JP3313828B2 - Biaxially oriented 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 biaxially oriented polyester film having excellent flat lubricity, abrasion resistance and strength.

[0002]

2. Description of the Related Art Polyester films, especially biaxially oriented films represented by polyethylene terephthalate, have excellent physical and chemical properties, and are used as base films for magnetic recording media or capacitor derivatives. However, in recent years, as video tapes have been increased in recording density, lengthened and reduced in size and capacitor capacity increased, and miniaturized, the base film has been made smoother, thinner and thinner. The demand for increased strength is remarkable. However, it is difficult for the conventional biaxially oriented polyester film to satisfy such requirements. The main cause is that the added particles, which are effective for smoothing and smoothing the biaxially oriented polyester film, generally fall off the film surface when stretched at high magnification in both the vertical and horizontal directions to increase the strength during film production. On the contrary, the additive particles which are unlikely to fall off from the film surface generally have a small effect of smoothing.

[0003]

In view of such circumstances, the present inventors have made intensive studies to provide an excellent film which can satisfy flatness, smoothness and high strength. It has been found that such a target can be achieved by the combination of the particles added, and the present invention has been completed. That is, the gist of the present invention is that the average particle size is 0.05 to 0.6.
silica particles having a spherical shape ratio of 1.0 to 1.2 μm.
A crosslinked polymer having an average particle diameter of 0.1 to 2 μm, a sphere ratio of 1.0 to 1.2, and a degree of deformation by biaxial stretching of 1.0 to 1.5 0.00 particles
There is a biaxially oriented polyester film characterized by containing 5 to 1% by weight.

Hereinafter, the present invention will be described in detail. In the polyester of the present invention, 80% or more of the repeating structural units are ethylene terephthalate units or ethylene-2,6.
-Refers to polyesters having naphthalate units. In addition, the polyester film of the present invention refers to a biaxially oriented polyester film using such a polyester as a starting material, and a known method can be used for producing the polyester film. For example, after being melt-extruded into a sheet at 270 to 330 ° C, it is cooled and solidified at 40 to 80 ° C to form an amorphous sheet, and then at 80 to 170 ° C in the vertical and horizontal directions with an area magnification of 4 to 20 times. It is possible to use a method in which the film is biaxially stretched sequentially or simultaneously, and then heat-treated at 170 to 270 ° C. When stretching in the longitudinal and transverse directions, each may be stretched in one step, and if necessary,
Stretching may be performed in multiple stages, or a heat treatment section for relaxing orientation may be provided between the multiple stages.

The most important feature of the present invention resides in that the following two types of particles are simultaneously contained as particles to be incorporated into a film. The first particles have an average particle size of 0.05 to 0.6 μm.
m, preferably 0.1 to 0.3 μm, more preferably 0.1 to 0.2 μm, and silica particles having a sphere ratio of 1.0 to 1.2. The spherical ratio in the present invention is defined as the ratio between the maximum diameter and the minimum diameter of the particles before being contained in the film. When the sphere ratio is 1.0, it is a true sphere. If the sphere ratio exceeds 1.2, the lubricity of the film becomes insufficient. When the average particle size of the silica particles is less than 0.05 μm, the film has insufficient lubricity, and when it exceeds 0.6 μm, the surface flatness and abrasion resistance of the film become insufficient.
The reason why the abrasion resistance is insufficient is that silica particles having a large particle diameter easily fall off from the film surface.

[0006] The content of silica particles in the film is 0.0
It needs to be 1 to 1% by weight. When the content is less than 0.01% by weight, the lubricity of the film becomes insufficient. Also,
If it exceeds 1% by weight, the surface flatness and abrasion resistance of the film become insufficient. The reason why the wear resistance is insufficient is that the amount of the silica particles falling off from the film surface increases. The content of the silica particles is preferably from 0.01 to 0.3% by weight. Silica particles can be obtained mainly by the following two types of production methods, but are not limited thereto. The first production method is a method in which an alkoxysilane is used as a starting material and subjected to hydrolysis and condensation reaction.
As the alkoxysilane, a compound such as tetramethoxysilane, tetraethoxysilane, or tetrabutoxysilane is preferably used. The second production method is a method of hydrolyzing sodium silicate.

