JPH1125450A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium having excellent corrosion resistance and has a saturation magnetization quantity stable with lapse of time. SOLUTION: This medium is constituted by applying a magnetic layer 3 contg. magnetic particles 4 consisting essentially of Fe coated with any one or both of a silica compd. or aluminum compd. on its surface on a film-film base 2. In such a case, metal ions M<n+> (n=2, 3) which are given by the complexing agent of R1-CO-CH2 -CO-R2 (R1: CH3 , C(CH3 )3 , CF3 , C3 F7 , C4 H4 O (furan), C4 H4 S (thiophene); R2: CH3 , C(C3 )3 , CF3 , C3 F7 , C4 H4 O (furan), C4 H4 S (thiophene) and is of >=-0.44 V in standard electrode potential are adsorbed on the surfaces of the magnetic particles 4. As a result, the corrosion resistance is improved and the stability of the saturation magnetization quantity with lapse of time is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin-layer coating type magnetic recording medium, and more particularly to improving the corrosion resistance of magnetic particles in a magnetic layer.

[0002]

2. Description of the Related Art As a measure for preventing oxidation of magnetic particles used in a magnetic layer of a coating type magnetic recording medium, a technique of treating the magnetic particles with various metals is known. Most of these conventional techniques reduce the immersion of magnetic particles in an aqueous solution of metal ions to be deposited, and then reduce the oxidized particles in the liquid or gas phase to achieve the desired oxidation. This is to obtain a coating.

[0003]

However, it is known that the oxide film has a non-uniform distribution and a concentration gradient, so that the corrosion resistance is not sufficient, and the metal element constituting the oxide film is not known. In some cases, the dispersibility deteriorated. In particular, as the miniaturization of magnetic particles progresses,
In spite of the fact that the magnetic particles themselves are easily oxidized, it becomes more difficult to apply a uniform metal film as the magnetic particles become finer in the above-described method, which further reduces the corrosion resistance. However, there has been a problem that the stability of the change over time such as saturation magnetization is significantly deteriorated.

If the magnetic particles collide with the dispersion medium during the dispersion of the magnetic paint, the surface of the magnetic particles and its oxide film are damaged at this time, the exposed inside is corroded, and furthermore the saturation magnetization and the like are further reduced. There is a problem that the stability of the change with time is reduced. The present invention has been made in view of the above problems, and has been conceived in order to effectively solve the problems. The purpose of the present invention is to provide a magnetic recording medium which has excellent corrosion resistance and a stable magnetization over time. Is to do.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention comprises magnetic particles containing Fe as a main component, the surface of which is coated with one or both of a silica compound and an aluminum compound. in the magnetic recording medium formed by coating a magnetic layer on the film-like support, the surface of the magnetic _{particles, R1-CO-CH 2 -CO} -R2 (R
1: CH ₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄
H ₄ O (furan), C ₄ H ₄ S (thiophene); R2:
CH ₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄ H ₄
The metal ion M ^{n +} (n = 2, 3) provided by the complexing agent of O (furan) and C ₄ H ₄ S (thiophene) is adsorbed.

Accordingly, the corrosion resistance can be improved, and the stability of the saturation magnetization over time can be improved. In this case, the metal electrode has a standard electrode potential of -0.440.
At least one kind of metal ion having a value of V or less is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic recording medium according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing a magnetic recording medium according to the present invention.
As shown in the figure, the magnetic recording medium 1 is formed by coating a magnetic layer 3 on the surface of a thin film-shaped support 2 made of polyethylene terephthalate or the like. The magnetic layer 3 contains a large amount of magnetic particles 4. The thickness of the dried magnetic layer 3 is set, for example, in a range of about 0.1 to 0.3 μm. The magnetic particles 4 contain Fe (iron) as a main component, and the surface thereof is coated with a silica compound, an aluminum compound, or both. The surface of the magnetic particles _{4, R1-CO-CH 2} -CO-R2 (R1: C
H ₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄ H ₄ O
(Furan), C ₄ H ₄ S (thiophene); R2: CH
₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄ H ₄ O,
C ₄ H ₄ S) complexing agent and a standard electrode potential of -0.440
At least one metal ion given by chelation with at least one or more metal ions selected from M ^{n +} (n = 2, 3) metal ions of V or less is adsorbed.

