JPH05303767A - Reloadable optical recording medium and information recording method and erasing method - Google Patents

Abstract

PURPOSE:To obtain the reloadable optical recording medium which can stably and surely reproduce tracking information. CONSTITUTION:A thin layer 3 of a hard material having the refractive index higher than the refractive index of a transparent substrate 1 having guide grooves 2 is provided on the surface of the substrate 1 and a recording layer 4 consisting of single layer constitution constituted by incorporating a light absorbent into a thermosetting polyurethane resin, the modulus of elasticity of which degrades at the temp. higher than the temp. range of room temp. is provided on the thin layer 3. The recording light entering from the substrate 1 side is passed through the recording layer 4 so that recording bits in the state of build-up parts are easily generated on the side opposite from the substrate 1 by the thermal expansion of the recording layer. The thickness of the thin layer 3 provided on the surface of the substrate 1 does not change regardless of the presence or absence of the recording bits and, therefore, the thin layer is helpful for generating the reflected light including the always good tracking information. The recording layer is heated by irradiation with continuous light from the substrate side 1 and is slowly cooled, by the recording layer is flattened and the erasing of the recording information is well executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable optical recording medium, an information recording method and an information erasing method.

[0002]

2. Description of the Related Art As the demand for recording various information signals at a high recording density has increased, information signals have recently been formed using information recording media made on the basis of various constitutional principles and operation principles. High-density recording / reproducing has become possible. For example, an unevenness corresponding to the information signal is formed on the signal surface of the information recording medium to record the information signal, and the recorded information signal is reproduced by an optical means. The recording / reproducing apparatus thus configured has already been widely used for recording / reproducing video signals and audio signals. In order to meet the demands for high-density recording / reproducing in various technical fields, the recording layer of the information recording medium is irradiated with a beam whose intensity is modulated by the information signal, so that the recording layer of the information recording medium responds to the information signal. Research has also been conducted on an information recording medium in which an information signal is recorded by causing a physical change or a chemical change, but in recent years, it has become easier to obtain a semiconductor laser that operates stably. As a result, various types of optical recording media designed for high-density recording and reproduction using laser light have already been put to practical use, or are being researched and developed for practical use. Is well known.

That is, the above-mentioned optical recording medium capable of recording and reproducing in a non-contact state has the advantages that, as is well known, it is resistant to scratches and dust and that a high storage capacity can be obtained by high-density recording. Therefore, in addition to being used as a file memory for offices, large-capacity files for computers, and the like, research on rewritable optical recording media has been actively conducted. Among various conventionally proposed rewritable optical recording media, for example, Japanese Patent Laid-Open No. 60-69846 has a double layer of an elastomer containing an organic dye and a thermosetting / plasticizing resin. It is configured, on the expansion layer containing a dye having the property of absorbing light near the wavelength λ1,
It has a structure in which a holding layer containing a dye having the property of absorbing light near the wavelength λ2 is laminated, and the recording layer is irradiated with light of the wavelength λ1 to heat the expansion layer to thermally expand the expansion layer. By raising the holding layer corresponding to the thermally expanded portion in, to record information by using the raised portion of the holding layer as a recording bit, the holding layer is irradiated with light of wavelength λ2 to heat the holding layer. A rewritable optical recording medium is disclosed in which by softening it, the raised state of the holding layer is flattened by the residual stress stored in the expansion layer to erase the recording bit.

Further, for example, JP-A-63-16404.
In Japanese Patent Laid-Open No. 2 (1994), a guide groove for generating information for tracking control is provided on a substrate, and a compression layer made of a soft and highly elastic silicon resin having a refractive index that is significantly different from that of the substrate is bonded to the substrate, Disclosed is a rewritable optical recording medium having a structure in which a holding layer made of a polymer material dyed on a compression layer and an expansion layer made of a polymer material dyed so as to show optical characteristics different from those of the holding layer are laminated. In this optical recording medium, the expansion layer is heated by a writing laser beam having a wavelength of λ1, and when the expansion layer thermally expands, a holding layer corresponding to the thermally expanded portion of the expansion layer is formed on the substrate. The compression layer made of soft, highly elastic silicon resin that is adhered is raised in a manner that it is compressed, and the raised portion of the holding layer is used as a recording bit to record information. By softening it by heating the retention layer by irradiating, and so as to erase the recorded bits by flattening the raised state of the retention layer by the residual stress accumulated in the expansion layer.

Further, for example, Japanese Patent Laid-Open No. 2-252143
Japanese Patent Laid-Open Publication No. 2003-242242 provides a transparent substrate with a recording layer formed by containing a dye in a polyurethane resin that exhibits a resin state at a low temperature and undergoes a reversible change such that it exhibits a rubber state at a high temperature.
By heating the recording layer with a strong writing laser beam and quenching it, the thermally expanded portion of the recording layer is raised to record information as a recording bit, and the recording layer is irradiated with a weak laser beam. There has been disclosed a rewritable optical recording medium in which a recording layer is flattened by heating and softening the recording layer to erase recorded bits.

