JPH09156056A - Protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide adhesion to adhere to a surface hardening layer as a covering matter and to an adhesive layer, and improve durability by forming a laminated film mainly out of a polyester resin and a melamine crosslinking agent and adding a carboxylic acid and/or its salt to the side chain of the polyester resin. SOLUTION: A protective film having high surface hardness, excellent wear resistance, and excellent durability can be manufactured in such a manner that a laminated film consisting of a polyester resin having a carboxylic acid and/or its salt as a side chain and a melamine crosslinking agent is provided on both faces of a biaxially oriented polyester film and a surface hardening layer consisting of an active hardening matter is provided on one face. To a face opposite to the face having the surface hardening layer of the protective film, a metal as an opposite material is stuck through an adhesive, thereby it comes to have excellent adhesion to be adhered to each interface, high surface hardness, and excellent wear resistance. At the same time, durabilities of the surface hardening layer and an adhesive layer become excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film, and more specifically, it is a protective film having a surface hardening layer provided on one surface of a base polyester film with a laminated film interposed between the polyester film and the other surface. The present invention relates to a protective film which is used for bonding with a mating material via an adhesive layer and has high surface hardness and excellent abrasion resistance, and at the same time, excellent durability.

[0002]

2. Description of the Related Art Biaxially stretched polyester films are characterized by their transparency, toughness, dimensional stability and the like, so that they are laminated with metal, wood, glass, etc. to prevent rust,
It is used for the purpose of surface protection such as cosmetics and anti-scattering.

Polyester film has a low surface hardness,
In addition, because it lacks abrasion resistance, the surface is easily damaged by contact with other hard objects, friction, scratching, etc., and the damage caused on the surface significantly reduces the product value, or it is used in a short period of time. It becomes impossible. For this reason, a method has been adopted in which a surface hardening layer is provided on the film surface and an adhesive layer is provided on the other surface, and the film is attached to a substrate or the like.

However, since the surface of the base polyester film is highly crystallized, the adhesion to the surface hardening layer is poor, and the surface hardening layer is peeled off, which is substantially inferior in durability. It has drawbacks. Further, the same applies to the pressure-sensitive adhesive layer, and there is a drawback in that the adhesive layer is peeled off at the interface with the base polyester film and is also inferior in durability when it is attached to a mating material. For this reason, studies have been made to impart easy adhesion to the surface of the polyester film by various methods.

As a method for facilitating adhesion, a surface activation method by subjecting the surface of the base polyester film to corona discharge treatment, ultraviolet irradiation treatment, plasma treatment or the like, or surface etching with a chemical such as an acid, alkali or amine aqueous solution Method, a method of forming various resins such as acrylic resin, sulfonate group-containing polyester resin and urethane resin on the film surface as a primer layer (JP-A-55-15).
825, JP-A-58-78761, JP-A-60-248232, etc.) are already known.
In particular, as a method of providing easy adhesion by providing the primer layer by coating, a coating containing the resin component is applied to a polyester film before crystal orientation is completed, dried, stretched, and subjected to heat treatment to crystallize. A method of completing the orientation (in-line coating method) is considered to be a promising one in terms of process simplification and manufacturing cost, and is performed in the industry.

[0006]

However, the above-mentioned prior art has the following problems.

That is, when an acrylic resin is laminated, the adhesion to the surface hardening layer or the pressure-sensitive adhesive layer, which is a coating, is excellent, but the adhesion to the base polyester film is insufficient, and the polyester Adhesion to the base material is good when a resin or urethane resin is laminated, but sufficient adhesion to the surface hardening layer or pressure-sensitive adhesive layer is not obtained, and the durability of the surface hardening layer is poor. However, there is a drawback that it is peeled off from a mating material such as metal, wood, or glass.

The present invention solves these drawbacks and provides a protective film which has sufficient adhesion to the surface-hardened layer and the pressure-sensitive adhesive layer to be coated and has excellent durability.

[0009]

The present invention provides a protective film in which a surface hardening layer (B) is provided on one surface through a laminated film (A) provided on both surfaces of a polyester film, A protective film having a polyester film and a melamine-based cross-linking agent as main constituent components of the laminated film (A) and a carboxylic acid and / or salt thereof in the side chain of the protective film. Is.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester of the polyester film used in the present invention is a general term for polymers having an ester bond as the main bonding chain of the main chain. Preferred polyesters are ethylene terephthalate and ethylene-2. , 6-naphthalate, butylene terephthalate, ethylene-α, β-bis (2-chlorophenoxy)
It is possible to use those containing at least one kind of constituent selected from ethane-4,4-dicarboxylate and the like as a main constituent. These constituent components may be used alone or in combination of two or more kinds, and among them, polyester having ethylene terephthalate as a main constituent component is particularly preferable in view of quality, economy and the like. In addition, in applications in which heat acts on a base material, or applications in which a resin shrinks during curing such as an ultraviolet curable resin as a coating, polyethylene-2,6-
Naphthalate is more preferred.

