JPH07235041A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To ensure high electromagnetic transducing characteristics and reliability by adding a prescribed percentage of a silane coupling agent or a titanium coupling agent to magnetic powder of iron nitride having a specified compsn. CONSTITUTION:A magnetic layer is formed on the surface of a filmlike substrate by coating with a magnetic coating material prepd. by kneading magnetic powder with a binder to obtain the objective magnetic recording medium. At this time, the magnetic powder is represented by a prescribed chemical formula and has an acicularity ratio of 5-15, 0.05-0.15mum major axis size, 160-210emu/g saturation magnetization sigmas and 1,500-2,500Oe coercive force Hc. A silane coupling agent or a titanium coupling agent has been added to the magnetic powder by 0.2-10wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium among magnetic recording mediums capable of high density recording.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Magnetic recording media in which a magnetic coating is applied to the surface of a film-shaped support such as polyethylene or naphthalate (PEN) to form a magnetic layer are widely used, and various proposals have been made to improve the characteristics of the magnetic recording medium. Has been done. For example, JP-A-49-59608 proposes to add a silane coupling agent in order to enhance the binding force between a film-shaped support which is an organic substance and a magnetic powder which is an inorganic substance.

[0003]

The magnetic powders disclosed in the above publications cannot achieve high electromagnetic conversion characteristics that can cope with recent high-density recording. On the other hand, the present applicant has previously proposed iron nitride-based magnetic powder as the magnetic powder having high electromagnetic conversion characteristics. In order to achieve higher electromagnetic conversion characteristics and reliability with such magnetic powder, it is necessary to use fine magnetic powder with high saturation magnetization, but fine magnetic powder with high saturation magnetization is Has a strong magnetic attraction, is prone to agglomeration, and is difficult to disperse when a magnetic coating is prepared.

[0004]

In order to solve the above-mentioned problems, the present invention provides a magnetic recording medium having a magnetic layer formed by applying a magnetic coating material prepared by kneading a binder and magnetic powder on the surface of a film-like support. Magnetic powder is represented by the following (chemical formula) and (chemical formula)

[Chemical 2] Needle ratio 5 to 15, major axis length 0.05 to 0.15μ
m, a saturation magnetization amount (σs) of 160 to 210 emu / g, a coercive force (Hc) of 1500 to 2500 (Oe), and a silane coupling agent of 0.2 wt% to 10 wt% with respect to the magnetic powder. Alternatively, a titanium coupling agent was added.

Here, the needle-like ratio of the magnetic powder is set to 5 to 15 when the needle-like ratio is less than 5, the magnetic powder cannot be oriented well and the squareness ratio is low. When the acicular ratio exceeds 15, the dispersibility of the magnetic powder is remarkably deteriorated, the magnetic powder is broken, the magnetostatic characteristics are deteriorated, and high reproduction output cannot be realized. The saturation magnetization (σs) of the magnetic powder is 160 to 210 emu / g is 1
When it is less than 60 emu / g, the saturation magnetic flux density (Bm) of the coating film after mediumization is low and the reproduction output is low, and the magnetic layer formed by the magnetic powder exceeding 210 emu / g is reliable and chemically stable. Due to the problem. When the major axis length of the magnetic powder is 0.05 to 0.15 μm, if the length is less than 0.05 μm, the magnetic properties cannot be made good values and the dispersibility deteriorates, resulting in a medium. The magnetic properties of the subsequent magnetic layer are reduced,
If it exceeds 0.15 μm, the reproduction output and C / N at the time of recording / reproducing a short wavelength signal become low. Further, the coercive force (Hc) is set to 1500 to 2500 (Oe) because the reproduction output at the time of recording / reproduction of a short wavelength signal is low when it is less than 1500 (Oe) and the long wavelength signal is recorded when it exceeds 2500 (Oe). This is because the reproduction output during reproduction is low and the erasing rate is deteriorated.

On the other hand, the addition ratio of the silane coupling agent or the titanium coupling agent to the magnetic powder is set to 0.2% by weight to 10% by weight, when the amount is less than 0.2% by weight, the dispersibility is not improved. This is because if it exceeds 10% by weight, the electromagnetic conversion characteristics are affected. Here, as the silane coupling agent, vinyltriethoxysilane, vinyltris (2-methoxy-ethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyl-trimethoxysilane, N-β (amino ethyl)
-Γ-aminopropyl trimethoxysilane, β- (3,
4-epoxycyclohexyl) ethyl-trimethoxysilane, γ-glycidoxy-propyltrimethoxysilane,
γ-mercaptopropyl-trimethoxysilane and the like can be mentioned. Further, as the titanium coupling agent, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) Examples thereof include titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, and bis (dioctylpyrophosphate) ethylene titanate.

