JPH0636343A - Deep recording optical disc - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an optical disc capable of greatly improving the storage capacity without changing the laser spot and the shape of the disc. [Structure] A first recording layer 11, a first protective layer 12, a second recording layer 13, and a second protective layer 15 are provided in this order on the upper surface of a substrate 2. The spiral groove 1 is formed in the second recording layer 13.
4 is provided, a laser spot is irradiated along this groove, and a signal is recorded / reproduced independently on the first and second recording layers 11 and 13. With this configuration, more information can be recorded and reproduced without increasing the size of the disc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep recording optical disc for recording and reproducing signals on and from recording layers provided in upper and lower layers of the disc.

[0002]

2. Description of the Related Art In a conventional signal recording / reproducing system using an optical disc, a single recording layer is provided on a substrate in the disc, and a laser beam is applied to the recording layer to record / reproduce a signal.

FIG. 2A is a sectional view showing the structure of such a conventional optical disc and optical system, and FIG. 2B is a conceptual diagram during recording and reproduction. In FIG. 2A, the optical disc 1
Has a structure in which a recording layer 3 is provided on a disc substrate 2 and a protective layer 4 is attached thereon. The recording layer 3 is, for example, a phase change type medium, and a signal is recorded or reproduced by changing the phase state to an amorphous state or a crystalline state. The protective layer 4 protects the recording layer 3 and maintains the rigidity of the optical disc 1, and is made of, for example, a translucent polycarbonate resin.

As shown in FIG. 2 (b), at the time of recording / reproducing on / from the optical disc 1, the laser light emitted from the laser generator 5 passes through the focusing lens 6 of FIG. 2 (a) to the optical disc 1.
To form a laser spot having a predetermined diameter on the recording layer 3. Assuming that the recording layer 3 is in an amorphous state before recording, when the intensity-modulated laser spot is irradiated, the recording layer 3 in the portion A is crystallized according to the signal.

In order to reproduce the optical disc 1 recorded in this way, a laser beam having a constant intensity is irradiated from the laser generating section 5 to perform track servo and focus servo of the optical disc 1, and the reflectance of the recording layer 3 The amount of reflected light changes due to the difference, and the signal is reproduced.

[0006]

However, in such a structure, the laser spot obtained on the recording layer 3 is determined by the laser wavelength of the laser generator 5, and the accuracy of the optical system including the focusing lens 6 is improved. However, it was difficult and limited to make the spot size of the portion A smaller. Generally, the recording capacity of the optical disc 1 is determined by the track pitch and the spot size, assuming that the focus servo and the tracking servo are sufficient. In recent years, the oscillation wavelength of laser light tends to be shorter, but it has been difficult to significantly increase the storage capacity without increasing the size of the optical disc 1.

The present invention has been made in view of the above conventional problems, and uses an ordinary laser spot,
Moreover, it is an object of the present invention to realize a deep-layer recording optical disc capable of significantly improving the storage capacity of the optical disc without increasing the shape of the optical disc.

[0008]

The present invention provides a disc substrate, a first recording layer provided on the disc substrate for recording and reproducing information by a first laser spot, and an upper portion of the first recording layer. A second laser having a light-transmitting first protective layer and a groove notched in a spiral shape formed above the first protective layer and having a wavelength different from that of the first laser spot. A second recording layer for recording and reproducing information by irradiating a spot around the groove, and a second protective layer provided on the second recording layer and having a light-transmitting property. It is a feature.

[0009]

According to the present invention having such a feature, the first recording layer is provided on the disc substrate, and information is recorded / reproduced by the first laser spot. Further, the second recording layer is provided on the first recording layer with the first protective layer interposed therebetween. A spiral groove is provided in the second recording layer, and a second laser spot having a wavelength different from that of the first laser spot is irradiated around the groove. In this way, signals can be independently recorded and reproduced on the first and second recording layers simultaneously, and an optical disc having a large recording capacity can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk for deep layer recording according to an embodiment of the present invention will be described with reference to FIG. Incidentally, the same parts as those of the conventional example shown in FIG. As shown in FIG. 1, the optical disc 10 of this embodiment is a disc having two recording layers for recording and reproducing signals independently of each other. That is, the first recording layer 11 is provided on the upper surface of the disk substrate 2. The first recording layer 11 is the same writable and readable medium as the conventional example. For example Ge, T
It is a multi-layered amorphous structure composed of e, Sb, etc., and changes its phase from an amorphous state to a crystalline state by irradiation with a laser spot.

