Adhesive protective film and composition for producing adhesive protective film

Abstract

To provide an adhesive protective film capable of preventing deformation of an adhesive layer and occurrence of poor appearance even when winding an adhesive protective film to form a roll body, and an adhesive protective film manufacturing composition.SOLUTION: An adhesive protective film includes a laminate having an adhesive layer laminated on a film base material. The adhesive layer is the cured product of an adhesive composition; the adhesive composition includes at least an acrylic copolymer and an isocyanate cross linking agent; the adhesive layer has a storage elastic modulus G'(25°C) at 25°C of 1.5 MPa or more; and when setting a storage elastic modulus at 80°C to G'(80°C), the following formula (1) is satisfied: 0.65≤G'(80°C) / G'(25°C)≤1.0 (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive protective film and a composition for producing an adhesive protective film. [Background technology]

[0002] Adhesive protective films are used to be attached to panels made of, for example, glass or plastic, and such adhesive protective films can not only protect the panel surface but also impart design features, etc. Adhesive protective films have an adhesive layer provided on a film (film substrate) that serves as a substrate, and the adhesive layer is attached to the panel surface to bond them together.

[0003] For example, acrylic adhesives are widely known as pressure-sensitive adhesive layers, and in recent years, pressure-sensitive adhesive layers containing various acrylic adhesives with improved properties such as adhesiveness have been proposed. The pressure-sensitive adhesive layer used in the pressure-sensitive adhesive protective film must have a high degree of smoothness to enhance adhesion to the panel, and various pressure-sensitive adhesive layers have been proposed from this perspective. As a pressure-sensitive adhesive layer with improved smoothness, a pressure-sensitive adhesive sheet containing an acrylic polymer with a storage modulus adjusted to an appropriate range has been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-105974 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a conventional pressure-sensitive adhesive layer is applied to an adhesive protective film, the pressure applied when the adhesive protective film is wound into a roll can cause deformation of the adhesive, resulting in a problem of poor appearance of the adhesive protective film. Such poor appearance is caused, for example, by unevenness in the film substrate used to form the adhesive protective film, or, when a release film is further attached to the adhesive protective film, by unevenness in the release film.

[0006] From this viewpoint, there has been a strong demand for an adhesive protective film in which the adhesive layer is less likely to deform and the appearance is less likely to be defective even when the adhesive protective film is wound into a roll.

[0007] The present invention has been made in view of the above, and aims to provide an adhesive protective film and a composition for manufacturing an adhesive protective film in which the adhesive layer is less likely to deform and poor appearance occurs even when the adhesive protective film is wound into a roll. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the inventors discovered that the above-mentioned object can be achieved by using a pressure-sensitive adhesive layer formed from specific components, and thus completed the present invention.

[0009] That is, the present invention includes, for example, the subject matter described in the following sections. Item 1 An adhesive protective film comprising a laminate in which an adhesive layer is laminated on a film substrate, the pressure-sensitive adhesive layer is a cured product of a pressure-sensitive adhesive composition, The pressure-sensitive adhesive composition contains at least an acrylic copolymer and an isocyanate crosslinking agent, The pressure-sensitive adhesive layer has a storage modulus G'(25°C) of 1.4 MPa or more at 25°C, and when the storage modulus G'(80°C) at 80°C is taken as G', the following formula (1) is satisfied: 0.65≦G'(80℃) / G'(25℃)≦1.0 (1) Meet the adhesive protective film. Section 2 Item 2. The pressure-sensitive adhesive protective film according to item 1, wherein the pressure-sensitive adhesive composition contains 5 parts by mass or more of the isocyanate crosslinking agent relative to 100 parts by weight of the acrylic copolymer. Section 3 Item 3. The adhesive protective film according to item 1 or 2, wherein the adhesive composition contains a crosslinking accelerator and a crosslinking retarder. Section 4 Item 4. The adhesive protective film according to any one of items 1 to 3, having an adhesive strength to glass of 0.1 N / 25 mm or less. Section 5 Item 1 to 4, comprising the adhesive protective film according to any one of items 1 to 4 and a release film; The release film is attached to the pressure-sensitive adhesive layer, forming a release film-attached adhesive protective film. Section 6 A composition for producing an adhesive protective film according to any one of items 1 to 4, A composition for producing an adhesive protective film, comprising the above adhesive composition. [Effects of the Invention]

[0010] In the pressure-sensitive adhesive protective film of the present invention, even when wound into a roll, the pressure-sensitive adhesive layer is less likely to deform and poor appearance is less likely to occur. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0012] 1. Adhesive protective film The pressure-sensitive adhesive protective film of the present invention includes a laminate in which a pressure-sensitive adhesive layer is laminated on a film substrate, the pressure-sensitive adhesive layer being a cured product of a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition containing at least an acrylic copolymer and an isocyanate crosslinking agent, the pressure-sensitive adhesive layer having a storage modulus G'(25°C) of 1.4 MPa or more at 25°C, and a storage modulus G'(80°C) at 80°C that satisfies the following formula (1): 0.65≦G'(80℃) / G'(25℃)≦1.0 (1) Meet the following.

