JP4330129B2 - Optical recording medium, method for manufacturing the optical recording medium, optical recording / reproducing method, and optical information recording / reproducing apparatus - Google Patents

Description

  The present invention relates to an optical recording medium and recording, erasing and reproduction using the same, and more particularly to an optical recording medium capable of high-density recording, a recording method therefor, and a recording apparatus.

In recent years, because of high-quality image recording, an increase in the amount of data used in a computer, and the like, development of a recording technology with a larger capacity has been strongly desired, and various new recording technologies have been studied.
As one of them, optical recording layers containing multiple materials that have different light absorption regions and react optically nonlinearly with recording light irradiation are laminated to exceed the number of types of the materials. There has been proposed an optical recording medium in which optical recording layers containing these materials are laminated so that the distance between the layers is larger than the focal depth of the recording light beam spot (see, for example, Patent Document 1).

  In order to record information on the optical recording medium, the optical recording layer of the optical recording medium is condensed and irradiated with a recording beam light having a wavelength corresponding to the light absorption region of each material. Information is recorded with multiplicity according to the number.

In this optical recording medium, as shown in FIG. 6, the recording layer 10 is constituted by laminating optical recording layers containing three types of optical recording materials A, B, and C, each having a different light absorption region. ing. The optical recording layer 21 containing the material A, the optical recording layer 22 containing the material B, and the optical recording layer 23 containing the material C are repeatedly laminated in this order, and are composed of 13 optical recording layers as a whole. Irradiating light of wavelength lambda _A is the optical recording layer 21 containing the material A, is irradiated with light of wavelength lambda _B in the optical recording layer 22 containing a material B, and the optical recording layer 23 containing a material C is performing recording by irradiating a light of the wavelength lambda _C. In this case, as shown in FIG. 6, since the optical recording layers having different light absorption regions are arranged in the upper and lower layers by recording on one optical recording layer, recording on one optical recording layer is performed. Thus, no crosstalk is caused in the upper and lower optical recording layers.

In other words, this optical recording medium is configured by laminating a plurality of optical recording layers 21, 22, and 23 that have different light absorption regions and respond nonlinearly to the irradiation of absorbed light, and the same kind of optical recording layers. Are stacked so that the interlayer distance becomes larger than the focal depth of the recording beam spot. In such an optical recording medium, an optical recording layer that reacts nonlinearly with the light absorption region is applied. In this case, in order to perform nonlinear recording using a two-photon process, the second type (1 In the case of a material that does not absorb photons and absorbs when two photons come at the same time and transitions from the ground state G to the excited state E ₂ ), as compared with recording by a normal one-photon process, The intensity of light is too strong to compare.

In addition, the first type (non-linearity due to the two-photon process, in which the molecule in the ground state G absorbs the font and is excited to the intermediate state E _1. In the case of a material that exhibits non-linearity if it can absorb another font during the lifetime of E _{1 in} the intermediate excited state, it is further excited and transitions to the excited state E _2. The speed is rather slow, and high-density recording is difficult over time. Further, since the interlayer distance of the optical recording layer is laminated so as to be larger than the focal depth of the recording beam spot, the interlayer distance cannot be further reduced.

Japanese Patent Laid-Open No. 7-114747

  An object of the present invention is to provide an optical recording medium that achieves an improvement in recording density in the depth direction using a normal one-photon process without using a non-linear recording using a two-photon process, and an optical device using the optical recording medium. It is to provide a recording method.

  (1) Composed of a combination of three layers: an optical recording layer using a material exhibiting photochromic properties when heated, a conductive heating layer, and an intermediate layer, and the optical recording layer and the heating layer are adjacent to each other. And an optical recording medium characterized in that the recording layer, the heating layer, and the intermediate layer are each composed of multiple layers.

  (2) The optical recording medium according to (1), wherein heating layers are provided above and below the optical recording layer.

  (3) The optical recording medium according to (1) or (2), wherein a heat insulating material having a low thermal conductivity is used for the intermediate layer.

  (4) Any one of (1) to (3) above, wherein a part of the surface of the heating layer in contact with each optical recording layer having a multilayer structure is exposed so as to be in contact with another member. The optical recording medium described.

  (5) The above-mentioned (4), wherein a metal layer is formed on the surface exposed portion of the heating layer in contact with each optical recording layer having a multilayer structure so that other members can come into contact with the metal layer. Optical recording media.

