JP2003281723A - Phase-change optical recording medium and its recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase-change optical recording medium having a crystallization promoting layer, suited to high-density recording without any necessity of an initializing operation, and capable of reducing a difference between recording sizes especially regarding the expansion of an amorphous mark in a direction (lateral direction) vertical to a laser beam advancing direction. <P>SOLUTION: (1) The recording method is adapted to reduce a difference between recording sizes regarding the expansion of an amorphous mark in a direction (lateral direction) vertical to a laser beam advancing direction when recording is carried out by irradiating a phase-change optical recording medium having a crystallization promoting layer adjacent to a recording layer with a laser beam to form a crystal phase and an amorphous phase. (2) The recording method of (1) changes at least one of a multipulse width, a head pulse width and head pulse radiation start time between the case of recording by the irradiation with two pulses and the case of recording by the irradiation with three or more pulses. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical recording medium having a crystallization promoting layer, which does not require an initializing operation and is suitable for high density recording, and a recording method thereof.

[0002]

2. Description of the Related Art In manufacturing a phase change recording RW medium, it is necessary to perform a step of causing a phase change recording film to undergo a phase transition from amorphous (non-crystalline) to crystalline. This step is generally called an initialization step. For example, in the manufacture of DVD + RW media, a semiconductor laser having a length of 100 μm in the radial direction is used, and a method of performing annealing while focusing on the recording layer is adopted. In the above DVD + RW media manufacturing, a process time of about 100 seconds is required to form a uniform crystal in the initialization step. 100
The process time of second means that the process time of other process is 10
Because it is very long compared to being less than a second,
Many initialization devices are installed in parallel. However, according to this means, problems such as laser output profile management occur in mass production.

A method using a crystallization promoting layer has been invented as a method requiring no initialization step. That is, in the film forming step, a crystallization promoting layer is formed prior to the formation of the recording layer, whereby a crystallized recording film can be formed with energy equivalent to that at the time of forming the recording layer. The film thickness of the crystallization promoting layer is about 10% or less of the film thickness of the recording layer. However, the crystallization promoting layer does not participate in the phase change despite being mixed with the recording layer at the time of recording by laser irradiation. Therefore, the limit recording density when the crystallization promoting layer is used is The recording density will be lower than the limit recording density when used alone. More specifically, when the crystallization promoting layer is in contact with the recording layer, there is a large difference between the case where the amorphous mark is formed by two laser irradiation pulses and the case where the amorphous mark is formed by three or more laser pulses. It turns out that there is.

In binary recording of reflectance High and reflectance Low, the boundary between the crystal portion and the amorphous mark portion in the groove direction of the recording disk is recorded as information. In the case of having a crystallization promoting layer, when the thermal energy input at the time of recording becomes small, when the length of the amorphous mark is accurately recorded in the groove direction, that is, the laser beam traveling direction,
There is a large difference in the spread in the lateral direction of the amorphous mark, that is, the direction perpendicular to the laser beam traveling direction, between the case where the amorphous mark is formed by two laser irradiation pulses and the case where the amorphous mark is formed by three or more laser pulses. Cause If there is a large difference in the lateral spread of the amorphous mark, there will be a difference in the symmetry between the reflectance High and the reflectance Low, and reproduction will be impossible in extreme cases.
Such a phenomenon is caused by, for example, a reference frequency of 64.V for a medium having a structure in which Bi _X Ge _1-X is used as a crystallization promoting layer.
DVD with 7 MHz and recording linear velocity of 8.5 m / sec
It is also observed when performing 2.5X recording in the standard.

In the case of the DVD + RW, in order to accurately record the length of the amorphous mark in the laser beam traveling direction, in the case of recording with two laser pulse irradiation, that is, in the case of forming the minimum amorphous mark, three or more marks are formed. Since the lateral spread of the amorphous mark is extremely smaller than that in the case where the amorphous mark is formed by the laser pulse irradiation, the symmetry standard of the reflectance High and the reflectance Low is not satisfied. Further, since the minimum amorphous mark is small, the standard for the signal amplitude of the minimum recording is not satisfied. Amorphous marks formed by two laser irradiation pulses are generally narrower than other cases. However, depending on the combination of the material and film thickness of the crystallization promoting layer and the material and film thickness of the recording layer, there is a possibility that the amorphous mark formed by two laser irradiation pulses may be wider.

