JPH0827945B2 - Reproduction method of optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reproducing method for a high density optical recording medium.

2. Description of the Related Art Optical recording media currently in practical use can record only 1 bit of information per minimum area irradiated with a laser beam. On the other hand, a method has been proposed in which a plurality of bits of information are recorded at the same location by providing a recording layer containing a plurality of types of dyes having different absorption bands of the electronic spectrum.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, when the absorption bands of the electron spectra of a plurality of types of dyes contained in the recording layer overlap each other, it is possible to accurately detect the recording state of each dye by absorption. It was difficult, and I couldn't find any reports on how to regenerate it in such cases.

The present invention solves the above problems, and an object of the present invention is to accurately perform reproduction on an optical recording medium containing a plurality of types of dyes whose absorption bands overlap with each other.

Means for Solving the Problems In order to solve the above problems, the present invention provides an optical recording medium provided with a recording layer comprising a plurality of types of dyes in which absorption bands of the longest wavelength of an electronic spectrum overlap each other. In contrast,
The information recorded on the optical recording medium is reproduced by using fluorescence, and at this time, a dye that forms a J-aggregate and a dye of a monomer are used as plural kinds of dyes, or a dye that forms a J-aggregate, and The composition is characterized by having a dye that forms an aggregate other than the J-aggregate.

Action Generally, when there are no differences in the absorption wavelengths of the electron spectra among a plurality of types of dyes, there is no significant difference in the fluorescence wavelengths. However, if the absorption bands of the dye that forms the J-aggregate and the dye that does not form the J-aggregate (monomer, dimer, and dye that forms the H-aggregate) overlap each other, use fluorescence. Thus, it becomes possible to perform reproduction with a small overlap. This is because the Stokes shift (difference between the absorption maximum wavelength and the fluorescence maximum wavelength) of the dye forming the J aggregate is J.
This is because the difference between the fluorescence wavelengths of both dyes (monomer, dimer, and dye forming an H-aggregate), which is smaller than the Stokes shift, does not form an aggregate. In this way, even if the absorption bands overlap each other, by detecting the fluorescence, the overlap is small, and it is possible to reproduce the recording with high accuracy.

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

Example 1 FIG. 1 is a sectional view showing the structure of the optical recording medium of this example. Reference numeral 1 is a substrate, 2 is a first recording layer containing the dye 1, 3 is a second recording layer containing the dye 2, and 4 is a protective film. Dye 1,
The chemical structural formula of Dye 2 is shown below.

After making Dye 1 a CHCl ₃ solution and Dye 2 an aqueous solution,
This was gelled with gelatin and sequentially laminated on the substrate 1 by a spin coating method. Here, the longest wavelength absorption bands of the electronic spectra of the dye 1 and the dye 2 overlap each other. Further, the dye 1 forms a J-aggregate and has a small Stokes shift (difference between the absorption maximum wavelength and the fluorescence maximum wavelength), whereas the dye 2 is a monomer and has a large Stokes shift.

FIG. 2 is a characteristic curve diagram showing the fluorescence spectrum of the recording layer of this example. C is a spectrum of fluorescence from the recording layer when excitation light of 545 nm is used, A is a spectrum of fluorescence from dye 1, and B is a spectrum of fluorescence from dye 2. Comparing this with the absorption spectrum of the recording layer shown in FIG. 3 (A 'is the dye 1, B'is the dye 2, and C'is the absorption spectrum of the entire recording layer) It can be seen that what overlapped in the absorption band of the longest wavelength of the electronic spectra of the two dyes can be reproduced by detecting the fluorescence with almost no overlap.

FIG. 4 is a block diagram of the information recording / reproducing system of the present invention. Reference numeral 5 is the optical recording medium shown in FIG. 1, and 6 and 7 are light sources. 6 irradiates with light of 545 nm and 7 irradiates with light of 580 nm. Both are individually turned on and off according to the input signal. Reference numeral 8 denotes a light collector for collecting the light from the light source on the optical recording medium 5. Reference numeral 9 is a spectroscope which extracts light of 560 nm and 600 nm and guides the light to the sensors of 10 and 11. The light thus received is independently converted into an electric signal. Recording and reproduction will be described below.

(A) Recording Now, in order to record "1" only on the second recording layer 3, only the light source 7 is turned on and 6 is turned off. At this time, the second recording layer 3 selectively absorbs light, decomposes due to heat generation, and does not emit fluorescence. In this way, "1" is recorded only on the second recording layer 3.

Further, in order to record "1" also on the first recording layer, the light source 6
Turn only on and turn off 7. At this time, the recording layer 2 selectively absorbs light, decomposes due to heat generation, and does not emit fluorescence. In this way, "1" is also recorded on the first recording layer 2.

