JP2006344374A - Optical recording medium - Google Patents

Abstract

A phase change type optical recording medium is formed of two layers to enable recording / reproduction from one side, to have a structure with sufficient heat dissipation, to have a large capacity, good recording / reproduction erasing characteristics, and a repetitive characteristic. To provide an excellent phase change optical recording medium.
A first dielectric layer, a recording layer, a second dielectric layer on a transparent substrate, or a third dielectric layer, a first dielectric layer, a recording layer, a second dielectric layer on a transparent substrate, Or a first optical recording medium in which a first dielectric layer, a recording layer, a second dielectric layer, and a third dielectric layer are sequentially formed on a transparent substrate; and a reflective layer, a first dielectric layer on the transparent substrate, The recording layer and the second optical recording medium on which the second dielectric layer is sequentially formed are in contact with each other on the second dielectric layer surface, or the third dielectric layer surface of the first optical recording medium and the second optical recording medium An optical recording medium using a phase change material as each recording layer, which is bonded with a transparent adhesive so that the surface of the second dielectric layer is in contact.
[Selection] Figure 1

Description

  The present invention relates to a rewritable phase change optical recording medium that records, reproduces, and erases information at a high density by causing a recording material to undergo phase change by condensing and irradiating an optical recording medium with laser light.

  Optical disks put to practical use with a large capacity include a read-only type known as a compact disk and a laser disk (registered trademark), a write-once type that can be recorded once, and a rewritable type that can be repeatedly recorded and erased.

  A read-only optical disk represented by a CD-ROM has a capacity of 650 MB, and as a result of further increasing the capacity, a single-sided 4.7 GB DVD-ROM has been developed. Write-once optical discs have been commercialized as CD-Rs, and development aimed at the same capacity as DVD-ROMs is underway. The rewritable type includes a phase change type optical disk and a magneto-optical disk. In particular, phase change optical discs are becoming important as rewritable optical discs. Currently, CD-RWs with a capacity of 650 MB and DVD-RAMs with a capacity of 2.6 GB have been commercialized, and the capacity and density are further increased. Is being considered in the direction of

  In addition, a double-sided disc in which the above-described optical disc is bonded is proposed. This double-sided disk can double the capacity, but it requires two heads, or the disk is flipped over with one head for recording and reproduction, which is problematic for practical use. . On the other hand, in the DVD standard for reproduction only, a dual-layer disc is defined, and information on both layers is reproduced from one side to increase the capacity.

  In the case of phase change type optical discs, a “rewritable two-layer phase change optical disc” has been proposed by the Japan Society of Applied Physics (September 1998). An optical disk that satisfies the characteristics at the same time and has excellent repetitive characteristics has not been realized.

  In addition, the optical information recording medium proposed in Patent Document 1 (Japanese Patent Laid-Open No. 10-293942) is formed by laminating a plurality of phase change type optical recording media via a transmissive spacer, and recording / reproducing from one side as described above. However, a disk having a large capacity and recording / reproducing characteristics at the same time and having excellent repetitive characteristics has not been realized. In particular, thermal deterioration occurs because the cooling structure does not have a heat dissipation function that is important during a heat-cooling heat cycle.

Japanese Patent Laid-Open No. 10-293942

  An object of the present invention is to make the above-described phase change type optical recording medium into two layers to enable recording / reproduction from one side, to have a structure with sufficient heat dissipation, and to have a large capacity and good recording / reproduction erasure characteristics. Another object of the present invention is to provide a disc having excellent repetitive characteristics.

  According to the present invention, first, a first optical recording medium in which a first dielectric layer, a recording layer, and a second dielectric layer are sequentially formed on a transparent substrate, and a reflective layer and a first dielectric on the transparent substrate. The second optical recording medium in which the body layer, the recording layer, and the second dielectric layer are sequentially formed are bonded with a transparent adhesive so that the surfaces of the second dielectric layer are in contact with each other. An optical recording medium characterized by using a change material is provided.

  Second, in the first, a third dielectric layer is further provided between the transparent substrate of the first optical recording medium and the first dielectric layer, and the film thickness d and refractive index of the third dielectric layer are provided. An optical recording medium is provided in which a product nd of n satisfies 43 nm ≦ nd ≦ 645 nm.

  Third, in the first, a third dielectric layer is further provided on the second dielectric layer of the first optical recording medium, and the third dielectric layer surface and the second dielectric of the second optical recording medium are provided. The optical recording is characterized in that it is bonded with a transparent adhesive so as to be in contact with the body layer surface, and the product nd of the film thickness d and the refractive index n of the third dielectric layer satisfies 43 nm ≦ nd ≦ 645 nm. A medium is provided.

