KR100708184B1 - Optical recording medium having multi recording layer and method for fabricating the same - Google Patents

Abstract

The present invention relates to a multilayer optical recording medium and a method of manufacturing the same, which can simultaneously initialize the recording layer during the curing of the intermediate layer without a separate initialization device and an initialization process. A multilayer optical recording medium according to a preferred embodiment of the present invention has a structure in which a reflective layer, a crystallization promoting layer and a recording layer are repeatedly stacked at least twice on a substrate, and an intermediate layer is interposed between adjacent recording layers and the reflective layer. A transparent cover layer is formed on the uppermost recording layer, and the crystallization promoting layer is characterized by absorbing UV-light for curing the intermediate layer.

Description

Optical recording medium having multi recording layer and method for fabricating the same

1 is a sectional view schematically showing the structure of a conventional multilayer optical recording medium.

2 is a schematic diagram showing a conventional process of initializing a multilayer optical recording medium.

3 is a sectional view schematically showing the structure of a multilayer optical recording medium according to a preferred embodiment of the present invention.

4A to 4E are schematic diagrams showing a process for producing a multilayer optical recording medium according to the present invention.

5 is a graph showing the thickness of each layer along the radial direction in the multilayer optical recording medium according to the present invention.

※ Explanation of code about main part of drawing ※

100 ..... optical recording media 110 ..... substrate

120,130,140 ..... reflective layer 121,131,141 ..... crystallization facilitating layer

122,132,142 ..... Recording layer

The present invention relates to a multilayer optical recording medium and a method of manufacturing the same, and more particularly, to a multilayer optical recording medium capable of simultaneously performing initialization on a recording layer during the curing of an intermediate layer without a separate initialization device and an initialization process, and a It relates to a manufacturing method.

Background Art Optical recording media such as optical discs generally realize a high capacity information storage function by forming a recording layer in a multilayer structure. For example, an optical recording medium such as a Blu-ray disc (BD) can store up to about 25GB of information using a single recording layer, but in the future, 100 ~ It is expected that an optical recording medium having a capacity of 200 GB will be introduced.

1 exemplarily shows a general structure of such a multilayer optical recording medium. The optical recording medium of the two-layer structure shown in FIG. 1 includes a substrate 1, a first reflective layer 2, a first recording layer 3, an intermediate layer 4, a first reflective layer 5, and a second recording layer. (6) and a transparent cover layer (7). Further, the first and second recording layers 3 and 6 usually have a three-layer structure of a lower dielectric layer, an information recording layer and an upper dielectric layer. The lower and upper dielectric layers are for preventing deformation such as oxidation of the information recording layer. In addition, the intermediate layer 4 is for maintaining a gap between the first recording layer 3 and the second recording layer 6. As shown in Fig. 1, a track is formed in each layer in a groove shape, so that information can be recorded in the recording layer along the track.

In the optical recording medium having the above-described structure, various materials for forming the information recording layer may be used. In particular, in the case of a rewritable optical recording medium capable of repeating recording / reproducing of information, when in the crystalline state, The phase change material is mainly used to change the reflectance when in the amorphous state. However, in the case of the RW type optical recording medium using such a phase change material, since the recording layer immediately after film formation is in an amorphous state, the reflectance is very low to 5% or less, making focusing and tracking difficult. Therefore, an initialization process for changing the recording layer to crystalline is required. However, in the case of an optical recording medium having two or more recording layers, it takes a long time to initialize each layer, and there is a problem that it is difficult to uniformly initialize each layer.

For example, in Japanese Patent Laid-Open No. 9-91700, as shown in Fig. 2, the plurality of recording layers 3, 6 are simultaneously initialized using a plurality of laser light sources 10a, 10b having a predetermined initialization wavelength. Doing. At this time, the plurality of detectors 11a and 11b can be used to confirm whether the laser beams emitted to the respective light sources 10a and 10b are correctly irradiated onto the corresponding recording layers 3 and 6. However, in this case, there is a problem in that the recording layer 6, which is relatively forward, cannot adequately initialize the recording layer 3, which is relatively backward, unless it has some degree of light transmission at the initialization wavelength. Furthermore, since the reflectance of each layer is very low, the laser beam is selectively focused accurately for each layer, making it difficult to initialize, and the recording layer 3 at the rear by the laser beam for initializing the front recording layer 6 is difficult. The crystallization state of is likely to be affected.

