JP2003201357A - Optical polyester film - Google Patents

Abstract

(57) [Summary] [Problem] After providing an active energy ray-curable resin layer,
Provided is an optical polyester film which has less curl due to heat history during annealing and processing, has excellent appearance as an optical film, and has excellent adhesion to an active energy ray-curable resin layer. The film haze is 2.0% or less, and the
C., the heat shrinkage values in the vertical and horizontal directions after the treatment for 30 minutes are both in the range of 1.5 to 0.6%, and the difference between the heat shrinkage values in the vertical and horizontal directions is 0.5%. An optical polyester film having a coating layer provided on at least one surface in a film forming step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical polyester film, and more specifically, curling due to thermal history during annealing or processing after providing an active energy ray-curable resin layer is reduced, and workability and productivity are improved. The present invention relates to an optical polyester film having excellent adhesion to an active energy ray-curable resin layer.

[0002]

BACKGROUND OF THE INVENTION Biaxially stretched polyester films are excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, chemical resistance, etc., and are used as packaging materials, electrical insulating materials, metal deposition materials, plate-making materials. , Magnetic recording materials, display materials, transfer materials,
It is used in many applications including window sticking materials. In particular, recently, antistatic, antireflection, and electromagnetic wave shields have been used for pasting on the front panel glass surface of so-called flat displays such as base films for cathode-ray tubes for transparent touch panels and prism sheets used in liquid crystal display devices, cathode ray tubes, LCDs, PDPs and the like. Although it is widely used for various optical applications such as for base films of protective films provided with functional layers such as, the polyester film has a drawback that the appearance and optical properties are easily damaged because it is easily scratched. In order to prevent scratches, it is generally used by providing an active energy ray-curable resin layer. In particular, for personal digital assistants (PDAs), which have recently been in increasing demand, the precision of conductive circuits is remarkably high in order to achieve both light weight and small size and high functionality, and dimensional stability in the circuit forming process is also a strict requirement. Has become.

Conventionally, as a measure for improving the dimensional stability in the circuit forming process, a technique of reducing the heat shrinkage of the base polyester film by annealing or the like has been used. However, in recent years, the active energy ray-curable resin layer itself has been changed to a resin composition of a type having a large heat shrinkage rate in response to a demand for improving the surface hardness of the active energy ray-curable resin layer, and the base polyester film has a low heat shrinkage. The dimensional stability cannot be maintained only by rationalization. Therefore, recently, not only the base polyester film is annealed alone, but it is also possible to improve the dimensional stability by annealing after coating the active energy ray-curable resin layer, before the circuit forming step, or during the forming step. The number of cases is increasing. In this case, depending on the heat treatment conditions, curling occurs due to the difference in thermal shrinkage between the active energy ray-curable resin layer and the base polyester film, which may cause a decrease in workability and productivity, which is a problem. .

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is that curling due to thermal history during annealing or processing for improving dimensional stability is reduced. Another object of the present invention is to provide a useful film having excellent workability and excellent adhesiveness with an active energy ray-curable resin layer.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above circumstances, and as a result, found that a polyester film having a specific constitution can easily solve the above problems, and completed the present invention. I arrived.

That is, the gist of the present invention is that the film haze is 2.0% or less, and the heat shrinkage values in the longitudinal and transverse directions after treatment at 150 ° C. for 30 minutes are both 1.5 to 0.6%.
And the difference between the heat shrinkage values in the machine direction and the transverse direction is 0.5% or less, and at least one surface has a coating layer provided in the film forming step. Exists in the film.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the present invention, the polyester is a polyester obtained from an aromatic dicarboxylic acid or its ester and a glycol as main starting materials, and for example, 80% or more of repeating structural units are ethylene terephthalate units or ethylene-2,6-naphthalate. Unit or 1,4
-Refers to polyesters with cyclohexane terephthalate. Further, other third component may be contained as long as it does not deviate from the above range. As the aromatic dicarboxylic acid component, other than terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, one kind of isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxybenzoic acid), etc. Alternatively, two or more kinds can be used. As the glycol component, other than ethylene glycol, for example, diethylene glycol, propylene glycol, butanediol,
One or more of 1,4-cyclohexanedimethanol and neopentyl glycol can be used.

