JPS58166552A - Electrostatic capacity type video disk stylus - Google Patents

Abstract

PURPOSE:To prevent a decrease in signal reproduction level, by interposing a Ti thin film between a diamond base and a thin electrode film made of corrosion- resistant metal or alloy. CONSTITUTION:On one flank of a stylus after flushing, Ti6 is vapor-deposited to about 0.05mum by ion plating and then Ni is vapor-deposited to about 0.2mum as an electrode 5 in the same tank. The stylus is equipped to a pickup system and keel work is carried out. In a life test, signal detectin characteristics do not deteriorate at all even 300hr later. The same result is obtained even when (Ni- Cr) alloy, Co, Ta, or Nb is used instead of Ni.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode structure and electrode material for a stylus for a capacitive video disc.

An explanation will be given by taking as an example the case of the CED method (RCA method) as a conventionally well-known stylus for an electric power type video disc. FIG. 1 is a schematic diagram showing the vicinity of the tip of a stylus for the same system, in which 1 is a diamond base, 2 is a keel, 5 is a sliding surface that slides on a disk, and 4 is an electrode.

As the electrode 4, a T1 thin film having a film thickness of 0.25 #m is generally used. As a method for forming the T1 electrode, a vapor deposition method, a sputtering method, an ion blating method, etc. are used. The reason for using T1 as the electrode material is due to the fact that the adhesion strength of this thin film to diamond is relatively high compared to other materials.

Now, when a stylus having the above-mentioned structure is attached to a pickup system and signal reproduction is performed, there are problems regarding reliability, which will be described later.

That is, when a signal is reproduced using the stylus, the reproduction level of one signal suddenly drops after 50 to 60 hours, and in extreme cases, it becomes impossible to reproduce the signal. Also, in cases other than those described above, the signal reproduction level gradually decreases, and the S/N ratio decreases after 100 to 200 hours.

The nine phenomena mentioned above seem to appear more prominently as the T1 film thickness increases and as the supporting temperature of the diamond substrate during formation of the Ti electrode decreases.

It goes without saying that measures were taken to prevent charge-up on the discs in the players that underwent the life test.

As mentioned above, the conventional stylus has the above-mentioned problems that need to be solved.

SUMMARY OF THE INVENTION An object of the present invention is to provide a stylus for a capacitive video disk that solves the reliability problems of the prior art mentioned above and does not cause a drop in signal reproduction level.

The gist of the present invention is to solve the problems of the prior art by using a material superior to T1 in terms of high temperature oxidation resistance as an electrode material.

Hereinafter, the main points of the present invention will be explained in more detail.

As a result of observing the vicinity of the tip of the stylus with a reduced signal detection level using an SEM and conducting a systematic study, it was found that there are several modes as shown in FIG. 2. FIG. 2 is a schematic side sectional view in the longitudinal direction of the stylus, schematically showing the state of electrode damage.

That is, in the first mode, as shown in FIG. 2-a, T
The damaged part of the first electrode has a very gentle taper shape, and in the second mode, as shown in FIG. 2-b, a protrusion of T1 can be seen in the damaged part.

Further, although crystal grains of T1 were clearly observed in the undamaged part, no crystal grains were observed in the damaged part in any case.

It is clear that the cause of the damage mode described above is not simply insufficient adhesion strength between the diamond and the T11 pole. Furthermore, from the damage mode,
There is evidence that the damaged part of the electrode was in a very high temperature state.

The first cause of the stylus tip becoming hot is
Sparks may be caused by charging up the disc. However, as mentioned above, countermeasures have been taken against this, and the probability that this is the cause of this damage is extremely low.

Now, as Tl metal's q# enemy -Tt (block-like)
is the only metal that spontaneously combusts under normal pressure, and in an Oa atmosphere of 25 atmospheres, the block-shaped T1 is quickly oxidized and completely turns into titanium oxide. The reason for this is said to be that the titanium oxide formed at the initial stage of IIk dissolves into the Ti metal, and new T1 metal always appears on the surface. The rate at which this new surface of T1 metal appears increases with increasing temperature. Also, the reason why a normal T1 block does not spontaneously ignite at room temperature and pressure is that the surface is covered with an oxide film, and at room temperature, the T1 block of titanium oxide does not ignite spontaneously.
This is due to its low solubility in metals.

