JPS62248131A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the traveling performance and durability without deteriorating the electromagnetic transducing characteristics by roughening one of two surfaces of a biaxially stretched laminated film of a prescribed polyester and flattening the other so that each of the resulting rough and flat surfaces contains projections having a prescribed distribution. CONSTITUTION:A biaxially strentched laminated film is made of aromatic polyester contg. aromatic dicarboxylic acid as the principal acid component and aliphatic glycol as the principal glycol component. One of two surfaces of the film contg. inert particles has 0.010-0.025mum surface roughness and the projections has a distribution curve which does not intersect a straight line represented by a formula log10y=-9.8x+4.4 (where x is <=0.87mum height of the projections and y is the number of the projections) in the range of 2>log2y>1.3. A curve in a part larger than the maximum value of the distribution curve is within the range of log10y>=-18x+3.7. The other of two surfaces of the film is a flat surface having <0.10mum surface roughness. The height (x) in a part larger than the maximum value of the distribution curve of the projections intersects a curve represented by a formula log10y=-1.8x+3.7. The height (x) is <=0.13mum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium, and more particularly, two stretched 1-polyester films with different surface properties are used as a support and an electron beam hard pillow on a flat surface. In particular, a videotape characterized in that it is provided with a magnetic layer formed from a mold paint,
Concerning magnetic/magnetic recording media useful for audio tapes, etc.

BACKGROUND OF THE INVENTION Magnetic recording media based on polyester films, such as video tapes, audio tapes, computer tapes, and FP disks, are known and widely used.

In recent years, demands for higher density recording and higher quality have been increasing in these application fields, and with this, the polyester film that serves as the pace has a flat surface, excellent slipperiness, and durable running performance.

There is an increasing demand for excellent abrasion resistance.

Conventionally, methods for improving slipperiness have been proposed, such as adding inorganic particles such as silicon oxide or lucium carbonate to polynisdel, or precipitating fine particles containing calcium, lithium, or phosphorus within the polymerization system during polyester synthesis. has been done. In both methods, polyester film formation 1. 17. Protrusions are formed on the film surface due to fine particles. This improves the slipperiness of the film.

Only 1. Therefore, in the above-mentioned method of improving the slipperiness of a film using projections made of fine particles, the slipperiness improves as the film surface becomes rougher, but on the other hand, due to the roughening, it is difficult to apply magnetic paint. The subsequent surface tends to become rough and the electromagnetic conversion characteristics deteriorate.

As a way to solve these contradictory problems of flatness and slipperiness, a method has been proposed that uses composite particles that combine large-sized particles and small-sized particles. Layered films have a limit because both sides of the film have the same surface properties, and are not at a satisfactory level.

Therefore, several different surface films have been proposed in which one exposed surface has excellent slip properties and the other exposed surface is flat. ing.

However, even if the surface of the film to which Kmfim is applied, which is a flat, easy-to-slide film with different front and back sides, is applied using this method, if the opposite surface is too rough, the magnetic properties of the applied material may deteriorate. The unevenness of the rough surface of the film is transferred onto the layer surface, causing unevenness on the surface of the magnetic layer, resulting in loss of flatness and insufficient electromagnetic conversion characteristics.

The surface roughness of this base film does not affect the surface roughness of the magnetic layer, and the mechanism winds up the coating after applying the paint.
It is believed that when held at a curing temperature of 10 to 72 hours, so-called show-through occurs and surface roughness is transferred. In order to reduce this bleed-through phenomenon, the surface roughness of the base film should be made as small as possible1. Video tapes using such materials have a large coefficient of friction and have very poor running performance. To this end, attempts have been made to improve running properties by providing a back coat layer containing carbon blank, calcium carbonate, etc. on the base film on the side opposite to the magnetic layer. but,
The surface roughness of the back coat layer is also transferred from set-off K, and the electromagnetic conversion characteristics are lower than those without the bank coat layer.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium that improves the above-mentioned problems and has improved runnability and durability without impairing electromagnetic conversion characteristics.

Structure and Effects of the Invention The object of the present invention is to provide a two-wheel stretch laminate film comprising a film-forming aromatic polyester containing an aromatic dicarboxylic acid as the main acid component and an aliphatic glyfur as the main glyfur component.

