JP2945444B2 - Coating type magnetic recording medium for coating type magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention can improve the strength of a coating film such as an elastic modulus, a breaking strength and a scratching strength when dispersed in a coating film of a coating type magnetic recording medium. The present invention relates to a magnetic particle powder that can be obtained.

[Conventional technology]

Currently, magnetic recording media such as magnetic tapes and magnetic disks used for video and audio applications are based on a plastic film or an aluminum plate, on which a magnetic coating material in which magnetic particles are dispersed in a vehicle is coated. A so-called coated magnetic recording medium formed by coating is in the mainstream.

In the case of a coating type magnetic recording medium, particularly a magnetic tape, during recording and reproduction, it is used under severe conditions in which the magnetic recording medium is run in close contact with a magnetic head and various guide systems at a speed of 1 cm to 10 m / sec.

Recently, magnetic tapes are in the direction of high density recording,
Since the magnetic tape and the magnetic head need to be brought into closer contact with each other and run, it is necessary to strongly calender the coating surface to finish it to a mirror surface, and it is necessary to withstand more repeated use. The usage conditions are becoming increasingly severe, and in order to withstand such severe conditions, it is strongly required to improve the strength of the coating film itself such as the elastic modulus, the breaking strength and the scratching strength.

This fact can be found in the 74th to 75th of "Development of Magnetic Materials and Technology for Highly Dispersing Magnetic Powder" (1982) published by Sogo Gijutsu Center.
"The magnetic tape must have the mechanical properties as summarized in Table 1 after taking these problems into consideration," and "Table 1 Desirable mechanical properties of the magnetic tape # 8 Elastic modulus" 9, high breaking strength and low residual elongation. 9 No scratches or falling off of the magnetic powder.

Here, the "elastic modulus" means that in a range of elasticity where the stress σ does not exceed the proportional limit (compulsory limit) determined by the material, the elastic strain e and the stress σ corresponding thereto are proportional to each other. Means the ratio of elastic strain to stress σ / e.

"Breaking strength" refers to the magnitude of stress when a material breaks when a stress is applied to the material and the stress is gradually increased.

The term "scratch strength" refers to the magnitude of the load applied to the needle when the test piece breaks when a hard needle such as diamond is placed on the surface of the test piece and the stylus pressure is gradually increased.

Conventionally, as a method for improving mainly the abrasion resistance and durability of the mechanical properties of a coating film, a method of adding and mixing an abrasive having high hardness into the coating film (Japanese Patent Publication No. 47-18572)
JP-B-52-28642, JP-A-57-58227), a method of coating a magnetic particle powder dispersed in a coating film with a titanium coupling agent (JP-B-55-4804, JP-A-55-4804, 62−76
508, JP-A-63-129519, JP-A-63-29881
No. 4, JP-A-1-245424) and the like.

[Problems to be solved by the invention]

A coating type magnetic recording medium having excellent coating film strength is the most demanded at present, but the former method among the above-mentioned known methods is based on the fact that an abrasive having a high hardness is present on the surface of the coating film to thereby reduce the wear resistance. It does not improve the strength of the coating film surface itself.

The latter method improves the coating strength by improving the conformity between the particle surface of the magnetic particles and the resin in the vehicle, but is not yet satisfactory.

Therefore, an object of the present invention is to provide a magnetic particle powder capable of improving the strength of a coating film when dispersed in the coating film.

[Means for solving the problem]

The technical problem can be achieved by the present invention as described below.

That is, the present invention is a coating-strengthening magnetic particle powder for a coating-type magnetic recording medium, comprising magnetic particles whose surface is coated with a titanium coupling agent chelated with lactic acid.

[Action]

First, the most important point in the present invention is that when magnetic particles coated with a titanium coupling agent whose surface is chelated with lactic acid are dispersed in a coating film, elastic strength, breaking strength, This is the fact that the scratching strength is improved and a coating film having excellent coating film strength is obtained.

When the magnetic particle powder according to the present invention is used, regarding the reason that a coating film having excellent coating film strength is obtained, the present inventor has found that a titanium coupling agent chelated with lactic acid has a property between the particles and the resin. It is believed that they strongly bind to the hydrophilic groups on the surface of the magnetic particles and the hydrophobic groups or functional groups of the resin through the intermediary of the magnetic particles, and as a result, the magnetic particles and the resin are strongly bonded.

