JP5489971B2 - Laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film, and relates to a film suitable for applications that require reduction of interference unevenness due to reflection of external light, such as liquid crystal displays, plasma display panels, and organic electroluminescence.

  In recent years, polyester films have been used for touch panels, antireflection films, prism sheets, light diffusion sheets, electromagnetic wave shielding films, and the like, which are members of liquid crystal displays and plasma display panels. The base film used for these members is required to have excellent transparency and visibility.

  These films are often hard-coated to prevent curling, improve scratch resistance, and improve performance such as surface hardness. Moreover, as a base material, the polyester film excellent in transparency and a mechanical characteristic is generally used. In order to improve the adhesion between the polyester film and the hard coat layer, an easy-adhesion coating layer is generally provided as an intermediate layer, but the reflected light at the interface between the hard coat layer and the coating layer, and the coating layer When the reflected light at the interface between the polyester film and the polyester film interferes, rainbow pattern unevenness (interference unevenness) may occur.

  If a film with interference unevenness is used for a display member such as a touch panel, the visibility is poor and it is difficult to use. For this reason, a film with reduced interference unevenness is desired. In order to reduce interference unevenness, it is considered that the refractive index of the coating layer should be close to the geometric mean of the refractive index of the biaxially stretched polyester film of the substrate and the refractive index of the hard coat layer. It is ideal to adjust to. Since the refractive index of the polyester film is high, it is generally necessary to design the coating layer with a high refractive index.

  An example of improving interference unevenness by increasing the refractive index of the coating layer includes, for example, a method of blending a metal chelate compound or metal fine particles having a high refractive index in the coating layer. In the case of chelate compounds, the stability of the coating solution may not be sufficient depending on the combination due to the instability of the metal chelate in the aqueous solution, and there is a possibility of increasing the liquid replacement work when producing for a long time. Yes (Patent Document 1). In addition, an example in which the refractive index is increased by a combination of a polyester resin and metal fine particles is also known, but in this case, there is a case where it is not possible to sufficiently exhibit the strict moist heat-resistant adhesion demanded in recent years (Patent Document). 2, 3).

JP 2005-97571 A JP 2004-54161 A JP 2008-169277 A

  The present case has been made in view of the above circumstances, and the problem to be solved is to provide a laminated polyester film with reduced interference unevenness due to external light reflection and excellent adhesion to various surface functional layers such as hard coats. There is to do.

  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 problems, and have completed the present invention.

That is, the gist of the present invention is derived from polyester resin, titanium oxide particles, and an epoxy compound on at least one surface of a polyester film containing 0.001 to 5% by weight of particles having an average particle diameter of 0.1 to 0.5 μm . It exists in the laminated polyester film characterized by having the coating layer containing a compound.

  According to the laminated polyester film of the present invention, when various surface functional layers such as a hard coat are laminated, there is little interference unevenness due to reflection of external light, and a film excellent in adhesiveness with various surface functional layers is provided. And its industrial value is high.

The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.
The polyester used 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. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  In the polyester layer of the film of the present invention, it is preferable to blend particles mainly for the 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. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-5 micrometers normally, Preferably it is the range of 0.1-3 micrometers. If the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted, or the particles may be aggregated to make the dispersibility insufficient, thereby reducing the transparency of the film. On the other hand, if it exceeds 5 μm, the surface roughness of the film becomes too rough, and a problem may occur when a functional layer such as a prism layer or a light diffusion layer is formed in a later step.

  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. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is a case.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for 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, ultraviolet absorbers, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

  The thickness of the polyester film of the present invention is not particularly limited as long as it can be formed into a film, but is usually 10 to 350 μm, preferably 25 to 250 μm.

  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 be adopted for the production of the polyester film constituting the laminated 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, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by so-called in-line coating, which treats the film surface during the stretching process of the polyester film, or may be applied outside the system on the film once produced, so-called off-line coating may be adopted, You may use both together. In-line coating is preferably used in that it can be applied at the same time as film formation, and thus can be manufactured at low cost, and the thickness of the coating layer can be changed by the draw ratio.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  In the present invention, it is an essential requirement to have a coating layer containing a polyester resin, titanium oxide particles, and an epoxy compound-derived compound on at least one surface of the polyester film.

