KR100431544B1 - Magnetic Memory Media - Google Patents

Abstract

In a magnetic recording medium applying a magnetic coating composed of a magnetic material, a binder, a lubricant, a dispersant, and a solvent on a polyester film, the surface of the iron oxide is treated with 1.4 to 2.5 parts by weight of a surface treating agent containing silicon, aluminum, and zinc. By using a surface-treated magnetic substance having an amount of 0.4 to 1.5 parts by weight, it is possible to provide a magnetic recording medium having no calender roll contamination occurring during the production process, no adhesion in the final product, and excellent running durability.

Description

Magnetic Recording Media {Magnetic Memory Media}

The present invention relates to a coated magnetic recording medium.

In general, a coating type magnetic recording medium is prepared by dissolving an additive such as a lubricant and a dispersant in a solvent, using a magnetic material and various kinds of binders as a main component to prepare a magnetic coating, and then applying the magnetic coating onto a polyester film. The solvent remaining inside acts as a factor of lowering the tape strength, thereby lowering the running durability characteristic, which is a basic characteristic of the magnetic recording medium, and also acting as a cause of calender roll contamination and adhesion.

1 is a graph showing the relationship between coating strength and durability according to the remaining solvent present in the coating film. In case of Sample A having a residual solvent of 1000 ppm, the head contamination frequency is 20 when the coating film strength is 73 kgf / mm 2 or more. In case of Sample B having a residual solvent of 200 ppm, the head contamination occurrence frequency was maintained within 20% even if the coating film strength was 60 kgf / mm 2 or more, so that the high temperature durability was maintained stably.

At this time, the coating film strength is defined as Young's Modulus at 5% elongation.

Due to these phenomena, research has been conducted to reduce the amount of solvent used in the magnetic paint within the range that does not affect the dispersibility and coating property of the magnetic paint in the industrial field, but there is a limit to reducing the overall solvent amount There was.

Accordingly, the study of reducing the solvent effect in the magnetic paint was limited to rearranging the solvent input order during the process or adjusting the proportion of the solvent constituting the magnetic paint.

Figure 2 is a result of measuring the reactivity between the solvent and the magnetic body commonly used in the manufacture of magnetic paint using a micro-calorimeter (S1 is cyclo hexanon, S2 is methyl ethyl ketone, S3 is toluene of As a related data, it can be seen that cyclohexanone has a greater affinity with a magnetic body than other solvents.

Considering these results, the dimer formed by the condensation reaction by heat, as shown in Chemical Formula 1, has not been found between the magnetic material and the cyclohexanone, and remains in the coating film without being volatilized during the drying process. It is estimated that the running durability of the tape is adversely affected, and in particular, the reaction is promoted in the presence of a magnetic body.

As a result, studies have been conducted to control the proportion of the solvent constituting the magnetic paint. However, if the ratio of cyclohexanone is lowered, the drying speed of the coating film is too fast, so that the coating film is easily broken, or the surface tension difference between the coating film surface and the polyester surface. This will cause a problem.

Accordingly, the influence of the remaining solvent may be reduced by minimizing the adsorption of the additive and the solvent to maximize the dispersibility and maximizing the adsorption of the binder.

As an example, studies have been conducted to surface-treat iron organic materials with organic materials. According to Japanese Patent Application Laid-open No. Hei 5-89449, a magnetic powder in a reduced state was treated with an organic rust preventive agent. According to 9-320828, the magnetic body was subjected to surface treatment with 1 to 3.5 mol% of calcium, 4 to 9 mol% of alumina, 1 to 5 mol% of nickel and 1 to 5 mol% of silicon.

However, in the case of using the surface-treated magnetic material as described above, the dispersibility improvement effect is excellent, but the calendar roll contamination occurs during the production process and the adhesion phenomenon occurs in the final product, and the treated materials become impurities in the magnetic recording medium. Because of this problem, it had to be applied only to products with low recording density.

Accordingly, an object of the present invention is to provide a magnetic recording medium which is free of calender roll contamination, no adhesion in the final product, and excellent in running durability and magnetic properties.

1 is a diagram showing the relationship between coating film strength and durability according to the remaining solvent in the coating film

2 is a solvent adsorption characteristics for the magnetic body

In order to achieve the above object, the present invention provides a magnetic recording medium comprising a magnetic material, a binder, a lubricant, a dispersant, and a solvent, on a polyester film, the silicon, aluminum and zinc on the surface of iron oxide or pure iron. Treatment of the surface treatment agent comprising 1.4 to 2.5 parts by weight, characterized in that the use of a surface-treated magnetic material is 0.4 to 1.5 parts by weight of silicon.

