JP3027267B2 - Biaxially oriented laminated polyester film for magnetic recording media - Google Patents

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, and more particularly, to a magnetic recording medium having excellent abrasion resistance and scratch resistance and little wear of a slit blade during processing. The present invention relates to a biaxially oriented laminated polyester film.

[0002]

2. Description of the Related Art Biaxially oriented polyester films represented by polyethylene terephthalate film are widely used for magnetic recording media because of their excellent physical and chemical properties.

[0003] In a biaxially oriented polyester film, its slipperiness and abrasion resistance are major factors that affect the quality of work in the film manufacturing and processing steps, and further, the product quality.

[0004] If these are insufficient, for example, when a magnetic layer is applied to the surface of a biaxially oriented polyester film and used as a magnetic tape, the friction between the coating roll and the film surface is so high that shaving powder is generated or the film surface is damaged. Scratch occurs. Also, when used for VTRs and data cartridges, shavings and scratches are generated in the process of high-speed winding into a cassette, causing D / O.

[0005] Particularly in VTR applications, recently, guide posts fixed in a cassette for cost reduction have been used.
Although a metal guide or a plastic guide whose surface is not sufficiently finished may be used, the surface of the guide post is extremely rough. For this reason, conventional techniques for improving the slipperiness and abrasion of a film, for example, a method of adding inorganic particles such as silicon oxide, titanium dioxide, calcium carbonate, talc, clay, calcined kaolin, etc. 57562
Or a method of precipitating fine particles containing calcium, lithium or phosphorus in a polymerization system (for example,
No. 32914), a magnetic tape without a back coat generates shavings and scratches in the process of high-speed winding into a cassette, and the D / O level increases.

To solve such a problem, a method of adding fine particles having a high Mohs' hardness to reduce the damage (for example, JP-A-1-306220, JP-A-2-185533)
No.) have been proposed.

However, although this method has an effect on a guide post for cost reduction, it has an insufficient improvement effect on a conventionally used metal guide having a good surface finish. There is also a method of improving the occurrence of scratches on a metal guide having a good surface finish by using inert particles that are slightly larger than the above-mentioned fine particles in combination. Have been.

[0008] Further, since high hardness particles are added, when a polyester film is produced or processed into a magnetic tape, the slit blade used is remarkably worn, and the life of the slit blade is shortened. This tends to cause an increase in D / O due to an increase in swarf and deterioration of the cut edge to make the sharpness of the garnish worse.

[0009]

SUMMARY OF THE INVENTION The inventor of the present invention has found that a metal guide having a good surface finish, a metal guide having a good surface finish, and a newly developed rough metal guide and plastic guide have been provided with good abrasion resistance. As a result of intensive research to develop a biaxially oriented polyester film for magnetic recording media having excellent scratch resistance, excellent slipperiness, and excellent abrasion of slit blades in production and processing steps, the present invention Reached.

[0010]

That is, the present invention relates to a laminated polyester film in which a polyester layer A is laminated on one side or both sides of a polyester layer B. The polyester layer A has a specific surface area of 50 m ² / g or more and 120 m ² or more. ² /
g and the total pore volume is 0.5 ml / g or more and 1.0 ml or less.
/ G or less, and θ-type aluminum oxide particles having an average particle size of 0.02 μm to 0.3 μm.
1% by weight or more and 1.0% by weight or less and one or more inert particles having an average particle diameter of more than 0.3 μm and 1.2 μm or less, and the sum of the thickness of the polyester layer A is 2 to 30% or less of the total thickness of the laminated polyester film, and the content per unit weight of θ-type aluminum oxide particles in the total thickness is less than 0.1% by weight. It is an axially oriented laminated polyester film.

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film forming properties, especially film forming by melt molding.

Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, anthracene dicarboxylic acid and the like. Can be mentioned.

The aliphatic glycol is, 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 cyclohexanedimethanol. Alicyclic diols and the like can be mentioned.

In the present invention, polyesters containing alkylene terephthalate and / or alkylene naphthalate as a main component are preferably used.

Among such polyesters, particularly, 80% by mole or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, especially polyethylene terephthalate and polyethylene-2,6-naphthalate. A copolymer in which 80% by mole or more of all glycol components is ethylene glycol is preferred.

At this 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 also fatty acids such as adipic acid and sebacic acid. Alicyclic dicarboxylic acids 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. For example, hydroquinone, resorcinol, 2,2
Aromatic diols such as 2-bis (4-hydroxyphenyl) propane; aliphatic diols having an aromatic ring such as 1,4-dihydroxydimethylbenzene; polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol (Polyoxyalkylene glycol) and the like.