[0006]

The rewritable optical recording media disclosed in the above-mentioned documents (1) to (3) irradiate the recording layer with writing light whose intensity is modulated by the recording information, and are irradiated with the writing light. The recorded information can be recorded by using the raised portion generated by thermal expansion of the recording layer as a recording bit, and the recording layer is irradiated with an erasing light to flatten the raised portion to record the recorded information. However, in the rewritable optical recording medium disclosed in the above-mentioned documents, the rewritable optical recording medium causes thermal expansion by irradiation of writing light, and the thermal expansion by the above-mentioned thermal expansion. Since the recording layer is composed of two constituent parts, that is, a constituent part that retains the raised state, a different constituent material is used for each of the constituent parts, and each constituent part is formed. Since it is necessary to stack the portions, the structure of the recording layer is complicated and there are many manufacturing steps, and the light for writing the recorded information and the light for erasing the recorded information are separated. Since the light having the wavelength of 10 .mu.m has to be used, the recording and reproducing apparatus using the rewritable optical recording medium requires a complicated and expensive structure having two light sources. There is.

Since the rewritable optical recording medium disclosed in the above-mentioned document has a single recording layer, the rewritable optical recording medium disclosed in the above-mentioned will be described. There is no such problem,
Since the recording layer having a refractive index that is not much different from the refractive index of the substrate is adhered and formed on the surface of the substrate, good tracking information can be obtained even if the substrate is provided with irregularities for obtaining tracking information. Therefore, there is a problem that the writing operation in high density recording cannot be stably performed by using the recording / reproducing device having a simple structure. That is, in order to write (record) recording information at a high recording density on the recording medium, it is naturally necessary to narrow the recording mark interval (track pitch). In order to form a good recording trace on a recording medium with an extremely narrow recording trace interval by relying only on the mechanical precision of the mechanism, it is necessary to perform extremely advanced machining to make a transfer mechanism. A recording / reproducing apparatus configured with such a transfer mechanism becomes extremely expensive. For example, a recording / reproducing apparatus for a manufacturer of a recorded recording medium does not need to know and it is required to be inexpensive. It cannot be used at all in recording / playback devices.

Therefore, in order to facilitate high-density recording with a recording / reproducing apparatus which is inexpensive and has a transport mechanism having a moderate mechanical accuracy, tracking information is obtained in advance on a recording medium. However, in the rewritable optical recording medium disclosed in the above-mentioned document, a refractive index that is not significantly different from the refractive index of the substrate is used. Since the recording layer is attached to the surface of the substrate, good tracking information cannot be obtained even if the substrate is provided with irregularities for obtaining tracking information. Therefore, it is not possible to stably perform the writing operation of (3) using the recording / reproducing apparatus having a simple structure. In the rewritable optical recording medium disclosed in the above-mentioned document in relation to this point, the substrate is provided with a guide groove for generating information for tracking control, and the substrate is provided with a refractive index of the substrate. Tracking information is obtained by using a structure in which a compression layer made of a silicone resin with a large difference in softness and high elasticity is adhered. However, the refraction of the substrate in the rewritable optical recording medium disclosed in The compression layer made of soft and highly elastic silicone resin, which is significantly different from the elastic modulus, is a soft layer that can be deformed according to the state of the ridge in the recording layer, so the tracking layer obtained by changing the layer thickness depending on the recording bit Since the size of the information changes, it is difficult to obtain stable tracking information.

[0009]

According to the present invention, a transparent substrate having a geometrical shape changing portion capable of generating tracking information is formed on one surface of the transparent substrate. Also has a thin layer of a hard material having a large refractive index, and a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than the room temperature range and which contains a light absorber on the thin layer. A rewritable optical recording medium provided with a recording layer of a single layer, and a portion of a transparent substrate having a geometrical shape changing portion capable of generating tracking information formed on one surface, A thin layer of a hard substance having a refractive index larger than that of the transparent substrate is provided, and a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than the temperature range of room temperature contains a light absorber on the thin layer. Single layer structure Recording light whose intensity is modulated by recording information is incident from the substrate side of the rewritable optical recording medium provided with the recording layer, and a ridge corresponding to the recording information is formed on the surface of the recording layer opposite to the substrate. A method of recording information using a rewritable optical recording medium for generating and recording recording information, and a transparent portion having a geometrically changed portion capable of generating tracking information on one surface. On the surface of the substrate, provided with a thin layer of a hard substance having a larger refractive index than the transparent substrate,
A recording layer having a single-layer structure is provided on the thin layer, which comprises a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than the room temperature range and which contains a light absorber. The rewritable optical recording medium in which information is recorded by forming a ridge corresponding to the recorded information on the surface opposite to the substrate irradiates continuous light from the substrate side to erase the recorded information. Provided is a method of erasing recorded information on a rewritable optical recording medium.

