JP2012223927A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film having superior durability of a coating layer against various solvents at a high level and exhibiting superior adhesion after treatment by the solvent.SOLUTION: The polyester film includes a coating layer obtained by a coating/stretching method. Polyurethane including polycarbonate polyol obtained by copolymerization of two kinds of carbonate diols having different backbone structures is included in the coating layer as a constituent, in this laminated polyester film.

Description

  The present invention relates to a laminated polyester film having a coating layer excellent in durability.

  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 In addition to materials, it is widely used for antireflection films used for membrane switches and 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 of the methods for improving the adhesiveness of the biaxially stretched polyester film, a method of applying various resins to the surface of the polyester film and providing a coating layer having easy adhesion performance is known. A technique for improving the adhesiveness by providing is also known as one of them.

  As the resin provided in these coating layers, a water-based material is attracting attention while a reduction in volatile organic substance concentration (VOC) is targeted as an approach to environmental problems in recent years. Compared to solvent-based polyurethane, the coating film performance tends to be inferior, and the durability of the coating layer to the solvent also tends to be inferior.

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092

  The present invention has been made in view of the above circumstances, and the problem to be solved is a laminated polyester that has a highly excellent durability of the coating layer with respect to various solvents and can exhibit excellent adhesion even after treatment with a solvent. To provide a film.

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

  That is, the gist of the present invention is a polyester film having a coating layer obtained by a coating stretching method, and a polycarbonate polyol in which two types of carbonate diols having different main chain structures are copolymerized in the coating layer as a constituent component. It exists in the laminated polyester film characterized by containing the polyurethane which has.

  ADVANTAGE OF THE INVENTION According to this invention, the durability of the coating layer with respect to various solvents is highly excellent, the laminated polyester film which can show the outstanding adhesiveness after the process by a solvent can be provided, and the industrial of this invention Value is high.

  The base film of the coated film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. 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 in 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 of 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 used are selected according to the use and purpose of the film, but the average particle size is usually in the range of 0.01 to 5.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film may become too rough, or the particles may easily 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 transparency, smoothness, etc. of the film, it is possible to adopt a configuration that does not substantially contain particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

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

  The coating layer of the present invention is obtained by coating a coating composition on a polyester film. Various methods can be applied for coating, but 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 employed.

  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, so that it is flat without wrinkles or the like in heat setting. 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.

  Next, the coating layer provided on the film in the present invention will be described.

  In the present invention, the polyurethane constituting the coating layer is a polyurethane having, as a constituent component, a polycarbonate polyol in which two types of carbonate diols having different main chain structures are copolymerized.

  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, as the diol component used in the above reaction, 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. The copolymerized polycarbonate polyol used in the present invention is, for example, by adding carbonate to these diol components to form a monomer unit having carbonate at the terminal, and copolymerizing two or more of these monomer units, or two or more The diol component can be obtained by a method such as copolymerization while adding carbonate. These copolymer polycarbonate polyols are used as a polyol component of polyurethane.

  The copolymer polycarbonate polyol constituting the copolymer polycarbonate polyurethane has a polystyrene-equivalent number average molecular weight (Mn) by gel permeation chromatography (GPC), preferably 100 to 3000, more preferably 200 to 2500, particularly preferably 400. It is in the range of ˜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.

  The polyurethane used in the present invention may contain other polyols such as polyether diol and polyester diol as long as the above-described copolymer polycarbonate polyol is contained.

  The polyurethane having a copolymerized polycarbonate as a constituent component used 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 a polyurethane resin, and 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 the hydrophilic group is small, the water solubility or water dispersibility of the polyurethane is poor, and when the amount of the hydrophilic group is large, the water resistance of the coating layer after coating is poor, or the film tends to stick to each other due to moisture absorption. Because there are things.

  In the coating solution for providing the coating layer in the present invention, components other than those described above can be contained as necessary. For example, surfactants, other binders, crosslinking agents, 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.

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

  As the particles, 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 is too small, the effect of reducing blocking is difficult to obtain, and if it is too large, the particles tend 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.).

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 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 of the coating agent to the film, the film may be subjected to chemical treatment, corona discharge treatment, plasma treatment or the like before coating.

The coating amount of the coating layer provided on the polyester film, when it also received a final coating, typically 0.002~1.0g / m ^2, preferably from 0.005 to 0.5 / m ^2, More preferably, it is 0.01-0.2 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, film blocking, 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.

-Solvent-resistant adhesiveness The cotton layer which fully contains methyl ethyl ketone was put on the application layer of the polyester film, and the rubbing test was done by applying a load of 450 g / cm < ² > on it. The rubbing was performed under three conditions of 1 round trip, 3 round trips, and 5 round trips. A rubbing tester manufactured by Ohira Rika Kogyo Co., Ltd. was used for the rubbing test. Next, UV curable ink FD Carton X black M manufactured by Toyo Ink Manufacturing Co., Ltd. is applied on the coating layer after the rubbing test using an RI tester manufactured by IHI Machinery Systems Co., Ltd. A layer was provided and the ink was cured using a 160 W / cm metal halide lamp to produce a laminated film. The integrated light quantity of the active energy ray applied when curing was 90 mJ / cm ² . A cross cut was made on the ink layer of the laminated film prepared by the above method, and a peel test was performed using a cello tape (registered trademark).
○: UV ink does not peel off and is good ○ △: Part of UV ink is peeled Δ: About half of UV ink is peeled off
Δ ×: UV ink is almost peeled off ×: UV ink is peeled off entirely.