One of the exposed surfaces (Side A) of the line laminated film has a surface roughness RaA of 0.025 μm or less and 0.010/n or more, and the number of protrusions determined in an area with 20 protrusions/mm2 or more (
The distribution curve representing the relationship between y: x/mm2) and the height of the protrusion (x: μm) is expressed by the formula (S10gt*F--9.8)C+4.4
+++ ・-(1) straight line and 2) log
It has a protrusion distribution that does not intersect in the range of t*F>1.3, and j! The curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the formula (2) 10aB)'≧-18x+3.7
-- Within the range of (2), and the protrusion height (x) is 0.
Those with a diameter of 87 μm or more provide a smooth surface that is substantially free of
The other exposed surface (Side B) of the laminated film has a surface roughness 11aB of less than 0.0 I 0 μm, and the number of protrusions (y: number of protrusions calculated in an area of 20 protrusions/mm2 or more).
mm2) and the height of the protrusion (x: μm), the curve of the portion larger than the maximum value of the protrusion distribution curve intersects the formula (3)% formula (3), and the protrusion height The laminated film provides a flat surface that is substantially free of particles having a diameter of 0.13 μm or more, and the laminated film has a thickness of 7.
The laminated film has a heat shrinkage rate of 0.1% or less in the longitudinal direction when subjected to heat treatment under no load for 1 hour at 0°C, and
This is achieved by a magnetic recording medium characterized in that a magnetic layer is provided by coating an electron beam-curable magnetic paint on the surface.

The biaxially oriented laminated polyester film used as the base film in the present invention is a laminated film comprising a layer providing a smooth surface and a layer providing a flat surface.

The layer providing this easy-slip surface (Side A) has a surface roughness RaA of 0.025 μm or less and a surface roughness of 0.01 μm or less.
The number of protrusions (y: x/mm2) and height of protrusions determined in an area where the protrusion height is 0 μm or more and the protrusion height Xl is 0.87 μm or more, and the number of protrusions is 20/mm2 or more. The distribution curve representing the relationship with the size (x: μm) is expressed by the following formula (
1) There is a protrusion distribution that does not intersect in the range of linear M2>logny>t and a, which is expressed by the formula % (1), and furthermore, the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the following formula ( 2) % formula %
(2) It has characteristics within the range of. If this surface roughness RaA is larger than 0.025 μm, the surface of the base film will be too rough, and even if the magnetic surface is mirror-finished in the magnetic powder coating process, the S surface will not be sufficiently flattened. , the electromagnetic conversion characteristics deteriorate 17, which is not preferable. Also, RaA is o
, if it is smaller than o t ops, the running performance will deteriorate,
Preferably L <no.

Preferable surface roughness RaA is 0.020μm or less 0.01
It is 25 μm or more.

Yet again. The distribution curve representing the relationship between the number of protrusions (y) and the protrusion height
If they intersect in the range of 7>1.3, the flatness of the in-plane surface will be impaired and the electromagnetic conversion characteristics will deteriorate, so 1.
(In addition to this, protrusions may be scraped off during the tape processing process, especially during the calender process.)

In addition, repeated use of the tape causes abrasion during use, which is undesirable because it increases the coefficient of friction and causes abrasion particles to adhere to the tape surface, increasing dropouts. Moreover, if the curve in the portion larger than the maximum value of the above distribution curve is not within the range of the above formula (2), the film surface will be too flat and the coefficient of friction (μk) after 200 repetitions will be 0.
．． It is difficult to satisfy the range of 15 to 0.35, so 1. is preferable. <No. In the above distribution curve, [the curve on the side exceeding the maximum value is -181+3.7≦10L*)'≦-9,8x+4.4
It is preferable to satisfy the range (however, "gn"> 1.3).
The presence of protrusions of .mu.m or more improves the running properties of the tape, but is not preferable because it causes the protrusions to be scraped during the processing process and also causes dropouts.

Furthermore, in the laminated polyester film of the present invention, the layer providing a flat surface (side B) has a surface roughness RaB of less than 0.010 μm and a protrusion height (x) of 0.13 μm as film *m* properties. The number of protrusions (y:
In the distribution curve representing the relationship between the protrusion height (x:μm') and the protrusion height (x: μm'), the curve of the portion larger than the maximum value of the protrusion distribution curve intersects the equation (3). We are prepared. This surface roughness RaB is 0
．． If the thickness is larger than 0.010 μm, it is not preferable because the electromagnetic conversion characteristics required for a high-quality magnetic recording tape cannot be maintained in the 12 spaces of the magnetic surface. Also, the number of protrusions is 2
In the distribution curve representing the relationship between the number of protrusions (y) and the height of the protrusions (xl) determined in the area of 0 pieces/mm2 or more, the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by the above formula (3).
If the film does not intersect with the 1-1 high-quality magnetic recording It is not preferred because it cannot maintain the necessary properties as a commercial tape.