[0010]

In a transparent substrate having a geometrical shape changing portion capable of generating tracking information on one surface, a hard material having a refractive index larger than that of the transparent substrate provided on the surface is formed. The thin layer allows recording light whose intensity is modulated by the recording information incident from the substrate side at the time of recording to pass through a single recording layer, and is elastic at a temperature higher than the room temperature temperature range forming the recording layer. It is applied to a recording layer having a single layer structure in which a light-absorbing agent is contained in a thermosetting polyurethane resin whose rate decreases. In the recording layer, thermal expansion due to the light incident on the recording layer causes a recording bit in the state of a ridge on the side opposite to the substrate. The thin layer of a hard substance, which has a larger refractive index than the transparent substrate provided on the surface of the transparent substrate described above, does not change in thickness regardless of the presence or absence of the recording bit, and thus always has good tracking. Helps generate reflected light that contains information. Further, when continuous light is irradiated from the substrate side of the rewritable optical recording medium in which information is recorded by generating a ridge corresponding to recorded information on the surface of the recording layer opposite to the substrate, By heating the recording layer, the recording layer is flattened, and the recorded information can be erased well.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific contents of the optical recording medium of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a rewritable optical recording medium and a rewritable optical recording medium for explaining an information recording method and an information erasing method of the present invention. In FIG. 1, reference numeral 1 denotes a transparent substrate having geometrical shape change portions 2, 2 ... Which can generate tracking information on one surface. The transparent substrate 1 is used for recording, reproducing and erasing. A material that is transparent to the light used for each operation, such as polycarbonate resin, acrylic resin,
It is made of a plastic material such as an epoxy resin or a polyolefin resin, or a material such as glass which is usually used as a substrate of an optical recording medium.
The geometrically changing portions 2, 2 ... Which can generate tracking information to be formed on one surface of the transparent substrate 1 are formed as spiral grooves, concentric circular grooves, or pit rows, for example. Has been done.

Geometrical shape change portion 2 capable of generating tracking information in the transparent substrate 1 described above.
On the surface on which 2 ... is formed, a thin layer of a hard substance having a refractive index larger than that of the transparent substrate 1 (usually, the refractive index n = 1.5 to 1.6). (Thin layer of high refractive index material)
3 is provided. The thin layer 3 of the high refractive index material is a material that does not cause a large loss to the recording light, the reproducing light, and the erasing light that pass through the thin layer 3 and enter the recording layer 4. The constituent substances include, for example, inorganic compounds such as ZnS, TiO2, Ta2O5, InO2 and SiN, high refractive index glass, high refractive index resin, Si,
In addition to semiconductors such as Ge, metals such as Au, Al and Cu, organic dyes such as phthalocyanines and cyanines, those having desired characteristics can be selected and used.
A resin or glass in which a metal, a semiconductor, an inorganic / organic pigment, or an organic dye is dissolved or dispersed can be selected and used having a desired property. As a means for forming the thin layer 3 of the high refractive index material on the transparent substrate 1, a vacuum film forming method (evaporation method, sputtering method, ion plating method, plasma CVD method) is used depending on the material used. ), Coating method (spin coating method,
Any suitable method among spray method, dip method and blade coating method can be used.

A recording layer 4 is composed of a resin and a light absorber. The resin used for the constitution of the recording layer 4 in the rewritable optical recording medium of the present invention shows (1) a state change function of reversibly repeating curing and softening in the polymer chain in view of its operation function. A reversible phase and (2) a stationary phase having a fixed point that fixes the positional relationship of the polymer, and the two phases are not separated but are uniformly present in the recording layer 4. belongs to. The characteristic required for the resin is that the elastic modulus greatly changes with temperature changes, and that the elastic modulus change has a clear threshold value. Specifically, in an operating environment, for example, in a temperature range of room temperature, the dynamic elastic modulus is 5 times 10 9 dyne per square cm or more, and the dynamic elastic modulus is higher than the above-mentioned room temperature temperature range. Is selected from the resins having the physical properties such that the value falls below 2 times 10 8 dynes. Then, as a result of a study of a large number of resins by the present inventor, (A) good transparency required for use as a recording layer of an optical recording medium, which satisfies the above conditions, (B) It was found that a thermosetting polyurethane resin is most suitable as a resin having various characteristics such as exhibiting a good bulge shape upon thermal expansion and (C) having good film-forming property.

