KR20050045735A - Worm type optical recording medium - Google Patents

Abstract

Disclosed is a recordable optical recording medium having a structure capable of multi-layer recording.

The disclosed write-once optical recording medium includes a substrate; A volume of the region where information is recorded by the incident recording light beam, the recording layer being formed of a metal oxide reflecting a portion of the incident light; The information is reproduced by the difference in optical characteristics.

In addition, the disclosed write-once optical recording medium includes a substrate; A first dielectric layer formed on the substrate; A first recording layer made of a metal oxide for reflecting a portion of the incident light; A second dielectric layer formed on the first recording layer; A spacer formed on the second dielectric layer to form a gap between the recording layers; A third dielectric layer formed on the spacer; A second recording layer made of a metal oxide; A fourth dielectric layer formed on the second recording layer; And a cover layer formed on the fourth dielectric layer.

Description

Recordable optical recording medium {Worm type optical recording medium}

The present invention relates to a recordable optical recording medium, and more particularly, to a recordable optical recording medium having a structure capable of multi-layer recording.

The optical recording medium is used as an information storage medium of an optical pickup apparatus for performing non-contact recording and reproducing of information. The optical recording medium is read only memory type (ROM type), write once read many type (WORM type), and recording / erasing / rewriting according to its function. Free rewritable.

1 is a schematic cross-sectional view showing a conventional write-once optical recording medium of a single layer structure.

Referring to the drawings, the substrate 11, the reflective layer 12, the first protective layer 13, the recording layer 14, the second protective layer 15, in order on the substrate 11, The cover layer 16 has a laminated structure.

The reflective layer 12 is a layer that transmits the cover layer 16 to reflect the light L incident on the recording layer 14 toward the cover layer 16.

The first and second protective layers 13 and 15 are dielectric films, which protect the recording layer 14 and between an area where information about the recording layer 14 is recorded and an unrecorded area. Increase the refractive index difference of.

The recording layer 14 is a layer that can be recorded once by a recording laser beam having an intensity greater than that of the reproduction laser beam. The recording layer 14 is generally composed of an organic material or a phase change material. In addition, the recording layer 14 may be made of an inorganic material such as a silicon-copper (Si-Cu) alloy film or a bismuth-germanium (Bi-Ge) alloy. The recording layer 14 made of such a material has a very low reflectance compared with the case made of a metal oxide.

Therefore, the reflective layer 12 is essential, and in the case where the reflective layer 12 is not provided, it is practically difficult to reproduce the signal.

On the other hand, in the optical recording medium, it is required to implement two or more layers of recording layers in order to increase the recording density thereof.

2 is a schematic cross-sectional view showing a recordable optical recording medium having a four-layer structure.

Referring to the drawings, the substrate 21, one layer of reflective layer 22 formed on the substrate, and one to four layer structures (I) (II) (III) sequentially stacked on the reflective layer 22 are shown. (IV) and a cover layer 38 formed thereon. Here, spacers 26, 30 and 34 are provided between the one- to four-layer structures (I) (II) (III) (IV). Each of the one- to four-layer structures (I) (II) (III) (IV) is formed of the first dielectric layers 23, 27, 31, 35, and the recording layers 24, 28, which are sequentially formed. (32) 36 and second dielectric layers 25 (29) 33 (37).

In such a configuration, the interval between the topmost recording layer 36 and the reflective layer 22 is increased, so that the reproduction of the information on the topmost recording layer 36 is performed by the other recording layers 24, 28 and 32. There is a problem that the reproducing ability is lowered than the reproducing of the information about.

Therefore, the conventional optical recording medium has a problem in that it is impossible to have a multi-layer structure of four or more layers in the realization of a multi-layer structure, which acts as a limit in increasing the recording density.

Accordingly, an object of the present invention is to provide an optical recording medium having a structure capable of multi-layer recording by allowing information to be reproduced without a separate reflective layer.

In order to achieve the above object, the write-once optical recording medium according to the present invention comprises a substrate; A recording layer formed on the substrate, wherein the volume of the region where information is recorded by the incident recording light beam is made of a metal oxide that reflects a portion of the incident light; The information is reproduced by the difference in optical characteristics of the outer region.

