JP3206012B2 - Laminated polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film. More specifically, the present invention relates to a laminated polyester film having excellent slipperiness, smoothness, easy adhesion, transparency, abrasion resistance, running properties, and durability.

[0002]

2. Description of the Related Art In recent years, as magnetic recording media have become smaller and lighter or have been recorded for a longer time, it has become necessary to record information at a higher density. For high-density recording, it is necessary to shorten the recording wavelength and reduce the spacing loss between the magnetic recording medium and the magnetic head as much as possible. With this, the surface of the magnetic recording medium becomes smoother. It is desirable. Above all, a magnetic recording medium obtained by forming a ferromagnetic thin film on a base film by a method such as electroplating, vacuum deposition, sputtering, or ion plating has a larger magnetic layer than a conventional coating type magnetic recording medium. Since the thickness can be reduced to about 1/30 or less, it is possible to reduce the thickness loss due to the shortening of the recording wavelength and to use a smooth base film to make the surface of the magnetic recording medium smoother. This is extremely effective for high-density recording, for example, by reducing the spacing loss between magnetic heads. Research and development of such a ferromagnetic thin film type magnetic recording medium have been actively conducted, and various studies have been made on the base film. As such a base film, for example, a coating layer having fine projections made of a mixed composition of a fluorine-based compound, a resin and fine inert particles on a base film as disclosed in JP-A-60-957 is used. Provided laminated polyester films are disclosed. Japanese Patent Application Laid-Open No. 60-76340 discloses a laminated polyester film in which a particulate substance composed of a primer is fixed on a base film composed of a polyester film in an area of 1% or more of the total surface area of the polyester film. .

[0003]

However, the above-mentioned laminated polyester film has the following problems. That is, as described in JP-A-60-957, a laminated polyester film provided with a coating layer having fine projections made of a mixed composition of a fluorine compound, a resin and fine inert particles retains excellent lubricity. However, it is difficult to uniformly disperse the fine inert particles in the coating layer, and furthermore, it is difficult to obtain a stable smoothness because coarse projections are easily generated by the aggregated particles. The running durability and the electromagnetic conversion characteristics of the magnetic recording medium were reduced due to the falling off of the magnetic recording medium. Also, as described in JP-A-60-76340, in a laminated polyester film in which the occupied area of the particulate material composed of the primer is 1% or more of the total surface area of the polyester film, if the occupied area of the particulate material increases, the sliding occurs. The phenomenon that the property became extremely bad was seen.

The present invention has been made to solve the above-mentioned drawbacks of the prior art and to provide a laminated polyester film having excellent lubricity, smoothness and adhesiveness.

[0005]

The present invention employs the following means in order to solve the above problems. That is, the laminated polyester film of the present invention, on at least one surface of a polyester film, have bombarded cause such to substantially nucleus 1 × 10 ⁵ cells / mm ² or more and is protrusion height 1 nm to 20 nm, The ratio of "height of protrusion / base length of protrusion in width direction" is 1 to 0.02, and the ratio of length / width direction is 3 or more. It is assumed that.

[0006] The polyester constituting the polyester film in the present invention is a general term for polymers having an ester bond as a main bonding chain, and particularly preferable polyesters are polyethylene terephthalate and polyethylene 2 , 6-naphthalate, polybutylene terephthalate, polyethylene α, β-bis (2-chlorophenoxy) ethane 4,4-dicarboxylate, etc.
Among them, polyethylene terephthalate is most preferable in consideration of quality, economy and the like. Therefore, hereinafter, polyethylene terephthalate (hereinafter abbreviated as PET) will be described as a typical example of polyester.

PET is at least 80 mol%, preferably 9 mol%.
At least 5 mol% of ethylene phthalate is used as a repeating unit, but other dicarboxylic acid components and diol components may be used within this limited amount range. Also known additives in this PET, for example, heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, A nucleating agent may be blended. The intrinsic viscosity (measured in orthochlorophenol at 25 ° C.) of the above PET film is 0.4
0 to 1.20 dl / g, preferably 0.50 to 0.80 d
Those in the range of 1 / g are suitable for the content of the present invention.

