JPH03171427A - Method for initial crystallization of phase-transition type information recording medium - Google Patents

Abstract

PURPOSE:To obtain a uniform state of initial crystallization over the whole recording layer by irradiating the information recording medium with a beam for initial crystallization in a manner that the irradiation power of the beam differs for the outer circumferential area and for the center area of the medium. CONSTITUTION:Laser light from a semiconductor laser source 13 is changed into a parallel beam by a collimator lens 14, directed to enter an objective lens 16 by a beam splitter 15, and focused on a recording layer of a disk substrate 10. A position detector 17 detects the position of the optical unit 12 and sends signals according to the detected position to a controller 18. The controller 18 controls output of the semiconductor laser source 3 according to the input signal from the detector, for example, the output of the laser light gradually increases from the center part of the disk substrate to the outer circumference. By this method, the recording layer of the disk substrate can be uniformly irradiated with the beam in a constant energy density. Thus, the whole recording layer can be initially crystallized at the same level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Field of Application) The present invention is to irradiate a recording layer with a light beam such as a laser beam or an electron beam to reverse phase changes between different phases. The present invention relates to an initial crystallization method for a phase change information recording medium in which information is recorded and erased by causing the crystallization to occur.

(Prior Art) So-called phase change type media have been developed as information recording media capable of recording and erasing information. Recording is performed on this phase change type information recording medium as follows. First, the entire surface of the information recording medium is irradiated with a light beam to bring the recording layer into a highly crystalline state (a state in which atoms are arranged relatively correctly, hereinafter referred to as a crystalline state). By irradiating this recording layer with short pulsed light, that portion is heated and rapidly cooled, resulting in a state in which the crystallinity is reduced (a state in which the atomic arrangement is disordered, hereinafter referred to as an amorphous state). Since each part has a different atomic arrangement structure, the optical properties such as reflectance and light transmittance are different, and information is written in the recording layer.

Furthermore, the written information can be erased by irradiating the information recording portion of the recording layer with long pulsed light and slowly cooling it.

In this way, information can be recorded and erased using phase changes, and the information can be reproduced by detecting the optical characteristics of f' [corresponding to this change.

In addition, the so-called overwrite method, which uses a light beam consisting of continuous light and short pulsed light to erase information written on the recording layer and write new information at the same time, has been attracting attention recently. The above-mentioned phase change can also be realized in

Incidentally, the recording layer of such a phase change information recording medium is formed by a vacuum process such as a sputtering method or a vacuum evaporation method.
Immediately after film formation, the film is in an amorphous state, and this amorphous state is stable. In order to initially crystallize such an amorphous recording layer, it is necessary to irradiate the recording layer with light having higher energy than the energy used when erasing information. Normally, the method of initial crystallization of the recording layer is to irradiate the track forming part of the recording layer with continuous light multiple times while rotating the disc, gradually turning that part into a viscous substance, and then repeating this operation to the entire disc. Another example is one in which the entire recording layer is crystallized by scanning a light source while irradiating a relatively high-intensity light beam while rotating the disk.

(Problem to be Solved by the Invention) However, in such a method, if the rotational speed of the disk is constant, that is, the angular velocity of the disk is constant, the rotational speed of the disk increases from the outer circumference toward the center of the disk. The process slows down gradually, so if the initial crystallization of the entire disk is performed using a light beam with constant energy,
The degree of crystallization differs between the outer peripheral portion and the central portion of the recording layer. Therefore, the optical characteristics such as the reflectance of the recording layer differ between the outer circumferential portion and the central portion of the disk, resulting in a difference in initialization level.

As a result, when information is recorded or erased, information is left unerased or recorded incorrectly.

