JPH04117428A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain the title film having a flat and uniform surface and excellent traveling properties and abrasion resistance by adding thereto a specified amount of CaCO3 particles which have a specified particle diameter and are surface-coated with an organic crosslinked polymer. CONSTITUTION:This film contains 0.01-4wt.% CaCO3 particles which have a mean particle diameter of 0.05-3mum and are surface-coated with an organic crosslinkd polymer (e.g. acrylic acid/methyl methacrylate/ethylene glycol dimethacrylate/divinylbenzene copolymer).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-wheel oriented polyester film having a uniform surface and excellent slip properties and abrasion resistance.

More specifically, the present invention uses calcium carbonate particles as a core,
This invention relates to a polyester film that is given excellent film surface properties by incorporating particles whose surface is coated with an organic crosslinked polymer.

[Issues to be solved by the prior art and the invention i! ] Polyester films, particularly biaxially oriented films represented by polyethylene terephthalate, have excellent physical and chemical properties and are prized as base films for magnetic recording media and capacitor derivatives. In addition, due to its excellent transparency, it is widely used in fields such as graphic arts, displays, and packaging materials.

Incidentally, film runnability and abrasion resistance are particularly required in terms of process passability in the molding process to obtain the above product, secondary processing processes such as coating and vapor deposition, and handling of the product itself. This was not always fully achieved.

For example, when films come into contact with each other or a film and a base material at high speed, the friction and abrasion between the two increases, causing scratches on the film and generation of abrasion powder. For example, in magnetic recording applications, this causes loss of recording signals, ie, dropouts, which significantly reduces the commercial value of the film.

It is generally known that in order to improve the running properties and abrasion resistance of a film, the surface of the film can be appropriately roughened. For this purpose, a method has been adopted in which fine particles are present in the raw material polyester, and although this method has been put into practical use in some cases, it has not yet reached the point where these characteristics are highly satisfied.

For example, when precipitated particles formed from catalyst residues during polyester production are used as fine particles, the fine particles are easily destroyed by stretching, resulting in poor runnability and wear resistance, and it is also difficult to reuse them. . In addition, silicon oxide,
When inert inorganic compound particles are added to polyester such as calcium carbonate, titanium dioxide, calcium phosphate, etc., the particles are not destroyed or deformed by stretching.
Although the running properties of the film are improved by providing relatively steep protrusions, these particles have poor affinity with polyester, so the particles are easily detached from the film surface, resulting in the production of a white powdery substance.

On the other hand, when heat-resistant organic particles are used as particles to be added, the particles generally have excellent affinity with polyester and deform following stretching, so there is little particle detachment from the film surface. The protrusions of the particles tend to become smooth, and combined with the elasticity of the particles themselves, the running properties of such films are not sufficient.

Of course, there is also a method of using an appropriate mixture of inorganic particles and organic particles, but this only provides an average effect and cannot be a fundamental solution.

[Means for Solving the Problems] The present inventors have conducted extensive studies in order to provide an excellent film that satisfies the requirements for runnability and abrasion resistance at the same time, and also has sufficient mechanical properties necessary for a film. As a result of repeated efforts, it was discovered that these required characteristics could be highly satisfied by incorporating certain specific particles into the film, and the present invention was completed.

That is, the gist of the present invention is to provide a biaxially oriented polyester film containing 0.001 to 4% by weight of calcium carbonate particles having an average particle size of 0.05 to 3 μm and whose surface is coated with an organic crosslinked polymer. exists in

The present invention will be explained in more detail below.

The polyester referred to in the present invention refers to terephthalic acid, 2.6
- It refers to a polyester obtained using an aromatic dicarbonate such as naphthalene dicarboxylic acid or its ester and ethylene glycol as the main starting materials, but it may contain other third components.

In this case, as the dicarboxylic acid component, one of, for example, isophthalic acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, and sebacic acid can be used. Further, as glycol components, diethylene glycol, propylene glycol, butanediol, 1.
One or more of 4-cyclohexane dimetatool and neopentyl glycol can be used. In any case, the polyester of the present invention refers to a polyester in which 80% or more of repeating structural units have ethylene terephthalate units or ethylene-2,6-naphthalate units.

