JPH091755A - Coating film - Google Patents

Abstract

PURPOSE: To provide a stretched polyester film having excellent productivity, antistatic property, slidable property, and releasability. CONSTITUTION: A coating film is manufactured by an in-line coating method having a process wherein at least one face of a unstretched polyester film is coated with an antistatic coating agent and dried so as to provide a coating layer. Thereafter, it is stretched in at least one direction. Further thereafter, the top of at least one face of the coating layer is applied with a water-based silicone coating agent so as to provide a silicone layer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to productivity, antistatic property,
The present invention relates to a stretched polyester film excellent in slipperiness, releasing property and the like.

[0002]

2. Description of the Related Art A laminate of a polyester film and a silicone layer is widely used as a surface-cured film, a release film, a slippery film, etc. depending on the characteristics of the silicone. In this case, one of the important properties other than surface hardness, releasability, and slipperiness is antistatic property. In general, antistatic property is a property required for all plastic films, but it is strongly required for the above-mentioned applications. The reason is,
This is because these films are exposed to processes such as friction, abrasion, and peeling that tend to cause electrostatic charges. When strongly charged, the films adhere to each other or repel each other. Also, it adsorbs dust from the surroundings. As a result, the peeling of the film becomes heavy, the peeling is not smoothly performed, scratches are caused by dust, and slipperiness becomes unstable. This greatly affects the quality of the product.

As a method of imparting antistatic properties to a laminate of a polyester film and a silicone layer, there has been proposed a method of incorporating a compound having an antistatic property into the silicone layer. However, in this case, the following problems often occur. That is, the crosslinking reactivity for forming the silicone layer is lowered, and the properties of the silicone layer such as transparency, surface hardness, releasability and slipperiness are lowered. In addition, repeated use of the finished product not only causes the antistatic agent to transfer to other base materials with which it comes into contact, which not only reduces the antistatic effect of the silicone layer, but also contaminates other base materials with the antistatic agent. There are also problems.

In order to solve these problems, the present inventors have proposed a composite film having a structure in which an antistatic layer and a silicone layer are laminated on a polyester film (JP-A-1-171940, 3-256741). No. However, in the above method, after the antistatic layer is provided in the polyester film manufacturing process, it is rolled up once and the silicone layer is applied in another process, so it takes time to produce it, and there is another factory other than the polyester film manufacturing factory. Will be needed.

[0005]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventor has solved the above problems by applying a specific compound by a specific method during the polyester film manufacturing process. That is, the gist of the present invention is:
(1) An antistatic coating agent is applied to at least one surface of an unstretched polyester film and dried to form a coating layer,
(2) After that, stretching in at least one direction, and (3) after that, coating a water-based silicone coating agent on at least one surface of the coating layer provided in (1) to provide a silicone layer. It exists in the coating film manufactured by the in-line coating method which has.

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.

Examples of the aromatic dicarboxylic acid component include, 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 is usually 0.45 or more, preferably 0.50 to 1.0, more preferably 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 protrusions on the surface of the film for the purpose of imparting slipperiness to the film and improving handleability. Examples of such particles include calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, inorganic particles such as molybdenum sulfide, crosslinked polymer particles, oxalic acid. Examples thereof include organic particles such as calcium, and precipitated particles generated during polyester polymerization.

The average particle size is preferably 0.005 to 5.0 μm, more preferably 0.0, although the particle size and amount of the particles to be contained in the film in the present invention depend on the use.
It is in the range of 1 to 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. Also, the particles easily fall off the film surface,
It may cause "powder drop" when using the film.
If the average particle size is less than 0.005 μm, the protrusion formation by these particles is insufficient, and the effect of improving the slipperiness tends to be weakened. That is, if a large amount of particles is not added, the effect of improving the slipperiness does not appear, and if a large amount is added, the mechanical properties of the film may be impaired.

Further, the content of particles relative to polyester 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 amount 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.

Two or more kinds of such 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 subjected to a process such as crushing, dispersion, classification, and filtration, if necessary, beforehand. As a method of adjusting the content of particles,
It is effective to prepare a master raw material containing a high concentration of particles by the above-mentioned method, and dilute it at the time of film formation with a raw material substantially free of particles to adjust the particle content.

