JP2022131478A - Surface protective film - Google Patents

Abstract

To provide a surface protective film which has good adhesion to a silicone adhesive layer and anti-scratching properties.SOLUTION: The surface protective film includes a cured resin layer (1) containing a cured resin layer composition (1) containing the following compounds (A) and (B) and an adhesive layer in order on one surface of a polyester film and also includes a cured resin layer (2) containing (D) a (meth)acrylate on the opposite surface of the polyester film. (A) is at least one crosslinking agent selected from the group consisting of epoxy compounds and carbodiimide compounds; and (B) is a polyester resin having a glass transition temperature (Tg) of 0°C or higher.SELECTED DRAWING: None

Description

The present invention relates to a surface protective film and a film laminate using the same.

Polyester films have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, and optical properties, and are excellent in cost performance, so they are used in various applications.

Conventionally, as one method for bonding optical members together, a silicone adhesive layer, which is excellent in transparency and durability, has been used in various applications such as displays.
When a resin film is used as an optical member, it may be incorporated into a display while being attached to a silicone adhesive layer. In this case, it is required that the optical member does not easily peel off from the silicone adhesive layer and has particularly good adhesion to the silicone adhesive layer when the peeling is not necessary.
Therefore, a technique for improving adhesion from the side of the adhesive layer has been proposed. For example, in Patent Document 1, there is no entrainment of air bubbles at the time of application, and after application, it does not shift or peel off by itself, but it is easy to peel off by hand, and is suitable for application to flat panel displays. It is described to provide a film and an adhesive composition for the film.

JP 2006-152266 A

However, attempts to improve the adhesion from the side of the silicone adhesive layer often tend to increase the adhesive strength, making it difficult to obtain the desired adhesive strength. Furthermore, when an easy-adhesion layer is provided on the resin film surface, the curability of the silicone adhesive layer may be affected depending on the constituent material of the easy-adhesion layer.
Therefore, there is a need for a resin film provided with an easy-adhesion layer with good adhesion that does not inhibit curing when the silicone adhesive layer is cured, and yet can exhibit the adhesive properties that the silicone adhesive layer originally has. .
Furthermore, as a surface protective film, it also plays a role in protecting the adherend to be bonded from external shocks, so the film surface is sometimes required to have an appropriate surface hardness in order to prevent adhesion of scratches.

Accordingly, the problem to be solved by the present invention is to provide a surface protection film that has good adhesion to a silicone adhesive layer and is scratch-resistant.

The present inventors have made intensive studies in view of the above circumstances, and as a result, have found that the above problems can be solved by using a surface protection film having a specific configuration, and have completed the present invention. That is, the present invention provides the following [1] to [19].
[1] On one surface of the polyester film, a cured resin layer (1) containing a cured resin layer composition (1) containing the following compounds (A) and (B) and an adhesive layer are provided in order, and the polyester film A surface protection film having a cured resin layer (2) containing (D) (meth)acrylate on the opposite side.
(A) at least one cross-linking agent selected from the group consisting of epoxy compounds and carbodiimide compounds (B) a polyester resin having a glass transition temperature (Tg) of 0° C. or higher [2] the cured resin layer composition (1) , and further comprising at least one selected from the group consisting of an oxazoline compound and a melamine compound, the surface protection film according to [1] above.
[3] The surface protection film of [1] or [2] above, wherein the compound (B) is a polyester resin composed of a dicarboxylic acid component having 10 or less carbon atoms as an acid component.
[4] The above [1] to [3], wherein the compound (B) is a polyester resin containing, as a diol component, ethylene glycol and at least one selected from 1,4-butanediol, diethylene glycol and triethylene glycol. ] The surface protection film according to any one of .
[5] The surface protective film of any one of [1] to [4] above, wherein the compound (B) is a polyester resin containing a polycyclic compound as an acid component.
[6] The above [1], wherein the compounding ratio (A)/(B) (mass ratio) of the compounds (A) and (B) in the cured resin layer composition (1) is 10/90 to 50/50. ] to [5].
[7] The surface protective film of any one of [1] to [6] above, wherein the adhesive layer is a silicone adhesive layer or an acrylic adhesive layer.
[8] The surface protection film of any one of [1] to [7] above, wherein the (D) (meth)acrylate is a polyfunctional acrylate.
[9] The surface protection film according to any one of [1] to [8] above, wherein the (D) (meth)acrylate is a polyfunctional acrylate and a urethane acrylate.
[10] The surface protection film according to any one of [1] to [9] above, wherein the cured resin layer (2) has a surface hardness of H or higher.
[11] A film laminate in which another resin film or glass substrate is bonded to the surface protection film according to any one of [1] to [10] above.
[12] The film laminate according to [11] above, wherein the other resin film is selected from any one of a polyester film, a polyimide film, and a cyclic polyolefin film.
[13] The film laminate according to [11] or [12] above, wherein a functional layer is provided on the surface of the other resin film that is in contact with the silicone adhesive layer.
[14] The film laminate according to [13] above, wherein the functional layer is a release layer.
[15] The film laminate according to [14] above, wherein the release layer contains at least one selected from the group consisting of a curable silicone resin, a fluorine-based compound, and a long-chain alkyl compound. .
[16] The film laminate according to any one of [11] to [15] above, which has a total thickness of 200 μm or less.
[17] The surface protective film according to any one of [1] to [10] above, which is used for displays.
[18] The film laminate according to any one of [11] to [16] above, which is used for displays.
[19] The film laminate according to [18] above, which is for vehicle use.

According to the present invention, it is possible to provide a surface protective film that has good adhesion to a silicone adhesive layer, has appropriate surface hardness, and is scratch-resistant, and has high industrial utility value.

An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and can be arbitrarily modified without departing from the gist of the present invention.
In this specification, the term "A to B" regarding numerical values means "A or more and B or less" (when A<B) or "A or less than B" (when A>B). . In the present invention, a combination of preferred aspects is a more preferred aspect.
In this specification, when the expression "(meth)acrylic acid" is used, it means one or both of "acrylic acid" and "methacrylic acid". Similarly, "(meth)acrylate" means one or both of "acrylate" and "methacrylate", and "(meth)acryloyl" means one or both of "acryloyl" and "methacryloyl".

The surface protective film of the present invention comprises a cured resin layer (1) containing a cured resin layer composition containing the following compounds (A) and (B), and an adhesive layer on one surface of a polyester film. A cured resin layer (2) containing (D) (meth)acrylate is provided on the opposite side of the film.
(A) at least one cross-linking agent selected from the group consisting of epoxy compounds and carbodiimide compounds (B) a polyester resin having a glass transition temperature (Tg) of 0°C or higher

<Polyester film>
The polyester film (substrate) that constitutes the surface protective film may have a single-layer structure or a multilayer structure. In the case of a multilayer structure, it may be a two-layer structure, a three-layer structure, or the like, or may be a multilayer structure of four or more layers, and the number of layers is not particularly limited unless it deviates from the gist of the present invention. As the polyester film, a biaxially oriented polyester film is preferable from the viewpoints of thinning and dimensional stability.

The polyesters used may be homopolyesters or copolyesters. When it is made of homopolyester, it is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate and the like.
On the other hand, the dicarboxylic acid component of the copolymerized polyester includes one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, sebacic acid and oxycarboxylic acid. Glycol components include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol and neopentyl glycol.

The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used, such as titanium compounds, germanium compounds, antimony compounds, manganese compounds, aluminum compounds, magnesium compounds and calcium compounds.

In order to suppress the precipitation amount of the oligomer component, the film may be produced using a polyester having a low content of the oligomer component as a raw material. As a method for producing a polyester having a low content of oligomer components, various known methods can be used. Further, the polyester film may have a structure of three or more layers, and the outermost layer of the polyester film may be a layer using a polyester raw material having a low content of the oligomer component, thereby suppressing the precipitation amount of the oligomer component. The polyester may also be obtained by subjecting it to esterification or transesterification, followed by melt polycondensation under reduced pressure at a higher reaction temperature.

