JPH08337664A - Polyester film and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] (Correction) [Structure] A polyester film containing polyester A as a main component, wherein the projections on at least one surface of the polyester film are projections mainly caused by crystals of polyester A The ratio of the parameter Rz / Ra is 4 or more and less than 12, the variation of Ra (= 100 × (maximum value of Ra−minimum value of Ra) / average value (unit%)) is 30% or less, and A polyester film having a particle density of 10,000 particles / mm ² or less in a region having a depth 5 times the average protrusion height in the vicinity of the surface of the cross-sectional structure in the film thickness direction. [Effect] Since the formation of protrusions that suppress void formation and are not easily broken, the abrasion resistance of the film surface can be greatly improved, and because the protrusions are fine and the protrusion height is uniform, the protrusion height is uniform. In the past, it was possible to greatly improve the film roll appearance and output characteristics, which had been difficult to achieve at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film having fine projections uniformly formed on its surface, and a method for producing the same.

[0002]

2. Description of the Related Art Polyester films are excellent in mechanical properties, electrical properties, thermal properties, optical properties, and chemical properties, so that they are used for magnetic recording media, electrical insulation, capacitors, packaging, thermal transfer. Widely used for various purposes such as photography.

In these applications, not only the flatness of the surface but also the slipperiness is required due to the workability during film formation and processing and the handleability of the product. Heretofore, it has been known that uniformly forming fine projections on the film surface is effective as a method for improving the slipperiness.

A polyester film containing substantially spherical silica particles derived from colloidal silica in order to form fine projections on the film surface is known (for example, JP-A-59-171623). . Also,
There is also known a technique of forming protrusions on the surface by crystallization without adding particles (for example, JP-A-58-55222).

[0005]

However, the polyester film containing particles (for example, inert particles) and having projections formed on the surface thereof by the conventional method has the following problems.

Since particles such as inert particles, which are different from polyester, are present immediately below the projections, voids are often generated. Therefore, when the film is run in contact with a guide roll or the like, particles are generated. It is easily scraped off and becomes powdery (hereinafter referred to as scraped powder) and adheres to the surface of the contact partner, causing a problem of contamination. Also for condenser applications,
This may cause a decrease in dielectric breakdown voltage.

Further, when used as a base film for a magnetic recording medium, recently, an extremely flat and slippery surface is often required because a very high level of output characteristics is required. It is necessary to make the size of the particles ultra-fine and make the particle content high. However, the finer the particles, the easier it becomes to form coarse protrusions due to the aggregation of the particles during polyester polymerization or during melt extrusion, which may result in excessively large surface roughness or due to coarse protrusions on the surface. The winding shape such as the protrusions becomes poor. On the contrary, if the particle content is reduced and the surface is simply flattened, the slipperiness of the roll in contact with the film-forming step or the processing step is poor and the surface is easily scratched, and the roll is heated. In this case, there is a problem in that the film and the roll adhere to each other and the roll becomes dirty, or spots of sticky marks are generated on the film. In addition, the slipperiness between the films is poor, and when the films are wound into a roll, wrinkles occur, resulting in a defective roll appearance, leading to problems in product performance.

On the other hand, as described above, there is known a technique of forming protrusions on the film surface by utilizing the crystallization of the polymer regardless of the particles, but in the conventional method, the crystallinity of the polymer is Since it is too large, the surface roughness becomes large.
Therefore, it could not be applied to applications requiring flatness of the surface such as base films for magnetic media. Further, problems such as stretch unevenness and stretch breakage tended to occur when the film was stretched. Further, in order to crystallize the film, the film is softened and loosened at the stage of heating the unstretched film, and problems such as stretching unevenness and winding around a stretching roll were likely to occur. For this reason, there is a problem that the formation of surface protrusions in the longitudinal direction is not uniform.