As additives other than the above-mentioned protrusion-forming agent, if necessary, antistatic agents, stabilizers, lubricants, crosslinking agents, antiblocking agents, antioxidants, colorants (dyes,
(Pigment), a light blocking agent, an ultraviolet absorber, etc. may be contained. The polyester film of the present invention may have a multilayer structure. 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 biaxially stretched polyester film is manufactured by
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. Alternatively, the operation may be divided and some of them may be alternately performed. For example, a method of manufacturing a high-strength film by a re-stretching method corresponds to this.

The unstretched film referred to 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 0.00.
5 is more preferable, and 0.000 to 0.0 is more preferable.
02. When ΔP is small, the interlayer adhesion between the coating layer and the base polyester film is excellent, which is preferable. The degree of plane orientation (ΔP) is nγ for the refractive index in the main orientation direction of the film and n for the refractive index in the direction perpendicular to the main orientation direction.
Let β be the refractive index in the thickness direction, and nα be the refractive index in the thickness direction.

[0016]

## EQU1 ## ΔP = (nγ + nβ) / 2−nα.

The antistatic coating agent used in the present invention 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, anionic, cationic and amphoteric compounds.

Examples of the nonionic antistatic agent include polyether compounds or their derivatives. Specific examples include polyethylene glycol, polypropylene glycol, polyethylene glycol / polypropylene glycol block copolymers, polyoxyethylene diamine, polyether / polyether. This is the case for polyester / polyamide block copolymers.

Examples of the anionic antistatic agent include compounds having sulfonic acid, carboxylic acid, phosphoric acid, boric acid and salts thereof. Among them, a sulfonic acid type antistatic agent is often used because of its antistatic property 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, other copolymerizable monomers, styrene sulfonic acid and its salts,
Copolymers with and are also included. In addition, low molecular sulfonic acid compounds are also effective. For example, alkyl sulfonate,
Examples thereof include 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, it is advisable to mix a binder having suitable flexibility.
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.

Polyester, poly (meth) acrylate, polyurethane, polyolefin, ethylene vinyl acetate copolymer, polyamide, polyvinylidene chloride, polyvinyl chloride, chlorinated polyolefin, vinyl chloride vinyl acetate copolymer, chloroprene, styrene resin, Carbonate resins, arylate resins, vinyl butyral resins, vinyl alcohol resins, the above-mentioned composite polymers. The composite polymer here is a random, block, or graft copolymer, or a 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. Various compounds are generally known as cross-linking agents, and the following compounds are mentioned as cross-linking agents that are easy to use in water-based paints. Amino resin, especially melamine-based crosslinking agent and urea-based crosslinking agent, epoxy-based crosslinking agent, aziridine compound, blocked isocyanate-based crosslinking agent, oxazoline-based crosslinking agent, silane coupling agent, titanium coupling agent, zirco-aluminate coupling agent , 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 that are easy to use include carnauba wax, polyethylene wax, and a viscosity average molecular weight of 500 to 2
0000 of the following polymers are mentioned.

Polypropylene, ethylene / acrylic acid copolymer, 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 containing two or more carbon-carbon double bonds in one molecule (for example, divinylbenzene). Further, particles of the thermosetting resin synthesized by the condensation reaction include melamine-formaldehyde, benzoguanamine-formaldehyde, phenol-formaldehyde, epoxy and the like.
Further, such as polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, polychlorotrifluoroethylene and the like Particles of a fluorine-based resin and particles of a cross-linked silicone resin are exemplified. 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,
Examples thereof include molybdenum sulfide and antimony oxide. Of these, silicon dioxide is inexpensive and has a wide variety of particle sizes, so it is easy to use. 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.

Other additives may include compounds such as defoaming agents, coating improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes and pigments. The silicone-based coating agent for forming the silicone layer in the present invention is an aqueous coating material containing a silicone compound. The silicone compound here is a water-soluble or water-dispersible silicone (organopolysiloxane) compound. Examples thereof include water-soluble or water-dispersible silicone compounds such as amino-modified silicone oil, polyether-modified silicone oil, and carboxy-modified silicone oil, and dispersions in which a surfactant is added to dimethyl silicone oil and forcibly emulsified. .

