JPH05266478A - Optical memory element and reproducing method using the same - Google Patents

Abstract

PURPOSE:To obtain an excellent regenerative signal from a bit recorded with high density without degrading the regenerative signal by reading out the finer bit than the beam diameter of a reproduced light beam individually. CONSTITUTION:The reproduced beam 7 controlled so that a central part 9 in an irradiating area has a prescribed light intensity or above irradiates a part between a substrate 1 and a recording layer 3 in the optical memory element 5 though the part is non-transmissible to the reproduced beam 7 as usual. Thus, a masking film 2 is formed which has a characteristic that only the central part 9 shows transmissibility to the reproduced beam 7 and shows non- transmissibility again after the reproduced beams transmits.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the recording of information by light,
The present invention relates to an optical memory device that performs reproduction and erasure and a reproduction method using the same.

[0002]

2. Description of the Related Art In recent years, the need for optical memory devices for recording, reproducing and erasing information by light has been increasing year by year as high density and large capacity memory devices. In response to such demands, magneto-optical disks and phase change disks have been developed. At present, magneto-optical disks are ahead, but since phase change type disks utilize reversible changes between amorphous state and crystalline state by laser light,
One-beam overwriting can be realized without using an external magnetic field at the time of recording / erasing, the material is relatively inexpensive, and the information recorded on the disk can be detected as a change in the amount of reflected light so that the reproduction signal can be increased.
It is advantageous for magneto-optical disks and has recently been receiving attention.

On the other hand, large-capacity and high-density recording on a phase-change type disk has been actively studied, and "Jap. JA.
ppl. Phys. , 28, Supplement28-
3, 141 (1989). ", By using GeSbTeCo-based material, bit length 0.25μm, pitch
It has been reported that high density recording at 0.5 μm can be realized.

In addition to the above-mentioned optical memory device, recently, research and development of a photochromic optical memory device utilizing reversible change between a colored state and a colorless state by light have been actively conducted. The photochromic material generally has a feature that it shifts from a colorless state to a colored state by irradiation with short-wavelength light such as ultraviolet rays, and changes to a colorless state again by irradiation with visible light. Therefore, the photochromic optical memory device is capable of recording with a bit length of 0.4 μm by using light with a short wavelength of, for example, 310 nm, and thus is attracting attention as one of candidates for a high-density recording optical memory device.

[0005]

However, although it is possible to realize high-density recording by using the above-mentioned phase-change type disk or photochromic optical memory element, an effective means for reading out high-density recorded information. Has not been found. For example, when a semiconductor laser beam of 780 nm is focused on a disk by using a lens with an aperture ratio of 0.55, the beam diameter becomes about 1.2 μm. Using such a light beam, as described above, the bit length is 0.25 μm,
When attempting to read out information recorded at a high density with a pitch of 0.5 μm, three marks are included in the beam spot, which causes a problem that the reproduction signal is significantly deteriorated. In addition to narrowing the recording bit,
When the recording track pitch is also reduced to achieve high density recording, the reproduction signal is further degraded.

The present invention has been made in view of the above-mentioned conventional problems, and an optical memory device capable of favorably reproducing information recorded at high density without inferior reproduction signal and an optical memory device therefor. The purpose is to provide the used reproducing method.

[0007]

In order to solve the above-mentioned problems, an optical memory device according to a first aspect of the present invention is provided with a recording layer on a light-transmitting substrate, and records information by light.
In an optical memory device that performs reproduction and erasure, it is usually impermeable to reproduction light, but by irradiating reproduction light controlled so that the central portion of the irradiation region has a predetermined intensity or more, A mask film having a property that only the central portion is transparent to the reproducing light and returns to non-transmissive after passing the reproducing light is formed between the substrate and the recording layer. It has a feature.