That is, a thermosetting polyurethane resin having a chemically crosslinked structure remembers its initial shape by being chemically crosslinked, and the memory does not disappear even after deformation, and is recorded. This is because it has excellent characteristics as a constituent material of the recording layer of the optical recording medium in that it is also excellent in the repeating characteristics of the operation and the erasing operation. The thermosetting property can be imparted to the polyurethane resin by using, for example, an isocyanate as a curing agent, adding a suitable catalyst such as an organic tin compound, and heating. The thermosetting polyurethane resin having a chemically cross-linked structure used for the construction of the recording layer 4 in the rewritable optical recording medium of the present invention is reversible at a temperature higher than the room temperature range. A material having such a property that the elastic modulus changes is used. Specifically, it exhibits a high elastic modulus in the operating environment temperature, that is, a room temperature temperature range, and at a temperature higher than the above-mentioned room temperature temperature range. A material having such a property that the elastic modulus sharply decreases is selected and used.

If the temperature at which the elastic modulus of the thermosetting polyurethane resin changes abruptly will now be described as the temperature Ts, first, the recording / reproducing operation is performed on the optical recording medium whose temperature Ts is rewritable. When the ambient temperature Tr is lower than the ambient temperature Tr, the rewritable optical recording medium is irradiated with the recording light to maintain the state of the protrusion even if the recording layer 4 is raised by thermal expansion. I can't let you do it. If the temperature Ts is significantly higher than the ambient temperature Tr when the recording / reproducing operation is performed on the rewritable optical recording medium, a large amount of light energy is required for recording information. The temperature Ts at which the elastic modulus of the thermosetting polyurethane resin changes abruptly must be set to a desired temperature in consideration of various conditions such as the output of the laser light source used in the recording / reproducing apparatus and the recording speed. However, the above-mentioned temperature Ts
Can be freely determined by adjusting the molecular structure of the resin, the addition amount of the curing agent, or the concentration of the light absorber, so that it is easy to obtain a rewritable optical recording medium having desired characteristics. Is.

The light absorber used as one of the constituent materials of the recording layer 4 is selected from those having an ability to absorb light, such as inorganic pigments, organic pigments, and metal fine particles. Can be used. That is,
Examples of the light absorber include materials that are dispersed or dissolved in a resin, such as inorganic pigments such as carbon black, cobalt blue, cobalt green and viridian, azo pigments, indanthrene, thioindigo, perylene, dioxazine and phthalocyanine. Organic pigments, cyanines, pyryliums, squaryliums, croconiums, azulenes, pentamethines, thioindigos, anthraquinones, phthalocyanines, naphthalocyanines, porphyrins, tetrahydrocholines, dithiols, diamines, indoanilines , Organic dyes such as dioxazines and dithiazines, Au, Ag, Cu, Te, Se,
In, Sn, Al, Si, Ge, Pb, Bi, Zn, N
Examples thereof include fine metal particles such as i, Pt, Co and Cr.

Using the above-mentioned resin material and light absorber,
The recording layer 4 having a single-layer structure made of a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than the room temperature range and containing a light absorber is a spin coat method, a spray method, a dip method, or a blade coat method. Among the various coating methods described above, a suitable coating method is selected and used to deposit and form on the above-mentioned thin layer 3 of the high refractive index material. It is also possible to dispose the recording layer 4 on the undercoat layer by selectively using an appropriate coating method from among the various coating methods described above. The recording layer 4 has a thickness of 10 nm to 5000.
However, the preferable thickness of the recording layer 4 is 1
It is in the range of 00 nm to 2000 nm. When a protective film for protecting the recording layer 4 is provided, a buffer layer made of a flexible material may be provided between the recording layer 4 and the protective film, and the reflective layer may be provided under the protective film. May be provided.

Next, a description will be given of specific manufacturing examples, recording and reproducing characteristics of the rewritable optical recording medium of the present invention configured as described above. [Manufacturing Example 1] On a surface of a transparent substrate (refractive index n = 1.59) having a thickness of 1.2 mm and provided with a guide groove having a depth of 60 nm, which is provided with the guide groove. , ZnS (refractive index n =
A thin film having a thickness of 100 nm according to 2.2) is deposited using a vacuum evaporation method. Next, Sanyo Kasei Co., Ltd.'s trade name Sampren (dimethylformamide solution with a resin concentration of 30 wt%) 96.3 wt% used as a polyurethane type shape memory resin, and Sanyo Kasei's trade name Suprene as a curing agent. CA-075N (isocyanate-based crosslinking agent) 2.9% by weight and organotin-based catalyst 0.3% by weight
And 0.5% by weight of bistriethoxysiloxynaphthaphthalocyanine, and the recording layer material obtained by filtering the solution with a 0.5 μm filter was used.
The thin film 3 of the high refractive index material is applied by spin coating in a stream of dry nitrogen gas having a relative humidity of 25%. Then, heat treatment is performed in an oven at 80 degrees Celsius for 10 hours to form the recording layer 4 having a desired thickness.

