JP6773151B2 - Laminated polyester film and manufacturing method - Google Patents

Description

The present invention relates to a laminated polyester film, and for example, in an application for forming a functional layer such as a hard coat layer such as a transparent electrode such as a touch panel or a film for molding, it is easy to distinguish between processed and unprocessed functional layers. It relates to a laminated polyester film suitable for this purpose.

In recent years, polyester films are often used in various optical films and molding films, such as transparent electrodes such as touch panels, which are members of various displays, antireflection films, prism sheets, light diffusion sheets, electromagnetic wave shielding films, and labels. It is used in applications such as mold transfer film and in-mold label film. The base film used for these members is required to have excellent transparency and visibility.

Therefore, films used for these purposes are generally those having high transparency. However, due to its high transparency, it is not possible to easily distinguish between the processed film on which various functional layers are formed and the unprocessed film before processing, and it is processed especially when it is made into a single-wafer form. There is a possibility of mistaken product for raw product.

Japanese Unexamined Patent Publication No. 2005-97571

The present invention has been made in view of the above circumstances, and the problem to be solved is that it is possible to easily distinguish between processed and unprocessed functional layers in applications for forming functional layers such as hard coat layers. The purpose is to provide an excellent laminated polyester film.

As a result of diligent studies in view of the above circumstances, the present inventors have found that the above-mentioned problems can be easily solved by using a laminated polyester film having a specific structure, and have completed the present invention.

That is, the gist of the present invention is that the polyester film has a coating layer on at least one side, and fine irregularities having an arithmetic mean roughness (Sa) of 25 nm or more on the surface of the coating layer are present on the coating layer. The laminated polyester film is characterized in that the haze value is reduced by 1.0% or more when the functional layer is formed on the coating layer.

According to the laminated polyester film of the present invention, by forming various functional layers such as a hard coat layer, the haze is greatly lowered, and it is possible to easily distinguish between processed and unprocessed functional layers. It can be provided and its industrial value is high.

The polyester film constituting the laminated polyester film in the present invention may have a single-layer structure or a multi-layer structure, and has four or more layers as long as the gist of the present invention is not exceeded in addition to the two-layer and three-layer structure. It may be a multi-layered structure, and is not particularly limited.

The polyester used in the present invention may be a homopolyester or a copolymerized polyester. When it is made of homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. 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. Examples of typical polyesters include polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, p-oxybenzoic acid). One or more of them may be mentioned, and examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol and the like.

The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used. Examples thereof include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds and calcium compounds. Among these, titanium compounds and germanium compounds are preferable because they have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film is high. Further, since the germanium compound is expensive, it is more preferable to use a titanium compound.

In the case of polyester using a titanium compound, the titanium element content is preferably in the range of 50 ppm or less, more preferably 1 to 20 ppm, and further preferably 2 to 10 ppm. If the content of the titanium compound is too high, the deterioration of the polyester may be accelerated in the process of melt extrusion of the polyester, resulting in a film with a strong yellow tint. If the content is too low, the polymerization efficiency is poor and the cost is high. It may not be possible to obtain a film that is up or has sufficient strength. When a polyester made of a titanium compound is used, it is preferable to use a phosphorus compound in order to reduce the activity of the titanium compound for the purpose of suppressing deterioration in the melt extrusion process. As the phosphorus compound, orthophosphoric acid is preferable in consideration of polyester productivity and thermal stability. The phosphorus element content is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, still more preferably 5 to 100 ppm with respect to the amount of polyester to be melt-extruded. If the content of the phosphorus compound is too high, it may cause gelation or foreign matter, and if the content is too low, the activity of the titanium compound cannot be sufficiently reduced, resulting in a yellowish color. It may be a film.

The polyester film of the present invention may contain an ultraviolet absorber in order to improve the weather resistance of the film and prevent deterioration of the liquid crystal of the liquid crystal display used for the touch panel and the like. The ultraviolet absorber is a compound that absorbs ultraviolet rays and is not particularly limited as long as it can withstand the heat applied in the manufacturing process of the polyester film.

Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, but an organic ultraviolet absorber is preferable from the viewpoint of transparency. The organic ultraviolet absorber is not particularly limited, and examples thereof include cyclic iminoesters, benzotriazoles, and benzophenones. From the viewpoint of durability, cyclic iminoester type and benzotriazole type are more preferable. It is also possible to use two or more types of ultraviolet absorbers in combination.

Particles can also be blended into the polyester layer of the film of the present invention for the main purpose of imparting slipperiness and preventing scratches in each step. When the particles are blended, the type of the particles to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, and sulfuric acid. Examples thereof include inorganic particles such as calcium, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin and benzoguanamine resin. Further, during the polyester manufacturing process, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can also be used. Among these, silica particles are particularly preferable in that a small amount is likely to produce an effect.

The average particle size of the particles is usually 5 μm or less, preferably 0.01 to 3 μm. If the average particle size exceeds 5 μm, the surface roughness of the film may become too coarse, and problems may occur when various functional layers or the like are formed in a subsequent step.

Further, the particle content in the polyester layer is usually less than 5% by weight, preferably in the range of 0.0003 to 3% by weight. If there are no or few particles, the transparency of the film will be high and the film will be good, but the slipperiness may be insufficient. Therefore, by putting particles in the coating layer, the slipperiness can be improved. It may be necessary to take measures such as improving it. Further, when the particle content exceeds 5% by weight, the haze may not be sufficiently lowered even if the functional layer is formed, and the transparency of the film may be insufficient.