The intrinsic viscosity of polyester is usually 0.52.
˜0.80, preferably 0.55 to 0.75, more preferably 0.58 to 0.75. IV value is 0.52
When the amount is less than the above, the heat resistance and mechanical strength, which are excellent features of the polyester film used as a film, tend to be inferior. On the other hand, if the IV value exceeds 0.80, the negative tendency in the extrusion step during the production of the polyester film tends to be too large, which may reduce the productivity.

The film haze of the film of the present invention is 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less. The film of the present invention is widely used for optical applications because of its excellent transparency, but when the film haze exceeds 2.0%, it becomes unsuitable for optical applications. The total film thickness of the film of the present invention is usually 50 μm to 300 μm, preferably 75 μm to 250 μm. The total film thickness is 50
If it is less than μm, the film is not stiff, and even if the heat shrinkage ratio value is within the range of the present invention, curling may occur due to the heat shrinkage stress of the active energy ray-curable resin layer.
If it is thicker than 0 μm, workability tends to deteriorate due to its rigidity.

In the present invention, in order to impart slipperiness to the film and improve handleability, particles may be contained in the polyester to form appropriate protrusions on the film surface. Examples of such particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, inorganic particles such as molybdenum sulfide, crosslinked polymer particles, and oxalic acid. Examples thereof include organic particles such as calcium, and precipitated particles generated during polyester polymerization. These particles may be used in combination of two or more of the same or different types.

The average particle diameter of the above particles is usually 3.0 μm.
The range is preferably 2.5 μm or less, more preferably 2.0 μm or less. If the average particle size exceeds 3.0 μm, the life of the filter provided in the melt extrusion step in film production may be shortened. The content of particles in polyester is usually 30% by weight or less,
It is preferably 20% by weight or less, more preferably 10% by weight or less. If the content of particles exceeds 30% by weight, the strength of the film tends to decrease. The particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method of adding it as a slurry in which particles are dispersed in ethylene glycol or the like at any stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, it is used as dry particles, or when it has water or a boiling point of 2 or less.
2 as a slurry dispersed in an organic solvent at a temperature of 00 ° C or lower
A method of mixing with polyester using a shaft kneading extruder is preferable. Particles to be added may be crushed in advance, if necessary.
You may perform processes, such as dispersion, classification, and filtration.

As a method for adjusting the content of particles, it is effective to prepare a master raw material containing a high concentration of particles by the above-mentioned method, and add a raw material containing substantially no particles to the master raw material to dilute it. Is. In the present invention, if necessary, an antistatic agent, a stabilizer, a lubricant, a cross-linking agent, an anti-sticking agent, an antioxidant, a colorant (dye, pigment), a light-blocking agent, an ultraviolet absorber, etc. may be added to polyester. It may be contained. In the present invention, the polyester film may have a multilayer structure as long as the finally obtained properties satisfy the requirements of the present invention. For example, it may be a coextrusion laminated film. In the case of a multilayer structure, the above description applies to the outermost polyester.

In the present invention, the biaxially stretched polyester film is produced by either simultaneous biaxial stretching or sequential biaxial stretching, and sequential biaxial stretching is preferably adopted. In the sequential biaxial stretching, first, the molten polyester is extruded on the surface of the cooling rotary drum to obtain a sheet, and then this is stretched in the longitudinal direction of the film by a group of rolls having different peripheral speeds (longitudinal stretching), The film is stretched (transversely stretched) while being held by a clip in a direction orthogonal to the longitudinal direction. The above-mentioned longitudinal stretching and transverse stretching may be performed several times. Further, the divided longitudinal stretching and transverse stretching may be alternately performed. For example, a method of producing a high-strength film by a re-stretching method corresponds to this. In order to improve the surface hardness, the polyester film of the present invention is usually provided with an active energy ray-curable resin layer. In this case, the polyester film is generally inactive and thus has poor adhesiveness, and in order to improve the adhesiveness with the active energy ray-curable resin layer, a coating layer for improving the adhesiveness should be provided in advance. is necessary.

As a method for forming such a coating layer, a so-called in-line coating method in which coating is performed before the entrance of the tenter (before the completion of the oriented crystallization) and drying is performed in the tenter is preferable. Further, if necessary, various coatings may be performed by an off-line coating after the production of the polyester film. Such a coat may be either single-sided or double-sided. The material of the coating may be either water-based and / or solvent-based in the case of off-line coating, but is preferably water-based or water-dispersed in the case of in-line coating. Further, when the optical polyester film of the present invention is used for a display, the active energy ray-curable resin layer provided for improving the surface hardness is further provided thereon to prevent reflection of external light, electric shock due to static electricity, and prevention of dust adhesion. Further, a functional multilayer thin film for the purpose of electromagnetic wave shielding may be formed.

