JP2005174499A - Manufacturing method of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium having a substrate with in-groove pits formed thereon and capable of reducing a reproduction error rate by surely detecting signals from the pits, and its manufacturing method. <P>SOLUTION: Media information is not recorded on a recording layer by a drive but recorded in grooves of the substrate as emboss pits beforehand in a disk substrate manufacturing step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium and a manufacturing method thereof, a stamper used for manufacturing a substrate of the optical information recording medium, and a manufacturing method thereof, for example, a recording medium having a dye layer in a recording layer such as a DVD-R. The present invention relates to an optical information recording medium in which media information such as a manufacturer name and information for copyright protection measures is written in a pre-pit form.

  In recent years, a DVD (digital versatile disc) having a recording capacity several times that of a CD (compact disc) has been widely used as an information recording medium for recording information such as images and sounds such as movies. Also, with this DVD, a DVD-R (recordable digital versatile disc) that allows the user to record information only once, and a DVD-RW (rewritable) that allows information to be rewritten. Type digital versatile disc) has already been commercialized and is widely used as a future large-capacity information recording medium.

  Usually, in a write-once recording medium such as a DVD-R, information such as the type and recording range of the disk, information for copyright protection measures (hereinafter referred to as media information) is located at a predetermined place on the innermost periphery of the disk. Pre-recorded. These pieces of media information are recorded by modifying the recording layer by light irradiation or the like using a recording device at the final stage of the disc manufacturing process. For this reason, enormous costs such as process management and installation of a recording device are required.

  On the other hand, a method is disclosed in which ROM data to be formed such as a partial ROM is recorded in the form of embossed pits (hereinafter referred to as in-groove pits) in advance on the substrate groove in the disk substrate manufacturing stage (for example, Patent Document 1). reference). A part of the optical information recording medium manufactured by using this method is shown in FIG. FIG. 1A is a partially enlarged plan view of an optical information recording medium, and schematically shows an area where an in-groove pit is formed (hereinafter referred to as an in-groove pit area). Moreover, FIG.1 (b) and (c) are the figures which respectively showed the AA line cross section and BB line cross section of Fig.1 (a). In this optical information recording medium, as shown in FIG. 1B, the depth to the bottom surface (lowermost surface) 107a of the in-groove pit 107 with reference to the land surface 101a of the substrate 101 on which lands and grooves are formed. Similarly, the depth dp ″ is formed deeper than the depth dg ″ from the land surface 101a to the bottom surface (lowermost surface) 105a of the groove 105. Thus, when the recording layer 102 and the reflective layer 103 are formed on the pattern formation surface of the substrate 101, the portion where the in-groove pit 107 is formed and the portion of the groove where the in-groove pit 107 is not formed A difference occurs in the surface height of each layer to be formed. Therefore, by utilizing the difference in depth between the in-groove pit portion and the groove portion, data such as media information can be recorded in the groove.

  In DVD-R and DVD-RW substrates, pits (hereinafter referred to as land pre-pits) are provided on lands formed between grooves, and address information of a disc is recorded (for example, patents). References 2 and 3). Further, the height of the groove and the height of the land pre-pit are limited (for example, see Patent Document 4). In addition, in a master exposure process for manufacturing a substrate having pits, a method is known in which the exposure intensity is switched while a pattern corresponding to one pit is exposed (see, for example, Patent Document 5).

Japanese Patent Laid-Open No. 2001-67733 (page 5-6, FIG. 1-3) JP 09-326138 A (pages 1-8, FIGS. 3 and 15) JP 2001-118288 A (page 1-8, FIG. 1) JP 2001-319379 (page 1-5, FIG. 1) JP 63-153743 A (pages 278, 280-282, FIG. 3)

  In an optical information recording medium having in-groove pits, as shown in FIG. 1, the in-groove pits are closer to the middle part in the track direction than the end part in the track direction (that is, the groove direction) (hereinafter referred to as the middle part) The width (the length in the radial direction of the disk) is formed wide. This is considered to be caused by the fact that the integrated exposure amount of the laser beam to be irradiated becomes large in the middle part of the pattern when exposure for forming a pattern corresponding to the in-groove pits on the master is performed. As a result, the width of the intermediate portion of the in-groove pit is wider than the width of the groove, and the side wall of the adjacent land is eroded. That is, the width of the land adjacent to the in-groove pit is narrowed. In particular, when a land pre-pit is formed on a land adjacent to the in-groove pit, the integrated exposure amount between the in-groove pit and the land pre-pit increases due to the influence of the laser light of the in-groove pit and the land pre-pit. However, the width and height of the land surface could not be secured sufficiently. As a result, as shown in FIG. 2B, the jitter of the detection signal of the land pre-pit becomes large, the aperture ratio (AR) does not satisfy the predetermined required value, and the error rate increases. . For this reason, there has been a problem that it is impossible to achieve both the reproduction error rate of the groove having in-groove pits and the reproduction error rate of the groove not having in-groove pits.

  As far as the present inventor knows, in order to control the shape of the in-groove pit formed deeper than the groove, the exposure intensity of the in-groove pit formation pattern is controlled in the master exposure, and adjacent to the in-groove pit. There is no example of controlling the exposure intensity of the land pre-pit.

  Further, when information is actually recorded / reproduced using such an optical information recording medium having in-groove pits, an in-groove pit area and an area in which only a groove which is a user-side recording area is formed ( In the following, when tracking the boundary with the groove region), an error that often goes out of tracking has been confirmed. At this boundary, the difference in shape between the in-groove pit and the groove is large, and the center of the radial push-pull signal obtained when tracking is performed so as to cross this boundary. As a result, the balance of the radial push-pull signal is greatly lost, the amplitude level of the radial push-pull signal is lowered, and an error in tracking error occurs. In particular, in DVD-R and DVD-RW, tracking is performed using a radial push-pull signal, and prevention of the tracking error is an indispensable problem.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical information recording medium having a substrate on which in-groove pits are formed and capable of reliably detecting a signal from the pits to reduce a reproduction error rate and a method for manufacturing the same. Is to provide.