The magnetic particle powder according to the present invention is intended for a resin having a strong polar functional group such as a COOH group or a SO ₃ Na group that is currently in practical use for the purpose of improving the dispersibility of the magnetic particle powder in a vehicle. In this case, a coating film having excellent coating strength is obtained.

Next, conditions for implementing the present invention will be described.

As the magnetic particles used in the present invention, maghemite particles, magnetite particles, the belt write compounds _{(FeOx · Fe 2 O 3,} 0 <x <1) magnetic iron oxide particles such as, in these magnetic iron oxide particles Particles containing different metals such as Co other than Fe or these magnetic iron oxide particles
Any of particles coated with Co and plate-like composite ferrite particles containing Ba or Sr can be used. Also,
The shape of the magnetic particle powder may be any of a needle shape, a spindle shape, a cubic shape, a plate shape, and the like.

The magnetic particles coated with a titanium coupling agent chelated with lactic acid according to the present invention are prepared by mixing magnetic particles in a commercially available aqueous solution of “TIZOR LA (trade name, the same applies hereinafter)” manufactured by DuPont. And dispersing and mixing, or a method of adding and dispersing and mixing “TIZOR LA” in an aqueous suspension containing magnetic particle powder.

The above-mentioned "TIZOR LA" is a water-soluble titanium coupling agent chelated with lactic acid represented by the following structural formula, coated on the surface of magnetic particles, and then dried to be deaminated by drying. Is done.

The coating amount of the titanium coupling agent chelated with lactic acid in the present invention is calculated in terms of Ti relative to the magnetic particles.
It is 0.05 to 5.0% by weight.

If the amount is less than 0.05% by weight, the coating-film-strengthening magnetic particles intended for the present invention cannot be obtained.

When the content exceeds 5.0% by weight, the coating-strengthening magnetic particles intended for the present invention can be obtained, but the saturation magnetization of the magnetic particles decreases due to an increase in the amount of the titanium coupling agent not involved in magnetism. It is not preferable because it will do.

〔Example〕

 Next, the present invention will be described with reference to Examples and Comparative Examples.

In addition, the elastic modulus and the breaking strength of the coating film in the present invention are shown by values measured using a tensile strength tester Autograph AG-1000B (manufactured by Shimadzu Corporation).

The scratching strength was indicated by a value measured using an ultra-thin film scratching tester CSR-02 type (manufactured by Resca Corporation).

 The Ti content was indicated by a value measured by fluorescent X-ray analysis.

The magnetic properties of the magnetic particle powder and the magnetic tape are values measured using an “oscillating sample magnetometer VSM-3S-15” (manufactured by Toei Industry Co., Ltd.) under an external magnetic field of 10 KOe.

<Surface Treatment of Magnetic Particle Powder> Examples 1-4, Comparative Examples 1-2; Example 1 Long axis 0.2 μm, axial ratio (long axis; short axis) 7: 1 and holding power
820 Oe, Co-coated needle-like γ-Fe ₂ O having a saturation magnetization of 78.5 emu / g
_{Using three} particles (Co / magnetic particle powder = 4.5% by weight), 100 g of the magnetic particle powder was dispersed and mixed in water 10 to prepare an aqueous suspension.

6.1 g of an aqueous solution of TIZOR LA, a titanium coupling agent chelated with lactic acid in the above aqueous suspension (in terms of Ti)
After adding 8.2% by weight of Ti (the amount of addition corresponds to 0.5% by weight in terms of Ti with respect to the magnetic particles), the mixture was stirred and mixed to obtain the Co-coated acicular γ-Fe ₂ O _3. Brown precipitate particles were obtained which had been deposited by titanium coupling in which the particle surfaces were chelated with lactic acid.

The suspension containing the brown precipitate particles is filtered by an ordinary method,
Dried.

The amount of Ti in the titanium coupling agent chelated with lactic acid coated on the surface of the obtained brown particles was 0.5% by weight based on the magnetic particle powder as a result of fluorescent X-ray analysis.

Examples 2 to 4 Except that the type of the magnetic particle powder and the amount of the titanium coupling agent were variously changed, a magnetic particle powder whose particle surface was coated with the titanium coupling agent was obtained in the same manner as in Example 1. .

 Table 1 shows the main conditions at this time.

