JPH0453021A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability by incorporating a nonmagnetic material containing alumina of specified particle size and specified wt.% of silicon dioxide into the uppermost layer, by a specified amt. of this nonmagnetic material to the ferromagnetic powder, and incorporating nonmagnetic metal oxide of specified particle size into other layer by a specified amt. of this nonmagnetic metal oxide to the ferromagnetic powder. CONSTITUTION:The magnetic recording medium has a first magnetic layer 1 and a second magnetic layer (uppermost layer) 2 deposited on a nonmagnetic supporting body S. The nonmagnetic material to be incorporated into the uppermost layer consists of alumina of <=0.4 mum average particle size and 2-10 wt.% silicon dioxide, and is incorporated by 3-15 pts.wt. to 100 pts.wt. of the ferromagnetic powder. The nonmagnetic metal oxide has <=0.4 mum average particle size and is incorporated by <=10 pts.wt. to 100 pts.wt. of the ferromagnetic powder into the layer except for the uppermost layer. In the production process, the nonmagnetic supporting body 5 released from a roll 4 is coated with a magnetic coating material by a coater 6, treated with front and rear magnetic orienting devices 7, 8, and dried with a drier 9. Then the medium is subjected to surface smoothening treatment by a supercalendering device 10 and wound up on a winding roll 11. Thus, the obtd. medium has excellent traveling durability, still property and electromagnetic conversion characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium that is excellent in running durability, still characteristics, and electromagnetic conversion characteristics.

[Prior Art and Problems to be Solved by the Invention] Recent magnetic recording media (video tapes, audio tapes, etc.) are required to have high density recording, and efforts are being made to smooth them.

According to such a method, it is possible to improve the electromagnetic conversion characteristics of the magnetic recording medium, but on the other hand, there is a problem that running stability is impaired.

That is, when recording or playing back using this type of magnetic recording medium, friction may increase when it comes into contact with the guide post of the magnetic head or the cylinder for the rotating head, and scratches may occur on the surface of the magnetic layer. Furthermore, ferromagnetic powder may fall out of the magnetic layer (dropout).

Such a phenomenon shortens the life of the magnetic layer (still life), especially under conditions in which still images are continuously reproduced (still image).

Therefore, in order to improve the running durability of the magnetic recording medium, Cry'3. AItO3, Ti0a, 5i
It is practiced to contain an abrasive such as Oz.

However, this conventional method has a problem in that it is difficult to select the amount of abrasive to be added and the particle size.

For example, if too much abrasive is added, the running stability of the magnetic recording medium will certainly improve, but the contact between the magnetic layer and the magnetic head will decrease, and as a result, the electromagnetic conversion characteristics of the magnetic recording medium will deteriorate. It will drop.

On the other hand, if the amount of abrasive added is too small, sufficient running stability cannot be obtained.

Furthermore, if the particle size of the abrasive is small, the amount of head wear will be small but the still characteristics will deteriorate; on the other hand, if the particle size of the abrasive is large, the still characteristics will be improved but the amount of head wear will be increased.

The present invention has been made to improve the above situation.

That is, one object of the present invention is to provide a magnetic recording medium that has good electromagnetic conversion characteristics, has a running durability of 8, and has improved still characteristics and the like.

[Means for Solving the Problems] The present invention for achieving the above-mentioned object has a structure in which, among a plurality of magnetic layers stacked on a non-magnetic support, the upper layer has an average grain size of 0 or 0.
．． A nonmagnetic material made of alumina of 4 gtn or less containing 2 to 1% by weight of silicon dioxide is contained in 3 to 15 parts by weight per 1 part by weight of ferromagnetic powder, and is added to the magnetic layers other than the outermost E layer. The present invention is a magnetic recording medium characterized in that a nonmagnetic metal oxide having an average particle size of 0.4 pLm or less is contained in an amount of 10 parts by weight or less per 100 parts by weight of ferromagnetic powder.

Hereinafter, one aspect of the present invention will be explained in detail.

Single Layer Structure The magnetic recording medium of the present invention has a plurality of magnetic layers laminated on a nonmagnetic support.