[0008] The polyester film of the present invention, bombarded cause such to substantially nucleus (hereinafter, sometimes simply referred to as protrusions)
Is preferably biaxially oriented in view of mechanical and thermal properties in the laminated state, for example, biaxially oriented PE when the above PET is used as polyester.
The T film is formed by stretching a non-stretched PET sheet or film in the longitudinal direction and the width direction by about 2.5 to 5 times each, and is a biaxially oriented pattern by wide-angle X-ray diffraction. -Indicates a negative Although the thickness of the PET film is not particularly limited, it is usually 1 to 500 μm.
Is preferable, and may be arbitrarily selected depending on the use.

[0009] The projection having substantially no nucleus is a projection substantially free of inorganic particles, inorganic colloids, organic particles, crosslinked particles and the like in the formed projections. Therefore, external cross-linking with a cross-linking agent, a cross-linking accelerator or the like is not preferable in the present invention. In order to obtain such a projection having substantially no nucleus, it is possible to apply a self-crosslinkable polymer, especially a self-crosslinkable acrylic resin, onto a polyester film, and then dry and horizontally stretch the film.

In the present invention, the projection having substantially no nucleus is preferably made of a self-crosslinkable polymer. A self-crosslinkable polymer is a polymer having a crosslinkable functional group in the molecule and capable of performing a crosslinking reaction by heat or light to generate a three-dimensional network structure. A typical example is acrylic. It is possible, but not limited to. However, in the present invention, acrylic is preferably used in terms of miniaturization of the projections, the number of projections formed, slidability, transparency, and the like. In addition, the projection without a nucleus refers to a projection containing 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more of a crosslinkable polymer. Further, self-crosslinkable polymers may be blended with each other as long as the properties of the present invention are not impaired, or other substances such as a surfactant may be appropriately added.

In the present invention, such projections without nuclei are provided on at least one surface of the polyester film. In the case where the projections are provided on both surfaces, the description of the projections without nuclei described below applies to at least one of them. Things.

The self-crosslinkable acrylic copolymer in the present invention refers to a copolymer of a functional group-containing vinyl polymerizable monomer, a hydrocarbon vinyl polymerizable monomer, and a hydrocarbon non-conjugated divinyl polymerizable monomer. Although a polymer compound is mentioned, in the present invention, a copolymer of a functional group-containing vinyl polymerizable monomer is preferably used. Examples of the functional group-containing vinyl polymerizable monomer include acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-butoxymethylacrylamide, diacetone acrylamide, methylol diacetone acrylamide, 2- Hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate
And 3-chloro-2-hydroxypropyl methacrylate, which are selected from, but not particularly limited. The average particle diameter of the water-dispersible self-crosslinkable acrylic copolymer is in the range of 0.01 to 1 μmφ, preferably 0.01 to 0.5 μmφ, and the one having a uniform particle size distribution is the smoothness of the projections. Is more preferable.

It is preferable that the projections do not contain inorganic particles, organic particles, inorganic colloids, etc. from the viewpoint of abrasion resistance and the like, but a small amount is added as long as the properties of the laminated film of the present invention are not impaired. No problem. In that case, the addition amount of the particles is preferably 10 parts by weight or less, more preferably 5 parts by weight or less based on 100 parts by weight of the resin.

If the effects of the present invention are not impaired, the flatness and lubricity of the projections are improved.
Cellulose polymers such as methyl cellulose and ethyl cellulose may be added to the self-crosslinkable acrylic copolymer. The addition amount is 5 to 30 with respect to the solid content of the acrylic resin.
%, Preferably in the range of 10 to 20%. If the added amount of cellulose exceeds 30%, the smoothness of the projections is undesirably deteriorated. On the other hand, if the addition amount is less than 5%, the effect of improving smoothness and lubricity is not sufficient, which is not preferable.

