JP2007179718A - Stamper, reproduction only optical disk, and manufacturing method of this disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of pit deviation in molding a reproduction only high density optical disk. <P>SOLUTION: A stamper is provided with an irregular pattern which forms a dummy irregular shape (outer periphery dummy area Odm) such as a dummy pit at least on the outer periphery side of the disk as an area excepting for an information area of the disk. In addition it is possible to form a dummy irregular shape (inner periphery dummy area Idm) on the inner periphery side of the disk. By manufacturing a disk substrate as the reproduction only optical disk using the stamper like this, the reproduction only optical disk where pit deviation never occurs as a pit in the information area is manufactured. The surface of the molding die of the disk substrate is made pearskin finished as to finish the label surface side of the disk substrate to be pearskin like. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stamper used for manufacturing a read-only optical disc, a read-only optical disc to be manufactured, and a method for manufacturing a read-only optical disc, and more particularly to a technique suitable for a high-density optical disc.

JP 2003-109252 A JP 2002-304775 A

In general, in a read-only optical disc, a high level (H) and a low level (L) of a reproduction signal are switched in synchronization with a clock that is a reference unit time, and information is recorded by a combination of the lengths of H and L. In a read-only optical disc, H and L are usually represented by a pit row arranged on a track. That is, the pits and the pit rows formed by the land portions between the pits are reproduced and scanned by the laser beam, so that H and L as reproduction signals are obtained.
For a read-only optical disc on which a so-called embossed pit row is formed, as a mastering process, in order to form a pit row according to recorded data, laser exposure is performed to produce a master disc. A stamper is created from the master disc, and a large number of optical discs are manufactured using the stamper.

For recording pit formation of CD (Compact Disc) and DVD (Digital Versatile Disc), accurate transfer of stamper pit patterns is required, and high-precision molding technology is required.
Here, in the Blu-ray Disc (registered trademark), which is a higher density optical disc developed recently, the track pitch of the pit row is 0.32 μm, which is about half that of a DVD. The width, length, and depth of the plate are also small. Therefore, when a disc substrate is molded using a stamper, pit deformation (hereinafter referred to as pit deviation) on the molded substrate is likely to occur, and a slight amount Even a slight pit shift will greatly affect the reproduction signal.

The state of pit shift is shown in FIG. FIG. 14A shows an example in which pits 1 are normally formed when a disc substrate is manufactured using a stamper.
However, especially on the inner circumference side of the disc, a pit shift occurs in such a shape that the pit 1 flows on the inner circumference side as shown in FIG. 14B, or as shown in FIG. 14C on the outer circumference side of the disc. A pit shift is likely to occur as if the pit 1 flowed on the outer peripheral side.

This pit shift depends on the adhesion between the stamper and the disk substrate during molding. For example, if the adhesion between the stamper and the disk substrate is weak, pit displacement tends to occur when the resin is cooled in the mold and when the clamping force is released. On the other hand, if the adhesion is too strong, pit deviation is likely to occur when the disk substrate is peeled from the stamper.
Therefore, moderate adhesion is required. However, if the size of the pit itself is reduced as in a high-density optical disk such as a Blu-ray disc, it is difficult to obtain sufficient adhesion between the stamper and the disk substrate during molding. Deviation tends to occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical disc having good reproduction performance by preventing such a pit shift even in a read-only optical disc as a high-density optical disc.

The stamper of the present invention is a stamper for manufacturing a read-only optical disc. Then, unevenness for forming embossed pits based on recorded information in a range corresponding to an information area set as an information recording area of a read-only optical disc manufactured by performing pit transfer using this stamper A pattern is formed, and a concavo-convex pattern for forming a dummy concavo-convex shape is formed at a position corresponding to the outer peripheral side of the disc with respect to the information area.
Furthermore, a concave / convex pattern for forming a dummy concave / convex shape is also formed at a position corresponding to the inner peripheral side of the disc from the information area.
Further, the dummy uneven shape formed on the read-only optical disc is a dummy pit row, and each dummy pit of the dummy pit row is an emboss pit deeper than an emboss pit formed in the information area, The concave / convex pattern is formed so that the track pitch of the dummy pit row is wider than the track pitch of the embossed pit row formed in the information area.
Alternatively, the dummy concavo-convex shape formed on the read-only optical disc is a dummy pit row, and the concavo-convex pattern is formed so that each dummy pit of the dummy pit row is an embossed pit having a pit length not less than a predetermined length. Is formed.
Or the said uneven | corrugated shape formed in the said read-only optical disk has the said uneven | corrugated pattern formed so that it may become a dummy continuous groove | channel.

The read-only optical disc of the present invention is a read-only optical disc in which information is recorded by embossed pits in an information area set as an information recording area. A shape is formed.
Further, a dummy uneven shape is also formed on the inner peripheral side of the disc from the information area.
The dummy concavo-convex shape is formed of a dummy pit row, and each dummy pit of the dummy pit row is an emboss pit deeper than the emboss pit formed in the information area, and the track pitch of the dummy pit row. The track pitch is wider than the track pitch of the embossed pit rows formed in the information area.
Alternatively, the dummy concavo-convex shape is formed by a dummy pit row, and each dummy pit of the dummy pit row is an embossed pit having a predetermined pit length or more.
Alternatively, the dummy uneven shape is formed by a dummy continuous groove.
The read-only optical disk has the embossed pits and dummy irregularities formed on one surface of the disk substrate, and the other surface is a matte surface. The reflective film and the light are formed on the one surface of the disk substrate. A transmission layer (cover layer) is formed, and a printing layer is formed on the other surface of the disk substrate. In this case, it is assumed that the maximum roughness of the matte surface on the other surface of the disk substrate is 0.5 μm to 5 μm.

