JPH0259526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording medium in which information is recorded using a light beam, and in particular to an optical information recording medium that is a disk-shaped recording medium and has recording sensitivity gradually increased from the inner circumference to the outer circumference. It is related to.

As optical information recording media, there are perforated recording media that use Te alloy thin films or dye thin films, and density type recording media that utilize amorphous-crystalline transition or magnetic domain reversal, but both media are difficult to store information. The light energy required to record is constant at any location on the medium. When an optical information recording medium is disk-shaped and information is recorded and reproduced by rotating the medium at a constant angular velocity, the linear velocity at the outer circumference is higher than that at the inner circumference, so the optical energy required to record the information is becomes larger toward the outer periphery. Generally, it is necessary to gradually increase the recording energy from the inner circumference to the outer circumference to perform uniform recording, and it is necessary to change the optical energy depending on the information recording position.

The present invention has been made to improve these drawbacks, and when recording information on a disc-shaped optical information recording medium that rotates at a constant angular velocity, it is not possible to change the optical energy according to the information recording position as in the conventional method. The object of the present invention is to provide an optical information recording medium on which uniform recording can be performed even without the use of an optical information recording medium.

Therefore, the present invention utilizes Ge _1-x Sn _x Te (0<x
≦0.7) It uses a thin film whose main component is an alloy.
The feature lies in that the value of x gradually increases from the inner circumference to the outer circumference of the disc-shaped recording medium.

Hereinafter, the present invention will be explained in detail based on examples.

FIG. 1 shows an example of an apparatus for manufacturing an optical information recording medium according to the present invention. A rotating substrate holder 12 is provided in the vacuum chamber 11, and a disk-shaped substrate 13 is mounted on the substrate holder 12.
It is installed below the . A first evaporation source 14 is placed at a distance H ₁ directly below the central axis of the disk-shaped substrate 13 and is used to evaporate GeTe. The amount of GeTe evaporated from the evaporation source 14 is controlled by changing the output of the power source 16. The second evaporation source 15 is placed horizontally at a distance L from the first evaporation source 14 and is made of SnTe.
used to evaporate. from evaporation source 15
The amount of SnTe evaporated is controlled by changing the output of the power source 17.

In the above configuration, the amount of GeTe particles evaporated from the evaporation source 14 flying to the substrate 13 is
It is large at the center and gradually decreases towards the periphery. The ratio of the amount of flying GeTe particles at the inner and outer peripheries can be adjusted to a desired value by changing the distance H _1. If H ₁ is increased, the ratio of the GeTe particles at the outer periphery to the inner periphery _increases . approaches 1. Conversely, if H ₁ is made small, R ₁ moves away from 1. Similarly, the amount of SnTe particles evaporated from the evaporation source 15 arriving at the substrate 13 can be made larger at the outer periphery and smaller at the inner periphery by changing L and H ₂ . and
By selecting appropriate values for H ₁ , H ₂ , L and the outputs of the power supplies 16 and 17, a Ge _1-x Sn _x Te alloy thin film is formed on the disc-shaped substrate 13 with the same film thickness on the inner and outer peripheries. As a result, an alloy thin film having a composition in which x continuously increases from the inner circumference to the outer circumference is obtained.

Here, the Ge _1-x Sn _x Te alloy thin film used in the aforementioned application, which was proposed by the present applicant as an "optical information recording medium" dated April 16, 1980, has a value of x as shown in FIG. As the temperature increases, the temperature at the transition point decreases as shown by curve 21, and the light energy required to record information decreases as shown by curve 22. Therefore, in the disc-shaped optical information recording medium having the above-described structure, information can be recorded continuously from the inner circumference to the outer circumference with small optical energy. Therefore, when recording information by rotating the optical information recording medium obtained as described above at a constant angular velocity, the optical information recording medium obtained as described above can be rotated at a constant angular velocity to record information without changing the optical energy depending on the position where information is recorded as in the past. It is possible to record information uniformly at any position on the medium.

The value of x is usually between 0 and 0.7, but the reason for this is that when x > 0.7, as shown in curve 21 in Figure 2,
This is because the amorphous-crystalline transition point of the Ge _1-x Sn _x Te alloy thin film is near room temperature, and the transition may occur before information is recorded. Therefore, when used in a high-temperature ambient environment, it is necessary to further reduce the maximum value of x. If the inner diameter of the area for recording information in a disc-shaped recording medium is r ₁ and the outer diameter is r ₂ , it is generally selected so that r ₂ /r ₁ = 2, and the linear velocity ratio during rotation of the medium at the inner and outer peripheries is r Proportional to ₂ /r ₁ ,
The energy ratio required to record information is √ _{2 1}
The value will be in the range ~r ₂ /r ₁ . Therefore, as shown in FIG. 2, the value of x may be selected to be small at the inner circumference and large at the outer circumference so that the ratio of recording light energy is 1.4 to 2. For example, when x=0.1 at the inner circumference, it is appropriate that x=0.4 to 0.6 at the outer circumference.
The value of x is from x=0 to the inner circumference when r ₂ /r ₁ = 2 above.
0.25, x can be selected from 0.3 to 0.7 at the outer periphery.

Note that the evaporation source 14 and the evaporation source 15 can be either a resistance heating type evaporation source or an electron beam heating type evaporation source. Furthermore, the recording thin film manufacturing method is not limited to the vacuum evaporation method shown in this example, but may also be a sputtering method, in which case it is sufficient to simply replace the target at the position of the evaporation source shown in Figure 1 as the source of particle generation. . In this case, the particle generation source is not limited to being below the turntable; for example, it may be placed above the turntable by turning the positional relationship shown in Figure 1 upside down, or it may be placed sideways to the side of the turntable. Of course, this is a good thing.

As described above, in the disc-shaped optical recording medium according to the present invention, the recording sensitivity increases continuously from the inner circumference to the outer circumference, so that the energy required to record information decreases from the outer circumference. Since it is small in size, it is possible to record information uniformly at any position on the medium.

[Brief explanation of drawings]

FIG. 1 is an example of an apparatus for manufacturing the optical information recording medium of the present invention, and FIG. 2 is a diagram showing the relationship between the recording film composition of the optical information recording medium of the present invention and the recording light energy. 12... Turntable, 13... Optical information recording medium, 14, 15... Evaporation source.

Claims (1)

[Scope of Claims] 1. A disk-shaped optical information recording medium that has a base and a thin film formed on the base and records information by irradiating the thin film with a light beam, the thin film being Ge _1-x Sn _x Te
(0<x≦0.7), and the value of x of the alloy film is gradually increased from the inner circumference to the outer circumference of the disk-shaped optical information recording medium. An optical information recording medium characterized by: 2. A turntable that rotates a disk, and a position facing the disk mounting surface of the turntable on an extension of the rotation axis of the turntable.
An apparatus for producing an optical information recording medium, wherein a GeTe particle generation source is provided, and a SnTe particle generation source is provided at a position away from the extension line and facing the disk mounting surface.