JP2004273055A - Information holding medium, and information recording method and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-speed optical information recording method, an information holding medium, and system. <P>SOLUTION: Electrode layers 213 and 216 hold both sides of: an information layer 214 which includes a conductive polymer electrochromic material the light absorbance of which changes when the material enters into a polaron state or biopolaron state; and an electrolytic layer 215 which is disposed in contact with the information layer and has the ions to diffuse into the information layer by voltage application. By employing such configuration, the high-speed optical information recording method and a large-capacity information recording medium and system allowing multilayering with a simple configuration are obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an information storage medium for recording and reproducing information using light, an information recording method, and an information recording device.
[0002]
[Prior art]
In the present specification, a medium for recording and reproducing information, such as an optical disk, is referred to as an information holding medium.
[0003]
2. Description of the Related Art Conventionally, there have been DVDs using a phase change film as a recording film, such as a DVD-RAM, and optical disks using an organic material as an information layer, such as a CD-R or a DVD-R. An optical disc using an organic material as an information layer has an information layer containing a dye that absorbs at the wavelength of a recording light source, and performs recording by changing the surface of a substrate in contact with the information layer by laser irradiation.
[0004]
2. Description of the Related Art Conventionally, as described in, for example, Japanese Patent Application Laid-Open No. 63-123202, a field effect type optical disc in which information is recorded on a phase change recording film by irradiating a laser beam while an electric field is applied to the recording film. It has been known. This is used in an element structure in which a phase change information layer such as a GeSbTe system is sandwiched between upper and lower electrodes. By applying an electric field to the recording film, phase change (crystallization) is promoted more than by laser light irradiation alone.
[0005]
Also, Japanese Patent Application Laid-Open No. 5-101454 discloses a WO which shows an optical intercalation effect or an optical deintercalation effect.₃There is described an optical information recording medium in which a semiconductor film made of and an electrolyte film are arranged in contact with each other, and when irradiated with light, ions of the electrolyte film are taken into the optical semiconductor to change to a transparent state.
[Patent Document 1] JP-A-63-123232.
[Patent Document 2] JP-A-5-101454
[Problems to be solved by the invention]
However, in JP-A-5-101454 described above, a liquid electrolyte having a higher response speed than a solid electrolyte is used as an electrolyte membrane. However, as a result of the study by the present inventors, there was a problem that the time required for the transmitted light intensity of the cell to become 70% of the incident light intensity required at least several tens of seconds, and was extremely slow.
[0006]
An object of the present invention is to provide a high-speed optical information recording method, an information holding medium and an apparatus.
[0007]
[Means for Solving the Problems]
The configuration of the present invention for solving the above problems will be described below.
[0008]
The basic structure of the information storage medium of the present invention is a configuration as shown in the sectional structure of FIG. The basic unit is an information layer 1 containing a conductive polymer electrochromic material, an electrolyte layer 2 provided adjacent to the information layer 1 and having ions that diffuse into the information layer 1 by applying a voltage, It has a structure in which both sides of the electrolyte layer 2 are sandwiched between the first electrode 3 and the second electrode 4. A voltage is applied to the electrodes 3 and 4 by a power supply 5.
[0009]
Here, the conductive polymer electrochromic material is a polymer having semiconductor-like conductivity, and a material whose color (absorption spectrum) reversibly changes when a voltage is applied. Examples of the conductive polymer electrochromic material include polyacetylene, polyaniline, polypyrrole, polythiophene, and derivatives thereof, which are conjugated polymers connected by conjugated double bonds or triple bonds. The electrochromism of these conductive polymer electrochromic materials is based on the following principle. Here, polythiophene will be described as an example. FIG. 2 shows an electron resonance structure in the ground state of polythiophene, and two structures, an aromatic structure 8 and a quinoid structure 9, are possible. Among the aromatic type structure 8 and the quinoid type structure 9, the aromatic type structure 8 has lower energy and is not energetically equivalent, so that the ground state of polythiophene is not degenerate. Similarly, polyaniline, polypyrrole, polythiophene, polyphenylenevinylene, and the like other than polythiophene are non-degenerate conductive polymers whose ground state is not degenerated. The electrochromism of a non-degenerate conductive polymer is explained by the following polarons and bipolarons. C. Physical Review B, Vol. 28, No. 4, p. 2140-2145. FIG. 3 shows a change in molecular structure accompanying doping of polythiophene. When the acceptor is doped into the neutral state 12 of polythiophene, first, one-electron oxidation 13 occurs, and the state becomes one-electron oxidation state 14. Here, the acceptor used for doping is Br₂, I₂, Cl₂Halogens such as BF₃, PF₅, AsF₅, SbF₅, SO₃, BF₄ ^―, PF₆ ^―, AsF₆ ^―, SbF₆ ^―Lewis acids such as HNO₃, HCl, H₂SO₄, HClO₄, HF, CF₃SO₃Protic acid such as H, FeCl₃, MoCl₃, WCl₅And organic substances such as tetracyanoethylene (TCNE), 7,7,8,8-tetracyanoquinodimethane (TCNQ). The one-electron oxidation state 14 becomes a positively charged polaron state 16 through a relaxation process 15. According to the Physical and Chemical Dictionary, 5th Edition (1998, Iwanami Shoten), a polaron refers to a state in which conduction electrons in a crystal are moving with a deformation of the crystal lattice around it. In the polaron state, "crystal" is replaced with "neutral state of polythiophene molecule", and "deformation of crystal lattice" is considered as "appearance of partial quinoid structure of polythiophene molecule by one-electron oxidation". If the polythiophene in the polaron state 16 is further doped with an acceptor, the oxidation proceeds further, and a positive bipolaron state 17 is obtained. On the other hand, even by the donor doping, negatively charged polarons and bipolarons are generated by the reduction reaction 18. Here, examples of the donor used for doping include alkali metals such as Li, Na, K, and Cs, and quaternary ammonium ions such as tetraethylammonium and tetrabutylammonium. Both polarons and bipolarons move on polymer chains and contribute to current. In addition to the above dopants, it is also possible to use a polymer electrolyte called a polymer dopant. For example, there are polystyrene sulfonic acid, polyvinyl sulfonic acid, and sulfonated polybutadiene. When polyaniline, polythiophene, and polypyrrole are polymerized in the presence of these polymer electrolytes, the resulting conductive polymer is obtained as an ion complex with the used polymer electrolyte. Use of a polymer dopant is effective for improving processability, such as solubilization of a conductive polymer insoluble in a solvent.
[0010]
The relationship between polarons and bipolarons and electrochromism is illustrated by FIG. 4, in which the electronic state of a non-degenerate conductive polymer is represented by a band structure. Here, changes in the electronic state due to acceptor doping are shown. In the neutral band structure 21 without doping, the difference between the energy at the top of the valence band 22 and the energy at the bottom of the conduction band 23 is a difference in the energy 25 of the electrons, called the forbidden band width 24. As an allowable transition 26, light having an energy corresponding to the forbidden band width 24 is absorbed. When the wavelength of the absorbed light is in the visible light wavelength range, it appears colored. Here, the forbidden band width 24 of the non-degenerate conductive polymer is generally 0.1 eV to 3 eV, similarly to the inorganic semiconductor. In the band structure 27 in the positive polaron state generated as a result of acceptor doping, the polaron level P is located between the valence band 22 and the conduction band 23.⁺28 and polaron level P⁻Twenty-nine polaron levels are generated. The allowable transition 30 in the polaron state differs from the allowable transition 26 in the neutral state in terms of the transition energy width and the transition probability, so that the light absorption characteristics change, and the change in the visible light region changes the color. Observed as a change. In the band structure 31 in the bipolaron state in which doping is further advanced, a new bipolaron level BP is added between the valence band 22 and the conduction band 23.⁺32 and bipolaron level BP⁻Since two bipolaron levels 33 are generated and the allowable transition 34 in the bipolaron state is further changed, the light absorption characteristics are further changed. Similarly, by donor doping of the non-degenerate conductive polymer, a change in the allowable transition behavior due to a change in the band structure accompanying the generation of the polaron level and the bipolaron level is also observed as electrochromism.
