JPH04271017A - Rerecording method for optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the destruction of recording information by a change with lapse of time and rereproducing light and the consequent failure in reading out by recording original signals in original positions by light for recording if the optical recording medium is reproduced and the reproduced signals exist in a reference range. CONSTITUTION:If indolyl furgit is adopted as an example of a photochromic material, this material changes partly to an excited state (state B) and the ratio of the material in the states A, B attains 3:7 when the base state (state A) is irradiated with light of 403nm wavelength. The state returns completely to the state A if this state is irradiated with light of 633nm. A laser 6 for reproducing of 633. wavelength is reflected by scanning a certain part of the recording medium 1 and the reflected light is made into an electric signal by a sensor. This signal enters a decision circuit 7. A delay circuit 8 acts if the magnitude of the reproduced signal attains a reference value. The same information as the original information is then rerecorded in the same part as the original part of the optical recording medium 1 by a laser 5 of 325nm for rerecording modulated by the same signal as the reproduced signal. The delay circuit 8 delays the recording by as much as the time when the same part as the original part of the medium 1 comes in.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a re-recording method for a rewritable optical recording medium.

0002

BACKGROUND OF THE INVENTION Recently, research on the use of photochromic materials in the recording layer of optical recording media has been actively conducted. When such photochromic materials are irradiated with a certain amount of light,
It has the property that the structure of the molecule changes due to a photochemical reaction, and the optical characteristics for light having a specific wavelength change in accordance with the change in the structure of the molecule.

[0003] Also, when light of another specific wavelength is irradiated,
It has the property that the changed molecular structure returns to its original structure.

However, the above photochromic materials generally react with heat or light when left at room temperature, resulting in the problem that information is destroyed.

[0005] Furthermore, by using reproduction light for reading information,
There was also the problem that information was destroyed because a reaction occurred in the photochromic material.

[0006] In order to solve the problem of information being destroyed at room temperature, for example,
No. 214148 (G11B 7/24) discloses a method in which a polymer is added to an optical recording medium containing a photochromic material, the polymer prevents the chemical reaction of the photochromic material at room temperature, and heat is applied appropriately during recording to prevent the chemical reaction. An optical recording method that causes this phenomenon has been proposed.

However, the above-mentioned method has the problem that information cannot be recorded at high speed because the time required for the chemical reaction depends on the temperature of the optical recording medium.

[0008]

SUMMARY OF THE INVENTION It is an object of the invention to ensure that information recorded on an optical recording medium is retained and to reproduce the information at high speed.

[0009]

[Means for Solving the Problems] The method of the present invention is such that when an optical recording medium is reproduced, if the magnitude of the reproduced signal is within the reference range, the original information is re-recorded using recording light. I made it.

0010

[Operation] When the magnitude of the reproduced signal based on the information recorded on the optical recording medium is within the standard range, the original signal is re-recorded with the recording light, so the recorded information is not stored on the optical recording medium. Retained.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As the photochromic material contained in the recording layer of the optical recording medium according to this embodiment, fulgide-based, diarylethene-based and spiropyran-based photochromic materials can be used.

The structural formula of indolylfulgide, a fulgide type used as an example, is shown in FIG. 1 and will be explained.

[0014] Such a material is in the A state (ground state) in FIG.
For example, when something is irradiated with light with a wavelength of 403 nm, a part of it changes to the B state (excited state), and changes to a photosteady state in which the A state and the B state are contained in a ratio of about 3:7. However, if the above steady state state is continuously irradiated with light having a wavelength of 633 nm, for example, it has the property of completely returning to the A state.

FIG. 2 is an absorption spectrum of a solution of the above material dissolved in toluene, where the broken line indicates the A state and the solid line indicates the 403 state.
The photosteady state after irradiation with nm light is shown.

As can be seen from FIG. 2, information can be recorded on the above material by changing the A state to the photosteady state using light having a wavelength of 300 to 400 nm, for example. or,
Information can be reproduced by detecting optical characteristics such as absorbance at a wavelength of 550 to 700 nm.

FIG. 3 shows the optical recording medium 1 used in this example.
It has a configuration in which a recording layer 3 and a reflective layer 4 are sequentially formed on a substrate 2.

The recording layer 3 was prepared by dissolving 0.5 g of indolylfulgide and 5 g of polystyrene shown in FIG. It was formed on a glass substrate 2 with a diameter of 130 mm to a thickness of about 1 μm by spin coating, and a reflective layer 4 made of copper or the like was deposited on the recording layer 3 to a thickness of about 1500 angstroms by a vapor deposition method.

FIG. 4 is a schematic diagram showing an embodiment of a recording/reproducing apparatus using such an optical recording medium.

In the figure, 1 is the optical recording medium mentioned above;
Here, the A state is assumed to be an unrecorded state, and the optical steady state is assumed to be a recorded state. Further, this optical recording medium 1 is rotated by a rotating device (not shown).

5 is a recording laser device using a He-Cd laser with a wavelength of 325 nm, and 6 is a recording laser device using a He-Cd laser with a wavelength of 633 nm.
This is a laser device for reproducing Ne laser. When reproducing information, the recording laser device 5 is moved by a drive device (not shown) so as to scan the portion of the optical recording medium 1 scanned by the reproducing laser device 6.

The laser beam output from the reproducing laser device 6 enters the optical recording medium 1 from the substrate 2 side (see FIG. 3), is reflected by the reflective layer 4, and is transmitted to the reproducing system sensor (see FIG. 3). (not shown).