And not only the silicone oil,
A high molecular weight silicone polymer and a silicone resin having a three-dimensional structure are more preferable. As a case corresponding to this, there is also a method in which a silicone compound having a relatively small three-dimensional structure is blended in a water-based paint and a crosslinking reaction is carried out during heating and drying. As a form of this crosslinking reaction, any known method can be used. For example, a silicone compound containing a methyl group, preferably a vinyl group, is mixed with a peroxide to cause a crosslinking reaction, or a silicone compound containing a silanol group has a silane compound having a hydrolyzable functional group (eg, silane coupling). Agent) to cause a cross-linking reaction, a silicone compound containing a vinyl group is reacted with a silicone compound containing three or more Si-H groups in the presence of a platinum catalyst, and known functional groups that react with each other. Examples of the reaction include, but are not limited to, reaction of silicone compounds introduced with (for example, mixing and curing an epoxy-modified silicone and an amino-modified silicone).

Although the properties of silicone are weakened,
Graft polymers and block polymers of silicone compounds and other known polymers (for example, poly (meth) acrylate) can also be used. Alternatively, a kind of composite polymer in which a water-soluble polymer is used as a dispersant and a silicone compound is dispersed in water can be used. For example, polyvinyl alcohol, water-soluble polyester, water-soluble poly (meth) acrylate, water-soluble polyurethane, etc. may be used as the dispersant. In addition, a method in which a block polymer or a graft polymer is prepared by mixing the dispersant in an amount not less than the amount of the dispersant and reacting with a functional group-containing silicone compound is also included.

Examples of the components other than the silicone compound in the silicone coating composition of the present invention include the compounds which can be added to the antistatic coating composition described above. The coating agent in the present invention is preferably an antistatic coating agent or a silicone coating agent, which is a coating agent using water as a medium for safety and hygiene, but within a range not exceeding the gist of the present invention, it is water-soluble or water-soluble. An organic solvent may be contained as an auxiliary agent for the dispersible resin. The same applies to the “water-based paint” in the above description.

As a method for applying the above-mentioned coating solution to a polyester film, for example, Yuji Harasaki, Maki Shoten, 1
It is possible to use a reversing roll coater, a gravure coater, a rod coater, an air doctor coater or a coating device other than these as shown in "Coating system", issued in 979. it can. The upper limit of the ultimate temperature of the film when the coating solution is dried after application is preferably (Tg + 20 ° C.), more preferably (Tg + 10 ° C.), and most preferably (Tg + 5 ° C.) of the finally obtained film. It is. If the temperature reached by the film is too high, the film-forming property of the film is deteriorated, which is not preferable.

The thickness of the coating layer thus obtained is
The dry solid content in the final product for each layer is preferably in the range of 0.005 to 5.0 μm.
The thickness of the coating layer is preferably as thin as the coating characteristics allow. If the thickness of the coating layer increases, problems such as blocking may occur. However, in the present invention, the silicone layer is provided on the surface when wound into a roll, and therefore the problem of blocking is less than in the case of other in-line coated films. On the other hand, the thickness of the coating layer is 0.00
If the thickness is less than 5 μm, 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, a uniaxially stretched film stretched in the machine direction is coated with the coating solution and then appropriately dried, or the uniaxially stretched film is immediately dried in the transverse direction. The method of stretching and heat treating (hereinafter abbreviated as conventional in-process coating method) was general. In the present invention, in-line two-layer coating is carried out by providing an antistatic layer on at least one surface of an unstretched polyester film, then stretching in at least one direction, and then providing a silicone layer on at least one surface of the antistatic layer. It has a feature in obtaining a film. By adopting such a constitution, it is possible to stably produce a film having a silicone coating film having an unprecedented antistatic property. That is, there are the following advantages.

