JPH0224838A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent electromagnetic conversion characteristics and durability by incorporating cyclohexanone which is one component of the org. solvent in a magnetic coating compd. into said compd. at a specific ratio of a binder resin or above. CONSTITUTION:The magnetic recording medium is obtd. by coating the surface of a nonmagnetic substrate with the magnetic coating compd. prepd. by dispersing a compsn. contg. magnetic powder and the binder resin, etc., into the org. solvent. The magnetic coating compd. contg. The cyclohexanone at >=40% ratio of the cyclohexanone which is one component of the org. solvent and the binder resin is used in the production of this magnetic recording medium. Of the total solvent, 5-25wt.% is preferably composed of the cyclohexanone and the remaining 95-75wt.% of a solvent mixture composed of methyl ethyl ketone and toluene. The ratio of the methyl ethyl ketone and toluene is characteristic set at 40/60-60/40. The adverse influence by the org. solvent is eliminated in this way and the excellent electromagnetic conversion characteristics and durability are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a magnetic recording medium, and more particularly, to an improvement in the fL manufacturing method thereof.

[Conventional technology]

In recent years, magnetic recording media have become more densely recorded and more reliable.
More and more magnetic recording media are equipped with a back coat layer. Both Maku Magnetic Recording TD and Backcoat 71111 have problems with their surface properties and durability, and the binder resins used are nitrocellulose, vinyl chloride co-electrolyte, polyurethane UB ¥1, and polyester resin (glass transition point +5).
0゛C or less, average molecular weight 10.000-100,000
) and polyincyanate, etc., can now be used in combination. with this.

The selection of organic bath agents that ferment these substances is also an important consideration. Until now, MS drugs have generally been methyl ethyl ketone,
Methyl isobutyl ketone, toluene xylene, cyclohexanone, tetrahydrone dione, etc. have been used alone or in combination.

The evaporation rate g shown in AS'f'MD 3539 is 1°6
Use the above (methyl ethyl ketone, 4 methyl isobutyl ketone, toluene, tetrahydrofuran, etc.) or something similar alone! 2&! One of the problems when using them together is paint! ! During the coating process, the evaporation rate is high, so the 1A solvent on the surface of the M material evaporates locally, causing output fluctuations and dropouts in that part of the recording medium, which is not very desirable. Therefore, it has been proposed to mix and use cyclohexanone with an evaporation rate of 0.32, but since the evaporation rate of 7-chlorohexenone is extremely slow, it tends to remain in the formed magnetic recording layer, resulting in a decrease in durability. [Problems to be solved by the present invention] The present invention solves the problems of magnetic recording caused by the organic solvent used in the production of coated magnetic recording media. Eliminate negative effects on records, etc.
Therefore, it is an object of the present invention to provide a magnetic recording medium having excellent magnetic IR reciprocity 2 and durability.

Means for Solving Problem C] Regardless of whether it is a magnetic paint or a backcoat paint, there is no local evaporation of the organic bath agent during the paint manufacturing process and coating process, and the paint has good fluidity.

In the magnetic coating material, it is desirable to have flowability M to such an extent that the magnetic powder can be easily oriented during the magnetic field orientation treatment after the coating process. In the subsequent drying step, it is desirable that the material be thoroughly dried. This kind of obstetric dry m rate is A
For shaking, a mixture of organic solvents with different evaporation rates is used. Methyl ethyl ketone (evaporation at 3.7.
n point 79.6°C) and cyclohexanone (evaporation rate 0.3
As shown in JP-A-62-154323, a small amount of toluene 't-11. It is also proposed to use them together.

However, methyl ethyl ketone and cyclohexanone have high resolution v, -4: The smaller the amount of stool, the better the bottle i7,'tf
Even if toluene is mixed, the effect is not sufficient.

Therefore, 1) the minimum required amount of cyclocarbonate, which has a slow evaporation rate and is a good solvent for the binder resin; 2) the short amount of methyl ethyl ketone, which has a fast evaporation rate and is a good solvent for the binder resin; and 3) ) The evaporation rate is jl<)Although it is a poor solvent for fat extraction of the mixture, in order to reduce the cost by 1 mm, we investigated the maximum allowable amount of toluene used as the #1 diluent.

