JP2512045B2 - Optical recording medium and optical recording method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical recording medium and an optical recording method.

Conventional technology Compact discs have better sound quality than LP records.
It is easy to handle and reliable, and has shown remarkable growth as the price of players has dropped. In addition, a CD-ROM that utilizes the access function of a CD and uses it as an external memory for digital data is also expected to develop because of its large capacity, economy, and reliability. by the way,
In order to manufacture these compact discs,
Each software required a nickel stamper that could only be manufactured using expensive manufacturing equipment. (The software mentioned here refers to music software, game software, and business software in general.) Because of the high cost required to manufacture this nickel stamper, and because the manufacturing equipment is extremely accurate and large-scale , I couldn't easily make a few or tens of discs of the same software.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention intends to easily manufacture an optical disk that can be reproduced by a conventional commercially available compact disk player without requiring the above-described nickel stamper and stamper manufacturing apparatus for each software. As a result, the flexibility of software production can be dramatically increased and the cost can be reduced for small-volume production.

Means for Solving the Problems In order to solve the above problems, the optical recording medium of the present invention is an optical recording medium having an optical recording layer on a transparent substrate and further having a transparent layer and a reflective layer thereon. The optical recording layer records a signal as a change in optical property by irradiation with laser light used for recording, and the recording portion retains the change in optical property with respect to laser light after the recording layer is made transparent. By using such an optical recording medium, an optical recording layer is formed on a transparent substrate on which guide grooves for tracking servo are previously formed, a transparent layer is formed on the optical recording layer, and then a reflection layer is formed on the transparent recording layer. The optical recording medium on which the layer is formed is irradiated with a laser beam to cause the optical recording layer to change its optical properties, and the optical recording layer is made transparent. Irradiated and recorded area and transparent area According to an optical recording method capable of reproducing a signal as a difference in the amount of reflected light from the recording portion.

The transparent substrate, which is one component of the optical recording medium of the present invention,
A guide groove for tracking servo is formed on the surface, and a signal is recorded while being tracked by the guide groove by utilizing a part of reflection of recording light at the interface between the transparent substrate and the optical recording layer. Since the change in the optical properties caused by recording is retained even after the optical recording layer is made transparent, the difference in the amount of reflected light between the signal recorded portion and the unrecorded portion during irradiation of the reproducing light after the transparentization is Can play the signal. At this time, adjust the optical system so that the spot diameter of the light on the recording layer is 0.5-1.5 μm,
In addition, by setting the recording conditions so that the width of the gap formed by recording does not exceed 1.6 μm, and by making the reflectance of the reproducing laser light incident from the transparent substrate side 70% or more, It can be played on a commercially available compact disc player.

Embodiment One embodiment of the present invention will be specifically described below with reference to the drawings.

