JPH01106332A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics and traveling durability by specifying the layer thickness of a 2nd magnetic layer to a specific value and specifying the average particle size of an abrasive material which is incorporated into the 2nd magnetic layer and has the Mohs hardness of a specific hardness with respect to the layer thickness of the 2nd magnetic layer. CONSTITUTION:A coating liquid for the 1st magnetic layer is coated on the front face of a traveling nonmagnetic base. A coating liquid for the 2nd magnetic layer which contains the abrasive material having >=6 Mohs hardness and the average particle size of >=1/3 the layer thickness of the 2nd magnetic layer is coated continuously on the coated layer while the coated layer is in a wet state in such a manner that the layer thickness after drying of the 2nd magnetic layer attains >=0.5mum. The abrasive effect of the abrasive material is effectively obtd. as the abrasive material projects adequately to the surface of the magnetic layer. In addition, the degree of the projection is not excessive and the amt. of the abrasive material to be added is adequate; therefore, not only the traveling durability is improved but also the electromagnetic conversion characteristics are improved. The content of the abrasive material to be incorporated into the 2nd magnetic layer is preferably 2-15pts.wt. per 100pts.wt. ferromagnetic powder in order to maintain the traveling durability.

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to a magnetic recording medium comprising a non-magnetic support and a magnetic layer, and more particularly to a magnetic recording medium having at least two magnetic layers and its magnetic recording medium. This relates to a manufacturing method.

[Background of the Invention] Magnetic recording media are widely used as recording tapes, video tapes, floppy disks, and the like. A magnetic recording medium basically consists of a magnetic layer in which ferromagnetic powder is dispersed in a binder, which is laminated on a non-magnetic support.

Magnetic recording media are required to have high levels of various properties such as electromagnetic conversion properties, running durability, and running performance. That is, audio tapes for music recording and playback are required to have higher original sound playback capabilities. Furthermore, video tapes are required to have excellent electromagnetic conversion characteristics, such as excellent original picture reproduction ability.

In addition to having such excellent electromagnetic conversion characteristics, magnetic recording media are required to have good running durability as described above. And in order to obtain running durability,
Normally, the function of abrasives plays an important role. In other words, the abrasive contained in the magnetic layer is distributed throughout the magnetic layer, but the negative part exists on the surface of the magnetic layer, and when the magnetic recording medium runs while contacting a traveling member such as a head, ,
The abrasive material present on the surface of the magnetic layer exerts a polishing effect at the contact surface between the surface of the magnetic layer and a head or the like. Therefore, by incorporating an abrasive into a magnetic recording medium, it is possible to improve running durability. However, the amount of abrasive present on the surface of the magnetic layer is only a fraction of the amount actually added to the magnetic layer, making it difficult to obtain sufficiently excellent running durability. For example, if the amount of abrasive added is increased to improve running durability, the content of ferromagnetic powder will decrease, and if an abrasive with a large particle size is used, the surface of the magnetic layer will Since the abrasive material tends to protrude excessively, the above-mentioned electromagnetic conversion characteristics deteriorate, causing a problem.

In order to solve this problem, we created two magnetic layers, an upper layer and a lower layer, with the upper layer being a magnetic layer with particularly excellent running durability and the lower layer being a magnetic layer with particularly excellent electromagnetic conversion characteristics. It has been proposed to improve running durability (Japanese Unexamined Patent Publication No. 58-20042β). In other words, the content of ferromagnetic powder is increased without adding additives such as abrasives to the lower layer to improve electromagnetic characteristics, and the layer thickness of the upper layer is reduced to 0.
．． 5~! , 5 μm, and by using an abrasive with a maximum particle diameter that does not exceed the thickness of the upper layer, it is possible to improve running durability without impairing electromagnetic conversion characteristics.

However, although it is possible to obtain a magnetic recording medium with good electromagnetic conversion characteristics and running durability to some extent by forming the magnetic layer into two layers as described above, it is still not possible to obtain sufficiently excellent performance in terms of the above performance, especially in terms of running durability. I can't say that there is.

[Object of the Invention] An object of the present invention is to provide a magnetic recording medium, such as an audio tape or a video tape, which has excellent electromagnetic conversion characteristics and improved running durability, and a method for manufacturing the same.