Furthermore, the above-mentioned biaxially stretched laminated polynisdel film has the above-mentioned 1- film surface properties and at the same time
The heat shrinkage rate in the longitudinal direction is 0 when heat treated under no load for hours.
．． It is necessary to have the characteristic that it is 1% or less. Heat shrinkage rate is 0. If it exceeds 5%, the heat shrinkage rate after becoming a magnetic tape will be high and the skew characteristics will deteriorate.1. Preference 1. <No. In particular, when applying the electron beam curable magnetic paint of the present invention,
Because there is no long hardening process after application.

The heat shrinkage rate of the base film directly affects the heat shrinkage rate of the magnetic tape, and if the heat shrinkage rate is high, the skew characteristics will deteriorate.

Furthermore, in the present invention, an electron beam curable magnetic paint is applied on the flat surface (B side) of the above-mentioned base film.11. Form a magnetic layer. By forming this magnetic layer, even if the surface roughness of the opposite surface (A) of the base film is large, there will be no bleed-through or deterioration of the surface properties of the magnetic layer, and the bank foot layer will not deteriorate. Good electromagnetic conversion characteristics without the need for 1. A magnetic recording medium with good running properties can also be obtained.

As the electron beam curable magnetic paint, those used in this field can be used, and the basic ingredients are magnetic powder and electron beam curable binder; Other ingredients such as inhibitors are included.

Magnetic powder includes, for example, ferromagnetic γ-Feρ.

Co-containing 7Fa, 0. , metallic iron, Fe-Co
, Fe-Nt.

Fe-Co-Ni, Fe-Co-B, Fe-C
Examples include powders such as o-Cr-B.

As a binder, there is no limit to the q# as long as it is a compound having an unsaturated double bond that can be cured by electron beam. Preferred examples include compounds having groups and prepolymers (for example, unsaturated polyesters).

Dispersing aids include 1, for example lecithin or oleic acid,
Preferred examples include higher fatty acids such as valmitic acid.

The abrasive is 1, for example, α-alumina, α-FelO.
Examples of @ include chromium oxide. Examples of the antistatic agent include Kettin Black E, C, and Black Pearl L.

Various types of crosstalk devices can be used to disperse magnetic paint crosstalk. For example, three roll mill, 7 triter mill, high speed stone mill, ball mill, 7 stage mill, pebble mill,
Sand grinder, high-speed mixer, homomitsuku linef g+ -.

A homogenizer, an ultrahigh wave disperser, a high-speed impeller disperser, a disperser, a pressure kneader, etc. are used alone or in combination.

The aromatic polyester in the present invention is a polyester containing aromatic dicarboxylic acid as the main acid component (11) and aliphatic glycol as the main glycol component. Such polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid + ') phenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and 7thracene dicarboxylic acid. Examples include acids. Examples of aliphatic glycols include ethylene glycol, trimethylene glycol;
Examples include polymethylene glycols having 2 to 10 carbon atoms such as tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and alicyclic diols such as hexane dimetatool.

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

Among such polyesters, for example, not only polyethylene terephthalate and polyethylene naphthalate, but also terephthalic acid and/or dicarboxylic acid account for 80 mole or more of the total dicarbo/acid component, and 80 mole or more of the total glycol component (1). Particularly preferred are copolymers in which 1. is ethylene glyfur. stomach. In this case, up to 20 molar dicarboxylic acids in the entire fermentation can be the above-mentioned aromatic dicarboxylic acids, and also aliphatic dicarboxylic acids such as adipic acid, cepatic acid; cyclohexane 7-1.4
-Alicyclic dicarboxylic acids such as dicarboxylic acids.

Further, up to 20 moles of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or, for example, noheidoquinone.

Aromatic diols such as resorcinol, 2,2-bis(4-hydroxyphenyl)propane; aliphatic diols containing six aromatics such as 1,4-dihydroxymethylbenzene; such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol It can also be polyalkylene glycol (polyoxyfulkylene glycol) and the like.