An embodiment of the present invention is illustrated in FIGS. 1 and 2. That is, the optical recording medium of the present invention comprises a transparent substrate 1, a recording layer 2, a transparent layer 3 and a reflective layer 4. It is also possible to further form a protective layer on the reflective layer 4. In a state before recording a signal, the recording layer 2 needs to have a property of absorbing light used for recording, and at the same time have a property of reflecting a part of the recording light. In such a recording layer, the focus of light is focused on the interface between the recording layer 2 and the transparent substrate 1, so that the guide groove for tracking servo formed on the transparent substrate 1 effectively acts, and the recording light is emitted. It is scanned along the guide groove. The shape of the guide groove at this time depends on the recording light, but is preferably about 1/4 to 1/8 of the wavelength of the recording light. The width of the groove is preferably the same as the wavelength or within a range up to about 1/2 of the wavelength. The material of the transparent substrate is required to be transparent to the light used for recording and reproduction, and various transparent plastics such as glass, polycarbonate, polymethylmethacrylate, polyimide, polymethylpentene can be used. When a transparent plastic is used as the transparent substrate, a transparent protective layer may be formed between the transparent substrate 1 and the recording layer 2 in order to prevent the substrate from being damaged when the recording film is formed. The guide groove on the transparent substrate may be formed by injection molding, or may be formed on the smooth transparent substrate using a photocurable resin. The method of forming the recording layer 2 on the transparent substrate 1 depends on the material of the recording layer.
The vacuum vapor deposition method and the solution coating method are selected. Among the solution coating methods, spin coating, dip coating, web coating and the like are suitable. For forming the transparent layer 3 on the recording layer 2, the same method as that used for forming the recording layer can be used. Several methods such as heating, photooxidation, and chemical reaction can be considered as the method for making the recording layer transparent, but in the optical recording medium of the present invention, the recording layer 2 is not exposed on the surface, and the substrate is not exposed. Considering the use of heat-sensitive plastic as the material, it is most suitable to make it transparent by photooxidation. Therefore, as a material for the optical recording layer, an organic dye material exhibiting a photobleaching property is suitable, and specifically, a cyanine dye, a squarylium dye, a virylylium dye and the like are available, and a cyanine dye is most suitable. The fading organic dye may be used alone in the recording layer, or may be dispersed in a binder such as a transparent resin and used. The transparent layer 3 laminated on the recording layer 2 is
It is necessary that the recording layer is not eroded during formation, and in the case of solution coating, it is selected from organic materials soluble in solvents that do not dissolve organic dye materials such as alcohol, hexane, and water. Specifically, one or a mixture of polyvinyl alcohol, polyvinylpyrrolidone, polyamide and cellulose is suitable. The reflective layer 4 is formed on the transparent layer 3. The reflective layer 4 itself needs to reflect 80% or more of the reproduction light, and it is preferable to form one or an alloy of gold, platinum, silver, aluminum, indium, and copper by vacuum vapor deposition or sputtering. If the unevenness of the interface between the transparent layer 4 and the reflective layer 3 is 1/3 or more of the wavelength of the reproduction light, tracking during reproduction is likely to be inconvenient, so it should be 1/3 or less. The thickness of each layer constituting the optical recording medium will be described below. First, the thickness of the recording layer 2 is preferably 20 nanometers (nm) to 400 nm, and it is difficult to detect a signal below this range, and crosstalk becomes large beyond this range. Next, the thickness of the transparent layer 3 must be 1000 nm or less, and if it exceeds this range, the recorded signal and the reflective layer become too far apart from each other, which deteriorates the tracking property during reproduction. Although the thickness of the reflective layer 4 varies depending on the material used, it is sufficient if the reflective layer 4 has a film thickness such that the reflectance is 80% or more. Next, the recording and reproducing mechanism of the recording medium of the present invention will be described. The optical recording medium of the present invention is
During recording, the light is reflected at the interface between the recording layer 2 and the transparent substrate 1, so that the recording light is scanned along the guide groove formed on the transparent substrate 1. At the portion irradiated with the recording light, the recording layer absorbs the light and generates heat, resulting in decomposition. By this heat decomposition, voids 6 are formed in the recording layer 2 and a region including a part of the transparent layer 3. After the recording is completed, light is irradiated from the transparent substrate 1 side to make the recording layer 2 transparent. After it becomes transparent, almost all the reproduction light is reflected by the reflection layer 4. In this state, as shown as a model in FIG. 3, the void 6 is formed so as to be slightly raised from the reflective layer 4. When the reproducing light 7 is irradiated onto this, the void 6 is detected as a discontinuous portion of the refractive index in the medium having a substantially uniform refractive index for the reproducing light 7. That is, the amount of reflected light is reduced in the void portion. Therefore, the reproduction light 7 can be tracked along the recorded gap 6, and the recorded signal can be reproduced. In this way, a signal recording plate having a high reflectance of 70% or more of the reproduced light as a whole is completed. The laser used for playback here has a wavelength of 770 nm to 840 nm, similar to that used in commercially available compact disc players.
On the other hand, the laser used for recording may have the same wavelength as the reproducing laser, but is not limited to the same wavelength. The size of the void formed by recording depends not only on the thickness of each constituent layer but also on the recording conditions. Recording conditions cannot be uniquely determined because they depend on the physical properties of the recording layer. In order to ensure compatibility with a CD, which is the object of the present invention, it is necessary that the size of the void formed by recording is 0.3 μm or more and 1.6 μm or less.

Example 1 A groove for tracking servo having a width of 0.8 μm and a depth of 90 nm was formed.
Diameter of spirally formed surface at 1.6 μm pitch 1
A chloroform solution of dye (1) was applied to a glass plate having a thickness of 2 cm and a thickness of 1.2 mm to a thickness of 200 nm.

