JPS60136028A - Composition for magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electrical characteristics, above all, resolving power as well as heat resistance and reliability of a coated film by dispersing ferromagnetic powder in a high polymer binder consisting of at least one kind of resin selected from the group consisting of a phenol aralkyl resin and polyvinyl phenol resin as well as an epoxy resin and polyvinyl butyral resin and forming a titled compsn. CONSTITUTION:A high polymer binder is so constituted that at least one kind of resin selected from the group consisting of a phenol aralkyl resin and polyvinyl phenol resin is contained at 25-62wt%, an epoxy resin at 25-62wt% and a polyvinyl butyral resin at 8-22wt%. A paint is required to have good wettability in order to coat a thin film and a linear polymer is preferable as the binder to meet such requirement. The polyvinyl phenol resin B having a linear structure and having the mol.wt. much larger than the mol.wt. of the conventional phenol resin and the phenol aralkyl resin A are used together with the epoxy resin and polyvinyl butyral resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording medium, particularly a high-density disk having excellent electrical properties, resolution, and reliability.

[Background of the invention]

The patent for magnetic recording medium composition is JP-A-57-183.
625, JP 54-66803, JP 47-146
49, Japanese Patent Publication No. 55-816, and Japanese Patent Application No. 45-125963, etc., and are used in various magnetic disks. Most of these patents use a polymeric binder in which vinyl resin, acrylic resin, cellulose, etc. are added to a bisphenol type epoxy resin and a phenol intermediate (alkylphenol, allylphenol, etc.). When magnetic materials using these polymeric binders are diluted with a large amount of solvent, agglomeration of the magnetic powder occurs. protrusions due to agglomeration;
Streaks and the like occurred in the radial direction of the disk, and a satisfactory thin film of 0.5 μm or less could not be obtained.

[Purpose of the invention]

The object of the present invention is to provide a high-density disk with excellent electrical properties, especially resolution, excellent heat resistance, and coating film reliability, as well as to provide a magnetic coating material that has excellent leakage properties and can be applied in a thin film.

[Summary of the Invention] The binder system consisting of epoxy resin/phenol resin/polyvinyl butyral and the phenol resin used in the indash system of other companies mentioned above are phenol intermediates such as alkylphenol and allylphenol, and have a molecular weight of 100 to 300. It was customary to use something of a certain degree.

In order to apply a thin film, it is first required that the paint has good wettability.
We thought that Linear Polymer would be preferable. Phenolic resins in conventional binder systems have low molecular weights and are generally not linear. The present invention uses polyvinylphenol resin and phenol aralkyl resin, which have a linear structure and a much larger molecular weight than conventional phenol resins, in place of conventional phenolic resins, together with epoxy resins and polyvinyl butyral resins. It has been found that it has excellent wettability and can be applied in a thin film (0.5 μm or less). It has also been found that a heat-resistant coating film can be obtained by adding an imidazole compound to this indica compound.

The structures of phenol aralkyl resin (Al) and polyvinylphenol (Bl) are as follows.

fB+ [Embodiments of the invention] Examples of the present invention are shown below.

Example 1 700 parts by weight of ferromagnetic powder, 60 parts by weight of PVB (polyvinyl butyral) resin powder, and particle size of 0.7 μm
A 60-grade portion of single crystal alumina was put into a kneader and kneader, and mixed for about 15 minutes. Next, selonulp acetate 8
20 parts by weight was gradually added and mixed in a kneader for about 8 hours. 780 parts by weight of the obtained mixture was placed in a ball mill pot, 390 parts by weight of cellosolve acetate was added, and ball mill mixing was carried out for 3 days to disperse the magnetic powder.

Next, polyvinyl phenol resin (manufactured by Kusaki Oil Co., Ltd., trade name Resin M1106 parts by weight and an average molecular weight of tvIJ of about 100
O bisphenol Am epoxy resin 106 parts by weight and 2
- A solution prepared by dissolving 2 parts by weight of heptazinolimidazole in butyl celeryl bu 1260 heavy duty was added to prepare a magnetic paint. The viscosity of the magnetic paint obtained was 1 8 Q cps when measured using a BIi rotational viscometer at 6 Q rpm.

Next, the above-mentioned paint was applied to the aluminum substrate whose surface had been roughened and cleaned, and then the magnetic powder in the paint film was oriented by a known method. Spin coating was used as the coating method. Apply this paint on a 14-inch At disk at 20 rpm.
It was dropped over 39 seconds, and the rotation speed was increased to 150 rpm for 20 seconds.

