JPH03205614A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve antistatic property, light shielding property and electromagnetic conversion characteristics, and to reduce sliding noise and whitening of a head by constituting a magnetic layer of the uppermost layer and at least one lower layer so that each layer contains specified carbon black. CONSTITUTION:Carbon black of 10 - 30mmu average particle size is incorporated into at least one layer 2 of the lower layers of the magnetic layer, which reduces the surface specific resistivity and properly smoothens the surface. Carbon black of >=40mmu average particle size is also incorporated into the lower layer 2, which properly roughens the surface of the layer 2 and also the surface of the upper layer 4 owing to the influence thereof. The uppermost layer 4 contains carbon black of >=10mmu average particle size, which assists the effect of the carbon black in the lower layer 2. Thereby, antistatic property, light shielding property and electromagnetic conversion characteristics can be improved and sliding noise and head whitening can be improved.

Description

[Detailed description of the invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

mouth. BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it. Since conventional magnetic recording media have only one magnetic layer, it is necessary to cover a wide frequency band from low to high frequencies with one type of magnetic powder.

In particular, with the recent trend toward higher recording densities, magnetic powders with high Hc and high BET values are used because recording characteristics in high frequencies are improved and low noise is required.

However, since magnetic recording media are made of a single type of magnetic powder (magnetic layer), high H
c. Since it is necessary to use magnetic powder with a high BET value, the low-frequency characteristics become insufficient.

On the other hand, in magnetic recording media for video, media having multiple magnetic layers have been proposed in order to increase the magnetic recording capacity or to improve and balance the magnetic recording characteristics of the medium in both the high frequency region and the low frequency region. There is (Unexamined Japanese Patent Application Publication No. 1973-
98803, JP 59-172142, JP 32-2218, JP 51-64901, JP 56-12937, JP 58-56228,
JP-A No. 63-146211, etc.).

According to these known techniques, relatively fine magnetic powder is used in the upper layer of the magnetic layer, and larger magnetic powder is used in the lower layer, so that the upper layer receives video output and the lower layer receives chroma audio output. It was designed to. Generally, in magnetic recording media, the surface resistivity of the magnetic layer,
Carbon blank is added for light blocking properties and the like.

For example, the lower layer contains carbon black with a particle size of less than 30 mμ, and the upper layer contains at least one type of carbon black with a particle size of less than 30 mμ, and at least one type of carbon black with a particle size of 30 mμ or more (particle size difference of 10 mμ or more). This is shown in Japanese Patent Application Laid-Open No. 191321/1999. In the case of this conventional example, the use of fine particulate carbon black in the lower layer results in a smooth surface, which results in a fairly smooth surface for the upper layer as well, which results in excellent electromagnetic conversion characteristics. Also, JP-A-1-205726
According to the issue, the lower layer contains 1.0 to 20 parts by weight of fine carbon plastic particles with a particle size of less than 20 mμ, and the upper layer contains a particle size of 40 to 8.
0.1 to 10 carbon black with slightly coarse particles of 0 mμ
It is stated that it is contained in parts by weight. in this case,
The lower layer contains a fine-grain carbon blank with a particle size of 20 mμ or less, which is said to provide excellent antistatic and light-shielding properties. Furthermore, in JP-A-62-136364,
A medium is shown in which the upper layer contains coarse carbon plank particles with a particle size of 80 mμ or more, and the lower layer contains fine particle carbon black with a particle size of less than 40 mμ.

However, in a medium provided with a magnetic layer consisting of multiple layers as described above, the upper layer of the magnetic layer is very thin (usually 1.5
micrometers or less), it is extremely difficult to achieve both surface properties (ie, electromagnetic conversion characteristics) and other performances unless the particle size of carbon black and other factors are appropriately set. In any of the above known examples, the lower layer is
It uses fine particle carbon black, and has good antistatic and light shielding properties, but because the surface of the upper layer is smooth, it has good electromagnetic conversion properties, but there are problems with sliding noise and liquid clouding. In other words, because the surface of the upper layer is smooth, the coefficient of friction is large, and the sliding contact with the head is poor, which tends to cause noise in the signal.The durability is also insufficient, causing deposits on the head and causing the head to deteriorate. Cloudiness ↓ causes deterioration of characteristics.