The coating layer of the polyester film of the present invention is preferably a combination of a crosslinking agent and various binder resins, and the binder resin is selected from polyester, acrylic polymer and polyurethane from the viewpoint of adhesiveness. At least one polymer selected from the above. Each of the above polymers shall also include their derivatives. The derivative refers to a copolymer with another polymer or a polymer in which a functional group is reacted with a reactive compound. Polyvinylidene chloride, chlorinated polyolefin, etc. also form a tough film and show good adhesion with the topcoat, but since they contain chlorine, they may generate harmful dioxin compounds containing chlorine when burned. However, this is not preferable in this respect. In addition, when the scrap of the coated film is reused, there is a problem that coloring and generation of corrosive gas occur, which is also not preferable.

The above polyester, acrylic polymer and polyurethane will be described in detail below. First, the following polyvalent carboxylic acid and polyvalent hydroxy compound can be exemplified as components constituting the polyester resin used as a coating agent in the present invention. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid,
2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,
2-potassium sulfoterephthalic acid, 5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-Hydroxybenzoic acid, trimellitic acid monopotassium salt and their ester-forming derivatives can be used, and as the polyvalent hydroxy compound, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A
-Ethylene glycol adduct, diethylene glycol,
Triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol
And polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate and the like can be used. A polyester resin is synthesized by a conventional polycondensation reaction.

In addition to the above, Japanese Patent Laid-Open No. 16563/1989
The polyester-based resin of the present invention also includes a composite polymer having a polyester component such as so-called acrylic graft polyester and polyester polyurethane in which a polyester polyol is chain-extended with isocyanate, which is described in JP-A No. The polyester resin used in the present invention is a coating agent using water as a medium, and may be a coating agent forcibly dispersed with a surfactant or the like, but is preferably a hydrophilic nonion such as polyethers. Ingredients,
It is a self-dispersion type coating agent having a cationic group such as a quaternary ammonium salt, and more preferably a water-soluble or water-dispersible polyester resin coating agent having an anionic group. The polyester having an anionic group is a compound having a compound having an anionic group bonded to the polyester by copolymerization or grafting, and sulfonic acid,
It is appropriately selected from carboxylic acid, phosphoric acid and their lithium salts, sodium salts, potassium salts, ammonium salts and the like.

The amount of anionic groups in the polyester resin is preferably in the range of 0.05 to 8% by weight. When the amount of the anionic group is less than 0.05% by weight, the water-solubility or water dispersibility of the polyester resin is poor, and when the amount of the anionic group exceeds 8% by weight, the water resistance of the coating layer is inferior or the coating layer absorbs moisture. The films stick to each other. The acrylic polymer used as a coating agent in the present invention is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as represented by acrylic and methacrylic monomers. These may be either homopolymers or copolymers. Also included are copolymers of these polymers with other polymers (eg, polyester, polyurethane, etc.). For example, it is a block copolymer or a graft copolymer. Alternatively, a polymer (polymer mixture in some cases) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion liquid is also included. Similarly, a polymer (polymer mixture in some cases) 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 (polymer mixture in some cases) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion is also included.

The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but typical examples of the compound are as follows. Various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid and citraconic acid, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth ) Various hydroxyl group-containing monomers such as acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxyfumarate, monobutylhydroxyitaconate; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) Various (meth) acrylic acid esters such as acrylate, butyl (meth) acrylate, lauryl (meth) acrylate; (meth) acrylamide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile Various nitrogen-containing vinyl monomers such as; styrene,
Various styrene derivatives such as α-methylstyrene, divinylbenzene and vinyltoluene, various vinyl esters such as vinyl acetate and vinyl propionate; γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, Chisso Corporation Made "Sila plane FM-
07 ”(methacryloyl silicon macromer) and the like, various silicon-containing polymerizable monomers; phosphorus-containing vinyl-based monomers; vinyl chloride, vinylidene chloride, vinyl fluoride,
Various vinyl halides such as vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene and hexafluoropropylene; various conjugated dienes such as butadiene.

