JPH01319127A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the recording medium which withstands the higher speed of a calendering stage and the higher speed of dubbing and winding by forming the magnetic recording medium which is incorporated with org. high-polymer particles in a base material film and contains inorg. particles in one of magnetic layers and specifying the sphericity of the org. high-polymer particles and the standard deviation of the height distribution of surface projections to specific ranges. CONSTITUTION:The magnetic layer is provided on one face of the base material film essentially consisting of polyester. The magnetic layer 0.1-20wt.% inorg. particles and the base film contains 0.01-8.0wt.% inert high-polymer particles. The org. high-polymer particles are required to be the inert particles which do not make covalent bonding, etc., with the polyester. The sphericity of the high-polymer particles is 1.2 and the standard deviation of the projection height distribution on at least one face of the base material film is in a 40-250nm range. The surface resistant to flawing is obtd. in this way and the degradation in image quality by dubbing is obviated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to magnetic recording media.

[Prior Art] As a magnetic recording medium, there is known a magnetic recording medium in which a magnetic layer is provided on at least one side of a film made of polyester containing inorganic particles (for example, JP-A-59
-203228, etc.).

[Problems to be Solved by the Invention] However, with the above-mentioned conventional magnetic recording media, as the process speed of film processing steps, such as magnetic layer coating and calendering steps, increases, the film surface is scratched by the contacting rolls. This shortcoming has recently become a problem. In addition, videotape, which is a type of magnetic recording medium, is recently often used for software (recording and fixing produced video works on packaged media, duplicating and increasing production), and in this case, the conventional videotape mentioned above is used in many cases. However, when dubbing (copying) from a master tape at high speed in the ``process of recording a video work'', there is a problem in that the S/N (signal/noise ratio, image quality parameter) decreases significantly and the image quality deteriorates. It's coming.

The present invention improves this problem and prevents scratches on the surface.
An object of the present invention is to provide a magnetic recording medium (hereinafter referred to as "good scratch resistance") with less deterioration in image quality (S/N>) due to dubbing (hereinafter referred to as "good dubbing resistance").

[Means for Solving the Problems] The present invention provides a magnetic recording medium comprising: (1) a magnetic layer provided on one side of a base film containing polyester as a main component;
The magnetic layer contains 0.1 to 20% by weight of inorganic particles based on the magnetic material, the base film contains 0.01 to 8.0% by weight of inert organic polymer particles, and The sphericity (major axis/minor axis) of the polymer particles is 1.2 or less, and the standard deviation of the protrusion height distribution on at least one side of the base film is 40 to 25.
(2) A magnetic recording medium comprising a base film mainly composed of polyester, with a magnetic layer on one side and a back coat layer on the opposite side. The back coat layer contains 5 to 400% by weight of inorganic particles based on the organic binder, the base film contains 0.01 to 8.0% by weight of inert organic polymer particles, and , a magnetic recording medium characterized in that the sphericity (major axis/minor axis) of the polymer particles is 1°2 or less, and the standard deviation of the protrusion height distribution on at least one side of the base film is 150 nm or less. It is something.

The polyester in the present invention includes ethylene terephthalate, ethylene α, β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate, ethylene 2.6
- Contains at least one structural unit selected from naphthalate units as a main constituent. However, other components may be copolymerized within a range that does not impede the present invention, preferably within 15 mol%.

In addition, polyester containing ethylene terephthalate as a main component is particularly desirable because it provides even better scratch resistance and dabbing resistance.

The organic polymer particles in the present invention need to be inert particles that do not form covalent bonds with polyester. Reaction with polyester is not preferred because scratch resistance becomes poor.

The organic polymer particles in the present invention have a temperature at 10% weight loss in a heating loss curve of 360°C, preferably 380°C.
C., more preferably 400.degree. C. or higher, is particularly desirable because scratch resistance and dubbing resistance are even better and sphericity within the range of the present invention is easily obtained.