[0006]

DISCLOSURE OF THE INVENTION The present invention has a crystallization promoting layer and is suitable for high-density recording without the need for an initialization operation. In particular, it is an amorphous mark in a direction (transverse direction) perpendicular to the laser light traveling direction. It is an object of the present invention to provide a phase change type optical recording medium and a recording method therefor capable of minimizing the difference between the recording sizes regarding the spread of the recording medium.

[0007]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 8). 1) A phase change type optical recording medium having a crystallization promoting layer adjacent to the recording layer is irradiated with a pulsed laser beam,
When recording by forming a crystalline phase and an amorphous phase, the direction perpendicular to the laser beam traveling direction (lateral direction)
The recording method is characterized in that the difference between the recording sizes related to the expansion of the amorphous mark is minimized. 2) When the head pulse is the first pulse and the pulses after the second pulse are multi-pulses and recording is performed by irradiation of a total of two pulses consisting of the head pulse and one multi-pulse, and when the head pulse and two or more pulses are recorded. The recording method according to 1), wherein at least one of the multi-pulse width, the head pulse width, and the head pulse irradiation start time is changed when recording with a total of three or more pulse irradiations composed of multi-pulses. . 3) Linear velocity of 7.
When recording is performed with an objective lens NA of 0.65 or less and 0 m / sec or more, an amorphous mark whose length in the laser beam traveling direction is less than 0.5 μm is formed, and when an amorphous mark is 0.5 μm.
The recording method according to 1), wherein at least one of the multi-pulse width, the head pulse width, and the head pulse start time is changed when the above amorphous mark is formed. 4) When the crystallization promoting layer is made of Bi _X Ge _1-X and the phase change optical recording medium is recorded by irradiation with two pulses in total consisting of the head pulse and one multi-pulse, The recording method according to 1), wherein the recording is performed with a pulse width longer than a pulse width when recording is performed with a total of three or more pulse irradiations each including a pulse and two or more multi-pulses. 5) A phase change type optical recording medium having a crystallization promoting layer adjacent to a recording layer, wherein recording is performed by forming a crystalline phase and an amorphous phase by irradiation with a pulsed laser beam,
A phase-change type optical recording medium characterized in that an amorphous mark having a small difference in recording size with respect to the spread of the amorphous mark in a direction (transverse direction) perpendicular to the laser light traveling direction is formed. 6) When the head pulse is the first pulse and the pulses after the second pulse are multi-pulses, recording is performed by irradiation of a total of two pulses consisting of the head pulse and one multi-pulse, and when the head pulse and two or more pulses are recorded. It is characterized in that at least one of the multi-pulse width, the head pulse width, and the head pulse irradiation start time is changed in the case of recording with a total of three or more pulse irradiations composed of multi-pulses. ) The described phase change type optical recording medium. 7) Linear velocity of 7.
When recording is performed at 0 m / sec or more and NA of the objective lens is 0.65 or less, and an amorphous mark having a length in the laser beam traveling direction of less than 0.5 μm is formed, and an amorphous mark of 0.5 μm or more is formed. And at least one of a multi-pulse width, a head pulse width, and a head pulse start time is changed for recording. 8) The crystallization promoting layer is made of Bi _X Ge _1-X , and the pulse width in the case of recording by a total of two pulse irradiations consisting of a head pulse and one multi-pulse, the head pulse and two or more multi-pulses. The phase change type optical recording medium according to 5), wherein the recording is made longer than the pulse width in the case of recording with a total of three or more pulse irradiations.

The present invention will be described in detail below. In the present invention, since the laser light is emitted in a pulsed form, the length of the amorphous mark in the laser light traveling direction can be controlled by adjusting the pulse width. Further, when the crystallization promoting layer is provided, the difference in the number of laser pulse irradiations regarding the spread of the amorphous mark in the lateral direction caused by the shortage of the total energy amount required for recording (that is, the difference between the recording sizes) is two. Since it occurs most significantly when recording with 3 laser pulses and when recording with 3 or more laser pulses, the multi-pulse width, head pulse width, and head pulse irradiation start in the former case and the latter case. By changing at least 1 of the time, it becomes possible to make the difference between the recording sizes related to the spread of the amorphous marks in the direction perpendicular to the laser light traveling direction small.