In addition, the aromatic polyester used in the present invention may contain a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydroxycarboxylic acid, or a dicarboxylic acid. It also includes those containing 1.20 molar or less per in of the component and the oxycarboxylic acid component. Furthermore, the aromatic polyester in the present invention may contain a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound 1, such as trimellitic acid, in an amount within a substantially linear range, for example, 2 mole or less based on the total acid components. Copolymerization of pentaerythritol 1. It also includes those who

The above-mentioned aromatic polyester is known per se, and can be produced by a method known per se.

The above-mentioned aromatic polyester was prepared using a solution in O-chlorophenol: 1. Measured at 35°C. It is preferable to have an intrinsic viscosity of about 0.4 to about 0.9.

In the present invention, inert particles and I
, for example, calcium carbonate.

It contains inorganic fine particles such as silicon oxide, kaolin, titanium oxide, or precipitated fine particles containing phosphorus.

The other surface exposed in the present invention (Side B: flat surface)
It is preferable that inorganic microparticles such as silicon oxide or titanium oxide be included in the polyester film layer forming the layer to an extent that does not impair flatness.1. However, it is not necessary to include inorganic fine particles.

Although the thickness structure of the laminated film in the present invention is not particularly limited, the easy-slip surface (side A) G2. In order to maximize the effect of the contained inert particles, the layer thickness after biaxial stretching is preferably 2 μm or more, more preferably 3 μm.
It is particularly preferable that the thickness be 4 μm or more. If the thickness of the slippery layer is too thin, protrusions, especially protrusions caused by small copying particles, will appear, resulting in poor runnability and scratch resistance.In addition, the layer that provides a flat surface (Side B) will In order to maintain this, the circumferential thickness after biaxial stretching is preferably 3 μm or more, and K is preferably 4 μm or more, particularly 5 μm or more.

stomach. If the thickness of the flat island is too thin, the flatness will be impaired due to the influence of inert particles in the slippery layer, which is not preferable (5).

Although the laminated film of the present invention has a multi-layer structure of two or more layers, a two-layer structure is particularly preferred. stomach. 3) In the case of the above laminated film, as long as the outermost layer is the polyester film layer of surfaces A and H described above, the intermediate layer may be a single layer of any polymer.

The laminated film of the present invention can be manufactured using conventional laminated film manufacturing methods. For example, a polyester layer forming surface A and a polyester layer forming surface B can be laminated in a molten state or in a cooled and solidified state. More specifically, for example, coextrusion
It can be manufactured using methods such as extrusion coding. The film laminated by the above-mentioned method is sequentially biaxially stretched or biaxially stretched in a manner similar to the conventional method for producing biaxially stretched films, and then heat-treated. At this time, the surface characteristics of the film vary depending on the shape, diameter, amount, etc. of the inert particles, and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions.

For example, the stretching temperature is such that the first stage stretching temperature (for example, longitudinal stretching temperature: T) is (Tg - l O) to (Ti + 45) °C.
range (however, Tg is polyester glass rolling temperature 8 K)
, the second-stage stretching temperature (e.g. lateral stretching temperature 2T,
) is preferably selected from the range of (T□+15) to (Ti+40)°C. In addition, the stretching ratio in the uniaxial direction is 2.
．． It is preferable to select from a range in which the area magnification is 5 times or more, especially 3 times or more, and the area magnification is 8 times or more, especially 10 times or more.

Furthermore, the heat setting temperature is 180 to 250°C, and even 20°C.
It is preferable to select from the range of 0 to 230°C. Note that the stretching temperature in the longitudinal direction is (Ti+25)°C or higher, and the stretching speed in the *direction is 1.
It is desirable that the speed is 500%/second or less, preferably 900%/second or less.

Magnetic recording brass media based on unreleased 11C is used for high-grade magnetic tapes at 1% and 1. Therefore, it has excellent properties even without the use of a back coat layer.

Example The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics in the present invention were measured and defined as follows (1).

(1) Average particle size of inert solid particles
Particle 5ize Analysar).

50 mass percent (ma
particle size reading corresponding to ss percent);
This value was taken as the above average particle diameter ("Particle Size Measurement Technique", published by Nikkan Kogyo Shimbun, 1975).

Pages 242-247 (see page 242-247).