[0007]

By adding a silane coupling agent or a titanium coupling agent in a predetermined ratio to the iron nitride magnetic powder having a specific composition, the reproduction output and the still resistance can be improved.

[0008]

EXAMPLES Next, specific examples of the first invention will be described. First, a mixture having the following composition ratios was mixed and dispersed by a sand mill to obtain a magnetic coating material. (Magnetic paint) Magnetic powder --- 100 parts by weight Coupling agent ---- Addition amount is shown in (Table 2) Polyvinyl butyral --- 10 parts by weight Polyurethane ---・ ・ ・ ・ ・ ・ ・ ・ ・ 10 parts by weight α-alumina ・ ・ ・ ・ ・ ・ 2 parts by weight Palmitic acid ・ ・ ・ ・ ・ ・ 2 parts by weight Carbon black ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 2 parts by weight Isocyanate ・・ ・ ・ ・ 3 parts by weight Cyclohexanone ・ ・ ・ ・ 100 parts by weight Methyl ethyl ketone ・ ・ ・ 100 parts by weight

As the magnetic powder, iron nitride magnetic powders (magnetic powder A) and (magnetic powder C) having the composition ratios specified by the claims of the present invention shown in (Table 1) below and conventional metal powders are used. (Magnetic powder B) was used. Further, the addition ratio of the coupling agent to the magnetic powder and the name of the coupling agent are shown in (Table 2) below.

[0010]

[Table 1]

[0011]

[Table 2]

The glossiness during dispersion was measured for each of the magnetic paints of Examples 1 to 7 and Comparative Examples 1 to 4 shown in Table 2 above. The result is shown in FIG. From FIG. 1, Examples 1 to 7 using the iron nitride-based magnetic powder having the composition according to the present invention and adding the coupling agent in the range shown in the present invention,
It can be seen that the glossiness, which is an index of dispersibility, is higher than that of the conventional metal magnetic powder or the iron nitride-based magnetic powder having the composition according to the present invention as compared with the one without the addition of the coupling agent.

Each of the magnetic paints of Examples 1 to 7 and Comparative Examples 1 to 4 was applied to a polyester film having a thickness of 10 μm and cut into 1/2 inch to prepare a D-3 format tape. On the other hand, a D-3 VTR (AJ-D350 manufactured by Matsushita Electric Industrial Co., Ltd.) was used to input a 40 MHz sine wave signal, and the reproduction output was measured. Further, a still resistance test was conducted using the same VTR in an environment of a temperature of 20 ° C. and a humidity of 10%. The respective results are shown in (Table 3) below.

[0014]

[Table 3]

From Table 3 below, in Examples 1 to 7 in which the iron nitride magnetic powder having the composition according to the present invention was used and the coupling agent was added within the range shown in the present invention, the reproduction output was high,
It was also found that the steel has excellent resistance to stills. On the other hand, even when the iron nitride-based magnetic powder of the composition according to the present invention is used, no coupling agent is added, or even if a coupling agent is added at a predetermined ratio, the magnetic properties are improved. It can be seen that Comparative Examples 1 to 4 using metal powder as the powder cannot satisfy both the reproduction output and the still resistance.

[0016]

As described above, according to the present invention,
When creating a magnetic paint using iron nitride-based magnetic powder with high magnetic properties by adding a silane coupling agent or titanium coupling agent in a specified ratio to iron nitride-based magnetic powder with a specific composition The dispersibility of
As a result, the reproduction output can be improved, and the electromagnetic conversion characteristics such as the noise level can be improved. Further, the resin is adsorbed on the surface of the magnetic powder to increase the mechanical strength and reliability.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the dispersion time of a magnetic paint and the gloss level.

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Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer formed by applying a magnetic coating material prepared by kneading a binder and magnetic powder on the surface of a film-like support, wherein the magnetic powder is represented by the following (chemical formula): (Chemical formula) Needle ratio 5 to 15, major axis length 0.05 to 0.15μ
m, the saturation magnetization (σs) is 160 to 210 emu / g, the coercive force (Hc) is 1500 to 2500 (Oe), and the silane coupling agent is 0.2 wt% to 10 wt% with respect to the magnetic powder. Alternatively, a magnetic recording medium containing a titanium coupling agent.