According to the first aspect of the present invention, in an optical information recording medium having a circular substrate having a plurality of lands and grooves formed thereon, and a recording layer and a reflective layer on the circular substrate, One pit and a second pit whose length in the track direction is longer than the first pit are formed, and the maximum width in the substrate radial direction of the first pit is represented by W ₁ , and the maximum in the substrate radial direction of the second pit is expressed as W _1. Provided is an optical information recording medium characterized in that 1 <W ₂ / W ₁ <1.2, where W ₂ is a significant value.

  A plurality of lands and grooves are formed on the substrate of the optical information recording medium of the present invention, and pits (in-groove pits) are formed at the bottoms of some of the grooves. The in-groove pit has a reduced width in the substrate radial direction regardless of the length in the groove direction, and the land shape adjacent to the in-groove pit also has a constant land and groove shape without the side wall being greatly shaved. Is maintained.

  Here, the first pit and the second pit are arbitrary lengths determined based on a unit of length determined by data to be modulated. For example, in the EFM modulation adopted in the DVD standard, the first pit and the second pit are in the range of 3T to 14T. A pit with a length.

  Adjacent land pre-pits in a groove having no in-groove pits have a small integrated exposure amount between the grooves and the land pre-pits, and therefore a sufficient land surface (hereinafter referred to as a land pre-pit side wall) can be formed. However, this resulted in an increase in the number of playback errors in recording / playback of a groove having no in-groove pits. As a result of experiments conducted by the inventors on the formation conditions of the groove and the land prepit, the land height dg from the groove bottom surface and the height dlg of the side wall adjacent to the land prepit are as shown in FIG. It was found that the number of reproduction errors increased unless the condition of 0.3 ≦ dlg / dg ≦ 0.7 was satisfied. In order to create this shape, it is necessary to generate a certain amount of integrated exposure amount of the laser light for exposing the groove to the land portion and the laser light for exposing the land prepit.

  In particular, an optical information recording medium manufactured using a substrate in which pits (land prepits) are formed on lands adjacent to in-groove pits can reliably detect land prepit recording signals. As a result of the inventors' experiment on the formation conditions of the in-groove pits and the land pre-pits, as shown in FIG. 3B, the height of the land pre-pit side wall from the groove bottom surface is dlp, and the groove bottom surface Since the land height from is the same as the depth from the land surface, dg is preferably set to 0.4 ≦ dlp / dg <1.

  In the present invention, the recording layer is preferably formed of a dye material. Moreover, it is desirable that the dye material is an azo dye material.

  In the present invention, a groove on which the first and second pits are not formed is further formed on the circular substrate, land pre-pits are formed between the grooves, and the land height from the groove bottom surface is the land surface. Therefore, it is desirable that 0.3 ≦ dlg / dg ≦ 0.7 when dg is the height of the side wall adjacent to the land prepit with respect to the groove bottom surface.

According to a second aspect of the present invention, there is provided a method for manufacturing an optical information recording medium according to the first aspect, wherein a photosensitive material formed on a master is divided into a first exposure intensity and a first exposure intensity. By exposing the photosensitive material to a pattern corresponding to at least the second pit by exposing the photosensitive material while changing to a lower second exposure intensity, the photosensitivity is increased with a third exposure intensity lower than the second exposure intensity. Exposing the photosensitive material to a pattern corresponding to the groove by exposing the material;
The first pit, the second pit, the land adjacent to the groove, the first land pre-pit exposed by the photosensitive material with a fourth exposure intensity, and the photosensitive material with a fifth exposure intensity higher than the fourth exposure intensity. Exposing a second land pre-pit to expose a pattern corresponding to the land,
After the exposure, the master is developed to form a pattern corresponding to the first pit, the second pit, the first land prepit, the second land prepit, and the groove;
Forming a substrate using a master on which the pattern is formed;
There is provided a method of manufacturing an optical information recording medium including forming a recording layer and a reflective layer on the substrate.
By using the method of the present invention, the optical information recording medium of the present invention can be produced.

  Preferably, the method for manufacturing an optical information recording medium includes exposing the photosensitive material to a pattern corresponding to a first pit by exposing the photosensitive material with a first exposure intensity. The exposure intensity when the pattern corresponding to the second pit is exposed to the photosensitive material may be changed to the first exposure intensity, then the second exposure intensity, and further changed to the first exposure intensity. preferable. Furthermore, it is desirable to include setting the exposure intensity to 0 before and after exposing the pattern corresponding to the first pit and the second pit. It is desirable that the development includes performing etching by RIE.

  According to a third aspect of the present invention, in the optical information recording medium having a substrate on which a plurality of lands and grooves are formed, and a recording layer and a reflective layer on the substrate, the groove is the first groove; A second groove wider than the first groove; a third groove formed with pits; and a fourth groove formed with pits narrower than the pits of the third groove; An optical information recording medium is provided in which four grooves are arranged in the order of a first groove, a second groove, a fourth groove, and a third groove.

  A plurality of lands and grooves are formed on the substrate of the optical information recording medium of the present invention, and in-groove pits are formed in some of the grooves. In addition, a boundary pit area is provided between the in-groove pit area and the groove area, and a groove (boundary groove) wider than a normal groove is provided between the boundary pit area and the groove area. Yes. In the optical information recording medium using this substrate, by providing the boundary groove area, the change in the groove width adjacent to each other from the groove area to the boundary pit area becomes gradual. Therefore, the optical information recording medium according to the first aspect In comparison, the disturbance of the radial push-pull signal can be further suppressed. Further, since the boundary groove area is provided between the groove area and the boundary pit area, the size of the in-groove pit in the boundary pit area can be increased as compared with the case where the boundary groove area does not exist. This makes it possible to obtain a reproduction signal with a high degree of modulation from the in-groove pit in the boundary pit area.

  In the present invention, the half width of the first groove is represented by Wg, the half width of the second groove wider than the first groove is represented by Wgb, and the half width of the third groove including the in-groove pit is represented by Wp. When the half width of the fourth groove including the in-groove pits is expressed by Wpb, Wg ≦ Wgb ≦ Wpb ≦ Wp may be satisfied. The ratio Wp / Wpb between the half width Wp and the half width Wpb is preferably 1.05 ≦ Wp / Wpb ≦ 1.15. As described above, when Wp / Wpb <1.05, the radial push-pull signal in the first groove is likely to be offset or disturbed, and when 1.15 <Wp / Wpb, the input formed in the third groove. This is not desirable because the signal modulation degree from the groove pit is lowered. In order to sufficiently suppress the offset and disturbance of the radial push-pull signal, the ratio Wgb / Wg of the half width Wgb to the half width Wg is preferably 1.03 ≦ Wgb / Wg ≦ 1.15.