[Summary of the Invention] The present invention provides a magnetic recording medium in which a first magnetic layer and a second magnetic layer are provided in this order on the surface of a non-magnetic support, in which the second magnetic layer has a layer thickness of 0.5 μm or more. In a magnetic recording medium, the average particle size of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 1/3 or more of the layer thickness of the second magnetic layer. The magnetic recording medium is prepared by applying a first magnetic layer coating liquid to the surface of a non-magnetic support while it is running;
While the coating layer is in a wet state, a magnetic layer with a Mohs hardness of 6 or more and an average particle size of 1 of the layer thickness of the second magnetic layer is continuously applied to the coating layer.
A method for manufacturing a magnetic recording medium, comprising applying a coating liquid for a second magnetic layer containing an abrasive having an abrasive content of /3 or more so that the thickness of the second magnetic layer after drying is 0.5 μm or more. It can be advantageously manufactured by using.

[Effects of the Invention] As shown above, the magnetic recording medium of the present invention has at least two magnetic layers, the second magnetic layer (upper layer) has a layer thickness of 0.5 μm or more, and the second magnetic layer (upper layer) has a layer thickness of 0.5 μm or more. The average particle diameter of the abrasive having a Mohs hardness of 6 or more contained in the magnetic layer is 1 of the layer thickness of the second magnetic layer.
/3 or more.

By adopting such a configuration, the abrasive material becomes magnetic -
The polishing effect of the abrasive material can be effectively exerted by protruding moderately on the surface of the electromagnetic layer, and since the degree of protrusion is not excessive and the amount added is appropriate, running durability can be improved without impairing electromagnetic conversion characteristics. It is possible.

Moreover, by using the above-described specific manufacturing method, even an extremely thin second magnetic layer can be coated with a uniform layer thickness and with an extremely smooth surface.

Thereby, it is possible to provide the magnetic recording medium of the present invention which has excellent running durability and does not impair electromagnetic conversion characteristics.

[Detailed Description of the Invention] The magnetic recording medium of the present invention basically has a structure in which at least two magnetic layers containing ferromagnetic powder dispersed in a binder are provided on a non-magnetic support. have

Non-magnetic supports that can be used in the present invention include:
Polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyamide, and polyamideimide. , films or sheets made of synthetic resin such as polyimide: non-magnetic metal foils such as aluminum and copper; metal foils such as stainless steel foils; paper, ceramic sheets, etc.

The thickness of these supports ranges from 2.5 to 100 μm, preferably from 3 to 80 μm.

The present inventors have conducted various studies in order to particularly improve the running durability of magnetic recording media. As mentioned above, when the amount of abrasive added is increased to improve running durability, the content of ferromagnetic powder decreases, and when an abrasive with a large particle size is used, the magnetic layer Since the abrasive material tends to protrude excessively from the surface, the running durability is improved, but the electromagnetic conversion characteristics are deteriorated.

Therefore, it can be said that the magnetic recording medium of the present invention makes it possible to improve running durability without deteriorating the electromagnetic conversion characteristics. That is, the magnetic recording medium of the present invention has at least two magnetic layers obtained by providing a first magnetic layer and a second magnetic layer in this order on the surface of a non-magnetic support, and a second magnetic layer which is an upper layer. has a layer thickness of 0.5 μm or more, and the average particle diameter of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 1/3 or more of the layer thickness of the second magnetic layer. There is. By adopting such a configuration, the abrasive material protrudes moderately from the surface of the magnetic layer, and the polishing effect of the abrasive material can be effectively exerted.Also, the degree of protrusion is not excessive and the amount added is appropriate, making it easy to run. Not only is the durability improved, but the electromagnetic conversion characteristics are also excellent. That is, when the average particle diameter of the abrasive becomes 1/3 or more of the layer thickness of the second magnetic layer, the abrasive has a particle size distribution, so that the abrasive is substantially larger than the layer thickness of the magnetic layer; Since the abrasive itself tends to be easily distributed on the surface of the magnetic layer, the abrasive material protrudes appropriately from the surface of the magnetic layer. It is preferable that the average particle diameter is 172 or more than the layer thickness because it is more effective in polishing.

