JP6492572B2 - Surface protection film - Google Patents

Description

  The present invention relates to a surface protective film, such as a synthetic resin plate, a glass plate, a metal plate, an optical member, an automobile member, an electric / electronic member, a building material member, a stationery / office supplies member, and the like. The present invention relates to a surface protective film suitable for protection. More specifically, for optical members that require particularly high visibility, for example, glass substrates, light diffusion films, liquid crystal displays (polarizing plates, retardation plates, light guide plates, prism plates, etc.), touch panels, When used in an organic EL display, a plasma display, etc., the present invention relates to a surface protective film having good visibility after heat treatment and adhesion to a hard coat layer.

  Conventionally, synthetic resin plates, glass plates, metal plates, optical members (glass substrates, light diffusion films, liquid crystal display members (polarizing plates, retardation plates, light guide plates, prism plates, etc.), touch panels, organic EL displays, plasma displays In order to prevent surface contamination, scratches, dust, etc., such as automobile parts, electrical / electronic parts, building material parts, stationery / office supplies parts, etc. A surface protective film provided with an adhesive layer on one side is used.

  As the surface protective film, for example, a surface protective film using a low-density polyethylene resin as a substrate and an ethylene-vinyl acetate copolymer (EVA) as an adhesive has been proposed (for example, Patent Document 1). ).

  For example, in a state where such a surface protective film is stuck to an adherend, a heat treatment step in a high temperature atmosphere, or a situation where the surface protection film is exposed to a high temperature atmosphere during transportation or storage (for example, Patent Document 1, When used in 2), deformation due to melting or shrinkage of the base film is large, making it difficult to use.

  Therefore, when using a surface protection film based on a polyester film having better heat resistance, after heat treatment in a high temperature atmosphere, low molecular weight substances and oligomers in the polyester film constituting the surface protection film ( Visibility may decrease as the film haze rises mainly due to precipitation and crystallization of the ester cyclic trimer).

  For this reason, in order to solve the above problems, when taking an oligomer precipitation prevention measure, for example, when the oligomer precipitation prevention layer described in Patent Document 3 is laminated on the polyester film surface, the oligomer precipitation is suppressed, Adhesion with the functional layer, for example, adhesion with the hard coat layer is poor.

  On the other hand, when an easy-adhesion layer for a hard coat layer (for example, Patent Document 4) that is generally used is laminated on a polyester film, adhesion to the hard coat layer is good, but oligomer precipitation is prevented. The situation was inadequate. For this reason, when used as a surface protective film, a coating layer is required which is compatible with a high level of conflicting characteristics such as prevention of oligomer precipitation after heat treatment and adhesion to a functional layer, for example, a hard coat layer. .

JP 2006-299162 A JP 2008-68564 A Japanese Patent No. 5236586 JP 2010-89307 A JP 2012-173354 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is to prevent oligomer precipitation after heat treatment by using a coating film having a coating layer having a specific configuration as a constituent unit of a surface protection film. Another object of the present invention is to provide a surface protective film that can achieve a high level of conflicting properties such as adhesion to a functional layer, for example, a hard coat layer.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the above problems can be easily solved by a surface protective film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is to form a coating layer on one side of a multilayer polyester film having a laminated structure of at least three layers, the uppermost polyester layer having a softening point higher than the softening point of the intermediate layer, and A surface protective film comprising an adhesive layer on one surface, wherein the coating layer is formed from a coating solution containing 70% by weight or more of a crosslinking agent with respect to a nonvolatile component. It exists in a protective film.

  The surface protective film of the present invention is suitable for surface protection of various adherends such as synthetic resin plates, glass plates, metal plates, optical members, automobile members, electrical / electronic members, building material members, stationery / office supplies members, etc. For optical members that require particularly high visibility (for example, glass substrates, light diffusion films, liquid crystal displays (polarizing plates, retardation, light guide plates, prism plates, etc.), touch panels, organic EL displays, plasma displays Etc.), the visibility after the heat treatment and the adhesion to the hard coat layer are good, and its industrial value is high.

  In the present invention, the polyester film constituting the surface protective film is required to have a laminated structure of at least three layers. For example, as long as it does not exceed the gist of the present invention other than the three-layer configuration, it may be a multilayer of four layers or more, and is not particularly limited.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester which is polyethylene terephthalate or the like in which 60 mol% or more, preferably 80 mol% or more is an ethylene terephthalate unit.

  The polyester film constituting the film of the present invention must have a multilayer structure of at least three layers, and the essential requirement is that the softening point of both outermost layers is higher than the softening point of the intermediate layer. It is. Preferably, the difference in softening point between the polyester layers of the outermost layers and the intermediate layer is 3 ° C. or higher, preferably 5 ° C. or higher.

As a specific method for satisfying the conditions, preferably by containing 80% or more of polyester having an oligomer (cyclic trimer) content of 0.5% by weight or less in the polyester layer constituting both outer layers The difference between the softening points can be further increased.

  When polyester with an oligomer content of more than 0.5% by weight is used, or when the content is less than 80%, the coated film is subjected to heat treatment for a long time at 150 ° C or high tension. When used in processing processes under severe conditions, such as under-sputtering processes and durability tests in high-temperature and high-humidity atmospheres, the film haze increases greatly, and after processing, the optical properties or visibility In some cases, it may be inappropriate for an optical member.

  In the present invention, it is preferable to blend particles in the polyester layer mainly for the purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and magnesium phosphate. , Particles of kaolin, aluminum oxide, titanium oxide and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, 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.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  The average particle size of the particles contained in the polyester film is preferably in the range of 0.2 to 1.5 μm. When the average particle size is less than 0.2 μm, the film surface may be flattened and the winding characteristics in the film production process may be inferior. On the other hand, when the average particle size exceeds 1.5 μm, it may be difficult to adapt to applications in which visibility is important due to generation of bright spots due to particles contained in the film.

  Furthermore, the particle content in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the coating film which comprises the surface protection film of this invention will not be specifically limited if it is a range which can be formed into a film as a film, It is preferable that it is 20-250 micrometers from a use, More preferably, 25 It is preferably in the range of ˜125 μm.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all.