[0011]
The band structure of a non-degenerate conductive polymer is completely different from the band structure of an inorganic semiconductor represented by a silicon-based material. FIG. 5 shows an electronic state of the inorganic semiconductor crystal in the vicinity of the lattice constant by a band structure. The upper part of the figure shows that the electron energy 40 is higher. A forbidden band 43 is formed between the lower end of the conduction band 41 and the upper end of the valence band 42, and the energy difference therebetween is a forbidden band width 44.
[0012]
For example, in an N-type semiconductor in which a silicon crystal is doped with P, As, Sb which is a group V atom, one electron in the outermost shell of the group V atom is located at a donor level 45 immediately below the conduction band 41. I do. Since the energy difference between the bottom 46 of the conduction band and the donor level 45 is small, electrons in the donor level 45 easily move to the conduction band 41, and when an electric field is applied to the electrons, the electrons move to the positive potential side, and a current is observed. You.
[0013]
On the other hand, in a P-type semiconductor in which a silicon crystal is doped with boron (B), which is a group III atom, the boron atom replaces the silicon atom, and an acceptor level 47 is formed at an energy level slightly above the valence band 42. The electrons existing in the valence band 42 are easily captured by the acceptor level, and holes, which are traces of the electrons in the valence band 42, move freely in the valence band 42 and are observed as a current.
[0014]
Tungsten oxide, which is a typical inorganic electrochromic material and has the properties of an inorganic semiconductor, is colorless (with intercalation of alkali metal ions such as hydrogen ions or lithium ions into the crystal lattice by voltage application). Or pale yellow) to dark blue reversibly. Such electrochromism of tungsten oxide is due to intervalence transition absorption in a mixed valence state in which hexavalent tungsten atoms are partially reduced to pentavalent, and can be described with reference to FIG. 240 indicates the energy of the electrons. The conduction band of tungsten oxide is constituted by 5d orbitals of tungsten atoms. In the mixed valence state, an intervalence transition 243 from the tungsten atom (pentavalent) energy level 241 to the tungsten atom (hexavalent) energy level 242 occurs, and this transition causes coloring. The electrochromism of molybdenum oxide, iridium oxide, manganese dioxide, nickel oxide, Prussian blue (a divalent and trivalent mixed valence iron cyano complex), etc. is based on the same principle. As described above, the electrochromism of the inorganic electrochromic material is due to the intercalation of ions into the crystal lattice, so that both the coloring speed and the decoloring speed are slow, and it takes one minute or more to switch between the colored state and the decolored state. Cost.
[0015]
Since the electrochromic property accompanying the doping of the non-degenerate conductive polymer is used for recording, the non-degenerate conductive polymer exhibiting electrochromism is particularly referred to herein as “conductive polymer electrochromic material”.
[0016]
In addition, as a result of a publicly known example investigation after the invention was completed, JP-A-11-185288 and JP-A-2002-184056 were found.
[0017]
JP-A-11-185288 describes a medium having an electrochromic layer. The electrochromic layer includes a colored layer made of a substance that causes an electrochemical reaction and an electrolyte layer made of an electrolyte that mediates the electrochemical reaction. Then, the irradiated light is reflected by the colored electrochromic layer. However, Japanese Patent Application Laid-Open No. H11-185288 does not specifically describe what kind of material is used for the electrochromic layer and uses the electrochromic layer as a reflective layer, which is different from the present application.
[0018]
Japanese Patent Application Laid-Open No. 2002-184056 describes a method of utilizing a recording head having electrodes and electrochromism generated only in a portion sandwiched between a recording layer and an electrode layer on the medium side. In JP-A-2002-184056, a Prussian blue film is used as a recording film, which is different from a film using a conductive polymer electrochromic material as in the present application. Japanese Patent Application Laid-Open No. 2002-184056 discloses a method in which a recording head having an electrode on its surface is brought into contact with a recording layer formed on an electrode layer to perform recording. Can not be converted.
[0019]
Here, an optical recording and reproducing method when the information layer is a single layer will be described with reference to FIG.
[0020]
The information layer 1 containing a conductive polymer electrochromic material is provided with an electrolyte layer 2 adjacent thereto, and the ions contained in the electrolyte layer 2 cause the first electrode 3 and the second electrode 3 sandwiching the information layer 1 and the electrolyte layer 2 therebetween. By applying a voltage between the electrodes 4 using a power supply 5, the voltage is diffused into the information layer 1. Diffusion of the ions in the electrolyte layer 2 into the information layer 1 is hereinafter referred to as doping. By the voltage control, the light absorption characteristic of the information layer 1, that is, the color is reversibly changed, and a state having absorption for the recording light 6, that is, a colored state and a state having no absorption, that is, a decolored state, can be arbitrarily selected. it can. In a state where the recording light 6 is absorbed, when the light 6 is irradiated, recording by the generated heat, that is, thermal recording is performed in the irradiated area, and the electrochromic property is reduced. Here, the decrease in electrochromic property means that, although both the colored state and the decolored state can be originally taken, no coloring occurs. When recording is performed, under the constant voltage application condition applied to color the information layer, the light transmittance of the information layer in the colored state before recording is calculated from the light transmittance (percentage%) of the information layer after recording. It is defined that the value obtained by subtracting (percentage%) is 10% or more. Irradiation of the light 6 for recording may be performed from the side of the electrolyte layer 2 in the opposite direction. Recording of information is performed by laser irradiation or laser heating.
[0021]
Once recorded, the area is no longer colored even under the condition that the unrecorded area is colored. Therefore, when reproducing a recording, when a voltage is applied between the first electrode 3 and the second electrode 4 using the power source 5 under the same conditions as those for coloring the information layer 1 before recording, the recording is performed. Since the colored area is not colored, it can be performed by detecting the transmittance and the reflectance of the light 6 for reproduction. Here, the reproduction needs to be performed at a light intensity that does not cause a decrease in the electrochromic property, and is 30% or less of the light intensity required for recording. The voltage between the first electrode 3 and the second electrode 4 required for recording and reproduction is 3 V to 10 V when the first electrode 3 side is positive.
[0022]
The following four recording mechanisms are possible as a recording mechanism in which the electrochromic property is reduced by heat.
a. The rate of change into the polaron state and the bipolaron state due to doping is reduced by cutting of the conjugate portion of the electrochromic conductive polymer in the information layer, conversion from a double bond to a single bond, oxidation, and the like.
b. Due to a curing reaction or a crystallization reaction due to cross-linking or polymerization reaction in the electrolyte layer, the resistance locally increases, making it difficult for the information layer to be reversibly doped.
c. At the interface between the information layer and the electrode layer adjacent thereto, a chemical reaction such as thermosetting occurs, and the resistance value increases.
d. At the interface between the information layer and the electrolyte layer adjacent thereto, a chemical reaction such as thermosetting occurs, and the resistance value increases.
If at least one of the above a to d occurs, recording is possible, but if a plurality occurs at the same time, high sensitivity of recording can be achieved.
[0023]
As the conductive polymer electrochromic material used for the information layer, as shown in FIG. 6, polythiophene 51, polypyrrole 52, polyaniline 54, poly (3,4-ethylenedioxythiophene) 55, poly (3,4-ethylenedioxy) Conductive polymers such as pyrrole) 56 and poly (3,4-ethylenedimethoxythiophene) 57 and their ionic complexes with polystyrene sulfonic acid, polyvinyl sulfonic acid and the like can be used. That is, the conductive polymer electrochromic material contains at least one compound selected from polythiophene and its derivatives, polypyrrole and its derivatives, polyaniline and its derivatives. Here, n in FIG.₁, R₂, R₃And R₄Represents a hydrogen atom, an alkyl group, an alkyl ether group, a carboxyl group, or the like. In the polythiophene 51 and the polypyrrole 52, the substituent R₁Is selected from among alkyl groups such as butyl, hexyl, octyl, and decyl, because it is soluble in organic solvents, it can be used for forming an information layer by casting or spin coating. Suitable. The ionic complex of the conductive polymer and polystyrene sulfonic acid is water-soluble, and is suitable for forming an information layer by casting or spin coating. The information layer can be formed by dissolving a conductive polymer electrochromic material in water or an organic solvent, casting or spin coating, vapor deposition, or electric field polymerization on an electrode using a monomer. The information layer may be laminated on the electrolyte layer formed on the electrode by spin coating or vapor deposition. It is desirable that the information layer has a light transmittance of 90% or more in a decolored state and a light transmittance of 60% or less in a colored state. The thickness of the information layer is desirably 100 nm or less.