[0013] By having the above-mentioned constitution, the pressure-sensitive adhesive protective film of the present invention is less likely to deform and less likely to have poor appearance even when wound into a roll.

[0014] (Adhesive layer) In the pressure-sensitive adhesive protective film of the present invention, the pressure-sensitive adhesive layer is formed from a cured product of a pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition, and in particular, can be formed by curing the pressure-sensitive adhesive composition as described below. The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer will be described below.

[0015] As described above, the pressure-sensitive adhesive composition contains at least an acrylic copolymer and an isocyanate crosslinking agent.

[0016] <Acrylic copolymer> The acrylic copolymer is the main component of the pressure-sensitive adhesive layer and is a component that allows the pressure-sensitive adhesive layer to exhibit adhesive properties. The type of acrylic copolymer is not particularly limited, and examples thereof include a wide range of (meth)acrylic copolymers used in conventional pressure-sensitive adhesive layers. In this specification, "(meth)acrylic" means "acrylic" or "methacrylic", "(meth)acrylate" means "acrylate" or "methacrylate", and "(meth)allyl" means "allyl" or "methallyl".

[0017] The acrylic copolymer may have, for example, a (meth)acrylic acid alkyl ester unit. In this specification, the term "unit" refers to a repeating structural unit (also referred to as a monomer unit) that constitutes a polymer. The (meth)acrylic acid alkyl ester unit is derived from a (meth)acrylic acid alkyl ester. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic copolymer may contain one type of (meth)acrylic acid alkyl ester unit alone, or may contain two or more types of units.

[0018] Among the above alkyl (meth)acrylates, methyl (meth)acrylate, n-butyl (meth)acrylate, etc. are preferred because they increase adhesiveness.

[0019] The acrylic high molecular weight polymer (A) contains a carboxyl group-containing monomer unit as an essential structural unit. Examples of the carboxyl group-containing monomer for forming the carboxyl group-containing acrylic monomer unit include acrylic acid and methacrylic acid.

[0020] The acrylic copolymer may contain a monomer unit other than the (meth)acrylic acid alkyl ester unit. Examples of the other monomer unit include a monomer unit having a crosslinkable functional group, such as a carboxyl group-containing monomer unit or a hydroxyl group-containing monomer unit. By containing the monomer unit having a crosslinkable functional group, the acrylic copolymer is more likely to form a crosslinked structure in the pressure-sensitive adhesive layer by reaction with an isocyanate crosslinking agent.

[0021] The carboxyl group-containing monomer unit is a monomer unit formed by a carboxyl group-containing monomer, such as acrylic acid or methacrylic acid.

[0022] The hydroxyl group-containing monomer unit is a monomer unit formed by a hydroxyl group-containing monomer. Examples of the hydroxyl group-containing acrylic monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, (meth)acrylic acids [(mono-, di-, or poly)alkylene glycols] such as mono(diethylene glycol) (meth)acrylate, and (meth)acrylic acid lactones such as monocaprolactone (meth)acrylate.

[0023] When the acrylic copolymer contains a monomer unit having a crosslinkable functional group, the monomer unit having a crosslinkable functional group is preferably a hydroxyl group-containing monomer unit, in which case the pressure-sensitive adhesive layer can be easily adjusted to a desired storage modulus and the formula (1) can be easily satisfied.

[0024] The acrylic copolymer may contain monomer units other than the (meth)acrylic acid alkyl ester units and the monomer units having a crosslinkable functional group, or may consist solely of the (meth)acrylic acid alkyl ester units and the monomer units having a crosslinkable functional group.

[0025] The acrylic copolymer preferably contains 50% by mass or more of (meth)acrylic acid alkyl ester units, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less.

[0026] In terms of making it easy to adjust the storage modulus of the pressure-sensitive adhesive layer to the desired range and to satisfy the formula (1), the acrylic copolymer preferably contains 0.5% by mass or more of monomer units having a crosslinkable functional group (particularly hydroxyl group-containing monomer units), more preferably 1% by mass or more, even more preferably 2% by mass or more, and particularly preferably 3% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less.

[0027] The mass average molecular weight of the acrylic copolymer is not particularly limited and can be set within an appropriate range so that the pressure-sensitive adhesive layer has the desired G' (25°C) and gel fraction. The mass average molecular weight of the acrylic copolymer can be, for example, 500,000 or more and 2,000,000 or less. The mass average molecular weight of the acrylic copolymer is preferably 600,000 or more, more preferably 700,000 or more, and is preferably 1,800,000 or less, more preferably 1,600,000 or less, even more preferably 1,500,000 or less, and particularly preferably 1,300,000 or less.

[0028] The mass average molecular weight of the acrylic copolymer is a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. The measurement conditions for gel permeation chromatography (GPC) are as follows: Solvent: tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (four columns connected together, manufactured by Showa Denko K.K.) Column temperature: 40℃ Sample concentration: 0.5% by mass Detector: RI-2031plus (JASCO) Pump: RI-2080plus (JASCO) Flow rate (flow rate): 0.8ml / min Injection volume: 10μL Calibration curve: A calibration curve using 10 samples of standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko) with Mw = 1320 to 2500000 is used.