The coating thickness of the obtained magnetic disk was 0.0 mm at R105 m/m.
25/! jm, R, l 7 Qm/m is 0.4 (1
m, Paint film baking is 0.030 μml after coating surface
A: 9. No visible protrusions, streaks, etc. were observed on the coating surface.

Example 2 80 parts by weight of butyl cellosolve was added to 600 parts by weight of the magnetic paint obtained in Example 1, diluted, and the viscosity was 125.
A Cp8 magnetic paint was obtained. This paint was dripped onto a 14-inch At disc at 20 rpm for 15 seconds, and then heated at 1500 rpm.
Coating was performed for 20 seconds. The coating thickness of the obtained magnetic disk was R105m/m, 2oμm, and R170m/m.
m is 0.30 μm 1 coating surface roughness is 0.032 μm'1%
No visible protrusions, streaks, etc. were observed on the p1 coating surface in a.

Example 3 To 600 parts by weight of the magnetic coating material obtained in Example 1, 220 parts by weight of Butelselon Lup was added and diluted to give a viscosity of 75.
A CPS magnetic paint was obtained. Apply this paint to 14 inch At
Dropped onto a disc at 20 rpm for 15 seconds, and then at 1500 rpm.
Coating was performed for 20 seconds. The coating thickness of the obtained magnetic disk was 0.10μm at R105m/m x R170m
/m is 0.18μm, coating film thickness is 0.034μm
l(, a'), and there were no visually visible protrusions, streaks, etc. on the heavy membrane surface.

Example 4 A magnetic disk was obtained by carrying out the same treatment as in Example 1.2 without adding 2-hebutadecylimidazole. The coating thickness of the obtained magnetic disk was 0.19 at R105m/m.
μmXR170m/m 0.28μm1 Coated surface roughness is 0
．． There was no visible protrusion, streak, etc. on the coating surface.

Example 5 700 parts by weight of ferromagnetic powder, 60 parts by weight of PVB (polyvinyl butyral) resin powder, and 60 parts by weight of single-crystal alumina with a particle size of 0.7 μm were placed in a kneader mixer and mixed for about 15 minutes. . Next, 1 acetic acid Cellosolve 820
Parts by weight were gradually added, and kneader cross-mixing was performed for about 8 hours. 780 parts by weight of the obtained mixed wire was placed in a ball mill pot, and 390 parts by weight of cellosolve acetate was added.
Ball mill kneading was performed for several days to disperse the magnetic powder. Next, 106 parts by weight of phenol aralkyl resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., part name Mirex XL225), 106 parts by weight of bisphenol Am epoxy resin having an average molecular weight of about 1400, and 2 parts by weight of 2-heptadicylimidazole were added to butyl celeryl resin. A solution containing 1700 parts by weight was added to prepare a magnetic paint. The viscosity of the obtained magnetic paint was 170 CpS when measured using a B-type rotational viscometer at 69 rpm.
I failed. This paint was applied on a 14-inch K1 disk in the same manner as in Example 1. No defects such as protrusions or streaks were visually observed on the coating surface. The coating thickness is R105m/
m is 0.24 μm, R170 m/m is 0.368 m1, and the coating surface roughness is 0.033 μrt11 (, measured in a).

Examples 6 to 9 Ferromagnetic powder 330 parts by weight Single crystal alumina 30 PVB 30 Solvent 780 A mixture of the above composition was kneaded under the same conditions as in Example 1, and the composition in Table 1 was further added to give Example 1. A coating composition was produced in a similar manner. A magnetic disk similar to that in Example 1 was manufactured using this paint.

All of them showed superior effects of the same strain as those mentioned above.

The results are shown in Table 1. In addition, the numerical values in the table mean parts by weight.

Table 1 Example 10 700 parts by weight of ferromagnetic powder, 60 parts by weight of PVB (polyvinyl butyral) resin powder, and 60 parts by weight of single crystal alumina with a particle size of 0.4 μm were put into a kneader mixer and heated for about 15 minutes. Perform mixing. Next, cellosolve acetate 820
Parts by weight were gradually added, and kneader cross-mixing was performed for about 8 hours. 780 parts by weight of the obtained mixture was placed in a ball mill bot, and 390 parts by weight of acetic acid + Rosolve were added thereto.
Ball mill kneading was performed for 3 days to disperse the magnetic powder. Next, polyvinyl phenol resin (product name: Resin M manufactured by Maruzen Oil Co., Ltd.) 106 and novolac type epoxy resin (product name: Dow Chemical Co., Ltd., Den431) with an average molecular weight of about 500.
A solution of 106 parts by weight and 2 parts by weight of 2-hebutadicylimidazole dissolved in 1700 parts by weight of butyl celeryl was added, and 11 parts by weight of the magnetic paint was removed. The viscosity of the obtained magnetic paint is B type rotational viscosity Wt measured at 60 rpm: 9
I rarely used Qcps. This paint was applied onto an At disc in the same manner as in Example 1. No defects such as protrusions or streaks were visually observed on the coating surface. The coating film thickness is 0.12 μm at R105 m/m and 0.34 μm% I at R, 170 m/m.
No. 11 film surface roughness was 0.032 μmRa.

