JPH02278519A - Recording method for optical recording medium - Google Patents

Abstract

PURPOSE:To record information with a high recording sensitivity on the optical recording medium by using laser beams of the wavelengths different at the time of recording and at the time of reproducing and using an org. dye of a low absorptivity at the reproducing wavelength and a high absorptivity at the recording wavelength. CONSTITUTION:The optical disk is constituted of an org. dye layer 12 consisting of a recording material layer which makes optothermo conversion by absorbing the laser beam of 680nm wavelength, a reflecting film 13 and a protective film 14 on a transparent substrate 11 formed with grooves 11a. Plastics, such as polycarbonate and acryl, or glass, etc., are used as the material of the substrate 11. The org. dye which has the high reflectivity (>=70%) to the light of 780nm wavelength and the low reflectivity, i.e. high light absorptivity to the light of 680nm wavelength is used for the org. dye layer 12. The interchangeability in specifications with reproduction-only type disks, such as CD, is obtd. by using the laser beams corresponding to these wavelengths in executing the recording. The recording with the high recording sensitivity is thus possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording method for a recordable optical recording medium in which information is recorded using a laser beam.

[Summary of the invention]

The present invention is a recording method for an optical recording medium in which information is recorded and reproduced on an optical recording medium using a laser beam. The purpose of the present invention is to provide a recording method for an optical recording medium that can improve recording sensitivity by using a wavelength-dependent organic dye that has a low absorption rate at the recording wavelength and a high absorption rate at the recording wavelength.

[Conventional technology]

In recent years, disk-shaped recording media such as optical disks and magneto-optical disks that utilize optical or magneto-optical signal recording and reproducing methods have been developed and are being supplied to the market. These disc-shaped recording media include so-called compact discs (
Read-only recording media such as CDs and optical video discs, so-called write-once recording media that allow the user to write data once, and old data storage media such as magneto-optical discs. Optical recording media and the like that are capable of this are known.

Here, for example, CDs, which are especially produced in large quantities as playback-only optical disks, have a unified standard.For example, the wavelength of the laser beam during playback is 780 nm, and at that time, the optical disk has a reflection rate of 70% or more at this wavelength. It is standardized that the rate is necessary.

On the other hand, write-once and rewritable optical disks include, for example, magneto-optical disks and organic dye-based optical disks.
Unlike optical disks such as magneto-optical disks, there are write-once organic dye-based optical disks on which information is written, which can be played back by a playback device for read-only optical disks such as the above-mentioned CDs.

In other words, in the write-once optical disc using the above-mentioned organic dye, if the optical disc after information recording H has standard compatibility with the above-mentioned read-only optical disc, then the read-only disc replay device can be used. This means that the recorded organic dye-based optical disc can be reproduced using this method.

[Problems to be Solved by the Invention] Here, as described above, in order to make an organic dye-based write-once optical disc compatible with, for example, a CD, etc., as described above, The reflectance of a laser beam with a wavelength of 780 nm on the disk must be 70% or more. However, since the organic dye-based write-once optical disc forms recording bits by irradiating the optical disc with a pulsed laser beam, it is difficult to use the optical disc with high reflectance as described above. When forming recording pits by irradiating a laser beam on the
A high-power laser beam is required.

Generating such a high-power laser beam is too much of a burden for a laser diode that emits a laser beam with a wavelength of 780 nm, which is used to reproduce read-only discs such as the CDs mentioned above. For this reason, it is difficult to record using a pulsed laser beam, and the difference in the level of the laser beam required for recording and playback is large (for example, the difference in laser beam level required during recording is approximately 16 times during playback). (Requires high power.) Therefore, the servo circuit that controls the output of the laser beam is likely to be burdened, and a servo gain with a wide dynamic range is required. Furthermore, in order to prevent the power of the laser beam generated from the laser diode from decreasing, the precision of the optical system must also be improved.

The present invention has been proposed in view of the above-mentioned circumstances, and provides a recording method for a write-once dye-based optical recording medium that is compatible with read-only optical discs such as CDs in terms of standards. The purpose is to provide the following.

[Means for Solving the Problems] The recording method for an optical recording medium of the present invention has been proposed in order to achieve two objectives: recording and reproducing information on an optical recording medium using a laser beam; 1, the wavelength of the laser beam during recording is a laser beam having a shorter wavelength (for example, 680 nm) than the wavelength during reproduction (for example, 780 nm). 2) The optical recording medium contains an organic dye that has a low absorption rate (i.e., a reflectance of 70% or more) at the laser beam wavelength during recording and reproduction, and has a high wavelength dependence of absorption rate at the laser beam wavelength during recording. It is characterized by its use.

[Effect]

According to the present invention, the wavelength dependence of the light absorption rate of the optical recording medium is low in the wavelength range of 780 nm, for example, and high in the wavelength range of the laser beam during recording.

