JPS61160827A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder and to obtain an excellent magnetic recording medium by incorporating >=1 kinds of a vinyl chloride copolymer and polyvinyl butyral resin and isophorone diisocyanate type isocyanate compd. as a binder component into the magnetic powder. CONSTITUTION:The mixture composed of >=1 kinds selected from the vinyl chloride copolymer such as vinyl chloride/vinyl acetate/vinyl alcohol copolymer and polyvinyl butyral resin and isophorone diisocyanate type polyisocyanate compd. is used as the binder for the oxide magnetic powder, ferromagentic (alloy) metallic powder, etc. The coating liquid prepd. by dispersing the magnetic powder into the soln. of the above-mentioned binder is coated on a base body and is dried to form a magnetic layer. The magnetic recording medium having the high adhesiveness to the base, excellent uniform dispersibility of the magnetic powder, excellent electromagnetic conversion characteristic with high sensitivity and excellent wear resistance and durability is thus obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium that has good dispersibility of magnetic powder, excellent electromagnetic conversion characteristics, and excellent durability. .

[Conventional technology]

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 this case, the binder component used is desired to be one that has excellent dispersibility of the magnetic powder, can impart excellent electromagnetic conversion characteristics such as high sensitivity to the magnetic recording medium, and has excellent durability.

For this reason, various research and developments have been conducted on binder resins.
For example, a vinyl chloride-vinyl acetate copolymer or polyvinyl butyral resin, which has excellent dispersibility of magnetic powder, is used, and in order to improve durability, a curing agent such as a tolylene diisocyanate-based polyisocyanate compound is used in combination. is being carried out. (Special Public Interest Publication No. 54-4148
No. 4) [Problem to be solved by the invention] However, when a tolylene diisocyanate-based polyisocyanate compound is used in combination with a vinyl chloride-based copolymer or polyvinyl butyral resin, which has excellent dispersibility for these magnetic powders, the durability deteriorates. Although this is an improvement, there are drawbacks such as the dispersibility of the magnetic powder being impaired and the electromagnetic conversion characteristics being deteriorated, and the curing reaction occurring rapidly, shortening the pot life of the magnetic paint.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and includes a combination of at least one selected from vinyl chloride copolymers and polyvinyl butyral resins and isophorone diisocyanate-based polyisocyanate compounds as binder components of the magnetic layer. By doing so, the dispersibility of the magnetic powder is improved, the electromagnetic conversion characteristics are improved, and the durability is sufficiently improved.Furthermore, by using polyurethane resin in combination with these, the electromagnetic conversion characteristics and durability are further improved. It is something that

The isophorone diisocyanate-based polyisocyanate compound used in this invention is formed into an adduct by reacting isophorone diisocyanate with an active hydrogen-containing compound such as trimethylolpropane, trimethylolethane, hexanetriol, or glycerin, or isocyanurate. It is preferable to use isophorone diisocyanate monomers which have been converted into a compound or biuret, have more than two NCO groups per molecule, and have significantly reduced toxicity of the isophorone diisocyanate monomer. Specific examples include Mytic NY series manufactured by Mitsubishi Kasei Corporation and polyisocyanate IPDI-T1B manufactured by Huels.
90, etc. This type of isophorone diisocyanate-based polyisocyanate compound is trifunctionalized by adducting or trimerizing isophorone diisocyanate, so when it is used in combination with vinyl chloride-based copolymer and polyvinyl butyral resin, The three-dimensional crosslinking reaction is sufficiently carried out to form a strong magnetic layer, which further improves durability. In addition, this type of isophorone diisocyanate-based polyisocyanate compound has better solubility in organic solvents than tolylene diisocyanate-based polyisocyanate compounds, diphenylmethane diisocyanate-based polyisocyanate compounds, etc., and is highly soluble in vinyl chloride-based copolymers and polyvinyl butyral resins. The compatibility is good (and the curing reaction is mellow), so the pot life of the magnetic paint is extended, the dispersibility of the magnetic powder is not impaired, and the surface smoothness of the magnetic layer is improved, providing sufficient electromagnetic conversion characteristics. will be improved.

Furthermore, the vinyl chloride copolymer and polyvinyl butyral resin used in this invention both have good affinity with magnetic powder and have excellent dispersibility of the magnetic powder. When at least one resin selected from resins is used in combination with an isophorone diisocyanate-based polyisocyanate compound, the compatibility improves, the dispersibility of the magnetic powder improves, the surface smoothness of the magnetic layer improves, and the electromagnetic conversion characteristics improve. At the same time, the three-dimensional crosslinking reaction is sufficiently performed to form a strong magnetic layer and the durability is sufficiently improved.

