JPH087331A - Recording medium and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] The present invention eliminates the disadvantages of SiC and selects a protective film material suitable for a DC sputtering method with good production efficiency, and forms a film without arc discharge. Provide a recording medium with few pinholes. In a recording medium in which a protective film and a recording film are formed on a substrate, the protective film is made of Si CTi, and the content of Ti is 0.5 to 7 atomic%, an optical recording medium, a magneto-optical recording medium, and a magnetic recording medium. A recording medium and a method of manufacturing a recording medium in which the protective film is formed by a DC sputtering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium useful for recording / reproducing a large amount of information and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, a recording medium having a high density and a large capacity has been required with the progress of information society, and various recording media have been put into practical use. Some of these recording media have a protective film, and this protective film plays the following important roles in the recording medium. First, in some optical recording media, a transparent protective film is used for the purpose of protecting the recording film and increasing the signal intensity by utilizing light interference. For example, in a magneto-optical recording medium, the recording film has Tb-Fe-Co
An alloy of a rare earth element and a transition metal is generally used, but this material is easily corroded by oxygen and moisture in the atmosphere, so the purpose of improving the corrosion resistance is to reduce the signal written to the recording medium. The purpose is to increase the difference in optical rotation between when the recording film used for reading is facing the S pole and when facing the N pole with respect to the light incident direction, and to further reduce the power of light necessary for writing. A light-transmissive protective film is provided on the substrate, and generally comprises a four-layer film including a first protective film, a recording film, a second protective film, and a reflective film from the side of the substrate (JP-A-2-240845, Japanese Examined Patent Publication No. 4-32449, JP-A-57-124
No. 28). Further, in this four-layer film structure, the one without the first protective film (see Japanese Patent Publication No. 4-30098) and the one without the second protective film (Japanese Patent Publication No. 44333/44).
Japanese Patent Publication) is also proposed.

Separately, in a phase change recording medium which reproduces written information by utilizing the difference in reflectance between the crystalline phase and the amorphous phase, a protective film increases the reflectance difference between the crystalline phase and the amorphous phase. Although the thermal conductivity is adjusted, it is said that the above-mentioned four-layer film structure is particularly effective for improving the power margin and the repeating characteristics (refer to the 2nd Phase Change Recording Workshop Symposium Proceedings, 1991). There is. Further, a protective film is also used in a magnetic recording medium in which a magnetic material such as Co alloy or Fe alloy is used for a recording film to perform writing in an external magnetic field and reproduction is performed by using electromagnetic induction or magnetoresistance. In general, a base film such as Cr, a recording film,
The protective film is composed of a protective film and a lubricating film, and the protective film is used for the purpose of improving wear resistance and durability (see Japanese Patent Application Laid-Open No. 1-184722). The protective film used for such a recording medium includes
It is required that 1) the film is dense, 2) does not react with the recording film, 3) has few pinholes, and 4) has an optically appropriate refractive index in the case of an optical recording medium. Since such characteristics are satisfied, SiC has been proposed as a protective film for a recording medium and put to practical use (Japanese Patent Laid-Open Nos. 61-45441 and 62-289).
No. 945 and Japanese Patent Laid-Open No. 1-184722).

[0004]

Although the CVD method, the sputtering method and the like are known as the SiC film forming method, the sputtering method is widely used because a uniform film over a large area can be obtained relatively easily at a low temperature. It is used. When forming a film by the sputtering method, the protective film generally has a slower film forming speed than the recording film or the reflective film,
In addition, since the protective film is often thicker than the recording film and the reflective film, the manufacturing time of the recording medium is limited by the film formation rate of the protective film. The sputtering method includes a direct current sputtering method and a high frequency sputtering method, but the high frequency sputtering method has a drawback that the film forming speed is slower and the power supply device becomes expensive. Therefore, it is desired to form a film by the DC sputtering method. However, when SiC is used as a target, arc discharge easily occurs in the film formation chamber of the sputtering device, the discharge becomes unstable, and a pinhole is formed in the protective film. For example, in a recording film which is easily oxidized such as a rare earth iron group transition metal alloy used in a magneto-optical recording medium for the recording film, pitting corrosion occurs and causes an error during reproduction. The present invention is intended to eliminate such defects of SiC and select a protective film material suitable for the DC sputtering method with high production efficiency to provide a pinhole-free recording medium.

