JPH03220549A - Optical recording medium and recording method thereof - Google Patents

Abstract

PURPOSE:To form the medium which can make various kinds of recording with one kind of photochromic materials by having plural recording layers contg. the photochromic materials and varying the orientation directions of the molecules of the respective recording layers. CONSTITUTION:The medium is formed of a transparent substrate 1, the 1st recording layer 2 and the 2nd recording layer 3. The photochromic materials are incorporated into the layers 2, 3 in such a manner that the orientation directions of the molecules in the layers 2, 3 vary. The layers 2, 3 are irradiated with plural kinds of linearly polarized beams in such a manner that the planes of polarization coincide with the molecular orienting directions of the photochromic materials of the layers 2, 3. The respective photochromic materials generate a large photochemical reaction when the materials are irradiated with the beam having the plane of polarization coinciding with the orienting direction of the molecules thereof and do not generate the photochemical reaction too much when the materials are irradiated with the other beam. The use of the same kind of the photochromic materials for the recording layers is possible in this way.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an optical recording medium in which a recording layer contains a photochromic material and a recording method thereof (particularly related to one capable of recording on a ridge). .

(b) Prior Art Features 1) Research on the use of reflective materials in the recording layer of media is actively underway. Such a medium? When recording, 7
A photochemical reaction occurs in ol-chromic materials. Data is recorded by two steps. in this case,
A recording laser beam is used that has a wavelength range that is absorbed by the photochromic material.

chromic materials used in the recording layer)
(Once determined, 1.1"Ck depending on the material.

The wavelength of the recording laser beam is determined.

When multiplexing data on such a medium, several types of recording layers are stacked so that each layer contains several types of photochromic materials having different absorption wavelengths, and during recording,
A commonly used method is to irradiate several types of laser beams having wavelengths depending on the photochromic material of each layer to cause a photochemical reaction in each layer.

(c) Problems to be solved by the invention However, in such a method, different types of photochromic materials must be prepared as the recording layer, and several types of recording lasers with different wavelengths must be used. must be used. Therefore, the present invention aims to provide an optical recording medium and a recording method thereof, in which the same type of photochromic material can be used for the recording layer and a laser beam of the same wavelength can be used for recording.

(d) Means for Solving the Problems The medium is controlled by disposing a plurality of recording layers on the medium and containing a photochromic material in each recording layer so that the directions of molecular orientation are different from each other.

Further, data is recorded by irradiating such a medium with a linearly polarized beam such that the polarization direction matches each alignment direction.

In yet another recording method, data is recorded by irradiating an optical recording medium containing a photochromic material in the recording layer so that the molecular orientation direction is non-oriented with linearly polarized beams so that the planes of polarization are different from each other. I do.

(E) Function: The smaller the angle between the orientation direction of the molecules and the polarization plane of the beam, the better the photochemical reaction of a photochromic material will occur.

The present invention utilizes this principle for multiplex recording of data.

When a medium is formed by containing a photochromic material in each layer so that the molecular orientation direction in each layer is different, and several types of linearly polarized beams are irradiated so that the plane of polarization matches the molecular orientation direction of the photochromic material in each layer. , each photochromic material causes a large photochemical reaction when irradiated with a beam with a polarization plane that matches the orientation direction of its molecules, and does not cause much photochemical reaction when irradiated with other beams. Therefore, according to this method, even if different types of photochromic materials are used or the wavelength of the laser beam is not changed, it is possible to use the same type of photochromic materials as long as the orientation direction of the molecules in each recording layer is different. In addition, since it is only necessary to change the polarization plane of the beam, there is no need to change the wavelength of the recording laser beam.

In addition, when a photochromic material is contained in a recording layer so that the orientation direction of the molecules is non-oriented, and when this recording layer is irradiated with a linearly polarized beam, the polarization plane and orientation direction of the linearly polarized beam in the photochromic material are changed. Matching molecules often cause a photochemical reaction. Therefore, when such a recording layer is irradiated with several types of linearly polarized beams having different planes of polarization, multiple recording of data can be performed depending on the orientation direction of molecules that cause a photochemical reaction.

(F) Embodiment FIG. 1 is a sectional view of a medium according to a first embodiment of the present invention. In the figure, (1) is a transparent substrate, (2) is a first recording layer, and (3) is a second recording layer. The first and second recording layers (2) and (3) contain the same organic photochromic material, but the molecular orientation directions of each photochromic material are orthogonal to each other.The first recording layer ( 2
) is perpendicular to the plane of the paper, and the direction of molecular alignment of the second recording layer (3) is parallel to the plane of the paper.

When such a medium is irradiated from above with a linearly polarized beam having a plane of polarization parallel to the plane of the paper, only the photochromic material of the second recording layer (3) undergoes a photochemical reaction with this beam. Furthermore, when the medium is irradiated with a linearly polarized beam having a plane of polarization perpendicular to the plane of the paper, only the photochromic material of the first recording layer (2) causes a photochemical reaction. Here, each linearly polarized beam has the same wavelength that can be absorbed by the photochromic material and differs only in the plane of polarization.

