JPH0911425A - Coated film - Google Patents

Abstract

PURPOSE: To provide a biaxially oriented polyester film having a new coated layer excellent in productivity, antistatic properties an adhesion. CONSTITUTION: An easily bondable coating agent is applied to at least one side of an undrawn polyester film. By drying the resultant film, and easy bonding layer is formed. By providing an antistatic layer on at least one side of the easy bonding layer after being stretched in at least one direction, the coating film is manufactured.

Description

Detailed Description of the Invention

[0001]

The present invention relates to productivity, antistatic property,
The present invention relates to a biaxially stretched polyester film having a novel coating layer having excellent adhesiveness.

[0002]

BACKGROUND OF THE INVENTION Biaxially stretched polyester films exhibit excellent properties in mechanical strength, dimensional stability, flatness, smoothness, heat resistance, chemical resistance, transparency and the like. Therefore, it is used in a wide range of applications including base films for magnetic recording media and films for plate making. However, in spite of having such excellent characteristics, problems common to all plastic films are that they are easily charged with static electricity, and that they have poor runnability or stains during film processing or processed products. Further, while it is excellent in chemical resistance and solvent resistance, it is inferior in adhesiveness to various top coat agents. For example, the adhesiveness with the printing ink or the magnetic layer may be insufficient.

As one of methods for solving the above problems, it is known to provide a so-called undercoat layer on the surface of a polyester film. In particular, the "coating-stretching" method of coating during the film manufacturing process is economically and characteristically interesting. This is also called in-line coating.
And, conventionally, it is a method which has been carried out on the film after longitudinal stretching and before transverse stretching. The reason is as follows.
This is as described in the publication. That is, if it is applied before the longitudinal stretching, there is a problem in the stretchability of the film depending on the processing conditions, or even if the stretchability is good, the surface of the coating layer becomes rough due to adhesion with the stretching roll. This is because the coating layer may be peeled off to the stretching roll.

In order to solve the above problems, it is necessary to provide a coating layer having antistatic properties and easy adhesion of a topcoat. And a high technique was required for how to adjust the paint for this purpose. Although it is relatively easy to formulate a paint formulation that exhibits only antistatic properties and a formulation that exhibits only easy adhesion, it is very difficult to develop a formulation that combines both. One reason is that, in most cases, simply mixing both paints does not satisfy both properties. Another reason is that the pot life of the paint is short. The reason is that when an antistatic agent and another binder are mixed, the antistatic agent often functions as a flocculant. Examples of antistatic agents which are industrially inexpensive and can be obtained in large quantities include organic nonionic, anionic, cationic and amphoteric compounds having strong hydrophilicity. Some of these compounds act as dispersants, but many act as flocculants.

[0005]

Means for Solving the Problems As a result of extensive studies on the above problems, the present inventors have solved the above problems by applying a specific compound by a specific method during a polyester film manufacturing process, and expected They succeeded in improving the external effect and completed the present invention.

That is, the gist of the present invention is: (1) coating an easily adhesive coating agent on at least one side of an unstretched polyester film and drying to form an easily adhesive layer, and (2) then stretching in at least one direction. (3) A coated film produced by further providing an antistatic layer on at least one surface of the easy-adhesion layer.

Hereinafter, the present invention will be described in detail. The polyester constituting the film of the present invention is a polyester obtained by using aromatic dicarboxylic acid or its ester and glycol as main starting materials, and 80% or more of repeating structural units are ethylene terephthalate units or ethylene-2,6- Refers to polyesters with naphthalate units or 1,4-cyclohexane terephthalate. And, under the conditions that do not deviate from the above range,
You may contain the other 3rd component.

As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxy). Benzoic acid etc.) and the like can be used. As the glycol component, other than ethylene glycol, for example, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol,
One or more of neopentyl glycol and the like can be used.

The intrinsic viscosity of the polyester used in the present invention is usually 0.45 or more, preferably 0.50 to 1.0,
More preferably, it is in the range of 0.52 to 0.80. When the intrinsic viscosity is less than 0.45, there may occur a problem that productivity during film production is lowered and mechanical strength of the film is lowered. On the other hand, it is preferable that the intrinsic viscosity does not exceed 1.0 from the viewpoint of melt extrusion stability of the polymer.