Furthermore, the wavelength of the laser beam during recording is shorter than the wavelength during reproduction.

[Example] Hereinafter, an example to which the present invention is applied will be described with reference to the drawings.

FIG. 1 shows the wavelength dependence of the light absorption rate (absorbance) of a disk-shaped optical recording medium manufactured using an organic dye as a recording material. In other words, in Fig. 1, for example, Combat I.
The wavelength of the laser beam for disc (CD) reproduction is 780.
nm, and in order to be compatible with this, the wavelength dependence of the manufactured optical disk is set to have a high reflectance (north of 70%) by lowering the light absorption near 780 nm. That is, by doing as described above, compatibility with the above-mentioned CD is ensured. Furthermore, during recording, a laser beam is used in a wavelength range that has a high light absorption rate for the organic dye used in the optical disc, that is, a laser beam with a shorter wavelength than the laser beam during reproduction. Here, in the above laser beam,
By using a laser diode that emits a laser beam with a short wavelength during recording and an optical pick amplifier incorporating the laser diode, it is possible to make the beam spot for recording smaller, which makes it possible to reduce the reproduction signal of the optical disc after recording. It becomes possible to improve the spatial frequency (MTF) and modulation degree. In addition, since the organic dye uses a laser beam with a wavelength of high light absorption, the sensitivity of the recording film of the optical disc can be increased, and therefore recording can be performed with a low-power laser beam.

However, for example, if the wavelength of the laser beam during recording is long, the beam spot focused on the optical Y disk by the optical system will become large, causing the recording pitch of the disk to increase. The recording density (spatial frequency (MTF)) becomes low. For this reason, the laser beam has a short wavelength as described above. Here, by condensing a laser beam with a short wavelength, for example, with a high NA lens, the heemspot on the optical disk at the time of recording is
・It is possible to reduce the spatial frequency and the modulation degree.

As mentioned above, for generating a laser beam with a wavelength shorter than the 780 nm wavelength laser beam used during recording, a recently developed laser diode, for example, an AlGa1nP laser diode that emits a laser beam with a wavelength of 670 to 680 nm, is used. It is preferable to do so. Therefore, the recording material used for the optical disc is an organic dye that has a low light absorption at a wavelength of 780 nm and a high light absorption at a wavelength around 680 nm.

Further, FIG. 2 schematically shows a cross section of an optical disk using the above-mentioned organic dye as a recording material. That is, the optical disc has an organic dye layer 12, which is a recording material layer that absorbs the above-mentioned laser beam with a wavelength of 680 nm and performs photothermal conversion, on a transparent substrate 11 in which groups 11a are formed, and an organic dye layer 12 that increases reflectance. Reflective films 13 are sequentially laminated, and a protective film 14 is further provided on the reflective films 13.

The material of the substrate 11 is one used in ordinary optical recording media, such as plastics such as polycarbonate and acrylic, and glass. Further, as mentioned above, the organic dye layer 12 has a high reflectance (70% or more) for light with a wavelength of 780 nm, and has a low reflectance, that is, a high light absorption rate, for light with a wavelength of 680 nm. It is something.

Therefore, as in this embodiment, an organic dye-based optical disc having a high reflectance at a wavelength of 780 nm and a high light absorption at a wavelength of 680 nm is used, and recording is performed on the optical disc using a laser beam corresponding to each wavelength mentioned above. Therefore, it has standard compatibility with playback-only discs such as CDs,
This means that recording can be performed on the optical disc with high recording sensitivity, ie, high MTF and modulation degree.

〔Effect of the invention〕

In the present invention, when recording and reproducing information on an optical recording medium using a laser beam, laser beams with different wavelengths are used for recording and reproduction, and the optical recording medium has a low absorption rate at the reproduction wavelength and a laser beam having a low absorption rate at the recording wavelength. By using organic dyes with high absorption and wavelength dependence, it has become possible to record information on optical recording media with high recording sensitivity.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the wavelength dependence of light absorption rate (absorbance) of an organic dye-based optical recording medium to which the present invention is applied, and Fig. 2 is a cross-section of an optical disk using the organic dye shown in Fig. 1 as a recording material. FIG. 11a ・ ・ 11 ・ ・ ・ ・ 12 ・ ・ ・ ・ 13 ・ ・ ・ ・ 14 ・ ・ ・ ・ ・ Group, substrate, organic dye, reflective film, protective film

Claims (1)

[Claims] A recording method for an optical recording medium that uses a laser beam to record and reproduce information on an optical recording medium, the method comprising: a laser beam having a shorter wavelength during recording than a wavelength during reproduction; , an optical recording medium characterized in that the optical recording medium uses a wavelength-dependent organic dye that has a low absorption rate at the laser beam wavelength during reproduction and a high absorption rate at the laser beam wavelength during recording. Recording method.