In order to improve the weather resistance of the film and prevent deterioration of the adherend (for example, liquid crystal), the polyester film may contain an ultraviolet absorber. The ultraviolet absorber is a compound that absorbs ultraviolet rays and is not particularly limited as long as it can withstand the heat applied during the manufacturing process of the polyester film.

As the UV absorber, there are organic UV absorbers and inorganic UV absorbers, and organic UV absorbers are preferable from the viewpoint of transparency. The organic UV absorber is not particularly limited, and examples thereof include cyclic iminoester-based, benzotriazole-based, and benzophenone-based. From the viewpoint of durability, cyclic imino esters and benzotriazoles are more preferable. It is also possible to use two or more types of ultraviolet absorbers in combination.

Particles can be blended into the polyester film for the main purpose of imparting slipperiness and preventing scratching in each step. The type of particles to be blended is not particularly limited as long as it is a particle capable of imparting lubricity. Specific examples include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, phosphorus Inorganic particles such as magnesium oxide, kaolin, aluminum oxide and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, benzoguanamine resin and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

The shape of the particles to be used is not particularly limited either, and any of spherical, lumpy, rod-like, flattened and the like may be used. Moreover, there are no particular restrictions on its hardness, specific gravity, color, and the like. Two or more types of these series of particles may be used in combination, if necessary.

Also, the average particle size of the particles used is usually 5 μm or less, preferably in the range of 0.01 to 3 μm. When it is 5 μm or less, the surface roughness of the film does not become too rough, and problems do not occur when various surface functional layers are formed in subsequent steps, which is preferable.

Furthermore, the particle content in the polyester film is usually less than 5% by weight, preferably in the range of 0.0003-3% by weight. If there are no particles or if there are few particles, the transparency of the film will be high and the film will be good, but the slipperiness may be insufficient. It may be necessary to devise ways to improve Moreover, when the particle content is less than 5% by mass, the transparency of the film can be sufficiently ensured.
When particles are contained, it is preferable, for example, to provide a surface layer and an intermediate layer and to contain the particles in the surface layer. In this case, it is more preferable to have a multi-layer structure having a surface layer containing particles, an intermediate layer, and a surface layer containing particles in this order.

The method of adding particles to the polyester film is not particularly limited, and conventionally known methods can be employed. For example, in the case of a multi-layered polyester film, it can be added at any stage in the production of the polyester constituting each layer, but it is preferably added after the esterification or transesterification reaction is completed.

In addition to the particles described above, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film, if necessary.

The thickness of the polyester film is not particularly limited as long as it can be formed into a film.

Next, production examples of the polyester film will be specifically described, but the following production examples are not limited at all. For example, when producing a biaxially oriented polyester film, the above-described dried pellets of the polyester raw material are extruded as a molten sheet from a die using an extruder, and cooled and solidified with a cooling roll to obtain an unstretched sheet. preferable. In this case, it is preferable to increase the adhesion between the sheet and the rotating cooling drum in order to improve the flatness of the sheet, and the electrostatic application adhesion method and/or the liquid coating adhesion method are preferably employed.
The resulting unstretched sheet is then biaxially stretched. In that case, first, the unstretched sheet is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120° C., preferably 80 to 110° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in a direction perpendicular to the stretching direction of the first stage. In this case, the stretching temperature is usually 70 to 170° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. be.
Subsequently, heat treatment is performed at a temperature of usually 180 to 270° C. under tension or under relaxation of 30% or less to obtain a biaxially oriented film. In the above stretching, a method of stretching in one direction in two or more stages can also be employed. In that case, it is preferable to carry out so that the stretching ratios in the two directions finally fall within the above ranges.

A simultaneous biaxial stretching method can also be employed in the production of the polyester film. The simultaneous biaxial stretching method is a method of simultaneously stretching and orienting the unstretched sheet in the machine direction and the width direction while the temperature is controlled at usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is is preferably 4 to 50 times, more preferably 7 to 35 times, still more preferably 10 to 25 times in terms of area magnification.
Subsequently, heat treatment is carried out at a temperature of usually 170 to 250° C. under tension or under relaxation of 30% or less to obtain a stretched and oriented film. Conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be used for the simultaneous biaxial stretching apparatus that employs the above-described stretching methods.

<Cured resin layer composition (1)>
The surface protective film of the present invention comprises a cured resin layer (1) on one surface of a polyester film, and the cured resin layer (1) contains compounds (A) and (B) described below ( 1) is an essential requirement. By having the cured resin layer (1), the surface protective film of the present invention can improve the adhesion to the silicone adhesive layer. In addition, when the adhesive layer is formed on the cured resin layer (1), inhibition of curing of the adhesive layer can be suppressed, so desired adhesiveness can be obtained.

(Compound (A): cross-linking agent)
The cured resin layer composition (1) according to the present invention contains an epoxy compound and a carbodiimide compound for the purpose of improving the adhesion between the cured resin layer (1) and the adhesive layer and improving the durability of the cured resin layer. It must contain at least one selected cross-linking agent.
From the viewpoint of improving the adhesiveness of the adhesive layer, the cured resin layer composition (1) according to the present invention preferably further contains at least one compound selected from the group consisting of oxazoline compounds and melamine compounds. .

(epoxy compound)
Epoxy compounds are compounds having an epoxy group in the molecule, and include condensates with hydroxyl groups and amino groups such as epichlorohydrin, ethylene glycol, polyethylene glycol, glycerin, polyglycerin and bisphenol A, and polyepoxy compounds. , diepoxy compounds, monoepoxy compounds and glycidylamine compounds.
Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether and trimethylolpropane poly glycidyl ether and the like. Examples of diepoxy compounds include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. Ether and polytetramethylene glycol diglycidyl ether and the like. Examples of monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether and phenyl glycidyl ether, and examples of glycidylamine compounds include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (N,N-diglycidylamino)cyclohexane and the like. From the viewpoint of improving adhesion, a polyether-based epoxy compound is preferred. As for the amount of epoxy groups, a polyepoxy compound having a polyfunctionality of 3 or more is preferable to a bifunctional one.

(carbodiimide compound)
A carbodiimide compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. More preferred is a polycarbodiimide compound having

A carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and both aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate and dicyclohexylmethane 4,4'-diisocyanate.

The content of the carbodiimide group contained in the carbodiimide compound is usually 100 to 1000, preferably 250 to 800, more preferably 300 to 300, in terms of carbodiimide equivalent (weight [g] of the carbodiimide compound to give 1 mol of carbodiimide group). 700 range. By using it in the above range, the durability of the coating film is improved.

Furthermore, in order to improve the water-solubility and water-dispersibility of the polycarbodiimide compound, a surfactant may be added, polyalkylene oxide, a quaternary ammonium salt of a dialkylamino alcohol, and a hydroxy Hydrophilic monomers such as alkylsulfonates may be added and used.

(oxazoline compound)
An oxazoline compound is a compound having an oxazoline group in its molecule, and a polymer containing an oxazoline group is particularly preferable. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is suitable because it is easily available industrially. Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers. , n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, Unsaturated carboxylic acids such as styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-alkyl (Meth)acrylamide and N,N-dialkyl(meth)acrylamide (as alkyl groups, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; vinyl chloride and vinylidene chloride Halogen-containing α,β-unsaturated monomers such as; α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene; be able to. From the viewpoint of improving adhesion, the oxazoline group content of the oxazoline compound is preferably 0.5 to 10 mmol/g, more preferably 1 to 9 mmol/g, still more preferably 3 to 8 mmol/g, particularly preferably 4 to 6 mmol/g. g range.

(melamine compound)
A melamine compound is a compound having a melamine skeleton in the compound, and examples thereof include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures thereof. can be used. Methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used as the alcohol used for etherification. Moreover, the melamine compound may be either a monomer or a polymer of dimers or higher, or a mixture thereof. Further, melamine may be partially co-condensed with urea or the like, and a catalyst may be used to increase the reactivity of the melamine compound.

(Other cross-linking agents)
Other cross-linking agents may be used in combination, for example, at a ratio of 5% by mass or less, preferably 3% by mass or less, relative to the nonvolatile components in the cured resin layer, as long as the gist of the present invention is not impaired.