(A) Conventionally, it has become possible to use a combination of an antistatic agent and a silicone coating agent, which causes mixing and aggregation, by dividing into two layers. (B) Conventionally, in order to apply two layers, off-line coating had to be used to provide at least the second layer. In this case, the coating and drying steps are separately provided. Therefore, there arise problems such as the necessity of separately constructing a place requiring a high degree of cleanliness, the necessity of separately introducing a coater and a dryer, and the change in 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. The physical properties of the film can be freely selected within the range of a normal biaxially stretched polyester film. On the other hand, when the second layer is coated off-line, so-called heat wrinkles are formed in the drying process to some extent, resulting in poor flatness. That is, the film of the present invention is a film that is difficult to achieve by off-line coating. In addition, the advantage of shortening the time 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 silicone layer is provided by off-line coating. When the second layer contains a cross-linking agent, the coating film produced by in-line coating is more cross-linked and has excellent durability. Recently, paints are becoming more water-based to protect the environment, but water-based paints are more difficult to dry than organic solvent-based paints, and off-line coating produces a film that is sufficiently cured or adheres well to the substrate. Requires a more advanced coating-drying technology than ever before.

(D) A coating material containing an antistatic agent can be applied at a low speed, which leads to an improvement in the state of the applied surface. Generally, the antistatic agent exhibits the properties of a surfactant or is a water-soluble polymer. For this reason, the coating agent containing the antistatic agent often has high viscosity or easily foams. Therefore, it is difficult to apply it neatly at high speed. That is, coating stripes and coating unevenness are likely to occur. In this respect, since the film of the present invention is coated with the coating agent containing the antistatic agent at a low speed, the above-mentioned film having few defects can be obtained.

(E) The heat-sensitive transfer substrate is required to have not only heat-resistant slipperiness but also antistatic property. However, since the thermal transfer head is exposed to high temperatures, alkali metal ions,
The head is corroded when alkaline earth ions and halide ions come in high concentration. Therefore, for the antistatic of the thermal transfer substrate, it is not possible to use a large amount of ionic antistatic agents that are industrially available at low cost, and in order to impart a strong antistatic property, it is necessary to rely on other methods. It was In this regard,
In the present invention, since the antistatic layer is provided on the lower surface of the two-layer coating,
Even if an ionic antistatic agent is used, the effect on the head is much smaller than before.

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 that at least one surface of the antistatic coating liquid is applied and then dried. The thus-obtained unstretched sheet is first stretched in the machine direction. The stretching temperature range is 7
The stretching ratio is preferably in the range of 0 to 150 ° C. and 2.5 to 6 times. Stretching can be performed in one step or two or more steps. After that, an easily adhesive layer is applied and provided on at least one surface of the antistatic coating layer. Next, in the transverse direction, that is, in the direction orthogonal to the longitudinal direction, the uniaxially oriented film is once cooled to a glass transition point or lower, or is preheated to a temperature range of 90 to 150 ° C. without cooling,
Further, at about the same temperature, 2.5 to 5 times, preferably 3.
The film is stretched 0 to 4.5 times to obtain a biaxially oriented film.

The film thus obtained 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 technique such as a relaxation treatment within 10%, preferably within 5% in the longitudinal direction in the heat treatment step or after the heat treatment can also be adopted in order to bring the heat shrinkage ratio in the longitudinal direction into a suitable 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 1, the heat shrinkage of the film becomes large, which is not preferable. 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 of the coating layer of the biaxially stretched polyester film of the present invention, the coating property, and the like,
After forming the coating layer, the coating layer may be subjected to discharge treatment.

[0044]

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] (d
1 / g) 1 g of polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in 100 ml of a mixed solvent.
Measured in ° C. (2) Surface orientation degree (ΔP) Using an Abbe type refractometer manufactured by Atago Optical Co., Ltd., the maximum value nγ of the refractive index in the film plane, 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.

[0046]

(Equation 2)

(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.

(Preparation of Coating Agent) The aqueous coating solution shown in Table 1 below was mixed to prepare an aqueous coating composition having the composition shown in Table 2 below. S1 to S4 and T3 are represented by solid composition.
However, T1 and T2 are shown by the composition by volume% of commercially available water-based paints L1-L4. The compounds shown in S5 of Table 1 were synthesized as follows.

