JP3378072B2 - Biaxially oriented polyester film - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biaxially oriented polyester film, and more specifically, it contains crosslinked polymer particles having a specific particle size distribution ratio, an average particle size and a specific shape,
The present invention relates to a biaxially oriented polyester film which has a flat film surface, few coarse projections, and excellent running and winding properties.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used in many applications such as magnetic tapes, electricity, photography, metallization and packaging due to their excellent properties. In particular, because of its high strength and elastic modulus, it is widely used as a base film for magnetic recording media such as video tapes, audio tapes, computer tapes and floppy disks.

In these fields of application, demands for high-density recording and high quality have been increasing in recent years, and along with this, the base polyester film is required to maintain running properties and have a flat surface. Is becoming more and more demanding.

As a method for improving the running property of a film, conventionally, inert inorganic particles have been added to polyester and fine projections derived from the particles are formed on the surface of the film during film formation, and the running property is provided by the fine projections. Is used. The inert inorganic particles usually have a wide particle size distribution and include coarse particles, and therefore, it is necessary to classify and remove the coarse particles before adding them to the polyester, but this classification causes an increase in cost. , The cost increases dramatically as the degree of classification increases. Moreover, there is a limit to narrowing the particle size distribution by classification,
It is difficult to eliminate coarse particles completely.

Therefore, in recent years, it has been studied to industrially produce particles having a uniform particle size without containing coarse particles, especially crosslinked polymer particles, and some particles are industrially produced. However, such particles have a relatively large average particle size, and there is a problem to be solved in order to produce particles having a uniform and smaller particle size, and therefore the production cost also increases.

[0006]

According to the research conducted by the present inventors, when a biaxially oriented polyester film having a flat surface is produced using the above-mentioned inorganic particles or crosslinked polymer particles, a certain degree of running property is imparted. Even if the film is wound, a good winding shape may not always be obtained, and this tendency becomes large when cross-linked polymer particles having a uniform particle size are used. It was found that the end face of the film roll was disturbed by the displacement. The reason for this is probably that the protrusion heights on the film surface are uniform and air is trapped between the films when the film is wound into a roll. Therefore, in order to obtain a film roll having a good winding shape with no disturbance on the end faces, it is necessary to reduce the amount of air entrained as much as possible, and the film is required to be easy to escape the air between the films.

In order to facilitate the escape of air between the films, it is effective to make the heights of the projections on the film surfaces uneven, rather to disturb them, and it is effective to use particles having a relatively wide particle size distribution. . In this respect, the inert inorganic particles are more advantageous than the crosslinked polymer particles having uniform particle size. But,
The inert inorganic particles include coarse particles, and since the surface protrusions formed by the coarse particles become too high, the flatness of the film surface is impaired. It causes a drop and the protrusion itself causes dropout. Therefore, the use of inorganic particles cannot meet the ever-increasing demand for higher quality.

The present inventors have solved the disadvantages of the conventional inert inorganic particles and crosslinked polymer particles, have a flat film surface with few coarse projections, and have wrinkles and disordered end faces during high-speed winding. As a result of diligent research to develop a biaxially oriented polyester film that does not generate, a proper amount of pulverized particles of a specific form obtained by pulverizing crosslinked polymer particles having a specific particle size distribution ratio and an average particle size is contained. By
The inventors have found that the above problems can be solved and arrived at the present invention.

Accordingly, an object of the present invention is to provide a biaxially oriented polyester film which has a flat surface, has few coarse projections, and is excellent in winding property at high speed.

[0010]

Thus, according to the studies by the present inventors, the objects of the present invention are: (1) the particle size distribution ratio (γ) is 1.3 to 3.5, and (2) the average. Crosslinking characterized in that the particle size is 0.1 to 2 μm, (3) the non-circularity is 3.4 or more, and (4) the standard deviation value of the non-circularity is at least 0.16. 0.
Formed from polyester containing from 01 to 5% by weight ,
Coarse particles with a major axis of 2.5 μm or more in the area of 1 mm ²
Has been found to be achieved with a biaxially oriented polyester film having less than 1 . In addition, 1m here
One coarse particle with a major axis of 2.5 μm or more in the m ² region
Less than means that the method for measuring coarse particles described later,
Then, using a scanning electron microscope, 5000 to 10000 times
Particles with a major axis of 2.5 μm or more are observed by observing a 1 mm ² area.
Is counted and evaluated as Δ or × 2.5 μm major axis
Substantially coarse particles containing one or more of the above particles
Means that the cross-linked polymer particles containing the child are not wrapped
It

The biaxially oriented polyester film of the present invention will be described in detail below.

