JPS62185266A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance without spoiling recording and reproducing characteristics by adding tungsten into an optical recording layer of a recording layer recording medium constituted by providing the optical recording layer on a substrate. CONSTITUTION:The tungsten is added into the optical recording layer of the optical recording medium constituted by providing the optical recording layer on the substrate. The optical recording layer which can be improved in the corrosion resistance by the addition of the tungsten is exemplified by an amorphous magnetic alloy essentially consisting of a magnetic material which exhibits a magnetooptic effect. The improvement in the corrosion resistance is particularly remarkable with the amorphous magnetic alloy of >=1 kinds of transition metals and >=1 kinds of rare earth metals. The amt. of the tungsten to be added at which the corrosion resistance is improved without deteriorating the recording and reproducing characteristics of the optical recording layer is in a 1-30wt%, more preferably 5-20wt% range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium that can perform recording and reproduction using a light beam and has excellent corrosion resistance.

[Conventional technology]

Conventionally, optical recording media used in optical disks include rare earth-transition metal alloy thin films, reducing oxide sources 11Q such as chalcogen compounds that utilize phase transition from amorphous to crystalline, and heat sources. Recording media, thermoplastic recording media, etc. are known. For example, as a magneto-optical recording medium formed of a rare earth-transition metal alloy thin film, M
nB1. Polycrystalline thin films such as MnCuB1, GdCo,
GdFe, TbFe, Dyke.

GdTbFc, TbDyFe, GdFeCo, T
Amorphous thin film such as bFcCo, GdTbCo, Gd1
Late crystal thin films such as G are known.

Among these thin films, the film forming efficiency when producing a large-area thin film at a temperature near room temperature, -7 writing efficiency for writing signals with small photothermal energy, and -) the written signal Considering the readout efficiency for reading out with a good S/N ratio, the amorphous thin film is recently considered to be excellent as a photothermal magnetic recording medium. GdTbFe has a large Kerr rotation angle and a Curie point of around 150° C., so it is suitable as a photothermal magnetic recording medium.

As a result of research aimed at improving the Kerr rotation angle, the inventor discovered that GdTbFc(:o) is a magneto-optical recording medium with a sufficiently large Kerr rotation angle and capable of reading with a good S/N ratio. Ta.

(Problems to be Solved by the Invention) However, in general, amorphous magnetic materials used in magnetic recording media, including magneto-optical recording media such as GdTbFe, have a drawback of poor corrosion resistance. When exposed to air or water vapor, the magnetic properties deteriorate and eventually become completely oxidized and become transparent.This problem is common not only to magneto-optical recording media, but also to the optical recording media mentioned above. This is an issue.

In order to eliminate these drawbacks, various types of protective layers have been conventionally provided on the optical recording layer, or disk-shaped optical recording with an air sandwich structure or a bonded structure in which the magnetic recording layer is sealed with an inert gas has been developed. Although media have been proposed, they have not been able to provide sufficient corrosion resistance for practical use.

The purpose of the present invention is to improve the recording/reproducing characteristics by
We provide optical recording media with improved corrosion resistance! 1■
It is in.

(Means for Solving the Problems) The present invention provides an optical recording layer material in which an optical recording layer is provided on a substrate, +ii
The present invention is an optical recording medium characterized in that tungsten is added to the optical recording layer.

[Effect]

In accordance with the present invention, the optical recording layer has its recording +IT
Corrosion resistance against moisture and oxygen is improved without any substantial reduction in raw properties. The reason why corrosion resistance is improved in this way is that by adding tungsten, even if the optical recording layer begins to corrode due to moisture or oxygen that has entered from the outside, the tungsten immediately forms a passive film, preventing further corrosion. This is thought to be due to the fact that the progress of the process is suppressed and the pinholes that occur are also closed. Therefore, the pit error rate, which indicates the degree of film defects due to pinholes, etc., hardly changes from the initial state.

[Embodiment]

In the present invention, examples of the optical recording layer whose corrosion resistance is improved by adding tungsten include those whose main component is a magnetic material exhibiting a magneto-optic effect, such as an amorphous magnetic alloy. In particular, amorphous magnetic alloys of one or more transition metals and one or more rare earth metals, such as Gd(:o,
GdFe, TbFe, DyFe, GdTbFe%T
bDyFc, GdTbCo, GdFeCo.

TbFe(:o, TbDyFeCo, GdTbFe
When the present invention is applied to an optical recording layer made of Co,
Its corrosion resistance is significantly improved. The amount of tungsten added (ratio to the total amount of the optical recording layer) that can improve the corrosion resistance without reducing the recording/reproducing characteristics of the optical recording layer is 1 to 30 @
%, preferably in the range of 5-20%.

