepared by applying the adhesive to at least one surface of the base material using an applicator, roll coater, gravure coater, reverse coater, spray coater, air knife coater, die coater, etc., and drying the adhesive film. It can be manufactured by In addition, the adhesive film is prepared by applying the adhesive on the surface of a release liner in advance using a knife coater, roll coater, die coater, etc. and drying it to form an adhesive layer. It can be manufactured by a transfer method in which it is attached to at least one surface of a base material.

The release liner is not particularly limited, but may include resin films such as polyethylene, polypropylene, and polyester films, paper, nonwoven fabrics, cloth, foam sheets, metal foils, and laminates thereof, on at least one side of the base material. Examples include those that have been subjected to release treatments such as silicone treatment, long-chain alkyl treatment, and fluorine treatment to improve releasability from adhesives.
Among these, high-quality paper laminated with polyethylene having a thickness of 10 to 40 μm on both sides, and a release liner in which one or both sides of a polyester film are subjected to a silicone release treatment are preferable.

Examples of methods for drying the adhesive layer include drying at 50° C. to 140° C. for 30 seconds to 10 minutes. Further, after the drying, aging may be further performed at a temperature in the range of 30° C. to 50° C. in order to accelerate the curing reaction.
The adhesive film of the present invention is crimped onto an optical film at a temperature of 23°C and a relative humidity of 50% RH using a 2 kg roller in one round trip. The 180° peeling adhesive force at a peeling speed of 300 mm/min after being left standing in an environment for 1 hour is 0.5 to 4.0 N/25 mm, preferably 0.7 N/25 mm to 2.5 N/25 mm. The range is more preferably 0.9N/25mm to 1.7N/25mm. In addition, the optical film was pressed with a 2 kg roller in an environment of a temperature of 23°C and a relative humidity of 50% RH, and was peeled off after being left standing for 30 seconds in an environment of a temperature of 120°C. The 180° peeling adhesive force at a speed of 300 mm/min is 0.5 to 4.0 N/25 mm, preferably in the range of 0.7 N/25 mm to 2.5 N/25 mm, and more preferably 0.9 N/25 mm. A range of 25 mm to 1.7 N/25 mm is preferable in order to obtain excellent peelability and peeling resistance. Note that the 180° peel adhesive strength of the pressure-sensitive adhesive film and the 180° peel adhesive strength after being placed in a 120° C. environment refer to values measured by the method described in Examples.

Since the adhesive film of the present invention has suitable easy peelability and peel resistance, it can be applied to various uses. Among these, the adhesive film of the present invention can be suitably applied to optical films. In particular, since the adhesive film of the present invention has suitable peelability and peeling resistance, it can be suitably applied as a carrier film and a protective film in the processing process of optical films, and prevents scratches on the surface of the optical film. Optical films can be transported without peeling even in high-temperature environments.

Examples of the optical film include polarizing plates, retardation plates, and films with high light transmittance. As the polarizing plate, a general one in which a polarizer protective layer is laminated on both sides or one side of a polarizer can be used.
As the polarizer, for example, one obtained using polyvinyl alcohol resin can be used. The polyvinyl alcohol resin can be produced by saponifying polyvinyl acetate resin. Further, the polarizer can be manufactured by, for example, adsorbing and orienting a dichroic dye onto a formed polyvinyl alcohol resin film.
A polarizing plate can be manufactured by laminating a polarizer protective layer such as a triacetyl cellulose film on both sides of the polarizer obtained above via an adhesive layer.

As the dichroic dye, iodine or a dichroic organic dye can be used. A polyvinyl alcohol resin film can be dyed with a dichroic dye by immersing the polyvinyl alcohol resin film in an aqueous solution containing these dyes. When using iodine as a dichroic dye, a method of dyeing by immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide is usually employed.

The polarizer protective layer is not particularly limited, but it is preferable to use one obtained using a resin with excellent transparency, assuming that it will be used as a display material.

Examples of the polarizer protective layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, and polyethylene terephthalate. Vinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, cycloolefin resin film, polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyether Examples include imide film, polyimide film, fluororesin film, nylon film, and acrylic resin film.

