JPH0734270B2 - Optical recording medium - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a writable optical recording medium.

2. Description of the Related Art Optical recording media, especially optical discs, have made remarkable progress in recent years, and it is expected that they will be used for various purposes and applications as the market expands. Optical discs are roughly classified into two types. That is, a read-only disc and a writable disc,
The former uses a stamper on which information is recorded in advance and deposits aluminum on the transparent substrate 6 (FIG. 4) onto which the information on the stamper has been transferred by molding to manufacture tens of thousands or more disks of the same information. Since it is a compact disc for music (hereinafter, referred to as a CD), the maker mass-produces it, so that it can be relatively inexpensively produced even if an expensive stamper is used.

However, this method cannot be applied to small-scale production, especially to personal information files and personal music discs in terms of cost performance. Further, in a writable optical disk which has recently been in the spotlight, an optical recording film 9 is formed on a transparent substrate 8 on which a groove 12 for tracking is previously formed as shown in FIG. It was a double-layered structure with 11 facing each other. Therefore, although it is suitable for personal use, the manufacturing cost is very high. In addition, because it is a structure in which two sheets are stuck together, the thickness is more than double that of a CD, and the reflectance is low, and the signals written by conventional CD players could not be reproduced. (Reference “Video Disc and DA
D "Introduction, Corona).

Problems to be Solved by the Invention In other words, in each of the conventional methods, it is very expensive for one individual to make his / her own music software. Since it is necessary to purchase a device that can reproduce, it has been a major obstacle to restrain the expansion of the optical disc market.

Means for Solving the Problems The present invention provides a writable optical disc at a low cost, and the overall thickness of the written optical disc is thin, so that it can be reproduced on a commercially available CD player by increasing the reflectance of the recording surface. It is possible to do.

That is, according to the present invention, as shown in FIG. 2, the bleaching recording film 2 is formed on the transparent substrate 1 on which a groove for performing tracking servo is formed in advance so that the groove and the surface on the reflection side are smooth. The first step of forming the pits, the second step (FIG. 3) of writing a signal as a pit train by the focused laser light while applying the tracking servo on the smooth recording surface, and the remaining recording film. It is established by four steps of manufacturing an optical recording medium by a third step of bleaching 2 without being deformed and a fourth step of forming a reflective layer 3 on a recording film having recorded pit rows. There is. The third and fourth steps may be performed before or after either. Of these, the grooved transparent substrate 1 used in the first step is preferably made of a material that does not have characteristic absorption in the wavelength range of the semiconductor laser. Specifically, polycarbonate or polymethacrylic resin is used. A molded substrate that has been formed, or a substrate in which grooves are formed using a photocurable resin on a smooth transparent substrate made of glass or methacrylic resin is used. The optical recording film used has spectral absorption characteristics in the wavelength range of the semiconductor laser, and a perforated pit row is formed by the focused semiconductor laser, and by irradiating with specific light, the unrecorded part is bleached. However, it is necessary to use a material in which the absorption of the above-mentioned spectral characteristics disappears, and an organic dye or a dye in which a dye is dispersed in a transparent resin, and a cyanine dye is particularly suitable. The spin coating method is the most suitable method for coating the recording film on the substrate, but it can also be prepared by a method such as dipping, roll coating, or kiss coating. In order to improve the solvent resistance of the surface of the grooved substrate, it is possible to form a thin protective film on the surface of the grooved substrate before coating the recording film to such an extent that the groove shape does not change. As the third bleaching step of the recording film, a method of irradiating a light beam to oxidatively decompose the functional groups of the dye molecules forming the recording film is excellent, and this method changes the shape of the recorded pits. Can be bleached without. In addition to bleaching with light, chemical bleaching and thermal bleaching are also possible. As the fourth reflective layer forming method, high reflectance can be easily obtained by vapor deposition of aluminum. After the formation of the reflective layer to protect the reflective layer,
A fifth step of applying a protective film from above may be added.

Action As described above, in the optical recording medium of the present invention, a signal from an external information source such as a magnetic tape can be directly written as a perforated pit train on the recording film whose surface on the medium is smoothed. Since the expensive stamper required for CD manufacturing is not required for each information source, the cost can be reduced for small-scale applications, and by forming a highly reflective layer after bleaching, an optical disc with exactly the same structure as a conventional CD Therefore, it has an excellent feature that it can be played on a commercially available CD player, and it is an optimal optical recording medium for personal software and small-scale software production.

Examples An optical recording medium according to an example of the present invention will be described below with reference to the drawings.

(Example 1) On a surface having a groove on a methacrylic resin molded substrate 1 in which a tracking groove having a thickness of 1.2 mm, a depth of 0.08 μm and a width of 0.8 μm was spirally formed at a pitch of 1.6 μm, 10 nm
Sputtered a protective film of SiO ₂ of
A methylene chloride solution of 1'-diethyl-2,2'-quinotricarbocyanine was spin-coated at 500 rpm to form a recording film 2 having a thickness of 20 nm. While rotating the substrate on which the recording film was formed and applying the tracking servo, a semiconductor laser beam of wavelength 830 nm at 4 mW was irradiated at a linear velocity of 1.4 m / sec through the transparent substrate. The written signal 4 is a pulse with a duty ratio of 50/50 at 500 KHz. After recording, 50 nm of aluminum 3 was vapor-deposited on the surface, and 3000 mJ / cm ² of ultraviolet light was irradiated through the base substrate to bleach the unrecorded area. When the completed optical disc shown in Fig. 1 was played back using a commercially available CD player, a playback C / N ratio of 50 dB was obtained with a bandwidth of 30 KHz, demonstrating that playback is possible with a CD player. It was

(Example 2) On the same grooved substrate as in Example 1, Si of 10 nm was similarly used.
After forming the O ₂ layer, the following dye was applied by a 200 nm spin coating method, and the same signal was recorded under the same conditions as in Example 1.

After recording, irradiate the entire surface with 3000 mJ / cm ² of ultraviolet light, and after bleaching,
50 nm of aluminum was vapor-deposited on the surface to form a reflective layer. When this was played on a commercially available CD player, the bandwidth
A reproduction C / N ratio of 53 dB was obtained at 30 KHz, demonstrating that reproduction by a commercial player is possible.

EFFECTS OF THE INVENTION By using the optical recording medium according to the present invention, it is possible to inexpensively manufacture an optical recording medium having small-scale and multi-kind information, and the manufactured optical recording medium can be reproduced by a conventional CD player. It has the following characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining an optical disc of the present invention, FIGS. 2 and 3 are perspective views showing a state of a medium in a manufacturing process, FIG. 4 is a sectional view of a commercially available compact disc, and FIG. FIG. 3 is a sectional view of a writable optical disc having an air sandwich structure. 1 ... Transparent substrate, 2 ... Recording film, 3 ... Reflective layer, 4 ...
The written pit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuaki Oshima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP 62-137745 (JP, A)

Claims (3)

[Claims] 1. A second transparent layer having a flat surface on a first transparent layer which has a groove for tracking servo on the surface in advance and is transparent to light of a specific wavelength. An optical recording medium in which a signal is recorded as a surface deformation on the transparent layer, and a reflective layer is provided on the surface having the deformation. 2. The second transparent layer is a recording film capable of perforating recording in response to light having a specific wavelength, and can be made transparent to the specific wavelength by bleaching after recording. ) Optical recording medium according to the item. 3. The optical recording medium according to claim 1, wherein the second transparent layer has a reflectance at the interface with the first transparent layer in the unbleached state.