JPH0322899B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a biaxially oriented polyester film with improved adhesiveness by providing an undercoat layer on the polyester film. Biaxially oriented polyester films, especially biaxially oriented polyethylene terephthalate films, have excellent transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, gas barrier properties, chemical resistance, etc., and are used as packaging materials and electrical insulation materials. It is used as a base material for photosensitive materials, drafting materials, electrophotographic materials, magnetic recording materials, etc. using metal vapor deposition materials, silver salts, diazo compounds, photosensitive resins, etc. In these applications, biaxially oriented polyester films are required to have adhesive properties. for example,
For packaging materials, adhesiveness with printing ink and laminating materials; for photosensitive materials, adhesiveness with photosensitive layers with binders such as gelatin and polyvinyl alcohol;
Metal vapor deposition materials are required to have adhesion to the vapor deposited metal, and magnetic recording materials are required to have adhesion to the magnetic layer. Methods for improving the adhesion of biaxially oriented polyester films include copolymerization of specific polyester-forming components, methods using compositions containing specific resins, flame treatment, corona discharge treatment, plasma discharge treatment, ultraviolet ray treatment, etc. Methods using surface treatments such as irradiation treatment and chemical treatment using specific organic compounds or inorganic compounds are known. However, these methods tend to have adhesive properties that change over time, only adhere to certain things, or even if they do have adhesive properties, they do not have high adhesive strength, and are used only as an auxiliary method. Practically speaking, a method is used in which an undercoat layer is provided on a polyester film using a coating agent. Various coating agents have been proposed as undercoat layers for polyester films, and they can be broadly classified into those using organic solvents and those using water. Recently, there has been a demand for water-based coating agents from the standpoints of occupational safety and health, pollution control, and resource and energy conservation. In general, coating agents that have adhesive properties with polyester films have poor adhesion with surface materials, especially water-soluble resins such as polyvinyl alcohol; Adhesive properties are often inferior.
Even if a coating agent has good adhesion to both a polyester film and a specific surface material, it does not necessarily have good adhesion to many of the various surface materials. In addition, even if the coating agent has good adhesion to the polyester film and the surface material, the wettability of the coating agent to the polyester film is poor, and depending on the conditions, it may not be possible to apply uniformly, or the coating layer may not be coated properly. Problems often arise in secondary processability, such as the charging property of the film, blocking property (hereinafter abbreviated as adhesion), and poor coating agent for the surface layer material. This is also due to restrictions on the coating agent that must be selected from those that use water as a medium. For example, water-soluble or water-dispersible polyester resins containing sulfonic acid groups are excellent in terms of coating properties, adhesion properties, and charging properties of coated films to polyester films, but they are not suitable for specific surface layer materials, especially polyvinyl alcohol, etc. It has low adhesion to water-soluble resins, etc., and has a tendency to stick due to moisture absorption. On the other hand, water-dispersible styrene-butadiene copolymers or water-dispersible acrylonitrile-butadiene copolymers have poor coating and adhesion properties to polyester films. However, the present inventors found that a coating agent containing a water-soluble or water-dispersible polyester resin and a water-dispersible styrene-butadiene copolymer or a water-dispersible acrylonitrile-butadiene copolymer has poor coating properties on polyester films. We have discovered that a film with excellent adhesive properties and provided with this coating layer has good adhesive properties to various surface materials including polyvinyl alcohol, which has been considered difficult to adhere to in the past, leading to the present invention. That is, the present invention provides a water-soluble polyester film containing a water-dispersible styrene-butadiene copolymer and/or a water-dispersible acrylonitrile-butadiene copolymer and a sulfonic acid group on at least one side of a polyester film containing polyethylene terephthalate as a main component. Alternatively, the present invention relates to an easily adhesive biaxially stretched polyester film coated with a water-dispersible polyester resin. The polyester film constituting the substrate in the present invention is a polyethylene terephthalate film in which 90 mol% or more of its constituent units are ethylene terephthalate. The water-soluble or water-dispersible polyester resin having a sulfonic acid group (hereinafter abbreviated as polyester resin) used in the present invention is
No. 47-40873, Japanese Patent Application Publication No. 1983-83497, Japanese Patent Application Publication No. 1983-
Polyesters known in No. 121336, JP-A-52-155640, etc., or polyesters similar thereto can be used. For example, the dicarboxylic acid component of polyester is
Examples of aromatic dicarboxylic acids include terephthalic acid,
Isophthalic acid, 2,5-naphthalene dicarboxylic acid and their ester-forming derivatives are used. Examples of aliphatic dicarboxylic acids include adipic acid, azelaic acid, sebacic acid and their ester-forming derivatives. Examples of monocarboxylic acids include oxybenzoic acid and its ester-forming derivatives. Further, as the glycol component of polyester, aliphatic, alicyclic, aromatic diols, etc. can be used, and examples thereof include ethylene glycol, 1,4-
Butanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, p-xylene diol, etc. are used, and examples of poly(oxyalkylene) glycols include so-called polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. It will be done. Polyesters include not only saturated linear polyesters consisting of the above-mentioned ester-forming components, but also
A polyester made of a compound having an ester-forming component having a valence of 3 or more or a polyester having a reactive unsaturated group can also be used. A polyester having a sulfonic acid group can be produced using a compound having a sulfonic acid group that can be used as a polyester component together with the above-mentioned polyester forming component. Examples of compounds having sulfonic acid groups include:
Sulfoisophthalic acid, sulfoterephthalic acid, 4-
There are metal salts such as sulfonaphthalene-2,7-dicarboxylic acid and its ester-forming derivatives.