The present invention has been made in view of this point, and has an eleventh object to provide an initial crystallization method for an information recording medium that can initially crystallize the entire recording layer to the same level.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a film that contains an amorphous phase in the as-formed state and that changes phase in different phases when irradiated with a light beam to record and record information. An initial crystallization method for an information recording medium, which comprises crystallizing the recording layer by irradiating a disk-shaped phase change information recording medium with a recording layer to be erased with a light beam, the method comprising: The information recording medium is characterized in that the beam is irradiated with different irradiation powers on the outer circumferential portion and the central portion of the information recording medium.

(Function) According to the method for initial crystallization of an information recording medium of the present invention, the irradiation of the light beam for initial crystallization is performed such that the illumination power is different between the outer peripheral part and the central part of the information recording medium. irradiated.

That is, initial crystallization is performed while increasing or decreasing the power of the light beam so that a constant energy density is obtained depending on the linear velocity of the information recording medium. Therefore, the degree of crystallization is the same in the outer peripheral portion and the central portion of the information recording medium, and the same level of initial crystallization is performed throughout the recording layer.

As a result, when recording or erasing information, it is possible to sufficiently prevent information from remaining unerased or from being erroneously recorded.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view of an information recording medium used in the method according to the present invention. 1 in the figure is a disk substrate. The disk substrate 1 is made of a transparent material that does not change much over time, such as glass or a plastic material such as polymethyl methacrylate resin or polycarbonate resin.

A recording layer 2 is provided on the surface of a disk substrate 1.

Materials forming the recording layer 2 include Te, Se, Ge,
Metals such as Sb, In, semimetals, or GeTe
Examples include alloys such as Sb and InSbTe. These metals, alloys, etc. can undergo a phase change between a crystalline phase and an amorphous phase by being irradiated with a light beam under different conditions.

In addition, the recording layer formed using these materials has the characteristics of a large reproduced signal, high recording sensitivity, and high stability of the amorphous state as a recording state. Furthermore, since these recording layers have a high crystallization rate, their initial crystallization rate is high. Such a recording layer is formed by a sputtering method, a vacuum evaporation method, or the like.

A right machine object protection IW 3 is provided on the surface of the recording layer 2. This preservation layer 3 is provided to preserve the surface of the recording layer 2 during handling of the information recording medium.通')
:9, the protective layer 3 uses an ultraviolet curing resin.

Furthermore, as shown in FIG. 3, inorganic protection layers 4.5 may be provided between the cutting board 1 and the recording layer 2 and between the recording layer 2 and the storage layer 3 so as to support the recording layer 2. can. Feed for the inorganic protective layer 4.5 includes metal or metalloid oxides, fluorides, sulfides, and nitrides. The inorganic protective layers 4 and 5 are provided to prevent the recording layer 2 from deteriorating over time.

Furthermore, as shown in FIG. 4, it may be of horizontal structure in which a layer 6 is provided between the inorganic protective layer 4 and the organic protective layer 3.

Next, an example of the initial antagonization method for the information recording medium of the present invention will be explained with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of an apparatus used in an embodiment of the method of the present invention. In the figure, 10 is a disk substrate. Disk prefecture board 10
is rotatably mounted on a motor 1 which rotates a disk substrate [0]. An optical device 12 for condensing laser light onto the disk substrate 10 is installed above the disk substrate 10.

The optical device 12 includes a semiconductor laser source] 3, a collimator lens 14, a beam splitter 15, and a phantom lens 16.
It is equipped with The collimator lens 14 is located on the side of the semiconductor laser source 13, and the beam splitter 15 is located on the side of the collimator lens 14 so as to receive the light emitted from the semiconductor laser source 13 through the collimator lens 14. Further, the objective lens 16 is located below the beam splitter 15.

A position detection means 17 is installed below the optical device 12. This position detection means 17 is connected to a control means 18. The control means 18 is connected to the semiconductor laser source 13 in order to control the power of the beam light irradiated onto the recording layer.

In such an apparatus, initial crystallization is performed as follows.

First, a laser beam is emitted from the semiconductor laser source 13.