The shape of the particles to be used is not particularly limited, and any of spherical, lumpy, rod-shaped, flat-shaped and the like may be used. Further, the hardness, specific gravity, color and the like are not particularly limited.
Two or more kinds of these series of particles may be used in combination, if necessary.

The method of adding the 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 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 above-mentioned particles, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film of the present invention, if necessary.

The thickness of the polyester film in the present invention is not particularly limited as long as it can be formed as a film, but is usually in the range of 10 to 350 μm, preferably 20 to 300 μm.

As a film-forming method for the film of the present invention, a generally known film-forming method can be adopted, and there is no particular limitation. For example, in the case of producing a biaxially stretched polyester film, first, the polyester raw material described above is melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and the liquid coating adhesion method are preferably adopted. Next, the obtained 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. Then, in the direction orthogonal to the stretching direction of the first stage, stretching is usually performed at 70 to 170 ° C. and a stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. A method of subsequently performing heat treatment at a temperature of 180 to 270 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film can be mentioned. In the above stretching, a method of stretching in one direction in two or more steps can also be adopted. In that case, it is preferable to finally set the stretching ratios in the two directions within the above ranges.

Further, in the present invention, a simultaneous biaxial stretching method can be adopted for producing a polyester film constituting a laminated polyester film. The simultaneous biaxial stretching method is a method in which the unstretched sheet is simultaneously stretched and oriented in the mechanical direction and the width direction in a state where the temperature is controlled at usually 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in area magnification. Then, the heat treatment is subsequently performed at a temperature of 170 to 270 ° C. under tension or relaxation within 30% to obtain a stretch-oriented film. As for the simultaneous biaxial stretching device that employs the above-mentioned stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be adopted.

Next, the formation of the coating layer constituting the laminated polyester film in the present invention will be described. Regarding the coating layer, the film surface may be treated during the film forming process of the polyester film, which may be provided by in-line coating, or an offline coating which is applied outside the system on the once produced film may be adopted. More preferably, it is formed by in-line coating.

The in-line coating is a method of coating in the process of manufacturing a polyester film, and specifically, a method of coating at an arbitrary stage from melt extrusion of polyester to heat fixing and winding after stretching. Usually, it is coated on any of an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat fixing, and a film after heat fixing and before winding. Although not limited to the following, for example, in sequential biaxial stretching, a method of coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) and then stretching in the lateral direction is particularly excellent. According to such a method, since the film formation and the coating layer formation can be performed at the same time, there is an advantage in manufacturing cost, and the thickness of the coating layer can be changed by the stretching ratio in order to perform stretching after coating. , Thin film coating can be performed more easily than offline coating. Further, by providing the coating layer on the film before stretching, the coating layer can be stretched together with the base film, whereby the coating layer can be firmly adhered to the base film. Further, in the production of a biaxially stretched polyester film, the film can be restrained in the vertical and horizontal directions by stretching while gripping the end of the film with a clip or the like, and in the heat fixing step, a flat surface without wrinkles or the like. High temperature can be applied while maintaining the sex. Therefore, since the heat treatment applied after coating can be set to a high temperature which cannot be achieved by other methods, the film-forming property of the coating layer can be improved, and the coating layer and the base film can be more firmly adhered to each other. Furthermore, a strong coating layer can be formed, and performance such as adhesion to various functional layers that can be formed on the coating layer and moisture heat resistance can be improved.

In the present invention, there is a coating layer having a coating layer, and when a functional layer is formed on the coating layer, the coating layer has fine irregularities having an arithmetic mean roughness (Sa) of 25 nm or more on the surface. When the functional layer is formed on the coating layer, it is an essential requirement that the haze value is reduced by 1.0% or more.

The film of the present invention is designed to make it easier to distinguish between processed and unprocessed functional layers by reducing the haze after forming a functional layer such as a hard coat layer.

In order to reduce the haze value by 1.0% or more when the functional layer is formed on the coating layer, the surface unevenness formed by the polyester film of the base material or the coating layer is reduced by forming the functional layer. The method is effective. The formation of surface irregularities is possible from both the design of the polyester film as the base material and the design of the coating layer, as in the case of adjusting the film haze. When adjusting by designing the polyester film of the base material, for example, a method of forming a multilayer structure and including particles in the outermost polyester film layer on the coating layer side (the side forming the functional layer) of the polyester film intermediate layer. However, it is preferable because it easily forms surface irregularities. Further, the method of forming the surface unevenness mainly by the adjustment by the design of the coating layer which is the outermost layer of the laminated polyester film of the present invention, which is in direct contact with the functional layer rather than the adjustment by the design of the base material, formed the functional layer. It is more preferable because the haze reduction at the time becomes efficient.

In the present invention, it is essential that the arithmetic mean roughness (Sa) of the surface of the coating layer is in the range of 25 nm or more in the three-dimensional roughness parameter.

Specifically, the arithmetic mean roughness (Sa) is a three-dimensional extension of two-dimensional Ra, and is the volume of the part surrounded by the surface shape curved surface and the average surface divided by the measurement area. Yes, it is calculated from the following formula. When the surface is the XY plane and the height direction is the Z axis, A: the defined region (the entire image), Z (x, y): the image point (x, y) from the plane at height 0. The height is expressed by the following formula.

Further, as a preferable form, it is assumed that the surface height distribution sharpness (Sku) is 12 or less.

The surface height distribution sharpness (Sku) is a measure of the sharpness of the surface shape curved surface, which characterizes the spread of the surface height distribution, and is defined by the following equation.

