JPH0444638A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve surface smoothness and electrical characteristics and to simultaneously improve durability by mixing and dispersing magnetic powder together with a binder resin and solvent and preparing a coating material while heating. CONSTITUTION:Since the magnetic coating material is prepd. while heating at >=50 deg.C, the viscosity of the magnetic coating material is decreased by a temp. rise and the molecules of the binder resin are easily moved even if the binder resin having a large mol. wt. and an intrinsically high viscosity is used. The magnetic powder is thus well dispersed. The dispersibility of the magnetic powder is improved even if the binder resin having the large mol. wt., the intrinsically high viscosity and the excellent mechanical characteristics is used. If such magnetic coating material is applied on a base body and is dried, the magnetic layer having the excellent mechanical characteristic simultaneously with the dispersibility of the above-mentioned powder is formed and the magnetic recording medium having the excellent surface smoothness and electrical characteristics and the excellent durability is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a magnetic recording medium, and more specifically, the present invention relates to a method for manufacturing a magnetic recording medium, and more specifically, a magnetic recording medium having a magnetic layer having good dispersibility of magnetic powder and excellent electrical properties and durability. The present invention relates to a method of manufacturing a magnetic recording medium.

[Conventional technology]

Magnetic recording media are usually produced by dissolving a binder resin in a solvent, mixing and dispersing magnetic powder and other necessary components in this solution7 to make a magnetic paint, and applying this magnetic paint to a substrate such as a polyester film. It is made by coating and drying the magnetic powder, and requires good dispersibility of magnetic powder, excellent electrical properties, and excellent durability.

Therefore, as the binder resin used, a binder resin that has excellent dispersibility of magnetic powder, good mechanical strength, and tough properties is selected and used.

[Problem to be solved by the invention]

However, in general, when binder resins with the same molecular structure are used, using one with a smaller molecular weight provides a magnetic layer with lower solution viscosity, higher dispersion ability, and superior surface smoothness and electrical properties. However, if a material with a large molecular weight is used, the solution viscosity is high, and while it has good mechanical properties and excellent durability, it has poor dispersion of magnetic powder, resulting in poor surface smoothness and electrical properties. A magnetic layer cannot be obtained. However, with conventional manufacturing methods, it has been difficult to improve surface smoothness and electrical properties as well as durability.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation, and when magnetic powder is mixed and dispersed with a binder resin, a solvent, and other necessary components to make magnetic paint from steel, it is necessary to heat the paint to 50°C or higher. By making steel while heating,
The dispersibility of the magnetic powder is improved, the surface smoothness and electrical properties are sufficiently improved, and at the same time, the mechanical properties are improved and the durability is sufficiently improved.

According to this invention, since the magnetic paint is made of steel while being heated to 50°C or higher, even if a binder resin with a large molecular weight and originally high viscosity is used, the viscosity of the magnetic paint decreases due to the temperature increase. The molecules of the binder resin become mobile and the magnetic powder is well dispersed. Therefore, it is possible to improve the dispersibility of magnetic powder by using a binder resin that has a large molecular weight, inherently high viscosity, and excellent mechanical properties. If you apply it and dry it,
A magnetic layer with excellent dispersibility and mechanical properties of the magnetic powder is formed, and a magnetic recording medium with excellent surface smoothness and electrical properties as well as excellent durability is obtained.

In this way, when mixing and dispersing magnetic powder with binder resin, solvent, and other necessary ingredients while heating to make magnetic paint into steel, the desired effect cannot be obtained if the temperature is lower than 50°C. Therefore, the temperature is preferably 50°C or higher, and preferably as high as possible as long as it is below the boiling point of the solvent used, but it is preferable to make the steel while heating it to a temperature in the range of 50°C to 90″C.

Here, the binder resin used is vinyl chloride-
Vinyl acetate copolymer, polyvinyl butyral resin,
Any conventionally commonly used resins can be used, such as cellulose resins, polyurethane resins, polyester resins, and isocyanate compounds.

In addition, as a solvent, any solvent commonly used in magnetic paints can be used, such as cyclohexanone,
Methyl ethyl ketone, methyl/rbutyl ketone, ethyl acetate, benzene, toluene, xylene, dimethylformamide, tetrahydrofuran, dioxane, etc. are used alone or in combination of two or more.

Furthermore, as magnetic powder, 7-Fez0z powder, Fe
,,04 powder, 7-Fe, intermediate oxide powder of 03 powder and Feff04 powder, CO-containing -Fe203 powder, Co
Containing Fe+04 powder, Cry.

Any magnetic powder commonly used in magnetic recording media is suitably used, such as powder, barium ferrite powder, strontium ferrite powder, and metal powders such as Fe powder, CO powder, and Fe-Ni powder.

In addition, the dispersing machine used to mix and disperse the magnetic powder with the binder resin, solvent, and other necessary ingredients while heating is the one that is generally used when making magnetic paints from steel. For example, a ball mill, a sand grinder mill, a disper, etc. are used.