The contents of the polyester raw materials used in the examples and comparative examples are as follows.
(Polyester 1): Polyethylene terephthalate having an intrinsic viscosity of 0.66 substantially containing no particles (Polyester 2): Intrinsic viscosity of 0.66 containing amorphous silica having an average particle diameter of 2.5 μm Polyethylene terephthalate

Moreover, the following were used as a coating composition. However, “part” in the text represents the weight ratio of the active ingredient.
(U1): 400 parts of polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts of neopentyl glycol, 58.4 parts of isophorone diisocyanate, and 74. parts of dimethylolbutanoic acid. Polyurethane resin aqueous dispersion obtained by neutralizing 3 parts of prepolymer with triethylamine and extending the chain with isophoronediamine (U2): polycarbonate having a number average molecular weight of 800 consisting of 1,6-hexanediol and diethyl carbonate Water dispersion of polyurethane resin obtained by neutralizing a prepolymer consisting of 320 parts of polyol, 505.7 parts of hydrogenated diphenylmethane diisocyanate and 148.6 parts of dimethylolbutanoic acid with triethylamine and extending the chain with isophoronediamine (U3) Takelac of ether-based polyurethane WS6021 (manufactured by Mitsui Chemicals, Inc.)
(U4) 160 parts of a polycarbonate diol having a number average molecular weight of about 800 obtained by copolymerizing the structures of the following formulas (2) and (3) at a ratio of 50 mol% / 50 mol%, and hydrogenated diphenylmethane diisocyanate. An aqueous dispersion of a urethane resin obtained by neutralizing a prepolymer comprising 78.6 parts of styrene and 6.7 parts of dimethylolpropionic acid with triethylamine and extending the chain with 8.4 parts of isophoronediamine.




(U5) F2967D (Daiichi Kogyo Seiyaku Co., Ltd.), which is a polyurethane having a copolymerized polycarbonate polyol as a constituent component
(U6) 202 parts of polycarbonate diol having a number average molecular weight of about 1000 obtained by copolymerizing the structures of the following formulas (1) and (3) at a ratio of 70 mol% / 30 mol%, and hydrogenated diphenylmethane diisocyanate An aqueous dispersion of a urethane resin obtained by neutralizing a prepolymer comprising 78.6 parts of styrene and 6.7 parts of dimethylolpropionic acid with triethylamine and extending the chain with 6.5 parts of dipropylenetriamine

(S) Silica sol aqueous dispersion having an average particle size of 0.07 μm

Comparative Example 1:
Polyester 1 and polyester 2 are blended at a weight ratio of 95/5, dried thoroughly, heated and melted to 280-300 ° C., extruded into a sheet from a T-shaped die, and the surface using an electrostatic adhesion method. It cooled and solidified, making it closely_contact | adhere to the mirror surface cooling drum of temperature 40-50 degreeC, and the unstretched polyethylene terephthalate film was created. The film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. A 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, and the coating composition was dried using the heat, and stretched 4.0 times in the width direction at 100 ° C., and further heat-treated at 230 ° C., and the film thickness was 38 μm. A laminated polyester film having a 0.05 g / m ² coating layer on a biaxially oriented polyethylene terephthalate film was obtained. The coating solution composition and film characteristics of this film are shown in Table 1 below.

Comparative Examples 2-3:
In the same process as Comparative Example 1, a coating film was obtained in which the coating layer shown in Table 1 was provided on a base film having a film thickness of 38 μm. The properties of this film are shown in Table 1.

Comparative Example 4:
In the same process as Comparative Example 1, a film was obtained in which a coating layer was not provided on a base film having a film thickness of 38 μm. The solvent resistance was very poor.

Examples 1-4:
In the same process as Comparative Example 1, a coating film was obtained in which the coating layer shown in Table 1 was provided on a base film having a film thickness of 38 μm. The properties of this film are shown in Table 1.
By applying the copolymer-type polycarbonate polyurethane, the properties of the coating layer were not lost even after the solvent treatment, and a result of excellent adhesion was obtained.

  Examples of the film of the present invention include, for example, packaging materials, plate making materials, display materials, transfer materials, window paste materials, antireflection films used for membrane switches and flat displays, diffusion films, optical films such as prism sheets, It can utilize suitably in various uses, such as a transparent touch panel.

Claims (1)

A polyester film having a coating layer obtained by a coating stretching method, wherein the coating layer contains a polyurethane having as a constituent component a polycarbonate polyol in which two types of carbonate diols having different main chain structures are copolymerized. A laminated polyester film.