  First, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a 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. Subsequently, the extending | stretching temperature orthogonal to the 1st step | paragraph extending | stretching direction is 70-170 degreeC normally, and a draw ratio is 3.0-7 times normally, Preferably it is 3.5-6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  The simultaneous biaxial stretching method can also be adopted for the production of the polyester film in the present invention. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows: The area magnification is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Furthermore, a so-called coating stretching method (in-line coating) in which the film surface is treated during the above-described polyester film stretching step can be applied. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio, producing a film suitable as a polyester film. it can.

  The coating layer constituting the surface protective film in the present invention has good adhesion to the adhesive layer, and the film haze increases even after heat treatment in a high-temperature atmosphere (for example, 150 ° C., 90 minutes). It is preferable to be as small as possible.

  The coating layer constituting the surface protective film of the present invention has an essential requirement to have a coating layer formed from a coating solution containing 70% by weight or more of a crosslinking agent as a nonvolatile component. The coating solution may contain other components as long as the gist of the present invention is not impaired.

  Various known crosslinking agents can be used as the crosslinking agent, and examples thereof include oxazoline compounds, melamine compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Among these, especially when using for the use which provides a functional layer on a coating layer, an oxazoline compound is used suitably from a viewpoint that durable adhesiveness improves. Moreover, a melamine compound is used suitably from a viewpoint of prevention of precipitation of the ester cyclic trimer on the film surface by heating and improvement of durability and applicability of the coating layer.

  The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. 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 preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  The amount of the oxazoline group of the oxazoline compound contained in the coating solution forming the coating layer constituting the coating film in the present invention is usually 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g, more preferably 5 to 5. The range is 8 mmol / g. By using it in the above range, the durability of the coating film is improved.

  The melamine compound is a compound having a melamine structure in the compound, for example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and these Mixtures can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin with ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like hydroxyl groups and amino groups, There are polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N′-tetraglycidyl-m-xylyl. Examples include range amine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. 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 state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as methyl isobutanoyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, mercaptan compounds such as butyl mercaptan, dodecyl mercaptan, ε-caprolactam, δ-valerolactam, etc. Lactam compounds, amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, Examples include oxime compounds such as maldehyde, acetoald oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule, but for better adhesion, etc., the polycarbodiimide having two or more in the molecule More preferred are system compounds.

  The 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 any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  The content of the carbodiimide group contained in the carbodiimide compound is a carbodiimide equivalent (weight of carbodiimide compound to give 1 mol of carbodiimide group [g]), and is usually 100 to 1000, preferably 250 to 700, more preferably 300. It is in the range of ~ 500. By using it in the above range, the durability of the coating film is improved.

  Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

  These cross-linking agents may be used singly or in combination of two or more kinds, but by combining two or more kinds, adhesion to the functional layer, which has been difficult to be compatible, and oligomer after heating (ester cyclic trimer) ) Was improved. Among them, a combination of an oxazoline compound that can improve adhesion to a functional layer and a melamine compound that is excellent in preventing precipitation of an oligomer (ester cyclic trimer) after heating is optimal and preferable.

  In addition, the present inventors have found that it is effective to combine three kinds of crosslinking agents in order to further improve the adhesion to the functional layer. As a combination of three or more kinds of cross-linking agents, it is preferable to select a melamine compound as one of the cross-linking agents. As a cross-linking agent to be combined with the melamine compound, an oxazoline compound, an epoxy compound, and a carbodiimide type are used. Particularly preferred are compounds and epoxy compounds.

  When such a crosslinking agent is contained, a component for promoting crosslinking at the same time, for example, a crosslinking catalyst can be used in combination.

  In addition, in the formation of the coating layer of the present invention, the binder polymer is used within the range that does not impair the gist of the present invention in order to improve the coating appearance and the adhesion when the functional layer is formed on the coating layer. It is also possible to use together.

  The binder polymer constituting the coating layer in the present invention is a number average molecular weight measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). It is defined as a polymer compound having (Mn) of 1000 or more and having a film-forming property.

  Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like. Among these, it is preferable to use a polyester resin, an acrylic resin, or a urethane resin from the viewpoint of improving adhesion with various surface functional layers. However, when the content increases, the precipitation prevention property of the ester cyclic trimer after heating may deteriorate, and it is usually 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less. When the ratio which occupies in a coating layer exceeds the said range, the precipitation inhibitory effect of the oligomer (ester cyclic trimer) after a heating may become inadequate.

In addition, particles can be used in combination for the purpose of blocking and improving slipperiness in forming the coating layer. The average particle diameter is preferably 1.0 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less from the viewpoint of transparency of the film. Further, the lower limit is preferably 0.01 μm or more, more preferably 0.03 μm or more, and particularly preferably a range larger than the film thickness of the coating layer in order to improve the slipperiness more effectively. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, and organic particles.

  Further, in the range not impairing the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are formed as necessary for forming the coating layer. It is also possible to use a foaming agent, a dye, a pigment and the like in combination.

  From the viewpoint of preventing oligomer (ester cyclic trimer) precipitation after heat treatment, when melamine is selected as one of the crosslinking agents, the ratio of melamine as the ratio to the total nonvolatile components in the coating liquid forming the coating layer is: The range is usually from 5 to 95% by weight, preferably from 15 to 80% by weight, particularly preferably from 30 to 65% by weight. When the ratio of the crosslinking agent is out of the above range, precipitation suppression of the ester cyclic trimer after heating may be insufficient, or the coating appearance may be deteriorated.

  Further, the thickness (after drying) of the coating layer of the coating film is usually in the range of 0.003 to 1 μm, preferably 0.005 μm to 0.5 μm, more preferably 0.01 to 0.2 μm. It is. When the thickness is less than 0.003 μm, the amount of ester cyclic trimer precipitated from the film may not be sufficiently reduced. On the other hand, when the thickness is larger than 1 μm, there are cases where problems such as deterioration of the appearance of the coating layer and lowering of blocking properties may occur.

