JPS59223938A - Production for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium where the occurrence of dropout is less and the electromagnetic conversion characteristic is excellent, by leading the recording medium, where a magnetic paint is applied and dried, between metallic pressure rolls, which have phenol resin films on surfaces, to subject the recording medium to a specular face processing. CONSTITUTION:A base film 6 where a magnetic layer is formed by application is subjected to the specular face processing while it is run between a roll 1 and a pressure elastic roll 2 and between a roll 3 and the roll 2 in the state where a magnetic layer side 7 of the base film 6 is brought into contact with metallic specular face rolls 1 and 3. A film consisting of a phenol resin is formed on the surface of a metallic roll to obtain the pressure elastic roll 2. Therefore, the surface of the pressure elastic roll itself is finished to a specular face easily. The film has a good surface smoothness and it strong against heat. Consequently, if the roll 2 is used as a pressure roll, the specular face processing of the magnetic layer is performed well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium, and more specifically, to a method for producing a magnetic recording medium, which is capable of producing a magnetic layer that is well mirror-finished using a mirror-finishing roll, has excellent surface smoothness, and has few defects such as dropouts. The present invention relates to a method of manufacturing a magnetic recording medium comprising:

Magnetic recording media are usually made by applying a magnetic paint consisting of magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as a polyester film, and drying the coating.
In order to improve the surface smoothness and filling properties of the magnetic layer, mirror finishing is generally performed. This mirror polishing process is usually done on paper,
Pressure molding of cotton, non-woven fabric, etc. or nylon
A plurality of pressing elastic rolls made by covering an iron core with a polyamide resin outer cylinder such as No. This is done by running the fuel at a predetermined temperature and pressure.

However, the conventional pressure elastic rolls used for this mirror finishing process have low surface hardness, making it difficult to finish the surface of the roll itself to a mirror finish.In particular, the mirror finishing process is performed at a temperature of around 100 degrees Celsius. In some cases, the hardness further decreases and good mirror finishing cannot be performed. In addition, fine powders that have fallen off from the base film or magnetic layer and dust generated from the equipment are likely to get stuck in such a pressure elastic roll with low hardness, and the surface of the magnetic layer may be damaged or
Alternatively, there is a problem that these particles are likely to re-adhere and cause dropout.

This invention was made to eliminate such drawbacks, and is used as an elastic roll for pressure during mirror finishing.
The intended purpose was achieved by using a metal roll with a coating made of phenolic resin on its surface, and by ensuring sufficient hardness and surface smoothness.

The present invention will be described below with reference to the drawings.

FIG. 1 is a schematic side view showing an embodiment of the essential parts of the mirror finishing apparatus of the present invention, in which 1 is a metal mirror roll, 2 is an elastic pressure roll, 3 is a metal mirror roll, These are arranged adjacent to each other alternately. 4 is a feed roll; 5 is a take-up roll; a base film 6 coated with a magnetic layer is fed out from the feed roll 4 with the magnetic layer side 7 in contact with fully bent mirror-finished rolls 1 and 3; Mirror rolls 1 and 3 and pressure elastic roll 2
While traveling in an S-shape between the two, a mirror polishing process is performed.

Here, as shown in FIG. 2, the pressurizing elastic roll 2 is made up of a metal roll 20 with a coating 21 made of phenol-based 11 fat formed on the surface of the metal roll 20. Since the coating made of phenolic resin is also hard, the surface hardness is higher than that of conventional elastic rolls, and it is easy to finish the surface of the elastic pressure roll itself to a mirror finish. Furthermore, the coating made of this phenolic resin has good surface smoothness, and is resistant to heat, with no decrease in hardness or surface smoothness at temperatures around 100°C. Therefore, when this elastic roll 2 is used as a pressure roll, the magnetic layer can be well mirror-finished and a magnetic layer with good surface smoothness can be obtained. In addition, because the hardness is high and the surface has a good mirror finish, it is difficult for fine powders that have fallen off the base film or magnetic layer or dust generated from the equipment to get stuck in. As a result, the magnetic layer may be damaged or re-adhered. Therefore, a magnetic recording medium with excellent electromagnetic conversion characteristics can be obtained with less dropout.