The average particle size of the organic polymer particles in the present invention is not particularly limited, and the required particle size varies depending on the temperature at the time of 10% weight loss, but is 0.1 to 1.0 μm, preferably 0.1 μm.
A range of 0.45 μm is desirable because it is easy to obtain a standard deviation of the protrusion height distribution within the range of the present invention.

However, it is necessary that the sphericity (major axis/breadth axis) of the organic polymer particles used in the present invention be 1.2 or less, preferably 1°1 or less. If the sphericity of the organic polymer particles is larger than the above range, the scratch resistance and dubbing resistance will be poor, which is not preferable. The lower limit of sphericity is 1, which is the ideal state in which all particles are perfectly spherical.

The relative standard deviation of the particle size of the organic polymer particles in the present invention is not particularly limited, but is 0.6 or less, preferably 0.45
The following cases are particularly desirable because the protrusion height distribution within the range of the present invention is easily obtained and the dubbing resistance is further improved.

The content of organic polymer particles in the film in the present invention is 0.
．． The amount should be 0.01 to 8.0% by weight, preferably 0.03 to 5.0% by weight, and most preferably 0.1 to 2.0% by weight. If the content is less than the above range, the scratch resistance will be poor, and if it is too much, the dubbing resistance will be poor, which is not preferable. When two or more types of organic polymer particles are contained, the total amount thereof needs to be within the above range.

The crystallization promotion coefficient of the organic polymer particles in the present invention is -2
A temperature range of 0 to 20°C, particularly -20 to 10°C, is desirable because the dubbing resistance and scratch resistance become even better.

The film of the present invention has the above-mentioned composition as a main component, but other polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. Inorganic or organic additives such as agents, nucleating agents, etc. may be added to the extent that they are normally added.

The film constituting the present invention is a film in which the above composition is biaxially oriented. An unstretched film or a -axially oriented film is not preferred because it has poor scratch resistance and dubbing resistance.

In addition, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but is 0.935 to 0.975, particularly 0.94
Scratch resistance when in the range of 0 to 0.970;
This is particularly desirable because the dubbing resistance becomes even better.

The base film constituting the present invention has a single particle index of organic polymer particles in the film of 0.5 or more, preferably 0.5 or more.
A value of 7 or more, more preferably 0.8 or more is particularly desirable because scratch resistance and dubbing resistance become even better. Although the upper limit of the single particle index is not particularly limited, it is 1 in the case of complete monodispersion, and it is theoretically impossible for it to exceed 1.

The base film constituting the present invention preferably has particularly good scratch resistance and dubbing resistance when the average distance between the protrusions on at least one surface is 20 μm or less, particularly 15 μm or less.

The present invention relates to a magnetic recording medium using the above-mentioned film as a base film, and there are the following two types.

(1) First, a case of a magnetic recording medium in which a magnetic layer is provided on one side of the base film will be described.

In this case, the base film has a standard deviation of protrusion height distribution on at least one side of 40 to 250 nm, preferably 40 to 250 nm.
It needs to be 200 nm, more preferably in the range of 50 to 150 nm.

If the protrusion height distribution on both sides is smaller than the above range, the scratch resistance will be poor, and if it is larger, the dubbing resistance will be poor, which is not preferable.

Further, the type of the magnetic layer is not particularly limited, but known magnetic materials such as γ-iron oxide, Co-containing iron oxide, chromium dioxide, iron, cobalt, or alloys thereof may be used. Further, the type of binder is not particularly limited, and vinyl chloride/vinyl acetate copolymer, polyvinyl butyral, polyurethane, etc. can be used.

The magnetic layer constituting the present invention contains inorganic particles in an amount of 0.1 to 20% by weight, preferably 0.5 to 10% by weight, based on the magnetic powder.
Must contain. If the content is less than the above range, the scratch resistance will be poor, and if it is too much, the dubbing resistance and scratch resistance will be poor, which is not preferable. When two or more types of inorganic particles are contained, the total amount thereof must be within the above range.

The average particle size of the inorganic particles is not particularly limited, but is 3 to 600n.
m, especially in the range of 7 to 300 nm, is particularly desirable because the scratch resistance becomes even better.