The polyester film of the present invention may contain particles in the polyester to form appropriate projections on the surface of the film for the purpose of imparting slipperiness to the film and improving handleability. Examples of particles used for such purpose include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, inorganic particles such as molybdenum sulfide, and crosslinked polymer. particle,
Examples thereof include organic particles such as calcium oxalate, and precipitated particles generated during polyester polymerization.

The average particle size is preferably 0.005 to 5.0 μm, and more preferably 0.01 to 5.0, although the particle size and amount of the particles contained in the film of the present invention depend on the intended use.
It is in the range of 3.0 μm. If the average particle size exceeds 5.0 μm, the film surface tends to be too rough. Also, with a thin film, the insulation may be reduced. Further, the particles are likely to fall off the surface of the film, which may cause "powder drop" when the film is used. If the average particle size is less than 0.005 μm, protrusion formation by these particles tends to be insufficient, and the effect of improving slipperiness may be weakened. That is, if it is not added in a large amount, the effect of improving the slipperiness may not appear, and if added in a large amount, the mechanical properties of the film may be impaired.

Further, the content of particles is
0.0000-30.0% by weight, more preferably 0.010
Desirably, it is 20.0% by weight. If the amount of particles is large, the mechanical properties of the film may be impaired. The minimum particle content depends on the intended use of the film.
It is preferable that the amount of the highly transparent film is small, and the amount of particles contained is also small in order to provide appropriate slipperiness. Sliding property is an important property in magnetic recording applications, and usually 0.1% by weight or more is necessary although it depends on the particle size to be added.
Further, in the case of a white film produced by adding a white pigment such as calcium carbonate or titanium oxide, the amount of 2% by weight or more is usually required. However, this is a case where a film having a high light-shielding rate is produced, and in the case of a semitransparent film, this lower limit may be smaller.

Two or more kinds of the above-mentioned particles may be mixed in the film, or particles of the same kind but having different particle diameters may be mixed. In any case, it is preferable that the average particle diameter of all the particles contained in the film and the total content thereof satisfy the above-mentioned ranges. In the production of polyester containing particles, the particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method in which the particles are added as a slurry in which the particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, a method of adding and mixing to the polyester as a dried particle or as a slurry dispersed in water or an organic solvent having a boiling point of 200 ° C. or less using a twin-screw kneading extruder is preferable. . The particles to be added may be previously subjected to treatments such as disintegration, dispersion, classification and filtration, if necessary. As a method for adjusting the content of particles, a master raw material containing particles at a high concentration is prepared by the above-mentioned method, and at the time of film formation, it is diluted with a raw material that does not substantially contain particles and the particle content is The method of adjusting is effective.

Further, as an additive other than the above-mentioned protrusion forming agent, if necessary, an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a colorant (a dye, a dye,
(Pigment), a light blocking agent, an ultraviolet absorber, etc. may be contained. The polyester film of the present invention may have a multilayer structure as long as the properties finally obtained satisfy the requirements of the present invention. For example, it may be a co-extruded laminated film. In this case, the above description of the base film applies to the outermost polyester.

The production of a biaxially stretched polyester film comprises:
It is carried out by either simultaneous biaxial stretching or sequential biaxial stretching, but particularly sequential biaxial stretching is often performed. That is,
The melt-extruded polyester is cooled on a cooling drum to create an unstretched film, which is stretched (longitudinal stretching) with a group of rolls with different peripheral speeds, and then clipped in a direction perpendicular to the longitudinal direction of the film. Stretching (horizontal stretching) while maintaining. As a modification of this, the longitudinal stretching and the lateral stretching may be divided into several times. Further, it may be divided and a part thereof may be alternately implemented. For example, a method of manufacturing a high-strength film by a re-stretching method corresponds to this.

