KR100618999B1 - High density optical disk - Google Patents

Abstract

Disclosed is a high-density optical disc that can greatly increase the recording density by resetting the thickness of the information board to the total thickness of the optical disc, minimizing the influence of the tilt of the optical disc, and forming a recording surface with three or more layers on each light incident surface. It is.

The disclosed high density optical disc includes: a first information substrate having a first incident surface on which recording / reproducing light is incident and a first recording surface on which an information signal is recorded; A first reflection layer formed on the first recording surface and reflecting a part of the incident light; At least one first recording layer formed on the first reflection layer, and a second reflection layer formed on each of the first recording layers to reflect a part of the incident light; 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 reflection layer formed on the second recording surface and reflecting a part of the incident light; At least one second recording layer formed on the third reflection layer, and a fourth reflection layer formed on each of the second recording layers to reflect a part of the incident light; A third recording surface which is formed between the first information substrate and the second information substrate, on which the information signal is recorded / reproduced by the light transmitted through the first and second reflection layers, and the light transmitted through the third and fourth reflection layers. A third information substrate having a fourth recording surface on which information signals are recorded / reproduced; A fifth reflection layer formed on the third recording surface to reflect incident light; And a sixth reflection layer formed on the fourth recording surface to reflect incident light.

Description

High density optical disk

1 is a schematic cross-sectional view showing an optical disk of a conventional double-sided one-layer structure.

2 is a schematic cross-sectional view showing a high density optical disk according to the first embodiment of the present invention;

3 is a schematic cross-sectional view showing a high density optical disc according to a second embodiment of the present invention;

4 is a schematic cross-sectional view showing a high density optical disc according to a third embodiment of the present invention.

<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 115 The first recording layer 117 The second reflective layer

121 ... Second information board 121a ... Second entrance face 121 b ... Second recording face

123 ... 3rd reflective layer 125 ... 2nd recording layer 127 ... 4th reflective layer

131 ... 3rd information board 131a ... 3rd recording surface 131b ... 4th recording surface

133 The fifth reflective layer 135 The sixth reflective layer 141, 143 Spacer

The present invention relates to a high-density optical disk, and in detail, by resetting the thickness of the information substrate to the total thickness of the optical disk to minimize the influence of the tilt of the optical disk and to form a recording surface of at least three layers for each light incident surface The present invention relates to a high-density optical disc that can significantly increase the recording density.

In general, an optical disc is employed 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 optical disc (CD) and a digital multifunction optical disc (DVD) according to the information recording capacity. Each of the CD and the DVD is standardized as shown in Table 1 in consideration of mutual compatibility and information recording density.

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

Here, the optical disc diameter and the optical 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 optical disc player and the specification of the optical disc tray for loading / unloading the optical disc. On the other hand, in order to increase the information recording capacity of the DVD to about 4.7 GB on a single substrate, the DVD has standardized different wavelengths, track pitches (track and track spacing), and minimum pit sizes. In particular, when the DVD is standardized to the same thickness as the substrate thickness of the CD, the tolerance of the optical disc tilt due to the densification becomes small, so that there is a high possibility that an error occurs when recording / reproducing information. In view of this, the board thickness of the DVD has been standardized to 0.6 mm.

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

On the other hand, when the thickness of the information substrate is normalized to 0.6 mm, that is, when the thickness ratio of the information substrate to the total thickness is maintained at about 0.5, a short wavelength optical pickup of about blue wavelength region (about 410 nm) is employed to achieve one surface per side. In recording / reproducing high-density information on the order of 15GB, the allowable range of the optical disc inclination which does not affect recording / reproducing is drastically reduced. This is because the amount of coma aberration according to the tilt of the optical disk is proportional to the wavelength, inversely proportional to the third power of the objective lens numerical aperture, and inversely proportional to the optical disk thickness.

Therefore, even when a light source having a condition suitable for recording high density optical information and an optical pickup device having an objective lens are employed, the DVD having the above-described structure as a recording medium, i.e., the thickness of the information substrate is normalized to 0.6 mm. In the case of employing the optical disc, the optical disc tilt allowance is reduced. Accordingly, it is impossible to record / reproduce high density information of about 15GB per side.

