JPS63239616A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the running durability and electromagnetic conversion characteristic of a magnetic layer simultaneously and to improve runnability by incorporating inorg. granular particles having >=5 Mohs' hardness subjected to a coating treatment on the surface into the magnetic layer and increasing the existence ratio thereof near the surface of the magnetic layer. CONSTITUTION:The magnetic layer formed by dispersing ferromagnetic material powder in a binder is provided on a nonmagnetic base. The magnetic layer is formed by incorporating the inorg. granular particles (polishing agent) subjected to the coating treatment on the surface and having >=5 Mohs' hardness therein in such a manner that the existence ratio of the inorg. granular particles is large near the surface of the magnetic layer. The excellent electromagnetic conversion characteristic and running durability are thereby provided and the high practicability is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium comprising a magnetic layer containing ferromagnetic powder and a binder as main components on a non-magnetic support. Particularly, the present invention contains abrasive particles in the magnetic layer,
The present invention relates to a magnetic recording medium with improved running durability and electromagnetic conversion characteristics.

[Conventional technology]

Conventionally, γ-F has been used as a tape-shaped or disk-shaped magnetic recording medium for audio, video, co/vinitor, etc.
A magnetic recording medium is used in which a magnetic layer in which ferromagnetic powder such as e2O3, Co-containing iron oxide, chromium dioxide, or ferromagnetic alloy powder is dispersed in a binder is coated on a nonmagnetic support. Recently, the density of such magnetic recording media has increased, and high S/
Along with N conversion, magnetic materials are being made into finer particles, but with this finer graining, the abrasiveness of the magnetic materials decreases.
For this reason, the running durability of a magnetic recording medium using such a magnetic material deteriorates. Moreover, this tendency is remarkable when a ferromagnetic alloy powder with low hardness is used.

As a measure to prevent such deterioration of running durability, conventionally, granular Al2O3, SiC, C! It has been proposed to add an abrasive such as r203 to the magnetic layer. Particles of substances with high hardness are used as abrasives, specifically, PM oxide, fused alumina, silicon carbide, corundum, diamond oxide, emery (main components: corundum and magnetite), silica, and silicon nitride. , boron nitride, tungsten carbide, titanium oxide, and the like. These abrasives can be used alone or in combination of two or more of them. As a result of our research into combinations of these abrasives, we have found that the major axis diameter is tOμ or less, and the minor axis diameter is 0. 1. Less than μ, needle ratio 5~
α-Al1203.20 with acicular CrzOs. St
The magnetic powder contains at least one type of inorganic powder selected from C, and TIG, the ratio of the acicular Cr2o3/inorganic powder is greater than 2A, and the total amount of the acicular Cr2o3 and inorganic powder is It was discovered that the running durability and electromagnetic conversion characteristics of the magnetic layer could be significantly improved by using a magnetic layer of 1 to 20% by weight based on the weight of the magnetic layer.
9) I did.

[Problem that the invention seeks to solve]

Adding a large amount of the above-mentioned abrasive to increase the running durability will cause deterioration of the magnetic field orientation of the magnetic recording medium, the degree of filling of the magnetic powder, and the dispersibility, resulting in electromagnetic conversion due to deterioration of surface properties. Deterioration of characteristics becomes a problem.

In addition, reducing the amount of abrasive added to improve the surface properties improves the electromagnetic characteristics, but the friction coefficient of the magnetic layer increases.
Problems arise such as poor running performance of the magnetic recording medium, such as sticking during running.

Therefore, an object of the present invention is to simultaneously improve the running durability and electromagnetic conversion characteristics of a magnetic layer, and to provide a magnetic recording medium with improved running properties.

In magnetic recording media, problems such as scratch resistance and running durability of the magnetic layer occur between the surface of the magnetic layer and the surface of the magnetic spatula. Even when an abrasive is contained, only the part of the abrasive particles exposed on the surface of the magnetic layer is involved in the action.
Abrasive particles buried within the magnetic layer do not work effectively. For this reason, the surface of the abrasive particles plays an important role, but conventional abrasives only provide known characteristics, and great improvements could not be expected.

[Means to solve the problem]

The present inventors previously reported that particles of a substance with a Mohs hardness of 5 or more were Cr
We discovered that running durability and electromagnetic conversion characteristics could be significantly improved by incorporating particles coated with 2o3 or α-Fe 203 as an abrasive into the magnetic layer, and filed a patent application (Japanese Patent Application No. 1983-281866). and patent application 1986.-
No. 281867).