In the present invention, a polyester having an alkylene terephthalate unit or an alkylene naphthalene dicarboxylate unit as a main repeating unit is preferably used as the polyester constituting the film.

Among such polyesters, especially polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate, for example, 80 mol% or more of all dicarboxylic acid components are terephthalic acid or 2,6-naphthalenedicarboxylic acid, Copolymerized polyesters in which 80 mol% or more of all glycol components are ethylene glycol are preferred. At that time, 20 mol% or less of the dicarboxylic acid of the total acid component is terephthalic acid or 2,6-
It can be an aromatic dicarboxylic acid other than naphthalenedicarboxylic acid, an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid. Specific examples of such other dicarboxylic acids include:
Aromatic dicarboxylic acids such as isophthalic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid and sebacic acid; for example cyclohexane-1 Examples thereof include alicyclic dicarboxylic acids such as 4-dicarboxylic acid. Also, 20 mol% or less of the total glycol component may be a glycol other than ethylene glycol. Specific examples thereof include aliphatic glycols such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol; alicyclic glycols such as cyclohexanedimethanol; hydroquinone, resorcin, 2,2- Aromatic diols such as bis (4-hydroxyphenyl) propane; Aliphatic diols containing an aromatic ring such as 1,4-dihydroxymethylbenzene; Polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. You can also

Further, the polyester in the present invention includes aromatic oxyacids such as hydroxybenzoic acid,
Also included are those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as ω-hydroxycaproic acid is copolymerized or bonded at 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component. .

Further, in the polyester of the present invention, the polycarboxylic acid or polyhydroxy compound having 3 or more functional groups, such as trimellitate, is contained in a substantially linear range, for example, in an amount of 2 mol% or less based on the total acid components. A copolymer of acid, pentaerythritol and the like is also included.

The above polyester is known per se and can be produced by a method known per se.

The above polyester preferably has an intrinsic viscosity in the range of about 0.4 to 0.8 obtained by measuring at 35 ° C. as a solution in o-chlorophenol, and 0.5
To 0.7 is more preferable, and 0.55 to
The range of 0.65 is particularly preferable.

The crosslinked polymer particles incorporated in the polyester film of the present invention have a morphology characterized by the following (1) to (4). (1) The particle size distribution ratio (γ) is 1.3 to 3.5,
(2) The average particle size is 0.1 to 2 μm, (3) the non-circularity is 3.4 or more, and (4) the standard deviation value of the non-circularity is at least 0.16.

The crosslinked polymer particles are contained in the polyester film in an amount of 0.01 to 5% by weight, preferably 0.01 to 3% by weight.
%, Particularly preferably 0.01 to 1% by weight. If the content is less than 0.01% by weight, the effect of adding the crosslinked polymer particles is small, while if it is too large, the flatness of the film surface is impaired, and coarse projections due to overlapping of particles increase, which is not preferable. Further, it is desirable that the polyester film does not substantially contain coarse particles having a particle diameter of 2.5 μm or more.

Next, the above (1) to (4) will be described in more detail.

The particle size distribution (γ) of the crosslinked polymer particles is a value defined by the following formula.

[0022]

## EQU1 ## γ = D ₂₅ / D ₇₅ (I) (where γ is the particle size distribution ratio, D ₂₅ is the average particle size (μm) when the cumulative weight of the particles is 25%, and D
₇₅ is the average particle size (μm) when the cumulative weight of particles is 75%
Is. However, the cumulative weight ratio shall be measured from the larger particle size. )

The crosslinked polymer particles blended in the polyester film of the present invention have a particle size distribution ratio (γ) of 1.3 to.
It is in the range of 3.5. The value of the particle size distribution ratio (γ) means that the sizes of the particles are distributed at a certain ratio, and the sizes of the particles are not uniform. The particle size distribution ratio (γ) is preferably in the range of 1.4 to 3, and more preferably in the range of 1.5 to 2.5.
If the particle size distribution ratio (γ) is less than the above range, the height of the protrusions formed on the film surface becomes too uniform,
On the other hand, if the film winding property becomes poor and the particle size distribution ratio (γ) exceeds the above range, the number of coarse projections due to coarse particles increases, which is not preferable.

The average particle size of the crosslinked polymer particles is 0.1.
˜2 μm, preferably 0.2 to 1.7 μm, more preferably 0.3 to 1.5 μm.
If the average particle size is too small, the running property of the film is insufficient, which is not preferable in terms of handling. On the other hand, if it is too large, the flatness of the film surface is impaired, which is not preferable.

