JPH06198731A - Polyester film - Google Patents

Abstract

(57) [Summary] [Object] To provide a polyester film having excellent scratch resistance and abrasion resistance, which is useful as a base film of a magnetic recording medium. [Structure] Provided on at least one surface of a polyester film containing 0.005 to 0.5% by weight of particles A having an average particle diameter (Da) of 0.2 to 2 μm in the polyester film forming step. The obtained film thickness (T) is 0.01
Particle B having an average particle diameter (Db) of 0.005 to 0.5 μm.
0.1 to 50% by weight is contained, and the following formula is satisfied. 0.9Db ≦ T ≦ 0.5Da

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film having excellent running properties, winding properties, electromagnetic conversion properties and abrasion resistance when used as a magnetic recording medium.
More specifically, the present invention relates to a base film suitable for high-density magnetic recording in which the occurrence of sliding scratches and abrasion powder during tape running is extremely small and the occurrence of dropout is suppressed.

[0002]

BACKGROUND OF THE INVENTION Polyester films are widely used as industrial substrates because of their excellent physical and chemical properties. Among them, the biaxially oriented polyethylene terephthalate film is now indispensable as a base film for magnetic recording media because it is particularly excellent in mechanical strength, dimensional stability, flatness, etc. Improvements are being made at a rapid pace, and along with this, the demands on base films are becoming even more stringent. For example, in the case of high-density recording such as a video tape, the magnetic layer is thinned. In this case, the unevenness of the base film itself is reflected on the surface of the magnetic layer, and when the degree is large, electromagnetic conversion is performed. It causes deterioration of characteristics and frequent dropouts. Therefore, the surface of the base film is desired to be flatter, but when the surface of the film becomes flat, the slipperiness deteriorates, it becomes easy to stick to the transport roll in the production process of the film, and the film surface is scratched, It becomes difficult to run meandering or even roll up as a roll.
Industrial production of such films is virtually impossible.

When such a film having poor running property becomes a product such as a magnetic tape, friction and wear between the film and a base material, for example, a guide pin becomes large, and the film is scratched and abrasion powder is generated. Come to do. Such scratches and abrasion powder on the film cause deterioration of the electromagnetic conversion characteristics of the magnetic tape and dropout, which significantly reduces the commercial value of the product. As a means for improving the running property, abrasion resistance, scratch resistance, etc. of a polyester film, a method in which inert fine particles are present in a conventional film and the film surface is appropriately roughened, specifically, so-called precipitated particles Method and additive particle method are known. Precipitated particle method is a method for precipitating catalyst residues and the like in the polyester as fine particles in the polyester production process, the operation is simple and the polymer can be produced at low cost, and the filter life during production is long. It has advantages. Furthermore, it has an excellent affinity with polyester, less particles fall off from the film, and relatively excellent abrasion resistance. However, since the main component of the deposited particles is an organic component, scratch resistance is poor.

The additive particle method is a method in which fine particles of calcium carbonate, kaolin, silica, titanium oxide and the like are added and contained during polyester production or molding. This method generally tends to lack the affinity between particles and polyester, but it is known to be effective in improving scratch resistance. Particularly, as described in JP-A-1-306220, it is known that scratch resistance and abrasion resistance can be remarkably improved by using a specific amount of particles having high hardness. Generally, the larger the particle size of the particles added to the polyester film, the easier it is to fall off from the polyester film, which causes problems such as dropout when used as a magnetic recording material. Therefore, as the particles added for the purpose of improving scratch resistance and abrasion resistance, fine particles of 0.2 μm or less are preferably used. However, when the surface of the polyester film is covered only with fine protrusions, the coefficient of friction is reduced, but when the film is wound up into a roll, air is lost between the films, so that the roll is laterally displaced. Misalignment occurs, reducing the commercial value of the product. In order to improve this air release, it is the actual situation that large particles are added to some extent at the expense of falling off of particles and electromagnetic characteristics.

[0005]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventor has found that a coating solution containing specific aluminum oxide particles is used in the production process of a polyester film containing specific particles. We have found that the film obtained by coating has excellent properties, and completed the present invention.