Examples of the vinyl chloride copolymer used here include vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl propionate copolymer, etc. Specific examples of vinyl chloride-vinyl acetate-vinyl alcohol copolymers that are preferably used include VAGH1 manufactured by U, C, C, USA, S-LEC A manufactured by Sekisui Chemical Co., Ltd., and the like. Further, specific examples of vinyl chloride-vinyl acetate-maleic acid copolymers include VMCH manufactured by U, C, C, USA, S-LEC M manufactured by Sekisui Chemical Co., Ltd., and specific examples of vinyl chloride-vinyl propionate copolymers. Examples include Ryuron QS-430, QS-530, QA-431 manufactured by Toyo Soda Co., Ltd.
Examples include QA-433 and QJ-1.

Specific examples of polyvinyl butyral resins include XYHL and XYSG manufactured by U, C, and C companies in the United States, Eslesoku BLS and Eslesoku BMS manufactured by Block Chemical Industry Co., Ltd., Denka Butyral 3000K manufactured by Denki Kagaku Kogyo Co., Ltd., and Mobital B manufactured by Hoechst Japan. Can be mentioned.

Among these, vinyl chloride copolymers having OH groups such as vinyl chloride-vinyl acetate-vinyl alcohol copolymers,
When used in combination with the above-mentioned isophorone diisocyanate-based polyisocyanate compound, good dispersion can be achieved no matter which magnetic powder is used. Also, vinyl chloride-
When a vinyl chloride copolymer having a C0OH group, such as a vinyl acetate-maleic acid copolymer and a vinyl chloride-vinyl propionate copolymer, is used in combination with an isophorone diisocyanate-based polyisocyanate compound, BE
Co-containing iron oxide magnetic powder with a specific surface area of 35 m/g or more by the T method, or a specific surface area of 50 m/g by the BET method.
It is possible to disperse the metal magnetic powder with a particle size of 1.5 g or more, and the surface smoothness of the magnetic layer can be improved and the gloss can be improved. Furthermore, polyvinyl butyral resin is
If you try to use metal magnetic powder as the magnetic powder in combination with tolylene diisocyanate-based polyisocyanate compounds, the magnetic paint will gel and cannot be used, but when used in combination with isophorone diisocyanate-based polyisocyanate compounds, the curing reaction will be mellow. , the magnetic paint does not gel, and the metal magnetic powder can be well dispersed, so it is particularly preferably used when using the metal magnetic powder.

The ratio of the vinyl chloride copolymer or polyvinyl butyral resin to the isophorone diisocyanate polyisocyanate compound used is the weight ratio of the vinyl chloride copolymer or polyvinyl butyral resin to the isophorone diisocyanate polyisocyanate compound. It is preferable to use the vinyl chloride copolymer or polyvinyl butyral resin in a ratio of 70:30 to 95:5. If the ratio of vinyl chloride copolymer or polyvinyl butyral resin is too small, the dispersibility of the magnetic powder may deteriorate; If the proportion of the polyisocyanate compound used is too small, durability will not be sufficiently improved.

Furthermore, as the polyurethane resin to be used in combination with the vinyl chloride copolymer and polyvinyl butyral resin, and the isophorone diisocyanate polyisocyanate compound, a direct polyurethane resin having free isocyanate groups at both ends is used. A chain-like urethane prepolymer with an average molecular weight of about 2,000 to 10,000,
Alternatively, the molecular weight without free isocyanate groups is 1.
A urethane elastomer having a molecular weight of 0,000 or more, or a urethane resin having an OH group and a molecular weight of 5,000 to 100,000 is preferably used. Specific examples of the urethane prepolymer include Takenate L manufactured by Takeda Pharmaceutical Company Limited.
1007, Coronate C-4 manufactured by Nippon Polyurethane Industry Co., Ltd.
Specific examples of urethane elastomers include Paraprene 2 manufactured by Nippon Polyurethane Industries, Ltd.
2S, Bandex T-52 manufactured by Dainippon Ink Chemical Industries, Ltd.
01, Pandesox T-5205, Bandesox T-5
250, etc.