However, if the average particle size of the abrasive becomes too large, the abrasive tends to protrude excessively from the surface of the magnetic layer, the surface of the magnetic layer tends to become rough, and the electromagnetic conversion characteristics tend to deteriorate. Therefore, the average particle diameter is preferably at most 1.0 μm or less. Further, in view of the relationship with the layer thickness of the second magnetic layer, it is preferable that the average particle diameter is equal to or less than the layer thickness of the second magnetic layer.

The content of the abrasive material of the present invention having a Mohs hardness of 6 or more contained in the second magnetic layer is 2 parts by weight per 100 parts by weight of the ferromagnetic powder.
It is preferable that the amount is 15 parts by weight to maintain running durability. As an abrasive with a Mohs hardness of 6 or higher, α-A
l120. (Mohs hardness 9), Ti02 (Mohs hardness 6.5),
5i02 (7), 5n02 (6.5), Cr2
0) (same 9), 5iC (same 9) and TiC (same 9). Preferably, α-Al120° and Cr2O are used.

As mentioned above, it is necessary that the average particle diameter of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer of the magnetic layer of the present invention is 1/3 or more of the layer thickness of the second magnetic layer. For example, if the average particle diameter of the abrasive is 0.2 μm, the layer thickness of the second magnetic layer must be 0.6 μm or less, and 0.5 μm.
In this case, the thickness must be 1.5 μm or less.

Usually, when two magnetic layers are provided, the magnetic layer is formed by applying a first magnetic layer coating liquid, drying it, and then applying a second magnetic layer coating liquid. However, if the second magnetic layer is applied after drying the first magnetic layer, the
．． It is difficult and almost impossible to obtain a uniform layer thickness as thin as around 0 μm. 1 like this
．． In order to obtain a thin layer of around 0 μm, after applying the coating liquid for the first magnetic layer as described later, the coating liquid for the second magnetic layer must be continuously applied while the coating layer is still wet. It is necessary to form a magnetic layer by using the above method, thereby making it possible to obtain a thin second magnetic layer with a uniform layer thickness.

In the magnetic recording medium of the present invention, the second magnetic layer, which is the upper layer, has sufficient running durability. It is preferable that the amount is less, and more preferably that it is not contained.

There are no particular limitations on the binder resin used to form each magnetic layer of the present invention. As the binder resin, vinyl chloride copolymers (e.g., vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinyl acetate/acrylic acid copolymer, chloride (vinyl/vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/vinyl acetate copolymer), cellulose derivatives such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin,
Epoxy resin, phenoxy resin, polyurethane resin (
Examples include polyester polyurethane resins, polyether polyurethane resins, polycarbonate polyurethane resins, and the like. These resins may contain polar groups such as hydroxyl groups, carboxyl groups, epoxy groups, sulfonic acid metal bases, phosphoric acid groups, and phosphoric ester groups.

These can be used alone or in combination.

Furthermore, when a curing agent is used, a polyisocyanate compound is usually used. The polyisocyanate compound is selected from those commonly used as curing agent components for polyurethane resins and the like. Examples of polyisocyanate compounds include a reaction product of tolylene diisocyanate and 1 mol of trimethylolpropane (e.g., Desmodur L-75 (manufactured by Ba5inil)), diisocyanates such as xylylene diisocyanate or hexamethylene diisocyanate. Reaction product of 3 moles of trimethylolpropane with 1 mole of trimethylolpropane, biuret addition compound of 3 moles of hexamethylene diisocyanate, isocyanurate compound of 5 moles of tolylene diisocyanate, isocyanate of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate. Mention may be made of nurate addition compounds, polymers of isophorone diisocyanate and diphenylmethane diisocyanate.

Further, when performing curing treatment by electron beam irradiation, a compound having a reactive double bond (eg, urethane acrylate) can be used.

The total weight of the resin component and curing agent is 100% of the ferromagnetic powder.
It is usually preferably in the range of 5 to 40 parts by weight, more preferably 10 to 20 parts by weight.

Examples of the ferromagnetic powder used in the present invention include γ-Fe2O
Metal oxide-based ferromagnetic powder such as No. 3, dissimilar metal/metal oxide-based ferromagnetic powder such as γ-Fe2O3 containing other components such as cobalt, and ferromagnetic powder such as iron, cobalt or nickel. Examples include ferromagnetic metal fine powder containing metal.