As a result of further research after this application, we found that the improvement in the above characteristics was due to the surface localization of the coated particles in the magnetic layer. It has been found that a large number of coated particles gather near the surface of the magnetic layer, thereby improving the above-mentioned characteristics.

Furthermore, when we focused on this point and proceeded with our research, we discovered that the coating material is not limited to Cr2o3 or α-Fe203 (
, and other various so-called solid acids cause the above-mentioned phenomenon and have achieved the present invention by discovering that the above-mentioned properties can be improved.

That is, the present invention provides a magnetic recording medium in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support, and the magnetic layer has a Mohs hardness of 5, the surface of which is coated.
The magnetic recording medium is characterized in that it contains the above-described inorganic powder particles (abrasive) and that the proportion of the inorganic powder particles present is large near the surface of the magnetic layer.

The present invention will be explained in detail below.

The particles of the substance having a Mohs hardness of 5 or more used in the present invention have an A-body of FF-#203. TiC, SiC, 5no2.
5in2°TzO, ZrO2, α-Fe203, etc., any substance having a Mohs hardness of 5 or more may be used, but it is generally an inorganic compound.

At this time, it is preferable that the inorganic powder particles to be coated and the coating oxide are different substances.

The particle size having a Mohs hardness of 5 or more is preferably about 1 μm or less, and the shape may be acicular, granular, irregular, etc.

In order to coat the surface of the inorganic powder particles, the present inventors used the previous patent applications C% 1982-281866 and 1983. −
281.867), Cr2O3 and α-Fe2o3
However, the present inventor newly discovered that the above-mentioned "surface localization of inorganic powder particles" is due to the increase in the acidity of the inorganic powder surface by coating with Cr2O3 or α-Fe203. I found it. In other words, the binder normally used for the magnetic layer has an acidic group, and when the inorganic powder particles with increased surface acidity are dispersed in the binder using an organic solvent and applied as described above, It is thought that the binding agent and the inorganic powder particles are repelled, causing the inorganic powder particles to be localized on the surface. Therefore, the substances to be coated on the surfaces of inorganic powder particles include the above-mentioned Cr2O3 and α-F.
It has been found that any so-called solid acid that can increase the acidity of the surface of the inorganic powder particles and cause the above-mentioned surface localization can be used without being limited to e20aK.

As such a coating material, the above-mentioned Cr2O3゜α-F
In addition to e203, B2O3, ZnO, Tie2. CeO
2, elemental oxides such as V2O5, The2-CuO,
Tt02-MgO.

Tie. -ZnO, Tie□-CaO, TiO□-Al
2O3, Tie□-ZrO2゜Tie2-PbO, Ti
e2-Bi□03. Tie2-F'e203. Zn
O-MgO.

ZnO-Al2O3, ZnO-ZrO2, ZnO-Pb
O, ZnO-5b203゜ZnO-B1□03. A12
03-Mg01A1203-B203. A1203-Z
A complex oxide such as rO2 is used.

When the inorganic powder particles are oxides, the particles may be reacted with a coating substance to form the above-mentioned composite oxide with the oxide on the particle surface.

Furthermore, sulfates, phosphates, sulfides, chlorides, etc. of various metals can also increase the acidity of the powder particle surface without adversely affecting the ferromagnetic fine powder, binder or other additives. Any material that can cause corrosion can be used as a coating material.

In addition, as an invention similar to the present invention, Japanese Patent Application Laid-Open No. 58-1.59
No. 236 discloses the coating with S10□, but the effects described in the publication are smoothing of the magnetic layer surface and wear resistance, which are thought to be due to improved dispersibility with the binder. This is a completely different idea from localization of the inorganic powder on the surface of the magnetic layer, which is the gist of the present invention. That is, when a similar attempt was made regarding the same invention, an increase in acidity was observed, but surface localization of the inorganic powder particles was caused. This is probably 5i0
2 It is expected that this is due to the interaction between the silanol groups on the surface and the binder.

In the present invention, the coating amount of the coating material is 0.1 to 20% by weight relative to the material constituting the particles.

In the present invention, various methods are used to coat inorganic powder particles having a Mohs hardness of 5 or more depending on the type of the two substances.