[0029] The acrylic copolymer can be produced by a known method, for example, by a polymerization reaction of (meth)acrylic monomers. In this case, various polymerization methods can be used, such as solution polymerization, emulsion polymerization, and suspension polymerization.

[0030] <Isocyanate crosslinking agent> The isocyanate crosslinking agent contained in the pressure-sensitive adhesive composition is a component for crosslinking the acrylic copolymer. By including the isocyanate crosslinking agent in the pressure-sensitive adhesive composition, it becomes easier to adjust the gel fraction of the pressure-sensitive adhesive layer within a desired range, and deformation of the pressure-sensitive adhesive layer can be suppressed, thereby making it less likely for poor appearance to occur.

[0031] Examples of the isocyanate crosslinking agent include a wide range of isocyanate compounds used to form pressure-sensitive adhesive layers. The isocyanate compound preferably has two or more isocyanate groups, more preferably three or more, and preferably six or less.

[0032] Examples of isocyanate compounds include polyisocyanates such as tolylene diisocyanate, isophorone diisocyanate, chlorophenylene diisocyanate, diphenylmethane diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate and cyclohexylene diisocyanate; and aromatic isocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate. The isocyanate compounds can be used alone or in combination of two or more different types. Examples of commercially available products include a tolylene diisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), a xylylene diisocyanate compound (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.), and "Crosslinker N" manufactured by Lion Specialty Chemicals.

[0033] The pressure-sensitive adhesive composition may contain a crosslinking agent other than an isocyanate crosslinking agent, as long as the effects of the present invention are not impaired. Such a crosslinking agent may be selected from known crosslinking agents such as epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds. The crosslinking agent contained in the pressure-sensitive adhesive composition may be an isocyanate crosslinking agent alone. The pressure-sensitive adhesive composition may contain one or more crosslinking agents.

[0034] The content of the isocyanate crosslinking agent in the pressure-sensitive adhesive composition is not particularly limited. For example, the pressure-sensitive adhesive composition preferably contains 5 parts by mass or more of the isocyanate crosslinking agent per 100 parts by weight of the acrylic copolymer, since this makes it easier to adjust the storage modulus and gel fraction of the pressure-sensitive adhesive layer to the desired range and to satisfy formula (1). The pressure-sensitive adhesive composition more preferably contains 6 parts by mass or more of the isocyanate crosslinking agent per 100 parts by weight of the acrylic copolymer, more preferably contains 7 parts by mass or more, even more preferably contains 7.5 parts by mass or more, and particularly preferably contains 8 parts by mass or more. Furthermore, the pressure-sensitive adhesive composition preferably contains 30 parts by mass or less of the isocyanate crosslinking agent per 100 parts by weight of the acrylic copolymer, more preferably contains 25 parts by mass or less, and even more preferably contains 20 parts by mass or less.

[0035] <Adhesive composition> The pressure-sensitive adhesive composition of the present invention may contain other components as long as the effects of the present invention are not impaired. For example, the pressure-sensitive adhesive composition may contain a crosslinking accelerator and / or a crosslinking retarder. When the pressure-sensitive adhesive composition contains a crosslinking accelerator and / or a crosslinking retarder, the storage modulus and gel fraction of the pressure-sensitive adhesive layer formed are easily adjusted to the desired range, and the formula (1) is easily satisfied. As a result, the pressure-sensitive adhesive protective film is less likely to suffer from poor appearance. When the pressure-sensitive adhesive composition contains both a crosslinking accelerator and a crosslinking retarder, the storage modulus and gel fraction are particularly easily adjusted to the desired range, and the formula (1) is easily satisfied. As a result, the pressure-sensitive adhesive protective film is particularly less likely to suffer from poor appearance. This is because the crosslinking reaction by the isocyanate crosslinking agent that occurs during the formation of the pressure-sensitive adhesive layer proceeds at an appropriate speed due to the actions of both the crosslinking accelerator and the crosslinking retarder.

[0036] The crosslinking accelerator can be exemplified by a wide range of known crosslinking accelerators used for forming known pressure-sensitive adhesive layers. Examples of the crosslinking accelerator include organotin compounds; amino compounds such as N,N,N',N'-tetramethylhexanediamine, triethylamine, and imidazole; metal complexes such as aluminum complexes; and acid catalysts such as paratoluenesulfonic acid, phosphoric acid, hydrochloric acid, and ammonium chloride. Among these, the crosslinking accelerator is preferably an organotin compound from the viewpoint of catalytic action.

