JP2002092940A - Optical recording medium and recording method for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium which can suppress the increase of a heat interference at a high recording linear velocity, the aggravation of jitter and cross talk, the deterioration of resolution or the increase of a modulation degree, and a large change of recording strategy, and conforms to a constant angular velocity(CAV) method or a zoned constant angular velocity(ZCAV) method excellent in recording/reproducing characteristics. SOLUTION: In the optical recording medium provided with at least a recording layer and a reflective layer successively on a base and which performs recording and reproduction by the CAV or ZCAV method, the film thickness of the recording layer is made thinner toward the outer periphery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CAV (Constant
Angular Velocity or ZCAV (Zoned Co.)
The present invention relates to an optical recording medium that supports the Angular Velocity (nstant Angular Velocity) method and a recording method for the optical recording medium.

[0002]

2. Description of the Related Art In a recording apparatus of an optical information recording medium for recording on a recordable optical information recording medium, the recording linear velocity is increased to shorten the time required for recording.
One of the techniques for increasing the recording linear velocity is CAV recording or ZCAV recording. For example, in order to shorten the recording time in a write-once DVD, CAV recording, ZCAV,
When recording is considered, if the innermost circumference is set to 1 × speed recording (reference speed), the outermost circumference is 2.5 × speed recording (determined by the recordable innermost radius and outermost radius).

Incidentally, a recording strategy corresponding to a high recording linear velocity is disclosed in, for example, Japanese Patent Application Laid-Open No. H11-232652.
Japanese Patent Application Laid-Open Publication No. H11-209,086 discloses a recording method capable of performing good recording even at a high speed recording of 1 × speed or higher. This recording method sets a pulse width of a leading pulse and a pulse width of a succeeding pulse larger than a pulse width of a leading pulse and a pulse width of a trailing pulse in the recording at 1 × speed when performing high-speed recording exceeding 1 × speed. Alternatively, when performing high-speed recording exceeding 1 × speed, the power of the recording laser beam is set to be larger than that in the case of 1 × speed recording. However, a disc configuration suitable for a high recording linear velocity has not been sufficiently studied.

[0004]

The limit value of the recording speed at which the recorded information can be correctly reproduced differs depending on the type of the optical information recording medium, the manufacturer, or the recording apparatus. Therefore, for example, in the case of CAV or ZCAV recording, even if good recording with few errors can be performed on the inner peripheral side, the recording linear velocity on the outer peripheral side is higher than the recording linear velocity on the innermost peripheral side, so that there are many errors. Alternatively, an optical recording medium that cannot be reproduced is produced. This is because the thermal interference between the marks increases as the recording linear velocity increases, and more recording power is required as the recording linear velocity increases, so that jitter and crosstalk increase.

Further, the recording strategy is usually optimized to the reference recording linear velocity (the recording linear velocity at the innermost circumference). However, when the recording linear velocity increases, the optimal recording strategy at a high recording linear velocity becomes higher. In contrast to the recording strategy optimized at the reference recording speed, if the recording strategy cannot be finely controlled with respect to the recording linear speed, the jitter may deteriorate as the recording linear speed increases. That is, the same recording strategy cannot be used at the time of the low recording linear velocity (inner circumference side) and at the time of the high recording linear velocity (outer circumference side), and it is necessary to perform fine control according to the recording linear velocity (the same recording). The recording position that can be recorded by the strategy becomes very narrow).

In general, at a low recording linear velocity (inner side)
At high recording linear velocities (on the outer circumference side), the resolution (the ratio of the amplitude of the shortest mark to the amplitude of the longest mark) and the degree of modulation differ greatly.

[0007] The present invention has been made in view of the above-mentioned problems, and thermal interference is not caused even on an optical recording medium configuration suitable for CAV recording or ZCAV recording, specifically, on the outer peripheral side where a high recording linear velocity is obtained. It is an object of the present invention to provide an optical recording medium having reduced jitter and increased crosstalk.