The crosslinked polymer particles of the present invention are obtained by pulverizing comparatively uniform particles synthesized as described below, and therefore the particles are non-circular and relatively non-uniform. Is. Thus, in the crosslinked polymer particles of the present invention, the particle size distribution ratio (γ) and the average particle diameter are in the above ranges, and the non-circularity and the standard deviation value of the non-circularity have a constant value. Also has features.

That is, the non-circularity of the crosslinked polymer particles in the polyester film of the present invention (the definition of the non-circularity and the calculation method thereof will be described later) is 3.4.
It is above, It is the range of 3.5-5 preferably. If the non-circularity is less than 3.4, the height and shape of the protrusions formed are too uniform, resulting in poor rollability. On the other hand, if the non-circularity exceeds 5, the film has poor slipperiness. In addition, there is a tendency that the existence probability of high protrusions decreases and the winding property decreases.

The crosslinked polymer particles used in the present invention must have a standard deviation of non-circularity of at least 0.16. The standard deviation of the non-circularity means the variation (spreading) of the non-circularity in a large number of particles, as is clear from the definition described later. Thus, the crosslinked polymer particles used in the present invention are non-circular to some extent, and are not uniform non-circular and have variations, and the degree of variation (standard deviation value) is at least 0.16. , And preferably in the range of 0.18 to 0.50. If the standard deviation of the non-circularity is less than 0.16, the degree of pulverization is not sufficient, the film surface becomes too uniform, and the film winding property deteriorates, or large residual particles remain. This causes inconvenience that causes coarse protrusions.

The studies conducted by the present inventors have revealed that the cross-linked polymer particles having the specific morphology can be obtained by pulverizing the cross-linked polymer particles having a certain morphology. In the present specification, the particles before the pulverization treatment are referred to as "crosslinked polymer particles A" or "particles A" in order to distinguish them from the crosslinked polymer particles contained in the polyester film of the present invention.

The crosslinked polymer particles A before pulverization have an average particle size of 0.5 to 5 μm, preferably 0.6 to 4 μm.
Particularly preferably, the range is 0.7 to 3 μm. Then, it is suitable that the crushing treatment is performed so that the value of the average particle diameter before the crushing treatment is smaller than 0.1. If the average particle size before crushing is smaller than 0.5 μm, it becomes difficult to form protrusions on the film surface that are large enough to impart the running property of the film when the particles after crushing treatment are added to the film. . Therefore, it becomes substantially impossible to reduce the entrainment of air when winding the film. On the other hand, in the case of particles having an average particle size of more than 5 μm, there are large particles that are not completely ground even if the grinding process is sufficiently performed, which causes coarse projections in the film, which is not preferable.

The cross-linked polymer particles A preferably have a non-circularity in the range of π (about 3.14) to 3.3. A non-circularity value of π (pie) means a perfect circle. Therefore, a particle having a non-circularity within the above range means that the cross-sectional shape is a circle or a shape relatively close to a circle. In the present invention, the particles A having such a non-circularity are pulverized and particles having a non-circularity of 3.4 or more are added to the polyester film for use.

Further, it is advantageous that the crosslinked polymer particles A have a particle size distribution ratio (γ) of 1.4 or less, preferably in the range of 1 to 1.3, particularly preferably in the range of 1 to 1.25. Is. It is desirable that the particles A be pulverized so that the particle size distribution ratio is 0.1 or more larger than the particle size distribution ratio. If the particle size distribution ratio (γ) of the particles A before pulverization is larger than 1.4, the proportion of large particles becomes too high, and even if such particles are pulverized, large particles that are not completely pulverized Is present, which causes coarse protrusions in the film, which is not preferable.

As means for pulverizing the particles A, a rod mill,
A method using a wet pulverizer such as a ball mill, a vibrating rod mill, a vibrating ball mill, or a medium agitation type pulverizer is preferably used. Among these, the medium stirring type pulverizer is particularly suitable for fine pulverization, and the particles can be pulverized in a short time. Also, in order to prevent re-aggregation of particles during crushing,
It is preferable to use a dispersant such as sodium polyacrylate or sodium pyrophosphate because the effect of the present invention becomes remarkable.

Explaining the concrete pulverizing method, for example, the raw material particles A are mixed with ethylene glycol to obtain 5-2.
A slurry of 0 wt% was prepared, and this slurry was preliminarily 40 to 8
0% (volume) of media (for example, glass beads or ceramic beads having a diameter of 0.5 to 3 mm) was placed in a vessel and the stirring disk in the vessel was rotated to remove the media and particles in the slurry. Particles in the slurry can be finely pulverized by shear stress generated due to the difference in flow rate. The concentration of the slurry, the material of the medium, the amount and the particle size, and the stirring conditions (rotation speed, processing time, etc.) were determined by experiments depending on the type and size of the polymer of the raw material particles A and the target characteristics of the crushed particles. Can be optimized.

