JPH01151029A - Optical recording medium and optical recording method - Google Patents

Abstract

PURPOSE:To enhance the flexibility of software production and to reduce the cost at the time of small-quantity production by constituting the title medium in such a manner that the change in the optical properties formed on an optical recording layer is maintained even after the treatment to make the recording layer transparent prior to reproduction. CONSTITUTION:The optical recording layer 2 of the optical recording medium which is provided with the optical recording layer 2 on a transparent substrate 1 and has further a reflecting layer 3 thereon is recorded with signals as the change in optical properties by irradiation of laser light to be used for recording. The medium is so constituted that the recording part maintains the change in the optical properties with the laser light even after the treatment to make the recording layer 2 transparent. The change in the optical properties generated at the time of recording is, therefore, maintained even after the optical recording layer 2 is made transparent. The signals can be consequently reproduced as the difference in the quantity of the reflected light between the signal recording part and the unrecording part at the time of irradiation of light of the reproduction light after the recording layer is made transparent. The need for the process for producing a costly stamper in the manufacture of CDs is thereby eliminated and the small-quantity production of the CDs and CD-ROMs of the same software is executed at the low cost with ease.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an optical recording medium and an optical recording method.

Conventional technology] Compared to LP records, compact discs have lower sound quality,
It is easy to use and has excellent credibility, and is showing remarkable growth as players become cheaper. Furthermore, CD-ROMs, which utilize the access functions of CDs and use them as external memories for digital data, are also expected to develop because of their large capacity, economy, and reliability. By the way, in order to manufacture these compact discs, a nickel stamper has conventionally been required for each piece of software, which can only be manufactured using expensive manufacturing equipment.

(Software here refers to music software, game software,
Refers to business software in general. ) This nickel stamper
Because it requires a high cost to produce, and the production equipment is extremely high-precision and large-scale, it is not possible to simply produce just a few or even dozens of discs of the same software. Ta.

Problems to be Solved by the Invention The present invention solves the above-mentioned nickel stamper and stamper.
The aim is to make it possible to easily manufacture optical discs that can be played on conventional commercially available compact disc players without requiring manufacturing equipment for each piece of software, thereby dramatically increasing the flexibility of software production. It is also possible to reduce costs when producing small quantities.

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 that has an optical recording layer on a transparent substrate, and further has a transparent layer and a reflective layer thereon. A signal is recorded as a change in optical properties when the optical recording layer is irradiated with a laser beam used for recording, and the recording portion retains the change in optical properties against the laser beam even after the recording layer is made transparent. Using such an optical recording medium, an optical recording layer is formed on a transparent substrate on which a guide groove for tracking servo is formed in advance, a transparent layer is formed on top of the optical recording layer, and a reflective layer is formed on top of the transparent substrate. A laser beam is applied to an optical recording medium with a layer formed thereon through an optical recording process in which the optical recording layer is irradiated with a laser beam to cause a change in the optical properties of the optical recording layer, and a process in which the optical recording layer is made transparent. An optical recording method is used in which a signal can be reproduced as a difference in the amount of reflected light between the green area that has been irradiated and the unrecorded area that has been made transparent.

Function The transparent substrate, which is a component of the optical recording medium of the present invention, has a guide groove for tracking servo formed on its surface, and reflects a portion of the recording light at the interface between the transparent substrate and the optical recording layer. The changes in optical properties that occur during recording are retained even after the optical recording layer is made transparent, so it is difficult to irradiate the reproduction light after the transparentization. In this case, the signal can be reproduced as the difference in the amount of reflected light between the signal recorded area and the unrecorded area. At this time, the optical system was adjusted so that the spot diameter of the light on the recording layer was 0.5-1.5 μm, and the recording conditions were adjusted so that the width of the gap formed by recording did not exceed 1.6 μm. By setting and further setting the reflectance of the reproducing laser beam incident from the transparent substrate side to 70% or more, it becomes possible to reproduce the disc on a conventional commercially available compact disc player.