The type of inorganic particles is not particularly limited, but s other than magnetic materials
11 particles, and α-iron oxide, alumina, silica, zirconia, titanium dioxide, and carbon black are particularly desirable because they provide even better scratch resistance.

The thickness of the magnetic layer is not particularly limited, but a thickness of 1.5 to 8 .mu.m is particularly desirable since scratch resistance becomes even better.

(2) Next, a case of a magnetic recording medium in which a magnetic layer is provided on one side of the base film and a back coat layer is provided on the opposite side will be described. In this case, the base film has a protrusion height distribution standard Q = deviation σ of 150n on at least one side.
It is necessary that the thickness is not more than m, preferably not more than 1100 nm, and more preferably not more than 75 nm. If the protrusion height distribution on both surfaces is larger than the above range, the dubbing resistance will be poor, which is not preferable. Although the lower limit of the standard deviation of the height distribution is not particularly limited, about 5 nm is the manufacturing limit.

The type of magnetic layer is not particularly limited, but may be made of known magnetic materials, such as γ-iron oxide, Co-containing iron ffi,
Chromium dioxide, iron, cobalt, or alloys thereof are used. Further, the type of binder is not particularly limited, and vinyl chloride/vinyl acetate copolymer, polyvinyl butyral, polyurethane, etc. can be used. Further, in this case, a metal thin film type magnetic layer formed by a method such as vapor deposition or sputtering without using substantially an organic binder can also be used. The bank coat layer may also be made of a binder based on known binders such as vinyl chloride, vinyl acetate, vinyl alcohol, copolymers thereof, polyurethane, and cellulose derivatives. However, the back coat layer must contain inorganic particles.

The content of the inorganic particles is 400% of the organic binder.
~5% by weight, preferably 300-20% by weight. If the content is more than the above range, the dubbing resistance and scratch resistance will be poor, and if the content is less than the above range, the scratch resistance will be poor, which is not preferable.

The average particle size of the inorganic particles is not particularly limited, but is 3 to 600n.
m, especially in the range of 7 to 300 nm, is particularly desirable because the scratch resistance becomes even better.

The thickness of the magnetic layer is not particularly limited, but the scratch resistance is 1.5 to 8 μm when it contains an organic binder, and 0.05 to 1.5 μm in the case of a metal thin film type that does not contain an organic binder. This is particularly desirable because it provides even better results.

The thickness of the back coat layer is not particularly limited, but is 0.05
A thickness of 2.51 m to 2.51 m, particularly 0.1 to 1.5 m, is particularly desirable because scratch resistance and dubbing resistance are even better.

Although the type of inorganic particles is not particularly limited, it is particularly preferable to use α-alumina, silica, zirconia, titanium dioxide, or carbon black as the inorganic particles in the back coat layer because the scratch resistance will be even better.

Next, a method for producing the film of the present invention will be explained.

First, organic polymer particles can be incorporated into a given polyester by adding them before, during, or after polymerization, but they can be added in the form of a slurry to ethylene glycol, which is the diol component of the polyester. , the method of dispersing and adding is effective in satisfying the desired range of relative standard deviation and single particle index of the present invention. Also,
As a method for adjusting the content of particles, a method according to the present invention is to dilute a master pellet with a high concentration, preferably 1 to 10% by weight, with polyester pellets that do not substantially contain organic polymer particles during film formation. It is effective in satisfying the desired range of single particle index. In addition, the crystallization parameter ΔTCg can be adjusted to 65 to 80'C by adjusting the intrinsic viscosity of the master pellet with a high concentration, preferably 1 to 10% by weight.
By adjusting the intrinsic viscosity, the crystallization parameter ΔTCCI is larger than that of this master pellet before film formation, preferably the crystallization parameter ΔTCQ is 75 to 9.
Protrusion height distribution within the scope of the present invention using organic polymer particles, the content of which can be adjusted by diluting with polyester pellets containing substantially no inert organic polymer particles at 5° C. It is very effective in satisfying the desired range of single particle index. In order to obtain the above relationship of ΔTCg, it is effective to use copolyester as the master polymer.