[0037] Examples of organotin compounds include organotin compounds such as dimethyltin dichloride; fatty acid salts of organotin compounds such as dimethyltin dilaurate, dimethyltin di(2-ethylhexanoate), dimethyltin diacetate, dibutyltin dilaurate, dihexyltin diacetate, and dioctyltin dilaurate; thioglycolic acid ester salts of organotin compounds such as dimethyltin bis(isooctylthioglycolic acid ester) salt and dioctyltin bis(isooctylthioglycolic acid ester) salt; and metal soaps such as tin octoate and tin decanoate. Among these, fatty acid salts of organotin compounds are preferred from the viewpoint of catalytic activity, and dibutyltin dilaurate is particularly preferred.

[0038] The pressure-sensitive adhesive composition may contain one or more types of cross-linking accelerators. The content ratio of the cross-linking accelerator in the pressure-sensitive adhesive composition is not particularly limited. For example, in order to facilitate adjustment of the storage modulus and gel fraction of the pressure-sensitive adhesive layer to the desired ranges and to facilitate satisfying the formula (1), the pressure-sensitive adhesive composition preferably contains 0.001 part by mass or more of the cross-linking accelerator per 100 parts by weight of the acrylic copolymer, more preferably 0.005 part by mass or more, and even more preferably 0.01 part by mass or more, and preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and even more preferably 0.1 part by mass or less.

[0039] The crosslinking retarder is a component that inhibits the progression of the effect of the pressure-sensitive adhesive composition before it forms a pressure-sensitive adhesive layer (e.g., during storage of the pressure-sensitive adhesive composition). Examples of the crosslinking retarder include a wide range of known crosslinking retarders used to form known pressure-sensitive adhesive layers. Examples of crosslinking retarders include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, and β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. Among these, acetylacetone is preferred as the crosslinking retarder, as it allows for easy adjustment of the storage modulus and gel fraction of the pressure-sensitive adhesive layer to the desired ranges.

[0040] The pressure-sensitive adhesive composition may contain one or more types of crosslinking retarders. The content ratio of the crosslinking retarder in the pressure-sensitive adhesive composition is not particularly limited. For example, in order to easily adjust the storage modulus and gel fraction of the pressure-sensitive adhesive layer to the desired range and easily satisfy the formula (1), the pressure-sensitive adhesive composition preferably contains 0.01 parts by mass or more of the crosslinking retarder relative to 100 parts by weight of the acrylic copolymer, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.5 parts by mass or less.

[0041] The PSA composition may contain a solvent as needed. When the PSA composition contains a solvent, the PSA composition has improved coatability, facilitating the formation of a PSA layer.

[0042] Examples of the solvent include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate, and derivatives thereof.

[0043] The content of the solvent in the pressure-sensitive adhesive composition is not particularly limited, and is preferably 25 to 500 parts by mass, more preferably 30 to 400 parts by mass, relative to 100 parts by mass of the acrylic copolymer. In addition, the content of the solvent relative to the total mass of the pressure-sensitive adhesive composition is preferably 10 to 90% by mass, more preferably 20 to 80% by mass. The pressure-sensitive adhesive composition may contain one or more solvents.

[0044] The pressure-sensitive adhesive composition may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. The other components may be selected as needed from, for example, tackifiers, silane coupling agents, plasticizers, antioxidants, metal corrosion inhibitors, ultraviolet absorbers, and light stabilizers such as hindered amine compounds. Furthermore, dyes or pigments may be added for the purpose of coloring.

[0045] When a so-called after-cure type pressure-sensitive adhesive layer is to be obtained, the pressure-sensitive adhesive composition contains a photopolymerization initiator and a monofunctional or polyfunctional monomer to impart after-cure properties. However, in the present invention, the pressure-sensitive adhesive layer does not need to be an after-cure type pressure-sensitive adhesive layer, and therefore, it is preferable that the pressure-sensitive adhesive composition does not contain a photopolymerization initiator, a monofunctional monomer, or a polyfunctional monomer.

[0046] The method for preparing the pressure-sensitive adhesive composition is not particularly limited, and for example, a wide range of known methods for preparing pressure-sensitive adhesive compositions can be employed.

[0047] <Adhesive layer> The pressure-sensitive adhesive layer is a layer formed by curing the pressure-sensitive adhesive composition as described above, and is formed by curing the pressure-sensitive adhesive composition. Therefore, the cured product of the pressure-sensitive adhesive composition includes, for example, a crosslinked structure formed by crosslinking an acrylic copolymer with an isocyanate crosslinking agent. In the cured product, volatile components such as the solvent of the pressure-sensitive adhesive composition can be removed as much as possible. The pressure-sensitive adhesive layer may contain other components in addition to the cured product of the pressure-sensitive adhesive composition, or the pressure-sensitive adhesive layer may be formed only from the cured product of the pressure-sensitive adhesive composition.

[0048] The method for forming a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition (i.e., a method for curing the pressure-sensitive adhesive composition) is not particularly limited, and for example, a wide variety of known methods can be employed. Among these, it is preferable to form a pressure-sensitive adhesive layer by a production method including a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of heating this coating film. If the pressure-sensitive adhesive composition contains a solvent, the solvent is removed in the heating step, and at the same time, the reaction between the acrylic copolymer and the isocyanate crosslinking agent proceeds to form a cured product.

