JPS5873026A - Optical disc provided with groove - Google Patents

Abstract

PURPOSE:To accurately count the number of tracks at address reading and accessing, by providing grooves having the same altitude as those of a data section for an address section to the surface of a disc and maximizing the SN ratio for both address and track signals. CONSTITUTION:An address section 40 of a groove disc has a lambda/8 height (where; lambda is the wavelength of light from a light source) of an upper part 43 and a lambda/4 depth d4 of a bottom part 44, by taking a disc surface 42 as a reference. A data section 41 has a bottom 45 having lambda/8 depth to the surface 42. At accessing, when a light beam crosses a track, in case of the crossing of the address section 40 as shown in arrows 49a, 49b as well as the crossing of the data section 41 as shown in the arrow 49, the depth of grooves is detected as lambda/8, the SN ratio of the track signal is maximized. Further, the depth is lambda/4 to the address signal, the highest SN ratio can also be obtained in this case. Thus, the count of the number of tracks can accurately be performed not only at the reading of address but also at accessing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording grooved optical disc structure for recording and generating information using a light beam.

Conventionally, in this type of optical disk, a structure as shown in FIG. 1 has been used to facilitate tracking and access of a light beam.

That is, concentric or spiral O grooves 12 are provided on a disk substrate 11 made of glass or plastic, and an information recording medium 13 made of a metal thin film such as Te or To-based compound is added on the O grooves to form a grooved disk. Configure. The laser beam 1 passes through the base m1ll at the bottom of this groove.
4 is focused and irradiated by the objective lens 15 for recording and writing.

FIG. 2 shows an example of information on one such groove.

In the figure, 21 is an index i-ka, λ is a synchronization mark, and 23 is a track (!Ill), which are pre-engraved with a digital code as groove information.Furthermore, following <24. 25゜..., 27 each indicate a sector) In the diagonally shaded part at the beginning of each sector, sector gap, synchronization @ sign, sector number, etc. are pre-engraved with digital code as groove information as mentioned above. There is.

In this way, you can prepare pho in advance! The shaded area is called the address area, and the other areas are called the data area used for additional recording.

In this case, in the conventional grooved disc I, seven grooves OI
In the address section, the I ratio is set to λ/4 so that the reproduction scratch 101) i ratio is the best, and in the data section, the track signal 011N ratio is the best. □, 7°2°11. □3. two:! :: Shows “”°“.

Figure 3 shows the structure of a conventional zero-groove optical disc.
[K shown in detail. The handicapped figure (1) is 0, 1, and the same figure is OA-MU! fNll, indicating l1llI
In, 3. is the address part, St is the data part],
Based on the tisf table m32, the address part sOO hawk part 5set deep name is d1m++1J/4, and the data part 310 bottom part 84#1 is -1wmλ,4. In Oka g(a), 3I is recorded in data 1 part 31 and has 9 bits. This beep) 3! is the metal thin mS1 deposited on Kasha11S@0
It is formed by evaporating it by laser light. 'l living time Kti
The presence or absence of bit 35 is detected based on the reflectance of extracted light of 11. Note that this bit 35 is omitted in #iii (Figure 3).

In the grooved optical disk having the above structure, the following problem occurs during access. That is, the light beam
When crossing the data area 31 as shown by the arrow 38 in FIG. 3(a), the depth of the groove relative to the disk surface 1132 is λ/8 at any position, so it is difficult to detect good quality track No. 1. However, in the address section 3, the depth of the groove is λ/4, so the track signal deteriorates. Occasionally, one-off meetings occur. Therefore, in the address section 30, the IN ratio of the track signal is lower than that of the data section SIK, which causes problems in accessing the number of tracks.

Conventionally, methods for solving this problem include (1) making the groove depth a uniform value between λA and 1 for both the address @Th and data parts, and (2) making the groove depth s1! A method of recording the address @ number later on the 10th disk was proposed.
Ru.

However, in the method (1) above, the number of O tracks in the address field and the data field is balanced to 1:9], and the overall KSN ratio decreases compared to the best case.
) Method O has the disadvantage that it requires a huge amount of work because the address information is recorded anew in the footer for each disk created by the press. There is.

The present invention has been developed in view of the above-mentioned circumstances, and its purpose is to not only read the address signal O but also to easily determine the number of tracks at the time of access, and to reduce the work of recording address information 0. Another object of the present invention is to provide a grooved optical disc that is easy to create.

In order to achieve such an object, the present invention sets the address portion ovso depth to λ/ in the direction along the track.
4. For the direction across the track, %O is set to λ/8.
There is "t". Below is 1j! The present invention will be explained in detail using jIIf1.

No. 411 (a plan view showing the groove structure of the mtIA example of the present invention, the same figure) is a cross-sectional view of the seventh intestine.
4. is an address field, and 41 is a data field. Here, the address portion 4 has a groove structure in which the height of the upper portion 43t is d3=W1 and the depth of the bottom portion 44 is d4=λ/80 with respect to the disk 1liii42.