These polyesters may be copolymerized with 20 mol% or less of other dicarboxylic acid components and diol components.

Further, in the polyester, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic slippery agent, a pigment, etc. are added within a range not impairing the effects of the present invention. Dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents and the like may be added.

The intrinsic viscosity of the above-mentioned polyester (25 ° C.)
Measured in o-chlorophenol) of 0.4-1.2d
1 / g is preferable, more preferably 0.5 to 0.8 dl
Those in the range of / g are suitable for carrying out the present invention.

From the viewpoint of further improving the adhesiveness to the laminated film, the amount of carboxyl terminal groups of the base polyester film is preferably 37 equivalents / ton or more, more preferably 40.
Equivalent / ton or more.

The polyester film using the above polyester is preferably biaxially oriented when the laminated film is provided. The biaxially oriented polyester film is obtained by stretching an unstretched polyester sheet or film by 2.5 to 5 times in each of the longitudinal direction and the width direction, and then subjecting it to heat treatment to complete the crystal orientation. X-ray diffraction refers to a biaxially oriented pattern.

The thickness of the polyester film is not particularly limited, but from the viewpoint of mechanical strength and thermal conductivity,
It is usually 0.5 to 500 μm, preferably 1 to 300 μm. Further, the obtained films can be laminated by various methods to form a thicker film.

The polyester resin which is a constituent of the laminated film (A) according to the present invention has an ester bond in the main chain or side chain, and has a carboxylic acid and / or its salt in the side chain. Is. Such a polyester resin can be obtained by copolymerizing a polyester resin obtained by polycondensing a dicarboxylic acid and a diol with a polyvalent carboxylic acid.

As the carboxylic acid component constituting the polyester resin, an aromatic, aliphatic or alicyclic dicarboxylic acid or a trivalent or higher polycarboxylic acid can be used. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid,
1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p, p'-dicarboxylic acid, phenylindanedicarboxylic acid and the like can be used. From the viewpoint of strength and heat resistance of the laminated film, these aromatic dicarboxylic acids are preferably 30 mol% or more, more preferably 35 mol% or more, and most preferably 40 mol% or more of the total dicarboxylic acid components. Examples of the aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-
Cyclohexanedicarboxylic acid and the like and their ester-forming derivatives can be used.

As the glycol component of the polyester resin, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3
-Butanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,7
-Heptanediol, 1,8-octanediol, 1,
9-nonanediol, 1,10-decanediol, 2,
4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3 -Methyl-1,5
-Pentanediol, 2,2,4-trimethyl-1,6
-Hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-
Cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4′-thiodiphenol, bisphenol A, 4,4′-methylenediphenol, 4,4 ′-(2 -Norbornylidene)
Diphenol, 4,4′-dihydroxybiphenol,
o-, m-, and p-dihydroxybenzene, 4,
4'-isopropylidenephenol, 4,4'-isopropylidenebindiol, cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol and the like can be used.

Examples of polyvalent carboxylic acids include trimellitic acid, trimellitic anhydride, pyromellitic acid,
Pyromellitic dianhydride, 4-methylcyclohexene-1,
2,3-tricarboxylic acid, trimesic acid, 1,2,3
4-butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3 -Methyl-3-cyclohexene-1,2-dicarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene-1,2-
Dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,
3,6,7-naphthalenetetracarboxylic acid, 1,2,
5,6-naphthalenetetracarboxylic acid, ethylene glycol bistrimellitate, 2,2 ', 3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-
Tetracarboxylic acid, ethylene tetracarboxylic acid, etc., or their alkali metal salts, alkaline earth metal salts, ammonium salts, etc. can be used, but not limited thereto.

The glass transition point of the polyester resin obtained by these copolymerizations is preferably 40 ° C. or lower, more preferably 35 ° C. or lower, and most preferably 30 ° C. or lower in terms of adhesion to the base film and the coating. Is. According to the knowledge of the present inventors, the particularly preferable glass transition point is 0 to 35 ° C, and more preferably 5 to 30 ° C.
As the polyester resin, it is also possible to use a modified polyester copolymer, for example, a block copolymer modified with acryl, urethane, epoxy or the like, or a graft copolymer.

Preferred polyester resins include terephthalic acid, isophthalic acid, sebacic acid, trimellitic acid, pyromellitic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene as the acid component. -1,2-dicarboxylic acid, ethylene glycol as a glycol component, diethylene glycol, 1,4
-The one using a copolymer selected from butanediol and neopentyl glycol can be used.