The recording / reproducing characteristics of the rewritable optical recording medium of the present invention manufactured as described in the above [Production Example 1] were examined using an evaluation machine (recording / reproduction machine for evaluation). However, the following results were obtained. Attach a rewritable optical recording medium to the turntable of the evaluation machine and keep it in a rotating state such that the linear velocity of the incident portion of the reproducing laser beam is 1.4 meters per second. The laser light for reproduction (1 milliwatt) with a wavelength of 780 nm was made to enter into the device, and the detection status of the tracking information was investigated. As a result, the evaluation device could detect a tracking control signal with a voltage value of 1.7 V, which would ensure stable and reliable operation. The tracking control operation could be performed. In FIG. 1, 5 is a condenser lens and 6 is a laser beam. A rewritable optical recording medium manufactured for use as a comparative example, ie 60
The guide groove is directly formed on the surface of the transparent substrate made of polyolefin resin (refractive index n = 1.53) having a thickness of 1.2 mm and provided with the guide groove having a depth of nm.
A rewritable optical recording medium having a recording layer made of the same recording layer material as shown in [Production Example 1] was attached to the turntable of the evaluation machine, and the line of the incident portion of the reproducing laser beam was attached. When the state of rotation is set so that the speed is 1.4 meters per second, and the state of tracking information detection is investigated by injecting a reproducing laser beam with a constant intensity (1 milliwatt) having a wavelength of 780 nm from the transparent substrate 1 side. In addition, the evaluation machine could detect only the tracking control signal having a voltage value of 0.08 volt and could not perform the tracking control operation.

Further, the rewritable optical recording medium of the present invention manufactured as shown in the above [Production Example 1] is attached to the turntable of the evaluation machine, and the incident portion of the recording laser beam is inserted. 780 nm emitted from a semiconductor laser by rotating so that the linear velocity is 1.4 meters per second.
A recording laser in a state in which the radiated light (8 mw) of the wavelength is modulated by a modulation signal of 720 KHz is incident on the rewritable optical recording medium from the transparent substrate 1 side to perform the recording operation on the recording layer 4. After that, a reproducing laser beam with a constant intensity (1 milliwatt) having a wavelength of 780 nm is made incident on the portion of the recorded recording layer 4 from the transparent substrate 1 side,
When the playback operation was performed, the evaluation machine had a C / N of 48d.
The reproduction signal of B could be obtained. When the surface of the recording layer 4 of the rewritable optical recording medium on which the recording information was recorded as described above opposite to the substrate 1 was observed with an optical microscope, it was irradiated with a recording laser beam. It was confirmed that the surface of the recording layer portion had ridges 4a, 4a ... Which can function as recording bits due to thermal expansion of the recording layer. Further, when the heights of the ridges 4a, 4a on the surface of the recording layer 4 were observed by a scanning tunneling microscope, it was found that the ridges 4a having a maximum height of 100 nm were formed.

Further, in order to erase the recording bits recorded as the ridges 4a ... In the recording layer 4 of the rewritable optical recording medium according to the above-mentioned [Manufacturing Example 1], the rewritable optical table can be rewritten on the turntable of the evaluation machine. A recording medium was attached, the laser beam for erasing was rotated so that the linear velocity of the incident portion was 0.7 meters per second, and the laser beam was emitted from the semiconductor laser.
Continuous light of radiated light (5 mw) having a wavelength of 80 nm is made to enter once from the transparent substrate 1 side of the rewritable optical recording medium, and then a constant intensity (1 milliwatt) with a wavelength of 780 nm from the transparent substrate 1 side. When the reproducing operation was performed by injecting the reproducing laser beam of, the reproduced signal obtained by the evaluation machine is from the state where the C / N before the erasing operation is 48 dB to the state where the C / N is 16 dB. The recording bit due to the ridges 4a formed on the recording layer 4 was erased well. Then, when the portion of the recording layer in the erased state is observed by an optical microscope, the recording layer 4 heated by the irradiation of the laser beam for erasing is gradually cooled, and the recording operation described above is performed. Ridges 4a, 4 generated on the recording layer 4 by
It can be confirmed that a ... Is flattened and returns to the recording layer 4 having a flat surface state before recording, and the recorded bits are erased. .. shown by dotted lines in FIG. 1 indicate a state in which the ridges 4a, 4a .. It should be noted that the C / N of the reproduced signal is the same as that described above even if information is recorded on the rewritable optical recording medium that has been erased as described above by another recording operation and the information is reproduced. As in the case, it was 48 dB.

