JP2003301057A - Easily adherent polyester film for optical application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily adherent film in which interference irregularities after formation of a hard coat layer are hard to be seen, which has good adhesion to the hard coat layer at a high temperature and high humidity, and is suited for optical applications. <P>SOLUTION: The easily adherent polyester film for optical applications is a polyester film having a coating layer provided in the film-forming step on at least one surface thereof, and it is characterized in that a film haze is ≤2.0%, and a ΔR to be defined by the formula: ΔR=Rs-Rc(min) is ≤2.0% (wherein Rs is a mean value of the absolute reflection factor at a wavelength of 2,400-2,000 nm on the surface of the coaling layer; and Rc(min) is a minimum value of the absolute reflection factor at a wavelength of 300-800 in the surface of the coating layer). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an easy-adhesive polyester film for optics, and more specifically, it is a polyester film in which unevenness of interference is hardly visible after forming a hard coat layer, and has a hard coat durable adhesion, transparency, scratch resistance, The present invention relates to an optical easy-adhesion polyester film having excellent workability and the like.

[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 attaching to base films for transparent touch panels and prism sheets used in liquid crystal display devices, and for attaching the front panel glass surface of so-called flat displays such as cathode ray tubes, LCDs and PDPs. 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 a hard coat layer. In addition, in order to enhance the adhesion to the hard coat layer, it is common to provide an optical polyester film with an easy adhesion layer to the hard coat layer.

When used as a surface sticker for a display, the unevenness of interference seen when light from a fluorescent lamp or the like is reflected on the hard coat layer side is regarded as an important appearance characteristic, but generally polyester is used as a base material. When the hard coat film is liable to show the interference unevenness, particularly when the easy adhesion layer is provided between the hard coat layer and the polyester film of the substrate, the interference unevenness is more noticeable due to the refractive index and the thickness of the easy adhesion layer. There is. In terms of appearance characteristics, the polyester film has a drawback that it is inferior in interference unevenness to a hard coat film based on triacetyl cellulose (TAC). Has become a big problem when it is used for pasting on the surface of a high quality display. As an improved method to make interference unevenness less visible,
Although a method of reducing the thickness unevenness of the base film (for example, JP 2001-71439 A) has been proposed,
This method has the effect of making it difficult to see the interference unevenness of the base film itself, but has not improved the appearance of the interference unevenness of the hard coat layer-formed product. Further, in order to improve the adhesiveness between the polyester film and the hard coat layer, it has been proposed to provide an easy-adhesion layer in JP-A-10-100349, but in order to improve the adhesiveness with the hard coat layer. When the compounding amount of the acrylic resin is increased, the adhesiveness with the hard coat is improved, but the refractive index of the easy-adhesion layer is lowered, so that there is a problem that unevenness of interference appears more conspicuously.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the problem to be solved is that interference unevenness after formation of a hard coat layer is difficult to see, and a hard coat layer is formed at high temperature and high humidity. An object of the present invention is to provide an easy-adhesion film having good adhesiveness and suitable for optical applications.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the above-mentioned circumstances, and as a result, found that a polyester film having specific spectral absolute reflectance characteristics can easily solve the above problems. The present invention has been completed.

That is, the gist of the present invention is a polyester film having a coating layer provided in the film-forming step on at least one surface, and having a film haze of 2.0% or less, and ΔR defined by the following formula: Is 2.0% or less. ΔR = Rs−Rc (min.) (In the above formula, Rs is the wavelength 2400 to the coating layer surface.
The average value of absolute reflectance at 2000 nm, Rc (min.) Means the minimum absolute reflectance value at the wavelength of 300 to 800 nm on the surface of the coating layer)

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The optical easy-adhesion polyester film of the present invention,
It may be a single layer or a multilayer of three or more layers. The optical easy-adhesion polyester film referred to in the present invention is a polyester film extruded by a so-called extrusion method that is melt-extruded from an extrusion die, and if necessary, oriented in the biaxial directions of the longitudinal direction and the transverse direction. It is a film made.