[0049] The PSA composition can be applied using a known coating device, such as an applicator, blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0050] The substrate used when applying the pressure-sensitive adhesive composition may be, for example, a film substrate constituting a pressure-sensitive adhesive protective film, a release film described below that can be provided on a pressure-sensitive adhesive protective film, or a substrate other than these.

[0051] The thickness of the pressure-sensitive adhesive composition after application is not particularly limited, and can be appropriately set depending on the desired thickness of the pressure-sensitive adhesive layer.

[0052] In the step of heating the coating film, the heating temperature is not particularly limited, and is preferably, for example, 50 to 150°C. This heating promotes the curing reaction and removes as much volatile matter as possible, such as the solvent, from the pressure-sensitive adhesive composition. The heating time can be adjusted appropriately depending on the heating temperature, the thickness of the coating film, and the content of the solvent in the pressure-sensitive adhesive composition, and can be, for example, 1 to 60 minutes. Known heating devices such as a heating furnace or an infrared lamp can be used to heat the coating film. After heating, it is preferable to subject the pressure-sensitive adhesive sheet to an aging treatment in which it is left to stand at a constant temperature for a certain period of time. The aging treatment can be performed, for example, by leaving it to stand at 23°C for 7 days.

[0053] The pressure-sensitive adhesive layer has a storage modulus G'(25°C) of 1.4 MPa or more at 25°C. If the storage modulus G'(25°C) of the pressure-sensitive adhesive layer is less than 1.4 MPa, it becomes difficult to satisfy the formula (1) above, and when the pressure-sensitive adhesive protective film is wound into a roll, the pressure-sensitive adhesive layer will deform, resulting in poor appearance. The storage modulus G'(25°C) of the pressure-sensitive adhesive layer is preferably 1.5 MPa or more, more preferably 1.6 MPa or more, and particularly preferably 1.7 MPa or more. The upper limit of the storage modulus G'(25°C) of the pressure-sensitive adhesive layer can be, for example, 3 MPa or less, preferably 2 MPa or less.

[0054] When the storage modulus of the pressure-sensitive adhesive layer at 80°C is G'(80°C), the following formula (1) 0.65≦G'(80℃) / G'(25℃)≦1.0 (1) If G'(80°C) / G'(25°C) is less than 0.65, when the adhesive protective film is wound into a roll, the adhesive layer will deform, resulting in poor appearance.

[0055] The value of G'(80°C) / G'(25°C) is preferably 0.67 or more, more preferably 0.7 or more, even more preferably 0.75 or more, and particularly preferably 0.8 or more. The value of G'(80°C) / G'(25°C) is preferably 0.99 or less, more preferably 0.98 or less.

[0056] Furthermore, the pressure-sensitive adhesive layer preferably satisfies the relationship 0.65≦G′(T°C) / G′(25°C)≦1.0 over the entire temperature range from 25°C to 80°C, where G′(T°C) is the storage modulus at T°C (where 25≦T≦80). That is, the value of G′(T°C) / G′(25°C) (25≦T≦80) is preferably 0.65 or more and 1.0 or less. This makes the pressure-sensitive adhesive layer less likely to deform and less likely to cause poor appearance even when the pressure-sensitive adhesive protective film is wound into a roll. The value of G′(T°C) / G′(25°C) (25≦T≦80) is preferably 0.67 or more, more preferably 0.7 or more, even more preferably 0.75 or more, particularly preferably 0.8 or more, and is preferably 0.99 or less, more preferably 0.98 or less.

[0057] Although we do not necessarily wish to make a restrictive interpretation, it is presumed that when formula (1) is satisfied, or when the relationship 0.65≦G'(T°C) / G'(25°C)≦1.0 is satisfied, the change in storage modulus of the adhesive layer with temperature is reduced, which makes it easier to suppress deformation of the adhesive layer in response to changes in the external environment during storage of the roll body.

[0058] The gel fraction of the pressure-sensitive adhesive layer is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more, which makes the pressure-sensitive adhesive layer less likely to deform and less likely to cause poor appearance even when the pressure-sensitive adhesive protective film is wound into a roll.

[0059] In particular, the gel fraction of the pressure-sensitive adhesive layer is preferably 95% or more 24 hours after the pressure-sensitive adhesive layer is formed. In this case, even when the pressure-sensitive adhesive protective film is wound into a roll, the pressure-sensitive adhesive layer is particularly resistant to deformation and poor appearance is particularly unlikely to occur. Furthermore, the gel fraction of the pressure-sensitive adhesive layer is 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more 1 hour after the pressure-sensitive adhesive layer is formed. Although no restrictive interpretation is desired, it is presumed that a gel fraction of 95% 24 hours or 1 hour after the pressure-sensitive adhesive layer is formed allows the crosslinking reaction to proceed quickly during the formation of the pressure-sensitive adhesive layer, making it easier to suppress deformation of the pressure-sensitive adhesive layer due to unevenness in the film substrate or release film, as described below.

