JP3163790B2 - Optical recording medium and optical recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a recording layer whose optical properties change on a substrate by means of light, heat, etc., and records, reproduces and erases information by utilizing the changes in the optical properties. The present invention relates to an optical recording medium to be used, and more particularly to an optical recording medium utilizing a phase separation phenomenon in which an initial phase of a material system is separated into two phases having mutually different compositions by a thermal process meeting respective conditions, and the use thereof. Optical recording method.

[0002]

2. Description of the Related Art First, the technical flow of conventional optical recording will be briefly described. First, the theory of reading was established, and along with that, CDs and LDs, which are read-only memory disks utilizing light diffraction, were developed. After that, an optical recording system of a type in which a user can write once was developed. This is called a WO (Write Once) type, and as a typical method, a hole punching method, a bubble method, and the like have been proposed. Further, thereafter, a magneto-optical method and a phase transition method have been developed as rewritable recording methods, and their practical use and improvement are still being studied. The advantages and disadvantages of these optical recording technologies will be described below.

[Drilling method] It is easy to realize by using an appropriate material, and has the advantages of high contrast. However, if the shape of the holes becomes uneven, S / N degradation will occur. Therefore, it is necessary to select a material capable of forming uniform and uniform holes, and in the case of LD, the structure must be an air sandwich structure. However, there is a problem that a special technique is required for manufacturing. As for the stability, there is no problem of deterioration of the opened hole, but the stability of the film itself becomes a problem. That is, since the stability of the material alone cannot be ensured, various materials are often mixed or used as an alloy. However, the base material of such a mixture or alloy is usually T
Although e is often used, even if it is a mixture or alloyed, the tendency to oxidize cannot be stopped in a long time, and there is a problem that the life is short. In addition, there is a problem in that the manufacturing method is complicated and there is large variation between lots. And, of course, this drilling method cannot be rewritten.

[Bubble system] In the bubble system, an alloy such as NiTi is plastically deformed by the pressure of a gas generated from a plastic material on the substrate side by the heat of laser irradiation, and a bubble is formed. Stability is a problem. Also, this bubble method cannot be rewritten, of course.

[Phase transition system] This phase transition system generally utilizes an amorphous-crystal phase transition.
Although there is no S / N deterioration due to the swelling of the holes as compared with the hole forming method, the magnitude of the contrast due to the phase transition is not as large as that of the holes, and it is difficult to secure the S / N.
Another problem is the stability of the metastable amorphous state. Further, the constituent materials are mainly made of chalcogenides (Te, Se, etc.), and there is a problem in the stability of the materials themselves. In addition, some materials take a long time to crystallize, which may degrade the performance of the system. However, there is a material that can be rewritten between amorphous and crystal, and there is a great merit that overwriting can be performed with one beam as compared with the magneto-optical method described below, and it is attracting attention as a promising rewriting method in the future.

[Magneto-optical system] This magneto-optical system is a system in which a change in the Kerr rotation angle is detected and converted into a signal. But,
Usually, since the rotation angle is small, it is difficult to secure S / N, and various contrivances have been made on the medium configuration. Further, in general, Tb or Fe is contained as a metal, so that the material is easily oxidized, which also complicates the medium structure and makes the manufacturing method difficult. However, since it is rewritable, many manufacturers are studying stability and S / N improvement.

[0007] In contrast to the above method, we have disclosed in
No. 96,389 proposed an optical recording system utilizing phase separation. According to this, irradiating a large laser power causes a quenching effect, causing spinodal decomposition, realizing an LH (Low to High) mode, and irradiating a small laser power to phase separation by nucleation and growth. And an HL (High to Low) mode is realized. Moreover, due to the difference between the large power and the small power, it is possible to perform rewriting between spinodal decomposition and phase separation by nucleation and growth. First, the advantage of the recording method using this phase separation is that the material is mainly composed of polycrystalline oxide, the possibility of change over time such as structural change and oxidation is small, and the long-term storage is excellent. Second, the reaction rate is very high.
In addition, oxide materials have high light transmittance in the visible and infrared regions, have a high degree of freedom in optical design and thermal design when optimizing optical and thermal characteristics with a multilayer film structure, and have high contrast in reproduced signals. Can be increased.

As described above, many types of optical recording systems have been proposed, but CDs and LDs have been strictly standardized, so that they have been mass-produced as read-only memories at low cost, and have been widely used in society. It has become very popular. on the other hand,
The WO and rewritable types have also been standardized or are being standardized, but the technological innovation is intense and various companies are developing them. However, compared to LD, it is not yet widely spread. The various recording systems developed in this way are not necessarily compatible with each other, and are currently achieved by different production processes and different drives. A drive between different recording methods,
The compatibility between the disc and the production process is very poor, so both the user and the supplier are costly,
It was also inconvenient to use, and was one of the causes of delay in spread.