For example, to produce particles coated with Cr20a, the particles to be coated are (NH4)2Cr207, K2Cr20□
, or can be obtained by soaking in an aqueous solution of a chromate such as Na2Cr2O7, drying, and pyrolyzing at 300-800°C for 15 minutes to 6 hours, dispersing the particles in an aqueous chromate solution and acidifying the voice. By adjusting the side, Cr(OH)3 is deposited on the particle surface and heated at 300-800℃ for 15 minutes.
It can be obtained by pyrolysis for ~6 hours, and after immersing the particles in the above chromate aqueous solution, reduction (S02,
(in the presence of glycerin, starch), and can be obtained by pyrolysis. When using the aqueous solution of chromate, the chromate may be dissolved in water while stirring in a mortar and used as a saturated aqueous solution.

To produce particles coated with α-1i″e203, the particles to be coated are prepared using B'e SO4, Fe2(So, )3,
FeCl2, FeC1a-Fe(Noa)z, F
It can be carried out by immersing the iron salt in a saturated aqueous solution of iron salt such as e (No3)3, drying, and thermally decomposing it at 400 to 1000'C for 15 minutes to 6 hours. To explain this method more specifically, for example, alumina particles and F'e
The SO4 saturated aqueous solution is put into a Laikai machine and stirred for 1 hour to fully impregnate the alumina particles with the aqueous solution, taken out and dried for half a day to one day. Grind the dried material in a coffee mill for 10 minutes and grind it for 1000'
Bake at C for 1 hour. The baked product is washed with water for 1 to 2 days to remove impurity ions, dried for half a day, and ground in a coffee mill for 10 minutes to obtain a predetermined particle size.

In addition, as another preparation method, K F
e (OH)a is deposited and it is 400-1000'
FeCA! Heat and vaporize s.

It can be obtained by depositing Bi'eC13 on the particles to be coated and exposing it to water vapor.

To produce particles coated with B2O3, e.g.
The particles to be coated are dispersed in the aqueous solution of step 3, evaporated to dryness, and then heated at about 400° C. for 1 hour.

To produce particles coated with -〇, for example, the particles to be coated are dispersed in an aqueous zinc oxalate solution, evaporated to dryness, and then heated at about 400°C for about 11 hours.

When coating with CaO2, for example, a cerium acetate aqueous solution is used and the same treatment as above is performed.

When coating with ko-xz, for example, a mixed aqueous solution of zinc oxalate and zirconium acetate in a desired ratio is used, and the same treatment as above is performed.

Other materials may also be coated according to the above method.

The nonmagnetic support used in the present invention is not particularly limited, and any commonly used nonmagnetic support can be used. An example of a material forming the non-magnetic support is polyethylene tele7.
Examples include various synthetic resin films such as PET (PET), polypropylene, polycarbonate, polyethylene natulate, boria oxide, polyamide imir, and polyimide, and metal foils such as amyl foil and stainless steel foil. The thickness of the non-magnetic support is also not particularly limited, but is generally 3 to 50μ, preferably 5 to 3μ.
It is 0 μ inertia.

The nonmagnetic support may be provided with a backing layer on the side on which the magnetic layer described below is not provided.

The magnetic recording medium of the present invention is one in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a nonmagnetic support as described above.

The ferromagnetic powder used in the magnetic layer of the present invention includes fine ferromagnetic alloy powder containing iron as a main component, γ-Fθ2o3, Fe3
In addition to O4, CO-modified ferromagnetic iron oxide, and Cr0z, there are modified barium ferrite and modified strontium ferrite. This is particularly effective when a higher ferromagnetic alloy powder is used as the ferromagnetic powder.

As an example of this ferromagnetic alloy powder, the metal content in the ferromagnetic alloy powder is π% by weight or more, and the weight proportion of the metal content is at least one type of ferromagnetic metal or alloy.
Examples include alloys that are gold and may contain other components within a weighted amount of % or less of the metal content. Further, the ferromagnetic metal component may contain a small amount of water, hydroxide, or oxide. Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powder, which is a typical example of the ferromagnetic powder used in the present invention, can also be produced according to these known methods.

When using ferromagnetic alloy powder, there are no particular restrictions on its shape, but needle-like, granular, dice-like, rice-grain-like, and plate-like shapes are usually used.

The specific surface area (S:BET) of this ferromagnetic alloy powder is preferably 42x4 or more, and more preferably 45x9 or more.

As the binder used to form the magnetic layer of the present invention, commonly used thermoplastic resins, thermosetting resins, reactive resins, and the like can be used.

These resins can be used alone or in combination.