It is an object of the present invention to provide a polyester film having desired fine projections uniformly formed on the surface thereof by utilizing the optimum crystallization of polyester essentially without depending on the contained particles, and a method for producing the same. Yes, the surface protrusions are formed uniformly, the amount of shavings is small and good (hereinafter referred to as the resistance to shavings is good), and when the film is wound into a roll, there are no pimple-like protrusions or wrinkles. It is to provide a polyester film (hereinafter referred to as a good winding form) and having a high signal-to-noise ratio S / N when formed into a magnetic tape (hereinafter referred to as a good output characteristic).

[0010]

The polyester film of the present invention for this purpose is a polyester film containing polyester A as a main component, and projections on at least one surface of the polyester film are mainly caused by crystals of polyester A. And the surface roughness parameter Rz / Ra ratio is 4 or more and less than 12, and the variation (= 1) of the Ra.
00 x (maximum value of Ra-minimum value of Ra) / average value (unit%)) is 30% or less, and is 5 times the average protrusion height in the vicinity of the surface of the cross-sectional structure in the film thickness direction. It is characterized in that the particle density in the depth region is 10,000 particles / mm ² or less. By setting the ratio of the surface roughness parameter Rz / Ra to 4 or more and less than 12, preferably 5 or more and less than 10, the film surface protrusion height is uniformly formed, and the variation of the surface roughness parameter Ra (= 100 × ( Ra
Maximum value-minimum value of Ra) / average value (unit%)) is 30
% Or less, and preferably 20% or less, the number of protrusions on the film surface is uniformly formed, and the surface has excellent abrasion resistance, winding shape, and output characteristics. Further, particles may be supplementarily added in order to reduce friction and impart slipperiness, but in this case, in the vicinity of the surface of the cross-sectional structure in the film thickness direction, the average protrusion height is 5 times the average projection height. The particle density in the depth region is 10,000 particles / mm ² or less, preferably 8000 particles / mm ² or less, and more preferably 60.
It is necessary that the number is 00 / mm ² or less. 10,000 /
If it exceeds mm ² , the proportion of protrusions formed by the contained particles increases, and the proportion of protrusions that are easily broken due to void formation increases, so that favorable abrasion resistance and output characteristics cannot be obtained. That is, in the film of the present invention, generation of shavings itself can be suppressed by forming high-strength fine protrusions.

Further, when the ratio of the surface roughness parameter Rt / Ra is 15 or less, abrasion resistance and output characteristics are further improved, which is desirable.

In the film of the present invention, the number of protrusions on at least one surface is 5000 / mm.
It is desirable to be ² or more. By forming a large number of protrusions in this way, it is possible to reduce the friction between the film and the contact partner, which improves abrasion resistance and the rolling appearance, which is desirable.

The surface roughness parameter Ra of the surface is not particularly limited, but is 2 to 100 nm, preferably 5 to 60 n.
In the case of m, abrasion resistance, output characteristics, and roll winding are further improved, which is desirable.

The surface roughness parameter Rz of the surface is from 10 to 10.
When the thickness is 1000 nm, preferably 30 to 700 nm, and more preferably 40 to 400 nm, abrasion resistance, output characteristics, and roll winding are further improved, which is desirable.

The surface roughness parameter Sm of the surface is not particularly limited, but is 15 μm or less, more preferably 10 μm.
When it is m or less, abrasion resistance, output characteristics, and roll winding are further improved, which is desirable. Further, when the value of Sm on one side is 20% or more larger than that on the other side in the longitudinal direction and width direction of the film, abrasion resistance and roll winding form are further improved, which is desirable.

Further, in the polyester film of the present invention, it is necessary that the protrusions on the surface are protrusions mainly caused by crystals of polyester A. That is, the protrusions on the surface are formed by utilizing the crystallization of polyester A itself. Therefore, the problem of void formation when particles are added is substantially eliminated, and high-strength protrusions that are not easily broken are formed at high density.

The number of protrusions (n) due to the crystals of polyester A is the number of protrusions on the surface of the polyester film of the present invention.
And the ratio (n / N) of the total number of protrusions (N) on the surface is 0.7 or more, preferably 0.8 or more, and more preferably 0.9 or more, abrasion resistance, output characteristics, It is desirable because it makes the roll appearance better.

