JPH10751A - Biaxially oriented laminated polyester film for magnetic recording media - Google Patents

Abstract

(57) [Abstract] (with correction) [Problem] Surface flatness, winding property of tape pancake,
Provided is a polyester film for a magnetic recording medium, which has excellent running durability (scratch resistance and scratch resistance) and electromagnetic conversion characteristics and can be manufactured at low cost. SOLUTION: This is a biaxially oriented laminated polyester film in which a polyester A layer (A1 layer, A2 layer) is laminated on both sides of a polyester B layer, and the thickness of each layer is B layer> A1 layer>
A2 layer, and the polyester A layer has a large particle size of 0.00
1-0.1% by weight, 0.05-0.5% by weight of medium-sized particles, and 0.01-0.5% of small-sized aggregated particles having an average secondary particle size of 0.01-0.3 μm. %, And the polyester B layer contains particles having an average particle size of 0.3 to 3.0 μm, and the air bleeding time (T: seconds) and the average sharpness (L) of the protrusions of the medium-sized inert particles. Ratio (T / L) is 50 to 500
8000. A biaxially oriented laminated polyester film for magnetic recording media, wherein

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film for a magnetic recording medium.
In particular, a magnetic recording medium that is excellent in pancake winding property, running durability (abrasion resistance and scratch resistance) and electromagnetic conversion characteristics when formed into a tape with a flat surface, and can be manufactured at low cost. The present invention relates to an axially oriented laminated polyester film.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate films are widely used as base films for magnetic recording media, for example, for magnetic tapes and floppy disks, because of their excellent physical and chemical properties. ing.

[0003] In such a biaxially oriented polyester film, the winding property of the magnetic tape is generally to ensure the slipperiness of the polyester film.
The abrasion resistance and scratch resistance typified by slipperiness and running durability are important factors that determine the workability of the film manufacturing process and the machining process in each application, as well as the quality of the product quality. ing.

[0004] If the slipperiness of the polyester film is insufficient, for example, when the film is wound into a roll, wrinkles are formed or blocking occurs, and the roll surface becomes uneven, lowering the yield of the product, and tension, contact pressure, and The proper range of speed is narrowed and it is very difficult to wind up. Also, when processed as a magnetic tape and run in a video tape recorder, if the slippage is poor, the running tension increases and the running stops or shavings are generated, and the lack of the magnetic recording signal, that is, the cause of dropout Also. Also, when winding into a magnetic tape cassette, the winding becomes soft, which makes the running on the video tape recorder unstable. May occur.

In general, to improve the slipperiness of a polyester film, (1) a method of precipitating inert particles from a catalyst residue in a production process of a raw material polymer, (2) a method of adding inert particles to the film, and the like. A method of imparting irregularities to the surface is adopted. These particles are
The larger the size and the higher the content,
Great improvement in slipperiness.

On the other hand, a base film for a magnetic recording medium is required to be as flat as possible.
If the surface roughness of the base surface is rough, when processing into a magnetic tape, irregularities on the surface of the base film protrude from the magnetic layer surface even after the application of the magnetic layer, deteriorating the electromagnetic conversion characteristics. In this case, the larger the size of the particles in the base film and the greater the content thereof, the rougher the surface roughness becomes, and the worse the electromagnetic conversion characteristics become.

[0007] As a means for achieving both the contradictory characteristics of the improvement of the slipperiness and the improvement of the electromagnetic conversion characteristics as described above, by forming a laminated film, the surface on which the magnetic layer is applied is flattened to improve the electromagnetic conversion characteristics. Means for improving the slipperiness by roughening the opposite surface are widely known.

However, this method has drawbacks in that the slipperiness of the two surface layers is significantly different, so that wrinkles are generated in the processing step, and that the coating speed cannot be increased due to poor slipperiness on the magnetic layer application surface side. Was.

In the method for producing a biaxially oriented polyester film, the molten polyester extruded into a sheet is cooled and solidified to obtain an unstretched film, which is subsequently subjected to sequential biaxial stretching to obtain desired mechanical properties. However, at this time, in order to stretch the film in the horizontal direction, it is common practice to grip the edge of the film with a clip and move the film on a rail installed so as to gradually increase the width. This edge portion cannot be a final product and is discarded, or is collected and reused.

However, in the case of a two-layer laminated film, when the recovered film is reused as a raw material polymer, the surface roughness changes due to the mixture of particles of both surface layers. Also, JP-A-51-53585
No. 3 proposes to reuse the film collected in the core layer of the three-layer film, but in order to prevent the particles contained in the core layer from affecting the surface layer, it is necessary to increase the thickness of the surface layer. However, there is a drawback that only characteristics which are not different from those of a single-layer film can be obtained.