There is no particular limitation on the production of the polymer from the above acrylic monomer, and it can be produced by a conventional method. For example, an organic solvent can be mixed with the above-mentioned various monomers and a polymerization initiator, and the mixture can be heated and stirred for polymerization. Alternatively, polymerization may be carried out by dropping the above-mentioned various monomers and the polymerization initiator while heating and stirring the organic solvent. Further, the organic solvent, the above-mentioned various monomers and the polymerization initiator may be polymerized at a high pressure in the autoclave. Further, water may be used in place of the organic solvent, and a surfactant may be used in combination if necessary, to carry out emulsion polymerization or suspension polymerization. The polymerization initiator required for reacting these monomers is not particularly limited.
However, the typical compounds among them are as follows.

Inorganic peroxides such as ammonium persulfate, hydrogen peroxide and the like; Acyl peroxides such as benzoyl peroxide and the like; Tertiary butyl hydroperoxide; Various alkyl hydros such as p-menthane hydroperoxide. Peroxide; various dialkyl peroxides such as di-tert-butyl peroxide, and further organic peroxides; various azo compounds such as azobisisobutyronitrile and azodi-tert-butane; The inorganic peroxide can also be used as a so-called redox catalyst in combination with a reducing agent. In this case, each component may be used as a single compound or a plurality of compounds may be used in combination. Typical compounds as the above reducing agent are as follows.

Organic amines, L-ascorbic acid, L-
Sorbic acid, cobalt naphthenate, cobalt octenoate, iron naphthenate, iron octenoate, etc. Examples of the polyurethane resin in the present invention include, for example, Japanese Examined Patent Publication No.
194, Japanese Patent Publication No. 46-7720, Japanese Patent Publication No. 4
6-10193, JP-B-49-37839, JP-A-50-123197, JP-A-53-1.
Known polyurethane-based resins disclosed in JP-A-26058, JP-A-54-138098, and the like, or polyurethane-based resins similar thereto can be used. For example, as the polyisocyanate, tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4 '
Examples thereof include dicyclohexylmethane diisocyanate and isophorone diisocyanate.

As the polyol, polyoxyethylene glycol, polyoxypropylene glycol,
Examples thereof include polyether polyols such as polyoxytetramethylene glycol, polyester adipates such as polyethylene adipate, polyethylene-butylene adipate and polycaprolactone, acrylic polyols, polycarbonate polyols and castor oil. Usually, a polyol having a molecular weight of 300 to 2000 is used. As the chain extender or crosslinking agent, ethylene glycol, propylene glycol, butanediol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, 4,4'-diaminodiphenylmethane, 4,4 '
-Diaminodicyclohexylmethane, water, etc. can be mentioned.

The above-mentioned polyurethane resin is an anionic substituent, for example, -SO3H group, -OSO3H group,-, for the purpose of improving the solubility in a solvent containing water as a main medium.
It preferably has a COOH group and an ammonium salt, an alkali metal salt or an alkaline earth metal salt thereof. Examples of the method for producing the polyurethane resin include the following production methods (1) to (3), but the present invention is not limited thereto.

(1) Polyisocyanate, polyol,
Production Method Using Compound Having Anionic Substituent for Chain Extender etc. For example, polyisocyanate having an anionic substituent can be obtained by a method of sulfonating an aromatic isocyanate compound. Further, an isocyanate compound having a sulfuric acid ester salt of amino alcohol or a diaminocarboxylic acid salt can also be used. (2) Production method of reacting a compound having an anionic substituent with an unreacted isocyanate group of the generated polyurethane As the compound having an anionic substituent, examples of the anionic substituent include bisulfite and amino. A compound having sulfonic acid and salts thereof, aminocarboxylic acid and salts thereof, sulfuric acid ester of amino alcohols and salts thereof, hydroxyacetic acid and salts thereof and the like can be used.

(3) Active hydrogen-containing group (O
(H, COOH, etc.) and a specific compound in the production method include, for example, dicarboxylic acid anhydride,
Tetracarboxylic acid anhydride, sultone, lactone, epoxycarboxylic acid, epoxysulfonic acid, 2,4-dioxo-oxazolidine, isatoic acid anhydride, hoston and the like can be used. It is also possible to use a 3- to 7-membered cyclic compound showing a salt type group such as carbyl sulfate or a group capable of forming a salt after ring opening.

