JP5455315B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film, such as a liquid crystal display (hereinafter abbreviated as LCD), a plasma display panel (hereinafter abbreviated as PDP), organic electroluminescence (hereinafter abbreviated as organic EL), and the like. The present invention relates to a laminated polyester film suitable for optical applications such as for display members.

  Conventionally, polyester films, especially biaxially stretched films of polyethylene terephthalate and polyethylene naphthalate, have excellent mechanical properties, heat resistance, and chemical resistance. For 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 widely used for various optical films, especially base films such as light diffusion sheets, prism sheets, reflectors and touch panels for LCD members, antireflection base films, display explosion-proof base films, and PDPs. It is used for various applications such as filter films. In these optical products, in order to obtain a bright and clear image, a base film used as an optical film is required to have excellent transparency, visibility, and color tone from its usage form.

  These optical films are made by laminating surface functional layers such as a light diffusion layer, prism layer, hard coat layer, antireflection layer, etc. on a base film, and a transparent polyester film is generally used as the base film. In order to improve the adhesion between the base polyester film and the surface functional layer, a configuration in which an easily adhesive coating layer is provided as an intermediate layer is generally used. As the coating layer, a polyester resin is generally used because of its good adhesion to the base film, but may be inferior to the adhesion to the surface functional layer. For this reason, various films with an easy-adhesion layer made of acrylic resin, polyurethane resin, etc. have been proposed, but when adhesion is improved by acrylic resin, sufficient adhesion cannot be obtained unless a melamine compound is used in combination. There is also. Particularly in recent years, in order to guarantee various products, it is required that adhesion does not decrease even under high temperature and high humidity conditions, and a polyester resin or an acrylic resin alone may not be sufficient.

  By the way, it is desired that the polyester film be reused from the polyester which is a non-product part generated in the film forming process or the like from the viewpoint of economy. However, when a film containing a polyurethane resin or a polyester containing a cross-linking agent such as a melamine compound is reused as a component, a polyester film colored yellow is produced due to heat and oxidative degradation, resulting in a display screen. In some cases, there is a problem that the color tone is deteriorated and the product quality is lowered.

In order to solve the disadvantage of yellowing for various reasons, colored beads are contained in the bead coat layer for the light diffusion plate (Patent Document 1), or a colorant is contained in the polyester (Patent Documents 2 to 7). It is known that a colorant is contained in the sliding layer (Patent Document 7).
JP 2002-127341 A JP 2005-88340 A JP 2006-70166 A JP 2006-152139 A JP 2006-152140 A JP 2006-182858 A Japanese Patent No. 3845435

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the laminated polyester film which has the outstanding adhesiveness and has a suitable color tone.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

That is, the gist of the present invention is a polyester film having a coating layer on at least one side, and C.I. I. Pigment Violet 23, C.I. I. Pigment Violet 32, Acid Violet 48, Acid Violet 66, Acid Violet 126, C.I. I. Solvent Violet 13, and C.I. I. It exists in the laminated polyester film characterized by including the coloring agent only of the 1 or more types of purple colorant chosen from Solvent Violet 36 , and a melamine compound.

Hereinafter, the present invention will be described in more detail.
The polyester film in the present invention may have a single layer structure or a multilayer structure, and may have a multilayer structure of four layers or more as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. Well, not particularly limited.

  The polyester used in the present invention is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol, and may be a polyester comprising one kind of aromatic dicarboxylic acid and one kind of aliphatic glycol. It may be a copolyester obtained by copolymerizing one or more other components. 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. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid used as a component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, and sebacic acid, and glycol components include ethylene glycol, diethylene glycol, and propylene. Examples include glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. Oxycarboxylic acids such as p-oxybenzoic acid can also be used.

  Further, as a material for the polyester film, it is also possible to reuse polyester having a history of molding, that is, melt extrusion / film formation. The reuse of polyester is useful from the viewpoint of economy and resource saving. The amount of reuse is preferably larger in view of economic efficiency alone, but is generally 50% by weight or less, preferably 30% by weight or less in consideration of transparency, colorability and the like.