[0011]

SUMMARY OF THE INVENTION The present inventor satisfies the aforementioned conflicting demands of improving the slipperiness of the film surface and improving the electromagnetic conversion characteristics, and dramatically improving the winding property of a magnetic tape. As a result of extensive research on the issue of how to achieve low scratch resistance at the same time as satisfying both scratch resistance and abrasion resistance represented by running durability, as a result of reducing the thickness of the surface layer Focusing on the lowering of the surface roughness, the particle size and content of the particles contained in the surface layer,
The type, shape, and the type and content of the surface treatment agent for improving the dispersibility of the particles and the particles, and the particle size and the content of the particles included in the surface layer thickness and the core layer are determined by a specific method. If it is in the range, it is excellent in winding property when running as a magnetic tape, running durability, slipperiness, electromagnetic conversion characteristics, and it is possible to obtain a biaxially oriented laminated polyester film at lower manufacturing cost, The present invention has been reached.

[0012]

That is, the present invention provides a polyester A layer (A1 layer, A2 layer) on both sides of a polyester B layer.
Layers), the thickness of each layer is B layer> A1 layer> A2 layer, and the polyester A layer has a large particle diameter of 1.0 to 3.0 μm. 0.001 to 0.1% by weight of at least one of the active particles, 0.05 to 0.5% by weight of at least one of the medium-sized inert particles having an average particle diameter of 0.3 to 1.0 μm, Further, the polyester B layer contains 0.01 to 0.5% by weight of small-sized inert particles (agglomerated particles) having an average secondary particle size of 0.01 to 0.3 μm, and the polyester B layer has an average particle size of 0.3 μm. 3.0μ or more
m or less, and the volume shape factor ratio of medium-sized inert particles to large-sized inert particles in the particles (medium particle size / large particle size)
Is 0.5 to 1, and the ratio (T / L) of the air bleeding time (T: second) to the average sharpness (L) of the protrusions of the medium-sized inert particles is 5
The biaxially oriented laminated polyester film for a magnetic recording medium, wherein the sum of the content of the medium-sized particles and the large-sized particles (CB) satisfies the following formula.

[0013]

CB = CA × (DA / DB) × (R / (1-R)) (where CA is the content of the large-sized inert particles in the polyester A layer and the content of the medium-sized inert particles) Sum of contents (% by weight),
CB is the sum (wt%) of the content of the large-sized inert particles and the content of the medium-sized inert particles in the polyester B layer, DA is the total thickness of the polyester A layer (μm), and DB is the polyester B layer , R is a numerical value of 0.3 to 0.7. )

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and a fatty acid glycol as a main glycol component. Such polyesters are substantially linear and have film forming properties, in particular by melt molding. Examples of the aromatic dicarboxylic acid include, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Can be. As the aliphatic glycol, for example, a polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol or the like, or an alicyclic ring such as cyclohexanedimethanol is used. Group diols and the like.

In the present invention, it is preferable that the polyester is mainly composed of alkylene terephthalate and / or alkylene naphthalate.

Among such polyesters, in particular, polyethylene terephthalate, polyethylene-2,6-naphthalate and the like, for example, 80% of all dicarboxylic acid components
A copolymer in which at least mol% is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid and at least 80 mol% of all glycol components is ethylene glycol is preferred. At that time, not more than 20 mol% of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Acid; an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid; Further, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol.
Resorcinol, 2,2-bis (4-hydroxyphenyl)
Aromatic diols such as propane; and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol can also be used.

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

Further, the polyester in the present invention includes:
An amount in the range that is substantially linear, for example, 2 for the total acid component
It also includes those obtained by copolymerizing a polycarboxylic acid or a polyhydroxy compound having a functionality of 3 or more, such as trimet acid and pentaerythritol, in an amount of not more than mol%.

The polyester is known per se and can be produced by a method known per se.
The polyester has an intrinsic viscosity of about 0.3 measured at 35 ° C. as a solution in o-chlorophenol.
Those having 4-0.9 are preferred.

In the biaxially oriented laminated polyester film of the present invention, the polyester A layer and the polyester layer B are made of the above polyester, but the polymer of each layer may be the same or different. Among them, the same is preferable.