Whether or not the surface protrusions are made of fine crystals of polyester A is the reason why the protrusions are formed by etching below the target protrusion in the thickness direction of the film with an appropriate solvent. When the substance remains as an insoluble substance, it is treated as particles added from the outside or particles precipitated internally. When there is substantially nothing that remains as an insoluble matter, it can be inferred that the substance that forms the protrusion is a fine crystal. As the above-mentioned solvent, for example, a mixed solvent of phenol / carbon tetrachloride (weight ratio: 6/4) is preferably used. However, the method for determining whether or not the surface protrusions are made of fine crystals of polyester A is not limited to the above method, and an appropriate method can be selected.

The formation of surface protrusions utilizing the crystallization of polyester A as described above is carried out as follows.

In producing a biaxially oriented film containing polyester A as a main component, at least one surface of the unstretched film is heat treated, and then the unstretched film is biaxially stretched to form a desired surface protrusion. It

By first subjecting the unstretched film to a heat treatment, crystallization of the surface of the unstretched film proceeds,
A large number of fine crystals are formed. This unstretched film is biaxially stretched, the film is biaxially oriented and the target strength of the film itself is achieved, and due to the difference in hardness between the crystal and the other part, the uniform crystal resulting from the fine crystals is obtained. Fine surface protrusions are formed.

In the present invention, the crystallization parameter ΔTcg of polyester A is 10 ° C. or more and less than 70 ° C., preferably 15 ° C. or more and less than 65 ° C., more preferably 20 ° C.
It is preferably above 60 ° C.

In the present invention, the kind of the polyester A is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-
It is particularly desirable when at least one structural unit selected from 4,4′-dicarboxylate and ethylene naphthalate units is the main constituent. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly desirable. In order to form a large number of protrusions in a short heat treatment time, polyethylene terephthalate having a high crystallization rate is particularly desirable due to the effect of a crystal nucleating agent. In order to enhance the crystal nucleating agent effect, it is effective to allow the presence of lithium acetate, magnesium acetate, potassium acetate, phosphorous acid, phosphonic acid, phosphinic acid or their derivatives, antimony oxide and germanium oxide during transesterification and polymerization. is there. Particularly desirable magnesium acetate and phosphonic acid (or a derivative thereof) and antimony oxide, and the phosphonic acid derivative includes dimethyl phenylphosphonate. The addition amount of magnesium acetate is 2 to 30 with respect to the weight of the film formed using polyester A.
0 ppm, dimethyl phenylphosphonate 5 to 700 pp
It is good to add m. However, the method for producing the polyester A is not limited to the above. Two or more types of polyesters may be mixed or a copolymerized polymer may be used as long as the object of the present invention is not impaired. Also,
It is desirable that the polyester A contains substantially no particles.

The polyester film of the present invention may be used as a biaxially oriented film single layer containing polyester A as a main component, or as a laminated film laminated on at least one side of a film containing polyester B as a main component. You may be asked.

The type of polyester B is not particularly limited. Polyester B preferably contains no particles, but may contain them.

Next, the method for producing the polyester film of the present invention will be described more specifically.

In the present invention, at least one surface of the unstretched film is heat treated and then biaxially stretched. Here, the unstretched film refers to a film extruded from a die and cooled and solidified to a film slightly finely stretched (up to about 2 times) in a uniaxial direction. The purpose of this heat treatment is to enhance the crystallinity of the film surface before stretching to a preferable crystallinity.

To obtain a desired film surface of the unstretched film when the molten polyester is extruded from the die by a draft ratio (= die lip polymer flow rate / film on casting drum (polymer) flow rate) of 5 to 30. Is more desirable.

In the widthwise thickness of the unstretched film, the film thickness (maximum thickness) at the end is generally t.
₁ is made larger than the thickness t ₂ of the central portion, but this ratio t ₁
It is more desirable that the desired film can be obtained when / t ₂ is 1.5 to 7.0.