In the course of this technology, as one of means for eliminating these problems, a technology for making the format the same as that of a CD or LD and enabling WO or rewriting has been studied, and some of them have been commercialized. Some have been done.
However, these formats originally require that the reflectance be set to at least 70%. However, if the initial reflectance is set to 70% or more, the absorptance becomes 30% at the maximum, and the sensitivity is greatly deteriorated. There is.
That is, the initial reflectance is 7 for the CD format.
WO is realized by setting it to 0% or more. However, since the medium sensitivity itself is set large, the medium stability must be sacrificed to a considerable extent. Further, when applied to LD, the linear velocity reaches at least 10 to 20 times that of CD. A larger laser power is required, and therefore, the absorption must be set higher at the expense of reflectivity, which deviates from the standard and impairs compatibility with LD players. As described above, when trying to realize WO in the CD or LD format, there is a major problem that the medium design becomes difficult in terms of reflectance and sensitivity.

[0010]

The present inventors have attempted to apply the phase-separated optical recording system to CD and LD formats, and as a result, have obtained a high sensitivity, a high reflectance and a high contrast. Found a method that complies with the standards of
The present invention has been reached. Accordingly, it is an object of the present invention to provide a writable optical recording medium (complying with the CD and LD formats) having high sensitivity, high reflectance and high contrast, and an optical recording method. It is another object of the present invention to provide an optical recording medium and an optical recording method that can reduce the loss due to the reflection of an energy beam during writing as much as possible and can use the energy of the energy beam more effectively.

[0011]

That is, the present invention relates to an optical recording medium having a recording layer in which a phase separation is caused by irradiation of an energy beam such as light in a multilayer film provided on a substrate. The recording layer is made of a material having the composition of a spinodal decomposition region, and (b) after the irradiation of the energy beam to the recording layer, the irradiated recording layer is rapidly cooled to cause phase separation by spinodal decomposition. is allowed and reflects irradiated beam at the time of reading, provided to be positioned on the opposite side to the base material of the recording layer a reflecting quenching layer made of a metal material having high thermal absorptivity, this
The reflection quenching layer irradiates the recording layer with the energy beam.
Light before phase separation due to spinodal decomposition
The energy applied to the recording layer rather than the reflectance of the recording medium
Set so that the reflectance of the optical recording medium becomes higher in after phase separation by spinodal decomposition is Ji raw <br/> by Bimu irradiation
This is an optical recording medium which is manufactured by using the optical recording medium. The present invention also relates to an optical recording method for writing and reading information on and from a recording layer in a multilayer film provided on a substrate by an energy beam such as light, wherein (a) the recording layer is formed from a composition of a spinodal decomposition region. And (b) after the irradiation of the energy beam onto the recording layer, the irradiated recording layer is rapidly cooled to cause phase separation by spinodal decomposition, and the irradiated beam is reflected upon reading. Provide a reflective quenching layer made of a metal material having a high heat absorption coefficient so as to be located on the opposite side of the recording layer from the base material ,
This reflection quenching layer is used to apply the energy beam to the recording layer.
Before phase separation by spinodal decomposition occurs
Than the reflectivity of the optical recording medium of
Phase separation by spinodal decomposition by Lugie beam irradiation
The reflectance of the optical recording medium after the occurrence of
In respect to the optical recording medium thus provided, an energy beam such as light intensity, such as phase separation by spinodal decomposition occurs in accordance with the information to be written in the recording layer where there is no phase separation by (c) spinodal decomposition Irradiation and recording are performed by utilizing the fact that the reflectance in the phase-separated portion of the recording layer is increased. (D) The written information is illuminated with light having an intensity such that phase separation does not occur due to the spinodal decomposition. This is an optical recording method for reading out by irradiating an energy beam.

That is, according to the present invention, (a) the recording layer is made of a material having a composition of a spinodal decomposition region, and the initial reflectance of the recording layer is set to a relatively low value, that is, 30% or less, preferably 25%. (B) When the irradiation of the energy beam to the recording layer is completed, the specific heat and the thermal conductivity are large so that the recording layer heated by the irradiation of the energy beam is rapidly cooled. Optical recording with a high heat absorption rate, which allows the recording layer to be quenched after the end of energy beam irradiation, and a multilayer quenching layer made of metal such as aluminum or gold for smooth spinodal decomposition. Medium.

The optical recording method of the present invention is a method of irradiating a recording layer of such an optical recording medium with an energy beam such as light to write information on the recording layer or read information from the recording layer. At the time of writing, (c) the recording layer in which phase separation due to spinodal decomposition has not occurred is irradiated with an energy beam having an intensity such that phase separation due to spinodal decomposition occurs according to the information to be written, and that portion is reflected. The reflectance is a value sufficiently higher than the initial reflectance, that is, 39% or more, preferably 4% or more, higher than the initial reflectance.
Information is written under the condition that the value is about 0% higher and the reflectivity is increased to about 65% or more, preferably about 70 to 80%. At the time of reading, (d) phase separation occurs due to spinodal decomposition. This is an optical recording method for reading out written information by irradiating an energy beam having such an intensity that phase separation due to spinodal decomposition does not occur on a recording layer.