As a specific example of a magnetic recording medium, for example, Fig. 1 (a)
As shown in the figure, a first magnetic M1 and a second magnetic 3! (Top layer) A magnetic recording medium formed by laminating 2.
As shown in figure (b), a first magnetic layer l is placed on a non-magnetic support S.
Examples include a magnetic recording medium formed by laminating a second magnetic layer 2 and a third magnetic layer (uppermost layer) 3.

In addition, in the present invention, an adhesive layer (adhesive layer is also included in this concept) can be provided between the non-magnetic support and the magnetic layer. A back coat layer can be provided on the (back side).

Magnetic Layer: The magnetic layer basically contains ferromagnetic powder, a binder, and a nonmagnetic substance.

In the present invention, there are specific conditions for this nonmagnetic substance, and it is important to decide in which magnetic layer it should be contained and in what amount.

That is, the uppermost magnetic layer contains a nonmagnetic material, and the other magnetic layers than the uppermost layer contain a nonmagnetic metal oxide.

The above-mentioned non-magnetic material is made of alumina having an average particle size of 0.4 μm or less and contains 2 to 10% by weight of silicon dioxide, and the uppermost layer contains 3 to 15 parts by weight per 100 parts by weight of ferromagnetic powder. Ru.

In addition, the above non-magnetic metal oxides have the same average particle size <0.4
μm or less, and 1 ferromagnetic powder in the magnetic layer other than the top layer
It is contained in an amount of 10 parts by weight or less per 00 parts by weight.

Only when this condition is satisfied can the magnetic recording medium have excellent electromagnetic conversion characteristics, improved running durability, and improved still characteristics.

On the other hand, if the content of silicon dioxide in the non-magnetic material is less than 2% by weight, the treatment effect of silicon dioxide will not be exhibited, resulting in poor monodispersity and deterioration of electromagnetic conversion characteristics. Moreover, if the content exceeds 10% by weight, the surface of the non-magnetic material will be covered with silicon dioxide, which may cause the head to become cloudy due to a decrease in polishing power, which is not preferable.

Further, if the average particle size of the alumina exceeds 0.4 JLm, the surface of the magnetic coating film becomes rough, spacing loss with the head increases, and electromagnetic conversion characteristics deteriorate, which is not preferable.

Furthermore, if the amount of the non-magnetic material added to the ferromagnetic powder is less than 3 parts by weight, the polishing power will decrease, causing deterioration of durability, and if the amount added exceeds 15 parts by weight, the relative In some cases, the amount of ferromagnetic powder or binder added may be reduced, and the respective functions may not be fully demonstrated.

On the other hand, the average particle size of the nonmagnetic metal oxide used in the present invention is 0.
．． If it exceeds 4 .mu.m, the surface of the underlying magnetic layer will become rough, which will have an adverse effect on the i&1- layer, causing deterioration of the electromagnetic conversion characteristics, which is not preferable.

Also, if the amount of non-magnetic metal oxide added to the ferromagnetic powder exceeds 10 parts by weight, the amount of the ferromagnetic powder and binder will be relatively small, and their respective functions will not be fully demonstrated. be.

If the non-magnetic material contains alumina and -1 silicon oxide bonded to each other, the structure may not be adopted, or in particular, the surface of α-alumina particles may be coated with a silicon monoxide layer. structure or preferred.

Such a non-magnetic material can be manufactured by a known method, or preferably by adding silicon dioxide when classifying alumina with water, heating the resulting mixture, and then drying it. It is.

In addition, there are favorable conditions for the alumina in terms of pH.

That is, the pH is preferably in the range of 3 to IO, preferably 7 to IO.
A range of 8 is more preferable.

If this pH is less than 3, the surface of the alumina will be covered with silicon monoxide, which may cause the head to become cloudy due to the low polishing power.If the pH exceeds 0, the treatment effect of silicon dioxide will be lost. Both are undesirable because they may cause poor dispersibility and deterioration of electromagnetic conversion characteristics.

Examples of the nonmagnetic metal oxide used in the present invention include:
Alumina [α-A l 20 ! (corundum, etc.), artificial corundum, fused alumina (all alumina is not treated with silica), diiron trioxide, chromium oxide, and emery (main ingredients: corundum and magnetite).

These nonmagnetic metal oxides can be used alone or in combination of two or more.

Examples of the ferromagnetic powder used in the present invention include C.

