JPS63259826A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent degradation in an electromagnetic conversion characteristic and to improve durability by constituting a magnetic layer provided on a nonmagnetic base of 2 magnetic layers into which respectively specific ratios of carbon blacks (CB) are incorporated and forming the upper layer to the content of CB higher than the content in the lower layer. CONSTITUTION:The 1st and 2nd magnetic layers are successively provided on the nonmagnetic base. The CB is incorporated at 0.1-0.5pts. (pts.wt., hereafter the same) per 100pts. in the 1st magnetic layer (lower layer) into said layer and the CB is incorporated at >=0.5pts. per 100pts. magnetic powder into the 2nd magnetic layer (upper layer); in addition, the CB is incorporated into the upper layer at the ratio higher than by 0.2pts. than in the lower layer. The content of CB in the upper layer is preferably 1-10pts. per 100pts. magnetic powder and the average particle size of the primary particles of the CB is preferably in a 20-150mmu range in the case of the CB in the lower layer and in a 20-80mmu range in the case of the CB in the upper layer. The layer thickness is preferably in a 2.0-5.0mum range in the case of the lower layer and in a 0.2-2.0mum range in the case of the upper layer. The deterioration in the electromagnetic conversion characteristic is obviated and the durability is improved by constituting the magnetic layer of the combination of the above-mentioned two layers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to magnetic recording media, and more particularly to improvements in magnetic recording media having at least two magnetic layers.

[Technical Background of the Invention] Generally, magnetic recording media for audio, video, computers, etc. are magnetic recording media in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support. It is used.

Conventionally, the magnetic layer of such a magnetic recording medium contains carbon black mainly for the purpose of preventing static electricity.

However, the magnetic layer containing carbon black,
Since the surface smoothness of the magnetic layer deteriorates, there is a remarkable tendency for electromagnetic conversion characteristics to deteriorate as the amount added increases, especially in video tapes that require high-density recording. Also in audio tapes, a magnetic layer containing a large amount of carbon black has a reduced filling degree of magnetic particles in the magnetic layer, resulting in deterioration of electromagnetic conversion characteristics in the same manner as described above. However, a magnetic layer that does not contain carbon black has no antistatic effect, resulting in extremely poor durability.

For this reason, as a method for obtaining a magnetic recording medium with excellent durability and good electromagnetic conversion characteristics, Japanese Patent Application Laid-Open No. 58/200425
There is the following disclosure in the publication.

The magnetic layer consists of two magnetic layers, and only the second magnetic layer (upper layer) contains carbon black, thereby increasing the antistatic effect and improving durability. Further, the first magnetic layer (lower layer) does not contain carbon black, and by increasing the filling rate of magnetic particles in the magnetic layer, the electromagnetic conversion characteristics are improved. However, since the two-layer magnetic tape has a thin layer thickness of 0.5 to 1.5 μm, the antistatic effect is insufficient if only the upper layer contains carbon black. This results in increased dropouts due to dust adhesion during use.

Therefore, it cannot be said that the method described above provides a magnetic recording medium with excellent durability and good electromagnetic conversion characteristics.

[Object of the Invention] An object of the present invention is to provide a magnetic recording medium having at least two magnetic layers and having excellent electromagnetic conversion characteristics and durability.

[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 first magnetic layer has 100% by weight of magnetic powder in the magnetic layer. The second magnetic layer contains 0.5 parts by weight or more of carbon black per 100 parts by weight of the magnetic powder, and the second magnetic layer contains 0.5 parts by weight or more of carbon black per 100 parts by weight of the magnetic powder The magnetic recording medium is characterized in that the carbon black content of the layer is 0.2 parts by weight or more greater than the carbon black content of the first magnetic layer.

[Effects of the Invention] The present invention is composed of the above-mentioned -l-th magnetic layer (lower layer) and second magnetic layer (upper layer). This combination of two layers makes it possible to improve durability without deteriorating electromagnetic conversion characteristics. That is, by including carbon black in the range of 0.1 to 0.5 parts by weight not only in the second magnetic layer (upper layer) but also in the first magnetic layer (lower layer), durability can be significantly improved. This is thought to have made it possible to suppress the carbon black content of the second magnetic layer (first layer), and also contributed to improving the electromagnetic conversion characteristics.

