JPH04370599A - Optical recording medium - Google Patents

Abstract

PURPOSE:To write with a high speed and a high sensitivity by alternately accumulating compounds which show a thermal phase transition against an optical recording medium utilizing a photochromic reaction. CONSTITUTION:The recording medium consists of organic molecules A and B which show photochromism, molecular association body JB and an organic molecule C which shows a thermal phase transition. The molecule A undergoes isomerization to a molecule B which has a molecular association body configuration capability by a light excitation L1 and the molecule B configures molecular joint body JB by heating. Furthermore, the molecular association body JB goes back to the molecule A by a light excitation L2. On the other hand, the molecule C exists in a phase condition P1 at a temperature T1 and the molecule C performs a phase transition between the temperature T1 to a temperature T2 (where T1<T2) and it exists in a different phase condition P2 in the temperature T2. Using this LB membrane as the recording medium, one to one mixture of spiropyran and arachic acid (being called spiropyran) and one to one mixture of L-alpha-phosphatidylcholine and dimyristoyl (being called lecithin) are alternately laminated to make a twenty layer laminate. Thus, a high speed and high sensitive writing is realized.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an optical recording medium, and provides an optical recording medium with excellent recording speed and recording sensitivity by accumulating a photochromic compound and a compound exhibiting a thermal phase transition. be.

0002

2. Description of the Related Art In optical recording media using photochromic compounds, compounds such as fatty acids are often added in order to improve film formability and film quality during the thin film manufacturing process.

Although photochromic compounds have many advantages such as high resolution and multi-recordability, they have not yet been applied to optical recording media because of insufficient sensitivity.

[0004] When putting photochromic materials into practical use, a high writing speed is required for optical recording media. 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 are being actively developed.

[0005]

[Problem to be solved by the invention] Compounds such as fatty acids are
It is added to the optical recording medium simply to satisfactorily accumulate the photochromic compound on the substrate, and does not have any effect on increasing the recording speed and recording sensitivity of the medium.

Although improvements in the recording speed and sensitivity of photochromic compounds have been made for individual photochromic molecules, no efforts have been made for molecular aggregates, which have better recording stability than individual molecules.

[0007]

SUMMARY OF THE INVENTION The present invention provides a medium for optical recording that utilizes photochromic reactions and allows writing at high speed and sensitivity. The recording medium uses organic molecules exhibiting photochromism (hereinafter referred to as molecule A, molecule B, and molecular association JB) and organic molecules exhibiting thermal phase transition (hereinafter referred to as molecule C) having the following characteristics. Molecule A is isomerized into molecule B having the ability to form molecular aggregates by photoexcitation L1. Molecule B becomes molecular association JB by heating
form. Molecular association JB becomes molecule A by photoexcitation L2
Return to On the other hand, molecule C exists in a certain phase state P1 at temperature T1. Molecule C changes from temperature T1 to temperature T2 (T1<T2
), and at temperature T2, a different phase state P2 occurs.
exists in

In an optical recording medium in which molecules C and molecular aggregates JB are accumulated in the structure shown in FIG. 1, the absorption characteristics of the medium due to light irradiation, that is, the rate of change, differ sharply between temperatures T1 and T2.

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

0010

[Operation] The molecular association JB of the optical recording medium OM1, in which molecules C and molecular associations JB are alternately accumulated, exhibits significantly different decay behavior in the phase states P1 and P2 of the molecule C due to optical excitation L2, and the phase state with the molecule C In this state, compared to the collapse of the molecular association JB of the optical recording medium OM2 in which molecules C are not accumulated, many molecules C are isomerized.

[0011] Therefore, an 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 of the molecules are isomerized. .

0012

[Examples] Examples of the present invention will be described in detail below, but the present invention is not limited thereto.

[0013]

[Chemical formula 1]

[0014]

[Case 2]

The JB film used as a recording medium is a mixture of spiropyran and arachidic acid (1:1) shown in 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 the water surface of pH 7, and 20 layers are accumulated alternately by vertical immersion method. It is prepared by Organic molecular associations (J-aggregates) absorb 365 nm ultraviolet light at 2
After irradiating for 0 minutes and isomerizing to photomerocyanine by photochromic reaction, it is formed by heating at 40° C. for 20 minutes.

In addition, for comparison with the above recording medium, a mixture of spiropyran and arachidic acid (1:
An LB film was prepared by stacking 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 with a wavelength of 615 nm, a repetition rate of 10 Hz, and a pulse width of 200 ps. By repeating the operation of irradiating the J-aggregate with a laser for a predetermined period of time and measuring its absorption several times, the change in the absorption spectrum over time during the J-aggregate disintegration process was measured, and the reaction rate constant was determined. The amount of change in the absorption spectrum was determined as the amount of change in the integral 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 figure, white circles indicate the characteristics of the recording medium according to this embodiment in which spiropyran J aggregates and lecithin were alternately accumulated, and black circles indicate the characteristics of the conventional medium of spiropyran J aggregates. shows the characteristics according to The spiropyran J aggregate is at least 10°C to 40°C.
It does not exhibit thermal isomerization in the temperature range of . The medium in which spiropyran J aggregates and lecithin were alternately accumulated showed a bending point around 30°C, and the slope differed greatly at temperatures before and after that point. On the other hand, the conventional spiropyran J aggregate medium did not show a clear inflection point.

FIG. 3(a) shows the reaction rate number plotted against the laser energy density of one pulse at a sample temperature of 40°C. In the medium in which spiropyran J-aggregates and lecithin were alternately accumulated (white circles in the figure), the J-aggregates disintegrated 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., there was no significant difference in the behavior of the J-aggregate collapse with respect to the laser energy density between the two media.

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

[0021] From the above, the optical recording medium of the spiropyran J aggregate can be obtained by alternately accumulating lecithin.
A significant improvement in the writing speed and sensitivity of the recording medium was observed.

[0022]

According to the present invention, writing can be performed at high speed and sensitivity on an optical recording medium that utilizes a photochromic reaction by alternately accumulating compounds that exhibit a thermal phase transition.

The present invention not only proposes an optical recording medium on which writing can be performed at high speed and sensitivity, but also can be used as a recording medium for next-generation optical content addressable memory elements.

[Brief explanation of the drawing]

FIG. 1 is a cumulative structural model diagram of an optical recording medium of the present invention.

FIG. 2 is a diagram of write temperature characteristics of an embodiment 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 molecule aggregates in an example according to the present invention and a conventional example.

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

Claims (1)

[Claims] 1. An optical recording medium characterized in that a monomolecular film of a compound exhibiting thermal phase transition is inserted and accumulated between monomolecular films of photochromic compounds.