JPS59167839A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve dispersibility, durability, heat resistance, etc. of the magnetic powder in a magnetic recording medium by incorporating polyalkylene oxide alkyl phosphate (salt) and an org. fluorine compd. having a perfluoroalkyl group and an urethane group in a molecule in a magnetic layer. CONSTITUTION:A magnetic layer incorporated therein with the phosphate expressed by the formulas I , II, III [R1, R2, R3 are hydrocarbon of C1-32, R4, R5, R6 are H, CH3, C2H5, M1, M2 are univalent metals such as H, Na, and K, or -N(R7)q(R8)4-q, R7, R8 are H, CH3, C2H5, (m), (n) and (q) are 1-60, q is 1-4] or the salt thereof as a dispersant and further an org. fluorine compd. having a perfluoroalkyl group and an urethane group in a molecule as a dispersant respectively at 0.001-5pts.wt. the dispersant and lubricant by 100pts.wt. magnetic powder is coated and formed on a base. The magnetic tape in which the magnetic powder and lubricant are uniformly dispersed in the binder and which suppresses the surface bleed-out of the lubricant and dispersant and is highly resistant to heat and durable is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium that has excellent dispersibility, roughness, durability, and heat resistance of magnetic powder.

The magnetic layer of a magnetic recording medium is generally formed by applying a magnetic paint in which magnetic powder and its binder are dissolved and dispersed onto a substrate such as a polyester film. The magnetic properties or electromagnetic conversion properties of the magnetic layer thus formed depend on the state of dispersion of the earthen magnetic powder. In order to improve such dispersibility, various dispersants have been investigated.

It is known that polyalkylene oxide alkyl phosphate ester or its salt acts effectively as the above-mentioned dispersant, improves the filling properties and orientation of magnetic powder, and imparts excellent magnetic properties or electromagnetic conversion properties. . However, when the above-mentioned dispersant is used, there are drawbacks such as a decrease in the bonding force between the magnetic powder and the binder resin, or a tendency for the dispersant to ooze out onto the surface of the magnetic layer. This results in poor durability properties such as noticeable powder falling, large output fluctuations, and tape squeal, and poor heat resistance that causes interlayer adhesion under high temperature and high humidity.

On the other hand, in order to address the above problem, attempts have been made to incorporate general lubricants such as silicone oil into the magnetic layer, and this has improved durability and heat resistance. In this case, since the compatibility between the lubricant and the dispersant and binder is poor, the dispersibility of the magnetic powder is adversely affected and the magnetic properties or electromagnetic conversion properties are deteriorated.

From the above point of view, the magnetic recording medium of the present invention uses a polyalkylene oxide alkyl phosphate ester or a salt thereof as a dispersant in a magnetic paint (this lubricant has a perfluoroalkyl group and a urethane group in the molecule). It is made by adding an organic fluorine compound and coating it on a substrate such as a polyester film.The use of the above lubricant improves the durability and durability of the magnetic layer without impairing the dispersibility of the magnetic powder. It has been found that heat resistance can be improved.

The organic fluorine compound used as a lubricant in this invention has a urethane group in its molecule that is easily compatible with the binder and dispersant, so it is compatible with the binder and dispersant and is suitable for magnetic powder. This type of lubricant has good results in dispersibility and improves magnetic properties or electromagnetic conversion properties.In addition, this type of lubricant has a perfluoroalkyl group with excellent lubricity in its molecule, so it is useful for lubricating the magnetic layer. In addition to improving the properties and wear resistance, the good compatibility suppresses excessive surface oozing of the dispersant and lubricant themselves, and also provides good results for the bonding force between the magnetic powder and the binder. , a magnetic layer with good lubricity and abrasion resistance (excellent scratch resistance) with less output fluctuations and tape squeal caused by powder falling off,
This magnetic layer also has excellent heat resistance.

Such organic fluorine compounds can be widely used as long as they have a perfluoroalkyl group and a urethane group in the molecule, and a specific example of a commercially available product is Megafac F182. manufactured by Dainippon Ink Chemical Co., Ltd. Examples include the F183 and the F184.

The polykylene oxide alkyl phosphate ester or its salt used in combination with the above lubricant is represented by the general formula: , R4, R5, R6 are hydrogen atoms, methyl groups or ethyl groups, Ml is a hydrogen atom, -valent metallic odor (e.g. sodium atom, potassium atom, etc.) or -N (R7) Q (R8) 4
It is Q. Further, R, and R8 above represent a hydrogen atom, a methyl group, or an ethyl group, m, n, and P are integers of 1 to 60, and q is an integer of 1 to 4.

Commercially available products of such polyalkylene oxide alkyl phosphate esters or salts thereof include, for example, GAFAC-RE41Q and RE5 manufactured by Toho Chemical Industry Co., Ltd.
10, R5410 [in the general formula] R1, R2, and 3 are -CH2(CH2) n CH3, R4・R5, R61
M, ・M2ka water NF'Q child, m-n, pka3 ]
, R5710, LO=529, etc.

The amount of lubricant and dispersant mentioned above is 10% of the magnetic powder.
O, O'01~Sit respectively against 0 city Jit department
If these amounts are too large, problems such as a decrease in dispersibility and bleed-out (surface acid ratio) may occur, resulting in a decrease in output.

The magnetic powder applied to this invention includes γ-Fe2O3, F
In addition to magnetic oxide powders such as e3O4 and their intermediate iron oxide powders, and Go-containing iron oxide powders, Fe
, Ni, or alloys thereof can be used. Furthermore, any of the various conventionally known resins can be used as the binder gE.

Next, examples of this invention will be described.

Example CO Gold-containing 7 Fe2O3 powder 80 fine parts VAGH (U, vinyl chloride GAFACR8 manufactured by C-C
410 (dispersant mentioned above) 1 part by weight Organic fluorine compound (Megafac F184 mentioned above) 0.05
'Cyclohexanone 50 l Methyl ethyl ketone 5 o The above ingredients were mixed and dispersed in a ball mill for about 70 hours to make a magnetic paint, which was coated on an 11 μm thick polyester film to a dry thickness of 6 μm and dried. A magnetic tape was prepared by mirror-finishing it by a conventional method and cutting it into a predetermined length.

Comparative Example 1 KF-96 manufactured by Shin-Etsu Chemical Co., Ltd. was used instead of the organic fluorine compound.
A magnetic tape was produced in the same manner as in Example except that 1 part of (dimethylpolysiloxane) was used.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example except that no organic fluorine compound was used.

The electromagnetic conversion characteristics, durability, and heat resistance of each of the magnetic tapes of the Examples and Comparative Examples were determined according to the Magnetic Tape Industry Association Standard M.
The results measured according to TS-2o2 + are shown in Table 1 below.
It was as shown. The electromagnetic conversion characteristics are 333
The sensitivity (output) at Hz was examined, and the durability was examined by examining the output fluctuation after running 600 times. In addition, the heat resistance is 3'6 m in diameter.
After wrapping it around a glass tube with a tension of 200y,
The interlayer adhesion was examined after being left for 24 hours at ℃ and 80% RH. No adhesion was observed at all (○), some adhesion was observed (△), and significant adhesion was marked (x).
rated it as.

As is clear from the table above, the magnetic tape of the present invention has excellent electromagnetic conversion characteristics due to the good dispersibility of magnetic powder, and is also superior in durability and heat resistance. .

=1

Claims (1)

[Claims] (1) A magnetic recording medium characterized in that a magnetic layer contains a polyalkylene oxide alkyl phosphate ester or a salt thereof and an organic fluorine compound having a perfluoroalkyl group and a urethane group in the molecule.