KR100257895B1 - Erasable optical recording medium - Google Patents

Abstract

PURPOSE: A rewritable optical recording media is provided to construct each conductive layer on an upper and lower surface of an eliminating layer, and to write an optical disk by an electric field and a single laser. Therefore, a CNR(Carrier To Noise Ratio) of a recording media can be improved. Also, it is possible to write/play/eliminate the optical disk by the single laser. CONSTITUTION: A reflect layer(12), a recording layer(13), the first conductive layer(14), an eliminating layer(15) and the second conductive layer(16) are successively deposited on a substrate(11). The substrate(11) is a glass substrate. The reflect layer(12) is formed as a metal film available of performing a vacuum deposition. The eliminating layer(15) is a complex substance of a polymer and a liquid crystal. The first and second conductive layers(14,16) are applied with a power(17) by a switch operation. The first and second conductive layers(14,16) perform a vacuum deposition to conductive substances such as ITO(Indium Tin Oxide), Au and Pb.

Description

Erasable Optical Recording Media

1A to 1C are cross-sectional explanatory diagrams of a conventional optical recording medium.

2 is a cross-sectional view of the present optical record carrier.

3 (a) and 3 (b) are explanatory diagrams of the recording method of the present optical recording medium.

4 is an explanatory diagram of a reproduction method of the present optical record carrier.

5 (a) and 5 (b) are explanatory diagrams of the erasing method of the optical recording medium.

* Explanation of symbols for main parts of the drawings

11 substrate 12 reflective layer

13 recording layer 14 first conductive layer

15: erase layer 16: second conductive layer

17: power 18: switch

19: laser

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of recording, reproducing and erasing using a single laser, and to a high density high capacity erasable optical recording medium applicable to an optical disc, an optical card, and the like.

Recently, with the diversification of information and the increase in the amount of information, optical recording materials that can have a high density and a large memory have attracted attention. These media can be broadly divided into a read only memory (ROM type), a write once type optical record medium (WORM type), and an erasable optical recording medium (Rewritable type).

WORM type is a recording layer in which a pigment capable of absorbing a laser on a reflective layer is mixed with a polymer resin, as mentioned in Japanese Laid-Open Patent Publication Nos. 57-46362, 58-197088, 59-5096, 63-179792, and the like. After coating, it is made by coating a protective layer thereon. In this case, when the laser is focused on the recording layer within 1 µm, heat is generated by the dye absorbing the laser, and the polymer resin is decomposed to form a pit, thereby enabling recording. At the time of reproduction of the recording, the information (logic 1 or 0) is read based on the difference in reflectance between the portion with and without the pit. In the WORM type, since the recorded portion becomes the decomposition form of the polymer, erasure of the recording is impossible.

In addition, the rewritable type has been actively studied as a thermal method using light as heat and a photon method using photons. In the case of the thermal method, recording light is irradiated onto the recording layer to locally melt, evaporate, thermally deform, heat transfer, or the like to record and reproduce by optical changes occurring at that time. The erasable type is mainly composed of an alloy or an inorganic metal thin film, but due to various disadvantages, development of an organic optical recording medium using organic dyes has been actively conducted in recent years.

In the case of the WORM type, a pit type medium is mainly available in the market in the form of a disk or a tape, and as an erasable type material, MOD (Magneto-Optical Disk) using magnetic and laser is practically used. In the case of MOD, there are problems in manufacturing process due to complicated layer structure and complexity in device configuration.

In addition, as a highly practical material, a bump-type recording medium having a two-layer structure proposed by the ODI (Optical Data, Inc.) of the United States has been proposed (US Patent Nos. 4,719,615; 4,825, 430; 4,852,075; 4,780,867; 4,896,314; 4,901,304; 4,912,696).

