JPH0370294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an information recording medium that records information in bits using a high energy density light beam.

2. Description of the Related Art In recent years, optical disks have been used as information recording media that can be recorded and reproduced in real time, and are highly anticipated as large-capacity, high-density memories. In this method, for example, a laser beam is irradiated onto a disk that rotates at high speed to record bits on an information recording layer, and the bits are read out using reproduction light. Since recording and playback is performed without contact, it has the advantage of not damaging the pickup or disk, and that information can be accessed at high speed.

A TeOx (0<x<2) thin film is a recording film that makes such an optical memory disk possible. This TeOx is a mixture of TeO ₂ and Te. This thin film undergoes phase transformation due to heat generated by laser beam irradiation.
Recorded bits are formed by increasing the reversal rate and decreasing the transmittance. This TeOx thin film has Pd
It is also possible to create a thin film that is even more resistant to temperature and humidity by incorporating additives such as
192003, and can be said to be a very suitable recording film for optical memory disks that require long-term storage stability.

Problems to be Solved by the Invention Figure 3 shows the relationship between recording power and C/N at the inner and outer circumferences of an optical memory disk with an outer diameter of 120 mm, with the disk rotation speed at 1200 rpm. The disk structure in this case is as shown in FIG. 4, in which a recording film 43 mainly made of TeOx is formed on a polycarbonate disk substrate 42 having a tracking guide groove 41, and a polycarbonate protective substrate is further bonded via an adhesive layer 44. The composition of the recording film is such that the x value of TeOx is 1.1 and Pd is contained in an amount of 12 atomic % based on the total content. Figure 3a shows the case of an inner circumference with a diameter of 60 mm, and the highest C/N value (55 dB) was obtained with a recording power of 6 mW. On the other hand, Fig. 3b
shows the case of outer circumference of 110mm in diameter, and 9mW
The highest C/N value (56 dB) was obtained at the recording power of , and the optimum recording power at which the C/N value is highest is different between the inner and outer circumferences. This is because the linear velocity on the outer circumference is faster than on the inner circumference, and in order to optimize the recording power, it is necessary to continuously increase the recording power from the inner circumference toward the outer circumference. However, this requires the addition of a mechanism for changing the recording power depending on the positional relationship of the pickups, which poses the problem of increased costs. Another possibility is to change the rotation speed so that the linear velocity remains constant regardless of the inner or outer circumference, but this would require the addition of a mechanism to change the rotation speed based on the positional relationship of the pickups, which would also be costly. Become.

Therefore, the present invention provides that even if the rotation speed is constant,
It is an object of the present invention to provide an information recording medium that can perform recording while maintaining the highest C/N value at a constant recording power regardless of the inner, middle, or outer circumference.

Means for Solving the Problems In order to solve the above problems, the present invention provides TeOx
In an information recording medium in which a recording thin film mainly composed of (O<x<2) is formed on a disk substrate, the recording thin film contains 5 atomic percent or more of Pd, and the The recording thin film contains a large amount of Pd in a portion near the center of rotation.

Effect: With the above configuration, the recording sensitivity can be made higher in a portion far from the center of rotation than in a portion close to the center of rotation. That is, the increase in linear velocity toward the outer periphery is not compensated for by the improvement in recording sensitivity, and it is possible to maintain an optimum state with a constant recording power regardless of the inner or outer periphery. This applies to the TeOx film.
This is based on the fact that the temperature at which phase transformation occurs (transition temperature) increases as Pd is added.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

The disk in the example of the present invention had the same structure as the disk shown in FIG. 4, and in an optical memory disk with an outer diameter of 120 mm, the composition of the recording film was as follows. The x value of TeOx is set to 1.1, and the Pd content in the entire recording film is increased from the inner circumference to the outer circumference.
The gradient was changed as shown in the figure. A vacuum deposition method is one method for realizing such a recording film. Three evaporation sources, Te, Teo ₂ and Pd, were prepared, and for Te and TeO ₂ , a uniform thin film (130 nm) was formed over the entire disk, and for Pd, as shown in Figure 1. It is formed to have a slope in the radial direction as shown. The optical memory disk thus formed was rotated at 1200 rpm, and the relationship between recording power and C/N was determined, and the results are shown in FIG. Figure 2 a shows the inner circumference (Pd) with a diameter of 60 mm.
content: 15 atomic%), and the highest C/N value was obtained at a recording power of 6 mW.
On the other hand, Fig. 2b shows the case of the outer circumference with a diameter of 110 mm (Pd content: 10 atomic%), and the highest C/N value is obtained at a recording power of 6 mW, similar to the case of the inner circumference in Fig. 2a. Therefore, it is possible to maintain the highest C/N value at a constant recording power regardless of the inner, middle, or outer circumference of the disk.

In addition, if the Pd content is 5 atomic% or more,
We have confirmed that there are no problems with the long-term storage of the disk.

Effects of the Invention The present invention provides an information recording medium in which a recording thin film mainly composed of TeOx (0<x<2) is formed on a disk substrate. Far part (outer circumference)
On the other hand, the recording thin film is set to contain a large amount of Pd, an additive substance, in the near part (inner periphery), so that the recording sensitivity is continuously improved from the inner periphery to the outer periphery, and at a constant rotation speed. , the highest C/ at a constant recording power, regardless of inner, middle, or outer circumference.
It is possible to record while maintaining the N value. As a result of the above, there is no need to add a complicated mechanism to the recording/reproducing device, and its industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing the content of Pd in an information recording medium according to an embodiment of the present invention, and FIG. 2 is a C/N of the inner and outer circumferences of the information recording medium obtained according to the present invention.
FIG. 3 is a characteristic diagram showing the relationship between C/N and recording power of a conventional information recording medium, and FIG. 4 is a sectional view of the information recording medium. 42...Disk substrate, 43...Recording film.

Claims (1)

[Claims] 1 A recording thin film mainly composed of TeOx (0<x<2) is formed on the disk substrate, and Pd is added to the recording thin film.
5 atomic % or more of Pd, and the recording thin film contains more Pd in a portion near the rotation center than in a portion radially far from the rotation center.