Preferred examples of metals for the metal salt include lithium, sodium, potassium, and magnesium.
Among these, a very suitable compound is 5-
Sodiosulfoisophthalic acid or sodiosulfodimethyl isophthalate. Another method for introducing sulfonic acid groups into polyester is to sulfonate the unsaturated groups of polyester containing an ester-forming aliphatic unsaturated compound as a copolymerization component with a sulfonating agent such as sodium bisulfite or sodium metabisulfite. Methods can also be exemplified. The amount of aromatic dicarboxylic acid in the dicarboxylic acid component of the polyester resin is preferably in the range of 50 mol% to 100 mol%. This is to increase the softening point of the polyester resin and improve its adhesion. The sulfonic acid group in the polyester resin must be present in an amount necessary to make the resin water-soluble or water-dispersible.
It is preferable to use it within the range of . If the amount of sulfonic acid base is less than 2 mol%, water solubility or water dispersibility will be insufficient, and if the amount of sulfonic acid group is more than 20 mol%, the water resistance of the undercoat layer after coating may be poor, or the film may absorb moisture. This is because they tend to stick together. The water-dispersible styrene-butadiene copolymer (hereinafter referred to as styrene-butadiene copolymer) or water-dispersible acrylonitrile-butadiene copolymer (hereinafter referred to as acrylonitrile-butadiene copolymer) used in the present invention is: For example, "Revised New Edition Synthetic Rubber Handbook" edited by Kambara et al., Vol.
Pages 169 to 240, Asakura Shoten, published in November 1962, or the text of the 13th Rubber Technology Symposium (Rubber Industry Technology Committee Report No. 8203), "Practical latex processing technology and development of new applied products" ,Showa
As shown in June 1957, it is a copolymer mainly composed of butadiene and styrene or acrylonitrile, with other components copolymerized as necessary. in particular,
As SBR latex or NBR latex, JSR (trade name) from Japan Synthetic Rubber Co., Ltd., Nipole (trade name) from Nippon Zeon, Naugatex (trade name) from Sumitomo Naugatatsu, Crossren (trade name) from Takeda Pharmaceutical Co., Ltd., Asahi Dow Commercially available products such as Asahi Dowratex (trade name) from Dainippon Ink and Chemicals and other overseas manufacturers can be used. For water-dispersible resins, the particle size of the water-dispersed particles is
It is 5μ or less, preferably 1μ or less, and more preferably 0.1μ or less. If the particle size is large,
There are problems such as agglomeration of particles during the coating process and poor film transparency and gloss. Furthermore, if it is necessary to reduce the thickness of the coating layer, the particle size must be reduced accordingly. The ratio of the styrene-butadiene copolymer and/or acrylonitrile-butadiene copolymer to the total amount of the polyester resin and the styrene-butadiene copolymer and/or acrylonitrile-butadiene copolymer in the coating layer is expressed as solid weight. 30% to 99% by weight, preferably 50% to 95% by weight. If the proportion of styrene-butadiene copolymer and/or acrylonitrile-butadiene copolymer is small, adhesion to surface materials such as polyvinyl alcohol will decrease, and since there is a large amount of polyester resin, sticking will occur easily due to moisture absorption. . If the proportion of the polyester resin is small, the coating properties and adhesion of the coating agent to the polyester film will decrease. The method of applying polyester resin and styrene-butadiene copolymer and/or acrylonitrile-butadiene copolymer as a coating agent is to apply the polyester resin to a polyester film in advance, and then apply the styrene-butadiene copolymer and/or acrylonitrile to the polyester film. - A method of applying a butadiene copolymer, and a method of applying a mixture of a polyester resin and a styrene-butadiene copolymer and/or an acrylonitrile-butadiene copolymer. The device for applying coating agent to polyester film is Yuji Harasaki, "Coating Method", Maki Shoten.
