JP2009269302A - Easily adhesive and biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily adhesive polyester film which is excellent in dimensional stability and transparency and is soluble in water and includes good adhesive properties to a hydrophilic resin. <P>SOLUTION: The easily adhesive and biaxially oriented polyester film includes an easily adhesive layer on at least one side. The easily adhesive layer contains a self-crosslinking polyurethane resin as a main component and includes a haze of 7.0% or below and thermal shrinkage percentage at 150°C of 4.0% or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an easily-adhesive biaxially oriented polyester film, and more particularly to an easily-adhesive biaxially-oriented polyester film excellent in adhesiveness with a functional layer mainly composed of a water-soluble and hydrophilic resin.

  Polyester films represented by polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) have excellent properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, and cost. Because of its excellent performance, it is used as a support film in various applications. In particular, the biaxially oriented polyester film is excellent in mechanical strength, dimensional stability, and transparency, and is used as a support film provided with various functional layers such as antistatic, antireflection, and hard coat.

  The biaxially oriented polyester film has a strong cohesion due to its highly crystallized surface, and therefore has a drawback of poor adhesion to the functional layer for each application. In order to eliminate such drawbacks, a method of laminating a polyester layer with low crystallinity on the surface of a polyester film by coextrusion as in the following patent document, and applying a water-dispersible polyester resin or acrylic resin as an easy adhesion layer A method to do this has been proposed.

Japanese Patent Publication No.49-10243 JP-A-52-19786 JP 52-19787 A JP 54-43017 A

  However, in the above known method, a support film using a polyester resin or an acrylic resin as an easy-adhesion layer is suitable for adhesion to a functional layer mainly composed of a polyester resin or an acrylic resin. ), And has a disadvantage of poor adhesion to a functional layer mainly composed of a water-soluble / hydrophilic resin such as gelatin.

  In addition, the above-described polyester film has many uses such as display for display, signboard, label, notebook computer, PDA, plasma display and the like, and the conventional polyester film sometimes has insufficient light resistance. For the purpose of improving the light resistance of the polyester film, a film such as the following patent document has been proposed, but the adhesiveness to the functional layer mainly composed of the water-soluble / hydrophilic resin is not satisfactory. There wasn't.

JP 2002-244247 A JP 2003-1703 A JP 2003-191390 A Japanese Patent Laid-Open No. 2003-237006 JP 2004-10875 A JP 2004-10875 A JP 2004-54160 A JP 2004-58435 A JP 2004-149548 A JP 2004-202890 A JP 2004-250624 A JP 2004-285310 A

  In addition, polyester films are used as optical substrates such as liquid crystal displays and plasma displays. For example, they are used for applications such as a decrease in transparency due to the precipitation of oligomers and the occurrence of rainbow unevenness in combination with hard coat layers and polarizing elements. Depending on the characteristics, it may be required. However, conventionally, even those satisfying these optical characteristics have not been satisfactory in adhesion to a functional layer or the like mainly composed of the water-soluble / hydrophilic resin described above.

  The present invention has been made in view of the above circumstances. That is, the problem of the present invention is that the biaxially oriented polyester film has excellent dimensional stability and high transparency, yet has easy adhesion with excellent adhesion to a functional layer mainly composed of a water-soluble / hydrophilic resin. It is in providing the easily-adhesive polyester film which has a layer. Moreover, it is providing the said easily-adhesive polyester film which has the outstanding optical characteristic also in various optical uses.

That is, the present invention is as follows.
(1) An easy-adhesive biaxially oriented polyester film having an easy-adhesion layer on at least one surface, wherein the easy-adhesion layer is mainly composed of a self-crosslinkable polyurethane resin, and has a haze of 7.0% or less, 150 An easy-adhesive biaxially oriented polyester film having a heat shrinkage at 4.0 ° C. of 4.0% or less.
(2) The easy-adhesive biaxial orientation characterized by having a refractive index (ny) in the width direction, a refractive index (nx) in the longitudinal direction, and a refractive index difference (Δn) of 0.005 or more and 0.10 or less. Polyester film.
(3) The easy-adhesive biaxially oriented polyester film, wherein the light transmittance at a wavelength of 380 nm is 20% or less.
(4) The easy-adhesive biaxially oriented polyester film, wherein a film haze change amount ΔHz (ΔHz = haze after heating−haze before heating) when heat-treated at 90 ° C. for 200 hours is less than 2.5.
(5) The easy-adhesive biaxially oriented polyester film, wherein the orientation main axis has a strain of 15 ° or less.

  The easy-adhesive biaxially oriented polyester film of the present invention has excellent adhesion to water-soluble and hydrophilic resins while having high dimensional stability and transparency. Moreover, as a preferred embodiment of the present invention, while having the above effects, precipitation by oligomers is small even in heat processing, and high transparency is maintained. Moreover, as a preferred embodiment of the present invention, it has excellent optical characteristics and good visibility such as rainbow spot while having the above-mentioned effects.

  The easy-adhesive biaxially oriented polyester film of the present invention has the above-described effects as a preferred embodiment. Therefore, the main component is a water-soluble / hydrophilic resin such as polyvinyl alcohol typified by an inkjet printing ink image-receiving layer and a polarizer protective film. And a support film provided with a functional layer mainly composed of a water-soluble and hydrophilic resin such as gelatin as represented by a photographic film.

(polyester)
Hereinafter, the present invention will be described in detail.
In the present invention, the polyester as a raw material for the polyester film is a crystalline polyester that can be obtained by polycondensation of an aromatic dicarboxylic acid or its ester and a diol. The aromatic dicarboxylic acid typically includes terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, and the diol includes ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, and the like. It is done.

  The above polyester can be obtained by directly polycondensing an aromatic dicarboxylic acid and a glycol, or by subjecting a dialkyl ester of an aromatic dicarboxylic acid and a glycol to a transcondensation reaction, followed by polycondensation or a diglycol ester of an aromatic dicarboxylic acid. It can also be obtained by a polycondensation method.