When using a ferromagnetic metal fine powder, it is a ferromagnetic metal fine powder containing iron, cobalt or nickel, and has a specific surface area of 42rn"/g or more (particularly preferably 45rn"/g or more).
The ferromagnetic metal powder is preferably a fine ferromagnetic metal powder with a particle diameter of n''/g or more.

As an example of this ferromagnetic metal fine powder, the metal content in the ferromagnetic metal fine powder is 75% by weight or more, and the metal content is 8% by weight.
0% by weight or more of at least one ferromagnetic metal or alloy (e.g., Fe, Co, Ni, Fe-Co, Fe-Ni
%Co-Ni.

Co-N1-Fe), and other components (e.g., AIL, Si, S%Sc%T
i, V, Cr, Mn, Cu, Zn.

Y, Mo%Rh, Pd, Ag, Sn%Sb, B.

Ba, Ta, W, Re, Au, Hg, Pb%P.

Mention may be made of alloys that may contain (La%Ce, Pr%Nd, Te%Bi). Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide.

Methods for producing these ferromagnetic powders are already known, and the ferromagnetic powder used in the present invention can also be produced according to known methods.

There are no particular restrictions on the shape of the ferromagnetic powder, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used. In particular, it is preferable to use acicular ferromagnetic powder.

The above resin component, curing agent, and ferromagnetic powder are mixed and dispersed together with a solvent (e.g., methyl ethyl ketone, dioxane, cyclohexanone, ethyl acetate) that is normally used in the preparation of magnetic paint to obtain a magnetic paint. Crosstalk dispersion can be performed according to conventional methods.

In addition to the above components, magnetic paints contain commonly used additives or fillers such as antistatic agents (e.g. carbon black), lubricants (e.g. fatty acids, fatty acid esters, silicone oil), dispersants, etc. It goes without saying that it may also contain agents.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described. For coating, a magnetic paint prepared from the above materials is applied onto a non-magnetic support by the following method. First, a coating liquid for the first magnetic layer is prepared by cross-dispersing magnetic layer forming components such as a resin component for the first magnetic layer, a ferromagnetic powder, and a curing agent blended as desired with a solvent. For the second magnetic layer, in addition to the above-mentioned magnetic layer forming components, an abrasive having a Mohs hardness of 6 or more and an average particle diameter of 1/3 or more of the second magnetic layer is added to form the second magnetic layer. Prepare a layer coating solution.

The method for manufacturing a magnetic recording medium of the present invention is characterized by applying a first magnetic layer coating liquid to the surface of a non-magnetic support while it is running;
While the coating layer is in a wet state, the coating liquid for the second magnetic layer is continuously applied onto the coating layer so that the layer thickness after drying of the second magnetic layer is 0.
The purpose is to apply the coating to a thickness of 5 μm or more. For example, when a reverse roller is used as the coating machine, two reverse rollers may be installed in succession so as to sandwich the non-magnetic support running under the running direction. Alternatively, two magnetic layers may be installed with an interval within a range that allows the first magnetic layer to maintain a wet state (that is, a state in which the coating layer still contains a solvent and exhibits tackiness).

The second magnetic layer obtained by using the above manufacturing method can be coated with a uniform layer thickness and an extremely smooth surface even if the magnetic layer is extremely thin. As a result, the present invention has excellent running durability,
Furthermore, it is possible to manufacture a magnetic recording medium that does not impair electromagnetic conversion characteristics.

The coating layer of the magnetic paint is applied so that the thickness of the magnetic layer of the obtained magnetic recording medium (the total layer thickness of the first magnetic layer and the second magnetic layer) is usually within the range of 0.5 to 10 μm. applied.

A backing layer may be provided on the surface of the nonmagnetic support used in the present invention that is not coated with the magnetic paint. Normally, the back layer is made by applying a back layer forming paint made of particulate components such as abrasives and antistatic agents and a binder dispersed in an organic solvent to the side of the non-magnetic support that is not coated with the magnetic paint. This is a layer created by

Note that an adhesive layer may be attached to the surface of the nonmagnetic support on which the magnetic paint and the back layer forming paint are applied.