The formation of the coating 21 made of phenolic resin on the surface of the metal roll 20 shown in FIG.
.

First, the surface of the metal roll is chromium plated, mirror-finished, and then pre-treated such as degreasing and cleaning.
The phenolic resin is pretreated with the metal by coating or spraying a solution obtained by dissolving the phenolic resin in a suitable organic solvent, or by dipping the metal roll 20 in this solution. It is applied to the surface of the roll to form a coating film, and then heat treated to harden the coating film,
Formation of this coating film and curing by heat treatment are repeated several times. If the thickness of the coating 21 formed in this way is too thin, polishing in the post-process will be difficult and pinholes will easily occur.On the other hand, if it is too thick, peeling and cracking will easily occur. It is preferable to keep it within this range.

The phenolic resin forming the coating 21 is phenol,
Cresol, xylenol, p-alkylphenol,
A resin obtained by adding and condensing aldehydes such as formalin and furfural to substances containing phenolic -OH such as p-phenylphenol, chlorophenol, bisphenol A1 phenolsulfonic acid, resorcinol, and cashew lacquer. As the resin, phenol/formalin resin, cresol/formalin resin, modified phenol resin, phenol/furfural resin, resorcinol resin, etc. are preferably used.

Solvents for dissolving these phenolic resins include alcohols such as methanol and ethanol, aromatic hydrocarbon solvents such as benzene and toluene, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and ester solvents such as ethyl acetate. Solvents and the like are preferably used.

Incidentally, a plasticizer, filler, etc. may be optionally added to the resin liquid prepared using these resins.

Formation of a magnetic layer to be mirror-finished using such an elastic pressure roll can be carried out according to a conventional method. For example, magnetic powder is mixed and dispersed with a binder resin, an organic solvent, etc. to form a magnetic paint. This magnetic paint may be applied onto a substrate such as a polyester film, and dried.

The magnetic powders used here include r-Fe203 powder, Fe3O4 powder, CO-containing r-Fe203 powder, Co
Contains Fe3O4 powder, Fe powder, CO powder, Fe −
Various conventionally known magnetic powders such as Ni powder are widely included, and binder resins include conventionally widely used binder resins such as vinyl chloride-vinyl acetate copolymers, polyvinyl butyral resins, polyurethane resins, cellulose resins, and isocyanate compounds. Binder resins are widely used.

Further, as the organic solvent, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, ethyl acetate, tetrahydrofuran, dimethyl formamide, etc. are used alone or in combination of two or more.

Next, embodiments of the invention will be described.

Example I Co deposition 7 Fe2O3 powder 100 parts by weight Nitrocellulose HIGI (Asahi 10 Nitrocellulose manufactured by Kasei Co., Ltd.) Nistan 5702 (Gusodori 9 Polyurethane resin manufactured by Chi Chemical Co., Ltd.) Coronate Japan Polyurethane 1 Polyisocyanate compound manufactured by Kogyo Co., Ltd. ) Carbon black 5 Stearin rI11 Methyl ethyl ketone 100 Toluene
100 This composition was mixed and dispersed in a ball mill for 78 hours to prepare a magnetic paint. This magnetic paint was applied onto a 15 μm thick polyester film to a dry thickness of 5 μm and dried.