  Examples of methods for applying a coating solution to a polyester film include air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, and kiss roll coating. Conventional coating methods such as cast coating, spray coating, curtain coating, calendar coating, and extrusion coating can be used.

  In order to improve the coating property and adhesion of the coating agent to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment or the like before coating.

  Analysis of various components in the coating layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, and the like.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 80 to 200 ° C. The heat treatment may be performed for 40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

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

  In addition, in the coating film which comprises the surface protection film obtained by this invention, it is preferable that a film haze is 10% or less. More preferably, it is 5% or less, More preferably, it is 3% or less. When the film haze of the coating film exceeds 10%, it may be difficult to cope with an application requiring particularly high visibility as a surface protective film of the optical member.

  Moreover, you may give surface treatments, such as a corona treatment and a plasma treatment, to the coating film which comprises a surface protection film previously.

  Next, the pressure-sensitive adhesive layer constituting the surface protective film in the present invention will be described below.

  In the surface protective film in the present invention, it is an essential requirement to provide an adhesive layer on the surface of the film on which no coating layer is provided.

  By adopting the above configuration, the characteristics of the coating layer are utilized, and the film surface is protected by the coating layer having high heat resistance even when the film surface is exposed to a severe heat treatment process for a long time. Precipitation can be suppressed.

  The pressure-sensitive adhesive layer in the present invention means a layer composed of a material having adhesiveness, and a conventionally known material such as a silicone pressure-sensitive adhesive or an acrylic pressure-sensitive adhesive is used within a range not impairing the gist of the present invention. Can do. In the present invention, as one specific example, the case where an acrylic pressure-sensitive adhesive is used will be described below.

  In the present invention, the acrylic pressure-sensitive adhesive means a pressure-sensitive adhesive layer containing, as a base polymer, an acrylic polymer formed using an acrylic monomer as an essential monomer component. The acrylic polymer has (meth) acrylic acid alkyl ester and / or (meth) acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as an essential monomer component (more preferably as a main monomer component). ) It is preferably an acrylic polymer to be formed. Further, the acrylic polymer is particularly preferably an acrylic polymer formed using (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as essential monomer components. That is, the pressure-sensitive adhesive layer of the present invention is an acrylic pressure-sensitive adhesive layer formed using (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester having a linear or branched alkyl group as essential monomer components. It is particularly preferred.

  In addition, the monomer component forming the acrylic polymer that is the base polymer in the pressure-sensitive adhesive layer of the present invention further contains a polar group-containing monomer, a polyfunctional monomer, and other copolymerizable monomers. It may be contained as a polymerization monomer component.

  In addition, said "(meth) acryl" represents "acryl" and / or "methacryl", and others are the same. Further, although not particularly limited, the content of the acrylic polymer as the base polymer in the pressure-sensitive adhesive layer of the present invention is preferably 60% by weight or more, more preferably based on the total weight (100% by weight) of the pressure-sensitive adhesive layer. 80% by weight or more.

  As an essential monomer component for forming the acrylic polymer, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group (hereinafter simply referred to as “(meth) acrylic acid alkyl ester”) may be used. ) Can be suitably used. Specific examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, (meth ) Isobutyl acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate , Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylic acid Isodecyl, undecyl (meth) acrylate, dodecyl (meth) acrylate, (Meth) acrylic acid tridecyl, (meth) acrylic acid tetradecyl, (meth) acrylic acid pentadecyl, (meth) acrylic acid hexadecyl, (meth) acrylic acid heptadecyl, (meth) acrylic acid octadecyl, (meth) acrylic acid nonadecyl, (meta ) (Meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group such as eicosyl acrylate. Moreover, the (meth) acrylic acid alkyl ester may be used alone or in combination of two or more. Among them, (meth) acrylic acid alkyl ester having 2 to 14 carbon atoms in the alkyl group is preferable, and (meth) acrylic acid alkyl ester having 2 to 10 carbon atoms in the alkyl group is more preferable. In particular, 2-ethylhexyl acrylate (2EHA) is preferable.

  Moreover, (meth) acrylic acid alkoxyalkyl ester [alkoxyalkyl (meth) acrylate] can also be suitably used as the essential monomer component (more preferably, the main monomer component) for forming the acrylic polymer. Particularly preferred is an acrylic acid alkoxyalkyl ester [alkoxyalkyl acrylate]. Although it does not specifically limit as (meth) acrylic-acid alkoxyalkylester, For example, (meth) acrylic-acid 2-methoxyethyl, (meth) acrylic-acid 2-ethoxyethyl, (meth) acrylic-acid methoxytriethylene glycol, (meta ) 3-methoxypropyl acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate, and the like. The said (meth) acrylic-acid alkoxyalkylester can be used individually or in combination of 2 or more types. Among these, 2-methoxyethyl acrylate (2MEA) is preferable.

In addition, the content of the essential monomer component [(meth) acrylic acid alkyl ester and / or (meth) acrylic acid alkoxyalkyl ester] forming the above acrylic polymer is selected from the viewpoint of adhesiveness of the pressure-sensitive adhesive layer. The amount is preferably 5% by weight or more (for example, 5 to 100% by weight), more preferably 5 to 95% by weight, based on the total amount (100% by weight) of monomer components forming the polymer. In addition, when both (meth) acrylic acid alkyl ester and (meth) acrylic acid alkoxyalkyl ester are used as monomer components, the content of (meth) acrylic acid alkyl ester and (alkyl) alkoxyalkyl (meth) acrylate The total amount of ester content (total content) only needs to satisfy the above range.