In the present invention, the surface roughness of the heating roll is not particularly limited, but the surface roughness parameter Ra is 0.1 to 3.0 μm, preferably 0.2 to 2.0 μm,
More preferably, the temperature of at least one side of the unstretched film that has been cooled and solidified is heated to 120 ° C. or higher by using a heating roll having a film-roll adhesion start temperature of 130 ° C. or higher, which is 0.4 to 1.5 μm. It is desirable that the desired surface protrusions are formed by the treatment and subsequent biaxial stretching at a temperature not lower than the glass transition temperature Tg of the polyester and not higher than the cold crystallization temperature Tcc (Tcc + 20 ° C.). When the surface roughness parameter Ra of the roll and the sticking start temperature of the roll deviate from the above ranges, the crystallinity of the film cannot be sufficiently obtained, and it becomes difficult to obtain a desired surface, or conversely, the roll and the film stick, It becomes a sticking mark and causes variation in the film surface roughness Ra.

The sticking start temperature of the film and roll is
It is calculated by the following method. First, an unstretched film having a width of 10 mm and a thickness of 150 μm is brought into close contact with a heated roll, and the stress at the time of peeling at an angle of 90 ° is measured with a strain gauge (stiffness sensor) at a speed of 3 cm / min. At the same time, the film surface temperature is measured. The roll temperature is raised and the peel stress for each temperature is measured. This peeling stress can be expressed by obtaining the maximum film temperature when the peeling stress is 2 g or less and setting this temperature as the sticking start temperature of the film and the roll.
It is preferably 0 ° C. or higher and does not stick when the film is heat-treated at 120 ° C. or higher in order to obtain a desired film surface.

The surface material of the heating roll is not particularly limited, but it is preferable to use a roll made of any one of ceramic, silicone and Teflon roll. Particularly, the material is silicone and the adhesion starting temperature on the surface layer is 130 ° C. or more. In the case of a two-layer structure using silicone having excellent adhesiveness to the roll iron core as the lower layer, it is desirable to obtain a desired film.

Although the number of the heating rolls may be one, it is more effective to use a plurality of heating rolls to obtain a desired surface protrusion. In this case, since the film-forming process becomes long, the upper limit of the heating roll before stretching is 20 rolls, but it is not limited to this.

When a plurality of heating rolls are used, the free path between the heating rolls and /
Alternatively, the free path between the heating roll and the roll located next (roll for lowering to the stretching temperature), and when the number of heating rolls is singular, the heating roll and the roll located next (up to the stretching temperature) The free path between the rolls for lowering is 1500 times or less, preferably 1000 times or less, more preferably 80 times the thickness of the unstretched film.
When it is 0 times or less, it is desirable because the unstretched film can be heat-treated without slack between the rolls to obtain a desired film surface. As used herein, the free path is defined as the free path when the unstretched film is conveyed between rolls and the distance from the point where the unstretched film separates from the preceding roll to the contact with the next roll.

In the present invention, when heat-treating an unstretched film that has been cooled and solidified, the surface (or surface layer) temperature of at least one side thereof is 120 ° C. or higher and 0.5-10.
It is preferable that the desired surface protrusions are formed by heat treatment so that the surface is kept for 0 second, preferably 0.5 to 50 seconds. More preferably, at 130 ° C. or higher, 0.5 to
50 seconds, more preferably 0.5 to 2 at 140 ° C. or higher
The heat treatment is such that it is held for 0 seconds. The upper limit of the temperature is not particularly limited, but the high temperature crystallization temperature Tm of polyester A is
It is desirable in terms of film forming conditions that the temperature is 40 ° C. higher than (c) (Tmc + 40 ° C.) or lower.

The heat treatment required for crystallization in the film-forming process is the method of reheating the film once cooled and solidified as described above to crystallize it, or by slightly stretching in the uniaxial direction,
There is a method in which birefringence is set to 0.2 × 10 ⁻³ to 50 × 10 ^−3, and then heat treatment is performed so that the surface (or surface layer) temperature of at least one side of the slightly stretched film is 120 ° C. or higher. The above method can be carried out in a film forming process to obtain a target surface morphology.

