JP2512043B2 - 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 has excellent reliability, and has shown remarkable growth as the price of players has dropped. In addition, a CD-ROM that utilizes the access performance of a CD and uses it as an external memory for digital data is also expected to develop due to 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 produced using expensive manufacturing equipment (software here means music software, game software, and business software in general). The production of this nickel stamper is expensive. Due to the high cost and the extremely high precision and large scale of the production equipment, no one could make several or tens of discs.

Problems to be Solved by the Invention The present invention does not require the above-mentioned expensive nickel stamper and stamper manufacturing apparatus for each software,
The purpose of the present invention is to easily manufacture an optical disk that can be reproduced by a commercially available compact disk player. This will dramatically increase the flexibility of software production and reduce the cost for small-volume production.

Means for Solving the Problems In order to solve the above problems, in the optical recording method of the present invention, a transparent substrate on which guide grooves for tracking servo are formed is provided except for a specific absorption wavelength range. An optical recording medium on which a transparent optical recording layer is formed and on which a reflective layer is formed is irradiated with recording light having a wavelength belonging to a specific absorption region of the optical recording layer so that the optical recording layer has optical properties. A signal recording process that causes a change, and a reproducing process that detects a signal recorded as the above-mentioned change in optical properties on the optical recording layer by reproducing light having different wavelengths that does not belong to the absorption wavelength region of the recording layer. The optical recording medium used at this time is an optical recording medium having a transparent optical recording layer on a transparent substrate except a specific absorption wavelength range, and a reflective layer on the transparent optical recording layer. The layer belongs to the specific absorption band The recording light is absorbed to cause a change in the optical property, and the change in the optical property is retained even for the reproduction light having a wavelength not belonging to the specific absorption band.

The transparent substrate, which is one of the constituent elements of the optical recording medium of the present invention, has a guide groove for tracking servo formed on the surface thereof to prevent reflection of a part of the recording light at the interface between the transparent substrate and the optical recording layer. The signal is recorded while using the guide groove to track. The change in optical properties that occurred during recording is almost over the entire wavelength range. Therefore, for the reproduction light that does not belong to the absorption wavelength range of the recording layer (that is, the recording layer is transparent to the reproduction light). The signal is detected as a discontinuity in the amount of light emitted. At this time, coherent light is used for recording, and the spot diameter of the light on the recording layer is 0.5 to 1.5 μm.
By adjusting the optical system so that the width of the gap formed by recording does not exceed 1.6 μm, and the reflectance of the reproducing light incident from the transparent substrate side is 70 μm. By setting the ratio to be at least%, it is possible to play on a conventional 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 and a recording layer.
2 and the reflective layer 3. It is also possible to further form a protective layer on the reflective layer 3. 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. With respect to such a recording layer, since the focus of light is focused on the interface between the recording layer 2 and the transparent substrate 1, 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 the groove depth 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 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. Further, the guide groove on the surface of the transparent substrate may be formed by an injection molding method or may be formed by using a photocurable resin. As a method for forming the recording layer 2 on the transparent substrate 1, a vacuum vapor deposition method or a solution coating method is selected depending on the material of the recording layer. Among the solution coating methods, spin coating, dip coating,
A web coat is suitable. As an optical recording material,
Organic dye-based materials having absorption only in a specific wavelength band are suitable.

Specifically, it can be selected from cyanine dyes, squarylium dyes, phthalocyanine dyes, cholines, pyrylylium dyes, metal complex compounds and the like. These organic dye-based materials may be used alone in the recording layer, or may be dispersed in a binder such as a transparent resin and used. The reflective layer 3 is formed on the recording layer 2. The reflective layer 3 itself emits reproduction light.
It is necessary to reflect 80% or more, 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 recording layer 2 and the reflective layer 3 is 1/3 or more of the wavelength of the reproduction light, inconvenience is likely to occur in the tracking during reproduction, 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 20 nanometers (nm) to 10
00 nm is suitable, and it is difficult to detect a signal below this range, and crosstalk increases if it exceeds this range. The thickness of the reflective layer 4 varies depending on the material used, but may be any film having a reflectance of 80%.