Further, by using a laser beam having a wavelength in the red region, the recording linear velocity is 7.0 m / sec or more, and the NA of the objective lens is
When forming an amorphous mark below 0.65,
When forming an amorphous mark with a length of less than 0.5 μm, it is formed with two laser pulses and 0.5 μm
In the case of forming the above amorphous mark, it is the easiest to control the length in the laser light traveling direction by forming the amorphous mark with three or more laser pulses. Therefore,
Even in this case, by changing at least one of the former multi-pulse width, the latter multi-pulse width, the head pulse width, and the head pulse irradiation start time, the difference between the recording sizes related to the spread of the amorphous mark in the direction perpendicular to the laser beam traveling direction can be reduced. It becomes possible to make it minute. Further, Bi _X is added to the crystallization promoting layer.
When Ge _1-X is used, the total amount of energy required for recording is insufficient. As a result, the lateral spread of the amorphous mark when recording with two laser pulses is extremely smaller than when recording with three or more laser pulses, so recording with two laser pulses is performed. In this case, by increasing the multi-pulse width, it becomes possible to minimize the difference between the recording sizes regarding the spread of the amorphous mark in the direction perpendicular to the laser light traveling direction.

FIG. 3 shows, as an example, a laser light pulse irradiation pattern for forming an amorphous mark corresponding to a reference clock oscillation frequency of 5 times. In order to eliminate the difference between the recording sizes related to the lateral spread of the amorphous mark as described above, a case where the amorphous mark is formed by two laser pulses and a case where the amorphous mark is formed by three or more laser pulses And with
It is effective to change the laser pulse width or change the leading laser pulse irradiation start time. In the case of a material with a large lateral spread of the amorphous mark,
It is effective to reduce the multi-pulse width when forming an amorphous mark with two laser pulses.
Further, in the case of a material in which the lateral spread of the amorphous mark is small, it is effective to increase the multi-pulse width when forming the amorphous mark with two laser pulses. Further, in the latter case, it may be effective to shorten the irradiation start time of the first laser pulse when forming an amorphous mark with two laser pulses.

[0011]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1, Comparative Example 1 A phase change type optical recording medium having the layer structure shown in FIG. 1 was prepared. The material and film thickness of each layer are as shown in the figure. Recording was performed on this optical recording medium at a recording speed of 2.5X in the DVD-standard. That is, the groove width is 0.3 μm, the disk rotation speed is 8.5 m / sec, and the reference clock frequency is 64.7.
Recording power of 14 mW, erasing power of 7.4 using a recording head of wavelength 660 nm and NA 0.65 under GHz conditions.
Recording was performed at mW. In the following [Table 1], when recording with two pulses, that is, the pulse width (pulse irradiation time) when recording the minimum mark, and the pulse width (pulse irradiation time) when recording with three or more pulses ) Is shown. The relationship between the laser light pulse irradiation and the reference clock is shown in FIG.

[Table 1] Further, the DVD + RW standard conformity of the jitter, the signal symmetry, and the signal amplitude of the minimum mark is shown in the following [Table 2]. In the table, "○" indicates conformity, and "x" indicates nonconformance.

[Table 2]

Example 2, Comparative Example 2 A phase change type optical recording medium having the layer structure shown in FIG. 2 was prepared. The material and film thickness of each layer are as shown in the figure. Recording was performed on this optical recording medium in the same manner as in Example 1.
In the following [Table 3], when recording with two pulses, that is,
The pulse width (pulse irradiation time) when recording the minimum mark and the pulse width (pulse irradiation time) when recording with three or more pulses are shown.

[Table 3] Further, the DVD + RW standard conformity of the jitter, the signal symmetry, and the signal amplitude of the minimum mark is shown in the following [Table 4]. In the table, "○" indicates conformity, and "x" indicates nonconformance.

[Table 4]

[0014]

According to the present invention, it has a crystallization promoting layer,
A phase-change optical recording medium that does not require an initialization operation and is suitable for high-density recording, and in particular, can minimize the difference in recording size regarding the spread of amorphous marks in the direction (transverse direction) perpendicular to the laser light traveling direction. And a recording method therefor.

