JPH0489619A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium having excellent traveling durability by applying a magnetic coating material which is prepd. by mixing and dispersing magnetic powder together with a binder resin, solvent and other necessary components on a base body and drying the coating, then resting the base body under specific environment. CONSTITUTION:The magnetic coating material is prepd. by mixing and dispersing the magnetic powder together with the binder resin, the solvent and other necessary components. After this magnetic coating material is applied on the base body and is dried, the base body is rested under the environment of 80<=T.logt<=200 (where T is the temp. in a 40 deg.C<=T<=100 deg.C range; t is time). Since the base body is heated for a prescribed period of time at temp. within a prescribed range in this case, the molecules of the binder resin are liable to move and generates crosslinking bonds among the binder resins already adsorbed on the magnetic powder or the binder resins, etc., which are not yet adsorbed. The dispersibility of the magnetic powder is improved in this way and the mechanical strength of the magnetic layer is sufficiently improved. The strength and toughness as well as wear resistance of the magnetic layer are additionally improved and the traveling durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly, to a method for manufacturing a magnetic recording medium with excellent running durability.

[Conventional technology]

Magnetic recording media are usually produced by mixing and dispersing magnetic powder with a binder resin, an organic solvent, and other necessary ingredients to prepare a magnetic paint, and applying this magnetic paint onto a substrate such as a polyester film and drying it. Therefore, it is required that the magnetic powder has good dispersibility, excellent electrical properties, and excellent durability.

Therefore, as the binder resin to be used, a binder resin that has excellent dispersibility of magnetic powder, is strong, and has excellent mechanical properties is selected and used.

[Problem to be solved by the invention]

However, in recent years, demands for high recording density and high reliability during recording and reproduction have increased for magnetic recording media, and in particular, magnetic recording media with excellent wear resistance and toughness are required.
As has been the case in the past, simply selecting and using a binder resin that is strong and has excellent mechanical properties does not sufficiently improve running durability.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation, and consists of preparing a magnetic paint by mixing and dispersing magnetic powder with a binder resin, a solvent, and other necessary components.
After coating this magnetic paint on the substrate and drying it, 80≦T・1ogt≦200 (where T is a temperature within the range of 40℃≦T≦100℃, L
is time. ), the mechanical strength of the magnetic layer is sufficiently improved, the toughness and abrasion resistance are further improved, and the running durability is sufficiently improved.

According to this invention, after applying the magnetic paint onto the substrate and drying it,
is time. ) and heated at a predetermined temperature range for a predetermined period of time, the molecules of the binder resin become more mobile, causing the binder resin that has already been adsorbed to the magnetic powder and the bonds that have not yet been adsorbed. Because cross-linking occurs between the agent resins, etc., the dispersibility of the magnetic powder is improved, and at the same time, the mechanical strength of the magnetic layer is sufficiently improved, and its toughness and abrasion resistance are further improved, resulting in long running durability. sexuality is further improved.

In this way, when magnetic paint is applied onto a substrate, dried, and left for heat treatment, the desired effect cannot be obtained if the environmental temperature is lower than 40°C, and the effect becomes more pronounced as the temperature rises. However, if the temperature exceeds 100°C, the glass transition temperature of the polyethylene terephthalate film commonly used as the substrate will be exceeded, deformation of the magnetic recording medium will occur, and blocking will occur between the magnetic layer and the substrate.
It is preferable to carry out the heat treatment at an ambient temperature of 50 to 80 degrees Celsius. Such heat treatment at an ambient temperature is determined within the above range, taking into account the characteristics required of the resulting magnetic recording medium, the type of substrate used, the composition of the magnetic layer, etc.

In addition, if the treatment time of such heat treatment is shorter than 1 hour, the desired effect will not be obtained, and if it is longer than 200 hours, it will be disadvantageous in terms of space energy consumption and cause an increase in cost. It is preferable to carry out the heat treatment within the range of 200 hours, and more preferably within the range of 20 to 150 hours.

The magnetic layer to be subjected to such heat treatment can be formed according to a conventional method, and a magnetic paint is prepared by mixing and dispersing magnetic powder, binder resin, organic solvent, and other additives. The paint may be applied onto a substrate such as a polyethylene terephthalate film by any means such as spraying or rolling and allowed to dry. At this time, a magnetic layer may be provided on the surface of the substrate and a hack layer may be provided on the opposite surface, or magnetic layers may be provided on both surfaces of the substrate.

