JPH02265022A - Optical disk medium - Google Patents

Abstract

PURPOSE:To minimize the information loss by defects by disposing identification signal parts, such as track addresses and sector addresses, with the deviation in position corresponding to the approximate length of the identification signal parts from the positions of the identification signal parts of the adjacent tracks. CONSTITUTION:An optical disk medium 1 is provided with the tracks 2(1) to 2(n) of pregrooves and the identification signal parts 3(1) to 3(n) provided in the top parts of the respective sectors of the tracks 2(1) to 2(n). The identification signal parts 3(1) to 3(n) are so disposed as to deviate to the right side from the adjacent identification signal parts by as much as the position corresponding to the length of these parts. The identification signals, such as track addresses and sector addresses, are provided in the respective identification signal parts 3(1) to 3(n). The propagation of an error to the identification signal parts of the adjacent tracks arising from the expansion of the generated defect after the defect is generated in the certain identification signal part is prevented in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk medium in which information is recorded, reproduced and erased using laser light.

[Conventional technology]

Optical disk recording systems using laser light are capable of large-capacity recording and non-contact high-speed access, so they are beginning to be put into practical use as large-capacity memories. Optical discs are classified into read-only types known as compact discs and laser discs, write-once types that allow users to record, and rewritable types that allow users to repeatedly record. Write-once and rewritable optical discs are being used as external memory for computers or as document/image files.

In optical discs currently in use, guide grooves (pre-groups) for lagging laser light are formed in advance on the disc in order to achieve high-speed access. The pre-groups are spiral or concentric, and are usually formed at a pitch of 1.6 μm when a semiconductor laser with a wavelength of 780 to 830 nm is used as a light source. Further, the pre-group is divided into a plurality of sectors per trunk. Each sector has an identification signal (ID code) that indicates the track address and sector address.
is added in advance in the form of a preformat when molding the substrate. For example, in a standardized optical disc of 5.25 inches in size, as shown in FIG. 3, a triple identification signal is added to the beginning of each sector as a brief name mark. At the time of data access, the disk device determines whether the currently accessed sector is the sector to be accessed by reading this identification signal.

The reason why three identification signals are added is that if there is any error in the identification signal section, the three identification signals read by the device are compared and one identification signal is found to be in error. This is because the logical configuration is such that if the other two identification signals are the same, then that is used as the identification signal for that sector.

As shown in FIG. 4, the identification signal section 30 of a conventional optical disk medium is arranged adjacent to the identification signal section 30 of an adjacent l/rack 31 in the disk radial direction.

[Problem to be solved by the invention]

Conventional optical disc media have the following drawbacks.

In optical discs, since recorded information on the order of .mu.m is recorded, reproduced, and erased using a condensing laser on the order of .mu.m, defects on the order of .mu.m cause errors. This also applies to the identification signal section, and if there is an error in two of the three identification signals in the triplexed identification signal section 30, this error will cause a reading error and the sector will be Certain information will no longer be accessible. This means that the information is effectively lost. The causes of defects in optical disks include early-onset defects, which are caused by impurities mixed in during substrate molding or recording film formation, and so-called late-onset defects, which occur due to changes over time. For early defects, it is possible to detect the defective area before the disk is used and take preventive measures, but for late defects, the data recording section must rely on the ability of the error correction code. Become.

However, since the identification signal section 30 is not provided with an error correction code, it is not possible to perform error correction.
As a result, if an error occurs in the identification signal section due to a late-onset defect, the information in that sector cannot be accessed. In addition, since the identification signal sections 30 are arranged adjacent to each other in the disk radial direction, a late defect occurring in the identification signal section 30 of an adjacent trunk will affect the identification signal section of the adjacent trunk, and the adjacent identification signal section There was a risk that errors would occur even in the section.

An object of the present invention is to solve the above-mentioned problems and to provide an optical disk medium that can minimize information loss due to defects by suppressing reading errors in the identification signal section caused by the occurrence and spread of late defects. It is about providing.

[Failure to solve the problem]

The present invention is an optical disc medium having a format structure in which a track is divided into a plurality of sectors and recording/reproduction/erasing is performed in units of sectors, wherein the position of an identification signal part such as a trunk address or sector address is relative to the position of an identification signal part of an adjacent track. The identification signal portions are arranged at a position offset from each other by approximately the length of the identification signal portion.

