JP2000043415A - Phase change optical recording medium - Google Patents

Abstract

(57) [Problem] To provide a phase change optical recording medium which can be used at a high recording density and has good repetitive recording characteristics. SOLUTION: In an optical recording medium having a phase change recording material having Sb and Te as a recording layer, the recording layer has a space group F
A phase-change optical recording medium having a metastable Sb ₃ Te phase belonging to m3m.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical recording disk and the like, in which a recording layer material is optically changed by irradiating a light beam to record, reproduce, and rewrite information. The present invention relates to a novel phase change optical recording medium.

[0002]

2. Description of the Related Art As one of optical recording media capable of recording, reproducing and erasing information by irradiating a laser beam, a so-called phase-change optical recording medium utilizing a transition between a crystal and an amorphous phase or between a crystal and a crystal phase. Is well known.
It can be overwritten with a single beam,
Since the optical system on the drive side is simpler, it has been applied as a recording medium related to computers and audiovisual.

[0003] As one of the recording materials, a recording material of Sb ₂ Te ₃ and a recording layer near a eutectic composition of a Sb ₂ Te ₃ -Sb pseudo-binary system are known. And, for this crystallization speed control, it was added an additive element (Sb _x Te _1-x) having composition formula of _1-y M _y is disclosed in JP-A-1-277338. Here, M is Ag, Al, As, Au, Bi, C
u, Ga, Ge, In, Pb, Pt, Se, Si, Sn
And at least one element selected from Zn and a composition range of 0.4 ≦ x <0.7 and y ≦ 0.2. The structure in this composition range is based on Sb ₂ Te ₃ . In the case of the recording layer having this structure, there was a problem in the repetitive recording characteristics in the region where y was 0.7 or more.

On the other hand, a recording layer near the eutectic composition of the Sb ₂ Te ₃ -Sb pseudo-binary system is disclosed in Japanese Patent Application Laid-Open No. 9-161316. In this case, the composition of the recording layer is 0.6 ≦ x ≦ 0.
In the region of 85, initial crystallization is extremely difficult, and Sb _z (T
e _1-z ) (0.2 ≦ z ≦ 0.7), and a Sb _z (Te _1-z ) (0.2 ≦ z ≦ 0.7)
A recording layer of an optical recording medium having a crystal structure similar to that of the above is disclosed.

Sb _z (Te _{1 -z} ) (0.2 ≦ z ≦ 0.7)
Then, Te + Sb ₂ Te ₃ , Sb ₂ Te ₃ , Sb ₂ Te ₃ + S
The structure corresponds to Sb ₂ Te ₃ + Sb from the composition of the recording layer. This Sb ₂ Te ₃ -Sb
The eutectic composition near the quasi-two-element, there is a difference Sb and Sb ₂ Te ₃ in the crystallization rate, the boundary of the crystallized portion and the amorphous portion, the disturbance in the grain boundaries of the effects of Sb and Sb ₂ Te ₃ Easy to occur. Therefore, it can be applied to a medium having a relatively low recording density, but it is difficult to obtain good recording characteristics at a high recording density equal to or higher than that of a DVD-RAM or DVD-ROM.

In a material system in which an additive element is added to this material, _a composition formula of (Sb _x Te _1-x ) _a M _1-a (M is Au, Ag,
A phase change recording material represented by at least one element of Cu) is disclosed in JP-A-9-71046. This composition range is 0 <x <0.9 and 0 <a <1.
And the structure is Sb ₂ Te ₃ + Sb, which still has the problems described above.

[0007]

As described above, Sb-T
The e-M system, the structure of _{Sb 2 Te 3, Sb 2 Te} 3 + Sb as a base, Ag, Al, As, Au , Bi, Cu,
With Ga, Ge, In, Pb, Pt, Se, Si, Sn, and Zn as additional elements, only a recording material having improved amorphous state stability, high-speed erasing characteristics, or repeated recording characteristics is used. there were. For this reason, there has been no optical recording medium having a high recording density, for example, a recording density equal to or higher than that of a DVD-RAM or DVD-ROM, and having good recording characteristics. In fact, the relationship between the composition region having good repetition and the recording linear velocity has not been clarified yet.

