JP2001126320A - Information recording method for optical disk medium and method for manufacturing optical disk master - Google Patents

Abstract

(57) [Summary] To create a recording pit row having a constant recording pit width, it is possible to prevent a decrease in modulation degree due to a variation in phase pits and an increase in crosstalk between adjacent tracks. According to both a method for manufacturing an optical disk master and a method for recording an optical disk substrate, a photoresist film is formed on a substrate, and then the stabilizer film is formed on the photoresist film from a laser according to a predetermined format.
1, a laser condensed beam is irradiated and exposed through an E / O modulator 32, an E / O deflector 33, a formatter 34, a beam expander 35, and an objective lens 36, and is developed to form a pre-pit row. Form. In that case, x
Is the exposure power when PL / BD = 0.5 and y is the exposure power when y = 0.878 * x ^-1.74 ±
The exposure power for the pit length is determined by 0.05. Also, the ratio between the beam diameter and the pit width is set to 0.4 <Wp / BD.
<0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium having a preformat and, more particularly, to a method of exposing pits for producing a high-density optical disk master and an optical disk medium produced thereby. The present invention relates to a method of recording pits when recording information in a pit.

[0002]

2. Description of the Related Art In general, in a manufacturing process of an optical disk, a photoresist film is first formed on a substrate, and then a laser beam is focused on the photoresist film and exposed to light, thereby forming a pit row according to a predetermined format. A master is created by forming a groove or the like and developing it. The exposure pulse uses the original digital signal as EF
M (Eight to Fourteen Modul)
ation) is a pulse signal generated by modulation. Next, based on the cut optical disc master, a mold called a stamper in which a pre-pit pattern of the optical disc master is reversely transferred is manufactured, and a substrate for the optical disc is duplicated from the stamper. At this time, the pre-pit pattern formed on the optical disc master is transferred to the optical disc substrate to form a pit pattern. Therefore,
An optical disk is manufactured by forming various film-like layers such as a recording layer and a protective layer on the pit pattern forming surface of the optical disk.

[0003] In recent years, the recording density of optical information recording media has been increasing, and various studies have been made. In order to increase the recording density, recording marks (recording pits) must be made smaller and the spacing must be increased. It is necessary to narrow it. In the case of pre-pits provided in advance as phase pits on a substrate, the shape and spacing of phase pits formed when exposing and developing a resist master directly affect storage capacity. When manufacturing an optical disc with such a high density, it is necessary to reduce the size of the pre-pit row at the time of exposing the resist master to reduce the track pitch. However, since the amplitude of the signal at the time of reproducing the pre-pit train becomes smaller, the CN ratio deteriorates. In order to minimize this and record and reproduce information at high density, it is necessary to keep the size of each phase pit at an appropriate value.

Conventionally, laser exposure at the time of manufacturing a master of an optical disk is usually performed as shown in FIG.
Each phase pit is formed by changing the irradiation time of the focused beam according to the length of the phase pit. According to this method, the formed phase pit is as shown in FIG.
The pre-pit shape becomes narrower as shown by 41a and 42a with respect to the exposure pulses 41 and 42 of the shorter phase pit, and the pre-pit shape becomes wider as shown by 43a with respect to the exposure pulse 43 of the longer phase pit. As a result, fluctuations as shown in FIGS. 4A and 4B become a serious problem in a higher-density optical disk having a narrower track pitch. In order to solve this problem, a method has been proposed in which, when exposing a long phase pit, the phase pit is divided into a plurality of pulses and exposed (see, for example,
-231569). Thereby, when exposing a long pre-pit, the laser beam power does not become excessive and its width becomes wider than a prescribed dimension, and the length and width of the long pre-pit are formed as prescribed dimensions. .

On the other hand, when exposing a long phase pit, a method has been proposed in which the exposure power is decreased from the front end to the end according to the length of the phase pit (Japanese Patent Laid-Open No. 8-96363). reference). That is, on a formatted optical disk, V pits in which short pits are continuously created
An FO portion and an ID portion in which long pits are arranged are provided in advance. In manufacturing a master, short pits are formed with normal laser power, whereas long pits are formed in accordance with the length. The laser power is attenuated at a certain inclination from the leading end of the power pit toward the end thereof.

[0006]

As described above, in an optical disk having a high density, the fact that the phase pit width differs depending on the length of the phase pits means that the modulation degree of modulation due to the narrow phase pit width is small in the short phase pits. Insufficiency occurs, and a long phase pit causes problems such as crosstalk to an adjacent track due to an excessively wide phase pit width, thereby deteriorating the CN ratio. In addition, when the phase pit is exposed, it is divided into several parts and the exposure is performed by the multi-pulse method or the exposure power is varied during the exposure of one phase pit. Modulator is required.