The biaxially oriented laminated polyester film of the present invention comprises a polyester A layer and a polyester B layer.
The layer contains large, medium and small inert particles, B
The layer contains at least large and medium size inert particles. These inert particles include, for example, (1) silicon dioxide (including hydrate, silica sand, quartz, etc.); (2) alumina of various crystal forms; and (3) at least 30% by weight of SiO _2. Silicates (eg, amorphous or crystalline clay minerals, aluminosilicates (including calcined and hydrated products), hot asbestos, zircon, fly ash, etc.); (4) Mg, Z
oxides of n, Zr, and Ti; (5) Ca, and B
(6) Li, Ba, and Ca phosphates (including monohydrogen and dihydrogen salts); (7) Li, Na, and K benzoates; (8) Ca, Ba , Zn, and terephthalates of Mn; (9) Mg, Ca, Ba, Z
titanates of n, Cd, Pb, Sr, Mn, Fe, Co and Ni; (10) chromates of Ba and Pb;
(11) carbon (eg, carbon black, graphite, etc.); (12) glass (eg, glass powder, glass beads, etc.); (13) carbonates of Ca and Mg; (14) fluorite; (15) ZnS; 16) a spinel oxide such as MgAl ₂ O ₄ or a modified spinel oxide comprising alumina and another oxide; (17) heat-resistant polymer particles (for example, cross-linked silicone resin particles, cross-linked acrylic resin particles, cross-linked polystyrene particles) , Crosslinked styrene-acrylic resin particles, crosslinked polyester particles, Teflon particles, polyimide particles,
Polyimide-amide particles, melamine resin particles and the like). More preferably, heat-resistant polymer particles and synthetic inorganic particles (for example, calcium carbonate, silica, etc.) are exemplified. These preferably have a narrow particle size distribution, and have a relative standard deviation of 0.3 or less, more preferably 0.2 or less, especially 0.1 or less.
It is preferably 5 or less.

In the present invention, the inert particles having a large particle diameter contained in the polyester A layer have an average particle diameter of 1.0 to 3.0.
It needs to be 0 μm. Preferably 1.0 to
2.0 μm, more preferably 1.0 to 1.5 μm
m. If the average particle size exceeds 3.0 μm, the difference in the height of the protrusions formed by the large-sized inert particles and the medium-sized inert particles becomes too large, so that the surface becomes rough, and the winding properties and the electromagnetic conversion characteristics are increased. And the shaving property also worsens. On the other hand, when the thickness is less than 1.0 μm, the running property deteriorates, which is not preferable. The content of the large inert particles is 0.001 to
0.1% by weight is required, preferably 0.005 to
It is 0.08% by weight, more preferably 0.01 to 0.05% by weight. If the content is less than 0.005% by weight, the electromagnetic conversion characteristics are improved, but the running property is deteriorated. On the other hand, if it exceeds 0.1% by weight, the electromagnetic conversion characteristics and the shaving property deteriorate. The types of the large-sized inert particles may be two or more, but in that case, the total content needs to be 0.001% by weight or more and 0.1% by weight or less.

The polyester A layer simultaneously has an average particle size of 0.3 to 1.0 μm, preferably 0.3 to 0.8 μm,
More preferably, 0.3 to 0.65 μm of the medium-sized inert particles are contained in an amount of 0.05 to 0.5% by weight, preferably 0.1 to 0.5% by weight.
It is necessary to contain 4% by weight, more preferably 0.15 to 0.3% by weight. The medium-sized inert particles are particles existing between the small-sized inert particles in the background portion of the film and the large-sized inert particles contributing to the improvement of the winding property. If the medium-size inert particles are not contained, or if the average particle size is less than 0.3 μm or the content is less than 0.05% by weight, the film This slows air release, and in spite of the addition of large particles, deteriorates the winding property and the slipperiness. On the other hand, if the average particle size is larger than 1.0 μm or the content exceeds 0.5% by weight, the film surface is roughened, and the electromagnetic conversion characteristics are deteriorated. There may be two or more kinds of medium-sized inert particles contained in the polyester A layer, but in that case, the total content needs to be 0.05 to 0.5% by weight.

Further, the ratio (T / L) of the average sharpness (L) of the projections of the medium-sized particles to the air bleeding time (T: seconds) of the film is 50 to 500,000, preferably 500 to 500.
In the case of 500,000, it is possible to further improve the winding property of a magnetic tape. This air bleeding time (T) is preferably 3,000 seconds or less, and more preferably 2,500 seconds or less.

The polyester A layer further has an average secondary particle size of 0.01 to less than 0.3 μm, preferably 0.05 to 0.3 μm.
0.25 μm small particle size inert particles (agglomerated particles)
It is necessary to contain 1 to 0.5% by weight. The small-sized inert particles are often generated in order to prevent the background portion of the film from becoming too flat and / or when rubbing against a metal pin such as a guide pin or a plastic pin which has been recently adopted for cost reduction. It is used to prevent scratches (scratch on the film) and shavings of the film. If the small-sized inert particles are not contained, or the average secondary particle size is less than 0.01 μm, or if the content is less than 0.01% by weight, blocking between films increases, Not only does the winding property of the magnetic tape deteriorate, but also the scratch resistance and the abrasion resistance decrease. If the average secondary particle size is larger than 0.3 μm or the content exceeds 0.5% by weight, the film surface is roughened, the plastic pin is shaved, and the electromagnetic conversion characteristics are reduced due to the generation of shaving powder. make worse. The type of the small-sized inert particles contained in the polyester A layer may be two or more.

