JPH03173948A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To improve an information recording density by alternately forming grooves and lands with spiral, concentrical or parallel rugged shapes on an optical information recording surface and setting the effective depth of the ruggedness at the specific ratios of the wavelength of a laser beam. CONSTITUTION:The magneto-optical recording film 2 which consists of metals, such as Te and Bi or the alloy thereof and is formed on a transparent substrate 1 consisting of a transparent material, such as glass, is alternately formed with the grooves 4, 5 and the lands 7 with the spiral, concentrical or parallel rugged shapes. The depth of the grooves 4, 5 is set at 3/8 to 5/8 of the wavelength of the laser beam used so that the pitch between the tracks in the case of formation of a plane by elongating the grooves is increased. The grooves are formed as the guide grooves at the time of the execution of the tracking control of an optical pickup. The arrival of the condensed beam at the adjacent land an the interference thereof by the setting of the above-mentioned depth are prevented by increasing the distance between the tracks. The crosstalks between the tracks is decreased in this way and the quality of reproduced signals and the information recording density are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an optical information recording medium, and more particularly to the structure of uneven portions formed on the medium.

(Prior Art) As is well known, there is an optical disk as an optical information recording medium, and as partially shown in FIG. It is constructed by forming a guide groove B-C and forming a light-absorbing and reflective recording film thereon.

In the above-mentioned optical disc, the land E located between the grooves B and C is irradiated with a focused laser beam F to record information as recording pits G.

The depths of the grooves B and C mentioned above are determined by the laser condensed beam F.
The shape is selected to be 1/16 to 174 times the light wavelength of , and is convenient for detecting track deviation by detecting the distribution of the diffraction pattern of reflected light.

In addition, the depth of the above-mentioned groove is approximately 178 times the wavelength of light when the groove is rectangular, and furthermore, the depth of the groove is approximately 1/6 times the wavelength of light when the groove is V-shaped. has been done (
For example, JP-A-60-50733, JP-A-63-
32746).

(Problem to be Solved by the Invention) However, in the recording medium having the above-mentioned structure, as the laser output during recording is increased, the width of the recording pit tends to widen, and therefore the adjacent track, that is, the land It is easy to get mixed in with the pit signal, so-called.
In some cases, the quality of the reproduced signal deteriorates due to increased crosstalk between tracks.

Therefore, in conventional recording media, it has been difficult to increase the information recording density by narrowing the track pitch.

SUMMARY OF THE INVENTION In view of the problems with conventional recording media, an object of the present invention is to improve the quality of a reproduced signal by reducing the crosstalk between tracks by making it difficult for the width of recording pits to widen, and to narrow the pitch between tracks. The object of the present invention is to obtain an optical information recording medium that can improve the information recording density by making it possible to do this.

(Means for Solving the Problems) In order to achieve this object, the present invention forms grooves and lands alternately in a spiral, concentric or parallel uneven shape on an optical information recording surface. Alternatively, in an optical information recording medium in which information is recorded using one of the lands as an information track, the effective depth of the above-mentioned unevenness is set to 378 to 578 times the wavelength of the laser beam used for recording and reproduction. This is what I am proposing.

(Function) According to the present invention, since the groove is deep, the recording film is bent at the groove, so that even if the recording pit intrudes the same distance along the recording film, it will not be able to reach the adjacent track. The amount of penetration can be reduced in appearance.

(Embodiment) Hereinafter, details of an embodiment of the present invention will be explained with reference to FIGS. 1 to 3.

FIG. 1 is a perspective view showing the main structure of an optical information recording medium according to an embodiment of the present invention, in which reference numeral 1 denotes a transparent substrate;
2 shows a light-absorbing and reflective recording film.

In addition, code 3 is a focused laser beam for recording and reproduction;
．． 5 is the tracking guide groove and 6.7 is the groove 4.
The land provided between the land 5 and the land 6, and the recording pit 8 recorded on the land 6, respectively.

The transparent substrate 1 described above is made of a known transparent material such as glass, polymethyl methacrylate, polycarbonate, amorphous polyolefin, epoxy resin, etc.
The recording film 2 includes Te, Bi, and Sn.

Magneto-optical recording films made of metals such as Se or their alloys, organic dye films such as cyanine dyes, amorphous films of transition metals and rare earth elements, etc. are used.
Recording films of chalcogen glasses such as Ox, TeSe, TeGeSn, TeGeSb, InSe, and TeGeSb are also applicable.

This recording film 2 may be in contact with gas such as air, but a protective film may be provided on its surface.

The grooves 4.5 mentioned above are set to a depth of 378 to 5/8 times the wavelength of the laser used and the light used, and this allows the distance between the tracks when the grooves 4 or 5 are extended to form a flat surface. This is done so that the pitch becomes larger.

This groove is formed as a guide groove for tracking control of the optical pickup, but by setting the depth as described above, it is possible to prevent the focused beam from reaching and interfering with the adjacent land. By increasing the distance between tracks for the light beam to reach, the loss of the information reproduction signal can be suppressed, and by making it possible to form more adjacent lands, information recording density can be improved. ing.

In other words, the above-mentioned interference between tracks is considered to occur because the width of recorded pits increases due to strong irradiation with a focused beam, and some of the recorded pits invade adjacent tracks.

One possible reason for this is that when the intensity of the focused beam is high, the energy necessary for recording is also given to the periphery of the focused beam.

Additionally, apart from this, it is conceivable that the distribution of heat generated by absorption of laser light spreads in the surface direction of the recording film.