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 has a recording layer 2 at the time of recording.
Since the light is reflected at the interface between the transparent substrate 1 and the transparent substrate 1, the recording light is scanned along the guide groove formed on the transparent substrate 1. The recording layer absorbs the light and generates heat in the portion irradiated with the recording light,
This results in decomposition. A void 5 is formed in the recording layer 2 by this heat decomposition. Recording layer 2 for the wavelength of reproducing light
Is transparent, almost all the reproduction light is reflected by the reflection layer 3. In this state, as shown as a model in FIG. 3, the voids 5 are formed so as to be slightly raised from the reflective layer 3. When the reproducing light 6 is irradiated onto this, the void 5 is detected as a discontinuous portion of the refractive index in the medium having a substantially uniform refractive index for the reproducing light 6. That is, the amount of reflected light is reduced in the void portion. Therefore, the reproduction light 6 can be tracked along the recorded gap 5, 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.

Now, for the laser used for reproduction here, the same wavelength as the semiconductor laser used in the commercially available compact disc player, that is, 770 nm to 840 nm is used, while for recording, if a laser of a wavelength not belonging to the above wavelength is used,
Compatible with CD. The size of the void formed by recording depends not only on the thickness of each constituent layer but also on the recording conditions. The recording condition cannot be uniquely determined because it depends 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 0.6 μm and a depth of 70 nm is 1.6.
Diameter 12c spirally formed on the surface with a pitch of μm
A chloroform solution of dye (1) was applied to a glass plate having a thickness of m and a thickness of 1.2 mm to a thickness of 300 nm.

Aluminum was vacuum-deposited on it to a thickness of 50 nm. A 633 nm He-Ne gas 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 is performed by light irradiation from the transparent substrate side, and the recording conditions are output 2.8 mW and linear velocity.
At 1.3 m / s, an objective lens with NA 0.5 was used, and the frequency duty ratio was 50/50. The reflectance of the signal surface after recording was 80% or more from 780 nm to 830 nm. The reproduced C / N when reproduced with a 780 nm semiconductor laser while applying tracking servo to the recorded signal was 42 dB. Further, the optical disc manufactured in this way could be reproduced by a commercially available compact disc player.

Example 2 A groove for tracking servo having a width of 0.6 μm and a depth of 90 nm is 1.6.
Diameter 12c spirally formed on the surface with a pitch of μm
SiO ₂ was vacuum-deposited in a thickness of 20 nm on a polycarbonate plate having a thickness of 1.2 mm and a thickness of 300 nm using a Victoria blue chloroform solution.

Aluminum was vacuum-deposited on it to a thickness of 50 nm. A 633 nm He-Ne gas 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 is performed by light irradiation from the transparent substrate side, and the recording conditions are output 3 mW, linear velocity 1.
At 3 m / s, an objective lens with NA 0.5 was used, and the frequency duty ratio was 50/50. The reflectance of light from the transparent substrate side of this disk at a wavelength of 830 nm was 80% or more. When the recorded single signal of 500 KHz was reproduced with a semiconductor laser of 830 nm, a reproduction C / N of 42 dB was obtained.
In addition, any of the optical discs manufactured in this manner could be reproduced by a commercially available compact disc player.

Example 3 A groove for tracking servo having a width of 0.6 μm and a depth of 90 nm is 1.6.
Diameter 12c spirally formed on the surface with a pitch of μm
SiO ₂ was vacuum-deposited on a polycarbonate plate having a thickness of m and a thickness of 1.2 mm to a thickness of 280 nm using a chloroform solution of a cyanine dye (NK-1511 manufactured by Nihon Sensitive Dye Co., Ltd.).