  Furthermore, as the above-mentioned reused polymer, a reused polymer or a polymer used for film formation three or more times can be used. As the reusable polymer, a film composed of the same kind of polyester and the same kind of coating layer is preferably used in that the color tone can be easily controlled.

  When using recycled polymer, it has a lot of thermal history, so when the amount of oligomers contained increases or when it contains low molecular weight compounds such as amine compounds that are decomposed from the coating layer There is. In that case, the said oligomer and low molecular weight compound precipitate on the polyester film surface, and may cause deterioration of transparency and a fall of adhesiveness with a surface functional layer. In order to prevent this, there is a method in which the polyester film has a three-layer structure, for example, and a recycled polymer is used for the intermediate layer.

  In the film of the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness and preventing scratches in each step. 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 of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. 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. Two or more kinds of these particles may be used in combination as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-2 micrometers. When the average particle diameter 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 diameter exceeds 3 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient, while when it exceeds 5% by weight, the transparency of the film may be insufficient.

  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 of producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

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

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

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-350 micrometers, Preferably it is the range of 50-250 micrometers.

  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. That is, 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 preferable 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 is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can also be adopted for the production of the polyester film. 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. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

  Next, the formation of the coating layer constituting the laminated polyester film in the present invention is provided by coating the film with a coating solution, and is preferably provided by in-line coating performed in the film manufacturing process. An off-line coating that is applied outside the system may be employed.

  Specifically, the in-line coating is a method in which the coating is performed at any stage from melt extrusion of the polyester to stretching, heat setting, and winding. Normally, it is coated on a substantially amorphous unstretched sheet obtained by melting and quenching, followed by a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In these, the method of drying and extending | stretching to a horizontal direction after coating to a uniaxially stretched film, and also heat-processing with a base film is excellent. According to this method, since film formation and coating layer formation can be performed at the same time, there is an advantage in manufacturing cost, and heat treatment applied after coating is so high that it is difficult to achieve with other coatings. Therefore, there is an advantage that the film forming property of the coating layer is improved and the coating layer and the polyester film are firmly adhered.

  Although the film of this invention has a specific coating layer, the said coating layer needs to contain a blue or purple colorant and a melamine compound.

  The colorant used in the present invention is used to adjust the color tone of the film, and is mainly used to correct yellowishness generated when the film is reused. The blue colorant refers to those generally indicated as “blue” and “Blue” among commercially available colorants. Similarly, the purple-based colorant refers to those generally expressed as “purple” and “Violet” among commercially available colorants.

  Specific examples of the blue colorant include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15: 4, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 28, C.I. I. Pigment Blue 60, C.I. I. Pigment Blue 61, C.I. I. Pigment Blue 80, etc., Acid Blue 3, Acid Blue 9, Acid Blue 80, Acid Blue 93, Acid Blue 182 and C.I. I. Solvent Blue 35, C.I. I. And dyes such as Solvent Blue 45. From the viewpoint of weather resistance, it is more preferable to use a pigment.

  Specific examples of purple colorants include C.I. I. Pigment Violet 23, C.I. I. Pigment Violet 32, Acid Violet 48, Acid Violet 66, Acid Violet 126, C.I. I. Solvent Violet 13, C.I. I. And dyes such as Solvent Violet 36. From the viewpoint of weather resistance, it is more preferable to use a pigment.

  These colorants may be used alone or in combination. A method of using a mixture of a blue colorant and a purple colorant in an appropriate ratio is effective in that the yellowish color tone by the reuse polymer can be finely adjusted. In order to obtain a more neutral color tone, a colorant such as a red colorant and an orange colorant can be used in combination as long as the gist of the present invention is not impaired.