In this way, pellets containing a predetermined amount of organic polymer particles and polyester pellets containing substantially no organic polymer particles were mixed in a predetermined ratio, and the pellets were sufficiently dried and fed to a known melt extruder, It is extruded into a slit-shaped die sheet at ~330°C and cooled and solidified on a casting roll to produce an unstretched film.

In this case, the ratio of the slit width (gap) of the die to the thickness of the unstretched film (slit width/unstretched film) is 5 to 30.
, preferably in the range of d to 20, which is effective in obtaining the sphericity within the range of the present invention, the standard deviation of the protrusion height distribution, and the single particle index within the desired range.

Next, this unstretched film is subjected to two-wheel stretching to achieve biaxial orientation. As the stretching method, a sequential two-wheel stretching method or a simultaneous two-wheel stretching method can be used. However, using a sequential biaxial stretching method in which stretching is performed first in the longitudinal direction and then in the width direction, the stretching in the longitudinal direction is divided into two stages, especially three or more stages. , is effective in obtaining a desired range of single particle indices. The stretching temperature in the longitudinal direction is 70
~140° C. and a speed of 20,000 to 100,000%/min are preferred. The stretching temperature and speed in the width direction are 80~
A range of 160'C and 1000 to 20000%/min is suitable. The stretching ratio is preferably 3 to 5 times in both the longitudinal and width directions. Next, this stretched film is heat treated. In this case, the heat treatment conditions may be any of a constant length, a relaxed state, and a slightly stretched state, and the temperature is 150 to 220°C, preferably 17°C.
The temperature is preferably 0 to 200°C for 0.5 to 60 seconds.

Next, a magnetic layer is formed on this film, which is manufactured by the following manufacturing method depending on the type.

(1) A magnetic layer is formed on one side of the above film.

In this case, it can be manufactured by applying a paint containing a magnetic substance, drying, and then calendering.

Known methods can be used for these conditions.

(2) Form a magnetic layer on one side of the above film and a back coat layer on the opposite side. In addition to the above-mentioned method, the magnetic layer in this case can be formed by a method of forming a magnetic gold RH film by vapor deposition or sputtering. Further, the back coat layer is formed by applying a solution having a predetermined composition and drying it. The back coat layer is formed before the magnetic layer is formed.
It may be performed after forming the magnetic layer, before calendering, after calendering, or after a curing process.

[Function] The present invention is a magnetic recording medium in which organic polymer particles are contained in the base film and inorganic particles are contained in at least one of the magnetic layer and the back coat layer. It is presumed that the effects of the present invention were obtained through this interaction.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Plasma low-temperature ashing process (
For example, the particles are removed using Yamato Scientific Model PR-503. The processing conditions are selected so that the polyester is incinerated but the particles are not damaged. This is an SEM
(scanning electron microscope), connect the image of the particles (S-light of light produced by the particles) to an image analyzer (for example, QTM900 manufactured by Cambridge Instruments), change the observation point, and then increase the number of particles at r & 5000 or more. The number average diameter obtained thereby is taken as the average particle diameter.

D=ΣDi　/N Here, Di is the circular diameter of the particle, and N is the number of particles.

(2) Average particle size of inorganic particles in magnetic layer and back coat layer Materials other than inorganic particles such as magnetic particles and organic binder were removed from the magnetic layer and back coat layer, and measurements were made in the same manner as above.

(3) Glass transition point Tg, cold crystallization temperature TCC Measured using a DSC (differential scanning calorimeter) type II manufactured by PerkinElmer. The DSC measurement conditions are as follows. That is, 10m0 of the sample was set in the DSC device, and 300m
Melt the mixture for 5 minutes at a temperature of 50°C and quench it into liquid nitrogen.

This rapidly cooled sample was heated at a rate of ]0°C/min to reach the glass transition point Tg.
Detect.