Furthermore, the polyester film of the present invention refers to a polyester film that uses such a polyester as a starting material and is oriented in at least one axis, and any known method can be used for its production. For example, after melt-extruding into a sheet at 270 to 320°C,
It is cooled and solidified at 40 to 80°C to form an amorphous sheet, and then heated to 80 to 130°C at an area magnification of 4 to 2 in the vertical and horizontal directions.
Stretch two wheels sequentially or simultaneously so that the
A method of heat treatment at 0 to 250"C (for example,
The method described in Japanese Patent No.-5639) can be used. When stretching in the longitudinal and transverse directions, stretching may be performed in each stage, or, if necessary, stretching may be performed in multiple stages, or a heat treatment section for orientation relaxation may be provided between multi-stage stretching. Further, after biaxial stretching, the film may be stretched again before being subjected to the next heat treatment step. This re-stretching can be performed in either the longitudinal or lateral direction, or in both directions.

A feature of the present invention is that particles made of a composite of an inorganic compound and an organic compound are used as particles in the polyester film.

Inorganic particles that are commonly used as additives for polyester originally have poor affinity with the polyester matrix, and when a strong stress is applied during stretching, the particles do not deform and voids are created around the particles. When a void occurs,
When the film surface is abraded, particles easily separate from the film starting from that point.

In addition, as the field of magnetic recording media, etc., advances in higher densities, higher precision, and faster film forming processes, there is a need for films that are flat, have excellent running properties, and do not damage the base materials they come into contact with during running. The current situation is to select inorganic particles that give the film excellent runnability and have appropriate hardness in consideration of damage to the base material.

For example, calcium carbonate particles are known as such particles, but although they are excellent in terms of runnability and resistance to scratches on the substrate, they lack compatibility with polyester, so the film surface The reality is that when the inorganic particles are worn out, particles come off, which is characteristic of inorganic particles, making them difficult to use.

The present inventors focused on improving the wear characteristics of calcium carbonate particles while taking advantage of their characteristics, and as a result,
The above problem was solved by coating the surface with an organic crosslinked polymer that has good affinity with polyester.

There are no particular restrictions on the calcium carbonate that forms the core of the composite particles used in the present invention, and natural or synthetic calcium carbonate can be used. The crystal type may be calcite type, aragonite type, or vaterite type, and the shape may be lump-like, spindle-like, plate-like, spherical, or
Although the effects of the present invention can be enjoyed regardless of the shape of the particles, such as ellipsoids, particles having a sharp particle size distribution are particularly preferable. In other words, the particle size distribution [γ] value (the diameter at the point where the weight fraction is 25% and the weight fraction is 75% when integrated from the large particle side)
It is preferable that the ratio of the point diameters) is 2.5 or less,
[The γ value is more preferably 2°0 or less, particularly preferably 1.8 or less. By using such particles,
The film has excellent surface uniformity and can be preferably used in high-grade applications such as magnetic recording media and capacitor derivatives.

A typical example of calcium carbonate particles with a sharp particle size distribution is one produced by a so-called synthesis method in which a calcium hydroxide aqueous solution is reacted with a carbon dioxide-containing gas, as disclosed in JP-A No. 59-69425. Examples include precipitated calcium carbonate particles, and preferably vaterite-type monodisperse calcium carbonate obtained by carbonation reaction in which carbon dioxide is blown into an alcoholic medium, typically methanol. .

In this reaction, particles having a spherical shape, an elliptical spherical shape, a cylindrical shape, an elliptic cylindrical shape, etc. can be obtained by appropriately selecting the conditions, and the particle size distribution [rl value can also be set to 1.8 or less.

In the present invention, the surfaces of such calcium carbonate particles are coated with an organic crosslinked polymer. A monovinyl compound (A) having only one aliphatic unsaturated bond in the molecule as an organic crosslinked polymer, and a compound (B) having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent. An example is a copolymer with In this case, such a copolymer may have a group that reacts with the polyester.

Examples of the compound (A) which is a component of the copolymer include acrylic acid, methacrylic acid and their alkyl or glycidyl esters, maleic anhydride and their alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene, alkyl-substituted styrene, etc. be able to. Examples of the compound (B) include divinylbenzene, divinyl sulfone, and ethylene glycol dimethacrylate. Although at least one type of each of the compounds (A) and (B) is used, a compound having a nitrogen atom or ethylene may be copolymerized. Note that a silane coupling agent or a titanium coupling agent may be mixed in addition to the compounds (A) and (B).

