JPH0559494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical disk that includes a recordable RAM section and a ROM section containing fixed information within one disk.

[Background of the invention]

Optical disks have entered the practical stage as media for recording large amounts of information.

Optical disks can be roughly divided into read-only optical disks (ROM disks) in which information is recorded in advance and only played back, and optical disks (RAM disks) in which information can be recorded and played back. Furthermore, when the above two types exist in the optical disk, each area is
They are called the ROM section and RAM section.

A ROM disk is a transparent disk substrate with information recorded as a row of uneven pits. To reproduce the recorded information, the pit surface is scanned with a laser beam spot, and the reflected light from the pits and the area around the pits are detected. It takes advantage of the fact that the amount of detected light changes due to interference between the reflected light and the reflected light. This will be explained in detail with reference to FIG.

FIG. 5 is a schematic diagram for explaining the ROM disk playback method, and 1 is an optical disk (ROM disk).
2 is an information pit surface, 3 is a semiconductor laser, 4 is a magnifying lens, 5 is a half mirror, 6 is an objective lens, 7 is a condensing lens, and 8 is a detection element (for example, a photodiode).

In the figure, laser light from a semiconductor laser 3 is transmitted through a magnifying lens 4, a half mirror 5, and an objective lens 6.
The light is focused on the information pit surface 2 of the ROM disk 1 through the ROM disk 1. The reflected light from the information pit surface passes through the objective lens 6, half mirror 5, and condensing lens 7 and enters the photodiode 8, which converts optical information based on the information recorded on the information pit surface 2 into an electrical signal. read out. In addition, retrace (tracking) and focusing of pit rows are
The spot of reflected light from the pit surface is controlled by inputting it to, for example, a four-division light-receiving element.

A RAM disk records information on a transparent disk substrate using changes in reflectance due to heat mode, and reproduces information by detecting changes in reflectance. , we will explain how to record and play back on this RAM disk.

FIG. 6 is a schematic diagram illustrating a RAM disk recording and reproducing method, and 6 is an objective lens, which constitutes an optical system similar to that shown in FIG. 10 is
RAM disk transparent substrate, 11 is information recording layer,
12 is a protective adhesive layer.

In the figure, information is recorded on the information recording layer 11 in a heat mode by laser light passing through an objective lens 6. The information recording layer 11 is made of, for example, a chalcogenide-based material, and utilizes the fact that the reflectance changes due to a phase change of the information recording layer caused by laser beam irradiation. When reading the information recorded in this way, the information recording layer is irradiated with a laser beam weaker than that used during recording, and the reflected light is extracted by an optical system similar to that shown in Figure 5, and then the laser beam is emitted from a photodiode or the like. The detection element converts it into an electrical signal. Furthermore, as shown in Figure 6.
The RAM disk is a double-sided optical disk made by bonding two disks together, and the protective adhesive layer 12 is
Although shown as a layer, it can also be separated into a protective film and an adhesive layer.

Optical disks have the advantage of large storage capacity compared to other information recording devices, and
Regarding ROM disks, it is possible to reproduce large amounts of fixed information using a replication process such as injection molding.

ROM disk as mentioned above, and RAM
Examples that describe disks in detail include pages 108 to 110 and pages 128 to 129 of "Introduction to Video Discs and DAD" edited by Iwamura (January 10, 1982, published by Corona Publishing), or pages 128 to 129 of 1982. There is an article titled ``Optical disk memory beginning to be used for image files'' in Nikkei Electronics, published on January 4, 2015, pages 86 to 112.

By combining the features of ROM disks and RAM disks as explained above, the fields of application of optical disk systems can be expanded. Specifically, it is sufficient to consider a single optical disk in which a ROM section and a RAM section are mixed.

In order to obtain such a RAM-ROM mixed disk, the following problems arose.

(1) Normally, ROM disks are equipped with an Al reflective layer, and the reflectance is about 80%, but RAM
The disk is equipped with an information recording layer made of chalcogenide material, and its reflectance is 10 to 20%.
That's about it. Therefore, when these are formed in one disk area, the reflectances of the two are too different, making it extremely difficult to handle systems such as focusing and tracking control.