C. Purpose of the Invention The purpose of the present invention is to significantly reduce sliding noise and head cloudiness while exhibiting good antistatic properties, light shielding properties, and electromagnetic conversion properties in a magnetic recording medium consisting of multiple magnetic layers. It is in.

two. The principle of the invention, that is, the present invention is such that a magnetic layer provided on a non-magnetic support is formed of an uppermost layer and a lower layer consisting of at least one layer, and at least one layer of the lower layer has an average particle size of 10 mμ or more, Carbon brass with a diameter of 30mμ or less and an average particle size of 40m
The present invention relates to a magnetic recording medium containing carbon black having an average particle diameter of 10 mμ or more, and in which the uppermost layer contains carbon black having an average particle size of 10 mμ or more.

Since the magnetic recording medium of the present invention has a plurality of magnetic layers (the uppermost layer and at least one lower layer), the upper layer has good high-frequency recording and playback characteristics for video output, etc. , and each layer can be formed so that relatively low-frequency recording and reproduction characteristics such as chroma and audio output are improved in the lower layer. For this purpose, it is generally necessary that the coercive force (Hc) of the upper layer (especially the top layer) be larger than that of the lower layer, and that the film thickness (or layer thickness) of the upper layer be thin, especially 1.5μ.
It is desirable that it be less than m. Further, it is desirable that the thickness of the lower layer adjacent to this upper layer is 1.5 to 4.0 μm.

In the present invention, it is desirable that the plurality of layers constituting the magnetic layer are adjacent to each other. The above-mentioned lower layer may be one layer, or may be two or more layers, but at least one of these layers is coated with carbon black (hereinafter referred to as first carbon black) having an average particle size of 10 mμ or more and 30 mμ or less. ) and carbon black with an average particle size of 40 mμ or more (hereinafter referred to as second carbon black), and the uppermost layer contains carbon black with an average particle size of Ionμ or more (hereinafter referred to as third carbon black). (referred to as carbon black). However, in addition to cases in which there is substantially a clear boundary between each layer, there may be a boundary area where both layers coexist at a certain thickness; Alternatively, the lower layer is each of the above layers. In particular, the medium of the present invention is suitable when each magnetic layer is coated and formed by a wet simultaneous multilayer coating (weton-wet) method. Of course, apply the upper layer after drying the lower layer.
- An on-dry method may also be used.

According to the magnetic recording medium of the present invention, the first carbon black and the second carbon black are contained in the lower layer of the magnetic layer, and since the first carbon black has a relatively small particle size, Lowering the surface resistivity improves the antistatic effect, and also smooths the surface appropriately! Magnetic conversion characteristics can be maintained favorably. For this purpose, the average particle size of the first carbon black should be 30 mμ or less. However, if the average particle diameter becomes too small, the surface properties will become too much, which is inappropriate, so the lower limit should be 10 mμ.

In addition to this first carbon black, the lower layer contains the second carbon black, so that
The second carbon black, which has a relatively large particle size, not only improves the light-shielding property, but also makes the surface of the lower layer (interface with the upper layer) moderately, preferably slightly rough, so that the surface of the upper layer is also moderately roughened due to this effect. You can face it. As a result, in addition to improving the above-mentioned properties, the sliding contact property and durability of the uppermost layer with respect to the head can be improved, and sliding noise and head cloudiness can be greatly reduced. For this purpose, the average particle size of the second carbon black should be 40 mμ or more, and the difference from the average particle size of the first carbon black should be 10 mμ or more.

In addition, since the top layer contains a third carbon black with an average particle size of 10 mμ or more, the antistatic properties, light shielding properties, durability, electromagnetic conversion properties, sliding properties, etc. of the top layer can be controlled as appropriate. This can enhance the effect of the car pump rack in the lower layer as described above, and at the same time directly bring out the performance of the top layer itself.

In the above, the average particle size of the first carbon black is 1
5 to 25 μm, the average particle size of the second carbon black is 4
0 to 120 μm, more preferably 40 to 80 μm. As with the lower layer described above, the third carbon black is preferably a mixture of carbon black with an average particle size of 10 mμ or more and 30 mμ or less and carbon black with an average particle size of 40 mμ or more.

