JP2002050079A - Optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk having good heat radiating property in which reproducing signals can be read out with good accuracy and the number of rewritable times is improved. SOLUTION: The optical disk 1 consists of a reflection layer 4, first protective layer 5, phase change type recording layer 6 and second protective layer 7 successively laminated on guide grooves 3 formed in a first substrate 2, and further a second substrate 9 adhered with an adhesive layer 8 on the second protective layer 7. The reflection layer 4 consists of a first reflection layer 41, first smooth layer 42 and second reflection layer 43 successively laminated. The thickness d1 of the first reflection layer 41, thickness d2 of the first smooth layer 42 and thickness d3 of the second reflection layer 43 are controlled to satisfy the relation of 0 nm<d1<=75 nm, 0 nm<d2<=10 nm, 0 nm<d3<=75 nm and d1+d3<=150 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk capable of optically recording and reproducing information.

[0002]

2. Description of the Related Art Optical disks are DVD-RAM and DVD.
-Widely used for applications such as RW. A conventional optical disk will be described with reference to FIG. FIG. 3 is a sectional view showing an optical disc of the first conventional example. As shown in FIG. 3, the optical disk 10 has a first protective layer 1 on a guide groove 3 formed of a land L and a groove G formed on a first substrate 2.
1, phase change recording layer 12, second protective layer 13, reflective layer 14,
The third protective film 15 is sequentially laminated, and the second substrate 9 is attached on the third protective film 15 via the adhesive layer 8.

Next, writing, erasing, and
Reproduction will be described. First, the first substrate 2 of the optical disc 10 whose entire surface has been made to have a high reflectance by initialization.
The phase change recording layer 12 is melted and quenched by locally irradiating a laser beam from the side to change the phase to an amorphous state. The reflectivity and the complex refractive index of the phase change recording layer 12 change with this phase change, and information is recorded on the phase change recording layer 12.

[0004] Reproduction is performed by irradiating a weak laser beam from the first substrate 2 side that does not cause a phase change to detect a reflectance difference between a high reflectance state and a low reflectance state. At this time, the laser light is reflected by the reflection layer 14 and is emitted again from the first substrate 2 side. In the rewriting, the recording peak power superimposed on the bias power of the energy causing crystallization is applied to the phase change recording layer 12 to overwrite the already recorded recording mark without going through the erasing process. Do. During this overwriting, the phase change recording layer 12
A new recording mark formed by heating to a high temperature, melting and quenching is written in the.

[0005]

However, when the aperture ratio NA is increased, it is necessary to reduce the thickness of the first substrate 2 in order to suppress the aberration of the laser beam.
There has been a problem that the substrate 2 is warped to be large. As a countermeasure, an optical disc 16 shown in FIG. 4 in which the thickness of the first substrate 2 is increased and the order of laminating the thin films is reversed.

FIG. 4 is a sectional view showing an optical disk of a second conventional example. The same components as those of the optical disk of the first conventional example are denoted by the same reference numerals, and description thereof will be omitted. The optical disc 16 of the second conventional example has a reflection layer 1 made of Al, an Al alloy, an Ag alloy or the like on an uneven guide groove 3 formed on a first substrate 2.
7, first protective layer 18, phase change recording layer 12, second protective layer 1
1 are sequentially laminated, and a second substrate 9 is attached on the second protective layer 11 via an adhesive layer 8.

The writing, erasing, and reproducing operations on the optical disk 16 are the same as those in the first conventional example except that the laser beam is irradiated from the second substrate 9 side. As a method of manufacturing the optical disk 16, the first substrate 2
Each layer of the reflective layer 17 to the second protective layer 11 is sequentially laminated on the guide groove 3 of FIG.
1 alloy and the like are liable to form columnar crystals, and this thickness is 75%.
If it is not less than nm, large irregularities are generated on the surface. As a result, an uneven portion is generated at the interface between the reflective layer 17 and the first protective layer 18.

For this reason, at the time of reproduction, the laser beam reflected by the reflection layer 17 is scattered by the concave and convex portions.
And the reading quality of the signal recorded in the groove G was poor. In addition, when the above-described layers are formed on the reflective layer 17 having the irregularities formed on the surface as described above, the overall flatness is deteriorated. There has been a problem that the number of times is reduced. Furthermore, in recording / reproducing using a blue semiconductor laser, it is necessary to reduce the size of the recording mark, emboss pit or land L and groove G of the guide groove 3. A signal pattern recorded on the land L and the groove G is buried depending on the crystal grain size, and a problem has arisen that a signal cannot be read.