[Detailed Description of the Invention] The magnetic recording medium of the present invention includes a first magnetic layer and a second magnetic layer provided in this order on the surface of a nonmagnetic support. The first magnetic layer (lower layer) contains carbon black in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of magnetic powder in the magnetic layer, and has a layer thickness of 2.0 to 5.0 μm. The second magnetic layer (bilayer) contains 0.5 parts by weight or more of carbon black per 100 parts by weight of magnetic powder,
(2) The layer thickness is within the range of 0.2 to 2.0 μm. As described above, it is possible to obtain a magnetic recording medium with excellent electromagnetic conversion characteristics and durability by varying the content and layer thickness of carbon black in the upper and lower layers and combining them optimally.

The second magnetic layer (upper layer) has excellent durability by increasing the antistatic effect by increasing the carbon black content than the first magnetic layer (lower layer) as described above. The content of carbon black is 0.5 parts by weight or more, preferably 1.0 to 10 parts by weight, based on 100 parts by weight of the magnetic powder.
．． It is in the range of 0 parts by weight. If the carbon black content is too low, the antistatic effect will be insufficient, while if it is too high, the smoothness of the surface of the magnetic layer will deteriorate.

The average particle diameter of the primary particles of carbon black is 20 to 80
It is preferable that the thickness is within the range of mμ because the smoothness of the surface of the magnetic layer is excellent. Carbon black having a particle size larger than this range is not preferred because the surface smoothness of the magnetic layer is poor and the electromagnetic conversion characteristics are poor.

On the other hand, as described above, the first magnetic layer (lower layer) contains less carbon black than the second magnetic layer (upper layer), and contains 0.1 to 0.5 parts by weight per 100 parts by weight of magnetic powder. ing. If only the second magnetic layer (-1 layer) contains carbon black and the first magnetic layer (lower layer) does not, the antistatic effect is considerably inferior as described above. Above 0.
It has been found that the antistatic effect is particularly improved by containing 1 to 0.5 parts by weight. Further, if the carbon black content exceeds 0.5 parts by weight, the filling rate of the magnetic powder will decrease, which is not preferable.

The average particle diameter of the primary particles of carbon black is 20 to 15
It is preferably within the range of 0 mμ. Carbon black having a particle size larger than this range is not preferred because the surface smoothness of the magnetic layer is poor and the electromagnetic conversion characteristics are poor.

In addition, in order to exhibit the effect of the above-mentioned two-layer system, the difference in carbon black content (content per 100 parts by weight of magnetic powder in each layer) must be at least 0.2 parts by weight. The amount must be 0.2 parts by weight or more greater than that of the first magnetic layer.

The carbon black used in the above two magnetic layers includes, for example, Asahi Thermal, #35, #
60 (manufactured by Asahi Carbon Company): Conductex'7 SC [C0NDIICTEX SO], Leben 500
[RAVEN 500] (manufactured by Nikolon Hiakahon Co., Ltd.); Vulcan XC Knee 72 [VUIJA
N XC-72] (manufactured by Cabot Corporation).

These are merely examples of specific commercial products of carbon black, and any carbon black that satisfies the above-mentioned average particle size can be used. Moreover, there is no problem even if they are used in combination.

The ratio of the magnetic powder to the binder contained in the first magnetic layer and the second magnetic layer of the present invention is such that the magnetic powder/binder is 2.
．． 5 to 10.0, and the difference in the ratio between the first magnetic layer and the second magnetic layer is 5 or less.

The magnetic recording medium of the present invention can be manufactured, for example, as follows.

After coating the first magnetic layer on the non-magnetic support, magnetic field orientation treatment and calender treatment were performed, and then the second magnetic layer was coated at 45 L/, and the magnetic field orientation treatment and calender treatment were performed in the same manner as the first magnetic layer. to form a magnetic layer coating.

The nonmagnetic support used in the present invention includes polyolefins such as polyethylene terephthalate (PET), polyesters of polyethylene naphthalate, and polypropylene;
Films or sheets made of cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, synthetic resins such as polycarbonate, polyamide, polyamideimide, and polyimide; non-magnetic metals such as aluminum and copper Foil; selected from metal foil such as stainless steel foil; paper, ceramic sheet, etc.

