JP2007254653A - Easy-adhesive film - Google Patents

Abstract

The surface of a coating layer formed as an easy-adhesion layer is a very flat surface having a center surface average surface roughness of 5 nm or less. Providing an easy-to-adhere film with excellent properties.
An easily adhesive film comprising a biaxially oriented polyester film and a coating layer using a water-dispersible copolyester resin and inert particles on one side thereof, (1) The water-dispersible copolymer polyester resin has a resin reduced viscosity in the range of 0.5 to 1.0 g / dl, (2) the inert particles have an average particle diameter in the range of 10 to 50 nm, and (3) the coating layer layer. The thickness is in the range of 4 to 25 nm, and (4) the surface of the easy-adhesion film on the coating layer side is an easily-adhesive film having a center plane average roughness (WRa) in the range of 0.5 to 5 nm.
[Selection figure] None

Description

  The present invention relates to an easily adhesive film in which a coating layer made of a water-dispersible copolyester is formed as an easily adhesive layer on the surface of a biaxially oriented polyester film, and more particularly to a base for high-density magnetic recording media, particularly data storage media. The present invention relates to an easily adhesive film suitable as a film.

Biaxially oriented polyester film represented by polyethylene terephthalate film is used for a wide range of applications, particularly as a base film for magnetic recording media, because of its excellent physical and chemical properties.
In magnetic recording media, higher capacities and higher densities are being promoted, and accordingly, magnetic powders having excellent magnetic properties are being used and magnetic powders are being highly filled. Along with this, the ratio of the binder resin in the magnetic layer decreases, and the adhesion between the polyester film as the base film and the magnetic layer becomes insufficient, and the polyester film has an adhesive property to the magnetic layer. There is an increasing demand for improvement.

  As a means for improving the adhesiveness of such a polyester film, it is conventionally known to provide an easy-adhesion layer on the surface of the polyester film. When this easy-adhesion layer is formed, the adhesiveness is improved, but there is a problem of blocking that the films adhere to each other while being stored and transported while being rolled. For this problem, for example, Patent Document 1 proposes to employ a water-dispersible copolymer polyester resin having a specific composition that hardly causes blocking.

However, in recent years, the surface of an easy-adhesion film on which a magnetic layer is formed, that is, the surface of an easy-contact layer is a center plane in accordance with the demand for higher recording signal capacity and higher density in a magnetic recording medium or the like. Flatness such as an average surface roughness WRa of 5 nm or less is required. When such a flat surface is used, friction with the die portion of the coater used when applying the magnetic layer in the magnetic tape manufacturing process. As a result, the easy-adhesion layer is scraped, and the magnetic layer cannot be applied successfully.
JP-A-6-116487

  The object of the present invention is to solve the above-mentioned problems of the prior art, even if the surface of the coating layer formed as the easy-adhesion layer is a very flat surface having a center surface average surface roughness of 5 nm or less. An object of the present invention is to provide an easy-adhesion film having excellent wear resistance and blocking resistance without impairing the properties.

Thus, according to the present invention, an easily adhesive film comprising a biaxially oriented polyester film and a coating layer using a water-dispersible copolyester resin and inert particles on one side thereof,
(1) The water-dispersible copolymer polyester resin has a resin reduced viscosity in the range of 0.5 to 1.0 g / dl,
(2) the inert particles have an average particle size in the range of 10 to 50 nm;
(3) The thickness of the coating layer is in the range of 4 to 25 nm, and (4) the surface on the coating layer side of the easy-adhesion film has a center plane average roughness (WRa) of 0.5 to 5 nm. An easy-adhesive film having at the same time is provided.

  Further, as a preferred embodiment of the easy-adhesive film of the present invention, a value obtained by dividing the thickness of the coating layer by the average particle size (nm) of the inert particles (thickness of the coating layer / average particle size of the inert particles) is The water-dispersible copolymer polyester resin has an acid component mainly of 2,6-naphthalenedicarboxylic acid component and a glycol component mainly of cyclohexanedimethanol or ethylene glycol. The biaxially oriented polyester film is a biaxially oriented laminated polyester film comprising at least two polyester layers, and the center plane average roughness (WRa) of the surface on the side different from the coating layer side is 5.5 to 15 nm. An easily-adhesive film having any of the following ranges is also provided.