The polyester resin used in the protective film of the present invention can be manufactured by various manufacturing techniques. Further, as a method for obtaining a polyester resin having a large amount of carboxylic acid at the terminal and / or side chain, JP-A-54-46294 and JP-A-60-20907 are known.
No. 3, JP-A-62-240318, JP-A-Sho 5
3-26828, JP-A-53-26829, JP-A-53-98336, and JP-A-56-11.
It can be produced by using a resin obtained by copolymerizing a polyvalent carboxylic acid having a valence of 3 or more as described in JP-A-6718, JP-A-61-212484, JP-A-62-240318 and the like, but other methods May be The melamine-based cross-linking agent which is a constituent component of the laminated film (A) according to the present invention is not particularly limited, but melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, and a methylolated melamine are reacted with a lower alcohol. Partially or completely etherified compounds, and mixtures thereof can be used. As the melamine-based cross-linking agent, a monomer, a condensate composed of a multimer of dimers or more, or a mixture thereof can be used. As the lower alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like can be used. As the functional group, those having an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, an imino group-type methylated melamine resin, a methylol group-type melamine resin, and a methylol group-type Methylated melamine resin,
For example, fully alkylated methylated melamine resin. Among them, the methylolated melamine resin is the most preferable. Further, an acidic catalyst such as p-toluenesulfonic acid may be used in order to promote the thermal curing of the melamine-based crosslinking agent.

The polyester resin and the melamine-based cross-linking agent may be mixed in any ratio, but in order to bring out the effect of the present invention more remarkably, they may be mixed in the following ratios (solid content weight ratio).

That is, for example, polyester resin 100
The amount of the melamine-based crosslinking agent is preferably 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, and most preferably 2 to 20 parts by weight, based on parts by weight.

The laminated film of the present invention is obtained by applying a coating material containing the above-mentioned two kinds of constituent components as main components, followed by drying and heat treatment. The main components are 50% by weight in the laminated film.
It means to occupy the above. Especially in the present invention, the ratio of the two components is preferably 80% by weight or more, more preferably 90% by weight or more.

In the laminated film, other resins, for example, polyester resins other than the above-mentioned polyester resins used in the present invention, acrylic resins, urethane resins, epoxy resins, silicone resins may be used as long as the effects of the present invention are not impaired. ,
A urea resin, a phenol resin or the like may be blended.

Further, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic slippery agent, a pigment, etc. may be added to the laminated film as long as the effects of the present invention are not impaired. Dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents and the like may be added.

In particular, a material in which inorganic particles are added and blended in the coating material and biaxially stretched is more preferable because slipperiness is improved.

In this case, as the inorganic particles to be added, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate and the like can be used. The inorganic particles used have an average particle size of 0.01
-10 μm is preferable, and more preferably 0.05-5 μm.
m, most preferably 0.08 to 2 μm, and the mixing ratio with respect to the solid content in the coating agent is not particularly limited, but is preferably 0.05 to 8 parts by weight, more preferably 0.1.
３3 parts by weight.

In the production of the protective film of the present invention, the most preferable method for providing the laminated film is a method in which the polyester film is applied during the production process and stretched together with the base film. For example, a melt-extruded polyester film before crystal orientation is stretched in the longitudinal direction by about 2.5 to 5 times, the surface to be coated is subjected to corona discharge treatment, and the coating agent is continuously applied to the treated surface. The applied film is dried while passing through a stepwise heated zone, and is stretched about 2.5 to 5 times in the width direction. Further, it can be obtained by a method in which the crystal orientation is continuously guided to a heating zone of 150 to 250 ° C. to complete the crystal orientation. The coating solution used in this case is preferably an aqueous solution from the viewpoint of environmental pollution and explosion proof.

The laminated film provided by such a method has excellent adhesion to the base polyester film.

The thickness of the coating film is not particularly limited, but is preferably in the range of 0.01 to 5 μm, more preferably 0.02 to 2 μm, most preferably 0.05 μm to 0.
5 μm. If the thickness of the laminated film is too thin, the adhesion may be poor.

Various coating methods such as reverse coating method, gravure coating method,
Rod coating, bar coating, die coating, spray coating and the like can be used.

The laminated film (A) according to the present invention is provided on both sides of the polyester film. At this time, it is preferable that the laminated films provided on the respective surfaces are substantially the same.

The surface hardened layer (B) according to the present invention can be formed of an acrylic type, a urethane type, a melamine type, an organic silicate, a silicone type, a metal oxide or the like. Silicone type and acrylic type are particularly preferable in terms of hardness and durability, and acrylic type, particularly actinic ray curable acrylic type is preferable in terms of curability, flexibility and productivity.

The actinic ray-curable acrylic resin contains an acryl oligomer and a reactive diluent as actinic ray polymerization components, and optionally contains a photoinitiator, a photosensitizer and a modifier. You may use what has been done.

The acrylic oligomer includes polyester acrylic, urethane acrylic, epoxy acrylic, polyether acrylic and the like, including those in which a reactive acrylic group is bonded to an acrylic resin skeleton, and melamine, isocyanuric acid, etc. A rigid skeleton having an acrylic group bonded thereto can be used, but is not limited thereto.

