JP2002260285A - Phase change optical recording medium and initialization method - Google Patents

Abstract

(57) [Problem] To provide an optical recording medium having a multi-layered recording surface so that initial crystallization of a recording film can be easily performed after all of substrate forming and film forming processes are completed. SOLUTION: This is a phase change type multilayer recording medium in which there is a translucent recording layer as viewed from recording / reproducing light, and then a transparent layer is inserted to provide a next recording layer at a distance. A phase change type optical recording medium characterized in that a reflection layer is provided on a recording layer farthest from the incident surface, and an antireflection film is provided between the reflection layer and the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art At present, CD-RW and DVD-RW are widely used as rewritable optical disks. In these, the recording film is made amorphous or crystallized by quenching or gradual cooling with the heat of laser, and recording marks with different reflectivities etc. are created on the disk surface using the difference in optical properties between them. , An optical recording medium for recording and reproducing information. As means for further improving these recording capacities, attempts have been made to increase the number of recording layers. For example, a DVD is prepared by bonding a 0.6 mm substrate together, and one sheet is formed of a translucent thin recording layer. Is formed, and a recording medium formed from a reflective film on a substrate is formed on another substrate in the reverse order to the normal case, and the recording medium is bonded to perform recording and reproduction from the translucent film side. In this case, the initial crystallization of the translucent layer is easy,
The recording layer at the back is difficult to initialize because the initialization laser is absorbed by the translucent layer at the front. Therefore, at present, a method is adopted in which after each substrate is formed, it is initialized in a single plate state and bonded.

However, according to this method, the handling is repeated before the disks are bonded, and initialization is performed. When the disks are bonded, the possibility of entrapment of dust increases. 1
In the case of an optical disc of the type in which a recording layer is formed on a single substrate, a sheet is laid thereon, and another film is formed again to form another recording layer, the sheet is attached by sputtering, , Spattering, attaching a sheet, and initializing, the process is complicated, and there is also a problem of entrapping dust and complicating a production line.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to easily perform initial crystallization of a recording film in an optical recording medium having a multi-layer recording surface after the substrate forming and film forming processes are all completed. That is.

[0004]

As a result of intensive studies to solve the above problems, the present inventors have found that the initialization of the recording layer on the back side when viewed from the side of incidence of the reproduction light has become a problem. Focusing on this fact, this layer can be initialized from the side opposite to the reproduction light incident side. In this case, since this surface is a reflective layer, it is almost reflected when an initialization laser is applied. Therefore, it is necessary to form an antireflection layer on the disk. It has been found that the above problem can be solved by injecting an activated laser.

[0005] That is, the above problem is solved by (1) the present invention.
"From the viewpoint of recording / reproducing light, there is a semi-transparent recording layer, and after that, the next recording layer exists at a distance by inserting a transparent layer. This is achieved by a "phase-change type optical recording medium, wherein a recording layer remote from the surface has a reflection layer, and an antireflection film is provided between the reflection layer and the substrate."

[0006] The above-mentioned problem is also solved by the problem described in (2) of the present invention in that there is a translucent recording layer as viewed from the recording / reproducing light, and after that, the next recording layer is spaced apart by inserting the transparent layer. An existing method for initializing a phase change type multilayer recording medium, wherein a recording layer farthest from an incident surface has a reflective layer, and initialization is performed by irradiating a laser for initial crystallization from the reflective layer side. A method for initializing a phase-change optical recording medium characterized by the above-mentioned feature. "

[0007] The present invention also provides (3) a phase-change type liquid crystal display device according to the above (1), wherein the antireflection film is a material which is easy to form a film having small irregularities. Optical recording medium ", (4)" Phase change type optical recording medium according to item (3), wherein the antireflection film is high-density silicon carbide. "

When the initialization laser is incident from the reflective layer side, the energy of the initialization laser can be efficiently increased because the anti-reflection layer having a thickness to confine light of the wavelength of the initialization laser is formed on the substrate. To be able to initialize. The recording layer on the back side as viewed from the reproduction light is formed on the substrate in the order of an antireflection layer, a reflection layer, a dielectric protection layer, a phase change recording layer, and a dielectric protection layer. Therefore, if the first anti-reflection layer does not have small irregularities on the film surface, the smoothness of the recording film is impaired, and when recording is performed at a high density, recording marks cannot be formed clearly and S / N deteriorates. In the present invention, this problem has been solved by forming a film of silicon carbide or the like having relatively small film stress and small unevenness on the first layer.

