KR100708104B1 - High density optical disk - Google Patents

Abstract

Disclosed is a high-density optical disc capable of reflecting incident light by using a reflectance of the protective substrate / information substrate itself, and capable of storing approximately 15 gigabytes or more of information on each information recording surface.

The disclosed high density optical disc includes: a first information substrate having a first incident surface on which light is incident and a first recording surface on which an information signal is recorded; A second information substrate having a second incident surface on which light is incident and a second recording surface on which an information signal is recorded; A third having a third recording surface which is formed between the first information substrate and the second information substrate and has a third recording surface which is capable of reflecting most incident light to the surface where the information signal reproduced by the light transmitted through the first recording surface is recorded. Information board; characterized in that it comprises a.

In addition, the high-density optical disk includes a protective substrate having an incident surface on which light is incident; And an information substrate having a recording surface bonded to the protective substrate, the recording surface being able to reflect most incident light to the surface where the information signal is recorded / reproduced by the light transmitted through the protective substrate.

Description

High density optical disk

1 is a schematic cross-sectional view showing a conventional double-sided one-layered optical disk.

FIG. 2 is a schematic cross-sectional view showing a high density optical disc having a single layer and a double layer structure on each side of three pieces according to a first embodiment of the present invention; FIG.

3 is a schematic cross-sectional view showing a high-density optical disk in which both surfaces of each of the three pieces according to the second embodiment of the present invention have a single layer and a double layer structure;

4 is a schematic cross-sectional view showing a high-density optical disk having a two-piece cross section structure according to a third embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing a high density optical disk having a three-piece double sided structure according to a fourth embodiment of the present invention; FIG.

FIG. 6 is a schematic cross-sectional view showing a high density optical disk having a single layer and a double layer structure on each of the three pieces of both surfaces according to the fifth embodiment of the present invention; FIG.

<Description of Symbols for Main Parts of Drawings>

111 The first information board 111a ... the first entrance plane 111b ... the first recording plane

113 The first reflective layer 121 The second information substrate 121a The second entrance surface

121b ... 2nd recording surface 123 ... 2nd reflective layer 131 ... 3rd information board

131a ... 3rd recording side 141, 143 ... Spacer

The present invention relates to a high-density optical disk, and more particularly, to a high-density optical disk capable of reflecting incident light by using the reflectance of the protective substrate / information substrate itself, and storing approximately 15 gigabytes or more of information on each information recording surface. It is about.

In general, an optical disc is widely used as an information recording medium of an optical pickup apparatus for recording / reproducing information in a non-contact manner, and is classified into a compact disc (CD) and a digital multifunction disc (DVD) according to the information recording capacity.

Each of the CD and DVD is standardized as shown in Table 1 in consideration of mutual compatibility and information recording density.

CD DVD Disc diameter (mm) 120 120 Disk thickness (mm) 1.2 1.2 Information board thickness (mm) 1.2 0.6 Track Pitch (μm) 1.6 0.74 Minimum Feet Size (μm) 0.83 0.4 Wavelength (nm) 780 635/650 Single Board Capacity (GB) 0.65 4.7

Here, the disc diameter and the disc thickness represent the external appearance of the CD and the DVD, and are set to the same size in consideration of the internal space of the compatible disc player and the specifications of the disc tray for loading / unloading the disc.

On the other hand, in order to increase the information recording capacity of the DVD to about 4.7 GB, the DVD has standardized different wavelengths, track pitches (track and track spacing), and minimum pit size. That is, by shortening the light emitted from the light source of the optical pickup device, for example, a semiconductor laser, into the 635/650 nm wavelength region, the size of the light spot formed on the disk can be reduced, so that the track pitch and the minimum pit size can be reduced.

In addition, when the CD was initially developed, it was difficult to produce a disc making thickness of 1.2 mm or less, so that the disc thickness was 1.2 mm to minimize degradation of the playback signal due to foreign matter on the substrate surface. On the other hand, when DVDs are standardized to the same thickness as the substrate thickness of the CD, errors in the disc recording / reproducing are high because the tolerance of the disc tilt due to the densification becomes small. In view of this, the board thickness of the DVD has been standardized to 0.6 mm. Here, the DVD records signals digitally, so that signal degradation due to contamination of the disk surface can be processed in a circuit.

DVDs having the above-described standards can be divided into single-sided one-layer structure, double-sided one-layer structure, single-sided two-layer structure and double-sided two-layer structure in consideration of information recording capacity.