Accordingly, a first object of the present invention is to provide a DVD-
An object of the present invention is to provide a phase-change optical recording medium such as a RAM, a DVD-RW, or an S-DVD-RAM that can be used at a high recording density and has good repetitive recording characteristics. A second object of the present invention is to provide a phase-change optical recording medium capable of easily improving the storage characteristics and expanding the recordable linear velocity region.

[0009]

The present inventors have studied the recording material having Sb and Te from various angles. As a result, the recording layer having the metastable crystal belonging to the space group Fm3m was repeatedly recorded. Was found to be resistant to thermal shock and to form a favorable composition region. The present invention has been made based on this.

The first aspect of the present invention is that the recording layer has a space group Fm3m
And a metastable Sb ₃ Te recording material, wherein the recording layer changes optical properties in a phase transition between a crystalline phase and an amorphous phase.
The lattice constant is about 0.62 nm.

A second aspect of the present invention is that, in the first aspect, the recording layer includes a group Ib element, a group II element, a group III element, a group IV element,
A phase-change optical recording medium characterized by adding at least one element selected from group IV elements, group VI elements, rare earth elements and transition metal elements. The addition of the above-mentioned element is set to a composition range that does not inhibit the appearance of the metastable crystal phase described above.

A third aspect of the present invention is the crystal according to the first or second aspect, wherein the crystal belongs to the same space group Fm3m as the metastable Sb ₃ Te phase and has a lattice constant in the range of 0.62 ± 0.02 nm. A phase-change optical recording medium characterized in that the same substance as a crystal constituting a phase is added to a Sb ₃ Te recording layer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The Sb-Te binary recording material used firstly belongs to the space group Fm3m as a recording layer of the optical recording medium, and has metastable Sb ₃ Te having a lattice constant of about 0.62 nm.
A recording layer is used. This metastable phase is formed by rapid cooling after melting. FIG. 1 shows an X-ray diffraction pattern of this metastable phase. This metastable phase is different from the recording layer having the Sb-Te eutectic structure, does not separate into Sb and Sb ₂ Te ₃ , does not disturb recording marks due to crystal grain boundaries, and is suitable for high-density recording. Phase.

In the second method, for the purpose of adjusting the crystallization speed of the recording layer, and improving the storage characteristics and the repetitive recording characteristics, the group Ib element, the group II element, the group III element, the group IV element and the V
At least one element selected from the group consisting of group IV elements, group VI elements, rare earth elements and transition metal elements is added. nitrogen,
B, C, rare earth elements, and transition metal elements have the effect of improving the long-term storage characteristics of the first recorded data. Here, with respect to the repetitive recording characteristics, it is preferable that the crystal phase of the additive substance alone has a lattice matching relationship with the metastable Sb ₃ Te, as seen in the third above. For example, if the composition of the recording layer is (S
b ₃ Te) _1-x (AgSbTe ₂ ) _x or (Sb ₃ Te)
_1-y (In ₃ SbTe ₂ ) _y and the like. Note that the structure of the recording layer having the additive element is such that the additive element forms a solid solution in the metastable Sb ₃ Te lattice, a phase-separated structure of the additive substance and Sb ₃ Te, or a solid solution of several types. In some cases, the phase separation structure is formed. When a phase separation structure is used, the added element is 20 Vol. % Is preferable from the viewpoint of suppressing the disturbance of the shape of the recording mark described above.