[Manufacturing Example 2] A transparent substrate (refractive index n = 1.59) having a thickness of 1.2 mm provided with a guide groove having a depth of 70 nm is provided with a guide groove. On the surface, as a thin layer 3 of a high refractive index material, a thickness of 50 n made of Cu phthalocyanine (refractive index n = 1.9)
A thin film of m is deposited using a vacuum evaporation method. next,
After the solvent resistant layer is provided on the thin layer 3 of the high refractive index material, the recording layer material described in [Production Example 1] and the recording layer material similar to the manufacturing process are provided on the solvent resistant layer. The recording layer 4 is deposited by using the above and manufacturing processes. The above-mentioned solvent resistant layer is, for example, a product name Colcoat N-103X manufactured by Colcoat Co., Ltd. (a material capable of forming a glassy thin film on the surface of a plastic when naturally dried on the surface of the plastic. ). The rewritable optical recording medium according to the above [Production Example 2] was attached to the turntable of the evaluation machine, and was set in a rotating state such that the linear velocity of the incident portion of the reproducing laser beam was 1.4 meters per second. When the laser light for reproduction (1 milliwatt) having a wavelength of 780 nm was made incident from the transparent substrate 1 side and the detection state of the tracking information was investigated, the evaluation device detected a tracking control signal with a voltage value of 1.6 volts. As a result, the tracking control operation could be stably and reliably performed.

The rewritable optical recording medium according to the above [Production Example 2] was attached to the turntable of the evaluation machine, and the linear velocity of the recording laser beam incident portion was 1.4 per second.
The emitted light (8 mw) with a wavelength of 780 nm emitted from the semiconductor laser was rotated at 720K.
A transparent substrate 1 of an optical recording medium capable of rewriting a recording laser beam whose intensity is modulated by a modulation signal of Hz.
After the recording operation is performed on the recording layer 4 by irradiating it from the side, a reproducing laser beam having a constant intensity (1 milliwatt) with a wavelength of 780 nm is incident on the recorded recording layer 4 from the transparent substrate 1 side. Then, when a reproducing operation was carried out, a reproducing signal having a C / N of 46 dB could be obtained in the evaluation machine. When the surface of the recording layer 4 of the rewritable optical recording medium on which the recording information is recorded as described above, which is opposite to the substrate 1, is observed by an optical microscope, the recording is irradiated with the laser light for recording. The surface of the layer portion has a ridge 4 which can function as a recording bit due to thermal expansion of the recording layer.
It was confirmed that a, 4a ...

Next, in order to erase the recording bits recorded as the ridges 4a ... In the recording layer 4 of the rewritable optical recording medium according to the above-mentioned [Production Example 2], the turntable of the evaluation machine can be rewritten. An optical recording medium was attached, the laser beam for erasing was rotated so that the linear velocity of the incident portion was 0.6 m / sec, and the laser beam was emitted from the semiconductor laser.
Continuous light of radiated light (5 mw) having a wavelength of 80 nm was made to enter once from the transparent substrate 1 side of the rewritable optical recording medium, and then a constant intensity (1 milliwatt) having a wavelength of 780 nm from the transparent substrate 1 side. Inject the laser light for reproduction of
When the reproducing operation was performed, the reproduced signal obtained by the evaluation device was lowered from the state where the C / N before the erasing operation was 46 dB to the state where the C / N was 16 dB. The recorded bits due to the formed ridges 4a, 4a ... Are in a state where they are satisfactorily erased. Then, when the portion of the recording layer in the erased state is observed with an optical microscope, the recording layer 4 heated by the irradiation of the laser beam for erasing is gradually cooled, and the recording operation described above is performed. Protuberances 4a, 4a formed on the recording layer 4
Is flattened and returns to the recording layer 4 having a flat surface state before recording, and it can be confirmed that the recording bit is erased, and the rewritable optical recording in which the erasing operation is performed as described above is performed. Information is recorded on the medium by the re-recording operation, and even if the information is reproduced, the C / N of the reproduced signal is reproduced.
Was 46 dB as in the case described above.

[Manufacturing Example 3] A guide groove provided on a transparent substrate (refractive index n = 1.59) made of polycarbonate resin having a thickness of 1.2 mm provided with a guide groove having a depth of 60 nm. On the surface, as a thin layer 3 of high refractive index material, Ta2
A thin film of O5 (refractive index n = 2.0) having a thickness of 200 nm is deposited by reactive sputtering. The above [Production Example 1] is formed on the thin layer 3 of the high refractive index material.
The recording layer 4 is deposited by using the recording layer material and the manufacturing process similar to the recording layer material and the manufacturing process described in 1. .. A rewritable optical recording medium according to [Production Example 3] above,
Attach a rewritable optical recording medium to the turntable of the evaluation machine, and keep it in a rotating state such that the linear velocity of the incident portion of the reproducing laser beam is 1.4 meters per second.
When the reproduction laser light (1 milliwatt) with a wavelength of 780 nm was made incident from the transparent substrate 1 side and the detection state of the tracking information was investigated, the evaluation device could detect a tracking control signal with a voltage value of 1.3 V. As a result, the tracking control operation could be performed stably and reliably.