That is, the gist of the present invention is that the average particle diameter (Da) of the particles A within the range of 0.2 to 2 μm is 0.00.
At least one surface of the polyester film containing 5 to 0.5% by weight has a coating layer having a thickness (T) within the range of 0.01 to 1 μm provided in the polyester film forming step, The coating layer has an average particle size (Db) of 0.00
0.1 to 50% by weight of particles B in the range of 5 to 0.5 μm
It exists in the polyester film characterized by containing and satisfying the following formula. 0.9Db ≦ T ≦ 0.5Da

The polyester referred to in the present invention for explaining the present invention in more detail below means an aromatic dicarboxylic acid such as terephthalic acid, 2.6-naphthalenedicarboxylic acid or an ester thereof and ethylene glycol as a main starting material. It refers to the obtained polyester, but may contain other third component. In this case, examples of the dicarboxylic acid component include isophthalic acid, terephthalic acid, and 2.
6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like can be used. As the glycol component, diethylene glycol, propylene glycol,
Butanediol, 1.4-cyclohexanedimethanol, neopentyl glycol and the like can be used. In any case, the polyester referred to in the present invention is
80% or more of the repeating structural unit refers to a polyester having ethylene terephthalate units or ethylene-2.6-naphthalate units.

Further, the polyester film of the present invention refers to a polyester film using such polyester as a starting material, and a known method can be adopted as a manufacturing method thereof. For example, after melt-extruding into a sheet form at 270 to 320 ° C., cooling and solidifying at 40 to 80 ° C. to form an amorphous sheet, the area ratio becomes 4 to 20 times in the vertical and horizontal directions at 80 to 150 ° C. As described above, a method of performing sequential biaxial stretching or simultaneous biaxial stretching and heat treatment at 160 to 250 ° C. (for example, the method described in JP-B-30-5639) can be used. Stretching in the machine direction and the transverse direction may be carried out in one step each, or if necessary, in multiple steps,
A heat treatment section for relaxing orientation may be provided during the multi-stage stretching. Further, after biaxial stretching, it may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching
It can be performed either vertically or horizontally.

The particles A to be blended with the polyester in the present invention may be particles having an average particle diameter of 0.2 to 2 μm. Such particles include kaolin, talc, carbon, molybdenum sulfide, gypsum, rock salt, calcium carbonate,
Examples thereof include barium sulfate, lithium fluoride, calcium fluoride, zeolite, calcium phosphate, silicon dioxide, titanium dioxide and heat-resistant polymer fine powder. The blending amount of the particles A with respect to the polyester is 0.005
Select from the range of 0.5% by weight. If the average particle size of the particles A is less than 0.2 μm, air escape when wound on a roll is insufficient, and if it exceeds 2 μm, the electromagnetic characteristics of the magnetic recording material are adversely affected. If the content of the particles A is less than 0.005% by weight, air bleeding when wound into a roll will be insufficient, and if it exceeds 0.5% by weight, the electromagnetic characteristics of the magnetic recording material will be adversely affected. The greatest feature of the present invention resides in that large particles for improving winding characteristics are present in the polyester film, and a coating layer containing particles B having a specific particle size is provided on the surface layer thereof. Furthermore, this coating layer not only improves the scratch resistance and abrasion resistance of the film by the particles B present therein, but the coating layer having this scratch resistance and abrasion resistance is present in the polyester film. It also has the function of a protective layer that prevents the large particles from falling off. Furthermore, the coating layer having such a function prevents large particles in the film from falling off without impairing the winding property improving effect.