In the present invention, in order not to impair the smoothness and particle morphology of the projections, it is preferable to form the projections only with the self-crosslinking polymer. However, as long as the effects of the present invention are not impaired, In order to further improve the adhesion and the mechanical strength, the projections may contain a crosslinking agent. The cross-linking agent referred to in the present invention is a cross-linking reaction with a functional group present in a self-cross-linkable acrylic copolymer, for example, a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, and finally a three-dimensional network structure. The crosslinking agent is not particularly limited as long as it is a cross-linking agent for forming projections having no nucleus, but typical examples thereof include methylolated or alkylated urea-based, melamine-based, acrylamide-based, polyamide-based resins, and epoxy resins. Compounds, isocyanate compounds, aziridine compounds and the like can be mentioned. Of these, methylolated melamine and isocyanate compounds are preferred in terms of adhesion to the base film, mechanical strength, and the like. These crosslinking agents may be used alone or in combination of two or more in some cases.
The amount of the cross-linking agent to be added is appropriately selected depending on the type of the cross-linking agent.
The amount is preferably 1 to 50 parts by weight, more preferably 0.1 to 30 parts by weight. If the addition amount is less than 0.01 part by weight, the crosslinking effect is low, and if it exceeds 50 parts by weight, the adhesion of the projections is reduced, and the coatability is further deteriorated, making it difficult to form a uniform layer. A crosslinking catalyst may be used in combination with the crosslinking agent. Known catalysts such as salts, inorganic substances, organic substances, acid substances, and alkaline substances can be used as the crosslinking catalyst. The amount of the crosslinking catalyst to be added is 0.00
It is 1 to 10 parts by weight, preferably 0.1 to 5 parts by weight. The coating agent to which the crosslinking agent is added is cross-linked by heating, ultraviolet rays, electron beams or the like after being applied to the base film, but a method by heating is generally used.

In the present invention, the projection without a nucleus is formed of a granular self-crosslinkable acrylic copolymer formed on the surface of a base polyester film, and the self-crosslinkable acrylic copolymer is heated or melted or heated. It is formed by adhering to the base polyester film by softening and adhering to the base polyester film by adhesive force or the like.

The polyester film which is the base film constituting the film of the present invention may be uniaxially oriented, but is desirably biaxially oriented in terms of mechanical strength, dimensional stability, rigidity and the like. The thickness of the polyester film is not particularly limited, but is preferably 1 to 500 μm,
The range of 80 μm is more preferable, and the handleability in practical use as a base film is excellent. The surface roughness (Ra) and optical haze of the polyester film are not particularly limited, but the surface roughness (Ra) is 0.02.
μm or less, preferably 0.01 μm or less.

The protrusions having substantially no nucleus constituting the film of the present invention are defined as having a thickness of 0.001 to 0.5 μm including the protrusions.
m is preferable, and the range of 0.005 to 0.25 μm is more preferable. If the lamination thickness is less than 0.001 μm, not only uniform lamination is difficult but also lubricious projections are difficult to obtain. 0.
If the diameter exceeds 5 μm, the protrusions have a film forming property,
It is not preferable because it becomes difficult to form a projection. The projections may contain a reactive compound such as an epoxy compound, an aziridine compound, a vinyl compound, or a silane coupling agent as an adhesion promoter for the base polyester film or the magnetic layer. Further, if necessary, known additives in an amount that does not impair the effects of the present invention, for example, a coating improver, an antistatic agent, an antioxidant, an ultraviolet absorber, a rust inhibitor,
A dye, an antifoaming agent, a thickener and the like may be added.

The average length of the projections in the width direction (hereinafter, sometimes abbreviated as TD direction) is 0.005 to 1 μm,
Preferably, it is in the range of 0.05 to 0.5 μm. When the average diameter length of the projections is in the above range, when a ferromagnetic thin film is formed, the sliding property between the magnetic surface and the metal guide is further improved, and the wear of the ferromagnetic thin film due to repeated running, Clogging is further reduced. The height of such projections is 1n
m to 20 nm. If it is lower than 1 nm, the slip
Poor and poor runnability.
In addition, the surface is easily shaved and the electromagnetic conversion characteristics deteriorate.