[0060] Here, "X hours after the formation of the pressure-sensitive adhesive layer" refers to the time when X hours have elapsed from the starting point immediately after the pressure-sensitive adhesive composition is applied to a substrate, heated to promote a curing reaction, and then the pressure-sensitive adhesive layer is formed.

[0061] The gel fraction of the adhesive layer is a value measured by the following method. First, approximately 0.1 g of the adhesive layer is collected in a sample bottle, 30 ml of ethyl acetate is added, and the mixture is shaken for 24 hours. The contents of the sample bottle are then filtered through a 150-mesh stainless steel wire mesh, and the residue on the mesh is dried at 120°C for 1 hour to measure the dry mass (g). The obtained dry mass is then calculated using the following formula: Gel fraction (mass%) = (dry mass / collected mass of adhesive layer) × 100 The gel fraction can be calculated by

[0062] The pressure-sensitive adhesive layer can have a single-layer structure, or can have a multi-layer structure in which multiple single-layer pressure-sensitive adhesive layers are laminated. The thickness of the pressure-sensitive adhesive layer can be appropriately set depending on the application and is not particularly limited. For example, the thickness of the pressure-sensitive adhesive layer is preferably 5 to 50 μm, and more preferably 10 to 40 μm. When the pressure-sensitive adhesive layer has a multi-layer laminate structure, the thickness of the pressure-sensitive adhesive layer refers to the total thickness of each layer.

[0063] (Film substrate) In the adhesive protective film of the present invention, the film substrate is a component that serves as the base material of the adhesive protective film, and its type is not particularly limited; for example, substrates used in known adhesive protective films can be widely applied.

[0064] As the film substrate, for example, a wide variety of known films can be used, and specific examples thereof include polyethylene terephthalate film, acrylic film, polycarbonate film, polyolefin film, triacetyl cellulose film, and cycloolefin polymer film.

[0065] The film substrate may be transparent or translucent. The thickness of the film substrate is not particularly limited and may be, for example, the same thickness as that of a known protective film. The thickness of the film substrate may be, for example, 10 to 200 μm.

[0066] (Adhesive protective film) The pressure-sensitive adhesive protective film of the present invention includes a laminate in which a pressure-sensitive adhesive layer is laminated on a film substrate. The pressure-sensitive adhesive layer can be provided directly on the film substrate, or another layer may be interposed between the pressure-sensitive adhesive layer and the film substrate, but it is preferable that the pressure-sensitive adhesive layer is provided directly on the film substrate.

[0067] The adhesive protective film of the present invention has an adhesive strength to glass of, for example, 0.1 N / 25 mm or less. The adhesive strength of the adhesive sheet to glass is measured in accordance with the adhesive strength measurement method described in JIS Z 0237, and the details of the measurement conditions are as described in the Examples.

[0068] The adhesive protective film of the present invention may be an adhesive protective film with a release film, i.e., the present invention encompasses an adhesive protective film with a release film. The adhesive protective film of the present invention comprises the adhesive protective film of the present invention and a release film. The release film is attached to the surface of the adhesive protective film on the side of the adhesive layer.

[0069] As the release film, a wide variety of known release sheets can be used, including a release laminate sheet formed by forming a release agent layer on one side of a release sheet substrate. The release agent constituting the release agent layer is not limited, and examples thereof include general-purpose addition or condensation type silicone release agents and long-chain alkyl group-containing compounds. The release laminate sheet can also be obtained commercially, including a heavy-duty separator film made by Toyobo Co., Ltd., which is a release-treated polyethylene terephthalate film, and a light-duty separator film made by Toyobo Co., Ltd., which is a release-treated polyethylene terephthalate film.

[0070] The adhesive protective film of the present invention includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and therefore the pressure-sensitive adhesive layer is less likely to deform and cause poor appearance even when wound into a roll. Conventionally, when an adhesive protective film is wound into a roll, the pressure of the winding can cause the adhesive to deform, resulting in a problem of poor appearance of the adhesive protective film. However, the adhesive protective film of the present invention is less likely to deform and cause poor appearance even when wound into a roll, and is less likely to develop the so-called orange peel pattern. Therefore, even if the film substrate for forming the adhesive protective film has irregularities, or if a release film having irregularities is attached to the adhesive protective film, the adhesive protective film of the present invention is less likely to suffer from deformation of the adhesive layer due to these irregularities.

[0071] Therefore, the pressure-sensitive adhesive protective film of the present invention is suitable for use as a film for protecting panels made of various glass substrates, plastic substrates, etc., and can provide high designability as well as protecting the panel.

[0072] 2. Composition for manufacturing adhesive protective film The pressure-sensitive adhesive composition can be suitably used as a raw material for producing a pressure-sensitive adhesive protective film, and is particularly suitable as a raw material for forming a pressure-sensitive adhesive layer of the pressure-sensitive adhesive protective film. Therefore, the composition for producing a pressure-sensitive adhesive protective film of the present invention preferably contains the pressure-sensitive adhesive composition.

[0073] The composition for producing an adhesive protective film of the present invention may contain components other than the adhesive composition, or may consist solely of the adhesive composition.