In the present invention, after heat-treating at least one surface of the film obtained by the above method, the unstretched film is biaxially stretched to be biaxially oriented. As a stretching method, a known method such as a sequential biaxial stretching method or a simultaneous biaxial stretching method, or a biaxially stretched film may be further restretched in at least one direction.

The use of the polyester film in the present invention is not particularly limited, but it is particularly useful as a support for magnetic recording in which the surface roughness and the uniformity of the height of protrusions are problems in terms of electromagnetic conversion characteristics. Also, since the film has very few voids, it is suitable for capacitors, photography, and electrical insulation. Further, since the surface is uniform and dense, it is suitable for a drawable film, a light diffusion film used for liquid crystal screens, packaging, etc.

[0039]

[Measurement Method of Physical Properties and Evaluation Method of Effect] The measurement method of the characteristic value and the evaluation method of the effect of the present invention are as follows.

(1) Number of projections on film surface, projection height 2 Scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and cross-section measuring device [PMS-1, manufactured by Erionix Co., Ltd.] The image processing apparatus [IBAS2000, Carl Zeiss Co., Ltd.] was used to measure the height of protrusions when scanning was performed with the height of the flat surface of the film as 0.
Manufactured] to reconstruct the film surface protrusion image on the image processing device. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is set as the projection height of the projection, and this is calculated for each projection. Repeat this measurement 500 times at different locations for 20n
The number of protrusions and the average height of protrusions were determined by using protrusions having a size of m or more. The magnification of the scanning electron microscope is 1000 to
Select between 8000 times. Depending on the case, a high-precision optical interference type three-dimensional surface analysis device (TOP manufactured by WYKO)
O-3D, objective lens: 40 to 200 times, use of high precision camera is effective), and height information and number information such as peak count may be read as the SEM value. Regarding the number of protrusions, in order to capture the protrusions three-dimensionally, the film is tilted by 82.5 ° and the magnification is from 3000 to
It can also be measured by a method of taking a photograph with an electron microscope (SEM) at 10000 times, or a method of using an atomic force microscope. The number of protrusions is 1 mm from the average value of 100 visual fields.
^It may be converted to around ² .

(2) Number of particles contained in the vicinity of the surface In the present invention, the vicinity of the surface means a part up to a depth of 5 times the average protrusion height obtained by the method (1). The term "particles" as used herein means that when the cross section of a film is observed with a TEM, the particles observed in the thickness direction are those having an average protrusion height greater than or equal to the average protrusion height obtained by the above method. But particles smaller than that are not considered as particles.

The cross section of the film was observed as an ultrathin section by a transmission electron microscope (TEM), and the number of particles present in a portion from the surface to a depth of 5 times the average protrusion height was magnified 30 times.
Observing 500 fields of view from 00 to 10,000 times, 1m
Converted per m ² .

(3) Crystallization parameter ΔTcg This was measured using a Perkin-Elmer DSC (differential scanning calorimeter) type II. The measurement conditions of DSC are as follows. That is, 10 mg of the sample was set in the DSC device, and 3
After melting for 5 minutes at a temperature of 00 ° C., it is quenched in liquid nitrogen. The temperature of this quenched sample is raised at 10 ° C./min, and the glass transition point Tg is detected. The temperature was further raised, and the crystallization exothermic peak temperature from the glass state was set as the cold crystallization temperature Tcc. The difference between Tcc and Tg (Tcc-Tg) is defined as the crystallization parameter ΔTcg.

(4) Birefringence The refractive index nMD in the longitudinal direction and the refractive index nTD in the width direction of the uniaxially oriented film were measured using an Abbe refractometer, and the difference between these two values, that is, | nMD-nTD | was defined. . The light source was a sodium D line (wavelength 589 nm), and the mount station was methylene iodide at 25 ° C. and 65% RH.

(5) Film temperature A radiation thermometer, a contact surface thermometer, or a thermolabel was attached to the film for measurement.

(6) Surface roughness parameters, Ra, Rz,
Rt / Ra, Sm High-precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory Ltd.
It measured using. The conditions are as follows.