The optical recording medium of the present invention is basically composed of a substrate and an optical recording medium laminated on the substrate and having such an intensity that phase separation by spinodal decomposition occurs in accordance with information to be written (that is, a predetermined threshold value or more). A) a recording layer capable of forming a recording bit having a high reflectivity by causing phase separation by spinodal decomposition by irradiating the energy beam of (a), and a reflective quenching layer laminated on the recording layer. The above energy beam irradiation
Maximum reflectance when the recording frequency at the time of recording of 196KHz is 65% or more, when the recording <br/> frequency in reading digital is 720 kHz, the reflection contrast of the maximum reflectivity from 0.3 to 0 It is necessary that the initial reflectance is 0.4 times or less of the maximum reflectance. Here, as the recording material constituting the recording layer, a material that causes only spinodal decomposition by irradiation of the recording layer with an energy beam of the threshold or more, or irradiation of an energy beam of the threshold or more is used. By the spinodal decomposition or after binodal decomposition occurs, but a composition that causes spinodal decomposition by quenching after irradiating an energy beam above a threshold by providing a reflective quenching layer described later, such recording materials include Particularly preferred are those of the general formula S
bO _X (where, x is 0 to 1.0 or 1.5 to 2.3, preferably 0.3 to 0.6 or 1.8 to 2.1) antimony oxide system represented by There are materials.

In addition to the above-mentioned antimony oxide-based materials, PbTe-GeTe may be used as a material capable of forming a composition capable of phase-separating the recording material of the recording layer by spinodal decomposition by means of light, heat, or the like. Mixed system, A
u-Pt mixed system, Au-Ni mixed system, PbS-PbT
e mixed system, GeSe ₂ -GeSe mixed system, As-Ge-
Alloys such as Te mixed systems, Li ₂ O—SiO ₂ mixed systems, N
a ₂ O—SiO ₂ mixed system, BaO—SiO ₂ mixed system, A
l ₂ O ₃ -SiO ₂ mixed system, B ₂ O ₃ -SiO ₂ mixed _{system, Li 2 O-B 2 O} 3 mixed _{system, Na 2 O-B 2 O} 3 mixed _{system, K 2 O-B 2 O} 3 mixed _{system, Rb 2 O-B 2 O} 3 mixed _{system, Cs 2 O-B 2 O} 3 mixed system, PbO-B ₂ O ₃ mixture system such as oxides of - or oxide mixture-based material, ZrO ₂ -Th
O ₂ mixed system, CaO-SiO ₂ mixed system, B ₂ O ₃ -Pb
O mixed _{system, B 2 O 3 -V 2 O} 5 mixed system, SnO ₂ -Ti
O ₂ mixed system, NiO-CoO mixed system, Al ₂ O ₃ -Cr
₂ O ₃ mixed system, SiO ₂ -Al ₂ O ₃ mixed system, ZnWO
₄ -MnWO ₄ mixed system, CaWO ₄ -NaSm (WO
₄ ) ₂ mixed system, CaWO ₄ -Sm ₂ (WO ₄ ) ₃ mixed system, MnMoO ₄ -ZnMoO ₄ mixed system, Fe ₂ TiO
₄ -Fe ₃ O ₄ mixed _{system, Ca 3 Cr 2 Si 3 O} 12 -Ca
₃ Fe ₂ Si ₃ O ₁₂ mixed system, 65MgSiO ₃ / 35F
eSiO ₃ -CaSiO ₃ mixed system, LiAl ₅ O ₈ -L
NiFe ₅ O ₈ mixture system, NaAlSi ₃ O ₈ -KAlSi
₃ O ₈ mixture _{system, Na 2 O-B 2 O} 3 -SiO 2 mixture system such as oxides - oxide mixture-based material and, LiCl-NaCl mixed system, KCl-NaCl mixed system, CsCl-TlCl mixed system, CaCl _2- MnCl ₂ mixed system, CaCl ₂ -S
rCl ₂ mixed system, LiBr-AgBr mixed system, AgBr
-NaBr mixed system, KBr-NaBr mixed system, TlBr
-CsBr mixed system, KI-NaI mixed system, NaI-Ca
I ₂ mixed system, (GaI ₂ ) ₂ -NaGaI ₄ mixed system,
(GaI ₂ ) ₂ -KGaI ₄ mixed system, (GaI ₂ ) _2-
Halide-halide mixed materials such as RbGaI ₄ mixed system, GaAlI ₄ -Ga ₂ I ₄ mixed system, and CeO
_n system, Bi-Bi ₂ O ₃ mixed system, CaCO ₃ -MnCO
₃ Non-stoichiometric compounds such as oxides and halides such as mixed systems, and further polymer blends called `` polymer alloys '' that cause binodal decomposition or spinodal decomposition, and random copolymers that cause microphase separation, Organic materials such as an alternating copolymer, a block copolymer, and a graft copolymer are exemplified. As for the composition of such a recording material, a phase diagram of phase separation is drawn for the selected recording material according to an ordinary method, and the composition is determined according to the obtained spinodal line.