Referring to FIG. 1, a DVD having a double-sided one-layer structure includes a first and second information substrates 11 and 21 having a thickness of 0.6 mm, and recording surfaces 11a of each of the first and second information substrates 11 and 21. And a bonding layer 15 provided between the first and second reflection layers 13 and 23 coated on the shell 21a and the first and second reflection layers 13 and 23. The optical disc of the double-sided single layer structure thus constructed has an information recording capacity of about 9.4 GB, which is twice the information capacity of the optical disc having the single-sided single layer structure.

The DVD having the structure as described above has the advantage that the information capacity is larger than that of the conventional CD while maintaining the total thickness of the 0.6 mm thick information substrate.

On the other hand, when the thickness of the information substrate is normalized to 0.6 mm as described above, a short wavelength optical pickup of about blue wavelength region (approximately 410 nm) is employed and 15 gigabyte per side is adopted. In the recording / reproducing level of ultra high density information, the allowable range of the disc tilt which does not affect the recording / reproducing is drastically reduced. This is due to the coma aberration allowance according to the inclination of the disk being proportional to the wavelength, inversely proportional to the third power of the objective lens opening, and inversely proportional to the disk thickness.

Therefore, even when the optical pickup apparatus having a light source and an objective lens suitable for optical ultra-high density information recording is employed, the disc tilt allowance is reduced when the recording medium is employed in the DVD having the above-described structure. byte There is a problem that it is impossible to record / reproduce ultra-high density information at a level.

In addition, in order to reproduce the information recorded on all the information recording surfaces, a reflective layer that reflects incident light is employed as an essential component. Therefore, there is a disadvantage that the manufacturing process of the optical disc of the multi-layer structure is difficult because the process becomes complicated as the reflection layer is formed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above disadvantages, and provides a high-density optical disc of the same standard as DVD and CD in terms of overall thickness and size, and having an information capacity of 15 gigabytes per side, and at least one information recording surface. It is an object of the present invention to provide a high-density optical disc capable of reproducing information without a reflective layer.

In order to achieve the above object, a high-density optical disk according to the present invention comprises: a first information substrate having a first incident surface on which light is incident and a first recording surface on which an information signal is recorded; A second information substrate having a second incident surface on which light is incident and a second recording surface on which an information signal is recorded; A third recording surface formed between the first information substrate and the second information substrate, the third recording surface being configured to reflect most incident light to a surface on which an information signal reproduced by the light transmitted through the first recording surface is recorded. And a third information substrate.

In addition, the high-density optical disk according to the present invention includes a protective substrate having an incident surface on which light is incident; And an information substrate having a recording surface bonded to the protective substrate and having a recording surface capable of reflecting most incident light to a surface on which the information signal is recorded / reproduced by the light transmitted through the protective substrate.

In addition, the high-density optical disk according to the present invention includes a first protective substrate having a first incident surface to which light is incident; A second protective substrate having a second incident surface on which light is incident; A first junction formed between the first protective substrate and the second protective substrate, wherein the first reflective substrate reflects most of the incident light to a surface on which the information signal is recorded / reproduced by the light transmitted through the first and second protective substrates; And an information substrate having a second recording surface.

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

Referring to FIG. 2, the high density optical disc according to the first embodiment of the present invention is composed of three pieces. The first and second information substrates 111 and 121 in which an information signal is recorded on one surface thereof, And a third information substrate 131 disposed between the first information substrate 111 and the second information substrate 121 and having an information signal recorded on one surface thereof.

The first information substrate 111 has a first incident surface 111a on which the reproduction light L is incident and a first recording surface 111b on which an information signal is recorded. A first reflective layer 113 is formed on the first recording surface 111b to reflect part of incident light and transmit the remaining part toward the third information substrate 131.

The first information substrate 111 is made of any one material selected from polycarbonate (PC), polymethyl methacrylate (PMMA), amorphous polyolefin (APO), and glass materials. When the thickness of the first information substrate 111 is D ₁ , the thickness of the first information substrate 111 is preferably set as shown in Equation 1 in consideration of the tilt margin of the optical disk. .

Here, when used exclusively for reproduction, the first recording surface 111b forms a desired physical pit on the material of the first information substrate 111 itself, without adding any other configuration, and the formation thereof is completed. do. On the other hand, in the case of forming a structure capable of recording and reproducing by using a phase change method, a dielectric film made of ZnS-SiO ₂ material or a GeSbTe system is formed between the first recording surface 111b and the first reflection layer 113. Alternatively, a recording film and a dielectric film made of AgInSbTe-based material are stacked in this order. Since the configuration of such a phase change film itself is well known, its detailed description and drawings will be omitted.