The unstretched film in the present invention is, for example, a film having a degree of plane orientation (ΔP) of 0.000 to 0.010, preferably 0.000 to 0.0.
Range of 0. 05, more preferably 0.000-0.
The range is 002. When ΔP is small, the interlayer adhesion between the coating layer and the base polyester film is excellent, which is preferable.

The degree of surface orientation (ΔP) is ΔP = (nγ + nβ) where nγ is the refractive index in the main orientation direction of the film, nβ is the refractive index in the direction perpendicular to the main orientation direction, and nα is the refractive index in the thickness direction. ) / 2−nα. The antistatic coating agent in the present invention,
It is a coating layer containing an antistatic agent in the coating agent. The antistatic agent here is an organic compound that has an effect of appropriately absorbing moisture to release static electricity, an organic electronic conductive compound, and conductive fine particles.

The organic compound that absorbs moisture to release static electricity is a compound that has been called a so-called antistatic agent selected from nonionic compounds, anionic compounds, cationic compounds, and amphoteric compounds. Examples of the nonionic antistatic agent include polyether compounds or derivatives thereof. Specific examples include polyethylene glycol, polypropylene glycol, polyethylene glycol / polypropylene glycol block copolymers, polyoxyethylenediamine, polyether / polyester / polyamide. Block copolymers correspond to this.

Examples of the anionic antistatic agent include compounds having sulfonic acid, carboxylic acid, phosphoric acid, boric acid and salts thereof. Among them, sulfonic acid-based antistatic agents are often used because of their strong antistatic properties and industrial availability. For example, polystyrene sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, potassium polystyrene sulfonate, cesium polystyrene sulfonate, ammonium polystyrene sulfonate, and the like. Of course, copolymers of other copolymerizable monomers with styrenesulfonic acid and salts thereof are also included. In addition, low molecular sulfonic acid compounds are also effective. Examples thereof include alkyl sulfonates and alkyl sulfates. Examples thereof include sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate, sodium lauryl sulfate ester, sodium cetyl sulfate ester, sodium stearyl sulfate ester, sodium oleyl sulfate ester, and the like.

Representative examples of the cationic antistatic agent include, as low molecular weight compounds, primary amine hydrochloride, secondary amine hydrochloride, tertiary amine hydrochloride, and quaternary ammonium salt. . As the amine used, monomethylamine, dimethylamine, trimethylamine, laurylamine, dilaurylamine, lauryldimethylamine,
Examples include stearylamine, distearylamine, stearyldimethylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, N, N-diethylethylenediamine, aminoethylethanolamine, pyridine, morpholine, guanidine, hydrazine and the like. Examples of the quaternary ammonium salts include lauryltrimethylammonium chloride, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, cetylpyridinium bromide, stearamidomethylpyridinium chloride, lauryltrimethylammonium methosulfate, and the like. As the high molecular weight cationic antistatic agent, a quaternary ammonium salt type styrene polymer,
Examples thereof include quaternary ammonium salt type aminoalkyl (meth) acrylate polymers and quaternary ammonium salt type diallylamine polymers. Specific examples include polyvinylbenzyltrimethylammonium chloride, quaternized polydimethylaminoethyl methacrylate, and polydiallyldimethylammonium chloride.

Examples of the amphoteric antistatic agent include a carboxylate type amphoteric surfactant having an amine salt type cation and a carboxylate type amphoteric surfactant having a quaternary ammonium salt type cation (so-called betaine type amphoteric surfactant). Activator) is famous. For example, sodium lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine and the like can be mentioned.

Examples of the organic electronic conductive compound include polyacetylene, poly (p-phenylene), polypyrrole, polythiophene, polyaniline, poly (arylene vinylene), polyacene and the like. These are conventionally expensive and usually have poor solubility in solvents. However, for example, a type that is soluble in water by introducing a sulfonic acid residue has been developed. Examples of the conductive fine particles include carbon black, fine metal powder, and fine metal oxide powder. For example, fine powder of silver, copper, nickel, etc.,
Alternatively, it is a fine powder of antimony oxide, indium oxide, or the like.