(isocyanate compound)
An isocyanate compound is a compound having an isocyanate derivative structure represented by isocyanate or blocked isocyanate. Examples of isocyanates include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate and naphthalene diisocyanate; aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate and hexamethylene diisocyanate; Alicyclic isocyanate etc. are illustrated. Polymers and derivatives of these isocyanates such as buret products, isocyanurate products, uretdione products and carbodiimide modified products are also included. These may be used alone or in combination of multiple types. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

When used in the form of blocked isocyanate, blocking agents include, for example, bisulfites; phenolic compounds such as phenol, cresol and ethylphenol; alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol and ethanol. Compounds; active methylene compounds such as methyl isobutanoylacetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; ε-caprolactam, δ-valerolactam and the like lactam compounds; amine compounds such as diphenylaniline, aniline and ethyleneimine; acid amide compounds such as acetanilide and acetic acid amide; These may be used alone or in combination of two or more.

Also, the isocyanate compound may be used alone, or may be used as a mixture or combination with various polymers. From the viewpoint of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or combination with a polyester resin or a urethane resin.

(Compound (B): polyester resin)
The polyester resin in the compound (B) includes, as main constituents, for example, those composed of the following acid component and diol component.
Examples of acid components include the following polyvalent carboxylic acids, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid. acids, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, Dicarboxylic acids such as dodecanedicarboxylic acid, glutaric acid and succinic acid; tricarboxylic acids such as trimellitic acid and trimesic acid; tetracarboxylic acids such as pyromellitic acid; acid anhydrides such as trimellitic anhydride and phthalic anhydride; Hydroxybenzoic acid; trimellitic monopotassium salt; and ester-forming derivatives thereof, and the like can be used.
Diol components include the following polyvalent hydroxy compounds, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexane Diol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol , polytetramethylene glycol, polytetramethylene oxide glycol, and the like can be used. One or more of these compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.
Moreover, the polyester resin may be in the form of an aqueous dispersion, in which case a hydrophilic functional group or the like may be appropriately introduced into the polyester resin.

In the present invention, the glass transition temperature (Tg) of the polyester resin in the compound (B) must be 0°C or higher, preferably 40°C or higher, more preferably 80°C or higher. When the Tg of the polyester resin in the compound (B) is in the above range, the cured resin layer (1) is excellent in solvent resistance when processing the adhesive layer, and when used at room temperature, the cured resin layer (1) is It has the advantage of being difficult to fall off from the polyester film.

In the present invention, the polyester resin of the compound (B) preferably contains a dicarboxylic acid component having 10 or less carbon atoms as an acid component from the viewpoint of improving adhesion, and a dicarboxylic acid component having 8 or less carbon atoms. It is more preferable to contain The dicarboxylic acid components having 10 or less carbon atoms may be used alone, or two or more of them may be used in combination.
As the dicarboxylic acid component, the carboxylic acids listed above can be preferably used, and terephthalic acid, isophthalic acid, and 5-sodiumsulfoisophthalic acid are more preferably used.

Furthermore, in the present invention, the polyester resin of the compound (B) is a polyester resin containing at least one selected from ethylene glycol and 1,4-butanediol, diethylene glycol and triethylene glycol as a diol component from the viewpoint of adhesion. is preferred.
When the polyester resin contains the diol component, the mass ratio of the content of ethylene glycol to the content of the diol component other than ethylene glycol ([Content of ethylene glycol]/[Content of diol component other than ethylene glycol ]) is preferably 40/60 to 90/10, more preferably 40/60 to 80/20, and even more preferably 45/55 to 75/25.

Moreover, in the present invention, the compound (B) is preferably a polyester resin containing a polycyclic compound as an acid component. By containing a polycyclic compound as an acid component in the polyester resin of the compound (B), the glass transition temperature of the polyester resin can be easily increased, and the glass transition temperature can be adjusted within the range described above. The physical properties of the cured resin layer (1) can be made suitable.
The polycyclic compound is preferably a polycyclic aromatic compound, more preferably a polycyclic aromatic compound having 12 or more carbon atoms, and still more preferably a polycyclic aromatic compound having a naphthalene ring. As the polycyclic aromatic compound, the carboxylic acids listed above can be suitably used, and 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2 ,7-naphthalenedicarboxylic acid is preferably used, and 2,6-naphthalenedicarboxylic acid is more preferably used. A polycyclic compound may be used independently and may use 2 or more types together. Moreover, the dicarboxylic acid component having 10 or less carbon atoms and the polycyclic compound may be used in combination.

(binder resin)
In the range that does not impair the gist of the present invention, for example, in the cured resin layer (1), a resin other than the compound (B) (binder resin ) may be used together. Examples of binder resins include (meth)acrylic resins.

((meth)acrylic resin)
The (meth)acrylic resin is a polymer composed of polymerizable monomers including acrylic and methacrylic monomers. These may be homopolymers, copolymers, or copolymers with polymerizable monomers other than acrylic and methacrylic monomers. The (meth)acrylic polymer is a polymer having (meth)acrylic acid or (meth)acrylic acid alkyl ester as a structural unit, and is composed of styrene or a styrene derivative and (meth)acrylic acid or (meth)acrylic acid alkyl ester. It may be a copolymer with.
Copolymers of these polymers with other polymers (eg, polyester, polyurethane, etc.) are also included. Examples are block copolymers and graft copolymers. That is, the (meth)acrylic resin may be a (meth)acryl-modified polyester resin or a (meth)acryl-modified polyurethane resin.
Furthermore, polymers obtained by polymerizing polymerizable monomers in polyester solutions or polyester dispersions (sometimes mixtures of polymers) are also included. Also included are polymers obtained by polymerizing polymerizable monomers in polyurethane solutions and polyurethane dispersions (mixtures of polymers in some cases). Similarly, other polymer solutions or polymers obtained by polymerizing polymerizable monomers in dispersions (polymer mixtures in some cases) are also included, and these are also referred to herein as (meth)acrylic modified polyester resins and , (meth)acrylic-modified polyurethane resin. The polyester and polyurethane used in the (meth)acrylic resin can be appropriately selected from those exemplified as the polyester and polyurethane used in the binder resin.
In addition, the (meth)acrylic resin may contain a hydroxy group and an amino group in order to further improve adhesion to the base film.

The polymerizable monomer is not particularly limited, but particularly representative compounds include various carboxyl group-containing compounds such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid. Monomers and their salts; various such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyfumarate, monobutylhydroxyitaconate hydroxyl group-containing monomers; various (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate; ) various nitrogen-containing compounds such as acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth)acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene; various vinyl esters; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl halides; and various conjugated dienes such as butadiene.

(Other ingredients)
For the formation of the cured resin layer (1), particles may be used in combination for the purpose of improving blocking properties and slipping properties within the scope of the present invention.

The ratio of the compound (A) to the total non-volatile components in the cured resin layer composition (1) is preferably 5-70% by mass, more preferably 15-60% by mass. When the ratio of the compound (A) is equal to or less than the upper limit, the strength and transparency of the cured resin layer (1) are good. On the other hand, when the ratio of the compound (A) is at least the lower limit, the durability of the coating film is good and desired adhesion can be obtained.

The compound (B) accounts for preferably 30 to 95% by mass, more preferably 40 to 85% by mass as a proportion of all non-volatile components in the cured resin layer composition (1). When the ratio of the compound (B) is equal to or less than the above upper limit, the ratio of other components is high, so sufficient adhesion can be obtained and the coating appearance is not insufficient. On the other hand, when the ratio of the compound (B) is equal to or higher than the above lower limit, good adhesion can be obtained, sufficient film-forming properties can be secured, and a uniform coating film can be obtained.

The total content of the compounds (A) and (B) in the cured resin layer composition (1) is preferably 80% by mass or more, more preferably 90% by mass, relative to 100% by mass of the cured resin layer composition (1). % by mass or more, more preferably 95% by mass or more, more preferably 97% by mass or more, and 100% by mass or less.
The compounding ratio (A)/(B) (mass ratio) of the compounds (A) and (B) in the cured resin layer composition (1) is preferably 10/90 to 50/50, more preferably 30/70. ~40/60. When the mixing ratio (A)/(B) is within the above range, a cured resin layer (1) having good strength and transparency can be obtained, and desired adhesion can be obtained.