Further, the number of surface projections occupying per unit area must be 1 × 10 ⁵ / mm 2 or more, preferably 1 × 10 ⁶ / mm ² or more, more preferably 1 × 10 ⁶ / mm ² or more.
× 10 ⁷ pieces / mm ² or more. When the value is more than this value, when a ferromagnetic thin film is formed, the lubricity on the formed surface is sufficient, and the electromagnetic conversion characteristics are further improved. The ratio of the length of the projection in the longitudinal direction to the length in the width direction is 3 or more (vertical (MD)).
Long in the direction) Ru Der.

Further, the ratio of the height of the protrusion / the base length in the width direction of the protrusion is in the range of 1 to 0.02, more preferably 1 to 0.02.
It is in the range of 0.05, more preferably in the range of 1 to 0.1. The ratio of the height of the protrusion to the base length in the width direction of the protrusion is 0.
If it exceeds 02 , the projections are too flat and the slipperiness becomes extremely poor. Also, after the present invention the film oriented in projecting Kiga one direction, further extends (re transverse stretching) in the same direction, to strengthen the alignment, it is desirable to subsequently heat-treated, the stretching and re-stretching and heat treatment by the action, the projections are more uniform, since it is possible to fine desirable.

Next, the manufacturing method of the present invention will be described, but the present invention is not limited to this.

First, the polyester pellets polymerized by a conventional method are sufficiently dried, and then supplied to a known extruder, preferably a melt extruder having a compression ratio of 3.8 or more. It is melt-extruded in a sheet form from a slit die at a temperature lower than the decomposition temperature, and cooled and solidified to form an undrawn sheet. At this time, the intrinsic viscosity of the unstretched sheet is desirably 0.5 or more from the viewpoint of film properties. Next, a coating material prepared in a predetermined amount of the composition is applied on a film obtained by stretching the unstretched sheet 2.0 to 5.0 times at 70 to 120 ° C., and the coating film is dried. After providing a predetermined coating layer, it is horizontally stretched 2.0-5.0 times at 70-150 ° C. Further, if necessary, the film may be re-laterally stretched.
Further, the biaxially oriented film is 0-1 at 150-250 ° C.
Heat-treat for 1 to 60 seconds while giving 0% relaxation.

The coating method is not particularly limited, and the extruded
Although a coating method and a melt coating method may be used, a gravure coating method, a reverse coating method,
It is preferable to apply a known method such as a kiss-coat method, a die-coat method, or a metaling-bar-coat method. At this time, by applying a known surface treatment such as a corona discharge treatment in air or other various atmospheres as necessary before coating on the film, not only the coating properties are improved, but also the protrusions are formed. It can be formed more firmly on the film surface. The concentration of the coating material and the conditions for drying the coating film are not particularly limited, but the drying conditions for the coating film are preferably set within a range that does not adversely affect the properties of the polyester film. In addition, in order to obtain the protrusion of the present invention, the coating amount is 0.0003 to 0.05.
g / m ² , preferably 0.0015 to 0.026 g /
m ² , more preferably 0.003 to 0.007 g / m ²
(All of them are in the range of Dry). 0.0%
003g / m is less than ² can not be imparted to less sufficient lubricity number projections, it exceeds 0.05 g / m ² and the projection becomes to have film-forming properties, the formation of projections is difficult Not preferred.

As described above, the laminated polyester of the present invention can be produced, and a ferromagnetic thin film type magnetic recording medium can be manufactured by providing a ferromagnetic thin film layer on the projection forming surface of the laminated polyester. Here, the ferromagnetic thin film refers to a ferromagnetic metal such as iron, cobalt, and nickel, or Fe—Co, Fe—Ni, Fe—Rh, Fe
-Cu, Fe-Au, Co-Cu, Co-Au, Co-
Y, Co-La, Co-Pr, Co-Gd, Co-S
n, Co-Pt, Ni-Cu, Fe-Co-Nd, Mn
A magnetic alloy such as Bi, Mn-Sn, Mn-Al formed on a film by a vacuum deposition method, an ion plating method, a sputtering method, an ion beam deposition method, an electrolytic deposition method, an electrolytic plating method, etc. is there. The ferromagnetic thin film applied to the laminated polyester film of the present invention may be of course any one produced by any of the methods described above, but the deposition direction is inclined in the longitudinal direction (90 ° to 30 °) and It is preferable to use a material which is not inclined and which is deposited at 1 × 10 ⁻⁴ Torr while introducing O ₂ or O ₂ and Ar as an atmosphere.
The thickness of the ferromagnetic thin film is usually 0.01 to 1 μm, preferably 0.05 to 0.3 μm.