[0008] A magnetic paint obtained by using such magnetic particles having metal ions adsorbed thereon is coated on the surface of a support, and then dried with an oxygen-containing gas at a temperature of 100 ° C to 150 ° C to obtain a magnetic particle. An oxide film of metal M is formed on the surface. In the present invention, any kind of complexing agent may be used, but preferably one or two kinds, and an amount of 2 mol or less per 100 g of magnetic particles is desirable. The metal ion M ^{n +} used for the metal oxide film is not particularly limited as long as the standard electrode potential is −0.440 V or less of Fe ²⁺ , but preferably Ca ²⁺ , Ba ²⁺ , C ²⁺
r ²⁺ , Mg ²⁺ , Mn ²⁺ , Zn ²⁺ , and Al ³⁺ .
The oxygen content of the oxygen-containing gas at the time of drying is 1 to 30 by volume concentration.
%, But preferably 5 to 25%, and the drying time is preferably about 20 to 60 seconds.

According to the present invention, in order to form an oxide film of metal ions upon drying after coating, the surface of the substrate other than the surface of Fe and its Fe compound, silicon (Si) and its silicon compound, and aluminum and its aluminum compound is not used. In addition, the metal ions M ^{n +} can also be adsorbed to the inside of the magnetic particles exposed by the damage received from the dispersion medium during the dispersion of the magnetic particles. For this reason, it is possible to perform adsorption without unevenness on the entire surface of the magnetic particles, and as a result, when dried in an atmosphere of an oxygen-containing gas, an oxide film made of the metal M is uniformly and uniformly formed on the entire magnetic particles. Will be able to do it. Therefore, there is little change over time in the saturation magnetization and the like, and the corrosion resistance can be improved. In particular, the effect can be enhanced in a magnetic recording medium in which the thickness of the magnetic layer is 0.3 μm or less.

More specifically, the production and surface treatment of magnetic particles are performed by a known method, and R1-CO-CH
_{2 -CO-R2 (R1: CH} 3, C (CH 3) 3, CF
_{3, C 3 F 7, C} 4 H 4 O, C 4 H 4 S; R2: CH
₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄ H ₄ O,
A ketone or aromatic organic solvent obtained by melting or mixing a C ₄ H ₄ S) complexing agent with an appropriately pH-adjusted aqueous phase containing M ^{n +} (n = 2, 3) metal ions; The organic phase from which the metal ions were chelated and extracted by shaking was separated, and the magnetic particles were immersed in the solution and treated. The magnetic particles were made into a paint in a wet state.

After applying these coatings to a film-like support, the coatings were dried in a gas atmosphere at 130 ° C. containing 20% oxygen. When the surface of the magnetic layer of the obtained magnetic recording medium was examined with an X-ray photoelectron analyzer (ESCA),
It was confirmed that most of the surface was covered with metal M. The produced magnetic powder had a major axis length of 0.10 μm, a coercive force Hc of 1800 Oe, and a saturation magnetization σs of 130.
What was applied by wt% was used.

Next, Examples 1 to 16 and Comparative Examples 1 to 9 for producing a video tape as a magnetic recording medium will be described. A to H were selectively used as complexing agents, and a to e were selectively used as metal ions M ^{n +} . The magnetic powder α-Fe is roughly classified into the following three types, which is to obtain a metal oxide film using a complexing agent, is to obtain a metal coating by a conventional method, It was produced without performing a process for obtaining a metal film. still,
For the above, the magnetic particles are immersed in an aqueous solution of the metal to be deposited, then reduced at 400 ° C., and then gradually oxidized by blowing oxygen gas into the organic phase. By depositing a metal oxide film.

100 parts by weight of α-Fe Treatment with complexing agent (1 mol / 100 g of magnetic particles) R1-CO—CH ₂ —CO—R2 (A: R1 = CH ₃ , R2 = CH ₃ ) (B: R1 = _{C (CH 3) 3, R2} = C (CH 3) 3) (C: R1 = CF 3, R2 = CF 3) (D: R1 = CF 3, R2 = C 4 H 4 O) (E: R1 = _{CH 3, R2 = CF 3)} (F: R1 = CF 3, R2 = C (CH 3) 3) (G: R1 = CH 3, R2 = C 4 H 4 S) (H: R1 = CH 3, R2 = C ₃ F ₇ ) Metal ion: M ^{n +} (a: Cr ²⁺ (standard electrode potential −0.56 V)) (b: Mg ²⁺ (standard electrode potential −2.37 V)) (c: Zn ²⁺ ( (Standard electrode potential -0.76 V)) (d: Al3 ⁺ (Standard electrode potential-1.66 V)) (e: Cu2 ⁺ (Standard electrode potential + 0.34 V)) Metal aqueous solution Treatment by immersion method (1 mol / 100 g of magnetic particles) Metal ion: ^{Mn +} (a: Cr2 ⁺ (standard electrode potential -0.56 V)) (b: Mg2 ⁺ (standard electrode potential -2.37 V)) ( c: Zn ²⁺ (standard electrode potential −0.76 V)) (d: Al ³⁺ (standard electrode potential −1.66 V)) (e: Cu ²⁺ (standard electrode potential +0.34 V)) Untreated vinyl chloride-vinyl acetate copolymer 10 parts by weight Polyester polyurethane 15 parts by weight Aluminum oxide 5 parts by weight Methyl ethyl ketone 110 parts by weight Toluene 110 parts by weight Stearic acid 1 part by weight 1 part by weight butyl stearate