The first reflective layer 113 is a translucent film, and is preferably made of any one material selected from silver (Ag), Ag alloy of AgPdCu system, SiC, AlN, and Au alloy. In addition, the first reflecting layer 113 is set to a different thickness depending on the material selected to obtain approximately 28% of the reflectance required to reproduce the information recorded on the first recording surface 111b. For example, when AgPdCu material is selected, the reflectance of approximately 28% can be obtained by setting the thickness to approximately 20 nm and the Al reflecting film to approximately 60 nm.

The second information substrate 121 has a second incident surface 121a through which the reproduction light L is incident, and a second recording surface 121b on which the information signal is recorded. The second recording layer 123 is formed on the second recording surface 121b to totally reflect incident light.

Like the first information substrate 111, the second information substrate 121 is made of any one material selected from polycarbonate (PC), polymethyl methacrylate (PMMA), amorphous polyolefin (APO), and glass materials. In addition, when the thickness is D ₁ , it is set as shown in Equation 1 above. In the recording / reproducing of the information on the second information substrate 121, the configuration in the case of being used exclusively for reproduction and the configuration in which both recording and reproduction are possible are as described with reference to the first information substrate 111. Since it is substantially the same, detailed description is abbreviate | omitted. In addition, the second reflection layer 123 is a total reflection film.

The third information substrate 131 is formed to be joined between the first reflection layer 113 and the second reflection layer 123, and the information signal is recorded / reproduced by the light transmitted through the first reflection layer 113. Has a third recording surface 131a.

The third information substrate 131 is made of any one material selected from aluminum, polystyrene, ABS resin, polycarbonate, and polymethyl methacrylate. It has a thickness of approximately 0.4 mm to satisfy the same specification of 1.2 mm. In the case where the third information substrate 131 is manufactured from such a material, since its own reflectance is high, there is an advantage that information recorded on the recording surface can be reproduced without providing a separate reflection layer.

When the third information substrate 131 is used exclusively for reproduction, the configuration is completed by forming physical pits on the third recording surface 131a. On the other hand, in order to be able to record and reproduce the third recording surface 131a, a phase change film is required to be formed on the third recording surface 131a. That is, a phase change film can be formed by stacking the dielectric film, the recording film, and the dielectric film on the third recording surface 131a in this order.

As described above, the configured optical disk is formed to be bonded through two bonding processes, and the first and second spacers 141 and 143 having a predetermined thickness are required at the time of bonding by the bonding material. Here, the first spacer 141 is required at the time of bonding between the first reflective layer 113 and the third recording surface 131a, and the second spacer 143 is the second reflective layer 123 and the third information substrate. It takes at the junction between 131. The first and second spacers 141 and 143 preferably have a thickness of approximately 20 to 40 mu m, which is a range that does not affect the overall thickness setting. That is, the first to third information substrates 111, 121 and 131 have a thickness in the order of 10 ^-1 mm order, and the first and second reflection layers 113 and 123, and Since the second spacers 141 and 143 have a thickness in the order of several tens of micrometers, the overall thickness of the optical disc is determined by the thicknesses of the first to third information substrates 111, 121, and 131.

Referring to FIG. 3, the high-density optical disk according to the second embodiment of the present invention includes first and second information substrates 211 having first and second incident surfaces 211a and 221a to which reproduction light is incident. And a third information substrate 231 formed to be bonded between the first and second information substrates 211 and 221.

The thickness D ₁ of the first and second information substrates 211 and 221 is set to satisfy the condition of Equation 1, and transmits most of the incident light and reflects a part thereof. Compared with the first and second information substrates 111 and 121 in the first embodiment described above, the first and second information substrates 211 and 221 may be separated by changing their materials. The feature is that the reflective layer is excluded.

That is, the first and second information substrates 211 and 221 are made of any one material selected from polystyrene, ABS resin, polycarbonate, and polymethyl methacrylate. When the first and second information substrates 211 and 221 are manufactured from such a material, the reflectivity of the first and second information substrates 211 and 221 is high. Therefore, there is an advantage that information recorded on each of the first and second recording surfaces 211b and 221b can be reproduced without providing a separate reflective layer. On the other hand, a part of the light incident on the first recording surface 211b is transmitted to form the third recording surface 431a. Here, since the third information substrate 231 is substantially the same as the third information substrate 131 according to the first embodiment, a detailed description thereof will be omitted.