EXAMPLE Hereinafter, an example of the present invention will be described in detail 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 includes a transparent substrate 1, a recording layer 2,
It consists of a transparent Ji 3 and a reflective layer 4. It is also possible to further form a protective layer over the reflective layer 4. Before recording a signal, the recording layer 2 must have the property of absorbing the light used for recording, and at the same time, must also have the property of reflecting a part of the recording light. For such a recording layer, the light is focused on the interface between the recording layer 2 and the transparent substrate l, so the guide groove for the tracking servo formed on the transparent substrate 1 acts effectively, and the recording light is scanned along the guide groove. The shape of the guide groove at this time depends on the recording light, but it is preferably about 1/4 to 1/8 of the wavelength of the recording light, and the width of the groove is about the same as the wavelength or about 1/2 of it. It is preferable that the range is up to . The material of the transparent substrate needs to be transparent to the light used for recording and reproduction, and various transparent plastics such as glass, polycarbonate, polymethyl methacrylate, polyimide, and polymethylpentene can be used. When using transparent plastic ink as the transparent substrate, a transparent protective layer may be formed between the transparent substrate 1 and the recording layer 2 to prevent damage to the substrate during formation of the recording film. may be made by injection molding, or may be formed using a photocurable resin on a smooth transparent substrate. As a method for forming the recording layer 2 on the transparent substrate 1, a vacuum coating method or a solution coating method is selected depending on the material of the recording layer.

Among solution coating methods, spin coating, dip coating, web coating, etc. are suitable. The same method used for forming the recording layer can also be used to form the transparent layer 3 on the recording layer 2. Methods of making the recording layer transparent include heating, photooxidation,
Several methods such as chemical reactions are possible, but in the optical recording medium of the present invention, the recording layer 2 is not exposed on the surface and the substrate is made of heat-resistant plastic. Clarification by oxidation is the most common. Therefore, organic dye materials exhibiting photobleaching properties are suitable as materials for the optical recording layer, specifically cyanine dyes,
There are squarylium dyes, virylium dyes, etc., and among them, cyanine dyes are the most suitable. The fading organic dye may be used alone as a recording layer, or may be dispersed in a binder such as a transparent resin. It is necessary that the material does not corrode, and in the case of solution coating, it is selected from organic materials that are soluble in solvents that do not dissolve organic coloring materials, such as alcohol, hexane, and water. Specifically, one of polyvinyl alcohol, polyvinyl and lolidone, polyamide, and cellulose, or a mixture thereof is suitable. The reflective N4 itself that forms the reflective layer 4 on the transparent layer 3 must reflect 80% or more of the reproduction light, and must be made of one of gold, platinum, silver, aluminum, indium, and copper or an alloy thereof. It is preferably formed by vacuum evaporation or sputtering. If the unevenness of the interface between the transparent layer 4 and the reflective layer N3 is 1/3 or more of the wavelength of the reproducing light, problems will likely occur in tracking during reproduction, so each layer constituting the optical recording medium must have an unevenness of 1/3 or less. The thickness of is described below. First, the thickness of the recording layer 2 is 20 nanometers (nm).
4 (11) nm is suitable; below this range, it is difficult to detect a signal, and above this range, crosstalk becomes large. Next, the thickness of the transparent layer 3 is 11
(11) It must be less than 0n; if it exceeds this, the recorded signal and the reflective layer will be too far apart, resulting in poor tracking performance during reproduction. Note that the thickness of the reflective layer 4 varies depending on the material used, but it is sufficient as long as it has a thickness that provides a reflectance of 80% or more.

Next, the recording and reproducing mechanism of the recording medium of the present invention will be explained. In the optical recording medium of the present invention, during recording, since light is reflected at the interface between the recording layer 2 and the transparent substrate 1, the recording light is scanned along the guide groove formed on the transparent substrate 1. In the area irradiated with the recording light, the recording layer absorbs the light and generates heat, resulting in decomposition. Due to this exothermic decomposition, t! A gap 6 is formed in a region including the transparent layer 12 and a part of the transparent layer 3. After recording is completed, light is irradiated from the side of the transparent substrate 1 to make the recording layer 2 transparent. After becoming transparent, almost all of the reproduced light is reflected by the reflective layer 4. In this state, as shown schematically in FIG. 3, a void 6 is formed in a state slightly raised from the reflective layer 4. When the reproduction light 7 is irradiated here, the gap 6 is detected as a discontinuous part of the refractive index in a medium having a substantially homogeneous refractive index. In other words, the amount of reflected light is reduced in the gap. Therefore, the reproduction light 7 can be tracked along the recorded gap 6, and the recorded signal can be reproduced. In total, 70% of the regenerated light
A signal recording plate with a high reflectance of more than % reflected is completed. Now, the laser used for playback here is
The wavelength is the same as that used in commercially available compact disc players, from T70nm to 840nm; however, the laser used for recording may have the same wavelength as the laser for playback, but it is limited to the same wavelength. isn't it. The size of the void formed by recording is determined not only by the thickness of each constituent layer but also by 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 CD, which is the objective of the present invention, the size of the gap formed by recording should be 0. 3μm or more1
．． It is necessary that the thickness be 6 μm or less.