  In order to reduce interference unevenness to a high degree, the present inventors have designed a method in which the refractive index of the surface functional layer such as the hard coat layer and the refractive index of the coating layer are designed to be close to the refractive index of the biaxially stretched polyester film. I found. Ideally, the refractive index of the coating layer to reduce interference unevenness should be adjusted around the geometric mean of the refractive index of the biaxially stretched polyester film of the substrate and the refractive index of the hard coat layer. By setting the refractive index in the vicinity of the same, reflection at each interface is further suppressed, so that interference unevenness is further reduced. Further, the interference unevenness is also caused by the thickness fluctuation of the coating layer. However, in the coating layer of the present invention, it is considered that the interference unevenness hardly occurs even if the coating layer has a thickness fluctuation. In the present invention, in order to realize this design concept, the refractive index of the coating layer is designed in the vicinity of the polyester film.

  The polyester resin used in the present invention 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. In particular, the difference in refractive index between coating layers should be reduced. In the interference unevenness can be suppressed, it is preferable to having a naphthalene structure.

  Examples of the polyvalent hydroxy compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2- Methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, ethylene glycol modified bisphenol A, diethylene glycol modified bisphenol A, diethylene glycol, triethylene glycol, polyethylene Glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, dimethylo Or the like can be used potassium Rupuropion acid. Among these polyvalent hydroxy compounds, it is preferable to have an aromatic compound such as a bisphenol A structure because the refractive index of the polyester resin can be further increased. One or more of these polyvalent carboxylic acids and polyvalent hydroxy compounds may be appropriately selected, and a polyester resin may be synthesized by a conventional polycondensation reaction.

  The titanium oxide particles used in the present invention are mainly used for adjusting the refractive index of the coating layer. In particular, since the refractive index of the resin used in the coating layer is low, it is preferable to use titanium oxide particles having a high refractive index, and in order to obtain a coating layer having a refractive index close to that of the polyester film, refraction is required. It is preferable to use a rate of 1.7 or more. If necessary, two or more types of titanium oxide particles may be used in combination.

  From the viewpoint of transparency, the average particle size of the titanium oxide particles is preferably 100 nm or less, more preferably 50 nm or less, still more preferably 25 nm or less, and particularly preferably 15 nm or less.

  The compound derived from the epoxy compound in the present invention includes, for example, a compound containing an epoxy group in the molecule, a prepolymer, a cured product, and a reaction product thereof. Examples include condensates of epichlorohydrin with hydroxyl groups and amino groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and bisphenol A, and polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. is there. Examples of the polyepoxy compound include sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylol. Examples of the propane polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether. Ether, polypropylene glycol diglycidyl ether, Ritetramethylene glycol diglycidyl ether and monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N ′,-tetraglycidyl-m. -Xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like and their reactants. These may be used alone or in combination of two or more.

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

  An oxazoline compound is a compound having an oxazoline group in the molecule. In particular, a polymer containing an oxazoline group is preferable, and it can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  The isocyanate compound is a compound derived from an isocyanate derivative typified by isocyanate or blocked isocyanate. Examples of the isocyanate include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, and aromatics such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic diisocyanates having a ring, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, etc., cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis (4-cyclohexyl isocyanate), isopropylidene Alicyclic diisocyanates such as emissions dicyclohexyl diisocyanates. These may be used alone or in combination.

  Examples of the blocking agent for blocked isocyanate include phenolic compounds such as bisulfites, phenol, cresol, and ethylphenol, alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol, dimethyl malonate, and malon. Active methylene compounds such as diethyl acid, methyl acetoacetate, ethyl acetoacetate and acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam, diphenylaniline, aniline, ethylene Amine compounds such as imine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoaldoxime, acetoneoxy And oxime compounds such as methyl ethyl ketone oxime and cyclohexanone oxime, which may be used alone or in combination.