  Fourth, there is provided an optical recording medium according to the second or third aspect, wherein the third dielectric layer is made of a nitride dielectric material.

  Fifth, in the fourth aspect, there is provided an optical recording medium characterized in that the nitride dielectric material is made of a nitride containing Al, Ga, Si, Ge, or B as a main component.

  Sixth, in any one of the first to fifth, the recording layer of the first optical recording medium is made of a phase change material mainly composed of Ag, In, Sb, and Te, and the recording layer thickness d is An optical recording medium characterized in that 5 nm ≦ d ≦ 15 nm is provided.

Seventh, in the second case, when the first and second dielectric layers of the first optical recording medium are made of a material mainly composed of ZnS and SiO ₂ and the respective film thicknesses are d1 and d2, An optical recording medium characterized by satisfying the following formula is provided.
15 nm ≦ d1 ≦ 40 nm, 20 nm ≦ d2 ≦ 300 nm

Eighth, in the first aspect, the first and second dielectric layers of the first optical recording medium are made of a nitride dielectric material or a material mainly composed of ZnS and SiO ₂ , and each film thickness is If d1 and d2, an optical recording medium characterized by satisfying the following equation is provided.
20 nm ≦ d1 ≦ 300 nm, 20 nm ≦ d2 ≦ 300 nm

Ninth, in the third, the first and second dielectric layers of the first optical recording medium is made of a material mainly containing ZnS and SiO _2, and each of the thickness and d1, d2, An optical recording medium characterized by satisfying the following formula is provided.
20 nm ≦ d1 ≦ 300 nm, 15 nm ≦ d2 ≦ 40 nm

  Tenth, in any one of the first to third aspects, an optical recording medium is provided in which the transparent adhesive is made of a photocurable resin.

Eleventhly, in any one of the first to ninth, the first and second dielectric layers of the second optical recording medium are made of a material mainly composed of ZnS and SiO ₂ , and each film thickness is Where d1 and d2 are provided, an optical recording medium characterized by satisfying the following equation is provided.
15 nm ≦ d1 ≦ 40 nm, 60 nm ≦ d2 ≦ 300 nm

  Twelfth, in any one of the first to ninth, the recording layer of the second optical recording medium is made of a phase change material mainly composed of Ag, In, Sb, and Te, and the recording layer thickness d Is 12 nm ≦ d ≦ 20 nm, and an optical recording medium is provided.

  Thirteenth, there is provided an optical recording medium according to the sixth or twelfth aspect, wherein nitrogen is added to the recording layer.

  On the first dielectric layer, recording layer, second dielectric layer, or transparent substrate on the transparent substrate, on the third dielectric layer, first dielectric layer, recording layer, second dielectric layer, or transparent substrate The first dielectric layer, the recording layer, the second dielectric layer, and the third dielectric layer are sequentially provided, and the material and film thickness of each layer are appropriately set to provide sufficient heat dissipation and high transmittance. A first optical recording medium having the same is realized. It is a structure in which a reflective layer, a first dielectric layer, a recording layer, and a second dielectric layer are sequentially provided on a transparent substrate. Sufficient heat dissipation action and high sensitivity in which the material and film thickness of each layer are set appropriately, A second optical recording medium with high reflectivity is realized. By bonding the first and second optical recording media with a transparent adhesive, a two-layer optical recording medium is realized. An optical recording medium having a two-layer structure enables recording / reproduction from one side with one optical head, realizing a large-capacity optical recording medium, and at the same time, both layers have good recording / reproduction characteristics and good repetition characteristics. An optical recording medium is obtained.

  Hereinafter, the present invention will be described in more detail. 1 and 2 are schematic cross-sectional views showing the configuration of an optical recording medium using the phase change recording film of the present invention. FIG. 1 shows a first optical recording medium in which a third dielectric layer, a first dielectric layer, a recording layer, and a second dielectric layer are sequentially formed on a transparent substrate, a reflective layer on the transparent substrate, A second optical recording medium in which a first dielectric layer, a recording layer, and a second dielectric layer are sequentially formed by sputtering is bonded with a transparent adhesive.

  FIG. 2 shows a first optical recording medium in which a first dielectric layer, a recording layer, a second dielectric layer, and a third dielectric layer are sequentially formed on a transparent substrate, a reflective layer on the transparent substrate, A second optical recording medium in which a first dielectric layer, a recording layer, and a second dielectric layer are sequentially formed by sputtering is bonded with a transparent adhesive.

  The transparent adhesive acts as an optical separation layer and optically separates the first optical recording medium and the second optical recording medium. The film thickness of the transparent adhesive is set to about 40 μm, and is formed by spin coating using a photocurable resin.

