JP2022131474A - Surface protective film - Google Patents

Abstract

To provide a surface protective film which has good adhesion to a silicone adhesive layer and good antistatic 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) on the opposite surface of the polyester film. The surface of the cured resin layer (2) has a surface resistivity of 1×1012 Ω/sq. or less. (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

TECHNICAL FIELD 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. .
In addition, when a high level of visibility is required, such as in display members, adhesion of foreign matter from the outside is extremely unfavorable.

Accordingly, the problem to be solved by the present invention is to provide a surface protective film that has good adhesion to a silicone adhesive layer and good antistatic properties.

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 [17].
[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 protective film having a cured resin layer (2) on the opposite surface, wherein the cured resin layer (2) has a surface resistivity of 1×10 ¹² Ω/□ or less.
(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] Any one of the above [1] to [7], wherein the cured resin layer (2) is obtained by curing a cured resin layer composition (2) containing the following compounds (D) to (F): The surface protection film according to 1.
(D) A polymer obtained by doping a compound consisting of thiophene or a thiophene derivative with another anionic compound, or a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative (E) Polyhydroxy Compound (F) One or more compounds selected from the group consisting of polyurethane resins, polyester resins and acrylic resins [9] The surface protective film according to any one of the above [1] to [8], another resin A film laminate in which films or glass substrates are bonded together.
[10] The film laminate according to [9] above, wherein the other resin film is selected from any one of a polyester film, a polyimide film, and a cyclic polyolefin film.
[11] The film laminate according to [9] or [10] above, wherein a functional layer is provided on the surface of the other resin film that is in contact with the silicone adhesive layer.
[12] The film laminate according to [11] above, wherein the functional layer is a release layer.
[13] The film laminate according to [12] 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. .
[14] The film laminate according to any one of [9] to [13] above, which has a total thickness of 200 μm or less.
[15] The surface protective film of any one of [1] to [8] above, which is used for displays.
[16] The film laminate according to any one of [9] to [14] above, which is used for displays.
[17] The film laminate according to [16] above, which is for vehicle use.

According to the present invention, it is possible to provide a surface protective film having good adhesion to a silicone pressure-sensitive adhesive layer and antistatic properties.

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) is provided on the opposite surface of the film, and the surface resistivity of the surface of the cured resin layer (2) is 1×10 ¹² Ω/□ or less.
(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; alcohols 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 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 improving adhesion. Resin 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. Similarly, polymers obtained by polymerizing polymerizable monomers in polyurethane solutions and polyurethane dispersions (mixtures of polymers in some cases) are also included. 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 cured resin layer composition (1) 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)>
The surface protection film of the present invention is provided with a cured resin layer (2) on the opposite surface of the polyester film to the surface on which the cured resin layer (1) is provided, from the viewpoint of preventing foreign matter from adhering to and mixing from the outside. Make it a mandatory requirement. The cured resin layer (2) is preferably formed by curing a cured resin layer composition (2) containing compounds (D) to (F) described below.

(Compound (D): a polymer obtained by doping a compound consisting of thiophene or a thiophene derivative with another anionic compound, or a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative)
The compound (D) includes a polymer (polymer (a)) obtained by doping a compound comprising thiophene or a thiophene derivative with another anionic compound (polymer (a)), and a compound comprising thiophene or a thiophene derivative having an anionic group. Self-doped polymers (polymer (b)) may be mentioned. Incidentally, the polymer (a) and the polymer (b) may be used together.
Examples of the compound (D) include those obtained by polymerizing a compound represented by the following formula (1) or (2) in the presence of a polyanion.

上記式（１）中、Ｒ^１およびＲ^２は、それぞれ独立して、水素原子、または炭素数が１～２０の脂肪族炭化水素基、脂環式炭化水素基、芳香族炭化水素基を表す。

In the above formula (1), R ¹ and R ² each independently represent a hydrogen atom, or an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. .

上記式（２）中、ｎは１～４の整数を表す。

In the above formula (2), n represents an integer of 1-4.

Examples of polyanions used in polymerization include poly(meth)acrylic acid, polymaleic acid, polystyrenesulfonic acid, polyvinylsulfonic acid and the like. As a method for producing such a polymer, for example, the method disclosed in JP-A-7-90060 can be employed.

In the present invention, the compound of formula (2) wherein n is 2 and polystyrene sulfonic acid is used as the polyanion is preferably used.

Moreover, when these polyanions are acidic, they may be partially or wholly neutralized. Ammonia, organic amines, and alkali metal hydroxides are preferable as the base used for neutralization.

As a proportion of all non-volatile components in the cured resin layer composition (2), the compound (D) is usually 5 to 80% by mass, preferably 10 to 50% by mass, more preferably 15 to 40% by mass. be. If the ratio of the compound (D) is within this range, the strength and transparency of the cured resin layer (2) are sufficient, and good antistatic properties can be obtained.