The antistatic coating agent in the present invention may contain a binder in addition to the above antistatic agent in the coating agent. When an organic polymer is employed among the above antistatic agents, a sufficient film is often formed by itself. However, in some organic polymer antistatic agents, the coating film may not follow the stretching of the polyester. In this case, a binder having appropriate flexibility may be mixed. On the contrary, in some organic polymer antistatic agents, the coating film formed may be too soft. In this case, a slightly hard binder may be mixed. When an organic low molecule is used as the antistatic agent, the coating film is often too soft. When conductive fine particles are used, it is necessary to use them together with a binder. The binder here is an organic polymer, specifically, at least one compound selected from the following compounds, and these are mixed with an antistatic agent in the form of an aqueous paint.

That is, as organic polymer, polyester, poly (meth) acrylate, polyurethane, polyolefin, ethylene vinyl acetate copolymer, polyamide, polyvinylidene chloride, polyvinyl chloride, chlorinated polyolefin, vinyl vinyl acetate Polymers, chloroprene, styrene-based resins, carbonate-based resins, arylate-based resins, vinyl butyral-based resins, vinyl alcohol-based resins, the above-mentioned composite polymers are mentioned, and the composite polymers referred to here are random, block, and graft. It is a copolymer or shell-core type conjugate.

The antistatic coating agent in the present invention may contain a crosslinking agent, wax, crosslinked organic particles and inorganic particles in addition to the above. Especially when a highly transparent film containing few particles in polyester is used as a base material, it is convenient to include wax or particles in the antistatic coating layer. This is because scratches due to rolls are prevented during the longitudinal stretching process of the film. Although various compounds are generally known as cross-linking agents, amino resins, particularly melamine-based cross-linking agents and urea-based cross-linking agents, epoxy-based cross-linking agents, aziridine compounds, blocked isocyanate cross-linking are known as cross-linking agents that are easy to use in aqueous paints Agents, oxazoline-based cross-linking agents, silane coupling agents, titanium coupling agents, zirco-aluminate coupling agents, and reactive vinyl compounds.

Examples of the waxes include waxes selected from natural waxes, synthetic waxes and waxes containing them. The natural wax is a vegetable wax, an animal wax, a mineral wax, or a petroleum wax. Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogen waxes, fatty acids, acid amides, amines, imides, esters and ketones. Among these waxes, carnauba wax, polyethylene wax, and a viscosity average molecular weight of 500 to 20 are used.
000 polymers, polypropylene, ethylene
Examples thereof include acrylic acid copolymers, polyethylene glycol, polypropylene glycol, and block or graft conjugates of polyethylene glycol and polypropylene glycol.

Examples of the organic particles include polystyrene or polyacrylate polymethacrylate having a crosslinked structure achieved by a compound having two or more carbon-carbon double bonds in one molecule (eg, divinylbenzene). Further, as thermosetting resin particles synthesized by the condensation reaction, melamine-formaldehyde, benzoguanamine-
Formaldehyde, phenol-formaldehyde, epoxy and the like can be mentioned. Furthermore, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer,
Examples thereof include polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, particles of fluorine-based resin such as polychlorotrifluoroethylene, and particles of crosslinked silicone resin. The surface of these particles may be treated with an organic substance. For example, it may be surface-treated with a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, or the like.

As the inorganic particles, silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black,
Molybdenum sulfide, antimony oxide, and the like can be given. Among them, silicon dioxide is easy to use because it is inexpensive and has various particle sizes. The surface of these particles is
It may be surface-treated with an organic substance. For example, it may be surface-treated with a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, or the like.
As other additives, a defoaming agent, a coatability improving agent, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment and the like may be contained.

The coating agent in the present invention is preferably a coating agent using water as a medium for safety and hygiene, but as long as it does not exceed the scope of the present invention, it serves as an auxiliary agent for a water-soluble or water-dispersible resin. It may contain an organic solvent. The same applies to the “water-based paint” in the above description. When water is used as the main medium, the compound described above may be a coating agent forcibly dispersed with a surfactant or the like, but a self-dispersing coating agent is used in view of the dispersion stability of the coating material. preferable.
The self-dispersing coating composition is a coating composition in which various hydrophilic groups are introduced into the above compound by chemical bonding. For example, the nonionic group includes a hydroxyl group, a polyether, the anionic group includes a sulfonic acid, a carboxylic acid, a phosphoric acid and salts thereof, and the cationic group includes a hydrophilic component such as an onium salt such as a quaternary ammonium salt. However, these chemical species can be introduced by copolymerization or grafting to form a self-dispersing coating agent.