Hereinafter, the optical recording medium according to the present invention will be described in detail. FIG. 1 is a schematic sectional view showing an example of the optical information recording medium of the present invention. In FIG. 1, an antireflection layer (2), a reflection heat dissipation layer (3), a dielectric protection layer (4), a recording layer (5), a dielectric protection layer (6),
Light transmitting layer (7), dielectric protective layer (8), translucent recording layer (9), dielectric protective layer (10), protective film (1
1) shows an example in which the hard coat (12) is accumulated in that order. The light transmitting layer (7) can be formed relatively easily by inserting, for example, a transparent resin layer and a transparent glass layer.

The material of the substrate (1) is usually glass, ceramics or resin, and a resin substrate is suitable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, and the like. A polycarbonate resin and an acrylic resin which are excellent in moldability and cost are preferable. An uneven pattern is formed on one side of the substrate surface, and a heat-resistant layer and a recording layer are formed on this side. The thickness and color of the substrate are not particularly limited.

The antireflection layer (2) may be transparent and have a different refractive index from the substrate, and many transparent dielectrics such as silicon nitride, aluminum nitride, alumina, silicon carbide and germanium nitride can be considered. However, it is a material formed first on the substrate, and the stress and surface properties of the film greatly affect the recording layer, and the reproduction S / N of the recording mark is greatly changed by the antireflection layer. Silicon nitride, aluminum nitride, alumina, silicon carbide, germanium nitride, chromium dioxide, a mixture of germanium nitride and chromium oxide were formed by sputtering, and compared. Silicon carbide has the best reproduction signal quality and storage reliability. It was good.

For example, aluminum nitride causes film floating due to thermal stress of initial crystallization, and silicon nitride has a larger jitter than silicon carbide when recorded and reproduced at a density of about 80% of the cutoff frequency. In addition, since the refractive index of alumina was small and the light confinement was weak, initialization could not be performed at 1 W or less. Germanium nitride has good characteristics like silicon carbide, but has disadvantages such as being expensive and a sputtering target being easily broken when formed at a high rate. The thickness of the anti-reflection layer depends on the wavelength of the initialization laser and the optical constants of the reflection layer and the anti-reflection layer, but may be set to a thickness under anti-reflection conditions derived from general diffraction theory. An example is shown in FIG.

As the reflection heat radiation layer (3), Al, Au,
A metal material such as Ag or Cu, or an alloy thereof can be used. In addition, Cr,
Ti, Si, Cu, Ag, Pd, Ta and the like are used. Such a reflective heat dissipation layer can be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, a plasma CVD method,
It can be formed by a photo CVD method, an ion plating method, an electron beam evaporation method, or the like. Among them, the sputtering method is excellent in mass productivity, film quality, and the like. Especially Au, Au-
Pt alloys, Ag alloys, and the like are excellent because of their high thermal conductivity, high reflectivity, and few surface irregularities. The thickness of the reflective heat dissipation layer is preferably about 20 to 200 nm, particularly 50 nm.
Good characteristics near.

The dielectric protective layers (4) and (6) are recording layers.
Prevents deterioration and deterioration of (5) and increases the adhesive strength of the recording layer (5)
And has the effect of improving recording characteristics, etc.
For example, SiO, SiO_Two, ZnO, SnO_Two, Al_TwoO_Three,
TiO_Two, In_TwoO_Three, MgO, ZrO_TwoSuch as metal oxidation
Object, Si_ThreeN_Four, AlN, TiN, BN, ZrN
Compound, ZnS, In_TwoS_Three, TaS_FourSuch as sulfide, Si
C, TaC, B_FourCarbonization of C, WC, TiC, ZrC, etc.
Objects, diamond-like carbon, or mixtures thereof
Is mentioned. These materials can be used alone as a heat-resistant layer.
However, they may be mixed with each other. Also necessary
May be included depending on the conditions. The melting point of the dielectric protection layer is
It needs to be higher than the recording layer. Film thickness is 5-60n
m in many cases. Thickness in terms of optical and thermal properties
But the protective layer between the reflective heat dissipation layer and the recording layer is thick
Is likely to greatly affect the cooling rate after recording.
It is a sensitive layer. Therefore, the wavelength around 400 nm,
In systems where the NA of the objective lens is 0.7 or more, the reflective layer
It is desirable that the distance between the layer and the recording layer is 10 nm or less. More than this
Heat fluctuates, and the recording mark recording position fluctuates greatly.
It will be good. The protective layer (6) between the recording film and the transparent sheet is
Generally, gain modulation degree near the optical confinement condition
I do. Therefore, general ZnS-SiO _Two, Wavelength 40
If the refractive index is around 2.3 at 0 nm, the thickness of the protective layer (6)
The length is about 30 to 60 nm. Such dielectric protection
The layer may be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method.
Ring method, plasma CVD method, photo-CVD method, ion press
Coating, electron beam evaporation, etc.
You. Among them, the sputtering method is used for mass production, film quality, etc.
Are better.