  Specific examples of such polyester include polyethylene terephthalate, polyethylene-2,6-naphthalate, polytetramethylene terephthalate, polytetramethylene-2,6-naphthalate, and the like. The polyester may be a copolyester obtained by copolymerizing various components in addition to the homopolyester. Further, it may be a polymer blend of polyester and another copolymer. Examples of other copolymers that can be blended include polyolefins and other polyesters. A blend of a homopolymer and a polyalkylene copolymer polymer, in particular a polyetherester copolymer or a blend of different polyalkylene glycol copolymer polymers is preferred.

  Among these, in particular, polyethylene terephthalate is most preferably used from the comprehensive performance such as transparency, mechanical properties, surface smoothness, solvent resistance, scratch resistance, moisture permeability, cost, etc. with few impurities.

  The intrinsic viscosity of the polyester resin is preferably in the range of 0.45 to 0.70. When the intrinsic viscosity is lower than 0.45, the effect of improving the tear resistance is lowered. When the intrinsic viscosity is higher than 0.70, the increase in the filtration pressure is increased and high-precision filtration becomes difficult.

(Oligomer)
In the present invention, when heat processing is performed in a post-processing step or when used as a member for a display application or the like for a long time at a high temperature, the amount of change in film haze ΔHz (ΔHz = heating) when heat-treated at 90 ° C. for 200 hours It is desirable that the post haze-the haze before heating) is less than 2.5%. The upper limit of the film haze change ΔHz is more preferably 2.0% or less, and particularly preferably 1.8% or less. This increase in ΔHz due to heat treatment is a phenomenon that occurs due to the precipitation of oligomers on the film surface. When it exceeds 2.5%, the oligomers crystallize on the surface when used in the above applications, and the transparency of the film. , And may cause problems such as influencing properties by being dissolved in a functional layer provided on the film.

  In order to make the oligomer precipitation amount on the film surface by heat treatment within the above range, a laminated polyester film composed of at least three layers by coextrusion is used, and a polyester having a low oligomer content is used for the outermost layer constituting the surface layer. it can. Or, by suppressing the amount of oligomer deposition on the film surface after heat treatment by suppressing the oligomer deposition on the film surface by providing a coating layer with an oligomer precipitation prevention effect inline / offline, ΔHz is in the above range It can be.

  The film of the present invention can be formed into a laminated structure using a co-extrusion method. In this case, the outermost layer thickness is preferably 3 μm or more, more preferably 5 μm or more, and only one side thickness. It is 25% or less of the total thickness, more preferably 20% or less, and particularly preferably 10% or less. If the thickness is less than 3 μm, oligomers contained in the inner layer may precipitate on the film surface due to heat history during processing, etc., and there may be contamination of the production line and an increase in the amount of foreign matter on the film surface. If the thickness is greater than 25% of the total thickness, the amount of particles blended in the outermost layer may increase, and transparency may be impaired.

  The oligomer includes cyclic oligomers mainly composed of cyclic trimers, linear oligomers and linear oligomers mainly composed of linear trimers, terephthalic acid, terephthalic acid monoglycol ester, etc. The oligomer of the present invention mainly consists of a cyclic trimer. A method for forming such a polyester film layer having a small amount of oligomer is not particularly limited, but is once polymerized as disclosed in JP-A-48-101462, JP-A-49-32973, and the like. By further polymerizing the chip in a solid phase, low molecular weight substances such as oligomers are reduced in the chip state, and a film is formed using these raw materials, or low molecular weight substances such as oligomers in the chip using a solvent. A method of forming a film by removing the film and a method of extracting and removing low molecular weight substances such as oligomers from a biaxially stretched heat-set film using a solvent are suitable. In particular, in the former method of adding a solid phase polymerization operation, if the temperature in the extrusion process to the film is high and the time is long, low molecular weight substances such as oligomers with a reduced angle increase due to thermal equilibrium. Therefore, it is preferable to extrude at as low a temperature as possible and in a short time.

(UV absorber)
In the present invention, when providing weather resistance as a packaging member used outdoors, or when suppressing deterioration of optical functional dyes used in displays such as near-infrared absorbers, iodine dyes, and color dyes, As for the film of invention, it is desirable for the light transmittance of wavelength 380nm to be 20% or less. In particular, when used as a packaging material or for preventing deterioration of pigments such as iodine pigments and color pigments, the light transmittance at 380 nm is more preferably 15% or less, further preferably 10% or less, and particularly preferably 5% or less. When used as a plasma display panel filter, the light transmittance at 380 nm is more preferably 5% or less, and further preferably 2% or less. If the light transmittance is 20% or less, it is possible to suppress alteration by ultraviolet rays of optical functional dyes such as near-infrared absorbing dyes and iodine dyes contained in the functional layer as packaging members used outdoors. . In addition, the transmittance | permeability in this invention is measured by the perpendicular | vertical method with respect to the plane of a film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).

  In order to reduce the transmittance of the film of the present invention at a wavelength of 380 nm to 20% or less, it is desirable to appropriately adjust the concentration of the ultraviolet absorber and the thickness of the base film. The ultraviolet absorber used in the present invention is a known substance. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. Examples of the organic ultraviolet absorber include benzotoazole, benzophenone, cyclic imino ester, and combinations thereof, but are not particularly limited as long as the absorbance is within the range defined by the present invention. However, from the viewpoint of durability, benzotoazole and cyclic imino ester are particularly preferable. When two or more kinds of ultraviolet absorbers are used in combination, ultraviolet rays having different wavelengths can be absorbed simultaneously, so that the ultraviolet absorption effect can be further improved.

  Examples of the benzophenone ultraviolet absorber, benzotriazole ultraviolet absorber, and acrylonitrile ultraviolet absorber include 2- [2′-hydroxy-5 ′-(methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2 ′. -Hydroxy-5 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxypropyl) phenyl] -2H-benzotriazole, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2- ( 2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5 Lorobenzotriazole, 2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol, 2,2′-methylenebis (4- (1,1,3 , 3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, etc. Examples of cyclic imino ester UV absorbers include 2,2 ′-(1,4-phenylene) bis ( 4H-3,1-benzoxazinon-4-one), 2-methyl-3,1-benzoxazin-4-one, 2-butyl-3,1-benzoxazin-4-one, 2-phenyl-3 , 1-benzoxazin-4-one, etc. However, it is not particularly limited thereto.