The second particles contained in the polyester film of the present invention have an average particle size of 0.1 to 2 μm, preferably 0.2 to 1.2 μm, and more preferably 0.2 to 0.2 μm.
Crosslinked polymer particles having a diameter of 6 μm, a spherical ratio of 1.0 to 1.2, and a degree of deformation by biaxial stretching in a range of 1.0 to 1.5. If the average particle size of the crosslinked polymer particles is less than 0.1 μm, the lubricity and abrasion resistance of the film become insufficient. If it exceeds 2 μm, the surface flatness of the film becomes insufficient. When the sphere ratio exceeds 1.2, the lubricity and abrasion resistance of the film become insufficient. The degree of deformation referred to in the present invention is defined by the ratio between the maximum diameter and the minimum diameter of the crosslinked polymer particles present in the stretched film. The degree of deformation is more preferably in the range of 1.0 to 1.2. If the degree of deformation exceeds 1.5, the lubricity and abrasion resistance of the film become insufficient.

The content of the crosslinked polymer particles in the film must be 0.005 to 1% by weight. Content is 0.
If the content is less than 005% by weight, the lubricity and abrasion resistance of the film become insufficient. If it exceeds 1% by weight, the surface flatness of the film becomes insufficient. The content of the crosslinked polymer particles is preferably from 0.01 to 0.3% by weight. The method for producing the crosslinked polymer particles is not particularly limited, but a typical example is a method in which at least one monovinyl compound (A) having only one aliphatic unsaturated bond in a molecule is crosslinked with one or more monovinyl compounds. A so-called emulsion polymerization method is carried out using one or more compounds (B) having two or more aliphatic unsaturated bonds in the molecule and one or more compounds (C) having an ethylene glycol unit in the molecule as an agent. Good to apply. The compounds (B) and (C) can be the same compound. The term “emulsion polymerization method” as used herein refers to a broad definition of emulsion polymerization that also includes concepts such as soap-free emulsion polymerization and seed emulsion polymerization.

The compound (A) includes acrylic acid, methacrylic acid and their alkyl or glycidyl esters, maleic anhydride and its alkyl derivatives, vinyl glycidyl ether, vinyl acetate, styrene, alkyl-substituted styrene and the like. Examples of the compound (B) include divinylbenzene and divinylsulfone. Examples of the compound (C) include ethylene glycol monoacrylate, ethylene glycol methacrylate, ethylene glycol diacrylate, and ethylene glycol dimethacrylate. If the degree of cross-linking is too large, the affinity between the particles and the polyester is inferior. If the degree of cross-linking is too low, the heat resistance of the particles and the degree of deformation in the film are undesirably large. Therefore, in order to satisfy both, the weight ratio of the compound (B) as a crosslinking agent in the particles is usually 10 to 70%, preferably 20 to 55%, and more preferably 30 to 45%.

The content of ethylene glycol units in the crosslinked polymer particles is usually at least 3% by weight, preferably at least 5% by weight, more preferably at least 10% by weight. If the content of the ethylene glycol unit is less than 3% by weight, the affinity between the particles and the polyester tends to be insufficient, and the dispersibility in the polyester tends to be insufficient. One embodiment of the production of crosslinked polymer particles in the present invention is as follows. That is, after dissolving a predetermined amount of a water-soluble polymerization initiator such as hydrogen peroxide and potassium persulfate in an aqueous medium, a predetermined amount of a mixed solution of the compounds (A), (B) and (C) is added. Added. Thereafter, the reaction is carried out at a temperature equal to or higher than the decomposition start temperature of the polymerization initiator, preferably at 30 to 90 ° C. for about 3 to 10 hours with stirring. At this time, depending on the monomer composition, some aggregated particles may be formed. In this case, a dispersion stabilizer such as an emulsifier may be added to maintain the dispersion stability of the particles. In any case, the particles are obtained as a uniformly dispersed water slurry.