Furthermore, it is also conceivable that if the distance from the adjacent track is short, the influence of the spread of recording pits will be strong.

Therefore, in this embodiment, as described above, since the grooves are deep and the recording film 2 is bent at the grooves 4 and 5, the recording pits 8 are arranged in the same position along the recording film 2. Even if the track intrudes by a certain distance, the amount of intrusion into the adjacent track is apparently small.

In other words, when looking at the information recording surface from the perspective of the heat distribution generated by focused beam irradiation, it is equivalent to making a flat surface by stretching the bends of the grooves, and the effect is that the track pitch is wider than it actually is. It will be done.

In addition, since the groove portion is not perpendicular to the incident focused beam, the irradiation energy density is lower than that with normal incidence, and the recording sensitivity appears to be lower than that of the land portion. recording pits are formed locally on the land portions, and inter-track crosstalk can be reduced.

To explain the effect of this embodiment described above in terms of concrete numbers, in the case of a groove having the shape shown in Fig. ↓, the groove width is 0.6μ.
m, and if the depth of the groove is 0.35 μm, the distance of the slope of the groove to cross the groove is (0,32+0.35”)
There is a distance of In such cases, 1.6-0
．． The result was that only 32 = 1.2Lzn was required, and the track density and S
/ 1.28 = 1.25 (times).

The cross-sectional shape of the groove described above is not limited to a V-shape with an inclined surface as shown in FIG. 1, but may be a U-shape. Around double is good<,
The best value is 3/8 to 578 times.

In addition, the depth of the groove in this case is 1 wavelength of the laser beam used.
A magnification of 72 times is advantageous because it reduces scattering and diffraction of reflected light, prevents deterioration of the information reproduction signal, and facilitates the processing of grooves.

In the case of the above-mentioned V-shaped groove, the maximum depth should be approximately 1.4 times the condition for the U-shaped groove. In this case, divide the maximum depth by 1.4 and take this as the effective depth.The effective depth is 3/8 to 3/8 of the wavelength of the laser beam used
It may be set to 5/8 times.

Further, in the above example, the groove is recessed relative to the transparent substrate 1, but the groove may be convex or when an undercoat layer is provided under the recording layer. Even if a protective film is provided on the recording layer, the gist of the present invention is not changed.

In this example as described above, the width of the recording pit caused by the irradiation of the laser beam used for recording was compared with the conventional one with respect to the laser output, as shown in Fig. 2. Got the results.

That is, the results shown in Figure 2 were obtained by forming grooves on a polycarbonate substrate, coating the grooves with a light-absorbing and reflective cyanine dye to a thickness of about 60 OA, and forming a light-absorbing and reflective recording film. , a semiconductor laser with an optical wavelength of 780 nm is focused to a half-value beam diameter of 0.9 μm, and the land part is 5.6n+/
This is the result of recording a pit at s, and determining the pit width as the half-width by scanning a focused beam in a direction across the pit.

In FIG. 2, the results shown by the solid line are for the conventional example, in which the track pitch is 1.6 μm and the groove width is 0.6 μm.
The results show the characteristics in the case of a V-shaped groove in which the maximum depth of the groove is 0.16 μm, and the results indicated by the broken line in the same figure are based on this example. The track pitch is 1.25 μm and the groove width is 0.
6 μm and the maximum depth of the groove is 0.40 μm.

As is clear from this result, in the case of this example, even in the area where the recording laser output is large, the expansion of the pit width is suppressed, and the cross stroke between 1 and racks is reduced.

Furthermore, the above-mentioned groove is provided for 1-racking control, and the tracking deviation due to the diffraction effect from this groove is caused by the effective depth of the groove being 378 mm below the wavelength of the laser beam used.
The maximum value is reached when the number is 578 times, and the minimum value is obtained when the number is 4/8 times, so this may be used to detect the tracking deviation signal.

Furthermore, as shown in FIG. 3, wobbled pits 10 are partially provided on the information track, separate from the grooves 4.5 located between the lands 6.7, to detect and process these signals. By doing so, a ranking deviation signal of 1 to 1 may be obtained. In this case, there is no need to strictly control the depth 14 (for the purpose of making it easier to obtain a deviation signal), which is advantageous in terms of manufacturing control.

(Effects of the Invention) According to the present invention, the effective depth of the uneven grooves provided on the recording medium-1 is set to 3/8 of the wavelength of the laser beam used.
By setting ~578 times, even if the laser output during recording increases, the spread of the recorded pits is suppressed and interference with adjacent pits is suppressed, thereby reducing crosstalk between tracks and improving the reproduction signal. In addition to improving quality, it is also possible to narrow the pitch between tracks and improve information recording density.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of an optical information recording medium according to an embodiment of the present invention, and FIG. 2 compares the difference in recording pit width obtained between the recording medium shown in FIG. 1 and a conventional recording medium. A diagram showing the results, FIG. 3 is a plan view showing a modification of the main part of the recording medium shown in FIG. 1, and FIG. 4 is a perspective view showing the main part of the conventional optical information recording medium. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Recording film, 3... Laser light, 4.5... Groove, 6, 7... Land.

Claims (1)

[Claims] An optical information recording medium in which grooves and lands are alternately formed in a spiral, concentric, or parallel uneven shape on an optical information recording surface, and information is recorded using either the groove or the land as an information track, The effective depth of the above-mentioned irregularities is 3/8 to 5/8 of the wavelength of the laser beam used for recording and reproduction.
An optical information recording medium characterized in that the optical information recording medium is set to double.