JP3429521B2 - Optical recording medium and optical recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a structure in which a dye film and a substrate made of a material having a heat radiation effect are combined and an optical recording method therefor.

[0002]

2. Description of the Related Art In recent years, with the aim of increasing the density and speed of recording, erasing and reproducing information, the organic dye forming the recording layer or recording film is destroyed by irradiation with laser light, and the change in the absorption spectrum is utilized. Research is being conducted on information recording media in which recording is performed and information is read out by light. For example, cyanine dyes have been put into practical use as optical recording materials for destructive writing because they form stable films. Further, a photochromic compound (an organic compound having a photoreversible isomerization reaction) is promising as an optical recording material capable of repetitive recording, and improvement of repetitive characteristics has been studied. In addition, since some cyanine dyes and photochromic compounds (typically spiropyrans) form J-aggregates and have a sharp absorption peak in the visible light region, the recording sensitivity by light and the recording sensitivity by light are higher than those in the conventional monomer state. Easy to obtain high reading sensitivity, thermally stable and good recording characteristics. By thinning these optical recording materials, an optical recording medium capable of high-density and high-speed recording can be manufactured.

A dye molecule-associated LB film formed of a photochromic dye compound has been investigated as a stable optical recording medium. Among them, a spiropyran dye J-aggregate having a sharp absorption peak as shown in FIG. 1 (particularly, SP1822,
E. Ando, et al. Proc. Int. Sym
p. on Further Electron Dev
Ices, 47 1985) is known to be stable at room temperature without breaking and to have good recording sensitivity to light.
It is known that this J-aggregate is broken by irradiation with light of strong power [several 100 W / cm ^2] for a few milliseconds, and the decolorization reaction (a phenomenon of reverse isomerization of colored molecules inside the aggregate) proceeds. ing. As a recording medium or a recording method using this J-aggregate, light with a specific wavelength range is used to make a decrease in absorption and write, and the absorption is read out with light that does not change the absorption, and light with a different wavelength range is used. A high-density recording medium or recording method for erasing has been proposed. Further, a wavelength multiplexing recording medium or recording method has been proposed in which various kinds of aggregates having such narrow absorption width and sharp absorption are formed into a film to record at the same place for each absorption peak wavelength of each aggregate. ing.

[0004]

An optical recording medium using a conventional dye film (for example, a dye film of a spiropyran dye J-aggregate) has low sensitivity at room temperature, and has a high power (for destroying at room temperature) for recording. Irradiation time is several msec on the order of 1
A laser having an intensity of 00 W / cm ² was required, and recording could not be performed at a lower power than that. Also, the process of destroying the dye-aggregate coating film by heat for recording cannot be performed at a high density in a short time as with light. Further, since the dye film itself does not easily retain heat, recording by photothermal conversion is difficult, and a recording process using high power light or a recording process of further condensing low power light by a lens is required. Therefore, it is necessary to consider a recording medium and a recording method which are low in energy cost and can be recorded by a simple optical system using low-power light. In particular, a medium or method that can expect the heat accumulation effect of the medium by light is required.

An object of the present invention is to enable recording with light of low power at room temperature (10 W / cm ² or less, which does not break in a short time by light alone) and has improved recording sensitivity, and an optical recording method therefor. Is to get.

[0006]

Therefore, in order to achieve the above object, the present invention has a structure in which a dye film (including an LB film) and a substrate made of a material having a heat radiation effect are combined. A characteristic optical recording medium is provided.

Further, there is provided a recording method in which a visible light irradiation step and an infrared irradiation step or a heating step are used in combination for this optical recording medium.

As shown in FIG. 2, the recording medium 1 of the present invention has a dye coating 3 on a substrate 2 made of a material having a heat radiation effect.
It has a structure with.