The reactive diluent serves as a medium for the coating agent and functions as a solvent in the coating step, and also has a group which itself reacts with a monofunctional or polyfunctional acrylic oligomer to form a coating film. It is a copolymerization component.

Further, particularly in the case of crosslinking by ultraviolet rays,
Since the light energy is small, it is preferable to add a photopolymerization initiator and / or a sensitizer in order to promote conversion or initiation of light energy.

Specific examples of these acrylic oligomers, reactive diluents, photopolymerization initiators, sensitizers, crosslinking devices, etc. are as follows:
Shinzo Yamashita, Tosuke Kaneko, "Handbook of Crosslinking Agents", published by Taiseisha in 1981, pages 267 to 275, 56.
Pages 2 to 593 can be referred to, but are not limited to these. Commercially available multi-functional acrylic UV-curable coatings Mitsubishi Rayon Co., Ltd., Fujikura Kasei Co., Ltd., Dainichi Seika Kogyo Co., Ltd., Dainippon Ink and Chemicals Co., Ltd., Toa Gosei Chemical Co., Ltd. (stock),
Products such as Nippon Kayaku Co., Ltd. can be used, but are not limited to these.

As a modifier for the surface hardening layer, a coating property improver, a defoaming agent, a thickener, an antistatic agent, an inorganic particle, an organic particle, an organic lubricant, an organic polymer, a dye, a pigment. , Stabilizers, etc. can be used as the composition of the coating layer within a range that does not impair the reaction by actinic radiation, and the characteristics of the surface-hardened layer can be improved depending on the application.

Among these, particularly at least one kind of monomer having three or more (meth) acryloyloxy groups in one molecule and 1-2 ethylenically unsaturated double bonds in one molecule. The surface-hardening layer made of an actinic radiation-cured product whose main constituent is an actinic radiation-curable monomer mixture composed of at least one kind of a monomer having It is preferable because it has excellent flexibility.

In the present invention, three or more (meth) acryloyloxy groups in one molecule (however, in the present invention, the (meth) acryloyloxy group is abbreviated to acryloyloxy group and methacryloyloxy group). A compound having a hydroxyl group of a polyhydric alcohol having 3 or more alcoholic hydroxyl groups in one molecule is an esterified product of 3 or more (meth) acrylic acid. Can be used.

Specific examples include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth). ) Acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate and the like can be used. These monomers may be used alone or in combination of two or more.

The proportion of these monomers having three or more (meth) acryloyloxy groups in one molecule is preferably 20 to 90% by weight, more preferably 30% by weight, based on the total amount of the polymerizable monomers. ~ 80% by weight, most preferably 30 ~
70% by weight.

When the proportion of the above-mentioned monomer used is less than 20% by weight, it may not be sufficient to obtain a cured coating having sufficient abrasion resistance, and the amount thereof may be 90% by weight.
If it exceeds, the shrinkage due to the polymerization is large, and the strain may remain in the cured film, the flexibility of the film may be reduced, or the curled film may be greatly curled, which is not preferable.

As the monomer having 1 to 2 ethylenically unsaturated double bonds in one molecule in the present invention, any ordinary monomer having radical polymerizability may be used without particular limitation. be able to.

As the compound having two ethylenically unsaturated double bonds in the molecule, the following (meth) acrylates (a) to (f) can be used.

That is, (a) (meth) acrylic acid diesters of alkylene glycol having 2 to 12 carbon atoms: ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) ) Acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, etc. (b) (meth) acrylate diesters of polyoxyalkylene glycol: diethylene glycol di (meth) acrylate, triethylene Glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) (Meth) acrylic acid diester of polyhydric alcohol (c) such as acrylate: pentaerythritol di (meth) acrylate (d) (meth) acryl of ethylene oxide and propylene oxide adduct of bisphenol A or bisphenol A hydride Acid diesters: 2,2'-bis (4-acryloxyethoxyphenyl) propane, 2,2'-bis (4-acryloxypropoxyphenyl) propane, etc. (e) Diisocyanate compound and two or more alcoholic hydroxyl groups Urethane (meth) having two or more (meth) acryloyloxy groups in the molecule obtained by further reacting a terminal isocyanate group-containing compound obtained by reacting a containing compound with an alcoholic hydroxyl group-containing (meth) acrylate Acrylate, (f) minutes Use of epoxy (meth) acrylates having two or more (meth) acryloyloxy groups in the molecule obtained by reacting acrylic acid or methacrylic acid with a compound having two or more epoxy groups in the molecule And compounds having one ethylenically unsaturated double bond in the molecule include methyl (meth) acrylate, ethyl (meth) acrylate, n- and i-propyl (meth) acrylate, n-, sec- , And t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Lauryl (meth) acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, glycidyl (Meth) acrylate, tetrahydrofurfuryl (meth) acrylate, N
-Hydroxyethyl (meth) acrylamide, N-vinylpyrrolidone, N-vinyl-3-methylpyrrolidone, N
-Vinyl-5-methylpyrrolidone and the like can be used. These monomers may be used alone or in combination of two or more.