Each recording layer (
2) Data is recorded in (3). FIG. 2 shows a cross-sectional view of a medium on which data is recorded. In the figure, the diagonally shaded area is the area where data is recorded. In the medium shown in FIG. 1, for example, B (Langmuir Blodgett) is used to form each of the recording layers (2) and (3).

FIG. 3 shows the configuration of a medium according to a second embodiment of the present invention. In this example, the recording layer (4) is made of -M, and the recording layer (4) contains a photochromic material in a non-oriented state without aligning the molecular orientation. When such a medium is irradiated with a linear optical beam of a wavelength that is absorbed by the photochromic material, the orientation direction of the linearly polarized beam of the photochromic material is -.
・Molecules that react mainly cause photochemical reactions.

Furthermore, when a medium is irradiated with a linearly polarized beam having the same wavelength as this beam but with a plane of polarization perpendicular to it, photochemical reactions occur mainly with molecules in an orientation direction perpendicular to the orientation direction. Sameness of the medium in the beam
When a track is scanned, data with different orientation directions of molecules in which photochemical reactions have occurred are recorded in the same recording layer in multiple ways. Figure 4 shows a side sectional view of a medium on which data has been recorded.

In the figure, the shaded area is the area where data is recorded.

Next, a medium having the configuration of the first embodiment was actually created and an experiment related to recording and reproduction was conducted, so this will be explained.

Quartz was used as the substrate material, and a photochromic material to be contained in the recording layer and a spiropyran type organic material (shown in - in Figure 5) were used. It changes into a merocyanine type, and changes from a merocyanine type to a spiropyran type by being irradiated with i1J visual light or being heated.The film containing such an odochromic material is processed by the L TJ method. Firstly, a first recording layer (2) is formed on the substrate (1) using the same method, and then a film is further disposed on the first recording layer (2) using the same material and the same method. second
A recording layer (3) is formed. However, at this time, the films are formed by the LB method so that the orientation directions of the molecules in each film are orthogonal to each other.

The optical recording medium formed in this way is irradiated with two types of linearly polarized beams independently so that the plane of polarization corresponds to the orientation direction of the molecules in each recording layer (2) and (3), so that the photochromic properties of each layer are Causes a reaction in the material. The beams to be removed are both linearly polarized argon ion laser beams with a wavelength of 360 nm.

Irradiation with such a beam is performed using an optical system shown in FIG. The beam emitted from the argon laser (101) (
! , and is converted into a pulsed-L beam by passing through the pulsed light generating A-0 element (102). The beam is
Furthermore, a wavelength selection filter (103) and a linear polarizer (1
04), it is adjusted to a line-side light beam with a wavelength of 360 nm. The thus adjusted beam is expanded by a beam expander (+05) and then transmitted through a dichroic mirror (106) to obtain a Faraday rotator.
−(107). Faraday rotating element-(1
07) rotates the polarization plane of the linearly polarized beam by being controlled by a control device (not shown). The beam that has passed through the Faraday rotation element f is transferred to the recording layer (2) (3) i of the medium (M) using an object lens (108).
recording on each recording layer.

The recorded data can be erased using a helium neon laser (1
This is done using a visible beam with a wavelength of 633 nm emitted from 09). (110) and (111) are a wavelength selection filter and a linear polarizer that perform the same functions as (103) and (N14) above. The erasing beam is expanded by a beam expander (112), reflected by a dichroic mirror (106), and then focused onto a medium (N1).

(113) and (114) are a converging lens and a photoelectric converter that constitute a light receiving section that receives the beam transmitted through the medium (M).

First, the medium (M) is irradiated with an argon ion laser beam so that the molecular orientation direction of the first recording layer (2) and the plane of polarization are the same. The irradiation power and irradiation time of such a beam are 4 mw and 5 μsec, respectively.

The irradiation time is adjusted by controlling the pulsed light generating A-0 element (102). After that, the same argon ion laser beam was used at a low power (irradiation power I o =0, 2 m) such that no reaction occurred in the photochromic material.
- and measure the absorbance of the medium. Here, the absorbance is the irradiation power of the beam.

When the transmitted power is I, log. It can be calculated by calculating the knee. The transmitted power ■ is the photoelectric converter (14)
Obtained by measuring the output of Such absorbance measurements are performed in several ways based on the rotation angle (θ) of the beam polarization plane with reference to the molecular orientation direction of the first recording layer (2). The rotation angle (θ) of the beam polarization plane is adjusted by controlling the Faraday rotation element (7).

Next, on the medium, the deflection surface is set at θ=90 with respect to the reference.
Recording is performed on the recording layer by irradiating the argon laser beam so that the The beam irradiation power and irradiation time in such recording are 4 mw and 5 μsec as described above. After that, the absorbance is measured in the same manner as above.

