JPH0218086A - Optical recording medium and optical recording reproducing method - Google Patents

Abstract

PURPOSE:To obtain a reproducing signal of high reflectance and high quality since a recording layer is difficult to be influenced by flaws, corrosion, and oxidation irrespective of alight weighted single plate by a method wherein a quenching coefficient at a wavelength of a recording reproductive laser beam of a recording layer is made to be a specific value or over, and a thickness of the recording layer is made to be a specific value or under. CONSTITUTION:A quenching coefficient at a wavelength of a recording reproductive laser beam of a recording layer is preferably 0.1 or over and a thickness of the recording layer is 100nm or under. Further, the quenching coefficient is more preferably 0.3 or over and the thickness of the recording layer is 50nm or under. Recording laser beams are concentrated on the recording layer through a transparent substrate, and the recording layer on which recording laser beams are concentrated generates optical change. Reflectance of a light irradiated part becomes higher than that of a light non-irradiated part, and this variance in reflectance is detected with the reproductive laser beams to perform recording reproduction of information. A recording layer 2 containing an organic pigment generating resolution or optical variance by absorbing the recording laser beams, for instance, a pigment to be selected among cyanine dye, naphthoquinone pigment, phthalocyanine dye, squarilium pigment, etc. is applied on a substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording medium capable of recording and reproducing information using a focused laser beam, and an optical recording and reproducing method.

BACKGROUND OF THE INVENTION In recent years, many recordable and reproducible optical recording media using organic dyes as recording materials have been announced due to their ease of mass production and versatility in material selection.

Conventional recordable and reproducible optical recording media include, for example, Japanese Patent Application Laid-open No. 58
As shown in Japanese Patent No. 112794, the configuration was as shown in FIG. That is, a recording layer 2 made of an organic dye that absorbs laser light and decomposes or sublimates is formed on a transparent substrate 1. In the optical recording medium having this structure, the focused laser beam is absorbed by the recording layer and converted into heat, whereby the organic dye is decomposed or sublimated, forming pits 6, and recording is performed. Further, reproduction is performed by irradiating a weak laser beam and detecting changes in reflectance in the bit 6.

Problems to be Solved by the Invention However, the above-mentioned optical recording medium has pits exposed on the surface of the medium and is exposed to the atmosphere, making it susceptible to scratches (
To prevent corrosion and oxidation from occurring, and to prevent scratches on the media surface, use a spacer to protect the media. In the case of an air sandwich structure in which the substrates are bonded together, the medium becomes thicker and heavier. Furthermore, organic dyes have a low reflectance of about 10 to 30%, and the decrease in reflectance of pits formed by condensing the recording laser beam is detected as a signal, so the reflection level of the reproduced signal is low. There were problems such as the inability to play the discs on playback-only discs such as commercially available compact disc players.

In view of the above-mentioned problems, the optical recording medium and optical recording/reproducing method of the present invention are made of a lightweight single plate, the recording layer is less susceptible to scratches, corrosion, and oxidation, and has a high reflectance and high quality reproduction signal, and is currently commercially available. The object of the present invention is to provide an optical recording medium and an optical recording and reproducing method that can be reproduced even on compact disc players and the like.

Means for Solving the Problems In order to solve the above problems, the optical recording medium and optical recording/reproducing method of the present invention have a recording layer made of an organic dye that absorbs in a specific wavelength range on a transparent substrate. It has a transparent layer on the recording layer, and further has a reflective layer on the transparent layer, and the extinction coefficient of the recording layer at the wavelength of the recording/reproducing laser beam is 0.1 or more and the thickness of the recording layer is 1100 nm or less. is preferable, and more preferably, the extinction coefficient is 0.3 or more and the thickness of the recording layer is 50 nm or less, and the recording laser beam is focused on the recording layer through the transparent substrate, and the recording laser beam is focused. The recording layer undergoes an optical change, and the reflectance of the light-irradiated portion becomes higher than the reflectance of the non-light-irradiated portion, and this change in reflectance is detected by a reproduction laser beam to record and reproduce information.

Operation With the above configuration, recording is performed by irradiating laser light from the side of the transparent substrate, causing a thermal or photochemical change in the recording layer to form bits.

Further, reproduction is performed by focusing laser light onto the recording layer from the side of the transparent substrate and detecting changes in reflectance at the pits.

In this way, since the bit is formed inside the medium and is not exposed to the atmosphere, it is resistant to scratches, corrosion, and oxidation, and high reliability can be obtained. Further, the light incident on the medium causes multiple interference due to the above-described configuration, and the extinction coefficient at the wavelength of the recording/reproducing laser beam of the recording layer is reduced to 0.
1 or more, and by appropriately selecting the thickness of the transparent layer, it is possible to increase the light absorption rate in the recording layer and record a high-quality signal even with a low-output laser beam, and the thickness of the recording layer is By reducing the thickness to 1100n or less, the organic dye contained in the recording layer decomposes in the recorded bit area and loses absorption in the laser light wavelength range, allowing the laser light to reach the reflective layer without being absorbed by the recording layer. , it will show a high reflectance.