In order to polymerize these organic components on the surface of calcium carbonate particles in the present invention, it is preferable to apply, for example, an emulsion polymerization method (emulsion polymerization in a broad sense that includes concepts such as soap-free emulsion polymerization and seed emulsion polymerization). Although this emulsion polymerization uses calcium carbonate particles as a nucleus, it can also be carried out without adding an emulsifier. Although it depends on the type of monomer used, it is advantageous to keep the amount of emulsifier as low as possible because it can suppress the generation of only organic particles.

One embodiment of composite particle production in the present invention is as follows. First, calcium carbonate particles are dispersed in water, a predetermined amount of a monovinyl compound having a carboxylic acid such as acrylic acid or methacrylic acid is added, and the mixture is stirred at room temperature for 10 to 60 minutes to adsorb the monovinyl compound on the particle surface. Add a predetermined amount of a polymerization initiator such as hydrogen peroxide or potassium persulfate to form compounds (A) and (B).
Add a mixed solution of Thereafter, at a temperature higher than the decomposition start temperature of the polymerization initiator, preferably at 30 to 90°C, with stirring for 3 to 10 minutes.
The reaction takes about an hour.

Due to this reaction, composite particles are obtained as a uniformly dispersed water slurry, so it is preferable to replace it with ethylene glycol slurry for blending with polyester or take it out as dry particles. However, depending on the bath ratio and monomer composition, agglomeration may occur. A dispersion stabilizer may be used in combination during polymerization, since particles are likely to be generated. In any case, any method of coating with the organic crosslinked polymer component may be used as long as it satisfies the gist of the present invention.

The coating component is preferably thermally stable, and for this purpose, the crosslinking density, that is, the ratio of compound (B) to the total weight of compound (A) and compound CB), is usually 1 to 90% by weight. %, preferably 5 to 80% by weight. The degree of heat resistance of the obtained particles varies depending on the type of monomer, but specifically, it is
The weight loss rate after the time heat treatment is preferably 20% by weight or less, more preferably 10% by weight or less based on the total organic components.

Further, it is preferable that the coating component of the present invention contains a group capable of reacting with polyester, such as an ester group, a carboxyl group, a hydroxyl group, an epoxy group, etc., but if the coating component has excellent dispersibility in the polyester. , there are no particular restrictions.

Further, the coating layer may have a multilayer structure as required.

The thickness of the coating layer is usually 1/100 of the diameter of the core particle.
~1/2, preferably 1150~1/2, more preferably 1/30~1/2. This value is 1/10
If it is less than 0, the elastic effect of the organic crosslinked polymer component is insufficient, and it is the same as a single layer coating when treated with a silane coupling agent, etc. When strong stretching stress is applied, the stress cannot be absorbed and particles Peeling occurs. Also, this value is 1/
If it exceeds 2, the elastic effect becomes too strong and running properties become insufficient, which is not preferable.

The thickness of the coating layer can be determined easily by performing sedimentation separation in a solvent with a higher specific gravity than the organic crosslinked polymer of the coating layer, and then measuring the particle size before and after coating, using a centrifugal sedimentation type particle size distribution analyzer, for example. can be asked for. Particles having a multilayer structure can be easily confirmed, for example, by measuring the infrared absorption spectrum of the particles after coating.

The average particle diameter of the composite particles coated with the organic crosslinked polymer used in the present invention is 0.05 to 3 μm, preferably 0.1 to 3 μm.
It is 1 μm. If the average particle size is less than 0.05 μm, the running properties and abrasion resistance of the film will be insufficient. Moreover, if the average particle diameter exceeds 3 μm, the surface roughness becomes too large, which is not preferable.

The amount of composite particles blended into the polyester film is 0.001 to 4% by weight, preferably 0.01 to 1% by weight.
It is. If the blending amount is less than o, o o i weight %, the running properties and abrasion resistance of the film will be insufficient, and if the blending amount exceeds 4 weight %, the surface roughness will become too large, which is not preferable.

The method of blending it into the composite particle polyester used in the present invention is not particularly limited, and any known method can be employed. For example, it may be added as an ethylene glycol slurry to proceed with the polycondensation reaction at any stage of the polyester production process, preferably after the completion of the esterification or transesterification reaction but before the start of the polycondensation reaction.
The particles and polyester chips may be blended directly.

