JP2005179486A - Highly transparent polyester film for optics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film which, when used as a liquid crystal component part such as a liquid crystal polarizing plate and a retardation plate or as a PDP component part, is less in scratches on the film surface and surface defects of oligomers and the like and shows good transparency, good optical performances and superior adhesion. <P>SOLUTION: The highly transparent polyester film for optical use less in the surface defects is a film which is obtained by providing at least one face of a biaxially oriented polyester film formed by use of a simultaneous biaxial orientation apparatus with a coating layer and which is characterized in that its film haze is ≤2.0% and the total amount of the oligomers of the front and reverse faces of the film is ≤15 mg/m<SP>2</SP>when the film is heat treated at 180°C for 10 min. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a polyester film for highly transparent optics, and more particularly to a polyester film for highly transparent optics used for various optics of members such as liquid crystal displays (hereinafter sometimes abbreviated as LCD) and PDP applications. It is.

  Conventionally, polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance. Magnetic tape, ferromagnetic thin film tape, photographic film, packaging It is widely used as a material for films, films for electronic parts, electrical insulation films, metal laminate films, films to be attached to glass surfaces such as glass displays, and protective films for various members.

  In recent years, polyester films have been frequently used for various optical films, such as prism lens sheets for liquid crystal display members, base films such as touch panels and backlights, antireflection base films, display explosion-proof base films, and PDP It is used for various applications such as filter films. The base film used for such an optical film is required to have excellent transparency, to have no foreign matter or scratches, and to have good adhesion to the functional layer depending on the application.

  There are several possible causes of foreign matter and scratches, but a normal stretching apparatus may cause scratches in contact with a roll during longitudinal stretching. In addition, oligomers deposited on the film surface adhere to the film surface and cause foreign matters, and accumulate in the tenter and eventually fall on the film surface to cause foreign matters. When an LCD or PDP is manufactured using such a film having foreign matter or scratches such as an oligomer, a product with poor visibility is produced, which makes it unsuitable for an optical film.

  Conventional methods for preventing scratches during longitudinal stretching have been dealt with strictly by controlling the particle size and the amount of particles contained in the film and increasing the peripheral speed difference between the roll and the film. However, the film haze has become too high, and the roll speed has fluctuated, causing scratches and causing problems.

On the other hand, as a method for preventing oligomer precipitation, reduction of the oligomer contained in the raw material by solid phase polymerization or improvement of the hydrolysis resistance of the polyester film using a terminal blocking material is performed. I came. However, in the case of solid phase polymerization, depending on the extrusion conditions, there are problems that oligomers increase at the time of extrusion or costs increase due to solid phase polymerization.
JP 2003-191413 A Japanese Patent Laid-Open No. 2003-301057

  The present invention has been made in view of the above circumstances, and the problem to be solved is that when used as a liquid crystal constituent member such as a liquid crystal polarizing plate or a retardation plate, or a PDP member, surface defects such as film surface scratches and oligomers are present. The object of the present invention is to provide a film having a small amount, good transparency, good optical performance and excellent adhesion.

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

That is, the gist of the present invention is a film in which a coating layer is provided on at least one side of a polyester film biaxially stretched using a simultaneous biaxial stretching apparatus, and the film haze is 2.0% or less, 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.

Hereinafter, the present invention will be described in more detail.
The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like. On the other hand, in the case of copolymerized polyester, a copolymer containing 20 mol% or less of the third component is preferable. The dicarboxylic acid component of the copolyester is a kind of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, P-oxybenzoic acid, etc.) or the like Two or more types can be mentioned, and examples of the glycol component include one or more types such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.

  In any case, the polyester referred to in the present invention is usually 80 mol% or more, preferably 90 mol% or more of polyethylene terephthalate having ethylene terephthalate units and polyethylene-2,6-naphthalate having ethylene-2,6-naphthalate units. Refers to a polyester that is the like.

