JPH05329997A - Laminated biaxially-oriented polyester film - Google Patents

Abstract

PURPOSE:To provide the present polyester film excellent in slip properties, shaving resistance and scratch resistance and especially useful as the base film of a magnetic recording medium. CONSTITUTION:A layer composed of polyester containing 0.05-1.5wt.% of inert particles A with Mohs hardness of 6 or more and a mean particle size dA of 0.02-0.3mum and O 001-1wt.% of inert particles B with Mohs hardness of below 3 and a mean particle size dB of 0.2-1.5mum larger than the mean particle size dA and having a thickness 0.2-0.5 times the mean particle size dB of the inert particles B is laminated on at least the single surface of a biaxially oriented polyester film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated biaxially oriented polyester film, and more particularly to a laminated biaxially oriented polyester film which is excellent in slipperiness, abrasion resistance and scratch resistance and is particularly useful as a base film for magnetic recording media. Regarding

[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.

Recently, these fields of application are used for high density recording,
The demand for higher quality is increasing more and more, and accordingly, the demand for a flat surface of the polyester film as a base is becoming stronger.

However, when the surface of the film becomes flat, the coefficient of friction of the film becomes high, for example, in magnetic tape applications, causing problems such as poor running and easy scratching. Further, when the film surface becomes flat, there is a problem that the film winding shape in the process of winding the film into a roll during film production is significantly deteriorated, and it is difficult to obtain a film roll with a good winding shape. With increasing productivity, the film winding speed has been further increased,
In addition, it is necessary to widen the width, but with the speeding up and widening, it is difficult to obtain a film roll having an even better winding shape.

Therefore, the polyester film as the base is required to have excellent smoothness as well as flatness in order to obtain a good film winding appearance.

Conventionally, a method of adding inorganic fine particles such as silicon oxide and calcium carbonate to polyester as a method for improving the slipperiness of the film, or precipitation of fine particles containing calcium, lithium or phosphorus in the polymerization system during the synthesis of polyester Proposals have been made. In either method, when the polyester is formed into a film, fine projections are formed on the surface of the film due to the fine particles to improve the slipperiness of the film.

However, in the method for improving the slipperiness of the film by the projections by the fine particles as described above, the slipperiness is usually improved as the film surface is roughened,
On the other hand, due to the roughening, for example, in a magnetic recording medium application, the surface of the magnetic layer after applying the magnetic coating is rough,
The electromagnetic conversion characteristics tend to deteriorate.

As one of the measures for simultaneously solving the contradictory flatness and slipperiness, one surface of the film is flat and the other is rough so that it is easy to slip. A method using an axially oriented film has been proposed.

However, in this method, in order to improve the slipperiness, it is necessary to add a large amount of inert particles to the thin layer constituting the rough surface to roughen the surface, and as a result, the sharpness during tape processing is reduced. There is a problem that the number of dropouts is increased due to deterioration and generation of scratches and shavings during running as a magnetic recording tape after processing.

Further, in recent years, as the speed of the tape manufacturing process has become faster, the conditions for the calendar and coater have tended to become more severe, and it has become even more important to improve the abrasion resistance of the film in the processing process.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned problems, have both flatness and good slipperiness applicable to high-quality magnetic recording application fields, and have good abrasion resistance. As a result of earnest research to develop a film having high resistance and scratch resistance, it was found that the particles contained in the thin layer have two or more different hardnesses and particle sizes and are optimized. The present invention has been accomplished by finding that the problems can be solved and that a film having excellent abrasion resistance and scratch resistance can be obtained.

Therefore, an object of the present invention is to provide a laminated layer having excellent slipperiness, abrasion resistance, scratch resistance and the like while maintaining flatness capable of accommodating high density recording and high quality recording of a magnetic recording medium. An object is to provide an axially oriented polyester film.

[0013]

The present invention has the following constitution in order to achieve such an object.