Reverse coater shown in October 1979 issue,
Examples include, but are not limited to, gravure coaters, rod coaters, and air doctor coaters. The timing for applying the coating agent to the polyester film is before biaxial stretching, after biaxial stretching, or immediately before applying the surface layer material. Particularly preferably
A coating agent is applied to a uniaxially stretched polyester film using the roll stretching method as exemplified in No. 8470, and the film is immediately stretched in a direction perpendicular to the previous stretching direction, with or without appropriate drying, and heat treated. (hereinafter abbreviated as coating and stretching method).
If the coating and stretching method is used, it is possible to dry the coating layer at the same time as stretching, and by stretching the coating layer, the coating thickness can be made thinner, and it is possible to create a wide width that is difficult to achieve with methods other than coating and stretching. A laminated film is obtained. Note that it is also possible to improve the applicability and adhesion of the coating agent to the polyester film by subjecting the polyester film before the coating treatment to surface treatment such as corona discharge treatment. Furthermore, by subjecting the biaxially stretched polyester film of the present invention to surface treatment such as corona discharge treatment, the adhesion to the surface layer material can be further improved. The thickness of the coating layer on the biaxially stretched polyester film is preferably in the range of 0.01μ to 5μ, more preferably in the range of 0.01μ to 1μ. If the thickness of the coating layer is less than 0.01 μm, it is difficult to coat the coating uniformly, resulting in uneven coating on the product and insufficient adhesion in various applications. If the thickness of the coating layer exceeds 5 μm, the films tend to stick to each other, and the stiffness of the film becomes low compared to the overall thickness of the film. The coating layer of the biaxially oriented polyester film of the present invention may optionally contain adhesion improvers, coating improvers, antifoaming agents, ultraviolet absorbers, antioxidants, antistatic agents, lubricants, and inorganic fine particles. , dyes, pigments, etc. may be contained. Furthermore, since the coating agent uses water as a medium, water-soluble resins such as gelatin, cellulose resins, polyethers, silicone resins, epoxy resins, vinyl resins, urethane resins, and polyamide resins and water-dispersible resins are used in the coating layer. It can also contain a resin. Crosslinking agents commonly used for crosslinking styrene-butadiene copolymers or acrylonitrile-butadiene copolymers to improve the adhesion, water resistance, solvent resistance, mechanical strength, etc. of coating layers, as well as general An aqueous solution or dispersion of a methylolated or alkylolated urea-based, melamine-based, acrylamide-based, polyamide-based resin, epoxy compound, blocked polyisocyanate, etc. may also be used. The thickness of the biaxially stretched polyester film of the present invention is generally 5μ to 500μ. The biaxially stretched polyester film of the present invention is
It has improved adhesion to various surface materials, making it useful as a base material for packaging materials, photosensitive materials, drafting materials, electrophotographic materials, magnetic recording materials, etc., especially water-soluble materials such as polyvinyl alcohol and gelatin. It is useful for applications using a surface layer material using a resin as a binder or for magnetic recording applications using a dispersion type magnetic layer. The present invention will be explained below with reference to Examples. Note that the evaluation in the examples is based on the method described below. 1. Applicability The applicability when applying a coating agent to a polyester film was evaluated based on the following criteria. ○: Can be applied uniformly, causing no practical problems. Δ: Poor wettability, with some repellency observed on the coated surface. ×: Poor wettability and repels coating agent. 2 Transparency Cloudiness measured by integrating sphere type light transmittance measuring device,