This type of polyurethane resin has excellent dispersibility of magnetic powder, and is also highly compatible with the above-mentioned vinyl chloride copolymer, polyvinyl butyral resin, and isophorone diisocyanate-based polyisocyanate compound, and is suitable for these binder resins. On the other hand, it plays a role as a plasticizer and makes the magnetic layer moderate in flexibility. Therefore, when this kind of polyurethane resin is further used in combination, the dispersibility and q-abrasion resistance of the magnetic powder are further improved, and the electromagnetic conversion characteristics and durability are further improved. In addition, when used together with polyvinyl butyral resin and isophorone diisocyanate-based polyisocyanate compounds, it is recommended to use urethane prepolymer because urethane elastomer has poor compatibility and good electromagnetic conversion characteristics and durability cannot be obtained. preferable. The amount of these polyurethane resins to be used is preferably within the range of 5 to 60% by weight based on the total amount of the binder components; too little will result in hardness, brittleness, and poor adhesion; (It becomes too sticky.

Examples of the magnetic powder used in this invention include γ-
Fe203 powder, Fe3O4 powder, intermediate oxide powder of T-Fe203 powder and Fe3O4 powder, Go-containing r-Fe
203 powder, Co-containing Fe304 powder, CrO2 powder, Fe powder, G.

powder, Ni powder, and various alloy powders thereof, or these powders contain A I, Cr, Mn, and St.

Various conventionally known metal magnetic powders such as alloy powders containing elements such as Zn and barium ferrite powders are widely used (
Included.

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

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, at least one member selected from magnetic powder, vinyl chloride copolymer, and polyvinyl butyral resin is coated on a substrate such as a polyester film. , a binder component containing isophorone diisocyanate-based polyisocyanate compound, or a binder component in which a polyurethane-based resin is further added to these binder resins, a magnetic paint containing an organic solvent and other additives, etc. by spraying or roll coating. It may be applied by any means and dried.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Co-containing r-Fe203 powder 80 parts by weight (BET
Specific surface area by method 42m/g) VAGH (15 vinyl chloride manufactured by U, C, C, USA)
Vinyl acetate-vinyl alcohol copolymer) Mytic NY-315 (Mitsubishi 5 Sophorone diisocyanate-based polyisocyanate compound manufactured by Kasei Corporation) Lauric acid 5 Methyl isobutyl ketone 50 Toluene
50 Among the above compositions, Mytic NY-3
After putting each component except 15 in a ball mill and dispersing for 120 hours, Mytic NY-315 was added and further 2
After mixing and dispersing for a period of time, the mixture was taken out and a magnetic paint was prepared.

This magnetic paint was applied onto a 12 μm thick polyester film to a dry thickness of 6 μm, dried, surface treated, and then cut to a predetermined width to produce a magnetic tape.

Example 2 A magnetic tape was produced in the same manner as in Example 1, except that 3 parts by weight of Takenate L1007 (urethane prepolymer manufactured by Shikinichi Yakuhin Kogyo Co., Ltd.) was further added to the composition of the magnetic paint in Example 1.

Example 3 The composition of the magnetic paint in Example 1 was the same as Example 1 except that the same amount of VMCH (vinyl chloride-vinyl acetate-maleic acid copolymer manufactured by U, C, C, USA) was used instead of VAGH. and made magnetic tape.

Example 4 The composition of the magnetic paint in Example 1 was the same as in Example 1 except that the same amount of Luron QS-430 (vinyl chloride-vinyl propionate copolymer manufactured by Toyo Soda Co., Ltd.) was used in place of VAGH. I made magnetic tape.

Example 5 A magnetic tape was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 1, the same amount of Eslec BLS (polyvinyl butyral resin manufactured by Tanezu Chemical Industry Co., Ltd.) was used in place of VAGH.

Example 6 In the composition of the magnetic paint in Example 1, CO-containing r
-In place of Fe2Q3 powder, α-Fe powder (coercive force 12
50 oersted, specific surface area 33m/g by BET method
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of magnets were used.

Example 7 In the composition of the magnetic paint in Example 2, α-Fe powder (coercive force 12
50 oersted, specific surface area 33rd by l5ET method
A magnetic tape was produced in the same manner as in Example 2, except that the same amount of magnetization was used.

Example 8 In the composition of the magnetic paint in Example 3, α-Fe powder (coercive force 12
50 oersted, specific surface area 55 m/g by BET method
A magnetic tape was produced in the same manner as in Example 3, except that the same amount of the magnetic tape was used.

Example 9 In the composition of the magnetic paint in Example 4, α-Fe powder (coercive force 12
50 oersted, specific surface area 55 m/g by BET method
A magnetic tape was produced in the same manner as in Example 4, except that the same amount of magnetization was used.