On the other hand, Japanese Patent Laid-Open No. 2004-95092 discloses an optical recording medium in which a thermal diffusion layer having high thermal conductivity is formed on an upper surface of a recording layer so that the recording layer irradiated with a laser beam can be quenched. In this case, the initialization may be performed by completely irradiating a laser light to the entire surface of the optical recording medium after the optical recording medium is completely manufactured, and performing the initialization of one recording layer immediately after forming one recording layer. The following recording layer may be formed. According to this method, however, in actual mass production, not only is it inconvenient because the initialization of the optical recording medium has to be performed off the mass production line, but also the repetitive initialization operation needs to be performed as many times as the number of recording layers. There is a problem that productivity deteriorates.

It is an object of the present invention to improve the problems of the conventional multilayer optical recording medium described above. More specifically, it is an object of the present invention to provide a multilayer optical recording medium and a method for manufacturing the same, which can simultaneously initialize the recording layer in the manufacturing process of the optical recording medium without a separate initialization device and an initialization process.

A multilayer optical recording medium according to a preferred embodiment of the present invention has a structure in which a reflective layer, a crystallization promoting layer and a recording layer are repeatedly stacked at least twice on a substrate, and an intermediate layer is interposed between adjacent recording layers and the reflective layer. A transparent cover layer is formed on the uppermost recording layer, and the crystallization promoting layer is characterized by absorbing UV-light for curing the intermediate layer.

According to the present invention, the crystallization promoting layer is characterized in that formed of at least one material selected from the group consisting of Sb ₂ Te ₃ , Al, Au, Cr and Sb.

In addition, the recording layer includes a lower dielectric layer, an information recording layer, and an upper dielectric layer, wherein the lower and upper dielectric layers for protecting the information recording layer are formed of at least one material of ZnS-SiO ₂ , SiN, and SiO ₂ . The information recording layer is formed of at least one of GeSbTe and AgInSbTe.

According to the present invention, the information recording layer is characterized in that in the process of curing the intermediate layer, the phase change from amorphous to crystalline by the heat of UV-light absorbed by the crystallization promoting layer.

On the other hand, a method of manufacturing a multilayer optical recording medium according to a preferred embodiment of the present invention includes a first step of sequentially laminating a reflective layer, a crystallization promoting layer and a recording layer on a substrate; A second step of discharging an optical polymer resin on the recording layer; A third step of forming an intermediate layer having a predetermined thickness by pressing the optical polymer resin with a transparent stamper having a predetermined groove pattern and rotating the substrate; And a fourth step of curing the intermediate layer by irradiating UV-light onto the light-transmitting stamper, and then separating the light-transmitting stamper, the crystallization facilitating layer repeats at least two times. In the fourth step of absorbing light and curing the intermediate layer, the recording layer is phase-changed from amorphous to crystalline by the heat of UV-light absorbed by the crystallization promoting layer.

Hereinafter, with reference to the accompanying drawings, a structure of a multilayer optical recording medium and a method of manufacturing the multilayer optical recording medium according to a preferred embodiment of the present invention will be described in detail.

3 is a sectional view schematically showing the structure of a multilayer optical recording medium according to a preferred embodiment of the present invention.

Referring to FIG. 3, a multilayer optical recording medium 100 according to a preferred embodiment of the present invention having n recording layers has a structure in which a reflective layer, a crystallization promotion layer and a recording layer are repeatedly stacked n times on a substrate, and adjacent to each other. An intermediate layer is interposed between the recording layer and the reflective layer, and a transparent cover layer is formed on the uppermost recording layer. That is, the first reflective layer 120, the first crystallization promotion layer 121, and the first recording layer 122 are sequentially stacked on the substrate 100, and the first intermediate layer is again on the first recording layer 122. The 125, the second reflective layer 130, the second crystallization promoting layer 131, and the second recording layer 132 are sequentially stacked. In this manner, the n-th intermediate layer 135, the n-th reflective layer 140, the n-th crystallization promotion layer 141, and the n-th recording layer 142 are stacked, and a transparent cover is placed on the last n-th recording layer 142. A cover layer 150 is formed. Here, as shown in FIG. 3, the substrate 100, the first reflective layer 120, the first crystallization promotion layer 121, and the first recording layer 122 are represented by an L0 layer, and the first intermediate layer 125 is represented. ), The second reflective layer 130, the second crystallization promoting layer 131, and the second recording layer 132 are represented by the L1 layer, and the n-1 intermediate layer 135, the nth reflective layer 140, and the nth layer The crystallization promotion layer 141 and the nth recording layer 142 are represented by an Ln layer.