On at least one surface of the biaxially oriented polyester film, inactive particles A having a Mohs hardness of 6 or more and an average particle diameter dA of 0.02 to 0.3 μm are prepared.
0.001 to 0.51% by weight of inert particles B having a Mohs hardness of less than 3 and an average particle size dB of 0.2 to 1.5 μm and larger than the average particle size dA. 1
A laminated biaxially oriented polyester film comprising a polyester containing 10% by weight and having a layer thickness of 0.1 to 5 times the average particle size dB of the inert particles B.

In the present invention, as the polyester constituting the film, those having alkylene terephthalate and / or alkylene naphthalate as a main constituent are preferably used.

Among such polyesters, especially polyethylene terephthalate, polyethylene-2,6-naphthalate, etc., for example, 8 of all dicarboxylic acid components are used.
A copolymer in which 0 mol% or more is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid and 80 mol% or more of all glycol components is ethylene glycol is preferable. In that case, 20 mol% or less of the total acid component is an aromatic dicarboxylic acid other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, such as isophthalic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylethanedicarboxylic acid, It may be diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid or the like, and may be aliphatic dicarboxylic acid such as adipic acid or sebacic acid or the like, alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid or the like.
The glycol of 20 mol% or less of the total glycol component may be a glycol other than ethylene glycol, such as trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, etc., and cyclohexanedimethanol. Aliphatic glycols, hydroquinone, resorcin, aromatic diols such as 2,2-bis (4-hydroxyphenyl) propane, and aliphatic diols containing aromatic rings such as 1,4-dihydroxymethylbenzene, polyethylene glycol, polypropylene glycol It can also be a polyalkylene glycol (polyoxyalkylene glycol) such as polytetramethylene glycol.

The polyester of the present invention includes
Aromatic oxyacids such as hydroxybenzoic acid, ω-
Also included are those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as 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, a polycarboxylic acid or polyhydroxy compound having a functionality of 3 or more, such as trimellitate, can be used in an amount in a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component. Also included are those obtained by copolymerizing acid, pentaerythritol and the like.

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 of about 0.4 to 0.8 measured at 35 ° C. as a solution in o-chlorophenol, and 0.5 to 0.
7 is more preferable, and 0.55 to 0.65 is particularly preferable.

The laminated biaxially oriented polyester film of the present invention comprises at least two layers. The two layers of polyester may be the same or different, but the same is preferred.

In the present invention, the polyester layer forming at least one surface of the laminated biaxially oriented polyester film has a Mohs hardness of 6 or more and an average particle diameter dA of 0.0.
Inert particles A of 2 to 0.3 μm and Mohs hardness of 3
It is necessary to contain the composite particles in which the average particle size dB is less than 0.2 to 1.5 μm and the inactive particles B larger than the average particle size dA of the inactive particles A are combined. is there.

The inert particles A in the present invention have a Mohs hardness of 6 or more, preferably 8 or more. If the Mohs hardness is too low, the film surface hardness becomes low and the scratch resistance deteriorates, which is not preferable.

The average particle diameter (average secondary particle diameter: dA) of the inert particles A is required to be 0.02 to 0.3 μm. If this average particle size is too small, the particles become too fine and scratch resistance, and it becomes impossible to form fine projections necessary for abrasion resistance, while if too large, agglomeration is too large and shavings are likely to occur, Not preferable.
The amount of the inert particles A added is 0.05 to 1.5% by weight,
Preferably 0.1 to 1.0% by weight, particularly preferably 0.1.
It is 23 to 0.58% by weight. If the addition amount is too small, the effect of adding fine particles is small, while if the addition amount is too large, the particles are overlapped with each other and shavings are easily generated, which is not preferable.

As the inert particles A in the present invention, aluminum oxide and titanium oxide are particularly useful, but aluminum oxide having a high effect of improving the abrasion resistance and scratch resistance is preferable. The crystal form of this aluminum oxide is preferably selected from α, θ, and γ-types, and it is more preferable that the α-form is included in the θ-type or γ-type crystal form, and the θ-form is particularly preferable. Is preferred.