In the above equation, Sq is a three-dimensional extension of the two-dimensional Rq (RMS), which represents the standard deviation σ in statistics. It is a curved surface obtained by squared the distance between the surface shape curved surface and the average surface, and the square root mean square deviation obtained by dividing the volume of the portion sandwiched by the average surface by the measurement area and then calculating the square root, which can be obtained from the following equation. ..

It should be noted that when Sku is 3, it means that the distribution is normal, and as this value becomes smaller, the surface height distribution has a gentle shape, and as the value becomes larger, the protrusion becomes sharper. ..

Examples of the method of forming the surface unevenness in which the haze is lowered by the functional layer include a method of making the coating layer itself uneven and a method of incorporating particles.

Examples of the method of making the coating layer itself uneven include a method of forming a coating layer by mixing anionic and cationic polymers with each other, and a film stretching step of applying a polymer having a high glass transition temperature (Tg). A method of forming a coating layer through the above can be mentioned. A method of forming a coating layer by mixing anionic and cationic polymers with each other is preferable because surface irregularities can be effectively formed.

In the case of the method of containing particles in the coating layer, the method of forming irregularities on the coating layer itself is preferable because particles may easily fall off from the coating layer as the amount of particles contained increases. Further, since the surface area is increased by making the surface of the coating layer uneven, there is also an effect that it can contribute to the improvement of the adhesion with the functional layer.

The Tg of the polymer used in the coating layer of the polyester film of the present invention is usually 50 ° C. or higher, preferably 60 ° C. to 150 ° C., and more preferably 70 ° C. to 130 ° C. By using a polymer in the above range, irregularities are formed in the coating layer itself by the film stretching step, and a film having a high haze can be obtained.

Various polymers can be used to form irregularities on the surface of the coating layer, and conventionally known polymers can be used as the polymer. Specific examples of the polymer include polyester resin, acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methyl cellulose, hydroxycellulose, starches and the like. ..
Among these, it is more preferable to use an acrylic resin, a urethane resin, or a polyester resin from the viewpoints of forming irregularities on the surface of the coating layer, improving the adhesion to the functional layer such as the hard coat layer, and improving the coating appearance. From the viewpoint of good adhesion to various functional layers, it is more preferable to use an acrylic resin or a urethane resin.

Acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by an acrylic-based or methacrylic-based monomer. These may be either homopolymers or copolymers. Also included are copolymers of these polymers with other polymers (eg polyester, polyurethane, etc.). For example, block copolymers and graft copolymers. Alternatively, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or a polyurethane dispersion is also included. Similarly, a polymer (in some cases, a polymer mixture) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion is also included. Further, it is also possible to contain a hydroxyl group and an amino group in order to further improve the adhesion.

The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but typical compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citracon. Various carboxyl group-containing monomers such as acids and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroquilfumarate, Various hydroxyl group-containing monomers such as monobutyl hydroxyitaconate; various (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate. Meta) Acrylate esters; Various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene Various styrene derivatives, various vinyl esters such as vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl-based monomers; chloride Various vinyl halides such as vinyl and billidene chloride; various conjugated dienes such as butadiene.

The urethane resin is a polymer compound having a urethane bond in the molecule. Urethane resins are usually made by the reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols, and these compounds may be used alone or in a plurality of types.

Polycarbonate polyols are obtained from polyhydric alcohols and carbonate compounds by a dealcohol reaction. Examples of polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Examples thereof include diol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 3,3-dimethylol heptane. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate and the like, and examples of the polycarbonate-based polyols obtained from these reactions include poly (1,6-hexylene) carbonate and poly (3-). Methyl-1,5-pentylene) carbonate and the like can be mentioned.

Polypolypolyols include polyvalent carboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Products and polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-Methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol , 2-Methyl-2-propyl-1,3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2 , 5-Diol-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2 -Hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamine, lactonediol, etc.) can be mentioned.

Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol and the like.

Among the above-mentioned polyols, polycarbonate polyols and polyester polyols are more preferably used in order to improve the adhesion to various functional layers.

Examples of the polyisocyanate compound used to obtain a urethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylenedi isocyanate, naphthalene diisocyanate, and trizine diisocyanate, α, α, α', and α'. -Adiocyanate having an aromatic ring such as tetramethylxylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate and other aliphatic diisocyanates, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Examples thereof include alicyclic diisocyanates such as methane diisocyanate and isopropyridene dicyclohexyl diisocyanate. These may be used alone or in combination of two or more.

A chain extender may be used when synthesizing the urethane resin, and the chain extender is not particularly limited as long as it has two or more active groups that react with the isocyanate group, and is generally a hydroxyl group. Alternatively, a chain extender having two amino groups can be mainly used.

Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. Examples of glycols such as glycols can be mentioned. Examples of the chain extender having two amino groups include aromatic diamines such as tolylene diamine, xylylene diamine and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine and 2,2-dimethyl-1,3-. Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprovilitincyclohexyl-4,4'-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexane and other alicyclic diamines and the like.

The urethane resin in the present invention may use a solvent as a medium, but is preferably water as a medium. To disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, a water-soluble type, and the like. In particular, the self-emulsifying type in which an ion group is introduced into the structure of the urethane resin to form an ionomer is preferable because it is excellent in storage stability of the liquid and the water resistance, transparency and adhesion of the obtained coating layer.