  The polyester in the present invention is a conventionally known method, for example, a method of directly obtaining a low-polymerization degree polyester by reaction of a dicarboxylic acid and a diol, or a lower alkyl ester of a dicarboxylic acid and a diol reacted with a conventionally known transesterification catalyst. Then, it can obtain by the method of performing a polymerization reaction in presence of a polymerization catalyst. As the polymerization catalyst, a known catalyst such as an antimony compound, a germanium compound, or a titanium compound may be used. Preferably, the amount of antimony compound is zero or 100% or less as antimony to reduce film dullness. .

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dl / g or more, and more preferably 0.40 to 0.90 dl / g.

  You may mix | blend particle | grains in the polyester layer in this invention with the main objective of providing lubricity. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples thereof include particles of magnesium silicon oxide, kaolin, aluminum oxide, titanium oxide and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

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

  The average particle size of the particles used is usually preferably 0.01 to 3 μm. When the average particle size is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle size exceeds 3 μm, the surface roughness of the film becomes too rough and transparent. May be inferior.

  Furthermore, the particle content in the polyester is usually in the range of 0.0003 to 0.7% by weight, preferably 0.0005 to 0.4% by weight. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 0.7% by weight, the transparency of the film is insufficient. There are cases.

  The method for adding particles to the polyester is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester, but the polycondensation reaction may proceed preferably after the esterification stage or after the transesterification reaction. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, heat stabilizers, lubricants, dyes, pigments and the like can be added to the polyester film in the present invention as necessary. Depending on the use, an ultraviolet absorber, particularly a benzoxazinone-based ultraviolet absorber, may be contained.

  The thickness of the polyester film of the present invention is not particularly limited as long as it can be formed as a film, but is usually 9 to 300 μm, preferably 20 to 200 μm, and more preferably 25 to 188 μm.

  The film of the present invention has a film haze of 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. However, when the film haze exceeds 2.0%, it is unsuitable for optical use.

  The polyester film for optical use of the present invention, particularly a display, has a color tone b * value measured by one transmission method of usually 1.5 or less, preferably 1.0 or less, more preferably 0.8 or less. If the b * value exceeds 1.5, the yellow color is strong and may be inappropriate for display.

In the film of the present invention, the total amount of oligomer (cyclic trimer) deposited on the film surface after heat treatment at 180 ° C. for 10 minutes is 15 mg / m ² or less, more preferably 10.0 mg / m ^2. m ² or less, particularly preferably 8.0 mg / m ² or less. When the oligomer precipitation amount on the film surface exceeds 15 mg / m ² , the problem described above is likely to be caused.

  In order to make the oligomer precipitation amount on the film surface by heat treatment within the above range, it is particularly preferable to use a laminated film composed of at least three layers by coextrusion and use a polyester with a low oligomer content in the outermost layer constituting the surface layer. The amount of oligomer deposition on the film surface after heat treatment can be suppressed to the above range.

  The film of the present invention preferably has a laminated structure. In this case, the outermost layer thickness is preferably 3 μm or more and ¼ or less of the total thickness in terms of the thickness of only one side. When the thickness is less than 3 μm, oligomers (cyclic trimers) contained in the inner layer are deposited on the film surface due to heat history during processing, etc., and contamination of the production line and an increase in the amount of foreign matter on the film surface are observed. On the other hand, if it is thicker than 1/4 of the total thickness, the amount of particles blended in the outermost layer may increase and the transparency may be impaired.

  In the case of a laminated structure, it is also preferable that the particles are contained only in the outermost layer forming the surface layer and the particles are not contained in the other inner layers.

  On the other hand, when a single-layer structure is used, it is also preferable that particles be contained in the front and back coating layers so that the film does not contain particles as much as possible.

Moreover, when adding various additives, such as a ultraviolet absorber, it is preferable to mix | blend with the intermediate | middle layer of a laminated | multilayer film.
When the film of the present invention is used for optical applications, it is essential to provide a coating layer in order to provide a hard coat layer or a vapor deposition layer. In this case, as a method of forming the coating layer on the polyester film, a so-called in-line coating method in which coating is performed before the tenter entrance and drying is performed in the tenter is preferable. Of course, if necessary, an off-line coat may be applied after the production of the film. Moreover, it does not matter on one side or both sides. The coating material may be either water-based and / or solvent-based for off-line coating, but is preferably water-based or water-dispersed for in-line coating.