The reason for this is the same as in the case of the lower layer described above; by using carbon black with a relatively small particle size and carbon black with a relatively large particle size, the surface of the top layer can be appropriately roughened, resulting in electromagnetic conversion properties. This is because sliding noise and the like can be further reduced.

In addition, the amount of the first carbon black added was 100% of the magnetic powder.
0.5 to 5.0 parts by weight, more preferably 1 to 3 parts by weight, and the amount of second carbon black added is 100 parts by weight of magnetic powder.
1.0 to 12.0 parts by weight, even 5.0 parts by weight
It is desirable to set it as 10.0 parts by weight. When the amount of the first carbon blank is 0.5 parts by weight or more, conductivity is easily obtained, and when the amount is 5.0 parts by weight or less, the surface properties are not deteriorated. If the amount of the second carbon blank is 12.0 parts by weight or less, it will not adversely affect the surface properties;
When the amount is more than 1 part by weight, the surface can be appropriately roughened. Also,
The amount of third carbon black added is 0.1 to 5.0 parts by weight, more preferably 0.2 to 2.0 parts by weight, per 100 parts by weight of magnetic powder.
Parts by weight are desirable for the above-mentioned performance. When this third carbon black is the above-mentioned mixture, the amount of carbon blank with small particle size added is 0.1 to 4 parts by weight, more preferably 0.2 to 2 parts by weight, per 100 parts by weight of magnetic powder.
The amount of carbon black with large particle size added is 100% magnetic powder.
It is desirable that the amount is 0.1 to 4 parts by weight, more preferably 0.2 to 2 parts by weight.

In the present invention, if the thickness of the uppermost layer is too thick, the effect of adding carbon black to the lower layer may be difficult to show on the surface, and the surface may become too flat, further reducing the performance of the lower layer.
The thickness of the uppermost layer is desirably 1.5 μm or less because there is a tendency for the output (on the low frequency side) to decrease.

In addition, in the above, the "average thread diameter" of the carpon crank
is an electron micrograph of a medium such as a tape at a magnification of 20,000 times, and the 1gI/A of carbon black particles photographed there.
River 7 Measure at least 50 diameters with a caliper, distinguishing between those with a diameter of 30 Fφ or less and those with a thickness of 40/thick or more (for the lower layer), or 10;
Means the average of 50 or more measurements (in the case of the top layer) that are above a whisper.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
Non-magnetic support 1 made of polyethylene terephthalate etc.
A first magnetic layer 2 and a second magnetic layer 4 are laminated thereon in this order. Further, although a back coat layer 3 is provided on the support surface opposite to the laminated surface, this need not necessarily be provided. An overcoat layer may be provided on the second magnetic layer. In the example of FIG. 2, the upper layer is further divided into layers 5 and 6.

In the magnetic recording media shown in FIGS. 1 and 2, the thickness of the first magnetic layer 2 is 1.5 to 4.0 μm (for example, 3.0 μm).
m), and the thickness of the second magnetic layer 4 or the total thickness of the second and third magnetic layers 5 and 6 is preferably 0.1 to 1.5.
pm (for example, 0.5 μm).

Although the magnetic layers 2, 4, 5, and 6 may contain magnetic powder,
Such magnetic powders include 1-Fe20, Co-containing 7
F et 03 , F e3 04 , Co-containing F
e. O. Iron oxide magnetic powder such as; Fe, Ni, Co, Fe-
Ni-Co alloy, Fe-Ni alloy, Fe-Al alloy, F
e-Al-Ni alloy, Fe-Al-Co alloy, Fe-A
ffi-Ca alloy, Fe-Mn-Zn alloy, Fe-Ni
-Zn alloy, Fe-Al-Ni-Co alloy, Fe-Af
-Ni-Cr alloy, Fe-Al-Co-Cr alloy, F
e-Co-NiCr alloy, Fe-Co-Ni-P alloy,
Examples include various ferromagnetic powders such as metal magnetic powders mainly containing Fe, Ni, Co, etc. such as Co--Ni alloys. The outermost magnetic layers 4 and 6 and the other magnetic layers 2 and 5 (and/or 2) are:
According to the invention, the former 4 and 6 are the top layer and the latter 2 and 5 or 5 and 2 are the lower layer.