  As the transparent substrate, an acrylic or plastic substrate such as polycarbonate (PC) or a glass substrate is used.

As the first and second dielectric layers in the first and second optical recording medium, comprising a mixture of ZnS and SiO ₂ ZnS: While using the SiO _2, it may use other dielectric materials.

  As the third dielectric layer, a nitride dielectric material containing Al, Ga, Si, Ge, or B as a main component is used. Since these nitride dielectric materials have a large thermal conductivity, the recording layer is cooled and has an effect of preventing thermal deterioration. A dielectric material having a high thermal conductivity other than nitride may be used.

  For the recording layer, a material mainly composed of Ag, In, Sb, and Te is used, but other materials such as a chalcogenide-based material such as a GeSbTe-based material or an InSbTe-based material may be used. In addition, the crystallization temperature can be increased by adding nitrogen to the recording layer containing Ag, In, Sb, and Te as main components. For example, when the nitrogen addition amount is 0, the crystallization temperature Tc is about 200 ° C., and when the nitrogen gas flow rate during sputtering is 3 sccm, Tc is about 270 ° C. Therefore, the thermal stability is improved by the addition of nitrogen, and the recorded information is stably stored without losing the record information for long-term storage.

  The reflective layer is made of a material having a high thermal conductivity such as a metal so that the reflective layer and the recording layer of the second optical recording medium can have a heat radiation function at the same time. For example, metal materials, such as Au, Ag, Cu, Al, an Al-Ti alloy, are mentioned.

  First, an embodiment of the optical recording medium having the configuration shown in FIG. 1 will be described. FIGS. 3A and 3B show the reflectance and transmittance of the crystalline phase and the amorphous phase of the first optical recording medium when the optical recording medium having the configuration shown in FIG. 1 is used. An example is shown. 4A and 4B show the reflectance and transmittance of the crystal phase and the amorphous phase of the second optical recording medium when the optical recording medium having the same configuration is used. In these figures, the reflectance and transmittance of the multilayer thin film are calculated using a generally well-known matrix method, and the horizontal axes of FIGS. The thickness of the second dielectric layer of the optical recording medium is shown.

  In the figure, Rc is the reflectance of the crystalline phase with the recording layer initialized, and Ra is the reflectance of the amorphous phase in the recording state. Tc is the transmittance of the crystal phase, and Ta is the transmittance of the amorphous phase.

A first optical recording medium shown in FIGS. 3A and 3B is a third dielectric layer and film using aluminum nitride (AlN) having a thickness of 60 nm on a transparent polycarbonate substrate (PC substrate). First dielectric layer using ZnS: SiO ₂ with a thickness of 20 nm, recording layer using a recording material mainly composed of AgInSbTe with a thickness of 8 nm, second dielectric layer using ZnS: SiO ₂ , transparent adhesive It is the structure which formed the layer one by one.

  The layer thickness of the second dielectric layer is suitably in the range of 20 nm or more and 300 nm or less, and the layer thickness can be set such that the reflectance R and the transmittance T are increased within this layer thickness range. For example, in this example (FIGS. 3A and 3B), when the thickness of the second dielectric layer is set to 80 nm and 240 nm, Rc = 10% and ΔR = Rc−Ra = 5%. Further, the transmittances Tc and Ta both increase to 50% or more. Therefore, the more preferable film thickness of the second dielectric layer is set in the range of 60 nm to 240 nm.

  The first dielectric layer acts as a protective film in the same manner as the second dielectric layer. The film thickness is suitably 15 nm to 40 nm, and if it is thicker than this, as described above, the heat radiation to the AlN film will not be sufficiently performed, and the recording film will be poorly cooled at the time of overwriting, especially when rapid cooling is necessary. , You can not record satisfactory.

  The AlN film of the third dielectric layer acts as a heat sink, and the effect increases as the film thickness increases. In order to obtain a sufficient heat dissipation effect, it is appropriate to set the product nd of the film thickness d and the refractive index of the AlN film or other nitride film in the range of 43 nm ≦ nd ≦ 645 nm as shown in the examples described later. .