Production method of S5: 97.7 g of octamethylcyclotetrasiloxane, 4.6 g of γ-glycidoxypropyltrimethoxysilane and 2.0 g of γ-methacryloxypropyltrimethoxysilane were mixed, and this was mixed with dodecylbenzenesulfone. Deionized water 3 in which 1.0 g of acid was dissolved
In addition to 00 g, the mixture was dispersed with a homomixer, and then homogenized with a homogenizer to obtain an aqueous dispersion of a silanol compound. Then, 31 g of dodecylbenzene sulfonic acid and 217 g of ion exchange resin were charged into the flask and, after being well dissolved, the temperature was raised to 80-85 ° C., and the aqueous dispersion of the silanol compound was added dropwise thereto over 2 hours. .
After completion of the dropwise addition, the mixture was aged at 85 ° C. for 1 hour. After completion of aging, the mixture was cooled to room temperature and neutralized with sodium carbonate to complete polycondensation to obtain an aqueous dispersion of polyorganosiloxane. Finally, 483 g of ion-exchanged water and 1.5 g of potassium persulfate were dissolved in this aqueous dispersion, transferred to a flask, and heated to 70 ° C. while flowing nitrogen into the flask to obtain 50 g of methyl methacrylate and ethyl acrylate. 50 g was slowly added dropwise. After completion of dropping, the mixture was aged for 3 hours to obtain an aqueous dispersion of polysiloxane-polymethacrylate copolymer. The solid content concentration of this water dispersion was 19.1 wt% and the average particle diameter was 0.06 μm.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

Comparative Example 1 SiO ₂ having an intrinsic viscosity of 0.65 and a particle diameter of 0.1 μm.
Of 0.1% by weight of polyethylene terephthalate is 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 by an electrostatic application adhesion method to obtain an amorphous shape. It was a sheet. 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. Then, the film was introduced into a tenter and stretched 4.2 times in the transverse direction at 120 ° C.
Heat treatment was performed at 30 ° C. to obtain a biaxially stretched polyester film having a thickness of 38 μm as the base polyester film. The obtained film was a film having extremely excellent transparency. However, it was a film having excellent releasability and antistatic property. The surface specific resistance of the film is shown in Table 3 below.

Examples 1 to 4 Unstretched sheets were obtained in the same manner as in Comparative Example 1. The water-based paint shown in "Application I" of Table 3 was applied to one surface of this film. Thereafter, hot air of 70 ° C. was blown onto the film to dry the coating liquid layer. Then, in the same manner as in Comparative Example 1, the sheet was longitudinally stretched using a roll stretching method. Then, before being transversely stretched by a tenter, the aqueous coating material shown in "Application II" of Table 3 was applied onto the coating film shown in "Application I". Immediately, it was introduced into a tenter, dried, transversely stretched and heat treated to obtain a biaxially stretched film. In each case, the coating thickness is as shown in Table 3, which shows the thickness as a dry solid content of the coating film on the polyester film after being biaxially stretched.
The characteristics of the obtained biaxially stretched film are shown in Table 3. Both are films having excellent antistatic properties and releasability. For example, it was an excellent film as a retainer for magnetic tape cassettes. In other words, it has excellent antistatic properties, and when this audio film is installed in an audio cassette and the audio tape is run, no dust is generated, no dust is attached, and even if the tape is run for a long time, it is stable and stable. Was.

Examples 5 to 6 Coating agents having the compositions shown in Table 3 were applied in the same manner as in Examples 1 to 4 to obtain films of Examples 5 to 6. Each of the obtained films was useful as a release separate film. That is, it could be easily peeled off from the adhesive tape or label, the peeling was stable, and the peeled film did not adhere to the surroundings due to static electricity.

Comparative Example 2 An attempt was made to mix the two types of compounded liquids used in Example 1 into one liquid and apply this liquid just before the tenter. However, the mixed coating agent could not be coated immediately because aggregates were generated. Comparative Example 3 The two types of formulation solutions used in Example 1 were separately applied by in-line coating and outline coating (abbreviated as OLC). That is, the coating agent S1 was applied to the polyester film after longitudinal stretching just before the tenter. The resulting biaxially stretched film was once wound up, and the coating agent T1 was applied onto the S1 coated surface in a separate step. The dry thickness of the coating film was the same as in Example 1. Drying was performed at 150 ° C. for 1 minute. Although the coating film was uniform, the durability of the coating film was inferior to that of Example 1. That is, when the coating film was repeatedly rubbed with a fingertip, the coating film of Comparative Example 3 was easily peeled off. This is probably because the crosslinking reaction of the silicone layer is insufficient.