Further, the medium structure of the optical recording medium of the present invention is preferably a multilayer structure in which the recording layer heated during writing is rapidly cooled. Aluminum, Al-Ti and other aluminum-based metals, gold, which have a large heat absorption rate and can rapidly cool the recording layer after the end of the energy beam irradiation.
It is preferable to provide a reflection quenching layer formed of a material having a high heat absorption rate such as copper. This reflection quenching layer is preferably provided on the upper surface side of the recording layer, and has a melting point higher than that of the recording material forming the recording layer and has a high wettability with respect to the recording material melt. Formed through a top-side dielectric layer made of a protective material selected from a nitride.
Further, on the upper surface side and / or lower surface side of the recording layer, there are provided other various materials, for example, a lower surface side dielectric layer similar to the upper surface side dielectric layer provided on the lower surface side of the recording layer,
For the purpose of further protecting the surface of the reflection quenching layer, a protective film such as an ultraviolet curable resin, acrylic, polycarbonate, or epoxy resin may be provided, and on the recording layer for the purpose of increasing the amount of light reflected from the recording layer. May be provided with a high refractive index layer such as ZnS. Specifically, as a preferable example of the medium structure of the optical recording medium of the present invention, the structure of a substrate / lower side dielectric layer / recording layer / upper side dielectric layer / reflection quenching layer / ultraviolet curable resin, substrate / recording Layer / upper dielectric layer / reflection quenching layer / ultraviolet curable resin structure, substrate / lower dielectric layer /
Various structures such as a recording layer / reflection quenching layer / ultraviolet curable resin structure can be given.

In the multilayer structure formed on the substrate as described above, the initial reflectance of the recording layer must be a relatively low value, that is, 30% or less, preferably 25% or less. A multilayer optical thin film can be designed by using the type of recording material constituting the recording layer and the refractive index and the thickness of each layer constituting the multilayer film as variables, and the film layer of each layer can be determined and designed by simulation.

As a method for producing the optical recording medium of the present invention, a conventionally known method can be adopted, and a recording layer is formed by applying a recording material on a substrate, or
Applying a protective material to form a dielectric layer,
Means for forming a reflective quenching layer by depositing a material having a high heat absorption rate include, for example, thermal evaporation, ion plating, reactive sputtering, chemical vapor deposition (CVD), and ion assisting. Evaporation method (IAD), molecular beam epitaxy method (MBE), etc., a method in which a copolymer or the like is directly polymerized on a substrate and applied thereto, or a method in which a secondary compound in which the copolymer or the like is dissolved is appropriately applied to the substrate A method of coating and applying on top can be used.

As an optical recording method using such an optical recording medium, a phase separation by spinodal decomposition occurs in a recording layer in which phase separation by spinodal decomposition does not occur at the time of writing according to information to be written. Information writing is performed by irradiating an energy beam having such an intensity (that is, an intensity equal to or higher than a threshold). That is, when the signal level of the information to be written is preferably H (High), H laser power is applied to the recording layer to form a recording bit with high reflectivity in that portion, and the signal level of this information is L At the time of (Low), writing is performed in such a manner that no laser power is applied to the recording layer or an L laser power of an intensity that does not cause phase separation due to spinodal decomposition (that is, an intensity below a threshold) is applied. . At the time of reading, the information written is read out by irradiating the recording layer in which phase separation due to spinodal decomposition has occurred with an energy beam having such an intensity that phase separation due to spinodal decomposition does not occur.

Here, with respect to the optical recording medium configured as described above, the intensity of the energy beam that causes phase separation by spinodal decomposition at the time of writing is determined.
To determine the intensity of the energy beam such that phase separation due to spinodal decomposition does not occur during readout,
Although it is also possible to theoretically obtain from the structure of the constituted medium by calculation, it is preferable to experimentally obtain a graph showing the relationship between the intensity of the energy beam, the reflectance and the contrast, and obtain the experimentally determined graph. According to the graph, the intensity of the energy beam necessary for writing, that is, the reflectance is increased by 39% or more, preferably 45% or more from the initial reflectance, and sufficient contrast can be obtained, and the reflectance is about 65% or more. The intensity of the energy beam is set so that it becomes the value of, and the intensity of the energy beam required for reading is set by selecting an appropriate value from the range where the initial reflectance does not change even if the energy beam is irradiated. It is desirable to do. By setting the intensity of the energy beam necessary for writing and the intensity of the energy beam required for reading from the graph showing the relationship between the intensity of the energy beam, the reflectance, and the contrast obtained experimentally in this way, Reliable operation of the designed medium can be ensured.