  Among the above, it is preferable that both (meth) acrylic acid alkyl ester and acrylic acid alkoxyalkyl ester are used as essential monomer components for forming the acrylic polymer. In that case, the content of the (meth) acrylic acid alkyl ester is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, based on the total amount of monomer components (100% by weight) forming the acrylic polymer. %, More preferably 65-80% by weight, most preferably 65-75% by weight. If the content exceeds 95% by weight, the adhesiveness may decrease, and if it is less than 5% by weight, the elastic modulus of the pressure-sensitive adhesive layer may be too high. Further, the content of the alkoxyalkyl ester of acrylic acid is preferably 10 to 45% by weight, more preferably 10 to 40% by weight, and still more preferably with respect to the total amount (100% by weight) of monomer components forming the acrylic polymer. 20 to 35% by weight. If the content exceeds 45% by weight, the elastic modulus of the pressure-sensitive adhesive layer may be too high, and if it is less than 10% by weight, the adhesiveness may decrease.

  Examples of the polar group-containing monomer include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and other carboxyl group-containing monomers or anhydrides thereof (maleic anhydride, etc. ); Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate Hydroxyl group (hydroxyl group) -containing monomers such as vinyl alcohol and allyl alcohol; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-hydro Amide group-containing monomers such as ethyl acrylamide; Amino group-containing monomers such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; ) Glycidyl group-containing monomers such as glycidyl acrylate and methyl glycidyl (meth) acrylate; Cyano group-containing monomers such as acrylonitrile and methacrylonitrile; N-vinyl-2-pyrrolidone, (meth) acryloylmorpholine , N-vinyl pyridine, N-vinyl piperidone, N-vinyl pyrimidine, N-vinyl piperazine, N-vinyl pyrrole, N-vinyl imidazole, N-vinyl oxazole and other heterocyclic ring-containing vinyl monomers; sodium vinyl sulfonate, etc. Sulfonic acid group-containing monomer of 2-hydroxyethyl Chestnut phosphoric acid group-containing monomers such as acryloyl phosphate; cyclohexyl maleimide, imide group-containing monomers such as isopropyl maleimide; 2-methacryloyloxy such acryloyl isocyanate group-containing monomers such as methacryloyloxyethyl isocyanate. The said polar group containing monomer can be used individually or in combination of 2 or more types. Among the above-mentioned polar group-containing monomers, carboxyl group-containing monomers or acid anhydrides thereof, hydroxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, heterocyclic-containing vinyls Monomers are preferable, and acrylic acid (AA), 4-hydroxybutyl acrylate (4HBA), N-vinyl-2-pyrrolidone (NVP), and N-hydroxyethylacrylamide (HEAA) are particularly preferable.

  The content of the polar group-containing monomer is preferably 15% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When it exceeds 15% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high. As a result, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered. If it is less than 0.01% by weight, the adhesion may be lowered.

  Among the above, the content of the hydroxyl group-containing monomer is preferably 5% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When the content exceeds 5% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered. Content of polar group-containing monomers other than hydroxyl group-containing monomers (particularly carboxyl group-containing monomers, amide group-containing monomers, amino group-containing monomers, heterocyclic-containing vinyl monomers) Is preferably 15% by weight or less with respect to 100% by weight of the monomer component forming the acrylic polymer. When the content exceeds 15% by weight, the cohesive force of the pressure-sensitive adhesive layer becomes too high, the storage elastic modulus (23 ° C.) becomes too high, and the stress relaxation property may be lowered.

  Examples of the polyfunctional monomer include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, and (poly) propylene glycol di (meth) acrylate. , Neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methanetri (meth) ) Acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate and the like. The said polyfunctional monomer can be used individually or in combination of 2 or more types. Among the above, as the polyfunctional monomer, trimethylolpropane triacrylate (TMPTA) is preferable.

  The content of the polyfunctional monomer is preferably 0.5% by weight or less with respect to 100% by weight of the total amount of monomer components forming the acrylic polymer. When the content exceeds 0.5% by weight, for example, the cohesive force of the pressure-sensitive adhesive layer becomes too high, and the stress relaxation property may be lowered.

  Examples of copolymerizable monomers (other copolymerizable monomers) other than the above polar group-containing monomers and polyfunctional monomers include cyclopentyl (meth) acrylate and cyclohexyl (meth). (Meth) acrylates having an alicyclic hydrocarbon group such as acrylate and isobornyl (meth) acrylate, and (meth) acrylates having an aromatic hydrocarbon group such as phenyl (meth) acrylate and the like (meth ) (Meth) acrylic acid esters other than alkyl acrylates, alkoxyalkyl (meth) acrylates, polar group-containing monomers and polyfunctional monomers; vinyl esters such as vinyl acetate and vinyl propionate; styrene , Aromatic vinyl compounds such as vinyl toluene; ethylene, butadiene, isoprene, isobutylene, etc. Olefins or dienes; vinyl ethers such as vinyl alkyl ethers; and vinyl chloride.

  The acrylic polymer can be prepared by polymerizing the above monomer components by a conventionally known or conventional polymerization method. Examples of the polymerization method of the acrylic polymer include a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, and a polymerization method by active energy ray irradiation (active energy ray polymerization method). Among them, the solution polymerization method and the active energy ray polymerization method are preferable in terms of transparency, water resistance, production cost and the like, and particularly when forming a relatively thick pressure-sensitive adhesive layer, active energy ray polymerization (photopolymerization and Method), and an ultraviolet polymerization method by ultraviolet irradiation is particularly preferable.

Examples of the active energy rays irradiated in the above active energy ray polymerization (photopolymerization) include ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, and ultraviolet rays, among others. Ultraviolet rays are suitable for the use of the present invention. Further, the irradiation energy, irradiation time, irradiation method, and the like of the active energy ray are not particularly limited as long as they do not impair the gist of the present invention.

  In the solution polymerization, various common solvents can be used. Examples of such solvents include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; cyclohexane and methylcyclohexane Organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. A solvent can be used individually or in combination of 2 or more types.

  In preparing the acrylic polymer, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) can be used depending on the type of polymerization reaction. A polymerization initiator can be used individually or in combination of 2 or more types.

  The photopolymerization initiator is not particularly limited. For example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photo An active oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, a thioxanthone photopolymerization initiator, and the like can be used. The amount of the photopolymerization initiator used is not particularly limited, but is preferably in the range of 0.01 to 0.2 parts by weight with respect to 100 parts by weight of the total amount of monomer components forming the acrylic polymer.