The data section 41 includes the data table Ti! as in the conventional case. It has a bottom portion 4S with a depth of λ/8 for each side. Bit 4e is recorded in this data section 41. This bit 4 @
Since it is made of acrylic resin, it can be formed by evaporating the thin metal layer 48 that is made of To and coated on the surface of the disk substrate 470 by irradiating it with a laser beam. In addition, the same I! 11
In 1), the pip) 41 has been omitted.

Because of this groove structure, when the light beam crosses the track at the time of access, it can of course cross the data section 41 as shown by arrow 4-.
Even if it crosses address 1140 as shown by 1-,
Relative groove # in relation to the disk I reference plane 42! is always λA. That is, the reference plane 420 is lower with respect to the upper part 43 of the address section 400, and the wiK reference plane 42 is higher with respect to the bottom part 44, but the difference in both cases is λβ. Therefore, the ratio of truck I @ No. O8N is always the highest. On the other hand,
For each address, λ/4t) @fil and'&
>, the highest 8N ratio is obtained in this case as well.

Such a groove structure can be formed by the following method.

First, as shown in FIG. 5, a λ/80 height 0 center strip is formed at a track forming position on a disk substrate.

That is, in the same figure, 10
Two layers s2 are deposited to a thickness of λ/8. Then add C on top of it.
An r layer 5s is deposited to a thickness of several tens of AO, and then a 0JcK7 photoresist layer S4 is spin-coded. In this case, Cr
, layer S3 is exposed with photoresist 0!1-5) at the rack formation position. Develop this and use Seikyu Photoresist i-sk! ! Use 5 to make CF4gaJ! Rite CrJI
Etch S3 and 810g layer s2 (shown in bold). After 70 days, remove the remaining 7 Otresist mass/Il and the OCr layer under Jto), λ/84
A ridge II can be formed.

Next, as shown in FIG. 1, on the protrusion 56 of such a grooved disk, there is an address part having a height of ±2/8 with respect to the reference plane and an address part having a height of 1 λ/8. A data section is formed. That is, in the figure, a recording layer 61 made of a metal material such as Aj is deposited to a thickness of λ/4 on the surface of the glass substrate 1 provided with the protrusions 5-. Next, address information of a digital code is optically recorded in the address portion and DC information is optically recorded in the data portion on the portion of the recording layer ε1 above the protrusion 5s. Area where light is irradiated by WA @2. At @l, the recording layer 61 is melted and evaporated to form a hole. As a result, an O-groove structure can be formed in the recording layer 61, with the reference plane 65 always having a depth of λ/8 in the direction across the track and a depth of λ/4 in the direction along the track.

Therefore, using this grooved disk as a mask plate, silver was vapor-deposited for electrodes, and a test stand was made by nickel electroforming. Furthermore, by molding a plastic material such as acrylic resin using this standber, a disk S* having a groove structure as shown in FIG. 4 can be obtained.As explained above, the present invention Accordingly, the depth of the groove is λ/4 in the data area, and λ/4 in the direction along the track in the address area, but λ/4 in the direction across the track. 8, both the playback address signal and track signal
The N ratio becomes maximum.

Therefore, it is possible to not only read the address but also accurately measure the track aotta when accessing the track.
The address signal is mass! It has the excellent effect that the preparation process is easy because it is recorded in advance at the IILO stage.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the outline of #1 structure of a conventional grooved optical disc, Fig. 2 is an explanatory diagram showing an example of formatting information on the grooves, and Fig. 3 (a) is a plane showing the groove structure. Figure, same figure-
) is an A-A cross-sectional view, FIG. 4(a) is a plan view showing the groove structure of one embodiment of the present invention, FIGS. FIG. 3 is an explanatory diagram showing a step of forming a one-star plate for forming a grooved optical disk according to a first embodiment of the invention. 40...Address I'll, 41...Data section, 42--Working disk reference plane, 43-Φ...Top, 4
4.45--Bottom, 46--Bit, 47--
...Disk substrate, 48mII...Metal thin film. % Applicant: Japan Denka Telephone Public Corporation Agent: Masaki Yamakawa Figure 1 Figure 2 Figure 3 Figure 4 -4041-

Claims (1)

[Claims] In a grooved optical disk that optically records information by adding an information recording medium to a tissue-shaped O substrate and providing concentric or spikele-shaped O grooves consisting of an address area and a data area, each *In the tV address area, groove information is recorded in a digital code consisting of the top and bottom of the 02 state by forming unevenness along the groove in advance, and the upper part is The groove is characterized in that the bottom portion is formed to be λ/8 (λ is the wavelength of the light source light) high and the bottom portion is λ/8 low, and the bottom portion of the data area is formed to be λ/8 low relative to the surface of the disk 1!1. Optical disc.