Further, according to the present invention, fluctuations in the resolution (amplitude ratio of the shortest mark to the amplitude of the longest mark) and the degree of modulation at the disk radial position are suppressed, and the fluctuation of the recording strategy at the disk radial position is reduced. An object of the present invention is to provide an optical recording medium suitable for CAV recording or ZCAV recording that can be suppressed.

[0009]

That is, according to the present invention, a recording layer and a reflective layer are sequentially provided at least on a substrate, and recording and reproduction are performed by a CAV (Constant Angular Velocity) system or a ZCAV (Zoned Constant Angular Velocity) system. An optical recording medium characterized in that the recording layer is thinner toward the outer periphery.

The present invention also relates to a method for recording on the optical recording medium, wherein the recording light emission pattern is the same at all recording positions.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the cause of an increase in thermal interference between marks with an increase in recording linear velocity is as follows.
This is because, when the recording linear velocity is increased, the influence of heat inflow from the position (previous mark) where the laser was irradiated in the past becomes large, particularly between marks via a short space.

As shown in FIG. 1, when a second 3T mark is formed via a 3T space after forming a first 3T mark, the temperature distribution of the second 3T mark depends on the recording linear velocity. (The first 3T)
A rectangular wave pulse for 1.5 to 3.0 (T) is applied to form a mark, and a rectangular wave pulse for 7.5 to 9.0 (T) is applied to form a second 3T mark. Was irradiated).

The calculation conditions are as follows: the recording layer (film thickness 1) on the substrate
50 (nm)), a gold reflective layer (thickness 100 (nm)), and a protective layer (thickness 1000 (nm)).
The recording wavelength is 650 (nm), the temperature of the first 3T mark is 2.5 (T), and the temperature of the second 3T mark is 8.
At 5 (T), the temperature distribution in the in-plane direction of the disk was calculated (the depth position of the recording layer for which the temperature distribution in the in-plane direction of the disk was calculated is the interface between the recording layer and the reflective layer, and between the recording layer and the substrate). The position was 75 (nm) away from the interface).

FIG. 3 shows the result of calculating the temperature distribution of the second 3T mark, and the result is that the recording linear velocity is 3.5 (m / s).

FIG. 4 shows the result of calculating the temperature distribution of the second 3T mark, and the result is that the recording linear velocity is 14.0 (m / s). 2.5 of recording linear velocity 3.5 (m / s)
The case of a recording linear velocity of 8.5 (m / s), which is a double speed, should be considered. However, in order to grasp a change due to a higher recording linear velocity, a reference recording linear velocity of 3.5 (m / s) is used. s)
14.0 (m / s), which is 4 times faster than the above, was calculated).

When the recording linear velocity is 14.0 (m / s), the recording power is determined by the temperature distribution of the first 3T mark and the recording linear velocity when the recording linear velocity is 3.5 (m / s). 14.0 (m
/ S), the recording power was selected such that the temperature distribution of the first 3T mark was the same. Therefore, the temperature distribution of the first 3T mark is the same as shown in FIG. 2 at both the recording linear velocity of 3.5 (m / s) and 14.0 (m / s).

The contour lines shown in FIGS.
℃, 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300
Shows contours in ° C.

As can be seen from these calculation results, the temperature distribution of the second 3T mark is asymmetrical as the recording linear velocity is increased, and its size is significantly different from that of the first 3T mark. Therefore, at a high recording linear velocity, the emission pulse length for forming the first 3T mark (ie, when the preceding space is long) and the emission pulse length for forming the second 3T mark (ie, when the preceding space is short) Cannot be the same. In other words, for the recording mark to be recorded, it is necessary to control the emission pulse length for forming the mark to be recorded based on the preceding or following space length in consideration of the preceding or following space length. (A recording strategy suitable for a low recording linear velocity in which the temperature distribution of a recording mark to be recorded does not depend much on the front space length or the rear space length becomes unsuitable at a high recording linear velocity).