(Embodiment) A method of increasing the corrosion resistance of a coating type magnetic recording medium is as follows. A method in which magnetic particles are immersed in an aqueous solution of a metal to be coated is reduced, and then a liquid phase, Alternatively, the desired oxide film is generally obtained by oxidizing the metal deposited in the gas phase,
Corrosion resistance is not yet sufficient. Accordingly, the corrosion resistance was remarkably improved by forming a metal oxide film when applying a coating material while adsorbing metal ions to the magnetic particles and then drying the coating.

Regarding this effect, the metal chelate formed by the combination of the complexing agent and the metal ion M ^{n +} used in the present invention dissociates the metal ion M ^{n +} when subjected to heat at 100 to 150 ° C., and the complexing agent itself becomes dissociated. by evaporating, Snap active sites of the magnetic particle surface (adsorption)] ⇔M n ⁺ ⇔ equilibrium of the complexing agent (chelating)] becomes the only suction side, resulting in metal ion M ^{n +} is a magnetic particle surface It is supposed that this is oxidized by oxygen in the atmosphere to form an oxide film of metal M on the surface of the magnetic particles.

After the above composition was mixed and dispersed in a ball mill for 30 hours, 10 parts by weight of a polyisocyanate compound was added, and the mixture was further stirred for 1 hour to prepare a paint. This paint was applied on polyethylene terephthalate (PET) so as to have a thickness of 0.3 μm after drying, subjected to surface treatment after orientation drying, and subjected to a heating effect treatment at a temperature of 50 ° C. for 40 hours. This was slit to a width of 1/2 inch to obtain a magnetic tape. The evaluation was performed by measuring the change over time of the saturation magnetization σs of the obtained magnetic recording medium (measured after storage for a certain period in an environment of a temperature of 60 ° C. and a humidity of 90%).
The evaluation results are shown in Tables 1 and 2.

[0017]

[Table 1]

[0018]

[Table 2]

Tables 1 and 2 show the rate of change with time of the saturation magnetization σs of each magnetic tape. As is clear from Tables 1 and 2, the standard electrode potential is -0.440.
When metal ions of V or more are used (Comparative Examples 1 to 3), when magnetic particles having a metal oxide film treated by a conventional deposition method are used (Comparative Examples 4 to 8), and when no metal coating is applied (Comparative Example 9), the rate of change over time of the magnetic recording medium was reduced by 10% or more at 170 hours. This causes a practical problem because the output of the magnetic recording medium is significantly reduced. In particular, 34
At 0 hr, the rate of change with time is undesirably reduced by 16% or more.

On the other hand, in the magnetic recording media of Examples 1 to 16, the rate of change with time is 170 hrs and the maximum is 8.
About 8% (Example 7), and 1 at 340 hr.
It is about 2.5%, and all show better values than Comparative Examples 1 to 9. That is, a magnetic recording medium having a metal oxide satisfying the claims of the present application (Examples 1 to 1)
6) shows that the magnetic layer is hardly oxidized and the stability with time is good.

[0021]

As described above, according to the magnetic recording medium of the present invention, the following excellent functions and effects can be exhibited. By adsorbing the metal ions provided by the complexing agent on the surface of the magnetic particles, the corrosion resistance is improved, and the change over time in the saturation magnetization can be significantly suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a magnetic recording medium according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic recording medium, 2 ... Support, 3 ... Magnetic layer, 4 ... Magnetic particles.

Claims (1)

[Claims] The present invention relates to a magnetic recording medium obtained by applying a magnetic layer containing magnetic particles containing Fe as a main component and having a surface coated with one or both of a silica compound and an aluminum compound on a film-like support. , the surface of the magnetic _{particles, R1-CO-CH 2 -CO} -R2 (R
1: CH ₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄
H ₄ O (furan), C ₄ H ₄ S (thiophene); R2:
CH ₃ , C (CH ₃ ) ₃ , CF ₃ , C ₃ F ₇ , C ₄ H ₄
O (furan), C ₄ H ₄ S (thiophene) complexing agent, and adsorbed a metal ion M ^{n +} (n = 2, 3) having a standard electrode potential of −0.440 V or less. Characteristic magnetic recording medium.