The present invention has been made in view of the above-mentioned point, and minimizes the influence of the tilt of the optical disk by resetting the thickness of the information substrate with respect to the entire thickness of the optical disk and has a structure of at least three layers for each light incident surface. It is an object of the present invention to provide a high-density optical disc that can form a recording surface so as to significantly increase the recording density.

In order to achieve the above object, the high-density optical disc according to the present invention comprises: a first information substrate having a first entrance surface on which recording / reproducing light is incident and a first recording surface on which an information signal is recorded; A first reflection layer formed on the first recording surface and reflecting a part of the incident light; At least one first recording layer formed on the first reflection layer, and a second reflection layer formed on each of the first recording layers to reflect a part of the incident light; A second information substrate having a second entrance surface on which recording / reproducing light is incident, and a second recording surface on which an information signal is recorded; A third reflection layer formed on the second recording surface and reflecting a part of the incident light; At least one second recording layer formed on the third reflection layer, and a fourth reflection layer formed on each of the second recording layers to reflect a part of the incident light; A third recording surface which is formed between the first information substrate and the second information substrate, and has an information signal recorded / reproduced by light transmitted through the first and second reflection layers, and the third and fourth reflection layers. A third information substrate having a fourth recording surface on which information signals are recorded / reproduced by one light; A fifth reflection layer formed on the third recording surface to reflect incident light; And a sixth reflection layer formed on the fourth recording surface to reflect incident light.

In addition, the high-density optical disk according to the present invention comprises: a first information substrate having a first incident surface on which recording / reproducing light is incident and a first recording surface on which an information signal is recorded; A first reflection layer formed on the first recording surface and reflecting a part of the incident light; At least one first recording layer formed on the first reflection layer, and a second reflection layer formed on each of the first recording layers to reflect a part of the incident light; A dummy substrate having a second incidence surface to which recording / reproducing light is incident; A second recording surface which is formed between the first information substrate and the dummy substrate, and has an information signal recorded / reproduced by light transmitted through the first and second reflection layers, and an information signal by light transmitted through the dummy substrate; A second information substrate having a third recording surface on which is recorded / reproduced; A third reflection layer formed on the second recording surface to reflect incident light; And a fourth reflection layer formed on the third recording surface to reflect incident light.

Hereinafter, a high density optical disc according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 2, the high-density optical disk according to the embodiment of the present invention is configured as three pieces, and includes first and second information substrates 111 and 121, on which information signals are recorded on one surface thereof. And a third information substrate 131 disposed between the information substrate 111 and the second information substrate 121 and having information signals recorded on both surfaces thereof.

The first information substrate 111 has a first incident surface 111a on which the recording / reproducing 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 reflection layer 113 includes a first recording layer 115 on which an information signal is recorded, and a second reflection layer 117 formed on the first recording layer 115 to reflect part of incident light. do.                     

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 and the first recording layer 115 form a desired physical pit in their own material 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, between the first recording surface 111b and the first reflection layer 113 and between the first recording layer 115 and the second reflection layer Between 117, a dielectric film made of ZnS-SiO ₂ material, a recording film made of GeSbTe or AgInSbTe material, and a dielectric film are laminated 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 reflection layer 113 and the second reflection layer 117 is a translucent film, and is preferably made of any one material selected from Ag alloy made of silver (Ag) and AgPdCu, SiC, AlN, Au alloy. . In addition, the first and second reflection layers 113 and 117 have different thicknesses according to the selected material so as to obtain a reflectance required for reproducing the information recorded on the first recording surface 111b. For example, when the reflectance of the first reflecting layer 113 requires approximately 28%, when AgPdCu material is selected, the desired reflectance can be obtained by setting the thickness of about 20 nm and the Al reflecting film to about 60 nm. have.

The second information substrate 121 has a second incident surface 121a through which the recording / reproducing light L is incident, and a second recording surface 121b on which the information signal is recorded. A third reflection layer 123 is formed on the second recording surface 121b to reflect part of the incident light. The third reflection layer 123 is provided with a second recording layer 125 on which an information signal is recorded, and a fourth reflection layer 127 formed on the second recording layer 125 to reflect part of 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 third and fourth reflective layers 123 and 127 are semitransparent films and are made of substantially the same material as the materials of the first and second reflective layers 113 and 117 described above.