  Specific examples of the benzoin ether photopolymerization initiator include, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one. And anisole methyl ether. Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). Examples include dichloroacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. . Specific examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzyl photopolymerization initiator include benzyl.

  Specific examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Specific examples of the ketal photopolymerization initiator include benzyldimethyl ketal. Specific examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

  Specific examples of the thermal polymerization initiator include azo polymerization initiators [for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis. (2-methylpropionic acid) dimethyl, 4,4′-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [ 2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-di) Methyleneisobutylamidine) dihydrochloride], peroxide-based polymerization initiators (eg, dibenzoyl peroxide, tert-butylpermaleate, etc.), redox Scan type polymerization initiators and the like. The amount of the thermal polymerization initiator used is not particularly limited as long as it does not impair the gist of the present invention, and may be any range that can be conventionally used as a thermal polymerization initiator.

  In the pressure-sensitive adhesive layer of the present invention, a crosslinking agent, a crosslinking accelerator, a tackifier (for example, a rosin derivative resin, a polyterpene resin, a petroleum resin, an oil-soluble phenol resin, etc.), an anti-aging agent, a filler, Colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, etc. are used as necessary within the range that does not impair the characteristics of the present invention. be able to.

  The said crosslinking agent can control the gel fraction of an adhesive layer by bridge | crosslinking the base polymer of an adhesion layer. As crosslinking agents, isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents Agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, amine crosslinking agents, and the like, and isocyanate crosslinking agents and epoxy crosslinking agents can be preferably used. A crosslinking agent can be used individually or in combination of 2 or more types.

The thickness (after drying) of the adhesive layer of the surface protective film in the present invention is 10 to 200 μm, preferably 20 μm to 150 μm, and more preferably 25 to 100 μm.
When the thickness of the adhesive layer (after drying) is less than 10 μm, it may be difficult to obtain a desired adhesive force. On the other hand, when the thickness of the pressure-sensitive adhesive layer (after drying) exceeds 200 μm, the pressure-sensitive adhesive layer is not sufficiently cured, and problems such as workability deterioration may occur.

  In the surface protective film of the present invention, a heat treatment (150 ° C., 90 minutes) is performed in order to ensure good visibility even in a step of heat treatment in a high temperature atmosphere, or in a situation where it is exposed to a high temperature atmosphere during transportation and storage. ) The rate of change in film haze before and after (ΔH) is preferably 1.0% or less. More preferably, ΔH is 0.7% or less. When ΔH exceeds 1.0%, the visibility decreases as the film haze increases due to precipitation of the oligomer (ester cyclic trimer). For example, for optical members (for example, glass substrates, light diffusion films, When used in liquid crystal displays (polarizing plates, retardation plates, light guide plates, prism plates, etc.), touch panels, organic EL displays, plasma displays, etc., it may be difficult to apply.

  In the present invention, when an electronic member that is an adherend to which a surface protective film is bonded is used in a display device or an input device, the adherend is corroded so as not to cause a failure or malfunction. It is preferable not to generate it. (For example, Patent Document 5 also describes.)

  From such a viewpoint, in the surface protective film of the present invention, it is preferable to use a material that does not substantially contain a halogen element as a material constituting the coating layer, not only in the pressure-sensitive adhesive layer but also in the coating film to be configured. . Specifically, the total amount of halogen ions detected after leaving the coated film in pure water at room temperature for 24 hours is preferably 1 ppm or less.

  As a countermeasure against corrosion in the adhesive layer, for example, a technique described in Japanese Patent Publication No. 2012-246407 can be employed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

(1) Measurement of intrinsic viscosity (dl / g) of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed and mixed with phenol / tetrachloroethane = 50/50 (weight ratio). 100 ml of solvent was added and dissolved, and measurement was performed at 30 ° C.

(2) Average particle diameter (d50)
The average particle size d50 was defined as the particle size having an integrated volume fraction of 50% in an equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation.

(3) Measuring method of contained ester cyclic trimer contained in polyester raw material:
About 200 mg of the polyester raw material is weighed and dissolved in 2 ml of a mixed solvent having a ratio of chloroform / HFIP (hexafluoro-2-isopropanol) of 3: 2. After dissolution, add 20 ml of chloroform, and then add 10 ml of methanol little by little. The precipitate is removed by filtration, and the precipitate is washed with a mixed solvent of chloroform / methanol ratio 2: 1. The filtrate / washing solution is collected, concentrated by an evaporator, and then dried. After the dried product was dissolved in 25 ml of DMF (dimethylformamide), this solution was supplied to liquid chromatography (“LC-7A” manufactured by Shimadzu Corporation) to determine the amount of ester cyclic trimer in DMF. The value is divided by the amount of the polyester raw material dissolved in the chloroform / HFIP mixed solvent to obtain the amount of ester cyclic trimer (weight%). The amount of ester cyclic trimer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).

  The standard sample was prepared by accurately weighing the ester cyclic trimer previously collected and dissolving it in accurately measured DMF.

The conditions for the liquid chromatograph were as follows.
Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Thickness of Laminated Polyester Layer After fixing a small piece of film with an epoxy resin, it was cut with a microtome, and the cross section of the film was observed with a transmission electron micrograph. Two of the cross-sections are observed in parallel with the film surface, and the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was defined as the laminated thickness.

(5) Measurement of softening point of each polyester layer of multilayer polyester film After confirming the layer structure of the sample film in advance as described in (4), in the exposed film cross section, one central part of each polyester layer is placed at Nano NaviII. Using / E-Sweep / nano-TA2 (manufactured by SII Nano Technology), measurement was performed under the following measurement conditions, and the average value of N = 3 was used as the softening point of the polyester layer.
In addition, regarding the measured value, the tangent in each curve of a temperature rising curve and a temperature falling curve was drawn from the obtained measurement chart, and the intersection of the tangent was calculated | required. Next, a point passing through the intersection of the obtained tangent lines and intersecting the measurement temperature axis perpendicularly was defined as a softening point.
"Measurement condition"
Temperature increase rate: 5 ° C / sec
Probe: Thermal cantilever AN2-200
Measurement temperature range: normal temperature (23 ° C) to 300 ° C
Measurement atmosphere: atmospheric pressure

(6) Measurement of film haze The film haze of the sample film for measurement was measured with a haze meter “HM-150” manufactured by Murakami Color Research Laboratory Co., Ltd. according to JIS-K-7136.

