JP2506857B2 - Method for manufacturing magnetic paint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a magnetic coating material such as a so-called coating type magnetic tape or magnetic disk which uses a ferromagnetic metal powder as a magnetic material, and particularly to dropout, C / N. The present invention relates to a method for producing a coating type magnetic paint having an improved ratio.

2. Description of the Related Art In general, magnetic recording media such as magnetic tapes and magnetic disks using video and audio equipment or computers are more and more suitable for high density recording. Therefore, recording wavelengths are short and recording track widths are narrow. There is a tendency to reduce the minimum recording unit by reducing the thickness. as a result,
Defects on the surface of small magnetic coatings, which have not been affected in the past, adversely affect the dropout, and eventually the decrease in C / N ratio becomes a problem. As measures against this, as magnetic surface smoothing for reducing void loss, fine particles of magnetic particles, high dispersion of magnetic paint, calendering after coating, and the like are performed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, even by the above method, it is difficult to obtain a magnetic recording medium satisfying both dropout and C / N ratio at the same time.

Normally, magnetic paint is prepared by kneading magnetic powder and a binder to disperse the magnetic powder and fix it on polyethylene terephthalate (PET) at a high solid content concentration (hereinafter referred to as NV), and then mix with other additives in the Glen mill dispersion process. Disperse and paint with low NV together. In this grain mill dispersion, glass or ceramic (such as ZrO ₂ or
Since Al ₂ O ₃ ) is used, it is inevitable that the abrasion powder of the medium is mixed in the paint. PET in this state
When applied on top, since abrasion powder is contained in the coating film, protrusions are generated on the coating film, and in the process of winding the coating film, the upper and lower coating films are further imaged to increase surface defects of the coating film. As a result, the normal running of the magnetic head is obstructed at the coating film defect area and void loss occurs, increasing dropout and C /
This led to a decrease in the N ratio.

Means for Solving the Problems In order to solve the above problems, a method for producing a magnetic coating material of the present invention comprises a dispersion step of kneading a ferromagnetic metal powder, a binder and a solvent, glass beads or zirconium oxide (ZrO ₂ ) Is used as a dispersion medium in a method for producing a magnetic coating comprising a dispersion step using a Glen mill, the dispersion step using the Glen mill is divided into the first half and the second half, and the dispersion time after the abrasive is added in the latter half is mixed in the paint. It is characterized in that the abrasion of the dispersion medium is completed within the range of 0.2 to 1.5% by weight based on the total solid content in the paint.

By the above method, the content of glass beads or zirconium oxide in the dispersion medium is 1.5 wt% with respect to the magnetic layer 100.
It will be regulated below, which will reduce dropout and improve C / N ratio.

EXAMPLES Examples of the present invention will be specifically described below. All parts in the component ratios shown in the examples are parts by weight.

(Example 1) Ferromagnetic metal powder (average particle size major axis =
0.2μm, acicular ratio = 10, coercive force = 1550Oe, specific surface area = 50m ² )
With the compounding ratios shown in Table 1 by the process shown in FIG.
8mm video tape was made.

First, magnetic powder, a binder, an antistatic agent, and 100 parts of a solvent are used to knead for 5 hours with a disper. Next, the remaining 200 parts of the solvent is added to reduce the solid content concentration, and dispersion (primary dispersion) is performed by a Glen mill for 5 hours. Alumina is added to this and further dispersed for 5 Hr (secondary dispersion) by a Glen Mill. next,
Add a lubricant and hardener, and pass through a 1 μm filter.
After coating on a polyester film (PET) with a thickness of 10 μm, magnetic field orientation, and drying, the magnetic layer is surface-treated with a super calender (surface treatment machine), and after curing treatment, it is cut into 8 mm wide and 3 μm thick magnetic layer. 8mm video tape was made.

Here, there were two types of media used in the Glen Mill, 1 mmφ glass beads and 1 mmφ ZrO ₂ beads, and each of the beads was used alone for the preparation of the coating material.

(Example 2) With the compounding ratio of Example 1, the primary dispersion of the grain mill was adjusted to 7 Hr, 2
Next dispersion was performed for 3 hours. Other than this, the same as Example 1 8
mm video tape was produced.

(Example 3) With the compounding ratio of Example 1, the primary dispersion of the grain mill was set to 9 Hr, 2
Dispersion was performed for 1 hour. Other than this, the same as in Example 1, 8 mm
A video tape was made.