(2) Film surface roughness Ra) JIS B
0601 k Measurement was carried out in the same manner. Using a stylus type surface roughness meter (SDRFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd., a film surface roughness curve was drawn on a chart under the conditions of a needle radius of 2 μm and a load of 0.079. A part of measurement length L is extracted from the film surface roughness curve in the direction along its center line, and the center line of this extracted part is set as the X axis and the direction of 1-1 longitudinal magnification is set as the Y axis, and the roughness curve is =f(When expressed as xl, the value (Ra:μ+a) given by the following formula is defined as the film surface roughness and 1.

In the present invention, the standard length is 0.25 ta, and 8 measurements are taken, and 5 (3) protrusion distribution measurement method, excluding 3 from the one with the largest value. using a needle diameter of 2 μm ILl (, needle force of 309, measurement length of 1 am, sampling pinch of 2 μm, cutoff of 0.25 wr, vertical magnification of 20,000 times, horizontal magnification of 200 times, number of scans of 15
Under the condition of 0 protrusions, the U7 film of the protrusions on the film surface is made into a three-dimensional (stereoscopic) K image.

When the ρ file is cut in a plane perpendicular to the thickness direction of the film, the plane where the total cross-sectional area of the ρ file of each protrusion is 70% of the area of the measurement area of the film is set at the reference level ( 0 level), and let y be the number of protrusions cut when cutting with a plane parallel to the plane of the reference level and separated by a distance X in the height direction of the protrusions. Increase or decrease X sequentially, read the number of y at that time,
Draw a protrusion distribution curve by plotting it on a graph.

(4) Film friction coefficient (μk) shown in Figure-2 I,
Measurement 1 was carried out as follows using the same equipment. In Figure 2, l is unwinding 1. Reel, 2 is tension controller +
31s, s, s, 9 Oyohi 11 is free roller, 4
is tension detector (inlet), 7 is stainless copper SUS
A fixed rod made of 304 (outer diameter 5 mm), 10 a tension detector (outlet), 12 a guide ruler, and 13 a take-up reel.

In an environment with a temperature of 20°C and a humidity of 60%, cut a 1-inch film to a width of 1/2 inch using a fixing rod of 7 (surface roughness: 0.3 μm).
) at an angle θ = 1-5-noπradi 7/(152°) and moved at a speed of 200 C1l per minute (°C! II). Adjust the tension controller 2 so that the inlet tension TI is 351.1. The film ran for 90m at the time of departure (Tlg)! , and later detected by an exit tension detector 11, and the running friction coefficient μk is calculated using the following formula.

(5) Electromagnetic conversion characteristics of magnetically coated tape Using a commercially available home VTR, a 50% white level signal (100%
White level signal is peak; two; peak voltage is 0.71
4 volts) K, 100 chroma level signal is recorded 1-1 The reproduced signal is measured using a Shibaku noise meter type 925R. The definition of chroma S/N is as follows according to Shibak's definition.

Here, ES (p-p) is the peak-to-peak voltage difference (p-p) of the reproduction signal of the white level signal.

ES (p-p) = 0.714 v (p-p) and s EN (rms) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

(6) Apply dropout magnetic coating tape (1/2 inch width) to a commercially available dropout counter (e.g. Shibasop VHOIB
The dropout of 5p element x 10dB was counted 1 for Z type > VC, and the number of counts per minute was calculated 1-.

(7) Scratch Judgment Magnetic coating tape (1/2 inch width)
) using a friction coefficient measuring device, apply K so that the base film surface of the tape contacts the fixed rod at an angle of 152°, and
Run 10m at a speed of 0cIIL/seC,
After repeating the process several times, the thickness, depth, and number of scratches on the surface of the 1/2 inch wide base film were calculated as follows: Next 5
The stage judgment is 1-.

<5-level evaluation> ◎ No scratches are observed on the 1/2 inch wide base film. 0 Almost no scratches are observed on the 1/2 inch wide base film. △ Scratches are observed on the 1/2 inch wide base film. (Several pieces) (8) The skew skinny characteristic is normal @ (20℃) A videotape recorded under normal humidity is heat treated at 70℃ for 1 hour 1. After that, read the playback 17 again at normal temperature and humidity, and read the amount of deviation at the head switching point.