  In the present invention, the recording layer is preferably formed of a dye material. Moreover, it is desirable that the dye material is an azo dye material. Furthermore, the recording layer may contain tellurium.

In the present invention, the maximum depression depth of the recording layer from the boundary surface between the recording layer and the reflective layer in the first groove is represented by Tg, and the maximum recording layer from the boundary surface between the recording layer and the reflective layer in the second groove. The depression depth is represented by Tgb, the recording layer maximum depression depth from the boundary surface between the recording layer and the reflective layer in the third groove is represented by Tp, and the boundary surface between the recording layer and the reflective layer in the fourth groove. It is desirable that Tg ≦ Tgb ≦ Tpb ≦ Tp when the maximum depth of the recording layer is expressed by Tpb. The pits formed in the same groove of the groove are composed of a first pit and a second pit whose length in the groove direction is longer than that of the first pit. When the maximum width is represented by W ₁ and the maximum width of the second pit in the substrate radial direction is represented by W ₂ , it is desirable that 1 <W ₂ / W ₁ <1.2.

  According to a fourth aspect of the present invention, there is provided a method for producing an optical information recording medium according to the third aspect, wherein the photosensitive material formed on the master is irradiated with four different exposure intensities, Exposing the photosensitive material to patterns corresponding to the pits of the first groove, the second groove, the third groove, and the fourth groove; after the exposure, the master is developed to develop the first groove, the second groove, Forming a pattern corresponding to the third groove with pits and the fourth groove with pits; forming a substrate using the master on which the pattern is formed; forming a recording layer and a reflective layer on the substrate; There is provided a method for manufacturing an optical information recording medium.

  By using the manufacturing method of the present invention, the optical information recording medium of the third aspect of the present invention can be manufactured.

  In the present invention, the exposure intensity at the time of exposing the pattern corresponding to the pit is set to the first exposure intensity, then to the second exposure intensity lower than the first exposure intensity, and further to the first exposure intensity. It is desirable to change. Thereby, even when an in-groove pit having a long pit length is formed, the spread of the width in the substrate radial direction can be suppressed. Further, it is desirable that the second exposure intensity is 70% of the first exposure intensity. When the clock period for reproducing the optical information recording medium is represented by T, it is desirable to set the period of exposure at the first exposure intensity to 1T to 1.5T, respectively. Furthermore, it is desirable to include setting the exposure intensity to 0 in addition to the above four kinds of exposure intensity when the master is exposed. It is desirable that the development includes performing etching by RIE.

  According to the present invention, in an optical information recording medium having an in-groove pit using a dye recording material for a recording layer, the shape due to the pit length of the in-groove pit shape is suppressed, and the land pre-pit signal is reliably transmitted. Because it can be detected, the error rate can be reduced, and by providing a boundary area between the in-groove pit area and the groove area, the characteristics of the recording / reproducing signal can be improved and tracking errors can be suppressed. Media information such as protection information can be detected stably, and it is not necessary to record media information for each medium, thereby reducing costs.

  Hereinafter, examples according to the present invention will be described, but the present invention is not limited thereto.

[Manufacturing method of master and stamper for substrate manufacture]
As shown in FIG. 4, the substrate 1 of the optical information recording medium in the present invention is partitioned into a groove region 71, an in-groove pit region 73, and a groove region 75 in order from the inner peripheral side of the substrate 1. A master and a stamper manufacturing method for manufacturing the substrate 1 will be described with reference to FIGS. As shown in FIG. 5 (a), a glass master 50 having a diameter of 200 mm and a thickness of 6 mm was prepared. Next, as shown in FIG. 5B, a photoresist 52 was uniformly applied to a thickness of 200 nm on one surface 50a of the glass master 50 by using a spin coating method. Next, the glass master disc 50 on which the photoresist 52 was formed was mounted on a cutting device (not shown). The cutting device (master exposure device) is mainly composed of a Kr gas laser light source that oscillates laser light with a wavelength of 351 nm, a light modulator composed of an acoustic light modulator, a condensing lens, and a drive device for rotating the glass master. Has been. As shown in FIG. 5C, the laser light LS emitted from the laser light source of the cutting apparatus is irradiated onto the photoresist 52 on the glass master 50 through the light modulator and the condenser lens. At this time, the glass master 50 was rotated around the central axis AX of the glass master 50 at a predetermined rotational speed. Further, the laser beam LS is moved so that the irradiation position of the laser beam LS on the glass master 50 moves from the inside to the outside of the glass master 50 along the radial direction of the glass master 50 (arrow AR2). .

  As described above, while moving the laser beam LS, the exposure intensity of the laser beam LS applied to the glass master 50 is changed using the optical modulator. A region having a radius of 19 mm to 24 mm from the central axis AX of the glass master 50 corresponds to the groove region 71 of the substrate 1 shown in FIG. 4 (hereinafter referred to as a first groove forming region). An area having a radius of 24 mm to 24.1 mm corresponds to the in-groove pit area 73 of the substrate 1 (hereinafter referred to as an in-groove pit formation area). Furthermore, an area having a radius of 24.1 mm to 58.9 mm is a user data area and corresponds to the groove area 75 of the substrate 1 (hereinafter referred to as a second groove forming area). In this embodiment, the exposure intensity in the first and second groove forming areas was set to a low level (hereinafter referred to as the groove level). Further, in the in-groove pit formation region, as shown in FIG. 6, the exposure intensity of the laser beam was changed in three steps: low level, medium level and high level. The exposure intensity when forming the portion corresponding to the in-groove pit in the in-groove pit formation region (hereinafter referred to as the in-groove pit formation portion) is high (hereinafter referred to as the first pit level) and intermediate (hereinafter referred to as second). The exposure intensity of the groove portion other than that was set to the groove level. In this embodiment, when the signal output of the first pit level is 100%, the second pit level is set to 70% and the signal output of the groove level is set to 50%. Further, land pre-pits are formed in lands between the grooves in the entire area of radius 19 mm to 58.9 mm in FIG. 4, and correspond to land pre-pits formed in the in-groove pit area having a radius of 24 mm to 24.1 mm. The portion is (hereinafter referred to as a first land preset forming portion), and as shown in FIG. 6, the intensity level of the laser beam is set to a low level (hereinafter referred to as a first LPP level), a radius of 19 mm to 24 mm, and a radius of 24.1 mm. A portion corresponding to the land prepits in the first and second groove forming areas of ˜58.9 mm (hereinafter referred to as a second land prepit forming portion) is defined as a second land prepit level (hereinafter referred to as a second LPP level). The intensity level of the laser beam was set at a high level in two stages. When the signal output of the second LPP level is 100%, the signal output of the first LPP level is 90%.