The coating layer thickness of the film of the present invention is 0.01
Select from the range of ˜1 μm. Coating layer thickness is 0.01μ
If it is less than m, the effect of preventing the large particles from falling off in the polyester film cannot be exhibited, and the strength of the coating film is lowered, causing the coating film itself to fall off. When it exceeds 1 μm, running property and blocking property are deteriorated, which is not preferable. Further, in selecting the thickness of the coating layer, consideration should be given to the fact that the relationship with the particle size of the particles added therein greatly affects the characteristics of the coating film.
That is, the thickness (T) of the coating layer and the particles A in the film
With respect to the average particle diameter (Da), and further with respect to the average particle diameter (Db) of the particles B in the coating layer must be set to satisfy the following formula. 0.9Db ≦ T ≦ 0.5Da

The thickness (T) of the coating layer is the particle A in the film.
If it exceeds 0.5 times the average particle diameter of, the effect of improving the winding property by the particles will be impaired. If the film thickness (T) of the coating layer is less than 0.9 times the average particle diameter of the particles B in the coating layer, the scratch resistance deteriorates. The average particle diameter of the particles B used in the present invention (D
b) is within the range of 0.005 to 0.5 μm. If the average particle size is less than 0.005 μm, the effects of scratch resistance and abrasion resistance are not exhibited. On the other hand, if it exceeds 0.5 μ, the electromagnetic characteristics of a magnetic recording material are deteriorated, which is not preferable. As a specific example of the particles B, aluminum oxide is preferable, and the average particle size of primary particles produced by, for example, hydrolysis of anhydrous aluminum chloride by the flame method or hydrolysis of aluminum alkoxide is 0.005 μm to 0.5 μm.
Particles of μm are used. The aluminum oxide particles are preferably used by completely dispersing them up to the primary particles,
As long as it does not adversely affect the surface condition of the film, it may be aggregated to some extent and behave as secondary particles. Further, a part of aluminum oxide, for example, less than 30% by weight is Si, T
It may be replaced with an oxide such as i, Fe, Na and K.

The particle size distribution of the particles B is not particularly limited,
In the present invention, a sharper one, specifically, a weight fraction of 75% and 25% when integrated from the smaller particle size is used.
% Particle size ratio of 2.0 or less, and more preferably 1.5 or less. Further, the shape of these particles is not particularly limited, but generally, particles having a shape close to a lump or a sphere are preferably used. Specifically, for example, Japanese Patent Publication No. 53-1
The volume shape defined in Japanese Patent No. 4583 is 0.1 to π /
Particles such as 6, preferably 0.2 to π / 6, are preferred.

The specific surface area of the particles B used is not particularly limited. For example, average particle size 0.5 μm, density 2
A true spherical particle having g / cm ² has a specific surface area of about 6 m ² / g, but a porous particle having a specific surface area of about 500 m ² / g can be preferably used. The surface of these particles may be modified with various surface treatment agents for the purpose of improving the affinity with water-based paints. In the present invention, the particles B
Is used as one component of the coating agent, but in this case, it is dispersed in water in advance. At this time, it is preferable to use a small amount of a dispersant because the compounding stability with the aqueous resin can be improved. Further, the particles B are blended with the aqueous resin through operations such as pulverization, classification and filtration, if necessary. For example, the particles B and water can be dispersed and adjusted using a high-speed stirrer having a plurality of shearing blades parallel to the rotating direction of the stirring blade, a homomixer, an ultrasonic disperser, or the like. Further, the dispersed slurry is preferably filtered with a cartridge type filter having 3 μm perforations for the purpose of removing coarse particles and undispersed aggregated particles in the slurry.

The particles B are usually blended in a resin and applied to a polyester film.
The range of 0.1 to 50% by weight, more preferably 0.5 to 20% by weight is preferable. If the blending amount is less than 0.1% by weight, the density of the particles B on the surface of the film tends to be low and the effect of improving scratch resistance tends to be small. If the blending amount exceeds 50% by weight, the mechanical strength of the coating layer may be poor. The film having aluminum oxide only in the coating layer has a feature that the wear rate of the slit blade during slitting is significantly reduced as compared with the film compounded in the film. The reason why the wear rate of the slit blade is reduced is probably that the amount of particles used for the entire film is concentrated by concentrating the aluminum oxide on only the surface layer of the film.
Compared to the case of blending in a conventional film, 0.05-
This is considered to be because it was possible to significantly reduce it to about 0.2 times.