Among the above polyesters, acrylic polymers and polyurethanes used as coating agents in the present invention,
A preferred polymer has a glass transition temperature (Tg) of 0 ° C. or higher, more preferably 40 ° C. or higher, is a polyester polyurethane among polyurethanes, has a carboxylic acid residue, at least a part of which is amine or ammonia. It is a polymer that has been made water-based. Polyester polyurethane is a polyurethane in which polyester is used as a polyol, and when used in an in-line coating in combination with the melamine resin of the present invention, a comprehensively excellent film is formed. Specifically, it exhibits strong adhesion with a topcoat, a transparent film, and excellent adhesion resistance. Polyether polyurethanes, polycarbonate polyurethanes and the like are industrially known as polyurethanes, but polyester polyurethanes are generally preferred when combined with the melamine resin of the present application.

Further, it is particularly preferable that the coating liquid of the present invention contains a water-soluble organic solvent having a boiling point higher than that of water. This improves the transparency of the coating film and the adhesiveness with the top coat agent. Specifically, the boiling point is 100 ° C. or higher and 300 ° C. or lower,
It is an organic solvent having a solubility in water at 1 ° C of 1% or more. For example, n-butyl alcohol, diacetone alcohol, cellosolve acetate, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, butyl carbitol, 3-methyl-methoxybutanol, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether. Ether, ethylene glycol monoisobutyl ether, texanol, dimethylformamide, N-methyl-2-pyrrolidone and the like can be mentioned.

As the cross-linking agent resin, melamine-based, epoxy-based, and oxazoline-based resins are generally used, but melamine-based resins are particularly preferable from the viewpoint of coatability and durable adhesiveness. Melamine-based resin is not particularly limited, melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting a lower alcohol with methylolated melamine, And mixtures of these and the like can be used.

The melamine resin is a monomer,
Alternatively, it may be either a condensate composed of a dimer or higher polymer, or a mixture thereof. As the lower alcohol used for the etherification,
Methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like can be preferably used. As the functional group, those having an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, an imino group-type methylated melamine resin, a methylol group-type melamine resin, and a methylol group-type Methylated melamine resin, complete alkyl type methylated melamine resin, etc. can be used. Among them, the methylolated melamine resin is the most preferable. Furthermore, an acidic catalyst such as p-toluenesulfonic acid may be used to accelerate the thermal curing of the melamine-based crosslinking agent.

The content of the melamine resin in the coating agent is usually 1 to 50% by weight, preferably 5 to 30% by weight. When the amount of the cross-linking agent resin is less than 1% by weight, the durable adhesiveness may not be sufficiently exhibited, and the effect of improving the solvent resistance tends to be insufficient, and when it exceeds 50% by weight, it is sufficient. Adhesiveness may not be exhibited. In the present invention, in order to further improve slipperiness, stickiness and the like, it is preferable to include inorganic particles or organic particles in the coating layer. The content of particles in the coating agent is usually 0.5 to 10% by weight, preferably 1 to 5% by weight.
Is. If the content is less than 0.5% by weight, the blocking resistance may be insufficient, and if it exceeds 10% by weight, the transparency of the film may be impaired and the sharpness of the image tends to decrease.

As the inorganic particles, silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black,
Examples thereof include molybdenum sulfide and antimony oxide. Of these, silicon dioxide is inexpensive and has a wide variety of particle sizes, and thus is easy to use. Examples of the organic particles include polystyrene or polyacrylate polymethacrylate having a crosslinked structure achieved by a compound containing two or more carbon-carbon double bonds in one molecule (for example, divinylbenzene).

The above-mentioned inorganic particles and organic particles may be surface-treated. Examples of the surface treatment agent include a surfactant, a polymer as a dispersant, a silane coupling agent, and a titanium coupling agent. The content of particles in the coating layer is preferably 10% by weight or less, and more preferably 5% by weight or less, as an appropriate addition amount that does not impair transparency. Further, the coating layer may contain an antistatic agent, an antifoaming agent, a coating property improving agent, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like. The coating agent is
As long as water is the main medium, a small amount of an organic solvent may be contained for the purpose of improving dispersion in water or improving film forming performance. It is necessary to use the organic solvent within the range of being soluble in water. As the organic solvent, n
-Aliphatic or alicyclic alcohols such as butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol, glycols such as propylene glycol, ethylene glycol, and diethylene glycol, n-butyl cellosolve, ethyl cellosolve, methyl cellosolve, Examples thereof include glycol derivatives such as propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, and amides such as N-methylpyrrolidone. Two or more kinds of these organic solvents may be used in combination, if necessary.

