JP5599359B2 - Laminated polyester film - Google Patents

Description

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

  Biaxially stretched polyester film excels in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, gas barrier properties, chemical resistance, etc., packaging materials, plate making materials, display materials, transfer materials, window stickers It is used for materials such as membrane switches, antireflection films used for flat displays, optical films such as diffusion sheets and prism sheets, and transparent touch panels.

  However, when other materials are applied and laminated on the polyester film in such applications, there is a drawback that the adhesiveness is poor depending on the materials used.

  As one method for improving the adhesiveness of a biaxially stretched polyester film, a method is known in which various resins are applied to the surface of the polyester film and an application layer having an easy adhesion property is provided. For example, Patent Documents 1 and 2 disclose the use of a polyester resin, an acrylic resin, or a specific crosslinking agent.

  However, in such an existing easily-adhesive coating layer, depending on the type of the topcoat layer, loose adhesion may still not be sufficient. Moreover, depending on the kind of these easily-adhesive coating layers, the appearance of the coating layers is poor and it is difficult to use depending on the application.

JP-A-8-281890 JP-A-11-286092

  This invention is made | formed in view of the said situation, Comprising: The solution subject is providing the polyester film which has a coating layer excellent in the easily adhesiveness with respect to topcoat.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a coating layer containing a specific type of compound, and the present invention has been completed. .

That is, the gist of the present invention is a polyester film having a coating layer formed by a coating stretching method from a coating solution containing polyurethane and an oxazoline compound, and the polyurethane comprises two types of carbonate polyols having different main chain structures. It exists in the laminated polyester film characterized by having the polycarbonate polyol whose copolymerized number average molecular weight is 100-1000 as a structural component.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester film which has a coating layer excellent in the easily adhesiveness with respect to a coating material can be provided, and the industrial value of this invention is high.

  The polyester of the laminated polyester film in the present invention is terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid, etc. Manufactured by melt polycondensation of dicarboxylic acid or its ester with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol Polyester. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.

  For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles to be used are selected according to the use and purpose of the film. Regarding the average particle size (d50), 0.01 μm to 3 μm, preferably 0.02 to 2.5 μm, more preferably It is in the range of 0.03 to 2 μm. If the average particle size exceeds 3.0 μm, the surface roughness of the film becomes too rough, or the particles are likely to fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained.

  About particle | grain content, it is 0.0003 to 1.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 0.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 1.0% by weight, the transparency of the film is poor. It may be enough.

  In addition, when it is particularly desired to ensure the transparency and smoothness of the film, the film may be substantially free of particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

  The turbidity (haze) of the laminated polyester film of the present invention is preferably 10% or less. More preferably, it is 5% or less, More preferably, it is 3% or less. If it is larger than this range, it may become unusable in appearance for optical film applications.

  As the film forming method of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

  The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on the purpose.

  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.

  As the coating layer in the present invention, a so-called in-line coating in which a coating layer is provided during film formation, particularly a coating stretching method in which stretching is performed after coating is suitably used.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent.

  According to such a method, since film formation and coating layer coating can be performed simultaneously, there is an advantage in manufacturing cost, and since stretching is performed after coating, a uniform coating with a thin film is achieved, so that adhesion performance is stabilized. . Moreover, the polyester film before biaxially stretching is first covered with an easy-adhesive resin layer, and then the film and the coating layer are stretched simultaneously, whereby the base film and the coating layer are firmly adhered.

  In addition, biaxial stretching of the polyester film is achieved by stretching the film in the lateral direction while holding the film edge with a tenter, so that the film is constrained in the longitudinal / lateral direction. High temperature can be applied while maintaining Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. For example, as an easily-adhesive polyester film, the uniformity of the coating layer, the improvement of the film-forming property, and the adhesion between the coating layer and the film often produce favorable characteristics.

  In this case, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, and water as the main medium, as long as it does not exceed the gist of the present invention. An organic solvent may be contained.