The method for manufacturing a read-only optical disc according to the present invention forms an embossed pit uneven pattern based on recorded information in a range corresponding to an information area set as an information recording area of the read-only optical disc. A master generating step for generating a master disc by forming a concave / convex pattern for forming a dummy concave / convex shape at a position corresponding to the outer peripheral side of the disc from the area; and a stamper manufacturing step for manufacturing a stamper using the disc master. And a disc manufacturing step of manufacturing a read-only optical disc using the stamper.
In the disk manufacturing step, the disk substrate is manufactured using a mold in which the stamper manufactured in the stamper manufacturing step is arranged on one inner surface and the other inner surface is a matte surface, and then the disk is manufactured. On the substrate, a reflective film and a light transmission layer (cover layer) are formed on one surface on which the embossed pits and dummy irregularities are formed, and printing is performed on the other surface of the disk substrate formed in a satin shape. Form a layer.
In this case, the maximum roughness of the matte surface on the other inner surface of the mold is 0.5 μm to 5 μm.

In the present invention, dummy uneven patterns such as dummy pits are formed in areas other than the information area of the read-only optical disk, that is, areas where normal pits are not formed.
The information area is an area defined for recording main data (audio / video contents, various files, programs, etc.) and recording management information of these main data, physical information of discs, identification information, and the like. is there. The information area also includes an area that has some meaning for the optical disc reproducing apparatus, such as an outer peripheral lead-out and an inner peripheral BCA (Burst Cutting Area).
That is, the area other than the information area is usually an area where pits and grooves (continuous grooves) that are particularly meaningful for the recording operation and the reproducing operation of the optical disc recording / reproducing apparatus are not formed.
In the present invention, a stamper having a concavo-convex pattern that forms a dummy concavo-convex shape at least on the outer periphery side of the disk as an area other than the information area is manufactured. In addition, a dummy uneven shape may also be formed on the inner peripheral side of the disk. When such a stamper was used, it was confirmed that an appropriate adhesion was obtained between the stamper and the disk substrate when manufacturing a disk substrate as a read-only optical disk.

Furthermore, in the present invention, the other surface of the disk substrate on which the embossed pits and the dummy irregularities are formed is a matte surface. For example, when manufacturing a disk substrate, the stamper having the above-described uneven pattern is arranged in a mold so that embossed pits and dummy uneven shapes are formed on one surface of the disk substrate. The inner surface on the opposite side is a matte surface, and the other surface of the disk substrate is matte. Even when the other inner surface of the mold is satin-like, moderate adhesion is obtained when the disk substrate is molded by the mold and the stamper, and shrinkage when the resin is cooled in the mold It was confirmed that the effect of preventing the occurrence of pit deviation at the time of releasing the mold clamping force was obtained.
“Nashiji” refers to a state in which fine irregularities are uniformly formed on the surface by mechanical or scientific treatment as defined in JIS (Japan Industrial Standard) (“pear finish”).
The maximum roughness of the satin is 0.5 μm to 5 μm, but 0.5 μm is the minimum roughness to obtain the effect of preventing pit shift, and 5 μm is the label surface after the printing process. It is the maximum roughness that maintains aesthetics.

  According to the present invention, when forming a substrate of a high-density optical disk having a small pit size and a narrow track pitch, appropriate adhesion can be obtained between the stamper and the disk substrate, thereby preventing occurrence of pit deviation in the information area. Pit transfer accuracy is improved. Therefore, the manufactured read-only optical disk can form normal embossed pits, and can be an optical disk that provides stable reproduction signal characteristics.

Embodiments of the present invention will be described below.
First, with reference to FIG. 6, the manufacturing process of the read-only optical disk will be described.
FIG. 6A shows a substrate 100 constituting a disc master. First, a resist layer 102 made of, for example, an inorganic resist material is uniformly formed on the substrate 100 by a sputtering method (resist layer forming step, FIG. 6B). Later, PTM mastering using an inorganic resist material will be described as a mastering process for manufacturing a disk master. In this case, an incomplete oxide of a transition metal is used as a material provided for the resist layer 102. Specific examples of the transition metal include Ti, V, Cr, Mn, Fe, Nb, Cu, Ni, Co, Mo, Ta, W, Zr, Ru, and Ag.
Note that a predetermined intermediate layer 101 may be formed between the substrate 100 and the resist layer 102 in order to improve the exposure sensitivity of the resist layer 102, and FIG. 6B shows the state. The thickness of the resist layer 102 can be arbitrarily set, but is preferably in the range of 10 nm to 80 nm.

Next, the resist layer 102 is subjected to selective exposure corresponding to a pit row as a signal pattern using a master manufacturing apparatus described later (resist layer exposure step, FIG. 6C). Then, by developing the resist layer 102, the master disc 103 on which a predetermined uneven pattern (pit row) is formed is generated (resist layer developing step, FIG. 6D).
Subsequently, a metallic nickel film is deposited on the concave / convex pattern surface of the disk master 103 generated as described above (FIG. 6 (e)), and after peeling this from the master 103, a predetermined process is performed. A molding stamper 104 to which the uneven pattern is transferred is obtained (FIG. 6F).
Using the stamper 104, a resin disc substrate 105 made of polycarbonate which is a thermoplastic resin is formed by injection molding (FIG. 6G).
Thereafter, the stamper 104 is peeled off (FIG. 6H), a reflective film 106 such as an Ag alloy (FIG. 6I) is formed on the uneven surface of the resin disk substrate, and a light transmission layer having a film thickness of about 0.1 mm. (Cover layer) 107 is formed. Further, a hard coat 108 is applied to the light transmission layer 107, and a printing layer 109 is formed on the opposite label surface side. Thus, the optical disc is manufactured (FIG. 6 (j)). In some cases, the hard coat 108 is not applied.

