JPS6020331A - Disk for recording and reproducing optical information - Google Patents

Abstract

PURPOSE:To eliminate disturbance in the waveform of a detection signal by specifying the pitch and width of the rugged grooves and pits of a disk for recording and reproducing optical information with respect to the diameter of a laser spot for recording and reproduction and specifying the depth of the rugged grooves and pits with respect to the wavelength of the laser. CONSTITUTION:A light absorptive thin film 1 which changes thermally the state when irradiated with light is formed by using a lower oxide of Te or the like, with the groove forming part of a UV curing resin, on a substrate 3 formed with rugged grooves or rugged pits 2 on a resin plate of polycarbonate or polymethacrylate then a tight protective layer 4 is provided over the entire surface thereby forming a disk. The pitch of the grooves 6 and rugged pits of such disk is made <=2 times the diameter of a laser spot 10 for recording and reproduction and the width thereof is made 60-80% the diameter of the spot 10 as shown in the magnified view. The depth of the grooves 6 and pits is made within + or -10% the optical path length of lambda/8 with respect to the wavelength lambda of the laser. The disturbance in the waveform of the detection pit signal is thus eliminated, the signal detection is made possible at high S/N and the tracking stability and the access speed to a track address are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Use The present invention is for optical information recording and reproducing that can be used in the fields of office automation and converters, such as video and audio signal recording and reproducing, still image single documents, and large-capacity filing of various data. It is about disks.

Conventional Structure and Its Problems Concave and convex pits The concave and convex shape of the optical information reproducing disk provided with pits is such that the pit depth that minimizes the reflectance is set to about λ/4 width. With this shape, the signal quality deteriorates in a disc on which all information is recorded and then reproduced. Also, in the recording track, the groove depth is λ/8. In the reproduced signal section, the groove depth is λ/4.
The composition of is also known. This method has a practical problem because the groove forming process requires two-step depth control.

OBJECTS OF THE INVENTION An object of the present invention is to reproduce high-quality signals from recording grooves and to reproduce high-quality reproduction signals (TJ) in optical information recording and reproducing discs.
The present invention provides an optical information recording and reproducing disc that enables both signal reproduction.

Structure of the Invention The present invention provides a light-absorbing thin film whose state completely changes thermally by light irradiation on a substrate on which uneven grooves and pits have been formed in advance, and the pitch of the grooves and pits is twice or less than the total recording/reproducing laser spot diameter. The optical information recording and reproducing disk is such that the depth of the grooves and pits is within ±10% of the optical path length of λ coating, and the width of the grooves and pits is 60% to 80% of the spot diameter.

Description of Examples: Examples of the sewage invention will be described. As shown in FIG. 1, the optical information recording/reproducing disk is made of a substrate 3 on which uneven grooves and uneven pits 2 are formed (C, a light-absorbing thin film whose state changes thermally by laser beam irradiation). 1 is provided.The groove part becomes a signal recording part by laser beam irradiation, and the uneven pit part records a reproduction-only signal unique to the disc, such as a track address signal encoded from a video, audio, etc. signal.
Alternatively, it can serve as various other data signal sections. The groove tracking section generates a tracking signal output of the laser spot light, which is selected near the optical path length of the groove depth λ/8. In the region of this depth, the amount of reflected light is thicker than in the long optical path groove of λ/4 depth, and signal detection after recording can be easily performed.

On the other hand, the concave and convex bit section generates a signal output that is generally larger than the recording signal of the groove section due to changes in the amount of reflected light due to diffraction.
The waveform of the detection signal changes using the width and depth of the groove and pit as parameters.

In this example, in particular, using a live conductor laser,
In a disc that records and reproduces information at a high-density track pitch and reproduces pit signals, the lower surface of the uneven pits, the upper surface between tracks, adjacent tracks, and pit
For the detection signal waveform of the diffracted light of the reflected light from the sensor, we provide all shape conditions without waveform disturbance.

