JPS62167631A - Recording signal reproducing method for optical recording medium - Google Patents

Abstract

PURPOSE:To decrease the quantity of light energy necessary for writing and to improve the recording sensitivity of a recording medium by recording signals as an array of the part where fluorescence is generated and part where the fluorescence is substan tially not generated to the recording medium, irradiating light to the recording medium and detecting the presence or absence of the generation of the fluorescence. CONSTITUTION:The generation of the fluorescence is used as a means for detecting the signal in this method, by which the detection ability is made extremely higher than the detection of the signal by the difference in degree. More specifically, 1pt.wt. 3'-methyl-3-ethoxy-6-nitro-8-methoxyspiro and 10pts.wt. phenoxy resin are dissolved in 100pts.wt. 1:1 solvent mixture composed of a methyl ethyl ketone and cyclohexanone and the soln. is coated on a quartz glass substrate 1 subjected to optical polishing by a spinner and is dried. UV light having 365nm wavelength is irradiated to the coating so that the entire surface forms a color. Then the fluorescence does not appear in the region of a long wavelength in the case B is which the surface is not made to form the color. The fluorescence is observed only in the case A in which the surface is made to form the color. The value of 10% is obtd. as the percentage modulation of the signal when such medium is used for an optical recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reproducing a recorded signal from an optical recording medium.

[Summary of the invention]

The present invention provides a method for reproducing a recorded signal from an optical recording medium, in which a signal is recorded on the recording medium as a row of a fluorescent portion and a portion that does not substantially generate fluorescent light, and the signal is By irradiating the recording medium and detecting the presence or absence of fluorescence, the recording signal is read out, and the signal is reproduced by detecting changes in the fluorescence generated from the recording medium material corresponding to the recording signal. This is how it was done.

[Conventional technology]

Conventionally, methods used for reproducing recorded signals from optical recording media include (1) a method of detecting the intensity difference of read light transmitted through the recording medium caused by the recorded signal, and (2)
) The main method has been to detect the difference in intensity of reflected light or scattered light from a recording medium caused by a recording signal.

[Problem that the invention seeks to solve]

A drawback of these conventional methods is that if the difference in light intensity is minute, a high-quality reproduction signal cannot be obtained, so recording must be performed with a large difference in light intensity. In order to increase the difference in light intensity, it is necessary to make the change meter of the recording material in the medium larger, or to provide a layer of high refractive index material to increase the apparent change. It won't happen. Therefore, there have been problems such as a decrease in the recording sensitivity of the recording medium and major restrictions on the structure of the recording medium.

The present invention solves the above-mentioned problems of the prior art, and makes it possible to obtain a high-quality reproduction signal even with writing at a lower level than in the past.Therefore, the amount of optical energy required for writing is small, and the recording sensitivity of the medium is improved. It is an object of the present invention to provide a recorded signal reproducing method that can bring about an increase in the number of recorded signals.

[Means for solving problems]

In order to solve the above-mentioned problems, the recorded signal reproducing method of the present invention records a signal on a recording medium as an array of fluorescent light generating portions and substantially non-fluorescent generating portions, and irradiates the recording medium with light. The recording signal is read out by detecting the presence or absence of fluorescence.

In the present invention, since fluorescence emission is used as a signal detection means, highly sensitive detection with zero background can be performed in principle. That is, since a signal is detected based on the presence or absence of light emission, in principle, the presence or absence of a signal can be detected immediately based on the presence or absence of light emission, and the detection ability is extremely high compared to detecting signals based on differences in degree. In terms of the substrate, the concentration that can be detected by normal detection methods is on the order of ppb for light absorption and ppm5 luminescence, and the sensitivity for detecting luminescence is much higher. Additionally, methods for detecting the emission of several levels of photons are established in the current state of the art. Therefore, even minute fluorescence emissions can be detected, and the sensitivity of signal detection and reproduction is extremely high. The present invention
The difference in detection sensitivity between the detection methods described above is applied to a method for reproducing signals from optical recording media, and it can be said to be a technology with extremely excellent performance.