FIGS. 5A and 5B show the relationship between the recording layer thickness of the first optical recording medium, the transmittance T, and the reflectance R when a material mainly composed of AgInSbTe is used for the recording layer. Show. In FIGS. 5A and 5B, the thickness of the second dielectric layer ZnS: SiO ₂ is set to 80 nm. As the thickness of the recording layer increases, the transmittance T decreases and the reflectance R increases. Assuming that the average transmittance of the first optical recording medium is Tav and the reflectance of the second optical recording medium alone is R ₂ , the reflectance r ₂ from the second optical recording medium in the configuration of FIG. Given in.
r ₂ = R ₂ · Tav ² (1)

When R ₂ = 33% and Tav = 40% in the above formula, r ₂ = 5.3%, and the reflectance r ₂ from the _second optical recording medium is the average transmittance Tav of the first optical recording medium. Depends greatly on In order to secure the light utilization efficiency of the second optical recording medium of about 5% or more, the average transmittance Tav of the first optical recording medium needs to be 40% or more. The film thickness of the recording layer may be set to 15 nm or less. Further, Tav = 50% is required to increase the light utilization efficiency of the second optical recording medium to 8% or more. By setting the film thickness of the recording layer of the first optical recording medium to about 10 nm or less, The value of is realized.

  On the other hand, when the thickness of the recording layer is reduced, the transmittance Tav is increased, but the reflectances Rc and Ra of the first optical recording medium are decreased. Therefore, an appropriate film thickness is obtained to obtain a desired reflectance. Must be set to For example, when the reflectance Rc of the first optical recording medium is 5% or more, the recording layer thickness is 5 nm or more, and when Rc is 8% or more, the recording layer thickness is 7 nm or more. Must be set to

  4- (a) and-(b) show that the film thickness of the second dielectric layer is set to 80 nm and the film thickness of the third dielectric layer AlN film is changed in the previous example (FIG. 3). It is an Example which shows the change of the reflectance R and the transmittance | permeability T. FIG. The thickness of the AlN film is preferably in the range of 20 nm to 300 nm (43 nm ≦ nd ≦ 645 nm), and the reflectance R and transmittance T can be increased within this range. For example, when the film thickness of the AlN film is 60 nm and 220 nm, Rc = 10%, ΔR = Rc−Ra = 5%, Rc = 15%, ΔR = Rc−Ra = 5%, and the transmittances Tc, Ta Takes a large value of 50% or more.

  Therefore, a more preferable thickness of the AlN film is preferably set in a range of 40 nm to 240 nm. If the refractive index of the AlN film is n = 2.15 (635 nm), the product nd of the film thickness d and the refractive index n is preferably in the range of 86 nm ≦ nd ≦ 516 nm.

In the embodiment of the first optical recording medium described above, a layer structure without the third dielectric layer AlN is also possible. In this case, the first dielectric layer, the recording layer, and the second dielectric layer are sequentially formed on the transparent substrate by sputtering. For the first dielectric layer and the second dielectric layer, it is preferable to use a material having high thermal conductivity in order to effectively dissipate the heat of the recording layer. For example, a nitride dielectric material such as an AlN film, ZnS: SiO ₂ or the like. ZnS: SiO _2, since the thermal conductivity as the mixing ratio of SiO ₂ is large becomes high, ZnS: in the case of using a SiO ₂ to use a large value of the mixing ratio of SiO ₂ are suitable. As the nitride dielectric material, a nitride containing Ga, Si, Ge, or B as a main component in addition to Al is used.

When AlN or ZnS: SiO ₂ is used for the first and second dielectric layers and the respective film thicknesses are expressed as d1 and d2, it is appropriate to set both in the ranges of 20 nm ≦ d1 and d2 ≦ 300 nm. . As described above, the film thickness of the recording layer AgInSbTe needs to be in the range of 5 nm ≦ recording layer film thickness ≦ 15 nm in order for the first optical recording medium to obtain appropriate reflectance and transmittance. .

  Next, an example of the optical recording medium having the configuration shown in FIG. 2 will be described. 6 (a) and 6 (b), the reflectance and transmittance of the crystal phase and the amorphous phase of the first optical recording medium when the optical recording medium having the configuration shown in FIG. An example is shown. FIGS. 7A and 7B show the reflectance and transmittance of the crystal phase and the amorphous phase of the second optical recording medium when the optical recording medium having the same configuration is used. In these figures, the reflectance and transmittance of the multilayer thin film are calculated using a generally well-known matrix method, and the horizontal axes of FIGS. 6 (a) and 6 (b) are the first axis. Represents the film thickness of the first dielectric layer of the optical recording medium.

  In the figure, Rc is the reflectance of the crystalline phase with the recording layer initialized, and Ra is the reflectance of the amorphous phase in the recording state. Tc is the transmittance of the crystal phase, and Ta is the transmittance of the amorphous phase.