Nitrocellulose as binder resin, BoIJ '71/
Using tan resin and polyinsyanate, the solubility in mixed solvents and the evaporability of al-containing solvents in the drying process were investigated. As a result, the blending ratio of the binder resin and 7-chlorohexanone was 40% by weight or more of cyclohexanone, and 5 to 25% of the total solvent was cyclohexanone, and the remaining 95 to 751% was a mixture of methyl ethyl ketone and toluene. Use as a solvent. The mixing ratio of methyl ethyl ketone is preferably 60/40 to 40/60.

In paints using the above mixed solvent and nitrocellulose, polyurethane resin, or polyisocyanate as the binder resin, the solubility of the resin component is good, and the dispersibility of magnetic powder is also good. precipitation,
It became clear that problems such as precipitation did not occur.

When the mixing ratio of toluene and methyl ketone is 65 or more, the solubility of the binder resin decreases.

On the other hand, when methyl ethyl ketone is 65 to 1, the organic solvent on the surface of the coating material evaporates locally during the paint manufacturing process, resulting in f.

However, when the compounding ratio of 7-chlorohexanone in the mixed bath agent exceeds 25% by weight, it dries and is slowly formed. If the particles remain, sufficient coating strength cannot be obtained, and the durability of the magnetic recording medium is reduced.

Furthermore, if the blending ratio of cyclohexanone in the total solvent is 3% by weight or less, paint! I! During the manufacturing process, the binder resin becomes insoluble and is formed, reducing the mechanical strength of the material and its adhesion to the non-magnetic substrate.

The method for producing a magnetic recording medium according to the present invention involves dispersing magnetic powder, a binder resin, other flavoring agents such as -T'', and an organic bath agent according to the present invention using a conventionally known separator.

FA'fr, conduct polyester film HVC coating,
It may be dried, roughly calendered, and then cut into a desired shape.

As magnetic powder, 7-Fe 10m, Co-containing r-F
Any known materials such as e20m barium ferrite and gold I14 fine powder containing iron, cobalt, and nickel 4 can be used.

As the binder resin, nitrocellulose, vinyl chloride comonomer, and polyvinyl butyral resin are used.

Polyurethane juzuki, polyester sword, polycarbonate urethane resin. Any conventionally known resin such as acrylic resin can be used.

The back coat according to the present invention is prepared by separating a mixture of carbon black, the above-mentioned binder resin, other additives and the organic bath agent according to the present invention using a conventionally known dispersing machine and then applying the mixture to a coating. This is coated and dried on the other side of the non-magnetic substrate to form a magnetic recording mark on one side. By cutting this into a desired width, a videotape with a back coat layer is produced.

Carbon blacks used for the back coat include furnace black and channel black.

Lamp black, graphitized carbon black, etc. having an average particle diameter of 10 to 300 fiμ can be used. [Example] Next, the ¥ legend of the present invention and comparative examples are shown. 2 below indicates a direct filtration section.

Example 1 CO-containing -FexOs (specific surface area, 40r//71
) 100 parts carbon black (average particle size, 0.025μ嘱) 4
Part α-AhOs (average particle size, 0.4μfi)
4il stearin wave zinc 0.5 parts Nitrocellulose (l/2sec grade) 9g polyurethane-fat 8': f5 polyisocyanate 3a myristic acid
2 g n-butyl stearate 1 part M solvent (composition shown in Table 1) 270 parts were separated using a 7-part machine such as a high-speed disper or sand mill, and filtered using a filter with an average pore diameter of 1 μm.

After drying, apply it on a polyester film (thickness: 14μ) so that the coating thickness after drying is approximately 4μ, and
The film was subjected to 8 orientation treatment and drying, followed by 4 calendering treatments and cut into 2-inch width portions to produce a videotape.

Examples 2 to 8. In Comparative Examples 1 to 4, the compositions other than the V-organic solvent were the same as in Example 1, and the organic solvent was Composition 1w shown in Table 1.
used.

Table I NIB Solvent Composition Ratio (Weight Ratio) The video tapes prepared as described above were evaluated by the method shown below.

Using a custom-made Stell VkLS system VTR, at 5°C.

40%R) Test tape in environment f of Z play in still mode and then Main output signal level changes from initial value Measure the time until it drops by 3dB comparison.

Durability - e+ vms method OV'jRe used, 40
℃.

