KR19990081349A - Optical recording medium, apparatus and method for manufacturing same - Google Patents

Abstract

The present invention relates to an optical recording medium for optically recording information and reproducing the recorded information.

The optical recording medium according to the present invention has a pit whose tip and end portions have a width wider than that of the center portion.

Accordingly, the optical recording medium of the present invention is adapted to high density.

Description

Optical Recording Medium and Fabricating for Apparatus and Methods Thereof

The present invention relates to an optical recording medium, and more particularly to an optical recording medium in which information is recorded and / or reproduced optically. The present invention also relates to an apparatus and method for manufacturing an optical recording medium.

In general, an optical recording medium stores information in pits formed to have a predetermined length on an information recording surface, such as a compact disk (hereinafter referred to as "CD"). The optical recording medium is copied from a master disk for forming an optical disk (hereinafter referred to as an "optical disk disk"), which will be described in detail. After forming a photoresist film on a substrate, laser light is generated by an exposure pulse corresponding to a desired pit shape. Is exposed to a photoresist film to form a desired pit array and to develop it. A disk substrate is duplicated when a stamper manufactured by inverting and transferring the pit pattern formed by this method is installed in a molding machine, the substrate material is injected into the molding machine, and then solidified. The manufacturing process of such an optical recording medium is capable of recording once in a write once read many (WORM) type such as a CD-R (Recordable) or a DVD-R, as well as a play-only disc such as a DVD-ROM including a generalized CD-ROM. It is also applied to discs and rewritable discs such as CD-RW (Rewritable) and DVD-RAM. Looking at the actual structure of the disk substrate formed by the above method, pit rows corresponding to the information are formed in the uneven shape on the substrate of the optical recording medium. A reflective film made of a material such as aluminum (Al) having a high reflectance is deposited on the substrate on which the pit rows are formed, and a protective layer made of a material such as plastic is formed on the reflective film to prevent deterioration of the reflective film. When the reflected light is detected by irradiating light onto such an optical recording medium, a radio frequency (hereinafter referred to as an "RF signal") according to the presence or absence of a pit, that is, a recorded channel bitstream; Hereinafter referred to as "CHBS".

Recently, high-density recording media such as digital versitile disks (hereinafter referred to as "DVDs") have been developed following the dissemination of CDs, etc., but the capacity for storing large amounts of information such as compressed video information is still small. There is a demand for more and more dense media. To this end, in order to increase the recording density of the optical recording medium, a technique of forming a small pit on the optical recording medium and a technique of reducing the beam spot size on the optical recording medium in a reproducing optical system have been researched and developed. As an example of forming a small pit on the optical recording medium, an optical recording medium disk recording technology using Kr ion laser light having a wavelength of 351 nm enables processing of small pit compared to a conventional Ar ion laser. In addition, in the case where the beam spot size is made small on the optical recording medium, the spot diameter of the beam can be made smaller by shortening the wavelength of the reproducing laser beam and increasing the numerical aperture (NA). However, even if the method of forming a small pit on the optical recording medium and the method of forming a small beam spot on the optical recording medium is used, the width of the pit increases as the length of the pit increases, thereby increasing the crosstalk between adjacent tracks. The problem arises.