In the present invention, in CAV or ZCAV recording, in order to reduce this thermal interference, it is important that heat is not excessively accumulated in the recording layer, which increases the recording linear velocity. It has been found that improvement can be achieved by reducing the thickness of the recording layer toward the outer periphery of the disk.

Therefore, with the optical recording medium of the present invention, an increase in thermal interference due to an increase in the recording linear velocity can be suppressed, and a change in the recording linear velocity or the optimum recording strategy for the recording position can be reduced. .

[0021] Next, a phenomenon that it is difficult to form a short mark with respect to a long mark due to an increase in the recording linear velocity, and a power equal to or more than a power that compensates for an energy decrease with respect to a reference recording linear velocity due to the increase in the recording linear velocity The reason why the recording power is required will be described.

FIGS. 5 and 6 show the results of verifying the change in temperature distribution due to the recording linear velocity by simulation. FIG. 5 shows recording using a simple rectangular wave pulse, and FIG. 6 shows the result of calculating the recording layer temperature for each mark length when the recording linear velocity is 3.5 (m / s) (DVD reference linear velocity). In the recording by pulse, the recording linear velocity is 14.0 (m
/ S) (4 times the DVD reference linear velocity) is the result of calculating the recording layer temperature for each mark length. A quadruple speed calculation was performed to facilitate comparison of the results).

The calculation conditions are as follows: the recording layer (film thickness 1)
50 (nm)), a gold reflective layer (thickness 100 (nm)), and a protective layer (thickness 1000 (nm)).
The recording wavelength was 650 (nm), and the depth position of the recording layer for which the temperature was calculated was a position 75 (nm) away from the interface between the recording layer and the reflective layer, and from the interface between the recording layer and the substrate.

5 and 6, the horizontal axis represents the recording clock frequency (when the recording linear velocity is 3.5 (m / s),
26.16 MHz. When 1T = 38.2 ns and the recording linear velocity is 14.0 (m / s), 104.64 MH
z. 1T = 9.55 ns), and the recording mark length is normalized, and the vertical axis represents the temperature normalized by the maximum attained temperature.

From the result of calculation of the recording layer temperature for each mark length, short marks such as 3T and 4T do not sufficiently raise the temperature with respect to the long marks. As a result of calculating the dependence of the temperature distribution on the recording layer in the depth direction, it was found that the variation in the temperature distribution in the depth direction of the recording layer was larger for the short mark than for the long mark. Therefore, at a high recording linear velocity, in order to form a short mark clearly, a higher recording power is required than a recording power for compensating for a decrease in energy due to an increase in the recording linear velocity.

That is, the CD-R (the shortest recording mark length 0.
83 (μm)), the change in the recording power with respect to the recording linear velocity is (recording power) ≦ (recording power of the reference recording speed) × (speed ratio to the reference recording speed) ^1/2. (Shortest recording mark length 0.40
(Μm)), for example, “Jpn.J.Appl.Phys.Vol.39 (200
0) Pt.1, No. 2B ”, the relationship of (recording power) = (recording power of reference recording speed) × (speed ratio to reference recording speed) ^1/2 does not hold, but rather , (Recording power)> (recording power of reference recording speed) × (speed ratio to reference recording speed) ^1/2 , and extra recording power is required at high recording linear velocity, so recording at higher recording linear velocity It was found that the characteristics were deteriorated (see FIG. 8). Δ represents the relationship between the recording linear velocity and recording power of the DVD-R, ▲ represents the relationship between the recording linear velocity and the recording power, and Δ represents the CD-R of 1
Based on the result of double speed recording, (recording power) = (recording power at reference recording speed) × (speed ratio to reference recording speed)
^{This shows} the result of estimating the recording power at a high recording linear velocity using the relational expression of ^1/2 . The horizontal axis in FIG. 8 is the recording linear velocity ratio of each medium to the reference linear velocity.)