[0026]

[Measurement method] The method for measuring the characteristics and the method for evaluating the effect in the present invention are as follows.

(1) Coating Layer Thickness Using a transmission electron microscope HU-12 manufactured by Hitachi, Ltd., an ultra-thin section of the laminated film is observed to determine the thickness.

(2) Surface roughness (Ra) According to JIS-B-0601, using a stylus type surface roughness meter BE-3E manufactured by Kosaka Laboratory Co., Ltd., a cutoff of 0.0
The average surface roughness Ra (μm) was measured at 25 mm and a measurement length of 4 mm.

(3) Slipperiness (static friction coefficient μs, dynamic friction coefficient μk) The coefficient of friction between films is ASTM-D-1894.
The coefficient of static friction μs was measured in accordance with Example No. 63. Generally, the range in which the lubricity is excellent is 1.6 or less in μs, preferably 1.2 or less.

Dynamic friction coefficient μk between film and metal post
Is measured using a kinetic friction coefficient meter (TBT-300, manufactured by Yokohama System Research Institute) at 25 ° C. and 50% relative humidity in an atmosphere of coating surface or ferromagnetic thin film-formed surface.
SUS420J2 in mm [phi], at a speed of the post surface roughness 0.2S is contacted with wrap angle 180 ° 3.3 cm / sec, after moving, control tension as entry side tension T ₁ is a 25g - and Le, calculates the dynamic friction coefficient μk from the exit side tension T ₂ value (g) by the following equation.

Μk = (2.303 / π) log (T ₂ / T ₁ ) = 0.733 log (T ₂ / T ₁ ) (4) Easy adhesion Bell jar type high vacuum deposition apparatus (Nihon Vacuum Technology Co., Ltd. ) E
(BH-6 type) and a commercial cellophane tape manufactured by Nichiban Co., Ltd. was stuck to the aluminum deposition surface at a degree of vacuum of about 1 × 10 ⁻⁵ mmHg, and a load of about 5 kg was applied using a hand roller. After the pressure bonding, evaluation was made on the aluminum remaining adhesion surface after forcible peeling in the 180 ° direction. Evaluation criteria are:
The remaining deposited area of the aluminum vapor-deposited film layer was rated as good (○) when it was 90% or more, poor (％) when 75 to 90%, and poor (x) when less than 75%. The larger the remaining adhesion area, the better the adhesiveness.

(5) Number, shape, height, M of granular projections
D, TD width width SEM (scanning electron microscope, Akashi Seisakusho Co., Ltd., DS
-130 type), magnification 10,000 to 30,000 times, angle 80
The photograph was taken with ゜ to count the number of granular projections, and the number of projections per piece / mm ^{2 was} calculated by area conversion. The shape of the protrusion and the length in the vertical or horizontal direction were measured from a SEM photograph.

The height, average roughness, average depth, maximum roughness, etc. of the protrusions were measured using a non-contact three-dimensional fine shape measuring device ET-30HK manufactured by Kosaka Laboratory Co., Ltd. Calculated as an average).

(6) Thickness of Magnetic Layer In the case of a magnetic layer formed by vacuum evaporation, sputtering, or the like, a fluorescent X-ray micropart thickness meter STF-15 manufactured by Daini Seikosha Co., Ltd.
6 (unit: nm).

(7) Runnability The coefficient of dynamic friction μ between the film and the metal post in the above item (3)
In the same manner as in the measurement of k, the initial μk value of the base material after traveling 300 times is measured. Next, after repeating 50 times in the magnetic recording medium in which the lubricant is not applied to the surface after the formation of the ferromagnetic thin film, and after 300 times in the magnetic recording medium in which the lubricant is applied to the surface after forming the ferromagnetic thin film. Those having a μk value smaller than the value obtained by increasing the initial μk value by 25% were determined to be “good runnability”, and the others were determined to be “poor runnability”.