Thermoplastic resins generally have an average molecular weight of 1,000 to 10,000.
Additionally, those having a degree of polymerization of approximately 200 to 2,000 are used. Examples of such thermoplastic resins include vinyl chloride/vinyl acetate copolymer resins, vinyl chloride/vinylidene chloride copolymers, acrylic resins, cellulose derivatives, and various synthetic resins! rubber-based thermoplastic resin, urethane elastomer,
Examples include polyvinyl fluoride, polyamide resin, polyvinyl butyrate, styrene/butadiene copolymer, and polystyrene resin, and these can be used alone or in combination.

Thermosetting resins or reactive resins are generally resins that have an average molecular weight of less than 10,000 yen in the coating liquid state, and after coating, the molecular weight becomes almost infinite due to condensation reactions or addition reactions. . However, when these resins are thermosetting resins, it is preferable that the resins do not harden or dissolve due to heating during the process leading to curing.

Examples of such resins include phenol/formalin novolak resin, phenol/formalin resol resin, phenol/furfural resin, xylene/formaldehyde-free resin, urea resin, melamine resin, drying oil-modified alkyd resin, and phenolic resin-modified alkyd resin. Resin, maleic acid resin-modified alkyd resin, unsaturated polyester resin, combination of epoxy resin and curing agent, terminal incyanate polyether moisture-curable resin, polyincyanate prepolymer, combination of polyincyanate prepolymer and resin containing active hydrogen These can be used alone or in combination.

The amount of binder used is, based on 100 parts by weight of ferromagnetic powder,
Generally in the range of 10 to 100 parts by weight, preferably 15 to 100 parts by weight.
The range is 50 parts by weight.

In the present invention, the above-mentioned abrasive whose particles are coated with Cr2O3 is applied to the ferromagnetic powder contained in the magnetic layer.
It is contained in the magnetic layer in an amount of 20% by weight, preferably 0.2 to 10% by weight.

The magnetic recording medium of the present invention may contain other commonly used particulate additives (for example, antistatic agents with an average particle size of 0.01.5 to 0.000
．． It is also possible to add 2 μm of carbon black).

When manufacturing the magnetic layer of the magnetic recording medium of the present invention, first the above-mentioned coated inorganic powder particles are mixed with a ferromagnetic powder such as a ferromagnetic alloy powder and a binder.

If necessary, other particulate fillers are kneaded together with a solvent to form a magnetic paint, which is coated on a support, subjected to magnetic field orientation, etc., and then dried.

As the solvent used in the crosstalk, a solvent commonly used for preparing magnetic paints can be used.

For the kneading method, a method commonly used as a method for mixing wires in magnetic paints can be used. Further, the order of addition of each component can be set as appropriate.

Various techniques are known as techniques for preparing magnetic paints, and any of these known techniques can be used in manufacturing the magnetic recording medium of the present invention.

When preparing a magnetic paint, known additives such as dispersants, antistatic agents, lubricants, etc. can also be used.

Examples of dispersants include fatty acids having 12 to 18 carbon atoms, metal soaps made of the above fatty acids and alkali metals or alkaline earth metals, esters of the above fatty acids, and compounds in which some or all of the hydrogen atoms of the above fatty acids are replaced with fluorine atoms. Substituted compounds, amides of the above fatty acids, fatty acid amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphates, alkyl borates,
Known dispersants such as sarcosi*-), furkyl ether esters, realkyl polyolefin oxy quaternary ammonium salts, and lecithin can be mentioned. When a dispersant is used, it is usually used in an amount of 0.5 to 2.0 parts by weight per 100 parts by weight of the binder used. ．． It is used in a range of 0 parts by weight.

Examples of antistatic agents include natural surfactants; nonionic surfactants; cationic surfactants; anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester groups, and phosphate ester groups; Agents: Examples include amphoteric activators such as amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like. Obi t
When a conductive fine powder such as carbon black is used as a VJ inhibitor, it is used in an amount of 0.12 to 20 parts by weight based on parts of binder i and ooii, and when a surfactant is used, It is used in a range of 0.1 to 10 parts by weight.

Examples of lubricants include monobasic fatty acids with 12 to 2 carbon atoms, such as the above-mentioned fatty acids, higher 7'lu-rustearate, and sorbitan oleate, and monovalent or polyhydric fatty acids with 3 to 20 carbon atoms. In addition to fatty acid esters consisting of alcohols, mineral oils, animal and vegetable oils, olefin low polymers, and α-olefin low polymers, known lubricants such as gutphite fine powder and plastic lubricants can be mentioned. The amount of lubricant added can be arbitrarily determined according to known techniques.

