JPH047019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk substrate, and more particularly to an optical disk substrate having an optical disk track having a spiral or concentric signal recording track.

[Common technology]

In general, optical disk substrates used in write-once type optical disk devices called DRAW type and erasable type optical disk devices that can be read and then erased after writing have guide grooves or signal recording tracks as tracking guides. is formed. Conventionally, glass, vinyl chloride, polymethyl methacrylate, polycarbonate resin, and the like have been used as substrates for optical disks. When forming grooves as tracking guides on a substrate, a photopolymer method, an injection molding method, an injection compression molding method, etc. are used. usually,
When polymethyl methacrylate or polycarbonate resin is used, injection molding or injection compression molding is generally used. Regardless of which of the above manufacturing methods is used, it is necessary to check whether the grooves as tracking guides formed on the optical disk substrate are formed in a predetermined shape. In other words, it is necessary to know whether the predetermined shape of the stamper used as the master has been accurately transferred, or in other words, whether the molding conditions for forming grooves on the optical disk substrate have been optimized. Conventionally, the groove shape of an optical disk substrate with signal recording tracks has been measured by observing the surface image and cross-sectional shape using a scanning electron microscope, or by directly scanning the groove shape with a mechanical contact stylus. ing. Furthermore, there has been no method for quantitatively grasping the defect occurrence rate after coating a recording medium on an optical disk substrate having signal recording tracks.

[Conventional technology]

Several types of optical disc substrates having conventional signal recording tracks are known.
One type is that a guide groove as a tracking guide, that is, a signal recording track is formed in almost the entire area of the optical disk substrate, and another type is that a guide groove as a tracking guide is formed in a specific sector on the circumference of the guide groove. There is a type with preformatted relief pits. Next, a conventional optical disk substrate will be described in detail with reference to the drawings. FIGS. 4 and 5 are plan views showing an example of a conventional optical disk substrate. The optical disk substrate 1 shown in FIG. 4 has a guide groove as a tracking guide, that is, a signal recording track 2 formed over almost the entire area of the substrate. In the optical disk substrate 1' shown in FIG. 5, a signal recording track 2 as a tracking guide is formed over the entire substrate area, and a specific sector part 3 on the circumference of the signal recording track 2 is preformatted. It has 4 relief bits.

[Problem that the invention seeks to solve]

Although the conventional optical disc substrate described above may have a format in which relief bits are included in specific sectors on the circumference of the signal recording track, basically only the signal recording track covers almost the entire area of the optical disc substrate. This has the disadvantage that sophisticated observation techniques and groove shape measurement techniques are required to manage and guarantee the quality of the groove shape of the formed signal recording track. As mentioned above, when observing the groove shape of a signal recording track using a scanning electron microscope, there are disadvantages in that it requires the preparation of a special sample for observation, and it requires a long time and a high level of skill for observation. It had the necessary flaws. Furthermore, the method of measuring the groove shape using a mechanical contact stylus has the drawback of inducing destruction of the observation sample due to the problem of measurement stylus pressure. Above all, conventional optical disk substrates with signal recording tracks have a disadvantage in that they do not have a structure in which it is not possible to quantitatively grasp, manage, and guarantee the defect rate of each optical disk substrate after coating with a recording medium. It was hot. Therefore, the present invention has developed a conventional optical disk substrate in which only a guide groove as a tracking guide, that is, a signal recording track was formed, by newly forming unevenness at a predetermined frequency in an area outside the signal recording track area. By additionally forming a signal area in the pit row, only the signal area of the uneven pit row can be tracked with an optical pickup, and the level of the difference in the amount of reflected light returned from a place without pits and a place with pits can be detected. It is possible to identify whether or not the groove shape of each optical disk substrate is optimally formed after coating the actual recording medium by using a relatively simple method of coating the actual recording medium. By quantitatively understanding the defect occurrence rate at this stage, we are now able to manage and guarantee board quality. An object of the present invention is to make it possible to ascertain whether the groove depth of the signal recording track of each substrate is formed to a predetermined depth at the stage when a recording medium is coated on an optical disk substrate. The purpose of the present invention is to provide an optical disk substrate having a spiral or concentric signal recording track that can quantitatively grasp the defect occurrence rate after coating a recording medium on the substrate and control and guarantee the quality of the substrate. shall be.

[Means for solving problems]