In such an optical disc manufacturing process, in the present example, the following read-only optical disc is manufactured.
FIG. 1 shows the area configuration of the read-only optical disk of this example.
For example, FIG. 1 shows an optical disk having a diameter of 12 cm in the Blu-ray Disc format, and a diameter of 15 mm at the center of the disk is a center hole.
An annular area having a diameter of 42 mm to 117 mm is defined as an information area.
In the information area, for example, a BCA, a lead-in area, a data area, and a lead-out area are formed from the inner peripheral side. The BCA is an area where a radial barcode pattern is formed by forming pits arranged in the radial direction, and for example, disc identification information is recorded. In the lead-in area, physical information on the disc, recommended information on the operation of the playback device, area information, management information on content data and file data, and the like are recorded. In the data area, content data and files that are main data are recorded. The lead-out area is used as a buffer area on the outer peripheral side.

In the Blu-ray Disc format, the thickness of the disc is defined by the standard except for the information area, but the pit formation is not particularly defined.
In this example, an outer peripheral dummy area Odm is formed on the outer peripheral side of the information area. Further, an inner peripheral dummy area Idm is formed on the inner peripheral side from the information area.
The outer periphery dummy area Odm and the inner periphery dummy area Idm are regions where dummy irregularities are formed as dummy pits and dummy grooves.
These dummy concavo-convex shapes are formed on a read-only optical disc after manufacture by forming a concavo-convex pattern on the stamper 104 for avoiding pit shift during molding of the disc substrate.

Two specific examples will be described below.
As a first specific example, the stamper 104 was formed with a concave / convex pattern in which dummy pits were formed in a diameter range of 38 mm to 41 mm and a diameter range of 117.5 mm to 120.0 mm. That is, the disc substrate 105 is formed using the stamper 104 in which the read-only optical disc has a diameter of 38 mm to 41 mm as the inner dummy area Idm in FIG. 1 and a diameter of 117.5 mm to 120.0 mm as the outer dummy area Odm. To do.
The dummy pit formed by the uneven pattern of the stamper 104 is as follows.

The pit length and signal pattern of the dummy pits are 2T to 8T pit row patterns (T is a channel clock cycle) conforming to the Blu-ray Disc standard.
• The track pitch of the dummy pit row is 0.64 μm. The normal track pitch of the pit row formed in the information area of the Blu-ray disc is 0.32 μm.
-The pit depth of the dummy pit is 70 nm. The normal pit depth formed in the information area of the Blu-ray disc is 50 nm.

FIG. 2 shows how the pits are formed. The normal pits in FIG. 2 (a) are embossed pits formed in the information area. That is, the track pitch is 0.32 μm according to the Blu-ray disc format, and 2T˜ according to the modulation signal of the recording data. A pit row of pits 1 having a pit length of 8T is formed. The pit depth is 50 nm.
On the other hand, FIG. 2B shows a pit row of dummy pits 2 formed in the outer periphery dummy area Odm and the inner periphery dummy area Idm. As described above, the track pitch is 0.64 μm and the pit depth is 70 nm.
In the case where a pit deeper than the normal pit 1 is formed as the dummy pit 2, the laser power is increased during the exposure of the disc master as will be described later. As a result, the pit depth is increased and the width PW2 of the dummy pit 2 is wider than the width PW1 of the normal pit 1. Thereby, a sufficient pit volume is secured in the dummy areas Odm and Idm.

  FIG. 3 schematically shows a disk substrate 105 having such normal pits 1 and dummy pits 2 and a stamper 104 for forming the disk substrate 105. The concavo-convex pattern 6 for forming the dummy pit 2 and the concavo-convex pattern 5 for forming the normal pit 1 are formed on the stamper 104, thereby forming a pit row as shown in FIGS. The read-only optical disc is generated.

With the read-only optical disc formed in this way, when it was reproduced and jitter was measured, good results were obtained with 5.7% or less over the entire circumference of the disc. That is, in the normal pit 1 in the information area, the reproduction signal characteristics were not deteriorated due to the pit deviation.
Further, in order to confirm the molding stability, even when 10000 sheets were continuously molded, the jitter was not deteriorated even when the sampling evaluation was performed.

Next, as a second specific example, the stamper 104 is provided with a concavo-convex pattern in which dummy pits are formed in a diameter range of 22 mm to 38 mm and a diameter range of 117.5 mm to 120.0 mm of the disk substrate to be formed. Formed. That is, the disc substrate 105 is formed using the stamper 104 in which the read-only optical disc has a diameter of 22 mm to 38 mm as the inner dummy area Idm in FIG. 1 and a diameter of 117.5 mm to 120.0 mm as the outer dummy area Odm. To do.
The dummy pit formed by the uneven pattern of the stamper 104 is as follows.

・ The dummy pit is a pit string with a pit length of only 8T. That is, a pit row of only the longest pit among 2T to 8T pits conforming to the Blu-ray Disc standard is used.
The track pitch of the dummy pit row is 0.32 μm and the pit depth is 50 nm. That is, the same as the track pitch and pit depth of the normal pit row formed in the information area.

FIG. 4 shows a state of pits to be formed. 4A shows normal pits formed in the information area, and FIG. 4B shows pit rows of dummy pits 2 formed in the outer periphery dummy area Odm and the inner periphery dummy area Idm.
In this case, as can be seen by comparing FIGS. 4A and 4B, the dummy pit row has the same track pitch, pit width, and pit depth as the normal pit row. However, since the pit lengths of the dummy pits 2 are all 8T pits, which is the longest pit in the normal pit row, a sufficient pit volume is secured in the dummy areas Odm and Idm.

The reproduction-only optical disk thus formed was also reproduced and measured for jitter. As a result, a good result of 5.7% or less over the entire circumference of the disk was obtained. No deterioration of the reproduction signal characteristics due to the shift was observed.
Further, in order to confirm the molding stability, even when 10000 sheets were continuously molded, the jitter was not deteriorated even when the sampling evaluation was performed.