6A and 6B, a first optical recording medium includes a first dielectric layer using ZnS: SiO ₂ and AgInSbTe having a thickness of 8 nm on a transparent polycarbonate substrate (PC substrate). Recording layer using recording material as main component, second dielectric layer using ZnS: SiO ₂ with a thickness of 20 nm, third dielectric layer using aluminum nitride (AIN) with a thickness of 60 nm, transparent adhesive It is the structure which formed the layer one by one.

  The thickness of the first dielectric layer is suitably in the range of 20 nm or more and 300 nm or less, and the layer thickness can be set such that the reflectance R and the transmittance T are large within this layer thickness range. For example, in this example (FIGS. 6A and 6B), when the thickness of the first dielectric layer is set to 80 nm and 240 nm, Rc = 10%, ΔR = Rc−Ra = 5% and Rc = 15%, ΔR = Rc−Ra = 5%, and the transmittances Tc and Ta are both 50% or more. Therefore, the more preferable film thickness of the first dielectric layer is set in the range of 60 nm to 240 nm.

  The second dielectric layer acts as a protective film in the same manner as the first dielectric layer. The film thickness is suitably 15 nm to 40 nm, and if it is thicker than this, as described above, the heat radiation to the AlN film will not be sufficiently performed, and the recording film will be poorly cooled at the time of overwriting, especially when rapid cooling is necessary. , You can not record satisfactory.

  The AlN film of the third dielectric layer acts as a heat sink, and the effect increases as the film thickness increases. In order to obtain a sufficient heat dissipation effect, it is appropriate to set the product nd of the film thickness d and the refractive index of the AlN film or other nitride film in the range of 43 nm ≦ nd ≦ 645 nm as shown in the examples described later. .

FIGS. 8A and 8B show the relationship between the recording layer thickness of the first optical recording medium and the transmittance T and the reflectance R when a material mainly composed of AgInSbTe is used for the recording layer. Show. In FIGS. 8A and 8B, the thickness of the first dielectric layer ZnS: SiO ₂ is set to 80 nm. As the thickness of the recording layer increases, the transmittance T decreases and the reflectance R increases. Assuming that the average transmittance of the first optical recording medium is Tav and the reflectance of the second optical recording medium alone is R ₂ , the reflectance r ₂ from the second optical recording medium in the configuration of FIG. Given in.
r ₂ = R ₂ · Tav ² (1)

When R ₂ = 33% and Tav = 40% in the above formula, r ₂ = 5.3%, and the reflectance r ₂ from the _second optical recording medium is the average transmittance Tav of the first optical recording medium. Depends greatly on In order to secure the light utilization efficiency of the second optical recording medium of about 5% or more, the average transmittance Tav of the first optical recording medium needs to be 40% or more. The film thickness of the recording layer may be set to 15 nm or less. Further, Tav = 50% is required to increase the light utilization efficiency of the second optical recording medium to 8% or more, and the above value can be obtained by setting the recording layer thickness of the first optical recording medium to about 10 nm or less. Is realized.

  On the other hand, when the thickness of the recording layer is reduced, the transmittance Tav is increased, but the reflectances Rc and Ra of the first optical recording medium are decreased. Therefore, an appropriate film thickness is obtained to obtain a desired reflectance. Must be set to For example, when the reflectance Rc of the first optical recording medium is 5% or more, the recording layer thickness is 5 nm or more, and when Rc is 8% or more, the recording layer thickness is 7 nm or more. Must be set to

  7- (a) and-(b) show that in the previous example (FIG. 6), the thickness of the first dielectric layer was set to 80 nm, and the thickness of the third dielectric layer AlN film was changed, It is an Example which shows the change of the reflectance R and the transmittance | permeability T. FIG. The thickness of the AlN film is preferably in the range of 20 nm to 300 nm (43 nm ≦ nd ≦ 645 nm), and the reflectance R and transmittance T can be increased within this range. For example, when the film thickness of the AlN film is 60 nm and 220 nm, Rc = 10%, ΔR = Rc−Ra = 5%, and the transmittances Tc and Ta also take large values of 50% or more.

  Therefore, a more preferable thickness of the AlN film is preferably set in a range of 40 nm to 240 nm. If the refractive index of the AlN film is n = 2.15 (635 nm), the product nd of the film thickness d and the refractive index n is preferably in the range of 86 nm ≦ nd ≦ 516 nm.

  Next, an example of the second optical recording medium common to the optical recording medium shown in FIGS. 1 and 2 will be described. FIG. 9 shows an example in which the reflectances Rc and Ra of the crystalline phase and the amorphous phase are obtained in the case of the second optical recording medium alone. The horizontal axis represents the film thickness of the second dielectric layer of the second optical recording medium.