  As shown in FIG. 6, in the exposure of the in-groove pit formation portion, the exposure is performed at the first pit level (high level) for 1T to 1.5T (T: clock cycle) from the start, and then the exposure intensity is set to the first level. The exposure was reduced to the 2-pit level (medium level). Further, during the period from 1T to 1.5T until the end of the in-groove pit formation portion, exposure was performed with the exposure intensity returned to the first pit level again. As a result, the width of the in-groove formation portion in the master disk radial direction does not increase near the middle portion of the in-groove pit formation portion. This is presumably because the integrated exposure amount during exposure at the second pit level is reduced, and the expansion of the exposure range in the radial direction of the master during that time is suppressed. The in-groove pits in the in-groove pit region of the substrate are formed in a desired pattern with a channel bit length of 3T to 11T or 14T in the track (groove) direction. The in-groove pit formation portion formed with the shortest channel bit length of 3T has almost no width expansion due to the influence of the integrated exposure amount, so the two-step exposure intensity switching as described above is not performed, and the first pit level is fixed. And exposed. In this embodiment, by switching the exposure intensity as described above, the width of the in-groove pit formation portion having a channel bit length longer than the shortest channel bit length is changed to the width of the in-groove pit formation portion having the shortest channel bit length. Was able to be the same size. Note that the clock period T can be adjusted as appropriate according to the reproduction apparatus used.

  Further, in this embodiment, as shown in FIG. 6, the exposure intensity of the laser beam is temporarily changed every time the exposure intensity is switched from the first pit level to the groove level or from the groove level to the first pit level. A period for setting to 0 level was provided. The period of the 0 level was changed according to the channel bit length of the pit to be formed. At the time of exposure of the in-groove pit formation portion having the shortest channel bit length of 3T, the period of 0 level was set to 0.2T. Thereby, the processing accuracy of the in-groove pit formation portion of the master is improved.

  Next, the glass master on which the photoresist was exposed was taken out of the cutting apparatus and developed. 7A and 7B, the groove forming part 40, the in-groove pit forming part 44, and the first land prepit forming part 42 in the in-groove pit forming area are formed on the glass master 50. Been formed. The groove forming portion 40 and the first land prepit forming portion 42 are formed so as to have a V-shaped groove shape in cross section. At this time, the groove width drl1 of the first land prepit forming part 42 is narrower than the groove width drg of the groove forming part 40. Further, in the in-groove pit forming portion 44, the photoresist 52 on the glass master 50 is removed by development processing, and the surface 50a of the glass master 50 appears as an exposed portion 44a as shown in FIG. 7B.

Next, as shown in FIG. 8 (a), the surface of the photoresist 52 formed on the glass master 50 is made of C ₂ F ₆ gas using a RIE (reactive ion etching) apparatus (not shown). Etched in atmosphere. Thereby, the in-groove pit forming portion 44 is etched from the surface 50a of the glass master 50 to a depth of 90 nm. At this time, the etching amount of the glass and the photoresist is about 2: 1. Next, as shown in FIG. 8B, in order to expose the surface 50a of the glass master 50 in the groove forming portion 40 and the land pit forming portion 42, a photoresist ashing apparatus using O ₂ (not shown) is used to form a photoresist. 52 was shaved by a predetermined thickness. Thus, the glass master surface 50a of the groove forming portion 40 and the land prepit forming portion 42 was exposed. Further, as shown in FIG. 8C, RIE was performed again in a C ₂ F ₆ gas atmosphere on the surface of the glass master 50 where the photoresist 52 was formed. As a result, the groove forming portion 40 was etched from the glass master surface 50a to a depth of 170 nm. Further, since the land pre-pit forming portion 42 has the same bottom surface as the groove forming portion, the side wall height dlp of the first land pre-pit is 170 nm with reference to the groove bottom surface. At the same time, the in-groove pit formation portion 44 was etched from the glass master surface 50a to a depth of 260 nm. Next, as shown in FIG. 8D, the photoresist 52 on the glass master 50 was removed again using a resist ashing device (not shown). As a result, a glass master 50 having a desired pattern formed on the surface was obtained.

  Similarly, in the first and second groove forming regions, a groove forming portion 40 and a second land prepit forming portion 43 as shown in FIGS. 9A and 9B were formed on the glass master 51. The groove forming portion 40 and the second land prepit forming portion 43 are formed so as to have a V-shaped groove shape in cross section. At this time, the land portion adjacent to the second land pre-pit is affected by the integrated exposure intensity of the exposure intensity of the second land pre-pit and the exposure intensity of the groove, and is slightly developed and formed in a state slightly lower than the land surface. Is done.

Next, as shown in FIG. 10, the same processing as in FIG. 8 was performed, and etching was performed in a C 2 F 6 gas atmosphere using an RIE apparatus (not shown) as shown in FIG. At this time, since the glass surface is not exposed, it is not etched. Next, as shown in FIG. 10B, the photoresist 52 was shaved by a predetermined thickness using a resist ashing apparatus using O2 (not shown). Thereby, the glass master disk surface 51a of the groove formation part 40 and the land prepit formation part 43 was exposed. Furthermore, as shown in FIG. 10C, RIE was performed again in a C ₂ F ₆ gas atmosphere on the surface of the glass master 51 where the photoresist 52 was formed. As a result, the groove forming portion 40 was etched from the glass master surface 50a to a depth of 170 nm. The second land pre-pit forming portion 43 starts to be etched in the middle of the C ₂ F ₆ process because the photoresist on the side wall is thinner than the other portions. Since the bottom surface of the second land prepit is the same as the groove, the side wall height dlg of the second land prepit is formed to a height of 90 nm on the basis of the groove bottom surface. Next, as shown in FIG. 10D, the photoresist 52 on the glass master 51 was removed using a resist ashing device (not shown) again. Thus, a glass master 51 having a desired pattern formed on the surface was obtained.