As shown in FIG. 1, the optical disk has a cross-sectional structure of three layers of the substrate 1, the recording layer 2, and the erasing layer 3. As shown in FIG. The substrate 1 is made of transparent resin such as polycarbonate and polymethyl methacrylate, and the recording layer 2 is made of an elastic polymer resin and a dye capable of absorbing a recording laser. ) Is composed of a thermoplastic polymer resin and a pigment that can absorb the laser for erasing. At the time of recording using such an erasable optical disc, the dye absorbs the laser by causing the recording laser to concentrate on the recording layer, thereby thermally expanding the resin. Accordingly, a bump is formed by inducing irreversible deformation of the erase layer 3 by the force of thermal expansion. Once the irradiation of the laser is completed, the erasing layer 3 is quenched and hardened, so that the adhesive force with the recording layer moderates the original return force of the recording layer 2, so that the bump is maintained as it is (as shown in FIG. 1 (b)). Bump is part “B”). When reading this record, when the recording medium is irradiated with the weak output of the recording laser, a difference in reflectance between the unrecorded part and the recorded part in the bump form occurs, and the record is read according to the difference (for example, the logic of the bump type is read). 1, read normal state to logic 0). At the time of erasing, the erasing laser condenses on the erasing layer 3 so that the dye absorbs the laser. Accordingly, when the erasing layer 3 is heated above the glass transition temperature Tg, the resistance to the restoring force of the recording layer 2 is increased. It is weakened and returned to its original state by the restoring force of the recording layer 2 (as shown in FIG. 1 (c)). In this case, at least one of phthalocyanine, carbon black, azos (monoazo, diazo), anthroquinone, nigrosine, and xanthene was used as the dye used in the recording layer 2 and the erasing layer 3. .

Therefore, the ODI patent is designed with two layers, a recording layer 2 and an erasing layer 3, each having a pigment having a different absorption wavelength band, so that the recording laser light is absorbed well by the recording expansion layer 2 during recording. At the time of erasing, the erasing laser light absorbed well by the erasing layer 3 is irradiated, and the respective lasers are selectively irradiated to the two layers for recording and erasing. As a result, the ODI patent has a disadvantage that the apparatus is complicated by using two types of lasers for recording and erasing, and the storage capacity is limited due to the area limit of the disk.

The present invention is to solve the optical system configuration difficulties caused by the use of two lasers in the ODI patent, characterized by providing an optical recording medium capable of recording, reproducing, and erasing using a single laser.

That is, according to the present invention, in the erasable optical recording medium including the recording layer and the erasing layer, a conductive layer to which a power supply can be provided is formed on the polymer resin and the erasing layer containing liquid crystal and dye, respectively. An object of the present invention is to provide an erasable optical recording medium that is recorded, reproduced, and erased by a combination of an electric field and a laser.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view of the present invention, in which a substrate 11, a reflective layer 12, a recording layer 13, a first conductive layer 14, an erase layer 15, and a second conductive layer 16 are sequentially stacked. The first and second conductive layers 14 and 16 are configured to receive the power source 17 by operating the switch 18. The substrate 11 in the present invention may be a glass substrate, and the reflective layer 12 is formed of a general aluminum or gold, or a metal film capable of vacuum deposition corresponding thereto. If the thickness of 13) is very thick, it may be omitted because it may not have great effectiveness.

In the present invention, the recording layer 13 is generally an acrylic resin capable of thermosetting or UV curing, such as a resin used in a bump-type medium, and has a good structure in which no plastic deformation occurs due to internal crosslinking reaction, and a suitable light absorption wavelength band. It is preferable to mix dyes having a better absorption of laser light during recording. In the present invention, the erasing layer 15 is a complex of a polymer and a liquid crystal, and is controlled to have a composition and a polymer material which is not transparent at the heat erasing temperature in a general bump type recording medium. Of course, it is easy to absorb light, and most resins currently used in bump-type media can be used. In addition, the first conductive layer 14 between the recording layer 13 and the erasing layer 15 and the second conductive layer 16 on the surface of the erasing layer 15 may be formed of indium tin oxide (ITO), Au, or Pb. The conductor is vacuum deposited to a thickness such that the transmittance is 80% or more and does not significantly affect the thermal expansion properties of the expanded layer, and the thicknesses of the preferred conductive layers 14 and 16 are 70 to 80 kPa, respectively.

In the recording of the present invention, the electric field 17 is applied to the first conductive layer 14 and the second conductive layer 16, as shown in FIG. 3 (a), between the two conductive layers 14, 16. After the light transmittance of the erased layer 15 is increased, the laser 19 is irradiated to the recording layer 13 through the erased layer. The irradiated light is mainly absorbed by the recording layer 13 together with the erasing layer 15 having a very high light transmittance to expand the irradiated portion. The other layers in the upper portion are also lifted up by the expanded recording layer 13 to form a bump. At this time, the plastic layer deformation occurs in the case of the erasing layer 15. When the light irradiation ends and the power source 17 is turned off, By cooling, the recording layer 13 having a crosslinking degree is contracted to its original state, thereby preventing the bumps from sinking and maintaining the shape of the bumps (Fig. 3 (b)). At this time, the recording layer 13 has a tension with respect to the upper erase layer 15 because it is in a state where the temperature is to shrink.

