JP3287498B2 - Biaxially oriented polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially oriented polyester film, and more particularly to a biaxially oriented polyester film suitable as a base film for a magnetic tape.

[0002]

2. Description of the Related Art Polyester, particularly polyethylene terephthalate, has excellent physical and chemical properties, and a biaxially oriented polyester film obtained by adding fine particles of an inorganic compound or an organic compound called lubricant particles to a polyester is a magnetic tape. Widely and generally used as a film.

Recently, the demand for scratch resistance (scratch resistance) has increased for magnetic tape base films. Scratch is caused by abrasion (for example, abrasion of a tape by a metal or plastic cassette pin at the time of dubbing by a high-speed sprinter) or abrasion powder generated by a traveling system in a tape deck. Abrasion. When a magnetic tape is manufactured using a base film having poor scratch resistance, the inside of the manufacturing apparatus is contaminated with powder generated by abrasion in the manufacturing process, and dropout occurs in the obtained magnetic tape.

[0004] The improvement of the scratch resistance is very important because it leads to the improvement of the quality of the magnetic tape.

[0005] As a method for improving the abrasion resistance, inert fine particles having a specific hardness (for example, inert fine particles having a Mohs hardness of 6 or more) or alumina fine particles having a specific crystal form (for example, inert fine particles) are used as a lubricant in a polyester film. , Δ-alumina or γ-alumina) are known (for example, JP-A-1-31131, JP-A-3-6238, JP-A-3-6239, and Japanese Patent Publication No. Hei 4-6239). No. 40375). However, in the above method, the scratch resistance of the film to the plastic cassette pins is improved, but the scratch resistance to the metal cassette pins during high-speed dubbing is not sufficient. That is, it has been found that it is not important to use inert particles of high hardness or to use alumina having the above-mentioned specific type of crystal form in order to increase the scratch resistance.

In a base film for a magnetic tape,
If the scratch resistance can be satisfied, the improvement of the quality of the tape is promoted, and it is industrially very useful.

[0007]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and its object is to
An object of the present invention is to provide a biaxially oriented polyester film which is excellent in abrasion resistance and therefore has little occurrence of scratches on the surface of a tape in a high-speed dubbing step.

[0008]

Means for Solving the Problems The present inventors have intensively studied measures for the above problem from the viewpoint of a lubricant or a filler contained in the polyester film, and as a result, the present invention has been achieved.

The biaxially oriented polyester film of the present invention contains, as a main component, a polyester containing an acid component mainly containing an aromatic dicarboxylic acid and at least one glycol component, and contains composite oxide particles (A). The composite oxide particles (A) include Al (aluminum), Si
It is composed of a substantially amorphous compound having (Si) and O (oxygen) as main constituent elements, and the Al content (Al / (Al + Si) molar ratio) of the compound is 0.3 or more and 0.9 or less. The average particle diameter of the particles is 0.01 to 5 μm
It is. The composite oxide particles (A) are contained in a range from 100 ppm to 50,000 ppm.

Next, the present invention will be described in detail.

The biaxially oriented polyester film of the present invention contains polyester as a main component. This polyester contains an acid component mainly composed of an aromatic dicarboxylic acid and at least one glycol component, and 95 mol% or more of its constituent units are ethylene terephthalate units (composed of terephthalic acid and ethylene glycol). Is preferred.

Other acid components other than terephthalic acid include:
Isophthalic acid, p-β-oxyethoxybenzoic acid, 2,
6-naphthalenedicarboxylic acid, 4,4-dicarboxyphenyl, 4,4-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4- Dicarboxylic acids such as dicarboxylic acids; and oxycarboxylic acids such as p-oxybenzoic acid. Examples of the glycol component other than ethylene glycol include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol, an ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. In addition, it may contain a small amount of a compound containing an amide bond, urethane bond, ether bond, carbonate bond or the like.

The composite oxide particles (A) used in the present invention are composed of a compound containing Al, Si and O as main constituent elements. ".

The “amorphous” refers to the X of the composite oxide particles.
In the line diffraction, from the area of a broad peak (P _am ) appearing in the range of 2θ = 10 ° to 45 ° and the area of a sharp peak (P _cr ) appearing in the range of 2θ = 65 ° to 70 °, the following is obtained. It is indicated by the area ratio obtained by the equation (see FIG. 1), and when its value is 0.7 or more, it is said to be "amorphous". When calculating the area, a base line is set for each peak as shown in FIG.
Each area between the peaks and the baseline and P _am and P _cr. Degree of amorphousness = P _am / (P _cr + P _am ).