As the grooved substrate, a PMMA resin plate with an ultraviolet curing resin groove forming layer provided thereon is used. 9 in FIG. 2 shows the cross section of the grooves and pits. There are 6 trunk grooves for signal recording. 7 is a concavo-convex pit signal and contains an address signal. The light-absorbing thin film 8 is mainly composed of tellurium low oxide.

The recording and reproducing laser is a cow conductor and has a wavelength λ = 830 nm.
i was used, and the spot diameter was narrowed down to i0.83 μm. The pitch is 1.66 μm, and the crosstalk is −40 dBpJ. The shallower the groove depth and the wider the groove width, the higher the detection signal level after recording.

Since signal detection is performed by diffraction based on the phase difference of reflected diffracted light from the top surface and wall surface, the grooves or piers) increase in the depth direction of λ/4.

Regarding the width, an increase in the detection signal can be seen as the width becomes narrower in relation to the spot diameter.

However, in all of these regions, there were regions where waveform disturbances occurred in addition to changes in the amplitude of the detection signal. In this example, as shown in FIG. 3, the waveform disturbance disappears in the region of 63 nm to 78 nm for the groove and pit depth, and the width is 0.48 μm.
Waveform disturbances could be removed in the -0.68 μm region.

The depth and width vary depending on the wavelength of the laser used, the spot diameter, and the track pitch, but the depth λ is a condition that does not cause diffraction disturbance of reflected light from each part.
/sn±10%, width, Dμφ×(60% to 80%)
, a region with pitch<2D was obtained. n is the substrate refractive index, D
is the spot diameter.

Effects of the Invention As described above, according to the present invention, by selecting the concavo-convex grooves, concavo-convex pits, and track pitches provided on the optical information recording/reproducing disk all within the range of the present invention, the waveform disturbance of the detected pit signal is eliminated and a high S. /N enables signal detection.

Further, the tracking stability of the laser beam and the access speed of the track address are improved.

[Brief explanation of drawings]

1 is a sectional view of an optical information recording and reproducing disk on which a light-absorbing thin film is formed according to an embodiment of the present invention, FIG. 2 is a plan view and a sectional view of a portion of the disk, and FIG. 3 is a sectional view of the same disk. FIG. 3 is a diagram showing the relationship between the depth and width of grooves and pits. DESCRIPTION OF SYMBOLS 1... Light-absorbing thin film, 2... Concave-convex groove or concave-convex pit, 3... Substrate with concavo-convex formations, 4
...Adhesive protective layer, 5... Disc center hole, 6... Concave and convex groove, 7... Concave and convex pit, 8... Light Absorbent thin film, 9...Groove and pit forming substrate, 1o...Irradiation laser point diameter. Name of agent: Patent attorney Toshio Nakao and one other name
1@J Figure 2 Figure 3 Seat Tp ()αmノ

Claims (1)

[Scope of Claims] (1) A light-absorbing thin film whose state changes thermally when irradiated with light is provided on a substrate on which uneven grooves and pits are formed in advance, and the pitch of the grooves and pits is adjusted using a recording/reproducing laser. The total depth of the grooves and pits should be less than twice the spot diameter, and the total depth of the grooves and pits should be λ/
8, and the width of the groove and pit is 60% to 80% of the spot diameter. (2) The pitch of the grooves or pits is set to be 1.7 µm lower, and the pitch of the grooves or pits is 0.48 µm to 0.48 µm.
68 μm, and the depth is from 63 nm.
The disc for optical information recording and reproducing according to claim 1 selected between yanmO. (3) An optical information recording/reproducing disc according to claim 1, in which a low oxide film is used as the light-absorbing thin film. (4) An optical information recording/reproducing disc according to claim 1, wherein the groove forming portion is made of ultraviolet curing resin gold. (6) An optical information recording/reproducing disc according to claim 1, in which a polycarbonate resin plate is used as the grooved substrate. (6) The optical information recording/reproducing disc according to claim 1, wherein an adhesive protective layer is provided on the light-absorbing thin film.