Contains FetO,l powder, Fe50<powder with COO, Fed with COO, (4/3<x<3/2) powder, or Fe-^Kou metal powder, Fe-Ni metal powder, Fe-A4-)li metal powder.

Fe-AM-P metal powder, Fe-Xl-3i-A metal powder, Fe-Ni-9i-Al1-11n metal powder,
Nu-Co metal powder, Fe-1lln-Zr+metal powder, Fe-Ni-Zn metal powder, Fe-Go-Ni-C
r Metal powder, Fe-Go-Ni-P metal powder, Co-
Examples include fine ferromagnetic metal powders such as Ni metal powder and Go-P metal powder.

These ferromagnetic powders can be used alone or in combination of two or more.

Among these, particularly preferred are fine CO-containing -
Fetus powder.

Such ferromagnetic powder has large saturation magnetization and coercive force (Hc), and is excellent in high-density recording.

Also, the specific surface area is large (for example, the BET value is 40m2/
(7) By using ferromagnetic powder, it is possible to easily realize a medium that allows high-density recording and has an excellent S/N ratio.

On the other hand, various resins can be used as the binder in the present invention.

First, in order to have good compatibility with the ferromagnetic powder and improve its dispersibility, it is preferable to use a resin modified by introducing a functional group, particularly a modified polyurethane resin, a modified vinyl chloride resin, or a modified polyester resin.

Examples of the functional group include -So, M, -0SO*
M, -COOM and OM" (In the formula, M is a hydrogen atom or an alkali metal such as lithium or sodium, and M' and M2 are each a hydrogen atom, lithium, potassium, sodium, or an alkyl group. , Ml and M2 may be the same or different.), etc. are preferable.

When the modified resin contains such a functional group, the compatibility between the modified resin and the ferromagnetic powder is improved, and the dispersibility of the ferromagnetic powder is further improved.

Not only that, it also prevents agglomeration, which improves the stability of the coating solution, which in turn improves the frequency characteristics from high to low frequencies in a well-balanced manner, improving the electromagnetic conversion characteristics and the durability of the magnetic recording medium. Sexuality also improves.

The modified resin is a vinyl chloride resin, a polyurethane resin, or a polyester resin, and a compound having an eyelid functional group and chlorine in the molecule, such as a compound having an eyelid functional group and chlorine.
, C sentence-CH, C)1. O20,llll,CM
-CH2COO11,0111'C1-C)! ”-P
It can be produced by combining compounds such as -O O Rei 2 (Tatashi, M, Ml, M2 have the same meanings as above) through a dehydrochloric acid reaction.

Next, we will discuss the magnetic materials used in the present invention, that is, magnetic materials and odor-magnetic gold! As a binder suitable for increasing the dispersibility of the E oxide, the above-mentioned modified resins are preferred, and modified polyurethane resins are particularly preferred.

Among the raw materials for the polyurethane resin, preferred diisocyanates include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and isophorone diisocyanate, and preferred polyester polyols include polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, and polycaprolactone. , polyoxypropylene diol, polytetramethylene glycol ether, etc. are preferable as the polyether polyol.

In addition, as glycol, ethylene glycol, 1.2
-Propylene glycol, 1,3-butanediol, 1
．． 6-hexanediol, neopentyl glycol,
Trimethylolpropane, glycerin, etc. are preferred;
Preferred dicarboxylic acids include adipic acid, sebacic acid, maleic acid, and isophtheric acid.

Furthermore, in the present invention, in addition to the above, thermoplastic resins, thermosetting resins 1-reactive resins, electron beam curable resins, or mixtures thereof, which are conventionally known in the field of magnetic recording media, are used as binders. or they can be used in combination with the modified resin.

Examples of the thermoplastic resin include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, and acrylic ester-vinylidene chloride copolymer. Polymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral,
Cellulose derivative (cellulose acetate butyrate)
, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.)
, styrene-butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, and synthetic rubber-based thermoplastic resin.

As the thermosetting resin or reactive resin.

For example, phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, methacrylate copolymers and cyisocyanates. Examples include mixtures with brevolimer, urea formaldehyde resins, and polyamine resins.