The metastable Sb used in the above third case_ThreeTe
A crystal phase that belongs to the same space group as the phase and has a similar lattice constant
AgSbTe as an additive substance constituting_Two, AuS
bTe_Two, InTe, InSbTe_Two, AlSbTe_Two,
CuMgSb, BiMgNi, SmSe, Cu_TwoInM
n, PbSe, In-Sb-Te, AuCuZn_Two, I
n_FourSbTe_Three, SbSn, InMgNi_Two, AgBiT
e_Two, Co_TwoSnTi, CuMgSb, AuGa_Two, Cu_Two
AlMn, AlCo_TwoZr, AlHfNi_Two, ZnTe,
Al_TwoAu, Cu_ThreeSb, Cu_TwoSnTe_Three, MnNiS
b, GeTe, Co _TwoMnSn, GdTe, SbTb,
Ni_TwoSnTi, Fe_TwoSnTi, AuCuZn_Two, Ni
Se_Two, AlCu_TwoTi, Ni_TwoSnV, LaSe, Gd
Sb, AlCu _TwoZr, Cu_TwoInTi, Sb_TwoSnZ
n, AgAuZn_Two, GeInLi, BiTb, AlC
u_Four, NdTe, Ag_TwoS, CaTe, PbTe, SnT
e, Cu_TwoExamples thereof include AlMn and a mixture thereof. This
Here, for example, AlSbTe is added to the Sb-Te recording layer._TwoAdd
In this case, the composition of the recording layer is approximately (Sb_ThreeTe)
_1-x(AlSbTe_Two)_xIt is represented by And InTe
When adding, (Sb_ThreeTe)_{1-x -y}(AlSbTe
_Two)_x(InTe)_yIt is represented by In addition, the description of this composition
The structure of the recording layer after the initial crystallization has a structure having a metastable crystal phase.
Quenching from the molten state.
Crystallization takes place.

FIG. 2 is a schematic view showing a cross section of an example of the phase change optical recording medium of the present invention. Basically, a first protective layer 2, a recording layer 3, a second protective layer 4, a reflective heat radiation layer 5, and an environmental protective layer 6 made of an ultraviolet curable resin are provided on a base 1 having a guide groove. If necessary, an intermediate layer may be provided between the reflective heat radiation layer 5 and the environmental protection layer 6, and a hard coat layer may be provided on the back surface of the base 1. The first protective layer 2 and the second protective layer 4 are not necessarily provided on both sides of the recording layer. However, when the substrate 1 is made of a material having low heat resistance such as a polycarbonate resin, the first protective layer may be provided. desirable.

The thickness of the recording layer 3 is preferably 5 to 100 nm, more preferably 10 to 50 nm, and particularly preferably 15 to 25 nm. This recording layer is formed by sputtering, ion plating, vacuum deposition, plasma CVD.
It can be produced by a method or the like.

The material of the base 1 is usually glass, ceramics, or resin. Among them, the resin base is suitable in terms of moldability, cost, and weight. Typical 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, etc. Polycarbonate resins and acrylic resins are preferred from the viewpoints of properties, optical properties, heat resistance properties, and the like. The thickness of the substrate is 1.2 mm, 0.6 mm, 0.
Any material such as 3 mm can be used, but it is preferably about 0.5 to 1.2 mm in consideration of difficulty in film formation and yield.

In the case of a resin substrate, the glass transition temperature Tg of the resin is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, preferably 200 ° C. or lower, more preferably 180 ° C. or lower. If the glass transition temperature Tg of the resin of the substrate is lower than this temperature, there is a problem that the substrate is easily deformed, and if it is higher than this temperature, molding becomes difficult.

The first protective layer 2 and the second protective layer 4 are made of Si
O, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ ,
Oxides such as In ₂ O ₃ , MgO, ZrO ₂ , Si ₃ N ₄ ,
Nitrides such as AlN, TiN, BN, ZrN, ZnS,
Sulfides such as In ₂ S ₃ and TaS ₄ , SiC, TaC, B
Carbides such as 4C, WC, TiC, and ZrC, diamond-like carbon, and mixtures thereof are preferable. The first protective layer and the second protective layer have a thickness of sputtering, ion plating, vacuum deposition, plasma CVD.
And the like. The thickness of the first protective layer is 50 to 5
00 nm, preferably 100 to 300 nm, more preferably 150 to 250 nm. The thickness of the second protective layer is
It is 5 to 200 nm, preferably 10 to 50 nm.

The reflective heat dissipation layer 5 can be made of a metal material such as Al, Ag, or Au, or a material obtained by adding Ti, Cr, Si, Ta, or the like thereto. The reflective heat dissipation layer is formed by sputtering, ion plating, vacuum deposition, plasma C
It can be manufactured by VD or the like. Its thickness is preferably 3
It is 0 to 300 nm, more preferably 50 to 250 nm, particularly preferably 70 to 200 nm.

The environmental protection layer is preferably formed of an ultraviolet curable resin, and its thickness is suitably about 2 to 15 μm.

[0023]

Next, the present invention will be described in detail with reference to examples.

