JP2007004902A - Method and apparatus for initializing information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To initialize a recording medium having a recording film high in sensitivity to heat. <P>SOLUTION: In the method and apparatus for initializing the recording medium, an oval laser spot having longitudinal and lateral directions is formed, and is arranged so that the longitudinal direction forms an angle other than parallel with a direction of a recording track. As for the longitudinal light intensity distribution of the elliptic laser spot, the maximum value of the light intensity is represented by H1 (H1>0), and the left end and the right end in the moving direction are defined as a front end part and a rear end part, respectively, and the light intensity of the front end part is represented by H2 (H2>0), the light intensity of the backward end part is defined as H3 (H3>0), and an average value of the light intensity except that in the backward end part is defined as H4 (100>H4>0). When the front end part H1 is defined as 100%, a width of a gradient part of the front end part is represented by W1, and a width of a gradient part of the backward end part is represented by W2, the relationships among the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 are set to H2≥90% or H3≥90%, H4≥85%, W1≤4um or W2≤4um on the basis of 100% of the light intensity H1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an initialization method and initialization apparatus for an information recording medium capable of recording information by a recording beam such as a laser beam, and more particularly to an information recording medium having a recording film more sensitive to heat. The present invention relates to an initialization method and an initialization apparatus that can be initialized to high quality.

  2. Description of the Related Art In recent years, a phase change type disc having a phase change type recording film whose reflectivity is changed by irradiation heat of a laser spot has been put to practical use as an rewritable large recording capacity optical disc. This phase-change optical disc records and reproduces data using the reversible characteristics of the crystal and amorphous film of the recording surface film by changing the reflectivity by changing the phase of the recording surface by heat by irradiating a laser spot. It is.

  The recording film of this phase change type optical disk is formed by a sputtering method or the like in the disk manufacturing process, and the recording film immediately after the formation is in an amorphous state called As-deposited and has a low film surface reflectance. A crystal suitable for recording / reproducing information in the process of gradually heating or cooling the recording film after the recording film is formed because automatic focus control and tracking control become unstable during recording / reproducing operation in an optical disc apparatus or the like. A process of changing the disk recording film surface to the state is necessary, and this process is called initialization.

  In such a phase change type optical disc that records information by utilizing the phase change between the crystal and the amorphous phase of the recording film, high-speed erasing that can be crystallized in approximately the same time as the laser irradiation time for recording. When a recording film capable of recording is used, the power of one energy beam is divided into a reading power level and two levels higher than the reading power level, that is, a high power level and an intermediate power level. Thus, it is possible to perform so-called overwriting (rewriting by overwriting) in which new information is recorded while erasing existing information.

  Initialization (initial crystallization) of a phase change optical disk having such a recording film is performed by, for example, forming an elliptical laser spot 3 from a high-power laser beam having an output of 500 mW to 10 W, as shown in FIG. Irradiation is performed so that the longitudinal direction of the elliptical laser spot 3 substantially coincides with the radial direction of the optical disk 4, and the recording film is controlled so as to be in a temperature range between the crystallization temperature and the melting point or less. The rotation and the laser spot 3 are performed by moving the laser spot 3 so as to slightly overlap each other from the inner circumference side of the disk to the outer circumference side as in the traveling direction A.

Incidentally, as a document describing a technique related to initialization of the phase change optical disc, for example, the following patent document can be cited.
JP-A-2005-071514

  In recent phase change optical discs, as the speed of information recording media increases, the film material becomes more sensitive to heat. For this reason, when initialization is performed by the conventional method described above, the front end of the laser spot is changed. There was a problem that the trace of initialization remained at the rear or rear end. This will be described with reference to the drawings. As shown in FIG. 2, when the laser spot 3 is moved in the traveling direction A, which is the radial direction of the optical disk 4, the front end of the laser spot 3 is formed on the recording film. There was a problem that the trace 20 or the trace 21 at the rear end portion remained.

  As shown in FIG. 3, the reflectance fluctuation on the track in the phase change optical disc in which the front end trace 20 and the rear end trace 21 are generated in this way is uneven in the reflectance up and down with respect to the time axis on the track. As a result, the reflectance fluctuation is so large that the recording / reproduction characteristics may be adversely affected.

  An object of the present invention is to eliminate the above-mentioned problems caused by the prior art, and an initialization method and initialization capable of obtaining a higher-quality initialization state even with a heat-sensitive recording film Is to provide a device.