The above amorphous composite oxide can be produced by various methods. For example, a heterogeneous coprecipitation method prepared by hydrolyzing a mixed aqueous solution of an aluminum salt and a silicon salt with aqueous ammonia, a uniform precipitation method prepared using urea instead of aqueous ammonia, aluminum hydroxide and silicon A method of kneading the hydroxide of the above, a method of immersing the other oxide in a solution of one of aluminum or silicon salts, or a method of calcining a solution obtained by adding aqueous ammonia thereto, covalent bonding AlCl ₃ , Si
There is a method of burning a chloride such as Cl _{4 in} the presence of hydrogen and oxygen. The above combustion method is most suitable for producing the amorphous composite oxide used in the present invention. The structure of the composite oxide thus obtained is considerably different from the mixture of each single oxide (aluminum oxide and silicon oxide) contained in the composite oxide. That is, the composite oxide has a structure in which different elements are bonded by oxygen (for example, Al-
O-Si) is formed of a composite oxide having a bond represented by O-Si) as a main component, and the structural characteristics (for example, crystal form) of each single oxide are extremely small depending on the abundance of elements. Most are crystalline oxides.

The composite oxide particles (A) used in the present invention
In addition, impurities such as chlorine ions derived from the production process can be contained up to a ratio of 5% by weight or less based on the composite oxide. If the chloride ion concentration exceeds 5% by weight, thermal decomposition of the polyester becomes remarkable at the time of polyester polymerization and at the time of film formation, which is not preferable.

The composite oxide particles can be particles of any shape.

The composite oxide particles (A) used in the present invention
Has an average particle size of 0.01 to 5 μm, preferably 0.05 to 2 μm. When the average particle diameter of the composite oxide particles (A) is less than 0.01 μm, the aggregation of the composite oxide particles (A) in the polyester becomes severe, and the effect of improving the scratch resistance of the obtained film is observed. I can't. When the average particle diameter of the composite oxide particles (A) exceeds 5 μm, coarse protrusions are formed on the obtained film. When such a film is used for a magnetic tape, the tape surface may be damaged by the coarse protrusions. Or dropouts occur.

The above average particle diameter is defined as 50% of the equivalent sphere particle size distribution calculated based on the Stokes equation.
It refers to the particle size at a point. The particle size distribution of the composite oxide particles (A) is sharp and does not contain particles having a particle size of 5 μm or more in order to prevent film breakage and dropout when used for a magnetic tape. It is particularly preferable that the volume content of particles having a particle diameter of 2 μm or more be 5% or less of the total composite oxide particles contained.

The content of the composite oxide particles (A) in the biaxially oriented polyester film of the present invention is from 100 to 50.
000 ppm, preferably 10
00 to 10000 ppm. When the content of the composite oxide particles (A) is less than 100 ppm, the obtained polyester film does not have sufficient scratch resistance.
The content of the composite oxide particles (A) is 50,000 ppm
When the ratio is more than 1, the proportion of the composite oxide particles contained in the obtained film that falls off when the film is run is large, and the dropped particles have a higher hardness than the polyester film and damage the film surface. Further, the heat resistance of the polyester film also decreases. When the obtained film is laminated and used, the content means the content in the outermost layer and does not mean the content in the whole multilayer.

The surface of the composite oxide particles (A) may be modified with various surface treating agents. For example, as a surface treatment agent used for the purpose of improving the affinity with a glycol component or a polyester, an ammonium salt of polyacrylic acid, an ammonium salt of polymethacrylic acid, an alkali metal hydroxide, an alkali metal phosphate, Examples thereof include a silane coupling agent and a titanium coupling agent, and sodium hydroxide is particularly preferred. The surface treating agent is generally used in an amount of 5% by weight or less based on the composite oxide particles (A).