  In addition to the ultraviolet absorber, the polyester resin constituting the base film can contain various additives in addition to the catalyst as long as the effects of the present invention are not hindered. Examples of additives include inorganic particles, heat resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, light proofing agents, flame retardants, thermal stabilizers, antioxidants, and antigelling agents. And surfactants

  As a method of blending the ultraviolet absorber into the base film, a known method can be used in combination.For example, a master batch is prepared by blending the dried ultraviolet absorber and the polyester raw material in advance using a kneading extruder. It can be prepared and blended by a method of mixing a predetermined master batch and a polyester raw material at the time of forming a base film.

  At this time, the concentration of the UV absorber in the master batch is preferably 5 to 30% by weight in order to uniformly disperse the UV absorber and economically blend it. As a condition for producing the master batch, it is preferable to use a kneading extruder and to extrude it at a temperature not lower than the melting point of the polyester raw material and not higher than 290 ° C. for 1 to 15 minutes. Above 290 ° C, the weight loss of the UV absorber is large, and the viscosity of the master batch is greatly reduced. When the extrusion temperature is 1 minute or less, uniform mixing of the UV absorber becomes difficult. At this time, if necessary, a stabilizer, a color tone adjusting agent, and an antistatic agent may be added.

  Specifically, a base film having a three-layer structure containing an ultraviolet absorber in the intermediate layer can be produced as follows. PET pellets alone for the outer layer, and master batches containing UV absorbers for the intermediate layer and PET pellets are mixed at a predetermined ratio, dried and then fed to a known melt laminating extruder, Extruded into a sheet form from a die and cooled and solidified on a casting roll to make an unstretched film. That is, using two or more extruders, a three-layer manifold or a merging block (for example, a merging block having a square merging portion), a film layer constituting both outer layers and a film layer constituting an intermediate layer are laminated, An unstretched film is formed by extruding a three-layer sheet from the die and cooling with a casting roll. In the present invention, it is preferable to perform high-precision filtration during melt extrusion in order to remove foreign substances contained in the raw material polyester that cause optical defects. The filter particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filter particle size of the filter medium exceeds 15 μm, removal of foreign matters of 20 μm or more tends to be insufficient.

(particle)
The base film used in the present invention can contain particles in order to impart slipperiness. Moreover, in order to obtain high transparency, it is also a preferable aspect that the laminated polyester contains particles only in the surface layer. In this case, it is desirable that the intermediate layer does not substantially add particles. However, when the recovered raw material is used in the intermediate layer, the intermediate layer has a lubricant concentration of 300 ppm or less in order to make the transparency in a favorable range. More preferably, it can be adjusted to 200 ppm or less, and more preferably 150 ppm or less.

  Typical examples of the inorganic particles to be added include silica, colloidal silica, alumina, aluminum sol, kaolin, talc, mica, calcium carbonate, calcium phosphate, and the like. Moreover, acrylic particles, styrene particles, olefin particles, imide particles or the like can be used as the organic particles.

  In addition, it is preferable to use particles having an average particle diameter of 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 8 μm or less, and most preferably 0.1 μm or more and 3 μm or less. It is good to use. When the average particle size of the particles is smaller than 0.01 μm, it is necessary to increase the amount of addition in order to maintain the slipperiness, and it is difficult to control the haze value and the film surface roughness within the necessary ranges. In addition, when the average particle size of the particles is larger than 10 μm, it is not preferable because the added particles drop off significantly during the film forming process and contaminate the process.

  Further, the content of the particles in the polyester film is preferably 0.01% by weight or more and 5% by weight or less, more preferably 0.05% by weight or more and 1% by weight or less. When the content of the particles is less than 0.01% by weight, the slipperiness is inferior, and scratches are generated due to friction with a roll or the like in the process, which is not preferable. Moreover, when the content of the particles is more than 5% by weight, it is difficult to control the haze value and the film surface roughness within the necessary ranges.

  When the film of the present invention requires a high degree of transparency, it is possible to take a method in which the base film does not substantially contain particles that cause a decrease in transparency.

  The above-mentioned “substantially contain no particles” means, for example, in the case of inorganic particles, a content of 50 ppm or less, preferably 10 ppm or less, most preferably less than the detection limit when inorganic elements are quantified by fluorescent X-ray analysis. Means quantity. This means that even if particles are not actively added to the base film, contaminants derived from foreign substances and raw material resin or dirt adhering to the line or equipment in the film manufacturing process will be peeled off and mixed into the film. It is because there is a case to do.

  Even if particles for the purpose of imparting slipperiness are not added to the base film, it is good if, for example, the easy-adhesion layer laminated in-line is provided with slipperiness by containing fine particles with a uniform particle size. Addition of particles into the base film is not necessary because it can provide a roll-up property and a function to prevent scratches.

  Examples of particles to be included in such an easy-adhesion layer include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and other inorganic particles, Examples thereof include organic particles such as crosslinked polymer particles and calcium oxalate. Of these, silica is most preferable because it has a relatively close refractive index to that of the polyester resin and can easily provide high transparency.

(Easily adhesive layer)
The easy-adhesive biaxially oriented polyester film of the present invention has an easy-adhesive layer on at least one side of the biaxially oriented polyester film. In the present invention, the easy-adhesion layer is mainly composed of a self-crosslinkable polyurethane resin. Here, the “principal component” means containing 50% or more of all resin components contained in the easy-adhesion layer. The easy-adhesion layer is preferably a coating layer that is stretched in at least one direction after the aqueous coating solution is applied and dried. The said coating layer produces | generates a uniform film | membrane by a self-crosslinking reaction by heating with the heat | fever in the extending process of a polyester film. Here, the self-crosslinkable polyurethane resin refers to a urethane resin having a network structure produced by reacting a polyisocyanate compound with moisture in the system to form a urea bond.

  In the self-crosslinkable polyurethane resin constituting the coating layer, functional groups that are unreacted in the state of the coating solution regenerate active isocyanate groups by heating or mixing with catalyst components, react with moisture in the system, and chain It is generated by the occurrence of an elongation reaction or a crosslinking reaction that constitutes a crosslinking network. As a compound which is a raw material for such a self-crosslinkable polyurethane resin, a polyfunctional isocyanate compound such as a bifunctional or higher functional polyisocyanate compound or a bifunctional or higher functional blocked isocyanate is desirable. Examples of the blocking agent include bisulfites, phenols and oximes, which are known isocyanate blocking agents.