Example 1 [Production method of polymer for film] 100 parts by weight of dimethyl terephthalate and 0 parts of ethylene glycol were added to 0 parts by weight of dimethyl terephthalate.
．． 015 mol of manganese acetate, and Q, 010 mol%
of sodium acetate was added, and the transesterification reaction was carried out at 150 to 250°C while distilling off methanol. At that time, adjust in advance 1. An ethylene glyfur slurry (10%) of distilled calcium carbonate particles was added.

After 1% of the reaction was completed, trimethyl phosphate, which had been heated under reflux in the presence of niburene gelylcol, was added to dimethyl terephthalate (K) in an amount of 15 ml of O,O. Next, 0.030 mole of 7thimony trioxide was added to t of dimethyl terephthalate, and a polycondensation reaction was carried out under high vacuum at less than ITorr. After the polycondensation reaction is completed, the polymer is water-cooled and cut.1. As a result, polyethylene terephthalate pellets containing calcium carbonate particles dispersed therein were obtained (hereinafter referred to as Polynisdel ■).

Transesterification and polycondensation reactions were carried out in the same manner as above, except that the ethylene glycol slurry of titanium dioxide particles prepared in advance was added instead of the ethylene glycol slurry of calcium carbonate particles, and the titanium dioxide particles were dispersed. Polyethylene terephthalate pellets (hereinafter referred to as polyester) were obtained.

Next, transesterification and polycondensation reactions were carried out in the method for producing polyester I without adding any inert particles to obtain polyethylene terephthalate pellets to which no external inert particles were added (see below).

It is called polyester.

[Film forming]

Polyester I, Polyester■, and Polyester■
were mixed so that the calcium carbonate particle content was 0.30% by weight and the titanium dioxide particle content was 0.15% by weight to obtain a blend, and polyester (1) and polyester (2) were mixed with titanium dioxide particles [Blend B] was obtained by mixing so that the content was 0.25% by weight. Then, the blend A is fed to separate extruders of the IC backing machine, K so that the blend A becomes the layer forming the A side, and the blend B becomes the layer forming the B side, and the polyester that forms the AIr Extrude through the die so that the layer thickness accounts for 60% of the laminated film thickness! , to obtain an unstretched film of 11,200 μm.

This Mishima stretched film was sequentially biaxially stretched at a longitudinal stretching temperature of 15°C, a longitudinal stretching ratio of 3.7 times, a transverse stretching temperature of 120°C, and a transverse stretching ratio of 3.8 times, and then heat treated at 225°C. 1. Ta. Further, the biaxially oriented polyester film was subjected to longitudinal relaxation treatment under the conditions of a temperature of 120° C., a tension of 30, and 9/cd (film cross-sectional area).

The thickness of the obtained film was 14 μm.

The properties of the laminated polyester film thus obtained are shown in Table IK, and the distribution of unevenness on the film surface is shown as Curve IK in Figure A.

Note that the symbol A means the A side, and the symbol B means the B side.

On the other hand, the following composition O ferromagnetic CO coated γ-Fat's 100 parts by weight 0
Oleic acid 1 part by weight 0
Nitrocellu p-s 5 parts by weight 0
20M parts polyurethane resin with acrylic groups in the meat 0 carbon black 3 parts O stearic acid 1 part by weight 0 α-alumina 5 parts by weight Q EK-) Luene-cyclohexane 2
Using a pressure kneader and a 7 digit mill, mix and disperse 11 parts of 5 o for 3 hours. Adjust the magnetic paint again.

The obtained magnetic paint was passed through a filter with an average pore size of 1 μm.

This magnetic paint was applied on the 8 sides of the 7-lumen using a reverse roll coater, and then irradiated with 4 Mrad electron beam under a nitrogen stream to harden the magnetic layer. A magnetic tape with a thickness of 5 μm was obtained.

The properties of the magnetic tape thus obtained are shown in Table 5.

This tape has 1. compared to standard tape. [The electromagnetic conversion characteristics were improved, and the running properties and scratch resistance were good even without the use of a back coat.

Example 2 A biaxially stretched laminated film was produced in the same manner as in Example 1 except that the composition of blend A was changed.
Furthermore, a magnetic tape was obtained in the same manner.

The results are shown in Table 19, Figure tK.

This magnetic tape also had good electromagnetic conversion characteristics and running properties as in Example 1.

Comparative Examples 1 to 3 Magnetic tapes were obtained in the same manner as in Example 1 except that the composition of blend A or B was changed. The results are shown in Table 12, Figure IK.