Also, the small-sized inert particles (agglomerated particles)
Has an average cohesion of 5 or less in the film,
5, preferably 3-5. As the particle type, those having a high Mohs hardness are preferable, and specifically those having a Mohs hardness of 5 to 9, and more preferably 6 to 8 are preferable. In this case, scratch resistance is well exhibited. Specific examples of the particle type include alumina, spinel-type oxide, silicon oxide, and titanium oxide. Among them, alumina (especially, θ-type crystal) and spinel-type oxide (especially, alumina and other oxides) Complex oxides, especially those composed of alumina and magnesium oxide) are good.

Further, in the polyester A layer, alkali metal salts of carboxylic acids (for example, 2Na succinate, 3Na citrate, 2Na tartaric acid, especially succinic acid) are used as a surface treatment agent for improving the dispersibility of the inert particles having a small particle diameter. 2Na) in an amount of 0.01 to 1% by weight, and more preferably 0.1 to 1% by weight based on the amount of the inert particles having a small particle diameter.
The content is preferably 1 to 1% by weight, particularly 0.3 to 1% by weight. By adding this surface treatment agent, the winding property and the scratch resistance can be further improved.

In the present invention, the polyester A layer (A1
(A2 layer) must be thinner than the polyester B layer. If the thickness of the A layer is larger than that of the B layer, the surface will not be flat and will have the same characteristics as a single-layer film. Further, the A1 layer needs to be thinner than the A2 layer. A
The thickness of the two layers is preferably 0.1 μm or more. When the thickness is less than 0.1 μm, the polyester layer containing and retaining the inert particles becomes too thin, and the contained inert particles (particularly, large particles) easily fall off, and the surface property is further flattened. As a result, the slip property deteriorates.

If the thickness of the polyester A layer is smaller than the layer B, the surface roughness is reduced. If the thickness is within this range, the particles contained in the core layer (layer B) may protrude into the surface layer (layer A). Three factors can be considered: the number of particles decreases, the number of particles in the surface layer decreases, and the arrangement regularity of particles develops. As a phenomenon, the surface roughness decreases as the layer becomes thinner. At this time, the high protrusions on the surface layer do not change, and the small protrusions on the background portion decrease in large quantities, so that the surface roughness sharply decreases. The thickness difference between the polyester A layers, that is, the A1 layer and the A2 layer, is preferably 0.3 μm or more from the viewpoint of achieving both the slipperiness and the electromagnetic conversion characteristics. More preferably, it is 0.5 μm or more.

Further, in the present invention, the polyester B layer comprises inert particles having an average particle size of 0.3 to 3.0 μm, ie, large inert particles having an average particle size of 1.0 to 3.0 μm and an average particle size of 0.3 to 3.0 μm. Contains 0.3 to 1.0 [mu] m of medium-sized inert particles, and the content (CB) of the following formula:

[0031]

CB = CA × (DA / DB) × (R / (1-R)) (where CA is the content of large-sized inert particles and the content of medium-sized inert particles in the polyester A layer) Sum of weight (% by weight), C
B is the sum (% by weight) of the contents of the large particle size inert particles and the medium particle size inert particles in the polyester B layer, DA is the total thickness of the polyester A layer (μm), and DB is the thickness of the polyester B layer ( μm) and R are numerical values of 0.3 to 0.7. )

Satisfies the following. When R (value) in the above formula exceeds 0.7, the content of the large-sized inert particles and the medium-sized inert particles contained in the polyester B layer increases,
The difference from the single layer film is reduced, and polyester B
When the recovered film is used as the raw material of the layer, the fluctuation of the surface roughness of the polyester A layer becomes large. While R
Even when the (value) is less than 0.3, the fluctuation of the surface roughness of the polyester A layer becomes large when the recovered film is used. Preferred R (value) is 0.4 to 0.6.

When the average particle size of the large-sized inert particles contained in the polyester B layer is larger than 3.0 μm, the influence on the surface properties of the polyester A layer is increased, and the electromagnetic conversion characteristics are deteriorated.

The polyester B layer has an average particle size of 0.3 μm.
It may or may not contain inert particles having a small particle size less than. For example, when the recovered film is used as a part of the raw material, the average particle size of the polyester B layer is 0.01 μm.
Although the inert particles having a small particle diameter of 0.3 μm or less are contained, the inert particles having a small particle diameter have no or little effect on the surface characteristics of the polyester A layer. Particles may be contained.