Furthermore, recording was performed by independently irradiating two types of argon laser beams to the same location on the same medium so that the deflection plane was at θ = 06 and θ = 90° with respect to the reference (each beam Irradiation power and irradiation time are both 4 mw, FJsec)
, After that, the absorbance is measured in the same manner as above.

After fIi, the absorbance of the non-beam irradiated portion of the medium is measured in the same manner as above.

FIG. 7 shows the results of measuring absorbance in the above experiment. 5
From Figure J1, when recording at θ = O°, absorbance characteristics depending on the photochromic material in the molecular orientation direction of θ = 0° can be seen (as the beam deflection plane approaches the molecular orientation direction of θ = 90°, the beam absorbance increases). Similarly, when recording at θ=90°, absorbance characteristics corresponding to the photochromic material in the molecular orientation direction of θ=0° are observed.

Such a characteristic is that when recording is performed with the polarization plane set to θ = 0°, the photochromic material in the recording layer @1 whose molecular orientation direction coincides with this polarization plane reacts and changes into a merocyanine type. This confirms that when recording was performed with the deflection plane set to θ=90°, the photochromic material in the second recording layer whose molecular orientation direction coincided with this deflection plane reacted and changed into a merocyanine type.

As can be seen from the characteristics in Figure 7, when the rotation angle of the deflection plane of the measurement beam is set to around θ = 30°, when the medium is in an unrecorded state (×), recording is made at θ = 0°. Time (△)
, when recorded at θ=90゛(), θ=0.90
The absorbance of the medium can be clearly distinguished for the four states (b) when both are recorded. Therefore, when data is multiplexed onto a medium as described above, by using a beam of θ=300 as a reproduction beam, each recording layer is Data can be created simultaneously.

Furthermore, the medium shown in FIG. 3 was actually prepared, an experiment similar to the above was conducted, and the absorbance characteristics were measured. The medium was prepared by applying the spiropyran-based photochromic material shown in FIG. 5 after dissolving it in a solvent to form a 1 m thick recording layer in the same manner as described above on the upper surface of a substrate made of quartz glass. still,
In such a case.

When creating the recording layer, the photochromic material was simply coated, so the J photochromic material was not coated. When such a medium was irradiated with two types of beams whose polarization planes were orthogonal to each other in the same manner as above, recording was performed on the recording layer, and then the absorbance characteristics were measured in the same manner as above. Absorbance characteristics similar to those in the above experimental example were obtained. However, in this experiment, the irradiation power of the recording laser beam was 6 mw, which was slightly lower than the 4 mw of the previous experimental example. This is because when the photochromic material is in a non-oriented molecular state, the reaction sensitivity is reduced compared to the previously oriented state.

Therefore, when considering the sensitivity of the recording layer, it is better to make the medium illuminating as shown in FIG. However, in this case, the recording layer must be formed into two layers, and a special method such as the LB method must be used to form the recording layer. It is better to use the configuration shown in

Note that the polarization plane of normal light often refers to the magnetic field oscillation plane, but in this application, it refers to either the magnetic field oscillation plane or the t-field oscillation plane, whichever is effective for photochromic reactions. shall be taken as a thing.

(G) Effects of the Invention As described above, according to the present invention, it is possible to create a medium capable of recording various types of recording using one type of photochromic material, and furthermore, when recording, a beam of one type of wavelength can be used. It is possible to perform multiplex recording.

[Brief explanation of drawings]

The figures relate to embodiments of the present invention; FIGS. 1 and 2 are cross-sectional views of a medium according to the first embodiment, and FIGS. 3 and 4 are cross-sectional views of a medium according to the second embodiment. FIG. 5 is a diagram showing the skeleton of the photochromic material used in both Examples, FIG. 6 is a diagram showing the optical system, and FIG. 7 is a diagram showing the measurement results. (2)...first recording layer, (3)...second recording layer, (4)...recording layer.

Claims (5)

[Claims] (1) An optical recording medium characterized in that it has a plurality of recording layers containing a photochromic material, and the orientation directions of molecules in each recording layer are different from each other. (2) A recording method in which data is recorded by irradiating a beam onto an optical recording medium having a plurality of recording layers containing a photochromic material and in which orientation directions of molecules in each recording layer are different from each other, A recording method for an optical recording medium, characterized in that a linearly polarized beam is irradiated so that the plane of polarization coincides with the molecular orientation direction of each recording layer. (3) The recording layer is 2
The optical recording medium or the recording method thereof according to claim 1 or 2, wherein the optical recording medium is arranged in layers, and the orientation directions of molecules in each layer are orthogonal to each other. (4) A recording method for an optical recording medium, which comprises irradiating a recording layer containing a photochromic material in a non-oriented state with several types of beams with different polarization planes. (5) The method for recording an optical recording medium according to claim (4), wherein the polarization planes of the beams are orthogonal to each other.