Since condensates of cyclohexanone tend to decrease with the surface treatment of the magnetic body, it is preferable to treat 1.4 to 2.5 parts by weight of the surface treating agent containing silicon, aluminum and zinc on the surface of the magnetic body, and when comparing the surface treatment materials, Silicon rather than aluminum or zinc plays a leading role in reducing condensation.

When the total surface treatment amount is less than 1.4 parts by weight or the amount of silicon is less than 0.4, there is a problem in that durability of cyclohexanone is increased, resulting in poor durability. When the total surface treatment exceeds 2.5 parts by weight, the materials treated on the surface It acts as an impurity, causing a problem of inferior magnetic properties inherent in the magnetic body.

In addition, even if the total surface treatment amount does not exceed 2.5 parts by weight, when the silicon treatment amount exceeds 1.5 parts by weight, there is a problem that the dispersibility is deteriorated due to the lack of a surface treatment agent such as aluminum or zinc.

The detailed reaction mechanism that suppresses condensation reaction by surface treatment is unknown, but it is estimated to be related to the oxidation of ferrosine (Fe ⁺⁺ ). do.

Surface treatment with silicon is one in which the oxidation of ferros is reduced so that the production of condensates can be suppressed.

In addition, the magnetic material used in the present invention can be applied to both iron oxide or pure iron irrespective of surface oxidation, in particular, in the case of iron oxide, the specific surface area is more than 28㎡ / g, the bed ratio is 8 to 10 and the switching field distribution (Switching Field) More preferably, Distribution, SFD) is 0.45 to 0.48.

The surface treatment is performed by applying an aqueous solution containing silicon, aluminum, zinc and the like to the surface of the magnetic body, and then removing water through a dehydration reaction.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

Experimental Example

-Cyclohexan condensate measurement

As shown in Table 1, 1 g of a magnetic substance having a different throughput of a surface treatment agent was placed in 20 ml of a mixed solvent composed of 1: 1 of toluene and cyclohexanone, and a reference sample containing only 20 ml of a mixed solvent without magnetic materials. After leaving for 4 hours in a water bath maintained at 60 ° C., 2- (1-cyclohexane-1-cyclohexanone) was added as an internal standard reagent to use a flame ion detector as a detector, and the column was The free fatty acid column CB is used, and the temperature of the inlet is 240 ° C., the oven temperature of the column box is 150 ° C., and the temperature is linearly increased to 180 ° C. over 10 minutes. The dimer and trimer condensate were analyzed and the results are shown in Table 1.

Solvent Reaction Calorimetry

As shown in Table 1, 1 g of a magnetic substance having a different amount of surface treatment agent was placed in the bottom of a metal cell, 20 ml of a material composed of 1: 1 of toluene and cyclohexanone were put in a glass ampoule, (TCC-23) was used to measure the amount of heat of reaction of the magnetic body to cyclohexanone. The results are shown in Table 1.

Surface throughput (%) Cyclohexanone condensates Solvent Reaction Calorie (cal / g) silicon all Dimer Trimmer Experimental Example 1 0.6 1.7 3.74 92.0 11.12 Experimental Example 2 0.9 2.0 3.67 90.7 9.86 Experimental Example 3 1.3 2.2 3.57 86.8 7.22 Comparative Example 1 0.2 1.1 27.6 169.3 37.72 Comparative Example 2 1.7 2.8 3.56 87.1 8.36 Sample 0.0 0.0 0.72 39.8 -

As can be seen from the results of Table 1, it can be seen that the condensate production of cyclohexanone generally increases by 5 to 10 times when the magnetic material is present compared to the reference sample without the magnetic material. In the case of Comparative Example 1 having a throughput of less than 1.4 parts by weight, the amount of silicon produced was 0.4 to 1.5 parts by weight, and the amount of dimer produced was nine times higher than that of Experiments 1 to 3, in which the total amount of the treatment agent was 1.4 to 2.5 parts by weight. It can be seen that is increased by about 2 times.

However, the amount of surface treatment is 0.4 to 1.5 parts by weight for silicon, 1.4 to 2.5 parts by weight as a whole of the treatment agent, even if exceeded, the effect of suppressing the formation of condensates was not significant .

<Example>

As shown in Table 2, 0.74 parts by weight of alumina, 0.25 parts by weight of butyl stearate, 0.25 parts by weight of mystic acid, 0.74 parts by weight of carbon black, 6.62 parts by weight of polyurethane binder, and isocyanate based on 24.8 parts by weight of the magnetic substance having different surface treatment agents 1.64 parts by weight of a curing agent, 21.7 parts by weight of methyl ethyl ketone, 21.7 parts by weight of toluene, and 21.7 parts by weight of cyclone nucleusone were added to a ball mill, and stirred for 4 hours to prepare a magnetic paint. Then, the gravure printing machine dried the polyester film having a thickness of 14.5 μm. Was applied to 4.0㎛ to evaluate the roll contamination, adhesion degree, running durability and magnetic properties and the results are shown in Table 2.