[0024]
A liquid electrolyte, a gel electrolyte, and a solid electrolyte can be used for the electrolyte layer. However, liquid electrolytes and gel electrolytes are excellent in conductivity, but have poor mechanical strength, and require a spacer and a sealing mechanism. For this reason, it is difficult to reduce the film thickness and the manufacturing cost is increased. Therefore, a solid electrolyte is preferable. When a liquid electrolyte or a gel electrolyte is used, there is an advantage that the response speed is increased. The solid electrolyte is formed from an ion conductive polymer as a supporting medium and an electrolyte salt as a dopant for the information layer. Examples of the ion conductive polymer used here include poly (methyl methacrylate), polyethylene oxide, polypropylene oxide, a copolymer of ethylene oxide and epichlorohydrin, polycarbonate, and polysiloxane. As the electrolyte salt, lithium perchlorate (LiClO)₄), Lithium triflate (CF₃SO₃Li), lithium hexafluorophosphate (LiPF₆), Lithium tetrafluoroborate (LiBF₄), N-lithiotrifluoromethanesulfonimide (LiN (SO₃CF₃)₂) Can be used. In order to increase the ion conductivity of the electrolyte layer, a plasticizer such as propylene carbonate or ethylene carbonate or a surfactant may be added.
[0025]
The electrolyte layer is formed by dissolving an ion conductive polymer and electrolyte salt in an organic solvent such as acetone, acetonitrile, 2-propanol, diethylene glycol dimethyl ether, methyl ethyl ketone, cyclohexanone, etc., and spin-coating on the electrodes or information layer. After that, the solvent is evaporated. Preferably, the thickness of the electrolyte layer is between 10 nm and 100 nm.
[0026]
ITO (indium tin oxide) and indium oxide (In) are provided on the information layer and the electrode layer sandwiching the adjacent electrolyte layer.₂O₃), Tin oxide (SnO)₂), Metal oxides such as indium zinc oxide (IZO), and metals such as aluminum, gold, silver, copper, palladium, chromium, platinum, and rhodium. When viewed from the direction in which the recording and reproduction light is incident, the electrode layer on the near side is required to have a high light transmittance, and preferably has a light transmittance of 85% or more. Examples of the method for forming the information layer include RF sputtering, reactive sputtering, chemical vapor deposition (CVD), ion plating, vacuum deposition, and oxidation treatment.
[0027]
In FIG. 1, when an uneven structure is formed at the interface between the information layer 1 and the electrolyte layer 2 adjacent to each other, and the thickness ratio is partially changed and sandwiched between the first electrode 63 and the second electrode 64, for example, The structure is as shown in FIG. In such a structure, when a voltage is applied between the first electrode 63 and the second electrode 64, the ions in the electrolyte layer 62 move in the direction of the electric field and in the horizontal direction. Therefore, the coloring density of the information layer 61 depends on the ratio between the thickness of the information layer 61 and the amount of ions in the electrolyte layer 62 as a dopant. If the amount of ions is sufficiently large compared to the amount necessary to color the information layer 61, the thickness of the information layer 61 and the coloring concentration are positively correlated, and if the amount of ions is insufficient, the electrolyte layer 2 There is a negative correlation between thickness and coloring density. Although the electrolyte layer 62 and the information layer 61 are used here, the electrolyte layer 61 and the information layer 62 may be formed in reverse.
[0028]
When a voltage is applied by the power supply 65 to color the information layer, a region having a different light transmittance (coloring density) corresponding to the thickness of the information layer 61 and the thickness of the electrolyte layer 2 is generated. Can be used as an information storage medium for reproduction.
[0029]
As shown in FIG. 8, an information layer 71 is formed in a concave portion of an electrolyte layer 72 having irregularities on one surface, and the information layer 71 is separated by a convex portion of the electrolyte layer 72, and these are separated by a first electrode 73 and a second electrode 73. The structure sandwiched between the electrodes 74 can be used as an information medium for reproduction. Alternatively, a structure in which an electrolyte layer 78 separated by a convex portion of the information layer 77 is formed in a concave portion of the information layer 77 and sandwiched between the first electrode 79 and the second electrode 80 may also be used as an information medium. Can be. In the two types of structures shown in FIG. 8, a portion where both the information layer and the electrolyte layer are sandwiched between a pair of electrodes is colored when a voltage is applied, but a portion where only one of them is not colored is not colored. Information can be reproduced by the reflection at 76.
[0030]
The information storage medium of the present invention is suitable for use in the form of an optical disk, such as a CD-R or DVD-R, having a mechanism for supplying a current to the information layer in a recording / reproducing device. FIG. 9 shows the configuration of the medium at this time. Light is shown as being incident from the top of the figure. From the light incident side 101, the medium is a substrate 97, a protective layer 91, a first electrode layer 92 as a transparent electrode, an electrolyte layer 93, an information layer 94, a second electrode layer 95, an ultraviolet curable resin layer 96, and a lamination. It is composed of a protection substrate 97, 99 corresponds to a groove portion, and 100 corresponds to a land portion.
[0031]
In the present invention, a groove portion in a concave portion of a substrate is called a groove. The land between the grooves is called a land. When light enters the film through the substrate, the groove looks convex when viewed from the incident side. In the case of so-called in-groove recording, in which recording is performed on only one of the land and the groove, when the light is incident from the substrate side or from the opposite side of the substrate, recording on the convex portion when viewed from the light incident side has better recording characteristics. In many cases, it is good, but since there is no large difference, the information may be recorded in the concave portion when viewed from the light incident side.
[0032]
At least one of the first electrode and the second electrode is preferably divided into a plurality of parts. Radially dividing into a plurality of pieces makes it easy to adapt to CAV (constant angular velocity) recording and ZCAV (zoned CAV) recording, and can reduce the interelectrode capacity, thereby improving the response speed.
[0033]
The information storage medium of the present invention is suitable for multilayer recording for improving the recording density. By stacking a plurality of the above unit structures to form a multilayer structure, it is possible to increase the capacity of the medium by improving the recording density. In conventional media, it is desirable to increase the number of layers in order to increase the effective recording density (effective area density). However, for three or more layers, there is a trade-off between the transmittance of each layer and the recording sensitivity. Either sensitivity had to be sacrificed. It is also known to record three-dimensionally on a transparent organic material including the thickness direction, but the recording sensitivity using two-photon absorption is extremely poor, and the storage stability and recording sensitivity using photopolymerization are very poor. Is bad. However, in the present invention, the target information layer has light absorption only at the time of recording / reproducing, so that the information layer other than the target does not hinder the recording / reproducing. Unlike the conventional multi-layer DVD, which does not require a spacer layer as in the conventional multi-layer DVD in which the layer is selected by moving the focal point of the recording or reading laser beam, many layers can be arranged within the focal depth of the focusing lens. Multi-layer disc and multi-layer capacity. For information layers that do not fall within the depth of focus, recording / reproducing may be performed by moving the focal position. In such a case, the pits or grooves representing address information may be deformed when the layers are stacked, but in some cases, a layer in which the pits or grooves are transferred may be provided again, for example, in the middle, so that at least Some layer addresses need to be readable.
[0034]
The lamination may be performed by multi-layering a medium having the same type of structure selected from the structure shown in FIG. 1, the structure shown in FIG. 7, and the two structures shown in FIG. 8, or by combining media having different structures. It is also possible to combine a reproduction medium and a write-once medium.
[0035]
The recording laser power can be set at 0.2 mW or more and 2 mW or less even under the condition that the recording linear velocity is 15 m / s or more when the information holding medium of the present invention is used as an optical disk. By increasing the sensitivity in this way, power is insufficient even in the case of high linear velocity recording and in the case where an array laser or a surface emitting laser is used as a means for simultaneously irradiating light to a plurality of locations on the information storage medium. High transfer speed can be realized without any problem. At least two pairs of voltages may be simultaneously applied to the plurality of electrode pairs of the information storage medium. This is necessary when a material that changes color unless a low sustaining voltage is applied is used.
[0036]
A voltage is applied between many pairs of electrodes using an information storage medium having a plurality of information layers. However, during recording or reading, a voltage different from that between the other electrodes is applied only between the electrodes on both sides of the layer where the information is recorded or read. You may do it.