Here, examples of the magnetic powder used in the magnetic layer include 7-Fe2O3 powder, Fe50. Powder, co containing 7-
In addition to Fe2O3 powder, Co-containing Fe3O4 powder, Cry□ powder, Fe powder, CO powder, Co ferrite powder, B
Various conventionally known magnetic powders such as metal powders such as a-ferrite powders are widely included.

In addition, the binder resin includes vinyl chloride-vinyl acetate copolymer, cellulose resin, polyvinyl butyral resin, urethane resin, polyester resin, epoxy resin Hu, OH group, C0OH group in the molecule, Any of those commonly used in magnetic recording media can be used, such as acrylic acid resins and isocyanate compounds having functional groups reactive with epoxy groups such as NH groups and SH groups.

Furthermore, as organic solvents, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate,
Solvents suitable for dissolving the binder resin to be used, such as benzene, toluene, xylene, dimethyl sulfoxide, tetrahydrofuran, and dioxane, may be used alone or in a mixture of two or more without particular limitation.

In addition, as the substrate, any of those commonly used as a substrate such as various synthetic resin films such as polyethylene terefucrete, polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil can be suitably used. be done.

In addition, magnetic paint contains myristic acid, stearic acid,
Lubricants such as n-butyl stearate, octyl stearate, isoamyl stearate, silicone oil, paraffin, abrasives such as alumina, Crz03, red iron, etc.
Dispersants such as carbon black or lecithin, etc.
Anything that is generally added to magnetic paints can be added as needed.

〔Example〕

Next, embodiments of the invention will be described.

Example I Co-containing TFezO3C preservation M! L100 weight part force 65
0 Oersted, BET Specific surface area 40 I/g) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (manufactured by U, C, C, USA, VAGH) Polyurethane resin 1 o Carbon black 4 n-butyl stearate
1 Palmitic acid 1
Methyl ethyl ketone 120 Toluene 120 The above compositions were mixed and dispersed in a sand mill for 20 hours to prepare a magnetic paint. This magnetic paint was applied onto a polyethylene terephthalate film with a thickness of 15 μm using opposing magnetic forces so that the thickness after drying would be 5 μm, dried, and calendered to prepare a magnetic recording medium original.

Next, the magnetic recording medium material obtained in this way was
After being left for 40 hours and heat treated in an environment of 80°C, 1
A magnetic tape was produced by slitting the tape into a width of 2 inches.

Example 2 In Example 1, the heat treatment conditions for the original magnetic recording medium were changed from 40 hours at 80°C to 1 hour at 60°C.
A magnetic tape was produced in the same manner as in Example 1 except that the time was changed to 20 hours.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1, except that the heat treatment of the original magnetic recording medium was omitted.

Comparative Example 2 In Example 1, the heat treatment conditions for the original magnetic recording medium were changed from 40 hours in an environment of 80°C to 5 hours in an environment of 25°C.
A magnetic tape was produced in the same manner as in Example 1 except that the time was changed.

Regarding the magnetic tapes obtained in each example and comparative example,
Dropout and still life were tested and measured using the following methods.

<Dropout> Record the color bar signal on the obtained magnetic tape and
The vehicle was run repeatedly, and the number of dropouts after each run was measured. The number of dropouts was expressed as the number of dropouts in which the playback output level decreased by 16 dB or more in a period of 1.5×10 −6 seconds or more using a dropout counter in 15 minutes.

<Still Life> A color par signal was recorded on the obtained magnetic tape and reproduced in still mode, and the time until the reproduced signal level decreased by 6 dB was measured.

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the magnetic tapes obtained by the present invention (Examples 1 and 2) have a lower In both cases, the number of dropouts is small (and the still life is long), which indicates that the magnetic recording medium obtained by the manufacturing method of the present invention has further improved running durability.

Claims (1)

[Claims] 1. A magnetic paint is prepared by mixing and dispersing magnetic powder with a binder resin, a solvent, and other necessary components, and this magnetic paint is applied onto a substrate, and after drying, 80≦T・logt ≦
200 (T is a temperature within the range of 40℃≦T≦100℃, t
is time. ) A method for manufacturing a magnetic recording medium characterized by leaving it in an environment of