The polymer constituting the crosslinked polymer particles of the present invention is not particularly limited as long as it satisfies the characteristics of the particles, but it is preferable that the particles are soft and the pulverization treatment is easy, Silicon resin particles or crosslinked polystyrene particles are preferred.

Next, the silicone resin particles and the crosslinked polystyrene particles will be described in detail.

The particles of the silicone resin have the following formula (A):

[0037]

## STR1 ## Composition represented by RxSiO _{2 -x / 2} (A) (wherein R is a hydrocarbon group having 1 to 7 carbon atoms, and x is in the range of 1 to 1.2). Have.

R in the above formula (A) is a hydrocarbon group having 1 to 7 carbon atoms, and for example, an alkyl group having 1 to 7 carbon atoms, a phenyl group or a tolyl group is preferable. Carbon number 1
The alkyl group of ~ 7 may be linear or branched, for example, methyl, ethyl, n-propyl, iso.
-Propyl, n-butyl, iso-butyl, tert-
Butyl, n-pentyl, n-heptyl and the like can be mentioned.

Of these, methyl and phenyl are preferable as R, and methyl is particularly preferable.

X in the above formula (A) is in the range of 1 to 1.2. When x is 1 in the above formula (A), the above formula (A) is represented by the following formula (A-1)

[0041]

Embedded image RSiO _1.5 (A-1) (where R is defined as above).

The composition of the above formula (A-1) has the following structural portion in the three-dimensional polymer chain structure of the silicone resin;

[0043]

[Chemical 3] It is derived from.

When x is 1.2 in the above formula (A), the above formula (A) is represented by the following formula (A-2).

[0045]

_{Embedded image} R _1.2 SiO _1.4 (A-2) (where R is the same as above).

The composition of the above formula (A-2) has the above (A-
Structure (1) 0.8 mol and the following formula (A-3)

[0047]

Embedded image R ₂ SiO ... (A-3) (wherein R has the same definition as above) and can be understood to consist of 0.2 mol of the structure.

The above formula (A-3) represents the following structural portion in the three-dimensional polymer chain of the silicone resin;

[0049]

[Chemical 6] Derived from.

As can be understood from the above description, the composition of the above formula (A) consists essentially of, for example, only the structure of the above formula (A-1), or the structure of the above formula (A-1). It can be seen that and the structure of the above formula (A-2) is a structure that coexists in a state of being randomly bonded in an appropriate ratio.

The silicon resin particles preferably have a value of x between 1 and 1.1 in the above formula (A).

The crosslinked polystyrene particles include, for example, styrene-based monomers such as styrene monomer, methylstyrene monomer, α-methylstyrene monomer and dichlorostyrene monomer, as well as conjugated diene monomer of butadiene and unsaturated compounds such as acrylonitrile. Nitrile monomers; monomers such as methacrylic acid esters such as methyl methacrylate; functional monomers such as unsaturated carboxylic acids; monomers having hydroxyls such as hydroxyethyl methacrylate; monomers having epoxide groups such as glycidyl methacrylate and One or more monomers selected from unsaturated sulfonic acids and a polyfunctional vinyl compound such as divinylbenzene as a cross-linking agent for forming polymer particles into a three-dimensional structure.
Ethylene glycol dimethacrylate, trimethylolpropane triacrylate, diallyl phthalate, etc. are dispersed and polymerized in a solvent such as lower alcohol using polymethacrylic acid as a dispersion stabilizer, after which a centrifugal separation method or a semipermeable membrane is used. It is obtained by using a dialysis method to remove polymethacrylic acid adhering to the particle surface. When polymethacrylic acid remains on the particle surface, sufficient particle dispersion cannot be obtained when it is added to polyester, and aggregated particles form coarse protrusions, which is not preferable. The residual amount of polyacrylic acid is preferably 5% by weight or less, more preferably 3% by weight or less, based on the crosslinked polystyrene particles.

The polyester film of the present invention contains the above-mentioned specific crosslinked polymer particles, but may further contain other particles as long as the object of the invention is not impaired. Such other particles may be those which are usually added as a lubricant for polyester film, and may be either inorganic particles or organic particles, and the content thereof is 0.01 to 1% by weight, preferably 0.02 to 0%. A range of 0.5% by weight is suitable. When other particles are used in combination, the ratio of the crosslinked polymer particles of the present invention to the other particles is from 100: 0 to 10: 9 by weight.
Advantageously, the proportion is 0, preferably from 100: 0 to 20:80, particularly preferably from 100: 0 to 30:70.