The substrate of the optical disk of the present invention includes a predetermined row of pits along the outer periphery and/or the inner periphery of a spiral or concentric signal recording track area.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional perspective view showing a first embodiment of the present invention. The optical disk substrate 5 according to the present invention shown in FIG. 1 has a guide groove as a tracking guide, that is, a signal recording track area 6 and a signal area 7, which is a row of concave and convex pits formed at a constant frequency, on the substrate. are doing. The signal area 7 of the uneven pit array formed outside the signal recording track area 6 of the optical disk substrate 5 of the present invention is a means for monitoring whether the grooves in the signal recording track area 6 are formed optimally or a recording medium. It is used to quantitatively understand the defect incidence rate of optical disk substrates after coating, and to control and guarantee the quality of the substrates. Next, the effectiveness of the optical disk substrate 5 of the present invention will be explained in detail. Figure 2 shows the difference in the amount of reflected light between the flat part and the uneven part due to the difference in unevenness (optical path difference) in the signal area 7 of the uneven pit array, and the change characteristics of the amount of reflected light from the grooves in the signal recording track area 6. be. In the figure, the difference signal a in the amount of reflected light reaches its maximum when the level difference between the concave and convex portions of the pit row in the signal area 7 is 1/4 of the wavelength of the incident light;
It decreases as it becomes larger or smaller.
In the figure, the amount b of reflected light from the grooves in the recording track area 6 is maximum when the groove level difference in the recording track area 6 is zero, and decreases as the groove level difference becomes larger. In other words, it is shown that when the step size of the unevenness is approximately in the range of 1/6 to 12/12, it becomes optimal for both the signal area 7 of the uneven pit row and the groove of the signal recording track area 6. By the way, the pitch of the signal recording track 2 of recent optical disk substrates is on the order of 1.6 to 2.5 μm, and the depth of the groove is determined by the error of the tracking servo when a tracking servo method called push-pull method is adopted. The wavelength of the incident light is set to 1/8 to maximize the signal. Now, optical disk board 5
When checking whether the grooves in the signal recording track area 6 are formed to the optimum depth, as can be understood from the explanation of FIG. The difference in the amount of reflected light between the surface and the uneven surface is at a predetermined level, that is, the depth of the groove in the signal recording track area 6 is 1/8 of the wavelength of the incident light.
By tracking and monitoring with an optical pickup that the groove depth is at a level corresponding to , it is possible to grasp the groove depth of each signal recording track area 6 at the stage when the recording medium is coated on the optical disk substrate. . Furthermore, above all, if the structure of the optical disk substrate according to the present invention is adopted, the written data in the signal area 7 of the uneven pit row during master recording and the reproduced read data after coating the recording medium on the optical disk substrate 5 can be transferred. Since it is possible to compare and check, it is possible to quantitatively grasp the defect occurrence rate of optical disk substrates having signal recording tracks after coating a recording medium, and to control and guarantee the quality of the substrates. Figure 3 a, b
FIG. 3 is a plan view showing the second and third embodiments. Third
The optical disk substrate 5' shown in FIG. The area 7 is arranged in the outer peripheral area of the substrate.Incidentally, the formation area of the signal area 7 of the concave-convex pit array can basically achieve its function even if it has only a few tracks. Basically, the area dedicated to the signal recording track is reduced, but for example, if the track pitch is set to 1.6 μm, even if the signal area is formed for 100 tracks, the overall recording capacity of the optical disk substrate will decrease by 0.16 mm. The influence is small.Although the embodiments of the present invention have been described above, it is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention.For example, in the above-mentioned embodiments, uneven pits Although the column signal areas are arranged on both sides of the signal recording track area or on one side of the inner or outer circumference of the board, they are basically used to monitor the structure formation and control and guarantee the defect rate. Other configurations may be used as long as the signal area of the concavo-convex pit row and the signal recording track area are arranged in zones in the radial direction of the substrate.

〔Effect of the invention〕

The optical disc substrate of the present invention is different from the conventional optical disc substrate in which only a spiral or concentric tracking guide groove centered around the center of rotation, that is, a signal recording track was formed. By newly forming a new signal area of a row of uneven pits formed at a predetermined frequency in an area outside the signal recording track area, a special sample for groove shape observation is created, and advanced observation skills are required. Therefore, there is no need to directly observe the surface or cross-sectional shape using a scanning electron microscope, which requires a long observation time, or to use a mechanical contact stylus that can cause sample destruction, or to use advanced groove shape measurement equipment. By tracking only the signal area of the row of uneven pits formed at the additionally formed predetermined frequency with an optical pickup, it is possible to detect the level of the difference in the amount of reflected light returned from a place without pits and a place with pits. At the stage when the final recording medium is coated on the disk substrate, it is possible to determine whether the groove depth of the signal recording track on each substrate is formed to a predetermined depth. The present invention has the advantage that it is possible to provide an optical disk substrate having a spiral or concentric signal recording track, which allows the quality of the substrate to be managed and guaranteed by quantitatively understanding the defect occurrence rate after coating the recording medium.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional perspective view showing one embodiment of the present invention;
FIG. 2 is a diagram showing the change characteristics of the amount of reflected light with respect to the uneven pit array and the level difference of the signal recording track, FIGS. 3a and 3b are plan views showing other embodiments of the present invention, and FIG.
FIG. 5 is a plan view showing the structure of a conventional optical disk substrate. 1, 1'... Optical disk substrate, 2... Signal recording track, 3... Specific sector section, 4... Relief bit, 5, 5', 5''... Optical disk substrate, 6... Signal. Recording track area, 7...Signal area of uneven pit row.

Claims (1)

[Claims] 1. An optical disk substrate characterized in that a predetermined row of pits is formed along the outer circumference, inner circumference, or both of a spiral or concentric signal recording track area.