In the present invention, the polyester is obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. As the aromatic dicarboxylic acid, terephthalic acid,
2,6-naphthalenedicarboxylic acid and the like can be mentioned, and as the aliphatic glycol, ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol and the like can be mentioned. Typical polyesters include polyethylene terephthalate (PET), polyethylene-2,
6-naphthalene dicarboxylate (PEN) and the like are exemplified. Further, the polyester used in the present invention may be a homopolyester or a copolyester. In the case of copolymerized polyester, it is a copolymer containing 30 mol% or less of the third component. Examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid,
One or more of adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid) can be mentioned, and the glycol component can be ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4. -One or more kinds of cyclohexanedimethanol, neopentyl glycol and the like can be mentioned.

The film haze of the present invention is 2.0% or less, preferably 1.5% or less, and 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 film of the present invention has a difference ΔR (specifically, the following formula) between absolute reflectance values of at least one coating layer surface side of 2.0% or less, preferably 1.7% or less, and most preferably 1 It is less than 0.5%. ΔR = Rs−Rc (min.) (In the above formula, Rs is the wavelength 2400 to the coating layer surface.
The average value of absolute reflectance at 2000 nm, Rc (min.) Means the minimum absolute reflectance value at wavelengths of 300 to 800 nm on the surface of the coating layer.) When ΔR is larger than 2.0%, the hard coat layer is After being provided, the interference unevenness becomes clearly visible, which is a serious drawback in terms of appearance characteristics.

The effect of making uneven interference less visible in the present invention is the same for both the thermosetting resin type and the active energy ray-curing resin type as the hard coating agent, but the refractive index of the hard coating layer is 1.59. -1.50, and even more noticeable when it is in the range of 1.58-1.52. The total film thickness of the film of the present invention is
Usually 50 to 300 μm or more, preferably 75 to 250 μm
m. If the total film thickness is less than 50 μm, the workability of the final inspection and sticking to the display, which is carried out for each sheet after punching into single sheets, tends to be poor because the film has a weak stiffness. If it is thick, its rigidity may deteriorate workability.

The film of the present invention preferably has a total amount of oligomers (cyclic trimers) deposited on the front and back surfaces of the film, when heat-treated at 180 ° C. for 10 minutes, of not more than 15.0 mg / m ^2. , And more preferably 10.0 mg
/ M ² or less, particularly preferably 8.0 mg / m ² or less. Oligomer deposition on the film surface is 15.0 mg
If it exceeds / m ² , the film haze tends to deteriorate due to the heat history during processing. Further, in order to improve the durability and adhesion of the hard coat layer, it is preferable that the oligomer deposition amount on the film surface is 15.0 mg / m ² or less. In order to keep the amount of oligomers deposited on the surface of the film by heat treatment within the above range, a method using polyester having a low content of oligomers can be mentioned. Also, in the case of a co-extruded laminated film, by using polyester having a low oligomer content in the outermost layer, the oligomer deposition amount on the film surface after heat treatment can be suppressed within the above range. Specifically, the amount of oligomer contained in the polyester film is 5000 ppm or less, and further 4
By setting the content to 000 ppm, especially 3000 ppm or less, oligomers deposited on the film surface when heated can be prevented.

It is known that the oligomer in the polymer increases due to the melting step in film formation, and the amount of increase is strongly influenced by the water content in the polymer, the temperature during melting and the residence time. , About 100 to 5000 ppm. In order to make the amount of oligomer contained in the above-mentioned film, considering the increase in the melting step,
The amount of oligomer in the polyester raw material is 4000
ppm or less, further 3000 ppm or less, especially 250
0 ppm or less is preferable. As a method for reducing the amount of oligomer in the polyester, conventionally known solid-phase polymerization can be used.

