JPH01273220A - Method for treatment with corona discharge - Google Patents

Abstract

PURPOSE:To prevent a local damage to a surface to be treated caused by a corona discharge and to efficiently improve the quality of the surface so as to improve the wettability of the coating of a magnetic tape, etc., and adhering strength of an applied film by blowing wet air on the discharging section of an electrode when processing is made with corona discharges. CONSTITUTION:When a corona discharge treatment is performed on PET film 3 which is an object to be treated while the film 3 is put around a metallic roller 1 and moved at a prescribed speed, wet air is blown to a discharging section from an air blowing nozzle through a humidifier 5. When the humidity of the wet air to be blown is set to >=60%, a large treating effect can be obtained. Moreover, the blowing speed of the wet air is decided to an extent within which the discharge is not disturbed in accordance with the position and shape of the nozzle, gap between the electrode, and electric power. When such arrangement is made, surface improvement can be performed efficiently without giving any damage, such as a discharge trace, etc., to the surface to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention improves the wettability of coatings and the adhesion strength of coatings, especially in magnetic tapes, magnetic disks, etc., and improves magnetic recording and reproduction, which is known as the dropout phenomenon caused by discharge marks. The present invention relates to a corona discharge treatment method for obtaining a magnetic recording medium with few defects.

Conventional technology Recently, the performance of magnetic recording has been improved through digitization, miniaturization, and longer recording times.As a result, high-density recording media are required, and materials and configurations need to be considered. In magnetic recording tapes in particular, there is a transition from conventional γ-Fe2O3 tapes to metal tapes and metal thin film tapes. The performances required of magnetic recording media include sensitivity and noise, which are properties unique to magnetic materials.

Distortion, erasing characteristics, etc., and running performance, durability, etc. obtained by processing the front and back surfaces of the magnetic layer are highly praised. In addition, there are dropouts, uneven magnetic properties, and uneven processing on the front and back surfaces that are affected by manufacturing control, and the higher the density of recording, the more stringent the manufacturing control is needed to deal with these problems. In particular, extremely short-term signal loss called dropout has a higher impact as the wavelength of recording becomes shorter.The cause of this dropout is signal loss due to partial defects (protrusions, pinholes, etc.) in the magnetic layer. Alternatively, there may be a case where a signal is dropped due to spacing caused by a foreign object between the head and the recording medium. Regarding the above-mentioned partial defects in the magnetic layer, as tapes become longer and have higher performance, tapes become thinner, and the thickness of the magnetic layer also becomes thinner.
．． 5 to 2,01m, and 0.2m for metal thin film tape.
Since the base film is extremely thin (μm), defects such as protrusions and dents on the base film have become a major influence.

Therefore, development of base films with good surface properties is underway.

In addition, regarding the source of the foreign matter mentioned below, in addition to dust etc. during the process, there may be cases where a part of the recording body itself is missing, and such a thing may be detected as a missing foreign matter at the time of recording. Even if there is no such problem, if it occurs during playback, dropouts may occur. Normally, dust etc. in the process are well controlled, but due to these factors, controlling the manufacturing process alone is not sufficient to completely eliminate dropouts.

After conducting various studies on the causes of this dropout, we found that the adhesion strength of the coating layer was insufficient.

It was found that the main factors were agglomeration of filler in the coating material due to local coating unevenness.

In order to solve these problems, it is possible to improve the adhesion strength and spreadability of the coating by modifying the surface by glow/discharge treatment in a vacuum or corona discharge treatment in the atmosphere. Are known.

Problems to be Solved by the Invention However, in the conventional method of glow discharge treatment in a vacuum, there are problems such as an enormous amount of equipment and high manufacturing costs. On the other hand, corona discharge treatment has problems such as not being able to obtain sufficient effects and causing damage such as discharge marks on the surface to be treated.

Currently, in magnetic recording media, there is a trend toward thinner magnetic layers and even thinner metal films in order to improve performance and increase the length of time. Therefore, slight protrusions and defects on the base film have come to affect the surface of the magnetic layer, and it is necessary to minimize such protrusions and defects that affect electromagnetic conversion characteristics. The above is the process of cycorona discharge treatment, which efficiently modifies the surface of the base film.
Moreover, it is important to prevent the occurrence of extremely fine defects due to discharge marks on the surface. Electrodes for corona discharge treatment include metals such as blades and wires, rubber,
Dielectric materials such as ceramics, glass, and plastics are widely used, but due to their versatility, stability of discharge, and ensuring surface quality of the surface to be treated, dielectric materials have recently been changed from metal materials to dielectric materials. The weight is changing.

Using these electrodes, we investigated the distance between the electrodes, the processing frequency, etc., and found that the surface modification effect was almost the same for all electrodes, but the damage to the surface of the base film to be processed was It turned out that they both received it. The present invention performs surface modification by such corona discharge treatment without damaging the surface to be treated, has fewer surface defects, reduces chipping from the tape due to running, and has magnetic properties with good electromagnetic conversion characteristics. The present invention provides a corona discharge treatment method for securing a recording medium.