  The easy-adhesion film of the present invention has an average particle size in the coating layer having a resin-reduced viscosity of the binder resin of the coating layer in the range of 0.5 to 1.0 g / dl and a thickness of 4 to 25 nm. Since it contains 10 to 50 nm of inert particles, even if it is a very flat surface with a center plane average roughness (WRa) of 5 nm or less, it has excellent wear resistance and blocking resistance without impairing adhesion. Excellent.

  In the present invention, the water-dispersible copolyester resin forming the coating layer (adhesive layer) has a resin reduced viscosity of 0.60 to 1.00 g / dl, preferably 0.65 to 0.95 g / dl, More preferably, it is necessary to be in the range of 0.70 to 0.90 g / dl. When the resin reduced viscosity is less than the lower limit, the abrasion resistance is impaired. On the other hand, when the resin reduced viscosity exceeds the upper limit, the dispersibility in water used as a solvent when applying as a coating film becomes poor, the coating layer cannot be formed uniformly, and the abrasion resistance is also impaired. . One of the features of the present invention is that the resin-reduced viscosity of the water-dispersible copolyester resin has a great influence on the abrasion resistance, and the water-dispersible copolyester resin has a range that does not impair the dispersibility in water. This is because the resin reduced viscosity is increased as compared with the prior art. Such a resin reduced viscosity can be adjusted by the composition and degree of polymerization of the water-dispersible copolyester resin.

  In the present invention, the water-dispersible copolyester resin has a relatively reduced resin viscosity because the acid component is mainly 2,6-naphthalenedicarboxylic acid component and the glycol component is mainly cyclohexanedimethanol or ethylene glycol. And since it is easy to improve the abrasion resistance of the film obtained, it is preferable. From such a viewpoint, more specifically, an aromatic dicarboxylic acid in which 50 to 85 mol% of the acid component has a 2,6-naphthalenedicarboxylic acid component and 0.1 to 5 mol% of a sulfonate group. The component and those comprising 10 to 45 mol% of other aromatic dicarboxylic acids are preferred, and among the glycol components, 30 to 90 mol% of ethylene glycol and 10 to 70 mol% of cyclohexanedimethanol are preferred.

  In the acid component of the copolyester resin, when the proportion of 2,6-naphthalenedicarboxylic acid is excessively decreased or the proportion of aromatic dicarboxylic acid having a sulfonate group is excessively increased, the blocking resistance of the film is increased. On the other hand, when the proportion of 2,6-naphthalenedicarboxylic acid is excessively increased or the proportion of aromatic dicarboxylic acid having a sulfonate group is excessively decreased, the dispersibility in water tends to be poor. Further, in the glycol component of the copolymerized polyester resin, when the proportion of cyclohexanedimethanol is excessively decreased or the amount of ethylene glycol is excessively increased, the blocking resistance of the film is liable to be lowered, while the proportion of cyclohexanedimethanol is excessively increased. If the ratio is too large or the proportion of ethylene glycol is excessively small, the dispersibility in water tends to be poor.

  Preferred examples of the aromatic dicarboxylic acid having a sulfonate group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, and 5-phosphonium sulfoisophthalic acid. For improving dispersibility, alkali metal salts such as 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, and 5-lithium sulfoisophthalic acid are more preferable, and 5-sodium sulfoisophthalic acid is most preferable.

  The acid component of the copolyester resin may be, for example, terephthalic acid, isophthalic acid, phthalic acid, biphenyl, in addition to the 2,6-naphthalenedicarboxylic acid component and the aromatic dicarboxylic acid component having a sulfonate group. A dicarboxylic acid component or the like may be copolymerized, and among these, those obtained by copolymerizing isophthalic acid are preferable from the viewpoint of the effect of the present invention.

  In the present invention, the inert particles contained in the coating layer have an average particle size of 10 to 50 nm, preferably 15 to 40 nm, and more preferably 15 to 30 nm. If this average particle size is less than the lower limit, the properties of blocking resistance will be insufficient, while if it exceeds the upper limit, the inert particles will easily fall off, while if the coating layer is thickened to prevent it, blocking resistance will be insufficient. It becomes. The content of the inert particles is preferably 5 to 50 parts by weight, preferably 5 to 35 parts by weight, and more preferably 5 to 25 parts by weight per 100 parts by weight of the copolyester resin. If this amount is less than the lower limit, the blocking resistance tends to be insufficient, while if it exceeds the upper limit, the agglomeration of inert particles tends to occur and the abrasion resistance is likely to be impaired.