[0005]

As a result of searching for a protective film material instead of SiC in order to solve such disadvantages and problems, the present inventors have found that Si CTi is suitable, and The present invention has been completed by establishing film forming conditions, and the gist thereof is that in a recording medium in which a protective film and a recording film are formed on a transparent substrate, the protective film is made of Si CTi, and the content of Ti is An optical recording medium having a content of 0.5 to 7 atomic%, a magneto-optical recording medium, a magnetic recording medium, and a method for manufacturing a recording medium in which the protective film is formed by a DC sputtering method.

The present invention will be described in detail below.

The recording medium using Si CTi for the protective film of the present invention can adopt a high productivity DC sputtering method for forming the protective film, which cannot be formed by the conventional SiC protective film. It has become possible to suppress discharge and form a protective film with few pinholes. This effect remarkably appears when the Ti content in Si CTi is within the range of 0.5 to 7 atomic%.

The greatest feature of the present invention is that in a recording medium including at least a protective film and a recording film on a substrate, Si CTi is used for the protective film, and the ratio of Ti is 0.5 to 0.5. It is preferably 7 atomic%, and the film formation method is preferably a DC sputtering method. That is, in this range, arc discharge can be suppressed even when the film is formed by the DC sputtering method, and the pinhole in the film after the film formation can be reduced. In addition, since the film forming rate can be increased as compared with the high frequency sputtering method, the productivity of the recording medium can be improved, and the power source can be simplified, so that the film forming apparatus can be manufactured at low cost. is there.

The Si CTi compound and the Si CTi target are produced by a conventionally known method such as the Acheson method, the silica reduction method, the high frequency plasma CVD method or the like, and a predetermined amount of Ti C or Ti powder is produced. It suffices to add and fire this to produce a Si CTi target.

The protective film may be formed by a direct current sputtering method by a known method. The sintered Si CTi target is mounted on a direct current sputtering device, and the power per unit area of the target is 0.6 to 20 W / cm ² , deposition pressure 0.
Film formation may be performed in an Ar gas atmosphere with a distance between the target substrates of 15 to 6 Pa and a distance between the target substrates of 30 to 150 mm. If the distance between the target substrates is too short, the film thickness distribution becomes poor, and if it is long, the film formation rate becomes slow. If the power is too low, the film formation rate becomes slow, and if it is too high, the substrate becomes hot. If the gas pressure is too low, the discharge becomes unstable, and if it is too high, the film becomes less dense. Especially when used as an optical recording medium, the refractive index of the film is important, but the refractive index changes by changing the film forming pressure and power, so the film forming conditions should be selected so that the desired refractive index can be obtained. .

The scope of application of the present invention is a recording medium having a recording film and a protective film, and examples thereof include an optical recording medium and a magnetic recording medium. Here, the optical recording medium is a recording medium in which writing and reproduction are performed by using light, and for example, the recording film is Tb-F.
Magneto-optical recording media, which consist of alloys of rare earth elements such as e-Co and iron group transition metal elements, that record information in the direction of magnetization of the recording film, and compounds containing chalcogenite such as Sb-Te-Ge. A phase change recording medium or the like which has a recording film and records by the phase difference, that is, the crystal phase and the amorphous phase. The magnetic recording medium is a recording medium which has a Co alloy or a Fe alloy as a recording film, performs recording with an external magnetic field, and reproduces by utilizing the magnetic field created by the magnetization of the recording film.