The inert particles B in the present invention preferably have a Mohs hardness of less than 3, more preferably 2 or less, especially 1 or less. If the Mohs hardness is too large, in the calendering step during the processing step, the stress concentration on the inactive particles B forming the protrusions when high stress (high shear force) is applied becomes large, and the inactive particles B fall off. This is not preferable because it becomes easier and shavings are generated.
When the Mohs hardness is reduced to less than 3, it is presumed that the inert particles B are deformed when stress is concentrated on the surface protrusions in the calendering process, but the particles are less likely to fall off and the shavings are less.

The average particle size (dB) of the inert particles B is 0.2 to 1.5 μm, preferably 0.3 to 1.0 μm,
It is necessary that the particle size is more preferably 0.4 to 0.9 μm, particularly preferably 0.6 to 0.8 μm, and larger than the average particle size of the inert particles A. If this average particle size (dB) is too small, the height of the protrusions will be insufficient, the slipperiness will be insufficient, and the end face deviation will easily occur in the film winding state.
Not preferable. On the other hand, if the average particle size (dB) is too large, the abrasion resistance is deteriorated even if the Mohs hardness of the particles is less than 3, which is not preferable. The amount of the inert particles B added is 0.001 to 1% by weight, preferably 0.005.
~ 0.6 wt%, more preferably 0.007-0.3
%, Particularly preferably 0.01 to 0.1% by weight. If the amount added is too small, the coefficient of static friction becomes high and the slipperiness becomes insufficient, which is not preferable. On the other hand, if the amount of addition is too large, the number of protrusions formed on the film surface will be too large and shavings will be more likely to occur, or the film surface will become too rough, and the magnetic surface will be affected when the magnetic recording medium is manufactured. The film roughness is not preferable because it causes transfer to cause deterioration of electromagnetic conversion characteristics. The amount of the inert particles B added is 40% by weight or less of the total amount of the inert particles,
30% by weight or less, especially 20% by weight or less, especially 10
It is preferably not more than weight%. If this ratio is too large, the scratch resistance decreases, which is not preferable.

The inert particles B in the present invention are not particularly limited as long as they satisfy the above-mentioned characteristics, but organic particles such as particles made of a cross-linked polymer such as silicone resin, cross-linked polystyrene resin and cross-linked acrylic resin can be used. It is preferable that the particles easily obtain the above characteristics.

In the present invention, the silicone resin particles have the following formula (A) R _x SiO _{2-x / 2} (A) (wherein R is a hydrocarbon group having 1 to 7 carbon atoms, and x Is a number from 1 to 1.2.).

R in the above formula (A) is a hydrocarbon group having 1 to 7 carbon atoms, for example, an alkyl group having 1 to 7 carbon atoms,
Phenyl or tolyl is preferred. 1 to 7 carbon atoms
The alkyl group of may be linear or branched, and examples thereof include 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 a number from 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 RSiO _1.5 (A) -1 (where R is defined as above). Can be represented by.

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

[0034]

[Chemical 1]

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 R _1.2 SiO _1.4 (A) -2 (where R is the definition of R). Is the same as above).

The composition of the above formula (A) -2 is the same as that of the above (A)-
It is to be understood that it is composed of 0.8 mol of the structure of No. 1 and 0.2 mol of the structure represented by the following formula (A) R ₂ SiO ... (A) ′ (where R is defined as above). You can

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

[0039]

[Chemical 2]

Derived from.

As can be understood from the above description, the composition of the above formula (A) in the present invention is, for example, the above formula (A)-
It is found that the structure essentially consists of only the structure 1 or the structure of the above formula (A) -1 and the structure of the above formula (A) -2 coexist in a state in which they are randomly bonded at an appropriate ratio. ..

The silicone resin particles used in the present invention are
Preferably, in the above formula (A), x has a value between 1 and 1.1.