  In addition, since the film of the present invention is used for optics, it is also preferable to form a functional multilayer thin film for the purpose of preventing dust reflection due to reflection of external light and static electricity, as well as electromagnetic shielding, in addition to improving adhesiveness. .

  The coating layer of the polyester film of the present invention is preferably composed of 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 derivatives thereof. The derivative here refers to a polymer obtained by reacting a reactive compound with a copolymer or a functional group with another polymer. Polyvinylidene chloride, chlorinated polyolefin, etc. also form a tough film and show good adhesion to the topcoat, but since these contain chlorine, they may generate harmful dioxin compounds containing chlorine during combustion. This is not preferable in this respect. Moreover, there is a problem of coloring and generation of corrosive gas when the scrap of the coated film is reused, which is not preferable in this respect.

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 illustrated as a component which comprises the polyester-type resin used as a coating agent by this invention. That is, as 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-sodium sulfoisophthalic 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 ester-forming derivatives thereof can be used. Examples of polyvalent hydroxy compounds include ethylene glycol, 1,2-propylene glycol, 1,3 -Propylene glycol, 1,3-propane Diol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol Additives, 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, a composite polymer having a polyester component such as a so-called acrylic graft polyester described in JP-A-1-165633 and a polyester polyurethane in which a polyester polyol is chain-extended with an isocyanate is also used in the polyester system of the present invention. Included in the resin.

  The polyester-based resin used in the present invention is a coating agent using water as a medium, and may be a coating agent forcibly dispersed by a surfactant or the like, but preferably a hydrophilic nonion such as a polyether. A self-dispersing coating agent having a cationic group such as a component or a quaternary ammonium salt, 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 in which a compound having an anionic group is bonded to the polyester by copolymerization or grafting, etc., and sulfonic acid, carboxylic acid, phosphoric acid and lithium salt, sodium salt, potassium salt thereof. And an ammonium salt or the like.

  The amount of the anionic group of the polyester resin is preferably in the range of 0.05 to 8% by weight. If the anionic group amount is less than 0.05% by weight, the water-solubility or water-dispersibility of the polyester resin tends to be poor. If the anionic group amount exceeds 8% by weight, the water resistance of the coating layer may be poor. The film 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 typified by an acrylic or methacrylic monomer. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but a typical compound is exemplified as follows.

  Various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citraconic acid, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meta ) Various hydroxyl group-containing monomers such as acrylate, 4-hydroxybutyl (meth) acrylate, monobutylhydroxy fumarate, monobutylhydroxy itaconate; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) Various (meth) acrylic esters such as acrylate, butyl (meth) acrylate, lauryl (meth) acrylate; (meth) acrylimide, diacetone acrylamide, N-methylol acrylamide, (meth) acrylonitrile, etc. Various nitrogen-containing vinyl monomers such as: various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene and vinyltoluene, various vinyl esters such as vinyl acetate and vinyl propionate; γ-methacryloxypropyl Various silicon-containing polymerizable monomers such as trimethoxysilane, vinyltrimethoxysilane, “Silaplane FM-07” (methacryloilosilicon macromer) manufactured by Chisso Corporation; phosphorus-containing vinyl monomers; vinyl chloride, Various types of vinyl halides such as bilidene chloride, vinyl fluoride, vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene; various conjugated dienes such as butadiene.

  There is no restriction | limiting in particular in manufacture of the polymer from the said acrylic monomer, It can manufacture by a conventional method. For example, an organic solvent, the above-mentioned various monomers and a polymerization initiator can be mixed, heated and stirred, and polymerized. Or you may superpose | polymerize by dripping said various monomers and a polymerization initiator, heating and stirring an organic solvent. Furthermore, you may superpose | polymerize an organic solvent, said various monomers, and a polymerization initiator at high pressure within an autoclave. Further, water may be used in place of the organic solvent, and emulsion polymerization or suspension polymerization may be performed using a surfactant in combination as necessary.

  The polymerization initiator required for reacting these monomers is not particularly limited. However, typical compounds among them are as follows.

