JP3204515B2 - Biaxially stretched coated polyester film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched coated polyester film in which a thin coating is firmly adhered to a base polyester film and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a coated polyester film, a method in which a coating agent is applied to a polyester film stretched in a longitudinal direction after melt extrusion, then dried and stretched in a transverse direction has been widely used.

However, various problems arise when an attempt is made to obtain a thinner coating which is firmly adhered to the base polyester film. First, regarding the film thickness of the coating, it is considered that the lower limit is 1-2 μm in the case of a dry coating film in order to ensure a uniform film thickness in view of the mechanical accuracy of a coating device currently in practical use. . Also, the thickness of the coating in the dry state depends on the solid content of the coating agent, and the lower the solid content, the thinner the coating should be.However, if the solid content becomes too low, repelling phenomenon occurs on the polyester film surface. As a result, uniform coating becomes difficult.

It is considered that the repelling phenomenon is due to a decrease in the surface tension and viscosity of the coating liquid due to a decrease in the solid content, and a deterioration in wettability with the polyester film.
Therefore, as a means to prevent such a repelling phenomenon,
It is also conceivable to add a leveling agent, a thickener, etc., but when such a low-molecular substance is added to the coating agent, not only the physical properties of the coating are reduced, but also the adhesion to the substrate film is reduced. The problem arises.

[0005] Further, as a general tendency, when the thickness of the coating is extremely thin, there is a problem that the adhesiveness to the polyester film is deteriorated. In particular, the coating weight is 0.1 g / m ^2.
In the case of an ultra-thin coating as described below, it is not easy to firmly adhere the coating to the polyester film.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a biaxial film in which an extremely thin coating is firmly adhered to a base polyester film. It is intended to provide a stretch-coated polyester film. Further, another object of the present invention is to provide such a method.
An object of the present invention is to provide a method capable of efficiently producing an axially stretched coated polyester film.

[0007]

Means for Solving the Problems The constitution of the coated polyester film according to the present invention which can solve the above-mentioned problems is that a coating agent containing an aqueous polymer as a film-forming component is stretched on at least one surface of the polyester film. It has a gist in that it is coated so that the later coating weight is 0.005 to 0.2 g / m ² . In addition, such a biaxially stretched coated polyester film is prepared by applying and drying a coating agent containing an aqueous polymer as a film-forming component on at least one surface of an unoriented polyester film, and then stretching the first stage in a transverse direction. Multi-stage stretching including longitudinal stretching in the second and subsequent stages is performed so that the total stretching ratio is 10 times or more, and the coating weight after stretching is set to 0.005 to 0.2 g / m ² to improve productivity. Can be manufactured.

[0008]

The polyester film constituting the substrate in the present invention includes ethylene terephthalate and ethylene-
α, β-bis (2-chlorophenoxy) ethane-4,4
Polyesters containing -dicarboxylate, ethylene-2,6-naphthalenedicarboxylate and the like as polymerized units are listed, and among these, polyethylene terephthalate is particularly preferred.

The aqueous polymer used as a film-forming component of the coating agent includes acrylic resins, styrene resins, polyester resins, polyurethane resins, polyvinyl resins, polyamide resins, and various modified resins thereof. For example, any aqueous polymer that can be dissolved or dispersed in water and has a film forming property can be used, and these resins are dissolved or dispersed in water or a mixed solvent of water and an organic solvent, and an aqueous solution, an emulsion, A coating agent composed of a colloidal dispersion or the like.

In the present invention, the coating agent obtained as described above is melt-extruded, and preferably applied to the surface of an unoriented polyester film immediately after casting. As a coating method employed here, for example, a roll coating method, a gravure coating method, a roll brushing method, an air knife coating method, a curtain coating method, a die coating method, or the like can be applied alone or in an appropriate combination.

The application of the coating agent is carried out in the state of a non-oriented and low-crystallinity film which has not been stretched while being melt-extruded as described above, so that the adhesion of the coating film to the base polyester film can be improved. The biaxially stretched coated polyester film, in which the coating film is simultaneously stretched and thinned at the stage of enhancing the physical properties of the base film by subsequent stretching in the horizontal and vertical directions, and the extremely thin film is firmly adhered. Can be obtained.

Among the above methods, when applied to an unoriented, non-crystalline polyester film immediately after being melt-extruded and cast, not only can the coating film adhesion be improved more effectively, but also thinning is promoted. It is preferred. After the coating agent is applied and dried, the first stage is stretched in the horizontal direction,
Adopting a procedure to perform multi-stage stretching including longitudinal stretching after the stage,
Biaxial stretching is performed so that the total stretching ratio is 10 times or more, and more preferably 13 times or more. In this case, in each stretching step, it is desired to perform heat setting at about 160 ° C. or more for about 2 seconds or more, thereby further improving the adhesion of the coating film to the base film.