  The melamine compound used in the present invention is a compound having a melamine skeleton in the compound after the surface functional layer is laminated and used for increasing the strength of the coating film so that the adhesion does not decrease even under high temperature and high humidity conditions. That is. For example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and a mixture thereof can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  In the laminated polyester film of the present invention, it is preferable to use a binder polymer in combination in order to improve the coated surface, and to improve the transparency and adhesion when various surface functional layers are laminated on the coated surface.

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

  Specific examples of the binder polymer include polyester resin, acrylic resin, polyurethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, methyl cellulose, hydroxy cellulose, starches and the like. It is done.

  The polyester resin includes, for example, the following polyvalent carboxylic acid and polyvalent hydroxy compound as main components. That is, as the polyvalent carboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used. As the polyvalent hydroxy compound, ethylene Recall, 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, and the like can be used. One or more compounds may be appropriately selected from these compounds, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The acrylic resin is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester etc.) is also contained. 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 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 particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing vinyl monomers such as (meth) acrylimide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, Various vinyl esters such as vinyl acetate and vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl chloride , Vinylidene chloride, vinyl fluoride, vinylidene fluoride, trifluorochloroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and other vinyl halides; butadiene and other conjugated dienes And the like.

  The polyurethane resin is a polymer compound having a urethane bond in the molecule. In consideration of appropriateness of in-line coating, a water-dispersible or water-soluble urethane resin is preferable. In order to impart water dispersibility or water solubility, it is important to introduce a hydrophilic group such as a hydroxyl group, a carboxyl group, a sulfonic acid group, a sulfonyl group, a phosphoric acid group, or an ether group into the urethane resin. Among the hydrophilic groups described above, a carboxylic acid group or a sulfonic acid group is preferable from the viewpoint of coating film properties and adhesion.

  One method for producing a polyurethane resin, which is a constituent component of the coating layer used in the present invention, is a reaction between a hydroxyl group and an isocyanate. As the hydroxyl group used as a raw material, a polyol is preferably used, and examples thereof include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

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

  Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides. Product and polyhydric alcohol (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol 2-methyl-2-propyl-1 3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexane Diol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyl dialkanolamine, lactone diol, etc.).

  Examples of polycarbonate polyols include polycarbonate diols obtained by dealcoholization reaction from polyhydric alcohols and dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, and the like, such as poly (1,6-hexylene) carbonate, poly ( And 3-methyl-1,5-pentylene) carbonate.

  Examples of the polyisocyanate compound used for obtaining the polyurethane resin include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic diisocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl methane Isocyanates, alicyclic diisocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination.

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

  Examples of the chain extender having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol and butanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, and esters such as neopentyl glycol hydroxypivalate. Examples of the chain extender having three hydroxyl groups include trimethylolpropane. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, diphenylmethanediamine, 4,4′-methylenebis-o-chloroaniline, ethylenediamine, propylenediamine, and hexane. Diamine, 2,2-dimethyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octane Aliphatic diamines such as diamine, 1,9-nonanediamine, 1,10-decanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isopropylidine cyclohexyl-4,4 '-Diamine, 1,4-diaminocyclohexane Sun, 1, alicyclic diamines such as 1,3-bis-aminomethyl cyclohexane.

  In general, a polyurethane resin using an aromatic isocyanate as a raw material is deteriorated by light or heat and tends to be colored yellow as compared with an aliphatic resin. Therefore, it may be necessary to increase the amount of the colorant for suppressing yellowness.

  Further, in the coating layer, a crosslinking agent other than the melamine compound can be used in combination as long as the gist of the present invention is not impaired, and examples thereof include an oxazoline compound, an epoxy compound, and an isocyanate compound.

  The oxazoline compound is a compound having an oxazoline ring in the molecule, and includes a monomer having an oxazoline ring and a polymer synthesized using the oxazoline compound as one of raw material monomers.

  As an epoxy compound, the compound containing an epoxy group in a molecule | numerator, its prepolymer, and hardened | cured material are mentioned, for example. A typical example is a condensate of epichlorohydrin and bisphenol A. In particular, a reaction product of a low molecular polyol with epichlorohydrin gives an epoxy resin having excellent water solubility.