In the present invention, a signal is recorded by forming a fluorescent light-generating portion and a substantially non-fluorescent portion on a recording medium. Alternatively, a color-erasing substance can be used. For example, as such a substance, a substance that does not generate fluorescence in its initial state but becomes capable of emitting fluorescence by some means such as ultraviolet light or laser light irradiation can be used. Alternatively, it is possible to use a substance that originally emits fluorescence, but which can be selectively rendered non-fluorescent by some means.

Examples of recording materials that can be used in the present invention include: ■ photochromic compounds (spiropyran, fulgide, dihydropyrene, polycyclic aromatic compounds, etc.), ■ fluorescent chromophores, ■ fluorescent substances (compounds containing rare earth elements, etc.) ) etc. A photochromic compound is one that reversibly develops or discolors upon irradiation with light. In the case of this photochromic compound, it is possible to both write and read signals due to its reversibility. In other cases, it is possible to record by burning out a substance that originally emits fluorescent light to form a part that does not emit fluorescent light, but in this case, the recording is fixed, and therefore, the recording is done in advance. It can only play back certain signals and can be used as a so-called ROM card.

Typical examples of compounds that can be used as recording materials in the present invention are illustrated below.

■ Examples of photochromic compounds (1) Fulgide Representative example Literature: IEE Proceedings
Proceedings), 130 Pt 1(5)
(1983) Journal of the Chemical Society (J, Chem, Soc,)
Perkin Trans, r1981, 1
97 Journal of Chemical Society (J,
Chem, Soc,) Perkin
Trans, l11981, 341 C1! .

C113CH:+ (E)-isopropylidene (2+ 4+
6-trimethylbenzylidene)
5uccinic anhydride (E)-isopropylidene (2,4,6-dimethylhenzylidene) succinic anhydride C113CH3 (E)-α-2,5-dimethyl-3-fury
lethylidene (isopropylidene)
e) 5uccinic anhydride, (H)
-α-2,5-dimethyl-3-furylethylidene (isopropylidene) Succinic anhydride (2) Representative examples of polycyclic compounds Literature: Photochemistry/Photobiol (Photo
chem, Photobiol, ), 37 (5
) (1983) 5R7 dibenzo [aj] perylene-L
16-dione dibenzo[aj]]perylene-8
, 16-Sion Literature Journal of Physical Chemistry (J, Phys, Chem,)
+86 (1982) 3,10-dimeth
ylnaphtho [L 2+ 3+ 4-rst]
Pentaphene-5,8-dione3.10-
Dimethylnaphtho[1,2,3,4-rst]pentaphene-5,8-dione Literature
r-forsch) 39a (1984) 998
tetrabenzo [bc, fg, 1m+p
q] pentacene tetrabenzo [bc, fg
+ In, pq] Pentacene (3) Dihydropyrene 4+ 5+ 15+ 16-tetrahydropy
rene4, 5.15.16-titrahydropyrene (4
) Spiropyran short wavelength type Long wavelength type For example, 3'-methyl-3-ethoxy-6-nitro-8-methoxyspiro [2H-1-benzopyran-2,2'-benzothiazoline] ■ Representative examples of fluorescent dyes Coumarin type : tlt 7-diethylamino-4-methylcoumarin 7-hydroxy-4-methylcoumarin System with element as localized luminescence center: Host crystal Activator Color development YF: + Er green 1 (o green 'l'mi!? and red 1, aF, Er green Tm blue and red YOCj2 Er red Ho green Y 30 CIt t E r Green, Yellow, Red HO Green Y2O2Er Red YzOzS Er The green and red recording media can be configured as shown in FIG. 2, for example.

In this configuration example, a recording layer (2) made of a photochromic compound such as spiropyran is formed on a substrate (I) made of glass or other suitable material with a reflective layer (2) made of Ar or the like interposed therebetween. Signals recorded on this recording layer (1) as an array of fluorescent light generating portions and substantially non-fluorescent light generating portions are reproduced by detecting the presence or absence of the fluorescent light generation.