  The inert particles in the coating layer are preferably those having a relatively low specific gravity that do not easily settle in the coating solution, and those that do not easily aggregate with each other. For example, fine particles made of heat-resistant polymers (eg, crosslinked silicone resin, crosslinked acrylic resin, crosslinked polystyrene, melamine / formaldehyde resin, aromatic polyamide resin, polyamideimide resin, crosslinked polyester, wholly aromatic polyester, etc.), core shell Preferred examples include type organic fine particles (core: crosslinked polystyrene, shell: polymethyl methacrylate, etc.), silicon dioxide (silica), calcium carbonate and the like. Among these, cross-linked acrylic resin (polymethyl methacrylate cross-linked product) fine particles and core / shell type organic fine particles (core: cross-linked polystyrene, shell: polymethyl methacrylate etc.) are particularly preferable.

  In the present invention, the thickness of the coating layer is 4 to 25 nm, preferably 5 to 20 nm, and more preferably 6 to 15 nm. If this thickness exceeds the upper limit, the blocking resistance properties are insufficient. On the other hand, if the thickness is lower than the lower limit, the inert particles easily fall off. On the other hand, if the inert particles are made smaller to prevent this, the blocking resistance becomes insufficient.

  In the present invention, the thickness (nm) of the coating layer divided by the average particle size (nm) of the inert particles in the coating layer (thickness of the coating layer / average particle size of the inert particles), blocking resistance Since it is easy to provide high performance and wear resistance, it is 0.2 to 2.0, more preferably 0.3 to 1.5, even more preferably 0.4 to 1.0, particularly 0.5 to 0.8. It is preferable that it exists in the range. When the value of (the thickness of the coating layer / the average particle diameter of the inert particles) is less than the lower limit, it becomes difficult to retain the inert particles, and the inert particles are not formed in the film forming process or the magnetic tape manufacturing process. It may drop off, increase dropouts and increase data errors. On the other hand, if the value of (the thickness of the coating layer / the average particle diameter of the inert particles) exceeds the upper limit, the protruding amount of the particles from the binder decreases, and the anti-blocking performance tends to decrease.

Next, the biaxially oriented polyester film constituting the easy-adhesion film of the present invention will be described.
In the present invention, the polyester forming the biaxially oriented polyester film is a polyester having aromatic dicarboxylic acid as the main acid component and aliphatic glycol as the main glycol component. This polyester is substantially linear and has film-forming properties, particularly film-forming properties by melt molding.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenylether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenylketone dicarboxylic acid, and anthracene dicarboxylic acid. Etc. Examples of the aliphatic glycol include fats such as polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, or cyclohexanedimethanol. A cyclic diol etc. can be mentioned. Among these, those having alkylene terephthalate or alkylene-2,6-naphthalate as the main constituent are preferable, and polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable. Of course, it is not limited to a homopolymer, and other components may be copolymerized as long as the effects of the present invention are not impaired.

  The polyester is known per se and can be produced by a method known per se. The intrinsic viscosity of the polyester is an intrinsic viscosity determined by measuring at 35 ° C. as a solution in o-chlorophenol, preferably 0.4 to 0.9, and preferably 0.5 to 0.7. More preferred is 0.55 to 0.65.

  In the present invention, the biaxially oriented polyester film preferably contains inert particles such as inorganic and heat-resistant polymer particles in order to provide slipperiness and flatness. Preferred inorganic particles include silicon dioxide (silica), calcium carbonate, and the like. Preferred examples of the heat resistant polymer particles include crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, crosslinked polyester particles, polyimide particles, and melamine resin particles. Among these, it is preferable to use silicon dioxide (silica) because the effect of the present invention becomes more remarkable. The average particle size of the inert particles contained in the biaxially oriented polyester film is preferably 0.05 to 0.2 μm. The content of inert particles is preferably in the range of 0.002 to 0.1 wt% based on the weight of each polyester layer.

  The biaxially oriented polyester film in the present invention is not limited to a single layer film, but rather is preferably a laminated film because the surface roughness of each surface can be changed. For example, one is a flat film on which a magnetic layer is formed. A laminated film having a rough surface on the other side is preferred.