  Isocyanate compound refers to a compound having an isocyanate group in the molecule, and specifically, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, tolylene diisocyanate, and the like. And polymers and derivatives thereof.

  The crosslinking agent in the present invention may be used alone or in combination of two or more. Furthermore, when consideration is given to application to in-line coating, it is preferable to have water solubility or water dispersibility.

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be contained, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like.

  Furthermore, as long as the gist of the present invention is not impaired, an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foaming agent and the like are contained as necessary. May be.

The content of the blue and / or purple colorant in the coating layer constituting the laminated polyester film in the present invention is determined so as to correct the color tone of the film. It depends on the amount of recycled polymer, the thickness of the polyester film, the spectral characteristics of the colorant, and the number of surfaces of the coating layer. The amount per unit is in the range of 0.01 to 5 mg / m ² , more preferably in the range of 0.1 to 1 mg / m ² . When the amount is less than 0.01 mg / m ^{2, the} effect of reducing yellowness may be small due to the small amount of the colorant. When the amount exceeds 5 mg / m ² , the blueness is too strong, or the transparency is lowered. There is a case.

  Moreover, content of the melamine compound in a coating layer is 10% or more by the weight ratio of the whole coating layer, Preferably it is the range of 10-50%. If it is less than 10%, the adhesion with the surface functional layer may be poor.

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

Regarding the laminated polyester film in the present invention, the thickness of the coating layer provided on the polyester film is usually 0.005 to 1 g / m ² , preferably 0.005 to 0.5 g / m ² , more preferably 0.02. It is the range of -0.3g / m < ² >. When the coating amount is less than 0.005 g / m ² , the uniformity of the coating thickness may be insufficient. On the other hand, when it coats exceeding 1 g / m < ² >, malfunctions, such as a fall of slipperiness and a reflection prevention ability, may arise.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment should be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

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

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

  The polyester film of the present invention has a color tone b * value measured by 5 reflection methods, preferably in the range of -3.0 to +3.0, more preferably in the range of -2.0 to +2.0, and still more preferably. It is in the range of −1.5 to +1.5. When the b * value exceeds +3.0, the color tone of the image may be inferior due to the strong yellowishness, for example, when used for display. On the other hand, when it is lower than −3.0, the blueness is strong, and for example, when it is used for a display, the luminance may be lowered and the color tone of the image may be inferior. However, in general, the b * value is on the plus side and is yellowish. Therefore, in order to obtain a neutral color tone, a small amount of colorant is used in the range of 0.0 to +1.5. It is preferable to adjust so that it may contain.

  According to the laminated polyester film of the present invention, a film having excellent adhesion and a suitable color tone can be provided, and its industrial value is 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 measurement method and evaluation method used in the present invention are 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) b * value measurement (5 reflection methods)
Using a spectrocolorimeter (CM-3700d manufactured by Konica Minolta Sensing Co., Ltd.), five films were stacked and measured by a reflection method. The b * value is preferably in the range of -3.0 to +3.0, more preferably in the range of -2.0 to +2.0, and still more preferably in the range of -1.5 to +1.5.

(4) Color tone evaluation method When the polyester film cut to the size of A4 is stacked so as to have a thickness of 2 mm and the color tone when viewed from the end face is neutral, the yellow color is too strong or the blue color is If it was too strong and the color was not neutral, it was marked as x.