Electroless plating was applied to the pattern forming surface of the glass master 50 as a pretreatment for plating. Further, by using this plating layer as a conductive film, a Ni layer having a thickness of 0.3 mm was formed by electroforming. Next, the surface of the Ni layer formed on the glass master 50 was polished, and the Ni layer was peeled from the glass master to obtain a stamper. In addition, you may perform the electrically conductive film formation in the pre-processing of the said plating using a sputtering method or a vapor deposition method.
[Method of manufacturing information recording medium]

  The above stamper was mounted on an existing injection molding apparatus, and the substrate 1 was obtained by injection molding. The substrate 1 is a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm, and a pattern having the same shape as the concavo-convex pattern formed on the glass master is transferred onto one surface of the substrate 1 as shown in FIG. Has been. As described above, the substrate 1 is formed with the groove area 71, the in-groove pit area 73, and the groove area (user data area) 75. In the in-groove pit area 73, as shown in FIG. 12A, a groove 80, a land pre-pit 82, and an in-groove pit 84 are formed. Among these, the width in the substrate radial direction of the in-groove pit having the shortest channel bit length 3T and the width in the substrate radial direction of the in-groove pit having a longer channel bit length are measured using a scanning probe microscope manufactured by Digital Instruments. Measured. The maximum width of the in-groove pit having the shortest channel bit length 3T was 0.34 μm. The maximum width of the in-groove pit having the channel bit length 11T was 0.38 μm. Further, the maximum width of the in-groove pit having the channel bit length 14T was 0.4 μm. According to experiments by the present inventors, the ratio of the maximum width of the in-groove pit having a channel bit length longer than the shortest channel bit length 3T to the maximum width of the in-groove pit having the shortest channel bit length 3T is 112 to 118%. It can be seen that in the in-groove pit longer than the shortest channel bit length, the spread of the width in the substrate radial direction is suppressed.

  A solution having a concentration of 1% by weight of an azo dye represented by the following chemical formula (1) is spin-coated on the pattern forming surface of the substrate 1 so as to have a thickness of 30 nm between the grooves, that is, between the lands. It was applied using the method. At this time, the application amount of the solution was 1 g, and the substrate was rotated at a rotation speed of 100 rpm for 30 seconds from the start of application, and then at a rotation speed of 800 to 1000 rpm for 30 seconds. In addition, when apply | coating the said pigment | dye solution, it was set as the azo dye solvent by using tetrafluoropropanol as a solvent, and it filtered with the filter, and removed the impurity. Subsequently, the board | substrate 1 which apply | coated the said pigment | dye material was dried at 70 degreeC for 1 hour, and also it cooled at room temperature for 1 hour. Thus, the recording layer 2 was formed on the substrate 1 (see FIG. 12B).

  Further, as shown in FIG. 12B, an Ag alloy was formed as the reflective layer 3 on the recording layer 2 by a sputtering method so as to have a thickness of 100 nm. Next, a UV resin material was applied on the reflective layer 3 by a spin coating method so as to have a thickness of 10 μm, and a polycarbonate substrate (dummy substrate) having a thickness of 0.6 mm was placed thereon. . In this state, the substrate on which each layer was formed was irradiated with UV, whereby the substrate on which each layer was formed and the dummy substrate were bonded to obtain an optical information recording medium.

  With respect to the optical information recording medium thus obtained, the maximum depth of the in-groove pit, the groove and the land pre-pit in the in-groove pit area 73 was measured using a scanning probe microscope manufactured by Digital Instruments. These depths were set to the depth from the surface of the land 81 of the substrate as shown in FIG. The maximum depth dg of the groove was 170 nm, and the maximum depth dp of the in-groove pit was 260 nm. The maximum depth dlp of the land prepits was 170 nm, which is the same as the maximum depth dg of the grooves. In addition, the in-groove pit, the groove and the first land prepit recording layer recess depth in the in-groove pit region 73 were measured using a scanning probe microscope manufactured by Digital Instruments. Here, the recording layer recess depth refers to the maximum recess amount of the recording layer 2 with respect to the surface 2 a of the recording layer 2 formed on the land 81. The recording layer recess depth Tg of the groove was 100 nm, and the recording layer recess depth Tp of the in-groove pit was 170 nm. The recording layer recess depth Tlp in the land pre-pit was 90 nm.

  Further, the depths of the grooves and land prepits in the groove forming part were measured using a scanning probe microscope manufactured by Digital Instruments. With respect to the height of the side wall of the second land prepit, no land surface is formed. Therefore, in FIG. 13B, the side wall height dlg of the first land prepit is 90 nm with the groove bottom as the reference plane. It was. The groove depth (height) dg was 170 nm. Further, the depths of the grooves in the groove forming region and the recording layer of the second land prepit were measured using a scanning probe microscope manufactured by Digital Instruments. The depth of the recording layer recess was the same as described above, the recording layer recess Tg of the groove was 100 nm, and the recording layer recess Tlg of the second land prepit was 110 nm.

  The optical information recording medium obtained in the above example was reproduced using a laser beam having a wavelength of 650 nm and an optical pickup having a lens with a numerical aperture of 0.6. Signal detection and reproduction could be performed stably, and the signal modulation degree of the reproduction signal at this time was 61% and the jitter was 7.2%, and good results were obtained in both cases. Further, as shown in FIG. 2A, the land pre-pit recording signal can be stably detected. As a result, the aperture ratio also satisfies the required value, and the error rate can sufficiently satisfy the standard 5%.

  Also, the reproduction error was good in the groove forming area where recording / reproduction was performed, and the standard could be satisfied over the entire surface.

  In the optical information recording medium of the above embodiment, polycarbonate is used as the substrate, but polymethyl methacrylate, amorphous polyolefin, or the like may be used.