The reproducing method according to the invention of claim 2 is
In order to solve the above problems, it is usually non-transmissive to reproducing light, but by irradiating the reproducing light controlled so that the central part of the irradiation region has a predetermined intensity or more, the central part A mask film having a property of transmitting only the reproduction light and returning to the non-transmission after passing the reproduction light is formed between the light-transmitting substrate and the recording layer. When reproducing the information recorded in the optical memory device, the reproducing light is irradiated to the recording layer through the area that is made transparent by the irradiation of the reproducing light, and the reflected light obtained through this area is reproduced. The feature is that it is a signal.

[0009]

According to the structure of the first aspect, when the optical memory element is irradiated with the reproduction light, the mask film which is provided between the substrate and the recording layer and which is normally impermeable to the reproduction light is formed in the irradiation area. Only the central part is transparent to the reproduction light. Therefore, even if the bit length recorded in this optical memory element is smaller than the beam diameter of the reproduction light, the area of the reproduction light that is actually irradiated to the recording layer is the center of the irradiation area where the mask film is transparent. Part only. Accordingly, it is possible to prevent a plurality of bits from being simultaneously irradiated by the reproduction light, and it is possible to provide an optical memory element capable of individually reading the high density recorded bits.

Further, according to the method of claim 2, the recording layer is irradiated with the reproducing light through the region of the mask film whose transmissivity is changed by the irradiation of the reproducing light, and the recording layer is irradiated through the region of the same mask film. Reproduction is performed on the basis of the reflected light thus obtained. Therefore, when reading information recorded with a bit length smaller than the beam diameter of the reproduction light, the recording layer irradiated with the reproduction light by the mask film that is transparent only in the central portion of the irradiation region when the reproduction light is irradiated. Since the area can be adjusted, the high-density recorded bits can be individually reproduced without inferior reproduction signals.

[0011]

【Example】

[Embodiment 1] One embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following.

As shown in FIG. 2, the optical memory device of the present embodiment comprises a substrate (base) 1 made of glass, on which a mask film 2, a recording layer 3 and a reflective film 4 are sequentially formed. There is.

It has been reported that the mask film 2 exhibits reverse photochromism (8th Society of Organic Electronics Materials, 7th page, 1985). Indoline spiropyran is dispersed in a vinyl chloride polymer, for example, The film is formed by a spin coating method. The above-mentioned reverse photochromism is usually a colored state, but when it is irradiated with visible light, it becomes colorless and returns to a colored state by ultraviolet light or heat. This change is reversible. The mask film 2 usually has an absorption peak near 550 nm, and changes to a colorless state by light having a wavelength near this, for example, Ar laser light having a wavelength of 514 nm.

The recording layer 3 is formed by sputtering a GeSbTe-based material film used as a recording layer of a phase-change optical memory device, and is reversible between an amorphous state and a crystalline state by irradiation with laser light. Information is recorded by using dynamic changes. The reflective film 4 is formed of Al as a material.

In the recording layer 3 of the optical memory element 5 having the above structure,
Bit length of 0.3μ using semiconductor laser light of 830 nm
When high density recording is performed by phase change at m and pitch of 0.6 μm, as shown in FIG.
Is recorded as. At this time, the mask film 2 is in a colored state, and its absorption peak wavelength is 550 n as described above.
It is around m.

When this optical memory device 5 is irradiated with Ar laser light of 514 nm near the absorption peak wavelength of the mask film 2 as the reproduction light 7, a decoloring reaction occurs at the peripheral portion 8 of the irradiation region of the reproduction light 7 on the mask film 2. Does not occur, central part 9
Only the state changes to colorless.

This is a polymer binder (in this embodiment,
The photochromic reaction that takes place in a vinyl chloride-based polymer binder requires a certain amount of energy or more, and due to the heat of the irradiation of the reproduction light 7, the coloring reaction also occurs at the peripheral portion 8 of the irradiation region. It is caused by things that happen at the same time. Therefore, as shown in FIGS. 3A and 3B, in the mask film 2, the decoloring reaction occurs only in the central portion 9 of the irradiation region where the laser light intensity is I or more.