[Function] When a late-onset defect that occurs in a certain identification signal portion of the optical disk medium of the present invention grows and spreads to an adjacent track, the adjacent 1-rank identification signal portion is the same length as the identification signal portion where the defect has occurred. Since the two parts are separated by a length of 10 minutes, most of the defects will penetrate into the part where there is no identification signal part. Therefore, it is possible to prevent the defect from spreading to the adjacent I-rank identification signal section.

(Example] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of an optical disc medium according to an embodiment of the present invention.

Optical disk medium 1 has trunk 2 (1
)~2(n) and pre-group tracks 2(1)~2
(n) Identification signal section 3 installed at the beginning of each sector
(1) to 3(n) are provided.

The tracks 2(1) to 2(n) of the pre-group are guide grooves used for tracking a laser beam for recording, reproducing, and erasing information, and are formed in a spiral or concentric shape on the optical disc medium 1.

As shown in the figure, the identification signal sections 3(1) to 3(n) are arranged so as to be shifted to the right by an amount corresponding to the length of the adjacent identification signal section. Each identification signal section 3 (1) (~
3(n)) is provided with three identification signals 3a, 3b, and 3c, as shown in FIG. This identification signal 3a
is composed of a track address 3a+ of its own sector, a sector address 3az, and an error detection code 3a3. The other identification signals 3b and 3c also have a similar configuration.

Since the present embodiment is configured as described above, the following effect of preventing the expansion of late-onset defects is achieved.

A late defect occurs in the identification signal section 3(1) and the identification signal 3a
, 3b, 3c, if an error occurs in two or more of the identification signals, the identification signal section 3(1) is determined to be in error.

As this late-onset defect grows, it spreads from the identification signal section 3(1) to the adjacent track 2(2), but most of the defects invade the area where there is no identification signal section 3(2), so the identification signal Defects will not penetrate to part 3(2).

Optical disk medium 1 of this example and a conventional optical disk medium were prepared, and an accelerated test was conducted under high temperature and high humidity conditions in order to compare the reliability of the two. The substrate used was polycarbonate with a diameter of 130 nm and on which the identification signal portion shown in FIGS. 1 and 4 was formed in advance.

On both substrates, a first protective film, a recording film, and a second protective film were sequentially formed simultaneously in the same chamber by magnetron sputtering. The first protective film and the second protective film are Si3N.
4 was formed to a thickness of 80 nm each, and a recording film of TbFeCo was formed to a thickness of 80 nm. Next, heat these two discs at 80°C.
It was placed in a high temperature bath of 90% R, I+. After 1000 hours, these two optical disk media were taken out and the identification signal portions were read. When reading 318,750 sectors on one side of a disc, an optical disc medium with a conventional identification signal part configuration had a reading error of 12 sectors, but in this example, identification signal parts 3(1) to 3(n )
In the case of the optical disk medium 1 having this arrangement, only 3 sector reading errors occurred.

FIG. 2 is a schematic diagram showing the main parts of an optical disc medium according to another embodiment of the present invention.

In the optical disc medium 11 of this embodiment, the identification signal section 13 of the pre-group tracks 12(1) to 12(n)
This differs from the optical disk medium 1 of FIG. 1 in that (1) to 13(n) are arranged alternately offset by an amount corresponding to the length of adjacent racks.

The other functions of the configuration 1 are the same as those of the optical disk medium 1 shown in FIG. 1, and therefore, repeated description will be omitted.

〔Effect of the invention〕

As explained above, in the optical disk medium of the present invention, the position of the identification signal portion such as the track address or sector address is shifted from the position of the identification signal portion of the adjacent track by approximately the length of the identification signal portion. As a result, it is possible to prevent errors from spreading to the identification signal areas of adjacent tracks due to the expansion of late-onset defects that occur in one identification signal area, thereby providing an optical disc medium with high reliability. There is an effect that it can be done.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of an optical disc medium according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the main parts of an optical disc medium according to another embodiment of the invention, and FIG. 3 is an identification diagram. FIG. 4 is a schematic diagram of the main parts of a conventional optical disc medium. 1.11...Optical disc medium

Claims (1)

[Claims] (1) An optical disc medium with a format structure in which a track is divided into a plurality of sectors and recording/reproduction/erasing is performed in sector units, where the position of an identification signal such as a track address or sector address is relative to the position of an identification signal of an adjacent track. An optical disc medium characterized in that the identification signal portions are arranged with a difference corresponding to approximately the length of the identification signal portion.