On top of this, using an aqueous solution of polyvinylpyrrolidone,
A transparent layer having a thickness of 100 nm was formed, and 50 nm of aluminum was vacuum-deposited on the transparent layer. A 780 nm semiconductor laser was irradiated onto the dye while tracking servo was applied in the guide groove, and a single signal with a frequency of 500 KHz and a modulation signal were recorded in the guide groove. Recording was performed by irradiating light from the transparent substrate side. The recording conditions were an output of 3 mW, a linear velocity of 1.3 m / s, an NA 0.5 objective lens, and a frequency duty ratio of 50/50. The recorded disc was irradiated with light from a xenon lamp to make the recording layer transparent for 5 hours. The reflectance of light from the transparent substrate side after transparentization at the wavelength of 780 nm to 830 nm is 80.
% Or more. 48 dB was obtained as the reproduction CN of the recorded single signal of 500 KHz. Further, the optical disc thus manufactured could be reproduced by a commercially available compact disc player.

Example 2-4 A groove for tracking servo having a width of 0.6 μm and a depth of 90 nm is formed.
Diameter of spirally formed surface at 1.6 μm pitch 1
20 nm of SiO ₂ on a polycarbonate plate with a thickness of 2 cm and a thickness of 1.2 mm
After vacuum evaporation, each of the dyes (2), (3) and (4) was applied in chloroform to a thickness of 150 nm.

Dye (4): CY-9 (manufactured by Nippon Kayaku Co., Ltd.) On this, a 2: 1 mixture of polyvinylpyrrolidone and hydroxyethyl cellulose was used to form a transparent layer with a thickness of 150 nm. To
It was vacuum-deposited at 50 nm. A 830 nm semiconductor laser was irradiated onto the dye while tracking servo was applied in the guide groove, and a single signal with a frequency of 500 KHz and a modulation signal were recorded in the guide groove. Recording was performed by irradiating light from the transparent substrate side. The recording conditions were an output of 3 mW, a linear velocity of 1.3 m / s, an NA 0.5 objective lens, and a frequency duty ratio of 50/50. The recorded disk was irradiated with light from a xenon lamp, and the recording layer was made transparent for 5 hours as in Example 1. The reflectance of light at a wavelength of 780 nm to 830 nm from the transparent substrate side after being transparent is obtained by using Example 2 using dye (2), Example 3 using dye (3), and dye (4). Both Example 4 was 80
% Or more. 45 dB, 45 dB, and 46 dB were obtained for each of Examples 2, 3, and 4 as the reproduced CN of the recorded single signal of 500 KHz. In addition, any of the optical discs manufactured in this way could be reproduced by a commercially available compact disc player.

Comparative Example 1 On the polycarbonate substrate with the SiO ₂ layer used in Example 4, the dye 4 used in Example 4 was coated to a thickness of 300 nm, and a 2: 1 mixture of polyvinylpyrrolidone and hydroxyethyl cellulose was applied. 150n with aqueous solution
A transparent layer having a thickness of m was formed, and aluminum was vacuum deposited on the transparent layer to a thickness of 50 nm. A 830 nm semiconductor laser was irradiated onto the dye while tracking servo was applied in the guide groove, and a single signal with a frequency of 500 KHz and a modulation signal were recorded in the guide groove. Recording was performed by irradiation with light from the transparent substrate side. The recording conditions were an output of 9 mW, a linear velocity of 1.3 m / s, an NA 0.5 objective lens, and a frequency duty ratio of 50/50. The recorded disk was irradiated with light from a xenon lamp, and the recording layer was made transparent for 5 hours as in Example 1. The reflectance of the light at the wavelength of 780 nm to 830 nm from the transparent substrate side after being transparent was 50%. Tracking servo could not be written for both the recorded 500 KHz single signal and the modulated signal, and therefore the signal could not be reproduced. This is because the voids formed by recording became too large.