Example 1 On a glass plate with a diameter of 123 mm and a thickness of 1.2 mm, on which tracking servo grooves with a width of 0.8 μm and a depth of 9 Q nm were formed in a spiral shape at a pitch of 1.6 μm, a dye of +1
A chloroform solution of 1 was applied to a thickness of 2 (11) nm.

On top of this, using an aqueous solution of polyvinylpyrrolidone, 1
A transparent layer having a thickness of 1 (11) nm was formed, and aluminum was further vacuum-deposited to a thickness of 50 nm thereon.

A 780 nm semiconductor laser was irradiated onto the dye while applying tracking servo in the guide groove, and a single signal with a frequency of 5 (11) KHz and a modulation signal were recorded in the guide groove.

Recording was performed by light irradiation from the transparent substrate side, and the recording conditions were an output of 3 mW, a linear velocity of 1.3 m/s, an objective lens with NAo of 5, and a frequency duty ratio of 501.
It was set at 50.

Irradiate the recorded disc with light from a xenon lamp, and
The recording layer was made transparent over time. The reflectance of light at wavelengths from 780 nm to 830 nm from the transparent substrate side after transparentization was 80% or more. Recorded.

5 (11) KHz sheep - 48 dB as signal reproduction CN
was gotten. Furthermore, the optical disc produced in this way could be played on a commercially available compact disc player.

Example 2-4 SiO□ was deposited on a polycarbonate plate with a diameter of 12′C and a thickness of 1.211 mm, on which tracking servo grooves of 0.6 μm in width and 90 nm in depth were spirally formed on the surface at a pitch of 1.6 μm. 20 nm vacuum evaporated, then dye (2
) and the chloroform solution of (3) and (4) as dye f4.
1: CY-9 (Nippon Kayaku Rui) On this, a 150 nm thick transparent layer was formed using an aqueous solution of a 2:1 mixture of polyvinylpyrrolidone and hydroxyethyl cellulose, and on top of that a 50 nm thick layer of aluminum was deposited under vacuum. Deposited. Do not apply tracking servo in guide groove 830
A semiconductor laser of 5 nm is irradiated onto the dye, and a frequency of 5 (
11) A KHz single signal and a modulated signal were recorded in the guide groove. Recording was performed by light irradiation from the transparent substrate side, and the recording conditions were an output of 3 mW, a linear velocity of 1.3 + m/s, and an NAo
, 5 objective lenses were used, and the frequency duty ratio was set to 50150. The recorded disc was irradiated with light from a xenon lamp, and the recording layer was made transparent over a period of 5 hours as in Example 1. 780n from the transparent substrate side after transparentization
The reflectance of light at a wavelength from m to 830 nm was 80% or more in Example 2 using dye (2), Example 3 using dye (3), and Example 4 using dye (4). there were.

The reproduction CN of the recorded single signal of 5 (11) KHz is 45 dB and 45 dB for Examples 2.3.4, respectively.

46dB was obtained. Furthermore, all of the optical discs produced in this way could be played on commercially available compact disc players.

Comparative Example 1 Dye 4, which was also used in Example 4, was deposited at 3 (11) nm on the polycarbonate substrate with the SiO□ layer used in Example 4.
A transparent layer with a thickness of 150 nm was formed thereon using an aqueous solution of a 2:1 mixture of polyvinylpyrrolidone and hydroxyethyl cellulose, and aluminum was further vacuum-deposited to a thickness of 50 nm thereon. A semiconductor laser of 830 nm was irradiated onto the dye without applying tracking servo in the guide groove, and a single signal with a frequency of 5 (11) Kllz and a modulated signal were recorded in the guide groove.

Recording was performed by light irradiation from the transparent substrate side, and the recording conditions were an output of 9 mW, a linear velocity of 1.3 m/s, and an NAo of 5.
objective lens, and the frequency duty ratio is 5.
It was set to 0150. The recorded disc was irradiated with light from a xenon lamp, and the recording layer was made transparent over a period of 5 hours as in Example 1. The reflectance of light at wavelengths from 780 nm to 830 nm from the transparent substrate side after transparentization was 50%.