Alternatively, transparency was evaluated by visual observation using the following criteria. ○: There is no practical problem. △: There are uses that pose a practical problem. ×: Not practically usable. 3 Adhesion (A) Adhesion between the base polyester film of the biaxially oriented polyester film provided with the coating layer of the present invention and the coating agent layer, and also between the biaxially oriented polyester film of the present invention and the surface layer material shown in Table 2. The adhesion was evaluated by the following method. A cellophane tape made by Nichiban Co., Ltd. with a width of 18 mm is applied to a length of 7 cm on the coated layer of the film to avoid air bubbles, and a constant load is applied thereto with a 3 kg manual load roll. Adhesion was evaluated by fixing the film, connecting one end of the cellophane tape to a 500 g weight, allowing the weight to fall naturally over a distance of 45 cm, and then starting a peel test in a 180° direction. Adhesion was evaluated using the following 5-level criteria. 3 or more is a practical range. 5: No peeling at all on the cellophane tape surface. 4: Less than 10% peels off from the cellophane tape surface. Practically speaking, if the index is 4 or more, it can be used without any problem. 3: 10 to 50% of the part peels off to the cellophane tape side. 2: More than 50% of the part peels off to the cellophane tape side. 1: Completely peel off to the cellophane tape side. 4 Adhesion (B) A magnetic layer was coated on the coating layer of the biaxially oriented polyester film of the present invention, and the peel strength was measured. The composition of the magnetic paint forming the magnetic layer is 50 parts of polyurethane, 20 parts of nitrocellulose, 30 parts of vinyl chloride-vinyl acetate resin, 7.5 parts of isocyanate compound, 12 parts of carbon black, 4 parts of lecithin, r-
460 parts of Fe ₂ O ₃ was added to methyl ethyl ketone, toluene,
An equal amount of methyl isobutyl ketone was dispersed in 900 parts (by weight) of a mixed solvent. Peel strength was measured by coating the film with magnetic paint, drying it at 80°C for 1 minute, and then heat-treating it at 80°C for 24 hours.
Paste 17.7mm width Scotchi tape (product name),
By T-peel test using a tensile tester. 5 Adhesion The adhesion (blocking) test was carried out by overlapping the polyester film surface and the coated surface, or the coated surfaces together, at a temperature of 20℃ or 40℃, and a load of 50g/
cm ³ or 100 g/cm ³ for 20 hours. The criterion for evaluation is a method of visually observing what percentage of the total area of the film is occupied by the fixed portion. Comparative Example 1 A biaxially stretched polyethylene terephthalate film having a thickness of 50 μm was coated with various coating agents shown in Table 2 at a concentration of 5% by weight using a #8 rod, and dried at 80° C. for 2 minutes. The thickness of this coating layer was approximately 0.6μ.
The adhesion between the biaxially oriented polyethylene terephthalate film and the coating agent was poor as shown in Table 1, and it was found that the biaxially oriented polyethylene terephthalate film could not be put to practical use as it was. Comparative Example 2 A biaxially oriented polyethylene terephthalate film with a thickness of 50 μm was coated with Finetex ES-670, a water-dispersible polyester resin manufactured by Dainippon Ink and Chemicals.
(trade name) was applied at a concentration of 10% by weight using a #8 rod. The coating properties of the coating agent on the biaxially stretched polyethylene terephthalate film were extremely good. The thickness of this coating layer was approximately 1.2μ. However, the adhesion of this film was poor.
By the way, when applying to a large amount of film, winding the film into a roll, and storing it in a normal room, the stickiness is greater towards both ends and the surface layer.
It was found that it tends to stick due to moisture absorption. Various coating agents shown in Table 2 were applied to the coating layer surface of this film in the same manner as in Comparative Example 1, and the adhesion was evaluated. As shown in Table 1, the adhesion of this film was completely poor to any of the three types of polyvinyl alcohol coating agents. That is, this film had poor adhesion and was only adhesive to a specific coating agent, and could not be put to practical use as it was. Example 1 A biaxially stretched polyethylene terephthalate film with a thickness of 50 μm was coated with Finetex ES-670, a water-dispersible polyester resin manufactured by Dainippon Ink and Chemicals.