Means for Solving the Problems In order to solve the above problems, the corona discharge treatment method of the present invention is characterized in that air containing humidity is blown onto the corona discharge section.

Function As described above, the present invention makes the discharge state milder by blowing humid air into the corona discharge area, and efficiently modifies the surface without causing local damage to the surface to be treated. It is something that can do quality.

EXAMPLE Hereinafter, a corona discharge treatment method according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows a conceptual diagram of a corona discharge treatment method according to an embodiment of the present invention, where ■ indicates a hard chrome-plated metal roller.

(2) is a ceramic electrode, (1) is a PET film to be treated, (2) is a nozzle for blowing air to the discharge part, and (2) is a humidifier. The processing conditions were: line speed 60 m, gap between electrodes 3, electrode area 500 mn x 30 mm, power 20
KHz 300 W, blowing wind speed 0, 1 m/se
e, humidity 20~9ochi (supply air humidity 20℃~35℃
). The results obtained in this way are shown in Figures 2 to 6.
As shown in the figure. Figure 2 shows the effect after treatment, the vertical axis is the contact angle of pure water, and the horizontal axis is untreated and air to the discharge area (humidity 70 degrees).
The presence or absence of spraying is shown, and the measured value of the contact angle of pure water at this time shows the average value of n = 5. Furthermore, FIG. 3 shows the humidity of the blown air and the measurement results of the contact angle of pure water as described above.

From these results, it was found that blowing air containing high humidity has a greater treatment effect. Figure 4 shows the results of measuring the dropouts of the evaporated magnetic symbol tape obtained by this process using a Sony V8 type dropout measuring device, and the vertical axis represents the number of dropouts occurring per minute (10).
The average value, maximum, and minimum values measured twice are shown, and a signal dropout time of 16 microns or more and a signal drop of 1 sdB or more were defined as dropouts. The horizontal axis is the humidity of untreated and discharge part 60
%Indicates whether or not air is blown. FIG. 6 similarly shows the measurement results of dropouts, where the vertical axis shows the number of dropouts similar to the above, and the horizontal axis shows the humidity of the air blown to the discharge section. Items treated by blowing air have fewer dropouts than untreated items or items that are not blown with air, and the variation in dropouts is also small.
As shown in the figure, it was found that the effect was further enhanced when the humidity of the blown air was 60% or more. FIG. 6 shows the results of observing these dropout factors using the bitter phenomenon. The vertical axis shows the exclusive rate of dropout factors, and the horizontal axis shows the dropout factors. Humidity 60 like this
% or more is mostly due to defects such as protrusions, scratches, dents, etc. inherent in the base film, but if the air humidity is less than rso% or no air is blown It was found that the treated specimens were more likely to be attributable to discharge marks, and the untreated specimens were more likely to be attributable to attached foreign matter.

As described above, by blowing air containing humidity of so% or more onto the discharge portion, surface modification could be efficiently carried out without causing damage such as discharge marks to the surface to be treated.

In addition to ceramic electrodes, these results also apply to metal electrodes such as quartz glass, steel wire, and steel plates, resin-based electrodes such as fluorine, urethane, and polyester, as well as butyl, silicon, and chloroprene.

The same effect could be obtained with any of the CI near-ium electrodes such as nitrile butadiene, urethane, and EPT. Further, the air blowing speed may be determined within a range that does not cause discharge disturbance depending on the position and shape of the nozzle, the gap between the electrodes, and the electric power.

Effects of the Invention As described above, according to the present invention, the applicability of the coating,
In corona discharge treatment to improve adhesion strength, by blowing humid air onto the discharge area of the electrode,
It is possible to efficiently modify the surface without causing damage to the surface to be treated due to discharge.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of a corona discharge treatment method according to an embodiment of the present invention, and Figs. 2 to 6 show the processing effects with and without air blowing to the electrode discharge part in the corona discharge treatment of the same embodiment. ,
Figure 2 is a characteristic diagram showing the relationship between the contact angle of pure water and air blowing, Figure 3 is a characteristic diagram showing the relationship between the humidity of the blown air and the contact angle of pure water, and Figure 4 is towards the electrode discharge section. Figure 5 shows the humidity of the air blown onto the electrode discharge area and the resulting dropout measurement results for the vapor-deposited magnetic tape. The characteristic diagram shown in FIG. 6 is a characteristic diagram showing the factors of dropout and their occupancy rates. 1...Metal roller (hard chrome plating), 2.
... Ceramic electrode, 3 ... PET film, 4 ... Air blowing nozzle, 6 ...
···humidifier. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
4-A roller 2- Ceramic J ---P E film 4--Nozzle for one tank blower,! ;-M mixer Fig. 1 Fig. 2 Unfilled Empty fluffy copper, shoulder (1 crush 70z) Fig. 3 (s) IO leaf Fig. 4 Tsuwako Shoulder Otsu θ2 (RH) Fig. 5 Hemp 4 U (7 Total 2 humidity Figure 6 ♀ Δ

Claims (1)

[Claims] 1. A corona discharge treatment method, which comprises blowing air containing humidity onto a corona discharge portion when subjecting a film transported at a predetermined speed to corona discharge treatment.