As described above, the intermediate layer is for maintaining a gap between the respective recording layers. As will be described later, the intermediate layers may be formed by applying a thin photo polymer resin and curing with UV-light. In addition, for example, the reflective layers 120, 130, and 140 may use silver (Ag) or an Al-based alloy. On the other hand, according to a preferred embodiment of the present invention, the role of the crystallization promoting layer (121, 131, 141) is to absorb the UV-light in the process of irradiating the UV-light to cure the intermediate layer to change the recording layer from amorphous to crystalline To do that. Therefore, the crystallization promoting layer (121, 131, 141) preferably has a high absorbency to UV-light for curing the intermediate layer. Then, in the process of irradiating UV-light to cure the intermediate layer, the recording layer 122, 132, 142 may be changed from amorphous to crystalline by the heat of UV-light absorbed by the crystallization promoting layer (121, 131, 141). That is, according to the present invention, by arranging the crystallization promotion layers 121, 131, and 141 under the recording layers 122, 132, and 142, initialization of the recording layers 122, 132, and 142 may be simultaneously performed while curing the intermediate layer. As the material of the crystallization promotion layers 121, 131, 141, for example, Sb ₂ Te ₃ , Al, Au, Cr, Sb, and the like can be used, and among them, Sb or Sb ₂ Te ₃ is particularly preferable. In addition, the thickness of the crystallization promoting layer (121, 131, 141) is preferably formed to about 50nm or less.

3, the first recording layer 122 is composed of a lower dielectric layer 122a, an information recording layer 122b, and an upper dielectric layer 122c as in the prior art. Although not shown in FIG. 3, the second to nth recording layers 132 and 142 also have the same configuration. In the above configuration, as the information recording layer 122b in which the phase change actually occurs and the information is recorded, for example, a chalconite compound such as GeSbTe, AgInSbTe, or the like can be used. In addition, the lower and upper dielectric layers 122a and 122c for protecting the information recording layer 122b may use, for example, ZnS—SiO ₂ , SiN, or SiO ₂ .

4A to 4E, a process of manufacturing a multilayer optical recording medium according to the present invention will be specifically described.

First, a first reflective layer 120, a first crystallization promotion layer 121, and a first recording layer 122 are sequentially stacked on the substrate 110 to form an L0 layer, and then the L0 layer thus formed is illustrated in FIG. 4A. As shown in Fig. 1, the spindle jig 20 is mounted on a disk-shaped spindle jig. At this time, the optical recording medium of the L0 layer mounted on the spindle jig 20 is disposed such that the substrate 110 faces downward and the first recording layer 122 faces upward. Then, the photopolymer resin 25, which is a material of the intermediate layer 125, is discharged onto the L0 layer.

Then, as shown in FIG. 4B, a light-transmitting stamper 30 is mounted on the LO layer. At this time, a groove pattern is formed on a contact surface of the light-transmitting stamper 30 facing the optical polymer resin 25 so that tracks of the groove pattern as shown in FIG. 1 can be duplicated in the L1 layer to be formed later. Is formed. In order to make a light-transmissive stamper having such groove pattern information of the L1 layer, first, an L1 father stamper is mounted on a mold to perform injection molding, thereby manufacturing a light-transmissive plastic substrate having groove pattern information of the L1 layer. Thereafter, Ni, APC (Ag-Pd-Cu alloy), a fluorine resin, or the like is formed on the information surface of the optically transparent plastic substrate on which the groove pattern information is formed to form a release layer. For example, Ni, APC (Ag-Pd-Cu alloy) or a fluorine-based resin may be thinly coated on the information surface of the light-transmissive plastic substrate to a thickness that allows light transmission. When coated with the material as described above, since the roughness of the surface of the stamper 30 is excellent, the contact surface area with the photopolymer resin 25 is small so that it can be separated from the intermediate layer 125 to be formed later. do. The thickness of the thin film coating is preferably formed to 100nm or less, preferably 50nm or less so that UV-light can pass through. In particular, in the case of Teflon coating, it is preferable to form a thickness of several nm or less.

