KR100686104B1 - Recording medium and Method for recording/playbacking data - Google Patents

Abstract

An optical recording medium capable of recording and reproducing in a blue and red band, wherein a first recording layer and a second recording layer having different refractive indices according to wavelengths are sequentially formed on a substrate, and the first recording layer and the second recording layer are sequentially formed. By forming the intermediate reflection layer so as to transmit only the blue wavelength band and reflect the red wavelength band between the layers, mutual compatibility in the red wavelength band and the blue wavelength band is achieved and the recording density is greatly improved.

Description

Recording medium and method for recording / playbacking data}

1 is a graph showing the reflectance and transmittance according to the wavelength of the Au-SiO ₂ layer of the present invention,

2 is a structural sectional view showing an optical recording medium according to the present invention.

Explanation of symbols for main parts of the drawings

1 substrate 2 first dielectric layer

3: first recording layer 4: second dielectric layer

5: intermediate reflection layer 6: third dielectric layer

7: second recording layer 8: fourth dielectric layer

9: reflective layer 10: protective film

The present invention relates to an optical recording medium and a recording / reproducing method capable of recording and reproducing in blue and red bands.

Record records, which were once an important means of enjoying music, have grooves with fine continuous waveforms on their surfaces, and pickups read signals as they move along the grooves. I am writing to and reading from the media.

On the other hand, a compact disc (CD), which shows an example of recording and reproducing information by light, reads sound and images remotely by using light instead of a needle on a disc having a discontinuous groove-shaped pit instead of a continuous groove.

Therefore, in the optical recording method, since information on the surface of the disk is read in a non-contact manner, it is possible to prevent the loss of information due to the damage of the disk, and there is no noise caused by the needle.

An optical disk differs from a floppy disk which is a portable recording medium in that a laser diode optical system (LD head) is used to separate characteristics of a medium and a head.

Therefore, optical discs are evaluated as multimedia recording media because of their large capacity and high portability and reliability.

Such optical discs include read-only memory (ROM), which is popular for home appliances such as CDs and laser discs (LDs), and write-once read-many for recording encoded data for business purposes. WORM) and three types of rewritable (RW).

Commercially available optical discs generally have a recording density of 1 bit per square micrometer, which translates to 645 mbit / in ² (˜80 MB / in ² ) per square inch.

On the other hand, DVD, referred to as an abbreviation for digital multifunction disc, is one of the next generation package type optical recording media which further sublimates recording and reproduction of information by laser light.

Compared to the widely used CD (-ROM), the DVD (-ROM) has the same disc size as 12cm in diameter, but the information storage capacity is 4.7 giga-bytes (GB), which is more than 7 times of CD-ROM.

Such large capacity improvement was possible because the NA of the objective lens was increased to 0.60 with respect to 0.45 of the CD-ROM, and the wavelength of the semiconductor laser was reduced from 780 nm to 650 nm of the CD-ROM.

Currently, the CD-ROM reproducing laser is 780 nm in GaAlAs system, but the short wavelength is 650 nm and 635 nm in the same GaAlAs system in DVD.

In the GaAlAs system, it is considered that the wavelength in this vicinity is the limit, and the development of the short wavelength laser light source is actively underway.

Recently, it succeeded in continuously oscillating a blue laser having a wavelength of 490 nm at room temperature, and raised the price of oscillating a blue violet laser having a wavelength of 410 nm.

If a semiconductor laser with a wavelength of 410 nm is put into practical use, it is expected that the storage capacity of the current DVD using 650 nm can be more than doubled.

Considering this, it is expected that the implementation of optical disks compatible with both short and long wavelengths will be needed in the future.

An object of the present invention is to provide an optical recording medium and a recording / reproducing method which are compatible in the red wavelength band and the blue wavelength band and have an improved recording density.

An optical recording medium according to the present invention includes a first recording layer, an intermediate reflection layer, and a second recording layer sequentially formed on a substrate. Here, the first recording layer is recorded in the wavelength region of 400-450nm, the second recording layer is recorded at 600-650nm. In addition, the intermediate reflection layer transmits or reflects only a specific wavelength band. The wavelength band to transmit is 400-450 nm, and the wavelength band to reflect is 600-700 nm. The thickness of the intermediate reflection layer is 100-1000 mm 3.

In the recording and / or reproducing method according to the present invention, a light having different wavelengths is applied to the first recording layer and the second recording layer in a recording medium in which a first recording layer, an intermediate reflection layer, and a second recording layer are sequentially formed. Investigate to record and / or reproduce.

Referring to the accompanying drawings, preferred embodiments of the present invention having the features as described above are as follows.

First, the concept of the present invention is to form a material layer having high transmittance and low reflectivity in the blue wavelength band and a high reflectance and low transmittance in the red wavelength band between the first recording layer and the second recording layer, thereby forming the blue wavelength band and the red color. The present invention provides a high density optical disc capable of recording / reproducing information in all wavelength bands.

In order to achieve the basic concept, it is important to select materials having high transmittance and low reflectivity in the blue wavelength band and high reflectivity and low transmittance in the red wavelength band.

Materials having such basic properties include Au-SiO ₂ , Au-TiO ₂ , Au-Cr ₂ O ₃ , Ag-SiO ₂ , Ag-TiO ₂ , Ag-Cr ₂ O ₃ , Pt-SiO ₂ , Pt-TiO ₂ , Pt-Cr ₂ O ₃ , and the like.

Here, noble metal elements such as Au, Ag, and Pt of the VIIA group of the Periodic Table IB are materials that do not transmit well due to high light absorption.