Therefore, a first object of the present invention is to solve these conventional problems and to provide conditions necessary for obtaining a phase pit row having a constant width regardless of the length of the phase pits. Even for high density optical discs, CN
An object of the present invention is to provide a method of manufacturing an optical disc master capable of producing a master whose ratio does not deteriorate. A second object of the present invention is to provide a method of manufacturing an optical disk master in which a condition of a phase pit width which can easily obtain a phase pit array having a constant width irrespective of the length in the master exposure is provided. That is. Further, a third object of the present invention is to provide a condition for obtaining a recording pit row which can secure a degree of modulation and has less interference between adjacent tracks, not only in a ROM but also in a recordable or rewritable recording medium. It is an object of the present invention to provide a method for recording information on an optical disk medium which can be performed. Further, a fourth object of the present invention is to provide an information recording method for an optical disk medium which provides a condition of a recording pit width capable of easily obtaining a constant recording pit row regardless of the length.

[0008]

In order to achieve the above object, in the method of manufacturing an optical disk master according to the present invention, after forming a photoresist film on a substrate, a laser beam is focused on the photoresist film according to a predetermined format. In the method of manufacturing an optical disc master in which a pre-pit row is formed by irradiating and exposing a pre-pit row, the diameter of the portion where the intensity of the exposure beam is 1 / e ² is BD, and the length of the phase pit is PL. And the horizontal axis (x) is PL / BD and the vertical axis (y)
Is the exposure power, where PL / BD = 0.5 when forming a phase pit having a length of 0.5, and y = 0.878 * x ^{− 1.74 with} respect to x. The range is ± 0.05. Further, in the information recording method for an optical disc medium according to the present invention, an optical disc having a recordable or rewritable recording film on a substrate having a guide groove, and irradiating the recording film with a laser focused beam according to a predetermined format In the medium, the diameter of the portion where the recording beam intensity is 1 / e ² is BD, the length of the recording pit is PL, and the horizontal axis (x) is PL.
/ BD, where the vertical axis (y) is PL / BD = recording power of 1 when a recording pit having a length of 0.5 is formed,
When the value of the recording power y is x, y = 0.778 * x
The range is ^-1.74 ± 0.05. Under the above conditions, when the recording pit width is Wp, 0.4
A recording pit row having a constant recording pit width is formed in the range of <Wp / BD <0.8.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, in order to manufacture an optical disc master, prepare a glass substrate whose surface is precisely polished,
Clean the surface. Next, the washed glass substrate is placed on a spinner, and a positive photoresist is applied by a spin coating method so that the film thickness in the glass substrate surface becomes uniform.
In this embodiment, the thickness of the photoresist is set to about 1000 °. Here, the thickness of the photoresist corresponds to the depth of a pit formed on the surface of the stamper. After that, pre-bake is performed. The optical disk master prepared in this manner is placed on a turntable of a master exposure machine, a gas laser beam is focused on a photoresist layer of the master, and the master disc is exposed by rotating the turntable. At the time of exposure, exposure is performed spirally from the inner periphery at a constant linear velocity (CLV).

FIG. 1 is a block diagram of a master exposure machine applied to the master manufacturing method of the present invention. Stabilizer 31 is applied to laser light emitted from gas laser 30.
After the light is fixed by the above, the light intensity is modulated by the light modulator 32 to form a predetermined pit row. here,
By transmitting a signal according to a predetermined format from the formatter 34 to the optical modulator 32, the light intensity can be modulated. In this manner, the laser beam light-modulated by the light modulator 32 is subjected to an operation on the light beam by the beam expander 35 and then condensed on the glass substrate 37 through the objective lens 36, whereby the glass The photoresist on the substrate 37 is exposed. The exposed master is developed at a low speed by a spinner turntable 38, rinsed with pure water, rotated at a high speed, and dried. Thus, since the positive type photoresist is used, the exposed portions are removed, and a desired uneven pattern of prepits is formed.

FIG. 2 is a diagram showing the relationship between the phase pit length and the phase pit width when the exposure power is changed. When a pre-pit pattern is formed as shown in FIG.
When the phase pits having different lengths are exposed with the same exposure power by adjusting the irradiation time in accordance with the length of the phase pits, the short phase pits 4 as shown in FIG.
1 and 42, the phase pit width becomes narrow like 41a and 42a, and the long phase pit 43 has a phase pit width of 42a.
And the variation occurs. For example,
In this case, the relationship between the phase pit length and the phase pit width depending on the exposure power could be represented as shown in FIG. Here, the horizontal axis is the axis in which the length of the phase pit is standardized by the exposure beam diameter BD, and the vertical axis is the axis in which the phase pit width is standardized by the exposure beam diameter BD. Here, BD is the diameter of the portion where the intensity of the exposure beam is 1 / e ² . Each line in the figure is a line indicating a change in the pit width when the exposure power is changed. That is, assuming that the exposure power at which the width becomes 3/4 * BD when forming a group is 1, the lowest solid line is 1.4 times, the second lowest line is 1.6 times, and the lowest line is 1.6 times. The third line indicates that the exposure was performed with the exposure power of 1.8 times and the top line was performed with the exposure power of twice. From this figure, it can be seen that when phase pits having different lengths are generated using the same exposure power, the phase pit width greatly differs depending on the phase pit length as shown by each line.