At this time, a method of first stretching in the longitudinal direction and then stretching in the horizontal direction is also conceivable. However, if this stretching procedure is adopted, when the coating amount is increased, the first longitudinal stretching step is performed to stretch the film onto the stretching rolls. Adhesion of the coating film occurs, and a uniform coated film cannot be obtained. However, when the transverse stretching is performed in the first step, the coating film does not adhere to the roll in the subsequent stretching step, and the stretching can be smoothly performed. In the present invention, it is essential that the first stage be subjected to the horizontal stretching and the second and subsequent stages be subjected to the multi-stage stretching including the longitudinal stretching. Specific stretching procedures include horizontal → vertical two-stage stretching and horizontal stretching. → vertical → horizontal three-stage stretching, horizontal → vertical → horizontal → vertical four-stage stretching, etc. are included.

The amount of the coating is 0.005 to 0.2 g / m ² , preferably 0.00 to 0.2 g / m ² after biaxial stretching, in order to achieve a good balance between the surface shape and abrasion resistance of the coating.
The range of 1 to 0.1 g / m ² is appropriate, and the coating amount is 0.2 g / m ^2.
tend to blocking resistance is deteriorated when it exceeds m ^2,
On the other hand, if it is less than 0.005 g / m ² , the effect of improving the adhesiveness by the formation of the coating will not be effectively exhibited. The surface roughness of the obtained coated polyester film is Ra in the range of 0.001 to 0.1 μm from the viewpoint of securing excellent surface characteristics.
m, preferably in the range of 0.005 to 0.06 μm.

[0015]

The present invention is constituted as described above, wherein a thin coating made of an aqueous polymer material is firmly joined to a base polyester film as an adhesion improving layer. Adhesion to various substances, such as printing inks and toners for electrophotography, which cannot be obtained with conventional polyester films, can be ensured by an extremely thin coating. Accordingly, the coated polyester film can be widely used as a magnetic recording sheet material, a film base material for electrophotography, various packaging materials, and the like.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction, operation and effect of the present invention will be specifically described below with reference to embodiments. The measuring method employed in the following examples is as follows.

[Coating weight] Coated polyester (20 × 2
0 cm), and weigh 5 sheet-shaped sample pieces,
Thereafter, the coating resin on the surface of each sample piece is wiped clean with a solvent. Thereafter, the solvent is volatilized and removed, and then the weight is measured again. The difference in weight before and after wiping is defined as the coating weight.

[Evaluation of Adhesion] Paint 1 for evaluation (magnetic coating) Co-γ-Fe ₂ O ₃ 100 parts by weight Vinyl chloride-vinyl acetate copolymer 15 parts by weight Urethane modified saturated polyester resin 15 parts by weight α-alumina 3 parts by weight Carbon black 1 part by weight Toluene 105 parts by weight Methyl ethyl ketone 105 parts by weight Cyclohexanone 105 parts by weight The above ingredients are mixed and uniformly dispersed in a ball mill for about 12 hours. Next, 1 part by weight of palmitic acid, 2 parts by weight of dodecyl stearate, and 2 parts by weight of oleic acid were added to the dispersion, and the mixture was further mixed for 30 minutes. Then, a 75% solids solution of a triisocyanate compound in ethyl acetate was added to the mixture.
After adding 0 parts by weight, the mixture is further mixed for 1 hour to prepare a magnetic paint.

Evaluation paint-2 (backcoat paint) Carbon black 50 parts by weight Vinyl chloride-vinyl acetate copolymer 30 parts by weight Triisocyanate 30 parts by weight Polyurethane elastomer 30 parts by weight Nitrocellulose 30 parts by weight Stearamide 5 parts by weight Parts, 120 parts by weight of toluene and 120 parts by weight of methyl ethyl ketone are uniformly mixed to prepare a backcoat paint.

Among the above-mentioned evaluation paints, the magnetic paint is applied on a polyester film so that the thickness after drying becomes 3 μm, subjected to a magnetic field orientation treatment, dried at 60 ° C., and then dried at 100 ° C.
And then cured at 60 ° C. for 72 hours. On the other hand, the back coat paint is applied on a polyester film so that the thickness after drying becomes 1 μm.
After drying at 0 ° C, calendering is performed at 100 ° C,
Further curing is performed at 60 ° C. for 72 hours.