The average particle size of the other particles is 0.01 to 1.0 μm.
m, preferably 0.05 to 0.8 μm. Specific examples of such other particles include (1) spherical polymer particles (for example, silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, polyamide resin, polyimide resin, polyamideimide resin and crosslinked polyester), (2) ) Metal oxides (eg aluminum oxide, titanium oxide, silicon dioxide, magnesium oxide, zinc oxide and zirconium oxide), (3) metal carbonates (eg magnesium carbonate and calcium carbonate), (4) metal sulfates (eg Calcium sulfate and barium sulfate), (5) carbon (eg carbon black, graphite and diamond), and (6) clay minerals (eg kaolin, clay and bentonite). Among these, silicone resin, crosslinked polystyrene, melamine-formaldehyde resin, polyamideimide resin, aluminum oxide, titanium oxide, silicon dioxide, zirconium oxide, calcium carbonate, barium sulfate, diamond and kaolin are preferable, and particularly, silicon resin, crosslinked polystyrene, Aluminum oxide, titanium oxide, silicon dioxide and calcium carbonate are preferred.

The method of adding the crosslinked polymer particles of the present invention or the other particles thereof to polyester is as follows. These particles are added before or during the polymerization of the polyester, or when pelletized after the completion of the polymerization. A method of sufficiently kneading with the polyester in a machine or in an extruder at the time of melt extrusion into a sheet form can be mentioned.

The biaxially oriented polyester film of the present invention made of a polyester containing crosslinked polymer particles has an intrinsic viscosity of 0.4 to 4 by melting the polyester at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. 0.8 dl /
g of unstretched film, and the unstretched film is uniaxially (longitudinal or transverse) in the range of (Tg-10) to (Tg + 7).
At a temperature of 0) ° C. (Tg: glass transition temperature of polyester), the film is stretched at a ratio of 2.5 to 10 times, preferably 3 to 8 times, and then stretched in the direction perpendicular to the stretching direction (the first stage stretching is the longitudinal direction). In the case of, the second stage drawing is in the lateral direction)
It can be produced by stretching at a temperature of (° C.) to (Tg + 70) ° C. at a draw ratio of 2.5 to 10 times, preferably 3 to 8 times.
In this case, the area stretching ratio is 9 to 50 times, preferably 12 times.
It is desirable to increase the value by 35 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching.

Further, the biaxially oriented polyester film is
It can be heat-set at a temperature of (Tg + 70) ° C. to Tm (° C.). For example, polyethylene terephthalate film is preferably heat set at 190 to 230 ° C. The heat setting time is, for example, 1 to 60 seconds.

The biaxially oriented polyester film of the present invention suitably has a plane orientation coefficient of 0.14 or more, preferably 0.16 or more.

Various physical properties and characteristics in the present invention are measured as follows.

(1) Average Particle Size of Particles CP-50 Model Centrifugal Particle Size Analyzer (Centrifugal Particle S ) manufactured by Shimadzu Corporation
ize Analyzer). The particle diameter corresponding to 50 mass% is read from the integrated curve of the particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is taken as the above average particle diameter (Book Technology "Published by Nikkan Kogyo Shimbun, 1975, pages 242-24
7).

(2) Particle size distribution ratio of particles (γ) Based on the centrifugal sedimentation curve obtained in the measurement of the average particle size of particles, an integrated curve of particles of each particle size and the amount thereof is calculated and drawn. , A particle diameter (D ₂₅ ) corresponding to an integrated weight of particles of 25 mass% and a particle diameter equivalent to 75 mass% of a particle (D ₇₅ )
And divide the former value by the latter value (D ₂₅ /
D ₇₅ ) and the particle size distribution ratio (γ) are calculated.

(3) Non-circularity A sample film piece is fixed on a sample stage for a scanning electron microscope, and a sputtering device (JFC-made by JEOL Ltd.) is used.
1100 type ion etching apparatus) is used to perform ion etching treatment on the film surface under the following conditions. The condition is that the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, the voltage is 0.25 kV, and the current is 1
Ion etching is performed at 2.5 mA for about 10 minutes. Further, the film surface was subjected to gold sputtering with the same apparatus and observed with a scanning electron microscope at 20000 times, and at least 100 particles randomly selected by Luzex 500 manufactured by Nippon Regulator Co., Ltd. The peripheral length (L) and the diameter (R) corresponding to the area circle are calculated, the non-circularity is calculated by the following formula, and the average value is taken as the non-circularity of the particle.

[0063]

## EQU00002 ## Non-circularity (.phi.) = Circumferential length (L) / area circle equivalent diameter (R) (4) of non-circularity of at least 100 particles determined by standard deviation value (1) of non-circularity The standard deviation is calculated by the following formula.