The binder for the coating layer of the present invention is usually a binder.
A water-based resin is used, but the water-based resin referred to here means the manufacturing process of the magnetic recording material after being coated on the surface of the polyester film, and the use environment under high temperature and high humidity after being processed into the magnetic recording material. Withstanding heat resistance and moisture resistance, when the topcoat layer such as a magnetic layer or a backcoat layer is coated with this layer as an undercoat layer, it is a resin having excellent adhesiveness with the layer, for example, polyester, Although it can be selected from resins such as polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, polyurethane and copolymers and mixtures of these resins, However, the present invention is not limited to these. The most preferable resin among these is a polyester resin.

Examples of the component that constitutes the polyester resin include the following polyvalent carboxylic acids and polyvalent hydroxy compounds. That is, as the polycarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid,
Phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5
-Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and their ester-forming derivatives can be used. As the compound, ethylene glycol, 1,2-propylene glycol, 1,3
-Propylene glycol, 1,3-propanediol,
1,4-butanediol, 1,6-hexanediol,
2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p
-Xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, dimethylolethyl Sodium sulfonate, potassium dimethylolpropionate and the like can be used.

Usually, one or more of these compounds are appropriately selected and a polyester resin is synthesized by a conventional polycondensation reaction. In addition to the above, JP-A-1-
A composite polymer having a polyester component such as so-called acrylic graft polyester or polyester polyurethane in which polyester polyol is chain-extended with isocyanate described in 165633 can also be suitably used as the polyester resin used in the present invention.

The aqueous resin in the present invention may be a coating agent in which a liquid containing 70% by weight or more of water is used as a medium and forcedly dispersed by a surfactant or the like, but it is preferable to use a coating material such as polyethers. It is a self-dispersion type coating agent having a hydrophilic nonionic component or a cationic group such as a quaternary ammonium salt, and more preferably a water-soluble or water-dispersible resin coating agent having an anionic group. The resin having an anionic group is a resin having a compound having an anionic group bonded to the resin by copolymerization or grafting, and sulfonic acid, carboxylic acid, phosphoric acid and their lithium salts, sodium salts, potassium salts. , Ammonium salt and the like. The ratio of the anionic group to the coating solid content is preferably 0.05 to 8% by weight. If the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin tends to deteriorate, and if the amount of the anionic group exceeds 8% by weight, the water resistance and hygroscopicity of the coating layer are This can cause problems.

In order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer, the coating solution for obtaining the coating layer in the present invention may be modified with methylol or an alkyl group as a cross-linking agent. Rolled urea compounds, melamine compounds, guanamine compounds, acrylamide compounds, polyamide compounds, epoxy compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, zirco-aluminate coupling agents, It may contain a peroxide, a heat- or photoreactive vinyl compound, a photosensitive resin, or the like.

Further, if necessary, it may contain an antifoaming agent, a coating property improving agent, a thickener, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, etc., The effect of the present invention is sufficiently exhibited even in a system containing them. The film of the present invention can be particularly effective when used as a base film for a video tape and also as an audio film. In other words, in this field, models that have double high-speed dubbing function more than double that of the conventional ones such as double radio-cassette, compo stereo, etc. have become widespread, and as a result, tapes and bases have been used during the dubbing process, fast-forwarding and rewinding. The materials come into contact with each other at a higher speed, but in this case, the effect of the present invention is effectively exhibited.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measuring methods and definitions of various physical properties and characteristics in the present invention are as follows. In addition, in Examples and Comparative Examples, "part"
"Parts by weight" means "parts by weight". (1) Average particle diameter The particle diameter of the particles in the coating layer was determined by observing the cross section of the coating layer with a transmission electron microscope, and the diameter having an equivalent volume conversion of 50% as the equivalent sphere was taken as the average particle diameter. Regarding the particles in the dry powder and the slurry, the particle size was determined using a scanning electron microscope. (2) Travelability Two films cut out to a width of 15 mm and a length of 150 mm are stacked on a smooth glass plate, a rubber plate is placed on the film, and a load is further placed on the film to make contact between the two films. The pressure was set to 2 g / cm ² , and the films were slid at 20 mm / min to measure the frictional force. The friction coefficient at the point of sliding by 5 mm was defined as the dynamic friction coefficient (F / F μd), and the running property was evaluated.