As shown in Fig. 1, in order to obtain a desired pit length, the photoresist film is exposed using laser light by an exposure pulse corresponding to the pit length. That is, shorter pits are exposed to the photoresist film by a laser light with a short exposure time (e.g., 3T, 4T, etc.) corresponding to the length, and long pits are long corresponding to the pit length. By being exposed for an exposure time (eg 10T), a desired pit shape can be obtained. However, when the laser light corresponding to the exposure pulse signal corresponding to the pit length is exposed to the photoresist film to form the pit 2, an exposure pulse of 10T is larger than the width of the pit formed by short exposure pulse widths such as 3T and 4T. The width of the pit formed by the width becomes large. This phenomenon occurs because the length of the exposure pulse and the power of the laser light irradiated onto the exposure surface are directly proportional to each other. When the length of the exposure pulse becomes short, the power of the laser light irradiated onto the exposure surface becomes weak and when the length of the exposure pulse becomes long, the exposure surface. It is because the power of the laser beam irradiated to becomes strong. If the pit width is maintained so that the signal / noise ratio (hereinafter referred to as the "S / N ratio") of the reproduction signal is sufficiently obtained in the case of a short pit such as 3T in such an optical recording medium, a long pit such as 11T may be used. In this case, there is a problem in that the pit width becomes larger than the short pit, so that crosstalk between adjacent tracks is increased. In view of this, even when the optical recording medium of Fig. 1B is formed in which all the recording feet rows from 3T to 14T have the same pit width, the pit length is short when the pit is long (space low frequency pit). It is generally known that the crosstalk in adjacent tracks becomes larger than in the case, and the calculation example is well shown in Fig. 6 of Japanese Patent Application Laid-Open No. 9-81969. Therefore, in the prior art, in order to avoid the cross talk problem between adjacent tracks, the track pitch should be increased compared to the spot diameter of the reproduction light beam. Therefore, the recording density is only increased by shortening the wavelength of the reproduction light and increasing the numerical aperture (NA) of the objective lens. As a result, the optical recording medium of high density becomes difficult to improve.

It is therefore an object of the present invention to provide an optical recording medium capable of recording and / or reproducing information at a high density.

Another object of the present invention is to provide an apparatus and method for manufacturing a high density optical recording medium.

1A and 1B schematically show the shape of a pit formed in an optical recording medium according to the prior art.

Fig. 2 is a diagram schematically showing the shape of a pit formed in the optical recording medium according to the present invention.

3 is a diagram showing waveforms of a reproduction signal detected at the pit of FIG. 2;

4 is a view showing an optical recording medium manufacturing apparatus according to the present invention.

5 is a view showing another optical recording medium manufacturing apparatus according to the present invention.

6 is a view showing an embodiment of the light beam control unit of FIG.

7 is a characteristic diagram showing the distribution of a super resolution light beam;

<Description of Symbols for Main Parts of Drawings>

2,12: 14 feet: laser resonator

16 beam expander 18 optical modulator

20: data processing unit 22: objective lens

24: optical recording medium 26: photoresist film

28: light beam control unit 30: spindle motor

In order to achieve the above object, the optical recording medium according to the present invention has a pit whose tip and end portions have a width wider than that of the central portion.

Further, another optical recording medium according to the present invention includes a first pit having a tip portion and a terminal portion having a width wider than that of the center portion, and a second pit having a uniform width of the tip portion, the center portion, and the terminal portion.

Further, the optical recording medium manufacturing apparatus according to the present invention includes a substrate on which a photoresist film is formed, and exposure means for exposing a laser beam having a power level of the front end portion and the end portion of the photoresist film higher than the power level of the center portion.

Further, another apparatus for manufacturing an optical recording medium according to the present invention includes a substrate on which a photoresist film is formed, and exposure means for exposing a laser beam having a tip diameter and a beam diameter at the end of the photoresist film larger than that at the center.

In addition, a method of manufacturing an optical recording medium according to the present invention includes forming a photoresist film on an upper portion of a substrate, and exposing a laser light having a power level of a front end portion and a terminal portion of the photoresist film higher than a power level of a central portion. .

In addition, another optical recording medium manufacturing method according to the present invention includes the step of forming a photoresist film on the upper portion of the substrate, and the step of exposing the laser light in the photoresist film with the beam diameter of the tip and the end of the terminal is larger than the central beam diameter do.

Other objects and features of the present invention other than the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

With reference to Figures 2 to 5 will be described a preferred embodiment of the present invention.