(B) Reproduction The irradiation energy during reproduction is 1/10 of the energy during recording.
Light is emitted from the light source 6 as follows. The fluorescence intensity from each recording layer changes depending on whether or not the dye is decomposed in the recording layer, and this can be taken out as an electric signal through the sensor.

Example 2 FIG. 5 shows the structure of the optical recording medium of this example, 12 is a substrate, 13 is a first recording layer containing dye 3, 14 is a separation layer made of cadmium arachiate, and 15 contains dye 4. The second recording layer 16 is a protective film. The chemical structural formulas of Dye 3 and Dye 4 are shown below.

The first recording layer, the separation layer and the second recording layer are substrates by the LB method.
Over 12 accumulated in this order. Dye 3 is 1/1 with arachidic acid
And the dye 4 is a 1/1 mixed film with hexadecane. Here, the longest wavelength absorption bands of the electronic spectra of the dye 3 and the dye 4 overlap each other. Further, while the dye 4 forms a J-aggregate and has a small Stoke shift (difference between the absorption maximum wavelength and the fluorescence maximum wavelength), the dye 3 forms an H-aggregate and has a larger Stoke shift than the dye 4.

FIG. 6 is a characteristic curve diagram showing the fluorescence spectrum of the recording layer of this example. F is the spectrum of fluorescence from the entire recording layer when excitation light of 485 nm is used, and D is the dye 4
Is the spectrum of fluorescence from Dye 3. Comparing this with the absorption spectrum of the recording layer shown in FIG. 7 (D 'is the dye 4, E'is the dye 3, and F'is the absorption spectrum of the entire recording layer) It can be seen that what overlapped in the absorption band of the longest wavelength of the electronic spectra of the two dyes can be reproduced by detecting the fluorescence with almost no overlap. Recording and reproduction can be performed in the same manner as in the first embodiment.

As the dye forming the J-aggregate, there are squarylium dyes, spiropyran-based compounds, etc. in addition to the cyanine dyes and merocyanine dyes shown in Examples 1 and 2, and the same reproducing method is applied to optical recording media using these. Can be applied. In Examples 1 and 2, the recording layer is formed by the spin coating method and the LB method, but it may be formed by the vapor deposition method or the like, and the reproducing method of the present invention can be applied without depending on the recording layer forming method. The optical recording medium may have a separation layer between the recording layers. It can also be applied to the case where a rewritable recording medium is formed by using a photochromic compound such as the above-mentioned spiropyran-based compound as a dye.
Although Examples 1 and 2 describe the case where two kinds of dyes are contained in the optical recording medium, there is no essential difference in the case where two or more kinds of dyes are contained in a plurality of dyes.

EFFECTS OF THE INVENTION As described above, according to the present invention, even when the absorption bands at the longest wavelength of the electronic spectra of a plurality of types of dyes contained in the recording layer overlap each other, at least one of the dyes having the absorption bands overlaps each other. When a species forms a J-aggregate and another does not form a J-aggregate (monomer, dimer, or H-aggregate), fluorescence is used to perform regeneration using fluorescence detection. By doing so, it is possible to reproduce accurately with a small overlap. Therefore, reproduction on a wavelength-division multiplex recording medium in which high density recording is performed at one location becomes easy, and the ripple effect is great.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of the optical recording medium of Example 1,
2 is a characteristic curve diagram showing the fluorescence spectrum of the recording layer of Example 1, FIG. 3 is a characteristic curve diagram showing the absorption spectrum of the recording layer of Example 1, and FIG. 4 is the information of Example 1. 5 is a configuration diagram of a recording / reproducing system, FIG. 5 is a sectional view showing a configuration of an optical recording medium of Example 2, FIG. 6 is a characteristic curve diagram showing fluorescence spectrum of a recording layer of Example 2, and FIG. 6 is a characteristic curve diagram showing an absorption spectrum of a recording layer of Example 2. FIG. 1,12 ... Substrate, 2,13 ... First recording layer, 3,15 ... Second recording layer, 4,16 ... Protective film, 5 ... Optical recording medium, 6,7 ... Light source, 8 ...... Concentrator, 9 …… Spectroscope, 10,11 …… Sensor, 1
4 ... Separation layer.

Claims (2)

[Claims] 1. An optical recording medium provided with a recording layer containing a plurality of dyes whose absorption bands at the longest wavelength in the electronic spectrum overlap each other. Information recorded on the optical recording medium by using fluorescence. A method for reproducing an optical recording medium, which comprises a dye forming a J-aggregate and a monomer dye as the plurality of kinds of dyes. 2. An optical recording medium provided with a recording layer containing a plurality of kinds of dyes whose absorption bands at the longest wavelength in the electronic spectrum overlap each other, and information recorded on the optical recording medium by using fluorescence. A method for reproducing an optical recording medium for reproducing an optical recording medium, comprising: a dye forming a J-aggregate and a dye forming an aggregate other than the J-aggregate as the plurality of kinds of dyes. How to play.