JPH0444261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a detection method using fluorescence for reading out a wavelength multiplexed optical recording medium.

2. Description of the Related Art As a means for further increasing the density of optical information recording, a method of recording multiple bits of information per light spot, that is, wavelength multiplexing recording, is known. For this purpose, there are known methods that use a combination of recording layer groups made of many types of dyes and light flux groups corresponding to the respective dyes. However, no reading method has been reported that is effective especially when there is overlap in the absorption of each dye.

Problems to be Solved by the Invention Although the overlap between the first absorption bands of each dye in the recording layer is small, the first absorption band of one dye may overlap the second absorption band of another dye or an even higher energy absorption band. They may overlap. For example, two dyes A and B
is included in the recording layer, the first absorption band of A and the first absorption band of B
The second absorption bands of overlap. However, the overlap between the first absorption band of A and the first absorption band of B can be ignored. In this case, if you try to detect the recording state by absorption, the first absorption band of dye A will be hidden by the second absorption band of dye B, so it will be difficult to detect dye A, which has absorption on the high energy side. becomes difficult. Therefore, it becomes difficult to read the recorded state. Similarly,
When there are three or more types of dyes, it becomes difficult to detect dyes that absorb on the high energy side.

In addition, when detecting the recording state by absorption,
If there is any disturbance in the film surface of the recording medium, the S/N ratio of absorption obtained will decrease due to the influence of diffused reflection.

Furthermore, when examining fluorescence by irradiating monochromatic light corresponding to the first absorption band of each dye as excitation light, a plurality of light sources with different wavelengths are required.

Means for Solving the Problem The first absorption band of the electronic spectrum of at least one of the two or more contained dyes overlaps with the absorption band of the other dye, and the first absorption band of the contained dye overlaps with the absorption band of the other dye. Using a wavelength multiplexing optical recording medium having dyes in the recording layer with almost no overlap between absorption bands, the recording layer is irradiated with the same ultraviolet light from a single ultraviolet light source to detect fluorescence from multiple types of the dyes. A reading detection method for a wavelength multiplexed optical recording medium is used.

Effect When detecting with fluorescence, only the fluorescence corresponding to the first absorption band of each dye is detected. At this time, the fluorescence of each dye hardly overlaps.
Therefore, it becomes possible to detect the state of each dye. This is because, for example, molecules excited to a highly excited state by irradiation with ultraviolet light emit fluorescence after falling to the lowest excited singlet state. Only the fluorescence corresponding to the absorption band is observed at a time.

Furthermore, for the reasons stated above, a single ultraviolet light source is sufficient as an excitation light source, and light sources of other wavelengths are not required. Moreover, since ultraviolet light is used as the excitation light source in this case, when detecting fluorescence in the visible region, even if the film surface of the recording layer is disturbed, noise due to this does not occur and good fluorescence detection can be achieved. can be performed, and the detection sensitivity of reading increases.

Example Two types of compounds shown by the following structures (hereinafter
A recording layer shown in FIG. 1 is formed from the following materials (SP, TP). A recording layer 2 made of TP and a recording layer 1 made of SP/stearic acid=1/2 are formed on a substrate 3.

The above SP and TP are photochromic compounds, and each reversibly assumes two states, colored and colorless, upon irradiation with light. Therefore, the recording layers 1 and 2 containing them each independently become a colored state and a colorless state,
The recording medium can be in four states. Here, the first absorption band in the colored state of the recording layer 1 and the recording layer 2
The second absorption bands of the colored states overlap. However, there is almost no overlap between the first absorption bands.

Below, we will specifically discuss the four states that the recording medium takes.

a colorless state in which the recording layer 1 absorbs only in the ultraviolet region;
The initial state of the recording layer 2 is a colored state with absorption in the visible region. At this time, when ultraviolet light was used as excitation light, the fluorescence was as shown in a in FIG. 2, and the absorption was as in a in FIG. 3.

Subsequently, when laser light (340 nm) is irradiated for writing, the recording layer 1 selectively absorbs the light and changes to a colored state. As a result, both recording layers 1 and 2 become colored. (Writing status 1)
At this time, fluorescence using ultraviolet light as excitation light is as shown in b in FIG. 2, or absorption is as shown in b in FIG. 3.

When laser light (680 nm) is irradiated for further writing, the recording layer 2 selectively absorbs the light and becomes colorless. As a result, only the recording layer 1 becomes colored. (Writing state 2) Fluorescence using ultraviolet light as excitation light at this time is c in Figure 2.
The absorption will be as shown in Figure 3c.

Next, when writing is performed by irradiating a laser beam of 480 nm, the recording layer 1 selectively absorbs the light and changes to a colorless state. As a result, recording layers 1 and 2
Both become colorless. (Writing state 3) At this time, fluorescence using ultraviolet light as excitation light is as shown in d in FIG. 2, and absorption is as shown in d in FIG. 3.

Regarding the above results, first looking at the absorption side, among the four states (a, b, c, d in Fig. 3), the initial state (a in Fig. 3) and the recording state 1 (b in Fig. 3) ) is difficult to determine. This is because the first absorption band of the colored state absorption of the recording layer 1 is hidden by the second absorption band of the colored state absorption of the recording layer 2.

On the other hand, in the case of fluorescence, since there is almost no overlap between the fluorescence in the colored state of recording layer 1 and the fluorescence in the colored state of recording layer 2, there are four states (a, b in Fig. 2,
c and d) can be clearly identified.

Additionally, while the absorption pattern is generally dull due to the influence of scattered light caused by disturbances in the film structure, fluorescence is not affected by scattered light and can be detected favorably. .

Effects of the Invention According to the present invention, since the first absorption band of one dye overlaps with the second absorption band of another dye or an absorption band of higher energy, it is possible to use a recording medium that is difficult to read by absorption. It also becomes easier to read out.

Furthermore, if ultraviolet light is used as a light source for detecting fluorescence, only one light source is required for detecting the recording state, and the fluorescence from each dye is detected by one ultraviolet light irradiation with this light source. It is possible to read multiple pieces of information. In addition, good fluorescence is obtained that is not affected by noise caused by disturbances in the film surface, and the detection sensitivity for readout is increased.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a recording medium according to an embodiment of the present invention, and FIGS. 2 and 3 are fluorescence and absorption spectra of the same medium in an initial state and a written state, respectively. 1... Recording layer 1, 2... Recording layer 2, 3... Substrate.

Claims (1)

[Claims] 1 At least one of the two or more pigments contained
A wavelength multiplexing optical recording having a recording layer containing a dye in which the first absorption band of the electronic spectrum of the seed dye overlaps with the absorption band of other dyes, and the first absorption bands of the contained dyes hardly overlap with each other. 1. A method for reading and detecting a wavelength multiplexing optical recording medium, which comprises using a medium, irradiating the recording layer with the same ultraviolet light from one ultraviolet light source, and detecting fluorescence from a plurality of types of the dyes.