When heat-treated, they are irregularly present in the form of grains in materials such as amorphous SiO ₂ , TiO ₂ , Cr ₂ O _3, and these precious metal grains have optical properties reflecting only light of a specific wavelength band.

That is, the precious metal materials used in the present invention must satisfy the following conditions.

First, when mixed in an amorphous material and then heat treated, they should be bonded to each other to form granules having a predetermined size.

Second, these grains must be present in the form of a mixture that is not mixed with water and oil in the amorphous state.

These conditions are required to have an optical characteristic that can reflect or transmit only light of a specific wavelength.

If they are mixed in the form of a compound, they become completely different third materials, so that the desired optical properties are not visible in the present invention.

For example, the reflectance and transmittance according to the wavelength of the Au-SiO ₂ layer having a thickness of about 100 μs are shown in FIG. 1.

As shown in FIG. 1, the Au-SiO ₂ layer has reflectance and transmittance according to wavelength, and there is a radical increase in reflectivity and a decrease in transmittance in the long wavelength band based on the wavelength region of 500 nm, and the reflectivity in the short wavelength band. There is a decrease and an increase in permeability.

Embodiments of the present invention using materials having such optical properties are as follows.

FIG. 2 is a structural cross-sectional view showing an optical recording medium according to the present invention. As shown in FIG. 2, first, an RF-magnetron sputtering method is performed using a ZnS-20 mol% SiO ₂ target on a polycarbonate substrate 1. RF power is applied while argon gas is injected to form the first dielectric layer 2 to a predetermined thickness.

After the first recording layer 3 is formed on the first dielectric layer 2 using a Ge ₂ Sb ₂ Te ₅ target by a DC-magnetron sputtering method to a predetermined thickness, the first recording layer 3 is formed on the first dielectric layer 2. The second dielectric layer 4 is formed under the same conditions as the first dielectric layer 2.

Here, the first recording layer 3 has a refractive index of about 600 to 700 nm which is a red wavelength band.

Then, on the second dielectric layer 4, Au-SiO ₂ , Au-TiO ₂ , Au-Cr ₂ O ₃ , Ag-SiO ₂ , Ag-TiO ₂ , Ag-Cr ₂ O ₃ , Pt-SiO ₂ , Pt An intermediate reflection layer 5 made of any one of -TiO ₂ and Pt-Cr ₂ O ₃ is formed.

Here, the thickness of the intermediate reflection layer is about 100 to 1000 mW.

Then, the third dielectric layer 6, the second recording layer 7, and the fourth dielectric layer 8 are sequentially formed on the intermediate reflection layer 5 in the same manner as described above.

Here, the second recording layer 7 has a refractive index of about 400 to 450 nm, which is a blue wavelength band, and the third dielectric layer 6 and the fourth dielectric layer 8 may be omitted.

Subsequently, the reflective layer 9 is formed to a predetermined thickness on the fourth dielectric layer 8 using an Al alloy target, and the ultraviolet curable resin is spun into the protective film 10 on the reflective layer 9 in the range of 3 to 6 μm. After coating while rotating at 2000 to 5000rpm using a spin coater (curve coater), using an ultraviolet (UV) lamp to cure at a light amount of 1500 ~ 2000 mj / cm ² to produce an optical disk.

Information recording and reproducing of the optical disk thus produced are as follows.

That is, when a short wavelength band laser beam of 400 to 450 nm is irradiated onto the optical disk, the laser beam passes through the first recording layer and the intermediate reflection layer to record information on the second recording layer and to reflect information on the second reflection layer to reproduce the information. This is done.

Further, when a long wavelength band laser beam of 600 to 700 nm is irradiated to the optical disk, the laser beam is recorded in the first recording layer and reflected in the intermediate reflection layer to reproduce information.

As described above, the optical disk of the present invention not only records and reproduces information in the red wavelength band by using materials having optical characteristics as shown in FIG. 1, but also records and reproduces information in the blue wavelength band, which will be put to practical use in the future. It is expected to be able to fulfill its role as the next generation optical recording medium.

The optical recording medium according to the present invention has the following effects.

The optical disc of the present invention can record and reproduce information in the red wavelength band and the blue wavelength band, respectively, so that they are mutually compatible in the two wavelength bands and the recording density is greatly improved.

Claims (7)

In a recording medium in which a first recording layer, an intermediate reflection layer and a second recording layer are sequentially formed on a substrate, And the first recording layer is recorded in the wavelength region of 400-450 nm, and the second recording layer is recorded at 600-650 nm. The method of claim 1, The intermediate reflection layer transmits or reflects only a specific wavelength band. The method of claim 2, The wavelength band of transmission is 400-450nm, the wavelength band of reflection is 600-700nm characterized in that the recording medium. The method according to any one of claims 1 to 3, And the thickness of the intermediate reflective layer is 100-1000 mm 3. A method of recording and / or reproducing data on a recording medium, the method comprising: The recording medium includes a first recording layer, an intermediate reflection layer, and a second recording layer sequentially. And recording and / or reproducing by irradiating light of different wavelengths to the first recording layer and the second recording layer. The method of claim 5, wherein The first recording layer is irradiated with light in the wavelength band of 400-450nm, and recording and / or reproduction is performed, and the second recording layer is irradiated with light in the wavelength range of 600-700nm, and recording and / or reproduction is performed. Recording and / or reproducing method. The method of claim 5 And the intermediate reflection layer transmits or reflects only light of a specific wavelength band and has a thickness of 100-1000 Hz.

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