Note that the above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is a lubricant, Alternatively, it may act as an antistatic agent. Therefore, it goes without saying that the effects of compounds etc. exemplified by the above classifications are not limited to those listed in the above classifications, and when using substances that have multiple effects, the amount of is preferably determined by considering the action and effect of the substance.

The magnetic paint thus prepared is coated on the above-mentioned non-magnetic support according to a known method. Coating is usually carried out directly on the non-magnetic support. However, it can also be applied onto a non-magnetic support via an adhesive layer or the like.

There is no particular limit to the thickness of the magnetic layer coated in this way, but the thickness after drying is generally in the range of about 0.5 to 10 μm, usually in the range of 1.5 to 70 μm. applied.

A magnetic layer coated on a non-magnetic support is usually subjected to a treatment for orienting the ferromagnetic powder in the magnetic layer, that is, a magnetic field orientation treatment, and then dried. Also, if necessary, surface smoothing treatment is performed. The magnetic recording medium that has been subjected to surface smoothing treatment is then cut into a desired shape.

Note that the magnetic recording medium of the present invention may also be provided with a commonly used 7912 layer.

〔Example〕

Next, Examples will be shown to specifically explain the present invention, but the present invention is not limited to these Examples. In addition, a comparative example will be shown to clarify the difference in effect between the present invention and the prior art. Note that "parts" in Examples and Comparative Examples indicate "parts by weight."

Preparation of abrasive Particle size: 0.2 A (7) α-AJ203100g A saturated aqueous solution of (NH4)20r207 was mixed in a Raikai machine (mortar mixer), dried, heated at 400°C for 2 hours, and then ground in a pulverizer. Process with. The amount of (NH4)2Cr207 added was changed (a) 1.259, (b) 6.259,
(c) 12.5g and sita. The first thing is Cr2O
3 coating α-A1203(a), and the same applies hereinafter.

α-AJ2Q3 with a particle size of 0.06μ is (NH4)2Cr2
The product obtained by mixing with a saturated aqueous solution of 07 and adding (NH4)2Cr207 in an amount of 12.59 is referred to as Cr2O3-coated α-AJ2o3(d).

In addition, the particle size is 0.3. SiC1,009 and (NH4
) A saturated aqueous solution of 2Cr20° was mixed in a Raikai machine, and (
The amount of NH4)xCrp7 added is 13.5g, and the following is as follows:
An abrasive was prepared in the same manner as above.

Example 1 A magnetic paint having the composition shown below was prepared and coated on a polyethylene terephthalate nonmagnetic support having a thickness of 1.0 Am so that the thickness of the magnetic layer after drying was 3.0 μm.

Magnetic paint composition Ferromagnetic alloy powder 100 parts (F
e-Ni alloy, N1 approximately 5% by weight) (Specific surface area (S-BET): 45 m'/g) Vinyl chloride/vinyl acetate/maleic anhydride copolymer
12 parts (Nippon Zeon Co., Ltd.: 400
X110A) Polyurethane resin
8 parts (manufactured by Nippon Polyurethane Co., Ltd.: N-2301)
12 parts of polyincyanate (manufactured by Nippon Polyurethane Co., Ltd.: Coronate L) 1 part of carbon black (average particle size: 0
．． 1μ regret) Methyl ethyl ketone 300 parts Cr
2O3 coated α-AJzO3(a)
The non-magnetic support coated with 10.0 parts of magnetic paint is subjected to magnetic field orientation treatment while the magnetic paint is not dry, and after drying, calender treatment is performed and slit into 8W width to form 8 chicken-shaped videos. manufactured the tape.

The magnetic properties of this videotape are determined by measuring the B-H curve (B: magnetic flux density, H: external magnetic field) using a VSM (vibrating magnetometer; manufactured by Fukuei Kogyo Co., Ltd.), and from this value The ratio (Br/Bm, (Br: maximum residual magnetic flux density, Bm: maximum magnetic flux density)) was determined.

The resulting videotape video recorder (FUJ Engineering
8) to record and reproduce a 5 MHz signal. When the 5 MHz reproduction output recorded on the reference tape (8 mm video tape obtained in Comparative Example 1) was set to Od3, the relative reproduction output of the video tape and the output decrease after 10100 pa were measured.