The coating method of the coating agent is, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater or the like, as shown in "Coating system" by Yuji Harazaki, published by Maki Shoten, 1979. Can be used.
The coating layer may be formed on only one side or both sides of the polyester film. When it is formed on only one surface, a coating layer different from the above-mentioned coating layer may be formed on the opposite surface to give other characteristics, if necessary.
The film may be subjected to a chemical treatment or an electric discharge treatment before the coating in order to improve the coating property and the adhesive property of the coating agent to the film. Further, in order to further improve the surface characteristics, discharge treatment may be performed after forming the coating layer.

The final dry thickness of the coating layer is usually 0.02 to 0.5 μm, preferably 0.03 to
It is in the range of 0.3 μm. Coating layer thickness is 0.02μm
If it is less than the above range, the effect of the present invention may not be sufficiently exhibited. When the thickness of the coating layer is more than 0.5 μm, the films tend to stick to each other, and particularly when the coated film is re-stretched to increase the strength of the film, it may stick to the roll during the process. It tends to be easier. The above-mentioned problem of sticking appears remarkably when the same coating layer is formed on both surfaces of the film. Further, the polyester film of the present invention has other thermoplasticity as long as it does not impair the effects of the present invention. Resins such as polyethylene naphthalate and polytrimethylene terephthalate can be mixed. Further, an ultraviolet absorber, an antioxidant, a surfactant, a fluorescent brightening agent, a lubricant, a light shielding agent, a matting agent, and a coloring agent such as a dye or a pigment may be added. If necessary, for the purpose of improving the slipperiness and abrasion resistance of the film, it is possible to add inert inorganic or organic fine particles to the polyester.

In the optical polyester film of the present invention, the biaxially stretched polyester film having a coating layer has a heat shrinkage ratio value of 1.5 to 0.6% in the longitudinal and transverse directions at 150 ° C. for 30 minutes. In addition, the difference between the heat shrinkage values in the vertical and horizontal directions must be 0.5% or less. When the heat shrinkage ratio is larger than 1.5%, a curl larger than 10 mm is generated on the polyester film surface by the annealing treatment after providing the active energy ray-curable resin layer, and the heat shrinkage ratio value is less than 0.6%. In this case, a curl larger than 10 mm occurs on the surface of the active energy ray-curable resin layer. Further, when the difference between the heat shrinkage rates in the vertical and horizontal directions is 0.5% or more, a curl larger than 10 mm occurs even within the above range of heat shrinkage rate values. The heat shrinkage in the longitudinal and transverse directions is preferably 1.3.
.About.0.9%, and the difference between the heat shrinkage values in the longitudinal and transverse directions is preferably within 0.3%.

The optical polyester film of the present invention comprises
It is used by forming an active energy ray-curable resin layer on the coating layer of a biaxially stretched polyester film. In the present invention, as the curing component of the active energy ray-curable resin layer,
Unsaturated polyester resin system, acrylic system, addition polymerization system,
A thiol / acrylic hybrid system, a cationic polymerization system, a hybrid system of cationic polymerization and radical polymerization, and the like can be used. Among these, acrylic curing components are preferable from the viewpoints of curability, scratch resistance, surface hardness, flexibility and durability. The acrylic curing component contains an acrylic oligomer as an active energy ray polymerizing component and a reactive diluent. And a photopolymerization initiator, a photosensitizer, and a modifier are contained as needed.

The acrylic oligomer typically includes an oligomer having a reactive acryloyl group or a methacryloyl group bonded to an acrylic resin skeleton. Other acrylic oligomers include polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, silicone (meth) acrylate, polybutadiene (meth) acrylate and the like. Further, an oligomer in which an acryloyl group or a methacryloyl group is bonded to a rigid skeleton such as melamine, isocyanuric acid, or cyclic phosphazene can be used.

The reactive diluent functions as a solvent in the coating step as a medium for the coating agent, and also has a group capable of reacting with a polyfunctional or monofunctional acrylic orgomer, so that the reactive diluent is It becomes a copolymerization component. Specific examples of the reactive diluent include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate. ) Acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, (meth) acryloyloxypropyl triethoxysilane, (meth) acryloyl Examples thereof include oxypropyltrimethoxysilane.