The rewritable optical recording medium according to the above [Production Example 3] is attached to the turntable of the evaluation machine, and the linear velocity of the incident portion of the recording laser beam is 1.4 per second.
The emitted light (8 mw) with a wavelength of 780 nm emitted from the semiconductor laser was rotated at 720 KH.
After the recording laser light whose intensity is modulated by the z modulation signal is incident from the transparent substrate 1 side of the rewritable optical recording medium to perform the recording operation on the recording layer 4,
When a reproducing laser beam having a constant intensity (1 milliwatt) having a wavelength of 780 nm was made incident on the recorded recording layer 4 from the transparent substrate 1 side to perform a reproducing operation, the C / N ratio was evaluated by the evaluation machine. A reproduction signal of 45 dB could be obtained.
When the surface of the recording layer 4 of the rewritable optical recording medium on which the recording information has been recorded as described above, which is opposite to the substrate 1, is observed by an optical microscope, the recording irradiated with the laser light for recording is shown. On the surface of the layer portion, ridges 4a, 4a that can function as recording bits due to thermal expansion of the recording layer.
I was able to confirm that ...

Next, in order to erase the recording bits recorded as the protrusions 4a on the recording layer 4 of the rewritable optical recording medium according to the above-mentioned [Manufacturing Example 3], the turntable of the evaluation machine can be rewritten. An optical recording medium was attached, the laser beam for erasing was rotated so that the linear velocity of the incident portion was 0.6 m / sec, and the laser beam was emitted from the semiconductor laser.
Continuous light of radiated light (5 mw) having a wavelength of 80 nm was made to enter once from the transparent substrate 1 side of the rewritable optical recording medium, and then a constant intensity (1 milliwatt) having a wavelength of 780 nm from the transparent substrate 1 side. Inject the laser light for reproduction of
When the reproducing operation was performed, the reproduced signal obtained by the evaluation device was lowered from the state where the C / N before the erasing operation was 45 dB to the state where the C / N was 14 dB. The recorded bits due to the formed ridges 4a, 4a ... Are in a state where they are satisfactorily erased. Then, when the portion of the recording layer in the erased state is observed with an optical microscope, the recording layer 4 heated by the irradiation of the laser beam for erasing is gradually cooled, and the recording operation described above is performed. Protuberances 4a, 4a formed on the recording layer 4
Is flattened and returns to the recording layer 4 having a flat surface state before recording, and it can be confirmed that the recording bit is erased, and the rewritable optical recording in which the erasing operation is performed as described above is performed. Information is recorded on the medium by the re-recording operation, and even if the information is reproduced, the C / N of the reproduced signal is reproduced.
Was 45 dB as in the case described above.

[Manufacturing Example 4] A transparent substrate (refractive index n = 1.59) having a thickness of 1.2 mm and provided with a guide groove having a depth of 60 nm is provided with a guide groove. Cyanine dye on the surface of the above-mentioned Colcoat N-103X manufactured by Colcoat Co., Ltd. (a material that can form a glassy thin film on the surface of a plastic when naturally dried on the surface of the plastic). The material of which is dissolved by spin coating has a film thickness of 200 nm.
The thin layer 3 of the high-refractive index material is formed, and the recording layer material and the manufacturing step similar to the recording layer material and the manufacturing step described in the above [Production Example 1] are formed on the thin layer 3 of the high-refractive index material. The recording layer 4 is deposited by using and. .. The rewritable optical recording medium according to the above [Production Example 4] was attached to the turntable of the evaluation machine, and was set in a rotating state such that the linear velocity of the incident portion of the reproducing laser beam was 1.4 meters per second. Then, a laser beam for reproduction (1 milliwatt) having a wavelength of 780 nm was made incident from the transparent substrate 1 side and the detection state of the tracking information was investigated.
The tracking control signal of the bolt could be detected, so that the tracking control operation could be performed stably and reliably.

Further, the rewritable optical recording medium according to the above [Production Example 4] was attached to the turntable of the evaluation machine, and the linear velocity of the recording laser beam incident portion was 1.4 per second.
The emitted light (8 mw) with a wavelength of 780 nm emitted from the semiconductor laser was rotated at 720K.
A transparent substrate 1 of an optical recording medium capable of rewriting a recording laser beam whose intensity is modulated by a modulation signal of Hz.
After the recording operation is performed on the recording layer 4 by irradiating it from the side, a reproducing laser beam having a constant intensity (1 milliwatt) with a wavelength of 780 nm is incident on the recorded recording layer 4 from the transparent substrate 1 side. Then, when the playback operation was performed,
With the evaluation machine, a reproduced signal with a C / N of 45 dB could be obtained. When the surface of the recording layer 4 of the rewritable optical recording medium on which the recording information has been recorded as described above, which is opposite to the substrate 1, is observed by an optical microscope, the recording irradiated with the laser light for recording is shown. The surface of the layer portion has a ridge 4 which can function as a recording bit due to thermal expansion of the recording layer.
It was confirmed that a, 4a ...