[0064]

[Equation 3]

(5) Coarse particles Pretreatment of the sample similar to the measurement of non-circularity in (3) above was performed, and 5000 to 10000 was observed using a scanning electron microscope.
The area of 1 mm ² is observed twice, and particles having a major axis of 2.5 μm or more are counted and judged according to the following criteria.

<Judgment> ◯: No particles with a major axis of 2.5 μm or more Δ: 1 to 10 particles having a major axis of 2.5 μm or more X: 11 or more particles having a major axis of 2.5 μm or more

(6) Plane Orientation Coefficient The sodium D line (589 nm) is used as a light source, methylene iodide is used as a mount solution, the refractive index is measured at 25 ° C. and 65% RH, and the plane orientation coefficient is calculated by the following formula. .

[0068]

[Equation 4]

(7) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra). In the present invention, the stylus surface roughness meter of Kosaka Laboratory Ltd. is used in the present invention. (SURFCORDER SE-30C) is used for measurement. The measurement conditions are as follows. (A) Stylus tip radius: 2 μm (b) Measuring pressure: 30 mg (c) Cut-off: 0.08 mm (d) Measuring length: 1.0 mm (e) Data compilation method: Repeated 5 times for the same sample , The one with the largest value is removed, and the average value of the remaining four data is rounded off to the fifth decimal place and displayed up to the fourth decimal place.

(8) Roll-up non-defective rate The film is 500 mm in width and 4000 m in roll shape,
The number of non-defective products obtained by winding 0 rolls is shown in percentage.
At this time, the non-defective product is the following. The film roll has no wrinkles or minute protrusions. The end faces of the film rolls are evenly arranged.

(9) Number of Coarse Protrusions Two monolithic films that were in close contact were irradiated with Na monochromatic light, and 100 cm ² was observed using a stereoscopic microscope. The number of protrusions of two rings (height 0.58 μm) or more generated corresponding to the protrusion height of the protrusions is counted and set as the coarse protrusion number.

(10) Intrinsic viscosity [η] A value measured at 35 ° C. using o-chlorophenol as a solvent, the unit is 100 cc / g.

(11) Running Friction Coefficient It is measured as follows using the device shown in FIG.
In FIG. 1, 1 is an unwind reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4
Is a tension detector (inlet), 7 is stainless steel SUS
304 fixed rod (outer diameter 5 mmφ, surface roughness Ra = 20
nm), 10 is a tension detector (exit), 12 is a guide roller, and 13 is a take-up reel.

In the environment of temperature 20 ° C. and humidity 60%, the non-magnetic surface of the magnetic tape is fixed to the fixing rod 7 by θ = (152/180)
It is brought into contact with π radians (152 °) and moved (rubbed) at a speed of 200 cm per minute. The entrance tension T ₁ is 35
outlet tension when adjusting the tension controller 2 such that g (T _2: g) a is film detected by the outlet tension detector into After traveling 90m, and calculates the running friction coefficient μk by the following equation.

[0075]

Equation 5] μk = (2.303 / θ) log (T 2 / T 1) = 0.868log (T 2/35)

[0076]

EXAMPLES The present invention will be further described below based on examples. In addition, "part" in an example means a weight part.

Example 1 As the crosslinked polymer particles A, silicon resin fine particles having an average particle size of 1.4 μm, a particle size distribution ratio (γ) of 1.1 and a non-circularity of 3.2 were used.
5 parts of sodium pyrophosphate and 895 parts of ethylene glycol were mixed with 00 parts, and mixed and dispersed for 5 minutes with a tabletop mixer (National MX-M3 manufactured by Matsushita Electric Industrial Co., Ltd.) to form a slurry. Next, the obtained slurry was subjected to a wet pulverization treatment using a sand glider (SGL-1 / 4G manufactured by Igarashi Kikai). The processing conditions are as follows.

Media: Glass beads having a diameter of 0.8 mm, media amount: 500 ml, slurry volume: 500 m
1, rotation speed: 1800 rpm, processing time: 2 hours. The average particle size after pulverization was 0.8 μm, the particle size distribution ratio (γ) was 1.5, the non-circularity was 3.5, and the standard deviation value of the non-circularity was 0.19.

Then, manganese acetate was added as an ester exchange catalyst to 100 parts of dimethyl terephthalate and 60 parts of ethylene glycol to carry out an ester exchange reaction, and 5 parts of the above-mentioned slurry of finely divided fine particles was added immediately before the completion of the reaction.