Examples of the ionic group to be introduced include various types such as a carboxyl group, a sulfonic acid, a phosphoric acid, a phosphonic acid, and a quaternary ammonium salt, and a carboxyl group is preferable. As a method for introducing a carboxyl group into the urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, at the time of prepolymer synthesis, there are a method of using a resin having a carboxyl group as a copolymerization component and a method of using a component having a carboxyl group as one component of a polyol, a polyisocyanate, a chain extender and the like. In particular, a method of using a carboxyl group-containing diol and introducing a desired amount of carboxyl groups according to the amount of this component charged is preferable.
For example, copolymerizing dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid, etc. with the diol used for polymerizing the urethane resin. Can be done. Further, this carboxyl group is preferably in the form of a salt neutralized with ammonia, amines, alkali metals, inorganic alkalis and the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, the carboxyl group from which the neutralizing agent has been removed in the drying step after coating can be used as a cross-linking reaction point by another cross-linking agent. As a result, the stability of the liquid before coating is excellent, and the durability, solvent resistance, water resistance, blocking resistance, etc. of the obtained coating layer can be further improved.

Examples of the polyester resin include those composed of the following polyvalent carboxylic acids and polyvalent hydroxy compounds as main constituents. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaru Acids, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, monopotassium trimellitic acid and ester-forming derivatives thereof can be used. As polyvalent hydroxy compounds, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanedioyl, 2 -Methyl-1,5-pentandiol, neopentylglycol, 1,4-cyclohexanedimethanol, p-xylyleneglycol, bisphenol A-ethyleneglycol adduct, diethyleneglycol, triethyleneglycol , Polyethylene glycol, Polypropylene glycol, Polytetramethylene glycol, Polytetramethylene oxide glycol, Dimethylolpropionic acid, Glycerin, Trimethylolpropane, Sodium dimethylolethylsulfonate, Dimethylolpropion Potassium acid or the like can be used. One or more of each of these compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.

Acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by an acrylic-based or methacrylic-based monomer. These may be either homopolymers or copolymers. Also included are copolymers of these polymers with other polymers (eg polyester, polyurethane, etc.). For example, block copolymers and graft copolymers. Alternatively, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or a polyurethane dispersion is also included. Similarly, a polymer (in some cases, a polymer mixture) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion is also included. Further, it is also possible to contain a hydroxyl group and an amino group in order to further improve the adhesion.

The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but typical compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citracon. Various carboxyl group-containing monomers such as acids and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroquilfumarate, Various hydroxyl group-containing monomers such as monobutyl hydroxyitaconate; various (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate. Meta) Acrylate esters; Various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene Various styrene derivatives, various vinyl esters such as vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, etc .; phosphorus-containing vinyl-based monomers; chloride Various vinyl halides such as vinyl and billidene chloride; various conjugated dienes such as butadiene.

Further, in order to improve the strength of the coating layer, it is also possible to use a cross-linking agent in combination. Conventionally known materials can be used as the cross-linking agent, and examples thereof include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, and silane coupling compounds. Further, it is also possible to use two or more kinds of cross-linking agents in combination in order to further improve the adhesion with the functional layer. From the viewpoint of good adhesion, among the above, oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds and carbodiimide compounds are preferable, and oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds and carbodiimide compounds are particularly selected. It is more preferable to use two or more kinds of cross-linking agents in combination because the adhesion is remarkably improved. Further, from the viewpoint of increasing the strength of the coating layer, the melamine compound is more preferable.

The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and it can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. Additive 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, Examples thereof include 2-isopropenyl-4-methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline, and one or a mixture of two or more thereof can be used. Of these, 2-isopropenyl-2-oxazoline is industrially readily available and suitable. The other monomer is not limited as long as it is a monomer copolymerizable with the addition polymerizable oxazoline group-containing monomer, and is, for example, an alkyl (meth) acrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, etc. (Meta) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylate, 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 and methacrylonitrile; (meth) acrylamide, N-alkyl ( Meta) acrylamide, N, N-dialkyl (meth) acrylamide, (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl Unsaturated amides such as groups (groups, cyclohexyl groups, etc.); 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 vinyl fluoride; α, β-unsaturated aromatic monomers such as styrene, α-methylstyrene, etc., and one or more of these. Monomer can be used.

The content of the oxazoline group contained in the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 1 to 9 mmol / g, more preferably 3 to 8 mmol / g, and further preferably 4 to 6 mmol in terms of the amount of the oxazoline group. It is in the range of / g. Use within the above range is preferable because the adhesion to various functional layers is improved.

The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include a condensate of epichlorohydrin and an ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, or the like with a hydroxyl group or an amino group. 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, triglycidyltris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane. Examples of the polyglycidyl ether and the 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, Polytetramethylene glycol diglycidyl ether, Monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenylglycidyl ether, glycidylamine compounds N, N, N', N ′ -Tetraglycidyl-m-xylylene diamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like can be mentioned.

A melamine compound is a compound having a melamine skeleton in the compound, for example, an alkylolated melamine derivative, a compound obtained by reacting an alkylolated melamine derivative with an alcohol to partially or completely etherify, and these. A mixture can be used. As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Further, the melamine compound may be either a monomer or a multimer of a dimer or more, or a mixture thereof may be used. Further, a melamine that is copolymerized with urea or the like can be used, or a catalyst can be used to increase the reactivity of the melamine compound.