The shortest recording mark of a CD-R is D
It corresponds to about 6T of VD. Therefore, from the results shown in FIGS. 5 and 6, the CD-R originally has a recording layer temperature difference between the short mark and the long mark that is not so large as that of the DVD-R, and even if the recording linear velocity increases, the recording layer of the short mark and the long mark increases. Temperature difference is DV
Since it does not become as large as DR, the technical problem and the countermeasure of the present invention are not found in the published technology found based on CD-R.

As described above, it is difficult to form a short mark due to an increase in the recording linear velocity, thereby further increasing the optimum recording power. On the outer periphery), the resolution (the ratio of the length of the long and short marks to the amplitude of the longest mark) decreases and the degree of modulation increases. As described above, since the resolution (the ratio of the amplitude of the shortest mark to the amplitude of the longest mark) and the degree of modulation are different depending on the recording linear velocity, it is necessary to finely change the recording strategy depending on the recording position (the same). The radial position that can be recorded by the recording strategy of (1) becomes narrower).

According to the present invention, in CAV or ZCAV recording, a difference in resolution (amplitude ratio of long and short marks with respect to the amplitude of the longest mark) and a degree of modulation depending on the recording linear velocity, and a recording linear velocity with a wide recording strategy It has been found that the problem that cannot be dealt with in the range (radial position range) can be improved by making the recording layer film thickness thinner at the outer periphery where the recording linear velocity becomes higher.

Next, as the recording linear velocity increases,
The cause of the increase in jitter and crosstalk is that, as the recording linear velocity increases, short marks are more difficult to form, and higher recording power is required. , Recording layer deformation,
This is because the amount of deformation of the reflective layer and the like increases.

The recording mechanism will be described below. A recording portion of an optical recording medium having a structure in which a recording layer is directly formed on a substrate showing thermoplasticity is formed mainly by deformation due to thermal expansion of the substrate and decomposition of the recording layer material. The decomposition of the recording layer material means, for example, when the recording layer material is an organic material, decomposes the basic skeleton of the organic substance, detaches a substituent introduced into the basic skeleton, or decomposes the substituent. Some of these decomposed products are thermally expanded and diffuse into the reduced density substrate. In addition, elimination of a substituent from the basic skeleton or decomposition of the substituent adds to a phenomenon in which steric hindrance is alleviated, and the volume of the recording layer is reduced. Due to the decrease in the volume of the recording layer material, the reflective layer and the protective layer provided on the recording layer are similarly deformed in the direction in which the volume of the recording layer changes. That is, the reflective layer and the protective layer provided on the recording layer are also dented on the substrate side.

In the decomposition of the recording layer material, if the decomposition does not completely occur in a narrow temperature range equal to or higher than the threshold (corresponding to the case where the slope of the weight change with respect to the temperature during decomposition is small in thermogravimetric analysis), or When the thermal expansion amount of the recording layer is large (for example, when the recording layer thickness is large or when the recording power is high), a large rim portion is formed outside the recording area due to the pressure due to the decomposition of the recording layer material. Deform.

Deformation occurs in the reflective layer on the recording layer due to the deformation of the substrate and the volume change (concave deformation) due to the decomposition and alteration of the material of the recording layer, and the rim portion (convex deformation) around the recording area. According to the present invention, it has been found that the increase in the recording linear velocity increases the size of the convex portions and concave portions generated in these recording layers, and there is a possibility that the recording layer and the reflective layer are separated.

The separation of the recording layer and the reflective layer occurs when the convex deformation and the concave deformation are generated independently or when the amount of the deformation is significantly increased, but when both the convex deformation and the concave deformation are present at the same time. This occurs even when the respective deformation amounts are relatively small. Also, this recording layer and the peeling phenomenon
This occurs frequently when the recording material does not decompose sharply or when the recording layer thickness is large. In these cases, a large rim portion is formed outside the recording mark.