  In the easy-adhesive film of the present invention, the center surface average roughness WRa on the side where the coating layer is provided is 0.5 to 7 nm, preferably 1 to 4.5 nm, more preferably 2 to 4 nm. When the center surface surface roughness WRa is less than the lower limit, when the film is wound in a roll shape, the film slips and the fluffing occurs and the winding property is impaired. On the other hand, when WRa exceeds the upper limit, the magnetic surface becomes rough when the magnetic layer is applied, and sufficient electromagnetic conversion characteristics do not appear, and the present invention provides a magnetic recording medium with a high magnetic recording density. become unable.

  Further, the surface on the side different from the coating layer side of the easy-adhesive film preferably has a center surface average roughness WRa of 5 to 15 nm, more preferably 6 to 13 nm, and particularly preferably 7 to 12 nm. If the center surface surface roughness WRa is less than the lower limit, the slip property of the pass roll and the film in the film forming process or the magnetic tape manufacturing process is likely to be deteriorated, the winding shape is deteriorated, and the product yield is decreased. On the other hand, when WRa exceeds the upper limit, the surface on the coating film layer side may be roughened by protrusion protrusion or transfer. As described above, such a surface roughness can be a laminated film and can be adjusted by the size and amount of inert particles contained in each layer.

  The easily adhesive film of the present invention preferably has a thickness of 2 to 11 μm, more preferably 2 to 10 μm, particularly 3 to 9 μm. When the thickness of the easily adhesive film is less than the lower limit, the film is frequently cut during film formation, and the product yield is remarkably deteriorated. On the other hand, when the upper limit is exceeded, the thickness of the magnetic tape increases, and when the data cartridge is used, the tape winding length that can be wound in the cartridge is shortened, and a high recording capacity cartridge cannot be obtained.

  The easily adhesive film of the present invention can be produced by a known production method known per se. For example, it can be produced by extruding molten polyester into a sheet by an extruder, cooling and solidifying, then biaxially stretching sequentially or simultaneously, and further heat-treating under tension or limited shrinkage, and in the process What is necessary is just to apply | coat and form a layer.

  Preferably, the polyester is melt-extruded at a temperature of the melting point (Tm: ° C.) to (Tm + 70) ° C. of the polyester to obtain an unstretched film, and the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) It is stretched at a temperature of ˜ (Tg + 70) ° C. (however, Tg: glass transition temperature of polyester) at a magnification of 3.0 to 7.0 times, preferably 3.5 to 6.0 times. Then, the coating solution is applied at a temperature of Tg to (Tg + 70) ° C. in the direction perpendicular to the stretching direction, and is 3.0 to 7.0 times, preferably 3.5 to 6.0 times, more preferably 4.0. It is preferable to stretch at a magnification of ˜6.0 times. Further, if necessary, the film may be stretched again in the longitudinal direction and / or the transverse direction. Thus, the total draw ratio is preferably 10 to 35 times, more preferably 12 to 30 times, and particularly preferably 15 to 30 times as the area draw ratio. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180-250 ° C., further 190-240 ° C., particularly 200-230 ° C. Is preferred. The heat setting time is preferably 1 to 60 seconds.

The coating liquid is preferably applied to a uniaxially stretched film, but may be applied to an unstretched film or a biaxially oriented film. As a coating method, for example, kiss coating, reverse coating, gravure coating, die coating and the like can be used. Further, the concentration of the coating liquid is preferably 0.5 to 5.0% by weight, more preferably 1.0 to 4.0% by weight, and particularly preferably 1.5 to 3.0% by weight. The coating amount (wet) As the 1 to 10 g / ^{m 2,} further 1.5~8g / ^{m 2,} in particular 2 to 6 g / ^{m 2} is preferred.

  Hereinafter, the present invention will be further described with reference to examples. In the examples, “parts” means parts by weight, and each characteristic was measured and evaluated by the following methods.

(1) Center plane average roughness (WRa)
Using a WYKO non-contact three-dimensional roughness meter (Veeco: NT-2000), the film surface was rough under the conditions of a measurement magnification of 25 times and a measurement area of 246.6 μm × 187.5 μm (0.0462 mm ² ). Measure. Then, the surface analysis software incorporated in the roughness meter performs a calculation process represented by the following equation to obtain the center surface average roughness (WRa) of the surface. In the following equation, Zjk is a two-dimensional coarseness at the j-th and k-th positions in each direction when the measurement direction (246.6 μm) and the direction orthogonal thereto (187.5 μm) are divided into M and N, respectively. It is the height above. Moreover, the measurement was performed 10 times at different positions, and the average value thereof was defined as the center plane average roughness (WRa).