  In the substrate of the optical information recording medium in the present invention, as shown in FIG. 13, in order from the inner peripheral side of the substrate 1, a groove region 71, a boundary groove region 76, a boundary pit region 72, an in-groove pit region 73, a boundary pit A region 74, a boundary groove region 77, and a groove region 75 are formed.

  An embodiment of the present invention will be described with reference to FIGS. In this embodiment, between the groove area of the substrate used for the optical information recording medium and the in-groove pit area 73, a groove having a width wider than the groove in the boundary pit area and the groove area (hereinafter referred to as the boundary groove) is formed for one track. The configuration was the same as in Example 1 except that. Hereinafter, a method for manufacturing a master, a stamper, and an optical information recording medium used for manufacturing the substrate will be described.

  In the present embodiment, as in the first embodiment, the laser light is moved on the glass master, and the exposure intensity of the laser light irradiated on the glass master is changed using the optical modulator. In this example, as shown in FIG. 14, the exposure intensity of the laser beam was changed in four stages of level 1, level 2, level 3, and level 4 in order from the lowest. The ratio of each level in the present example was set so that level 3 was 90%, level 2 was 60%, and level 1 was 55% when level 4 was 100%. As shown in FIG. 14, the exposure intensity in the first and second groove forming areas was set to level 1. In the in-groove pit formation region, the exposure intensity of the in-groove pit formation portion was set to level 4, and the exposure intensity of the other groove portions was set to level 1. The exposure intensity of the groove forming portion in the boundary groove forming region was set to level 2. The exposure intensity of the in-groove pit formation portion in the boundary pit formation region was set to level 3, and the exposure intensity of the other groove portions was set to level 1. In the optical information recording medium of the present embodiment, by providing boundary grooves and boundary pits, the change in groove width from the boundary groove area to the boundary pit area becomes gradual, so that the radial push-pull signal is less likely to be offset or disturbed. Become. Thereby, a sufficient degree of modulation can be obtained even in the in-groove pit formed in the boundary pit. Therefore, the in-groove pit pattern formed in the boundary pit is not limited to a random pattern such as a dummy, but may be a recording signal pattern of user information. As a result, a pattern corresponding to the in-groove pit is also formed in the pattern of the in-groove pit formation portion in the boundary pit formation region of the master.

  Next, the glass master on which the photoresist was exposed was developed in the same manner as in Example 1, and the glass master was etched using an RIE apparatus or the like according to the remaining photoresist pattern. This obtained the glass original disc in which the desired uneven | corrugated pattern was formed in the surface. In this example, the groove forming portion and the boundary groove forming portion were etched to a depth of 170 nm from the glass master surface, and the in-groove pit forming portion and the boundary pit forming portion were etched to a depth of 260 nm from the glass master surface. Further, the boundary groove forming part was formed wider than the groove forming part.

  In the present embodiment, as in the first embodiment, when changing the exposure intensity during exposure, a period for temporarily setting the exposure intensity of the laser beam to 0 level is provided every time the exposure intensity is switched. Further, in this embodiment, the master exposure was performed in the in-groove pit formation region while controlling the exposure intensity of each in-groove pit formation portion having a predetermined pit length as follows. As shown in FIG. 14, exposure is performed at level 4 for 1T to 1.5T (T: clock cycle) from the start of exposure, and then the exposure intensity is reduced to 70% of level 4 for a predetermined period. Exposed. Further, exposure was performed again by returning the exposure intensity to level 4 for 1T to 1.5T until the end of the in-groove pit formation portion. As a result, the width of each in-groove pit formation portion in the master disk radial direction is prevented from spreading near the intermediate portion in the track direction of the in-groove pit formation portion. The exposure intensity of the in-groove pit formation portion in the boundary pit formation area may be similarly controlled.

  Using the master thus obtained, a substrate was produced using an injection molding method in the same manner as in Example 1. Next, as shown in FIG. 15B, the recording layer 2 and the reflective layer 3 were formed in the same manner as in Example 1. An optical information recording medium was obtained by attaching a dummy substrate to the obtained substrate via a photocurable resin.

  For the optical information recording medium thus obtained, the maximum depths of the in-groove pit portion of the in-groove pit region 73, the boundary pit portion of the boundary pit region 74, the groove portion of the boundary groove region 76, and the groove portion of the groove region 75 are Measurement was performed using AFM manufactured by Digital Instruments. As shown in FIG. 15B, the maximum depth dg of the groove portion was 170 nm. The maximum depth dgb of the boundary groove portion was 170 nm. The maximum depth dpb of the boundary pit portion was 260 nm. The maximum depth dp of the in-groove pit portion was 260 nm. Note that the maximum depth dg of the groove portion and the maximum depth dp of the in-groove pit portion are 1.4 ≦ dp / dg ≦ 1.7 in order to obtain good recording / reproduction signal characteristics such as the degree of signal modulation and jitter. It is desirable to satisfy the following conditions.

  Further, with reference to the surface of the land 80, the half-value width Wp of the in-groove pit portion of the in-groove pit region 73, the half-value width Wpb of the boundary pit portion of the boundary pit region 74, the half-value width Wgb of the groove portion of the boundary groove region 76, The full width at half maximum Wg in the groove portion of the groove region 75 was measured using AFM manufactured by Digital Instruments. The full width at half maximum Wg was 320 nm, the full width at half maximum Wgb was 330 nm, the full width at half maximum Wpb was 360 nm, and the full width at half maximum Wp was 400 nm. From this, it can be seen that the relationship of Wg ≦ Wgb ≦ Wpb ≦ Wp is established. It can also be seen that the ratio of the half width Wp to the half width Wpb is Wp / Wpb = 1.11 and the condition of 1.05 ≦ Wp / Wpb ≦ 1.15 is satisfied. Further, it is understood that the ratio Wgb / Wg = 1.03 of the half width Wgb and the half width Wg satisfies the condition of 1.03 ≦ Wgb / Wg ≦ 1.15.

  Further, in the optical information recording medium obtained in the present embodiment, as shown in FIG. 15A, the track direction of the in-groove pit 73a in the in-groove pit area 73 as a result of exposure with the exposure schedule as described above. The spread of the width in the substrate radial direction is suppressed near the intermediate portion. Thereby, a land surface having a sufficient area can be secured also in the land portion 77 adjacent to the in-groove pit. Therefore, a stable radial push-pull signal can be obtained from this optical information recording medium.