By the mechanism described above, that is, by increasing the recording linear velocity, a higher recording power is required than the recording power for compensating for the energy decrease due to the increase in the recording linear velocity. The deformation of the substrate, the deformation of the dye, and the deformation of the reflective layer are further increased, or the recording layer and the reflective layer are separated from each other, thereby deteriorating jitter and crosstalk at a high recording linear velocity.

In the present invention, in CAV or ZCAV recording, the problem that the recording power sharply increases due to the increase in the recording linear velocity, and the problem that the jitter and the crosstalk deteriorate due to the increase in the recording linear velocity. It has been found that it can be improved by making the disk thinner toward the outer periphery of the disk where the speed is increased.

The present invention can be widely applied to an optical recording medium in which a recording layer is formed on a substrate and a reflection layer is further provided on the recording layer. A recording layer is formed on a substrate, and a reflective layer is further provided on the recording layer. This is particularly effective for an optical recording medium in which the volume of the recording layer material changes due to recording.

The present invention is effective when the same recording light emission pattern is used at all recording positions. The use of the same recording light emission pattern means, for example, DVD Speci
fications for Recodable Disk (DVD-R) Par
t1 PHYSICAL SPECIFICATIONS
When multi-pulse recording, which is a recording strategy described in Version 1.0 July 1997, is used, the relationship between the length of a recording mark to be formed and the number of recording light emission pulses must be the same at all recording positions (recording linear velocity). Means

That is, DVD Specifications for DVD
Recordable Disk (DVD-R) Part1 PHYSI
CAL SPECIFICATIONS Version1.0
In the multi-pulse recording described in July 1997, so-called n-2 recording is performed (3T mark is recorded with one light emission pulse, 4T is recorded with two light emission pulses, 5T
Is a method in which an arbitrary recording mark is recorded with (recording mark length) -2 light emitting pulse trains, such as recording with three light emitting pulses), and this n-2 recording pattern is recorded at all recording positions (recording linear velocity). Is the same, the optical recording medium of the present invention is particularly effective.

This is because the present invention is intended to absorb the change in the recording / reproducing characteristics due to the increase in the recording linear velocity on the optical recording medium side. If the recording strategy attempts to compensate for this, that is, if the recording light emission pattern is changed at the recording position, the effectiveness of the present invention may be reduced.

Since the method of the present invention is very effective when the same recording light emission pattern is used at all recording positions, it is possible to cope with a conventional recording apparatus and to greatly reduce the load on the recording apparatus. There is an advantage that you can.

[0042]

Next, an embodiment of the present invention will be described. The following chemical formula (1) is formed on a polycarbonate substrate having a thickness of 0.6 mm and a track pitch of 0.74 (μm) (for 4.7 GB):

[0043]

Embedded image

An optical recording medium was prepared by forming a recording layer mainly comprising spin-coating, and providing a gold reflecting layer or a silver reflecting layer having a changed thickness by sputtering on the recording layer.

Further, on a polycarbonate substrate (corresponding to 4.7 gigabytes) having a thickness of 0.6 mm and a track pitch of 0.74 (μm), a recording layer having the above-mentioned chemical formula (1) as a main component is formed by spin coating. An optical recording medium having a gold reflective layer or a silver reflective layer having a thickness changed by sputtering provided thereon, and having a protective layer made of an ultraviolet curable resin thereon, and a protective layer made of the ultraviolet curable resin. An optical recording medium was prepared by laminating a second disc with an adhesive layer interposed therebetween.

The recording device (recording / reproducing device) is a DDU-1000 manufactured by Pulstec Industrial (having a wavelength of 660 (nm),
An aperture ratio NA of 0.63) was used.