Rc represents the reflectance of the crystal phase in which the recording layer of the second optical recording medium is initialized, and Ra represents the reflectance of the amorphous phase in the recording state. The second optical recording medium is formed on a transparent polycarbonate substrate (PC substrate), a reflective layer using an Al—Ti alloy with a film thickness of 25 nm, a first dielectric layer using ZnS: SiO ₂ with a film thickness of 20 nm, and a film thickness. In this configuration, a recording layer using a material mainly composed of 13 nm of AgInSbTe, a second dielectric layer using ZnS: SiO _2, and a transparent adhesive layer are sequentially formed.

  Since the second optical recording medium records and reproduces information through the first high recording medium, it is important to adopt a highly sensitive and high reflectance configuration in order to increase the light utilization efficiency. Higher sensitivity can be realized by providing a reflective layer as in the configuration of this example and setting the recording layer as thin as 13 nm. This is because the thinner the recording layer, the lower the energy required for melting. A high reflectivity configuration is realized by appropriately setting the thickness of the second dielectric layer. For example, in FIG. 9, by setting the film thickness of the second dielectric layer to 120 nm, a high reflectance is obtained with Rc = 34% and Ra = 18%.

As a preferable range of the film thickness of the second dielectric layer, when the reflectance r ₂ is 5% or more and the average transmittance Tav of the first optical recording medium is 60% in the above-described equation (1), R ₂ Since (Rc) is 14% or more, it is 60 nm or more and 180 nm or less from FIG. Further, when r ₂ is 8% or more and Tav = 60%, R ₂ (Rc) is 22% or more and has a high reflectivity. From FIG. 9, a more preferable range of the film thickness of the second dielectric layer is 82 nm or more, What is necessary is just to set to 170 nm or less.

In addition to the film thickness range of the second dielectric layer, the film thickness at which R ₂ (Rc) is 14% or more, or 22% or more exists at 220 nm or more, so the film thickness of the second dielectric layer is The application range of d is preferably 60 nm ≦ d ≦ 300 nm.

The first dielectric layer ZnS: SiO ₂ of the second optical recording medium functions as a protective film in the same manner as the second dielectric layer ZnS: SiO ₂ . The film thickness is suitably in the range of 15 nm to 40 nm, and if it is thicker than this, the heat dissipation to the Al—Ti film becomes worse, and satisfactory recording cannot be performed at the time of overwriting.

  FIG. 10- (a) shows the reflectance of the second optical recording medium when the thickness of the recording layer AgInSbTe is changed. In order to increase the sensitivity, the thinner the recording layer, the better. However, if the recording layer is too thin, the reflectance difference Rc-Ra is reduced, and the contrast of the reproduction signal is reduced. Therefore, in order to make the reflectance difference Rc-Ra 15% or more, the recording layer thickness is suitably 12 nm or more and 20 nm or less.

  FIG. 10B shows the reflectance difference Rc-Ra of the second optical recording medium when the thickness of the reflective layer Al-Ti is changed. When the thickness of the reflective layer is 10 nm or more, the reflectance difference Rc−Ra is 15% or more. However, in order to make the heat dissipation action of the reflective layer effective, the film thickness is preferably 20 nm or more.

  Specific examples of the optical recording medium and recording / reproducing in the present invention will be described below, but the present invention is not limited to these.

Example 1
A third dielectric layer made of AlN having a thickness of 70 nm on a PC substrate, a first dielectric layer made of ZnS: SiO ₂ having a thickness of 20 nm, and N ₂ on AgInSbTe having a thickness of 8 nm at a flow rate during sputtering of 0.5 sccm. The added recording layer and a 240 nm thick ZnS: SiO ₂ second dielectric layer were sequentially formed by sputtering and initialized to produce a first optical recording medium.

Next, reflective layer of Al-Ti having a thickness of 40nm on the PC board, with a thickness of 25 nm ZnS: a first dielectric layer made of SiO _2, the thickness of 13 nm AgInSbTe the _{N 2} at a flow rate in the sputtering A recording layer added with 0.5 sccm and a second dielectric layer made of ZnS: SiO _{2 having} a thickness of 260 nm were sequentially formed by sputtering, initialized to produce a second optical recording medium, and then the second coating layer was formed by spin coating. An ultraviolet curable resin was applied to a thickness of 40 μm on the surface of the two dielectric layers. Thereafter, the first and second optical recording media were bonded together such that the surfaces of the second dielectric layers were in contact with each other through an ultraviolet curable resin, and were bonded by irradiating ultraviolet rays from the first optical recording medium side.