[0037]
When recording or reading, when moving from one information layer to another information layer, stop the laser irradiation for recording or reading, and then change the voltage applied to the electrodes. Alternatively, decoloring of a layer from which reading was performed and coloring of a layer on which recording or reading is newly performed are performed.
[0038]
For speeding up, only when moving from the near side to the far side when viewed from the recording or reading laser incident direction, recording or reproduction of the near side layer is completed to shorten the waiting time by layer switching. Before the decoloring, the coloring of the back layer may be started.
[0039]
As the device, a plurality of electrodes are arranged in a portion of the rotating shaft of the disk rotating motor or a disk receiving part mounted on the rotating shaft in contact with the center hole of the disk. Means are provided for positioning so as to face each other, and means for bringing the rotating shaft side electrode and the disk side electrode into contact with each other. Thus, a predetermined voltage can be applied to each electrode.
[0040]
At least one circumferential position on the side surface of a rotating shaft of a disk rotating motor or a disk receiving component attached to the rotating shaft, in which a plurality of divided electrodes are added to a portion where the disk is set. , An information recording apparatus characterized in that a projection with a taper in the vertical direction is provided. As a result, it is possible to position the disk in the rotation direction, and to accurately supply power to the multilayered electrode.
[0041]
The present invention is effective when the recording density (track pitch, bit pitch) is higher than the standard of 2.6 GB DVD-RAM, and is particularly effective when the recording density is higher than the standard of 4.7 GB DVD-RAM. . When the wavelength of the light source is not near 660 nm or when the numerical aperture (NA) of the condenser lens is not 0.6, the effect can be obtained at a recording density higher than the recording density calculated in terms of the wavelength ratio and the NA ratio in both the radial and circumferential directions. It is effective and is effective even when a blue-violet laser having an emission wavelength of about 410 nm is used.
[Non-Patent Document 1] Physical Review B, Vol. 4, p. 2140-2145
[Patent Document 3] JP-A-11-185288
[Patent Document 4] JP-A-2002-184056
BEST MODE FOR CARRYING OUT THE INVENTION
<Example 1>
(Structure and manufacturing method)
FIG. 10 is a diagram showing the structure of the disk-shaped information information storage medium according to the first embodiment of the present invention. FIG. 10 shows a structure diagram of a quarter of the disk. There are many radial transparent electrodes in the upper part of FIG. 10 having the same shape so as to fill the disk surface, but only two of them are drawn. The recording / reproducing light enters through the substrate from above, but the uppermost substrate is omitted in the figure. FIG. 11 shows an enlarged view of a part of the disk. Usually, recording / reproducing is often performed on a portion called a groove which is convex when viewed from the light spot, but this embodiment shows a case where recording is performed on a land portion. The cuts in the upper electrode in FIG. 10 correspond to the gaps between the radial electrodes in FIG. The entire A-A 'cross section is as shown in FIG.
[0042]
This medium was manufactured as follows. First, as shown in FIG. 11, a tracking groove for in-groove recording (here, land recording as viewed from a light spot) having a diameter of 12 cm, a thickness of 0.6 mm, a track pitch of 0.74 μm and a depth of 23 nm on the surface is used. (Width 0.35 μm) and (In) on the polycarbonate substrate 136 on which the address is expressed by the groove wobble.₂O₃)₉₀(SnO₂)₁₀A transparent electrode (ITO) 135 (film thickness: 50 nm) having the following composition was formed. The transfer of the groove pattern to the substrate surface was performed using a mother once transferred from a nickel master plated on the photoresist of the master. This is because the grooves exposed on the photoresist correspond to the lands. FIG. 11 shows a process for forming a film on a substrate. This transparent electrode is separated into 20 radial regions corresponding to the recording sectors by being formed by sputtering using a mask.
[0043]
Next, the information layer 134 was formed with an average thickness of 100 nm. The conductive polymer electrochromic material used for the information layer is an aqueous dispersion of poly (3,4-ethylenedioxythiophene) (0.5% by weight) and polyvinylsulfonate (0.8% by weight). Was applied under the conditions of a rotation speed of 3000 rpm for 2 minutes, and then heated on a digital hot plate at 100 ° C. for 5 minutes to remove water.
[0044]
Next, an electrolyte layer 133 was formed to a thickness of 100 nm. A solution of polymethyl methacrylate (number average molecular weight 30,000) (5% by weight), propylene carbonate (15% by weight), and lithium perchlorate (7% by weight) in acetonitrile was rotated by a spin coater at 1,000 rpm for 3 minutes. After coating under the conditions, the mixture was heated on a digital hot plate at 100 ° C. for 5 minutes to remove acetonitrile.
[0045]
On the electrolyte layer 133, W₈₀Ti₂₀A reflective layer / second electrode layer 132 made of a film was formed with a thickness of 50 nm. The formation of the laminated film was performed using a magnetron sputtering apparatus. On the second electrode, a protective layer 131 having a thickness of 0.5 mm was formed using a UV resin. In the figure, reference numeral 139 denotes a land portion 140 and a groove portion.
[0046]
In order to prevent the voltage from being hardly applied to the outer periphery due to the influence of the sheet resistance of the transparent electrode and the formation of the thin portion on the transparent electrode at the corners of the groove irregularities, the transparent electrode is placed on the substrate. Before attachment, as shown in FIG. 10, thin metal (Al) electrodes 118, 119 extending from the inner periphery to the outer periphery having an average width in the radial direction of about 100 μm and a film thickness of 50 nm to 200 nm, which are narrower than the radial transparent electrodes. , One for each radial transparent electrode. This electrode was formed by sputtering the information holding medium with a mask. Recording / reproduction is performed avoiding this electrode portion. In the figure, 110 is a substrate, 111 is a laminated film, 112 and 113 are transparent electrodes, 114 and 115 are extraction electrodes from the transparent electrodes, 116 is a disk center, and 117 is a space between electrodes.
[0047]
In order to perform recording in a state in which the groove looks as seen from the light spot contrary to the present embodiment, the transparent electrode and the reflective layer / electrode may be reversed and light may be incident from the bonded substrate side. In this case, the substrate was formed using a nickel master instead of a mother. In this case, the bonded substrate may be thinned to about 0.1 mm, and the NA of the focusing lens may be increased to 0.85. In this case, the track pitch can be reduced to about ／, that is, about 0.54 μm.
[0048]
When a compound film of an element having a smaller ionic radius than Li, such as SiO2 and GeO2, having a thickness of about 1 to 5 nm is provided between the transparent electrode and the electrochromic material layer, penetration and transmission of Li into the transparent electrode are achieved. This is preferable in that it can suppress However, the applied voltage needs to be several volts higher.
[0049]
The transparent electrode is not divided into a plurality of sector-shaped transparent electrodes, and the entire disk may be one electrode. However, it is preferable to separate the electrodes because the capacitance between the electrodes becomes smaller, so that the voltage rises and falls faster. It is particularly desirable that the inter-electrode capacitance be 0.1 F or less because the time and current required for coloring and decoloring are within the practical range. Good to do. The transparent electrode may not be separated into a plurality of sector electrodes, but may be separated from the metal electrode. Also, the upper and lower electrodes may be separated. In this case, the positions of the cuts between the upper and lower electrodes may coincide, but do not have to coincide.
[0050]
An extraction electrode is provided at the innermost periphery of each of the reflective layer / electrode and the transparent electrode, and the extraction electrode reaches the innermost periphery of the disk. As shown in FIG. In order to connect to each other electrode on the shaft, it is connected to a plurality of electrodes 114 and 115 on the end face of the disc center hole. As shown in FIG. 12, in the portion where the disk is set on the side of the rotating shaft 141 of the disk rotating motor penetrating the disk receiving disk 148, the case of a multilayer disk as described in the second embodiment is used. Six separate electrodes are adhered so that they can correspond to up to five layers (three of the six electrodes are 145, 146, and 147 in the figure), and one point on the circumference of the rotating shaft. In this case, there is a protrusion 150 or a concave portion tapered in the vertical direction, the positioning can be performed by fitting the concave portion or the convex portion at one place of the center hole of the disk, and predetermined electrodes come into contact with each other. Each electrode of the disk rotating shaft is supplied with power from the circuit board of the recording device by a combination of a plurality of brushes and rings 142, 143, 144. Other power supply methods may be used.