The temperature was continued to rise gradually, and the peak temperature of crystallization exotherm from the glass state was defined as the cold crystallization temperature TCC.

Here, the difference between Tcc and Tg (TCC-Tq>) is defined as ΔTcg.

<4) Temperature at 10% heating loss Using a thermogravimetric analyzer model T030M manufactured by Shimadzu Corporation,
Measurement was performed in nitrogen at a temperature increase rate of 10° C./min.

Note that the sample weight was 5 mQ.

(5) Crystallization promotion coefficient (unit: °C) 610% of the film containing organic polymer particles obtained by the above method
g (■), and 610 g (II) of polyester of the same viscosity from which organic polymer particles were removed,
Difference between ΔTCQ (II) and 610g (I) [ΔTco
(II) - ΔTco (I>1 was taken as the crystallization promotion coefficient.

(6) Refractive index Measured using an Atsube refractometer using sodium D line (589 nm) as a light source. Methylene iodide was used as the mounting solution, and the measurement was performed at 25° C. and 65% RH.

(7) Planar orientation index The refractive index in the thickness direction of the biaxially oriented film (
The refractive index in the thickness direction (denoted as B) of a non-oriented (amorphous) film made by melt-pressing and quenching into 10° C. water was measured, and A/B was taken as the planar orientation index.

(8) Average distance between protrusions Sm Measured using a high-precision thin film step measuring instrument ET-1O manufactured by Koita Research Institute. The conditions were as follows, and the average value of 20 measurements was taken as the value.

・Stylus tip radius = 0.5μm ・Stylus load: 5rl ・Measurement length: 1mm ・Cutoff value: 0.08mm The definition of the average spacing of protrusions of 3m can be found, for example, in “Surface Roughness” by Jibu Nara. ``Measurement and Evaluation Methods'' (Sogo Technological Center, 1983).

(9) Photo-observe the cross section of the single particle index film using a transmission electron microscope (TEM>) to detect particles of inert organic polymers.If the magnification is set to about 100,000 times, it is possible to separate the particles further. One particle that cannot be observed can be observed.If the total area occupied by the particles is A1, and the area occupied by aggregates in which two or more particles are aggregated is B, then (A-8>/A, the simple One particle index is used.The TEM conditions are as follows, and one field of view area: 2 μm2 is measured at different locations, and 500 fields of view are measured.

・Equipment: JEOL! I! JEM-1200EX Observation magnification: 100,000 times Accelerating voltage: 100 kV Section thickness: Approximately 1000 angstroms (lω Standard deviation of surface protrusion distribution σ 2-detector scanning electron microscope [ESM-3200,
manufactured by Elionix Co., Ltd.] and a cross-sectional measuring device [PMS-1,
Elionix Co., Ltd.! 141, the height of the protrusion was measured when scanning with the height of the flat surface of the film set as O.
Co., Ltd.@] and reconstruct the film surface protrusion image on an image processing device. Next, the circular diameter is determined from the area of each protrusion obtained by binarizing the protrusion portion using this surface protrusion image, and this is taken as the average diameter of the protrusion. Furthermore, the highest value among the binarized individual protrusion portions is determined as the height of the protrusion, and this value is determined for each protrusion. This measurement was repeated 500 times at different locations, and the height distribution of the measured protrusions was approximated by the least squares method, assuming that it was half of the normal distribution centered on the protrusion height O (flat surface). Further, the magnification of the scanning electron microscope is selected to be between 1000 and 8000 times.

θ1) Sphericity In the measurement of (1) above, it is the ratio of the long axis (average value)/breadth axis (average value) of each particle determined by the following formula.

Long axis - ΣDli/N Short axis = Σ[)2i/N [)1i and [)2i are the long axis (R
(large diameter), short diameter (minimum diameter), and N are the total number.

(2) Relative standard deviation of particle diameter The individual particle diameter Di1 average mean diameter 0 pre-II difference σ (-f(Σ (Di-D>2/N)) measured by the method in (1) above is the average diameter It is expressed as the value divided by (σ/D>).