-Stylus tip radius: 0.5 μm-Stylus load: 5 mg-Measurement length: 1 mm-Cutoff: 0.08 mm-Stylus speed: 4 μm / sec Ra, Rt, Rz , Sm is defined, for example, by Jiro Nara "Measurement / Evaluation Method of Surface Roughness" (General Technology Center,
1983).

The variation of Ra is 4 in the longitudinal direction of the film.
Sampling is performed on 25 squares in 25 cm and a total length of 100 cm, and an arbitrary point is measured 6 times for each sheet,
The measurement was performed 150 times in total. Variation = 100 x (measured value 1
Maximum Ra value in 50-Minimum Ra value in 150 measured values
The value was divided by the average Ra value of 150 measured values (unit:%).

(7) Resistance to chipping powder 1 in a guide pin (guide material: SUS, surface roughness: 0.2S) having an outer diameter of 6 mmφ in an atmosphere of 20 ° C. and 60% relative humidity.
A tape film with a width of 1/2 inch has an angle θ = π / 3 (r
ad), the entering tension T1 = 50 g, and after repeatedly running 50 times at a speed of 100 m / min, the shavings adhering to the guide pins were visually observed. Shaving resistance to shavings that have no shavings attached: Excellent, Shaving resistance to shavings that are minimal, shaving resistance to powder: Good, Shaving resistance to shavings that adhere to a large amount It was judged to be defective. It is desirable that the abrasion resistant powder is excellent, but if it is good, it can be practically used without problems.

(8) Winding shape A film roll wound up to a length of 2000 m at a winding speed of 250 m / min is visually observed to inspect for the presence of acne-like protrusions due to coarse protrusions. After leaving the film roll free from acne-like protrusions for a further week, the degree of vertical wrinkles is checked with the naked eye (when the film is unwound, visible marks of wrinkles are inferior to vertical wrinkles). The above inspection was performed on 100 film rolls, and the number of film rolls with acne-like protrusions and film rolls with vertical wrinkles was less than 3 rolls: Excellent, 3 rolls or more and less than 5 rolls: Good: A case of 5 or more windings was determined as bad. It is desirable that the winding shape is excellent, but if it is good, it can be used practically without problems.

(9) Output characteristics The surface roughness of the front and back surfaces of the film of the present invention was measured by the method (6) above, and the following composition was mixed and dispersed by a ball mill for 48 hours on the surface side having a small surface roughness Ra. The kneaded product obtained by adding 6 parts of the curing agent is filtered with a filter to apply a magnetic coating material with a gravure roll, magnetically oriented, and dried at 110 ° C. Furthermore, using a small test calender device (still roll / nylon roll, 5 steps), temperature 70 ° C, linear pressure 2
After calendaring at 00 kg / cm, 70 ℃, 48
Cure for hours. Slit the above tape roll,
I made a pancake. This pancake was incorporated into a VTR cassette to obtain a VTR cassette tape.

(Composition of magnetic coating) Fe 100 parts Average particle size Length: 0.3 μm Needle ratio: 10/1 Coercive force: 2000 Oe Polyurethane resin 15 parts Vinyl chloride / vinyl acetate copolymer 5 parts・ Nitrocellulose resin 5 parts ・ Aluminum oxide powder (average particle size: 0.3 μm) 3 parts ・ Carbon black 1 part ・ Lecithin 2 parts ・ Methyl ethyl ketone 100 parts ・ Methyl isobutyl ketone 100 parts ・ Toluene 100 parts ・ Stearic acid 2 parts A 100% chroma signal was recorded on the tape thus obtained by a Shiba Soku TV test waveform generator using a household Hi8 VTR, and the chroma S / N was measured from the reproduced signal by a color video noise measuring instrument. This chroma S / N is 0.2
Compared with a tape made by using a single-layer polyester film containing 0.4% by weight of spherical silica having a diameter of μm as a base material, when the output is 2 dB or more, the output characteristic is good, and when it is less than 2 dB, the output characteristic is poor. It was determined.

[0053]

EXAMPLES Next, the present invention will be explained based on examples.