(2) Average particle size (A) Particles added to biaxially oriented polyester film Measured using a CP-50 type centrifuggle particle size analyzer (Centrifugal Particle Size Analyzer) manufactured by Shimadzu Corporation. The particle size “equivalent sphere diameter” corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is used as the average particle size. (See Book “Particle Size Measurement Technology” published by Nikkan Kogyo Shimbun, 1975, pages 242-247).
(B) Inert particles in the coating layer Photograph each particle at a magnification according to the size used with a scanning electron microscope, and use an image analysis processing device Luzex 500 (manufactured by Japan Regulator) to make each particle 1000 area circle equivalent diameters were measured, and the average value thereof was defined as the average particle diameter.

(3) Thickness of coating layer A small piece of film is fixed and molded with an epoxy resin, and an ultrathin section (cut parallel to the film flow direction) of about 600 angstrom thickness is prepared with a microtome. This sample is observed with a transmission electron microscope (manufactured by Hitachi, Ltd .: Model H-800), and at the portion where inert particles do not exist, the boundary surface between the coating layer and the biaxially oriented polyester film is searched for. The thickness was determined. The measurement was repeated 10 times, and the average value thereof was taken as the thickness of the coating layer.

(4) Adhesiveness
The surface of the easy-adhesion film on the coating layer side (Comparative Example 1 is a surface having a smaller center plane average roughness) is coated with the following magnetic paint, and heated and dried at 100 ° C. to form a magnetic layer. On the surface of the formed magnetic layer, Scotch tape No. 600 (manufactured by 3M) having a width of 19.4 mm and a length of 8 cm was pasted. C2701 (1975) described in a manual load roll, using a Tensilon UM-11 manufactured by Toyo Baldwin Co., Ltd., and T-peel this sample at a head speed of 300 mm / min, The peel strength at this time is obtained, and this is divided by the tape width to obtain g / cm. In T-type peeling, the laminate is taken with the tape side down, and the gap between the chucks is 5 cm.

[Preparation of magnetic paint for evaluation]
Nitrocellulose RS1 / 2 (Flux containing 25% isopropanol: manufactured by Daicel Corporation) is dissolved in a lacquer thinner for paints to prepare a 40 wt% solution, and 43.9 parts of the solution is added, followed by a polyester resin (desmophen # 1700). 32.5 parts, manufactured by Bayer), 26.0 parts of chromium dioxide magnetic powder, soybean oil fatty acid (Resion P: manufactured by Riken Vitamin Co., Ltd.) as a dispersing agent / wetting agent, cationic activator (cationic AB: Nippon Oil & Fats) Co., Ltd.) and squalene (carp liver oil) are charged into 1 part, 0.5 part and 0.8 part ball mill, respectively. Further, 282 parts of a mixed solution consisting of methyl ethyl ketone / cyclohexanone / toluene = 3/4/3 (weight ratio) is further mixed and sufficiently pulverized to prepare a mother liquid paint (45 wt%). To 50 parts of this mother liquor, 48 parts of an addition reaction product of trimethylolpropane and tollane diisocyanate (Coronate L: manufactured by Nippon Polyurethane Industry Co., Ltd.) and 6.25 parts of butyl acetate are added, and finally the solid content is increased. A magnetic coating material for evaluation of 42.7 wt% was obtained.
In addition, evaluation is performed on the following reference | standard from peeling strength.
○: 40 g / cm or more Δ: 30 g / cm or less to less than 40 g / cm x: less than 30 g / cm

(5) Blocking resistance Two easy-adhesion films are prepared, and a flat surface and a rough surface are overlapped so as to be wound on a roll, and a pressure of 150 kg / cm ² is applied to this in an atmosphere of 60 ° C. × 80% RH. Take 65 hours. Then, it peels by the method similar to having described in above-mentioned (4), and evaluates with the peeling force (g number per 5 cm). In addition, evaluation is performed on the following reference | standard from peeling force.
○: 0 to less than 5 g Δ: 5 g or more and less than 10 g ×: 10 g or more to tearing