Example 10 In the composition of the magnetic paint in Example 5, CO-containing r
- Instead of Fe203 powder, α-Fe powder (coercive force 12
50 oersted, specific surface area 33rd/ by BET method
A magnetic tape was produced in the same manner as in Example 5, except that the same amount of magnets (150 emu/g, 150 emu/g, and 0.5 square magnets) was used.

Comparative Example 1 The composition of the magnetic paint in Example 1 was the same as in Example 1, except that the same amount of Coronate (a trilene isocyanate polyisocyanate compound manufactured by Nippon Polyurethane Industries, Ltd.) was used instead of Mytic NY-315. I made magnetic tape.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 1 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 1.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 2, except that in the composition of the magnetic paint in Example 2, the same amount of Coronate L was used in place of Mytic NY-315.

Comparative Example 4 A magnetic tape was produced in the same manner as in Example 2 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 2.

Comparative Example 5 A magnetic tape was produced in the same manner as in Example 3, except that in the composition of the magnetic paint in Example 3, the same amount of Coronate L was used in place of Mytic NY-315.

Comparative Example 6 A magnetic tape was produced in the same manner as in Example 3 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 3.

Comparative Example 7 A magnetic tape was produced in the same manner as in Example 4, except that the same amount of Coronate L was used in place of Mytic NY-315 in the composition of the magnetic paint in Example 4.

Comparative Example 8 A magnetic tape was produced in the same manner as in Example 4 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 4.

Comparative Example 9 A magnetic tape was produced in the same manner as in Example 5, except that in the composition of the magnetic paint in Example 5, the same amount of Coronate L was used in place of Mytic NY-315.

Comparative Example 10 A magnetic tape was produced in the same manner as in Example 5 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 5.

Comparative Example 11 A magnetic tape was prepared in the same manner as in Example 6, except that in the composition of the magnetic paint in Example 6, the same amount of Coronate L was used instead of Mytic NY-315.

Comparative Example 12 A magnetic tape was produced in the same manner as in Example 6 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 6.

Comparative Example 13 A magnetic tape was produced in the same manner as in Example 7, except that in the composition of the magnetic paint in Example 7, the same amount of Coronate L was used in place of Mytic NY-315.

Comparative Example 14 A magnetic tape was produced in the same manner as in Example 7 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 7.

Comparative Example 15 A magnetic tape was made in the same manner as in Example 8, except that the same amount of Coronate L was used in place of Mytic NY-315 in the composition of the magnetic paint in Example 8. Comparative Example 16 Example 8 A magnetic tape was prepared in the same manner as in Example 8 except that Mytic NY-315 was omitted from the composition of the magnetic paint.

Comparative Example 17 A magnetic tape was produced in the same manner as in Example 9 except that the same amount of Coronate L was used in place of Mytic NY-315 in the composition of the magnetic paint in Example 9.

Comparative Example 18 A magnetic tape was produced in the same manner as in Example 9 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 9.

Comparative Example 19 A magnetic tape was produced in the same manner as in Example 10, except that the same amount of Coronate L was used in place of Mytic NY-315 in the composition of the magnetic paint in Example 10.

Comparative Example 20 A magnetic tape was produced in the same manner as in Example 10 except that Mytic NY-315 was omitted from the composition of the magnetic coating material in Example 10.

The squareness and sensitivity of the magnetic tapes obtained in each Example and each Comparative Example were measured, and the durability was tested. Durability was determined by running the obtained magnetic tape 200 times while slidingly contacting a magnetic head at a running speed of 4.75 tapes/sec, and then measuring the level drop and output fluctuation.

Tables 1 and 2 below are the results.

Table 1 Table 2 [Effects of the Invention] As is clear from Tables 1 and 2 above, the magnetic tapes obtained by the present invention (Examples 1 to 10) are different from the conventional magnetic tapes (Comparative Examples 1 to 10). 20), as a result of the improved dispersibility of the magnetic powder, the squareness is high, high sensitivity is obtained, and there is less level drop and output fluctuation.Therefore, the magnetic recording medium obtained by this invention , it can be seen that it has excellent electromagnetic conversion characteristics and durability.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer containing at least one member selected from a vinyl chloride copolymer and a polyvinyl butyral resin and an isophorone diisocyanate polyisocyanate compound as a binder component. 2. The magnetic recording medium according to claim 1, further containing a polyurethane resin as a binder component.