[0074] By using the composition for producing an adhesive protective film of the present invention, for example, a pressure-sensitive adhesive layer can be formed on the film substrate, and this can be used as an adhesive protective film. Since the obtained adhesive protective film has the pressure-sensitive adhesive layer, even when wound into a roll, the pressure-sensitive adhesive layer is less likely to deform and poor appearance is less likely to occur. [Example]

[0075] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] (Production Example 1-1: Acrylic Copolymer A) A mixed monomer mixture of butyl acrylate (BA) and hydroxyethyl acrylate (HEA) in a mass ratio of 95:5 was polymerized in the presence of AIBN (azobisisobutyronitrile) in ethyl acetate, a polymerization solvent, by heating to 60°C. This yielded a solution of acrylic copolymer A with a solids concentration of 30% by mass. The weight-average molecular weight (Mw) of acrylic copolymer A was 500,000.

[0077] (Production Example 1-2: Acrylic Copolymer B) A solution of acrylic copolymer B having a solid content of 30% by mass and a Mw of 500,000 was obtained in the same manner as in Production Example 1-1, except that the mixed monomer was changed to a mixed monomer having a mass ratio of BA and HEA of 85:15.

[0078] (Production Example 1-3: Acrylic Copolymer C) A solution of acrylic copolymer C having a solid content of 30% by mass and a Mw of 500,000 was obtained in the same manner as in Production Example 1-1, except that the mixed monomer was changed to a mixed monomer having a mass ratio of BA and HEA of 70:30.

[0079] Example 1 A pressure-sensitive adhesive composition was prepared by adding 100 parts by weight of acrylic copolymer A to 10 parts by weight of "Crosslinker N" (Lion Specialty Chemicals) as an isocyanate crosslinking agent, 0.02 parts by weight of a lead-based compound (Toyochem BXX-3778-10) as a crosslinking accelerator, and 0.2 parts by weight of acetylacetone (Toyochem BXX5638) as a crosslinking retarder. The raw materials were mixed with ethyl acetate to a concentration of 25% by weight and stirred. The pressure-sensitive adhesive composition was uniformly applied to the surface of a 50 μm polyethylene terephthalate film (Toray U403) substrate using an applicator to form a coating. The coating was then dried at 100°C for 3 minutes in an air-circulating thermostatic oven to form a 15 μm thick pressure-sensitive adhesive layer. Next, a 75 μm thick release film (E7002 manufactured by Toyobo Co., Ltd.) was attached to the adhesive layer to obtain a laminate consisting of the film substrate, adhesive layer, and release film as an adhesive protective film with a release film.

[0080] Example 2 An adhesive protective film with a release film was obtained in the same manner as in Example 1, except that the crosslinking accelerator and crosslinking retarder were not used.

[0081] Example 3 An adhesive protective film with a release film was obtained in the same manner as in Example 1, except that the amount of isocyanate crosslinking agent used was changed to 7.5 parts by mass.

[0082] Example 4 An adhesive protective film with a release film was obtained in the same manner as in Example 2, except that acrylic copolymer B was used instead of acrylic copolymer A.

[0083] (Comparative Example 1) An adhesive protective film with a release film was obtained in the same manner as in Example 2, except that acrylic copolymer C was used instead of acrylic copolymer A, and the isocyanate crosslinking agent was changed to a tolylene diisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) instead of "Crosslinking agent N," and the amount used was changed to 0.2 parts by mass.

[0084] (Comparative Example 2) An adhesive protective film with a release film was obtained in the same manner as in Example 1, except that the amount of isocyanate crosslinking agent used was changed to 1 part by mass.

[0085] (Comparative Example 3) An adhesive protective film with a release film was obtained in the same manner as in Comparative Example 2, except that the crosslinking accelerator and crosslinking retarder were not used.

[0086] Comparative Example 4 An adhesive protective film with a release film was obtained in the same manner as in Example 1, except that acrylic copolymer B was used instead of acrylic copolymer A and the amount of isocyanate crosslinking agent used was changed to 3 parts by mass.

[0087] <Gel fraction of adhesive layer> For the adhesive protective films with release film obtained in Examples and Comparative Examples, the adhesive layer was peeled off 1 hour and 24 hours after the formation of the adhesive layer, and approximately 0.1 g was collected in each sample bottle, to which 30 ml of ethyl acetate was added and shaken for 24 hours. Thereafter, the contents of the sample bottles were filtered through a 150 mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100 ° C for 1 hour to measure the dry weight W (g). From the obtained dry weight, the following formula was used: Gel fraction (%) = (dry mass W / collected mass of adhesive sheet) × 100 The values ​​calculated from the above were taken as the gel fractions 1 hour and 24 hours after the formation of the pressure-sensitive adhesive layer.