  As a result of intensive investigations on a resin composition having high transparency and high adhesion to both water-soluble and hydrophilic resins, the present inventor has achieved high transparency by forming an easy-adhesion layer having the above-described configuration. It has been found that the adhesiveness with water-soluble / hydrophilic resins such as gelatin, methoxycellulose, polyvinyl alcohol and the like is improved. Unlike other water-based resins, by using a self-crosslinkable polyurethane resin, a highly crosslinked network structure by the polyurethane resin is formed in the coating layer. Since it has such a special structure, while exhibiting very high transparency, when it adheres to water-soluble and hydrophilic resins, it swells appropriately with polyurethane resin with water molecules, which is It is considered to have a good effect. Moreover, it is thought that the unreacted functional group which did not lead to self-crosslinking contributes to the said adhesiveness by using a lot of self-crosslinking resin. Such an unreacted functional group can be detected by, for example, infrared spectroscopy. In any case, the use of a self-crosslinkable polyurethane resin has been found to significantly improve the adhesion to water-soluble and hydrophilic resins, leading to the present invention.

  As an isocyanate compound used as a raw material for the polyisocyanate compound and polyblock isocyanate compound added to the coating solution in order to produce the self-crosslinking polyurethane resin constituting the coating layer, aromatic tolylene diisocyanate And aliphatic isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and the like. The compound used in the coating solution is preferably water-based, and as the isocyanate compound used as the raw material for the water-based polyblock isocyanate compound, the use of an aliphatic isocyanate compound improves the temporal stability of the coating layer. Therefore, it is preferable.

  Polyether-based diol, polyester-based diol, polycarbonate-based diol and the like can also be used as a diol component used as a raw material for the polyisocyanate compound and polyblock isocyanate compound added to the coating solution and used for chain extension reaction. Among these, it is preferable to use a polyester-based diol or a polycarbonate-based diol because adhesion and hydrolysis resistance are improved. The self-crosslinkable polyurethane resin of the present invention is characterized by having an advanced network structure in which unreacted functional groups remain from the viewpoint of adhesiveness. In order to produce such a self-crosslinkable polyurethane resin, It is desirable that there are more isocyanate components than diol components (OH groups). When the polyurethane polymer prepolymer is produced, assuming that the number of moles of the diol component is (a) and the number of moles of the isocyanate component is (c), the mixing ratio (a) / (b) is 40 / 60-2. / 98 is preferable, and 30/70 to 10/90 is more preferable.

  Examples of the water-based polyblock isocyanate compound include those in which a hydrophobic polyurethane resin is forcibly emulsified with an emulsifier, and those that are water-soluble or self-dispersible by introducing a hydrophilic group or a hydrophilic segment. However, it is preferable to use a self-emulsifying type because the transparency and the coating appearance are good.

  In the coating layer, a resin other than the main component, for example, an acrylic resin, a polyurethane resin, a polyester resin, an alkyd resin, a vinyl resin such as polyvinyl alcohol, etc. is used in a range that does not affect the effect of the present invention. It doesn't matter. Among these, it is preferable to use water-soluble polyester, water-soluble polyurethane, or polyvinyl alcohol in combination. When the mass of the self-crosslinkable polyurethane resin is (c) and the mass of the other combined resin is (d), the mixing ratio (c) / (d) is preferably 100/0 to 50/50, 80 / 20-60 / 40 is more preferable.

  Further, the combined use of other crosslinking agents is not particularly limited as long as the effect of the present invention is not affected. Examples of crosslinking agents that can be used include adducts of urea, melamine, benzoguanamine, and the like with formaldehyde, amino resins such as alkyl ether compounds composed of these adducts and alcohols having 1 to 6 carbon atoms, polyfunctional epoxy compounds, Examples thereof include a polyfunctional isocyanate compound, a blocked isocyanate compound, a polyfunctional aziridine compound, and an oxazoline compound.

  When applying the above aqueous coating solution to the surface of the polyester film, an appropriate amount of a known anionic surfactant or nonionic surfactant is added to improve the wettability to the film and coat the coating solution uniformly. It is preferable to do.

  In addition, in the aqueous coating solution, inorganic and / or heat-resistant polymer particles, antistatic agents, ultraviolet absorbers, etc. in order to impart other functions such as handling properties, antistatic properties and antibacterial properties to the film. Additives such as organic lubricants, antibacterial agents, and photo-oxidation catalysts can be included. Examples of the antistatic agent used in the present invention include organic boron compounds.

  As the solvent used in the coating solution, alcohols such as ethanol, isopropyl alcohol and benzyl alcohol may be mixed in addition to water in a range of less than 50% by mass with respect to the total coating solution. Furthermore, if it is less than 10 mass%, you may mix in the range which can melt | dissolve organic solvents other than alcohol. However, the total amount of alcohols and other organic solvents in the coating solution is preferably less than 50% by mass.

The easy-adhesion layer of the present invention preferably has a coating layer after drying of 0.01 g / m ² or more and less than 1 g / m ² . When the coating amount after drying is less than 0.01 g / m ² , the adhesiveness may decrease, while when the coating amount after drying is 1 g / m ² or more, it is easily affected by the drying air in the drying furnace, Application spots are likely to occur. The lower limit of the coating amount is more preferably ^{0.05g / m 2, 0.1g / m} 2 is more preferred. The upper limit of the coating amount is more preferably ^{0.8g / m 2, 0.5g / m} 2 is more preferred.

(Film characteristics)
Further, it is important that the easily adhesive biaxially oriented polyester film of the present invention has a haze of 7.0% or less, preferably 5.0% or less, more preferably 3.0% or less. In packaging applications, it is preferable that transparency is good from the viewpoint of the finish of printing and the hue. Also, in industrial applications, particularly in optical applications, high transparency is required. Therefore, the upper limit of the haze is more preferably 3.0% or less, further preferably 2.0% or less, and 1.0% or less. Is particularly preferred.

