JPH0573886A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To sufficiently improve traveling durability by incorporating a vinyl chloride resin contg. at least one kind of the polar groups expressed by a specific formula, a polyurethane resin, polyol having 40 to 320 hydroxyl group value, and a polyisocyanate compd. into a magnetic layer. CONSTITUTION:This magnetic recording medium has the magnetic layer into which the vinyl chloride resin of >=300 degree of polymn. contg. at least one kind of the polar groups expressed by the general formula-O-PO(OM1) (OM2) or-CO2M1 or-SO3M1 (where M1 is H or alkaline metal; M2 is H or <=4C amine compd.), the polyurethane resin having >=20 deg.C glass transition temp., the polyol having 40 to 320 hydroxyl group value, and the polyisocyanate compd. are incorporated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium,
More specifically, it relates to a magnetic recording medium having excellent running durability.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium prepared by coating a magnetic coating material comprising a magnetic powder, a binder resin, an organic solvent and other necessary components on a substrate such as a polyester film and drying the magnetic coating medium has improved recording density. There is a demand for improvement in durability, and as the use environment of the magnetic recording medium expands, it is particularly required to secure sufficient running durability. Therefore, the dispersibility of the magnetic powder and the durability of the magnetic layer are improved by using a dispersant of the magnetic powder or a binder resin having excellent dispersibility of the magnetic powder. For example, polyester polyurethane having a sulfone bond is used. (JP-A-62-262220)

[0003]

However, when a polyurethane having a sulfone bond of this kind is used, the dispersibility of the magnetic powder and the durability of the magnetic layer are improved, but this is not sufficient. In particular, the running durability is not improved. Not enough yet.

[0004]

SUMMARY OF THE INVENTION
In the magnetic layer
To the general formula, —O—PO (OM₁) (OM₂) Or -CO₂M₁if
Kuha-SO₃M₁  (However, M₁Is H or alkali metal, M₂Is H or
It is an amine compound having 4 or less carbon atoms. ) Polarity
Vinyl chloride containing at least one group and having a degree of polymerization of 300 or more
Nyl resin and polyuree with glass transition temperature of 20 ℃ or higher
Ton resin and a polyol having a hydroxyl value of 40 to 320,
By containing a polyisocyanate compound,
Improve the dispersibility of the magnetic powder, and
The mechanical strength is sufficiently improved, and with the base film
Adhesiveness was improved and running durability was sufficiently improved.
Of.

According to the present invention, the dispersibility of the magnetic powder is improved by the vinyl chloride resin containing at least one of the polar groups represented by the above general formula and having a degree of polymerization of 300 or more,
The polyurethane resin having a glass transition temperature of 20 ° C. or higher imparts appropriate flexibility to the magnetic layer and improves durability. Further, since a polyol having a hydroxyl value of 40 to 320 and a polyisocyanate compound are used in combination, the vinyl chloride resin and the polyurethane resin described above and a hydroxyl value of 4 are used.
The polyol having a number of 0 to 320 is crosslinked with the polyisocyanate compound to enhance the mechanical strength of the magnetic layer, and the polyol having a hydroxyl value of 40 to 320 has all the hydroxyl groups as a polyisocyanate compound. A part of it remains unreacted without reacting, and the residual hydroxyl group improves the adhesion to the base film.

Therefore, when the above-mentioned vinyl chloride resin, polyurethane resin, polyol and polyisocyanate compound are contained in the magnetic layer, the dispersibility of the magnetic powder is improved and the tough magnetic layer is improved. Is formed, and further, the adhesion between the magnetic layer and the base film is improved, and the running durability is sufficiently improved.

Vinyl chloride system used in the present invention
The resin has a degree of polymerization of 300 or more and is represented by the general formula: -O-PO (OM₁) (OM₂) Or -CO₂M₁if
Kuha-SO₃M₁  (However, M₁Is H or alkali metal, M₂Is H or
It is an amine compound having 4 or less carbon atoms. ) Polarity
Those containing at least one group are preferably used.
The polar groups represented by these general formulas are all magnetic powder particles.
Adsorbs firmly on the surface of the child. So, affinity with magnetic powder
And the dispersibility of the magnetic powder is sufficiently improved. Well
Also, this type of vinyl chloride resin is a polyisocyanate.
When used in combination with a compound, it crosslinks and mechanical strength of the magnetic layer
To strengthen. The amount used is sufficient to improve the dispersibility of magnetic powder.
In the range of 5 to 33% by weight with respect to the magnetic powder.
Is preferably used.

