JPH0327971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium such as a coated magnetic tape suitable for high-density recording.

In order to obtain a coated magnetic tape suitable for high-density recording, it is sufficient to increase the coercive force and magnetic flux density. In this case, when the concentration of the magnetic powder was increased, the resin content decreased, resulting in negative effects such as a decrease in adhesion strength, a decrease in slipperiness, and poor dispersion of the magnetic powder during coating. The current method of increasing magnetic flux density is to use magnetic powder with high magnetic flux density, and the change from the conventional use of iron oxide to metal magnetic powder is for this purpose. It is something. Considering the principle of magnetic recording, the magnetic layer used for high-density recording is limited to the surface layer, so if this layer is the only layer with high-density magnetic flux, it will be possible to achieve high-density recording or high-frequency characteristics. You can get good magnetic tape.

Several techniques, such as a two-layer coating method, have already been developed to obtain a tape with excellent high frequency characteristics by changing the magnetic properties of only the surface layer. However, conventional methods such as a two-layer coating method have had the problem of complicating the manufacturing process. The present invention aims to solve such problems in the prior art, and will be explained below.

The present invention provides a magnetic recording medium with excellent high frequency characteristics by a simple method. The manufacturing method according to the present invention can be obtained, for example, as follows.

That is, a mixture of magnetic powder and liquid resin having an appropriate mixing ratio is used as the magnetic coating liquid for forming the magnetic layer, but the liquid resin used at this time has a low boiling point of, for example, about 100°C to 300°C. It is an ultraviolet curing resin. When such a coating liquid is applied and then passed through a hot air oven maintained at a temperature close to the boiling point of the resin, the resin in the surface layer is scattered and the concentration of magnetic powder in that area becomes high. Thereafter, the resin is cured by irradiation with ultraviolet rays, and the surface is smoothed using a calender roller to finish it as a magnetic recording medium.

Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows an outline of a manufacturing apparatus used in an embodiment of the present invention. In the figure, reference numeral 1 denotes a plastic film that serves as the substrate of the magnetic tape, and polyethylene terephthalate (PET) is mainly used, but other heat-resistant polyimide, polyamide films, etc. are also used. 2 is a gravure roll, and 3 is a magnetic coating liquid. 4 is Backup Prowl. From coating liquid 3 to gravure roll 2
The coating liquid transferred onto the film 1 and measured by a doctor (not shown) is transferred onto the film 1 under pressure with a backup roll 4 and a gravure roll 2 to form a magnetic layer. Among the components of the coating liquid 3, in addition to the commonly used γ-Fe ₂ O ₃ , iron powder, iron-cobalt alloy powder, etc. can be used as the magnetic powder. On the other hand, as the resin, a low-molecular liquid composition and an ordinary ultraviolet curable paint can be used, but particularly preferred are 1
The main component is a monomer with a boiling point of 300°C or less under atmospheric pressure, and if it is a radical polymerization type, monomer acrylates such as cyclohexyl methacrylate, t-butylstyrene, dibutyl maleate, 1-4 butanediol acrylate , diethyl glycol diacrylate, and other polyfunctional acrylates, or mixtures thereof, with photosensitizers such as benzoin isopropyl ether and benzophenone, and paint additives added. In addition, in the case of ionic polymerization, alicyclic epoxies such as vinylcyclohexene dioxide, dicyclopentadiene dioxide, dipentene dioxide, 3-4 epoxycyclohexylmethyl, 3-4 epoxycyclohexane carboxylate, and allyl A curing catalyst that decomposes with epoxies such as glycidyl ether and phenyl glycidyl ether to form a Lewis acid when irradiated with ultraviolet light, such as P-nitrobenzenediazonium hexafluorophosphate, 2-4
There are compositions consisting of dichlorobenzenediazonium tetrafluoroboride and the like and stabilizers such as acetonitrile and propionitrile, to which various paint additives are added as necessary.

In the description of this example, a case will be described in which an alicyclic epoxy is used as the resin.
The coating liquid is made by mixing γ-Fe ₂ O ₃ powder and resin at a weight ratio of 1:1, stirring it with a mixer, etc.
It is adjusted by thoroughly dispersing the γ-Fe ₂ O ₃ powder and resin, and then adding an ultraviolet curing agent thereto.

Now, in FIG. 1, numeral 5 is a magnet for orienting magnetic particles in the coating solution applied onto the plastic film 1, and 6 is a hot air stove. 7 is a hot air inlet, and 8 is an exhaust port. 9 is an ultraviolet generator, and 10 and 11 are a supply roll and a take-up roll for the plastic film 1, respectively. As shown in the figure, a film 1 coated with a magnetic coating liquid
After the magnetic coating liquid is oriented in a magnetic field by a magnet 5, it is introduced into a hot air stove 6. In the hot air oven, the temperature and air volume are selected so that the resin is scattered without deforming the substrate film. For example, on the board
When using PET, the temperature is 120℃ and the air volume is 20m ³ /
minutes is appropriate. The furnace length at this time was 7m.
The film width is 50cm. Air volume also varies depending on the size of the furnace. When the film 1 coated with the magnetic coating liquid is heated in a hot air oven and some of the resin on the surface of the coating liquid is scattered, the concentration of magnetic particles in that area increases. After increasing the magnetic particle concentration in this manner, the magnetic coating liquid is cured by irradiation with ultraviolet rays to form a magnetic layer. The film 1 on which the magnetic layer is formed is wound onto a winding roll 11.
Thereafter, the surface of the magnetic layer is smoothed by calendering, and a magnetic tape as shown in FIG. 2 is completed. In addition, in Figure 2, 1
2 is a plastic film, 13 is a magnetic layer, 14
15 is a resin cured by ultraviolet rays, and 15 is a magnetic powder dispersed in the resin 14. The characteristics of the magnetic tape thus completed will be explained with reference to FIG.
FIG. 3 shows the frequency characteristics of the recording/reproduction output. The measurement conditions were: tape speed 4.75 cm/sec, recording head gap length 3 μm, playback head gap length 1 μm,
The bias frequency is 100kHz. In the figure, the horizontal axis represents the frequency of the signal, and the vertical axis represents the output. Line A in the figure shows the case of a magnetic tape made without passing it through a hot air oven as in the conventional case, and line B shows the case of a tape made by passing it through a hot air oven according to the present invention. As can be seen from the figure, the tape according to the present invention made through a hot air oven has a large output in the high frequency range, and at 20kHz there is a difference of 2.5 dB compared to the conventional tape that is not passed through a hot air oven.

As described above, according to the present invention, a magnetic recording medium with excellent high frequency characteristics can be easily obtained through a simple manufacturing process.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of a manufacturing apparatus used in an embodiment of the present invention, FIG. 2 is a sectional view of a magnetic tape in an embodiment of the present invention, and FIG. 3 is a diagram showing a magnetic tape according to the present invention and a conventional magnetic tape. FIG. 3 is a diagram showing frequency-output characteristics of each magnetic tape. 1, 12...Plastic film, 2...Gravure roll, 3...Coating liquid, 4...Backup roll, 6...Hot air oven, 9...Ultraviolet generator, 10...Supply roll, 11...Volume Take-up roll, 13...Magnetic layer, 14...Resin, 15...Magnetic powder.

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic recording medium in which a magnetic layer made of magnetic powder dispersed in a resin is provided on a substrate, after coating a mixture of a photocurable resin and magnetic powder on the substrate to form a coating layer. . A method for producing a magnetic recording medium, comprising: evaporating the resin on the surface of the coating layer; and then photo-curing the coating layer to form a magnetic layer.