  In addition, it is important that the heat shrinkage rate at 150 ° C. for 30 minutes in the width direction and the longitudinal direction of the film is 4.0% or less, preferably 3.0% or less. When the value of the heat shrinkage rate is 3.0% or more, the film is greatly shrunk due to overheating in both packaging and industrial applications, resulting in poor flatness, wrinkles, curls, etc., which is not preferable. In particular, when heat processing is performed in a post-processing step, or when used for a long time as a member such as a display application, the upper limit of the heat shrinkage rate at 150 ° C. × 30 minutes in the longitudinal direction of the film is 5 0.0% or less is more preferable, 4.0% or less is more preferable, and 3.0% or less is particularly preferable.

  The film of this invention should just be the thickness which can be formed into a film as a film, and film thickness is normally selected from the range of 9-300 micrometers, and also 12-250 micrometers.

  In the present invention, when heat treatment is performed in post-processing, or when preventing rainbow unevenness when used in certain optical applications, the optical main axis and the mechanical axis (longitudinal direction) are formed with the full width of the biaxially oriented polyester film. (Or width direction) is preferably approximated. In such a case, in the present invention, it is desirable that the maximum strain of the orientation main axis of the film measured with a microwave transmission type molecular orientation meter is 15 degrees or less, preferably 13 degrees or less, more preferably 10 degrees or less.

  When the strain of the orientation main axis is larger than 15 degrees, when the strain of the main axis becomes large due to the so-called bowing phenomenon, in the packaging application, the heat shrinkage characteristics in the width direction are uneven, and the printed design is distorted after heating. Causes problems such as non-uniformity. Also, in industrial applications, dimensional non-uniformity in the width method becomes a problem, and in optical applications, when color unevenness (rainbow unevenness) occurs in polarized light or is incorporated as a liquid crystal display member, the brightness of the display is reduced. It causes a decrease. When it is desired to reduce the distortion of the orientation main axis, it is desirable to reduce the stretching ratio in the longitudinal direction or set the stretching temperature higher in the film stretching step.

  In addition, when used in the above-mentioned applications, the difference in refractive index (Δn = | ny−nx |) between the refractive index (ny) in the width direction and the refractive index (nx) in the longitudinal direction is 0.005 or more and 0.10 or less. It is desirable to be. By setting the refractive index difference (Δn) within the above range, a film having excellent mechanical properties and good optical properties can be obtained.

(Film production method)
Next, although the manufacturing method of the easily-adhesive polyester film of this invention is demonstrated, naturally it is not limited to this.
After sufficiently vacuum-drying PET pellets that do not contain particles for the purpose of imparting easy slipping, they are supplied to an extruder, melted and extruded into a sheet at 270 to 290 ° C., cooled and solidified, and unstretched A PET sheet is formed. At this time, high-precision filtration is performed in order to remove foreign substances contained in the resin at an arbitrary place where the molten resin is maintained at 270 to 290 ° C. The filter medium used for high-precision filtration of molten resin is not particularly limited, but the filter medium of the sintered stainless steel is excellent in removal performance of aggregates and high-melting-point organic substances mainly composed of Si, Ti, Sb, Ge, Cu. It is. Furthermore, the filter particle size (initial filtration efficiency 95%) of the filter medium is preferably 15 μm or less.

  In the extrusion method, polyester is melted and extruded from an extrusion die, and cooled and solidified with a cooling roll to obtain an unstretched sheet. If necessary, lamination may be performed using 2 or 3 extruders, 2 or 3 layers of multi-nihold, or a feed block. In order to improve the sheet flatness, it is preferable to use an electrostatic application adhesion method or a liquid application adhesion method in order to improve the adhesion between the sheet and the rotary cooling drum.

  The unstretched film obtained above is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented polyester film. In order to reduce the distortion of the orientation main axis due to the so-called bowing phenomenon, a method in which the stretching temperature is set high so that the stretching ratio in the longitudinal direction is reduced within a range where there is no problem of unevenness in thickness may be employed.

  Although it does not specifically limit as a method of forming the easily bonding layer of this invention in the said uniaxially-oriented polyester film surface which is a base film, The coating method is used preferably. For example, as a coating method, air doctor coating method, knife coating method, rod coating method, forward rotation roll coating method, reverse roll coating method, gravure coating method, kiss coating method, bead coating method, slit orifice coating method, cast coating method, Examples include spray coating.

  A coating liquid is apply | coated to the single side | surface or both surfaces of a uniaxially-oriented polyester film by the method as described above. Next, both ends of the film are gripped with clips, guided to a hot air zone heated to 80 to 180 ° C., and stretched 2.5 to 5.0 times in the width direction after drying. Subsequently, it is guided to a heat treatment zone of 220 to 240 ° C., and heat treatment is performed to complete crystal orientation. In this heat treatment step, a relaxation treatment of 1 to 12% may be performed in the width direction or the longitudinal direction as necessary.

  In addition, the base film is a surface activity such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, ozone treatment, etc. within the range not impairing the object of the present invention. The treatment may be performed.

  Next, the description will be further described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

(1) Adhesiveness with water-soluble resin Adhesive evaluation with water-soluble resin was performed based on JIS-K5600.
The following coating material was apply | coated to the surface of the easily bonding layer of the obtained easily-adhesive biaxially-oriented polyester film with the number 10 wire bar, and it dried at 110 degreeC for 1 minute. As the coating material, a material to which a red dye was added so as to facilitate the determination was used. Nichiban 031B was used as a test tape, and 100 squares having a cut interval of 2 mm were evaluated by the number of residual squares after a single peel test.

<Gelatin>
To 95 g of ion-exchanged water, 5 g of gelatin (manufactured by Nitta Gelatin Co., Ltd., photographic grade) was added little by little with stirring, heated to 40 to 50 ° C. and stirred to prepare a 5% by weight gelatin aqueous solution. After gelatin was dissolved, about 0.2 g of an aqueous red dye (Leva Fix Brill Red E2B, manufactured by Bayer) was added little by little to make peeling observation easier.

<Methoxycellulose>
1 g of carboxydimethylcellulose sodium salt (manufactured by Nacalai Tesque Co., Ltd., reagent) was gradually added to 99 g of ion-exchanged water, heated to 40 to 50 ° C. and stirred to prepare a 1% by mass methoxycellulose aqueous solution. After the methoxycellulose was dissolved, about 0.2 g of an aqueous red dye (Leva Fix Brill Red E2B, manufactured by Bayer) was added little by little so that peeling observation was easy.