The magnetic layer in the magnetic recording medium of the present invention is a layer in which ferromagnetic powder is dispersed in a binder. There are no particular limitations on the magnetic powder used in the present invention. An example is γ-F
e2O3, Co-containing γ-Fe2O3, Fe3O4, C
o-containing Fe3O4, CrO2, Co-N1-P alloy,
Known ferromagnetic powders such as Fe-Co-Ni alloy can be used.

Furthermore, in the present invention, it is preferable to use an abrasive in addition to the carbon black described above. The abrasive used is not particularly limited, but has a Mohs hardness of 6 or more, preferably 8 or more. For example, MgO (Mohs hardness 6), Cr2O3 (Mohs hardness 8.5), a-
AJZ20z (%-S hardness 9), y-A120z (-
[--Hs hardness 7 to B), 5iC (α or β, Mohs hardness 9.5), and the like. The particle size is o, oi~1.
50 μm or more, preferably 0.10 to 0.80 μm
It is m. The content of the abrasive is preferably 0.5 to 10 parts by weight, more preferably 1 part by weight per 100 parts by weight of the magnetic particles.
~5 parts by weight. If necessary, particles of different types and particle sizes may be mixed and used.

The above-mentioned abrasive material is particularly preferably used for the second magnetic layer.

The binder solution for manufacturing the magnetic paint used in the present invention is a binder solution containing a resin component, a solvent, and, if necessary, a lubricant.

The resin component is a conventionally known thermoplastic resin, thermosetting resin,
Alternatively, reactive resins or mixtures thereof are used. Examples of resin components include vinyl chloride copolymers (e.g., vinyl chloride/vinyl acetate copolymers, vinyl chloride/vinyl acetate copolymers,
Vinyl alcohol copolymer, vinyl chloride, vinyl acetate,
Acrylic acid copolymer, vinyl chloride/vinylidene chloride copolymer, vinyl chloride/acrylonitrile copolymer, ethylene/vinyl acetate copolymer, -5OINa or -3O2
Vinyl chloride copolymers with Na and epoxy groups introduced), cellulose derivatives such as nitrocellulose resins, acrylic resins, polyvinyl acetal resins, polyvinyl butyral resins, epoxy resins, phenoxy resins, polyurethane resins ( Examples include polyester polyurethane resins, polyurethane resins into which polar groups such as -3OINa or -3O2Na are introduced, and polycarbonate polyurethane resins.

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.

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

Examples of solvents used in the production of magnetic paints include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, and acetic acid glycol monoethyl ether; Glycol ethers such as ether, glycol dimethyl ether, and dioxane; Aromatic hydrocarbons such as benzene, toluene, and xylene; Methylene chloride, ethylene chloride,
Carbon tetrachloride, chloroform, ethylene chlorohydrin,
Examples include chlorinated hydrocarbons such as dichlorobenzene, and these solvents can be used alone or in combination. Particularly preferred are polar solvents such as ketones or solvents containing polar solvents.

When producing magnetic paint, magnetic powder is uniformly kneaded and dispersed together with a binder solution. For this kneading and dispersion, a method is generally used in which surface dispersion is performed using a Miki roll mill, Miki roll mill, oven kneader, pressure kneader (one continuous kneader), etc., and then post-dispersion is performed using a sand grinder, a ball mill, etc.

In magnetic paint, lubricants, dispersants,
Of course, any one of various additives such as these may be added depending on the purpose.

Methods for applying magnetic paint include air doctor coating, blade coating, rod coating, extrusion coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, Spin codes and other methods are available.

Up to now, the manufacturing method of the magnetic recording medium of the present invention has been described in terms of an upper and lower two-layer system, but as long as it includes two magnetic layers that maintain the above specified properties, the magnetic layers may have three or more layers as a whole. It's okay.

Next, Examples and Comparative Examples will be shown to further specifically explain the present invention. In each case, part 1 means "part by weight" unless otherwise specified.

First, examples and comparative examples of manufacturing a Phillips-type compact cassette tape will be shown.

[Example 1] 7, - and 100 parts of Co-yFe202 [Hc: 6
500e.