The recorded signal reproducing method of the present invention can be embodied by various devices. For example, the recording/reproducing optical system shown in FIG. 1 can be used. In the configuration example shown in FIG. 1, an Ar laser light source is used as the light source 1, and the laser light from the Ar laser light source is transmitted through a photoacoustic modulator 2 and a mirror 3 to a polarization beam splinter 4.
The light is irradiated onto a recording medium 7 through a quarter-wave plate 5 and an objective lens 6. The recording medium 7 is placed inside the integrating sphere 8. When the recording layer of the recording medium 7 is excited by the laser beam and fluorescence is generated, this is dispersed and reflected by the reflective portion of the inner surface of the integrating sphere 8 (dispersed by magnesium oxide or the like). This is detected by the fluorescence detection detector 9. In this way, the presence or absence of fluorescent light is detected and the recorded signal is thereby read. In Figure 1, 10
1 is a laser beam cut filter, 11 is a cylindrical lens, and 12 is a focus servo optical detector.

Using this device, it is possible to record and reproduce with high sensitivity.

Furthermore, when a photochromic compound is used as a recording material, recording and reproduction can be repeated due to its reversible photochemical reactivity.

〔Example〕

An embodiment of the present invention will be described below. In this example, a photochromic compound was used, and fluorescence was measured when the compound was colored by light irradiation and when it was not colored.

That is, in this example, 1 part by weight of 3'-methyl-3-ethoxy-6-nitro-8-methoxyspiro[2H-1-benzopyran-2,2'-penzothiazolinco, phenoxy resin (Union Carbide Co., Ltd. A solution of 10 parts by weight of PKHT manufactured by Manufacturer Co., Ltd. in 100 parts by weight of a 1:1 mixed solvent of methyl ethyl ketone and cyclohexanone was applied onto a quartz glass substrate that had been optically polished using a spinner.The coating conditions were as follows: The rotation time was 5 seconds at 2300 revolutions per minute.Next, it was dried in a vacuum dryer under reduced pressure at a temperature of 80°C for 2 hours.The film thickness after drying was approximately 1.2μ.
It is m. A 500W ultra-high pressure mercury lamp is used as the light source, and Toshiba UV-D36C and TRA-25S are used as optical filters.
was used to irradiate the sample with ultraviolet light with a wavelength of 365 nm for io seconds to cause color development on the entire surface of the sample. The fluorescence spectra of case B without color development and case A with color development were compared with MPF-
It was measured using a 2A type fluorometer. Symbols A and B in Figure 3
shows the fluorescence spectrum. In case B, when no color is generated, no fluorescence appears in the long wavelength region (as shown in the figure, it is almost only the noise of the equipment), and when color is generated, only fluorescence is observed in A. Therefore, when this medium is used as an optical recording medium, a signal modulation degree of 100% can be obtained.

For a sample made with the same composition and the same manufacturing conditions as this sample, the degree of modulation of the signal obtained from the difference in the intensity of light transmitted through the sample is about 5% at maximum when the same light irradiation conditions are used to develop color and when it is not. In this example, the modulation depth is 2.
A difference of more than 0 times was observed.

Note that the degree of modulation here refers to the high level H and low level L of color development.
It means the ratio of the difference and the sum (HL)/(H+L).

It should be noted that, as a matter of course, the present invention is not limited to this embodiment.

〔Effect of the invention〕

By using the present invention, (1) it is possible to obtain a high-quality reproduction signal even with writing at a lower level than in the past;
2) The amount of optical energy required for writing is small, and the recording sensitivity of the medium can be increased.

[Brief explanation of drawings]

FIG. 1 shows an example of the configuration of a recording/reproducing optical system to which the present invention is applied. FIG. 2 shows an example of the structure of a recording medium. FIG. 3 is a fluorescence spectrum diagram according to Example 4. A... Spectrum in a colored state, B... Spectrum in a decolored state. ■... Substrate, ■... Reflective layer, ■... Recording layer. l...Light source, 2...Photoacoustic modulator, 3...Mirror, 4...Polarization beam splitter, 5...1/4 wavelength plate, 6...Lens, 7... Recording medium, 8... Integrating sphere, 9... Fluorescence detection detector, 10... Laser light cut filter.

Claims (1)

[Claims] 1. Recording a signal on a recording medium as an array of fluorescence-generating portions and substantially non-fluorescence-generating portions, and irradiating the recording medium with light to determine whether fluorescence occurs or not. A method for reproducing a recorded signal from an optical recording medium, which reads a recorded signal by detecting.