Specific examples of such vinyl chloride copolymers include, for example, vinyl chloride-vinyl acetate-vinyl alcohol copolymers each having a phosphoric acid group, a carboxyl group, a sodium sulfonate group, and a potassium sulfonate group introduced therein. Polymer, vinyl chloride-hydroxypropyl acrylate copolymer having phosphoric acid group or sulfonic acid group introduced, vinyl chloride-hydroxypropyl methacrylate copolymer having phosphoric acid group or sulfonic acid group introduced, phosphorus Specific examples thereof include a vinyl chloride-hydroxyethyl acrylate copolymer having an acid group or a sulfonic acid group introduced therein, and a vinyl chloride-hydroxyethyl methacrylate copolymer having a phosphoric acid group or a sulfonic acid group introduced therein. Examples include, for example, MR110 manufactured by Nippon Zeon Co., Ltd.

The polyurethane resin used in combination preferably has a glass transition temperature of 20 ° C. or higher, and this type of polyurethane resin has excellent dispersibility of magnetic powder and at the same time has suitable elasticity. .. Thus, when this type of polyurethane resin is used in combination, the dispersibility of the magnetic powder is improved, and at the same time, the magnetic layer having appropriate flexibility is obtained and the durability is improved. When this type of polyurethane resin is used in combination with a polyisocyanate compound, the hydroxyl group contained in the molecule reacts with the isocyanate group of the polyisocyanate compound to form a cross-linking bond, and the mechanical strength of the magnetic layer. To strengthen. The amount used is preferably in the range of 5 to 33% by weight with respect to the magnetic powder in order to sufficiently improve durability. Specific examples of such a polyurethane resin having a glass transition temperature of 20 ° C. or higher include:
Examples include UR8300 manufactured by Toyobo Co., Ltd.

Further, the polyol to be used in combination is preferably one having a hydroxyl value of 40 to 320, and this polyol is a polyisocyanate in which all the hydroxyl groups are used in combination.
Part of the compound remains unreacted without reacting with the compound, and the remaining hydroxyl group improves the adhesion to the base film. On the other hand, a polyol having a hydroxyl value of less than 40 has less hydroxyl groups remaining without reacting with the polyisocyanate compound when used in combination with the polyisocyanate compound, and the adhesiveness with the base film is improved. Therefore, the running durability is not sufficiently improved. Further, a polyol having a hydroxyl value of more than 320 has a poor solubility in a magnetic paint, so that the dispersion of the magnetic powder in the magnetic paint decreases.

The amount used is preferably 1 to 50% by weight in the total binder resin including vinyl chloride resin, polyurethane resin and polyisocyanate compound, and if less than 1% by weight, the desired effect is obtained. If it exceeds 50% by weight, the reaction between the polyol and the polyisocyanate compound proceeds too much, the distance between the crosslinking points becomes too short, the magnetic layer becomes brittle, and the durability is lowered. Specific examples of such a polyol having a hydroxyl value of 40 to 320 include, for example, Nippon Polyurethane Industry Co .; Nipporan N13.
6, Nipporan N131, Nipporan N121 and the like.

Suitable polyisocyanate compounds include, for example, Nippon Polyurethane Industry Co .; Coroneate L, Coroneate HL, Coroneate HX, and Coroneate N, which are preferably used. When used together with a vinyl chloride compound, the vinyl chloride resin, the polyurethane resin and the polyol are cross-linked to strengthen the mechanical strength of the magnetic layer and sufficiently improve the running durability. The amount used is preferably in the range of 5 to 100% by weight with respect to the total amount of the binder resin, and the amount of 5% by weight or less does not sufficiently improve the mechanical strength of the magnetic layer. Too many bonds make the magnetic layer hard and brittle.

The magnetic recording medium of the present invention may be produced according to a conventional method. For example, the above-mentioned vinyl chloride resin, polyurethane resin, polyol and polyisocyanate compound may be mixed with a magnetic powder and an organic solvent. A magnetic paint may be prepared by mixing and dispersing it with other additives, and the magnetic paint may be applied onto a substrate such as a polyester film by any means such as spraying or roll coating, and dried.

The magnetic powder used here is γ-
Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂
In addition to O ₃ powder, Co-containing Fe ₃ O ₄ powder and CrO ₂ powder, various conventionally known magnetic powders such as Fe powder, Co powder, Co ferrite powder, and Ba ferrite powder are widely included.

As the organic solvent, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, benzene, toluene, xylene, tetrahydrofuran, dioxane and the like suitable for dissolving the binder resin to be used are not particularly limited. It is used alone or as a mixture of two or more kinds without being used.