The optical recording medium according to the present invention is a CD.
Alternatively, since the recording medium is a medium such as an LD, there is a case where a function as a ROM, for example, various indexes or fixed information is naturally required to be added. There are two such means. That is, first, ROM information is preliminarily provided on a substrate as a pre-pit separately from a data writing area and is separated from the data writing area, and the portion is collectively exposed by a collective exposure device or a multi-track writing device to cause spinodal decomposition. The optical power causes phase separation by spinodal decomposition to increase the reflectivity of this portion, and is preferably set to a reflectivity of 65% or more or 75% or more, which is the standard of CD or LD. Of course, ROM information is preliminarily provided on the substrate as pre-pits in a mixed manner in the data write area, and the part is irradiated with laser continuously in advance with a laser power that causes spinodal decomposition, and phase separation by spinodal decomposition is performed. It is possible to increase the reflectivity of this portion by causing it, preferably set to a reflectivity of 70 or 75% or more according to the CD or LD standard, and mix ROM information in the data area.

[0022]

The present invention will be specifically described below based on examples and comparative examples.

Example 1 A medium disk having the structure shown in FIG. 1 was formed by using antimony oxide as a recording material. That is, in this medium disk, a lower surface side dielectric layer 2 having a thickness of 1,000 mm is formed by depositing SiO ₂ on a substrate 1 made of PMMC (or PC) by sputtering. Layer 2
A recording layer 3 having a thickness of 300 ° is formed by high-frequency ion plating on the
₂ to form an upper surface side dielectric layer 4 having a thickness of 1,000 .ANG., And a 500 .ANG. Thick aluminum (Al) film as a quenching reflection layer 5 is formed on the upper surface side dielectric layer 4. Then, on the quenching reflection layer 5, an ultraviolet protection resin 6 is laminated.

Here, the deposition of the recording layer 3 by the high-frequency ion plating is performed using an ion plating apparatus shown in FIG. That is, Ar gas and O ₂ are introduced from a gas inlet 10 into a chamber 9 having an RF power source 7 and a matching box 8, and tens to hundreds of W of RF power is applied to the RF coil 11 to generate plasma. And Sb is converted into an electron beam (E
This is performed by evaporating and ionizing by B) and depositing antimony oxide on the rotating substrate 1. Reference numeral 12 denotes a motor, and reference numeral 13 denotes a motor.
Is an exhaust port. In this case, there are mainly three film forming parameters: RF power, Ar gas pressure, and O ₂ gas pressure. Among them, the Ar gas pressure and the O ₂ gas pressure are respectively set to 6 × 10 ⁻⁴ torr, 3 × RF power was controlled by setting to 10 ^-4 torr. In this case, R
As a result of monitoring Vdc as a measure of the magnitude of the F power, the dependence of the recording mode on the laser power was as shown in FIG. 3 according to the value of Vdc. Here, HL corresponds to occurrence of phase separation due to nucleation and growth, and LH corresponds to occurrence of phase separation due to spinodal decomposition. As a result, a state diagram as shown in FIG. 3 is estimated. In the state diagram shown in FIG. 3, a region where only the LH mode occurs was selected as a spinodal region, and a film was formed at the Vdc value.

Information was recorded on the thus prepared medium disk under the following conditions: write laser power: 16 mW, read laser power: 1 mW, rotation speed: 1,800 rpm, and recording signal: standard NTSC signal. When writing was performed on this disk medium, laser power characteristics (characteristics showing changes in reflectance and contrast with respect to laser power) as shown in FIG. 4 were obtained. The reflectance is as
It was about 45% in the depo part, the absorptance was about 40%, and the maximum reflectivity by writing was about 75%. Therefore, if the FM-modulated video signal is inverted and written,
It was confirmed that this change in reflectance satisfied the LD standard. Actually, the result of measuring the S / N by writing the NTSC signal was about 48 dB. Further, an environmental test was performed under environmental conditions of 50 ° C., 60 ° C. and 70 ° C., 85% RH and 1,000 hours, but there was almost no change in reflectance.
A medium having such recording characteristics was reproduced on a commercially available video disc player, but it was reproduced on the same level as a commercially available video disc, and it was confirmed that there was no problem.

FIG. 5 shows a transition model of the information signal at this time, the writing laser power corresponding to the information signal, and the information signal indicating the reproduction signal. From the above results, the reflectance was set to 70% or more, which is the standard for CD or LD,
It has been found that spinodal decomposition is the principle of increasing the reflectivity, and that it is sufficient to invert and write the signal. For comparison, FIG. 6 shows a transition model of an information signal in a conventional optical recording medium in which the reflectance of the as depo portion is set to 70%. In this case, the absorptance was about 15%, which required twice or more laser power as compared with the case of the present invention.

Example 2 Using a medium prepared under the same conditions as in Example 1,
A reproduction-only area was provided between 50 and 200, and fixed image information was previously provided in this area as pre-pits. The information is a normal NTSC signal, and the pit shape is the same as that of a normal video disc. As a result of the batch exposure of the portion with a xenon flash lamp in advance, the reflectance became about 75% or more. The reflectance was in accordance with the standard, and the other portions were masked at that time so that light for exposure was not applied. As a result, it has been found that this disc can be used by being divided into a read-only section and a WO section.