Usually, the coated layer of magnetic paint is dried after being subjected to a treatment for orienting the ferromagnetic powder contained in the coated layer of magnetic paint, that is, a magnetic field orientation treatment.

After being dried in this manner, the coated layer is subjected to surface smoothing treatment. For example, a super calender roll is used for the surface smoothing process. By performing the surface smoothing treatment, the pores generated by the removal of the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer increases, making it possible to obtain a magnetic recording medium with high electromagnetic conversion characteristics. can.

The thus cured laminate is then cut into a desired shape.

The cutting can be carried out under normal conditions using a normal cutting machine such as a slitter.

Although the magnetic recording medium of the present invention has been described as having an upper and lower two-layer system, it may have three or more layers as a whole as long as it maintains the above specified properties and includes two magnetic layers.

Next, Examples and Comparative Examples will be shown to further specifically explain the present invention. On each side, 2 parts 1 means 1 part by weight unless otherwise specified.

[Example 1] 100 parts of Co-yFe203 [Hc:
6500e.

5BET specific surface area: 35♂/gl Vinyl chloride/vinyl acetate/12 parts maleic anhydride copolymer (composition ratio 86:13:1, degree of polymerization 400) Polyester polyurethane resin 6 parts carbon black 3 parts butyl stearate 1 part stearin acid
2-part butyl acetate
200 parts・2-t Co-7Fe202 100 parts [11c
Near 000e.

S BET ratio 4 sides M: 40 m"/gl Vinyl chloride/vinyl acetate/12 parts maleic anhydride copolymer (composition ratio 86:13:1, degree of polymerization 400) Polyester polyurethane resin 6 parts α-AIL20
6 parts (average particle size = 0.6
μm) - carbon black 3 parts butyl stearate 1 part stearic acid 2 parts butyl acetate
200 parts of each of the above two paints were cross-dispersed using a sand mill. 6 parts of polyisocyanate and 40 parts of butyl acetate were added to the obtained dispersion, and the mixture was filtered using a filter having an average pore size of 1 μm to form coating solutions for forming the first magnetic layer and for forming the second magnetic layer, respectively. Prepared.

The obtained coating liquid for the first magnetic layer has a thickness of 3.0 after drying.
While running a polyethylene terephthalate support with a thickness of 15 μm at a speed of 60 m/min, it was coated on the surface of the support using a reverse roll,
Immediately after that (while the first magnetic layer is in a wet state), apply the coating liquid for the second magnetic layer using a reverse roll so that the thickness after drying is 1.0 μm, so that the magnetic layer is in a wet state. While the film was still in use, it was oriented using the magnet, dried, supercalendered, and slit into a 172-inch width to produce a videotape.

[Example 2] A videotape was manufactured in the same manner as in Example 1 except that the thickness of the second magnetic layer was changed from 1.0 μm to 0.8 μm.

[Example 3] A videotape was manufactured in the same manner as in Example 1 except that the thickness of the second magnetic layer was changed from 1.0 μm to 0.6 μm.

[Example 4] In Example 3, α-AJ2. O, with an average particle diameter of 0.3 μm
A videotape was produced in the same manner as in Example 3 except that α-AM, 03 was used.

[Example 5] A videotape was produced in the same manner as in Example 3, except that 3 parts of α-A4220 with an average particle size of 0.6 μm in the second magnetic layer coating solution was changed from 3 parts to 3 parts. .

[Example 6] In Example 1, α-AI1203 having an average particle size of 0.6 μm in the coating liquid for the second magnetic layer was replaced with α-AI1203 having an average particle size of 0.6 μm.
A videotape was produced in the same manner as in Example 1 except that Cr2O3 was used.

[Example 7] In Example 3, α-AIl with an average particle diameter of 0.6 μm and 0.6 μm in the coating liquid for the second magnetic layer were used. The average particle size is 0.6μm
A videotape was produced in the same manner as in Example 5 except that Cr201 was used.

Comparative Example 1 A videotape was produced in the same manner as in Example 1 except that the thickness of the second magnetic layer was changed from 1.0 μm to 2.0 μm.

[Comparative Example 2] A videotape was produced in the same manner as in Example 4 except that the thickness of the second magnetic layer was changed from 0.6 μm to 1.0 μm.