(2) In order to equalize the reflectance of both, it is possible to make the reflective layer of the ROM part the same as the information recording layer of the RAM part, but in this case, the ROM part may be accidentally irradiated with the recording laser beam. Then, the ROM
There is a risk that the department's information may be destroyed.

(3) It is possible to make the RAM section and the ROM section using different materials, but this would make the optical disk manufacturing process extremely complicated.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide an optical disk that is equipped with a RAM section and a ROM section and is highly reliable and mass-producible.

[Summary of the invention]

To achieve this objective, the present invention uses RAM
The feature is that the same information recording medium is formed in both the ROM section and the ROM section, and only the ROM section on which fixed information is recorded is in a recording state.

Putting the information recording medium in the ROM section into the recording state means that the ROM section of the information recording medium, which is a RAM disk formed on the entire surface of the optical disk, is in the recorded state in the RAM section, that is, the reflectance changes when irradiated with a recording laser beam. It is to make it equivalent to the state Note that a state equivalent to when the information recording medium is not irradiated with a recording laser beam is referred to as an unrecorded state.

To put the ROM section into recording state, press the optical disc.
An information recording medium as a RAM disk is formed across the ROM section and the RAM section, and a mask is used so that only the ROM section is irradiated with light, and light is emitted from a light source containing a wavelength that the information recording medium absorbs. irradiate.

Since the difference in reflectance between the recorded state and the unrecorded state of the information recording medium is at most 2 to 3 times, system control such as focusing control and tracking control is relatively easy. Even if a light beam (laser beam) for recording the RAM section is accidentally irradiated onto the ROM section in the recording state, the reflectance will hardly change and the ROM information will remain unchanged since it is already in the recording state. Saved.

Since the recorded state of the ROM section can be obtained by irradiating light using a mask as described above, the manufacturing process of the optical disk according to the present invention becomes extremely simple.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional structural diagram showing an embodiment of the optical disk according to the present invention, in which 10 is an optically transparent PMMA (acrylic resin) substrate, 13 is Sb ₂ Se ₃
14 is a Bi layer, 15 is a protective film made of ultraviolet curing resin, 16 is an adhesive, and 20 is an uneven portion.

In the figure, a two-layer structure recording film consisting of an Sb ₂ Se ₃ layer 13 and a Bi layer 14 is formed by vapor deposition to constitute an information recording layer, and a protective film 15 made of an ultraviolet curable resin is formed on this, and adhesive is applied. A double-sided optical disk is obtained by bonding two disks together using the agent 16.

The thickness of each layer is 300 Å for Sb ₂ Se ₃ layer 13, and 300 Å for Bi layer 1.
4 has a thickness of 250 Å, and the protective film 15 has a thickness of 30 μm.

A concavo-convex portion 20 is provided on the PMMA substrate 10. In the ROM section, fixed information is formed using pits on the concave-convex portion 20, and in the RAM section, tracking is performed on the concave-convex portion 20 during recording. A guide groove and an address pit for address information are formed in advance.

Next, a method of putting the information recording layer of the ROM portion of the disk into a recording state will be explained.

FIG. 2 is a conceptual diagram showing an example of the method for forming an optical disk according to the present invention, in which 19 is a xenon lamp, 20 is an irradiation light beam, 21 is a mask, 22 is a mask substrate, 23 is a light blocking member, and 24 is a light beam. It's a disk.

In the figure, the information recording layer is designed to have a film thickness that utilizes the coherence of light so as to obtain large energy absorption in the wavelength range of the semiconductor laser used during recording. Therefore, in order to bring the information recording layer into a recording state by light irradiation, it is necessary to select a light emitting source that generates light having a wavelength near the semiconductor laser wavelength range. In the illustrated example, a xenon lamp is used as the light source. Xenon lamps are used for photography or for illuminating squares, and their spectral energy distribution is not only close to natural daylight, but their spectral energy distribution extends to wavelengths around 800 nm, which is the wavelength range of semiconductor lasers. There is. Therefore, a xenon lamp is a preferred light source for practicing the present invention.

The mask 21 is for shielding the RAM portion of the optical disk 24 from the irradiation light beam 20, and is provided with a light shielding member (light shielding member) 23 on an optically transparent substrate 22, such as glass. It is something. As the light blocking member 23, a thin film of Cr, Al, etc.
Alternatively, it can be formed using a paint containing an opaque dye or pigment, an opaque adhesive tape, or the like.