The third information substrate 131 is formed between the second reflection layer 117 and the fourth reflection layer 127 by light transmitted through the first and second reflection layers 113 and 117. And a third recording surface 131a in which the information signal is recorded / reproduced, and a fourth recording surface 131b in which the information signal is recorded / reproduced by the light transmitted through the second and fourth reflection layers 123 and 127. Like the first information substrate 111, the third information substrate 131 is made of any one material selected from polycarbonate (PC), polymethyl methacrylate (PMMA), amorphous polyolefin (APO), and glass materials. In this configuration, the high-density optical disc has a thickness of approximately 0.6 mm so that the overall thickness D satisfies a standard disc, i.e., 1.2 mm, such as a CD or DVD.

A fifth reflective layer 133 is formed on the third recording surface 131a, and a sixth reflective layer 135 is formed on the fourth recording surface 131b. The fifth and sixth reflection layers 133 and 135 are made of a material such as Al alloy and Ag alloy as a total reflection film.

In the case where the third information substrate 131 is used for reproduction only, the configuration is completed by forming physical pits for the third and fourth recording surfaces 131a and 131b. On the other hand, in order to enable recording and reproducing on at least one recording surface of the third information substrate 131, the deposition of a phase change film on the fifth reflective layer 133 and / or the sixth reflective layer 135 is required. That is, a phase change film may be formed by stacking on the fifth reflective layer 133 and / or the sixth reflective layer 135 in the order of a dielectric film, a recording film, and a dielectric film.

As described above, the configured optical disk is formed to be bonded through two bonding processes, and spacers 141 and 143 having a predetermined thickness are required at the time of bonding by the bonding material. Here, the spacers 141 and 143 are required to be bonded between the second reflective layer 113 and the fifth reflective layer 133, and between the sixth reflective layer 135 and the fourth reflective layer 123, and have an overall thickness. It is preferable to have a thickness of approximately 20 to 40 µm which is a range that does not affect the setting of D.

The first to third information substrates 111, 121, and 131 have a thickness in a unit of 10 ^-1 mm order, and the first to sixth reflective layers 113, 117, 123, and 127 are provided. 133 and 135 and the spacers 141 and 143 have a thickness in the order of several tens of micrometers, so the total thickness D of the optical disc is the first to third information substrates 111, 121 and 131. ) Is determined by the thickness. Although the drawing shows a structure in which three recording layers are formed on one surface as an example, this is merely exemplary and may further include a plurality of reflecting layers that partially reflect other recording layers and incident light on the second reflecting layer. Of course.

In this case, the first information substrate 111 or the second information substrate 121 may be replaced with a dummy substrate in which no information is recorded. As described above, in the case of employing the dummy substrate, the reflective layer is not formed on the dummy substrate.

Referring to FIG. 3, the high-density optical disc of the double-sided six-layer structure according to the second embodiment of the present invention is composed of four pieces, and includes first and second information substrates 211 (information signal) recorded on one surface thereof. 221, and third and fourth information substrates 231 and 241 disposed between the first information substrate 211 and the second information substrate 221 and in which information signals are recorded on opposite surfaces thereof.

Each of the first and second information substrates 211 and 221 may include first and second incident surfaces 211a and 221a through which light L is incident, and first and second recording surfaces on which information signals are recorded. 211b) and 221b. Each of the first recording surface 211b and the second recording surface 221b reflects a part of incident light, and the first and third transmit the remaining light toward the third and fourth information substrates 231 and 241, respectively. Reflective layers 213 and 223 are formed. In addition, a first recording layer 215 on which an information signal is recorded and a second reflection layer 217 reflecting a part of incident light are formed on the first reflection layer 213. do. In the third reflection layer 223, a second recording layer 225 on which an information signal is recorded and a fourth reflection layer 227 formed on the second recording layer 225 to reflect part of incident light are formed. do.

Here, each of the first and second information substrates 211 and 221 and the first to fourth reflection layers 213, 217, 223, and 227 may be the first and second information substrates according to the first embodiment. Since (111) 121 and the first to fourth reflective layers 113, 117, 123, and 127 have substantially the same structure, detailed description thereof will be omitted.