FIG. 3 is a diagram showing the relationship between the phase pit length and the exposure power for forming a pit train having a certain phase pit width. FIG. 5 shows the relationship between the exposure pulse intensity and the phase pit length. FIG. 3 is a diagram showing a shape of a pre-pit row of FIG. Here, in order to make the phase pit width constant regardless of the phase pit length, as shown in FIG. 5, the exposure power is changed according to the phase pit length, and the phase pit width is kept constant. It is necessary to make adjustments. FIG.
Then, when the exposure power when exposing a phase pit having a length of PL / BD = 0.5 is set to 1, the exposure power when exposing phase pits having different lengths while keeping the phase pit width constant. Is shown. As is apparent from FIG. 5, the exposure power at that time generally becomes smaller as the length of the phase pit becomes longer. That is, the pit widths of the pre-pit shapes 51a, 52a, and 53a are all the same, but for that purpose, it is necessary to increase the exposure power of the short phase pits 51 and 52 and reduce the exposure power of the long phase pits 53.

The pit width Wp / BD with respect to the beam diameter
3 can be obtained by setting the exposure power at which PL / BD = 0.5 to 1, even if the exposure power is set to 1.
Can be confirmed from. That is, PL / BD =
Assuming that the exposure power of 0.5 is 1, PL / BD = 1.
The exposure power at 0, 1.5, 2.0, and 2.5 is 0.8 to 0.9 as shown by triangles and squares, respectively.
, 0.8 to 0.85, around 0.8, and 0.75 to 0.8, and it can be seen that they exist on a common curve. From FIG. 3, the horizontal axis (x) is PL /
When the BD and the vertical axis (y) are set to an exposure power of 1 when forming a phase pit having a length of PL / BD = 0.5, y =
It was found that if the exposure power y was determined in the range of 0.878 * x ^-1.74 ± 0.05, it would be possible to form a phase pit row having a constant phase pit width regardless of the phase pit length.

The phase pit width satisfying the above conditions is:
Using the value Wp / BD normalized by the beam diameter, 0.4 <W
p / BD <0.8. When forming a pre-pit row having a constant phase pit width and trying to form a narrow phase pit row, the power margin is extremely reduced, and the pit width is changed even by a slight power fluctuation, which is not desirable. Also, when trying to form a prepit row having a wide pit width, it becomes difficult to form a phase pit having a short phase pit length. Therefore, as the limited range of the created phase pit width, 0.4 <Wp / BD <0.8
In this range, it is possible to stably form a pre-pit row having a constant phase pit width. According to such a method, since the phase pit length is standardized with respect to the beam diameter, even if the light source has a shorter wavelength and the beam diameter changes, it can be used as it is. Also, P
Since the equation based on the exposure power that satisfies L / BD = 0.5 is used, the same relational expression remains unchanged even if the photoresist film thickness, the sensitivity of the photoresist to the laser beam, the exposure linear velocity, etc. change. Can be used.

Further, this equation is not limited to the exposure power when a master is prepared by exposing a photoresist, but also in a recording pit in an optical disk recording medium having a recordable or rewritable recording film on a substrate having a guide groove. Can also be used when irradiating with a laser beam. For example, on a polycarbonate substrate having a guide groove, an SiO ₂ / ZnS layer, Ag-In-Sb-T
By using a phase change recording medium having a layered structure in which a quaternary phase change recording film of e, a SiO ₂ / ZnS layer, and an Al alloy are laminated, a recording pit row having a constant recording pit width can be obtained. It is possible to prevent the CN ratio from deteriorating due to densification. Also, as in the case of the master exposure, 0.4 <Wp / BD
By setting <0.8, it is possible to form a stable recording pit row having a constant recording pit width.