  Further, in order to adjust the effect of suppressing the spread of the width of the in-groove pit 73a, in the in-groove pit region 73, the width of the in-groove pit having the shortest channel bit length 3T in the substrate radial direction and a longer channel bit length are set. The width of the in-groove pits in the substrate radial direction was measured using a scanning probe microscope manufactured by Digital Instruments. The maximum width of the in-groove pit having the shortest channel bit length 3T was 0.34 μm. The maximum width of the in-groove pit having the channel bit length 11T was 0.38 μm. Further, the maximum width of the in-groove pit having the channel bit length 14T was 0.4 μm. According to experiments by the present inventors, the ratio of the maximum width of the in-groove pit having a channel bit length longer than the shortest channel bit length 3T to the maximum width of the in-groove pit having the shortest channel bit length 3T is 112 to 118%. It can be seen that in the in-groove pit longer than the shortest channel bit length, the spread of the width in the substrate radial direction is suppressed.

  Further, in the same manner as in Example 1, the in-groove pit portion of the in-groove pit region 73, the boundary pit portion of the boundary pit region 74, the groove portion of the boundary groove region 76 and the groove region 75 of the obtained optical information recording medium are obtained. The depth of the recording layer recess was measured using an AFM manufactured by Digital Instruments. As shown in FIG. 12B, the recording layer recess depth Tp in the in-groove pit region 73 was 170 nm. The recording layer recess depth Tpb in the boundary pit region 74 was 135 nm. The recording layer recess depth Tgb of the boundary groove region 76 was 110 nm. The recording layer recess depth Tg of the groove region 75 was 100 nm. Note that the recording layer recess depth Tp and the recording layer recess depth Tg are set to 1.6 ≦ Tp / Tg ≦ to obtain a recording / reproduction signal characteristic such as a good signal modulation degree and jitter as in the first embodiment. It is desirable to satisfy the condition of 2.0.

  Further, the recording layer recess depth Tpb in the boundary pit region 74, the recording layer recess depth Tp in the in-groove pit region 73, the recording layer recess depth Tgb in the boundary groove region 76, and the recording layer recess depth in the groove region 75 are recorded. The relationship with the thickness Tg is Tg ≦ Tgb ≦ Tpb ≦ Tp from the relationship between the groove half-value widths of the respective regions.

The optical information recording medium obtained in the above example was reproduced using a laser beam having a wavelength of 650 nm and an optical pickup having a lens with a numerical aperture of 0.6. Signal detection and reproduction could be performed stably, and the signal modulation degree of the reproduction signal at this time was 61% and the jitter was 7.2%, and good results were obtained in both cases.
(Comparative Example 1)

  Next, a comparison result between the radial push-pull signal output of the optical information recording medium manufactured in the above embodiment and the radial push-pull signal output of the conventional information recording medium having in-groove pits is shown. FIG. 16A shows the detection result of the optical information recording medium manufactured in the above embodiment. The upper stage shows the output of the sum signal sa from the two-divided detector of the optical pickup during seek, and the lower stage shows the difference signal ( The output of the radial push-pull signal (ppa) is shown. FIG. 16B shows the detection result of a conventional optical information recording medium having in-groove pits. The upper stage shows the output of the sum signal sb at the time of seek, and the lower stage shows the difference signal (radial push-pull signal) ppb. Each output is shown. 16 (a) and 16 (b), the amplitude levels of the sum signals sa and sb are greatly changed (represented by reference numeral 16b in FIG. 16 (a) and reference numeral 16b in FIG. 16 (b)). Is the boundary between the in-groove pit area and the groove area. The difference signal (radial push-pull signal) ppa shown at the lower stage at the position corresponding to the reference numeral 16a in FIG. 16A, that is, at the boundary between the in-groove pit area and the groove area in the optical information recording medium of the above embodiment. There is almost no disturbance. On the other hand, at the position corresponding to the reference numeral 16b in FIG. 16B, that is, at the boundary between the in-groove pit area and the groove area in the conventional optical information recording medium having the in-groove pit, It was confirmed that the disturbance of the push-pull signal) ppb was large. As described above, in the DVD-R and DVD-RW, tracking is performed using this radial push-pull signal, and the balance of the amplitude of the radial push-pull signal is lost at the boundary between the in-groove pit region and the groove region. That is, the tracking error is likely to occur due to the deviation of the center of the amplitude.

  Further, in the optical information recording medium manufactured in the above embodiment, the amount of fluctuation between the radial push-pull signal in the groove part and the radial push-pull signal in the in-groove pit part is the amplitude of the radial push-pull signal in a normal state. When it is 100%, it is 36%. Although not specified in the DVD-R standard, in the DVD-RW standard, the fluctuation amount of the radial push-pull signal in the groove part and the radial push-pull signal in the pre-pit part is specified as 20% or more. Therefore, the optical information recording medium of the above embodiment sufficiently satisfies this standard and does not cause a tracking error (tracking error). On the other hand, in the conventional optical information recording medium having in-groove pits, the fluctuation amount is about 18 to 20%. Therefore, the conventional optical information recording medium having in-groove pits is lower than the lower limit value of the DVD-RW standard or less, and is likely to be out of tracking (tracking error).

  In the optical information recording medium of the above embodiment, polycarbonate is used as the substrate, but polymethyl methacrylate, amorphous polyolefin, or the like may be used. In the optical information recording medium of the above embodiment, each layer was formed in the order of the recording layer and the reflective layer on the substrate. First, the reflective layer was formed on the pattern formation surface on the substrate, and then on the reflective layer. Each layer may be formed by forming a recording layer. Even when the optical information recording medium is manufactured with such a layer structure, the same effect as in the above embodiment can be obtained.

  In this embodiment, the boundary pit area and the boundary groove area are provided between the in-groove pit formation area and the groove area. However, either the boundary pit alone or the boundary groove alone may be used. Even when a medium is manufactured as such a boundary condition, the same effect as in the above-described embodiment can be obtained.