In the present invention, the ratio of the average particle size of the silica particles to the average particle size of the crosslinked polymer particles (the average particle size of the silica particles / the average particle size of the crosslinked polymer particles) is 0.9 or less. Preferably, it is more preferably 0.7 or less. When the ratio exceeds 0.9, the abrasion resistance of the film becomes insufficient. The method for blending the silica particles and the crosslinked polymer particles used in the present invention with the polyester as a film forming raw material is not particularly limited, and a known method can be employed.
For example, when the particles are obtained as an ethylene glycol slurry dispersion, the polycondensation reaction is added at any stage of the polyester production process, preferably after the completion of the esterification or transesterification reaction and before the start of the polycondensation reaction. Good to go. Further, if necessary, other particles, for example, particles of kaolin, talc, calcium carbonate, aluminum oxide and the like can be used in combination within a range not to impair the purpose of the present invention. Particularly when fine aluminum oxide particles are used in combination, the scratch resistance of the film is improved.

It is preferable that the polyester film of the present invention further has an F ₅ value in the longitudinal and transverse directions satisfying the following formula (1). F ₅ ^MD + F ₅ ^TD ≧ 26 (1) (In the above formula, F ₅ ^MD is the F ₅ value in the vertical direction (kg / mm
² ), F ₅ ^TD is the F ₅ value in the lateral direction (indicating kg / mm ² ) More preferably, the above formula (1), the following formulas (3) and (4) are simultaneously satisfied, or 1) Formula,
This satisfies the following expressions (5) and (6) simultaneously. ^{_{| F 5 MD -F 5 TD |}} ≦ 3 ... (3) 13 ≦ F 5 MD ≦ 17 ... (4) | F 5 MD -F 5 TD | ≧ 5 ... (5) F 5 MD ≧ 18 ... (6) When these conditions are satisfied, the film properties, especially when the film is made thin, are improved. That is, if the strength is insufficient, for example, in the case of a base film for a magnetic tape for a long time, running the magnetic tape a number of times repeatedly deteriorates the running property and electrical characteristics of the tape, resulting in poor durability of the tape.

In order to obtain a film having high strength in the machine direction or in both the machine direction and the machine direction, a prescription is adopted in which after biaxial stretching, the film is stretched again before being subjected to the next heat treatment step.
This re-stretching can be performed in any of vertical and horizontal directions,
Further, it may be performed in both directions. For example, after biaxial stretching, re-stretching at a temperature of 110 to 200 ° C. in the longitudinal direction or in both the longitudinal and transverse directions by 1.05 to 4.0 times is performed, followed by heat treatment. At this time, a method such as heat setting before re-stretching, relaxation after re-stretching, or micro-magnification stretching before or after re-stretching can be appropriately adopted. The polyester film of the present invention,
Furthermore, the surface center line average roughness Ra value is from 0.003 to
It is preferably in the range of 0.015 μm, more preferably in the range of 0.005 to 0.010 μm. R
If a is less than 0.003 μm, the lubricity and abrasion resistance of the film may be insufficient, and if it exceeds 0.015 μm, the surface roughness tends to be too large. The polyester film of the present invention is excellent in lubricity, abrasion resistance and mechanical strength, and thus is more suitable for a base film for a long time magnetic tape, for example. Also,
It is extremely useful as a base film in various fields such as for condensers and thermal transfer.

[0014]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. The methods and definitions for measuring various physical properties and characteristics in the examples are as follows. In Examples and Comparative Examples,
"" Means "parts by weight". (1) Average particle diameter The maximum diameter and the minimum diameter of each particle were measured by scanning electron microscope observation, and the arithmetic mean was defined as the particle diameter (diameter) of one particle. The particle size was measured for at least 100 particles, and their arithmetic mean was defined as the average particle size. (2) Spherical ratio The maximum diameter and the minimum diameter of each particle are measured by scanning electron microscope observation of the particles, the ratio of maximum diameter / minimum diameter is calculated, and the ratio is obtained for at least 100 particles. The arithmetic mean was defined as the spherical ratio. (3) Deformation ratio A small piece of a stretched film containing particles was fixed and molded with an epoxy resin, cut with a microtome, and a cross section in the longitudinal direction (longitudinal direction) of the film was observed with a transmission electron microscope. For particles existing within 5 μm from the film surface, the maximum diameter and minimum diameter are measured for each particle to calculate the ratio of maximum diameter / minimum diameter, and the ratio is determined for at least 100 particles, and the addition of those values is performed. The average was defined as the deformation ratio.