Further, antimony trioxide was added as a polymerization catalyst and phosphorous acid was added as a stabilizer, and the mixture was polymerized by a conventional method to give polyethylene terephthalate (raw material A) having an intrinsic viscosity of 0.62.
I got). The content of fine particles in this polymer was 0.
It was 5% by weight.

Polyethylene terephthalate containing substantially no fine particles was polymerized by a conventional method to obtain pellets.

Raw material A was mixed with pellets of polyethylene terephthalate containing substantially no fine particles, and the raw material A was diluted so that the particle concentration shown in Table 1 was obtained.
After drying at 0 ° C. for 3 hours, it is fed to an extruder hopper and melted at a melting temperature of 280 to 300 ° C.
Extruded on a rotary cooling drum with surface finish of about 0.3s and surface temperature of 20 ℃ through a slit die of 200μm
Of unstretched film was obtained.

The unstretched film thus obtained is preheated at 75 ° C., and further 15 m between low speed and high speed rolls.
m from above, heated by one IR heater having a surface temperature of 900 ° C., stretched to 3.6 times, rapidly cooled, then fed to a stenter, and stretched 3.7 times in the transverse direction at 105 ° C. .
The obtained biaxially oriented film was heat set at a temperature of 205 ° C. for 5 seconds to obtain a biaxially oriented polyethylene terephthalate film having a thickness of 15 μm.

Table 1 shows the characteristics of the obtained film.

The surface roughness Ra of this film is 0.022.
It is as flat as μm and the rate of non-defective products is as high as 98%.
The number of coarse projections was also very small, one.

Thus, a specific average particle size in the film,
By containing a specific amount of fine particles having a particle size distribution ratio, a range of non-circularity and a standard deviation value of non-circularity, a film which is flat and has a good winding property and a small number of coarse projections can be obtained.

[Examples 2 to 3] Particle A used in Example 1
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the particles shown in Table 1 were used instead of the above. This characteristic is shown in Table 1.

These films showed flatness and good winding property, and the number of coarse projections was also small.

[Examples 4 to 7] Particle A used in Example 1
In the same manner as in Example 1 except that the particles shown in Table 1 were used instead of the above, and the particles shown in Table 1 were used as the other particles to obtain a biaxially oriented polyethylene terephthalate film. This characteristic is shown in Table 1.

These films also satisfy the requirements of flatness, a high yield rate of good products, and a small number of coarse projections. It can be seen that the effect of the present invention is not lost even if the fine particles obtained by crushing the particles A and other particles are contained.

[Examples 8 to 9] The same mole number of dimethyl-2,6-naphthalenedicarboxylate was used in place of the dimethyl terephthalate of Example 1, and the particles A and other particles were as shown in Table 1. Example 1 except that
The same procedure as described above was carried out to obtain pellets of biaxially oriented polyethylene-2,6-naphthalenedicarboxylate.

The polyethylene-2,6-naphthalenedicarboxylate pellets were dried at 170 ° C. for 5 hours, melt-extruded at 300 ° C., rapidly cooled and solidified on a casting drum kept at 60 ° C. to obtain 20.
An unstretched film of 0 μm was obtained.

The unstretched film thus obtained is preheated at 120 ° C., and the rolls are rolled at low speed and high speed for 15 minutes.
mm from the upper side, heated by one IR heater having a surface temperature of 950 ° C., stretched 3.6 times, rapidly cooled, and then supplied to a stenter and stretched laterally 3.7 times at 125 ° C. . The obtained biaxially oriented film was heated at a temperature of 215 ° C. for 10
Heat-fixed for 15 seconds, biaxially oriented polyethylene with a thickness of 15 μm
A 2,6-naphthalenedicarboxylate film was obtained.

The characteristics of this film are shown in Table 1. Even when the type of polyester was changed, the film according to the present invention was a film having a flat surface, excellent winding property, and a small number of coarse projections.

[0095]

[Table 1]

Comparative Example 1 As the crosslinked polymer particles A, silicon resin fine particles having an average particle diameter of 0.8 μm, a particle size distribution ratio (γ) of 1.1 and a non-circularity of 3.2 were used and the particles were crushed. A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that it was not added.

Table 2 shows the characteristics of this film. The added particles have the same average particle size as the fine particles obtained by crushing the particle A in Example 1, but since the particles having a sharp particle size distribution were added without crushing, the surface protrusions were uniform. Was too high and the winding property was poor.

Comparative Example 2 Particle A has an average particle size of 0.8.
A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that crosslinked polystyrene particles having a particle size distribution ratio of 1.2 and a non-circularity of 3.2 were used and the particles were added without crushing. It was

Table 2 shows the characteristics of this film. The characteristics of this film were similar to those of Comparative Example 1, and the winding property was poor.