(Compound (E): polyhydroxy compound)
Compound (E) is one or more polyhydroxy compounds, and is defined as a compound having two or more hydroxyl groups in its molecular structure. In the polyhydroxy compound, it is preferable to use sugars and sugar alcohols from the viewpoint of conductivity.
Also included are sugar alcohol derivatives such as, for example, condensates of mono- or disaccharides and polyhydroxy compounds. Specific examples of sugar alcohols include maltitol and isomaltulose reduced products obtained by reducing isomaltulose (trade name “Palatinit”), lactitol, erythritol, sorbitol, xylitol, mannitol, ribitol, arabitol, iditol, It refers to general compounds of C4 or higher in the category exemplified by talitol, galactitol, and the like. In addition, sugar alcohols may be used alone, or two or more of them may be used in combination.
Among the sugar alcohols, sugar alcohols obtained by reducing disaccharides or trisaccharides are preferable from the viewpoint of achieving both high conductivity and high transparency, and the sugar alcohols have a molecular weight of 200 or more and 600 or less and hydroxyl groups, etc. More preferably, the amount is 40 or less, and among these, maltitol, lactitol, and isomaltulose reduced products of sugar alcohols corresponding to disaccharides are particularly preferable.

As a proportion of the total nonvolatile components in the cured resin layer composition (2), the compound (E) is usually in the range of 5 to 80% by mass, preferably 10 to 50% by mass, more preferably 15 to 40% by mass. . If the ratio of the compound (E) is within the range, good antistatic properties can be obtained without the ratio of the other components being too low, precipitation of oligomers can be sufficiently suppressed, and uniform appearance can be obtained. A good coating film can be obtained.

(Compound (F): polyurethane resin, polyester resin, acrylic resin)
Compound (F) is at least one compound selected from the group consisting of polyurethane resins, polyester resins and acrylic resins.
When the cured resin layer composition (2) contains at least one compound selected from the group consisting of polyurethane resins, polyester resins and acrylic resins, the cured resin layer has improved film formability, transparency, antistatic properties, and the like. improves.

(polyester resin)
As the polyester resin, the same polyester resin as the polyester constituting the polyester film or the polyester resin as the compound (B) can be used.

(urethane resin)
A urethane resin is a polymer compound having a urethane bond in its molecule. Urethane resins are usually produced by the reaction of polyols and isocyanates. Polyols include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols, and these compounds may be used singly or in combination. The urethane resin may be an aqueous dispersion, in which case a hydrophilic functional group may be appropriately introduced into the polyol, for example.

(acrylic resin)
Acrylic resins are polymers 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.
Copolymers of these polymers with other polymers (eg, polyester, polyurethane, etc.) are also included. Examples are block copolymers and graft copolymers. That is, the acrylic resin may be an acrylic-modified polyester resin or an acrylic-modified polyurethane resin.
Furthermore, polymers obtained by polymerizing polymerizable monomers in polyester solutions or polyester dispersions (sometimes mixtures of polymers) are also included. Similarly, polymers obtained by polymerizing polymerizable monomers in polyurethane solutions and polyurethane dispersions (mixtures of polymers in some cases) are also included. 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 acrylic-modified polyester resins and acrylic-modified Polyurethane resin is used. The polyester and polyurethane used in the acrylic resin can be appropriately selected from those exemplified as the polyester and polyurethane used in the binder resin.
In addition, the acrylic resin may contain a hydroxyl group or 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 salts thereof; such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutylhydroxyl fumarate, monobutylhydroxyitaconate various 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 meth)acrylamide, diacetoneacrylamide, N-methylolacrylamide or (meth)acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene; various vinyl esters such as; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl halides; and various conjugated dienes such as butadiene.

The ratio of the compound (F) to the total nonvolatile components in the cured resin layer composition (2) is usually 10 to 85% by mass, preferably 40 to 65% by mass, more preferably 45 to 60% by mass. . If the ratio of the compound (F) is within this range, the ratio of other components will not be too low, and good antistatic properties and film-forming properties can be obtained, and the cured resin layer will have good transparency. be.

<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 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 even more preferably 0.02 μm or more and 0.10 μm or less. When the thickness of the cured resin layer (2) 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 (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.

In addition, 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.

(Antistatic property)
The surface resistivity of the surface of the cured resin layer (2) in the surface protective film of the present invention is 1×10 ¹² Ω/□ or less. The antistatic properties of the surface protective film can be evaluated by measuring the surface resistivity of the antistatic layer surface. It can be said that the lower the surface resistivity of the antistatic layer, the better the antistatic properties. If the surface resistivity is 1×10 ¹² Ω/□ or less, it can be said to have antistatic properties, and if it is 1×10 ⁸ Ω/□ or less, it can be said to have good antistatic properties, and further 1×10 ⁶ Ω. /□ or less is preferable because it can be said that the antistatic performance is extremely good. There is no particular lower limit to the surface resistivity, but considering the cost of the conductive agent, it is preferably 1×10 ⁴ Ω/□ or more.

<Film laminate>
The film laminate of the present invention is in a form in which another resin film or glass substrate is laminated via the adhesive layer of the surface protection film described above.