(4) Average Roughness of Film Surface According to the method described in Japanese Industrial Standard JIS B0601, a surface roughness measuring instrument (SE-
Using 3F), the center line average roughness (Ra) was determined. (5) F ₅ value of the film Co. Intesco Ltd. tensile tester in Tesco model 20
Using a type 01, a sample piece having a length of 50 mm and a width of 15 mm was pulled at a pulling rate of 50 mm / min, the load at 5% elongation was read from the obtained SS curve, and the F ₅ value was calculated according to the following equation. Was calculated. Sectional area of F ₅ = 5% elongation when a load [kg] / specimen [m
m ² ] (6) Runnability Evaluated by the slipperiness of the film. The slipperiness was measured by winding a film around a fixed hard chromium-plated metal roll (diameter 6 mm) and contacting it at an angle (θ) of 135 °, applying a load of 53 g to one end and running it at a speed of 1 m / min. The resistance force (T ₁ , g) was measured, and the friction coefficient during running (μd) was determined by the following equation. _{μd = 0.424 · ln (T 1} /53)

(7) Abrasion resistance Abrasion resistance was evaluated based on the amount of white powder generated as shown below. <Amount of white powder> A film was wound around a fixed hard chrome fixing pin having a diameter of 6 mm and was brought into contact with the film at an angle of 135 °. The speed was 10 m / min.
m, and the amount of abrasion white powder adhering to the pins was visually evaluated and evaluated according to the rank shown below. Rank A: White powder does not adhere at all Rank B: A small amount of white powder adheres Rank C: Small amount (more than Rank B) white powder adheres Rank D: Extremely large amount of white powder adheres

(8) Magnetic tape characteristics 200 parts of magnetic fine powder, 30 parts of polyurethane resin, 10 parts of nitrocellulose, 10 parts of vinyl chloride-cellulose acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone,
After mixing and dispersing 100 parts of methyl isobutyl ketone and 300 parts of methyl ethyl ketone in a ball mill for 48 hours,
A magnetic paint is prepared by adding 5 parts of a polyisocyanate compound,
After this was applied to a polyester film, it was magnetically oriented before the paint was sufficiently dried and solidified, and then dried and dried.
A magnetic layer having a thickness of m was formed. <Calendar Stain> Then, when the obtained magnetic layer coating film was subjected to a surface treatment with a calender, the degree of stain on the roll surface contacting the base film was evaluated. That is,
Using a 5-stage super calender composed of a mirror-finished metal roll and a polyester-based composite resin roll, under the conditions of a roll temperature of 85 ° C., a linear pressure of 250 kg / cm, and a running speed of 80 m / min. Tape 5000m 7
It was repeatedly run twice, and the amount of white powder adhering to the resin roll was visually evaluated and evaluated according to the rank shown below. 〇: Adhesion of white powder is hardly observed on the resin roll △: Extremely slight adhesion of white powder is observed ×: Adhesion of white powder is clearly observed

<Dropout number (DO)> A video tape on which a signal of 4.4 MHz is recorded is reproduced, and the number of dropouts is measured for about 20 minutes by a dropout counter of Okura Industry Co., Ltd. It was converted to a number. <Durability of tape> Magnetic tape manufactured by the above method
The tape was actually placed on a VCR and subjected to 400 repeated running tests, and the running state of the tape and the deformed state of the tape at that time were evaluated. 〇: good △: slightly poor ×: poor (9) Scratch resistance A magnetic tape slit to a width of 1/2 inch is 6 mm in diameter.
A film is wound around a hard chrome-plated metal pin (finish 3S) of 135 °, running speed 4 m / min, tension 5
The base film surface of the magnetic tape was rubbed once with 0 g. Next, aluminum was vacuum-deposited on the rubbed surface so as to have a thickness of about 1000 mm, the amount of scratches was visually observed, and the following judgment was made. Rank 1: The amount of scratches is extremely high. Rank 2: The amount of scratches is high. Rank 3: The amount of scratches is between 2 and 4. Rank 4: The amount of scratches is low.

