JP2890638B2 - Optical recording medium and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium and a method for manufacturing the same.

2. Description of the Related Art Conventionally, a photochromic material has been known as a material that causes a reversible color change. Spiropyran is one of the most studied photochromic materials.

Many spiropyrans have been published to date.
For example, spiropyran (A) shown below changes to merocyanine (B) upon irradiation with ultraviolet light and exhibits a red color. The merocyanine (B) returns to the original spiropyran (A) upon irradiation with visible light.

Such properties of the photochromic material can be applied to an optical recording medium. That is, the photochromic thin film converted into a colored body after or after the thin film is formed can be recorded by being rendered colorless by a visible laser, and can be erased by being colored by an ultraviolet laser.

Problems to be Solved by the Invention Generally, in order to increase the density of an optical recording medium, it is essential to use a semiconductor laser as a light source. However, the conventional photochromic material has no sensitivity in the semiconductor laser oscillation region, or it is difficult to store the colored material for a long period of time because of the low stability of the colored body even with the sensitive material.

An object of the present invention is to provide an optical recording medium using a photochromic material having sensitivity in a semiconductor laser region and good long-term storage properties, and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides an optical recording medium using a photochromic material having the following general formula.

(R ₁ and R _{2 each} represent hydrogen or an alkyl group.) By the above means, an optical recording medium having sensitivity in the semiconductor laser region and stable colored body can be realized.

The above photochromic material has a spiropyran skeleton 5 ′.
A compound having a nitro group at the 1- and 6-positions, an alkyl group at the 1'-position, and an alkanoyloxymethyl group at the 8'-position. An optical recording medium has high stability of a colored body and can be recorded by a semiconductor laser.

Examples Hereinafter, the present invention will be described using specific examples.

Example 1 The photochromic material used in this example was R ₁ = C
Spiropyran of the following structure of ₁₈ H ₃₇ , R ₂ CC ₂₁ H ₄₃ (hereinafter NSP
Called 1822. ), But when R ₁ and R ₂ are hydrogen or an alkyl group, the same properties are exhibited.

NSP1822 / benzene = 10 ^-3 M solution on quartz substrate
Spin coating at 000 rpm to form a recording layer. Next, the photochromic material is changed from a colorless body to a colored body by irradiating ultraviolet rays for 3 minutes, and the recording layer is initialized. The recording layer in the initial state was stable even when left in a dark place for one day, and there was no change in its absorbance, and no change was observed on the film surface by microscopic observation, and the recording layer was stable.

By irradiating the recording layer of this example with a semiconductor laser having a wavelength of 700 nm, the spot portion changed to a colorless body, and recording could be performed. Further, the recording spot could be initialized again by irradiation with ultraviolet rays.

Example 2 A solution having a concentration of NSP1822 / benzene = 10 ⁻³ M was prepared under the following conditions using L
The recording layer was formed by laminating on a quartz substrate hydrophobically treated with trimethylchlorosilane by Method B.

Film forming conditions Sub-phase: phosphate buffer (pH = 6.8, temperature 18.0 ° C) Compression speed: 10 mm / min Cumulative pressure: 20 mN / m Cumulative number of layers: 4 The recording layer formed by the above method was used in the same manner as in Example 1. Initialized by UV irradiation. The recording layer in the initial state had no change in absorbance even when left for one day in a dark place, and was stable with no change observed on the film surface even by microscopic observation. Further, the recording layer of the present example was capable of recording by a semiconductor laser and erasing by irradiation with ultraviolet rays, as in Example 1.

The thickness of this thin film was as extremely thin as 100 mm, and the uniformity was very high.

FIG. 1 shows the absorption spectra of the recording layer thus obtained in the initial state (A) and after recording (B). From Figure 1,
60 existed in the initial state by irradiation of semiconductor laser
It is confirmed that the absorption around 0 nm has disappeared, and that the data has been recorded.

Example 3 NSP1822 / dioctadecyldimethylammonium chloride =
Mix at a 1/1 ratio to make a benzene solution with a concentration of 10 ^-3 M under ultraviolet light. Then, this solution is spin-coated at 1000 rpm on a quartz substrate under ultraviolet irradiation to form a recording layer. Since the recording layer formed by the above method is a colored body from the beginning, it is not necessary to initialize it. Further, the recording layer obtained by using the present configuration and the present manufacturing method is easily irradiated with ultraviolet light in a solution state, so that a colored spiropyran easily forms an aggregate, and the stability of the aggregate is extremely high. Even when left in a dark place at room temperature for several months, there was almost no change in the absorbance.

This recording layer was capable of recording by a semiconductor laser and erasing by ultraviolet irradiation in the same manner as in Example 1. FIG. 2 shows the absorption spectra of the recording film thus obtained in the initial state (A) and after recording (B). From FIG. 2, it can be seen that the embodiment 2
Similarly to the above, it is confirmed that the absorption around 650 nm disappears by the irradiation of the semiconductor laser, and that the recording is performed.

In this example, dioctadecyldimethylammonium salt (18 carbon atoms) was used as the surfactant.
Other surfactants having different carbon numbers have the same recording characteristics. An ammonium salt is most preferable for forming an aggregate, but other surfactants such as phospholipids can obtain almost the same stability.

Example 4 In Examples 1 to 3 above, spiropyran having a substituent of R1 as an octadecyl group and a substituent of R2 as a heneicosyl group was used. showed that. Spiropyran in which R2 has a methyl group also exhibited similar properties.

 Table 1 shows the absorption maximum wavelength of each colored body.

According to the present invention, unlike a recording medium using a conventional photochromic material, because it has an absorption maximum in a long wavelength region,
Recording by a semiconductor laser became possible, and an optical recording medium having high storage stability was provided.

[Brief description of the drawings]

FIG. 1 is an initial state and a visible absorption spectrum after recording in Example 2 of the present invention, and FIG. 2 is an initial state and a visible absorption spectrum after recording in Example 3 of the present invention.

Claims (6)

(57) [Claims] 1. An optical recording medium wherein the recording layer comprises a photochromic material having the following general formula. (R ₁ and R ₂ each represent an alkyl group having 1 to 30 carbon atoms.) 2. The optical recording medium according to claim 1, wherein the recording layer comprises an association of a colored body of a photochromic material. 3. The optical recording medium according to claim 1, wherein the recording layer comprises an LB film of a photochromic material. 4. The optical recording medium according to claim 1, wherein the recording layer comprises a surfactant having at least one long-chain hydrocarbon group and a photochromic material. 5. The optical recording medium according to claim 4, wherein the surfactant has the following structural formula. (R ₁ = alkyl group _{R 2 = C 1 ~C 30,} R 3 = R 4 = methyl,
X represents a halogen group. ) 6. A method for manufacturing an optical recording medium, wherein at least one of a solution preparation step and a film formation step of a photochromic material having the following general formula is performed under irradiation of ultraviolet light. (R ₁ and R ₂ each represent an alkyl group having 1 to 30 carbon atoms.)