This laser light becomes parallel light by passing through a collimator lens]4. The direction of this parallel light is changed by the beam splitter 15, reaches the objective lens 16, and is thereby focused onto the recording layer of the disk substrate 10.

On the other hand, the position detection means]7 detects the position of the optical device 12 and sends a signal corresponding to the position to the control means 18. The control means 18 adjusts the output of the semiconductor laser source 3 based on the manually inputted signal.

For example, the output of the semiconductor laser is gradually increased from the center to the outer periphery of the disk irregular plate.

In this way, the beam light can be irradiated with a constant energy density at any location on the recording layer of the disk base plate. Therefore, the entire recording layer is initially crystallized to the same level.

Information is recorded on the initially crystallized recording layer by irradiating the recording layer with a light beam having a short pulse width and heating and rapidly cooling the target portion to change it into an amorphous state. Further, erasing of information is performed by shining a light beam with a lower power than that used during information recording, for example, a light beam with a longer pulse width, onto the recording layer I1. In addition, to reproduce recorded information, the recording layer is irradiated with a light beam with a lower power than when erasing information, and the optical characteristics, such as the difference in reflectance, between the information recording area and the non-information recording area are detected. Do by doing.

Test Example Initial crystallization of an information recording medium was actually carried out using the apparatus shown in FIG.

First, an lnsb alloy was formed into a film by sputtering on the surface of a polycarbonate resin substrate having an outer diameter of 5.25 inches. Next, the ]0 InSb alloy layer was coated with an ultraviolet curing resin and cured with ultraviolet light to form an organic protection layer. In this way, a disk substrate was produced.

The obtained disk substrate was placed in the apparatus shown in FIG.

The disk substrate was rotated at 180 O rpm.

Initial crystallization was performed by irradiating the rotating disk substrate with a beam of light over a distance of 30 mm to 60 m+e from the center of the disk substrate while scanning with an optical device. At this time, the energy density of the beam light is always 2.7 nJ/c.
The power of the beam light was adjusted so that -.

The relationship between the distance from the center of the disk substrate and the reflectance of the recording layer at this time is shown by characteristic line 20 in FIG. For comparison, the relationship between the distance from the center of the disk substrate and the reflectance of the recording layer is shown when initial crystallization was performed using a beam with an optical power of 12 mW without adjusting the power at the beam destination. is also shown in FIG. 5 as a characteristic line 21.

As is clear from FIG. 5, the reflectance of the recording layer initially crystallized by the method of the present invention is constant in any part 11 of the recording layer, and the entire recording layer is initially crystallized to the same level. Met. On the other hand, when initial crystallization is performed without adjusting the power of the beam light, the reflectance varies depending on the location of the recording layer, and the level of initial crystallization varies depending on the location of the recording layer. It was something.

[Effects of the Invention] As explained above, the method for initial crystallization of an information recording medium of the present invention can initially crystallize the entire recording layer to the same level.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of an apparatus used in an embodiment of the method of the present invention, FIGS. 2 to 4 are cross-sectional views of an information recording medium used in the method of the present invention, and FIG. The figure is a graph showing the relationship between reflectance and distance from the center of the disk substrate. 1, 10... Disc substrate, 2... Recording layer, 3...
・Organic substance protective layer, 4.5... Inorganic substance protective layer, 6...
Reflective layer, 11... Motor 12... Optical device, 1
3... Semiconductor laser source, 14... Collimator lens, 15... Bi12 splitter, 1 6... Objective lens, 1 7... Position detection means, 18... Control means.

Claims (1)

[Claims] A disk-shaped phase-change information recording medium that includes a recording layer that contains an amorphous phase in the as-formed state and that changes phase between different phases when irradiated with a light beam to record and erase information. A method for initial crystallization of an information recording medium in which the recording layer is crystallized by irradiating a light beam, the light beam for initial crystallization having an irradiation power that is different from the outer periphery and the center of the information recording medium. 1. A method for initial crystallization of a phase change information recording medium, characterized in that irradiation is performed in different ways.