In this example, approximately 1000
A light shielding layer of a thin Cr film with a thickness of 1.5 Å was used.

The mask 21 formed in this way is attached to the optical disk 2.
4, the xenon lamp 19 is made to emit light, and the information recording layer of the ROM section of the optical disk 24 is put into a recording state by the irradiation light 20.

FIG. 3 is a top view showing an embodiment of the optical disk according to the present invention, in which 24' is a ROM-RAM mixed type optical disk, 25a and 25b are RAM sections, and 24' is a ROM-RAM mixed type optical disk;
6 is a ROM section.

In the figure, a ROM section 26 corresponds to a portion where light is not blocked by the mask 21 in the forming method shown in FIG. 2 and where the information recording layer is in a recording state.

FIG. 4 is a circuit diagram showing an example of a xenon lamp light emitting circuit for putting the ROM section of an optical disk into a recording state according to the present invention, in which 19 is a xenon lamp, E is a power source, Tr is a step-up transformer, C ₁ , _C2 is a capacitor, _R1 , _R2 , _R3 are resistors, _SW1 , _SW2 are switches, and G is a trigger electrode.

In the figure, by closing the switch _SW1 , the capacitor C is charged with electric charge from the power source E. After that, when SW ₂ is closed, a current flows through the transformer Tr due to the discharge of the capacitors C ₁ and C ₂ , and a high voltage of several thousand to tens of thousands of volts is applied to the trigger electrode G of the xenon lamp 19 due to the step-up action of the Tr. Ru.
As a result, the gas within the xenon lamp 19 is ionized, the internal resistance is reduced, and a discharge is instantaneously generated between the two poles of the xenon lamp 19, causing light to be emitted. This light emission time is 2 mS to 0.5 mS.

In the above embodiments, a xenon lamp was used as the light emitting source, but the present invention is not limited to this, and since the information recording medium absorbs energy widely, mainly in the semiconductor laser wavelength range, various gas lasers may be used. be able to. It is also possible to use a semiconductor laser to expose the ROM section of the optical disk one track at a time to bring it into a recording state.

In addition, Sb ₂ Se ₃ and Bi 2 are used as information recording media.
Although a layered structure recording film is used, it goes without saying that the present invention can also be applied to other chalcogenide compounds or information recording media that utilize diffusion.

Furthermore, in the above embodiments, the ROM section in the recorded state was formed by light irradiation, but conversely, the RAM section in the unrecorded state may be formed by light irradiation.

In addition, in the above embodiment, the optical disk
Although the entire ROM section is set to the recording state, the present invention is not limited to this, and for example, a part of the ROM section may be set to the recording state, or a part of the RAM section may be set to the recording state.

[Effects of the Invention] As explained above, according to the present invention, it is possible to easily obtain an optical disk in which a RAM section and a ROM section are mixed together by a simple method, and it is possible to expand the application system of optical disks. This makes it possible to provide an optical disk with excellent functionality by eliminating the drawbacks of the prior art described above.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram showing an embodiment of an optical disk according to the present invention, FIG. 2 is a conceptual diagram showing an example of a method for forming an optical disk according to the present invention, and FIG. 3 is an embodiment of an optical disk according to the present invention. FIG. 4 is a circuit diagram showing an example of a xenon lamp light emitting circuit for putting the ROM section of an optical disk into a recording state according to the present invention, and FIG. 5 is a top view showing an example. The configuration diagram, FIG. 6, is a schematic diagram illustrating a method for recording and reproducing a RAM disk. 10...PMMA substrate 13...Sb ₂ Se ₃ layer 1
4... Bi layer 15... Protective film 16... Adhesive layer 19... Xenon lamp 20... Uneven part 2
1... Mask 22... Mask substrate 23... Light blocking member 24, 24'... Optical disk 25a,
25b...RAM section 26...ROM section.

Claims (1)

[Claims] 1. In an optical disk equipped with a RAM area where information can be stored and reproduced, and a ROM area where information is formed in advance as pit rows and only reproduced, the optical disk has a RAM area and a ROM area.
An information recording layer is provided between the RAM area and the ROM, and the RAM area of the information recording layer is in an unrecorded state and the ROM area is in a recorded state.
An optical disk characterized in that areas have approximately equal reflectance.