The optical disc according to the present embodiment is characterized in that the third information substrate 131 disclosed in the first embodiment is manufactured by dividing into two information substrates 231 and 241 and bonded to each other. A third recording surface on which the third information substrate 231 faces the third reflection layer 217 so that an information signal is recorded / reproduced by light transmitted through the first and second reflection layers 213 and 217. Has 231a. A fifth reflective layer 233 is formed on the third recording surface 231a to reflect incident light.

The fourth information substrate 241 is formed to be bonded between the second information substrate 221 and the third information substrate 231, and is disposed to face the fourth reflection layer 227 so as to face the fourth reflection layer 227. And a fourth recording surface 241b in which the information signal is recorded / reproduced by the light passing through. A sixth reflective layer 243 is formed on the fourth recording surface 241b to reflect incident light.

Here, the thickness from the first incident surface 211a to the first recording surface 211b and the thickness from the second incident surface 221a to the second recording surface 221b is D ₁ . D ₁ preferably satisfies Equation ₁ described above.

The material of each of the third and fourth information boards 231 and 241 is formed of substantially the same material as the third information board 131 in the first embodiment, and the thickness of each of the third and fourth information boards 231 and 241 is the total thickness of the high density optical disk. It has a thickness of approximately 0.3 mm so that D satisfies 1.2 mm, which is a standard such as a CD or DVD.

Since each of the fifth and sixth reflective layers 233 and 243 has substantially the same configuration as the fifth and sixth reflective layers 133 and 135 of the first embodiment, detailed description thereof will be omitted.

As described above, the configured optical disk is formed to be bonded through three bonding processes, and spacers 251, 253 and 255 of a predetermined thickness are required for bonding by the bonding material. Here, the spacers 251, 253, and 255 are formed between the second reflection layer 217 and the fifth reflection layer 233, between the third information substrate 231 and the fourth information substrate 241, and the sixth reflection layer. It is required at the time of bonding between the 243 and the fourth reflection layer 227, and preferably has a thickness of approximately 20 to 40 µm which is a range that does not affect the overall thickness D setting.

In this way, the third information board structure of the first embodiment in which the information recording surface is formed on both sides is produced by dividing the third and fourth information substrates having the information recording surface formed on one side thereof, and then bonded to each other to produce the information substrate located in the middle. Thereby, there exists an advantage that the manufacturing process using a stamper can be made easy.

Referring to FIG. 4, the high-density optical disc of the double-sided six-layer structure according to the third embodiment of the present invention is composed of three pieces, and the first and second information substrates 311 having information signals recorded on one surface thereof. 321, and a third information substrate 331 disposed between the first information substrate 311 and the second information substrate 321 and in which information signals are recorded on opposite surfaces.

Each of the first and second information substrates 311 and 321 includes first and second incident surfaces 311a and 321a to which light L is incident, and first and second recording surfaces on which information signals are recorded. 311b) 321b. The first and third reflection layers 313 and 323 reflect a part of incident light on each of the first recording surface 311b and the second recording surface 321b and transmit the remaining light toward the third information substrate 331. ) Is formed.

In addition, the first reflection layer 313 is formed with a first recording layer 315 on which an information signal is recorded and a second reflection layer 317 formed on the first recording layer 315 to reflect a part of incident light. do. The third reflection layer 323 includes a second recording layer 325 on which an information signal is recorded and a fourth reflection layer 327 formed on the second recording layer 325 to reflect a part of incident light. do. Here, each of the first and second information substrates 311 and 321 and the first to fourth reflection layers 313, 317, 323, and 327 is the first and second information substrates according to the first embodiment. Since (111) 121 and the first to fourth reflective layers 113, 117, 123, and 127 have substantially the same structure, detailed description thereof will be omitted.                     

In addition, the third information substrate 331 has third and fourth recording surfaces 331a and 331b which are capable of recording information signals. Fifth and sixth reflective layers 333 and 335 are formed on the third and fourth recording surfaces 331a and 331b, respectively. The material of the third information substrate 331 and the material and configuration of the fifth and sixth reflective layers 333 and 335 are the third information substrate 131 and the fifth and sixth reflective layers according to the first embodiment. Since it is substantially the same as (133) and 135, the detailed description is abbreviate | omitted.