<Cured resin layer (1)>
The cured resin layer (1) according to the present invention is formed from the resin composition described above.
The thickness of the cured resin layer (1) is preferably 0.002 μm or more and 1.0 μm or less, more preferably 0.005 μm or more and 0.25 μm or less, and still more preferably 0.02 μm or more and 0.10 μm or less. When the thickness of the cured resin layer (1) is within the above range, precipitation of oligomer components can be suppressed and good antistatic properties can be imparted.
The content of the cured resin layer composition (1) in the cured resin layer (1) is preferably 90% by mass or more, more preferably 95% by mass or more, relative to 100% by mass of the cured resin layer (1). It is preferably 98% by mass or more and 100% by mass or less. It can be assumed that the cured resin layer (1) contains unreacted compounds of various compounds of the cured resin layer composition (1), compounds after reaction, or mixtures thereof.

<Cured resin layer composition (2)>
From the viewpoint of imparting scratch resistance, the surface protective film of the present invention must be provided with a cured resin layer (2) on the surface opposite to the surface of the polyester film on which the cured resin layer (1) is provided. and The cured resin layer (2) is preferably formed by curing a cured resin layer composition (2) described below.
The cured resin layer (2) has a function of protecting the optical member, for example. The cured resin layer composition (2) contains a component that becomes a polymer by polymerization, and specifically may contain either a photopolymerizable compound or a thermally polymerizable compound. The cured resin layer composition (2) contains a photopolymerizable compound and is preferably a photocurable resin composition. By using the photocurable resin composition, it is not necessary to heat-treat the composition at a high temperature to cure the curable resin composition, so that the generation of impurities and the generation of thermal shrinkage due to the heat treatment can be prevented. Moreover, the polymerizable compound includes a monomer having one or two or more polymerizable functional groups in one molecule.

The cured resin layer composition (2) contains a (meth)acrylate as the (D) component, and preferably further contains a solvent as the (E) component. Typically, the (meth)acrylate as component (D) is preferably a polyfunctional acrylate, more preferably a polyfunctional acrylate and a urethane acrylate.

((D) component: (meth)acrylate)
The cured resin layer composition (2) contains a (meth)acrylate as the component (D), so that the layer (cured resin layer) formed by curing the curable resin composition has scratch resistance and resistance to the substrate film. It becomes easy to raise adhesiveness etc., too.
Specific examples of (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and tris-2-hydroxyethylisocyanate. Nurate tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylol Ethylenically unsaturated groups such as propane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane hexa(meth)acrylate, etc. trifunctional or higher polyfunctional (meth)acrylates containing 3 or more; modified polyfunctional (meth)acrylate compounds in which a portion of these (meth)acrylates are substituted with alkyl groups or ε-caprolactone; isocyanurate structure Polyfunctional (meth)acrylates having a nitrogen atom-containing heterocyclic structure such as multifunctional (meth)acrylates; Polyfunctional (meth)acrylate having a resinous structure; diisocyanate, polyisocyanate such as triisocyanate, or a trimer (isocyanurate) thereof, such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth) Examples include urethane (meth)acrylates to which (meth)acrylates having hydroxyl groups such as acrylates and dipentaerythritol penta(meth)acrylates are added. The (meth)acrylate having a hydroxyl group is preferably polyfunctional having two or more ethylenically unsaturated groups. Also, the (meth)acrylate preferably contains urethane (meth)acrylate.

Specific examples of (meth)acrylates include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta (meth)acrylates, urethane (meth)acrylates that are reaction products of pentaerythritol tri(meth)acrylate and hexamethylene diisocyanate, urethane (meth)acrylates that are reaction products of pentaerythritol tri(meth)acrylate and isophorone diisocyanate acrylate, urethane (meth)acrylate which is the reaction product of dipentaerythritol penta(meth)acrylate and hexamethylene diisocyanate, and urethane (meth)acrylate which is the reaction product of dipentaerythritol penta(meth)acrylate and isophorone diisocyanate. preferable. These may be used alone or in combination of two or more.

Among the above, more trifunctional to hexafunctional polyfunctional (meth)acrylates, or urethane (meth)acrylates obtained by adding polyfunctional (for example, trifunctional to pentafunctional) (meth)acrylates having hydroxyl groups to polyisocyanate. Preferably, it is more preferable to use the polyfunctional (meth)acrylate and urethane (meth)acrylate together. Moreover, it is more preferable that the polyisocyanate used for the urethane (meth)acrylate is a diisocyanate.

The (meth)acrylate has a weight average molecular weight of, for example, 250 to 8,000, preferably 300 to 7,000, more preferably 400 to 5,000, still more preferably 500 to 3,000. By satisfying the above range, the bleed-out suppressing effect of the ultraviolet absorber is improved.
The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene.

The (meth)acryloyl group equivalent of the (meth)acrylate is, for example, 80 g/eq or more and less than 150 g/eq, preferably 85 g/eq or more and less than 135 g/eq, more preferably 90 g/eq or more and less than 120 g/eq. Moderate surface hardness can be provided because the (meth)acryloyl group equivalent of (meth)acrylate is in the said range.

The (meth)acryloyl group equivalent (g/eq) indicates the (meth)acryloyl group concentration of a compound having a (meth)acryloyl group, and is the average molecular weight per one (meth)acryloyl group. For example, when there are 10 (meth)acryloyl groups per molecule of a (meth)acrylate compound with a number average molecular weight of 10,000, the (meth)acryloyl group equivalent is 10,000/10=1,000 g/eq. becomes.

The urethane (meth)acrylate as component (D) is, as described above, a reaction product of polyisocyanate or isocyanurate and hydroxyl group-containing (meth)acrylate. It may be produced by reacting a mixture of a (meth)acrylate having a hydroxyl group and a (meth)acrylate having no hydroxyl group. At this time, the (meth)acrylate having no hydroxyl group remains as an unreacted product, but it is preferable to use it as the component (D) by incorporating it into the curable resin composition as it is.

((E) component: solvent)
The cured resin layer composition (2) may be diluted with a solvent to form a coating liquid. The cured resin layer composition (2) may be applied to the substrate film as a liquid coating liquid, dried, and cured to form the cured resin layer (2). Each component (component (D), etc.) constituting the cured resin layer composition (2) may be dissolved in a solvent, or may be dispersed in the solvent. The cured resin layer composition (2) contains a solvent as the component (E), and when the coating liquid is dried and cured, wrinkles, curls, and the like may occur. ) component can prevent the occurrence of wrinkles and curls.

Organic solvents are preferred as solvents. Specific examples of organic solvents include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone (MEK), acetone, methyl isobutyl ketone (MIBK), cyclohexanone and diisobutyl ketone; diethyl ether, isopropyl ether and tetrahydrofuran. Ether solvents such as , dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether (PGM), anisole, phenetol; ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol diacetate, etc. dimethylformamide, diethylformamide, dimethylacetamide, N-methylpyrrolidone and other amide solvents; methyl cellosolve, ethyl cellosolve, butyl cellosolve and other cellosolve solvents; methanol, ethanol, propanol, isopropanol, butanol and other alcohol solvents Solvent; Halogen-based solvents such as dichloromethane and chloroform can be used. One of these organic solvents may be used alone, or two or more thereof may be used in combination. Among these organic solvents, ester solvents, ether solvents, alcohol solvents and ketone solvents are preferably used.