As a material of the recording layer (5), a chalcogen alloy thin film is often used. For example, Ge-Te
System, Ge-Te-Sb system, Ge-Sn-Te system, Ag-
In-Sb-Te quaternary alloy thin film and the like,
A eutectic thin film obtained by adding Ag and / or In and / or Ge to Sb-Te has a very good recording (amorphization) sensitivity / speed and erasing ratio, and thus is suitable as a material for the recording layer. Other elements and impurities can be added to these recording layer materials for the purpose of further improving performance and reliability. The recording layer using an inorganic material can be formed by various vapor deposition methods, for example, a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method, an ion plating method, an electron beam deposition method, or the like. Among them, the sputtering method is excellent in mass productivity, film quality, and the like. The thickness of the recording layer is desirably 15 nm or less in a system in which the wavelength is around 400 nm and the NA of the objective lens is 0.7 or more in order to prevent thermal bleeding during recording.
About 13 nm is desirable.

When a short wavelength laser in the blue light region is used, the light transmitting layer (7) is required to have a thickness of 0.3 mm or less. As the material, for example, polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin,
Urethane resins and the like can be mentioned, but polycarbonate resins and acrylic resins which are excellent in optical properties and cost are preferable. As a method of forming the light transmitting layer using the transparent sheet, there is a method of attaching a transparent sheet via an ultraviolet curable resin or a transparent double-sided pressure-sensitive adhesive sheet. Further, the ultraviolet curable resin is coated with a dielectric protection layer (6).
The light transmitting layer may be formed by applying the composition on the top and curing the applied composition. Further, an uneven pattern may be formed on the transparent sheet.

The dielectric protective layers (8) and (10) and the translucent recording layer (9) are formed in the same manner as the dielectric protective layers (4) and (6) and the recording layer (5) by the same film forming method and material. It is. However, the translucent recording layer has no reflective layer, and has a different temperature profile during recording. In particular, since the rate of temperature decrease during recording is different, it is necessary to adjust the rate of amorphization and crystallization by the composition of the recording layer. Therefore, when the recording layer (5) and the translucent recording layer (9) have the same composition, recording may not be performed well. The thickness of the translucent recording layer is 10 nm or less because it must be translucent, and the optimum film thickness is about 5 to 10 nm from the necessity of a uniform film. The dielectric protection layer has a thickness of 30 to protect the resin sheet from the heat of phase change recording.
A thickness of about nm or more is necessary. The rest is determined by optical conditions. As the protective film (11) in the present invention,
Conventionally known ones can be used as they are.

As the hard coat (12), an ultraviolet curable resin produced by spin coating is generally used. An appropriate thickness is 1 to 8 μm. If it is 1 μm or less, sufficient scratch resistance cannot be obtained. If the thickness is 8 μm or more, the internal stress increases, which greatly affects the mechanical properties of the disk. The hardness must be equal to or higher than H, which is a pencil hardness that does not cause significant damage even when rubbed with a cloth.
It is also effective to mix a conductive material as needed to prevent charging and prevent dust and the like from adhering. As the ultraviolet curable resin of the hard coat layer to be used, a resin having a viscosity of 40 cps or more is desirable in order to control the application position with good reproducibility and accuracy.

[0019]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Example 1 An anti-reflection layer 5 made of SiC was formed on a polycarbonate substrate having a diameter of 12 cm, a thickness of 1.1 mm, and a tracking guide with a continuous groove on the surface having a pitch of 0.5 μm.
0 nm, reflective heat dissipation layer made of Ag 60 nm, (GeCr)
Nx, Ge: Cr = 4: 1 molar ratio, and film made dielectric protective layer 6 nm, the recording layer 10nm made of Ag1In7Sb68Te22Ge2at%, by sputtering device in the order of the dielectric protective layer 40nm made of ZnS-SiO ₂ from the further two-sided A polycarbonate film having a thickness of 40 μm was attached via an adhesive sheet. An ultraviolet curing resin is dropped on this, a pre-groove is formed using a stamper, and a dielectric protection layer 50n made of ZnS-SiO ₂ is formed thereon.
m, the recording layer 7nm consisting Ag1In3Sb60Te33Ge3at%, the dielectric protective layer made of ZnS-SiO ₂ 40
nm was formed. A 40 μm-thick polycarbonate film was stuck on top of this, further hard-coated,
A layer type optical recording medium was formed. This disc is recorded and reproduced from the hard coat side.