In the magnetic coating composition, various commonly used additives such as lubricants, abrasives, antistatic agents and dispersants may be optionally added and used.

[0017]

EXAMPLES Next, examples of the present invention will be described. Example 1 α-Fe powder (saturation magnetization 135 emu / g, coercive force 1500 e 80 parts by weight Rusted, BET specific surface area 50 m ² / g, Al content 5% by weight) MR110 (manufactured by Zeon Corporation; -SO ₃ K) Containing vinyl chloride type 10 〃 resin UR8300 (manufactured by Toyobo Co., Ltd .; polyurethane resin, glass transition 4 〃 temperature 20 ° C) Nipporan N136 (manufactured by Nippon Polyurethane Industry Co., Ltd .; poly-4 〃, hydroxyl value 41) Alumina 8 〃 carbon Black 4 〃 Oleyl oleate 8 〃 Methyl ethyl ketone 83 〃 Cyclohexanone 83 〃 Toluene 83 〃 After mixing and dispersing this composition in a ball mill for 48 hours,
Further, 2 parts by weight of Coronet L (manufactured by Nippon Polyurethane Industry Co., Ltd .; polyisocyanate compound) was added, and after mixing for 30 minutes, a magnetic paint was prepared through a filter. Apply this magnetic paint to both sides of a 62 μm thick polyester film.
A magnetic layer was formed by coating and drying so that the thickness after drying was 0.5 μm. Then, after curing it at 60 ° C for 48 hours, it was punched out into a 3.5-inch disk,
A magnetic disk was produced.

Example 2 Example 1 was repeated except that in the composition of the magnetic coating material of Example 1, the same amount of Nipporan N121 (manufactured by Nippon Polyurethane Industry Co .; Polyol, hydroxyl value 300) was used instead of Nipporan N136. A magnetic disk was produced in the same manner as in.

Example 3 In the composition of the magnetic coating material of Example 1, instead of Nipporan N136, Nipporan N131 (manufactured by Nippon Polyurethane Industry Co .; Polyol, hydroxyl value 150) was used, and Nipporan N131 and UR8300 were mixed. A large number of magnetic disks were manufactured in the same manner as in Example 1 except that the ratio was changed variously.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that in the composition of the magnetic coating material in Example 1, Niprolan N136 was omitted and the amount of UR8300 used was changed from 4 parts by weight to 8 parts by weight. did.

A large number of magnetic disks obtained in Example 3 were
Loaded in 3.5 inch FDD and left under conditions of 0 ° C and 50 ° C alternately, durability under temperature cycle environment and 50
The durability under high temperature of ℃ was investigated. FIG. 1 is a graph showing the results, where graph A shows the durability under a temperature cycle environment, and graph B shows the durability under a high temperature of 50 ° C. From these graphs, it can be seen that the combined use of the polyurethane resin and the polyol has better durability than those obtained by mixing only the polyurethane resin with the vinyl chloride resin and the crosslinking agent. It can be seen that the case where the mixing ratio of the polyol is 1: 3 to 3: 1 is good.

Further, the magnetic disks obtained in Examples 1 and 2 and Comparative Example 1 were loaded in a 3.5 inch FDD, and the durability in a temperature cycle environment in which they were left alternately under conditions of 0 ° C. and 50 ° C. The durability under a high temperature of 50 ° C. was examined. Table 1 below shows the results.

[0023]

[0024]

As is apparent from Table 1 above, the magnetic disks obtained in the present invention (Examples 1 and 2) are superior in temperature cycle durability to the magnetic disks obtained in Comparative Example 1. Also, the high temperature durability is good, which means that the running durability of the magnetic recording medium obtained by the present invention is further improved.

[0025]

[Brief description of drawings]

FIG. 1 shows the magnetic disk obtained by the present invention at 0 ° C. and 50 ° C.
FIG. 3 is a diagram showing the relationship between the durability under a temperature cycle environment in which it is left alternately under the condition of ° C and the durability under a high temperature of 50 ° C, and the compounding amounts of polyurethane resin and polyol.

Claims (1)

[Claims] 1. A general formula, —O—PO (OM₁) (OM₂) Or -CO₂M₁if
Kuha-SO₃M₁  (However, M₁Is H or alkali metal, M₂Is H or
It is an amine compound having 4 or less carbon atoms. ) Polarity
Vinyl chloride containing at least one group and having a degree of polymerization of 300 or more
Nyl resin and polyuree with glass transition temperature of 20 ℃ or higher
Ton resin and a polyol having a hydroxyl value of 40 to 320,
Having a magnetic layer containing a polyisocyanate compound
Magnetic recording medium