  Inorganic peroxides such as ammonium persulfate and hydrogen peroxide; acyl peroxides such as benzoyl peroxide; tertiary butyl hydroperoxide; various alkyl hydroperoxides such as p-menthane hydroperoxide Oxides; various dialkyl peroxides such as di-tert-butyl peroxide; and organic peroxides; various azo compounds such as azobisisobutyronitrile and azodi-tert-butane. Organic or inorganic peroxides can also be used as so-called redox catalysts in combination with a reducing agent. In this case, each component may be performed with one compound, or plural components may be used in combination. Typical examples of the reducing agent include organic amines, L-ascorbic acid, L-sorbic acid, cobalt naphthenate, cobalt octenoate, iron naphthenate, and iron octenoate.

  Examples of the polyurethane resin in the present invention include, for example, Japanese Patent Publication No. 42-24194, Japanese Patent Publication No. 46-7720, Japanese Patent Publication No. 46-10193, Japanese Patent Publication No. 49-37839, Japanese Patent Publication No. 50-123197. Known polyurethane resins disclosed in JP-A-53-126058, JP-A-54-138098, or the like, or polyurethane resins based thereon can be used.

  Examples of the polyisocyanate include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and the like.

  Polyols include polyether polyols such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol, polyester polyols such as polyethylene adipate, polyethylene-butylene adipate, and polycaprolactone, acrylic polyols, and polycarbonates. A polyol, a castor oil, etc. can be mentioned. Usually, a polyol having a molecular weight of 300 to 2000 is used.

  Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, butanediol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodicyclohexylmethane, Water etc. can be mentioned.

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

(1) Production method using a compound having an anionic substituent in polyisocyanate, polyol, chain extender, etc. For example, a polyisocyanate having an anionic substituent is obtained by a method of sulfonating an aromatic isocyanate compound. Can do. In addition, an isocyanate compound having a sulfate or diaminocarboxylate of an amino alcohol can also be used.

(2) Process for reacting a compound having an anionic substituent with an unreacted isocyanate group of the produced polyurethane As the compound having an anionic substituent, examples of the anionic substituent include bisulfite, amino A compound having a sulfonic acid and a salt thereof, an aminocarboxylic acid and a salt thereof, a sulfate of an amino alcohol and a salt thereof, hydroxyacetic acid and a salt thereof, and the like can be used.

(3) Process for reacting active hydrogen-containing groups (OH, COOH, etc.) of polyurethane with specific compounds Specific compounds include, for example, dicarboxylic acid anhydride, tetracarboxylic acid anhydride, sultone, lactone, epoxycarboxylic acid , Epoxysulfonic acid, 2,4-dioxo-oxazolidine, isatoic anhydride, hoston, and the like can be used. A 3-membered 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 can also be used.

  Among the polyesters, acrylic polymers, and polyurethanes that are used as coating agents in the present invention, particularly preferred polymers have a glass transition temperature (Tg) of 0 ° C. or higher, more preferably 40 ° C. or higher. It is a polyurethane having a carboxylic acid residue, at least a part of which is made water-based using an amine or ammonia.

  Polyester polyurethane is a polyurethane using polyester as a polyol, and forms a comprehensively excellent film when used in in-line coating in combination with a melamine resin. Specifically, it exhibits strong adhesion to the top coat, a transparent coating, and excellent adhesion resistance. Polyurethanes, polycarbonate-based polyurethanes and the like are known industrially from polyurethane, but polyester-based polyurethanes are generally preferred when combined with the melamine resin of the present application.

  In particular, the coating liquid of the present invention preferably contains a water-soluble organic solvent having a boiling point higher than that of water. Thereby, transparency of a coating film and adhesiveness with a topcoat improve. Specifically, the organic solvent has 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 Examples include ether, ethylene glycol monoisobutyl ether, texanol, dimethylformamide, N-methyl-2-pyrrolidone and the like.

  As the crosslinking agent resin, melamine-based, epoxy-based, and oxazoline-based resins are generally used, but melamine-based resins are particularly preferable from the viewpoints of coatability and durable adhesiveness. The melamine resin is not particularly limited, but melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound partially or completely etherified by reacting methylolated melamine with a lower alcohol, And a mixture thereof can be used.

