JPH033116A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate projections of several mum height which cause magnetic defects from a magnetic coating film and to improve the yield of the medium by controlling the temp. of a magnetic coating material in the range 10 - 20 deg.C in the process of filtering the magnetic coating material. CONSTITUTION:The magnetic coating material is reserved in a pool tank 1 under stirring with a stirrer 2. The magnetic coating material in the tank 1 is transferred to a jacketed filter housing 5 by a feeder pump 3. The coating material is filtered in the filter housing 5 while maintained at 10 - 20 deg.C by a coolant running in the jacket. In this process, gel-state material not dissolved or decomposed in the coating material has less fluidity or flexibility at the specified temp. range, and is trapped by the filter. The coating material filtered is then transferred through a feeding pipe 11 into a coating machine to be applied on a nonmagnetic supporting body. A jacket 13 is preferably provided on the pipe 11 to maintain the temp. of the coating material near room temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes and magnetic disks.

[Conventional technology]

Generally, magnetic recording media are produced by preparing a magnetic paint by thoroughly mixing and dispersing a paint formulation containing magnetic powder, a binder, and a dispersion medium such as an organic solvent or water using a ball mill or sand mill. It is produced by coating on a non-magnetic support such as a polyester film.

The electromagnetic conversion characteristics of magnetic recording media produced in this way are affected by foreign matter that may be contained in the magnetic paint, so in order to remove these foreign matter and obtain stable characteristics,
Usually, prior to coating on a non-magnetic support, the magnetic coating material is subjected to a filtration process in which it is filtered through a filter with an absolute filtration accuracy of about 1 to 30 .mu.m.

[Problem to be solved by the invention] However, despite the use of magnetic paint that has gone through such a filtration process, there are still particles of several μm in the applied magnetic paint film.
These protrusions have been recognized, and in today's society where recording with shorter wavelengths is becoming more common, even protrusions of a few micrometers are causing magnetic defects and lower yields in magnetic recording media.

In view of the above-mentioned circumstances, it is an object of the present invention to eliminate protrusions several μm in size that cause magnetic defects, and to provide a high-yield magnetic recording medium.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventors found that, in the conventional method, undecomposed and insoluble substances in the magnetic paint, which are the cause of protrusions in the magnetic paint, are removed from the gel. I learned that these substances can easily pass through the filter's mesh structure because they are highly fluid and flexible.

In addition, if the magnetic paint itself is subjected to a filter with higher filtration accuracy to remove the undecomposed and insoluble materials, the solid content and solvent will separate from the magnetic paint itself.
It has also been found that it is extremely difficult to remove undecomposed and insoluble substances using only the filtration accuracy of the filter.

Therefore, the inventors conducted further studies to overcome the above-mentioned problems, and as a result, upon filtration with a filter,
When the temperature of the magnetic paint was cooled to below room temperature and subjected to the above filtration, the fluidity and flexibility of the gel-like undecomposed substances and insoluble substances contained in the paint decreased, and these foreign substances were filtered out. After this filtration, a magnetic coating film coated on a non-magnetic support has a particle size of several μm.
It has been found that the above-mentioned protrusions are hardly observed, making it possible to produce a high-yield magnetic recording medium.

This invention was completed based on the above knowledge, and its gist is that after filtering a magnetic paint containing magnetic powder and a binder, it is coated on a non-magnetic support. In the method for producing a magnetic recording medium, when filtration is performed using the above-mentioned filter, one coat of magnetic paint is added.
A method of manufacturing a magnetic recording medium characterized by adjusting the temperature within a range of 0 to 20°C.

In the above method of this invention, the temperature of the magnetic paint is 20°C.
If the temperature exceeds 10°C, the effect of capturing undecomposed and insoluble substances will not be sufficiently obtained. On the other hand, if the temperature falls below 10°C, the viscosity of the paint will increase as the paint temperature decreases, and the pressure on the primary side of the filter will increase, causing the filter to Since the permissible pressure of

In order to adjust the temperature of the magnetic paint to a range of 10 to 20°C, it is best to use a filter housing provided with a jacket, and water is suitable as the cooling medium. Further, the magnetic paint after passing through the filter is gradually returned to room temperature during the piping up to the paint discharge section, but it is better to provide a heating section in the piping as necessary to bring it closer to room temperature.