The amount of the organic solvent to be used is not particularly limited, and is appropriately determined in consideration of the coatability of the cured resin layer composition (2) to be prepared, the viscosity and surface tension of the liquid, the compatibility with the solid content, and the like. The cured resin layer composition (2) is prepared as a coating liquid having a solid concentration of preferably 15 to 80% by mass, more preferably 20 to 70% by mass, using the solvent described above. The "solid content" in the cured resin layer composition (2) means the components excluding the solvent, which is a volatile component, and not only solid components but also semi-solid and viscous liquid substances. shall also include those of

Component (E) is usually in the range of 10 to 85% by weight, preferably 40 to 65% by weight, and more preferably 45 to 60% by weight as a proportion of all non-volatile components in the cured resin layer composition (2). . If the ratio of component (E) is higher than this, the ratio of other components will be low, and there is a concern that antistatic properties and film-forming properties will be insufficient. On the other hand, if the ratio of component (E) is below the lower limit, there is a concern that the transparency of the cured resin layer may be insufficient.

((F) component: other components)
Various additives can be added to the cured resin layer composition (2), if necessary, as long as they do not impair the gist of the present invention. Additives include, for example, photoinitiators, light stabilizers, antioxidants, antistatic agents, organic pigments, organic particles, inorganic particles, flame retardants, leveling agents, dispersants, thixotropy-imparting agents (thickeners). , an antifoaming agent, etc. may be used in combination.

(photoinitiator)
When the cured resin layer composition (2) is a photocurable resin composition, the cured resin layer composition (2) preferably contains a photoinitiator in order to improve curability. A photoinitiator is a photoinitiator, and can use a well-known thing. Photopolymerization initiators include, for example, photoradical generators and photoacid generators.

Among the photopolymerization initiators that can be used in the cured resin layer composition (2), examples of photoradical generators include benzoin and alkyl ethers thereof, such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether. ; acetophenone, 2,2-dimethoxy-2-phenylacetophenone [eg, trade name “Omnirad (registered trademark) 651” manufactured by IGM RESINS], 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone [for example, trade name “Omnirad (registered trademark) 184” manufactured by IGM RESINS], 2-hydroxy-2-methyl-1-phenylpropan-1-one [for example, trade name “Omnirad (registered trademark) Trademark) 1173”, manufactured by IGM RESINS], 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one [for example, trade name “Omnirad (registered trademark) 127, manufactured by IGM RESINS”], 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one [for example, trade name “Omnirad (registered trademark) 2959”, manufactured by IGM RESINS], 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one [for example, the trade name “Omnirad (registered trademark) 907”, IGM RESINS], alkylphenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone; 2,4,6-trimethylbenzoyldiphenylphosphine oxide [for example, trade name " Omnirad (registered trademark) TPO", manufactured by IGM RESINS], bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide [for example, trade name "Omnirad (registered trademark) 819", IGM RESINS Anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, and 2-amylanthraquinone; Benzophenone and its various derivatives; Methyl benzoylformate, Benzoyl Examples thereof include formic acid derivatives such as ethyl formate. These may be used alone or in combination of two or more.

Among these photo-radical generators, alkylphenones, phosphine oxides and formic acid derivatives are preferred from the viewpoint of light resistance of cured products, and 1-hydroxycyclohexylphenyl ketone and 2-hydroxy- 1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpho Linopropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, methyl benzoylformate, and particularly preferred is 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one.

Known photoacid generators can be used, but among them, diaryliodonium salts and triarylsulfonium salts are preferable from the viewpoint of curability, acid generation efficiency, and the like. Specific examples include anion salts of di(alkyl-substituted)phenyliodonium (specifically, PF6 salt, SbF5 salt, tetrakis(perfluorophenyl)borate salt, etc.). As a specific example of the (alkyl-substituted) phenyliodonium anion salt, the PF6 salt of dialkylphenyliodonium [trade name “Omniad (registered trademark) 250”, manufactured by IGM RESINS] is particularly preferred. These photoacid generators may be used alone or in combination of two or more.

The content of the photoinitiator is preferably 0.01 part by mass from the viewpoint of improving curability with respect to a total of 100 parts by mass of the compound having a (meth)acryloyl group in the cured resin layer composition (2). or more, more preferably 0.1 parts by mass or more, and particularly preferably 1 part by mass or more. On the other hand, from the viewpoint of maintaining the stability of the coating liquid when the cured resin layer composition (2) is made into a solution and the viewpoint of the flatness of the cured coating film, the amount is preferably 10 parts by mass or less, more preferably 7 parts by mass. parts by mass or less, and particularly preferably 4 parts by mass or less.

<Cured resin layer (2)>
The cured resin layer (2) according to the present invention is preferably formed from the cured resin layer composition (2) described above.
The thickness of the cured resin layer (2) is, for example, 1 to 10 μm, preferably 1 to 8 μm, more preferably 1 to 5 μm, particularly preferably 1 to 3 μm. When the thickness of the cured resin layer (2) is at least these lower limit values, the substrate film can be appropriately protected by the cured resin layer (2), and weather resistance and the like can be easily improved. Further, when the thickness of the cured resin layer (2) is set to these upper limits or less, it is possible to prevent curling and heat wrinkles in a laminate structure having the cured resin layer (2) such as a laminated film, and to ensure good flatness. .

The cured resin layer (2) formed from the cured resin layer composition (2) contains (meth)acrylate, urethane (meth)acrylate, or an acrylic resin obtained by polymerizing both of them as component (D). In addition to these, any resin may be used as long as it does not impair the gist of the present invention.
However, the cured resin layer (2) is preferably an acrylic resin layer whose main component resin is an acrylic resin. Note that the main component resin means a resin having the largest mass ratio among the resins constituting the cured resin layer (2), and is 50% by mass or more, or 75% by mass of the resin constituting the cured resin layer (2). % or more, or 90% or more, or 100% by weight.

The content of the cured resin layer composition (2) in the cured resin layer (2) is preferably 90% by mass or more, more preferably 95% by mass or more, relative to 100% by mass of the cured resin layer (2). It is preferably 98% by mass or more and 100% by mass or less. It can be assumed that the cured resin layer (2) contains unreacted compounds of various compounds of the cured resin layer composition (2), compounds after reaction, or mixtures thereof.

<Method for Forming Cured Resin Layers (1) and (2)>
Next, a method for forming the cured resin layers (1) and (2) constituting the surface protection film will be described.
The method of forming the cured resin layers (1) and (2) is not particularly limited, and conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, and curtain coating may be used. can be done.
Methods for forming the cured resin layers (1) and (2) include in-line coating and off-line coating. Drying and curing conditions are not particularly limited. For example, when a cured resin layer is provided by offline coating, the temperature is usually 80 to 200° C. for 3 to 40 seconds, preferably 100 to 180° C. for 3 to 40 seconds. As a guideline, heat treatment is recommended.
On the other hand, when the cured resin layer is provided by in-line coating, it is generally preferable to perform heat treatment at 70 to 280° C. for 3 to 200 seconds.

In the present invention, it is preferably formed by in-line coating, which treats the film surface during the film-forming process of the polyester film.
In-line coating is a method of coating in the process of polyester film production, specifically, a method of coating at any stage from melt extrusion of polyester to stretching, heat setting and winding. Usually, it is coated on an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, or a film after heat setting and before winding up. Although it is not limited to the following, for example, in sequential biaxial stretching, a method in which a uniaxially stretched film stretched in the longitudinal direction (machine direction) is coated and then stretched in the transverse direction is excellent. According to this method, the film formation and the formation of the cured resin layer can be performed at the same time, which is advantageous in terms of manufacturing cost. In addition, since the film is stretched after coating, the thickness of the cured resin layer can be changed by the stretching ratio. Also, thin film coating can be performed more easily compared to off-line coating films. Further, by providing the cured resin layer on the film before stretching, the cured resin layer can be stretched together with the polyester film, thereby firmly adhering the cured resin layer to the polyester film. Furthermore, in the production of biaxially stretched polyester film, the film can be restrained in the vertical and horizontal directions by holding the ends of the film with a clip or the like while the film is stretched. High temperature can be applied while maintaining the properties. Therefore, since the heat treatment applied after coating can be performed at a high temperature that cannot be achieved by other methods, the film-forming property of the cured resin layer is improved, and the cured resin layer and the polyester film can be adhered more firmly. Furthermore, a strong cured resin layer can be formed, and performance such as adhesion with various functional layers that can be formed on the cured resin layer and resistance to moist heat can be improved.