(7) Measurement of film haze change rate (ΔH) of surface protection film before and after heat treatment (practical property substitution evaluation)
In a hot-air circulating furnace (manufactured by Tabai: model PVH-210), heat treatment is performed at 150 ° C. for 90 minutes in a state where the sample film (10 cm square) is hung with a clip. Thereafter, the film haze was measured by the method of (4). (Haze 1)
Using the same sample, ΔH was calculated with a difference from the unprocessed film haze (haze 2).

ΔH = (haze 1) − (haze 2)
The lower ΔH, the less oligomer precipitation due to the wet heat treatment, which is better.

(Criteria)
◎: ΔH is 0.3% or less, particularly good visibility ○: ΔH is more than 0.3% and 0.7% or less, Good △: ΔH is more than 0.7% and 1.0 % Or less (may be problematic in practical use)
X: ΔH exceeds 1.0% (practically problematic level)

(8) Adhesion evaluation with hard coat layer An active energy ray curable resin composed of the following active energy ray curable resin composition was applied to the coating layer surface of the film with a # 16 wire bar and dried at 80 ° C. for 1 minute. Then, ultraviolet rays were irradiated from an ultraviolet irradiator with a metal halide lamp 120 w / cm so that the integrated light amount was 180 mJ / cm ^2, and a hard coat layer having a thickness (after drying) of 5 μm was provided. Next, using the hard coat layer surface of the obtained sample film, 100 grid-shaped cuts were made using a cutter guide with a gap interval of 1 mm. Next, an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied to the cut surface on the grid, and the 2.0 kg roller was reciprocated 20 times to completely adhere to it. The peeled surface after peeling off rapidly at the peeling angle was observed and judged according to the following criteria.

<Active energy ray curable resin composition>
A mixed coating solution of 72 parts by weight of dipentaerythritol acrylate, 18 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, 1 part by weight of a photopolymerization initiator (Irgacure 651, manufactured by Ciba Specialty Chemicals), and 200 parts by weight of methyl ethyl ketone.
(Criteria)
A: Peeling area is less than 5% B: Peeling area is 5% or more and less than 20% C: Peeling area is 20% or more and less than 50% D: Peeling area is 50% or more

(9) Quantitative determination of halogen ion content in coated film A sample film is cut into 10 cm square and immersed in pure water at room temperature for 24 hours. Thereafter, the amount of halogen ions detected was measured by the following measurement by an iochromatographic method.
(Ion chromatograph measurement conditions)
Analyzing device: DX-320, manufactured by DIONEX
Separation column: Ion Pac AS15 (4 mm x 250 mm)
Guard column: Ion Pac AG15 (4mm x 50mm)
Removal system: ASRS-ULTRA (external mode, 100 mA)
Detector: Electrical conductivity detector Eluent: 7 mM KOH (0 to 20 minutes)
45 mM KOH (20-30 minutes)
(Using eluent generator EG40)
Eluent flow rate: 1.0 ml / min Sample injection amount: 250 μl
(Criteria)
A: The total amount of halogen ions is 1 ppm or less (a level that causes no problem in practical use).
B: The total amount of halogen ions exceeds 1 ppm (which is practically a concern)

(10) Corrosion resistance evaluation of surface protective film (practical property substitution evaluation)
A test piece was prepared by bonding the adhesive surface of the sample film to the surface of a copper foil having a thickness of 70 μm. Using a test piece, after holding in a constant temperature and humidity chamber at 60 ° C. and 95% RH for 200 hours, peel off the surface protective film on the surface of the copper foil where the surface protective film is bonded. Then, visual observation was performed, and the degree of discoloration (corrosion) on the copper foil surface was determined according to the following criteria.
(Criteria)
A: No discoloration (corrosion) is observed on the copper foil surface B: Slight discoloration (corrosion) is confirmed on the copper foil surface

(11) Visibility evaluation after surface protection film heat treatment (I)
(Practical property substitution evaluation of oligomer sealing)
Each surface protective film of Examples and Comparative Examples was cut into 5 cm squares in advance, and then heated with a float glass plate (size: 7 cm square, thickness 2 mm, conforming to JIS R 3202) and an adhesive layer. It heat-processed at 150 degreeC for 90 minute (s) in the type | formula circulation furnace (product made from TABAI: model PVH-210). Thereafter, whether or not the adhesive layer is observable was determined according to the following criteria in the state of being bonded.
(Criteria)
A: The adhesive layer can be inspected with the surface protective film still attached, and the inspection is particularly easy (practically no problem level).
B: The adhesive layer can be inspected while the surface protective film is still adhered, and inspection is easy (practical level).
C: The adhesive layer can be inspected while the surface protective film is still bonded, but in rare cases, the inspection may be slightly difficult.
(Practical level that may cause problems)
D: Since the film haze of the surface protective film is rising, it is difficult to inspect the adhesive layer with the surface protective film still attached (practically problematic level)

(12) Visibility evaluation after heat treatment of surface protective film (II)
(Practical property substitution evaluation of oligomer sealing)
After applying an anchor layer composed of the following anchor layer composition to one side of a 50 μm thick PET film (Mitsubishi Resin Co., Ltd .: Diafoil T600 type) so that the thickness (after drying) is 30 nm, on the anchor layer ITO having a thickness of 25 nm is formed by reactive sputtering using a sintered body material of 95% by weight of indium oxide and 5% by weight of tin oxide in an atmosphere of 0.4 Pa composed of 95% argon gas and 5% oxygen gas. A film (transparent conductive thin film) was formed.
Next, on the surface of the ITO layer, the pressure-sensitive adhesive layer surface of each surface protective film obtained in Examples and Comparative Examples in the present invention was bonded to obtain a laminate.