  The coating liquid used in the present invention contains polyurethane obtained by using a copolymer polycarbonate polyol having a structure in which two types of carbonate polyols having different main chain structures are copolymerized as a constituent component.

  The polycarbonate polyol can be obtained, for example, by a reaction from diphenyl carbonate and diol, a reaction from dialkyl carbonate and diol, or a reaction from alkylene carbonate and diol.

  For example, the diol component used in the above reaction includes the following. 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1 , 10-decanediol, neopentyl glycol, cyclohexanediol and the like.

  Copolymerized polycarbonate polyol, for example, by adding carbonate to these diol components to form a monomer unit having carbonate at the end and copolymerizing two or more of these monomer units, or adding two or more types of diol carbonate It can be obtained by a method such as carrying out copolymerization while making it occur. These copolymer polycarbonate polyols are used as a polyol component of polycarbonate polyurethane.

  The copolymer polycarbonate polyol constituting the copolymer polycarbonate polyurethane preferably has a polystyrene-reduced number average molecular weight (Mn) of 100 to 3000 by gel permeation chromatography (GPC). More preferably, it is 200-2500, More preferably, it is 400-2000. When it is larger than this range, the blocking resistance is deteriorated, and when it is smaller than this range, the adhesion may be inferior.

  Further, the structure of these copolymers is not particularly limited, such as random copolymerization, graft copolymerization, and block copolymerization.

  As the copolymer polycarbonate polyurethane, other polyols (for example, polyether polyol and polyester polyol) may be contained as long as the copolymer polycarbonate polyol is contained.

  Examples of the polyisocyanate component of the polyurethane comprising the copolymerized polycarbonate in the present invention include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'- Examples include dicyclohexylmethane diisocyanate and isophorone diisocyanate. In particular, aliphatic isocyanates and alicyclic isocyanates are preferable because they have excellent adhesion properties of the coating layer and are difficult to color.

  The polyurethane comprising the copolymerized polycarbonate in the present invention may be one using a solvent as a medium, but is preferably one containing water as a medium. In order to disperse or dissolve polyurethane in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into the polyurethane resin, or a water-soluble type. In particular, the self-emulsification type in which a hydrophilic group is introduced into the skeleton of the polyurethane resin is preferable because of excellent storage stability of the liquid and water resistance and transparency of the resulting coating layer.

  Examples of the hydrophilic group to be introduced include various groups such as a carboxyl group, a sulfone group, phosphoric acid, phosphonic acid, quaternary ammonium, and polyethylene glycol.

  The amount of the hydrophilic group in the polyurethane is preferably 0.05 to 8% by weight. When the amount of hydrophilic group is small, the water solubility or water dispersibility of polyurethane tends to be poor, and when the amount of hydrophilic group is large, the water resistance of the coating layer after coating is poor, or the film adheres to each other due to moisture absorption. It may be easier.

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

  In the present invention, particles may be contained in the coating layer in order to give the film slidability or reduce blocking. If the content of the particles is too large, the transparency of the coating layer may decrease, the continuity of the coating layer may be impaired, the coating strength may decrease, or the easy adhesion may decrease. Therefore, 15% by weight or less, further 10% by weight or less is preferable. Moreover, there is no limitation in particular about the minimum of particle content.

  As the particles to be used, for example, inorganic particles such as silica, alumina and metal oxide, or organic particles such as crosslinked polymer particles can be used. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  If the particle size of the particles is too small, it is difficult to obtain the effect of slipperiness or blocking prevention, and if the particle size is too large, the particles are likely to fall off the coating film. The average particle size is preferably about 1/2 to 10 times the thickness of the coating layer. Furthermore, if the particle size is too large, the transparency of the coating layer may be inferior, so the average particle size is preferably 300 nm or less, and more preferably 150 nm or less. The average particle diameter of the particles described here can be obtained by measuring the 50% average diameter of the number average of the particle dispersion with Microtrac UPA (Nikkiso Co., Ltd.).