When the cured resin layer is provided by in-line coating, the above-mentioned series of compounds are used as an aqueous solution or aqueous dispersion, and the solid content concentration (total non-volatile components) is adjusted to about 0.1 to 50% by mass. The composition of the cured resin layer. It is preferred to prepare the laminated polyester film in such a manner that the material is coated onto the polyester film.

Further, regardless of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used together as needed. The polyester film constituting the laminated polyester film of the present invention may be previously subjected to surface treatment such as corona treatment or plasma treatment.

The surface protection film of the present invention has cured resin layers on both sides of the polyester film. That is, one surface of the polyester film is provided with a cured resin layer (1), and the opposite surface of the polyester film is provided with a cured resin layer (2).

<Adhesive layer>
The surface protective film of the present invention comprises an adhesive layer on the cured resin layer (1). The adhesive layer is preferably a silicone adhesive layer or an acrylic adhesive layer, more preferably a silicone adhesive layer.

(Silicone adhesive layer)
The silicone pressure-sensitive adhesive that constitutes the silicone pressure-sensitive adhesive layer may be a pressure-sensitive adhesive containing silicone as a main component resin. The "main component resin" means a resin having the largest content ratio (mass) among the resins constituting the pressure-sensitive adhesive.
Examples of silicone pressure-sensitive adhesives include addition reaction type, peroxide curing type and condensation reaction type silicone pressure-sensitive adhesives. Among them, the addition reaction type silicone pressure-sensitive adhesive is preferably used from the viewpoint that it can be cured at a low temperature in a short period of time. These addition-reactive silicone pressure-sensitive adhesives cure when the pressure-sensitive adhesive layer is formed on the support. When an addition-reactive silicone pressure-sensitive adhesive is used as the silicone pressure-sensitive adhesive, the silicone pressure-sensitive adhesive may contain a catalyst such as a platinum catalyst.
For example, an addition reaction type silicone pressure-sensitive adhesive can be prepared by adding a catalyst such as a platinum catalyst to a solution of silicone resin diluted with a solvent such as toluene, if necessary, and stirring it so that it becomes uniform, then coating it on the support. , 100-130° C./1-5 minutes. If necessary, a cross-linking agent or an additive for controlling adhesion may be added to the addition-reactive silicone pressure-sensitive adhesive, or the base film may be subjected to a primer treatment before forming the pressure-sensitive adhesive layer.

Examples of commercially available silicone resins used for addition reaction type silicone pressure-sensitive adhesives include SD4580PSA, SD4584PSA, SD4585PSA, SD4587LPSA, SD4560PSA, SD4570PSA, SD4600FCPSA, SD4593PSA, DC7651ADHESIVE, DC7652ADHESIVE, LTC-755, LTC-310 (all of which are Toray manufactured by Dow Corning), KR-3700, KR-3701, KR-3704, X-40-3237-1, X-40-3240, X-40-3291-1, X-40-3229, X-40- 3323, X-40-3306, X-40-3270-1 (all manufactured by Shin-Etsu Chemical Co., Ltd.), AS-PSA001, AS-PSA002, AS-PSA003, AS-PSA004, AS-PSA005, AS-PSA012, AS-PSA014, PSA-7465 (all manufactured by Arakawa Chemical Industries, Ltd.), TSR1512, TSR1516, TSR1521 (all manufactured by Momentive Performance Materials) and the like can be mentioned.

(Acrylic adhesive layer)
The acrylic adhesive layer contains a (meth)acrylic acid ester (co)polymer and a visible light initiator, optionally a cross-linking agent, optionally a silane coupling agent, and optionally other materials. It can be formed from the containing adhesive composition. The acrylic pressure-sensitive adhesive layer can be formed from a conventionally known pressure-sensitive adhesive composition, for example, the pressure-sensitive adhesive composition described in JP-A-2019-210446 may be used.

The thickness of the adhesive layer (after drying) is preferably 1 to 100 μm, more preferably 5 to 80 μm, even more preferably 10 to 60 μm, still more preferably 20 to 50 μm.

The total thickness of the surface protective film of the present invention is preferably 125 μm or less, more preferably 9 μm or more and 100 μm or less, still more preferably 12 μm or more and 100 μm or less, still more preferably 25 μm or more and 75 μm or less, from the viewpoint of handling.

(surface hardness)
The surface hardness of the cured resin layer (2) in the surface protective film of the present invention is preferably H or higher, more preferably 2H or higher, still more preferably 3H or higher. If the surface hardness is H or more, the scratch adhesion prevention property is excellent. The surface hardness of the cured resin layer (2) is measured by the method described in Examples.

<Film laminate>
The film laminate of the present invention is in a form in which another resin film or glass substrate is laminated on the cured resin layer of the surface protective film via a silicone adhesive layer.

(Other resin films or glass substrates)
The other resin film is preferably a resin film selected from polyester film, polyimide film, and cyclic polyolefin film.

Moreover, it is preferable to provide a functional layer on the surface of the other resin film that is in contact with the silicone adhesive layer. The functional layer is preferably a release layer.
The release layer is preferably a release layer containing at least one selected from the group consisting of curable silicone resins, fluorine-based compounds and long-chain alkyl compounds.

As an example of the release layer, a first layer formed from a silicone composition containing a curable silicone containing no fluorine substituent as a main component, and a second layer containing a component having a fluorine substituent are sequentially provided. can be exemplified.

Another example of the release layer is a layer formed from a silicone composition containing a fluorine-substituted curable silicone as a main component.

Further, another example of the release layer is a layer formed from a silicone composition containing, as a main component, a curable silicone containing no fluorine substituents.

The total thickness of the film laminate of the present invention is preferably 200 μm or less, more preferably 9 μm or more and 125 μm or less, and more preferably 12 μm or more and 125 μm or less, especially 25 μm or more and 125 μm or less. is more preferred.

<Uses of laminated polyester film and film laminate>
The laminated polyester film of the present invention can be suitably used as a base material of an optical member, etc., from the viewpoint of having excellent adhesion to a silicone pressure-sensitive adhesive. Moreover, it can be suitably used as a protective material by pasting it on the surface of an optical member or the like via a silicone pressure-sensitive adhesive. However, it is not limited to such usage.

Examples of optical members include resin films selected from polyester films, polyimide films, and cyclic polyolefin films, glass substrates, and the like.
The film laminate of the present invention can use a silicone adhesive with good durability and transparency.
Therefore, taking advantage of the heat resistance, cold resistance, weather resistance, and high transparency of the silicone pressure-sensitive adhesive itself, it can be suitably used for displays such as touch panels, and is particularly suitable for in-vehicle displays such as car navigation systems. be able to.

<Method for producing film laminate>
The method for producing the film laminate of the present invention is not particularly limited. The layer forming liquid is applied with an applicator to form a silicone adhesive layer to form the surface protective film of the present invention, and then another resin film or glass substrate is laminated on the silicone adhesive layer to form the surface protective film of the present invention. Film laminates can be produced. The method of applying the liquid for forming a silicone adhesive layer is not particularly limited, and conventionally known methods can be used. Further, as described above, other resin films may be provided with a functional layer on the surface in contact with the silicone adhesive layer.

Various components in the cured resin layer can be analyzed by TOF-SIMS, ESCA, fluorescent X-ray analysis, or the like.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples without departing from the gist thereof. Moreover, the measuring method and evaluation method used in the present invention are as follows.

<Measurement method and evaluation method>
(1) Intrinsic viscosity of polyester Precisely weigh 1 g of polyester from which components incompatible with polyester have been removed, add 100 mL of a mixed solvent of phenol / tetrachloroethane = 50/50 (mass ratio) and dissolve, viscosity (IV) Measurement was performed at 30° C. using a measuring device “VMS-022UPC/F10” (manufactured by Rigosha Co., Ltd.).

(2) Average particle size of particles Using a transmission electron microscope (TEM) (manufactured by Hitachi High-Tech Co., Ltd., "H-7650", acceleration voltage 100 kV), the laminated polyester films of Examples and Comparative Examples were observed, The average value of the particle sizes of 10 particles was taken as the average particle size.