BET method Specific surface area: 30rn”/g] Vinyl chloride
Vinyl acetate/10 parts Vinyl alcohol copolymer (composition ratio 92:3:5, degree of polymerization 600) Polyester polyurethane resin 7 parts (Dainippon Ink & Chemicals ■ Crisbon 72 (19) Lauric acid 2.0 parts Carbon black = 51 mμ 0.3 parts (#60: manufactured by Asahi Carbon ■) Polyisocyanate 5 parts (Coronate L-75 manufactured by Nippon Polyurethane ■) Butyl acetate 300 parts I Co-yFe203 100 parts [Hc Near 000e.

BET method Specific surface area: 30rn”/g] Vinyl chloride
Vinyl acetate/16 parts vinyl alcohol copolymer (composition ratio 92:3:5, degree of polymerization 600) Polyester polyurethane resin 4 parts (Crispon 7209 manufactured by Dainippon Ink & Chemicals ■) Lauric acid 2.0 parts Carbon black: 51 mμ 2. 0 copies (#fiO:
Asahi Carbon ■) a-AjlL203 1.0 parts (average particle size 0.5 μm) Polyisocyanate 5 parts (Japan Polyurethane ■ Coronate L-75) Butyl acetate 300 parts For each of the above two paints, excluding polyisocyanate Each component was cross-dispersed using a sand mill. After the cross-dispersion was completed, the removed polyisocyanate was added to a ball mill and mixed for 20 minutes. The obtained dispersion liquid was filtered using a filter having an average pore size of 1 μm to prepare a magnetic paint.

The obtained paint for the first magnetic layer was applied to the surface of a polyethylene terephthalate support having a thickness of 7 μm while running a reverse roll at a speed of 60 m/min so that the thickness after drying was 4 μm. While the magnetic layer coated using the same method is in a wet state, it is oriented using a 1500 Gauss magnet.
After drying, super calender treatment was performed. After that, the final magnetic layer thickness after drying the paint for the second magnetic layer was 5.5 μm.
While the magnetic layer is still wet, it is oriented using the above magnet, and after drying, it is subjected to super calendering treatment, slit to a width of 3.81 mm, and housed in a cassette to form a Phillips-type cassette. Manufactured compact cassette tapes.

[Example 21 In Example 1, 0.3 parts of carbon black in the paint for the first magnetic layer was changed to 0.2 parts, and 2.0 parts of carbon black in the paint for the second magnetic layer was changed to 1.0 parts. A Phillips-type compact cassette tape was manufactured in the same manner as in Example 1 except for this.

[Comparative Example 1] A Phillips-type compact cassette tape was produced in the same manner as in Example 1 except that 0.3 parts of carbon black in the paint for the first magnetic layer was changed to 0 parts.

[Comparative Example 2] In Example 1, 0.3 parts of carbon black in the paint for the first magnetic layer was changed to 1.0 parts, and 2.0 parts of carbon black in the paint for the second magnetic layer was changed to 2.0 parts. A Phillips-type compact cassette tape was manufactured in the same manner as in Example 1 except for the following.

[Comparative Example 3] A Phillips-type compact cassette tape was produced in the same manner as in Example 1, except that 2.0 parts of carbon black in the paint for the second magnetic layer was changed to 0.3 parts.

The physical properties of the Phillips-type compact cassette tapes obtained in the above Examples and Comparative Examples were measured as follows. The results are shown in Table 1.

Setting method L 1) MOL315 Using a commercially available tape deck (Model 582 manufactured by Nakamichi ■), FR- manufactured by Fuji Photo Film ■ in bi-position.
Relative values were measured when the sensitivity of rl (315 Hz) was expressed as OdB.

2) Output drop When a 45 minute long recording was made using a commercially available tape deck (model 582 manufactured by Nakamichi ■) and the playback was repeated 20 times, the output during recording was set to the OdB of the first playback output. The way the output was reproduced was measured to determine whether there was a decrease in output.

As is clear from Table 1 above, Examples 1 and 2 have good sensitivity and output reduction, and are excellent in electromagnetic conversion characteristics and durability.