Examples of the photopolymerization initiator include 2,2-
Ethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothioxanthone, anthraquinone, phenyldisulfide, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone and the like can be mentioned. Examples of the photosensitizer include tertiary amines such as triethylamine, triethanolamine and 2-dimethylaminoethanol, alkylphosphine such as triphenylphosphine and thioether such as β-thiodiglycol.

As the modifier, a coatability improving agent, a defoaming agent,
Examples thereof include thickeners, inorganic particles, organic particles, lubricants, organic polymers, dyes, pigments, stabilizers and the like. They are,
It is used in a range that does not hinder the reaction by active energy rays, and the characteristics of the active energy ray-curable resin layer can be improved depending on the application. An organic solvent can be added to the composition of the active energy ray-curable resin layer in order to improve workability during coating and control the coating thickness. The active energy ray-curable resin layer is formed by applying the curable resin composition onto the surface of the coating layer and then irradiating the active energy ray to crosslink and cure the resin composition. The active energy rays include ultraviolet rays, visible rays, electron rays, X rays, α rays,
β rays and γ rays can be used. Irradiation with active energy rays is usually carried out from the coating layer side, but it may be carried out from the film surface side in order to enhance the adhesion to the film, and further, a reflection plate capable of reflecting active energy rays is provided on the film surface side. May be provided.

The thickness of the active energy ray-curable resin layer is usually 0.5 to 15 μm, preferably 1 to 10 μm. If the thickness of the cured resin layer is less than 0.5 μm, the surface hardness may be insufficient, and if it exceeds 15 μm, the curing shrinkage of the cured resin layer becomes large and the film curls toward the cured resin layer side. I have something to do. In the present invention, the surface hardness of the cured resin layer side is usually H or higher, preferably 2
It is H or more. If it is less than H, the scratch resistance is insufficient.

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EXAMPLES The present invention will now 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 evaluation methods in the examples are as follows. In the examples and comparative examples, "part" means "part by weight".

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester in which other components and pigments incompatible with the polyester are removed are precisely weighed and added to 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio). It melt | dissolved and it measured at 30 degreeC. (2) Average particle size centrifugal sedimentation type particle size distribution measuring device ("S" manufactured by Shimadzu Corporation)
A-CP3 type ") was used to measure the particle size by a sedimentation method based on the Stokes resistance law. Integration in equivalent spherical distribution of particles obtained by measurement (volume basis)
The value of 50% was taken as the average particle size.

(3) Heat shrinkage rate Using a hot air circulating furnace (manufactured by Tabai Seisakusho Co., Ltd.), the film was heat-treated for 30 minutes in a tensionless state in an atmosphere of 150 ° C., and the length of the sample before and after that was measured. Was calculated by the following formula. Thermal shrinkage (%) = (L0−L1) × 100 / L0 (where L0 is the sample length (mm) before heat treatment,
L1 means the sample length (mm) after heat treatment)

(4) Film haze According to JIS K 7105, the turbidity was measured by an integrating sphere type turbidimeter NDH-20H manufactured by Nippon Denshoku Industries Co., Ltd. (5) Curling amount of heat The active energy ray-cured resin layer coated product is cut into a size of 10 cm square, left standing in a hot air circulation oven at 150 ° C. for 30 minutes to be heat treated, left standing at room temperature for 30 minutes, and then cooled. It was placed on top and the amount of lifting at the four corners from the glass surface was measured and the maximum value was taken as the curl value. The concave curl was positively displayed on the side of the active energy ray-curable resin layer, and the concave curl was negatively displayed on the side of the polyester film, and the following absolute values of the curl values were ranked as follows. ⊚: Curling amount is less than 5 mm ◯: Curling amount is 5 to 10 mm ×: Curling amount is greater than 10 mm

(6) Adhesiveness of active energy ray-curable resin layer Immediately after the formation of the active energy ray-curable resin layer, 1 is applied to the cured layer.
A cross cut was inserted so that 100 grids were formed in the inch width, and a rapid peeling test was immediately performed with Cellotape (registered trademark), and the peeled area was evaluated. The judgment criteria are as shown in Table 3 below. ⊚: Number of cross-cuts peeled <5 ○: 5 ≦ number of cross-cuts peeled ≦ 10 Δ: 10 ≦ number of cross-cuts peeled ≦ 20 ×: 50 <number of cross-cuts peeled

(7) Appropriate active energy ray curable resin layer for optics For curling after heat treatment of the coated article, adhesiveness to the active energy ray curable resin layer, haze and other characteristics, it is suitable for optical applications such as touch panels. The appropriateness of
It was judged according to the following criteria. ◯: Good adhesion, low haze value, little curl after treatment, suitable for optical applications, and high in productivity. X: Not suitable for optical use because of problems such as adhesiveness, haze value, and large curl after heat treatment.