  In addition, the melamine resin may be either a monomer or a condensate composed of a dimer or higher multimer, 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. The functional group has an imino group, a methylol group, or an alkoxymethyl group such as a methoxymethyl group or a butoxymethyl group in one molecule, and an imino group type methylated melamine resin, a methylol group type melamine resin, or a methylol group type. A methylated melamine resin, a fully alkyl type methylated melamine resin, or the like can be used. Of these, methylolated melamine resins are most preferred. Further, an acidic catalyst such as p-toluenesulfonic acid can be used to accelerate the thermal curing of the melamine-based crosslinking agent.

  The compounding quantity of the melamine resin in a coating agent is the range of 1 to 50 weight% normally. When the blending amount of the crosslinking 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. There is a risk that the good adhesion will not be demonstrated.

  In the present invention, it is preferable to contain inorganic particles or organic particles in the coating layer in order to further improve the slipperiness, adhesion and the like. The amount of the particles in the coating agent is usually 0.5 to 10% by weight, preferably 1 to 5% by weight. When the blending amount is less than 0.5% by weight, the blocking resistance may be insufficient. When the blending amount exceeds 10% by weight, the transparency of the film is hindered and the sharpness of the image tends to be lowered.

  Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among these, silicon dioxide is easy to use because it is inexpensive and has various particle sizes.

  Examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound (for example, divinylbenzene) containing two or more carbon-carbon double bonds in one molecule.

  The above 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, a titanium coupling agent, and the like. The content of the particles in the coating layer is preferably 10% by weight or less, more preferably 5% by weight or less as an appropriate addition amount that does not impair the 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.

  As long as water is the main medium, the coating agent may contain a small amount of an organic solvent for the purpose of improving dispersion in water or improving the film-forming performance. It is necessary to use the organic solvent as long as it is soluble in water. Examples of the organic solvent include aliphatic or alicyclic alcohols such as n-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, Glycol derivatives such as ethyl cellosolve, methyl cellosolve, 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, amides such as N-methylpyrrolidone Can be mentioned. These organic solvents may be used in combination of two or more as required.

  As a coating method of the coating agent, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, or a coating apparatus other than these as shown in Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method” Can be used.

  The coating layer may be formed only on one side of the polyester film or on both sides. When formed only on one side, other characteristics can be imparted by forming a coating layer different from the above-mentioned coating layer on the opposite surface as necessary. In addition, in order to improve the applicability | paintability and adhesiveness to the film of a coating agent, you may give a chemical process and an electrical discharge process to a film before application | coating. Further, in order to further improve the surface characteristics, a discharge treatment may be performed after the coating layer is formed.

  The thickness of the coating layer is usually in the range of 0.02 to 0.5 μm, preferably 0.03 to 0.3 μm, as the final dry thickness. When the thickness of the coating layer is less than 0.02 μm, the effect of the present invention may not be sufficiently exhibited. When the thickness of the coating layer exceeds 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 adheres to the roll in the process. There is a tendency to become easy. The above problem of sticking appears particularly when the same coating layer is formed on both sides of the film.

In the film of the present invention, foreign matter having a maximum diameter of 150 μm or more present in the film is usually 0.0 pieces / m ² , and foreign matter having a maximum diameter of 30 μm or more is usually 1.5 pieces / m ² or less, preferably 1. 0 / m ² or less. Defects in the resulting LCD or PDP image occur if the foreign matter with a maximum diameter of 150 μm or more deviates from the condition of 0.0 particles / m ² or less than 1.5 μm / m ² May not be a product. Further, the number of scratches having a width of 10 μm or more present on the film surface is preferably 10 / m ² or less, more preferably 5 / m ² or less. If the number of scratches having a width of 10 μm is more than 10 / m ² , the product may not be produced in the same manner.

  As one method for satisfying the above-described requirements, the present invention must use a simultaneous biaxial stretching apparatus as a stretching method. For the simultaneous biaxial stretching apparatus, a conventionally known stretching method such as a screw method, a pantograph method, or a linear drive method can be adopted. The “screw method” is a method in which a clip is placed in a groove of a screw to widen a clip interval. The “pantograph method” is a method of expanding the clip interval using a pantograph. The “linear drive system” has an advantage that the clip interval can be arbitrarily adjusted by applying the linear motor principle and controlling the clips individually.