Referring to FIG. 2, the optical recording medium according to the present invention adjusts an exposure light beam focused on an exposure surface to form a shape of a long pit (for example, a pit having a pit length of 7T or more) with a leading edge 12a. The width of the trailing edge 12b is wider than the width of the center 12c. At this time, in order to narrow the width of the center portion 12c, the exposure light beam is controlled by signal power control of the exposure pulse or optically control the size of the exposure light beam. This will be described in detail by way of example. In the case of forming a pit having a pit length of 11T by signally adjusting the power of the exposure pulse, the power of the exposure pulse is set to a predetermined level so that the pit width is equal to the track pit width W and the pit length is 3T. It is formed to have a leading edge (12a) and a trailing edge (12b), and the power of the exposure pulse is set to be lower than a predetermined level to have a central portion 12c having a narrower pit width than W and a pit length of 5T. To form. In addition, when the pit length of 11T is formed by optically adjusting the size of the light beam, the pit width is W and the pit width is such that the size of the exposure light beam focused on the exposure surface has the same light beam size as the track pitch width W. It is formed to have a leading edge (12a) and trailing edge (12b) having a length of 3T, and the pit width is reduced by making the size of the light beam focused on the exposure surface smaller than the track pitch width (W) It is formed to have a central portion 12c that is narrower than W and has a pit length of 5T. On the other hand, when the pit length is 3T to 6T, the pit is formed into a normal pit shape having a uniform pit width, and when the pit length is 7T or more, the pit of the leading edge 12a and the trailing edge 12b is formed. The width is made wider than the pit width of the center portion 12c.

Referring to Fig. 3, the waveform of the reproduction signal detected at the pit according to the present invention is shown. The reproduced signal reflected by irradiating the laser light to the pit whose width of the tip portion 12a and the terminal portion 12b is wider than the width of the center portion 12c is shown as a dotted line in FIG. 3, and the laser light is applied to the pit having a uniform width. The reflected signal reflected by this is shown by the solid line in FIG. The reproduction signal corresponding to the center portion 12c of the pit among the reproduction signals shown by the dotted line has a lower signal level than the reproduction signal shown by the solid line. This is due to the narrowing of the pit corresponding to the center portion. However, since the detection of the reproduction signal is performed by a mark edge detection method (i.e., the reproduction signal is detected at the position where the reproduction signal and the slice level intersect), the reproduction signal level is increased at the center of the pit. Even if lowered, the playback signal detection is not affected.

Meanwhile, the improvement effect of crosstalk will be described with reference to FIG. 6 of the above-described Japanese Patent No. Hei 9-81969. If the pit length is short (i.e., the spatial frequency is high), the increase in crosstalk as the width of the pit is wide is not large, but if the pit is long (i.e., the spatial frequency is low), the pit is wide It can be seen that when the ground crosstalk increases rapidly and the pit width decreases, the cross talk amount is greatly improved (that is, when the spatial frequency is about 1.3 or less in FIG. 6). Thus, when the pit length is long as in the embodiment of the present invention, Therefore, the crosstalk amount can be improved by narrowing the width of the center portion of the pit, and it can be seen that the structure is suitable for a high density optical recording medium. In addition, when the pit length is short (for example, 3T-6T), the pit width is kept wide, thereby securing all the signals due to the MTF characteristics of the pickup. On the other hand, when the length of the pit is long (for example, 7T or more), the width of the tip and the end is kept wide, thereby maintaining the signal size in the slice. In other words, while the signal size is kept the same as that of the optical recording medium using a conventional pit structure, noise due to crosstalk is reduced, so that the effect of improving the S / N ratio is obtained.

4 is a block diagram schematically showing an apparatus for manufacturing an optical recording medium according to a first embodiment of the present invention.