Scratch-resistant magnetic recording tape (width 1 x 2 inches) was tested with a guide pin (surface roughness: Ra = 100 n) using a tape running tester.
m) Run the reel on the tape (travel speed 500 m/min, winding angle: 180', tape load 20OC+>, then reel it up. This reel is set in the above tape runnability tester again and run. After repeating 10 times,
Observe the scratches on the non-magnetic surface with a microscope. If there are almost no scratches, the scratch resistance is good.
If more than one book was contained, it was determined that the scratch resistance was poor. Therefore, if both the magnetic and non-magnetic surfaces are not strong, powder scraped from the magnetic surface will damage the non-magnetic surface, and the scratch resistance will be good or bad depending on the compatibility between the wood film and the back coat layer. This method is an evaluation method that shows the resistance to scratches during the actual tape processing process.

(b) Dubbing resistance The original magnetic recording tape was slit into 1/2 inch pieces to make pancakes. A length of 250 m from this pancake was assembled into a VTR cassette to make a VTR cassette tape.

This tape was 100% tested using a home VTR and a Shibaku TV test waveform generator (TG7/LI706).
Record the chroma signal, and check the chroma S/N from the playback signal using a color video noise meter (925D/1) made by Shibaku.
was measured and designated as A. In addition, a tape recorded with the same signals as above is dubbed onto a pancake of the same type of tape (unrecorded) using a magnetic field transfer type video software high-speed print system (for example, Sony Magnescale ■ Sprinter). The chroma S/N of the sample was measured in the same manner as above and designated as B. When the chroma S/N reduction (A-B) due to dubbing was less than 4.0 dB, it was determined that the dubbing resistance was good, and when it was 4.0 dB or more, it was determined that the dubbing resistance was poor. 09 Content of Particles Only particles were taken out from polyester, binder, etc., and their weight was determined.

[Example] The present invention will be explained based on examples.

Examples 1 to 3, Comparative Examples 1 to 7 Ethylene glycol slurries containing divinylbenzene/styrene crosslinked copolymer particles (organic polymer particles) having different average particle diameters and temperatures at weight loss of 103 were prepared. The heat treatment conditions for this slurry were variously changed, and the ethylene glycol slurry and dimethyl terephthalate were transesterified and then polycondensed to produce a master pellet of polyethylene terephthalate particles containing the particles. In addition, the intrinsic viscosity and copolymerization component of the master pellet were changed, and the ΔTCQ of the master pellet was changed as shown in Table 1. These particle master pellets and
Pellets of polyethylene terephthalate containing substantially no organic polymer particles (ΔTCCI: 80°C) were mixed so that the content of organic polymer particles became a predetermined amount, and the pellets were dried under reduced pressure (3 Torr) at 180°C for 3 hours. Ta.

This pellet was fed into an extruder, melt-extruded at 300°C, wound around a casting drum with a surface temperature of 30°C using an electrostatic casting method, and cooled and solidified to produce an unstretched film. At this time, unstretched films were produced by variously changing the ratio of the slit width of the die/unstretched film thickness. This unstretched film was stretched 4.5 times in the longitudinal direction at 80°C.

This stretching was carried out using a difference in the circumferential speed of the rolls, and the number of stretching stages was divided into three stages. The average stretching speed was 1oooo%/min. This -axially stretched film was stretched 3.6 times in the width direction at 100°C at a stretching rate of 2000%/min using a stenter, and then heat-treated at 190°C for 5 seconds under slight stretching of 1.01 times. A biaxially oriented film with a length of 15 km was obtained.

A magnetic paint having the following composition was applied to this film using a gravure roll, magnetically oriented, and dried.

Rani, small test calendar device (steel roll/
Nylon roll, 5 stages), temperature = 70°C, linear pressure: 2
After calendering at 00kg/cm, 70'C, 4
I cured it for 8 hours.

The original tape was slit into 1/2 inch pieces to make pancakes. A length of 250 m from this pancake was assembled into a VTR cassette to make a VTR cassette tape.