The ITO layer was crystallized from the obtained laminate by a heat treatment at 180 ° C. for 90 minutes in a hot air circulating furnace (manufactured by Tabai: model PVH-210).
<< Anchor layer composition >>
Colcoat P (manufactured by Colcoat)
A 1% strength solution was prepared using isopropyl alcohol.
Thereafter, whether or not the ITO layer can be observed was determined according to the following determination criteria in the state of being bonded.

(Criteria)
A: It is possible to inspect the ITO layer with the surface protective film still attached, and the inspection is particularly easy (practically no problem level).
B: The ITO layer can be inspected while the surface protective film is still bonded, and inspection is easy (practically no problem level).
C: The ITO layer can be inspected with the surface protective film still attached, but in rare cases, the inspection may be slightly difficult.
(Practical level that may cause problems)
D: Since the film haze of the surface protective film is rising, it is difficult to inspect the adhesive layer with the surface protective film still attached (practically problematic level)

(13) Comprehensive evaluation (practical property substitution evaluation)
Using the surface protective films produced in Examples and Comparative Examples, comprehensive evaluation was performed according to the following criteria for each evaluation item of visibility after heat treatment and hard coat adhesion.
(Criteria)
A: Visibility after heat treatment, hard coat adhesion, and corrosion resistance are all B or more, and at least two are A (a level that causes no problem in practical use)
B: Visibility after heat treatment, hard coat adhesion, and corrosion resistance are all B or more and A is at most one (a level that is practically acceptable)
C: At least one of visibility after heat treatment, hard coat adhesion, and corrosion resistance is C (a level that may cause a problem in practical use)
D: At least one of visibility (hard coat adhesion) and corrosion resistance after heat treatment is D (practically problematic level)

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
<Method for producing polyester (A)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added, and a polycondensation reaction was carried out for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The obtained polyester (A) had an intrinsic viscosity of 0.63 and an ester cyclic trimer content of 0.97% by weight.

<Method for producing polyester (B)>
The polyester (A) is pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C., and has an intrinsic viscosity of 0.75 and an ester cyclic trimer content of 0.46% by weight. Polyester (B) was obtained.

<Method for producing polyester (C)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the resulting polyester, and 100 ppm of magnesium acetate tetrahydrate with respect to the resulting polyester as the catalyst at 260 ° C. in a nitrogen atmosphere at 260 ° C. The reaction was allowed to proceed. Subsequently, 50 ppm of tetrabutyl titanate was added to the resulting polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to 0.3 kPa in absolute pressure, and melt polycondensation was further carried out for 80 minutes. A polyester (C) having a polyester (A) ester cyclic trimer content of 0.61 and a content of 1.02% by weight was obtained.

<Method for producing polyester (D)>
Polyester (C) was pre-crystallized at 160 ° C. in advance, and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 210 ° C., with an intrinsic viscosity of 0.72 and an ester cyclic trimer content of 0.50% by weight. Polyester (D) was obtained.

<Method for producing polyester (E)>
In the production method of polyester 1, after adding 0.04 part of ethyl acid phosphate, 0.5 part of silica particles having an average particle diameter (d50) of 1.6 μm dispersed in ethylene glycol and 0.04 of antimony trioxide are added. A polyester (C) was obtained using the same method as the production method of polyester 1 except that the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65. The obtained polyester (C) had an intrinsic viscosity of 0.65 and an ester cyclic trimer content of 0.82% by weight.

(Manufacture of polyester film F1)
Polyester B and E are blended at a ratio of 90% and 10%, respectively, as surface layer raw material, and polyester A 100% raw material as intermediate layer raw material is supplied to two vented extruders and melt extruded at 290 ° C. After that, an amorphous film having a thickness of about 1500 μm was obtained by cooling and solidifying on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method. This film was stretched 3.4 times in the machine direction at 85 ° C. Thereafter, a coating layer comprising the following coating solution was coated on one side so that the coating thickness (after drying) was 0.04 g / m2, and the film was guided to a tenter and stretched 4.0 times in the transverse direction at 100 ° C. After heat treatment at 230 ° C., a relaxation treatment of 2% in the lateral direction was performed to obtain a polyester film F1 having a thickness of 50 μm (thickness composition ratio = 2.5 μm / 45 μm / 2.5 μm).

Moreover, the following was used as a composition contained in a coating liquid.
(A1): Hexamethoxymethylolmelamine (A2): Epocros (made by Nippon Shokubai Co., Ltd.) which is an oxazoline compound. Oxazoline group amount 7.7 mmol / g
(A3): Epocros (made by Nippon Shokubai Co., Ltd.) which is an oxazoline compound. Oxazoline group amount 4.5 mmol / g
(A4): Polyglycerol polyglycidyl ether (A5): Block polyisocyanate synthesized by the following method

1000 parts of hexamethylene diisocyanate was stirred at 60 ° C., and 0.1 part of tetramethylammonium capryate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to stop the reaction, and an isocyanurate type polyisocyanate composition was obtained. 100 parts of the obtained isocyanurate type polyisocyanate composition, 42.3 parts of methoxypolyethylene glycol having a number average molecular weight of 400, and 29.5 parts of propylene glycol monomethyl ether acetate were charged and maintained at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was kept at 60 ° C., 35.8 parts of methyl isobutanoyl acetate, 32.2 parts of diethyl malonate, and 0.88 part of 28% methanol solution of sodium methoxide were added and kept for 4 hours. 58.9 parts of n-butanol was added and held at a reaction solution temperature of 80 ° C. for 2 hours, and then 0.86 part of 2-ethylhexyl acid phosphate was added to obtain a blocked polyisocyanate.
(A6): Carbodilite (manufactured by Nisshinbo Chemical Co., Ltd.) which is a polycarbodiimide compound Carbodiimide equivalent 340