In the polyester of the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid and an aliphatic oxyacid such as ω-hydroxycaproic acid may be used. Also included are those which copolymerize or bind at 20 mol% or less based on the total amount of the acid components.

Further, the polyester in the present invention may contain a tricarboxylic or polyfunctional polycarboxylic acid or polyhydroxy compound such as trimellit in an amount in a substantially linear range, for example, 2 mol% or less based on the total acid components. Those obtained by copolymerizing an acid, pentaerythritol and the like are also included.

The above polyesters are known per se and can be produced by a method known per se.

As the above polyester, those having an intrinsic viscosity of about 0.4 to about 0.9 measured at 35 ° C. as a solution in o-chlorophenol are preferred.

In the present invention, the θ-type aluminum oxide particles contained in the polyester layer A have a specific surface area of 50 m ^2.
/ G or more and 120 m ² / g or less, preferably 60 m ² / g
100 m ² / g or less, and the total pore volume is 0.5 ml
/ G to 1.0 ml / g, preferably 0.6 ml / g to 0.9 ml / g, and an average particle size of 0.02
It is not less than μm and not more than 0.3 μm.

When the specific surface area is less than 50 m ² / g, the primary particle diameter becomes large and the scratching property becomes good, but shaving powder is easily generated, and the metal guide having a good surface finish is often damaged. Become. 120
If it exceeds m ² / g, the primary particle diameter becomes too small and no more sufficient protrusions can be obtained, so that the generation of shavings is reduced, but the scratching property is deteriorated.

On the other hand, if the total pore volume is less than 0.5 ml / g, the particles are not porous, the affinity with the polyester is lowered, and shavings are easily generated. Meanwhile, 1.
If it exceeds 0 ml / g, the particles become brittle and break during stretching for biaxial orientation, and cannot be formed into relatively large projections which are effective in damaging a metal guide having a good surface finish.

Furthermore, the average secondary particle size is 0.02 μm
If it is less than 1, the particles become too fine, and fine projections required for scratch resistance and chipping resistance cannot be formed. On the other hand, when it is larger than 0.3 μm, agglomeration of particles is too large and shaving powder is easily generated.

The content of the θ-type aluminum oxide particles is from 0.1% by weight to 1.0% by weight based on the polyester. When the content is less than 0.1% by weight, the effect of containing the particles is reduced. On the other hand, when the content exceeds 1.0% by weight, the particles are overlapped and shaving powder is easily generated.

[0027] The θ-type aluminum oxide particles are most suitable for satisfying both scratch resistance, abrasion resistance and slit blade wear resistance among the eight crystal forms of aluminum oxide.
In the case of α-type aluminum oxide particles harder than the θ-type aluminum oxide particles, even when the content is reduced, the wear of the slit blade is not improved. On the other hand, the particles softer than the θ-type aluminum oxide particles have poor scratch resistance.

In the present invention, the polyester layer A has an average particle diameter of 0.3 μm in addition to the θ-type aluminum oxide particles.
It is necessary to contain inert particles B exceeding 1.2 μm. This is because if there are no particles larger than the θ-type aluminum oxide particles, the coefficient of friction with respect to various guides will increase, not only deteriorating scratch resistance and chipping resistance, but also in the process of manufacturing a biaxially oriented laminated polyester film. This makes it difficult to handle, and the runnability when used as a base film for magnetic recording deteriorates.

The type of the relatively large inert particles is not particularly limited. For example, calcium carbonate, silicon dioxide, titanium oxide, aluminum oxide,
Any of inorganic inert particles such as kaolin, organic inert particles such as silicon particles and cross-linked polystyrene particles, and particles internally deposited by a polymerization catalyst may be used.

The content of the relatively large inert particles is as follows:
The content is preferably 0.05% by weight or more and 1% by weight or less based on the polyester.

In the present invention, the polyester layer A is laminated on one side or both sides of the polyester layer B, and the total thickness of the polyester layer A is 3% or more and 30% or less, preferably 7% or more of the total thickness of the laminated polyester film. 20% or less. Although the total thickness is not particularly specified,
m or more and 25 μm or less.

The content of the θ-type aluminum oxide per unit weight with respect to the total thickness is less than 0.1% by weight. If the content is 1.0% by weight or more, the abrasion of the slit blade deteriorates.

In the present invention, the polyester layer B contains
In particular, the inert particles need not be contained, but may be contained if they are softer than the θ-type aluminum oxide particles. The above-mentioned θ-type aluminum oxide particles may be contained as long as the content per unit weight of the total thickness does not exceed 0.1% by weight.

In the present invention, as a method for laminating the polyester layers A and B, a method conventionally known in the art can be used.