Comparative Example 3 A videotape was produced in the same manner as in Example 6 except that the thickness of the second magnetic layer was changed from 1.0 μm to 2.0 μm.

Regarding the video tapes obtained in the above Examples and Comparative Examples, the abrasive used in the second magnetic layer, its average particle diameter, its usage amount, its layer thickness, and each tape measured by the following measurement method. The physical properties of are shown in Table 1.

(1) Still Life Play each videotape in still mode and check the S/N of the screen.
The time required for this to decrease by 6 dB was measured. The output level was measured using an NV-870HD output level measuring device manufactured by Matsushita Electric Industrial ■.

(2) Head clogging Each videotape was recorded and played back using a VHS-VTR (NV8200, manufactured by Matsushita Electric Industrial ■) under high humidity conditions of 25°C and 80% RH, with 10 rolls of 1 hour long tape. . The number of rolls of tape that caused head clogging was investigated.

Margin below Table 1 I A O,661,010002A O,
660,81200 3A O,6fi 0.6 1
20< 04 A O, 3B 0.6
100 05 A O,630,610006
B O,661,0120< 01 A
O,662,0400 2A O,361,0202 38O,662,0600 In the abrasive types in Table 1 above, A represents α-A1.203 and B represents Cr2O3.

As is clear from Table 1 above, in the present invention, the second magnetic layer (upper layer) has a layer thickness of 0.5 μm or more, and the average particle size of the abrasive contained therein is 1/3 or more of the layer thickness. It can be seen that the magnetic recording medium has excellent still life and head clogging, and particularly has improved running durability.

On the other hand, comparative examples using an abrasive whose average particle size is smaller than the layer thickness of the second magnetic layer within the specified range of the present invention have particular problems in still life and poor running durability.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a first magnetic layer and a second magnetic layer are provided in this order on the surface of a non-magnetic support, the second magnetic layer has a layer thickness of 0.5 μm or more and is included in the second magnetic layer. A magnetic recording medium characterized in that the average particle size of the abrasive having a Mohs hardness of 6 or more is 1/3 or more of the layer thickness of the second magnetic layer. 2. The magnetic recording medium according to claim 1, wherein the average particle size of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 1/2 or more of the layer thickness of the second magnetic layer. . 3. 2. The magnetic recording medium according to claim 1, wherein the second magnetic layer has a thickness in the range of 0.5 to 1.5 μm. 4. 2. The magnetic recording medium according to claim 1, wherein the average particle size of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is equal to or less than the layer thickness of the second magnetic layer. 5. Claim 1, characterized in that the content of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 2 to 15 parts by weight based on 100 parts by weight of the ferromagnetic powder contained in the magnetic layer. The magnetic recording medium according to item 1. 6. 2. The magnetic recording medium according to claim 1, wherein the first magnetic layer does not contain an abrasive. 7. A coating solution for the first magnetic layer is applied to the surface of the non-magnetic support while it is running, and while the coating layer is in a wet state, a layer with a Mohs hardness of 6 or more and an average particle size of A coating solution for the second magnetic layer containing an abrasive whose thickness is 1/3 or more of the layer thickness of the second magnetic layer is applied so that the layer thickness of the second magnetic layer after drying is 0.5 μm.
A method for manufacturing a magnetic recording medium, characterized in that the coating is applied so that the magnetic recording medium is coated to a thickness of m or more. 8. The magnetic recording medium according to claim 7, wherein the average particle diameter of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 1/2 or more of the layer thickness of the second magnetic layer. manufacturing method. 9. 8. The method of manufacturing a magnetic recording medium according to claim 7, wherein the second magnetic layer has a thickness in the range of 0.5 to 1.5 μm. 10. 8. The method of manufacturing a magnetic recording medium according to claim 7, wherein the average particle size of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is less than or equal to the layer thickness of the second magnetic layer. 11. Claim 1, characterized in that the content of the abrasive having a Mohs hardness of 6 or more contained in the second magnetic layer is 2 to 15 parts by weight based on 100 parts by weight of the ferromagnetic powder contained in the magnetic layer. 7. The method for manufacturing a magnetic recording medium according to item 7. 12. 8. The method of manufacturing a magnetic recording medium according to claim 7, wherein the first magnetic layer does not contain an abrasive.