The easily-adhesive layer in the present invention is a layer having improved adhesiveness with an antistatic agent, and is, for example, a compound group excluding the antistatic agent from the compound group constituting the above antistatic agent. A layer composed of a selected compound. Alternatively, there is a case where the amount is so small that it does not substantially exhibit antistatic properties even if it contains an antistatic agent. Its composition is
It varies depending on the compound coated or printed on the film in order to adhere well to the compound coated or printed on the film. The main component is a binder, and the auxiliary agent includes a crosslinking agent and particles.

As a method of applying the above-mentioned coating liquid to a polyester film, for example, the coating as shown in "Introduction to coating equipment and operation technology" by Yuji Harazaki, Sogo Gijutsu Center Co., Ltd., 1990. A device can be used. For example, forward rotation roll coater, reverse roll coater, gravure coater, knife coater, blade coater, rod coater, air doctor coater, curtain coater, fountain coater, kiss coater, kiss roll coater, bead coater, immersion coater, screen coating, cast coating, spray coating Coating or impregnating machines, coaters or coating schemes such as the LB method can be used, but are not limited thereto.

The upper limit of the ultimate temperature of the film when the coating solution is applied and dried is preferably (Tg + 20 ° C.) of the finally obtained film, and more preferably (Tg +
10 ° C.), and most preferably (Tg + 5 ° C.). If the temperature reached by the film is too high, the film-forming property of the film may be deteriorated.

The thickness of the coating layer thus obtained is
As dry solids in the final product for each layer, preferably in the range of 0.005 to 1.0 μm,
More preferably in the range of 0.01 to 0.5 μm,
The most preferable range is 0.015 to 0.2 μm.
The thickness of the coating layer is preferably thin. In particular, if the thickness of the coating layer exceeds 1.0 μm, problems such as blocking may occur. On the other hand, the thickness of the coating layer is 0.005 μm.
If it is less than the above range, desired performance may not be obtained, and coating unevenness or coating drop tends to occur.
As a conventional coating method in the polyester film manufacturing process, after applying the coating solution to the uniaxially stretched film stretched in the longitudinal direction, appropriate drying is performed, or the uniaxially stretched film is immediately stretched in the transverse direction without being dried. A method of performing heat treatment (hereinafter abbreviated as a conventional in-process coating method) has been generally used.

In the present invention, by providing an easy-adhesion layer on at least one surface of the unstretched polyester film, then stretching in at least one direction, and then providing an antistatic layer on at least one surface of the easy-adhesion layer. The feature is that a two-layer coated film is obtained in-line. By adopting such a configuration, it is possible to stably produce an antistatic and easily adhesive film which has not been heretofore available, and there are the following advantages.

(A) Conventionally, it has become possible to use a combination of an antistatic agent which causes mixing and agglomeration and a binder exhibiting easy adhesion by dividing into two layers. That is, in the present invention, the coating agent can be divided into a coating agent containing an antistatic agent and a coating agent exhibiting adhesiveness,
A stable coating material can now be used as a paint.

(B) Conventionally, in order to coat two layers, off-line coating was unavoidable for providing at least the second layer. In this case, the coating and drying steps are separately provided. Therefore, it is necessary to separately build a place that requires high cleanliness, coater,
There are problems such as the necessity of introducing a dryer separately and changes in the physical properties of the film during drying. In the present invention, although it is necessary to introduce a coater and a dryer, it is not necessary to construct a new coater building with a high degree of cleanliness. In addition, the physical properties of the film can be freely adopted within the range of a normal biaxially stretched polyester film. That is, a film that cannot be achieved by off-line coating. In addition, the advantage of in-line coating is that a coated film can be formed at the same time as film production.