In the recording and reproducing according to the present invention, as shown in FIG. 4, the power supply 17 is cut off by the switch 18, and recording and reproduction are performed using the difference in reflectance caused by bumps as if a normal bump type recording medium is read without any electric field.

In the case of recording erasing of the present invention, the electric field is not applied as in the case of recording and reproduction as in the case of FIG. 5, and accordingly, the erasing layer 15 exhibits a somewhat opaque characteristic. In this state, when the laser 19 having a lower power than the recording time is irradiated, the light has little effect on the recording layer 13 due to the low transmissivity erasing layer 15, and mainly contains dyes at a low concentration. Only the erase layer 15 is irradiated as shown in FIG. 5 (a). Therefore, the erasing layer 15 softened by the heat caused by the light irradiation sinks due to the tension of the recording layer 13 at the lower portion, thereby causing the erasing of the recording as shown in FIG. 5 (b).

Hereinafter, the present invention will be described with reference to Examples.

EXAMPLE

As the substrate 11, a glass substrate capable of maintaining a sufficient shape in any case was used, and the reflective layer 12 was not deposited because the thickness of the recording layer 13 was made very thick, such as 3,000 Å. The recording layer 13 was dissolved in methyl ethyl ketone by mixing EB284 and EB1290 of Ebecryl Co., Ltd., a photocurable acrylic resin in a 9: 1, and undergoing UV crosslinking reaction after spin coating. No. of Irgacure 184 was mixed at a ratio of 0.2 g per resin, and as a dye for laser light absorption, IR-820 of Nippon Kayaku Co., Ltd. was mixed at a ratio of 0.14 g per resin. The thickness of this recording layer 13 was 3,000 kPa. The first conductive layer 14 and the second conductive layer 16 were sputtered with ITO and adjusted to have a thickness of about 70 to 80 kPa. As the scavenging layer 15, NOA-65, a photocurable acrylic resin, and BL001, E. Merk, a liquid crystal monomer, were uniformly mixed at 8: 2, and then dye IR-820 was used. A small amount (3%) was mixed and spin-coated on the first conductive layer 14. It was irradiated with ultraviolet light for about 5 minutes and cured to obtain an optical recording medium in which a polymer crystal composite of 600 Hz was formed. When the 10 V electric field was applied to the optical recording medium and the oscillation wavelength was 8.9 mW and the power was 8.9 mW and 4 to 6 m / sec, the CNR at the time of recording was measured about 40 to 50 dB, and the laser was 4.5 mW at the time of erasing. When examined by power, the CNR dropped to within about 10 dB. The same results were obtained in subsequent repeated recording, reproducing and erasing experiments under the same conditions.

[Comparative Example]

The recording medium was manufactured by the same method as the above embodiment, but the CNR value of 25-30dB was recorded under the conditions of 8.9 mW and 4 to 6 m / sec using a laser having an oscillation wavelength of 830 nm without applying an electric field to the recording medium. Got.

At the time of erasure, irradiation with a laser power of 4.5 mW yielded a CNR of about 10 dB.

As described above, the optical recording medium of the present invention comprises a conductive layer capable of supplying power to the upper and lower surfaces of the erasing layer composed of a polymer resin, a liquid crystal composite, and a dye, respectively, so that recording is performed by an electric field and a single laser. The optics configuration is simple because it improves the CNR and enables recording, reproducing and erasing by a single laser.

Claims (4)

In an erasable optical recording medium comprising a recording layer and an erasing layer, conductive layers 14 and 16 are formed on the upper and lower surfaces of the erasing layer, respectively, and the erasing layer 15 is formed of a polymer-liquid crystal complex and a dye. And an erasable optical recording medium. 2. The erasable optical record carrier as claimed in claim 1, wherein the conductive layer (14, 16) is adapted to provide a power source (17) only during recording. The erasable optical recording medium according to claim 1, wherein the conductive layers (14, 16) are each vacuum-deposited at least one of indium tenoxide (ITO), gold (Au), and lead (Pb). 2. The polymer-liquid crystal-composite of claim 1, wherein the erasing layer 15 between the first conductive layer 14 and the second conductive layer 16 comprises a liquid crystal and a pigment in an acrylic resin capable of thermosetting or UV curing. And an erasable optical recording medium.