On the other hand, in Comparative Examples, a decrease in output was observed in Comparative Example 1, in which the first layer (lower layer) did not contain carbon black, and Comparative Example 3, in which the second layer (upper layer) contained less carbon black. This indicates that there is a problem. Comparative Example 2, in which the first layer (lower layer) contains a large amount of carbon black, has poor sensitivity and problems with electromagnetic conversion characteristics.

Next, examples and comparative examples of videotape production will be shown.

[Example 3] 100 parts of “-coated Co-yFe203 [) 1c:
6000e.

BET method Specific surface area: 30rn'/g] Vinyl chloride
Vinyl acetate/10 parts Maleic anhydride copolymer (composition ratio 87:8:5, degree of polymerization 600) Polyester polyurethane resin 7 parts (Crysbon 7209 manufactured by Inuhiki Ink Chemical Industry ■) Stearic acid 3.0 parts Butyl stearate 1 .0 part Carbon black = 51 mμ 0.3 parts (#60: manufactured by Asahi Carbon ■) Polyisocyanate 5 parts (Coronate -75 manufactured by Nippon Polyurethane ■) Butyl acetate 300 parts γ72
P Coating Co-yFe203 100 parts [Hc Near 000e.

BET method Specific surface area: 40rn'/g] Vinyl chloride
Vinyl acetate/10 parts Maleic anhydride copolymer (composition ratio 87:8:5, degree of polymerization 600) Polyester polyurethane resin 7 parts (Dainippon Ink & Chemicals ■ Crisbon 7209) Stearic acid 3.0 parts Butyl stearate 1. 0 parts Carbon black: 51 mμ 2.0 parts (#60: manufactured by Asahi Carbon ■) α-Afi20. 1.0 parts (average particle size 0.3 μm) Polyisocyanate 5 parts (Coronate L-75 manufactured by Nippon Polyurethane ■) Butyl acetate 300 parts For each of the above two paints, each component except the polyisocyanate was mixed using a sand mill. Dispersed. After the cross-dispersion was completed, the removed polyisocyanate was added to a ball mill and mixed for 20 minutes. The obtained dispersion liquid was filtered using a filter having an average pore size of 1 μm to prepare a magnetic paint.

The obtained paint for the first magnetic layer has a thickness of 3.0 μm after drying.
While running a polyethylene terephthalate support with a thickness of 15 μm at a speed of 60 m/min, a 1500 Gauss magnet was applied to the surface of the support while the magnetic layer coated using a reverse roll was still wet. After drying, super calender treatment was performed. Thereafter, the final magnetic layer thickness after drying the paint for the second magnetic layer was 4.
Coat the magnetic layer to a thickness of 5 μm using a reverse roll, orient it using the magnet while the magnetic layer is still wet.
After drying, it was subjected to supercalender treatment and slit into a width of 172 inches to produce a videotape.

[Example 4] In Example 3, 0.3 parts of carbon black in the paint for the first magnetic layer was changed to 0.2 parts, and 2.0 parts of carbon black in the paint for the second magnetic layer was changed to 5.0 parts. A videotape was produced in the same manner as in Example 3 except for the following.

[Comparative Example 4] A videotape was produced in the same manner as in Example 3 except that 0.3 parts of carbon black in the paint for the first magnetic layer was changed to 0 parts.

[Comparative Example 5] A videotape was produced in the same manner as in Example 3 except that 0.3 parts of carbon black in the coating for the first magnetic layer was changed to 1.0 parts.

[Comparative Example 6] A videotape was produced in the same manner as in Example 3 except that 2.0 parts of carbon black in the paint for the second magnetic layer was changed to 0.3 parts.

The physical properties of the videotapes obtained in the above Examples and Comparative Examples were measured as follows. The results are shown in Table 2.

Determining method L 1) Video output Relative values are shown when the VH5 type video cassette tape Super HG manufactured by Fuji Photo Film ■ is set to Od B (629 kHz).

2) Using a dropout videotape, the relative speed between the tape and the head is 6 m/see, the head track width is 60 μm,
Record 10 minutes on a VTR under the condition that the recording signal is 5MHz,
After reproducing this tape 25 times, the number of dropouts (1.5 psec, -18 dB) occurring per minute was measured.

Table 2 As is clear from Table 2 above, Examples 3 and 4 have good video output and dropout, and are excellent in electromagnetic conversion characteristics and durability.