As described above, in the present invention, after a photoresist film is formed on a substrate, the photoresist film is exposed to a laser condensed beam according to a predetermined format, exposed, and developed. In a method of manufacturing a master optical disc for forming a prepit array, x
Is the exposure power when PL / BD = 0.5 and y is the exposure power when y = 0.878 * x ^-1.74 ±
By determining the exposure power for the pit length by 0.05, it is possible to easily form a phase pit row having a constant phase pit width regardless of the phase pit length. As a result, it is possible to prevent problems such as a decrease in the degree of modulation due to variations in the phase pit width and an increase in crosstalk with an adjacent track. In the master exposure, by setting the ratio of the beam diameter to the pit width to 0.4 <Wp / BD <0.8, a power margin can be secured when the phase pit width is constant regardless of the phase pit length. In addition, it is possible to form a pre-pit row in which short phase pits can be formed.

Also, in a recording film that can be additionally written on a substrate having a guide groove in advance or an optical disc medium that has a rewritable recording film, when recording pits are formed on the recording film, y = 0.778 * x ^When recording is performed so as to satisfy the relational expression of ^-1.74 ± 0.05, a recording pit row having a constant recording pit width can be similarly formed, and variation in the recording pit width can be suppressed. In recording on the information recording medium, the ratio between the beam diameter and the recording pit width is set to 0.1.
By setting 4 <Wp / BD <0.8, it is possible to secure a power margin when the recording pit width is constant irrespective of the recording pit length, and to form a recording pit row capable of forming a short recording pit. Can be.

[0018]

As described above, according to the present invention,
Even in the case of master disk exposure, or in the case of an optical disk medium having a writable recording film or a rewritable recording film on a substrate having guide grooves in advance, a certain relational expression is required when forming recording pits on the recording film. By recording so as to satisfy, it is possible to create a recording pit row with a constant recording pit width, so that problems such as a decrease in modulation due to phase pit variations and an increase in crosstalk with adjacent tracks are prevented. Can be. Also, in the case of exposure of both the master and the optical disk medium, if the ratio between the beam diameter and the pit width is limited to a certain range, a power margin can be secured when the phase pit width is constant regardless of the phase pit length. A pre-pit row including short phase pits can be formed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a master exposure machine to which a master manufacturing method according to the present invention is applied.

FIG. 2 is a diagram showing the relationship between the phase pit length and the phase pit width when the exposure power is changed.

FIG. 3 is a diagram showing the relationship between phase pit length and exposure power for forming a pit row having a certain phase pit width.

FIG. 4 is a diagram showing a shape of a prepit row when exposure is performed with a constant exposure pulse intensity.

FIG. 5 is a diagram showing a shape of a pre-pit row when an exposure pulse intensity is changed according to a phase pit length.

[Explanation of symbols]

30 gas laser, 31 stabilizer, 32 E
/ O modulator, 33 ... E / O deflector, 34 ... formatter,
35: beam expander, 36: objective lens and focus actuator, 37: glass master disk, 38: turntable, 41, 42: exposure pulse of short phase pit, 43: exposure pulse of long phase pit, 41a, 42
a: shape of long phase pit, 43a: shape of long phase pit, 51, 52: exposure pulse of short phase pit, 53
... Exposure pulses of long phase pits, 51a, 52a. Shape of short phase pit, 53a. Shape of long phase pit.

Claims (4)

[Claims] After a photoresist film is formed on a substrate, the photoresist film is exposed to a laser condensed beam according to a predetermined format and exposed, and the exposed portion is developed to form phase pits. In the method for manufacturing an optical disk master for forming a formed prepit array, the diameter of a portion where the intensity of the exposed laser condensed beam is 1 / e ² is BD, the length of a phase pit is PL, and the horizontal axis is
When (x) is PL / BD and the ordinate (y) is 1 when the exposure power for forming a phase pit having a length of PL / BD = 0.5 is 1, the exposure power y is y = 0.878. * A method for manufacturing an optical disk master, wherein the optical disk is driven in a range of ^-1.74 ± 0.05. 2. The method of manufacturing an optical disk master according to claim 1, wherein, when the width of the phase pit is Wp, 0.4 <Wp / BD.
A method for manufacturing a master optical disc, comprising forming a prepit row having a constant phase pit width in a range of <0.8. 3. An optical disc medium having a recordable or rewritable recording film on a substrate having a guide groove, and recording information by irradiating the recording film with a laser focused beam according to a predetermined format, The diameter of the portion where the recording beam intensity is 1 / e ² is BD, the length of the recording pit is PL, the horizontal axis (x) is PL / BD, and the vertical axis is
Assuming that (y) is a recording power that is 1 when a recording pit having a length of PL / BD = 0.5 is formed, the recording power y is y = 0.878 * x- ^1.74 ± 0.05. An information recording method for an optical disk medium, wherein the information recording method is performed in a range of: 4. The information recording method for an optical disk medium according to claim 3, wherein when the recording pit width is Wp, 0.4 <Wp / BD <
An information recording method for an optical disk medium, wherein a recording pit row having a constant recording pit width is formed in a range of 0.8.