JPH01144252A - Optical disk - Google Patents

Abstract

PURPOSE:To reproduce information included in a pit and the information recorded on a magneto-optical recording film simultaneously or separately by providing a recordable, reproducable and erasable magneto-optical recording film on an optical disk for reproduction only in which the information is formed as the pit on a transparent disk substrate. CONSTITUTION:The recordable, reproducable, and erasable magneto-optical recording film 4 is provided on the optical disk 3 for reproduction only in which the information is formed as the pit 2 on the transparent disk substrate 1. Therefore, the information included in the optical disk 3 for reproduction only can be reproduced as the strength of the reflecting diffracted light of an incident laser beam. Meanwhile, the recording of the information on the magneto-optical recording film 4 is performed in such a way that the magnetization of a part where a temperature rises can be inversed in a direction of impressing magnetic field only by applying a weak magnetic field by projecting a laser beam, and erasure can be realized by performing inversion by adding the magnetic field opposite to the magnetization of a recording part and applying the laser beam again. In such a way, it is possible to record the information on the same optical disk for reproduction only in such a way that it can be erased and rewritten and reproduced, and also, to reproduce the information simultaneously or separately with the information included in the pit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the improvement of optical discs, and more specifically to a read-only optical disc provided with a magneto-optical recording film that allows recording, playback, and erasing.

[Prior Art] Optical discs, particularly read-only optical discs, have pits containing information formed on a transparent disc substrate.

In such an optical disc, when attempting to reproduce information contained in pits, the pits are traced with a laser beam, the intensity of light reflected and diffracted from the pits is detected, and the information is reproduced.

Therefore, unlike the TED method, it is a non-contact method and has a high recording density and a large capacity.

Incidentally, recently, laser discs (hereinafter abbreviated as LD) have been developed that can record a plurality of pieces of information, such as image information and audio information, on the same optical disc and reproduce the image information and audio information simultaneously. CD-ROM (CD-ROM) that can play multiple pieces of information
n ly Mewo ry) has been put into practical use. In addition, compact discs with a small diameter of 12 cm (hereinafter referred to as C
It is abbreviated as D.

Compact discs with video (hereinafter abbreviated as CD-V) that can play back moving images and audio from DVDs have also been commercialized.

Furthermore, it is believed that the commercialization of magneto-optical disks, on which information can be freely recorded, erased, rewritten, and reproduced by users themselves, will be in the near future.

[Problems to be solved by the invention]However, it is possible to freely record information that is different from the information in the pits formed on the same read-only optical disc, erase it, replace it,
There is no optical disc yet that can reproduce recorded information at the same time as the pit information.

Therefore, the present invention has been made to solve the problems of conventional optical discs, especially read-only optical discs. It is an object of the present invention to provide an optical disc on which information can be recorded in a reproducible manner and on which the information can be reproduced simultaneously with or separately from the information contained in the above-mentioned p.y.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configuration.

That is, the present invention is characterized in that a read-only optical disk formed by forming information in the form of pits on a transparent disk substrate is further provided with a magneto-optical recording film that can be erased during recording and playback.

[Function] With the configuration as described above, the information contained in the read-only optical disc can be reproduced as the intensity of the reflected and diffracted light of the incident laser light. On the other hand, when recording information on a magneto-optical recording film, the magnetization of the part whose temperature has risen by irradiation with laser light can be reversed in the direction of the applied magnetic field by simply applying a weak magnetic field.
Erasing can be achieved simply by applying a magnetic field opposite to the magnetization of the recorded area and reversing it by applying laser light again. moreover,
During reproduction, when the laser beam incident on the magneto-optical recording film is reversed, it rotates in the opposite direction depending on the direction of magnetization of the incident part (Kerr effect).
Therefore, by detecting the reflected laser light through an analyzer, it can be detected as a change in light intensity.

[Implementation example] Next, typical embodiments of the present invention will be described.

FIG. 1 is a cross-sectional view of a main part showing the schematic structure of the optical disc of the present invention, in which a transparent disc base [11] made of polycarbonate (hereinafter abbreviated as PC) is attached according to information as shown in FIG. On the pit-forming side of the playback-only optical disc 3 on which a large number of pits 2 with the same shape and size are formed, a G
A magneto-optical recording film 4 made of a magnetic film such as dTbFe or TbFeCo is provided.

The magneto-optical recording film 4 usually has upper and lower surfaces made of Al2O3 and Y2O3.
, 5i03, or a nitride material such as S t NNAIN.

Also, a pin formed on the transparent disk substrate 1.

2 has a depth of 1/of the wavelength of the light in the substrate 1 of the incident laser light.
4, and is formed so that the phase difference between the laser beam reflected from the top of the pit 2 and the laser beam reflected from the top is exactly half a wavelength.

Magneto-optical recording provided on the read-only optical disk 3 [4 is
It is deposited on the pit-forming surface side of the read-only optical disc 3 by vacuum evaporation or sputtering.