Since the range of the central portion 9 where the decoloring reaction occurs depends on the intensity of the reproducing light 7, it is possible to adjust the range of the central portion 9 to the width of the mark 6 by controlling the intensity of the reproducing light 7. it can. Therefore, as shown in FIG. 3B, three marks 6 ... Are included in the beam spot of the reproduction light 7, but the mask film 2 has the central portion 9 of the irradiation region.
However, only the mark 6 on the recording layer 3 is irradiated with the reproduction light 7 because the reproduction light 7 is not transmitted except the central part 9 except the central portion 9. Further, after the reproduction light 7 passes through, the coloring reaction due to the irradiation heat described above occurs, so that the mask film 2 becomes colorless, and the region that is transparent to the reproduction light 7 is immediately changed to the colored state. To do.

When the bits recorded under the above conditions were actually reproduced using Ar laser light of 514 nm, it was confirmed that a good reproduction signal could be obtained.

As described above, the mask film 2 having an inverse photochromism formed between the substrate 1 and the recording layer 3 in the optical memory element 5 does not normally transmit the reproduction light, but by irradiating the reproduction light, Only the central portion of the irradiation area has the property of transmitting the reproduction light, and when the irradiation of the reproduction light is stopped, the state where the reproduction light is not transmitted is quickly returned. Therefore, when the information recorded with the bit length smaller than the beam diameter of the reproduction light 7 is reproduced by using the optical memory element 5 having such a mask film 2, the reproduction signal is not deteriorated and the high density is achieved. It becomes possible to read the recorded bits individually.

[Embodiment 2] Next, another embodiment of the present invention will be described.

The optical memory element of this example has the same structure as the optical memory element 5 of Example 1 except that a diarylethene photochromic material is used as the recording layer. That is, a mask film exhibiting reverse photochromism is formed between the substrate made of glass and the recording layer made of the diarylethene-based photochromic material, as in the first embodiment. The recording layer is
A diarylethene-based photochromic material is dispersed in a polymer binder such as a polycarbonate resin, and this is deposited on a substrate by, for example, spin coating. The diarylethene-based photochromic material changes from a colorless state to a colored state by irradiating short wavelength light such as ultraviolet light, while irradiating with visible light,
It has the property of changing from a colored state to a colorless state.

A dye laser is used for this optical memory element, and the recording layer is near the wavelength at which a photochromic reaction occurs.
Information was recorded at high density by irradiating with light of 10 nm. When the recorded bit was reproduced with Ar laser light of 514 nm, a good reproduction signal could be obtained.

As described above, even when a diarylethene-based photochromic material is used as the recording layer, it is usually impermeable to reproducing light between the substrate and the recording layer, but the central portion of the irradiation region is present. By irradiating the reproduction light controlled so that only the intensity thereof is equal to or higher than a predetermined intensity, a mask film having a property that the central portion thereof is transparent to the reproduction light is formed. Since it is possible to obtain the same effect as, it is possible to satisfactorily reproduce the information recorded at high density with a bit length equal to or smaller than the beam diameter of the reproduction light.

The present invention is not limited to the above-mentioned first and second embodiments, and various modifications can be made within the scope of the present invention. For example, as a substrate of an optical memory device, in addition to the above glass substrate, if it has a light-transmitting property, polycarbonate, PMMA (Polymethyl methacry)
late) or other plastic substrate may be used. Further, as the material for forming the mask film, a photochromic material exhibiting reverse photochromism can be used. Examples of the material exhibiting such a phenomenon include spiropyran compounds,
Examples thereof include polycyclic aromatic compounds.

As a material for forming the recording layer, a material used in a phase change type optical memory, a photochromic material or the like is suitable. In the above Example 1, GeSbTe
The recording layer was formed by the sputtering method using a system material,
It is not limited to this, and for example, InSbTe system,
A film can be formed using a SbTe-based material, an InSe-based material, or a GaSeTe-based material by a vacuum evaporation method, an electron beam evaporation method, or the like. Further, in Example 2, the recording layer was formed by the spin coating method using the diarylethene-based photochromic material dispersed in the polycarbonate resin. Can also be used, and as the polymer binder in which the photochromic material is dispersed, a vinyl chloride resin, an acrylic resin, or the like can be used. The recording layer can also be formed by a roll coater method, a vapor deposition method, or the like.