(8) Electromagnetic conversion characteristics When the output signal when reproducing the sample magnetic recording medium is viewed on one screen, a signal having a strong output signal and a flat signal waveform (good) is regarded as an output signal. Were weak or the signal waveform was deformed, it was judged as (defective).

(9) Abrasion resistance The laminated polyester film is 25 to 30 cm long and 1 width wide.
/ 2 inch, when the laser blade is run at an angle of 90 ° to the coating layer surface, 0.5 mm depth, load 500 g / 0.5 inch, speed 6.7 m / sec. Next, the width in the depth direction of the shaving powder adhering to the laser blade was determined by microphotographing (× 160). When the width of the shavings in the depth direction is 3 μm or less (○), 3 μm to 5 μm
m was (△), and 5 μm or more was (×). It goes without saying that the smaller the adhesion depth of the shaving powder, the better the shaving property.

(10) Solution haze of the chip In a known polyethylene terephthalate solvent of 20 ml,
3 g of the chip was dissolved and placed in a quartz cell having a thickness of 20 mm, and the solution haze was measured (measuring temperature 25 ° C.).

[0039]

(1) In the film of the present invention, the projections are made finer and uniform by crack fracture of the projections by transverse stretching, and are arranged in the vertical direction. Very good running performance.

(2) Since the film of the present invention has projections made of a flowable crosslinkable acrylic resin, the hardness of the projections is constant and the head touch property when processed into a magnetic tape or the like. Is excellent.

(3) Since the film of the present invention does not use inorganic particles, crosslinked particles of polystyrene, acrylic or the like, or organic particles at all, it is difficult for projections to fall off and is excellent in abrasion resistance, durability and the like. ing.

[0042]

EXAMPLE 1 A homopolymer chip of 0.8% solution haze of polyethylene phthalate (intrinsic viscosity) containing as little as possible internal particles and inert particles based on the residue of a polymerization catalyst produced by a conventional method and the like. = 0.62, melting point: 259 ° C) to 180 ° C
For 2 hours under reduced pressure (3 mmHg). 280 ℃
Is supplied to an extruder having a screw with a compression ratio of 3.8 at T
Melt extrusion from mold die, surface temperature 2 using electrostatic application method
After being wound around a cooling drum at 0 ° C. to be cooled and solidified to form an unstretched film, the obtained film was stretched 3.5 times in the longitudinal direction by roll stretching at 90 ° C., and the surface was subjected to corona discharge treatment. Thereafter, a water-dispersible acrylic copolymer composed of methyl methacrylate / ethyl acrylate / acrylic acid / N-methyl acrylamide (manufactured by Nippon Carbide Industrial Co., Ltd., solid content: 46% by weight) was added. It was diluted with pure water to prepare a coating material having a concentration of 0.5% by weight. This coating material,
After coating on one side of the uniaxially stretched film by a metalling bar coating method, the coated layer was stretched 3.6 times in the transverse direction at 100 ° C. while drying, and further stretched 5% in the transverse direction at 200 ° C. Thereafter, the film was subjected to a heat treatment at 225 ° C. for 5 seconds while relaxing 2% in the horizontal direction to obtain a laminated polyester film having a thickness of 12 μm and a coating amount of 0.015 g / m ² (Dry). The properties of this laminated polyester film are shown in Tables 1 and 2. Then, a Co-Ni alloy (Ni 20% by weight) was added to the film by an electron beam evaporation method.
Angstrom oblique deposition. A solid content of about 30 mg of a perfluoropolyalkyl ether metal salt in which trichlorotrifluoroethane is dispersed on the vapor deposition surface of the vapor deposition film.
/ M ² was applied, polyisocyanate further comprises an alkyl phosphoric acid ester to the back surface of the film - DOO, polyurethanes and secondary Toroseruro - a mixture of scan thickness after drying was applied so as to 0.8μm back coating - After the formation of the magnetic tape, the tape was slit to a width of 1/2 inch to obtain a magnetic tape. The results of evaluating the magnetic tape characteristics are also shown in Table 2.