[Disc format]
A specific information recording medium structure using the first and second embodiments will be described in a third embodiment. FIG. 17 shows a sector structure arranged on the DVD-R. Lead-in, data area, and lead-out structures are formed from the inner periphery, and the data area starts from Physical sector number: 030000h. The recording / reproducing area is wobbled in the radial direction at a frequency of about 140 kHz at a distance of about 1.3% to 2.7% with respect to the track pitch. In the present invention, the wobble amount is 0.2%. did. When the track pitch is 0.74 μm, the wobble amount is about 0.015 μm. In the recording / reproducing area, land pre-pits LPP having information such as addresses are arranged in the land area.

  As shown in FIG. 18, the lead-in area is composed of the initial zone, buffer zone 0, R-Physical format information zone, buffer zone 1, exclusive zone, or zone, from the inner circumference of the recording / playback area. The control data zone (in-groove pit region) is a groove having a depth from the land portion of about λ / 2.4n (n: refractive index of the substrate) with respect to the recording / reproducing wavelength λ (λ = 650 nm). 170nm) and about λ / 1.6n pits (260nm in the case of λ = 650nm), and has lead-in information such as copyright protection information, recording strategy information, disc type and version There. The groove shape of the recording / reproducing area excluding the control data zone has a depth of 170 nm of about λ / 2.4n.

In the optical information recording medium of the present invention, when performing a reproducing operation, a seek operation is performed to the control data zone. As shown in the second embodiment, the inner and outer peripheral portions adjacent to the control data zone (in-groove pit region) are used. By providing boundary regions such as boundary pits and boundary grooves for one track or several tracks, the disturbance of the radial push-pull signal can be suppressed, and the control data zone information can be reproduced without tracking failure. In addition, as shown in Example 1, the width of the first pit in the control data zone and the second pit formed longer than the first pit is 1 <W ₂ / W ₁ <1.2, and When the height of the land pre-pit side wall from the groove bottom surface is dlp, and the land height from the groove bottom surface is the same as the depth from the land surface, dg is assumed, and 0.4 ≦ dlp / dg <1 , LPP detection is good, and reproduction errors are also good.

  Using the optical information recording medium obtained in the above embodiment, a recording signal of the control data zone (in-groove pit area) was reproduced using an optical pickup having a laser beam having a wavelength of 650 nm and a lens having a numerical aperture of 0.6. . Signal detection and reproduction can be performed stably, and the signal modulation degree of the reproduction signal at this time is 61%, and the jitter is 7.2%, both of which can provide good results.

  Therefore, it is possible to reliably detect the recording strategy required for recording, to faithfully set the conditions in each drive, and to enable recording with few errors.

  Further, in the recording operation with the optical information recording medium of the present invention, even when the control proceeds to the data area through the control data zone and the extra border zone, since the detection of the LPP having the address information is good, the data area The physical sector number can be recorded well starting from 030000h.

(A) is the schematic top view which showed a part of optical information recording medium which has the conventional in-groove pit, (b) is the sectional view on the AA line of (a). FIG. 2 is a diagram showing a land pre-pit reproduction signal, (a) is a diagram showing a signal of an information recording medium created in Example 1, and (b) is a conventional information recording having an in-groove pit. It is the figure which showed the signal of the medium. (A) is a graph showing the relationship between the dlg / dg ratio and the number of reproduction errors, and (b) is a graph showing the relationship between the dlp / dg ratio and the number of reproduction errors. 1 is a schematic view of a substrate obtained in Example 1. FIG. 2 is a diagram illustrating a method for producing a glass master in Example 1. FIG. It is the figure which showed the time change of the exposure intensity of the laser beam irradiated to the glass original disk in Example 1. FIG. It is the schematic diagram of the in-groove pit formation area in Example 1, (a) is a schematic top view which showed a part of glass original disk immediately after photoresist exposure and image development, (b) is A of (a). FIG. 3 is a diagram illustrating a method for producing a glass master in an in-groove pit formation region in Example 1. FIG. It is a schematic diagram of the area | region which has not formed the in-groove pit in Example 1, (a) is a schematic top view which showed a part of glass original disk immediately after photoresist exposure and image development, (b) is ( It is A'-A 'sectional view taken on the line of a). It is the figure explaining the preparation methods of the glass original disc of the field which has not formed the in-groove pit in Example 1. It is a schematic perspective view of the pattern formation surface of the board | substrate obtained in Example 1. FIG. (A) shows a schematic top view of the vicinity of the in-groove pit of the substrate in Example 1, and (b) shows a state in which a recording layer and a reflective layer are formed on the substrate in addition to the cross section taken along the line CC of (a). FIG. 6 is a schematic view of a substrate obtained in Example 2. FIG. It is the figure which showed the time change of the exposure intensity of the laser beam irradiated to the glass original disc in Example 2. FIG. (A) is a schematic top view in the vicinity of the boundary pit region of the optical information recording medium in Example 2, and (b) is a diagram showing a cross section along line DD in (a). It is the figure which showed the sum signal and difference signal (radial push pull signal) of the boundary part of an in-groove pit area | region and a groove area | region, (a) is each of those of the information recording medium produced in Example 1 It is the figure which showed the signal, (b) is the figure which showed each those signals of the information recording medium which has the conventional in-groove pit. FIG. 10 is a diagram showing an arrangement of a physical sector of an optical information recording medium in Example 3. FIG. 6 is a diagram showing a structure of Lead-in in Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Reflective layer 40 Groove formation part 42 Land pre-pit formation part 44 In-groove pit formation part 50 Glass master 52 Photoresist 71,75 Groove area 73 In-groove area 101 Substrate 101a Land surface 102 Recording layer 103 Reflective layer 105 Groove 107 In-groove pit AX Central axis

Claims (4)

  A method of manufacturing an optical disc having lands and grooves, wherein a dye recording layer is formed by spin coating on a substrate on which management information is injection-molded using a stamper previously formed by pits, and the dye recording layer is formed on the dye recording layer. A method for producing an optical disc, comprising: forming a reflective layer, and forming a UV resin layer on the reflective layer.   The optical disc manufacturing method according to claim 1, wherein the management information includes a write strategy.   The optical disc manufacturing method according to claim 1, wherein the management information includes information related to copyright protection. The method of manufacturing an optical disk according to claim 1, wherein the pit is provided in the groove, and the pit is deeper than the groove.

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