  In the coating liquid for providing an easily-adhesive coating layer, components other than those described above can be included as necessary. For example, surfactants, other binders, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments and the like. These additives may be used alone or in combination of two or more as necessary.

  The coating solution may contain other components. When each component has not reacted, the obtained coating layer contains both unreacted products and reaction products of each component.

  As a method for applying the coating solution to the polyester film in the present invention, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, 1979, can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And techniques such as an extrusion coater and a bar coater.

  In addition, in order to improve the applicability | paintability to the film of a coating liquid and adhesiveness, you may give a chemical process, a corona discharge process, a plasma process, etc. to a film before application | coating.

The coating amount of the coating layer provided on the polyester film is usually 0.002 to 1.0 g / m ² , preferably 0.005 to 0.5 g / m ² , more preferably when viewed as the final coating. Is 0.01 to 0.2 g / m ² . If the coating amount is less than 0.002 g / m ^2, sufficient adhesion performance may not be obtained. If the coating layer exceeds 1.0 g / m ² , the appearance / transparency deteriorates, the film is blocked, It is easy to invite cost increase.

  The present invention will be described in more detail with reference to the following 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) Average particle size of particles added to the polyester film (d50)
The particle size was measured by a sedimentation method based on Stokes' resistance law using a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3.

(3) Adhesive The active energy ray-curable resin composition as shown below is applied on the polyester film coating layer so that the thickness after curing is 7 μm, and a high-pressure mercury lamp with an energy of 120 W / cm is used. Then, curing was performed by irradiation for about 10 seconds at an irradiation distance of 100 mm to obtain a laminated film having a structure of <polyester film / easy-adhesive coating layer / active energy ray-curable resin layer>. The active energy ray-cured resin layer of the obtained laminated film is cross-cut so that there are 100 grids in an inch width, and an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) is formed thereon. ) Was attached, a rapid peel test was performed, and the adhesion was evaluated by the peeled area. The judgment criteria are as follows.
A: Number of cross-cuts = 0
○: 1 ≦ Number of cross cuts ≦ 10
Δ: 11 ≦ number of cross-cuts ≦ 20
X: 21 <Number of cross-cuts peeled XX: Whole surface peeled Cured resin composition: Nippon Kayaku KAYARAD DPHA 80 parts, Nippon Kayaku KAYARAD R-128H 20 parts, Ciba Specialty Chemicals IRGACURE 651 5 parts composition

(4) Transparency-1
According to JIS K 7136 (ISO14782), the turbidity (haze) of the film was measured using a turbidimeter NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.). It can be said that the lower the haze, the better the transparency.

(5) Transparency-2
In the transparency-1 evaluation method, the turbidity (haze) of the film provided with the coating layer was measured, and the increase in haze relative to the film without the coating layer measured in the same manner was determined. It can be said that the transparency of a coating layer is excellent, so that the raise of the haze by providing a coating layer with respect to the film which does not provide a coating layer is small. Transparency was determined according to the following criteria.
○: Haze increase is less than 0.3% ×: Haze increase is 0.3% or more

(6) Blocking resistance Two polyester films to be measured are prepared, and a surface provided with one film coating layer and a surface not provided with another film coating layer are overlapped to obtain a 12 cm × 10 cm surface. Press the area. The conditions are 40 ° C., 80% RH, 10 kg / cm ² , 20 hours. Thereafter, the films are peeled according to the method specified in ASTM-D-1893, and the peel load is measured. It can be said that the lighter the peeling load, the better the blocking. When the load exceeds 150 g / 10 cm, there may be a problem in practice. In addition, when the coating layer is provided on both surfaces, a film without another coating layer can also be used.