  In the coating layer of the film of the present invention, a binder polymer other than the above-described polyester resin is used to improve the adhesion to the surface functional layer, the coated surface, and the visibility and transparency when the surface functional layer is formed. It is also possible to use together.

  In the present invention, the “binder polymer” 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). It is defined as a polymer compound of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include acrylic resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches, and the like. Can be mentioned.

  Furthermore, as long as it does not impair the gist of the present invention, the coating layer has an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, foaming as necessary. Agents, dyes, pigments and the like may be contained.

  The content of the polyester resin used in the coating layer constituting the laminated polyester film in the present invention is usually in the range of 10 to 90% by weight, more preferably in the range of 40 to 85% by weight. By using within this range, the refractive index of the coating layer can be easily adjusted, and interference unevenness can be easily suppressed when a surface functional layer such as a hard coat layer is provided. Moreover, when it uses outside this range, adhesiveness with a surface functional layer may fall.

  The content of the titanium oxide particles used in the coating layer constituting the laminated polyester film in the present invention is usually 5 to 60 parts by weight, preferably 8 to 50 parts by weight, and more preferably 20 to 40 parts by weight. When the content of titanium oxide particles is 5 parts by weight or less, the refractive index of the coating layer does not increase, so that interference unevenness may not be reduced. When the content is 60 parts by weight or more, the haze of the coating layer may deteriorate.

  The content of the compound derived from the epoxy compound used in the coating layer constituting the laminated polyester film of the present invention is usually in the range of 1 to 50% by weight, preferably in the range of 5 to 30% by weight, more preferably 10 to 20% by weight. Range. When the amount is less than 1% by weight, there is a concern that the adhesion to a surface functional layer such as a hard coat layer may be lowered. When the amount exceeds 50% by weight, the haze of the coating layer may be deteriorated.

  The polyester film in the present invention has a coating layer on at least one surface, but even if a similar or other coating layer or functional layer is provided on the opposite surface of the film, it is naturally included in the concept of the present invention.

  The analysis of various components in the coating layer can be performed by surface analysis such as TOF-SIMS, XRF, and XPS.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated 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 coating thickness of the coating layer provided on the polyester film is 0.01 to 1.00 μm, more preferably 0.03 to 0.30 μm, and still more preferably 0.04 to 0.15 μm. Range. If the coating amount is less than 0.01 μm, sufficient adhesion may not be obtained, and if it exceeds 1.00 μm, the appearance, transparency, and film blocking properties may be deteriorated.
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.

  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 may 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, heat treatment is usually performed 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 minimum value of the absolute reflectance of the polyester film on which the easy adhesion layer is laminated in the present invention is usually in the range of 5.5 to 6.5% at an arbitrary wavelength of 400 to 800 nm, preferably 5.6 to 6 It is in the range of 0.4%, more preferably in the range of 5.7 to 6.3%. When the reflectance is out of this range, interference unevenness is increased when a surface functional layer such as a hard coat is provided on the coating layer, and the visibility may be lowered.

  In the present invention, a film having high transparency is more preferred for use in applications requiring transparency, such as display applications. For example, haze is mentioned as one index of transparency, and the value thereof is preferably 2.0% or less, more preferably 1.8% or less, and further preferably 1.6% or less. When the haze is high, the visibility of the film may be lowered.

  The polyester film of the present invention is generally provided with a surface functional layer such as a hard coat layer on the coating layer. Although it does not specifically limit as a material used for a hard-coat layer, For example, hardened | cured materials, such as reactive silicon compounds, such as monofunctional (meth) acrylate, polyfunctional (meth) acrylate, and tetraethoxysilane, are mentioned. Among these, from the viewpoint of achieving both productivity and hardness, a polymerization cured product of a composition containing an ultraviolet curable polyfunctional (meth) acrylate is particularly preferable.

  It does not specifically limit as a composition containing a ultraviolet curable polyfunctional (meth) acrylate. For example, a mixture of one or more known ultraviolet curable polyfunctional (meth) acrylates, a commercially available UV curable hard coating agent, or other than these, in a range not impairing the purpose of the present embodiment, What added the other component further can be used.