(6) Using the optical recording medium according to any one of (1) to (5), a plurality of heating layers in contact with the plurality of optical recording layers are simultaneously energized, and simultaneously with the energization, the plurality of optical recording layers are simultaneously energized. in addition to performing recording signals for, when reading the recorded signal is an optical recording which comprises using a confocal detection method in which a pinhole at the position of the focal plane and the confocal in the middle of an optical system for reading Playback method .

( 7 ) An optical information recording / reproducing apparatus using the optical recording / reproducing method described in ( 6 ).

( 8 ) The method for producing an optical recording medium according to (4), wherein the area of the heating layer is changed, and the other optical recording layer and the intermediate layer are laminated with the same surface shape as the heating layer. A method for producing an optical recording medium.

  The optical recording medium according to claim 1 is composed of an optical recording layer using a material exhibiting photochromic characteristics when heated, an electrically conductive heating layer, and an intermediate layer, and the optical recording layer and the heating layer are adjacent to each other. In addition, these layers are configured to be multi-layered (several layers). For this reason, when irradiating recording light, it is possible to heat the optical recording layer by passing an electric current through a heating layer adjacent to the specific optical recording layer, and to make the photochromic characteristics effective only for the specific optical recording layer. Light can be recorded by changing the absorptance and refractive index. For this reason, the distance between the optical recording layers can be reduced, and light can be recorded even at an optical recording interlayer distance equal to or less than the focal depth of the objective lens used in the optical system for optical signal recording.

  The optical recording medium according to claim 2 is characterized in that, in addition to the optical recording medium according to claim 1, heating layers are provided above and below the optical recording layer. For this reason, in addition to the effect of claim 1, in order to improve the heating capability of the specific optical recording layer, the temperature rise is accelerated to enable faster optical recording.

  The optical recording medium of claim 3 is characterized in that in addition to the optical recording medium of claim 1 or 2, a heat insulating material having a low thermal conductivity is used for the intermediate layer. For this reason, in addition to the effect of claim 1, since the thermal conductivity of the intermediate layer is low, the temperature of the optical recording layer can be increased with lower heating power. As a result, the temperature of the optical recording layer can be increased quickly to enable faster optical recording.

  The optical recording medium according to claim 4 is a part of the optical recording medium according to any one of claims 1 to 3 so that the surface of the heating layer in contact with each optical recording layer having a multilayer structure can come into contact with another member. Is exposed to the air. For this reason, in addition to the effect of Claims 1-3, it can be made to contact each heating layer using another member, and it can carry out an electric current only to a specific heating layer easily. I can do it.

  In the optical recording medium of claim 5, in the optical recording medium of claim 4, a metal layer is formed on the surface exposed portion of the heating layer in contact with each optical recording layer having a multilayer structure so that other members can be in contact with each other. It is characterized by that. For this reason, in addition to the effect of claim 4, since the metal layer is formed on the surface exposed portion of each heating layer, the contact resistance of the contact portion can be reduced, and the current flowing through each heating layer can be made smaller. can do.

In an optical recording / reproducing method according to a sixth aspect of the present invention , in the optical recording medium according to any one of the first to fifth aspects, a plurality of heating layers in contact with the plurality of optical recording layers are energized simultaneously, in addition to the recording signal to the recording layer, characterized by using during the reading of the recording signal, a confocal detection method in which a pinhole at the position of the focal plane and the confocal in the middle of an optical system for reading And In the confocal detection method, the resolution below the focal depth of the objective lens is obtained by the effect of the pinhole, so that the signal is read at the optical recording interlayer distance below the focal depth of the objective lens used in the optical system for optical signal recording. Can be done easily.

An optical information recording / reproducing apparatus according to a seventh aspect uses the optical recording / reproducing method according to the sixth aspect. Therefore, according with effects for reading up method in claim 6, it can be configured optical information recording and reproducing apparatus having improved recording density in the depth direction as compared with the prior art.

The manufacturing method of claim 8 is characterized in that in the manufacturing method of the optical recording medium of claim 4, the heating layer is changed in area, and the other layers are stacked in the same surface shape as the heating layer. And For this reason, the structure which exposed the surface of the heating layer of the optical recording medium of Claim 4 can be produced easily.