(C) When the same compound is subjected to in-line coating and off-line coating, the in-line coating is superior in adhesive strength to the substrate. That is, the adhesiveness is excellent as compared with the case where the second layer is also provided by offline coating. In this respect as well, the film of the present invention is a film that has never existed before.

(D) By using the outermost layer as an antistatic layer,
The antistatic property can be exerted more strongly than when the easily adhesive layer is the outermost layer. The easily-adhesive layer and the antistatic layer can be arbitrarily selected to form a two-layer coating. When it is desired to exert the antistatic property strongly, a strong antistatic layer may be applied thickly. When it is desired to exert strong adhesiveness strongly, the thick adhesive layer may be applied and the antistatic layer may be applied in a slightly thin film. The content of the easy-adhesion layer is appropriately selected depending on the coating layer (overcoat layer) finally coated on the antistatic layer. That is, a known undercoat layer may be selected as the easy-adhesion layer with respect to the overcoat layer selected depending on the application.

Next, the method for producing the film of the present invention will be specifically described. The polyester raw material is supplied to the extrusion device,
It is melt-extruded at a temperature equal to or higher than the melting point of the polyester and extruded as a molten sheet from a slit die. Next, the molten sheet is rapidly cooled and solidified on the rotary cooling drum to a temperature not higher than the glass transition temperature to obtain a substantially amorphous unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

The electrostatic application adhesion method is usually a method in which a linear electrode is placed on the upper surface of the sheet in a direction orthogonal to the flow of the sheet, and a DC voltage of about 5 to 10 kV is applied to the electrode to statically apply the sheet. This is a method of applying an electric charge to improve the adhesion to the drum. In addition, the liquid application adhesion method is a method of improving the adhesion between the drum and the sheet by uniformly applying the liquid to the entire or a part of the surface of the rotary cooling drum (for example, only the part in contact with both ends of the sheet). It is. In the present invention, both may be used as needed. In the present invention, at this stage, it is preferable to apply the above-mentioned easy-adhesive coating liquid to at least one surface and then perform a drying treatment.

The coating-treated unstretched sheet thus obtained is first stretched in the machine direction. Stretching temperature range is 70-1
It is preferable that the stretching ratio is 50 ° C. and the stretching ratio is 2.5 to 6 times. Stretching can be performed in one step or two or more steps. After that, an antistatic layer is applied and provided on at least one surface of the easy-adhesion layer. Next, the uniaxially oriented film is cooled in the transverse direction, that is, in the direction orthogonal to the longitudinal direction to a temperature not higher than the glass transition point, or it is preheated to a temperature range of 90 to 150 ° C. without cooling, and the film is further heated to almost the same temperature. The film is stretched 2.5 to 5 times, preferably 3.0 to 4.5 times, to obtain a biaxially oriented film.

The thus-obtained film is heat-treated for 1 second to 5 minutes under an elongation of 30%, a limited shrinkage, or a fixed length. At this time, a method of performing a relaxation treatment within 10%, preferably within 5% in the longitudinal direction within the heat treatment step or after the heat treatment can be adopted in order to bring the heat shrinkage ratio in the longitudinal direction into a preferable range. . The heat treatment temperature is preferably 180 to 250 ° C, more preferably 200 to 230 ° C, although it depends on the stretching conditions. Heat treatment temperature is 250 ℃
If it exceeds, the film density becomes too high. In addition, a part of the coating layer may be thermally decomposed. On the other hand, 180 ° C
If it is less than the above range, the heat shrinkage rate of the film may increase.
Note that the film may be subjected to a chemical treatment or a discharge treatment before application in order to improve the coating property and adhesion of the coating agent to the film. Further, in order to improve the adhesiveness and coatability of the coating layer of the biaxially stretched polyester film of the present invention, the coating layer may be subjected to a discharge treatment after the coating layer is formed.

[0043]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “parts” means “parts by weight”. (1) Intrinsic viscosity of polymer [η] (dl / g) 1 g of polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in a mixed solvent of 100 ml
It was measured at 0 ° C.