Example 1 As polyester A, polyethylene terephthalate polymerized by a conventional method (polymerization catalyst: magnesium acetate 0.2
0% by weight, antimony trioxide 0.03% by weight, dimethyl phenylphosphonate as a phosphorus compound 0.35% by weight
Was used. ) Pellets (intrinsic viscosity: 0.62, melting point:
259 ° C, Tg: 74 ° C, Tcc: 130 ° C) 180
After vacuum drying (3 Torr) at ℃ for 3 hours, melt extrusion was performed at 290 ℃ using a known extruder, and was wound on a casting drum having a surface temperature of 25 ℃ using an electrostatic applied casting method, and cooled, Solidified to make a single layer unstretched film. This unstretched film was passed through four silicone heating rolls having a surface temperature of 165 ° C. (adhesion start temperature: 183 ° C., free path: 64 mm) to perform heat treatment. The heat-treated film was stretched at a temperature of 93 ° C. in the longitudinal direction by 3.4 times, and further stretched at a stretching speed of 2000 using a known stenter.
% / Min, stretched 4.0 times in the width direction at 95 ° C., and further heat-treated at 210 ° C. for 5 seconds under a fixed length to obtain a thickness of 10 μm.
A biaxially oriented film of m was obtained.

Example 2 The amount of magnesium acetate in the polymerization catalyst for polyethylene terephthalate of Example 1 was changed to 0.1% by weight and dimethylphenylphosphonate was 0.6% by weight (intrinsic viscosity: 0.6).
0, melting point: 257 ° C., Tg: 78 ° C., Tcc: 127
C.), a biaxially oriented monolayer film having a thickness of 10 μm was obtained in the same manner as in Example 1 except that the surface temperature of the heating roll was changed to 175 ° C.

Examples 3, 4, 5 A / B / A three-layer laminated film was prepared. Polyester A dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours (the addition amount of the polymerization catalyst of Example 1 was changed, Tg: 70 to 75 ° C.,
(Tcc: 123 to 140 ° C.) and polyethylene terephthalate polymerized by a conventional method using 0.06% by weight of magnesium acetate, 0.008% by weight of antimony trioxide and 0.02% by weight of trimethyl phosphate as polyester B. Pellets using (intrinsic viscosity:
0.62, melting point: 259 ° C, Tg: 75 ° C, Tcc: 1
68 ° C.) was supplied to each of two extruders, melted at 290 ° C., and combined and laminated in a rectangular confluent block (feed block) for three layers. Hereinafter, after heat-treating the unstretched film with four silicone heating rolls similar to those in Examples 1 and 2, a total thickness of 7.5 μm (A
A biaxially oriented laminated film having a layer thickness of 1 μm) was obtained. However, in Example 4, the stretching ratio was 3.6 in the longitudinal direction.
And 4.5 times in the width direction. In Example 5, the stretching temperature was 95 ° C. and the stretching ratio was 3.6 times in the longitudinal direction and 4.5 times in the width direction. The surface temperature of the heating roll is 165 ° C. in Example 3, 155 ° C. in Example 4, and 170 in Example 5.
° C.

Comparative Example 1 Inactive particles were added to the polyester B of Example 3 (colloidal silica particles having an average particle size of 0.2 μm were dispersed in ethylene glycol and added at the time of polymerization), and pellets (particle content: 0) were added. .4% by weight) in the same process as in Example 1 to obtain a monolayer film having a total thickness of 10 μm.
However, the surface temperature of the heating roll was 85 ° C. The number of protrusions due to crystals of the obtained film was examined, and all the protrusions were due to particles.

Comparative Examples 2 and 3 Inactive particles were added to the polyester A of Example 1 (calcium carbonate particles having an average particle size of 0.55 μm were added during polymerization).
Comparative Example 2 was prepared in the same process as in Example 1 using the pellets (particle content: 0.3% by volume).
Four silicone heating rolls having a surface temperature of 30 ° C. (adhesion starting temperature: 143 ° C., free path: 64 mm), and Comparative Example 3 has a silicone heating roll 4 having a surface temperature of 190 ° C.
Book (Adhesion start temperature: 183 ° C, Free pass: 64 mm)
Using a heating roll of, a biaxially oriented monolayer film having a thickness of 10 μm was obtained. In both Comparative Example 2 and Comparative Example 3, the stretching ratio was 4.0 times in the longitudinal direction and 4.0 times in the width direction.