(3) Thickness of Cured Resin Layer The surface of the cured resin layer of the laminated polyester films of Examples and Comparative Examples was dyed with RuO ₄ and embedded in an epoxy resin. After that, the cross section of the cured resin layer was measured using a transmission electron microscope (TEM) (manufactured by Hitachi High-Tech Co., Ltd., "H-7650", acceleration voltage 100 kV) for the section prepared by the ultra-thin section method.

(4) Tg of polyester resin
The glass transition temperature (Tg) was measured using a differential scanning calorimeter (manufactured by PerkinElmer, "DSC7"). 6 mg of the sample film was set in a DSC device, the sample was heated from 0° C. to 300° C. at a rate of 10° C./min, held molten at 300° C. for 5 minutes, and then quenched with liquid nitrogen. The temperature of the quenched sample was raised from 0°C at a rate of 10°C/min, and the glass transition temperature was detected according to the reading of the DSC curve of JIS K7121:2012.

(5) Evaluation of adhesion and curability of silicone adhesive layer On the silicone adhesive layer side of the surface protective film, an uncoated film (manufactured by Mitsubishi Chemical Corporation, biaxially oriented polyethylene terephthalate film, "T100" type, thickness 38 µm) to prepare a sample for evaluation. The structure of the evaluation sample was a laminated polyester film (cured resin layer (2)/polyester film/cured resin layer (1))/silicone adhesive layer/uncoated film.

5-1) Evaluation of Initial Adhesion The uncoated film was peeled off from an evaluation sample stored for one day at 23° C. and 50% RH, and the exposed surface of the silicone adhesive layer was cross-cut. Next, the surface of the silicone adhesive layer in the cross-cut portion was rubbed five times with fingers to evaluate whether or not the silicone adhesive layer was peeled off from the laminated polyester film based on the following evaluation criteria.
5-2) Evaluation of adhesion after aging The uncoated film was peeled off from the evaluation sample stored at 23°C and 50% RH for one month, and the exposed surface of the silicone adhesive layer was cross-cut. Next, the surface of the silicone adhesive layer in the cross-cut portion was rubbed five times with fingers to evaluate whether or not the silicone adhesive layer was peeled off from the laminated polyester film based on the following evaluation criteria.
5-3) Evaluation of Curability of Silicone Adhesive Layer Whether or not the silicone adhesive layer transferred to the surface of the uncoated film peeled off from the evaluation sample stored at 23° C.×50% RH for 1 day was evaluated as follows. Confirmed based on the evaluation criteria.

(Evaluation criteria for adhesion evaluation at the initial stage and after aging)
A: The silicone adhesive layer did not separate from the laminated polyester film.
B: Slight peeling of the silicone adhesive layer occurred at the edges of crosscuts and the like.
C: The silicone adhesive layer was completely peeled off from the laminated polyester film.
In adhesion evaluation, A and B are acceptable, and C is unacceptable.

(Evaluation Criteria for Evaluation of Curability of Silicone Adhesive Layer)
A: The silicone adhesive layer did not transfer to the surface of the peeled uncoated film.
B: The silicone adhesive layer was slightly transferred to the peeled uncoated film surface.
C: The silicone adhesive layer was transferred to the surface of the peeled uncoated film.
In the curability evaluation, A is a pass, and B and C are a fail.

(6) Scratch resistance of surface protective film (pencil hardness of cured resin layer (2) surface)
Based on JIS K 5600-5-4, the pencil hardness was evaluated with a pencil hardness tester (manufactured by Yasuda Seiki Co., Ltd.) under a load condition of 750 g. Based on the results, the scratch adhesion prevention property was determined according to the following evaluation criteria.
(Evaluation Criteria for Anti-Scratch Adhesion)
A (good): Pencil hardness is H or higher.
B (poor): less than H in pencil hardness.

Polyester raw materials for polyester films used in Examples and Comparative Examples are as follows.

<Production of polyester for polyester film>
(Method for producing polyester (1))
100 parts by mass of dimethyl terephthalate and 55 parts by mass of ethylene glycol were used as starting materials, and 0.04 parts by mass of magnesium acetate tetrahydrate as a catalyst was placed in a reactor. The reaction temperature was gradually raised to 230°C after 3 hours. After that, the reaction was allowed to proceed for an additional hour to substantially complete the transesterification reaction.
After adding 0.02 parts by mass of ethyl acid phosphate to this reaction mixture, 0.04 parts by mass of antimony trioxide was added to carry out a polycondensation reaction. At this time, the reaction temperature was gradually raised from 230°C and finally reached 280°C. Also, the pressure was gradually reduced from normal pressure to 0.3 mmHg finally. After 4 hours from the start of the reaction, it was confirmed from changes in the stirring power of the reaction vessel that the intrinsic viscosity of the reactant had reached 0.65 dL/g. It was discharged to obtain a polyester (1) having an intrinsic viscosity of 0.65 dL/g.

(Method for producing polyester (2))
100 parts by mass of dimethyl terephthalate and 45 parts by mass of ethylene glycol were used as starting materials, and 0.06 parts by mass of magnesium acetate tetrahydrate as a catalyst was placed in a reactor. The reaction temperature was gradually raised to 230°C after 3 hours. After that, the reaction was allowed to proceed for an additional hour to substantially complete the transesterification reaction.
After adding 0.03 parts by mass of ethyl acid phosphate to this reaction mixture, 0.3 parts by mass of silica particles having an average particle size of 2.7 μm dispersed in ethylene glycol and 0.03 parts by mass of antimony trioxide were added. Then, a polycondensation reaction was carried out. At this time, the temperature was gradually raised from 230.degree. C. and finally reached 280.degree. Also, the pressure was gradually reduced from normal pressure to 0.3 mmHg finally. After 4 hours from the start of the reaction, it was confirmed from changes in the stirring power of the reaction vessel that the intrinsic viscosity of the reactant had reached 0.65 dL/g. It was discharged to obtain a polyester (2) having an intrinsic viscosity of 0.65 dL/g.

<Cured resin layer composition (1)>
The following materials were used for the resin composition (cured resin layer composition (1)) for forming the cured resin layer (1).

(Compound (A): cross-linking agent)
(A1): Epoxy compound Water-soluble polyglycerol polyglycidyl ether (A2): Carbodiimide compound Polycarbodiimide compound “Carbodilite SV-02” (carbodiimide equivalent: 430) (manufactured by Nisshinbo Inc.)
(A3): melamine compound hexamethoxymethylol melamine

(Compound (B): polyester resin)
(B1): Aqueous dispersion of a polyester resin having a glass transition temperature (Tg) of 52° C., copolymerized with the following composition Monomer composition: (acid component) terephthalic acid/isophthalic acid/5-sodium sulfoisophthalic acid //( Diol component) Ethylene glycol/1,4-butanediol/diethylene glycol = 56/40/4//70/20/10 (molar ratio)
(B2): Aqueous dispersion of a polyester resin having a glass transition temperature (Tg) of 110°C, copolymerized with the following composition Monomer composition: (acid component) 2,6-naphthalene dicarboxylic acid/5-sodium sulfoisophthalic acid/ / (diol component) ethylene glycol / diethylene glycol = 92/8 // 80/20 (molar ratio)
(B3): Aqueous dispersion of a polyester resin having a glass transition temperature (Tg) of -20°C, copolymerized with the following composition Monomer composition: (acid component) terephthalic acid/isophthalic acid/5-sodium sulfoisophthalic acid/dodecane Diacid // (diol component) ethylene glycol / butanediol = 40/40/8/2 // 60/40 (mol%)

(binder resin)
(C1): Aqueous dispersion of urethane resin copolymerized with the following composition Monomer composition: isophorone diisocyanate/terephthalic acid/isophthalic acid/ethylene glycol/diethylene glycol/dimethylolpropanoic acid = 12/19/18/21/25/5 ( mol ratio)

<Cured resin layer composition (2)>
The following (D), (E), (F1) and (F2) are mixed at a mass ratio of (D) / (E) / (F1) / (F2) = 100 / 233 / 5 / 1 and cured A resin layer composition (2) was obtained.