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1): Polyethylene terephthalate having an intrinsic viscosity of 0.66 that does not substantially contain particles (Polyester 2): containing 0.3% by weight of amorphous silica having an average particle diameter (d50) of 1.6 μm, Polyethylene terephthalate with intrinsic viscosity of 0.65

Moreover, the following was used as a coating composition. However, “part” in the text represents the weight ratio of the active resin component.
(U1): F-2967D (Daiichi Kogyo Seiyaku Co., Ltd.), which is a polyurethane having a copolymerized polycarbonate polyol as a constituent component
(U2): 202 parts of polycarbonate diol having a number average molecular weight of about 1000 of a structure obtained by copolymerizing the structures of the following formulas (1) and (2) at a ratio of 70 mol% / 30 mol%, and hydrogenated diphenylmethane An aqueous dispersion of urethane resin obtained by neutralizing a prepolymer comprising 78.6 parts of diisocyanate and 6.7 parts of dimethylolpropionic acid with triethylamine and extending the chain with 6.5 parts of dipropylenetriamine

(U3): 400 parts of a polycarbonate polyol having a number average molecular weight of 2000 consisting of 1,6-hexanediol and diethyl carbonate, 10.4 parts of neopentyl glycol, 58.4 parts of isophorone diisocyanate, 74.3 parts of dimethylol butanoic acid. Polyurethane resin aqueous dispersion (F1): silica sol aqueous dispersion (C1) having an average particle diameter of 0.07 μm: oxazoline group is acrylic Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.)
(C2): Epocross WS-500, which is a polymer type crosslinking agent having an oxazoline group branched to an acrylic resin (manufactured by Nippon Shokubai Co., Ltd., containing about 38% by weight of 1-methoxy-2-propanol solvent)
(C3): Epocross WS-300 (manufactured by Nippon Shokubai Co., Ltd.), which is a polymer type cross-linking agent having an oxazoline group branched to an acrylic resin
(C4): Elastolone MF-25K (Daiichi Kogyo Seiyaku Co., Ltd.) which is an alicyclic polyfunctional isocyanate crosslinking agent

Example 1:
A blend of polyester 1 and polyester 2 at a weight ratio of 92/8 was used as the raw material for layer A, and polyester 1 alone was used as the raw material for layer B. To the outer layer (surface layer) and the B layer as an intermediate layer, and coextruded in a layer configuration of two types and three layers (A / B / A) using an electrostatic adhesion method. The film was cooled and solidified while being in close contact with a mirror surface cooling drum having a surface temperature of 40 to 50 ° C., and an unstretched polyethylene terephthalate film having a thickness composition ratio of A / B / A = 3/94/3 was prepared. This film was stretched 3.7 times in the longitudinal direction while passing through a heated roll group at 85 ° C. to obtain a uniaxially oriented film. The coating composition as shown in Table 1 was applied to one side of this uniaxially oriented film. Next, this film was guided to a tenter stretching machine, stretched 4.0 times in the width direction at 100 ° C., further heat treated at 230 ° C., and then subjected to a relaxation treatment of 2% in the width direction. On the axially oriented polyethylene terephthalate film, a laminated polyester film was obtained in which a coating layer having the coating amount shown in Table 1 was provided. The properties of this film are shown in Table 2.

Examples 2-11, Comparative Examples 1-8:
In the same process as in Example 1, the coating solution was changed as shown in Table 1 to obtain a coated film in which a coating layer of the amount shown in Table 1 was provided on a base film having a film thickness of 100 μm. The properties of this film are shown in Table 2.

  The film of the present invention can be suitably used as a biaxially stretched polyester film in applications requiring excellent adhesion.

Claims (1)

A polyester film having a coating layer formed from a coating solution containing polyurethane and an oxazoline compound by a coating stretching method, wherein the polyurethane has a number average molecular weight obtained by copolymerization of two types of carbonate polyols having different main chain structures. A laminated polyester film comprising a polycarbonate polyol of 100 to 1000 as a constituent component.