The film structure is, for example, a magneto-optical recording medium,
The first protective film, the recording film, the second protective film, and the reflective film are formed in this order on a transparent substrate that is generally used in phase-change recording media, and the protective film, the recording film, and the reflective film are sequentially formed. A film, a first protective film, a recording film, and a second protective film formed in this order, and a base film, a recording film, a protective film, and a lubricating film on a nonmagnetic substrate that is generally used in magnetic recording media. The film formed in this order is mentioned.

[0012]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Examples 1 and 2, Comparative Examples 1 and 2) Particle diameter is 0.01 to 0.2 μ
A Si CTi target having a composition shown in Table 1 having a diameter of 75 mmφ and a thickness of 5 mmt obtained by sintering fine powder of m was prepared and mounted on a DC sputtering device SPF332H type (product name manufactured by ANEVA),
Using this, a power was 200 W, a film formation pressure was 0.67 Pa, a distance between target substrates was 50 mm, and a film was formed on a glass substrate by a DC sputtering method in an Ar gas atmosphere, and the arc discharge in the sputtering chamber was visually observed during the sputtering. As a result, Example 1
No arc discharge was observed in No. 2, but arc discharge was observed in Comparative Examples 1 and 2.

Example 3 and Comparative Example 3 As Example 3,
Using a substrate having a Teflon tape as a mask on a part of a glass substrate, DC sputtering was performed for 30 minutes using the same target as in Example 2 above, and then the Teflon tape was peeled off to obtain a stylus type surface shape. The film thickness was determined by measuring the level difference between the part where the film was formed and the part where the film was not formed by a measuring machine, and the film formation rate was calculated from this to be 74 nm / min. In Comparative Example 3, a film was formed under the same film forming conditions as in Example 3 except that the DC sputtering was changed to the high frequency sputtering, and the film forming rate was 45 nm / min.

(Example 4, Comparative Example 4) Tb ₂₅ -on glass
Fe ₆₉ -Co ₆ film by DC sputtering method in Ar gas atmosphere, film formation pressure 0.67Pa, power 100W, target substrate distance 50mm
A film having a thickness of 100 nm was formed under the film forming conditions of Example 2, and then Example 2 and Comparative Example 1
DC sputtering is performed under the same target and deposition conditions as
A 30 nm film was formed. This was immersed in 1N saline for 1 minute, washed with pure water, dried with a drier, and the pitting density was determined using a 100 × optical microscope. In Example 4, 6 /
cm ² , and in Comparative Example 4, it was 34 pieces / cm ² .

(Examples 5 and 6) SiC having the composition shown in Table 1
A film was formed on a glass substrate by a DC sputtering method under the same conditions as in Example 1 except that a Ti target was used, arc discharge in the sputtering chamber was visually observed during sputtering, and the results are also shown in Table 1.

[0016]

[Table 1]

[0017]

According to the present invention, Si is used as the protective film material.
By using CTi, DC sputtering is possible, the film formation speed is increased, production efficiency is improved, arc discharge is suppressed, and a dense protective film with few pinholes is obtained.
It is possible to provide a high-quality recording medium with few errors during reproduction, and the power source can be simplified compared to the high frequency sputtering method, so that the film forming apparatus can be made inexpensive and its industrial utility value is extremely high.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Tawara 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa Shin-Etsu Chemical Co., Ltd. Corporate Research Center

Claims (6)

[Claims] 1. A recording medium having a protective film and a recording film formed on a substrate, wherein the protective film is made of Si CTi. 2. The recording medium according to claim 1, wherein the content of Ti in Si CTi is 0.5 to 7 atom%. 3. The method of manufacturing a recording medium according to claim 1, wherein the Si CTi protective film is formed by a DC sputtering method. 4. The recording medium is an optical recording medium.
The recording medium according to any one of 1. 5. The recording medium according to claim 4, wherein the optical recording medium is a magneto-optical recording medium. 6. The recording medium is a magnetic recording medium.
The recording medium according to any one of 3 above.