The ratio of the volume shape factor of the large-sized inert particles to the medium-sized inert particles contained in the polyester B layer (large particle size /
(Medium particle size) is 0.5 to 1. If this ratio is less than 0.5, the winding property is reduced, and it is difficult to adjust the air bleeding time. The volume shape factor of the large inert particles is 0.3 to
It is preferably 0.52.

The total thickness of the polyester film of the present invention is preferably at least 10 μm. When the thickness is less than 10 μm, when the recovered film is applied to the polyester B layer, the effect on the polyester A layer is manifested, and specifically, protrusions due to particles contained in the recovered film on the film surface are remarkable. Therefore, it is not preferable because desired surface properties cannot be obtained.

The biaxially oriented laminated polyester film of the present invention can be basically obtained by a method conventionally known or accumulated in the art. For example,
First, a laminated unstretched film is produced, and then the film is biaxially oriented. This laminated unstretched film can be produced by a conventionally accumulated method for producing a laminated film. For example, a method of laminating a film layer (polyester A layer) forming a surface and a film layer (polyester B layer) forming a core layer in a molten state or a state of being cooled and solidified can be used. More specifically, it can be manufactured by a method such as co-extrusion or extrusion lamination.

The unstretched film laminated by the above-mentioned method can be further made into a biaxially oriented film according to a conventionally accumulated method for producing a biaxially oriented film. For example, a single-layer unstretched film and a laminated unstretched film are uniaxially (longitudinal or transverse) (Tg-10) to
Stretched at a temperature of (Tg + 70) ° C. (however, Tg: glass transition temperature of polyester) at a magnification of 2.5 to 7.0 times,
Next, in the direction perpendicular to the above-mentioned stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching becomes the horizontal direction).
It can be produced by stretching at a temperature of +70) ° C at a magnification of 2.5 to 7.0 times. In this case, the area stretching ratio is 9 to 32.
It is preferably doubled, more preferably 12 to 28 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching. Further, the biaxially oriented film is (Tg + 70) to Tm (° C.)
Can be heat-set at a temperature of For example, for a single-layer or laminated polyethylene terephthalate film, 19
It is preferable to heat set at 0 to 230 ° C. The heat setting time is, for example, 1 to 60 seconds.

The biaxially oriented laminated polyester film of the present invention can be used as a polymer for a core layer by a simple device using the edge portion of a biaxially stretched film which cannot be a final product as long as the above conditions are satisfied. It is possible to supply biaxially oriented polyester film at a low cost, which makes it possible to reuse, and as a result, has excellent surface properties, i.e., excellent slipperiness, excellent abrasion, and excellent electromagnetic conversion properties when used as a magnetic tape. It has the feature of being able to.

The various physical properties and properties in the present invention are measured and defined as follows.

(1) Average particle size (DP) of large particle size inert particles and medium particle size inert particles CP-50 type centrifugal particle size analyzer (Centrifugal Paticl) manufactured by Shimadzu Corporation
e Size Analyzer). The particle size corresponding to 50 mass% is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the residual amount, and this value is defined as the above average particle size. (Book "Particle Size Measurement Technology", published by Nikkan Kogyo Shimbun, 1975, pages 242-2)
47).

(2) Average secondary particle size of small-sized inert particles (agglomerated particles) A film containing the particles is formed into an ultra-thin section having a thickness of 100 nm in the cross-sectional direction, and the transmission electron microscope (for example, JEOL JE)
When the particles are observed at a magnification of about 100,000 times using M-1200EX), aggregated particles (secondary particles) can be observed.
Using this photograph, the diameter equivalent to the area circle of each particle was measured for 1000 particles using an image analyzer or the like, and the average particle diameter was determined to be alumina and / or a composite oxide composed of alumina and other oxide particles. The average particle size of the particles was used. The identification of the particle type can be performed using SEM-XMA, quantitative analysis of metal elements by ICP, or the like.

(3) Average Agglomeration Degree of Small Particle Inert Particles (Agglomerated Particles) For the 1000 agglomerated particles observed from the photograph obtained in the measurement of the average secondary particle size, several primary particles ( It is counted whether the particles are made of the smallest particles that cannot be further divided), and the value obtained by dividing the sum of the primary particles by 1,000 is defined as the degree of aggregation.

(4) Mohs hardness of inert particles (agglomerated particles) having a small particle diameter After purifying the inert particles having a small particle diameter, a value obtained by measuring the purified piece with a hardness meter is adopted.