Among these magnetic powders, each of the above magnetic layers 2, 4, 5,
6 can be selected.

Each magnetic layer also contains lubricants such as silicone oil, graphite, molybdenum disulfide, tungsten disulfide, monobasic fatty acids with 12 to 20 carbon atoms (such as stearic acid), and lubricants with a total number of carbon atoms of 3 to 40. Fatty acid esters, abrasives (for example, fused alumina), dispersants (powdered lecithin), etc. may be added.

The binder that can be used for the magnetic layers 2, 4, 5, and 6 preferably has an average molecular weight of about 10,000 to 200,000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, Vinyl-acrylonitrile copolymer, polyvinyl chloride, urethane resin, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate,
cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various rubbers, phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin, acrylic resin Examples include reactive resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/isocyanates, and mixtures thereof.

These binders are -So,M,-COOM,P○(O
A resin containing a hydrophilic polar group such as M'L (where M is hydrogen or an alkali metal such as lithium, potassium, or sodium, and M' is an alkali metal such as hydrogen, lithium, potassium, or sodium, or a hydrocarbon residue). It's good to have one. That is,
The polar groups in the molecules of these resins improve their compatibility with the magnetic powder, which further improves the dispersibility of the magnetic powder and prevents agglomeration of the magnetic powder, further improving the stability of the coating liquid. This can also improve the durability of the medium.

Such a binder, especially a vinyl chloride copolymer, can be obtained by copolymerizing a vinyl chloride monomer, a copolymerizable monomer containing an alkali salt of sulfonic acid or phosphoric acid, and other copolymerizable monomers as necessary. I can do it.

Since this copolymer is based on vinyl polymerization, it is easy to combine, and various copolymerization components can be selected, so that the properties of the copolymer can be optimally adjusted.

The metal of the above-mentioned salt of sulfonic acid or phosphoric acid is an alkali metal (especially sodium, potassium, lithium), and potassium is particularly preferred in terms of solubility, reactivity, yield, etc.

Further, when providing the bank coat layer 3, the above-described binder contains non-magnetic particles such as barium sulfate and is applied to the back surface of the support.

Further, as the material for the support 1, there may be used plastics such as polyethylene terephthalate and polypropylene, metals such as Zn, glass, BN, Si carbide, ceramics such as porcelain, ceramics, and the like.

Next, an example of the above-mentioned medium manufacturing apparatus is shown in FIG.

In this manufacturing apparatus, when manufacturing the medium shown in FIG. 1, the film-like support 1 fed out from the supply roll 32 is coated with the above-mentioned paints for the magnetic layers 2 and 4 by extrusion coaters 10 and 11. After that, for example 2000G
It is oriented by a front-stage orientation magnet 33 of Gauss, and further introduced into a dryer 34 equipped with a rear-stage orientation magnet 35 of, for example, 2000 Gauss, where it is dried by blowing hot air from nozzles arranged above and below. Next, the dried support 1 with each coated layer is led to a supercalender device 37 consisting of a combination of calender rolls 38, where it is calendered and then wound onto a winding roll 39.

Each paint may be supplied to the extrusion coaters 10 and 11 through an in-line mixer (not shown). In addition, in the figure, arrow D indicates the conveyance direction of the nonmagnetic base film. The extrusion coaters 10 and 11 have liquid reservoirs 13 and 1, respectively.
4 is installed to wet-on the paint from each coater.
Layer using the wet method. To manufacture the media shown in Figure 2,
In FIG. 3, one more extrusion coater may be added.

Ho. Example Examples of the present invention will be described below.

The proportions, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the present invention. In addition, in the following examples, all "parts" are parts by weight.

1-6, 1-7 First, each of the following combinations was kneaded using a kneader and then dispersed using a sand mill to prepare each magnetic paint.