In the present invention, the particles of the crosslinked polystyrene resin include, for example, styrene derivative monomers such as styrene monomer, methylstyrene monomer, α-methylstyrene monomer and dichlorostyrene monomer, as well as butadiene conjugated diene monomer and acrylonitrile. Unsaturated nitrile monomers, monomers such as methacrylic acid esters such as methylmethacrylate, functional monomers such as unsaturated carboxylic acids, monomers with hydroxyls such as hydroxyethylmethacrylate, epoxide groups such as glycidylmethacrylate. A monomer, an unsaturated sulfonic acid, or the like having one or more kinds of monomers, and a polyfunctional vinyl compound such as divinylbenzene as a cross-linking agent for forming a three-dimensional structure of polymer particles. Tylene glycol dimethacrylate, trimethylolpropane triacrylate, diallyl phthalate, etc. are emulsion polymerized in an aqueous medium in which a water-soluble polymer is dissolved as a protective colloid to prepare an emulsion of polymer particles, which is then jet milled. It is obtained by crushing in, and then classifying.

The crosslinked polystyrene resin particles in the present invention do not melt or melt during polymerization of polyester, and do not melt during melting of the polymer during film molding.

In the present invention, in addition to the particles mentioned as the above-mentioned inert particles A and B, other inert particles may be contained within a range that does not impair the characteristics of the inert particles A and B. However, if the amount of the inert particles other than the inert particles A and B is large, the abrasion resistance is deteriorated, which is not preferable. From this point of view, the amount of the other inert particles is preferably 25% by weight or less, more preferably 10% by weight or less of the total amount of the inert particles.

The laminated biaxially oriented polyester film of the present invention has a laminated structure of two or more layers, and at least one of the outermost layers is made of the polyester containing the inert particles A and B. The other film layers constituting this laminated biaxially oriented polyester film may or may not contain the inert particles. However, when the inert particles are contained, the particle size of the inert particles is
It is preferable that the particle size is smaller than the particle size of No. 1 and the addition amount is such that the surface property of the film layer is flatter than the surface property of the layer containing the inert particles A and B.

In the laminated biaxially oriented polyester film of the present invention, the thickness of the film layer containing the inert particles A and B must be 0.1 to 5 times the average particle diameter of the inert particles B. is there. When the thickness of the film layer is less than 0.1 times the average particle size, the particles contained therein are likely to fall off, which is not preferable. On the other hand, if the average particle size exceeds 5 times, the particles contained in the film layer are likely to overlap with each other, and coarse projections are formed on the film surface, which is not preferable. The thickness of the film layer is 0.2 to 4 times, more preferably 0.3 to 3 times, especially 0.4 to 2 times the average particle diameter of the inert particles B.
It is preferably double.

The laminated biaxially oriented polyester film of the present invention can be obtained by a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing a laminated unoriented film and then biaxially orienting the film. This laminated non-oriented film can be manufactured by a conventionally accumulated manufacturing method of a laminated film. For example, a method of laminating a film layer forming the surface and a film layer forming the opposite surface or the core layer in a melted state or a cooled and solidified state of polyester can be used. More specifically, it can be produced by a method such as coextrusion / extrusion lamination.

The film laminated by the above-mentioned method can be made into a biaxially oriented film by further carrying out according to the conventionally accumulated manufacturing method of the biaxially oriented film. For example, polyester is melted and coextruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. and an intrinsic viscosity of 0.4 to 0.
A laminated unstretched film of 8 dl / g was obtained, and the laminated unstretched film was uniaxially (longitudinal or transverse) (Tg-10).
At a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polyester) at a draw ratio of 2.5 times or more, preferably 3 times or more, and then T in a direction perpendicular to the drawing direction.
It is preferred to stretch at a temperature of g to (Tg + 70) ° C. at a draw ratio of 2.5 times or more, preferably 3 times or more. Further, if necessary, it may be stretched again in the machine direction and / or the transverse direction. In this way, the total draw ratio is preferably 9 times or more, more preferably 12 to 35 times, as the area draw ratio,
It is particularly preferably 15 to 25 times. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to (Tm-10) ° C. (where Tm: melting point of polyester), and preferably 180 to 250 ° C., for example. The heat setting time is preferably 1 to 60 seconds.