The present invention is described in further detail below.
FIG. 1 shows the basic structure of the optical recording medium of the present invention. An optical recording layer 3 made of a photochromic material is formed on the intermediate layer 2, and a heating layer 4 made of a transparent conductive material is further formed thereon. Further, the intermediate layer 2 is formed thereon again, and although not shown in FIG. 1, this is repeated so that a multilayer optical recording medium is formed. Here, the laser beam 1 is condensed and applied to the optical recording layer 3 in the optical recording medium. Here, the optical recording layer 3 is made of a material that exhibits photochromic properties as the temperature rises.

  When a current is passed through the heating layer 4 adjacent to the optical recording layer 3, the heating layer 4 generates heat due to electric resistance, and the optical recording layer 3 is also heated at the same time. In this state, when a part of the light of the laser beam 1 is absorbed by the optical recording layer 3, the photochromic material of the optical recording layer 3 undergoes an isomerization reaction, and the absorptance and refractive index change. Thereby, information is recorded on the optical recording layer 3.

  Further, the recording signal is erased by irradiating the optical recording layer 3 in the same manner using a laser light source having a different wavelength, thereby causing an isomerization reaction in the direction opposite to that of the recording, so that the change in the absorptance and the refractive index is based. Return. This makes it possible to delete information.

  Further, when reading a signal, no current is passed through the heating layer 4 and a change in refractive index or a change in absorptance is detected as a change in the amount of returned light with a light power weaker than that during recording.

  For the optical recording layer 3, for example, a diarylethene-based material that exhibits photochromic properties when heat is applied by a photochromic material, and a derivative of 1,2-bis (2-methylbenzo [b] thiophen-3-yl) perfluorocyclopentene In addition, a compound in which carboxyethyl, carboxymethyl, and carboxy groups are attached to the benzothiophene ring, a diheteroallyl perfluorocyclopentene derivative that is a diarylethene-based molecule whose photochromic reaction depends on temperature, and the like can be applied.

For the heating layer 4, a transparent conductive film such as ITO (indium oxide added with tin oxide), zinc oxide, tin oxide, or the like is applicable. The resistivity is about 10 ⁻³ to 10 ⁻⁴ Ωcm. As a preparation method, a low-temperature film formation method such as sputtering, vacuum deposition, or sol-gel method can be considered.

For the intermediate layer 2, a heat insulating material having a conductivity and thermal conductivity of 0.05 to 1.0 W / m · ° C. such as PMMA and polycarbonate can be applied.
In the optical recording medium of the present invention, the surface and the bottom are preferably composed of the intermediate layer 2 as seen in FIG.

  The thickness of each layer is suitably about 0.1 to 5.0 μm for the optical recording layer 3, about 0.1 to 2.0 μm for the heating layer 4, and about 10 to 30 μm for the intermediate layer.

The number of stacked layers is limited by the absorptance of the optical recording layer 3 with respect to the light source wavelength. If the absorption rate is large, the number of stacked layers is small.
The recording light source is not limited to the laser, and other lamps, fluorescent lamps, SHG light sources, and the like can be applied.

  FIG. 2 shows the configuration of the optical recording medium of the present invention. A heating layer 4 made of a transparent conductive material is formed on the intermediate layer 2, an optical recording layer 3 made of a photochromic material is further formed thereon, and a heating layer 4 is also formed thereon. Further, the intermediate layer 2 is formed again thereon, and thereafter, the optical recording medium is formed by being laminated in such a manner that this is repeated. Again, the optical recording layer 3 is made of a material that exhibits photochromic properties as the temperature rises.

  The laser beam 1 is condensed and applied to the optical recording layer 3 in the optical recording medium. Here, when a current is passed through the two heating layers 4 adjacent to the optical recording layer 3, the heating layer 4 generates heat due to electric resistance, and the optical recording layer 3 is also heated at the same time. In this state, when a part of the light of the laser beam 1 is absorbed by the optical recording layer 3, the photochromic material of the optical recording layer 3 undergoes an isomerization reaction, and the absorptance and refractive index change. Thereby, information is recorded on the optical recording layer 3. Further, the recording signal is erased by irradiating the optical recording layer 3 in the same manner using a laser light source having a different wavelength, thereby causing an isomerization reaction in the direction opposite to that of the recording to restore the change in the absorptance and refractive index. . This makes it possible to delete information.

An example of another optical recording medium of the present invention will be described with reference to FIGS.
In the optical recording medium of FIG. 3, a heating layer 4 made of a transparent conductive material is formed on the intermediate layer 2, and further an optical recording layer 3 made of a photochromic material is formed on the heating layer 4. A heating layer 4 is formed. Further, the intermediate layer 2 is formed thereon again. The steps so far are the same as in the above example. However, in this example, the end of the heating layer 4 is stepwise exposed as shown in FIG. 3, and the difference is that the metal layer 7 is further loaded on the surface.