(Evaluation of Adhesion of Paint) After coating the above paint on a test film under a predetermined condition, a scotch tape No. 1 was applied to the coating surface of the obtained film at 23 ° C. and 50% RH. 610 (manufactured by 3M, width 10 mm, length 1
0 cm) was adhered so as to prevent air bubbles from entering, and a roll was smoothed on the top, and the coating adhesion was measured at a tensile speed of 100 cm / min and 360 ° peeling using Tensilon manufactured by Toyo Baldwin Co., Ltd. The adhesive portion was 1 cm, and the chuck interval was 8 cm.

Example 1 (a) Preparation of aqueous polyester liquid 36 parts by weight of Bironal MD1200 (manufactured by Toyobo Co., Ltd.) (solid content: 25%) 29.5 parts by weight of water 29.5 parts by weight of isopropyl alcohol 5 parts by weight of benzyl alcohol ( b) Manufacture of an easily adhesive film A polyethylene terephthalate resin is melt-extruded on a rotating drum maintained at a surface temperature of about 20 ° C., and the thickness is 200 μm
After obtaining an unstretched film of m, the coating liquid obtained in the above (a) was applied to one surface of the film by a kiss coating method. After the application, the film was passed through a preheating zone at 90 ° C., stretched 3.2 times in the transverse direction at 100 ° C., and further stretched 4.7 times in the longitudinal direction.
Heat treatment at 00 ° C for 3 seconds, average coating amount 0.05g /
thickness in m ² was obtained biaxially oriented coated polyester film of 14.5 [mu] m. The adhesiveness of the coated surface of the film was measured using the evaluation paints 1 and 2.

Examples 2 and 3 Experiments were carried out in exactly the same manner as in Example 1 except that the average coating amount was changed. Example 4 An experiment was performed in the same manner as in Example 1 except that the stretching ratio in Example 1 was changed to 4 times in the horizontal direction and 3.2 times in the vertical direction. Examples 5 and 6 Experiments were performed in exactly the same manner as in Example 4 except that the average coating amount in Example 4 was changed.

Example 7 An experiment was performed in the same manner as in Example 1 except that the stretching ratio in Example 1 was changed to 4 times in the horizontal direction and 4 times in the vertical direction. Example 8 An experiment was carried out in exactly the same manner as in Example 1 except that the coating liquid in Example 1 was changed to the one having the following composition. (Coating liquid composition) 30 parts by weight of water-dispersible polyurethane [HW350 (manufactured by Dainippon Ink), 30% solid content] and 70 parts by weight of water were uniformly mixed to prepare a coating liquid.

Comparative Examples 1 to 5 Experiments were carried out in the same manner as in Example 1 except that the total stretching ratio in Example 1 was 10 times or less and the average coating amount was changed. Comparative Example 6 An experiment was performed in exactly the same manner as in Example 1 except that the average coating amount in Example 1 was changed to 0.002 g / m ^2, and Comparative Example 6 was performed. Comparative Example 7 An experiment was performed in exactly the same manner as in Example 1 except that the average coating amount in Example 1 was changed to 0.3 g / m ^2.
And Comparative Example 8 In Example 1, the longitudinal stretching ratio was 4 and the transverse stretching ratio was 4.
The experiment was performed in exactly the same manner as in Comparative Example 8 except that the stretching was performed in the order of doubling and the average coating amount was 0.1 g / m ² .
Table 1 shows the adhesiveness of each film obtained in the above Examples and Comparative Examples.
Are shown together.

[0026]

[Table 1]

Continuation of the front page (56) References JP-A-64-9242 (JP, A) JP-A-62-162540 (JP, A) JP-A-61-261325 (JP, A) JP-A 60-141555 (JP, A) , A) JP-A-59-79732 (JP, A) JP-A-4-235019 (JP, A) JP-A-4-248116 (JP, A) Edited by Research Institute of Comprehensive Chemistry Problems and Solutions) Stretching Technology ”(Showa 46-11), Maruzen, p. 53-54 (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 55/00-55/30 C08J 7/04 G11B 5/62-5/738

Claims (2)

(57) [Claims] 1. A coating agent containing an aqueous polymer as a film-forming component is applied to at least one surface of an unoriented polyester film.
Dry it, then make the first stage a horizontal stretch
Multi-stage stretching including longitudinal stretching, the total stretching ratio is 10 times or more
The coating weight after stretching is 0.005 to 0.2
g / m ² , biaxially stretched coated polyester
Telfilm manufacturing method. 2. A method according to claim 1, wherein
Biaxially stretched coated polyester, characterized in that
Tell film.