JP2011224849A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film that is suitably used in an optical application such as a backlight unit of liquid crystal display, being the application requiring superior adhesion to a microlens layer, a prism lens layer, or the like.SOLUTION: The laminated polyester film has, on at least one side of the polyester film, a coating layer containing an urethane resin and an isocyanate compound derived from an aliphatic or an alicyclic isocyanate.

Description

The present invention relates to a polyester film having a coating layer having excellent adhesion to various topcoats.

In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. Since these liquid crystal displays do not have a light emitting function by a liquid crystal display unit alone, a method of displaying by irradiating light using a backlight from the back side is widespread.

The backlight system has a structure called an edge light type or a direct type. Recently, there is a tendency to reduce the thickness of liquid crystal displays, and an edge light type is increasingly used. The edge light type is generally configured in the order of a reflection sheet, a light guide plate, a light diffusion sheet, and a prism sheet. As the flow of light, the light incident on the light guide plate from the backlight is reflected by the reflection sheet and emitted from the surface of the light guide plate. The light beam emitted from the light guide plate enters the light diffusion sheet, is diffused and emitted by the light diffusion sheet, and then enters the next existing prism sheet. The light beam is condensed in the normal direction by the prism sheet and emitted toward the liquid crystal layer.

The prism sheet used in this configuration is for improving luminance by improving the optical efficiency of the backlight. As the transparent base film, a polyester film is generally used in consideration of transparency and mechanical properties. In order to improve the adhesion between the base polyester film and the prism layer, these intermediate layers are easily bonded. In general, a conductive coating layer is provided. As an easily adhesive coating layer, for example, polyester resin, acrylic resin, and urethane resin are known (Patent Documents 1 to 3).

As a method for forming the prism layer, for example, an active energy ray-curable coating material is introduced into a prism type, irradiated with active energy rays while being sandwiched between polyester films, the resin is cured, and the prism type is removed to remove polyester. The method of forming on a film is mentioned. In the case of such a method, it is necessary to use a solventless active energy ray-curable coating material in order to form the prism type with precision. However, solventless paints are less permeable and swellable to the easy-adhesion layer laminated on the polyester film than solvent-based paints, and tend to have insufficient adhesion. A coating layer made of a specific urethane resin has been proposed to improve the adhesion, but even with such a coating layer, the adhesion is not necessarily sufficient for solventless paints. (Patent Document 4).

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633

The present invention has been made in view of the above circumstances, and its solution is to have good adhesion even when the amount of active energy rays is small. For example, the present invention is a micro-device used for a backlight unit of a liquid crystal display. It is providing the laminated polyester film which can be utilized suitably as a member for lenses or prism sheets.

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 resides in a laminated polyester film having a coating layer containing a urethane resin and an isocyanate compound derived from aliphatic or alicyclic isocyanate on at least one surface of the polyester film.

According to the laminated polyester film of the present invention, when a microlens, a prism layer, or the like is formed, a laminated polyester film having excellent adhesion and heat and moisture resistance can be provided, and its industrial value is high.

Hereinafter, the present invention will be described in more detail.
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.

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, but a catalyst that reduces the dullness of the film by setting the metal element amount to 100 ppm or less is preferable. Of the polymerization catalysts, germanium compounds and titanium compounds are more preferable than antimony compounds from the viewpoint that luminance does not decrease.

When using a titanium compound as a polymerization catalyst in the polyester film of the present invention, it is preferable to contain both a titanium compound and a phosphorus compound. The titanium element content in at least one layer of the film of the present invention needs to be 20 ppm or less, preferably 10 ppm or less, and the lower limit is usually 1 ppm, but preferably 2 ppm. When there is too much content of a titanium compound, there exists a concern about the fall of a brightness | luminance and coloring of a film. Further, when no titanium element is contained, the productivity at the time of production of the polyester raw material is inferior, and the polyester raw material reaching the target degree of polymerization cannot be obtained. On the other hand, the amount of phosphorus element is preferably 1 ppm or more, more preferably 5 ppm or more, and the upper limit is 300 ppm, preferably 200 ppm, and more preferably 100 ppm. When there is too much content of a phosphorus compound, gelatinization will occur and it may become a foreign material and cause the quality of a film to fall. By containing a titanium compound and a phosphorus compound within the above range, oligomer by-products can be prevented and a highly transparent film can be produced.

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 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 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 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, when the thickness exceeds 3 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.

Furthermore, the content of particles in the polyester layer is usually in the range of 0.0001 to 5% by weight, preferably 0.0003 to 3% by weight. When the particle content is less than 0.0001% 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.