As described above, in the present invention, by stretching polyester containing specific composite particles in which calcium carbonate particles are coated with an organic crosslinked polymer, it is possible to obtain a film with excellent properties that have not been achieved before. However, if necessary, other particles, such as particles of kaolin, talc, calcium carbonate, silicon dioxide, aluminum oxide, etc., can be used in combination without departing from the gist of the present invention.

In addition, in the present invention, when the resulting polyester film satisfies certain physical properties, the running properties and abrasion resistance of the film can be further improved, making it more suitable as a base film for, for example, magnetic tape. Become something.

One preferable physical property of the polyester film is that the refractive index in the thickness direction is 1.492 or more. If this value is less than 1.492, even if the particles of the present invention are used, slipperiness and abrasion resistance will often be insufficient. This value preferably ranges from 1.494 to 1.505. In order to obtain a film having such physical properties, for example, in the case of sequential longitudinal and transverse biaxial stretching, the longitudinal stretching temperature may be set to about 105 to 115°C, which is 5 to 30°C higher than the normal stretching temperature. Alternatively, such a film can also be obtained by subjecting the film to significant lateral relaxation after two-wheel stretching and before heat treatment.

In addition, the film of the present invention can be particularly suitably used as a base film for magnetic recording media by taking advantage of its high abrasion resistance, but its characteristics are particularly exhibited when used for high strength, thin, and high recording density applications. can do. Specifically, the vertical F-54I! is 12.0 kg/mm” or more, preferably 14.0 kg/mm” or more, and the film thickness is 12.0 μm or less, preferably 10.0 μm or more.
It is particularly effective in applications requiring wear resistance of less than μm.

The polyester film of the present invention takes advantage of its excellent runnability and abrasion resistance, and can be used as a base film for magnetic recording media such as magnetic tapes and floppy disks, as well as for capacitors, photolithography, thermal transfer, and packaging. It is extremely useful as a base film in a variety of fields, such as for printing, transfer marks, and gold and silver thread.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, the measurement methods and definitions of various physical properties and characteristics in Examples are as follows. Furthermore, in Examples and Comparative Examples, "parts" indicate "parts by weight."

(1) Average particle size and particle size distribution Centrifugal sedimentation type particle size distribution analyzer manufactured by Shimadzu Corporation (SA-CF
Cumulative volume fraction 5 in the equioblate spherical distribution measured with type 2)
The particle size of 0% was taken as the average particle size. At the same time, the diameter at the point where the weight fraction is 25% and the weight fraction is 75% when integrated from the large particle side.
The ratio 'TJ value of the diameter at the point was used as an index of particle size distribution.

(2) Weight reduction rate 10% from room temperature under nitrogen gas flow (200+nf!/min) using a thermal analyzer DT-20Bs manufactured by Shimadzu Corporation.
Heating to 300°C at a temperature increase rate of °C/win,
After holding at C for 30 minutes, the weight loss rate of the organic component constituting the coating layer of the composite particles was determined.

(3) Running property Evaluation was made based on the slipperiness of the film. The slipperiness was measured by winding the film around a fixed hard chrome-plated metal roll (diameter 6III11) using the device shown in Figure 1 at an angle (θ) of 135.
°, and a load of 53 g (Tz) was applied to one end.
Run this at a speed of 1 m/min, and the resistance force at the other end (
TI (9)) is measured, and the wear coefficient (
μd) was calculated.

(6) Number of coarse protrusions Aluminum was deposited on the film surface and measured using a three-beam interference microscope. The measurement wavelength is 0.54 μm, and 3
The number of interference fringes showing the following or higher interference fringes is calculated per 10 cm 2 and shown.

(4) II! Wear characteristics Wear characteristics were evaluated using two methods. The first method is to quantify the number of particles after they fall off. In other words, gold was deposited on the surface of the film, a photograph was taken at a magnification of 20,000 times using a scanning electron microscope, and the number of protrusions that were thought to have been formed by particles that disappeared and became depressed was measured, and the unit area ( 1mm").

The smaller this value is, the better.

The second method is to evaluate the amount of white powder generated. That is,
The film was run for 1000 m using the running system shown in FIG. 2, and the amount of abrasion white powder adhering to a fixed bottle made of hard chrome 611I11 was visually evaluated and evaluated according to the ranks shown below. In addition, the film speed is 13 m/min,
The tension was approximately 200 g and θ=1356.