The proportion of the monomer having 1 to 2 ethylenically unsaturated double bonds in one molecule is preferably 10 to 80% by weight, more preferably 20% by weight, based on the total amount of the monomers. Is about 70% by weight.

When the proportion of the above-mentioned monomer used exceeds 80% by weight, it is difficult to obtain a cured coating having sufficient abrasion resistance, which is not preferable. Further, if the proportion used is less than 10% by weight, the flexibility of the coating film may be reduced, or the adhesion to the laminated film provided on the base polyester film may be reduced, which is not preferable.

As a method for curing the actinic radiation curable composition in the present invention, a method of irradiating with ultraviolet rays can be used, and in the case of using this method, it is desirable to add a photopolymerization initiator to the composition. Specific examples of the photopolymerization initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4′-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methylbenzoylformate, p
-Isopropyl-α-hydroxyisobutylphenone,
carbonyl compounds such as α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenylketone, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone And sulfur compounds such as benzoyl peroxide and di-t-butyl peroxide. These photopolymerization initiators may be used alone or in combination of two or more.

The amount of the photopolymerization initiator used is appropriately 0.01 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer composition. When electron beam or gamma ray is used as the curing means, it is not always necessary to add a polymerization initiator.

The actinic radiation curable composition used in the present invention includes
Hydroquinone, hydroquinone monomethyl ether, to prevent thermal polymerization during production and dark reaction during storage
It is desirable to add a known thermal polymerization inhibitor such as 2,5-t-butylhydroquinone. The addition amount is preferably 0.005 to 0.05% by weight based on the total weight of the polymerizable compound.
The actinic ray-curable composition used in the present invention may be blended with an organic solvent for the purpose of improving workability at the time of coating and controlling the coating film thickness, as long as the effect of the present invention is not impaired. it can.

The organic solvent has a boiling point of 50 to 150 ° C.
The ones are easy to use in terms of workability during coating and drying properties before and after curing. Specific examples include alcohol solvents such as methanol, ethanol and isopropyl alcohol, acetic ester solvents such as methyl acetate, ethyl acetate and butyl acetate, ketone solvents such as acetone and methyl ethyl ketone, aromatic solvents such as toluene. A cyclic ether solvent such as dioxane or the like can be used.
These solvents can be used alone or in combination of two or more.

The actinic radiation curable composition used in the present invention includes
Various additives can be blended as needed as long as the effects of the present invention are not impaired. For example, stabilizers such as antioxidants, light stabilizers, and ultraviolet absorbers, surfactants, leveling agents, and antistatic agents can be used.

The actinic ray-curable composition used in the present invention contains silicon oxide particles and silicon oxide particles in order to reduce the brightness and clarity of the reflected image of an external light source, as long as the effects of the present invention are not impaired. A matting agent such as an organic filler can be blended, and the surface of the surface-hardened layer can be provided with irregularities by, for example, an embossing method or a sand mat method. As a means for applying the actinic radiation curable composition, use a commonly used coating method such as brush coating, dip coating, knife coating, roll coating, spray coating, flow coating, spin coating (spinner, whaler, etc.). You can Each method has its own characteristics, and the coating method may be appropriately selected depending on the required characteristics of the laminate, the intended use, and the like. Here, the actinic ray means an electromagnetic wave for polymerizing an acrylic vinyl group such as ultraviolet ray, electron beam, radiation (α ray, β ray, γ ray, etc.), and in practice, ultraviolet ray is simple and preferable. . As the ultraviolet ray source, an ultraviolet fluorescent lamp, a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a xenon lamp, a carbon arc lamp or the like can be used. In addition, the electron beam method requires an expensive apparatus and requires operation under an inert gas, but is advantageous in that it does not need to contain a photopolymerization initiator or a photosensitizer in the coating layer. .

The thickness of the surface-hardened layer may be determined according to the application, but is usually preferably 0.5 μm to 10 μm, more preferably 1 μm to 5 μm. When the thickness of the surface-hardened layer is less than 0.5 μm, the surface hardness is insufficient and scratches are likely to occur. On the other hand, when it exceeds 10 μm, the cured film tends to become brittle and the laminate is bent. Moreover, the cured film is apt to be cracked, which is not preferable.

A printing layer such as a pattern may be provided as the outermost layer of the surface-hardened layer as long as the effect of the present invention is not impaired.