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.

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 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.

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.

Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. As for the coating layer, it may be provided by in-line coating, which treats the film surface during the stretching process of the polyester film, or may be applied off-system on the film once manufactured, and may employ both offline coating. You may use 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.

As a result of various investigations, it has been found that the adhesion between the prism layer and the microlens layer is improved by forming a coating layer containing a urethane resin and an isocyanate compound derived from an aliphatic or alicyclic isocyanate. It was.

The coating layer in the present invention can particularly improve the adhesion with the solventless active energy ray-curable layer. For example, a prism layer or a microlens layer can be formed on the coating layer. it can.

In the present invention, it is an essential requirement to have a coating layer containing a urethane resin and an isocyanate compound derived from aliphatic or alicyclic isocyanate on at least one surface of the polyester film.

The urethane resin contained in the coating layer of the film of the present invention is a polymer compound having a urethane resin in the molecule. Usually, urethane resin is prepared by reaction of polyol and isocyanate. Examples of the polyol include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination.

Polycarbonate polyols are obtained from a polyhydric alcohol and a carbonate compound by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentane. Diol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decane Diol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like can be mentioned. Examples of the carbonate compound include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate. Examples of polycarbonate polyols obtained from these reactions include poly (1,6-hexylene) carbonate, poly (3- And methyl-1,5-pentylene) carbonate.

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

Among the above polyols, polycarbonate polyols are more preferably used in order to improve adhesion with various topcoat layers.

  Examples of the polyisocyanate compound used to obtain the urethane resin include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate, α, α, α ′, α ′. -Aliphatic isocyanates having aromatic rings such as tetramethylxylylene diisocyanate, aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl Methane diisocyanate Over DOO, alicyclic isocyanates such as isopropylidene dicyclohexyl diisocyanates. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates from the viewpoint of preventing yellowing due to ultraviolet rays.

A chain extender may be used when synthesizing the urethane 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, butanediol and pentanediol, aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene, neopentyl glycol and neopentyl. Examples include glycols such as ester glycols such as glycol hydroxypivalate. Examples of the chain extender having two amino groups include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine, ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3- Propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10- Aliphatic diamines such as decane diamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isoprobilitincyclohexyl-4,4′-diamine, 1,4-diaminocyclohexane, 1 , 3-Bisaminomethylcyclohexa And alicyclic diamines such as isophorone diamine.

The urethane resin in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the urethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into the skeleton of a urethane resin to form an ionomer is preferable because of excellent storage stability of the liquid and water resistance, transparency, and adhesion of the resulting coating layer.
Examples of the ionic group to be introduced include various groups such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium salt, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, there are a method of using a carboxyl group-containing resin as a copolymer component during prepolymer synthesis, and a method of using a component having a carboxyl group as one component such as polyol, polyisocyanate, and chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine.

The isocyanate compound derived from an aliphatic or alicyclic isocyanate in the present invention refers to a compound derived from an aliphatic isocyanate and a blocked isocyanate derivative in which the isocyanate group is blocked. For example, an aliphatic isocyanate having an aromatic ring such as α, α, α ′, α′-tetramethylxylylene diisocyanate, an aliphatic isocyanate such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, Examples thereof include alicyclic isocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), and isopropylidene dicyclohexyl diisocyanate. These may be used alone or in combination. Among the above isocyanates, hexamethylene diisocyanate is preferable from the viewpoint of improving the adhesion with the active energy ray-curable resin.

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

  Further, a crosslinking agent may be used in the coating layer within the range not impairing the gist of the present invention, and various known resins can be used, for example, amino resin-based melamine, benzoguanamine, oxazoline-based, carbodiimide-based, epoxy System compounds and the like. Moreover, what is called a polymer type crosslinking agent etc. which copolymerized the reactive group of the above crosslinkable functional groups in the frame | skeleton of another polymer is illustrated.

In order to improve slipperiness and blocking, it is preferable to contain particles as a constituent component of the coating layer.
The average particle diameter of the particles is preferably in the range of 0.15 μm or less, more preferably in the range of 0.12 μm or less, from the viewpoint of the transparency of the film. Further, from the viewpoints of adhesion and slipperiness, the average particle size is preferably in the range of 0.03 μm or more, more preferably in the range of 0.05 μm or more.
The content of the particles is preferably in the range of 3 to 25% by weight, more preferably in the range of 5 to 15% by weight, and in the range of 5 to 10% by weight, based on the weight ratio of the entire coating layer. More preferably it is. If it is less than 3% by weight, the effect of imparting slipperiness or preventing blocking may be insufficient. Moreover, when it exceeds 25 weight%, there exists a concern about the fall of the transparency of a coating layer, the fall of the coating film strength by the continuity of a coating layer being impaired, or the fall of adhesiveness easily.