Organic substances such as dyes are media in which heat easily diffuses and escapes easily. However, on the contrary, it has a property that it is easily activated by far infrared rays, and at that time, the reaction easily occurs due to another environmental element (light, heat, reactive molecule, etc.). Therefore,
A method has been considered in which a material having a high photothermal conversion is used as a substrate and the dye coating film is efficiently destroyed by utilizing the heat accumulation effect and the thermal catalyst effect of the substrate. Low power on the recording part of the dye film (10 W / cm which does not break in a short time with light alone)
⁽² or less) to destroy the dye or the dye molecule aggregates even with visible light, that is, to record information, to perform photothermal conversion with high efficiency and radiate heat for a long time to accelerate the photodegradation reaction of the dye film recording part. It is effective to use a substrate made of a material having various heat radiation effects.

In particular, the method of using a transparent substrate made of a far-infrared radiation substance as the substrate on which the dye coating is applied is most effective. A dye film is evenly deposited on this substrate and used as a recording layer. During recording, a part of the light energy that was not absorbed by the dye film in the excitation energy of the irradiated light is converted into heat in the photothermal conversion substrate to further promote the photodegradation reaction of the dye (energy of the irradiated light. However, not all of them are spent on photochemical reactions such as photochromic reactions, aggregate decay reactions, dye decay reactions, etc. Some are lost as molecular vibrations and heat, and also fluorescence, reflection, and scattered light energy. include.).

When a substrate made of a material having a heat radiating action (including a substrate made of a far infrared ray radiating material) is used, infrared rays are simultaneously radiated to the laser light radiated portion of this optical recording medium to efficiently dye the dye. It breaks or increases the molecular vibration of the dye aggregate inside the dye film, and promotes the collapse of the dye aggregate by light.

Alternatively, by heating the substrate to raise the temperature and maintaining the state for a long time, the molecular vibration of the dye aggregate in the irradiated portion can be increased, and the dye aggregate can be destroyed by low-power light.

As a material most suitable for maintaining the substrate temperature for a long time, a substance (including a far infrared ray emitting substance) having a heat radiating action is also considered. Among them, a recording medium having a structure in which a dye coating is applied to a substrate made of a far-infrared emitting substance (particularly a far-infrared emitting ceramic substrate) is particularly promising. Both are recording methods capable of recording by destroying the dye molecule or the dye molecule aggregate at a faster response speed than ever before.

Next, regarding the reading method, the transmission type reading method uses far-infrared radiation glass for the substrate. In the reflection type reading method, a thin film of a visible light total reflection mirror is vapor-deposited or sputtered on a substrate (an opaque substrate) made of a far-infrared radiation material and used as a base of a dye film. Other than that, the conventional technique is sufficient.

As a recording method, in addition to the conventional photochromic reaction (optical isomerization reaction) with a laser in the visible region to the near infrared region, the heat accumulated in the substrate by the photothermal conversion following the heating or the substrate heating or infrared rays (far Infrared rays) are released from the substrate made of the photothermal conversion material to the dye LB film attached to the upper portion, so that the J-aggregates in the irradiated portion are activated by the heat (far infrared rays) to accelerate the decay reaction. That is, the recorded state and the erased state are discriminated by the difference in the absorbance before and after the laser irradiation by the reading light, which corresponds to the recording of the collapsed portion of the J aggregate.

Therefore, in the optical recording method for the optical recording medium of the present invention, the visible light irradiation step is combined with the infrared irradiation step or the heating step.

[0017]

[Function] By using a substrate made of a photothermal conversion material as the base of the dye film, the light energy of the irradiation light that does not contribute to the dye decay reaction is converted into heat (infrared), and the binding force inside the dye and the cohesive force between the dyes are changed. To weaken and further improve the decolorization reaction rate. Further, by using a substrate made of a material having a heat radiation effect (particularly, a far infrared radiation ceramics substrate), a recording sensitivity superior to that of a conventional recording medium relying only on a dye film can be obtained.

Further, by simultaneously irradiating the recording medium with visible light and infrared light, the recording sensitivity is improved. At this time, infrared rays cannot be used alone for recording, but have a function as a catalyst for the photo-bleaching reaction.

