JPS63181120A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve an electromagnetic conversion characteristic and reliability in a high-density recording region by rotating a cylindrical grinding wheel which is formed by solidifying diamond abrasive grain having grain sizes of a specific range by a binder, thereby polishing the surface of a magnetic layer. CONSTITUTION:The magnetic layer 14 mainly consisting of magnetic powder and resin binder is coated on a nonmagnetic base and is dried and after said layer is cured by subjecting the layer to a calender treatment, the cylindrical grinding wheel 13 formed by solidifying the diamond abrasive grain having 0.5-2.0mum grain size by the binder is rotated to polish the surface of the magnetic layer 14. Almost all the projections which are the cause for signal drop- outs are removed. The dust sticking to the surface of the magnetic layer 14 in the stage for forming the magnetic layer 14 and the layer essentially consisting of the binder resin without contg. the magnetic powder existing on the surface of the magnetic layer 14 are removed and reduced as well. The electromagnetic conversion characteristic which is excellent in the high-density recording region as well is thereby obtd.; in addition, the signal defects are decreased and the reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium such as a tape or flexible disk that can be used in video-related equipment, audio equipment, information-related equipment, etc. The present invention relates to a method of manufacturing a high-density recording medium with improved defects and electromagnetic characteristics.

Conventional technology With the increasing image quality in the video equipment field, digital signal processing in the audio equipment field, and the spread and diversification of computer equipment, these external memories are required to be smaller, larger in capacity, and higher in quality. It has become. Accordingly, it has become necessary to improve the electromagnetic conversion characteristics and reliability of the magnetic recording media widely used as external memories in high-density recording areas.

Currently, the mainstream of these magnetic recording media is a coated type medium that mainly consists of magnetic powder and a resin binder. Due to the limitations of the coating film forming technology when forming the layer, the surface condition after forming the magnetic layer did not satisfy the electromagnetic conversion characteristics and reliability in the high-density recording area. Specifically, signal loss occurs due to the adhesion of protrusions and dust on the surface of the magnetic layer, and due to the uneven distribution of magnetic powder in the magnetic layer downward in the film thickness direction, a layer rich in binder resin is formed on the surface layer of the magnetic layer. For example, the electromagnetic conversion characteristics may be damaged due to

As means for improving these, the following examples are known in the prior art.

As a first example, cleaning is performed by pressing a ceramic blade against the surface of the magnetic layer of a running tape-shaped magnetic recording medium.

The above-mentioned conventional example will be described below with reference to one drawing.

FIG. 2 is a diagram showing an example of a conventional magnetic tape surface finishing process, in which 1 is a knife type cleaner, 2 is a tape-shaped magnetic recording medium, and 3 is a guide roll. FIG. 3 is an enlarged view of a knife type cleaner, and 4 is a ceramic knife whose cutting edge has a radius R of the own vehicle.

The finishing process of the tape-shaped magnetic recording medium configured as described above is carried out during the magnetic tape manufacturing process or between slitting a wide raw long medium into a tape shape and winding it onto a cassette or reel. .

The tape-shaped magnetic recording medium subjected to the above treatment has the following properties: the Knifetsu type cleaner touches the surface of the magnetic layer during running;
Small protrusions and dirt on the surface are removed with the H-shaped cutting edge,
As a result, signal loss is reduced.

As a second example, abrasive tape made of abrasive grains of alumina, chromium oxide, silicon carbide, etc. coated with a resin binder or the like is applied to the surface of a magnetic recording medium to scrape off protrusions on the surface of the medium.

The second conventional example will be described below with reference to the drawings.

FIGS. 4 and 5 are diagrams showing an example of a conventional surface finishing process for a magnetic recording medium. 6 is abrasive tape.

6 is an abrasive tape unwinding roll, 7 is an abrasive tape winding roll, and 8 is an abrasive tape rolling roll. Further, numeral 9 in FIG. 4 is a tape-shaped magnetic medium.

10 is a guide roll. In FIG. 6, 11 is a disk-shaped magnetic medium, and 12 is a disk rotation system.

The magnetic recording medium that has undergone the surface treatment process configured as described above comes into contact with the new surface of the abrasive tape at a relatively high relative speed, so that the protrusions formed on the surface of the magnetic layer and foreign matter adhering to it are scraped off. As a result, excellent surface properties with few signal defects can be obtained.

Problems to be Solved by the Invention However, the above-described configuration has a problem in that as the recording density increases, sufficient or stable signal loss reduction cannot be achieved. In the first example, ■ a decrease in the ability due to the adhesion of shavings to the cutting edge of the blade, ■ a limit in the protrusion scraping ability due to the relative speed and pressing force with the blade, ■ scraping due to the relative speed, pressing force, etc. Factors that can be cited include increased changes in the cutting edge over time when the capacity is increased, and the occurrence of scratches.

In the second example, better results than the first example have been reported due to changes in the abrasive grain size, ■ changes in the abrasive tape feeding speed, etc. However, there are also increases in cost, ■ abrasive tape and magnetism, etc. Difficulties in contact stability with media.

■ Sufficient reliability in terms of variations in polishing chip quality, etc.
This is a situation where no benefits can be obtained.

In view of the above-mentioned problems, the present invention can stably guarantee reduction of signal loss even under severe conditions in high-density recording areas.
The present invention also provides a method for manufacturing a magnetic recording medium that takes into account productivity.

Means for Solving the Problems In order to solve the above problems, the method for producing a magnetic recording medium of the present invention involves coating and drying a magnetic layer containing magnetic powder and a resin binder as main ingredients on a non-magnetic support. , the surface of the magnetic layer is polished by rotating a cylindrical grindstone formed by hardening diamond abrasive grains having a grain size of 0.6 to 20 μm with a binder after being hardened by calendering. It is.