[0051]
The recording / reproducing laser light was incident from the substrate side. The last electrode layer to be formed may be a transparent electrode, and laser light may be incident from the transparent electrode side, that is, the bonded substrate side. However, in this case, the recording film thickness was determined so that the reflectance was about 10% and a readout contrast ratio was obtained.
[0052]
(Electrochromic characteristics)
The electrochromic characteristics of the information layer of the information storage medium manufactured as described above were evaluated. FIG. 13 is an absorption spectrum of the information layer in the visible region (wavelength from 500 nm to 700 nm). One minute after starting to apply a voltage between the electrodes at the center of the disk, the measurement was performed in a state where a sufficiently steady state was reached. The direction of voltage application is positive on the electrolyte layer side of the information layer and the electrolyte layer adjacent to each other. In FIG. 13, when a voltage is not applied, almost completely transparent from a wavelength of 550 nm to 700 nm as indicated by a dotted line 151, but when +3.0 V is applied as indicated by a solid line 152, an absorption band having a wavelength of 660 nm as a maximum. Appeared. At this time, the transmittance at a wavelength of 660 nm was 40%.
[0053]
FIG. 14 shows the change over time in the light transmittance of the information layer at a wavelength of 660 nm accompanying the switching of the applied voltage between +3 V and -3 V. This voltage switching was performed every 10 seconds. 153 indicated by a broken line indicates a light transmittance of 60%, which is the minimum coloring density required for recording / reproducing, indicating that the coloring density of the information layer of the manufactured information storage medium is sufficient. The time required to reach the color density required for recording / reading from the decolored state and the time required to return from the colored state to the decolored state were both about 1 second.
[0054]
(Record and playback)
Recording and reproduction of information were performed on the information holding medium. Hereinafter, the operation of the information recording / reproduction will be described with reference to FIG. First, as a motor control method at the time of recording / reproducing, a method adopting a ZCAV (Zone Constant Constant Velocity) system which changes the number of rotations of a disk for each zone where recording / reproducing is performed will be described. In FIG. 15, reference numeral 166 denotes a preamplifier circuit, 167 denotes an L / G servo circuit, 168 denotes a motor, 169 denotes a signal input, and 170 denotes a signal output.
[0055]
Information from the outside of the recording device is transmitted to the 8-16 modulator 161 in units of 8 bits. When recording information on an information storage medium (hereinafter, referred to as an optical disk) 160, recording was performed using a modulation method for converting 8 bits of information into 16 bits, a so-called 8-16 modulation method. In this modulation method, information having a mark length of 3T to 14T corresponding to 8-bit information is recorded on a medium. The 8-16 modulator 161 in the figure performs this modulation. Here, T represents a clock cycle at the time of information recording. The disk was rotated so that the relative speed with respect to the light spot became a linear speed of about 8 m / s.
[0056]
The 3T to 14T digital signal converted by the 8-16 modulator 161 is transferred to the recording waveform generation circuit 162, and a multi-pulse recording waveform is generated.
[0057]
At this time, the power level for forming the recording marks was 5 mW, the intermediate power level at which the recording marks could be erased was 2 mW, and the reduced power level was 0.1 mW. The laser power for forming the recording mark can be reduced by increasing the applied voltage, and good recording was performed in the range of 0.5 mW to 5 mW. Even if the linear velocity was changed from 8 m / s, there was no significant change in this range. Reading was performed at 1 mW without applying a voltage. Practical reading was performed in the range of 0.2 mW or more and 2 mW or less. Reading for a long time at a power exceeding 2 mW deteriorated the recorded data. In the recording waveform generating circuit, signals of 3T to 14T are made to correspond to "0" and "1" alternately in time series. At this time, the region irradiated with the high power level pulse has a reduced electrochromic property and is less likely to be colored. When forming a series of high-power pulse trains for forming a mark portion, the recording waveform generating circuit 162 determines the first pulse width and the last pulse width of the multi-pulse waveform according to the length of the space before and after the mark portion. It has a multi-pulse waveform table that supports the method of changing the pulse width of the tail (adaptive recording waveform control), which enables the multi-pulse recording waveform to minimize the effect of inter-mark thermal interference generated between marks. It has occurred.
[0058]
The recording waveform generated by the recording waveform generating circuit 162 is transferred to the laser driving circuit 163, and the laser driving circuit 163 causes the semiconductor laser in the optical head 164 to emit light based on the recording waveform.
[0059]
A semiconductor laser having a light wavelength of 660 nm is used as a laser beam for information recording in the optical head 164 mounted on the recording apparatus. The laser light was focused on the information layer of the optical disk 160 by an objective lens having a lens NA of 0.65, and information was recorded by irradiating a laser beam.
[0060]
Further, in the case of an information layer using a conductive polymer electrochromic material, the reflectance of the medium is higher in the colored state, and the reflectance in the recorded and uncolored area is lower. During recording by laser beam irradiation, a voltage of 3 volts is continuously applied between the upper and lower electrodes of the information layer.
[0061]
In the information storage medium structure of the present embodiment, the upper and lower electrodes are close to each other only in the groove portion, so that the range in which a high electric field is applied to the recording film is narrow. Therefore, even if the position of the light spot and the degree of condensing are slightly changed, the same recording is performed, which is not only tolerant to the deviation of AF and tracking and has high sensitivity to light, but also suitable for high-speed rotation recording in this aspect. I have.
[0062]
Further, in the information storage medium of this embodiment, a contrast ratio of a light reflectance of about 2: 1 was obtained between the recording mark and the other portions. If the contrast ratio is lower than this, the fluctuation due to the noise of the reproduction signal exceeds 9% of the upper limit value, which falls outside the range of the practical reproduction signal quality. SiO for transparent electrode₂(SiO 2₂)₄₀(In₂O₃)₅₅(SnO₂)₅In this case, the refractive index of the electrode layer is reduced, which is optically advantageous, and the contrast ratio is 2.5: 1.
[0063]
A plurality of light spots can be formed on the same or different recording tracks from a single optical head or from a plurality of optical heads, and recording can be easily performed simultaneously.
[0064]
This recording apparatus is compatible with a method of recording information on a land out of a groove and a land (a variation of the so-called in-groove recording method).
[0065]
Reproduction of the recorded information was also performed using the optical head. A reproduction signal is obtained by irradiating a laser beam onto the recorded mark and detecting reflected light from the mark and a portion other than the mark. The amplitude of the reproduced signal is increased by a preamplifier circuit, and the 8-16 demodulator 165 converts the 16-bit data into 8-bit information. With the above operation, the reproduction of the recorded mark is completed.
[0066]
When mark edge recording is performed under the above conditions, the mark length of the shortest mark 3T mark is about 0.20 μm, and the mark length of the longest mark 14T mark is about 1.96 μm. The recording signal includes dummy data of a repetition of a 4T mark and a 4T space at the start and end of the information signal. The start end also includes VFO.
[0067]
(Mark edge recording)
The DVD-RAM and the DVD-RW employ a mark edge recording method capable of realizing high-density recording. In the mark edge recording, the positions of both ends of the recording mark formed on the recording film correspond to one of the digital data, thereby reducing the length of the shortest recording mark to two or three instead of one reference clock. It is also possible to increase the density in correspondence. The DVD-RAM adopts the 8-16 modulation method, and corresponds to three reference clocks. The mark edge recording method has an advantage that high-density recording can be performed without making the recording mark extremely small as compared with mark position recording in which the center position of the circular recording mark corresponds to 1 of digital data. However, the information storage medium is required to have a small shape distortion of the recording mark.
[0068]
(ZCLV recording method, CAV recording method)
In the case of an information storage medium using a conductive polymer electrochromic material, it is desirable to record at an optimum linear velocity in order to obtain good recording / reproducing characteristics when the recording waveform is not changed. However, when accessing between recording tracks of different radii on a disk, it takes time to change the number of revolutions to make the linear velocity the same. Therefore, in a DVD-RAM, the radial direction of the disk is divided into 24 zones so that the access speed is not reduced, and a constant rotation speed is set in each zone, and the rotation speed is changed only when it is necessary to access another zone. (Constant Linear Velocity) method. In this method, the recording speed is slightly different because the linear velocity is slightly different between the innermost track and the outermost track in the zone, but it is possible to record at almost the maximum density over the entire area of the disk.