In Figure 1, curve C shows Comparative Example 1, curve 2 shows Comparative Example 2, and curve E shows Comparative Example 3. Furthermore, the symbol A means the characteristic of the A side, and the symbol B means the characteristic of the 8th side.

The additive particles on the easy-slip surface (A side) of Comparative Example 1 had an average particle size of 1.1.
In the case of μm calcium carbonate, the runnability was good, but there were high protrusions, the electromagnetic conversion characteristics were poor, and furthermore, the calendering was poor, there was a lot of drudging out, and it could not withstand the (il!) use.

In addition, if the easy-sliding surface (Side A) in Ratio 42 Example 2 is too flat, the friction coefficient (μk) after 200 repetitions will be high (
This resulted in poor running performance and poor scratch resistance, making it unusable.

Further, when the flat surfaces (8 surfaces) in Comparative Example 3 were too rough, the electromagnetic conversion characteristics were insufficient.

Comparative Example 4 A magnetic tape was obtained in the same manner as in Example 1, except that the longitudinal relaxation treatment of the biaxially stretched film was not performed in Example 1.

The results are shown in Table-1. This magnetic tape had a large skew value and was unusable.

Comparative Example 5 On the flat surface (8 sides) of the laminated polyester film obtained by the same method as in Example 1, K, the following composition: Co-containing iron oxide powder 100 parts by weight Eslec A
(Vinyl chloride-vinyl acetate copolymer manufactured by Tanesui Chemical Co., Ltd.) 107 Nimboran 2304 (Polyurethane elastomer made of 8 polyurethane) 10
#Coronate L (polyisocyanate made by Nippon Polyurethane) 5z Lecithin 1 part by weight Methyl nysoule ketone 75 1 Methyl inbutyl ketone 75 1 Toluene 75 N additive (lubricant, silicone resin) a, Magnetic powder coating with rsz is coated with a gravure roll. The magnetic paint layer is smoothed using a doctor knife (12), and while the magnetic paint is still dry, it is magnetically oriented using a conventional method, and the magnetic paint layer is guided through I5 to the rear open area and dried for curing (1). Ta. Further eζ calendar processing 1
- Evenly coat the surface 11. 1. Create a 1/2 inch wide magnetic coating tape by slitting it to form a magnetic layer of about 5μ. Ta.

Table 1 shows the characteristics of the magnetic tape obtained in this way.
if: Show. In this magnetic tape, the surface roughness of the smooth surface (side A) of the base film is transferred onto the surface of the magnetic layer. The t11 magnetic conversion characteristics were insufficient.

[Brief explanation of drawings]

Figure 1 shows the protrusion height on the film surface: ! It is a figure which shows the relationship between (micrometer) and the number of protrusions (ke/-). FIG. 2 is a diagram showing the film p- of the device used to measure the coefficient of friction (μk). 1]-2

Claims (1)

[Scope of Claims] A biaxially oriented laminated film comprising a film-forming aromatic polyester containing aromatic dicarboxylic acid as the main acid component and aliphatic glycol as the main glycol component, comprising: The surface (Side A) has a surface roughness RaA of 0.025 μm or less and 0.010 μm or more, and the number of protrusions (y: ke/mm^2) and protrusions determined in the area where the number of protrusions is 20 protrusions/mm^2 or more. The distribution curve representing the relationship between the height (x: μm) of
The straight line represented by 1) and 2>log_1_0y>1.3
The curve having a protrusion distribution that does not intersect in the range of , and the curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by formula (2) lo
g_1_0y≧-18x+3.7 (2), and provides an easy-smooth surface substantially free of protrusion heights (x) of 0.87 μm or more, and improves the laminated film. The other exposed surface (Side B) has a surface roughness RaB of 0.
．． In the distribution curve that expresses the relationship between the number of protrusions (y: x/mm^2) and the height of the protrusions (x: μm) determined in a region where the number of protrusions is less than 010 μm and the number of protrusions is 20 / mm^2 or more. The curve of the portion larger than the maximum value of the protrusion distribution curve is expressed by equation (3) log_1_0y=-18x+3.7 (3
) and substantially free of protrusion heights (x) of 0.13 μm or more. 1. A magnetic recording medium having a heat shrinkage rate of 0.1% or less, and comprising a magnetic layer provided by applying an electron beam curable magnetic coating on the B side of the laminated film.