The isocyanate-based 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, phenylenedi isocyanate and naphthalene diisocyanate, and aromatic rings such as α, α, α'and α'-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanates, methylene diisocyanates, propylene diisocyanates, lysine diisocyanates, trimethylhexamethylene diisocyanates, hexamethylene diisocyanates, cyclohexanediisocyanates, methylcyclohexanediisocyanates, isophorone diisocyanates, methylenebis (4-cyclohexylisocyanates), isopropyridene dicyclohexyldiisocyanates and the like. The alicyclic isocyanate of the above is exemplified. In addition, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimides of these isocyanates can also be mentioned. These may be used alone or in combination of two or more. 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, phenolic compounds such as heavy sulfites, phenol, cresol and ethylphenol, and alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, and lactam compounds such as ε-caprolactam and δ-valerolactam. , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acid amide compounds of acetanilide and acetate amide, oxime compounds such as formaldehyde, acetoaldoxime, acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime, and these alone Two or more kinds may be used in combination. Among these, an active methylene compound is particularly preferable from the viewpoint of easily improving the adhesion to the functional layer.

Further, the isocyanate-based compound in the present invention may be used alone, or may be used as a mixture or a bond with various polymers. In terms 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.

The carbodiimide-based compound is a compound having a carbodiimide structure, and is used for improving the adhesion to various surface functional layers that can be formed on the coating layer and improving the moisture and heat resistance of the coating layer. is there. The carbodiimide-based compound is a compound having one or more carbodiimide or a carbodiimide derivative structure in the molecule, but a polycarbodiimide-based compound having two or more in the molecule is more preferable for better adhesion and the like.

The carbodiimide-based compound can be synthesized by a conventionally known technique, and a condensation reaction of a diisocyanate compound is generally used. The diisocyanate compound is not particularly limited, and any aromatic type or aliphatic type can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylenediisocyanate, naphthalenediisocyanate, hexa Examples thereof include methylene diisocyanis, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyldiisocyanis, dicyclohexylmethane diisocyanate and the like.

Further, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound within the range where the effect of the present invention is not lost, a surfactant may be added, or a polyalkylene oxide or a quaternary ammonium salt of a dialkylamino alcohol may be added. Hydrophilic monomers such as hydroxyalkyl sulfonate may be added and used.

The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight [g] of the carbodiimide compound for giving 1 mol of the carbodiimide group), and is usually 100 to 1000, preferably 250 to 800, and more preferably 300. It is in the range of ~ 700, more preferably 350 ~ 650. Use within the above range is preferable because the adhesion to various functional layers is improved.

These cross-linking agents are used in a design to improve the performance of the coating layer by reacting them in the drying process and the film forming process. It can be inferred that unreacted products of these cross-linking agents, compounds after the reaction, or mixtures thereof are present in the completed coating layer.

In the coating layer of the polyester film of the present invention, it is preferable to use particles in combination with the formation of the coating layer in order to improve slipperiness and blocking. The average particle size of the particles is preferably in the range of 0.001 μm to 1.0 μm, more preferably 0.005 μm to 0.5 μm, and even more preferably 0.01 μm to 0.2 μm.

Examples of the particles to be used include inorganic particles such as silica, alumina and metal oxide, and organic particles such as crosslinked polymer particles. In particular, silica particles are preferable from the viewpoint of dispersibility in the coating layer.

Further, as long as the gist of the present invention is not impaired, a defoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are necessary for forming the coating layer. , Foaming agents, dyes, pigments and the like can also be used in combination.

As a ratio to the total non-volatile components in the coating liquid forming the coating layer forming the laminated polyester film in the present invention, the polymer is preferably in the range of 97% by weight or less, more preferably 20 to 95% by weight, and further preferably 30 to 30% by weight. It is in the range of 90% by weight. When used in the above range, it is effective in forming irregularities on the surface of the coating layer.

The ratio of the cross-linking agent to the total non-volatile components in the coating liquid forming the coating layer forming the laminated polyester film in the present invention is preferably 45% by weight or less, more preferably 3 to 35% by weight, still more preferably. It is in the range of 5 to 25% by weight. By using in the above range, a strong coating layer can be obtained in addition to forming irregularities on the surface of the coating layer.

In the polyester film of the present invention, it is also possible to provide a coating layer on a surface opposite to the surface on which the coating layer is provided as described above. As a component of the coating layer formed on the opposite surface, conventionally known ones can be used. Examples thereof include polymers such as polyester resin, acrylic resin and urethane resin, cross-linking agents such as oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds and melamine compounds, and these materials may be used alone. , A plurality of types may be used in combination.

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

Regarding the formation of the coating layer, the above-mentioned series of compounds are used as a solution or a dispersion of a solvent, and a coating liquid adjusted to have a solid content concentration of about 0.1 to 80% by weight is applied onto a polyester film. It is preferable to produce a polyester film. In particular, when the coating layer is provided by in-line coating, it is more preferable to use an aqueous solution or an aqueous dispersion, but for the purpose of improving dispersibility in water, film formation, etc., a small amount of organic solvent is added to the coating liquid. It may be contained. Further, only one type of organic solvent may be used, and two or more types may be used as appropriate.

Regarding the laminated polyester film in the present invention, the thickness of the coating layer provided on the polyester film is usually in the range of 0.001 to 1 μm, preferably 0.01 to 0.5 μm, and more preferably 0.03 to 0.2 μm. Is. If the film thickness is out of the above range, the appearance of the coating may be deteriorated and the adhesion to the functional layer may be deteriorated.