Under an 80% R1-10 environment, the R1i' signal was recorded and the nine sample tapes were run 7fc 100 times, and the output low 1Fjtt after running with respect to the initial playback output signal level was measured.

Friction Coefficient The initial friction coefficient against the stainless steel bottle and the friction coefficient' after running 100 times with a VTR were measured.

Table 2 Results of Videotape Evaluation Results 1 Friend Videotague was made from a3: paint using an organic solvent having a composition based on the present invention.

Solubility of binder resin FC'dI! Since there is no problem with the evaporability of agent #I, it shows excellent performance in each evaluation item.

Next, Examples and Comparative Examples of the present invention for back coat J-use are shown.The sensitivity JFll in Examples and Comparative Examples below t0 is shown in Example 1, and good magnetic properties are not included.

Performance example 9 Carbon black (average particle size, 0.0254m) 50
part calcium carbonate (average particle size 0.08μta) 404 granular red iron (average particle size 0.1μm) 10 parts Nitoku cellulose CL/21) grade) 27g polyurethane IM resin is@s polyisocyanate 8 cities myristic acid
1 part Organospheric agent (composition shown in Table 3) 5130 parts After separating the Joki Ij1 component using a high-speed disper, Tendomill, etc.,
After passing through a filter with an average pore diameter of lμ, the coating thickness after drying is approximately 0.5 to 1'. Width: IJ1! A cut-out videotape was made.

Examples 10-14, ratio #f15-sri, 7f#m
Backcoat 1- was prepared in the same manner as in Example 9 except for the AI agent.
t-provided. Table 3vc shows the composition ratio of the organic solvent.

Examples 9 to 14 obtained as follows. Comparative example 5~
The videotape No. 8 was evaluated using the method shown below.

Durability Note: VH 80,000 Type (2) VTR't'', 40''
C. Test tape (run +-100 times in an environment of 80% kLH, test to the extent that there is no scratch on the back coat, and no fJJI is recognized. 4) What can be recognized correctly? Indicated by l-X marks.

4 Change in Coefficient of Friction A sample was taken from the sample tape before and after the durability g test described above, and the back coat was placed on top of a stainless steel bottle with a diameter of 20axφ so that the longitudinal direction of the tape was perpendicular to the bottle! Then, apply a load of zOg to one end of the tape, and then pull the tape with -5111 at a V feed speed of 3 un/sec. Find the number of V friction yarns and the ratio.

Table 4 As is clear from the evaluation results and the results described below, the back coat 4 using the mixed solvent according to the present invention was not easily scratched even after running. There is little change in the coefficient, and it has excellent durability.

〔Effect of the invention〕

As explained above, one method is to prepare an LDI paint or a back coat paint using the mixed solvent according to the present invention,
The magnetic recording medium produced by coating and rotating this material has a poor surface quality. A highly durable single film! ! ! It is clear that it is a quality product.

Applicant: Hitachi Maxell, Ltd. Representative Atsushi Mizu

Claims (5)

[Claims] (1) In a method for manufacturing a magnetic recording medium in which a magnetic paint in which a composition containing magnetic powder, binder resin, etc. is dispersed in an organic solvent is applied onto a non-magnetic substrate, cyclohexanone, which is one component of the organic solvent, is used. 1. A method for producing a magnetic recording medium, comprising using a magnetic coating material containing cyclohexanone in a ratio of 40% by weight or more to a binder resin. (2) Applying a back coat paint in which a composition containing carbon black, binder resin, etc. is dispersed in an organic solvent to the opposite side of the magnetic sheet, which has a magnetic recording layer on one side of the non-magnetic substrate. In the magnetic recording medium made of
1. A method for manufacturing a magnetic recording medium, characterized by using a paint having a content of at least % by weight. (3) The method according to claim (1) or claim (2), characterized in that the proportion of cyclohexanone in the organic solvent component used in the magnetic recording layer paint and the back coat paint is 5 to 25% by weight. A method for manufacturing magnetic recording media. (4) In a mixed solvent using a mixture of cyclohexanone, methyl ethyl ketone and toluene as an organic solvent, the ratio of methyl ethyl ketone to toluene is 40/60 to 60.
/40
1), (2), or (3) the method for manufacturing a magnetic recording medium. (5) The method for manufacturing a magnetic recording medium according to claim (1) or (2), wherein the binder resin is made of nitrocellulose, polyurethane resin, or polyisocyanate.