JPH0536114A - Optical disk medium - Google Patents

Abstract

PURPOSE:To record information with a specific recording power without depending on linear velocity on an optical disk and to reduce the limit of laser power at an outer circumference by making film thickness of a heat radiating film thinner from the center of the disk to the outer circumference. CONSTITUTION:A information recording film 3 is formed with the protective film 2 on the optical disk substrate 1 made of glass, plastics or the like and the heat radiating film 5 is formed with the protective film 4 on the information recording film 3. Thickness of the radiating film 5 is thinner in order from the center of the optical disk to the outer circumference. The thicker film thickness of the heat radiating film 5 is, the larger recording power is. They, by changing thickness of the inner and outer circumference of the heat radiating film 5, it is possible to change level of heat releasing of the inner and the outer circumference of the optical disk and recording power is kept constant without depending on linear velocity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical disk medium.

[0002]

2. Description of the Related Art The structure of a conventional optical disk medium is shown in FIG. As shown in FIG. 4, the structure of a conventional optical disc medium is such that a protective film 2, an information recording film 3, and an optical disc substrate 1 are provided on an optical disc substrate 1.
The protective film 4 and the heat dissipation film 5 are laminated.

By the way, the heat radiation film 5 has the same thickness from the inner circumference to the outer circumference of the optical disk.

[0004]

The optical disk medium is used with a constant rotational speed of the disk in order to increase the access speed. When an optical disc is used at a constant rotation speed,
The linear velocity will change between the inner and outer circumference sides of the optical disk medium.

Actually, a 1800 optical disc of 130 mm is used.
When rotated by rotation, the inner circumferential linear velocity is 5.3 m / s, and the outer circumferential linear velocity is about double to 11.6 m / s.

Since the recording power for recording information changes depending on the linear velocity of the optical disk medium, when the linear velocity becomes high as shown in FIG. 5, high recording power is required for recording.

Since the emission power of the semiconductor laser used for recording on the optical disk is limited, it becomes impossible to record information on the optical disk at a high linear velocity. Therefore, the number of rotations used for the optical disc medium is limited.

Specifically, the power of a semiconductor laser currently available is about 40 mW (wavelength: 780 nm), so that the magneto-optical disk medium has a limit of 2400 rotations.

An object of the present invention is to provide an optical disk medium which can change the recording film structure of the optical disk medium to eliminate the difference between the inner and outer sides of the recording power and can record at a high linear velocity.

[0010]

In order to achieve the above object, an optical disk medium according to the present invention is an optical disk medium having a protective film, an information recording film, and a heat dissipation film laminated on an optical disk substrate. The heat dissipation film is thinned from the center of the disk toward the outer circumference.

The film thickness ratio of the film thickness on the inner circumference and the film thickness on the outer circumference of the heat dissipation film is 1.1 or more and 5 or less.

[0012]

In the present invention, how to escape the heat generated by the laser power is controlled by changing the film thickness of the heat radiation film.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, an information recording film 3 is formed on an optical disk substrate 1 made of glass, plastic or the like via a protective film 2, and a heat dissipation film 5 is formed on the information recording film 3 via a protective film 4. There is.

Here, the protective films 2 and 4 and the information recording film 3
Is set to have the same film thickness from the inner circumference to the outer circumference of the optical disk.

In this embodiment, the thickness of the heat dissipation film 5 is reduced from the center of the optical disk toward the outer circumference.

In this embodiment, the film thickness ratio of the film thickness on the inner circumference side to the film thickness on the outer circumference side of the heat dissipation film 5 is set to 1.1 or more and 5 or less.

As shown in FIG. 2, the recording power increases as the thickness of the heat dissipation film 5 increases.

According to the present embodiment, by changing the film thickness on the inner and outer peripheries of the heat dissipation film 5, it is possible to change how the heat escapes on the inner and outer peripheries of the optical disk, as shown in FIG. The recording power can be kept constant regardless of the linear velocity.

[0021]

As described above, according to the present invention, information can be recorded on an optical disk with a constant recording power regardless of the linear velocity.

As a result, the limit of the laser power on the outer circumference can be reduced. Further, since recording can be performed with a substantially constant laser power, the laser power control in the device becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a relationship between a film thickness of a heat dissipation film and recording power.

FIG. 3 is a conceptual diagram showing a relationship between linear velocity and recording power according to an example of the present invention.

FIG. 4 is a cross-sectional view showing a conventional example.

FIG. 5 is a conceptual diagram showing the relationship between linear velocity and recording power in a conventional example.

[Explanation of symbols] 1 Optical disc media 2,4 protective film 3 Information recording film 5 Heat dissipation film

Claims (2)

[Claims] 1. An optical disk medium having a protective film, an information recording film, and a heat dissipation film laminated on an optical disk substrate, wherein the thickness of the heat dissipation film is reduced from the center of the disk toward the outer circumference. Optical disc medium. 2. The optical disk medium according to claim 1, wherein the film thickness ratio of the film thickness on the inner circumference and the film thickness on the outer circumference of the heat dissipation film is 1.1 or more and 5 or less.