As the reflective film formed on the recording layer, in addition to Al used in the first and second embodiments, metals such as Au and Ag can be used. Furthermore, it is possible to provide a structure in which a protective film made of an ultraviolet curable resin or the like is provided on the reflective film.

The above-mentioned optical memory device is specifically applicable to, for example, an optical disk, an optical card, an optical tape and the like. still,
When applied to an optical tape, a flexible tape base (base) may be used instead of the glass substrate. Examples of tape base materials include polystyrene terephthalate.

[0029]

According to the optical memory device of the first aspect of the present invention,
As described above, it is usually impermeable to the reproduction light, but by irradiating the reproduction light controlled so that the central portion of the irradiation region has a predetermined intensity or more, only the central portion is reproduced. A mask film having a property of transmitting light and returning to a non-transmissive property after passing the reproducing light is formed between the substrate and the recording layer.

Therefore, even when the bit length recorded in the optical memory element is smaller than the beam diameter of the reproduction light, the reproduction light area actually irradiated to the recording layer is an irradiation area where the mask film is transparent. Only the central part of. As a result, it is possible to prevent a plurality of bits from being simultaneously irradiated by the reproduction light, and it is possible to provide an optical memory element capable of individually reading the high density recorded bits.

The reproducing method according to the invention of claim 2 is
As described above, it is usually impermeable to the reproduction light, but by irradiating the reproduction light controlled so that the central portion of the irradiation region has a predetermined intensity or more, only the central portion is reproduced. A mask film, which has a property of transmitting light and returning to non-transmissivity after passing the reproducing light, is formed on the optical memory element formed between the light-transmitting substrate and the recording layer. When reproducing recorded information, the recording layer is irradiated with reproduction light through an area that is made transparent by irradiation of reproduction light, and reflected light obtained through this area is used as a reproduction signal. It is a thing.

Therefore, when reading information recorded with a bit length smaller than the beam diameter of the reproducing light, the reproducing light is irradiated by the mask film which is transparent only in the central portion of the irradiation region by the irradiation of the reproducing light. Since the area of the recording layer to be recorded can be adjusted, the bits recorded at high density can be individually read, and an excellent reproduction signal can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a state in which an optical memory device in one embodiment of the present invention is irradiated with reproduction light.

FIG. 2 is a sectional view showing a structure of the optical memory device.

FIG. 3A is a graph showing an intensity distribution of reproduction light applied to the optical memory element, and FIG. 3B is a schematic diagram showing a recording layer of the optical memory element.

[Explanation of reference numerals] 1 substrate (base) 2 mask film 3 recording layer 5 optical memory element 7 reproducing light 9 central portion

Claims (2)

[Claims] 1. An optical memory device in which a recording layer is provided on a light-transmissive substrate, and information is recorded, reproduced, and erased by light, which is normally non-transparent to reproduction light, but is irradiated. By irradiating the reproduction light that is controlled so that the central part of the area has a predetermined intensity or more, only the central part is transparent to the reproduction light, and after the reproduction light passes, it is non-transparent again. An optical memory element, wherein a mask film having a property of returning to the above is formed between the substrate and the recording layer. 2. Normally, it is non-transparent to reproducing light,
By irradiating the reproduction light that is controlled so that the central part of the irradiation area has a predetermined intensity or more, only the central part is transparent to the reproduction light, and after the reproduction light passes, it is not transmitted again. When the information recorded in the optical memory element formed between the light-transmitting substrate and the recording layer is reproduced, the mask film having the property of returning to the property causes transmission of light by irradiation of reproduction light. The reproducing method is characterized in that the recording layer is irradiated with reproducing light through the area and the reflected light obtained through this area is used as a reproducing signal.