(Comparative Example 1) With the compounding ratio of Example 1, the primary dispersion of the grain mill was set to 3 Hr, 2
Next dispersion was performed for 7 hours. Other than this, the same as Example 1 8
mm video tape was produced.

(Comparative Example 2) With the compounding ratio of Example 1, the primary dispersion of the grain mill was adjusted to 1 Hr, 2
Next dispersion was performed for 9 hours. Other than this, the same as Example 1 8
mm video tape was produced.

Table 2 shows the characteristics of each of the above samples and the analysis results of the amount of glass or the amount of ZrO ₂ in the coating film. The evaluation method is also shown below.

Magnetic layer surface roughness: The center line surface roughness (value of R) of the magnetic layer surface of each 8 mm video tape was measured using a stylus type surface roughness meter.

Dropout: Measure how much an output drop of 16 dB or 3 μs-10 dB or more per 15 μs occurs per unit time (1 min). As the 8 mm tape recorder for dropout measurement, MVS-5000 (manufactured by KODAK) was used.

C / N (5MHz / 4.5MHz); The ratio of the signal at 5MHz and the noise at 4.5MHz was measured. The 8 mm tape recorder for C / N measurement is MVS-5000 (KOD
AK) was used. An amorphous alloy was used for the recording / reproducing head, and the C / N of the 8 mm video tape of Example 1 (1) was shown as a reference (0 dB) relative value.

Analytical values (glass and ZrO ₂ ); When the same composition as in Example 1 was made into a paint without using a Glen mill, and the same glass and ZrO ₂ pulverized powder as that used in the Glen mill was applied as a coating film. Magnetic layer 100
The amount was changed so as to be 0 to 5 wt%, and then several kinds of coating films having a thickness of 3 μm were prepared. Then, using this as a standard sample, Si is analyzed in the case of glass and Zr is analyzed in the case of SrO ₂ by fluorescent X-ray analysis, and Si is compared with the amount of glass or ZrO _2.
Alternatively, a calibration curve for the amount of Zr was prepared, and the amount of each glass or ZrO ₂ was determined from the fluorescent X-ray analysis of each sample. The relationship between the amount of glass in the coating film and DO obtained from the analysis results
The relationship between the amount of ZrO ₂ in the coating film and DO is shown in Fig. 3.

Further, FIG. 4 shows the relationship between the time from the start of dispersion and the amount of glass and ZrO ₂ contained in the coating film at the time of secondary dispersion by the Glen Mill.

From this, it is understood that a clear relationship between the bead abrasion powder (glass or ZrO ₂ ) from the Glen mill contained in the coating film and DO can be obtained.

From FIGS. 2 and 3, it can be seen that the amount must be 1.5 wt% or less in order to satisfy the desired DO characteristics for the 8 mm VTR. Further, the abrasion powder is generated after the addition of the abrasive in the dispersion process of the Glen Mill, and has a proportional relationship with the dispersion time thereafter. From this, it is understood that it is necessary to shorten the secondary dispersion time of the Glen Mill in order to reduce the amount of wear powder to 0.2 to 1.5 wt%.

Effects of the Invention As described above, in the method of manufacturing the magnetic recording medium of the present invention,
The input magnetism of the abrasive in the paint preparation process is the latter half of the dispersion process by the Glen Mill, and the dispersion time is 0, the wear amount of the dispersion medium mixed in the paint is 0 relative to the total solid content in the paint.
By finishing within the range of 2 to 1.5% by weight, the abrasion powder of glass or ZrO ₂ from the Glen mill contained in the coating film is reduced, and it has a great effect of reducing dropout and improving C / N ratio. can get.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of an 8 mm VTR tape according to an embodiment of the present invention, FIGS. 2 and 3 are graphs showing the relationship between the glass amount or ZrO ₂ amount and DO, and FIG. 4 is a dispersion. 3 is a graph showing the relationship between time and the amount of glass and ZrO ₂ mixed in the coating film.

Claims (1)

(57) [Claims] 1. A method for producing a magnetic coating material, which comprises a dispersion step of kneading a ferromagnetic metal powder, a binder and a solvent, and a dispersion step of a Glen mill using glass beads or zirconium oxide (ZrO ₂ ) as a dispersion medium. The dispersion process by the Glen Mill is divided into the first half and the second half, and the dispersion time after adding the abrasive in the latter half is in the range of 0.2 to 1.5% by weight of the dispersion medium wear amount mixed in the paint with respect to the total solid content in the paint. A method for producing a magnetic paint, which is characterized in that it is finished in the inside.