Further, the C/N is shown by comparing the reproduction output at 5 MHz and the nozzle at 4 MHz.

Next, use the video recorder and run it repeatedly,
The number of runs until the magnetic head became clogged was investigated.

In addition, the surface gloss was measured by the total reflectance at an incident angle of 45° and a reflection angle of 45° using a standard gloss meter. According to J Engineering 5Z8741,
The specular gloss of glass with a refractive index of 1.56 at an incident angle of 45° was set as 100, and its relative value was determined.

Measuring device: Digital standard color difference light meter A manufactured by Suga Test Instruments Co., Ltd.
UD -CH-GV3゜Example 2 In Example 1, Cr2O3 coated α-Al2O2 (a
) instead of Cr2O3 coated α-Al! A videotape was produced in the same manner except that 203(b) was used and the amount added was 5.0 parts.

Example 3 In Example 1, Cr20a coated α-A1203 (a
A videotape was produced in the same manner except that Cr 203 coated α-M2O3 (C) was used instead of Cr203 coated α-M2O3 (C) and the added portion was Z5 parts.

Example 4 Example 1. In IC, CrzOa coated α-A120s
A videotape was produced in the same manner except that the Cr2O3 coated SIG was used instead of (a) and the amount added was 5.0 parts.

Example 5 Example 1. In , Cr2O3 coated α-A1203 (
A videotape was produced in the same manner except that Cr2O3 coated α-A72o3(c) was used in place of a) and the amount added was 0.5 parts.

Example 6 In Example 1, Cr2O3 coated α-M2O3(a)
Using Cr2O3 coated α-A1203 (4) instead of
A videotape was produced in the same manner except that the amount added was 2.5 parts.

Comparative Example 1 In Example 1, Cr2O3 coated α-AJ203 (a
) A videotape was produced in the same manner, except that α-A1203 with a particle size of 0.2 μm was used in place of α-A1203, and the amount added was 5.0 parts.

Comparative Example 2 In Example 1, Cr2O3 coated α-M2O3(a)
A videotape was produced in the same manner, except that α4M203 having a particle size of 0.3 μm was used instead of α4M203, and the amount added was 10.0 parts.

Comparative Example 3 In Example 1, Cr2o3 coated α-Li 203(a)
Instead, α-1'4203 with a particle size of 0.3μ was used, and the amount added was 2. ．． A videotape was produced in the same manner except that 5 copies were used.

Comparative Example 4 In Example 1, Cr2O3 coated α-A1203 (a
) A videotape was produced in the same manner except that StC with a particle size of 0.4 μm was used in place of StC, and the amount added was 0.5 parts.

Comparative Example 5 Same as Example 1''C, Cr2O, coated α-Al 20
A videotape was produced in the same manner except that α-A1203 having a particle size of 0.06 was used in place of 3(a), and the amount added was 5.0 parts.

For each of the above samples, the temperature was also tested in the same way as in the example.
The results obtained are shown in Table 1.

Particle size of abrasive: 0.2 μ') (1-AA!2031.009
A saturated aqueous solution of
The mixture was mixed in a mortar mixer), dried, heated at 600°C for 2 hours, and then processed in a pulverizer. The amount of F'eSOa・7H20 added was changed to (a) 2.8 g, (b) 1409, (
(2aO9).The product obtained with the addition amount of (a) was α
-Fe2o3 coated α-Az, referred to as 03(a), and the same shall apply hereinafter. α-AJ203 with a particle size of 0.06 μ
Mix with a saturated aqueous solution of 4-7H20, F'eSO4.7
α-F's is obtained by adding H2o in an amount of 2 & 09.
203 Coating U -'J20a (d) Toy 5° Also, S1c 1.009 and Pe5o with particle size 0.3μ,
, 7H20 saturated aqueous solution was mixed in a Raikai machine, and Fe
A fretting agent was produced in the same manner as described below, with the amount of SO4.7H2o added being 1.5.0 g.

Example 7 A magnetic paint having the composition shown below was prepared and coated on a polyethylene terephthalate nonmagnetic support with a thickness of about 10 μm so that the thickness of the magnetic layer after drying was 3.0 μm.