(Preparation of Coating Agent) The aqueous coating solutions shown in Table 1 below were mixed in the proportions shown in Table 2 to prepare aqueous coating agents P1 to P5.

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[Table 1]

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[Table 2]

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 containing 30 ppm of silica particles having an average particle diameter of 1.5 μm was dried by an ordinary method and supplied to an extruder, melted at 290 ° C. and extruded into a sheet. Then, the electrostatic application adhesion method was applied to quench on a cooling rotating roll to obtain an amorphous sheet having a thickness of 1950 μm. The obtained sheet is roll-stretched at 85 ° C. in the machine direction.
2.5 times, and further drawn at 95 ° C. for 1.3 times, and then coated with the aqueous coating agent P1 shown in Table 2, introduced into a tenter, and laterally drawn at 120 ° C. for 3.2 times. After heat treatment at 225 ° C., the film was wound into a roll at a production rate of 30 m / min, with a lateral rail relaxation of 0% and a constant rail width thereafter. The film thickness is 188μ
m, the intrinsic viscosity was 0.60. Then, an active energy ray-curable resin is applied on the coating layer of the above film so that the thickness after curing becomes 3 μm, and a high pressure mercury lamp with an energy of 120 W / cm is used for irradiation for about 15 seconds at an irradiation distance of 150 mm. Then, the polyester film of the present invention was obtained under the condition that curling did not occur in the state of the coated product. As the active energy ray curing resin, dipentaerythritol hexaacrylate 30 parts, tetrafunctional urethane acrylate 4
0 parts, bisphenol A type epoxy acrylate 2
A composition consisting of 7 parts and 1 part of 1-hydroxycyclohexyl phenyl ketone was used. The evaluation results are shown in Table 3 below.
And 4 are shown.

Examples 2 to 3 and Comparative Examples 1 to 8 In Example 1, the heat shrinkage temperature after heat treatment at 150 ° C. for 30 minutes was set to a predetermined value, and relaxation in the lateral direction after heat fixation was performed. The polyester film was produced in the same manner as in Example 1 except that the rate and the rail width until winding into a master roll were changed, and the type of coating layer formed during film formation was changed as shown in Table 3 below. Got (However, only in Comparative Example 1, a predetermined sample was obtained with the amount of silica particles contained in the polyester film being 70 ppm).

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[Table 3]

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[Table 4]

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According to the polyester film of the invention,
It is possible to provide a useful film with little curling due to heat history during the annealing treatment or processing process for improving dimensional stability, excellent workability, and excellent adhesiveness with the active energy ray-curable resin layer, Its industrial value is high.

Continued front page    F-term (reference) 2H042 BA02 BA20                 4F006 AA35 AB24 AB35 AB54 AB65                       AB76 BA01 CA05 DA04                 4F100 AA20 AK01D AK01E AK25                       AK36B AK36C AK42 BA02                       BA03 BA04 BA05 BA06 BA07                       BA10B BA10C BA10D BA10E                       BA15 CC00B CC00C DE01                       EH46 EJ38 EJ54 GB41 JA02A                       JB14D JB14E JL02 JL04                       JL04D JL04E JL11 JN01A                       YY00A YY00D YY00E

Claims (3)

[Claims] 1. A film haze of 2.0% or less, 15
The heat shrinkage ratio values in the vertical and horizontal directions after treatment at 0 ° C. for 30 minutes are both in the range of 1.5 to 0.6%, and the difference between the heat shrinkage ratio values in the vertical direction and the horizontal direction is 0. It is 5% or less, and has a coating layer provided in at least one surface in a film forming step, and is a polyester film for optics. 2. The optical polyester according to claim 1, wherein the curl amount after heating after applying an active energy ray-curable resin layer on the coating layer at 150 ° C. for 30 minutes is 10 mm or less. the film. 3. The optical polyester film according to claim 1, wherein the coating layer contains a melamine resin.