In the case of a film having a laminated structure, the thickness of the outermost layer, which is the thickness of only one side, is usually 3 μm or more and preferably 1/4 or less of the total thickness. Such thickness is 3 μm
If it is less than, due to heat history during processing, the oligomer (cyclic trimer) contained in the inner layer is deposited on the film surface,
There is a case that the production line is contaminated and the film haze is deteriorated. If it is thicker than 1/4 of the total thickness, the haze value due to the lubricant particles mixed in the outermost layer film to improve the winding property of the film (particularly, The internal haze value) becomes high, and the transparency of the film tends to deteriorate. The average particle size of the particles to be blended in the polyester film is not particularly limited, but is usually 0.02 μm to 3 μm, preferably 0.02 μm to 2.5 μm, and more preferably 0.02 μm to 2 μm. Is. Average particle size 0.0
When particles having a particle size of less than 2 μm are used, the film surface tends to be flat and the winding properties in the film manufacturing process tend to be poor. Further, when the average particle size exceeds 3 μm, the degree of roughening of the film surface may be too large, and the film may be hazy.

In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage of producing a polyester, but is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification, or after the completion of the transesterification reaction and before the start of the polycondensation reaction, The polycondensation reaction may proceed. Also, using a kneading extruder with a vent, a method of blending a slurry of particles dispersed in ethylene glycol or water with a polyester raw material, or using a kneading extruder, blending dried particles with a polyester raw material. It is done by the method.

The method for producing the film of the present invention will be specifically described below, but as long as the gist of the present invention is satisfied,
The present invention is not particularly limited to the following examples. The polyester chips dried by a known method are supplied to a melt extrusion device, and heated to a temperature higher than the melting point of each polymer to be melted. Next, the melted polymer is extruded from a die and rapidly cooled and solidified on a rotating cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to enhance the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid coating adhesion method is preferably adopted. In the present invention, the sheet thus obtained is biaxially stretched to form a film. Describing the stretching conditions specifically, the unstretched sheet is preferably 70
Stretching 2 to 6 times at ~ 145 ° C to form a longitudinal uniaxially stretched film, then stretching 2 to 6 times at 90 to 160 ° C in the transverse direction, and heat treating at 150 to 240 ° C for 1 to 600 seconds. Is preferred. Further, in this case, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the exit of the heat treatment is preferable. Further, it is also possible to add re-longitudinal stretching and re-transverse stretching if necessary.

The polyester film of the present invention is usually provided with a hard coat layer in order to improve the surface hardness. In this case, the polyester film is generally inactive and therefore has poor adhesiveness, and it is necessary to previously provide a coating layer for improving the adhesiveness in order to improve the adhesiveness with the hard coat layer. is there. As a method for forming such a coating layer, a so-called in-line coating method, in which the coating layer is coated before the entrance of the tenter (before the completion of oriented crystallization) and dried in the tenter, is preferable. In addition, if necessary, various coatings may be performed by off-line coating after the production of the 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.

When the polyester film of the present invention is used for optics, an antistatic agent, a coloring agent, a conductive material or the like is added to the hard coat layer provided for improving the surface hardness in order to impart other functionality. In addition, a functional multilayer thin film for the purpose of reflection of external light, electric shock due to static electricity, prevention of dust adhesion, and further electromagnetic wave shielding may be formed thereon. 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 at least selected from polyester, acrylic polymer and polyurethane from the viewpoint of adhesiveness. One polymer is used in combination. Each of the above polymers shall also include their derivatives. The term "derivative" as used herein means a copolymer with another polymer or a polymer obtained by reacting a functional group 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. Also,
When the scrap of the coated film is reused, there are problems such as coloring and generation of corrosive gas, 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, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, potassium dimethylolpropionate, etc. 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. If the amount of anionic groups is less than 0.05% by weight, the water solubility or water dispersibility of the polyester resin tends to deteriorate, and if the amount of anionic groups exceeds 8% by weight, the water resistance of the coating layer may be poor. , In some cases, the films may stick to each other due to moisture absorption.