Examples of the electron beam irradiation curable resin include unsaturated prepolymers such as maleic anhydride type, urethane acrylic type, epoxy acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, and needle acrylic. Examples include multifunctional polymers such as urethane acrylic type, epoxy acrylic type, Nisdel phosphate acrylic type, aryl type, and hydrocarbon type.

In the present invention, one type of binder may be used alone, or 211 or more binders may be used in combination.

The amount of the binder in each magnetic layer is usually 1 to 200 parts by weight, preferably 1 to 50 parts by weight, per 190 parts by weight of the ferromagnetic powder.

If the amount of binder blended is too large, the amount of ferromagnetic powder blended will be reduced, resulting in a decrease in the recording density of the magnetic recording medium, and if the blended amount is too small, the strength of the magnetic layer will be reduced. However, the running durability of the magnetic recording medium may be reduced.

In the present invention, a curing agent can be appropriately used in combination with the binder.

Suitable examples of this curing agent include aromatic polyisocyanates and/or aliphatic polyisocyanates.

Examples of aromatic polyisocyanates include tolylene diisocyanate (TD I) and combinations thereof with active hydrogen compounds, and have an average molecular weight of 100 to 30.
A value in the range of 00 is preferred.

As the aliphatic polyisocyanate, for example, hexamethylene diisocyanate (HMD 1 ), 4.4゛-
These include diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and adducts of these with active hydrogen compounds, and have an average molecular weight of 100.
-3000 is preferred, and non-alicyclic polyisocyanates and adducts of these with active hydrogen compounds are more preferred.

The amount of curing agent added to the binder is usually 1/1 by weight.
20-7'/10. Preferably it is 1/10 to 1/2.

In the magnetic recording medium of the present invention, the magnetic layer may contain various additive components such as a lubricant, conductive powder, and surfactant, if necessary.

Examples of the above-mentioned lubricants include silicone oil, graphite, molybdenum disulfide, carbon atoms of 12 to 2
Examples include fatty acid esters consisting of about 0 monobasic fatty acids (for example, stearic acid) and monohydric alcohols having about 3 to 26 carbon atoms.

In addition, when the lubricant is particularly contained in the uppermost magnetic layer, the contact characteristics with the head (sliding performance, wear resistance, etc.) can be improved.

Examples of the conductive powder include carbon black, graphite, silver powder, and nickel powder.

The average particle size of these conductive powders is usually 10 to 1
A range of 1 mIL is preferred.

The surfactant is natural or nonionic.

Examples include anionic, cationic, and amphoteric surfactants.

By incorporating these conductive powders and surfactants into the magnetic layer, especially the top layer, it is possible to effectively lower the surface electrical resistance, thereby preventing the generation of noise due to the discharge of electrical charges and the occurrence of dropouts due to the adhesion of dust. It can be prevented.

The thickness of the magnetic layer is not particularly limited, but the thickness of the uppermost layer is preferably from 0.1 to 1.54 m, and the thickness of the entire magnetic layer is preferably from 0.5 to 4.5 pm.

-Nonmagnetic support- Examples of the material forming the nonmagnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, and cellulose derivatives such as cellulose triacetate and cellulose diacetate. ,polyamide,
Plastic such as polycarbonate, Cu, A4, Z
Examples include metals such as n, glass, boron meride, St carbide, and ceramics.

There is no particular restriction on the form of the non-magnetic support, and it is mainly tape-like,
There are film, sheet, card, disk, and drum shapes.

There is no particular limit to the thickness of the non-magnetic support, and in the case of a tape, film, or sheet, it is usually 3 to 100 mm.
μm, preferably 5 to 50 p, rn, and in the case of a disk or card shape, it is usually 30 to 1, Jtm,
In the case of drums, it is determined appropriately depending on the recorder, etc.

Note that the nonmagnetic support may have a single layer structure or a multilayer structure.

Further, this nonmagnetic support may be subjected to a surface treatment such as a corona discharge treatment.

-Manufacture of magnetic recording medium- There is no particular restriction on the manufacturing method of the magnetic recording medium of the present invention, and it can be manufactured according to a known manufacturing method of a multi-calendar structure type magnetic recording medium.

For example, generally, a magnetic coating is prepared by cross-dispersing magnetic layer forming components such as ferromagnetic powder, a binder, and a non-magnetic substance in a solvent, and then this magnetic coating is applied to the surface of a non-magnetic support sequentially or simultaneously. Apply.