Furthermore, when forming polarizer protective layers on both sides of the polarizer layer, it is possible to form polarizer protective layers made of different resins on each side. For example, a polarizer protective layer made of a triacetyl cellulose film can be formed on one side of the polarizer layer, and a polarizer protective layer made of a cycloolefin resin film can be formed on the other side.

Further, hard coat layers may be formed on both sides of the polarizer protective layer. The resin used for forming the hard coat layer is not particularly limited, but includes UV-curable resins such as UV-curable acrylic urethane resins, UV-curable polyester acrylate resins, and UV-curable epoxy acrylate resins. Can be mentioned.
It is preferable to use a polarizing plate having a thickness of 50 μm to 200 μm because it can contribute to reducing the weight and thickness of information display devices and portable electronic terminals.

The present invention will be explained in more detail below using Examples and Comparative Examples.

[Adjustment example 1]
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 65 parts by mass of n-butyl acrylate, 28 parts by mass of methyl acrylate, 7 parts by mass of 2-hydroxyethyl (meth)acrylate, and 200 parts by mass of ethyl acetate were added. Parts by mass were charged and held at 72°C for 4 hours while stirring, and then held at 75°C for 5 hours.
Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) dissolved in ethyl acetate in advance was added to the first mixture, and the mixture was heated at 72°C under stirring. After holding for 4 hours, it was held at 75°C for 5 hours.
Next, ethyl acetate was added to the previous mixture, mixed uniformly, and filtered through a 200-mesh wire mesh to obtain an acrylic copolymer (A-1) solution with a weight average molecular weight of 570,000.
An adduct of tolylene diisocyanate and trimethylolpropane ("Burnock D-40" manufactured by DIC Corporation, hereinafter "D-40") was added to the acrylic copolymer (A-1) so that the gel fraction was 60%. ) was blended to obtain an adhesive composition (P-1).

[Adjustment example 2]
82 parts by mass of 2-ethylhexyl acrylate, 14 parts by mass of methyl acrylate, 4 parts by mass of 2-hydroxyethyl acrylate, and 200 parts by mass of ethyl acetate were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer. After charging and holding at 72°C for 4 hours while stirring, the mixture was held at 75°C for 5 hours.
Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) dissolved in ethyl acetate in advance was added to the first mixture, and the mixture was heated at 72°C under stirring. After holding for 4 hours, it was held at 75°C for 5 hours.
Next, ethyl acetate was added to the previous mixture, mixed uniformly, and filtered through a 200-mesh wire mesh to obtain an acrylic copolymer (A-2) solution with a weight average molecular weight of 880,000.
D-40 was blended into the acrylic copolymer (A-2) so that the gel fraction was 81% to obtain an adhesive composition (P-2).

[Adjustment example 3]
An adduct of tolylene diisocyanate and trimethylolpropane ("Burnock D-40" manufactured by DIC Corporation, hereinafter "D-40") was added to the acrylic copolymer (A-1) so that the gel fraction was 43%. A pressure-sensitive adhesive composition (P-3) was obtained in the same manner as in Preparation Example 1, except for blending.

[Adjustment example 4]
An adduct of tolylene diisocyanate and trimethylolpropane ("Burnock D-40" manufactured by DIC Corporation, hereinafter "D-40") was added to the acrylic copolymer (A-1) so that the gel fraction was 91%. A pressure-sensitive adhesive composition (P-4) was obtained in the same manner as in Preparation Example 1 except for blending .

[Comparison adjustment example 1]
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 88 parts by mass of 2-ethylhexyl acrylate, 8 parts by mass of 2-methoxyethyl acrylate, 1 part by mass of acrylic acid, and 3 parts by mass of 4-hydroxybutyl acrylate. Then, 150 parts by mass of ethyl acetate were charged, and then 2 parts by mass of a solution of 2,2'-azobis(2-methylbutyronitrile) dissolved in ethyl acetate in advance (solid content 0.1% by mass) was added to the previous mixture. was added and held at 72°C for 4 hours while stirring, and then held at 75°C for 5 hours.
Next, ethyl acetate was added to the above mixture, mixed uniformly, and filtered through a 200 mesh wire mesh to obtain a solution of acrylic copolymer (B-1) having a weight average molecular weight of 1.2 million.
D-40 was blended with the acrylic copolymer (B-1) so that the gel fraction was 89% to obtain a pressure-sensitive adhesive composition (Q-1).