In the film of the present invention, as a method of forming a coating layer, for example, a gravure coat, a reverse roll coat, a die coat, an air doctor coat, a blade coat, a rod coat, a bar coat, a curtain coat, a knife coat, a transfer roll coat, and a squeeze. Conventionally known coating methods such as coating, impregnation coating, kiss coating, spray coating, calender coating, and extrusion coating can be used.

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 offline coating, it is usually 3 to 40 at 80 to 200 ° C. It is preferable to perform the heat treatment for 3 to 40 seconds at 100 to 180 ° C. for 2 seconds.

On the other hand, when the coating layer is provided by in-line coating, it is usually preferable to perform heat treatment at 70 to 270 ° C. for 3 to 200 seconds as a guide.

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

The amount of reduction in the haze value due to the formation of the functional layer on the coating layer of the polyester film of the present invention is preferably 1.0% or more, more preferably 3.0% or more, still more preferably 5.0% or more. It is particularly preferably in the range of 8.0% or more, and most preferably in the range of 10% or more. By setting the above range, it becomes easy to distinguish between processed and unprocessed functional layers according to various places such as conference rooms, work rooms, and inspection rooms, and how the film is viewed.

The haze of the polyester film of the present invention is preferably in the range of 3.0% or more, more preferably 5.0% or more, still more preferably 10% or more, and particularly preferably 12% or more.
By setting the haze within the above range, it is possible to make it easier to distinguish between processed and unprocessed functional layers.

It is essential that the arithmetic mean roughness (Sa) of the unevenness formed on the coating layer of the polyester film of the present invention is 25 nm or more, preferably 35 nm or more, more preferably 42 nm or more, still more preferably 46 nm or more. The range. The upper limit of the preferable range is 60 nm. The sharpness (Sku) of the surface height distribution is preferably in the range of 12 or less, more preferably 9 or less, further preferably 6 or less, and particularly preferably 4 or less. As a lower limit of the preferred range, Sk is 1. By setting the above range, a film having a high haze can be obtained by forming irregularities on the surface of the coating layer.

In the polyester film of the present invention, a functional layer is generally formed on the coating layer. The functional layer is a layer provided for imparting various functions, such as a hard coat layer, a light diffusion layer, a prism layer, a microlens layer, an ink layer, an adhesive layer, and an adhesive layer. The functional layer is not particularly limited as long as the haze is lowered when formed on the coating layer, but it is usually preferable that the haze is not so high, and the haze of only the functional layer is preferably 8.0% or less. It is more preferably 3.0% or less, further preferably 1.0% or less, and particularly preferably 0.5% or less. Similarly, the thickness of the functional layer is not particularly limited as long as the haze is lowered when formed on the coating layer, but is preferably 0.1 to 50 μm, more preferably 1 to 15 μm, and further preferably 1 to 1. The range is 8 μm.

As an example of the functional layer, for example, in the case of a hard coat layer, the material used is not particularly limited, but for example, a reactive silicon compound such as a monofunctional (meth) acrylate, a polyfunctional (meth) acrylate, or a tetraethoxysilane. Such as a cured product can be mentioned. Of these, from the viewpoint of achieving both productivity and hardness, a polymerized cured product of a composition containing an active energy ray-curable (meth) acrylate is particularly preferable.

The composition containing the active energy ray-curable (meth) acrylate is not particularly limited. For example, a mixture of one or more known active energy ray-curable monofunctional (meth) acrylates, bifunctional (meth) acrylates, and polyfunctional (meth) acrylates is commercially available as a resin material for active energy ray-curable hard coats. In addition to these, those having other components added can be used as long as the object of the present embodiment is not impaired.

The active energy ray-curable monofunctional (meth) acrylate is not particularly limited, and is, for example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth). ) Acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, alkyl (meth) acrylate such as isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and the like hydroxy Ekoxyalkyl (meth) acrylates such as alkyl (meth) acrylates, methoxyethyl (meth) acrylates, ethoxyethyl (meth) acrylates, methoxypropyl (meth) acrylates, and ethoxypropyl (meth) acrylates, benzyl (meth) acrylates, and phenoxyethyl. Aromatic (meth) acrylates such as (meth) acrylates, diaminoethyl (meth) acrylates, amino group-containing (meth) acrylates such as diethylaminoethyl (meth) acrylates, methoxyethylene glycol (meth) acrylates, phenoxypolyethylene grill (meth) ) Acrylate, ethylene oxide-modified (meth) acrylate such as phenylphenol ethylene oxide-modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylic acid and the like.

The active energy ray-curable bifunctional (meth) acrylate is not particularly limited, but is, for example, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-. Alcandiol di (meth) acrylates such as hexanediol di (meth) acrylates, 1,9-nonanediol di (meth) acrylates and tricyclodecanedimethylol di (meth) acrylates, bisphenol A ethylene oxide-modified di (meth) acrylates. , Bisphenol F ethylene oxide modified di (meth) acrylate and other bisphenol modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate, epoxy di (meth) acrylate and the like. Can be mentioned.

The active energy ray-curable polyfunctional (meth) acrylate is not particularly limited, but for example, dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, and ditrimethylolpropantetra (meth) acrylate. , Pentaerythritol tri (meth) acrylate, trimethylolpropantri (meth) acrylate, isocyanuric acid ethylene oxide-modified tri (meth) acrylate, ε-caprolactone-modified tris (acroxyethyl) isocyanurate-modified tri (meth) Examples thereof include acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer and the like.

Other components contained in the composition containing the active energy ray-curable (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers and leveling agents. Further, in the case of drying after forming a film in the wet coating method, an arbitrary amount of solvent can be added.