<Polyvinyl alcohol A>
5 g of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd., Gohsenol GL-05) was added little by little to 95 g of ion-exchanged water, and the mixture was heated to 40 to 50 ° C. and stirred to prepare a 5 mass% PVA-A aqueous solution. After the polyvinyl alcohol was dissolved, about 0.2 g of a water-based red dye (Leva Fix Brill Red E2B, manufactured by Bayer) was added little by little so as to facilitate peeling observation.

<Polyvinyl alcohol B>
5 g of polyvinyl alcohol (Kuraray Co., Ltd., Poval PVA-117) was added little by little to 95 g of ion-exchanged water, and the mixture was heated to 40 to 50 ° C. and stirred to prepare a 5 mass% PVA-B aqueous solution. After the polyvinyl alcohol was dissolved, about 0.2 g of a water-based red dye (Leva Fix Brill Red E2B, manufactured by Bayer) was added little by little to make peeling observation easier.

(2) Stamp adhesion The adhesive surface of a government-made 10-yen stamp (issued in 2007) was moistened with ion-exchanged water and pasted on the surface of the easy-adhesion layer of the obtained easy-adhesive biaxially oriented polyester film. After air-drying at room temperature for 24 hours, the attached stamp corner was peeled about 5 mm long with a cutter blade, the peeled portion was pulled by hand, and the adhesion was evaluated according to the state of the stamp after peeling. Judgment was good when the stamp destroyed the material, and others (when peeled off on the adhesive surface) were judged as bad.

(3) Haze and haze change (ΔHz)
The obtained easy-adhesive biaxially oriented polyester film was cut into a 50 mm square, and the haze was measured in accordance with JIS K 7105 “Testing methods for optical properties of plastic” haze (cloudiness value). NDH-300A type turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. was used for the measuring instrument.
After the measurement, the film was set in an oven heated to 90 ° C., and the film was taken out after 200 hours. The haze of the heated film was measured by the same method as above to obtain a haze after heating. The haze difference before and after heating according to the following formula was defined as the amount of change in haze (ΔHz).
ΔHz = (haze after heating−haze before heating)

(4) Longitudinal thermal shrinkage at 150 ° C. The longitudinal dimensional change rate (%) was measured in accordance with JIS C 2318-1997 5.3.4 (dimensional change).

(5) Refractive index In accordance with JIS K 7142-1996 5.1 (Method A), the refractive index (nx) in the longitudinal direction of the film and the refractive index (ny) in the width direction were measured with an Abbe refractometer using sodium D line as a light source. The refractive index difference (Δn) between the refractive index (ny) in the width direction and the refractive index (nx) in the longitudinal direction was calculated according to the following formula.
Δn = | ny−nx |

(6) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (manufactured by Hitachi, U-3500 type), the light transmittance at a wavelength of 300 to 500 nm is measured using an air layer as a standard, and the light transmittance at a wavelength of 380 nm. Asked.

(7) Distortion of orientation main axis Using a MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments, the orientation angle (θ) of the molecular chain main axis with respect to the film longitudinal direction is measured. The optical principal axis of the film is formed by the direction of the molecular chain principal axis and its orthogonal direction. Therefore, the tilt angle (ξ) of the optical principal axis with respect to the mechanical axis defined by the following formula was used as the distortion of the orientation principal axis.
When | θ | ≦ 45 ° ξ = | θ |
When | θ |> 45 °, ξ = | 90 ° − | θ ||.

(8) Rainbow unevenness observation under polarized light A polarizing plate was placed on a light source in a crossed dicol state, and an easy-adhesive biaxially oriented polyester film obtained therebetween was inserted horizontally. The film inserted in a crossed Nicol state is rotated to make it the darkest state, and then the film is further rotated by 8 °, so that the rainbow unevenness is observed with an inclination of 8 ° with respect to the absorption axis of the polarizing plate.
A: No rainbow unevenness occurs.
○: Very thin rainbow spots can be observed.
×: Rainbow irregularities can be clearly observed.

(9) Thickness of film A tape-like sample (5 cm in the horizontal direction × 1 m in the vertical direction) that is continuous in the vertical direction is collected, and a thickness of 20 points is obtained at a pitch of 1 cm using an electronic micrometer manufactured by Seiko EM Co., Ltd. and Millitron 1240. It measured and calculated | required as the average value.

(10) Amount of application The obtained film was cut into an area of 10 cm × 10 cm to prepare 10 sample films. Wipe the easy-adhesive layer surface of the sample film with a cloth soaked with a mixed organic solvent of methyl ethyl ketone / toluene = 1/1, and use a precision balance (AUW120D manufactured by Shimadzu Corporation) to minimize the influence of dust before and after wiping. In order to do this, the cleanness was measured in a class 1000 environment. The coating amount (mg / m ² ) was calculated from the measured weight difference per square meter. The organic solvent for wiping off the easy-adhesion layer surface is not limited to this as long as the coating layer can be removed.

(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged and 0.017 parts by mass of antimony trioxide as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Subsequently, the pressure was raised and the esterification reaction was performed under the conditions of a gauge pressure of 0.34 MPa and 240 ° C., and then the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Next, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and further 0.1 wt% of sodium tripolyphosphate aqueous solution was contained as sodium atoms with respect to the silica particles. 0.2 parts by mass of ethylene glycol slurry of silica particles having an average particle diameter of 2.5 μm, which was filtered through a metal filter having an opening of 5 μm, was added as the particle content. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to a polycondensation reaction at 280 ° C. under reduced pressure.
After completion of the polycondensation reaction, it is filtered through a NASRON filter with a 95% cut diameter of 5 μm, extruded into a strand from a nozzle, and cooled and solidified using cooling water that has been filtered (pore diameter: 1 μm or less) in advance. And cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g, an oligomer content of 0.96% by weight, and contained substantially no inert particles and internally precipitated particles. (Hereafter, abbreviated as PET (A).)

(Production Example 2-Polyester B)
On the other hand, in the production of PET (A), a polyethylene terephthalate resin (B) having an intrinsic viscosity of 0.62 dl / g and containing no silica particles was obtained. (Hereafter, abbreviated as PET (B).)