(6) Scratch resistance Measurement is performed as follows using an apparatus shown in FIG. 1 in an environment of a temperature of 20 ° C. and a humidity of 60%. In FIG. 1, 1 is an unwinding reel, 2 and 8 are tension controllers, 4 and 6 are free rollers, 3 is a tension detector (inlet), 5 is a friction body, 7 is a tension detector (exit), and 9 is a winding. The take-up reels and 10 represent films. The film cut to a width of 1/2 inch is brought into contact with the friction body of 7 at an angle θ = 5 °, and is run for 300 m at a speed of 500 m / min and an inlet tension of 100 g. The shavings adhering on the friction body 5 after traveling is evaluated. At this time, as a friction body, a fan-shaped column body (surface roughness Ra = 15 nm) obtained by dividing a cylinder made of SUS304 and having a sufficiently finished surface and having a radius of 18 mm in cross section into 6 parts is used.
<Shaving powder judgment>
○: No shaving powder is seen. △: Shaving powder is seen slightly. ×: Shaving powder is badly attached.

[Example 1]
<Manufacture of copolyester resin>
60 mol% of dimethyl 2,6-naphthalenedicarboxylate, 36 mol% of dimethyl isophthalate, 4 mol% of 5-sodium sulfoisophthalic acid, 40 mol% of ethylene glycol and 60 mol% of cyclohexanedimethanol were charged into a transesterification reactor, and tetrabutoxy titanium 0 .05 parts was added and heated under a nitrogen atmosphere while controlling the temperature at 230 ° C., and the produced methanol was distilled off to conduct a transesterification reaction.

Next, 0.6 parts of Irganox 1010 (Ciba Geigy) was added to the reaction system, and then the temperature was gradually raised to 255 ° C., the pressure inside the system was reduced to 1 mmHg, and a polycondensation reaction was carried out to obtain an intrinsic viscosity. A 0.64 copolyester resin was obtained. The composition of this copolyester resin is shown in Table 1.

<Preparation of aqueous polyester dispersion>
20 parts of this copolyester resin was dissolved in 80 parts of tetrahydrofuran, and 180 parts of water was added dropwise to the resulting solution under high speed stirring at 10,000 rpm to obtain a bluish milky white dispersion. Subsequently, this dispersion was distilled under a reduced pressure of 20 mmHg to distill off the tetrahydrofuran. In each case, an aqueous polyester dispersion having a solid content concentration of 10 wt% was obtained. An aqueous coating solution having a composition comprising 10 parts of crosslinked acrylic resin particles having an average particle diameter of 25 nm and 14 parts of polyoxyethylene nonylphenyl ether having an HLB of 12.8 as a surfactant (solid content concentration: 1) .8 wt%).

<Manufacture of easy-adhesive polyester film>
Dimethyl-2,6 naphthalate and ethylene glycol are used as a transesterification catalyst, manganese acetate is used as a polymerization catalyst, antimony trioxide is used as a stabilizer, phosphorous acid is used as a stabilizer, and the lubricant for the coated side layer has an average particle size of 0.1 μm. Spherical silica particles are added at 0.20 wt%, and for the coating opposite surface layer, 0.02 wt% of spherical silica particles with an average particle size of 0.3 μm and 0.20 wt% of spherical silica particles with an average particle size of 0.1 μm are used. % And polymerized by a conventional method to obtain polyethylene-2,6-naphthalate (PEN) for the coated surface side layer and coated opposite side layer having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.61. .

  These polyethylene-2,6-naphthalate pellets are dried at 170 ° C. for 6 hours, then supplied to two extruder hoppers, melted at a melting temperature of 280 to 300 ° C., and then two layers using a multi-manifold coextrusion die. Were laminated and extruded onto a rotary cooling drum having a surface finish of about 0.3 S and a surface temperature of 60 ° C. to obtain an unstretched film having a thickness of 150 μm.

The unstretched film thus obtained is preheated to 120 ° C., further heated by an IR heater having a surface temperature of 900 ° C. from 15 mm above between low-speed and high-speed rolls, stretched 5.1 times, and cooled. After that, the coating solution prepared as described above was applied to the coating layer side of the uniaxially stretched film so that the final thickness was 10 nm. Then, it supplied to the stenter and extended | stretched 4.9 times in the horizontal direction at 145 degreeC. The obtained biaxially stretched film was heat-fixed with hot air at 210 ° C. for 4 seconds to obtain a biaxially oriented polyester film having a thickness of 6.0 μm.
Table 1 shows the properties of the easily adhesive film obtained.