(3) Abrasion characteristics While contacting the film with the hard chrome fixing pin, 10
After running for 100 m, the abrasion white powder adhering to the fixed pin made of hard chrome was visually observed and evaluated according to the following three grades of A, B and C. The film speed was 13 m / min, the hearing was about 200 g, and the film winding angle around the pin was 135.
It was °. A: No white powder generation B: Small white powder generation C: Large white powder generation

(4) Scratch resistance A polyester film is fixed to a hard chromium fixing pin (diameter 6).
mm, surface roughness 3S), wrap angle 135 degrees, tension 20
They were contacted with each other at 0 g and run for 100 m at a speed of 13 m / min. Next, aluminum was vapor-deposited on the contact surface of the polyester film with the fixing pin, and the degree of scratches was visually judged and classified into the following ranks. A: Almost no scratches B: Slight scratches are recognized, but satisfactory level C: Scratch amount is relatively small, deep scratches are slight D: Scratch amount is comparable There are many deep and deep scratches E ... There are many scratches and often deep scratches

(5) Winding characteristics The appearance of the end surface of the film roll when wound into a roll was judged as follows. A: The end faces are aligned B: The end faces are slightly irregular C: The end faces are significantly irregular (6) Electromagnetic characteristics First, 200 parts of magnetic fine powder, 30 parts of polyurethane resin,
10 parts of nitrocellulose, 10 parts of vinyl chloride / acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone and 300 parts of methyl ethyl ketone are mixed and dispersed in a ball mill for 48 hours, and then 5 parts of a polyisocyanate compound is added to obtain a magnetic paint, which is a polyester. After coating the non-coated surface of the film so that the film thickness after drying was 5 μm, the coating was magnetically oriented before the coating was sufficiently dried and solidified, and then dried. further,
The coated film was surface-treated with a super calendar and slit into a 1/2 inch width to obtain a video tape. This video tape is NV-370 manufactured by Matsushita Electric Co., Ltd.
The following magnetic tape characteristics were evaluated at a constant speed using a 0 type video deck. VTR Head Output (S / N) The VTR head output at a measurement frequency of 4 MHz was measured with a synchroscope, the reference tape was 0.0 decibel (dB), and the relative value (dB) was measured. Dropout (DO) Number 4 or 4 megahertz signal recorded video tape was played back, Okura Industry Co., Ltd. dropout counter measured the number of dropouts for about 20 minutes, and converted to the number of dropouts per minute .

Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were heated and heated, and methanol was distilled off to carry out a transesterification reaction, which required 4 hours from the start of the reaction. Then, the temperature was raised to 230 ° C. to substantially end the transesterification reaction. Next, 0.1 part of SiO ₂ particles having an average particle size of 0.7 μm was added, 0.04 part of ethyl acid phosphate was further added, and 0.04 part of antimony trioxide was further added to carry out a polycondensation reaction, After 4 hours and 30 minutes, intrinsic viscosity 0.660
Of polyethylene terephthalate was obtained.

After drying the obtained polyester, 290 ° C.
Melt extruded to form an amorphous sheet, then 90 ° C in the machine direction
After being stretched 3.5 times, the aluminum oxide particle-containing coating material shown below is dried and stretched by a bar coating method to give a coating thickness of 0.1.
It was coated so as to have a thickness of .mu.m, then laterally stretched at 110.degree. C. by 3.7 times and heat-treated at 210.degree. Aluminum oxide particle-containing paint Aluminum oxide (average particle size 0.1 μm) 3 parts; Polyester resin (Plus Coat Z-461 manufactured by Kyosho Chemical Co., Ltd.) 97
Part; water 900 parts