4, an apparatus for manufacturing an optical recording medium according to the present invention includes a laser resonator 14 for generating laser light, a beam expander 16 for causing the laser light to have a constant numerical aperture, and a channel bit stream ( An optical modulator 18 for intermitting laser light according to CHBS), an objective lens 22 for focusing the laser light on the photoresist film 26 in the form of a light spot, and a spindle motor for rotating the substrate 24. And a data processor 20 for converting exposure data supplied through an input line into a channel bit stream CHBS. The laser light generated from the laser resonator 14 is secured to the optical modulator 18 by the reflector 15 while securing a constant numerical aperture by the beam expander 16. The data processor 20 converts the exposure data into the channel bit stream CHBS having the signal waveform shown in FIG. 4. The optical modulator 18 is connected to the data processing unit 20 to turn on / off the laser light according to the channel bit stream CHBS supplied from the data processing unit 20 to control the interruption. In detail, the data processor 20 supplies a channel bit stream CHBS corresponding to the exposure data to the optical modulator 18 in order to record a long pit (that is, a pit having a pit length of 7T or more). The optical modulator intercepts the laser light according to the channel bit stream CHBS and outputs laser light having different power levels. The laser light is incident on the objective lens 22 via the light modulator 18. The objective lens 22 focuses the laser light in the form of a spot on the exposure surface of the photoresist film 26. The spindle motor 26 rotates the substrate 24 on which the photoresist film 26 is formed. Here, since the exposure data includes position information indicating the physical position of the sector included in the pit 12, the channel bit stream CHBS generated by the data processor 20 also includes the physical position information of the sector. . On the other hand, when the pit length is 3T to 6T, a pit having a uniform pit width is formed.

As a result, the optical recording medium manufacturing apparatus intercepts the laser light in the optical modulator 18 in response to the channel bit stream CHBS having a different power level of the laser light in accordance with the exposure data, so that the front end portion 12a and the end portion 12b are separated. A pit shape having a pit width wider than that of the central portion 12c is formed in the optical recording medium.

5 is a block diagram schematically showing an apparatus for manufacturing an optical recording medium according to a second embodiment of the present invention.

Referring to FIG. 5, another apparatus for manufacturing an optical recording medium according to the present invention includes a laser resonator 14 for generating laser light, a beam expander 16 for causing the laser light to have a constant numerical aperture, and a channel bit. An optical modulator 18 for interfering the laser light along the stream CHBS, an optical beam control unit 30 for adjusting the beam diameter of the laser light, and an object for focusing the laser light on the photoresist film 26 in the form of a light spot A lens 22, a spindle motor 26 for rotating the substrate 24, and a data processor 20 for converting exposure data supplied through an input line into a channel bit stream CHBS. The laser light generated from the laser resonator 14 is secured to the optical modulator 18 by the reflector 15 while securing a constant numerical aperture by the beam expander 16. The optical modulator 18 is connected to the data processing unit 20 to turn on / off the laser light according to the channel bit stream CHBS supplied from the data processing unit 20 to control the interruption. The light beam controller 30 is connected to the data processor 20 to adjust the intensity distribution of the light beam interrupted by the optical modulator 18 or the phaser distribution of light under the control of the data processor 20. In this case, as the light beam control unit 30, a light modulation device having a fast time response such as an electro-optic crystal is used. The light beam control unit 18 corresponds to the channel bit stream CHBS of the data processing unit 20 so as to record a long pit (for example, a pit longer than 7T). Turns the sea effect on or off. In detail, as shown in FIG. 6, in the light beam control unit 30 which blocks the amount of incident beam center portion light or reverses the phase, when the pit length is recorded at the tip and the end of the 3T-6T signal or the 7T or more signal, When blocking the incident beam and recording the central part of the signal of 7T or more, a voltage can be applied to the transparent electrode part of the Electro-Optic-Crystal (that is, the part to be blocked) to obtain a blocking effect. At this time, the light beam control unit 30 blocks the amount of light in the center portion of the incident beam or inverts the phase under the control of the data processing unit, so that the main lobe of the beam collected by the objective lens as shown in FIG. You get a super resolution effect that narrows. The laser light modulated to produce a super resolution effect from the light beam control unit 30 is incident on the objective lens 22 to adjust the size of the focused light. The objective lens 22 focuses the laser light in the form of a spot on the exposure surface of the photoresist film 26. The spindle motor 26 rotates the substrate 24 on which the photoresist film 26 is formed. Here, since the exposure data includes position information indicating the physical position of the sector included in the pit 12, the channel bit stream CHBS generated by the data processor 20 also includes the physical position information of the sector. . On the other hand, when the pit length is 3T to 6T, a pit having a uniform pit width is formed.