(2) Degree of plane orientation (ΔP) Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., the maximum value nγ of the refractive index in the film plane and the refractive index nβ in the direction perpendicular thereto,
Further, the refractive index nα in the film thickness direction was measured, and the plane orientation degree ΔP was calculated from the following equation. The measurement of the refractive index was performed at 23 ° C. using sodium D line.

[0045]

(Equation 1)

(3) Surface resistivity (ρ _s ) Inner electrode 5 of Yokogawa / Hewlett-Packard Co.
A concentric circular electrode with a diameter of 0 mm and an outer electrode of 70 mm 1
The sample was placed in 6008A (trade name) in an atmosphere of 23 ° C. and 50% RH, a voltage of 100 V was applied, and the surface resistivity of the sample was measured by 4329A (trade name), a high resistance meter of the same company. The unit is Ω. It is desirable that it is smaller than 1 × 10 ¹² Ω.

(4) Adhesiveness of magnetic layer A magnetic paint "MAG3000" manufactured by Dainichiseika Kogyo Co., Ltd. is applied to the surface of the film by a bar coater in an amount of about 36 g / m ² . This is dried at 80 ° C. for 2 minutes. Stick Nitto Denko "Polyester adhesive tape No. 31B" to the surface of the magnetic layer, being careful not to let air bubbles enter. On this tape, a metal roll having a load of 2 kg is reciprocated 20 times. After this, the base polyester film side is bent at 180 degrees and a peeling test is performed. A peeling test was conducted by connecting one end of a polyester film to a weight of 1 kg, and allowing the weight to spontaneously drop for a distance of 45 cm so that peeling in the direction of 180 ° was started. Adhesiveness is based on the following 5 grades. A rating of 4 or higher is preferred. Evaluation 5: Excellent. The magnetic layer does not peel off at all on the side of the cellophane tape. Evaluation 4: Good. Greater than 0% and less than 33%, the magnetic layer peels off to the side of the cellophane tape. Evaluation 3: Somewhat poor. 33% or more and less than 67% of the magnetic layer peels off to the side of the cellophane tape. Evaluation 2: Poor. 67% or more and less than 100% of the magnetic layer peels off to the side of the cellophane tape. Evaluation 1: Remarkably poor. 100% magnetic layer peels off to the side of cellophane tape

(Preparation of Coating Agent) Aqueous paint stock solutions shown in Table 1 below were mixed to prepare aqueous paints having the compositions shown in Table 2 below.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

Comparative Example 1 Si having an intrinsic viscosity of 0.65 and an average particle diameter of 0.1 μm
Polyethylene terephthalate containing 0.05% by weight of O ₂ was dried by an ordinary method and supplied to an extruder, melted at 290 ° C. and extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method, Amorphous sheet was used. The ΔP of the unstretched sheet was 0.000. The obtained unstretched sheet was stretched 2.5 times in the longitudinal direction at 85 ° C. using a roll stretching method, and further stretched 1.3 times at 95 ° C. The obtained uniaxially stretched film was introduced into a tenter, laterally stretched 4.2 times at 120 ° C., and heat-treated at 225 ° C. to obtain a biaxially stretched polyester film having a thickness of 12 μm as a base polyester film. The obtained film was a flat film having excellent transparency. However, it lacked in slipperiness, antistatic property and adhesiveness. Table 3 below shows the magnetic layer adhesiveness as an example of the surface resistivity and adhesiveness of the film.

Comparative Examples 2 to 7 Unstretched sheets were obtained in the same manner as in Comparative Example 1. A coating composition having the composition shown in Table 3 was applied to one surface of this film.
"Application I" in Table 3 indicates application to an unstretched sheet,
"Application II" refers to application to a film after longitudinal stretching and before transverse stretching. In each case, the coating thickness indicates the thickness as a dry solid content of the coating film on the polyester film after being biaxially stretched. All of the following examples were applied by a rod coater. After this, a hot air of 70 ° C is blown on this film,
The coating liquid layer was dried. Then, in the same manner as in Comparative Example 1,
The sheet was subjected to longitudinal stretching using a roll stretching method, lateral stretching using a tenter, and heat treatment to obtain a biaxially stretched film. The surface resistivity and the magnetic layer adhesiveness are measured values of the film after biaxial stretching. Both are films having excellent magnetic layer adhesiveness. However, the antistatic property was insufficient. The slip properties are all good. This is because the coating layer contains fine particles of silica.