[0088] <Storage modulus of adhesive layer> The adhesive layer was peeled from the adhesive protective film with release film obtained in the Examples and Comparative Examples, and laminated to a thickness of 100 μm. This was then pressurized in an autoclave at 30°C and 0.5 MPa for 10 minutes to prepare a measurement sample. The storage modulus G'(T) of the measurement sample was measured using a dynamic viscoelasticity measuring device "Rheogel-E4000" (manufactured by UBM) over a temperature range of -20 to 120°C, a heating rate of 2°C / min, and a frequency of 1 Hz. This resulted in a temperature-storage modulus G'(T) graph, and the value G'(80°C) / G'(25°C) was calculated.

[0089] <Adhesion strength of adhesive protective film to glass> The adhesive strength was measured according to the method described in JIS Z 0237. First, the obtained adhesive protective film with a release film was cut to a size of 25 mm wide and 50 mm long, the release film was peeled off from the adhesive protective film with a release film, and the surface of the adhesive layer was attached to soda glass and pressed with a 2 kg roller. Then, 24 hours after pressing, the adhesive strength was measured at a peeling speed of 300 mm / min, and this adhesive strength was defined as the adhesive strength to glass.

[0090] <Appearance evaluation (citrus peel)> The release film was peeled off from the adhesive protective film with release film of each of the Examples and Comparative Examples, and the exposed adhesive layer was attached to a black acrylic plate (manufactured by Mitsubishi Chemical Corporation). After that, the film was observed by reflecting fluorescent light, and the image of the fluorescent light reflected on the film substrate was observed and evaluated according to the following criteria. ⊚: The image of the fluorescent lamp reflected on the film substrate was visible without distortion, and the appearance was extremely good. ◯: The image of the fluorescent lamp reflected on the film substrate was only slightly distorted, and the appearance was good. △: The image of the fluorescent lamp reflected on the film substrate appeared slightly distorted, but the appearance was good. ×: The image of the fluorescent lamp reflected on the film substrate was noticeably distorted, and the appearance was poor.

[0091] [Table 1]

[0092] Table 1 shows the component ratios of the pressure-sensitive adhesive compositions used to produce the pressure-sensitive adhesive protective films and the evaluation results of the obtained pressure-sensitive adhesive protective films. Note that blank spaces in Table 1 indicate 0 parts by mass.

[0093] The adhesive protective films obtained in the examples had a storage modulus G'(25°C) of 1.4 MPa or more and satisfied formula (1), so orange peel was suppressed and the appearance was good. Furthermore, although not shown in the table, the value of the storage modulus G'(T°C) / G'(25°C) of the adhesive layer satisfied the relationship 0.65≦G'(T°C) / G'(25°C)≦1.0 over the entire temperature range from 25°C to 80°C.

[0094] On the other hand, the adhesive protective film obtained in the comparative example did not prevent the orange peel from occurring, causing poor appearance.

[0095] Therefore, it can be said that an adhesive protective film in which the storage modulus G' (25°C) of the adhesive layer is 1.4 MPa or more and which satisfies formula (1) is less likely to cause deformation of the adhesive layer and less likely to suffer from poor appearance even when wound into a roll.

Claims

1. An adhesive protective film comprising a laminate in which an adhesive layer is laminated on a film substrate, the pressure-sensitive adhesive layer is a cured product of a pressure-sensitive adhesive composition, The pressure-sensitive adhesive composition contains at least an acrylic copolymer and an isocyanate crosslinking agent, The acrylic copolymer contains 2% by mass or more and 30% by mass or less of a hydroxyl group-containing monomer unit, The pressure-sensitive adhesive layer has a storage modulus G'(25°C) of 1.4 MPa or more at 25°C, and when the storage modulus G'(80°C) at 80°C is taken as G', the following formula (1) is satisfied: 0.65≦G'(80℃) / G'(25℃)≦1.0 (1) Meet the adhesive protective film.

2. The pressure-sensitive adhesive protective film according to claim 1 , wherein the pressure-sensitive adhesive composition contains 5 parts by mass or more of the isocyanate crosslinking agent relative to 100 parts by weight of the acrylic copolymer.

3. An adhesive protective film comprising a laminate in which an adhesive layer is laminated on a film substrate, the pressure-sensitive adhesive layer is a cured product of a pressure-sensitive adhesive composition, The pressure-sensitive adhesive composition contains at least an acrylic copolymer, an isocyanate crosslinking agent, a crosslinking accelerator, and a crosslinking retarder, The pressure-sensitive adhesive layer has a storage modulus G'(25°C) of 1.4 MPa or more at 25°C, and when the storage modulus G'(80°C) at 80°C is taken as G', the following formula (1) is satisfied: 0.65≦G'(80℃) / G'(25℃)≦1.0 (1) Meet the adhesive protective film.

4. The adhesive protective film according to any one of claims 1 to 3, which has an adhesive strength to glass of 0.1 N / 25 mm or less.

5. A pressure-sensitive adhesive protective film according to any one of claims 1 to 4 and a release film, The release film is attached to the pressure-sensitive adhesive layer, forming a release film-attached adhesive protective film.

6. The composition for producing an adhesive protective film according to any one of claims 1 to 4, A composition for producing an adhesive protective film, comprising the above adhesive composition.

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