On the other hand, in Comparative Example 4, where the first layer (lower layer) does not contain carbon black, and Comparative Example 6, where the second layer (two-layer) contains a small amount of carbon black, dropouts are extremely common. , indicating that there is a problem with durability. Comparative Example 5, in which the first layer (lower layer) had a high carbon black content, had poor video output and problems with electromagnetic conversion characteristics.

Patent Applicant Fuji Photo Film Co., Ltd. Agent Patent Attorney Yasushi Yanagawa Procedural Amendment 1, Indication of the Case 1988 Patent Application No. 94739 2, Title of Invention Magnetic Recording Medium 3, Amendment to the Person Making the Amendment Related Patent applicant name (520) Fuji Photo Film Co., Ltd. 4, agent address Mitsuya Yotsuya Building 8, 2-14 Yotsuya, Shinjuku-ku, Tokyo
Floor 6. Number of inventions increased by amendment None 7. Subject of amendment (1) "Detailed description of the invention" column of the specification.

(2) “Claims” column of the specification.

8. Contents of amendment (1) As shown in the attached sheet.

(1) The "Detailed Description of the Invention" column of the specification will be amended as follows.

(1) The 1 larger J on the 3rd to 4th lines of page 5 of the specification is corrected to 1 larger J.

(2) 1 carbon black on page 10, lines 10 to 12 of the specification...preferable. In addition to A in 1 carbon black, an abrasive may be used if necessary. Correct it to 1.

(3) rlB section J on page 16, line 1 of the specification is rlO
Correct with part J.

(4) 17 copies of "14 copies" on page 16, line 4 of the specification.
and correct it.

(5) Delete "For the first and second magnetic layer...10 parts to 2.0 parts" on page 18, lines 10 to 11 of the specification.

(2) The “Claims” column of the specification will be amended as follows.

Note 1'l. In a magnetic recording medium comprising a first magnetic layer and a second magnetic layer provided in this order on the surface of a non-magnetic support, the first magnetic layer contains carbon black of O91 to 100 parts by weight of magnetic powder in the magnetic layer. Contains in the range of 0.5 parts by weight,
The second magnetic layer contains 0.5 parts by weight or more of carbon black based on 100 parts by weight of magnetic powder, and the carbon black content in the second magnetic layer is equal to the carbon black content in the first magnetic layer. 0.2 parts by weight or more” - Moxibustion! A magnetic recording medium characterized by:

2. The magnetic recording medium according to claim 1, wherein the carbon black content of the second magnetic layer is 1 to 10 parts by weight based on 100 parts by weight of the magnetic powder.

3゜The average particle size of the primary particles of carbon black contained in the first magnetic layer is within the range of 20 to 150 ml, and the average particle size of the primary particles of carbon black contained in the second magnetic layer is within the range of 20 to 150 ml. , 20 to 80 m p.

4゜The layer thickness of the first magnetic layer is within the range of 2.0 to 5.0 gm, and the layer thickness of the second magnetic layer is 0.2 to 2.0 gm.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is within the range of gm. ”-I”21

Claims (1)

[Claims] 1. In a magnetic recording medium comprising a first magnetic layer and a second magnetic layer provided in this order on the surface of a non-magnetic support, the first magnetic layer comprises 100 parts by weight of magnetic powder in the magnetic layer. , the second magnetic layer contains carbon black in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the magnetic powder, and the second magnetic layer A magnetic recording medium, wherein the carbon black content in the first magnetic layer is 0.2 parts by weight or more greater than the carbon black content in the first magnetic layer. 2. The magnetic recording medium according to claim 1, wherein the second magnetic layer has a carbon black content of 1 to 10 parts by weight based on 100 parts by weight of the magnetic powder. 3. The average particle size of the primary particles of carbon black contained in the first magnetic layer is within the range of 20 to 150 mμ, and the average particle size of the primary particles of carbon black contained in the second magnetic layer is 20 mμ. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a particle diameter in the range of .about.80 m.mu. 4. The layer thickness of the first magnetic layer is within the range of 2.0 to 5.0 μm, and the layer thickness of the second magnetic layer is 0.2 to 2.0 μm.
The magnetic recording medium according to claim 1, characterized in that the magnetic recording medium is within the range of μm.