[0019]

EXAMPLE The LB method (Langmuir-Blodgett method or monomolecular film accumulation method) is used as a method for producing a dye film for recording.

The samples used in the examples are several types of LB films of cyanine dye J-aggregate already known and spiropyran dye J.
It is an aggregate LB film (The spiropyran dye is known as an organic compound having photochromism, and in particular,
It is known that spiropyran SP1822 synthesized by the research group of Matsushita Electric Co., Ltd. forms a J-aggregate stable on an LB film even at room temperature and can be efficiently destroyed unless it is a visible light laser with high power. ).

The former dye film is formed by adsorbing a chloroform solution prepared by mixing several kinds of cyanine dyes and a special fatty acid at an appropriate mixing ratio on the water surface to form a monomolecular film, which is then attached to a substrate. is there. The latter dye coating is also formed in the same manner by using the spiropyran dye SP1822 represented by the following structural formula (I).
(FIG. 3) and arachidic acid of the following structural formula (III) (FIG. 4) were mixed at a molar ratio of 1: 1 to form a chloroform solution:
It is spread on the water surface and compressed to form a monomolecular film. As a method of transferring to the substrate, a vertical dipping method (LB film manufacturing method) can be used to form a cumulative film. In this case, both dyes and fatty acids are amphipathic organic substances having a hydrophilic group (a) and a hydrophobic group (b).

The structural formula (I) is represented by spirobenzopyran
Spiropyran SP with two long chain alkyl groups
An organic compound named 1822, which is usually colorless.

The structural formula (II) is represented by spiropyran SP18
22 is an ion cleaved by ultraviolet rays and is a colored body called photomerocyanine.

The cluster formed by combining the colored bodies with each other is a J-aggregate.

The arachidic acid of the structural formula (III) is a kind of fatty acid and is an amphipathic organic compound having a hydrophobic long-chain alkyl group and a hydrophilic carbonyl group.

[0026]

[Chemical 1]

[0027]

[Chemical 2]

As a recording substrate, a non-fluorescent glass substrate was prepared by subjecting its surface to a hydrophobic treatment with trimethylchlorosilane, and the above monomolecular film whose molecular orientation was controlled was adsorbed on 20 layers on one side by vertical dipping. (Fig. 2). In the latter spiropyran dye coating, after drying, 1
After irradiation for a minute and heating at about 35 to 40 ° C. for a while, a spiropyran dye J aggregate is formed on the entire surface of the substrate. This J-aggregate has an absorption spectrum as shown in FIG. The former J-aggregates of several types of cyanine dyes also have sharp absorption bands although their absorption peak wavelengths are different. FIG. 5 shows the experimental results of measuring the change in absorption spectrum for each irradiation number by irradiating and destroying this visible light laser in the vicinity of the absorption peak wavelength of the J-aggregate. The irradiation time per irradiation is 1/8 second. The absorption spectrum decreases with each irradiation. Recording can be performed using this change.

The spiropyran J-aggregate has a photochromic property and not only breaks but reforms. On the contrary, the original absorption by the ultraviolet irradiation step, that is, the J-aggregate is recovered to erase the record. You can

Here, the examination results of only recording except erasure are shown below.

1) First, when the reaction rate of the spiropyran dye J-aggregate due to the photodegradation reaction, that is, the substrate temperature dependence of the recording speed was investigated, it was found that the absorption peak wavelength of the J-aggregate was the same as 618 nm, as shown in FIG. When the visible light laser of the excitation wavelength was irradiated with the same irradiation light intensity, the recording speed was increased as the substrate temperature was increased. From this result, it was found that the photolysis reaction rate of the J-aggregate was increased and the recording rate was improved by slightly heating from room temperature. However, it is known that when it reaches 50 ° C., it is thermally broken even without light, so the temperature is raised up to 40 ° C. at most. This temperature of 40 ° C is the temperature of spiropyran SP182.
2 is also the temperature at which the J aggregate is formed. 2) When the entire substrate is heated, it takes time to change the substrate temperature, and it is impossible to control it. Even if it is locally heated, the damage is uneven. difficult. In order to solve this point, the same experiment as in FIG. 5 was performed, and it was attempted to control the temperature of the irradiation part by applying infrared rays at the same time as the recording laser irradiation without heating the substrate. When the laser-irradiated portion was irradiated with infrared rays to raise the temperature of the irradiated portion, it was found that the J-aggregate was broken at a high speed as in the equilibrium state when heated. The results are shown in FIG.