Rank A: All (no adhesion) Rank C: A small amount of adhesion Rank C: A small amount of adhesion (more than rank B) Rank D = Very much adhesion (5) Evaluation of electromagnetic properties First, a magnetic tape was manufactured. Fine powder 20
0 parts, polyurethane resin 30 parts, nitrocellulose 10 parts
After mixing and dispersing 10 parts of vinyl chloride-cellulose acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone, 100 parts of methyl isobutyl ketone, and 300 parts of methyl ethyl ketone in a ball mill for 48 hours, 5 parts of a polyisocyanate compound was added. This was applied to a polyester film, magnetically oriented before the paint was sufficiently dried and solidified, and then dried to form a magnetic layer with a thickness of 2 μm. The obtained coated film was subjected to surface treatment using a supercalender, and each portion was slit to a width of 2 inches to prepare a videotape. Next, the obtained magnetic tape was wound around a hard chrome-plated metal pin (diameter 61, surface roughness 3S) at a corner of 135° with a tension of 50 g, and the base film surface was brought into contact with the pin, and the tape was rubbed for 200 m at a running speed of 4 m/min. Next, the following electromagnetic properties of the tape after rubbing were measured using Matsushita Electric's NV-370.
Measurements were made using a Type 0 video deck.

O3/N (VTR head output) The VTR head output at a measurement frequency of 4 MHz was measured using a synchroscope, and the relative value was expressed in decibels with a blank as O decibels.

Number of Dropouts: A videotape recording a 4.4 MHz signal was played back, and the number of dropouts was measured for about 20 minutes using a Daikin Industry Dropout Counter, and the number was converted into the number of dropouts per minute.

Example 1 [Manufacture of composite particles] 100 parts of vaterite-type monodisperse synthetic calcium carbonate particles (VAN-RO50 manufactured by Maruo Calcium ■) having an average particle diameter of 0.52 μm and a [γ] value of 1.42 and acrylic Add 1 part of acid to 3000 parts of demineralized water using a homomixer (TK-Homomixer manufactured by Tokushu Kika Kogyo) at 110000 rpm.
After dispersing for 30 minutes, the mixture was filtered through a #3600 mesh wire mesh. Next, add 0.6% of potassium persulfate as a water-soluble polymerization initiator.
% and sodium lauryl sulfate as dispersion stability side 0.02
After adding 1.0 parts and uniformly dissolving it, a mixed solution of 7 parts of methyl methacrylate, 25 parts of ethylene glycol dimethacrylate, and 4 parts of divinylbenzene was added. Next, polymerization was carried out at 70°C for 6 hours with stirring under a nitrogen gas atmosphere. As a result, the average particle size of the obtained particles was 0.62μ
The m, [γ] value was 1.42, and the reaction rate of the organic component was 98%. Substantially no particles other than composite particles were observed in the reaction system, and the infrared absorption spectrum of the particles was 1725 cm-
' and 1,300 to 1,150 cm-' It was confirmed that the surface of the calcium carbonate particles was uniformly coated with the organic crosslinked polymer by showing absorption based on the ester bonds of methyl methacrylate and ethylene glycol dimethacrylate. Note that the weight decrease of the organic component of the composite particles upon heating was 5.9%.

Next, 2,500 parts of ethylene glycol was added to the obtained water slurry of the composite particles, heated, and water was distilled off under reduced pressure to obtain an ethylene glycol slurry.

[Manufacture of polyethylene] 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol, and 0.09 parts of magnesium acetate tetrahydrate were placed in a reactor, and the temperature was raised while methanol was distilled off to perform a transesterification reaction. The temperature was raised to 230°C over time, and the transesterification reaction was substantially completed.

Next, after adding 4 parts of the above ethylene glycol slurry, 0.04 part of ethyl acid phosphate was added,
Further, 0.04 part of antimony trioxide was added and a polycondensation reaction was carried out for 5 hours to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65.

After drying the obtained polyester, it was melt-extruded at 290°C to form an amorphous sheet, and then heated in the longitudinal direction at 110°C for 3.5
Stretched 3.7 times in the transverse direction at 120″C, 210°C
Heat treatment was performed for 3 seconds to obtain a film with a thickness of 15 μm.