(Production Example 3-Polyester C)
The PET (B) obtained by the above method was pre-crystallized in advance at 160 ° C. and then solid-phase polymerized in a nitrogen atmosphere at a temperature of 220 ° C., with an intrinsic viscosity of 0.63 dl / g and an oligomer content of 0.1. 27 weight% of polyethylene terephthalate resin (C) was obtained. (Hereafter, abbreviated as PET (C).)

(Production Example 4-Polyester D)
10 parts by weight of a dried UV absorber (2,2 ′-(1,4-phenylene) bis (4H-3,1-benzoxazinon-4-one), PET (B) containing no particles (inherent viscosity Was 0.62 dl / g) and 90 parts by mass were mixed, and a polyethylene terephthalate resin (D) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter abbreviated as PET (D)).

(Production Example 4-Polyester E)
Dried ultraviolet absorber (2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol (Asahi Denka Co., Ltd., LA31 ) 10 parts by weight, 90 parts by weight of PET (B) containing no particles (intrinsic viscosity 0.62 dl / g) were mixed, and a polyethylene terephthalate resin (E) containing an ultraviolet absorber was obtained using a kneading extruder. (Hereinafter abbreviated as PET (E))

(Production Example 4-Polyester F)
10 mass of dried ultraviolet absorber (2- (5-chloro (2H) -benzotriazol-2-yl) -4-methyl-6- (tert-butyl) phenol (TINUVIN 326, manufactured by Ciba Specialty Chemicals) And 90 parts by mass of PET (B) containing no particles (intrinsic viscosity is 0.62 dl / g) were mixed, and a polyethylene terephthalate resin (F) containing an ultraviolet absorber was obtained using a kneading extruder (hereinafter referred to as “a UV absorber”). And abbreviated as PET (F).)

(Production Example 5-Water-based polyblock isocyanate compound D)
In methyl ethyl ketone solvent, polyester polyol (adipic acid / isophthalic acid // 1,6-hexanediol = 50/50 // 100 (molar ratio), average molecular weight 1700) 100 parts by mass, 1.4 butanediol 9 parts by mass, After adding 80 parts by mass of tolylene diisocyanate to 8 parts by mass of trimethylolpropane and reacting at a system temperature of 75 ° C. for 60 minutes, 12 parts by mass of dimethylolpropionic acid, polyethylene glycol (average molecular weight 600) 16 parts by mass and an amine catalyst were added, and the reaction was carried out at a system temperature of 75 ° C. to obtain an isocyanate group-containing urethane prepolymer. Next, 16 parts by mass of methyl ethyl ketoxime was added at an internal temperature of 55 ° C., and a blocking reaction was performed to obtain a 3.5 wt% blocked isocyanate group-containing urethane prepolymer in terms of regenerated isocyanate groups (acid value 20. 8). The urethane prepolymer was mixed with 7.2 parts by weight of triethylamine, emulsified in 450 parts by weight of water, and then 2.9 parts by weight of a chain extender triethylenetetramine (equivalent to 1.5% by weight in terms of recycled isocyanate group). And the methyl ethyl ketone solvent is distilled off under reduced pressure to obtain a thermally crosslinkable water-based polyblock isocyanate compound D (weight average molecular weight 35,000, containing 2.0% by weight of a blocked isocyanate group in terms of regenerated isocyanate group). Obtained.

Example 1
After drying 100 parts by mass of PET (B) resin pellets having an intrinsic viscosity of 0.62 dl / g and containing no particles as a raw material for the base film intermediate layer at 135 ° C. for 6 hours under reduced pressure (1 Torr), the extruder 2 (intermediate layer) II layer), PET (A) and PET (B) are mixed and adjusted so that the content of silica particles is 0.10% by mass, dried by a conventional method, and then extruder 1 (for outer layer I layer) ) And 3 (for the outer layer III layer), respectively, and dissolved at 285 ° C. These two polymers are each filtered through a filter material of stainless steel sintered body (nominal filtration accuracy 10 μm particle 95% cut), laminated in a three-layer confluence block, extruded into a sheet form from the die, and then electrostatically applied. It was wound around a casting drum having a surface temperature of 30 ° C. using a casting method, and solidified by cooling to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer was 5: 90: 5.

  This unstretched film was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with a roll group having a difference in peripheral speed to obtain a uniaxially oriented PET film.

Next, an aqueous polyurethane resin (manufactured by DIC, Hydran HW345) and an aqueous polyblock isocyanate compound A (manufactured by Mitsui Chemicals Polyurethanes, Takenate WB-920, TDI lactam block type) were mixed at a solid content mass ratio of 30/70. The coating liquid (A) having a solid content concentration of 14.6% by mass was prepared with a solvent having a solvent mass ratio of water / isopropanol = 70/30. The coating liquid is microfiltered with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency 95%) of 25 μm, and the coating amount after drying on one side of a uniaxially oriented PET film is 0.2 g / m ² by the reverse roll method. After coating, the film was dried at 80 ° C. for 20 seconds.

The uniaxially stretched film on which the coating layer was formed was guided to a tenter stretching machine, guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.2 times in the width direction. Next, while maintaining the width stretched in the width direction, the treatment was performed at a temperature of 225 ° C. for 30 seconds, and further a 3% relaxation treatment was performed in the width direction, so that the coating amount of the easy adhesion layer was 0.2 g / m ² , An easy-adhesive biaxially oriented polyester film having a film thickness of 70 μm was obtained.