3) A medium was prepared by using a ceramic glass having characteristics as a heat storage material or a heat radiation material, that is, a far infrared radiation ceramics substrate as a heating substrate, and attaching a spiropyran J-aggregate LB film by the vertical dipping method. According to the above methods 1) and 2), strong visible light was applied to take an absorption spectrum. The visible light laser (wavelength 618 nm, intensity 10 W / cm ² ) was used as the excitation light for breaking the J aggregate.
The absorption spectrum was taken every 1/8 second of irradiation time. This is to investigate the far-infrared catalytic effect of photothermal conversion. Next, changes in absorption spectra were also examined when the substrate was heated and when the infrared light was irradiated simultaneously with the visible light laser. In all cases, the decrease in absorbance was further increased, and the recording sensitivity was improved several tens of times. All of these are higher than when using a normal transparent glass substrate.

[0033]

By using a substance having a heat radiation effect (particularly a far-infrared radiation substance) as a material of the transparent substrate sandwiching the recording layer or the substrate underlying the recording film, the dye can be converted by the photothermal conversion and the radiation heat catalytic effect. Disintegration due to a photochemical reaction, especially decolorization due to a photochromic reaction of the J-aggregate was promoted, and the recording sensitivity was further improved.

The combined use of radiant heat and infrared light with light enhances the effect of locally promoting molecular vibrations in the recording area and accelerates the collapse of the molecular associations inside the recording medium, further recording as compared with conventional light alone. Improved sensitivity. Further, it is possible to record with low power light (10 W / cm ² or less, which does not break in a short time by light alone) onto a dye molecule or a molecular association in a room temperature atmosphere.

[Brief description of drawings]

FIG. 1 is an absorption spectrum of a spiropyran dye (SP1822) J aggregate.

FIG. 2 is a sectional view of a recording medium of the present invention.

FIG. 3 is a schematic diagram of a spiropyran dye (SP1822).

FIG. 4 is a schematic diagram of arachidic acid.

FIG. 5 is a diagram showing a change in absorption spectrum by disintegrating a spiropyran dye (SP1822) J aggregate by irradiation with visible light laser.

FIG. 6 is a diagram showing a change in absorption spectrum when a spiropyran dye (SP1822) J aggregate is destroyed by irradiation with visible light laser and infrared irradiation.

FIG. 7 is a diagram showing the substrate temperature dependence of the reaction rate of the spiropyran dye (SP1822) J-aggregate due to the photodegradation reaction.

[Explanation of symbols]

1 Recording medium 2 Substrate 3 Dye coating a Spiropyran dye (SP1822) and arachidic acid hydrophilic part b Spiropyran dye (SP1822) and arachidic acid hydrophobic part c Spiropyran dye (SP1822) light absorbing part

Claims (4)

(57) [Claims] 1. An optical recording medium comprising a substrate on which a dye film containing at least a photochromic dye is formed,
An optical recording medium, wherein the substrate is a ceramic substrate that emits far infrared rays . 2. The at least photochromic dye
Is a molecular aggregate of a dye, which is a spiropyran J aggregate
The optical recording medium according to claim 1, characterized in that. 3. A ceramic substrate for emitting far infrared rays ,
A recording method in the optical recording medium to form a dye-be film containing at least a photochromic dye, a recording method for an optical recording medium which comprises a visible light irradiation step, the substrate heating step. 4. A ceramic substrate for radiating far infrared rays ,
A recording method in the optical recording medium to form a dye-be film containing at least a photochromic dye, a recording method for an optical recording medium which comprises a visible light irradiation step, and an infrared irradiation step.