JPH04276330A - Optical recording medium - Google Patents

Abstract

PURPOSE:A variable track pitch system as a technique for increasing the density of a sample system optical dish has the drawback that the data of adjacent tracks is affected if a specific track is rewritten many times and the purpose of this invention is td provide the variable track pitch system optical disk having high rewriting reliability. CONSTITUTION:The positions of individual bits for rewriting the data are determined and, therefore, projecting parts or recessed parts are previously provided in these positions on the surface of the optical disk. A recording film, protective film, reflection film, etc., are formed thereon. The inflow of heat to the adjacent tracks is prevented by the heat insulating effect of the level difference of the projecting parts or the recessed parts when the projecting parts or the recessed parts are heated. Consequently, the specific tracks can be rewritten many times without affecting the adjacent tracks.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of an optical recording medium.

0002

2. Description of the Related Art In recent years, optical disks have been put into practical use as large capacity memories. Playback-only discs called compact discs and laser discs are rapidly becoming popular in homes. 2. Description of the Related Art Write-once optical discs, which allow a user to record information only once, are becoming popular in offices for storing document files. Furthermore, rewritable optical disks were put into practical use and began to be used as backup memory and multimedia memory.

[0003] There are roughly two types of formats of optical discs that users can write to. This basically depends on the difference in the Yubo method; one is called the continuous groove method and the other is called the sample method. The continuous groove method is suitable for high-speed disk rotation, and the sample method is suitable for multi-function drive devices that can handle read-only optical discs, write-once optical discs, and rewritable optical discs. Recently, sample-type drive devices have been introduced to support partial ROM disks, which have a read-only area and a rewritable area, and rewritable disks, in which the entire area is rewritable, with a single drive device. It is being actively researched.

Methods for increasing the density of sample-type optical discs include shortening the wavelength of the laser and variable track pitch. For variable track pitch,
SPIE, Vol. 695, Optical Mas
s Storage II (1986), 230-23
Details are provided on page 8. The principle of variable track pitch is shown in FIGS. 3, 4, and 5. In each figure, the straight line indicates the center of the track, and the circle indicates the written pit. FIG. 3 shows the innermost circumference of the disk, and FIG. 4 shows the outermost circumference of the disk. The track pitch is constant from the inner circumference to the outer circumference, 1.3 μm, and the pit interval is 1.1 μm at the innermost circumference and 2.2 μm at the outermost circumference. At the outermost periphery in FIG. 4, the gaps between pits are large and the areal recording density is lower than in FIG. 3. Therefore, by setting the track pitch to 0.7 μm as shown in FIG. 5, the gaps between pits can be reduced and the areal recording density can be increased. In this way, by gradually decreasing the track pitch toward the outer circumference, the recording capacity can be increased up to 1.5 times. This method is called variable track pitch.

[0005] In the conventional sample type optical disk, there are no pits or grooves other than wobbling pits for tracking, clock pits for clock extraction, and address pits for addressing. That is, the area for reading and writing data is flat.

[0006]

[Problems to be Solved by the Invention] However, in the conventional example described above, since the track pitch at the outer circumference is narrow, if a particular track is rewritten many times, the data of the adjacent track will be affected, and when the adjacent track is reproduced, the reproduced signal amplitude will be There is a problem in that the value decreases.

SUMMARY OF THE INVENTION The present invention aims to solve these problems and provides an optical disc recording medium that improves the reliability of recording and reproduction of a variable track pitch type optical disc.

[0008]

[Means for Solving the Problems] The optical recording medium of the present invention includes:
In a sample-type optical disc that uses wobbling pre-pits to apply tracking servo, a)
Tracks are arranged such that the track pitch gradually narrows from the inner circumference to the outer circumference of the optical disc, and b) individual pits written by the user are shifted in position between adjacent tracks by a distance equal to the radius of the pit. , c) A recess-shaped or convex-shaped difference is provided at the position where the pit is written.

[0009] As the recording layer, a magneto-optical recording medium, a rewritable phase change recording medium, or the like is used.