Next, the recording layer of the disk was initialized by an initialization device having a large-diameter semiconductor laser. The initialization laser has a wavelength of 830 nm. Initialization of the translucent recording layer is first performed from the reproduction surface side. Linear velocity 3m / s, laser power 400mW, beam diameter 1
Initial crystallization was performed under the conditions of 00 μm and a head feed of 50 μm / rotation.

Next, the recording layer having the reflective layer was initialized from the substrate side. Linear velocity 2m / s, laser power 80
0 mW, beam diameter 100 μm, head feed 50 μm /
Initial crystallization was performed under rotating conditions.

This disk was set at a wavelength of 405 nm and an NA of 0.
Recording and reproduction were performed with 65 pickups. In the back side recording layer, the reflectivity of the portion was greatly increased from the state immediately after the film formation, and the back side recording layer was crystallized. The random data is modulated by 1-7 so that the recording density is 0.
A signal was recorded on both recording layers at 2 μm / bit and reproduced. The recording linear velocity is 3 m / s. Regeneration was also performed at the same linear speed. Reproduction power is 0.5mW. The translucent layer has a recording peak power of 5 mW and a bottom power of 2.4 mW, and the back side recording layer has a recording peak power of 8 mW and a bottom power of 4.4 mW.
Recorded. As a result, good eye patterns were obtained for both recording layers. In the present embodiment, the initialization is performed after all processes such as film formation, bonding, coating, etc., which are likely to involve dusts, are completed, so that the defect generation rate in the disk production process is reduced.

Example 2 On a polycarbonate substrate having a diameter of 12 cm, a thickness of 1.1 mm, and a tracking guide having a pitch of 0.5 μm formed by continuous grooves on the surface thereof, an antireflection layer made of TiO ₂ having a thickness of 50 nm and a reflection made of Ag were used. Heat dissipation layer 60 nm, (GeC
r) Nx, Ge: Cr = 4: 1 molar ratio, and film made dielectric protective layer 6 nm, the recording layer 10nm made of Ag1In7Sb68Te22Ge2at%, by sputtering device in the order of the dielectric protective layer 40nm made of ZnS-SiO ₂ from
Further, a polycarbonate film having a thickness of 40 μm was attached via a double-sided pressure-sensitive adhesive sheet. An ultraviolet curing resin is dropped on this, a pre-groove is formed using a stamper, and a dielectric protection layer 5 made of ZnS-SiO ₂ is formed thereon.
0 nm, the recording layer 7nm consisting Ag1In3Sb60Te33Ge3at%, was deposited dielectric protective layer 40nm made of ZnS-SiO _2. A polycarbonate film having a thickness of 40 μm was stuck thereon and hard-coated to form a two-layer optical recording medium. This disc is
Recording and playback from the hard court side.

Next, the recording layer of the disk was initialized by an initialization device having a large-diameter semiconductor laser. The initialization laser has a wavelength of 830 nm. Initialization of the translucent recording layer is first performed from the reproduction surface side. Initial crystallization was performed under the conditions of a linear velocity of 3 m / s, a laser power of 400 mW, a beam diameter of 100 μm, and a head feed of 50 μm / rotation.

Next, the recording layer having the reflective layer was initialized from the substrate side. Linear velocity 2m / s, laser power 80
0 mW, beam diameter 100 μm, head feed 50 μm /
Initial crystallization was performed under rotating conditions.

This disk was set at a wavelength of 405 nm and an NA of 0.
Recording and reproduction were performed with 65 pickups. In the back side recording layer, the reflectivity of the portion was greatly increased from the state immediately after the film formation, and the back side recording layer was crystallized. The random data is modulated by 1-7 so that the recording density is 0.
A signal was recorded on both recording layers at 2 μm / bit and reproduced. The recording linear velocity is 3 m / s. Regeneration was also performed at the same linear speed. Reproduction power is 0.5mW. The translucent layer has a recording peak power of 5 mW, a bottom power of 2.4 mW, and the back side recording layer has a
Recording was performed with a recording peak power of 8 mW and a bottom power of 4.4 mW. As a result, good eye patterns were obtained for both recording layers.