  Furthermore, simultaneous biaxial stretching may be performed in two or more stages. In that case, the stretching location may be performed in one tenter or a plurality of tenters may be used in combination.

  In addition, the incidental effect by employ | adopting simultaneous biaxial stretching prescription | regulation in this invention is preventing the oligomer precipitation on the film surface by the reduction of the film surface damage at the time of polyester film manufacture. For example, in the present invention, when a film surface of a polyester film is locally applied with a pencil or the like, and the film is heat-treated, the surrounding area may be precipitated in a larger amount than in other areas. They know. Moreover, when the part where a film surface flaw exists is similarly heat-treated, the region around the film surface flaw may precipitate more oligomers than other regions. Although the mechanism is unknown, the presence of scratches on the film surface often induces oligomer precipitation.

  The polyester film of the present invention can be mixed with other thermoplastic resins such as polyethylene naphthalate and polytrimethylene terephthalate as long as the effects of the present invention are not impaired. Moreover, you may mix | blend coloring agents, such as a ultraviolet absorber, antioxidant, surfactant, a fluorescent whitening agent, a lubricant agent, a light-shielding agent, a matting agent, and a dye, a pigment. In addition, for the purpose of improving the slipperiness and abrasion resistance of the film, inert inorganic or organic fine particles can be blended with the polyester as necessary.

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

  A method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method are preferably employed.

  For the longitudinal and transverse stretching of the unstretched film thus obtained, it is essential to adopt a simultaneous biaxial stretching method. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film.

  In addition, a so-called coating stretching method (in-line coating) for treating the film surface during the above-described stretching process of the polyester film can be performed. When a coating layer is provided on a polyester film by a coating stretching method, coating can be performed simultaneously with stretching and the thickness of the coating layer can be reduced according to the stretching ratio. Can be manufactured.

  Regarding the coating layer provided on the polyester film constituting the release film in the present invention, the binder polymer constituting the coating layer is not particularly limited, but the present invention employs a simultaneous biaxial stretching method, It is important to select a coating agent that has good follow-up to the stretching of the coating layer because the stretch ratio after coating is larger than the former because it coats an unstretched sheet compared to conventional longitudinal stretching and before lateral stretching. It is.

  When it is necessary to further suppress the amount of oligomer extracted from the surface of the release layer of the release film after heat treatment (180 ° C., 10 minutes), the release film of the present invention contains polyvinyl alcohol in the coating layer. Is also preferable. The content of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) in the coating layer is not particularly limited, but is preferably 10 to 100% by weight, more preferably 20 to 90% by weight, most preferably It is in the range of 30 to 80% by weight. If the PVA content is less than 10% by weight, the oligomer precipitation preventing effect may be insufficient. Further, the degree of polymerization of PVA is not particularly limited, but usually 100 or more, preferably 300 to 40,000 is suitably used for applications. On the other hand, the saponification degree of PVA is not particularly limited, but 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is suitably used. As a specific example, saponified vinyl acetate is used. Etc.

  In the present invention, when coating is performed off-line as necessary, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, etc. may be used as a method of providing a coating layer on the polyester film. it can. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

The coating amount of the coating layer from the viewpoint of coating property, usually 0.005~1g / ^{m 2,} preferably in the range from 0.005 to 0.5 / ^{m 2.} If the coating amount is less than 0.005 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, if it is thicker than 1 g / m ² , the coating film adhesion and curability of the release layer itself may be lowered.

  Furthermore, in the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided as long as the gist of the present invention is not impaired, and the polyester film has a surface such as corona treatment or plasma treatment. Processing may be performed.

    Since the film thus obtained has no scratches, it is preferably applied to a highly transparent film used for a flat panel TV (LCD, PDP, etc.) having a size of 30 inches or more. In particular, it is applied to a television of 40 inches or more, more preferably 50 inches or more.