[Brief description of drawings]

FIG. 1 is a diagram showing a layer configuration of a phase change optical recording medium of Example 1 and Comparative Example 1.

FIG. 2 is a diagram showing a layer structure of a phase-change optical recording medium of Example 2 and Comparative Example 2.

FIG. 3 is a diagram showing a pattern of laser light pulse irradiation.

[Explanation of symbols]

a Leading pulse start delay time b Leading pulse width c Multi-pulse width d Cooling pulse width e Recording power f Erase power g Cooling power

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaru Makai             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yuji Miura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Masato Hariya             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2H111 EA23 EA32 FA01 FA11 FA23                 5D029 JA01 JB03 JB18                 5D090 AA01 BB05 CC02 CC14 CC16                       DD01 EE01 EE05 KK04 KK05                       KK20                 5D119 AA23 AA26 BA01 BB04 DA02                       HA25 HA27 HA47 HA60                 5D789 AA23 AA26 BA01 BB04 DA02                       HA25 HA27 HA47 HA60

Claims (8)

[Claims] 1. When recording is performed by irradiating a phase change type optical recording medium having a crystallization promoting layer adjacent to the recording layer with a pulsed laser beam to form a crystalline phase and an amorphous phase, A recording method, characterized in that the difference between recording sizes regarding the spread of amorphous marks in the direction (transverse direction) perpendicular to the laser light traveling direction is made minute. 2. The first pulse is the first pulse, the pulses after the second pulse are multi-pulses, and the first pulse and 1
When recording with a total of 2 pulse irradiation consisting of one multi-pulse and when recording with a total of three or more pulse irradiation consisting of a head pulse and two or more multi-pulses, the multi-pulse width and the head pulse width 2. The recording method according to claim 1, wherein at least one of the head pulse irradiation start times is changed. 3. When recording with a laser beam having a wavelength in the red region at a linear velocity of 7.0 m / sec or more and an NA of the objective lens of 0.65 or less, the length in the laser beam traveling direction is 0.
When forming an amorphous mark of less than 5 μm,
2. The recording method according to claim 1, wherein at least one of the multi-pulse width, the head pulse width, and the head pulse start time is changed when forming an amorphous mark of 0.5 μm or more. 4. A pulse width when recording is performed on a phase change type optical recording medium having a crystallization promoting layer made of Bi _X Ge _{1-X with} a total of two pulse irradiation consisting of a head pulse and one multi-pulse. 2. The recording method according to claim 1, wherein the recording is performed with a pulse width longer than a pulse width when recording is performed with a total of three or more pulse irradiations including a head pulse and two or more multi-pulses. 5. A phase-change optical recording medium having a crystallization promoting layer adjacent to a recording layer, wherein recording is performed by forming a crystalline phase and an amorphous phase by irradiation with a pulsed laser beam, and a laser beam progresses. 1. A phase-change optical recording medium characterized in that an amorphous mark having a small difference in recording size with respect to the spread of the amorphous mark in a direction (transverse direction) perpendicular to the direction is formed. 6. The first pulse is the first pulse, and the pulses after the second pulse are multi-pulses, and the first pulse and 1
When recording with a total of 2 pulse irradiation consisting of one multi-pulse and when recording with a total of three or more pulse irradiation consisting of a head pulse and two or more multi-pulses, the multi-pulse width and the head pulse width 6. The phase change type optical recording medium according to claim 5, wherein at least one of the head pulse irradiation start time is changed and recorded. 7. Recording is performed with a laser beam having a wavelength in the red region at a linear velocity of 7.0 m / sec or more and an NA of the objective lens of 0.65 or less, and the length in the laser beam traveling direction is 0.5 μm.
When forming an amorphous mark of less than m, 0.5
6. The phase change type recording apparatus according to claim 5, wherein at least one of a multi-pulse width, a head pulse width, and a head pulse start time is recorded differently when an amorphous mark of μm or more is formed. Optical recording medium. 8. The pulse width when the crystallization promoting layer is made of Bi _X Ge _1-X and the recording is performed by irradiation of a total of two pulses consisting of the head pulse and one multi-pulse, and the pulse width of the head pulse is 2 or more. 6. The phase change type optical recording medium according to claim 5, wherein the phase change type optical recording medium is recorded with a pulse width longer than a pulse width in the case of recording with a total of three or more pulse irradiations.