  As shown in these first and second specific examples, when a concave / convex pattern for dummy pits is formed on the stamper 104 and a dummy pit 2 is formed outside the information area by the stamper 104, a read-only optical disk is manufactured. It was possible to prevent the reproduction signal quality from deteriorating due to the pit shift.

As a comparative example, a signal pattern and pit (track pitch 0) conforming to the Blu-ray disc standard are used as dummy pits in a diameter range of 38 mm to 41 mm (an area corresponding to the inner peripheral dummy area Idm) of a Blu-ray disc molding stamper. The case where a dummy pit having a thickness of .32 μm and a depth of 50 nm is inserted will be described.
The dummy pits entered here are used to express the characters and bar codes for confirming the part number of the stamper in order to express the contrast between the pit part and the mirror part.
In addition, dummy pits are not formed on the outer peripheral side from the information area.
The jitter of the read-only optical disk molded with such a stamper was good at 5.7% or less in the middle part of the disk, but the jitter became unstable on the inner and outer circumferences in the information area. When the deterioration was remarkable, it sometimes exceeded 10%. Therefore, there is little margin for molding conditions and stable production is difficult. Further, when the pit state of the jitter deteriorated portion was observed with an SEM (Scanning Electron Microscope), the pit shift of the portion was confirmed.

  From the above results, as shown in the above specific example, by manufacturing the stamper 104 so that suitable dummy pits are formed, the pit deviation at the time of forming the disk substrate is suppressed, and the signal characteristics are deteriorated due to the forming. It was confirmed that it can be suppressed. In addition, it is effective that at least the outer periphery dummy area Odm is formed on the outer periphery side of the information area, and it is effective that the dummy pits can ensure a sufficient pit volume. I found out that For example, in the case of the first and second specific examples, the dummy pit 2 is formed in the outer peripheral dummy area Odm. In the first specific example, the dummy pit 2 is an embossed pit region having a larger volume than the normal pit 1 because the dummy pit 2 is deeper and wider than the normal pit 1. In the case of the second specific example, the dummy pit 2 has the same pit width and pit depth as the normal pit 1, but all the pits have a pit length of 8T (the longest pit in the normal pit). Thus, a sufficient volume is secured.

Moreover, the dummy uneven shape capable of preventing the pit shift is not limited to the dummy pit 2 in the first and second specific examples.
For example, a dummy groove (continuous groove) may be used instead of the dummy pit 2.
5A and 5B show the dummy groove 4 formed in the normal pit 1 of the information area and the outer dummy area Odm, or both the outer dummy area Odm and the inner dummy area Idm. For example, the dummy groove 4 can be considered to have a significantly longer pit length than the 8T dummy pit 2 of the second specific example. Therefore, as in the second specific example, the dummy groove 4 is formed with a track pitch of 0.32 μm, that is, the concave / convex pattern for forming the dummy groove 4 is formed on the stamper 104. Similar effects can be obtained.
In addition, the specific ranges of the dummy areas Odm and Idm that form dummy uneven shapes such as the dummy pit 2 and the dummy groove 4 are not limited to the above example.
Moreover, although the above embodiment was shown as an example of a Blu-ray disc, the present invention can also be applied to other types of optical discs. It is particularly suitable for high density optical discs.

Incidentally, as described with reference to FIG. 6, the stamper 104 is manufactured using the disc master 103. That is, when manufacturing the stamper 104 having the concavo-convex pattern for forming the dummy concavo-convex shape as described above, the concavo-convex pattern is also exposed when the disc master 103 is manufactured.
Hereinafter, a mastering process (master disk manufacturing process) in manufacturing the stamper 104 and the optical disk shown in the first specific example will be described.

When manufacturing ROM discs such as CD (Compact Disc) and DVD (Digital Versatile Disc), first prepare a master disc coated with photoresist, and use a mastering device (master exposure device) on the master disc. A laser was irradiated from a light source such as a gas laser to form an exposure pattern corresponding to the pit. In this case, laser light from a laser light source that is a continuous wave laser is modulated by, for example, an AOM (Acousto-Optical Modulator), and the laser light subjected to the intensity modulation is guided to a disk master by an optical system and exposed. That is, a pit modulation signal such as an NRZ (Non Return to Zero) modulation signal is given to the AOM, and the laser light is subjected to intensity modulation corresponding to the pit pattern by this AOM, so that only the pit portion is exposed on the master. To go.
For example, FIG. 8B shows one pit shape, and the laser emission intensity modulated by AOM is as shown in FIG. Since the exposure of the photoresist on the master disk is so-called optical recording, the portion exposed by the laser as shown in FIG. 8 becomes a pit as it is.

On the other hand, in recent years, as known as PTM (Phase Transition Mastering), an exposure method has been developed in which a master disk coated with an inorganic resist is irradiated with laser light from a semiconductor laser to perform thermal recording.
In this case, in order to suppress the accumulation of heat due to laser irradiation and to make the pit width uniform, exposure is usually performed with pulsed light as shown in FIG. That is, in this case, in general, the NRZ modulation signal synchronized with the clock is converted into a pulse signal having a time width shorter than the clock cycle according to the length of the H level, and directly modulated in synchronization with the converted pulse modulation signal. Power is supplied to possible semiconductor lasers. As a result, the laser output as the pulse light emission Pp for heating as shown in FIG. 8A and the pulse light emission P1 to Pn for heating corresponding to the pit length is performed.

In the present invention, any exposure method may be used. Here, as an example, a case where mastering is performed by the PTM method will be described.
FIG. 7 shows a configuration example of the master disc manufacturing apparatus. This master production apparatus exposes a pit pattern by a thermal recording operation by laser irradiation on the master 103 coated with an inorganic resist as described above.