Example 3 A medium prepared under the same conditions as in Example 1 was used, and the entire area was used as a data area. A part of the track was used exclusively for reproduction. Video information was provided, and the portion was written while tracing the track one by one with a laser beam to generate an HL mode and used as a reproduction-only image.

Example 4 In the same manner as in Example 1, antimony oxide was used as a recording material to form a medium disk having the structure shown in FIG. That is, a lower surface side dielectric layer 2 having a thickness of 800 mm was formed by depositing SiO ₂ on a substrate 1 made of PC by sputtering, and used on the lower surface side dielectric layer 2 in Example 1. Use the same high frequency ion plating as
Ar gas pressure was set to 6 × 10 ^-4 torr, and O ₂ gas pressure was set to 3 × 1
Set to 0 ^-4 torr and apply RF power of several hundred watts to RF coil 1
1 to generate plasma, evaporate and ionize Sb by an electron beam (EB), and deposit antimony oxide on a rotating substrate 1 to form a recording layer 3 having a thickness of about 400 °. Formed. At this time, a plurality of disks were manufactured by changing the energy applied to the RF coil, that is, Vdc. SiO ₂ is deposited by sputtering on the recording layer 3 of each disk thus obtained to form an upper dielectric layer 4 having a thickness of 600 °. The quenching reflective layer 5 is made of aluminum (A
1) A film was deposited, and a UV protection resin 6 of about 2 μm was laminated on the quenching reflection layer 5 to produce a plurality of optical recording media.

Here, the composition of antimony oxide in the recording layer 3 corresponding to the Vdc value changed during the production of the recording layer 3 was measured by Rutherford Scattering. A laser beam of about 12 mW was irradiated at 0.4 m / sec, the phase state of the recording layer 3 after the irradiation was examined, and the relationship between the composition of the recording layer 3 and the phase state was examined. FIG. 7 shows the results. 7, the vertical axis indicates the temperature of the recording layer 3, and the horizontal axis indicates the oxygen atom number ratio x of SbO _x forming the recording layer 3. In the figure, x is 1.0 to 1..
In the area of No. 5, the recording material of the recording layer 3 causes only binodal decomposition, and in the area of x of 0.3 to 0.6 and 1.9 to 2.05, only spinodal decomposition occurs. In the region, it was found that either binodal decomposition or spinodal decomposition occurred depending on the cooling conditions after laser beam irradiation. The area of the recording layer 3 that has undergone spinodal decomposition by laser beam irradiation becomes a high reflectivity area showing a higher reflectivity than the initial reflectivity. This means that the reflectivity of this recording area is in the LH recording mode. Means. On the contrary, the area where the binodal decomposition is performed by the irradiation of the laser beam becomes a low reflectivity area showing a reflectivity lower than the initial reflectivity, which means that the reflectivity of this recording area becomes the HL recording mode. . Note that, in FIG.
1 and a broken line 102 correspond to a phase diagram of a recording material and antimony oxide constituting the recording layer 3, a solid line 101 shows a binodal decomposition curve, and a broken line 102 shows a spinodal decomposition curve. In the fourth embodiment, x = which causes spinodal decomposition regardless of the cooling condition of the recording layer.
Antimony oxide having a composition of 2.0 was used as a recording material.

Next, CDWO (Compact Disc Write Onc)
e) The standard will be described. In FIG. 8, the vertical axis indicates the reflectance of the recording medium, and the horizontal axis indicates the recording time.
Is a schematic representation of the standard. As shown in the figure,
According to the DWO standard, when laser recording is performed on a recording medium at a frequency of 196 KHz (when an 11T signal is applied)
The maximum reflectance R _top of the recording area is 65% or more and 720
When laser recording is performed at a frequency of KHz (when a 3T signal is applied), the reflectance amplitude R ₃ is 0.3 times or more and 0.6 times or less the maximum reflectance R ₀ , and the initial reflectance R _{0 of the} recording medium is used. Is 0.4 times or less of the maximum reflectance R _top . FIG. 9 shows this relationship.
The vertical axis in FIG. 9 represents the reflectance (R ₃ or R _0), the horizontal axis represents the reflectivity R _top, 103 is a straight line R ₃ = 0.6R _top, 104 are R ₃ = 0.3R _top Line of 105
Represents a straight line of R ₀ = 0.4R _top , and it can be seen that the region satisfying the CDWO standard is in the overlapping portion of the hatched portion in FIG. Specifically, R _top = 65
%, R _top ≧ 65%, R ₀ ≦ 26
% And R ₃ ≧ 19.5% correspond to the CDWO standard.