  The present invention that achieves the above object provides an initialization method for a recording medium that initializes an information recording medium capable of recording information by irradiating a laser beam, wherein an elliptical laser spot having a longitudinal direction and a transverse direction is provided. The elliptical laser spot is arranged so that the longitudinal direction of the elliptical laser spot forms an angle other than parallel to the recording track direction, and the light intensity distribution in the longitudinal direction of the elliptical laser spot is set to the maximum value of the light intensity H1. (H1> 0), the front end in the moving direction, the right end is called the rear end, the light intensity at the front end is H2 (H2> 0), the light intensity at the rear end is H3 (H3> 0), The average value of the light intensity excluding both ends is H4 (100> H4> 0), the light intensity H1 is 100%, the width of the gradient portion at the front end is W1, and the width of the gradient portion at the rear end is When W2 is set, the light intensity H1 is 100%. The initialization is performed in a state where the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is set to H2 ≧ 90%, or H3 ≧ 90%, and H4 ≧ 85%. According to a first feature of the recording medium initialization method, the initialization is performed with the widths W1 and W2 set to W1 ≦ 4 μm or W2 ≦ 4 μm.

  The present invention also relates to a recording medium initialization apparatus for initializing an information recording medium capable of recording information by irradiating a laser beam, wherein the laser head forms an oval laser spot having a longitudinal direction and a short direction. And a carriage that moves in the radial direction of the recording medium with the longitudinal direction of the elliptical laser spot arranged at an angle other than parallel to the recording track direction, In the light intensity distribution, the maximum value of the light intensity is called H1 (H1> 0), the front end in the moving direction, the right end is called the rear end, the light intensity at the front end is H2 (H2> 0), the rear end The light intensity of the part is H3 (H3> 0), the average value of the light intensity excluding both ends is H4 (100> H4> 0), the light intensity H1 is 100%, and the width of the gradient part at the front end is W1, the slope of the rear end When the width of the portion is W2, the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is as follows: the light intensity H1 is 100%, and H2 ≧ 90% or H3 ≧ 90%. The initialization is performed in a state where H4 ≧ 85% is set as a third feature, and in the recording medium initialization apparatus, the widths W1 and W2 are set to W1 ≦ 4 μm or W2 ≦ 4 μm The fourth feature is that the initialization is performed.

  According to the present invention, the light intensity distribution in the longitudinal direction of the elliptical laser spot for initializing the recording medium is represented by the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4. By performing the initialization in a state where ≧ 90% or H3 ≧ 90%, H4 ≧ 85%, W1 ≦ 4 μm or W2 ≦ 4 μm, the light intensity at the edge of the laser spot is strong and the intensity gradient is sharp. By irradiating a laser spot having an intensity distribution, a high-quality initialization state can be obtained as compared with the conventional case.

  Hereinafter, a recording medium initialization method and initialization apparatus according to an embodiment of the present invention will be described. First, the principle of the present invention will be described. First, it is desirable that the initialization state irradiated with the laser beam is uniform within the laser spot, but there is a difference in the thermal energy applied depending on the presence or absence of adjacent light intensity at the center and end of the spot. The inventors have considered that the above-described problems improve the sensitivity of the recording film to heat, and the laser intensity distribution in the laser spot 3 that has not been a problem in the past is more at the end of the laser spot 3 It was discovered that many thermal reactions occurred and the above-mentioned traces occurred.

  That is, the inventors diffuse heat only in the circumferential direction because the same light intensity exists in the track direction at the center of the laser spot, but in addition to the circumferential direction at the end of the laser spot. Since heat diffuses also in the track direction, it is difficult to be in the same initialization state as the center portion of the laser spot, and the light intensity distribution of the laser spot condensed using a high-power semiconductor laser has a light intensity distribution at the edge. Since the gradient always exists, the thermal energy to be applied is weaker than that at the center of the laser spot.

  In order to solve the above-mentioned problems, the inventors have increased the light intensity at the end of the laser spot that performs the above-described initialization and has a light intensity distribution with a sharp gradient at the end of the laser spot. By performing the initialization using the spot, the present invention in which the above-described trace does not occur is achieved.

  Hereinafter, an embodiment of a recording medium initialization method and initialization apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 4 is a diagram for explaining the light intensity distribution with respect to the spot moving direction at the time of initialization of the laser spot applied to this embodiment, and FIG. 5 is a configuration of a phase change optical disk change initialization apparatus suitable for this embodiment. It is a figure for demonstrating.

  As shown in FIG. 5, the initialization apparatus according to the present embodiment includes a spindle motor 9 that rotationally drives the phase change optical disk 4, and a laser head 1 that irradiates the phase change optical disk 4 with the laser spot 3 through the objective lens 2. A carriage 6 that supports the laser head 1 and moves linearly in the radial direction 5 of the phase change optical disk 4, a carriage motor 7 that drives the carriage 6, and a linear that detects the movement distance of the carriage 6. The scale 8, the rotary encoder 10 for detecting the rotation angle of the spindle motor 9, the movement control of the laser spot 3 by the carriage motor 7 based on the detection signals from the linear scale 8 and the rotary encoder 10, and the spindle motor 9 And a microprocessor 11 that performs rotation control of the The processor 11 is configured to initialize the entire surface of the phase change optical disk 4 by controlling the movement of the laser spot 3 in the radial direction of the phase change optical disk 4 while controlling the rotation speed of the phase change optical disk 4. .