Comparative Example 1 An antireflection layer 5 made of AlN was placed on a polycarbonate substrate having a diameter of 12 cm, a thickness of 1.1 mm, and a tracking guide having a pitch of 0.5 μm formed by continuous grooves on the surface.
0 nm, Ag reflective heat dissipation layer 60 nm, (GeC
r) Nx, Ge: Cr = 4: 1 molar ratio, and film made dielectric protective layer 6 nm, the recording layer 10nm made of Ag1In7Sb68Te22Ge2at%, by sputtering device in the order of the dielectric protective layer 40nm made of ZnS-SiO ₂ from
Further, a polycarbonate film having a thickness of 40 μm was attached via a double-sided pressure-sensitive adhesive sheet. An ultraviolet curing resin is dropped on this, a pre-groove is formed using a stamper, and a dielectric protection layer 5 made of ZnS-SiO ₂ is formed thereon.
0 nm, the recording layer 7nm consisting Ag1In3Sb60Te33Ge3at%, was deposited dielectric protective layer 40nm made of ZnS-SiO _2. A polycarbonate film having a thickness of 40 μm was stuck thereon and hard-coated to form a two-layer optical recording medium. This disc is
Recording and playback from the hard court side.

Next, the recording layer of the disk was initialized by an initialization device having a large-diameter semiconductor laser. The initialization laser has a wavelength of 830 nm. Initialization of the translucent recording layer is first performed from the reproduction surface side. Initial crystallization was performed under the conditions of a linear velocity of 3 m / s, a laser power of 400 mW, a beam diameter of 100 μm, and a head feed of 50 μm / rotation.

Next, the recording layer having the reflection layer was initialized from the substrate side. Linear velocity 2m / s, laser power 80
0 mW, beam diameter 100 μm, head feed 50 μm /
Initial crystallization was performed under rotating conditions.

At this time, the film floated due to the thermal stress caused by the initialization, and the portion where the film floated could not be recorded / reproduced. This is considered to be related to the large film stress of aluminum nitride and the magnitude of the adhesive force.

[0031]

As described above, according to the detailed and specific description, according to the optical recording disk of the first aspect of the present invention, the use efficiency of the initialization laser beam is increased by the addition of the optical confinement layer. Initialization became possible by laser irradiation from the opposite side of the reflective film. According to the initialization method of the present invention, the light irradiation from the reflection film side eliminates the absorption of the initialization laser to the translucent recording layer.
Initialization of the second recording layer can be easily performed directly. Furthermore, in the optical recording medium according to the third aspect, the unevenness of the recording layer is reduced by using a film with less unevenness for the anti-reflection layer, which is the layer formed first on the substrate, and the recording mark is reproduced. , The S / N was improved, and higher density recording became possible. Further, according to the optical recording medium of the fourth aspect, an anti-reflection film with less unevenness can be formed at a high speed with an inexpensive material. In addition, the optical recording medium of the present invention performs initialization after all processes that easily involve dust such as film formation, bonding, and coating are completed, so that an excellent effect that the defect occurrence rate in a disk production process is reduced. To play.

[Brief description of the drawings]

FIG. 1 is a diagram showing one example of an optical recording medium of the present invention.

FIG. 2 is a diagram showing the relationship between the antireflection film of the present invention and the reflectance for light having an initialization laser wavelength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Antireflection layer 3 Reflection heat dissipation layer 4 Dielectric protection layer 5 Recording layer 6 Dielectric protection layer 7 Light transmission layer 8 Dielectric protection layer 9 Translucent recording layer 10 Dielectric protection layer 11 Protective film 12 Hard coat

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/26 531 B41M 5/26 X (72) Inventor Hiroyuki Iwasa 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 F-term in Ricoh Co., Ltd. (Reference) 2H111 EA03 EA04 EA12 EA23 EA36 FB05 FB09 FB12 FB17 5D029 HA06 JA01 JB13 JB18 JC01 MA21 MA22 5D090 AA01 BB05 BB12 CC11 KK09 5D121 AA01 GG26

Claims (4)

[Claims] 1. A phase change type multi-layer recording medium having a translucent recording layer as viewed from recording / reproducing light, and a transparent layer being interposed between the recording layer and the next recording layer at a distance. A phase-change optical recording medium, wherein a reflection layer is provided on the recording layer farthest from the incident surface, and an antireflection film is provided between the reflection layer and the substrate. 2. A phase change type multi-layer recording medium having a semi-transparent recording layer as viewed from recording / reproducing light, and a next recording layer at a distance by inserting a transparent layer. A phase change type optical recording medium, characterized in that a recording layer located farthest from the incident surface has a reflection layer, and initialization is performed by irradiating a laser for initial crystallization from the reflection layer side. Initialization method. 3. The phase-change optical recording medium according to claim 1, wherein the anti-reflection film is made of a material that easily forms a film having small irregularities. 4. The phase-change optical recording medium according to claim 3, wherein said antireflection film is made of high-density silicon carbide.