As a result, the optical recording medium manufacturing apparatus adjusts the beam diameter of the laser light beam in accordance with the channel bit stream CHBS in the light beam control unit 30 under the control of the data processing unit 20 to control the front end portion 12a and the end portion 12b. ), A pit shape having a pit width wider than that of the central portion 12c is formed on the optical recording medium.

As described above, the optical recording medium manufacturing apparatus and method according to the present invention, by adjusting the power level of the laser light or the beam diameter of the laser light beam in accordance with the exposure data, the pit width of the front end portion 12a and the end portion 12b A pit shape wider than the pit width of the central portion 12c is formed on the optical recording medium.

As described above, the optical recording medium according to the present invention is formed so that the pit widths of the tip and the end portions have a pit shape wider than the pit width of the center portion, so that it is suitable for high density.

In addition, the optical recording medium manufacturing apparatus and method according to the present invention by adjusting the power level of the laser light in accordance with the exposure data, or by adjusting the beam diameter of the laser light beam, the pit width of the front end and the terminal end is wider than the center pit width By forming the optical recording medium, the optical recording medium suitable for high density can be formed.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. For example, those skilled in the art will appreciate that the pit recording method according to the detailed embodiment of the present invention can be applied to a phase change disk and a magneto-optical disk.

Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (16)

An optical recording medium comprising a pit wider than the width of the center portion of the tip and the end portions. The method of claim 1, And the pit is formed on an optical recording medium for reproduction only. The method of claim 1, And the pit is formed on a recordable optical recording medium. A first pit wider than the width of the center portion at the tip and the end portions, And a second pit having a uniform width at the tip, center, and end portions. The method of claim 4, wherein And the first pit has a length of 7T or more. The method of claim 4, wherein And the second pit has a length of 3T to 6T. The method of claim 4, wherein And the first and second pits are formed on an optical recording medium for reproduction only. The method of claim 4, wherein And the first and second pits are formed on a recordable optical recording medium. A substrate on which a photoresist film is formed; And the exposure means for exposing the laser light having a power level of the leading end portion and the ending portion higher than the power level of the central portion in the photoresist film. The method of claim 9, Laser generating means for generating laser light, Data processing means for converting the exposure data supplied from the input line into a channel bit stream whose power level at the tip and the end is higher than the power level at the center; And optical modulating means for interrupting the laser light by the channel bit stream. A substrate on which a photoresist film is formed; And an exposure means for exposing a laser beam in which the beam diameter of the tip and the end of the photoresist film is larger than that of the central part. The method of claim 11, Laser generating means for generating laser light, Data processing means for converting the exposure data supplied from the input line into a channel bit stream; Optical modulation means for intermitting the laser light by the channel bit stream; And an optical beam adjusting means for controlling the focused laser beam beam mirror of the tip and the terminal portions to be larger than the laser beam beam diameter of the central portion by the control of the data processing means. Depositing a photoresist film on the substrate; And exposing a laser light to the photoresist film, the laser light having a power level higher than the power level at the front end and the end. The method of claim 13, Generating laser light, Converting the exposure data into a channel bit stream having a different power level; And intermitting the laser light by the channel bit stream. Depositing a photoresist film on the substrate; And exposing the photoresist film to the photoresist film with a laser beam whose tip and end beam speeds are larger than the beam speed in the center portion. The method of claim 15, Generating laser light, Converting the exposure data into a channel bit stream; Interrupting the laser light by the channel bit stream; And adjusting the beam diameter of the laser beam interrupted by the channel bit stream.