Examples of the particles used include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

The coating layer in the present invention is other than the urethane resin described above in order to improve the coating surface shape, improve the visibility when various microlens layers and prism layers are formed on the coating surface, and improve the transparency. These binder polymers can also be used in combination.

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 polyester resin, acrylic resin, urethane resin having no polycarbonate structure, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose. , Hydroxycellulose, starches and the like.

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 and the like may be contained.

In the present invention, the content of the urethane resin in the coating layer is usually 5 to 90% by weight, preferably 10 to 75% by weight, and more preferably 25 to 65% by weight. When the amount is less than 5% by weight, the adhesion may not be sufficient due to the small amount of the urethane resin component. When the amount exceeds 90% by weight, the coating layer is formed by a small amount of the aliphatic or alicyclic isocyanate-derived isocyanate compound. It may become brittle and adhesion may not be sufficient, or heat and humidity resistance may not be sufficient.

In the present invention, the content of the isocyanate compound derived from the aliphatic or alicyclic isocyanate in the coating layer is usually 5 to 90% by weight, preferably 10 to 85% by weight, more preferably 20 to 70% by weight. . If it is less than 5% by weight, the coating layer becomes brittle due to the small amount of isocyanate compound, and adhesion may not be sufficient or heat and humidity resistance may not be sufficient. If the amount is small, the adhesion may not be sufficient.

Analysis of various components in the coating layer can be performed by surface analysis such as TOF-SIMS.

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.

Respect laminated polyester film of the present invention, the coating amount of the coating layer provided on the polyester film is usually 0.002~1.0g / ^{m 2,} more preferably 0.005 to 0.5 / ^{m 2,} more preferably The range is 0.01 to 0.2 g / m ² . If the coating amount is less than 0.002 g / m ^2, sufficient adhesion may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties may be deteriorated. There is sex.

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 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.

Generally, a prism layer, a microlens layer, or the like is provided on the coated layer of the laminated polyester film of the present invention in order to improve luminance. In recent years, various shapes have been proposed for the prism layer in order to improve the luminance efficiently. Generally, prism layers are formed by arranging prism rows having a triangular cross section in parallel. Similarly, various shapes of the microlens layer have been proposed, but in general, a large number of hemispherical convex lenses are provided on the film. Any layer can have a conventionally known shape.

Examples of the shape of the prism layer include a triangular cross section having a thickness of 10 to 500 μm, a pitch of prism rows of 10 to 500 μm, and an apex angle of 40 ° to 100 °. As the material used for the prism layer, conventionally known materials can be used, for example, those made of an active energy ray-curable resin, such as polyester resin, epoxy resin, polyester (meth) acrylate, epoxy Examples include (meth) acrylate resins such as (meth) acrylate and urethane (meth) acrylate.

Examples of the shape of the microlens layer include a hemispherical shape having a thickness of 10 to 500 μm and a diameter of 10 to 500 μm, but may have a shape such as a cone or a polygonal pyramid. As the material used for the microlens layer, conventionally known materials can be used as in the prism layer, and examples thereof include an active energy ray curable resin.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example and a comparative example 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) Adhesion evaluation method On the polyester film coating layer, the active energy ray-curable resin composition shown below was applied to a thickness of 3 μm after curing, and ultraviolet rays were applied from an ultraviolet irradiation device to a mercury lamp 80W. The resin was cured by irradiation with 25 mJ / cm ² to obtain a laminated film having a structure of <polyester film / coating layer / active energy ray curable resin layer>. Immediately thereafter (adhesion 1) and scratches are made at intervals of 5 mm with a cutter knife (adhesion 2), a 24 mm width tape (Cello Tape (registered trademark) CT-24 manufactured by Nichiban Co., Ltd.) is applied, and 180 degree peeling is performed. After peeling off at an angle, the peeled surface is observed. If the peeled area is 5% or less, ◎ if it exceeds 5% and 20% or less, ○, if it exceeds 20% and 50% or less, Δ, exceeds 50%. Then, it was set as x.
Active energy ray curable resin composition: Nippon Kayaku KARAYAD DPHA 80 parts by weight, Nippon Kayaku KARAYAD R-128H 20 parts by weight, Ciba Specialty Chemicals IRGACURE 651 5 parts by weight.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol are used as starting materials, tetrabutoxy titanate as a catalyst, and a Ti (titanium) content of 5 ppm in a reactor, the reaction start temperature is 150 ° C., methanol The reaction temperature was gradually raised as the solvent was distilled off, and the temperature reached 230 ° C. 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, and orthophosphoric acid was added to a P (phosphorus) content of 1000 ppm, and then 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), polyester was used except that 0.2 parts of silica particles having an average particle diameter of 2 μm dispersed in ethylene glycol were added and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.66. Using a method similar to the production method of (A), a polyester (C) having an intrinsic viscosity of 0.66 was obtained.