Example 1 [Production of silica particles] 30.4 g of tetramethylsilane was dissolved in 400 g of methanol and kept at 20 ° C. (A
Liquid) On the other hand, 110 g of water was added to 900 g of methanol, and 28%
243 g of an aqueous ammonia solution was added, mixed, and maintained at 20 ° C. (Solution B) Next, Solution A was added thereto while stirring Solution B, and after stirring and holding for 2 hours, 103 g of ethylene glycol was added.
Excessive water, methanol and ammonia were distilled off by heating under reduced pressure to obtain an ethylene glycol slurry containing 10% -concentration spherical silica fine particles. The average particle diameter of the spherical silica fine particles in the slurry was 0.20 μm, and the spherical ratio was 1.05. [Production of crosslinked polymer particles] To 1500 parts of demineralized water, 3.2 parts of potassium persulfate as a water-soluble polymerization initiator and 0.004 parts of sodium lauryl sulfate as a dispersion stabilizer were added and uniformly dissolved, and then methyl methacrylate was added. A mixed solution of 5 parts, 65 parts of ethylene glycol dimethacrylate and 30 parts of divinylbenzene was added. Next, polymerization was carried out at 70 ° C. for 8 hours while stirring under a nitrogen gas atmosphere. Reaction rate is 9
At 8%, the resulting particles had an average particle size of 0.30 μm and a sphericity of 1.05. 2000 parts of ethylene glycol was added to the obtained water slurry of the particles, and the water was distilled off under heating and reduced pressure to obtain an ethylene glycol slurry.

[Production of polyester film] 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor, heated and heated, and methanol was distilled off to carry out a transesterification reaction. 4 hours from the start of the reaction and 230
The temperature was raised to ° C. to substantially terminate the transesterification reaction. Next, 0.1 part of crosslinked polymer particles and 0.1 part of spherical silica particles were added as an ethylene glycol slurry, and 0.03 part of phosphoric acid and 0.0 part of antimony trioxide were further added.
One part was added to carry out a polycondensation reaction to obtain polyethylene terephthalate having an intrinsic viscosity of 0.61. The obtained polymer was extruded into a sheet at 285 ° C. from an extruder, and an amorphous sheet was obtained by using an electrostatic application cooling method. Next, the film is stretched 2.3 times in the longitudinal direction at 85 ° C., and 1.3 times in the same direction at 110 ° C., and then stretched 3.5 times in the transverse direction at 140 ° C. by a tenter and heat-set at 150 ° C. Then, again stretched 1.3 times in the machine direction at 130 ° C. and 1.2 times in the transverse direction at 140 ° C.
Finally, it was heat-set at 200 ° C. to obtain a polyethylene terephthalate film having a thickness of 8 μm, and its characteristics were evaluated.
Further, a magnetic layer was applied to the obtained film to obtain a magnetic tape, and the characteristics were measured.

Example 2 A polymer containing crosslinked polymer particles and spherical silica particles was obtained in the same manner as in Example 1 and extruded at 285 ° C. from an extruder into a sheet. I got Next, after stretching at 90 ° C. in the longitudinal direction by 4.0 times, stretching by a tenter in the transverse direction at 100 ° C. by 3.5 times,
Then, it was stretched again at 130 ° C. in the longitudinal direction by 1.2 times, and finally heat-set at 200 ° C. to obtain a polyethylene terephthalate film having a thickness of 8 μm, and its characteristics were evaluated. Further, a magnetic layer was applied to the obtained film to obtain a magnetic tape, and the characteristics were measured.