[0069]
On the other hand, the CAV recording method in which the rotation speed is constant is preferable in that it is not necessary to change the rotation speed even if a large access is made in the radial direction, and it is suitable for mobile devices because the power consumption when changing the rotation speed can be suppressed. . According to the present invention, a constant heating time can be obtained irrespective of the position in the radial direction, as described above.
[0070]
(Electrode material)
It is important for the electrode material to have an optical property that it has no absorption at the wavelength of the recording laser beam, that is, it is transparent. As a material of the transparent electrode, (In₂O₃) X (SnO₂) A material having a composition of 1-x, wherein x is in the range of 5% to 99%, more preferably a material in which x is in the range of 90% to 98%, and a material having x in the range of 90% to 98%, and SiO₂With SnO, SnO₂2-5% Sb in mole%₂O₃For example, those to which other oxides are added can be used. In addition, SnO doped with fluorine₂Can be used because of its low resistance and high light transmittance. Alternatively, IZO (indium zinc oxide) can be used for an electrode layer because it has an advantage that a film can be formed with less surface irregularities. Since high transparency is not necessarily required for the electrode layer on the back side when viewed from the side where the laser beam enters the information holding medium, metals that are preferable for optical disks can also be used. In the case of Al or Al alloy, the metal layer having high reflectivity and thermal conductivity is a high thermal conductivity material containing 4 atomic% or less of additional elements such as Cr and Ti. Is preferred. Next, elemental elements of Au, Ag, Cu, Ni, Fe, Co, Cr, Ti, Pd, Pt, W, Ta, Mo, Sb, Bi, Dy, Cd, Mn, Mg, V, or an Au alloy, Ag Alloys containing these as main components, such as alloys, Cu alloys, Pd alloys, Pt alloys, Sb—Bi, SUS, Ni—Cr, or layers composed of alloys of these may be used. As described above, the electrode / reflection layer is composed of a metal element, a metalloid element, an alloy thereof, and a mixture. Among them, Cu, Ag, Au alone or a Cu alloy, an Ag alloy, particularly those having an additive element of 8 atomic% or less such as Pd and Cu, and those having a large thermal conductivity such as an Au alloy are those of organic materials. Suppress thermal degradation. Conductive organic materials such as polythiophene derivatives, polypyrrole derivatives, and polyacetylene having no bandgap in the visible region and having a narrow bandgap structure can also be used.
[0071]
(substrate)
In the present embodiment, a polycarbonate substrate having tracking grooves directly on the surface was used. A substrate having a groove for tracking is a substrate having a groove having a depth of λ / 15n (n is the refractive index of the substrate material) or more when the recording / reproducing wavelength is λ on the entire surface or a part of the substrate surface. is there. The groove may be formed continuously in one round or may be divided in the middle. It was found that when the groove depth was about λ / 12n, it was preferable in terms of the balance between tracking and noise. Further, the groove width may be different depending on the location. A substrate having a format in which recording / reproducing can be performed on both the groove and the land, or a substrate having a format in which recording can be performed on either one may be used. In the type in which recording is performed only in the groove, it is preferable that the track pitch is about 0.7 times the wavelength / NA of the focusing lens and the groove width is about 1/2 of that.
[0072]
(Recording laser power)
In the information storage medium of this embodiment, for example, the recording laser power was set to 10 mW under the condition that the recording linear velocity was 8 m / s or more.
[0073]
(Read laser power)
The read laser power was set to 1 mW.
[0074]
When a four-element array laser is used as the laser light source, the data transfer speed can be increased four times.
[0075]
(Conductive polymer electrochromic material)
Recording and reproduction could be performed even when poly (3,4-ethylenedioxypyrrole) or poly (3-hexylpyrrole) was used as the conductive polymer electrochromic material used for the information layer.
[0076]
However, as a conductive polymer electrochromic material, Li⁺The polythiophene and the polythiophene derivative, which are easily susceptible to doping of a donor represented by, and are excellent in stability against oxidation in a neutral state, are more excellent. Information using polythiophene, poly (3,4-propylenedioxythiophene), poly (3,4-dimethoxythiophene), poly (3-hexylthiophene) instead of poly (3,4-ethylenedioxythiophene) In the case of the holding medium, recording and reproduction could be performed similarly.
[0077]
(Material of electrolyte layer)
As a polymer used for the electrolyte layer, instead of poly (methyl methacrylate), an information storage medium using polyethylene oxide, polypropylene oxide, a copolymer of ethylene oxide and epichlorohydrin (70:30), polycarbonate, and polysiloxane. In this case, recording and reproduction could be performed similarly.
[0078]
Even when lithium triflate, lithium hexafluorophosphate, lithium tetrafluoroborate, or N-lithiotrifluoromethanesulfonimide is used instead of lithium perchlorate as an electrolyte salt, recording and reproduction can be performed in the same manner. Was.
[0079]
<Example 2>
This embodiment relates to an information storage medium in which a short-wavelength laser can be used for recording and reading. The structure and manufacturing method of the medium are the same as in the first embodiment.
[0080]
There is a tracking groove (width 0.25 μm) for in-groove recording (here, land recording viewed from the light spot) having a diameter of 12 cm, a thickness of 0.6 mm, and a track pitch of 0.45 μm and a depth of 23 nm on the surface. Then, the SnO is placed on the polycarbonate substrate whose address is expressed by the groove wobbles.₂Was formed (film thickness 30 nm). The transfer of the groove pattern to the substrate surface was performed using a mother once transferred from a nickel master plated on the photoresist of the master. This transparent electrode was formed by sputtering using a mask, and was separated into 20 radial regions corresponding to the recording sectors.
[0081]
Next, an information layer was formed to a thickness of 100 nm. The conductive polymer electrochromic material used for the information layer is an aqueous dispersion of poly (3,4-dimethoxythiophene) (0.5% by weight) and polyvinylsulfonate (0.8% by weight). After coating at 3000 rpm, the solvent was removed by heating at 100 ° C. for 5 minutes on a digital hot plate.
[0082]
Next, an electrolyte layer was formed to a thickness of 100 nm. A cyclohexanone solution of polymethyl methacrylate (number average molecular weight 30,000) (5% by weight), propylene carbonate (15% by weight), and lithium perchlorate (7% by weight) is applied by a spin coater at a rotation speed of 3000 rpm. After that, the mixture was heated at 100 ° C. for 5 minutes on a digital hot plate to remove cyclohexanone. On the electrolyte layer, W₈₀Ti₂₀A reflective layer and a second electrode layer made of a film were formed with a thickness of 50 nm. The formation of the laminated film was performed using a magnetron sputtering apparatus. On the second electrode, a protective layer having a thickness of 0.5 mm was formed using a UV resin.
[0083]
FIG. 16 is an absorption spectrum when a voltage is applied between the first and second pairs of electrodes of the information storage medium of the present example. One minute after the start of voltage application, the measurement was performed in a state where the steady state was sufficiently reached. The direction of voltage application is positive on the electrolyte layer side of the information layer and the electrolyte layer adjacent to each other. In FIG. 16, a dotted line 171 is a spectrum when -1.0 V is applied, and a solid line 172 is a spectrum when +3.0 V is applied. When +3.0 V was applied, an absorption band appeared around a wavelength of 400 nm. Therefore, this medium is suitable for recording using a blue-violet semiconductor laser having a wavelength of 400 nm.
[0084]
In the same manner as in Example 1, recording / reproduction of the produced information storage medium was performed according to the method of FIG.
A semiconductor laser having a light wavelength of 400 nm was used as a laser beam for information recording. The laser beam is focused on the information layer with an objective lens having a lens NA of 0.65, and information is recorded by irradiating a laser beam having an intensity of 6 mW, and then reproduction is performed using a laser beam having an intensity of 0.5 mW. Was completed.
[0085]
Recording / reproducing could also be performed in the case of an information storage medium using poly (3,4-ethoxythiophene) or poly (3-butylthiophene) as the conductive polymer electrochromic material.
[0086]
<Example 3>
This embodiment relates to a multilayer information storage medium and a recording apparatus using the same.