As a countermeasure, the thickness of the reflection layer 17 is set to 75
It is conceivable to improve the flatness of the surface by setting the thickness to not more than nm, but usually, in order to efficiently radiate the heat generated in the phase change recording layer 12, the thickness of the reflective layer 17 needs to be 150 nm or more. Therefore, it could not be reduced to 75 nm or less. Thus, the heat generated in the phase change recording layer 12 cannot be efficiently radiated and the flatness of the reflection layer 17 cannot be satisfied at the same time. Therefore, the present invention has been made to solve the above-described problems, and provides an optical disc having good heat radiation, capable of reading a reproduced signal with high accuracy, and improving the number of rewrites. The purpose is to:

[0010]

According to a first aspect of the optical disc of the present invention, a reflective layer, a first protective layer, a phase change recording layer, and a reflective layer sequentially laminated on a guide groove formed in a first substrate are provided. An optical disc comprising a second protective layer and a second substrate adhered on the second protective layer via an adhesive layer, wherein the reflective layer is a second optical disk sequentially laminated on the first reflective layer. 1
When the thickness of the first reflective layer is d ₁ , the thickness of the first smooth layer is d ₂ , and the thickness of the second reflective layer is d ₃ , 0 nm <d ₁ ≦ 75 nm, 0 nm <d
₂ ≦ 10 nm, 0 nm <d ₃ ≦ 75 nm, and d ₁ + d ₃ ≦ 1
It is characterized by having a relationship of 50 nm.
According to a second aspect of the present invention, a reflective layer, a first protective layer, a phase change recording layer, a second protective layer, and a reflective layer sequentially laminated on a guide groove formed in a first substrate are bonded to the second protective layer. An optical disk comprising a second substrate adhered via an agent layer, wherein the reflective layer includes a first smooth layer sequentially laminated on the first reflective layer, a second smooth layer, and a metal layer. consists of a second reflective layer laminated alternately and repeatedly, the thickness of the first reflective layer d _1, the thickness of the first smooth layer d _2, the thickness of the metal layer and d ₄ 0 nm <d ₁ ≦ 75 nm, 0 nm <d ₂ ≦ 1
0 nm, 0 nm <d ₄ ≦ 75 nm, and d ₁ + 2d ₄ ≧ 15
It is characterized by having a relationship of 0 nm.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk according to the present invention will be described with reference to the drawings. The same components as those of the first and second conventional examples are denoted by the same reference numerals, and description thereof will be omitted. Figure 1
1 is a cross-sectional view illustrating an optical disc according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of FIG. 1 with three reflective layers.

First, an optical disk according to an embodiment of the present invention will be described below with reference to FIGS. Figure 1
As shown in FIG. 1, an optical disc 1 according to an embodiment of the present invention has a reflection layer 4, a first protection layer 5, and a phase change recording layer 6 on a guide groove 3 formed of a land L and a groove G formed on a first substrate 2. , A second protective layer 7 are sequentially laminated, and a second substrate 9 is attached on the second protective layer 7 via an adhesive layer 8.

Examples of the material of the first substrate 2 include a plastic substrate such as polycarbonate, polyolefin, and acrylic, a glass substrate, and a metal plate. A pre-groove for guiding a laser beam to the land L or the groove G, a pre-pit or a non-rewritable reproduction signal is provided in the emboss pit. These guide grooves 3 and pre-pits are formed by directly injection molding on the first substrate 2 or by dropping a photopolymer on a stamper, placing the first substrate 2 thereon, and curing the polymer. (Photopolymer method).

The reflection layer 4 includes a first smoothing layer 42 and a second reflection layer 43 sequentially laminated on the first reflection layer 41.
The thickness d ₁ of the first reflection layer 41 and the thickness d ₃ of the second reflection layer 43
Are 0 <d ₁ ≦ 75 nm, 0 <d ₃ ≦ 75 nm, and d ₁ +
d ₃ ≦ 150 nm. When the first reflective layer 41 and the second reflective layer 43 are made of Ag, even if their thickness is 50 nm or less, the flatness of the surface of these reflective layers 4 becomes good,
The sum of the thicknesses of the first reflection layer 41 and the second reflection layer 43 is 100
If it is not less than nm, the heat generated in the phase change recording layer 6 can be efficiently dissipated, so that the first reflection layer 41 and the second reflection layer 4
3 can be set as described above.