(Product name) 20 parts (solid weight) and Zeon's water-dispersible styrene-butadiene copolymer Nipol LX-432A (trade name) 80 parts (solid weight) at a concentration of 10 parts by weight % water dispersion was applied with a #8 rod and dried at 80°C for 2 minutes. The coating agent had good applicability to the biaxially stretched polyethylene terephthalate film. The thickness of the coating layer of this film was approximately 1.2μ. The coating agent shown in Table 2 was applied to the coating layer surface of this film in the same manner as in Comparative Example 1, and the adhesion was evaluated. Regarding the adhesion, as shown in Table 1, it showed good adhesion to polyvinyl alcohol, and in Table 2, the adhesion to PVDC and PMA was good with an evaluation rank of 5. The film of the present invention can be put to practical use. Comparative example 3 Without using Finetex ES-670 (product name),
Only Nipole LX-432A (trade name) was applied at a concentration of 10% by weight in the same manner as in Example 1. however,
There were many coating omissions, and the film could not be used for practical use. Example 2 Same as Example 1 except that Nipole LX-430 (trade name), a water-dispersible styrene-butadiene copolymer manufactured by Nippon Zeon Co., Ltd., was used instead of Nipole LX-432A (trade name) in Example 1. Similarly, coating properties and adhesive properties were evaluated. The coating properties of the coating agent were good.
As for adhesion, as shown in Table 1, it is good for polyvinyl alcohol-based emulsions for screen printing, and is practically useful. Comparative example 4 Without using Finetex ES-670 (product name),
Nipol LX-430 (product name) only at a concentration of 10% by weight
The coating properties and adhesive properties were evaluated in the same manner as in Example 2. Although the coating properties of the coating agent were good, the adhesive properties were poor as shown in Table 1, and the film could not be put to practical use. Example 3 Water-dispersible acrylonitrile from Nippon Zeon Co., Ltd. was used instead of Nipol LX-432A (trade name) in Example 1.
The coating properties and adhesive properties were evaluated in the same manner as in Example 1, except that the butadiene copolymer Nipole 1561 (trade name) was used. The coating properties of the coating agent were good. As shown in Table 1, the film has poor adhesion to polyvinyl alcohol-based emulsions for screen printing, but is good to water-soluble polyvinyl alcohol and gelatin, making this film practically useful. be. Comparative example 5 Without using Fantex ES-670 (product name),
Only Nipole 1561 (trade name) has a concentration of 10% by weight,
The coating properties and adhesive properties were evaluated in the same manner as in Example 3. Although the coating properties of the coating agent were good, the adhesive properties were poor as shown in Table 1, and this film could not be put to practical use. Example 4 Polyethylene terephthalate with an intrinsic viscosity of 0.65
It was melted at 285°C and extruded onto a cooling drum at 60°C to form a film. This film was stretched 3.5 times in the longitudinal direction with rolls at about 95°C to obtain a film with a thickness of 185μ. This film was further coated with the coating agent of Example 1 and 0.5 part (solid weight) of Megafuc F-116 (trade name), a fluorine-based surfactant manufactured by Dainippon Ink and Chemicals.
was mixed and applied at a concentration of 10% by weight. This film was stretched 3.7 times in the transverse direction at 110°C and heat-treated under tension at 220°C. The biaxially stretched polyester film thus obtained had a polyethylene terephthalate film layer of 50μ and a coating layer of 0.45μ. The coating layer of this biaxially stretched polyester film has good uniformity, appearance, transparency, and adhesion.
The adhesiveness was also good as shown in Table 1, and the film could be put to practical use. Example 5 Polyethylene terephthalate with an intrinsic viscosity of 0.65
It was melted at 285°C and extruded onto a cooling drum at 60°C to form a film. This film was stretched 3.5 times in the longitudinal direction with rolls at about 95° C. to obtain a film with a thickness of 56 μm. The coating agent of Example 3 was applied to this film at a concentration of 3% by weight. This film was stretched 3.7 times in the transverse direction at 110°C and heat-treated under tension at 220°C. The biaxially stretched polyester film thus obtained had a polyethylene terephthalate film layer of 15μ and a coating layer of 0.042μ. The coating layer of this biaxially stretched polyester film had good uniformity, appearance, transparency, and adhesion, and the film also had good slipperiness. A magnetic paint was applied to the coated layer surface of this film, and the peel strength was measured. The peel strength of the film of the present invention is 106 g, which is the peel strength between a magnetic paint and a biaxially stretched polyethylene terephthalate film with a thickness of 15 μ without a coating layer.
31 g, the film of the present invention has excellent adhesive strength and is useful as a magnetic recording material.

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Claims (1)

[Claims] 1 A water-soluble or water-dispersible polyester containing a water-dispersible styrene-butadiene copolymer and/or a water-dispersible acrylonitrile-butadiene copolymer and a sulfonic acid group on at least one side of a polyester film containing polyethylene terephthalate as a main component. A biaxially oriented polyester film coated with a polyester resin and having easy adhesion properties.