Effect: With the above configuration, almost all protrusions that cause signal loss can be removed, including minute protrusions on the magnetic coating that are difficult to remove using conventional methods. Furthermore, dust attached to the surface of the magnetic layer during the magnetic layer forming process,
It is also possible to remove or reduce the layer on the surface of the magnetic layer, which is mainly composed of binder resin and does not contain magnetic powder.

This improves the surface properties and surface structure of the magnetic layer, resulting in excellent electromagnetic conversion characteristics even in high-density recording areas, and also reduces signal defects and improves reliability.

EXAMPLE A magnetic recording medium according to an example of the present invention will be described below with reference to the drawings.

Fig. 1 is a diagram showing the process after slitting a 5x VTR tape. In Fig. 1, 13 is a cylindrical diamond grindstone, 14 is a magnetic recording medium (original roll), and 16 is an unwinding roll for the original roll. , 16 is 8flf -j winding R'Q crawl 17 is nip roll, 18 is 81 shoulder width slitter,
19 is a guide roll, 20 is a cleaning terrace running system, and 21 is an 81 tape.

Here, one cylindrical diamond grinding wheel 13 is made of diamond abrasive grains with a grain size of 0.5 to 4 μm, which is suitable for 8-frame VTR tape, and is arranged so as to touch the magnetic layer side of the medium, and is independent of the slitter running system. To.

It is designed to be driven freely in forward and reverse directions at any rotation speed. After the original fabric medium 14 attached to the original fabric medium unwinding roll 16 is slit by an 8 shoe width slitter 18,
After being subjected to the polishing process, which is a feature of the present invention, by a cylindrical diamond grindstone 13 rotating at 4,000 to 6,000 rpm, the tape is wound onto an 87!1M tape winding roll 16. The diamond particle size is preferably 0.5 to 20 μm, fine as 0.5 to 4 μm for high-density recording tape such as Avar tape, and 10 to 4 μm for regular tape.
20 μm is appropriate. If it is larger than 20 μm, it will be too rough to be effective, and if it is too fine, it will be difficult to polish and it will be difficult to form abrasive grains.

Example 1 A magnetic paint with the following composition was prepared.

・Acicular alloy magnetic powder 100 weight 1 part ・Binder resin 22 〃・Dispersant
2.5// ・Lubricant 2 ・Alumina 7 〃 e-silica 1 〃 ・Incyanate 4 〃When making it into a paint.

The solid content concentration was adjusted to 26% under the solvent ratio of . A kneader, a disperser, and a sand mill were used as the coating equipment, and sufficient time was taken to ensure that the coating was uniformly dispersed.

The thus prepared magnetic paint was coated onto a 10 μm thick polyethylene terephthalate film to a dry film thickness of 4 μm. A gravure coating method was used as the coating method.

After coating, the magnetic coating film was subjected to a mirror finishing treatment, and then the coating film was cured.

After this, a back coat layer composed of polyurethane, vinyl chloride, carbon, alumina, and a hardening agent was formed on the back side of the magnetic layer to a thickness of about 0.5 μm.

Sample 4#O is a cassette made by slitting the product completed through the above process into 8-screen width. In addition, tapes made according to the first example and the second example described in the conventional example were used as sample #1. Set it as #2.

On the other hand, the tape according to the present invention obtained through the surface treatment process shown in FIG. 1 is designated as sample #3.

For the above samples #0 to #3, the number of dropouts when recording and reproducing an NTSC full color bar video signal and the C/N value when recording and reproducing an sMHz single sine wave were compared. What equipment did you use?

It is. Table 1 shows the results.

As evident from Table 1, sample #3 according to the invention
The number of dropouts is reduced to one-eighth compared to the conventional example f#1°#2, indicating that the effect is high. In addition, with the improvement in surface properties, the C/N value of the electromagnetic conversion characteristics has improved by about 0.6 to 1.0 compared to the conventional example. □ Improvement in 4H characteristics can be seen.

The method of the present invention can be carried out by simply adding a simple device to a commonly used slitter device, and -1) does not require consumables such as the polishing tape shown in the conventional example, making it excellent in terms of mass production.

Although the above embodiment describes an 8ff VTR tape, it can also be applied to other VTR tapes, magnetic tapes, etc. Also, by processing the original magnetic medium and punching it into a disk shape, it can be used as a magnetic disk such as a flexible disk. is also applicable.

Effects of the Invention As described above, according to the present invention, a highly reliable medium with extremely little signal loss even in a high-density recording area and improved electromagnetic conversion characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention. FIG. 2 is a diagram showing a conventional surface finishing process, and FIG. 3 is a partially enlarged view of a knife type cleaner used in FIG. 2. FIGS. 4 and 5 are diagrams showing other examples of the conventional surface finishing process. 13... Cylindrical diamond whetstone, 14...
...Magnetic recording medium (original fabric), 15...Original medium unwinding roll, 16...8N tape winding reroll, 21...8N tape. Name of agent: Patent attorney Toshio Nakao and one other person J-
Sword I'D-L! Figure 3

Claims (1)

[Claims] A magnetic layer containing magnetic powder and a resin binder as main ingredients is coated and dried on a non-magnetic support, and after hardening by calendering, diamond abrasive grains having a particle size of 0.5 to 20 μm are applied as a binder. A method of manufacturing a magnetic recording medium, comprising polishing the surface of the magnetic layer by rotating a cylindrical grindstone formed by hardening the magnetic layer.