The laminated biaxially oriented polyester film obtained by the above method has a film surface hardness of 21.
As described above, it is preferably 23 or more, particularly 28 or more. If the film surface hardness is too low, scratch resistance deteriorates, which is not preferable.

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

(1) Average particle size of particles (d) Shimadzu CP-50 type Centrifugal particle size analyzer (Centrifugal Particle S
ize Analyzer). The particle diameter corresponding to 50 mass% is read from the integrated curve of 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 242-247
reference).

(2) Film surface roughness (Ra) It is a value defined by JIS-B0601 as the center line average roughness (Ra). In the present invention, a 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 fifth decimal place of the average value of the remaining four data is rounded off and displayed up to the fourth decimal place.

(3) Coefficient of static friction (μs) A fixed glass was placed under the two laminated films, and the film under the laminated films (the film in contact with the glass plate) was rolled at a constant speed. Pick up at (about 10
cm / min), the detector is fixed to one end of the upper film (the end opposite to the take-up direction of the lower film), and the tensile force (F) between the films is detected. The thread used at that time has a lower area of 50 cm ² (80 mm × 62.5 mm), the surface in contact with the film is 80 ° neoprene rubber, and its weight (P) is 1 kg.

The static friction coefficient is calculated by the following formula.

[0056]

[Equation 1]

(4) Scraping property of calendar The scraping property of the running surface of the base film is evaluated by using a three-stage mini super calender. The calender is a three-stage calender of nylon roll and steel roll, the processing temperature is 80 ° C, the linear pressure applied to the film is 200 kg / cm,
The film speed is 100 m / min. The running film is run for a total length of 4,000 m, and the abrasion of the base film is evaluated by the dirt attached to the top roller of the calender at the time. <5 step judgment> 1st class: Nylon roll has no stains 2nd class: Nylon roll has almost no stains 3rd class: Nylon roll has stains, but it can be removed easily by wiping 4th grade: Nylon roll stains It is difficult to remove with a wipe,
Can be wiped off with a solvent such as acetone Grade 5: Nylon rolls are extremely dirty and difficult to remove even with solvents

(5) Scratch Judgment The base film was slit into a 1/2 inch width, and the film was applied to the same fixed rod as in the above (2) friction coefficient measurement up to an angle of 30 °, and the film speed was 4 m / sec for 200 m.
The thickness, depth, and number of scratches that entered the surface of the 1 / 2-inch wide base film were made to run, and the judgment was made in the following five stages. <5-level judgment> Grade 1: No scratches are found on the 1/2 inch width base film Class 2: Almost no scratches are found on the 1/2 inch width base film (1-2 pieces) Class 3: 1 / Scratches are found on the 2-inch width base film (3 to 8 lines) Grade 4: 1/2 inch width base film with some thick scratches (9 to 19 lines) Grade 5: 1/2 inch width base A large number of thick and deep scratches are found on the film (20 or more)

(6) Blade Scraping Property The following measurement is performed using the apparatus shown in FIG. Figure 1
Among them, 1 is an unwind reel, 2 is a tension controller, 3, 5, 6 and 8 are free rollers, 4 is a tension detector, 7 is a blade (a blade for an industrial razor tester manufactured by US GKI), and 9 is a guide roller. Denoted at 10 are take-up reels, respectively.

A sample film slit to a width of 1/2 inch was run for 100 m at a tension of 50 g and a running speed of 100 m / min so that the blade edge had an angle of 6 degrees, and was sharpened by the amount of shavings adhering to the blade edge. Evaluate.