  The UV-curable polyfunctional (meth) acrylate is not particularly limited. For example, dipentaerythritol hexa (meth) acrylate, tetramethylolmethanetetra (meth) acrylate, tetramethylolmethanetri (meth) acrylate, (Meth) acryl derivatives of polyfunctional alcohols such as trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,6-bis (3-acryloyloxy-2-hydroxypropyloxy) hexane And polyethylene glycol di (meth) acrylate and polyurethane (meth) acrylate.

  Other components contained in the composition containing an ultraviolet curable polyfunctional (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers and leveling agents. Moreover, when making it dry after film forming in the wet-coating method, arbitrary amounts of solvents can be added.

  As a method for forming the hard coat layer, when an organic material is used, a general wet coat method such as a roll coat method or a die coat method is employed. The formed hard coat layer can be subjected to a curing reaction by heating, irradiation with active energy rays such as ultraviolet rays and electron beams as necessary.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example in the range which does not exceed the summary. 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 The coating layer was observed using TEM (H-7650 manufactured by Hitachi, accelerating voltage 100 V), and the average value of the particle diameters of 10 particles was defined as the average particle diameter.

(3) Measurement of coating layer thickness


The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by the ultrathin section method was stained with RuO _4, and the cross section of the coating layer was measured using TEM (H-7650 manufactured by Hitachi, accelerating voltage 100 V).

(4) Measurement of absolute reflectance from one coating layer surface in polyester film A black tape (made by Nichiban Co., Ltd., vinyl tape VT-50) was previously pasted on the measurement back surface of the polyester film, and a spectrophotometer (JASCO Corporation) Using a company-made UV-visible spectrophotometer V-570 and automatic absolute reflection measuring device AM-500N), synchronous mode, incident angle 5 °, N polarization, response Fast, data collection interval 1.0 nm, bandwidth The absolute reflectance of the coating layer surface in the wavelength range of 400 to 800 nm was measured at 10 nm and scanning speed of 1000 nm / min.

(5) Measurement of haze The haze was measured according to JIS K 7136 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory.

(6) Interference unevenness evaluation On the coating layer side of the polyester film, 60 parts by weight of dipentaerythritol acrylate, 15 parts by weight of 1,6-hexanediol acrylate, 25 parts by weight of antimony pentoxide, a photopolymerization initiator (trade name: Irgacure (184, manufactured by Ciba Specialty Chemicals) 1 part by weight of a mixed coating solution of 200 parts by weight of methyl ethyl ketone is applied to a dry film thickness of 5 μm, cured by irradiating with ultraviolet rays, and has a refractive index equivalent to that of a polyester film. A coat layer was formed. The obtained film is visually observed under a three-wavelength type fluorescent lamp for interference non-uniformity. If the interference non-uniformity is not confirmed, ◎, thin sparse interference non-uniformity is confirmed, thin, linear The case where the interference unevenness was confirmed was indicated by Δ, and the case where clear interference unevenness was confirmed was indicated by ×.

(7) Evaluation of adhesiveness In order to evaluate adhesiveness, examination was made with materials obtained by removing antimony pentoxide from the hard coat liquid used in the evaluation of (6) above. That is, a mixed coating liquid of 80 parts by weight of dipentaerythritol acrylate, 20 parts by weight of 1,6-hexanediol acrylate, 5 parts by weight of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Specialty Chemical), and 200 parts by weight of methyl ethyl ketone. It was applied so that the dry film thickness was 5 μm, and cured by irradiation with ultraviolet rays to form a hard coat layer. After 100 hours in an environment of 60 ° C. and 90% RH, the obtained film was subjected to 10 × 10 cross-cut, and an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was used. The peeled surface after being peeled off and abruptly peeled off at a 180 ° peel angle was observed. The peeled area was less than 3%, 3% to less than 10%, 10% to 50%, and 50% or more. Was evaluated as x.

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, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part by weight of ethyl acid phosphate to this reaction mixture, 0.04 part by weight of antimony trioxide was added, and a polycondensation reaction was carried out 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 of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester (A) having an intrinsic viscosity of 0.65.