The laser light source 11 as a semiconductor laser outputs a laser with a wavelength of 405 nm, for example. The laser light source 11 is supplied with a laser drive signal DL1 obtained by converting an NRZ modulation signal such as RLL (1-7) pp into a pulse modulation signal as shown in FIG. In accordance with the light emission.
The laser light emitted from the laser light source 11 is collimated by the collimator lens 12 and then reaches the beam splitter 19. In the beam splitter 19, the transmitted light component and the reflected light component are separated, and the transmitted light component is irradiated to the photodetector 21 through the lens 20.
The photodetector 21 outputs a light intensity monitor signal SM1 corresponding to the received light amount level (light intensity).

  The reflected light component reflected by the beam splitter 19 reaches the dichroic mirror 25. In this case, the dichroic mirror 25 reflects light in a wavelength region including 405 nm and transmits light in a wavelength region including 680 nm. Accordingly, the laser beam reflected by the beam splitter 19 is reflected by the dichroic mirror 25 and is irradiated onto the inorganic resist surface of the master 103 via the infinite system objective lens 26. That is, an exposure pattern as a pit row is formed on the master 103 by thermal recording with laser light from the laser light source 11.

On the other hand, the laser light source 22 is a laser light source that outputs laser light for focus control by an off-axis method, and is, for example, a semiconductor laser that outputs laser light having a wavelength of 680 nm. The laser light source 22 continuously emits laser light based on the laser drive signal DL2.
The output laser light having a wavelength of 680 nm passes through the lens 32 and the polarization beam splitter (PBS) 23, and further reaches the dichroic mirror 25 via the λ / 4 wavelength plate 24. Then, the light passes through the dichroic mirror 25 and is irradiated from the objective lens 26 to the master 103.
The return light from the master 103 passes through the objective lens 26, the dichroic mirror 25, and the λ / 4 wavelength plate 24 and reaches the polarization beam splitter 23. In this case, the polarization plane is rotated by 90 ° by passing through the λ / 4 wavelength plate 24 twice in the forward path and the return path, and is reflected by the polarization beam splitter 23. The return light reflected by the polarization beam splitter 23 is received by the position sensor diode 27.
The position sensor diode 27 is set to irradiate the center of the return light when the focus is on, that is, when the objective lens 26 is controlled to the correct focus position, and a signal that is information on the light receiving position. Outputs SM2. That is, the signal SM2 indicating the amount of deviation from the center of the light receiving position on the position sensor diode 27 becomes a focus error signal. The position sensor diode 27 supplies the focus error signal to the focus control circuit 28.
The focus control circuit 28 generates a servo drive signal FS of the actuator 29 that holds the objective lens 26 movably in the focus direction based on the signal SM2 as a focus error signal. Then, the actuator 29 drives the objective lens 26 in the direction in which the objective lens 26 comes in contact with and separates from the master 103 based on the servo drive signal FS, whereby focus servo is executed.
At this time, the exposure laser beam from the laser light source 11 having a wavelength of 405 nm irradiated onto the master 103 through the objective lens 29 as described above is focused on the exposure master 103. The master 103 is formed by depositing an inorganic resist made of a metal oxide on a silicon wafer. By absorbing a 405 nm laser beam, a portion heated to a high temperature near the center of the irradiated portion is polycrystallized. Then, as described in FIG. 6D, by developing the exposed master with an alkaline developer such as NMD3, only the exposed portion is eluted and a desired pit shape is formed.
On the other hand, the laser beam for focus control has no exposure sensitivity, for example, has a wavelength of 680 nm, and thus has no influence on exposure.

The laser drive signal DL1 for the laser light source 11 is generated by a recording data generation unit 43, a laser drive pulse generation unit 42, and a laser driver 41.
The recording data generation unit 43 outputs data DT1 to be recorded on the master 103 as a pit exposure pattern. For example, video signals, audio signals, physical information, management information, and other data are output as main data. Data for forming a pit exposure pattern as the dummy pit 2 is also output.
The data DT1 is supplied to the laser drive pulse generator 42. The laser drive pulse generator 42 generates a laser drive pulse for actually driving the laser light source 11 to emit pulses based on the data DT1. That is, as shown in FIG. 8A, a pulse waveform for generating laser light emission at the timing and light intensity as the preheating pulse Pp and the pulses P1 to Pn is generated according to the pit length to be formed. To do.
This laser driving pulse is supplied to the laser driver 41. The laser driver 41 applies a driving current to the semiconductor laser as the laser light source 11 based on the laser driving pulse. As a result, laser light emission is performed at a light emission intensity corresponding to the laser drive pulse.
The light intensity monitor signal SM1 obtained from the photodetector 21 is supplied to the laser driver 41. The laser driver 41 performs control to maintain the laser emission intensity at a predetermined level by comparing the light intensity monitor signal SM1 with a reference value.

The disc master 103 is rotationally driven by a spindle motor 44. The spindle motor 44 is rotationally driven while the rotational speed is controlled by the spindle servo / driver 47. As a result, the disc master 103 is rotated at a constant linear velocity.
The slider 45 is driven by a slide driver 48 and moves the entire base including the spindle mechanism on which the disc master 103 is loaded. That is, the disk master 103 rotated by the spindle motor 44 is exposed by the optical system while being moved in the radial direction by the slider 45, so that a track by the exposed pit row is formed in a spiral shape. It will follow.
The movement position by the slider 45, that is, the exposure position (disk radial position) of the disk master 103 is detected by the sensor 46. The position detection information SS from the sensor 46 is supplied to the controller 40.

  The controller 40 controls the entire mastering apparatus. That is, an instruction for data generation operation from the recording data generation unit 43, control of processing in the laser drive pulse generation unit 42, laser power setting for the laser driver 41, spindle rotation operation control by the spindle servo / driver 47, slide The movement operation of the slider 45 by the driver 48 is controlled.