As shown in FIG. 2, the second reflection layer 43 in the reflection layer 4 may be configured as follows. That is, the second reflection layer 43 includes a second smoothing layer 45 on the lower metal layer 44a,
This is a configuration in which the upper metal layer 44b is sequentially laminated. In this case, the thickness of the lower metal layer 44a and the upper metal layer 44b are both in d _4. When the thickness of the first reflection layer 41 is d ₁ and the thickness of the first smoothing layer 42 is d ₂ , 0 <d ₁ ≦ 75 nm and 0 <
d ₂ ≦ 10 nm, 0 <d ₄ ≦ 75 nm, and d ₁ + 2d ₄ ≧
Set to 150 nm.

In this manner, the thickness d ₁ of the first reflection layer 41, the thickness d _{4 of} the lower metal layer 44a, and the thickness d ₄ of the lower metal layer 44a
Since the thickness d ₄ is less than 75 nm, it can ensure the flatness of the reflective layer 4, also, the first reflective layer 41, the lower metal layer 44
Since the total thickness of a and the upper metal layer 44b is 150 nm or more, the heat generated in the phase change recording layer 6 can be efficiently radiated. The material of the first reflection layer 41, the lower metal layer 44a, and the upper metal layer 44b is Au, Ag, C
u, Ni, In, Ti, Cr, Pt, Si, Ge, M
o, W, Ta, Zr and other metals; Al, Ti, Cr, Z
Ag-Pd-Cu with additives such as r and Si added
Alloys or semiconductors. In addition, the second reflection layer 43
May have a configuration in which the second smoothing layer 45 and the lower metal layer 44a or the upper metal layer 44b are alternately repeated. When a blue semiconductor laser having a wavelength of the order of 400 nm is used as the reproduction light, a high reflectance can be obtained by using an Al-based alloy or an Ag-based alloy.

As the material of the first smoothing layer 42 and the second smoothing layer 45, a material which is hardly crystallized is selected, and Te, Se, S
And the like, metal compounds of elements having different ionic radii, and dielectrics such as oxides, nitrides, sulfides, carbides and fluorides. Generally, this thickness is between 1 and 10 n
Although m is used, the thickness which does not lower the heat radiation performance is preferably 1 to 5 nm. These first smooth layer 42 and second
The smooth layer 45 is formed by DC sputtering or RF sputtering. If necessary, an additional gas may be added to form the layer by reactive sputtering.

The material of the first protective film 5 and the second protective film 7 is ZnS-SiO ₂ , ZnS, SiO ₂ , Ta ₂ O ₅ ,
Si ₃ N ₄ , AlN, Al ₂ O ₃ , AlSiON, Zr
There are O ₂ , TiO _{2 and the} like, and mixtures thereof. Second protective film 7
Is preferably 10 to 200 nm, and more preferably 40 to 150 nm to increase the reproduction signal. When a blue laser beam is used for recording and reproduction, the thickness is set to 40 to
The modulation degree can be increased by setting it to 60 nm. Further, the first protective film 5 is preferably made thinner than the second protective film 7 to reduce the thermal damage to a thickness of 2 to 50 nm.

As a material of the phase change recording layer 6, a phase change material utilizing a change in reflectance or a change in refractive index between amorphous and crystal is selected, and a Ge—Sb—Te system, Ag—In
There are -Te-Sb-based, Cu-Al-Sb-Te-based, and alloys containing Te or Se as a main component. This thickness is 5-10
0 nm, preferably 5 nm to 30 nm to increase the recording sensitivity and increase the reproduction signal.

The material of the adhesive layer 8 comprises a prepolymer, a monofunctional acrylate monomer, a polyfunctional acrylate monomer and the like, and a photopolymerization initiator. This adhesive layer 8
Has a thickness of 1 to 200 μm and is transparent to recording / reproducing light. This refractive index is equal to that of the second substrate 9,
The decrease in reflectance is suppressed. The adhesive layer 8 is formed by spin coating, spraying, dipping, blade coating, roll coating, screen printing, or the like.

As a material of the second substrate 9, a transparent plastic substrate such as polycarbonate, polyolefin, acrylic or the like or a glass substrate is used. This thickness is 0.
01 to 1.2 mm. When the NA of the objective lens is large, the thickness of the second substrate 9 is reduced to suppress the influence of spherical aberration.

The writing, erasing, and reproducing operations on the optical disk 1 are the same as those in the second conventional example, and the description thereof is omitted.

Next, the recording and reproduction characteristics of the optical disk 1 were examined by measuring the jitter, carrier level and reproduction noise level. The recording on the optical disc 1 is performed by setting the laser wavelength to 635 nm, the NA of the objective lens to 0.6, the modulation signal, the recording strategy and the like to the DVD-RW Bookver. 0.
9, a peak power of 1515.0 mW,
The laser beam was modulated with a bias power of 7.5 mW and a bottom power of 0.5 mW. In addition, reproduction is 0.7 mW
The laser beam was used.