<Magnetic paint A for upper layer> Cor-Fet 0.100 parts (H c = 8000 e, particle size = 0.16 μm) PVC resin containing potassium sulfonate 10 parts (MRI
IO, manufactured by Nippon Zeon ■) Sodium sulfonate-containing polyurethane 5 parts (UR-
8300, manufactured by Toyobo ■) α-AlzOz 6 parts (abrasive, average particle size 0.3 μm) Carbon blanks A, B (average particle size and amount added are shown in Table 1 below) Myristic acid 1 part Stearin acid
1 part putyl stearate
1 part methyl ethyl ketone
50 parts cyclohexanone
150 parts toluene
50 parts Coronate L 5 parts (manufactured by Nippon Polyurethane Industry ■) Magnetic paint B for lower layer> Cor-Fez Os 100 parts (H c = 7000 e, particle size = 0.24 am
) 10 parts of PVC resin containing potassium sulfonate (
MRIIO, manufactured by Nippon Zeon ■) Sodium sulfonate-containing polyurethane 5 parts (UR-
8300, manufactured by Toyobo ■) α-Altos S part (abrasive, average particle size 0.3 μm) Carbon blank A (average particle size and amount added are shown in Table 1 below) Carbon black B (average particle size , the amount added is shown in Table 1 below.) Myristic acid 1 part stearic acid
1 part butyl stearate
1 part methyl ethyl ketone
50 parts cyclohexanone
150 parts toluene
50 parts Coronate L 5
(manufactured by Nippon Polyurethane Industries ■) Next, various types of lower layer magnetic paint B and upper layer magnetic paint A were sequentially coated on the 14.5 μm thick polyethylene terephthalate base film using the apparatus shown in Figure 3, and the orientation and After drying, calendering was performed. In this case, the upper layer is 0.5μ
The dry film thickness of the lower layer was 3.0 μm.

Thereafter, a paint for the BC layer according to the following composition was applied to the surface opposite to the magnetic layer to a dry thickness of 0.8 μm.

Carbon black (Raven 1035)
40 parts barium sulfate (average particle size 300mm) 1
0 parts Nitrocellulose 25 parts N
-2301 (manufactured by Nippon Polyurethane Co., Ltd.) 25 parts Coronate L ( ) 10 parts Cyclohexanone 400 parts Methyl ethyl ketone 250 parts Toluene
250 copies of a wide magnetic film was thus obtained and wound up. This film was cut into % inch widths to produce video tapes shown in Table 1 below.

Then, the following performance evaluations were performed on each of the above tapes, and the results are shown in Table 1 below.

(a), RF output, Lumi S/N, Ku07 S/N, chroma output: Color video noise meter r Shibasoku9
52D/IJ was used, "HR-S70" manufactured by Victor Company of Japan
Value for reference tape (dB) with 00J deck
).

The frequencies of each signal are as follows.

RF output: 6MHZ IS/N: 6MHz Chroma S/N: 629KHz Chroma output: 629KHZ O)). Sliding noise (measurement conditions = 20°C, 10%, measurement deck: HR-37000 manufactured by Victor Japan)
:(i) Perform playback without running the tape, and measure system noise with a spectrum analyzer. (ii)
The sample tape is played back 10 times for 1 minute each, and the sliding noise is measured using a spectrum analyzer. (iii)
Regarding the noise level around 8 MHz, the noise value of 10 paths is read as an average value using the system noise as a reference (OdB).

(C). Head cloudiness was measured according to the following procedures.
■ Before measurement, clean the head to ensure that there is no cloudy head.

■ On the sample tape (Thl) (unused),
A single frequency of 6 MHz was recorded for 10 minutes at a recording level of +20% with respect to the reference tape, and after playing back three times, the frequency of 8 MHz was recorded.
A single frequency is recorded for 2 minutes at a recording level of +20% with respect to the reference tape, and this is played back to measure the output (these values are taken as OdB).

■ At room temperature and low humidity of 20%, sample tape (N(
L2) <Unused> Run in SP mode while recording the video signal from the beginning to the end of winding.

■ Record a single frequency of 8 MHz on the sample tape (Nllll) again for 2 minutes at the same recording level as ■, and play it back.
Measure the output, and find the difference in output reduction from the value (OdB) measured in (■).

(Note) Two sample tapes (Nal,
Shame 2) Measurements are taken using.

<Evaluation> ○: There is little or no deposit on the glass portion of the head.

×: There is deposits on the entire surface of the head. (d
). Light transmittance: The light shielding property of the tape was measured using a light source with a wavelength of 900 nm.