[Comparative Example 1]
In Example 1, the same operation was repeated except that the application for forming the easy-adhesion layer was not performed. Table 1 shows the properties of the easily adhesive film obtained.

[Comparative Example 2]
In Example 1, the same operation was repeated except that inert particles were not included in the coating liquid for forming the easy-adhesion layer. Table 1 shows the properties of the easily adhesive film obtained.

[Example 2, Comparative Examples 3 to 4]
The same operation was repeated except that the composition or coating thickness of the easy adhesion layer was changed as shown in Table 1. Table 1 shows the properties of the easily adhesive film obtained.

[Example 3]
Polyethylene terephthalate (PET) was obtained in the same manner as in Example 1 except that dimethyl terephthalate was used instead of dimethyl-2,6 naphthalate.
These polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours, and then the same operation as in Example 1 was repeated except that the surface temperature of the rotary cooling drum was changed to 20 ° C. to obtain an unstretched film.

  The unstretched film thus obtained was preheated at 78 ° C., and further heated by an IR heater with a surface temperature of 850 ° C. from above 15 mm between low speed and high speed rolls and stretched 4.2 times. After cooling, an easy adhesion layer was applied in the same manner as in Example 1. Then, it supplied to the stenter and extended | stretched 3.3 times in the horizontal direction at 110 degreeC. The obtained biaxially stretched film was heat-fixed with hot air at 220 ° C. for 4 seconds to obtain a biaxially oriented polyester film having a thickness of 6.0 μm.

[Examples 4 and 5]
The same operation was repeated except that the composition or coating thickness of the easy adhesion layer was changed as shown in Table 1. Table 1 shows the properties of the easily adhesive film obtained.

  In Table 1, PEN is polyethylene-2,6-naphthalate, PET is polyethylene terephthalate, IA is an isophthalic acid component, QA is a 2,6-naphthalenedicarboxylic acid component, and S-IA is a 5-sodium sulfoisophthalic acid component. EG is an ethylene glycol component, CHDM is a cyclohexanedimethanol component, BPA-P is a propylene oxide component of bisphenol A, silica is silica particles, acrylic is polymethylmethacrylate crosslinked particles, core shell is core-shell type particles (core is crosslinked polystyrene, Shell: polymethacrylate).

  The easy-adhesive polyester film of the present invention has excellent adhesion, abrasion resistance, and blocking resistance. Therefore, it is particularly suitable for a digital data recording medium as a base film for a high-capacity, high-density magnetic recording medium. Useful as a base film.

It is the schematic of the abrasion-resistance measuring method.

Explanation of symbols

1 Unwinding reel 2 Tension controller 3 Tension detector (entrance)
4 Free roller 5 Friction body 6 Free roller
7 Tension detector (exit)
8 Tension controller 9 Take-up reel 10 Film

Claims (5)

An easy-adhesive film comprising a biaxially oriented polyester film, and a coating layer using a water-dispersible copolymer polyester resin and inert particles on one side thereof,
(1) The water-dispersible copolymer polyester resin has a resin reduced viscosity in the range of 0.5 to 1.0 g / dl,
(2) the inert particles have an average particle size in the range of 10 to 50 nm;
(3) The thickness of the coating layer is in the range of 4 to 25 nm, and (4) the surface on the coating layer side of the easy-adhesion film has a center plane average roughness (WRa) of 0.5 to 5 nm. An easily-adhesive film characterized by being simultaneously included in the range.   The value (the thickness of the coating layer / the average particle size of the inert particles) obtained by dividing the thickness of the coating layer by the average particle size (nm) of the inert particles is in the range of 0.2 to 2.0. Easy adhesion film of description.   The easy-adhesive film according to claim 1, wherein the water-dispersible copolyester resin has an acid component mainly of 2,6-naphthalenedicarboxylic acid component and a glycol component mainly of cyclohexanedimethanol or ethylene glycol.   The biaxially oriented polyester film is a biaxially oriented laminated polyester film comprising at least two polyester layers, and the center plane average roughness (WRa) of the surface on the side different from the coating layer side is 5.5 to 15 nm. The easy-adhesion film according to claim 1, which is in the range of   The easily adhesive film according to claim 1, wherein the coating liquid for the magnetic layer is applied to the surface of the coating layer.

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