The pressure-sensitive adhesive used for bonding the protective film of the present invention to the mating material is not particularly limited as long as it can bond two objects by virtue of the pressure-sensitive adhesive action.
As the adhesive, rubber type, acrylic type, silicone type,
It is possible to use those made of polyvinyl ether or the like. Of these, rubber-based ones are generally used, and silicone-based ones have good heat resistance and adhere to fluororesins and the like, but have the drawback of being expensive. Acrylic resins are preferred because they also have heat resistance, have a large adhesive strength, and do not have the oxidative deterioration of rubber.

Further, the pressure sensitive adhesive is roughly classified into a solvent type pressure sensitive adhesive and a solventless pressure sensitive adhesive. Solvent-based pressure-sensitive adhesives excellent in drying property, productivity, and processability are still mainstream, but in recent years, they have been shifted to solvent-free pressure-sensitive adhesives in terms of pollution, energy saving, resource saving, safety, and the like. Above all, it is preferable to use an actinic ray-curable pressure-sensitive adhesive which is a pressure-sensitive adhesive that is cured in seconds by irradiation with actinic radiation and has excellent properties such as flexibility, adhesion, and chemical resistance.

Specific examples of the actinic ray curable acrylic pressure-sensitive adhesive can be referred to "Adhesive Data Book" edited by The Japan Society of Adhesion Science, 1990, published by Nikkan Kogyo Shimbun, Ltd., pages 83 to 88. However, it is not limited thereto. Hitachi Chemical Polymer Co., Ltd., Toho Kasei Kogyo Co., Ltd.
Products such as Three Bond Co., Ltd., Toa Gosei Chemical Industry Co., Ltd., Cemedine Co., Ltd., and Nippon Kayaku Co., Ltd. can be used, but not limited thereto. When this type of pressure-sensitive adhesive is applied to an ordinary biaxially stretched polyester film, the adhesion becomes insufficient, and good adhesion is achieved only when the pressure-sensitive adhesive layer is provided via the laminated film (A) of the present invention. Have sex.

Next, the method for producing the protective film of the present invention will be described by taking polyethylene terephthalate (hereinafter abbreviated as PET) as an example of the substrate film.
It is not limited to this.

The protective film of the present invention, which has a high surface hardness and is excellent in abrasion resistance and durability at the same time, is a biaxially oriented polyester film having a carboxylic acid and / or a salt thereof on its side chain. It can be manufactured by providing a laminated film composed of the polyester resin and a melamine-based cross-linking agent, and providing a surface hardening layer composed of an actinic radiation cured product on one surface.

More specifically, the PET pellets are sufficiently vacuum-dried and then fed to an extruder for 260-300.
It is melt-extruded into a sheet at a temperature of ° C. and solidified by cooling to produce an unstretched PET sheet. This sheet is 70-120
The film is stretched 2.5 to 5 times in the longitudinal direction with a roll heated to 0 ° C. to obtain a uniaxially oriented PET film. Both sides of this film are subjected to corona discharge treatment, and the treated surface is coated with a laminated film forming water-based coating agent having a predetermined concentration. After the application, the end portion of the film is gripped with a clip and guided to a hot air zone heated to 70 to 150 ° C., dried, and then stretched 2.5 to 5 times in the width direction.
Subsequently, it is led to a heat treatment zone of 160 to 250 ° C.
A heat treatment is performed for 30 seconds to complete the crystal orientation. If necessary, a relaxation treatment of 1 to 12% may be performed in the width direction or the longitudinal direction during this heat treatment step. In this case, the coating solution to be used is preferably an aqueous solution in view of environmental pollution and explosion-proof properties.

The protective film of the present invention can be obtained by providing a surface hardening layer on one surface of the laminated polyester film. The surface hardened layer can be obtained by applying a composition containing an actinic ray-curable monomer mixture as a main constituent, drying the composition if necessary, and then curing the composition with actinic rays.

In the above example, the base film provided with the laminated film may also contain at least one selected from melamine resins and polyester resins. In this case, there are effects such that the adhesiveness between the laminated film and the base film is improved, and the slipperiness of the laminated polyester film is improved. When a melamine-based resin or polyester resin is contained, the addition amount is 5 ppm or more 2
It is preferably less than 0% by weight from the viewpoint of easy adhesion and slipperiness. Of course, the melamine-based resin and the polyester resin may be a coating composition or a regenerated pellet that constitutes a laminated film provided on the base film.

The protective film thus obtained, which is bonded to the opposite material such as metal, wood, glass or the like through the adhesive layer on the surface opposite to the surface on which the surface hardening layer is provided, The adhesiveness to each interface is excellent, the surface hardness is high, the abrasion resistance is excellent, and the durability of the surface hardening layer and the pressure-sensitive adhesive layer is excellent.

[0070]

[Method for measuring characteristics and method for evaluating effects] The method for measuring characteristics and the method for evaluating effects in the present invention are as follows.

(1) Thickness of coating layer It was determined from a photograph of a cross section of a biaxially oriented polyester film provided with a laminated film, using a transmission electron microscope HU-12 type manufactured by Hitachi, Ltd. Thickness is 30 within the field of view
The average value was used.