Recorded 5 (11)! It was not possible to write a tracking servo for either the Iz single signal or 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 S i Ox iJ used in Example 4, 150 n of the same dye 4 used in Example
On top of this, a transparent layer with a thickness of 15 (11) nm was formed using an aqueous solution of a 2:1 mixture of polyvinylpyrrolidone and hydroxyethyl cellulose, and on top of this, aluminum was coated with a thickness of 50 nm. Vacuum deposited. Without applying tracking servo in the guide groove, an 830 nm semiconductor laser is irradiated onto the dye, and the frequency is 5 (11) K.
A single Hz signal and a modulated signal were recorded in the guide groove. Recording was performed by light irradiation from the transparent substrate side, and the recording conditions were an output of 3 mW, a linear velocity of 1.3 m/s, an objective lens with NAo of 5, and a frequency duty ratio of 5015.
It was set to 0. The recorded disc was irradiated with light from a xenon lamp, and the recording layer was made transparent over a period of 5 hours as in Example 1. 83 from 780 nm from the transparent substrate side after transparentization
The reflectance of light at a wavelength of 0 nm was 80% or more.

Tracking servo could not be applied to either the recorded 5 (11) KHz single signal or the modulated signal, and therefore the signals could not be reproduced. This is because the gap formed by recording was too far away from the reflective layer, so tracking servo was not applied.

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

Effects of the Invention As explained in the above embodiments, the present invention eliminates the need for the expensive standby manufacturing process that has been indispensable in the production of CDs.
Small quantity production of ROMs etc. can be done cheaply and easily. Furthermore, since the recording is performed on an optical recording medium on which a reflective film is formed in advance, it is convenient because it can be reproduced as soon as it becomes transparent.

[Brief explanation of the drawing]

FIG. 1 is a sectional view illustrating 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 medium sectional view illustrating the reproduction process of the optical recording medium of the present invention. 1...Transparent substrate, 2...Recording layer, 3.
...Transparent layer, 4...Reflection layer, 5...
...Guide groove, 6--...Gap due to recording. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1

Claims (1)

[Scope of Claims] (1) An optical recording medium having an optical recording layer that can be made transparent by a specific treatment on a transparent substrate, a transparent layer on top of the optical recording layer, and a reflective layer on top of the transparent layer, The optical recording layer absorbs the laser beam used for recording and a signal is recorded as a change in optical properties, and the change in optical properties formed on the optical recording layer causes the recording layer to become transparent prior to reproduction. An optical recording medium that is retained even after processing. (2) Optical recording according to claim (1), characterized in that voids are formed in the optical recording layer as a form of change in optical properties by irradiation with a laser beam used for recording. Medium. (3) When the reproduction light is incident from the substrate side,
Spectral reflectance at the wavelength of the laser beam used for reproduction is 70%
An optical recording medium according to claim (1), which is characterized by the above. (4) The 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 as at least one component an organic dye-based material that can be made transparent by a specific treatment. (6) The optical recording medium according to claim (5), wherein the optical recording layer contains as at least one component an organic dye-based material that can be made transparent by photobleaching. (7) Laser light is applied onto an optical recording medium that has an optical recording layer on a transparent substrate on which a guide groove for tracking servo is formed in advance, a transparent layer on top of that, and a reflective layer on top of that. An optical recording process that causes a change in the optical properties of the optical recording layer by irradiation, a process that makes the optical recording layer transparent, and a process that irradiates the optical recording layer with a reproduction laser to create the recorded area and the unrecorded area that has been made transparent. 1. An optical recording method characterized by comprising a process in which a signal can be reproduced as a difference in the amount of reflected light between the two parts. (8) Claims characterized in that the optical recording process is of a type in which a gap is created in the irradiated area between the transparent substrate and the reflective layer by irradiating the optical recording layer with the light used for recording. The optical recording method described in paragraph (7). (9) The reproduction process is characterized in that a signal is detected as a difference in the amount of reflected light by utilizing discontinuity in the refractive index caused by a gap between the transparent substrate and the reflective layer.
) The optical recording method described in section 2. (10) The optical recording process is characterized in that recording is performed while the recording light scans the optical recording layer along a guide groove for a tracking servo formed on the surface of the transparent substrate. ) The optical recording method described in section 2. (11) The optical recording method according to claim (7), wherein the optical recording layer contains as at least one component an organic dye-based material that can be made transparent by a specific treatment. (12) The optical recording method according to claim (11), wherein the optical recording layer contains as at least one component an organic dye-based material that can be made transparent by photobleaching.