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, in a polyurethane solution or polyurethane dispersion, carbon-
A polymer obtained by polymerizing a polymerizable monomer having a carbon double bond (a mixture of polymers in some cases) 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 above-mentioned polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds 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
Various nitrogen-containing vinylic monomers such as methylol acrylamide or (meth) acrylonitrile;
Various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene and vinyltoluene, various vinyl esters such as vinyl acetate and vinyl propionate; γ-methacryloxypropyltrimethoxysilane,
Various silicon-containing polymerizable monomers such as vinyltrimethoxysilane, "Cilaplane FM-07" (methacryloylose silicon macromer) manufactured by Chisso Corporation; phosphorus-containing vinyl-based monomers; vinyl chloride, vinylidene chloride, fluorine Various vinyl halides such as vinyl chloride, 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. That is, inorganic peroxides such as ammonium persulfate, hydrogen peroxide, etc .; acyl peroxides such as benzoyl peroxide, etc .; tertiary butyl hydroperoxide;
various alkyl hydroperoxides such as p-menthane hydroperoxide; various dialkyl peroxides such as di-tert-butyl peroxide,
Further, organic peroxides; various azo compounds such as azobisisobutyronitrile and azodi-tert-butane can be mentioned. The above-mentioned organic or inorganic peroxide is combined with a reducing agent to form a so-called redox catalyst. Can also be used as 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 reducing agent include organic amines, L-ascorbic acid, L-sorbic acid, cobalt naphthenate, cobalt octenoate, iron naphthenate,
Examples thereof include iron octenoate.

Examples of the polyurethane resin in the present invention include, for example, Japanese Patent Publication No. 42-24194 and Japanese Patent Publication No. 4-4.
6-7720, Japanese Patent Publication No. 46-10193,
JP-B-49-37839, JP-A-50-1231
Known polyurethane-based resins disclosed in JP-A-97, JP-A-53-126058, JP-A-54-138098, and the like or polyurethane-based resins similar thereto can be used. Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-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-based resin is an anionic substituent such as --SO ₃ H group or --OSO ₃ H group for the purpose of improving the solubility in a solvent containing water as a main medium.
It is preferable to have 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) Method for reacting the compound having an anionic substituent with the unreacted isocyanate group of the polyurethane produced As the compound having an anionic substituent, for example, bisulfite can be used as the anionic substituent. A compound having a salt, aminosulfonic 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) The 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 the coating agent in the present invention, particularly preferable polymers have a glass transition temperature (Tg) of 0 ° C.
As described above, further, the temperature is 40 ° C. or higher, it is a polyester polyurethane among polyurethanes, and it is a polymer having a carboxylic acid residue, at least a part of which is hydrophilized with amine or ammonia.

Polyester polyurethane is a polyurethane using polyester as a polyol,
When used for in-line coating in combination with melamine resin, it forms a comprehensively excellent film. 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, it is an organic solvent having a boiling point of 100 ° C. or higher and 300 ° C. or lower and a solubility in water at 20 ° C. of 1% or higher.
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, ethylene glycol monoisobutyl ether, texanol, dimethylformamide, N-methyl-2-
Examples thereof include pyrrolidone.

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-based resin may be either a monomer or 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 a 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, and imino group-type methylated melamine resin, methylol group-type melamine resin, methylol group-type methylated melamine resin, Complete alkyl type methylated melamine resin and the like 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. If the amount 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 is impaired, and the sharpness of the image tends to decrease. As the inorganic particles, silicon dioxide, alumina, zirconium oxide, kaolin, talc,
Examples thereof include calcium carbonate, titanium oxide, barium oxide, carbon black, 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, reverse roll coater, gravure coater, rod coater, 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 0.02-0.5 μm, preferably 0.03-.
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, inactive inorganic or organic fine particles may be added to the polyester.

[0038]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples and comparative examples, “part” means “part by weight”. The measuring method used in the present invention is as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester in which other polymer components incompatible with polyester and pigment are removed are precisely weighed, and a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) 10
0 ml was added and dissolved, and it measured at 30 degreeC.