Example 11-13 Magnetic powder 330 parts by weight Alumina 3O1 PVB 30 #Solvent 780 parts or more were blended and kneaded under the same conditions as in Example 10, and the compositions shown in Table 2 were further added to produce Example 1. A coating composition was produced in a similar manner. A magnetic disk was manufactured in the same manner as in Example 1 using this paint. All of them had excellent effects similar to those mentioned above. The results are shown in Table 1. The numbers in the table refer to the major prize division.

Table 2 51! The magnetic powder contents of Examples 11, 12, and 13 are approximately 60%, 65%, and 45%, respectively;
It showed the same excellent characteristics as when the magnetic powder content was 55%.

Example 14 700 parts by weight of ferromagnetic powder and 60 parts by weight of PVB (polyvinyl butyral) resin powder were charged into a kneader mixer and mixed for about 15 minutes. Next, cellosolve acetate 7
Gradually add 60 parts by weight and mix the kneader to about 8 ai?
I did it for a while. 750 parts by weight of the obtained mixed material was placed in a ball mill bot, 360 parts by weight of cellosolve acetate was added thereto, and ball mill kneading was carried out for 3 days to disperse the magnetic powder. Next, 1 part by weight of phenol aralkyl resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name Mirex XL-2251106) and 1 part by weight of bisphenol A type epoxy resin having an average molecular weight of about 350.
A magnetic paint was prepared by adding a solution prepared by dissolving 0.6 parts by weight of 0.06 parts by weight with 2100 parts by weight of butyl celeryl. The viscosity of the obtained magnetic coating material was 100 cps when measured using a B-type rotational viscometer at 5 Q rpm. Next, this paint was used in Example 1.
Apply it on the At disc using the same procedure as above. No defects such as protrusions or streaks were visually observed on the coating surface. The coating thickness is R
0.15#m at 105m/mXR 0.2 at 170m/m
6-1) Friends at 4 μm. Paint surface roughness is 0.025μm
Rarely in FLa.

Example 15 700'N parts of ferromagnetic powder, 60 parts by weight of PVB T (polyvinyl butyral) resin powder, and 60 parts by weight of single crystal alumina with a particle size of 0.4 μm were charged into a kneader mixer.
Mix for approximately 15 minutes. Next, celonol acetate 182
0 parts by weight was gradually added and mixed in a kneader for about 8 hours. 7,801 parts by weight of the kneaded material was put into a ball mill bot, and 390 parts by weight of cellosolve acetate was added.
Ball mill kneading was performed for 3 days to disperse the magnetic powder. Next, a solution prepared by dissolving 53 parts by weight of phenol aralkyl resin, 53 parts by weight of polyvinylphenol resin, 106 parts by weight of novolak type epoxy resin, and 2 parts by weight of 2-hebutazinolimidazole in 2300 parts by weight of butyl celeryl was added, and a magnetic Mixed the paint. The viscosity of the obtained magnetic paint was 100 when measured with a B-type rotational viscometer at 6 Orpm.
I had a hard time with cps. Next, this paint was applied onto an At disc in the same manner as in Example 1. No defects such as protrusions or streaks were visually confirmed on the coating surface. Coating thickness is R105
0-13 A m at m/m 0 at XR170m/m
．． It was 17 μm.

Example 16 700 parts by weight of ferromagnetic powder, 60 parts by weight of PVB (polyvinyl butyral) resin powder, and 60 parts by weight of single crystal alumina with a particle size of 0.7 μm were charged into a kneader mixer and mixed for about 15 minutes. . Next, cellosolve acetate 820
Parts by weight were gradually added, and kneader cross-mixing was performed for about 8 hours. 780 parts by weight of the obtained 9-mixture was placed in a ball mill pot, and 390 parts by weight of cellosolve acetate was added.
Ball mill kneading was performed for several days to disperse the magnetic powder. 21 parts by weight of polyvinylphenol resin and 85 parts of phenol intermediate (allylphenol)! 1 and bisphenol Am epoxy resin with an average molecular weight of about 1000
A magnetic coating material was prepared by adding a solution prepared by dissolving 6 parts by weight of 0.06 parts by weight and 2 parts by weight of 2-hebutadicylinimif seal in 170.0 parts by weight of butyl celeryl. The viscosity of the obtained magnetic paint was 125 when measured at a rotational viscosity of type B i60 rpm.
697t in Cps. Next, this paint was applied on the At disk in the same manner as in Example 1, and the surface of the film was coated with protrusions and m.
Defects such as streaks could not be visually confirmed. The coating thickness is l
(0.1874m at 105m/mXR0 at 170m/m
．． The roughness of the coating film surface was 0.037 μmR,a.