(5) Adhesive evaluation method On the coating layer side of the laminated polyester film, 50 parts by mass of a binder (Halus Hybrid UV-G301 manufactured by Nippon Shokubai Co., Ltd.), isocyanate (Desmodule N-3200 manufactured by Sumika Bayer Urethane Co., Ltd.) 5 A coating solution was prepared by mixing 50 parts by mass of acrylic beads (MBX-20 manufactured by Sekisui Plastics Co., Ltd.), 50 parts by mass of toluene, and 50 parts by mass of 2-butanone. This coating solution was applied with a # 16 wire bar and dried at 100 ° C. for 1 minute to obtain a film having a light diffusion layer. The film is held for 50 hours under high temperature and high humidity (60 ° C./80% RH) conditions, and then a cross cut (100 squares of 1 mm ² ) is applied to the film, and an 18 mm wide tape ( Nichiban Co., Ltd. cello tape (registered trademark) CT-18) is applied and peeled off rapidly at a peeling angle of 180 degrees, and then the peeled surface is observed. If less than%, Δ, and if more than 50%, ×.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed for 4 hours.
That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (A) having an intrinsic viscosity of 0.63.

<Method for producing polyester (B)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is set to 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, orthophosphoric acid was added, and germanium dioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65 due to a change in stirring power in the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (B) having an intrinsic viscosity of 0.65.

<Method for producing polyester (C)>
In the production method of polyester (A), 0.2 part of silica particles having an average particle diameter of 2.0 μm dispersed in ethylene glycol was added and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.66. Obtained polyester (C) having an intrinsic viscosity of 0.66 using a method similar to the method for producing polyester (A).

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Blue colorant: (I1) C.I. I. Pigment Blue 15: 3
Purple colorant: (I2) C.I. I. Pigment Violet 23
Hexamethoxymethyl melamine (II)
Urethane resin: (III) Hydran AP-40 manufactured by Dainippon Ink & Chemicals, Inc.
Acrylic resin: (IV) Methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 molar ratio emulsion polymer (emulsifier: anionic surfactant)
Polyester resin: (V)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)
Particle: (VI) Silica sol with an average particle size of 65 nm

Example 1:
Polyesters (A), (B), and (C) are mixed at a ratio of 85%, 5%, and 10%, respectively, and the raw materials for the outermost layer (surface layer) are used as polyester (A), (B), and recycled. Polymer (having a coating layer provided on both sides with coating solution 1 not containing a colorant, and a mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 95% and 5%, respectively, as an intermediate layer Polyester film, which is the same as in the present embodiment except that it is used) is mixed at 66%, 4%, and 30%, respectively, and mixed raw materials are fed to two extruders as intermediate layer raw materials. Then, each was melted at 290 ° C., and then coextruded with a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set at 40 ° C. to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating liquid 2 shown in Table 1 below was applied to one side of the longitudinally stretched film, which was led to a tenter. After stretching 4.0 times at 120 ° C in the transverse direction and heat treatment at 225 ° C, the coating layer is relaxed by 2% in the transverse direction and the coating amount (after drying) is 0.1 g / m ² on one side. A polyester film having a thickness of 100 μm (surface layer: 5 μm, intermediate layer: 90 μm) was obtained. The b * value of the finished polyester film measured by the reflection method of 5 sheets was 1.1. In addition, the yellow and blue colors were not strong and the color was neutral. The properties of this film are shown in Table 3 below.

Examples 2-7:
A polyester film was obtained in the same manner as in Example 1 except that the amount of recycled polymer and the composition of the coating agent were changed as shown in Table 2 in Example 1. The properties of the finished polyester film are shown in Table 3.

Comparative Examples 1 and 2:
A polyester film was obtained in the same manner as in Example 1 except that the amount of recycled polymer and the composition of the coating agent were changed as shown in Table 2 in Example 1. Table 3 shows the characteristics of the finished laminated polyester film.

  The concentration of the coating solution was 10% by weight.

  The film of the present invention can be suitably used, for example, for optical applications such as LCD, PDP, and display member production, and for applications that place importance on color tone.

Claims (1)

A polyester film having a coating layer on at least one side, and C.I. I. Pigment Violet 23, C.I. I. Pigment Violet 32, Acid Violet 48, Acid Violet 66, Acid Violet 126, C.I. I. Solvent Violet 13, and C.I. I. A laminated polyester film comprising a colorant composed of only one or more purple colorants selected from Solvent Violet 36 and a melamine compound.