The recording layer may include at least one material selected from a metal oxide consisting of gold oxide (AuO _X ), palladium oxide (PdO _X ), platinum oxide (PtO _X ), and tungsten oxide (WO _X ). do.

In addition, the present invention is a substrate; A first dielectric layer formed on the substrate; A first recording layer formed on the first dielectric layer, wherein the volume of the region where information is recorded by the incident recording light beam is made of metal oxide that reflects a portion of the incident light; A second dielectric layer formed on the first recording layer; A spacer formed on the second dielectric layer to form a gap between the recording layers; A third dielectric layer formed on the spacer; A second recording layer formed on the third dielectric layer, wherein the volume of the region where information is recorded by the incident recording light beam is made of metal oxide which reflects a part of the incident light; A fourth dielectric layer formed on the second recording layer; And a cover layer formed on the fourth dielectric layer to protect the first to fourth dielectric layers and the first and second recording layers.

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

3 and 4 are schematic cross-sectional views showing a state before and after recording of a recordable optical recording medium according to an embodiment of the present invention.

Referring to the drawings, the recordable optical recording medium according to the present embodiment is formed on the substrate 41 and the substrate 41, and the recording layer 45 capable of recording the information once and reproducing the recorded information 45 ).

The recording / reproducing of the information on the optical recording medium 40 is made in a non-contact manner through the optical pickup device. The optical pickup apparatus includes a light source (not shown) for irradiating laser light of a predetermined wavelength, an objective lens OL for focusing the light L irradiated from the light source onto the optical recording medium 40, and an optical recording. And a photodetector for receiving the light diffracted and reflected by the medium 40 to detect an error signal and an information signal.

In this embodiment, an optical pickup apparatus for recording and reproducing information on the optical recording medium 40 includes a light source for irradiating light having a wavelength of 300 to 800 nm and an objective lens having a numerical aperture of 0.6 to 0.85. (OL) is used.

The substrate 41 is formed to a thickness of approximately 1.1 [mm], and is made of any one material selected from polycarbonate, polymethyl methacrylate (PMMA), amorphous polyolefin (APO), and glass materials. .

The recording layer 45 is a layer made of a metal oxide that reflects a portion of incident light in which the volume of the area where information is recorded is changed by the incident recording light beam. Here, by changing the volume of the recording area, the optical characteristic change and the optical path difference of the recording area are generated as compared with the non-recording area where the volume is not changed.

The recording layer 45 is preferably made of at least one material selected from metal oxides consisting of gold oxide (AuO _X ), palladium oxide (PdO _X ), platinum oxide (PtO _X ) and tungsten oxide (WO _X ). .

Since the recording layer 45 is made of metal oxide as described above, the reflectance is higher than that of the material of the conventional recording layer (14 in FIG. 1). Therefore, even when the reflective layer (12 of FIG. 1) is not provided, the information recorded on the optical recording medium can be reproduced. Therefore, as described below, the structure may have a multi-layer structure such as four or more layers.

Here, the thickness D _r of the recording layer 45 preferably satisfies the condition of Equation (1).

3.5 ≤ D _r ≤ 100 [nm]

In this way, by setting the thickness of the recording layer 45, the optical recording property between the information recording area and the other area for the recording layer 45 is different. In addition, the absorption coefficient K value can be set to a value between 1.0 and 2.0, so that a high transmittance characteristic can be maintained as compared with the reflective layer of the conventional optical recording medium. Therefore, an optical recording medium having a multilayer structure can be realized.

In addition, the write-once optical recording medium according to the present embodiment preferably further includes at least one or more dielectric layers 43 and 47 on the substrate 41. Referring to FIG. 3, a dielectric layer is divided into a first dielectric layer 43 provided between the substrate 41 and the recording layer 45, and a second dielectric layer 47 provided on the recording layer 45.

The first and second dielectric layers 43 and 47 serve to protect the heat sink and the recording layer 45, which are zinc sulfide-silicon dioxide compounds (ZnS-SiO ₂ ) and silicon oxide (SiO _X ). And it is preferably made of any one material selected from a dielectric material consisting of silicon nitride (SiN _X ).

In addition, the thickness D _d of each of the first and second dielectric layers 43 and 47 preferably satisfies the condition of Equation 2.