The optical disk according to the present embodiment is characterized in that the thicknesses of the first to third information substrates 311, 321, and 331 are set differently from those of the first embodiment.

In other words, when the thickness of each of the first and second information substrates 311 and 321 is D ₂ , the first and second information substrates 311 and 321 are represented by Equation 2 in consideration of the tilt margin of the optical disk in setting the thickness. Similarly, the thickness is preferably set.

As described above, the configured optical disk is formed to be bonded through two bonding processes, and spacers 341 and 343 having a predetermined thickness are required for bonding by the bonding material. Here, the spacers 341 and 343 are required to be bonded between the second reflection layer 317 and the fifth reflection layer 333, and between the sixth reflection layer 343 and the fourth reflection layer 327. It is preferable to have a thickness of approximately 20 to 40 µm which is a range that does not affect the setting of D. Here, the first information substrate 311 or the second information substrate 321 may be replaced by a dummy substrate on which no information is recorded. As described above, in the case of employing the dummy substrate, the reflective layer is not formed on the dummy substrate.

As described above, the configured high density optical disc maintains the overall thickness of the disc in accordance with the CD and DVD standards, while setting the thicknesses D ₁ and D ₂ of the information substrate as shown in Equation 1 or 2 above, thereby increasing the tilt margin of the optical disc. As a result, the problem caused by the tilt of the optical disc can be overcome.

In addition, by securing 6 or more information recording surfaces, 13.5 GB of recording per layer is possible, as applied to the HD-DVD standard, thereby increasing the capacity of the information. For example, in the case of the six-layer structure, the capacity of the recording capacity can be increased to about 80 gigabytes.

Claims (8)

A first information substrate having a first entrance surface to which recording / reproducing light is incident and a first recording surface on which an information signal is recorded; A first reflection layer formed on the first recording surface and reflecting a part of the incident light; At least one first recording layer formed on the first reflection layer, and a second reflection layer formed on each of the first recording layers to reflect a part of the incident light; A second information substrate having a second entrance surface on which recording / reproducing light is incident, and a second recording surface on which an information signal is recorded; A third reflection layer formed on the second recording surface and reflecting a part of the incident light; At least one second recording layer formed on the third reflection layer, and a fourth reflection layer formed on each of the second recording layers to reflect a part of the incident light; A third recording surface which is formed between the first information substrate and the second information substrate, and has an information signal recorded / reproduced by light transmitted through the first and second reflection layers, and the third and fourth reflection layers. A third information substrate having a fourth recording surface on which information signals are recorded / reproduced by one light; A fifth reflection layer formed on the third recording surface to reflect incident light; And a sixth reflection layer formed on the fourth recording surface to reflect incident light. 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 are D ₁ . A thickness D ₁ is a high density optical disc, characterized in that the following conditional expression is satisfied. <Conditional expression>

The method of claim 2, wherein the third information substrate, A high density optical disc comprising: bonding one substrate having the third recording surface and the fifth reflective layer on one surface thereof, and another substrate having the fourth recording surface and the sixth reflective layer formed on one surface thereof. 4. The high density optical disc of claim 3, wherein the spacer thickness required when joining two substrates of the third information substrate is approximately 20 to 40 µm. 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 according to any one of claims 1 to 5, wherein each of the first to third information substrates, 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 3 and 5, And a spacer thickness required for bonding between the second reflective layer and the fifth reflective layer, and between the sixth reflective layer and the fourth reflective layer, is about 20 to 40 μm. A first information substrate having a first entrance surface on which recording / reproduction light is incident and a first recording surface on which an information signal is recorded; A first reflection layer formed on the first recording surface and reflecting a part of the incident light; At least one first recording layer formed on the first reflection layer, and a second reflection layer formed on each of the first recording layers to reflect a part of the incident light; A dummy substrate having a second incidence surface to which recording / reproducing light is incident; A second recording surface which is formed between the first information substrate and the dummy substrate, and has an information signal recorded / reproduced by light transmitted through the first and second reflection layers, and an information signal by light transmitted through the dummy substrate; A second information substrate having a third recording surface on which is recorded / reproduced; A third reflection layer formed on the second recording surface to reflect incident light; And a fourth reflection layer formed on the third recording surface to reflect incident light.

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