[Comparison adjustment example 2]
93.4 parts by mass of 2-ethylhexyl acrylate, 3.5 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, and 0.0 parts of 2-hydroxyethyl acrylate were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer. 1 part by mass and 100 parts by mass of ethyl acetate were charged and held at 72°C for 4 hours while stirring, and then held at 75°C for 5 hours.
Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) dissolved in ethyl acetate in advance was added to the first mixture, and the mixture was heated at 72°C under stirring. After holding for 4 hours, it was held at 75°C for 5 hours.
Next, to 100 parts by mass of the previous mixture, 9.4 parts by mass of "Superester A100" (glycerin ester of disproportionated rosin) manufactured by Arakawa Chemical Co., Ltd. and "Haritac PCJ" (pentaerythritol of polymerized rosin) manufactured by Harima Kasei Co., Ltd. ester), ethyl acetate was added thereto, mixed uniformly, and filtered through a 200-mesh wire gauze to obtain an acrylic copolymer (B-2) solution with a weight average molecular weight of 1 million.
D-40 was blended with the acrylic copolymer (B-2) so that the gel fraction was 51% to obtain a pressure-sensitive adhesive composition (Q-2).

[Comparison adjustment example 3]
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 95 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of ethyl acrylate, 1.0 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate. After holding at 72°C for 4 hours under stirring, the mixture was held at 75°C for 5 hours.
Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) dissolved in ethyl acetate in advance was added to the first mixture, and the mixture was heated at 72°C under stirring. After holding for 4 hours, it was held at 75°C for 5 hours.
Next, ethyl acetate was added to the previous mixture, mixed uniformly, and filtered through a 200-mesh wire mesh to obtain an acrylic copolymer (B-3) solution with a weight average molecular weight of 290,000.
D-40 was blended into the acrylic copolymer (B-3) so that the gel fraction was 55% to obtain an adhesive composition (Q-3).

[Example 1]
The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm and one side was release-treated) to the thickness of the adhesive layer after drying. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer so that it had a thickness of 5 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-1) with a thickness of 55 μm was obtained by aging for 48 hours in an environment of 40°C.

[Example 2]
The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm and one side was release-treated) to the thickness of the adhesive layer after drying. A pressure-sensitive adhesive layer having a thickness of 10 μm was prepared by coating the adhesive layer so that the adhesive layer had a thickness of 10 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-2) with a thickness of 60 μm was obtained by aging for 48 hours in an environment of 40° C.

[Example 3]
The adhesive composition (P-2) obtained in Preparation Example 2 was applied to the release-treated surface of a mold release liner (a 75 μm thick polyethylene terephthalate film that was release-treated on one side) to the thickness of the adhesive layer after drying. A pressure-sensitive adhesive layer having a thickness of 10 μm was prepared by coating the adhesive layer so that the adhesive layer had a thickness of 10 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-3) with a thickness of 60 μm was obtained by aging for 48 hours in an environment of 40°C.

[Example 4]
The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm and one side was release-treated) to the thickness of the adhesive layer after drying. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer so that it had a thickness of 5 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.20%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-4) with a thickness of 55 μm was obtained by aging for 48 hours in an environment of 40° C.

[Example 5]
The adhesive composition (P-3) obtained in Preparation Example 1 was applied to the release-treated side of a release liner (75 μm thick polyethylene terephthalate film with one side peel-treated) to the thickness of the adhesive layer after drying. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer so that it had a thickness of 5 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-5) with a thickness of 55 μm was obtained by aging for 48 hours in an environment of 40° C.

[Example 6]
The adhesive composition (Q-1) obtained in Comparative Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm that was release-treated on one side), and the thickness of the adhesive layer after drying was applied. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer to a thickness of 5 μm and drying at 100° C. for 3 minutes.
Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (T-6) with a thickness of 55 μm was obtained by aging for 48 hours in an environment of 40° C.