(1) Causes of Jitter Deterioration Associated with High Recording Linear Velocity Here, the cause of deterioration in jitter and crosstalk due to an increase in recording linear velocity was examined. FIG. 9 shows the result of evaluation of the recording linear velocity dependency of the modulation degree (measurement of the modulation degree when recording was performed with the optimum recording power at each recording speed up to the highest possible recording speed). In the figure, Δ indicates the substrate / recording layer /
Gold reflective layer (thickness 10 nm), △: substrate / recording layer / gold reflective layer (thickness 100 nm), ▲: substrate / recording layer / gold reflective layer (thickness 100 nm) / protective layer, ×: substrate / recording layer / Gold reflective layer (100 nm thick) / Protective layer / Adhesive layer / Second disk, ○: substrate / recording layer / Silver reflective layer (100 nm thick)
It is a result of measuring a modulation degree of a medium having a configuration of / protective layer / adhesive layer / second disk when recording was performed at an optimum recording power at each recording linear velocity. As a result, in FIG. 9, a region where the degree of modulation sharply increases (portion surrounded by a broken line)
It was found that jitter and crosstalk rapidly deteriorated. That is, it was found that the deterioration of jitter and crosstalk due to the increase of the recording linear velocity was caused by the rapid change of the modulation degree (an inflection point appears in the change of the modulation degree with respect to the recording linear velocity).

FIG. 10 shows a substrate / recording layer / gold reflective layer (film thickness 1).
Recording speed of 5.0 (m)
/ S), and FIG. 11 shows a recording linear velocity of 7.0.
The eye pattern at (m / s). From this result,
It was found that the deterioration of jitter and crosstalk due to the increase in the recording linear velocity was caused by a rapid change (turbulence) in the modulation degree (in the optical recording medium in which a rapid increase in the modulation degree was observed in FIG. Increase in modulation and disturbance were observed).

Next, as a result of examining the cause of the sudden increase or disturbance of the modulation degree, as shown in FIG. 12 (SEM photograph on the dye surface from which the reflective layer was peeled off), the recording mark was shown on the recording mark. It was found that a third recording mark (thick arrow) was formed in addition to the rim portion (thin arrow) and the rim portion (thin arrow), and it was confirmed that this was a cause of a sudden increase in modulation factor or disturbance. (The third recording mark appears at a high power near the recording power at which the degree of modulation sharply increases).

The third recording mark is likely to appear in the long mark, appears to cover the entire recording mark via the short space, and is formed over a considerably larger area than the rim portion. And the change in the volume of the recording layer or the change in the refractive index of the material of the recording layer are continuous changes, and do not change discontinuously with an increase in the recording power or the recording linear velocity (such as gradually saturating). The third recording mark is not observed in the recording material having a very small rim portion of the recording layer. Therefore, the reflection layer is formed by the expansion of the substrate and the increase in the rim portion of the recording portion. It is considered to be a trace that peeled off from. From these results, the technical content shown in the present invention was supported.

(2) Confirmation of the effect of reducing thermal interference when the thickness of the recording layer is reduced toward the outer periphery in CAV or ZCAV recording. As shown in FIG. When the second 3T mark was formed, it was calculated how the process of cooling the temperature near the temperature center position of the second 3T mark changes depending on the recording linear velocity (forming the first 3T mark). 1.5-3.
A rectangular wave pulse was applied for 0 (T) to form a second 3T mark, and a rectangular wave pulse for 7.5 to 9.0 (T) was applied.

The calculation conditions are as follows: the recording layer (film thickness 1) on the substrate
50 (nm)), a gold reflective layer (thickness 100 (nm)), and a protective layer (thickness 1000 (nm)).
The recording wavelength was 650 (nm), and the temperature change at the temperature center position of the second 3T mark was calculated (the depth position of the recording layer at which the temperature change was calculated was the interface between the recording layer and the reflective layer, and the recording layer). 75 (nm) away from the substrate interface). FIG. 13 shows the result at a recording linear velocity of 3.5 (m / s). FIG. 14 shows a recording linear velocity of 14.0 (m / s).
(When CAV or ZCAV recording is originally considered, it is necessary to consider the case where the recording linear velocity is 8.5 (m / s). 14.0 (m / s), which is four times the reference speed of 3.5 (m / s), was calculated.)