On the other hand, a mixture consisting of 150 parts by weight of phenol, 160 parts by weight of formalin (30%), 160 parts of ammonia (0.9%) and 7.5 parts by weight was gradually heated to boiling, dehydrated under reduced pressure, and cooled under conditions of 75-b. Next, this phenol-formalin resin was dissolved in 300 parts by weight of methyl alcohol, and the solution obtained by dissolution was chromium-plated on the surface, mirror-finished, degreased, and washed. It was applied onto the surface of a metal roll that had been pretreated, and the coating film was cured by heat treatment at a temperature of 150°C. This coating and heat treatment are repeated five times to form a phenol-formalin resin film with a thickness of 0.1 mm on the surface of the metal roll, and the phenol-formalin resin is coated on the surface of the metal roll 20 as shown in FIG. An elastic pressure roll 2 on which a coating 21 was formed was obtained. The elastic roll 2 thus obtained is installed between the metal mirror rolls 1 and 3 as shown in FIG. 1 to form a three-stage calender device, and each roll 1.2 of the three-stage calender device The polyester film 6 on which the above-mentioned magnetic layer has been applied and formed between 3 and wound around the feed roll 4 is run in an S-shape so that the magnetic layer side 7 is in contact with the metal mirror rolls 1 and 3, and the mirror roll is rolled. 10 and 3, the temperature was 80°C and the pressure was 300 kg/cm.

The mirror polishing treatment was performed at a web speed of 50 m/min. After that, they were cut to the specified width and made into video tapes. ' Example 2 An elastic roll was produced in the same manner as in Example 1, except that the same amount of cresol was used instead of phenol in the composition of the resin solution applied to the surface of the metal roll 20, and a videotape roll was prepared. I made it.

Example 3 In the composition of the resin solution applied to the surface of the metal roll 20 in Example 1, the same amount of p-tert-butylphenol was used instead of phenol, and the same amount of hydrochloric acid (1%) was used instead of ammonia. An elastic roll was prepared in the same manner as in Example 1, except that 20 parts by weight of drying oil was newly added, and a videotape was made.

Example 2 An elastic roll was produced in the same manner as in Example 1, except that the same amount of cashew lacquer was used instead of phenol in the composition of the resin solution applied to the surface of the metal roll 20 in Example 1, I made a videotape.

Comparative Example 1 A videotape was made in the same manner as in Example 1, except that an elastic roll covered with a nylon 6 outer cylinder was used instead of the elastic roll with a phenol/formalin resin coating formed on the surface. .

Surface roughness, gloss, video S/N ratio, color S/N ratio, and dropout were measured for the video tapes obtained in each Example and Comparative Example. The surface roughness was measured using a surfcom made by Tokyo Seimitsu Co., Ltd., and the centerline average (C1
14, A). In addition, the glossiness was measured using a gloss meter manufactured by Murakami Color Co., Ltd., and the dropout was measured by recording and playing a predetermined signal on the obtained videotape and measuring 20 dB of the playback output.
The number of pieces that continued to fall for 5 μsec or more was measured for 30 minutes, and the average was expressed per back.

The table below shows the results.

As is clear from the table above, all the videotapes obtained in Examples 1 to 4 had better surface roughness and gloss than those obtained in Comparative Example 1. , high video S/N ratio, high color S/N ratio, and low dropouts. Therefore, according to the manufacturing method of the present invention, the mirror finishing process is good, the surface smoothness of the magnetic layer is excellent, and the dropouts are low. It can be seen that a magnetic recording medium with excellent electromagnetic conversion characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing a main part of an embodiment of the mirror finishing apparatus of the present invention, and FIG. 2 is an enlarged side view in partial section of an elastic pressure roll of the present invention. 1.3...Metal mirror roll, 2...Elastic roll for pressure, 20...Metal roll, 21...Coating made of phenolic resin, 6...Base film (substrate) Fig. 1 Figure 2

Claims (1)

[Claims] 1. A mirror finishing roll that uses at least one metal roll with a phenolic resin coating formed on its surface as a pressure roll when applying a magnetic paint on a substrate, drying it, and then subjecting it to a mirror finish. A method for producing a magnetic recording medium characterized by introducing the medium between the two and subjecting it to a mirror finish.