In the biaxially oriented polyester film of the present invention, in addition to the composite oxide particles (A), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), calcium fluoride (CaF ₂ ), talc, kaolin , Titanium oxide, silicon oxide (SiO ₂ ), alumina and other inert inorganic compound particles; and organic particles made of cross-linked polystyrene, cross-linked polymethacrylate, cross-linked polyacrylate, and the like can also be included as a lubricant. . From the viewpoint of traveling properties, silicon oxide (silicon oxide having a spherical particle shape),
Alternatively, particles made of calcium carbonate (CaCO ₃ ) are preferable. Kaolin particles are particularly preferred from the viewpoint of abrasion resistance.

The calcium carbonate particles are classified into three types of crystals, calcite classified into trigonal or hexagonal system, aragonite classified into orthorhombic system, and vaterite classified into hexagonal or pseudo hexagonal system. Although it is classified into a type, any crystal type may be used, and the shape thereof can be arbitrarily selected, such as a sphere, a cube, a spindle, a column, a needle, a sphere, and an egg.

The above-mentioned kaolin particles may be of any type, regardless of whether they are natural kaolin, synthetic kaolin, calcinable or unburnable, and their shape can be arbitrarily selected, such as plate-like, columnar, spherical, spindle-like, oval, and the like. .

When the above-mentioned inert inorganic compound particles and organic particles are contained in the biaxially oriented polyester film of the present invention, the content of these particles depends on the particle diameter of the particles. The amount is preferably 500 to 10000 ppm, more preferably 1500 to 700 ppm.
It is 0 ppm. When the content of the inert inorganic compound particles and the organic particles is less than 500 ppm, the obtained polyester film does not have sufficient slipperiness. When the content of the inert inorganic compound particles and the organic particles is 100
If it exceeds 00 ppm, coarse projections are likely to be formed on the surface of the film due to the inert inorganic compound, which causes dropout.

In producing the polyester of the present invention, the dispersibility of lubricants (ie, composite oxide particles, inert inorganic compound particles, and organic particles) is improved, and the electrostatic adhesion of the resulting film is improved. For at least one of a hydroxide or salt of an alkali metal, and an alkaline earth metal salt; phosphoric acid, an alkyl phosphate,
Alternatively, a derivative thereof or the like can be added. In this case, the molar ratio of the additive represented by the following formula is preferably from 0.4 to 1.0.

[0027]

(Equation 1)

When the above molar ratio is less than 0.4 or more than 1.0, the added composite oxide particles and the particles of the inert inorganic compound such as calcium carbonate tend to agglomerate. Coarse particles are generated, and therefore, a magnetic tape using such a polyester,
Easy to drop out.

The method of mixing the composite oxide particles (A) with the polyester includes a method of adding the composite oxide particles to a polyester polycondensation reaction system to complete the polycondensation, and a method of mixing the composite oxide particles in a molten polyester. There is a method in which particles are added and kneaded, and both methods can be adopted. Usually, the former method is preferred from the viewpoint of dispersibility of the composite oxide particles in the polyester. In this case, the composite oxide particles are usually added to the reaction system as a slurry in addition to the glycol component. The timing of the addition depends on the type, particle size, and chloride ion concentration of the composite oxide particles to be used, the slurry concentration when the particles are used as a slurry, the temperature of the slurry, and the like. Usually, the timing of the addition is preferably before the start of the polycondensation reaction.

Generally, the above-mentioned surface treating agent is added to a slurry comprising the above-mentioned composite oxide particles (A) and a glycol component at the time of preparing the polyester.
The dispersibility of the particles in the resulting polyester is further increased. At this time, by heating the slurry to the boiling point of the glycol component, the dispersibility of the particles in the polyester is further improved.

The method for producing the biaxially oriented polyester film of the present invention is not particularly limited, and any method may be employed. For example, the following production methods are available. First, a polyester film prepared by adding the inert inorganic or organic compound particles to the composite oxide particles and, if necessary, for forming projections on the film surface, for example, in a vertical and horizontal direction. It is biaxially stretched in the direction. The stretching order may be any of vertical and horizontal, horizontal and vertical, and simultaneous two axes. Alternatively, the stretching may be performed in three or more stages by appropriately combining transverse stretching, longitudinal stretching, and simultaneous biaxial stretching.

After biaxially stretching the polyester film,
Usually, heat treatment is performed in a tenter. Heat treatment is 190-2
It is preferable to perform the stretching at 30 ° C. for 2 to 10 seconds, and it is preferable to perform re-stretching by 2 to 30% in the horizontal direction or both the vertical and horizontal directions simultaneously with the heat treatment.