Comparative Example 1 The same Co-coated acicular γ-Fe ₂ O ₃ particles as in Example 1 were thoroughly dried in advance, and 1000 g of the magnetic particle powder was charged into a Henschel mixer. 99.8 g of TTS (manufactured by Ajinomoto Co., Inc.) (the same applies hereinafter) (the amount of addition corresponds to 0.5% by weight in terms of Ti relative to the magnetic particle powder) was gradually dropped into the Henschel mixer. Subsequently, after stirring was continued for 30 minutes, the treated magnetic particle powder was taken out of the Henschel mixer, and was placed in a stream of N ₂ gas.
After drying at 100 ° C. for 2 hours to remove the remaining solvent, the titanium coupling agent KR-TTS is coated on the particle surface.
Adhered needle-like γ-Fe ₂ O ₃ particles were obtained.

Comparative Example 2 A titanium coupling agent KR-TTS was applied to the particle surface in the same manner as in Comparative Example 1 except that the same plate-like composite ferrite particle containing Ba as in the example was used as the magnetic particle powder. A plate-like composite ferrite particle powder containing Ba was obtained.

<Production of Coating Film and Magnetic Film> Examples 5 to 8, Comparative Examples 3 to 6; Example 5 The surface of the particles obtained in Example 1 is coated with a titanium coupling agent chelated with lactic acid. 100 parts by weight of magnetic particle powder composed of magnetic particles, 8 parts by weight of MR-110 (vinyl chloride-vinyl acetate-vinyl alcohol copolymer) having a strong polar functional group (manufactured by Nippon Zeon Co., Ltd.), 30 parts by weight of toluene, 30 parts by weight of methyl ethyl ketone,
After kneading 5 parts by weight of Al ₂ O ₃ powder and 3 parts by weight of carbon black using a kneader for 90 minutes, toluene is added to the kneaded material.
The mixture was diluted by adding 45 parts by weight of methyl ethyl ketone and 45 parts by weight of methyl ethyl ketone, and then mixed and dispersed by a sand grinder for 6 hours.

A polyurethane resin (product name TI-10) was added to the mixed dispersion.
75, 140 parts by weight of a methyl ethyl ketone solution containing 8 parts by weight of a solid content of Sanyo Chemical Industry Co., Ltd.) and 1 part by weight of myristic acid were added and mixed for 3 hours. A magnetic material was produced by mixing 3 parts by weight of a trifunctional low molecular weight isocyanate compound (manufactured by Nippon Polyurethane Industry Co., Ltd.).

The above magnetic paint is applied on a polyester base film having a thickness of 14 μm, and then oriented in a magnetic field of 3000 Gauss,
After a magnetic layer having a thickness of 4 μm was formed by drying, calendering was performed, and then the film was cut into a width of 12.7 mm to form a coating film.

 Table 2 shows various characteristics of the coating film.

Furthermore, the magnetic paint adjusted in the same manner as above
500μ on a Teflon plate using an applicator
m, dried at 60 ° C. for 24 hours, and peeled off to produce a magnetic film.

Table 2 shows the results of measuring the strength of the coating film using this magnetic film as a test piece.

Examples 6 to 8 and Comparative Examples 3 to 6; Example 5 except that the type of the magnetic particle powder was variously changed.
A coating film and a magnetic film were prepared in the same manner as described above.

 Table 2 shows properties of the magnetic tape and the magnetic film.

[Effects of the Invention] The magnetic particle powder according to the present invention is, as shown in the above Examples, a coating film due to the fact that the particle surface is coated with a titanium coupling agent chelated with lactic acid. Since it can improve the elastic strength, the breaking strength and the scratching strength when it is dispersed therein, it is most suitable for a coating type magnetic recording medium which is currently most required and has excellent coating strength.

Continuation of the front page (72) Inventor Hiroko Itamochi 4-1-2, Funariminami, Naka-ku, Hiroshima-shi, Hiroshima Examiner, Toda Kogyo Co., Ltd. Creative Center Yutaka Nakamura (56) References JP-A-61-54033 (JP, A) JP-A-60-175213 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01F 1/00-1/117 G11B 5/712

Claims (1)

(57) [Claims] 1. A coating-strengthening magnetic particle powder for a coating type magnetic recording medium comprising magnetic particles coated with a titanium coupling agent whose surface is chelated with lactic acid.