[Comparative example 1]
The adhesive composition (Q-1) obtained in Comparative Preparation Example 1 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm that was release-treated on one side), and the thickness of the adhesive layer after drying was applied. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer to a thickness of 10 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (U-1) with a thickness of 60 μm was obtained by aging for 48 hours in an environment of 40°C.

[Comparative example 2]
The adhesive composition (Q-2) obtained in Comparative Preparation Example 2 was applied to the release-treated surface of a release liner (a polyethylene terephthalate film with a thickness of 75 μm and one side was release-treated), and the thickness of the adhesive layer after drying was applied. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer to a thickness of 10 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (U-2) with a thickness of 60 μm was obtained by aging for 48 hours in an environment of 40°C.

[Comparative example 3]
The adhesive composition (Q-3) obtained in Comparative Preparation Example 3 was applied to the release-treated side of a release liner (75 μm thick polyethylene terephthalate film with one side peel-treated), so that the thickness of the adhesive layer after drying was adjusted. A pressure-sensitive adhesive layer having a thickness of 5 μm was prepared by coating the adhesive layer to a thickness of 10 μm and drying it at 100° C. for 3 minutes.
Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (heat shrinkage rate: 0.03%), and from the top surface of the release liner, Lamination was performed using a roll with a linear pressure of 5 kg/cm.
Thereafter, the adhesive film (U-3) with a thickness of 60 μm was obtained by aging for 48 hours in an environment of 40°C.

[180° peeling adhesive strength]
The 180° peeling adhesive strength of the adhesive films of Examples and Comparative Examples was measured by the following method.
(1) Pressure was attached to an optical film (polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) at 23° C. and 50% RH using a 2 kg roller in one reciprocating motion.
(2) After being allowed to stand at 23° C. and 50% RH for 1 hour, the strength was measured when it was peeled off in a 180 degree direction at 23° C. and 50% RH at a tensile rate of 300 mm/powder (unit: N/25 mm).

[180° peeling adhesive strength after being placed in a 120°C environment]
The adhesive strength of the adhesive films of Examples and Comparative Examples was measured after being exposed to a 120° C. environment and peeled off at 180° using the following method.
(1) Pressure was attached to an optical film (polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) at 23° C. and 50% RH using a 2 kg roller in one reciprocating motion.
(2) After standing at 23°C, 50% RH for 1 hour, standing at 120°C for 30 seconds, and peeling in 180 degree direction at 23°C, 50% RH at a tensile speed of 300 mm/min. It was measured (unit: N/25mm).

[Easy peelability]
The easy peelability of the adhesive films of Examples and Comparative Examples was measured by the following method.
1) Press an adhesive film with an outer diameter of 25 mm x 50 mm on an optical film with an outer diameter of 30 mm x 100 mm (polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) at 23°C and 50% RH with one round trip of a 2 kg roller. Attached.
2) After leaving the adhesive film at 23°C and 50% RH for 1 hour, leaving it at 120°C for 30 seconds, and peeling off the adhesive film by hand at 23°C and 50% RH, the ease of peeling and the optical film. Assessed the condition.
◎: The adhesive film could be peeled off without deformation or destruction of the optical film.
○: There was resistance to peeling, but the adhesive film could be peeled off without deformation or destruction of the optical film.
×: Unable to peel off and the optical film was destroyed.

[Peeling resistance at 120°C]
The peel resistance of the adhesive films of Examples and Comparative Examples at 120° C. was measured by the following method.
(1) An optical film with an outer diameter of 25 mm x 25 mm was attached to the center of an adhesive film with an outer diameter of 50 mm x 50 mm under pressure at 23° C. and 50% RH with one reciprocation of a 2 kg roller.
(2) After standing at 23° C. and 50% RH for 1 hour, a 500 g weight was placed on the center of the adhesive film from the adhesive film side at 120° C. and left standing for 30 seconds. Thereafter, the weight was removed, and the degree of peeling of the optical film was checked at 23° C. and 50% RH.
◎: The optical film was not peeled off from the adhesive film at all.
○: Peeling occurred about 1 to 2 mm from the edge of the optical film.
Δ: Peeling occurred about 5 to 10 mm from the edge of the optical film.
x: The optical film peeled off from the adhesive film.