That is, the cause of the electrode damage seen in the prior art is the deterioration of the oxidation resistance of T1 in the above-mentioned high temperature condition.

That is, when the disk is sliding, the T1 electrode at the tip of the stylus always exposes a new metal surface. In addition, it is estimated that the temperature at one tip of the barrel has increased considerably due to frictional heat. Under such conditions, T1 is likely to spontaneously ignite as described above. If other additional factors are added to this condition, T1 will spontaneously ignite, causing the electrode damage described above.

It goes without saying that in the nine models mentioned above, the thicker the electrode film, the greater the degree of damage.

Furthermore, it is a well-known fact that the higher the diamond substrate temperature during T1 deposition, the more carbon diffuses into the Ti thin film, resulting in improved oxidation resistance.

This explains the aforementioned fact that the higher the temperature of the diamond substrate during T1 deposition, the less damage occurs.

As mentioned above, in order to solve the problems of the prior art, it is sufficient to use a corrosion-resistant metal or alloy material that has better high-temperature oxidation resistance than T1 as an electrode. However, as a result of a systematic study, it was found that such materials have a lower adhesion strength to diamonds than Ti, and there is a problem in which the materials such as '#1 and others peel off when the disk slides. In view of this, we have devised a method in which a T1 thin film is interposed as a bonding layer between a diamond substrate and an electrode thin film made of a corrosion-resistant metal or alloy.

The present invention will be further explained using examples.

FIG. 5 is a schematic view of the vicinity of the tip of the stylus according to the present invention. In the figure, 5 is a nine electrode made of a corrosion-resistant metal or alloy according to the present invention, and 6 is a T1 thin film (thickness: approximately 0.
05. am).

(Example 1) T1 was deposited to a thickness of about 0.05 μm on the 11111 surface of the stylus after cleaning using the ion blating method,
Thereafter, N1 was evaporated to a thickness of about 0.2 μm as an electrode 5 in the same tank. Thereafter, the same stylus was attached to the pickup system, and keel processing was performed as shown in Fig. 3.

As a result of carrying out a life test on the stylus made by the method described above, no deterioration was observed in the signal detection characteristics even after 500 hours.

(Example 2) Even when a (Nl-Cr) alloy was used in place of N1 in Example 1, the same results as in Example 1 were obtained.

(Example 5) Even if Co is used as a substitute for N1 in Example 1, Example 1
The same results were obtained.

(Example 4) Even when '1'a was used in place of N1 in Example 1, the same results as in Example 1 were obtained.

(Example 5) Even if Nb is used as substitute 9 for N1 in Example 1, Example 1
The same results were obtained.

(Example 6) The same results as in Example 1 were obtained by using a Ni-Cr alloy in place of N1 in Example 1.

In this example, the ion blating method was used as the electrode forming method, but it goes without saying that the same effect can be obtained by using other methods such as vapor deposition and sputtering.

As described above, the present invention makes it possible to provide a stylus for capacitive video discs in which signal detection characteristics hardly deteriorate. In this sense, the contribution of the present invention to improving the reliability of the stylus is extremely large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the vicinity of the tip of a conventional ID system video disk stylus, FIG. 5g2 is a schematic side sectional view of the stylus showing an outline of the electrode damage mode, and FIG. FIG. 2 is a schematic diagram of the vicinity of the tip of a stylus for a CKD video disc. 1...Diamond base 2...Keel part 3...
Sliding surface 4...Electrode 5...Electrode made of corrosion-resistant metal or alloy 6...Ti1il membrane agent Patent attorney Usui 1) 利、Kyo1 (P t)・-;-・I 2 figure 3 figure

Claims (1)

[Claims] t In a stylus that detects a skeleton information signal as a change in capacitance by relatively scanning a medium on which an information signal is recorded as a change in geometric shape, at least one side surface in the longitudinal direction of the stylus is used. A stylus for a capacitive video disc, in which an electrode is formed, and the scissors electrode has a two-layer structure consisting of a T1 thin film and a corrosion-resistant metal thin film or a corrosion-resistant alloy thin film.