Here, the spacers 241 and 243 required for bonding between the first information substrate 211 and the third information substrate 231 and between the third information substrate 231 and the second information substrate 221 are further included. It is provided. The thickness of the spacers 241 and 243 is a range which has little influence on the total thickness D of the optical disk, and is preferably about 20 to 40 m.

Referring to FIG. 4, the high-density optical disk having a single-layered cross-sectional structure according to the third embodiment of the present invention is composed of two pieces, and includes information on a protective substrate 311 and a surface facing the protective substrate 311. And an information substrate 321 on which signals are recorded.

The protective substrate 311 has an incident surface 211a through which light L is incident, and has a thickness D ₂ . Here, the protective substrate 311 is made of substantially the same material as the first information substrate 211 according to the first embodiment, and the point and thickness of the first recording surface (211b in FIG. 3) are excluded. _The difference is set at ₂ .

The thickness D ₂ is preferably set as shown in equation (2) so as to be suitable for an optical disc that requires a higher density than the high density optical discs according to the first and second embodiments described above.

Here, the information substrate 321 has a recording surface 321a formed on a surface facing the protective substrate 311, and has a thickness of approximately 0.9 mm so that the total density D of the high density optical disk satisfies 1.2 mm, which is the standard of a conventional disk. It is. The information substrate 321 is composed of substantially the same material as the third information substrate (131 in FIG. 2) according to the first embodiment, and performs the same function, a detailed description thereof will be omitted.

As described above, the configured optical disk is formed by bonding through one bonding process, and the spacer 341 having a predetermined thickness during bonding by the bonding material is required when bonding between the protective substrate 311 and the information substrate 321. It is preferable to have a thickness of approximately 20 to 40 µm which is a range that does not affect the overall thickness setting.

Referring to FIG. 5, the high-density optical disc of the double-sided one-layer structure according to the fourth embodiment of the present invention is composed of three pieces, and includes first and second protective substrates 411 and 431, and the first and second protective substrates 411 and 431. And an information substrate 421 provided between the second protective substrates 411 and 431.

Each of the first and second protective substrates 411 and 431 has first and second incident surfaces 411a and 431a to which light L is incident. Each of the first and second protective substrates 411 and 431 has a thickness D _{2. Since} the first and second protective substrates 411 and 431 have a thickness D ₂ , the first and second protective substrates 411 and 431 have substantially the same material and the same configuration as those of the protective substrate 311 of FIG. 4. Description is omitted. Here, the thickness D ₂ satisfies the condition of the above expression (2).

The information substrate 421 has first and second recording surfaces 431a and 431b on which information signals are written on surfaces facing the first and second protection substrates 411 and 431, respectively. The information substrate 421 has a thickness of approximately 0.8 mm so that the high-density optical disk overall thickness D satisfies 1.2 mm, which is the standard for ordinary disks. The information substrate 431 configured as described above is made of substantially the same material as the third information substrate 131 of FIG. 2 according to the first embodiment, and is substantially identical to the information substrate according to the embodiment described above for each recording surface. Since the same function is performed, detailed description thereof will be omitted.

As described above, the configured optical disk is formed to be bonded through two bonding processes, and spacers 441 and 443 having a predetermined thickness are required for bonding by the bonding material. Here, the spacers 441 and 443 are required to be bonded between the first protective substrate 411 and the information substrate 431, and the second protective substrate 431 and the information substrate 431. It is desirable to have a thickness of approximately 20 to 40 µm which is a range that does not affect the setting.

Referring to FIG. 6, the high-density optical disc according to the fifth embodiment of the present invention includes first and second information substrates 511 and 521 having first and second incident surfaces 511a and 521a to which light is incident. ) And a third information substrate 531 bonded to the first and second information substrates 511 and 521.

In the high-density optical disk according to the present embodiment, the thickness of the first and second information substrates 511 and 521 is set differently while maintaining the thickness D as the thickness of the optical disk described above. It is distinguished from the high density optical disc according to the second embodiment. That is, the thickness of each of the first and second information substrates 511 and 521 according to the present embodiment is set to D ₂ , and this thickness D ₂ preferably satisfies the condition of Equation 2 described above. Here, the material and optical function of each of the first to third information substrates 511, 521, 531 are substantially the same as that of each of the first to third information substrates 211, 221, 231 according to the second embodiment. Since it is the same, detailed description thereof will be omitted.