When the recording linear velocity is 14.0 (m / s), the recording power is determined by the temperature distribution of the first 3T mark and the recording linear velocity when the recording linear velocity is 3.5 (m / s). 14.0 (m
/ S), the recording power was selected such that the temperature distribution of the first 3T mark was the same. From this result, it was confirmed that the temperature cooling time was prolonged (time standardized by the recording clock frequency) and the heat flow backward increased due to the apparent increase in the recording linear velocity.

Next, the effect of the present invention was verified. That is,
Recording with a simple rectangular wave pulse, the recording linear velocity is 14.0
In order to suppress the thermal interference (m / s) (to shorten the temperature cooling time), the recording layer thickness was set to 120 (nm). FIG.
5 shows the result of calculating the process of cooling the temperature near the temperature center position of the second 3T mark when the thickness of the recording layer is 120 (nm) (depth position of the recording layer at which the temperature was calculated). Was set at a position 60 (nm) away from the interface between the recording layer and the reflective layer and from the interface between the recording layer and the substrate.

From these results, it is confirmed that the cooling time after the temperature rise can be shortened by reducing the thickness of the recording layer, and the heat inflow to the rear side can be suppressed, that is, the heat interference can be suppressed. Was done.

(3) Confirmation of Short Mark Modulation Improvement Effect in CAV or ZCAV Recording When Recording Layer Thickness is Decreased on the Outer Periphery FIG. 5 shows recording using a simple rectangular wave pulse and a recording linear velocity of 3.5 (m). / S) (DVD reference linear velocity), the recording layer temperature for each mark length was calculated. As a result, FIG. 6 shows recording using a simple rectangular wave pulse, and the recording linear velocity was 14.0 (m / cm).
s) This is the result of calculating the recording layer temperature for each mark length in the case of (4 times the DVD reference linear velocity) (it should be calculated in the case of 2.5 times speed, but the result of 1 time speed). Was calculated at a quadruple speed in order to make the comparison easier.)

The calculation conditions are as follows: the recording layer (film thickness 1) on the substrate
50 (nm)), a gold reflective layer (thickness 100 (nm)), and a protective layer (thickness 1000 (nm)).
The recording wavelength was 650 (nm), and the depth position of the recording layer for which the temperature was calculated was a position 75 (nm) away from the interface between the recording layer and the reflective layer, and from the interface between the recording layer and the substrate.

5 and 6, the horizontal axis represents the recording clock frequency (when the recording linear velocity is 3.5 (m / s),
26.16 MHz. When 1T = 38.2 ns and the recording linear velocity is 14.0 (m / s), 104.64 MH
z. 1T = 9.55 ns), and the recording mark length is normalized, and the vertical axis represents the temperature normalized by the maximum attained temperature.

From this result, the temperature of the short mark with respect to the long mark is further reduced due to the increase in the recording linear velocity, and the resolution is reduced due to the increase in the recording linear velocity, thereby increasing the recording power. You can see that.

Next, the effect of the present invention was verified. That is,
Recording with a simple rectangular wave pulse, the recording linear velocity is 14.0
The recording layer thickness was set to 120 (nm) in order to suppress a decrease in the temperature of the short mark with respect to the long mark (m / s). The relationship between the mark length and the temperature at this time is shown in FIG. 7 (the depth position of the recording layer where the temperature was calculated was a position 60 (nm) away from the interface between the recording layer and the reflective layer and between the interface between the recording layer and the substrate. ).

From this result, it is possible to increase the temperature of the short mark with respect to the long mark (suppress the temperature of the long mark with respect to the short mark from increasing too much) by reducing the thickness of the recording layer. It was proved.