Magnetic paint composition Ferromagnetic alloy powder 1.00 parts (
Fa-Ni alloy, N1 approximately 5 qb by weight) (specific surface area (S
-BIT): 45 Kushi'9) Vinyl chloride Ah vinyl acid/
Maleic anhydride copolymer
12 parts (manufactured by Nippon Zeon 00: 400X110 A) Polyurethane resin 8 parts (manufactured by Nippon Polyurethane 00: N-2301,) Polyisocyanate 12 parts (manufactured by Nippon Polyurethane Co., Ltd.: Coroneni L) Carbon black 1 part (average particle size :0
1jt) Methyl ethyl ketone 300 parts α
-Fe203 coating α-AJ203 (a)
The non-magnetic support coated with 10-0 parts of magnetic paint was subjected to magnetic field alignment treatment while the magnetic paint was not yet dry, and after drying, calender treatment was performed, and the material was slit into 8 m wide pieces to form an 8-inch video tape. manufactured the tape.

Assuming the magnetic properties of this videotape - (, B-H song! (B
: magnetic flux density, H: external magnetic field), and from this value squareness ratio (Br/Bm, (Br: maximum residual magnetic flux density, B
m: maximum magnetic flux density]) was determined.

The obtained videotape video recorder (FU, T
-8) was used to record and reproduce a 5 MHz signal. Standard tape (8mm video tape obtained in Comparative Example 1)
The relative playback output of the above video tape when the playback output of 5MHz recorded in OdB and 1.00pass
The subsequent output drop was measured.

Further, the C/N is shown by comparing the reproduction output at 5 MHz and the noise at 4 MHz using the comparative example as a reference.

Next, use the video recorder and run it repeatedly,
The number of runs until the magnetic head became clogged was investigated.

In addition, the surface gloss was measured by the total reflectance at an incident angle of 45° and a reflection angle of 45° using a standard gloss meter. According to J Engineering 5Z8741-, the specular gloss of glass with a refractive index of 1.567 at an incident angle of 45° was set as 100, and its relative value was determined.

Measuring device: Digital standard color difference photometer A manufactured by Suga Senki Co., Ltd.
UD-, CH-Gv3゜Example 8 In Example 7, α-F'e 203 coated α-Az2
α-Fe203 coating α-)t203 instead of 03(a)
A videotape was produced in the same manner except that (b) was used and the amount added was 5.0 parts.

Example 9 In Example 7, α-Fe203 coated α-N20a
Instead of (a), α-Fe203 coated α-A1203 (C
), and a videotape was produced in the same manner except that the amount added was 2.5 parts.

Example 10 In Example 7, α-Fe203 coated α-N20a
Using the α-F8□03 coated SiC instead of (a),
A videotape was produced in the same manner except that the amount added was 5.0 parts.

Example 11 α-F'a 203 coating α-#203 in Example 7
Substitute for (a) F) Kα-Fe203 coating α-A1203 (
A videotape was produced in the same manner except that c) was used and the amount added was 0.5 part.

Example 12 In Example 7, α-Fe203 coated α-A72o3 (
α-Iile203 coating α-AX 203 instead of a)
A videotape was produced in the same manner except that (d) was used and the amount added was 2.5 parts.

Comparative Example 6 In Example 7, α-Fe20. Coating α-AA'20
A similar videotape was produced except that α-)J1203 having a particle size of 012μ was used in place of (a), and the amount added was 5.0 parts.

Comparative Example 7 In Example 7, α-F'5203 coated α-kl 2
The same procedure was followed except that α-Fe203 with a particle size of O13μ was used instead of 03(a), and the amount added was 10.0 parts.
produced a videotape.

Comparative Example 8 In Example 7, α-F'620a coating α-)J20
A videotape was produced in the same manner except that α-M20a having a particle size of 0.3 μm was used in place of 3(a), and the amount added was 2.5 parts.

Comparative Example 9 In Example 7, α-FIS203 coated α-AJ20
An evideotape was produced in the same manner except that SiC with a particle size of 0.4 μm was used instead of 3 (IL) and the amount added was 5.0 parts.

Comparative Example 10 In Example 7, α-Fe 203 coated α-A120
A videotape was produced in the same manner except that α-AJz○3 having a particle size of 0.06 μm was used in place of 3(a), and the amount added was 5.0 parts.

The same tests as in the example were conducted for each of the above samples.
The results obtained are shown in Table 2.

Examples 13 to 1B Magnetic tapes were produced using the same composition and method as in Example 1, except for the abrasive, and the same performance tests were conducted.

The type and size of the coated particles of the abrasive, the type of coating material, the amount of coating, etc. are shown in Table 3.

When α-AJ 203 particles are coated with Cr2O3 (Example 13), the abrasive is manufactured in the same manner as the abrasive used in Example 1, and α-M203 particles such as α-Fe203
In the case of coating with T1C particles (Example 14), the abrasive was manufactured in the same manner as the abrasive used in Example 7, and in the case of coating with T1C particles or 203 (Example 15), 'hC particles were coated with B2O
After dispersing in an aqueous solution of 3 and evaporating to dryness, 1
The T10 particles were produced by heating for a time of ZnO.
(Example 16), T10 particles were dispersed in an aqueous zinc oxalate solution, evaporated to dryness, and then heated at 400°C.
When S10 particles are coated with CeO□ (Example 17), SIC particles are dispersed in an aqueous solution of cerium acetate, evaporated to dryness, and then heated at 400°C for about 1°. In the case of coating SzC particles with ZnO-ZrOx (Example 18), SIC particles were dispersed in a mixed aqueous solution of zinc oxalate and zirconium acetate, and evaporated to dryness. After that, the product was manufactured by heating to 400°C. In this case, the amount added to the coating material was adjusted to the values shown in Table 3.

Furthermore, in these Examples, coating the abrasive particles increases the surface acidity of the particles, and when an abrasive with such a high surface acidity is dispersed in the magnetic layer, the magnetic In order to show that the abundance ratio near the layer surface increases, the acidity and basicity of each abrasive were measured as follows, and the abundance ratio of the abrasive in the surface layer of the magnetic layer was measured as follows.

In addition, the degree of head wear was also measured in degrees Celsius as described below.

Method for measuring O acidity and basicity 1) Inorganic powder particles are put into an inoctane solution with a fixed acidity of n-butylamine, stirred at °C, and the acidity is determined from the amount of n-butylamine adsorbed to the powder. Calculated.

2) Basicity Inorganic powder particles were put into an isooctane solution of benzoic acid and stirred, and the basicity was calculated from the amount of benzoic acid adsorbed to the particles.

O Method for measuring the abundance ratio (distribution) of inorganic powder particles in the magnetic layer 1) Measuring method for the entire layer The integrated intensity of the representative peak of the magnetic material and the representative peak of the inorganic powder particles over the entire layer of the magnetic layer is determined by X-ray diffraction. The ratio was measured.

In addition, in the X-ray diffraction method, the absolute value is determined by relative comparison with a reference (in this case, the iron component of the magnetic material) because the error is large in quantifying the absolute value.

11) Method for measuring surface layer Using a thin film X-ray diffraction device (manufactured by Rigaku Denki Co., Ltd.), measure the integrated intensity of the representative peak of the magnetic material and the peak of the inorganic powder particles at a distance of approximately 0.5 μm from the surface. It was measured.

From the result of If) above, it is possible to know the abundance ratio of inorganic powder particles in the vicinity of the surface to the entire magnetic layer.

O-head wear amount Video tape recorder (FU, T-engineering X-8) at 23°C.
The wear amount of the head 9 was measured after 100 hours under the condition of 70% RH.

The results obtained are shown in Table 3.

〔Effect of the invention〕

As is clear from the results shown in the above tables, the magnetic recording medium of the present invention has superior electromagnetic conversion characteristics and running durability compared to conventional magnetic recording media, and is highly practical.

Looking at its specific properties, as shown by the measured values in Examples and Comparative Examples, the magnetic recording medium of the present invention has Br,
The values of SQ, video output, and C/N are higher than those of the comparative example using α-#zO3 without coating, and it has excellent effects.

Also, looking at the measurement results of the output drop after 100 passes, the degree of output drop is small, and the number of runs until the magnetic head becomes clogged during repeated runs is large1.
Excellent running durability. What is more important is that the present invention achieves such excellent effects with a small amount of abrasive added, as well as the same or higher zero head wear compared to conventional products. The amount added to the magnetic powder is about half or less than that in conventional magnetic recording media, and is therefore very economical. Since the amount of abrasive added can be small in this way, the amount of ferromagnetic powder in the magnetic layer can be increased, resulting in improved electromagnetic conversion characteristics.

Procedural amendment June 23, 1986

Claims (1)

[Claims] (1) In a magnetic recording medium in which a magnetic layer in which ferromagnetic powder is dispersed in a binder is provided on a non-magnetic support, the magnetic layer is coated on the surface of inorganic powder particles with a Mohs hardness of 5 or more. 1. A magnetic recording medium characterized in that the inorganic powder particles are present in a large proportion near the surface of the magnetic layer.