(D) mixture of dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate and urethane (meth)acrylate compound) In a four-necked flask equipped with a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet, isophorone diisocyanate 6.6 g (0.03 mol), 93.4 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value: 48 mg KOH/g), 0.6 g of 2,6-di-tert-butyl cresol as a polymerization inhibitor. 06 g, and 0.02 g of dibutyltin dilaurate as a reaction catalyst were charged and reacted at 60° C. When the residual isocyanate groups became 0.3% or less, the reaction was terminated, and a urethane (meth) acrylate compound (weight average molecular weight was 2,000), 8.6 g of dipentaerythritol pentaacrylate and 47.4 g of dipentaerythritol hexaacrylate.
(E): Solvent methyl ethyl ketone (MEK)
(F1): Photoinitiator "Omnirad 127" (manufactured by IGM Resin)
(F2): leveling agent "BYK-UV3570" (manufactured by BYK-Chemie, both ends Pes-modified silicone)

(Example 1)
A blend of polyester (1) and polyester (2) at a mass ratio of 82/18 is used as a raw material for layer A, and only polyester (1) is used as a raw material for layer B, and each is supplied to an extruder and heated to 285 ° C. It is melted and divided into two layers, the A layer is the outermost layer (surface layer), and the B layer is the intermediate layer. They were co-extruded so that A = 5/90/5, and cooled and solidified while being brought into close contact with a mirror surface cooling drum having a surface temperature of 40 to 50°C to prepare an unstretched polyethylene ester film. This film was stretched 3.7 times in the longitudinal direction while being passed through a group of heating rolls at 85° C. to obtain a uniaxially oriented polyester film.
On both sides of this uniaxially oriented polyester film, the cured resin layer composition (1) shown in Table 1 below was applied, then this film was led to a tenter stretching machine, and stretched 4.3 times in the width direction at 100 ° C., Further, after heat treatment at 230° C., relaxation treatment of 2% in the width direction is performed, and a biaxially oriented laminated polyester with a thickness of 50 μm having a cured resin layer (1) with a thickness (after drying) of 0.05 μm. got the film.
Next, a cured resin layer (2) was formed by coating and curing the cured resin layer composition (2) on the opposite side of the cured resin layer (1) in the following manner.
On the opposite side of the cured resin layer (1) of the polyester film, after corona treatment (100 W) in advance, the cured resin layer composition (2) prepared by the above formulation was applied so that the thickness (after curing) would be 3 μm. After drying at 80° C. for 30 seconds, ultraviolet irradiation (accumulated light quantity: 400 mJ/cm ² ) and N ₂ purge were performed to form a cured resin layer (2).
Silicone adhesive "KR-3704" (manufactured by Shin-Etsu Silicone, solvent addition type) and catalyst "CAT-PL-50T" (manufactured by Shin-Etsu Silicone) were blended at a ratio of 99.5:0.5 to form a silicone adhesive layer forming liquid. was made. On the cured resin layer (1) of the laminated polyester film obtained above, the liquid for forming a silicone adhesive layer is applied with an applicator so that the thickness (after drying) becomes 5 μm, heat treated at 100 ° C. for 6 minutes, and the silicone An adhesive layer was formed to obtain a surface protective film of Example 1.

(Examples 2-3)
Laminated polyester films of Examples 2 and 3 were obtained in the same manner as in Example 1, except that the composition of the cured resin layer composition (1) was changed to the composition shown in Table 1.

(Comparative Examples 1 and 4)
A laminated polyester film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the composition of the cured resin layer composition (1) was changed to the composition shown in Table 1.

(Comparative example 2)
A laminated polyester film of Comparative Example 2 was obtained in the same manner as in Example 1, except that the composition of the cured resin layer composition (1) was changed to the composition shown in Table 1.
In addition, in the surface protective film obtained in Comparative Example 2, the curability evaluation of the adhesive layer was "B" evaluation, which was at a practically problematic level.

(Comparative Example 3)
A surface protective film of Comparative Example 3 was obtained in the same manner as in Example 1, except that the cured resin layer (2) was not provided.

(Discussion)
According to the results of investigation by the present inventors, it was found that the adhesion between the cured resin layer (1) composed of a specific cross-linking agent and a polyester resin and the silicone adhesive layer is particularly good.
Among them, it was found that the combination of an epoxy resin and a polyester resin in particular is capable of both improving the adhesion to the silicone adhesive layer and suppressing inhibition of curing of the silicone adhesive layer.
In addition, since the silicone adhesive layer used in this evaluation is of the slightly adhesive type, it is presumed that it is difficult to expect further adhesion improvement effects from the adhesive layer side compared to the normal type. However, it is considered that a remarkable effect of improving adhesion can be obtained in that good adhesion is maintained even one month after the adhesive layer is applied on the cured resin layer (1). . The cured resin layer (1) in the present invention has a composition (non-silicone type) different from that of a conventional silicone adhesive layer primer (silicone type), and a thin film (application thickness (after drying) of 0.1 μm or less). It is characterized by being
Furthermore, by providing a cured resin layer (2) on the opposite side of the film surface on which the adhesive layer is provided, the surface hardness is as good as H or higher, and from the viewpoint of protecting the adherend, it is possible to impart scratch adhesion prevention properties. have the advantage of being able to

Claims (19)

On one surface of the polyester film, a cured resin layer (1) containing a cured resin layer composition (1) containing the following compounds (A) and (B) and an adhesive layer are sequentially provided, and on the opposite side of the polyester film (D) A surface protection film comprising a cured resin layer (2) containing (meth)acrylate.
(A) at least one cross-linking agent selected from the group consisting of epoxy compounds and carbodiimide compounds (B) a polyester resin having a glass transition temperature (Tg) of 0°C or higher 2. The surface protection film according to claim 1, wherein said cured resin layer composition (1) further contains at least one selected from the group consisting of oxazoline compounds and melamine compounds. 3. The surface protection film according to claim 1, wherein the compound (B) is a polyester resin composed of a dicarboxylic acid component having 10 or less carbon atoms as an acid component. Any one of claims 1 to 3, wherein the compound (B) is a polyester resin containing, as a diol component, ethylene glycol and at least one selected from 1,4-butanediol, diethylene glycol and triethylene glycol. The surface protection film described in . The surface protection film according to any one of claims 1 to 4, wherein the compound (B) is a polyester resin containing a polycyclic compound as an acid component. Claims 1 to 5, wherein the compounding ratio (A)/(B) (mass ratio) of the compounds (A) and (B) in the cured resin layer composition (1) is 10/90 to 50/50. The surface protective film as described in any one. The surface protective film according to any one of claims 1 to 6, wherein the adhesive layer is a silicone adhesive layer or an acrylic adhesive layer. The surface protection film according to any one of claims 1 to 7, wherein the (D) (meth)acrylate is a polyfunctional acrylate. The surface protection film according to any one of claims 1 to 8, wherein the (D) (meth)acrylate is a polyfunctional acrylate and a urethane acrylate. The surface protective film according to any one of claims 1 to 9, wherein the cured resin layer (2) has a surface hardness of H or higher. A film laminate comprising the surface protection film according to any one of claims 1 to 10 and another resin film or glass substrate laminated together. 12. The film laminate according to claim 11, wherein the other resin film is selected from polyester film, polyimide film, and cyclic polyolefin film. 13. The film laminate according to claim 11 or 12, wherein a functional layer is provided on the surface of the other resin film that contacts the silicone adhesive layer. 14. The film laminate according to claim 13, wherein the functional layer is a release layer. 15. The film laminate according to claim 14, wherein the release layer contains at least one selected from the group consisting of curable silicone resins, fluorine compounds and long-chain alkyl compounds. The film laminate according to any one of claims 11 to 15, having a total thickness of 200 µm or less. The surface protective film according to any one of claims 1 to 10, which is used for displays. The film laminate according to any one of claims 11 to 16, which is for display. 19. The film laminate according to claim 18, which is for vehicle use.