[0087]
FIG. 17 shows the structure near the rotation axis of the recording apparatus of this embodiment, and FIG. 18 shows a block diagram of the recording apparatus control circuit. From the recording device, a voltage and a signal for selecting the layer of the information storage medium are supplied to the three slip rings 182, 183, and 184 of the rotating shaft. The circuit of FIG. 18 including the capacitor is built in the hollow space of the disk receiving part 188, and the wiring to the rightmost layer of the circuit block diagram via the applied voltage switching / control circuit is the electrode 185, 186, 187 of the rotating shaft. It is connected to the. In FIG. 18, 201 is a layer selection signal, 202 is a variable power supply, 203 is a layer selection circuit, 204 is a current controller, 205 is a first layer selection signal, 206 is a second layer selection signal, and 207 is a third layer selection signal. A selection signal 208 is a fourth layer selection signal. In FIG. 17, there are eight electrodes, but the other five are omitted because they are on the surface where the rotation axis is not visible. As a result, a positive voltage is applied to the layer to be colored, and a negative voltage is applied when the color is erased. In FIG. 17, reference numeral 181 denotes a rotating shaft, 185 denotes a first contact electrode, 186 denotes a second contact electrode, 187 denotes a third contact electrode, 189 denotes an insulator, and 190 denotes a positioning projection.
[0088]
The information storage medium has the same basic structure as that of the first embodiment. As shown in FIG. 19, a tracking groove for in-groove recording having a diameter of 12 cm, a thickness of 0.6 mm, a track pitch of 0.74 μm, a depth of 23 nm and a groove width of 0.35 μm on the surface is provided. On a polycarbonate substrate 211 having information as wobble of the groove, SiO₂A first layer 219 was formed in the order of a layer (10 nm) 212, an IZO transparent electrode (30 nm) 213, an information layer (80 nm) 214, an electrolyte layer (80 nm) 215, and an IZO transparent electrode (30 nm) 216. On top of that, ZnS / SiO₂After an insulating layer (100 nm) 217 is formed, a second layer 220, a third layer 221, and a fourth layer 222 are formed in the same manner, and a polycarbonate substrate 218 having a diameter of 120 mm and a thickness of 0.6 mm is bonded thereon. I attached. Light was incident from the side of the bonded substrate.
The materials used for the information layer 214 and the electrolyte layer 215 are the same as in the first embodiment.
[0089]
The recording / reproducing method is the same as in the first embodiment. When a voltage is applied to the transparent electrodes on both sides of the information layer on which recording or reading is to be performed while irradiating a laser beam having a wavelength of 660 nm, only that layer is colored and the laser beam is absorbed and reflected. Information could be recorded and read.
[0090]
Although all of the multilayer films may be within the focal depth of the aperture lens, recording / reproducing is performed on each layer by changing the focal position by interposing a spacer layer having a thickness of 20 to 40 μm every several layers (for example, every three layers). May be. In this case, when using two or more spacer layers, it is better to provide an element for compensating for spherical aberration in the optical system.
[0091]
<Example 4>
This embodiment relates to an information reproduction-only medium. FIG. 20 shows the structure of the medium of this embodiment.
[0092]
After forming an uneven structure representing information with a minimum pit length of 0.4 μm and a depth of 90 nm on the surface of a polycarbonate substrate 230 having a diameter of 12 cm and a thickness of 0.6 mm at the time of injection molding, Ag94Pd4Cu2 having a thickness of 50 nm as a reflective layer was formed. The layer and the ITO transparent electrode (thickness: 50 nm) 231 were formed by a sputtering method. Next, an electrochromic layer 232 was formed by coating. This uneven structure includes read-only (ROM) information. A 1: 1 (molar ratio) composite of poly (3-butylthiophene-2,5-diyl) and polystyrenesulfonic acid was used for the electrochromic layer. Next, an acetonitrile solution of polyethylene oxide (number average molecular weight 30,000) (5% by weight), ethylene carbonate (25% by weight), and lithium perchlorate (3% by weight) was applied using a spin coater, and electrochromic was applied. The electrolyte layer 233 was formed so as to fill the unevenness of the layer 232. After forming an upper ITO transparent electrode (50 nm) 234 thereon, a UV curable resin protective coat was applied, and a polycarbonate substrate 235 having a diameter of 120 mm and a thickness of 0.6 mm was attached. An information reproducing laser beam having a wavelength of 660 nm was made incident from the bonded substrate side. The film thickness of the electrochromic layer and the electrolyte layer at the convex portion of the substrate was 20 to 30 nm. In the substrate recess, the thickness of both layers is large.
[0093]
When a voltage of +5 V is applied between the two ITO transparent electrodes 231 and 234 with the ITO transparent electrode 234 side being positive, the region where the electrolyte layer is present is colored, and information is reproduced by irradiating a laser beam with an intensity of 1 mW. I was able to.
[0094]
In addition, using the same material and the same manufacturing method as the information reproducing medium shown in FIG. 20, an ITO transparent electrode, an electrochromic layer, an electrolyte layer, and a transparent electrode are formed in this order on an uneven substrate, and then UV-cured to a thickness of about 15 nm. Cover the sheet, irradiate ultraviolet rays, place the stamper on top, pass the heating roller, press the stamper, transfer the irregularities representing the information on the surface of the stamper to the sheet surface, then cure, then cure In the same manner as above, formation of the ITO transparent electrode layer by sputtering, application of an electrochromic material layer, application of an electrolyte material, and sputtering of the upper ITO transparent electrode layer were performed. The steps of covering the sheet and thereafter were repeated four times, a protective coat of an ultraviolet curable resin was applied, and then a polycarbonate substrate was bonded, thereby producing a four-layer read-only medium. Layer selection / reproduction was performed using the recording / reproduction device and the control circuit described in Example 3. A spherical aberration compensating element was used for the optical system. The S / N of the reproduction signal of each layer was 46 dB or more, and it was found that a good reproduction signal was obtained.
[0095]
Further, instead of the above-mentioned sheet covering, a liquid UV resin was spin-coated so as to have a thickness of 1 μm, and then UV irradiation was performed thereon to cure the resin, thereby similarly producing a four-layer read-only medium. . Further, without using the sheet covering or the UV resin layer, (1) ITO transparent electrode layer, (2) electrolyte layer coating, (3) pattern transfer, (4) electrochromic material layer coating so as to fill concave portions, Subsequently, (1) to (4) were repeated three more times to produce a four-layer read-only medium. Layer selection / reproduction was performed using the recording / reproduction device and the control circuit described in Example 3. A spherical aberration compensating element was used for the optical system. The S / N of the reproduction signal of each layer was 46 dB or more, and it was found that a good reproduction signal was obtained.
[0096]
【The invention's effect】
According to the above configuration, it is possible to obtain an information storage medium, an optical information recording method, and an apparatus capable of recording at high speed.
[Brief description of the drawings]
FIG. 1 is a diagram showing the structure of an information storage medium according to the present invention.
FIG. 2 is a diagram illustrating a resonance structure of polythiophene, which is a conductive polymer electrochromic material used for the information layer of the information storage medium of the present invention.
FIG. 3 is a diagram showing a change in molecular structure when polythiophene is doped.
FIG. 4 is a diagram showing an electronic state of a non-degenerate conductive polymer by a band structure.
FIG. 5 is a diagram showing an electronic state of an inorganic semiconductor by a band structure.
FIG. 6 is a view showing the chemical structure of a conductive polymer electrochromic material used for the information layer of the information storage medium of the present invention.
FIG. 7 is a diagram showing a structure of an information storage medium according to the embodiment of the present invention.
FIG. 8 is a diagram showing a structure of an information storage medium according to the embodiment of the present invention.
FIG. 9 is a diagram showing a structure of an information storage medium according to the embodiment of the present invention.
FIG. 10 is a diagram showing a structure of an information storage medium according to the embodiment of the present invention.
FIG. 11 is a diagram showing the structure of an information storage medium according to an embodiment of the present invention.
FIG. 12 is a diagram showing electrodes of a disk holder portion for setting an information holding medium according to the embodiment of the present invention.
FIG. 13 is a diagram showing an absorption spectrum of the information layer of the information storage medium in the example of the present invention.
FIG. 14 is a diagram showing a time change of the light transmittance at a wavelength of 660 nm accompanying the switching of the applied voltage of the information layer of the information storage medium in the example of the present invention.