(5) Addition amount of inert particles having a large particle diameter, inert particles having a medium particle diameter, and inert particles having a small particle diameter.
Burn for 3 hours or more in a furnace at about 0 ° C., mix the burning material in the crucible with terephthalic acid (powder) to make a 50 g tablet-shaped plate,
The addition value of the particles is determined by converting the count value of each element from the calibration curve for each element prepared in advance using the line. Fluorescent X
The X-ray tube used for measuring the X-ray is preferably a Cr tube, and may be a Rh tube. The X-ray output is set to 4 KW, and the spectral crystal is changed for each element to be measured.

(6) Film surface roughness (Ra) This is a value defined by JIS-B0601 as the center line average roughness (Ra). In the present invention, a stylus type surface roughness of Kosaka Laboratory Co., Ltd. Measure using a total meter (SURFCORDER SE-30C). The measurement conditions and the like are as follows.

(A) Palpation tip radius: 2 μm (b) Measurement pressure: 30 mg (c) Cutoff: 0.25 mm (d) Measurement length: 2.5 mm (e) How to summarize data: Repeat 6 times for the same sample Measure and remove the largest one, and display the average of the remaining five data.

(7) Surface protrusion peakness of inert particles of medium particle size Using a two-detection scanning coordinate electron microscope (EMM-3000) manufactured by Elionix Inc. and a shape profile at an accelerating voltage of 25 KV. A projection profile is output at 5000 times for 500 projections made of medium-sized inert particles. The projection apex of the output profile is A, the bending points at both ends of the projection are B and C, and the point D intersects perpendicularly with the connected straight line BC. The ratio of the length (μm) of the straight line AD to the straight line BC (AD / BC) ) Is defined as surface projection peakness: L.

(8) Volume Shape Factor of Inactive Particles A photograph of the inactive particles was taken with a scanning electron microscope at 5,000 magnifications in 10 fields of view, and the average value of the maximum diameter was measured using an image analyzer Luzex FS (manufactured by Nireco Co., Ltd.). Is calculated for each field of view, and an average value of 10 fields of view is calculated to be D. Using the average particle diameter d of the particles determined in the above item (1), the volume of the particles is calculated by V = (π / 6) × d ³ , and the shape factor f is calculated by the following equation.

[0050]

During Equation 4] f = V / D ³ expression, the volume of V is the particle (μm ^3), D is the maximum diameter of the particles (mu
m).

(9) Air bleeding time Using a digital Beck smoothness tester manufactured by Toyo Seiki Co., Ltd., 20 pieces of film were stacked, and the diameter of the 19 pieces except for the one in contact with the top of the sample table was measured. A hole of 5 mm is provided and placed on the sample stage. A load of 1 kg / square cm is applied and the degree of vacuum reached is set at 560 mmHg. After reaching 560 mmHg, air flows between the films in order to recover to normal pressure. The degree of vacuum is measured once every 30 seconds from the time when air starts to flow, and the measurement is performed for one hour. A straight line approximation was obtained from the degree of vacuum with respect to the obtained time.
The time required for the descent to fall by mmHg is defined as air bleeding time (seconds): T.

(10) Coefficient of running friction (μk) of the film Measured by using the apparatus shown in FIG. 1 as follows. In FIG. 1, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (entrance), and 7 is a stainless steel SUS304 fixing rod (outside). Diameter 5mmφ, surface roughness Ra
= 20 nm), 10 is a tension detector (outlet), 12
Denotes a guide roller, and 13 denotes a take-up reel.

In an environment at a temperature of 20 ° C. and a humidity of 60%, the surface of the non-magnetic layer of the magnetic tape is fixed at an angle θ = (152/1)
80) Contact with π radians (152O 2)
Move (friction) at a speed of 0 cm. When adjusting the tension controller 2 so that the entrance tension T1 becomes 35 g, the film is adjusted to have an exit tension (T2: g) of 5 gm.
After traveling 0 times, the exit tension detector detects the traveling friction coefficient, and calculates the traveling friction coefficient μk by the following equation.

[0054]

Μk = (2.303 / θ) log (T2 / T
1) = 0.868 log (T2 / 35)

(11) High-speed pin shaving (abrasion resistance and scratch resistance) A surface obtained by cutting a SUS sintered plate into a cylindrical shape from a film cut to a width of 1/2 inch in an environment of a temperature of 20 ° C. and a humidity of 60%. An angle θ = (60/180) π radian (60) is applied to a fixed guide pin having insufficient finish (surface roughness Ra = 0.15 nm).
O 2) Contact and run (friction) at a speed of 250 m / min and an entrance tension T1 = 50 g. 20 films
After traveling 0 m, the number of shavings adhering to the fixed guide pins and the number of film scratches after traveling were evaluated.