[Measurement method of loss tangent (Tandδ ₁₂₀ ) at 120°C]
Each of the adhesive compositions obtained above was applied to the surface of a release liner and heated in an oven at 85°C for 4 minutes to produce an adhesive layer with a thickness of 50 μm, and the resulting adhesive A pressure-sensitive adhesive layer having a thickness of 2 mm was prepared by stacking the layers.
Next, the pressure-sensitive adhesive layer was cut into a circular shape with a diameter of 8 mm to prepare a test piece.
Next, using a viscoelasticity tester (manufactured by Rheometrics, trade name: Ares 2KSTD), the test piece was sandwiched between parallel disks, which are the measurement parts of the tester, and tested at a temperature of 120°C and a frequency of 1Hz. The storage modulus (G') and loss modulus (G'') of the sample were measured, and the loss tangent (Tan δ ₁₂₀ ) was calculated from the G' and G''.

[Heat shrinkage rate at 120°C]
The base material (A) cut into an outer diameter of 100 mm x 100 mm was left standing at 120°C for 30 seconds, the outer dimensions were measured at 23°C and 50% RH, and the heat shrinkage rate at 120°C was determined by the following formula. Ta.
Heat shrinkage rate at 120°C = [(100-L)/100] x 100 (unit: %)
(L is the external dimension after standing at 120℃ for 30 seconds, and the unit is mm)

[Checking for adhesive residue after peeling off the adhesive film]
After measuring the adhesion strength by peeling off at 180° after being placed in the 120°C environment, we visually confirmed the location where the adhesive film was attached to the optical film (polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface). It was confirmed that no adhesive residue from the adhesive film remained on the optical film.
Next, the water contact angle (AN1) of the optical film where the adhesive film was attached was measured and compared with the water contact angle (AN2) of the polarizing plate before the adhesive film was attached.
◎: There was no adhesive residue and no change in water contact angle.
○: There was no adhesive residue, but AN1 was higher than AN2.
×: Adhesive residue remained on the optical film.

Claims (2)

An adhesive tape having an adhesive layer (B) on at least one surface of a base material (A), either directly or via another layer,
The base material (A) was cut into a size of 100 mm x 100 mm and left to stand at 120°C for 30 seconds, and then the outer dimension L was measured at 23°C and 50% RH, and the calculation formula [(100-L)/100] The shrinkage rate of the base material (A) calculated by ×100 (unit: %) is 0.03 to 0.1%,
The adhesive composition constituting the adhesive layer (B) is a (meth)acrylic adhesive composition,
The (meth)acrylic adhesive composition contains an acrylic copolymer whose main monomer component is a (meth)acrylate monomer having 1 to 12 carbon atoms,
The content of the (meth)acrylate monomer having 1 to 12 carbon atoms is 80 to 98.5% by mass in the monomer components constituting the acrylic copolymer,
The adhesive layer (B) contains an isocyanate-based crosslinking agent,
The adhesive layer (B) has a gel fraction of 50% to 90%,
A 2 kg roller was used to press the optical film in an environment of a temperature of 23°C and a relative humidity of 50% RH in one round trip, and the film was left for one hour in an environment of a temperature of 23°C and a relative humidity of 50% RH. The adhesive strength after 180° peeling at a peeling speed of 300 mm/min is 0.5 to 4 N/25 mm,
A 2 kg roller was used to press the optical film in a 23 degree Celsius environment and a relative humidity of 50% RH, and the film was left to stand for 30 seconds in a 120 degree Celsius environment, with a peeling speed of 300 mm. /min 180° peeling adhesive strength is 0.5 to 4N/25mm,
An adhesive film having a loss tangent (Tan δ120) of 1.0 or less at 120° C. and 1 Hz. The adhesive film according to claim 1, which is used for protecting the surface of a polarizing plate.