Example 3 The amount of potassium persulfate in the water-soluble polymerization initiator was 1.5 parts,
Crosslinked polymer particles having an average particle diameter of 0.60 μm and a sphere ratio of 1.05 were obtained in the same manner as in Example 1 except that the synthetic polymerization time was changed to 9 hours. 0.02 parts of crosslinked polymer particles, spherical silica particles having an average particle size of 0.15 μm and a sphere ratio of 1.05
A polymer containing these particles was obtained in the same manner as in Example 1 except that 1 part was added as an ethylene glycol slurry. Next, using the obtained polymer, a polyethylene terephthalate film having a thickness of 8 μm was obtained in the same manner as in Example 2, and further a magnetic tape was obtained.

Example 4 The average particle size used in Example 1 was 0.30 μm, and the sphere ratio was 1.0.
0.1 part of crosslinked polymer particles of 5, average particle size 0.20 μm,
Example 1 except that 0.1 part of spherical silica particles having a sphere ratio of 1.05 and 0.3 parts of fine alumina particles having an average particle size of 0.08 μm were added as an ethylene glycol slurry.
In the same manner as in the above, a polymer containing these particles was obtained.
Then, using the polymer, a polyethylene terephthalate film having a thickness of 8 μm was obtained in the same manner as in Example 1, and a magnetic tape was obtained.

Example 5 The amount of potassium persulfate in the water-soluble polymerization initiator was 2.5 parts,
Crosslinked polymer particles having an average particle size of 0.40 μm and a sphere ratio of 1.05 were obtained in the same manner as in Example 1 except that the synthetic polymerization time was changed to 8.5 hours. Instead of dimethyl terephthalate, dimethyl naphthalene-2,6-dicarboxylate 100
Parts, and 0.01 parts of the above crosslinked polymer particles,
Except for adding 0.1 part of spherical silica particles having an average particle diameter of 0.20 μm and a sphere ratio of 1.05 as an ethylene glycol slurry, a polyethylene-2,6- Naphthalate was obtained. Extruding the polymer into a sheet at 295 ° C. from an extruder,
An amorphous sheet was obtained by using an electrostatic cooling method. Then
After stretching 2.5 times in the longitudinal direction at 135 ° C., stretching 4.2 times in the transverse direction at 138 ° C. with a tenter,
The film was stretched 1.8 times in the machine direction at 1.8 ° C., and then heat-treated at 1.1 ° C. in the transverse direction at 220 ° C. to give a thickness of 6 μm.
Polyethylene-2,6-naphthalate film of
Further, a magnetic layer was applied to the obtained film to obtain a magnetic tape, and its characteristics were measured.

Comparative Example 1 The average particle size used in Example 1 was 0.30 μm, and the sphere ratio was 1.0.
A polymer containing only crosslinked polymer particles was obtained in the same manner as in Example 1 except that only 0.2 part of the crosslinked polymer particles of No. 5 was added as an ethylene glycol slurry. Next, using the obtained polymer, a polyethylene terephthalate film having a thickness of 8 μm was obtained in the same manner as in Example 1, and a magnetic tape was obtained. Comparative Example 2 A polymer containing only spherical silica particles in the same manner as in Example 1 except that only 0.2 parts of spherical silica particles having an average particle size of 0.20 μm and a spherical ratio of 1.05 were added as an ethylene glycol slurry. Obtained. Next, using the obtained polymer, a polyethylene terephthalate film having a thickness of 8 μm was obtained in the same manner as in Example 1, and a magnetic tape was obtained.

Comparative Example 3 The procedure of Example 1 was repeated, except that a mixed solution of 30 parts of methyl methacrylate, 65 parts of ethylene glycol dimethacrylate and 5 parts of divinylbenzene was used. Crosslinked polymer particles were produced. 0.1 part of the obtained crosslinked polymer particles and 0.1 of spherical silica particles having an average particle size of 0.20 μm and a sphere ratio of 1.05
A polyethylene terephthalate film having a thickness of 8 μm was obtained in the same manner as in Example 1, and a magnetic tape was obtained. Comparative Example 4 The average particle size used in Example 1 was 0.30 μm, and the spherical ratio was 1.0.
0.1 part of crosslinked polymer particles of 5, and an average particle size of 0.70 μm,
An 8-μm-thick polyethylene terephthalate film was obtained in the same manner as in Example 1 except that 0.01 part of spherical silica particles having a sphere ratio of 1.05 was contained, and a magnetic tape was obtained.