After the laser light that has entered the sensor is converted into an electrical reproduction signal, it enters a signal determination circuit 7 that determines the magnitude of the reproduction signal (in this case, the C/N value based on reflectance).

When the magnitude of the reproduced signal is within the reference range, the delay circuit 8 operates, and the re-recording laser beam modulated with the same signal as the reproduced signal is transmitted to the recording laser device 5.
The same information as the original is re-recorded in the same part of the optical recording medium 1 as the original.

The delay circuit 8 irradiates the re-recording laser beam onto the portion where the information has been reproduced as described above.
a time period from when the reproduction laser beam is irradiated to the portion to when the re-recording laser beam is irradiated to the portion;
This is to equalize the time required for the above portion to move to the position of the re-recording laser beam.

If the magnitude of the reproduced signal is not within the reference range, the delay circuit 8 does not work and the recording laser device 5 does not output a laser beam for re-recording.

An experiment was actually conducted using this recording/reproducing apparatus. At this time, the optical recording medium 1 was rotated at a linear velocity of 1.2 m/s. Further, the reference range of the signal determination circuit 7 is set to a range of −3 dB or more with respect to the initial signal value.

As a first step, the optical recording medium 1 is irradiated with a laser beam with a power of 10 mW output from the reproducing laser device 6 in order to bring it into an initial state (unrecorded state).
The photochromic material was completely brought into the A state.

As a second step, the recording laser device 5
500K with a laser beam of 10mW output from
Information of a recording signal of Hz was recorded on the optical recording medium 1.

As the third step, the reproducing laser device 6
Information recorded on the optical recording medium 1 was reproduced using a laser beam with a power of 0.1 mW output from the optical recording medium 1.

At this time, the signal determination circuit 7 is activated, and only when the magnitude of the reproduced signal value is within the reference range, the delay circuit 8 is activated, and the recording laser device 5 has a power of 10 mW.
A laser beam is output, and the same signal as the previously recorded signal is re-recorded on the optical recording medium 1 in the same portion where the previous signal was recorded.

After performing the above-described first and second steps once, the third step was repeatedly performed to measure the time course of the signal values. The results are shown in FIG.

Next, as a comparative example, after the first and second steps were performed on the optical recording medium 1, only repeated reproduction was performed under the same conditions as the third step, and the time course of the signal value was measured. The results are shown in FIG.

It can be seen from FIG. 6 that in the comparative example, the signal value decreases with time after information is recorded. On the other hand, it can be seen from FIG. 5 that in this example, the signal value is held substantially constant even after 100 minutes have passed after information was recorded.

In this embodiment, since heating is not required when recording or reproducing information, information can be reproduced or recorded at high speed.

In the above embodiment, the erased state is set to the A state, but the erased state may be set to the optical steady state, and other wavelengths may be used as appropriate for recording and reproducing information. good. Further, although changes in absorbance are used for recording and reproducing the above-mentioned information, other optical properties such as optical rotation and birefringence may also be used. In this way, the characteristics of the material used for the recording layer may be appropriately utilized.

Further, in this embodiment, a reflective disc optical recording medium is used, but a reflective disc having a structure other than that of this embodiment may be used, a transmissive disc may be used, or an optical tape may be used. Furthermore, the material of the recording layer is not limited to photochromic materials, but may be other materials that react with light. Furthermore, in the case of a material that needs to be heated appropriately during recording or reproduction of information, it may be used by heating it appropriately during recording or reproduction.

Furthermore, the wavelengths of the recording and reproducing laser beams can be changed as appropriate, and other laser devices such as semiconductor laser devices can also be used.

[0039] Further, the above reference range can be set as appropriate, and may be, for example, a range of not less than the reference value Xmin and not more than the reference value Xmax. Alternatively, instead of setting the above-mentioned Xmin to a range below the reference value Xmax, re-recording may be prohibited when the signal value is constant.

Furthermore, the angle formed by the positions of the recording laser device 5 and the reproducing laser device with respect to the rotation center of the optical recording medium 1 is as follows:
The device 5 and device 6 may be set at any angle within a range that does not interfere with each other.

Furthermore, the re-recording method of the present invention can be used not only for recording/reproducing apparatuses but also for reproducing apparatuses or recording apparatuses.

[0042]

[Effect of the invention] In the present invention, when reproducing an optical recording medium,
When the reproduced signal is within the reference range, the original signal is re-recorded at the original position using recording light, so that the information recorded on the optical recording medium hardly deteriorates.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the reaction of a photochromic material used in an example of the present invention.

FIG. 2 is a diagram showing the absorbance characteristics of a solution of this photochromic material dissolved in toluene.

FIG. 3 is a cross-sectional view of an optical recording medium used in an example of the present invention.

FIG. 4 is a schematic diagram of an optical recording medium recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 5 is a diagram showing the time course of reproduced signal values in the embodiment of the present invention.

FIG. 6 is a diagram showing the time course of reproduced signal values in a comparative example.

[Explanation of symbols]

1 Optical recording medium 5 Recording laser device 6 Laser device for reproduction 7 Signal judgment circuit

Claims (1)

[Claims] [Claim 1] Re-recording of an optical recording medium, characterized in that when the optical recording medium is reproduced and the magnitude of the reproduced signal is within a reference range, the original information is re-recorded using recording light. Method.