Example 17 700 parts by weight of ferromagnetic powder, 60 parts by weight of powder of PVB I (polyvinyl butyral) resin, and 60 parts by weight of single crystal alumina with a particle size of 0.7 μm were charged into a kneader mixer and mixed for about 15 minutes. Let's do it. Next, cellosolve acetate 820
Gradually add parts by weight and mix in a kneader. was carried out for about 8 hours. 780 weight tffll of the obtained kneaded product was placed in a ball mill pot, 1390 parts by weight of celonol acetate was further added, and the mixture was ball milled for 3 rounds to disperse the magnetic powder. Next, 40 parts by weight of phenol aralkyl resin, 1 part by weight of phenol intermediate (alkylphenol + 66H, 2 parts by weight of bisphenol A type epoxy resin having an average molecular weight of about 1000, and 2 parts by weight of 2-hebutadicylimidazole) were mixed into 1700 parts by weight of butyl celeryl resin. Add fA to the solution dissolved in Part 1 and prepare a magnetic paint.The viscosity of the obtained magnetic paint is 1 when measured with a B-type rotational viscometer at 6 Orpm.
I rarely got 30 cps. Next, this paint was applied onto an At disc in the same manner as in Example 1. No defects were visually observed on the coated surface. Coating thickness is R105
0.23μm at m/m, 0.34μm at R170m/m
The coating surface unevenness was 0.035 μm la.

In this paint system, the wettability of the paint was slightly lower than in Example 1-15.

Comparative Example 700 parts by weight of ferromagnetic powder, 60 parts by weight of PVB (polyvinyl butyral) resin powder, and 60 parts by weight of single-crystal alumina with a particle size of 0.7 μm were charged into a kneader mixer.
Mix for approximately 15 minutes. Next, cellosolve acetate 82
0 parts by weight were gradually added and kneaded in a kneader for about 8 fF#. 780 parts by weight of the obtained mixed material was placed in a ball mill pot, 390 parts by weight of cellosolve acetate was added, and the mixture was kneaded in a ball mill for 3 days to disperse the magnetic powder. Next, phenol intermediate (allylphenol) 10
6 parts by weight, 106 parts by weight of bisphenol A type epoxy resin with an average molecular weight of approximately 4000, and 2-heptadicylimita.
Sol 2 parts and Butyl celeryl 1700 parts
Magnetic obstetrics was prepared by adding the bath solution t-m dissolved in . The viscosity of the obtained magnetic coating material was 130 cps when measured using a B-type rotational viscometer at 6 orpm. Next, this paint was applied onto an At disc in the same manner as in Example 1. The paint had even worse wettability than Example 16. When the coated surface was observed, countless streaks were observed running in the radial direction of the disc. In addition, 91 to 2 protrusions considered to be agglomerates of magnetic powder were visually observed from one side. The film thickness of the coated film is 0.19 μm 1 at R1.05 m/m.
0.30 weight m at 70m/m, coating surface roughness 0.040μ
mRa and ahfc.

〔Effect of the invention〕

Claims (1)

[Claims] 1. Ferromagnetic powder is dispersed in a polymeric binder consisting of at least one resin selected from the group consisting of phenol aralkyl resin and polyvinyl phenol resin, epoxy resin, and polyvinyl butyral resin. A magnetic recording medium composition characterized in that: 2. The magnetic recording medium composition according to claim 1, further comprising a phenol resin in the polymeric binder. 3. In the polymer binder, at least one resin selected from the group consisting of the phenol aralkyl resin and polyvinylphenol resin is 25 to 62% by weight, and the epoxy resin is 25 to 62% by weight, The magnetic recording medium composition according to claim 1, wherein the polyvinyl butyral resin is 8 to 22% by weight. 4. In the polymer binder, at least one resin selected from the group consisting of the phenol aralkyl resin and polyvinylphenol In, and the phenol resin are 6
The above epoxy resin is 25 to 62% by weight in total.
The magnetic recording medium composition according to claim 2, wherein the content of the polyvinyl butyral resin is 8 to 22% by weight. 5. The magnetic recording medium composition according to any one of claims 1 to 4, characterized in that an imidazole compound is mixed with the polymeric binder.