Comparative Example 4 Pellets of Polyester A of Example 3 and Polyester B
Each pellet is fed to 2 extruders, 290 ℃
Melted in a three-layer rectangular merging block (feed block), merging and stacking, using the electrostatic applied cast method,
It was wound on a casting drum having a surface temperature of 25 ° C., cooled and solidified to prepare an A / B / A three-layer laminated unstretched film. This unstretched film was subjected to a surface temperature of 170
℃ 8 silicone heating rolls (adhesion start temperature: 18
3 ° C, silicone roll 4th and 5th free pass:
200 mm, other free path between rolls: 64 mm)
Heat treatment was performed by passing through. This heat-treated unstretched film was stretched 3.4 times in the longitudinal direction at a temperature of 95 ° C., and further, using a known stenter, at a stretching rate of 2000% / min, at 95 ° C., 4.0 times in the width direction. Stretched and further heat-treated at 210 ° C for 5 seconds under constant length, total thickness 7.5 μm
A biaxially oriented film (A layer thickness: 0.2 μm) was obtained.

Comparative Example 5 As in Comparative Example 2, pellets obtained by adding inert particles to polyester A and pellets of polyester B of Example 3 were respectively fed to two extruders and melted at 290 ° C. Rectangular confluence block (feed block) for 3 layers
Then, three layers of A / B / A were combined and laminated. This unstretched film was heated on a heating roll having a surface temperature of 145 ° C. and a ceramic surface material (adhesion start temperature: 110 ° C.). Heat treatment was performed. This heat-treated film was heat-treated. This heat-treated film was subjected to the same process as in Example 5 to give a total thickness of 10
A biaxially oriented laminated film having a thickness of μm (A layer thickness of 0.2 μm) was prepared.

The results of evaluating the films prepared in the above Examples and Comparative Examples are shown in Tables 1 and 2. It can be seen that all the samples belonging to the scope of the present invention are superior to the comparative example in abrasion resistance, roll winding appearance, and output characteristics.

[0062]

[Table 1]

[Table 2]

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Claims (6)

[Claims] 1. A polyester film containing polyester A as a main component, wherein protrusions on at least one surface thereof are protrusions mainly caused by crystals of polyester A, and a ratio of the surface roughness parameter Rz / Ra. Is 4 or more and less than 12 and the variation of Ra (= 100 × (R
maximum value of a-minimum value of Ra) / average value (unit:%)) is 3
It is 0% or less, and the particle density in a region having a depth of 5 times the average protrusion height in the vicinity of the surface of the cross-sectional structure in the film thickness direction is 10,000 particles / mm ² or less. Polyester film. 2. The ratio (n /) of the number (n) of protrusions due to the crystals of the polyester A and the total number (N) of protrusions on the surface.
N) is 0.7 or more, The polyester film of Claim 1 characterized by the above-mentioned. 3. The polyester film according to claim 1, wherein the crystallization parameter ΔTcg of the polyester A is 10 ° C. or more and less than 70 ° C. 4. A polyester film comprising the polyester B as a main component, and the polyester film according to claim 1 laminated on at least one surface of the film. 5. A heating roll having an adhesion starting temperature of 130 ° C. or higher is applied to at least one side of a cooled and solidified unstretched film containing polyester A as a main component.
Heat treatment is performed at 0 ° C. or higher, and then 20 ° C. or higher than the glass transition temperature Tg of polyester A and the cold crystallization temperature Tcc.
The method for producing a polyester film according to any one of claims 1 to 4, wherein the polyester film is biaxially stretched at a temperature not higher than (Tcc + 20 ° C). 6. The free path between the heating rolls and / or the free path between the heating rolls and the roll positioned next is 1500 times or less the thickness of the unstretched film. Manufacturing method of polyester film.