After the heat treatment, relaxation treatment may be performed in the horizontal and vertical directions. 130 to 17 for lateral relaxation
It is preferably performed in a tenter at 0 ° C. The relaxation in the vertical direction is preferably performed on a heating roll at a temperature of 80 to 150 ° C.

A multilayer film obtained by using at least one film obtained by the present invention as the outermost layer is also useful.

[0035]

The biaxially oriented polyester film of the present invention contains complex oxide particles containing amorphous Al and Si as main constituent elements. Therefore, when a magnetic tape is prepared using this as a base film, The abrasion resistance to plastic cassette pins and the abrasion resistance to metal cassette pins are greatly improved.

[0036]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The methods for measuring the films obtained in Examples and Comparative Examples are described below.

(1) Average particle diameter of composite oxide particles and other inorganic compound particles (lubricants) Centrifugal sedimentation type particle size distribution analyzer (SA manufactured by Shimadzu Corporation)
The value at the point of 50% integration in the equivalent spherical distribution of particles obtained by CP-3) was defined as the average particle diameter.

(2) Amorphous Property of Composite Oxide Particles The amorphous property of the composite oxide was determined by a reflection method using a high-intensity X-ray diffractometer manufactured by Rigaku Corporation. Measurement conditions: Nickel-filtered Cu-Kα ray Measurement angle 2θ = 10 to 90 degrees 45 kV, 150 mA Scan rate = 2 degrees / min The degree of amorphousness is the degree of the composite oxide particles containing SiO ₂ / Al ₂ O ₃ as a component. In X-ray diffraction, the broad peak area (P _am ) appearing in the range of 2θ = 10 ° to 45 ° and 2θ
= The area (P _cr ) of the sharp peak appearing in the range of 65 ° to 70 ° was calculated by the following equation (see FIG. 1). When calculating the area, a base line was set for each peak as shown in FIG. 1, and the area between the peak and the base line was defined as P _am and P _cr , respectively. Degree of amorphousness = P _am / (P _cr + P _am ).

(3) Average surface roughness of film Using a Surfcom 300A type surface roughness meter (manufactured by Tokyo Seimitsu), needle diameter 1 μm, load 0.07 g, measurement standard length 0.8 m
m, the center line average roughness (Ra: μm) when the film surface was measured under the conditions of a cutoff of 0.08 mm.

(4) Slip Properties of Film (Coefficient of Friction) According to ASTM D-1894-63, the coefficient of static friction between two films was measured at 23 ° C. and 65 RH% using a threaded strip tester. It was measured.

(5) Abrasion Resistance of Film to Metal Pin The polyester film cut to a width of 10 mm was subjected to Fe-C
The pin is made to run while being rubbed once at a tension of 100 g, a winding angle of 45 degrees, and a running speed of 300 m / min. Next, the amount of scratches was visually determined with a microphotograph of actual conditions, and the scratches were ranked as follows. ◇ 1: No scratches are recognized 2: Slight scratches are recognized but extremely small 3: Small scratches are recognized 4: Large scratches are recognized

(6) Abrasion Resistance of Film to Plastic Pin A polyester film cut to a width of 10 mm is run on a plastic pin while rubbing once at a tension of 100 g, a winding angle of 90 °, and a running speed of 150 m / min. Next, aluminum was deposited on the friction surface, and the aluminum-deposited surface was visually judged for the amount of scratches by a microscopic photograph of the actual state, and ranked as follows. 1 ... no scratches are recognized 2 ... slight scratches are recognized but extremely minute 3 ... small scratches are recognized 4 ... large scratches are recognized

The obtained polyester film was ranked 1
If it is and 2, there is no problem in practical use.

Example 1 Preparation of Polyester Composition A AlCl ₃ and Si
Al / Si having an average primary particle diameter of 0.02 μm and an average secondary particle diameter of 0.5 μm (molar ratio = 66/3) was obtained by a method of burning under a gaseous phase of hydrogen and oxygen using Cl ₄ as a starting material.
The composite oxide particles of 3) were obtained. FIG. 1 shows the results of X-ray diffraction for determining the degree of amorphousness of the obtained composite oxide particles. The obtained composite oxide particles are wet-pulverized in ethylene glycol to obtain an average particle diameter of 0.05 μm and 20% by weight.
A slurry was obtained.