<Determination of shaved powder> 削: No shaved powder is observed at all ○: Shaved powder is slightly observed △: Existence of shaved powder is apparent at a glance ×: Shaved powder is strongly adhered <Scratch judgment > ：: No scratches are observed ○: 1 to 5 scratches are observed △: 6 to 15 scratches are observed ×: 16 or more scratches are observed

(12) Electromagnetic conversion characteristics VHS system VTR (BR640 manufactured by Victor Company of Japan, Ltd.)
0) was modified, and a 4 MHz sine wave was input to the recording / reproducing head through an amplifier, and recorded on a magnetic tape and reproduced.
The reproduced signal is input to a spectrum analyzer.
Measure the noise that occurs 0.1 MHz away from the carrier signal 4 MHz and measure the carrier to noise ratio (C / N).
Was expressed in dB. The magnetic tape was measured using this method, and the magnetic tape obtained in Comparative Example 1 was used as a reference (± 0d).
As B), the difference from this magnetic tape was taken as the electromagnetic conversion characteristic.

The magnetic tape was manufactured by the following method. 100 parts by weight of γ-Fe ₂ O ₃ (hereinafter simply referred to as “parts”) and the following composition were kneaded and dispersed in a ball mill for 12 hours.

Polyester polyurethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black 1 part Butyl acetate 70 parts Methyl ethyl ketone 35 parts Cyclohexanone 100 parts After dispersion further fatty acid: oleic acid 1 part Fatty acid : 1 part of palmitic acid Fatty acid: 1 part of ester (amyl stearate) was added and kneaded for 10 to 30 minutes. Further, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added,
The magnetic coating solution was prepared by high-speed column dispersion for 1 hour.

The obtained coating solution was applied on a polyester film so as to have a dry film thickness of 3.5 μm (applied to the polyester A1 layer side). Next, after performing an orientation treatment in a DC electromagnetic field, it was dried at 100 ° C. After drying, it is calendered and slit to 1/2 inch width.
A magnetic tape was obtained.

(13) Blade shaving In an environment of a temperature of 20 ° C. and a humidity of 60%, a film cut to a width of イ ン チ inch was attached to the blade edge of a blade (a blade for an industrial razor testing machine manufactured by GKI, USA) at an angle θ = (6). / 180)
π radian (60) contact and speed of 100m / min,
Run (friction) with entrance tension T1 = 50 g.
After the film has traveled 100 m, the amount of shavings attached to the blade is evaluated. 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 calender or a die coater in the magnetic tape manufacturing process.

<Judgment> A: The width of the shaving powder adhering to the blade tip is 0.5 mm
Less than ○: The width of the shaving powder adhering to the blade edge is 0.5 mm
Above and less than 1.0 mm △: The width of the shaving powder adhering to the blade tip is 1.0 mm
Above and less than 2.0 mm ×: The width of the shaving powder adhering to the blade tip is 2.0 mm
Less than

(14) Ra when recycled polymer is used
Fluctuation width The obtained laminated polyester film was pulverized by a cutter, extruded again and extruded into a sheet, and cut into chips. This recycled polymer was used in the polyester B layer at a ratio of 50% to the total thickness, and the shortage was supplemented with a particle-free polyester. The use of this recycled polymer was repeated 10 times, and the original Ra value and Ra of the laminated polyester film obtained at the 10th time were obtained.
And the difference.

<Judgment> A: Difference is 1 nm or less or does not change X: Difference exceeds 1 nm

[0065]

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

Examples 1 to 5, Comparative Examples 1 to 5 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and a lubricant as a lubricant By adding the additive particles shown in the polyester A layer of Tables 1 and 2,
Polymerization was carried out by a conventional method to obtain 0.56 intrinsic polyethylene (orthochlorophenol, 35 ° C.) polyethylene terephthalate used for the polyester A layer.

For the polyester B layer, Table 1
The added particles shown in the polyester B layer No. 2 were added, and polyethylene terephthalate was obtained in the same manner as described above.

After drying these polyethylene terephthalate pellets at 170 ° C. for 3 hours, they are supplied to two extruder hoppers and melted at a melting temperature of 280 to 300 ° C., and are coated on both sides of layer B using a multi-manifold type coextrusion die. Was extruded on a rotating cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain a 200 μm-thick unstretched laminated film. Here, the drum surface side was an A1 layer, and the opposite drum surface side was an A2 layer.