[Comparative Example 3] Instead of the particles A, an average particle size of 0.
A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that calcium carbonate having a particle size distribution ratio (γ) of 2.8 and a degree of non-circularity of 3.7 was used and added without crushing.

The properties of this film are shown in Table 2. The obtained film had a good winding property, but had many coarse particles and many coarse protrusions caused by it.

[Comparative Examples 4 to 8] A biaxially oriented polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the particles shown in Table 2 were used as the particles A or other particles.

Table 2 shows the characteristics of this film.

In Comparative Example 4, since the average particle size of the particles A before crushing was too large, a large number of uncrushed large particles remained even after crushing, and the number of coarse projections was extremely large.

In Comparative Example 5, since the average particle size of the particles A before and after crushing was too small, the projection height on the film surface was not sufficiently obtained, and the winding property was poor.

In Comparative Example 6, since the degree of pulverization was not sufficient, the height of protrusions on the film surface was uniform, and the winding property was poor.

In Comparative Example 7, since the addition amount of the particles A after pulverization was too small, the running property was poor, and a good product could not be wound.

In Comparative Example 8, since the calcium carbonate particles originally containing a large amount of coarse particles were crushed and added, the number of coarse protrusions became extremely large.

[0109]

[Table 2]

[0110]

According to the present invention, a cross-linked polymer particle having a specific particle size distribution ratio, average particle diameter, non-circularity and standard deviation value of non-circularity is contained in the film, whereby the surface is flat and coarse. It is possible to economically provide a biaxially oriented polyester film that has few protrusions and is excellent in winding property at high speed.

This film has excellent characteristics as a base film for a magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for measuring a running friction coefficient of a film.

[Explanation of symbols]

1 Unwind reel 4 Tension detector (entrance) 7 fixed rod 10 Tension detector (exit) 13 Take-up reel

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C08L 25:04) B29K 67:00 B29K 67:00 C08L 67:02 C08L 67:02 (56) Reference JP-A-55-155029 (JP, A) JP 55-155030 (JP, A) JP 2-11640 (JP, A) JP 4-201233 (JP, A) JP 2-155948 (JP, A) Kaihei 2-194049 (JP, A) JP-A 1-123836 (JP, A) JP-A 4-339833 (JP, A) JP-A 63-60732 (JP, A) JP-A 4-198328 ( JP, A) JP 61-246919 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 5/18

Claims (14)

(57) [Claims] 1. A particle size distribution ratio (γ) of 1.3 to 3.
5, (2) the average particle size is 0.1 to 2 μm, (3) the non-circularity is 3.4 or more, and (4) the standard deviation value of the non-circularity is at least 0.16. There is 0.01 crosslinked polymer particles characterized by
Formed from polyester containing ~ 5% by weight , and 1
Coarse particles with a major axis of 2.5 μm or more in the area of mm ² are 1
A biaxially oriented polyester film having less than 40 pieces . 2. The particle size distribution ratio (γ) of the crosslinked polymer particles.
Is 1.4 to 3, and the polyester film according to claim 1. 3. The crosslinked polymer particles have an average particle size of 0.2.
The polyester film according to claim 1, which is about 1.7. 4. The non-circularity of the crosslinked polymer particles is 3.5.
The polyester film according to claim 1, which is -5. 5. The polyester film according to claim 1, wherein the crosslinked polymer particles have a standard deviation of non-circularity of 0.18 to 0.3. 6. The polyester film according to claim 1, wherein the crosslinked polymer particles are silicone resin particles. 7. The polyester film according to claim 1, wherein the crosslinked polymer particles are crosslinked polystyrene particles. 8. The polyester film according to claim 1, wherein the crosslinked polymer particles are particles obtained by pulverization. 9. The crosslinked polymer particles have an average particle size of 0.5.
The polyester film according to claim 8, which is a particle obtained by pulverizing particles having a particle size of -5 μm so that the average particle diameter becomes 0.1 or more. 10. The crosslinked polymer particles have a non-circularity of π to
The polyester film according to claim 8, which is a particle obtained by pulverizing particles having a particle size of 3.3. 11. The polyester film according to claim 1, wherein the polyester film is formed of polyester further containing 0.01 to 1% by weight of inorganic particles or organic particles having an average particle diameter of 0.01 to 1.0 μm. 12. The polyester film according to claim 1, which has a plane orientation coefficient of 0.14 or more. 13. The polyester film according to claim 1, wherein the polyester is a polyester having ethylene terephthalate units as main repeating units. 14. The polyester is ethylene-2,6.
-The polyester film according to claim 1, which is a polyester containing naphthalene dicarboxylate as a main repeating unit.