EXAMPLE Hereinafter, an optical recording medium according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a partial cross section of the optical recording medium of the present invention. In FIG. 1, l is a substrate made of glass, polycarbonate, polymethyl methacrylate, etc. that is transparent to the reproduction laser beam, and on this substrate l is an organic dye that absorbs the recording laser beam and causes decomposition or optical change. For example, a recording layer 2 containing a dye selected from cyanine dyes, naphthoquinone dyes, phthalocyanine dyes, squarylium dyes, etc. is coated. At this time, a resin such as polymethyl methacrylate or polyvinyl chloride may be used as a binder. In addition, when polycarbonate or polymethyl methacrylate is used for the substrate l, surface treatment may be performed to increase the solvent resistance of the base Fi1 before coating the recording layer 2. Then, a resin that is transparent and can be coated with a solvent that does not attack the recording layer is applied. Specifically, a resin such as gelatin, cellulose, polyvinylpyrrolidone, or polyvinyl alcohol can be applied using a solvent such as water. In addition, as another method for forming the transparent layer 3, 5i02 etc. are recorded 1
112 may then be sputtered on the transparent layer 3 with a metal having a high reflectance to the reproduction laser beam, for example gold, silver.

A reflective layer 4 made of aluminum, nickel, chromium, etc. is formed. Furthermore, a thermosetting resin or a photocuring resin may be formed as a protection WJ5 on the reflection N4.

Next, one embodiment of the optical recording medium and optical recording/reproducing method of the present invention will be described in more detail. FIG. 2 is a partial sectional view of an optical recording medium showing an example of the present invention and a comparative example.

(Example 1) The thickness is 1.2 mm, the depth is 0.08 μm, and the width is 0.8 μm on the surface.
After increasing the solvent resistance of the substrate 1 by sputtering 5i02 on the surface of the polycarbonate transparent substrate I on which tracking grooves of m are spirally formed at a pitch of 1.6 μm, the solvent resistance of the substrate 1 is improved. A chloroform solution of a dye having the structure shown in the figure and polymethyl methacrylate (1:5) is
Recording layer 2 of 1100n by spin coding at 1000rp
was formed. On this surface, an aqueous solution of hydroxyethyl cellulose was spin-coded at 200 rpm to 1100 nm.
Transparent rr! Aluminum was sputtered on the 0-order transparent Ji3 on which i3 was formed to form a reflective N4 of 1100 nm, and a photocurable resin was further coated and polymerized to form a protective layer 5. Thereafter, while applying tracking servo, a semiconductor laser beam with a wavelength of 830 nm and a power of 15 mW was applied at 1.3 m/sec from the side of the transparent substrate l.

It was irradiated at a linear velocity of The recorded signal is 500kH
It is a pulse with a Z duty ratio of 50150, and when the recorded signal is reproduced from the transparent substrate l side with a 0.5 mW, 830 nm semiconductor laser, the reproduction C/ ratio is 45 d.
It was B. Also, the extinction coefficient of the recording layer at this time is 0.
2, the reflectance of the area irradiated with the recording laser beam was 50%, and the reflectance of the area not irradiated was 20%.

(Example 2) The thickness is 1.2 m, the depth is 0.08 μm, and the width is 0.8 μm on the surface.
After increasing the solvent resistance of the substrate 1 by sputtering SlO□ onto the grooved surface of the polycarbonate transparent substrate 1 on which tracking grooves of m are spirally formed at a pitch of 1.6 μm, the solvent resistance of the substrate 1 is increased. Spin code the dye having the structure shown in the formula in chloroform solvent at 100 Or p m to 20
A recording layer 2 of nm thickness was formed. A transparent layer 3 of 1100 nm was formed by spin-coding an aqueous solution of hydroxyethyl cellulose at 200 rpm on this surface.
A reflective layer 4 having a thickness of 1100 nm was formed by sputtering aluminum thereon, and a photocuring resin was further applied thereon and polymerized to form a protective layer 5. After that, while applying the tracking servo, from the side of the transparent substrate l, a wavelength of 83
Semiconductor laser light of 0 nm was irradiated at a linear velocity of 1.3 m/sec. The recorded signal was a pulse with a duty ratio of 50150 at 500 kllz, and when the recorded signal was reproduced from the side of the transparent substrate l using a 0.5 mW, 830 nm semiconductor laser, the reproduced C/N ratio was 53 dB. Further, the extinction coefficient of the recording layer at this time was 1.2, the reflectance of the portion irradiated with the recording laser beam was 75%, and the reflectance of the portion not irradiated was 20%. When a signal in the same format as a compact disc was recorded on this optical recording medium,
It could be played on a commercially available compact disc player.