Comparative Example 2 On the polycarbonate substrate with the SiO ₂ layer used in Example 4, the dye 4 used in the same example was applied to a thickness of 150 nm, and an aqueous solution of a 2: 1 mixture of polyvinylpyrrolidone and hydroxyethylcellulose was applied onto the same. Using 1500nm
Was formed into a transparent layer, and 50 nm of aluminum was vacuum-deposited on the transparent layer. Irradiate a 830 nm semiconductor laser onto the dye while applying tracking servo in the guide groove,
A single signal with a frequency of 500 KHz and a modulated signal were recorded in the guide groove. Recording was performed by irradiating light from the transparent substrate side. The recording conditions were an output of 3 mW, a linear velocity of 1.3 m / s, an NA 0.5 objective lens, and a frequency duty ratio of 50/50.
The recorded disk was irradiated with light from a xenon lamp, and the recording layer was made transparent for 5 hours as in Example 1. The reflectance of the light from the transparent substrate side after the transparentization at the wavelength of 780 nm to 830 nm was 80% or more. Tracking servo could not be applied to both the recorded 500 KHz single signal and the modulated signal, and therefore the signal could not be reproduced.
This is because the void formed by recording was too far away from the reflective layer and tracking servo was not applied.

Although the present invention has been described by applying it to a compact disc, it should be additionally noted that image information can be recorded and reproduced by adjusting the size of the substrate and the recording conditions.

EFFECTS OF THE INVENTION As described in the above embodiments, according to the present invention, an expensive stamper manufacturing process, which has been indispensable until now in the manufacture of a CD, is unnecessary, so that a CD or a CD-ROM of the same software is used.
It is possible to produce small quantities such as at low cost and easily. In addition, since it is a method of recording on an optical recording medium on which a reflective film has been formed in advance, it has the convenience that it can be reproduced immediately if it is made transparent.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining the structure of the optical recording medium of the present invention,
FIG. 2 is a perspective view of the optical recording medium of the present invention, and FIG. 3 is a sectional view of the medium for explaining the reproducing process of the optical recording medium of the present invention. 1 ... Transparent substrate, 2 ... Recording layer, 3 ... Transparent layer, 4 ...
Reflective layer, 5 ... Guide groove, 6 ... Recording gap.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshihiko Nakatani Yoshihiko Nakatani 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toru Tamura 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-62-119755 (JP, A)

Claims (12)

(57) [Claims] 1. An optical recording medium comprising an optical recording layer which can be made transparent by a specific treatment on a transparent substrate, a transparent layer formed on the transparent recording layer, and a reflective layer formed on the transparent layer. , A signal is recorded as a change in optical property by absorbing a laser beam used for recording, and the change in optical property formed on the optical recording layer is retained even after the transparentizing treatment of the recording layer prior to reproduction. An optical recording medium characterized by the following. 2. The irradiation with a laser beam used for recording forms a void in the optical recording layer as a form of a change in optical property, according to claim (1). Optical recording medium. 3. The light according to claim 1, wherein the spectral reflectance at the wavelength of the laser light used for reproduction is 70% or more when the reproduction light is incident from the substrate side. recoding media. 4. An optical recording medium according to claim 1, wherein a guide groove for tracking servo is formed on the surface of the transparent substrate. 5. The optical recording medium according to claim 1, wherein the optical recording layer contains at least one component of an organic dye material which can be made transparent by a specific treatment. 6. The optical recording medium according to claim 5, wherein the optical recording layer contains at least one component of an organic dye material which can be made transparent by a light bleaching treatment. 7. An optical recording medium having an optical recording layer on a transparent substrate on which guide grooves for tracking servo are previously formed, a transparent layer on the transparent substrate, and a reflective layer on the transparent layer.
An optical recording process in which the optical recording layer is irradiated with laser light to cause a change in optical properties, a process of making the optical recording layer transparent, and a reproducing laser is irradiated to make the recording portion transparent. An optical recording method comprising the step of reproducing a signal as a difference in the amount of reflected light from an unrecorded portion. 8. The optical recording process is of a type in which an optical recording layer is irradiated with light used for recording to form a gap in an irradiated portion between a transparent substrate and a reflective layer. The optical recording method according to item (7). 9. The reproduction process detects a signal as a difference in the amount of reflected light by utilizing the discontinuity in the refractive index due to the air gap formed between the transparent substrate and the reflective layer. The optical recording method according to the item (7). 10. The recording light is recorded while scanning the optical recording layer along a guide groove for tracking servo formed on the surface of the transparent substrate in the optical recording process. The optical recording method according to the item (7). 11. The optical recording method according to claim 7, wherein the optical recording layer contains, as at least one component, an organic dye material which can be made transparent by a specific treatment. 12. The optical recording method according to claim 11, wherein the optical recording layer contains at least one component of an organic dye material which can be made transparent by a photobleaching treatment.