JP2768567B2 - Optical recording medium - 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, and provides an optical recording medium excellent in recording speed and recording sensitivity by accumulating a compound exhibiting a thermal phase transition with a photochromic compound. is there.

[0002]

2. Description of the Related Art An optical recording medium using a photochromic compound is often added with a compound such as a fatty acid in order to improve film formability and film quality in the process of forming a thin film.

[0003] Photochromic compounds have many advantages such as high resolution and multiple recording properties, but have not yet been applied to optical recording media due to insufficient sensitivity.

When a photochromic material is put to practical use, a high writing speed is required for an optical recording medium. This rate depends on the isomerization rate, isomerization quantum yield, and extinction coefficient of the molecule, and organic molecule synthesis techniques such as molecular design have been actively developed.

[0005]

The compounds such as fatty acids are
It is added to the optical recording medium merely to satisfactorily accumulate the photochromic compound on the substrate, and has no effect on the increase in the recording speed and the recording sensitivity of the medium.

[0006] The increase in recording speed and sensitivity for photochromic compounds has been performed for individual photochromic molecules, but has not been performed for molecular aggregates that are more excellent in recording stability than individual molecules.

[0007]

SUMMARY OF THE INVENTION The present invention provides a medium for writing at high speed and high sensitivity to optical recording utilizing a photochromic reaction. The recording medium is composed of an organic molecule exhibiting photochromism having the following properties (hereinafter, molecule A, molecule B, and molecular aggregate JB) and an organic molecule of lecithin exhibiting thermal phase transition (hereinafter, molecule C).
Is used. The molecule A is isomerized into the molecule B having a molecular aggregate forming ability by the light excitation L1. The molecule B forms a molecular aggregate JB by heating. The molecular aggregate JB returns to the molecule A by the light excitation L2. On the other hand, the molecule C exists in a phase state P1 at a temperature T1. The molecule C is changed from the temperature T1 to the temperature T2 (T1
The phase transition occurs during <T2), and exists in another phase state P2 at the temperature T2. Here, the molecular association JB is at the temperature T1.
Shows no thermal isomerization between to T2. Also this
Such an optical recording medium has a structure in which the hydrophilic group of the organic molecule is provided on the substrate side.
This is realized by arranging them in a matrix.

An optical recording medium in which the molecule C and the molecular association JB are accumulated in the structure shown in FIG.
Both hydrophilic groups are arranged so as to face the substrate side,
The absorption characteristics of the medium due to light irradiation, that is, the change speed, are sharply different between the temperatures T1 and T2.

The present invention provides an optical recording medium having excellent writing speed and sensitivity by inserting and accumulating a monomolecular film of a compound exhibiting a thermal phase transition between monomolecular films of a photochromic compound.

[0010]

The molecular aggregate JB of the optical recording medium OM1 in which the molecule C and the molecular aggregate JB are accumulated alternately exhibits a significantly different decay behavior between the phase states P1 and P2 of the molecule C due to the photoexcitation L2. In the state, many molecules are isomerized compared to the collapse of the molecular association JB of the optical recording medium OM2 in which the molecules C are not accumulated.

Therefore, the optical recording medium in which the molecule C and the molecular association JB are accumulated can perform high-speed and high-speed writing by utilizing the phase state of the molecule C in which many molecules are isomerized. .

[0012]

The present invention will now be described in detail with reference to Examples, but it should not be construed that the present invention is limited thereto.

[0013]

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[0014]

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The JB film used as the recording medium is a mixture of spiropyran and arachidic acid (1: 1) represented by the above formula 1,
A mixture (1: 1) of L-α-phosphatidylcholine, dimyristoyl (hereinafter abbreviated as lecithin) and arachidic acid shown in the above formula 2 is spread on a water surface of pH 7, respectively, and 20 layers are alternately accumulated by a vertical immersion method. It is produced by the following. Organic molecular aggregates (J aggregates) emit 365 nm ultraviolet light for 2
Irradiation for 0 minutes, isomerization to photomerocyanine by a photochromic reaction, and formation by heating at 40 ° C. for 20 minutes.

For comparison with the recording medium, a mixture of spiropyran and arachidic acid represented by the above formula (1)
An LB film was formed by accumulating 10 layers in the same manner as in 1), and a J-aggregate was formed.