On the other hand, 100 parts by weight of terephthalic acid, 70.7 parts by weight of ethylene glycol, 0.0
697 parts by weight, 0.271 parts by weight of triethyleneamine and 0.0931 parts by weight of magnesium acetate were added, and 25
The esterification was carried out at 0 ° C. under a pressure of 2.5 kg / cm ² .

After the completion of the esterification, 0.0327 parts by weight of trimethyl phosphate was added to the solution, and
Stirring was performed at 0 ° C. After 30 minutes, the composite oxide concentration is 2% by weight based on the produced polyester.
A predetermined amount of the slurry was added, and the mixture was further stirred for 30 minutes. Thereafter, a polycondensation reaction is performed under vacuum, and the intrinsic viscosity η =
A polyethylene terephthalate composition of 0.60 was obtained (polyester composition A).

<Preparation of Polyester Composition B> In the production of the polyester composition A, calcium carbonate (inorganic) having an average particle size of 0.45 μm was used instead of the Al / Si (molar ratio = 66/33) composite oxide particles. (Polyethylene terephthalate composition) having a calcium carbonate concentration of 2% and an intrinsic viscosity η = 0.62 (polyester composition B).

<Preparation of Polyester Composition C> In the preparation of the polyester composition A, kaolin (inorganic compound having an average particle diameter of 0.4 μm) was used instead of the Al / Si (molar ratio = 66/33) composite oxide particles. (Polymer terephthalate composition) having a kaolin concentration of 2% and an intrinsic viscosity η = 0.61 (polyester composition C).

<Preparation of Polyester Composition D> In the production of the polyester composition A, the intrinsic viscosity η was 0.6 in the same manner except that the composite oxide particles were not contained.
Polyethylene terephthalate composition No. 2 was obtained (polyester composition D).

The obtained polyester composition A, polyester composition B, polyester composition C and polyester composition D are mixed at a predetermined weight ratio, and the Al / (Al + Si) molar ratio of the composite oxide particles to the mixture and The concentrations of the calcium carbonate and kaolin particles were set so as to be the concentrations shown in Table 1, respectively. After drying the mixture, the mixture was melted at 280 ° C. and cast on a cooling drum at 30 ° C. to obtain an unstretched film having a thickness of 220 μm. Then, the film was heated using a roll heated to 75 ° C. and an infrared heater having a surface temperature of 600 ° C. (installed at a position 20 mm away from the film), and then vertically moved between a low-speed roll and a high-speed roll. The film was stretched three times. Then, put this film in a tenter
The film was stretched 4.4 times in the transverse direction at 00 ° C. In the tenter,
Subsequent to the transverse stretching, heat treatment, re-lateral stretching, and relaxation in the transverse direction were performed. Next, the film was brought into contact with a roll heated to 120 ° C., and the tension in the longitudinal direction was controlled by controlling the tension between the heated roll and the rolls before and after the heated roll to obtain a biaxially oriented polyester film having a thickness of 15 μm. . Table 1 shows the characteristics of the film thus obtained.
Shown in Table 1 also shows Examples 2 to 10 and Comparative Examples 1 to 3 described later.

Examples 2 to 10 Polyester Composition A
As shown in Table 1, the types of the composite oxide particles contained in and the inorganic compound particles contained in the polyester composition B, the respective average particle diameters, and the amounts of the respective additions are shown in Table 1, and the film forming conditions were further appropriately changed. A biaxially oriented polyester film was obtained in the same manner as in Example 1 except for the above.

(Comparative Examples 1 to 3) Table 2 shows the types, average particle diameters, and contents of the inorganic compound particles contained in the polyester B which did not contain the composite oxide particles and which were contained in the polyester B. As shown, a biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were further changed as appropriate.

[0054]

[Table 1]

As is clear from Table 1, Examples 1 to 10
While the biaxially oriented polyester films obtained in the above are all excellent in scratch resistance to metal cassette pins, Comparative Examples 1 to 3 have poor scratch resistance to metal cassette pins. You can see that.

[0056]

As is apparent from the above description, the detailed mechanism of the composite oxide particles containing Al and Si as main constituent elements contained in the biaxially oriented polyester film of the present invention is unknown. In addition, the abrasion resistance to the metal cassette pin during high-speed running is greatly improved.