The biaxially oriented laminated polyester film is prepared by melt-extruding polyester A and polyester B at a temperature of, for example, melting point (Tm: ° C.) to (Tm + 70) ° C. using two extruders, and using a co-extrusion method. And stack
Obtain an unstretched film having an intrinsic viscosity of 0.35 to 0.9 dl / g, and place the unstretched film in a uniaxial direction (longitudinal or transverse direction).
(Tg-10) to (Tg + 70) ° C (T
g: glass transition temperature of polyester) of 2.5 to 5.0.
Then, the film is stretched at a temperature of Tg (° C.) to (Tg + 70) ° C. in a direction perpendicular to the stretching direction (when the first-stage stretching is in the longitudinal direction, the second-stage stretching is in the transverse direction). .5-
It can be manufactured by stretching at a magnification of 5.0 times. In this case, the area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching.

Further, the biaxially oriented film is (Tg + 7
0) It can be heat-set at a temperature of from 0 ° C. to Tm (° C.).
For example, a polyethylene terephthalate film is preferably heat-set at 190 to 230 ° C. The heat fixing time is, for example, 1 to 60 seconds.

The biaxially oriented laminated polyester film of the present invention contains a specific amount of aluminum oxide particles having a specific range of a specific surface area, a total pore volume, an average particle size and a θ-type crystal form, and further has a larger inertness. Since the polyester layer A containing one or more kinds of particles is laminated with the other polyester layer B, excellent clutch resistance can be obtained over all the metal guides with good surface finish, metal guides with insufficient surface finish, and plastic guides. It is highly useful for magnetic recording media because it has good abrasion and powder resistance and has little wear on the slit blade.

In the present invention, various physical properties and properties are measured and defined as follows.

(1) Average particle size (DP) of particles CP-50 type centrifugal particle size analyzer (Centrifugal Particle Size An) manufactured by Shimadzu Corporation
alyzer). The particle size corresponding to 50% by mass is read from the integrated curve of the particles of each particle size and its abundance calculated on the basis of the obtained centrifugal sedimentation curve, and this value is defined as the above average particle size (see Book “Particle Size Measurement Technology ”, published by Nikkan Kogyo Shimbun, 1975, pp. 242 to 247).

(2) Specific surface area of powder and total pore volume BET was performed using Autosorb-1 manufactured by Kantachrome.
The specific surface area and total pore volume are measured by the method.

(3) Flatness of Film Surface Ra (center line average roughness) is measured according to JIS B0601. Using a stylus type surface roughness meter (SURFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd., the radius of the needle is 2 μm and the load is 0.07.
A chart (film surface roughness curve) is drawn under the condition of g, and a portion of the measured length L is extracted from the obtained film surface roughness curve in the direction of the center line, and the center line of the extracted portion is defined as the X axis. When the roughness curve is represented by Y = f (x) using the direction of the vertical magnification as the Y axis, the value (Ra; μm) given by the following equation (Equation 1) is defined as the flatness of the film surface.

[0042]

(Equation 1)

In the present invention, when the reference length is set to 0.25 mm, 8
The number is measured, and Ra is expressed as an average value of five pieces excluding three pieces from the larger value.

(4) Scratch property and scraping property Measured as follows using the apparatus shown in FIG.
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), 7 is a fixed rod, 10
Is a tension detector (exit), 12 is a guide roller,
Reference numeral 13 denotes a take-up reel.

In an environment at a temperature of 20 ° C. and a humidity of 60%, the width 1 /
The film cut into 2 inches is fixed to the 7 fixed rod at an angle θ = 3.
The vehicle is run at a speed of 300 m / min at a speed of 300 m / min so that the inlet tension becomes 50 g, and the vehicle travels 200 m. The shavings attached to the fixed bar 7 after running and the scratches of the tape after running are evaluated.

At this time, a 6φ tape guide (surface roughness R) made of SUS304 and having a sufficiently finished surface was used as a fixing rod.
a = 0.015 μm) using the A method, and using a 6φ tape guide (surface roughness Ra = 0.15 μm) obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish. The method C is a method using a carbon black-containing polyacetal tape guide of 6φ.

<Determination of shaved powder> No shaved powder is observed at all. ○ Sharp powder is slightly observed. Not seen at all ○ 1-5 scratches are seen △ 6-15 scratches are found × 16 or more scratches are seen

(5) Low-speed repeated scratching In a device similar to FIG. 1 used for measuring the running friction coefficient μk, the fixed rod is reciprocated 50 times with a running length of 10 m. Then, the scratch of the tape after running is evaluated.