Here, irrespective of the cooling condition, only spinodal decomposition is generated by laser beam irradiation.
Using an optical recording medium having a recording layer 3 of about 2.0, a test was performed to determine whether the recording medium conformed to the CDWO standard. An actual recording test was performed. That is, the relationship between the values of R _top , R ₃ , and R ₀ of the optical recording medium with x = 2.0 and the laser power was examined. The conditions and results at that time were as follows. [Conditions] Writing laser power: Changed by 1 mW in the range of 0 to 15 mW Reading laser power: 1 mW Linear velocity of recording medium: 1.4 m / sec Recording signal: Changed at 196 to 720 KHz (duty ratio: 50%) [ Results] FIG. 10 shows the laser power dependence of the reflectance in the recording area. FIG. 11 shows the laser power dependence of the reflectance in the non-recording area. FIG. 12 shows the laser power dependence of the contrast of the reflectance based on the above. The ratio (R _f / R) between the reflectance amplitude (R _f ) of the recording frequency f in the recording area and the maximum reflectance (R _top )
FIG. 13 shows the laser power dependence of R _top ). FIG. 14 shows the recording frequency dependence of the reflectance. FIG. 15 shows the recording frequency dependence of the ratio ( _Rf / _Rtop ) between the reflectance amplitude ( _Rf ) and the maximum reflectance ( _Rtop ) at the recording frequency _f .

As is clear from FIG. 14, in this optical recording medium, when the writing laser power is 12 mW or more, the maximum reflectance R at a recording frequency of 200 KHz is obtained.
It turned out that _top is more than 65%. FIG.
From the reflectance amplitude (R
_f ) and the maximum reflectance (R _top ) have a ratio (R _f / R _top ) of 0.31 or more, and the initial reflectance is 26% as is clear from FIGS. 10 and 11. I understand. Furthermore,
FIG. 15 shows that the ratio (R _f / R) between the reflectance amplitude (R _f ) and the maximum reflectance (R _top ) at a recording frequency of 200 KHz.
It is also clear that the value of _top ) is 0.61 or more. After all, this optical recording medium has R ₀ = 26% and R _top > 65%
And R _f / R _top> is 0.31 or more conditions are satisfied that, it was confirmed that meets the standards of CdWO.

Next, this optical recording medium is replaced with a commercially available CD-RO
It was played back with the M drive, but it was played back just like a normal CD-ROM disc. 50 ° C, 60 ° C, 70 ° C
An environmental change test was conducted at each temperature of 85 ° C. and at a temperature of 85 ° C. for 1000 hours, but almost no change in reflectance was observed.

In this recording medium, recording bits are formed as a high reflectance area by spinodal decomposition (the non-recording area is a low reflectance area, and the recording area is a high reflectance area). As shown in FIG. 5, the relationship between the information signal, the writing laser power, and the reproduction signal is as follows.
In this case, it is necessary to perform writing using pulse signals whose intensities correspond in proportion to each other. On the other hand, in the writing of the conventional gold / organic dye-based CDWO, as shown in FIG. 6, the writing is performed in such a manner that the intensity of the information signal and the writing laser power have mutually opposite pulses.

Example 5 In the optical recording medium of Example 4, antimony oxide having a composition of x = 2.0, which causes spinodal decomposition, was used as a recording material regardless of the cooling condition of the recording layer. As shown, x = 0 to 0.3, 0.6 to 1.0, 1.5 to
In the regions 1.9 and 2.05 to 2.2, either spinodal decomposition or binodal decomposition occurs by selecting the cooling condition of the recording layer. In order to cause spinodal decomposition in this region, a reflection quenching layer 5 made of a metal such as aluminum is provided near the recording layer 3 so that the recording layer 3 is quenched. Is necessary, and thus the reflection quenching layer 5
As a result, even if antimony oxide having the above composition other than x = 2.0 is used as a recording material, an optical recording medium similar to that of Example 4 can be obtained. In addition, aluminum-based metals have a high laser beam reflectivity and have almost no wavelength dependence of the change in reflectivity (the gold used as the reflective layer of the conventional gold / organic dye-based CDWO has a short wavelength region, especially The reflectance is sharply reduced around 500 nm), and it can be used not only for short-wavelength lasers but also at low cost, and is very preferable as a material for forming the reflection quenching layer 5.

Embodiment 6 In Embodiment 4, as shown in FIG. 12, the region where the laser power is small, specifically, the laser power is 3 to 5 m.
In the region of W, a decrease in reflectance is observed. It is considered that binodal decomposition occurs in this region and the reflectance is lowered. From this, at least the non-recording area of the optical recording medium is irradiated with low laser power in advance to cause binodal decomposition, thereby lowering the initial reflectance, and then irradiating higher laser power to perform spinodal decomposition. A recording area composed of a high reflectance area may be formed by causing the recording area, and thereby recording with a higher reflectance contrast can be performed.

Example 7 Using an optical recording medium prepared under the same conditions as in Example 4,
A reproduction-only area is provided between a radius of 50 mm and 80 mm,
In this area, fixed information was previously provided as pre-pits. Further, as a result of collective exposure of other regions in advance by a xenon flash lamp, the reflectance was about 75%. The value of this reflectivity conforms to the CDWO standard. The other portions were masked during the batch exposure using the xenon flash lamp. As a result, the optical recording medium of Example 7 could be divided into a read-only area and a WO area and used as a partial ROM.