  The disk thus obtained was rotated at a rotational speed of 2000 rpm, focused on the track of the first optical recording medium at a radius of 30 mm, and repeated recording / reproducing erasure was performed using a signal with a modulation frequency of 40 MHz on the same track. Executed. At this time, the laser wavelength was set to λ = 635 nm, the NA of the objective lens was set to 0.6, and the recording power and the erasing power were set to 10 mW and 5 mW. As a result of reproducing the same track after overwriting, a good reproduction signal was obtained. From the reproduced signal, the reflectance of the crystal phase as the erasing portion was 10%, and the reflectance of the amorphous phase recording mark as the recording portion was 4%.

  Next, the focus servo offset is changed to focus on the track of the second optical recording medium on the back side of the disk, rotate at a disk rotation speed of 2000 rpm, and use a signal with a modulation frequency of 40 MHz at a radius of 30 mm. The recording / playback erasure was repeated. The recording power and erasing power at this time were set to 12 mW and 6 mW. As a result of reproducing the same track after overwriting, a good reproduction signal was obtained. From the reproduced signal, the reflectance of the crystal phase as the erasing portion was 9%, and the reflectance of the amorphous phase recording mark as the recording portion was 3%.

(Example 2)
A first dielectric layer made of ZnS: SiO ₂ having a thickness of 80 nm on a PC substrate, a recording layer in which 0.5 sccm of N ₂ is added to AgInSbTe having a thickness of 8 nm at a flow rate during sputtering, and ZnS: SiO _{2 having} a thickness of 20 nm. A first dielectric recording layer and a third dielectric layer made of AlN having a thickness of 220 nm were sequentially formed by sputtering to produce a first optical recording medium.

Next, reflective layer of Al-Ti having a thickness of 40nm on the PC board, with a thickness of 25 nm ZnS: a first dielectric layer made of SiO _2, the thickness of 13 nm AgInSbTe the _{N 2} at a flow rate in the sputtering A recording layer added with 0.5 sccm and a second dielectric layer made of ZnS: SiO _{2 having} a thickness of 260 nm are sequentially formed by sputtering to produce a second optical recording medium, and then the second dielectric layer is formed by spin coating. An ultraviolet curable resin was applied to a thickness of 40 μm on the body layer surface. Thereafter, the first and second optical recording media are initialized, and the third dielectric layer surface of the first optical recording medium and the second dielectric layer surface of the second optical recording medium are bonded so as to be in contact with each other via an ultraviolet curable resin. In addition, the first optical recording medium side was irradiated with ultraviolet rays and bonded.

  The disk thus obtained was rotated at a rotational speed of 2000 rpm, focused on the track of the first optical recording medium at a radius of 30 mm, and repeated recording / reproducing erasure was performed using a signal with a modulation frequency of 40 MHz on the same track. Executed. At this time, the laser wavelength was set to λ = 635 nm, the NA of the objective lens was set to 0.6, and the recording power and the erasing power were set to 10 mW and 5 mW. As a result of reproducing the same track after overwriting, a good reproduction signal was obtained. From the reproduced signal, the reflectance of the crystal phase as the erasing portion was 11%, and the reflectance of the amorphous phase recording mark as the recording portion was 5%.

  Next, the focus servo offset is changed to focus on the track of the second optical recording medium on the back side of the disk, rotate at a disk rotation speed of 2000 rpm, and use a signal with a modulation frequency of 40 MHz at a radius of 30 mm. The recording / playback erasure was repeated. The recording power and erasing power at this time were set to 12 mW and 6 mW. As a result of reproducing the same track after overwriting, a good reproduction signal was obtained. From the reproduced signal, the reflectance of the crystal phase as the erasing portion was 10%, and the reflectance of the amorphous phase recording mark as the recording portion was 4%.