  In the laser spot 3 according to the present embodiment, as shown in FIG. 4 showing the light intensity distribution when the laser spot is viewed from the longitudinal direction, the maximum value of the light intensity is H1, the left end in the drawing is the front end in the laser spot moving direction, and the right end is Called the rear end, the light intensity at the front end is H2, the light intensity at the rear end is H3, and both ends are excluded (excluding the light intensity of width W and width 1W2 described later). When the light intensity H1 is 100%, the light intensity of 20% is H5, the light intensity of 80% is H6, the width of the gradient portion at the front end is W1, and the width of the gradient portion at the rear end is When W2, the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is set as W1 ≦ 4 μm or W2 ≦ 4 μm, H2 = H3 ≧ 90%, and H4 ≧ 85%. As a result, the marks 20 and 21 shown in FIG. Reduction characteristics were confirmed from experiments that it is good. The maximum light intensity H1 is H1> 0, the light intensity at the front end H2 is H2> 0, the light intensity H3 at the rear end is H3> 0, and the average light intensity excluding both ends is 100 for H4. > H4> 0.

In this experiment, the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is expressed as follows: when W1 ≦ 4 μm or W2 ≦ 4 μm, and H2 = H3, H2 = 100%, 95%, 90%, This is the result of investigating and finding the initialization characteristics when initialization is performed with laser spots of 85%, 80%, H4 = 95%, 90%, 85%, and 80%. Note that the relationship between the width W1 and the width W2 and the relationship between H2 and H3 are preferably similar, but need not be the same.

  From the above results, it was found that the light intensity distribution in the longitudinal direction of the laser spot has good initialization characteristics when W1 ≦ 4 μm or W2 ≦ 4 μm, H2 = H3 ≧ 90%, and H4 ≧ 85%.

  Therefore, in the recording medium initialization method and initialization apparatus according to this embodiment, the microprocessor 11 outputs the output distribution of the laser spot output from the semiconductor laser element (not shown) of the laser head 1 and through the objective lens. W1 ≦ 4 μm or W2 ≦ 4 μm, H2 = H3 ≧ 90%, H4 ≧ 85%, or the output distribution of the laser spot through the objective lens is W1 ≦ 4 μm or W2 ≦ 4 μm, H2 = H3 ≧ 90%, By selecting a semiconductor laser element (including a combination with an objective lens if necessary) such that H4 ≧ 85%, high-quality initialization that does not cause a mark even with a heat-sensitive recording film The state can be obtained. The initialization method of the present invention can also be applied to a multilayer recording medium having two or more recording layers.

The present invention can also be expressed as follows.
<Embodiment 1>
In an initialization method in which an information recording medium on which information can be recorded can be recorded first by irradiating a laser beam, an elliptical beam spot having a longitudinal direction and a transverse direction is formed, and the elliptical beam An average value when the longitudinal direction of the spot is arranged at an angle other than parallel to the recording track direction, and the maximum value of the light intensity is 100% in the light intensity distribution in the longitudinal direction of the elliptical beam spot. Is initialized using a beam spot whose light intensity at both ends is 90% or more.
<Embodiment 2>
In the initialization method of the information recording medium described in the first embodiment, at both ends of the light intensity distribution in the longitudinal direction, the interval from 20% when the maximum value of light intensity is 100% to an average value of 80% is 4 μm or less. An initialization method for an information recording medium, characterized in that initialization is performed using an elliptical beam spot having a steep gradient.
<Embodiment 3>
In an initialization method in which an information recording medium on which information can be recorded can be recorded first by irradiating a laser beam, an elliptical beam spot having a longitudinal direction and a transverse direction is formed, and the elliptical beam An average value when the longitudinal direction of the spot is arranged at an angle other than parallel to the recording track direction, and the maximum value of the light intensity is 100% in the light intensity distribution in the longitudinal direction of the elliptical beam spot. Is initialized using an oval beam spot having a light intensity of 85% or more and a light intensity at one end of 90% or more.