After compressing the photopolymer resin 25 with the light-transmitting stamper 30 having a predetermined groove pattern, the L0 layer including the substrate 110 and the photopolymer resin 25 are attached to the spindle jig 20. It is rotated at a high speed using the intermediate layer having a predetermined thickness.

Next, as shown in FIG. 4C, UV-light is irradiated onto the light-transmitting stamper 30 to cure the intermediate layer 125. In this process, some of the UV-light is transmitted through the intermediate layer 125 and absorbed by the first crystallization promoting layer 121 of the L0 layer. Then, the information recording layer 122b of the first recording layer 122 is phase-changed from amorphous to crystalline by the heat of UV-light absorbed by the first crystallization promoting layer 121. That is, the first recording layer 122 is initialized. According to the present invention, crystallization tended to occur more easily as the amount of Sb was increased in the chalconitrile compounds such as GeSbTe, AgInSbTe, etc. constituting the information recording layer 122b.

When the curing of the intermediate layer 125 and the initialization of the first recording layer 122 are completed as described above, the light-transmitting stamper 30 is separated as shown in FIG. 4D. Then, as shown in FIG. 4E, the optical recording medium including the L0 layer and the intermediate layer 125 is detached from the spindle jig 20. Thereafter, a second reflective layer 130, a second crystallization promotion layer 131, and a second recording layer 132 are stacked on the intermediate layer 125 to complete the L1 layer, and the intermediate layer shown in FIGS. 4A to 4E. The process of forming and initializing the recording layer is repeated. After forming the nth recording layer 142 in this manner, and finally forming a transparent cover layer 150 on the nth recording layer 142, the optical recording medium according to the present invention can be manufactured. In this case, the transparent cover layer 150 may also be formed through the same process as that shown in FIGS. 4A to 4E. However, when the transparent cover layer 150 is formed, the light-transmitting stamper 30 does not have to have a groove pattern.

Fig. 5 is a graph showing the thicknesses of the L0 layer, the L1 layer and the cover layer CL along the radial direction in the multilayer optical recording medium in the form of a disc according to the present invention thus completed. As shown in FIG. 5, the thickness of each layer was measured at radial positions of 25 mm, 30 mm, 40 mm, 50 mm and 55 mm. In the case of the L0 layer, there was a variation in thickness from a minimum of 8.8 μm to a maximum of 10.3 μm, and in the case of an L1 layer, there was a variation in the thickness from a minimum of 12.5 μm to a maximum of 15 μm. In addition, the total thickness of the optical recording medium varied in thickness from at least 94.5 µm to at most 97.5 µm. Therefore, the total thickness of the optical recording medium according to the present invention manufactured by the above-described method was 96 ± 1.5 μm, which satisfies the deviation range of ± 3 μm, which is the thickness standard of the Blu-ray disc BD.

As described so far, in the present invention, upon irradiation of UV-light in the process of curing the intermediate layer, the crystallization promoting layer absorbs the heat of UV-light, so that the heat forms the recording layer composed of chalconite-based compound from amorphous to crystalline. Will change. Therefore, according to the present invention, since the initialization of the recording layer can be simultaneously performed during the curing of the intermediate layer without a separate initialization device and an initialization process, the manufacturing time and manufacturing cost of the multilayer optical recording medium can be reduced.

Claims (5)

delete delete delete delete A first step of sequentially laminating a reflective layer, a crystallization promotion layer and a recording layer on the substrate; A second step of discharging an optical polymer resin on the recording layer; A third step of forming an intermediate layer having a predetermined thickness by pressing the optical polymer resin with a transparent stamper having a predetermined groove pattern and rotating the substrate; And A method of manufacturing a multilayer optical recording medium by repeating at least twice a fourth step of curing the intermediate layer by irradiating UV-light over the light transmissive stamper, and then separating the light transmissive stamper. The crystallization promoting layer is absorbable to UV-light for curing the intermediate layer, and the recording layer becomes amorphous to crystalline by the heat of UV-light absorbed by the crystallization promoting layer in the fourth step of curing the intermediate layer. A method of manufacturing a multilayer optical recording medium, characterized in that the phase change.

Images