[Brief description of the drawings]

FIG. 1 shows the results of X-ray diffraction of the composite oxide particles used in Example 1.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-221158 (JP, A) JP-A-5-170943 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 67/00-67/02

Claims (5)

(57) [Claims] An acid component mainly containing an aromatic dicarboxylic acid,
And a composite oxide particle (A) containing a polyester containing at least one glycol component as a main component , and
Alkali metal hydroxide or salt, and alkaline earth
At least one metal salt, phosphoric acid, alkyl phosphate
A biaxially oriented polyester film containing an ester or a derivative thereof , wherein the composite oxide particles (A) are Al (aluminum), S
It is composed of a substantially amorphous compound having i (silicon) and O (oxygen) as main constituent elements, and has an Al content (Al / (Al + Si) molar ratio) of 0.3 or more and 0.9 or more. Or less, the average particle diameter of the particles is 0.01 to 5 μm, and the composite oxide particles (A) are 100 ppm or more and 5000 or more.
A biaxially oriented polyester film, which is contained in a range of 0 ppm or less. 2. AlCl _Three And SiCl _Four The hydrogen and
Combustion in the presence of oxygen to produce composite oxide particles (A)
Step; The composite oxide particles (A) are mainly composed of an aromatic dicarboxylic acid.
Acid component and at least one glycol component
After being added to the mixture, the polycondensation reaction
Obtaining a ester composition; and the polyester
Step of forming the composition into a film and biaxially stretching the film
About; , The composite oxide particles (A) are composed of Al (aluminum), S
Substantially containing i (silicon) and O (oxygen) as main constituent elements
Composed of a non-crystalline compound, the Al content of the compound
(Al / (Al + Si) molar ratio) is 0.3 or more and 0.9 or less
The average particle diameter of the particles is 0.01 to 5 μm.
Yes, The composite oxide particles (A) have a content of 100 ppm or more and 5000 or more.
Contained in a range of 0 ppm or less, A method for producing a biaxially oriented polyester film. 3. AlCl _Three And SiCl _Four The hydrogen and
Combustion in the presence of oxygen to produce composite oxide particles (A)
Step; The composite oxide particles (A) are mainly composed of an aromatic dicarboxylic acid.
Acid component and at least one glycol component
Polycondensation reaction system
Completing the reaction to obtain a polyester composition; and
Into a film of the polyester composition,
Biaxial stretching; , The composite oxide particles (A) are composed of Al (aluminum), S
Substantially containing i (silicon) and O (oxygen) as main constituent elements
Composed of a non-crystalline compound, the Al content of the compound
(Al / (Al + Si) molar ratio) is 0.3 or more and 0.9 or less
The average particle diameter of the particles is 0.01 to 5 μm.
Yes, The composite oxide particles (A) have a content of 100 ppm or more and 5000 or more.
Contained in a range of 0 ppm or less, A method for producing a biaxially oriented polyester film. 4. AlCl _Three And SiCl _Four The hydrogen and
Combustion in the presence of oxygen to produce composite oxide particles (A)
Step; An acid component mainly containing an aromatic dicarboxylic acid, and at least
Polycondensation of a kind of glycol component
And adding the composite oxide particles (A) to the polyester.
Obtaining a polyester composition; and the polyester
To form a film from the polyester composition and biaxially stretch the film.
About; , The composite oxide particles (A) are composed of Al (aluminum), S
Substantially containing i (silicon) and O (oxygen) as main constituent elements
Composed of a non-crystalline compound, the Al content of the compound
(Al / (Al + Si) molar ratio) is 0.3 or more and 0.9 or less
The average particle diameter of the particles is 0.01 to 5 μm.
Yes, The composite oxide particles (A) have a content of 100 ppm or more and 5000 or more.
Contained in a range of 0 ppm or less, A method for producing a biaxially oriented polyester film. 5. The method according to claim 1, wherein the step of obtaining the polyester composition comprises:
And hydroxides or salts of alkali metals
(B) and at least an alkaline earth metal salt (C)
One and phosphoric acid, phosphoric acid alkyl ester, or it
These derivatives (D) , The following formula: Molar ratio of additive = mol number of (D) / (mol number of ((B))
/ 2) + (C) mole number)
Ratio "is 0.4 to 1.0.
The biaxial orientation according to any one of claims 2 to 4,
A method for producing a polyester film.