(2) Average particle size (d50) Centrifugal sedimentation type particle size distribution analyzer SA manufactured by Shimadzu Corporation
Particle size was measured by the sedimentation method based on Stokes's resistance law using -CP3 type.

(3) Content of Oligomer (Cyclic Trimer) in Polyester A predetermined amount of polyester raw material or polyester film is dissolved in o-chlorophenol, reprecipitated with tetrahydrofuran and filtered to obtain linear polyethylene terephthalate. After removing the above, the obtained filtrate was then supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in the polyester, and this value was used as the amount of polyester used for measurement. It is divided to obtain the amount of oligomer (cyclic trimer) contained in the polyester. The amount of oligomer (cyclic trimer) determined by liquid chromatography was determined from the peak area ratio of the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing the preliminarily collected oligomer (cyclic trimer) and dissolving it in the accurately weighed DMF (dimethylformamide). The conditions of the liquid chromatograph were as follows. Mobile phase A: acetonitrile Mobile phase B: 2% acetic acid aqueous solution column: Mitsubishi Chemical Co., Ltd. MCI GEL ODS
1HU Column temperature: 40 ° C Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) Heat treatment of film A4 size Kent paper and polyester film to be heat treated are combined. At that time, clip the four corners with a paper clip etc. so that the measurement surface is on the outside, and stop the Kent paper and the polyester film. Under a nitrogen atmosphere, the polyester film is left to stand in an oven at 180 ° C. for 10 minutes for heat treatment.

(5) Amount of oligomer on the film surface The amount of oligomer on the surface of the film was measured by the method described below, and the total amount of oligomer on the surface of the film was used as the amount of oligomer on the surface of the film. The heat-treated polyester film is folded so that the top is open and the area of the bottom is 250 cm ² , thereby forming a square box. Then, in the box created by the above method, DMF10
Add 3 ml and let stand for 3 minutes, and collect DMF. Collected D
MF was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer in DMF, and this value was used as DMF.
Is divided by the contacted film area to obtain the film surface oligomer amount (mg / m ² ). The oligomer amount in DMF was determined from the peak area ratio of the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing the preliminarily collected oligomer (cyclic trimer) and dissolving it in the accurately weighed DMF. The concentration of the standard sample is 0.001 mg / ml to 0.01 mg /
The range of ml is preferred. The measurement conditions of the liquid chromatograph were as follows. Mobile phase A: acetonitrile Mobile phase B: 2% acetic acid aqueous solution column: Mitsubishi Chemical Co., Ltd. MCI GEL ODS 1H
U Column temperature: 40 ° C Flow rate: 1 ml / min Detection wavelength: 254 nm

(6) Film Haze after Heat Treatment A polyester film which has been heat treated by leaving it in an oven at 180 ° C. for 10 minutes under a nitrogen atmosphere is JIS-K710.
According to No. 5, integrating sphere type turbidimeter NDH-2 manufactured by Nippon Denshoku Industries Co., Ltd.
The turbidity of the film after heat treatment was measured by OD.

(7) Thickness of Laminated Polyester Layer A film piece was fixed and molded with an epoxy resin, cut with a microtome, and the cross section of the film was observed with a transmission electron microscope photograph. Of the cross section, two parallel to the film surface, the interface is observed by light and dark. The distance between the two interfaces and the film surface was measured from 10 photographs, and the average value was taken as the laminate thickness.

(8) Adhesion of Hard Coat (Initial Adhesion) Immediately after the formation of the hard coat layer, a cross-cut was made in the hard coat layer so that 100 squares per 1 inch width were obtained. A scotch tape (registered trademark) rapid peeling test was performed, and the peeled area was evaluated. The judgment criteria are as follows. ◎: Cross-cut peeling number = 0 ○: 1 ≤ cross-cut peeling number ≤ 10 △: 11 ≤ cross-cut peeling number ≤ 20 ×: 21 <cross-cut peeling number (durable adhesion) Before putting a cross-cut into the hard coat layer Further, the adhesiveness was evaluated in the same manner as the initial adhesiveness evaluation, except that it was aged in a humid heat oven at 60 ° C. and 90% RH for 100 hours.