The jitter is obtained by calculating σ / Tw, where σ is the standard deviation and Tw is the window width, and the carrier level and the reproduction noise level are obtained by measuring the 3T signal (0.4 μm length), which is the shortest mark. Sought by. As a result, the initial jitter was 7.5%, and the jitter after 1000 direct overwrite rewrites was increased by 2.5% compared to the initial. The initial carrier level was 23.4 dBm, and the initial reproduction noise level was 71.5 dBm.

As described above, the first smoothing layer 42 in which the reflective layer 4 is sequentially laminated on the first reflective layer 41 made of Ag,
When made from the second reflective layer 43 made of Ag, and the first reflective layer 41, the first smoothing layer 42, the thickness of the second reflective layer 43 and _{d 1, d 2, d 3} , 0nm <d 1 ≤75 nm, 0n
m <d ₂ ≦ 10 nm, 0 nm <d ₃ ≦ 75 nm, and d ₁ +
Since d ₃ ≦ 150 nm, the reflection layer 4 becomes flat,
The heat generated in the phase change recording layer 6 can be efficiently radiated. In addition, since the laser light incident on the optical disc 1 is not scattered, the reproduced signal can be read with high accuracy.
Jitter is reduced, and the number of times of rewriting can be improved.

Further, a first smoothing layer 42 in which the reflecting layer 4 is sequentially laminated on the first reflecting layer 41 made of Al, a lower metal layer 44a made of Al, a second smoothing layer 45, and an upper metal layer made of Al 44b and the first reflective layer 41, the first
When smoothing layer 42, the lower metal layer 44a, the thickness of the upper metal layer 44b and _{d 1, d 2, d 4} , d 4, 0nm <d 1 ≦ 75n
m, 0 nm <d ₂ ≦ 10 nm, 0 nm <d ₄ ≦ 75 nm, d
_{Since 1} + 2d ₄ ≧ 150 nm, the reflection layer 4 becomes flat, and the heat generated in the phase change recording layer 6 can be efficiently radiated. Further, since the laser light incident on the optical disc 1 is not scattered, the reproduced signal can be read with high accuracy, the jitter can be reduced, and the number of times of rewriting can be improved.

Next, the second reflection layer 43 is formed by the lower metal layer 44a.
A method of manufacturing the optical disc 1 when the second smoothing layer 45 and the upper metal layer 44b are laminated thereon will be described. First, a pre-group 3 having a track pitch of 0.74 μm and a groove depth of 30 nm (groove width 0.3 μm, land width 0, 44 μm)
A first substrate 2 made of polycarbonate having a thickness of 0.6 mm and having m) formed thereon is prepared. Next, the first substrate 2 is introduced into the sputtering apparatus, evacuated to 1 × 10 ⁻⁶ Torr or less, and then Ar gas is introduced to 2 mTorr, and then the guide groove 3 of the first substrate 2 Al (99.99
%) The target is DC-sputtered to form a first reflective layer 41 having a thickness of 200 nm. At this time, the film formation rate was 0.1
nm / s.

Next, ZnS-SiO ₂ (SiO _{2 20} mol)
1%) The target is RF-sputtered to form a first smooth layer 42 having a thickness of 10 nm. Next, Al (99.99%)
The target was formed at a deposition rate of 0.6, which is six times that of the first reflective layer 41.
DC sputtering is performed at a rate of nm / s to form a lower metal layer 44a having a thickness of 65 nm. Next, the same ZnS-SiO
_{A 2} (SiO ₂ 20 mol%) target is RF-sputtered to form a second smooth layer 45 having a thickness of 10 nm.

Next, an Al (99.99%) target was deposited at a deposition rate of 0.6 nm / s, which is six times that of the first reflective layer 41, and was subjected to D
The upper metal layer 44b having a thickness of 500 nm is formed by C sputtering. Further, ZnS-SiO ₂ (SiO ₂ 20 mol
%) The target is RF-sputtered to form a first
The protection layer 5 is formed. Next, Ag (4 at%)-In
(4 at%)-Sb (63 at%)-Te (29 at%)
%) A phase change recording layer 6 having a thickness of 20 nm is formed by DC sputtering of an alloy target.

Further, ZnS-SiO ₂ (SiO _{2 20} mol)
1%) The target is RF-sputtered to form a second protective layer 7 having a thickness of 75 nm.