(Example 2)
Water-based polyester (Toyobo Co., Ltd., Vironal), water-based polyblock isocyanate compound B (Daiichi Kogyo Seiyaku Co., Ltd., sulfite block type), water-based polyblock isocyanate compound C (Daiichi Kogyo Seiyaku Co., Ltd., Elastron BN11) ) And a semipolar organic boron compound (Boron International Co., Ltd., high boron) as an antistatic agent are mixed at a solid content mass ratio of 30/33/3/34, and a solvent mass ratio of water / isopropanol = 93/7 The coating liquid (B) having a solid content concentration of 14.6% by mass was prepared.
Except that the coating liquid (B) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain a 70 μm-thick easy-adhesive biaxially oriented polyester film. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

(Example 3)
An aqueous polyester (manufactured by Toyobo Co., Ltd., Vylonal) and an aqueous polyblock isocyanate compound D (TDI oxime block type) obtained in Production Example 5 were mixed at a solid content mass ratio of 40/60, and the solvent mass ratio was A coating solution (C) having a solid concentration of 14.6% by mass was prepared with a solvent of water / isopropanol = 93/7.
Except that the coating liquid (C) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain a 70 μm-thick highly adhesive biaxially oriented polyester film. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

Example 4
Polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd., Gohsenol GL-05) and aqueous polyblock isocyanate compound B (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sulfite block type) are mixed at a solid content mass ratio of 35/65 to obtain a solvent. A coating liquid (D) having a solid content concentration of 14.6% by mass was prepared using a solvent having a mass ratio of water / isopropanol = 93/7.
Except that the coating liquid (D) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain an easily adhesive biaxially oriented polyester film having a thickness of 70 μm. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

(Example 5)
Using a water-based polyblock isocyanate compound A (manufactured by Mitsui Chemicals Polyurethanes, Takenate WB-920, TDI lactam block type) and a solvent mass ratio of water / isopropanol = 93/7, a solid content concentration of 14.6% by mass A coating solution (E) was prepared.
Except that the coating liquid (E) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain an easily adhesive biaxially oriented polyester film having a thickness of 70 μm. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

(Example 6)
The same procedure as in Example 1 was carried out except that the casting speed was changed to obtain an easily adhesive biaxially oriented polyester film having a thickness of 55 μm.

(Example 7)
The same procedure as in Example 1 was carried out except that the casting speed was changed to obtain an easily adhesive biaxially oriented polyester film having a thickness of 40 μm.

(Example 8)
The thickness is the same as in Example 1 except that the mixing ratio of PET (A) and PET (B) in the outer layers I and III is changed and the silica particle content is adjusted to 0.20% by mass. A 70 μm easy-adhesive biaxially oriented polyester film was obtained.

Example 9
An easy-adhesive biaxially oriented polyester film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that 90 parts by mass of PET (B) and 10 parts by mass of PET (D) were used as the intermediate layer II. It was.

(Example 10)
An easy-adhesive biaxially oriented polyester film having a thickness of 70 μm was obtained in the same manner as in Example 1, except that 90 parts by mass of PET (B) and 10 parts by mass of PET (E) were used as the intermediate layer II. It was.

Example 11
An easy-adhesive biaxially oriented polyester film having a thickness of 70 μm was obtained in the same manner as in Example 1 except that 90 parts by mass of PET (B) and 10 parts by mass of PET (F) were used as the intermediate layer II. It was.

Example 12
In Example 1, the outer layer I and the outer layer III were changed to only PET (C), and the ratio of the thicknesses of the I layer, the II layer, and the III layer was set to 7: 86: 7, and the casting speed was adjusted, and the film was not stretched. A sheet was obtained. The obtained unstretched sheet was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 2.6 times in the longitudinal direction with a roll group having a difference in peripheral speed to obtain a uniaxially oriented polyester film.

  Thereafter, the coating liquid (A) shown in Example 1 was microfiltered with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency of 95%) of 25 μm, applied on both sides by a reverse roll method, and dried. Thereafter, the film was guided to a tenter, preheated at 110 ° C. for about 5 seconds in a preheating zone, and then stretched in the width direction at 120 ° C. and a stretching ratio of 4.3 times. Subsequently, the film was heat treated at a constant length of 225 ° C. in the same tenter, and then subjected to a 2.0% relaxation treatment in the width direction. After the film temperature was cooled to the glass transition temperature or lower, the film was removed from the clip, and the ears were cut. Later, the film was wound up as usual to obtain a 70 μm-thick easy-adhesive biaxially oriented polyester film.

  Assuming that the positioning in the film width direction is 100%, only the position of the central part 50% of the entire film width (25% from the center position to the left and right) was adopted as the product. The inclination angle of the optical principal axis was measured for a film at a position of 25% on the left and right sides from the center, and the maximum strain of the non-oriented principal axis in this film was determined.

(Comparative Example 1)
Using a water-based polyurethane resin (manufactured by DIC, Hydran HW345), a coating liquid (F) having a solid content concentration of 14.6% by mass was prepared using a solvent having a solvent mass ratio of water / isopropanol = 93/7.
Except that the coating liquid (F) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain an easily adhesive biaxially oriented polyester film having a thickness of 70 μm. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

(Comparative Example 2)
A coating liquid (G) having a solid content concentration of 14.6% by mass was prepared using an aqueous polyester resin (manufactured by Toyobo Co., Ltd., Vylonal) and a solvent mass ratio of water / isopropanol = 93/7.
Except that the coating solution (G) was used instead of the coating solution (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain a 70 μm-thick highly adhesive biaxially oriented polyester film. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

(Comparative Example 3)
Using polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd., Gohsenol GL-05), a coating liquid (H) having a solid content concentration of 14.6% by mass was prepared with a solvent having a solvent mass ratio of water / isopropanol = 93/7.
Except that the coating liquid (H) was used instead of the coating liquid (A), it was applied and dried in the same manner as in Example 1 and then subjected to lateral stretching to obtain an easily adhesive biaxially oriented polyester film having a thickness of 70 μm. It was. The coating amount after drying of the coat layer was 0.2 g / m ² by a wiping weight method.

  The obtained evaluation results are shown in Table 1.

  The easy-adhesive biaxially oriented polyester film of the present invention has high dimensional stability and transparency, and has excellent adhesion to water-soluble and hydrophilic resins. Therefore, it is suitable for use as a substrate film for display materials such as packaging materials, window pasting materials, ink jet recording materials, substitute papers, polarizer protective films, photographic film, liquid crystal displays, plasma displays, organic EL and electronic paper. Is done.

Claims (1)

An easy-adhesive biaxially oriented polyester film having an easy-adhesion layer on at least one side,
The easy-adhesion layer is mainly composed of a self-crosslinkable polyurethane resin,
Haze is 7.0% or less,
The thermal shrinkage at 150 ° C. is 4.0% or less,
Easy-adhesive biaxially oriented polyester film.