Surface throughput (%) Roll pollution degree Adhesion Driving durability (%) Residual solvent (ppm) Magnetic properties silicon all Example 1 0.6 2.2 A A 0 600 1200 Example 2 0.9 1.8 A B 0 400 1270 Example 3 1.3 2.4 A A 0 350 1180 Comparative Example 1 0.2 1.1 D C 20 1,600 1250 Comparative Example 2 1.7 2.8 C C 30 1,900 11000

-Roll pollution

After the calendering process was completed, the degree of contamination of the metal rolls was visually observed and divided into 4 grades according to the following criteria.

A: No pollution

B: pollution degree is less than 10%

C: pollution degree is 10 to 30%

D: Pollution degree exceeds 30%

-Adhesion

The magnetic film-coated polyester film was hot-air dried in a conventional manner, cut into 1 / 2-inch widths, left in a constant temperature and humidity chamber at a temperature of 60 ° C. and a relative humidity of 80% for 2 hours, and the film was then leveled. In one state, the time of 200m unwinding from the initial end under the influence of gravity was measured and divided into 4 grades according to the following criteria.

A: less than 60 seconds

B: 60 or more and less than 90 seconds

C: 90 or more and less than 150 seconds

D: more than 150 seconds

-Driving durability

In a video tape recorder installed in a constant temperature and humidity chamber with a relative humidity of 80% and a temperature of 60 ° C, the degree of contamination occurring at the head of the recorder when the tape was continuously run for 72 hours was evaluated.

-Residual solvent

The film was placed in the pyroprobe, and the temperature of the inlet was 240 ° C., the oven temperature of the column box was 150 ° C., and the temperature was linearly increased to 180 ° C. over 10 minutes. 1-cyclohexane-1-cyclohexanone) was added as an internal standard reagent, using a flame ion detector as a detector, the column using free fatty acid column CB, and the content of cyclohexanone calculated.

-Magnetic properties

Using a sample vibration magnetometer (VSM), a tape was cut to 0.5 mm in diameter on a Pyrex rod and the residual magnetic flux density (Br, unit gauss) was measured.

The results measured by the reaction conditions and test methods prepared in the same manner as in Examples 1 to 3 and Comparative Example 1 and Comparative Example 2 are as shown in Table 2.

In the case of Examples 1 to 3, wherein the magnetic surface is treated with 1.4 to 2.5 parts by weight of a surface treating agent containing silicon, aluminum and zinc, and the surface treated magnetic material has an amount of silicon of 0.4 to 1.5 parts by weight. There was no calendar roll contamination, no sticking in the final product, and excellent driving durability and magnetic properties.

On the contrary, in Comparative Example 1 in which the amount of silicon treated was less than 0.4 part by weight or the total amount of the treating agent was less than 1.4 part by weight, contamination of calender rolls occurred and adhesion was severely occurred in the final product. Appeared.

On the contrary, in Comparative Example 2 in which the amount of silicon treatment exceeded 1.5 parts by weight or the total amount of the treatment agent exceeded 2.5 parts by weight, the degree of improvement in roll contamination, adhesion and running durability was not remarkable, but the surface treatment agent acted as an impurity. As a result, it was confirmed that the magnetic properties fell.

As described above, the present invention uses a magnetic material treated with alumina and silicon on the surface of iron oxide or pure iron to prepare a magnetic paint together with a binder, a lubricant, a dispersant, and a solvent, so that there is no calendar roll contamination and no adhesion in the final product. A magnetic recording medium having excellent running durability and magnetic characteristics can be provided.

Although the present invention has been described as an embodiment, it is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible.

Claims (2)

In a magnetic recording medium applying a magnetic coating composed of a magnetic material, a binder, a lubricant, a dispersant, and a solvent on a polyester film, the surface of the iron oxide is treated with 1.4 to 2.5 parts by weight with a surface treating agent containing silicon, aluminum, and zinc, Magnetic recording medium characterized by using a surface-treated magnetic material with an amount of silicon of 0.4 to 1.5 parts by weight The magnetic recording medium of claim 1, wherein the surface-treated magnetic material has a specific surface area of 28 m 2 / g or more, an acicular ratio of 8 to 10, and a Switching Field Distribution (SFD) value of 0.45 to 0.48.