Example 8 Using an optical recording medium prepared under the same conditions as in Example 4,
In order to use the whole as a data area and to use a part of a track as a read-only area, information is stored in advance as pre-pits on necessary tracks, and that part is written by tracing a laser beam one track at a time to generate the HL mode. In this way, a read-only area was set. The optical recording medium of Example 8 could also be used as a partial ROM having a read-only area and a WO area.

[0040]

According to the present invention, a writable optical recording medium having high sensitivity, high reflectivity and high contrast can be realized and implemented, and recording with a low reflectivity can be realized. Since writing is performed by irradiating the layer with a laser beam, the loss due to the reflection of the laser beam during this writing is small, and the energy of the laser beam can be used efficiently. In addition, by using the same process as the ISO standard WO digital data disc, a recording film or the like can be deposited on a CD or LD format substrate and used as a CD or LD. Can respond. Further, since this medium can be reproduced by an ordinary video disc player, it can be used as a distribution medium for image information.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an optical recording medium according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an ion plating apparatus used for depositing a recording layer according to the first embodiment.

FIG. 3 is an explanatory diagram showing laser power dependence of a recording mode in the optical recording medium of Example 1.

FIG. 4 is an explanatory diagram showing laser power dependence of contrast in the optical recording medium of Example 1.

FIG. 5 is an explanatory diagram showing a transition model of an information signal in the optical recording medium of the present invention.

FIG. 6 is an explanatory diagram showing a transition model of an information signal in a conventional optical recording medium.

FIG. 7 is a phase diagram showing the relationship between the composition and phase state of antimony oxide in an optical recording medium according to Example 4 of the present invention.

FIG. 8 is an explanatory diagram illustrating a relationship between a recording time and a reflectance for explaining a CDWO standard.

FIG. 9 is an explanatory diagram showing R _top dependence of the reflectance in the optical recording medium of Example 4.

FIG. 10 is an explanatory diagram showing laser power dependence of the reflectance of a recording area in the optical recording medium of Example 4.

FIG. 11 is an explanatory diagram showing the laser power dependence of the reflectance of a non-recording area in the optical recording medium of Example 4.

FIG. 12 is an explanatory diagram showing the dependence of the reflection contrast on the laser power in the optical recording medium of Example 4.

FIG. 13 is an explanatory diagram showing laser power dependence of R _f / R _top of a recording area in the optical recording medium of Example 4.

FIG. 14 is an explanatory diagram showing the frequency dependence of the reflectance in the optical recording medium of Example 4.

FIG. 15 is a diagram showing R in the optical recording medium of Example 4.
FIG. 4 is an explanatory diagram showing the frequency dependence of _f / R _top .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Lower surface side dielectric layer, 3 ... Recording layer, 4 ... Upper surface side dielectric layer, 5 ... Rapid reflection layer, 6 ... UV protection resin.

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Claims (2)

(57) [Claims] 1. An optical recording medium comprising a multilayer layer provided on a substrate and a recording layer which undergoes phase separation by irradiation of an energy beam such as light, wherein (a) the recording layer is formed from a composition of a spinodal decomposition region. And (b) after the irradiation of the energy beam onto the recording layer, the irradiated recording layer is rapidly cooled to cause phase separation by spinodal decomposition, and the irradiated beam is reflected at the time of reading. A reflective quenching layer made of a metal material having a high heat absorption coefficient is provided on the opposite side of the recording layer from the base material, and the reflective quenching layer provides the energy beam to the recording layer.
Before phase separation by spinodal decomposition occurs
Than the reflectance of the optical recording medium, said energy to said recording layer
Phase separation by spinodal decomposition by Lugie beam irradiation
As the reflectance of the optical recording medium becomes higher in after has occurred
Optical recording medium characterized by comprising provided. 2. An optical recording method for writing and reading information to and from a recording layer in a multilayer film provided on a substrate by an energy beam such as light, wherein: (a) the recording layer has a composition of a spinodal decomposition region. And (b) after the irradiation of the energy beam onto the recording layer, the irradiated recording layer is rapidly cooled to cause phase separation by spinodal decomposition, and reflects the irradiated beam at the time of reading. A reflective quenching layer made of a metal material having a high heat absorption coefficient is provided so as to be located on the opposite side of the recording layer from the base material, and the reflective quenching layer is provided on the recording layer.
Spinodal decomposition by the energy beam irradiation
Than the reflectance of the optical recording medium before phase separation occurs,
The recording layer is irradiated with the energy beam by a spinoder.
Of the optical recording medium after phase separation due to
For an optical recording medium provided so as to have a high emissivity, (c) an optical recording medium having a strength such that phase separation by spinodal decomposition occurs in accordance with information to be written in the recording layer in which phase separation by spinodal decomposition does not occur. An energy beam such as light is irradiated, and recording is performed by utilizing the fact that the reflectance in the phase-separated portion of the recording layer is increased. (D) The written information is not subjected to phase separation due to the spinodal decomposition. An optical recording method characterized by irradiating an energy beam such as light with such intensity to read out.