(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 surface protection film and film laminate>
The surface protection film of the present invention can be suitably used as a base material for optical members, 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) Antistatic property of surface protective film (surface resistivity)
The surface resistivity of the surface of the cured resin layer (2) of the surface protection film was measured according to the method (6-1) below. Since the surface resistivity higher than 1×10 ⁸ Ω cannot be measured by the method (6-1), the method (6-2) was used for the samples that could not be measured by the method (6-1).
(6-1) A low resistance resistivity meter "Loresta GP MCP-T600" (manufactured by Nitto Seiko Analytic Tech Co., Ltd.) is equipped with a four-probe ESP probe (probe interval: 5 mm, probe tip shape: cylinder with a diameter of 2 mm, Probe pressing pressure: 240 g/tube, RCF value was fixed at 4.235), and after conditioning the sample for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH, the surface resistivity near the center was measured. .
(6-2) Using a high resistance measuring device "HP4339B" and a measuring electrode "HP16008B" manufactured by Hewlett-Packard Japan Co., Ltd., the surface resistivity was measured after conditioning the sample for 30 minutes in a measurement atmosphere of 23 ° C. and 50% RH. It was measured.

(Evaluation criteria for antistatic properties)
A: 1×10 ⁶ Ω/□ or less.
B: More than 1×10 ⁶ Ω/□ and 1×10 ⁸ Ω/□ or less.
C: more than 1×10 ⁸ Ω/□ and 1×10 ¹² Ω/□ or less.
D: Exceeds 1×10 ¹² Ω/□.
In antistatic property evaluation, A, B and C are acceptable, and D is unacceptable.

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 (molar ratio)

(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) and (F) were mixed at a mass ratio of (D)/(E)/(F) = 7/78/15 to obtain a cured resin layer composition (2). .
(D): Thiophene-based antistatic agent Conductive agent "Orgacon ICP1010" (manufactured by Agfagewald, aqueous dispersion of polyethylenedioxythiophene and polystyrenesulfonic acid) was neutralized with concentrated aqueous ammonia to pH = 9. .
(E): Aqueous dispersion of a polyester resin having a condensed polycyclic structure, copolymerized with the following composition Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid/5-sodium sulfoisophthalic acid // (diol Component) Ethylene glycol/diethylene glycol = 92/8//80/20 (mol%)
(F): Other additives Polyglycerin with an average degree of polymerization of 4

(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 polyester 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 and the cured resin layer composition (2) were applied, respectively. After being stretched 4.3 times in the width direction and further subjected to heat treatment at 230 ° C., relaxation treatment of 2% in the width direction is performed, and the cured resin layer (1) having a film thickness (after drying) of 0.05 μm, A biaxially oriented laminated polyester film having a thickness of 50 μm and having a cured resin layer (2) having a thickness (after drying) of 0.05 μm was obtained.
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 2-4)
Surface protection films of Examples 2 to 4 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 2)
Surface protective films of Comparative Examples 1 and 2 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.
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 prepared 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 and the cured resin layer (2) was not provided. got
In addition, in the measurement of the surface resistivity of the surface protective film obtained in Comparative Example 3, the surface resistivity was too high, and the surface resistivity was not measured by either method (6-1) or (6-2). could not be measured. Therefore, the surface resistivity in Table 1 was indicated as "over", and the antistatic property was evaluated as "D".

(Comparative Example 4)
A surface protective film of Comparative Example 4 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.

(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) having antistatic properties on the opposite side of the film surface on which the adhesive layer is provided, an effect of reducing adhesion of foreign matter from the outside can be expected.

Claims (17)

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 A surface protective film comprising a cured resin layer (2), wherein the surface resistivity of the cured resin layer (2) is 1×10 ¹² Ω/□ or less.
(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 according to any one of claims 1 to 7, wherein the cured resin layer (2) is obtained by curing a cured resin layer composition (2) containing the following compounds (D) to (F): the film.
(D) A polymer obtained by doping a compound consisting of thiophene or a thiophene derivative with another anionic compound, or a self-doped polymer having an anionic group in a compound consisting of thiophene or a thiophene derivative (E) Polyhydroxy Compound (F) At least one compound selected from the group consisting of polyurethane resins, polyester resins and acrylic resins A film laminate comprising the surface protection film according to any one of claims 1 to 8 and another resin film or glass substrate laminated thereon. 10. The film laminate according to claim 9, wherein the other resin film is selected from polyester film, polyimide film, and cyclic polyolefin film. 11. The film laminate according to claim 9 or 10, wherein a functional layer is provided on the surface of the other resin film that contacts the silicone adhesive layer. 12. The film laminate according to claim 11, wherein said functional layer is a release layer. 13. The film laminate according to claim 12, 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 9 to 13, which has a total thickness of 200 µm or less. The surface protective film according to any one of claims 1 to 8, which is for display. The film laminate according to any one of claims 9 to 14, which is for display. 17. The film laminate according to claim 16, which is for vehicle use.