  The film of the present invention is excellent in transparency as a film used for liquid crystal constituent members such as liquid crystal polarizing plates and retardation plates and PDP members, has little oligomer generation and surface defects, and is excellent in adhesiveness. Value is extremely high.

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

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

(2) Measurement of average particle diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Measurement of film surface oligomer amount (OL) By the method shown below, the film surface oligomer amount of front and back was measured, and the sum total of the film surface oligomer amount of the surface and back was made into the film surface oligomer amount. A square box is created by folding the polyester film after heat treatment (180 ° C., 10 minutes) so that the upper part is opened and the area of the bottom side is 250 cm 2. Next, 10 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to a liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of oligomer in DMF, and this value was divided by the film area in contact with DMF to determine the amount of film surface oligomer (mg / m ² ). The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing an oligomer (cyclic trimer) collected in advance and dissolving it in accurately measured DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml. The conditions for the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(4) 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 gem clip or the like 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 in an oven at 180 ° C. for 10 minutes for heat treatment.

(5) Film haze Film haze was measured with an integrating sphere turbidimeter “NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS-K-7105.

(6) Light transmittance Shimadzu Corporation spectrophotometer UV3100 detects the light transmittance at a wavelength of 380 nm by measuring the light transmittance continuously in a scanning speed of 2 nm, a sampling pitch of 2 nm, and a wavelength of 300 to 700 nm. did.

(7) Film haze after heat treatment The film haze of a polyester film that was heat-treated by being left in an oven at 180 ° C. for 10 minutes under a nitrogen atmosphere was measured by the method described above.

(8) Hard coat adhesion (initial adhesion)
Immediately after the hard coat layer was formed, the hard coat layer was cross-cut so that there were 100 grids with a width of 1 inch. Immediately after that, a rapid peel test was performed three times on the same part using a cello tape, and the peel area was evaluated. . The judgment criteria were as follows.
A: Number of cross-cuts = 0
○: 1 ≦ Number of cross cuts ≦ 10
Δ: 11 ≦ number of cross-cuts ≦ 20
×: 21 ≦ Number of cross-cuts peeled

(Durable adhesion)
Adhesiveness was evaluated in the same manner as the initial adhesiveness evaluation, except that the hard coat layer was aged in a wet heat oven at 60 ° C. and 90% RH for 100 hours before cross-cutting.

(9) Measurement of the number of foreign matters A polyester film having a width of 700 nm and a length of 10 m (area 7 m ² ) is visually inspected using a crossed Nicols method, and the size of all detected foreign matters is measured using an optical microscope. The number of foreign matters having a major axis of 150 μm or more and the number of foreign matters having a length of 30 μm or more were counted, and then converted per unit area. In this embodiment, the foreign matter inspection is performed using a long sample. However, the number of foreign matters can be estimated depending on conditions by converting even a small material such as an A4 size into an area of 7 m ² .

(10) Measurement of the number of scratches Light is applied to the film surface with a width of 1500 mm and a length of 10 m (area 15 m ² ) with a halogen lamp, the film surface is visually observed, and the number of scratches appearing as bright spots is counted. The width of all the scratches was measured with an optical microscope, and the number of scratches having a width of 10 μm or more was calculated. In this example, the number of scratches having a width of 10 μm or more was counted for the long sample, but it can also be estimated by measurement using an A4 cut plate as described above.

Examples / Comparative Examples are shown below, and the production method of the polyester used in this is as follows.
<Manufacture of polyester>
<Method for producing polyester (A)>
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethylene glycol slurry ethyl acid phosphate and 0.04 part of antimony trioxide were added, and then the temperature was increased to 280 ° C. in 15 minutes and the pressure was gradually reduced to 100 mm. To 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyester A having an intrinsic viscosity of 0.63. The content of the oligomer (cyclic trimer) was 0.83% by weight.

<Method for producing polyester (B)>
The polyester (A) is pre-crystallized at 160 ° C. in advance and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C. to obtain a polyester (B) having an intrinsic viscosity of 0.75 and an oligomer content of 0.24% by weight. It was.