When manufacturing the stamper 104 and the optical disc of the first specific example described above, the controller 40 performs mastering by performing the control process of FIG.
When starting mastering, the controller 40 activates the spindle motor 44 by the spindle servo / driver 47 in step F101 to establish rotation at a predetermined linear velocity. Further, the slide driver 48 is instructed so that the slider 45 starts sliding at a speed corresponding to the above-described dummy pit row track pitch (0.64 μm).
In step F102, the controller 40 monitors the position detection information SS from the sensor 46, and determines whether or not the slide movement of the exposure position has reached the position as the inner peripheral dummy area Idm, that is, the position having a diameter of 38.0 mm. Determine.

When the position corresponding to the inner peripheral dummy area Idm is reached, the process proceeds to step F103 to perform dummy pit formation processing. That is, in this case, the controller 40 generates dummy pit data from the recording data generation unit 43. The generated data may be, for example, random data for forming 2T to 8T pits corresponding to the Blu-ray Disc standard. Further, the laser driver 41 is caused to execute laser driving with higher power than usual.
As a result, an exposure pattern corresponding to the dummy pit row in FIG. 2B is formed on the master disc 103.
During this dummy pit formation process, the controller 40 monitors the position detection information in step F104. When it is detected that the movement by the slider 45 has reached the end position of the inner periphery dummy area Idm, that is, the position reaching the diameter of 41.0 mm, the dummy pit forming process is finished, and the process proceeds to Step F105.

In Step F105, the controller 40 instructs the slide driver 48 to slide the slider 45 at a speed corresponding to the track pitch (0.32 μm) for the pit row in the information area. That is, the slide moving speed is reduced.
In step F106, the controller 40 monitors the position detection information SS from the sensor 46, and determines whether or not the slide movement of the exposure position has reached the position as the information area, that is, the position having a diameter of 42 mm.
When the position corresponding to the information area is reached, the process proceeds to step F107 to perform normal pit formation processing. That is, in this case, the controller 40 records the physical data of the lead-in area, the recording data as management information, the recording data as video / audio information as main data, the pit pattern data of the lead-out area, etc. Data to be generated is generated sequentially. Further, the laser driver 41 is caused to execute normal power laser driving.
As a result, an exposure pattern corresponding to the normal pit row in FIG. 2A is formed on the disc master 103.

During this normal pit formation process, the controller 40 monitors the position detection information in step F108. When it is detected that the movement by the slider 45 has reached the end position of the information area, that is, the position having a diameter of 117 mm, the normal pit formation processing is finished and the routine proceeds to step F109.
In step F109, the controller 40 instructs the slide driver 48 to slide the slider 45 at a speed corresponding to the track pitch (0.64 μm) for the dummy pit row. That is, the slide moving speed is increased.
In step F110, the controller 40 monitors the position detection information SS from the sensor 46, and determines whether or not the slide movement of the exposure position has reached the position as the outer peripheral dummy area Odm, that is, the position having a diameter of 117.5 mm. .

When the position corresponding to the outer periphery dummy area Odm is reached, the process proceeds to step F111 to perform dummy pit formation processing. In this case, the controller 40 generates dummy pit data, for example, random data, from the recording data generation unit 43. Further, the laser driver 41 is caused to execute laser driving with higher power than usual.
As a result, an exposure pattern corresponding to the dummy pit row in FIG. 2B is formed on the master disc 103.
During this dummy pit formation process, the controller 40 monitors the position detection information in step F112. When it is detected that the movement by the slider 45 has reached the end position of the outer periphery dummy area Odm, that is, the position reaching the diameter of 120 mm, the dummy pit formation process is finished, and the process proceeds to Step F113. In step F113, the spindle motor 44, slider 45, and laser output are stopped, and the mastering process is terminated.

The stamper 104 is formed from the master disc 103 generated by performing the mastering as described above, as described in FIGS. 6 (d), 6 (e), and 6 (f). The optical disk manufactured from the stamper 104 is the one described as the first specific example.
FIGS. 10 and 11 show the optical disk manufactured in the steps of FIGS. 6G to 6J in this case.
FIG. 10A schematically shows a mold for molding the disk substrate 105 using the stamper 104 as the step of FIG.
The disk substrate 105 is molded by injection molding of a polycarbonate resin. The mold shown in FIG. 10A includes a lower cavity 120 and an upper cavity 121, and a stamper 104 is disposed on the inner surface of the lower cavity 120.
The stamper 104 manufactured from the master disc 103 manufactured by the above mastering process has a concave / convex pattern 5 for forming the normal pit 1 in an area corresponding to the information area, and the outer peripheral dummy area Odm and the inner dummy area Odm. The concave / convex pattern 6 for forming the dummy pit 2 is formed at a position corresponding to the circumferential dummy area Idm.

The disk substrate 105 is formed by injection molding using such a mold, and the formed disk substrate 105 is as shown in FIG.
In other words, the center of the disk substrate 105 made of polycarbonate resin is a center hole, and the normal pit 1 and the pits and bumps 5 and 6 formed on the stamper 104 are transferred to one surface (information reading surface side). A dummy pit 2 is formed.
The disk substrate 105 thus formed is formed with a layer structure as the steps of FIGS. 6 (i) and 6 (j). This is shown in the enlarged views of FIGS. 11 (a) and 11 (b).
First, as shown in FIG. 11B, a reflective film 106 made of, for example, an Ag alloy is formed on the signal reading surface side where the normal pits 1 and the dummy pits 2 are formed.
Next, as shown in FIGS. 11A and 11B, a light transmission layer 107 is formed by a technique such as application of a polycarbonate film or spin coating with an ultraviolet curable resin. Then, a hard coat layer 108 is formed as a surface treatment on the signal readout surface side.
Thereafter, a printed layer 109 is formed on the other surface (label surface side) of the disk substrate 105 as shown in FIG. For example, as offset printing, a white coat is applied to the entire surface on the label surface side, and color printing is performed, for example, to form the print layer 109.
Thus, the optical disc is completed. This optical disc has normal pits 1 and dummy pits 2 as shown in FIG.