(Composition of monochromatic paint) -Co-containing iron oxide (BET value 50m2/10): 1
00 parts by weight・Eslec A (Sekisui Chemical vinyl chloride/vinyl acetate copolymer: 10 parts by weight・Nilaboran 2
304 (Polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight, Polyisocyanate made by Nippon Polyurethane)
:5 parts by weight・Lecithin=1 part by weight・Methyl ethyl ketone 5 parts by weight・
Methyl isobutyl ketone 5 parts by weight, toluene 5 parts by weight, lauric acid
: 1.5 parts by weight α-alumina: Co
The weight ratio to the iron oxide contained was changed as shown in Table 1.

The performance of these magnetic recording media is shown in Table 1, and a magnetic recording medium that satisfies the requirements of the present invention has excellent scratch resistance and dubbing resistance. However, in cases where this is not the case, It can be seen that scratch resistance and dubbing resistance cannot be achieved at the same time.

Examples 4 to 6, Comparative Examples 8 to 13 Two samples containing divinylbenzene/styrene crosslinked copolymer particles (organic polymer particles) having different average particle diameters and temperatures at 10% weight loss were prepared in the same manner as in Example 1. An axially oriented polyethylene terephthalate film was made. The height distribution σ of the surface projections of these films was as shown in Table 2.

One side of this film was coated with CO/N by electron beam evaporation.
i alloy (Co/N i =75/25 weight ratio) with a thickness of 1
A magnetic thin film was formed by oblique deposition at a thickness of 80 nm with a minimum incident angle of 5 o'. The following composition was applied to the opposite side to form a back coat layer with a thickness of 0.5 μm.

(Back coat composition) - Polyester (Toyobo Vylon 200 > 80 parts by weight - Nitrocellulose 20 parts by weight - Silica particles (average particle size 0.01 μm) (weight ratio changed relative to organic binder) - Methyl ethyl ketone 200
Weight part・Toluene 200 weight ω part・
Cyclohexanone 200 parts by weight The performance of these magnetic recording media is shown in Table 2, and the magnetic recording medium that satisfies the requirements of the present invention has excellent scratch resistance and dubbing resistance. However, if this is not the case, scratch resistance and dubbing resistance cannot be achieved at the same time.

[Effects of the Invention] The present invention provides a magnetic recording medium in which organic polymer particles are contained in a base film, inorganic particles are contained in at least one of a magnetic layer and a back coat layer, and the organic polymer particles are By setting the sphericity and the standard deviation of the height distribution of surface protrusions within specific ranges, we have obtained a magnetic recording medium that has both scratch resistance and dubbing resistance, and is resistant to recent harsh usage conditions, i.e. A magnetic recording medium with excellent scratch resistance that can withstand high-speed coating, calendering, dubbing and winding speeds can be obtained, and high-quality magnetic recording compatible with future dubbing systems can be obtained. The medium is obtained.

Claims (2)

[Claims] (1) A magnetic recording medium comprising a magnetic layer provided on one side of a base film containing polyester as a main component, the magnetic layer containing 0.1 to 20% by weight of inorganic particles based on the magnetic material, The base film contains 0.01 to 8.0% by weight of inert organic polymer particles, and the sphericity (major axis/breadth axis) of the polymer particles is 1.2 or less, the base material The standard deviation of the protrusion height distribution on at least one side of the film is 40 to 250.
A magnetic recording medium characterized in that the magnetic recording medium is in the nanometer range. (2) A magnetic recording medium formed by providing a magnetic layer on one side of a base film mainly composed of polyester and a back coat layer on the opposite side, wherein the back coat layer contains 5 to 400% by weight of the organic binder. The base film contains inorganic particles, the base film contains 0.01 to 8.0% by weight of inert organic polymer particles, and the sphericity (major axis/breadth axis) of the polymer particles is 1. 2 or less, a magnetic recording medium characterized in that the standard deviation of the protrusion height distribution on at least one side of the base film is 150 nm or less.