From the above results, the optical recording medium of the present invention can suppress an increase in thermal interference at a high recording linear velocity and a decrease in the temperature of a short mark relative to a long mark. In this case, the amount by which the recording strategy is changed (pulse correction 1) can be reduced, and the range of the recording linear velocity (recording position) that can be supported by a specific recording strategy can be expanded.

[0063]

As described above, according to the optical recording medium of the present invention, an increase in thermal interference at a high recording linear velocity, an increase in jitter and crosstalk, a decrease in resolution and an increase in modulation degree, and CAV or Z, which can suppress a large change in the recording strategy and have excellent recording / reproducing characteristics.
An optical recording medium compatible with CAV can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a mark formed on an optical recording medium and a rectangular wave pulse.

FIG. 2 shows recording linear velocities of 3.5 (m / s) and 14.0 (m / s).
It is a figure showing the result of having computed the temperature distribution of the first 3T mark in s).

FIG. 3 shows a second 3 at a recording linear velocity of 3.5 (m / s).
It is a figure showing the result of having computed the temperature distribution of T mark.

FIG. 4 is a diagram showing a result of calculating a temperature distribution of a second 3T mark at a recording linear velocity of 14.0 (m / s).

FIG. 5 is a diagram showing the relationship between each mark length and the recording layer temperature when the recording linear velocity is 3.5 (m / s) (DVD reference linear velocity) and the recording layer thickness is 150 (nm). .

FIG. 6 is a diagram showing the relationship between each mark length and the recording layer temperature when the recording linear velocity is 14.0 (m / s) (DVD reference linear velocity) and the recording layer thickness is 150 (nm). .

FIG. 7 is a diagram showing the relationship between each mark length and the recording layer temperature when the recording linear velocity is 14.0 (m / s) (DVD reference linear velocity) and the recording layer thickness is 120 (nm). .

FIG. 8 is a diagram showing a relationship between a recording linear velocity ratio with respect to a reference linear velocity of each medium and recording power.

FIG. 9 is a diagram showing the results of measuring the degree of modulation of various media when recording at the optimum recording power at each recording linear velocity.

FIG. 10: substrate / recording layer / gold reflective layer (100 nm thick)
FIG. 7 is a diagram showing an eye pattern of the constituent medium of FIG. 5 at a recording linear velocity of 5.0 (m / s).

FIG. 11: substrate / recording layer / gold reflective layer (film thickness 100 nm)
FIG. 7 is a diagram showing an eye pattern of the configuration media at a recording linear velocity of 7.0 (m / s).

FIG. 12 is a view showing an SEM photograph on a dye surface from which a reflection layer is removed.

FIG. 13: recording layer thickness 150 (nm), recording linear velocity 3.
FIG. 9 is a diagram showing a temperature change near the temperature center position of the second 3T mark in the case of 5 (m / s).

FIG. 14: recording layer thickness 150 (nm), recording linear velocity 1
It is a figure which shows the temperature change in the case of 4.0 (m / s) near the temperature center position of a 2nd 3T mark.

FIG. 15: recording layer thickness 120 (nm), recording linear velocity 1
It is a figure which shows the temperature change in the case of 4.0 (m / s) near the temperature center position of a 2nd 3T mark.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) B41M 5/26 Y

Claims (4)

[Claims] At least a recording layer and a reflection layer are sequentially provided on at least a substrate, and recording and reproduction are performed by CAV (Constant Angular
Velocity) method or ZCAV (ZonedConstant An)
An optical recording medium that uses a gular velocity (velocity) method, wherein the thickness of the recording layer is smaller toward the outer periphery. 2. The substrate according to claim 1, wherein the substrate is a thermoplastic substrate.
2. The optical recording medium according to claim 1, wherein the volume of the recording layer material changes due to the recording. 3. The optical recording medium according to claim 1, wherein the recording light emission pattern is the same at all recording positions. 4. A method for recording on an optical recording medium according to claim 1, wherein the recording light emission pattern is the same at all recording positions.