JPH0519205B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for writing and reading optical information recording media.

BACKGROUND ART Conventionally, various types of recording media have been proposed for use in information recording and reproducing apparatuses that record and reproduce information by irradiating a rotating disk-shaped information recording medium with a laser beam. Among these, the optical information recording medium proposed by the present inventors uses an organic dye thin film that exhibits metallic light reflection (bronze luster) as a recording layer, so it has excellent sensitivity and resolution (therefore, S/N is low). It also has the advantage of being low in manufacturing cost. However, the higher the sensitivity, the faster the deterioration with respect to the readout light.For example, with a sensitivity of 5mW, reading can be repeated more than 1 million times even with a readout power of 0.4mW, but with a sensitivity of 2.5mW, with the same readout power It will drop considerably. Therefore, when writing information to a highly sensitive recording medium, it is necessary to lower the readout optical power, but when the readout power is lowered, the ratio of laser diode noise and optical sensor noise components increases, resulting in a decrease in S/N. Come. Therefore, a method for writing and reading information suitable for highly sensitive optical information recording media is desired.

Purpose The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide a method for writing and reading an optical information recording medium that has high sensitivity and can withstand reading light.

Structure The present invention is based on the characteristics of the absorption spectrum and specular reflection spectrum of an organic dye that exhibits metallic light reflection characteristics. This was done by taking advantage of the existence of

To explain this point in the case where a cyanine dye having the following structural formula is used as an organic dye, for example, the relationship between the absorption spectrum and the specular reflection spectrum of a thin film formed with this dye is as shown in FIG.

As is clear from FIG. 1, the recording medium having the organic dye film has an absorption spectrum peak at 800 nm, but a reflection spectrum peak at 890 nm. Therefore, writing information with 800 nm light provides optimal sensitivity, while reading information with 890 nm light provides the highest contrast.

Therefore, the writing/reading method of the present invention, which is applied to an optical information recording medium having an organic dye recording layer exhibiting metallic light reflection characteristics on a substrate, uses a wavelength higher in the optical absorption of the recording layer when writing optical information. On the other hand, when reading optical information, light of a wavelength with a higher light reflectance of the recording layer is used.

The organic dye recording layer in the present invention is composed of an organic dye exhibiting metallic light reflection characteristics, either alone or in a mixture with other components such as a binder. It can be easily formed by coating and drying.

The organic dye forming the recording layer of the present invention may be any dye as long as it exhibits metallic light reflection characteristics. ), and it is actually preferable to have a reflectance of 20% or more, preferably 30%, with respect to the laser wavelength used for writing and reading. Typical examples of organic dyes include cyanine dyes and merocyanine dyes.

The laser beam used in the method of the present invention must be selected depending on the absorption wavelength of the dye used, but relatively inexpensive He--Ne lasers or semiconductor lasers are preferred.

Further, the writing/reading device used in the method of the present invention has a reading optical system 1 as shown in FIG.
Although the writing optical system 2 and the writing optical system 2 are independently provided, for example, the actuator portion and the like can be shared.

EXAMPLES The present invention will be further illustrated by the following non-limiting examples.

Example 1 1.25% ethylene dichloride solution of dye
A recording medium was obtained by coating on an acrylic plate with a thickness of mm to form a thin film of about 500 Å. The optical spectral characteristics of this recording medium are as shown in FIG.

An 800 nm semiconductor laser was used for writing, and an 850 nm semiconductor laser was used for reading.

Writing at linear speed of 1.24 m, recording surface power of 2.5 mW,
The experiment was conducted at 0.6875MHz using light with a beam diameter of 1.4μm.
When reading was performed by reducing the recording surface power to 0.5mW and reading with a bandwidth of 30KHz,
A C/N of 52 dB was obtained, but after reading out several hundred times, the C/N decreased to 30 dB. Also
When reading at 0.1 mW, a C/N of only 45 dB was obtained. If the readout laser beam is 850nm, the readout power is 0.5mW and C/
N was obtained at 52 dB, and no decrease in C/N was observed even after reading out several hundred times.

Example 2 Writing and reading were carried out in the same manner as in Example 1, except that the dye in Example 1 was replaced with the above dye, and similar results were obtained.

Effects According to the method of the present invention, it is possible to prevent deterioration of an optical information recording medium due to read light.

[Brief explanation of the drawing]

1 and 3 are diagrams showing the relationship between the absorption spectrum and the reflection spectrum of an organic dye according to the present invention, and FIG. 2 is a schematic diagram showing an example of an apparatus used in the method of the present invention. 1... Reading optical system, 2... Writing optical system, 3... Motor, 4... Optical disk, 5... Rotating axis.

Claims (1)

[Claims] 1. Information is written on an optical information recording medium having an organic dye recording layer on a substrate that exhibits metallic light reflection characteristics and whose light absorption peak and light reflection peak have different wavelengths, using light at a wavelength with a higher light absorption rate, and A method for writing and reading an optical information recording medium, characterized by reading information using light of a wavelength with a higher optical reflectance.