<Method for producing polyester (C)>
In the polyester (A) production method, 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 1.5 μm and 0.04 part of antimony trioxide were added. In addition, polyester (C) was obtained using the same method as the production method of polyester (A) except that the polycondensation reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65. The obtained polyester (C) had an intrinsic viscosity of 0.65 and an oligomer amount of 0.81% by weight.

<Manufacture of polyester film>
Two vents using the above-mentioned polyester (B) and (C) mixed at a ratio of 88% and 12%, respectively, as the A-phase raw material and 100% of the polyester (A) as the B-layer raw material. Each is supplied to a twin screw extruder and melted at 285 ° C., and each layer is composed of two layers and three layers (A / B / A) with the A layer as the outermost layer (surface layer) and the B layer as the intermediate layer. The sheet was extruded and extruded from the die, and cooled and solidified on a cooling roll having a surface temperature set to 40 ° C. using an electrostatic application adhesion method to obtain an unstretched sheet. After applying the coating agent having the following composition to the obtained sheet, the film was guided to a tenter and stretched at 90 ° C in the longitudinal direction 3.5 times and in the transverse direction 3.7 times, and simultaneously biaxially stretched at 225 ° C. The film was heat-set to obtain a laminated film having a coating layer with a thickness of 0.1 μm and a thickness of 188 μm and an intrinsic viscosity of 0.60. The resulting laminated film had a thickness configuration of 8 μm / 172 μm / 8 μm.
When the surface scratch of the obtained film was examined, it was not found at all.

(Coating agent composition: weight ratio)
A / B / C / D = 47/20/30/3
Here, details of A to D are as follows.
A: Polyester dispersion of terephthalic acid / isophthalic acid / 5-sodiumsulfoisophthalic acid / ethylene glycol / diethylene glycol / triethylene glycol = 31/16/3/22/21 (molar ratio) B: methyl methacrylate / ethyl acrylate / Emulsion polymer of acrylonitrile / N-methylolmethacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant)
C: Hexamethoxymethylmelamine (melamine crosslinking agent)
D: aqueous dispersion of silicon oxide having a particle size of 0.06 μm (inorganic particles)

  A hard coat resin was applied on the coating layer of the film thus obtained so that the thickness after curing was 6 μm, and irradiated with a high-pressure mercury lamp with an energy of 120 W / cm for about 10 seconds with an irradiation distance of 100 mm. Thus, a surface cured film was obtained. As a hard coat resin, KAYANOVA FOP-1700 manufactured by Nippon Kayaku was used.

  In Example 1, a film was formed and coated in the same manner as in Example 1 except that the inner layer material was 100% polyester (B). There were no surface scratches as in Example 1.

(Comparative Example 1)
Instead of stretching with the simultaneous biaxial stretching machine of Example 1, film forming and coating were performed in the same manner as in Example 1 except that roll stretching was used for roll stretching and tenter stretching was used for lateral stretching. When the surface flaw of the obtained film was measured, a surface flaw of 13 pieces / m ² was observed.

(Comparative Example 2)
Example 1 except that the A / A / A 1-type 3-layer film is used instead of the A / B / A 2-type 3-layer film of Example 1, and the amount of silica particles contained in the polyester film is 70 ppm. Film formation and coating were performed in the same manner as in 1. No surface scratch was observed as in Example 1.

(Comparative Example 3)
A film was formed and applied in the same manner as in Example 1 except that in-line application was not performed in Example 1. There were no surface scratches.

(Comparative Example 4)
In Example 1, except that the raw material composition of the A layer is (B) :( C) = 88: 12 instead of (A) :( C) = 88: 12, film formation is performed in the same manner as in Example 1. Coated. The surface scratch was the same as in Example 1.
The evaluation results of the films obtained in the above examples and comparative examples are shown in the following table.

  The film of the present invention can be suitably used as, for example, a highly transparent optical film used for various optics of members such as LCD and PDP applications.

Claims (1)

A film in which a coating layer is provided on at least one side of a polyester film biaxially stretched using a simultaneous biaxial stretching apparatus, the film haze of which is 2.0% or less, and heat treatment at 180 ° C. for 10 minutes A highly transparent optical polyester film having few surface defects, wherein the total amount of oligomers on the front and back surfaces of the film is 15 mg / m ² or less.