[For production]

In this invention, as mentioned above, since the magnetic paint is filtered through a filter at a temperature range of 10 to 20°C,
The fluidity and flexibility of foreign matter consisting of undecomposed and insoluble matter in the paint decreases, and as a result, these foreign matter are easily captured by filters, causing magnetic defects in the magnetic coating film. The protrusion of the size disappears.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a piping diagram showing an example of the method for producing a magnetic recording medium of the present invention, from a pool tank that temporarily stores magnetic paint mixed and dispersed by a ball mill, sand mill, etc. to a unidirectional supply to a coating machine. This is what is shown.

In the pool tank 1, while being stirred by the stirrer 2,
Magnetic paint is stored. This IF paint contains magnetic powder, a binder, a dispersion medium such as an organic solvent and water, and various known additives such as lubricants, antistatic agents, surfactants, abrasives, and fillers as necessary. The formulation made by
It is uniformly mixed and dispersed by the above-mentioned means.

As the magnetic powder, γ-Fez Oz, Co-containing -
In addition to oxide-based magnetic powders such as Fe203 and barium ferrite, conventionally known magnetic powders such as metal-based magnetic powders made of metals or alloys such as Fe s Co and Ni are used, and as a binder, vinyl chloride is used. - Conventionally known materials such as vinyl acetate copolymers, polyurethane resins, polyester resins, cellulose resins, and polyisocyanate compounds can be similarly used.

The magnetic paint inside the pool tank 1 is attached to the joint 9 and the valve 1.
0 to the filtration section by the liquid feeding pump 3 connected to the liquid feeding pump motor 4.

This filtration section is equipped with a jacketed filter 1 housing 5, and cooling water flows in the jacket so that the temperature of the magnetic paint being filtered is 10 to 20°C. The temperature of this cooling water is controlled by a temperature controller 8, a temperature regulating water pump motor 7, and a temperature regulating water pump 6 while constantly circulating within the jacket.

Since magnetic paint is cooled to 10-20℃ during filtration,
After mixing and dispersing, gel-like undecomposed substances and insoluble substances in the magnetic paint lose their fluidity and flexibility and are captured by the filter. The magnetic paint that has passed through the filtration section in this way is transferred to the valve 10.
is supplied to the coating machine (not shown) through the supply pipe 1), but if necessary, a jacket pipe 1 is inserted in the middle of the piping.
3 to bring the paint after filtration closer to room temperature.

In this case, water at a temperature equal to room temperature may be circulated within the jacket using the same system as in the case of the filtration section, that is, the temperature controller 8, the temperature-controlled water pump motor 7, and the temperature-controlled water pump 6.

FIG. 2 shows that, in the method shown in FIG.
5 is provided to circulate a portion of the magnetic paint after filtration to the pool tank 1 via the circulation pipe 12.The other configurations are the same as in Figure 1, so the same numbers are attached to them. The explanation will be omitted. The circulating supply system shown in FIG. 2 is employed as an advantageous method when the magnetic paint is supplied for a long time.

The magnetic paint finally supplied to the coating machine through the supply pipe 1) is coated on a non-magnetic support such as a polyester film by a conventional method to form a magnetic coating film of a predetermined thickness, and then A magnetic recording medium such as a magnetic tape or a magnetic disk is produced by performing necessary post-processes such as calendering and cutting.

〔Effect of the invention〕

As described above, according to the present invention, foreign substances such as gel-like undecomposed substances and undissolved substances in magnetic paint are almost completely captured by filtration, and the magnetic paint that causes magnetic defects can be removed. Since the generation of protrusions on the order of several μm in the film is suppressed, a high-yield magnetic recording medium can be provided.

[Brief explanation of drawings]

FIG. 1 is a piping diagram showing an example of the method for manufacturing a magnetic recording medium of the present invention, and FIG. 2 is a piping diagram showing another example of the manufacturing method described above. 5...Filter housing with jacket Figure 1

Claims (2)

[Claims] (1) In a method for manufacturing a magnetic recording medium in which a magnetic paint containing magnetic powder and a binder is filtered through a filter and then coated on a non-magnetic support, the magnetic paint is coated at a temperature of 10 to 20°C during filtration through the above filter. 1. A method for manufacturing a magnetic recording medium, comprising adjusting the temperature within a range of . (2) The method for manufacturing a magnetic recording medium according to (1), wherein filtration with a filter is performed using a jacketed filter housing.