When preparing the magnetic paint, the non-magnetic powder and the ferromagnetic powder are not mixed together from the beginning (simultaneous dispersion).
It is preferable to separately disperse each in the form of a slurry (separate dispersion) and then mix the dispersions.

This is because magnetizable substances have binders suitable for dispersing them, and ferromagnetic powders have binders suitable for dispersing them.
Which binder is suitable for which dispersion is as described above.

The solvents required for the preparation of magnetic paint include ketones such as acetone, methyl ethyl ketone (IIEK), methyl isobutyl ketone (MILK), and cyclohexanone, alcohols such as methanol, ethanol, propatool, methyl acetate, ethyl acetate, Nisder series such as butyl acetate, propyl acetate, ethyl lactate, ethylene glycol monoacetate, etc.: thiethylene glycol dimethyl ether, 2-ethoxyethanol, detrahydrofuran,
Ethers such as dioxane: Aromatic carbonized wood such as benzene, toluene, xylene, etc. Halogenated hydrocarbons such as methylene chlorite, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. can be used. .

Various kneaders can be used for cross-dispersing the magnetic layer forming components.

Examples of this kneading machine include a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a side grinder, a Sqegvari attritor, a high-speed impeller dispersion machine, a high-speed stone mill, a high-speed impact mill, a disper kneader-1 high-speed mixer homogenizer, and a super-high-speed mixer homogenizer. Examples of coating methods that include a sonic dispersion machine include wet-on-wet (wet-on-wet) and wet-on-dry (wet-on-dry) methods.
y) Ho 2 2, etc. can be mentioned.

Among these, the wet-on-wet method is particularly preferred.

Compared to other coating methods, this method causes fewer troubles such as dust adhesion during manufacturing, and the film thickness can be easily controlled.

Application methods for magnetic paint include, for example, gravure coating, knife coating, wire bar coating, doctor blade coating, reverse roll coating, dip coating, air knife coating, calendar coating, and squeegee coating. , kiss coating method, and fantine coating method.

After applying a magnetic paint to the surface of a non-magnetic support, the undried paint film is generally subjected to a magnetic field orientation treatment, and then a surface smoothing treatment is performed using a super calender roll, etc. You can get

FIG. 2 shows the process, in which the non-magnetic support 5 unwound from the roll 4 is coated with magnetic paint in the coating device W6, and then transferred to the former magnetic field orientation device 7 and the latter magnetic field orientation device 8. After being processed (for example, at 2000 G) and further passed through a drying device 9, it is wound up onto a super calender device 1 (subjected to surface smoothing treatment by a roll) 1.

A magnetic recording medium can be obtained by cutting the raw material thus obtained into desired shapes and dimensions.

[Example] Next, the present invention will be explained in more detail by referring to Examples and Comparative Examples.

In addition, "parts" in 1 or less represent "parts by weight."

(Examples 1 to 3. Comparative Examples 1 to 3)) In order to produce a magnetic recording medium having a two-layered magnetic layer consisting of a calendar and a lower layer, the following compositions were mixed and dispersed to prepare a magnetic paint for the lower layer. and a paint for the upper layer was prepared.

Lower 1s11 size Co-γ-Fe, O, powder 100 parts Vinyl chloride-vinyl acetate copolymer 10 parts Polyurethane resin 7 parts Magnetism Metal oxide (
Type II, physical properties, etc. are listed in Table 1)...Amounts listed in Table 1 Stearic acid...1 part Butyl stearate...
・・・・・・ 1 part cyclohexanone・・・・・・・
- 200 parts Methyl ethyl ketone Toluene Carbon black Polyisocyanate - 100 parts 1.00 parts 1 part 3 parts JLJJL material Co-γ-FeO 03 powder 100 parts Chloride Vinyl-vinyl acetate copolymer...10 parts Polyurethane resin...7i Non-magnetic material (physical properties, type, etc. are listed in Table 1)...Amount listed in Table 1 Stearic acid・・・・・・・・・・・・ 1 part butyl stearate・・
・・・・・・ 1 part cyclohexanone・・・・・・・
・ 200 parts methyl ethyl ketone 1
00 parts Toluene・・・・・・・・・・・・ 10 [1
fi polyisocyanate... Part 3 Next,
The magnetic paint for the lower layer and the paint for the upper layer were dried on the surface of a polyethylene terephthalate base (film) with a thickness of 14 μm, and the thickness of the lower layer after drying was 2.5 μm and the thickness of the upper layer was 0.3 μm.
jLnn, further subjected to alignment magnetic field treatment, and then supercalender treatment.