Example 1 In FIG. 2, a first protective layer 2 made of ZnS.SiO ₂ having a thickness of 160 nm was formed on a polycarbonate substrate 1 having a guide groove, and a Sb-Te recording having a thickness of 20 nm was formed on the first protective layer. Layer 3, a 20 nm thick ZnS.SiO ₂ layer on this recording layer
A second protective layer 4 consisting of
An Al-Ti reflective heat dissipation layer 5 nm in thickness and an environmental protection layer 6 made of a 5 [mu] m thick UV curable resin are laminated on this reflective heat dissipation layer.

Table 1 shows the composition dependency of the repetitive recording characteristics of the optical recording medium when the composition of the Sb ₃ Te metastable recording layer was changed. The recording linear velocity is m / s. The recording strategy (LD emission pattern during recording) is CD-RW
The one adopted in was used. The number of recordable times is determined by the maximum number of repetitive recordings in which the jitter value σ / Tw normalized by the window width Tw does not exceed 13%. The composition stable to thermal shock in the repetitive recording of the crystal phase is Sb (75 at.%) Te (25 at.
%), And Sb ₃ Te having a stoichiometric composition has excellent repetitive recording characteristics. When the composition of the recording layer is Sb (75a
t. %) As it deviates from Te (25 at.%)
Alternatively, Sb ₂ Te ₃ is easily precipitated, and the boundaries of the recording marks are easily disturbed.

[0026]

[Table 1]

Example 2 In the recording layer of Example 1, nitrogen, which is a Vb group element, was added almost to 1a.
t. FIG. 3 shows the fluctuation of the jitter value in the storage test with respect to the initial recording in the example in which the% addition was performed. The storage test conditions are 80 ° C. and 85% relative humidity. The storage characteristics are improved by adding nitrogen.

Example 3 Sb (75 at.%) Te (25 at.%) Of Example 1
AgSbTe on the recording layer _TwoOf the recording layer when
FIG. 4 shows the linear velocity dependency of the jitter. In this case, the recording layer
The composition is (Sb_ThreeTe)_0.9(AgSbTe_Two)_0.1It is.
AgSbTe_TwoThe optimum recording linear velocity is low by adding a small amount of
Shift to the linear velocity side.

[0029]

As described above, the present invention has the following effects. According to the invention of claim 1, the DVD-
Recording at a higher recording density than that of a RAM or DVD-ROM became possible, and the number of repetitive recordings was improved. Claim 2
According to the invention, storage characteristics are improved. According to the third aspect of the present invention, the recordable linear velocity region is extended.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction pattern of a metastable Sb ₃ Te phase in the present invention.

FIG. 2 is a sectional view of an example of the phase change optical recording medium of the present invention.

FIG. 3 is a diagram showing a fluctuation of a jitter value in a storage recording as an initial recording of a phase change optical recording medium according to a second embodiment.

FIG. 4 is a diagram showing the linear velocity dependence of initial jitter of the phase change optical recording medium of Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 First protective layer 3 Recording layer 4 Second protective layer 5 Reflective discharge layer 6 Environmental protective layer

Continued on the front page F term (reference) 2H111 EA04 EA12 EA23 EA31 EA32 EA40 FA01 FB04 FB08 FB09 FB12 FB16 FB17 FB18 FB20 FB22 FB23 FB28 5D029 JA01 JB18 JB35

Claims (3)

[Claims] 1. An optical recording medium using a phase change recording material having Sb and Te as a recording layer, wherein the recording layer is a space group F
An optical recording medium having a metastable Sb ₃ Te phase belonging to m3m. 2. The recording layer according to claim 1, wherein the recording layer comprises an element selected from the group consisting of a group Ib element, a group II element, a group III element, a group IV element, a group V element, a group VI element, a rare earth element and a transition metal element. An optical recording medium, wherein at least one is added. 3. The recording layer according to claim 1, wherein the recording layer belongs to a space group Fm3m and has a lattice constant of 0.62 ±
A substance having the same composition as the crystal phase in the range of 0.02 nm is added, and the crystal phase of the recording layer after the initial crystallization has a metastable crystal phase belonging to the space group Fm3m. An optical recording medium characterized by the following.