  As shown in FIG. 3, the exposed portion of the heating layer 4 has a structure in which a current is supplied to each heating layer 4 through the metal layer 7 when the conductor 5 contacts the metal layer 7. Further, FIG. 4 shows an overall view of the optical recording medium of this embodiment. The circular optical recording medium 6 has a multilayer structure shown in FIG. In addition, the end 6a of the optical recording medium 6 is made of a conductive material, so that a current is supplied to all the heating layers 4 of the optical recording medium 6. In addition, a large number of ring-shaped heating layers 4 are formed in the center of FIG. 4, and the metal layer 4 has a step structure as shown in the cross-sectional structure in FIG. A current can be individually supplied to the heating layer 4. Further, the metal layer 7 provided on the heating layer 4 is not necessarily required here, and the conductor 5 can be directly in contact with the heating layer 4.

  FIG. 5 is a diagram for explaining the signal reading method from the optical recording medium described so far. The light from the light source 11 passes through the collimating lens 12, the beam splitter 13, and the objective lens 14 and is condensed near the optical recording layer 3 in the optical recording medium 6 having a multilayer structure. Reflected light from the interface between the optical recording layer 3 and the other layer passes through the objective lens 14, and part of the return light passes through the collimator lens 15 by the beam splitter 13, passes through the pinhole 16, and passes through the photo detector 17. Is incident on.

  Here, a change in the amount of reflected light due to a change in the interface refractive index between the optical recording layer 3 and another layer is detected as a recording signal. Due to the effect of the pinhole 16, the resolution in the depth direction of the objective lens 14 is increased, and scattered light and stray light are shielded in the reflected light from the focal portion of the objective lens 14, and the focal point of the objective lens 14 is detected by the photodetector 17. A signal in a portion smaller than the depth can be detected.

  The optical recording medium of the present invention is useful not only in optical storage devices but also in information processing devices, optical file systems, video system storage devices, and the like.

It is a figure showing the basic composition of the optical recording medium of the present invention. It is a figure of the optical recording medium of this invention. It is a figure of the other optical recording medium of this invention. 1 is a perspective view showing an entire optical recording medium of the present invention. It is a figure for demonstrating a mode that recording is performed on the optical recording medium of this invention. It is a figure for demonstrating the conventional optical recording medium.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam 2 Intermediate | middle layer 3 Optical recording layer 4 Heating layer 5 Conductor 6 Optical recording medium 6a End part of optical recording medium 7 Metal layer 11 Light source 12 Collimating lens 13 Beam splitter 14 Objective lens 15 Collimating lens 16 Pinhole 17 Photo detector

Claims (8)

  It consists of a combination of three layers: an optical recording layer that uses a material that exhibits photochromic properties when heated, a heating layer that is conductive, and an intermediate layer, and the optical recording layer and the heating layer are adjacent to each other, and An optical recording medium characterized in that each of the recording layer, the heating layer, and the intermediate layer is composed of multiple layers.   The optical recording medium according to claim 1, wherein heating layers are provided above and below the optical recording layer.   3. The optical recording medium according to claim 1, wherein a heat insulating material having a low thermal conductivity is used for the intermediate layer.   4. The optical recording medium according to claim 1, wherein a part of the surface of the heating layer in contact with each optical recording layer having a multilayer structure is exposed so as to be in contact with another member.   5. The optical recording medium according to claim 4, wherein a metal layer is formed on an upper portion of the exposed surface portion of the heating layer in contact with each optical recording layer having a multilayer structure so that other members can contact the metal layer. . Using the optical recording medium according to any one of claims 1 to 5, a plurality of heating layers in contact with the plurality of optical recording layers are simultaneously energized, and simultaneously with the energization, signal recording is performed on the plurality of optical recording layers. performing it in addition, the optical recording and reproducing method which comprises using a confocal detection method in which a pinhole at the position of the focal plane and the confocal in the middle of the optical system for reading during the reading of the recording signal.   An optical information recording / reproducing apparatus using the optical recording / reproducing method according to claim 6.   5. The method of manufacturing an optical recording medium according to claim 4, wherein the area of the heating layer is changed, and the other optical recording layer and the intermediate layer are laminated in the same surface shape as the heating layer. A method for producing a medium.

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