(2) Adhesiveness-1 100 crosscuts of 1 mm ² were put in the surface-hardened layer provided in the example, and cellophane tape manufactured by Nichiban Co., Ltd. was stuck thereon, and after strongly pressed with fingers. , Rapid peeling in the direction of 90 degrees, and four-level evaluation according to the number of remaining (⊚: 10
0, ◯: 80 to 99, Δ: 50 to 79, ×: 0 to 49)
did. (⊚) and (∘) have good adhesion and excellent durability.

(3) Adhesion-2 AGR-100 manufactured by Nippon Kayaku Co., Ltd. as an adhesive has a thickness of 3 mm.
After applying about 100 μm on the aluminum plate of (1) and pasting the laminated body together, 1000 mJ / cm ² energy is applied by an ultraviolet irradiator to cure with ultraviolet light. The laminate was peeled from the horizontally placed aluminum surface in the direction of 90 degrees, and the peeled state was observed and evaluated according to the following criteria.
(∘) has good adhesion and excellent durability.

◯: Peeled between the aluminum plate / adhesive layer Δ: Peeled between both the aluminum plate / adhesive layer and the base film / adhesive layer X: Base film / adhesive layer (3) Pencil hardness According to JIS-K5400, pencils of various hardness are applied to the surface-hardened layer at an angle of 90 degrees, and scratched with a load of 1 kg.
It is indicated by the hardness of the pencil when scratches occur.

(4) Abrasion resistance The surface of the surface hardened layer was rubbed with steel wool # 0000, and the scratch condition was evaluated according to the following criteria.

◯: Almost no scratch is given even when strongly rubbed.

Δ: Slightly scratched when considerably rubbed.

X: Scratches are attached even with weak friction.

[0079]

EXAMPLES Next, the present invention will be explained based on examples.

Example 1 PET (intrinsic viscosity 0.65 dl / g) pellets containing 0.2% by weight of silica particles having an average particle size of about 0.5 μm were sufficiently vacuum-dried, and then extruded under heating at 280 ° C. It was supplied to a machine, extruded in a sheet form from a T-shaped die, and wound around a mirror surface casting drum having a surface temperature of 30 ° C. by an electrostatic applied casting method to be cooled and solidified. This unstretched film was stretched 3.5 times in the longitudinal direction while passing through a group of heating rolls at 95 ° C. to obtain a uniaxially oriented film. Both sides of this film were subjected to corona discharge treatment, and the treated surface was coated with the following water-based coating agent. Guide the coated uniaxially stretched film to the preheating zone while gripping with a clip,
After drying at 110 ° C., the film is continuously stretched 3.5 times in the width direction in a heating zone of 125 ° C., and further heat-treated in a heating zone of 225 ° C. so that the base PET film has a thickness of 188 μ
Thus, a laminated PET film having a thickness of 0.15 μm and a laminated film thickness of 0.15 μm was obtained.

[0081] An ammonium salt type aqueous dispersion of a polyester resin (glass transition point: 20 ° C.) comprising the above acid component and glycol component.

(B): Methylolated melamine resin 5 parts by weight of (B) was mixed in a solid content ratio to 100 parts by weight of the solid content of (A) to prepare a laminated film forming coating agent.

Then, 70 parts by weight of dipentaerythritol hexaacrylate and N were added onto the laminated PET film.
A composition obtained by stirring and mixing 30 parts by weight of vinylpyrrolidone and 4 parts by weight of 1-hydroxycyclohexylphenyl ketone was cured with a bar coater to a thickness of 3 μm.
Was applied uniformly. 9c from the coated surface
The protective film having a surface-hardened layer on the laminated PET film was obtained by irradiating with ultraviolet rays for 15 seconds with a high-pressure mercury lamp having an irradiation intensity of 80 W / cm set at a height of m to cure the laminated PET film. Further, after using AGR-100 manufactured by Nippon Kayaku Co., Ltd. as a pressure-sensitive adhesive on the surface on which the surface hardened layer is not provided, it was bonded to an aluminum plate, and then 1000 mJ / cm ²
It was irradiated with ultraviolet light. Table 1 shows the results.

[0084]

[Table 1] Example 2 A protective film was obtained in the same manner as in Example 1 except that the thickness of the laminated film was adjusted to 0.08 μm using the coating material of Example 1. Table 1 shows the results.

Comparative Example 1 A protective film was obtained in the same manner as in Example 1 except that the coating material of Example 1 was used without adding a melamine-based crosslinking agent.
Table 1 shows the results.

Comparative Example 2 A protective film was obtained in the same manner as in Example 1 except that the polyester resin of the coating material of Example 1 was replaced by the copolymerized polyester resin of the following components. Table 1 shows the results.