Here, spacers 541 and 543 are further provided between the first information substrate 511 and the third information substrate 531 and between the third information substrate 531 and the second information substrate 521. On the other hand, since each of the spacers 541 and 543 is substantially the same as the spacers 241 and 243 according to the second embodiment, detailed description thereof will be omitted.

The high-density optical disk according to the present invention configured as described above can reflect incident light using the reflectance of the protective substrate and / or the information substrate itself, so that the manufacturing process of the reflective layer for the intermediate information substrate in the manufacturing process of the optical disk of the multilayer structure is performed. The fundamental elimination has the advantage of greatly simplifying the manufacturing process. In addition, by resetting the thickness of the protective substrate and / or the information substrate, there is an advantage that it is easy to apply to an optical recording / reproducing apparatus which requires a light spot relatively smaller than the size of the light spot required in the DVD.

Claims (16)

A first information substrate having a first incident surface on which light is incident and a first recording surface on which an information signal is recorded; A second information substrate having a second incident surface on which light is incident and a second recording surface on which an information signal is recorded; A junction formed between the first information substrate and the second information substrate, the information signal being reproduced by the light transmitted through the first recording surface, and having a third recording surface facing the first recording surface. And a third information substrate on which the reflective layer is not formed on the third recording surface. The thickness of the first incident surface to the first recording surface and the thickness of the second incident surface to the second recording surface is D ₁ . A thickness D ₁ is a high density optical disc, characterized in that the following conditional expression is satisfied. <Conditional expression>

The thickness of the first incident surface to the first recording surface and the thickness of the second incident surface to the second recording surface is D ₂ . A high density optical disc, characterized in that the thickness D ₂ satisfies the following conditional expression. <Conditional expression>

The method of claim 1, And a spacer thickness required for bonding between the first reflective layer and the third information substrate, and between the third information substrate and the second reflective layer, 20 to 40 μm. The light emitting device according to any one of claims 1 to 4, further comprising: a first reflection layer formed on the first recording surface and reflecting a part of incident light; And a second reflection layer formed on the second recording surface and reflecting a part of the incident light. The method of claim 5, wherein each of the first and second information substrate, A high density optical disc comprising any one selected from polycarbonate (PC), polymethyl methacrylate (PMMA), amorphous polyolefin (APO) and glass materials. The method according to any one of claims 1 to 4, wherein each of the first and second information substrates, A high density optical disc, characterized in that composed of any one selected from polystyrene, ABS resin, polycarbonate, polymethyl methacrylate. The method according to any one of claims 1 to 4, wherein the third information substrate, A high-density optical disc, characterized in that composed of any one material selected from aluminum, polystyrene, ABS resin, polycarbonate, polymethyl methacrylate. A protective substrate having an incident surface on which light is incident; And an information substrate bonded to the protective substrate and having a recording surface facing the protective substrate as a surface on which the information signal is recorded / reproduced by the light transmitted through the protective substrate and having no reflective layer formed thereon. High density optical disc characterized in that. 10. The method of claim 9, wherein when the thickness of the protective substrate D ₂ d, the high density optical disk, characterized in that the thickness D ₂ satisfying the conditional expression is to protect the substrate. <Conditional expression>

The method of claim 9, wherein the protective substrate, A high density optical disc, characterized in that composed of any one selected from polystyrene, ABS resin, polycarbonate, polymethyl methacrylate. The method according to any one of claims 9 to 11, wherein the information substrate, A high-density optical disc, characterized in that composed of any one material selected from aluminum, polystyrene, ABS resin, polycarbonate, polymethyl methacrylate. A first protective substrate having a first incident surface on which light is incident; A second protective substrate having a second incident surface on which light is incident; A junction formed between the first protective substrate and the second protective substrate, wherein the information signal is recorded / reproduced by light transmitted through the first and second protective substrates, respectively; And an information substrate having first and second recording surfaces disposed opposite to each other and having no reflective layer formed on each of the first and second recording surfaces. The high density optical disc of claim 13, wherein the thickness D ₂ of the first and second protective substrates satisfies the following conditional formula when the thickness of each of the first and second protective substrates is D ₂ . <Conditional expression>

The method of claim 13, wherein each of the first and second protective substrate, A high density optical disc, characterized in that composed of any one selected from polystyrene, ABS resin, polycarbonate, polymethyl methacrylate. The method according to any one of claims 13 to 15, wherein the information substrate, A high-density optical disc, characterized in that composed of any one material selected from aluminum, polystyrene, ABS resin, polycarbonate, polymethyl methacrylate.

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