10 ≤ D _d ≤ 200 [nm]

In the write-once optical recording medium according to the present embodiment, the cover layer 49 protects the recording layer 45 and the first and second dielectric layers 43 and 47 on the second dielectric layer 47. Is preferably formed. The cover layer 49 is formed to have a thickness of approximately 0.1 [mm] and is disposed to face the objective lens OL. Therefore, the recording and reproducing light beam L enters through the cover layer 49.

The one-time recording operation on the optical recording medium configured as described above will be described. Here, a case where platinum oxide (PtO _X ) is selected as the material of the recording layer 45 will be described as an example.

As shown in Fig. 3, in the optical recording medium 40 on which information is not recorded, the recording layer 45 has a uniform thickness. When the laser beam of predetermined recording power is irradiated to this recording layer 45, a predetermined heat distribution is formed by thermal energy around the light spot. That is, the temperature is the highest at the center of the light spot, and the further away from the center of the light spot forms a heat distribution.

At this time, based on a predetermined threshold temperature determined according to the material characteristics of the recording layer 45, the first and second dielectric layers 43 including the recording layer 45 in the portion having the heat distribution above the threshold temperature ( The optical properties of 45) change. That is, the platinum oxide (PtO _X ) of the portion having a heat distribution above the critical temperature is separated into platinum (Pt) and oxygen (O ₂ ), and is expanded in volume, thereby expanding into a bubble shape as shown in FIG. 4. . As a result, the optical constant value between the recording area and the other areas is changed to increase the contrast of the recording portion.

The recording mark m is formed through such a structural deformation, and the recording mark m thus formed is maintained even after the laser beam to be irradiated passes. Therefore, the recording can be performed on the basis of the above-described principle, and can be reproduced through the light beam having a weaker power than that of the recording light beam.

FIG. 5 is a graph showing a carrier to noise ratio (CNR) according to a change in mark length when PtO _X is used as the material of the recording layer of FIG. 3.

This graph shows the CNR according to the change of mark length while irradiating a reproducing light beam with an optical power of 0.6 [mW] while rotating the optical recording medium at a constant linear velocity (CLV) of 5 [m / sec]. to be.

Referring to the drawings, it can be seen that for the mark length range in the range of 150 to 300 [nm], which is the mark length more than the resolution, the CNR value has a value of 40 [dB] or more, which is a value in a sufficient range for reproduction.

In addition, when the jitter value is measured by simultaneously recording and reproducing various random composite signals with respect to the optical recording medium, the optical recording medium has a value of 8% or less, which is a standard level of a commercial product.

6 is a schematic cross-sectional view showing a recordable optical recording medium according to another embodiment of the present invention.

Referring to the drawings, the write-once optical recording medium according to the present embodiment includes a substrate 51, a first dielectric layer 53, a first recording layer 55, and a second formed sequentially on the substrate 51. And a third dielectric layer 57 and 61, a second recording layer 63, and a fourth dielectric layer 65.

In addition, a spacer 59 is further provided between the second dielectric layer 57 and the third dielectric layer 61 so that the first recording layer 55 and the second recording layer 63 are formed to be spaced apart from each other by a predetermined interval. Do. Meanwhile, the second dielectric layer 57 and the third dielectric layer 61 may be formed of one layer having a predetermined thickness instead of the spacer 59.

In addition, a cover layer on the fourth dielectric layer 65 may protect the first to fourth dielectric layers 53, 57, 61, and 65 and the first and second recording layers 55 and 63. 67) is further provided.

The recordable optical recording medium according to the present embodiment is distinguished from the recordable optical recording medium according to the embodiment in that the recording layer is composed of the first and second recording layers 55 and 63.

Here, the substrate 51, the first and second recording layers 55 and 63, and the first to fourth dielectric layers 53, 57, 61 and 65 are substrates according to an embodiment (Fig. 41, 3, the recording layer 45, and the first and second dielectric layers 43 and 47 are substantially the same in their materials and constructions, so detailed description thereof will be omitted.

Since the first and second recording layers 55 and 63 are made of metal oxide, the reflection characteristics are better than those of the conventional recording layer (14 in FIG. 1). Therefore, unlike the conventional write-once optical recording medium, there is an advantage that no reflective layer is required. Further, each of the first and second recording layers 55 and 63 has an absorption coefficient K between 1.0 and 2.0. Therefore, since the light transmittance is superior to that of the reflective layer (12 in FIG. 1) of the conventional recordable optical recording medium, recording and reproducing of information can be performed for each layer even when two recording layers are formed as shown.