1 is a schematic cross-sectional view showing a layer configuration of an example of a phase change optical recording medium of the present invention. It is a schematic cross section showing the layer constitution of another example of the phase change type optical recording medium of the present invention. (A) is a figure which shows the relationship between the reflectance of the crystal phase of the 1st optical recording medium of this invention, and an amorphous phase, and the film thickness of the 2nd dielectric material layer of a 1st optical recording medium, (b) FIG. 4 is a graph showing the relationship between the crystal phase and amorphous phase transmittances of the first optical recording medium of the present invention and the thickness of the second dielectric layer of the first optical recording medium. (A) is a figure which shows the relationship between the reflectance of the crystal phase of the 2nd optical recording medium of this invention, and an amorphous phase, and the film thickness of the 3rd dielectric material layer of a 1st optical recording medium, (b) FIG. 4 is a graph showing the relationship between the crystal phase and amorphous phase transmittances of the second optical recording medium of the present invention and the thickness of the third dielectric layer of the first optical recording medium. (A) is a figure which shows the relationship between the recording layer film thickness of the 1st optical recording medium of this invention, and the transmittance | permeability, and (b) is the recording layer film thickness of the 1st optical recording medium of this invention, and It is a figure which shows the relationship with a reflectance. (A) is a figure which shows the relationship between the reflectance of the crystal phase of the 1st optical recording medium of this invention, and an amorphous phase, and the film thickness of the 1st dielectric material layer of a 1st optical recording medium, (b) FIG. 4 is a graph showing the relationship between the crystal phase and amorphous phase transmittances of the first optical recording medium of the present invention and the thickness of the first dielectric layer of the first optical recording medium. (A) is a figure which shows the relationship between the reflectance of the crystal phase of the 2nd optical recording medium of this invention, and an amorphous phase, and the film thickness of the 3rd dielectric material layer of a 1st optical recording medium, (b) FIG. 4 is a graph showing the relationship between the crystal phase and amorphous phase transmittances of the second optical recording medium of the present invention and the thickness of the third dielectric layer of the first optical recording medium. (A) is a figure which shows the relationship between the recording layer film thickness of the 1st optical recording medium of this invention, and the transmittance | permeability, and (b) is the recording layer film thickness of the 1st optical recording medium of this invention, and It is a figure which shows the relationship with a reflectance. It is a figure which shows the relationship between the reflectance of a crystal phase and an amorphous phase in the case of the 2nd optical recording medium alone of this invention, and a 2nd dielectric material layer film thickness. (A) is a figure which shows the relationship between the reflectance of the crystal phase of the 2nd optical recording medium of this invention, and an amorphous phase, and the recording layer film thickness, and (b) is the 2nd optical recording medium of this invention. It is a figure which shows the relationship between the reflectance difference (Rc-Ra) of this, and the film thickness of a reflection layer.

Claims (11)

A first optical recording medium in which a first dielectric layer, a recording layer, and a second dielectric layer are sequentially formed on a transparent substrate, and a reflective layer, a first dielectric layer, a recording layer, and a second dielectric on the transparent substrate. The second optical recording medium in which the layers are sequentially formed is bonded with a transparent adhesive so that the surfaces of the second dielectric layers are in contact with each other, and a phase change material is used as each recording layer Optical recording medium. 2. The third dielectric layer according to claim 1, further comprising a third dielectric layer between the transparent substrate of the first optical recording medium and the first dielectric layer, and the product of the film thickness d and the refractive index n of the third dielectric layer. An optical recording medium wherein nd satisfies 43 nm ≦ nd ≦ 645 nm. 3. The optical recording medium according to claim 2, wherein the third dielectric layer is made of a nitride dielectric material. 4. The optical recording medium according to claim 3, wherein the nitride dielectric material is made of a nitride containing Al, Ga, Si, Ge, or B as a main component. 5. The recording layer of claim 1, wherein the recording layer of the first optical recording medium is made of a phase change material mainly composed of Ag, In, Sb, and Te, and the recording layer thickness d is 5 nm ≦ d ≦ 15 nm. An optical recording medium characterized by the above. 3. In claim 2, when the first and second dielectric layers of the first optical recording medium are made of materials containing ZnS and SiO ₂ as main components and the respective film thicknesses are d1 and d2, the following equation is satisfied. An optical recording medium characterized by the above.
15 nm ≦ d1 ≦ 40 nm, 20 nm ≦ d2 ≦ 300 nm According to claim 1, made of a material the first and second dielectric layers of the first optical recording medium is mainly composed of nitride dielectric material or ZnS and SiO _2, and the each of the film thickness d1, d2 Then, an optical recording medium characterized by satisfying the following formula:
20 nm ≦ d1 ≦ 300 nm, 20 nm ≦ d2 ≦ 300 nm 3. The optical recording medium according to claim 1, wherein the transparent adhesive is made of a photocurable resin. 8. The first optical recording medium according to claim 1, wherein the first and second dielectric layers of the second optical recording medium are made of a material mainly composed of ZnS and SiO ₂ , and the respective film thicknesses are d 1 and d 2. An optical recording medium characterized by satisfying the following formula:
15 nm ≦ d1 ≦ 40 nm, 60 nm ≦ d2 ≦ 300 nm 8. The recording layer of any one of claims 1 to 7, wherein the recording layer of the second optical recording medium is made of a phase change material mainly composed of Ag, In, Sb, and Te, and the recording layer thickness d is 12 nm ≦ d ≦ 20 nm. An optical recording medium characterized by the above. 11. The optical recording medium according to claim 5, wherein nitrogen is added to the recording layer.

Images