Example 2 In the production of composite particles of Example 1, the core particles of the particles had an average particle diameter of 0.50 μm and a [γ] value of 1.6.
Using calcite-type synthetic calcium carbonate particles as shown in No. 5, the components constituting the coating layer were 7 parts of methyl methacrylate,
A film was obtained in the same manner as in Example 1 except that 25 parts of ethylene glycol dimethacrylate and 4 parts of divinylbenzene were used, and its properties were measured.

Example 3 In the production of the composite particles of Example 1, the core particles of the particles had an average particle diameter of 0.50 μm, an [r] value of 6 months,
Using calcite-type synthetic calcium carbonate particles as shown in No. 5, the components constituting the coating layer were 4 parts of methyl methacrylate,
A film was obtained in the same manner as in Example 1 except that 14 parts of ethylene glycol dimethacrylate and 2 parts of divinylbenzene were used and the coating thickness was changed to 0.03 μm, and its properties were measured.

Example 4 In the production of the composite particles of Example 1, the core particles of the particles had an average particle diameter of 0.35 μm and a [γ] value of 1.5.
Using calcite-type synthetic calcium carbonate particles as shown in No. 5, the components constituting the coating layer were 10 parts of methyl methacrylate, 35 parts of ethylene glycol dimethacrylate, and 5 parts of divinylbenzene, and the amount of the composite particles to be blended into the polyester was A film was obtained in the same manner as in Example 1 except that the amount was changed to 0.3% by weight, and its properties were measured.

Comparative Example 1 A film was obtained in the same manner as in Example 1, except that calcite-type synthetic calcium carbonate particles not coated with an organic crosslinked polymer were used as particles to be blended with polyester, and its properties were measured. did.

Comparative Example 2 In Example 1, instead of coating with an organic crosslinked polymer, 100 parts of calcite-type synthetic calcium carbonate particles were subjected to surface treatment with 2 parts of T-glycidoxyprobyltrimethoxysilane. Next, a film was obtained using the obtained particles in the same manner as in Example 1, and its properties were measured.

Comparative Example 3 In Example 1, instead of the calcite-type synthetic calcium carbonate particles serving as the core of the composite particles, an average particle size of 0.50μ was used.
A film was obtained in the same manner as in Example 1, except that crosslinked polymer particles with m styrene/divinylbenzene = 9/1 were used.
Its properties were measured.

Comparative Example 4 Average particle size of particles added to polyester: 0°52μ
m[γ]! A film was obtained in the same manner as in Example 1 using kaolin No. 2.6, and its properties were measured.

that's all, The obtained results are summarized in Table 1 below.

As shown in Table 1, Examples 1-
All of the films in No. 4 have excellent running properties and abrasion properties, and are extremely useful as base films for magnetic tapes, for example, whereas the films in Comparative Example 1, which are not coated with an organic crosslinked polymer, have excellent abrasion resistance. inferior to sex. Also, comparative example 2
As shown in Figure 2, improvement in wear characteristics cannot be achieved by surface treatment with a silanka coupling agent.

Furthermore, as shown in Comparative Example 3, when the particles are composed only of organic components, although the wear characteristics are excellent, the running properties are poor.

Comparative Example 4 has an average particle size of 0.52 μm as an example of inorganic particles.
This shows the case of kaolin, which has poor abrasion properties, has a wide particle size distribution, and frequently produces coarse protrusions.

[Effects of the Invention] The film of the present invention has a flat and uniform surface, has excellent running properties and abrasion characteristics, can be applied to various uses, and has high industrial value.

[Brief explanation of drawings]

Figure 1 shows the running system for evaluating the dynamic wear coefficient with metal.
(I) is a hard chrome plated fixing pin with 6 mm diameter, (II)
is the inlet tension meter (I[I) is the outlet tension meter, and θ is 135°. FIG. 2 shows a running system for evaluating wear resistance, in which (IV) shows a hard chrome plated measuring pin with a diameter of 6 mm, (V) shows a tension meter, and θ is 135°.

Claims (1)

[Claims] (1) Surface coated with organic crosslinked polymer, average particle size 0
．． 0.001 to 4 calcium carbonate particles of 05 to 3 μm
A biaxially oriented polyester film characterized by containing % by weight.