Example 2 Based on Example 1, a laminated polyester film having a coating amount of 0.007 g / m ² (Dry) laminated with the same coating material as in Example 1 was obtained. Next, a magnetic tape was obtained after oblique deposition in the same manner as in Example 1. The properties of the laminated polyester film and the magnetic tape are shown in Tables 1 and 2. As shown in Tables 1 and 2, when the laminated polyester film is within the scope of the present invention, it is possible to obtain a magnetic recording medium having good running properties, particularly durability of repeated running and good electromagnetic conversion properties. I understand.

Example 3 On the basis of Example 1, a laminated polyester film having a coating amount of 0.003 g / m ² (Dry) laminated with the same coating material as in Example 1 was obtained. Thereafter, a magnetic tape was obtained in the same manner as in Example 1. The properties of the laminated polyester film and the magnetic tape are shown in Tables 1 and 2.

Comparative Example 1 Based on Example 1, organic particles of styrene / divinylbenzene / ethylenedivinylbenzene = 45/50/5% of Nippon Synthetic Rubber Co., Ltd. 0.3 μmφ particles per 100 parts by weight of solids
Wt%, and a laminated polyester film was obtained in the same manner except that 0.05 wt% of 0.8 μmφ particles were added. The coating amount was 0.0065 g / m ² (Dry). Thereafter, a magnetic tape was obtained in the same manner as in Example 1. The properties of the laminated polyester film and the magnetic tape are shown in Tables 1 and 2. However, since organic particles outside the present invention are used, the particles are often dropped off, and the abrasion resistance is poor. However, no excellent magnetic recording medium could be obtained.

Comparative Example 2 Based on Example 2, an aqueous melamine curing agent "Nikaratku" MW-12LF (Sanwa Chemical Co., Ltd.) was used as a cross-linking agent for 100 parts by weight of resin solids on the same coating material as in Example 2. Co., Ltd.) was added to obtain a laminated polyester film and a magnetic tape having a coating amount of 0.003 g / m ² (Dry) except that 5 parts by weight was added. The properties are as shown in Tables 1 and 2, and the projections of the laminated polyester film were high and the film was poor in smoothness because it was outside the present invention. The magnetic tape characteristics were not good either.

Comparative Example 3 Based on Example 3, a coating material similar to that of Example 3 was applied, and then dried by heating and wound up without being stretched in the horizontal direction. A polyester film and a magnetic tape on which m ² (Dry) was laminated were obtained. The properties are as shown in Tables 1 and 2. The surface on which the protrusions of the laminated polyester film were formed was significantly impaired in the smoothness due to surface roughness, the number of protrusions was extremely small, and the magnetic tape was used. The properties were also poor.

Comparative Example 4 A laminated polyester film was produced in the same manner as in Example 1 except that the amount of coating was 0.05 g / m ² (dry) using the same coating material as in Example 1. Obtained. The properties of the laminated polyester film and the magnetic tape are shown in Tables 1 and 2. However, since the film was formed, the slipperiness was poor, and a magnetic recording medium excellent in each property could not be obtained.

Comparative Example 5 Example 1 was repeated except that the amount of coating was changed to 0.0003 g / m ² (Dry) using the same coating material as in Comparative Example 1 based on Comparative Example 1.
A laminated polyester film was obtained in the same manner as described above. The properties of the laminated polyester film and the magnetic tape are shown in Tables 1 and 2. The film has extremely few protrusions and extremely poor slipperiness. Could not.

[0050]

[Table 1]

[0051]

[Table 2]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04

Claims (3)

(57) [Claims] On at least one surface according to claim 1 polyester film has bombarded cause such to substantially nucleus 1 × 10 ⁵ cells / mm ² or more, and, the protrusion height is 1 nm to 20 nm, "protrusion height / A laminated polyester film having a ratio of "base length in the width direction of the projection" of 1 to 0.02 and a directionality in which the ratio of the longitudinal direction / width direction is 3 or more. . 2. A projecting Kiga, laminated polyester film according to claim 1, characterized by comprising a self-crosslinkable polymer. 3. The laminated polyester film according to claim 2, wherein said self-crosslinkable polymer is a self-crosslinkable acrylic resin having a crosslinkable functional group.