Acid component: terephthalic acid 42 mol% 5-sodium sulfoisophthalic acid: 8 mol% Glycol component: ethylene glycol 47 mol% diethylene glycol: 3 mol% There is no carboxylic acid in the side chain consisting of the above acid component and glycol component. Polyester resin (glass transition point: 72
C) water dispersion.

Example 3 A protective film was obtained in the same manner as in Example 1 except that the amount of the melamine-based crosslinking agent added was 10 parts by weight with respect to 100 parts by weight of the polyester resin. . Table 1 shows the results.

Example 4 A protective film was obtained in the same manner as in Example 1 except that the polyester film was changed from a polyethylene terephthalate film to a polyethylene-2,6-naphthalate (hereinafter abbreviated as PEN) film. . Table 1 shows the results. Example 5 A protective film was obtained in the same manner as in Example 1 except that the polyester resin of the coating material of Example 1 was replaced by the copolyester resin of the following components. Table 2 shows the results.

[0090]

[Table 2] -Acid component terephthalic acid 5 mol% isophthalic acid 35 mol% 5- (2,5-dioxotetrahydrofurfuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid 10 mol% -glycol component diethylene glycol 20 mol % Neopentyl glycol 25 mol% 1,4-butanediol 5 mol% An ammonium salt type aqueous dispersion of a polyester resin (glass transition point: 32 ° C.) comprising the above acid component and glycol component.

Example 6 The same as Example 1 except that the laminated PET film obtained in Example 1 was crushed and pelletized as a substrate film, which was added to polyethylene terephthalate in an amount of 30% by weight and melt-extruded. To obtain a protective film. The same coating agent as that used in Example 1 was used. Table 2 shows the results.

Example 7 On the laminated PET film of Example 1, 60 parts by weight of pentaerythritol triacrylate, 2,2'-bis (4
-Acryloxydiethoxyphenyl) propane 10 parts by weight, N-vinylpyrrolidone 30 parts by weight, 1-hydroxycyclohexylphenyl ketone 4 parts by weight, toluene 90
A composition obtained by stirring and mixing parts by weight, 70 parts by weight of butyl acetate, and 70 parts by weight of isopropyl alcohol was uniformly applied using a bar coater so that the cured film thickness became 3 μm. This was dried at 80 ° C. for 20 seconds. A protective film was obtained in the same manner as in Example 1 except that this was irradiated with ultraviolet light in a nitrogen atmosphere. Table 2 shows the results.

Comparative Example 3 Table 2 shows the results when a polyester film having neither a laminated film nor a surface hardening layer was used as a protective film in Example 1.

Comparative Example 4 Table 2 shows the results of the protective film prepared in Example 1 except that the laminated film was not provided and the surface hardening layer was provided.

[0095]

The protective film of the present invention comprises a polyester film as a base material and a surface-hardened layer provided on one surface of the polyester film with a specific laminated film interposed therebetween. By bonding the protective film to the mating material via the pressure-sensitive adhesive layer, it is possible to obtain excellent adhesiveness, high surface hardness, excellent abrasion resistance, and at the same time excellent durability.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location C08F 2/48 MDP C08F 2/48 MDP C08J 7/04 CFD C08J 7/04 CFDK // B29L 9:00

Claims (8)

[Claims] 1. A surface-hardened layer (B) on one surface of a polyester film with a laminated film (A) provided on both surfaces of the film.
In the protective film provided with, the laminated film (A)
Is a polyester resin and a melamine-based cross-linking agent as main constituent components, and the polyester resin has a carboxylic acid and / or a salt thereof in a side chain. 2. The surface-hardened layer (B) comprises at least one monomer having 3 or more (meth) acryloyloxy groups in one molecule and 1 to 2 ethylenic groups in one molecule. An actinic radiation-cured product comprising an actinic radiation-curable monomer mixture composed of at least one kind of monomer having an unsaturated double bond as a main constituent. the film. 3. The laminated film (A) contains 0.5 to 40 parts by weight of a melamine-based cross-linking agent based on 100 parts by weight of a polyester resin in a solid content weight ratio. The protective film described in 2. 4. The polyester film is a polyethylene terephthalate film or a polyethylene-2,6-naphthalate film.
Or the protective film described in 3 above. 5. When the laminated film (A) is provided, the laminated film forming coating agent is applied to both surfaces of the polyester film before the crystal orientation is completed, and then the film is stretched in at least one direction and heat-treated to complete the crystal orientation. The protective film according to claim 1, 2, 3 or 4, which is obtained by 6. The polyester film comprises a composition containing 5 ppm or more and less than 20% by weight of a polyester resin, a melamine-based cross-linking agent, or at least one of the reaction products thereof. 2, 3,
The protective film as described in 4 or 5. 7. The protective film according to claim 1, wherein the polyester resin in the laminated film does not substantially contain a sulfonate group. 8. The protective film according to claim 1, wherein the polyester resin forming the laminated film has a glass transition point of 40 ° C. or lower. .