Examples of compounds constituting the coating layer are as follows. However, “part” in the text represents the weight ratio in the resin solid content.
(U1: urethane resin) 80 parts of a polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 4 parts of polyethylene glycol having a number average molecular weight of 400, 12 parts of methylenebis (4-cyclohexylisocyanate), dimethylol An aqueous dispersion of urethane resin obtained by neutralizing a urethane resin comprising 4 parts of butanoic acid with triethylamine.

(U2: urethane resin) 400 parts of polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 14 parts of butanediol, 15 parts of pentaethylene glycol, 100 parts of isophorone diisocyanate, 75 parts of dimethylolpropionic acid An aqueous dispersion of urethane resin obtained by neutralizing a urethane resin consisting of triethylamine.

(C1: Isocyanate compound derived from hexamethylene diisocyanate) Block isocyanate obtained by blocking the isocyanate group of polyisocyanate consisting of 158 parts of hexamethylene diisocyanate trimer and 26 parts of methoxypolyethylene glycol having a number average molecular weight of 1400 with 66 parts of methyl ethyl ketone oxime. And a prepolymer consisting of 115 parts of polycarbonate polyol consisting of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 1 part of trimethylolpropane, 40 parts of isophorone diisocyanate and 8 parts of dimethylolpropionic acid with triethylamine. An aqueous blocked isocyanate compound containing a urethane resin obtained by chain extension with diethylenetriamine.

(C2: isocyanate compound derived from tolylene diisocyanate) 100 parts of a trimethylolpropane adduct of tolylene diisocyanate, 21 parts of methoxypolyethylene glycol having a number average molecular weight of 2000, and 11 parts of tetramethylol ethylenediamine, the isocyanate group of polyisocyanate is converted to methyl ethyl ketone. An aqueous blocked polyisocyanate compound obtained by blocking with 23 parts of oxime.

(C3: Melamine compound) Methoxymethylol melamine.

(C4: Oxazoline compound) A polymer type crosslinking agent having an oxazoline group branched to an acrylic resin (manufactured by Nippon Shokubai Co., Ltd., WS-500).

(F1: Particle) Silica sol having a particle size of 65 nm

Example 1:
A mixed raw material obtained by mixing polyesters (A), (B), and (C) at a ratio of 85%, 5%, and 10%, respectively, is used as a raw material of the outermost layer (surface layer), and polyesters (A) and (B) are each 95 %, 5% mixed raw materials were used as intermediate layer raw materials, each was supplied to two extruders, melted at 290 ° C, and then on a cooling roll set at 40 ° C. A non-stretched sheet was obtained by coextrusion and cooling and solidification in a layer configuration of layers (surface layer / intermediate layer / surface layer = 1/18/1 discharge amount). 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 solution 1 shown in Table 1 below was applied to one side of the longitudinally stretched film, which was led to a tenter. Stretch 4.0 times at 120 ° C in the transverse direction, heat treatment at 225 ° C, relax 2% in the transverse direction, and the coating amount (after drying) has a coating layer whose thickness is 188 μm as shown in Table 2 A polyester film was obtained.

Examples 2-10:
In Example 1, it manufactured similarly to Example 1 except having changed a coating agent composition into the composition shown in Table 1, and obtained the polyester film. The finished polyester film had good adhesion as shown in Table 2.

Comparative Examples 1-4:
In Example 1, it manufactured similarly to Example 1 except having changed a coating agent composition into the composition shown in Table 1, and obtained the polyester film. When the finished polyester film was evaluated, it was as shown in Table 2 and had poor adhesion.

  The film of the present invention can be suitably used for applications that require good adhesion to a microlens layer or a prism layer, such as a backlight unit of a liquid crystal display.

Claims (2)

A laminated polyester film comprising a coating layer containing a urethane resin and an isocyanate compound derived from aliphatic or alicyclic isocyanate on at least one surface of the polyester film. The laminated polyester film according to claim 1, wherein the aliphatic isocyanate is hexamethylene diisocyanate.