Comparative Example 4 SiO ₂ having an intrinsic viscosity of 0.65 and a particle size of 1.3 μm.
Of 0.2% by weight of polyethylene terephthalate is dried by an ordinary method and supplied to an extruder, melted at 285 ° C. and extruded into a sheet, and rapidly cooled on a cooling roll using an electrostatic application adhesion method to obtain an amorphous shape. It was a sheet. The ΔP of the unstretched sheet was 0.000. The obtained unstretched sheet was stretched 3.5 times in the machine direction at 95 ° C. by a roll stretching method. Then, the film was guided to a tenter, stretched in the transverse direction at 110 ° C. by 4.0 times, and heat-treated at 230 ° C. to obtain a 6 μm-thick biaxially stretched polyester film as a base polyester film. A heat-meltable transfer ink having the following composition was hot-melt coated on one surface of the obtained film at a coating amount of ² g / mm ² to obtain a heat-sensitive transfer material.

(Heat-meltable transfer ink composition) Carbon black 20% by weight Paraffin wax 40% by weight Carnauba wax 30% by weight Ethylene vinyl acetate copolymer 10% by weight Line type thermal head using the transfer material obtained above. Was used to evaluate the sticking prevention property under the following conditions. Recording density 4 dots / mm Recording power 0.7 W / dot Head heating time 4 to 10 msec The transfer material obtained in Comparative Example 4 has a remarkable stick phenomenon.
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Example 7 An unstretched sheet was obtained in the same manner as in Comparative Example 4. The water-based paint shown in "Application I" of Table 3 was applied to one surface of this film. Thereafter, hot air of 70 ° C. was blown onto the film to dry the coating liquid layer. Then, in the same manner as in Comparative Example 1, the sheet was longitudinally stretched using a roll stretching method. Then, before being transversely stretched by a tenter, the aqueous coating material shown in "Application II" of Table 3 was applied onto the coating film shown in "Application I". Immediately, it was introduced into a tenter, dried, transversely stretched and heat treated to obtain a biaxially stretched film. In each case, the coating thickness is as shown in Table 3, which shows the thickness as a dry solid content of the coating film on the polyester film after being biaxially stretched.
The film was excellent in antistatic property and releasability. The film opposite to the silicone-coated surface was hot-melt coated with a hot-melt transfer ink in the same manner as in Comparative Example 4 to obtain a heat-sensitive transfer material, and the sticking prevention property was evaluated. The transfer material obtained in Example 7 was a good transfer material without sticking phenomenon and uneven running of the film due to static electricity.

Comparative Example 5 The two types of formulation solutions used in Example 7 were applied by in-line coating and outline coating. That is, the coating agent S4 was applied to the polyester film after longitudinal stretching just before the tenter. The finished biaxially stretched film with a thickness of 6 μm is wound up once and coated with a coating agent T in a separate step.
3 was coated on the coated surface of S4. The dry thickness of the coating film was the same as in Example 7. Drying at 100 ℃,
It was carried out in 1 minute. However, the heat shrinkage of the film reduced the flatness of the film.

The heat-transferable transfer ink was hot-melt coated on the side of the obtained film opposite to the silicone-coated surface in the same manner as in Comparative Example 4 to obtain a heat-sensitive transfer material, and the sticking prevention property was evaluated. However, since the flatness of the film was deteriorated, the application of the heat-meltable transfer ink was uneven. In addition, probably due to transfer of the silicone component on the opposite surface, application omission occurred partially during transfer ink application. Further, the transfer material obtained in Comparative Example 5 had some sticks and could not be said to be a good transfer material. The results obtained above are summarized in Table 3 below.

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[Table 4]

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The film of the present invention is a polyester film having a silicone layer having excellent antistatic properties, good flatness, and good curing degree, and more excellent in productivity than conventional production methods. It can be used as various industrial films, release films, cassette retainers, films for thermal transfer ink ribbons, and its industrial value is high.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display B29L 9:00

Claims (1)

[Claims] (1) An antistatic coating agent is applied to at least one surface of an unstretched polyester film and dried to form a coating layer, and (2) after that, stretching is performed in at least one direction,
(3) A coated film produced by an in-line coating method further comprising the step of coating a water-based silicone coating agent on at least one surface of the coating layer formed in (1) to form a silicone layer.