Comparative Example 5 A polymer containing crosslinked polymer particles and spherical silica particles was obtained in the same manner as in Example 1. The obtained polymer is
It was extruded at 85 ° C. from an extruder into a sheet, and an amorphous sheet was obtained using an electrostatic application cooling method. Next, the film is stretched at 90 ° C. by 3.8 times in the machine direction, and then stretched 100 times in the transverse direction by a tenter.
Stretched 3.8 times at 200 ° C. and finally heat-set at 200 ° C. to obtain a polyethylene terephthalate film having a thickness of 8 μm.
Further, a magnetic tape was obtained. The results obtained are shown in Tables 1 to 4 below.

[0028]

[Table 1] ──────────────────────────────────── Example 1 Example 2 Example 3 Example Example 4 Example 5 <Blended particles> A: Crosslinked polymer Particle average particle size (μm) 0.30 0.30 0.60 0.30 0.40 Particle content (% by weight) 0.1 0.1 0.02 0.1 0.01 Spherical ratio 1.05 1 .05 1.05 1.05 1.05 Deformation ratio 1.10 1.10 1.15 1.10 1.10 B: Spherical silica Average particle size (μm) 0.20 0.20 0.15 0.20 0.20 Particle content (% by weight) 0.1 0.1 0.1 0.1 0.1 Spherical ratio 1.05 1.05 1.05 1.05 1.05 C: Fine alumina Average particle size ( μm) − − − 0 .08 - particle content (wt%) - - - 0.3 - <Film Properties> Ra (μm) 0.009 0.008 0.005 0.009 0.006 F 5 value Vertical 14.5 19.0 19.1 14.4 16.2 ( kg / mm ² ) 14.2 11.2 11.0 14.2 16.0 Slippery 0.32 0.34 0.42 0.33 0.32 Abrasion A A A A A A <Magnetic tape Properties> Calendar-dirt 〇 〇 〇 〇 〇 DO (pieces / minute) 45 2 42 2 Durability 〇 〇 〇 〇 擦 Scratch resistance 3 33 35 3 ───────────── ───────────────────────

[0029]

表 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 ──────────────────────────────────── <Blended particles> A: Crosslinked polymer Particle average particle size (μm) 0.30-0.30 0.30 0.30 Particle content (% by weight) 0.2-0.1 0.1 0.1 Spherical ratio 1.05-1.041 .05 1.05 Deformation ratio 1.10-1.95 1.10 1.10 B: Spherical silica Average particle size (μm)-0.20 0.20 0.70 0.20 Particle content (% by weight) - 0.2 0.1 0.01 0.1 spherical ratio - 1.05 1.05 1.05 1.05 <film properties> Ra (μm) 0.009 0.009 0.009 0.008 0.009 F 5 value vertical 14.5 14. 4 14.5 14.5 11.2 (kg / mm ² ) width 14.2 14.2 14.1 14.3 11.1 Slippery 0.45 0.31 0.40 0.39 0.33 Abrasion resistance BC BDA <Magnetic tape characteristics> Calendar dirt △ × △ × △ DO (pieces / minute) 18 27 15 30 10 Durability × △ △ △ × Scratch resistance 33 33 33 33 ──────────────────────────────

[0030]

The film of the present invention has a uniform and fine surface structure, is particularly excellent in abrasion resistance and film strength, and is useful as an industrial material such as a base film for a magnetic recording medium. , Its industrial value is high.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/18 C08L 67/00-67/02

Claims (1)

(57) [Claims] 1. Silica particles having an average particle diameter of 0.05 to 0.6 μm and a sphere ratio of 1.0 to 1.2 are contained in an amount of 0.01 to 1% by weight, and an average particle diameter of 0.1 to 2 μm. , The spherical ratio is 1.
0 to 1.2, and the degree of deformation by biaxial stretching is 1.0 to 1.
0.005 to 1% by weight of the crosslinked polymer particles in the range of 5
A biaxially oriented polyester film characterized by containing.