When an organic material is used, a general wet coating method such as a roll coating method or a die coating method is adopted as a method for forming the hard coat layer. The formed hard coat layer can be heated or irradiated with active energy rays such as ultraviolet rays and electron beams as needed to carry out a curing reaction.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Method for measuring the ultimate viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed is precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved, and measured at 30 ° C.

(2) Measurement method of average particle size The coating layer was observed using TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, accelerating voltage 100V), and the average value of the particle size of 10 particles was taken as the average particle size. ..

(3) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi High Technologies Corporation H-7650, accelerating voltage 100 V). The film thickness was measured at a location not including the particle portion.

(4) Measurement method of haze The haze was measured by JIS K 7136 using a haze meter HM-150 manufactured by Murakami Color Technology Research Institute Co., Ltd.

(5) Method for measuring the amount of decrease in haze when the functional layer is formed As the functional layer, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, and a photopolymerization initiator (trade name). : Irga Cure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) A hard coat layer (the layer concerned) obtained by applying a mixed coating solution of 5 parts by weight and 200 parts by weight of methyl ethyl ketone so that the dry film thickness becomes 2 μm and irradiating with ultraviolet rays to cure the mixture. The haze was 0.1%), the haze was measured by the method according to (4), and the difference from the haze of the laminated polyester film before forming the functional layer was calculated.

(6) Discrimination evaluation method before and after functional layer processing The difference between the 20 cm × 20 cm film before and after the functional layer was formed was observed. As a method of observation, a film without a hard coat layer and a film with a hard coat layer were held in both hands, and the difference between the two when observed under a fluorescent lamp was confirmed. The case where the difference can be instantly discriminated is marked with ⊚, the case where it can be easily discriminated by observing for 3 seconds is marked with ◯, the case where it can be discriminated by looking closely is marked with Δ, and the case where it is difficult or impossible to discriminate is marked with ×.

(7) Arithmetic Mean Surface Roughness (Sa), Surface Height Distribution Sharpness (Sku)
For the three-dimensional surface roughness of the surface, the surface shape and surface roughness in a region of 260 μm × 260 μm were measured by a laser detection method using an Olympus laser microscope “LEXT OLS-4000”.

(8) Evaluation method of adhesion of coating layer 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) ) A mixed coating solution of 5 parts by weight and 200 parts by weight of methyl ethyl ketone was applied so that the dry film thickness was 5 μm, and was cured by irradiating with ultraviolet rays to form a hard coat layer. After 50 hours in an environment of 80 ° C. and 90% RH, the obtained film is cross-cut in 10 × 10 and 18 mm wide tape (Cellotape (registered trademark) CT manufactured by Nichiban Co., Ltd.) is applied. After attaching -18) and rapidly peeling it off at a peeling angle of 180 degrees, observe the peeled surface, and if the peeled area is less than 10%, ○, if 10% or more and less than 30%, △, if 30% or more It was marked with x.

The polyester used in Examples and Comparative Examples was prepared as follows.
<Manufacturing method of polyester (A)>
Ester 100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the produced polyester, and 100 ppm of magnesium acetate / tetrahydrate as a catalyst with respect to the produced polyester in a nitrogen atmosphere at 260 ° C. A chemical reaction was allowed. Subsequently, 50 ppm of tetrabutyl titanate was added to the produced polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to an absolute pressure of 0.3 kPa, and the mixture was further polycondensed for 80 minutes to achieve the ultimate viscosity. A polyester (A) of 0.63 was obtained.

<Manufacturing method of polyester (B)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and magnesium acetate tetrahydrate as a catalyst were produced and subjected to an esterification reaction at 225 ° C. with 900 ppm in a nitrogen atmosphere. Subsequently, 3500 ppm of positive phosphoric acid was added to the produced polyester and 70 ppm of germanium dioxide was added to the produced polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, and the pressure was reduced to an absolute pressure of 0.4 kPa. It was melt polycondensed for 85 minutes to obtain a polyester (B) having an ultimate viscosity of 0.64.

<Manufacturing method of polyester (C)>
In the method for producing polyester (A), polyester (C) is obtained by using the same method as the method for producing polyester (A) except that 0.3 parts by weight of silica particles having an average particle size of 2 μm are added before melt polymerization. It was.

Examples of compounds constituting the coating layer are as follows.
(Compound example)

-Acrylic resin: (IA) Acrylic resin polymerized with the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsified polymer (emulsifier: anionic surfactant)

・ Urethane resin (IB)
Hydrogenated diphenylmethane diisocyanate unit: Terminal OH-modified polyhexamethylene carbonate unit: Dioxyethyldimethylammonium salt unit = 30:57:13 (mol%), a carbonate-based urethane resin aqueous dispersion.

-Oxazoline compound: (IIA)
Acrylic polymer epocross having an oxazoline group and a polyalkylene oxide chain (oxazoline group amount = 4.5 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)

-Epoxy compound: (IIB) polyglycerol polyglycidyl ether

-Melamine compound: (IIC) Hexamethoxymethylol melamine

-Particles: (IV) Silica particles with an average particle size of 0.07 μm

Example 1:
A mixed raw material in which polyesters (A), (B) and (C) are mixed at a ratio of 91%, 3% and 6%, respectively, is used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) are 97, respectively. Using the mixed raw material mixed at a ratio of% and 3% as the raw material for the intermediate layer, each of them was supplied to two extruders, melted at 285 ° C., and then placed on a cooling roll set at 40 ° C. An unstretched sheet was obtained by coextrusion and cooling and solidifying in a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount).
Next, after stretching 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in roll peripheral speed, the coating liquid 1 shown in Table 1 below was applied to one side of the vertically stretched film and guided to a tenter. It is stretched 4.0 times at 120 ° C. in the lateral direction, heat-treated at 225 ° C., then relaxed by 2% in the lateral direction, and the thickness of the coating layer (after drying) is 0.10 μm. A 125 μm polyester film was obtained.