This evaluation relates to the impact strength of the projections formed on the film surface, and corresponds well to the generation of shavings on a calendar or die coater in the magnetic tape manufacturing process. <Judgment> ◎: Adhesion width of shavings adhering to the blade edge is less than 0.5 mm ◯: Adhesion width of shavings adhering to blade edge is 0.5 mm or more and less than 1.0 mm △: Adhesion of shavings adhering to blade edge Width is 1.0 mm or more and less than 2.0 mm x: Shaving powder adhesion width attached to the blade edge is 2.0 mm or more

(7) Film surface hardness A diamond pyramidal pyramid indenter (the tip is a pyramid type, the facing angle is 136 °) on the base film on the glass plate.
And the twist angle is 148 ° 7 ') and the load (P) is 25g.
Then, the value is obtained by dividing the load by pressing for 10 seconds and dividing the load by the area of the depression formed after the weight is removed.

[0063]

[Equation 2]

[0064]

EXAMPLES The present invention will be further described below with reference to examples.

[0065]

Examples 1 to 6 and Comparative Examples 1 to 3 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, and antimony trioxide as a polymerization catalyst,
Phosphorous acid was added as a stabilizer, and the additive particles shown in Table 1 were further added as a lubricant and polymerized by a conventional method to obtain polyethylene terephthalate for layer A and layer B having an intrinsic viscosity of 0.62 (orthochlorophenol, 35 ° C.). Obtained.

Next, the polyethylene terephthalate for the A layer and the B layer were each dried at 170 ° C. for 3 hours and then fed to separate extruders of the coextrusion film forming machine, and the thickness ratio of the A layer and the B layer was 3:97. Was coextruded from a two-layer die to obtain an unstretched film.

The unstretched film thus obtained is preheated at 75 ° C., and further 10 mm between low speed and high speed rolls.
It was heated from above by an IR heater having a surface temperature of 850 ° C., stretched 3.1 times, rapidly cooled, and then supplied to a stenter and stretched laterally 4.0 times at 100 ° C.

Subsequently, preheat at 110 ° C.,
The film was stretched 1.8 times in the machine direction between low speed and high speed rolls.
The obtained biaxially stretched film was heat set with hot air at 215 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 7.5 μm.

Table 1 shows these characteristics.

As is apparent from Table 1, the material according to the present invention has a low coefficient of static friction and good sliding property, and is also very excellent in scratching property, calendering property and blade sharpening property. In addition, F-of these films
5 value longitudinally 19 kg / mm ^2, was transverse 12 kg / mm ^2.

[0071]

[Table 1]

[0072]

According to the present invention, it is possible to provide a laminated biaxially oriented polyester film which is excellent in slipperiness, abrasion resistance and scratch resistance and is particularly useful as a base film for magnetic recording tapes.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for measuring blade sharpness of a film.

[Explanation of symbols]

 1 Feeding reel 2 Tension controller 3, 5, 6, 8 Free roller 4 Tension detector (entrance) 7 Blade 9 Guide roller 10 Take-up reel

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B29L 9:00 4F

Claims (4)

[Claims] 1. Inert particles A having a Mohs hardness of 6 or more and an average particle diameter dA of 0.02 to 0.3 μm are formed on at least one surface of a biaxially oriented polyester film in an amount of 0.05 to 1. 0.001 of inert particles B containing 5% by weight, having a Mohs hardness of less than 3, an average particle size dB of 0.2 to 1.5 μm and larger than the average particle size dA.
A laminated biaxially oriented polyester comprising a polyester containing 1 to 1% by weight and having a layer thickness of 0.1 to 5 times the average particle size dB of the inert particles B. Film. 2. The laminated biaxially oriented polyester film according to claim 1, wherein the inert particles A are aluminum oxide particles and / or titanium oxide particles. 3. The laminated biaxially oriented polyester film according to claim 1, wherein the inert particles B are particles made of a silicone resin. 4. The laminated biaxially oriented polyester film according to claim 1, wherein the inert particles B are particles made of a crosslinked polystyrene resin.