Thereafter, the first reflection layer 4 is removed from the inside of the sputtering apparatus.
And taking out the first substrate 2 on which the second protective layer 7 is formed,
UV curable resin (XR9, manufactured by Sumitomo Chemical Co., Ltd.) on the second protective layer 7
The adhesive layer 8 made of 8) is spin-coated, and a second substrate 9 made of polycarbonate having a thickness of 0.1 nm is placed in an uncured state. Next, ultraviolet rays are irradiated from the second substrate 9 side to cure the adhesive layer 8, and the optical disc 1 is manufactured. At this time, the thickness of the adhesive layer 8 is 20 μm.

[0032]

According to the optical disc of the present invention, the first substrate
A reflective layer sequentially laminated on a guide groove formed in
A protection layer, a phase change recording layer, a second protection layer, and a second protection layer.
Such as a second substrate attached on the protective layer via an adhesive layer
An optical disk comprising: a first reflective layer;
A first smoothing layer and a second reflecting layer sequentially laminated on
And the thickness of the first reflective layer is d₁The thickness of the first smoothing layer
D_Two, The thickness of the second reflective layer is d_Three0 nm
<d₁≦ 75 nm, 0 nm <d_Two≦ 10 nm, 0 nm <d _Three≤
75 nm and d₁+ d_Three≤ 150 nm
As a result, the reflective layer becomes flat and the phase change recording layer
The generated heat can be efficiently dissipated. In addition, the
Since the emitted laser light is not scattered,
Read the playback signal, reduce jitter,
The number of times of rewriting can be improved. Form on the first substrate
A reflective layer sequentially laminated on the formed guide groove, and a first protection
Layer, phase change recording layer, second protective layer, and second protective layer
And a second substrate adhered thereon via an adhesive layer.
An optical disc, wherein the reflective layer is provided on the first reflective layer.
The first smooth layer, the second smooth layer, and the metal layer sequentially laminated
The second reflection layer is alternately and repeatedly laminated,
The thickness of the first reflective layer is d₁, The thickness of the first smoothing layer
d_Two, The thickness of the metal layer is d_Four0 nm <d₁≦ 7
5 nm, 0 nm <d_Two≦ 10 nm, 0 nm <d_Four≤75n
m and d₁+ 2d_Four≧ 150 nm,
The reflective layer becomes flat, and the heat generated in the phase change recording layer is efficiently
Good heat dissipation. In addition, laser light incident on the optical disc
The reproduced signal is read accurately because
And reduce jitter and reduce the number of rewrites.
Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an optical disc according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG. 1 with three reflective layers.

FIG. 3 is a sectional view showing an optical disc of a first conventional example.

FIG. 4 is a sectional view showing an optical disc of a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... 1st board | substrate, 3 ... Guide groove, 4 ... Reflective layer, 5 ... 1st protective layer, 6 ... Phase change recording layer, 7 ... 2nd protective layer, 8 ... Adhesive layer, 9 ... No. 2 substrates, 41 ... first reflection layer,
42: first smooth layer, 43: second reflective layer, 44a: lower metal layer (metal layer), 44b: upper metal layer (metal layer), 45
... Second smooth layer

Claims (2)

[Claims] A reflective layer, a first protective layer, a phase-change recording layer, and a second reflective layer sequentially laminated on a guide groove formed in a first substrate.
An optical disc comprising a protective layer and a second substrate adhered on the second protective layer via an adhesive layer, wherein the reflective layer is a first smooth layer sequentially laminated on the first reflective layer. And a second reflective layer, wherein the thickness of the first reflective layer is d
₁ , when the thickness of the first smoothing layer is d ₂ and the thickness of the second reflecting layer is d ₃ , 0 nm <d ₁ ≦ 75 nm and 0 nm <d ₂ ≦
10 nm, 0 nm <d ₃ ≦ 75 nm, and d ₁ + d ₃ ≦ 15
An optical disc characterized by having a relationship of 0 nm. 2. A reflection layer, a first protection layer, a phase change recording layer, and a second layer, which are sequentially laminated on a guide groove formed in a first substrate.
An optical disc comprising a protective layer and a second substrate adhered on the second protective layer via an adhesive layer, wherein the reflective layer is a first smooth layer sequentially laminated on the first reflective layer. And a second reflective layer in which a second smooth layer and a metal layer are alternately and repeatedly laminated. The thickness of the first reflective layer is d ₁ , and the thickness of the first smooth layer is d ₂ When the thickness of the metal layer is d ₄ , 0 nm <d ₁ ≦ 7
5 nm, 0 nm <d ₂ ≦ 10 nm, 0 nm <d ₄ ≦ 75 n
An optical disc, wherein m and d ₁ + 2d ₄ ≧ 150 nm.