Next, a back coat paint with the following composition was applied to the back side of the polyethylene terephthalate base to a thickness of 10 mm after drying.
It was applied so that it became gnn.

Barkco Carbon black...40 parts (average particle size 20mjL) Carbon black...5 parts (average particle size 300mμ) Nitrocellulose... 25 parts (Seltsuba ETIII/2 manufactured by Asahi Kasei) Polyurethane...
・・・・・・ 25 parts (manufactured by Nippon Polyurethane Co., Ltd. N-2
301) Polyisocyanate 10 parts (Coronate manufactured by Nippon Polyurethane Co., Ltd.) Cyclohexanone 400 parts Methyl ethyl ketone
・・・・・・・・・ 250 parts toluene・・・・・・・・・
... 250 m of the original film thus obtained was cut into pieces of 2 inch diameter to produce a videotape, and its performance was measured according to the following procedure.

The results are shown in Table 141.

Sliding noise: (1) Play back the tape without running it, and measure the system noise with a spectrum analyzer.

(2) The sample tape is played back 10 times for 1 minute each, and the sliding noise is measured using a spectrum analyzer.

(:l) Read the noise value of 10 buses using the system noise as the reference (OdB) for the noise level around 811Hz.

Cloudy head: (1) Before measurement, clean the head so that it is not cloudy.

(2) Sample tape (No. 611H) <unused>
A single frequency of z was recorded for 10 minutes at a recording level of +20% with respect to the reference tape, and after playing it back three times, 811) It
The single frequency is recorded for 2 minutes at a recording level of +20% with respect to the reference tape, and this is reproduced to measure the output (these values are set as OdR).

(3) Sample tape (N
O, 2) <Unused> While recording the video signal from the beginning of winding to the end of winding, run it in SP mode.

(4) Record a single frequency of 8 kHz again on the sample tape (NOI) for 2 minutes at the same recording level as in (2), play it back, measure the output, and compare the output (OdB) measured in (2).
) to find the difference in output low.

Note) Two sample tapes (NOI,...
N02) is used to perform measurements.

The evaluation is as follows.

◎: There are no kimonos on the glass part of the head.

0 Some deposits are present.

×: There are +1 kimonos or 4 on the entire surface of Hera 1-.

Suguru.

Using a VTR deck (HR-7 [100), monitor a still image and measure the time it takes for the output to drop by more than 6 dB.

Measure S/N using a video deck HR-37000 and a noise meter (Shihasoku 925 D"").

Dropout (Dlo): In the video deck HR-37000, the dropout counter (V
HOIBZ).

[Effects of the Invention] According to the present invention, a magnetic recording medium having excellent running durability, still characteristics, and electromagnetic conversion characteristics can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the magnetic recording medium of the present invention.
(a) shows an example of a magnetic layer or a two-layer structure, and (b) shows an example of a magnetic layer or a three-layer structure. FIG. 2 is a diagram showing an example of manufacturing step 1 of the magnetic recording medium of the present invention in steps t<11. S... Nonmagnetic support, 1... First magnetic layer, 2...
second magnetic layer, 3... third magnetic layer, 4... roll, 5
... Magnetic support, 6... Coating device. 7... First-stage magnetic field orientation device, 8... Second-stage magnetic field orientation device, 9... Drying device, 1()... Super calender device i, 1.
1...Roll.

Claims (1)

[Claims] (1) Among multiple magnetic layers laminated on a non-magnetic support, the top layer is made of a strong non-magnetic material made of alumina with an average particle size of 0.4 μm or less and containing 2 to 10% by weight of silicon dioxide. 3 to 15 parts by weight per 100 parts by weight of magnetic powder, and 10 parts by weight of non-magnetic metal oxide with an average particle size of 0.4 μm or less in magnetic layers other than the top layer per 1000 parts by weight of ferromagnetic powder. A magnetic recording medium characterized by containing the following: