JPH056529A - Magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Object] To provide a magnetic recording medium having excellent durability, wear resistance, magnetic properties, and surface smoothness of a magnetic layer and an excellent cleaning effect of a magnetic head. In a magnetic recording medium comprising a magnetic layer containing magnetic fine powder and a binder on a non-magnetic support, the magnetic layer contains Ge, P, Sn, Nb, Ta, Mo and W elements. At least one oxide selected is alumina 100
A magnetic recording medium, characterized in that it contains about 0.1 to about 10 parts by weight of alumina having an average particle diameter of 1 μm or less.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium having excellent durability, wear resistance, magnetic characteristics, and surface smoothness of a magnetic layer and an excellent cleaning effect for a magnetic head.

[0002]

2. Description of the Related Art Magnetic recording media such as magnetic tapes, magnetic disks and magnetic sheets are widely used for audio, video and computers.

In order to improve the durability and abrasion resistance of the magnetic layer and to clean the magnetic head deposits, such a magnetic recording medium has Al ₂ O ₃ , Cr ₂ O ₃ , SiC, and
A method of adding a non-magnetic powder such as α-Fe ₂ O _{3 to the} magnetic layer as a reinforcing material and an abrasive is adopted.

However, when these non-magnetic powders are added, durability and wear resistance are improved, but on the other hand, the magnetic properties are deteriorated due to a decrease in the packing density of the magnetic powders, and the surface smoothness of the magnetic layer is deteriorated. It has the drawback of deteriorating the characteristics, and the non-magnetic powder is partly detached during running, which gradually deteriorates the running durability, causing clogging of the magnetic head and increase of noise. .

In particular, in recent years, the magnetic recording density has been increased by using metal magnetic powder or fine iron oxide magnetic powder to improve the surface smoothness and electromagnetic conversion characteristics of the magnetic recording medium and to improve the magnetic layer. However, when the conventional non-magnetic powder is applied, the above-mentioned drawbacks are further promoted while the abrasion resistance and the running durability are required to be improved.

In order to improve the dispersibility of the non-magnetic powder, a phosphoric ester,
A method of adding a dispersant such as a fatty acid and various surfactants is known. However, when these dispersants are added,
A so-called blooming phenomenon, in which the dispersant exudes to the surface of the magnetic layer during running, was not preferable.

Further, in order to improve the dispersibility of the non-magnetic powder and the reinforcing effect in the magnetic layer, a silane coupling agent,
A method of using a non-magnetic powder treated with a coupling agent such as a titanium coupling agent has been proposed. But,
These coupling agents were liable to be released from the non-magnetic powder under the conditions of mixing and dispersing under strong shearing force during the preparation of the magnetic coating material, and the dispersing and reinforcing effects were not satisfactory.

Further, it has been proposed to improve the magnetic properties, surface smoothness, abrasion resistance and durability of the magnetic layer by improving the acidity of the surface of the non-magnetic powder.

That is, the surface of the inorganic powder particles having a Mohs hardness of 5 or more is coated with an acidic substance or an acidic oxide to increase the acidity, thereby causing repulsion with the binder, and the presence of the inorganic powder particles. A magnetic recording medium characterized by a large proportion near the surface of the magnetic layer (JP-A-63-23961).
6), a magnetic recording medium having a magnetic layer containing an inorganic powder having an average particle size of 1 μm or less and a Mohs hardness of 6 or more and a magnetic powder and having a pH of less than 7 by deposition of an acidic substance (JP-A-1-201822). Etc.

However, even by these methods, the acidified coating substance impairs the surface hardness of the inorganic powder, reduces the polishing power, and cannot obtain a sufficient head cleaning effect, or the acidified adherent substance is magnetic. At the time of preparing the paint, it was easy to detach from the inorganic powder, and a satisfactory effect was not obtained.

[0011]

In view of such a situation,
The inventors of the present invention have excellent magnetic properties and surface smoothness, and at the same time, can withstand
Excellent durability, wear resistance and magnetic head cleaning effect
As a result of earnest studies to obtain a magnetic recording medium
Al having an average particle size and containing a specific component ₂O₃
When powder is used, the magnetic properties
To find that a recording medium can be obtained, and to complete the present invention
I arrived.

[0012]

That is, the present invention provides a magnetic recording medium comprising a magnetic layer containing magnetic fine powder and a binder on a non-magnetic support, and the magnetic layer contains the following (1).
Ge, P, Sn, obtained by the method of any one of to (3)
At least one oxide selected from the elements of Nb, Ta, Mo and W is added in an amount of about 0.1 with respect to 100 parts by weight of alumina.
Part by weight to about 10 parts by weight average particle diameter of about 1 μm
A magnetic recording medium containing the following alumina. (1) After firing in a solution containing an aluminum salt, Ge, P,
A method of uniformly mixing at least one oxide component selected from the elements Sn, Nb, Ta, Mo and W, and precipitating it as a carbonate by a neutralization method, a recrystallization method or the addition of a carbonic acid-containing substance. And then calcining the resulting aluminum compound, and (2) after calcining into a solution containing an organic aluminum compound, at least one kind of oxidation selected from the elements Ge, P, Sn, Nb, Ta, Mo and W (3) The aluminum salt is precipitated as a carbonate by a neutralization method, a recrystallization method, ammonium hydrogencarbonate, etc. To the aluminum compound obtained by the method described above or the aluminum compound obtained by the hydrolysis method of the organoaluminum compound, Ge, P, Sn, Nb, T
a, at least one metal oxide selected from Mo and W, or a method of mixing a compound of the metal to be a metal oxide after firing by a wet or dry method and firing the mixture.
To provide.

The present invention will be described in more detail below. Al ₂ O ₃ used in the present invention is Ge, Sn, Nb,
At least one oxide selected from Ta, Mo and W is about 0.1 part by weight to about 10 parts by weight, preferably about 0.5 part by weight, based on 100 parts by weight of Al ₂ O _3. About 8
Al ₂ O with an average particle size of about 1 μm or less
₃ powder.

Thus, the oxide-containing Al referred to in the present invention₂
O₃Powder means Al₂O₃The oxide in the powder is Al₂O₃
In the state of solid solution in the crystal, or with the oxide or the oxide
Al ₂O₃Is a complex oxide of Al₂O₃Dispersed precipitation in crystals
It means the state of₂O₃Powder and said
A simple mixture of oxide powders, and even Al₂O₃Powder surface
It does not include those in which the oxide is simply coated.
Yes.

When a powder obtained by simply coating the surface of the Al ₂ O ₃ powder with the oxide is used, the surface hardness of the Al ₂ O ₃ powder is originally impaired, and the polishing power is lowered, resulting in sufficient head cleaning. No effect can be obtained, and a mere mixture can obtain effects more than the physical properties of individual constituent materials, that is, excellent electromagnetic conversion characteristics aimed at by the present invention, and running durability of the magnetic layer, abrasion resistance, magnetic properties It is not possible to obtain a magnetic recording medium having an excellent head cleaning effect.

As a method for obtaining the oxide-containing Al ₂ O ₃ powder used in the present invention, Al ₂ O _{3 is used.}
At least one oxide selected from Ge, P, Sn, Nb, Ta, Mo and W in the powder is Al ₂ O ₃
State a solid solution in the crystal or, as long as the state of the composite oxide of the oxide or oxide and Al ₂ O ₃ was dispersed and precipitated in the Al ₂ O ₃ crystal, in particular to limit its production method Although not a thing, for example, aluminum halide such as aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum perchlorate and ammonium salt after uniformly mixing the components to be the oxide after firing in a solution containing an aluminum salt such as alum, Examples include a method of obtaining an aluminum compound by a neutralization method, a recrystallization method, a method of precipitating as a carbonate by ammonium hydrogencarbonate, and the like, and baking this.

Aluminum methoxide, aluminum ethoxide, aluminum isopropoxide,
Aluminum alkoxide such as aluminum butoxide, alkylaluminum such as trimethylaluminum and triethylaluminum, and a solution containing an organoaluminum compound such as aluminum carboxylate and aluminum dicarboxylate are uniformly mixed with components that become the oxide after firing. After mixing, an aluminum compound is obtained by hydrolysis and then fired.

Further, an aluminum compound obtained by a method of precipitating only the above-mentioned aluminum salt as a carbonate by a neutralization method, a recrystallization method, ammonium hydrogencarbonate or the like,
Ge, P, Sn, Nb, an aluminum compound obtained by hydrolysis or pyrolysis of only an organoaluminum compound,
Examples thereof include a method of mixing at least one metal oxide selected from Ta, Mo and W, or a compound of the metal to be a metal oxide after firing in a wet or dry manner, and firing the mixture.

In either method, the firing condition is about 1.
It may be carried out at 100 ° C. to about 1400 ° C. for about 1 hour to about 4 hours.

The form of the oxide component to be mixed is as follows:
As the final form, any oxide may be used, and a solution containing the element, a fine metal particle, a fine metal hydroxide, a fine metal oxide, or the like can be used.

In the present invention, although it becomes the oxide after firing, as specific examples, in addition to fine metal particles, W is an ammonium salt of tungstic acid such as tungstic acid, ammonium metatungstate, ammonium paratungstate, or tungsten chloride. Of tungsten halide,
Tungsten oxyhalide compounds such as tungsten oxychloride,

As Mo, molybdic acid, molybdenum oxide, molybdenum hydroxide, molybdenum halide compounds such as ammonium molybdate and molybdenum chloride,

As Nb, niobium alkoxide compounds such as niobium hydroxide, niobium methoxide, niobium ethoxide and niobium isopropoxide, niobium halide compounds such as niobium chloride,
Niobium oxyhalide compounds such as niobium oxychloride

As Ta, tantalum alkoxide compounds such as tantalum hydroxide, tantalum methoxide, tantalum ethoxide and tantalum isopropoxide, and tantalum halide compounds such as tantalum chloride.

As Ge, germanium ethoxide, germanium isopropoxide, germanium n
-Germanium alkoxide compounds such as butoxide, germanium halide compounds such as germanium chloride

As Sn, tin alkoxide compounds such as tin iron, tin hydroxide, tin ethoxide and tin isopropoxide, tin halide compounds such as tin chloride,
Examples thereof include tin sulfate.

As P, orthophosphoric acid, metaphosphoric acid,
Phosphoric acid compounds such as trimetaphosphoric acid, phosphorous acid, phosphinic acid, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid, pyrophosphoric acid, phosphorus halides such as phosphorus trichloride and phosphorus pentachloride, trimethyl phosphate, triethyl phosphate , Phosphoric acid ester compounds such as monoethyl phosphate, dimethyl phosphate and diethyl phosphate, ammonium salts such as ammonium phosphate and ammonium hydrogen phosphate, and the like.

The oxide content in the Al ₂ O ₃ powder is about 0.
If the amount is less than 1 part by weight, sufficient durability may not be obtained, probably because the number of active sites having an affinity with the binder decreases.
If it exceeds 0 parts by weight, the hardness of Al ₂ O ₃ becomes low, which is not preferable.

The average particle size of the Al ₂ O ₃ powder used in the present invention is essentially about 1 μm or less, preferably about 0.8 μm or less. When the average particle diameter is larger than about 1 μm, the surface smoothness and magnetic properties are deteriorated, which is not preferable.

In the practice of the present invention, the addition ratio of the oxide-containing alumina powder to the magnetic powder is generally about 0.1 to about 15% by weight, preferably about 0.5 to about 10% by weight. If the amount added is less than about 0.1% by weight, the durability and wear resistance of the magnetic layer will deteriorate, while if it exceeds about 15% by weight, the magnetic properties and surface smoothness will decrease, and the magnetic head It is not preferable because it causes large wear.

The magnetic material used in the present invention is a known magnetic material such as r-Fe ₂ O ₃ and Co-containing r-Fe.
₂ O ₃ , Co-deposited r-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , Co-deposited Fe ₃ O ₄ , CrO _{2 and} other oxide magnetic materials such as Fe, Ni, Co, Fe-Ni alloy,
Fe-Co alloy, Fe-Ni-P alloy, Fe-Ni-C
o alloy, Fe-Mn-Zn alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-Cr alloy, Fe-Co-Ni-
Various magnetic materials such as P alloys, Co-Ni alloys, Co-P alloys, Co-Cr alloys, and metal magnetic powders mainly containing Fe, Ni, and Co are used.

The particle size (average primary particle size) of the magnetic material is not particularly limited, but a particle size of about 0.05 to about 5 μm is generally used.

Additives to these metal magnetic materials include Si and C within the range used in the art.
Elements such as u, Zn, Al, P, Mn, and Cr, or compounds thereof may be contained.

It is also possible to contain hexagonal ferrite such as barium ferrite, iron nitride and iron carbide.

The binder used in the magnetic layer of the present invention may be any known binder used for magnetic recording media, and examples thereof include thermoplastic resins, thermosetting resins, reactive resins and electron beams. Radiation curable resins or mixtures thereof are used.

More specifically, a urethane resin, an epoxy resin, a urea resin, an amide resin, a silicone resin, a polyester resin, a phenol resin, a vinyl resin, a cellulose derivative resin, a rubber resin, or the like, or a copolymer of these resins is used. Alternatively, a mixture thereof may be used.

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, and polycarbonate. In addition to plastics such as polyamide and polysulfone, metals such as aluminum and copper, glass and ceramics such as alumina can be used.

The magnetic recording medium may be produced according to a known method and is not particularly limited, but the above magnetic powder, binder and oxide-containing alumina are mixed with various additives in an organic solvent. It may be prepared by mixing and dispersing it to prepare a magnetic coating material, coating it on a non-magnetic support, drying it, and optionally subjecting it to heat treatment, surface treatment and the like.

As described above, it is not clear why the magnetic recording medium using alumina containing a specific oxide and having a specific average particle size is effective in improving the durability and abrasion resistance of the magnetic layer. , P, Sn, Nb, Ta, Mo, and W are all oxides with high acidity, and the oxides of Ge, P, Sn, Nb, Ta, Mo, and W on the alumina powder surface are solid oxides. At the melting point or at the precipitation point of the oxide or a composite oxide of the oxide and alumina, an acidic point is developed, the affinity with the binder used in the magnetic layer is increased, and the alumina is firmly bonded to the magnetic layer. It is presumed that it is because of the connection.

[0040]

According to the present invention described in detail above, the durability of the magnetic layer is improved by the simple method of using alumina containing a specific oxide in place of the non-magnetic powder such as the alumina powder which has been conventionally used. Excellent in wear resistance, wear resistance and surface smoothness,
Moreover, it is possible to supply a magnetic recording medium having an excellent cleaning effect on the magnetic head, and its industrial value is extremely large.

[0041]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the present invention, the analysis was performed by the following method. Squareness ratio; Sample vibrating magnetometer (Riken Denshi BHV-5
The measurement was performed with a sweeping magnetic field of 15 K Gauss at 0).

Surface gloss: Total reflectance at an incident angle of 60 ° and a reflection angle of 60 ° with respect to the longitudinal direction of the sample tape was measured by a standard gloss meter, and a refractive index of 1. was measured according to JISZ8741.
The relative value of the specular gloss of 56 glass was defined as 100 at an incident angle of 60 °.

Still characteristics: Using a video deck modified for still measurement, a 4 MHz signal was recorded on a sample tape to be measured, 25 ° C., 60% RH, back tension 40.
Playback output is 1/2 when played back under static condition
The time until it dropped to the measured value was measured.

Head adhesion and head wear amount: Observation of adhesion status to magnetic head and measurement of head wear amount when a sample tape was run for 100 hours in a 40 ° C. 80% atmosphere using a Matsushita video deck NV-G21. I went.

Average particle diameter: When the average particle diameter is less than 0.3 μm, the particle diameter (average of long diameter and short diameter) is read from the scanning electron micrograph of the powder, and a cumulative frequency distribution chart is prepared. Was calculated as the average particle diameter. Average particle size 0.3μ
In case of m or more, centrifugal sedimentation type particle size distribution measuring instrument (Shimadzu CP-
50).

Example 1 A large excess of water was added to a solution of aluminum isopropoxide in isopropyl alcohol for hydrolysis. Ammonium tungstate was added thereto and mixed uniformly, and then the solvent was distilled off and then 1270 ° C. After firing for 3 hours, an alumina powder having an average primary particle diameter of 0.2 μm and containing 1.0 part by weight of WO ₃ was obtained. Using 5 parts by weight of this alumina powder, a magnetic coating material was prepared with the following weight mixing ratio.

100 parts by weight of Co-deposited r-Fe ₂ O ₃ (B-42 Titanium Industry Co., Ltd.) BET specific surface area 43 m ² / g Hc 6900e σs 72 emv / g major axis 0.25 μm minor axis 0.05 μm Polyurethane resin 10 parts by weight (product name SB-0853 Sumitomo Bayer Urethane Co., Ltd.) PVC / vinyl acetate / vinyl alcohol copolymer (product name MPR-TA5C manufactured by Nisshin Kagaku) 10 parts by weight Carbon black 2 parts by weight (product name Vulcan XC-72 manufactured by Cabot Co., Ltd.) Butyl stearate 1 part by weight Methyl ethyl ketone 100 parts by weight Toluene 100 parts by weight Cyclohexanone 50 parts by weight Polyisocyanate curing agent 2 parts by weight (Sumijour L Sumitomo Bayer Urethane Co., Ltd.)

The above composition was dispersed in a sand grinder for 5 hours, filtered with a filter having an average pore size of 1 μm, and then coated on a polyethylene terephthalate film having a thickness of 10 μm so that the magnetic layer had a thickness of 3 μm after drying. After drying and calendering, cure at 70 ° C for 24 hours and ½
A magnetic tape was prepared by cutting into an inch width. The surface gloss, still characteristics, head adhesion amount, and head wear amount of the obtained magnetic tape were measured. The results are shown in Table 1.

Examples 2 to 8 and Comparative Examples 1 to 4 As an alumina powder, a table obtained by changing the additive used at the time of preparing the alumina powder and the firing temperature to the conditions shown in Table 2 in the method of Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that the alumina powder having the physical properties shown in 1 was used. The surface gloss, still characteristics, head adhesion amount, and head wear amount of the obtained magnetic tape were measured. The results are shown in Table 1.

Example 9 Ammonium tungstate was added to an aqueous solution of ammonium alum, and a tungsten-containing ammonium alum was precipitated by a recrystallization method, which was fired under the conditions shown in Table 2 and had the physical properties shown in Table 1. A magnetic tape was prepared in the same manner as in Example 1 except that the alumina powder was used. The surface gloss, still characteristics, head adhesion amount, and head wear amount of the obtained magnetic tape were measured. The results are shown in Table 1.

Example 10 To a solution of aluminum isopropoxide in isopropyl alcohol, triethyl phosphate was added and uniformly mixed, and then a large excess of water was added to effect hydrolysis to distill off the solvent, and then 1280 ° C. for 3 hours. Average particle size 0.2 after firing
An alumina powder containing 0.8 parts by weight of P ₂ O ₅ was obtained at 3 μm. A magnetic tape was prepared in the same manner as in Example 1, and the surface gloss, still characteristics, head adhesion amount, and head wear amount of the obtained magnetic tape were measured. The results are shown in Table 1.

Comparative Example 5 High-purity alumina (AKP-5) having an average particle diameter of 0.2 μm
0; Sumitomo Chemical Co., Ltd.) was dispersed in water, ammonium tungstate was added and mixed well, and dried, 800 ° C.,
It was calcined for 3 hours to obtain an alumina powder coated with 1.0 part by weight of WO ₃ . A magnetic tape was prepared in the same manner as in Example 1 except that the thus obtained WO ₃ -coated alumina powder (average particle diameter 0.2 μm) was used. The results are shown in Table 1.

[0053]

[Table 1]

[0054]

[Table 2]

Claims (2)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer containing magnetic fine powder and a binder, the magnetic layer being obtained by any of the following methods (1) to (3). Also, at least one oxide selected from the elements Ge, P, Sn, Nb, Ta, Mo and W is contained in an amount of about 0.1 to about 10 parts by weight per 100 parts by weight of alumina. A magnetic recording medium containing alumina having an average particle diameter of about 1 μm or less. (1) After firing in a solution containing an aluminum salt, Ge, P,
A method of uniformly mixing at least one oxide component selected from the elements Sn, Nb, Ta, Mo and W, and precipitating it as a carbonate by a neutralization method, a recrystallization method or the addition of a carbonic acid-containing substance. After obtaining the aluminum compound by the method of baking, (2) after baking into a solution containing an organic aluminum compound, at least one kind of oxidation selected from the elements Ge, P, Sn, Nb, Ta, Mo and W (3) The aluminum salt is precipitated as a carbonate by a neutralization method, a recrystallization method, ammonium hydrogencarbonate, etc. To the aluminum compound obtained by the method described above or the aluminum compound obtained by the hydrolysis method of the organoaluminum compound, Ge, P, Sn, Nb, T
A method of mixing at least one metal oxide selected from a, Mo and W, or a compound of the metal to be a metal oxide after firing in a wet or dry manner, and firing the mixture. 2. The magnetic recording medium according to claim 1, wherein the addition ratio of alumina contained in the magnetic layer is about 0.1 to about 15% by weight.