The unstretched laminated film thus obtained was preheated to 75 ° C., and further 15 m between low-speed and high-speed rolls.
m, and it was stretched 3.2 times by heating with three IR heaters having a surface temperature of 800 ° C. from above, rapidly cooled, then supplied to a stenter, and stretched 4.3 times in the transverse direction at 120 ° C. .
The obtained biaxially oriented film was heat-set at a temperature of 205 ° C. for 5 seconds to obtain a heat-set biaxially oriented polyester film having a thickness of 14 μm.

The thickness of each layer of the co-extruded film is 2
The adjustment was performed by changing the discharge amount of the extruder, and when the thickness of the polyester A1 layer side was different from the thickness of the polyester A2 layer side, the adjustment was performed by narrowing the flow path on one side. The thickness of each layer was determined by the fluorescent X-ray method and the method of cutting a film into thin pieces and searching for a boundary surface by a transmission electron microscope.

Comparative Examples 6 and 7 A single-layer biaxially oriented polyester film was obtained in the same manner as in Example except that polyethylene terephthalate containing the particles shown in Table 3 was used and extruded with a normal single-layer die. Was.

The film characteristics thus obtained are shown in Tables 1 to 3. As is clear from Tables 1 to 3, when used according to the present invention for a magnetic recording medium, while exhibiting excellent electromagnetic conversion characteristics, it is excellent in slipperiness, abrasion, and even when a recycled polymer is used. , Ra are small and exhibit extremely excellent characteristics.

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

[Table 3]

[0076]

EFFECT OF THE INVENTION The biaxially oriented laminated polyester film of the present invention has a flat surface and a pancake winding property, running durability (scratch resistance, scratch resistance), and electromagnetic conversion characteristics, especially when formed into a tape. It has excellent characteristics as a base film of a magnetic recording medium and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a running friction coefficient measuring device.

[Explanation of symbols]

 Reference Signs List 1 unwinding reel 2 tension controller 3, 5, 6, 8, 9, 11 free roller 4 tension detector (entrance) 7 fixing rod 10 tension detector (exit) 12 guide roller 13 take-up reel

Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location // C08J 5/18 CFD C08J 5/18 CFD B29K 67:00 105: 16 B29L 7:00 9:00

Claims (5)

[Claims] 1. A biaxially oriented laminated polyester film in which a polyester A layer (A1 layer, A2 layer) is laminated on both sides of a polyester B layer, wherein the thickness of each layer is B layer> A1 layer>
A2 layer, the polyester A layer has an average particle size of 1.0 to
At least one kind of the large-sized inert particles having a diameter of 3.0 μm is used.
001-0.1% by weight, average particle size 0.3-1.0 μm
At least one of the inert particles having a medium particle size of 0.05 to 0.
5% by weight, and the average secondary particle size is 0.01 μm to 0.3
Inactive particles (agglomerated particles) having a small particle size of 0.01 μm to
5% by weight, and the polyester B layer contains particles having an average particle size of 0.3 μm or more and 3.0 μm or less, and has a volume shape factor of medium-sized inert particles and large-sized inert particles in the particles. The ratio (medium particle size / large particle size) is 0.5 to 1, and the ratio (T / L) between the air bleeding time (T: second) and the average peak degree (L) of the protrusions of the inert particles having a medium particle size. Is 50 to 500000,
A biaxially oriented laminated polyester film for a magnetic recording medium, wherein the sum (CB) of the content of the medium-sized particles and the large-sized particles satisfies the following expression. CB = CA × (DA / DB) × (R / (1-R)) (where CA is the content of the large particle inert particles in the polyester A layer and the content of the medium particle inert particles) Sum of contents (% by weight),
CB is the sum (% by weight) of the contents of the large particle size inert particles and the medium particle size inert particles in the polyester B layer, DA is the total thickness of the polyester A layer (μm), and DB is the thickness of the polyester B layer ( μm) and R are numerical values of 0.3 to 0.7. ) 2. The magnetic recording medium according to claim 1, wherein the large-sized inert particles contained in the polyester A layer are inert organic polymer particles, and have a volume shape factor of 0.3 to 0.52. Biaxially oriented laminated polyester film. 3. The small-sized inert particles contained in the polyester A layer are at least one selected from alumina particles having an average degree of aggregation of 1 to 5, spinel oxide particles, silicon oxide particles and titanium oxide particles. The biaxially oriented laminated polyester film for a magnetic recording medium according to claim 1. 4. A polyester A layer containing 0.01 mol of an alkali metal carboxylate as a surface treatment agent for inert particles having a small particle diameter.
The biaxially oriented laminated polyester film for a magnetic recording medium according to claim 1, wherein the content is from 1 to 1% by weight (based on the inert particles having a small particle diameter). 5. The biaxially oriented laminated polyester film for a magnetic recording medium according to claim 1, wherein the scratch resistance of the polyester A layer in a scratch resistance test is from 0 to 5.