The collapse of the J-aggregate was carried out using a dye laser excited by a nitrogen laser having a wavelength of 615 nm, a repetition rate of 10 Hz and a pulse width of 200 ps. By repeating the operation of irradiating a laser to the J-aggregate for a predetermined time and measuring the absorption several times, the time-dependent change of the absorption spectrum in the J-aggregate collapse process was measured, and the reaction rate constant was determined. The change in the absorption spectrum was determined as the change in the integrated value of the absorption curve of the J-aggregate from 590 nm to 700 nm.

FIG. 2 shows the writing temperature characteristics of the recording medium. In the drawing, the white circles indicate the characteristics of the recording medium according to the present embodiment in which spiropyran J aggregates and lecithin are alternately accumulated, and the black circles indicate the conventional medium of spiropyran J aggregates. Shows the characteristics according to Spiropyran J aggregates should be at least 10 ° C to 4 ° C.
Does not show thermal isomerization in the temperature range of 0 ° C. Spiropyran J
The medium in which the aggregates and lecithin were alternately accumulated showed a bending point around 30 ° C., and the inclination was significantly different at temperatures before and after that. On the other hand, the medium of the conventional spiropyran J aggregate did not show a clear inflection point.

FIG. 3 (a) plots the number of reaction rates at a sample temperature of 40 ° C. with respect to the laser energy density of one pulse. In the medium in which spiropyran J aggregates and lecithin were alternately accumulated (open circles in the figure), the disintegration of the J-aggregates was significantly faster than in the conventional medium of spiropyran J aggregates (black circles in the figure). On the other hand, as is clear from FIG. 3 (b), when the sample temperature was 10 ° C., the J-aggregate decay with respect to the laser energy density did not show a large difference in behavior between the two media.

FIG. 4 shows the results of DSC measurement of the lecithin used here. It was found that the lecithin used here caused a phase transition around 25 ° C.

From the above, the optical recording medium of spiropyran J aggregates is obtained by alternately accumulating lecithin.
A remarkable improvement in the writing speed and sensitivity of the recording medium was observed.

[0022]

According to the present invention, Residencial to an optical recording medium using a photochromic reaction, showing the thermal phase transition
By accumulating the Ching alternately, it can be written in the high speed and high sensitivity. At this time, in the present invention, the compound
The hydrophilic group of the daughter film is arranged on the substrate side, and in the temperature range where the photochromic compound monolayer does not show thermal isomerization, the compound monolayer consisting of lecithin that shows a thermal phase transition causes a thermal phase transition Thereby, the rate of the photochromic reaction of the photochromic compound monolayer is controlled by the lecithin monolayer adjacent thereto. Therefore, by performing reading and writing at different temperatures, it is possible to change the phase state of the lecithin monolayer and increase only the speed of the photochromic reaction at the time of writing.

Here, the present invention not only proposes an optical recording medium capable of performing writing at high speed and high sensitivity, but also can be used as a recording medium of a next generation optical associative memory element.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cumulative structure model of an optical recording medium according to the present invention.

FIG. 2 is a write temperature characteristic diagram of an example according to the present invention and a conventional example.

FIG. 3 is a diagram showing the influence of laser irradiation energy on the collapse of organic molecular aggregates in Examples according to the present invention and conventional examples.

FIG. 4 is a diagram showing the results of DSC measurement of lecithin.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-26848 (JP, A) LANGUIR, 6-9! (1990), p. 1451-P. 1454 THIN SOLID FILMS, 178 (1989), p. 103-P. 108 THIN SOLID FILMS, 160 (1988), p. 279-P. 28 DIE MAKROMOLEKULA RE CHEMIE RAPID CO MUNICATIONS, 5-6! (JUNE 1984), p. 327-P. 331

Claims (1)

(57) [Claims] Claims: 1. A photochromic compound monomolecular film comprising:
An optical recording medium obtained by inserting and accumulating a compound monolayer of lecithin exhibiting a thermal phase transition, wherein the hydrophilic groups of these compound monolayers are arranged on the substrate side.
In a temperature range in which the photochromic compound monolayer does not show thermal isomerization, the lecithin monolayer undergoes a thermal phase transition, so that the photochromic compound monolayer adjacent to the lecithin monolayer becomes photochromic. An optical recording medium characterized by controlling a reaction speed.