O...The tape runs smoothly until the end of the tape.
・Stopping or being unable to run on the way (e). Surface resistivity: Measured with a static honest meter (type S-4104) manufactured by Anamedo Co., Ltd. (sample voltage: 100 V).

(The following is a blank space, continued on the next page) From these results, based on the present invention, it was found that the lower layer had a particle diameter of 10 to 30
By containing comparatively coarse carbon black with a particle size of 40 mμ or more in addition to micro-particle carbon blank, the surface of the lower layer is slightly roughened, and the upper layer is also slightly roughened due to this effect. As for the conversion characteristics, sliding noise and head clouding are improved with almost no deterioration, and light shielding properties and conductivity are also improved.

Implementation Team 1 - Proofreader In the main upper layer magnetic paint A, Fe-Af ferromagnetic metal powder (Hc: Ku A, B) was used instead of Co-7-Fe203.
(The average particle size and amount added are shown in Table 2 below.Each videotape was produced in the same manner as in Example 1 except that cells were used.The performance was evaluated, and the results are shown in Table 2 below. Shown in 2.

Futoshi Group Main Comparison Group 1 In magnetic paint A for upper layer, Co T Fe203
Fe-Ni ferromagnetic metal powder (Hc: 1560
0 e , σs : 121 emu/g, B E T
Value: 58rrf/g, Fe:Ni-100: 5)
Each videotape was produced in the same manner as in Example 1, except that 100 parts of carbon blanks A and B (average particle size and amount added are shown in Table 2 below) were used. The results of the performance evaluation are shown in Table 2 below.

(The following margins continue on the next page) Table 2 From these results, when metal magnetic powder is used, if the medium is constructed based on the present invention, the electromagnetic conversion characteristics are further improved, and the sliding noise and head cloudiness are also improved. and has light blocking properties,
Conductivity is also further improved.

9~l2 ゞ 10 Next, when the magnetic layer is made up of three layers, layers 2, 5, and 6 as shown in Fig. is the intermediate Hc between the upper and lower layers (850
0e), the same as the other groups or the lower layer, the film thickness is 0 for the upper layer
．． When the performance was evaluated in the same manner as above, the results shown in Table 3 below were obtained. According to this, it can be seen that, as in the case of two layers, the configuration of the present invention provides sufficient performance.

(Margin below, continued on next page) Table 3 F. Effects of the Invention As described above, the present invention provides at least one of the lower layers of the magnetic layer.
Since the layer contains carbon black with an average particle size of 10 to 30 mμ, it lowers the surface resistivity and improves the antistatic effect, and also smoothes the surface appropriately to maintain good electromagnetic conversion characteristics. can. In addition, since the lower layer also contains carbon black with an average particle size of 40 mμ or more,
In addition to improving light shielding properties, the surface of the lower layer (interface with the upper layer)
Due to this effect, the surface of the upper layer can also be appropriately roughened, and in addition to improving the above-mentioned characteristics, it also improves the sliding contact of the top layer to the head, durability, and reduces sliding noise. and head cloudiness can be greatly reduced.

In addition, since the top layer contains carbon black with an average particle size of 10 mμ or more, it is possible to further control the antistatic properties, light shielding properties, durability, electromagnetic conversion properties, sliding properties, etc. of the top layer. This allows the effects of the carbon black in the lower layer described above to be promoted, while at the same time directly enhancing the performance of the top layer itself.

[Brief explanation of drawings]

The drawings are for exemplifying the present invention, and FIGS. 1 and 2 are sectional views of two examples of magnetic recording media, and FIG. 3 is a schematic diagram of a manufacturing apparatus for magnetic recording media. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Lower magnetic layer 3...Old...Back coat layer 4, 6... . . . Upper magnetic layer 5 . . . Middle rj1 magnetic layer.

Claims (1)

[Claims] 1. The magnetic layer provided on the non-magnetic support is formed of an uppermost layer and a lower layer consisting of at least one layer, and at least one layer of the lower layer has an average particle size of 10 mμ or more and 30 mμ.
A magnetic recording medium containing the following carbon black and carbon black with an average particle size of 40 mμ or more, and in which the uppermost layer contains carbon black with an average particle size of 10 mμ or more.