Next, in order to erase the recording bits recorded as the ridges 4a on the recording layer 4 of the rewritable optical recording medium according to the above-mentioned [Production Example 4], the rewritable optical of the turntable of the evaluation machine is used. The recording medium was attached, and the laser beam was emitted from the semiconductor laser by rotating so that the linear velocity of the erasing laser beam incident portion was 0.6 m / s.
A continuous light of radiated light (5 mw) having a wavelength of 0 nm is made to enter once from the transparent substrate 1 side of the rewritable optical recording medium, and then a constant intensity (1 milliwatt) having a wavelength of 780 nm from the transparent substrate 1 side. When a reproducing operation was carried out by injecting the reproducing laser beam of No. 3, the reproduced signal obtained by the evaluation machine was lowered from the state of erasing movement of 5 dB to the state of C / N of 14 dB. Protuberance 4 formed on the
The recorded bits of a, 4a ... Are in a good erased state. Then, when the portion of the recording layer in the erased state is observed with an optical microscope, the recording layer 4 heated by the irradiation of the laser beam for erasing is gradually cooled, and the recording operation described above is performed. The ridges 4a, 4a, ... Generated on the recording layer 4 are flattened and returned to the recording layer 4 having a flat surface state before recording, and it can be confirmed that the recording bit is erased, and the erasure is performed as described above. For the rewritable optical recording medium that has been operated,
Even if the information is recorded by the re-recording operation and the information is reproduced, the C / N of the reproduced signal is 45d as in the case described above.
It was B.

[0031]

As is clear from the above description, the rewritable optical recording medium, the information recording method and the information erasing method of the present invention have a geometrical shape capable of generating racking information. A thin layer of a hard substance having a refractive index larger than that of the transparent substrate provided on the above-mentioned surface of the transparent substrate having the changed portion formed on one surface is strong by recording information incident from the substrate side during recording. The modulated recording light is passed through a single recording layer, and a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than the room temperature temperature range forming the recording layer contains a light absorber. It is possible to easily give rise to a recording bit in the form of a ridge on the side opposite to the substrate by thermal expansion of the recording layer by applying it to a recording layer having a single-layer structure. Provided above A thin layer of a hard material with a larger refractive index than the transparent substrate does not change the thickness regardless of the presence or absence of recording bits, so it is useful for generating reflected light that always contains good tracking information. In addition, continuous light is emitted from the substrate side of a rewritable optical recording medium in which information is recorded by forming a ridge corresponding to recorded information on the surface of the recording layer opposite to the substrate. By irradiating, the recording layer is flattened by heating and cooling the recording layer, and the recorded information can be erased satisfactorily. The present invention can satisfactorily solve the above-mentioned conventional problems.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a rewritable optical recording medium and a rewritable optical recording medium for explaining an information recording method and an information erasing method of the present invention.

[Explanation of symbols]

1 ... Transparent substrate having geometrical shape changing portions 2, 2 ... Which can generate tracking information on one surface, 3 ... Thin layer of high refractive index material, 4 ... Recording layer, 5 ... Lens, 6 ... laser light,

Claims (3)

[Claims] 1. A hard substrate having a refractive index larger than that of the transparent substrate is formed on the surface of the transparent substrate having a geometrically changed portion capable of generating tracking information on one surface. A thin layer of a substance is provided, and a recording layer having a single-layer structure is formed on the thin layer. The recording layer has a single layer structure in which a light absorbing agent is contained in a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than a room temperature range. Rewritable optical recording medium. 2. A hard material having a refractive index larger than that of the transparent substrate on the surface of a transparent substrate having a geometrically changed portion capable of generating tracking information on one surface. Rewriting, in which a thin-layer recording layer having a single-layer structure made of a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than a room temperature range and containing a light absorber is provided on the thin layer. The recording light whose intensity is modulated by the recording information is made incident from the substrate side of the possible optical recording medium, and a ridge corresponding to the recording information is generated on the surface of the recording layer opposite to the substrate, thereby recording the recording information. A method of recording information using a rewritable optical recording medium for recording. 3. A hard material having a refractive index larger than that of the transparent substrate on the surface of the transparent substrate having a geometrically changed portion capable of generating tracking information on one surface. And a recording layer having a single-layer structure made of a thermosetting polyurethane resin whose elastic modulus decreases at a temperature higher than a room temperature range containing a light absorber, on the above-mentioned thin layer. The continuous light is irradiated from the substrate side of the rewritable optical recording medium in which information is recorded by forming a ridge corresponding to the recorded information on the surface of the recording layer opposite to the substrate. A method for erasing recorded information in a rewritable optical recording medium for erasing recorded information.