At this time, a 6φ tape guide (surface roughness R) made of SUS304 and having a sufficiently finished surface was used as a fixing rod.
a = 0.015 μm) using the A method, and using a 6φ tape guide (surface roughness Ra = 0.15 μm) obtained by bending a SUS sintered plate into a cylindrical shape and having an insufficient surface finish. The method C is a method using a carbon black-containing polyacetal tape guide of 6φ.

<Scratch Judgment> 見 No scratches are observed. ○ 1 to 5 scratches are observed. Δ 6 to 15 scratches are observed. × 16 or more scratches are observed.

(6) Abrasion of slit blade Using an industrial razor test blade manufactured by GKI USA,
The amount of wear of the blade blade when the slit is cut 500 m is measured using an electron microscope. <Judgment of slit blade wear> ◎ Wear amount of 1μm or less ○ Wear amount of more than 1μm and 2μm or less △ Wear amount of more than 2μm and 3μm or less × Wear amount of more than 3μm

[0052]

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

[0053]

Examples 1 to 3 and Comparative Examples 1 to 4 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 shown in Table 1 were used. The added particles shown in the polyester A layer are added, polymerized by a conventional method, and intrinsic viscosity (orthochlorophenol, 35 ° C.)
Polyethylene terephthalate to be used for 0.62 polyester layer A was obtained.

As the polyester B layer, polyethylene terephthalate was obtained in the same manner as described above except that no additional particles were added.

After drying these polyethylene terephthalate pellets at 170 ° C. for 3 hours, they are supplied to two extruder hoppers, melted at a melting temperature of 280 to 300 ° C., laminated using a multi-manifold type coextrusion die, and surface-finished. It was extruded on a rotating cooling drum having a surface temperature of 20 ° C. for about 0.3 s to obtain a 200 μm-thick unstretched laminated film.

The unstretched laminated film thus obtained is preheated to 75 ° C., and further cooled between low-speed and high-speed rolls.
mm, the sheet was heated by one IR heater having a surface temperature of 900 ° C., stretched 3.6 times, quenched, and subsequently supplied to a stenter, and stretched 3.9 times in the transverse direction at 105 ° C. .
The obtained biaxially oriented film was heat set at a temperature of 205 ° C. for 5 seconds to obtain a heat fixed biaxially oriented laminated polyester film having a thickness of 14 μm.

On the other hand, 100 parts by weight of γ-Fe ₂ O ₃ (hereinafter simply referred to as “parts”) and the following composition were 12 ball-milled.
The mixture was kneaded and dispersed for a time.

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 1 part of fatty acid ester (amyl stearate) was added and kneaded for 15 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 shearing dispersion for 1 hour.

The obtained coating solution was applied on the above-mentioned biaxially oriented laminated polyester film having a thickness of 14 μm to a dry film thickness of 3.5.
It was applied to a thickness of μm.

Next, after the orientation treatment in a DC magnetic field,
Dried at 0 ° C. After drying, it was calendered and slit to a 1/2 inch width to obtain a magnetic tape having a thickness of 17.5 µm.

Table 1 shows the characteristics of the magnetic tape thus obtained.

[0062]

[Table 1]

As is apparent from Table 1, the metal tape guide according to the present invention has excellent lubricity for magnetic recording media and has a sufficiently finished metal tape guide, and a metal whose surface is not sufficiently finished. Both the tape guide and the plastic tape guide have excellent abrasion resistance and scratch resistance, and also have excellent characteristics with respect to the abrasion of the slit blade.

[0064]

The biaxially oriented laminated polyester film of the present invention has excellent lubricity and has a metal tape guide with a sufficiently finished surface, a metal tape guide with a poorly finished surface, and plastic. The tape guide has excellent abrasion resistance and scratch resistance with respect to all the tape guides, and also has good abrasion resistance of the slit blade, and has extremely excellent characteristics as a base film of a magnetic recording medium.

[Brief description of the drawings]

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

[Explanation of symbols]

 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 Winding rule

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FIB29L 7:00 9:00

Claims (1)

(57) [Claims] 1. A laminated polyester film in which a polyester layer A is laminated on one side or both sides of a polyester layer B. The polyester layer A has a specific surface area of 50 m ² /
g or more and 120 m ² / g or less, and the total pore volume is 0.5
0.1 to 1.0% by weight of θ-type aluminum oxide particles having an average particle diameter of 0.02 to 0.3 μm. It contains one or more inert particles having an average particle size of more than 0.3 μm and not more than 1.2 μm, and the sum of the thickness of the polyester layer A is 3% of the total thickness of the laminated polyester film.
% To less than 30%, and the content per unit weight of θ-type aluminum oxide particles in the total thickness is less than 0.1% by weight. A biaxially oriented laminated polyester film for a magnetic recording medium.