<Embodiment 4>
In the initialization method of the information recording medium described in the third embodiment, at one end of the light intensity distribution in the longitudinal direction, an interval rising from 20% when the maximum value of light intensity is 100% to an average value of 80%. An initialization method for an information recording medium, wherein initialization is performed using an oval beam spot having a steep slope of 4 μm or less.
<Embodiment 5>
In an initialization apparatus that first puts an information recording medium capable of recording information by irradiating a laser beam into a recordable state, an elliptical beam spot having a longitudinal direction and a transverse direction is formed, and light in the longitudinal direction is formed. In the intensity distribution, there is an oval beam spot having an average value of 85% or more and a light intensity at both ends of 90% or more when the maximum value of the light intensity is 100%. Initialization device for recording media.
<Embodiment 6>
In the initialization apparatus for an information recording medium according to Embodiment 5, the interval from the 20% when the maximum value of the light intensity is 100% to the average value of 80% is 4 μm or less at both ends of the light intensity distribution in the longitudinal direction. An initialization apparatus for an information recording medium, characterized in that initialization is performed using an elliptical beam spot having a steep slope.
<Embodiment 7>
In an initialization apparatus that first puts an information recording medium capable of recording information by irradiating a laser beam into a recordable state, an elliptical beam spot having a longitudinal direction and a transverse direction is formed, and light in the longitudinal direction is formed. The intensity distribution has an elliptical beam spot having an average value of 85% or more when the maximum value of light intensity is 100% and a light intensity at one end of 90% or more. Device for initializing information recording medium.
<Eighth embodiment>
In the information recording medium initialization apparatus according to the seventh embodiment, at one end of the light intensity distribution in the longitudinal direction, there is an interval rising from 20% when the maximum value of light intensity is 100% to an average value of 80%. An initialization apparatus for an information recording medium, wherein initialization is performed using an oval beam spot having a steep slope of 4 μm or less.

The figure for demonstrating the initialization process of a phase change optical disk. The figure for demonstrating the malfunction by initialization by a prior art. The figure for demonstrating the reflectance waveform by initialization by a prior art. The figure which shows the light intensity distribution of the laser spot by one Embodiment of this invention. The figure which shows the structure of the initialization apparatus suitable for this embodiment.

Explanation of symbols

1: laser head, 2: objective lens, 3: laser spot, 4: phase change optical disk, 6: carriage, 7: carriage motor, 8: linear scale, 9: spindle motor, 10: rotary encoder, 11: microprocessor, 20: front end trace, 21: rear end trace, H1: maximum light intensity, H2: front end light intensity, H3: rear end light intensity, H4: average light intensity excluding both ends Value, W1: width of the gradient part at the front end, W2: width of the gradient part at the rear end.

Claims (4)

A method of initializing a recording medium for initializing an information recording medium capable of recording information by irradiating a laser beam,
An elliptical laser spot having a longitudinal direction and a lateral direction is formed, and the longitudinal direction of the elliptical laser spot is arranged at an angle other than parallel to the recording track direction. , The maximum value of the light intensity is called H1 (H1> 0), the front end in the moving direction, the right end is called the rear end, the light intensity at the front end is H2 (H2> 0), and the rear The light intensity at the end is H3 (H3> 0), the average value of the light intensity excluding both ends is H4 (100>H4> 0), the light intensity H1 is 100%, and the width of the gradient portion at the front end Is W1, and the width of the gradient portion at the rear end is W2,
When the light intensity H1 is 100%, the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is set to H2 ≧ 90% or H3 ≧ 90% and H4 ≧ 85% A method for initializing a recording medium, wherein the initialization is performed in step (b).   2. The recording medium initialization method according to claim 1, wherein the initialization is performed in a state where the widths W1 and W2 are set to W1 ≦ 4 μm or W2 ≦ 4 μm. In an initialization apparatus for a recording medium for initializing an information recording medium capable of recording information by irradiating a laser beam,
A laser head for forming an elliptical laser spot having a longitudinal direction and a transverse direction, and a radial direction of the recording medium by arranging the longitudinal direction of the elliptical laser spot to make an angle other than parallel to the recording track direction A carriage that moves to
The light intensity distribution in the longitudinal direction of the elliptical laser spot, the maximum value of the light intensity is called H1 (H1> 0), the front end in the moving direction, the right end is called the rear end, and the light intensity at the front end is H2 (H2> 0), the light intensity at the rear end is H3 (H3> 0), the average value of the light intensity excluding both ends is H4 (100>H4> 0), the light intensity H1 is 100%, When the width of the gradient portion at the front end is W1, and the width of the gradient portion at the rear end is W2,
When the light intensity H1 is 100%, the relationship between the width W1, the width W2, the light intensity H2, the light intensity H3, and the light intensity H4 is set to H2 ≧ 90% or H3 ≧ 90% and H4 ≧ 85% An initialization apparatus for a recording medium, wherein the initialization is performed at 4. The recording medium initialization apparatus according to claim 3, wherein the initialization is performed in a state where the widths W1 and W2 are set to W1 ≦ 4 μm or W2 ≦ 4 μm.

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