Example 2 In Example 1, after completion of the transesterification reaction, SiO ₂
0.8 μm calcium carbonate particles 0.0 instead of particles
A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that 4 parts were added and the coating material containing aluminum oxide particles was changed to that shown below. Aluminum oxide particle-containing coating aluminum oxide (average particle size 0.04 μm) 10 parts; polyester resin (Plus Coat Z-461 manufactured by Kyosho Chemical Co., Ltd.)
90 parts; water 900 parts

Example 3 In Example 2, after the completion of the transesterification reaction, 0.01 parts of 1.7 μm calcium carbonate particles were added in place of the calcium carbonate particles, and an aluminum oxide-containing coating was applied to a coating thickness of 0.6 μm. A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 2 except for coating.

Comparative Example 1 In Example 2, after completion of the transesterification reaction, 0.1 μm SiO ₂ particles 0.04 were used instead of the calcium carbonate particles.
A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 2 except that part of the film was added.

Comparative Example 2 A biaxially oriented polyethylene terephthalate film was prepared in the same manner as in Example 2 except that 0.1 part of 2.6 μm calcium carbonate particles was added instead of the calcium carbonate particles after the transesterification reaction. Got

Comparative Example 3 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 2 except that the aluminum oxide particle-containing coating material was changed to the one shown below. Aluminum oxide particle-containing paint Aluminum oxide (average particle size 0.2 μm) 10 parts; Polyester resin (Plus Coat Z-461 manufactured by Mutual Chemical)
0 part; water 900 parts

Comparative Example 4 In Example 2, after completion of the transesterification reaction, SiO ₂
A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 2 except that particles were not added.

Comparative Example 5 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 2 except that the coating material containing aluminum oxide particles was not provided.

Comparative Example 6 In Example 1, 0.7 μ after the completion of the transesterification reaction
A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that 0.3 parts of 0.1 μm aluminum oxide particles were added together with m SiO ₂ particles. The results obtained above are summarized in Tables 1 and 2 below.

[0035]

[Table 1]

[0036]

[Table 2]

The films of Examples 1 to 3 satisfying the requirements of the present invention are excellent in running property, abrasion resistance and scratch resistance, and therefore have a highly satisfactory level in electromagnetic characteristics.
Furthermore, since it has excellent winding characteristics, it was possible to produce with a high product yield. On the other hand, in Comparative Example 1, when the relationship between the film thickness T and the particle diameter Da of the particles in the film was out of the range of the present invention, the winding property was poor and the productivity was remarkably reduced. Comparative Example 2 is an example in which the particle size of the particles in the film exceeds the requirements of the present invention, but in this case, the electromagnetic characteristics are significantly reduced due to the large protrusions. In Comparative Example 3, the relationship between the film thickness T and the particle diameter Db of the aluminum oxide particles in the coating layer is outside the range of the present invention, and the scratch resistance and electromagnetic characteristics are insufficient. Comparative Example 4 was a case where particles in the film were not blended, and the productivity was remarkably reduced as in Comparative Example 1. Comparative Example 5 is a case where the coating layer of the present invention is not provided,
The film has extremely poor scratch resistance and abrasion resistance. Comparative Example 6 is an example in which the coating layer of alumina was not provided and was compounded in the film, but the scratch resistance and abrasion resistance are insufficient and the dropout is slightly increased. Also, the wear resistance of the blade during slitting tended to deteriorate. Further, in this manufacturing method, the particles must be filled in all layers, which results in an increase in cost.

[0038]

The film of the present invention has excellent abrasion resistance,
It has scratch resistance and winding properties, and its industrial value is high.

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Claims (1)

[Claims] 1. A polyester film containing 0.005 to 0.5% by weight of particles A having an average particle diameter (Da) in the range of 0.2 to 2 μm on at least one side of the polyester film forming step. The film thickness (T) provided in the above step is 0.
Having a coating layer in the range of 01 to 1 μm, the coating layer containing 0.1 to 50% by weight of particles B having an average particle diameter (Db) in the range of 0.005 to 0.5 μm, and A polyester film characterized by satisfying the following formula. 0.9Db ≦ T ≦ 0.5Da