In addition, in the magnetic paint made of steel in this way, substances that are generally added to magnetic paints, such as dispersants, abrasives, lubricants, and antistatic agents, are added as necessary. Ru.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Co-containing 7p'eZo3Mi powder 100 parts by weight (BET specific surface area 17 bo/g, coercive force 650 oersted) Polyurethane resin (number average molecule 32, weight 40,000
, diphenylmethane diisocyanate 11 mol%, polycaprolactone 62 mol%, isophthalic acid io mol%, 5-sulfoisophthalic acid sodium 4 mol%, neopentyl glycol 11 mol%, cyclohexane dimetatool 4 mol%) Trifunctional isocyanate crosslinking Agent 8 Carbon black 10 Alumina
10 oleyl oleate 10
〃:Nku ■..., Kirino], 200
=F.ru,no,n 20OA
・・・Put the above composition into temperature control・SoI=−Utsu , heat medium temperature in 1 liter J'8. Adjustment i<1+,''.

and ζ, -, 80 ``C et al.'' Heating and holding 1. Mix and disperse 1-1C boron-based paint from scratch.
J7 magnetic paint with a thickness of 1゛5μ+1.1, “
Input 2・Both sides of Rufilm 1, 1□': Paint 4i1 Dry 1
,Power! 2 ring treatment month 1,? , Itsu 4- is 1. ,
2/lxI: Forming a magnetic layer of t11. Six. [Next, I'm going straight]: 10, 711 disk-shaped punched magnetic, I'''Isuku flea''1 saw.

Example 2 The steel plate with magnetic coating 4 in Example 1? stomach? 2,
Heating temperature of magnetic layer H: 80"C to 60℃k'
-Since it has been changed! In A, a magnetic disk was prepared in the same manner as in Example 1.

Example 3 Composition of magnetic paint in Example 1 Nyl acetate di-le combination! (1 garden combination 1'9' 43O) ・i
, <5 Hayabusa, lid angle ノ;・J,), 4I・
□1: Create a C magnetic disk in the same manner as in Example 1.
! 1. ,,,Also.

゛ ス 施 施 例 実 実 （（（例 （（（（（（、 （（（（（（〕〕〕〕〕 （〕〕〕〕〕〕〕〕〕〕〕〕〕〕〕〕〕 （〕 （〕〕〕〕〕〕 （〕 （（料 料 料 料 料 料 （料 料 料 料 料 料 料 料 料Warm,
) The lever was set to 130'' at 60°C ps: Same as Example 34. except that Iζi was changed (rJ,': L,''-
(1, Magnetism...°, ISK 75, made by ISK 75,...
Pa 6゜Comparative Example J Example IC1 Month 1 1 Magnetic 1:・Coating 21 =);
O'c;,) 30 ℃i,,'l Change: Sleepy, except 1.11, Example 7! , Similarly, 1, I made a strainer, and 6...

Comparative Example 2゜Composition of the magnetic paint in Comparative Example 1 (,)? Riki Sairii ζ1,
A 6.5-magnetic disk was prepared in the same manner as in the comparative example, except that the same amount of polypartan with a few average molecular weights of 400 O0 and polyurethane resin with a 7-number average molecular weight of 15000 was used. It's 2.

Comparative Example 3 Example 3 1: Steel coating made of magnetic paint! 4 The procedure was the same as in Example 3, except that the heating and holding temperature of the adhesive paint was changed to R O "C 30"[:r,'? :1 Magnetic disk made in Italy 1. f..., 1 Comparative Example 4 Comparative Example 3 i. The composition of the magnetic paint is based on hydrogen chloride with a degree of polymerization of 430, .--vinyl acetate, A magnetic disk was prepared in the same manner as in Comparative Example 3, except that the degree of polymerization was 30OL:r) and the dinylonyl chloride-1o6-nyl acetate copolymer was used on the same day.

The ζ, S/N ratio, and durability of the magnetic 2'' disks obtained in each example and comparative example were measured at 17k. ;SN ratio is 74
5. , 2; j・indef t2ppi) ゛Isk l passi-so was measured using,, Comparative example] todB and 1,,
Relative (1) when it is 5. Also, durability is shown using a similar disk drive, fi O' (:, 1
Observe the drop in the playback output level while sliding the magnetic disk against the magnetic head in an environment of 0%RH; Table 1 shows the results of Table 8 and Table 1 shows the results of Table 1. , magnetic) "'isk (Example 1 to.

4) has a higher S/N ratio than the magnetic disks obtained in Comparative Examples 1 to 74, and has good durability. Therefore, according to the manufacturing method of the present invention, It can be seen that a magnetic recording medium with good dispersibility of magnetic powder, excellent electrical properties, and excellent durability can be obtained.

Patent applicant: Hitachi Maxell, Ltd.

Claims (1)

[Claims] 1. Magnetic powder is mixed and dispersed with binder resin, solvent, and other necessary ingredients while heating above 50°C to make a magnetic paint, and this magnetic paint is applied onto a substrate and dried to form a magnetic layer. A method for producing a magnetic recording medium characterized by forming