When recording information on the magneto-optical recording film 4, a weak magnetic field in the opposite direction to the magnetization of the part is applied to the information recording part on the upper side of the magneto-optical recording film (GdTbFe film) 4, and the transparent disc is When a laser beam is irradiated onto the part of the substrate 1 from below, the magnetization of that part is reversed in the same direction as the applied magnetic field (areas 4A, 4B, 4C in Fig. 3(a)).
, 4D) Irradiating the optical disk with information recorded on the focus 2 and the magneto-optical recording film 4 as described above with a laser beam,
The intensity waveforms of the reflected laser beam reflected and diffracted from the pit 2 and the magneto-optical recording film 4 are shown in the third diagram.
The waveform can be changed as shown in Figure (a).

Curve a in FIG. 3(a) is the waveform of the laser beam reflected and diffracted from the pit 2, and the curve a is the waveform of the laser beam reflected from the information recording areas 4A, 4814C, and 4D of the magneto-optical recording film 4. It is.

From the waveform a1b of the reflected laser beam shown in FIG.
It can be seen that O (magneto-optical) information can be read as changes in the intensity of light diffraction or as changes in the rotation angle of the plane of polarization and reproduced separately or simultaneously.

When reproducing information from Pit 2 of the Hikari Isk above,
For example, an optical head as shown in FIG. 4 is used. In the figure, 5 is a semiconductor laser, 6 is a collimator lens, 7 is a beam splitter, 8 is a 1/4 length plate, 9 is an objective lens, 1
0 is a pit information detector. The collimator lens 6 converts the diverging light from the semiconductor laser 5 into parallel light and directs it to a beam splitter. Also, the beam splitter 7 forms an optical isolator together with the quarter-wave plate 8. The reflected laser beam is detected by an information detector 10 as shown in the figure.

The detector 10 usually has a condensing lens (not shown) and a cylindrical lens (not shown), and is configured to receive light onto, for example, a four-part sensor (not shown) by the function of the cylindrical lens. has been done. Information is then reproduced by detecting the difference in light intensity of the reflected laser beams formed on the four-split sensor.

Further, for reproducing information from a magneto-optical recording film, a light beam having the configuration shown in FIG. 5 is usually used. In FIG. 5, 5.11 is a shaping prism, 12 is a polarizer, 13 is an analyzer, 14 is a half mirror, 15 is a magneto-optical recording film information detector;
9 are a semiconductor laser and a collimator lens, respectively.

An example has been shown in which the optical heads shown in FIGS. 4 and 5 are used to reproduce the information on the pits of the optical disk and the information on the magneto-optical recording film, respectively.
It is also possible to use a so-called magneto-optical head having a similar configuration.

Furthermore, the optical disc of this embodiment can simultaneously reproduce focus information and information on the Hikari magnetic recording film.
It is also possible to reproduce only one of the pieces of information independently, if necessary.

Furthermore, it is also possible to easily erase the recorded information on the magneto-optical recording film and rewrite it with new information, if necessary.

Regarding the material of the magneto-optical recording film of this example, GdTb
Although an example using Fe has been described, the magneto-optical recording film is not limited to GdTbFe, and may be a magneto-optical recording film made of other stacked-transition metal amorphous alloys such as TbFeCO1TbFe. In addition, the transparent substrate 1 is made of only PMMA.
However, other materials such as PC (polycarbonate) and glass are applicable.

[Effects of the Invention] As is clear from the above description, the optical disc of the present invention is a read-only optical disc in which information is formed in the form of pits on a transparent disc substrate, and further provided with a magneto-optical recording film that enables recording, playback, and erasing. Therefore, not only the information contained in the pits but also the information recorded on the magneto-optical recording film can be independently selected and reproduced freely. Therefore, the uses of optical discs are further expanded. Furthermore, the recording capacity that can be stored on one optical disc increases.

Furthermore, the information recorded on the magneto-optical recording film can be easily rewritten with other information if necessary.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part showing a schematic configuration of an example of an optical disk of the present invention, FIG. 2 is a partially cross-sectional perspective view of a main part showing a structure of a read-only optical disk of the optical head of FIG. 1, and FIG. (a)
and (b) are respectively reflection diffraction and intensity waveform diagrams of the reflected laser beam from the pit portion of the optical disk and the magneto-optical recording film. FIG. FIG. 5 is an explanatory diagram showing the configuration of the henodic head. FIG. 5 is an explanatory diagram showing the configuration of the optical head used when reproducing and detecting information on the magneto-optical recording film of the optical disk of the present invention. 1... Transparent disk plate, 2... Fist pin, 3... Read-only optical disk, 4Φ... Magneto-optical recording film, 4A, 4B, 4C, 4D. Information in the magneto-optical recording film. Recording Department. Patent Applicant: NEC Home Electro Co., Ltd. 1, Figure 3, IB2FI, Figure 3, Factor 4

Claims (3)

[Claims] (1) An optical disk characterized in that a read-only optical disk formed by forming information pits on a transparent disk substrate is provided with a magneto-optical recording film capable of recording, playback, and erasing. (2) The optical disk according to claim (1), wherein the magneto-optical recording film capable of recording, reproducing and erasing is sandwiched between upper and lower sides by protective films. (3) The magneto-optical recording film capable of recording, reproducing and erasing is TbFeC
It is composed of a rare earth-transition metal amorphous alloy film such as O, TbFe, GdTbFe, etc., and the protective film is Al_2O_3, Y
Claim No.
2) The optical disc described in section 2).