When the obtained polyester film was evaluated, the haze was as high as 7.2% and the amount of haze reduction was 6.6%, and the distinctiveness between the film without the functional layer and the film with the functional layer was high. It was good. The characteristics of this film are shown in Table 2 below.

Examples 2-9:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating agent composition was changed to the coating agent composition shown in Table 1. As shown in Table 2, the finished polyester film had good distinguishability between a film having no functional layer and a film having a functional layer.

Comparative Example 1:
A polyester film was obtained in the same manner as in Example 1 except that the coating layer was not provided in Example 1. When the finished polyester film was evaluated, as shown in Table 2 below, the discriminability between the film without the functional layer and the film with the functional layer was inferior.

Comparative Examples 2-3:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the coating agent composition was changed to the coating agent composition shown in Table 1. When the finished polyester film was evaluated, as shown in Table 2 below, the discriminability between the film without the functional layer and the film with the functional layer was not sufficient.

The film of the present invention is suitable for forming a functional layer such as a hard coat layer such as a transparent electrode such as a touch panel or a film for molding, and for an application in which it is desired to easily distinguish between processed and unprocessed functional layers. It can be used.

Claims (14)

The polyester film has a coating layer on at least one side of the polyester film , the polyester film has a multi-layer structure, and particles are blended at least on the surface layer on the coating layer side, and the surface of the coating layer has an arithmetic mean roughness (Sa). A laminated polyester film characterized in that fine irregularities having a roughness of 25 nm or more and 60 nm or less are present, and the amount of decrease in haze value by the following measuring method is 1.0% or more.

Measuring method: As a functional layer, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, and 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) , 200 parts by weight of methyl ethyl ketone is applied onto the coating layer so that the dry film thickness is 2 μm to form a hard coat layer cured by irradiating with ultraviolet rays, and haze according to JIS K 7136. The value is measured and the difference from the haze value of the laminated polyester film before forming the functional layer is calculated. The polyester film has a coating layer on at least one side, the polyester film has a multi-layer structure, and particles are blended at least on the surface layer on the coating layer side, and the surface of the coating layer has an arithmetic mean roughness (Sa). It is characterized by having a function of discriminating between processed and unprocessed functional layers by having fine irregularities having a roughness of 25 nm or more and 60 nm or less and a decrease in haze value of 1.0% or more by the following measuring method. Laminated polyester film.

Measuring method: As a functional layer, 80 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, and 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals Co., Ltd.) , 200 parts by weight of methyl ethyl ketone is applied onto the coating layer so that the dry film thickness is 2 μm to form a hard coat layer cured by irradiating with ultraviolet rays, and haze according to JIS K 7136. The value is measured and the difference from the haze value of the laminated polyester film before forming the functional layer is calculated. The polyester film has a coating layer on at least one side, the polyester film has a multi-layer structure, and particles are blended at least on the surface layer on the coating layer side, and the surface of the coating layer has an arithmetic mean roughness (Sa). There are fine irregularities of 25 nm or more and 60 nm or less, and when the hard coat layer is provided on the coating layer and the hard coat layer is formed on the coating layer, the haze value is 1.0% or more. A laminated polyester film characterized by a drop. The laminated polyester film according to claim 1 or 2, which has a functional layer on the coating layer. The laminated polyester film according to claim 4, wherein the functional layer is a hard coat layer. The laminated polyester film according to claim 5, wherein the hard coat layer is a polymerized cured product of a composition containing an active energy ray-curable (meth) acrylate. The laminated polyester film according to claim 1 or 2, wherein the surface height distribution of the coating layer has a sharpness (Sku) of 12 or less. The laminated polyester film according to any one of claims 1 to 7, wherein the coating layer is a layer formed by using a cross-linking agent in combination. The laminated polyester film according to any one of claims 1 to 8, wherein the coating layer contains particles. The laminated polyester film according to any one of claims 1 to 9, wherein the coating layer contains an acrylic resin or a urethane resin. A transparent electrode using the laminated polyester film according to any one of claims 1 to 10. A molding film using the laminated polyester film according to any one of claims 1 to 11. A coating layer is formed by in-line coating on the surface layer surface of at least one side of a polyester film having a multi-layer structure and having particles blended in at least one surface layer, and the coating layer and the polyester film are formed. It has a step of stretching to at least one side, and the surface of the coating layer has fine irregularities having an arithmetic mean roughness (Sa) of 25 nm or more and 60 nm or less, and a hard coat layer is provided as a functional layer on the coating layer. A method for producing a laminated polyester film, characterized in that the haze value is reduced by 1.0% or more when formed. It has a multi-layer structure, and has a step of forming a coating layer on the surface layer surface of at least one side of a polyester film in which particles are blended in at least one surface layer by heat treatment at 100 to 180 ° C. , There are fine irregularities with an arithmetic average roughness (Sa) of 25 nm or more and 60 nm or less, and when a hard coat layer is formed as a functional layer on the coating layer, the haze value decreases by 1.0% or more. A method for producing a laminated polyester film.