As a write-once optical recording medium according to an embodiment of the present invention, a case in which a single recording layer is shown in FIG. 3 is shown as an example, and a case in which two recording layers are shown in FIG. 5 is shown as an example. In addition, since the reflective layer is not included, it is possible to implement a recordable optical recording medium having three or more recording layers.

The write-once optical recording medium according to the present invention configured as described above has the advantage that the multilayer structure can be easily implemented by increasing the recording density of information by using the metal oxide as the recording layer and excluding the reflective layer.

In addition, there is an advantage that the number of parts and the manufacturing process can be simplified by excluding the reflective layer.

In addition, in the present embodiment, a single-layer or two-layer recording film structure is limited on the substrate, but this is merely exemplary and various modifications are possible within the scope of the invention described in the claims.

1 is a schematic cross-sectional view showing a conventional write-once optical recording medium of a single layer structure.

Figure 2 is a schematic cross-sectional view showing a conventional write-once optical recording medium of a multi-layer structure.

3 is a schematic cross-sectional view showing a pre-recording state of a recordable optical recording medium according to one embodiment of the present invention;

4 is a schematic cross-sectional view showing a state after recording of a recordable optical recording medium according to an embodiment of the present invention;

FIG. 5 is a graph showing CNR according to a change in mark length when PtO _X is employed as the material of the recording layer of FIG.

6 is a schematic cross-sectional view showing a pre-recording state of the optical recording medium according to another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

41, 51 substrate 43, 53 dielectric layer

45 recording layer 47,57 ... second dielectric layer

49,67 ... cover layer 55 ... first recording layer

59 ... Spacer 61 ... Third dielectric layer

63 second recording layer 65 fourth dielectric layer

Claims (9)

A substrate; A recording layer formed on the substrate, the recording layer being formed of a metal oxide that reflects a portion of the incident light, the volume of the region of which information is recorded by the incident recording light beam; The recordable optical recording medium of claim 1, wherein information is reproduced by the difference in optical characteristics of the region where the volume is changed and the other region. The method of claim 1, wherein the recording layer, A recordable optical recording medium comprising at least one material selected from a metal oxide consisting of gold oxide (AuO _X ), palladium oxide (PdO _X ), platinum oxide (PtO _X ), and tungsten oxide (WO _X ). The method of claim 1, And at least one dielectric layer on the substrate. The method of claim 3, wherein the dielectric layer, A write-once optical recording medium comprising a material selected from a dielectric material consisting of zinc sulfide-silicon dioxide compound (ZnS-SiO ₂ ), silicon oxide (SiO _X ), and silicon nitride (SiN _X ). The write-once optical recording medium according to claim 3, wherein the thickness D _d of each of the dielectric layers satisfies the following conditional expression. <Conditional expression> 10 ≤ D _d ≤ 200 [nm] The recordable optical recording medium according to claim 1, wherein the thickness D _r of each of the recording layers satisfies the following conditional expression. <Conditional expression> 3.5 ≤ D _r ≤ 100 [nm] The recording layer according to any one of claims 1 to 6, wherein Write-once optical recording medium, characterized in that consisting of a multi-layered metal oxide. A substrate; A first dielectric layer formed on the substrate; A first recording layer formed on the first dielectric layer, wherein the volume of the region where information is recorded by the incident recording light beam is made of metal oxide that reflects a portion of the incident light; A second dielectric layer formed on the first recording layer; A spacer formed on the second dielectric layer to form a gap between the recording layers; A third dielectric layer formed on the spacer; A second recording layer formed on the third dielectric layer, wherein the volume of the region where information is recorded by the incident recording light beam is made of metal oxide which reflects a part of the incident light; A fourth dielectric layer formed on the second recording layer; And a cover layer formed on the fourth dielectric layer to protect the first to fourth dielectric layers and the first and second recording layers. The method of claim 8, wherein each of the first and second recording layers, A recordable optical recording medium comprising at least one material selected from a metal oxide consisting of gold oxide (AuO _X ), palladium oxide (PdO _X ), platinum oxide (PtO _X ), and tungsten oxide (WO _X ).