(9) Uneven interference The hard coat layer-formed product is placed on a black board with the hard coat layer surface facing upward, and a three-wavelength neutral white 18 watt fluorescent lamp is illuminated from above to determine the shape and shade of uneven interference. It was visually inspected and judged according to the following criteria. ◯: The width of stripes with uneven interference is large (about 2 mm or more), and the boundary between stripes is unclear Δ: The width of stripes with uneven interference is large (about 2 mm or more), but the boundary between stripes is clear ×: The width of stripes of uneven interference is narrow and precise (within about 2 mm), and the boundary between stripes is clear.

(10) ΔR The back surface of the easy-adhesion layer (in the case of double-sided easy adhesion, the back surface of the measurement surface)
A black adhesive tape with a width of 50 mm (NITTO
O TAPE), after bonding, cut out the place without air bubbles into a sample piece of about 4 cm square, and use it for Shimadzu Corporation spectrophotometer UV3100 (multipurpose large sample chamber MPC-3100 installation type) Then, the 5 ° absolute reflectance of the surface of the easily adhesive layer was measured under the following measurement conditions. Measurement wavelength 300 to 2400 nm Sampling pitch 2 nm Scan speed Medium speed slit width 20 nm Next, 2n of absolute reflectance of wavelength 2000 to 2400 nm.
The average value Rs of m pitches and the minimum value Rc (min.) of absolute reflectance values at wavelengths of 300 to 800 nm were obtained, and the ΔR value was calculated from the following formula. ΔR = Rs-Rc (min.)

The method for producing the polyester used in the following Examples and Comparative Examples is as follows. <Production of Polyester> [Method of producing ester (A)] Dimethyl terephthalate 1
00 parts by weight and 60 parts by weight of ethylene glycol were used as starting materials, and magnesium acetate / tetrahydrate 0.09 was used as a catalyst.
Part by weight is placed in a reactor, the reaction start temperature is set to 150 ° C.,
With the evaporation of methanol, gradually raise the reaction temperature,
After 3 hours, the temperature was 230 ° C. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part of ethyl acid phosphate to this reaction mixture, 0.04 part of antimony trioxide was added and polycondensation reaction was performed for 4 hours. That is, the temperature is gradually raised from 230 ° C. to 280
℃ was made. On the other hand, the pressure was gradually reduced from atmospheric pressure, and finally set to 0.3 mmHg. After the reaction was started, the reaction was stopped at a time point corresponding to an intrinsic viscosity of 0.63 by changing the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (A) was 0.63, and the content of the oligomer (cyclic trimer) was 0.83% by weight.

[Production Method of Polyester (B)] The polyester (A) is pre-crystallized at 160 ° C. in advance and then
Solid phase polymerization was performed in a nitrogen atmosphere at a temperature of 220 ° C. to obtain a polyester (B) having an intrinsic viscosity of 0.75 and an oligomer (cyclic trimer) content of 0.24 wt%. [Method for producing polyester (C)] Polyester (A)
In the method for producing the above, after adding 0.04 part of ethyl acid phosphate, 0.2 part of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm and 0.04 part of antimony trioxide are added to obtain the ultimate limit. A polyester (C) was obtained by the same method as the method for producing the polyester (A) except that the polycondensation reaction was stopped at a time corresponding to a viscosity of 0.65. The obtained polyester (C) had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.82.
% By weight.

(Preparation of Coating Agent) The aqueous coating solutions shown in Table 1 below were mixed in the proportions shown in Table 2 below to prepare aqueous coating agents P1 to P3.