0010

According to the above structure of the present invention, since there is a gap around the pit portion where the user writes, the diffusion of heat is blocked by the gap, and heat does not flow into the adjacent pit portion. As a result, even if a specific track is repeatedly rewritten, adjacent tracks are not affected at all.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an enlarged view of the surface of a sample-type magneto-optical disk according to the present invention, as seen from the surface opposite to the surface on which the laser beam is incident. 1 is a line representing the center of the track. Reference numeral 2 denotes a recess provided at the pit position where the user intends to write. This portion is a convex portion when viewed from the surface on which the laser beam is incident. As shown in FIG. 2, four layers of films are formed on the surface with the uneven portions by sputtering or vacuum evaporation. 3 is a translucent substrate made of resin such as polycarbonate, amorphous polyolefin, acrylic, epoxy, etc., or a UV-transparent substrate made of a glass substrate with irregularities transferred thereto.
A hardened layer is used. A protective film 4 has the role of preventing the magneto-optical recording film 5 from being oxidized, and at the same time has the effect of increasing (enhancing) the Kerr rotation angle due to multiple reflections. 6 is a reflective film formed to strengthen enhancement. When rewriting data on the magneto-optical disk surface, the magneto-optical recording film 5 on the convex portion is rapidly heated through the objective lens 7.
The absorbed heat cannot reach the magneto-optical recording film of the adjacent convex part because of the difference between the convex parts. This is because the thermal conductivity of the transparent substrate 3 is orders of magnitude lower than that of the magneto-optical recording film 5. In the present invention, individual pit positions do not change even when data is rewritten. Further, even when data is rewritten using a different drive device, the data must be written at pit positions. In sample-type optical discs, clocks for recording and playback are generated from pre-pits formed in advance, that is, the clocks are embedded in the optical disc, so even if different drive devices are used,
Data can always be written to pit positions.

The present invention is suitable for optical recording media in which data is rewritten many times. For example, Tb, Dy, Gd, Nd
There are magneto-optical recording media such as amorphous rare-earth-transition metal alloys made of rare earths such as Co and transition metals such as Co and Fe, Pt/Co multilayer films, and Pd/Co multilayer films. In the case of magneto-optical recording media, overwriting becomes possible by making use of the exchange coupling effect by layering magneto-optical recording films with different coercive forces and Curie temperatures. Other recording media include phase change optical recording media such as Sb-Te-Ge. This can also be overwritten. By applying an exchange coupling type magneto-optical recording film and a phase change optical recording medium to the present invention, a large-capacity and high-speed optical disk can be realized.

[0013]

[Effects of the Invention] As explained above, according to the present invention,
In a variable track pitch type rewritable optical disc, no matter how many times a particular track is rewritten, data in adjacent tracks is not affected at all, and a highly reliable and large-capacity optical disc can be realized. The present invention is 3.5 inches, 5.25
If applied to inch-sized optical discs, each
A large capacity of 0 MB or more or 300 MB or more can be achieved, and high reliability can also be achieved.

Furthermore, as a secondary result, deterioration in rewriting performance due to mass transfer (recording film) of the phase change optical disk can be suppressed by the difference.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the surface of a sample type magneto-optical disk of the present invention.

FIG. 2 is an enlarged cross-sectional view of a sample type magneto-optical disk of the present invention.

FIG. 3 is a diagram showing the arrangement of data pits on the innermost circumference of a sample-type optical disc.

FIG. 4 is a diagram showing the arrangement of data pits on the outermost circumference of a sample-type optical disc.

FIG. 5 is a diagram showing the arrangement of data pits on the outermost circumference of a variable track pitch optical disc.

[Explanation of symbols]

1. Track center 2 Recess 3 Translucent substrate 4 Protective film 5 Magneto-optical recording film 6 Reflective film 7 Objective lens 8 Convex part

Claims (2)

[Claims] 1. A sample-type optical disc in which tracking servo is applied using wobbling pre-pits, wherein: a) tracks are arranged such that the track pitch gradually narrows from the inner circumference to the outer circumference of the optical disk, b)
) The individual pits written by the user are shifted in position between adjacent tracks by the radius of the pit, and c) A recess-shaped or convex-shaped difference is provided at the position where the pit is written. optical recording medium. 2. The optical recording medium according to claim 1, wherein the recording layer is a magneto-optical recording medium or a rewritable phase change recording medium.