On this, aluminum was vacuum-deposited with a thickness of 50 nm. A semiconductor laser of 750 nm 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 is performed by light irradiation from the transparent substrate side, and the recording conditions are an output of 2.9 mW and a linear velocity of 1.
At 3 m / s, an objective lens with NA 0.5 was used, and the frequency duty ratio was 50/50. The reflectance of light from the transparent substrate side of this disk at a wavelength of 830 nm was 80% or more. When the recorded single signal of 500 KHz was reproduced with a semiconductor laser of 830 nm, a reproduction C / N of 42 dB was obtained.
In addition, any of the optical discs manufactured in this manner 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 2, 1500 blue which was also used in Example 2 was applied.
It was applied to a thickness of nm. 50 more aluminum on it
nm was vacuum-deposited. Irradiate 633 nm He-Ne gas 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 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 reflectance of light from the transparent substrate side at a wavelength of 780 nm to 830 nm was 63%. The 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 voids formed by recording became too large.

Comparative Example 2 On the polycarbonate substrate with the SiO ₂ layer used in Example 2, the victoria blue used in the same example was applied to a thickness of 15 nm, and aluminum was vacuum-deposited to a thickness of 50 nm on this. 633nm while applying tracking servo in the guide groove
The He-Ne gas laser of
A single Hz signal and a modulated signal were recorded in the guide groove. Recording is performed by light irradiation from the transparent substrate side, and the recording conditions are
With an output of 3 mW and a linear velocity of 1.3 m / s, using an NA 0.5 objective lens,
The frequency duty ratio was set to 50/50. The reflectance of light from the transparent substrate side of this disk at a wavelength of 780 nm to 830 nm was 80% or more. The 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 gap formed by recording was too small and tracking servo was not applied.

Although the present invention has been described as applied to a compact disc, the present invention is not limited to a compact disc, and can be applied to recording / reproducing image information by adjusting a substrate and recording conditions.

EFFECTS OF THE INVENTION As described in the above embodiments, according to the present invention, the expensive stamper manufacturing process, which has been indispensable up to now in the manufacture of a CD, is unnecessary, and therefore the same software CD or CD-RO is used.
Small volume production of M etc. can be done cheaply and easily. In addition, because it is a method of recording with a laser having a wavelength different from that of reproduction on an optical recording medium on which a reflective film is formed in advance, it has the convenience of being able to reproduce immediately without any special operation if recording. .

[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 ... Reflective layer, 4 ...
Guide groove, 5 ... void due to recording.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Isomi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshihiko Nakatani 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Company (72) Inventor Toru Tamura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 62-119755 (JP, A) JP 1-151028 (JP, A) )

Claims (8)

(57) [Claims] 1. An optical recording medium having a transparent optical recording layer on a transparent substrate except for a specific absorption wavelength region, and a reflective layer thereon, wherein the optical recording layer has the specific absorption. An optical recording characterized by absorbing recording light belonging to a band to cause a change in optical properties and retaining the change in optical properties even with respect to reproducing light having a wavelength not belonging to the specific absorption band. Medium. 2. The optical recording medium according to claim 1, wherein the change in optical property caused by the absorption of recording light by the optical recording layer is formation of voids. 3. The optical recording medium according to claim 1, wherein the transparent substrate has a guide groove for tracking servo on its surface. 4. An optical recording in which a transparent optical recording layer except a specific absorption wavelength region is formed on a transparent substrate on which guide grooves for tracking servo are formed in advance, and a reflective layer is formed thereon. A signal recording process of irradiating the medium with recording light having a wavelength belonging to a specific absorption region of the optical recording layer to cause a change in optical properties of the optical recording layer, and not belonging to the absorption wavelength region of the recording layer. An optical recording method comprising a reproducing process of detecting a signal recorded as a change in the optical property on the optical recording layer by reproducing lights having different wavelengths. 5. A change in optical property is caused by irradiation of recording light.
The optical recording method according to claim (4), characterized in that the refractive index is discontinuous due to a gap formed between the transparent substrate and the reflective layer. 6. The optical recording process is characterized in that recording light is recorded while scanning an interface between the optical recording layer and the transparent substrate along a guide groove for tracking servo formed on the transparent substrate. The optical recording method according to claim (4). 7. The optical recording method according to claim 4, wherein reproduction is performed by laser light. 8. The reproducing process detects a signal as a difference in the amount of reflected light by utilizing discontinuity in the refractive index due to an air gap formed between the transparent substrate and the reflective layer. The optical recording method according to the item (4).