When manufacturing the stamper 104 and the optical disc of the second specific example shown in FIG. 4, the mastering process of FIG. 9 may be modified as follows.
In the case of the second specific example, the track pitch, pit depth, and pit width in the dummy areas Idm and Odm are the same as those in the normal pits in the information area. Accordingly, the slide movement started from step F101 is performed at a speed corresponding to a track pitch of 0.32 μm until the end of mastering, and the speed change in steps F105 and F109 is unnecessary.
Further, in the dummy pit formation process in steps F103 and F111, it is only necessary to generate data for forming an 8T pit row, and control for increasing the laser power is not necessary.

  Further, when the dummy groove shown in FIG. 5 is formed, the slider moving speed change control and the laser power switching are not required as in the case of the second specific example, and the dummy grooves Idm and Odm are continuously changed. It is only necessary to perform exposure.

Subsequently, another embodiment will be described. In the embodiment described below, the formation of the dummy pits 2 (or dummy grooves) is the same as described above, but the entire other surface (label surface side) of the disk substrate 105 is formed into a satin finish. Shall.
The mastering process for manufacturing the disc master 103 and the stamper 104 to be manufactured are the same as in the above embodiment.
FIG. 12 and FIG. 13 show the optical disk manufactured in the steps of FIGS. 6G to 6J in this case.
FIG. 12A schematically shows a mold for molding the disk substrate 105 using the stamper 104 as the step of FIG. 6G.
Similar to the above embodiment, the disk substrate 105 is molded by injection molding of a polycarbonate resin. As shown in FIG. 12A, a stamper 104 is disposed on the inner surface of the lower cavity 120 of the mold.
On the other hand, in the upper cavity 121, the label surface forming part is a matte surface 123.
The pear ground 123 can be formed by etching or a blaster method in which plastic beads, glass beads or the like collide.
As shown in FIG. 12B, the pear surface of the pear ground 123 has a maximum roughness as the size of the most uneven portion of the unevenness, for example, in the range of 0.5 μm to 5 μm. In practice, the thickness is preferably 2 to 3 μm.

A disk substrate 105 formed by injection molding using such a mold is as shown in FIG.
That is, the center of the disc substrate 105 made of polycarbonate resin is a center hole, and the normal pit 1 and the dummy pit 2 to which the uneven patterns 5 and 6 formed on the stamper 104 are transferred are formed on the information reading surface side. The
Further, the entire surface of the disc substrate 105 on the label surface side becomes a pear ground 110 to which a mold pear ground 123 is transferred. That is, the label surface side is a pear ground 110 having a maximum roughness of 0.5 μm to 5 μm (eg, 2 to 3 μm), for example.

The disk substrate 105 thus formed is formed with a layer structure as the steps of FIGS. 6 (i) and 6 (j). This is shown in the enlarged views of FIGS. 13 (a) and 13 (b).
First, as shown in FIG. 13B, a reflective film 106 made of, for example, an Ag alloy is formed on the signal reading surface side where the normal pits 1 and the dummy pits 2 are formed.
Next, as shown in FIGS. 13A and 13B, a light transmission layer 107 is formed by a technique such as affixing a polycarbonate film or spin coating with an ultraviolet curable resin. Then, a hard coat layer 108 is formed as a surface treatment on the signal readout surface side.
Thereafter, a printed layer 109 is formed on the other surface (label surface side) of the disk substrate 105 as shown in FIG. For example, as offset printing, a white coat is applied to the entire surface of the satin-like label surface, and then, for example, color printing is performed to form a printing layer 109. Thereby, the label surface side after printing becomes a flat printing surface in which no satin is exposed.
Thus, the optical disc is completed. This optical disc has normal pits 1 and dummy pits 2 as shown in FIG.

As described above, by providing the stamper 104 with the concave / convex pattern 6 for forming the dummy pits 2, it is possible to prevent the pit deviation from occurring when the disk substrate 105 is peeled from the stamper 104 and taken out from the mold.
In the example shown in FIGS. 12 and 13, the label surface side of the disk substrate 105 is further shaped like a textured surface by the textured surface 123 of the upper cavity 121 of the mold. This also prevents pit deviation. It is valid. That is, even when the inner surface of the upper cavity 121 of the mold is the matte surface 123, appropriate adhesion can be obtained when the disk substrate is molded by the mold and the stamper 104, and the resin is cooled in the mold. It is possible to prevent the pits from being displaced during the contraction or the depressurization of the clamping force.
As a result of confirmation by actual production, it was found that the maximum roughness of the satin texture is 0.5 μm or more, and the effect of preventing pit shift can be exhibited.

In the example described with reference to FIGS. 12 and 13, the effect of preventing the pit shift by the dummy pit 2 on the signal reading surface side (uneven pattern 6 of the stamper 104) and the pear ground 110 on the label surface side (the pear ground 123 of the upper cavity 121). ), The effect of preventing pit deviation is synergistically exhibited, and more stable disc production becomes possible.
With the read-only optical disc formed in this way, when it was reproduced and jitter was measured, a good result of 5.5% or less over the entire circumference of the disc was obtained. That is, in the normal pit 1 in the information area, the reproduction signal characteristics were not deteriorated due to the pit deviation. Further, in order to confirm the molding stability, even when 10000 sheets were continuously molded, the jitter was not deteriorated even when the sampling evaluation was performed.

  For example, even if the pear ground 110 on the label surface side (the pear ground 123 of the upper cavity 121) is formed without forming the dummy pit 2, the same pit deviation prevention effect as that when the dummy pit 2 is formed is used. It was confirmed that

In addition, the label surface, which is the pear surface 110, is flattened with a white coat in the printing process, so that the label surface side is not affected by the pear surface at the time of printing. As with the substrate, the aesthetic appearance of the flat printed surface can be maintained, so that the commercial value is not impaired.
In particular, since the maximum roughness of the satin is about 2 to 3 μm (at least 5 μm or less), the label surface side can be easily flattened with a white coat.
The white coat is also carried out in the normal printing process in order to obtain good color developability and fixability of the ink at the time of printing, and is particularly executed to fill the pear ground in this example. It is not a thing. That is, in this example, the labor of the printing process is not increased.