FIG. 15 is a block diagram of an applied voltage control circuit according to the embodiment of the present invention.
FIG. 16 is a diagram showing an absorption spectrum of the information layer in the example of the present invention.
FIG. 17 is a view showing electrodes of a disk holder portion for setting an information holding medium according to the embodiment of the present invention.
FIG. 18 is a block diagram of a circuit for controlling a voltage applied to a medium according to an embodiment of the present invention.
FIG. 19 is a view showing the structure of a four-layer information storage medium according to an embodiment of the present invention.
FIG. 20 is a diagram showing the structure of a read-only medium according to the embodiment of the present invention.
FIG. 21 illustrates an electronic state of a conduction band in a mixed valence state of tungsten oxide.
[Explanation of symbols]
1: Information layer
2: Electrolyte layer
3: First electrode
4: Second electrode
5: Power supply
6: Light
8: Aromatic structure of polythiophene
9: Quinoid structure of polythiophene
12: Molecular structure of neutral state of polythiophene
13: One-electron oxidation reaction by acceptor doping of polythiophene
14: Molecular structure of one-electron oxidation state of polythiophene
15: Relaxation process
16: Polaron state
17: Bipolaron state
18: One-electron reduction reaction by donor doping to polythiophene
19: One-electron oxidation reaction by acceptor doping of polythiophene
20: One-electron reduction reaction by donor doping to polythiophene
21: band structure in neutral state
22: Valence band
23: conduction band
24: Forbidden band width
25: Electron energy
26: Allowable transition
27: Band structure in positive polaron state
28: Polaron level P⁺
29: Polaron level P-
30: Allowable transition in polaron state
31: Band structure in bipolaron state
32: Bipolaron level BP⁺
33: Bipolaron level BP-
34: Allowable transition in bipolaron state
40: Energy of electron
41: conduction band
42: Valence band
43: Forbidden belt
44: Forbidden band width
45: Donor level
46: bottom of conduction band
47: Acceptor level
51: Polythiophene
52: Polypyrrole
54: Polyaniline
55: poly (3,4-ethylenedioxythiophene)
56: Poly (3,4-ethylenedioxypyrrole)
61: Information layer
62: electrolyte layer
63: first electrode
64: second electrode
65: Power supply
66: Light
71: Information layer
72: electrolyte layer
73: first electrode
74: second electrode
75: Power supply
76: Light
77: Information layer
78: Electrolyte layer
79: first electrode
80: second electrode
81: Power supply
91: protective layer
92: first electrode layer
93: Electrolyte layer
94: Information layer
95: second electrode layer
96: UV curable resin layer
97: Lamination protection substrate
98: Substrate
99: Groove part
100: Land section
101: incident laser light
110: bonded substrate
111: laminated film
112: transparent electrode
113: Transparent electrode
114: Extraction electrode from transparent electrode
115: Extraction electrode from transparent electrode
116: Disc center
117: Space between electrodes
118: Thin metal electrode
119: Thin metal electrode
131: protective layer
132: first electrode layer
133: Electrolyte layer
134: Information Layer
135: second electrode layer
136: UV curable resin layer
139: Land section
140: Groove section
141: Rotary axis
142: First slip ring
143: Second slip ring
144: Third slip ring
145: first contact electrode
146: second contact electrode
147: Third contact electrode
148: Disc receiving part
149: Insulator
150: convex for positioning
151: Visible absorption spectrum of information layer at applied voltage of 0 V
152: visible absorption spectrum of the information layer at an applied voltage of +3.0 V
153: Color density required for recording / reproduction
160: Optical disk
161: 8-16 modulator
162: recording waveform generation circuit
163: Laser drive circuit
164: Optical head
165: 8-16 demodulator
166: Preamplifier circuit
167: L / G servo circuit
168: Motor
169: Signal input
170: signal output
171: Visible absorption spectrum of information layer at applied voltage of -1 V
172: visible absorption spectrum of the information layer when the applied voltage is +3 V
181: Rotation axis
182: First slip ring
183: Second slip ring
184: Third slip ring
185: first contact electrode
186: second contact electrode
187: Third contact electrode
188: Disc receiving part
189: Insulator
190: Positioning projection
201: layer selection signal
202: Variable power supply
203: Layer selection circuit
204: current controller
205: signal for selecting the first layer
206: Second layer selection signal
207: Third layer selection signal
208: fourth layer selection signal
211: polycarbonate substrate
212: SiO₂layer
213: IZO transparent electrode
214: Information layer
215: electrolyte layer
216: IZO transparent electrode
217: ZnS · SiO₂Insulating layer
218: polycarbonate substrate
219: First layer
220: second layer
221: Third layer
222: fourth layer
230: polycarbonate substrate
231: ITO electrode layer
232: Electrochromic layer
233: electrolyte layer
234: ITO electrode layer
235: polycarbonate substrate
240: Energy of electron
241: Energy level of tungsten atom (pentavalent)
242: energy level of tungsten atom (hexavalent)
243: transition between valences.

Claims (20)

An information layer including a conductive polymer electrochromic material;
An electrode layer;
And an electrolyte layer containing ions that diffuse into the information layer by applying a voltage to the electrode layer. 2. The information storage medium according to claim 1, wherein the information layer changes its light absorptivity by being in a polaron state or a bipolaron state. The information storage medium according to claim 1, wherein there are a plurality of sets of the information layer, the electrode layer, and the electrolyte layer. 2. The information storage medium according to claim 1, wherein the electrolyte layer is a solid electrolyte. The information storage medium according to claim 4, wherein the solid electrolyte comprises an ion conductive polymer and an electrolyte salt. 2. The information storage medium according to claim 1, wherein the conductive polymer electrochromic material contains at least one compound selected from polythiophene and its derivatives, polypyrrole and its derivatives, polyaniline and its derivatives. The electrode layer, ITO (indium tin oxide), IZO (indium zinc oxide), information storage medium according to claim 1, wherein a is any one of tin oxide SnO _2. The electrode layer is a pair of electrode layers,
The information storage medium according to claim 1, wherein the pair of electrode layers is configured to sandwich the information layer and the electrolyte layer. 9. The information storage medium according to claim 8, wherein there are a plurality of sets of the pair of electrode layers, the information layer, and the electrolyte layer. The surface of the electrolyte layer has an uneven structure,
2. The information storage medium according to claim 1, wherein the thickness of the information layer is thick at a concave portion of the irregularities and thin at a convex portion. The surface of the electrolyte layer has an uneven structure,
2. The information storage medium according to claim 1, wherein the information layer exists in a concave portion of the concave and convex and is separated in a convex portion. The surface of the information layer has an uneven structure,
2. The information storage medium according to claim 1, wherein the thickness of the electrolyte layer is large in the concave portions of the irregularities and thin in the convex portions. The surface of the information layer has an uneven structure,
2. The information storage medium according to claim 1, wherein the electrolyte layer is present in a concave portion of the concave and convex, and is separated in a convex portion. Using an information storage medium having an information layer containing a conductive polymer electrochromic material, an electrode layer, and an electrolyte layer containing ions,
A voltage is applied to the electrode layer to diffuse the ions into the information layer,
Thereafter, information is recorded by irradiating the medium with light. 15. The information recording method according to claim 14, wherein the recording is performed by laser irradiation or laser heating. 15. The information recording is performed by changing the light transmittance of the light-irradiated area so as to be maintained higher than that of the light-irradiated area. Information recording method. The information holding medium has a plurality of sets of the information layer, the electrode layer, and the electrolyte layer,
15. The information recording method according to claim 14, wherein in the recording, light is applied after applying a voltage to a predetermined set of electrode layers of the plurality of sets. 15. The recording of the predetermined set of information layers in a state where the light transmittance of the predetermined set of information layers is smaller than the light transmittance of another set of information layers. Information recording method. An information layer containing a conductive polymer electrochromic material, an electrode layer, and a means for applying a voltage to the electrode layer of an information storage medium having an electrolyte layer containing ions;
A light source that irradiates light to the area to which the voltage is applied,
Means for relatively moving the irradiation position of the light from the light source and the position of the information holding medium,
A means for detecting a reflectance or a transmittance of the irradiated light. 20. The information recording apparatus according to claim 19, further comprising means for intermittently applying the voltage.

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