(B1): Acrylic resin aqueous dispersion polymerized with the following composition and having a glass transition point of 40 ° C. Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2 / 2 (% by weight) emulsion polymer (emulsifier: anionic surfactant)
(B2): 315 parts by weight of terephthalic acid, 299 parts by weight of isophthalic acid, 74 parts by weight of ethylene glycol, and 265 parts by weight of diethylene glycol as the component (B2a), (B2a) 953 parts by weight, isophorone diisocyanate Polyester polyurethane comprising 267 parts by weight, ethylene glycol 56 parts by weight, and dimethylolpropionic acid 67 parts by weight neutralized with ammonia and dispersed in water (concentration 23%, viscosity at 25 ° C., 30 mPa · s) )
(B3): Polymer having a pyrrolidinium ring in the main chain (Daiichi Kogyo Seiyaku Co., Ltd .: Charol DC902P)

(C1): 2-amino-2-methylpropanol hydrochloride which is a melamine crosslinking catalyst
(F) : Silica particles having an average particle size of 0.07 μm.

(Manufacture of polyester films F2-F31)
In the manufacturing method 5 of F1, it manufactured like the manufacturing method 5 of F1 except the kind of polyester film and the kind of coating layer differing, and each polyester film was obtained.

Example 1:
An adhesive layer composed of the following adhesive layer composition is applied to the surface of the film on which the polyester film F1 coating layer is not provided so that the thickness (after drying) is 25 μm, dried at 100 ° C. for 5 minutes, and the surface protective film Got.
(Adhesive layer composition A)
A solution of an acrylic copolymer having a weight average molecular weight of 600,000 (polystyrene equivalent) by copolymerizing butyl acrylate (100 parts by weight, acrylic acid 6 parts by weight) in ethyl acetate by a conventional method (solid content 30% by weight) ) To 100 parts by weight (solid content) of an acrylic copolymer, N, N-dimethylaminoethyl acrylate, 0.2 parts by weight, and 6 parts by weight of Tetrad C (manufactured by Mitsubishi Gas Chemical), which is an epoxy-based crosslinking agent, are added. An adhesive layer composition was obtained.

Examples 2 to 4, 7, 9, 10, 12, 13, 16, 17, 20 to 22, Reference Examples 5, 6, 8, 11, 14, 15, 18, 19 :
In Example 1, it manufactured similarly to Example 1 except changing the kind of polyester film, and a coating liquid composition, and obtained the surface protection film.

Example 23:
In Example 1, it manufactured similarly to Example 1 except having changed the adhesion layer composition into the following adhesion composition, and obtained the surface protection film.
(Adhesive layer composition B)
A solution of an acrylic copolymer having a weight average molecular weight of 600,000 (polystyrene equivalent) by copolymerizing butyl acrylate (100 parts by weight, acrylic acid 6 parts by weight) in ethyl acetate by a conventional method (solid content 30% by weight) ) To 100 parts by weight (solid content) of the acrylic copolymer, 6 parts by weight of tetrad C (manufactured by Mitsubishi Gas Chemical) as an epoxy crosslinking agent was added to obtain an adhesive layer composition B.

Comparative Examples 1-9:
In Example 1, it manufactured similarly to Example 1 except changing the kind of polyester film, and a coating liquid composition, and obtained the surface protection film.
Comparative Example 1 is an example in which no coating layer is provided, and Comparative Examples 2 to 5 are examples in which the softening point of both outermost polyester layers of the multilayer polyester film is the same as the softening point of the intermediate layer. Comparative Example 6 -9 is an example whose content of the crosslinking agent (A1-A6 of Table 4) in a coating liquid is less than 70 weight%.

  Tables 1 to 6 show the characteristics of the surface protective films obtained in the above Examples and Comparative Examples.

  The film in the present invention is suitable for surface protection of various adherends such as synthetic resin plates, glass plates, metal plates, optical members, automobile members, electric / electronic members, building material members, stationery / office supplies members, and the like. . For optical members that require particularly high visibility (for example, glass substrates, light diffusion films, liquid crystal displays (polarizing plates, retardation plates, light guide plates, prism plates, etc.), touch panels, organic EL displays, plasma displays, etc.) Can be suitably used.

Claims (5)

It is a surface protective film in which a coating layer is formed on one side of a multilayer polyester film and an adhesive layer is provided on the other side. The multilayer polyester film has a laminated structure of at least three layers, softening point of the polyester layer is rather higher than the softening point of the intermediate layer, prior Symbol coating layer is formed a cross-linking agent from a coating solution containing more than 70 wt% relative to nonvolatile components, the non-volatile components, the crosslinking agent and consists particles alone, the crosslinking agent is a melamine compound, carbodiimide compound and an epoxy compound or a melamine compound and an oxazoline compound, or surface protection characterized by either Kumiawasedea Rukoto oxazoline compounds and epoxy compounds films . It is a surface protective film in which a coating layer is formed on one side of a multilayer polyester film and an adhesive layer is provided on the other side. The multilayer polyester film has a laminated structure of at least three layers, The softening point of the polyester layer is higher than the softening point of the intermediate layer, and the coating layer is formed from a coating solution containing 70% by weight or more of a crosslinking agent with respect to the nonvolatile component. A surface protective film comprising only particles and the crosslinking agent has an oxazoline compound, a melamine compound, and an epoxy compound. It is a surface protective film in which a coating layer is formed on one side of a multilayer polyester film and an adhesive layer is provided on the other side. The multilayer polyester film has a laminated structure of at least three layers, The softening point of the polyester layer is higher than the softening point of the intermediate layer, and the coating layer is formed from a coating solution containing 70% by weight or more of a crosslinking agent with respect to the nonvolatile component, and the nonvolatile component is a crosslinking agent or a crosslinking catalyst. A surface protective film comprising only particles and the crosslinking agent has an oxazoline compound, a melamine compound, and an epoxy compound. The surface protective film according to claim 1, wherein the adhesive layer is formed of an acrylic adhesive. The laminated body which bonded together the adhesion layer surface of the surface protection film in any one of Claims 1-4, and the ITO layer surface of ITO film | membrane.