[0052]

[Table 1]

[0053]

[Table 2]

Example 1 90% of the above polyesters (B) and (C), respectively,
The mixed raw material mixed at a ratio of 0% is used as the raw material of the A layer, and the raw material of 100% of the polyester (B) is used as the raw material of the B layer.
Each of them was supplied to a single extruder and melted at 285 ° C., and then A layer was the outermost layer (surface layer) and B layer was an intermediate layer,
2 types, 3 layers (A
BA) was coextruded and solidified by cooling to obtain a non-oriented sheet. Then, the film was stretched 3.3 times in the machine direction at a film temperature of 81 ° C. using the roll peripheral speed difference, and then the water-based coating agent P1 shown in Table 2 was applied to both surfaces of this machine-stretched film and led to a tenter. Stretching 3.6 times in the transverse direction at 120 ° C, 2
After heat treatment at 25 ℃, relax by 2% in the lateral direction, and
The film was rolled up at a production rate of m / min to obtain a laminated polyester film having a coating layer having a thickness of 0.1 μm and a thickness of 188 μm and an intrinsic viscosity of 0.71. Then, a hard coat resin was applied onto the coating layer of the obtained film so that the thickness after curing was 6 μm, and 120 W /
Using a high pressure mercury lamp with energy of 10 cm, irradiation distance 10
Irradiation was performed at 0 mm for about 10 seconds to obtain a surface-cured film. As a hard coat resin, KAYAN manufactured by Nippon Kayaku
OVA FOP-1700 was used. FOP-170
After applying 0 to a glass plate, a high pressure mercury lamp with an energy of 120 W / cm was used, and an irradiation distance of 100 mm was about 10
After irradiating for 2 seconds to obtain a cured film of FOP-1700, the refractive index of the cured film was determined with an Abbe refractometer (light source D65) and found to be 1.54. The evaluation results are shown in Table 3 below.

Example 2 99% of the above polyesters (B) and (C), respectively,
285 is used as a raw material for the layer B.
A laminated polyester film was obtained in the same manner as in Example 1 except that the non-oriented sheet was obtained by extruding in a single-layer constitution onto a casting drum cooled at 40 ° C. and then extruded in a single layer constitution to be cooled and solidified after melting at 40 ° C.

Examples 3 and 4, Comparative Examples 1 to 4 In Example 1, the polyester raw materials used in the layers A and B and their compounding ratios, the types of coating layers formed during film formation, and the layers A and B A laminated polyester film was obtained in the same manner as in Example 1 except that the thickness constitution of the above was changed as shown in Table 3 below. The evaluation results of the films obtained in Examples and Comparative Examples are summarized in Tables 4 and 5 below.

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

As described above in detail, according to the polyester film of the present invention, it is difficult to see the unevenness of interference after the formation of the hard coat layer, and the optical use is excellent in the adhesiveness with the hard coat layer at high temperature and high humidity. It is possible to obtain an easily-adhesive film suitable for, and its industrial value is high.

Continued front page    F-term (reference) 4F006 AA35 AB24 AB35 AB37 BA01                       CA03 CA05                 4F100 AA20 AK41A AK41D AK41E                       AK42 BA02 BA03 BA06 BA10B                       BA10C CC00 CC00B CC00C                       EH20A EH20D EH20E EH46                       EH46B EH46C EJ54 GB41                       GB90 JK06 JK12 JK14 JL02                       JL11 JN01 JN06B JN06C                       YY00 YY00B YY00C

Claims (3)

[Claims] 1. A polyester film having a coating layer provided in a film-forming step on at least one surface, having a film haze of 2.0% or less and a ΔR defined by the following formula of 2.0% or less. An easy-adhesive polyester film for optics, which is ΔR = Rs−Rc (min.) (In the above formula, Rs is the wavelength 2400 to the coating layer surface.
The average value of absolute reflectance at 2000 nm, Rc (min.) Means the minimum absolute reflectance value at the wavelength of 300 to 800 nm on the surface of the coating layer) 2. The easily adhesive polyester film for optics according to claim 1, wherein the polyester film has a coextrusion laminated structure composed of at least three layers. 3. The easy-adhesive polyester film for optical use according to claim 1, wherein the total amount of oligomers on the front and back surfaces of the film when heat-treated at 180 ° C. for 10 minutes is 15 mg / m ² or less.