Although the embodiments of the present invention have been described above, the present invention can also be applied to a multilayer disc having two or more recording layers.
Further, the present invention can be applied to various discs such as a Blu-ray disc, a DVD (Digital Versatile Disc) disc, and a CD (Compact Disc) disc.

It is explanatory drawing of the area | region structure of the read-only optical disk of embodiment of this invention. It is explanatory drawing of the normal pit and dummy pit of the 1st specific example of embodiment. It is explanatory drawing of the stamper and disk substrate of embodiment. It is explanatory drawing of the normal pit and dummy pit of the 2nd specific example of embodiment. It is explanatory drawing of the normal pit and dummy groove of embodiment. It is explanatory drawing of the disc manufacturing process of embodiment. It is explanatory drawing of a structure of the original disc manufacturing apparatus of embodiment. It is explanatory drawing of the laser emission waveform of an original disc manufacturing apparatus. It is a flowchart of the mastering process of embodiment. It is explanatory drawing of disk board | substrate shaping | molding of embodiment. It is explanatory drawing of the layer formation of the optical disk of embodiment. It is explanatory drawing of disk board | substrate shaping | molding of other embodiment. It is explanatory drawing of the layer formation of the optical disk of other embodiment. It is explanatory drawing of a pit shift | offset | difference.

Explanation of symbols

  1 Normal pit, 2 Dummy pit, 4 Dummy groove, 5,6 Uneven pattern, 11, 22 Laser light source, 40 Controller, 41 Laser driver, 42 Laser drive pulse generator, 43 Recording data generator, 44 Spindle motor, 45 Slider 46 sensor, 103 disc master, 104 stamper, 105 disc substrate, 110 pear ground, 121 upper cavity, 123 pear ground

Claims (15)

A stamper for manufacturing a read-only optical disc,
An uneven pattern for forming embossed pits based on recorded information is formed in a range corresponding to an information area set as an information recording area of a read-only optical disc, and
A stamper, wherein a concave / convex pattern for forming a dummy concave / convex shape is formed at a position corresponding to the outer peripheral side of the disc with respect to the information area.   2. The stamper according to claim 1, wherein a concave / convex pattern for forming a dummy concave / convex shape is formed at a position corresponding to the inner peripheral side of the disc from the information area. The dummy uneven shape formed on the read-only optical disc is a dummy pit row,
Each dummy pit of the dummy pit row is an emboss pit deeper than the emboss pit formed in the information area, and the track pitch of the dummy pit row is the same as that of the emboss pit row formed in the information area. The stamper according to claim 1, wherein the uneven pattern is formed so as to have a track pitch wider than the track pitch. The dummy uneven shape formed on the read-only optical disc is a dummy pit row,
2. The stamper according to claim 1, wherein each of the dummy pits in the dummy pit row is formed with the concave / convex pattern so as to be an embossed pit having a pit length not less than a predetermined length.   2. The stamper according to claim 1, wherein the concave / convex pattern formed on the read-only optical disc has the concave / convex pattern formed so as to form a dummy continuous groove. 3. A read-only optical disc in which information is recorded by embossed pits in an information area set as an information recording area,
A read-only optical disc, wherein a dummy concavo-convex shape is formed on the outer peripheral side of the disc from the information area.   7. The read-only optical disc according to claim 6, wherein a dummy uneven shape is also formed on the inner peripheral side of the disc from the information area. The dummy uneven shape is formed by a dummy pit row,
Each dummy pit in the dummy pit row is an emboss pit deeper than the emboss pit formed in the information area,
7. The read-only optical disc according to claim 6, wherein the track pitch of the dummy pit row is wider than the track pitch of the embossed pit row formed in the information area. The dummy uneven shape is formed by a dummy pit row,
7. The read-only optical disc according to claim 6, wherein each dummy pit in the dummy pit row is an embossed pit having only a predetermined pit length or more.   7. The read-only optical disc according to claim 6, wherein the dummy uneven shape is formed by a dummy continuous groove. The embossed pits and dummy irregularities are formed on one surface of the disk substrate, and the other surface is a matte surface,
A reflective film and a light transmission layer are formed on the one surface of the disk substrate,
7. The read-only optical disc according to claim 6, wherein a printed layer is formed on the other surface of the disc substrate.   The read-only optical disc according to claim 11, wherein the maximum roughness of the matte surface on the other surface of the disc substrate is 0.5 µm to 5 µm. An uneven pattern of emboss pits based on the recorded information is formed in a range corresponding to the information area set as the information recording area of the read-only optical disc, and further at a position corresponding to the outer circumference side of the disc from the information area. , A master generating step for generating a disk master by forming a concave / convex pattern for forming a dummy concave / convex shape;
A stamper manufacturing step for manufacturing a stamper using the above-mentioned disc master,
A disc manufacturing step of manufacturing a read-only optical disc using the stamper;
A method for manufacturing a read-only optical disc, comprising: In the above disk manufacturing step,
After manufacturing the disk substrate using a mold in which the stamper manufactured in the stamper manufacturing step is arranged on one inner surface and the other inner surface is a matte surface,
In the disk substrate, a reflective film and a light transmission layer are formed on one surface on which the embossed pits and the dummy irregularities are formed,
14. The method for manufacturing a read-only optical disk according to claim 13, wherein a printed layer is formed on the other surface of the disk substrate formed in a satin shape.   The method for producing a read-only optical disc according to claim 14, wherein the maximum roughness of the matte surface on the other inner surface of the mold is 0.5 µm to 5 µm.

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