(Comparative Example 1) Thickness is 1.2 mm and surface depth is 0.08 μm and width is 0.8 μm.
After increasing the solvent resistance of the substrate 1 by sputtering 5I02 onto the grooved surface of a polycarbonate transparent substrate 1 on which tracking grooves of m are spirally formed at a pitch of 1.6 μm, formula (1) is applied. A dye having the structure shown in chloroform solvent was spin-coded at 1000 rpm to obtain 1
A recording layer 2 of 50 nm was formed. On this surface, a 1100n transparent layer 3 was formed by spin-coding an aqueous solution of hydroxyethyl cellulose at 200 rpm.Aluminum was sputtered on the zero-order transparent layer 3 to form a 1100n reflective N4, and further, on this A photocurable resin was applied and polymerized to form a protective layer 5. After that, while applying the tracking servo, from the transparent substrate 5 side, the wavelength 8
A 30 nm semiconductor laser beam was irradiated at a linear velocity of 1.3 m/sec. The recorded signal was a 500 kHz pulse with a duty ratio of 50150, and the recorded signal was 0.5 mW.

When reproduction was performed from the side of the transparent substrate 1 using a semiconductor laser of 830 nm, the reproduction C/N ratio was 45 dB. Further, the extinction coefficient of the recording layer at this time was 1.2, the reflectance of the portion irradiated with the recording laser beam was 10%, and the reflectance of the portion not irradiated was 20%. When the recording layer is thick as described above, the reflectance of the portion irradiated with the recording laser beam is lower than that of the unirradiated portion.

(Comparative Example 2) FIG. 2 is a partial sectional view of an optical recording medium showing a first example of the present invention. Thickness is 1.2a*, depth 0.08 on the surface
After increasing the solvent resistance of the substrate 1 by sputtering SiO □ on the groove-existing surface of a polycarbonate transparent substrate 1 on which tracking grooves of 0.8 μm and 0.8 μm pitch were spirally formed at a pitch of 1.6 μm, A chloroform solution of a dye having the structure shown in formula (1) and polymethyl methacrylate <l:15) was spin-coded at 1100 orp to give 110
A recording layer 2 of 0n was formed. On this surface, a transparent layer 3 of 80 nm was formed by spin-coating hydroxyethylcellulose.

Next, sputter aluminum onto transparent N3 to give 100%
A reflective layer N4 of nm was formed, and a photocurable resin was further applied thereon and polymerized to form a protective layer 5. After that, while applying the tracking servo, from the side of the transparent substrate l,
Semiconductor laser light with a wavelength of 830 nm is transmitted at 1.3 m/s using W.
ee. It was irradiated at a linear velocity of The recorded signal is 50
It is a pulse with a 0 kHz duty ratio of 5 015 0, and when the recorded signal is reproduced from the transparent substrate l side with a 0.5 mW, 830 nm semiconductor laser, the reproduction C
/N ratio was 30 dB. Further, the extinction coefficient of the recording layer at this time was 0.05, the reflectance of the portion irradiated with the recording laser beam was 62%, and the reflectance of the portion not irradiated was 60%. When the extinction coefficient of the recording layer is small in this way, laser light absorption is not sufficient and the contrast of the recorded portion is also low.

Effects of the Invention The present invention has a recording layer made of an organic dye that absorbs in a specific wavelength range on a transparent substrate, a transparent layer on the recording layer, and a reflective layer on the transparent layer. , the extinction coefficient of the recording layer at the wavelength of the recording/reproducing laser beam is 0.
．． 1 or more, and the thickness of the recording layer is 100 nm or less, the recording laser beam is focused on the previous recording layer through the transparent substrate, and the recording layer on which the recording laser beam is focused causes an optical change, The reflectance of the light-irradiated area becomes higher than the reflectance of the non-light-irradiated area, and by detecting this change in reflectance with a reproduction laser beam and recording and reproducing information, the recording layer is prevented from scratches and corrosion even though the veneer is lightweight. The present invention also provides an optical recording medium and an optical recording and reproducing method that are not easily affected by oxidation, have a high reflectance, and can provide high-quality reproduced signals, and can be reproduced by compact disc players currently on the market.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a first embodiment of the present invention, FIG. 2 is a partial cross-sectional view of another example of the present invention and a comparative example, and FIG. 3 is a partial cross-sectional view of a conventional optical recording medium. be. l...Transparent substrate, 2...Recording layer, 3.
...Transparent layer, 4...Reflection layer, 5...
・・Safety X! Layer, 6... bits.

Claims (2)

[Claims] (1) A light beam having a recording layer made of an organic dye that has light absorption properties at the wavelength of the recording/reproducing laser beam on a transparent substrate, a transparent layer on the recording layer, and a reflective layer on the transparent layer. 1. An optical recording medium, wherein the recording layer has an extinction coefficient of 0.1 or more at the wavelength of a recording/reproducing laser beam, and a thickness of the recording layer is 100 nm or less. (2) having a recording layer made of an organic dye that absorbs in a specific wavelength range on a transparent substrate, and having a transparent layer on the recording layer;
Furthermore, in an optical recording medium having a reflective layer on a transparent layer, the extinction coefficient of the recording layer at the wavelength of the recording/reproducing laser beam is 0.
．． 1 or more and the thickness of the recording layer is 100 nm or less, a recording laser beam is focused on the recording layer through the transparent substrate, and the recording layer on which the recording laser is focused undergoes an optical change. 1. An optical recording and reproducing method characterized in that the reflectance of a portion irradiated with light becomes higher than that of a portion not irradiated with light, and information is recorded and reproduced by detecting this change in reflectance with a reproduction laser beam.