Comparative Examples 8 to 12 Films were prepared in the same manner as in Comparative Example 1, and during the process, a coating material having the composition shown in Table 3 was applied after longitudinal stretching and before lateral stretching.
As it was, it was introduced into a tenter and dried, and transverse stretching and heat treatment were carried out to obtain a biaxially stretched film. The characteristics of the film are shown in Table 3.
As shown in FIG. Although it showed good antistatic property, it was inferior in magnetic layer adhesiveness.

Comparative Examples 13 to 14 The coating agents shown in Table 3 were applied in the same manner as in Comparative Examples 8 to 12. This coating agent is a coating agent composed of the coating agents used in Examples 1 and 2 described later. That is, in Comparative Example 13, the coating agents used in the coatings I and II of Example 1 were mixed to form one liquid and applied after the longitudinal stretching and before the lateral stretching. Similarly, in Comparative Example 14, the coating agents used in the coatings I and II of Example 2 were mixed to form one liquid and applied after the longitudinal stretching and before the lateral stretching. In all cases, the magnetic layer adhesion is good, but the antistatic property is particularly inferior to the corresponding Examples 1 and 2.

Comparative Examples 15 to 22 Attempts were made to apply the coating agents shown in Table 3 in the same manner as in Comparative Examples 8 to 12. However, U3-U0 which is a mixture of two kinds of coating agents
All of the coating agents of No. 1 could not be applied because they caused coagulated sediment.

Examples 1 to 10 Unstretched sheets were obtained in the same manner as in Comparative Example 1. A coating composition having the composition shown in Table 3 was applied to one surface of this film.
Thereafter, hot air of 70 ° C. was blown to this film to dry the coating liquid layer. Thereafter, in the same manner as in Comparative Example 1, the sheet was longitudinally stretched using a roll stretching method, and then a coating agent having the composition shown in Table 3 was applied. This was directly dried by a tenter, transversely stretched, and heat-treated to obtain a biaxially stretched film. The surface resistivity and the magnetic layer adhesiveness are measured values of the film after biaxial stretching. Both are films having excellent magnetic layer adhesiveness and antistatic properties.

Examples 1 and 3 are examples using a low molecular weight antistatic agent. The antistatic agent is more concentrated on the surface than when it is applied as a single layer as in Comparative Example 13.
Excellent durability. Moreover, the solvent penetrates into the undercoat layer, so that the magnetic layer adhesiveness of the undercoat layer is exhibited. Examples 2, 4 to 10 are examples using a polymer antistatic agent.
In particular, Examples 4 to 10 are examples using a cationic antistatic agent, which exhibited an excellent antistatic effect and also had magnetic layer adhesiveness. That is, these films are base films suitable for magnetic recording. The results obtained above are summarized in Table 3 below.

[0060]

[Table 5]

[0061]

[Table 6]

[0062]

[Table 7]

[0063]

INDUSTRIAL APPLICABILITY The film of the present invention is an undercoated polyester film which is excellent in antistatic property and adhesiveness and has good productivity, and it is possible to combine paints which could not be used in the past. High value.

Claims (4)

[Claims] (1) An easy-adhesive coating agent is applied to at least one surface of an unstretched polyester film and dried to form an easy-adhesion layer, (2) and then stretched in at least one direction,
(3) A coated film produced by further providing an antistatic layer on at least one surface of the easily adhesive layer. 2. The coated film according to claim 1, wherein the coating agents used for forming the antistatic layer and the easy-adhesion layer have different ionicities from each other. 3. The coating agent used for forming the antistatic layer contains a cationic compound, and the coating agent used for forming the easily adhesive layer is anionic or nonionic. The coated film according to claim 1, wherein: 4. The coated film according to claim 1, wherein the coating agent used for forming the antistatic layer contains a low molecular weight antistatic agent.