Typical methods for manufacturing the optical recording medium of the present invention include depositing an optical recording layer on a substrate made of glass, plastic, etc., either directly or through layers having various functions, such as by vacuum evaporation or ion deposition. Examples include a method of forming a film using a rating method, a sputtering method, a CVD method, or the like. When carrying out this method, it is advantageous to use a multi-source deposition source consisting of tungsten and other optical recording layer materials.

(Effects of the Invention) As explained below, the optical recording medium of the present invention in which tungsten is added to the optical recording layer has extremely excellent corrosion resistance, can withstand long-term use, and is extremely useful in practical use. It's convenient.

〔Example〕

Example 1 An optical disc according to the present invention whose partially omitted cross-sectional view is shown in FIG. 1 was produced. First, 200mmφ, thickness 1.1
A spiral guide groove is drilled into a 1-mm S'f plate glass by a method known as the 2P (photopolymer) method.
An ultraviolet curing resin layer 2 was formed, and this was used as a disk substrate. 7. 900 layers of Sin 3 were deposited as an underlayer on the ε substrate using a continuous acid single-layer apparatus. nS 4 steamed by 800 people 7
It was. Continuing: A first target consisting of four pieces of 10 mm square tungsten arranged on top of a 125 mmφ FcCo alloy (atomic ratio Fc: (:o=9:1);
GdTb alloy of 25fflIIlφ (atomic ratio Gd:Tb
= 1:5).
An optical recording layer 5 made of an amorphous magnetic alloy was formed by Z source sputtering. The tungsten content h1 in the recording layer at this time was about 6%. Subsequently, 600 layers of ZnS 6 and 800 layers of Si07 were applied to the optical recording layer 5.
People, eight! 500 layers of Sin 8 and 2000 layers of Sin 9 were sequentially deposited. This disc was bonded to a similarly prepared disc via an adhesive so that the S:09 side was on the inside to produce an optical disc.

Example 2.3 The present invention was carried out in the same manner as in Example 1 except that a polymethyl methacrylate substrate (Example 2) or a polycarbonate substrate (Example 3) was used instead of soda lime glass as the disk substrate. Two optical discs were manufactured.

Example 4 An optical disk according to the present invention was manufactured in the same manner as in Example 1 except that Tb with a diameter of 125 mm was used as the second target.

Example 5.6 All the results were the same except that a polymethyl methacrylate substrate (Example 5) or a polycarbonate substrate (Example 6) was used instead of blue plate glass as the disk substrate.
Two optical discs according to the present invention were manufactured in the same manner as 'es Example 4.

Example 7 As the first target, I
An optical disc according to the present invention was manufactured in the same manner as in Example 1 except that four pieces of n2 square tungsten pieces were used.

Example 8.9 All methods were the same as in Example 7, except that a polymethyl methacrylate substrate (Example 8) or a polycarbonate plate (Example 9) was used instead of glass as the disk substrate. Two optical discs according to the present invention were manufactured.

Comparative Examples 1 to 9 Nine optical disks were formed in the same manner as in Examples 1 to 9 except that four 10 mm square tungsten pieces were not added to the first target in the continuous film forming apparatus. Manufactured.

The optical recording media prepared in Example 1 and Comparative Example 1 were placed in a constant temperature and humidity chamber at a temperature of 70° C. and a humidity of 85% R1+, and a corrosion resistance test was conducted. The results are shown in FIG. In FIG. 2, the horizontal axis indicates the test time Cf1L (time (H)), and the vertical axis indicates the change in pit error rate. Here, the more severe the increase in pit error rate, the more advanced the corrosion. In FIG. 2, 11 indicates the test results of Example 1, and 2 indicates the test results of Comparative Example 1. Corrosion resistance tests were also conducted for all other Examples and Comparative Examples, and the results of the corresponding Examples and Comparative Examples are shown in a diagram with the same vertical and horizontal axes as in Figure 2. , the figure shows the same results as Figure 2.

It is clear from the above results that the optical recording medium of the present invention is
It can be seen that it has excellent corrosion resistance.

[Brief explanation of drawings]

FIG. 1 is a partially omitted schematic sectional view of an embodiment of the optical recording medium of the present invention. FIG. 2 is a diagram showing changes over time in the pit error rates of Example 1 and Comparative Example 1. ! : ノ, ζ plate 2: Ultraviolet curing resin layer 3, 7
．． 9: SiO layer 4, 6:7, nS layer 5: Optical recording layer 8: 8L layer lO: Adhesive 11: Curve showing change in pit error rate of Example 1 12: Comparative example 1 Curve showing changes in pit error rate

Claims (1)

Claims: 1) An optical recording medium comprising an optical recording layer provided on a substrate, characterized in that tungsten is added to the optical recording layer. 2) The optical recording medium according to claim 1, wherein the optical recording layer is made of an amorphous magnetic alloy comprising one or more transition metals and one or more rare earth elements.