Next, a first protective layer 12 is provided on the first recording layer 11. The first protective layer 12 is a transparent protective layer and is formed of, for example, a polycarbonate resin. The second recording layer 13 is provided on the upper surface of the first protective layer 12. The second recording layer 13 is made of the same material as the first recording layer 11, and the spiral groove 14 is formed in advance at the manufacturing stage of the optical disc 10. The groove 14 is a groove that allows a laser beam to pass through the first recording layer, and is formed on the entire optical disc 10 at a predetermined track pitch. The groove 14 is formed, for example, by sufficiently increasing the energy density of the laser spot emitted from the laser generator 5 and heating and evaporating a part of the second recording layer 13. Second recording layer 13
A second protective layer 15 identical to the first protective layer 12 on the upper surface of the
Is formed.

On the other hand, the laser generator 16 shown in FIG.
It is a light source that emits short-wavelength and long-wavelength laser light. These laser lights are focused by the focusing lens 17, and a first laser spot having a short wavelength is formed on the first recording layer 11 via the groove 14. The second laser spot having a long wavelength is formed on both sides of the groove 14 of the second recording layer 13.

In order to record a signal using such a deep recording optical disk 10, the groove 14 of the second recording layer 13 is tracked by using, for example, a laser spot having a long wavelength. In parallel with this, a laser spot having a short wavelength is irradiated on the first recording layer 11 to record a signal on the first recording layer 11. When recording signals on both the first and second recording layers 11 and 13, the intensity of the laser spots of short wavelength and long wavelength is modulated to cause a phase change of each recording layer.

Next, in order to reproduce a signal, the first or second recording layer 11, 13 is irradiated with a laser spot having a constant intensity, and the reflected light is read through the focusing lens 17. At this time, the reflectance of the recording layer changes according to the recording signal, and the intensity-modulated light is incident on the photoelectric conversion unit (not shown).

Since the optical disc 10 is provided with the two recording layers 11 and 13 as described above, by tracking one groove 14, two types of signals can be independently recorded and reproduced simultaneously. Further, within a range where two laser spots are formed on the first and second recording layers 11 and 13,
By reducing the track pitch of the grooves 14 as much as possible, the storage capacity of the optical disc 10 can be greatly improved. Although the recording method for the recording layer uses the phase change of the amorphous material here, other optical recording / reproducing methods may be used.

[0016]

As described above, according to the present invention, by providing the first and second recording layers parallel to each other,
Two kinds of signals can be simultaneously recorded and reproduced on the deep-layer recording optical disc. Further, by reducing the pitch of the spiral grooves, it is possible to realize an excellent optical disc in which the information recording density and recording capacity are significantly improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of an optical disc for deep recording of the present invention.

FIG. 2A is a sectional view showing a structure of a conventional optical disc, and FIG. 2B is a conceptual view showing a structure of a recording / reproducing apparatus.

[Explanation of symbols]

 2 Disc Substrate 10 Optical Disc 11 First Recording Layer 12 First Protective Layer 13 Second Recording Layer 14 Groove 15 Second Protective Layer 16 Laser Oscillator 17 Focusing Lens

Claims (1)

[Claims] 1. A disc substrate, a first recording layer provided on the disc substrate for recording and reproducing information by a first laser spot, and a light-transmitting layer provided on the first recording layer. And a second laser spot having a wavelength different from that of the first laser spot is formed on the first protective layer, and a groove cut out in a spiral shape is formed above the first protective layer. A second recording layer that records and reproduces information by irradiating the periphery of the groove, and a second protective layer that is provided above the second recording layer and has a light-transmitting property. Optical disc for deep layer recording.