<Method for producing polyester (B)>

In the method for producing polyester (A), after adding 0.04 part by weight of ethyl acid phosphate, 0.2 part by weight of silica particles dispersed in ethylene glycol having an average particle size of 2.3 μm and 0.04 part of antimony trioxide are added. A polyester (B) was obtained using the same method as the production method of the polyester (A) except that the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65 by adding parts by weight. The obtained polyester (B) had an intrinsic viscosity of 0.65.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
・ Polyester resin (E1)
Water dispersion monomer composition of polyester resin copolymerized with the following 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%)

・ Polyester resin having condensed polycyclic aromatic (E2)
Water dispersion of polyester resin copolymerized with the following composition: Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid / 5-sodium sulfoisophthalic acid // (diol component) diethylene glycol modified bisphenol A / ethylene glycol modified bisphenol A = 94/6 // 90/10 (mol%)

・ Epoxy compounds (C1A)
Denacol EX-521 (manufactured by Nagase ChemteX), which is polyglycerol polyglycidyl ether

・ Epoxy compounds (C1B)
Denacol EX-1410 (manufactured by Nagase ChemteX), an epoxy resin
・ Epoxy compounds (C1C)
Denacol EX-1610 (manufactured by Nagase ChemteX), an epoxy resin
・ Oxazoline compounds (C2)
Acrylic polymer having oxazoline group and polyalkylene oxide chain, Epocros WS-500 (manufactured by Nippon Shokubai)
・ Isocyanate compounds (C3)
200 parts of polyester having an average molecular weight of 1000 comprising maleic acid 2 mol adduct of bisphenol A and maleic acid, and obtained by blocking the isocyanate group of polyisocyanate comprising 33.6 parts of hexamethylene diisocyanate with 84 parts of sodium bisulfite, Polyester resin-containing blocked isocyanate compound.
Hexamethoxymethylmelamine (C4)
Titanium oxide particles (F1) having a refractive index of 1.9 and an average particle size of 15 nm

Example 1:
A mixed raw material in which polyesters (A) and (B) are mixed at a ratio of 90% and 10%, respectively, is used as a raw material for the outermost layer (surface layer), and polyester (A) is used as a raw material for the intermediate layer in each of two extruders. Are melted at 285 ° C. and then coextruded and cooled on a cooling roll set at 40 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount). Solidified 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 difference in peripheral speed of the roll, and then the coating liquid 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film, and led to a tenter. Polyester having a thickness of 125 μm having a coating layer having a thickness of 0.10 μm after stretching by 4.0 times at 120 ° C. in the transverse direction and heat treatment at 225 ° C. A film was obtained.

  When the absolute reflectance of the obtained polyester film was measured, the minimum reflectance at an arbitrary wavelength of 400 to 800 nm was 5.8%. The film after laminating the hard coat layer had no clear interference unevenness and good adhesion. Also, the haze was low and the transparency was good. The properties of this film are shown in Table 2 below.

Examples 2 to 19:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. The finished laminated polyester film had a high reflectance as shown in Table 2, and had good interference unevenness and adhesion.

Comparative Examples 1-6:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. As shown in Table 2, the finished laminated polyester film had poor interference unevenness and poor adhesion to the hard coat.

Comparative Example 7:
In Example 1, it manufactured like Example 1 except not providing an application layer, and obtained the polyester film. The finished laminated polyester film had poor adhesion to the hard coat as shown in Table 2.

  The film of the present invention is, for example, used in various optical films that are members of liquid crystal or plasma displays, molding films, and the like that emphasizes adhesion and visibility with a surface functional layer such as a hard coat layer. It can be used suitably.

Claims (2)

Having a coating layer containing a polyester resin, titanium oxide particles, and a compound derived from an epoxy compound on at least one surface of a polyester film containing 0.001 to 5% by weight of particles having an average particle diameter of 0.01 to 5 μm. A laminated polyester film characterized. The laminated polyester film according to claim 1, wherein the particles in the polyester film are silica particles.